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  • 1.
    Abbas, Ghulam
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Johansson, Gustav
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Alay-e-Abbas, Syed Muhammad
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad 38040, Pakistan.
    Shi, Yijun
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, J. Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Quasi Three-Dimensional Tetragonal SiC Polymorphs as Efficient Anodes for Sodium-Ion Batteries2023Ingår i: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 6, nr 17, s. 8976-8988Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, we investigate, for the first time, quasi 3D porous tetragonal silicon–carbon polymorphs t(SiC)12 and t(SiC)20 on the basis of first-principles density functional theory calculations. The structural design of these q3-t(SiC)12 and q3-t(SiC)20 polymorphs follows an intuitive rational approach based on armchair nanotubes of a tetragonal SiC monolayer where C–C and Si–Si bonds are arranged in a paired configuration for retaining a 1:1 ratio of the two elements. Our calculations uncover that q3-t(SiC)12 and q3-t(SiC)20 polymorphs are thermally, dynamically, and mechanically stable with this lattice framework. The results demonstrate that the smaller polymorph q3-t(SiC)12 shows a small band gap (∼0.59 eV), while the larger polymorph of q3-t(SiC)20 displays a Dirac nodal line semimetal. Moreover, the 1D channels are favorable for accommodating Na ions with excellent (>300 mAh g–1) reversible theoretical capacities. Thus confirming potential suitability of the two porous polymorphs with an appropriate average voltage and vanishingly small volume change (<6%) as anodes for Na-ion batteries.

    Ladda ner fulltext (pdf)
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  • 2.
    Abbas, Syed Adeel
    et al.
    Center for High Energy Physics, University of the Punjab, Quaid-e-Azam Campus, 54590 Lahore, Pakistan.
    Mahmood, I.
    Center for High Energy Physics, University of the Punjab, Quaid-e-Azam Campus, 54590 Lahore, Pakistan.
    Sajjad, Muhammad
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Noor, N.A.
    Department of Physics, RIPHAH International University, Campus Lahore, Pakistan.
    Mahmood, Q.
    Department of Physics, College of Science, Imam Abdulrahman Bin Faisal University, P O Box 1982, 31441 Dammam, Saudi Arabia.
    Naeem, M.A.
    Chemical Engineering Department, University of the Punjab, Lahore 54000, Pakistan.
    Mahmood, Asif
    College of Engineering Chemical Engineering Department King Saud University Riyadh, Saudi Arabia.
    Ramay, Shahid M.
    Department of Physics and Astronomy, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
    Spinel-type Na2MoO4 and Na2WO4 as promising optoelectronic materials: First-principle DFT calculations2020Ingår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 538, artikel-id 110902Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanical, thermodynamic, electronic, and optical properties of Na2MoO4 (NMO) and Na2WO4 (NWO) spinels are elaborated by density functional theory (DFT) based full potential augmented plane wave method (FP-LAPW + lo). Our optimized lattice constants for the studied spinels are in good agreement with that obtained experimentally. The enthalpy of formation ensures the thermodynamic stability of NMO and NWO in the cubic phase. The Born mechanical stability criteria guarantees their mechanical stability, while Poisson ratio (ν) and Pugh's ratio (B/G) infer their brittle behavior. The Debye temperature (θD) is significant for NMO than NWO. The wide bandgap of 3.5 eV for NMO and 4.4 eV for NWO show the maximum absorption in the ultraviolet region that increases their importance for optoelectronic applications. The optical properties are explained in term of dielectric constant, refractive index, absorption of light, reflection, and optical loss factor.

  • 3.
    Adeel, Muhammad
    et al.
    Department of Molecular Sciences and Nanosystems, Ca’Foscari University of Venice, 30172, Venice-Mestre, Italy. Pathology Unit, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081, Aviano, Italy.
    Canzonieri, Vincenzo
    Pathology Unit, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081, Aviano, Italy. Department of Medical, Surgical and Health Sciences, University of Trieste, 34127, Trieste, Italy.
    Daniele, Salvatore
    Department of Molecular Sciences and Nanosystems, Ca’Foscari University of Venice, 30172, Venice-Mestre, Italy.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Molecular Sciences and Nanosystems, Ca’Foscari University of Venice, 30172, Venice-Mestre, Italy.
    Rizzolio, Flavio
    Department of Molecular Sciences and Nanosystems, Ca’Foscari University of Venice, 30172, Venice-Mestre, Italy. Pathology Unit, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081, Aviano, Italy.
    Rahman, Md. Mahbubur
    Department of Energy and Materials, Konkuk University, Chungju, 27478, Republic of Korea.
    2D metal azolate framework as nanozyme for amperometric detection of glucose at physiological pH and alkaline medium2021Ingår i: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 188, nr 3, artikel-id 77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The synthesis of Co-based two-dimensional (2D) metal azolate framework nanosheets (MAF-5-CoII NS) is described using a simple hydrothermal method. The product was isostructural to MAF-5 (Zn). The as-prepared MAF-5-CoII NS exhibited high surface area (1155 m2/g), purity, and crystallinity. The MAF-5-CoII NS–modified screen-printed electrode (MAF-5-CoII NS/SPE) was used for nonenzymatic detection of glucose in diluted human blood plasma (BP) samples with phosphate buffer saline (PBS, pH 7.4) and NaOH (0.1 M, pH 13.0) solutions. The MAF-5-CoII NS nanozyme displayed good redox activity in both neutral and alkaline media with the formation of CoII/CoIII redox pair, which induced the catalytic oxidation of glucose. Under the optimized detection potential, the sensor presented a chronoamperometric current response for the oxidation of glucose with two wide concentration ranges in PBS-diluted (62.80 to 180 μM and 305 to 8055 μM) and NaOH-diluted (58.90 to 117.6 μM and 180 to 10,055 μM) BP samples, which were within the limit of blood glucose levels of diabetic patients before (4.4–7.2 mM) and after (10 mM) meals (recommended by the American Diabetes Association). The sensor has a limit of detection of ca. 0.25 and 0.05 μM, respectively, and maximum sensitivity of ca. 36.55 and 1361.65 mA/cm2/mM, respectively, in PBS- and NaOH-diluted BP samples. The sensor also displayed excellent stability in the neutral and alkaline media due to the existence of hydrophobic linkers (2-ethyl imidazole) in the MAF-5-CoII NS, good repeatability and reproducibility, and interference-free signals. Thus, MAF-5-CoII NS is a promising nanozyme for the development of the disposable type of sensor for glucose detection in human body fluids.

  • 4.
    Adjizian, J.J.
    et al.
    Department of Chemistry, University of Sussex, Falmer, Brighton.
    Latham, Chris
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Briddon, P.R.
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Heggie, M.I.
    Department of Chemistry, University of Sussex, Falmer, Brighton.
    DFT study of the chemistry of sulfur in graphite, including interactions with defects, edges and folds2013Ingår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 62, s. 256-262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sulfur has several roles, desirable and undesirable, in graphitization. We perform density functional theory calculations within the local density approximation to define the structures and energetics of sulphur in graphite, including its interactions with point defects and edges, in order to understand its role in the later stages of graphitization. We find sulphur does not cross-link layers, except where there are defects. It reacts very strongly with vacancies in neighbouring layers to form a six coordinate split vacancy structure, analogous to that found in diamond. It is also highly stable at basal edge sites, where, as might be expected, the size and valency of sulfur can be easily accommodated. This suggests a role for sulphur in stabilizing graphene edges, and following from this, we show that sulfur dimers can open, i.e. unzip, folds in graphite rapidly and exothermically.

  • 5.
    Adu, Cynthia
    et al.
    Manufacturing and Materials Department, Cranfield University.
    Berglund, Linn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Eichhorn, Stephen J.
    Bristol Composites Institute (ACCIS), Queens Building, School of Engineering, Bristol University.
    Jolly, Mark
    Manufacturing and Materials Department, Cranfield University.
    Zhu, Chenchen
    Bristol Composites Institute (ACCIS), Queens Building, School of Engineering, Bristol University.
    Properties of cellulose nanofibre networks prepared from never-dried and dried paper mill sludge2018Ingår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 197, nr 1, s. 765-771Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Paper mills yield large volumes of sludge materials which pose an environmental and economic challenge for disposal, despite the fact that they could be a valuable source for cellulose nanofibres (CNF) production. The aim of the study was to evaluate the production process and properties of CNF prepared by mechanical fibrillation of never-dried and dried paper mill sludge (PMS). Atomic force microscopy (AFM) showed that average diameters for both never-dried and dried paper sludge nanofibres (PSNF) were less than 50 nm. The never-dried and dried sludge nanofibres showed no statistical significant difference (p > 0.05) in strength 92 MPa, and 85 MPa and modulus 11 GPa and 10 GPa. The study concludes that paper mill sludge can be used in a dried state for CNF production to reduce transportation and storage challenges posed on industrial scale.

  • 6.
    Aftab, A.
    et al.
    Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia.
    Ismail, Abdul Razak
    Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia.
    Ibupoto, Zafar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akeiber, Hussein J.
    Faculty of Mechanical Engineering, Universiti Teknologi Malaysia.
    Malghani, M.G.K.
    Department of Environmental Management and Policy, BUITEMS Quetta, Pakistan.
    Nanoparticles based drilling muds a solution to drill elevated temperature wells: a review2017Ingår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 76, s. 1301-1313Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Demand of the oil and gas energy is increasing very drastically. Conventional hydrocarbon reservoirs contain below the sealing cap rock (shale) and easily move towards wellbore are at the depletion stage. Therefore, drilling engineers in collaboration with mud engineers, geologists and geophysicists are looking for innovative materials to drill unconventional hydrocarbons reservoir which are distributed at the basin scale and cannot approach easily. Geo-thermal energy wells and most of unconventional reservoirs are occurred at high pressure high temperature (HPHT) conditions. Conventional micro-macro organic drilling mud additives with heat insulator in nature can minimize efficiency while drilling HPHT wells. Oil-based muds (OBM) are strictly restricted due to high toxic level and poor emulsion stability at HT. However, this review suggests that addition of macro size organic particles and inorganic nanoparticles can enhance rheological performance, reduce filtrate loss volume and improve shale inhibition characteristics of environmental friendly water-based mud (WBM). Despite an impressive amount of experimental work has been done over drilling additives and their effect over rheological and shale inhibition, taking into account their literature review are rare. In addition, there is no review work of the knowledge gained to date. This work will hope fully trigger further development and new research topics in the area of drilling muds system.

  • 7.
    Aftab, Umair
    et al.
    Department of Metallurgy and Materials Engineering, Mehran University of Engineering and Technology, Jamshoro, Sindh, 76080, Pakistan.
    Tahira, Aneela
    Department of Science and Technology, Campus Norrköping, Linköping University, Norrköping, SE-60174, Sweden.
    Gradone, Alessandro
    CNR-IMM, Via Piero Gobetti 101, Bologna, 40129, Italy. Chemistry Department “G.Ciamician”, University of Bologna, Bologna, 40126, Italy.
    Morandi, Vittorio
    CNR-IMM, Via Piero Gobetti 101, Bologna, 40129, Italy.
    Abro, Muhammad Ishaq
    Department of Metallurgy and Materials Engineering, Mehran University of Engineering and Technology, Jamshoro, Sindh, 76080, Pakistan.
    Baloch, Muhammad Moazam
    Department of Metallurgy and Materials Engineering, Mehran University of Engineering and Technology, Jamshoro, Sindh, 76080, Pakistan.
    Bhatti, Adeel Liaquat
    Institute of Physics University of Sindh, Jamshoro, Sindh, 76080, Pakistan.
    Nafady, Ayman
    Department of Chemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, Venezia, Mestre, 30172, Italy.
    Ibupoto, Zafar Hussain
    Dr. M.A Kazi Institute of Chemistry University of Sindh, Jamshoro, Sindh, 76080 Pakistan.
    Two step synthesis of TiO2–Co3O4 composite for efficient oxygen evolution reaction2021Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 46, nr 13, s. 9110-9122Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For an active hydrogen gas generation through water dissociation, the sluggish oxygen evolution reaction (OER) kinetics due to large overpotential is a main hindrance. Herein, a simple approach is used to produce composite material based on TiO2/Co3O4 for efficient OER and overpotential is linearly reduced with increasing amount of TiO2. The scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) investigations reveal the wire like morphology of composite materials, formed by the self-assembly of nanoparticles. The titania nanoparticles were homogenously distributed on the larger Co3O4 nanoparticles. The powder x-ray diffraction revealed a tetragonal phase of TiO2 and the cubic phase of Co3O4 in the composite materials. Composite samples with increasing TiO2 content were obtained (18%, 33%, 41% and 65% wt.). Among the composites, cobalt oxide-titanium oxide with the highest TiO2 content (CT-20) possesses the lowest overpotential for OER with a Tafel slope of 60 mV dec−1 and an exchange current density of 2.98 × 10−3A/cm2. The CT-20 is highly durable for 45 h at different current densities of 10, 20 and 30 mA/cm2. Electrochemical impedance spectroscopy (EIS) confirmed the fast charge transport for the CT-20 sample, which potentially accelerated the OER kinetics. These results based on a two-step methodology for the synthesis of TiO2/Co3O4 material can be useful and interesting for various energy storage and energy conversion systems.

  • 8.
    Aguilar-Mamani, Wilson
    et al.
    Department of Chemistry, Faculty of Science and Technology, San Simon University, UMSS, Cochabamba.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Solution-mediated growth of NBA-ZSM-5 crystals retarded by gel entrapment2018Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 487, s. 57-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The synthesis of flat tablet-shaped ZSM-5 crystals from a gel using metakaolin as aluminosilicate source and n-butyl amine as structure directing agent was investigated. The evolution inside the solid phase was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetry and mass spectrometry. A kinetic study indicated that the nucleation of the majority crystals occurred concurrently with the formation of the gel upon heating the starting liquid suspension. Microstructural evidences undeniably showed that the gel precipitated on ZSM-5 crystals and mineral impurities originating from kaolin. As a result, crystal growth was retarded by gel entrapment, as indicated by the configuration and morphology of the embedded crystals. The results presented herein are harmonized with a solution-mediated nucleation and growth mechanism. Our observations differ from the autocatalytic model that suggests that the nuclei rest inside the gel until released when the gel is consumed. Our results show instead that it is crystals that formed in an early stage before entrapment inside the gel that rest inside the gel until exposed at the gel surface. These results illustrate the limitation of the classical method used in the field to determine nucleation profiles when the crystals become trapped inside the gel.

  • 9.
    Ahdikari, Rajesh
    et al.
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel-Boulet, Varennes, QC J3X1S2, Canada.
    Jin, Lei
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel-Boulet, Varennes, QC J3X1S2, Canada.
    Navarro-Pardo, Fabola
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel-Boulet, Varennes, QC J3X1S2, Canada.
    Benetti, Daniele
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel-Boulet, Varennes, QC J3X1S2, Canada.
    AlOtaibi, Bandar
    Dept. of Electrical and Computer Eng., McGill University, 3480 Univ. Str. W, Montreal, QC H3A 0E9, Canada.
    Vanka, Srinivas
    Dept. of Electrical and Computer Eng., McGill University, 3480 Univ. Str. W, Montreal, QC H3A 0E9, Canada.
    Zhao, Haiguang
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel-Boulet, Varennes, QC J3X1S2, Canada.
    Mi, Zetian
    Dept. of Electrical and Computer Eng., McGill University, 3480 Univ. Str. W, Montreal, QC H3A 0E9, Canada.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel-Boulet, Varennes, QC J3X1S2, Canada.
    Rosei, Frederico
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel-Boulet, Varennes, QC J3X1S2, Canada; Institute for Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu, PR China.
    High Efficiency, Pt-free Photoelectrochemical Cells for Solar Hydrogen Generation based on “Giant” Quantum Dots2016Ingår i: Nano Energy, ISSN 2211-2855, Vol. 27, s. 265-274Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quantum dot (QD) sensitized TiO2 is considered as a highly promising photoanode material for photoelectrochemical (PEC) solar hydrogen production. However, due to its limited stability, the photoanode suffers from degradation of its long-term PEC performance. Here, we report the design and characterization of a high-efficiency and long-term stable Pt-free PEC cell. The photoanode is composed of a mesoporous TiO2 nanoparticle film sensitized with “giant” core@shell QDs for PEC solar hydrogen generation. The thick shell enhances light absorption in the visible range, increases the stability of the QDs and does not inhibit charge separation, injection and transport, needed for proper operation of the device. We prepared thin films of Cu2S nanoflakes through a simple and reproducible procedure, and used them as counter-electrodes replacing the standard Pt film, resulting in equivalent performances of the PEC cell. We obtained an unprecedented photocurrent density (~10 mA/cm2) for “giant” QDs based PEC devices (and corresponding H2 generation) and a very promising stability, indicating that the proposed cell architecture is a good candidate for long-term stable QD-based PEC solar hydrogen generation.

  • 10.
    Ahmed, Shahbaz
    et al.
    Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Faisalabad, Pakistan.
    Zulfiqar, Waqas
    Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Faisalabad, Pakistan.
    Javed, Farrukh
    Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Faisalabad, Pakistan.
    Arshad, Hurriya
    Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Faisalabad, Pakistan.
    Abbas, Ghulam Gilani
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Laref, Amel
    Department of Physics and Astronomy, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
    Alay-e-Abbas, Syed Muhammad
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Faisalabad, Pakistan.
    Accurate First-Principles Evaluation of Structural, Electronic, Optical and Photocatalytic Properties of BaHfO3 and SrHfO3 Perovskites2022Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 892, artikel-id 162071Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A reliable first-principles account of experimentally observed physical properties of perovskite oxides is crucial for realizing their employment in electronic and optical devices. In this context, SCAN meta-GGA functional of DFT offers good approximation for the exchange-correlation energy; facilitating accurate determination of structural and energetic properties. However, SCAN is unable to reproduce electronic and optical properties of wide bad gap materials. In the present study, we report systematic DFT calculations to show that structural, energetic, electronic and optical properties of hafnium based BaHfO3 and SrHfO3 perovskite oxides can be accurately determined through a combine application of SCAN and Tran-Blaha modified Becke-Johnson (TB-mBJ) meta-GGAs. The structural and energetic properties computed using SCAN functional for both BaHfO3 and SrHfO3 are found to be in good agreement with experimental data; achieving a level of accuracy comparable to computationally expansive hybrid DFT calculations. On the other hand, TB-mBJ calculated band gaps computed using the SCAN optimized lattice parameters provide better agreement with experimental data at a low computational cost. The optical properties, band edge potentials and effective masses of the charge carriers in BaHfO3 and SrHfO3 are also computed to examine the combined application of SCAN and TB-mBJ meta-GGAs in predicting the photocatalytic performance of these wide band gap materials. Our results clearly show that the combination of the two meta-GGAs provide a computationally economical route for evaluating the photocatalytic performance of alkaline-earth metal hafnates.

  • 11.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Allard, Christina
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Samhällsvetenskap.
    Lin, Janet
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Sandström, Anders
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    LTU Teaching guide to e-learning: how to clear the mist of teaching through the cloud2015Konferensbidrag (Övrigt vetenskapligt)
    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 12.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Berglund, Linn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Noël, Maxime
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Linder, Tomas
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Light scattering in cellulose nanofibre suspensions: Model and experiments2016Ingår i: Computers in Chemistry Proceeding from ACS National Meeting San Diego: Proceeding from ACS National Meeting San Diego, American Chemical Society (ACS), 2016, s. 122-, artikel-id CELL 235Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Here light scattering theory is used to assess the size distribution in a suspension of cellulose as it is fibrillated from micro-scaled to nano-scaled fibres. A model based on Monte carlo simulations of the scattering of photons by different sizes of cellulose fibres was used to predict the UV-IF spectrum of the suspensions. Bleached cellulose hardwood pulp was tested and compared to the visually transparent tempo-oxidised hardwood cellulose nanofibres (CNF) suspension. The theoretical results show that different diameter size classes exhibit very different scattering patterns. These classes could be identified in the experimental results and used to establish the size class dominating the suspension. A comparison to AFM/microscope size distribution was made and the results indicated that using the UV-IF light scattering spectrum maybe more reliable that size distribution measurement using AFM and microscopy on dried CNF samples. The UV-IF spectrum measurement combined with the theoretical prediction can be used even at this initial stage of development of this model to assess the degree of fibrillation when processing CNF.

  • 13.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Jonoobi, Mehdi
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Impregnation of cellulose nanofibre networks with a thermoplastic polymer2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The emphasis of this study have been to study if impregnation of cellulose nanofibre networks can be made using a thermoplastic polymer as a matrix and to estimate the reinforcing efficiency of the cellulose nanofibres in this composite. A nanofibre network with higher porosity that water-dried nanofibre network was prepared from a cellulose waste byproduct (sludge). This was impregnated using a diluted solution of cellulose acetate butyrate polymer to produce a 60 wt. % CNF/CAB composite. This composite was characterized using microscopy and mechanical testing. High porosity is seen in the SEM images of the acetone-dried fibre network and SEM and film transparency was used to qualitatively assess the impregnation of the network. A significant improvement in the visible light transmittance was observed for the nanocomposite film compared to the nanofibre network as a result of the impregnation. The reinforcing efficiency was calculated based on a model of the nanocomposite and compared to other nanocomposites in the literature. The efficiency factor takes into account the volume fraction and the stiffness of the matrix. This showed that this CNF/CAB combination is similar in efficiency to CNF/PLA nanocomposites and more efficient that nanocomposites using when using stiffer matrices. It was also more efficient CNF nanocomposites based on Chitosan, which has the same stiffness. It is still however not as efficient as traditional glass polymer composites due to the random orientation of the fibres nor nanocomposites with very soft matrices due to the dominating network effect of the CNF in such composites. In conclusion, CAB impregnated cellulose nanofibre networks are promising biocomposite materials that could be used in applications where transparency and good mechanical properties are of interest. The key elements in the impregnation process of the nanocomposites were the use of a porous networks and a low viscosity thermoplastic resin solution.

  • 14.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Sounding Out Paper Pulp: Ultrasound Spectroscopy of Dilute Viscoelastic Fibre Suspensions Acoustics and Ultrasonics2006Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A model of attenuation of ultrasound in fibre suspensions is compared to a model of backscattering pressure from submersed cylinders subjected to a sound wave. This analysis is carried out in the region where the wavelength is of the same order as that of the diameter of the fibre. In addition we assume the cylinder scatterer to have no intrinsic attenuation and the longitudinal axis of the scatterer is assumed to be perpendicular to the direction of propagation of the incident wave. Peaks in the frequency response of both the backscattering pressure, expressed in the form of a form function, and the attenuation are shown to correspond. Similarities between the models are discussed. Since the peaks in the form function are due to resonance of the cylinder, we infer that the peaks in the attenuation are also due to resonance. The exact nature of the waves causing the resonance are still unclear however the first resonance peaks are related to the shear wave and hence the shear modulus of the material. The aim is to use the attenuation model for solving the inverse problem of calculating paper pulp material properties from attenuation measurements. The implications of these findings for paper pulp property estimation is that the supporting fluid could, if possible, be matched to density of that of pulp fibres and that the estimation of material properties should be improved by selecting a frequency range that in the region of the first resonance peaks.

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  • 15.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Estimating material properties of solid and hollow fibers in suspension using ultrasonic attenuation2013Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 60, nr 7, s. 1424-1434Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Estimates of the material properties of hollow fibers suspended in a fluid using ultrasound measurements and a simple, computationally efficient analytical model are made. The industrial application is to evaluate the properties of wood fibers in paper pulp. The necessity of using a layered cylindrical model (LCM) as opposed to a solid cylindrical model (SCM) for modeling ultrasound attenuation in a suspension of hollow fibers is evaluated. The two models are described and used to solve the inverse problem of estimating material properties from attenuation in suspensions of solid and hollow polyester fibers. The results show that the measured attenuation of hollow fibers differs from that of solid fibers. Elastic properties estimates using LCM with hollow-fiber suspension measurements are similar to those using SCM with solid-fiber suspension measurements and compare well to block polyester values for elastic moduli. However, using the SCM with the hollow-fiber suspension did not produce realistic estimations. In conclusion, the LCM gives reasonable estimations of hollow fiber properties and the SCM is not sufficiently complex to model hollow fibers. The results also indicate that the use of a distributed radius in the model is important in estimating material properties from fiber suspensions.

  • 16.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Moreno, Sergio
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Vacuum infusion of cellulose nanofibre network composites: Influence of porosity on permeability and impregnation2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 95, s. 204-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Addressing issues around the processing of cellulose nanofibres (CNF) composites is important in establishing their use as sustainable, renewable polymer reinforcements. Here, CNF networks of different porosity were made with the aim of increasing their permeability and suitability for processing by vacuum infusion (VI). The CNF networks were infused with epoxy using two different strategies. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated. Calculated fill-times for CNF networks with 50% porosity were the shortest, but are only less than the gel-time of the epoxy if capillary effects are included. In experiments the CNF networks were clearly wetted. However low transparency indicated that impregnation was incomplete. The modulus and strength of the dry CNF networks increased rapidly with decreasing porosity, but their nanocomposites did not follow this trend, showing instead similar mechanical properties to each other. The results demonstrated that increasing the porosity of the CNF networks to ≈ 50% gives better impregnation resulting in a lower ultimate strength, a higher yield strength and no loss in modulus. Better use of the flow channels in the inherently layered CNF networks could potentially reduce void content in these nanocomposites and thus increase their mechanical properties.

  • 17.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Moreno, Sergio
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Vacuum Infusion of Nanocellulose Networks of Different Porosity2015Ingår i: 20th International Conference on Composite Materials: Copenhagen, 19-24th July 2015, ICCM , 2015, artikel-id 4109-1Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cellulose nanofibres (CNF) have shown good potential as sustainable, biobased reinforcing materials in polymer composites. Addressing issues around the processing of these composites is an important part of establishing their use in different applications. Here, CNF networks of different porosity are made from nanofibrillated hardwood kraft pulp with the aim of increasing the impregnation of the CNF networks and to allow vacuum infusion to be used. Two different vacuum infusion strategies: in-plane and out of plane were used to infuse the CNF networks with a low viscosity epoxy. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated and compared to a micro-fibre based network. Using the out-of-plane permeability measurements and Darcy’s law, the fill-time was calculated and showed that the CNF network with 40% porosity had the lowest fill-time when an out-of-plane impregnation strategy is used. However this exceeded the gel-time of the epoxy system. In experiments, the resin reached the other side of the network but low transparency indicated that wetting was poor. The dry CNF preforms showed a very strong dependence on the porosity with both modulus and strength increasing rapidly at low porosity. Interestingly, the composite based on the 60% porosity network showed good wetting particularly with the in-plane infusion strategy, exhibiting a much more brittle fracture and a high yield strength. This shows that in CNF composites produced by VI, lowering the fibre volume content of the CNF composites gives better impregnation resulting in a lower ultimate strength but higher yield strength and no loss in modulus.

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    fulltext
  • 18.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Cellulose nanofibril nanocomposites processing2013Ingår i: Production and Applications of Cellulose Nanomaterials, Peachtree Corners, GA: TAPPI Press, 2013, s. 271-274Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Impregnation of a preformed network of nanofibrils leads to high fibre volume fraction nanocomposites and with this good mechanical properties have been achieved. However, comparing nanofibrils composite made with different volume fractions and different matrices is difficult. In order to do this, and in doing so gain insight into the most promising approaches, methods of measuring reinforcing efficiencies are being developed. The results show that for matrices with low stiffness the stiffness reinforcing efficiency is high. However with high fibre volume fraction and high stiffness, this network effect may lead to a lack of exploitation of the properties of the nanofibrils. Alignment of the nanofibrils is also a key in effective reinforcement. In addition, upscaling of the impregnation process requires a good understanding of permeability and adaptation of existing permeability models for cellulose nanofibrils networks as well as experiments on their permeability are ongoing.

  • 19.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Quantifying reinforcing efficiency of nanocellulose fibres2013Ingår i: Processing of fibre composites-challenges for maximum materials performance: Proceedings of 34th Risø International Symposium on Materials Science / [ed] Bo Madsen; Hans Lilholt; Y Kusano; S Fäster; B Ralph, Risö: Dept. of Wind Energy, Technical University of Denmark , 2013, s. 149-160Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cellulose nanofibres are found in all plants and have the potential to provide a sustainable biobased material source. These nanofibres can be used for reinforcing polymers and thus as structural materials. Very promising results have been reported for different nanocomposites but to compete with existing materials, it is important to understand what progress has been made towards structural materials using nanocellulose. To do this the reinforcing efficiency of the stiffness and strength of nanocellulose in different nanocomposites has been calculated for a number of reported nanocellulose fibre based composites. For the stiffness this is done by back-calculating a reinforcing efficiency factor from a Halpin-Tsai model and laminate theory. For the strength efficiency, two models are used: a classic short fibre composite model and a network model. The results show that orientation is key to the stiffness efficiency, as shown by the high efficiency of aligned natural fibres. The stiffness efficiency is, as expected, high in soft matrices but in stiff matrices, the network effect of the nanofibres is possibility limiting their reinforcing potential. The strength efficiency results show that in all the nanocomposites evaluated the network model is closer to predicting strength than the short fibre composite model. The correlation between the network strength and the composite strength suggest that much of the stress transfer is from fibre to fibre and strong nanocomposites depend heavily on having a strong network. Also noted is that in composite processing a good impregnation of the nanofibers is also seen as an important factor in the efficiency of both strength and stiffness.

  • 20.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Reinforcing efficiency and the manufacture nanocellulose fibre based composites by vacuum infusion2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Nanocomposites based on cellulose have received a rapidly rising attention over the last 10 years however the method of manufacturing these composites on a scale larger than that in the lab remains challenging. Another challenge is that low fraction nanocomposites, whilst they can show excellent improvement in polymer properties, have difficultly to compete with traditional fibre reinforced composites [1,2]. A commonly used liquid composite moulding method for producing composites is vacuum infusion and the possibility of trading glass fibre for nanocellulose networks sheets in this type of manufacturing could results in a upscale method for producing high volume fraction cellulose nanocomposites. CNF networks are stiff and strong but have high fibre packing and thus difficult to impregnate. This paper evaluates the effectiveness of increasing the porosity to improve their processability by VI.

  • 21.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Reinforcing efficiency of nanocellulose in polymers2014Ingår i: Reactive & functional polymers, ISSN 1381-5148, E-ISSN 1873-166X, Vol. 85, s. 151-156, artikel-id 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanocellulose extracted from renewable sources, is a promising reinforcement for many polymers and is a material where strong interfibre hydrogen bonds add effects not seen in microfiber composites. Presented is a tool for comparing different nanocellulose composites based on estimating the efficiency of nanocellulose reinforcement. A reinforcing efficiency factor is calculated from reported values of elastic modulus and strength from various nanocellulose composites using established micromechanical models. In addition, for the strength, a network model is derived based on fibre-fibre bond strength within nanocellulose networks. The strength results highlight the importance of the plastic deformation in the nanocellulose composites. Both modulus and strength efficiency show that the network strength and modulus has a greater effect than that of the individual constituents. In the best cases, nanocellulose reinforcement exceeds all model predictions.

  • 22.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Reinforcing Efficiency of Nanocelluloses in Polymer Nanocomposites2014Ingår i: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Kapitel i bok, del av antologi (Refereegranskat)
  • 23.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Westin, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. University of Jyvaskyla, Department of Physics.
    Korpimäki, Jani
    CSI Composites.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nanofibre distribution in composites manufactured with epoxy reinforced with nanofibrillated cellulose: model prediction and verification2016Ingår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 139, artikel-id 012011Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study a model based on simple scattering is developed and used to predict the distribution of nanofibrillated cellulose in composites manufactured by resin transfer moulding (RTM) where the resin contains nanofibres. The model is a Monte Carlo based simulation where nanofibres are randomly chosen from probability density functions for length, diameter and orientation. Their movements are then tracked as they advance through a random arrangement of fibres in defined fibre bundles. The results of the model show that the fabric filters the nanofibres within the first 20 µm unless clear inter-bundle channels are available. The volume fraction of the fabric fibres, flow velocity and size of nanofibre influence this to some extent. To verify the model, an epoxy with 0.5 wt.% Kraft Birch nanofibres was made through a solvent exchange route and stained with a colouring agent. This was infused into a glass fibre fabric using an RTM process. The experimental results confirmed the filtering of the nanofibres by the fibre bundles and their penetration in the fabric via the inter-bundle channels. Hence, the model is a useful tool for visualising the distribution of the nanofibres in composites in this manufacturing process.

  • 24.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Westin, Mikael
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hydrogel state impregnation of cellulose fibre-phenol composites: Effects of fibre size distribution2016Ingår i: ECCM 2016: Proceeding of the 17th European Conference on Composite Materials, European Conference on Composite Materials , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Whilst it has been well established that cellulose nanofibres (CNF) networks produce films that have high stiffness and strength, they are difficult to impregnate. Investigated in this study is whether by controlling the degree of nanofibrillation of cellulose, composites based on micro- and nano-size cellulose fibres can be made that are more easily manufactured and have better impregnation than solely cellulose nano-fibre based composites. To evaluate this, cellulose at different stages of ultrafine grinding, extracted at time intervals of 30, 60 and 290 mins, were used to make composites. To achieve good impregnation a novel strategy was used based on impregnation with phenol resin whilst the fibrillated cellulose is in a hydrogel state. The composites were subsequently dried and consolidated by hot press. The current results show that this method of impregnation is successful and the phenol matrix greatly improves the properties of the cellulose with a low degree of fibrillation. In general, as the degree of fibrillation and the proportion of nanofibres increases, the mechanical properties of the networks and their composites increase. The addition of the matrix appears to restrict the deformation of CNF network, increasing the modulus and yield strength but decreasing the ultimate strength. The method also appears to restrict the consolidation and voids remain in the composite, which reduces the modulus when compared to theoretical maximum values for this material. More work on the consolidation process is necessary to achieve the full potential of these composites.

  • 25.
    Akbar, Kamran
    et al.
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, Venezia Mestre, 30172 Italy.
    Moretti, Elisa
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, Venezia Mestre, 30172 Italy.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, Venezia Mestre, 30172 Italy.
    Carbon Dots for Photocatalytic Degradation of Aqueous Pollutants: Recent Advancements2021Ingår i: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 9, nr 17, artikel-id 2100532Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The immense progress of humanity on the technological, domestic, and industrial fronts comes at the cost of polluting the planet. Aquatic pollution is particularly dangerous since all life forms are directly linked to it. Each year tons of industrial and domestic pollutants make their way into aqueous systems. Efficient removal/degradation of these pollutants is of prime importance for the sustainable future. Among many technologies, photodegradation is an emerging and promising method for the successful removal of aqueous pollutants since it is powered by abundant solar light. The last decade had shown that carbon dots are among the most promising materials that can be utilized as an efficient tool to derive various solar-driven chemical reactions. Carbon dots possess unique photophysical and chemical properties such as light-harvesting over a broad-spectrum region, upconversion photoluminescence, photosensitizers, chemical inertness, and bivalent redox character, etc. The ease of synthesis of carbon dots at low cost also contributes hugely to their utilizations as an efficient photocatalyst for the degradation of aqueous pollutants. This review summarizes the recent progress made in the field of photodegradation of aqueous pollutants with the aid of carbon dots and their hybrids, highlighting the critical role carbon dots can play in the field. 

  • 26.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ceramic reinforced high modulus steel composites: processing, microstructure and properties2014Ingår i: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 53, nr 3, s. 253-263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ceramic reinforced steel matrix composites are materials for automotive, aerospace, wear and cutting applications. Such metal matrix composites (MMCs) combine attractive physical, mechanical and wear properties with ease of fabrication and low cost. The review focuses on the current state of the art of producing these metal matrix composites, ceramics reinforcements, composition of steel matrix, microstructure evolution and parameters influencing the mechanical and wear properties. Processing methods to fabricate ceramic reinforced steel matrix composites are discussed to produce these composites with low number of defects, homogeneous microstructure and high mechanical and wear performance. The influence of chemical nature of ceramic reinforcements and composition of steel matrix on the microstructure, mechanical and wear properties is presented. The strengthening mechanisms and parameters controlling wear performance of steel MMCs are described as a function of the content of ceramic reinforcements, microstructural design and structure of the steel matrix. Keeping in view the stability of ceramics in steels, suitable ceramic reinforcements and steel matrix materials are discussed. Moreover, the importance of microstructure and interface between ceramic reinforcement and steel matrix in controlling the mechanical properties of steel MMCs is highlighted. The review identifies area of research for development to fully appreciate and tailor the properties of these industrially important composites.

  • 27.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hierarchical zeolites for carbon capture2014Patent (Övrig (populärvetenskap, debatt, mm))
  • 28.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structuring gas adsorbents by processing of porous powders2014Konferensbidrag (Refereegranskat)
  • 29.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structuring of Aluminophosphates Monoliths for Carbon Capture2015Konferensbidrag (Refereegranskat)
  • 30.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structuring of Nanoporous Powders into Hierarchically Porous Nanostructured Adsorbents for Clean Energy2016Konferensbidrag (Refereegranskat)
  • 31.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structuring of nanoporous powders into hierarchically porous nanostructured adsorbents for decarbunization2015Konferensbidrag (Refereegranskat)
  • 32.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ogunwumi, Steven
    Laminates for rapid CO2 capture from gas mixtures2013Patent (Övrig (populärvetenskap, debatt, mm))
  • 33.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Keshavarzi, Neda
    Department of Materials and Environmental Chemistry, Stockholm University.
    Shakarova, Dilshod
    Department of Materials and Environmental Chemistry, Stockholm University.
    Cheung, Ocean
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, L.M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Aluminophosphate monoliths with high CO2-over-N2 selectivity and CO2 capture capacity2014Ingår i: RSC Advances, E-ISSN 2046-2069, Vol. 4, nr 99, s. 55877-55883Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Monoliths of microporous aluminophosphates (AlPO4-17 and AlPO4-53) were structured by binder-free pulsed current processing. Such monoliths could be important for carbon capture from flue gas. The AlPO4-17 and AlPO4-53 monoliths exhibited a tensile strength of 1.0 MPa and a CO2 adsorption capacity of 2.5 mmol g-1 and 1.6 mmol g-1, respectively at 101 kPa and 0°C. Analyses of single component CO2 and N2 adsorption data indicated that the AlPO4-53 monoliths had an extraordinarily high CO2-over-N2 selectivity from a binary gas mixture of 15 mol% CO2 and 85 mol% N2. The estimated CO2 capture capacity of AlPO4-17 and AlPO4-53 monoliths in a typical pressure swing adsorption (PSA) process at 20°C was higher than that of the commonly used zeolite 13X granules. Under cyclic sorption conditions, AlPO4-17 and AlPO4-53 monoliths were regenerated by lowering the pressure of CO2. Regeneration was done without application of heat, which would regenerate them to their full capacity for CO2 adsorption.

  • 34.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kocjan, Andraz
    The hydrolysis of AlN powder: powerful tool in advanced materials engineering2014Konferensbidrag (Refereegranskat)
  • 35.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden.
    Ogunwumi, Steven
    Crystalline Materials Research, Corning Incorporated, Corning, New York, USA.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden.
    Thin zeolite laminates for rapid and energy-efficient carbon capture2017Ingår i: Scientific Reports, E-ISSN 2045-2322, Vol. 7, artikel-id 10988Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin, binder-less zeolite NaX laminates, with thicknesses ranging between 310 to 750 μm and widths exceeding 50 mm and biaxial tensile strength in excess of 3 MPa, were produced by pulsed current processing. The NaX laminates displayed a high CO2 adsorption capacity and high binary CO2-over-N2 and CO2-over-CH4 selectivity, suitable for CO2 capture from flue gas and upgrading of raw biogas. The thin laminates displayed a rapid CO2 uptake; NaX laminates with a thickness of 310 μm were saturated to 40% of their CO2 capacity within 24 seconds. The structured laminates of 310 μm thickness and 50 mm thickness would offer low pressure drop and efficient carbon capture performance in a laminate-based swing adsorption technology.

  • 36.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
    Sjöberg, Erik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rayson, Mark
    Department of Chemistry, The University of Surrey, Guildford, Surrey GU2 7XH, UK.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
    Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H2 separation performance2015Ingår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 493, s. 206-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    raded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H2 separation factor of 12 at 0 °C and a CO2 permeance of 21.3×10-7 mol m-2 s-1 Pa-1 for an equimolar CO2/H2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.

  • 37.
    Akinwekomi, Akeem
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Adsorption Characteristics of Freeze-Cast Calf-20 Monoliths2021Konferensbidrag (Övrigt vetenskapligt)
  • 38.
    Akinwekomi, Akeem
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Metallurgical and Materials Engineering, Federal University of Technology Akure, Akure 340252, Ondo State, Nigeria.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Microstructural, Mechanical, and Electrochemical Characterization of CrMoNbTiZr High-Entropy Alloy for Biomedical Application2023Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 16, nr 15, artikel-id 5320Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-entropy alloys (HEA) with superior biocompatibility, high pitting resistance, minimal debris accumulation, and reduced release of metallic ions into surrounding tissues are potential replacements for traditional metallic bio-implants. A novel equiatomic HEA based on biocompatible metals, CrMoNbTiZr, was consolidated by spark plasma sintering (SPS). The relative sintered density of the alloy was about 97% of the theoretical density, indicating the suitability of the SPS technique to produce relatively dense material. The microstructure of the sintered HEA consisted of a BCC matrix and Laves phase, corresponding to the prediction of the thermodynamic CALPHAD simulation. The HEA exhibited a global Vickers microhardness of 531.5 ± 99.7 HV, while the individual BCC and Laves phases had hardness values of 364.6 ± 99.4 and 641.8 ± 63.0 HV, respectively. Its ultimate compressive and compressive yield strengths were 1235.7 ± 42.8 MPa and 1110.8 ± 78.6 MPa, respectively. The elasticity modulus of 34.9 ± 2.9 GPa of the HEA alloy was well within the range of cortical bone and significantly lower than the values reported for commonly used biomaterials made from Ti-based and Cr–Co-based alloys. In addition, the alloy exhibited good resistance to bio-corrosion in PBS and Hanks solutions. The CrMoNbTiZr HEA exhibited an average COF of 0.43 ± 0.06, characterized mainly by abrasive and adhesive wear mechanisms. The CrMoNbTiZr alloy’s mechanical, bio-corrosion, and wear resistance properties developed in this study showed a good propensity for application as a biomaterial.

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  • 39.
    Akinwekomi, Akeem Damilola
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Bibliometric Mapping of Literature on High-Entropy/ Multicomponent Alloys and Systematic Review of Emerging Applications2022Ingår i: Entropy, E-ISSN 1099-4300, Vol. 24, nr 3, artikel-id 329Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    High-entropy/multicomponent alloy (HEA/MCA) has received significant research attention in the last decade. There is a dearth of data-driven works dedicated to assessing and visualizing the HEA/MCA literature from a global perspective. To this end, we present the first bibliometric literature analysis of more than 3500 HEA/MCA articles, published between 2004 and 2021, in the Scopus database. We identify the most prolific authors, their collaborators, institutions, and most prominent research outlet. Co-occurrence networks of keywords are mapped and analyzed. A steep rise in research outputs is observed from 2013, when the number of annual publications doubled the previous years. The top five preferred research outlets include Journal of Alloys and Compounds, Materials Science and Engineering A, Scripta Materialia, Intermetallics, and Acta Materialia. Most of these publications emanate from researchers and institutions within China, USA, and Germany, although international scientific collaboration among them is lacking. Research gaps and future research directions are proposed, based on co-occurrence frequencies of author keywords. Finally, a brief systematic review of emerging applications, covering hydrogen storage, additive manufacturing, catalysis, and superconductivity, is undertaken. This work provides an important comprehensive reference guide for researchers to deepen their knowledge of the field and pursue new research directions.

  • 40.
    Akinwekomi, Akeem Damilola
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Tunability of mechanical and biodegradation properties of zinc-based biomaterial with calcium Micronutrient alloying2023Ingår i: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 140, artikel-id 105724Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biodegradable metals are being investigated as temporary implants that dissolve safely in the body after bone regeneration. Zinc (Zn) has an intermediate biodegradation rate between magnesium and stainless steels, yet its degradation rate is too slow to function as a temporary orthopedic implant. Alloying with nutrient elements is considered a strategy to tune its mechanical properties and in vivo biodegradability. Zn/calcium (Zn/Ca) alloys (with 0.5, 1, and 2 wt% Ca) were processed by spark plasma sintering and their microstructure, mechanical, and biodegradation properties were investigated. Ca was distributed in the grain boundary regions of Zn due to its low miscibility in Zn. Furthermore, the corrosion rates of Zn/Ca alloys determined from linear polarization measurements (0.164–0.325 mm/yr) accelerated by at least 10% compared with pure sintered Zn (0.149 mm/yr) with simultaneous dissolution of Zn and Ca, as verified from X-ray diffraction analysis of the corrosion products. The alloy specimens exhibited hardness (52–58 HV) and compressive strength (93–119 MPa) comparable with those of human cortical and cancellous bones (49 HV; 90–209 MPa). This study demonstrated the tunability of the mechanical and biodegradation properties of Zn-based materials by alloying them with a nutrient element for potential application as temporary orthopedic implants.

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  • 41.
    Akinwekomi, Akeem Damilola
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Taher, Mamoun
    Graphmatech AB, 753 18 Uppsala, Sweden.
    Characterization of Spark Plasma Sintered Graphene-Coated Stainless-Steel Compacts2022Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    We investigated the effect of sintering temperature and graphene content on the microstructure, densification, hardness, and wear properties of spark-plasma sintered (SPS) graphene-coated 316L stainless-steel powders. Four sintering temperatures (850, 900, 950, and 1000 °C) and graphene content of 0.01, 0.1, and 0.5 wt.% were investigated. Results showed that sintered density increased with the sintering temperature. Microstructural examination corroborated this result as distinct unsintered powder particles, sinter necks and large interparticle pores observed at 850 °C were annihilated at 1000 °C. The 316L stainless steel sintered specimen had a density of 7.27 g/cm3, which decreased slightly with increasing graphene content to 7.17 g/cm3 for the sample with 0.5 wt.% graphene coating. The sintering temperature and graphene content appeared not to have significant effect on the microhardness. For instance, microhardness for the reference 316L sintered specimen was 189 HV, compared to ~ 171 HV for all the graphene-coated 316L sintered specimens. X-ray diffraction analysis did not detect the formation of carbides in the sintered samples, which suggested that the sintering process minimized its formation. Raman spectroscopy indicated that sintering at 850 °C preserved the structure of graphene during the spark plasma sintering process. 

  • 42.
    Alay-e-Abbas, Syed Muhammad
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Pakistan.
    Abbas, Ghulam
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Zulfiqar, Waqas
    Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Pakistan; Department of Energy Conversion and Storage, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark.
    Sajjad, Muhammad
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Physics, Khalifa University of Science and Technology, Abu Dhabi, 127788, United Arab Emirates.
    Singh, Nirpendra
    Department of Physics, Khalifa University of Science and Technology, Abu Dhabi, 127788, United Arab Emirates; Center for Catalysis and Separation (CeCaS), Khalifa University of Science and Technology, Abu Dhabi, 127788, United Arab Emirates.
    Larsson, J. Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structure inversion asymmetry enhanced electronic structure and electrical transport in 2D A3SnO (A = Ca, Sr, and Ba) anti-perovskite monolayers2023Ingår i: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 16, nr 1, s. 1779-1791Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anti-perovskites A3SnO (A = Ca, Sr, and Ba) are an important class of materials due to the emergence of Dirac cones and tiny mass gaps in their band structures originating from an intricate interplay of crystal symmetry, spin-orbit coupling, and band overlap. This provides an exciting playground for modulating their electronic properties in the two-dimensional (2D) limit. Herein, we employ first-principles density functional theory (DFT) calculations by combining dispersion-corrected SCAN + rVV10 and mBJ functionals for a comprehensive side-by-side comparison of the structural, thermodynamic, dynamical, mechanical, electronic, and thermoelectric properties of bulk and monolayer (one unit cell thick) A3SnO anti-perovskites. Our results show that 2D monolayers derived from bulk A3SnO anti-perovskites are structurally and energetically stable. Moreover, Rashba-type splitting in the electronic structure of Ca3SnO and Sr3SnO monolayers is observed owing to strong spin-orbit coupling and inversion asymmetry. On the other hand, monolayer Ba3SnO exhibits Dirac cone at the high-symmetry Γ point due to the domination of band overlap. Based on the predicted electronic transport properties, it is shown that inversion asymmetry plays an essential character such that the monolayers Ca3SnO and Sr3SnO outperform thermoelectric performance of their bulk counterparts.

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  • 43.
    Alberoni, Chiara
    et al.
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, Venezia Mestre, Italy.
    Barroso-Martín, Isabel
    Departamento de Química Inorgánica, Cristalografía y Mineralogía (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain.
    Infantes-Molina, Antonia
    Departamento de Química Inorgánica, Cristalografía y Mineralogía (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain.
    Rodríguez-Castellón, Enrique
    Departamento de Química Inorgánica, Cristalografía y Mineralogía (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain.
    Talon, Aldo
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, Venezia Mestre, Italy.
    Zhao, Haiguang
    Qingdao University – College of Physics & State Key Laboratory of Bio-Fibers and Eco-Textiles, 308 Ningxia Road, Qingdao 266071, P. R. China.
    You, Shujie
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, Venezia Mestre, Italy.
    Moretti, Elisa
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, Venezia Mestre, Italy.
    Ceria doping boosts methylene blue photodegradation in titania nanostructures2021Ingår i: Materials Chemistry Frontiers, E-ISSN 2052-1537, Vol. 5, nr 11, s. 4138-4152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ceria-doped titania photocatalysts (ceria loading 0.25–5.0 wt%) were synthesized by hydrothermal methods for water remediation. Nanotubes (CeTNTx) and nanoparticles (CeTNPx) were obtained. Ceria doping was applied to tune the electronic properties of nanostructured titania, boosting its photocatalytic activity. CeTNT nanostructures contained anatase as the only titania phase, whereas the CeTNP series consisted of both anatase and rutile polymorphs. The Ce addition induced a decrease in the energy gap, allowing enhancement of visible light harvesting. The photodegradation of methylene blue, MB, in aqueous solution was chosen to study the influence of the morphology and the ceria loading on the photocatalytic response, under UV and solar light. Both CeO2–TiO2 nanoparticles and nanotubes were found to be very active under UV light. The highest MB degradation rates were obtained for the 0.25 wt% CeO2 doping, for both nanotubes and nanoparticles (0.123 and 0.146 min−1, respectively), able to photodegrade completely the dye after 120 min. The two samples are stable after a 3-cycle reusability test. The photo-response under simulated solar light confirmed that doping titania with ceria allows harvesting visible light absorption, enhancing its photoactivity. A maximum efficiency of 85% under simulated sunlight at a degradation rate of 0.054 min−1 was obtained. Transient photoluminescence confirmed that MB acts as a charge scavenger for the composite system. These results pointed out ceria-doped titania nanostructures as a promising class of photocatalysts for the degradation of dyes and other hazardous organic compounds in wastewater.

  • 44.
    Alekseeva, L.A.
    et al.
    B. I. Verkin Institute of Low-temperature Physics and Engineering, National Academy of Sciences of Ukraine.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Unusual changes in the shape of solid parahydrogen with higher than natural isotope content2016Ingår i: Low temperature physics (Woodbury, N.Y., Print), ISSN 1063-777X, E-ISSN 1090-6517, Vol. 42, nr 6, s. 484-490Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The relative elongation epsilon of samples of high purity (99.9999 mol. % with respect to nonhydrogenic impurities) parahydrogen (p-H-2, similar to 0.2% o-H-2) with different amounts of the stable hydrogen isotope deuterium is measured as a function of applied stress sigma at temperatures of 1.8-4.2 K. The samples were subjected to uniaxial tension by stepwise loading. The ratio [D]/[H] of the number [D] of deuterium atoms to the number [H] of p-H-2 hydrogen atoms ranged from 0.0055 +/- 0.0005 at. % up to 0.07 at. %. For deuterium enriched p-H-2, the easy slip dislocation stage vanished from the sigma(epsilon) curves and there was a significant reduction in the total relative elongation of the samples, as well as a substantial increase in the hardening coefficient d sigma/d epsilon. Deformation of samples of p-H-2 with deuterium contents higher than the natural amount produces an unusual change in their shape owing to the appearance of a rotational component of the low-temperature plastic mass transfer

  • 45.
    Alemandar, Ayse
    et al.
    Centre for Biocomposites and Biomaterials Processing, Faculty of Forestry, University of Toronto, Toronto, ON M5S 3B3, 33 Willcocks Street, Canada.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Centre for Biocomposites and Biomaterials Processing, Faculty of Forestry, University of Toronto, Toronto, ON M5S 3B3, 33 Willcocks Street, Canada.
    Sain, Mohini
    Centre for Biocomposites and Biomaterials Processing, Faculty of Forestry, University of Toronto, Toronto, ON M5S 3B3, 33 Willcocks Street, Canada.
    The effect of decreased fiber size in wheat straw/polyvinyl alchol composites2009Ingår i: Journal of Biobased Materials and Bioenergy, ISSN 1556-6560, E-ISSN 1556-6579, Vol. 3, nr 1, s. 75-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reinforcing potential of micro and nano-size fibers from wheat straw in polyvinyl alcohol (PVA) was studied. The microfibers were obtained by alkali treatment and disintegration process of wheat straw while nanofibers were obtained after applying further mechanical treatment of this alkali treated wheat straw. The results showed that the alkali treatment increased the α-cellulose content of the fibers from 38% to 73% due to hydrolysis of the hemicelluloses and lignin from the straw walls. The morphology and thermal properties of the micro and nano-size fibers were determined to show their potential as reinforcements. The transmission electron microscopy study showed that the size of the wheat straw fibers was decreased from micro to nano-size by the defibrillation process. Thermogravimetric analysis demonstrated the alkali treatment dramatically increased the thermal properties of the wheat straw fibers. The morphologies and thermal properties of the prepared composites were investigated by scanning electron microscopy and thermogravimetric analysis. The thermal stability of the nanofiber-reinforced composites increased with respect to the neat PVA. The mechanical properties of the composites increased significantly with the addition of microfibers and further increment was obtained with nanofibers. The tensile modulus increased from 2.1 GPa of pure PVA to 3 GPa with the addition of micro sized fibers and further to 3.8 GPa with the decreased fiber size to nano scale. The composites strength showed similar trend.

  • 46.
    Alemdar, Ayse
    et al.
    University of Toronto.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sain, Mohini
    University of Toronto.
    Reinforcement capability of wheat straw fibers from micro to nano size2007Ingår i: 9th International Conference on Wood & Biofiber Plastic Composites: held in Madison, Wisconsin, May 21 -23, 2007, Madison, Wis: Forest Products Society, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    The goal of this study was to explore the reinforcement capability of micro and nano-size fibers from wheat straw. Microfibers were obtained by alkali treatment and disintegration processes of the wheat straw while nanofibers were obtained after applying further mechanical treatment of this alkali treated wheat straw. The morphology and thermal properties of both fiber types were determined to show their suitability as reinforcements. TEM images showed that the diameters of the wheat straw fibers were decreased from micro to nano-size by the defibrillation process. Thermogravimetric analysis showed the alkali treatment dramatically increased the thermal properties of the wheat straw fibers. The composites were produced using, respectively, the microfibers and nanofibers as reinforcement, with both polyvinyl alcohol (PVA) and cellulose acetate butyrate (CAB) as the matrix. The morphology and thermal properties of the composites were investigated by scanning electron microscopy and thermogravimetric analysis. The mechanical properties of the composites were compared with those of neat polymer matrix and found to be considerably improved.

  • 47.
    Al-Jayyousi, Hiba
    et al.
    Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi 127788, United Arab Emirates.
    Eswaran, Mathan Kumar
    SRM Research Institute, SRM Institute of Science and Technology, Kattankulathur 603203, Tamil Nadu, India.
    Ray, Avijeet
    Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, India.
    Sajjad, Muhammad
    Department of Physics, Khalifa University of Science and Technology, Abu Dhabi 127788, United Arab Emirates.
    Larsson, J. Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Singh, Nirpendra
    Department of Physics, Khalifa University of Science and Technology, Abu Dhabi 127788, United Arab Emirates; Center for Catalysis and Separations, Khalifa University of Science and Technology, Abu Dhabi 127788, United Arab Emirates.
    Exploring the Superior Anchoring Performance of the Two-Dimensional Nanosheets B2C4P2 and B3C2P3 for Lithium-Sulfur Batteries2022Ingår i: ACS Omega, E-ISSN 2470-1343, Vol. 7, nr 43, s. 38543-38549Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Potential anchoring materials in lithium–sulfur batteries help overcome the shuttle effect and achieve long-term cycling stability and high-rate efficiency. The present study investigates the two-dimensional nanosheets B2C4P2 and B3C2P3 by employing density functional theory calculations for their promise as anchoring materials. The nanosheets B2C4P2 and B3C2P3 bind polysulfides with adsorption energies in the range from −2.22 to −0.75 and −2.43 to −0.74 eV, respectively. A significant charge transfer occurs from the polysulfides, varying from −0.74 to −0.02e and −0.55 to −0.02e for B2C4P2 and B3C2P3, respectively. Upon anchoring the polysulfides, the band gap of B3C2P3 reduces, leading to enhanced electrical conductivity of the sulfur cathode. Finally, the calculated barrier energies of B2C4P2 and B3C2P3 for Li2S indicate fast diffusion of Li when recharged. These enthralling characteristics propose that the nanosheets B2C4P2 and B3C2P3 could reduce the shuttle effect in Li–S batteries and significantly improve their cycle performance, suggesting their promise as anchoring materials.

  • 48.
    Allali, Naoual
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Covalent functionalization of carbon nanomaterials for bioelectrochemical applications2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Carbon nanotubes (CTNs) are renowned for their exceptional electronic and mechanical properties. Their structure can be considered as rolling up a graphene sheet along a specific crystallographic direction, leading to a 1D confinement of the electronic wavefunction of the delocalized electrons along the perimeter of the cylindrical structure thus obtained. This confinement produces the existence of defined spikes of high intensity in the electronic density of states, called van Hove singularities. These singularities are primordial to understand both the optical and electronic properties of CNTs through electronphonon coupling processes. If the electronic density of states (DoS) is non zero at the Fermi level the nanotube is metallic, otherwise the nanotube is semiconducting. The synthesis of CNTs always produces a mixture of both metallic and semiconducting nanotubes, and this material can be useful to be incorporated at the surface of electrodes for electrochemical devices. The high specific surface area, the high mechanical and thermal stability of CNTs and the low percolation threshold for electron transport in a mat of CNTs render them very attractive for such kind of applications. There is yet a drawback of using raw CNTs: they are not compatible with solvents and modification of their surfaces by chemistry is required to make good suspensions for easy deposition at the electrode surface and to introduce specific functional groups for promoting electron transfer, called electron shuttles.

    The final aim of this thesis is therefore the covalent functionalization of CNTs by electron shuttles and their incorporation at the surface of glassy carbon electrodes for electrochemical devices application. A strategy of chemical grafting in three steps has been chosen: i) a controlled oxidation step in acidic media assisted by microwave irradiation in order to keep the structural integrity of CNTs, so as to save their useful electronic properties; ii) a chloration step to produce acid chloride groups and iii) reaction of these groups with electron shuttles modified by specific linkers. The study was first conducted on very clean HiPCO single-walled CNTs (SWCNTs). This enabled to avoid any disturbing effects of carbonaceous impurities or residual catalytic particles, since their possible effects are extremely controversial in the literature. Once validated, this approach was then conducted with cheaper material including few-walls carbon nanotubes (FWCNTs). The use of FWCNTs compared to SWCNTs was not only beneficial for the production of costeffective electrochemical devices but also for a better durability ofthe final device, the inner nanotubes being not functionalized.

    The challenge was to obtain a functionalization process with enough grafted electron shuttles to obtain a good electrocatalytic activity but maintaining CNTs integrity. The first step is predominant to reach this goal, and requires a very accurate understanding of the nature and the number of defects created in the CNTs structure versus the physico-chemical conditions used. The introduction of defects in the crystallographic structure of CNTs has strong consequences both for the electronic DoS and for the phononic properties of the material. Spectroscopic methods are essential in probing these consequences. UV-visible-near IR absorption spectroscopy is the method of choice to directly probe the existence of van Hove singularities and the oscillator strength associated with the authorized electronic transitions between theses ingularities. Covalent grafting of chemical groups at the surface of CNTs changes both the energy and the intensity of these transitions. However, this spectroscopic method requires solubilizing CNTs in non-absorbing solvents using adequate surfactants. Interactions between surfactant molecules and CNT sidewalls may also alter the position and intensity of electronic transitions between van Hove singularities unrelated to the chemical groups covalently grafted.

    Raman spectroscopy of CNTs involves the electronphonon coupling processes through the resonant electronic enhancement of Raman modes. Double resonance processes are also observed in Raman spectrum of CNTs, for instance with the D-band mode that is actually related to the existence of defects in the graphene structure of CNTs. Therefore, Raman spectroscopy is a widespread analytical method to characterize the structural defects created by covalent functionalization processes. Indeed, the intensity ratio of the D and G bands in the Raman spectrum is correlated to the number of defects. However, CNTs are used as bundles when chemical functionalization is performed, which produces a heterogeneous distribution of chemical species grafted on CNTs. Therefore, we have developed a new protocol to obtain statistically significant data for most of the samples made in this thesis. Nevertheless, this statistical approach is still limited for samples slightly functionalized, whence the idea to use spectroscopic ellipsometry as an alternative method to characterize these samples.

    More specifically, ellipsometric data were collected from UV to the IR part of the electromagnetic spectrum for CNTs functionalized in different conditions. The complex dielectric function was retrieved from the experimental data. A Drude model was used to model the infrared part of the data for raw and acid oxidized CNTs. The optical conductivity of the samples was obtained. These results, combined with other information collected using a set of complementary analytical techniques (Raman scattering, UV-visible-NIR absorption, X-ray photoelectron spectroscopy, thermogravimetric analysis coupled to mass spectrometry, transmission electron microscopy and rare gas volumetric adsorption), show that the microwave-assisted oxidation process actually consists in removing amorphous carbon deposits away from the surface of CNTs and transforming the already existing defects in the CNT structure to oxygen-containing groups such as carboxylic acids.

    Rare gas volumetric adsorption was also used to compare the distribution of chemical groups at the surface of CNT bundles when two different acids are used (HNO3 and H2SO4). The chloration step was also studied by these methods, as well as the final grafting of electron shuttles. Finally, these functionalized CNTs were deposited at the surface of glassy carbon electrodes and used as electron mediators for diaphorase-catalysed oxidation of nicotinamide adenine dinucleotide (NADH). This was a good example of mediated electron transfer for development of electrochemical devices based on NADH recycling and it validated the good electrocatalytic properties of functionalized CNTs for making electrochemical sensors and actuators, opening new perspectives with potential market applications.

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  • 49.
    Allali, Naoual
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France; SRSMC, UMR CNRS-Université de Lorraine, Faculté des Sciences et Technologies, Vandoeuvre-lès-Nancy, France.
    Urbanova, Veronika
    LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France.
    Etienne, Mathieu
    LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France.
    Devaux, Xavier
    IJL, UMR CNRS-Université de Lorraine, Nancy Cedex, France.
    Mallet, Martine
    LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France.
    Vigolo, Brigitte
    IJL, UMR CNRS-Université de Lorraine, Faculté des Sciences et Technologies, Vandoeuvre-lès-Nancy Cedex, France.
    Adjizian, Jean-Joseph
    IMN, UMR CNRS-Université de Nantes, Nantes, France.
    Ewels, Chris
    IMN, UMR CNRS-Université de Nantes, Nantes, France.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    McRae, Edward
    IJL, UMR CNRS-Université de Lorraine, Faculté des Sciences et Technologies,Vandoeuvre-lès-Nancy Cedex, France.
    Fort, Yves
    SRSMC, UMR CNRS-Université de Lorraine, Faculté des Sciences et Technologies, Vandoeuvre-lès-Nancy, France.
    Dossot, Manuel
    LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France.
    Mamane, Victor
    Institut de Chimie de Strasbourg, UMR CNRS-Université de Strasbourg, Strasbourg, France.
    Accurate control of the covalent functionalization of single-walled carbon nanotubes for the electro-enzymatically controlled oxidation of biomolecules2018Ingår i: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 9, s. 2750-2762Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNTs) were functionalized by ferrocene through ethyleneglycol chains of different lengths (FcETGn) and the functionalized SWCNTs (f-SWCNTs) were characterized by different complementary analytical techniques. In particular, high-resolution scanning electron transmission microscopy (HRSTEM) and electron energy loss spectroscopy (EELS) analyses support that the outer tubes of the carbon-nanotube bundles were covalently grafted with FcETGn groups. This result confirms that the electrocatalytic effect observed during the oxidation of the reduced form of nicotinamide adenine dinucleotide (NADH) co-factor by the f-SWCNTs is due to the presence of grafted ferrocene derivatives playing the role of a mediator. This work clearly proves that residual impurities present in our SWCNT sample (below 5 wt. %) play no role in the electrocatalytic oxidation of NADH. Moreover, molecular dynamic simulations confirm the essential role of the PEG linker in the efficiency of the bioelectrochemical device in water, due to the favorable interaction between the ETG units and water molecules that prevents π-stacking of the ferrocene unit on the surface of the CNTs. This system can be applied to biosensing, as exemplified for glucose detection. The well-controlled and well-characterized functionalization of essentially clean SWCNTs enabled us to establish the maximum level of impurity content, below which the f-SWCNT intrinsic electrochemical activity is not jeopardized.

  • 50.
    Allali, Naoual
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Urbanova, Veronika
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Etienne, Mathieu
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mallet, Martine
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Devaux, Xavier
    Département P2M, Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine.
    Vigolo, Brigitte
    Département CP2S, Institut Jean Lamour UMR 7198 CNRS-Université de Lorraine.
    Fort, Yves
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Walcarius, Alain
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Noël, Maxime
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    McRae, Edward
    Département CP2S, Institut Jean Lamour UMR 7198 CNRS-Université de Lorraine.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mamane, Victor
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Electrocatalytic effect towards NADH induced by HiPco single-walled carbon nanotubes covalently functionalized by ferrocene derivatives2013Ingår i: 2012 MRS Fall Meeting: Symposium YY – Low-Voltage Electron Microscopy and Spectroscopy for Materials Characterization, Cambridge University Press, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    The present work reports the covalent functionalization of single-walled carbon nanotubes (SWCNTs) by ferrocene derivatives with polyethyleneglycol linkers. A very clean initial sample was chosen to avoid any residual catalyst and carbon impurities. Functionalized SWCNTs (f-CNTs) are deposited on the surface of a glassy carbon electrode (GCE) and this modified electrode is used for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide) in the presence of diaphorase. A clear electrocatalytic effect is evidenced, which can only be attributed to the f-CNTs.

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