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  • 1.
    Alekseeva, L.A.
    et al.
    B. I. Verkin Institute of Low-temperature Physics and Engineering, National Academy of Sciences of Ukraine.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Unusual changes in the shape of solid parahydrogen with higher than natural isotope content2016In: Low temperature physics (Woodbury, N.Y., Print), ISSN 1063-777X, E-ISSN 1090-6517, Vol. 42, no 6, p. 484-490Article in journal (Refereed)
    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

  • 2.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Schröppel, Birgit
    Natural and Medical Sciences Institute (NMI), University of Tübingen.
    Kaech, Andres
    Center for Microscopy and Image Analysis, University of Zurich.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Forsmo, Seija P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Microstructure of Bentonite in Iron Ore Green Pellets2014In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 20, no 1, p. 33-41Article in journal (Refereed)
    Abstract [en]

    Sodium-activated calcium bentonite is used as a binder in iron ore pellets and is known to increase strength of both wet and dry iron ore green pellets. In this article, the microstructure of bentonite in magnetite pellets is revealed for the first time using scanning electron microscopy. The microstructure of bentonite in wet and dry iron ore pellets, as well as in distilled water, was imaged by various imaging techniques (e.g., imaging at low voltage with monochromatic and decelerated beam or low loss backscattered electrons) and cryogenic methods (i.e., high pressure freezing and plunge freezing in liquid ethane). In wet iron ore green pellets, clay tactoids (stacks of parallel primary clay platelets) were very well dispersed and formed a voluminous network occupying the space available between mineral particles. When the pellet was dried, bentonite was drawn to the contact points between the particles and formed solid bridges, which impart strength to the solid compact.

  • 3.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Scanning probe microscopy studies of interaction forces between particles: emphasis on magnetite, bentonite and silica.2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Scanning probe microscopy (SPM), such as the atomic force microscope (AFM), using colloidal probes is a highly suitable technique to probe single particle-particle interactions in aqueous solution. The interaction force between a colloidal probe on the AFM cantilever and sample surface is measured. Ultrasmall intermolecular and surface forces, down to the piconewton level, can reliably be measured under controlled experimental conditions with AFM. The interaction between magnetite, bentonite and silica particles plays an important role in many different applications. One important application is in the steel production process where high-quality iron ore pellets are used. Moreover, the interaction between magnetite nanoparticles with Ca2+ ions and with silica particles has high importance in several medical applications and for nanoelectronics. It is known and widely studied that particle surface properties significantly affect the particle dispersion and aggregation. Also, the particles are often treated in aqueous suspensions or in moist conditions prior to the final aggregation, for instance in a pelletizing processes. Thus, different dissolved chemical species may modify the magnetite, bentonite and silica surfaces, which causes the surface properties to change. However, the exact mechanism how the dissolved chemical species influence the direct particle-particle interaction and particle adhesion is not well known.The main focus of this thesis was the study of magnetite particle force interaction with natural and synthetic magnetite, silica and bentonite particles in aqueous solution with SPM. In addition, complimentary methods, such as scanning electron microscopy (SEM), vertical scanning interferometry (VSI), energy dispersive spectroscopy (SEM-EDS), x-ray diffraction (XRD) and electrophoresis techniques were used for surface morphology investigation, chemical characterization, determination of atomic structure and measurements of zeta-potential. The particle interaction forces were examined in solutions with various Ca2+ ion concentrations and in NaCl solution to determine the effect of Ca2+ ions on the surface properties. Also, the effect of pH at various concentrations was studied. The colloidal probes in the studies were natural magnetite and bentonite particles, micrometer-sized spherical silica particles. Sample surfaces were natural magnetite particles, smooth layers of synthetic magnetite nanoparticles and bentonite flakes.Qualitative changes in adhesion forces, i.e. interaction trends, and forces on approach for magnetite-magnetite, magnetite-silica, magnetite-bentonite and bentonite-silica interaction systems with an increase of Ca2+ ion concentration and pH were measured and evaluated. The interaction trends were consistent in most cases with zeta-potential measurements. Possible surface modification and formation of calcium silicates and calcium carbonates at pH 10 on the magnetite surfaces was discussed. The long-range repulsive interaction, similar to a steric-like interaction, was observed in the interactions for bentonite-silica and magnetite-silica systems, likely due to the swelling of bentonite layers and rising of bentonite flakes from the surface. The rising of bentonite flakes in water was verified with cryo-scanning electron microcopy investigation. Furthermore, the measured adhesion forces were compared with calculated adhesion forces, which were evaluated with the use of a few contact mechanics models. The comparison revealed discrepancies, which could be explained by the particle surface roughness. Additionally, a comparison of VSI and AFM techniques for surface characterization was performed on samples possessing sharp periodic surface structures and three stage plateaux honed cast iron surface. This comparison is of high relevance to the accurate calculation of tribological surface roughness parameters. Moreover, force measurements on biological samples and between magnetic particles are also briefly discussed in the thesis.The work within this thesis shows that SPM methods can be successfully applied to measure and predict forces between natural particles, such as magnetite and bentonite, in solution. The obtained and presented results are new and of high interest in applications where the knowledge of the dispersion and aggregation of studied particle interaction is important.

  • 4.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Surface characterization and force measurements applied to industrial materials with atomic force microscopy2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The thesis focuses on the application of force measurements with atomic force microscopy (AFM) on materials with a few surface contacts/asperities and chemically modified surfaces. The technique allows measurements of ultra-small intermolecular and surface forces, down to the piconewton level. The force measurements between surfaces of well-defined geometry are often used to measure and model the interaction between different systems of charged and neutral surfaces in various environments. However, detailed knowledge of the contacting surface profile geometry and surface properties is required to model the fundamental forces involved in the interaction. The preparation of such well-defined and idealized surfaces is often time consuming and the surfaces may not possess the behavior and properties of a source material in real processes, such as in industry. Moreover, external factors such as magnetic fields, ionic strengths and pH-values in a solution, may further complicate the evaluation. Hence, it is desirable to explore and develop techniques for trustable measurements of forces between “real” surfaces. These are often a complex composition of various force interactions and multiple surface contacts.The AFM probe technique was explored to measure force interactions between “real” particle surfaces. The work shows the applicability of the AFM technique to study the interaction forces despite the forecasted difficulties with the roughness of the particles.A technique to measure the adhesion and work of adhesion from AFM force curves was implemented and used. The thermal tune method was implemented in our commercial NT-MDT microscope to determine cantilever spring constants. The force interactions between natural microsize (m-s) magnetite particles and synthetic nanosize (n-s) magnetite particles were studied in calcium solution with concentrations of 1, 10, 100 mM and at pH values 4, 6 and 10. The changes in force interactions, due to variations in calcium concentration and pH were investigated. The adhesion force change with the concentration and pH was similar for m-s/m-s and m-s/n-s systems, and the adhesion force increased with the concentration at pH 6, except for the highest calcium concentration of 100 mM at pH 10. It was found that the magnetite surface modification could appear at the highest calcium concentration at pH 10. Moreover, the thesis contains preliminary results of the force interaction study between natural and synthetic bentonite-magnetite particles in calcium solution with concentrations of 1, 10 and 100 mM at pH 6.The influence of roughness on the calculation of contact mechanics parameters were studied with AFM and Vertical Scanning Interferometry (VSI). This is important for future development of a model to describe and characterize the force interaction between samples with multiple surface contacts. It was found that the optical artifacts, induced by VSI, have a large influence on all the roughness parameters calculated on the calibration grids, which represent extreme surface topographies.

  • 5.
    Dobryden, Illia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Weber, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Yang, Xiaofang
    Scanning probe microscopy study of magnetite particle force interactions in a solution2011Conference paper (Other academic)
  • 6.
    Dobryden, Illia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Potapova, Elisaveta
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Weber, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Application of AFM to probe micro- and nano-sized magnetite particle interaction in Ca2+ solution2014In: Proceedings of the International Summer School on Application of Scanning Probe Microscopy in Life Sciences, Soft Matter and Nanofabrication", Aalborg: River Publishers, 2014Conference paper (Other academic)
    Abstract [en]

    Natural magnetite is used for producing iron ore pellets, one of the raw materials in steel production. The quality of produced pellets depends on many factors, including the properties of the magnetite concentrate fed to pelletization. To be able to minimize the effect of the variations in feed properties on pellets quality, investigation of magnetite particle interaction with a focus on the surface properties is required. Atomic force microscopy (AFM), using the colloidal probe technique, is a suitable tool for measuring such particle-particle interaction in-situ. Natural particles are usually of micro-sizes (m-s) and have different sizes and shapes, which complicates an accurate investigation of particle interaction with AFM. To overcome such difficulties, synthetic nanoparticles are used instead. Process water chemistry is one of the factors affecting magnetite surface properties. Partial dissolution of calcite and apatite minerals, present in iron ore, results in high Ca2+ concentrations in the process water, which has been shown to have a major effect on the charge of the magnetite particles [1, 2]. The aim of this study was therefore to investigate forces and aggregation between magnetite particles, of micro- and nano-size (n-s), in Ca2+ solutions at various pH values. The spherical monodispersed magnetite nano-sized particles, with a diameter of approx. 10 nm, were synthesized by the precipitation technique [3]. Measurements were performed for m-s probe/m-s layer and m-s probe/n-s layer systems. Natural magnetite particles of 10-30 µm size were glued to NP-S cantilevers (Digital Instruments/Bruker, Santa Barbara, CA) with a measured spring constant of 0.12 N/m. Nano-sized particles were deposited on the glass slides by dip-coating. Roughness (Ra) of the n-s layers was measured with AFM and was about 10 nm for areas 1×1µm2, a representative high-resolution image is shown in Figure 1. Particle interaction was similar for m-s and n-s magnetite particles at pH 4 and 6. At pH 10, the interaction behavior was different due to probable surface modification of natural magnetite particles by ions from process water. The adhesion force for both interacting systems was measured, see ref. [4] for a detailed description of the results. To verify that ϛ-potential measurements could be used to predict the interaction between charged particles (in this case silica and magnetite) in solutions containing inorganic ions, force measurements between n-s magnetite layer and a SiO2 spherical probe (3.5 µm in diameter) were performed and correlated with the ϛ-potential results for these particles in the same solutions. Also, a DLVO simulation was performed to theoretically confirm the experimental interaction based on surface charge trends. An example of the simulated force curves is shown in Figure 2. The interaction between the probe and the magnetite surface was attractive at pH 4 and 6 but became repulsive at pH 8 and 10, which is in agreement with what could be expected from the ϛ-potential results for these particles.

  • 7.
    Dobryden, Illia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Potapova, Elisaveta
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Weber, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Force interactions between magnetite, silica, and bentonite studied with atomic force microscopy2015In: Physics and chemistry of minerals, ISSN 0342-1791, E-ISSN 1432-2021, Vol. 42, no 4, p. 319-326Article in journal (Refereed)
    Abstract [en]

    Iron ore pellets consist of variety of mineral particles and are an important refined product used in steel manufacturing. Production of high-quality pellets requires good understanding of interactions between different constituents, such as magnetite, gangue residues, bentonite, and additives. Much research has been reported on magnetite, silica, and bentonite surface properties and their effect on pellet strength but more scant with a focus on a fundamental particle–particle interaction. To probe such particle interaction, atomic force microscopy (AFM) using colloidal probe technique has proven to be a suitable tool. In this work, the measurements were performed between magnetite–magnetite, bentonite–magnetite, silica–bentonite, and silica–magnetite particles in 1 mM CaCl2 solution at various pH values. The interaction character, i.e., repulsion or attraction, was determined by measuring and analyzing AFM force curves. The observed quantitative changes in interaction forces were in good agreement with the measured zeta-potentials for the particles at the same experimental conditions. Particle aggregation was studied by measuring the adhesion force. Absolute values of adhesion forces for different systems could not be compared due to the difference in particle size and contact geometry. Therefore, the relative change of adhesion force between pH 6 and 10 was used for comparison. The adhesion force decreased for the magnetite–magnetite and bentonite–silica systems and slightly increased for the magnetite–bentonite system at pH 10 as compared to pH 6, whereas a pronounced decrease in adhesion force was observed in the magnetite–silica system. Thus, the presence of silica particles on the magnetite surface could have a negative impact on the interaction between magnetite and bentonite in balling due to the reduction of the adhesion force.

  • 8.
    Dobryden, Illia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology, Stockholm, SE-100 44, Sweden.
    Touati, Baligh
    Physics Condensed Matter Laboratory, Faculty of Science of Tunis, University of Tunis El-Manar.
    Gassoumi, Abdelaziz
    Physics Condensed Matter Laboratory, Faculty of Science of Tunis, University of Tunis El-Manar.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Kamoun, Najoua
    Physics Condensed Matter Laboratory, Faculty of Science of Tunis, University of Tunis El-Manar.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Morphological and electrical characterization of Cu-doped PbS thin films with AFM2017In: Advanced Materials Letters, ISSN 0976-3961, E-ISSN 0976-397X, Vol. 8, no 11, p. 1029-1037Article in journal (Refereed)
    Abstract [en]

    Lead sulphide (PbS) is a direct band gap IV–VI intrinsic p-type semiconductor with good potential for application in solar cells, sensors, etc. Doping the films with Cu2+ ions may improve the electrical properties. Here, Cu-doped PbS films were deposited on conducting glass substrates. The morphology, topography and thickness of the doped PbS films were examined using atomic force microscopy (AFM) and high-resolution SEM. AFM analysis showed decreasing surface roughness and grain size with the increase of Cu2+ concentration from 0.5 to 2.0 at%. Local surface electrical measurements using conducting AFM and Kelvin probe force microscopy showed the possibility to probe semi-quantitatively the changes in surface potential, work function, and Fermi level upon doping of the films. The estimated apparent work function for the un-doped PbS grains in the film was slightly above 4.5 eV, while it decreased to a minimum value of 4.43-4.45 eV at 1–1.5 at% Cu-doping. Conducting AFM measurements showed that local resistance of the doped samples is lower than on pure PbS films. These results indicate Cu doping as an effective strategy to tune the electrical properties of PbS thin films toward the development of suitable optically active materials for application in photovoltaics.

  • 9.
    Dobryden, Illia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Yang, Xiaofang
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Weber, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    An atomic force microscopy study of the interaction between magnetite particles: the effect of Ca2 + ions and pH2013In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 233, p. 116-122Article in journal (Refereed)
    Abstract [en]

    Force interactions between a microsize (m-s) magnetite probe and thin layers of synthesized magnetite particles as well as microsize (m-s) magnetite particles from magnetite concentrate were investigated using atomic force microscopy (AFM). Of special interest was the influence of Ca2 + ions and pH on the interaction between the probe and the two different magnetite particle surfaces. The probe and the magnetite surfaces were immersed in aqueous Ca2 + solutions (100, 10, and 1 mM) at various pH values (4, 6, and 10). The colloidal probe technique and a self-made computer program for automatic evaluation of adhesion forces were used. The analysis revealed an increase in adhesion force with increased calcium concentration at pH 6 for both the systems investigated. However, the adhesion behavior between the probe and the m-s and n-s magnetite particle surfaces is different at pH 10. The possible appearance of calcium carbonate precipitated onto the magnetite surfaces as well as the possible influence of already adsorbed silicate on magnetite particles from the concentrate is discussed. In addition to Ca, Cl and Na atoms, added to the working solutions, and the Fe and O detected signals, the SEM-EDS analysis also detected Si atoms on the surface of the m-s particles.

  • 10.
    Dobryden, Illia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Yang, Xiaofang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Weber, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interaction forces between surface modified magnetite particles in aqueous solution2011Conference paper (Other academic)
  • 11.
    Furustig, Joel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The measurement of wear using AFM and wear interpretation using a contact mechanics coupled wear model2016In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 350-351, p. 74-81Article in journal (Refereed)
    Abstract [en]

    Detailed understanding of wear processes is required to improve the wear resistance and lifetime of machine components. Atomic force microscopy (AFM) is used to measure surface height profiles with high precision, before and after a wear experiment. The distribution and depth of wear on steel surfaces is then calculated using a relocation method. A numerical investigation of wear based on Archard's equation is conducted on the same measured surfaces. A good correlation was found between the model and experiment for wear larger than a hundred nm. The wear mechanisms considered in the numerical simulation was thus found to be the cause of the majority of the wear. On the scale of tens of nm the correlation was limited, but the measured wear was still analysed in detail.

  • 12.
    Sefer, Birhan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Division of Surface and Corrosion Science, KTH Royal Institute of Technology.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pederson, Robert
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Research and Technology Centre, GKN Aerospace Engine Systems.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Chemical Milling of Cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo Alloys in Hydrofluoric-Nitric Acid Solutions2017In: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 73, no 4, p. 394-407Article in journal (Refereed)
    Abstract [en]

    The behavior of cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo during chemical milling in hydrofluoric-nitric (HF-HNO3) acid solutions with 1:3 and 1:11 molar ratios was investigated using electrochemical and atomic force microscopy (AFM) techniques. Faster corrosion rate in 1:3 solutions was measured for Ti-6Al-4V than for Ti-6Al-2Sn-4Zr-2Mo, whereas in 1:11 solution Ti-6Al-2Sn-4Zr-2Mo exhibited higher corrosion rate. Scanning Kelvin probe force microscopy measurements revealed difference in the Volta potential between the α-laths and the β-layers in the Widmansttäten microstructure indicating operation of microgalvanic cells between the microconstituents when in contact with HF-HNO3 solution. The AFM topography measurements demonstrated faster corrosion of the α-laths compared to the β-layers, in both alloys. In 1:3 solutions, higher α/β height difference was measured in Ti-6Al-4V, whereas in 1:11 solution, the difference was higher in Ti-6Al-2Sn-4Zr-2Mo. The results revealed that the chemical milling behavior of the two investigated alloys is controlled by the microscopic corrosion behavior of the individual microconstituents.

  • 13.
    Spencer, Andrew
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Surface characterization with functional parameters2011Conference paper (Other academic)
    Abstract [en]

    Typically engineering surfaces are characterized with traditional roughness parameters that perform some type of height averaging over the surface. Although these parameters describe the topography of the surface none of them necessarily describe the ability of the surface to carry out its function in a tribological contact. In this study an ICE cylinder liner has been investigated.The traditional Rk parameters (based on the Abbott curve) have been calculated as well as functional ‘flow factors’which modify the Reynolds equation to incorporate the effects of surface topography.To calculate flow factors the homogenization technique has been implemented and a full 3D contact mechanics model has been incorporated so that surface functionality in mixed lubrication can be studied. Furthermore, the cylinder liner surface has been measured with both white light interferometery and an AFM so that the effect of measuring technique on roughness and functional parameters can be investigated.

  • 14.
    Spencer, Andrew
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The influence of AFM and VSI techniques on the accurate calculation of tribological surface roughness parameters2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 57, p. 242-250Article in journal (Refereed)
    Abstract [en]

    Vertical Scanning Interferometry (VSI) may induce optical artefacts in surface topography measurements. The influence of these optical artefacts on the calculation of Rk surface roughness parameters, contact stiffness and flow factors were studied. Two surface measurement techniques were used: Atomic Force Microscopy (AFM) and VSI. Calibration grids were used to make it easier to isolate the causes of these artefacts, while a real engineering surface was used to compare these two techniques in an industrially applied case. It was found that the optical artefacts have a large influence on all the roughness parameters, contact stiffness and flow factors calculated on the calibration grids. However, for the engineering surface the differences between AFM and VSI measurements were much smaller.

  • 15.
    Touati, Baligh
    et al.
    Physics Condensed Matter Laboratory, Faculty of Science of Tunis, University of Tunis El -Manar.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Salem, Yassine Ben
    Physics Condensed Matter Laboratory, Faculty of Science of Tunis, University of Tunis El -Manar.
    Gassoumi, Abdelaziz
    Physics Condensed Matter Laboratory, Faculty of Science of Tunis, University of Tunis El -Manar.
    Natile, Marta Maria
    CNR-IENI, Dipartimento di Scienze Chimiche, Università di Padova.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Kamoun, Najoua
    Physics Condensed Matter Laboratory, Faculty of Science of Tunis, University of Tunis El -Manar.
    Morphological and electrical characterization of Cu-doped PbS thin films2016Conference paper (Refereed)
    Abstract [en]

    Lead sulphide (PbS) thin films represent a direct band gap IV–VI p-type semiconductor material (Eg= 0.41 eV) and have a good potential application in solar cells, infrared detector devices, sensors, etc[1]. The electrical properties of PbS film can be tuned via doping with Cu2+ and Cd2+[2, 3]. These ions have good ability to substitute Pb2+ locations in the PbS crystal lattice, and thus tune its energy band gap. Also, the structural properties of the film, such as the grain size, can depend on the dopant concentration and will affect the PbS band gap and conductivity. These features are important for instance, when PbS film are applied as photoactive materials in solar cells[4]. Here we present an investigation on doping PbS thin films by Cu. Cu-doped PbS films were deposited on ordinary glass and conducting glass substrates through chemical bath deposition. The samples deposited on the F:SnO2 conducting layers were used for a high-resolution SEM measurements and scanning spreading resistance microscopy (SSRM) characterization using scanning probe microscopy (SPM). The morphology and topography of the doped PbS films were examined using tapping mode AFM (NT-MDT Ntegra) and high-resolution SEM (Magellan 400 XHR-SEM). The crystalline shape was triangular and did not change much with the dopant concentration increase from 0.5% to 2%. Films in the range 120 to 380 nm were considered. Good agreement was found between thickness measured through cross-section HR-SEM and Rutherford backscattering spectrometry (RBS). Also, the RBS investigation has shown that the film thickness tends to decrease for an increase of the dopant concentration. All the doped films seem having lower doping concentration, compared to the nominal one, as obtained from RBS analysis. XPS highlighted a Cu-enriched surface layer, possibly due to selective segregation of the doped films during their growth. Additionally, advanced electrical measurements using SSRM and Kelvin probe force microscopy (KPFM) are underway. The possibility of tuning both the electrical and optical properties of PbS thin films by doping represents a viable strategy for the development of suitable optically active materials for application in photovoltaics.

  • 16.
    Touati, Baligh
    et al.
    Université Tunis El Manar, Faculté des Sciences de Tunis, Département de Physique, LR99ES13 Laboratoire de Physique de la Matière Condensée (LPMC), 2092, Tunis.
    Gassoumi, Abdelaziz
    Université Tunis El Manar, Faculté des Sciences de Tunis, Département de Physique, LR99ES13 Laboratoire de Physique de la Matière Condensée (LPMC), 2092, Tunis.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Natile, Marta Maria
    Consiglio Nazionale delle Ricerche, Pisa, Universita Degli Studi di Padova, CNR-IENI, Dipartimento di Scienze Chimiche, Università di Padova.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Turki, Najoua Kamoun
    Université Tunis El Manar, Faculté des Sciences de Tunis, Département de Physique, LR99ES13 Laboratoire de Physique de la Matière Condensée (LPMC), 2092, Tunis.
    Engineering of electronic and optical properties of PbS thin films via Cu doping2016In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 97, p. 519-528Article in journal (Refereed)
    Abstract [en]

    Copper-doped PbS polycrystalline thin films were deposited by chemical bath deposition by adding small amount of Cu (ysolution = [Cu2+]/[Pb2+]) between 0.5 and 2 at%. The composition, structure, morphology, optical and electrical properties of the films were investigated by means of X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), UV–visible–near infrared (UV–Vis–NIR) spectrophotometry and Hall effect measurements. The XRD studies showed that the undoped films have PbS face centered cubic structure with (111) preferential orientation, while preferential orientation changes to (200) plane with increasing Cu doping concentration. The AFM and SEM measurements indicated that the film surfaces consisted of nanosized grains with pyramidal shape. Optical band gap was blue shifted from 0.72 eV to 1.69 eV with the increase in Cu doping concentration. The film obtained with the [Cu2+]/[Pb2+] ratio equal to 1.5 at% Cu showed the minimum resistivity of 0.16 Ω cm at room temperature and optimum value of optical band gap close to 1.5 eV. 1.5 at% Cu-doped PbS thin films exhibit the best optical and electrical properties, suitable for solar cells applications.

  • 17. You, Shujie
    et al.
    Mases, Mattias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Green, Alexander A.
    Department of Materials Science and Engineering, Northwestern University, Evanston, IL.
    Hersam, Mark C.
    Department of Materials Science and Engineering, Northwestern University, Evanston, IL.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Probing structural stability of double-walled carbon nanotubes at high non-hydrostatic pressure by Raman spectroscopy2011In: High Pressure Research, ISSN 0895-7959, E-ISSN 1477-2299, Vol. 31, no 1, p. 186-190Article in journal (Refereed)
    Abstract [en]

    Theoretical calculations predict that the collapse pressure for double-walled carbon nanotubes (DWCNTs) is proportional to 1/R3, where R is the effective or average radius of a DWCNT. In order to address the problem of CNT stability at high pressure and stress, we performed a resonance Raman study of DWCNTs dispersed in sodium cholate using 532 and 633 nm laser excitation. Raman spectra of the recovered samples show minor versus irreversible changes with increasing ID/IG ratio after exposure to high non-hydrostatic pressure of 23 and 35 GPa, respectively. The system exhibits nearly 70% pressure hysteresis in radial breathing vibrational mode signals recovery on pressure release which is twice that predicted by theory.

  • 18.
    Zhu, Chuantao
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ryden, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adsorption Behavior of Cellulose and Its Derivatives toward Ag(I) in Aqueous Medium: An AFM, Spectroscopic, and DFT Study2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 45, p. 12390-12400Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to develop a fundamental understanding of the adsorption behavior of metal ions on cellulose surfaces using experimental techniques supported by computational modeling, taking Ag(I) as an example. Force interactions among three types of cellulose microspheres (native cellulose and its derivatives with sulfate and phosphate groups) and the silica surface in AgNO3 solution were studied with atomic force microscopy (AFM) using the colloidal probe technique. The adhesion force between phosphate cellulose microspheres (PCM) and the silica surface in the aqueous AgNO3 medium increased significantly with increasing pH while the adhesion force slightly decreased for sulfate cellulose microspheres (SCM), and no clear adhesion force was observed for native cellulose microspheres (CM). The stronger adhesion enhancement for the PCM system is mainly attributed to the electrostatic attraction between Ag(I) and the negative silica surface. The observed force trends were in good agreement with the measured zeta potentials. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analyses confirmed the presence of silver on the surface of cellulose microspheres after adsorption. This study showed that PCM with a high content of phosphate groups exhibited a larger amount of adsorbed Ag(I) than CM and SCM and possible clustering of Ag(I) to nanoparticles. The presence of the phosphate group and a wavenumber shift of the P−OH vibration caused by the adsorption of silver ions on the phosphate groups were further confirmed with computational studies using density functional theory (DFT), which gives support to the above findings regarding the adsorption and clustering of Ag(I) on the cellulose surface decorated with phosphate groups as well as IR spectra.

  • 19.
    Zhu, Chuantao
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji p.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adsorption behavior of cellulose and its derivatives for Ag+ in aqueous medium: An AFM and spectroscopy study2015Conference paper (Refereed)
    Abstract [en]

    Cellulose particles in micro and nano scales has shown excellent potential to adsorb water pollutants such as dyes, pesticides, bacteria and virus, and a wide range of heavy metal ions, including Ag(Ⅰ), U(Ⅱ), Fe(Ⅲ), Cu(Ⅱ), Ni(Ⅱ), Cr(Ⅲ) and Zn(Ⅱ) 1, 2. However, mechanisms of adsorption and desorption the contaminants to/from cellulose micro or nano particles are largely unknown. The aim of the study was to develop fundamental understanding about the interaction and adsorption behavior of silver ions on cellulose surfaces using colloidal probe and spectroscopy techniques. Force interactions between three types of cellulose microspheres viz. native cellulose microspheres (CM), sulfate cellulose microspheres (SCM), phosphate cellulose microspheres (PCM) and silica surface in AgNO3 solution were studied with atomic force microscopy (AFM). The AFM results were further elaborated by extensive spectroscopy investigations.

1 - 19 of 19
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