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  • 1.
    Babu, Bijish
    et al.
    Swerim AB, Heating and Metalworking, Luleå, Sweden.
    Lundbäck, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of Ti-6Al-4V Additive Manufacturing Using Coupled Physically Based Flow Stress and Metallurgical Model2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 23, artikkel-id 3844Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Simulating the additive manufacturing process of Ti-6Al-4V is very complex due to the microstructural changes and allotropic transformation occurring during its thermomechanical processing. The α -phase with a hexagonal close pack structure is present in three different forms—Widmanstatten, grain boundary and Martensite. A metallurgical model that computes the formation and dissolution of each of these phases was used here. Furthermore, a physically based flow-stress model coupled with the metallurgical model was applied in the simulation of an additive manufacturing case using the directed energy-deposition method. The result from the metallurgical model explicitly affects the mechanical properties in the flow-stress model. Validation of the thermal and mechanical model was performed by comparing the simulation results with measurements available in the literature, which showed good agreement

  • 2.
    Eppanapelli, Lavan Kumar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    3D analysis of deformation and porosity of dry natural snow during compaction2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 6, artikkel-id 850Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study focuses on three-dimensional (3D) microstructure analysis of dry natural snow during compaction. An X-ray computed microtomography (micro-CT) system was used to record a total of 1601 projections of a snow volume. Experiments were performed in-situ at four load states as 0 MPa, 0.3 MPa, 0.6 MPa and 0.8 MPa, to investigate the effect of compaction on structural features of snow grains. The micro-CT system produces high resolution images (4.3 μm voxel) in 6 hours of scanning time. The micro-CT images of the investigated snow volume illustrate that grain shapes are mostly dominated by needles, capped columns and dendrites. It was found that a significant number of grains appeared to have a deep hollow core irrespective of the grain shape. Digital volume correlation (DVC) was applied to investigate displacement and strain fields in the snow volume due to the compaction. Results from the DVC analysis show that grains close to the moving punch experience most of the displacement. The reconstructed snow volume is segmented into several cylinders via horizontal cross-sectioning, to evaluate the vertical heterogeneity of porosity distribution of the snow volume. It was observed that the porosity (for the whole volume) in principle decreases as the level of compaction increases. A distinct vertical heterogeneity is observed in porosity distribution in response to compaction. The observations from this initial study may be useful to understand the snow microstructure under applied stress.

  • 3.
    Feng, Yan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. School of Resource and Safety Engineering, Central South University, Changsha 410083, China.
    Kero, Jakob
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Yang, Qixing
    Energy School, Xi'an University of Science and Technology, Xi'an 710054, China.
    Chen, Qisong
    School of Resource and Safety Engineering, Central South University, Changsha 410083, China.
    Engström, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Samuelsson, Caisa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Qi, Chongchong
    School of Resource and Safety Engineering, Central South University, Changsha 410083, China.
    Mechanical Activation of Granulated Copper Slag and Its Influence on Hydration Heat and Compressive Strength of Blended Cement2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 5, artikkel-id 772Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanical activation of granulated copper slag (GCS) is carried out in the present study for the purposes of enhancing pozzolanic activity for the GCS. A vibration mill mills the GCS for 1, 2, and 3 h to produce samples with specific surface area of 0.67, 1.03 and 1.37 m²/g, respectively. The samples are used to replace 30% cement (PC) to get 3 PC-GCS binders. The hydration heat and compressive strength are measured for the binders and derivative thermogravimetric /thermogravimetric analysis (DTG/TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are used to characterize the paste samples. It is shown that cumulative heat and compressive strength at different ages of hydration and curing, respectively, are higher for the binders blending the GCS milled for a longer time. The compressive strength after 90 d of curing for the binder with the longest milling time reaches 35.7 MPa, which is higher than the strength of other binders and close to the strength value of 39.3 MPa obtained by the PC pastes. The percentage of fixed lime by the binder pastes at 28 days is correlated with the degree of pozzolanic reaction and strength development. The percentage is higher for the binder blending the GCS with longer milling time and higher specific surface area. The pastes with binders blending the GCS of specific surface area of 0.67 and 1.37 m²/g fix lime of 15.20 and 21.15%, respectively. These results together with results from X-ray diffraction (XRD), FTIR, and SEM investigations demonstrate that the mechanical activation via vibratory milling is an effective method to enhance the pozzolanic activity and the extent for cement substitution by the GCS as a suitable supplementary cementitious material (SCM).

  • 4.
    Girardin, Bertrand
    et al.
    R2Fire Group/UMET-UMR CNRS 8207, Ecole Nationale Supérieure de Chimie de Lille, Unité Matériaux et Transformations (UMET), École Nationale Supérieure de Chimie de Lille, University of Lille.
    Fontaine, Geêlle
    R2Fire / UMET – UMR CNRS 8207, ENSCL, Avenue Dimitri Mendeleïev – Bât. C7a, CS 90108, 59652 Villeneuve d’Ascq, Unité Matériaux et Transformations (UMET), École Nationale Supérieure de Chimie de Lille, University of Lille.
    Duquesne, Sophie
    R2Fire / UMET – UMR CNRS 8207, ENSCL, Avenue Dimitri Mendeleïev – Bât. C7a, CS 90108, 59652 Villeneuve d’Ascq, Unité Matériaux et Transformations (UMET), École Nationale Supérieure de Chimie de Lille, University of Lille.
    Bourbignot, Serge
    R2Fire / UMET – UMR CNRS 8207, ENSCL, Avenue Dimitri Mendeleïev – Bât. C7a, CS 90108, 59652 Villeneuve d’Ascq, Unité Matériaux et Transformations (UMET), École Nationale Supérieure de Chimie de Lille, University of Lille.
    Försth, Michael
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Characterization of thermo-physical properties of EVA/ATH: Application to gasification experiments and pyrolysis modeling2015Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 8, nr 11, s. 7837-7863Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The pyrolysis of solid polymeric materials is a complex process that involves both chemical and physical phenomena such as phase transitions, chemical reactions, heat transfer, and mass transport of gaseous components. For modeling purposes, it is important to characterize and to quantify the properties driving those phenomena, especially in the case of flame-retarded materials. In this study, protocols have been developed to characterize the thermal conductivity and the heat capacity of an ethylene-vinyl acetate copolymer (EVA) flame retarded with aluminum tri-hydroxide (ATH). These properties were measured for the various species identified across the decomposition of the material. Namely, the thermal conductivity was found to decrease as a function of temperature before decomposition whereas the ceramic residue obtained after the decomposition at the steady state exhibits a thermal conductivity as low as 0.2 W/m/K. The heat capacity of the material was also investigated using both isothermal modulated Differential Scanning Calorimetry (DSC) and the standard method (ASTM E1269). It was shown that the final residue exhibits a similar behavior to alumina, which is consistent with the decomposition pathway of EVA/ATH. Besides, the two experimental approaches give similar results over the whole range of temperatures. Moreover, the optical properties before decomposition and the heat capacity of the decomposition gases were also analyzed. Those properties were then used as input data for a pyrolysis model in order to predict gasification experiments. Mass losses of gasification experiments were well predicted, thus validating the characterization of the thermo-physical properties of the material

  • 5.
    Greifzu, Moritz
    et al.
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    Tkachov, Roman
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Stepien, Lukas
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    López, Elena
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Leyens, Christoph
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Laser Treatment as Sintering Process for Dispenser Printed Bismuth Telluride Based Paste2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 20, artikkel-id 3453Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser sintering as a thermal post treatment method for dispenser printed p- and n-type bismuth telluride based thermoelectric paste materials was investigated. A high-power fiber laser (600 W, 1064 nm) was used in combination with a scanning system to achieve high processing speed. A Design of Experiment (DoE) approach was used to identify the most relevant processing parameters. Printed layers were laser treated with different process parameters and the achieved sheet resistance, electrical conductivity, and Seebeck coefficient are compared to tube furnace processed reference specimen. For p-type material, electrical conductivity of 22 S/cm was achieved, compared to 15 S/cm in tube furnace process. For n-type material, conductivity achieved by laser process was much lower (7 S/cm) compared to 88 S/cm in furnace process. Also, Seebeck coefficient decreases during laser processing (40–70 µV/K and −110 µV/K) compared to the oven process (251 µV/K and −142 µV/K) for p- and n-type material. DoE did not yet deliver a set of optimum processing parameters, but supports doubts about the applicability of area specific laser energy density as a single parameter to optimize laser sintering process.

  • 6.
    Gyhlesten Back, Jessica
    et al.
    Högskolan Dalarna, Industriell Teknik, Materialvetenskap.
    Engberg, Göran
    Högskolan Dalarna, Industriell Teknik, Materialvetenskap.
    Investigation of Parent Austenite Grains from Martensite Structure using EBSD in a Wear Resistant Steel2017Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 10, artikkel-id 453Artikkel i tidsskrift (Fagfellevurdert)
  • 7.
    Hassan, Mohammad
    et al.
    Cellulose and Paper Department & Centre of Excellence for Advanced Sciences, National Research Centre, Giza, Egypt; Egypt Nanotechnology Centre, Cairo University, 6th October City, Egypt.
    Berglund, Linn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Abou-Zeid, Ragab
    Cellulose and Paper Department & Centre of Excellence for Advanced Sciences, National Research Centre, Giza , Egypt.
    Hassan, Enas
    Cellulose and Paper Department & Centre of Excellence for Advanced Sciences, National Research Centre, Giza , Egypt.
    Abou-Elseoud, Wafaa
    Cellulose and Paper Department & Centre of Excellence for Advanced Sciences, National Research Centre, Giza , Egypt.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Fibre and Particle Engineering, University of Oulu, Oulu, Finland.
    Nanocomposite Film Based on Cellulose Acetate and Lignin-Rich Rice Straw Nanofibers2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 4, artikkel-id 595Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanofibers isolated from unbleached neutral sulfite rice straw pulp were used to prepare transparent films without the need to modify the isolated rice straw nanofibers (RSNF). RSNF with loading from 1.25 to 10 wt.% were mixed with cellulose acetate (CA) solution in acetone and films were formed by casting. The films were characterized regarding their transparency and light transmittance, microstructure, mechanical properties, crystallinity, water contact angle, porosity, water vapor permeability, and thermal properties. The results showed good dispersion of RSNF in CA matrix and films with good transparency and homogeneity could be prepared at RSNF loadings of less than 5%. As shown from contact angle and atomic force microscopy (AFM) measurements, the RSNF resulted in increased hydrophilic nature and roughness of the films. No significant improvement in tensile strength and Young’s modulus was recorded as a result of adding RSNF to CA. Addition of the RSNF did not significantly affect the porosity, crystallinity and melting temperature of CA, but slightly increased its glass transition temperature

  • 8.
    Humad, Abeer
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Habermehl-Cwirzen, Karin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Effects of fineness and chemical composition of blast furnace slag on properties of alkali-activated binder2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 20, artikkel-id 3447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract: The effects of fines and chemical composition of three types of ground granulated blast furnace slag (GGBFS) on various concrete properties were studied. Those studied were alkali activated by liquid sodium silicate (SS) and sodium carbonate (SC). Flowability, setting times, compressive strength, efflorescence, and carbonation resistance and shrinkage were tested. The chemical composition and microstructure of the solidified matrixes were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) coupled with EDX analyser. The results showed that the particle size distribution of the slags and the activator type had significantly stronger effects on all measured properties than their chemical composition. The highest compressive strength values were obtained for the finest slag, which having also the lowest MgO content. SC-activated mortar produced nearly the same compressive strength values independently of the used slag. The most intensive efflorescence and the lowest carbonation resistance developed on mortars based on slag containing 12% of MgO and the lowest fineness. The slag with the highest specific surface area and the lowest MgO content developed a homogenous microstructure, highest reaction temperature and lowest drying shrinkage. Thermogravimetric analysis indicated the presence of C-(A)-S-H, hydrotalcite HT, and carbonate like-phases in all studied mortars.

  • 9.
    Khalili, Pooria
    et al.
    Material and Computational Mechanics, Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Blinzler, Brina
    Material and Computational Mechanics, Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Kádár, Roland
    Division of Engineering Materials, Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Bisschop, Roeland
    Division Safety and Transport/Safety/Fire Research, RISE Research Institutes of Sweden, Borås, Sweden.
    Försth, Michael
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. Division Safety and Transport/Safety/Fire Research, RISE Research Institutes of Sweden, Borås, Sweden.
    Blomqvist, Per
    Division Safety and Transport/Safety/Fire Research, RISE Research Institutes of Sweden, Borås, Sweden.
    Flammability, Smoke, Mechanical Behaviours and Morphology of Flame Retarded Natural Fibre/Elium®Composite2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 17, artikkel-id 2648Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The work involves fabrication of natural fibre/Elium® composites using resin infusion technique. The jute fabrics were treated using phosphorus-carbon based flame retardant (FR) agent, a phosphonate solution and graphene nano-platelet (GnP), followed by resin infusion, to produce FR and graphene-based composites. The properties of these composites were compared with those of the Control (jute fabric/Elium®). As obtained from the cone calorimeter and Fourier transform infrared spectroscopy, the peak heat release rate reduced significantly after the FR and GnP treatments of fabrics whereas total smoke release and quantity of carbon monoxide increased with the incorporation of FR. The addition of GnP had almost no effect on carbon monoxide and carbon dioxide yield. Dynamic mechanical analysis demonstrated that coating jute fabrics with GnP particles led to an enhanced glass transition temperature by 14%. Scanning electron microscopy showed fibre pull-out locations in the tensile fracture surface of the laminates after incorporation of both fillers, which resulted in reduced tensile properties.

  • 10.
    Kledwig, Christian
    et al.
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Perfahl, Holger
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Reisacher, Martin
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Bliedtner, Jens
    SciTec Department, Ernst-Abbe-Hochschule Jena, Jena, Germany.
    Leyens, Christoph
    Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Analysis of Melt Pool Characteristics and Process Parameters Using a Coaxial Monitoring System during Directed Energy Deposition in Additive Manufacturing2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 2, artikkel-id 308Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The growing number of commercially available machines for laser deposition welding show the growing acceptance and importance of this technology for industrial applications. Their increasing usage in research and production requires process stability and user-friendly handling. A commercially available DMG MORI LT 65 3D hybrid machine used in combination with a CCD-based coaxial temperature measurement system was utilized in this work to investigate what information relating to the intensity distribution of melt pool surfaces could be appropriate to draw conclusions about process conditions. In this study it is shown how the minimal required specific energy for a stable process can be determined, and it is indicated that the evolution of a plasma plume depends on thermal energy within the base material. An estimated melt pool area—calculated by the number of pixels (NOP) with intensities larger than a fixed, predefined threshold—builds the main measure in analysing images from the process camera. The melt pool area and its temporal variance can also serve as an indicator for an increased working distance

  • 11.
    Maimaitiyili, Tuerdi
    et al.
    Photons for Engineering and Manufacturing Group, Paul Scherrer Institute, Villigen, Switzerland;Department of Materials Science and Applied Mathematics, Malmö universitet, Malmö, Sweden.
    Woracek, Robin
    European Spallation Source ERIC, Lund, Sweden; Nuclear Physics Institute of the CAS, Husinec—Řež, Czech Republic.
    Neikter, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Boin, Mirko
    Department of Microstructure and Residual Stress Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany.
    Wimpory, Robert C.
    Department of Microstructure and Residual Stress Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany.
    Pederson, Robert
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Strobl, Markus
    European Spallation Source ERIC, Lund, Sweden; Nuclear Physics Institute of the CAS, Husinec—Řež, Czech Republic; Neutron Imaging and Applied Materials Group, Paul Scherrer Institute, Villigen, Switzerland.
    Drakopoulos, Michael
    Imaging and Microscopy Group, Diamond Light Source Ltd., Oxfordshire , UK.
    Schäfer, Norbert
    Department of Nanoscale Structures and Microscopic Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany.
    Bjerkén, Christina
    Department of Materials Science and Applied Mathematics, Malmö universitet, Malmö, Sweden.
    Residual Lattice Strain and Phase Distribution in Ti-6Al-4V Produced by Electron Beam Melting2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 4, artikkel-id 667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Residual stress/strain and microstructure used in additively manufactured material are strongly dependent on process parameter combination. With the aim to better understand and correlate process parameters used in electron beam melting (EBM) of Ti-6Al-4V with resulting phase distributions and residual stress/strains, extensive experimental work has been performed. A large number of polycrystalline Ti-6Al-4V specimens were produced with different optimized EBM process parameter combinations. These specimens were post-sequentially studied by using high-energy X-ray and neutron diffraction. In addition, visible light microscopy, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) studies were performed and linked to the other findings. Results show that the influence of scan speed and offset focus on resulting residual strain in a fully dense sample was not significant. In contrast to some previous literature, a uniform α- and β-Ti phase distribution was found in all investigated specimens. Furthermore, no strong strain variations along the build direction with respect to the deposition were found. The magnitude of strain in α and β phase show some variations both in the build plane and along the build direction, which seemed to correlate with the size of the primary β grains. However, no relation was found between measured residual strains in α and β phase. Large primary β grains and texture appear to have a strong effect on X-ray based stress results with relatively small beam size, therefore it is suggested to use a large beam for representative bulk measurements and also to consider the prior β grain size in experimental planning, as well as for mathematical modelling.

  • 12.
    Memarian, Nafiseh
    et al.
    Faculty of Physics, Semnan University.
    Rozati, Seyed Mohammad
    Department of Physics, University of Guilan, Rasht.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Concina, Isabella
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Deposition of nanostructured Cds thin films by thermal evaporation method: Effect of substrate temperature2017Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 10, nr 7, artikkel-id 773Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanocrystalline CdS thin films were grown on glass substrates by a thermal evaporation method in a vacuum of about 2 × 10-5 Torr at substrate temperatures ranging between 25 °C and 250 °C. The physical properties of the layers were analyzed by transmittance spectra, XRD, SEM, and four-point probe measurements, and exhibited strong dependence on substrate temperature. The XRD patterns of the films indicated the presence of single-phase hexagonal CdS with (002) orientation. The structural parameters of CdS thin films (namely crystallite size, number of grains per unit area, dislocation density and the strain of the deposited films) were also calculated. The resistivity of the as-deposited films were found to vary in the range 3.11-2.2 × 104 Ω·cm, depending on the substrate temperature. The low resistivity with reasonable transmittance suggest that this is a reliable way to fine-tune the functional properties of CdS films according to the specific application.

  • 13.
    Murgau, Corinne Charles
    et al.
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Lundbäck, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Åkerfeldt, Pia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pederson, Robert
    Department of Engineering Science, University West, Trollhättan, Sweden. GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Temperature and Microstructure Evolution in Gas Tungsten Arc Welding Wire Feed Additive Manufacturing of Ti-6Al-4V2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 21, artikkel-id 3534Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, the gas tungsten arc welding wire feed additive manufacturing process is simulated and its final microstructure predicted by microstructural modelling, which is validated by microstructural characterization. The Finite Element Method is used to solve the temperature field and microstructural evolution during a gas tungsten arc welding wire feed additive manufacturing process. The microstructure of titanium alloy Ti-6Al-4V is computed based on the temperature evolution in a density-based approach and coupled to a model that predicts the thickness of the α lath morphology. The work presented herein includes the first coupling of the process simulation and microstructural modelling, which have been studied separately in previous work by the authors. In addition, the results from simulations are presented and validated with qualitative and quantitative microstructural analyses. The coupling of the process simulation and microstructural modeling indicate promising results, since the microstructural analysis shows good agreement with the predicted alpha lath size.

  • 14.
    Rajczakowska, Magdalena
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Habermehl-Cwirzen, Karin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Hedlund, Hans
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. Skanska, Stockholm, Sweden.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    The effect of exposure on the autogenous self-healing of Ordinary Portland cement mortars2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 23, artikkel-id 3926Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Exposure conditions are critical for the autogenous self-healing process of Portland cement based binder matrixes. However, there is still a significant lack of fundamental knowledge related to this factor. The aim of this paper was to investigate and understand the effects of various potentially applicable curing solutions on the efficiency of the crack closure occurring both superficially and internally. Four groups of exposures were tested, including exposure with different water immersion regimes, variable temperatures, application of chemical admixtures, and use of solutions containing micro particles. The self-healing process was evaluated externally, at the surface of the crack, and internally, at different crack depths with the use of optical and scanning electron microscopes (SEM). The phase identification was done with an energy dispersive spectrometer combined with the SEM. The results showed very limited self-healing in all pure water-based exposures, despite the application of different cycles, temperatures, and water volumes. The addition of a phosphate-based retarding admixture demonstrated the highest crack closure, both internally and externally. The highest strength recovery and a very good crack closure ratio was achieved in water exposure containing micro silica particles. The main phase observed on the surface was calcium carbonate, and internally, calcium silicate hydrate, calcium carbonate, and calcium phosphate compounds. Phosphate ions were found to contribute to the filling of the crack, most likely by preventing the formation of a dense shell composed of hydration phases on the exposed areas by crack unhydrated cement grains as well as by the additional precipitation of calcium and phosphate-based compounds. The micro sized silica particles presumably served as nucleation sites for the self-healing products growth. Changes in the chemical composition of the self-healing material were observed with a distance from the surface of the specimen.

  • 15.
    Rajczakowska, Magdalena
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Nilsson, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Habermehl-Cwirzen, Karin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Hedlund, Hans
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. Skanska, Stockholm, Sweden.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Does a High Amount of Unhydrated Portland Cement Ensure an Effective Autogenous Self-Healing of Mortar?2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 20, artikkel-id 3298Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is commonly accepted that the autogenous self-healing of concrete is mainly controlled by the hydration of Portland cement and its extent depends on the availability of anhydrous particles. High-performance (HPCs) and ultra-high performance concretes (UHPCs) incorporating very high amounts of cement and having a low water-to-cement ratio reach the hydration degree of only 70–50%. Consequently, the presence of a large amount of unhydrated cement should result in excellent autogenous self-healing. The main aim of this study was to examine whether this commonly accepted hypothesis was correct. The study included tests performed on UHPC and mortars with a low water-to-cement ratio and high cement content. Additionally, aging effects were verified on 12-month-old UHPC samples. Analysis was conducted on the crack surfaces and inside of the cracks. The results strongly indicated that the formation of a dense microstructure and rapidly hydrating, freshly exposed anhydrous cement particles could significantly limit or even hinder the self-healing process. The availability of anhydrous cement appeared not to guarantee development of a highly effective healing process.

  • 16.
    Riede, M.
    et al.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Knoll, M.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Wilsnack, C.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Gruber, S.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Cubillo, A.A.
    RUAG Space Germany GmbH, Coswig,Germany.
    Melzer, C.
    RUAG Space Germany GmbH, Coswig,Germany.
    Brandão, A.
    European Space Research and Technology Centre-ESTEC, Noordwijk, Netherlands.
    Pambaguian, L.
    European Space Research and Technology Centre-ESTEC, Noordwijk, Netherlands.
    Seidel, A.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Lopez, E.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, Germany..
    Material characterization of AISI 316L flexure pivot bearings fabricated by additive manufacturing2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 15, artikkel-id 2426Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, additive manufacturing (AM) by laser metal deposition (LMD) has become a key technology for fabricating highly complex parts without any support structures. Compared to the well-known powder bed fusion process, LMD enhances manufacturing possibilities to overcome AM-specific challenges such as process inherent porosity, minor build rates, and limited part size. Moreover, the advantages aforementioned combined with conventional machining enable novel manufacturing approaches in various fields of applications. Within this contribution, the additive manufacturing of filigree flexure pivots using 316L-Si by means of LMD with powder is presented. Frictionless flexure pivot bearings are used in space mechanisms that require high reliability, accuracy, and technical cleanliness. As a contribution to part qualification, the manufacturing process, powder material, and fabricated specimens were investigated in a comprehensive manner. Due to its major impact on the process, the chemical powder composition was characterized in detail by energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectrometry (ICP-OES). Moreover, a profound characterization of the powder morphology and flowability was carried out using scanning electron microscopy (SEM) and novel rheological investigation techniques. Furthermore, quantitative image analysis, mechanical testing, laser scanning microscopy, and 3D shape measurement of manufactured specimens were conducted. As a result, the gained knowledge was applied for the AM-specific redesign of the flexure pivot. Finally, a qualified flexure pivot has been manufactured in a hybrid manner to subsequently ensure its long-term durability in a lifetime test bench.

  • 17.
    Sabzezari, Behrouz
    et al.
    Department of Mining Engineering, Tarbiat Modares University, Tehran, Iran.
    Javad Koleini, Seyed Mohammad
    Department of Mining Engineering, Tarbiat Modares University, Tehran, Iran.
    Ghassa, Sina
    School of Mining, College of Engineering, University of Tehran, Tehran, Iran.
    Shahbazi, Behzad
    Department of Mining Engineering, Tarbiat Modares University, Tehran, Iran.
    Chelgani, Saeed Chehreh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Microwave-Leaching of Copper Smelting Dust for Cu and Zn Extraction2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 11, artikkel-id 1822Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Industrial wastes may contain high concentrations of valuable metals. Extraction and recovery of these metals have several economic and environmental advantages. Various studies showed positive effects of microwaves as a pretreatment method before the leaching of minerals. However, there are empty rooms for exploring simultaneous microwave and leaching (microwave-leaching) of industrial waste material for the production of valuable metals. This investigation examined the microwave-leaching method to extract copper and zinc from a copper-smelter dust (CSD). The results of microwave-leaching mechanism were compared with conventional heating leaching based on kinetics modelling. The final Cu recovery in the conventional heating and microwave irradiation was 80.88% and 69.83%, respectively. Kinetic studies indicated that the leaching reactions follow diffusion across the product layer. Based on X-ray powder diffraction (XRD) analyses, during conventional experiments sulfate; components formed with high intensity as an ash layer which prevents reagent access to the solid surface and decreases the Cu dissolution. While the sulfate components did not detect in the microwave-leaching residuals which means that microwave irradiation helped to decrease the ash layer formation. Taking all mentioned results into consider it can be concluded that microwave-leaching can be considered as an efficient method for extraction of valuable metals from waste materials.

  • 18.
    Shakarova, Dilshod
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ojuva, Arto
    Stockholm University, Department of Materials and Environmental Chemistry.
    Bergström, Lennart Magnus
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Methylcellulose-directed synthesis of nanocrystalline zeolite NaA with high CO2 uptake2014Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 7, nr 8, s. 5507-5519Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Zeolite NaA nanocrystals with a narrow particle size distribution were prepared by template-free hydrothermal synthesis in thermo-reversible methylcellulose gels. The effects of the amount of methylcellulose, crystallization time and hydrothermal treatment temperature on the crystallinity and particle size distribution of the zeolite NaA nanocrystals were investigated. We found that the thermogelation of methylcellulose in the alkaline Na2O-SiO2-Al2O3-H2O system played an important role in controlling the particle size. The synthesized zeolite nanocrystals are highly crystalline, as demonstrated by X-ray diffraction (XRD), and scanning electron microscopy (SEM) shows that the nanocrystals can also display a well-defined facetted morphology. Gas adsorption studies on the synthesized nanocrystalline zeolite NaA showed that nanocrystals with a size of 100 nm displayed a high CO2 uptake capacity (4.9 mmol/g at 293 K at 100 kPa) and a relatively rapid uptake rate compared to commercially available, micron-sized particles. Low-cost nanosized zeolite adsorbents with a high and rapid uptake are important for large scale gas separation processes, e.g., carbon capture from flue gas.

  • 19.
    Tole, Ilda
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Habermehl-Cwirzen, Karin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Rajczakowska, Magdalena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Activation of a Raw Clay by Mechanochemical Process: Effects of Various Parameters on the Process Efficiency and Cementitious Properties2018Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 11, nr 10, artikkel-id 1860Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The efficiency of the mechanochemical activation (MCA) is influenced by various process parameters as well as by the properties of the treated material. The main objective of this research was to optimize the MCA process, gaining enhancement of the chemical reactivity of a Swedish raw clay, which is going to be used as an alkali-activated cementitious binder. The effects of the amount of water, the filling ratio, the rotation speed, and the grinding duration on the amorphization degree were evaluated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Generally, wet and dry processes showed an extensive amorphization of both kaolinite and muscovite minerals present in the studied clay. On the contrary, quartz was amorphized mainly by the wet grinding process. The efficiency of both dry and wet grinding processes was enhanced by the increased number of grinding media versus the amount of the activated material. However, longer processing times caused significant agglomeration while a higher rotational speed enhanced the amorphization. Preliminary tests have shown that alkali activation of the processed clays produced hardened samples. Furthermore, the increased amorphization corresponded to the increased compressive strength values.

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