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1.	Mahade, Satyapal, 1987-, et al. (author) Incorporation of graphene nano platelets in suspension plasma sprayed alumina coatings for improved tribological properties 2021 In: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 570 Journal article (peer-reviewed)abstract Graphene possesses high fracture toughness and excellent lubrication properties, which can be exploited to enhance tribological performance of coating systems utilized to combat wear. In this work, suspension plasma spray (SPS) process was employed to deposit a composite, graphene nano-platelets (GNP) incorporated alumina coating. For comparison, monolithic alumina was also deposited utilizing identical spray conditions. The as-deposited coatings were characterized in detail for their microstructure, porosity content, hardness, fracture toughness and phase composition. Raman analysis of the as-deposited composite coating confirmed retention of GNP. The composite coating also showed good microstructural integrity, comparable porosity, higher fracture toughness and similar alumina phase composition as the monolithic alumina coating. The as-deposited coatings were subjected to dry sliding wear tests. The GNP incorporated composite coating showed lower CoF and lower specific wear rate than the pure alumina coating. Additionally, the counter surface also showed a lower wear rate in case of the composite coating. Post-wear analysis performed by SEM/EDS showed differences in the coating wear track and in the ball wear track of monolithic and composite coatings. Furthermore, Raman analysis in the wear track of composite coating confirmed the presence of GNP. The micro-indentation and wear test results indicate that the presence of GNP in the composite coating aided in improving fracture toughness, lowering CoF and specific wear rate compared to the monolithic coating. Results from this work demonstrated retention of GNP in an SPS processed coating, which can be further exploited to design superior wear-resistant coatings.
2.	Lindberg, Siv M, et al. (author) A product semantic study of the influence of the sense of touch on the evaluation of wood-based materials 2013 In: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 52, s. 300-307 Journal article (peer-reviewed)abstract Based on product semantics, this study investigated how the tactile attributes of wood and wood-based composites are perceived and interpreted semantically. The wood-based samples included ash, birch, elm, oak, pine, OSB (oriented strand board), two wood pulp-reinforced polylactide composites, Comp A and B and one wood-fiber reinforced polypropene composite, Comp C. The subjects rated the samples by the descriptive words natural, exclusive, eco-. friendly, rough, inexpensive, reliable, warm, modern, snug and solid. The most significant differences between the samples were found for roughness and for the descriptors, reliable, natural and solid. A principal component analysis yielded three attributes based on the tactile perceptions: reliable, old-. fashioned and smooth. The solid wood pieces were perceived as natural and oak was perceived as being exclusive. The composite materials presented a greater variation in terms of perceived attributes than the wood specimens.
3.	Åkerfeldt, Maria, 1982, et al. (author) Textile piezoelectric sensors – melt spun bi-component poly(vinylidene fluoride) fibres with conductive cores and poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) coating as the outer electrode 2014 In: Fashion and Textiles. - : Springer Science and Business Media LLC. - 2198-0802. ; 1:1 Journal article (peer-reviewed)abstract The work presented here addresses the outer electroding of a fully textile piezoelectric strain sensor, consisting of bi-component fibre yarns of β-crystalline poly(vinylidene fluoride) (PVDF) sheath and conductive high density polyethylene (HDPE)/carbon black (CB) core as insertions in a woven textile, with conductive poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) coatings developed for textile applications. Two coatings, one with a polyurethane binder and one without, were compared for the application and evaluated as electrode material in piezoelectric testing, as well as tested for surface resistivity, tear strength, abrasion resistance and shear flexing. Both coatings served their function as the outer electrodes in the system and no difference in this regard was detected between them. Omission of the binder resulted in a surface resistivity one order of magnitude less, of 12.3 Ω/square, but the surface resistivity of these samples increased more upon abrasion than the samples coated with binder. The tear strength of the textile coated with binder decreased with one third compared to the uncoated substrate, whereas the tear strength of the coated textile without binder increased with the same amount. Surface resistivity measurements and scanning electron microscopy (SEM) images of the samples subjected to shear flexing showed that the coatings without the binder did not withstand this treatment, and that the samples with the binder managed this to a greater extent. In summary, both of the PEDOT:PSS coatings could be used as outer electrodes of the piezoelectric fibres, but inclusion of binder was found necessary for the durability of the coating.
4.	Grolig, Jan Gustav, 1986 (author) Coated Ferritic Stainless Steels as Interconnects in Solid Oxide Fuel Cells - Material Development and Electrical Properties 2015 Doctoral thesis (other academic/artistic)abstract Solid oxide fuel cells (SOFCs) are attracting increasing interest as devices with potentialuses in decentralized and clean electricity and heat production. Several challengeswith respect to materials have to be overcome to achieve efficiencies and life-spansthat are sufficient for long-term applications.An important element of an SOFC stack is the interconnect component, which connectstwo adjacent fuel cell elements. Interconnects, which are commonly composedof ferritic stainless steels, have to be corrosion-resistant, mechanically stable and costoptimized.This work aimed to investigate economic solutions for interconnect materials and tounderstand the underlying mechanisms of degradation and electrical conduction ofthese materials. Mainly two substrates, a commercially available steel (AISI 441) anda ferritic stainless steel that was optimized for an SOFC application (Sandvik SanergyHT) were combined with different barrier coatings and exposed to a cathode-sideatmosphere. A method was developed that allows for the electrical characterizationof promising material systems and model alloys, thereby facilitating a fundamentalunderstanding of the dominant electrical conduction processes linked to the oxidescales that grow on interconnects. The AISI 441 steel coated with reactive elementsand cobalt showed good corrosion and chromium evaporation profiles, while AISI 441coated with cerium and cobalt also had promising electrical properties. The SanergyHT steel was examined with coatings of copper and iron and copper and manganese,respectively. The corrosion and chromium evaporation profiles of Sanergy HT wereimproved by coating with copper and iron. The copper and iron-coated Sanergy HTshowed lower area specific resistance values than cobalt-coated Sanergy HT. Chromia,which is the main constituent of oxide scales, was synthesized using differentmethods. The electrical properties of chromia were found to be sensitive to not onlyimpurities, but also heat treatment. Finally the electrical properties of cobalt- andcobalt cerium-coated Sanergy HT steels were investigated. It was revealed that theaddition of cerium improved the conductivity of the interconnect by both slowingdown chromia growth and preventing the outward diffusion of iron into the spinel.
5.	Duan, Shanghong, 1992, et al. (author) Determination of transverse and shear moduli of single carbon fibres 2020 In: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 158C, s. 772-782 Journal article (peer-reviewed)abstract Carbon fibres are extensively used for their high specific mechanical properties. Exploiting their high axial stiffness and strength, they are employed to reinforce polymer matrix materials in advanced composites. However, carbon fibres are not isotropic. Data of the elastic properties in the other directions of the fibres are still largely unknown. Furthermore, standardised methods to characterise these properties are lacking. In the present work, we propose a methodology to determine the transverse and shear moduli of single carbon fibres. An experimental procedure is developed to fabricate high-quality, flat fibre cross-sections in both longitudinal and transverse directions using Focused Ion Beam, which gives full control of the specimen geometry. Indentation modulus on those surfaces are obtained using both Atomic Force Microscopy (AFM) and nanoindentation tests. Hysteresis was found to occur in the nanoindentation tests. The hysteresis response was due to nano-buckling and reversible shear deformation of the carbon crystals. For this reason, indentation tests using AFM is recommended. From the AFM indentation tests the transverse and shear moduli of three different carbon fibres (IMS65, T800 and M60J) are successfully determined.
6.	Johansen, Marcus, 1994, et al. (author) Mapping nitrogen heteroatoms in carbon fibres using atom probe tomography and photoelectron spectroscopy 2021 In: Carbon. - : Elsevier BV. - 0008-6223. ; 179, s. 20-27 Journal article (peer-reviewed)abstract Carbon fibres show great potential as multifunctional negative electrode for novel structural battery composites – a rechargeable electrochemical cell with structural function. The electrochemical performance of carbon materials can be enhanced with nitrogen heteroatoms, which conveniently are inherent in polyacrylonitrile (PAN)-based carbon fibres. However, it is not fully understood how the electrochemical performance is governed by microstructure and composition of the carbon fibres, particularly the distribution and chemical states of nitrogen heteroatoms. Here we reveal the atom-by-atom three-dimensional spatial distribution and the chemical states of nitrogen in three PAN-carbon fibre types (M60J, T800 and IMS65), using atom probe tomography (APT) and synchrotron hard X-ray photoelectron spectroscopy (HAXPES), and correlate the results to electrochemical performance. The findings pave the way for future tailoring of carbon fibre microstructure for multifunctional applications.
7.	Johansen, Marcus, 1994 (author) Microstructure of Carbon Fibres for Multifunctional Composites: 3D Distribution and Configuration of Atoms 2021 Licentiate thesis (other academic/artistic)abstract Lightweight energy storage is a must for increased driving range of electric vehicles. “Mass-less” energy storage can be achieved by directly storing energy in structural components. In such multifunctional devices called structural composite batteries, carbon fibres carry mechanical load and simultaneously act as negative battery electrode by hosting lithium ions in its microstructure. Little is known of how the microstructure of carbon fibres is optimised for multifunctionality, and deeper understanding of the configuration and the distribution of atoms in carbon fibres is needed. Here synchrotron hard X-ray photoelectron spectroscopy and atom probe tomography are used to reveal the chemical states and three-dimensional distribution of atoms in commercial carbon fibres. This thesis presents the first ever guide for how to perform atom probe tomography on carbon fibres, and the first ever three-dimensional atomic reconstruction of a carbon fibre. The results show that the chemical states and distribution of nitrogen heteroatoms in carbon fibres affect the electrochemical performance of the fibres. Carbon fibres performed electrochemically better with higher amount of nitrogen with pyridinic and pyrrolic configurations. Additionally, the nitrogen concentration varies throughout the carbon fibre, which may suggest that the electrochemical properties also vary throughout the carbon fibre. The knowledge provided by this thesis can lead to future carbon fibre designs with enhanced electrochemical performance for multifunctional applications.
8.	André, Alann, et al. (author) Finite element delamination study of a notched composite plate under flexural loads 2009 In: ICCM-17, 17th International Conference on Composite Materials, Edinburgh, UK. - London : IOM Communications. Conference paper (peer-reviewed)abstract The delamination process in notched composite plates under flexural loading has been investigated using finite element analysis. Cohesive elements implemented in the commercial finite element package ABAQUS have been used in the region around the drilled-hole, and positioned between layers where delamination was observed during experiments presented in an accompanying paper. The delamination initiation and subsequent propagation was studied between the layers at the tension side separately and simultaneously. For all FE models, the load displacement curve was in good agreement with the one from experiments. However, the amount of damage reported from the fractography study was more extensive than that predicted by the models. Finally, it was shown that the models with only one cohesive layer show significantly different results to that of the model with four cohesive layers in terms of size of the degradation area.
9.	André, Benny, et al. (author) Enhancing silver through embedding of fullerene like WS2 for sliding electrical contacts Other publication (other academic/artistic)
10.	André, Benny (author) Nanocomposites for Use in Sliding Electrical Contacts 2011 Doctoral thesis (other academic/artistic)abstract In this thesis nanocomposite materials for use in high performance electrical contacts are tested. Self mating silver as coatings on cupper substrates are the most used material combination in power connectors today. In this work two new concepts were tested. The first one was to change one of the mating surfaces to a hard thin coating and keep the other surface made of silver. Tested coatings were nanocomposites with hard carbides in a matrix of amorphous carbon. TiC/a-C and Ti-Ni-C/a-C were tested both electrically and tribologically. The total amount of carbon and the amount of carbon matrix was important, both for the electrical and the tribological properties. The Ti-Ni-C coating also showed that substituting Ti in TiC with the weak carbide former Ni changed the stability of the carbides. The substitution resulted in more a-C matrix and less C in the carbides. Thin coatings of nc-TiC/a-C and Ti-Ni-C/a-C showed high potential as material candidates for use in electrical contacts. The other tested concept was to modify the used silver instead of replacing it. This was done by embedding nanoparticles of solid lubricant IF-WS2 in the silver. The results from reciprocating sliding displayed low friction and high wear resistance. The modified silver surfaces lasted for 8000 strokes with a friction of about 0.3 while at the same time allowing for a low contact resistance. The results for surfaces of pure silver coating displayed a friction of 0.8-1.2 and that the silver was worn through already after 300 strokes. A new method to investigate inherent hardness and residual stress of thin coatings, on complex geometries or in small areas, was also developed. An ion beam was used to create stress free coating as free standing micro pillars. Hardness measured on the pillars and on as-deposited coating were then used to calculate the residual stress in the coatings.
11.	Cho, Sung-Woo, et al. (author) Injection-molded nanocomposites and materials based on wheat gluten 2011 In: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 48:1, s. 146-152 Journal article (peer-reviewed)abstract This is, to our knowledge, the first study of the injection molding of materials where wheat gluten (WG) is the main component. In addition to a plasticizer (glycerol), 5 wt.% natural montmorillonite clay was added. X-ray indicated intercalated clay and transmission electron microscopy indicated locally good clay platelet dispersion. Prior to feeding into the injection molder, the material was first compression molded into plates and pelletized. The filling of the circular mold via the central gate was characterized by a divergent flow yielding, in general, a stronger and stiffer material in the circumferential direction. It was observed that 20–30 wt.% glycerol yielded the best combination of processability and mechanical properties. The clay yielded improved processability, plate homogeneity and tensile stiffness. IR spectroscopy and protein solubility indicated that the injection molding process yielded a highly aggregated structure. The overall conclusion was that injection molding is a very promising method for producing WG objects.
12.	He, Wenxiao, 1985 (author) Biomimetic Formation of Calcium Phosphate Based Nanomaterials 2014 Doctoral thesis (other academic/artistic)abstract The intercellular material in bone is a nanocomposite of aligned “hard” inorganics—calcium phosphate (CaP) platelets embedded in the long-range ordered “soft” organic collagen matrix. This elaborate structural arrangement redeems the weaknesses of the individual components (being soft protein or brittle mineral) and gives bone its excellent mechanical properties for the protection and support of our bodies. The structural order and hierarchy in the soft matrix is organized via self-assembly of collagen molecules and is reinforced by intermolecular crosslinking. The subsequent growth of “hard” crystallites inside the “soft” matrix compartments, likely through the deposition of a transient amorphous calcium phosphate (ACP) phase, results in the interpenetrated composite structure.The aim of this thesis was to prepare synthetic mimetics of “hard” material (CaP) with well-defined nanostructures, soft organic matrices with long-range order and interpenetrated composites composing of the two. The work was inspired by the material deposition process in natural bone. Lyotropic liquid crystal (LC) phases self-assembled by block copolymers were used to mimic the structural order of the collagen matrix. Both the inorganic morphogenesis of CaP in LCs and the controlled crystallization of ACP were investigated. To explore ordered organic matrices, crosslinking of the LCs and the self-assembly of an amphiphilic peptide with designed sequence were performed. In addition, controlled mineralization within crosslinked LCs was examined for the formation of nanocomposites.ACP nanospheres, CaP nanowires and nanosheets were prepared from LCs via templated growth. The ACP nanospheres were capable of transforming into bone-like apatite by controlled aging in water and the prepared nanoparticles were shown to affect osteoblast gene expression. Dicalcium phosphate crystals (brushite and monetite) with structural hierarchy and distinct features were also grown in LCs through epitaxial overgrowth or a self-organization regime. Polymerized LCs were successfully prepared from a modified block copolymer (diacrylate derivative of Pluronic® F127), which served as a resilient matrix for the deposition of ACP nanospheres. A subsequent in situ crystallization of ACP into bone-like apatite resulted in mechanically stable composites retaining nanostructures that resembled that of natural bone. An amphiphilic peptide was designed using mainly natural amino acids and it was shown to self-assemble into distinct structures at different concentrations. Based upon the results presented in this thesis, nanomaterials with assorted structures can be further designed for bio-related applications.
13.	Johansen, Marcus, 1994 (author) Atoms in Lithiated Carbon Fibres 2023 Doctoral thesis (other academic/artistic)abstract Carbon fibres are key constituents of structural batteries, in which electrochemical energy storage and mechanical load bearing are merged in one multifunctional device. Here carbon fibres simultaneously act as structural reinforcement by carrying load and as battery electrode by hosting lithium (Li)-ions in its microstructure. However, conventional carbon fibres are not designed to be multifunctional. To enable carbon fibres with optimised multifunctional capabilities, a fundamental understanding of their microstructure, chemical information and interaction with Li is required. In this thesis, mass spectrometry and electron spectroscopy techniques are developed and used to elucidate the atomic distribution, configuration, and interaction in commercial carbon fibres used in structural batteries. Here the methodology of analysing Li in carbon fibres with atom probe tomography (APT) and Auger electron spectroscopy (AES) is demonstrated. Synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES) reveals that certain chemical states of N heteroatoms, pyridinic and pyrrolic, are connected to enhanced electrochemical performance of carbon fibres. AES shows that: Li distributes throughout the entire carbon fibre; the amount of trapped Li is higher and concentrated towards the centre of the fibre at increased discharge rates; Li is initially inserted in amorphous domains and with increased states of lithiation in crystalline domains; and Li plating can occur on individual fibres without spreading to adjacent fibres. APT on lithiated carbon fibres shows that: the distribution of Li is independent of the distribution of N heteroatoms; trapped Li is distributed uniformly in all domains; and Li agglomerates at elevated states of lithiation. The work presented in this thesis paves the way for analysis of carbon-based battery materials with APT and AES. Furthermore, the work unveils much of the interplay between carbon fibre and Li and deepens the understanding of the design parameters for tailoring multifunctional carbon fibres used in improved structural batteries.
14.	Lindberg, Siv M, et al. (author) Hierarchic design and material identity 2013 Conference paper (peer-reviewed)
15.	Nikas, Dimitrios, 1984, et al. (author) High temperature bi-axial low cycle fatigue behaviour of railway wheel steel 2019 In: ICMFF12 - 12TH INTERNATIONAL CONFERENCE ON MULTIAXIAL FATIGUE AND FRACTURE. - : EDP Sciences. - 2261-236X. ; 300 Conference paper (peer-reviewed)abstract One of the most important aspects in railway operation is the interaction between rail and wheel. Railway wheels are commonly made from medium carbon steels (similar to 0.55 wt.% C), heat treated to a near pearlitic microstructure with some 5-10% pro-eutectoid ferrite. During the operation of freight trains, where block brakes are used, high thermal loads are evolved because of recurring braking and occasional slippage. Thus the combination of mechanical and thermal loads leads to changes in the mechanical properties of the material. The focus of the current investigation is to evaluate the mechanical behaviour of wheel material (UIC ER7T) subjected to non-proportional biaxial fatigue loading, as this simulates the actual working conditions in a better way than uniaxial loading. Axial-torsional low cycle fatigue tests were performed at room temperature and elevated temperatures using thin walled specimens to study the cyclic stress-strain properties of this material. The results showed large influence of temperature on the ratcheting behaviour of the material. Biaxial non-proportional loading gave much higher strain hardening as compared to uniaxial loading. Hardening due to dynamic strain ageing can be seen in the biaxial tests at temperatures around 300 degrees C.
16.	Persson, Henrik, 1983, et al. (author) A simple way of improving graphite nanoplatelets (GNP) for their incorporation into a polymer matrix 2012 In: Express Polymer Letters. - : Department of Polymer Engineering, Scientific Society of Mechanical Engineering. - 1788-618X. ; 6:2, s. 142-147 Journal article (peer-reviewed)abstract A simple method of solvent exfoliation/refining of direct-graphite nanoplatelets for their better incorporation into a polymer matrix is presented. We demonstrate the method for polystyrene. The method relies on sonication in N-methyl-2-pyrrolidone solvent, with surfactant assistance. A small amount of polystyrene is added to the solvent in order to increase the viscosity, this enhancing the exfoliation process and resulting in formation of a polymeric layer on graphene for its better incorporation in the polymer matrix. Polystyrene-coated thin graphene stacks form a stable dispersion, while thicker graphite nanoplatelets settle out. Thus bulk separation of thin and thick graphene stacks takes place.The polystyrene-coated thin graphene stacks are studied using Transmission Electron Microscopy in two ways: (i) we calculate the number of graphene layers forming thin graphene stacks, and (ii) we employ Selected Area Diffraction to confirm our image analysis results by checking the intensity ratio (1100) and (2100) deflections in the diffraction patterns. Five layers is found to be the cut-off number, that is there are no stacks >5 layers, and 3 layer stacks are dominantly present. The average largest in-plane dimension is found to be approximately 2.5 mu m (reduction by 50%).
17.	Yao, Yiming, 1957, et al. (author) Microstructure of plasma sprayed Al2O3-3wt%TiO2 coating using freeze granulated powder 2016 In: Journal of Materials Science and Chemical Engineering. - : Scientific Research Publishing, Inc.. - 2327-6045 .- 2327-6053. ; 4:7, s. 8-14 Journal article (peer-reviewed)abstract This study is aiming at controlling the microstructure of plasma sprayed Al2O3-TiO2 composite coatings using freeze granulated powders. As sprayed and sintered Al2O3+3wt%TiO2 powders were air plasma spayed with industry process parameters and compared with a commercial powder. The resulting coatings were investigated with respect to powder flowability, porosity and microstructure of the granules. The results showed that microstructure and melting fraction in the coatings could be tailored with the freeze granulation process and heat treatment conditions.
18.	Gaska, Karolina, 1986, et al. (author) Gas Barrier, Thermal, Mechanical and Rheological Properties of Highly Aligned Graphene-LDPE Nanocomposites 2017 In: Polymers. - : MDPI AG. - 2073-4360. ; 9:7, s. 294- Journal article (peer-reviewed)abstract This contribution reports on properties of low-density polyethylene-based composites filled with different amounts of graphene nanoplatelets. The studied samples were prepared in the form of films by means of the precoating technique and single screw melt-extrusion, which yields a highly ordered arrangement of graphene flakes and results in a strong anisotropy of composites morphology. The performed tests of gas permeability reveal a drastic decrease of this property with increasing filler content. A clear correlation is found between permeability and free volume fraction in the material, the latter evaluated by means of positron annihilation spectroscopy. A strong anisotropy of the thermal conductivity is also achieved and the thermal conductivity along the extrusion direction for samples filled with 7.5 wt % of GnP (graphene nanoplatelets) reached 2.2 W/m·K. At the same time, when measured through a plane, a slight decrease of thermal conductivity is found. The use of GnP filler leads also to improvements of mechanical properties. The increase of Young’s modulus and tensile strength are reached as the composites become more brittle.
19.	Shaikh, Abdul Shaafi, 1989, et al. (author) On the effect of building platform material on laser-powder bed fusion of a Ni-base superalloy HAYNES® 282® 2023 In: European Journal of Materials. - : Informa UK Limited. - 2688-9277. ; 3:1 Journal article (peer-reviewed)abstract Additive manufacturing (AM) by laser powder bed fusion (LPBF) involves melting of layers of powder onto a substrate, called a building platform. Due to cost or convenience considerations, building platform materials rarely match the LPBF material, especially for high temperature materials. To ensure tolerances in component geometries, AM components are often stress-relieved/heat-treated while still attached to the building platform. It is therefore important to understand the effect of dissimilar building platform materials on the properties of the built-up material. These effects may be particularly important for high performance materials such as Ni-base superalloys used for critical applications in the aerospace and energy industries. To investigate this effect, samples of a Ni-base superalloy HAYNES® 282® were built onto a carbon steel building platform in several configurations. The samples were removed from the building platform after heat treatment and subjected to detailed composition analysis and microstructural characterization to investigate the effect of the building platform material on the properties of the additively manufactured part. Room temperature and high temperature tensile testing were used to characterize the material. Results showed no risk of large-scale chemical composition change, or mechanical property degradation of built-up material from on-platform heat treatment.
20.	Angseryd, Jenny, 1979, et al. (author) Nanostructure of a cubic BN cutting tool material 2015 In: International Journal of Refractory Metals and Hard Materials. - : Elsevier BV. - 0263-4368 .- 2213-3917. ; 49:1, s. 283-287 Journal article (peer-reviewed)abstract Advanced microscopy techniques, laser assisted atom probe tomography and electron energy loss spectroscopy in transmission electron microscopy are used to investigate in detail the microstructure of a polycrystalline cubic boron nitride tool material. During sintering at high pressure superhard cubic boron nitride combines with hard ceramic Ti(C,N) to form a dense material. Diffusion in Ti(C,N) and reactions between Ti(C,N), cBN and additives result in the formation of several nitride, oxide and boride phases in a complex mixed microcrystalline and nano- crystalline microstructure.
21.	Forsgren, Lilian, 1990 (author) Processing and properties of thermoplastic composites containing cellulose nanocrystals or wood-based cellulose fibres 2020 Doctoral thesis (other academic/artistic)abstract Cellulose nanocrystals (CNC) were surface modified with dialkylamines to increase the compatibility between the CNC and the polymeric matrix, and promising results were obtained, with a 300 % stiffness increase when the mixed dispersion was compression moulded on a laboratory scale. The manufacturing process was up-scaled using water-assisted mixing in a twin-screw extruder (TSE) followed by a second compounding step and injection moulding (IM). The composites were successfully produced using conventional melt-processing techniques but these did not show the same improvement in mechanical performance, probably due to the formation of CNC aggregates. There were indications of network formation when CNC was added, especially in the case of surface-modified CNC. Cellulose fibres and thermomechanical pulp were used as reinforcement in similar types of polymer matrices and the mixtures were similarly processed by TSE and IM. These materials were characterized with regard to appearance and durability. The discoloration of the composites due to excessive heat during processing did not significantly affect their mechanical properties, and the addition of the cellulose-based reinforcement to the polymer did not reduce its resistance to thermo-oxidative degradation compared to that of the pure matrix. In fact, the resistance to degradation was increased when lignin was present in the reinforcing element, showing a synergistic effect together with the added anti-oxidant. Superior properties were expected for the CNC composites compared to those of the larger cellulose fibre reinforcements, but in continuous production the stiffening effects were similar regardless of reinforcement type. These results confirm that the processing method and properties strongly affect the final properties of the composite.
22.	Mellin, Pelle, 1985-, et al. (author) Nano-sized by-products from metal 3D printing, composite manufacturing and fabric production 2016 In: Journal of Cleaner Production. - Sweden : Elsevier. - 0959-6526 .- 1879-1786. ; 139, s. 1224-1233 Journal article (peer-reviewed)abstract Recently, the health and environmental perspective of nano-materials has gained attention. Most previous work focused on Engineered Nanoparticles (ENP). This paper examines some recently introduced production routes in terms of generated nano-sized by-products. A discussion on the hazards of emitting such particles and fibers is included. Fine by-products were found in recycled metal powder after 3D printing by Selective Laser Melting (SLM). The process somehow generated small round metal particles (~1e2 mm) that are possibly carcinogenic and respirable, but not small enough to enter by skin-absorption. With preventive measures like closed handling and masks, any health related effects can be prevented. The composite manufacturing in particular generated ceramic and carbonaceous particles that are very small and respirable but do not appear to be intrinsically toxic. The smallest features in agglomerates were about 30 nm. Small particles and fibers that were not attached in agglomerates were found in a wide range of sizes, from 1 μm and upwards. Preventive measures like closed handling and masks are strongly recommended. In contrast, the more traditional production route of fabric production is investigated. Here, brushing residue and recycled wool from fabric production contained few nano-sized by-products.
23.	Muneer, Faraz, et al. (author) Preparation, Properties, Protein Cross-Linking and Biodegradability of Plasticizer-Solvent Free Hemp Fibre Reinforced Wheat Gluten, Glutenin, and Gliadin Composites 2014 In: BioResources. - : BioResources. - 1930-2126. ; 9:3, s. 5246-5261 Journal article (peer-reviewed)abstract The present study is aimed at evaluating the use of plant-based polymers and fibres for the production of sustainable biocomposites. For the first time, plasticiser/solvent-free hemp fibre-reinforced wheat gluten and hemp-gliadin and glutenin composites were obtained by compression moulding at different temperatures. The plasticiser/solvent-free sample preparation method developed in this study facilitated the use of a powdered protein matrix with a mat of randomly oriented hemp fibres. The tensile and protein cross-linking properties, as well as the biodegradability, were investigated. The addition of hemp fibre to the protein matrix increased the E-modulus by 20 to 60% at 130 degrees C. An increase in moulding temperature from 110 to 130 degrees C resulted in an increase in maximum stress due to the formation of intermolecular bonds between protein chains. The gliadin composites had higher E-modulus and maximum stress and showed a larger increase in protein polymerisation with increased temperature compared to the gluten in composites. A comparison of tensile properties revealed that the composites were stiffer and stronger compared to several similarly produced biobased composites. The composites were found to be fully biodegradable under a simulated soil environment after 180 days. Biocomposites produced in the present study were found to be environmentally friendly with fairly good mechanical properties.
24.	Zhang, Hanzhu, 1991-, et al. (author) A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite 2019 In: Dalton Transactions. - : Royal Society of Medicine Press. - 1477-9226 .- 1477-9234. ; 48:16, s. 5161-5167 Journal article (peer-reviewed)abstract A multicomponent composite of refractory carbides, B4C, HfC, Mo2C, TaC, TiC and SiC, of rhombohedral, face-centered cubic (FCC) and hexagonal crystal structures is reported to form a single phase B4(HfMo2TaTi)C ceramic with SiC. The independent diffusion of the metal and nonmetal atoms led to a unique hexagonal lattice structure of the B4(HfMo2TaTi)C ceramic with alternating layers of metal atoms and C/B atoms. In addition, the classical differences in the crystal structures and lattice parameters among the utilized carbides were overcome. Electron microscopy, X-ray diffraction and calculations using density functional theory (DFT) confirmed the formation of a single phase B4(HfMo2TaTi)C ceramic with a hexagonal close-packed (HCP) crystal structure. The DFT based crystal structure prediction suggests that the metal atoms of Hf, Mo, Ta and Ti are distributed on the (0001) plane in the HCP lattice, while the carbon/boron atoms form hexagonal 2D grids on the (0002) plane in the HCP unit cell. The nanoindentation of the high-entropy phase showed hardness values of 35 GPa compared to the theoretical hardness value estimated based on the rule of mixtures (23 GPa). The higher hardness was contributed by the solid solution strengthening effect in the multicomponent hexagonal structure. The addition of SiC as the secondary phase in the sintered material tailored the microstructure of the composite and offered oxidation resistance to the high-entropy ceramic composite at high temperatures.
25.	Hosseini, Seyedehsan, 1994 (author) Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites 2023 Doctoral thesis (other academic/artistic)abstract Efforts to address environmental concerns have resulted in new regulations designed to plan the reduction of plastic and synthetic polymer usage, necessitating the search for sustainable natural alternatives with comparable cost-effectiveness and mechanical performance. Thermomechanical pulp (TMP) fibres are one of the most affordable natural fibres that have no chemical refining in production, production have a high yield of 90-98% and TMP fibres have been demonstrated to improve the mechanical characteristics (strength, stiffness and toughness) of wood-polymer composites (WPCs) compared to the pure polymer. The integration of TMP fibres with non-polar synthetic polymers remains a challenge due to surface polarity differences. This PhD thesis aims to ease the processing of TMP fibre composites through the incorporation of additives. The hypothesis posits that incorporating magnesium stearate (MgSt), molybdenum disulfide (MoS2) and alkyl ketene dimer (AKD) as additives in TMP composites will enhance interfacial properties, resulting in improved processability and flow behaviour at high temperatures. MoS2 is known for its interaction with lignin, which exists in TMP and MgSt is recognised for its ability to improve flow in pharmaceutical processing when combined with cellulose, also a component of TMP. AKD modifies the hydrophilic properties of lignocellulosic surfaces. The experimental work explores the effect of these additives on the properties of TMP composites of ethylene acrylic acid copolymer (EAA) and polypropylene (PP) matrices. The dynamic mechanical analysis (DMA) and mechanical analysis results reveal that MoS2 exhibits superior interaction with TMP fibres, yielding enhanced interfacial properties compared to MgSt in between EAA and TMP fibres. Rheological studies elucidate the transition from a fluid-like state to a network-like structure upon the incorporation of TMP into the PP matrix. The incorporation of AKD with C18 reduces the viscosity of TMP-PP composites and PP itself, and, as determined through theoretical Hansen solubility parameter (HSP) calculations, increases compatibility between cellulose in TMP fibres and PP. The addition of AKD influences both the colour (lighter) and shape (smoother surface) of the extrudate filaments in the TMP-PP composites, indicative of improved processing. In addition, frictional analysis demonstrates the reduction of the coefficient of friction (COF) between metal and TMP fibre by MgSt and AKD treatments.
26.	Ahlström, Johan, 1969, et al. (author) Effect of strain gradient on the microstructure and mechanical properties of pearlitic steel 2019 In: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 580:1 Conference paper (peer-reviewed)abstract Pearlitic steels, with a combination of good strength and wear properties, are commonly used for railway rails. The passage of trains creates large shear strain gradients in the surface layer of rails. Knowledge of the microstructural evolution and material properties as related to the shear strain in this layer is therefore important for prediction both of crack evolution and fatigue life. A bi-axial torsion-compression machine was used to deform fully pearlitic R260 rail steel test bars to create a similar gradient structure. Uniaxial tension and compression tests were performed on these pre-deformed test bars to evaluate the mechanical properties of the material. The local microstructural parameters, such as thickness of the ferrite and cementite lamellae, the dislocation density in the ferrite lamellae, the interlamellar spacing and eth local hardness at different places across the diameter of the bars, as well as microstructural evolution across the radius, were characterized. An attempt to set up a correlation between the local microstructural parameters, hardness and the macro mechanical properties is made and discussed in the present study.
27.	Anagnostopoulos, George, et al. (author) Strain Engineering in Highly Wrinkled CVD Graphene/Epoxy Systems 2018 In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 10:49, s. 43192-43202 Journal article (peer-reviewed)abstract Chemical vapor deposition (CVD) is regarded as a promising fabrication method for the automated, large-scale, production of graphene and other two-dimensional materials. However, its full commercial exploitation is limited by the presence of structural imperfections such as folds, wrinkles, and even cracks that downgrade its physical and mechanical properties. For example, as shown here by means of Raman spectroscopy, the stress transfer from an epoxy matrix to CVD graphene is on average 30% of that of exfoliated monolayer graphene of over 10 μm in dimensions. However, in terms of electrical response, the situation is reversed; the resistance has been found here to decrease by the imposition of mechanical deformation possibly due to the opening up of the structure and the associated increase of electron mobility. This finding paves the way for employing CVD graphene/epoxy composites or coatings as conductive "networks" or bridges in cases for which the conductivity needs to be increased or at least retained when the system is under deformation. The tuning/control of such systems and their operative limitations are discussed here.
28.	Andersson, Johanna, 1984 (author) Surface tension-driven flow in soft porous materials — An investigation of the mechanism of capillary flow in microchannels of hydrogels 2018 Doctoral thesis (other academic/artistic)abstract Spontaneous spreading of liquids in porous materials is of great industrial relevance and occurs in, for example, diapers, fabrics, paper or paint. Often, it is necessary to manipulate the spreading rate of liquids to result in the desired mass transport, for example to soak up large liquid volumes, as in a diaper. To do this, it is necessary to know the precise mechanism of surface tension driven flow. However, the process is complex and so are the porous materials in terms of both chemical composition and geometry. The mathematical and physical description of the process is often limited to specific cases – for example, the well-known Lucas-Washburn equation describes the speed of a meniscus in capillaries with circular cross-section in a hard material without interconnections. The objective of this thesis is to deepen the understanding of the mechanism with which a liquid spreads in a soft porous material only driven by surface tension. To this end, the liquid dynamics of water and water-based liquids were investigated in various model systems which are similar to porous 3D materials. In an alginate gel, capillaries with circular cross-sections were produced and the spreading rate of water was determined and compared to existing models. Using a method, which involves 3D printing, it was possible to fabricate open channels with rectangular cross-sections in the same alginate gel. The liquid spreading in these channels in geometries of branched channel systems was investigated. The results revealed that the spreading rate in capillaries of circular cross-sections in soft materials was much slower than that anticipated in existing models, which describe hard materials. In open channels of rectangular cross-sections, the presence of side channels slowed down the meniscus in the main channel; the meniscus stopped when it encountered junctions. The stop duration was longer when the side channels were longer, when they were wider, and when their tilting angle was low with respect to the main channel. An analysis of the volume flow indicated that those geometries that had long side channels but are few in number, resulted in faster volume flow. In a porous 3D material, this suggests that the interconnectivity could decrease the volume flow rate. Finally, a calcium alginate gel with straight-aligned pores was produced and characterised as an example of optimal liquid transport. The outcome of this thesis can be used to adjust the geometrical design of porous materials to result in desired liquid transport properties. The stiffness of the material may influence the liquid transport. The thesis also contributes to the discussion on how the liquid takes selective pathways in porous materials.
29.	Anilkumar, V., et al. (author) Impact of heat treatment analysis on the wear behaviour of al-14.2si-0.3mg-tic composite using response surface methodology 2021 In: Tribology in Industry. - : Faculty of Engineering, University of Kragujevac. - 0354-8996 .- 2217-7965. ; 43:4, s. 590-602 Journal article (peer-reviewed)abstract Al-14.2Si-0.3Mg Alloy reinforced with hard phased TiC coarse particulates (10 wt-%) was contrived using the liquid metallurgy route. The so fabricated aluminium metal matrix composites was made to undergo solutionising at 5250C for 12 hours in a heat treatment furnace and was subsequently water quenched to room temperature. The developed composite was then kept for age hardening at varying temperatures and time for enhanced tribological properties. A pin on disc Tribometer (ASTM-G99) was utilised to study the wear properties of the fabricated composite. Aging temperature (0C), applied load (N) and Aging time (hours) were chosen as the process parameters for analysing the material's resistance to wear. Using response surface methodology the influence of reinforcement in the wear properties of the composite was studied. The design of the regression equation was prepared and the impact of each experimental parameter was scrutinized. Results depict that with an increase in the aging temperature, aging time and load, there observed a variation in the materials wear properties. The worn-out surface of the metal matrix composite was then investigated with the help of the Scanning Electron Microscope (SEM).
30.	Bohlén, Martin, 1978 (author) Computational studies of Poly(vinylidene fluoride) and Poly(vinylidene fluoride) - Single Wall Carbon Nanotube Composites 2012 Licentiate thesis (other academic/artistic)abstract Poly(vinylidene fluoride) (PVDF) exhibits properties that allows the material to be used in such diverse areas as wire and cable products, electronic devices, membranes, exterior coatings for constructions and in the chemical, pharmaceutical and food industry as fluid-handling equipment. It is the inherent molecular structure of PVDF, where every second backbone carbon is bonded to two fluorine atoms, that gives the polymer several unique properties, among them piezo- and pyroelectricity. However, to obtain a material with a high piezoelectric activity, the amount of the crystal phase with the largest polarization, the β crystal phase, has to be large. Possibly, this could be achieved by the addition of different types of additives, carbon nanotubes (CNTs) being one of them. In this study, molecular modeling of PVDF and PVDF-single wall carbon nanotubes (SWCNTs) composites has been performed. Also, the molecular structure of PVDF around and above the melting point has been investigated using both computational and experimental techniques. The results obtained from first principles, molecular mechanics (MM) and molecular dynamics (MD) studies indicate that PVDF molecules have a larger affinity to be in the all-trans structure similar to the polar β-phase at temperatures above the melting point. However, when melt or solution cast the main PVDF crystal phase obtained is the non-polar α-phase. A prevention of this phase transformation from β to α during crystallization could yield a material with a strong piezoelectric effect. Furthermore, MM and MD studies of the mechanical properties of PVDF and PVDF-SWCNT nanocomposites showed that the reinforcing effect of SWCNTs on PVDF is dependent on the alignment of the SWCNTs. When aligned in the direction of applied stress, an increase of the Young’s modulus of about 1 GPa could be observed. A simulation of a pullout of a SWCNT from a PVDF matrix revealed that the interfacial shear stress is in the same range as other polymer-SWCNT systems and that this interface possibly can be strengthened by functionalization of the pristine carbon nanotubes.
31.	Bueno, Moises, et al. (author) Modification of asphalt mixtures for cold regions using microencapsulated phase change materials 2019 In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 9:1 Journal article (peer-reviewed)abstract Phase change materials (PCMs) may be used to regulate the temperature of road surfaces to avoid low-temperature damages when asphalt materials become brittle and prone to cracking. With this in mind, different asphalt mixtures were modified with microencapsulated phase change materials (i.e. tetradecane) to assess their thermal benefits during the phase change process. Likewise, the effect on the mechanical performance of PCMs as a replacement of mineral filler was assessed. Special attention was paid to dry and wet modification processes for incorporating the PCMs into the mixtures. The results showed that PCM modifications are indeed able to slow down cooling and affect temperatures below zero. Approximately, a maximum of 2.5 °C offset was achieved under the tested cooling conditions compared to the unmodified reference specimens. Regarding the mechanical response at 0 °C and 10 °C, the results indicated that the PCM modification significantly reduces the stiffness of the material in comparison with the values obtained for the reference mixture.
32.	Cantatore, Valentina, 1986, et al. (author) Towards multifunctional coating in the boron-doped graphene/copper system 2017 In: Carbon. - : Elsevier BV. - 0008-6223. ; 115, s. 375-379 Journal article (peer-reviewed)abstract A route to achieve multi-functional graphene coating is explored. Chemical bonding between copper substrate and coating results if the graphene is a priori boron doped. After pair-wise binding of boron sites to the Cu(111) surface, co-existence of pseudo-gap property in the graphene subsystem and a metallic density of states in the Cu subsystem at the common Fermi energy emerges. Apparently a paradox is that the two subsystems preserve and even recover their individual integrities upon formation of surface chemical bonds. Sensor capabilities are inferred. Employing pyridine as test molecule, conditioned ability of a nucleophile to offer competitive dative bonding, with the sub-strate, for boron sites is demonstrated. It is shown to occur for the case of half coverage and for adsorption to boron atoms originally bound to the on-top site on Cu(111). The ability of complementary boron sites to compensate for loss of binding between on-top site and boron, resulting from said bonding to the incoming nucleophile, is emphasized. Multifunctional substrate-coating system for catalysis as well as enhanced sensitization is inferred.
33.	Goel, Sneha, 1993-, et al. (author) Residual stress determination by neutron diffraction in powder bed fusion-built Alloy 718: Influence of process parameters and post-treatment 2020 In: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 195 Journal article (peer-reviewed)abstract Alloy 718 is a nickel-based superalloy that is widely used as a structural material for high-temperature applications. One concern that arises when Alloy 718 is manufactured using powder bed fusion (PBF) is that residual stresses appear due to the high thermal gradients. These residual stresses can be detrimental as they can degrade mechanical properties and distort components. In this work, residual stresses in PBF built Alloy 718, using both electron and laser energy sources, were measured by neutron diffraction. The effects of process parameters and thermal post-treatments were studied. The results show that thermal post-treatments effectively reduce the residual stresses present in the material. Moreover, the material built with laser based PBF showed a higher residual stress compared to the material built with electron-beam based PBF. The scanning strategy with the lower amount of residual stresses in case of laser based PBF was the chessboard strategy compared to the bi-directional raster strategy. In addition, the influence of measured and calculated lattice spacing (d0) on the evaluated residual stresses was investigated.
34.	Hammarström, Thomas, 1974 (author) Differences in partial discharge characteristics due to increased conductivity of the insulation material 2018 In: Proceedings of the IEEE International Conference on Properties and Applications of Dielectric Materials. - 2160-9241. ; 2018-May, s. 148-151 Conference paper (peer-reviewed)abstract This paper presents what influence the choice of PWM level and rise time has on the PD characteristics for two similar wire specimens insulated by different materials and exposed to short rise time voltage waveforms. The test objects were twisted pairs insulated by either polyamide-imid material (PAI) or the more conductive Cr 2 O 3 insulation. Here these test objects were fed from either two-, three-, four or five level inverter waveforms of similar type as used in actual applications. Observations are made on the importance of the voltage rise time, the size of the voltage step in relation to the extinction voltages (PDEV) and other observables. To compare the performances, measurements of the PD characteristics were conducted. Specifically, the total number of PDs and their average maximum amplitude per cycle were obtained together with the PRPDA pattern. Previous research suggests that the Cr 2 O 3 insulation shows improved degradation properties compared to conventional insulations for sinusoidal waveforms however less difference was observed when exposed to square and PWM waveforms. The experimental results presented in this work showed that the total summed PD magnitude (exposure) drops considerably already when applying a three or higher level inverter for both materials however the PD magnitude remains about the same for both materials tested. Thus to experience the expected advantages with the more conductive insulation a higher level than three appears required. Although in comparison both four and five levels show little influence in number of PDs, the maximum magnitude per cycle is reduced however for both insulation materials. The reduction is however more significant for the Cr 2 O 3 insulation. Initial studies suggest that the higher PWM level results in a reduction of the overvoltage level which helps reducing the PD amplitude. As the choice of material influences this phenomenon, the implications is that the advantages with an increased conductivity appears more significant at the higher PWM levels.
35.	Kahlin, Magnus (author) Fatigue Performance of Additive Manufactured Ti6Al4V in Aerospace Applications 2017 Licentiate thesis (other academic/artistic)abstract Additive Manufacturing (AM) for metals includes is a group of production methodst hat use a layer-by-layer approach to directly manufacture final parts. In recent years, the production rate and material quality of additive manufactured materials have improved rapidly which has gained increased interest from the industry to use AM not only for prototyping, but for serial production. AM offers a greater design freedom, compared to conventional production methods, which allows for parts with new innovative design. This is very attractive to the aerospace industry, in which parts could be designed to have reduced weight and improved performance contributing to reduced fuel consumption, increased payload and extended flight range. There are, however, challenges yet to solve before the potential of AM could be fully utilized in aerospace applications. One of the major challenges is how to deal with the poor fatigue behaviour of AM material with rough as-built surface.The aim of this thesis is to increase the knowledge of how AM can be used for high performance industrial parts by investigating the fatigue behaviour of the titanium alloy Ti6Al4V produced with different AM processes. Foremost, the intention is to improve the understanding of how rough as-built AM surfaces in combination with AM built geometrical notches affects the fatigue properties.This was done by performing constant amplitude fatigue testing to compare different combinations of AM material produced by Electron Beam Melting(EBM) and Laser Sintering (LS) with machined or rough as-built surfaces with or without geometrical notches and Hot Isostatic Pressing (HIP) treatment. Furthermore, the material response can be different between constant amplitude and variable amplitude fatigue loading due to effects of overloads and local plastic deformations. The results from constant amplitude testing were used to predict the fatigue life for variable amplitude loading by cumulative damage approach and these predictions were then verified by experimental variable amplitude testing.The constant amplitude fatigue strength of material with rough as-built surfaces was found to be 65-75 % lower, compared to conventional wrought bar, in which HIP treatments had neglectable influence on the fatigue strength. Furthermore, the fatigue life predictions with cumulative damage calculations showed good agreement with the experimental results which indicates that a cumulative damage approach can be used, at least for a tensile dominated load sequences, to predict the fatigue behaviour of additive manufactured Ti6Al4V.
36.	Khalilitehrani, Mohammad, 1984, et al. (author) The morphology of the deposited particles after a wet agglomerate normal surface impact 2019 In: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 345, s. 796-803 Journal article (peer-reviewed)abstract Through discrete element modeling, we investigate the breakage, deposition and attachment of wet dust agglomerates during normal surface impacts. The morphology and structure of the deposited dirt layer is studied through statistical analysis of the height profiles. It is found that the deposited layer is influenced by both the structural properties of the primary agglomerates and the impact conditions. The roughness of the deposited dirt layer shows a positive correlation to impact velocity and a negative correlation to the agglomerate moisture content. Within the pendular liquid regime the structural strength of the agglomerates shows a strong correlation to the moisture content while at higher moisture content the correlation becomes weaker. It is also observed that for a given impact velocity agglomerates of various sizes show similar deposition patterns. To unify the results for different agglomerate sizes, a dimensionless surface density is introduced.
37.	Kuzmenko, Volodymyr, 1987, et al. (author) FREESTANDING CARBON NANOFIBERS/GRAPHENE COMPOSITE ELECTRODES FOR SUPERCAPACITORS 2016 In: The World Conference on Carbon - Carbon 2016, July 10-15, State College, PA, USA. Conference paper (peer-reviewed)
38.	Kuzmenko, Volodymyr, 1987, et al. (author) Sustainable carbon nanofibers/nanotubes composites from cellulose as electrodes for supercapacitors 2015 In: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 90:2, s. 1490-1496 Journal article (peer-reviewed)abstract Supercapacitors are efficient energy storage devices with long lifetime and safe service. Their effectiveness,to a big extent, is dependent on electrode materials used for accumulation of energy in form ofelectrostatic charges. Over the last decades, variety of carbonaceous electrode materials has been used insupercapacitors. Mostly the production of such electrodes is still oriented on unsustainable fossil fuels asprecursors instead of sustainable renewable resources. In this study, freestanding carbonaceous electrodematerials for supercapacitors were derived from cellulose, the most abundant renewable resource. Theywere synthesized via carbonization of fibrillar cellulose impregnated with CNTs (carbon nanotubes). Theensuing composite materials consisted of a CNF (carbon nanofiber) scaffold (fiber diameter in the rangeof 50-250 nm) covered with layers of CNTs (tube diameter in the range of 1-20 nm). Moreover, thesecomposites were tested as electrode materials for supercapacitors. Incorporation of the CNTs into theCNFs improved electrical conductivity and also increased the surface area of the produced compositematerials, which led to high specific capacitance values (up to 241 F/g), cyclic stability, and powerdensity of these materials in electrochemical measurements. These results suggest that cellulose-derivedoriginal CNF/CNT composites are sustainable and efficient carbonaceous electrodes for supercapacitors.
39.	Larsson, Ragnar, 1960, et al. (author) Carbon-fibre composites with graphene filler for enhanced properties 2019 In: Proceedings of XVIII Brazil MRS Meeting. - 9788563273406 ; , s. 558- Conference paper (peer-reviewed)abstract Carbon fibre reinforced polymer (CFRP) is often used in applications where lightweight design is essential. The material however suffers from inherent drawbacks such as high brittleness, low electrical conductivity. This Swedish-Brazilian collaboration combines experimental studies with modelling and simulation to investigate the improvement of the CFRP material properties after addition of graphene. Graphene exhibits excellent electrical and thermal conductivity, barrier properties, unique strength which makes it an optimal additive. In this industrial-driven project, the electrical percolation threshold is studied and the strength of the reinforced polymer around the threshold value is investigated. The improvement is dependent on dispersion techniques and the grade of exfoliation of graphene. This has been shown both experimentally and from the modeling.
40.	Liu, Jun, et al. (author) Investigation of using limestone calcined clay cement (LC3) in engineered cementitious composites: The effect of propylene fibers and the curing system 2021 In: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 15, s. 2117-2144 Journal article (peer-reviewed)abstract Limestone calcined clay cement (LC3) is a new type of low-carbon cement that can reduce energy consumption and carbon dioxide emissions while meeting the performance requirements of ordinary cement. In this study, polypropylene (PP) fibers were mixed into limestone calcined clay cement-based materials to make new low-carbon ECCs. In this study, a total of 24 sets of specimens were designed for 4 groups of curing ages and 6 types of mix ratios. The compressive load–displacement data were measured the compressive curve characteristics were analyzed then, a compressive constitutive model of the composites was deduced and obtained. Through XRD, SEM-EDS and MIP experiments, the reasons and laws of the compressive strength ranges of adding PP fibers and LC3 to engineered cementitious composites (LC3-PP-ECCs) are further explained from the perspective of the pore size, microstructures and hydration products. The results show that, after 28 days, the compressive strength values of LC3-PP-ECCs generally decreases with increasing PP fiber content and the combined effect of PP fibers and hydration products causes the compressive strength of LC3-ECCs with 0.5% PP fibers to drop sharply. In addition, the specimens showed better properties in terms of toughness, ductility and energy absorption. However, in the microstructures, the addition of PP fibers will cause more internal defects and flaws. This results of this study can provide some theoretical experience and technical support for the engineering application of LC3-ECCs.
41.	Manai, Asma, 1990, et al. (author) A methodology for assessment and retrofitting by TIG dressing of existing pre-fatigued welded steel joints 2021 In: Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations - Proceedings of the 10th International Conference on Bridge Maintenaince, Safety and Management, IABMAS 2020. - : CRC Press. ; , s. 592-597 Conference paper (peer-reviewed)abstract Several fatigue life extension methods of a welded structure are coveted in the industry such as Tungsten-Inert-Gas Dressing (TIG dressing). This paper presents a framework for a fatigue assessment and retrofitting of welded structures by TIG dressing. The proposed framework provides in detail the parameters that have an influence on fatigue life which can be divided into two groups, the first is related to the structure prior to treatment such (e.g: crack dimension, toe radius, and residual stresses) while the second is related to the state of the structure following the treatment (e.g: treatment depth, residual stresses and resulted toe radius). Experimental results, from the current work, were complemented with tests from literature to verify the proposed framework. An analysis between our predictions and reported values of fatigue life from literature show an absolute error of 20%.
42.	Talebi, Nasrin, 1992, et al. (author) CRACK INITIATION CRITERIA FOR DEFORMED ANISOTROPIC R260 RAIL STEEL 2022 In: CM 2022 - 12th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Conference Proceedings. ; , s. 857-864 Conference paper (peer-reviewed)abstract Rail material selection and maintenance planning require accurate material failure criteria. While many of these criteria consider low-cycle fatigue of virgin materials, rail failure is known to occur after severe plastic deformations. It is, therefore, relevant to consider the applicability of such criteria during large plastic deformations. In this study, we simulate previously performed high-shear tension-torsion experiments using finite strain theory to evaluate the local stresses and strains. Based on these results, failure criteria are calibrated and validated. The Jiang-Sehitoglu criterion accurately fits and predicts failure. However, the identified parameter values are different from literature values for similar materials.
43.	Vega, Alberto, 1984, et al. (author) Degradation mechanisms in PUR foam of district heating pipes after accelerated ageing 2017 Conference paper (other academic/artistic)abstract Modern societies demand the use of non-fossil and sustainable energy resources. In this sense, district heating (DH) systems have been playing an important role in the last years. However, some questions still remains unanswered such as technical life time prediction, heat losses challenge or status assessment. These questions are the driving force of DH system development, especially for the DH pipe manufacturers. Pre-insulated heating pipes include a HDPE jacket, rigid polyurethane (PUR) foam and steel service pipe, and are used to transport the heat from a central point out to the customers and then back again for reuse. These pipes must withstand axial mechanical loads and have good long-term thermal properties. Therefore, it is important to have reliable methods to evaluate the current status of a DH system at any time. The main aim of the project is to determine the degradation mechanisms during natural and accelerated aging of DH pipes. In this project, the pipes have been aged using an accelerated thermal ageing and both mechanical and thermal properties were investigated. Mechanical property was evaluated using the SP plug method, which determined the remaining adhesion force between the PUR and the steel service pipe [1]. This method has also been designed for application in field for a quick status check. At the same time, the thermal property has also been measured in real-time using a transient plane source (TPS) technique instead of a steady-state method [2]. Characterization of the PUR material has been performed using a three-point flexural test, Fourier transform infra-red spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) analysis [3]. Preliminary results suggest three different phases where the degradation of DH pipes is a combination of physical and chemical phenomena. In the early aging period, the changes in both mechanical and thermal properties are caused by physical effects. After that, an upturn is observed due to changes in the PUR chemical structure observed in the FTIR analysis. Finally, the chemical degradation takes over which is an effect of thermo-oxidation. At the end a better model comprising all three phases for the entire degradation process is needed and will be proposed in order to determine the real technical life time of DH pipes.
44.	Zhang, Y., et al. (author) MDS study on tensile properties of defective graphene sheet 2021 In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021. Conference paper (peer-reviewed)abstract Low-dimensional materials such as graphene exhibit superior electrical, mechanical and thermal properties. However, structural defects occur during the growth or treatment process of carbon nanomaterial and greatly affect the material properties. In this paper, molecular dynamics simulation methods are used to study the effects of atomic defects in graphene sheets on the tensile strength, and the vacancy type and defect orientation are considered in the cases of graphene sheets under various mechanical loadings. The simulation results show that for the graphene sheets with structural defects, the fracture starts near the original vacancy position. The tensile strength of the graphene sheets with X1-type vacancy defects under zigzag direction is reduced by about 26.9% compared with that of the defect-free graphene sheet, while the graphene sheet with X2-type vacancy defects shows the least decrease in magnitude, which is 9.5% lower than that of the perfect graphene sheet. When stretched in the armchair direction, the tensile strength of the graphene sheet with H2 vacancy defects was greatly reduced by 27.1%, and the X1 vacancy defects shows the least influence, where tensile strength of the graphene sheets was reduced by 11.2%.
45.	Ahmad, Maqsood, et al. (author) Bending Fatigue Behavior of Blast Cleaned Grey Cast Iron 2017 In: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016). - : Materials Research Forum LLC. - 9781945291166 ; , s. 193-198 Conference paper (peer-reviewed)abstract This paper presents a detailed study on the effect of an industrial blast cleaning process on the fatigue behavior of a grey cast iron with regard to the residual stresses and microstructural changes induced by the process. A comparison was also made to the effect of a machining operation which removed the casting skin layer. The blast cleaning process was found to greatly improve the fatigue resistance in both the low and high cycle regimes with a 75% increase in the fatigue limit. Xray diffraction measurements and scanning electron microscopic analyses showed that the improvement was mainly attributed to compressive residual stresses in a surface layer up to 800 μm in thickness in the blast cleaned specimens. The machining also gave better fatigue performance with a 30% increase in the fatigue limit, which was ascribed to the removal of the weaker casting skin layer.
46.	Almgren, Karin M., et al. (author) Characterization of interfacial stress transfer ability by dynamic mechanical analysis of cellulose fiber based composite materials 2010 In: Composite interfaces (Print). - 0927-6440 .- 1568-5543. ; 17:9, s. 845-861 Journal article (peer-reviewed)abstract The stress transfer ability at the fiber-matrix interface of wood fiber composites is known to affect the mechanical properties of the composite. The evaluation of interface properties at the level of individual fibers is however difficult due to the small dimensions and variability of the fibers. The dynamical mechanical properties of composite and constituents, in this case wood fibers and polylactide matrix, was here used together with micromechanical modeling to quantify the stress transfer efficiency at the fiber-matrix interface. To illustrate the methodology, a parameter quantifying the degree of imperfection at the interface was identified by inverse modeling using a micromechanical viscoelastic general self-consistent model with an imperfect interface together with laminate analogy on the composite level. The effect of moisture was assessed by comparison with experimental data from dynamic mechanical analysis in dry and moist state. For the wood fiber reinforced polylactide, the model shows that moisture absorption led to softening and mechanical dissipation in the hydrophilic wood fibers and biothermoplastic matrix, rather than loss of interfacial stress transfer ability.
47.	Fu, L., et al. (author) Microstructure and tribological properties of Cr3C2/Ni3Al composite materials prepared by hot isostatic pressing (HIP) 2017 In: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 115:115, s. 203-212 Journal article (peer-reviewed)abstract Ni3Al-based composites with different Cr3C2 contents were fabricated by the hot isostatic pressing (HIP) technique.The microstructure, phase constitution, and tribological properties of the composites were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and pin-on-disk wear tests. The results revealed that the strengthening phase is distributed homogeneously in the Ni3Al matrix. During the HIP process, M7C3 (M = Cr, Fe) is formed by diffusion of Fe, C, and Cr to the interface between the Cr3C2 particles and Ni3Al matrix. The diffusion process binds the phases and is important for improving the wear resistance of Cr3C2/Ni3Al composites. The wear measurements demonstrated that micro-cutting and fatigue wear are the dominant mechanisms for this tribological pair. The wear resistance of Cr3C2/Ni3Al composites is significantly improved by the addition of Cr3C2 particles.When the content of Cr3C2 is within a certain range, the wear resistance of Cr3C2/Ni3Al composites increases as the Cr3C2 content increases. However, the addition of excess Cr3C2 (for example, 24 vol% in this work) could lead to a decrease in the wear resistance of the composites. In addition, the average friction coefficients and wear of the counterpart decrease with increasing Cr3C2 addition.
48.	Guo, Zengwei, et al. (author) Preparation of polypropylene/nanoclay composite fibers 2013 In: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 53:10, s. 2035-2044 Journal article (peer-reviewed)abstract Melt spinning of nanoclay (NA)/polypropylene (PP) composites into textile fibers is studied. The synthetic NA Perkalite F100 is prone to be exfoliated in PP matrix. With the help of a maleic anhydride-grafted low-molecular-weight PP as compatibilizer (Epolene E43), a highly exfoliated PP/NA composite was successfully prepared. However, the prepared PP/NA composite shows a poor spinnability because of the phase separation between Epolene E43 and PP matrix. The combination of two different groups of compatibilizers, which are Polybond 1001 (acrylic acid-grafted PP) for the dispersion of NA and Epolene G3216 (maleic anhydride-grafted PP-based copolymer) for the exfoliation of NA, can solve this problem. The PP/NA composite prepared by these two compatibilizers can be smoothly spun into fiber at the NA concentration below 1.9 wt%, which is found to be the percolation concentration of formation of NA network structure in PP matrix.
49.	Jacobsson, Jonny, et al. (author) Weldability of superalloys alloy 718 and ATI® 718Plus™ : A study performed by Varestraint testing 2017 In: Materialprüfung (München). - : Walter de Gruyter GmbH. - 0025-5300 .- 2195-8572. ; 59:9, s. 769-773 Journal article (peer-reviewed)abstract In this study, the old and well-known alloy 718 is compared with the newly developed ATI® 718Plus™ from the weldability point of view. This is done in order to gain new information that have not been documented and established yet among the high-temperature materials with high strength, oxidation resistance, thermal stability and sufficient weldability, yet. ATI® 718Plus™ shows a lower sensitivity to hot cracking than alloy 718 with approximately 10 mm total crack length (TCL) difference in Varestraint testing. In the solution-annealed condition at 982°C for 4.5 h followed by air cooling, the crack sensitivity is decreased as compared to the mill-annealed condition. Along the crack path and also ahead of the crack tip, γ-Laves eutectic is present in both alloys. The microhardness measurements showed similar hardness level of 250 HV in the weld metal of both alloys and even in the parent material of alloy 718. ATI® 718Plus™ parent metal had hardness of 380 HV and a small increase of less than 50 HV was observed for both studied alloys in the heat affected zone (HAZ). For the same grain size of ATI® 718Plus™ (8.3 μm) and alloy 718 (15.6 μm), the susceptibility to liquation cracking may increase with increasing grain size. With a small grain size, there is a possibility to accommodate more trace elements (B, S, P) due to the larger grain boundary area. The impurity elements were found in relatively small precipitates, typically borides (0.2 μm), phosphides (0.1 to 0.5 μm) and carbo-sulphides. The solidification sequence of alloy 718 and ATI® 718Plus™ is relatively similar, where the liquid starts to solidify as γ-phase followed by γ/MC reaction at about 1260 °C and then final γ/Laves eutectic reaction at around 1150 °C. Detailed knowledge about weldability of alloy 718 and ATI® 718Plus™ can be used for material selection.
50.	Karlsson, Kristina, 1988 (author) Foaming of cellulose derivatives and hemicellulose-containing materials 2018 Doctoral thesis (other academic/artistic)abstract Fossil-based polymeric foams are important materials due to their good mechanical properties relative their low density, the low price and the possibility for large-scale production. They are widely used in cushioning, absorbing and insulation applications. There are however a few disadvantages with these foamed products. The raw-material originates from a non-renewable resource. In the foaming process some possible less environmentally friendly additives/blowing agents are used. Also, the relatively low price of these foamed articles makes them ideal for single-use packaging and, unfortunately, they often end up in nature where the slow degradation will ensure that they stay for a long time, causing problems for marine living and other species. One possible way to solve at least some of the issues relating to fossil-based foamed products would be to use a renewable, non-fossil, raw material. There are several polymers of a non-fossil origin which could serve a primary material for foams and in this thesis two different types of cellulose derivatives (hydroxypropyl methylcellulose (HPMC) and ethyl hydroxyethyl cellulose (EHEC)) as well as a number of different hemicelluloses (xylan, arabinoxylan (AX), β-glucan concentrate and galactoglucomannan (GGM)) were studied as possible and interesting candidates. The foaming ability of some different grades of the two cellulose derivatives, xylan, AX and GGM, was initially evaluated using a hot-mould process with water as the only blowing agent and plasticiser. A simulated foaming process was assessed using dynamical mechanical thermal analysis (DMTA) for HPMC and the rheological properties of the polymer-water mixtures were determined. Three grades of the HPMC derivatives were evaluated in a small-scale batch extrusion experiment using a capillary viscometer. Also, the β-glucan concentrate (mixed with water) was foamed in the capillary viscometer and its shear and extensional viscosities were evaluated. The results pointed towards the existence of a possible processing window for foaming and extrusion experiments were therefore performed with the HPMC and the β-glucan polymers. For HPMC, water was the only added plasticiser and blowing agent and for the β-glucan concentrate also sodium bicarbonate and citric acid were used along with the water. The final foams from both foaming techniques were characterised with regard to their apparent density and foam structure. In conclusion, cellulose derivatives and hemicelluloses could be suitable candidates for production of lightweight, foamed material originating from non-fossil, renewable resources.

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