| 1. |
- Åkerfeldt, Maria, 1982, et al.
(author)
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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
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In: Fashion and Textiles. - : Springer Science and Business Media LLC. - 2198-0802. ; 1:1
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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.
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| 2. |
- Lindberg, Siv M, et al.
(author)
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A product semantic study of the influence of the sense of touch on the evaluation of wood-based materials
- 2013
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In: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 52, s. 300-307
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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.
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| 3. |
- Mahade, Satyapal, 1987-, et al.
(author)
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Incorporation of graphene nano platelets in suspension plasma sprayed alumina coatings for improved tribological properties
- 2021
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In: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 570
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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.
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| 4. |
- Grolig, Jan Gustav, 1986
(author)
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Coated Ferritic Stainless Steels as Interconnects in Solid Oxide Fuel Cells - Material Development and Electrical Properties
- 2015
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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.
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| 5. |
- Hosseini, Seyedehsan, 1994
(author)
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Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites
- 2023
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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.
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| 6. |
- Zhang, Hanzhu, 1991-, et al.
(author)
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A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite
- 2019
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In: Dalton Transactions. - : Royal Society of Medicine Press. - 1477-9226 .- 1477-9234. ; 48:16, s. 5161-5167
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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.
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| 7. |
- Cho, Sung-Woo, et al.
(author)
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Injection-molded nanocomposites and materials based on wheat gluten
- 2011
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In: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 48:1, s. 146-152
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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.
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| 8. |
- Mellin, Pelle, 1985-, et al.
(author)
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Nano-sized by-products from metal 3D printing, composite manufacturing and fabric production
- 2016
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In: Journal of Cleaner Production. - Sweden : Elsevier. - 0959-6526 .- 1879-1786. ; 139, s. 1224-1233
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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.
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| 9. |
- Duan, Shanghong, 1992, et al.
(author)
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Determination of transverse and shear moduli of single carbon fibres
- 2020
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In: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 158, s. 772-782
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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.
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| 10. |
- Johansen, Marcus, 1994, et al.
(author)
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Mapping nitrogen heteroatoms in carbon fibres using atom probe tomography and photoelectron spectroscopy
- 2021
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In: Carbon. - : Elsevier BV. - 0008-6223. ; 179, s. 20-27
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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.
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