| 1. |
- Wang, Lei, et al.
(författare)
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Preparation of functionalized protein materials assisted by mechanochemistry
- 2018
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Ingår i: Journal of Materials Science. - : SPRINGER. - 0022-2461 .- 1573-4803. ; 53:19, s. 13719-13732
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we investigate the suitability of hen egg-white lysozyme (HEWL) as a protein matrix for dispersal of various hydrophobic dyes. Moreover, we investigate the use of a mixer mill for grinding operation as an alternative to hand grinding by mortar and pestle. HEWL and various dyes are mixed by mechanochemistry, and the resulting composite material is dissolved in aqueous acid. The samples are then exposed to conditions promoting self-assembly of HEWL into protein nanofibrils (PNFs). The effect of PNF formation on dye photophysics is investigated by spectroscopic examination by absorption and luminescence spectroscopy, and product morphology is examined by scanning electron microscopy. The self-assembly process results in protein nanofibrils functionalized with luminescent dyes. Such structures may find future applications in various devices for light emission. In addition, we demonstrate that the anticancer drug camptothecin can be incorporated into protein nanofibrils giving materials that can find application as drug delivery agents.
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| 2. |
- Ahmadkhaniha, Donya, et al.
(författare)
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Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg
- 2018
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Ingår i: Journal of Materials Science. - : Springer. - 0022-2461 .- 1573-4803. ; 53:24, s. 16585-16597
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Tidskriftsartikel (refereegranskat)abstract
- High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing.
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| 3. |
- Arvhult, Carl, et al.
(författare)
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Thermodynamic assessment of the Ni-Te system
- 2019
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Ingår i: Journal of Materials Science. - : SPRINGER. - 0022-2461 .- 1573-4803. ; 54:16, s. 11304-11319
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Tidskriftsartikel (refereegranskat)abstract
- A thermodynamic assessment of the Ni-Te system has been performed using the Calphad method, based on experimental data available in the literature. The proposed description has been developed for use in the modeling of fission-product-induced internal corrosion of stainless steel cladding in Generation IV nuclear reactors. DFT calculations were performed to obtain 0 K properties of solid phases to assist the thermodynamic optimization. The ionic liquid two-sublattice model was used, and most solution phases were modeled using interstitial metal sub-lattices. With a strict number of parameters, the resulting description satisfactorily reproduces all thermodynamic properties and high-temperature phase transitions. The metastable miscibility gap in the Ni-rich liquid that is experimentally suggested is not present in the final description. The phase exhibits a metastable order-disorder transition between the CdI2 and NiAs types of interstitial nickel distribution. The CdI2 prototype is the stable space group at room temperature. Low-temperature ordering phase transitions have been disregarded in this description, since they are not of interest to the application of corrosion in nuclear reactors.
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| 4. |
- Avazkonandeh-Gharavol, M. H., et al.
(författare)
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Analysis of phase diagram and diffusion coefficient for modeling of microsegregation
- 2017
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Ingår i: Journal of Materials Science. - : Springer-Verlag New York. - 0022-2461 .- 1573-4803. ; 52:3, s. 1446-1460
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Tidskriftsartikel (refereegranskat)abstract
- Thermodynamic description of phase diagram and diffusion data are required to model microsegregation during solidification of metallic alloys. Knowledge about non-equilibrium phase diagrams is essential for modeling of microsegregation in practical situations. Therefore, the aim of this study is to theoretically analyze phase diagram and diffusion data for calculation of microsegregation. For this purpose, aluminum-rich part of the Al-Cu phase diagram was recalculated under non-equilibrium conditions. Effect of excess vacancies formed during solidification was considered on both the phase diagram and diffusion coefficient. The results show that by modifying the phase diagram, the calculated results have better consistency with the experimental results, but there is still room for improvement. When the effect of excess vacancies on diffusion coefficient is considered, the modeling results show a much better correlation with the experimental results. The origin of discrepancies between the calculations and experiments are deeply discussed using current theories in solidification.
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| 5. |
- Čermák, Petr, et al.
(författare)
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The effect of wetting cycles on moisture behaviour of thermally modified Scots pine (Pinus sylvestris L.) wood
- 2016
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Ingår i: Journal of Materials Science. - : Springer Publishing Company. - 0022-2461 .- 1573-4803. ; 51:3, s. 1504-1511
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Tidskriftsartikel (refereegranskat)abstract
- The moisture behaviour of thermally modified Scots pine (Pinus sylvestris L.) exposed to cyclic conditions was analysed. Specimens of dimensions 15 × 15 × 5 mm3 were thermally modified at 180 °C (TM1) and 220 °C (TM2) using atmospheric pressure and superheated steam. Radial, tangential, volumetric swelling and anti-swelling efficiency (ASE) were calculated during six consecutive drying–soaking cycles. Afterwards, additional specimens were exposed to ten relative humidity cycles (0 and 95 %) at temperature 25 and 40 °C in order to analyse its influence on sorption behaviour. Application of thermal modification led to significant reduction of swelling from original 18.4–13.3 % for TM1 and to 10.5 % for TM2. However, after exposure to six consecutive soaking–drying cycles, the swelling of control specimens slightly decreased, whereas the swelling of thermally modified specimens increased. Due to the increased swelling after repeated cycles, the original ASE (28.6 and 42.7 %) decreased to 22.5 % for TM1 and to 36.88 % for TM2. The presence of leachable compounds and release of internal stresses are mainly attributed to that phenomenon. The EMC of the reference specimens decreases over the repeated humidity cycles for approximately 1 %–units. Same trend was found for the mild thermal modification TM1, but decreasing only in the range of 0.5 %–units. However, the EMC of the TM2 specimens during humidity cycles behaved differently. The results provide a better insight into details of thermal modification of wood and its behaviour under cyclic conditions.
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| 6. |
- Ekström, Erik, et al.
(författare)
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Formation mechanism and thermoelectric properties of CaMnO3 thin films synthesized by annealing of Ca0.5Mn0.5O films
- 2019
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Ingår i: Journal of Materials Science. - : SPRINGER. - 0022-2461 .- 1573-4803. ; 54:11, s. 8482-8491
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Tidskriftsartikel (refereegranskat)abstract
- A two-step synthesis approach was utilized to grow CaMnO3 on M-, R- and C-plane sapphire substrates. Radio-frequency reactive magnetron sputtering was used to grow rock-salt-structured (Ca, Mn)O followed by a 3-h annealing step at 800 degrees C in oxygen flow to form the distorted perovskite phase CaMnO3. The effect of temperature in the post-annealing step was investigated using x-ray diffraction. The phase transformation to CaMnO3 started at 450 degrees C and was completed at 550 degrees C. Films grown on R- and C-plane sapphire showed similar structure with a mixed orientation, whereas the film grown on M-plane sapphire was epitaxially grown with an out-of-plane orientation in the [202] direction. The thermoelectric characterization showed that the film grown on M-plane sapphire has about 3.5 times lower resistivity compared to the other films with a resistivity of 0.077cm at 500 degrees C. The difference in resistivity is a result from difference in crystal structure, single orientation for M-plane sapphire compared to mixed for R- and C-plane sapphire. The highest absolute Seebeck coefficient value is -350 mu VK-1 for all films and is decreasing with temperature.
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| 7. |
- Forsgren, Lilian, 1990, et al.
(författare)
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Composites with surface-grafted cellulose nanocrystals (CNC)
- 2019
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 54:4, s. 3009-3022
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxyazetidinium salts were used to surface-modify cellulose nanocrystals (CNC) by grafting the salts onto the sulphate ester groups on the CNC surfaces. The grafting was confirmed by ζ-potential measurements and by the thermal degradation behaviour of the modified CNC. The thermal stability (onset of degradation) of the CNC was improved by the surface modification (almost 100 °C). Composites containing surface-modified or unmodified CNC (0.1, 1.0 and 10 wt%) with an ethylene-based copolymer as matrix were produced by compression moulding. The thermal stability of the composites was not, however, markedly improved by the surface grafting onto the CNC. It is suggested that this is due to a degrafting mechanism, associated with the alkaline character of the system, taking place at high temperatures. Model experiments indicated, however, that this did not occur at the conditions under which the composites were produced. Furthermore, in the case of a reference based on pH-neutralised polymeric system and modified CNC, an upward shift in the onset of thermal degradation of the composite was observed. The addition of the CNC to the polymer matrix had a strong influence of the mechanical performance. For example, the tensile modulus increased approximately three times for some systems when adding 10 wt% CNC. The surface grafting of the hydroxyazetidinium salts appeared mainly to affect, in a positive sense, the yield behaviour and ductility of the composites. The results of the mechanical testing are discussed in terms of interactions between the grafted units and the matrix material and between the grafted groups.
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| 8. |
- Garbrecht, Magnus, et al.
(författare)
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Microstructural evolution and thermal stability of HfN/ScN, ZrN/ScN, and Hf0.5Zr0.5N/ScN metal/semiconductor superlattices
- 2016
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Ingår i: Journal of Materials Science. - : SPRINGER. - 0022-2461 .- 1573-4803. ; 51:17, s. 8250-8258
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Tidskriftsartikel (refereegranskat)abstract
- Nitride-based metal/semiconductor superlattices for possible applications as thermoelectric, plasmonic, and hard coating materials have been grown by magnetron sputtering. Since long-time thermal stability of the superlattices is crucial for these applications, the atomic scale microstructure and its evolution under annealing to working temperatures were investigated with high-resolution transmission electron microscopy methods. We report on epitaxial growth of three cubic superlattice systems (HfN/ScN, ZrN/ScN, and Hf0.5Zr0.5N/ScN) that show long-time thermal stability (annealing up to 120 h at 950 degrees C) as monitored by scanning transmission electron microscopy-based energy-dispersive X-ray spectroscopy. No interdiffusion between the metal and semiconductor layers could be observed for any of the present systems under long-time annealing, which is in contrast to earlier attempts on similar superlattice structures based on TiN as the metallic compound. Atomically resolved high-resolution transmission electron microscopy imaging revealed that even though the superlattice curves towards the substrate at regular interval column boundaries originating from threading dislocations close to the substrate interface, the cubic lattice continues coherently across the boundaries. It is found that the boundaries themselves are alloyed along the entire growth direction, while in their vicinity nanometer-size inclusions of metallic phases are observed that could be identified as the zinc blende phase of same stoichiometry as the parent rock salt transition metal nitride phase. Our results demonstrate the longtime thermal stability of metal/semiconductor superlattices based on Zr and Hf nitrides.
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| 9. |
- Garbrecht, Magnus, et al.
(författare)
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Tailoring of surface plasmon resonances in TiN/(Al0.72Sc0.28)N multilayers by dielectric layer thickness variation
- 2018
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Ingår i: Journal of Materials Science. - : SPRINGER. - 0022-2461 .- 1573-4803. ; 53:6, s. 4001-4009
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Tidskriftsartikel (refereegranskat)abstract
- Alternative designs of plasmonic metamaterials for applications in solar energy-harvesting devices are necessary due to pure noble metal-based nanostructures incompatibility with CMOS technology, limited thermal and chemical stability, and high losses in the visible spectrum. In the present study, we demonstrate the design of a material based on a multilayer architecture with systematically varying dielectric interlayer thicknesses that result in a continuous shift of surface plasmon energy. Plasmon resonance characteristics of metal/semiconductor TiN/(Al,Sc)N multilayer thin films with constant TiN and increasing (Al,Sc)N interlayer thicknesses were analyzed using aberration-corrected and monochromated scanning transmission electron microscopy-based electron energy loss spectroscopy (EELS). EEL spectrum images and line scans were systematically taken across layer interfaces and compared to spectra from the centers of the respective adjacent TiN layer. While a constant value for the TiN bulk plasmon resonance of about 2.50 eV was found, the surface plasmon resonance energy was detected to continuously decrease with increasing (Al,Sc)N interlayer thickness until 2.16 eV is reached. This effect can be understood to be the result of resonant coupling between the TiN bulk and surface plasmons across the dielectric interlayers at very low (Al,Sc)N thicknesses. That energy interval between bulk and decreasing surface plasmon resonances corresponds to wavelengths in the visible spectrum. This shows the potential of tailoring the materials plasmonic response by controlling the (Al,Sc)N interlayer thickness, making TiN-based multilayers good prospects for plasmonic metamaterials in energy devices.
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| 10. |
- Germiniani, Luiz G.L., et al.
(författare)
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Poly(ε-caprolactone)/cellulose nanocrystal nanocomposite mechanical reinforcement and morphology : the role of nanocrystal pre-dispersion
- 2019
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 54:1, s. 414-426
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystal (CNC) incorporation in polymeric matrices is an environmentally friendly approach to mechanical reinforcement. In general, significant mechanical reinforcement can only be achieved by means of good CNC dispersion at random orientation. These primary characteristics are even more relevant for the preparation of nanocomposites based on hydrophobic matrices, such as poly(ε-caprolactone) (PCL). A straightforward approach to improve CNC dispersion in hydrophobic matrices is their surface modification. However, this extra step is usually complex and often impairs particle–particle interactions, which are also key to mechanical reinforcement. In this work, poly(ε-caprolactone)/neat cellulose nanocrystal nanocomposites were prepared by a specific procedure that combined solvent exchange and solvent casting methodologies, avoiding the use of any additives or chemical modification. These nanocomposites were investigated in terms of the CNC percolation network formation and its effect on the overall mechanical properties. The results showed that significant mechanical reinforcement was obtained, reaching a 155% Young’s modulus increase at 25 wt% CNC content. TEM showed a percolated network in the PCL/CNC25 nanocomposite. In terms of morphology and nanostructure, increasing CNC concentration also promoted a reduction in PCL spherulite size and lamellar thickness. These results pointed out to CNC preferential localization in the interfibrillar region. In conclusion, the solvent exchange methodology presented herein led to mechanically reinforced PCL/CNC nanocomposites with small crystalline domains intertwined with a percolated CNC network.
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