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A water-soluble exopolysaccharide (EPS) was produced by Leuconostoc ctireum NM105 from homemade manchurian sauerkraut. After culturing the strain in Man–Rogosa–Sharpe medium containing 5% sucrose at 25 °C for 48 h, the EPS was purified and a yield of 23.5 g/L was achieved. The EPS consisted exclusively of glucose and the weight-average molecular weight was 1.01 × 10 8 Da. The structural characterization of the purified EPS determined by FT-IR, 1 H, 13 C and two-dimensional NMR spectroscopy demonstrated that the glucan contained α-(1 → 6)-linked d -glucopyranose units, 2,6-linked d -glucopyranose units and terminal α- d -glucopyranose units at a ratio of 1:1:1. The microstructure of the dried dextran appeared a sheet-like smooth glittering and highly branched surface. The NM105 dextran showed high water solubility and excellent water retention. All the results suggested that the highly α-(1 → 2) branched dextran might have the potential to serve as valuable polymers applied in foods, cosmetics and other fields. [ABSTRACT FROM AUTHOR]

WC-5vol%TaC x (where x = 0.5, 0.7, 0.8 and 0.9) binderless cemented carbides with different carbon vacancy contents were prepared by spark plasma sintering (SPS) at a lower sintering temperature of 1800 °C. The phase evolution, microstructure and mechanical properties of these materials were investigated. The results show that the presence of WC, W 2 C and (Ta 1-x , W x)C n phases in the sintered body. The formation of (Ta 1-x , W x)C n solid solution is attributed to the dissolution of WC into TaC x , and the existence of vacancies promotes the atomic diffusion. (Ta 1-x , W x)C n solid solution was uniformly distributed around the WC matrix, which inhibited the WC grain growth. In terms of fracture mode, the WC-5vol%TaC x composites exhibit a combination of intergranular and transgranular fracture, with crack deflection and bridging contributing to enhanced fracture toughness. Compared to other WC-TaC x composites with varying carbon vacancy content, the WC-5vol%TaC 0.8 composite possesses the smallest average particle size and highest intrinsic hardness. Additionally, a semi-coherent interface is formed between (Ta 1-x , W x)C n and WC, leading to improved mechanical properties such as highest hardness (24.4 GPa) and fracture toughness (8.5 MPa·m1/2). The WC-5vol%TaC 0.8 composite, however, exhibits the lowest oxidation onset temperature attributed to its relatively smaller grain size. The introduction of carbon vacancies serves to facilitate atom diffusion and lower the densification temperature, while also functioning as a toughening agent. [ABSTRACT FROM AUTHOR]

Metal-matrix composite powders of W with Al 2 O 3 reinforcements were synthesized by a novel hydrothermal route, which includes calcination and hydrogen reduction steps. It was found that the pH value and reactant concentration in the hydrothermal reaction had a significant influence on the morphology and particle size of the powders produced. The precursor powder particle size was the smallest for pH values of < 1.0 and a reactant concentration of 0.5 g/ml. The addition of Al 2 O 3 led to significant refinement of W particles produced via this route, and these particles gradually become more spherical with increasing Al 2 O 3 content. Subsequently, bulk Al 2 O 3 -reinforced W composites were fabricated by spark plasma sintering. The Al 2 O 3 content was varied from 0 to 15 vol%, and sintering was performed under 30 MPa pressure for 5 min at temperatures of 1800–2100 °C. The density of the sintered samples increased with sintering temperature, reaching a value of about 97% of the theoretical value for a sintering temperature of 1900 °C. An increase in the Al 2 O 3 content from 0 to 6 vol% resulted in an increase in the micro-hardness of the sintered composite samples from 278 to 423 HV and a decrease in the W grain size from 4.25 to 2.78 μm. [ABSTRACT FROM AUTHOR]

Indium-based thermal interface materials are superior in thermal management applications of electronic packaging compared to their polymer-based counterparts. However, pure indium has rather low tensile strength resulting in poor reliability. To enhance the mechanical properties of such a material, a new composite consisting of electrospun randomly oriented continuous polyimide fibres and indium was fabricated. The composite has been characterised by tensile tests and in-situ transmission electron microscopy straining observations. It is shown that the composite's ultimate tensile strength at 20 °C is five times higher than that of pure indium, and the strength of the composite exceeds the summation of strengths of the individual components. Furthermore, contrary to most metallic matrix materials, the ultimate tensile strength of the composite decreases with the increased strain rate in a certain range. The chemical composition and tensile fracture of the novel composite have been analysed comprehensively by means of scanning transmission electron microscopy and scanning electron microscopy. A strengthening mechanism based on mutually reinforcing structures formed by the indium and surrounding fibres is also presented, underlining the effect of compressing at the fibre/indium interfaces by dislocation pileups and slip pinning. [ABSTRACT FROM AUTHOR]

In previous researches, there are few studies on the mechanisms involved in liquid-liquid doping techniques for preparing oxide particle doped tungsten powders. In this research, based on different polytungstate species, three liquid–liquid doping techniques for synthesizing different doped precursor powders were proposed and compared. The extremely homogeneous hexagonal (NH 4) 0.33 WO 3 ·H 2 O microspheres and flaky (NH 4) 6 H 2 W 12 O 40 ·5H 2 O were synthesized. The synthesis mechanisms of precursors, the doping processes and reaction mechanisms for preparing yttrium-stabilised ZrO 2 in ternary liquid phase system were discussed. The doped powder prepared through azeotropic distillation method exhibits higher quality due to the highly dispersed ZrO 2 (Y) phase uniformly distributed in flaky precursor, and the corresponding alloy possesses more excellent microstructure and mechanical properties. The proposed azeotropic distillation method offers a general pathway and is readily adapted to large-scale industrial production of high-quality oxide particle doped W powders. Image 1 • Three novel liquid–liquid doping technique for preparing precursors were proposed. • Extremely homogeneous microspherical and flaky precursors were synthesized. • Synthesis mechanism of three precursors were investigated in detail, respectively. • Reaction mechanisms for synthesizing cubic ZrO 2 in ternary liquid system were discussed. • Novel method offers a general pathway in industrial production of high quality ODS-W powders. [ABSTRACT FROM AUTHOR]