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We reported, for the first time, the fracture toughness of aluminum nitride ceramics at cryogenic temperatures. The fracture toughness increased from 3.98±0.19 to 4.59±0.28 MPa m1/2 with the decreasing temperature from 293 to 77 K. Increasing fraction of transgranular fracture (from 7.3% at 293 K to 14.5% at 77 K) was proposed as a governing mechanism for toughness improvement at cryogenic temperatures based on the experimental observations. The effect of residual stresses on crack propagation was theoretically analyzed, considering energy release rates of intergranular and transgranular fractures. The variation of crack paths would contribute to the change of fracture modes and fracture toughness at cryogenic temperatures. [ABSTRACT FROM AUTHOR]

The LiNi0.5Mn1.5O4 (LNM) spinel lithium-ion battery cathodes were prepared by a modified low temperature solution combustion synthesis method at 600 °C for 3 h. Structural analyses reveal that the modified method is an effective process to eliminate an impurity phase. In comparison with the LNM prepared by a conventional method, the modified sample has higher purity, better crystallinity, smaller amount of Mn3+ ions and higher structural ordering. It exhibits remarkably superior initial discharge specific capacity of 117.0 mAh/g, and delivers a reversible capacity of ~116.0, 116.6, 113.8, 108.9 and 85.9 mAh/g at 0.2 C, 0.5 C, 1 C, 2 C and 5 C, respectively. While the LNM prepared by the conventional method offers a lower reversible capacity of ~96.3, 95.4, 89.1, 77.0 and 40.6 mAh/g at the same rate. After 50 cycles, about 95.5% of reversible capacity is retained for the LNM prepared by modified method vs. 90.7% for the LNM prepared by the conventional method. It suggests that the modified method is a simple and effective method to prepare LiNi0.5Mn1.5O4 with high performance at low temperature and in short time. [ABSTRACT FROM AUTHOR]

A highly efficient oxidation of cyclohexane to cyclohexanone is accomplished over phenanthroline–CuCl2 catalyst in relatively mild conditions. This study realized nearly 100% selectivity for cyclohexanone at 24.4% conversion of cyclohexane. The reaction has been studied by various parameters like performance of copper(II) salts, effect of solvents, influence of bases, the ratio of o-phenanthroline: CuCl2, and reaction time. In order to further study this reaction system, the possible mechanism was proposed. [ABSTRACT FROM AUTHOR]