The controllable hydrolysis rate for LaMg12 hydride

In this work, the hydrogenation mechanism for LaMg₁₂ alloy is revealed by introducing hydrogen step by step and the hydrogenation degree is found to affect the hydrolysis properties of LaMg₁₂H_x hydrides. Because the hydrolysis performance of Mg is affected limitedly while MgH₂ is accelerated significantly by LaH₃, the hydrolysis rate is controllable through adjusting the ratio of LaH₃ to MgH₂. The synergistic effect of LaH₃ and MgH₂ leads to the complete hydrolysis of the fully hydrogenated LaMg₁₂H₂₇, yielding 9.73 wt. % (1089.55 ml g⁻¹) hydrogen.     

Comparative investigations on the hydrogenation characteristics and hydrogen storage kinetics of melt-spun Mg10NiR (R = La,Nd and Sm) alloys

The hydrogenation characteristics and hydrogen storage kinetics of the melt-spun Mg₁₀NiR (R = La, Nd and Sm) alloys have been studied comparatively. It is found that the Mg₁₀NiNd and Mg₁₀NiSm alloys are in amorphous state but the Mg₁₀NiLa alloy is composed of an amorphous phase and minor crystalline La₂Mg₁₇ after melt-spinning. The alloys can be hydrogenated into MgH₂, Mg₂NiH₄ and a rare earth metal hydride RH_x. The rare earth metal hydride and Mg₂NiH₄ synergistically provide a catalytic effect on the hydrogen absorption–desorption reactions in the Mg−H₂ system. The hydrogen storage kinetics is not influenced by different rare earth metal hydrides but by the particle size of the rare earth metal hydrides.     

Ti+Nb和Ti+V超低碳烘烤硬化钢的组织和性能研究

采用Gleeble-1500热模拟试验机对Ti+Nb和Ti+V复合处理超低碳BH钢的变形抗力和动态连续冷却转变进行研究,并观察了两种实验钢在不同冷却工艺条件下的金相组织。结果表明:在1100℃、应变速率1s-1时Ti+Nb超低碳BH钢的变形抗力比Ti+V超低碳BH钢高出约13MPa,在相同的变形条件下,两种实验钢的组织形貌及晶粒尺寸差别较大。两种超低碳BH钢在不同冷却条件下的室温金相组织均是多边形的铁素体,Ti+Nb超低碳BH钢铁素体晶粒较为细小,形状不规则,平均晶粒尺寸为16μm,Ti+V超低碳BH钢铁素体晶粒则较为粗大,形状规则,平均晶粒尺寸为26μm。     

TiC添加量对细晶Al2O3-TiC复合陶瓷热震疲劳抗力的影响

热压制备了Al2O3—TiC复合陶瓷。研究了Al2O3—TiC复合陶瓷的热震疲劳机制和TiC的添加量对其热震疲劳抗力的影响。热震过程中的微裂纹,裂纹桥接和偏转,热震裂纹表面的“碎粒”及粗糙性等的共同作用是Al2O3-TiC复合陶瓷热震疲劳产生的主要机制。具有一定微孔洞的材料,热震循环时微裂纹易于孔洞处产生,有益于热震疲劳抗力的提高。A30材料韧性最高且孔隙率最大,从而其热震循环疲劳抗力得到改善。     

Enhanced cycling stability of microsized LiCoO2 cathode by Li4Ti5O12 coating for lithium ion battery

The effect of Li₄Ti₅O₁₂ (LTO) coating amount on the electrochemical cycling behavior of the LiCoO₂ cathode was investigated at the high upper voltage limit of 4.5 V. Li₄Ti₅O₁₂ (≤5 wt.%) is not incorporated into the host structure and leads to formation of uniform coating. The cycling performance of LiCoO₂ cathode is related with the amount of Li₄Ti₅O₁₂ coating. The initial capacity of the LTO-coated LiCoO₂ decreased with increasing Li₄Ti₅O₁₂ coating amount but showed enhanced cycling properties, compared to those of pristine material. The 3 wt.% LTO-coated LiCoO₂ has the best electrochemical performance, showing capacity retention of 97.3% between 2.5 V and 4.3 V and 85.1% between 2.5 V and 4.5 V after 40 cycles. The coulomb efficiency shows that the surface coating of Li₄Ti₅O₁₂ is beneficial to the reversible intercalation/de-intercalation of Li⁺. LTO-coated LiCoO₂ provides good prospects for practical application of lithium secondary batteries free from safety issues.     

Influence of CO2 laser heat treatment on surface properties,electrochemical and tribological performance of HVOF sprayed WC–24%Cr3C2–6%Ni coating

In this investigation, the tribological and electrochemical performances of HVOF sprayed WC–24%Cr₃C₂–6%Ni coatings before and after laser heat (LH) treatment were investigated. In the wear test, the friction and wear resistance of the coatings were improved significantly with an optimized LH process. The improvement can be attributed to the improved roughness and hardness, as well as the formation of oxide tribofilms. With LH treatment, the local corrosion of the coating had a decrease and the pit corrosion resistance of the WC–24%Cr₃C₂–6%Ni coating was improved as a result of the decreasing the size and number of the porosities, especially compact interface achieved by LH treatment.     

Microstructure and mechanical properties of CaAl12O19 reinforced Al2O3-Cr2O3 composites

Al₂O₃-Cr₂O₃ refractories have excellent slag corrosion resistance and can adapt to the oxidation/reduction atmosphere in the smelting reduction ironmaking furnace. However, Al₂O₃-Cr₂O₃ refractories have poor mechanical properties and sintering properties. In order to improve the mechanical properties of Al₂O₃-Cr₂O₃ materials, the CaAl₁₂O₁₉ reinforced Al₂O₃-Cr₂O₃ composites were prepared by pressureless sintering process, and the influences of CaO content on the sintering properties, mechanical properties, and microstructure evolution of the composites were studied. The results show that a small amount of CaO can significantly improve the compactness of the composites, which is mainly due to the formed sheet-like CA6 fill the gap between the solid solutions, and reduces the porosity of the composites. In addition, the sheet-like CA6 makes the connection between solid solutions closer, and the intergranular fracture gradually transforms into a mixed mode of intergranular and transgranular fracture. The best mechanical propertie is observed at S4 with the CaO content of 2 wt.%. Compared with sample S0 without CaO, the hardness, compressive strength and flexural strength of the S4 were increased by 35.19 %, 49.69 %, and 68.34 %, respectively. The addition of excessive CaO will deteriorate the mechanical properties of the composites, because the formation of a large number of layered CA6 increases the porosity of the composites. Furthermore, a small amount of CaO addition can significantly improve the thermal shock resistance of the composites. After 10 and 20 thermal shock cycles, the strength loss rates of S4 are only 5.83 % and 8.74 %, respectively.     

Q235钢热浸渗铝复合渗硼层耐磨性的研究

用MM2型磨损试验机,在实验室条件下,对热浸渗铝和热渗铝复合渗硼试样进行了耐磨性的对比试验,并采用扫描电镜对磨损后的形貌进行观察分析.结果表明,在干摩擦条件下,热浸渗铝复合渗硼较单独热浸渗铝具有更好的耐磨性能.热浸渗铝的磨损机制以粘着磨损为主;而热浸渗铝复合渗硼以磨粒磨损为主要机制,同时伴有粘着磨损.     

A comparative study of hydrogen generation by reaction of ball milled mixture of magnesium powder with two water-soluble salts (NaCl and KCl) in hot water

Magnesium powder was ball milled with different weight percentages of NaCl and KCl. These mixtures were added to hot water (80 °C) and the hydrogen generation rate was measured. The results show that the hydrogen generation rate increased with an increase of the presence of both salts. Moreover, increase of the time of milling increased the hydrogen generation rate. The structure of magnesium salt mixtures was further investigated using SEM and EDS and it was demonstrated that higher hydrogen generation rate is correlated with the degree of penetration of the salt into magnesium particles. In addition, we determined that for the 15 h milled composite samples, Mg–KCl mixture generates 200 mL more hydrogen than Mg–NaCl for every 1 g Mg used. These results show that KCl salt addition is promising for hydrogen generation in presented experimental system.     

水热合成单晶La 1-x Ca x MnO3系列纳米线

采用水热法，成功地合成了一系列单晶La1-xCaxMnO3（x=0．3、0．5、0．75）纳米线．X射线衍射（XRD）的结果表明所制备的样品是纯的La1-xCaxMnO3正交相（x=0．3、0．5、0．75）纳米线．透射电子显微镜（TEM）的照片清晰地显示所制备的样品是由大量直径均匀（约90nm）、长度从几微米至几十微米的La1-xCaxMnO3的单晶纳米线构成．La0．5Ca0．5MnO3纳米线清晰的高分辨电子显微镜（HRTEM）的图片表明纳米线的表面是光滑的。没有任何缺陷且La0．5Ca0．5MnO3纳米线沿〈100〉方向生长．La0．5Ca0．5MnO3纳米线磁测量的结果表明相对于块材来说纳米线的疋有明显地提高，这是由于晶胞收缩和形状各向异性所致．