氢在不同成分和显微组织的Mg-Ni合金电极中的扩散能力研究

采用机械球磨的方法,制备了不同成分和显微组织的MgxNi(x=1%、1.5%、2%(原子分数))合金粉,并采用X射线衍射(XRD)和扫描电子显微镜的方法研究了Mg/Ni比对机械球磨过程中Mg-Ni合金粉末组织结构演变的影响。在不同的电位扫描速度下,对具有不同Mg/Ni比和显微组织结构的Mg-Ni合金电极循环伏安曲线进行了测量,并由此计算出了氢在这些电极中的扩散系数,分析了合金成分和显微组织对Mg-Ni合金电极中氢扩散能力的影响。其结果表明,降低Mg/Ni比,能提高Mg-Ni合金在球磨过程中非晶相的形成能力,Mg-Ni和Mg1.5Ni合金获得完全非晶相的球磨时间分别是120和160h。在由细小、分散并且完全非晶态的Mg-Ni合金颗粒制备的电极中,氢表现出较强的扩散能力,其扩散系数为1.98×10-8cm2/s。     

球磨参数对MgNi非晶热稳定性能的影响

采用带高温附件的X射线衍射仪(XRD)、差热分析仪(DTA)等研究了磨球配比、球料比、球磨速度、球磨时间等参数对MgNi样品的结构、热稳定性能的影响及其在加热过程中的相变规律。结果表明MgNi非晶的热稳定性能随着样品中球磨能量的增加而降低。当样品的球磨能量较低时(球磨时间短、球磨速度低、球料比小、磨球配比中大球质量大而小球数量少),非晶样品只有一个放热峰,对应着Mg2Ni和Mg Ni2晶体相的生成;当样品的球磨能量较高时则出现二个放热峰,分别对应着Mg2Ni、MgNi2晶体相的生成。     

机械合金化Fe─B非晶合金及纳米合金的形成

在适当条件下机械合金化可以形成急冷法难以得到的单一Ｆｅ６０Ｂ４０非晶合金，而在其他成分内形成亚稳纳米合金。在众多的球磨条件中，球磨机的转速是控制合金化的重要因素，空气中的氧对小颗粒界面产生了强烈的污染作用，从而抑制了原子的相互扩散，难以形成单一的非晶产物。不同球磨条件下的产物含有的非晶相的晶化温度比单一非晶相合金的晶化温度稍高，并且与球磨条件以及成分的关系不大。     

球磨工艺参数对MgNi非晶合金形成及性能的影响

通过机械合金化法制备了MgNi非晶合金,利用X射线衍射分析了非晶相的形成情况,并对其储氢性能和电化学性能进行了测试.对球磨工艺参数与合金微观结构及性能之间关系进行分析,结果表明,球磨机转速对MgNi非晶相的形成效率具有十分重要的影响,随着转速的增加,MgNi非晶相的形成时间大大缩短.随着球磨时间的延长,MgNi非晶相的形成趋于完全,粉末的粒径逐渐减小,粒度分布也较为均匀,但形成完全非晶后继续球磨过长时间会降低Mg-Ni合金的吸放氢性能和电化学性能.     

Fe70Zr10B20非晶合金的制备及其热稳定性和磁性能研究

采用机械合金化技术制备了Fe70Zr10B2。磁性非晶合金粉末。分析Fe70Zr10B20非晶合金的形成机制、晶化机制：研究Fe70Cr10B20非晶合金不同热处理温度下的磁性及球磨过程中样品的磁性。结果表明：Fe70Cr10B20非晶相的形成是由原子的扩散和晶格崩渍共同作用的结果；Fe70Cr10B20非晶合金的热致晶化模式为一次晶化；球磨过程厦非晶熟处理后样品的磁性与其结构、晶粒尺寸、应力和缺陷等因素有关。     

机械合金化Fe—B非晶合金及纳米合金的形成

在适当条件下机械合金化可以形成急冷法难以得到的单一Ｆｅ６０Ｂ４０非晶合金，而在其他成分内形成亚稳纳米合金，在众多的球磨条件中，球磨机的转速是控制合金化的重要因素。空气中的氧对小颗粒界面产生了强烈的污染作用，从而抑的原子的相互扩散，难以形成单一的非晶产物，不同球磨条件下的产物含有的非晶相的晶化温度比单一非上合金的晶化温度稍高，并且与球磨条件以及成分的关系不大。     

机械合金化制备Nd60 Fe20 Al10 Co10非晶粉末的研究

利用机械合金化制备Nd60Fe20Al10Co10非晶粉末，采用X射线衍射(XRD)和振动样品磁强计(VSM)研究Nd60Fe20Al10Co10非晶的形成过程、磁性能变化及其与成分结构的关系。结果表明，90min后Al原子溶入Nd原子形成固溶体。球磨2h后出现少量非晶，20h后Co单质和Nd单质消失．组织为非晶相(含少量的α-Fe)。球磨100h最终得到非晶 少量的α-Fe纳米晶。球磨过程中，矫顽力随着合金中非晶的量增加而升高．球磨20h矫顽力达到43kA／m。Nd60Fe20Al10Co10合金具有硬磁性是由于非晶相的存在而造成的。     

钛/20G钢爆炸焊接复合界面分析

用透射电镜、扫描电镜及能谱仪等手段,对钛/20G钢爆炸焊接复合界面进行了分析。结果表明,复合界面为带有前旋涡的准正弦波形;其复合界面由直接结合区、熔化层和旋涡区组成。电子衍射和衍衬分析证明,在熔化层及前旋涡内存在着非晶、微晶和微孪晶簇。相结构分析计算发现,直接结合区、熔化层和前旋涡内都存在有亚稳相α＂-Ti。成分分析表明,复合界面有元素扩散。     

高能球磨Mg-Zr-Ni合金组织演变

为了改善Mg-Ni合金的电化学性能,采用高能球磨技术合成了Mg-Zr-Ni储氢合金,通过改变球磨条件和添加合金元素Zr,利用XRD物相分析和电化学测量技术,研究了Mg-Ni合金的组织演变过程及其对电化学容量的影响.结果表明,高能球磨Mg-Ni和Mg-Zr-Ni合金都经历了非晶态向纳米晶态的转变过程,用少量Zr替代部分Mg后,促进了高能球磨Mg-Zr-Ni合金的非晶化和纳米晶化的过程.与非晶态Mg(Zr)Ni相比,纳米晶的Mg(Zr)Ni中氢更易放出,放电曲线主要呈现高电位放电特征,添加Zr后合金的放电容量有所下降.     

非晶化程度对不同成分Mg-Ni非晶合金电极充放电容量的影响

研究了球磨过程中的非晶化程度对不同成分Mg-Ni非晶合金电化学吸放氢性能的影响。研究结果表明,随着合金成分的不同,非晶化程度的影响不同。当Ni含量低于50％(原子分数)时,合金粉末中的非晶相所占比例越高,即非晶化程度越高时,合金电极的放电容量越大;而当Ni含量高于50％(原子分数)时,非晶合金中存在少量游离态的Ni相,可提高电极的放电量。分析认为这与Ni相的存在改善了合金的吸放氢动力学性能有关。     

Formation of a FCC Al_(54)Ti_(23)C_(23) Metastable Phase by Ball Milling

The powder mixture of Al, Ti and graphite has been mechanically alloyed in a planetary ball mill.The structural evolution of as-milled powder sample has been characterized by XRD, DTA. The results show that the amorphous phase is formed first at an early milling stage, then crystallization occurs during further milling, leading to formation of a nanocrystalline fcc metastable phase. In contrast, during annealing the amorphous phase is crystallized to the equilibrium phase instead of the fcc phase. This indicates that crystallization during ball milling is different from that induced by annealing     

球磨Mg0.97La0.03Ni合金的热稳定性及电性能研究

采用XRD、DTA、SEM及电池性能测试仪等对球磨Mg0.97La0.03Ni合金的结构、形貌、活化性能、热稳定性、电化学稳定性及容量衰减机理等进行了详细的研究。结果表明：样品的热稳定性及循环稳定性随着球磨时间的延长而增加。经400r／min球磨50h的样品在第二次活化时即达到最大值450mAh／g．经25次循环充放电后．该样品的容量与其最大值相比下降了53％．容量衰减的主要原因有：在循环充放电过程中．非晶体逐渐分解生成Mg2NiH4和Ni等晶体相，同时在颗粒表面形成腐蚀产物Mg(OH)2等。     

Polymorphic transformation and powder characteristics of TiO2 during high energy milling

Many studies have indicated that the reactivity of reactants can be enhanced greatly by mechanical activation through high energy ball milling. To understand this enhanced reactivity, the polymorphic transformation and the evolution of the powder characteristics of TiO₂ and graphite mixtures during high energy ball milling was investigated using various analytical instruments. It was found that polymorphic transformation of anatase to srilankite and rutile took place during milling. Furthermore, amorphization of crystalline phases and crystallization of the amorphous phase occurred at the same time during milling. High energy milling also led to ultrafine crystallites, large specific surface areas, and substantial amounts of defects in the powder particles. Effects of the graphite addition and the milling temperature on the polymorphic transformation and the evolution of the powder characteristics were also investigated. It was proposed that the polymorphic transformation of TiO₂ during milling could be explained in terms of the temperature-pressure phase diagram if the temperature rise and high pressure at the collision site were taken into consideration.     

Comparative study on sintering behavior of Al86Ni6Y4.5Co2La1.5 mechanically alloyed amorphous powder and melt-spun ribbon

In this research work, the sintering characteristics of Al₈₆Ni₆Y_4.5Co₂La_1.5 mechanically alloyed amorphous powders and milled melt spun ribbon have been compared. Mechanically alloyed amorphous powders were synthesized via 200?h high energy ball milling. Melt spun ribbons were synthesized by single roller melt spinning technique and grounded to powder form by ball milling. Mechanically induced partial crystallization occurred in the ribbons during milling. Significantly higher amount of contaminations such as carbon, oxygen and iron were observed in the mechanically alloyed amorphous powders compared to the milled ribbons. Both powders were consolidated via spark plasma sintering. Superior particle bonding was found in the sample consolidated from milled ribbons, ascribed to the lower amount of contamination that could not effectively restrict the viscous flow and diffusion of atoms. Various complex crystalline phases evolved in the sample consolidated from milled ribbon particles due to the presence of crystalline phases in the powders which acted as nucleation sites, whereas the amorphous phase was mostly retained in its counterpart. Vickers microhardness of the consolidated alloys from milled ribbon and mechanically alloyed amorphous powders were 3.60?±?0.13?GPa and 2.53?±?0.09?GPa, respectively. The higher hardness in the former case was attributed to the superior particle bonding and distribution of hard intermetallic phases in the amorphous matrix.     

锂离子电池Si/C复合负极材料的合成与性能

采用球磨-热解工艺制备了Si/C复合负极材料。研究了球磨时间对Si/C复合负极材料结构和电化学性能的影响,并分析了电极的失效机理。研究结果表明,通过球磨可以将纳米硅颗粒均匀分散于石墨基体材料表面,同时,葡萄糖热解后形成的无定形碳使两者紧密结合。球磨3h合成的材料具有最优的电化学性能。以100mA/g的电流密度放电,首次放电容量达到1340mAh/g,首次充放电效率为75.6%,循环50次后,容量保持率为34.2%。