Large-scale of oriented closely packed silica nanowire bunches have been synthesized by using large size (1-10mm in diameter), low melting point tin droplets as catalyst on silicon wafers at 980℃. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses show that the amorphous silica nanowires have lengths of 50-100mm and diameters of 100-200nm. Unlike any previous observed results using high melting point metal (such as gold and iron) as catalyst, the Sn catalyst growth exhibits many interesting phenomena. Each Sn ball can simultaneously catalyze the growth of many silica nanowires, which is quite different from the conventional vapor-liquid-solid process.

This article describes for the first time the direct observation of the nucleation and growth process of closely packed silica nanowires via a vapor-liquid-solid (VLS) mechanism by using tin (Sn) as a catalyst. Initially, Sn particles formed alloy liquids, followed by the nucleation of short silica nanowires, and closely packed silica nanowires finally formed. Interestingly, our results indicated that Sn has different catalytic behavior for nanowire growth than commonly used metal catalysts such as Au and Fe. The structural features associated with different growth stages were monitored by SEM, TEM, EDX, and XPS analysis. A possible mechanism for the formation of closely packed silica nanowires is proposed.

The Dy and Ga substituted NdFeB nanocomposite permanent magnetic alloys with high magnetic properties have been prepared by appropriate wheel speed of melt-spinning and post-annealing treatment. Under optimal conditions, compared with the best magnetic properties of ternary NdFeB alloy of Jr=1∶18 T, Hci=379∶5kA=m and ðBHÞmax=119∶5 kJ=m3, the best magnetic properties of the alloy with Dy and Ga substitutions are Jr=1∶16 T, Hci=580∶5kA=m, and ðBHÞmax=162∶7kJ=m3. The XRD and TEM results showed that each of two alloys consists of hard magnetic 2∶14∶1 phase and soft magnetic a-Fe phase. The grain size of the 2∶14∶1 phase is about equal in the two alloys. The grain size and content of a-Fe phase in Dy and Ga substituted alloy are finer and lower, respectively. # 2002 Elsevier Science B.V. All rights reserved.

The behavior of rare earth element Ce in 2090 Al-Li alloys was studied by the method of low frequency internal friction. The results showed that rare earth element Ce can increase the activation energy of grain boundary and improve the grain boundary strength of alloys. Rare earth element Ce can decrease the tendency of softening of elastic modulus of 2090 Al-Li alloys after heat cycle and keep high elastic modulus of initial state.

In order to investigate the effects of Ce on mechanical anisotorpy of Al-Li alloys, the texture of 2090 Al-Li alloy with different Ce content was determined using orientation distribution function technique, in which the mechanical properties with different angles to rolling direction were measured. The effects of Ce on texture and mechanical properties of 2090 alloys were discussed. The results show that the type of main texture of 2090 alloys is 1225t <554>. Ce will not change the type of main texture of the alloy, but make the distribution of main texture scattered. Ce can change the volume fractions of ideal texture components and will decrease the anisotropy of yield strength, hence the content of the texture components that enhance the anisotropy of yield strength can be reduced.

通过Co、Cu、Ga、Tb 联合添加，采用低温长时间细晶粒烧结技术，改善Nd-Fe-B烧结磁体的热稳定性，使其应用于电机磁钢。用SEM 电镜对显微组织进行分析，结果表明，添加Co、Cu、Ga、Tb 后晶粒大小均匀，形状规则化，富Nd 相厚度变薄，使反磁化核不易形成和扩展，从而提高Nd-Fe-B 磁体的矫顽力，改善磁体的热稳定性。

采用化学还原法制备了添加稀土元素Nd 的超细Fe2B非晶合金，研究了离子浓度对产物组成的影响和反应过程中溶液pH 值的变化，分析了反应过程中pH 值的变化规律对金属离子还原机理的影响。采用电感偶合等离子光谱（ICP）、光电子能谱（XPS）、X 射线衍射（XRD）和电子透射显微境（TEM）等手段对产物的组成、表面原子的价态、晶相和形貌及颗粒大小进行了表征。结果表明，调节离子浓度可以得到组成不同的非晶合金，溶液中Fe-B+和Nd3+相对独立反应，分别生成Fe-B 物相与Nd（BO2）3和Nd（OH）3的混合物相，表明Nd3+的存在没有直接对BH-4 还原Fe2+的过程产生影响。非晶Fe2B 物相呈链球状，粒径约为250nm，非晶Nd（BO2）3和Nd（OH）3的混合体颗粒粒径<100nm，呈网络絮状分布。样品表面Fe和Nd原子分别呈+2价和+3价，B以B0和B+3混合价态的形式存在。

采用快淬及退火工艺，通过非晶晶化制备了两种成分的纳米晶，即Nd-Fe14B/α2Fe 永磁合金。研究了添加Dy+Ga 和晶化工艺对合金磁性能的影响。研究结果表明，三元Nd8.5 Fe86B5.5合金晶化是由3个过程组成的，而添加Dy+Ga 的Nd7.5Dy1Fe85B4.5 Ga2合金晶化是由2个过程组成的，与三元合金相比，添加Dy+Ga可改变α2Fe和Nd2F14B 相的形成温度及细化两相晶粒，可以显著提高合金的磁性能。

研究了经过不同热处理的NdFeB系纳米品复合永磁合金的磁滞行为。根据磁滞回线一阶导数曲线dM/dH～H分析了双相磁体磁滞回线M～H的变化情况。采用XRD和TEM对各典型回线对应的样品组织结构进行了观测分析，在欠时效和过时效条件下，dM/dH～日曲线均出现双峰，但对应不同的显微组织和不同的机制。在峰值时效条件下，合金由2∶14∶1和a-Fe双相组成，dM/dH～日曲线由单峰组成，磁滞回线表现为单相磁体的磁滞行为。

利用X射线衍射仪和扫描探针显微镜研究了NdFeB 系双相永磁合金快淬带的织构与形貌。结果表明，合金快淬带自由面存在择优取向。与三元NdFeB 合金相比，复合添加Dy 和Ga具有增加合金快淬带织构和细化组织形貌的作用。