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.