Well aligned quasi-straight single-walled carbon nanotubes (SWCNTs) and straight SWCNTs bundle have been prepared in large scale by anode-arc vaporization of gr aphite with metallic catalysts. Various parameters such ...Well aligned quasi-straight single-walled carbon nanotubes (SWCNTs) and straight SWCNTs bundle have been prepared in large scale by anode-arc vaporization of gr aphite with metallic catalysts. Various parameters such as the catalyst preparat ion, the kinds and pressure of the buffer gases, the quantity of anode-arc curre nt intensity, and the method of purification have been examined. The influence o f these parameters on the deposited carbon yield is reported, together with obse rvations of the produced material. Improvement in synthetic techniques has resul ted in the optimal conditions for the production of large quantities of high qua lity SWCNTs in our semi-continuous synthesis method. The formation of carbon nan otubes (CNTs) was studied briefly in this paper. Owing to the magnetic pinching effect of arc current, the CNTs arrange in parallel lines along the arc current direction.展开更多
Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous ribbon and the annealed samples were closely examined by ...Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous ribbon and the annealed samples were closely examined by means of differential scanning calorimetric, conventional X-ray diffraction and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in primary crystallization into α-Al nanocrystalline particles, in order to understand structural characteristics of Al-based amorphous/nanocrystalline alloys, and nucleation and grain growth mechanism on the nanometer scale during primary crystallization. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale, but contain high density of quenched-in clusters or crystallite embryos. Primary crystallization mainly leads to formation of two-phase mixture of a-Al crystal and residual amorphous phase. The annealed ribbons exposed isother-mally at HOP C for 5, 130 minutes and heated continuously up to less than 310℃ at 40℃ C/min consist of large amount of α-Al fcc crystal nanoparticles dispersed uniformly in an amorphous matrix. However, a very little amount of finer orthorhombic Al3Ni intermetalics particles exist in the annealed ribbons heated up to 310℃. During primary crystallization, the leading kinetic mechanics to impede growth of the α-Al crystal is soft impingement, instead of geometric impingement.展开更多
基金This work was supported by Natural Science Foundation of Gansu provincethe Tackle Key Problems Foundation of Gansu pronince,China.
文摘Well aligned quasi-straight single-walled carbon nanotubes (SWCNTs) and straight SWCNTs bundle have been prepared in large scale by anode-arc vaporization of gr aphite with metallic catalysts. Various parameters such as the catalyst preparat ion, the kinds and pressure of the buffer gases, the quantity of anode-arc curre nt intensity, and the method of purification have been examined. The influence o f these parameters on the deposited carbon yield is reported, together with obse rvations of the produced material. Improvement in synthetic techniques has resul ted in the optimal conditions for the production of large quantities of high qua lity SWCNTs in our semi-continuous synthesis method. The formation of carbon nan otubes (CNTs) was studied briefly in this paper. Owing to the magnetic pinching effect of arc current, the CNTs arrange in parallel lines along the arc current direction.
文摘Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous ribbon and the annealed samples were closely examined by means of differential scanning calorimetric, conventional X-ray diffraction and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in primary crystallization into α-Al nanocrystalline particles, in order to understand structural characteristics of Al-based amorphous/nanocrystalline alloys, and nucleation and grain growth mechanism on the nanometer scale during primary crystallization. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale, but contain high density of quenched-in clusters or crystallite embryos. Primary crystallization mainly leads to formation of two-phase mixture of a-Al crystal and residual amorphous phase. The annealed ribbons exposed isother-mally at HOP C for 5, 130 minutes and heated continuously up to less than 310℃ at 40℃ C/min consist of large amount of α-Al fcc crystal nanoparticles dispersed uniformly in an amorphous matrix. However, a very little amount of finer orthorhombic Al3Ni intermetalics particles exist in the annealed ribbons heated up to 310℃. During primary crystallization, the leading kinetic mechanics to impede growth of the α-Al crystal is soft impingement, instead of geometric impingement.
