Qiangbing Wang

Highly Ordered Coaxial Bimodal Nanotube Arrays Prepared by Self-Organizing Anodization on Ti Alloy†

The fabrication of nanomaterials with well-ordered complex structures is one of the most important issues among advanced materials sciences, not only due to their potential applications, such as information-storage devices, microelectronics, and biosensors, but also due to their high technological impact. Electrochemical self-organization is an efficient approach towards building microblocks and nanoblocks into highly ordered macroscopic materials, which can be observed in deposition or dissolution reactions. In the past few years, highly ordered, vertically oriented tubular or porous nanostructures have been fabricated by simple anodization on Si, Al, Ti, and some other alloys. A method that provides control of the architecture of titania nanotube arrays is particularly desirable because, when such arrays are highly ordered, they possess many interesting properties. To date, the microstructure, diameter, and length of such oxide nanotubes in highly ordered arrays has been controlled by varying anodization parameters including the applied potential, concentration, pH value of electrolytes, anodization time, and suitable co-operation of alloying elements. TiO2 nanotube arrays have been the subject of extensive investigations to realize heteroatomic nanotubes, for example, Ti Nb O, Ti Al O, and Ti Fe O nanotube arrays. In the past few decades, progress has been made in fabricating coaxial nanotubular structures by filling the hollow cavities of nanotubes with nanorods, which may be shielded

Effect of sintering conditions on mechanical strength and gas permeability of long porous Inconel 625 tubes for hot gas filtration

The sintering responses of Inconel 625 prealloyed powder (powder size: 80–180 μm accounting for 96 wt-%) were first assessed using dilatometry. Then, sintering of Inconel 625 tubes (Φ54 mm × 1000 mm), shaped by cold isostatic pressing from prealloyed powder at 170 MPa, was studied at temperatures between 1180 and 1260°C in vacuum and hydrogen. Sharp, rapid shrinkage of Inconel 625 prealloyed powder was observed at 1240°C when sintered in vacuum, while this temperature was postponed to 1260°C when sintered in hydrogen due to the cooling effect of the large hydrogen gas flow. It is shown that sintering in hydrogen is better suited to the fabrication of high performance porous Inconel 625 tubes than sintering in vacuum. The preferred isothermal sintering conditions were determined to be sintering in hydrogen at 1240°C for 120 min, which resulted in balanced mechanical strength and gas permeability. The as sintered porous Inconel 625 tubes (Φ54 mm × 1000 mm) have been used to filter hot (up to 400°C) gas mixtures of SiHCl3 and HCl in continuous industrial operations for 6 months and demonstrated outstanding performance.