Aligned carbon nanofibers (CNFs) with a population density of about 3 × 108 cm−2 are synthesized on electrochemically roughened silicon using the bias-assisted chemical vapor deposition system. Isolated CNFs with much lower population density (∼3 × 106 cm−2) are formed on polished silicon wafer at the same growth conditions. The morphologies, microstructures, and components of the CNFs are accordingly characterized using scanning electron microscopy, Raman spectroscopy, transmission electron microscopy, and energy dispersive analysis of X-rays. On the basis of the surface barrier limited diffusion model, it is shown that electrochemical roughening of silicon surface can increase the population density of energetic carbon species that act as self-catalysts for the vertical growth of CNFs. The formation of CNFs with cone-shaped tips simultaneously involves the vertical growth and a continuous thinning of fiber tips by the bombarding of CH4 + and H+ ions in CH4/H2 plasma.

A uniform diamond nanocone array was formed by plasma etching of diamond film in a hot filament chemical vapor deposition (HFCVD) system. A surface amorphous carbon coating layer, which is formed during CH4/H2 plasma-etching process, was removed by Ar plasma in a reactive ion etching system. The hydrogenation of diamond nanocones was performed in H2 ambience by using the same HFCVD system. The air-diluted NH3 and NO2 gases sensing properties of the diamond cone arrays had been studied by using electric current versus measurement time characteristics at room temperature. The repeatable chemical sensing properties of the hydrogenated diamond cone array sensor are enhanced, in comparison with as-formed diamond film. Surface two-dimensional hole gas structure and greatly increased surface-to-volume ratio both play a key role for the excellent detection performance. As-formed diamond nanocone arrays show a promising prospect for applications as chemical sensor for both reducing (NH3) and oxidizing (NO2) gases.

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Both experimental and simulation studies were run to investigate the effects of deformation sequence on stress and strain states and thickness distribution during tailor-welded tube hydroforming. The effects of geometrical boundary condition were also studied. Then, an approach to improve thickness uniformity was put forward. Both stress and strain histories indicate that the deformation states of thinner and thicker tubes were obviously different duo to the difference in thickness during tailor-welded tube hydroforming. These induce tensile strain concentrates to happen near weld seam on thinner tube, but compressive strain on thicker tube, which lead to strain mutation around weld seam on tailor-welded tube components. As result, bigger thinning takes place on thinner tube. The difference in thinning ratio between thinner and thicker tubes reaches about 6.6%. By deformation sequence optimization, thickness distribution uniformity can be improved obviously. When deformation sequence altered from thicker tube to thinner tube, the difference in thinning ratio between two segments can be decreased to 1.5%. At last, the effects of geometrical parameters of preform component were analyzed and the suitable parameters were given.

Finite element analysis (FEA) and experiment were conducted to reveal the reason of weld seam movement and its effects on strain state and thickness distribution during tailor-welded tube (TWT) hydrobulging with dissimilar thicknesses. It is indicated that weld seam movement happens during TWT hydrobulging, and the direction is from the thinner tube to the thicker tube, which induces nonuniform thickness distribution. The different strain states during the bulging process are the intrinsic feature of weld seam movement. Weld seam movement is aggravated by thickness difference between thinner and thicker tubes increase, but is insensitive to weld seam position. When the thickness ratio is bigger than 1.4, movement would concentratedly occur during the late period of the hydrobulging process. Such kind of deformation character can bring out local thickness thinning on a thinner tube, but on the contrary for a thicker tube, especially at the zone adjacent to weld seam. Consequently, sharp fluctuation of thickness distribution is brought out near the weld seam, which obviously cuts down fatigue life of the tube component.