Role of Cu film texture in grain growth correlated with twin boundary formation

To understand the role of Cu film texture in grain growth at room temperature (RT) in relation to twin boundary formation Cu films were deposited on various barrier materials and the Cu film texture was investigated by X-ray diffraction. Cu grain growth was rapid on a barrierless SiO₂/Si substrate and very slow on a Ta barrier due to strong (1 1 1) texture. The growth rate and the average grain diameter after being kept at RT for up to ∼60 days were maximum at a (2 0 0)_Cu peak to (2 2 2)_Cu peak area ratio of ∼1.0, where {1 1 1}, {1 0 0} and {5 1 1} grains coexisted. Such coexistence of three or more orientations of grains is essential in facilitating Cu grain growth at RT. Similarly, the average twin boundary (TB) density was maximum when Cu grain growth was facilitated. TB formation in nano-sized Cu grains was not controlled by grain size, but due to grain growth. The TB could be annealing twins caused by irregularities in the stacking sequence during relatively fast grain growth. The Cu film texture is concluded to be determined at the beginning of deposition, and the wettability of various barrier materials by the Cu films plays a key role in determining the film texture.     

Optical assessment of silicon nanowire arrays fabricated by metal-assisted chemical etching

Silicon nanowire (SiNW) arrays were prepared on silicon substrates by metal-assisted chemical etching and peeled from the substrates, and their optical properties were measured. The absorption coefficient of the SiNW arrays was higher than that for the bulk silicon over the entire region. The absorption coefficient of a SiNW array composed of 10-μm-long nanowires was much higher than the theoretical absorptance of a 10-μm-thick flat Si wafer, suggesting that SiNW arrays exhibit strong optical confinement. To reveal the reason for this strong optical confinement demonstrated by SiNW arrays, angular distribution functions of their transmittance were experimentally determined. The results suggest that Mie-related scattering plays a significant role in the strong optical confinement of SiNW arrays.     

船用柴油机NOx等有害排放气体的评价及处理研究--燃料喷射系统对乳化燃料在船用柴油机上使用的影响及脱硝装置的适用性

对原试验用柴油机的燃料喷射系统进行了改造。改造后的燃料喷射系统不仅可降低 NOx 的排放 ,而且使高加水率乳化燃料的使用成为可能。但另一方面 ,在低负荷时 ,使用乳化燃料不但不能获得预期的降低 NOx 排放效果 ,反而使其它有害排放增加。所以 ,也对降低 NOx 排放方法之一的脱硝装置进行了探讨 ,对其在船用柴油机上的适用性进行了试验 ,并获得了较好的效果     

Intercritically annealed and isothermally transformed 0.15 Pct C steels containing 1.2 Pct Si-1.5 Pct Mn and 4 Pct Ni: Part II. effect of testing temperature on stress-strain behavior and deformation-induced austenite transformation

Stress-strain behavior and deformation-induced transformation of retained austenite were studied for intercritically annealed and isothermally transformed Si-Mn and Ni steels as a function of testing temperature between −80 °C and 120 °C. Rapid decrease of retained austenite at small strains dominates at low-temperature testing and in microstructures containing martensite. The austenite transformation in microstructures without martensite shifts to larger strains with increasing testing temperature. The accompanying increase of strain-hardening rates at larger strains deters the onset of necking and improves ductility. The benefits of the austenite transformation lead to a peak in ductility between 20 °C and 70 °C in the Si-Mn steel and at 70 °C in the Ni steel. The peaks are dependent on the nature of the dispersed microconstituents produced in the ferrite during isothermal transformation. Higher testing temperatures enhance the mechanical stability of the austenite and result in lower ductility.     

X-ray Diffraction Study of the Structure of Silicon Nitride Fiber Made from Perhydropolysilazane

Continuous stoichiometric silicon nitride fiber was produced by the pyrolysis of perhydropolysilazane. This high-purity silicon nitride fiber is colorless and has high strength, modulus of elasticity, and thermal stability which are properties suitable for reinforcing plastics, metals, glasses, and even ceramics. The structures of three kinds of amorphous silicon nitride fibers (with stoichiometric, Si-excess and O-excess composition) were investigated by X-ray diffraction followed by calculating the radial distribution functions. Radial distribution functions were calculated from several possible crystal structures and compared with observed radial distribution functions.     

Mechanical properties of silk fibroin–microcrystalline cellulose composite films

Silk fibroin–microcrystalline cellulose (cellulose whisker) composite films with varied compositions were prepared by casting mixed aqueous solution/suspensions of the two components. Silk fibroin was dissolved in 10M LiSCN followed by dialysis; a cellulose whisker suspension was prepared by sulfuric acid hydrolysis of tunicate cellulose. Macroscopically homogeneous films were obtained at all mixing ratios. While the Young's modulus of the composite films showed a linear, additive dependence on the mixing ratio, the tensile strength and ultimate strain showed a maximum at a 70–80% cellulose content, reaching five times those of fibroin‐alone or cellulose‐alone films. At the same mixing ratio, infrared spectra of the composite films showed a shift of the amide I peak from 1654 to 1625 cm^?1, indicating the conformational change of fibroin from a random coil to a β structure (silk II) at the whisker–matrix interface. This change seems to be induced by contact of fibroin molecules with a highly ordered surface of cellulose whisker. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3425–3429, 2002     

Analysis of particle trajectories of small particles in flotation when the particles and bubbles are both charged

The trajectory of a small particle moving to a bubble surface was analyzed by taking into account the effects of surface charges of the bubble and particle and the short range hydrodynamic interaction near the bubble surface, in a flotation process. The particle trajectories obtained theoretically were in good agreement with those obtained by direct observation. Even if the signs of the surface charges of the bubble and particle were the same, the particle adhered to the bubble surface when the net surface force, that is, the sum of the electrostatic force and the van der Waals force, was attractive. Particle capture efficiency, η_S, per bubble was estimated by trajectory analysis and the flotation efficiency, η_T, was calculated. The values of η_T calculated by the particle trajectory analysis were in reasonable agreement with those obtained experimentally. The dependence of particle diameter on η_T was also examined by the particle trajectory analysis.