分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Titania-hydroxyapatite (HA) nanocomposites were fabricated by wet chemical synthesis approach. HA exhibited crystallographic orientation of nucleation on nano titania particle, forming the composite particles with titania being partially enwrapped with HA. Microstructural characterization by high res- olution transmission electron microscopy revealed coherent interfacial bond of (110) and (222) planes of HA crystal with (101) plane of anatase. The HA layer promoted significantly recruitment of Escherichia coli bacteria onto the titania-based particles for subsequent photocatalytic killing. Less extent of enwrapping of HA on titania particle, as accomplished by increasing the aging time of HA suspension, gave rise to better capability of photocatalytic degradation of methylene blue and sterilization of the bacteria. The novel HA-enwrapped titania powder shows great potential for environmental applications.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: The friction coefficients of diamond and hydrogen-free diamond-like carbon films were reported to be in an intermediate range, from 0.2 to 0.4, in oxygen atmosphere, but the mechanism has not been explored. Herein, by using first-principles calculations, we attempt to fill this gap by providing atomistic insights into the bonding behaviors of oxygen atom(s) at interfaces constructed by two self-mated diamond (001) or (111) surfaces. The effect of the interfacial oxygen coverage on the optimized interfacial structures is highlighted. The results show that if the oxygen coverage is not higher than 0.5, the two surfaces tend to be connected by oxygen atoms by formation of CeOeC bonds, and thus high friction is expected. Otherwise, the two surfaces keep being separated, and thus low friction is expected. The interfacial electron distributions are manifested to underlie the structural optimizations. Insights gained here together with the findings of T. E. Derry et al. concerning oxygen coverage on diamond surfaces contribute to understanding the unusual frictional behavior of hydrogen-free diamond-like carbons in oxygen atmosphere.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Four CrN coatings were deposited on 316L stainless steel by multi-arc ion plating. The tribological behaviors of the CrN coatings were investigated by ball-on-disk tribometer in seawater. The microstructure and wear track were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and profilometer. The result shows delamination is critical to wear failure of CrN coatings in seawater and micro- cracks play an important role in the evolution of delamination. The most effective approach to eliminate the delamination is fabricating a proper multilayer structure, which could limit crack propagation only to the layer. A comprehensive wear model is established.