抗菌食品保鲜膜的研究与进展

从抗菌食品保鲜膜的制备、抗菌机理、力学性能等方面综述了抗菌食品保鲜膜的研究及发展情况,指出了抗菌食品保鲜膜的发展趋势。     

纹理表面滑动接触多尺度分析

采用分子动力学与有限元耦合的多尺度方法,求解二维刚性圆柱表面压头与弹性纹理表面的纳观黏着滑动接触问题。对表面纹理凸峰高度、凸峰间距、凸峰形状、压头下压深度以及压头半径等对滑动接触性能的影响进行了全面研究。通过不同条件下滑动摩擦力的比较,揭示了上述各参数对黏着滑动接触的影响规律。凸峰高度越高,滑动摩擦力越小且越稳定;凸峰间距越大,滑动摩擦力越小;表面纹理在不发生破坏的前提下可以有效降低摩擦力;压头下压深度越小,滑动摩擦力越小;相同作用条件下,滑动摩擦力随压头半径的增大而增大。     

Molecular dynamics simulation of nanoscale contact and sliding processes for probes with different tip radius of curvature

Three-dimensional simulations were carried out molecular dynamics （MD） to study the contact and sliding processes between diamond points with different tip radius of curvature and surfaces of single crystal copper. The material deformation, abrasion mechanism, lattice defects, the force of contact process, and the sliding friction process were investigated. The simulation results show that the contact force, dislocations, and stacking fault defects, increase during the contact process with increasing contact depth or tip radius of curvature. The dislocations emit along the [10i-] and [i-01] direction and then a glide band is formed. It was also found that a greater tip radius of cur- vature results in a larger groove and more material defor- mation. The normal force and friction increase with increasing tip radius of curvature, but the coefficient of friction decreases. The stacking faults spread along the sliding direction and increase with increasing tip radius of curvature. In addition, the number of upheaval atoms increases as the radius of tip curvature or sliding distance increases.     

Rational design of carbon shell-encapsulated cobalt nanospheres to enhance microwave absorption performance

Co@C core–shell nanospheres highly dispersed on carbon supports were rationally designed to improve the microwave absorbing property of the composite material, and fabricated by one pot thermal decomposition and simple annealing process. The Co nanospheres were completely encapsulated with thin carbon shells, which can effectively prevent the oxidation of the Co surface. Additionally, the particle size of Co nanospheres were properly controlled to optimize the electromagnetic property of the composite material. As a result, the lightweight Co@C/C composites with the particle size of 20 nm exhibited much enhanced microwave absorption properties. The improved microwave absorption performance is attributed mainly to the enhanced isotropic ratio and impedance matching of magnetic composites via tuning the Co particle size. Therefore, the welldesigned core-shell Co@C composite structure will provide a new insight for the development of high performance microwave absorbers.     

“金属-Si原子链-金属”纳米结点电子输运性质的计算

运用密度泛函理论结合非平衡格林函数,以5个Si原子构成的直线链,及其与2个半无限长Au(100)-3×3电极相连接构成的金属-原子链-金属"三明治"模型为研究对象,对该结构的纳米级结点的电子输运进行了计算.结果表明,在两极距离dz=1.95~2.39nm的拉伸过程中,结点电导值有数量级的变化.当dz=2.03nm时,结点的结合能最小(ΔE=-5.43eV),结点结构最稳定,原子链内部Si—Si键长平均值为0.216nm,此时结点的电导为0.44 G0(G0=2e2/h).Si原子的px与py轨道电子形成π键,构成了电子经过结点的主要传输通道;随着正负外偏电压的增大,电导减小,且成对称变化,其I-U曲线表现出非线性特征.     

Fe3O4/纳米级Fe0去除水中Cr(VI)的研究

本文考察了Fe3O4/纳米级Fe0对污染水中Cr(VI)的去除效果,以及Fe3O4投加量、腐殖酸投加量、温度对Fe3O4/纳米级Fe0去除水中Cr(VI)的影响。结果表明：Fe3O4/纳米级Fe0对水中Cr(VI)的去除效果很好,在2min时Cr(VI)的去除率就能够达到91.4%,这个值比纳米级Fe0单独作用120min时对 Cr(VI)的去除率还要高;Fe3O4与纳米级Fe0的配比为7.5:1时,Fe3O4/纳米级Fe0对Cr(VI)的去除效果最好。温度的升高加速了Fe3O4/纳米级Fe0对水中Cr(VI)还原降解反应的进行。     

Multiscale structures of Zr-based binary metallic glasses and the correlation with glass forming ability

Thermal behaviors and structures of three Zr-based binary glass formers, Zr50Cu50, Zr64Cu36 and Zr64Ni36, were investigated and compared using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), high energy X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). The high energy XRD results show that the bulk glass former Zr50Cu50 has a denser atomic packing efficiency and reduced mediumrange order than those of marginal glass formers Zr64Cu36 and Zr64Ni36. Based on TEM observations for the samples after heat treatment at 10 K above their crystallization onset temperatures, the number density of crystals for Zr50Cu50 was estimated to be 1023–1024 m?3, which was four-orders higher than that in Zr64Cu36 and Zr64Ni36 metallic glasses. SAXS results indicate that Zr50Cu50 has higher degree of nanoscale inhomogeneities than those in Zr64Cu36 and Zr64Ni36 at as-cast state. The observed multiscale structures are discussed in terms of the phase stability and glass-forming ability of Zr-based binary glass formers.     

纳米Ni-Fe-B催化还原剂的制备及表征

用NaBH4还原Fe2＋和Ni2＋制备了Ni-Fe-B合金粉末,利用TEM、XPS、XRD、BET-N2和AAS等表征手段,测定了合金中Ni、Fe和B等的含量,形状和大小,物相结构及其BET比表面积,表面组成及表面电子能态.TEM表明,Ni-Fe-B的平均粒径在30 nm左右,Ni含量为5 wt%时,其BET为22.8 m2g-1.XPS结果表明,表面Ni浓度较高.XRD谱图显示,仅在衍射角2θ为44.5°处有一宽峰,呈典型的非晶态合金衍射,因此可作为优良的加氢催化剂.