Influence of impurity hydrogen on the structure and properties of bulk Li and pressure effects

The structure and properties of a 16-atom body-centered cubic lithium cell with an interstitial hydrogen atom are studied using a pseudopotential-plane-wave method within the density functional theory at 0 K and high pressures. The host lattice is dramatically distorted by the introduction of H. Although the hydrogen atom is stable at the tetragonal site in perfect bcc host lattice, it favors the octahedral site formed by six non-equivalent Li atoms after full relaxation of the cell, showing P4/mmm symmetry within the pressures ranging from 0 to 6 GPa. The lattice ratio (a/c) changes irregularly with external pressure at about 3 GPa. The hydrogen band lies in the bottom of the valence band, separated by a gap from the metallic bands, illustrating the electronegativity of hydrogen. High reflectivity in the low frequency area induced by the impurity hydrogen is observed when only interband transitions are taken account of. A dip in reflectivity due to parallel band transitions is observed at ∼0.4 eV. Another dip at ∼4.3 eV appears when external pressure increases over 4 GPa.     

Nanosized multilayer films with concurrent photochromism and electrochromism based on Dawson-type polyoxometalate

An inorganic-organic composite multilayer film constructed of poly(vinyl alcohol) (PVA) with Dawson-type phosphotungstate anion [P₂W₁₈O₆₂]⁶⁻ (P₂W₁₈) and poly(allylamine hydrochloride) (PAH) were fabricated on quartz, ITO, silicon and CaF₂ substrates by a layer-by-layer self-assembly method. The film was provided with concurrent photochromism and electrochromism. IR spectra showed that the structure of the PVA was fully maintained in the multilayer film. And their photochromic and electrochromic properties were investigated by UV-vis spectra, cyclic voltammetry (CV), chronoamperometry (CA) measurement and X-ray photoelectron spectra (XPS). Atomic force microscopy (AFM) was used to investigate the surface topography. This study provides a new route to explore the possibility of application to polyoxometalate-based hybrid inorganic-organic materials.     

葡萄糖、肌醇与抗坏血酸的相互作用研究

利用电化学、密度泛函理论和分子中的原子理论,从微观角度研究了葡萄糖、肌醇与抗坏血酸的相互作用。两种混合体系在水溶液及磷酸盐缓冲溶液中的电化学结果表明,抗坏血酸中烯二醇羟基上的氢原子可与葡萄糖/肌醇羟基上的氧原子形成氢键,使得抗坏血酸的电氧化反应难以发生。量子化学计算进一步证明了上述两种混合体系中氢键的存在。     

Pyrolysis characteristics of cellulose derived from moso bamboo and poplar

To compare with pyrolysis characteristics of cellulose from moso bamboo and poplar, samples were pyrolyzed with different heating rates through thermogravimetric analysis (TG). The kinetics was calculated by Kissinger–Akahira–Sunose method. The results showed that pyrolysis process of moso bamboo and poplar fiber included three stages, and the main pyrolysis occurred in the second step. Moso bamboo fiber had a higher start temperature, a lower end temperature and a more mass loss at each heating rate in the main pyrolysis stage. With increase in heating rate, the temperature corresponding to the maximum of mass loss increased and the DTG curve shifted to higher temperature. The reaction rates varied at different heating rates. The activation energy of cellulose from moso bamboo was lower than poplar cellulose, indicating cellulose of moso bamboo was easier to be pyrolyzed. The results from this research will provide guidance to thermal conversion of moso bamboo and poplar.

     

一氧化碳加氢Fe_2O_3/AlPO_4-5催化剂的表面分散状态及性质

1.前言 采用具有ZSM-5,ZSM-11和ZSM-48沸石结构的高硅沸石作为CO加氢反应的催化剂载体,有效地控制了产物分布范围。AlPO_4-5分子筛的孔道结构和表面性质决定了它同样可作为催化剂载体以代替沸石。关于AlPO_4-n分子筛的研究,目前多着重于合成和结构方面,以其作为催化剂和催化剂载体的报道较少。由于AlPO_4-n分子筛无离子交换性,致使负载金属AlPO_4-n催化剂的制备受到限制。根据“某些盐类或氧化物与高比表面载体混合,在低于熔点的适当温度下焙烧,这些盐类或氧化物在载体表面能自发分散”的原理,本文采用固相焙烧法制备了系列Fe_2O_3/AlPO_4-5催化剂并用于CO加氢反应,研究铁活性组分在AlPO_4-5分子筛表面的分散状况及催化活性。     

荧光1,2,4-噻二唑-3,5-二酮衍生物的合成及其对精子的标记作用

合成了3个含有荧光基团的1,2,4-噻二唑-3,5-二酮衍生物,其结构经¹H NMR,¹³C NMR, HR-MS(ESI)表征,并考察了这些衍生物对精子的制动活性和荧光标记作用。结果表明：与先导化合物Tideglusib相比,目标化合物均保持了较强的杀精活性,且在紫外光激发下,具有相似的荧光标记模式。     

Unprecedented mid-infrared nonlinear optical materials achieved by crystal structure engineering,a case study of (KX)P2S6 (X = Sb,Bi, Ba)

Three acentric type-I phase-matchable infrared nonlinear optical materials KSbP₂S₆, KBiP₂S₆, and K₂BaP₂S₆, showing excellent balance between the second harmonic generation coefficient, bandgap, and laser damage threshold, were synthesized via a high-temperature solid-state method. KSbP₂S₆ is isostructural to KBiP₂S₆, which both crystallize in the β-KSbP₂Se₆ structure type. K₂BaP₂S₆ was discovered for the first time, which crystallizes in a new structure type. KSbP₂S₆ and KBiP₂S₆ exhibit close structural similarity to the parent compound, centrosymmetric Ba₂P₂S₆. The [P₂S₆] motifs, isotypic to ethane, exist in Ba₂P₂S₆, KSbP₂S₆, KBiP₂S₆, and K₂BaP₂S₆. The mixed cations, K/Sb pair, K/Bi pair, and K/Ba pair, play a dual-role of aligning the [P₂S₆] structure motifs, contributing to a high SHG coefficient, as well as enlarging the bandgap. KSbP₂S₆, KBiP₂S₆, and K₂BaP₂S₆ are direct bandgap semiconductors with a bandgap of 2.9(1) eV, 2.3(1) eV and 4.1(1) eV, respectively. KSbP₂S₆, KBiP₂S₆, and K₂BaP₂S₆ exhibit a high second harmonic response of 2.2× AgGaS₂, 1.8× AgGaS₂, and 2.1× AgGaS₂, respectively, coupled with a high laser damage threshold of 3× AgGaS₂, 3× AgGaS₂, and 8× AgGaS₂, respectively. The DFT calculations also confirm that the large SHG coefficient mainly originates from [P₂S₆] anionic motifs.

Three superior type-I phase-matching middle infrared nonlinear optical materials (E_a > 4.0 eV, d_ij > 2× AGS, LDT > 8× AGS) were achieved via crystal structure engineering.     

Porous Si/C composite as anode materials for high-performance rechargeable lithium-ion battery

A novel porous silicon was synthesized through a magnesiothermic reduction method of molecular sieve for the first time, the porous silicon was used as anode material, which shows a high initial specific capacity of 2018.5 mAh/g with current density of 0.1 A/g.     

PAMAM树枝状高分子自组装膜的微摩擦性能研究

自组装超薄膜的研究是近年来的热点课题，其制备与应用已深入到各个领域．研究表明，以高分子为构筑单元的有序结构超薄膜具有优良的微摩擦性能．在微摩擦学研究中，用C60作刚性基团，提高薄膜润滑材料的承载能力，已有不少报道．Tsukruk和Perry等分别研究了由C60组装形成的单层膜的微摩擦行为．薛群基等曾尝试在脂     

Response of a hypersonic blunt cone boundary layer to slow acoustic waves with assessment of various routes of receptivity

The hypersonic boundary-layer receptivity to slow acoustic waves is investigated for the Mach 6 flow over a 5-degree half-angle blunt cone with the nose radius of 5.08 mm. The plane acoustic wave interacts with the bow shock, and generates all types of disturbances behind the shock, which may take various routes to generate the boundary-layer unstable mode. In this paper, two routes of receptivity are investigated in detail. One is through the disturbance in the entropy layer. The other is through the slow acoustic wave transmitted downstream the bow shock, which can excite the boundary-layer mode due to the synchronization mechanism. The results show that, for a low frequency slow acoustic wave, the latter route plays a leading role. The entropy-layer instability wave is able to excite the first mode near the neutral point, but its receptivity efficiency is much lower.