Microstructure and Mechanical Properties of Cu Matrix Composites Reinforced byTiB2/TiN Ceramic Reinforcements

Cu matrix composites reinforced by TiB₂/TiN ceramic reinforcements (Cu/TBN composites) were prepared by hot pressing method. Prior to the hot pressing, Cu/TiB₂/TiN composite powders (CTBN powders), which were used as the starting materials of Cu/TBN composites, were fabricated by self-propagating high-temperature synthesis method. The CTBN particles were found to be in a special core-shell structure with a Cu-Ti alloy core and a TiB₂/TiN ceramic shell. The test results presented obvious improvements in mechanical properties. The highest ultimate tensile strength reached up to 297 MPa, 77 MPa higher than that of Cu. And the highest hardness reached up to 70.7 HRF, 15.7 HRF higher than that of Cu. A comparative study indicated that the core-shell structured particles could bring about more obvious strengthening effect than the traditional irregularly shaped particles, which was due to the improved Cu/ceramics interfacial bonding, the linkage strengthening effect of both TiB₂ and TiN, and higher load bearing ability of the core-shell structured reinforcements.     

Synthesis of high-entropy diboride nanopowders via molten salt-mediated magnesiothermic reduction

Powder synthesis is critical for implementing the wide applications of high-entropy diborides (HEBs). However, the low-temperature synthesis of HEB powders was rarely reported. Herein, the low-temperature synthesis of the single-phase HEB nanopowders via molten salt-mediated magnesiothermic reduction (MMR) method was reported for the first time. The results showed that the as-synthesized nanopowders consisted of the single-phase HEBs and their average particle sizes are in the range of 28-56 nm. Meanwhile, they possessed the good compositional homogeneity and the low-content oxygen impurity in the range of 4.13-6.12 at%. In addition, their formation mechanism could be well interpreted by a classical MMR growth process.     

The study of short-shot water-assisted injection molding of short glass fiber reinforced polypropylene

water penetration length and fiber orientation (along the melt flow direction) are important indicators for water-assisted injection molding products of the fiber-reinforced polymer. The effects of melt short shot size, water injection delay time and water injection pressure on these two important indexes are analyzed theoretically and experimentally. The study found that with the increase of the melt short shot size, the extension of the water injection delay time and the increase of the water injection pressure, the water penetration length changed from 216 to 96 mm, 170 to 210 mm, and 215 to 180 mm, respectively. Therefore, it can be known that melt short shot size has the greatest influence on water penetration length, followed by water injection delay time, and finally water injection pressure. Meantime, due to the fiber orientation and change degree of water-assisted injection-molded products along the melt flow direction, the fiber orientation in the water channel layer along the melt flow direction has the highest and lowest change degree, followed by the wall layer and finally the core layer. It can be known that the melt short shot size has the greatest influence on the fiber orientation and the degree of change along the melt flow direction, followed by the water injection delay time, and finally the water injection pressure.     

四种单萜类查尔酮的合成

以2, 4, 6-三羟基苯乙酮和柠檬醛为起始原料经过环化、羟醛缩合和催化加氢合成四种单萜类查尔酮;关键步骤2, 4, 6-三羟基苯乙酮和柠檬醛是在吡啶的催化下经过电子环化、质子迁移及Diels-Alder反应合成天然产物desbenzylidenerubramin (1),中间体1合成一种天然产物产物rubraine (2~5),其结构经~1H NMR和HREIMS表征。     

Proton-Detected Solid-State NMR of the Cell-Free Synthesized α-Helical Transmembrane Protein NS4B from Hepatitis C Virus

Proton-detected 100 kHz magic-angle-spinning (MAS) solid-state NMR is an emerging analysis method for proteins with only hundreds of microgram quantities, and thus allows structural investigation of eukaryotic membrane proteins. This is the case for the cell-free synthesized hepatitis C virus (HCV) nonstructural membrane protein 4B (NS4B). We demonstrate NS4B sample optimization using fast reconstitution schemes that enable lipid-environment screening directly by NMR. 2D spectra and relaxation properties guide the choice of the best sample preparation to record 2D ¹H-detected ¹H,¹⁵N and 3D ¹H,¹³C,¹⁵N correlation experiments with linewidths and sensitivity suitable to initiate sequential assignments. Amino-acid-selectively labeled NS4B can be readily obtained using cell-free synthesis, opening the door to combinatorial labeling approaches which should enable structural studies.     

苯并噁嗪树脂的合成及在形状记忆聚合物中的应用研究进展

苯并噁嗪树脂作为一类新型的热固性树脂，具有分子设计性强、阻燃性能和耐腐蚀性能优异、固化时不需要强酸、无小分子放出等优点，在航空、建筑、电子等领域获得了广泛应用。本文主要介绍了苯并噁嗪单体的合成方法（溶剂法、无溶剂法和悬浮法）、降低苯并噁嗪开环聚合温度的方法（合成具有特殊基团的苯并噁嗪单体、添加催化剂）及苯并噁嗪树脂在形状记忆聚合物中的应用（与其他聚合物混合，纯苯并噁嗪化学改性），对苯并噁嗪形状记忆聚合物目前存在的问题进行了概述并对苯并噁嗪形状记忆聚合物的发展前景做出了展望。     

Electrolytic synthesis of TiC/SiC nanocomposites from high titanium slag in molten salt

The molten salt electrolytic method for the preparation of titanium carbide and silicon carbide composites has been subjected to a systematic investigation by experimental analyses and thermodynamic calculations. It has been confirmed that the electrolysis of high titanium slag in the presence of mixed graphite powders generates intermediates CaTiO₃, Ti₂O₃, TiO, Fe₃Si and objective carbonous products TiC/SiC. It has been furthermore found that the deoxidization process depends critically on a number of process parameters, namely, electrolyte composition, graphitic regime, reaction temperature, cell voltage and reaction time. After careful optimization of these parameters, TiC/SiC nanocomposites with particle sizes of 10–174 nm has been produced by electrolysis of high titanium slag and graphite mixtures in molar ratio of 1:2 referred to Ti:C under 3.2 V at 900 °C for 6 h in 1 mol%CaO-CaCl₂-NaCl molten salt and with particle sizes of 12 nm~207 nm in 1 mol%CaO-CaCl₂ electrolyte.     

In vitro cytotoxicity of monticellite based bioactive ceramic powder synthesized from boron derivative waste

The cytotoxicity of monticellite based bioactive ceramic powder, which was synthesized from boron derivative waste has been determined by in vitro assays of MTT, NRU, and JC-1 staining. The toxicity of powder on different mammalian cell lines (3T3-L1, HUVEC, CRL-2120) was evaluated at the concentrations of 10, 100, 200, 400 and 800?µg/mL to justify its potential for biomedical applications. The obtained results showed that monticellite based bioactive ceramic powder possesses not only bioactive feature but also biocompatible characteristic at the concentration range of 10–200?µg/mL. Hence, monticellite based bioactive ceramics have high potential as a bone graft substitute for bone void filling and coating applications.     

A novel route for synthesis of alumina–chromium carbide composites from PTFE-activated Cr2O3/Al/C combustion

Fabrication of alumina-chromium carbide composites was investigated by PTFE-activated Cr₂O₃/Al/C combustion synthesis. PTFE was employed as not only a reaction promoter, but a carburizing agent. Three reaction systems were prepared with different contents of carbon for the synthesis of Cr₂₃C₆, Cr₇C₃, and Cr₃C₂. The amounts of PTFE were selected to ensure combustion synthesis in the SHS (self-propagating high-temperature synthesis) mode and to provide carbon in quantities of 15 and 25?mol% of the total carbon. Experimental results showed that the combustion wave velocity and temperature decreased with increasing carbon, but increased with PTFE. A correlation between combustion wave velocity and temperature contributed to determination of the activation energy E_a =?89.15?kJ/mol for the combustion reaction. The increase of PTFE also improved formation of chromium carbides. As a result, the Cr₂₃C₆– and Cr₇C₃–Al₂O₃ composites were produced with almost no impurities. Due to a loss of carbon in carbothermic reduction, the Cr₃C₂–Al₂O₃ composite was obtained with Cr₇C₃ as the secondary carbide. SEM micrographs and DES analyses indicated that spherical carbide grains with a size of 0.5–3.0 μm were synthesized.     

CuInS2/SiNWs/Si composite material for application as potential photoelectrode for photoelectrochemical hydrogen generation

This work aims at developing a new composite material based on nanosized semiconducting CuInS₂ (CIS) particles combined with silicon nanowires grown on a silicon substrate (SiNWs/Si) for photoelectrochemical (PEC)-splitting of water. The CIS particles were prepared via a colloidal method using N-methylimidazole (NMI) as the solvent and an annealing treatment. The SiNWs were obtained by chemical etching of silicon (100) substrates assisted by a metal. The CIS/SiNWs/Si composite material was obtained by deposition of an aliquot of a suspension of CIS particles onto the SiNWs/Si substrate, using spin coating followed by a drying step. The XRD pattern demonstrated that CuInS₂ grows in the tetragonal/chalcopyrite phase, while SiNWs/Si presents a cubic structure. The SEM images show semi-spherical particles (～10 nm) distributed on the surface of silicon nanowires (～10 μm). The EIS measurements reveal n-type conductivity for CIS, SiNWs/Si and CIS/SiNWs/Si materials, which could favour the oxidation reaction of water molecules.