Pressureless densification and mechanical properties of hafnium diboride doped with B4C: From solid state sintering to liquid phase sintering

A pressureless sintering process, using a small amount of boron carbide (≤2 wt%) as sintering aid, was developed for the densification of hafnium diboride. Hafnium diboride ceramics with high relative density were obtained when the sintering temperature changed from 2100 °C to 2350 °C. However, the sintering mechanism was varied from solid state sintering (SSS, below 2300 °C) to liquid phase sintering (LPS, above 2300 °C). Boron carbide addition improved densification by removing the oxide impurities during solid state sintering and by forming a liquid phase which was well wetting hafnium diboride grains during liquid phase sintering process. The different roles of B₄C on the microstructure development and mechanical properties of the sintered ceramics were investigated.     

Morphologies and thermal properties of flame-retardant polystyrene/α-zirconium phosphate nanocomposites

The phosphorus- and nitrogen-containing monomer, acryloxyethyl phenoxy phosphorodiethyl amidate (AEPPA), was synthesized and characterized. Poly(St-co-AEPPA)/α-zirconium phosphate (α-ZrP) nanocomposites with different amounts of α-ZrP were then prepared by in situ radical bulk copolymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the α-ZrP layers were exfoliated in the polymer matrix. Improvements in thermal stability and char residues of the copolymer and nanocomposites were observed by thermogravimetric analysis (TGA). The incorporation of AEPPA can reduce the flammability of polystyrene (PS). Moreover, further reductions were observed when α-ZrP was added. The reduction in flammability was attributed to a lower maximum mass loss rate and more char residues of the nanocomposites involved in thermal degradation.     

Compatible and crystallization properties of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) blends

Differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis (DMA) properties of poly(lactic acid)/ poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) specimens suggest that only small amounts of poor PLA and/or PBAT crystals are present in their corresponding melt crystallized specimens. In fact, the percentage crystallinity, peak melting temperature and onset re‐crystallization temperature values of PLA/PBAT specimens reduce gradually as their PBAT contents increase. However, the glass transition temperatures of PLA molecules found by DSC and DMA analysis reduce to the minimum value as the PBAT contents of PLA_xPBAT_y specimens reach 2.5 wt %. Further morphological and DMA analysis of PLA/PBAT specimens reveal that PBAT molecules are miscible with PLA molecules at PBAT contents equal to or less than 2.5 wt %, since no distinguished phase‐separated PBAT droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLA/PBAT specimens, respectively. In contrast to PLA, the PBAT specimen exhibits highly deformable properties. After blending proper amounts of PBAT in PLA, the inherent brittle deformation behavior of PLA was successfully improved. Possible reasons accounting for these interesting crystallization, compatible and tensile properties of PLA/PBAT specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studying protein–ligand interactions using protein crystallography

Protein X-ray crystallography is now a relatively high-throughput technique that plays a major role in structure-based drug design programs where the method of soaking small organic ligands into protein crystals is used to confirm or identify binding modes. In this review, we discuss some experimental approaches for ‘soaking-in’ ligands into protein crystals where the major problem is poor solubility of the ligand. We also provide examples showing how crystal soaking can be used as a technique for establishing ligand binding strength: K _c (the apparent ligand–protein dissociation constant in the crystal), which for some proteins at least, is found to be very similar to the solution K _d. Kinetic effects are also found to be important and the rate at which ligands soak into crystals is shown to vary by orders of magnitude from 10^?1 to 10⁷?s depending on the system.     

1,3-丁二醇的合成方法

1,3-丁二醇是合成各种活性化合物的重要活性中间体。本文综述了1,3-丁二醇工业生产的路线,并重点探讨了两种主要合成方法的优缺点。     

Functionalization of multi-walled carbon nanotube for electrocatalytic oxidation of nitric oxide

The multi-walled carbon nanotube (MWCNT) was functionalized with hydroxyl, carboxyl and amido groups on the surface. Electrocatalytic oxidation of nitric oxide (NO) at the MWCNT modified electrodes was investigated. It was found that the MWCNT modified electrode could speed up greatly the electron transfer rate compared with the glass carbon electrode, and there was an adsorptive step for the oxidation of NO at the MWCNT modified electrode. The activation energy of NO electrooxidation reaction at modified electrode of MWCNT treated by alkali and mixed acids (MWCNT-OH–COOH) decreased, and current density was almost two times that of the electrode modified with alkali treated MWCNT. The modified electrodes of MWCNT amidated with the aliphatic amines decreased the activation energy of NO oxidation compared with MWCNT modified electrode, but the reaction rate of amidated MWCNT electrodes decreased because of the steric effect. The results demonstrated that MWCNT-OH–COOH modified electrode is the best for NO electrocatalytic oxidation.     

Effect of Al2O3/CaO on the melting and mineral transformation of Ningdong coal ash

Coal ash melting characteristics has a direct impact on the smooth operation of entrained gasifier. Mineral conversion of coal ash is very significant to be investigated, because the mineral can affect the melting temperature and viscosity under high temperature conditions. In this paper, the effects of different Al₂O₃/CaO on the mineral conversion, melting temperature and viscosity of Ningdong coal ash are studied by the combination of experiment and simulation. The trend of melting temperature decreases firstly and rises with increasing Al₂O₃/CaO. The ash melting point reached to the lowest when the ratio is 1.23. XRD and Factsage software are used to analyze crystallization behavior of samples. The results show that the content of anorthite, albite and corundum increases and subsequently decreases, while the content of mullite decreases firstly and then rises with increasing Al₂O₃/CaO. High content with CaO can contribute to form albite and anorthite of low-melting. Besides, high content with Al₂O₃ can tend to produce mullite of high-melting. The results of experimental and simulation are basically the same, which lays a foundation for the melting characteristics of Ningdong coal ash and can provide technical support for the smooth operation of the entrained-gasifier.     

沂沭泗涉河建设管理问题及对策

沂沭泗地区涉河建设项目类型较多,涉及的省份也多,加之一些建设单位不履行相关报批手续,未经审批擅自强行施工,或未按批复要求建设等,给管理工作带来了许多困难。为加强涉河建设项目的管理,基层管理单位要提高认识,主动为地方政府提供服务,同时要建立健全相应的管理制度,加强项目的监管,严格程序,依法行政。     

伊洛河流域水资源系统优化调度模型研究

针对河流并联供水库群水资源优化分配问题,建立了以相对缺水率最小为目标的流域水量调度应用模型。该模型运用大系统分解协调的基本原理,将并联供水库群分解为多个独立的子系统,子系统间存在控制反馈的联系,同时考虑河道水流传播对系统的影响。利用建立的模型,以伊洛河流域供水库群为研究对象,通过建立虚拟水库,将伊洛河供水库群分为三个子系统,选用整体改进的遗传算法(GA)进行计算求解,并采用常规调度方法进行校核。以水平年2020年为例,得到不同来水条件下伊洛河流域水量调度方案,并对特枯来水情况制定供水三级预警系统。     

液氨处理对大麻纤维结构与性能的影响

针对大麻纤维刚性大,延伸性差,纤维硬而脆,在外力作用下易产生永久变形等问题,采用液氨处理来改善其理化性能。研究液氨处理对大麻纤维理化性能的影响,并对实验结果进行分析,结果表明:大麻纤维经过液氨处理后,纤维密度由处理前的1.537 7 g/cm3下降为处理后的1.531 9 g/cm3;压缩率和压缩弹性率得到提高;静摩擦因数和动摩擦因数有所减小;液氨处理对大麻纤维的束纤维强力影响不大,但使其染色性能得到改善。