The effect of reaction product on the rate of addition of acetic acid to epichlorohydrin in the presence of chromium(III) acetate

The kinetics of addition of acetic acid to epichlorohydrin carried out in the presence of both the reaction product and chromium(III) acetate catalyst have been studied. At an equimolar ratio of reagents the dilution of the reacting mixture with the reaction product has been found not to affect the reaction order. The presence of product in the starting mixture, as well as temperature increase, considerably reduces the selectivity of reaction. Side reactions of epichlorohydrin are activated. Activation energy, enthalpy and entropy of the reaction all decrease in the presence of reaction product. © 2001 Society of Chemical Industry     

梯度共聚物的最新进展

阐述了梯度共聚物的概念及梯度共聚物的研究意义,介绍了梯度共聚物分类及特点,以及与这些特点相对应的各种用途。重点综述了近年来各种梯度共聚物的制备方法如常规乳液聚合、原子转移自由基聚合(ATRP)、可逆加成-断裂链转移聚合(RAFP)和氮氧调控自由基聚合(NMCRP)等,以及梯度共聚物的各种表征方法,如红外光谱(FT-IR)、核磁共振(NMR)、薄层色谱(TLC)以及X射线光电子能谱(XPS),并进一步分析了梯度共聚物的研究方向和研究重点。     

Effects of Al addition on the phase transformation and interfacial evolution in multilayer Ti-B4C composite

The fully-dense multilayer Ti-B₄C composite doped with 6 wt% Al was fabricated via tape-casting and hot-pressing sintering at 1800 °C and under a uniaxial pressure of 30 MPa for 60 min. The effects of Al addition on the phase composition, interfacial microstructure and fracture toughness of the laminate composite were investigated. Based on the results of WDS and EDS, Al addition was proved to be effective on accelerating atom diffusion between Ti and B₄C due to the melting pool around interface where liquid Al enriched, besides, it helps to transform the interfacial bonding method of physical to metallurgical. Finally, the improvement on toughness of Al doped composite can be attributed to the strong metallurgical bonding and hybrid fracture mode of interface. Our study may provide a potential method for producing high strength and toughness multilayer metal/ceramic composites.     

Effect of SnO–P2O5–MgO glass addition on the ionic conductivity of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

NASICON-type structured compounds Li_1+xM_xTi_2-x(PO₄)₃ (M = Al, Fe, Y, etc.) have captured much attention due to their air stability, wide electrochemical window and high lithium ion conductivity. Especially, Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is a potential solid electrolyte due to its high ionic conductivity. However, its actual density usually has a certain gap with the theoretical density, leading the poor ionic conductivity of LATP. Herein, LATP solid electrolyte with series of SnO–P₂O₅–MgO (SPM, 0.4 wt%, 0.7 wt%, 1.0 wt%, 1.3 wt%) glass addition was successfully synthesized to improve the density and ionic conductivity. The SPM addition change Al/Ti–O bond and P–O bond distances, leading to gradual shrinkage of octahedral AlO₆ and tetrahedral PO₄. The bulk conductivity of the samples increases gradually with SPM glass addition from 0.4 wt% to 1.3 wt%. Both SPM and the second-phase LiTiPO₅, caused by glass addition, are conducive to the improvement of compactness. The relative density of LATP samples increases first from 0 wt% to 0.7 wt%, and then decreases from 0.7 wt% to 1.3 wt% with SPM glass addition. The grain boundary conductivity also changes accordingly. Especially, the highest ionic conductivity of 2.45 × 10^?4 S cm^?1, and a relative density of 96.72% with a low activation energy of 0.34 eV is obtained in LATP with 0.7 wt% SPM. Increasing the density of LATP solid electrolyte is crucial to improve the ionic conductivity of electrolytes and SPM glass addition can promote the development of dense oxide ceramic electrolytes.     

水分析中ICP-MS在线内标对分析结果的影响

通过实验分析了内标溶液中含有测试元素的背景时,对水分析结果产生的影响,确定当背景值与样品实际含量接近时,需要扣除在线内标溶液引入的背景。使用标准加入法可以准确测定内标溶液中的背景,并在样品中扣除。     

米饭用添加剂

从营养学角度来看,米饭的营养价值有待于营养强化。本文介绍一种“米饭添加剂”,采用的原料全部是天然源营养素。食用安全,且能提高米饭的风味和营养价值。     

用增补受拉钢筋对钢筋混凝土梁、板进行加固

由于承载力不足使钢筋混凝土梁的变形过大，裂缝过大，钢筋锈蚀严重等。为了保证钢筋混凝土梁、板能正常使用，可用增补受拉钢筋来保证梁的承载能力。     

Ni基合金+WC激光熔覆层再加热时的显微组织变化特性

采用Ni基自熔合金+块状WC混合粉末进行送粉激光熔覆并获得熔覆层,对熔覆层在不同温度下加热后空冷至室温,观察相应熔覆层的显微组织变化,结果表明：Ni基自熔合金+WC送粉激光熔覆层不适合在500℃～900℃再加热处理,再此温度区间对熔覆层再加热会导致块状WC出现裂纹。Ni基自熔合金基体的显微组织在700℃以上开始不稳定,发生形态和显微组织结构的变化。熔覆层中的块状WC加热至900℃以上时裂纹会被自行焊合,温度继续升高,块状WC会发生离散,分化成细小的WC颗粒,产生这种现象的根本原因是块状WC具有先天的超细纤维、颗粒混合结构。     

BTAMoPACA与Fe(Ⅲ)、Al(Ⅲ)显色反应

在pH5.9的邻苯二甲酸氢钾－氢氧化钠缓冲体系中，在CTMAB的存在下，Fe(Ⅲ)和Al(Ⅲ)与BTAMoPACA形成最大吸收分别为670nm和690nm的有色络合物，吸收光谱严重重叠。采用双波长标准加入法对该混合显色体系进行研究，建立铁、铝同时测定的新方法，应用硅砖中痕量铁、铝的同时测定获得满意结果。