用正电子湮没寿命谱法研究锡镀层缺陷

光亮镀锡工艺由于成本低、无毒、镀层稳定性好而广泛应用于电子元器件引线的电镀.但因锡镀层与基体之间会发生原子的相互扩散,致使产品在储存、焊接或使用期间因温度效应而使某些重要的物理和化学性能,如钎焊性、导电性和防腐性变差。金属界面原子的热扩散行为与金属晶体的结构缺陷密切相关,因此应用正电子湮没寿命谱法研究锡镀层在热处理过程中缺陷的运动规律,在理论和工艺方面都具有重要的意义。     

浅谈制药工程专业有机化学实验教学的心得和体会——以三苯甲醇的制备和重结晶实验为例

有机化学实验是制药工程专业的一门必修课,旨在训练学生有机合成基本实验技能。本文以三苯甲醇的制备和重结晶实验为例,讲述了笔者在多年教学中获得的一点感悟和经验:1)将实验步骤分解成片断讲解可以使学生更好地理解和记忆实验过程和操作目的;2)重要的基本操作应反复练习,即"学习、复习、提高",通过三次重复练习来实现巩固和熟练掌握该操作的目的。     

布洛芬晶体转晶与表征

利用两种不同的有机溶剂乙醇和异丙醇以及三种添加剂葡萄糖、聚乙烯吡咯烷酮、十二烷基苯磺酸钠,通过非溶剂法转晶制得不同形态的布洛芬晶体,使用电子扫描显微镜(SEM),差热扫描量热仪(DSC),X射线粉晶衍射(XRPD)等方法对其进行了表征.利用表征结果研究了结晶体系极性和氢键对晶体生长的影响,发现溶剂和添加剂通过不同的作用方式影响晶体的生长规律.     

W/Cu梯度功能材料的高热负荷性能研究

用等离子体喷涂和热压方法制作了W/Cu梯度功能材料(FGM)样品,用大功率ND∶YAG激光对其进行了高热负载模拟实验.结果表明,在100～400MW@m-2的瞬时(脉冲宽度为4ms)热负载下,经过200～700次热循环,未发现有W-Cu复合体开裂.在123MW@m-2的功率密度下作用700次,发现钨表面有再结晶现象及严重的晶界腐蚀和裂纹,再结晶的平均晶粒尺寸约为5～10μm,垂直于表面呈柱状结构,再结晶层厚度约20～30μm.由于激光的淬冷效应,晶粒生长的趋势并不明显.在398MW@m-2功率密度下出现了明显的腐蚀坑,坑内呈疏松的蜂窝结构,坑的边缘出现了明显沉积区,能谱分析表明沉积区集聚了大量的金属杂质.等离子体喷涂试样比热压试样更易产生晶界的断裂的裂纹.在相同的热负荷条件下,W/Cu FGM的重量损失低于石墨材料的重量损失.     

Synthesis,growth and characterization of organic nonlinear optical bis-glycine maleate (BGM) single crystals

A new organic compound of bis-glycine maleate was synthesized in the alkaline medium of 10% ammonium hydroxide solution. The bulk single crystals of Bis-Glycine Maleate (BGM) have been grown by slow cooling method. The grown crystals were characterized by employing single crystal and powder X-ray diffraction, Fourier transform infrared, optical absorption spectral studies and thermo gravimetric analysis. The microhardness studies confirmed that the BGM has a fairly high Vicker’s hardness number value (41 kg mm⁻²) in comparison to other organic NLO crystals. Second harmonic generation efficiency of the crystal measured by Kurtz–Perry powder method using Nd:YAG laser is found to be comparable to that of potassium dihydrogen phosphate (KDP). Frequency dependent dielectric studies were carried out along the major growth axis.     

Growth of (CH3)2NH2CuCl3 single crystals using evaporation method with different temperatures and solvents

The bulk single crystals of low-dimensional magnet (CH₃)₂NH₂CuCl₃ (DMACuCl₃ or MCCL) are grown by a slow evaporation method with different kinds of solvents, different degrees of super-saturation of solution and different temperatures of solution, respectively. Among three kinds of solvent, methanol, alcohol and water, alcohol is found to be the best one for growing MCCL crystals because of its structural similarity to the raw materials and suitable evaporation rate. The best growth temperature is in the vicinity of 35 °C. The problem of the crystals deliquescing in air has been solved through recrystallization process. The crystals are characterized by means of X-ray diffraction, specific heat and magnetic susceptibility.     

Lactose particle engineering: Influence of ultrasound and anti-solvent on crystal habit and particle size

This study focuses on ultrasound-assisted anti-solvent crystallization of lactose, expanding on previous studies and presenting, for the first time, the results of large scale implementation of sonocrystallization for lactose. The results further clarify the interplay between solution chemistry – namely the role of β-lactose – and crystallization, representing a step forward in the fine tuning of lactose properties for pharmaceutical manufacturing applications. Batches manufactured at laboratory and pilot scales were extensively characterised, including an approach for the quantification of β-lactose in α-lactose based on powder X-ray diffraction (PXRD), which is described here.     

Synthesis and X-ray information of substituted gem-difluoroallenyl amines

An O to N substitution in 4,4-difluorobutadiene-2,3-ol-1 has been accomplished in very satisfactory yields, and without compromising the gem-difluoroallenyl integrity, using modified Mitsunobu conditions. Recrystallization of the resulting tosyl-substituted amines furnished the first X-ray crystallographic analysis of difluoroallenes.     

Spectroscopic Characterization of Metamictization and Recrystallization in Zircon and Titanite

Recent applications of infrared and Raman spectroscopy in the study of the metamict (or "amorphized") state, high-temperature recrystallization and radiation-induced OH species in natural zircon (ZrSiO₄) and titanite (CaTiSiO₅) are reviewed.     

Elevated temperature directional recrystallization of high-purity nickel

Electron backscattered diffraction has been used to characterise the three different kinds of boundaries that occur in grains that are generated by secondary recrystallization during directional annealing of high-purity nickel. Boundaries between columnar grains (CC boundaries) can be twin boundaries, low-angle boundaries or high-angle grain boundaries. The frequency of low-angle CC boundaries dropped from 25% to 0% while the frequency of the high-angle CC boundaries increased from 19% to 67% when the annealing temperature was increased from 1000°C to 1200°C. The misorientation angles of boundaries between columnar grains and small equiaxed grains ahead of them (CE boundaries) was random at 1200°C but had a 40° rotation relationship about ?111? at 1000°C. It was found out that the character of the CC boundaries is determined by relative mobility of the CE boundaries, which is determined by the processing temperature rather than the energy of the CC boundaries themselves. The character of the island grain boundaries sometimes found with columnar grains was not affected by the annealing temperature or the drawing velocity.