尾叶远志中-酰基取代(口山)酮碳甙的结构

用2D NMR(¹H-¹H COSY,¹H-¹³C COSY,HMBC)技术研究了从尾叶远志中分离得到的一个苯甲酰基取代(口山)酮甙的结构,并对其碳氢信号进行了全归属.     

表面修饰纳米TiO2的贮氢合金电极的光充电行为

采用水解-沉淀法制备了锐钛矿结构的纳米级TiO2,研究了表面修饰TiO2的贮氢合金电极的光充电、循环伏安及交流阻抗特性.结果表明,表面未修饰TiO2的贮氢合金电极在光照下电极电位基本无变化,而表面修饰TiO2的贮氢合金电极在光照下,电极电位向负方向偏移,可达-0.835V,表明在光照射条件下电极表面有氢原子形成.电化学阻抗谱的结果也表明,表面修饰电极在光照时表面有吸附氢存在,并存在氢原子向贮氢合金内部的扩散过程.扫描电镜观察表明,表面修饰TiO2的贮氢合金电极在光充电后产生的氢原子被贮氢合金吸收引起膨胀,导致表面出现大量微裂纹.     

黄酮类化合物-O-甙的13C NMR谱

概述了黄酮类化合物-O-甙(包括双糖甙及寡糖甙)的¹³C NMR谱鉴定中涉及的溶剂选择,糖的数目与鉴定,糖的端基信号与甙化位移,甙元的鉴定,双糖及寡糖甙中各单糖的连接次序,以及糖链上的酰基取代等.     

Phase transition in Pd_(40)Ni_(10)Cu_(30)P_(20) bulk metallic glass under HP & HT

Bulk metallic glass (BMG) can be regarded as a metallic solid with a frozen-in melt structure which lacks atomic periodicity. Generally, BMG is not in an internal equilib- rium state (IES) but may change to the IES when it obtains an appropriate energy to overcome the energy barrier. High pressure and temperature can be a driving force to cause various transitions in amorphous materials, such as a transition from the amor- phous to the crystalline[1―8] or from the crystalline to the amorp…     

微重力条件下材料气相生长研究进展

本文概述了近二十多年来国外空间气相生长晶体材料及薄膜材料研究工作的进展状况．着重介绍了国外空间气相生长研究的历史过程、研究的主要内容及所采取的研究手段，详细地总结了关于空间气相生长的主要飞行结果，并对国外如何进行数值模拟和实验室模拟等地面准备工作做了较充分的描述．     

Synthesis of C3N4 crystals under high pressure and high temperature

C₃N₄ crystals with the size of several micrometers have been synthesized from C₃N₄H₄ in the presence of nickel-based alloy or cobalt as catalyst under high pressure of 7 GPa and temperature of about 1400°C for 10 min. Scanning electron microscopy, energy-disperse X-ray analysis, and X-ray diffraction were used to examine the grown crystals. The general rule on selecting the starting materials for synthesis of carbon nitride crystals at high pressures and high temperatures is suggested.     

Grain evolution of nano-crystals ZnO under HP and HT

Grain evolution of nano-crystals ZnO under high temperature and pressure is studied using a cubic high pressure apparatus. The structure, grain sizes and morphology of the samples are characterized by X-ray diffraction and field emission scanning electron microscopy. The results show that the grain sizes of ZnO grow rapidly at temperature 200°C under pressure. At temperature lower than 300°C (including 300°C), the grain sizes of the samples first increase with the pressure increasing from 1 to 3 GPa and later decrease from 4 to 6 GPa. The activation volume from 1 to 3 GPa and from 4 to 6 GPa is calculated respectively using the phenomenological kinetic grain growth equation at temperature 300°C. At temperature higher than 400°C (including 400°C), the grain sizes of the samples increase with the pressure increasing from 1 to 6 GPa. ZnO nano-bulks with good quality can be obtained under the specific conditions.     

Formation of new Zr-Ti-Cu-Ni-Be-C bulk amorphous alloy

The formation of the new bulk amorphous Zr-Ti-Cu-Ni-Be-C alloy with high strength is reported. The effects of the small size atoms on the glass forming ability, strength and thermal stability of the amorphous alloy are investigated. The formation mechanism of the bulk amorphous alloy is discussed.     

高压下的固态反应非晶化

 本文首次把压力引入固态反应非晶化过程，报道了Ni₅₀Ti₅₀多层膜在不同压力下低温退火后的X射线衍射结果。根据压力对反应热力学及动力学过程可能产生的影响，作者对所得结果作出分析，认为在2 GPa以上压力下，反应未能进行的原因是高压抑制了原子的低温快速扩散。提出在Ni-Ti系固态反应非晶化中，受抑制的扩散过程符合薄膜扩散的B类动力学模型。     

高压下制备高密度的Bi系超导体

 首次直接用高压烧结而不必进行任何退火后处理获得超导Bi_0.8Pb_0.2SrCa₂O_x陶瓷样品。此样品是由名义组分为Bi_0.8Pb_0.2SrCa·Cu₂O_x的超导体在1.0 GPa、500 ℃处理2 h后制得的，其零电阻转变温度为97 K。以前未见报导过如此好的结果。高压下烧结的Bi_0.8Pb_0.2SrCa·Cu₂O_x超导体的密度可达6.23 g/cm³（约为理论密度的95%），这比常规法制得的样品的密度（大约4~5 g/cm³）高得多。