超高压下CsBr的结构与相变

采用金刚石对顶压砧高压装置（DAC）、同步辐射X光源和能散法，对CsBr粉末样品进行了原位高压X光衍射实验，最高压力115GPa。观测到在53GPa左右压力下，CsBr的最强衍射峰（110）劈裂成两个峰，标志简单立方结构向四方结构的转变；在0至最高压力范围内（相应于V／V0为1至0.463)测量了晶轴比c/a；在115GPa内未观测到样品的金属化现象。     

Y2O3压致结构相变的研究

本文采用金刚石对顶砧高压装置（DAC），利用同步辐射X－ray衍射，对Y2O3粉末样品进行了原位高压X－ray衍射实验，最高压力达到23GPa。在研究的压力范围内观察到两个相变。在12.8GPa压力点，Y2O3由稀土倍半氧化物的立方结构转变为单斜结构。在21.8GPa压力点，样品由单斜结构转变为另一个新相，但由于样品峰的消失，无法判断其结构。卸压后样品为单斜结构，说明Y2O3第一个压致结构相变为不可逆相变。     

晶粒尺寸对锐钛矿TiO2相变压力的影响

采用在位高压Raman光谱和高压同步辐射能散X射线衍射技术，在室温下对晶粒尺寸为10nm的锐钛矿TiO2进行了压致相变研究，压力范围分别为42．9GPa和23．0GPa，实验结果表明，在16．3GPa TiO2发生了一次结构相变，由原来的锐钛矿结构变为α－PbO2结构（TiO2-Ⅱ），该相变是不可逆的。同体材料TiO2的高压相变结果比较，由于晶粒尺寸的效应，纳米尺寸的锐钛矿TiO2的相变压力明显高于体材料的相变压力。     

黄玉的原位高压X射线衍射研究

使用金刚石对顶砧(DAC,Diamond Anvil Cell)高压装置和同步辐射光源,对黄玉进行原位高压X射线衍射研究,实验最高压力达到29.7 GPa.在研究的压力范围内,随着压力的升高,晶胞体积逐渐被压缩,晶胞参数a的压缩率大于c和6.未观察到黄玉的结构相变.利用Murnaghan状态方程(K1=4)对黄玉的体积-压力数据拟合,获得等热体积模量K298为199.7(4.6)GPa.     

电气石的原位高压X射线衍射研究

使用金刚石对顶砧(DAC)高压装置和同步辐射光源,对黑色电气石进行了原位高压X射线衍射研究,实验最高压力达到27.8 GPa.在研究的压力范围内,随着压力的升高,晶胞体积逐步被压缩,晶胞参数a的压缩率小于c.未观察到电气石的结构相变.利用Murnaghan状态方程(K′=4)对电气石的体积-压力数据进行拟合,获得的等热体积模量K298为(183.5±4.2)GPa.     

层状钙钛矿结构锰氧化物Ca3Mn2O7的高压结构相变

利用金刚石压砧高压装置（DAC），对Ca3Mn2O7的粉末样品进行了高压能散X射线衍射实验。结果表明，由于岩盐层易被压缩，在压力作用下层状钙钛矿结构锰氧化物Ca3Mn2O7的结构不稳定。在0－35GPa压力范围内，Ca3Mo2O7晶体结构发生了两次相变。在1．3GPa左右，由原来的四方相变为正交相，在9．5GPa左右，又由正交相向新的四方相转变。     

纳米晶BaTiO3的高压研究

采用原位高压同步辐射X光衍射技术和Raman散射方法，对小于临界尺寸（120nm)的纳米晶BaTiO3(48nm)进行了研究，在实验压力范围内（0－21．2GPa,0-46.67GPa)，纳米晶BaTiO3始终处于稳定的立方相。     

纳米晶BaTiO3的高压研究

采用原位高压同步辐射X光衍射技术和Raman散射方法，对小于临界尺寸（120nm）的纳米晶BaTiO3(48nm）进行了研究，在实验压力范围内（0－21．2GPa,0-46.67GPa），纳米晶BaTiO3始终处于稳定的立方相。     

纳米硅化铁的高压研究

采用同步辐射能散X射线衍射技术和金刚石地顶砧高压装置,对硅化铁纳米微粉进行了原位高压X光衍射实验。在27．1－29．5GPa的压力范围内出现了两条的衍射峰,对该实验现象进行了讨论。     

方石英高温高压相变的实验研究

在1450℃高温下热处理天然的长白山硅藻土以获得含有一定量杂质元素的方石英,并以此为样品,利用对称型DAC装置在0-63GPa压力范围对其开展高温高压相变的实验研究。衍射方法采用同步辐射能量色散X射线衍射(EDXD)技术。实验结果表明,方石英的高压相变序列较复杂,在12、24、33GPa都有新的衍射线出现,在40GPa时仍存在明显的衍射线条而并未完全非晶化,并且为一种类似于α-PbO2型结构的高压相。在此压力下用YLF激光器加温到大约1600K,降温后样品相变为类似于斯石英的结构。随后继续加压到62．9GPa,样品未发生相变,并于此压力下给样品加温到大约1500K,降温后其结构仍不发生变化。卸压至常压,仍为类似于斯石英的结构。     

三聚氰胺(C3N6H6)分子晶体的压致结构相变研究

本文通过对三聚氰胺（C3N6H6）的室温高奈原位同步辐射能量散射X－ray衍射实验（EDXD），在14.7GPa压力范围内，观察到常压下为单斜晶系的三聚氰胺经历了两次压致结构相变。在1.3GPa下，三聚氰胺分子晶体从单斜相转变为三斜相；在8.2GPa又转变为正交相。本实验结果为利用三聚氰胺碳氮有机分子晶体高温高压合成超硬C3N4共价晶体的研究提供了重要信息。     

Preshock-induced phase transition in spalled U–0.75 wt% Ti

Uranium–0.75 wt% Ti samples were spalled in the range of 5–24 GPa shock pressure. One sample was preshocked to a pressure of 24 GPa, `soft' recovered, and then reloaded and spalled at 10 GPa. The spall strength of U–3/4 wt% Ti was found to range from −4.1 to −2.9 GPa when the Romanchenko correction is used in the spall strength calculation. The spall morphology of the sample that was preshocked and then spalled showed a significant change in microstructure from a parent alpha' martensite to a 2-phase eutectoid. The thermodynamically calculated temperature rise resulting from the preshock at 15–24 GPa in these samples is ∼555°C. This temperature is not sufficient to induce such a phase change. However, the preshock conditions additionally increase the flow stress of the U–34 wt% Ti, and it is postulated that this additional hardening is sufficient to increase the temperature above 885°C due to the increased amount of plastic work required during spall, thereby triggering the phase change.     

A Raman study of the nanocrystallite size effect on the pressure–temperature phase diagram of zirconia grown by zirconium-based alloys oxidation

The pressure–temperature phase diagrams of different zirconia samples prepared by oxidation of Zircaloy-4 and Zr–1%Nb–0.12O alloys were monitored by Raman spectrometry from 0.1 MPa to 12 GPa and from 300 to 640 K. These new diagrams show that the monoclinic–tetragonal equilibrium line is strongly downshifted in temperature compared to literature measurements performed on usual polycrystalline zirconia. In addition, the monoclinic–orthorhombic equilibrium line is slightly shifted to higher pressure (i.e. 6 GPa). The crystallite sizes smaller than 30 nm, are thought to be responsible for these equilibrium line displacements. The tetragonal phase obtained in temperature under high pressure can be quenched at room temperature, if the pressure is maintained, and it is destabilised and transforms completely into monoclinic phase if the pressure is released. These results confirm that coupled effects of stress, temperature and nanosized grain are responsible for the formation of the tetragonal phase near the metal/oxide interface during the oxidation of zirconium-based alloys.     

Microwave-assisted pre-ionization experiments on GLAST-Ⅲ

GLAss Spherical Tokamak(GLAST-Ⅲ) is a spherical tokamak with an insulating vacuum vessel that has a unique single-passage capability for incident microwaves.In this work,electron cyclotron resonance heating(ECRH)-assisted plasma pre-ionization in GLAST-Ⅲ is explored for three radio-frequency(RF) polarizations(the O-,X-,and M-modes) at different toroidal-field(TF) strengths and filled gas pressures.The optimum hydrogen pressure is identified for efficient plasma pre-ionization.A comparison of the plasma pre-ionizations initiated by the O-,X-,and M-modes shows prominent differences in the breakdown time,location,and wave absorption.In the case of O-mode polarization,microwave absorption occurs for a relatively shorter duration,resulting in a bell-shaped electron-temperature(T_e) temporal profile.Microwave absorption is dominant in the case of the X-mode,leading to a broader T_e temporal profile.The M-mode discharge contains features of both the X-and O-modes.Efficient plasma pre-ionization is achieved in the X-mode polarization for the intermediate TF strengths(with a central toroidal magnetic field B_0=0.075 T).Traces of the electron-number density show a similar tendency,as revealed by T_e.These results suggest that the X-mode is the best candidate for efficient plasma pre-ionization at low filled gas pressures(~10~(-2) Pa) in small tokamaks.     

立方烧绿石Gd_2Zr_2O_7的高温高压合成

为探索高温高压固相反应法合成Gd2Zr2O7烧绿石的可能性,以Gd2O3和ZrO2的混合粉体为原料,在5.2GPa压力、1473～1873K温度范围内进行了实验研究。通过XRD对合成样品进行了结构表征,结果证实,在5.2GPa和1873K条件下,保温保压30min,成功地合成出单一物相的、具有立方烧绿石结构的Gd2Zr2O7化合物。这种新的合成方法对于开展武器级多余钚和含钚高放废物固化具有重要的科学价值和实际意义。     

Absorption effect of pure nickel on the corrosion behaviors of the GH3535 alloy in tellurium vapor

In this study,pure Ni was demonstrated to pro-tect the GH3535 alloy from Te vapor corrosion because of its strong absorption capacity.Severe Te corrosion of a single GH3535 alloy sample occurred in Te vapor at 700℃,which manifested as complex surface corrosion products and deep intergranular cracks.However,when pure Ni and the GH3535 alloy were put together in the vessel,the GH3535 alloy was completely protected from Te corrosion at the expense of the pure Ni.Thermody-namic calculations proved that the preferential reaction between pure Ni and Te vapor reduced the activity of Te vapor considerably,preventing the corrosion of the GH3535 alloy.Our study reveals one potential approach for protecting the alloys used in molten-salt reactors from Te corrosion.     

Impact of core electron temperature on current profile broadening with radio-frequency wave heating and current drive in EAST

In recent EAST experiments, current profile broadening characterized by reduced internal inductance has been achieved by utilizing radio-frequency current drives (RFCD). In contrast to previous density scan experiments, which showed an outward shift of the current density profile of lower hybrid current drive (LHCD) in higher plasma density, the core electron temperature (Te(0)) is found to affect the LHCD current profile as well. According to equilibrium reconstruction, a significant increase in on-axis safety factor (q0) from 2.05 to 3.41 is observed by careful arrangement of RFCD. Simulations using ray-tracing code GENRAY and Fokker–Planck code CQL3D have been performed to thoroughly analyze the LHCD current profile, revealing the sensitivity of the LHCD current profile to Te(0). The LHCD current density tends to accumulate in the plasma core with higher current drive efficiency benefiting from higher Te(0). With a lower Te(0), the LHCD current profile broadens due to off-axis deposition of power density. The sensitivity of the power deposition and current profile of LHCD to Te(0) provides a promising way to effectively optimize current profile via control of the core electron temperature.     

Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel

In an attempt to investigate Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel, Cs–Te corrosion out-pile tests of two 9Cr steels with different distributions of chromium carbide were carried out at 975 K for 100 h, and their corrosion depths were compared. The corrosion is obviously more advanced in a specimen which has grain boundary carbide than in the one that does not. A considerable reason of the result is that the carbide distributed at grain boundaries promoted the corrosion reaction and the corrosion extended along the grain boundary. This is the first case in which the Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in Fe–Cr steel is clarified experimentally.     

Ion Implantation of Pb0.8Sn0.2Te

The ion implantations of many ions into single crystal epitaxial films of Pb0.8Sn0.2Te have been evaluated. Because of the wide spectrum of results, only those of the two most promising ions, S+ and In+, are presented. The S+ ions produced a p-type layer in Pb0.8Sn0.2Te. After a suitable post implant anneal In+ ions produced an n-type layer in p-type Pb0.8 Sn0.2Te. The In+ implants were used to produce detector arrays, while the S+ implants produced complete conversion of 4500 ? films.