Abnormal pressure dependence of the phase boundaries in TL/PEO/P(EO-b-DMS) ternary mixtures

The cloud-point temperatures (T-cl's) of both binary poly(ethylene oxide) (PEO)-poly(ethylene oxide-b-dimethylsiloxane) [P(EO-b-DMS)] and ternary[toluene/PEO/P(EO-b-DMS)] systems were determined by light scattering measurements at atmospheric pressure. The phase separation behavior upon cooling in the ternary system has been investigated at atmospheric pressure and under high pressure and compared to the phase behavior in the binary system. The phase transition temperatures have been obtained for all of the samples. As a result, the pressure induces compatibility in the binary mixtures, but for the ternary system, pressure not only can induce mixing but also can induce phase separation.

Sintering of nanopowders of amorphous silicon nitride under ultrahigh pressure

Nanopowders of amorphous silicon nitride were densified and sintered without additives under ultrahigh pressure (1.0-5.0 GPa) between room temperature and 1600 degrees C. The powders had a mean diameter of 18 nm and contained similar to 5.0 wt% oxygen that came from air-exposure oxidation, Sintering results at different temperatures were characterized in terms of sintering density, hardness, phase structure, and grain size. It was observed that the nanopowders can be pressed to a high density (87%) even at room temperature under the high pressure. Bulk Si3N4 amorphous and crystalline ceramics (relative density: 95-98%) were obtained at temperatures slightly below the onset of crystallization (1000-1100 degrees C and above 1420 degrees C, respectively. Rapid grain growth occurred during the crystallization leading to a grain size (>160 nm) almost 1 order of magnitude greater than the starting particulate diameters, With the rise of sintering temperature, a final density was reached between 1350 and 1420 degrees C, which seemed to be independent of the pressure applied (1.0-5.0 GPa), The densification temperature observed under the high pressure is lower by 580 degrees C than that by hot isostatic pressing sintering, suggesting a significantly enhanced low-temperature sintering of the nanopowders under a high external pressure.

High-yield extraction of endohedral rare-earth fullerenes

The technique of high-temperature high-pressure extraction with pyridine has been successfully utilized to extract a wide variety of endohedral rare-earth fullerenes of the type Ln@C-2n (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb). Ln@C-80, Ln@C-82, and Ln(2)@C-80 for most of the rare-earth metals can be produced with high-yield and selectively extracted from the carbon-are evaporation soot. Metallofullerenes containing Sm, Eu, and Yb (which could have +2 oxidation states) are especially difficult to extract. Some possible reasons for the high-yield extraction are discussed. The laser desorption mass spectrometric characterization results indicate a relationship between the extraction yields of metallofullerenes and the oxidation states and ionic radii of the rare-earths.

High-yield Synthesis and Extraction of Gd@C-2n

Endohedral metallofullerene Gd@C-2n were synthesized with high-yield using the carbon-arc discharge method of activating the Gd2O3-containing graphite anode in situ and back-burning technique. A series of Gd@C-2n for 2n from 70 to 96 were effectively extracted by toluene at high-temperature and under high-pressure condition. Gd@C-82, Gd@C-74 were considered to be fairly stable and soluble metallofullerene species.

三塘湖盆地牛圈湖区储层特征研究—以齐古组、头屯河组为例

In view of few researches into pore textures and anisotropy characteristics of Qiguzu-toutunhezu reservoir in Niuquanhu block in Santanghu Basin, in order to enhance the hydrocarbon recovery of the region of interest and improve the reservoir development effect, with the employment of the experiments like cast thin slice, scanning electron microscope, conventional high pressure mercury penetration, constant speed mercury penetration and nuclear magnetic resonance, the thesis makes a thorough research into pore texture characteristics and anisotropy characteristics of the sandstone reservoir. The research shows that the microscopic pore textures are complicated, the anisotropy is high and waterflood development water/oil displacement efficiency is low, which are mainly caused by the high microscopic anisotropy of the reservoir. Specially, the research shows that Qiguzu-toutunhezu reservoir belongs to braided delta front intrafacies, the intergranular pore is the main type of pores, which take up 65.50 percent of total pores, intergranular dissolved pores, feldspar dissolved pores and lithic dissolved pores are on the second place, and there are few carbonate dissolved pores. The reservoir belongs to mesopore-fine throat and mesopore-medium throat. The pore distribution of the sandstone reservoir is comparatively centralized. The reservoir inhomogeneity is mainly caused by the throat inhomogeneity. Diagenesis mainly includes compaction, cementation, metasomatism and dissolution. Compared with compaction， cementation exerts more direct impact on the decline of the porosity of the sandstone reservoir ( pore loss factor is 63.75 percent in the cementing process). Based on the classification of diagenetic stages, the reservoir diagenesis is on the stage of the late period of early diagenetic stage to early period of late diagenetic stage. The study area of the small sandstone reservoir layer of the anisotropy of the relatively strong; plane, the anisotropy of the relatively weak. microscopic anisotropy of its relatively strong.

Modified Simplified Rate Equation Model of Flowing Chemical Oxygen-Iodine Laser and its Application

A modified simplified rate equation (RE) model of flowing chemical oxygen-iodine laser (COIL), which is adapted to both the condition of homogeneous broadening and inhomogeneous broadening being of importance and the condition of inhomogeneous broadening being predominant, is presented for performance analyses of a COIL. By using the Voigt profile function and the gain-equal-loss approximation, a gain expression has been deduced from the rate equations of upper and lower level laser species. This gain expression is adapted to the conditions of very low gas pressure up to quite high pressure and can deal with the condition of lasing frequency being not equal to the central one of spectral profile. The expressions of output power and extraction efficiency in a flowing COIL can be obtained by solving the coupling equations of the deduced gain expression and the energy equation which expresses the complete transformation of the energy stored in singlet delta state oxygen into laser energy. By using these expressions, the RotoCOIL experiment is simulated, and obtained results agree well with experiment data. Effects of various adjustable parameters on the performances of COIL are also presented.

Spherical nanometer-sized diamond obtained from detonation

Ultrafine diamond (UFD) was synthesized under high pressure and high temperatures generated by explosive detonation. The structure, composition, surface and thermal stability of UFD were studied by use of XRD, TEM, Raman Spectroscopy, FTIR, etc. The influences of the synthesis conditions and purification conditions on the properties of UFD were analyzed. The UFD had an average size of 4-6 nm, commonly exhibiting a spherical shape. The highest yield was of up to 10 mass% of the explosive. Attempts were made to use UFD as an additive to metal-diamond sintering and as crystallite seeds of CVD diamond films. The results show that UFD can decrease the coefficient of friction of the composite by 30%, and raise the nucleation density in CVD diamond films by 2-3 times.

固井工程中的流动问题

同井是油气在建过程中的重要工程，一般分下套管和注水泥两个过程．本文结合作者近年来的研究，着重阐述了钻井液、前置液、水泥浆在环形空间中流动的流体力学问题，包括：高温高压下的水泥浆流变性、偏心环形空间中浆液的流动特性、钻井液-前置液和前置液-水泥浆界面的稳定性等，介绍了国内外学者对这些问题的研究进展，提出了今后应深入研究的问题.

Effect Of Load Triaxiality On Polymorphic Transitions In Zinc Oxide

Molecular dynamics (MD) simulations and first-principles calculations are carried out to analyze the stability of both newly discovered and previously known phases of ZnO under loading of various triaxialities. The analysis focuses on a graphite-like phase (FIX) and a body-centered-tetragonal phase (BCT-4) that were observed recently in [0 1 (1) over bar 0]- and [0 0 0 1]-oriented nanowires respectively under uniaxial tensile loading as well as the natural state of wurtzite (WZ) and the rocksalt (RS) phase which exists under hydrostatic pressure loading. Equilibrium critical stresses for the transformations are obtained. The WZ -> HX transformation is found to be energetically favorable above a critical tensile stress of 10 GPa in [0 1 (1) over tilde 0] nanowires. The BCT-4 phase can be stabilized at tensile stresses above 7 GPa in [0 0 0 1] nanowires. The RS phase is stable at hydrostatic pressures above 8.2 GPa. The identification and characterization of these phase transformations reveal a more extensive polymorphism of ZnO than previously known. A crystalline structure-load triaxiality map is developed to summarize the new understanding. (c) 2007 Elsevier Ltd. All rights reserved.

Microstructural evolution and formation of nanocrystalline intermetallic compound during surface mechanical attrition treatment of cobalt

Nanocrystalline intermetallic Co3Fe7 was produced on the surface of cobalt via surface mechanical attrition (SMA). Deformationinduced diffusion entailed the formation of a series of solid solutions. Phase transitions occurred depending on the atomic fraction of Fe in the surface solid solutions: from hexagonal close-packed (<4% Fe) to face-centered cubic (fcc) (4-11% Fe), and from fcc to body-centered cubic (>11% Fe). Nanoscale compositional probing suggested significantly higher Fe contents at grain boundaries and triple junctions than grain interiors. Short-circuit diffusion along grain boundaries and triple junctions dominate in the nanocrystalline intermetallic compound. Stacking faults contribute significantly to diffusion. Diffusion enhancement due to high-rate deformation in SMA was analyzed by regarding dislocations as solute-pumping channels, and the creation of excess vacancies. Non-equilibrium, atomic level alloying can then be ascribed to deformation-induced intermixing of constituent species. The formation mechanism of nanocrystalline intermetallic grains on the SMA surface can be thought of as a consequence of numerous nucleation events and limited growth. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

高压扭转铜试样的微观组织与压缩性能

通过高压扭转对铜试样施加不同程度的变形，研究了样品扭转面（ND面）和纵截面（TD面）上微观组织特征．对ND面，在较小的剪应变下，原始晶粒形貌模糊，晶粒内部形成等轴状的位错胞及亚晶结构；随变形量的增大，亚晶间取向差及亚晶内部的位错密度增大，最后形成亚微米尺度的等轴晶粒．对TD面，变形初期原始晶粒被拉长，晶粒内部为位错墙分割成的层状结构，层内为拉长的位错胞；随变形程度的增大，拉长晶粒的宽度减小，与剪切方向的夹角减小，晶内层状组织间距减小，并逐渐演化成拉长的亚晶组织；进一步增大变形，晶粒拉长痕迹消失，变形组织与ND面相似，为等轴状亚微米晶粒．压缩实验表明，经16圈扭转后，整个试样上的压缩性能基本均匀，σ0．2达到385MPa，应变率敏感性指数增大至0．021．

高压扭转致纯铜晶粒细化及与应变的关系

设计并加工了在材料试验机上使用的高压扭转夹持装置，并用装置获得了不同扭转变形量的纯铜试样．使用电子背散射衍射技术测量了处理后试样品粒尺寸沿径向的分布．对比分析了晶粒细化程度和应变量的关系，提出了一个描述晶粒细化的简单剪切球模型．结果表明，晶粒细化程度随着应变量的增大而增强，平均晶粒尺寸为原始平均尺寸的1／50．当剪切应变小于10对，晶粒尺寸随着剪切应变的增大迅速变小；当剪切应变大于10对，晶粒尺寸的变化趋于缓慢，晶粒细化程度与Stuwe等效应变之间有幂函数关系．依据简单剪切球形晶粒的模型，得到了晶粒细化程度随剪切应变增大而增强的规律，并与实验数据的变化趋势一致。

限定型高压扭转过程变形研究

文章制备了一套限定型高压扭转（HPT）设备。采用HPT处理纯铜试样，对比处理前后试样几何尺寸，观察试样与砧头之间的相对滑动，结果表明，HPT处理前后试样厚度变化小于5％，试样端面和模具不发生相对滑动。用量纲分析和有限元方法分析试样的变形，得到切应变和厚度／直径、压力／材料弹性模量以及模具侧面的摩擦状况相关；直径8mm厚0．86mm纯铜试样上r〈3．2mm区域的变形可以用纯扭转来描述。

Modified Simplified Rate Equation Model of Flowing Chemical Oxygen-Iodine Laser and its Application

A modified simplified rate equation (RE) model of flowing chemical oxygen-iodine laser (COIL), which is adapted to both the condition of homogeneous broadening and inhomogeneous broadening being of importance and the condition of inhomogeneous broadening being predominant, is presented for performance analyses of a COIL. By using the Voigt profile function and the gain-equal-loss approximation, a gain expression has been deduced from the rate equations of upper and lower level laser species. This gain expression is adapted to the conditions of very low gas pressure up to quite high pressure and can deal with the condition of lasing frequency being not equal to the central one of spectral profile. The expressions of output power and extraction efficiency in a flowing COIL can be obtained by solving the coupling equations of the deduced gain expression and the energy equation which expresses the complete transformation of the energy stored in singlet delta state oxygen into laser energy. By using these expressions, the RotoCOIL experiment is simulated, and obtained results agree well with experiment data. Effects of various adjustable parameters on the performances of COIL are also presented.

The Droplet Group Micro-Explosions, Viscosity and Atomization Characteristics of W/O Emulsions

The spray of emulsified fuel, composed of diesel fuel, water and methanol can make micro-explosion under high temperature conditions, and the viscosity and the atomization characteristics of emulsion have significant effects on the micro- explosion of emulsions. To clarify the combustion mechanism of water-in-oil emulsion sprays, combustion bomb experiments were carried out, and the droplet group micro- explosions in W/O fuel emulsion sprays in a high-pressure, high-temperature bomb were observed clearly by a multi-pulsed, off-axis, image-plane ruby laser holocamera and continuously by a high-speed CCD camera.The viscosity and atomization characteristics of emulsions were also studied experimentally. The experimental results show that the higher concentration of the aqueous phase (water-methanol) (<50%) increases the viscosity of the emulsions, especially for higher agent concentration, and higher aqueous phase concentration and higher viscosity results in lager Sauter Mean Diameter (SMD). The experiment results also show that the different kinds of emulsifying agents, with different Hydrophile-Lipophile Balance (HLB) values, have significant influence on the viscosity of the emulsions.