金刚石压砧内单轴应力场对物质状态方程测量的影响

金刚石压砧的几何结构使得在高压下封垫内的样品通常处于单轴应力场中：压砧轴向加载应力最大,径向应力最小.由于金刚石压砧内非静水压单轴应力场的影响,用传统的高压原位X射线衍射方法测得的物质压缩曲线一般位于理想静水压压缩曲线之上.利用金刚石压砧径向X射线衍射技术以及晶格应变理论,结合最近的钨、金刚石和硼六氧样品的高压原位同步辐射径向X射线衍射实验结果,从宏观差应力、样品强度、标压物质和待测物质强度的关系三个方面分析讨论了金刚石压砧内单轴应力场对物质状态方程测量的影响及解决方案. 关键词： 金刚石压砧 单轴应力场 高压原位X射线衍射 状态方程     

Three-dimensional X-ray diffraction in the diamond anvil cell: application to stishovite

Three-dimensional X-ray diffraction can be used for characterizing the orientation, position, and strain tensor of single grains in a polycrystalline aggregate. Here, we show how the method is well suited for diamond anvil cell data with heterogeneous grain sizes, with an application to two samples of stishovite at 15 and 26 GPa. For each grain, we obtain a well-defined orientation matrix and cell parameters. Center of mass position can also be adjusted to the experimental data, with errors in the present experiment. Finally, strain tensors are adjusted for the individual grains. The stress distribution obtained is in agreement with expectations from the diamond anvil cell geometry and previous measurements of stishovite strength. Advantages and potential for improvement of the method are then discussed.     

Miniature cryogenic diamond anvil cell

Abstract

The miniature cryogenic diamond anvil described previously [D.J. Dunstan and W. Scherrer, Rev. Sci. Instrum. 59, 627 (1988)] has been modified to facilitate its use, and has been taken to 26GPa. The modifications are described here, together with some details of operation.     

压电驱动金刚石对顶砧加压装置的研制和应用

金刚石对顶砧加压装置广泛用于物理、化学、材料等许多科学领域。自Bridgman发明金属对顶砧及随后发展金刚石对顶砧以来,对顶砧装置设计和加压技术得到不断发展。文章介绍采用压电驱动金刚石对顶砧来产生高压,实现低温20 K下原位连续加压,连续加压范围约2—4 GPa。该加压装置具有体积小、操作方便,可装在小型低温恒温器中使用等优点。     

The membrane diamond anvil cell

Abstract

A new design for a diamond anvil cell is described. Its main characteristic is that the force on the piston is generated by pressurized helium. Two of its main qualities are illustrated on recent measurements.     

基于金刚石对顶砧的高压下原位阻抗谱测量

借助薄膜集成技术,阻抗谱测量方法被应用到金刚石对顶砧压机上.通过对电极构型的改进和组装方法的优化,实现了对ZnS样品高压下原位阻抗谱的测量,实验压力达到30 GPa.实验结果显示,平行板构型的电极能够获得完整的阻抗谱.ZnS在压力作用下发生的结构相变,引起了电输运性质的变化,而这个变化,能够清晰地在阻抗谱测量中反映出来.     

Effect of deformation of diamond anvil and sample in diamond anvil cell on the thermal conductivity measurement

Studies show that the sample thickness is an important parameter in investigating the thermal transport properties of materials under high-temperature and high-pressure (HTHP) in the diamond anvil cell (DAC) device. However, it is an enormous challenge to measure the sample thickness accurately in the DAC under severe working conditions. In conventional methods, the influence of diamond anvil deformation on the measuring accuracy is ignored. For a high-temperature anvil, the mechanical state of the diamond anvil becomes complex and is different from that under the static condition. At high temperature, the deformation of anvil and sample would be aggravated. In the present study, the finite volume method is applied to simulate the heat transfer mechanism of stable heating DAC through coupling three radiative-conductive heat transfer mechanisms in a high-pressure environment. When the temperature field of the main components is known in DAC, the thermal stress field can be analyzed numerically by the finite element method. The obtained results show that the deformation of anvil will lead to the obvious radial gradient distribution of the sample thickness. If the top and bottom surfaces of the sample are approximated to be flat, it will be fatal to the study of the heat transport properties of the material. Therefore, we study the temperature distribution and thermal conductivity of the sample in the DAC by thermal-solid coupling method under high pressure and stable heating condition.     

Numerical optimization of diamond anvil cell design

Abstract

The procedure is presented for numerical optimization of geometrical parameters of a diamond anvil cell (DAC) and of loading conditions of DAC anvils. The calculation results are given which permit to increase the attainable pressure level more than 2,5-fold as compared with designs known from literature.     

Alvin Van Valkenburg and the diamond anvil cell

Abstract

As many of you may know already, Alvin Van Valkenburg died on December 5, 1991 in Tucson, Arizona at the age of seventy-eight. He was the last surviving scientist of four who share the honor of co-inventing the diamond anvil high pressure cell (DAC), now recognized as a world-class instrument for scientific research. In August of 1992 Professor A. Ruoff asked me to write a short article for AIRAPT describing Van Valkenburg's role in inventing the DAC because of its importance as a tool in high pressure research. He suggested that as a former colleague and as a scientist who has spent most of his professional career in high pressure research, I was perhaps the one person who could describe best the role Van Valkenburg played in the invention and development of the DAC. After some deliberation, I agreed to do it, mainly for three reasons: (1) the subject matter, indeed, is important to the history of science, and, in particular, to the high pressure community and should be documented; (2) all four co-inventors deserve the honor; and (3) it is true perhaps that there is no one more appropriate to undertake this task because I was at the National Bureau of Standards, NBS, (now the National Institute of Standards and Technology, NIST) at the time and personally witnessed the process of the invention of the DAC.     

High temperature diamond anvil cell with the laser heating

Abstract

Focusing laser radiation in the center of a diamond anvil cell (DAC) allows investigations up to P?100 GPa with the pulsed' and sustained heating to 5000 K^2,3. The use of laser radiation permits the exclusion of a heater if the sample itself strongly absorbs the radiation. Many materials are transparent for 1.06 μm YAG-laser radiation usually used for the heating. Therefore it is necessary to mix absorbing radiation powders, for example, graphite, platinum²³. The use of the powerful C0₂-laser for the heating considerably extends the scope of the materials under investigation, as the wavelength radiation Λ= 10 μm is in the range of the strong lattice absorption (absorption coefficient～ 10³-10⁴ cm-^l) of many oxides, nitrides and so on.     

Ultrahigh-pressure experiment with a motor-driven diamond anvil cell

A Pt sample was compressed to ultrahigh pressures in a diamond anvil cell (DAC) using a motorized gearbox to change pressure remotely from outside the synchrotron x-ray hutch. In?situ angle-dispersive x-ray diffraction (XRD) was used to determine pressure from known equations of state (EOS). The sample position was unperturbed during motor-driven pressure changes. By eliminating the need to realign the sample to the x-ray position after each pressure increment, 142 XRD patterns could be collected continuously over the course of three hours, and the maximum pressure of 230?GPa was reached before diamond failure ended the experiment. We demonstrate the advantages of this motor-driven assembly for smooth and efficient pressure change, and the possibility for fine pressure and temporal resolution.     

A diamond anvil cell for the study of fluid mixtures at high temperatures

Abstract

A new diamond anvil cell has been developed to study the phase behavior of fluid mixtures at high temperature. Special care has been taken to achieve good temperature stability and small temperature gradients. Preliminar experiments show that the cell performs well.     

Synthetic diamonds for multimegabar pressures in the diamond anvil cell

Abstract

Synthetic Type 1b yellow diamonds containing nitrogen in substitutional form and with extremely low birefringence were used as anvils for ultra high pressures in the diamond anvil cell. Pressures were measured by the ruby fluorescence technique to above 200 GPa. Using x-ray diffraction the maximum pressure was 210 GPa, while an x-ray based pressure of 245 GPa was achieved with natural diamonds with a somewhat more optimal geometry. Nitrogen platelets appear to be not essential for exceeding 200 GPa. The optical properties of synthetic diamond at ambient and megabar stresses will be discussed.     

A new hydrostatic medium for diamond anvil cells to 300 kbar pressure

We have shown that the rare gas xenon provides a hydrostatic medium for gasketed samples in a diamond anvil cell to pressures of 300 kbar. Previously, hydrostatic conditions were limited to ～100 kbar in a methanol-ethanol mixture. Three spectroscopic tests were used to determine that pressure gradients were small in the solidified gas. Since xenon has a convenient melting temperature, easy cell loading is possible. The small volume in the gasket requires only a few cm³ of gas. By analogy the other rare gases may be expected to show similar hydrostatic properties. Helium, for example, would be useful for X-ray studies.     

Single crystal diffraction under high pressure with synchrotron radiation and a diamond anvil cell

Abstract

A single crystal study on AlPO₄ was performed at 2.90 GPa with synchrotron radiation with a wavelength of only 0.54 ?. The diffracted intensity was high enough to measure even weak reflections with sufficient counting statistics. However, the search for the reflections needed to setup the orientation matrix required a lot of beamtime. A feasibility study was carried out using a proportional area counter to reduce this search time. The results demonstrate that such counters can considerably reduce the time needed for the orientation of the crystal and the data collection.

Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumentation for High Pressure Crystallography’. Daresbury Laboratory 20-21 July 1991     

Sound velocity and absorption measurements under high pressure using picosecond ultrasonics in a diamond anvil cell: application to the stability study of AlPdMn

We report an innovative high pressure method combining the diamond anvil cell device with the technique of picosecond ultrasonics. Such an approach allows us to measure sound velocity and attenuation of solids and liquids under pressure of tens of GPa, overcoming all the drawbacks of traditional techniques. The power of this experimental technique is demonstrated in studies of lattice dynamics and relaxation processes in a metallic single grain of AlPdMn quasicrystal, and in rare gas solids neon and argon.     

Crystallographic and magnetic structure of HAVAR under high-pressure using diamond anvil cell (DAC)

Annealed (H1) and cold-rolled (H2) HAVAR has been studied using high-pressure synchrotron X-ray diffraction. A structural phase transformation was discovered at ～13 GPa at ambient temperature, transforming from m ??3 m (S.G. 225) to P 63/m m c (S.G. 194) symmetry. The transition was not reversible on pressure release. The low-pressure cubic phase was found to be more compressible than the high-pressure hexagonal phase. Conventional Mössbauer and NFS shows that the HAVAR is not magnetic at room temperature and no splitting is observed. The SQUID indicates a huge difference in the temperature dependence of the magnetic susceptibility between the cold Rolled HAVAR compared to the annealed HAVAR.     

金刚石压腔蛇纹石原位拉曼光谱研究

在金刚石压腔中,运用激光拉曼光谱技术对高压下蛇纹石矿物结构及其稳定性进行了原位观测与研究。实验获得蛇纹石在常温下从0.1～5 140MPa的拉曼光谱数据。研究发现,蛇纹石低频拉曼谱峰388,471,692和705cm-1随压力增加有规律地向高频偏移;层内羟基3 664cm-1峰和层间羟基3 696cm-1峰与压力呈明显的正相关性。层内羟基3 664cm-1峰随压力变化的斜率为3.3cm-1.GPa-1,层间羟基3 696cm-1峰在2.0GPa时斜率由8.3cm-1.GPa-1变为1.1cm-1.GPa cm-1。在实验温压条件下,蛇纹石未发生脱水作用。     

X-ray absorption spectroscopy under high pressures in diamond anvil cells

Abstract

Although potentially extremely important for understanding the high-pressure microscopic behaviour of materials, over the years the area of high-pressure EXAFS in particular using diamond anvil cells has proved to be technically difficult. This has significantly hampered its development. The interference of X-ray dimaction from the diamonds in the diamond anvil cell with the absorption signal has proved to be a challenging problem to tackle, restricting the use of high-pressure EXAFS to energies below about 11 key Below 11 keV however the technique is also limited due to absorption of incident X-rays by the diamonds making it virtually impossible to conduct X-ray absorption experiments below about 9keV In this paper we describe in detail the methodology for scanriirig high-pressure EXAFS in diamond anvil cells and examine the origins of the associated problems and ways of dealing with them. We also demonstrate that it is possible to extend the useful range of studied absorption edges from 7keV up to at least 30keV This brings about new opportunities for high pressure EXAFS using diamond anvil cells.     

The numerical modelling of the stress-strained state of diamond anvil cell components

Abstract

The method of numerical modelling of the behaviour of main components (anvils and deformable gasket) in diamond anvil cells (DAC) in the process of pressure generation has been developed and realized in the form of programs packages. The optimization of the geometry and loading conditions for an anvil was conducted in line with the multilevel factor plan of major effects (MFPME). A combination of optimizing factors allowing to obtain the theoretically predicted pressure of 465 GPa has been found, the value that by 2.7 times higher than that obtained on anvils at an analogous external pressure distribution [1] and the same diamond strength.

FEM