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.     

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.     

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.     

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。     

Resistively heated,high pressure,membrane and screw driven diamond anvil cell

ABSTRACT

High temperature is of paramount importance in high pressure science. One of the leading tools in this respect is the resistively heated diamond anvil cell (DAC), where the heat is provided by small heaters, positioned close to the diamond/gasket/sample region (internally heated DAC, IHDAC) or by wrapping the DAC body into bigger heaters (externally heated DAC, EHDAC). Although IHDACs can reach sample temperatures higher than 1000?K, they are difficult to handle and the heater/diamond/gasket/sample region may be affected by strong thermal gradients potentially hindering accurate temperature measurements. Here we present a novel EHDAC, which overcomes these issues by uniquely joining: (i) high mechanical precision for multi-Mbar, (ii) high temperature alloys for operating to 1000?K, (iii) membrane or screw driven, easily switchable between each other, (iv) operation into a vacuum chamber, (v) uniform temperature, (vi) facile handling, and (vii) possibility to add internal heaters for achieving even higher temperatures.     

In situ study of calcite-III dimorphism using dynamic diamond anvil cell

The phase transitions among the high-pressure polymorphic forms of CaCO₃ (cc-I, cc-II, cc-III, and cc-IIIb) are investigated by dynamic diamond anvil cell (dDAC) and in situ Raman spectroscopy. Experiments are carried out at room temperature and high pressures up to 12.8 GPa with the pressurizing rate varying from 0.006 GPa/s to 0.056 GPa/s. In situ observation shows that with the increase of pressure, calcite transforms from cc-I to cc-II at ～ 1.5 GPa and from cc-II to cc-III at ～ 2.5 GPa, and transitions are independent of the pressurizing rate. Further, as the pressure continues to increase, the cc-IIIb begins to appear and coexists with cc-III within a pressure range that is inversely proportional to the pressurizing rate. At the pressurizing rates of 0.006, 0.012, 0.021, and 0.056 GPa/s, the coexistence pressure ranges of cc-III and cc-IIIb are 2.8 GPa-9.8 GPa, 3.1 GPa-6.9 GPa, 2.7 GPa-6.0 GPa, and 2.8 GPa-4.5 GPa, respectively. The dependence of the coexistence on the pressurizing rate may result from the influence of pressurizing rate on the activation process of transition by reducing the energy barrier. The higher the pressurizing rate, the lower the energy barrier is, and the easier it is to pull the system out of the coexistence state. The results of this in situ study provide new insights into the understanding of the phase transition of calcite.     

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     

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.     

Synthesis of Ge-Sn at high pressure and high temperature in a laser-heated diamond anvil cell

Ge–Sn compound is predicted to be a direct band gap semiconductor with a tunable band gap. However, the bulk synthesis of this material by conventional methods at ambient pressure is unsuccessful due to the poor solubility of Sn in Ge. We report the successful synthesis of Ge–Sn in a laser-heated diamond anvil cell (LHDAC) at ~7.6 GPa &; ~2000 K. In situ Raman spectroscopy of the sample showed, apart from the characteristic Raman modes of Ge TO (Г) and β-Sn TO (Г), two additional Raman modes at ~225 cm^?1 (named Ge–Sn₁) and ~133 cm^?1 (named Ge–Sn₂). When the sample was quenched, the Ge–Sn₁ mode remained stable at ~215 cm^?1, whereas the Ge–Sn₂ mode had diminished in intensity. Comparing the Ge–Sn Raman mode at ~225 cm^?1 with the one observed in thin film studies, we interpret that the observed phonon mode may be formed due to Sn-rich Ge–Sn system. The additional Raman mode seen at ~133 cm^?1 suggested the formation of low symmetry phase under high P–T conditions. The results are compared with Ge–Si binary system.     

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.     

Kinetic study of phase transformation of n-octane using hydrothermal diamond anvil cell

A kinetic study of phase transformation of n-octane has been performed using a hydrothermal diamond anvil cell. The results show that pressure has a negative effect on the solid–liquid reaction rate. The increase of pressure can accelerate the liquid–solid transformation rate. Upon the liquid–solid transformation, the light transmittance showed a decreased trend with time in the early stage, which was caused by the formation of a large quantity of crystal nuclei. In the later stage, the light transmittance almost remained the same, thus indicating a growth stage of crystal nuclei. The activation volume yields a value of 2.16×10^?5 and –1.35×10^?5 m³/mol for the solid–liquid and liquid–solid transformations. Based on the obtained activation energy, the solid–liquid transformation is dominated by the interfacial reaction and diffusion, and the liquid–solid transformation is controlled by diffusion. This technique is an effective and powerful tool for the transformation kinetics study of n-octane.     

Anvil design for slip-free high pressure deformation experiments in a rotational diamond anvil cell

A rotational diamond anvil cell is the most suitable deformation apparatus with which to investigate the rheological properties of deep-Earth materials at pressures similar to those found in the lower mantle and core. However, slip between the sample and piston is still a problem, since the slip prevents the attainment of a constant strain rate and interferes with the uniform deformation of a sample. In this paper, we report that using a diamond anvil with deep grooves results in a marked improvement in the coupling between the sample and the diamond anvils.     

电驱动金刚石对顶砧低温连续加压装置

采用电驱动压电陶瓷取代传统机械螺丝给金刚石对顶砧施加压力,设计制备了低温下可连续增加流体静压的金刚石对顶砧压力装置,实现了低温(19±1)K连续加压达到4.41 GPa.该装置具有电驱动方便灵活、调谐精度高的低温连续加压功能.利用该装置实现了InAs单量子点发光与微腔腔模的共振耦合调谐过程.该装置将在原位压力精确调谐及测量样品信号跟踪等实验得到应用.     

Numerical study of stress and plastic strain evolution under compression and shear of a sample in a rotational anvil cell

The large-strain problem on the evolution of distribution of the components of stress tensor and plastic strain in a sample under compression and torsion in a rotational anvil cell was formulated and studied in detail using the FEM. Results are obtained for compression by different axial forces and torsion under two different constant axial forces. The effects of redistribution of the friction radial and torsional stresses and the load on a sample and gasket on the resultant fields are elucidated. Small pressure self-multiplication effect is revealed during torsion after compression below some critical force, and significant heterogeneity of all fields is found. Strong shear strain localization near the contact surface between sample and anvil is quantified. Results are compared with the simplified solution and available experiments. The results obtained are important for the determination of elastic and plastic properties of materials under high pressure and for the interpretation of kinetics of strain-induced phase transformations and chemical reactions.     

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。     

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.     

金刚石对顶砧中触点位置误差对样品电阻率测量精度的影响

利用有限元分析方法,研究了金刚石对顶砧中电极与样品接触点位置变化对范德堡法测量样品电阻率精度的影响.结果表明:当电极中心与样品边缘的间距b≤d/9(d为样品直径)时能得到精确的电阻率测量结果;当电极位置远离样品边缘而逐渐接近样品中心时,其位置变化对电阻率测量精度的影响迅速增大;相同的电极位置变化对具有较大电阻率的半导体样品电阻率测量精度的影响更明显. 关键词： 电阻率 有限元方法 金刚石对顶砧     

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