Application of a new composite cubic-boron nitride gasket assembly for high pressure inelastic x-ray scattering studies of carbon related materials

We have developed a new composite cubic-boron nitride (c-BN) gasket assembly for high pressure diamond anvil cell studies, and applied it to inelastic x-ray scattering (IXS) studies of carbon related materials in order to maintain a larger sample thickness and avoid the interference from the diamond anvils. The gap size between the two diamond anvils remained ~80 μm at 48.0 GPa with this new composite c-BN gasket assembly. The sample can be located at the center of the gap, ~20 μm away from the surface of both diamond anvils, which provides ample distance to separate the sample signal from the diamond anvils. The high pressure IXS of a solvated C(60) sample was studied up to 48 GPa, and a pressure induced bonding transition from sp(2) to sp(3) was observed at 27 GPa.     

Note: An anvil-preformed gasket system to extend the pressure range for large volume cubic presses

An anvil-preformed gasket system has been developed to extend the pressure range for the widely used large volume cubic press without sacrificing the sample volume. The relationship of the sample chamber pressure versus press load for this system was calibrated at room temperature using transitions in Bi, Tl, and Ba. With similar sample volumes (8-11 mm in diameter and 8 mm in length), the anvil-preformed gasket system can generate pressures up to about 8.5 GPa, significantly higher than 6 GPa, which was generally the maximum pressure for the conventional anvil-gasket system. The details on the optimized design for the anvil-preformed gasket system are given in this note.     

A simple and inexpensive culture device for cell growth,quantitative microscopy and autoradiography

An inexpensive culture chamber suitable for subsequent preparations for cyto-chemical or radiographic work is demonstrated. The chamber consists of two glass microscope slides suitably prepared for cell growth and a gasket of silicone rubber. The slides and gasket are sealed and held together with two ordinary spring letter clips or clothes-pins. Cells may be inoculated by piercing the gasket with a hypodermic needle, or by removing the top slide and adding cells directly. Long-term cultivation with medium replacement is easy and efficient and addition of isotopes or other materials may be done aseptically.     

Chemical analysis of wear tracks on magnetic disks by TOF-SIMS

Surface reactions on magnetic recording disks have been studied during sliding with ceramic sliders in the main chamber of TOF-SIMS. Chemical change of lubricant oil in the wear track was observed by the chemical image of TOF-SIMS. The magnetic disk surface was covered with perfluoroalkyl polyether lubricant (Fomblin Zdol). The Si tip slider surface was covered with Al₂O₃, DLC, TiN or c-BN coating. Experimental conditions were as follows: 0.8 mN of load and a sliding speed of 0.01 m/s. Lubricant oils were decomposed with Al₂O₃ and TiN slider surfaces. Metal (Al, Ti) fluorides were detected by TOF-SIMS in the sliding track. Material transfer occurred by chemical wear of slider material. From TOF-SIMS observation, the decomposition of lubricant molecules was initiated at the end group of molecules (-CF₂CH₂OH). On the other hand, DLC and c-BN sliders suppressed the decomposition reaction of PFPE oils. In conclusion, hard and chemical inert materials such as DLC and c-BN are suitable for a long-life HDI.     

Density measurements of noncrystalline materials at high pressure with diamond anvil cell

We describe an x-ray absorption method for in situ density measurement of non-crystalline materials in the diamond anvil cell using a monochromatic synchrotron x-ray microbeam. Sample thickness, which is indispensable in the absorption method, can be determined precisely by extrapolating the thickness profile of the gasket obtained by x-ray absorption and diffraction measurements. Diamond deformation across the sample chamber becomes noticeable at high pressures above 10 GPa, which can be monitored with a precision better than 1%, as demonstrated by measurements on crystalline Ag. We have applied the developed method to measure densities of the classic network-forming GeO(2) glass in octahedral form at pressures up to 56 GPa. The fit to the pressure-volume data with the Birch-Murnaghan equation from 13 to 56 GPa gives parameters of V(0)=23.2+/-0.4 cm(3)mol and K=35.8+/-3.0 GPa, assuming that K(')=4. This method could be applicable for in situ determination of the density of liquids and other noncrystalline materials using a diamond anvil cell up to ultrahigh pressures.     

A Chamber for X-Ray Diffractometry of Gas Hydrates Samples for Pressures of Up to 700 atm

A chamber for X-ray diffractometry of gas-hydrate samples designed for operation at pressures of up to 700 atm and low temperatures is described. The leakproof character of the chamber at temperatures down to ?150°C is ensured by an Amaga-type seal with a fluoroplastic gasket pressed by disk springs. The chamber was used to study double hydrates using a synchrotron radiation source and a pressure generator based on a thermal multiplier.     

Design of a high-temperature and high-pressure liquid flow cell for x-ray absorption fine structure measurements under catalytic reaction conditions

The design and performance of a new high-pressure and high-temperature cell for measurement of x-ray absorption fine structure (XAFS) spectra of solid catalysts working in a flowing liquid are presented. The cell has flat, high-purity sintered cubic boron nitride (c-BN) windows which can tolerate high temperature (900 K) and high pressure (10 MPa). The c-BN is a new material which has the highest tensile strength, second only to diamond, and is also chemically and thermally stable. The use of the cell is demonstrated for measurements of PtPdAl(2)O(3) and Ni(2)PSiO(2) hydrodesulfurization catalysts at reaction conditions. A technique called delta chi (Deltachi), involving determining the difference between XAFS spectra of the sample at reaction conditions and the bare sample, is introduced.     

密封垫片高温综合性能试验机的研制

在总结分析目前国内外密封垫片综合性能评价技术的基础上,利用低压区作为密封测漏腔,克服高压区密封腔由于密封难带来试验误差大的问题,自主研制一种高温垫片综合性能试验机.介绍该试验机的设计原理和特殊功能,采用高斯误差估计方法对试验机的泄漏率测量范围和精度进行计算,并利用该试验机对不锈钢柔性石墨缠绕垫片和石棉橡胶板垫片的高温综合性能进行试验评定.试验结果表明,所研制的密封垫片高温综合性能试验机能够准确进行垫片的压缩回弹性能、蠕变性能和密封性能测试,为静密封连接的泄漏预测与控制提供可靠的试验依据.     

Analysis of defects on BN nano-structures using high-resolution electron microscopy and density-functional calculations

Cubic boron nitride (c-BN) nucleation takes place on hexagonal boron nitride (h-BN) layers growing perpendicular to the substrate surface during thin film synthesis. Studies focused on the nucleation of the cubic phase suggest the possibility that transient phases and/or defects on these h-BN structures have a role in sp3-bonded cubic phase nucleation. In this study, we have investigated the nature, energetics, and structure of several possible defects on BN basal planes, including point defects, 4-, and 5-fold BN rings, that may possibly match the experimentally observed transient phase fine structure. TEM image observations are used to build approximate atomic models for the proposed structures, and DFT calculations are used to relax these structures while minimizing their respective total energies. These optimized atomic geometries are then used to simulate TEM images, which are compared to the experimentally observed structures. Data from DFT calculations and analysis of simulated images from the proposed atomic structures suggest that 4-fold BN rings are more likely to exist on the transient phase possibly leading to c-BN nucleation.     

Environmental chamber for in situ dynamic control of temperature and relative humidity during x-ray scattering

We have designed, constructed, and evaluated an environmental chamber that has in situ dynamic control of temperature (25 to 90?°C) and relative humidity (0% to 95%). The compact specimen chamber is designed for x-ray scattering in transmission with an escape angle of 2θ = ±30°. The specimen chamber is compatible with a completely evacuated system such as the Rigaku PSAXS system, in which the specimen chamber is placed inside a larger evacuated chamber (flight path). It is also compatible with x-ray systems consisting of evacuated flight tubes separated by small air gaps for sample placement. When attached to a linear motor (vertical displacement), the environmental chamber can access multiple sample positions. The temperature and relative humidity inside the specimen chamber are controlled by passing a mixture of dry and saturated gas through the chamber and by heating the chamber walls. Alternatively, the chamber can be used to control the gaseous environment without humidity. To illustrate the value of this apparatus, we have probed morphology transformations in Nafion(?) membranes and a polymerized ionic liquid as a function of relative humidity in nitrogen.     

金属缠绕式垫片的预紧应力分析及试验研究

结合法兰连接的实际，按照ASME B16．20对缠绕式垫片压缩的要求，对管法兰用缠绕式垫片的预紧应力进行了分析，并就如何通过垫片工艺结构的调整，使其机械性能与紧固件的要求一致，从而使法兰接头符合操作时的密封性要求进行了试验研究。     

Design of a scanning probe microscope with advanced sample treatment capabilities: An atomic force microscope combined with a miniaturized inductively coupled plasma source

We describe the design and performance of an atomic force microscope (AFM) combined with a miniaturized inductively coupled plasma source working at a radio frequency of 27.12 MHz. State-of-the-art scanning probe microscopes (SPMs) have limited in situ sample treatment capabilities. Aggressive treatments such as plasma etching or harsh treatments such as etching in aggressive liquids typically require the removal of the sample from the microscope. Consequently, time consuming procedures are required if the same sample spot has to be imaged after successive processing steps. We have developed a first prototype of a SPM which features a quasi in situ sample treatment using a modified commercial atomic force microscope. A sample holder is positioned in a special reactor chamber; the AFM tip can be retracted by several millimeters so that the chamber can be closed for a treatment procedure. Most importantly, after the treatment, the tip is moved back to the sample with a lateral drift per process step in the 20 nm regime. The performance of the prototype is characterized by consecutive plasma etching of a nanostructured polymer film.     

典型复杂型面模件高效数控加工策略

以垫片模下模镶件为研究对象,重点研究了数控加工工艺的优化问题,旨在提高模具型腔数控加工效率、加工质量、降低刀具磨损,实施高效的数控加工策略;提出了模具型腔粗铣加工刀具组合方法,进行了粗铣加工走刀方式对比分析,针对深孔、薄壁、复杂轮廓曲面等难加工部分制定了相应的加工策略,优化了加工工艺,使用UG CAM进行编程,生成了高效的加工刀路,进行了加工仿真,并自行开发了后处理器,在华中文控铣床上加工出试样,该策略提高了加工效率、产生了良好的经济效益.     

Wear behavior of some cutting tool materials in hard turning of HSS

This study presents an assessment of the performance of four cutting tool in the machining of medium hardened HSS: polycrystalline c-BN (c-BN+TiN), TiN coated polycrystalline c-BN (c-BN+TiN), ceramic mixed alumina (Al₂O₃+TiC), and coated tungsten carbide (TiN coated over a multilayer coating (TiC/TiCN/Al₂O₃)). The Al₂O₃+TiC and the coated carbide tools can outperform both types of c-BN at high cutting speeds. Raman and SEM mapping revealed an alumina tribo-layer that protects the surface of the Al₂O₃+TiC cutting tool. The high chemical and thermal stability of Al₂O₃ tribo-films protects the tool substrate because it prevents the heat generated at the tool/chip interface from entering the tool core.     

Finite element design of double bevel anvils of large volume cubic high pressure apparatus

A double bevel anvil of the cubic high pressure apparatus (CHPA) was developed, adopting tungsten carbide as the anvil material. We have performed finite element analyses of conventional single bevel anvil and double bevel anvil. The results indicate that the double bevel anvil has two advantages. Firstly, to gain the same chamber pressure, the oil pressure of CHPA using double bevel anvil decreases about 10.8% than that using single bevel anvil. Secondly, double beveling can maintain the pressurized seal stability of the sample chamber, which is often sacrificed with improve the pressure of sample chamber. The results of finite element analyses are well consistent with the experimental results at CHPA (SPD-6x1200 type).     

Use of the environmental scanning electron microscope for the observation of the swelling behaviour of cellulosic fibres

We have developed a method for observing transverse swelling of cellulosic fibres in the environmental scanning electron microscope (ESEM). The presence of liquid water in the ESEM specimen chamber allows the observation of in situ hydration without the need for coating, freezing, or drying of the sample. For reproducibility of the hydration and dehydration process, specialised mounting techniques are required and control of the conditions for condensation and evaporation of liquid water is necessary. The sensitivity of these cellulosic materials to the electron beam was investigated, showing that some damage mechanisms are enhanced by the continual presence of water vapour in the chamber. A discussion is presented of the effect of various experimental parameters on the extent and time of onset of the damage, and we outline steps to maximise the amount of useful experimental time for these fibres.     

垫片外缘最大应力对螺栓法兰连接结构泄漏率影响

螺栓法兰连接广泛的应用于石油化工等过程装备中,其是最重要的静密封连接形式之一,失效的主要原因是泄漏。利用有限元法对垫片的平均应力和外缘最大应力关系进行分析研究;采用解析方法预测螺栓法兰连接结构的泄漏率,并与试验结果进行对比,研究了垫片外缘最大应力与泄漏率之间的关系。结果表明,随着螺栓载荷的增加,法兰偏转程度增加,垫片平均应力与垫片外缘最大应力的差值逐渐增大;垫片外缘最大应力较平均应力对连接结构泄漏率影响更大。     

柔性石墨波齿复合垫片的常温性能研究

本论述分析了波齿复合垫片的常温力学性能和密封性能试验研究。研究表明,波齿复合垫片具有良好的压缩回弹性能和密封性能;在试验的基础上得出了密封试验曲线及其关系方程式,可作为该种垫片密封设计的重要依据;因石墨纸与金属波齿的结合是采用粘贴方式,波谷内未能充实柔性石墨,因此反映出垫片初始压紧阶段的承载能力低,故建议垫片出厂前应进行预压缩。     

Thickness measurement of sample in diamond anvil cell

We report on an original method that measures sample thickness in a diamond anvil cell under high pressures. The method is based on two hypotheses: completely plastic deformation on the gasket and completely elastic deformation of the diamonds. This method can further eliminate the effect of diamond deformation on the thickness measurement of a sample, which permits us to measure the thickness of alumina up to 41.4 GPa.     

A chamber attached to the SEM for fracturing and coating frozen biological samples

A chamber for introducing, fracturing and coating frozen biological samples has been developed as an attachment to the sepcimen chamber of a scanning electron microscope. Together with a eucentric-tilt cold-stage, this chamber constitutes a complete system for viewing fractured biological surfaces of the type normally only seen by replica techniques. An air-lock on the chamber accepts a transfer module to allow insertion of the frozen sample without frost build-up. Fracturing is carried out with a precisely adjustable cooled knife under a 10--100X binocular microscope. The sample can tilt and rotate while being coated with carbon or metals evaporated from rechargeable sources introduced through the air-lock. Cooling in the chamber is provided by a cylindrical copper tank filled with liquid nitrogen. The chamber has its own LN2 trapped high vacuum system. After preparation the sample can be placed directly into the SEM through an isolation valve. The cold-stage utilizes a Joule-Thomson refrigerator. The sample can be kept below 103 K at all times though there are provisions for heating it in the fracturing and cold-stage positions. A system of controls, sensors and interlocks simplifies the operation of the system.