Polycrystalline diamond compact with enhanced thermal stability

Polycrystalline diamond compacts(PDC), which are composed of diamond and WC/Co substrate, and synthesized at high pressure and high temperature(HPHT), are widely applied as the tooth of drilling bit. However, the thermal stability of PDC will be reduced when diamond transforms into graphite due to cobalt in PDC acting as a catalyst during the drilling work. In this study, a new three-layer structured PDC with enhanced thermal stability has been successfully synthesized at pressures of 5.5–7.0 GPa and temperatures of 1650–1750?C. In this structure, the diamond-Si C composite acts as the working layer,and the diamond-Si C-Co composite and WC/Co cements are as the intermediate layer and substrate,respectively. It is found that the initial oxidizing temperature of the three-layered PDC is enhanced up to820?C, which is significantly higher than that(～780?C) of the conventional PDC counterpart.     

Polycrystalline diamond on self-assembled detonation nanodiamond: a viable route for fabrication of all-diamond preformed microcomponents

Surface assisted self-assembly of detonation nanodiamond particles (with typical sizes in the range 4-10?nm) has been obtained using different fractions of colloidal aqueous dispersions as starting material. The relationship between dispersion properties and structure/geometry of the aggregates deposited on Si or glass plates has been investigated. A series of differently shaped free-standing nanodiamond structures has been prepared, analysed and used as templates for the growth of polycrystalline diamond layers by the chemical vapour deposition (CVD) technique. The possibility of obtaining textured coating with a relatively strong [Formula: see text] preferred orientation (within a solid angle of about 0.6?srad) is also reported. Overall, the coupling of nanodiamond self-assembling to the CVD diamond growth enables one to produce specimens with complex 3D architectures. The proposed microfabrication methodology could represent a viable route for the production of free-standing all-diamond microcomponents, with tailored shapes and predefined crystalline features, to be used for advanced electronic applications.     

Ultrasonic thermoelectric receivers

Summary The thermoelectric ultrasonic receivers used for measuring medium and large intensities have certain advantages as compared with other types of receivers. These advantages comprise the following: 1) the nonresonating character of the thermal receivers (the difference in sensitivity at various frequencies can be partly eliminated by using efficient absorbents, which include in the range of 1.5–4.5 Mc diacetate cellulose films); 2) considerable inertia which leads to an averaging of the intensity fluctuations due both to cavitation and turbulence of the acoustic flow; 3) the thermal receivers measure intensity, a quantity which in the majority of cases is of the greatest interest.Among the disadvantages of the thermal receivers should be cited: 1) a big time interval between measurements since receivers with good lagging have a large thermal relaxation time which lowers considerably the speed of measurement; 2) operating conditions for keyed working in liquids with different temperature conductivity coefficients must be fixed for each liquid separately.     

Polycrystalline secondary ferroics

Domain walls in secondary ferroics can be displaced by electric fields, magnetic fields, mechanical stresses, or by some combination of the three. The expected physical properties of fully “poled” secondary ferroics are calculated and compared with those of the unpoled polycrystalline material, and with available experimental evidence. The effects of poling are most obvious for null properties such as piezoelectricity and magnetoelectricity, which depend entirely on domain alignment. Experiments on NH₄Cl provide the first demonstration of ferroelastoelectric “poling” in a polycrystalline material; piezoelectricity appears after annealing at ?30°C in parallel electric fields and mechanical stress. Other examples of “poled” polycrystalline secondary ferroics include ferromagnetoelectric Cr₂O₃, ferrobielastic SiO₂, and ferrobimagnetic MnO.     

GaAs MESFET and related processes

Since inception of GaAs MESFET in 1971, growth and processing technology of GaAs has matured to the extent that the analogue as well as digital IC production is persued at the industrial level. The ever increasing demand for higher frequency of operation, low noise figure and higher gain has led to newer device structures such as HEMT and HJBT based on GaAs and related compounds. Furthermore there exists exciting and proven capabilities in GaAs and related compounds to generate, detect and convert light into electrical signals. This has opened up vast field of opto-electronic devices and their integration with MESFET and other conventional devices. Basic building block of all these developmental activities still remains the GaAs MESFET, which have also been extensively used as low noise amplifiers, mixers, oscillators and high power amplifiers in descrete form. This paper reviews the design aspects, fabrication technology, d.c. and microwave characterization for both low noise and high power MESFET. Various technological advancements like via-hole for source grounding, air-bridge technology for low parasitic interconnects and polymide passivation, which have helped in further improvement in terms of higher frequency of operation, low noise and high power output are reviewed. Finally some representative results on the devices fabricated at CEERI are also presented.     

微波GaAs金属－半导体场效应管可靠性研究的进展

综述了近年来微波ＧａＡｓＭＥＳＦＥＴ可靠性的研究进展。重点介绍了影响其可靠性的因素如栅肖特基结和源／漏欧姆结的相互扩散及表面效应等。     

砷化镓MESFET器件的电路模拟

临于器件模拟参数在电路模拟中的重要性，本文选择了较为理想的模型参数提取方法－－统计试验法，并从理论上解决了该方法在迭代求解过程中存在的隐函数问题，以及解的唯一怀问题。同时提出了加速求的方法。在此基础上设计的软件可获得精确的器件模型参数。该软件与通用的ＳＰＩＣＥ３集成为一个针对ＧａＡｓＭＥＳＦＥＴ器件的电路模拟系统。本文给出了该系统对不同的电路形式基不同的器件参数下的模拟结果，为我们的ＧａＡｓ６００     

Fracture In Polycrystalline Iridium Coating

Iridium coating was prepared by the double glow plasma. The phase identification and the microstructure observation of the fracture surface of the coating were examined by X-ray diffraction and scanning electron microscopy, respectively. The deposition rate of the coating was up to 20μm/h. The iridium coating failed predominantly by grain boundary brittle fracture at room temperatures. Brittle intergranular fracture does not depend on grain size. Intergranular fracture in iridium coating has been considered to arise from low cohesive strength of the grain boundaries.     

Anomalous Properties of Polycrystalline BeO

Anomalous physicochemical properties of polycrystalline BeO (powder and ceramic) were studied. The results demonstrate that foreign magnetic ions, phase transitions, and strong electric fields have a significant effect on the ⁹Be spin–lattice relaxation time, lattice parameters of BeO, and carbon outdiffusion to the surface after Ar⁺ion bombardment.     

多晶硅太阳能电池片的回收再利用研究

从废弃的太阳能电池片中回收多晶硅原材料对于环境保护和材料的循环再利用具有重要意义。本文研究了用化学溶解和超声清洗回收电池片的最佳条件。分别对实验样品进行EDS、SEM、XPS分析, 得出结论: 电池片与质量分数为10%的氢氧化钠溶液反应18 min完全去除铝电极, 且硅晶片的损失率较小; 将完全去除铝电极的电池片在40 kHz超声清洗20 min后银电极完全剥落; 电池片与40%氢氟酸溶液反应10 min可以去除氮化硅膜。本研究对质量为8.9068 g的单片电池片进行了定量分析, 除去的铝电极质量为1.1102 g, 回收得到了0.0766 g的银电极和7.7169 g的硅晶片。     

Raman spectroscopy of diamond and doped diamond

The optimization of diamond films as valuable engineering materials for a wide variety of applications has required the development of robust methods for their characterization. Of the many methods used, Raman microscopy is perhaps the most valuable because it provides readily distinguishable signatures of each of the different forms of carbon (e.g. diamond, graphite, buckyballs). In addition it is non-destructive, requires little or no specimen preparation, is performed in air and can produce spatially resolved maps of the different forms of carbon within a specimen. This article begins by reviewing the strengths (and some of the pitfalls) of the Raman technique for the analysis of diamond and diamond films and surveys some of the latest developments (for example, surface-enhanced Raman and ultraviolet Raman spectroscopy) which hold the promise of providing a more profound understanding of the outstanding properties of these materials. The remainder of the article is devoted to the uses of Raman spectroscopy in diamond science and technology. Topics covered include using Raman spectroscopy to assess stress, crystalline perfection, phase purity, crystallite size, point defects and doping in diamond and diamond films.     

The friction of diamond sliding on diamond

Measurements are reported of the friction of diamond styli polished to a spherical tip sliding over a flat polished diamond surface. Particular attention was paid to maintaining standard conditions during the experiments, particularly the crystallographic orientations of the styli, the flat surface, and the directions of sliding, as well as the conditions of polish. The coefficient of friction was determined for sliding on both (001) and (011) faces, in different sliding directions, and for a range of loads and tip radii. The value of the friction and its variation with the direction of sliding depend quite strongly on the magnitude of the load and the radius of the stylus. However, the present results show that styli of different radii give quite similar friction when sliding under the same mean contact pressure. Hence, apparent discrepancies between previous measurements of the friction may be related to different regimes of pressure in the different experiments. When the stylus slides in the direction of easy abrasion of the flat the coefficient of friction passes through a pronounced minimum value as the contact pressure is increased. This behaviour suggests that at least two mechanisms contribute to the friction. A discussion based on the unusual topography of polished diamond surfaces, shows that the forces and energy losses associated with the friction may arise via at least three different mechanisms. The main features of the present results may be accounted for by two of these mechanisms in which surface asperities either ride over each other or push each other aside. (The third mechansim involving only fracture of the asperities appears to make no significant contribution.)     

Time transfer using multi-channel GPS receivers

This report is on time transfer experiments using a Global Positioning System (GPS) receiver constructed using a commercial GPS "engine" and a standard PC. The receiver measures the time difference between the local clock and a 1 pps signal synchronized to GPS time using data from up to 8 satellites. The receiver also reports the difference between GPS time as estimated using each of the satellites being tracked and the composite output pulses that have a rate of 1 Hz (1 pps signal). These data can be used to construct the standard 13-minute tracks as defined in the BIPM standard; the same data also can be averaged in other ways that make better use of the multi-channel capabilities of the hardware. The 13-minute averages can be directly compared with standard time-transfer receivers using common-view analysis. The results of the tests suggest that the methods currently used for national and international time and frequency coordination should be re-examined, and an alternative approach based on multi-channel receivers is suggested that should be more flexible, simpler, and easier to operate than the current system.     

Metrological use of Loran-C navigation receivers

The performance of accurate time and frequency measurements based on the Loran-C system using commercial navigation receivers is described. Techniques, criteria of choice, and suitability of commercial equipment, sources of errors, and experimental environment are discussed, and some results are compared with similar ones taken at IEN (Istituto Elettrotecnico Nazionale), the Italian national metrological laboratory. One of the two proposed methods does not require any alteration to the equipment, whereas with both of them continuous monitoring of all the transmitters of a chain is possible using a single receiver     

新金刚石

新金刚石是具有面心立方(Fcc)结构的金属性碳，其空间群为Fm-3m，晶格常数为0．3594nm。尽管新金刚石和金刚石的结构不同，但其某些晶面衍射峰与金刚石一致，1991年被日本科学家Hirai命名为新金刚石(New-Diamond，Ndjamond)。2001年Konyashin用实验证实新金刚石为面心立方结构的碳。在此以前，新金刚石在许多的实验过程中也曾获得过。     

Elastic Properties of Polycrystalline Solid Helium

Recent experiments have shown that the shear modulus of solid helium undergoes a large temperature variation in the range 20 to 200 mK, possibly due to changes in the pinning of dislocations. In this note we report on computer simulations of the elastic properties of polycrystalline solid helium. We calculate how the elastic coefficients of a sample made up of a large number of randomly oriented grains are affected by the changes in the shear modulus c ₄₄ of the individual grains.     

毫米波用六角铁氧体多晶材料

用普通陶瓷工艺制备了ＢａＡｌｘＦｅ１２－ｘＯ１９六角铁氧体多晶材料,随着Ｘ的增加,饱和磁化强度减小,居里温度下降,磁晶各向异性场增加。其结果可以通过假设Ａｌ＾３＋取代了２ａ位和１２Ｋ点阵位上的Ｆｅ＾３＋来解释。