关于金刚石微粉强度问题探讨

拉曼光谱通过测定金刚石微粉颗粒的晶体结构及内部缺陷和杂质含量评价微粉强度品级,是一种科学、有效、能快速检测金刚石微粉强度品级的方法.根据拉曼光谱测定金刚石微粉强度品级,研究了金刚石微粉强度与金刚石单晶原料强度、金刚石原材料的合成时间、微粉生产工艺和微粉表面处理工艺之间的关系.结果表明,金刚石微粉的强度虽然与原材料强度品...     

Influence of point defects on the thermal conductivity of diamond single crystals: state of the art

A new mechanism for the scattering of heat-carrying phonons has been suggested, based on the assumption of the activation of normal processes by isotopes. An attempt is made to explain the high response of the thermal conductivity of diamond single crystals to isotopic impurity concentration. On the basis of the mechanism suggested, the concentration and temperature dependences of the thermal conductivity of diamond have been calculated and compared with the experimental data available. For synthetic industrial diamond made by spontaneous crystallization, the effects of nitrogen impurities and vacancies on thermal conductivity have been estimated. An assumption has been made that nitrogen and vacancy defects are generated as structural elements in the process of diamond synthesis.     

Diamond synthesis by chemical vapor deposition: The early years

In the two decades following World War II there was a great surge in interest in high-pressure diamond synthesis, especially in Sweden, the United States and the Soviet Union. It is less well known that during this time major efforts were also made in low-pressure, metastable growth of diamond. All of these efforts, both high and low pressure, were characterized by great secrecy and a considerable lack of transparency. General Electric made the first public announcement of successful high pressure-high temperature diamond synthesis in 1955.The first reports of low-pressure diamond syntheses in the open literature were in 1962 (Eversole; Union Carbide Corporation) in 1968 (Angus et al.; Case Western Reserve University, Cleveland, and also in 1968 (Deryagin et al.; Physical Chemistry Institute, Moscow). In addition to skepticism about the veracity of these claims, a common view was that even if true, growth rates would always be far too slow to be of interest. Also, the apparent violation of thermodynamic laws was a continuing theme by many (but not all) during this time period. These attitudes changed dramatically in the early 1980s when the National Institute for Research in Inorganic Materials (NIRIM) in Japan (Kamo, Matsumoto, Sato, Setaka) announced diamond growth rates in the micron per hour range.The role of hydrogen in diamond synthesis was suggested in 1966 by Lander and Morrison at Bell Labs. An understanding of the critical role of atomic hydrogen grew incrementally, through sequential growth-cleaning cycles (Angus, Gardner) and culminating in its using during growth by the Moscow group (Deryagin, Fedoseev, Polanskaya, Spitsyn, Varnin, et al.).     

EXCLE函数替代编程实现原油压缩系数计算

探讨应用Office Excle函数,结合动态计量标准中原油压缩系数、体积压力修正系数公式,实现原油压缩系数查询计算,达到不用编程即可方便快捷精确原油计量的目的。     

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.     

Nucleation and Growth of Diamond Films on Ni-Cemented Tungsten Carbide: Effects of Substrate Pretreatments

The nucleation and growth of diamond films on Nicemented carbide is investigated. Substrates made of WC with 6 wt% of Ni were submitted to grinding, and then to different pretreatments (scratching, etching, and/or decarburization) before diamond deposition. Diamond synthesis was carried out by hot-filament chemical vapor deposition (HFCVD) using a mixture of CH₄ (1% v/v) and H₂. Depositions were performed for different lengths of time with the substrates at various temperatures. The specimens were analyzed before and after deposition by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffractometry (XRD). Raman spectra showed that the phase purity of the diamond films was not affected by the presence of nickel on the substrate surface. After wet etching pretreatments, the nucleation of diamond was enhanced, mainly at the WC grain boundaries. Continuous films were obtained on scratched and etched substrates. The decarburizing treatment led to the formation of metallic tungsten and of brittle nicke–tungsten carbide phases. These phases reacted in the early stages of diamond film formation with gaseous carbon species with a parallel process which competes with stable diamond nucleus formation. The diamond film formed after long-term deposition on these samples was not continuous.     

动压法合成金刚石的发展史——动压合成金刚石之一

文章论述了最早人们从陨石中发现金刚石,并从中受到启发,开始研究通过动态高压的方法合成金刚石的发展历程,并论述了我国金刚石行业动态高压法合成的发展和前景。     

含硼石墨碳源合成金刚石的试验

叙述了含硼石墨碳源合成金刚石的效果。讨论了石墨碳源含硼种类及其掺量对合成金刚石效果及其晶体生长性能的影响。在对含硼石墨碳源多种性能进行测试与分析的基础上，指出了选择合成金刚石碳源材料的原则和必要性。     

工艺对合成宝石级金刚石成核及品质的影响

根据国产六面顶液压机合成宝石级金刚石的合成块腔体内部过剩压减小及电阻变化的特点,使用天宏控制工程第三代操作系统检测六面顶压机设备的合成电流、合成电阻等参数重新编制宝石级大单晶合成工艺曲线.根据所设定的工艺曲线进行分阶段控制合成腔体内部的压力和温度,来稳定合成块内部金刚石的生长环境.研究发现合成宝石级金刚石前期10小时工...     

Experimental design methodology applied to study a diamond purification process

The synthesis of graphite at higher pressure and temperature conditions in the presence of a catalyst–solvent metallic alloy is a commonly applied process for industrial diamond production. The product obtained after this synthesis is an agglomerate composed by diamonds crystals, metallic particles, non-transformed graphite and other compounds. The diamond extraction from the agglomerates is known as purification. In this work the diamond purification process by alkaline melt was studied by statistical methods. It was shown that the alkaline melt could be a very efficient process and environmentally correct procedure for diamond purification.     

Structure and properties of Dalan detonation diamonds

This paper presents the results of an investigation of the fine crystal structure of Dalan diamonds synthesized from graphite and carbon black by detonation. The phase composition of the diamond powders was found to vary widely; the structural and structural-morphological states of diamond particles were studied. The main types and subtypes of detonation diamonds are characterized according to transmission electron microscopy data. Assumptions are made concerning diamond formation during detonation synthesis. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 108–116, January–February, 2009.     

Iron Oxide Nanoparticles Employed as Seeds for the Induction of Microcrystalline Diamond Synthesis

Iron nanoparticles were employed to induce the synthesis of diamond on molybdenum, silicon, and quartz substrates. Diamond films were grown using conventional conditions for diamond synthesis by hot filament chemical vapor deposition, except that dispersed iron oxide nanoparticles replaced the seeding. X-ray diffraction, visible, and ultraviolet Raman Spectroscopy, energy-filtered transmission electron microscopy , electron energy-loss spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to study the carbon bonding nature of the films and to analyze the carbon clustering around the seed nanoparticles leading to diamond synthesis. The results indicate that iron oxide nanoparticles lose the O atoms, becoming thus active C traps that induce the formation of a dense region of trigonally and tetrahedrally bonded carbon around them with the ensuing precipitation of diamond-type bonds that develop into microcrystalline diamond films under chemical vapor deposition conditions. This approach to diamond induction can be combined with dip pen nanolithography for the selective deposition of diamond and diamond patterning while avoiding surface damage associated to diamond-seeding methods.     

铁基触媒中铁含量对合成金刚石形貌及氮含量的影响(英文)

利用3种铁基粉末触媒,在国产六面顶压机上进行了金刚石单晶的合成实验,研究了高压高温条件下,铁基粉末触媒随铁含量的改变,石墨碳–铁基触媒体系合成金刚石条件的变化规律以及金刚石单晶的形貌,并利用红外光谱对金刚石中的含氮量进行了检测。结果表明:随着铁基粉末触媒中铁含量的增加,合成金刚石的压力和温度逐渐升高,金刚石生长的"V形区"上移,晶体的透明度变差,所合成晶体的含氮量逐渐减少。     

Determination of metallic impurities in high-purity type IIa diamond grown by high-pressure and high-temperature synthesis using neutron activation analysis

Metallic impurities in high-purity type IIa and conventional type Ib diamond single crystals grown by high-pressure and high-temperature (HPHT) synthesis were determined by neutron activation analysis using thermal neutrons. Metallic impurities of Fe, Co, Cr and other minor elements were detected in the high-purity type IIa diamond crystal. The typical quantities of these metallic impurities were a few ppb. The influence of these metallic impurities on the electrical properties of the type IIa diamond crystal was practically negligible compared with nitrogen and boron impurities behaving as a donor and an acceptor, respectively. In addition to the impurities detected in the type IIa diamond crystal, Ni impurities of several hundreds of ppb were detected in conventional type Ib diamond crystals. A difference in molten metal solvents used in the synthesis of each diamond crystal resulted in the difference in metallic impurities.     

Effect of hydrogen implantation on the graphite used in high pressure diamond synthesis

The objective of the present work is to investigate the effect of hydrogen implantation on graphite in the high pressure diamond synthesis. A comparison of the graphite/diamond conversion for different fluences of hydrogen implantation revealed that the diamond nucleation and the total mass yield are always higher (up to 46%) than in experiments without implantation. The maximum nucleation for the studied cases occurred at a fluence of 1×10¹⁷ hydrogen ions/cm². This behavior is not observed when other ions, such as krypton and argon, are implanted on the graphite, or when hydrogen is present in the reaction cell but not implanted on the graphite. The results were interpreted as a consequence of the creation of additional tetrahedral sp³ bonded carbon atoms when the graphite is hydrogen implanted, which would act as effective diamond nucleation sites in the high pressure synthesis.     

几种石墨材料合成金刚石的实验

对几种不同性能的碳源石墨材料进行了合成金刚石的实验。由实验结果可以看出,石墨材料的纯度,石墨化度,显微组织结构等因素,对金刚石的合成效果及其性能均有显著的影响。指出在金刚石合成的工业生产中,认真进行碳源石墨材料的选择,并根据碳源石墨材料优化合成工艺,是改善和提高金刚石合成中经济技术效益的重要因素。     

Illumination-induced charge transfer in polypyrrole–diamond nanosystem

Charge transfer in polypyrrole–diamond system is studied by conductivity measurements of a channel made of H-terminated diamond in the dark and under illumination. Micrometer-sized channels of conductive hydrogen-terminated diamond are lithographically fabricated on the surface of monocrystalline intrinsic diamond crystal by selective oxygen plasma treatment. The channels are interrupted by electrochemically synthesized micrometer-sized polypyrrole clusters. Similar characterizations are performed on channels interrupted by surface oxidation. Based on the increase and spectral response of the photo-current in the system, doping of diamond by charge carriers from polypyrrole is deduced.     

褐黄色IaA＋Ib型合成金刚石的光谱测试分析（上）

通过对褐黄色合成金刚石样品进行常规宝石学、红外光谱、紫外一可见光分光光度计,拉曼光谱等测试,结果表明：金刚石结构中的氮作为金刚石中的一种主要杂质,是金刚石呈现颜色的重要原因,并可用能带理论来解释,结构中的氮在金刚石呈色机制研究上有重要的意义。文章重点研究褐黄色合成金刚石的颜色成因,指出金刚石的呈色机制是一个很复杂的问题,它与金刚石中的杂质成分、色心、缺陷均有关系。