镀Ti金刚石/Al复合材料的热性能

通过盐浴镀方法实现金刚石表面镀Ti,并采用模压铸造方法制备镀Ti金刚石/Al复合材料。研究镀层对复合材料微观结构和热性能的影响。结果表明金刚石表面镀Ti改善了复合材料的界面结合,降低界面热阻,从而提高了复合材料的热性能,包括降低热膨胀系数,提高复合材料的热导率。采用850℃盐浴镀Ti,镀覆时间180min得到的镀Ti金刚石/Al复合材料热导率高达488W/(m.K),在温度范围50～300℃之间,其平均热膨胀系数为9×10-6/K。     

镀钛金刚石／铜复合材料的热导率

采用粉末冶金法在高温热压炉中制备金刚石／铜复合材料,研究了钛镀层、烧结温度、金刚石颗粒体积分数对金刚石／铜复合材料热导率的影响。结果表明：钛镀层能改善金刚石／铜复合材料的界面浸润性,降低孔隙率,提高热导率。烧结温度低于980℃时,烧结驱动力不足,致使金刚石／铜复合材料的致密度下降,热导率降低;烧结温度高于980℃时,由...     

Cr-Cu镀层对金刚石-铜复合材料热导率的影响

通过对金刚石进行两次施镀,首先采用磁控溅射的方法在金刚石表面镀Cr,然后将镀Cr金刚石放入滚筒内进行铜元素滚镀加厚;镀铜后的金刚石与铜的质量比可达到1∶1~1∶2,铜镀层的厚度可达3~20μm。将镀铜金刚石直接放入模具中进行放电等离子(SPS)烧结,得到金刚石-铜复合材料,经测定,该复合材料的热导率可达480W/(m.K)。该工艺能很好地解决金刚石与铜因为密度相差大而混合不均匀问题,极大地提高了材料的热导率。     

金刚石膜/氧化铝陶瓷复合材料的介电特性和热学性能研究

研究了金刚石膜/氧化铝陶瓷复合材料作为超高速、大功率集成电路封装基板材料的可行性。采用电容法测量了复合材料的介电性质,结果表明在氧化铝上沉积金刚石膜,能有效降低基片材料的介电系数。碳离子预注入处理使介电损耗降低(从5×10^-3降低到2×10^-3),且频率稳定性更好。金刚石膜的沉积可明显提高基片的热导率,随着薄膜厚度的增加,复合材料的热导率单调递增。当薄膜厚度超过100μm时复合材料的介电系数下降到6.5、热导率上升至3.98W/cm·K,热导率接近氧化铝的20倍。     

基体中Ti元素含量对金刚石/Cu-Ti复合材料热导率的影响

采用真空热压法制备了金刚石体积分数为63%的金刚石/Cu-Ti复合材料,研究了基体中Ti含量对金刚石/Cu-Ti复合材料界面显微结构和热导率的影响。随着Ti含量的增加,金刚石/Cu-Ti复合材料热导率先增加后减小。当基体中Ti含量为1.1wt%时热导率最高,为511 W/（m·K）。Ti含量小于1.1wt%时,烧结过程中两相界面间生成的碳化物数量和面积随Ti含量的增加而增加,优化了界面结合,提高了界面结合强度,增加了界面传热通道数量,使金刚石/Cu-Ti复合材料导热性能提高。Ti含量的增加同时伴随着碳化物热阻增加和基体导热性能的恶化。过量的Ti元素使低导热性能的碳化物层厚度增加,碳化物层本身热阻增加,界面热导降低,金刚石/Cu-Ti复合材料导热性能下降。     

人造金刚石表面化学镀W/Ni-P层的工艺优选及镀层质量

为改进人造金刚石的表面性能,先在其上化学镀W,再化学镀Ni-P,制备了W/Ni-P包覆人造金刚石粉末。以镀液稳定性和镀层与基体结合力为评价标准,用正交试验和单因素试验优选工艺,并用扫描电镜(SEM)、能谱仪和粒度分析仪考察了优化W/Ni-P复合镀层的组织结构和镀后粉末的粒度分布。结果表明:最优化学镀W工艺为50 g/L钨酸钠,32 g/L次亚磷酸钠,25 g/L柠檬酸三钠,0.002 0 g/L硫脲,p H值为8.5,温度为90℃,时间为1 h;最优化学镀Ni-P工艺为35 g/L硫酸镍,32 g/L次亚磷酸钠,25 g/L柠檬酸三钠,0.002 0 g/L硫脲,p H值为4.5,温度为80℃,时间为1 h;优化W/Ni-P层均匀细致,与金刚石结合良好,镀覆后的金刚石粉末粒度更均匀。     

低成本金刚石/铝复合材料的研究

采用无压浸渗工艺制备出低成本金刚石/铝复合材料,并对复合材料的显微组织、界面及导热性能进行了研究。实验结果表明,采用无压浸渗工艺制备的金刚石/铝复合材料,组织致密,颗粒分布均匀。金刚石/铝复合材料的热导率随着金刚石含量的增加而增加,热导率最高可达298W/(m·K)。     

超声波重复化学镀Cu—Ni合金对金刚石性能的影响

研究了金刚石表面超声波重复化学镀Ｃｕ－Ｎｉ合金工艺及其对金刚石性能的影响。结果表明：超声波重复化学镀是一种有效增加镀层厚度的化学镀覆新工艺。每次镀１ｈ，镀覆４次，金刚石增重１２０％，采用这些新工艺，金刚石的单颗粒抗压强度可提高近１倍，氧化可提高１００℃左在。     

高导热金刚石/铜电子封装材料:制备技术、性能影响因素、界面结合改善方法

随着电子行业的不断发展,第二代热沉材料如钨/铜封装材料、钼/铜封装材料、碳化硅/铝封装材料等已不能满足该领域日益增长的需求。金刚石的热导率为2 300 W/(m·K),是已知热导率最高的物质;铜的热导率为401 W/(m·K),在众多金属中仅次于Ag。金刚石/铜复合材料具有诸多优点:(1)热导率高、强度大;(2)热膨胀系数能够通过改变金刚石与铜的体积分数加以调控,以实现与硅、锗等半导体材料的匹配;(3)具有比金刚石/银复合材料更低的成本以及比金刚石/铝、钨/铜、钼/铜等材料更高的热导率。因此,金刚石/铜复合材料是一种理想的电子封装候选材料。金刚石/铜复合材料的制备技术多种多样,其中粉末冶金、放电等离子体烧结、液相渗透是最适合该复合材料特性也是研究最广泛的技术。液相渗透法又分为无压熔渗法和压力辅助熔渗法,与粉末冶金法和放电等离子体烧结法相比,该法成本低、操作性强,成为近年研究的重点方向。目前,国际上已制备出热导率高达900 W/(m·K)的金刚石/铜复合材料。另一方面,金刚石与铜界面润湿度较差,导致复合材料致密度不高且热导率不易提升。解决金刚石与铜界面润湿度较差的问题成为制备金刚石/铜复合材料的关键,也促使国内外研究者不断尝试在制备工艺环节引入改进措施。目前已探索出两种较为可行的方法:(1)在复合材料制备过程中添加少量B、Cr等活性元素,使这些活性元素与铜形成合金;(2)在制备金刚石/铜复合材料之前,采用化学镀、扩散烧结、盐浴、磁控溅射等手段预先在金刚石表面包覆一层均匀的碳化物。本文总结了金刚石/铜复合材料的国内外最新研究进展及主流制备技术,论述了影响复合材料的热膨胀系数及热导率的主要因素。文章还介绍了改善金刚石与铜的界面润湿度的方法,最后对金刚石/铜复合材料的发展进行了展望。     

不同镀层金刚石与铜基粉末烧结制备的锯片刀头性能及机理

为了研究金刚石表面不同镀层对锯片刀头性能的影响及作用机理,分别对金刚石作了化学镀Ni、真空微蒸发镀Ti及Ti-Ni复合镀处理,并与铜基粉末混合烧结制备了锯片刀头。分别采用L30W/TMP扫描电镜、自制的3点抗弯机和热蚀法,对锯片刀头的锋利度、抗弯强度、耐热蚀性进行了探讨。结果表明:金刚石镀覆后制备的锯片切削性能、胎体对金刚石的把持力比金刚石锯片均有不同程度的提高;高温下,镀覆层对金刚石起到了一定的保护作用,镀Ni金刚石的锯片金刚石脱落较严重,镀Ti金刚石锯片的锋利度提高不大,Ti-Ni复合镀金刚石锯片切割速度最快,较前2种分别提高了67%和56%,且加工质量最好。金刚石表面Ti-Ni复合镀是提高铜基金刚石锯片性能的最有效措施之一。     

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.)     

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.     

Characteristics of diamond regrowth in a synthetic diamond compact

A transmission electron microscopic study of a commercial sintered diamond compact is reported that identifies and characterizes the diamond that has regrown between the grains of the original diamond powder during the high-pressure, high-temperature manufacturing process of the compact. The majority of the original grains are strongly deformed whereas the regrown diamond shows little or no plastic deformation. The dislocations in diamond regrown between the original grains occur in low-angle boundaries and other configurations typical of grown-in dislocations in crystals. The manufacturing process involves infiltrating the diamond aggregate by molten cobalt, and the regrown diamond is characterized by the presence of cobalt inclusions in sizes ranging from a few tenths of a micrometre down to a few nanometres, possessing the same orientation and lattice parameter as the diamond host. Graphite inclusions also occur in regrown diamond, few in comparison with cobalt inclusions and in random orientation. The graphite crystals exhibit axial ratios, (c/a), lowered by several per cent due to the containment pressure exerted by the diamond host.     

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。     

Rhombellanic diamond

Rhombellanes are mathematical structures, proposed in 2017; they may appear both in crystal or quasicrystal networks, also in their homeomorphs, further possible becoming real molecules. The simplest rhombellane is the K_2.3 complete bipartite graph, a tile found in the linear polymeric staffanes. In this paper a new binodal crystal network, called here dia-rbl, is introduced; its repeating unit, ada-rbl, is a 4D structure. The crystal structure is characterized by connectivity and ring sequences and also by the Omega polynomial.     

Wear resistance of nano-polycrystalline diamond with various hexagonal diamond contents

Wear resistance of nano-polycrystalline diamond (NPD) rods containing various amounts of hexagonal diamond has been tested with a new method for practical evaluation of the wear-resistance rate of superhard ceramics, in addition to the measurements of their Knoop hardness. The wear resistance of NPD has been found to increase with increasing synthesis temperature and accordingly decreasing proportion of hexagonal diamond. A slight increase in Knoop hardness with the synthesis temperature also has been observed for these samples, consistent with the results of the wear-resistance measurements. These results suggest that the presence of hexagonal diamond would not yield any observable increase in both hardness and wear resistance of NPD, contradictory to a recent prediction suggesting that hexagonal diamond is harder than cubic diamond. It is also demonstrated that NPD is superior to single crystal diamond in terms of relatively homogeneous wearing without any significant chipping/cracking.     

Machining MMC engineering components with polycrystalline diamond and diamond grinding

Abstract

The high specific strength of metal matrix composite (MMC) materials is derived from the combined effects of light, ductile and hard, brittle materials being incorporated in a matrix composite. The hard, brittle phase in this composite can cause problems when machining such materials. The most commonly encountered problems are those involved in producing an acceptable surface finish, avoiding very rapid tool wear and achieving acceptable machining costs, through the use of higher machining speeds. However, in order for MMC materials to be widely accepted into the mainstream automotive, aerospace, and mechanical engineering industries, cost effective machining solutions will be required. Increasingly, machining with polycrystalline diamond (PCD) and grinding with diamond abrasives (two examples of ultra hard materials) are being utilised as the most effective machining methods in the manufacture of MMC components. The present paper explores the inherent problems involved in the machining of MMCs and the suitability of ultrahard tooling technology in overcoming many of these problems. The importance of PCD grade selection and optimised machining conditions are particularly important when machining MMCs, and these are reviewed in detail. The versatility of PCD for use in practically all metal cutting operations is also illustrated. The paper concludes with a number of case studies demonstrating how ultrahard tooling technology has been applied to produce economically a wide range of engineered MMC components in the automotive, aerospace, and mechanical engineering industries.     

Innovation in diamond

 This historical review of the progress of innovation in diamond research is discussed comparing it with the history of other materials. The innovation steps in current diamond technology are shaped by the fact that diamond is a functional material. This series of innovations was mainly brought about by the discovery of CVD methods of synthesizing diamond from the gas phase. Many kinds of expected applications have been proposed. Success in demonstrating diamond electronic devices has been achieved, and atomic scale observations on diamond growth are reported. Thus, even atomic scale control in synthesizing diamond looks quite realistic in the near future. Although such new data enhance the applications of diamond, most industrial applications of diamond still rely on its hardness. Innovation with diamond will be accelerated when a product using diamond as a functional material is used widely. Received: 2 January 1997 / Accepted: 27 March 1997     

Laser ablation of diamond fibres and a diamond fibre metal matrix composite

Continuous chemical vapour-deposited diamond-coated fibres with tungsten wire or SiC fibre cores are attractive for reinforcing metals and ceramics. The fibres have been embedded in Ti-6A1-4V alloy to produce a diamond fibre-reinforced composite. Both the fibres and the composite material are extremely difficult to cut without damage by conventional mechanical methods. The use of a Nd-YAG laser to cut these materials is described.