球状石墨的粉压成型及以其为原料的金刚石生长

本文研究了球状石墨的粉压成型特性。在国产SPD6×1 200型六面顶高温高压设备上,分别以鳞片石墨和球状石墨（均为400目）为碳源,以铁基粉末触媒为原料,在压力5.5 GPa,温度1 400℃左右,合成时间300 s的条件下合成出了优质金刚石单晶。通过球状石墨与鳞片状石墨生长的金刚石的对比,说明了球状石墨—铁基触媒体系生长金刚石的特点。结果表明球状石墨也可以用来合成优质磨料级金刚石单晶,但合成温度要比用片状石墨时高100℃左右,合成的金刚石粒度较鳞片石墨合成的金刚石粒度稍粗。     

粉末触媒与芯状触媒合成金刚石性能比较

本观察了粉末触媒与片状触媒合成金刚石的角色,晶形与杂质分布,并对其杂质元素含量,静压强度和冲击韧性进行了检测,结果表明粉末触媒合成的金刚石的性能优于片状触媒合成的金刚石。     

金刚石合成用粉末金属触媒

<正> 在高温高压条件下,在石墨向金刚石进行转变的过程中,有意识地加入一些材料,使得金刚石的相变活化能和合成温度和压力显著降低,这样的材料称之为人造金刚石用触媒材料,简称触媒材料或触媒。在没有触媒参与的情况下,石墨转化为金刚石需要13GPa的高压和2700℃以上的高温。采用触媒,可使金刚石的合成压力与温度分别降至5—6GPa和1200～1400℃,从而使工业生产金刚石成为可能。     

开孔隙对粉末触媒合成金刚石的影响

通过实验设计，对比研究了有、无表面开孔隙的ＮｉＭｎ粉末触媒在六面顶压机上合成金刚石效果的差异。结果表明：ＮｉＭｎ粉末触媒表面存在开孔隙，能提高合成腔体内触媒和石墨的接触面积和单位体积中金刚石的形核率，从而有利于高单产金刚石的合成；而粉末触媒表面的开孔隙存在与否，对合成金刚石的晶形无明显影响。     

无孔隙对粉末触媒合成金刚石的影响

通过实验设计，对比研究了有、无表面开孔隙的Ｎｉ－Ｍｎ粉末触媒在六面顶压机上合成金刚石效果的差异。结果表明：Ｎｉ－Ｍｎ粉末触媒表面存在开孔隙，能提高合成腔体内触媒和石墨的接触面积和单位体积中金刚石的形核率，从而有利于高单产金刚石的合成；而粉末触媒表面的开孔隙存在与否，对合成金刚石的晶形无明显影响。     

用铁基粉末触媒合成金刚石的研究

本文利用五种铁基粉末触媒 (FeNiXn,n =1,2 ,3 ,4,5Xn代表Fe在触媒中的含量 ,Xn>Xn -1)在国产六面顶压机上进行了金刚石单晶的合成实验 ,研究了高温高压条件下 (～ 5 4GPa ,～ 14 0 0℃ ) ,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生长特性 ,利用穆斯堡尔谱对金刚石中铁元素形成的包裹体进行了检测。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条件逐渐增高 ,金刚石生长的“V形区”上移 ,同时得出了铁基粉末触媒适合高温区 ( 110 )和 ( 111)面生长以及金刚石中铁元素以FeNi和Fe3 C形式存在的结论     

静压法合成金刚石的成核研究

针对静高压合成技术中片状样品的组装工艺特点,分析了在高温（约1500K)高压（约5GPa）下石墨与触媒之间的相互扩散过程和金刚石在合成腔中的成核几率。根据外界提供给石墨的能量大小,判断出纳米石墨微晶是形成金刚石晶核的基本单元。金刚石成核很可能是纳米石墨微晶转化为金刚石晶核的结构相变过程。讨论了在触媒的参与下金刚石的成核率与温度压力变化的关系,证明了压力是控制金刚石成核的有效参数,而温度不宜作为金刚石成核的控制参数。     

粉末触媒与片状触媒合成效果分析

就粉末触媒、片状触媒的合成效果进行了对比，并分析了粉末触媒合成金刚石的市场前景。     

“超硬材料生长、烧结机理学术讨论会”论文摘要(续完)

论人造金刚石晶体生长过程中的若干问题文中进行了固体相变的一般热力学分析,进而引伸到石墨金刚石相变系统中自由能变化的规律,从而得出了相变系统自由能与晶粒半径变化的两条曲线,分别说明了在触媒存在的挣压法和无触媒存在的直接转变或动压法金刚石生长的热力学规律。在进行了结构转化热力学     

铁触媒表面的氧化铁包覆层对金刚石成核的影响

为了研究氧化后的触媒对金刚石成核的影响，将α-Fe粉在400℃的空气氛中分别处理1，1．6，2．4和4小时，制备了不同包覆厚度的氧化铁包覆铁粉。采用氧化铁包覆的铁触媒粉末和石墨体系进行了金刚石合成研究。研究发现在5．7GPa和1600℃的条件下，铁触媒表面的氧化铁包覆层与石墨碳发生了氧化还原反应生成Fe3O4和FeO，同时包覆层内部的铁熔融渗出，并与石墨碳源接触促使了金刚石的成核生长。与纯铁触媒相比，氧化铁包覆层对金刚石成核具有明显的抑制作用，而且随着包覆层厚度的增加，抑制作用越明显。文中还借助穆斯堡尔谱、X-ray衍射和扫描电镜测试手段对上述实验机理进行了深入的探讨。     

Micro/nanometric investigations of the effects of laser ablation in the generation of micro-tools from solid CVD diamond structures

Using pulsed laser ablation, a novel method has been successfully developed for the generation of micro-features in diamond thus enabling the production of precision abrasive like micro-cutting elements into solid diamond micro-grinding tools. This paper examines the effects of the laser ablation on the generation of abrasive micro-features in diamond by using electron energy loss spectroscopy (EELS) and transmission electron microscopy (TEM). Site specific specimen preparation by a focus ion beam (FIB) material removal process has been made possible by the application of platinum and tungsten protective layers, providing the necessary specimen surface stability during the ion beam milling and lift-out operations. The prepared thin section orientated orthogonally to the cutting edge of a laser generated abrasive feature, has allowed the identification of the graphite and diamond allotropes across the ablated interface using EELS. A sequence of TEM images has revealed the extent of surface graphitisation and the high integrity of the diamond substructure. TEM examinations at nanometric resolutions have allowed the visualisation of the diamond and graphite allotropes at molecular level while depicting the abrupt graphite to diamond transition resulting in a highly defined boundary, thereby endorsing the capabilities of the laser ablation process to generate cutting edges with minimal structural damage.     

The effects of substrate compositions on adhesion of diamond films deposited on Fe-base alloys

Diamond deposition on a series of ferrous alloy substrates has been examined in a microwave plasma enhanced chemical vapor deposition reactor. The results show that the nucleation, growth, and adhesion properties of the diamond are strongly dependent on the types and relative concentrations of the alloy elements in the substrates. Along with high nucleation densities, continuous and adherent diamond films have been successfully fabricated on the Al-modified alloy substrates, even in the absence of inter-layers or nucleation enhancing surface pre-treatment. The mechanism is preliminarily clarified regarding the delicate competition and balance between the base metal and the alloying elements in terms of their activation and deactivation ability on catalyzing graphite formation during deposition process.     

纳米金刚石TiV色心的实验制备与性能研究

目的 利用磁控溅射辅助微波等离子体化学气相沉积技术制备钛掺杂纳米金刚石薄膜.方法 预先通过磁控溅射在石英玻璃基底上沉积纳米钛颗粒,然后使用微波等离子体化学气相沉积(MPCVD)设备在其表面沉积金刚石薄膜,通过活性氢原子将钛带入含碳生长基团中,从而将钛掺入纳米金刚石薄膜内.使用X射线光电子能谱(XPS)、拉曼光谱(Ram...     

氢、氧原子刻蚀CVD金刚石涂层石墨相的机理研究

采用第一性原理分子模拟计算方法对氢、氧原子刻蚀石墨相的过程进行分子动力学仿真,分析了2种原子在石墨相上的吸附过程及刻蚀反应的反应热和反应能垒。结果表明:氧原子在石墨相表面的吸附能强于氢原子吸附能,同时氧原子的化学反应活性大于氢原子的,更容易在石墨结构表面发生电子转移反应;氢原子促使石墨相表面的C—C键断裂需要两步反应,而氧原子则只需要一步反应,氢原子刻蚀石墨相的反应能垒比氧原子的高,所需能量更多。同时,通入含氧气源可以有效降低CVD金刚石涂层的沉积温度,提高金刚石涂层的质量。      

Interface between metallic film from Fe-Ni-C system and HPHT as-grown diamond single crystal

1　INTRODUCTIONAlthoughdiamondparticlesweresynthesizedsuccessfullyathigh pressureandhightemperature(HPHT)in 195 4[1] ,someissuessuchasthemetallicfilmsurroundingdiamondrequiretobeaddressed .Asweknow ,thereisamoltenmetallicfilmsurroundingthegrowingdiamondinthecourseofdiamondgrowthunderHPHT ,bymeansofthemethodthatgraphitediscsareplacedalternativelywithcatalystdiscs .Asdiamondcrystalgrowstowardgraphite ,thisfilmwillisolatethegrowingdiamondfromgraphiteanditwillexpandlikeaballoon .However ,d…     

Nucleation and growth of combustion flame deposited diamond on silicon nitride

The effect of substrate temperature (T_s) on the nucleation and growth of diamond on silicon nitride (Si₃N₄) based substrates deposited via the oxy-acetylene combustion flame technique was investigated. The diamond deposits were characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The nucleation density of the resulting deposits, which was of the order 10⁵ nuclei/cm², was used to approximate the activation energy for heterogeneous nucleation of diamond as32 – 40 kcal/mol. An Arrhenius plot of particle growth rate was used to calculate the activation energy for diamond growth as9.4 and 8.3 kcal/mol in the center and outside annulus of the deposit, respectively. These results suggest that the heterogeneous nucleation of diamond is a highly energetic process and may in fact be responsible for the observed low nucleation density of diamond on Si₃N₄. Thermodynamic analysis of gas/substrate reactions under conventional process conditions predicted that SiC formation, which is known to be a necessary precursor to diamond nucleation on Si, is energetically forbidden. Via kinetic and thermodynamic considerations, a patented in situ multistage deposition technique was developed which yielded continuous diamond coatings on Si₃N₄ substrates without extensive substrate preparation.     

Ag—Cu—Ti钎料中Ti元素在金刚石界面的特征

研究了金刚石钎焊接头中碳化物形成元素Ti与金刚石（或石墨）之间的相互作用行为。通过对接头界面处的成分分布和断口形貌观察,分析了Ti的作用机理、新生儿合物TiC的断口形及生长规律,结果表明：在一定的条件下,Ti元素与组成金刚石（或石墨）的碳元素发生反应形成TiC层;碳化物层使钎料与金刚石之间产生冶金结合;TiC与金刚石之间存在有明显的界面,TiC断口的微观表面形态呈韧窝状;在金刚石表面初始形成的TiC的生长方向与金刚石的晶向指数有关。     

金刚石低压气相生长的驱动力

以ＣＨ４／Ｈ２体系为例，研究了气相生长金刚石和石墨的驱动力随温度和ＣＨ４的摩尔分数的变化情况，若不考虑超平衡氢原子的作用，则石墨的生长驱动力总是大于金刚石的生长驱动力；如考虑超平衡氢原子的作用，则在一定的温度和ＣＨ４摩尔分数条件下，生长金刚石的驱动力将大于零且生长石墨的驱动力小于零，结果表明，此时气相中碳的化学势高于金刚石的化学势而低于石墨的化学势，因此，气相中将只生长金刚石而不生长石墨，甚至出现     

化学气相沉积金刚石微球的生长机制研究

采用微波等离子体化学气相沉积法,在过饱和碳离子浓度条件下,在单晶硅衬底上制备了球形结构的多晶金刚石微球,通过控制沉积气压与温度的变化,研究了金刚石由石墨生长区向纳米晶的球形结构、再到具有良好结晶性的金刚石生长区的过渡过程。结果表明:沉积气压与温度的升高导致微球的粒径增大,微球由sp3、sp2键共存相转变为较纯的金刚石相;在一定的碳离子过饱和度和气压、温度范围内,微球的形成主要受二次形核过程的控制。气压和温度升高后,微球呈<110>取向生长,微球的形成主要受（111）面高密度孪晶和层错缺陷的控制,揭示了化学气相沉积金刚石不同生长区内二次形核机制与孪晶层错机制诱导的金刚石微球的生长过程。      

THERMAL STUDY ON THE GRINDING OF GRANITE WITH SUPERABRASIVE TOOLS

Diamondabrasivetoolsareextensivelyusedintheprocessingofstone ,frominitialsawingtofinalfinishing .Infact,abrasiveprocessingofgraniteandmarbleforconstructionisthemostimportantfactorintheconsumptionofindustrialdiamond .Duringgrinding ,diamondabrasivegritsonthewheelsurfaceinteractwiththeworkpieceanddothecutting .Theenergyexpendedbythegrindingprocesscanleadtoelevatedtemperaturesatthegrindingzone ,whichmaycausethermaldamagetotheworkpieceandpromotewheelwear.Accordinglyextensivepastresearchhasbeenconc…