CVD金刚石条强化孕镶金刚石钻头的试验研究

本文将经过激光切割的CVD金刚石条镶嵌到传统的孕镶金刚石钻头胎体中,研制了一种新型的硬支点强化型金刚石钻头,以提高钻头在坚硬地层中的钻进效率和使用寿命。介绍了该新型钻头的设计及制造工艺,并进行了室内钻进试验。结果表明：与聚晶金刚石柱强化孕镶金刚石钻头相比,CVD金刚石条强化的孕镶金刚石钻头的钻进效率较高,达5．575m／h,且该钻头的磨损程度更小,使用寿命长。在钻进过程中更加稳定.     

CVD单晶金刚石的制备及红外性能研究

利用微波等离子化学气相沉积法,以H₂/CH₄/N₂为混合气源,在CVD金刚石单晶基底上同质外延生长金刚石。在一定的甲烷浓度下,分析衬底温度对金刚石结晶质量及光学性能的影响。利用光学显微镜、扫描电子显微镜(SEM)表征金刚石单晶,得到金刚石单晶的样品颜色、内部缺陷、表面形貌等信息。对金刚石样品进行抛光处理后,使用红外傅里叶变换光谱仪对金刚石进行检测,得到红外波段的光学透过率。结果表明:在生长温度为930 ℃左右时金刚石的结晶质量最好,红外透过率最高,可达70%以上;略高或略低的温度均会降低其红外透过率,相对来说略高的温度下生长的金刚石结晶质量和红外性能优于低温下生长的金刚石的。N₂的掺杂会导致单晶带有棕褐色,生长速率显著变快,严重降低红外波段的光学性能。      

金刚石单晶生长界面Auger电子能谱分析

本文用Auger电子能谱技术分别对金刚石单晶牛长界面的金属膜表面及附近碳原子的Auger谱精细结构、金刚石单晶附近及其表面的Auger谱精细结构进行了分析。Auger谱分析表明,金刚石晶体外的碳的Auger谱与石墨的类似,金刚石单晶上的碳的Auger谱与石墨的主跃迁峰能量相差约3．7eV,与金刚石单晶Auger谱形相同,介于两者之间的Auger谱反映出碳原子的电子杂化态介于石墨与金刚石单晶之间。结果表明高温高压条件下石墨中碳原子经过“金属催化剂层”才能将碳原子的电子构形从SP^2π态改变成Sp^3态,碳原子从而以金刚石四面体结构沉积到金刚石表面,金刚石晶格结构的形成是在金刚石表面层完成的。     

高温高压下金刚石成核机制的研究

本文以国产六面顶压机作为人造金刚石的合成设备,采用金属粉末触媒技术,进行了金刚石晶体的合成.实验中,通过对生长工艺的调整,考察了金刚石在合成区间内的不同合成习性.实验结果表明:金刚石的合成区间可以根据能否自发成核而分为成核区与生长区.在生长区内,金刚石不能自发成核,但金刚石晶种可以在此区间稳定存在并长大.在生长区内金刚...     

约束式热丝CVD法制备金刚石的研究

为提高热丝CVD法沉积金刚石薄膜的生长速率,以丙酮和氢气作为反应气源,利用自制的半封闭式空间约束装置,将热丝、衬底、反应气体聚集在狭小空间内,研究不同气体流速条件下的金刚石薄膜沉积情况;使用SEM和Raman光谱表征所合成的薄膜。结果表明:采用约束式沉积法可以显著提高沉积速率,本实验在230 cm3/min（标况）气体流速下获得最大沉积速率6.31 μm/h,比未约束时增大了近一倍。随着气体流速增大,沉积速率先增大后减小;气体流速86~115 cm3/min（标况）时,晶粒尺寸为微米级;气体流速115~575 cm3/min（标况）时,晶粒尺寸减小至纳米级。Raman光谱检测显示:约束式沉积所得薄膜总体质量较好,但随气体流速增大而逐渐降低。      

Effects of pre-treatments and interlayers on the nucleation and growth of diamond coatings on titanium substrates

During diamond deposition on titanium substrates, two processes exist: (1) diffusion of hydrogen into a titanium substrate and the formation of hydride thereby degrading the mechanical properties of the substrate; and (2) competition among the rapid diffusion of carbon atoms into substrates, the formation of carbide and the nucleation of diamond crystals (thereby affecting the nucleation and growth rate of the diamond coating). To increase the diamond nucleation rate and prevent the rapid diffusion of hydrogen and carbon into the substrate, different surface treatments and interlayers were studied in this paper. Results showed that polishing with diamond pastes and ultrasonic pre-treatment in diamond suspensions will significantly increase the nuclei density of diamond crystals. However, the diffusion of hydrogen into the substrate could not be prevented. Pre-etching of the titanium substrate using hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Results showed that on a TiN interlayer, there was no significant improvement in diamond nucleation and growth, and the deposited diamond coatings showed poor adhesion. New diamond crystals were formed on the DLC interlayer in which DLC acted as the precursor for diamond nucleation. However, the so-formed diamond coating showed spallation. The plasma nitrided layer could prevent the rapid diffusion of hydrogen and carbon into the titanium substrate, but results showed a relatively low nucleation density of diamond crystals and poor adhesion. A graded interlayer combining plasma nitriding followed by plasma carbonitriding was effective in preventing the rapid diffusion of hydrogen and carbon into the substrate and improving the nucleation rate and adhesion of diamond coating.     

单晶高温合金再结晶形核条件及长大机制

对DD6单晶高温合金进行表面压痕处理,然后在不同温度(1220、1270和1310℃)热处理2h,研究合金再结晶的形核和长大行为.结果表明:γ'相溶解是再结晶的必要条件;再结晶晶粒以外,产生大量的亚晶界,离压痕中心越近,亚晶界密度越大,亚晶聚合粗化是再结晶的形核和长大机制.在γ'相溶解温度以上,γ'相对再结晶的形核和长大无明显影响.     

CVD金刚石磨损性能的研究

提出了一种直接评价CVD金刚石磨损性能的实验方法,比较研究了热丝CVD法、微波等离子体CVD法和直流电弧等离子体CVD法制备的金刚石的磨损性能。研究结果表明:影响CVD金刚石磨损性能的主要因素是非金刚石相的相对含量,金刚石的内应力和晶粒大小对磨损性能的影响较小。     

正偏压对微波等离子体CVD法制备金刚石薄膜的影响

线形同轴耦合式微波等离子体CVD法是在硬质合金微型钻头(微钻)表面沉积金刚石涂层的最佳方法之一.本文首先研究了酸碱两步预处理后微钻表面的形貌和成分,然后研究了微钻工作表面金刚石的沉积情况,最后重点研究了正偏压对微钻不同位置金刚石生长的影响.结果表明,在微钻上施加50 V正偏压时,金刚石薄膜具有最佳的形貌和较好的均匀性.     

CVD单晶金刚石[NV]和[SiV]缺陷的抑制与消除

反应气体中添加体积分数0.001%的N₂,研究CVD金刚石PL(photoluminescence spectroscopy,PL)光谱发现,与N杂质相关的[NV]0与[NV]-和与Si杂质相关的[SiV]是金刚石中的主要杂质缺陷。经过高温高压(high temperature and high pressure,HPHT)处理后,[NV]0峰的强度被削弱,[NV]-峰的强度被增强,[SiV]峰的强度被显著增强,并新出现了[SiV]-宽峰。反应气体中N₂体积分数降至0.000 1%并添加0.5%的O₂后,[NV]0与[NV]-峰消失,O₂升高至1%后[SiV]峰强度出现了明显降低,继续升高O₂含量,[SiV]峰强度下降趋势变缓,这些现象证明了添加少量O₂有助于CVD金刚石中N和Si杂质缺陷的抑制与消除。      

不同碳源浓度下热丝CVD金刚石薄膜的惰性示踪气体发射光谱法研究

采用热丝化学气相沉积法制备金刚石薄膜,运用惰性示踪气体发射光谱法对等离子基团进行分析。实验所采用的惰性示踪气体为氩气。热丝CVD金刚石薄膜的表面形貌和断面形貌通过SEM进行表征,质量通过Raman光谱表征,从而对等离子体诊断结果进行验证。结果表明:保持其他工艺参数不变时,随碳源混合气体流量不断增加,电子温度总体呈下降趋势,但在50~70cm3/min出现反常的先增加后下降,在60cm3/min附近时出现最大值,此时的带电粒子到达基片时具有最大通量和能量,与此同时,CO、C₂、CH等几种含碳基团浓度在60cm3/min处出现最低,气相沉积过程向着金刚石薄膜沉积的方向发展,生长速率达到最大,金刚石薄膜的质量却随碳源混合气体流量的增加而降低。      

CVD金刚石厚膜刀具刃口半径研磨的实验研究

CVD金刚石膜具有与单晶金刚石相近的力学性能,是一种理想的高精度刀具材料.研磨是制作CVD金刚石厚膜高精度刀具的关键环节之一.本文针对与刀具刃口半径紧密相关的研磨工艺进行了一些研究工作.实验结果表明:研磨盘端面跳动控制在10 μm以内,动态不平衡度控制在0.3 g.mm/kg以内,选择1 μm以下的研磨粉粒度,研磨速度控制在20～30 m/s范围,金刚石厚膜刀具刃口半径可达80 nm,圆弧轮廓精度可以控制在0.5 μm左右;车削加工LY12外圆和端面,表面粗糙度可达Ra 0.02 μm,达到镜面效果,可以替代同等精度的单晶金刚石刀具.     

Effect of mechanical pretreatment on nucleation and growth of HFCVD diamond films on cemented carbide tools with a complex shape

To enhance the mechanical pretreatment efficiency for WC-Co complex-shaped cutting tools, a self-made vibrating grinding equipment and mixed abrasives made up of walnut shell and diamond particles are proposed. The technique can abrade the dozens of tools simultaneously, modify surface properties of tools, and maintain sharpness of the cutting edges. Several experiments are performed to explore effects of the different types and proportions of walnut shell and diamond powders on the properties of nucleation, growth, and adhesion of diamond films deposited via a chemical vapor deposition method. Subsequently, Field Emission Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM,), Laser scanning micro-gauge, Micro-Raman Spectroscopy, Stylus Profiler, and Rockwell hardness tester are adopted to characterize the as-pretreated substrates and as-deposited diamond films. According to the results, a low residual cobalt content around 0.2 wt% and a markedly increased surface defects are detected on the pretreated milling tools when the preferred types and proportions of mixed abrasives are applied, which can help to significantly enhance the nucleation density and growth rate of diamond films, and strengthen the adhesion between the films and substrates.     

氩气流量对等离子体喷射法制备的金刚石膜形核的影响

采用100kW级直流电弧等离子喷射法进行金刚石膜沉积,阐述了氩气对维持电弧稳定的重要作用,讨论了氩气流量对衬底表面轰击的影响,氩气流量和不同电弧分区对形核期金刚石表面形貌和晶粒尺寸的影响,以及时间和不同预处理方式对金刚石形核密度的影响。结果表明:随着氩气流量的增加,氩气对衬底表面的轰击作用增强,金刚石膜表面形貌呈现从(111)到(100)的变化规律,金刚石晶粒尺寸减小,晶形变得不完整;弧边位置(100)取向更明显;使用金刚石微粒对衬底进行研磨预处理能显著提高金刚石的形核密度。     

Epitaxial growth of diamond single crystal on surface of milled diamond seeds at high pressure and high temperature

Diamond single crystal was epitaxially grown on the surface of diamond seeds with rough planes at high pressure and high temperature （HPHT） conditions.Fe₈₀Ni₂₀ alloy powder was used as catalyst/solvent and natural flake-like graphite was used as carbon source.Diamond single crystals were grown on the diamond seeds at 4.8 GPa and 1500 K.The morphology of the samples was observed by SEM.The mechanism of diamond growth with smooth planes from original seed with rough planes was studied.      

CVD金刚石膜电火花抛光的机理研究

提出了一种用电火花加工法抛光CVD金刚石膜的新工艺,并对其加工去除机理进行了初步探讨,实验表明,不同的涂覆金属都对蚀除过程产生影响,加工中材料表面的石墨化是金刚石膜得以去除的重要因素。     

A review on polishing technology of large area free-standing CVD diamond films

Recently, with the rapid development of chemical vapor deposition (CVD) technology, large area free-standing CVD diamond films have been produced successfully. However, the coarse grain size on the surface and the non-uniform thickness of unprocessed CVD diamond films make it difficult to meet the application requirement. The current study evaluates several existing polishing methods for CVD diamond films, including mechanical polishing, chemical mechanical polishing and tribochemical polishing technology.      

MPCVD中双基片台结构对单晶金刚石生长的影响

在波导耦合的微波等离子体化学气相沉积制备金刚石的装置中引入双基片台结构,用光谱仪测量等离子体的发射光谱,用Raman光谱仪和SEM分析生长的单晶金刚石的Raman位移和表面形貌,对比研究双基片台结构对等离子体发射光谱和单晶金刚石生长的影响。研究表明:双基片台结构可以提高等离子体的功率密度。在相同的沉积参数下,双基片台结构有利于提高等离子体发射光谱的强度,从而显著提高单晶金刚石的生长速率,最快可达到24 μm/h。生长的单晶金刚石具有金刚石Raman特征峰的偏移度更小,Raman特征峰的半高宽更窄,非金刚石相含量更少的特点。      

新工艺提纯超细金刚石微粉的效果评价研究

通过对人造金刚石微粉进行提纯研究,提出了一种全新的提纯工艺：在强酸介质中利用超声波分散,中温高压的密闭体系中反应。国家发明专利公开号为CN1693188A。借助TG—DSC、XRD和激光拉曼光谱等测试方法对提纯前后的金刚石微粉进行对比分析,结果表明提纯后的超细金刚石微粉热稳定性提高近30℃;XRD图谱上无非金刚石物相衍射峰,提纯前后的晶体粒度根据X射线衍射理论,晶粒粒度变小引起衍射峰宽化,应用Scheer公式进行计算,晶体粒径变化不大;激光拉曼光谱显示石墨几乎被完全除去,并且获得的超细金刚石微粉在1000℃灼烧,不可燃残留物小于0．05％以及最有害成分SiO2的含量小于0．01％．是目前提纯超细金刚石微粉的一种行之有效的方法。     

触媒组织中碳化物的含量与金刚石的生长

采用粉末冶金铁基触媒在六面顶压机上高温高压合成金刚石.试验表明,在相同的工艺条件下,由于合成腔体温度和压力梯度的存在,压块不同断面上的合成效果存在明显差异.使用X射线衍射(XRD)和电子探针分析(EPMA)对不同断面上的触媒物相与成分进行了检测.结果发现,金刚石形核量较多,分布均匀,且晶形完整的触媒中存在大量碳化物;触媒中夹杂有原始石墨,碳化物形成不充分,则金刚石形核量较少.分析认为,触媒中的碳化物应该才是高温高压下金刚石生长的直接碳源.触媒熔体充分溶解石墨,碳化物充分形成对于提高金刚石的产量和质量是必需的.