Comparison of α particle detectors based on single-crystal diamond films grown in two types of gas atmospheres by microwave plasma-assisted chemical vapor deposition

Chemical vapor deposition(CVD)-grown diamond films have been developed as irradiation-resistant materials to replace or upgrade current detectors for use in extreme radiation environments. However, their sensitivity in practical applications has been inhibited by space charge stability issues caused by defects and impurities in pure diamond crystal materials. In this study, two high-quality CVD-grown single-crystal diamond(SCD) detectors with low content of nitrogen impurities were fabricated and characterized. The intrinsic properties of the SCD samples were characterized using Raman spectroscopy, stereomicroscopy, and X-ray diffraction with the rocking curve mode, cathode luminescence(CL), and infrared and ultraviolet-visible-near infrared spectroscopies. After packaging the detectors, the dark current and energy resolution under α particle irradiation were investigated. Dark currents of less than 5 pA at 100 V were obtained after annealing the electrodes, which is comparable with the optimal value previously reported. The detector that uses a diamond film with higher nitrogen content showed poor energy resolution, whereas the detector with more dislocations showed poor charge collection efficiency(CCE). This demonstrates that the nitrogen content in diamond has a significant effect on the energy resolution of detectors, while the dislocations in diamond largely contribute to the poor CCE of detectors.

Dispersion of Micro Diamond Particles in Electroless Nickel Solution

The dispersion behavior of micro-diamond particles ranging from 0 to 0.5 micron was compared between in DI water and in electroless nickel solution. The effects of the concentration of electroless solution, temperature, ultrasonic treatment, stirring speed, and baffles on the size distribution of micro diamond particles in electroless nickel solution were studied. Results show that the dispersion of micro diamond particles in DI water is obviously superior to that in electroless nickel solution. Micro diamond particles agglomerate evidently when the concentration of electroless solution Velect：VDI in dispersion media exceeds 5%0. Diamond particles agglomerate more and more seriously with the increase of the ion concentration. Applying ultrasonic, increasing stirring speed and adding baffles are helpful to improving the dispersion of diamond particles in the electroless nickel solution and its uniform distribution in the Ni-P coating.

Photoluminescence of SiV centers in CVD diamond particles with specific crystallographic planes

We prepared the isolated micrometer-sized diamond particles without seeding on the substrate in hot filament chemical vapor deposition. The diamond particles with specific crystallographic planes and strong silicon-vacancy(SiV) photoluminescence(PL) have been prepared by adjusting the growth pressure. As the growth pressure increases from 2.5 to 3.5 kPa,the diamond particles transit from composite planes of {100} and {111} to only smooth {111} planes. The {111}-faceted diamond particles present better crystal quality and stronger normalized intensity of SiV PL with a narrower bandwidth of 5 nm. Raman depth profiles show that the SiV centers are more likely to be formed on the near-surface areas of the diamond particles, which have poorer crystal quality and greater lattice stress than the inner areas. Complex lattice stress environment in the near-surface areas broadens the bandwidth of SiV PL peak. These results provide a feasible method to prepare diamond particles with specific crystallographic planes and stronger SiV PL.

Diamond Particles Deposited among Nickel/Copper Particles in Energy Controlled CH₄/H₂RF Discharge Plasmas

Formation of diamond particles was investigated in an energy-controlled CH4/H2 radio-frequency (RF) discharge plasma. Here, in particular, it was examined how diamond particles grew on a nickel substrate under an influence of Cu vapor that was supplied from a heated Cu wire. Here, the plasma was generated by a hollow-magnetron-type (HMT) RF plasma source at the frequency of 13.56 MHz. Total pressure was kept at 100 mTorr. Diamond particles grew besides Ni and Cu particles. From Raman spectrum the substrate surface was covered with thin graphite film deposited as a background layer. It was shown that diamond could grow in a self-organized manner even when the other atomic gas species such as Ni and Cu were contained in the gas at the same time during the growth process.

Effects of microwave oxygen plasma treatments on microstructure and Ge-V photoluminescent properties of diamond particles

The microstructure and Ge-V photoluminescent properties of diamond particles treated by microwave oxygen plasma are investigated.The results show that in the first 5 min of microwave plasma treatment,graphite and disordered carbon on the surface of the particles are etched away,so that diamond with regular crystal plane,smaller lattice stress,and better crystal quality is exposed,producing a Ge-V photoluminescence(PL)intensity 4 times stronger and PL peak FWHM(full width at half maximum)value of 6.6 nm smaller than the as-deposited sample.It is observed that the cycles of‘diamond is converted into graphite and disordered carbon,then the graphite and disordered carbon are etched’can occur with the treatment time further increasing.During these cycles,the particle surface alternately appears smooth and rough,corresponding to the strengthening and weakening of Ge-V PL intensity,respectively,while the PL intensity is always stronger than that of the as-deposited sample.The results suggest that not only graphite but also disordered carbon weakens the Ge-V PL intensity.Our study provides a feasible way of enhancing the Ge-V PL properties and effectively controlling the surface morphology of diamond particle.

金刚石粒径对金刚石/Cu-B合金复合材料热物理性能的影响

采用Cu-B合金为基体,选用粒径分别为110、230、550μm的金刚石颗粒作为增强体,利用气压熔渗工艺在1100℃、10 MPa气体压力下制备金刚石/Cu-B合金复合材料,研究金刚石颗粒粒径对复合材料组织结构、界面相分布及热物理性能的影响。结果表明,随着金刚石粒径的增大,复合材料热导率上升,热膨胀系数减小,复合材料界面处硼碳化合物含量增加,界面结合情况得到改善。由金刚石颗粒粒径为550μm时,复合材料热导率最高,可达680.3 W/(m·K),热膨胀系数最小,为4.905×10^(−6)K^(−1),符合高效热管理器件对金刚石/金属基复合材料的热物理性能要求,在电子产品散热器件方面具有良好的应用前景。

激光粉末床熔融成形金刚石增强铝基复合材料

添加质量分数3%金刚石颗粒并利用激光粉末床熔融技术制备6061铝基复合材料。采用光学显微镜、扫描电子显微镜、X射线衍射仪、电子密度计、电子式万能试验机对3%金刚石/6061铝基复合材料的微观组织、相对密度和拉伸性能进行了表征与分析。结果表明:金刚石与Al基体反应生成了针状Al4C3相,并沉积在α-Al基体上,导致晶界位错密度增加,强度提高,抗失效能力增强。金刚石的添加促使6061铝基体中热裂纹消失,但存在孔洞缺陷。较低的扫描速度增加了激光光斑与被加工材料接触的时间,导致金刚石颗粒部分石墨化,铝基体部分蒸发,进而形成内部缺陷,降低了复合材料的相对密度(97%)。金刚石的加入显著提高了激光粉末床熔融技术成形金刚石/6061铝基复合材料的抗拉强度,当激光功率为350 W、扫描速度为800 mm·s-1时,复合材料的极限抗拉强度达到最大值244.2 MPa,屈服强度211.6 MPa,伸长率2.1%。

Ti基镶嵌金刚石颗粒掺硼金刚石电极及其性能

利用粉末压片机在Ti片表面镶嵌金刚石颗粒,以此为衬底,通过热丝化学气相沉积技术沉积掺硼金刚石(boron-doped diamond, BDD)薄膜,制备新型Ti基镶嵌金刚石颗粒BDD (Ti/D/BDD)电极,并制备Ti基BDD (Ti/BDD)电极作为对比。采用扫描电子显微镜、拉曼光谱仪和电化学工作站表征电极的形貌、B掺杂水平和电化学性能,利用紫外可见分光光度计测试电极模拟废水降解的效果。结果表明:沉积时间相同时,Ti/D/BDD电极比Ti/BDD电极具有更大的电化学活性面积,更低的薄膜阻抗,使得电极对酸性橙G表现出更高的降解速率,更低的降解能耗。沉积10 h时,Ti/D/BDD电极具有最高的双电层电容(1.87 mF),最低的薄膜电阻(0.4?);降解120 min后,Ti/D/BDD电极的色度移除率比Ti/BDD电极最高可提升53.1%,同时能耗降低14.2%。

一种树脂金刚石复合材料的分子动力学模拟

本文研究一种用于制备微细砂轮的树脂金刚石复合材料,该复合材料由丙烯腈-丁二烯-苯乙烯(ABS)作为基体,聚氯乙烯(PVC)作为混料,邻苯二甲酸二辛酯(DOP)作为加工助剂,与金刚石磨粒混合而成。对5种不同配比的共混体系进行分子动力学模拟,结果显示:提高ABS的质量比,复合材料分子间作用力逐渐增强,密度逐渐降低,延展性和柔性先减小后增加,ABS和PVC的相容性先减小后增加,复合材料最佳配比为62.5wt%ABS、18.6wt%PVC、8.3wt%DOP和10.6wt%金刚石磨粒。

钨粉粒径对金刚石扩散镀钨影响的研究

金刚石镀钨能够改善铜与金刚石的润湿性,有助于合成金刚石/铜复合材料。采用扩散烧结法对金刚石表面进行处理,研究钨粉粒径对镀层的影响。并对试验机理及规模化生产的可行性进行了论述。试验结果表明:钨粉粒径过小或过大时均镀覆失败,其最佳镀覆粒径为金刚石粒径的1/3~2/3;金刚石烧结量对镀层影响关系很小,真空扩散镀钨烧结法适用于工业批量生产。

Effect of sintering parameters on the microstructure and thermal conductivity of diamond/Cu composites prepared by high pressure and high temperature infiltration

Pure Cu composites reinforced with diamond particles were fabricated by a high pressure and high temperature （HPHT） infiltration technique. Their microstructural evolution and thermal conductivity were presented as a function of sintering parameters （temperature, pressure, and time）. The improvement in interfacial bonding strength and the maximum thermM conductivity of 750 W/（m.K） were achieved at the optimal sintering parameters of 1200℃, 6 GPa and 10 min. It is found that the thermal conductivity of the composites depends strongly on sintering pressure. When the sintering pressure is above 6 GPa, the diamond skeleton is detected, which greatly contributes to the excellent thermal conductivity.

Study of the morphology and properties of diamond joints brazed with carbide-reinforced Cu-Sn-Ti filler metal

Cu-Sn-Ti brazing filler is a new type of copper-based brazing filler for brazing diamond tools currently used in industry,but it suffers from poor wear resistance,high brazing temperature and low bond strength.This paper provides a way to improve the strength of dia-mond-brazed joints by adding zirconium carbide and tungsten carbide reinforcing phase particles to the Cu-Sn-Ti alloy,respectively.Dia-mond particles were attached to Q460 steel using Cu-Sn-Ti composite filler with the addition of the reinforcing phase,and experimental in-struments such as scanning electron microscope,X-ray diffractometer and energy spectrometer were used to investigate the brazed joint per-formance of the composite brazing material for brazing diamond.The results show that the addition of enhanced phase particles resulted in a metallurgical reaction at the joint of the composite brazed diamond,achieving a higher strength joint with no obvious cracks at the interface,while the addition of 15 wt.%WC resulted in excellent wear resistance and the highest hardness at the joint interface.

Cr/Al/B/diamond体系中金刚石表面的热爆反应涂层

采用Cr/Al/B/diamond粉体为原料,并添加少量Cr2O3或B2O3以诱发热爆反应。结果表明:在高纯Ar保护下,热爆反应后的试样粉末化严重,易将结合剂与金刚石颗粒分离。添加Cr2O3的原料体系发生热爆反应后,结合剂中的主相为Cr2AlB2,金刚石表面会形成含Cr3C2和Al的复合涂层,涂层的晶粒大小为0.5~7.0μm。当金刚石质量分数为10%和20%时,试样中的金刚石颗粒表面涂覆良好,其起始和终止氧化温度都显著高于未涂覆金刚石的;而在金刚石质量分数较高时,其表面涂覆效果略差。添加B2O3的原料体系发生热爆反应后,金刚石表面的涂覆效果不佳,只有半数或以下数量的金刚石颗粒被涂覆。

ELECTROLESS PLATING COMPOSITE COATINGS OF Ni-Ti-Re ON THE SURFACE OF DIAMOND

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基于SPH方法的钢筋混凝土切削模拟研究

钢筋混凝土材料目前已得到广泛应用,但其加工切削过程十分复杂。为解决常规有限元模拟中网格变形尺寸有限的局限性,采用光滑粒子流体动力学(SPH)算法模拟研究金刚石磨粒对钢筋混凝土的切削破碎过程。在数值模拟中,根据金刚石出刃状态将其简化成方形、圆形2种磨粒,并以0.45 mm/ms的速度和0.1 mm的切削深度对钢筋、混凝土和不同组合的钢筋混凝土材料进行表面切削,分析不同情况下的基体碎屑形态特征、切削后基体材料表面形态变化、内部裂纹延伸变化以及磨粒切削面上的应力变化情况。模拟结果表明:SPH方法能够较好地模拟钢筋混凝土在切削过程中的裂纹扩展、碎屑形成和分离;磨粒在切削过程中受到间断性冲击后,会优先破坏混凝土和钢筋材料之间的连接强度,使2种材料逐渐分离,且磨粒以面切削方式进行加工时,相较于点切削方式,能够形成更大的破碎区域。

合成聚晶金刚石过程的颗粒冷压破碎

为提升聚晶金刚石的致密度,研究在初装、冷等静压后以及六面顶压机内等不同压力条件下,不同金刚石粉体粒径和配比在加压前后的粉体密度、粒径分布及重排微观结构变化,发现金刚石粉体的变化规律。合成过程包括初装料的无序排列到220 MPa等静压后的细颗粒填充孔隙与重排,再到超高压力下大颗粒被挤压破碎,孔隙被逐步填充。由于细颗粒的缓冲效应,大颗粒G_(20~30)在双粒径配方G_(2~4)和G_(20~30)中比在单一粒径G_(20~30)配方中破碎更少,更有利于提升金刚石粉体堆积密度。

超高速下单粒金刚石与岩石相互作用响应的研究

随着钻进深度的加深,破碎硬岩地层愈发困难,提高转速成为硬岩地层快速有效破碎的可行方法之一。孕镶金刚石钻头在硬岩层中具有较好的应用效果,常规转速下孕镶钻头与岩石之间相互作用机理较为完善,超高转速下也有相应的应用和研究基础,但碎岩机理尚未完全清晰。为探究常规速度至超高速下单粒金刚石对岩石的切削力和硬岩的破碎变化情况,以孕镶钻头和岩石相互作用界面响应模型为基础,利用ABAQUS软件建立单粒金刚石切削岩石的二维模型,并提出一种近似分析方法,并进一步推导单粒金刚石受力表达式。结果表明:(1)单粒金刚石对岩石的切削作用主要集中在切削具与岩石接触界面的中上部,高速下比常规切削速度下单粒金刚石受切削力减小,且主要作用部位受到切削速度改变的影响。(2)金刚石颗粒作用岩石中存在塑性破坏和脆性破坏且两种破坏模式交替产生,超高速下岩石产生脆性破坏的比例相比于常规切削速度有所增加,且超高速下切削力波动范围更小,岩石破碎所需的能量更少。(3)提出一种孕镶金刚石钻头碎岩响应近似分析方法,将产生碎岩作用的金刚石颗粒等价为具有“刀尖”和“前、后刀面”的切削具进行分析,推导得到单粒金刚石受力表达式,其受力与切削速度、切削深度等因素有关。研究结果可以为提高转速切削硬岩地层的进一步研究及应用提供依据和参考。

不同湿度环境下镀钛金刚石烧结聚晶金刚石的摩擦学性能

聚晶金刚石(Polycrystalline diamond,PCD)机具在钻探破岩与切削过程中服役于边界润滑环境,湿度条件是影响其摩擦磨损性能及切削钻进效率的重要因素。采用磁控溅射技术在金刚石微粉表面沉积厚度为~500 nm的钛薄膜,并选用镀钛金刚石微粉为原料烧结聚晶金刚石(Ti-polycrystalline diamond,Ti-PCD)。研究了Ti-PCD在5%~50%相对湿度(Relative humidity,RH)条件下对磨氮化硅的摩擦磨损性能,利用SEM、XRD、AES等表征镀钛金刚石微粉和Ti-PCD的微观组织、表面形貌及相结构。采用光学显微镜、白光三维形貌仪、拉曼光谱仪分析Ti-PCD和氮化硅球的磨损形貌。结果表明,Ti-PCD中金刚石晶粒与粘结剂钴界面处形成碳化钛过渡层。在相对湿度为5%~50%RH条件下,氮化硅磨斑处的碳质转移膜是影响Ti-PCD稳态摩擦因数的主要原因。5%RH干燥环境下,摩擦滑移过程中碳原子重杂化过程形成连续均匀的碳质转移膜,获得超低的稳态摩擦因数0.034。Ti-PCD表面相对较疏水,水分子钝化作用减弱,有助于形成具有减摩作用的碳质转移膜,致使湿度环境下的稳态摩擦因数比传统PCD降低~30%。Ti-PCD磨损在5%~50%RH湿度范围内逐渐减轻。Ti-PCD中的碳化钛相发挥结合桥作用,利用界面效应强化粘结剂钴和金刚石的界面结合,抑制摩擦滑移过程中的金刚石颗粒剥落,提高Ti-PCD的耐磨性。应用金刚石微粉表面涂层技术制备减摩Ti-PCD,从界面结合和补强增韧方面强化金刚石与粘结剂钴的界面状态,对设计制造高效长寿钻探机具有重要的研究意义。

多片式衬底HFCVD系统沉积金刚石颗粒物理场的仿真优化

探索热丝化学气相沉积(hot filament chemical vapor deposition,HFCVD)合成高效优质的金刚石已成为研究热点。采用可提高金刚石颗粒单次沉积产量的新型多片式栅状衬底,应用FLUENT流体仿真软件,在原有单个出气口数量及进气总流量保持不变的情况下,优化传统模型,将单个进气口拆分成5个大小相等的进气口,对影响金刚石单晶颗粒均匀性的进气口数量和排布方式工艺参数进行仿真,对比分析HFCVD系统内气体的物理场。结果显示:4组优化模型均提高了衬底温度及流速的均匀性,有利于金刚石单晶颗粒的均匀生长,但对其沉积速率影响不显著;进一步分析优化模型的温度场,发现5个进气口及单个出气口分别位于反应腔体顶部和底部的中间位置时系统的温度差最低,最满足金刚石单晶颗粒在多片式硅衬底上均匀生长的条件。HFCVD金刚石单晶颗粒沉积试验验证了仿真结果的正确性。