镀层厚度对镀钛金刚石/铝复合材料热导率的影响

通过在金刚石表面镀钛来改善金刚石和铝基体之间的弱界面结合,并用气压浸渗法制备体积分数为60%的镀钛金刚石/铝复合材料。研究镀钛后金刚石颗粒的物相组成、不同镀层厚度和不同颗粒尺寸下复合材料的热导率;用H-J和DEM模型预测复合材料的热导率,并将预测结果与实验值进行对比。结果表明,镀钛后金刚石颗粒的物相由金刚石、碳化钛和钛三相组成;随着镀层厚度的增加,界面传热系数减小,复合材料的热导率减小;颗粒的尺寸越小,这种变化趋势越明显;相对于H-J模型,DEM模型更能准确地预测镀钛金刚石增强的复合材料的热导率;通过计算得出镀钛金刚石/铝复合材料的临界镀层厚度为1.5μm,当超过此临界镀层厚度时,镀层反而不利于复合材料热导率的提高。     

金刚石表面镀钛及其在胎体中结合状态的研究

采用真空蒸发-扩散镀的方法在金刚石表面镀钛,研究了镀覆温度和保温时间对金刚石表面形貌、镀层厚度、镀层物相的影响规律,分析了镀钛金刚石的抗氧化性能,研究了镀钛金刚石及其在铁基胎体中的结合状态。结果表明:在低温下（680℃）镀覆时,金刚石表面开始出现TiC;随镀覆温度升高或保温时间延长,镀层逐渐致密并增厚,在720℃镀覆时出现Ti沉积,在820℃镀覆时由于应力原因产生裂纹并导致镀层的破坏;镀层可隔绝金刚石与氧的直接接触,大幅度延缓氧对金刚石的侵蚀作用;镀钛后金刚石在胎体中可实现牢固的冶金键合。      

金刚石微粉表面镀覆对线锯的关键作用分析

在分析电镀金刚石线锯工艺流程的基础上,指出了金刚石上砂是电镀线锯最关键的工艺环节.探讨了各种上砂方法及特点,分析了镀覆金刚石微粉对上砂的作用.指出,采用与金刚石形成化合物结合的镀覆金刚石,如镀钛、镀钨、镀钼、镀铬和复合镀的金刚石,有利于高质量金刚石线锯的生产;避免了采用单一镍镀层产生“双极性”效应,导致镍涂层脱落的问题;具有上砂速度快,上砂容易的特点;镍镀层对镀覆金刚石颗粒迅速整体覆盖,镍镀层生长迅速,与镀覆金刚石结合牢固,出刃高;解决了无镀层金刚石以及单一镀镍金刚石与基体结合力差的问题.因此,镀覆金刚石为生产高质量金刚石线锯提供了有力的技术支持.     

复合镀用纳米金刚石悬浮液制备和复合镀铬研究

通过对市售纳米金刚石进行适当的机械化学改性、分散及分级,制得了复合镀用纳米金刚石悬浮液,悬浮液粒度分布在150nm以内,浓度可调,长期保持稳定,不含污染镀液成分;研究了标准镀铬液和添加表面活性剂镀铬液中的复合镀情况,测试了镀层的显微硬度和表面形貌,结果表明,标准镀液中加入纳米金刚石镀层,显微硬度反而降低,添加表面活性剂,镀液中的复合镀层显微硬度有较大提高,晶粒明显细化.     

钎焊镀钛金刚石钻头的研制及其钻进性能分析

分别使用Ni-Cr和Cu-Sn-Ti等2种合金钎料真空钎焊制作镀钛和无镀层金刚石钻头,通过钻进玻化砖试验,研究了4类钻头的钻进性能。试验结果表明:Ni-Cr钎料钎焊制作的镀钛金刚石钻头与无镀层金刚石钻头比较,钻头平均寿命下降了41.7%;Cu-Sn-Ti钎料钎焊制作的镀钛与无镀层金刚石钻头比较,钻头平均寿命相当,但镀钛金刚石钻头的钻孔效率更高,并对其机理进行了分析。      

Cr镀层对金刚石/铝硼硅玻璃复合材料中金刚石氧化反应的抑制研究

为研究在镀铬金刚石/铝硼硅玻璃复合材料中Cr镀层对金刚石氧化反应的抑制作用,将不同镀层厚度的镀铬金刚石和铝硼硅玻璃在相同工艺下烧制成试样,检测试样的体积膨胀率和抗折强度,观察其断面形貌;同时分析烧结后金刚石单颗粒抗压强度和金刚石-结合剂界面的成分。结果表明：Cr镀层具有消耗和隔绝氧元素的双重保护作用,能有效抑制金刚石的氧化。同时,镀层厚度对金刚石氧化反应影响显著：镀层太薄,不能在高温烧结过程中持续保护金刚石;镀层太厚,会由于应力匹配问题产生裂纹或成片剥落,使金刚石暴露在有氧环境中,反而失去保护作用。对于粒度号为140/170的金刚石,最佳镀层厚度为1.58μm。     

热处理对金刚石颗粒表面钛包覆层组织与性能的影响

采用真空蒸发镀方法对金刚石颗粒表面进行镀钛处理,将镀钛金刚石分别在不同温度下进行真空热处理,用扫描电子显微镜、能谱仪和X射线衍射对金刚石颗粒的表面形貌、成分及其物相等进行分析,并采用金刚石单颗粒静压强度测定仪对其进行强度测试。结果表明:金刚石在880℃时开始碳化;钛包覆层只和碳化的金刚石发生界面反应,在880℃热处理温度下TiC先以点状形式析出,随着时间的延长,逐渐长大成雪花状,热处理温度为920℃时,镀层逐渐被氧化成TiO;TiC包覆层能够提高金刚石颗粒的热稳定性和静压强度,相对普通金刚石而言静压强度提高了14%。     

金刚石表面镀钛及界面微结构的研究

本文研究了应用真空微蒸发镀方法实现了金刚石表面镀钛.X-射线衍射分析表明:镀钛层物相为TiC和Ti,反应形成的界面结构层次为:金刚石-TiC-Ti.TiC层一般厚度在几百到上千埃,镀Ti层总厚度大约150 nm-200 nm.根据金刚石、TiC和Ti的晶体结构特点,应用结构对应原则,创建了金刚石/TiC/Ti共格界面模型.金刚石和TiC之间的共格界面为:(111)金刚石∥(111)TiC,C原子的周期性对应关系为:6 ×0.252 nm≈5×0.304 nm,C原子错配率为0.526%;金刚石和TiC界面间的C原子形成垂直的键、偏斜的键和桥式三中心键.六方结构α-Ti的和面心立方的TiC之间的共格界面为:(1000)α-Ti∥(111)TiC,形成垂直键,Ti原子错配率为0.66%.     

镀液成分对低碳钢板镀铬层的形成及其耐蚀性能的影响

镀铬的实质是钢板在含铬酸盐的镀液中通过电解沉积形成镀层。不同成分的镀液具有不同的特性,对镀铬层的性能有重要影响。采用循环伏安法(CV)、计时安培法以及交流阻抗法(EIS)研究了镀液成分对冷轧低碳钢板镀铬层的形成机制的影响,以及镀铬层孔隙率与其电化学性质之间的关系。结果表明:随着镀液中CrO_3含量的减少,基板镀铬层的形成机制由三维沉积转变为二维沉积;在CrO_3的质量浓度为150 g/L的镀液中形成的镀铬层孔隙率为1.05 mg/dm~2,镀层钝化膜电阻为259.2Ω。此外,三维沉积的镀铬层致密度好,耐蚀性优异。     

厚钛过渡层缓解铜基上热丝 CVD 金刚石薄膜内应力

以紫铜为基体,在紫铜上先采用磁控溅射技术镀一层金属钛,再以H2和CH4作为反应气体,采用热丝化学气相沉积法(HFCVD)在钛过渡层上合成金刚石薄膜,研究不同钛过渡层厚度对金刚石薄膜质量的影响。利用X射线(XRD)、激光拉曼光谱(Raman)、扫描电镜(SEM)分析薄膜的结构、成分和表面形貌,用能谱仪(EDS)对热处理前后样品的表面进行了元素分析。研究发现,当钛过渡层厚度为3μm时,生成的金刚石薄膜受到较大内应力而发生破裂;当钛过渡层厚度为25μm时,金刚石薄膜质量较好,薄膜受一定内应力,但没有破裂;850℃左右保温热处理12 h,铜原子与钛原子发生了扩散。     

陶瓷结合剂与金刚石高温下的界面结合机理研究

本文研究了陶瓷结合剂与金刚石的界面反应、界面结构和结合状况.通过对改性Li2O-Al2O3-SiO2微晶玻璃和B2O3-PbO-ZnO-SiO2低熔玻璃镀钛、不镀钛金刚石试样的电镜分析、XRD分析以及两种结合结合剂与镀钛、不镀钛金刚石试样的抗折强度测定,研究了结合剂(Li2O-Al2O3-SiO2微晶玻璃和B2O3-PbO-ZnO-SiO2玻璃)与金刚石(镀钛和不镀钛)的结合机理和结合状况.发现:改性Li2O-Al2O3-SiO2玻璃经过合适的热处理工艺能在金刚石试样中出现以Li2Al2Si3O10为主晶相的微晶体,试条的抗折强度是B2O3-PbO-ZnO-SiO2低熔玻璃金刚石试样的2.5倍以上;镀钛金刚石与微晶玻璃结合剂之间产生化学结合,抗折强度比不镀钛金刚石试条提高20%以上;而对B2O3-PbO-ZnO-SiO2玻璃结合剂而言,金刚石表面镀钛对试条的抗折强度的提高无明显作用.     

Effects of titanium coating on property of diamond

The titanium film was coated on the surface of diamond crystal in order to improve the chemical properties of diamond and the effect of titanium coating on the property of diamond was discussed. The anti-impacting strength, the oxidization process and the soakage property between vitrified bond and diamond were investigated. It is found that, when the titanium film is coated on the surface of diamond crystal, the soakage angle between vitrified bond and diamond decreases from 39.5° to 34.5° at 993 K, and the oxidization degree on the surface of diamonds is lowered greatly.     

The characterization and corrosion resistance of cerium chemical conversion coatings for 304 stainless steel

A golden yellow-colored cerium conversion coating was obtained on 304 stainless steel surface by immersing the steel into a solution containing cerium (III), KMnO₄ and sulfuric acid. The corrosion resistance of the coatings was evaluated by electrochemical methods, potentiodynamic polarization experiments and electrochemical impedance spectrum. The experimental results indicated that the corrosion resistance for the conversion coated 304SS in 3.5% NaCl solution increased markedly. The corrosion potential of the treated steel increased to a more noble level, the pitting corrosion potential increased also, the passive potential range was enlarged markedly and the passive current density decreased about one order compared to that of the untreated steel. The cathodic and anodic reaction were both inhibited to some extent. The chemical state of the elements in the coatings was investigated by XPS. The cerium element was in the form of tetravalent state. And AES depth profile analysis suggested that the thickness of the conversion coatings was less than 66 nm. The mechanisms of coatings formation and corrosion resistance are discussed.     

铁基体等离子体增强磁控溅射离子镀Ti－TiN涂层的组织结构

利用等离子体增强磁控溅射离子镀（ＰＥＭＳＩＰ），先在铁基体上镀一层很薄的钛中间层，继之沉积ＴｉＮ。对膜层进行俄歇电子能谱（ＡＥＳ）分析和透射电镜（ＴＥＭ）分析。结果表明，膜与基体之间有厚约５０ｎｍ的过渡层；膜基界面处有ＦｅＴｉ相；中间层与后继膜交接处Ｔｉ２Ｎ与α－Ｔｉ有取向关系。     

Reactive synthesis Ti （CN） -based metal ceramic coating by electric-spark deposition

Electric-spark deposition (ESD) was adopted for depositing a Ti(CN)-based ceramic coating on the TC4 titanium alloy substrate using a laboratory-developed electric-spark deposition system, a nitrogen-sealed atmosphere and graphite electrode. The surface morphology, microstructure, interfacial behavior between the coatings and substrate, phase and element composition of the coatings were investigated by scanning electron microscope(SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Microhardness profile was measured with a Vickers microhardness tester. The results show that metallurgical bond between the coating and substrate is realized and the phase of coatings are made up of Ti(CN ) spherocrystal and dendritic crystal, TiV and C. Ti(CN) ceramic particles, which is in-situ synthesized by the reaction among titanium from the substrate, carbon from the graphite electrode and nitrogen from the shielding nitrogen gas, is about 600nm and distributes dispersively among the coatings. Microhardness profile falls off with the coatings thickness increasing and the highest microhardness values of the superficial coating could be up to 1496HV, which is six times more than that of the substrate.     

真空微蒸发镀铬金刚石的制备与性能表征

采用真空微蒸发镀覆工艺制备不同镀层厚度的镀铬金刚石,对铬镀层的物相组成和镀层厚度进行分析和表征。结果表明：改变镀覆温度和保温时间,可控制镀铬金刚石的镀层厚度。镀层的物相组成可通过镀覆质量增加来控制：质量增加10%的铬镀金刚石,其镀层只出现Cr₃C₂相;质量增加为20%时,有少量Cr₇C₃出现。从金刚石基体到铬镀层,镀层结构由低Cr比例的碳化物向高Cr比例的碳化物逐渐过渡,即为Cr₃C₂/Cr₇C₃;在金刚石尺寸确定的情况下,使用理论分析镀层厚度与镀覆质量增加的关系,如质量增加10%和65%的金刚石对应的铬镀层厚度分别为0.77μm和4.76μm,此结果与试验观察相吻合。     

Atomic structure studies of chrome alloy coatings and their abrasion resistance

In this study, thin chrome alloy reflective coatings of less than 50 nm are prepared by magnetron co-sputtering chrome and a dopant material onto coated polymeric substrates. This report shows that the lattice parameter of the alloy of chrome and dopant can be used to control the macroscopic abrasion resistance of the coating. These alloy structures are not predicted by thermodynamic equilibrium phase diagrams, illustrating the ability of physical vapour deposition to generate novel coatings. As these coatings are deposited on substrates having a glass transition temperature below 150 °C, the structure after deposition but without post processing is critical because conventional post processing (high temperature annealing) cannot be applied.     

Characterization of Failed Surface of Ti and Imidex (PI) Film for Different Inter-layer Thicknesses of Ti Film

For miniaturized biomedical devices, laser joining of dissimilar materials offers excellent potential to make precise joints. An important system for consideration is titanium (Ti) coated glass joined with biocompatible imidex polyimide (PI). Metallic Ti with various thicknesses was deposited on top of pyrex 7740 borosilicate glass by using DC-magnetron sputtering deposition method. Effect of bond strength between Ti coated glass and imidex polyimide (PI), due to thickness variation of sputtered Ti coating was studied. Three different Ti inter-layer thicknesses were considered, 50, 200, and 400?nm. Tests results indicated that the thinner film produced lower shear strength and higher thickness produced higher shear strength. It has been observed that thicker film (200 and 400?nm) enhanced considerably the bond strength with enhancing the film roughness as well. Higher roughness resulted in more contact area at the interface, results higher number of chemical bonds and increased mechanical interlocking; which in turn increase the laser joint strength. For stronger bond with higher thickness, mixed mode failure was observed which included cohesive failure of polymer, interface failure of Ti/glass and failure on the glass itself. On the other hand, for weak bond with thinner film, mostly interface failure was observed for this system of Ti coated glass/imidex. For thicker film, chemical bond of Ti-C and Ti-O were observed. The role of both surface characteristics and chemical bonding for laser joints were investigated by using advanced techniques such as X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy.     

低压冷喷涂Cu-Zn复合涂层耐蚀性能的研究

本文使用低压冷喷涂技术,分别在45#钢基体与45#钢加镀铬层基体上制备铜锌涂层试样。通过静态浸泡与铜加速醋酸盐雾腐蚀试验（CASS）对涂层和涂层加镀铬层试样的腐蚀性能进行研究;采用SEM、XPS对腐蚀前后涂层与镀铬层的微观形貌与元素进行表征。结果表明：静态腐蚀过程中,铜锌涂层的耐腐蚀性优于铜锌涂层加镀铬层;CASS实验中,随着原始粉体中锌含量的增加,涂层试样与涂层加镀铬层试样的耐腐蚀性能提高,当铜锌比为6:4时,对应涂层试样、涂层加镀铬层试样与纯镀铬层的耐腐性能达到六级。铜锌涂层在腐蚀液中由于电化学腐蚀及氯化作用,导致铜锌均发生了腐蚀,其腐蚀产物主要为Zn(OH)2、Cu2O与CuCl2。铜锌涂层加镀铬层试样在腐蚀过程中,锌的腐蚀在一定成上可以起到减缓镀铬层腐蚀的作用,这种减缓的作用与镀铬层上析出的铜膜共同保护镀铬层,增强其耐腐蚀性能。     

Pack Cementation Coatings for High-Temperature Oxidation Resistance of AISI 304 Stainless Steel

Aluminum and titanium are deposited on the surface of steel by the pack cementation method to improve its hot-corrosion and high-temperature oxidation resistance. In this research, coatings of aluminum and titanium and a two-step coating of aluminum and titanium were applied on an AISI 304 stainless steel substrate. The coating layers were examined by carrying out scanning electron microscopy (SEM) and x-ray diffraction (XRD). The SEM results showed that the aluminized coating consisted of two layers with a thickness of 450???m each, the titanized coating consisted of two layers with a thickness of 100???m each, and the two-step coatings of Al and Ti consisted of three layers with a thickness of 200???m each. The XRD investigation of the coatings showed that the aluminized coating consisted of Al₂O₃, AlCr₂, FeAl, and Fe₃Al phases; the titanized layers contained TiO₂, Ni₃Ti, FeNi, and Fe₂TiO₅ phases; and the two-step coating contained AlNi, Ti₃Al, and FeAl phases. The uncoated and coated specimens were subjected to isothermal oxidation at 1050?°C for 100?h. The oxidation results revealed that the application of a coating layer increased the oxidation resistance of the coated AISI 304 samples as opposed to the uncoated ones.