流态化CVD制备TiO2—Al2O3复合粒子

本文探讨了流态化ＣＶＤ反应器中Ｔｉ（ＯＣ４Ｈ９）４水解制备ＴｉＯ２－Ａｌ２Ｏ３复合粒子新工艺，借助于ＳＥＭ、ＴＥＭ、ＢＥＴ、ＸＲＦ和ＥＰＭＡ等现代测试手段研究了复合粒子结构和包覆过程特征。结果表明，在流态化ＣＶＤ反应器中Ａｌ２Ｏ３超细颗粒以团聚体形式存在，ＴｉＯ２包覆量随Ｔｉ（ＯＣ４Ｈ９）４进料浓度升高而增加，但反应温度影响不大；在包覆过程中，同时存在成核和成膜，成核包覆使复合粒子比表面积增加，成     

流态化CVD制备TiO_2－Al_2O_3复合粒子

本文探讨了流态化ＣＶＤ反应器中Ｔｉ（ＯＣ４Ｈ９）４水解制备ＴｉＯ２－Ａｌ２Ｏ３复合粒子新工艺，借助于ＳＥＭ、ＴＥＭ、ＢＥＴ、ＸＲＦ和ＥＰＭＡ等现代测试手段研究了复合粒子结构和包覆过程特征．结果表明，在流态化ＣＶＤ反应器中Ａｌ２Ｏ３超细颗粒以团聚体形式存在，ＴｉＯ２包覆量随Ｔｉ（ＯＣ４Ｈ９）４进料浓度升高而增加，但反应温度影响不大；在包覆过程中，同时存在成核和成膜，成核包覆使复合粒子比表面积增加，成膜包覆使复合粒子比表面积减小．     

Fe-Ti-C系燃烧合成反应的热力学分析

利用相图计算技术（ＣＡＬＰＨＡＤ）对Ｆｅ－Ｔｉ－Ｃ燃烧合成反应体系进行热力学分析,着重研究Ｆｅ含量和Ｃ／Ｔｉ原子比对体系绝热燃烧温度Ｔ_ａｄ和平衡相组成的影响．研究结果表明,Ｆｅ含量对 Ｆｅ－Ｔｉ－Ｃ三元系的平衡相组成影响不大,但对绝热燃烧温度的影响非常大．当保持Ｃ／Ｔｉ原子比接近１．０时,不管Ｆｅ含量如何变化;在２９８Ｋ下均会得到理想的平衡相组织ＴｉＣ＋Ｆｅ 随Ｆｅ含量增加,体系的绝热燃烧温度大致呈线性降低．Ｆｅ－Ｔｉ－Ｃ体系发生ＳＨＳ反应的热力学条件之一（Ｔ_ａｄ＞１８００Ｋ）是Ｆｅ＜５５ｗｔ％．而 Ｃ／Ｔｉ原子比对绝热燃烧温度的影响比较小,但对平衡相组成影响非常大,主要表现在两个方面：①石墨相的析出温度不同．随Ｃ／Ｔｉ原子比降低,析出温度也随之降低．②在各温区石墨相的含量不同．当 Ｃ／Ｔｉ在１．０～１．４变化时,石墨相含量在低温区由１％提高到１６％．     

Ti-C-Fe体系自蔓延高温合成的反应动力学过程和结构形成过程

采用燃烧波峰铜楔块淬熄法和热分析法,研究Ｔｉ－Ｃ－Ｆｅ体系自蔓延高温合成的反应动力学过程的结构形成过程,在该体系ＳＨＳ过程中,首先形成Ｆｅ,Ｔｉ低共熔体,Ｃ在高温下溶解于熔体之中,进而形成富ＴｉＣｘ。在主波峰后Ｃ继续通过扩散与Ｔｉｃｘ反应形成接近化学计量比的ＴｉＣ。熔融金属的流动导致大团聚体形成,在团聚体内反应形成小颗粒ＴｉＣ在燃烧波过后的持续高温阶段,ＴｉＣ粒子继续长大。     

气相反应法合成超细粉末过程中的r~＊叶和晶型的研究

本文以ＳｉＣｌ４－ＮＨ３、ＳｉＣｌ４－Ｏ２、ＳｉＣｌ４－Ｎ２－Ｈ２、ＴｉＣｌ４－ＮＨ３－Ｈ２、ＴｉＣｌ４－Ｎ２－Ｈ２、ＴｉＣｌ４－Ｏ２、ＡｌＣｌ３－Ｏ２等为体系，运用均匀成核理论，研究了平衡常数Ｋｐ、过饱和比Ｓ及临界核半径，ｒ＊等因素对气相反应法中超细粉末的形成及粉末结构状态的影响．结果表明，当２ｒ＊大于某物质的晶格常数时，用气相反应法得到的该物质的超细粉末一般为晶体粉末，反之则得到无定形粉末．     

丙烯化学气相沉积热解碳的原位动力学

以丙烯为气源,在800℃～1200℃进行化学气相沉积热解碳。研究了温度、压力和滞留时间对沉积速率和气相产物的影响。采用磁悬浮天平原位实时称量反应过程中的固相产物进行动力学研究;采用气相色谱和质谱联用半定量分析了反应过程中的气体产物。动力学研究结果表明, 800℃～1000℃内活化能为137 kJ/mol±25 kJ/mol,沉积过程为化学动力学控制;高于1000℃时,沉积行为由气相分子的传质和气相成核控制。压力和滞留时间对沉积速率的影响说明,热解碳是经过一系列气相反应和固体表面反应后获得。气相产物分析说明,不同控制机制时形成热解碳的主要物质不同。在此基础上提出了丙烯分解形成热解碳的机制。      

气相氧化法制备超细TiO2粒子的研究进展

四氯化钛气相氧化是制备超细二氧化钛（ＴｉＯ２）粒子的重要方法，主要评述ＴｉＣｌ４氧化反应中ＴｉＯ２粒子的形成过程ＴｉＯ２粒子粒径分布的控制模型以及制备条件对为子形态的影响。     

化学气相淀积制备Si3N4超细粉末

本文研究了ＳｉＣｌ４－ＮＨ３－Ｎ２－Ｈ２系统平衡热力学，确定了Ｓｉ３Ｎ４合成的最佳热力学条件。采用电阻炉化学气相淀积法制备了Ｓｉ３Ｎ４超细粉末，并考察了工艺条件对颗粒形貌的影响。     

镍衬底上定向金刚石膜的成核与生长

提出了一种包括晶粒接种、高温退火、成核、生长四过程的薄膜沉积新方法,用射频率等离子体增强热丝化学气相沉积系统,在Ｎｉ衬底上制备了定向金刚石膜。通过对成核和生长两过程工艺条件的研究,掌握了提高成核密度和金刚石定向生长规律,实验还表明,膜与Ｎｉ衬底之间未见Ｎｉ－Ｃ－Ｈ界面层的形成。     

MPCVD合成β—C3N4晶态薄膜

采用微波等离子体化学气相沉积法（ＭＰＣＶＤ），以Ｎ２，ＣＨ４作为反应气体合成碳氢膜。通过控制反应温度，气体流量，微波功率，反应气压等工艺条件在Ｓｉ和Ｐｔ基片上，进行β－Ｃ３Ｎ４晶态薄膜的合成研究。扫描电镜下观察到生长在Ｓｉ基底上的薄膜晶有六角晶棒的密排结构。扫描隧道显微镜下观察到在Ｐｇ基底上生长的碳氮薄膜由针状晶粒组成。     

Interrupted cutting tests of cemented carbide tools coated by physical vapor deposition and chemical vapor deposition techniques

Refractory compound coatings prolong the life of cemented carbide inserts. The structure of these coatings is vastly different when the same coating is produced by chemical vapor deposition (CVD) and physical vapor deposition (PVD) methods. TiC and HfN coatings were applied to cemented carbide tools by both CVD and PVD processes. The coated inserts were tested under interrupted cutting conditions using slotted bar tests. The CVD-coated inserts failed after a few (less than 100) cycles whereas the PVD-coated inserts lasted well past 2000 cycles without failure as did the uncoated inserts. PVD coatings have a much greater fracture toughness than CVD coatings due to their very fine-grained microstructure with a distribution of fine cavities which act as crack stoppers. In contrast, CVD coatings have a fully dense microstructure with a large grain size which does not have much fracture toughness. Another reason for the difference in behavior is the much lower deposition temperature (about 500°C) used in the PVD process as compared with the much higher deposition temperature (about 1000°C) used in the CVD process. Chemical attack of the cemented carbide substrate occurs at high deposition temperatures, thus weakening the area near the coating-substrate interface.     

Raman spectroscopy characterization of diamond films on steel substrates with titanium carbide arc-plated interlayer

Diamond chemical vapour deposition (CVD) on steel represents a difficult task. The major problem is represented by large diffusion of carbon into steel at CVD temperatures. This leads to very low diamond nucleation and degradation of steel microstructure and properties. Recent work [R. Polini, F. Pighetti Mantini, M. Braic, M. Amar, W. Ahmed, H. Taylor, Thin Solid Films 494 (2006) 116] demonstrated that well-adherent diamond films can be grown on high-speed steels by using a TiC interlayer deposited by the PVD-arc technique. The resulting multilayer (TiC/diamond) coating had a rough surface morphology due to the presence of droplets formed at the substrate surface during the reactive evaporation of TiC. In this work, we first present an extensive Raman investigation of 2 μm, 4 μm and 6 μm thick diamond films deposited by hot filament CVD on TiC interlayers obtained by the PVD-arc technique. The stress state of the diamond was dependent on both the films thickness and the spatial position of the coating on the substrate. In fact, on the top of TiC droplets, the stress state of the diamond was much lower than that of diamond in flatter substrate areas. These results showed that diamond films deposited on rough TiC interlayers exhibited a wide distribution of stress values and that very large compressive stress exists in the diamond film grown on flat regions of steel substrates with a TiC interlayer. Diamond films could accommodate stresses as large as 10 GPa without delamination.     

Friction and erosive wear of controlled nucleation thermochemically deposited W-C alloys and SiC and chemically vapor-deposited Si3N4

The controlled nucleation thermochemical deposition (CNTD) process differs from the conventional chemical vapor deposition (CVD) process in that CNTD results in a fine-grained non-columnar deposit with superior mechanical properties. Materials made by this technique include CM 500 (a WC alloy) and CM 4000 (CNTD SiC). These two materials, together with CVD Si₃N₄, were evaluated for their erosion and sliding wear characteristics and the results were compared with those obtained for conventional refractory and ceramic materials. It is shown that the application of a dense CVD or CNTD coating significantly improves the erosion resistance of substrate materials.     

CVD nanocrystalline diamond coatings on Ti alloy: A synchrotron-assisted interfacial investigation

Diamond coating on Ti-6Al-4V alloy was carried out using microwave plasma enhanced CVD with a super high CH₄ concentration, and at a moderate deposition temperature close to 500 °C. The nucleation, growth, adhesion behaviors of the diamond coating and the interfacial structures were investigated using Raman, XRD, SEM/TEM, synchrotron radiation and indentation test. Nanocrystalline diamond coatings have been produced and the nucleation density, nucleation rate and adhesion strength of diamond coatings on Ti alloy substrate are significantly enhanced. An intermediate layer of TiC is formed between the diamond coating and the alloy substrate, while diamond coating debonding occurs both at the diamond-TiC interface and TiC-substrate interface. The simultaneous hydrogenation and carburization also cause complex micro-structural and microhardness changes on the alloy substrates. The low deposition temperature and extremely high methane concentration demonstrate beneficial to enhance coating adhesion strength and reduce substrate damage.     

空心叶片内腔化学气相沉积设备及抗氧化涂层研究

由于高效气冷空心叶片内腔的结构越来越复杂,采用物理气相沉积(PVD)和等离子喷涂(PS)技术不能进行空心叶片内腔冷却通道的涂层防护,化学气相沉积可以进行冷却通道内表面抗氧化涂层的防护.通过CVD涂层设备的研制、涂层沉积工艺、高温涂层性能等研究,对内腔涂层的涂覆机理、工艺方法和内腔涂层的应用进行了讨论.结果表明:研制的CVD设备可靠、工艺参数稳定、内腔表面涂层涂覆达到100%,所研究的化学气相渗铝涂层具有优良的高温抗氧化性能,其在先进航空发动机高效气冷空心叶片内腔表面有很好的工程应用前景.     

Deposition of diamond coating on pure titanium using micro-wave plasma assisted chemical vapor deposition

The nucleation and growth of diamond coatings on pure Ti substrate were investigated using microwave plasma assisted chemical vapor deposition (MW-PACVD) method. The effects of hydrogen plasma, plasma power, gas pressure and gas ratio of CH₄ and H₂ on the microstructure and mechanical properties of the deposited diamond coatings were evaluated. Results indicated that the nucleation and growth of diamond crystals on Ti substrate could be separated into different stages: (1) surface etching by hydrogen plasma and the formation of hydride; (2) competition between the formation of carbide, diffusion of carbon atoms and diamond nucleation; (3) growth of diamond crystals and coatings on TiC layer. During the deposition of diamond coatings, hydrogen diffused into Ti substrate forming titanium hydride and led to a profound microstructure change and a severe loss in impact strength. Results also showed that pre-etching of titanium substrate with hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Plasma power had a significant effect on the surface morphology and the mechanical properties of the deposited diamond coatings. The effects of gas pressure and gas ratio of CH₄ and H₂ on the nucleation, growth and properties of diamond coatings were also studied. A higher ratio of CH₄ during deposition increased the nuclei density of diamond crystals but resulted in a poor and cauliflower coating morphology. A lower ratio of CH₄ in the gas mixture produced a high quality diamond crystals, however, the nuclei density and the growth rate decreased dramatically.     

The CVD of Ceramic Protective Coatings on SiC Monofilaments for Use in Titanium Based Composites

TiB₂, TiC and TiN protective coatings have been deposited onto SiC monofilament fibers by the CVD technique using a cold-wall reactor at reduced pressure. The effect of deposition conditions on the morphology, microstructure, phase composition and adherence of the coatings were studied. The physical and chemical compatibility of these ceramic coatings with SiC filaments together with titanium-alloy matrices were assessed and compared. Dense and uniform TiB₂ coatings have been deposited successfully onto SiC monofilaments. The coating is stable on the SiC fiber and acts as an effective: barrier against the vigorous SiC/Ti-6Al-4V interfacial reaction. The adhesion of TiC on SiC fibers is comparatively weaker than the TiB₂ coating. There was no significant reaction found at the interface of TiC/Ti except at the interface of TiC/SiC. Examination of the TiN coatings showed severe cracking and spalling, hence TiN could not provide protection in a Ti-alloy matrix.     

CVD法与PCVD法TiN薄膜研究

用等离子增强化学气相沉积（ＰＣＶＤ）法和化学气相沉积（ＣＶＤ）法分别制备ＴiV系薄膜。采用扫描电镜、Ｘ射线衍射仪和连续加载压入仪研究分析薄膜的微观结构、相结构和薄膜的力学性能,并采用电极电位法测定了薄膜的耐腐蚀性能,研究表明,PCVD法ＴiN系薄膜的微观组织形态明显优于同类的ＣＶＤ法薄膜,ＰＣＶＤ法薄膜晶粒尺寸细小,均匀,形态圆整,组织致密;ＣＶＤ法薄膜晶粒形态为多边形,尺寸较粗大、不均匀,组织致密性差,ＰＣＶＤ法ＴiN系薄膜的声望生和结合力等力学性能可达或优于同类ＣＶＤ法薄膜,虽然ＰＣＶＤ法薄膜的氯含量（约为２％）远主ＣＶＤ法薄膜（约为０．５％）,但ＰＣＶＤ法薄膜的耐蚀性能却明显优于ＣＶＤ法薄膜,还研究分析了ＰＣＶＤ法和ＣＶＤ法成膜模式对薄膜微观结构和性能的影响机理。     

Growth morphology and phase analysis of titanium-based coating produced by thermochemical method

In the present study, high-speed tool steel was used to coat titanium by pack cementation technique. Coatings show a growth morphology similar to that of the chemical vapor deposition method. Time and temperature of the coating affects its growth morphology. Coating obtained at low temperature (900 °C) yields morphology with growth of tiny particles while coating produced at high temperature (1000 °C) has a morphology with coarser particles. Phase structure of the layers also varies depending on the process time and temperature. Short coating duration yields TiC_0.3N_0.7 phase structure, whose composition is close to TiN whereas long coating duration combined with high temperature yields TiC_0.7N_0.3, whose composition is close to TiC. Mechanical properties such as hardness and resistance to abrasion also reflect changes in phase structures of different types of coating.     

Correlations between gas phase supersaturation,nucleation process and physico-chemical characteristics of silicon carbide deposited from Si-C-H-Cl system on silica substrates

In the CH₃SiCl₃-H₂ CVD system, from which SiC-based films are prepared, the supersaturation of the gas phase increases when temperature and total pressure decreases and when a diffusion-controlled kinetic process is changed in a reaction-controlled one. These conditions variations seem to induce a transition from a growth regime to a nucleation regime, as evidenced by a study of the initial stages of the deposition. A transition from a crystallized film with columnar crystals to a nanocrystalline deposit is also reported on the basis of accurate experiments using TEM and related techniques.