热等静压在金属陶瓷制备中的应用研究进展

金属陶瓷复合材料是一种新兴的高性能材料。由于现有制造工艺等因素的制约,大大限制了其应用前景。热等静压技术的引入,使制造优良性能的金属陶瓷找到了新的突破口。经过热等静压制备金属陶瓷,可以大大提高金属陶瓷的密度、硬度、屈服强度、抗弯强度等性能,并解决了制备形状复杂的工件问题,减小了对于制品的机械加工。本文详细介绍了HIP技术在金属陶瓷制备中的应用情况,并就HIP工艺的技术关键及注意事项等问题作了简要的分析和总结。     

碳化硅陶瓷的热等静压烧结

系统地研究了不同添加剂（如Ａｌ２Ｏ３，ＡｌＮ和Ｂ４Ｃ等）在热等静压（ＨＩＰ）烧结条件下对ＳｉＣ陶瓷之致密机理，显微结构以及力学性能的影响，结果表明：在ＨＩＰ烧结过程中，Ａｌ２Ｏ３可以与ＳｉＣ颗粒表面的ＳｉＯ２生成低共熔的铝硅酸盐玻璃相，并有效地促进ＳｉＣ陶瓷的致密化，当添加３％（以质量计）Ａｌ２Ｏ３时，采用ＨＩＰ烧结工艺，在１８５０℃温度和２００ＭＰａ压力下降结１ｈ，就可获得相对密度和抗弯强度分别     

碳化硅陶瓷及其复合材料的热等静压氮化

通过对ＳｉＣ陶瓷，ＳｉＣ－ＴｉＣ复相陶瓷以及ＳｉＣ晶须补强ＳｉＣ基复合材料在氮气氛中进行高温的氮化处理，成功地实现了这些材料的开口气孔与表面裂纹的愈合。有关研究表明：热等静压氮化工艺可以显著提高ＳｉＣ陶瓷及其复合材料的抗强度，对断裂韧性也有较大的改善作用。     

热等静压（HIP）处理对Ba2Ti9O20陶瓷材料的作用

一、引言钛酸钡陶瓷材料具有优异的电学性能,在电子工业中被广泛应用。因其与铁氧体材料有较好的匹配性,可加工性而用作高密度磁盘机磁头的浮动块材料。制备Ba_2Ti_9O_(20)陶瓷材料过程中我们发现烧结材料内部总是残留有3-4%的气孔,影响材料的性能和使用。     

热等静压强化金刚石钻头性能研究

为提高热压孕镶金刚石钻头力学性能和耐磨性,使之更好地适用于强力规程钻探现场,提出常规热压+热等静压相结合的金刚石钻头制造方法。以2个优选的预合金体系钻头胎体配方为基础,分别采用常规热压、常规热压+热等静压的方式试制钻头胎体和孕镶金刚石钻头进行室内测试和现场试验对比分析。室内测试表明,相较于常规热压烧结方式,采用常规热压+热等静压烧结后,钻头胎体的硬度平均提高2.0 HRC,磨损量平均下降2.3 mg,相对密度达到98.7%和99.1%。现场试验结果表明,引入热等静压烧结之后,相同配方热压金刚石钻头其机械钻速相差不大,但耐磨性明显提高,使用寿命平均提高50.42%。     

热等静压技术在特种陶瓷制备中的应用

引言 特种陶瓷包括结构陶瓷和功能陶瓷。由于特种陶瓷所用原料大部分为共价键原料,使得烧结时的扩散速度相当低,故烧结性很差。若选用无压烧结,要获得致密的烧结体,不得不加入添加剂,而添加剂的加入,或多或少地影响材料的各种性能。若选用热压烧结,虽然可以得到致密的烧结体,但制品的形状和尺寸要受到限制。又因为热压烧结是采用单向加压,烧     

热等静压机循环水系统优化升级与实践

热等静压机在制造过程中处于高温、高压环境,循环冷却系统的稳定运行是根本保障,而实际制造过程中循环冷却系统出现的问题较多。本文介绍了某企业热等静压机的循环水冷却系统,对存在的冷却效果差、能耗高、维护不便等问题进行了分析并提出改进方案,改造后效果明显。     

热等静压技术在透明陶瓷研究中的应用进展

透明陶瓷具有与单晶材料相媲美的光学、力学和热学等性能,被广泛应用在透明装甲、红外窗口、高功率激光器、白光照明、医学诊疗等民用和军事领域。影响透明陶瓷光学透过率的主要因素是气孔,而热等静压（HIP）后处理是消除气孔,获得高质量透明陶瓷的有效办法之一。本文综述了近期利用热等静压技术研究透明陶瓷取得的成果和提出的一些机理,进而对热等静压技术开发透明陶瓷进行了讨论和展望。     

热等静压处理对IN792材料组织和持久性能的影响

本文研究了热等静压处理对IN792材料组织和持久性能的影响.结果表明,IN792材料经1180℃/150 MPa热等静压处理后显微疏松完全闭合.与直接热处理样品相比,热等静压处理后样品中的共晶含量减少;枝晶干处y’相的体积分数和尺寸增大,分别由34％,0.4 μm增大至42％,0.56μ.760℃/655 MPa和870℃/365 MPa条件下持久性能测试表明,热等静压处理均显著提高了材料的持久寿命.     

Rapid Formation of Zinc Oxide Films by an Atmospheric-Pressure Chemical Vapor Deposition Method

Zinc oxide films were prepared by an atmospheric-pressure chemical vapor deposition method using (acetylacetonato)-zinc as a source material. Transparent and uniform ZnO films of considerable area (20 × 70 mm, ∼0.3 μm thick) could be obtained easily on a crown glass (CGW #200) with a high deposition rate. The deposition rate first remained constant with increasing substrate temperature ( T _s), then increased abruptly from 120 nm/min at T _s= 550°C to 220 nm/min at T _s= 600°C, and finally stopped increasing above T _s= 600°C. The maximum preferred orientation and best crystallinity of the films were obtained at T _s= 550°C.     

Preparation of Zinc Titanate Thin Films by Low-Pressure Metalorganic Chemical Vapor Deposition

Homogeneous thin films of zinc titanate have been successfully prepared on Si(100) wafers by depositing a film of zinc and titanium oxides (ZnO-TiO₂) by low-pressure metalorganic chemical vapor deposition (MOCVD), followed by an annealing treatment. The precursors used for the deposition were diethylzinc (DEZ), tetraisopropoxide titanium (TPT), and water. By performing the deposition at temperatures between 140 and 350C, the stoichiometry of the as-deposited films could be effectively controlled over Zn/Ti ratios between 0.5 and 2.5, which cover the composition of various zinc titanate phases identified in the literature. The as-deposited ZnO-TiO₂ films are amorphous, and possess a fairly smooth surface. XPS and SIMS analysis showed that the composition of these films is uniform over the wafer as well as through the films bulk. An annealing treatment of the as-deposited films at high temperature     

化学气相沉积法合成纳米碳管阵列研究

研究以环己烷为前驱体采用化学气相沉积法制备纳米碳管阵列。将催化剂二茂铁定量溶解在环己烷中，通过载气夹带进入反应器中，采用化学气相沉积方法定向生长出炭纳米管阵列，此法有效地控制反应体系中的催化剂含量，使生产稳定性及重现性较好。并通过透射电子显微镜、扫描电子显微镜、拉曼光谱及X射线衍射对产品形态和结构进行分析和表征，所制备出的纳米碳管阵列形态比较规整，纯度较高，具有较好的石墨微晶结构；并对纳米碳管的生长机理进行了详细讨论。     

Influence of Isothermal Chemical Vapor Deposition and Chemical Vapor Infiltration Conditions on the Deposition Kinetics and Structure of Boron Nitride

An experimental study has been performed to gain some insight into the correlations between the deposition conditions and the structure of boron nitride (BN) coatings that are used in ceramic-matrix composites. BN has been deposited at 700°C from BCl₃-NH₃-H₂ mixtures on various substrates, by using chemical vapor deposition (CVD) and isothermal-isobaric chemical vapor infiltration (ICVI) processes, simultaneously in the same reactor. A kinetic study has shown that the CVD process is governed either by a combination of mass transfer with chemical kinetics at low flow rates or by the heterogeneous kinetics only at high flow velocities. In contrast, the limiting contribution of mass transfer always is observed for the ICVI process. The influence of diffusion cages that are positioned around the fibrous preforms is reported. The structure of BN deposits has been studied as a function of the various deposition conditions via transmission electron microscopy. The chosen CVD conditions lead to a poor organization of the BN deposits. Fairly well-organized BN coatings are deposited on all fibers of a fibrous preform via ICVI. The results are discussed in terms of supersaturation and deposition yields. The use of diffusion cages and the adjustment of the inlet composition and mass flow rate seem to be very important to obtain the best BN organization and thickness uniformity.     

Particle-Precipitation-Aided Chemical Vapor Deposition of Titanium Nitride

Particle-precipitation-aided chemical vapor deposition (PP-CVD) is a modification of the conventional CVD process, where an aerosol is formed in the gas phase and particles are deposited on a substrate. The driving force for particle deposition is thermophoresis. The synthesis of titanium nitride (TiN) has been studied. TiN is formed on the substrate, as well as in the gas phase. At low temperature differences, only dense microstructures with equiaxed grains are observed; porous coherent layers are found in experiments where larger temperature differences are applied. Additional increase in the temperature difference only leads to loose powder deposits. In principle, the PP-CVD process is a suitable method for the synthesis of thin porous layers of ceramics.     

Chemical Vapor Deposition in the Boron-Carbon-Nitrogen System

The preparation of a two-phase coating of B₄C-BN was addressed as a potential wear coating because of its likelihood of having a high fracture toughness resulting from its composite nature and inherent lubrication due to the presence of BN. Equilibrium analysis identified appropriate deposition conditions; however, deposited coatings were found to be single-phase BN with a high degree of substitution of carbon for nitrogen.     

Deposition Mechanism for Chemical Vapor Deposition of Zirconium Carbide Coatings

Zirconium carbide (ZrC) coatings were fabricated by chemical vapor deposition (CVD) using ZrCl₄, CH₄/C₃H₆, and H₂ as precursors. Both thermodynamic calculation results and the film compositions at different temperatures indicated that zirconium and carbon deposited separately during the CVD process. The ZrC deposition rates were measured for CH₄ or C₃H₆ as carbon sources at different temperatures based on coating thickness. The activation energies for ZrC deposition demonstrated that the CVD ZrC process is controlled by the carbon deposition. This is also proven by the morphologies of ZrC coatings.     

Chemical Vapor Deposition for Silicon Cladding on Advanced Ceramics

Polycrystalline Si was used to clad several advanced ceramic materials such as SiC, Si₃N₄, sapphire, Al₂O₃, pyrolytic BN, and Si by a chemical vapor deposition (CVD) process. The thickness of Si cladding ranged from 0.025 to 3.0 mm. CVD Si adhered quite well to all the above materials except Al₂O₃, where the Si cladding was highly stressed and cracked or delaminated. A detailed material characterization of Si-clad SiC samples showed that Si adherence to SiC does not depend much on the substrate surface preparation; that the thermal cycling and polishing of the samples do not cause delamination; and that, in four-point bend tests, the Si–SiC bond remains intact, with the failure occurring in the Si.     

Low-Temperature Metal-Organic Chemical Vapor Deposition of Silicon Nitride

Amorphous silicon nitride films have been deposited on single-crystal silicon from the gas mixture of methylsilazane and ammonia at 873 to 1073 K. The films have been characterized by ellipsometry, Fourier transform infrared spectroscopy, and Auger electron spectroscopy. The Si-C, Si-H, and C-H bonds in methylsilazane can be effectively cleaved and the associated C and H species removed. The structure and composition of the films do not show any apparent dependence on the deposition temperature.     

Microstructure of SiC Prepared by Chemical Vapor Deposition

Silicon carbide prepared by chemical vapor deposition at a substrate temperature of ∼1400425-429°C was investigated. Optical microscopy showed that the growth characteristic is dendritic; the deposits consist of columnar blocks within each of which the orientation of crystals is approximately the same. Small pores occur along the boundaries of these blocks. Transmission electron microscopy revealed finer details of the growth characteristics. The crystals were mostly 3 C in structure, but crystals with 2H and one-dimensionally-disordered structures were also found. The 3 C crystals are mostly dendritic, but some columnar growth with alternating twin bands occurs. Both 2 H and one-dimensionallydisordered crystals exhibit a columnar habit, reflecting the difference in crystal symmetry from 3 C . In all these crystals, the c axis (or one of the <111> axes in 3 C crystals) lies perpendicular to the substrate.