SiC窑具材料抗氧化涂层的研究和应用

针对ＳｉＣ窑具材料易在１４００℃左右氧化的弱点,研制了既能在半成品上,又能成品上喷涂的ＳｉＣ窑具抗化涂料,并通过试验表明,使用该涂料的制品烧后不剥落,无粘瓷现象,表面色白光滑,涂层的抗氧化效果明显。     

Si2N4结合SiC窑具材料抗氧化涂层的研究

本文针对Ｓｉ２Ｎ４结合ＳｉＣ窑具材料在９００－１１００℃易氧化的特点，研制了该材料的抗氧化涂层，并用试验验证了涂层的抗氧化性能。结果表明：抗氧化涂层的抗氧化效果十分显著，具有很好的推广价值。     

碳化硅基材表面涂层方法综述

碳化硅基陶瓷是应用于高温工作环境下的理想材料，但其高温氧化影响了它的进一步应用。本文简要叙述了碳化硅材料的氧化机理，重点总结了在其表面涂层的各种方法。同时也对目前所做工作的不足提出了见解。     

碳化硅—石墨陶瓷涂层热辐射性能的研究

阐述了以碳化硅—石墨为基料的高辐射陶瓷涂层的性能及应用效果。这种材料具有高辐射率、高粘结强度、抗热震性能好等特点,是一种高效节能的陶瓷新材料。     

碳纤维涂层碳化硅高温抗氧化性能研究

碳纤维材料以其良好的性能,在树脂基、陶瓷基、金属基等复合材料中得到了广泛的应用,但高温下容易被氧化,并严重的限制了碳纤维的应用范围。本文利用扫描电镜、透射电镜、电子探针、X射线光电子能谱分析、热重分析等对涂层碳纤维进行了高温(800℃)抗氧化性研究,得到了涂层的成分为SiC,通过可控气氛炉得到涂层碳纤维800℃高温下失重率与时间呈现抛物线规律变化,同时与无涂层碳纤维的氧化失重曲线相比发现：此涂层碳纤维在高温下具有一定的抗氧化性。     

在碳化硅陶瓷上用等离子喷涂莫来石涂层的新方法

莫来石作为一种用于高温工作环境的硅质陶瓷保护层的材料是大有前途的，在碳化硅上用传统等离子喷涂莫来石涂层，在受热循环时，易于产生裂纹和剥落。实验证实这是由于传统喷涂的莫来石中存在有非晶质莫来石所致。高温的碳化硅基质陶瓷在用新的等离子喷涂法喷涂莫来石涂层时，可消除产生的非晶质相，因此可以显著地改善涂层的性能。用此法喷涂的莫来石涂层，在从室温到１０００℃￣１４００℃的高温循环条件下，显示出优良的耐着性能     

钛合金表面抗氧化玻璃-陶瓷涂层研究进展

抗氧化性差是影响钛合金在航空航天领域广泛应用的重要因素,提高抗氧化性成为钛合金研究的一个主要方向。玻璃-陶瓷涂层具有较宽的软化温度范围、良好的化学稳定性、高的机械强度,可作为钛合金高温抗氧化涂层。总结了钛合金表面抗氧化涂层材料的性能要求及玻璃-陶瓷抗氧化涂层材料的优缺点,综述了国内外钛合金表面抗氧化玻璃-陶瓷涂层的研究进展;展望了钛合金表面抗氧化玻璃-陶瓷涂层的发展方向。     

碳纤维增强碳复合材料高温抗氧化硅基陶瓷涂层的研究进展(英文)

碳纤维增强碳(carbon fiber reinforced carbon,C/C)复合材料抗氧化问题一直是国际材料界研究的热点。硅基陶瓷作为C/C复合材料抗氧化涂层,是目前研究最深入的涂层体系。综述了国内外近几年C/C复合材料高温抗氧化硅基陶瓷涂层的研究进展,总结了C/C复合材料高温抗氧化硅基陶瓷涂层的制备工艺和对已有工艺的改进方法,分析了硅基陶瓷涂层在高温空气中、燃烧环境中的氧化失效机理。结合硅基非氧化物陶瓷(SiC,Si3N4等)环境障碍涂层的发展,展望了C/C复合材料在复杂环境中抗氧化涂层的研究方向。     

碳化硅涂层的离子注入改性

在SiC涂层表面注入Al^3＋,B^3＋,St^4＋,观察3种离子注入对涂层表面裂纹的封填情况,分析离子注入后涂层表面的相组成,考核离子注入对SiC-C／SiC材料抗氧化性能的影响。在1300℃模拟空气中氧化15h后,注入Al^3＋的复合材料的氧化质量损失比未经涂层改性的降低了0．3％,形成的玻璃氧化层中气泡和孔洞少,对涂层裂纹的封填效果较好但覆盖不均匀。注入B^3＋的复合材料的氧化质量损失比未经涂层改性的降低了0．1％,形成的玻璃氧化层的流动性好且覆盖均匀,但其表面多气泡和孔洞,破坏了玻璃氧化层对涂层裂纹的封填作用。注入Si^4＋的复合材料的氧化质量损失同注入B^3＋的试样基本相当,但是其氧化质量损失有增大趋势,表明Si^4＋的注入对改善材料的抗氧化性能无积极作用。     

Oxidation Resistance of Multiwalled Carbon Nanotubes Coated with Silicon Carbide

Multiwalled carbon nanotubes (MWCNTs) were coated with a SiC layer using SiO vapor. The growth mechanism of SiC and the oxidation resistance of the SiC-coated MWCNTs were studied. The growth of the SiC layer was controlled by adjusting the partial pressure of CO₂ using carbon felt placed in a crucible. The nanometer-sized SiC particles were deposited onto the tubes by the reaction between SiO( g ) and CO( g ). On the other hand, the thin surface of the MWCNTs was converted to the SiC layer when the carbon felt was not used. The oxidation durability of MWCNTs was improved by the SiC coating. MWCNTs were oxidized completely in air at 650°C for 60 min. However, about 90 mass% of the SiC-coated MWCNTs remained after the same oxidation test.     

Oxidation of Silicon and Silicon Carbide in Ozone-Containing Atmospheres at 973 K

The oxidation behavior of a silicon wafer, chemically vapor-deposited SiC, and single-crystal SiC was investigated in an oxygen—2%–7% ozone gas mixture at 973 K. The thickness of the oxide film that formed during oxidation was measured by ellipsometry. The oxidation rates in the ozone-containing atmosphere were much higher than those in a pure oxygen atmosphere. The parabolic oxidation kinetics were observed for both silicon and SiC. The parabolic rate constants varied linearly with the ozone-gas partial pressure. Inward diffusion of atomic oxygen formed by the dissociation of ozone gas through the SiO₂ film apparently was the rate-controlling process.     

Effects of Plasma-Sprayed Ceramic Coatings on the Strength Distribution of Silicon Carbide Materials

Sintered α-silicon carbide and siliconized silicon carbide tubular materials were plasma-spray coated with various ceramic oxides using conventional air plasma-spraying technology. The strength distributions of the coated tubes were evaluated by fracturing samples at room temperature using a c-ring test configuration. Changes in strength are explained using statistical treatments of the data, including a Weibull approach. Failure origins are characterized using fractography via scanning electron microscopy. The stength of plasma-spray coated SiC was equivalent or superior to that of as-received material, despite a surface pretreatment which induced surface flaws in the SiC substrate.     

Oxidation Resistance Evaluation of Silicon Carbide Ceramics with Various Additives

Five silicon carbide ceramics with various additives were evaluated for oxidation resistance at 1300°C in flowing dry and wet air. In the dry atmosphere, the oxidation of the five samples was diffusion-controlled, and in wet atmosphere they exhibited a linear relation beween weight gain by oxidation and water vapor content. Water vapor in the atmosphere strongly accelerated oxidation. The influence of oxidation on room-temperature strength was complex, but the samples were not as affected by oxidation.     

渗硅碳化硅材料的高温氧化

研究了全碳粉反应渗硅碳化硅(PCRBSC)材料,在1300℃静态空气中的高温氧化行为.研究结果表明:PCRBSC材料的氧化过程遵循直线-抛物线规律,其结构对高温氧化有很大的影响,特别是游离硅fsi和游离碳fc的含量对氧化影响更大,fsi含量高的PCRBSC材料单位面积氧化增重(Δm/s)明显,fc含量高的PCRBSC材料氧化后表现为先减重后增重,氧化层断口经扫描电镜观察有明显的气孔存在.     

Some New Perspectives on Oxidation of Silicon Carbide and Silicon Nitride

This study provides new perspectives on why the oxidation rates of silicon carbide and silicon nitride are lower than those of silicon and on the conditions under which gas bubbles can form on them. The effects on oxidation of various rate-limiting steps are evaluated by considering the partial pressure gradients of various species, such as O₂, CO, and N₂. Also calculated are the parabolic rate constants for the situations when the rates are controlled by oxygen and/or carbon monoxide (or nitrogen) diffusion. These considerations indicate that the oxidation of silicon carbide and silicon nitride should be mixed controlled, influenced both by an interface reaction and diffusion.     

Burner Rig Hot Corrosion of Silicon Carbide and Silicon Nitride

A number of commercially available SiC and Si₃N₄ materials were exposed to 1000°C for 40 h in a high-velocity, pressurized burner rig as a simulation of an aircraft turbine environment. Na impurities (2 ppm) added to the burner flame resulted in molten Na₂SO₄ deposition, attack of the SiC and Si₃N₄, and formation of substantial Na₂O. x (SiO₂) corrosion product. Room-temperature strength of the materials decreased as a result of the formation of corrosion pits in SiC and grain-boundary dissolution and pitting in Si₃N₄.     

Microstructure and Oxidation Behavior of Silicon Carbide Fibers Derived from Polycarbosilane

Polycarbosilane-derived SiC fibers (CG Nicalon, Hi-Nicalon, and Hi-Nicalon type S) were exposed for 1–100 h at 1273–1673 K in air. Oxide layer growth and changes in tensile strength for these fibers were examined after exposure. The three types of SiC fibers decreased in strength as the oxide layer thickness increased. Fracture origins were located near the oxide layer–fiber interface. The Hi-Nicalon type S showed better oxidation resistance than the other polycarbosilane-derived SiC fibers after exposure in air at 1673 K for 10 h. This result was attributed to the nature of the silicon oxide layer on the surface of the SiC fibers.     

Developing Interfacial Carbon-Boron-Silicon Coatings for Silicon Nitride-Fiber-Reinforced Composites for Improved Oxidation Resistance

C-B-Si coatings were formed on a Si₃N₄ fiber using chemical vapor deposition and embedded in a Si-N-C matrix using polymer impregnation and pyrolysis. The boron-containing layer was anticipated to form borosilicate glass and seal oxygen-diffusion passes. Two types of C-B-Si coatings were tested on the fiber–matrix interface, and they improved the oxidation resistance of the composite. The first coating was multilayered: a crystalline sublayer composed of B-Si-C was sandwiched between two graphitelike carbon sublayers. The second coating was a graphitelike carbon layer containing a small amount of boron and silicon. The carbon (sub)layer of both coatings weakened the fiber–matrix bonding, giving the composites a high flexural strength (1.1 GPa). The composites retained 60%–70% of their initial strength, even after oxidation at 1523 K for 100 h. The mechanism for improved oxidation resistance was discussed through the microstructure of the interface, morphology of the fracture surface, and oxygen distribution on a cross section of the oxidized composite.