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C/C-ZrB2(ZrC、TaC)超高温陶瓷基复合材料制备工艺及性能研究

Preparation and Properties of C/C-ZrB2(ZrC、TaC) Ultra-high Temperature Ceramic Matrix Composites

【作者】 杨国威

【导师】 胡海峰;

【作者基本信息】 国防科学技术大学 , 材料科学与工程, 2008, 硕士

【摘要】 高超音速飞行器再入过程中,所承受的环境非常恶劣,特别是端头和机翼前缘,需要在氧化性环境中耐受长时间超高温和高速气流冲刷作用,因此对其防热材料提出了苛刻的要求。本文在分析国内外耐超高温材料研究的基础上,开展了超高温碳基复合材料的研究,采用泥浆涂刷法引入超高温陶瓷组分(ZrB2、ZrC、TaC),采用先驱体浸渍裂解工艺引入基体碳,制备了新型的C/C-ZrB2(ZrC、TaC)超高温复合材料,考察了先驱体种类、交联、浸渍、穿刺等工艺参数对复合材料结构和性能的影响。采用呋喃树脂、酚醛树脂、沥青作为碳源,研究了交联或浸渍工艺对C/C-ZrB2复合材料结构和性能的影响。选用呋喃树脂作为碳源,采用浸渍-交联-裂解工艺制备C/C-ZrB2复合材料时,树脂交联过程中体积膨胀,而裂解过程中体积收缩,导致层间结合较差,最终影响到复合材料的综合性能;采用浸渍后直接裂解工艺制备的复合材料致密度高,力学性能和抗氧化性能较好。选用残碳率高的酚醛树脂作为碳源,经浸渍-交联-裂解工艺制备的C/C-ZrB2复合材料致密度高,从而可以大幅提高其力学、抗氧化及抗烧蚀性能;而采用浸渍后直接裂解工艺制备的复合材料密度低、开孔率高,相应的力学、抗氧化、抗烧蚀性能均较差。分别浸渍沥青溶液和熔融沥青制备了C/C-ZrB2复合材料,采用沥青溶液制备的复合材料密度较低,力学、抗氧化和抗烧蚀性能较差;熔融沥青制备的复合材料综合性能较好,但熔融浸渍工艺需要高温高压设备,成本较高,限制了沥青的应用。综上所述,酚醛树脂是适宜PIP工艺的先驱体,且采用浸渍-交联-裂解工艺制备的复合材料性能最佳。研究了耐超高温陶瓷粉体含量对C/C-ZrB2、C/C-ZrC、C/C-TaC复合材料结构和性能的影响。随ZrB2含量的增加,制备的C/C-ZrB2复合材料密度增加,线烧蚀率呈现先降低后增加的趋势,涂刷ZrB2体积含量为10%的泥浆制备的ZB10复合材料具有较为优异的综合性能,弯曲强度为250.37MPa,断裂韧性为13.84MPa·m1/2;经过1200℃氧化30min质量保留率达到90.65%,强度保留率达到85.14%;经60s氧乙炔焰烧蚀考核质量烧蚀率为0.01802g/s,线烧蚀率为0.0122mm/s。随着ZrC含量的增加,C/C-ZrC复合材料制备过程中膨胀现象愈加严重,开孔率逐渐增大,抗氧化、耐烧蚀性能显著降低,涂刷ZrC体积含量为15%的泥浆制备的ZC15复合材料综合性能较优,弯曲强度为217.54MPa,断裂韧性为12.00MPa·m1/2;经过1200℃氧化30min质量保留率达到90.91%,强度保留率达到82.04%;质量烧蚀率为0.01827g/s,线烧蚀率为0.0193mm/s。随着TaC含量的增加,制备的C/C-TaC复合材料密度增加,致密度的变化使复合材料的力学性能和抗烧蚀性能均呈现先升后降的趋势,涂刷TaC体积含量为15%的泥浆制备的TC15复合材料综合性能较好,弯曲强度为260.99MPa,断裂韧性为13.21MPa·m1/2;经过1200℃氧化30min质量保留率达到92.12%,强度保留率达到75.03%;质量烧蚀率为0.02510g/s,线烧蚀率为0.0290mm/s。研究了穿刺工艺对复合材料性能的影响。穿刺工艺可以提高C/C-ZrB2(TaC、ZrC)复合材料的致密度、降低开孔率;增强层间剪切强度;减轻高速气流冲刷,提高抗烧蚀能力。与未穿刺样品相比,C/C-ZrB2复合材料线烧蚀率从0.0135mm/s降低到0.0075mm/s。

【Abstract】 Hypersonic spacecrafts need withstand extreme conditions at re-entry in Earth’s atmosphere. Especially, the nose tip and leading edge need operate at ultra-high temperature and high heat flux for long time in oxidized environment, so that it is necessary to develop new thermal protection materials. On the base of ultra-high temperature materials research abroad and at home, this dissertation investigated ultra-high temperature carbon matrix composites. New ultra-high temperature composites C/C-ZrB2(ZrC, TaC) were fabricated by introduction of ceramic powder (ZrB2, ZrC, TaC) using slurry brushing process, and introduction of carbon matrix using polymer infiltration and pyrolysis method. We studied the influence of precursor, crosslinking, infiltrating and puncture techniques on the composites structure and property.We chose furan resins, phenolic resins and pitch as the source of carbon, and investigated the influence of crosslinking and infiltrating on the composites structure and property. The C/C-ZrB2 composites were prepared by infiltration-crosslinking-pyrolysis process by using furan resins, only to find that the resins will expand and shrink in process of crosslinking and pyrolysis, thus leading to poor adherence between layers and poor performance of the composites. The C/C-ZrB2 composites prepared by infiltration-pyrolysis furan resins display high densification, good mechanical properties and oxidation resistance.The composites prepared by using phenolic resins, on the other hand, can enhance densification effectively through infiltration-crosslinking-pyrolysis process, thus improve significantly mechanical properties, oxidation resistance and ablated resistance. The composites prepared by infiltration-pyrolysis process showed low density, poor mechanical, oxidation resistance and ablated resistance properties.The C/C-ZrB2 composites were also prepared by infiltrating pitch of molten and solution. The sample from melt pitch has good integration performance, while that from solution has lower density and poor mechanical properties. However, the melting infiltration process requires high temperature and high pressure equipment, and thus high cost. In conclusion, phenolic resins is the suitable precursor for polymer infiltration and pyrolysis process, and the composites prepared by infiltration-crosslinking-pyrolysis process is first-rank.We investigated the influence of ceramic content on the composites (C/C-ZrB2, C/C-ZrC, C/C-TaC) structure and property. The density of C/C-ZrB2 composites increases when the content of ZrB2 increase, while linear recession rates in oxyacetylene torch test decrease first and increase later. Among all samples ZB10 sample (10vol% ZrB2) has the best integration performance with 250.37MPa flexural strength and 13.84MPa·m1/2 fracture toughness. After being oxidated at 1200°C for 30min, its mass retention and strength retention were 90.65% and 85.14%, respectively. Meanwhile, it also shows best ablation resistance. After being ablated in oxyacetylene torch for 60 seconds, the sample showed mass loss rate of 0.01802g/s and linear recession rate of 0.0122mm/s. ZC15 sample (15vol% ZrC) shows the relatively excellent integration performance with 217.54MPa flexural strength and 12.00MPa·m1/2 fracture toughness. After being oxidated at 1200°C for 30min, its mass retention and strength retention were 90.91% and 82.04%, respectively. It also has better ablation resistance with the mass loss rate of 0.01827g/s and linear recession rate of 0.0193mm/s. The density of C/C-TaC composites increases when the content of TaC increase. TC15 sample (15%vol TaC) has the best integration performance with 260.99MPa flexural strength and 13.21MPa·m1/2 fracture toughness. After being oxidated at 1200°C for 30min, its mass retention and strength retention were 92.12% and 75.03%, respectively. It also presents relatively good ablation resistance with mass loss rate of 0.02510g/s and linear recession rate of 0.0290mm/s.The influence of puncture process on the composites performance was investigated. Puncture process can enhance densification of C/C-ZrB2(TaC, ZrC) composites, reduce the opening porosity, improve shear strength. At the same time, puncture process can also decrease high heat flux erosion and keep integration performance during ablation. Contrast with un-punctured sample, the linear recession rate of C/C-ZrBB2 composites was reduced to 0.0075mm/s from 0.0135mm/s.

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