原位反应法制备硼化物改性硅基超高温陶瓷涂层研究

发布时间：2018-07-03 10:46

本文选题：碳/碳复合材料 + 硅基陶瓷涂层　；参考：《西北工业大学》2015年博士论文

【摘要】：氧化敏感性是碳/碳(C/C)复合材料高温应用的瓶颈,尽管硅基陶瓷涂层在1500-1600℃温度范围内具有较佳的抗氧化效果,但是其较窄的防御温度范围以及超高温长时间使用时易产生孔洞和气泡等缺陷,极大限制了其对C/C复合材料的氧化防护寿命。将具有优异热物理化学特性的超高温陶瓷硼化物相引入硅基陶瓷涂层中对其进行改性,有希望提高硅基陶瓷涂层的性能。本文以硼化物改性硅基超高温陶瓷涂层为研究对象,选用原位反应法制备了ZrB2、TaB2、HfB2、(Zr,Ta)B2和(Ta,Hf)B2改性硅基涂层,考察了其在1773 K静态空气氧化环境、室温-1773 K动态氧化环境,热流为2400KW/m2的氧乙炔焰严苛高温烧蚀测试环境和1873K风洞燃气冲刷环境下的氧化防护能力,通过XRD、SEM和EDS等测试手段,对试样氧化测试前后的物相、形貌和元素组成等进行了分析,研究了硼化物改性对硅基超高温陶瓷涂层微观结构与防护性能的影响,并探讨其氧化失效机理,主要内容和结果如下:选取过渡族金属氧化物MxOy(MxOy=ZrO2、Ta2O5和HfO2)作为超高温陶瓷硼化物MB2中过渡族金属M的源材料,B2O3粉作为B源,C粉用作碳源,硅粉作为Si源,采用原位反应法,经过高温热处理,通过碳热还原反应与固相反应相结合的方式一步合成制备出一元硼化物改性硅基超高温陶瓷涂层MB2-SiC(M=Zr、Ta和Hf)。在一元硼化物改性硅基涂层研究基础上,根据固溶体合成理论,采用过渡族金属氧化物MxOy双源共存的方式,同时添加ZrO2粉和Ta2O5粉来提供Zr源和Ta源,或同时添加HfO2粉和Ta2O5粉来提供Hf源和Ta源,结合B2O3粉,C粉和Si粉,经过高温热处理,通过原位反应法,可一步合成制备出硼化物固溶体(Zr,Ta)B2或(Ta,Hf)B2改性硅基超高温陶瓷涂层。高温静态氧化试验结果表明,C/C复合材料在1773K静态空气中仅仅氧化25min后,试样的失重百分数高达23.1%。而在C/C表面制备出硼化物改性硅基超高温陶瓷涂层后,试样的氧化防护性能得到了显著的提高。在ZrB2-SiC/SiC涂层、TaB2-SiC/SiC涂层以及HfB2-SiC/SiC涂层的保护下,三种试样在1773K静态空气中分别氧化550、300以及265小时后,对应的失重率为0.22%、1.1%以及1.6%。而在硼化物固溶体改性硅基超高温陶瓷涂层(Zr,Ta)B2-SiC/SiC和(Ta,Hf)B2-SiC/SiC的保护下,试样的氧化防护能力得到进一步提升,分别可以在1773K静态空气中对C/C基体防护1412小时以及1480小时,而失重率仅为0.1%和0.57%,显示了其极大的应用潜力。热重试验结果表明,硼化物对硅基超高温陶瓷涂层的改性,可以有效提高涂层在室温到1773K的动态测试环境中的氧化防护能力,纯SiC涂层在测试结束后,试样失重21.8%,而经过ZrB2、TaB2、HfB2、(Zr,Ta)B2和(Ta,Hf)B2改性后,试样的失重百分数分别为10.3%、11.2%、8.7%、-1.8%和1.37%。在涂层表面生成的复相玻璃层是硼化物改性硅基超高温陶瓷具有优异氧化防护效果的主要原因。在氧化环境下,由于ZrB2改性相的存在,涂层表面覆盖着一层由SiO2、ZrO2和ZrSiO4组合而成的Zr-Si-O复相玻璃层;TaB2改性相的存在,使得涂层表面覆盖着一层由TaxOy、B2O3和SiO2等在内的多重氧化物所组合而成的复相Ta-Si-O玻璃层;HfB2改性相的存在,使得涂层表面覆盖着一层由HfO2、SiO2和HfSiO4所组合而成的Hf-Si-O复相玻璃层;而对于(Zr,Ta)B2和(Ta,Hf)B2固溶相而言,其在硅基超高温陶瓷涂层中的存在,使得涂层表面分别覆盖着一层由SiO2、ZrO2、ZrSiO4和TaxOy等组成的Zr-Ta-Si-O玻璃,以及由HfO2、SiO2、HfSiO4和TaxOy等组成的Hf-Ta-Si-O玻璃。在涂层表面生成的多重复相玻璃层在氧化环境下的防护机理呈现出明显的差异。对于Zr-Si-O和Hf-Si-O复相玻璃层而言,由于高熔点氧化物ZrO2、HfO2、HfSiO4和ZrSiO4以不兼容相在二氧化硅玻璃中的存在,二者呈现出类似“钉扎相”的镶嵌结构,“钉扎相”可以使玻璃层中生成的微裂纹在传播的过程中“偏转”或者“终止”,有效抑制了裂纹的扩展和传播,减少氧气向基体的渗透,从而提高了涂层的氧化防护能力。对于Ta-Si-O复相玻璃层而言,由于多组元钽氧化物与SiO2玻璃发生一定程度的熔合,呈现出由内层SiO2玻璃层和外层复相Ta-Si-O玻璃层组合而成的双重玻璃层;过渡族金属钽元素在SiO2玻璃中的存在,使得外层Ta-Si-O玻璃层的粘度以及稳定性得以提高,展现出比SiO2玻璃更强的对微裂纹的限制作用;Ta-Si-O/SiO2玻璃展现出“微裂纹强化”的机理,通过在内层SiO2玻璃中产生少量微裂纹,减少与空气直接接触的外层Ta-Si-O玻璃中的微裂纹数目以及降低形成“贯穿性裂纹”的可能性,从而进一步提高其高温稳定性。而Zr-Ta-Si-O和Hf-Ta-Si-O玻璃是由具有镶嵌结构的Zr-Si-O玻璃和Hf-Si-O玻璃与具有“微裂纹强化”效果的Ta-Si-O玻璃层复合而成的,兼具了二者的优异特性,展现出更加稳定的氧化防护能力。氧乙炔烧蚀试验结果表明,经过Zr B2、TaB2、HfB2、(Zr,Ta)B2和(Ta,Hf)B2改性后,涂层在热流为2400KW/m2的氧乙炔焰测试45s后,试样的质量烧蚀率分别为3.58×10-3g/cm2、3.98×10-3 g/cm2、3.87×10-3 g/cm2、2.07×10-3 g/cm2和1.89×10-3 g/cm2,线烧蚀率分别为4.32×10-3mm/s、5.62×10-3 mm/s、4.72×10-3 mm/、2.73×10-3 mm/s和2.37×10-3 mm/s。由于氧乙炔焰的热化学烧蚀以及机械剥蚀导致涂层发生损耗,而多组分氧化物的协同作用,是涂层烧蚀防护力得到提高的主要原因。分别对(Zr,Ta)B2相和(Ta,Hf)B2固溶体相改性硅基陶瓷涂层在1873K高温风洞冲刷条件下的氧化防护效果进行了研究,结果表明,前者在1873K高温风洞燃气环境下防护C/C基体76.5小时后,试样最终在温差较大的过渡区发生了断裂;后者则有效防护C/C基体长达97小时,测试结束后,试样没有发生断裂,基体也未发生明显的氧化;在高温风洞冲刷环境下涂层中贯穿性裂纹的形成是试样最终失效的主要原因。
[Abstract]:Oxidation sensitivity is the bottleneck of high temperature application of carbon / carbon (C/C) composites. Although silicon based ceramic coatings have better antioxidant effects in the temperature range of 1500-1600 C, the narrow defense temperature range and the long time use of ultra-high temperature are easy to produce holes and bubbles, which greatly restrict the oxidation of C/C Composites. In this paper, ZrB2, TaB2, HfB2, (Zr, Ta) B2 and (Ta, Hf) were prepared by in-situ inverse method. B2 modified silicon based coating was used to investigate its phase in 1773 K static air oxidation environment, room temperature -1773 K dynamic oxidation environment, 2400KW/m2 oxygen acetylene flame harsh high temperature ablation test environment and 1873K wind tunnel gas scour environment. The phase and morphology of the samples before and after oxidation test were measured by XRD, SEM and EDS test methods. The effect of boride modification on Microstructure and protective properties of silicon based ultra-high temperature ceramic coating was investigated and its oxidation failure mechanism was investigated. The main contents and results were as follows: the transition metal oxide MxOy (MxOy=ZrO2, Ta2O5 and HfO2) was selected as the transition metal M in the ultra-high temperature ceramic boride MB2. Source material, B2O3 powder is used as source of B, C powder is used as carbon source and silicon powder is used as source of Si. In situ reaction method, a one element boride modified silicon based super high temperature ceramic coating MB2-SiC (M=Zr, Ta and Hf) is prepared by the method of heat treatment in situ, through the combination of carbon thermo reduction reaction and solid state reaction. Based on the theory of solid solution synthesis, the ZrO2 powder and Ta2O5 powder are added to provide Zr source and Ta source, or HfO2 powder and Ta2O5 powder are added to provide Hf source and Ta source at the same time, and HfO2 powder and Ta2O5 powder are added at the same time, and B2O3 powder, C powder and Si powder are combined with B2O3 powder, C powder and Si powder. Through the high temperature heat treatment, the preparation can be made by one step synthesis by in situ reaction method. Boride solid solution (Zr, Ta) B2 or (Ta, Hf) B2 modified silicon based super high temperature ceramic coating. High temperature static oxidation test results show that the weight loss percentage of the C/C composite in 1773K static air is high as high as 23.1%. and the oxidation protection of the specimen after the preparation of a boride modified silicon based super high temperature ceramic coating on the C/C surface With the protection of ZrB2-SiC/SiC coating, TaB2-SiC/SiC coating and HfB2-SiC/SiC coating, three samples were oxidized for 550300 and 265 hours in the static air of 1773K, and the corresponding weight loss rate was 0.22%, 1.1% and 1.6%. in the boride solid solution modified silicon based ultra-high temperature ceramic coating (Zr, Ta) B2-SiC/SiC and (T). Under the protection of a, Hf) B2-SiC/SiC, the oxidation protection ability of the sample is further improved, which can protect C/C matrix for 1412 hours and 1480 hours respectively in the static air of 1773K, and the weight loss rate is only 0.1% and 0.57%, which shows its great potential application. To effectively improve the oxidation protection ability of the coating in the dynamic testing environment at room temperature to 1773K, the pure SiC coating was weighed 21.8% after the test, and the weight loss percentage of the sample was 10.3%, 11.2%, 8.7% after ZrB2, TaB2, HfB2, (Zr, Ta) B2 and (Ta, Hf) B2, respectively, and the composite phase glass layer formed on the surface of the coating was boron. The main reason for the excellent oxidation protection effect of the modified silicon based super high temperature ceramics is that the coating surface is covered with a layer of Zr-Si-O complex glass layer formed by the combination of SiO2, ZrO2 and ZrSiO4 in the oxidation environment. The existence of TaB2 modified phase makes the coating surface covered with a layer of TaxOy, B2O3 and SiO2, and so on. The complex phase Ta-Si-O glass layer composed of multiple oxides; the presence of HfB2 modified phase makes the coating surface covered with a layer of Hf-Si-O complex glass composed of HfO2, SiO2 and HfSiO4; and for the (Zr, Ta) B2 and (Ta, Hf) B2 solid solution, the existence of its presence in the silicon based ultra high temperature ceramic coating makes the coating surface covered separately. A layer of Zr-Ta-Si-O glass consisting of SiO2, ZrO2, ZrSiO4 and TaxOy, as well as Hf-Ta-Si-O glass consisting of HfO2, SiO2, HfSiO4 and TaxOy. The protective mechanism of the multiple duplicated glass layer on the coating surface is obviously different in the oxidation environment. For Zr-Si-O and Hf-Si-O complex glass layers, because of high melting point oxide ZrO2, HfO2, HfSiO4 and ZrSiO4 are in the presence of incompatible phase in silica glass. The two presents a mosaic structure similar to "pinning phase". "Pinning phase" can "deflect" or "terminate" in the propagation of the microcracks produced in the glass layer, which effectively inhibits the propagation and propagation of the cracks, and reduces the permeability of oxygen to the matrix. For the Ta-Si-O composite glass layer, because the multicomponent tantalum oxide is fused with the SiO2 glass to a certain extent, the double glass layer formed by the combination of the inner SiO2 glass layer and the outer complex Ta-Si-O glass layer is presented, and the existence of the over transition metal tantalum in the SiO2 glass is made. The viscosity and stability of the Ta-Si-O glass layer in the outer layer is improved, showing a stronger effect on the micro crack than the SiO2 glass; Ta-Si-O/SiO2 glass shows the mechanism of "micro crack strengthening", and a small amount of micro cracks are produced in the inner SiO2 glass to reduce the number of micro cracks in the outer Ta-Si-O glass directly contact with the air. And reduce the possibility of forming a "penetrating crack" to further improve its high temperature stability. Zr-Ta-Si-O and Hf-Ta-Si-O glass are composed of Zr-Si-O glass and Hf-Si-O glass with inlaid structure and the Ta-Si-O glass layer with "micro crack strengthening" effect, with the excellent characteristics of the two, showing more stability. The results of oxygen acetylene ablation test showed that after Zr B2, TaB2, HfB2, (Zr, Ta) B2 and (Ta, Hf) B2 modification, the quality ablative rate of the coating was 3.58 * * * * 10-3, 1.89 * 10-3 and 1.89 * 10-3. 4.32 x 10-3mm/s, 5.62 x 10-3 mm/s, 4.72 x 10-3 mm/, 2.73 x 10-3 mm/s and 2.37 x 10-3 mm/s. caused the coating loss due to the thermal chemical ablation of oxyacetylene flame and mechanical erosion, and the synergistic effect of the multi component oxide is the main reason for the improvement of the coating's ablation protection force. Respectively (Zr, Ta) B2 phase and (Ta, Hf) B2 solid solution, respectively. The oxidation protection effect of phase modified silicon based ceramic coating under the condition of 1873K high temperature wind tunnel was studied. The results showed that the former was finally broken in the transition zone with larger temperature difference in the 1873K high temperature wind tunnel gas environment for 76.5 hours, while the latter effectively protected the C/C matrix for up to 97 hours. After the test, the test was completed. There is no fracture in the specimen and no obvious oxidation occurs in the matrix. The formation of the penetrating crack in the coating of the high temperature wind tunnel is the main reason for the final failure of the specimen.
【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ174.758.16

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