有机含锆陶瓷前驱体的合成研究
发布时间：2019-06-25 20:23
【摘要】：近年来,前驱体转化法所制备的陶瓷材料综合性能优异,已成功应用于发动机热端、机翼前缘以及飞行器鼻锥等高温热防护部位或部件,但是该方法的难点在于其陶瓷前驱体的制备。碳化锆(ZrC)陶瓷是目前比较常用且性能优异的抗烧蚀材料,国内外研究者投入了大量的精力在ZrC陶瓷前驱体的合成上,且有机合成法已成为该前驱体制备的首选方法。然而该方法仍存在着原料成本高,制备工艺复杂,所得到的前驱体毒性大且不易存储等问题。另外,相比于单相陶瓷,多元复相陶瓷材料具备更加优异的综合性能,是未来复合材料的重要发展方向,但是目前关于复相陶瓷前驱体的制备鲜有报道。为此,开发更加优异的ZrC单相和复相陶瓷前驱体具有非常重要的实际价值和战略意义。本文选用低成本的苯酚、甲醛、八水氧氯化锆、硼酸、正硅酸乙酯、乙酰丙酮、乙醇为原料,通过简单易控的原位化学反应成功制备出了毒性低、易存储的ZrC单相和SiC/ZrC、ZrB_2/ZrC、SiC/ZrB_2/ZrC复相陶瓷前驱体。借助X射线光电子能谱(XPS)、核磁共振谱仪(NMR)、红外光谱(FTIR)、X-射线衍射仪(XRD)、拉曼光谱(Raman)、圆锥平板型流变仪、热重-差热分析仪(TG-DSC)以及扫描电镜(SEM)和能谱(EDS)揭示了不同前驱体的反应机理,分析了所制备的前驱体的性能,研究了其热解机理和陶瓷化机制。并在此基础上制备了不同锆含量的碳化锆陶瓷前驱体,揭示了锆的引入对前驱体性能及热解机制的影响规律,探讨了锆的引入对陶瓷产物热解碳的催化石墨化作用,并阐明了其催化机理。主要研究内容和结果如下:(1)采用苯酚、甲醛为碳源,八水氧氯化锆为锆源,乙酰丙酮为配位剂,乙醇为溶剂,经过水解反应、缩合反应、配位反应以及配体交换反应成功制备了不同锆含量的ZrC陶瓷前驱体PZC。该类前驱体是以Zr O和Zr O C为主链,羟甲基酚和乙酰丙酮为配体的一种直线双链型结构的配位化合物。所制备的前驱体毒性低、稳定性好,其中,锆含量约为16 wt%的PZC在较宽的温度范围内具有较低的黏度,浸渍性能良好;1200℃时的残碳率为55%,最大热解温度为700℃;800℃时完成陶瓷转化,陶瓷产物为芳香碳和ZrO2;1800℃热处理后,可得到高度晶化的ZrC C陶瓷相;2000℃时,热解碳的微观结构有序性达到最高,其结构有序性、微晶尺寸以及堆垛高度相比于锆含量为零的前驱体的陶瓷产物分别提高了57%、133%和22.3%。由于热解过程中ZrO2颗粒的强化作用以及Zr C键的连接作用,所得到的陶瓷产物致密,无明显的孔洞裂纹等缺陷,且陶瓷颗粒明显细化,均匀地分布在碳基体中。(2)高温热处理不同锆含量的ZrC陶瓷前驱体,得到了锆含量分别约为0、11、18和27 wt%的ZrC C陶瓷产物。锆含量对陶瓷产物热解碳的微观结构具有较大影响:随着锆含量的增加,锆原子的催化石墨化作用增强,热解碳的结构有序性、晶化度、晶粒生长程度以及石墨化度均得到了显著改善;但是锆含量过高时(锆含量为27 wt%),热解碳的结构有序性、晶化度以及晶粒生长速度反而下降。此外,引入了锆的陶瓷产物热解碳的石墨化碳含量相比于引入前提高了约6倍,然而随着锆含量的增加,石墨化碳的含量变化不大。(3)在合成碳化锆陶瓷前驱体的基础上,利用正硅酸乙酯与氧氯化锆的水解缩聚反应,可同时将Si和Zr引入到聚合物分子结构中,制备出SiC/ZrC复相陶瓷前驱体PSZC。800℃时,PSZC陶瓷转化完成,残碳率为70%,陶瓷产物为芳香碳、SiO2和ZrO2;升高温度至1500℃,SiC优先形成且转化完全,随后ZrO2与C在更高温度下通过碳热还原反应逐步转化为ZrC;1900℃热处理后可得到高度晶化的ZrC SiC C陶瓷相,陶瓷相致密,没有明显的孔洞裂纹等缺陷,ZrC和SiC陶瓷颗粒平均尺寸约100nm,均匀地分布在碳基体中。(4)以苯酚、甲醛、八水氧氯化锆、硼酸和乙酰丙酮为原料,利用硼酸和氧氯化锆的水解缩聚反应,成功制备出了Zr B_2/ZrC复相陶瓷前驱体PBZC。800℃时,PBZC陶瓷转化完全,残碳率为60%,陶瓷产物为芳香碳、B_2O3和ZrO2;由于ZrB_2的生成反应吉布斯自由能较低且热稳定性优于ZrC,因而,当热处理温度升高到1500℃时,ZrB_2在反应体系中优先生成,当B_2O3耗尽时,未反应的ZrO2和C发生碳热还原反应逐步生成ZrC陶瓷。1800℃热处理后,可得到高度晶化的ZrB_2 ZrC C陶瓷相,其中ZrC和ZrB_2陶瓷颗粒尺寸约200 nm,均匀地镶嵌在碳基体中。(5)结合PSZC和PBZC的合成工艺,成功制备出了SiC/ZrB_2/ZrC三元复相陶瓷前驱体PBSZ。800℃时,PBSZ陶瓷转化完全,残碳率为67%,陶瓷产物为芳香碳、B_2O3、SiO2和ZrO2;当热处理温度高于1600℃时,可得到高度晶化的SiC ZrB_2 ZrC C陶瓷相。对PBSZ作1800℃热处理,可原位生长出平均直径约2μm的SiC晶须且均匀地分散在高度晶化的ZrB_2 ZrC C陶瓷相周围,其中ZrC和ZrB_2的颗粒尺寸约200 nm,均匀镶嵌在碳基体中;进一步升高热处理温度到1900℃,直径约500 nm的SiC晶须均匀地生长在ZrB_2/ZrC/C陶瓷相基体表面,形成一种致密连续的包裹形貌,同时ZrC和ZrB_2的颗粒尺寸约500 nm,均匀镶嵌在碳基体中。
[Abstract]:In recent years, the comprehensive performance of the ceramic material prepared by the precursor conversion method has been successfully applied to the hot end of the engine, the leading edge of the wing and the high-temperature thermal protection part or component of the nose cone of the aircraft, but the difficulty of the method is the preparation of the ceramic precursor. The carbide-carbide (ZrC) ceramic is an anti-ablation material which is widely used and has excellent performance. The researchers at home and abroad have invested a lot of energy on the synthesis of the ZrC ceramic precursor, and the organic synthesis method has become the preferred method for the preparation of the precursor. However, the method still has the problems of high raw material cost, complex preparation process, large toxicity of the obtained precursor and difficult storage, and the like. In addition, compared with the single-phase ceramic, the multi-phase ceramic material has more excellent comprehensive performance, is an important development direction of the future composite material, but the preparation of the complex-phase ceramic precursor is rarely reported. To this end, the development of more excellent ZrC single-phase and multi-phase ceramic precursor has very important practical value and strategic significance. In this paper, low-cost phenol, formaldehyde, octahydro-oxychloride, boric acid, ethyl orthosilicate, ethanone and ethanol are used as raw materials. The low toxicity, easy-to-store ZrC single-phase and SiC/ ZrC, ZrB _ 2/ ZrC, SiC/ ZrB _ 2/ ZrC complex-phase ceramic precursors are successfully prepared by simple and easy-to-control in-situ chemical reaction. By means of X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectrometer (NMR), infrared spectroscopy (FTIR), X-ray diffractometer (XRD), Raman spectrum (Raman), and conical plate type rheometer, TG-DSC and scanning electron microscope (SEM) and energy spectrum (EDS) were used to reveal the reaction mechanism of different precursors, and the properties of the prepared precursor were analyzed. The mechanism of pyrolysis and the mechanism of the ceramics were studied. In this paper, the precursor of carbonized ceramic with different sulfur content is prepared, and the influence of the introduction of sulfur on the properties of the precursor and the pyrolysis mechanism is revealed, and the catalytic graphitization of the pyrolytic carbon of the ceramic product is discussed. The main research contents and results are as follows: (1) The phenol and formaldehyde are used as the carbon source, the octahydro-oxychlorination agent is a sulfur source, and the ethanone is a complexing agent, the ethanol is a solvent, the hydrolysis reaction and the condensation reaction are carried out, And the ZrC ceramic precursor PZC with different sulfur content is successfully prepared by the coordination reaction and the ligand exchange reaction. The precursor is a coordination compound of a linear double-stranded structure which takes the Zr O and the Zr O as the main chain, the hydroxymethyl phenol and the ethanone as the ligand. The prepared precursor has low toxicity and good stability, wherein the PZC with the sulfur content of about 16 wt% has a lower viscosity in a wide temperature range, the impregnation performance is good, the residual carbon rate at 1200 DEG C is 55 percent, the maximum pyrolysis temperature is 700 DEG C, and the ceramic conversion is finished at 800 DEG C, the ceramic product is aromatic carbon and ZrO2; after the heat treatment at 1800 DEG C, a highly crystallized ZrC-C ceramic phase can be obtained; at the temperature of 2000 DEG C, the microstructure order of the pyrolytic carbon reaches the highest, and the structure order is The ceramic products of the precursor with the micro-crystallite size and the stacking height of zero compared with the graphite content were increased by 57%,133%, and 22.3%, respectively. Due to the strengthening effect of the ZrO2 particles and the connection action of the Zr C bond during the pyrolysis process, the obtained ceramic product is compact, has no obvious hole crack and the like, and the ceramic particles are obviously refined and uniformly distributed in the carbon matrix. And (2) the ZrC ceramic precursor with different sulfur content is heat treated at high temperature to obtain the ZrC C ceramic product with the oxygen content of about 0,11,18 and 27 weight percent, respectively. The content of the graphite has a great effect on the microstructure of the pyrolytic carbon of the ceramic product. With the increase of the carbon content, the catalytic graphitization of the pyrolytic carbon is enhanced, the structure order of the pyrolytic carbon, the degree of crystallization, the degree of grain growth and the degree of graphitization are greatly improved; However, the structure of the pyrolytic carbon, the degree of crystallization, and the grain growth rate of the pyrolytic carbon decrease when the content of the carbon is too high (the content of the carbon is 27% by weight). In addition, the graphitized carbon content of the pyrolytic carbon of the ceramic product introduced is increased by about 6 times compared with that of the introduction, however, with the increase of the carbon content, the content of the graphitized carbon is not changed much. (3) on the basis of the synthesis of the carbonized ceramic precursor, the hydrolysis and polycondensation of the ethyl orthosilicate and the oxychlorination agent are utilized, and the Si and Zr can be simultaneously introduced into the molecular structure of the polymer to prepare the SiC/ ZrC complex-phase ceramic precursor PSZC.800 DEG C, the conversion of the PSZC ceramic is completed, the residual carbon rate is 70 percent, The ceramic product is aromatic carbon, SiO2 and ZrO2, the temperature is raised to 1500 DEG C, SiC is preferentially formed and is converted into complete, then ZrO2 and C are gradually converted into ZrC at higher temperature through a carbothermic reduction reaction, and then a highly crystallized ZrC SiC C ceramic phase is obtained after heat treatment at 1900 DEG C, and the ceramic phase is compact, And the average size of the ZrC and SiC ceramic particles is about 100 nm and is uniformly distributed in the carbon matrix. (4) The preparation of the Zr-B _ 2/ ZrC multi-phase ceramic precursor PBZC.800 鈩，
本文编号：2505977
[Abstract]:In recent years, the comprehensive performance of the ceramic material prepared by the precursor conversion method has been successfully applied to the hot end of the engine, the leading edge of the wing and the high-temperature thermal protection part or component of the nose cone of the aircraft, but the difficulty of the method is the preparation of the ceramic precursor. The carbide-carbide (ZrC) ceramic is an anti-ablation material which is widely used and has excellent performance. The researchers at home and abroad have invested a lot of energy on the synthesis of the ZrC ceramic precursor, and the organic synthesis method has become the preferred method for the preparation of the precursor. However, the method still has the problems of high raw material cost, complex preparation process, large toxicity of the obtained precursor and difficult storage, and the like. In addition, compared with the single-phase ceramic, the multi-phase ceramic material has more excellent comprehensive performance, is an important development direction of the future composite material, but the preparation of the complex-phase ceramic precursor is rarely reported. To this end, the development of more excellent ZrC single-phase and multi-phase ceramic precursor has very important practical value and strategic significance. In this paper, low-cost phenol, formaldehyde, octahydro-oxychloride, boric acid, ethyl orthosilicate, ethanone and ethanol are used as raw materials. The low toxicity, easy-to-store ZrC single-phase and SiC/ ZrC, ZrB _ 2/ ZrC, SiC/ ZrB _ 2/ ZrC complex-phase ceramic precursors are successfully prepared by simple and easy-to-control in-situ chemical reaction. By means of X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectrometer (NMR), infrared spectroscopy (FTIR), X-ray diffractometer (XRD), Raman spectrum (Raman), and conical plate type rheometer, TG-DSC and scanning electron microscope (SEM) and energy spectrum (EDS) were used to reveal the reaction mechanism of different precursors, and the properties of the prepared precursor were analyzed. The mechanism of pyrolysis and the mechanism of the ceramics were studied. In this paper, the precursor of carbonized ceramic with different sulfur content is prepared, and the influence of the introduction of sulfur on the properties of the precursor and the pyrolysis mechanism is revealed, and the catalytic graphitization of the pyrolytic carbon of the ceramic product is discussed. The main research contents and results are as follows: (1) The phenol and formaldehyde are used as the carbon source, the octahydro-oxychlorination agent is a sulfur source, and the ethanone is a complexing agent, the ethanol is a solvent, the hydrolysis reaction and the condensation reaction are carried out, And the ZrC ceramic precursor PZC with different sulfur content is successfully prepared by the coordination reaction and the ligand exchange reaction. The precursor is a coordination compound of a linear double-stranded structure which takes the Zr O and the Zr O as the main chain, the hydroxymethyl phenol and the ethanone as the ligand. The prepared precursor has low toxicity and good stability, wherein the PZC with the sulfur content of about 16 wt% has a lower viscosity in a wide temperature range, the impregnation performance is good, the residual carbon rate at 1200 DEG C is 55 percent, the maximum pyrolysis temperature is 700 DEG C, and the ceramic conversion is finished at 800 DEG C, the ceramic product is aromatic carbon and ZrO2; after the heat treatment at 1800 DEG C, a highly crystallized ZrC-C ceramic phase can be obtained; at the temperature of 2000 DEG C, the microstructure order of the pyrolytic carbon reaches the highest, and the structure order is The ceramic products of the precursor with the micro-crystallite size and the stacking height of zero compared with the graphite content were increased by 57%,133%, and 22.3%, respectively. Due to the strengthening effect of the ZrO2 particles and the connection action of the Zr C bond during the pyrolysis process, the obtained ceramic product is compact, has no obvious hole crack and the like, and the ceramic particles are obviously refined and uniformly distributed in the carbon matrix. And (2) the ZrC ceramic precursor with different sulfur content is heat treated at high temperature to obtain the ZrC C ceramic product with the oxygen content of about 0,11,18 and 27 weight percent, respectively. The content of the graphite has a great effect on the microstructure of the pyrolytic carbon of the ceramic product. With the increase of the carbon content, the catalytic graphitization of the pyrolytic carbon is enhanced, the structure order of the pyrolytic carbon, the degree of crystallization, the degree of grain growth and the degree of graphitization are greatly improved; However, the structure of the pyrolytic carbon, the degree of crystallization, and the grain growth rate of the pyrolytic carbon decrease when the content of the carbon is too high (the content of the carbon is 27% by weight). In addition, the graphitized carbon content of the pyrolytic carbon of the ceramic product introduced is increased by about 6 times compared with that of the introduction, however, with the increase of the carbon content, the content of the graphitized carbon is not changed much. (3) on the basis of the synthesis of the carbonized ceramic precursor, the hydrolysis and polycondensation of the ethyl orthosilicate and the oxychlorination agent are utilized, and the Si and Zr can be simultaneously introduced into the molecular structure of the polymer to prepare the SiC/ ZrC complex-phase ceramic precursor PSZC.800 DEG C, the conversion of the PSZC ceramic is completed, the residual carbon rate is 70 percent, The ceramic product is aromatic carbon, SiO2 and ZrO2, the temperature is raised to 1500 DEG C, SiC is preferentially formed and is converted into complete, then ZrO2 and C are gradually converted into ZrC at higher temperature through a carbothermic reduction reaction, and then a highly crystallized ZrC SiC C ceramic phase is obtained after heat treatment at 1900 DEG C, and the ceramic phase is compact, And the average size of the ZrC and SiC ceramic particles is about 100 nm and is uniformly distributed in the carbon matrix. (4) The preparation of the Zr-B _ 2/ ZrC multi-phase ceramic precursor PBZC.800 鈩，
本文编号：2505977
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