【摘要】：近年來,前驅(qū)體轉(zhuǎn)化法所制備的陶瓷材料綜合性能優(yōu)異,已成功應用于發(fā)動機熱端、機翼前緣以及飛行器鼻錐等高溫熱防護部位或部件,但是該方法的難點在于其陶瓷前驅(qū)體的制備。碳化鋯(ZrC)陶瓷是目前比較常用且性能優(yōu)異的抗燒蝕材料,國內(nèi)外研究者投入了大量的精力在ZrC陶瓷前驅(qū)體的合成上,且有機合成法已成為該前驅(qū)體制備的首選方法。然而該方法仍存在著原料成本高,制備工藝復雜,所得到的前驅(qū)體毒性大且不易存儲等問題。另外,相比于單相陶瓷,多元復相陶瓷材料具備更加優(yōu)異的綜合性能,是未來復合材料的重要發(fā)展方向,但是目前關(guān)于復相陶瓷前驅(qū)體的制備鮮有報道。為此,開發(fā)更加優(yōu)異的ZrC單相和復相陶瓷前驅(qū)體具有非常重要的實際價值和戰(zhàn)略意義。本文選用低成本的苯酚、甲醛、八水氧氯化鋯、硼酸、正硅酸乙酯、乙酰丙酮、乙醇為原料,通過簡單易控的原位化學反應成功制備出了毒性低、易存儲的ZrC單相和SiC/ZrC、ZrB_2/ZrC、SiC/ZrB_2/ZrC復相陶瓷前驅(qū)體。借助X射線光電子能譜(XPS)、核磁共振譜儀(NMR)、紅外光譜(FTIR)、X-射線衍射儀(XRD)、拉曼光譜(Raman)、圓錐平板型流變儀、熱重-差熱分析儀(TG-DSC)以及掃描電鏡(SEM)和能譜(EDS)揭示了不同前驅(qū)體的反應機理,分析了所制備的前驅(qū)體的性能,研究了其熱解機理和陶瓷化機制。并在此基礎上制備了不同鋯含量的碳化鋯陶瓷前驅(qū)體,揭示了鋯的引入對前驅(qū)體性能及熱解機制的影響規(guī)律,探討了鋯的引入對陶瓷產(chǎn)物熱解碳的催化石墨化作用,并闡明了其催化機理。主要研究內(nèi)容和結(jié)果如下:(1)采用苯酚、甲醛為碳源,八水氧氯化鋯為鋯源,乙酰丙酮為配位劑,乙醇為溶劑,經(jīng)過水解反應、縮合反應、配位反應以及配體交換反應成功制備了不同鋯含量的ZrC陶瓷前驅(qū)體PZC。該類前驅(qū)體是以Zr O和Zr O C為主鏈,羥甲基酚和乙酰丙酮為配體的一種直線雙鏈型結(jié)構(gòu)的配位化合物。所制備的前驅(qū)體毒性低、穩(wěn)定性好,其中,鋯含量約為16 wt%的PZC在較寬的溫度范圍內(nèi)具有較低的黏度,浸漬性能良好;1200℃時的殘?zhí)悸蕿?5%,最大熱解溫度為700℃;800℃時完成陶瓷轉(zhuǎn)化,陶瓷產(chǎn)物為芳香碳和ZrO2;1800℃熱處理后,可得到高度晶化的ZrC C陶瓷相;2000℃時,熱解碳的微觀結(jié)構(gòu)有序性達到最高,其結(jié)構(gòu)有序性、微晶尺寸以及堆垛高度相比于鋯含量為零的前驅(qū)體的陶瓷產(chǎn)物分別提高了57%、133%和22.3%。由于熱解過程中ZrO2顆粒的強化作用以及Zr C鍵的連接作用,所得到的陶瓷產(chǎn)物致密,無明顯的孔洞裂紋等缺陷,且陶瓷顆粒明顯細化,均勻地分布在碳基體中。(2)高溫熱處理不同鋯含量的ZrC陶瓷前驅(qū)體,得到了鋯含量分別約為0、11、18和27 wt%的ZrC C陶瓷產(chǎn)物。鋯含量對陶瓷產(chǎn)物熱解碳的微觀結(jié)構(gòu)具有較大影響:隨著鋯含量的增加,鋯原子的催化石墨化作用增強,熱解碳的結(jié)構(gòu)有序性、晶化度、晶粒生長程度以及石墨化度均得到了顯著改善;但是鋯含量過高時(鋯含量為27 wt%),熱解碳的結(jié)構(gòu)有序性、晶化度以及晶粒生長速度反而下降。此外,引入了鋯的陶瓷產(chǎn)物熱解碳的石墨化碳含量相比于引入前提高了約6倍,然而隨著鋯含量的增加,石墨化碳的含量變化不大。(3)在合成碳化鋯陶瓷前驅(qū)體的基礎上,利用正硅酸乙酯與氧氯化鋯的水解縮聚反應,可同時將Si和Zr引入到聚合物分子結(jié)構(gòu)中,制備出SiC/ZrC復相陶瓷前驅(qū)體PSZC。800℃時,PSZC陶瓷轉(zhuǎn)化完成,殘?zhí)悸蕿?0%,陶瓷產(chǎn)物為芳香碳、SiO2和ZrO2;升高溫度至1500℃,SiC優(yōu)先形成且轉(zhuǎn)化完全,隨后ZrO2與C在更高溫度下通過碳熱還原反應逐步轉(zhuǎn)化為ZrC;1900℃熱處理后可得到高度晶化的ZrC SiC C陶瓷相,陶瓷相致密,沒有明顯的孔洞裂紋等缺陷,ZrC和SiC陶瓷顆粒平均尺寸約100nm,均勻地分布在碳基體中。(4)以苯酚、甲醛、八水氧氯化鋯、硼酸和乙酰丙酮為原料,利用硼酸和氧氯化鋯的水解縮聚反應,成功制備出了Zr B_2/ZrC復相陶瓷前驅(qū)體PBZC。800℃時,PBZC陶瓷轉(zhuǎn)化完全,殘?zhí)悸蕿?0%,陶瓷產(chǎn)物為芳香碳、B_2O3和ZrO2;由于ZrB_2的生成反應吉布斯自由能較低且熱穩(wěn)定性優(yōu)于ZrC,因而,當熱處理溫度升高到1500℃時,ZrB_2在反應體系中優(yōu)先生成,當B_2O3耗盡時,未反應的ZrO2和C發(fā)生碳熱還原反應逐步生成ZrC陶瓷。1800℃熱處理后,可得到高度晶化的ZrB_2 ZrC C陶瓷相,其中ZrC和ZrB_2陶瓷顆粒尺寸約200 nm,均勻地鑲嵌在碳基體中。(5)結(jié)合PSZC和PBZC的合成工藝,成功制備出了SiC/ZrB_2/ZrC三元復相陶瓷前驅(qū)體PBSZ。800℃時,PBSZ陶瓷轉(zhuǎn)化完全,殘?zhí)悸蕿?7%,陶瓷產(chǎn)物為芳香碳、B_2O3、SiO2和ZrO2;當熱處理溫度高于1600℃時,可得到高度晶化的SiC ZrB_2 ZrC C陶瓷相。對PBSZ作1800℃熱處理,可原位生長出平均直徑約2μm的SiC晶須且均勻地分散在高度晶化的ZrB_2 ZrC C陶瓷相周圍,其中ZrC和ZrB_2的顆粒尺寸約200 nm,均勻鑲嵌在碳基體中;進一步升高熱處理溫度到1900℃,直徑約500 nm的SiC晶須均勻地生長在ZrB_2/ZrC/C陶瓷相基體表面,形成一種致密連續(xù)的包裹形貌,同時ZrC和ZrB_2的顆粒尺寸約500 nm,均勻鑲嵌在碳基體中。
[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，

本文編號：2505977