【作者】 陆有军；

【导师】 王燕民；

【作者基本信息】 华南理工大学 ， 材料学， 2014， 博士

【摘要】 陶瓷基复合材料（Ceramic Matrix Composite，简记为CMC）是以陶瓷材料为基体，以陶瓷纤维、晶须、晶片或颗粒为补强体，通过适当的复合工艺制备的、性能可设计的一类新型材料。本论文将碳纳米颗粒与碳化硅复合制备的碳颗粒/碳化硅陶瓷基复合材料，有效地改善碳化硅陶瓷的机械加工性能，并将其应用于玻璃夹具、模具材料，提高了使用寿命，具有一定的强度和硬度，且使该材料不与高温玻璃熔体发生粘接。本论文第一章首先综述C/SiC陶瓷基复合材料的研究现状及应用前景，归结了制备C/SiC陶瓷基复合材料的现代技术，其中主要是碳纤维增强的碳化硅（Cf/SiC）陶瓷基复合材料的制备技术。虽然，Cf/SiC陶瓷基复合材料各方面性能的研究较为成熟，然而，在C/SiC陶瓷基复合材料的未来工业领域，考虑到制备成本，可选用碳颗粒/碳化硅（Cp/SiC）陶瓷基复合材料。还阐述了机械力化学法合成复相陶瓷粉体材料是一种具有广阔应用前景的复相陶瓷材料制备方法，采用该方法制备在常规高温、高压条件下难以制备的特种陶瓷颗粒材料。同时，重点描述了机械力化学法制备陶瓷颗粒的原理和理论基础及其研究进展。另外，给出了本论文的研究目标和研究内容。论文第二章根据机械力化学反应机理、采用常温下机械力化学方法原位制备Cp/SiC复合粉体，探讨了机械力化学法原位合成复合粉体的复合机理。采用现代表征方法（如X光衍射、热重和差热分析、扫描电镜和透射电镜等）对制备的样品进行了表征。另外，还分析和研究了不同的合成参数（如球料比、研磨时间、研磨方式等）对合成β-SiC以及后续原位复合得到Cp/SiC复合粉体性质的影响。研究结果表明，采用优化机械力化学合成参数，可有效地合成β-SiC并与多余碳纳米颗粒原位复合得到Cp/SiC的复合粉体。论文第三章研究了采用喷雾造粒的方法以机械力化学原位合成Cp/SiC复合粉体为原料制备类球形Cp/SiC复合颗粒，并探讨了影响喷雾造粒过程的主要因素。另外，还研究了分散剂种类、分散剂用量、搅拌时间以及碳纳米颗粒含量等参数对合成Cp/SiC复合粉体在水介质中的分散性能的影响。结果表明，对Cp/SiC复合粉体固含量为45wt%的分散浆料采用喷雾造粒方法可有效地制得适宜的类球形实心Cp/SiC复合颗粒。论文第四章研究了采用无压烧结的方法制备不同碳纳米颗粒含量（即，5wt%、10wt%、15wt%和25wt%）的碳化硅陶瓷基复合材料，探讨了无压烧结Cp/SiC复合陶瓷的烧结致密化机理，以及碳纳米颗粒含量对复合陶瓷的力学性能的影响。结果表明，添加碳纳米颗粒的碳化硅陶瓷基复合材料的无压烧结致密化机理与SiC陶瓷的无压烧结机理是一致的，即，烧结初期，膨胀机制占主导；烧结中期，收缩机制占主导，并抵消膨胀机制的作用；烧结终结前，膨胀机制略占主导。同时，随着碳纳米颗粒含量的增加，碳纳米颗粒/碳化硅陶瓷基复合材料的弯曲强度逐渐降低，显气孔率逐渐增大，硬度逐渐降低，但断裂韧性先增大后减小，并在碳纳米颗粒为15wt%时达到了极大值（2.58MPa·m1/2）。当碳纳米颗粒含量为0～15wt%时，陶瓷基复合材料的烧失率控制在5～6%之间。当碳纳米颗粒含量超过15wt%时，烧失率急剧增大，当碳纳米颗粒含量为25wt%时，其烧失率达到18%以上。论文第五章研究了Cp/SiC复合陶瓷材料的氧化行为和抗热震性。结果表明，在400～700℃之间，Cp/SiC复合陶瓷在空气中的氧化过程受C-O2反应控制，呈均匀氧化，其显气孔率随氧化温度的升高而增加，弯曲强度随氧化温度增加而降低，当达到700℃时，为极小值；在700～1000℃之间，氧化过程受O2的气相扩散和O2通过微裂纹的扩散控制，可形成SiO2相。随温度增高，其显气孔率降低，弯曲强度增加，在1000℃时达到极大值；在1000～1100℃之间，O2通过SiC缺陷的扩散控制着复合陶瓷材料的氧化过程，显气孔率增加，弯曲强度降低。同时，随着碳纳米颗粒含量的增加，碳纳米颗粒大量聚集在晶界处，重复冷热循环容易降低复合材料的强度，出现裂纹的几率增大，抗热震性变差。因此，氧化温度和碳纳米颗粒含量是影响Cp/SiC复合陶瓷材料强度及氧化行为和抗热震性的关键因素。论文第六章研究了碳纳米颗粒含量对Cp/SiC陶瓷的机械加工性能。结果表明，添加在Cp/SiC陶瓷中并均匀分布在SiC晶界处的碳纳米颗粒可改善Cp/SiC陶瓷的机械加工性能。但是，当添加的碳纳米颗粒含量超过15wt%时，材料内部形成了网络孔洞结构，导致其陶瓷材料致密度急剧降低。另外，依据采用机械加工速度V、机械加工性指数M、脆性指数B及可加工性能参数n综合评价Cp/SiC陶瓷的机械加工性能可知，当碳纳米颗粒含量为15wt%时，极大值Mmax为0.921，极小值Bmin为1.09，可加工性能参数极大值nmax为+0.342，这表明碳纳米颗粒含量为15wt%的Cp/SiC陶瓷具有良好的机械加工性能。论文第七章采用此复合材料制备了玻璃夹具，并给出了实际应用结果。另外，经润湿性实验测试表明，当碳纳米颗粒含量为或大于15wt%时，Cp/SiC陶瓷基复合材料在1000℃以下与玻璃熔体不发生粘结，润湿性差。此时在复合材料中的碳纳米颗粒先于SiC基体氧化，抑制了基体表面SiO2膜的生成，从而有效地降低了基体与玻璃熔体的粘结和润湿效应，以达到适用作玻璃夹具材料的不粘结性质。最后，给出了通过研究所获得的论文结论以及今后工作的展望。更多还原

【Abstract】 Ceramic matrix composite (CMC) is one of advanced inorganic materials composed ofceramic substrate and reinforcing body such as ceramic fiber, whisker, chips or particles,which is prepared through developed composite technologies in recent years. In this thesis,carbon nanoparticles/silicon carbide (Cp/SiC) ceramic matrix composites (Cp/SiC-CMC) wereprepared as a promising material of glass fixtures in glass processing. The Cp/SiC-CMC canbe used as glass fixtures and mold materials due to the improved machinability, appropriatemechanical strength/hardness and unbonding with high-temperature glass melts.In Chapter1, recent development on the preparation and application of C/SiC-CMC wasreviewed. The existing preparation methods for carbon fiber reinforced silicon carbide(Cf/SiC) CMC were represented. Besides Cf/SiC-CMC, carbon nanoparticle (Cp) reinforcedSiC CMC can be used as a promising material instead of Cf/SiC-CMC due to the lowpreparation cost. In addition, a mechanochemical method for the preparation of ceramicand/or composite powders was also introduced. The mechanochemical method can be used toprepare some special ceramic materials that were commonly produced under high temperatureand/or high pressure conditions. The corresponding principle and theory of mechanochemicalmethod for the preparation of ceramic particles were described. In this chapter, the researchobjectives and contents of the thesis were given.In Chapter2, a carbon-silicon carbide (Cp/SiC) composite powder was prepared withnano-carbon (Cp) and silicon (Si) powders as starting materials via a mechanochemicaltreatment in Ar atmosphere in a dry stirred ball mill. The composite powder was characterizedby X-ray diffraction (XRD), thermogravimetry/differential scanning calorimetry (TG/DSC),scanning electron microscopy (SEM) and transmission electron microscopy/high resolutiontransmission microscopy (TEM/HRTEM). Effects of parameters (such as grinding time, ratioof ball to powder, grinding mode and atmosphere) on the synthesis of β-SiC particles, and the simultaneous preparation of Cp/SiC composite powder with the synthesized particles of β-SiCand the remaining Cpby the mechanochemical treatment were investigated. The results showthat β-SiC particles can be synthesized and the Cp/SiC composite powder in the presence ofexcessive nano-sized carbon can be simultaneously obtained via the mechanochemical route.In Chapter3, sphaeroid particles of Cp/SiC composite were fabricated with awell-dispersive aqueous slurry of Cp/SiC composite powder by a spray granulation technique.The parameter influences on the spray granulation process were investigated. In addition, theeffects of dispersant type, dispersant amount, stirring rate and carbon nanoparticle content onthe dispersibility of the aqueous slurry of Cp/SiC composite powder before the spraygranulation were also analyzed. The results show that the sphaeroid Cp/SiC compositeparticles can be effectively obtained with the well-dispersive aqueous slurry by the spraygranulation technique.In Chapter4, Cp/SiC-CMC with different contents of carbon nanoparticles (i.e.,5wt%,10wt%,15wt%and25wt%) was prepared by pressureless sintering. The densificationmechanism of Cp/SiC-CMC by pressureless sintering was discussed. The influence of carbonnanoparticles content on the mechanical properties of Cp/SiC-CMC was investigated. Theexperimental results reveal that the densification mechanism of Cp/SiC-CMC with carbonnanoparticles by pressureless sintering is consistent with that of pure SiC ceramic，i.e., theexpansion mechanism is dominant at the initial stage of sintering, the shrinkage mechanismbecomes dominant and offsetsagainst the expansion mechanism at the middle stage and theexpansion mechanism is slightly dominant before the end of sintering. It was also indicatedthat the bending strength and the hardness of Cp/SiC-CMC decrease andthe apparent porosityincreases with increasing carbon nanoparticle content in Cp/SiC-CMC. However, the fracturetoughness firstly increases and then decreases with increasing the nanoparticle content, givingan optimum value of2.58MPa·m1/2at the nanoparticle content of15wt%. When thenanoparticle content is in the range of0～15wt%, the ignition loss of Cp/SiC-CMC is5～6%. The ignition loss increases sharply atthe nanoparticle content of>15wt%, and becomes>18%at the content of25wt%.In Chapter5, the oxidative behavior and thermal shock resistance of Cp/SiC-CMC wereinvestigated. The results show that the oxidation of Cp/SiC-CMC in air atmosphere iscontrolled via the reaction of C-O2at400～700℃, exhibiting a homogeneous oxidation. Theapparent porosity of Cp/SiC-CMC increasesand the bending strength decreaseswith increasingthe oxidation temperature. The bending strength becomes minimum at700℃; At700～1000℃, the oxidation is controlled via the O2diffusion, and O2diffusion through themicrocracksleads to the formation of SiO2phase. The apparent porosity decreases and thebending strength increases with increasing the temperature. The bending strengthis maximumat1000℃; At1000～1100℃, the oxidation is controlled by the O2diffusion through thedefects of SiC. The apparent porosity increases and the bending strength decreases withincreasing the temperature. Also, since there exist massive carbon nanoparticles in the SiCgrain boundaries when the carbon nanoparticle content increases, readily causing the increaseof the crack probability inthe repeated psychro-thermal cycles,the strength andthe thermalshock resistance of the composite material thus reduce.It was indicated that the oxidationtemperature and carbon nanoparticle content both have effects on the strength, oxidationbehavior and thermal shock resistance of Cp/SiC-CMC.In Chapter6, the influence of carbon nanoparticle content on the machinability ofCp/SiC-CMC was investigated. The results show that the machinability of Cp/SiC-CMC canbe improved due to the presence of carbon nanoparticles evenly distributed through the SiCgrain boundary in Cp/SiC-CMC. However, the net-like hole structure in Cp/SiC-CMC canappear at carbon nanoparticle content of>15wt%, resulting in the decrease of the density ofCp/SiC-CMC. According to the evaluation of the machinability by machining speed V,machinability index M，brittleness index B and malleability parameter n, the maximummachinability index (Mmax) is0.921and the minimum brittleness index (Bmin) is1.09, and themaximum malleability parameter (nmax) is+0.342when the content of carbon nanoparticles is15wt%, showing a proper machinability of Cp/SiC-CMC with carbon nanoparticle content of 15wt%.In Chapter7, the preparation process and the practical application of Cp/SiC-CMC usedas glass fixtures were investigated.In addition, the wettability of Cp/SiC-CMC was also examined. The results show thatCp/SiC-CMC does not bond with molten glass at <1000℃when carbon nanoparticle content is≥15wt%, exhibiting a poor wettability. In this case, carbon nanoparticles are oxidized prior toSiC substrate, inhibiting the formation of SiO2film on the surface of substrate and thuspreventing the wetting effect between the substrate and molten glass, which can favor theapplication of Cp/SiC-CMC for glass fixtures.Finally, the conclusions obtained and some prospects for future research work weregiven.更多还原