Preparation And Performance Of Ceramizable Heat-resistant And Ablation-resistance Organic Silicon Adhesive

Owing to their excellent mechanical properties, high temperature resistance,thermal shock resistance, ablation resistance and abrasive resistance, ceramic matrixcomposite and ceramic material has been widely used as ideal high temperaturestructural materials in aeronautic and astronautic fields. However, the nature ofbrittleness restricts their application in fabricating structures with large dimensionsand complex shapes. Therefore, the joining process for ceramic matrix composite andceramic material discreteness is quite essential. Drawbacks of the traditionaltechnologies are for instance high porosity,stress concentration, mismatch of thermalexpansion coefficients and the low strength at joining sites. The use of heat-resistantorganic adhesive has been one of the most convenient and promising methods forjoining ceramic materials applied at high temperature. In this paper, a novelheat-resistant and ablation resistance ceramifiable organic adhesive was prepared byusing preceramic polymer polysiloxane as matrix, organic surface modification TiB2ceramic powder and low melting point glass powder as active fillers which applied tobondAl2O3ceramic at high temperature aerobic atmosphere.In this paper, we prepared and characterized organic surface modification TiB2ceramic powder by high-energy ball mill and coupling agent KH550. Fouriertransform infrared (FTIR) analysis found that formed the organic coating layer on thesurface of modified TiB2ceramics powder. SEM results showed that the modifiedTiB2particles dispersed in the resin matrix uniformly and had a better compatibilitywith the resin. According to orthogonal experiment, the optimum parameter oforganic surface modification TiB2ceramic powder is2.5wt%coupling agent KH550,ball mill speed of300r/min and ball mill for3h. When the content of surface organicmodification of TiB2ceramics powder is40wt%, the maximum bonding strength ofadhesive is6.75MPa in room temperature.The novel heat-resistant and ablation resistance ceramifiable adhesive wasprepared by filled the modification of TiB2ceramic powder into methyl phenylsilicone resin to join Al2O3ceramic. The results of the TG-DSC showed that activefiller TiB2ceramics powder could improve the thermal stability of adhesiveperformance. When the content of active filler TiB2ceramics powder was25wt%, the initial decomposition temperature of adhesive increased from200℃to504℃,the decomposition peak temperature increased from245℃to488℃and the ceramicretention rate of the adhesive increased from70wt%to102wt%. With elevatingtemperature，the bonding strength of adhesive exhibited a remarkable decreased dueto the dehydrogenation and decomposition of organic component of adhesive. Whenthe temperature exceeds600℃, active filler TiB2activated a ceramifying reactionwith pyrolysis products released from adhesives to produce refractory ceramic phaseTiO2and glassy B2O3, leading to excellent adhesion at high temperature. The bondingstrength of adhesive after fired at1200℃was24.33MPa, increased17.58MPa thanthat of at room temperature. The results of the SEM showed that the adhesive afterfired tended to form dense ceramic structures. The ceramic structure of XRD, EDSelemental analysis and FTIR analysis indicated that the adhesive after fired wascomposed by amorphous SiO2derived from silicone as matrix, refractory ceramicTiO2particles as reinforcement, and molten B2O3glass as repairing phase.When adding glass powder as the second additive, it facilitated ceramifyingreaction to shift at lower temperature and improved the mechanical properties ofadhesives at low temperature stage. The bonding strength of adhesive unfilled fillersand filled glass frits A, glass frits B, glass frits C at400℃were0.6,2.36,1.83and1.44MPa, respectively. Microstructure analysis showed that the incorporation of glassfrits C had greater impact on the microstructure of the adhesive at800℃-1000℃,glass frits C modified adhesive after ablated was more compact and integrity thanadhesive filled with glass frits B and A. The bonding strength of glass frits Cmodified adhesive after fired at800℃,1000℃were13.79and18.25MPa, muchhigher than that of glass frits B and A. However, the effect of the glass frit B wasbetter and the bonding strength of glass frits B modified after fired at1200℃was26.58MPa. According to orthogonal experiment (L9(34)), it showed the sequence offactor effect of the bonding strength of adhesive after fired at1200℃was TiB2＞glass frits B＞glass frits A＞glass frits C. In addition, it can be seen that the optimumparameter of the content of inorganic fillers was TiB2/glass frits A/glass frits B/glassfrits C＝30/6/3/15and the maximum bonding strength was54.27MPa.