Preparation And High Temperature Resistance Properties Of Silicone Resin Adhesive For Bonding Ceramic

High-temperature resistance adhesive,as a convenient and effective mean of connection,is an important part of aircraft design.With the development of space technology,the research focusing on high speed,high precision and stealth hypersonic vehicles become a hotspot.Under high Mach(>5Ma)flight conditions,aerodynamic heating causes the aircraft facing high temperature environment.Thus researches on heat-resistant adhesive in 1500? condition are of great significance to the development of hypersonic vehicle.Series of high temperature resistant adhesive(HTOA)were prepared using Tri Silanol Phenyl POSS modified Methylphenylsilicone resin(POSS-MPSR)as matrix resins,heat-resistant metal Ni particles as modified fillers and chopped carbon fiber as reinforcement.A serial of works were conducted based on engineering application and theory of HTOA including:(1)the thermal stability of POSS-MPSR,HTOA substrate high temperature reaction mechanisms and structural changes,(2)interface reaction of HTOA joints and reaction mechanism of interface self-growing Si C nanowires(Si CNWs),and(3)toughening mechanism of matrix self-growing Si CNWs and chopped carbon fiber-Si CNWs composite structures.After mixing MPSR,5% of trisilanolphenyl POSS and curing catalyst together,the hybrid POSS-MPSR was prepared through co-curing with weight loss of 9% at 1000?.This paper studied the thermal stability of POSS-MPSR resin in hot air condition.Using Zr B2,Si O2 and Si as high temperature resistance fillers,high temperature reaction mechanism of HTOA matrix,high-temperature structural evolution behavior,bonding strength and interface reaction with the Zr B2-Si Cgraphite ceramics(ZSG)were also studied.Experimental results showed that under the scouring of oxy-acetylene flame,dense Si O2 protective layer formed on the surface of HTOA,as well as the inner layer composed of Si O2,Zr O2,Zr Si O4,etc.At 1500?,reaction layers formed between HTOA and ZSG ceramics,and effective bonding with ZSG ceramic was realized under high temperature.After 1500?/1h processing,the bonding strength between HTOA and ZSG ceramic was 53.8MPa.With prolonging of heating time,the thickness of bonding interface layer increased and ZSG interface was oxidized to be a weak layer.Using Ni powder as modifier,the organizational structure and bonding strength of HTOA was studied by using different added weight of Ni powder 5 %,10% and 15%,respectively.Research results showed that at 1500?,molten Ni could effectively bridge the HTOA holes generated by high tempe rature decomposition,which further prevented oxygen diffusion to the adhesive layer,effectively reduced the partial pressure of oxygen at the interface,and changed the high temperature oxidation behavior of interface.When the nickel conte nt was 10%,after 1500?/1h processing,the shear strength of the HTOA was 36.5MPa and after 1500?/3h the shear strength retained 25.4MPa.Using Ni as catalyst,the CO(g)as carbon source and Si O(g)as the silica source which were produced by oxidation of HTOA layer and ZSG ceramic at high temperature,the self-growth of Si CNWs at interface was realized via vapor–liquid–solid(V-L-S)mechanism.The interface strength was improved due to the enhancing of the modulus and strength of adhesive layer..Since Si CNWs grew along ZSG ceramic grain boundary,when the interface was destroyed,unplug or broken of Si CNWs would consume more energy,which contributed to the improvement of the interface strength.Using graphite as modifier to further enhance toughness of HTOA at high temperature,the self-growth of Si CNWs was realized through the V-L-S mechanism,when CO(g)was generated by graphite under high temperature oxidation conditions.The influence of different treating time and different treating temperature on the morphology and shear strength of HTOA with self-growth Si CNWs was investigated in detail.It was found that with the increase of treating temperature,the diameter of Si CNWs became smaller,with the increase of heat time at 1500?,the density of Si CNWs got higher,the shear strength got higher at the temperature of 1500?.The shear strength and thermal shock resistance of HTOA with the self-growth Si CNWs were improved remarkably.(After 1500?/1h processing,the shear strength of the HTOA was 38.0MPa and after the oxygen acetylene thermal shock treatment the shear strength retained 13.6MPa,the strength retention was 35.79%.)Using chopped carbon whose surface was loaded with metal Ni as reinforcement,the mechanism of structure formation and action of chopped carbon fiber-Si CNWs hybrid structure were investigated.It was found that the chopped carbon fiber-Si CNWs hybrid structure could improve the strength and toughness of HTOA,after 1500?/1h processing,the shear strength of the HTOA was 37.0MPa and after the oxygen acetylene thermal shock treatment the shear strength retained 14.5MPa,the strength retention was 39.19%.It suggested that chopped carbon fiber-Si CNWs hybrid structure showed the optimal thermal shock resistance.