| The bonding technology has been used in various fields because it has the ability to overcome the defects effectively such as the stress concentration,the mismatch of coefficient of thermal expansion and the low bonding strength of traditional technology. The inorganic adhesive for high temperature has a broad prospect of application due to the excellent performance at high temperature, low curing contraction rate, durability, low cost, environment friendly, simple preparation process and easily to be used. In our study, the Al(H2PO4)3 and sodium silicate were selected as the adhesives matrix respectively, and B4C, Al2O3, A1(OH)3, SiO2 and homemade ZrSiO4 were used as the fillers to prepare the adhesives for high temperature. The influences of curing agents, fillers and their concentrations on the bonding performance of adhesives were investigated. The bonding strength was characterized by the compressive shear strength test. The thermal performance was studied by TG-DTA. The phase compositions, microstructures and elemental distribution were analyzed by XRD, SEM and EDS, respectively. And the mechanism was discussed. The results indicate that:1. ZrSiO4 was synthesized by sol-gel method at 1500℃. But it was only at 1200℃ to obtain the crystallinity ZrSiO4 with yield of 91% by adding the catalysts. According to the mechanism, Fe3+ cations enter into the ZrSiO4 structure to replace part of the Si4+, resulting in the vacancies which accelerate the diffusion of Si4+. This is the main factor affecting the formation of ZrSiO4, and the synthesis temperature can be reduced by promoting crystallization in this way.2. A phosphate adhesive was prepared by using Al(H2PO4)3 as adhesive matrix, CuO as curing agent, Al2O3, B4C, Cr2O3 and Si as fillers. The products were applied for Al2O3 ceramics bonding. The shear strength was measured to be 11.23MPa after heating treatment at 200℃, and reached to the maximum value with 27.04MPa at 600℃. It was still to have the 23.83MPa when the heating temperature rose to 1000℃. The shear strength could be increased from 11.59MPa to 14.56MPa at 1200℃ owing to adding ZrSiO4 as a filler.3. The phosphate adhesive added by Al(OH)3 as a filler was prepared and used to bond Al2O3 ceramics bonding. The shear strength was obtained with 7.62MPa after heating treatment at 200℃, and it reached to 10.56MPa at 1000℃. After been heating at 1200℃, the maximum value of the shear strength was referred to be 14.85MPa.4. The silicate adhesive was fabricated by using sodium silicate as adhesive matrix, SiO2 as curing agent, and Al2O3 as filler. It was applied for Al2O3 ceramics bonding. The highest value of the shear strength was related to 12.18MPa after heating at 200℃, and it was kept to 7.13MPa when the temperature rose to 1200℃.After adding ZrSiO4 as a filler, the shear strength can be increased to 7.79MPa and 7.89MPa at 1000℃ and 1200℃ respectively. However, it was reached to 33.20MPa at 1200℃ after adding Cu as fillers.5. Mechanism analysis indicated that B4C and Si can improve the shear strength of phosphate adhesive at high temperatures, furthermore Al(OH)3 can increase the shear strength of phosphate adhesive because of the formation of mullite ceramic. Cr2O3 can increase the mutual diffusion of the element between the ceramic bonding and adhesive matrix, and the shear strength can be enhanced.6. Adding Cu can improve the expansion coefficient of silicate adhesive and reduce the thermal stress between the adhesive matrix and the metal bonding. Meanwhile the ceramic and glass structure were formed when heating at high as 1200℃, leading to improve the shear strength of adhesive. This phenomena was carried out by adding ZrSiO4 as a filler, resulting to increase the shear strength. |
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