The effects of three types of electrically-inert fillers, calcium carbonate （CaCO_3）, talc and glass fiber （GF）, on electrical resistivity, crystallization behavior and dynamic mechanical properties of poly（m-xyl...The effects of three types of electrically-inert fillers, calcium carbonate （CaCO_3）, talc and glass fiber （GF）, on electrical resistivity, crystallization behavior and dynamic mechanical properties of poly（m-xylene adipamide） （MXD6）/multiwalled carbon nanotube （MWCNT） composites are investigated. The electrical resistivity of MXD6/MWCNT composites is significantly reduced with the addition of inert fillers due to the volume-exclusion effect that leads to increased effective concentration of MWCNTs in MXD6 matrix and also due to improved MWCNT dispersion. The crystallization temperature of MXD6 increases with the addition of MWCNTs, indicating that MWCNTs can act as nucleating agent and induce crystallization of MXD6. The incorporation of inert fillers has no further effect on crystallization behavior of MXD6, but significantly improves the storage modulus of MXD6/MWCNT composite, demonstrating that CaCO_3, talc and GF filled MXD6/MWCNT composites are very promising materials with not only improved electrical property but also excellent mechanical properties.展开更多
The joining of graphite, ceramic SiC and C_f/SiC composites via preceramic silicone resin(SR) at high temperature (8001400℃) was studied. The curing and pyrolysis process of SR, pyrolysis temperature, inert and a...The joining of graphite, ceramic SiC and C_f/SiC composites via preceramic silicone resin(SR) at high temperature (8001400℃) was studied. The curing and pyrolysis process of SR, pyrolysis temperature, inert and active fillers were especially discussed. The results show that the curing process of SR was accomplished by consuming Si—OH. The temperature of 1200℃ is the appropriate treating temperature for graphite and SiC ceramic, and the temperature of 1400℃ is suitable for C_f/SiC composites. Inert filler SiC powder(5%, mass fraction) has much positive influence on the shear strength of the joints. Active filler nano Ai, Si powder can greatly improve the properties of the joints treated at high temperature. The improvement is over 700%.展开更多
以聚硅氧烷为先驱体,采用先驱体转化法制备了SiCf/Si O C陶瓷复合材料。研究了惰性填料(SiC、SiO2及SiO2空心微珠)对材料的力学性能及热性能的影响。微观结构的分析表明,填料引起的界面结构与密度的变化是影响SiCf/Si O C复合材料性能...以聚硅氧烷为先驱体,采用先驱体转化法制备了SiCf/Si O C陶瓷复合材料。研究了惰性填料(SiC、SiO2及SiO2空心微珠)对材料的力学性能及热性能的影响。微观结构的分析表明,填料引起的界面结构与密度的变化是影响SiCf/Si O C复合材料性能的主要原因。展开更多
SiC-Si3N4 composite ceramics are successfully fabricated by pyrolysis of ferrocene-modified polycarbosilane(PCS) mixed with inert filler Si3N4 powders, followed by thermal treatment from 1100℃ to 1400℃ in Ar atmosph...SiC-Si3N4 composite ceramics are successfully fabricated by pyrolysis of ferrocene-modified polycarbosilane(PCS) mixed with inert filler Si3N4 powders, followed by thermal treatment from 1100℃ to 1400℃ in Ar atmosphere. The porosity of SiC-Si3N4 ceramics decreases to 6.4% due to the addition of inert filler Si3N4. And the content and crystallization degree of free carbon and SiC derived from PCS are improved simultaneously with the increase of thermal treatment temperature. Finally, the free carbon and SiC interconnect, forming the conductive network. As a result, the electromagnetic interference(EMI) shielding performance of the as-prepared ceramic annealed at 1400℃ reaches up to 36 d B, meaning more than99.9% of EM energy is shielded. The low porosity and high EMI shielding performance enable SiC-Si3N4 composite ceramics to be a promising electromagnetic shielding and structural material.展开更多
文摘The effects of three types of electrically-inert fillers, calcium carbonate （CaCO_3）, talc and glass fiber （GF）, on electrical resistivity, crystallization behavior and dynamic mechanical properties of poly（m-xylene adipamide） （MXD6）/multiwalled carbon nanotube （MWCNT） composites are investigated. The electrical resistivity of MXD6/MWCNT composites is significantly reduced with the addition of inert fillers due to the volume-exclusion effect that leads to increased effective concentration of MWCNTs in MXD6 matrix and also due to improved MWCNT dispersion. The crystallization temperature of MXD6 increases with the addition of MWCNTs, indicating that MWCNTs can act as nucleating agent and induce crystallization of MXD6. The incorporation of inert fillers has no further effect on crystallization behavior of MXD6, but significantly improves the storage modulus of MXD6/MWCNT composite, demonstrating that CaCO_3, talc and GF filled MXD6/MWCNT composites are very promising materials with not only improved electrical property but also excellent mechanical properties.
文摘The joining of graphite, ceramic SiC and C_f/SiC composites via preceramic silicone resin(SR) at high temperature (8001400℃) was studied. The curing and pyrolysis process of SR, pyrolysis temperature, inert and active fillers were especially discussed. The results show that the curing process of SR was accomplished by consuming Si—OH. The temperature of 1200℃ is the appropriate treating temperature for graphite and SiC ceramic, and the temperature of 1400℃ is suitable for C_f/SiC composites. Inert filler SiC powder(5%, mass fraction) has much positive influence on the shear strength of the joints. Active filler nano Ai, Si powder can greatly improve the properties of the joints treated at high temperature. The improvement is over 700%.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51332004, 51521061, 51602258 and 51725205)the 111 Project (B08040)
文摘SiC-Si3N4 composite ceramics are successfully fabricated by pyrolysis of ferrocene-modified polycarbosilane(PCS) mixed with inert filler Si3N4 powders, followed by thermal treatment from 1100℃ to 1400℃ in Ar atmosphere. The porosity of SiC-Si3N4 ceramics decreases to 6.4% due to the addition of inert filler Si3N4. And the content and crystallization degree of free carbon and SiC derived from PCS are improved simultaneously with the increase of thermal treatment temperature. Finally, the free carbon and SiC interconnect, forming the conductive network. As a result, the electromagnetic interference(EMI) shielding performance of the as-prepared ceramic annealed at 1400℃ reaches up to 36 d B, meaning more than99.9% of EM energy is shielded. The low porosity and high EMI shielding performance enable SiC-Si3N4 composite ceramics to be a promising electromagnetic shielding and structural material.
