The microstructure and surface state of three kinds of polyacrylonitrile-based carbon fibers （T700, T300 and M40） before and after high temperature treatment were investigated. Also, the pyrocarbon and thermal condu...The microstructure and surface state of three kinds of polyacrylonitrile-based carbon fibers （T700, T300 and M40） before and after high temperature treatment were investigated. Also, the pyrocarbon and thermal conductivity of carbon/carbon composites with different carbon fibers as preform were studied. The results show that M40 carbon fiber has the largest crystallite size and the least d002, T300 follows, and TT00 the third. With the increase of heat treatment temperature, the surface state and crystal size of carbon fibers change correspondingly. M40 carbon fiber exhibits the best graphitization property, followed by T300 and then T700. The different microstructure and surface state of different carbon fibers lead to the different microstructures of pyrocarbon and then result in the different thermal conductivities of carbon/carbon composites. The carbon/carbon composite with M40 as preform has the best microstructure in pyrocarbon and the highest thermal conductivity.展开更多
Coir fiber is derived from the coconut shells and considered to be an economical and natural material. In order to further extend its application fields,the geometry and microstructure of the coir fiber were thoroughl...Coir fiber is derived from the coconut shells and considered to be an economical and natural material. In order to further extend its application fields,the geometry and microstructure of the coir fiber were thoroughly investigated in this research. The single fiber length measurement was carried out,and it was revealed that the length of the coir fiber was between 8 and 337 mm. Length distribution of the coir fiber was simulated by using the computer technology,and was found to be in coincidence with that of most natural fibers. The grouping measurement analysis was used to study the length-weight distribution and length-linear density distribution of the fiber. It was found that the average linear density was 27.89 tex and the linear density was between 18.265 and 70.442 tex. The length-weight distribution of the coir fiber showed a Poisson pattern,and the weight of fibers with the length between 50 and 230 mm accounted for 85.28% of the total fibers measured. In this research,scanning electron microscope (SEM) was applied to observe the morphological changes of coir fiber before and after alkali treatment;and the result shows that alkali treatment leads to the removal of lignin and pectin from both the cuticle and the inside walls,which is beneficial for the interfacial adhesion with polymer matrix in composite fabrication.展开更多
NiO-In2O3 composite nanofibers are synthesized via electrospinning and calcining techniques. Micro-sensors are fabricated by sputtering Pt electrodes on Si chips to form sensor substrates, and then spinning the NiO-In...NiO-In2O3 composite nanofibers are synthesized via electrospinning and calcining techniques. Micro-sensors are fabricated by sputtering Pt electrodes on Si chips to form sensor substrates, and then spinning the NiO-In2O3 composite nanofibers onto the sensor substrate surface. The as-fabricated micro-sensors exhibit excellent H2S sensing properties at room temperature. The sensi- tivity of the micro-sensors is up to 6 when the sensors are exposed to 3 μL/L HzS, and the corresponding response and recovery times are 14 and 22 s, respectively. The micro-sensors also exhibit high selectivity and good stability. Especially, the micro-sensors can operate at various humidity conditions. The sensitivity of the micro-sensors is 3.8 to 3 μL/L HzS at 75% relative humidity. These characteristics make the micro-sensors good candidates for practical H2S sensors with high performance.展开更多
基金Project(201012200233)supported by the Freedom Explore Program of Central South University,China
文摘The microstructure and surface state of three kinds of polyacrylonitrile-based carbon fibers （T700, T300 and M40） before and after high temperature treatment were investigated. Also, the pyrocarbon and thermal conductivity of carbon/carbon composites with different carbon fibers as preform were studied. The results show that M40 carbon fiber has the largest crystallite size and the least d002, T300 follows, and TT00 the third. With the increase of heat treatment temperature, the surface state and crystal size of carbon fibers change correspondingly. M40 carbon fiber exhibits the best graphitization property, followed by T300 and then T700. The different microstructure and surface state of different carbon fibers lead to the different microstructures of pyrocarbon and then result in the different thermal conductivities of carbon/carbon composites. The carbon/carbon composite with M40 as preform has the best microstructure in pyrocarbon and the highest thermal conductivity.
基金Tianjin Universities Science and Technology Development Fund Project ,China (No.20041401)
文摘Coir fiber is derived from the coconut shells and considered to be an economical and natural material. In order to further extend its application fields,the geometry and microstructure of the coir fiber were thoroughly investigated in this research. The single fiber length measurement was carried out,and it was revealed that the length of the coir fiber was between 8 and 337 mm. Length distribution of the coir fiber was simulated by using the computer technology,and was found to be in coincidence with that of most natural fibers. The grouping measurement analysis was used to study the length-weight distribution and length-linear density distribution of the fiber. It was found that the average linear density was 27.89 tex and the linear density was between 18.265 and 70.442 tex. The length-weight distribution of the coir fiber showed a Poisson pattern,and the weight of fibers with the length between 50 and 230 mm accounted for 85.28% of the total fibers measured. In this research,scanning electron microscope (SEM) was applied to observe the morphological changes of coir fiber before and after alkali treatment;and the result shows that alkali treatment leads to the removal of lignin and pectin from both the cuticle and the inside walls,which is beneficial for the interfacial adhesion with polymer matrix in composite fabrication.
基金supported by the Special Fund for Agroscientific Research in the Public Interest of China(200903023)the Earmarked Fund for Modern Agroindustry Technology Research System of China([2011]3)the Guangdong Agricultural Mechanization Research Project([2010]605)
文摘NiO-In2O3 composite nanofibers are synthesized via electrospinning and calcining techniques. Micro-sensors are fabricated by sputtering Pt electrodes on Si chips to form sensor substrates, and then spinning the NiO-In2O3 composite nanofibers onto the sensor substrate surface. The as-fabricated micro-sensors exhibit excellent H2S sensing properties at room temperature. The sensi- tivity of the micro-sensors is up to 6 when the sensors are exposed to 3 μL/L HzS, and the corresponding response and recovery times are 14 and 22 s, respectively. The micro-sensors also exhibit high selectivity and good stability. Especially, the micro-sensors can operate at various humidity conditions. The sensitivity of the micro-sensors is 3.8 to 3 μL/L HzS at 75% relative humidity. These characteristics make the micro-sensors good candidates for practical H2S sensors with high performance.
