针对纳米ZnO在制备以及使用的过程中极易发生团聚从而影响其抗菌性能这一缺点,设计实验使得纳米ZnO在溶胶凝胶过程中与多孔SiO2进行复合。通过扫描电子显微镜(Scanning electron microscope, SEM)以及透射电子显微镜(Transmission elect...针对纳米ZnO在制备以及使用的过程中极易发生团聚从而影响其抗菌性能这一缺点,设计实验使得纳米ZnO在溶胶凝胶过程中与多孔SiO2进行复合。通过扫描电子显微镜(Scanning electron microscope, SEM)以及透射电子显微镜(Transmission electron microscopy, TEM)等可以发现,ZnO很好地复合在多孔SiO2的骨架上并且分散得较为均匀。通过表面积测试(Brunner-emmet-teller measurement, BET)以及光致发光光谱(Photoluminescence spectrum,PL)的测试可以发现,复合材料的比表面积得到提高且光学性能加强。通过菌落计数法探究复合材料与单组分纳米ZnO的抗菌性能差异以及复合材料中纳米ZnO含量的变化导致的抗菌性能的变化。结论证明,当纳米ZnO与多孔SiO2进行复合之后,材料的抗菌性能得到了极大的提高,抑菌率超过了99%。展开更多
航空级超细玻璃纤维是一种无机质纤维,具有体积密度小、热导率彽、保温绝热、吸音性能好、耐腐蚀以及化学性能稳定等优点,是大型客机保温隔音的关键材料。本文通过火焰喷吹法制备出航空级超细玻璃纤维,并涂覆酚醛树脂黏结剂,在获得优异...航空级超细玻璃纤维是一种无机质纤维,具有体积密度小、热导率彽、保温绝热、吸音性能好、耐腐蚀以及化学性能稳定等优点,是大型客机保温隔音的关键材料。本文通过火焰喷吹法制备出航空级超细玻璃纤维,并涂覆酚醛树脂黏结剂,在获得优异憎水性能的同时还具有优异的阻燃性能。然后采用扫描电镜（Scanning electron microscope,SEM）、光学显微镜、导热分析仪、驻波管以及接触角测试仪分别对棉毡的结构、声学性能以及憎水性能进行测试,结果表明：纤维直径在1.2~3.2μm之间呈正态分布,棉毡的接触角为142°,憎水性能高达98.9%,阻燃性能优异且无滴落现象;棉毡隔音隔热性能优良,随着棉毡的容重增加,棉毡的导热系数降低,隔声量随之增加;层状结构的设计以及纤维直径的超细化有利于提高棉毡的保温隔音性能。展开更多
Continuous oxide fiber/oxide matrix composites are attractive for use as high temperature structural materials. As SiO2 has good ablation-resistant property and high temperature dielectric property, it is an ideal pro...Continuous oxide fiber/oxide matrix composites are attractive for use as high temperature structural materials. As SiO2 has good ablation-resistant property and high temperature dielectric property, it is an ideal protective material for missile and antenna window. At present, 3D SiO2 matrix composites reinforced by silica fibers and high Si-O fibers are manufactured by impregnating the preform in colloidal aqueous silica sol repeatedly and then by sintering; C fiber reinforced SiO2 matrix composites are processed by infiltration of silica slurry and then hot-pressing. It is well known that CVI （Chemical Vapor Infiltration） is a near-net-shape and flexible process, which can be applied to preforms of complex and different shape. However, to our best knowledge, CVI has not been used to manufacture fiber-reinforced SiO2 matrix composites. In this article, APCVI （Atmospheric Pressure Chemical Vapor Infiltration） was used to manufacture Nextel 480/silica composites. The Nextel 480 fiber is a boria rich mullite composition containing 70wt%alumina, SiO228wt%silica, and 2wt%boria. TEOS （Tetra ethyl ortho silicate） was used as precursor. Argon was used as carrier gas. The phases were detected by X-ray diffractometer （XRD, Rigaku D/MAX-3C）. The microstructures were examined by scanning electron microscopy （SEM, JEOL JXA-840）. Fig.1 shows the relation of deposition rate versus deposition temperature for two different diameters of deposition furnace. The deposition rate was determined by weighing the samples before and after deposition. The results indicate that the deposition rate of silica increases with increasing temperature in the range of 400～750℃ and decreases with increasing temperature in the range of 750850℃. We found that the sample deposited at 750℃ had a smooth surface and the single filament fiber was clearly seen by SEM （Fig.2（a））. But the surface of another sample deposited at 800℃ was rough due to the piling up of SiO2 powder, which was very weakly bonded with the fiber preform and dropped easily even when lightly touched （Fig.2（b））. The transitional products of TEOS at 750℃ are liquid phase, which adheres to the fiber surface and keeps on decomposing to form the core of silica and ultimately solid silica results. Both the surface of the transitional liquid phase products and the fiber surfaces are well wetted, the bonding among silica particles formed after complete decomposition is strong and the silica surface is homogeneous and smooth. When the deposition temperature is 800℃, the solid silica is formed directly from vapor phase; the piling up of SiO2 powders on the surface of the preform made it very difficult for subsequent vapor to infiltrate and caused low deposition rate. The relatively lower temperature of 750℃ is the key in CVI processing. Fig.1 shows that the deposition rate is also dramatically affected by the inner diameter of deposition reactor. When the inner diameter decreases, the deposition rate increases, other deposition conditions being the same. The deposition rate in 12 mm-inner-diameter reactor is twice as high as that in 17 mm-inner-diameter reactor at 750℃. It indicates that the deposition process is controlled by mass transfer, which can create homogeneous and smooth film and is beneficial to fabricating fiber-reinforced silica matrix composites. Fig.3 shows the microstructure of the cross-sectional surface of the composites fabricated under the following conditions: carrier gas 400ml/min, TEOS 50℃, deposition temperature 750℃ and deposition time 60h. The silica coating is about 2.4 μm in thickness and the deposition rate is about 0.04μm per hour. It is found that each fiber is surrounded homogeneously by silica matrix and there are no cracks on the surface of the silica matrix. It indicates that good thermal match exists between the Nextel 480 fibers and silica matrix and that consequently high temperature or thermal shock produces only very small thermal stresses in the as-fabricated composites; thus life of the composites is prolonged. Fig.4 shows the XRD展开更多
文摘针对纳米ZnO在制备以及使用的过程中极易发生团聚从而影响其抗菌性能这一缺点,设计实验使得纳米ZnO在溶胶凝胶过程中与多孔SiO2进行复合。通过扫描电子显微镜(Scanning electron microscope, SEM)以及透射电子显微镜(Transmission electron microscopy, TEM)等可以发现,ZnO很好地复合在多孔SiO2的骨架上并且分散得较为均匀。通过表面积测试(Brunner-emmet-teller measurement, BET)以及光致发光光谱(Photoluminescence spectrum,PL)的测试可以发现,复合材料的比表面积得到提高且光学性能加强。通过菌落计数法探究复合材料与单组分纳米ZnO的抗菌性能差异以及复合材料中纳米ZnO含量的变化导致的抗菌性能的变化。结论证明,当纳米ZnO与多孔SiO2进行复合之后,材料的抗菌性能得到了极大的提高,抑菌率超过了99%。
文摘航空级超细玻璃纤维是一种无机质纤维,具有体积密度小、热导率彽、保温绝热、吸音性能好、耐腐蚀以及化学性能稳定等优点,是大型客机保温隔音的关键材料。本文通过火焰喷吹法制备出航空级超细玻璃纤维,并涂覆酚醛树脂黏结剂,在获得优异憎水性能的同时还具有优异的阻燃性能。然后采用扫描电镜（Scanning electron microscope,SEM）、光学显微镜、导热分析仪、驻波管以及接触角测试仪分别对棉毡的结构、声学性能以及憎水性能进行测试,结果表明：纤维直径在1.2~3.2μm之间呈正态分布,棉毡的接触角为142°,憎水性能高达98.9%,阻燃性能优异且无滴落现象;棉毡隔音隔热性能优良,随着棉毡的容重增加,棉毡的导热系数降低,隔声量随之增加;层状结构的设计以及纤维直径的超细化有利于提高棉毡的保温隔音性能。
文摘Continuous oxide fiber/oxide matrix composites are attractive for use as high temperature structural materials. As SiO2 has good ablation-resistant property and high temperature dielectric property, it is an ideal protective material for missile and antenna window. At present, 3D SiO2 matrix composites reinforced by silica fibers and high Si-O fibers are manufactured by impregnating the preform in colloidal aqueous silica sol repeatedly and then by sintering; C fiber reinforced SiO2 matrix composites are processed by infiltration of silica slurry and then hot-pressing. It is well known that CVI （Chemical Vapor Infiltration） is a near-net-shape and flexible process, which can be applied to preforms of complex and different shape. However, to our best knowledge, CVI has not been used to manufacture fiber-reinforced SiO2 matrix composites. In this article, APCVI （Atmospheric Pressure Chemical Vapor Infiltration） was used to manufacture Nextel 480/silica composites. The Nextel 480 fiber is a boria rich mullite composition containing 70wt%alumina, SiO228wt%silica, and 2wt%boria. TEOS （Tetra ethyl ortho silicate） was used as precursor. Argon was used as carrier gas. The phases were detected by X-ray diffractometer （XRD, Rigaku D/MAX-3C）. The microstructures were examined by scanning electron microscopy （SEM, JEOL JXA-840）. Fig.1 shows the relation of deposition rate versus deposition temperature for two different diameters of deposition furnace. The deposition rate was determined by weighing the samples before and after deposition. The results indicate that the deposition rate of silica increases with increasing temperature in the range of 400～750℃ and decreases with increasing temperature in the range of 750850℃. We found that the sample deposited at 750℃ had a smooth surface and the single filament fiber was clearly seen by SEM （Fig.2（a））. But the surface of another sample deposited at 800℃ was rough due to the piling up of SiO2 powder, which was very weakly bonded with the fiber preform and dropped easily even when lightly touched （Fig.2（b））. The transitional products of TEOS at 750℃ are liquid phase, which adheres to the fiber surface and keeps on decomposing to form the core of silica and ultimately solid silica results. Both the surface of the transitional liquid phase products and the fiber surfaces are well wetted, the bonding among silica particles formed after complete decomposition is strong and the silica surface is homogeneous and smooth. When the deposition temperature is 800℃, the solid silica is formed directly from vapor phase; the piling up of SiO2 powders on the surface of the preform made it very difficult for subsequent vapor to infiltrate and caused low deposition rate. The relatively lower temperature of 750℃ is the key in CVI processing. Fig.1 shows that the deposition rate is also dramatically affected by the inner diameter of deposition reactor. When the inner diameter decreases, the deposition rate increases, other deposition conditions being the same. The deposition rate in 12 mm-inner-diameter reactor is twice as high as that in 17 mm-inner-diameter reactor at 750℃. It indicates that the deposition process is controlled by mass transfer, which can create homogeneous and smooth film and is beneficial to fabricating fiber-reinforced silica matrix composites. Fig.3 shows the microstructure of the cross-sectional surface of the composites fabricated under the following conditions: carrier gas 400ml/min, TEOS 50℃, deposition temperature 750℃ and deposition time 60h. The silica coating is about 2.4 μm in thickness and the deposition rate is about 0.04μm per hour. It is found that each fiber is surrounded homogeneously by silica matrix and there are no cracks on the surface of the silica matrix. It indicates that good thermal match exists between the Nextel 480 fibers and silica matrix and that consequently high temperature or thermal shock produces only very small thermal stresses in the as-fabricated composites; thus life of the composites is prolonged. Fig.4 shows the XRD
