Poly(methyl methacrylate)-titania hybrid glasses were synthesized by sol-gel processes using acrylic acid or allyl acetylacetone as coupling agent. Titanium butoxide modified with acrylic acid (or titanium isopropoxid...Poly(methyl methacrylate)-titania hybrid glasses were synthesized by sol-gel processes using acrylic acid or allyl acetylacetone as coupling agent. Titanium butoxide modified with acrylic acid (or titanium isopropoxide modified with allyl acetylacetone) was hydrolyzed to produce a titania network, and then poly(methyl methacrylate) (PMMA)chains formed in situ through a radical polymerization were chendcally bonded to the fortheng titania network to synthesize a hybrid glass. Transparent hybrid glasses with different contents of titania were achieved. With the increase of the titania content, the color of the products changed from yellow to red. The synthesis process was investigated stepwise by using FTIR spectroscopies, and the experimental results demonstrated that acrylic or acetylacetonate groups bound to titanium remain in the final hybrid glasses.The thermal stability of the hybrid materials were considerably improved relative to pure PMMA. The hybrid glasses using allyl acetylacetone as coupling agent exhibited ther mochromatic effect which both pure PMMA and titan ia do not manifest.展开更多
Porous silicon (PS) fabricated by anodizing have recently become the subject of intense interest due to their room temperature visble light emission properties.However, highly porous silicon made by electrochemical et...Porous silicon (PS) fabricated by anodizing have recently become the subject of intense interest due to their room temperature visble light emission properties.However, highly porous silicon made by electrochemical etching is fragile and tends to craze during normal drying in air after taken out from HF based solution. The preparation of highly porous materials by sol-gel processing followed by supercritical drying was carried out by Kistler in 1931. Since 1985, the sucpercritical drying (SD) has been used successfully to prepare a variety of aerogels, comprising a void fraction of more than 90%. This technigue has now been applied to prepare luminescent porous silicon on both <100> and <111> C-Si substrates. Porosities up to 94% have been achieved, which were determined by gravimetric measurement. Its morphological feature, microstructure and photoluminescence properties exhibit novel characteristics from those conventionally anodized porous silicon. It has been demonstrated that anodization and supercritical drying can yield ultra-high porous luminescent PS with minimal damage and much higher degree of perfection than that of previously attained. It is very interested that the PL intensity may be inproved by SD method.展开更多
文摘Poly(methyl methacrylate)-titania hybrid glasses were synthesized by sol-gel processes using acrylic acid or allyl acetylacetone as coupling agent. Titanium butoxide modified with acrylic acid (or titanium isopropoxide modified with allyl acetylacetone) was hydrolyzed to produce a titania network, and then poly(methyl methacrylate) (PMMA)chains formed in situ through a radical polymerization were chendcally bonded to the fortheng titania network to synthesize a hybrid glass. Transparent hybrid glasses with different contents of titania were achieved. With the increase of the titania content, the color of the products changed from yellow to red. The synthesis process was investigated stepwise by using FTIR spectroscopies, and the experimental results demonstrated that acrylic or acetylacetonate groups bound to titanium remain in the final hybrid glasses.The thermal stability of the hybrid materials were considerably improved relative to pure PMMA. The hybrid glasses using allyl acetylacetone as coupling agent exhibited ther mochromatic effect which both pure PMMA and titan ia do not manifest.
文摘Porous silicon (PS) fabricated by anodizing have recently become the subject of intense interest due to their room temperature visble light emission properties.However, highly porous silicon made by electrochemical etching is fragile and tends to craze during normal drying in air after taken out from HF based solution. The preparation of highly porous materials by sol-gel processing followed by supercritical drying was carried out by Kistler in 1931. Since 1985, the sucpercritical drying (SD) has been used successfully to prepare a variety of aerogels, comprising a void fraction of more than 90%. This technigue has now been applied to prepare luminescent porous silicon on both <100> and <111> C-Si substrates. Porosities up to 94% have been achieved, which were determined by gravimetric measurement. Its morphological feature, microstructure and photoluminescence properties exhibit novel characteristics from those conventionally anodized porous silicon. It has been demonstrated that anodization and supercritical drying can yield ultra-high porous luminescent PS with minimal damage and much higher degree of perfection than that of previously attained. It is very interested that the PL intensity may be inproved by SD method.
