Cordierite- and anorthite-based binary glass ceramics of the CaO-MgO-Al2O3-SiO2 （CMAS） system were synthesized by mixing local and abundant raw minerals （kaolin and doloma by mass ratio of 82/18）. A kinetics study...Cordierite- and anorthite-based binary glass ceramics of the CaO-MgO-Al2O3-SiO2 （CMAS） system were synthesized by mixing local and abundant raw minerals （kaolin and doloma by mass ratio of 82/18）. A kinetics study reveals that the activation energy of crystalli- zation （Ea） calculated by the methods of Kissinger and Marotta are 438 kJ·mol^-1 and 459 kJ·mol^-1, respectively. The Avrami parameter （n） is estimated to be approximately equal to 1, corresponding to the surface crystallization mechanism. X-ray diffraction （XRD） analysis shows that the anorthite and cordierite crystals are precipitated from the parent glass as major phases. Anorthite crystals first form at 850℃, whereas the μ-cordierite phase appears after heat treatment at 950℃. Thereafter, the cordierite allotropically transforms to α-cordierite at 1000℃. Complete densification is achieved at 950℃; however, the density slightly decreases at higher temperatures, reaching a stable value of 2.63 kg·m^-3 between 1000℃ and 1100℃, The highest Vickers hardness of 6 GPa is also obtained at 950℃. However, a substantial decrease in hardness is recorded at 1000℃; at higher sintering temperatures, it slightly increases with increasing temperature as the ct-cordierite crystallizes.展开更多
In this work, it is presented the synthesis and characterization of transparent and colorless organic-inorganic hybrid anti-graffiti protective materials obtained by sol-gel method. This type of materials is based on ...In this work, it is presented the synthesis and characterization of transparent and colorless organic-inorganic hybrid anti-graffiti protective materials obtained by sol-gel method. This type of materials is based on MTES （methyltriethoxysilane）, TPOZ （tetrapropoxide of zirconium） and PDMS （polydimethylsiloxane）. The synthesis has been carried out at 25, 35 and 45 ℃ in order to evaluate the role of temperature in the structure, microstructure and anti-graffiti behavior as well. The incorporation of zirconium within the organic modified silica network, of sols after being gelled and dried, is evident by a shoulder which increased with temperature situated at 950 cml （Si-O-Zr bonds）, and it is homogenously dispersed inside the matrix avoiding the formation of large ZrO2 precipitates. As the temperature increases, the hydrolysis and condensation reactions occur in more extension and thus, the obtained sols are more cross-linked and present more Si-O-Zr linkages. The promising anti-graffiti beha＇4ior of the protectNe hybrids was qualitatively determined being the spot removal higher than 90%.展开更多
基金financially supported by the General Directorate for Scientific Research and Technological Development(No.7/u21/4835)
文摘Cordierite- and anorthite-based binary glass ceramics of the CaO-MgO-Al2O3-SiO2 （CMAS） system were synthesized by mixing local and abundant raw minerals （kaolin and doloma by mass ratio of 82/18）. A kinetics study reveals that the activation energy of crystalli- zation （Ea） calculated by the methods of Kissinger and Marotta are 438 kJ·mol^-1 and 459 kJ·mol^-1, respectively. The Avrami parameter （n） is estimated to be approximately equal to 1, corresponding to the surface crystallization mechanism. X-ray diffraction （XRD） analysis shows that the anorthite and cordierite crystals are precipitated from the parent glass as major phases. Anorthite crystals first form at 850℃, whereas the μ-cordierite phase appears after heat treatment at 950℃. Thereafter, the cordierite allotropically transforms to α-cordierite at 1000℃. Complete densification is achieved at 950℃; however, the density slightly decreases at higher temperatures, reaching a stable value of 2.63 kg·m^-3 between 1000℃ and 1100℃, The highest Vickers hardness of 6 GPa is also obtained at 950℃. However, a substantial decrease in hardness is recorded at 1000℃; at higher sintering temperatures, it slightly increases with increasing temperature as the ct-cordierite crystallizes.
文摘In this work, it is presented the synthesis and characterization of transparent and colorless organic-inorganic hybrid anti-graffiti protective materials obtained by sol-gel method. This type of materials is based on MTES （methyltriethoxysilane）, TPOZ （tetrapropoxide of zirconium） and PDMS （polydimethylsiloxane）. The synthesis has been carried out at 25, 35 and 45 ℃ in order to evaluate the role of temperature in the structure, microstructure and anti-graffiti behavior as well. The incorporation of zirconium within the organic modified silica network, of sols after being gelled and dried, is evident by a shoulder which increased with temperature situated at 950 cml （Si-O-Zr bonds）, and it is homogenously dispersed inside the matrix avoiding the formation of large ZrO2 precipitates. As the temperature increases, the hydrolysis and condensation reactions occur in more extension and thus, the obtained sols are more cross-linked and present more Si-O-Zr linkages. The promising anti-graffiti beha＇4ior of the protectNe hybrids was qualitatively determined being the spot removal higher than 90%.
