Influence of Drying Methods on Fractal Geometric Characteristics of Mesoporous Silica Aerogels
来源期刊：Journal Of Wuhan University Of Technology Materials Science Edition2013年第3期
论文作者：赵善宇 XU Haixun WANG Lijiu J William Suggs
文章页码：476 - 482
摘 要：Chemical modification/ambient drying method and freeze drying method were introduced to research the synthesis of mesoporous silica aerogels. By analyzing N2 gas adsorption/desorption isotherms, the fractal geometric characteristics of gels were focused. The overall surface fractal dimensions were determined by analyzing N2 gas adsorption branch and a Frenkel-Halsey-Hill （FHH） equation was empolyed to determine surface fractal dimension Df . It is found that, during ambient drying process, VTMCS/VWetgel ratio plays a crucial role in the changes of geometric feature, the key point is 50%, when the ratio is lower, and surface roughness increases with the ratio, when it exceeds 50%, the surface is almost unaffected by the modification. While freeze drying always tends to get larger Df , freeze drying process could cause a rough surface of the gels. Compared with traditional porosity and specific surface area analyses, fractal geometry may be expected to be favorable for mesoporous structural analyses of materials.
赵善宇1,2,3，XU Haixun2，WANG Lijiu2，J William Suggs3
1. School of Environmental and Safety Engineering, Changzhou University2. School of Civil and Hydraulic Engineering, Dalian University of Technology3. Department of Chemistry, Brown University
摘 要：Chemical modification/ambient drying method and freeze drying method were introduced to research the synthesis of mesoporous silica aerogels. By analyzing N2 gas adsorption/desorption isotherms, the fractal geometric characteristics of gels were focused. The overall surface fractal dimensions were determined by analyzing N2 gas adsorption branch and a Frenkel-Halsey-Hill （FHH） equation was empolyed to determine surface fractal dimension Df . It is found that, during ambient drying process, VTMCS/VWetgel ratio plays a crucial role in the changes of geometric feature, the key point is 50%, when the ratio is lower, and surface roughness increases with the ratio, when it exceeds 50%, the surface is almost unaffected by the modification. While freeze drying always tends to get larger Df , freeze drying process could cause a rough surface of the gels. Compared with traditional porosity and specific surface area analyses, fractal geometry may be expected to be favorable for mesoporous structural analyses of materials.
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