Study of thermal conductivity and effect of humidity on HMDZ modified TEOS based aerogel dried at ambient pressure
The experimental results on the study of thermal conductivity and effect of humidity on HMDZ modified TEOS based aerogels dried at ambient pressure, are reported. Silica sol was prepared by keeping the MeOH/TEOS molar ratio, Acidic water (Oxalic acid) and basic water (NH4OH) concentrations constant at 16.5, 0.001 and 1 M, respectively throughout the experiments and the HMDZ/TEOS molar ratio (h) was varied from 0.34 to 2.1. Finally, the surface modified wet gels were dried at an ambient pressure. The thermal conductivity of the aerogel samples was measured. Further, the humidity study was carried out in 80% humid surrounding at 30 °C temperature over 80 days. The best quality aerogels in terms of low bulk density, thermal conductivity and durability (no moisture absorption) with an only 2% of weight gain were obtained for TEOS: MeOH: Acidic H2O: Basic H2O: HMDZ molar ratio at 1:16.5:0.81:0.50:0.681, respectively. The thermal stability and hydrophobicity of the aerogel have been confirmed with Thermo gravimetric and Differential Thermal (TG–DT) analyses and Fourier Transform Infrared Spectroscopy (FTIR), respectively. Microstructural studies were carried out by Scanning Electron microscopy (SEM).
KeywordsSilica aerogels Thermal conductivity Humidity Ambient pressure drying Scanning Electron Microscopy (SEM)
The authors are grateful to the Department of Science and Technology (DST) New Delhi, Government of India, for the financial support for this work through a major research project on “Aerogels” (N0. SR/S2/CMP-67/2006). Also, grateful thank to Dr. S.D. Bhagat for his valuable help for microstructure (SEM) study of this paper and UGC ASSIST and DRS-phase IInd.
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