skip to main content

Rice Husk Ash as a Renewable Source for the Production of Value Added Silica Gel and its Application: An Overview

*Ram Prasad  -  Department of Chemical Engineering & Technology, Banaras Hindu University, Varanasi 221005, India
Monika Pandey  -  Department of Chemical Engineering & Technology, Banaras Hindu University, Varanasi 221005, India

Citation Format:

In recent years, silica gels have developed a lot of interest due to their extraordinary properties and their existing and potential applications in science and technology. Silica gel has a wide range of applications such as a desiccant, as a preservation tool to control humidity, as an adsorbent, as a catalyst and as a cata-lyst support. Silica gel is a rigid three-dimensional network of colloidal silica, and is classified as: aqua-gel, alco-gel, xero-gel and aero-gel. Out of all known solid porous materials, aero-gels are particularly known for their high specific surface area, high porosity, low bulk density, high thermal insulation value, ultra low dielectric constant and low index of refraction. Because of these extraordinary properties silica aero-gel has many commercial applications such as thermal window insulation, acoustic barriers, super-capacitors and catalytic supports. However, monolithic silica aero-gel has been used extensively in high energy physics in Cherenkov radiation detectors and in shock wave studies at high pressures, inertial confinement fusion (ICF) radio-luminescent and micrometeorites. Silica gel can be prepared by using various sol gel precursors but the rice husk (RH) is considered as the cheapest source for silica gel production. Rice husk is a waste product abundantly available in rice producing countries during milling of rice. This review article aims at summarizing the developments carried out so far in synthesis, properties, characterization and method of determination of silica, silica gel, silica aero-gel and silica xero-gel. The effect of synthesis parameters such as pH, temperature of burning the rice husk, acid leaching prior to formation of rice husk ash (RHA) on the properties of final product are also described. The attention is also paid on the application of RH, RHA, sil-ica, silica aero-gel and silica xero-gel. Development of economically viable processes for getting rice husk silica with specific properties assumes importance at this juncture. Copyright © 2012 by BCREC UNDIP. All rights reserved.

Received: 23th November 2011, Revised: 09th January 2012, Accepted: 10th January 2012

[How to Cite: R. Prasad, and M. Pandey. (2012). Rice Husk Ash as a Renewable Source for the Production of Value Added Silica Gel and its Application: An Overview. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (1): 1-25. doi:10.9767/bcrec.7.1.1216.1-25]

[How to Link / DOI: ]

Fulltext View|Download
Keywords: Rice husk; Rice husk ash; Sodium silicate; Silica gel; Review
Funding: Banaras Hindu University

Article Metrics:

  1. Jain, A. K.; Sharma, S. K.; and Singh, D. 1996. Reaction Kinetics of Paddy Husk Thermal Decomposition: Proceedings 31th Intersociety of Energy Conversion Engineeering Conference, 4: 2274-2279. Washington D.C. ASME." target="_blank">CrossRef
  2. Yalcin, N.; and Sevinc, V. 2001. Studies on silica obtained from rice husk. Ceram. Inter. 27: 219-224." target="_blank">CrossRef
  3. Pijarn, N.; Jaroenworaluck, A.; Sunsaneeyametha, W.; and Stevens, R. 2010. Synthesis and characterization of nanosized-silica gels formed under controlled conditions. Powder Technol. 203 (3): 462-468." target="_blank">CrossRef
  4. Rao, V. M. H. G. 1980. Utilization of rice husk—A preliminary analysis. J. Sci. Ind. Res. 39: 495-515
  5. Sharma, N. K.; Williams, W. S.; and Zangvil, A. 1984. Formation and structure of silicon carbide whiskers from rice hulls. J. Am. Ceram. Soc. 67: 715-720." target="_blank">CrossRef
  6. Patel, M.; Karera A.; and Prasanna, P. 1987. Effect of thermal and chemical treatments on carbon and silica contents in rice husk. J. Mater. Sci. 22: 2457-2464." target="_blank">CrossRef
  7. Patel, M.; Karera, A.; 1991. SiC whisker from rice husk: Microscopic study. Powder Metall. Int. 23 (1): 30-32
  8. Ding, M. 1992. Rice husk silicon and its applications. Inorg. Chem. Ind. 24 (6): 36-42
  9. Krishnarao, R. V.; and Godkhindi, M. M.; 1992. Distribution of silica in rice husks and its effect on the formation of silicon carbide. Ceram. Int., 18: 243-249." target="_blank">CrossRef
  10. Chandrasekhar, S.; Satyanarayana, K. G.; Pramada, P. N.; and Raghavan P. 2003. Review Processing, properties and applications of reactive silica from rice husk- an overview. J. Mat. Sci. 38: 3159 – 3168." target="_blank">CrossRef
  11. Rao, R. V. Krishna; Godkhindi, Andm. M.; 1992. Effect of Si additions on the formation of SiC whiskers from rice husks. Ceram. Int. 18:185." target="_blank">CrossRef
  12. Ismail, Muhammad Shoaib.; and Waliuddin, A. M. 1996. Effect of rice husk ash on high strength Concrete. Const. and Build. Mat. 10: 521-526." target="_blank">CrossRef
  13. Proctor, A.; Clark, P.K.; and Parker, C.A. 1995. Rice hull ash adsorbent performance under commercial soy oil bleaching conditions. J. Am. Oil Chem. Soc. 72: 459-462." target="_blank">CrossRef
  14. Proctor, A.; and Palaniappan, S. 1990. Adsorption of soy oil free fatty acids by rice hull ash. J. Am. Oil Chem. Soc. 67: 15-17." target="_blank">CrossRef
  15. Sun, L.; and Gong, K.; 2001. Review, silicon-based materials from rice husks and their applications. Ind. Eng. Chem. Res. 40: 5861–5877." target="_blank">CrossRef
  16. Krishna Rao, R. V.; Subrahmanyam, J.; and Kumar T. J. 2001. Studies on the formation of black particles in rice husk silica ash. J. Eur. Ceram. Soc. 21(1): 99-104." target="_blank">CrossRef
  17. Tang, Qi.; and Wang Tao. 2005. Preparation of silica aero-gel from rice hull ash by supercritical carbon dioxide drying. J. Supercritical Fluids 35: 91–94." target="_blank">CrossRef
  18. Bhattacharya S. C.; and Wu, W. 1989. Fluidized bed combustion of rice husk for disposal and energy recovery. Energy from Biomass & wastes 12: 591-601
  19. Boaterg, S. D. A. 1990. Incineration of rice hull for use as a cementitious material. Cem. Concr. Res. 20(5): 795-802." target="_blank">CrossRef
  20. Huang, S.; Jing, S.; Wang, J.; Wang, Z.; and Jin, Y. 2001. Silica white obtained from rice husk in fluidized bed. Powder Tech. 117: 232–238." target="_blank">CrossRef
  21. Mochidzuki, K.; Sakoda, A.; Suzuki, M.; Izumi, J.; and Tomonaga, N. 2001. Structural behavior of rice husk silica in pressurized hot-water treatment process. Indus. Eng. Chem. Res. 40: 5705 – 5709." target="_blank">CrossRef
  22. Liou, T.-H. 2004. Evolution of chemistry and morphology during the carbonization and combustion of rice husk. Carbon 42: 785–794." target="_blank">CrossRef
  23. Liou, T.-H. 2004. Preparation and characterization of nano-structured silica from rice husk. Mat. Sci. Eng. 364: 313–323." target="_blank">CrossRef
  24. Kalapathy, U.; Proctor, A.; and Schultz, J. 2000a. A simple method for production of pure silica from rice hull ash. Biores. Tech. 73: 257–262." target="_blank">CrossRef
  25. Shelke, V. R.; Bhagade, S. S.; and Mandavgane, S. A. 2010. Mesoporous Silica from Rice Husk Ash. Bull. Chem. React. Eng. Catal. 5(2): 63–67." target="_blank">CrossRef" target="_blank"><a href=" border="0" alt="" />
  26. Sidheswaran P.; and Bhat A. N. 1996. Recovery of amorphous silica in pure form from rice husk. Trans. Ind. Ceram. Soc. 55(4): 93-96
  27. Hamad, M. A.; and Khattab, I. A. 1981. Effect of the combustion process on the structure of rice hull silica, Thermochim. Acta 48: 343–349." target="_blank">CrossRef
  28. Real, C.; Alcala, M. D.; and Criado, J. M. 1996. Preparation of silica from rice husks. J. Am. Ceram. Soc. 79(8): 2012-2016." target="_blank">CrossRef
  29. Hanafi, S.; Abo-El-Enein, S. A.; Ibrahim, D. M.; and El-Hemaly, S. A. 1980. Thermochim. Acta 37: 137-143." target="_blank">CrossRef
  30. Chakraverty, A.; Mishra, P.; and Banerjee, H. D. 1988. Investigation of combustion of raw and acid-leached rice husk for production of pure amorphous white silica. J. Mater. Sci. 23(1): 21-24." target="_blank">CrossRef
  31. Liou, T.-H.; Yang, C.-C. 2011. Synthesis and surface characteristics of nanosilica produced from alkali-extracted rice husk ash. Mat. Sci. Eng. B 176: 521–529." target="_blank">CrossRef
  32. Kamath, S. R.; Proctor, A. 2004. Silica gel from rice husk ash: preparation and characterization. Cer. Chem.75:484–487." target="_blank">CrossRef
  33. Polska, K.; Radzki, S. 2008. Spectral and AFM characterization of trimethylammoniophenyl-porphyrin and concanavalin A associate in solution and monolithic SiO2 gels obtained by the sol–gel method. Opt. Mat. 30: 1644–1654." target="_blank">CrossRef
  34. Estella, J.; Echeverría, J. C.; Laguna, M.; Garrido, J. J. 2007. Effects of aging and drying conditions on the structural and textural properties of silica gels. Micro. Meso. Mat. 102: 274– 282." target="_blank">CrossRef
  35. Handy, B.; Walther, K. L.; Wokaun, A.; and Baiker, A. 1991. Influence of preparation parameters on pore structure of silica gels prepared from tetraethoxy orthosilicate. Stud. Sur. Sci. Cat. 63: 239–246." target="_blank">CrossRef
  36. Monde, T.; Fukube, H.; Nemoto, F.; Yoko, T.; and Konakahara, T.1999. Preparation and surface properties of silica gel coating films containing branched-polyfluoroalkylsilane. J. Non-Crystalline Solids 246: 54-64." target="_blank">CrossRef
  37. Kamath Savita R.; and Proctor Andrew ; 1998. Silica Gel from Rice Hull Ash: Preparation and Characterization. Cereal Chem. 75(4): 484-487." target="_blank">CrossRef
  38. Nayak, J. P.; and Bera J. 2009. Preparation of Silica Aero-gel by ambient pressure drying process using rice husk ash as raw material. Trans. Ind. Ceram. Soc. 68(2): 1-4
  39. Einarsruda, Mari-Ann; Haereida, Siv; and Wittwerb Volker; 1993. Some thermal and optical properties of a new transparent silica xero-gel material with low density, Solar Ener. Mat. Solar Cel. 31(3): 341-347." target="_blank">CrossRef
  40. Affandi, Samsudin; Setyawan, Heru; Winardi, Sugeng ; Purwanto, Agus ; and Balgis, Ratna; 2009. A facile method for production of high-purity silica xero-gels from bagasse ash. Advan. Powd. Technol. 20: 468–472." target="_blank">CrossRef
  41. Hong, Jung-Kyun; Yang, Hee-Sun; Moon-Ho Jo, Park Hyung-Ho; and Choi Se-Young; 1997. Preparation and characterization of porous silica xero-gel film for low dielectric application. Thin Solid Films 308: 495–500." target="_blank">CrossRef
  42. Chakraverty, A.; Kaleemullah, S. 1991. Conversion of rice husk into amorphous silica and combustible gas. Energy Convers. Manage. 32: 565-570." target="_blank">CrossRef
  43. Luan, T. C.; Chou, T. C. 1990. Recovery of silica from the gasification of rice husk/coal in the presence of a pilot flame in a modified fluidized bed. Ind. Eng. Chem. Res. 29: 1922–1927." target="_blank">CrossRef
  44. Iler, R. K. 1979. Silica gels and powders. The Chem. of Silica R. K. Iler. (Ed.) 462-599
  45. Kalapathy U.; Proctor A.; Shultz J. 2002. An improved method for production of silica from rice hull ash. Biores. Tech. 85: 285–289." target="_blank">CrossRef
  46. Hrubesh, L. W. 1990. Aero-gels: the world’s lightest Solids. Chem. Indus. 24: 824–827
  47. Fricke, J.; and Emmerling, A. 1992. Aero-gels, preparation, properties, applications, in Structure and Bonding. Springer Ser. Structure Bonding 77: 37–87." target="_blank">CrossRef
  48. Gurav, J. L.; Jung, I.-K.; Park, H.-H.; Kang E. S. and Nadargi, D. Y. 2010. Silica Aero- gel: Synthesis and Application. J. Nano Mat. 1—11." target="_blank">CrossRef
  49. Dorcheh A. Soleimani.; Abbasi M. H. 2008. Silica Aero-gel; Synthesis, Properties and Characterization. J. Mat. Proc. Tech. 199: 10–26." target="_blank">CrossRef
  50. Schwertfeger, F.; Frank D.; and Schmidt, M. 1998. Aero-gel-High Tenuous Solids with Fascinating Properties. J. Non-Cryst. Solids 225: 24-29." target="_blank">CrossRef
  51. Robert R. Keller, Sr. 2009. Aero-gel and method of manufacturing same. US Patent 7618608
  52. Lee, C. J.; Kim, G. S.; and Hyun, S.H. 2002. Synthesis of silica aero-gels from waterglass via new modified ambient drying. J. Mater. Sci. 37: 2237–2241." target="_blank">CrossRef
  53. Rao, A. P.; Pajonk, G.M.; and Rao, A.V. 2005. Effect of preparation conditions on the physical and hydrophobic properties of two step processed ambient pressure dried silica aerogels. J. Mater. Sci. 40: 3481–3489." target="_blank">CrossRef
  54. Husing, N.; and Schubert, U. 1998. Aero-gels-Airy materials: Chemistry, structure, and properties. Angew. Chem. Int. Ed. 37: 22-45.<22::AID-ANIE22>3.0.CO;2-I" target="_blank">CrossRef
  55. Rousset, J. L.; Boukenter, A.; Champagnon B. 1990. Granular structure and fractal domains of silica aero-gels J. Phy: Conden. Mat., 2(42): 8445–8455." target="_blank">CrossRef
  56. Liu, C.; Komarneni, S.; Smith, D. M.; Beck, J.S. (Eds.) 1995. Advances in Porous Materials. Mater. Res. Soc. Symp. Proc. 371: 217-222
  57. Komarneni, S.; Roy, R.; Selvaraj, U.; Malla, P. B.; and Breval, E. 1993. Biocompatibility of polymeric delivery systems for macromolecules. J. Mater. Res. 8: 3163- 3167." target="_blank">CrossRef
  58. Attia, Y.A.; Ahmed, M.S.; Zhu, M.; Attia, Y.A. (Ed.). 1994. Sol–Gel Processing and Applications. J. Sol-Gel Sci. Technol. 311-315
  59. Shi, F.; Wang, L.; and Liu, J. 2006. Synthesis and characterization of silica aero-gels by a novel fast ambient pressure drying process. Mater. Lett. 60: 3718–3722." target="_blank">CrossRef
  60. Wagh, P.B.; Begag, R.; Pajonk, G.M.; Rao, A.V.; Haranath, D. 1999. Comparison of some physical properties of silica aero-gel monoliths synthesized by different precursors. Mater. Chem. Phys. 57: 214–218." target="_blank">CrossRef
  61. Kim, G. S.; Hyun, S. H. 2004. Synthesis and characterization of silica aero-gel films for inter- metal dielectrics via ambient drying. Thin Solid Films 460: 190–200." target="_blank">CrossRef
  62. Drake, J. M.; Yacullo, L. N.; Levitz, P.; and Klafter, J. 1994. Nitrogen Adsorption on Porous Silica: Model-Dependent Analysis. J. Phys. Chem. 98: 380-382." target="_blank">CrossRef
  63. Reichenauer, G.; and Scherer, G.W. 2001. Nitrogen sorption in aero-gels. Adsorption isotherms –hysteresis. J. Non-Cryst. Solids 285: 167-174." target="_blank">CrossRef
  64. Moner-Girona, M.; Roig, A.; and Molins, E. 2003. Sol gel route to direct formation of silica aero-gel microparticles using supercritical solvents. J. Sol-Gel Sci Technol. 26: 645–649." target="_blank">CrossRef
  65. Woignier, T.; and Phalippou, J. 1987. Skeletal density of silica aero-gels. J. Non-Cryst. Solids 93: 17-21." target="_blank">CrossRef
  66. Kamiuto, K.; Saitoh, S.; and Tokita, Y. 1993. Scattering phase function of a silica aerogel at 450 nm wavelength J. Quant. Spectrosc. Radiant. Trans. 50: 293-327." target="_blank">CrossRef
  67. Beck, Caps, R.; Frick, J. 1989. Scattering of Visible Light from Silica Aero-gels. J. Phys. D 22: 730-734." target="_blank">CrossRef
  68. Jensen, K. I.; Schultz, J. M.; and Kristiansen, F. H. 2004. Development of windows based on highly insulating aero-gel glazing. J. Non-Cryst. Solids 350: 351–357." target="_blank">CrossRef
  69. Schultz, J. M.; Jensen, K.I.; and Kristiansen, F. H. 2005. Super insulating aerogel glazing:Sol. Sol. Ener. Mat. Sol. cells. 89: 275–285." target="_blank">CrossRef
  70. Buzykaev, A. R.; Danilyuk, A. F.; Ganzhur, S. F.; Kravchenko, E. A.; and Onuchin, A. P. 1999. Measurements of optical parameters of aero-gel. Nucl. Instr. Meth. Phys. Res. A 433: 396-400." target="_blank">CrossRef
  71. Rao, A. Venkateswara; Nilsen E.; and Einarsrud, M. A. 2001. Effect of Precursors, Methyalation Agents and Solvents on the Physicochemical Properties of Silica Aero-gels Prepared by Atmospheric Pressure Drying Method. J. Non-Cryst. Solids, 296: 165-171." target="_blank">CrossRef
  72. Kistler, S. S.; 1932. Coherent expanded aero-gels. J. Phys. Chem. 36: 52-64." target="_blank">CrossRef
  73. Lee, K.-H.; Kim, S.-Y.; and Yoo, K. P. 1995. Low-density, hydrophobic aero-gels. J. Non-Cryst. Solids 186: 18-22." target="_blank">CrossRef
  74. El Rassy, H.; Pierre, A.C.; 2005. NMR and IRspectroscopy of silica aerogels with different hydrophobic characteristics. J. Non-Cryst. Solids 351: 1603–1610." target="_blank">CrossRef
  75. Deshpande, R.; Smith, D.; and Brinker, C.J. 1996. Preparation of High Porosity Xero-gels by Chemical Surface Modification US Patent 5, 565,142
  76. Hrubesh, L. W. 1998. Aero-gel applications. J. Non-Cryst. Solids 225: 335-342." target="_blank">CrossRef
  77. Schmidt , M.; Schwertfeger, F. 1998. Applications for silica aero-gel products. J. Non-Crystal. Solids 225: 364–368." target="_blank">CrossRef
  78. Ulrich, D.R. 1990. Prospects for sol-gel processes. J. Non-Cryst. Solids 121: 465-479." target="_blank">CrossRef
  79. Fricke, J.; Tillotson, T. 1997. Aero-gels: production, characterization, and applications. Thin Solid Film 297: 212–223." target="_blank">CrossRef
  80. Pierre, A.C.; Pajonk, G. M. 2002. Chemistry of aero-gels and their applications. Chem. Rev. 102:4243-4265." target="_blank">CrossRef
  81. Adachi, I.; Sumiyoshi, T.; Hayashi, K.; Iida, N.; Enomoto, R.; Tsukada, K.; Suda, R.; Matsumoto, S.; Natori, K.; Yokoyama, M.; and Yokogawa, H. 1995. Study of threshold Cherenkov counter based on silica aerogels with low refractive indices. Nucl. Instr. Meth. Phys. Res. A 355: 390-398." target="_blank">CrossRef
  82. Asner, D.; Butler, F.; Dominick, J.; Fadeyev, V.; Masek, G.; Nemati, B.; Skubic, P.; and Strynowski, R. 1996. Experimental study of aero-gel Cherenkov detectors for particle identification. Nucl. Instr. Meth. Phys. Res. A 374: 286-292." target="_blank">CrossRef
  83. Sumiyoshi, T.; Adachi, I.; Enomotoi, R.; Iijima, T.; Suda, R.; Yokoyama, M.; and Yokogawa, H. 1998. Silica aero-gels in high energy physics. J. Non-Cryst. Solids 225: 369-374." target="_blank">CrossRef
  84. Ishino, M.; Chiba, J.; En’yo, H.; Funahashi, H.; Ichikawa, A.; Ieiri, M.; Kanda, H.; Masaike, A.; Mihara, S.; Miyashita, T.; Murakami, T.; Nakamura, A.; Naruki, M.; Muto, R.; Ozawa, K.; Sato, H.D.; Sekimoto, M.; Tabaru, T.; Tanaka, K. H.; Yoshimura, Y.; Yokkaichi, S.; Yokoyama, M.; and Yokgawa, H. 2001. Mass production of hydrophobic silica aero-gel and readout optics of Cherenkov light. Nucl. Instr. Meth. Phys. Res. A 457: 581-587." target="_blank">CrossRef
  85. DeLeo, R.; Lagamba, L.; Manzari, V.; Nappi, E.; Scognetti, T.; Alemi, M.; Becker, H.; Forty, R.; Adachi, I.; Suda, R.; Sumiyoshi, T.; Leone, A.; Perrino, R.; Matteuzzi, C.; Seguinot, J.; Ypsilantis, T.; Cisbani, E.; Frullani, S.; Garibaldi, F.; Iodice, M.; and Uriuoli, G.M. 1997. Electronic detection of focused Cherenkov rings from aero-gel. Nucl. Instr. Meth. Phys. Res A 401: 187-205." target="_blank">CrossRef
  86. Anappara, A. A.; Rajeshkumar, S.; Mukundan, P.; Warrier, P. R. S.; Ghosh, S.; Warrier, K. G. K. 2004. Impedence spectroscopic studies of sol-gel derived subcritically dried silica aero-gels. Acta Mater. 52: 369-375." target="_blank">CrossRef
  87. Rao, A. V.; Kulkarni, M. M.; Amalnerkar, D. P.; and Seth, T. 2003. Silica aero-gels based on methyltrimethoxysilane precursor. J. Non-cryst. Solids 330: 187-195." target="_blank">CrossRef
  88. Nyquist, R. A.; Putzig, C. L.; Leugers, M. A.; Kagel, R. O.; and Nyquist, R. A. 1997. The handbook of infrared and Raman spectra of inorganic compounds and organic salts. San Diego: Academic Press. 18th Edn
  89. Brinker, C. J.; and Sherer, G.W. 1990. The Physics and Chemistry of Sol-Gel Processing. Academic Press
  90. Nicolaon, G. A.; and Teichner, S.J. 1968. Preparation of silica aero-gels from methyl orthosilicate in alcoholic medium, and their properties. Bull. Soc. Chim., 5: 1906 -1911
  91. Poco, J. F.; Coronado, P. R.; Pekala, R. W.; and Hrubesh, L.W. 1996. A Rapid Supercritical Extraction Process for the Production of Silica Aero-gels. Mater. Res. Soc. Symp. 431: 297-302." target="_blank">CrossRef
  92. Gross, J.; Coronado, P.; and Hrubesh, L. 1998. Elastic properties of silica aero-gels from a new rapid supercritical extraction process. J. Non-Cryst. Solids 225: 282-286." target="_blank">CrossRef
  93. Scherer, G.W.; Gross, J.; Hrubesh, L. W.; and Coronado, P. R. 2002. Mechanical Properties of Silica Alco-gels and Aero-gels. J. Non-Cryst. Solids 311: 259-272." target="_blank">CrossRef
  94. Gauthier, B. M.; Bakrania, S. D.; Anderson, A. M.; and Carroll, M. K. 2004. Extraction Technique for Aero-gel Fabrication. J. Non-Cryst. Solids 350: 238–243." target="_blank">CrossRef
  95. Kirkbir, F.; Murata, H.; Meyers, D.; and Ray Chaudhuri, S. 1998. Proceedings of the Fifth International Symposium on Aero-gels. J. Non-Cryst. Solids 225: 14-18." target="_blank">CrossRef
  96. Tewari, P. H.; Hunt, A. J.; and Lofftus, K.D. 1985. Ambient-Temperature Supercritical Drying of Transparent Silica Aero-gels. Mater. Lett. 3: 363-367." target="_blank">CrossRef
  97. Novak, Z., Knez, Z., and Hadolin, M. 1999. Second European Congress of Chemical Engineering. Montpellier
  98. Wawrzyniak, P.; Rogacki, G.; Pruba, J.; and Bartczak, Z. 2001. Effective diffusion coefficient in the low temperature process of silica aerogel production. J. Non-Cryst. Solids 285: 50–56." target="_blank">CrossRef
  99. Ehrburger-Dolle, F.; Dallamano, J.; Elaloui, E.; Pajonk, G. 1995. Relations between the texture of silica aero- gels and their preparation. J. Non-Cryst. Solids 186: 9- 17." target="_blank">CrossRef
  100. Yoda, S.; Ohshima, S. 1999. Supercritical drying media modification for silica aero-gel preparation. J. Non-Cryst. Solids 248: 224-234." target="_blank">CrossRef
  101. Dieudonne, P.; Hafidi Alaoui, A.; Delord, P.; and Phalippou, J. 2000. Transformation of nanostructure of silica gels during drying. J. Non-Cryst. Solids 262: 155-161." target="_blank">CrossRef
  102. Tajiri, K.; and Igarashi, K. 1998. The effect of the preparation conditions on the optical properties of transparent silica aero-gels. Solar Ener. Mater. Solar Cel. 54: 189-195." target="_blank">CrossRef
  103. Land, V. D.; Harris, T. M.; and Teeters, D. C. 2001. Processing of low-density silica gel by critical point drying or ambient pressure drying. J. Non-Cryst. Solids. 283: 11-17." target="_blank">CrossRef
  104. Rao, A. Venkateswara.; Rao, A. Parvathy.; and Kulkarni, M. M. 2004. Influence of gel aging and Na2SiO3/H2O molar ratio on monolithicity and physical properties of water-glass-based aero-gel dried at atmospheric pressure. J. Non-Cryst. Solids, 350: 224-229." target="_blank">CrossRef
  105. Haereid, S.; Nilsen, E.; and Einarsrud, M. A. 1996. Properties of silica gels aged in TEOS. J. Non-Cryst. Solids, 204: 228-234." target="_blank">CrossRef
  106. Rao, A. P.; Pajonk, G. M.; and Rao, A. V. 2005a. Hydrophobic and physical properties of the ambient pressure dried silica aero-gels with sodium silicate precursor using various surface modification agents. J. Mater. Sci. 40: 3481–3489." target="_blank">CrossRef
  107. Davis, P. J.; Brinker, C. J.; and Smith, D. M. 1992a. Pore structure evolution in silica gel during aging/drying I. Temporal and thermal aging. J. Non-Cryst. Solids 142: 189-196." target="_blank">CrossRef
  108. Davis, P.J.; Brinker, C.J.; Smith, D. M.; and Assink, R. A. 1992b. Pore structure evolution in silica gel during aging/drying II. Effect of pore fluids. J. Non-Cryst. Solids 142: 197-207." target="_blank">CrossRef
  109. Deshpande, R.; Hua, D. W.; Smith, D. M.; and Brinker, C. J. 1992. Pore structure evolution in silica gel during aging/drying. III. Effects of surface tension. J. Non-Cryst. Solids 144: 32-34." target="_blank">CrossRef
  110. Bhagat, S. D.; Kim, Y. H.; Ahn, Y.S.; and Yeo, J. G. 2007. Textural Properties of Ambient Pressure Dried Water Glass Based Silica Aero-gel Beads: One Day Synthesis. Micro. Meso. Mater. 96: 237-244." target="_blank">CrossRef
  111. Sarawade, Pradip B.; Kim, Jong-Kil.; Hilonga, Askwar.; Kim, Hee Taik. 2010. Production of low-density sodium silicate-based hydrophobic silica aero-gel beads by a novel fast gelation process and ambient pressure drying process. Solid State Sci. 12: 911–918." target="_blank">CrossRef
  112. Gurav, J. L.; Rao, A.V.; Rao, A. P.; Nadargi, D. Y.; and Bhagat, S.D. 2009. Physical Properties of Sodium Silicate Based Silica Aerogels Prepared by Single Step Sol−Gel Process Dried at Ambient Pressure. J. Alloys Compound. 476: 397-402." target="_blank">CrossRef
  113. Klvana, D.; Chaouki, J.; Repellin-Lacroix, M.; and Pajonk, G. M. 1989. A new method of preparation of aero-gel like materials using a freeze-drying process. Le Journal de Physique Colloques 50: (C4-29–C4-32)
  114. Mathieu, B.; Blacher, S.; Pirard, R.; Pirard, J. P.; Sahouli, B.; and Brouers, F.1997. Freeze-dried resorcinol-formaldehyde gels. J. Non-Cryst. Solids, 212: 250–261." target="_blank">CrossRef
  115. Pajonk, G. M. 1989. Drying methods preserving the textural properties of gels. Le Journal de Physique Colloques, 50: (C4-13–C4-22)
  116. Stolarski, M.; Walendziewski, J.; Steininger, M.; Pniak, B. 1999. Synthesis and characteristic of silica aero-gels, Appl. Catal. A: Gen. 177: 139-148." target="_blank">CrossRef
  117. Yunos Nurul Hidayah Mohd; 2010. Loading capacity and release property of piperine loaded silica aero-gel and silica xero-gel. MSc Thesis. (Chemistry) Faculty of Science Universiti Teknologi Malaysia

Last update:

No citation recorded.

Last update:

No citation recorded.