Use of Drying Control Chemical Additives (DCCAs) in Producing Gel Monoliths

Abstract

Rapid, reliable production of gel monoliths is necessary to realize many of the potential advantages of this type of glass processing (1). Zarzycki has reviewed the many factors that lead to drying stresses and cracking of gels (2). He shows that the drying stress is a function of pore size and rate of evaporation of the pore liquor, which depends on the liquor vapor pressure. In a recent series of papers we have demonstrated the use of organic additions to alkoxide sols termed drying control chemical additives (DCCA), to control the pore liquor vapor pressure, pore size distribution, and drying stresses (3–8). By use of the DCCA’s, which includes formamide (NH2CHO) and glycerol (C3H8O3), it is possible to produce a wide range of sizes and shapes of dried gel monliths of SiO2, Li2O-SiO2, Na2O-SiO2, and Na2-B2O3-SiO2 within a 1–2 day processing schedule with 100% reliability (Fig 1).