Bonded Phosphate Ceramics

Ceramicrete is an ex situ stabilization technology that uses chemically bonded phosphate ceramics to stabilize low-level radioactive waste and hazardous waste containing radionuclides and heavy metals. The technology mixes phosphates with acidic solution, causing an exothermic reaction similar to that used in forming concrete. But while concrete is based on relatively weak hydrogen and van der Waals bonding, Ceramicrete uses a combination of ionic, covalenf and van der Waals bonds to stabilize contaminants. 

Low-temperature treatment of low-level mixed wastes has also been accomplished by solidification/stabilization with chemically bonded phosphate ceramics (CBPC). These are made by hydrothermal chemical reaction rather than by sintering. Chemical bonding develops when acid phosphates react with oxides to form crystalline orthophosphate (Singh et al. 1997). The ceramic matrix stabilizes the wastes by microencapsulation. The low temperature of the reaction allows volatile radionuclides to be treated (Singh et al. 1997). 

Singh, D., Wagh, A. S., Cunnane, J. C. Mayberry, J. L. 1997. Chemically bonded phosphate ceramics for low-level mixed-waste stabilization. Journal of Environmental Science and Health, Part A Environmental Science and Engineering Toxic and Hazardous Substance Control, A32, 527-541. 

Wagh, A. S., Strain, R., Jeong, S. Y., Reed, D., Krause, T. Singh, D. 1999. Stabilization of Rocky Flats Pu-contaminated ash within chemically bonded phosphate ceramics. Journal of Nuclear Materials, 265, 295-307. 

CASH CBM CBO CBPC CC CCB CCM CCP CDB CEC CFBC CFC CFR CMM COP CSH CT Calcium aluminosilicate hydrate Coal bed methane Carbon burn-out Chemically-bonded phosphate ceramics Carbonate carbon Coal combustion byproducts Constant capacitance model Coal combustion product Citrate-dithionate-bicarbonate Cation exchange capacity Circulating fluidized bed combustion Chlorofluorocarbon Cumulative fraction Coal mine methane Coefficient of performance Calcium silicate hydrate Collision theory... 

From a scientific viewpoint, calling all room-temperature-setting materials as cements is a misnomer. Highly crystalline structures, such as phosphate ceramics, are synthesized by chemical reaction at room temperature. They are ceramics because of their crystaHine structure, while they are cements because they are formed at room temperature. We would classify such materials as CBCs. If silicates are used to form them, they will be called chemically bonded silicate ceramics. When phosphates are used to form them, they are chemically bonded phosphate ceramics (CBPCs). By using the acronyms CBC and CBPC, we avoid the debate over the words cements and ceramics as the last letter C will stand for either of them. 

A.S. Wagh, D. Singh, and S.Y. Jeong, Chemically bonded phosphate ceramics for stabilization and solidification of mixed wastes, Hazardous and Radioactive Waste Treatment Technologies Handbook (CRC Press, Boca Raton, FL, 2001), pp. 6.3.1-6.3.18. 

A. Wagh, D. Singh, andS. Jeong, Method of waste stabilization via chemically bonded phosphate ceramics, US Patent No. 5,830,815, 1998. 

A.S. Wagh, S.Y. Jeong, D. Singh, A.S. Aloy, T.I. Kolytcheva, E.N. Kovarskaya, and Y.J. Macharet, Iron-phosphate-based chemically bonded phosphate ceramics for mixed waste stabilization, Proceedings on Waste Management 97, March 2—6 1997, (1997). 

Pictorial representation of formation of chemically bonded phosphate ceramic. 

A.S. Wagh, S. Grover, and S. Jeong, Chemically bonded phosphate ceramics. II. Warm-temperature process for alumina ceramics, J. Am. Ceram. Soc., 86 [11] (2003) 1845-1849. 

A.S. Wagh, R. Strain, S.Y. Jeong, D. Reed, T. Krause, and D. Singh, Stabilization of rocky flats Pu-contaminated ash within chemically bonded phosphate ceramics, J. Nucl. Mater., 265 (1999) 295-307. M.M. Sychev, I.N. Medvedeva, V.A. Biokov, and O.S. Krylov, Effect of reaction kinetics and morphology of neoformation on the properties of phosphate cements based on magnesium titanates, Chem. Abstr., 96, 222252e. 

Production of alumina aquosols from alumina has been well researched in sol-gel science [19]. Yoldas [20] was the first one to show that monolithic alumina gels could be formed by hydrolysis and condensation of aluminum alkoxide. As discussed in Chapter 5, formation of aquosols and their gel is an intermediate step in the formation of chemically bonded phosphate ceramics. Condensation of the hydrated alumina sols by reaction with phosphoric acid to form A1(H2P04)3-H20 gel is the first step toward synthesis of a berlinite-bonded alumina ceramic. When this gel is heated to 150°C, this gel reacts with additional alumina and releases water, and crystalline berlinite is produced. This Chapter... 

A. Wagh, S. Jeong, D. Singh, A. Aloy, T. Kolytcheva, and Y. Macheret, Iron-Phosphate-Based Chemically Bonded Phosphate Ceramics For Mixed Waste Stabilization, Proceedings of the Waste Management Annual Meeting, Session 29, Tuscon, March 2-6, 1997). 

Chemically Bonded Phosphate Ceramic Matrix Composites... 

Chapter 14 Chemically Bonded Phosphate Ceramic Matrix Composites Fig. 14.7. ... 

Chapter 15 Chemically Bonded Phosphate Ceramic Borehole Sealant... 

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