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Geopolymers are materials which are used for fire- and heat-resistant coatings and adhesives, medicinal applications, high-temperature ceramics, new binders for fire-resistant fiber composites, toxic and radioactive waste encapsulation and as cementing components to make concrete. The properties and uses of geopolymers are being explored in many scientific and industrial disciplines: modern inorganic chemistry, physical chemistry, colloid chemistry, mineralogy, geology, and in other types of engineering process technologies. Raw materials used in the synthesis of silicon-based polymers are mainly rock-forming minerals of geological origin, hence the name: ''geopolymer''. Joseph Davidovits coined the term in 1978〔An article published by the Commission of the European Communities in 1982, outlines the reasons why the generic term ''geopolymer'' was chosen for this new chemistry. See: J. Davidovits, The Need to Create a New Technical Language For the Transfer of Basic Scientific Information, in ''Transfer and Exploitation of Scientific and Technical Information, Proceedings of the symposium, Luxemburg,'' 10–12 June 1981, pp. 316-320. It is available as a pdf-file and may be downloaded from the European Parliament Bookshop. Go to < http://bookshop.europa.eu/en/transfer-and-exploitation-of-scientific-and-technical-information-pbCD3381271/> and click on 'download'.〕 and created the non profit French scientific institution (Association Loi 1901) ''Institut Géopolymère'' (Geopolymer Institute). According to T.F. Yen〔Kim, D.; Lai, H.T.; Chilingar, G.V.; Yen T.F. (2006), Geopolymer formation and its unique properties, ''Environ. Geol,'' 51(), 103–111.〕 geopolymers can be classified into two major groups: pure inorganic geopolymers and organic containing geopolymers, synthetic analogues of naturally occurring macromolecules. In the following presentation, a geopolymer is essentially a mineral chemical compound or mixture of compounds consisting of repeating units, for example silico-oxide (-Si-O-Si-O-), silico-aluminate (-Si-O-Al-O-), ferro-silico-aluminate (-Fe-O-Si-O-Al-O-) or alumino-phosphate (-Al-O-P-O-), created through a process of geopolymerization.〔See at http://www.geopolymer.org/science/introduction〕 This mineral synthesis (geosynthesis) was first presented at an IUPAC symposium in 1976.〔Pdf-file #20 ''Milestone paper IUPAC 76'' at http://www.geopolymer.org/category/library/technical-papers〕 The microstructure of geopolymers is essentially temperature dependent: * It is X-rays amorphous at room temperature, * But evolved into a crystalline matrix at temperatures above 500 °C.〔Zoulgami, M; Lucas-Girot, A.; Michaud, V.; Briard, P.; Gaudé, J. and Oudadesse, H. (2002); Synthesis and physico-chemical characterization of a polysialate-hydroxyapatite composite for potential biomedical application, ''Eur. Phys. J. AP'', 19, 173-179. See also: Kriven, W.M.; Bell, J.; Gordon, M. (2003), Microstructure and Microchemistry of Reacted Geopolymers and Geopolymer Matrix Composites, ''Ceramic Transactions'', 153, 227–250; Perera, D.S. and Trautman R.L. (2005), Geopolymers with the Potential for Use as Refractory Castables, ''Advances in Technology of Materials and Materials Processing'', 7(), 187–190.〕 One can distinguish between two synthesis routes: * In alkaline medium (Na+, K+, Li+, Ca++, Cs+ and the like); * In acidic medium with phosphoric acid and humic acids. The alkaline route is the most important in terms of R&D and commercial applications and will be described below. Details on the acidic route are to be found at the references〔Wagh, A.S. (2004), Chemically Bonded Phosphate Ceramics – A Novel Class of Geopolymers, ''Proceedings of the 106th Ann. Mtg. of the American Ceramic Society'', Indianapolis. See also, Chapter 13, Phosphate-based Geopolymers, in J. Davidovits' book ''Geopolymer Chemistry and Applications''.〕 and〔Perera, D.S., Hanna, J.V., Davis, J., Blackford, M.G., Latella ,B.A., Sasaki ,Y. and Vance E.R. (2008), Relative strengths of phosphoric acid-reacted and alkali-reacted metakaolin materials, ''J. Mater. Sci.,'' 43, 6562–6566. See also, Cao, D.; Su, D.; Lu, B. and Yang Y. (2005), Synthesis and structure characterization of geopolymeric material based on metakaolinite and phosphoric acid, ''Journal Chinese Ceramic Society'', 33, 1385–89.〕 == What is a geopolymer? == In the 1950s, Viktor Glukovsky, of Kiev, Ukraine, developed concrete materials originally known under the names "soil silicate concretes" and "soil cements",〔Gluchovskij V.D.:"Gruntosilikaty" Gosstrojizdat Kiev 1959, ''Patent USSR'' 245 627 (1967), ''Patent USSR'' 449894 (Patent appl. 1958, granted 1974).〕 but since the introduction of the geopolymer concept by Joseph Davidovits, the terminology and definitions of 'geopolymer' have become more diverse and often conflicting. The examples below were taken from 2011 scientific publications, written by scientists with different backgrounds. ''Definitions of the term geopolymer''〔See, Discussion at the Geopolymer Camp 2012, video ''Geopolymer definition in Wikipedia'' at http://www.geopolymer.org/camp/gp-camp-2012.〕 ''For chemists''〔Huang, Yi and Han, Minfang (2011) (China University of Mining and Technology, Beijing), The influence of α-Al2O3 addition on microstructure, mechanical and formaldehyde adsorption properties of fly ash-based geopolymer products, ''Journal of Hazardous Materials'', 193, 90–94〕 :'...Geopolymers consist of a polymeric Si–O–Al framework, similar to zeolites. The main difference to zeolite is geopolymers are amorphous instead of crystalline. The microstructure of geopolymers on a nanometer scale observed by TEM comprises small aluminosilicate clusters with pores dispersed within a highly porous network. The clusters sizes are between 5 and 10 nanometers.' ''For geopolymer material chemists''〔Pimraksaa, K.; Chindaprasirt, P.; Rungchet, A.; Sagoe-Crentsil, K. and Sato, T. (2011) (Department of Industrial Chemistry, Chiang Mai University, Thailand; CSIRO, Melbourne, Australia; Tohoku University, Sendai, Japan), Lightweight geopolymer made of highly porous siliceous materials with various Na2O/Al2O3 and SiO2/Al2O3 ratios, ''Materials Science and Engineering A'', 528, 6616–6623.〕 :'...The reaction produces SiO4 and AlO4, tetrahedral frameworks linked by shared oxygens as poly(sialates) or poly(sialate–siloxo) or poly(sialate–disiloxo) depending on the SiO2/Al2O3 ratio in the system. The connection of the tetrahedral frameworks is occurred via long-range covalent bonds. Thus, geopolymer structure is perceived as dense amorphous phase consisting of semi-crystalline 3-D alumino-silicate microstructure.' ''For alkali-cement scientists''〔Feng, Dingwu; Provis, John L. and van Deventer, Jannie S. J. (2012) (University of Melbourne, Australia), Thermal Activation of Albite for the Synthesis of One-Part Mix Geopolymers, ''J. Am. Ceram. Soc.'', 95 () 565–572.〕 :'... Geopolymers are framework structures produced by condensation of tetrahedral aluminosilicate units, with alkali metal ions balancing the charge associated with tetrahedral Al. Conventionally, geopolymers are synthesized from a two-part mix, consisting of an alkaline solution (often soluble silicate) and solid aluminosilicate materials. Geopolymerization occurs at ambient or slightly elevated temperature, where the leaching of solid aluminosilicate raw materials in alkaline solutions leads to the transfer of leached species from the solid surfaces into a growing gel phase, followed by nucleation and condensation of the gel phase to form a solid binder.' ''For ceramic scientists''〔Bell, Jonathan L.; Driemeyer, Patrick E. and Kriven, Waltraud M. (2009) (University of Illinois, USA), Formation of Ceramics from Metakaolin-Based Geopolymers. Part II: K-Based Geopolymer, ''J. Am. Ceram. Soc.'', 92 (), 607-615.〕 :'...Geopolymers are a class of totally inorganic, alumino-silicate based ceramics that are charge balanced by group I oxides. They are rigid gels, which are made under relatively ambient conditions of temperature and pressure into near-net dimension bodies, and which can subsequently be converted to crystalline or glass-ceramic materials.' 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Geopolymer」の詳細全文を読む スポンサード リンク
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