Synthesis of nanosized mullite from aluminosilicate precursors (CROSBI ID 558145)
Prilog sa skupa u zborniku | izvorni znanstveni rad | međunarodna recenzija
Podaci o odgovornosti
Buljan, Iva ; Kosanović, Cleo ;
engleski
Synthesis of nanosized mullite from aluminosilicate precursors
The type of precursors used for the synthesis and processing of mullite plays a key role on the shape-forming characteristics, sinterability, and the final properties of the product. While particulate or macromolecular colloids are preferred in fiber processing, powders are the most common form used in the fabrication of bulk objects. As it is found in our previous study [1], the controlled heating of ammonium-exchanged zeolite A resulted in the formation of an amorphous aluminosilicate, followed by desorption of water and ammonia. Except of bulginess formed on the particle surfaces as a result of the internal pressure of gas (NH3) developed by thermal decomposition of NH4+ ions inside zeolite A micro-crystals, the resulting particles of the amorphous aluminosilicate kept the size and shape of the precursor micro-crystals (NH4-exchanged zeolite A). A prolonged heating of the amorphous aluminosilicate resulted in its transformation into a mixture of mullite (63.4 wt. %), amorphous SiO2 (33.9 wt. %) and Na2SiO3 (2.7 wt. %). Resulting particles have the same size and shape as the particles of the starting amorphous aluminosilicate. The preserving of the particulate properties during the transformation processes led to the conclusion that each zeolite micro-crystal acted as a “closed” micro-reactor with a stable shell, and all relevant processes (crystal to amorphous transformation, nucleation and crystal growth of mullite from the amorphous aluminosilicate) occurred inside each single particle (crystal). This furthermore implied that mullite, SiO2 and Na2SiO3 did not appear as separate particulate systems, but that all phases existed as their physical mixture inside each single particle (micro-reactor). The intention of this study is to find a novel method for preparation of aluminosilicate-based ceramic materials by thermal treatment of amorphous aluminosilicates (zeolite precursors) as an alternative to conventional methods based on the thermal treatment of kaolin, feldspar, and other silicate, aluminosilicate and/or oxide mixtures, or by sol-gel method[2-6]. As the composition of the gel prepared for the synthesis of zeolite A is the same as the composition of the obtained crystalline product, and using the ability of the gel to exchange its hosts cations (sodium) with other cations from a solution as the zeolites did, in this study is used ammonium-exchanged gel as a precursor for preparation of mullite type ceramics.
mullite; thermal treatment; ceramic
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Podaci o prilogu
53-56.
2009.
objavljeno
Podaci o matičnoj publikaciji
Proceedings of 2nd Slovenian-Croatian Symposium on Zeolites
Bronić, Josip ; Novak Tušar, Nataša
Zagreb: Hrvatska zeolitna udruga (HZU)
978-953-55373-1-1
Podaci o skupu
Slovenian-Croatian Symposium on Zeolites
predavanje
01.10.2009-02.10.2009
Ljubljana, Slovenija