Effects of kaolinite layer expansion and impurities on the solid-state reaction of kaolinite

Abstract

Effects of kaolinite layer expansion and impurities on the rapid formation of metastable CaAl2Si2O8 with the supression of byproduct formation were demonstrated based on the solid-state reaction of calcium carbonate with methoxy-modified kaolinite.

Effect of kaolinite edge surfaces on formation of Tb3+-doped phosphor by solid-state reaction

“…In our previous studies, 7,9 the kaolinite grinding process was found to generate new hydroxyl groups by breaking Al-O-Si bonds 7 and the expanded kaolinite increased the available edge surfaces. 9 The present immersion method could therefore be an effective means of doping the ground mixture of Ex-Kaol and CaCO 3 . Because the ground raw material exhibited some green phosphorescence aer immersion in the Tb 3+ solution (Fig.…”

“…13 The raw materials and grinding conditions used in this research were identical to those employed in our previous study. 9 The kaolinite raw material was expanded Kanpaku kaolinite (JCSS-1101c, obtained from the Clay Science Society of Japan) without impurities (referred to herein as Ex-Kaol), a methoxy-modified kaolinite. 9 This material was used to rapidly generate metastable CaAl 2 Si 2 O 8 containing minimal byproducts (referred to herein as m-CAS).…”

“…9 This material was used to rapidly generate metastable CaAl 2 Si 2 O 8 containing minimal byproducts (referred to herein as m-CAS). 9 All the chemicals used in this study were reagent grade. In each reaction, a quantity of the kaolinite products was combined with CaCO 3 (Hayashi Pure Chemical Ind., Ltd.) in a 1 : 1 molar ratio and roughly mixed using an agate mortar and pestle.…”

“…1,2 This grinding procedure also disrupts the stacking order of layered inorganic solids. 3–9 In previous report by our group using expanded kaolinite as a raw material, this disordering process was facilitated by layer expansion, resulting in the rapid formation of target products. 9 Kaolinite is a layered clay mineral having the formula Al 2 Si 2 O 5 (OH) 4 and, while each layer in the kaolinite structure is neutral, each edge represents a crystal fracture surface bearing cation exchange sites.…”

“…3–9 In previous report by our group using expanded kaolinite as a raw material, this disordering process was facilitated by layer expansion, resulting in the rapid formation of target products. 9 Kaolinite is a layered clay mineral having the formula Al 2 Si 2 O 5 (OH) 4 and, while each layer in the kaolinite structure is neutral, each edge represents a crystal fracture surface bearing cation exchange sites. 10,11 The number of available kaolinite edges was also found to increase as a result of layer expansion in our previous study, and so we are interested in the possibility of using these edges to promote solid-state reactions.…”