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Crystals 2017, 7(1), 28; doi:10.3390/cryst7010028

Influence of Alkyl Trimethyl Ammonium Bromides on Hydrothermal Formation of α-CaSO4·0.5H2O Whiskers with High Aspect Ratios

Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
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Academic Editor: Helmut Cölfen
Received: 1 December 2016 / Revised: 11 January 2017 / Accepted: 16 January 2017 / Published: 18 January 2017
(This article belongs to the Special Issue Solution-Processed Inorganic Functional Crystals)
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Abstract

In this paper, the influence of alkyl trimethyl ammonium bromides (CnH2n+1(CH3)3NBr, n = 10, 12, 14, 16, 18, abbreviated as ATAB) on the formation of alpha calcium sulfate hemihydrate (α-CaSO4·0.5H2O) whiskers under a hydrothermal condition (135 °C, 3.0 h) was analyzed. Specifically, it focuses on cetyl trimethyl ammonium bromide (C16H33(CH3)3NBr, abbreviated as CTAB). The rising CTAB concentration from 0 to 9.2 × 10−4 mol·L−1 led to the increase of the average aspect ratio of α-CaSO4·0.5H2O whiskers from 80 to 430, since the selective adsorption of CTAB on the negatively-charged side facets of the whiskers inhibited the growth of the whiskers along the direction normal to the lateral facets. The further increase of CTAB concentration above the critical micelle concentration (abbreviated as CMC) showed little effect on the morphology of α-CaSO4·0.5H2O whiskers, considering that CTAB tended to form micelles instead of being adsorbed on the whisker surfaces. Similar phenomena were observed in other ATABs (n = 10, 12, 14, 18). View Full-Text
Keywords: α-CaSO4·0.5H2O whiskers; aspect ratio; CTAB; adsorption; critical micelle concentration α-CaSO4·0.5H2O whiskers; aspect ratio; CTAB; adsorption; critical micelle concentration
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Chen, R.; Hou, S.; Wang, J.; Xiang, L. Influence of Alkyl Trimethyl Ammonium Bromides on Hydrothermal Formation of α-CaSO4·0.5H2O Whiskers with High Aspect Ratios. Crystals 2017, 7, 28.

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