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).
Highlights
Calcium sulfate whiskers with high aspect ratios are promising reinforcing materials for composites as rubbers, plastics, plaster and friction materials, etc. [1,2,3,4], showing excellent thermal stability and mechanical strength [5,6,7]
Calcium sulfate whiskers can be produced by preparing α-CaSO4 ·0.5H2 O whiskers through hydrothermal, acidification, reverse micro-emulsion, and microwave-assisted approaches [8,9,10,11,12,13] followed by calcination of the α-CaSO4 ·0.5H2 O whiskers above 600 ◦ C [14,15]
Based on the adsorption and inhibition mechanism, previous work focused on studying the influence of inorganic ions on the growth of α-CaSO4·0.5H2O whiskers, aimed at preparing the whiskers with high aspect ratios
Summary
Calcium sulfate whiskers with high aspect ratios are promising reinforcing materials for composites as rubbers, plastics, plaster and friction materials, etc. [1,2,3,4], showing excellent thermal stability and mechanical strength [5,6,7]. Based on the adsorption and inhibition mechanism, previous work focused on studying the influence of inorganic ions on the growth of α-CaSO4·0.5H2O whiskers, aimed at preparing the whiskers with high aspect ratios. Are commonly-used cation surfactants that may inhibit the growth of the whiskers along2the direction normal to the lateral facets more effectively They have long alkyl chains, which possibly provide a strong steric hindrance and reduce the surfaceaspect energyratios of the sideFor facets of the Zhao whiskers. 18, abbreviated as ATAB) are commonly-used cation surfactants that may inhibit the growth of the whiskers along the direction normal to the lateral facets more effectively.
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