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Studies on the Preparation of Uniform Aragonite Whisker and Mechanism of Crystal Growth

Author: Zhang
Tutor: ZhangZhao
School: Sichuan University
Course: Applied Chemistry
Keywords: Aragonite Whiskers prepared Growth Mechanism Surface Modification
CLC: O782
Type: Master's thesis
Year: 2002
Downloads: 360
Quote: 5
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Abstract


Aragonite calcium carbonate whisker is a high performance single crystal fiber materials. Preparation of aragonite calcium carbonate whiskers in promoting China's traditional calcium carbonate industry, the development of new materials as well as the development of the theory of crystal growth have important theoretical and practical significance. In this paper, improved carbonization method aragonite calcium carbonate whiskers were prepared using a high power microscope combined with computer technology product morphology and crystal form analysis, scanning electron microscopy and X-ray diffraction (XRD), temperature, MgCl 2 concentration, initial pH value CO 2 flow rate, stirring speed and other factors on the preparation aragonite phase calcium carbonate whiskers. The experimental results show that the optimal process parameters for preparation aragonite calcium carbonate whiskers pH value maintained at around 9, the reaction temperature of 75 ° C, the the CO 2 flow rate of 4.5ml/min/gCaO, stirring speed is 250r/min. On this basis, further on Mg 2 participation of Ca (OH) 2 saturated solution-CO 2 liquid - gas system, CaCl the 2 -Na 2 CO 3 and CaCl 2 - the urea liquid - liquid system was investigated experimentally confirmed maintaining a suitably high temperature and low calcium carbonate supersaturation, to guarantee the separation of the nucleation and growth is a necessary condition to obtain the uniforming aragonite calcium carbonate whiskers, thereby revealing that the Ca (OH) 2 -MgCl 2 -CO 2 System role the MgCl 2 is not just adsorbed on Mg 20 calcium carbonate nuclei facilitate its aragonite development, but more important is the use mM MgCl 2 and the reaction of Ca (OH) 2 Ca (OH) 2 -CO 2 solid - gas reaction transformed into more readily liquid - gas reaction, avoid to the solid phase of Ca (OH) 2 crystal nucleation and growth of calcite. At the same time, the ratio of Ca (OH) 2 the more insoluble Mg (OH) 2 the pH of the system is maintained at about 9 effectively reduce CO 3 2 - distribution coefficient, to maintain higher Ca 2 concentration lower calcium carbonate supersaturation, to ensure the formation of aragonite calcium carbonate whiskers greatly improving the yield of the aragonite calcium carbonate whiskers. In order to solve as the inorganic filler due to the hydrophilic surface oleophobic poor dispersibility within the polymer material, the the poor disadvantage of force, must be combined with the polymer body of aragonite calcium carbonate whisker surface modification. In this paper, stearic acid and titanate surface modification of aragonite calcium carbonate whisker, the prepared modified text of Sichuan University, a master's degree thesis Stone phase of Calcium Carbonate Whisker. Infrared spectrometer and suspension experiments show that both can effectively implement modified on aragonite calcium carbonate whisker achieve complete modified titanate amount less than stearic acid.

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CLC: > Mathematical sciences and chemical > Crystallography > Crystal growth > Crystal growth process
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