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Preparation method of high length-diameter ratio anhydrous calcium sulfate whisker

An anhydrous calcium sulfate, calcium sulfate whisker technology, applied in chemical instruments and methods, calcium/strontium/barium sulfate, single crystal growth, etc. Application, enhancement effect reduction and other problems, to achieve the effect of high product added value, easy industrial promotion, and regular appearance

Active Publication Date: 2010-03-17
TSINGHUA UNIV
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Problems solved by technology

In addition, citric acid, sodium dodecylsulfonate, sodium polyacrylate, etc. can all affect the morphology of calcium sulfate whiskers at room temperature (Peng Jiahui, Zhai Jindong, Wu Li, Zhang Jianxin, citric acid on dihydrate gypsum The effect of crystal growth habit and crystal morphology, Journal of Southeast University, 2004, 34(3), 356-360; Ren Yinzhe, Wang Xiaodong, Wang Jianying, The control of sodium dodecylsulfonate and sodium polyacrylate on the morphology of calcium sulfate , Shanxi Normal University Journal (Natural Science Edition), 2005, 19(4), 53-56), but it is not beneficial to the increase of aspect ratio
In short, the shortcomings of the above methods are either large energy consumption or low aspect ratio
Adjusting the calcination temperature or heating rate can slow down the morphology destruction in the pyrolytic dehydration process of calcium sulfate hemihydrate to a certain extent (Han Yuexin, Wang Yubin, Yuan Zhitao, Yin Wanzhong, Effect of calcination on calcium sulfate whisker structure and stability impact, IM&P Chemical Minerals and Processing, 2008, 3, 13-16), but the pores produced by dehydration cannot be avoided, so that the product of anhydrous calcium sulfate whiskers has more structural defects, poor morphology, and reduced reinforcement effect
[0008] In a word, although the predecessors have carried out some work on the preparation of calcium sulfate whiskers with high aspect ratio, there are still problems such as harsh conditions or poor product morphology, which limit the further industrial application of related technologies

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preparation example Construction

[0020] The invention provides a method for preparing calcium sulfate whiskers with high aspect ratio. Using inorganic calcium salts and inorganic precipitants as raw materials and surfactants as dispersants, first prepare well-dispersed ultrafine calcium sulfate dihydrate precursors at room temperature; then use the selection of morphology control agents under hydrothermal conditions The one-dimensional directional growth of calcium sulfate hemihydrate is promoted by the adsorption effect; then the shrinkage cavity elimination and structural reformation are realized by flux roasting method, thus obtaining sulfuric acid with large aspect ratio, uniform and regular shape, high crystallinity and good dispersion calcium whiskers. Specific steps are as follows:

[0021] 1) Using inorganic calcium salt and inorganic precipitant as raw materials, using surfactant as dispersant, under the condition that the temperature is 10-90°C and the stirring speed is 50-500 rpm, the inorganic pr...

Embodiment 1

[0029] Prepare 100 mL of a mixed solution containing 0.1 mol / L calcium chloride and 0.001 mol / L cetyltrimethylammonium bromide, and 100 mL of a 0.1 mol / L sulfuric acid solution. Under the condition that the temperature is 10°C and the stirring speed is 50 rev / min, add the sulfuric acid solution into the mixed solution containing calcium chloride and cetyltrimethylammonium bromide at a speed of 20mL / min, and continue to React for 0.5 hours to obtain a white milky slurry; filter and wash the above-mentioned slurry and put it into a high-pressure reactor, add a sodium chloride solution with a molar concentration of 0.005mol / L, adjust the solid content to 0.1wt%, at a temperature of 100°C 1. Under the condition of stirring speed of 50 rev / min, the hydrothermal reaction was carried out for 10 hours, cooled, filtered, washed and dried (105° C., 4 hours) to obtain the intermediate product of calcium sulfate hemihydrate whiskers. Mix calcium sulfate hemihydrate whiskers with sodium ch...

Embodiment 2

[0031] Prepare 100 mL of a mixed solution containing 5 mol / L calcium nitrate and 0.5 mol / L sodium dodecylbenzenesulfonate, and 100 mL of a 5 mol / L potassium sulfate solution. At a temperature of 90°C and a stirring speed of 500 rpm, add the potassium sulfate solution to the mixed solution containing calcium nitrate and sodium dodecylbenzenesulfonate at a rate of 1 mL / min, and continue the reaction for 2 hours after the addition is complete. , to obtain a white milky slurry; the above-mentioned slurry is filtered and washed and put into an autoclave, adding a molar concentration of 5mol / L potassium chloride solution to adjust the solid content to 20wt%. Hydrothermal reaction under different conditions for 0.5 hours, cooling, filtering, washing, and drying (105°C, 4 hours) to obtain the intermediate product of calcium sulfate hemihydrate whiskers. Mix calcium sulfate hemihydrate whiskers with potassium chloride, control the weight ratio of the two to 100:10, place the mixture in...

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Abstract

A preparation method of high length-diameter ratio anhydrous calcium sulfate whisker belongs to the technical field of inorganic chemical material preparation. The method takes inorganic calcium saltand inorganic precipitant as raw materials and surfactant as dispersant, and includes the following steps: first preparing superfine calcium sulphate dihydrate precursor with good dispersion at the temperature of 10-90 DEG C; then adding the precursor into water solution containing shape control agent to conduct hydrothermal reaction for 0.5-10h at the temperature of 100-250 DEG C, and obtaining calcium sulfate hemihydrate whisker; mixing the calcium sulfate hemihydrate whisker with inorganic solvent; and roasting the mixture for 0.5-6h at the temperature 200-800 DEG C to obtain anhydrous calcium sulfate whisker with the length of 20-2000mum, the diameter of 0.5-20mum, the length-diameter ratio of 40-1000 and the main content greater than 95wt% after washing and drying. The technology is simple, the cost is low and the added value of the product is high. The prepared calcium sulfate whisker has large length-diameter ratio and regular shape and can be used as reinforcing material to beapplied in industries such as plastics, rubber, ceramics, cement, papermaking and the like.

Description

technical field [0001] The invention relates to a method for preparing anhydrous calcium sulfate whiskers with high aspect ratio, and belongs to the technical field of preparation of inorganic chemical materials. Background technique [0002] my country is a country rich in calcium resources. There are not only a large number of secondary calcium resources (such as calcium chloride and carbide slag produced in the inorganic chemical industry), but also abundant natural limestone resources, sulfate and sulfuric acid resources. And cheap, provide good conditions for the development of calcium sulfate whisker materials. [0003] Whiskers are single crystal fibers with an aspect ratio greater than 10. The atomic structure is highly ordered and there are few internal defects. It is an excellent reinforcing and toughening agent for composite materials. The earliest industrial whisker product (silicon carbide) appeared in 1962, and its application was limited due to its extremely h...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C30B29/62C30B29/22C30B7/10C01F11/46
Inventor 向兰罗康碧李春梅李沪萍
Owner TSINGHUA UNIV
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