Alpha Hemihydrate Gypsum Preparationed by Atmospheric Pressure Salt Solution Method Process Route Zhao Luo 1, a, Fenglan Han 2,b and Xinhua Huang 3,c

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1 Applied Mechanics and Materials Online: ISSN: , Vol. 327, pp doi: / Trans Tech Publications, Switzerland Alpha Hemihydrate Gypsum Preparationed by Atmospheric Pressure Salt Solution Method Process Route Zhao Luo 1, a, Fenglan Han 2,b and Xinhua Huang 3,c 1 BeifangUnivesity of Nationalities,Yinchuan,Ningxia,China 2 BeifangUnivesity of Nationalities,Yinchuan,Ningxia,China 3 BeifangUnivesity of Nationalities,Yinchuan,Ningxia,China a @qq.com, b @qq.com, c @qq.com Keywords: Alpha hemihydrate gypsum ;Rotating crystal ;Atmospheric pressure salt solution method. Abstract Alpha Hemihydrate gypsum was prepared through atmospheric pressure salt solution method based on orthogonal experiments. The morphology and phase composition of the samples were observed and analyzed by microscope and X-ray diffractmeter. The major experimental parameters of atmospheric salt solution that prepared alpha half water gypsum were determined. The experiment result indicates that the best speed is 190 R/min, most appropriate water slurry ratio is 3.5:1 and the most suitable reaction time is 4h. In addition, grain was growing longer first in one direction, but when the length of the gains reaches at a certain extent, they will grow in two dimentions to become thick. Introduction Recently, as a new type of mold material Alpha hemihydrate gypsum is widely used in many industries, involve precision casting, mechanical machining, automotive components, chemical technology, architecture, art and craft, and so on. Because their superior performances, the market demand of Alpha hemihydrate gypsum is getting bigger and bigger. In recent years, with the rapid development of economy, the demand of Alpha hemihydrate gypsum has been growing very fast. But the requirements of the high quality and improved performance of the α-gypsum powder have been also growing. Especially, the Alpha high strength gypsum produced by liquid phase method, which has high purity and perfect whiskers, so its mechanical properties improved greatly. The compressive strength of the dry powder is among 50~ 100 MPa, and the products made from the powder have high strength, hardness, good abrasion resistance, clear outline, spindle Angle prominent and good simulation ability. Atmospheric pressure salt solution method prepare for Alpha Hemihydrate gypsum. Without high temperature and high pressure, its products also have superior performance. But the process is more complex which has never been reported at inland and abroad in industrialization. If we can simplify the processor reduce the cost, the method will bring huge economic and social benefits. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-20/09/16,00:04:33)

2 24 Advanced Research on Materials, Applied Mechanics and Design Science Experimental 1. Alpha hemihydrate gypsum prepared by Atmospheric pressure salt solution method flow chart shown. Fig1.Process flow diagram Fig2. XRD patterns From the Figure2, we can conclude that the diffraction peak of β-dihydrate gypsum weakened dramatically, while the diffraction peak of α-hemihydrate gypsum enhanced dramatically. Through the designed crystal experiment, most of the β-dihydrate gypsum converted in to α- hemihydrate gypsum. 2. Mixer speed (R/Min) parameters on the influence of the experiment. This experiment have four groups, the other parameters were determined, and change the mixer speed (R/Min) to observe the influence of the reaction, to select an optimal speed. The solution PH is 5, ratio of slurry is 4:1, the reaction time is 4 h, as well as other reaction parameters under the condition of same, mixer speed (R/Min), respectively for 240 R/Min, 210 R/Min. 180 R/Min, (when speed modulation 180 R/Min will stir under centrifugal force can't will gesso raw materials mixed with salt solution fully, solid-liquid delamination phenomenon happens. It is the lowest of 180 R/Min)

3 Applied Mechanics and Materials Vol There are a group of experiment is in the case of 180 R/Min, because blender blades is higher, in the case of the rotational speed is low, cannot be gesso raw materials mixed with salt solution fully, therefore in the process of reaction in gypsum to block, lead to the failure phenomenon. Solutions, adjust the blender blades to the appropriate location, gypsum salt solution and raw materials can be fully mixed. Through the Olympus microscope observe the sample morphology and the XRD analyse of the composition of the sample. Find mixer speed (R/Min) parameters on the experiment, that the faster the speed is, the size of crystals is smaller, XRD spectrum difference is small, so the percent conversion of β-dihydrate gypsum is almost same. Choose the lower speed, not only can reduce energy consumption, but also can make crystal grow fully. The best speed of mixer is 190 R/Min. 3. Water slurry ratio (the quality of the salt solution/gypsum material quality) parameters on the influence of the experiment. This experiment five group, the other parameters were determined, and change the water slurry ratio, observe the influences of reaction parameters, to select an optimal water slurry ratio. The solution PH is 5, rotating at 190 (R/Min), reaction time was 4 h, as well as other reaction parameters under the condition of same, water slurry ratio respectively 3:1, 3.5:1, 4:1, 4.5:1, 5:1. Made of samples, based on the analysis comparison, choose a best water slurry ratio. Through the analysis and comparison samples, with the increase of the water slurry ratio, the growth of grain will be more suitable, grain obviously can grow up better. And it is the growth of the grain direction is toward the direction of the length to diameter ratio greater development. But this effect on the strength of the product will be. Analyse XRD map, water slurry ratio for beta - conversion of dihydrate gypsum and the influence of product composition of small. But, take the needs of production into consideration, an experiment of water slurry smaller the product quantity is much more, so water slurry ratio 3.5:1 is relatively appropriate. In this condition, the growth of grain is not very big and ensures the strength of the samples, also can get more products. 4. The reaction time (h) parameters on the influence of the experiment This experiment consists of 4 groups, the other parameters were determined, we change the reaction time (h) to observe the influences of reaction parameters, then to choose a best reaction time (h). The solution PH is 5, rotating at 190(R/Min), water slurry ratio is 4:1, and other parameters under the same reaction. Then we change the reaction time (h) for 2(h), 3(h), 4(h), 5(h), 6(h). We make of samples through the analysis and comparison to choose the best reaction time (h) parameters. a. reaction 2(h) b. reaction (3)

4 26 Advanced Research on Materials, Applied Mechanics and Design Science c. reaction (5h) b.reaction(6h) Fig3. Different reaction time From figure 3 indicates that as the reaction time extension, the grain grew up, grains was growing longer first in one direction, but when the length of the gains reaches at a certain extent, they will grow in two dimentions to become thick. According to compare the XRD spectrum of the samples, we can see that the response time is 2 h, and reaction time is 3 h, compared with reaction time is 5 h, there is a diffraction peaks that increase markedly. The diffraction peak isα- hemihydrate gypsum diffraction peak, The result is that the reaction time is 2 h, 3 h 4 h, The Diffraction peak enhance; 5h and 4h, 6h which change almost nonexistent. So 4h is the suitable reaction time. Conclusion 1. The mixer speed for preparation of Alpha hemihydrate gypsum have no great influence, the speed affect the grain size, but the influence is small. Finally we determined the speed is 190(r/min). 2. The smaller of the water slurry ratio, the more suitable for transfer of crystal experiment and more suitable for the growth of the grain size.considering the strength of samples and the efficiency of the samples production, The water slurry ratio 3.5:1 is the most appropriate. 3. Grains were growing longer first in one direction, but when the length of the gains reaches at a certain extent, they will grow in two dimentions to become thick. From all consideration we determined the best reaction time is 4h. References [1]Li Lin, Sun Yuanxi, Atmospheric salt solution prepared by α- hemihydrate gypsum Process conditions research,, Chemical Industry Times, vol. A247, pp , April [2]Wang Chaoyong, Tao Xian.α- hemihydrate gypsum production technology research and application, Non-Metallic Mines, Vol.124 No15,Sep2001. [3]Zorpas A A, Kapetanios E, Zorpas G, et al. Compost producedfrom organic fraction of municipal solid waste, primary stabilizedsewage sludge and natural zeolite[j]. Journal of HazardousK.Elissa, Title of paper if known, unpublished.r. Nicole, Title of paper with only first word capitalized, J. Name Stand. Abbrev., in press.

5 Applied Mechanics and Materials Vol [4]Zhao Jianhua, Sun Linwen, and Wang Wenzhong et al., Alpha High Strength Gypsum Liquid Phase Method Production Technology and Application, China Non-Metallic Mining Industry Herald.vol. No69, April2008. [5] Liu Hongxia,Peng Jiahui,Qu Jindong. Study on crystal modifier in preparation ofα-semi hydrated gypsum by aqueous salt solution method in atmospheric pressure.new building materials. April2010. [6] Wu Xiaoqin, Tong Shitang, Guan Baohong and Wu Zhongbiao. Transformation of Flue-Gas-Desulfurization Gypsum toα-hemihydrated Gypsum in Salt Solution at Atmospheric Pressure. Chin.J.Chem.Eng.Vol.19,No.2,April 2011