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Auteur : Grafiati
Publié le 8 juillet 2023

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1

MATSUI, Hiroshi, Kayoko AMITA, Genzo HASHIZUME, Gin-ya ADACHI et Jiro SHIOKAWA. « The formation of needlelike .ALPHA.-calcium sulfate hemihydrate from calcium sulfite hemihydrate. » NIPPON KAGAKU KAISHI, no 12 (1987) : 2279–85. http://dx.doi.org/10.1246/nikkashi.1987.2279.

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2

Liu, Xian Feng, Jia Hui Peng, Jian Xin Zhang, Ming Zheng Chen et Qian Dong. « Effect of Polycarboxylicacid Plasticizer on Characteristics of α-Calcium Sulfate Hemihydrate ». Applied Mechanics and Materials 423-426 (septembre 2013) : 1085–89. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.1085.

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Purpose: studied the mechanism of polycarboxylicacid plasticizing effect on α-calcium sulfate hemihydrate. Methods: the adsorbed amount was tested by ultraviolet visible absorption spectrum method, ζ potential was measured by micro-electrophoresis analysis, and the corresponding workability was studied. Results: firstly, polycarboxylicacid plasticizer was adsorbed on α-calcium sulfate hemihydrate by Van Der Waals force and the saturated adsorption quantity of polycarboxylicacid plasticizer (HC) was about 5.8mg/g; secondly, the decisive factor for polycarboxylicacid plasticizer to disperse α-calcium sulfate hemihydrate particles was the steric hindrance of polycarboxylicacid plasticizer, and the maximum ζ potential of α-calcium sulfate hemihydrate with polycarboxylicacid plasticizer was-9.360mv, much less than β-calcium sulfate hemihydrate under the same conditions; finally, the perfect mixing content of polycarboxylicacid plasticizer was 0.3%~0.6%; it increased fluidity by 66%, to the maximum 300mm.
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3

Feng, Yan, Rongxin Guo et Zhiwei Lin. « Effect of Aluminum Sulfate and Succinic Acid on the Growth Law of α-Calcium Sulfate Hemihydrate under Microwave Irradiation ». Advances in Materials Science and Engineering 2021 (12 avril 2021) : 1–13. http://dx.doi.org/10.1155/2021/6630638.

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The existing α-hemihydrate gypsum preparation process has low production efficiency and high energy consumption. In this paper, α-type hemihydrate gypsum was prepared by microwave irradiation using phosphogypsum as the raw material, calcium chloride solution as the reaction medium, and succinic acid and aluminum sulfate as crystal-transforming agents. Both aluminum sulfate and succinic acid were studied to determine the mechanism influencing the effect on the growth of α-type hemihydrate gypsum crystals. This study found that, without added succinic acid or aluminum ions, the crystal transformation rate of α-calcium sulfate hemihydrate reached 96% with the average length-diameter ratio reaching 21 after 1 h; when the dosage of succinic acid was 0.02%, the crystal transformation rate of α-calcium sulfate hemihydrate reached 96% with the average length-diameter ratio reaching 1.5 after 1.5 h; and when the aluminum ion dosage was 5 mM, the crystal transformation rate of α-calcium sulfate hemihydrate reached 97% with the average length-diameter ratio reaching 12.3 after 1 h. In addition, it was discovered that the reaction time was significantly shortened under microwave irradiation, and with an increase in succinic acid content, the regulation of the microscopic morphology of the calcium sulfate hemihydrate crystals was continuously enhanced and the aspect ratio of the crystals was continuously reduced. The EDS and Fourier transform infrared spectroscopy (FTIR) analysis showed that succinic acid did not adsorb onto the hemihydrate gypsum crystal during the reaction under microwave irradiation. The X-ray photoelectron spectroscopy (XPS) analysis revealed that aluminum ions affected crystal growth by incorporating into calcium sulfate hemihydrate crystals after reacting with sulfate radicals.
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MATSUI, Hiroshi, Genzo HASHIZUME, Gin-ya ADACHI et Jiro SHIOKAWA. « Formation of prismatic .ALPHA.-calcium sulfate hemihydrate during oxidation of calcium sulfite hemihydrate. » NIPPON KAGAKU KAISHI, no 6 (1988) : 892–98. http://dx.doi.org/10.1246/nikkashi.1988.892.

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5

Wang, Yu Bin, Le Yu, Hua Wang et Ting Shu He. « Effect of Sodium Citrate on the Hydration Capacity of Hemihydrate Calcium Sulfate Whiskers ». Applied Mechanics and Materials 584-586 (juillet 2014) : 1618–21. http://dx.doi.org/10.4028/www.scientific.net/amm.584-586.1618.

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The influence of sodium citrate on the hydration capacity of hemihydrate calcium sulfate whiskers was investigated. The products were characterized by FTIR, SEM and XRD.The results show that the absorption of the sodium citrate on the surface of the hemihydrate calcium sulfate whiskers is not uniform, and the adsorption state also changed with the amount of sodium citrate. Sodium citrate plays role on the hydration capacity of hemihydrate calcium sulfate whiskers.
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6

Liu, Xian Feng, Jia Hui Peng, Ming Zheng Chen, Leng Bai et Liu Liu. « Effect of Butane Diacid on Crystal Morphology and Reaction Process of α-Calcium Sulfate Hemihydrate in Preparation from Flue Gas Desulphurization Gypsum ». Advanced Materials Research 838-841 (novembre 2013) : 2681–84. http://dx.doi.org/10.4028/www.scientific.net/amr.838-841.2681.

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Modifying crystal morphology was the key technology of the preparation of α-calcium sulfate hemihydrate from flue gas desulphurization gypsum using the hydrothermal method under atmospheric pressure. For exploring the mechanism of butane diacid effect on crystal morphology of α-calcium sulfate hemihydrate in preparation from flue gas desulphurization gypsum, the crystal morphology, convert ratio, and reaction process of α-calcium sulfate hemihydrate were studied by scanning electron microscope observation, and crystal water testing. The results showed, firstly, crystal modifier made the growth rates of crystal in all directions equal and made the crystal into hexagonal short column, by selectivity adsorbing on (111) crystal plane of α-calcium sulfate hemihydrate to form buffer film layer which hindered combining and growing of crystallization unit on the crystal plane of c-axis direction. Secondly, butane diacid was a good crystal modifier. When adding butane diacid of optimal amount of 0.02%~0.05%, the crystal morphology of α-calcium sulfate hemihydrate was satisfactory, the crystal length-diameter ratio was 1:1, but the convert ratio was only 91%~93%.
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7

Zhu, Xin Feng, Yu Bin Wang, Xiao Wang et Liu Shuan Yang. « Integration of Preparation and Stabilization for Hemihydrate Calcium Sulfate Whiskers ». Advanced Materials Research 239-242 (mai 2011) : 3074–77. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.3074.

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The integration process of hemihydrate calcium sulfate whiskers with optimum additives was carried out, and the influence of reagents on the crystal shape and stability of hemihydrate calcium sulfate whiskers was investigated too. The products were characterized by FT-IR, SEM and XRD.The results show that the integration of preparation and stabilization of hemihydrate calcium sulfate whiskers can be achieved with addition of 0.025% sodium stearate and 0.15% sodium oleate by adding agents in different steps.
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Chen, Chang, Yu Bin Wang, Le Yu, Ying Jie Song, Shan Shan Zhang et Ai Zhang. « Hydration Ability of Hemihydrate Calcium Sulphate Whiskers with Different Content of Sodium Phosphate ». Applied Mechanics and Materials 638-640 (septembre 2014) : 1346–49. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.1346.

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Different content of sodium phosphate was added into the hemihydrates sulphate whiskers for 30 min to 2h of standing time. The treated products were researched by SEM, TG-DSC and XRD. The results indicate that when the dosage of sodium phosphate was more than 0.10%, the morphology of hemihydrate calcium sulphate whisker was fully maintained. However, the crystal structure of the products had changed and the half water calcium sulfate turned into of dihydrate calcium sulphate when 0.10 wt% sodium phosphate added. With the increase of standing time, half water calcium sulfate whisker converted into dihydrate calcium sulphate whisker. Sodium phosphate could reduce hydration ability of half water calcium sulfate whisker when the content of sodium phosphate was more than 0.10%.
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Wang, Xiao, Yu Bin Wang, Liu Shuan Yang, Xiao Fei Wang et Jia Kuan Yang. « Stabilization Effect of Sodium Phosphate on Hemihydrate Calcium Sulfate Whiskers ». Advanced Materials Research 287-290 (juillet 2011) : 535–38. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.535.

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Stabilization effect of sodium phosphate on crystalline phase and crystal shape of hemihydrate calcium sulfate whiskers was investigated. Morphology, thermal stability and phase composition of stabilized hemihydrate calcium sulfate whiskers were characterized by means of SEM, DSC-TG and XRD respectively. Results indicated that crystalline shape of hemihydrate calcium sulfate whiskers could be invariable in two hours at 100 °C with addition of 0.10 wt % sodium phosphate for 20 min. Meanwhile sodium phosphate had a good effect on whiskers morphology stabilization.
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Dai, Hao, Shu Peng Zhang, Cheng Lan Ju et Dong Xu Li. « Influence of Calcium Sulfate Varieties on Properties of Calcium Aluminate Cement-Based Self-Leveling Mortars ». Key Engineering Materials 680 (février 2016) : 455–61. http://dx.doi.org/10.4028/www.scientific.net/kem.680.455.

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The effect of calcium sulfates varieties on the properties of calcium aluminate cement-based self-leveling mortar have been investigated, and the hydration kinetics, hydrated products and microstructures are characterized by isothermal calorimeter, X-ray diffraction and mercury intrusion porosimetry, respectively. The results show that the technological properties of mortars are significantly affected by calcium sulfate varieties and content. The setting times are shortened drastically with the addition of calcium sulfates. Mortars with hemihydrate show higher early strength and less drying shrinkage. In contrast, using anhydrite in mortars cause lower strength and higher drying shrinkage at early age but larger growth of strength in the late. The increasing calcium sulfates content may result in the delay of main hydration peak in the heat evolution curve. For formulation with hemihydrate, the appearance of main hydration peaks are advanced compared with formulation without addition of calcium sulfates. Moreover, mortar microstructures are optimized by addition of β-hemihydrate, the proportion of large pores are lower than that of mortars with anhydrite.
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11

Liu, Hong Ye, et Yu Bin Wang. « Effect of Stabilizer on Morphology and Stability of Hemihydrate Calcium Sulfate Whiskers ». Advanced Materials Research 374-377 (octobre 2011) : 1495–98. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.1495.

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The influence of stabilizer on the crystal shape and stability of hemihydrate calcium sulfate whiskers was investigated in detail. Morphology, surface group and phase composition of stabilized hemihydrate calcium sulfate whiskers were characterized by means of SEM, FTIR and XRD, and then effect mechanism was discussed. The results showed that the absorption state of sodium oleate will be different with respectively additive amount which cause whiskers shape and stability to change, and that the stability of hemihydrate calcium sulfate whiskers can be achieved without affecting crystal growth by adding agents in different steps.
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12

Saenko, Y. V., A. M. Shiranov et A. L. Nevzorov. « MECHANICAL PROPERTIES OF PHOSPHOGYPSUM AND TRENDS ITS UTILIZATION ». Construction and Geotechnics 12, no 3 (15 décembre 2021) : 84–93. http://dx.doi.org/10.15593/2224-9826/2021.3.09.

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Phosphogypsum is a waste obtained by binding calcium in the process of sulfuric acid decomposition of phosphate raw materials in the production of phosphorus fertilizers. The article presents the results of complex laboratory studies of more than 500 samples of calcium sulfate hemihydrate and dihydrate. Calcium sulfate dihydrate (CaSO4·2H2O) is a solid fine-crystalline substance of white or gray color with the inclusion of large aggregates. Deformability, strength properties and permeability of calcium sulfate dihydrate were determined on specially prepared samples with a relative compaction of 0.95; 0.90 and 0.80 by the methods used in engineering and geological surveys. The internal friction angle, cohesion and coefficient of permeability have values typical for silty sands and sandy loam, and the compressibility characteristics are significantly lower due to the solubility of matter. This material is characterized by subsidence and suffusion sediment characteristic of carbonate rocks (dolomite, limestone). Calcium sulfate hemihydrate (CaSO4·0.5H2O) - a loose earthy mass of white or gray color, as the process of hydration and the appearance of cementation bonds turns into a semi-rocky technogenic soil of low strength. The characteristics of calcium sulfate hemihydrate were determined on the undisturbed samples taken from the dump after 1 and 6 months, 1, 5 and 10 years after storage. These characteristics are comparable to construction gypsum materials from lower grades. It is recommended to use calcium sulfate dihydrate as ground material when carrying out water-protective measures and neutralizing the acids contained in it, the use of calcium sulfate hemihydrate is significantly limited by its setting time.
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Liu, Xian Feng, Jia Hui Peng, Chen Yang Zou, Leng Bai et Mei Li. « The Effect of Process Conditions on the Preparation of α-Calcium Sulfate Hemihydrate from FGD Gypsum Using the Hydrothermal Method under Atmospheric Pressure ». Advanced Materials Research 250-253 (mai 2011) : 881–89. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.881.

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This paper studies the laws of crystal growth, percent conversion and the rate of reaction of α-calcium sulfate hemihydrate from FGD gypsum under different conditions using the hydrothermal method under atmospheric pressure. The crystal morphology was observed by using SEM, polarizing microscope profile, and percent conversion and the rate of reaction were obtained by assaying crystal water content and calculating. The results showed, (1) with the increase of reaction temperature, the dehydration rate increased and the formed α-calcium sulfate hemihydrate crystal had a larger particle size; (2) with the increase of salt concentration or slurry concentration, the formed α-calcium sulfate hemihydrate crystal was smaller, percent conversion and the rate of reaction was nearly unchanged; (3) with the increase of pH value of solution, the rate of reaction increased and percent conversion was nearly unchanged, and with pH value ranging from 5 to 7 the formed α-calcium sulfate hemihydrate crystal was crassitude. In conclusion, the perfect technological parameters were as follows: reaction temperature ranging from 95°C to 100°C, salt concentration ranging from 15% to 20%, slurry concentration ranging from 15% to 20%, pH value ranging from 5 to 7, and reaction time not exceeding 90min.
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Taherdangkoo, Reza, Miaomiao Tian, Ali Sadighi, Tao Meng, Huichen Yang et Christoph Butscher. « Experimental Data on Solubility of the Two Calcium Sulfates Gypsum and Anhydrite in Aqueous Solutions ». Data 7, no 10 (16 octobre 2022) : 140. http://dx.doi.org/10.3390/data7100140.

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Calcium sulfate exists in three forms, namely dihydrate or gypsum (CaSO4·2H2O), anhydrite (CaSO4), and hemihydrate or bassanite (CaSO4·0.5H2O) depending on temperature, pressure, pH, and formation conditions. The formation of calcium sulfates occurs widely in nature and in many engineering settings. Herein, a dataset containing the experimental solubility data of calcium sulfate minerals, i.e., gypsum and anhydrite, in aqueous solutions is presented. The compiled dataset contains calcium sulfates solubility values extracted from 42 papers published between 1906 and 2019. The dataset can be used for various scientific and engineering purposes such as environmental applications (e.g., gas treatment, wastewater treatment, and chemical disposal), geotechnical applications (e.g., clay-sulfate rock swelling), separation processes (e.g., crystallization, extractive distillation, and seawater desalination), and electrochemical processes (e.g., corrosion and electrolysis).
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15

Singh, Manjit, et Mridul Garg. « Calcium sulfate hemihydrate activated low heat sulfate resistant cement ». Construction and Building Materials 16, no 3 (avril 2002) : 181–86. http://dx.doi.org/10.1016/s0950-0618(01)00026-5.

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Wu, Xiao Pei, Wei Bo Zhu, Duan Cheng Wang et Qing Hua Chen. « A Modification of Spherical Particles Calcium Sulfate for Alveolar Bone Defect ». Applied Mechanics and Materials 377 (août 2013) : 199–203. http://dx.doi.org/10.4028/www.scientific.net/amm.377.199.

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Calcium sulfate hemihydrate has been used for many years as a biomaterial. However, too fast a degradation rate and lack of bioactivity have limited its application in orthopaedic field. Herein, α-Calcium sulfate hemihydrate is used as the raw material to prepare spherical particles calcium sulfate with stir method. Microstructures, degradation, and bioactivity of the materials were characterized by XRD, FT-IR and SEM. The effects of solutions of sodium silicate (Na2SiO3) on the structure and properties of the materials were analyzed. The results indicate that both the interface structure and the surface crystal binding state of the spherical particles calcium sulfate are changed by the solutions. The bioactivity was significantly improved by the solutions of Na2SiO3. With increasing the concentration of solutions in the materials, the degradation rate of the materials is decreased. Si-O network membrane which contains a large amount of Si-OH was formed on the surface of calcium sulfate. Therefore, the degradation rate was decreased and the bioactivity was significantly improved.
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Liu, Xian Feng, Jia Hui Peng, Jian Xin Zhang, Jin Dong Qu et Mei Li. « Effect of Organic Diacid Carbon Chain Length on Crystal Morphology of α-Calcium Sulfate Hemihydrate in Preparation from Flue Gas Desulphurization Gypsum ». Applied Mechanics and Materials 253-255 (décembre 2012) : 542–45. http://dx.doi.org/10.4028/www.scientific.net/amm.253-255.542.

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Modifying crystal morphology was the key technology of the preparation of α-calcium sulfate hemihydrate from flue gas desulphurization gypsum using the hydrothermal method under atmospheric pressure. For exploring crystal modifier, the crystal morphology of α-calcium sulfate hemihydrate in preparation from flue gas desulphurization gypsum with various organic diacid was studied, by polarizing microscope profile observation. The results showed, When the space between two carboxyls was triplicate length of C-C, the organic diacid had the best effect of modifying crystal morphology.
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Xu, Ling Lin, Pei Ming Wang, Guang Ming Wu et Guo Fang Zhang. « Effect of Calcium Sulfate on the Formation of Ettringite in Calcium Aluminate and Sulfoaluminate Blended Systems ». Key Engineering Materials 599 (février 2014) : 23–28. http://dx.doi.org/10.4028/www.scientific.net/kem.599.23.

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The formation of ettringite and the expansion associated with it were studied on paste made from Portland cement, two Al-bearing compounds such as calcium aluminate cement and calcium sulphoaluminate cement, and calcium sulfate with different reactivities (anhydrite, α-hemihydrate and gypsum). The hydration process and formation of ettringite in the binders with different content of calcium sulfate was investigated by free expansion testing, isothermal conduction calorimetry, X-ray diffraction (XRD) and environmental scanning electronic microscope (ESEM). Results showed that the reactivity and amount of the calcium sulfate determined the balance between the hydration products of ettringite and monosulfate, and also the early hydration kinetics including the formation content, size and location of ettringite. It was also found that all the ternary systems with higher addition of calcium sulfate expand significantly. When a higher content of α-hemihydrate was added, besides ettringite much secondary gypsum also forms in voids between cement granules, which exerted adverse effects on the properties of ternary systems. However, the formation content of ettringite appeared to have no connection with the expansion value.
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Liu, Yan, Ruicong Lu, Lu He, Ximan Wang, Lu Wang, Xinyan Lv, Kun Zhang et Fuwei Yang. « Consolidation of Fragile Oracle Bones Using Nano Calcium Sulfate Hemihydrate as a Protectant ». Coatings 12, no 6 (18 juin 2022) : 860. http://dx.doi.org/10.3390/coatings12060860.

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Herein, a nano calcium sulfate hemihydrate suspension in an alcohol solvent was prepared and explored as a novel protectant for fragile oracle bones. The consolidation method involved first introducing the suspension and then adding water into the bones. Through this method, cohesive calcium sulfate dihydrate formed in the bones and can act as a reinforcing material. The protective effect was studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), hardness, porosity, and color difference determination. The results showed that such consolidation increased the strength of the bone samples significantly, and only slightly changed the appearance and porosity of the bone samples, indicating a good prospect for applying nano calcium sulfate hemihydrate in the conservation of indoor fragile bone relics.
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Zhao, Wenpeng, Chuanhui Gao, Hongfei Sang, Jun Xu, Chuanxing Wang et Yumin Wu. « Calcium sulfate hemihydrate whisker reinforced polyvinyl alcohol with improved shape memory effect ». RSC Advances 6, no 58 (2016) : 52982–86. http://dx.doi.org/10.1039/c6ra03717h.

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Jing, Hong Jian, Xiao Xia Zheng, Cai Mei Fan, Jun Qiang Feng, Yun Fang Wang et Guang Yue Ding. « Study on the Crystalline Morphology of Calcium Sulfate in H3PO4 and HNO3 Aqueous Medium ». Advanced Materials Research 146-147 (octobre 2010) : 1066–69. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.1066.

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This study aims to investigate the morphologies and the existing phases of calcium sulfate crystal by the reaction of H2SO4 with Ca(NO3)2·4H2O in acid medium using microscopic method and XRD powder diffraction. A series of experiments were designed for studying the crystal morphology and the hydrated form under coexisitence of phosphoric acid and nitric acid at 338K. The micrograph results show that in the H3PO4-HNO3-H2O system, the crystal shapes are changed from thick-long rod to thin-short rod, then needle-like even tiny needle gradually with the increase of acid content in solution. The solubility of calcium sulfate increases gradually with the increase of phosphoric acid or nitric acid concentration in solution. The XRD results show that with the increasing of acid concentration, the form of calcium sulfate is transferred from dihydrate to hemihydrate, that is, at higher acid concentration condition calcium sulfate hemihydrate is more stable in solution with the particles to be tiny and needle-like; while at lower acid concentration condition the crystals are mainly calcium sulfate dihydrate with larger rod particles which indicate a good filtration properties.
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Tangboriboon, Nuchnapa, Wanitcha Unjan, Watchara Sangwan et Anuvat Sirivat. « Preparation of anhydrite from eggshell via pyrolysis ». Green Processing and Synthesis 7, no 2 (25 avril 2018) : 139–46. http://dx.doi.org/10.1515/gps-2016-0159.

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AbstractCalcium sulfate dihydrate (CaSO4·2H2O) was prepared from the chemical reaction between calcium carbonate from duck eggshell and sulfuric acid at 25°C. The CaSO4·2H2O was dried in an oven at 110°C and transformed into calcium sulfate hemihydrate or plaster of Paris (CaSO4·0.5H2O). The CaSO4·0.5H2O was calcined at 700, 800 and 900°C and transformed into anhydrite or anhydrous calcium sulfate (CaSO4). The raw material used in this research was the duck eggshell, the waste eggshell generated from food processing industries. The obtained anhydrous calcium sulfate or anhydrite has true density, color, specific surface area, pore diameter and particle size equal to 2.95 g/cm3, white powder, 3.57 m2/g, 96.98 Å and 3.983 μm, respectively. In addition, other characteristics, microstructures, phase transformation and physical properties of raw materials and calcium sulfates were investigated and reported here using X-ray fluorescencemeter, Fourier transform infrared spectrometer, differential thermal analyzer, thermogravimetric analysis, scanning electron microscope, X-ray diffractometer, pycnometer method and Brunauer-Emmett-Teller.
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Weiner, Steve, Iddo Pinkas, Anna Kossoy et Yishai (Isai) Feldman. « Calcium Sulfate Hemihydrate (Bassanite) Crystals in the Wood of the Tamarix Tree ». Minerals 11, no 3 (11 mars 2021) : 289. http://dx.doi.org/10.3390/min11030289.

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The most abundant mineral produced in the wood and leaves of trees is calcium oxalate monohydrate (whewellite), and after burning the wood the ash obtained is calcite. In the case of the Tamarix sp. tree, the freshly prepared ash is calcium sulfate (anhydrite). The aim of this study is to determine the calcium sulfate mineral phase in the fresh wood of Tamarix aphylla prior to burning. SEM images of the crystals show that they express smooth faces, are about 5–15 microns in their longest dimensions and are located in the ray cells. Fourier transform infrared spectroscopy (FTIR) and Raman microspectroscopy of the crystals in the wood and after extraction, both showed that the crystals are composed of calcium sulfate hemihydrate (bassanite). As elemental analyses of the crystals showed that in addition to calcium and sulfur, around 20 atom percent of the cations are sodium and potassium, we also obtained an X-ray powder diffraction pattern. This pattern excluded the possibility that the crystals are composed of another related mineral, and confirmed that, indeed, the crystals in the T. aphylla wood are composed of calcium sulfate hemihydrate (bassanite).
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Wang, Yun-Wei, et Fiona C. Meldrum. « Additives stabilize calcium sulfate hemihydrate (bassanite) in solution ». Journal of Materials Chemistry 22, no 41 (2012) : 22055. http://dx.doi.org/10.1039/c2jm34087a.

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25

Tan, H., et F. Dong. « Morphological regulation of calcium sulfate hemihydrate from phosphogypsum ». Materialwissenschaft und Werkstofftechnik 48, no 11 (novembre 2017) : 1191–96. http://dx.doi.org/10.1002/mawe.201600746.

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Pritzel, Christian, Mohammadamin Emami, Sandra Afflerbach, Manuela Killian et Reinhard Trettin. « Formation of α-Hemihydrate Inside of a Gypsum Crystal during the Dehydration Process ». Crystals 12, no 12 (8 décembre 2022) : 1780. http://dx.doi.org/10.3390/cryst12121780.

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Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world. During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to form dihydrate again. Therefore, the dehydration process of gypsum and the rehydration of hemihydrate were investigated. This dehydration process is technically performed in three different ways. Heating up, i.e., in a rotary kiln, leads to a preferred formation of β-hemihydrate, which crystallizes in comparatively small crystals. Similar results can be achieved by recrystallization from gypsum slurry around 100 °C in an autoclave or under a water steam atmosphere. However, in contrast, the recrystallization process here leads to the formation of a larger, needle-like morphology and sometimes branched α-hemihydrate crystals. The synthesis of β-hemihydrate was investigated in detail with a special thermal stage for optical microscopy on natural single gypsum crystals. It was observed that the crystal loses transparency because of the breaking surface of the crystals due to water evaporation. Furthermore, within a deeper layer of the crystal, new crystals become visible but disappear during dehydration of the upper layers. These are expected to be α-hemihydrate. This theory of the formation of α-hemihydrate inside of a gypsum crystal is experimentally proven in the present work. This work firstly shows that the observed crystallization inside of gypsum during dehydration is the formation of alpha-hemihydrate.
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Jiang, Guangming, Qiaoshan Chen, Caiyun Jia, Sen Zhang, Zhongbiao Wu et Baohong Guan. « Controlled synthesis of monodisperse α-calcium sulfate hemihydrate nanoellipsoids with a porous structure ». Physical Chemistry Chemical Physics 17, no 17 (2015) : 11509–15. http://dx.doi.org/10.1039/c5cp00804b.

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Monodisperse α-calcium sulfate hemihydrate nanoellipsoids are synthesized through a Na2EDTA-mediated self-assembly procedure. Further thermal annealing treatment could generate porous structure.
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Stav, Elisha, Arnon Bentur et David H. Kohn. « Polymerization of acrylamide in the presence of calcium sulfate dihydrate and calcium sulfate hemihydrate ». Journal of Applied Polymer Science 45, no 12 (25 août 1992) : 2079–89. http://dx.doi.org/10.1002/app.1992.070451203.

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Kaimonov, Maksim, Tatiana Shatalova, Yaroslav Filippov et Tatiana Safronova. « Fine Biocompatible Powders Synthesized from Calcium Lactate and Ammonium Sulfate ». Ceramics 4, no 3 (4 juillet 2021) : 391–96. http://dx.doi.org/10.3390/ceramics4030028.

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Fine biocompatible powders with different phase compositions were obtained from a 0.5 M solution of ammonium sulfate (NH4)2SO4 and calcium lactate Ca(C3H5O3)2. The powder after synthesis and drying at 40 °C included calcium sulfate dehydrate CaSO4·2H2O and calcite CaCO3. The powder after heat treatment at 350 °C included β-hemihydrate calcium sulfate β-CaSO4·0.5H2O, γ-anhydrite calcium sulfate γ-CaSO4 and calcite CaCO3. The phase composition of powder heat-treated at 600 °C was presented as β-anhydrate calcium sulfate β-CaSO4 and calcite CaCO3. Increasing the temperature up to 800 °C leads to the sintering of a calcium sulfate powder consisting of β-anhydrite calcium sulfate β-CaSO4 main phase and a tiny amount of calcium oxide CaO. The obtained fine biocompatible powders of calcium sulfate both after synthesis and after heat treatment at temperature not above 600 °C can be recommended as a filler for producing unique composites with inorganic (glass, ceramic, cement) or polymer matrices.
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Zhao, Wenpeng, Yumin Wu, Jun Xu et Chuanhui Gao. « Retraction : Effect of ethylene glycol on hydrothermal formation of calcium sulfate hemihydrate whiskers with high aspect ratios ». RSC Advances 6, no 102 (2016) : 99639. http://dx.doi.org/10.1039/c6ra90104b.

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Feng, Fu, Yu-xin Cui, Yong-qi Hu, Sheng Hu et Ai-dong Zhang. « Mussel-inspired dynamic facet-selective capping approach to highly uniform α-calcium sulfate hemihydrate crystals ». RSC Advances 13, no 22 (2023) : 15342–46. http://dx.doi.org/10.1039/d3ra00835e.

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Tang, Mingliang, Xuerun Li, Yusheng Shen et Xiaodong Shen. « Kinetic model for calcium sulfate α-hemihydrate produced hydrothermally from gypsum formed by flue gas desulfurization ». Journal of Applied Crystallography 48, no 3 (9 mai 2015) : 827–35. http://dx.doi.org/10.1107/s1600576715007141.

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Modeling of the kinetics of the synthesis process for calcium sulfate α-hemihydrate from gypsum formed by flue gas desulfurization (FGD) is important to produce high-performance products with minimal costs and production cycles under hydrothermal conditions. In this study, a model was established by horizontally translating the obtained crystal size distribution (CSD) to the CSD of the stable phase during the transformation process. A simple method was used to obtain the nucleation and growth rates. A nonlinear optimization algorithm method was employed to determine the kinetic parameters. The model can be successfully used to analyze the transformation kinetics of FGD gypsum to α-hemihydrate in an isothermal batch crystallizer. The results showed that the transformation temperature and stirring speed exhibit a significant influence on the crystal growth and nucleation rates of α-hemihydrate, thus altering the transformation time and CSD of the final products. The characteristics obtained by the proposed model can potentially be used in the production of α-hemihydrate.
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Stawski, Tomasz M., Rogier Besselink, Konstantinos Chatzipanagis, Jörn Hövelmann, Liane G. Benning et Alexander E. S. Van Driessche. « Nucleation Pathway of Calcium Sulfate Hemihydrate (Bassanite) from Solution : Implications for Calcium Sulfates on Mars ». Journal of Physical Chemistry C 124, no 15 (24 mars 2020) : 8411–22. http://dx.doi.org/10.1021/acs.jpcc.0c01041.

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Fu, Hailu, Baohong Guan et Zhongbiao Wu. « Transformation pathways from calcium sulfite to α-calcium sulfate hemihydrate in concentrated CaCl 2 solutions ». Fuel 150 (juin 2015) : 602–8. http://dx.doi.org/10.1016/j.fuel.2015.02.061.

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Dong, Faqin, Zheyuan Huang, Hongbin Tan, Chuanlong Wu et Ping He. « Effect of Additives on Calcium Sulfate Hemihydrate Whiskers Morphology from Calcium Sulfate Dehydrate and Phosphogypsum ». Materials and Manufacturing Processes 31, no 15 (28 avril 2016) : 2037–43. http://dx.doi.org/10.1080/10426914.2016.1176184.

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36

Tiemann, Henry, Ilka Sötje, Gerhard Jarms, Carsten Paulmann, Matthias Epple et Bernd Hasse. « Calcium sulfate hemihydrate in statoliths of deep-sea medusae ». Journal of the Chemical Society, Dalton Transactions, no 7 (11 mars 2002) : 1266–68. http://dx.doi.org/10.1039/b111524c.

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Jiang, Nan, Chao Zhang, Caihong Xue, Li Dang et Shiai Xu. « In situ synthesis of hydrophobic calcium sulfate hemihydrate whiskers ». Materials Research Express 5, no 7 (4 juillet 2018) : 075004. http://dx.doi.org/10.1088/2053-1591/aace63.

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Zhao, Wenpeng, Chuanhui Gao, Fangrong Guo et Yumin Wu. « Synthesis of calcium sulfate hemihydrate whiskers using oyster shells ». Research on Chemical Intermediates 42, no 4 (4 août 2015) : 2953–61. http://dx.doi.org/10.1007/s11164-015-2189-9.

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Nomura, Shunsuke, Kanji Tsuru, Shigeki Matsuya, Ichiro Takahashi et Ishikawa Kunio. « Fabrication of Spherical Carbonate Apatite Using Calcium Sulfate as a Precursor by W/O Emulsion Method ». Key Engineering Materials 529-530 (novembre 2012) : 78–81. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.78.

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We fabricated spherical carbonate apatite from spherical calcium sulfate which was prepared by w/o emulsion method. Calcium sulfate hemihydrate slurry was dropped in oil under continuous stirring and was kept at room temperature for 60 min to obtain set spherical calcium sulfate dihydrate (CaSO42H2O) with approximately 1 mm in diameter. The spherical CaSO42H2O was hydrothermally-treated at 120°C for 24 hours in the presence of 0.4 mol.L-1 disodium hydrogen phosphate and sodium hydrogen carbonate aqueous solution. X-ray diffraction patterns assigned to apatite single phase could be detected from the obtained spheres. Carbonate content in apatitic structure was found to be approximately 6.5wt%.
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Mori, T. « Thermal Behavior of the Gypsum Binder in Dental Casting Investments ». Journal of Dental Research 65, no 6 (juin 1986) : 877–84. http://dx.doi.org/10.1177/00220345860650060201.

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This study examined the thermal behavior of cast gypsum specimens, with and without additives, by means of simultaneous differential thermal analysis-thermogravimetry (DTA-TG) and dilatometry. Specimens were prepared from wet-calcined hemihydrates (Hydrocal and Den-site). The additives studied were boric acid (H3BO 3) and sodium chloride (NaCl), and these were added to the hemihydrate powders in concentrations of 2 wt% (in the case of H3BO3) and 0.5 wt% (in the case of NaCl). A large shrinkage was observed in the range of 300 to 500°C, and this was greatly reduced when either H3BO3 or NaCl was present. The dehydration of gypsum (calcium sulfate dihydrate) was not completed until the initial stage of this large shrinkage was reached, but the phase transition of calcium sulfate anhydrite (III-CaSO4 to II-CaSO4) was the major cause for the large shrinkage. This phase transition occurred over a much wider temperature range than that suggested by the DTA-TG results. Dehydration conditions similar to those employed in wet calcination of gypsum appeared to be produced under atmospheric pressure when NaCl was present.
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41

Mi, Yang, Deyu Chen et Aiwen Wang. « Effects of phosphorus impurities on the preparation of α-calcium sulfate hemihydrate from waste phosphogypsum with the salt solution method under atmospheric pressure ». CrystEngComm 21, no 16 (2019) : 2631–40. http://dx.doi.org/10.1039/c9ce00140a.

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Impurity is an important factor that determines the crystallization process of α-calcium sulfate hemihydrate (α-CSH), but the effects of phosphorus impurities in waste phosphogypsum on the α-CSH prepared using the salt solution method are still not well known.
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Petropavlovskaya, Victoria, Maria Zavadko, Kirill Petropavlovskii, Aleksandr Buryanov, Tatiana Novichenkova et Andrey Pustovgar. « Role of basalt dust in the formation of the modified gypsum structure ». E3S Web of Conferences 97 (2019) : 02036. http://dx.doi.org/10.1051/e3sconf/20199702036.

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Waste disposal in the production of building materials and the organization of waste-free technological processes require a large amount of multilateral research. The application of basalt dust in the production of gypsum materials has been little studied. The paper investigated the effect of basalt dust - waste production of basalt fibers, on the working mixtures and the properties of hemihydrate of calcium sulfate paste (standard consistency, setting time of gypsum dough, water absorption of the resulting gypsum stone). It is known that the addition of basalt waste has a positive effect on strength, but there is no data on its effect on the rheological properties of gypsum mixtures. It was revealed that the introduction of basalt dust into the composition of the gypsum composite contributes to the change of the plaster mix rheology and of the properties of the gypsum structure. This must be taken into account when selecting optimized formulations of working mixtures on the hemihydrate of calcium sulfate.
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Yan, Ting Ting, Xiao Pei Wu, Chong Yan Leng et Qing Hua Chen. « Preparation and Characterization of Calcium Sulfate Spherical Particles for Dentistry ». Advanced Materials Research 738 (août 2013) : 13–17. http://dx.doi.org/10.4028/www.scientific.net/amr.738.13.

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In this article, calcium sulfate spherical particles were prepared to be used in alveolar bone defect repairing. We used α-calcium sulfate hemihydrate powder to prepare spherical particles of calcium sulfate with stir pelletizing method. The effect of powder addition, pelletizing time and concentration of water-glass on properties of the spherical particles were studied. It was indicated that with increasing of the powder addition, the particle size of the spherical particles was decreased. Prolonging the pelletizing time can improve the compression strength in certain conditions. With increasing of the concentration of water-glass used in preparation process, the shape of the spherical particles becomes non-circular, the granulous stem yield was decreased and the compression strength of the spherical particles was improved.
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Chen, Xuemei, Qihong Wu, Jianming Gao et Yongbo Tang. « Hydration characteristics and mechanism analysis of β-calcium sulfate hemihydrate ». Construction and Building Materials 296 (août 2021) : 123714. http://dx.doi.org/10.1016/j.conbuildmat.2021.123714.

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Kong, Bao, Baohong Guan, Matthew Z. Yates et Zhongbiao Wu. « Control of α-Calcium Sulfate Hemihydrate Morphology Using Reverse Microemulsions ». Langmuir 28, no 40 (25 septembre 2012) : 14137–42. http://dx.doi.org/10.1021/la302459z.

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Jiang, Guangming, Hailu Fu, Keith Savino, Jiajing Qian, Zhongbiao Wu et Baohong Guan. « Nonlattice Cation-SO42– Ion Pairs in Calcium Sulfate Hemihydrate Nucleation ». Crystal Growth & ; Design 13, no 11 (14 octobre 2013) : 5128–34. http://dx.doi.org/10.1021/cg401361u.

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Tiemann, Henry, Ilka Sötje, Alexander Becker, Gerhard Jarms et Matthias Epple. « Calcium sulfate hemihydrate (bassanite) statoliths in the cubozoan Carybdea sp. » Zoologischer Anzeiger - A Journal of Comparative Zoology 245, no 1 (juillet 2006) : 13–17. http://dx.doi.org/10.1016/j.jcz.2006.03.001.

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Wang, Shuzhou, Deyu Chen et Keke Zhang. « Preparation, Characterization, and Formation Mechanism of Calcium Sulfate Hemihydrate Whiskers ». Journal of Wuhan University of Technology-Mater. Sci. Ed. 33, no 6 (décembre 2018) : 1407–15. http://dx.doi.org/10.1007/s11595-018-1983-9.

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Dong, Faqin, Jinfeng Liu, Hongbin Tan, Chuanlong Wu, Xiaochun He et Ping He. « Preparation of Calcium Sulfate Hemihydrate and Application in Polypropylene Composites ». Journal of Nanoscience and Nanotechnology 17, no 9 (1 septembre 2017) : 6970–75. http://dx.doi.org/10.1166/jnn.2017.14413.

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Xiang, Haibo, Yu Wang, Hong Chang, Shenyu Yang, Mei Tu, Xianrong Zhang et Bin Yu. « Cerium-containing α-calcium sulfate hemihydrate bone substitute promotes osteogenesis ». Journal of Biomaterials Applications 34, no 2 (14 mai 2019) : 250–60. http://dx.doi.org/10.1177/0885328219849712.

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