Mechanism and kinetics of calcium sulfate hemihydrate dehydration by nonisothermal and isothermal thermogravimetry

1973 ◽  
Vol 45 (1) ◽  
pp. 154-159 ◽  
Author(s):  
Vladimir. Satava ◽  
Jaroslav. Sestak
Keyword(s):  
Calcium Sulfate ◽  
Isothermal Thermogravimetry ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Calcium Sulfate Hemihydrate

The Kinetics and Mechanism of Formation of Calcium Sulfate Scale Minerals—The Influence of Inhibitors

CORROSION ◽  
1979 ◽  
Vol 35 (7) ◽  
pp. 304-308 ◽  
Author(s):  
GEORGE H. NANCOLLAS ◽  
WESLEY WHITE ◽  
FELIX TSAI ◽  
LARRY MAS LOW
Keyword(s):  
Calcium Sulfate ◽  
Mechanism Of Formation ◽  
Seeded Growth ◽  
Langmuir Adsorption ◽  
Calcium Sulfate Dihydrate ◽  
Calcium Sulfate Scale ◽  
Rate Of Reaction ◽  
Growth Method ◽  
Kinetics Of ◽  
Calcium Sulfate Hemihydrate

Abstract A seeded growth method has been used to study the kinetics of crystallization of calcium sulfate dihydrate at various temperatures and at ionic strengths up to 0.6M. Under all conditions, the rate of reaction is proportional to the square of the relative supersaturation and is controlled by a surface process. The same kinetics are applicable for the growth of calcium sulfate hemihydrate at temperatures above 110 C. The organic phosphonates effectively retard scale formation, and diethylenetriaminepenta (methylenephosphonic acid), when present at a concentration as low as 10−7M, completely inhibits the growth of calicum sulfate hemihydrate at 120 C. By assuming that the inhibitor molecules are adsorbed on growth sites on the surface of the crystals, the inhibition can be interpreted in terms of a simple Langmuir adsorption isotherm.

Solution-Mediated Transformation Kinetics of Calcium Sulfate Dihydrate to α-Calcium Sulfate Hemihydrate in CaCl2 Solutions at Elevated Temperature

2013 ◽  
Vol 52 (48) ◽  
pp. 17134-17139 ◽  
Author(s):  
Hailu Fu ◽  
Guangming Jiang ◽  
Hao Wang ◽  
Zhongbiao Wu ◽  
Baohong Guan
Keyword(s):  
Elevated Temperature ◽  
Calcium Sulfate ◽  
Transformation Kinetics ◽  
Calcium Sulfate Dihydrate ◽  
Kinetics Of ◽  
Calcium Sulfate Hemihydrate

Retarding effect of impurities on the transformation kinetics of FGD gypsum to α-calcium sulfate hemihydrate under atmospheric and hydrothermal conditions

Fuel ◽  
2017 ◽  
Vol 203 ◽  
pp. 445-451 ◽  
Author(s):  
Hailu Fu ◽  
Jianshi Huang ◽  
Linwan Yin ◽  
Jie Yu ◽  
Wenbin Lou ◽  
...  
Keyword(s):  
Calcium Sulfate ◽  
Transformation Kinetics ◽  
Hydrothermal Conditions ◽  
Fgd Gypsum ◽  
Retarding Effect ◽  
Effect Of Impurities ◽  
Kinetics Of ◽  
Calcium Sulfate Hemihydrate

Accelerated and Retarded Dental Plaster Setting Investigated by X-Ray Diffraction

1970 ◽  
Vol 49 (3) ◽  
pp. 502-507 ◽  
Author(s):  
J.K. Harcourt ◽  
E.P. Lautenschlager
Keyword(s):  
Calcium Sulfate ◽  
Continuous Monitoring ◽  
Product Formation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Setting Times ◽  
Diffraction Peaks ◽  
Dental Plaster ◽  
Kinetics Of ◽  
Calcium Sulfate Hemihydrate

Continuous monitoring of calcium sulfate hemihydrate and dihydrate X-ray diffraction peaks was done to determine the kinetics of gypsum-product formation during the setting of plaster mixtures containing various concentrations of accelerators and retarders. Amounts of product formation were then correlated to Gillmore setting times and to compressive strengths.

Effects of sterilization modes on the mechanical strengths of plaster of paris implants

1989 ◽  
Vol 47 ◽  
pp. 890-891
Author(s):  
K. Cowden ◽  
B. Giammara ◽  
T. Devine ◽  
J. Hanker
Keyword(s):  
Gamma Radiation ◽  
Calcium Sulfate ◽  
Significant Loss ◽  
Potassium Sulfate ◽  
Limiting Factors ◽  
Radiation Sterilization ◽  
Plaster Of Paris ◽  
Hardness Tester ◽  
Dry Heat ◽  
Calcium Sulfate Hemihydrate

Plaster of Paris (calcium sulfate hemihydrate, CaSO4. ½ H2O) has been used as a biomedical implant material since 1892. One of the primary limiting factors of these implants is their mechanical properties. These materials have low compressive and tensile strengths when compared to normal bone. These are important limiting factors where large biomechanical forces exist. Previous work has suggested that sterilization techniques could affect the implant’s strength. A study of plaster of Paris implant mechanical and physical properties to find optimum sterilization techniques therefore, could lead to a significant increase in their application and promise for future use as hard tissue prosthetic materials.USG Medical Grade Calcium Sulfate Hemihydrate Types A, A-1 and B, were sterilized by dry heat and by gamma radiation. Types A and B were additionally sterilized with and without the setting agent potassium sulfate (K2SO4). The plaster mixtures were then moistened with a minimum amount of water and formed into disks (.339 in. diameter x .053 in. deep) in polyethylene molds with a microspatula. After drying, the disks were fractured with a Stokes Hardness Tester. The compressive strengths of the disks were obtained directly from the hardness tester. Values for the maximum tensile strengths σo were then calculated: where (P = applied compression, D = disk diameter, and t = disk thickness). Plaster disks (types A and B) that contained no setting agent showed a significant loss in strength with either dry heat or gamma radiation sterilization. Those that contained potassium sulfate (K2SO4) did not show a significant loss in strength with either sterilization technique. In all comparisons (with and without K2SO4 and with either dry heat or gamma radiation sterilization) the type B plaster had higher compressive and tensile strengths than that of the type A plaster. The type A-1 plaster however, which is specially modified for accelerated setting, was comparable to that of type B with K2SO4 in both compressive and tensile strength (Table 1).

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