scholarly journals Thermodynamic Modeling of Calcium Sulfate Hydrates in the CaSO4–H2O System from 273.15 to 473.15 K with Extension to 548.15 K

2019 ◽  
Vol 64 (6) ◽  
pp. 2697-2709 ◽  
Author(s):  
Leiting Shen ◽  
Hannu Sippola ◽  
Xiaobin Li ◽  
Daniel Lindberg ◽  
Pekka Taskinen
Keyword(s):  
Thermodynamic Modeling ◽  
Calcium Sulfate

scholarly journals Thermodynamic Modeling of Calcium Sulfate Hydrates in a CaSO4–H2SO4–H2O System from 273.15 to 473.15 K up to 5 m Sulfuric Acid

2020 ◽  
Vol 65 (5) ◽  
pp. 2310-2324
Author(s):  
Leiting Shen ◽  
Hannu Sippola ◽  
Xiaobin Li ◽  
Daniel Lindberg ◽  
Pekka Taskinen
Keyword(s):  
Sulfuric Acid ◽  
Thermodynamic Modeling ◽  
Calcium Sulfate

scholarly journals Thermochemical Decomposition of Calcium Sulfate in Presence of Carbon and Hydrogen Mix

2010 ◽  
Vol 12 (2) ◽  
pp. 139
Author(s):  
V.K. Bishimbayev ◽  
A.A. Yerubay
Keyword(s):  
Gas Phase ◽  
Thermodynamic Modeling ◽  
Calcium Sulfate ◽  
Technological Parameters ◽  
Influence Of Temperature ◽  
Extreme Character ◽  
Influence Of Temperature On ◽  
Chemical Equation ◽  
Lower Temperature ◽  
Thermochemical Decomposition

<p>Results of research of thermodynamic modeling of thermochemical decomposition of CaSO<sub>4</sub> by a mix of carbon and hydrogen are given in the article. Influence of temperature on degree of carbon interchange by hydrogen on a degree of formation in systems CaO, СаСО<sub>3</sub>, CaS was determined. Interchange of C by Н<sub>2</sub> reduces formation of СаСО<sub>3</sub>, CaS, and formation of СаО has an extreme character. With the help of method of research planning adequate equation of regression has been defined and optimum technological parameters (Т = 1660 K and 40 % degree of carbon interchange by Н<sub>2</sub>), providing full decomposition of CaSO<sub>4</sub> to СаО were determined. The composition of a gas phase of CaSO<sub>4</sub> restoration, containing 16 components was established. By reduction of pressure to 0,001 МPа it is possible to lower temperature of process to 1400 K. The chemical equation of CaSO<sub>4</sub> interaction with carbon and hydrogen was found.<em></em></p>

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).

Identification of acid-insoluble filter-plugging compounds and optimal acid-washing procedures for tubular backpulse pressure filters

TAPPI Journal ◽  
2011 ◽  
Vol 10 (1) ◽  
pp. 17-23
Author(s):  
KEVIN TAYLOR ◽  
RICH ADDERLY ◽  
GAVIN BAXTER
Keyword(s):  
Calcium Sulfate ◽  
Membrane Filter ◽  
Sulfamic Acid ◽  
Xrd Analysis ◽  
Metal Sulfides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gypsum Formation ◽  
Acid Washing ◽  
Hydrolysis Of

Over time, performance of tubular backpulse pressure filters in kraft mills deteriorates, even with regular acid washing. Unscheduled filter replacement due to filter plugging results in significant costs and may result in mill downtime. We identified acid-insoluble filter-plugging materials by scanning electron microscope/energy-dispersion X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analysis in both polypropylene and Gore-Tex™ membrane filter socks. The major filter-plugging components were calcium sulfate (gypsum), calcium phosphate (hydroxylapatite), aluminosilicate clays, metal sulfides, and carbon. We carried out detailed sample analysis of both the standard acid-washing procedure and a modified procedure. Filter plugging by gypsum and metal sulfides appeared to occur because of the acid-washing procedure. Gypsum formation on the filter resulted from significant hydrolysis of sulfamic acid solution at temperatures greater than 130°F. Modification of the acid-washing procedure greatly reduced the amount of gypsum and addition of a surfactant to the acid reduced wash time and mobilized some of the carbon from the filter. With surfactant, acid washing was 95% complete after 40 min.

Immersion-Induced Changes in Structure and Properties of a Calcium Sulfate Cement

2012 ◽  
Vol 53 (6) ◽  
pp. 1154-1158 ◽  
Author(s):  
Wei-Luen Chen ◽  
Nai-Yen Fan ◽  
Jing-Wei Lee ◽  
Ruey-Mo Lin ◽  
Chien-Ping Ju ◽  
...  
Keyword(s):  
Calcium Sulfate ◽  
Structure And Properties ◽  
Induced Changes
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