Application of thermo-Raman spectroscopy to study dehydration of CaSO4·2H2O and CaSO4·0.5H2O

Chang, Hung-Chun; Pei, Huang; Hou, Sichao

doi:10.1016/s0254-0584(98)00239-9

Cited by 92 publications

(41 citation statements)

References 20 publications

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“…6a for observing a micro-scale Raman shift. The peak at 1015 cm À 1 corresponds to the water-reduced form of gypsum: hemihydrate, or bassanite (CaSO 4 Á 0.5H 2 O) [1,55]. A backscatter electron image of the material near the outer edge (hexagon and square locations) is shown in Fig.…”

Section: Raman Spectroscopymentioning

confidence: 99%

“…Understanding deformation and fracture mechanisms [1][2][3][4][5] in rocks and minerals is important in planetary science [6], blasting and mining industries [7], military and shielding applications [8,9], and in manufacturing industries [10]. Fracture mechanisms can take many forms depending on scale; with the bulk of the research being performed at scales greater than 100 mm.…”

Section: Introductionmentioning

confidence: 99%

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Micro-scale deformation of gypsum during micro-indentation loading

Hogan

Boonsue

Spray

et al. 2012

International Journal of Rock Mechanics and Mining Sciences

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Section: Raman Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Micro-scale deformation of gypsum during micro-indentation loading

Hogan

Boonsue

Spray

et al. 2012

International Journal of Rock Mechanics and Mining Sciences

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“…These changes suggest that there is a phase transition in gypsum. Previous studies have shown that on heating gypsum above 373 K causes gypsum to lose water molecules during the heating process forming γ-CaSO 4 (soluble form of anhydrite) and hemihydrate (CaSO 4 ·0.5H 2 O also known as bassanite) [15,[17][18]. The Raman ν 1 (SO 4 ) lines of hemihydrate and γ-CaSO4 appear at 1014 and 1026 cm -1 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Remote Raman spectroscopy of minerals at elevated temperature relevant to Venus exploration

Sharma¹,

Misra

Singh

2008

SPIE Proceedings

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We have used a remote time-resolved telescopic Raman system equipped with 532 nm pulsed laser excitation and a gated intensified CCD (ICCD) detector for measuring Raman spectra of a number of minerals at high temperature to 970 K. Remote Raman measurements were made with samples at 9-meter in side a high-temperature furnace by gating the ICCD detector with 2 micro-sec gate to minimize interference from blackbody emission from mineral surfaces at high temperature as well as interference from ambient light. A comparison of Raman spectra of gypsum (CaSO 4 .2H 2 O), dolomite (CaMg(CO 3 ) 2 ), and olivine (Mg 2 Fe 2-x SiO 4 ), as a function of temperature shows that the Raman lines remains sharp and well defined even in the high-temperature spectra. In the case of gypsum, Raman spectral fingerprints of CaSO 4 .H 2 O at 518 K were observed due to dehydration of gypsum. In the case of dolomite, partial mineral dissociation was observed at 973 K at ambient pressure indicating that some of the dolomite might survive on Venus surface that is at ~750 K and 92 atmospheric pressure. Time-resolved Raman spectra of low clino-enstatite (MgSiO 3 ) measured at 75 mm from the sample in side the high-temperature furnace also show that the Raman lines remains sharp and well defined in the high temperature spectra. These high-temperature remote Raman spectra of minerals show that time-resolved Raman spectroscopy can be used as a potential tool for exploring Venus surface mineralogy at shorter (75 mm) and long (9 m) distances from the samples both during daytime and nighttime. The remote Raman system could also be used for measuring profiles of molecular species in the dense Venus atmosphere during descent as well as on the surface.

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“…Most literature reported that gypsum dehydration undergoes a two-step process, via hemihydrate (25,28,(42)(43)(44), while some reports showed that γ-CaSO 4 is directly produced during gypsum dehydration of γ-CaSO 4 upon cooling with humidity air (45 (48) reported that under non-isothermal conditions and in two steps, via hemihydrate in "autogenous P H 2 O ", the dehydration of the gypsum contained in the "flue gas desulfurization gypsum (FGDG) occurs in one step (CaSO 4 2H 2 O→γ-CaSO 4 ), when the P H 2 O is negligible.…”

Section: Thermal Behaviour Of Phosphogypsummentioning

confidence: 99%

“…In the literature, there is a number of studies on kinetics dehydration of gypsum (25,27,(43)(44)(45)(46)(47)(48)(49). In general, all the studies of the CaSO 4 2H 2 O dehydration through DTA or DTG show the presence of two endothermic peaks.…”

Section: ) T O (°C) T E (°C) T P (°C) T O (°C) T E (°C) T P (°C) T O mentioning

confidence: 99%

Thermal dehydration kinetics of phosphogypsum

López¹,

Tayibi²,

García‐Díaz³

2015

Mater. construcc.

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ABSTRACT:Phsophogypsum is a by-product from the processing phosphate rock. Before the use of it in cement industry such as setting regulator is necessary a study of dehydration reaction of phosphogypsum to avoid the false setting during the milling.The aim is to study the thermal behavior of two different phosphogypsum sources (Spain and Tunisia) under non-isothermal conditions in argon atmosphere by using Thermo-Gravimetriy, Differential Thermal Analysis (TG-DTA) and Differential Scanning Calorimetry (DSC).DSC experiments were carried out at temperatures ranging from ambient to 350 °C at different heating rates. The temperatures of conversion from gypsum to hemihydrate and anhydrite states and heat of dehydration were determined. Various methods were used to analyze the DSC data for reaction kinetics determination. The activation energy and frequency factor were calculated for dehydration of phosphogypsum. Activation energy values of the main dehydration reaction of phosphogypsum were calculated to be approximately 61-118 kJ/mol. RESUMEN:Estudio cinético de la deshidratación térmica del fosfoyeso. El fosfoyeso es un subproducto procedente del procesado de la roca fosfato. Una de las posibles vías de reutilización y revalorización es su uso como regulador del fraguado en la industria cementera. Debido a los posibles problemas de falso fraguado asociado a los procesos de deshidratación que tienen lugar durante la molienda del cemento, esta investigación estudió el comportamiento térmico, bajo condiciones no-isotérmicas en atmósfera de argón, de dos fosfoyesos, mediante TG-DTA y DSC.Los ensayos de DSC se realizaron hasta los 350 °C a diferentes velocidades de calentamiento. La temperatura de conversión del yeso a las formas de hemihidrato y anhidrita y el calor de hidratación fueron determinados.Las cinéticas de reacción fueron obtenidas analizando los datos de DSC mediante varios métodos. Se calculó la energía de activación y el factor de frecuencia para las reacciones de deshidratación del subproducto. Los valores de energía de activación de las principales reacciones de deshidratación del fosfoyeso fueron obtenidos, aproximadamente 61-118 kJ/mol.

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Application of thermo-Raman spectroscopy to study dehydration of CaSO4·2H2O and CaSO4·0.5H2O

Cited by 92 publications

References 20 publications

Micro-scale deformation of gypsum during micro-indentation loading

Micro-scale deformation of gypsum during micro-indentation loading

Remote Raman spectroscopy of minerals at elevated temperature relevant to Venus exploration

Thermal dehydration kinetics of phosphogypsum

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