Nanocrystalline and metastable phase formation in vacuum thermal decomposition of calcium carbonate

Dash, S.; Kamruddin, M.; Ajikumar, P.K.; Tyagi, A. K.; Raj, Baldev

doi:10.1016/s0040-6031(00)00604-3

Cited by 64 publications

(41 citation statements)

References 34 publications

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“…A systematic TPD study of calcite has revealed formation of metastable nanocrystalline calcia under vacuum conditions whereas calcite decomposition in flowing helium gas resulted in formation of stable microcrystalline calcia (Dash et al 2000b). TEM analysis of partially decomposition calcite and in situ observation of its further decomposition under electron beam bombardment in the vacuum of TEM column indicated this transformation to occur via two mechanisms .…”

Section: Formation Of Nanocrystalline Materialsmentioning

confidence: 99%

Thermogravimetry-evolved gas analysis-mass spectrometry system for materials research

et al. 2003

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Abstract. Thermal analysis is a widely used analytical technique for materials research. However, thermal analysis with simultaneous evolved gas analysis describes the thermal event more precisely and completely. Among various gas analytical techniques, mass spectrometry has many advantages. Hence, an ultra high vacuum (UHV) compatible mass spectrometry based evolved gas analysis (EGA-MS) system has been developed. This system consists of a measurement chamber housing a mass spectrometer, spinning rotor gauge and vacuum gauges coupled to a high vacuum, high temperature reaction chamber. A commercial thermogravimetric analyser (TGA: TG + DTA) is interfaced to it. Additional mass flow based gas/vapour delivery system and calibration gas inlets have been added to make it a versatile TGA-EGA-MS facility. This system which gives complete information on weight change, heat change, nature and content of evolved gases is being used for (i) temperature programmed decomposition (TPD), (ii) synthesis of nanocrystalline materials, (iii) gas-solid interactions and (iv) analysis of gas mixtures. The TPD of various inorganic oxyanion solids are studied and reaction intermediates/products are analysed off-line. The dynamic operating conditions are found to yield nanocrystalline products in many cases. This paper essentially describes design features involved in coupling the existing EGA-MS system to TGA, associated fluid handling systems, the system calibration procedures and results on temperature programmed decomposition. In addition, synthesis of a few nanocrystalline oxides by vacuum thermal decomposition, gas analysis and potential use of this facility as controlled atmosphere exposure facility for studying gas-solid interactions are also described.

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Section: Formation Of Nanocrystalline Materialsmentioning

confidence: 99%

Thermogravimetry-evolved gas analysis-mass spectrometry system for materials research

et al. 2003

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“…CaO can be produced by thermal decomposition of CaCO 3 or Ca (OH) 2 ; specifically, when done under vacuum conditions, a nanostructured powder with a high specific surface area (SSA) can be obtained [3][4][5][6][7][8][9][10]. Nanometric CaO can be used as a catalyst, in sensors and also as oxide dispersion strengthened alloys [9].…”

Section: Introductionmentioning

confidence: 99%

Sintering kinetics of nanometric calcium oxide in vacuum atmosphere

Ramos

Fernandes

Stora

et al. 2015

Ceramics International

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“…The latter also showed high reactivity towards hydration. Dash et al, (2000) also observed a metastable-nanocrystalline calcia under vacuum and stable microcrystalline when calcined in helium. Beruto et al, (1980) conditions of the same environment, the rate of decomposition increases with temperature.…”

Section: Sub-atmospheric (Vacuum) Calcinationmentioning

confidence: 83%

Enhanced Hydrogen Production Integrated with CO2 Separation in a Single-Stage Reactor

Iyer¹,

Gupta²,

Wong³

et al. 2005

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Hydrogen production from coal gasification can be enhanced by driving the equilibrium limited Water Gas Shift reaction forward by incessantly removing the CO 2 by-product via the carbonation of calcium oxide. This project aims at using the OSU patented high-reactivity mesoporous precipitated calcium carbonate sorbent for removing the CO 2 product.Preliminary experiments demonstrate the show the superior performance of the PCC sorbent over other naturally occurring calcium sorbents. Gas composition analyses show the formation of 100% pure hydrogen. Novel calcination techniques could lead to smaller reactor footprint and single-stage reactors that can achieve maximum theoretical H 2 production for multicyclic applications. Sub-atmospheric calcination studies reveal the effect of vacuum level, diluent gas flow rate, thermal properties of the diluent gas and the sorbent loading on the calcination kinetics which play an important role on the sorbent morphology. Steam, which can be easily separated from CO 2 , is envisioned to be a potential diluent gas due to its enhanced thermal properties. Steam calcination studies at 700-850 o C reveal improved sorbent morphology over regular nitrogen calcination. A mixture of 80% steam and 20% CO 2 at ambient pressure was used to calcine the spent sorbent at 820 o C thus lowering the calcination temperature. Regeneration of calcium sulfide to calcium carbonate was achieved by carbonating the calcium sulfide slurry by bubbling CO 2 gas at room temperature.

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Nanocrystalline and metastable phase formation in vacuum thermal decomposition of calcium carbonate

Cited by 64 publications

References 34 publications

Thermogravimetry-evolved gas analysis-mass spectrometry system for materials research

Thermogravimetry-evolved gas analysis-mass spectrometry system for materials research

Sintering kinetics of nanometric calcium oxide in vacuum atmosphere

Enhanced Hydrogen Production Integrated with CO2 Separation in a Single-Stage Reactor

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