Dehydration of crystalline K2CO3·1.5 H2O

Deshpande, Deepak A.; Ghormare, K.R.; Deshpande, Niranjani; Tankhiwale, A.V.

doi:10.1016/0040-6031(93)85036-9

Cited by 24 publications

(12 citation statements)

References 5 publications

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“…5). This corresponds to a molar ratio of the oxides K 2 O:CaO:SiO 2 =1:1.17:1.17 which compares well with the initial values of 1:1:1 Because potassium carbonate sesquihydrate is known to dehydrate at temperatures above 235°C 16 it can be excluded that this compound formed in the course of the high‐temperature synthesis experiment. We attribute its presence to a reaction of the extremely air‐ and moisture‐sensitive K 2 O according to the formula K 2 O+CO 2 +1.5 H 2 O→K 2 CO 3 × 1.5 H 2 O during the sample preparation for the XRPD data collection.…”

Section: Resultssupporting

confidence: 69%

Does K2CaSiO4 Exist? A Phase-Analytical Study in the System K2O-CaO-SiO2 with Implications for the Characterization of Residual Materials

Arroyabe

Tessadri

Többens

et al. 2011

Journal of the American Ceramic Society

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K2CaSiO4 or K2O × CaO × SiO2 has been reported to be a major constituent of residual materials that are of interest for the field of applied mineralogy, including ashes from biomass combustion as well as fertilizers produced from the residues of oil‐shale industry or from steelmaking slags. Unfortunately, contradictory results concerning basic crystallographic and physicochemical data of this compound have been described in the literature. In a series of solid‐state reactions we tried to prepare this material for a more detailed investigation. The temperature regime for the subsolidus synthesis experiments was selected according to previous studies where the occurrence of this so‐called “1:1:1” phase had been reported. The samples were characterized by thermal and X‐ray fluorescence analysis as well as X‐ray powder diffraction. Our results indicate that “K2CaSiO4” does not exist as a crystalline phase in the ternary system K2O–CaO–SiO2 and that the 1:1:1 compound, mentioned in earlier studies is actually misinterpreted K2Ca2Si2O7. Furthermore, the start of melt formation of an oxide mixture with composition K2O × CaO × SiO2 has been determined to be 1170°C, which is dramatically lower than the value of 1630°C mentioned in the only available comprehensive but more than 80 years old phase analytical study on potassium calcium silicates.

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Section: Resultssupporting

confidence: 69%

Does K2CaSiO4 Exist? A Phase-Analytical Study in the System K2O-CaO-SiO2 with Implications for the Characterization of Residual Materials

Arroyabe

Tessadri

Többens

et al. 2011

Journal of the American Ceramic Society

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“…Therefore, we assume that starting materials in the first set of experiments were contaminated by water, i.e., conducted under wet conditions, whereas the second one was conducted under nominally dry conditions. The water contamination can be associated with the formation of K 2 CO 3 ⋅1.5H 2 O, which is almost impossible to prevent in air (Schneide and Levin 1973;Deshpande et al 1993).…”

Section: Discussionmentioning

confidence: 99%

Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900-1450 C

Shatskiy

Borzdov

Litasov

et al. 2014

American Mineralogist

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“…Anhydrous K2CO3, which normally forms at temperatures below 38 C [143], is monoclinic with unit cell dimensions a = 0.564 nm, b = 0.980 nm, c = 0.688 nm and  = 98.8° [144], and high-resolution AFM scans showed row periodicities that were close to the a and b unit cell dimensions, indicating that the c-axis would be perpendicular to the surface. The angle of 117° measured between these rows is not, however, consistent with the bulk monoclinic structure of K2CO3, which should give an angle of 90°, but rather suggests a hexagonal structure imposed by the underlying mica surface, as seems to be the case for the much larger crystallites imaged by AFM and shown in Figure 4 and also those published previously [125].…”

Section: Surface Analytical Studies Of Air-cleaved and Vacuum-cleavedmentioning

confidence: 99%

The nature of the air-cleaved mica surface

Christenson

Thomson

2016

Surface Science Reports

114

102

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The accepted image of muscovite mica is that of an inert and atomically smooth surface, easily prepared by cleavage in an ambient atmosphere. Consequently, mica is extensively used a model substrate in many fundamental studies of surface phenomena and as a substrate for AFM imaging of biomolecules. In this review we present evidence from the literature that the above picture is not quite correct. The mica used in experimental work is almost invariably cleaved in laboratory air, where a reaction between the mica surface, atmospheric CO2 and water occurs immediately after cleavage. The evidence suggests very strongly that as a result the mica surface becomes covered by up to one formula unit of K2CO3 per nm 2 , which is mobile under humid conditions, and crystallizes under drier conditions. The properties of mica in air or water vapour cannot be fully understood without reference to the surface K2CO3, and many studies of the structure of adsorbed water on mica surfaces may need to be revisited. With this new insight, however, the air-cleaved mica should provide exciting opportunities to study phenomena such as two-dimensional ion diffusion, electrolyte effects on surface conductivity, and two-dimensional crystal nucleation.

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Dehydration of crystalline K2CO3·1.5 H2O

Cited by 24 publications

References 5 publications

Does K2CaSiO4 Exist? A Phase-Analytical Study in the System K2O-CaO-SiO2 with Implications for the Characterization of Residual Materials

Does K2CaSiO4 Exist? A Phase-Analytical Study in the System K2O-CaO-SiO2 with Implications for the Characterization of Residual Materials

Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900-1450 C

The nature of the air-cleaved mica surface

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