Diagnostics of heterogeneous chemical reactions by cathodoluminescence

Мелихов, И. В.; Saparin, G. V.; Bozhevol’nov, V. E.; Obyden, S. K.; Kuleshova, O. V.

doi:10.1002/sca.4950130505

Cited by 4 publications

(1 citation statement)

References 2 publications

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“…Different organics were tried, but 2-propanol was the one that was chosen. Use of acetone is reported in the literature, , but 2-propanol was found to achieve better results. The final dry samples were examined with XRD (Philips PW1710 X-ray diffractometer) as well as DSC (PerkinElmer PYRIS differential scanning calorimeter) for phase identification, and with SEM (JEOL-840A SEM, coupled with energy-dispersive X-ray spectrometer and digital imaging system) for morphology characterization.…”

Section: Methodsmentioning

confidence: 95%

Preparation of α-Calcium Sulfate Hemihydrate by Reaction of Sulfuric Acid with Lime

Ling

Demopoulos

2005

Ind. Eng. Chem. Res.

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Direct preparation of R-calcium sulfate hemihydrate out of sulfuric acid solution by reaction with lime under atmospheric pressure conditions is systematically investigated. Two preparation methods are investigated: one involving addition of dry lime to sulfuric acid solution (standard procedure) and the other involving addition of sulfuric acid solution to slaked lime (reverse procedure). On the basis of the standard procedure, the operating window is first determined, followed by thorough examination of preparation conditions such as acidity, retention time and CaO/H 2 SO 4 molar ratio. Dihydrate was found to form as intermediate phase that converts to hemihydrate under all tested conditions. The typical morphology of R-hemihydrate crystals produced by the standard procedure is needle-shaped with 50-100 µm length and 1-3 µm thickness. However, when the reverse procedure was used, a different growth mechanism apparently applied yielding shorter (∼60 µm) but thicker (5-10 µm) column-shaped crystals within otherwise the same operating window.

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Section: Methodsmentioning

confidence: 95%

Preparation of α-Calcium Sulfate Hemihydrate by Reaction of Sulfuric Acid with Lime

Ling

Demopoulos

2005

Ind. Eng. Chem. Res.

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Phase transformation and dehydration of calcium sulphate dihydrate in solution studied by SEM

Sirota¹,

Dorozhkin²,

Кручинина³

et al. 1992

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The transformation of separate crystals of CaS04·2H20 (DH) into CaS04·0.5H20 (HR) in an aqueaus solution of H3P04 and H2S04 at 90-97°C was studied using a JSM-35CF SEM. The source DR and acids were reagent or eommereial (taken from the produetion of H3P04 by a wet process). DR was allowed to eonvert into HR and periodie samples of the suspension were drawn, filtered, and investigated in the solid phase by SEM. It was shown that the dehydration of reagent DH speeimens oeeurred through the reerystallization mechanism, whereas the transformation of eommereial DR into HH was basieally topoehemieal and developed by a relay race meehanism without any phase transformation front. The observed differenee between eommereial and reagent DR speeimens may be explained by differenees in their erystalline strueture, initial partiele size and by the presenee of impurities in DH and aeids. It is established that ehemieal impurities ean ehange the meehanism of the phase transformation of the erystals DH into HH.

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A hierarchical structure for apatite crystals

Dorozhkin¹

2007

J Mater Sci: Mater Med

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Based on the experimental results taken from the references, a reasonable hierarchical structure of apatite (both fluorapatite and hydroxyapatite) crystals has been proposed for the first time. The structure consists of four levels of the hierarchy: the smallest level is made of single unit-cells and/or Posner's clusters with the linear dimensions slightly below 1 nm, the second level comprises X-ray coherent scattering blocks of 50-80 nm in size, the third level is represented by dislocation blocks of 0.3-2.0 microm in size and, finally, there are macroblocks of 35-50 microm in size.

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Diagnostics of heterogeneous chemical reactions by cathodoluminescence

Cited by 4 publications

References 2 publications

Preparation of α-Calcium Sulfate Hemihydrate by Reaction of Sulfuric Acid with Lime

Preparation of α-Calcium Sulfate Hemihydrate by Reaction of Sulfuric Acid with Lime

Phase transformation and dehydration of calcium sulphate dihydrate in solution studied by SEM

A hierarchical structure for apatite crystals

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