Hydrothermal preparation and characterization of boehmites

Mishra, Dillip Kumar; Anand, S.; Panda, R. K.; Das, R.P.

doi:10.1016/s0167-577x(99)00156-1

Cited by 123 publications

(54 citation statements)

References 13 publications

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“…Gelatinous boehmite is the principal constituent of European bauxites". The expression "wellcrystallised boehmite" continued to be used [9][10][11] . Boehmite from bauxites (not in Brazil) is an important raw material for the production of aluminium oxide 12 .…”

Section: Boehmitementioning

confidence: 99%

Hydrothermal synthesis of well-crystallised boehmite crystals of various shapes

et al. 2009

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Aluminium monohydroxide, also known as aluminium oxyhydroxide (boehmite -AlO[OH]), is water insoluble but crystallises into microcrystals of various shapes. When, by X-ray diffraction, the microcrystals present a basal reflexion (d [020] ) of 0.611 nm, the crystalline structure is referred to as "well-crystallised" boehmite. Natural and synthetic crystals of well-crystallised boehmite can have a plate-like shape with either a rhombic or hexagonal profile. Synthetic crystals can also be lath-like or ellipsoid in shape. The purpose of this paper is to present a method of hydrothermal synthesis using a single temperature (200 °C) for preparing plate-like crystals of wellcrystallised boehmite with ellipsoid, rhombic, hexagonal, and lath-like profiles by using different precursors. Our observations suggest that all of these shapes are stages of growth of the microcrystals of well-crystallised boehmite along the c-axis direction of the rhombic crystals.

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Section: Boehmitementioning

confidence: 99%

Hydrothermal synthesis of well-crystallised boehmite crystals of various shapes

et al. 2009

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“…Boehmite can also be synthesized from liquid phase by hydrothermal/solvothermal routes 9,11,27,[40][41][42][43][44][45][46][47][48][49][50][51][52] or by sol-gel and precipitation techniques 8,[53][54][55][56][57][58][59] . Experimental conditions such as aluminum source, nature of the precipitating agent, pH, presence and nature of organic additives, temperature and time of thermal treatment (hydrothermal/solvothermal or thermal aging) may have a main influence in the resultant boehmite crystallite size and morphology…”

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confidence: 99%

Synthesis and Characterization of Boehmites Obtained from Gibbsite in Presence of Different Environments

et al. 2016

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“…The FT-IR spectrum of the autoclaved bulk #80 cement (a) encompassed the seven absorption bands at 3659, 3302, 3087, 1498, 1411, 1068, and 729 cm -1 . All bands, except for 3659, 1498 and 1411 cm -1 , were ascribed to boehmite-and katoite-related groups [19,20]; namely, at 3302 and 3087 cm -1 due to the O-H stretching vibrations, at 1068 cm -1 corresponding to Al-O-H bending mode, and at 729 cm -1 associated with the Al-O stretching mode. On the other hand, the band at 3659 cm -1 was an OH valence-stretching vibration of non-bonded hydroxyl group in water, and two other bands at 1498 and 1422 cm -1 are attributable to the stretching vibration of CO 3 in carbonated compounds.…”

Section: Xrd and Ft-ir Analysesmentioning

confidence: 99%

Thermal Shock-resistant Cement

Sugama¹,

Pyatina²,

Gill³

2012

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We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement's resistance to thermal shock. In one cycle, we heated the 200C-autoclaved cement at 500C for 24 hours, and then the heated cement was rapidly immersed in water at 25C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite  -Al 2 O 3 , katoite  calcite, and hydroxysodalite  carbonated sodalite. Among those, the hydroxysodalite  carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved cement, causing its volume to expand.4

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Hydrothermal preparation and characterization of boehmites

Cited by 123 publications

References 13 publications

Hydrothermal synthesis of well-crystallised boehmite crystals of various shapes

Hydrothermal synthesis of well-crystallised boehmite crystals of various shapes

Synthesis and Characterization of Boehmites Obtained from Gibbsite in Presence of Different Environments

Thermal Shock-resistant Cement

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