Study of phase transformations during hydration of rho alumina by combined loss on ignition and X-ray diffraction technique

Vaidya, S.D; Thakkar, N. V.

doi:10.1016/s0022-3697(00)00274-2

Cited by 22 publications

(14 citation statements)

References 5 publications

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“…Once during the milling in acidic-basic condition the pH increased from 4.1 to 8.4, probably at the initial stage, in acidic pH; gibbsite or an amorphous hydroxide was formed and gradually transformed to bayerite as the pH increased. This behavior has been reported in experimental observations of the effects of pH on the hydration ofalumina and -alumina and precipitation studies [28,31,32]. This phase transformation favors the appearance of a recrystallized structure, which eliminates defects previously introduced in the precursor phase (gibbsite); therefore, less defective bayerite crystals were formed.…”

Section: Starting and Milled Powderssupporting

confidence: 70%

Effects of Milling pH and Hydrothermal Treatment on Formation of Nanostructured Boehmite Binder for Alumina Extrusion

Lima

Tercini

Santos

et al. 2017

Journal of Nanomaterials

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The in situ formation of nanostructured aluminum hydroxides on the surface of alumina particles, which can work as inorganic binder, was reported in this paper. The effect of the suspension pH during milling of alumina powder and subsequent hydrothermal treatment for the hydroxide formation and microstructure was depicted. Under acidic pH condition, the formation of hydroxides was not observed. When the pH of suspension changed from acidic to basic during milling, bayerite [Al(OH) 3 ] nanoparticles were formed, but only a fraction of this hydroxide was converted to boehmite (AlOOH) during subsequent hydrothermal treatment. The aluminum hydroxide and oxyhydroxide formed in this condition improved the smoothness of extruded rods and the strength of presintered segments. For the powder milled under basic pH condition, the mechanochemically formed bayerite was completely converted into boehmite nanoparticles during the hydrothermal treatment. The presence of boehmite nanoparticles contributed to improving plasticity during extrusion, which allowed the reduction of organic binder and increased the strength of presintered alumina rods.

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Section: Starting and Milled Powderssupporting

confidence: 70%

Effects of Milling pH and Hydrothermal Treatment on Formation of Nanostructured Boehmite Binder for Alumina Extrusion

Lima

Tercini

Santos

et al. 2017

Journal of Nanomaterials

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“…After H2 treatment at 673 K, the evolution of Ni-Sn phase formation was , 9 (1), 2014, 55 Copyright © 2014, BCREC, ISSN 1978-2993 (Figure 1b). On the other hand, the diffraction peaks of bayerite and gibbsite completely disappeared after H2 treatment at 673 K indicating the transformation of crystalline bayerite or gibbsite into amorphous alumina which have no detectable peaks in XRD analysis [28,29]. In addition, the diffraction peaks of Ni metal at 2θ of 51.6 o and 76.2 o corresponding to Ni(200) and Ni(220) were also observed.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

Development of Nanoporous Ni-Sn Alloy and Application for Chemoselective Hydrogenation of Furfural to Furfuryl Alcohol

Rodiansono

Hara

Ichikuni

et al. 2013

Bull. Chem. React. Eng. Catal.

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A very simple synthetic procedure was developed for the preparation of Ni-Sn alloy catalysts that were utilised for chemoselective hydrogenation of furfural, producing furfuryl alcohol almost exclusively. The mixture of nickel nanoparticles supported on aluminum hydroxide (R-Ni/AlOH) and a solution containing tin was treated under hydrothermal condition, producing the as prepared nickel-tin alloy supported on aluminum hydroxide (Ni-Sn/AlOH). H2 treatment at range of temperature of 673-873 K for 1.5 h to the as prepared Ni-Sn/AlOH produced nanoporous Ni-Sn alloy catalysts. XRD patterns and SEM images revealed that the formation of Ni-Sn alloy of Ni3Sn and Ni3Sn2 phases and the transformation of crystalline gibbsite and bayerite into amorphous alumina were clearly observed after H2 treatment at 873 K. The formation of the Ni-Sn alloy may have played a key role in the enhancement of the chemoselectivity.

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“…This new binder system is composed of alumina hydrates such as pseudo‐boehmite and bayerite formed by hydration of hydraulic alumina (HA). HA has been studied as an inorganic binder for casting because of its unique properties such as rehydration and self‐binding 14–19 . In the new binder system, HA bodies with suitable amounts of water and cured at room temperature for over 2 days show good flowability and rigidity similar to natural clays 13 .…”

Section: Introductionmentioning

confidence: 99%

“…HA has been studied as an inorganic binder for casting because of its unique properties such as rehydration and self-binding. [14][15][16][17][18][19] In the new binder system, HA bodies with suitable amounts of water and cured at room temperature for over 2 days show good flowability and rigidity similar to natural clays. 13 HA is an inexpensive alumina substance because it is usually produced via flash calcination of gibbsite.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Alumina Binder for Extrusion of Alumina Ceramics

Nagaoka

Duran

Isobe

et al. 2007

Journal of the American Ceramic Society

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The present work describes the effect of hydraulic alumina (HA) as a new inorganic binder on extrusion of alumina ceramics. The addition of a small amount of HA imparted significant flowability and rigidity to the extruded alumina. Under optimum processing conditions such as amounts of HA and water, and curing period, alumina rods and tubes were successfully extruded using a single screw extruder. Sintered specimens have achieved a relative density of 97% after sintering at 1600°C for 2 h. Dense alumina samples prepared using organic and inorganic binders had similar mechanical properties, that is, Young's modulus >380 GPa and Hv>2000. These results suggest that HA is a new kind of inorganic binder applicable to the extrusion of ceramics.

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Study of phase transformations during hydration of rho alumina by combined loss on ignition and X-ray diffraction technique

Cited by 22 publications

References 5 publications

Effects of Milling pH and Hydrothermal Treatment on Formation of Nanostructured Boehmite Binder for Alumina Extrusion

Effects of Milling pH and Hydrothermal Treatment on Formation of Nanostructured Boehmite Binder for Alumina Extrusion

Development of Nanoporous Ni-Sn Alloy and Application for Chemoselective Hydrogenation of Furfural to Furfuryl Alcohol

Hydraulic Alumina Binder for Extrusion of Alumina Ceramics

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