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1344-28-1Relevant articles and documents
Synthesis of thermally stable χ-alumina by thermal decomposition of aluminum isopropoxide in toluene
Mekasuwandumrong, Okorn,Kominami, Hiroshi,Praserthdam, Piyasan,Inoue, Masashi
, p. 1543 - 1549 (2004)
Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ-alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ-alumina thus obtained directly transf
Effect of milling on the formation of nanocrystalline x-Al 2O3 from gibbsite
Chaitree, Wasu,Jiemsirilers, Sirithan,Mekasuwandumrong, Okorn,Praserthdam, Piyasan,Charinpanitkul, Tawatchai,Panpranotw, Joongjai
, p. 3377 - 3383 (2010)
Gibbsite (FG) with mean particle diameter (d50 = 3μm) was milled in an attrition mill for 12 and 24 h using alumina balls as grinding media and calcined at different temperatures in the range of 350°-600°C. The properties of the alumina obtained were determined by X-ray diffraction, N2 physisorption, thermogravimetric/ differential thermal analyses, and transmission electron microscopy.Without milling, the alumina obtained normally contained the mixed phases between γ- and x-phase alumina. On the other hand, high purity of nanocrystalline vphase alumina (100 wt%) can be produced by calcination of the 24-h milled FG at 600°C. The isothermal kinetics measurements revealed that the rate constant (κ) for phase transformation increased as the particle size of gibbsite decreased and the calculated activation energy for transformation from FG to alumina decreased from 20.6 to 14.7 and 6.8 kJ/mol after milling for 12 and 24 h, respectively. The physical properties of nanocrystalline x-alumina obtained by the calcination of milled FG were comparable to those produced by the solvothermal method. The present results offer a simple way to prepare a large amount of pure x-phase alumina for particular industrial applications.
Studies on the thermal reactions of aluminium oxides and hydroxides
Novak, C.,Pokol, G.,Tomor, K.,Koemives, J.,Gal, S.
, p. 765 - 770 (1988)
The gibbsite →χ-alumina decomposition (in air) and the χ-alumina →boehmite transformation (under hydrothermal conditions) were investigated isothermally. Reaction products were characterized by TG and X-ray diffraction. The rate of the gibbsite →χ-alumina
Preparation and microstructural and textural characterization of single-phase aluminum oxides
Kul'ko,Ivanova,Litvak,Kryukova,Tsybulya
, p. 714 - 721 (2004)
Conditions for the preparation of single-phase η-, -, and χ-aluminas were determined. The structures of η- and χ-aluminas were characterized. With the use of high-resolution electron microscopy, it was found that η-Al2O3 particles exhibited the most developed {111} face and consisted of coherently joined domains with a pronounced platelet shape. Planar defects in the (111) plane occurred in the η-Al2O3 particles. Microstructural differences between single-phase η-Al2O3 and γ-Al2O 3 with a defect spinel structure were revealed. It was found that the η-Al2O3, χ-Al2O3, and -Al2O3 oxides are characterized by uniformly porous structures with average pore diameters of 47, 55, and 110 A, respectively.
Formation of the morphology of continuous-precipitation aluminum hydroxides in the course of industrial synthesis
Lamberov,Aptikasheva,Egorova,Levin,Gil'manov
, p. 171 - 177 (2005)
X-ray phase and differential thermal analyses were used to study in detail how the morphology of aluminum hydroxides changes in separate stages of the technological process. The assumption that two pseudoboehmite modifications differing in crystallite dim
Hauthal, T.,Pap, I. S.,Mink, G.,Blumenthal, G.,Szekely, T.
, p. 79 - 90 (1990)
Optical, electrical and dielectric properties of mixed metal oxides derived from Mg-Al Layered Double Hydroxides based solid solution series
Lahkale,Sadik,Elhatimi,Bouragba,Assekouri,Chouni,Rhalmi,Sabbar
, (2021/11/04)
In this work, we investigated the effect of aluminum content on optical, electrical and dielectric properties of mixed metal oxides (MMOs), obtained from calcination at 726 K of solid solution series based on nitrate intercalated Mg1-xAlx Layered Double Hydroxides (x = 0.167, 0.20, 0.25, 0.33). Subsequently, the MMOs were characterized by X-Ray Diffraction, and analyzed by Inductively Coupled Plasma, Scanning Electron Microscopy, Diffuse Reflectance Spectroscopy and Impedance Spectroscopy. It was found a shift of light absorption towards shorter wavelengths, and an increase of conductivity and dielectric constant when the aluminum content increased. Higher aluminum content exhibited strong ultraviolet light absorption with average band gap of 6.29 eV, and also manifested high reflectance in visible and near-infrared wavelengths, whereas lower aluminum content showed lower values of conductivity, dielectric constant and dielectric loss tangent. Moreover, the electrical, dielectric and optical parameters of MMOs were reported and discussed.
Electroluminescent polycrystalline Er-doped Lu3Al5O12 nanofilms fabricated by atomic layer deposition on silicon
Ma, Zhiqiang,Sun, Jiaming,Xu, Jing,Yang, Li,Yang, Yang
, (2021/07/06)
The sub-nanometer composition and interlayer thicknesses of the silicon-based Lu2O3/Al2O3 nanolaminates are regulated by atomic layer deposition, to fabricate polycrystalline Er-doped Lu3Al5/sub
Synthesis and Thermal Degradation of MAl4(OH)12SO4·3H2O with M = Co2+, Ni2+, Cu2+, and Zn2+
Andersen, Anders B. A.,Hansen, Lars Pilsgaard,Henriksen, Christian,Nielsen, Ulla Gro,Ravnsb?k, Dorthe Bomholdt,Wang, Qian
supporting information, p. 16700 - 16712 (2021/11/13)
The synthesis and thermal degradation of MAl4(OH)12SO4·3H2O layered double hydroxides with M = Co2+, Ni2+, Cu2+, and Zn2+ ( MAl4-LDH ) were investigated by inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis, powder X-ray diffraction, Rietveld refinement, scanning electron microscopy, scanning tunnel electron microscopy, energy-dispersive X-ray spectroscopy, and solid-state 1H and 27Al NMR spectroscopy. Following extensive synthesis optimization, phase pure CoAl4- and NiAl4-LDH were obtained, whereas 10-12% unreacted bayerite (Al(OH)3) remained for the CuAl4-LDH. The optimum synthesis conditions are hydrothermal treatment at 120 °C for 14 days (NiAl4-LDH only 9 days) with MSO4(aq) concentrations of 1.4-2.8, 0.7-0.8, and 0.08 M for the CoAl4-, NiAl4-, and CuAl4-LDH, respectively. A pH ≈ 2 for the metal sulfate solutions is required to prevent the formation of byproducts, which were Ni(OH)2 and Cu3(SO4)(OH)4 for NiAl4- and CuAl4-LDH, respectively. The thermal degradation of the three MAl4-LDH and ZnAl4-LDH in a nitrogen atmosphere proceeds in three steps: (i) dehydration and dehydroxylation between 200 and 600 °C, (ii) loss of sulfate between 600 and 900 °C, and (iii) formation of the end products at 900-1200 °C. For CoAl4-LDH (ZnAl4-LDH), these are α-Al2O3 and CoAl2O4 (ZnAl2O4) spinel. For NiAl4-LDH, a spinel-like NiAl4O7 phase forms, whereas CuAl4-LDH degrades by a redox reaction yielding a diamagnetic CuAlO2 (delafossite structure) and α-Al2O3.
