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Precipitation of spherical boehmite from concentrated sodium aluminate solution by adding gibbsite as seed

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International Journal of Minerals,Metallurgy and Materials 2017年第8期24卷 954-963页

作者： Gui-hua Liu Zheng Li Xiao-bin Li Tian-gui Qi Zhi-hong Peng Qiu-sheng Zhou School of Metallurgy and Environment Central South University

The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The surface energy calculation results show that the(001) and(112) planes of gibbsite surfaces are remarkably stable because of their low surface energies. In addition, the(010) plane of boehmite grows preferentially during precipitation because of its low surface energy. Thus, we propose a method to precipitate spherical boehmite from a supersaturated sodium aluminate solution by adding gibbsite as seed in a heterogeneous system. In this method, gibbsite acts as the preliminary seed and saturation modifier. The results show that the fine boehmite first nucleates on the(001) and(112) planes of gibbsite and then grows vertically on the(001) and(112) basal planes of gibbsite via self-assembly, thereby forming spherical boehmite. Simultaneously, gibbsite is dissolved into the aluminate solution to maintain the saturation for the precipitation of boehmite. The precipitation ratio fluctuates(forming an M-shaped curve) because of gibbsite dissolution and boehmite precipitation. The mechanism of boehmite precipitation was further discussed on the basis of the differences in surface energy and solubility between gibbsite and boehmite. This study provides an environmentally friendly and economical method to prepare specific boehmite in a heterogeneous system.

关键词： precipitation sodium aluminate solution morphology boehmite gibbsite surface energy

Solvothermal Synthesis of boehmite and γ-Alumina Nanorods

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Journal of Materials Science & Technology 2008年第4期24卷 637-640页

作者： Mingguo MA Yingjie ZHU Guofeng CHENG Yuehong HUANG State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 China

boehmite nanorods were synthesized by a solvothermal method using AICl3·6H2O in mixed solvents of water and aniline. The solvothermal time, heating temperature and the concentration of aniline have effects on the morphology of boehmite. γ-alumina nanorods were prepared by a simple thermal transformation of boehmite nanorods. A rational mechanism based on the oriented attachment is proposed for the formation of boehmite nanorods. The products were characterized by X-ray powder diffraction （XRD） and transmission electron microscopy （TEM）. Photoluminescence （PL） spectrum of the boehmite nanorods was also investigated.

关键词： boehmite γ-Alumina Nanorods Solvothermal

Solvothermal preparations of α-alumina and boehmite crystallites and investigations on the formation of their morphologies

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Science China(Technological Sciences) 1998年第3期41卷 288-294页

作者：田明原施尔畏王步国元如林李文军仲维卓郭景坤 Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai China Department of Chemistry Jilin University Changchun China Department of Mathematics East-China College of Geology Jiangxi China

The solvothermal preparations of α alumina and boehmite crystallites have been investigated, and the effects of solvothermal conditions such as reactive medium and temperature on the phase, crystallization morphology and size of the crystallites have been discussed. The calculation of the stability energies of the growth units of the crystallites has been performed based on the model of anion coordinate polyhedron’s growth unit. The results could explain the formation mechanisms of the crystallites.

关键词： solvothermal synthesis α alumina and boehmite crystallites morphology stability energies of growth units formation mechanism.

Effect of boehmite sol on the crystallization behavior and densification of mullite formed from a sol-gel precursor

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Progress in Natural Science:Materials International 2013年第3期23卷 145-151页

作者： Pengchao Liu Yizheng Zhu Jinghong Ma Shuguang Yang Jinghua Gong Jian Xu State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Material Science and Engineering Donghua University

Hybrid mullite sol was synthesized from an aqueous solution of aluminum nitrate (AN), aluminum isopropoxide (AIP) and tetraethylorthosilicate (TEOS), doped with boehmite sol with different ratios. Pressureless sintering of the xerogel was carried out at different temperatures in the presence of boehmite doping. The xerogel and sintered powder were characterized by FTIR, TG-DSC, XRD, SEM and bulk density. The addition of boehmite caused the formation of metaphase spinel (6Al2O3·SiO2) crystal before the appearance of mullite phase, which could lead to the formation of amorphous phase and suppress the premature formation of mullite. Both of these effects improve the densification of mullite. A maximum density about 98% of the theoretical density (TD, 3.01 g/cm3 ) of mullite could be obtained for 5 wt% boehmite addition at 1200 1C pressureless sintering.

关键词： boehmite Sintering additive Mullite gel Densification Sol-gel

Ultralong and Mesoporous ZnO and γ-Al_2O_3 Oriented Nanowires Obtained by Template-assisted Hydrothermal Approach

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Journal of Materials Science & Technology 2014年第12期30卷 1167-1173页

作者： Carminna Ottone Vivian Farías Rivera Marco Fontana Katarzyna Bejtka Barbara Onida Valentina Cauda Center for Space Human Robotics Polito Istituto Italiano di Tecnologia Corso Trento 21 Turin Italy Dipartimento di Scienza Applicata e Tecnologia (DISAT) Politecnico di Torino Corso Duca Degli Abruzzi 24 Turin Italy

Highly mesoporous Zn O and g-Al2O3nanowires（NWs） are both synthesized by a hydrothermal method using commercially available porous anodic aluminium oxide（AAO） as template. AAO membrane acts as template for Zn O NWs and both as template and precursor for g-Al2O3 NWs. The formation of intermediate phases of porous Zn6Al2（OH）16CO3and boehmite（g-Al OOH） were observed, both occurring during the hydrothermal synthesis of porous Zn O and g-Al2O3 NWs, respectively, and disappearing after annealing at 600 C. This novel template-assisted hydrothermal process leads to the formation of porous Zn O and g-Al2O3NWs（specific surface area of 192 m2 g 1and 263 m2 g 1, respectively）, showing pore sizes around 4 nm in diameter. The influence of the reaction parameters on the nanostructure morphology was also investigated. A Zn O seed layer, deposited on the AAO channels prior to the hydrothermal synthesis, leads to more compact Zn O nanowires（99 m2 g-1） protecting the AAO host from the chemical attack of the precursor solution.

关键词： Mesoporous ZnO nanowires Mesoporous γ-Al2O3 nanowires boehmite Template-assisted method Hydrothermal synthesis

Synthesization and crystallization mechanism of nano-scale γ-AlOOH with various morphologies

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International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 376-379页

作者： Bao-hong Hao Ke-ming Fang Lan Xiang Qiang Liu School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Department of Mechanical Engineering Beijing Institute of Petrochemical Technology Beijing 102617 China Department of Chemical Engineering T singhua University Beijing 100084 China

Nano-scale γ-AIOOH with various morphologies, such as whisker, bar, ball, and sheet, was synthesized successfully and control- lably through a facile hydrothermal method just by adjusting the pH value of the solvent. Based on the analysis of the experimental data, the growth mechanism of nano-scale γ-AlOOH in the hydrothermal process was established. It is proposed that the growth unit and the growth direction are determined by the pH value of the solution and the growth unit, respectively. One-dimensional γ-AlOOH, such as whisker and bar, is formed in lower pH ranges, while two-dimensional γ-AlOOH sueli as sheet is formed only in high pH environment following the plane expansion crystallization mechanism.

关键词： boehmite morphology control crystallization mechanism growth unit aggregate

Effects of Nano-Filler on the Thermal and Fire-Resistant Properties of Ethylene-Vinyl Acetate Copolymer

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Journal of Beijing Institute of Technology 2010年第2期19卷 237-240页

作者：杜建新郝建薇崔艳霞 National Laboratory of Flame Retardant Materials Beijing Institute of Technology Beijing Add-Tech Consulting Company Limited

Sepiolite （S9, B10, B20, B40） and boehmite have been added to an intumecent flame retardant （IFR） system to produce the halogen-free and fire-resistant ethylene-vinyl acetate copolymer （EVM） rubber. The rubber contains ammonium polyphosphate （APP） as acid source, double pentaerythritol （D-PER） as carbon source and melamine （MN） as gas source. The effects of nano-filler sepiolite and boehmite on the fire-resistant property of EVM rubber based on IFR system were investigated. The test results show that the system with nano-filler of sepiolite B10 has the best fire-resistant property. The process of smoke emission and thermal decomposition, the element composition of char surface and the micro morphology of intumecent char layer of the EVM IFR system with nano-filler were also studied by NBS chamber, thermogravimetric （TG） analysis, X- ray photoelectron spectroscopy （XPS） and scanning electron microscope （SEM）.

关键词： ethylene-vinyl acetate copolymer （EVM） sepiolite boehmite nano-filler intumecent flame retardant （IFR）

Rehydration and Phase Transformation of Aluminas

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石油学报（石油加工） 1997年第S1期13卷 108-112页

作者： Zhang Minghai, Li Guanghui, Ye Gang (Research Institute of Petroleum Processing, Beijing 100083)

ＲｅｈｙｄｒａｔｉｏｎａｎｄＰｈａｓｅＴｒａｎｓｆｏｒｍａｔｉｏｎｏｆＡｌｕｍｉｎａｓＺｈａｎｇＭｉｎｇｈａｉ，ＬｉＧｕａｎｇｈｕｉ，ＹｅＧａｎｇ（ＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｏｆＰｅｔｒｏｌｅｕｍＰｒｏｃｅｓ... 详细信息

ＲｅｈｙｄｒａｔｉｏｎａｎｄＰｈａｓｅＴｒａｎｓｆｏｒｍａｔｉｏｎｏｆＡｌｕｍｉｎａｓＺｈａｎｇＭｉｎｇｈａｉ，ＬｉＧｕａｎｇｈｕｉ，ＹｅＧａｎｇ（ＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｏｆＰｅｔｒｏｌｅｕｍＰｒｏｃｅｓｉｎｇ，Ｂｅｉｊｉｎｇ１０００８３...

关键词： alumina rehydration phase transformation boehmite corundum

STUDY ON PREPARATION OF SUPPORTED ALUMINA MEMBRANE USING SOL- GEL METHOD

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Acta Metallurgica Sinica(English Letters) 1999年第5期12卷 1082-1085页

作者： W.L. Zhang, B.Q. Jiang, Y.S. Sun, F. Lin and L. Gu Chemical Engineering Department of Nanchang University, Nanchang 330029, China

A stable colloidal boehmite sol was made with the aluminium iso propoxide made in China and used to prepare the supported γ alumina membrane using sol gel method. The γ alumina thin layer was characterized by SEM, N 2 sorption method and permeation measurement. The γ alumina membrane was prepared with uniform surface, thickness of 3 μm and average diameter of about 5 nm. The permeabilities of the single gases of H 2, N 2, Ar and their separation factors were measured. The experimental data explained a behavior of Knudsen diffusion for the gas transport through the thin membrane.

关键词： boehmite sol gel method,γ alumina membrane permeability