Journal ArticleDOI
Alumina gels that form porous transparent Al2O3
TLDR
In this paper, the authors discuss the requirements for a porous transparent Al2O3 from aluminium alkoxides to retain its integrity during drying and pyrolysis, and show that there is a critical electrolyte concentration at which the gelling volume goes through a pronounced minimum.Abstract:
Formation of a porous transparent Al2O3 from aluminium alkoxides has been previously reported. During the process, alkoxides are hydrolyzed and the resultant hydroxide is peptized to a clear sol. The sol then must be gelled and pyrolyzed to 500° C to obtain the aluminium oxide. This paper discusses the gel state and the requirements for the system to retain its integrity during the drying and pyrolysis. Influence of electrolytes on the sol-gel transformation shows that there is a critical electrolyte concentration at which the gelling volume goes through a pronounced minimum. Deviation in either direction of this electrolyte concentration causes a sharp increase in the relative gelling volume and detrimentally effects the capability of the gel to retain its integrity. The sols that gel at concentrations less than ∼4 g equivalent oxide per 100 ml do not retain their integrity during pyrolysis.read more
Citations
More filters
Journal ArticleDOI
Chemistry of Aerogels and Their Applications
Alain Pierre,Gerard Pajonk +1 more
TL;DR: Aerogels form a new class of solids showing sophisticated potentialities for a range of applications, and can develop very attractive physical and chemical properties not achievable by other means of low temperature soft chemical synthesis.
Patent
Non-fused aluminum oxide-based abrasive mineral
TL;DR: In this article, a synthetic, non-fused, aluminum oxide-based abrasive mineral having a microcrystalline structure of randomly oriented crystallites comprising a dominant continuous phase of α-alumina and a secondary phase was described.
Journal ArticleDOI
Synthesis of High-Surface-Area Alumina Aerogels without the Use of Alkoxide Precursors
Theodore F. Baumann,Alexander E. Gash,Sarah C. Chinn,April M. Sawvel,Robert S. Maxwell,Joe H. Satcher +5 more
TL;DR: In this paper, high-resolution transmission electron microscopy, powder X-ray diffraction, solid-state NMR, acoustic measurements, and nitrogen adsorption/desorption analysis were used to characterize dry alumina aerogels.
Journal ArticleDOI
Aerogels: production, characterization, and applications
Jochen Fricke,T Tillotson +1 more
TL;DR: In this article, the authors present a historic review of aerogels while bringing the reader up-to-date on the latest technological developments, including the latest advances in aerogel technology.
Book ChapterDOI
Hydrogels: Methods of Preparation, Characterisation and Applications
TL;DR: This chapter reviews the preparation methods of hydrogels from hydrophilic polymers of synthetic and natural origin with emphasis on water soluble natural biopolymers (hydrocolloids).
References
More filters
Journal ArticleDOI
Hydrolysis of aluminium alkoxides and bayerite conversion
TL;DR: In this article, a study of hydrolysis of aluminium alkoxides as a function of water temperature was conducted, and structural transformation of the resultant hydroxides was conducted.
Journal ArticleDOI
Crystallization processes in aluminium hydroxide gels
G. C. Bye,J. G. Robinson +1 more
TL;DR: In this article, the formation of pseudoboehmite and bayerite from amorphous aluminium hydroxide was investigated using X-ray powder diffraction and electron microscopy.
Journal ArticleDOI
Surface chemistry of the calcination of gelatinous and crystalline aluminium hydroxides
TL;DR: The surface properties of a range of aluminas, obtained by calcination of crystalline and gelatinous aluminium hydroxides at temperatures from 300° to 1000° and characterised by X-ray powder diffractometry, have been examined by nitrogen adsorption as discussed by the authors.
Journal ArticleDOI
The surface properties of precipitated alumina. 111. Samples prepared from aluminium isopropoxide
M. R. Harris,K. S. W. Sing +1 more
TL;DR: In this paper, a range of high surface areas were found, the homogeneous precipitate having a particularly large initial area and pore volume, and the adsorption isotherms were of the type given by porous solids and resembled those obtained "activated" alumina rather than on the alumina prepared previously from aluminium chloride solution.