Galusek, Dušan

Lichvár, Peter

Prnová, Anna

DSpace at VSB Technical University of Ostrava

Sborník vědeckých prací Vysoké školy báňské - Technické u�nk'JIII-""'""'�""",_. ___ _ číslo I, rok 2008, ročník LI, řada hutnická článek č. 141 I THE PREPARA TION OF ALUMINATE GLASS MICROSPHERES BY SYNTHESIS IN CH.i/O2 FLAME A PRNOV Á, P. LICHVÁR. D. GALUSEK Vitrum laugaricio - Joint Glass Centre of the Institute of lnorganic Chemistry, S/ovak Academy of Sciences,Alexander Dubček University of Trenčín, and RONA,j.s.c., Trenčín, S/ovak Republic ABSTRACT: Binary alumina-rare-earth oxide glasses with high alumina content have been reported recently to have excellent mechanical properties, especially hardness, which is comparable to that of single crystal sapphire. The use of such glasses can be envisaged in transparent ballistic protection, or other applications, which at the same time require good transparency, outstanding mechanical properties, and high chemical durability. However, preparation of such glasses in bulk is difficult due to high crystallisation rates characteristic for th!;! system, which requ1re high cooling rates at the level 3 ., of I O 0C.s in order to preserve the matter in glassy state. To by-pass this obstacle, bulk glasses were prepared by hot pressing of quenched glass microspheres at temperatures, which are sufficiently high to facilitate densification by plastic flow, but still low enough to prevent crystallisation of glass. The equipment for tlame synthesis of glass microspheres from oxide precursors has been built in-house. Glass microspheres with dimensions < I O µm and with various compositions from the systems CaO­Al2O3, pure silica, and Y2O3-Al2O3 have been prepared and characterized. Hot pressing of the microspheres yielded bulk non-transparent glasses of respective compositions. KEY WORDS: glass microspheres, tlame synthesis, aluminium oxide, rare earth oxides I. INTRODUCTIONRare-earth and calcium-aluminate oxide glasses are of potential technological importance due to their exceptional mechanical and optical properties, including high hardness and elastic modulus, as well as transparency for radiation in mid infrared range. For many tlptical applications, it is therefore desirable to obtain single-phase glasses with uniform optical properties. Preparation ofthese glasses in bulk is difficult, because Al2O3 is a reluctant glass former, which necessitates the use of high quenching rates, in some instances as high as I 07 K.s·'. Special ways of preparation are therefore required. · Weber et al. used containerless melting techniques to prepare Y3AlsO'2 and Er3Al5O12 glasses.Containerless melting techniques with the use of an aero-acoustic levitator (AAL) or a conical nozzlelevitator (CNL) were used to eliminate heterogeneous nucleation on melting container surfaces andthus to suppress crystallisation on cooling [I]. McMillan et al. prepared CaO-AliO3 glasses,containing 50 mol % A!iO3 via splat quenching technique [2].The recent work of Rosenflanz [3] et al. describes a novel process for preparing of high aluminaglasses and glass ceramics with aluminate glass matrix and dispersed nanosized crystals of rare earthaluminates with hardness between 1 4.4 and 1 8,3 GPa and the fracture toughness between 2, 1 and 4,2MPa.m 112• Fully dense bulk glasses were obtained by pressure-assisted sintering of glass microbeads.Glass microspheres in the system Re2O3AlzO3 (Re = Y, La, Gd) composition were prepared by flame­spraying technique in a hydrogen-oxygen humer.Although a score of works describe preparation of alumina-rare-earth and calcium-aluminate oxide281 

The preparation of aluminate glass microspheres by synthesis in CH4/O2 flame

http://dspace.vsb.cz/bitstream/10084/67109/2/VSB%20HUF%202008-1_61_Prnova.pdf

The preparation of aluminate glass microspheres by synthesis in CH4/O2 flame

Abstract

Similar works

Full text

Available Versions

DSpace at VSB Technical University of Ostrava