Fundamental Condition of Glass Formation*

Abstract

6) Smelting tests indicated that oversmelting, as evi-were either rutile or anatase; in the large majority of denced by yellow-to-brown coloring of the frit, is detri-cases, rutile was found; effect of composition on form mental to reflectance; color of fired enamel is not af-of TiOz that recrystallizes in firing is not definite from fected by oversmelting; correct smelting temperature results of this investigation. It has been determined seemed to be 2150'F. and glass should be poured as that the crystal form of TiOz added to the smelter does soon as all material is in solution. Undersmelting as not control the form of Ti02 recrystallizing.indicated by some undissolved particles imbedded in the frit did not affect reflectance or color of fired Acknowledgment enamel. The yellow coloring of grass is due in part to reduction of Ti02 to a lower oxide.(7) Firing time and temperatures are important since opacity is produced in the enamel during the firing procoptimum time and temperature are indicated for this type of enamel, above which optimum the reflectance is not increased appreciably for feasible increasesThis investigation was carried out in the Department of Ceramic Engineering a t the University of Illinois and was financed by the Enameled Utensil Manufacturers' Council of Cleveland, Ohio. The authors wish to express their appreciation to the Technical Committee of the Council for its advice, suggestions, and cooperation. Thanks are due J. 0. Kraehenbuehl of the Department of Electrical Engineering for the spectrophotometric analyses. ess;in time or temperature. ABSTRACTThe fundamental condition for glass formation is the existence of stronglybonded large networks or long chains of atoms in the liquid. Such chains or networks prevent or hinder the orderly orientation of atoms in the chains or networks themselves and also that of atoms, not in the networks in the liquid, near the melting point or liquidus temperature. A liquid structure will persist when the liquid is cooled below the melting point or liquidus temperature and will continue until free, long-range movement of atoms becomes impossible. In order to obtain such long chains or large networks, it is necessary that (1) the bond strength of atoms in the chains or networks be verystrong;(2) the small ring formation of these strongly bonded atoms be at a minimum; and (3) the relative numbers of various atoms in the chains or networks be such that at least a continuous chain is configuratively and structurally possible; at the same time, the coordination numbers of the glassforming atoms should be as small as possible to keep the bond strong. The general treatment is applied to all kinds of glasses, particularly oxide glasses. The bond strengths of all M-0 single-bond linkages in these glasses are calculated and tabulated here for the first time. The bond strength of all the glassformers was found to be greater than 80 kilocalories per Avogadro bond, that of the intermediates between 60 and 80, and that of the modifiers below 60; the transition is continu...

Effect of Dealloying Condition on the Formation of Nanoporous Structure in Melt-Spun Al60Ge30Mn10Alloy

“…The interesting point is that nano-porous germanium oxide has an amorphous structure. As already pointed out in the previous study, the critical thickness for amorphous-crystalline transition in germanium oxide may be rather large (Sun, 1947), resulting in the amorphous structure in nano-porous GeO x . Fig.…”

Fluorophosphate glasses containing manganese

“…3) Sodium is considered as a network modifier, and its coordination number is large in the solid state: from 6 in NaF to 12 in NaWO 3 [17]. 4) Bond strength of P-O (110 kcal/mol) bond is larger than that of Mn-O, Zn-O and Na-O bonds [18]. 5) Ionic radii [19] of Mn 2+ and Zn 2+ are close: 83 and 72 pm respectively.…”

The formation of glass: a quantitative perspective

“…Schematic diagram of theories of glass formation with respective to the viscosities and cooling rates to which they apply: square, experimental data from [48,97]. Intermediate compounds can reconnect broken networks, increasing the viscosity and enhancing the GFA with respect to a melt with the same viscosity and a more broken network.…”

“…Sun [48,97] proposed a single-bond-strength criterion for glass formation. Based on Sun's theory, Rawson [49][50][51] considered the ratio of the single-bond-strength to the melting point as the criterion for the identification of glass formers.…”

“…In Myuller's opinion, the cause of the high viscosity and the increased activation energy of the atomic re-grouping, as observed in substances disposed toward glass formation, lay in this difference. Sun [48] recognized that the processes of melting and crystallization often involve the breaking of inter-atomic bonds. Stronger bonds result in more sluggish processes of structural rearrangement and hence a greater likelihood of glass formation upon cooling.…”