Phase Relations in the System Boron Oxide–Silica

Abstract

The suggested phase diagrams for the system B2O3‐SiO2 as drawn from the findings of previous investigators are presented. These diagrams show the wide controversy regarding this system. The principal difficulties in obtaining reliable equilibrium data are the volatilization of B2O3, the hydration of B2O3‐rich glasses, and the great viscosity of B2OrSiOz melts. In this investigation firings were made in sealed platinum capsules. Where necessary, they were opened and studied under xylene to eliminate hydration. Phases were identified by optical and X‐ray methods. The liquidus was obtained by determination of the temperatures at which the stable phases of SiO2 completely dissolved in the borosilicate melts. The criteria used for equilibrium are discussed.

Oxidation of Boron Carbide-Silicon Carbide Composite at 1073 to 1773 K

“…The silica concentration in the liquid borosilicate increased by the vaporization of B 2 O 3 , and then a solid SiO 2 phase formed in the liquid borosilicate when the SiO 2 concentration exceeded the solubility value. 23) Mass losses due to the oxidation of B 4 C 8) and the B 4 C-SiC composites in the present work are compared in Fig. 4.…”

Phase equilibria in the system niobium pentoxide - boric acid

“…As regard s the Nb20 s co mpone nt, the same re ma rks pertain as for the Nb20; -Ge02 sys te m [1]. For purposes of consiste ncy with previous publi cations the indicated melting te mperature of B20 3 is given as 450°C, although this value may be 5° to 10° low [5].…”

“…Percent B20 3 was es timated by difference from 100 perce nt. Analys es of three compositions (formulated at 25, 50, and 66.7 mole pe rcent Nb20 5) as well as analysis of the mechanically separated heavy and light devitrified liquids in the immi scibility region were made for both Nb20 5 and B20 3 • B20 3 was determined by titration of a neutral solution (PH 7.00) with standard NaOH solution, after th e additions of manitol. Nb20 5 was dete rmine d from the weight of the ignited residue.…”

Effect of B₂O₃ on crystallization behavior of ZnO–Al₂O₃–SiO₂ glasses

“…On the other hand, rutile was precipitated as a minor phase in 20AZ3B6T. B 2 O 3 would not incorporate into Gahnite because B 2 O 3 does not make solid solution with various oxides, 9),12), 13) so that the addition of B 2 O 3 changes only the composition of the glass phase. The precipitation of rutile would be caused by the decrease of TiO 2 solubility by the addition of B 2 O 3 into the glass phase.…”