Journal of the American Ceramic Society

Ishikawa, H.; Shinkai, N.

doi: 10.1111/j.1151-2916.1982.tb10496.xpmid: N/A

Critical load characteristics for the indentation‐induced median crack in ternary lead‐zinc‐borate and commercial silicate glasses were investigated. The critical load is directly proportional to the fracture toughness/Vickers microhardness term, supporting the Lawn‐Evans model; however, the magnitude of the load is considerably greater than that estiated from the model. The relation of critical load to deformation/fracture properties is discussed in terms of the stress field around the indent area and fractography.

Sawhill, Howard T.; Haggerty, John S.

doi: 10.1111/j.1151-2916.1982.tb10499.xpmid: N/A

Ultrafine amorphous Si3N4 powders were synthesized from laser‐heated gases and cold‐pressed into pellets for sintering experiments. At temperatures >1300°C, the powders crystallized with a concurrent, linearly proportional decrease in surface area. These powders densified on a local scale without additives or pressure.

Takamori, Takeshi; Tomozawa, Minoru

doi: 10.1111/j.1151-2916.1982.tb10497.xpmid: N/A

The swelling of microporous glasses in water was found to change as a function of the heat–treatment time and temperature required for phase separation in the original borosilicate glass (70SiO2‐23B2O3‐7Na2O (wt%)). The swelling appears to be determined primarily by the quantity of silica gel remaining in the micropores, which in turn is determined by the composition of the alkali‐borate‐rich phase of the phase‐separated glass.

Lange, F. F.

doi: 10.1111/j.1151-2916.1982.tb10493.xpmid: N/A

Weight loss which occurs while sintering composited Si3N4 powders requires the loss of one or more of the end‐member constituents through a volatilization reaction. By plotting the direction of the compositional change on the appropriate equivalence phase diagram, the principal volatilization reaction can be determined. For a particular composition in the system Si‐Y‐N‐O sintered at 1750°C, the principal volatilization reaction was Si3N4(s) +3SiO2(s)→6SiO(g) +2N2(g).

Messier, Donald R.; Broz, Alfred

doi: 10.1111/j.1151-2916.1982.tb10495.xpmid: N/A

Glasses containing up to 15 at.% N were prepared and tested. The glasses were translucent to transparent, very hard, and had elastic moduli as high as 186 GPa.

Ritter, J. E.; Jakus, K.; Young, G. M.; Service, T. H.

doi: 10.1111/j.1151-2916.1982.tb10501.xpmid: N/A

Soda‐lime glass was proof‐tested in heptane using three unloading rates. Observed after‐proof strength distributions shifted toward weaker strengths as the rate of unloading decreased. The theoretical implications of the results are discussed.

Govinda Rao, B.; Rao, K. J.

doi: 10.1111/j.1151-2916.1982.tb10503.xpmid: N/A

An empirical relation for temperature–independent molar polarization is suggested. When this relation was used, the thermal expansivity was estimated correctly from refractive index data.

Michel, D.; Perezy Jorba, M.

doi: 10.1111/j.1151-2916.1982.tb10502.xpmid: N/A

New phases in the ternary systems ZrO2 (HfO2)‐MgO‐Nb2O5 (Ta2Os) were identified. These M7O12 compositions have fluorite superstructures isomorphous with the rhombohedral Y6UO12 type.

Syed, R.; Gavin, D. L.; Moynihan, C. T.

doi: 10.1111/j.1151-2916.1982.tb10498.xpmid: N/A

Very precise electrical conductivity data on a series of six glasses (molar composition 25[xNa2O+(l−x)K2O]‐5Al2O3−70SiO2 with 0.95 ≤x≤l) have been obtained over a large temperature range (∼310°C). Analysis of these data suggests that the preexponential term in the Arrhenius conductivity equation is temperature independent.

Clarke, D. R.; Zaluzec, N. J.

doi: 10.1111/j.1151-2916.1982.tb10500.xpmid: N/A

An improved sensitivity analysis of the oxygen and nitrogen content of the phase‐separated intergranular glass phase in hot‐pressed silicon nitride is reported. The compositional ranges derived from the analyses are illustrated in the Si3N4‐SiO2‐MgO‐Mg3N2 behavior diagram.