Journal of the American Ceramic Society

Lamar, Richard S.

doi: 10.1111/j.1151-2916.1944.tb14476.xpmid: N/A

Abstract An attempt has been made to correlate the differential shrinkage of fired steatite pieces with the particle shape of the raw talc used in their manufacture. Various talcs of widely varying particle shape were used in making the steatite test pieces. It was found that the more irregular in shape the talc particles, the greater the differential shrinkage. A method is given for assigning arithmetical values to various particle shapes depending on their deviation from sphericity, this arithmetical value being known as specific shape factor. A direct relationship was found to exist between the differential shrinkage of a talc and its specific shape factor. As the talc particles became more irregular in shape, the “specific shape factor” value increased and the differential shrinkage was found to increase. The proper selection of the talc td be used and blends of various talcs were found to be helpful in the control of differential shrinkage.

White, J. S.

doi: 10.1111/j.1151-2916.1944.tb14477.xpmid: N/A

Abstract Experiments were made to determine which degree of fineness of ground talc would be most suitable for steatite‐type ceramics. A laboratory‐type air separator, Andreasen pipette, and the Casagrande hydrometer methods were used to measure the particle‐size distribution of commercial steatite talcs. The results indicate that, although wide variations in the particle‐size distribution of steatite talcs have a bearing on the firing shrinkage when the talc is incorporated in a body, the differences in grinding obtained in commercial talcs are not of great importance when proper milling practice is employed.

Amberg, C. R.

doi: 10.1111/j.1151-2916.1944.tb14478.xpmid: N/A

Abstract Diopside was substituted for both talc and feldspar in a typical wall‐tile body. It was found to lower the fusion temperature and to lower thermal expansion when compared with talc and to raise thermal expansion when compared with feldspar. Its effects on firing shrinkage, fired absorption, and moisture expansion were somewhat similar to those of talc.

Baumann, Henry N.

doi: 10.1111/j.1151-2916.1944.tb14479.xpmid: N/A

Abstract Various methods have been suggested and tried for modifying chrome ores for refractory use. Chrome ores vary widely in chemical composition but are made up chiefly of MgO, Al2O3, FeO, and Cr2O3 combined as a member of an isomorphous spinel‐type series. The problem of modifying chrome refractories by chemical and thermal treatment therefore involves a knowledge of the system MgO‐FeO‐Cr2O3‐Al2O3. The present study is based on experiments in which two series of chromium oxide‐alumina fusions containing 10% and 30% Cr2O3, respectively, were fused in an electric‐arc furnace with MgO up to 5% and with FeO up to 5%. The determination of the effect of silica and titania on the primary crystallization of these fusions, as indicated by a petrographic method of examination, was the chief purpose of this work.

Fabianic, William L.

doi: 10.1111/j.1151-2916.1944.tb14480.xpmid: N/A

Abstract Most of the various types of glass stones actually found under operating conditions in furnaces melting soda‐lime bottle glass are discussed. Each type is described in detail and photomicrographs of each kind of stone are shown. The possible source of each type of stone is considered along with general methods for its identification and elimination. Auxiliary aids to the petrographer, such as the use of solvent acids and chemical analyses, are mentioned. The stone specimens have been taken from flint, amber, and green‐colored glasses.

King, R. M.

doi: 10.1111/j.1151-2916.1944.tb14481.xpmid: N/A

Abstract The influence of manganese oxide alone and in combination with cobalt and nickel oxides on metal precipitation in ground coats has been studied. The previously developed electrical‐resistance method was used. Manganese dioxide present alone was not effective in precipitating metal. The results on the indirect influence of manganese dioxide in combination with cobalt and nickel oxides are not significant.

Martin, W. G.; Lauck, F. W.

doi: 10.1111/j.1151-2916.1944.tb14482.xpmid: N/A

Abstract Steel rings were glass coated, and some were split at one point immediately and others one or two years later. Identical movement of the rings caused by compressive forces in the glass indicated that no plastic flow takes place in the glass. The compressive forces were calculated and found to be of the general order of 10,000 Ib. per sq. in. The method of calculation is described. VI. Summary (1) Equal contraction of glass‐coated steel rings cut immediately after firing and those cut one and two years later indicates no plastic flow of the glass coating. (2) Calculations indicate a compressive stress of 10,900 lb. per sq. in. in the glass coating. (3) No definite explanation is advanced for the absence of plastic flow under such stress values except the suggestion that the cross‐section dimensions of the glass and relatively large surface area may account for restraining forces.