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Synthetic Mica Investigations: V, A Low‐Shrinkage Machinable Ceramic of Phosphate‐Bonded Synthetic Mica
Author(s) -
COMEFORO J. E.
Publication year - 1954
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1954.tb14062.x
Subject(s) - mica , talc , shrinkage , materials science , composite material , ceramic , absorption of water , pressing , phosphoric acid , porosity , phosphate , dielectric , mineralogy , metallurgy , chemistry , optoelectronics , organic chemistry
By using phosphoric acid as the binding agent for powdered synthetic mica, it was possible to produce by dry‐pressing a glass‐free machinable low‐shrinkage dielectric whose properties were controllable by varying the mica com‐ position, the forming pressure, the firing temperature, and the phosphate content. The total shrinkage was easily maintained at less than 3%, with the transverse strength in excess of 6000 lb. per sq. in. A zero‐shrinkage composition was also developed and its properties are discussed. A dense, impervious ceramic was not produced by this method; the water absorption seldom was less than 4% with forming pressures of 10,000 lb. per sq. in. or less. The dielectric characteristics of this ceramic approached those reported for hot‐pressed phosphate‐free synthetic mica when it had similar porosity. The dielectric loss factor was of the order of 1 to 2% at room temperature and 4 to 8% at 300°c. and 1 mc. This material is suggested as a replace‐ ment for natural block talc.