Accession Number : AD0704173

Title :   EFFECT OF EUTECTIC MICROSTRUCTURE ON THE PROPERTIES OF CERAMIC OXIDES.

Descriptive Note : Technical rept. 1 Feb 69-31 Jan 70,

Corporate Author : UNITED AIRCRAFT CORP EAST HARTFORD CONN RESEARCH LABS

Personal Author(s) : Hulse,Charles O. ; Batt,John A.

Report Date : 16 MAR 1970

Pagination or Media Count : 38

Abstract : A general survey was made of ceramic eutectics which involved making castings and metallographic examinations on twenty-nine different systems. Four different pieces of unidirectional solidification equipment which were constructed during this period or are in the latter stages of development are described. Information is included from thirty unidirectional solidification experiments. Most of these runs employed alumina tubes to contain eutectic melts which solidified below 1000C. In order to obtain high thermal gradients, these tubes were slowly lowered into a water bath which extended well into the furnace. It was observed with some eutectic systems that after about 1/2 in. of solidification, bubbles could be nucleated and porous ingots obtained. This problem was overcome either by inserting a high frequency vibrating probe into the liquid during solidification or by creating a vacuum over the melt before solidification. In order to avoid the complications due to impurity pickup from oxide containers, later solidification experiments were conducted in platinum. A composite crucible was developed for this purpose which consisted of a plasma sprayed coating of mullite on the outside of a platinum crucible. Upon cooling, the low thermal expansion of the mullite restricted the thermal expansion of the platinum bonded to it. This allowed ingots to be removed intact from the crucible while the platinum was clean and undamaged. (Author)

Descriptors :   (*CERAMIC MATERIALS, EUTECTICS), MICROSTRUCTURE, OXIDES, ANISOTROPY, FREEZING

Subject Categories : Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE