Compositions: coating or plastic – Coating or plastic compositions – Molds and mold coating compositions
Patent
1991-06-27
1994-09-13
Lieberman, Paul
Compositions: coating or plastic
Coating or plastic compositions
Molds and mold coating compositions
106 382, 501123, 505782, 505785, B28B 734, C04B 3502
Patent
active
053465385
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to moldings composed of sintered strontium indate of the formula (Sr,Ca)In.sub.2 O.sub.4, to a process for the preparation thereof and to the use of these moldings as vessel material for chemical reactions, during which bismuth oxide, if appropriate together with alkaline earth metal oxides, occur (sic) as a reactant at high temperatures.
The compound strontium indate has been known for a fairly long time (Z. Naturforschung 19b ( 1964 ) 955 ) . CaIn.sub.2 O.sub.4 is isotypic with SrIn.sub.2 O.sub.4. The crystal structure of these indates is known (Z. Anorg. Allg. Chemie 398 (1973) 24). The indates can be obtained from In.sub.2 O.sub.3 and an alkaline earth metal oxide by heating at 1200.degree. C.
Bismuth oxide shows--particularly at relatively high temperatures--markedly basic behavior. It melts at 824.degree. C. and strongly attacks melting crucibles and silicates. According to observations by Arpe and Muller-Buschbaum (J. Inorg. Nucl. Chem. 39 (1977) 233), even Al.sub.2 O.sub.3 is dissolved and converted to bismuth aluminates.
It was therefore the object to find a crucible material which is resistant at high temperatures, in particular at temperatures above 800.degree. C., to molten bismuth(III) oxide. The present invention achieves this object.
The invention is based on the finding that moldings composed of sintered strontium/calcium indate, (Sr,Ca)In.sub.2 O.sub.4, are stable in the presence of molten bismuth(III) oxide even at high temperatures.
These moldings can be produced by compacting a fine powder of strontium indate, calcium indate and/or solid solutions of the formula Sr.sub.x Ca.sub.1-x In.sub.2 O.sub.4 with 0<x<1, if appropriate with the addition of binders, to give a molding and heating the latter for several hours to temperatures from 1000.degree. to 1500.degree. C. Under these conditions, sintering takes place. The sintering time extends to at least 2 hours even at 1500.degree. C. At lower temperatures, the sintering takes longer. It should not be continued unnecessarily, since otherwise the formation of large crystals is promoted, which adversely affects the strength of the moldings.
Calcium indate melts above 1500.degree. C. Strontium indate melts only above 1600.degree. C. Fine grinding of the strontium indate powder used for sintering is advantageous. Molding can be carried out by known processes, for example by extrusion (bars, tubes) or by compaction (uniaxial or isostatic). Strontium indate can also be fused and allowed to solidify in molds, in order to obtain moldings.
The moldings obtained can assume the shape of spheres, tubes, ingots or bars, preferably that of reaction vessels such as crucibles, or the form of plates. Crucibles can also be produced by milling-out from an ingot.
A main difficulty in producing thin superconductive layers from the hitherto known oxidic materials on a carrier is the contamination of the superconductor by the carrier material. After the oxidic materials have been applied, a hermal aftertreatment is as a rule necessary in order to adjust the oxygen content in the superconductive layer. At this time, the superconductor reacts with the substrate material. This can be detected by measuring the concentration profile of the cations of the carrier material in the superconductor layer as a function of the distance from the surface of the carrier. Layers contaminated by cations have very poor superconductive properties (low T.sub.c, broad transitions). (Sr,Ca)In.sub.2 O.sub.4 is inert to the known oxidic superconductor materials (containing Bi.sub.2 O.sub.3, SrO, CaO, CuO) even at 1000.degree. C. It is therefore suitable, in the form of ceramic sintered bodies or bodies solidified from the melting point (sic), in particular in the form of plates, or in the form of single crystals, as a substrate material in the production of thin superconductive layers by processes such as, for example, CVD (chemical vapor deposition), spray coating, sputtering or ion beam vaporization, in which a thermal aftertreatment of t
REFERENCES:
Naturforschung, 19b (Aug. 1964), pp. 955-957, Schwartz and Bomment.
Z. Anorg. Allg. Chem. vol. 435 (1977), W. Muschick et al., pp. 56-60, no month given.
Einsmann Margaret
Hoechst Aktiengesellschaft
Lieberman Paul
LandOfFree
Molding of sintered strontium/calcium indate and the use thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Molding of sintered strontium/calcium indate and the use thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molding of sintered strontium/calcium indate and the use thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1117630