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AssigneeSchott Glaswerke
InventorsFriedrich Siebers, Werner Kiefer, Maria Sura
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A process for manufacturing open porous sintered bodies with large open pore volume and defined pore diameters and which at least predominantly consist of glass-ceramics. They are obtained by sintering a mixture of sinterable powder and an inorganic soluble salt with defined grade of grain, the melting point of which is above the densification temperature of the sinterable powder. For the formation of a molded body the mixture of sinterable powder and inorganic salt is submitted to a molding process. The molded body is sintered in a sintering process and the soluble salt being contained in the molded body is lixiviated. As a main constituent the sinterable powder contains a pulverized crystallizable glass powder. The sintering process is performed in such a way that the crystal phases being produced during the crystallization of the crystallizable glass, and therefore the material properties, too, are controlled by the guidance of the sintering process as well as by the ion exchange taking place between the sinterable powder and the inorganic salt and which is controlled by their composition. Afterwards, the sintered body is transformed to the final glass-ceramic texture.
A process for them manufacture of open porous sintered bodies at least predominantly consisting of glass ceramics comprising the steps of:
A process for the manufacture of open porous sintered bodies at least predominantly consisting of glass ceramics comprising the steps of:
A process for the manufacture of open porous sintered bodies at least predominantly consisting of glass ceramics comprising the steps of:
A process for the manufacture of open porous bodies having a large open pore volume and defined pore diameters, at least predominantly consisting of glass-ceramics comprising the steps of:
Dependencies are inferred from the claim text.
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Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product…:…
Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts: heat treatment
Other methods of shaping glass: by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by…
Thermal after-treatment of glass products not provided for in groups C03B19/00 , C03B25/00 - C03B31/00 or C03B37/00, e.g. crystallisation,…:…
Term ended 19 Sep 2008 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The invention deals with a process to make open porous sintered bodies which at least mainly consist of glass ceramics with a big open pore volume and a defined pore diameter. The sintered bodies are obtained by sintering a mixture of sinterable powder and an inorganic soluble salt of defined grade of grain the melting point of which is above the sintering temperature of the sinterable powder. The mixture of the sinterable powder and inorganic salt is subjected to a molding process to shape a molded body which is sintered by a sintering Process. The soluble salt contained in the sintered body is eliminated after cooling down.
In a well-known process to make open porous sintered bodies of glass, glass of definite grain size is heated in a mold to a temperature, which is close to the softening point of the glass. By softening the glass grains are sintered at the area of contact. A drawback of this procedure is that open pore volumes of more than 40% are not achievable with sufficient stability.
In a similar process to make open porous sintered bodies of glass ceramics, ground ceramic powders of definite grain size are sintered one to another. By such sintering ceramic powders, the open pore volume is also limited to at the most 40% with sufficient stability.
The process according to the invention is based on the fact that the sinterable powder comprises, as a main constituent, a powdered crystallizable glass. In sintering the mixture of sinterable powder and inorganic salt, the higher sinterability of the vitreous state in comparison with crystalline ceramics is used. In this way sintered bodies with a good mechanical resistance can be manufactured at low sintering temperatures, the temperatures being below the melting temperature and the temperature of decomposition of the admixed inorganic salts. The transformation to the desired glass ceramic state takes place by crystallization after the sintering process.
However, in sintering ceramic powder with admixed soluble salts or pore-forming material it is necessary to add binding or fluxing agents to the initial mixture in order to decrease sufficiently the sintering temperature.
The transformation of the open porous sintered bodies to the glass ceramic texture according to the invention takes place by means of surface crystallization starting from the initial surfaces of the crystallizable glass powder. The sintering process of the surface crYstallization must be interpreted as competitive Processes which must be mutually optimized for each existing mixture of sinterable powder and inorganic salt. If the surface crystallization begins too early, the continuous sintering process to a body of sufficient mechanical resistance is prevented. The crystallization starting from the surfaces of the powder causes a crystalline surface to be formed, which prevents the viscous melting and the contacting of areas of the crystalline glass powder which is essential for the sintering process.