A method of making a microstructure of a ceramic material is known from Weber, Tomandel, 1998: “Porous Al2O3 Ceramics with uniform Capillaries”, cfi/Berichte DKG 075 (1998), p. 22-24. For producing structured components of a ceramic material, inter alia for actuator applications, a potential-based method is applied. The actuator components may, for example, be used as broad band high frequency transformers, the material being a PZT-ceramic. The method is based on the principle of an ionotropic formation of capillaries, in which uniformly distributed pore channels running in parallel to each other are formed in a ceramic matrix due to cross-linking of organic polymer brines comprising bivalent or trivalent metal cations. The common starting material of this method is a homogeneous mixture of PZT-suspension and alginalsol. The structured pre-shapes are dried after ion exchange and exchanging the water for solvent, and sintered afterwards. Starting from the wet gel up to the sintered structure a shrinking in volume of over 99% occurs. Presently, PZT-ceramic structures can be produced which have a diameter of about 2 mm and a height of 0.5 to 1 mm, the single capillaries having a diameter of about 10 μm. Although the diameter and density of the capillaries can be modified by varying the process parameters, their actual arrangement, however, is mainly based on a random process. With a random determination of the sterical shape of a structure, however, no high performance structures can be made, which have to have a sterical shape optimized for a particular application.
In the production of microstructures of ceramic materials according to classic ceramic methods, in which first a green body is made of a ceramic raw mixture and sintered afterwards, general problems occur in the formation of sterical microstructures with thin walls. The internal stresses due to shrinkage processes occurring upon sintering have the result that cracks readily occur in the area of thin walls. Thus, it is impossible to considerably get below a magnitude of 1 mm with the wall thickness of sterical structures. This applies, even if the volume shrinking upon sintering is reduced by an optimized ceramic raw mixture.
In the field of quality enhancing surface treatment, it is known to heat up an element made of a metallic material locally at its surface by means of a laser to such an extent that the melting temperature of the metal is exceeded. Thus, the metal can rearrange itself under the influence of its surface tension at the surface of the element, to form a smoothened surface. This smoothened surface is conserved upon cooling the material again below its melting temperature.
There is a need of a method of forming a structure having an optimized sterical shape from a material, in which the desired sterical shape is unerringly achieved and in which problems with inner tensions due to shrinkage of the material are avoided.
USPTO Backgrounds
USPTO Backgrounds