CS257466B1 - A method of forming oxide or metal cobalt coatings on a ceramic substrate - Google Patents

Abstract

A method for forming well-adhering oxide and metallic cobalt coatings of varying thicknesses, comprising heating a ceramic substrate in the form of a powder or compact body, provided with a surface layer of a crystalline cobalt salt hydrate, to a temperature of 45 to 850 °C in the presence of air or in an inert atmosphere, whereby the coating decomposes. The ceramic substrate is subsequently annealed in an inert and/or reducing atmosphere at a temperature of 450 to 1,250 °C.

Description

257466

The present invention relates to a process for forming cobalt coatings on a ceramic substrate by melting salts, usually crystalline cobalt salt hydrates. Nowadays, cobalt coating technology processes are known, based mainly on physical principles. Vacuum coating by direct evaporation of cobalt and cobalt spraying in a protective atmosphere are among the most important ways.

The disadvantage of coating in vacuum by direct evaporation of cobalt lies in the fact that the cobalt coating formed is characterized by low adhesion to the surface of the ceramic substrate. The disadvantages of cobalt sputtering in the protective atmosphere are limited to the possibility of sub-microscopic and microscopic coatings, while only spraying is actively used to form macroscopic layers with considerable grain size, especially on large sections with a single profile.

The aforementioned drawbacks are eliminated by the method of forming oxide or metal cobalt coatings on a ceramic substrate in the form of a powder or a compact crystalline cobalt salt hydrate powder powder on the surface of a ceramic substrate or by immersion in a crystalline cobalt salt hydrate whose temperature is less than its temperature. thermal decomposition, wherein the ceramic substrate provided with the surface layer of crystalline cobalt salt hydrate is heated to a temperature higher than the thermal composition of the salt hydrate in the range of 45-850 ° C under air or inert atmosphere, and the coating is thermally decomposed and subsequently is lived in an inert and / or reducing atmosphere at a temperature of 450 to 1250 ° C.

Said method is applied to compact or powdered ceramic substrates. The advantages of the cobalt coating process on the ceramic substrate are that cobalt coatings exhibit very good adhesion to the surface of the ceramic substrate, and the overall process does not require heavy processing equipment. A further advantage of the invention is the high purity and smoothness of the cobalt coatings formed, the purity being readily obtainable by the use of crystalline salt hydrates of defined purity. Bis-bisucobalt (II) hexahydrate Co (NO4) · Ο Ο is used to form the cobalt coating on sintered corundum. The required amount of compound is determined according to the sample size, and the residue completely wetted all the desired sample areas.

The coating process proceeds as follows: - heating to 100 ° C and holding at constant temperature for 1 h with air access - after 1 h gradually raising the temperature to 850 ° C at 2 ° C per minute - after reaching 850 ° C the samples are cleaned from powder oxide residues and subjected to reductive annealing under a hydrogen atmosphere at 800 ° C for 1 h - after reducing annealing, the samples were cooled in a hydrogen stream to room temperature and the coating was terminated.

Cobalt hexobutyrate (Co) was used to form a cobalt coating on sintered corundum powder. Coating process was followed by the following mode.

Powdered corundum heated to 800 ° C was poured into a bath of molten crystalline hydrate. After 10 minutes, the powder mass was filtered off, washed with water from the residual melt and dried. The dry powder mass was annealed in the hydrogen atmosphere at 1000 ° C for 0.5 h. The coatings showed very good adhesion; to the sub-base. The coating is compact and also conductive from a certain ridge. It can even be soldered. The corundum coated with the method of the invention is good for thermal shock. The coating is only physically bonded but to some extent also chemically bonded. A method of forming cobalt coatings by melting crystalline cobalt hydrates on a ceramic base

Claims (1)

The substrate significant contributes to the application of ceramic materials as functional and structural elements, especially in the mechanical and electrical industries. The cobalt coating on the ceramic substrate allows the formation of multilayer purpose coatings, utilizing known physical, physical, chemical and chemical methods of coating conductive substrates. OBJECT OF THE INVENTION A method of forming oxide or metal cobalt coatings on a ceramic substrate in the form of a powder or compact body, characterized in that the cobalt salt salt crystals are powdered onto the surface of the ceramic substrate or the substrate is immersed in the melt of the crystalline cobalt salt hydrate, the temperature of which is lower than the temperature-sensitive decomposition of the salt hydrate; the ceramic substrate provided with the surface layer of the crystalline cobalt salt hydrate is heated to a temperature above the decomposition temperature of the salt hydrate of the range 45 to 850 ° C under air or in an inert atmosphere; annealing in an inert and / or reducing atmosphere at a temperature of 450 to 1200 ° C.