The method of applying a metallic coating on the surface of powders and substrates

 

(57) Abstract:

The invention relates to a process of applying a metallic coating on the surface of various materials (powders and substrates), including dielectrics, semiconductors, metals, and can be used, for example, metallization of abrasive particles, for applying a metal coating on the surface of the ceramic materials to create composite materials of the type metal-ceramics, and electronics in the manufacture of theprotocol and other devices. In this way carry out degreasing and cleaning the surface of the material, then it is applied mechanically particles of a substance selected from the group of metals, alloys, metal oxides, metal hydroxides, sulfides of metals, followed by heating up to 200-500°C in non-oxidizing atmosphere. The method allows to obtain a dense durable coating with a controlled thickness, is inexpensive and high-performance. 9 C.p. f-crystals.

Scope

The invention relates to a process of applying a metallic coating on the surface of various materials (powders and substrates), including dielectrics, semiconductors, metals, and morepowerful ceramic materials, and in electronics in the manufacture of items such electronic devices as teplosochi, circuit boards, resistors, electrodes, sensors, and magnetic storage media. Particles coated with the coating can be used for the manufacture of abrasive tools and composite materials such as metal-ceramics (used, for example, in the automotive industry).

Characterization of analogs of the invention

Currently using the following methods of applying metal coating on the surface of materials: vapor deposition, plasma-CVD method, the coating liquid molten metal, chemical precipitation from solution, the electrochemical method, a method of coating using solid-phase reactions.

In the method of deposition from the vapor phase (US 5250086, US 5232469, US 5224969, US 5126207, US 5024680, US 4399167, US 3924031, US 3871840, US 3650714) used gas mixtures at low pressures and high temperatures of the substrate for applying carbidopa metals such as chromium, titanium and zirconium. For example, in patent US 5224969 describes a process in which a fine powder of chromium is mixed with diamond powder and heated to 600-700oC in vacuum 10oC), which leads to degradation of the diamond; the use of expensive carbidopa metals; the necessity of applying the second layer of metal that is less prone to oxidation; the need for stirring to prevent sticking of the particles.

Plasma-chemical method (US 5489449) allows to obtain a durable metal coating on a planar dielectric substrate. In the case of coating the surface of the powder material requires the creation of pseudocapsule layer to prevent aggregation of the grains of the coated material, which leads to significant gas flow when using powders with a diameter of grains more than 40 μm. Other disadvantages of the method are the need for high temperatures, the complex construction of the reactor, the use of working gas, optionally purged of oxygen, the fragility of the electrodes.

In the method of coating of the liquid metal melt (US 5250086, US 5224969, US 5306318, US 5090969) abrasive particles immersed in a melt of one or more Gulidov del Obi, tantalum, molybdenum; the process is at temperatures of 600-1000oC; for chromium preferably between 800 and 950oC (US 5250086). In the patent US 5306318 described the process for coating particles of cubic boron nitride titanium; US patent 5090969 described the melt containing the fluoride of the alkali metal used for coating of diamond and cubic boron nitride. Disadvantages of the method are the use of high temperatures (600-700oC), which leads to degradation of the diamond; the use of expensive carbidopa metals; the necessity of applying the second layer of metal that is less prone to oxidation; the need for stirring to prevent sticking of the particles. Described melts containing titanium (US 3929432) and titanium hydride (US 4591363). In this case, a mechanical crushing the sintered aggregates, resulting in bare spots, cracks and other defects.

Electrochemical method (US 5421989) requires prior application to the dielectric materials of the metal sublayer using other methods. The method does not have the disadvantages of the above analogs, allows you to get more performance, but in the case of obtaining powders of metal content up to 50% of the coating quality of the su from the solution involves degreasing, cleaning, activation and sensitization of the surface of the dielectric, followed by reduction of metal on a dielectric surface from a solution of metal salt. The method is slow; increasing the concentration of metal in solution leads to the production of coarse metal precipitated separately from the cover material; the degree of coverage low coverage ratio 50-70%), which is associated with a low density of centers of crystallization of metal on a dielectric surface; in this way it is difficult to control the thickness of the metal layer.

In several patents (US 4063907, US 4063907, EP 0513821, EP 0508399) coating based on the use of solid-phase reactions. In the patent US 4063907 describes the process in which a machining abrasive particles and particles of a metal compound that can decompose or to recover under atmospheric pressure and the temperature of 800-1400oC, namely sulfides of molybdenum, tungsten, titanium, niobium, tantalum, chromium and zirconium. Disadvantages of the method are the use of high temperatures, incomplete coverage of the substrate metal. In the patent EP 0513821 described a process in which a thin film of a solution containing alkoxide noble metal nano is the long distance metals and/or oxidizing atmosphere to obtain a thin film of noble metal oxides. In the patent US 5256443 alkoxide noble metals are produced in the form of Zola and dried thin film until a gel. The drawbacks are the inability to obtain a thick durable coating and the high cost of the reagents (ORGANOMETALLIC compounds and salts of palladium).

Characteristics of prototype

The closest analogue, selected as a prototype, is the patent EP 0508399, in which the substrate and the organic salt of the metal is not heated above 400oC under reduced pressure in the presence of palladium salts. Organic salt of the metal when it is subjected to pyrolysis products which form the desired coating on the substrate.

Criticism of the prototype EP 0508399

The disadvantages of this method are:

1. Inability to obtain a dense durable thick layer, because in the process of decomposition of ORGANOMETALLIC compounds produce large quantities of gaseous products, loosening floor that leads to its porosity and low strength.

2. The complexity and high cost in the application of this method to the powder dielectric materials, because in this case, the required mixing of the powder in the process of pyrolysis of metal the tea required mechanical crushing the sintered aggregates, resulting in bare spots, cracks and other defects. This is a common drawback of all patents, including the operation of crushing the sintered agglomerates (US 3929432, US 4591363).

3. The high cost of the reagents (ORGANOMETALLIC compounds and salts of palladium).

The aim of the present invention to provide a dense, durable coatings with controlled thickness on the surface of various materials (powders and substrates), capable of withstanding temperatures up to 200-500oC (diamond, abrasives, ceramics, glass, dielectrics, semiconductors, metals) by increasing the continuity of the coating, and high productivity of the process and its cheaper.

The invention and its distinguishing from the prototype signs

This goal is achieved by the fact that after degreasing and cleaning the surface of the material it is applied mechanically particles of a substance selected from the group of metals, alloys, metal oxides, metal hydroxides, sulfides of metals, where the metal is copper, Nickel, aluminum, zinc, titanium, tungsten, germanium, gold, cobalt, molybdenum, tin, palladium, platinum, followed by recovery of the applied compound to metal in neace inorganic metal compounds during decomposition emit a small amount of gaseous substances, that allows to obtain a dense durable coating with high continuity. The thickness and continuity of the resulting layer was estimated by the method of x-ray phase analysis (see example 1). The adhesion strength of the coating was evaluated by comparing the x-ray metallized powder before and after treatment in an ultrasonic bath (example 3).

This method is less time-consuming and expensive than the prototype, because when it is applied to the powder materials it requires no pseudocapsule layer or spray drying; it does not use expensive reagents (salts of palladium and ORGANOMETALLIC compounds).

Degreasing surfaces are usually carried out in alkaline solution. Surface cleaning may be performed by etching in dilute acid or by other means, for example, laser processing surface of the substrate (S. M. Pimenov, G. A. Shafeev, V. A. Laptev, E. N. Loubnin, Appl. Phys. Lett., 64 (15) 1994, p. 1935-1937). As materials, which are coated with a coating, can be taken synthetic and natural diamond, cubic boron nitride, corundum, ruby, sapphire, silicon carbide, rhinestone beads, ceramics, glass, semiconductors, and other materials capable of withstanding temperatures up to above the s.

The coating may consist of copper, Nickel, titanium, zinc, aluminum, tungsten, germanium, gold, cobalt, molybdenum, tin, palladium, platinum and their alloys. Applying particles of the substances of which is formed a coating on the powder materials is in the process of mixing in different mills and mixers. Deposition of these particles on a flat surface produced by the method of knurling or by casting the slurry (slurry with a high solids content), followed by drying and rolling. The surface of complex shape can be processed by the method of spraying the suspension or solid powder material.

As substances of which the coating can be applied monoxide, carbon dioxide, copper, Nickel monoxide, oxides, hydroxides and sulfides of these metals. You can also use metal powder. Recovery can be carried out in an argon atmosphere, purified nitrogen, hydrogen, or under reduced pressure of 10-3mm RT.article The temperature value to which you want to heat depends on the degree of rarefaction, the nature and extent of the cleaning gas and the substance used, which later formed the floor. When IFs 200-500oC. the obtained metal layer can be applied one or more layers of metals using this or other methods.

The obtained metal layer is protected from oxidation by processing in organic solvents (CF2Cl2, CHClF2and CF4).

Sometimes in practice it is necessary to obtain a layer of metal oxide on the powder or the substrate. In this case, the metal layer is heated in an oxidizing atmosphere until the desired degree of oxidation.

Metallic coating obtained by applying the described method, has a high density and has a good adhesion to the surface of the coated material; it is possible to obtain coverage of a given thickness and continuity; continuity of coverage can be up to 100%; the process is performed at relatively low temperatures and does not require expensive equipment complex structures; the method is high, it does not use expensive reagents such as palladium compounds and ORGANOMETALLIC compounds); the process can be done without waste. The obtained metallic coating is rough, to achieve reliable the close of the Sabbath., and on an organic basis. Particles coated with the coating can be used for the manufacture of abrasive tools and composite materials such as metal-ceramics (used, for example, in the automotive industry). Materials coated with a metal coating can be applied as such elements of electronic devices, as teplosochi, circuit boards, resistors, electrodes, sensors, and magnetic storage media.

Example 1.

After degreasing, cleaning and drying the synthetic diamond powder (particle size 50 μm) was mixed with Cu2O in a ratio of 50 wt.% (on copper). In the mixer was laid pre-lined Cu2O the grinding body (diameter 5 mm) in the ratio of the mass of the load/weight of grinding bodies 2:1. The process of mixing continued for 20 minutes heating the resulting mixture up to 450oC was carried out in an atmosphere purged of oxygen and moisture in argon. The end of the recovery process was recorded by the cessation of gas evolution. After cooling, the powder was processed in CF2Cl2and dried. Performance in this example was 3 kg/h when the amount of used reactor 6 liters

We evaluated the sample is more than 3 μm. On the radiograph obtained sample showed diffraction peaks corresponding to the structure of diamond. Thus, we can conclude that the thickness of the coating is greater than 3 microns at 100% continuity of coverage (accuracy of 0.5%).

Example 2.

After degreasing, cleaning and drying the powder of cubic boron nitride (particle 50-60 μm) was introduced into a pre-prepared suspension. Suspension of aluminium powder was obtained by mixing within 15-30 min in a water-alcohol solvent. Next, the solvent is evaporated at a temperature of 100oC, followed by heating in a confined space at a temperature of 250-300oC. After cooling, the powder was processed in CHClF2and dried.

Was the assessment of the continuity and thickness of the coating using x-ray phase analysis. The continuity of the coating was 90-95% (accuracy of 0.5%).

Example 3.

After degreasing, cleaning and drying the powder of corundum Al2O3(particle size of 60-80 μm) was introduced into a pre-prepared suspension. Suspension of titanium powder was obtained by mixing within 15-30 min in a water-alcohol solvent. Gave the round 250-300oC. After cooling, the powder was processed in CF4and dried.

Adhesive strength was evaluated by comparing the radiographs before and after processing the obtained metal powder in an ultrasonic bath at a frequency of 20 kHz for 3 minutes Difference of the x-ray spectra of metallic powders before and after ultrasonic treatment is not detected, which indicates a high value of adhesion at the boundary of the metal/dielectric.

Example 4.

After degreasing, cleaning and drying the ceramic plates on the basis of zirconium dioxide on its surface by casting the slurry was deposited film of oxide of Nickel with a thickness of 10 μm. The slip was prepared from the Nickel monoxide (90%), polyvinylbutyral, plasticizer and stabilizer by mixing them in a ball mill. After drying the film was conducted by heating the plates in an atmosphere of dry hydrogen to 390oC. the End of the process was recorded by allocating the calculated amount of water. After cooling, the plate was processed in CF2Cl2and dried.

1. The method of applying a metallic coating on the surface of materials, including heating of the material it is applied mechanically particles of matter, selected from the group of metals, alloys, metal oxides, metal hydroxides and sulfides of metals, where the metals are copper, Nickel, aluminum, titanium, tungsten, germanium, gold, cobalt, molybdenum, tin, palladium and platinum, followed by heating in a non-oxidizing atmosphere.

2. The method according to p. 1, characterized in that the quality of the materials used powder materials, and particles of substances, of which later formed the floor, causing the powder material by mixing in the mills and mixers.

3. The method according to p. 1, characterized in that the particles of the substances of which later formed the floor, put on the flat surface of the material by the method of knurling or by casting the slurry, drying and rolling.

4. The method according to p. 1, characterized in that the particles of the substances of which the coating, is applied on the surface of materials having a complex shape, the method of spraying the suspension or solid powder material.

5. The method according to p. 1, characterized in that as the substances from which later formed the floor, using carbon monoxide, carbon dioxide, copper, Nickel monoxide, and heated in a non-oxidizing atmosphere osushestvljaem the coating, use the powder of metal or alloy, and heating in a non-oxidizing atmosphere to carry 200 - 300oC.

7. The method according to p. 1, characterized in that the obtained metal layer is applied one or more layers of metals and/or protect the metal layer from oxidation treatment in organic solvents.

8. The method according to p. 1,characterized in that the metal layer is heated in an oxidizing atmosphere to obtain the desired degree of oxidation.

9. The method according to p. 1, characterized in that the quality of the material, which is coated, use a powder of synthetic and natural diamond, cubic boron nitride, corundum, ruby, sapphire, and silicon carbide.

10. The method according to p. 1, characterized in that the material is coated with a metallic coating applied as element of the electronic device.

 

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