DE1902819A1 - Process for coating bodies made of carbon, graphite, iron or copper - Google Patents

Description

21JAN.1969

SIGRI BLSKTROGRAPHIT GMBH Meitingen, - the * »■

_; . . . ■ ■ ;. "' . ■■■ 69 / 3.603 _;

Process for coating bodies made of coal ", Graphite, iron or copper

The present invention "relates to a method for Application of a layer made of silicon, boron and / or transition metals of the IV.Ms VIII. group of the periodic Systems on bodies made of carbon, graphite, bison or copper.

The coating of bodies made of carbon, graphite, iron or copper with, for example, silicon or transition metals the IV. to YI. Group of the periodic table, e.g. titanium, is known. For example the coating of graphite with titanium has so far been common by thermal decomposition of titanium iodide or by reducing titanium chloride with hydrogen gas at high temperatures. The gas reaction or pyrolysis has the well-known disadvantage of all pyrolytic processes that they involve "considerable expenditure on equipment. connected is that relatively high temperatures must be used and that due to differences in concentration in the atmosphere, layers of unevenly thick layers are deposited after relatively long deposition times.

It is also known, "Metallschiehten" by melting of metal powder to be applied to the bodies to be coated. Here, too, must have very high temperatures - Difficulties still occur when heating parts with a complex shape. especially if the parts have different cross-sections on iron "

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It is also known to apply a silicon carbide layer to carbon or sapphite bodies by embedding it in a mixture of silicon carbide, titanium carbide, zirconium carbide, hafnium carbide and tantalum carbide as well as silicon metal or silicon dioxide powder, and there at a very high temperature in the area between 150 and 2200 ⁰ C is heated. A particular disadvantage of this process is the need to use very high temperatures. . "" ■ - ■ ■::. ■ -.- ■

The present invention is intended to provide a method for coating carbon, graphite, iron or copper, in which the disadvantages of the above-mentioned known methods are avoided. This object is achieved by a method of the type mentioned at the beginning, whereby according to the invention the bodies to be coated are embedded in a powder mixture of the metal to be applied a metal oxide ν metal nitride and / or metal carbide and = * a solid or vaporous metal halide and / or alkyl halide and there briefly heated ^{to 700 to 14QO 0} C in an inert atmosphere or under vacuum,. "

For applying a layer of one or more 'of the metals titanium, zirconium, liob, tantalum, molybdenum _s tungsten, platinum, iridium, "Ruthenium is preferably used a Pulvormischung of 3 to 70 wt .- ^ 5 to 55 GTQ \ -r. .-%., the applied metal, 0.2 to 15 parts by weight jS, preferably 0.5 to 12 wt .-? £, metal chloride or metal 'tallgodid.bzw "Alkylchloid and 15-97» 8 wt _o - ^ _t preferably 43 to 94s5 (xe \ r <, ~ fa, metal oxide, metal nitride and / odex ¹ metal carbide with a melting point above! TOO C and heats the body to be coated in it to temperatures in the range from 700 to 1400 ⁰ G ₅ T Probably 800 to 1200 ⁰ C ₀

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The grain of the ulvermisehung lies between T and 300 / α * preferably between 20 and 150yU.

The metal halides are used in powder mixing preferably chlorides and / or iodides of sodium, potassium, aluminum, zinc »lead, cadmium, tin, Cer, ΦΙtan, zircon, chromium, manganese, iron individually or to several. As chlorides and / or iodides, in particular Double salts can be used.

As metal oxides, metal nitrides and / or metal carbides are preferably oxides, nitrides in the powder mixture or carbides of the elements .silicon, magnesium, calcium, Aluminum, Trfen, Zircon, Hafnium individually or too several used.

In a preferred embodiment of the method according to the invention is a Pulverraischung from 4 to 55 Qe \ r, _t -fo preferably 10 wt .- $ _t Ms 45 of the metals titanium, molybdenum, Iridiumj ruthenium individually or in combination, 0,7 to 12 weight »- $ i preferably 1.5 to 10 Gev; .- ^, the chlorides of aluminum ₅ zirconium, zinc, iCitans, manganese, iron and 53r95» 3 wt .- ^, preferably 45 to 88.5 Gxde and / or liitride and / or carbides of Si-magnesium9 calcium , aluminum _s titanium, zirconium, hafnium are used and the heat treatment is carried out at a 3? empere.tur between 700 and 1200 ⁰ C, vorsugsvreise and 110O ⁰ C ₅ »

It has proven to be particularly useful to coat the. Body heat after BeschicJitungs'beliandlung in a kohleastoff- or nitrogen- Us / odes ¹ oxygen-containing atmosphere for a short time to 500 ms 1 000 ⁰ C zn, whereby the metallic surface in a metal compound having carbon, nitrogen snd / or oxygen is transferred.

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If necessary, the coating treatment may be one to one be repeated three times.

The coating is evidently carried out via the gas phase by thermal decomposition of intermediate metal halide. The coating mixture can be used "repeatedly" when the metal content is concentrated and the halide is added again. To further explain the invention, the following can be described Embodiments serve.

At S £ iel2

To coat graphite tubes 50/40 0 1500 mm on the inside, these are coated with a mixture of 20 wt .- ^ zirconium (<100 yu) + 2.5 wt .- ^ ZrGl. +77.5 Gevr.-fo ZrO ₂ (<40-150 / u) filled, then provided with sealing caps on both sides and then packed in a steel tank with coke fillings. The tub is then ^{pushed into an argon protective gas furnace at 1000 °} C. and kept at temperature for 4 hours. Then the tubes are covered over the entire length on the inside with a very even zirconium layer with a thickness of 15-20 / u. The layer is anchored in the wall of the pipes to a depth of 2 mm.

Niobium coating of graphite anodes for the chloroalkali

For the all-round coating of graphite plates 10 × 250 × 50 mm, these are placed in a brick-built bogie bogie x - standing vertically at a distance of 10 mm in a mixture of 50 Gev,% - $ Nb (20-100 / u), 7.5 wt .- ^ ZnCl ₂ + 42.5 wt. F * SiC (40-150 / u) packed. The bogie is then superiors in the already-500 ⁰ C

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heated ovens and then heated ^{Ms to 85O 0} C under argon in 5 hours. After a residence time of 6.5 hours at this temperature, the. '. The oven was switched off and the goods were cooled down inside. After unpacking from the plating mixture, the batteries have a niobium coating on all sides, with the walls of all open pores close to the edge being completely covered with niobium to a depth of about 3.5 minutes. Die'Platten have a type of niobium absorption of 7.6 + 1 wt .-? £.

For use in chlor-alkali electrolysis the plates then with an e £ wa 0.5 / U strong activation layer made of ruthenium as follows Mistake;

The already metallized plates are coated on one side with a thin coat of 0.5 wt .- ^ Ru + 2.5 wt .- $ + 97 devT.-fo SiOp? suspended in Zaponlack, ver ₂ p

see, then ^{dried up to 110 0} O in a heating cabinet and finally in stacks in a ceramic-bonded silicon carbide container rait SiO ₂ poured and heated in a vacuum at 10 Torr up to 80O ⁰ G for one hour. After this procedure, the graphite plates are very evenly provided with an approximately 20yu thick niobium base layer and a roughly 0.5 / U thick Ru top layer.

Titanium silicide coating of graphite electrodes for

The coating of graphite electrodes with 500 2100 mm takes place in the V / eise that the shaped bodies in steel containers with a bed of 10 wt .- $ Ti + 20 wt .- $ Si, 2.5 wt .- / ₀ Na ₅ AlP ₆ + 2.5 wt. ~ 5 ^ ZnGl ₂ + 65 wt .- ^ S Al ₂ O ₅ poured around in a layer thickness of 50 mm. The containers packed on the bogie are covered with an approx. 150 mm thick coke soot fill and then within 8 hours

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<Len _: heated up to 110O ⁰ C in a tunnel furnace. The.- ■ - ■; _r , so treated-bodies show evidence of the ^ plating _ ^; ;. a layer thickness of 30 / rev, "with about 5mm of the. near-surface pores completely lined with titanium silicide. 1. ^: .v .: -

Bie character are in einerar zylindrisoheh G-raphiti) he ehält 'at a distance of 10-15 mm ntit a mixture of ■' 30 / wt. -Fo ipitan "20-100 / u) + 30 parts by weight fb Ml ₂ O ^, 6Q-. ^"; 150 / Ui + 40 wt -% SiC 60 - umschüttet 150 / U and then used -in a preheated to 400 ⁰ G Yäkuumofen The oven then vrird up to 80-90 torr and heated to 1000 ° C. As soon as the temperature and the "vacuum" is reached, _{TiCl 7 is} blown into the furnace room for 2 hours via a valve, the dex '33ruclc being kept between 140-160 torr. After this treatment, the furnace is cooled under argon. The rods After reaction plating, they have a very smooth titanium layer with a thickness of 40 + 10 / U. Titanium is deposited by using a vacuum up to approx. 20-25 mm in the zone near the edge of the porous body.

9 claims

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IHSPECTED

Claims (9)

Paten ta η s ρ r Uc η e 1. A method for applying a layer of silicon, boron and / or transition metals from the P ?. Ms Viii. Group of the Periodic Table on bodies made of carbon, graphite, iron or copper, -due to this , the bodies to be coated are in a powder mixture of the metal to be applied, a metal oxide, metal nitride and / or metal carbide and a solid or vaporous metal halide or alkyl halide and briefly heated to 700 to 140 ° C there in an inert atmosphere or under vacuum. 2. The method according to claim 1 for applying a layer of one or more of the metals titanium, zircon, job, tantalum, molybdenum, tungsten, platinum, iridium, ruthenium, characterized geke η η ζ e I η et that a powder mixture of 3 to 70% by weight> preferably 5 to 55% by weight of the metal to be applied, 0.2 to 15% by weight, preferably 0.5 to 12% by weight, metal chloride and / or metal iodide and 15 to 97, 8 Gev; .- ^, preferably 43 to 94.5 Gevr.-fo metal oxide, metal nitride, and / or metal carbide with a melting point above 1700 ⁰ G is used and that the heating up to temperatures vo;
he follows. doors from 750 to HQO ⁰ G, preferably 800 to 1200 ° C, 3. The method of claim 1 or? .2, characterized ge indicates that the grain size of the powder mixture between 1 and 350 / u, preferably between 20 and 150 / U. 4 · Method according to one or more of the preceding Claims, characterized in that 009835/08 76 PA 9/462/313 Fc / The -8- OHIGlNAL that the powder powder as metal halides are chlorides and / or iodides of sodium, potassium, aluminum, zinc, lead, cadmium, tin, cerium, titanium, zirconium ,. Chromium, manganese, Contains iron singly or in groups. 5. The method according to claim 4, characterized in that g e k e η η that the chlorides and / or iodides are double salts. 6. The method according to any one of the preceding claims, characterized in that the powder mixture as metal oxides, metal nitrides and / or metal carbides, oxides, nitrides or carbides of the elements Contains silicon, magnesium, calcium, aluminum, titanium, zirconium, hafnium, individually or in groups. 7. The method according to one or more of the preceding claims, characterized in that a powder mixture of 4 to 55 wt .- $ »preferably 10 to 45 wt .- #, titanium, zirconium, molybdenum, iridium, ruthenium individually or in groups, 0.7 to 12% by weight, preferably 1.5 to 10% by weight, of the chlorides of aluminum, zirconium, zinc, titanium, manganese, iron and 3.3 to 95.3% by weight, preferably 45 to 88.5 wt .- $ oxides and / or nitrides and / or carbides of silicon, magnesium, calcium, aluminum, titanium, zirconium, hafnium is used and that the heat treatment at a temperature between 700 and 1200 ⁰ C, preferably 800 and 1100 ⁰ C. 8. The method according to claim 7, characterized in that g e k e η η ^{ζ ei ch η et that the bodies to be coated are briefly heated to 500 to 1000 0} C after the coating treatment in a carbon or nitrogen and / or oxygen-containing atmosphere, v / o by 009835/0876 PA 9/462/313 Fc / The -9- ORIGINAL INSPECTED 1902813 the metallic surface into a metal compound converted with carbon, nitrogen and / or oxygen. 9. The method according to one or more of the preceding Claims, characterized in that the coating treatment is repeated one to three times will. PA 9/462/313 Ιο / The Q _Q9 g3 $ / 0Ö? 6 ORIGINAL INSPEC