DE2323928A1 - PROCESS FOR PYROLYTIC PRODUCTION OF COAL COATS - Google Patents

Description

PafontanwSlt CMpMn-. :. ~ * ; - ~ TZ «Wrt»

Dr, i; - '. .-- ..: r Z Jr.

81-20.700P ii. 5th 1973

HITACHI, LTD., Tokyo (Japan)

Process for the pyrolytic production of coal coatings

The invention relates to a method for pyrolytic production of a carbon coating on the surface of an object to be coated in a hydrocarbon-containing atomosphere.

More specifically, the invention relates to a new and effective method for forming a graphitic carbon coating at relatively low temperatures, in particular below 700 ⁰ G on the surface of an object or "substrate" made of metal such as sheet iron or other material »where the formed carbon coating should have a predetermined thickness, high density and adhesive strength to the surface of the base.

81- (POS 29 703) height

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Coal is not only excellent in chemical resistance to corrosion, but also has good physical properties Properties such as high heat radiation. Also shows Carbon has a low secondary electron emission and is therefore used in electrical engineering as devices or components often to prevent secondary electron emission with Coal coated.

The production of carbon coatings on the surface of substrates takes place essentially by three different methods, namely by brushing or applying, steaming or spraying, and by decomposition or pyrolytic deposition. In the first of these three methods, a carbon-containing "paint" or a carbon suspension is applied or sprayed onto the substrate * Although this method is very simple, it involves problems with regard to the uniformity of the thickness of the applied coatings or reproducibility. In addition, this method has the deficiency that the carbon layer is easily peeled off or "delaminated" ^{11 from the base as a result of poor adhesion between the base and the applied coating} the surface of substrates.

The second method is vacuum evaporation. Dense and firmly adhering carbon coatings can be obtained by this process. For evaporation and deposition of carbon in a vacuum, however, the serving for the vapor deposition of carbon must be very high, to temperatures of at least 2500 ⁰ C, heated. The application of this method is therefore extremely problematic when a

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large numbers of substrates with a relatively large area are to be treated economically. In addition, is it is almost impossible to deposit carbon with the formation of carbon coatings of uniform thickness on a substrate of complex Shape to be deposited, since the carbon deposition shows directional dependencies in the vapor deposition process.

Both methods therefore have problems with the uniformity of the coating thickness and adhesiveness of the carbon coating on the surface of the substrate and the coatings formed tend to peel off or peel off.

In addition, a useful adhesion must be ensured even under conditions where organic binders cannot be used, for example when the substrate is part of an electron tube and is to be used in a vacuum. Thus, for example anodes of .Empfangsröhren which are coated with a view to a maximum heat radiation with coal, repeated under vacuum to temperatures between about 600 and 900 ⁰ G heated. Shadow masks for Parbfernsehröhren are coated with carbon in view of the prevention of secondary electron emission, the use of binders of the inorganic type with the secondary electron emission promoting üigenechaften is absolutely inadmissible, while the adhesive strength of the carbon coating must be very high, so that this even with one to two hours of heating in air to temperatures of about 400 to 500 ⁰ C is practically not removed by combustion and even with a thickness of 1 micron or more does not peel off the mask during handling during manufacture and assembly of the tube.

Furthermore, when using carbon-coated substrates, in particular in electron tubes, it is inside them

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a high voltage is applied, not only extremely important that the carbon coatings formed on the substrate firmly adhere to the base, but the coal particles themselves must also adhere firmly to one another within the coating, since when such coal coatings are "dusted" within the borehole, discharges may occur which are too serious Damage and malfunction of the electronics. TJm these demands to correspond, graphitic carbon (hereinafter referred to as "graphite") is preferably used for formation used by coal coatings for such purposes.

In addition, for the formation of corrosion-resistant carbon layers on boats, which are used for the formation of GaAs to be used in the liquid phase, for example graphite coatings are required that are not due to mechanical Stress during the process and at elevated temperatures take off from the shuttle.

It follows that a is preferred by thermal decomposition of a "graphitisehen" carbonaceous Heaktionsgases deposited on a substrate graphite coating at the most, since this practical even with heating under vacuum and / or mechanical stress or heating in air at temperatures of about 400 to 500 ⁰ C. suffers no weight loss and does not stand out from the substrate even under conditions under which neither organic nor inorganic binders can be used and which does not generate carbon dust.

According to the third method, carbon-containing gas is thus heated with the substrate to be coated in Brought in touch. The coal produced by this process

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The coating adheres firmly to the substrate and has a high degree of transparency. This method is therefore widely used, but a major disadvantage of this method is that the coal coating is formed by thermal decomposition in which the substrate is heated to high temperatures of 1200 to 2000, for example, in the presence of a reactive grass stream containing methane, propane and the like ⁰ C is heated.

In view of these high heating temperatures, the substrate therefore suffers, if it is formed, for example, by a thin metal foil or a material with low heat resistance, deformations or quality changes, which lead to the result that the carbon-coated substrate obtained is no longer usable. Even if the substrate consists of a material which is sufficiently resistant at the temperatures mentioned, there is still the risk of damage to the substrate due to thermal deformations when heated to such high temperatures. In the case of shadow masks for color television tubes in particular, which are very thin (usually 0.2 mm or less) and for which even slight deformations are not permitted, the heating should be limited to temperatures of about 700 ^° C. or below.

Numerous methods have therefore already been developed to improve high temperature decomposition, in which hydrocarbon-containing compounds or compositions of thermal decomposition at relatively low temperatures such as 850 ⁰ C or in this area for the deposition of carbon on a substrate to form a carbon coating with high density and excellent adhesiveness be subjected. Some of these procedures have also been

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table applied. However, if the substrate to be coated is, for example, a thin iron sheet such as that of a shadow mask for a color television tube !! treatment of the substrate at temperatures of 850 ⁰ C or above leads to numerous material parts such as carburization, the formation of iron carbide, thermal deformation and a reduction in rigidity or! spring-back *

To avoid such Kachteile so opportunities aur formation of coal coatings temperatures must by! Below 850 ⁰ O, for example about 65O ⁰ C or created under it. There are now few known techniques for coal stratification at low temperatures, which, however, have been found to be unsatisfactory overall. One example is a process in which a nickel disc made from nickel powder of 30 mm acidity and 2 mm thickness with a porosity of about 51 ¹ P for 20 minutes by mixing Propaagae with nitrogen ic a volume ratio of 1: 1 gas stream produced is orhitzt to about 650 ⁰ C, thereby depositing carbon on the surface of the disk to form a Kohlaüberauges (see US-PS 3,311,505). According to this process, a highly porous nickel disc made of nickel powder is coated on its surface with carbon and this process can therefore in no way be used, for example, for the coating of a thin brass foil with a thickness of 0.5 μm cfisr less for the formation of very precise carbon coatings.

A further example of the known techniques mentioned is to be cited in processes in which a brass substrate is exposed for 0.5 to 2 minutes in the presence of a gas mixture comprising 10% by volume of hydrocarbon and 0.75 to 2.0% by volume of carbon dioxide a temperature of woiiige? than about 650 ^° C

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is heated with the deposition of carbon on the substrate surface (see US Pat. No. 2,344,908). In this procedure however, if the hydrocarbon concentration is sufficient to form a coal coating of sufficient thickness in the mixed gas if, on the contrary, the hydrocarbon concentration is decreased to form dense coal coatings, none Coal coating of sufficient thickness has been preserved. According to this method, it is therefore not possible to form a dense carbon coating with a density of 1.9 g / cm2 and a thickness of 1 mg / cm on a substrate.

In order to overcome the various difficulties of the previous technique indicated above, a new one was therefore developed Process developed. The primary aim of the invention is therefore a new and effective method in which the surface of a substrate, such as an iron sheet in particular, with a dense coating of carbon without any formation of carbides the substrate surface can be coated without defects such as thermal deformation of the coated substrate or a reduction in the "rigidity" or cohesion of the resulting carbon coating occurring.

Another object of the invention is a method in which a carbonaceous grass can be made at relatively low temperatures of about 700 ⁰ G or less to form a dense carbon coating on a Substratoberfläehe to the reaction, showing firm adhesion to the substrate surface.

Koch Another object of the invention is a method after even surfaces of thin iron foil with a thickness of about 0.5 mm or less with carbon coatings of

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1 mg / cm thickness can be provided evenly and with accuracy, which have an extraordinarily high density of about 1 »9 g / cm and a high adhesive strength, 30 that the carbon coatings do not lift off the substrate surface, even if they are rapidly dissolving and Is subjected to cooling tests at a temperature of 600 ⁰ C or below.

It has been found that the above objectives in a process for depositing carbon on the surface of a substrate can be achieved by heating a hydrocarbon-containing gas when on the surface of the Substrate previously formed a suitable catalyst material and the carbon using the strong catalytic Effect of the catalyst material with the formation of a dense carbon coating is deposited on the surface firmly adheres to the substrate.

The process according to the invention, the most important feature of which is the formation of a catalytically active Mekelphosphorsehicht on the surface to be coated with carbon and the economical production of carbon coatings Exploitation of the catalytic activity of this layer is described below with reference to the attached drawings explained in more detail. Bs show:

Fig. 1 is a graph showing the relationship between pH a solution for depositing a nickel-phosphorus alloy and that in the obtained nickel-phosphorus alloy layer contained Phosphoraengej

FIG. 2 shows a sketch for a device for producing carbon layers; FIG.

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fig. 3 is a graph showing the relationship between the amount of phosphorus contained in the nickel-phosphorus alloy layer and the amount of carbon deposited. Porosity of carbon}

Pig. 4 is a graph showing the relationship between the amount of deposited carbon and the treatment time;

Pig. 5 is a graph showing the relationship between the concentration of liquefied gasoline or petroleum gas (hereinafter referred to as ¹¹ I) PG ") in the reaction gas and the amount of carbon deposited;

Pig. 6 is a graph showing the relationship between the acetylene concentration in the reaction gas and that deposited Amount of carbon;

Pig. 7 is a graph of the relationship between the duration of a preceding heating of a nickel-phosphorus alloy layer coulter to 600 ⁰ C and the resultant of a thermal decomposition reaction of Acetyleugaa amount of deposited carbon;

Pig. 8 is a graph showing the relationship between the Partiβία pressure of the thermal decomposition in a Acetylene gas atmosphere resulting from hydrogen in samples with a catalytic effect and one sample, which has lost its catalytic effect and the duration of the heat reaction;

Pig. 9 is a graph showing the relationship between the amounts of carbon deposited when an iron foil

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with nickel-phosphorus alloy coating as a catalyst in an atmosphere of 3 different reaction gases is heated with different compositions and the heating temperature}

FIG. 10 is a graph showing quantitative of the relationship between the deposited carbon and the amount of phosphorus and contained in a film formed on an iron substrate surface Mckelpnosphorlegierungsschicht with a bead of about 1; and

Pig. 11 is a graph showing the relationship between the oxygen concentration in a nitrogen stream and the amount of carbon deposited for the 1 * 311 of an iron-lead substrate coated on its surface with a nickel-phosphorus alloy layer 1 ^ i thick and then subjected to a previous oxidation treatment in a nitrogen-oxygen atmosphere at about 600 ^{0 was} subjected to O for 10 minutes.

As mentioned above was _f the invention is intended to coat the surface of a substrate such as a thin iron sheet or a heat-resistant material with a density at the substrate firmly adherent carbon film by reacting a kohlenwasserstoffiialtigen gas at a low heat treatment temperature such as 70o ⁰ C or lower, which temperature after the Previously customary procedures were by no means conceivable. At such low temperatures it is not possible to deposit carbon on the surface of a substrate simply by reacting a carbon-containing gas. According to the invention, however, such a separation is achieved in that the strong catalytic effect is aaa

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the surface of the substrate to be coated with carbon formed nickel phosphorus film is exploited.

Numerous investigations were carried out in which the surface of a substrate to be coated with carbon was subjected to various types of surface treatments and the substrates treated in this way for the formation (or the attempt to form) carbon layers at a relatively low temperature of about 450 to about 700 ⁰ C by contacting them with different types of carbonaceous gases. It was found that by producing a nickel-phosphorus alloy on the substrate surface, a reaction of a carbonaceous grass is ^{effectively achieved even at low temperatures of about 45O 0} C to about 700 ⁰ C due to the catalytic effect of the alloy and a dense carbon coating with firm adhesion by deposition of the carbon resulting from the reaction can be obtained.

According to the inventive method, the surface is thus coated of a substrate with a nickel phosphorus alloy of suitable composition and the thus-coated (plated) substrate in a certain amount of a hydrocarbon-containing gas grass atmosphere to a certain reaction temperature within the range 450-700 ⁰ C, preferably heated within a specified time to carry out the reaction with heating, whereby a dense carbon coating is formed on the surface of the substrate.

In addition, it is possible according to the method according to the invention, dense carbon coatings on substrates in one

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technical scale and at low temperatures seibat using such flammable and highly explosive Gases such as acetylene as starting hydrocarbons for coal removal together with a suitable diluent gas or by mixing with other gases in suitable proportions, so that the reaction gas mixture is non-flammable and non-explosive.

Acetylene is known to be one of the most unstable gases among hydrocarbons and its decomposition is accompanied by a large change in free energy over a relatively low temperature range, such as about 1000 ° 0 or below. Bhj generally belongs acetylene at low temperatures of about 1OQO ⁰ C or less (hereinafter referred to as "low! Temperature") to those among the hydrocarbon gases, which are susceptible to a thermal Sersetzung on. The boaction or decomposition of acetylene is an exothermic reaction and is, for example, the following at room temperature

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54.19 keal / fool

This generation of warmths in the Terla ^ f · 3 s- @ n? Aeaktion accelerates the "3jtiermisßh3 ^ rsa-fczungsres-rfeion --sn acetylene; so that the thssaisch * 3 ©;? 3« daily progresses like an explosion !.. "? s tlbeffaiäSig rsseiien Abscheiäu ^ gs» rate no crystals unn asigt tazu ₃ amorphous wi be Wsisja a sslohs iisa ^ tion in inöiistrisllfm ilaSstab fiurehgeführt to be, it is sia I2lr # isrige3 problem; AIAE such sxotherme Hasstaung under Ysäi ^ Prevention of an explosion suitable for controlling a, Seh., sin ^ iaactive point

for

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Enabling a process in which acetylene is used for thermal decomposition on an industrial scale is the reduction in the amount of ethylene gas used or the slowing down of this reaction by increasing the hydrogen partial duration or the prevention of a chain reaction thermal decomposition of acetylene through simultaneous use of methane (together with acetylene), whose decomposition reaction is endothermic.

As mentioned above, to enable selective thermal decomposition of acetylene in a controlled, Acetylene-containing atmosphere at a relatively low temperature in the presence of any substrate under deposition of carbon to form on the substrate surface of an adherent, dense, stable, crystalline carbon film is most effective under the surface of the substrate to provide the above-mentioned conditions with a catalyst material in accordance with the progress the selective thermal decomposition reaction of acetylene acts. Such a catalyst material is preferred a material »that can be applied to the surface of any substrate in both simpler and more economical Way can be applied.

The invention has been developed with various problems in mind, as detailed above explained technical problems in the previous processes, the properties of the thermal decomposition reaction of Acetylene gas, the utilization of the catalyst material as a kind of countermeasure against the acetylene gas reaction, etc. belong.

According to the invention on the substrate surface

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formed kickelphosphorus alloy can easily be chemically applied to any substrate - irrespective of whether it is electrically conductive or nonconductive - using the separation process * which are known as "electroless" or non-electrical coating devices, without the need for a direct current source The invention therefore fulfills the Jricrsemisse as a catalyst and is of cr.ij. ^ siehsndcE - / irtsehsftliehem value, In the case of ^{! i} electrolysis I? icksl ^i! there is a supersaturated solid solution of JxhQö ^ hz ^ £ - in ificksl sussnsisn with a Connection of Hicksl uiii Jkoaghor with such signature shafts that in the Irwärmarit; g-gi * kri3tsllin.es lü ^ k a Hiekelphos (phorverbiii5yajj Γ: - _; 1 · formed 'gird,' ^ as ketalytic effect isr "lGfeil"-;; os: -pfcisrlegis2rang tstri so play amorphous Kiclsel and siar ^{Eiofe9lpfcospho2;:.} "7erb Ni ^ JP, when χ 2 is etws, ei ^ oil as wirksamsts Eoile as a catalyst.

In practical Ilinsielit ££? M®z. i3? g®Mwelohe]: T: l-2kelphcE-phosphorus alloys prove their effectiveness as a catalyst for the implementation of the process according to the invention, as long as the amount of the vesacLtphosphorkomponsnte 4 weights or more. It has been found, however, that this alloy is converted into crystalline particles and the compound ^ when heated, whereby the catalj-tic effect for the formation of graphite by the thermal decomposition of acetylene is markedly reduced and finally disappears completely When a hydrocarbon gas is subjected to thermal decomposition, it is necessary to employ such a heating temperature or rate of temperature development that the catalytic effect of the nickel-phosphorus alloy is not lost.

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According to a Ausftihrungsart the invention -is a method of forming a carbon coating on a substrate surface is provided which is characterized by depositing on the substrate surface a Nickelphosphorlegiening with 4 to 12 wt. Fi phosphorus to form a Niekelphosphorlegierungeschicht and 1egierungsschicht Nickelphoaphor-with covered Substrate in a mainly composed of at least one inert gas such as nitrogen, helium or argon mixed with 0.1 to 1.5 vol. # Acetylene existing non-flammable reaction gas to a temperature of 450 to 700 ⁰ G with such a temperature development rate that a catalytically ^ The effectiveness of the nickel-phosphorus alloy for the formation of carbon from acetylene gas is maintained.

According to a further embodiment of the invention a method corresponding to the above type of implementation is provided, which is characterized by the use of the consisting mainly of at least one inert gas such as nitrogen, helium or argon and 0.1 to 1.5 vol. ^ acetylene gas containing reaction gas with the addition of at least one Representatives from the group 0.1 Vol. ^ Or more LPG and 0.1 Vol. # or more methane in an amount and within such a range that the resulting total mixed gas is incombustible will.

By using the above methods, it is possible to coat the surface of a thin substrate with a to coat a dense carbon layer with high adhesion, which is absolutely free from subsequent deformations must remain, such as in particular the surface of a thin metal foil and especially, for example, a shadow mask

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for a color television tube that is relatively thin and in which no subsequent deformations are permitted and heating to temperatures above about 70O ⁰ G must be avoided.

The following procedure may be applicable to the preparation of a coating or "plating solution" with which a nickel phosphorus alloy layer is provided which can be used as a catalyst material in the reaction of a carbonaceous gas according to the invention. The main material used is "STJMSR" (a product of Mhon Kanizen KK), to which an appropriate amount of hydrochloric acid or aqueous ammonia is added to keep the pH of the mixture within the range of 4 to 10.

Subsequently, a substrate coated with carbon (with a thickness of 0.1 mm.), such as, for example, sheet iron, is degreased and rinsed in the usual manner and then, in order to bring about the coating, the said "coating solution" is maintained while maintaining a temperature of the "coating solution "Immersed" from 8O ⁰ O after an "electroless plating process", whereby a fine phosphorous alloy layer is obtained, the content of which is shifted depending on the pH of the "plating solution".

Me dependence of the phosphorus gas contained in the resulting sealing layer ύομ pH value d®r "plating solution" is in Pig. 1 shown *

2 shows a sketch for one embodiment of a device for the production of koiile coatings that are coated in the above-mentioned manner with nickel-phosphorous alloy

* Bath for electroless metal deposition of not exactly known composition, which probably contains mainly 25 g / l nickel sulphate and 30 g / l sodium hypophosphate. The coating takes place over 30 minutes at 80 + 0.5 ° C

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Substrate 1 is placed in reaction tube 3, into which a reaction gas 2 is introduced, which is a gas mixture of, for example, 1.0 vol. Acetylene gas, 10 vol. O methane gas, 0.5 vol. $ Of a gas obtained by evaporation of LPG and the balance comprises nitrogen (88.5 vol. ^).

In the present case, the temperature in the reaction furnace 4 is previously set to a selectable temperature within the range from 450 to 700 ^° C. and the amount of reaction gas 2 is controlled beforehand and sufficiently so that a predetermined amount thereof flows through exactly. The substrate coated with the nickel-phosphorus alloy is heated in a very short time, such as within 0.5 to 1 minutes, to the suitable or selected heating ^{temperature within the range from 450 to 700 °} C. and the substrate is heated or heat treated in the atmosphere of said reaction gas 2 carried out for a predetermined period of time. After the end of the heat treatment, the substrate is removed from the reaction tube 3 via its end 5.

By performing a series of treatments of the type described above, it becomes possible to obtain varying amounts of carbon on the surface of nickel phosphorus layers depending on the composition of the liiclcelphosphorus alloy layer to be deposited on the substrate, the reaction time and reaction temperature.

Pig. 3 shows the amount of carbon deposited by the above treatment method (curve A) on the surface of a substrate and the porosity (curve B) of the deposited carbon. As you can see, they hang deposited carbon amount and porosity of the same from the

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Amount of phosphorus from that formed on the substrate Niekelphosphor alloyschicht is included. Generally it can be seen that with increasing phosphorus content of the alloy layer both values (deposited carbon and porosity of the same).

The relationship between the rate of deposition of carbon and the decomposition of the carbonaceous layer changes ηΐΰίαΐ correlatively to the extent that “even TRBxm the absolute value as? Eeakticnsgesohwinöigkeit corresponding to a change of Susaffiaionaetsiing ode ,? ! Deaiperatur dee reaction gases s "ve ^ änaert ~ i? CL Ss ie / s clearly '* that the catalytic effect of the iTi ^ kelphospäorls a great influence on the Eor.isnstoifsfcsGh at a low! Temperature of 450 Ms 700 ^G G fc & t.

The catalytic effect ß ^ 2? EtLolrelphosp schicht is closely related to Isii ^ at a ST phosphorus compound, ΈΙ ^ ι which in a very early stage of the reaction of the Kickelphc-spaorlsgi-srungssohiohi; separated or retired (separated) is "The higher the phosphorus content, the more significant is the retired or" separated amount Nip! ¹ and the more the catalytic activity of ßöher Legierungssehicht "As a _s follows that the amount of carbon deposited increases.

However, if the phosphorus content is 11 Sew. & , the porosity of the deposited carbon layer tends to be increased very much as shown in curve B of FIG. At phosphorus contents above 12 pounds, the porosity of the deposited carbon reaches 35 $ or more, with the result that the strength of the carbon thus obtained is thick of films

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is noticeably reduced. Accordingly, the upper limit for the phosphorus content of the ^H- plated "nickel-plated phosphorus alloy layer to achieve a dense carbon coating is preferably 12% by weight.

If the phosphorus content on the other hand is smaller than 4 i ", the amount of the deposited carbon is extremely small and the thickness of the obtained carbon coating is also non-uniform. Such a coal coating is thus considered unsuitable for practical use. As follows from the above, the phosphorus content of the "plated-on" nickel-phosphorus alloy layer is therefore preferably within the range of 4 to 12% by weight if dense and strong carbon films are to be obtained.

According to the method of the present invention, the thickness of the nickel-phosphorus alloy layer provided on the substrate surface does not so much affect the amount of deposited carbon and the like. The reason for this is to carry out the reaction at relatively low temperatures of around 450 to 700 ⁰ G, with the alloy layer being heated from room temperature to the reaction temperature in a relatively short time, whereby the alloy layer reacts with the carbon-containing gas before the alloy is in dna Substrate can diffuse and it then acts to deposit a very small amount of carbon particles, which further form nuclei for the carbon to be deposited.

That is, the hickel phosphorus alloy layer functions as a Catalyst for the deposition of carbon, itself

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when the thickness of the layer is extremely thin. In practice, however, the thickness of the nickel-phosphorus alloy on the substrate is preferably about 0.1μ or more, whereby the presence of the alloy layer on the substrate can be confirmed at least by visual inspection and the subsequent treatment steps can be stably ensured. However, even if the "plating layer" is thick, practically no adverse effect on the carbon deposition process is observed. However, since the "plating solution" for the deposition of the nickel phosphorus alloy is relatively expensive, the use of unnecessarily thick layers increases production costs and is not economically advantageous. Taking into account all these considerations, along with other factors, the thickness of the deposited nickel-phosphorus alloy layer is the ^t plated "bsw. Preferably β less fixed u to about, legierungsschiehten with unnecessarily large thickness are undesirable because such layers sometimes lift off from the substrate during the Kohlenstoffabseheidung.

As discussed in detail above, the nickel phosphor alloy layer plays a very important role for the deposition of carbon at low temperature and it is still a fact that the properties the layer exert a great influence on the deposition of carbon. To review this Sateach © was carried out the following experiment?

Examples were made by coating iron sheet substrates (from the solution) with nickel phosphorus with 8 wt. $ phosphorus under Formation of kickel phosphor alloy layers with a thickness

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▼ on 1 ^ u made. These samples were subjected to a heat treatment at 400, 500 and 600 ^° C. in a pure nitrogen gas stream for a certain period of time. The individual samples so treated were then incubated for 20 minutes under Kohleabseheidungsverauche long heating in a Heaktionsgas from 1.5 vol. I> acetylene, 14 vol. # Methane, 1 vol. ^ LPG and nitrogen as the remainder (83.5 by volume. ^) used to a temperature of 560 ⁰ C. In all cases, the increase in temperature from room temperature up to 56o C ⁰ in a very short period of time, such as within 30 seconds, brought about.

The experimental results, ie the determined relationship between the heat treatment time (in minutes) and the amount of coal deposited (mg / cm), are in Pig. 4 shown. The reproduced in Fig. 4 curves C, D and E were obtained with the heat-treated in nitrogen at 400, 500 and 600 ⁰ C nickelphosphorplattierten substrates. Like from Pig. 4 clearly shows, the longer the heat treatment time in the nitrogen gas flow, the lower the amount of deposited carbon.

In particular, this figure shows that the amount of carbon deposited by decomposition decreases very sharply when the Temperature for the heat treatment of the alloy layer is higher (curve B), and then already in extraordinary short time. It is believed that when heat is applied in the manner described in the "plating" obtained nickel-phosphorus alloy layer before deposition the carbon reduces the catalytic effectiveness of this layer.

This phenomenon is attributed to the fact that

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the catalytic efficiency of the layer is reduced by converting the compound Nipl ¹ within the layer into Ifi-zP and other compounds in the heat, as well as a heat-related healing of various lattice defects that arise during the formation of the layer (which are caused by "plating" after the Nickel-phosphorus alloy layers obtained by methods described above are generally known to be in the non-crystalline state).

In the case of the present invention, in which a "plated-on" or deposited nickel phosphorus alloy layer is used as a catalyst, heat treatment of this layer prior to the deposition of carbon to form carbon coatings should be avoided as much as possible. Baraus follows that! Should be temperature increase up to the reaction temperature from 450 to 700 ⁰ G made as promptly as possible.

Based on the above results, a test for confirming the influence of the (CemperaturerhShungsgeschwindigkeit was performed. In this experiment, samples were one with Ifickelphosphorlegierung with 8 wt. ^ Phosphorus to form an alloy layer of 1 μ thickness "plated" iron sheet substrate individually in a reaction gas mixture of 1 5 Vol.96 acetylene, U Vol.?* methane, 1 Vol.Ji LPG and nitrogen as the remainder (83.5 Vol. #) with different i'emperaturerhöhungsgeschwindigkeiten from room temperature to 56o ⁰ G heated and the temperature of 560 ⁰ G to coat the samples with charcoal for about 20 minutes, and it was found that the properties or behavior of the coatings were best when heated to reaction temperatures within one minute, while a very sharp decline when heated to reaction temperatures of more than one minute The consistency was recorded at times of more than 30 minutes was the coal Coating very little and at times of more than 120 minutes there was hardly any effect of the "plating obliquity"

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respect. That is, it is clear that the influence of the rate of temperature rise examined in this experiment is the reflects the same tendency as practically emerges from the dependency shown in FIG.

According to the above results, when heating a bisene substrate coated with a nickel phosphorus alloy in a carbon-containing reaction gas, it is certainly necessary that the temperature increase in the heating furnace up to the reaction temperature is carried out as quickly as possible, so that the catalytic effectiveness of the alloy layer for the deposition of carbon is not lost. In particular at temperatures below about 45O ⁰ G no deposition is observed of carbon on the Niekelphosphorlegierungeschicht while taking place within the layer itself, only a loss of catalytic activity. An effective measure and equally an important requirement is therefore to bring the temperature in the heating furnace up to the reaction temperature necessary for the deposition of carbon within the shortest possible times.

The following are results of studies on the Composition of the heating gas for the .invention Procedure communicated. Generally speaking, gases containing carbon are flammable and, when mixed with air or oxygen, have a tendency to become Explosions. When practicing the method according to the invention on an industrial scale, it should therefore Adequate care must be taken to avoid possible dangers. In view of this, this is the case with the method according to the invention carbon-containing gases such as acetylene and carbon monoxide used as starting material for the separation of carbon, which decompose at relatively low temperatures (and

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Carbon deposition) tend to use inert and non-flammable gases such as helium, argon or nitrogen are mixed, the mixing ratios being limited to such ranges that the resulting Reaction gas mixture becomes non-explosive, even if as a result of damage to the heated reaction tube large amounts of air flow into the apparatus.

Using carbonaceous gases with different Compositions, as mentioned above, which are completely free of possible explosion hazards, have been tried carried out to carry out the decomposition reaction under various conditions. The results obtained confirm that that with all of these gases carbon is deposited by reaction on a Hiekelphosphorlegierungsbelag as long as this coating has a high catalytic efficiency and suitable reaction conditions can be selected.

For example, it is possible to use a dense and "stiff" Coal (coherent) coating in a stabilized state without any risk of explosion as a result of the reaction gas to achieve by using a gas, the at least one of aolchen inert gases such as helium, argon or Nitrogen is mixed in.

As a result of further detailed experimental investigations of the above dependency, it was found that the coal deposition rate with the addition of a low one Amount of LFG to the aforementioned pulp component gas is accelerated faster, so that a dense carbon layer in one can be obtained in a very short time, which makes the addition of LPG - from an economic point of view - extraordinary makes appear advantageous.

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In addition, it was found that the influence of the current of the reaction gas to the decomposition of coal through heat reaction when part of the inert gases such as argon, helium are exchanged or nitrogen by methane in such an amount and within such a range that the resulting reaction gas mixture remains incombustible, becomes negligible, and the addition of methane is therefore extremely preferred, especially to achieve a uniform carbon layer on the surface of parts with complex shapes.

As stated above, the upper limits of LPG and methane were set with such safety of operation in mind that the reaction gas mixture containing IJEGr and / or methane never explodes even if it is mixed with air in any proportions. If the goal is only to achieve a dense and even coal coating, all of the argon, helium or nitrogen in the reaction gas can be replaced by methane, LPG or a mixture thereof. The effect of adding methane and / or LPG does not change within a wide range of their admixture ratios from a few percent to a few 10 $> .

Furthermore, some attention should be paid to the problem of toxicity of the source gas and in this regard Acetylene is safer than carbon monoxide and advantageous when carried out on an industrial scale.

The flow of gas mixtures of different compositions of the type indicated above on the amount of solute material deposited is explained below. For economic For reasons, nitrogen was used as the inert gas, i.e. carrier gas. Even if different hydrocarbons e.g. LPG, methane, acetylene etc. are present,

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is actually only acetylene with the deposition of carbon decomposed and the other added gases act to favor the decomposition of acetylene.

This fact has been experimentally confirmed. The effect of the LPG concentration (YoI. $) On the amount of deposited carbon (mg / cm) is shown in FIG. min into a reaction tube with an inner diameter of 35 mm (for the deposition of carbon through the reaction or decomposition of acetylene in the heat) for coating an iron sheet 23 m long, 23 mm wide and 0.1 mm thick with a nickel-phosphorus alloy coating 8 wt. $> Phosphorus was introduced. The reaction temperature, heating time and reaction time selected in this case were 54O ⁰ C, less than 30 seconds and 20 minutes.

Like from Pig. 5, the addition of a small amount of LPG has a great influence on the amount of carbon deposited and it can be seen that a sufficiently satisfactory coal coating can be achieved by adding LPG in an amount of at least 0.1 vol. $ can be obtained.

Otherwise, FIG. 5 shows the results of an investigation, where commercially available LPG was used. This LPG contains about 60 to about 80 vol. ^ Propane and the remainder butane and polluting gases such as propylene, butadiene, butene and others. However, these gas impurities are not disadvantageous on the deposition of carbon by reaction of reaction gases from nitrogen + acetylene + LPG, but serve to achieve good results overall. The upper limit of the amount of LPG to be added should be within such a range

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be limited so that the starting gas mixture remains incombustible even if it is brought into contact with any amount of air. Such a range is 7 to 15 vol. I>, but varies depending on the acetylene concentration in the starting mixed gas.

On the other hand, if a part (about 10 vol. # Or less) of the nitrogen in the mixed gas of nitrogen + acetylene + IPG is replaced by methane, the resulting mixed gas results from nitrogen + acetylene + LPG + methane no unevenness of the coating due to the gas flow - without a substantial one Change in the deposition rate of carbon - and the use of such a mixed gas system is thus extremely effective in the case of handling parts of very complex shape where it is difficult is to ensure an even transfer of the gas over all parts of the object. When a. cheap natural gas is used as a source of methane, the cost of the Auagangsgaemiachung can be further reduced and thus a noticeable economic effect can be expected.

The amount of acetylene gas to be used as the starting gas for the separation of carbon is explained below, fig. 6 shows the dependence of the amount of carbon deposited on the acetylene concentration in a mixed gas of nitrogen + LPG (0.5 vol.?*). In this case, the reaction temperature (heating temperature) were at 56o ⁰ C, the heating time up to Reaktionatemperatur at less than 30 seconds and the Heaktionsdauer at 20 minutes. The gas flow rate was 6 l / min and the other conditions were the same as in the Pig embodiment. 5.

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Like from Pig. 6, the higher the proportion of acetylene, the higher the rate of carbon deposition. However, if the amount of acetylene is more than 1.5 vol. #, A tendency is observed that the resulting carbon coating becomes somewhat porous. If the amount of acetylene is more than 2 Vol.S ^, dust-like coal particles come onto the surface of the deposited carbon film. In order to achieve a dense and hard or rigid or coherent carbon film, the upper limit of the amount of acetylene gas to be mixed with a carrier gas is preferably set at 1.5 vol. $. On the other hand, in order to achieve a practically usable deposition rate, at least 0.1% of the gas should be used. $> Acetylene can be added.

When hydrocarbon gases such as ethylene and methane become a mixed gas of nitrogen + acetylene + LPG or nitrogen + Acetylene + LPG + ethane can be added in an amount within such a range that the resulting mixed gas remains incombustible, even if it is with Lufi; is mixed, the addition has no particular adverse effect on the Deposition of carbon.

The embodiments of the invention explained above relate to the Pail, in which the coverage of the substrate surface with the Niekelphoephor alloy by a non-electric one and "Electroless Plating Process" respectively below Use of a "SUMBR" solution is brought about, but the invention is of course not limited thereto.

From the foregoing it is clear that the invention, compared with the conventional vacuum method in which the Deposition of carbon in an atmosphere with reduced

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Which pressure is brought about, has the advantage that the apparatus in view of the carbon deposition under atmospheric pressure are very simple, there is no restriction on the size of the object to be treated and the desired carbon coating can be obtained on a large scale and at a low cost.

Although the invention has been specifically described with reference to the case that the object (substrate) to be coated with carbon is formed by iron plate, any materials may of course be used as long as they can be "plated" as substrates with the present nickel-phosphorus alloy because the deposition of carbon may be achieved mainly as a result of the properties of this alloy and applied as long as these materials can withstand heating to temperatures of about 450 to about 700 ⁰ C as substrates. This is also to be seen as a special feature of the present invention.

According to a further embodiment of the invention a method of forming is provided by carbon coatings, which is characterized by heating a "plated" with nickel phosphorus alloy substrate to a temperature of about 500 extensive in an atmosphere of acetylene to about 700 ⁰ G reaction gas of reduced pressure of 100 Torr or less at such a rate of temperature increase that the nickel-phosphorus film does not lose its catalytic effectiveness for the deposition of carbon.

According to yet another embodiment of the invention, a method of forming coal coatings is provided,

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which is characterized by the use of a reaction gas in the procedure described above, acetylene and at least one of the gases contains hydrogen and methane.

Fig. 7 shows the results of the formation of carbon coatings on substrates in which samples of iron sheets of 0.18 mm thick using a "SUMIR ¹¹ -Platt ierungslö solution with an adjusted pH value of 6.0 to form an alloy layer of 1 u thickness with a Mckelphosphor alloy with 8 Gew. # Phosphorus were coated, which were then individually ^{heated for 5, 10 and 20 minutes in a vacuum of 10 "Torr to a temperature of about 600 0} C, after which acetylene gas with a pressure of about 10 Torr was introduced to bring about the thermal decomposition reaction.

Fig. 7 shows that the amount of deposited carbon, the lower the longer the preheating time before the implementation the thermal decomposition reaction of acetylene gas, and if the preheating time or pretreatment time is longer is longer than 20 minutes, there is practically no more deposition of carbon. This means that a state is thereby reached in which the effect of the catalytic material, the use of which is a particular feature of the invention, is complete has been lost.

Fig. 8 shows the results of a study on the efficacy of the nickel-phosphorus alloy films having a thickness of about 0.6 u on substrates which were each placed in a heated at 600 ⁰ G atmosphere of acetylene at a pressure of 10 torr to effect a reaction; the purpose of this study was to examine the relationship between the partial pressure of hydrogen formed by thermal decomposition of acetylene gas and the reaction time.

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In this figure, the curve A shows the partial pressure of hydrogen in a sample, which had been previously preheated under inactivation of the sample for 30 minutes in vacuo to about 600 ⁰ C.

Curve B, on the other hand, shows the partial pressure of Y / as hydrogen the other sample, in the "plated" state without preheating was used.

The temperature of the samples during the reaction period is shown by curve G.

As dea hydrogen partial pressure in the case of the sample is evident from the position shown in Fig. 8 change with catalytic action, the reaction begins when the temperature reaches about 500 ⁰ U and the thermal decomposition takes place in the first 10 minutes of -üeaktionsdauer rapidly and thereafter mild reaction conditions for 30 minutes or longer, that is, even after the catalytic effect has disappeared. In the case of the samples in which the catalytic effect has been completely eliminated, on the other hand, no development of hydrogen is observed. As a natural consequence of this, no deposition of carbon is observed.

The above facts-not only show that the catalyst plays a very important role in the initial stage of carbon deposition, but they also state that in the once carbon deposition is triggered, carbon is subsequently deposited even after the catalytic action disappeared.

In the above-mentioned cases, the thickness of the nickel-phosphorus alloy coating was sufficiently 0.1 ji or thicker. To the

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Achieving a dense carbon coating, the initial deposition of carbon by catalytic action, as mentioned above, is very important. If the time required to raise the temperature from 400.degree. C. to the temperature ("heating temperature") at which the thermal decomposition of ethylene gas begins is excessively long, dense coal coatings can no longer be obtained. This critical time period is referred to as "warm-up time critical. ¹¹ The critical heating time at different heating temperatures starting at 400 G ⁰ of the reproduced results in the table below was examined under obtain.

Heating tem
temperature critical on
heating time 400 ⁰ G 200 min 500 ⁰ C 120 min 600 ⁰ G 20 min

Within the critical heating time, as shown by the table above, a dense coal coating with an effective density of about 2.0 is formed in each case and the deposited carbon is found to be crystalline on the basis of X-ray diffraction studies.

Fig. 9 shows the relationship between the heating time (or temperature) and the amount of deposited carbon (mg / cm) that is obtained when taking samples that pass through "Plating" or coating of iron sheets of 20 mm

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Length, 20 mm .breite and 0.2 mm thickness according to the non-electric methods have been obtained with a Hickelphosphorlegierung, a reaction in a heated to a temperature range of 550 to 64o C oven ⁰
subjects for about 30 minutes.

furnace heated from 550 to 64O ⁰ C in 3 kinds of acetylene gas

Fig. 9 shows the results of reactions carried out individually by heating in an atmosphere of acetylene gas, 0 ₂ ^Η 2 ^> with a pressure of 10 Torr (curve D), of a mixed gas of acetylene with a pressure of 5 Torr and methane with a Pressure of 5 Torr and a mixed gas of acetylene at a pressure of 5 Torr and hydrogen, H ₂ , at a pressure of 5 Torr. As is apparent from the figure, in the case of using acetylene gas alone, an efficient thermal decomposition reaction takes place due to the action of the catalyst material at heating temperatures surrounding about 600 ⁰ O (as curve D shows), and an increase in the amount of deposited carbon is observed.

In the event that carbon is used in the thermal decomposition reaction is deposited in an amount of 2 mg / cm or more within a very short period of time, it is so However, the resulting carbon coating is quite prone to becoming porous and the carbon tends to be dust-like Assume a shape that in many cases easily flakes off the substrate. In view of this fact it is too an important feature of the present invention for effectively carrying out the present method is that means to suppress the thermal decomposition reaction with a view to setting and controlling the properties of the thereby formed carbon coating are provided.

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As a means of suppressing the thermal decomposition reaction Changing the components of the reaction gas proves more effective than controlling the oven temperature and changing the state of activation of the catalyst and introducing hydrogen or methane into it Acetylene gas is effective as a concrete agent for suppressing the reaction, being a particularly preferred agent the introduction of Ho into acetylene is to be seen. The curves E and P of Fig. 9 confirm the above. In particular it can be seen from the results shown as curve B that there is thermal decomposition of a Mixed gas comprising acetylene and hydrogen is possible, the deposition of carbon at any heating temperature to control to a certain extent. Furthermore, the addition of methane over that of hydrogen has the Effect that the decomposition reaction of methane is an endothermic reaction.

As curve Ja of Fig. 9 shows, the rapid deposition of carbon from acetylene gas by the action of the catalysis was
presses.

Catalyst at heating temperatures below about 60O ⁰ G under-

As a means for suppressing the rapid deposition of carbon by thermal decomposition of acetylene under the action of the catalyst, including a procedure in which the amount of acetylene is reduced and the reaction is carried out under reduced pressure, in addition to the above-mentioned means, it is preferable that temperatures below about 70O ⁰ G can be selected as heating temperatures. At temperatures above about 70O ⁰ G, the reaction takes place in an undesirable manner, since then not only an undesired one

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Effect τοπ increased temperatures given to the substrate may be, but also a decomposition of methane in the case of a methane-containing mixed gas takes place, whereby others Factors become important that should also be considered.

According to a further embodiment of the invention, a method for forming a carbon coating on the surface of a substrate is provided which is characterized by the "plating" of the surface of the substrate with a nickel-phosphorus alloy to form a nickel- phosphorus alloy layer with at least 5 "/> phosphorus} oxidation of the nickel-phosphorus alloy layer and heating includes the occupied with the oxidized nickel-phosphorus alloy layer substrate at temperatures of 500 to 65O ⁰ O in a non-oxidizing Heaktionsgas. $ £ acetylene which 0.015 to 5 vol.

According to this method, the formation of a desired carbon coating on a substrate can be achieved by the following four measures; The first of these consists in the limitation of the temperature to which the substrate (such as an iron plate) heated to the deposition of carbon, to a relatively low temperature of below about 65O ⁰ G; the second consists in a preliminary formation of a nickel-phosphorus alloy layer on the surface of the substrate (such as an iron sheet) by "plating"; the third is to preliminarily oxidize the nickel-phosphorus alloy layer prior to the deposition treatment by thermal decomposition, and the fourth is to select an optimal composition of a mixed gas from which carbon is deposited by reaction with heating.

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Fig. 10 shows the influence of the phosphorus content of the nickel phosphor alloy layer on the amount of deposited carbon, the "clad" alloy layer being formed to a thickness of about 1 µm on the surface of a sheet iron substrate. In the execution type whose results in Pig. 10, the carbon deposition was carried out under the following conditions: After a nickel-phosphorus alloy layer was deposited, a preliminary oxidation treatment for (partial) oxidation of the nickel-phosphorus alloy layer was carried out by heating for 10 minutes in a nitrogen atmosphere containing 0.005% by volume of oxygen at a temperature of about 580 ⁰ O. Subsequently, the carbon deposition was in a non-combustible Eeaktionsgas with 0.05 vol. # acetylene at about 600 ⁰ G carried out for 20 minutes.

Based on the results of the above procedure, it can be said that at least 4 wt. ^ Phosphorus necessarily in the Nickel-phosphorus alloy layer for the deposition of carbon present on the substrate surface to be coated should be.

Pig. .11 shows the effect of oxygen concentration in the nitrogen gas stream at the preceding oxidation treatment of the nickel-phosphorus alloy layer on the amount of deposited carbon, wherein the phosphorus content of Nickelphoephorlegierungsschicht 8 wt. $> Lag. In this case, the treatment following the foregoing oxidation treatment was carried out in a similar manner to that of Pig. 10 is performed, that is, the subsequent carbon-coating treatment was carried out in a about 0.05 VoI. ^ Acetylene-containing reaction gas at about 600 ⁰ C for 20 minutes.

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According to the results obtained in this embodiment, it can be said that the amount of carbon deposited is an oxygen concentration in the nitrogen gas stream of less

—4.

less than 1 IO 'Vol.5 * »decreases extraordinarily. Accordingly the oxygen concentration in the nitrogen gas stream should expediently be above 1 10 vol. '/ b.

The above-mentioned embodiment is to be regarded only as an illustrative example and the preceding oxidation treatment according to the invention is not limited to the treatment conditions mentioned. For example, a prior oxidation of the nickel-phosphorus alloy layer results in air at about 0.1 torr at about 600 ⁰ G for 10 or 60 (?) Minutes for (later) forming a low-carbon coating. j? erner not iet the heating temperature for the preceding oxidation treatment course, limited to 600 ^0G. Any conditions under which oxidation of the alloy layer is brought about to a slight extent may preferably be used in a manner as explained in the aforementioned Pail for the (subsequent) achievement of favorable carbon coatings. The effect of the foregoing oxidation treatment is that the catalytic activity of the alloy layer is revived thanks to such an oxidation treatment.

The invention is explained below with the aid of examples. All of the nickel-phosphorus alloy layers used in these examples were made by the "electroless plating process" using a commercially available plating solution known ^{as 11 SUMEE 11.} In Examples 1 to 4, all alloy layers contained 8 wt. Fi phosphorus. The previous oxidation

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_ ₅₈ _ 2323328

treatment was performed containing in each case in a 0.005 VoI, ^ oxygen nitrogen atmosphere at a temperature of about 600 ⁰ C for 10 minutes.

example 1

Was a Eisenbleehsubstrat of 0.15 mm thickness, the surface having a iiickelphosphorlegierungssehicht of about 1 i ^ thickness "plated", a previous oxidation was subjected. The substrate was then heated for 20 minutes in the presence of a reaction gas stream of nitrogen with 0.05 vol. $ (Based on the nitrogen) acetylene gas to a temperature of 56O ° O, whereby carbon contained in the reaction gas was deposited on the surface of the substrate covered with nickel phosphorous alloy Formation of a carbon coating was deposited. The coal coating obtained in this way proved to be extremely dense and corresponded to a deposited amount of coal of 1 mg / cm and a coal density of 1.94 g / cm.

Example 2

A sheet iron substrate 0.15 mm thick, the surface of which had been "plated" with a nickel-phosphorus alloy layer, was subjected to a preliminary oxidation treatment. The substrate was then heated for 20 minutes in the presence of a reaction gas stream comprising methane with 0.5 V0I.5 & (based on the methane) acetylene gas to 56O ⁰ C, whereby carbon contained in the reaction gas on the surface of the substrate covered with nickel-phosphorus alloy to form a carbon coating was deposited. The coal coating obtained in this way proved to be extremely dense and

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_ 39 -

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spoke of a deposited amount of carbon of 1.2 mg / cm and a carbon density of 2.20 g / cm.

In this example, the acetylene concentration in the Methane can be increased to a maximum of 5 vol. $. In this case, however, the density of the coal tends to be in the resultant Coal coating to a certain extent for acceptance.

Example 3

Mn iSisenbleeh substrate 0.15 mm thick "plated" on the surface with a nickel phosphor alloy layer was subjected to a preliminary oxidation treatment. ^{The substrate was then heated to a temperature of about 56O 0} C for 20 minutes in the presence of a reaction gas stream obtained by evaporation of LPG with 0.7 vol. # (Based on the LPG) with the carbon contained in the reaction gas being deposited on the surface of the Nickel-phosphorus alloy layer of the substrate to form a carbon coating. The carbon coating thus formed was found to be relatively thick and dense and corresponded to a deposited amount of carbon of about 2.5 mg / cm and a carbon density of 2.18 g / cm.

In this example, the acetylene concentration in the LPG can be increased to a maximum of 5 vol. #. In this case, however, the density of the coal tends in the resultant Coal coating to a decrease to some extent.

Example 4

A 0.15 mm thick tinplate substrate with a "plated-on" ¹ nickel-phosphorus alloy of about 1 µm thick

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Thickness was subjected to a preliminary oxidation treatment. The substrate was then for 20 minutes in the presence of a mixture of 0.2 $> ethylene gas, 1 $> IPG, 4 l> methane gas and 94.8 # nitrogen (in vol. #, Based on the mixture) to a Temperature of about 56O ⁰ O heated, whereby carbon contained in the reaction gas was deposited on the surface of the substrate covered with nickel-phosphorus alloy with the formation of a carbon coating. The coal coating thus obtained proved to be dense and the deposited amount of coal corresponded to 1.8 mg / cm at a carbon density of 1.96 g / cm

Since the reaction gas used in this example was non-flammable, it was found to be quite effective for favoring safe operation.

That is, it has been found that it is possible to use a reaction gas having any composition from which the carbon contained therein can be deposited as long as the reaction gas is 0.01 to 5 vol. $ (based on the reaction gas) contains acetylene and of a non-oxidizing composition free of oxidizing gases such as Is oxygen. In this case, the reaction gas can be appropriately mixed with such flammable gases as IPG or methane however, it is preferable to use a reaction gas which is a mixture of one from the viewpoint of handling Inert gas such as nitrogen or argon and a flammable gas such as LPG and / or methane in an amount and within one such a range that the resulting total gas mixture becomes non-flammable.

Although the preferred embodiments of the invention

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have been described with reference to cases where the nickel phosphorus alloy layer on the substrate surface was formed by "electroless plating ¹¹ using" SUMER "solution (trademark for a plating solution), of course, the invention is not limited thereto.

As was explained in detail above, it is possible according to the method according to the invention, the surface of a very thin iron sheet substrate 0.15 mm thick with a dense carbon layer of any given thickness to coat with accuracy and in a simple and safe manner, while it is close to the state of the art it was impossible to realize such coatings as according to the invention. The inventive method has more in addition, the property that, as a result of the, compared with the prior art, low temperatures that lead to the coal deposition reaction according to the invention are necessary, numerous disadvantages associated with high heating temperatures, as they were used in the past, could be effectively avoided.

Furthermore, the method according to the invention is particularly useful as a method for carbon coating a shadow mask Color television tubes extremely effective and leads to excellent Results regarding the improvement of the technique of creating shadow masks.

Example 5

A 0.15 mm thick shadow mask for color television tubes sheet iron was used to completely remove oxides

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washed from the surface with hydrochloric acid. The mask thus washed was dipped as such for about 2 minutes in a "SUMBR" solution (non-electric or electroless JSickelabscheidungsbad), the bath temperature was controlled at 8O ⁰ C and the pH was previously adjusted to 6.0 was. In this case, particular care was taken to ensure that the "plating bath" was stirred carefully to ensure a sufficiently uniform coverage of the vicinity of a large number of small pores or holes on the shadow mask, thereby ensuring uniform "plating" of all parts of the shadow mask with nickel-phosphorus alloy in one Thickness of about 0.3-0.5µ was achieved.

After completing the plating treatment, the shadow mask was pulled out from the bath, washed thoroughly with pure water, and then quickly dried. The interior of a heating furnace was then evacuated once until pressures of 10 "to 10 I Dorr were reached. This heating furnace consisted of a material such as quartz, for example, on which no carbon is ^{deposited by reaction with acetylene at about 600 °} C. Thereafter, acetylene was formed introduced into the heating furnace, so that the displayed on a Pirani Hanometer pressure in the furnace reached 5 Torr .. in the oven, the inside temperature was brought to about 600 ⁰ C, the shadow mask was placed, with care was taken that The above furnace conditions were not affected (in this case the shadow mask was preheated). The reaction took place at the stated temperature for about 30 minutes to form a carbon coating on the shadow mask surface with a deposited carbon amount of about 1 mg / cm and a thickness of about 4 »5 n. The carbon-coated shadow mask was then transferred to a cooling chamber and then au3 de r chamber removed.

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Microscopic examination of the carbon coating obtained at about 600 times magnification showed in some cases that some small carbon spheres in the form of ball of maste thread were present on the surface of the carbon layer. If such carbon spheres are present on the surface of the carbon coating formed on a shadow mask, they enter a floating or floating state within the color picture tube and cause spark discharges when a high voltage is applied; therefore, such carbon spheres must be completely removed by washing with water or rinsing treatment with ultrasonic waves before using the carbon-coated shadow mask.

After the above treatment, the carbon-coated shadow mask was mounted in a color picture tube and checked. As a result, excellent behavior in which secondary electron emission from the Shadow mask as a result of "heat electrons" under acceleration voltages from 25 to 30 kV are triggered, and a good color image without significant halo formation could be achieved.

Although the invention has been described above on the basis of preferred embodiments, the case in which a shadow mask substrate was ^{coated with a nickel-phosphorus alloy by non-electrical or electroless deposition using a "SUMEE 11} solution" was dealt with, the invention is self-evident not limited to that.

As explained above, it is in accordance with the invention

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possible, its substrate, the surface of which is to be provided with a carbon coating, with a nickel-phosphorus alloy to be provided, and on the non-phosphorus-coated substrate surface by thermal decomposition of Acetylene at relatively low temperatures using the catalytic effect of the nickel-phosphorus alloy layer Deposit carbon and the thermal decomposition reaction of acetylene gas by adjusting the composition to suppress or control the acetylene-containing reaction gas (largely) with the formation of a dense, evenly thick carbon coating on the substrate surface in a simple manner and with high operational stability. The present invention thus greatly contributes to improvement and further development of industrial technology and also brings great economic benefits.

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Claims (21)

Claims? 3? 3928 1. Process for the pyrolytic generation of a carbon coating on the surface of an object to be coated in a hydrocarbon-containing atmosphere, characterized first of all a nickel phosphorus alloy layer is applied to the surface of the object to be coated and then the object covered with nickel phosphorus alloy layer in a hydrocarbon-containing Gas with thermal decomposition of the gas and deposition of carbon contained in the gas on the to be coated The surface heats up with the formation of the carbon coating. 2. The method according to claim 1, characterized in that the object to be coated with carbon through a substrate made of iron and in particular through a shadow mask for a ! Color television tube is formed. 3. The method according to claim 1, characterized in that the nickel-phosphorus alloy layer by non-electrical Deposition is formed from an appropriate bath. 4. The method according to claim 5, characterized in that the phosphorus content of the nickel phosphor alloy layer through Adjustment of the pH of the solution for the non-electrical deposition is controlled. 5. The method according to claim 1, characterized in that 30B850 / 0843 ~ ^'46 "P323328 the amount of phosphorus contained in the nickel phosphor alloy layer based on the nickel weight at 4 to 12 Gfew4 and in particular at least 5 Gew.yo. 6. The method according to claim 1, characterized in that the thickness of the phosphorus alloy layer is 0.1 to 6 u lies. 7. The method according to claim 1, characterized in that as the hydrocarbon-containing gas, an acetylene-containing gas is used. 8. The method according to claim 7, characterized in that 'the acetylene-containing gas is a non-oxidizing gas, the 0.1 to 1.5 vol. $ Acetylene (based on the non-oxidizing Gas) are mixed in. 9. The method according to claim 8, characterized in that the non-oxidizing gas by nitrogen, helium and / or Argon is formed. 10. The method according to claim 8, characterized in that the non-oxidizing gas from the group consisting of methane and liquefied Petrol or petroleum gas is selected. 11. The method according to claim 7, characterized in that the acetylene-containing gas consists mainly of an inert gas from the group nitrogen, helium and argon and at least one representative from the group: 0.1 to 1.5 Vol.70 and in particular 0.15 to 1.5 vol / o acetylene gas, 0.1 ^c ß> or more liquefied gasoline gas and 0.1 70 or more methane in a quantity within such a range that the Ü843 resulting entire mixed gas becomes incombustible. 12. The method according to claim 11, characterized in that the acetylene-containing gas further comprises at least one representative the group of ethane and ethylene gases in a quantity and within such a range that the resulting entire mixed gas becomes incombustible. 13. The method according to claim 7, characterized in that the hydrocarbon-containing gas comprises acetylene and at least a representative from the group hydrogen and methane. H. The method according to claim 1, characterized in that the hydrocarbon-containing gas is the object to be coated as a negative pressure atmosphere of preferably 100 Torr or less. 15. The method according to claim 1, characterized in that the object coated with the nickel-phosphorus alloy layer is heated in the presence of the hydrocarbon-containing gas at such a rate to separation temperatures of 450 to 700 ⁰ G, in particular from 500 to 700 ⁰ G, that the catalytic effectiveness of The nickel phosphor alloy layer is not markedly decreased. 16. The method according to claim 5 and 11, characterized in that the nickel-phosphorus alloy layer has a thickness of at least 1 μ owns. 17. The method according to claim 14, characterized in that the nickel-phosphorus alloy layer, based on the nickel 309850 / 08A3 weight, contains at least 4 wt. ^ Phosphorus and preferably has a thickness of at least 1 micron and that the atmosphere of the hydrocarbon-containing gas is formed by an acetylene and at least one member from the group consisting of hydrogen and methane, aeetylenhaltiges gas with a pressure of 100 Torr or less. 18. The method according to claim 1, characterized in that the coated phosphorus alloy layer on the surface of the article before the deposition treatment in a hydrocarbon-containing atmosphere with thermal cracking the gas undergoes an oxidation treatment in oxygen-containing Atmosphere. 19. The method according to claim 18, characterized in that the hydrocarbon-containing atmosphere by a non-oxi- " Dierendes gas with 0.01 to 5 vol. # acetylene (based on the non-oxidizing gas) is formed. 20. The method according to claim 19 »characterized in that the hydrocarbon-containing gas consists mainly of an inert gas selected from the group consisting of nitrogen, helium and argon and at least one representative from the group 0.01 to 5 vol. $ acetylene, at least 0.1 vol and contains at least 0.1 vol. methane in an amount within such a range that the resulting total gas mixture becomes incombustible. 21. The method according to claim 18, characterized in that the nickel-phosphorus layer (based on the amount of nickel) —4- ' at least 5 thread> Contains phosphorus and in a nitrogen atmosphere containing more than 10 Torr of oxygen with an increase in temperature is subjected to an oxidation treatment. 309850/0843 Blank page