DE1771731A1 - Reinforced carbonaceous bodies - Google Patents

Description

1BERL1N33 «II0NCHEN27

ÄÄ ^ TSS "Dr.-fng. HANS RUSCHKE Dipl.-Ing. HEINZ AGULAR PATENT LAWYERS Bank account: _ Munch. «MJ Bank for HmkM and Induitrj. 17717 ^ 1 bank account: D ^ witoikott 82 * * * * * WI Dmdiwr Bank

MOnehwi

KIo. 327808 Account W615

Berlin CUi «* afur Munich

N Dr.V / G.

North American Eockwell Corporation, El Segundo,

California, V.St.A,

Reinforced carbonaceous bodies

The invention relates to a method of manufacture reinforced carbonaceous body. Previously, reinforced carbonaceous bodies were used a py rolyzable base material, such as tar or Pitch mixed with finely divided carbon and graphite, with reinforcing substances such as Carbon and graphite fibers incorporated. The composition was pyrolyzed, whereby a graphite structure containing the reinforcing materials was formed.

The previously known methods have the disadvantage that substances for the basic structure must be used which are at or below the temperatures for the lyrolysis

109883 / U2S

become plastic. As a result, it is a complicated one Mold design required to ensure uniformity in terms of size.

The property of parapolyphenyls, after which it is compressed into a coherent mass and then closed a coherent crystalline graphite structure has been described. Also is the resulting material is harder than graphite and has other distinguishing features. The material can generally be used whenever graphite would normally be used, e.g. for insulating Structures, materials for contact arm supports and projector carbon pins, to mention a few applications.

It has been found that the graphite-like material that results from the pyrolysis of parapolyphenyls for some applications is unsuitable what is on

a ο

its high modulus of elasticity below about 1500 C. is. This high modulus of elasticity naturally indicates a brittle material. This brittleness often causes structural destruction of the component by an accidental mechanical shock · If the component has a substrate with a high Thermal expansion coefficient is connected, a change in heat can also cause mechanical stresses cause the graphite-like component, what a decomposition

109883 / U25

Disturbance of the structure causes · At temperatures above 15 (X) ⁰ G, however, carbon is sufficiently flexible so that it can withstand minor stresses and mechanical vibrations. The Itobleir of resistance to vibration and breakage is dahejjnieht at a temperature above 150o ⁰ G serious way.

State of the art

One solution, according to which the structure destruction described can be countered, is to reinforce the carbon-containing structures. Ordinary reinforcing materials, however, such as fiberglass, glass cloth and steel wire, are unsatisfactory either because they react with carbon, as in the case of glass and steel, or because they do not have sufficient mechanical strength under temperature conditions as high as 150O ⁰ O · Furthermore The usual requirements for reinforcing fibers, e.g. strength, high degree of resistance, processability, etc., must be met.

It is an object of the invention to provide an improved method to develop for the manufacture of reinforced carbonaceous bodies

Another object of the invention is to develop Process for the formation of reinforced carbonaceous

109883 / U25

term bodies that do not have complicated shapes require.

According to a further aim of the invention, graphite bodies reinforced with materials other than carbon or graphite reinforcements.

Further advantages and objectives of the invention will become apparent from the following description.

Summary Description of the Invention The method of the present invention consists in that, in a form, a composition selected from the group consisting of parapolyphenyls, mixtures of parapolyphenyls and graphite, mixtures of parapolyphenyls and carbon, and mixtures of parapolyphenyls, carbon and graphite, together with reinforcing fibers coated with a material resistant to carbon diffusion metal or not) are coated and which are selected from the group consisting of boron, tantalum, titanium, tungsten and molybdenum group is introduced, the mixture at pressures of ^ Q _t 3-8436 kg / cm formed by pressure and pyrolyzing the molded mixture at a temperature of 65O ⁰ C bis25OO ° C 0.1 to 4 hours. One hour is advantageous. It has unexpectedly been found that the reinforcing material coated or not coated with carbon diffusion resistant metal is that of boron, tantalum, titanium, tungsten

109883 / H25

and molybdenum is selected satisfactorily as reinforcement of carbonaceous bodies acts according to the present invention. .For components, exposed to temperatures of around 900-1400 ° ö are materials selected from the group consisting of tantalum, titanium, tungsten, and molybdenum are, suitable · Above about 1400 ° G, however, these fabrics are less satisfactory because these fibers are supported by a certain carburization percentage are weakened. Accordingly, above these temperatures it is preferable to use a carbon diffusion resistant material on the fibers to provide metallic coating. The metals known to be suitable for this purpose include im generally to the class known as Group VIII metals, excluding iron but also including finally rhenium, these metals do not form light carbides, and under most conditions they do no carbides at all · However, some of these metals exhibit this property of diffusion resistance in a greater measure, the best metals in the group are hhenium, rhodium, and iridium, and of this preferred group is rhenium most favorable

Advantageously, the reinforcing materials are in the form of wires or fibers with a size ratio i.e. a ratio of length to diameter, from 10 to 1000. These fibers can be found in the

109883/1425

Graphite structure can be oriented arbitrarily, or they can be in an ordered state, whereby the reinforced bodies are given additional strength in the specific directions «In general the reinforcing fibers should be 5 to 80% by volume make up of the graphite structure · The fibers are in the polymer mixture introduced by simple mixing if no alignment is desired · if special If alignment is desired, the fibers can be arranged by manual means.

The parapolyphenylene material and the method for its Manufacture are well known · The polymer is infusible and consists of benzene rings that are bound in para position · If the polymer is unsubstituted, contains it is carbon and hydrogen in a weight ratio of about 18: 1. The hydrogen of parapolyphenylene can be substituted by halogens, e.g. chlorine. Parapolyphenylene can also be polynuclear This polynuclear state is indicated by an increase in the ratio of carbon to hydrogen. The polymer is not only infusible but also chemically inert and has a high degree of heat resistance on. This material is therefore called untreatable. The polymer is like it is with Process for its production is obtained, a flaky, brown powder with a very large upper

109683/1425

area. The polymers of the invention are compressed at pressures of at least 7.3 kg / cm. pressures as high as 8436 kg / cm can be used. The pressure used to compress the powder naturally affects the density of the compressed Final mass · It should be noted, however, that solid, pyrolyzable masses are within the total specified Range are available. For various specific applications, more compact masses or, in other words, higher pressures are advantageous. The squeezing can using any customary measures, including mechanical or isostatic methods, which in themselves do not form part of the invention will. The compression can be done at room temperature and performs within the specified ranges to a very dense body. On the other hand, the compression can take place at elevated temperatures. That Compressed material has a beneficial slipperiness, allowing it to detach from the shape entirely is easy. The parapolyphenylene, for example, has pestilence in the compressed, fresh state of up to 140.6 kg / cm. In addition, X-ray diffraction examinations a high degree of anisotropy was found.

The compressed powder containing the reinforcing fibers is then placed in an oven in which

the compressed mass is pyrolyzed. During 109883 / U25

During pyrolysis, hydrogen and atoms, which are present in addition to the carbon in the parapolyphenylene, are driven off as volatile substances, leaving a carbon-containing mass containing the reinforcing fibers. The material remains in the oven at the pyrolysis temperature for a period of time sufficient to pyrolysis the entire mass. The furnace can operate under negative pressure or with an inert atmosphere. In any case, the atmosphere in the furnace must not react with the parapolyphenylene. The pyrolysis temperatures can vary within the range from 650 to 250O ⁰ C. The glowing or residence time of the compressed mass under the influence of the temperature changes depending on the temperature. However, it has been found that, for practical use, a residence time of one hour in the specified temperature ranges is sufficient for the pyrolysis to be carried out.

In the manufacture of the reinforced carbonaceous articles, one problem may be encountered that the article changes shape after cooling. This change in shape is caused by the shrinkage of the parapolyphenylene, squeezing the fibers. To overcome this problem, powdered graphite or carbon can be added to the parapolyphenylene mixture, thereby reducing pyrolysis shrinkage and, consequently, crushing. In the preferred mini

109883 / U25

Research will be 65 percent by _# - · applied% carbon or graphite has been found, however, that an area of ~ * SSFC is suitable to 80% ·

After shaping and pyrolysis, the article can be machined to give it a desired shape. Included can standard machining operations using methods that are used in lechnik when shaping Graphite materials are known to be used »

The method and compositions of the present invention are illustrated by the following examples explained

example 1

A fiber reinforced article was prepared with 0.13 mm-boron "piping fibers consist of a precipitate of boron on a fine tungsten wire having a size ratio of about 100. The fibers were cut into short lengths, for example to 1.27 ^m c" cut, and 5% by weight of the aejan fibers were then mixed with polyphenylene and compressed into a 1.27 cm diameter disc at a pressure of 703O kg / cm. This disk was then ^{pyrolyzed in argon for one hour at 1000 °} C. The samples were then cut up and examined microscopically} it was found that the boron fibers had remained intact and that they were flat and perpendicular to the direction of pressure

109883/1425

- ίο -

Example 2

A reinforced carbonaceous article of superior strength, resistant to thermal and mechanical shock, is made by mixing 50 volume weight percent tantalum fibers with a size ratio of about 5 ^ 0 9 which were coated with rhenium, with parapolyphenyls, pressing the mixture at 3515kg / cm and pyrolyzing the compressed mixture for "45 minutes at 2000 ° C in a vacuum.

Example 3

A reinforced carbon-containing body is produced by mixing 75 V0I.-S titanium fibers having a Grössenverh älnis of 75Ο and Parapolyphenylen, compressing the mixture at a pressure of 1406 kg / cm and pyrolyzing at 800 ⁰ C for 3 hours in a helium atmosphere.

Example 4

A reinforced carbonaceous body is made by mixing 25% by volume molybdenum fibers with a size ratio of 20, which have been coated with osmium, with parapolyphenyls, compressing the mixture at a pressure of 7733 kg / cm and pyrolysing for 4 hours at 2200 ⁰ C in argon.

Example 5

A reinforced carbonaceous body is provided by Mi-109883/1425

- ii -

see of 20% by volume of titanium fibers with a size ratio of 200, which have been coated with iridium, with a mixture of 65% by weight of graphite and 35% by weight of parapolyphenylene, compressing the mixture with a pressure of 2109 kg / cm ² and pyrelysize for 2 hours at 17CK) ⁰ G in an argon atmosphere.

Example 6

A body is made by the same procedure as described in Example 5 using the same ingredients produced with the exception, however, that the body in addition to the fibers 25 wt .-% graphite, 20 wt .-% carbon and 55% by weight of parapolyphenylene.

Example 7

A body is made by the same procedure as described in Example 5 using the same components except that the body in addition to the fibers, 75% by weight of carbon and 25% by weight Contains parapolyphenyls.

Obviously, many changes and tweaks can be made may be made in the individual features described above, without departing from the essence and content of the invention to deviate. It goes without saying that the invention is not limited to such changes and modifications unless the limits have been specified in the associated claims,

109883 / U25

Claims (1)

177X131 - 12 patent claims 1 ·) Process for the production of reinforced carbon », containing bodies, characterized in that in a form a composition which consists of parapolyphenyls, mixtures of parapolyphenyls and graphite, mixtures of parapolyphenyls and carbon and mixtures" of parapolyphenyls, carbon and graphite, together with reinforcing fibers coated or uncoated with carbon diffusion resistant metal and selected from the group consisting of boron, tantalum, titanium, tungsten and molybdenum, introduces the mixture at pressures of 70, 05 to 8436 kg / cm is molded by pressing together and the molded mixtures are pyrolyzed at a temperature between 65O ⁰ C and 25CK) ⁰ C. '2.) A process according to claim 1, characterized in that the fibers have a G _r gssenverhältnis from 10 to Looo. 3.) The method according to claim 1 or 2, characterized in that the pyrolysis O _{1 is carried out} 1 to 4 hours lane. 4.) The method according to claim 1, 2 or 3, characterized in that the fibers are not coated and from the of titanium, tungsten, tantalum and boron consisting of- ' are chosen. 109883 / U25 5 ·) Reinforced carbonaceous body, characterized in that it is carbon and with carbon diffusion resistant Metal coated or uncoated fibers, those made from boron, tantalum, ^ itan, tungsten and molybdenum existing group are selected and a size ratio from lO to lOOO contain, and that it by pyrolysis of a shaped, ^ arapolyphenylen containing ■ the mixture is made · 6) The material of claim 5 »characterized in that the fibers are not coated and, and from the, group consisting of r tungsten, tantalum and B are selected from _O iitan. 109883 / U25