FR2494260A1 - PROCESS FOR TREATING FIBER AND PROCESS FOR PRODUCING COMPOSITE MATERIAL FROM FIBERGLASS, CERAMIC, METAL OR THE LIKE - Google Patents

Abstract

Glass fibres or ceramic fibres or other fibres, for example graphite fibres, which are protected in a suitable manner by an adhering ceramic coating or metal coating, are dipped into a liquid metal-organic solution which contains a rare metal compound as the main constituent, and are then dried and fired in air or a slightly oxidising atmosphere, so that a rare metal coating is produced on the fibres. The fibres can be individual filaments, multifil yarns or cables, or fabrics. The fibres coated with a rare metal are then incorporated in a metal matrix base material by dipping into a molten bath of the desired matrix metal, conversion of the fibres into suitable shape and casting of the matrix metal melt around the fibres, or by arranging the fibres between solid webs of matrix metal and compaction by diffusion bonding.

Description

 The invention relates to a process for the preparation of metal matrix composites, reinforced with ceramic or glass fibers or other fibers which have been suitably coated, these fibers being pretreated in a metallo-organic solution (resinate) of precious metal. , then heated in air to form a precious metal coating on the fibers. The coated fibers are then immersed in a molten bath of the metal desired for the matrix or bottom mass, placed in a suitable mold, then the molten metal of the matrix is poured onto the fibers, or else the latter are placed between solid sheets of matrix metal and consolidation is achieved by diffusion bonding.

 Composite materials with a metallic matrix, generally comprising non-metallic fibers with high resistance and high modulus, in a metallic matrix or ground mass, can be suitable for a large number of very diverse industrial and military applications, because they combine the physical properties of a metal (eg electrical conductivity and thermal conductivity, resistance to corrosion and wear) to the mechanical properties of the fibers. To obtain optimal mechanical properties in the composite, a good bond must be ensured between the fiber and the matrix. However, the formation of the bond should not significantly attack the fiber, as this could otherwise result in a substantial decrease in the strength of the fiber and, therefore, in the strength of the composite.

 In the preparation of a metal matrix composite, the fibers and the metal are joined together by bonding by solid state diffusion, or by infiltration of molten metal into a group of fibers. Generally, solid processes are used for fibers of large diameter (about 100 microns) or for chopped fibers, while liquid infiltration is used for fibers of small diameter (5 to 25 microns) which are usually present in multifilament yarns. Methods using liquid metal require wetting to occur between the fiber and the matrix. Often this wetting does not occur spontaneously, so a wettable coating is first applied to the fibers. Examples of coating and coating application methods used in the past include titanium boride coatings applied by chemical vapor deposition (United States Patent No. 3,860,443), nickel coatings applied by electrodeposition United States Patent No. 3,622,283) and sodium coatings applied by immersion of fibers in molten sodium (U.S. Patent No. 3,859,114) Although these three coating application methods are capable of promoting infiltration of molten metal into fiber bundles, the first two methods require the use of sophisticated equipment and close control of the processing parameters, while the third process poses significant safety problems when handling molten sodium. es solid state bonding methods, the bond between the fiber and the metal depends on a reaction between the two materials. If this reaction is not closely controlled, it may result in a loss of fiber strength. It is therefore sometimes advantageous to coat the fibers with an intermediate substance which binds to both the fibers and the matrix without excessively reacting with them during the bonding process.

 The subject of the invention is therefore the preparation of composite materials with a metallic matrix, consisting first of all in coating a noble metal with glass or ceramic fibers or other fibers such as graphite fibers suitably protected by a coating. suitable metallic or adherent ceramic. This coating of noble metal is produced by immersing the fibers in a liquid metallo-organic solution containing a noble metal compound as the main ingredient.

 The subject of the invention is also the production of a metal matrix composite material using said fibers coated with noble metal, by immersion of these fibers in a bath of the desired matrix material in fusion, by placing the fibers in a suitable mold and by casting the molten matrix metal around the fibers, or else by placing the fibers between solid sheets of the matrix metal and by carrying out consolidation by means of a diffusion bond. of ceramic or glass, or graphite fibers coated with a layer of ceramic or metal, a metallo-organic compound containing a noble metal, then by cooking (heating in air), a coating of adherent and continuous noble metal, which achieves an excellent bond with the matrix of the composite material, introduced subsequently.

Although silver is a preferred noble metal, it is also possible to use films of gold, palladium or platinum. All these films are continuous and adhere to fiberglass or ceramic. It has become apparent that graphite fibers are not suitable unless they are first coated with an adherent ceramic material or a suitable metal. Among the metallic materials for coating graphite fibers, nickel, aluminum, titanium, magnesium and stainless steel have been found to be useful.

 A metallo-organic material containing a noble metal and having proved very useful in the process of the invention is that described in the patent of the United States of America No. 2 984 575.

 The ceramic and glass fibers used in the present invention may include any of the commercially available glass fibers, for example "E" glass, "5-2" glass or quartz glass; any of the polycrystalline oxide fibers such as pure alumina or an alumina-boron oxide-silica mixture or any other non-metallic compound fiber such as silicon carbide, whether present in the form of a homogeneous material or in the form of a coating applied to a fiber of a different material. The fibers can be used in the form of monofilaments, multifilament yarns or a woven fabric.

 The matrix or bottom mass metals used in the present invention may include, without limitation, any of the following: aluminum and its alloys, lead and its alloys, or tin and its alloys. Methods for introducing the fibers into the metal matrix include immersing the fibers in a bath of molten matrix metal, the metal-coated fibers then being removed from the bath so that the metal attached to these fibers can solidify on the air; placing the fibers in a shell mold of suitable design and pouring molten matrix metal into the mold, preferably using a vacuum helping to fill the interstices between the fibers; and hot pressing the fibers between solid sheets made of the matrix metal, this process being most suitable for monofilaments of relatively large diameter (about 100 micrometers).

In all cases, the fibers are first pretreated by immersion in a metallo-organic solution (resinate) of precious metal (in the preferred embodiment, silver) containing suitable binding and pickling ingredients; an example of such a solution is marketed under the brand name "Organic Silves!
Ink Number A-2282 ", by the firm Engelhard Industries,
East Newark, New Jersey, EUA The solution can also be applied to the fibers by brushing or spraying.

The fibers can be treated individually or in bundles of a desired size for the metallic composite part. After treatment in the metalloorganic solution, the fibers are heated in air in accordance with the instructions of the manufacturer of the solution, so that the organic constituents of the solution volatilize and that a film of precious metal is deposited on the surface of the fibers. The fibers thus treated are then incorporated into a matrix or metal base mass, as described above.

 The following examples of fiber and matrix compositions illustrate, without limitation, the application of the invention to various materials.

EXAMPLE 1
A bundle of "S-2" glass fibers is immersed in a metallo-organic silver solution, sold under the name "Organic Silver Ink NO A-2282" (Engelhard
Industries). The immersion time is approximately 2 seconds after which the fiber bundle is removed from the solution at a moderate speed. The fibers are then placed in an air drying oven, at 125 "C, for 10 minutes. Then, the fibers are baked by air heating, the temperature being raised to 6000C at a rate of about 50 C / min, then being kept at 6000C for 10 minutes, the fibers are then air-cooled, the treated fibers, each coated with a uniform layer of silver, are then immersed for 10 seconds in a bath of molten lead at 4500C, After the fibers have been removed from the lead bath and cooled in air, examination shows that the lead has taken up and entered the bundle of fibers, forming a bar lead composite reinforced with glass fibers.

EXAMPLE 2
A ribbon of glass fibers (glass "S-2") woven 15 cm long and 2.5 cm wide, is immersed in the metallo-organic silver solution indicated in Example 1, dried at 1 air, then heated in air at 600 ° C for 10 minutes, as in Example 1. The silver-coated ribbon is immersed in air for 10 seconds in a bath of molten lead at 4500C. The tape is removed from the lead bath and cooled in air. The lead has coated the fabric formed by the fibers of the tape and has infiltrated this fabric, so that a lead composite reinforced with glass fiber, in two directions The resulting article is much more rigid and resistant than a part of the same dimensions made of unreinforced lead.

EXAMPLE 3
A bundle of ceramic oxide fibers, sold by the company 3M Company under the brand name "Nextel 312", is treated by the same process as that described in Example 1. An examination of the final product shows that the lead has coated the fiber bundle and infiltrated into this bundle, forming a lead composite reinforced with ceramic oxide fibers.

EXAMPLE 4
A bundle of quartz glass fibers is treated by the same process as that described in Example 1.

An examination of the final product shows that the lead has coated and infiltrated between the quartz glass fibers and the product obtained is a lead composite reinforced with quartz glass fibers.

EXAMPLE 5 4
A bundle of ceramic oxide fibers ("Nextel 312"), as in Example 3, is treated by the same process as that described in Example 1, except that the molten metal bath, instead of being lead, is an alloy of tin and regulates comprising approximately 90% of tin, the rest being copper and antimony. The temperature of this bath is 4000C. Immersion of the bundle of treated fibers in this air bath for 10 seconds gives a metallic coating and infiltration into the bundle of fibers.

EXAMPLE 6
A bundle of continuous silicon carbide filaments, each about 13 micrometers in diameter and produced by the firm Nippon Carbon Company (Japan) under the trademark "Nicalon", is immersed in the metallo-organic silver solution of the Example 1, dried and heated in air at 600 "C for 10 minutes, as in Example 1. The fibers thus coated with silver are placed in a rectangular cavity of 3.2 x 3.2 x 203 mm. length, formed in a plaster mold, the fibers then occupy about 10% of the volume of this cavity. The plaster contains a pouring funnel, a feed channel made of molten metal and an attack allowing the molten metal to enter the cavity containing the fibers.

An aluminum-based alloy (alloy 201) is heated to 8500C and poured into the plaster mold funnel; a vacuum is used to help fill the mold cavity. After the metal has solidified in the mold, the 3.2 x 3.2 x 203 mm bar is removed and examined.

It appears that the aluminum alloy covers the bundle of fibers, penetrates this bundle and fills the cavity.

EXAMPLE 7
"S-2" glass fibers are treated and placed in a mold, and pure molten lead is introduced to produce a rectangular bar reinforced with fibers, as in Example 6. After solidification of the metal inside the mold and removal of the bar, a gramen shows that the lead has coated the bundle of fibers, penetrated into this bundle and filled the cavity.

EXAMPLE 8
A bundle of pitch-based graphite fibers (of the "VSB-32" type from the firm Union Carbide) is treated in the metallo-organic solution of Example 1 and air-dried as in Example 1. However, during cooking at a higher temperature (600 ° C.), a luminescence of the red-heated fibers is observed and, after removal from the oven, most of the fibers have disappeared, probably by oxidation giving a gaseous reaction product.

We tried to preserve the fibers by heating them in a humid argon atmosphere rather than in air. The fibers thus treated do not disintegrate as is the case in the air. However, the silver coating does not adhere to the fibers and the lead does not infiltrate the bundle of treated fibers when the latter is immersed in a lead bath.

EXAMPLE 9
A bundle of pitch-based graphite fibers (of the "VSB-32" type from the firm Union Carbide), identical to the fibers of Example 8, is coated with nickel by electrodeposition. The nickel-coated fibers are then treated in the metallo-organic solution of Example 1 and air-dried as in Example 1. Then, the nickel-coated fibers are heated in air to a temperature of 6000C. at which they are raised at a rate of approximately 500C per minute, and they are maintained at 6000C for 10 minutes, then cooled in air. The nickel coating of the fibers prevents the fibers from disintegrating when exposed to this high temperature. Then, the treated fibers, now coated with nickel and silver, are immersed in a bath of molten lead at 4000C, in air, for 10 seconds. After the fibers have been removed from the lead bath and have cooled, examination shows that the lead has coated and penetrated the fiber bundle to form a lead composite reinforced with graphite fibers.

 The composite materials formed by this process are more rigid and more resistant than the unreinforced infiltration metal. The axial resistances of the fibers contained in the composite depend on the type of fibers, but they generally vary from approximately 700 MPa for glass of the "S-2" type to 1750 MPa for silicon carbide.

The strength of the composite material is a function of the type and amount of fibers present.

 It goes without saying that numerous modifications can be made to the process described without departing from the scope of the invention.

Claims (6)

 1. Method for treating a fiber chosen from the group comprising glass, ceramics, metal and any fiber coated with a material chosen from the group comprising glass, ceramics and metal, characterized in that '' it consists in coating the fiber with a liquid compound of metallo-organic type containing a noble metal and in heating said fiber, bringing the metallo-organic coating, to a temperature at which the noble metal is deposited on the fiber, said fiber chosen being made of a material which retains its structural integrity at said temperature at which the noble metal is deposited on the fiber.  2. Method according to claim 1, characterized in that the noble metal is silver.  3. Method for producing a composite material from a fiber chosen from the group comprising glass, ceramics, metal and any fiber coated with a material chosen from the group comprising glass, ceramics and of metal, the method being characterized in that it consists in coating said fiber with a metallo-organic liquid compound containing a noble metal, in heating said fiber, bringing the metallo-organic coating, to a temperature at which said noble metal is deposited on this fiber, and to bind the fiber coated with noble metal, thus obtained, of a matrix of a different metal, the fiber chosen being made of a material which retains the integrity of its structure at said temperature at which the noble metal is deposited on this fiber.  4. Method according to claim 3, characterized in that the fiber coated with noble metal is immersed in a different molten metal.  5. Method according to claim 3, characterized in that a different liquid metal is poured around the fiber coated with noble metal.  6. Method according to claim 3, characterized in that the fiber coated with noble metal is bonded by diffusion to a different metal forming a matrix.