Method for manufacture of composite fiber

Details Method for manufacture of composite fiber Method for manufacture of composite fiber

2000-02-10

2001-11-06

Cameron, Erma (Department: 1762)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C501S035000

Reexamination Certificate

active

06313051

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a composite fiber that can be used at higher temperatures in fields such as aerospace (engines and bodies for spacecraft, supersonic transport machines and the like), energy development (high efficiency gas turbines, atomic power, nuclear fusion reactors), and transport equipment (lightweight and high-strength materials), and to a method for the manufacture thereof.
BACKGROUND OF THE INVENTION
Technical advances in various fields in recent years have been accompanied by increasing demand for heat resistant materials that can be used in high temperature environments, and for lightweight and high-strength materials. In a case of conventional ceramic fibers, with regard to the fibers containing silica added for improving elastic modulus of them at normal temperature, where these are used in high temperature environments, a glass phase forms in the grain boundary area of them, which serves as a starting point for fracture, with the result that high strength of them is not achieved. Systems employing oxides exclusively have the drawback that once they are placed beyond a certain temperature environments, rapid particle growth and particle deformation occur in the systems, resulting a sharp decline in their strength. (References: T. F. Cooke, J. Am. Ceram. Soc., 74 (12) 2959-78 (1991), W. R. Cannon and T. R. Langdon, J. Mat. Sci., 18 (1983), and so on)
With the foregoing in view, it is an object of the present invention to provide a fiber having reduced matrix particle deformation in high temperature environments which can be used as a heat resistant material, and a method for the manufacture thereof.
SUMMARY OF THE INVENTION
The present invention provides a method for the manufacture of a ceramic composite fiber.
The present invention relates to a method for the manufacture of a composite fiber in which a second phase is dispersed within a matrix fiber, wherein the matrix consists of a substance selected from alumina, zirconia, mullite, YAG, silica, magnesia, nitrides, carbides, metals, alloys, and polymers; the second phase consists of a substance selected from zirconia, mullite, YAG, and other oxides, or from metals; and the composite fiber is produced by synthesizing a fiber from a precursor solution containing the substance of the matrix, and the starting solution which serves as the second phase, dispersed through the matrix solution, and then heating the fiber.
Through the present invention it is possible to reduce a deformation of the matrix particles in high temperature environments and to obtain a ceramic fiber which can be used as a heat resistant material.
DETAILED DESCRIPTION OF THE INVENTION
As a result of painstaking research conducted to achieve the object stated above, the inventors discovered that a composite fiber having a second phase dispersed within the fiber could be created, and that a strength of the fiber in high temperature environments could be improved, and thereby the present invention was perfected.
The first embodiment of the present invention for solving the aforementioned problems is a method for the manufacture of a composite fiber in which a second phase is dispersed within a matrix fiber; wherein the matrix consists of a substance selected from alumina, zirconia, mullite, YAG, silica, magnesia, nitrides, carbides, metals, alloys, and polymers; the second phase consists of a substance selected from zirconia, mullite, YAG, and other oxides, or from metals; and the composite fiber is produced by synthesizing a fiber from a precursor solution containing the substance of the matrix, and the starting solution which serves as the second phase, dispersed through the matrix solution, and then heating the fiber.
The second embodiment of the present invention is a method for the manufacture of a composite fiber in which a second phase is dispersed within a matrix fiber, wherein the matrix consists of a substance selected from alumina, zirconia, mullite, YAG, silica, magnesia, nitrides, carbides, metals, alloys, and polymers; the second phase consists of a substance selected from zirconia, mullite, YAG, and other oxides, or from nitrides, carbides, and metals; and the composite fiber is produced by synthesizing a fiber through a precursor solution containing the substance of the matrix, and the solid substance which serves as the second phase, evenly dispersed through the matrix solution, and then heating the fiber.
The third embodiment of the present invention is a method for the manufacture of a composite fiber in which a fiber characterized in that a second phase is dispersed within a single fiber and a matrix fiber of the fiber is coated on the surface thereof with a substance selected from zirconia, mullite, YAG, and other oxides, or from nitrides, carbides, metals, and polymers, whereby the surface of the matrix fiber is evenly coated with the second phase, wherein the composite fiber is produced by adding a starting solution containing the coating substance to a solution in which the fiber is dispersed, and reacting it with the fiber on the surface thereof.
To describe in further detail the method for producing a composite fiber comprising a second phase evenly dispersed within a matrix fiber which pertains to the first embodiment of the present invention, the method in question is characterized in that a starting solution which serves as the second phase is mixed with a matrix starting solution to which a stabilizer has been added, an acid such as hydrochloric acid, acetic acid, or nitric acid is added to produce a precursor solution for spinning, a threadline is formed therefrom, and this fiber is heated to manufacture a composite fiber in which the second phase is evenly dispersed.
In this method, mixing in of the second phase substance is conducted prior to fiber formation, and precipitation of the second phase substance produced by reaction of the matrix with the second phase starting material is conducted during sintering.
Examples of the starting material for the matrix used in this method are alumina sources such as aluminum isopropoxide, aluminum ethoxide, aluminum butoxide, and other alkoxides, as well as salts such as aluminum chloride and aluminum nitrate. Other examples are zirconia; mullite; YAG (Y
3
Al
5
O
12
); silica; magnesia; silicon nitride, titanium nitride, aluminium nitride and other nitrides; and silicon carbide, titanium carbide, zirconium carbide, and other carbides.
Examples of the solution used in this method are ethanol, normal propanol, isopropanol, and butanol. Examples of stabilizers for the alkoxide and so on which are added to this solution are ethyl 3-oxobutanoate, citric acid, diethanolamine, and triethanolamine. Favorable proportions for the stabilizer for the alkoxide are 25 mol %-200 mol %.
Regarding the substance used in this method, where YAG is to be precipitated, examples of the starting material are yttrium isopropoxide and other alkoxides, as well as yttrium chloride and other salts. The amount of this second phase favorably ranges from 0.1 wt %-40 wt% of the total fiber weight. Below 0.1 wt %, the amount versus total fiber weight is too small to produce the desired effect. Above 40 wt %, the undesirable effects of the second phase in terms of inhibiting densification cannot be ignored. Where zirconia or other oxide is to be precipitated, examples are, for zirconia, zirconium ethoxide, zirconium propoxide, zirconium butoxide, zirconium oxyacetate, zirconium oxychloride, zirconium oxynitrate, and other salts; for mullite, examples of aluminum sources are aluminum isopropoxide, aluminum chloride, aluminum nitrate, and the like, and examples of silicon sources are ethyl silicate, silicon tetrachloride, and other combinations.
The starting materials mentioned above are added and heated to 40-70° C. using a hot plate, mantle heater, or the like. The alcohol and solution formed are gradually removed to prepare a precursor solution, which is then spun. A composite fiber is synthesized by subjecting this fiber to heat treatment at 1300-1600° C.
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