JPS63290676A - Method and apparatus for producing ceramic fiber reinforced body - Google Patents

Abstract

PURPOSE:To obtain a reinforced body having high strength at the specific direc tion by dispersing ceramic fiber having electric insulating property into dispers ing liquid having electric insulating property and orientating the ceramic fiber to electric field direction by impressing DC high voltage in the unidirection, to form fiber proformed material. CONSTITUTION:The dispersing liquid 3, in which the ceramic fiber 2 are dis persed in a flask 1, is filled up. The flask 1 is formed according to number and shape of the staples and electrode plates 4 for forming electric field are arranged according to the direction to be reinforced and connected with the DC sorce 5. When the DC high voltage is impressed between the electrodes 4, the ceramic fiber 2 as dielectrics are polarized with the static electric field and supply the plus and minus charges at both end, to match and orientate the direction of electric line of force. Next, the dispersing liquid 3 is removed and frozen or hardened, to obtain the forming body composing of the orientated ceramic fiber. By using this forming body as the base material, the reinforced body having high strength at the specific direction in fiber reinforced plastic, metal ceramic, etc., is obtd.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides ceramic short fibers made of plastics, ceramics, metals, etc. reinforced with ceramic short fibers. The present invention relates to a method and apparatus for producing an I-fiber reinforced body, and in particular to a method and apparatus for producing a ceramic short fiber reinforced body that can be densified with the ceramic short fibers oriented in a direction that requires strength. .

[Prior art] Ceramics are used in plastic, ceramic, or metal parts such as gas turbines, superchargers, compressors, blowers, and centrifugal separators in the fields of energy, materials, and transportation, especially parts that require high strength. mlft has been mixed to increase its strength.

Conventionally, there are fiber-reinforced plastics, fiber-reinforced metals, fiber-reinforced ceramics, etc. in which these ceramic short fibers are dispersed, but the direction of the short fibers in these reinforced bodies is random.

[Problems to be solved by the invention] However, when strength is required against loads in a specific direction, such as when strength is required in the direction of centrifugal force in rotating machine parts, the direction of the dispersed fibers may be random. If so, there is a problem in that it is possible to improve the strength to some extent in all directions, or it is not possible to improve the strength in a specific direction as desired.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for manufacturing a ceramic short fiber reinforced body having strength in a specific direction and an apparatus for manufacturing the same.

[Means and effects for solving the problems] In order to achieve the above object, the present invention disperses ceramic short fibers having electrical insulation properties at least on the surface in a dispersion liquid having electrical insulation properties, and After filling a formwork and applying a DC high voltage in one direction within the formwork to orient the ceramic short fibers in the dispersion in the direction of the electric field, the oriented ceramic short fibers are used as a base material. A method for producing a ceramic short fiber reinforced body in which a densified matrix is formed, and a formwork having at least the surface formed of an insulating material to accommodate a dispersion liquid in which ceramics mH are dispersed;
It is equipped with a pair of electrodes provided on both sides of the mold in the direction in which the ceramic short fibers are oriented, and a variable DC power source for applying a DC high voltage between the electrodes.

First, when ceramic short fibers are dispersed in a dispersion liquid, the ceramic short fibers are randomly dispersed, but when they are filled in a mold and a high DC voltage is applied from both sides, the ceramic short fibers are dispersed. Because it is polarized by the action of a DC electric field,
Each ceramic type IIN is oriented along the direction of the electric field.

Therefore, in this state, for example, in the case of a plastic reinforced material, the dispersion liquid is used as a plastic raw material liquid and the dispersion liquid is cured after orientation, or in the case of a ceramic or metal reinforced material, the dispersion liquid is removed after orientation, and the dispersion liquid is removed. The oriented ceramic short fibers are densified by impregnating them with a ceramic precursor or molten metal to obtain a ceramic short fiber reinforced body made of plastic, ceramic, or metal.

First, the ceramic short fibers and the dispersion liquid are both electrically insulating (dielectric).

This is because if the material does not have electrical insulation, a current will flow through the short fibers or the dispersion liquid when forming a direct current electric field in a later step, making it impossible to form an effective electrostatic field.

Here, the electrical insulation property is 100.0111 or more, preferably 10 Ω, cI! It is necessary to have a specific resistance higher than that.

゛ Ceramic short fibers having such electrical insulation (dielectric) include alumina, mullite, silica, silicon nitrogen, silica glass, etc. Silicon carbide with a low impurity concentration may also be used. .

In addition, even if carbon itself does not have electrical insulating properties, like carbon [1], it can have electrical insulating properties (dielectric) by coating its surface with an electrically insulating coating such as another ceramic. You can do it like this.

In addition, electrically insulating dispersions include water that hardly dissolves electrolytes, organic solvents such as hydrocarbons, alcohols, and ketones, oils, waxes, and resins that are melted by heating to become liquid. or a mixture thereof.

In addition, in the dispersion liquid, the agglomeration of ceramic short fibers is prevented,
In order to improve dispersion in the liquid, it is desirable to add a nonionic (non-electrolyte) dispersant. Additionally, the dispersion may be a slurry containing electrically insulating colloidal particles or ceramic powder.

Next, such ceramics t&lg are uniformly dispersed in a dispersion liquid, and then filled into a female mold having a predetermined shape (for example, a compressor rotor blade or a gas turbine rotor blade).

In this filling method, depending on the temperature and viscosity of the mixture, for example, if the mixture is low in viscosity at room temperature, it may be poured under low pressure such as gravity or air pressure.
℃ or higher) and has a high viscosity, it may be cast by an injection molding method equipped with a high-pressure hydraulic device or by a transfer molding method. In this case, the short ceramic fibers in the dispersion are oriented slightly parallel to the inner surface of the mold near the inner surface of the mold, but are oriented in completely random directions as a whole.

A DC high voltage is applied in a predetermined direction (for example, the blade height direction of a compressor rotor blade or a gas turbine rotor blade) to the mixture of ceramic short fibers and dispersion liquid filled in this mold, and the mixture is Creates a direct current electrostatic field.

As a result, the ceramic short fibers are dielectric, so they are polarized under the action of an electric field, and both ends of the short fibers are charged with positive and negative polarization, and because they have a degree of freedom of rotation in the dispersion liquid, the electrostatic field The short fibers become oriented in the same direction as the electric lines of force formed.

In order to generate a rotational force that orients the short fibers against the viscosity of the dispersion liquid and the resistance due to contact with the short fibers, the electric field strength to be formed must be at least IKV/cm or more,
If possible, it is desirable that it is 2 to 3 KV/cm or more.

In order to create such an electrostatic field, the formwork itself must be made of an electrically insulating material (e.g. plastic, ceramics, plaster, etc.), or at least the inner surface of the formwork must be electrically insulating. It is necessary that the material be coated or lined with a protective coating or lining.

Further, it is desirable that the electrode for forming the electric field itself has a structure in which it directly contacts the dispersion liquid in the mold, and that inclusions that reduce the electrolytic strength formed therebetween are eliminated as much as possible.

Further, at the same time as this electrostatic field is formed, ultrasonic waves may be used to further promote the dispersion and orientation of the short fibers by applying vibrations within the mold.

After the ceramic short fibers in the dispersion are oriented in the direction of the electric field as described above, the molded body is taken out from the mold while maintaining this orientation state and the overall shape of the molded body.

As a method for this purpose, the dispersion liquid is removed within the mold, or the dispersion liquid is frozen or hardened.

To remove the dispersion, the surface of the mold is made porous with a large number of pores smaller in diameter than the diameter of the ceramic short fibers, and the dispersion is absorbed and removed through the pores by capillary action. Alternatively, it is effective to apply pressure to the dispersion liquid and filter it to remove it.

Further, as a method of freezing the dispersion, the mold is kept at a temperature below the freezing point of the dispersion and then removed from the form. In this case, the mold surface temperature may be controlled to an appropriate temperature of 0° C. or lower if the dispersion is aqueous, room temperature if the dispersion is a molten wax, or above room temperature if the dispersion is a molten resin.

In addition, as a method of curing the dispersion liquid, a particularly low-viscosity resinous precursor is used as the dispersion liquid, a polycondensation or crosslinking accelerator is added to this, and then the formwork is kept at the curing temperature. harden with

By removing, freezing or hardening the oriented dispersion in this manner, the molded body can be removed from the mold without destroying the orientation of the ceramic short fibers within the molded body and the shape of the molded body.

The molded body in which short ceramic fibers are oriented in this manner is used as a base material, and this can be made into a reinforced body of any of 4A11 reinforced plastics, fiber reinforced metals, and fiber reinforced ceramics.

First, when the dispersion liquid is a plastic raw material liquid, that is, a molten plastic or a resin precursor liquid, a molded article obtained by freezing or hardening the dispersion liquid can be used as it is as a fiber-reinforced plastic.

In addition, if the plastic raw material is a hydrocarbon thermosetting resin such as phenol resin or furan resin, the plastic can be thermally decomposed to carbonize it, and then subjected to densification treatment such as impregnation into a molded body. , it can be used as a fiber-reinforced carbon material.

Similarly, this plastic raw material is made into silica by thermal decomposition of polysiloxane, polyaluminoxane, polycarposilan, polysilazane, etc.

If it produces ceramics such as alumina, silicon carbide, and silicon nitride, it can be made into fiber-reinforced ceramics by performing densification treatment such as impregnation and sintering after thermal decomposition.

Even if the dispersion is frozen or hardened when taken out of the mold, this can be removed from the molded body by heating the dispersion to evaporate, thermally decompose, oxidize, etc., resulting in a molded body containing only oriented ceramic short fibers. It can be done. Thereafter, a fiber-reinforced metal can be obtained by impregnating the voids of this molded body with molten metal and solidifying it.

After impregnating molten glass in the same way, solidify it or
Alternatively, if it is further crystallized, fiber-reinforced glass or fiber-reinforced crystallized glass can be obtained.

In addition, a ceramic precursor polymer such as a hydrocarbon resin, polysiloxane, polyaluminoxane, polycarposilan, polysilazane, or colloidal silica is added to the voids of the ceramic short fiber molded body.

By impregnating a colloidal dispersion of a ceramic precursor such as alumina sol, and then performing a densification process! ! It can be made into miscellaneous reinforced ceramics.

In addition, CVI (Chemi
cal Vapor Infiltration)
It is also possible to form fiber-reinforced ceramics by forming ceramics in the voids of a short ceramic 111ffl molded body by the method.

In addition, if the dispersion liquid is a colloidal dispersion liquid or slurry containing ceramics in the form of colloidal particles or fine powder, a molded body consisting of oriented ceramic short fibers and ceramic particles dispersed in the voids thereof. This results in a molded body that can be used as a reinforced plastic or metal body reinforced by both short ceramic fibers and ceramic particles. Further, by further densifying this molded body, fiber reinforced ceramics can be obtained.

Embodiments] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 3 show each step of manufacturing the ceramic short fiber reinforced body of the present invention. In the figures, first, as shown in FIG. Fill it with.

The formwork 1 is formed according to the shape of the part to be molded, and depending on the direction in which the part is to be strengthened, electric field forming electrode plates are placed on both sides of the formwork 1 and in direct contact with the dispersion liquid 3, as shown in FIG. 4 is provided. A variable DC power supply 5 is connected between the electrode plates 4, so that a high DC voltage can be applied between the electrode plates 4.

When the formwork 1 is filled with the dispersion liquid 3 in which ceramic short fibers 2 are dispersed, the ceramics 1 [t2 direction is random as shown in FIG. When a high DC voltage is applied between the plates 4, an electric field is formed between them, and each ceramic short fiber 2, which is a dielectric substance in the dispersion liquid 3, is polarized by the electrostatic field, and both ends are charged with positive and negative charges. It happens. Therefore, each ceramic short fiber 2 is
If it is located in a direction that intersects the direction of the electric field formed between the electrodes 4.4, a rotational force will be generated and it will be oriented to align with the direction of the lines of electric force.

Each ceramic short as above! After orienting the fibers 2, the dispersion liquid 3 is removed, frozen and hardened, and the molded body 5 made of the oriented ceramic short fibers 2 is taken out from the mold 1 as shown in FIG. The body 6 is used as a base material to be reinforced with short ceramic fibers of plastics, ceramics, or metal.

Specific Examples 1 to 5 will be described in detail below.

Example 1 Silicon carbide whiskers coated with boron nitride using the CVD method to provide electrical insulation. An aqueous solution of an insulating nonionic dispersant was dispersed as a dispersion liquid. The blade height is approximately 501m1 due to the porous resin material.
A female gas turbine model was manufactured, and a pair of stainless steel electrode plates was attached to the tip and root of the rotor blade, so that the whisker dispersion liquid could be introduced from the root.

After filling the formwork with the whisker dispersion liquid by applying air pressure of 0.2 atm, a DC voltage of 5 KV was applied between the electrodes,
The whiskers in the dispersion were oriented. Thereafter, the pressure on the dispersion liquid was increased to 9 atmospheres, and the dispersion liquid was filtered and removed through the fine pores of the resin mold, and the formed body was taken out from the mold and further dried thoroughly.

Thereafter, this molded body is placed in a CVD device and heated while feeding a mixed gas of silicon tetrachloride, methane, and hydrogen to form silicon carbide in the voids of the molded body, and silicon carbide whiskers are formed in the height direction. A gas turbine rotor blade made of fiber-reinforced silicon carbide ceramics oriented in the following manner was manufactured.

Example 2 Silicon nitride whiskers were mixed into a dispersion of a melt of polysilastyrene, which is a ceramic precursor that produces silicon carbide ceramics by heating in an inert atmosphere, and were sufficiently dispersed by heating and kneading. I let it happen. A mold in the shape of the rotor blades of a high-temperature exhaust gas fan was fabricated as a formwork, and the cavity surface of the mold was lined with mica ceramics, which had electrical insulation properties and could be machined. The structure allows for movement. Furthermore, a pair of chrome-plated electrodes were attached to the tip and root of the rotor blade, and a gate for introducing molding material was provided at the root of the blade. This mold was attached to an injection molding machine, and while the temperature of the mold was kept at 60°C by hot water circulation, the silicon nitride whisker-dispersed polysilastyrene melt was introduced, and while ultrasonic imaging was applied to the mold, the temperature between the electrodes was A DC voltage of 15 kV was applied to the blade to orient the silicon nitride whiskers in the blade height direction. Thereafter, the hot water circulating in the mold was changed to cold water to freeze the polysilastyrene in the mold, and then the mold was opened and the molded product was taken out.

Thereafter, the molded body was heated to 1,000° C. in a nitrogen atmosphere of 9.8 atm to convert the polysilastyrene in the molded body into a ceramic mainly composed of silicon carbide. Thereafter, a tetrahydrofuran solution of polysilazane, another ceramics precursor, was injected into the molded body in a vacuum container and heated to 1,200°C in a nitrogen atmosphere of 9.8 atm to form silicon nitride. A ceramic consisting of a mixture of silicon carbide was produced in a molded body. After repeating this polysilazane impregnation three times, the alumina sol was finally impregnated once. Thereafter, this compact was hot press sintered in a graphite mold filled with nitrided boron powder. This manufacturing process combines silicon nitride as a matrix, reinforced by unidirectionally oriented silicon nitride whiskers,
A fiber-reinforced ceramic fan rotor blade for high-temperature exhaust gas made of dense ceramic containing silicon carbide and some alumina was obtained.

Example 3 A molten wax prepared by mixing silicon nitride with ceramic powder containing 15% by weight of alumina and 6% by weight of aluminum nitride was used as a dispersion liquid, into which silicon nitride whiskers were mixed and dispersed. Using the same molding equipment as in Example 2,
The same mold was molded while being kept at room temperature, the silicon nitride whiskers were oriented in one direction by forming a DC electrostatic field, the wax was frozen, and the molded body was removed from the mold.

Thereafter, the molded body was heated to 500° C. in dry air to remove wax inside the molded body.

After coating this molded body with nitride powder, capsules mainly composed of silica glass are formed, and the molded body is compacted by hot isostatic pressing. turned into

By such a manufacturing method, a fiber-reinforced ceramic component was obtained which was reinforced by unidirectionally oriented silicon nitride whiskers and had a dense sialon ceramic as a matrix.

Example 4 A fan blade shell mold made using the zero-stowax method was covered with a rubber membrane to prevent water leakage, and a pair of stainless steel electrodes were attached to the tip and root of the blade, and a whisker dispersion liquid could be injected from the root. I made it.

The whisker dispersion liquid was prepared by dispersing silicon carbide whiskers coated with boron nitride to provide electrical insulation using a CVD method in demineralized water having high electrical insulation.

In this case, silicon carbide whiskers are placed in the fan blades.
It was prepared to have a body volume fraction of 5. After filling this dispersion liquid into the shell mold, a DC voltage of 5 KV was applied between the electrodes to orient the whiskers, and then the rubber film was removed, the dispersion liquid was allowed to soak through the shell mold, and it was thoroughly dehydrated by vacuum drying. . This shell mold containing whiskers was placed in a predetermined metal frame, heated to 700°C in vacuum, and aluminum alloy was injected under high pressure to obtain an aluminum matrix composite fan blade with whiskers oriented in the blade length direction.

Example 5 In RIM (reactive injection molding) or nylon injection molding, short glass fibers or a metal voice car with an insulating coating are injected into the mold, and before assimilation proceeds, a direct current electric field is applied in a predetermined direction as described above. By applying this method, the fibers in the blades of the turbocharger's compressor impeller could be aligned in the radial direction.

[Effects of the Invention] As is clear from the above explanation, the present invention exhibits the following excellent effects.

(1) By orienting the short ceramic fibers in the dispersion in the direction of the electric field using an electrostatic field, a reinforced body with high strength in a specific direction can be obtained.

(2) The oriented ceramic short fibers can be used as a base material to reinforce fiber-reinforced plastics, metals, ceramics, and the like.

(3) Since the short ceramic fibers can be freely oriented in the direction where strength is required in the reinforcing body to be molded, performance, durability, and reliability as a mechanical part can be improved.

[Brief explanation of the drawing]

FIGS. 1 to 3 are process diagrams illustrating detailed explanations of the present invention. In the figure, 1 is a formwork, 2 is a ceramic short fiber, 3 is a dispersion liquid,
4 is an electrode, 5 is a variable DC power supply, and 6 is a molded body. Patent Applicant: Ishikawajima-Harima Heavy Industries Co., Ltd. Representative Patent Attorney Nobuo Kinuya 1...Formwork 2...Ceramic short fibers 3...Dispersion liquid 4...Electrode 5...Variable DC power supply 6...・Figure 1 of molded body

Claims (5)

[Claims] (1) Ceramic short fibers having at least an electrically insulating surface are dispersed in a dispersion liquid having electrically insulating properties and filled into a mold, and a high DC voltage is applied in one direction within the mold. A method for producing a ceramic short fiber reinforced body, which comprises orienting ceramic short fibers in a dispersion liquid in the direction of an electric field, and then forming a dense matrix using the oriented ceramic short fibers as a base material. (2) Production of a ceramic short fiber reinforced body according to claim 1, wherein the dispersion liquid is a plastic raw material liquid, and after orienting the ceramic short fibers, the dispersion liquid is directly cured to produce fiber reinforced plastics. Method. (3) The dispersion liquid is a ceramic precursor liquid or a liquid containing ceramic particles, and after orienting the ceramic short fibers, the dispersion liquid is frozen, hardened, or removed to remove the shape, and then densified to form fiber-reinforced ceramics. A method for producing a ceramic short fiber reinforced body according to claim 1. (4) After orienting the ceramic short fibers, remove the dispersion from the mold, take out the ceramic short fibers from the mold, use the oriented ceramic short fibers as a base material, and use the ceramic precursor liquid or gas or molten metal. 2. The method for producing a ceramic short fiber reinforced body according to claim 1, wherein the short ceramic fiber reinforced body is impregnated with fiber-reinforced ceramics or metal. (5) A mold whose at least the surface is made of an insulating material to accommodate a dispersion liquid in which ceramic short fibers are dispersed, and a pair of electrodes provided on both sides of the mold in the direction in which the ceramic short fibers are oriented. , and a variable DC power supply for applying a DC high voltage between the electrodes.