JP2593735B2 - Manufacturing method of functionally graded material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a functionally graded material having a gradient function in which characteristics continuously change from one surface to the opposite surface.

(Prior art)

For example, the materials used for the body and engine of the spacecraft are required to have excellent heat conduction properties on one side and heat resistance properties that can withstand extremely high temperatures on the other side. In order to meet this requirement, it is conceivable to use a metal and a ceramic material having excellent heat conduction properties in combination, but in this method, separation occurs due to thermal stress generated at the interface between the metal and the ceramic material. There's a problem. In order to address this problem, a concept of a so-called functionally graded material in which the composition of the material is continuously changed in the thickness direction has been proposed.

As a method of manufacturing a functionally graded material, which has been conventionally studied, a solid material is gasified to impart energy, and a physical vapor deposition (PVD) method in which the material is physically attached to a substrate or a film is formed by vapor deposition from a gas material. There are a vapor phase method such as a chemical vapor deposition (CVD) method in which a chemical reaction is caused in the process of performing, and a sintering method based on a sintering technique of powder material. These methods are described in detail in a paper by Masayuki Niino et al., "Functionally Functionally Gradient Materials-Aiming at Super Heat Resistant Materials for Space Equipment," published on pages 7 to 14 of Vol. 13, No. 6, of the Journal of the Society of Composite Materials, Japan. ing.

JP-A-63-42859 discloses a method for producing a functionally graded material by igniting a ceramic material and a metal or a mixed powder of a ceramic material and a ceramic material to cause a self-heating reaction. ing.

The various methods that have been conventionally studied do not include the melting method, which is a typical method for producing a material. The melting method has an advantage that the process is simpler than other methods.However, when this method is applied to the production of a functionally graded material, a weight segregation occurs due to a difference in specific gravity of raw materials, and a desired There is a problem that a change in the mixing ratio cannot be obtained.

[Problems to be solved by the invention]

An object of the present invention is to provide a method capable of eliminating gravity segregation which is a problem when the melting method is applied to the production of a functionally gradient material.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention is characterized in that melting and cooling and solidification of a material are performed in a zero gravity environment. That is, the method for producing a functionally graded material according to the present invention comprises a first material powder such as Cu or Ti having a high thermal conductivity and a powder or fiber of a second material such as an oxide, carbide or nitride having excellent heat resistance. The mixing ratio of the second material is the largest on the opposite surface, and the mixing ratio of the second material is the largest between the one surface and the opposite surface. Are mixed with a gradient such that they gradually increase toward the opposite surface to form a mixture, and the mixture is melted in a weightless environment while being held in a mold,
Then, it is cooled and solidified.

(Operation)

In the above-described method according to the present invention, since the melting and cooling and solidification of the material are performed in a zero-gravity environment, the material does not flow during the melting, and thus a change in the mixing ratio due to gravity segregation may occur. Absent. As a result, the manufactured material maintains the mixing ratio at the time of forming the mixture, and has a functionally graded characteristic.

In carrying out the method of the present invention, it takes about one hour to melt and cool and solidify the mixture. Therefore, it is a necessary condition that the weightless environment can be maintained for this time. At present, space is a possible zero-gravity environment. Like satellites, space shuttles,
The method of the present invention can be implemented in a space station or the like.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a functionally graded material plate 1 manufactured by the method of the present invention. This plate 1 is formed in a square shape and has a surface 1a on one side.
On the opposite side. The thickness t is 5 mm. In this example, oxygen-free copper (Cu) is selected as a material having excellent heat conduction characteristics. In addition, a material such as Ti is suitable as a raw material of the functionally gradient material. This copper is mixed with silicon oxide (SiO ₂ ). The mixing ratio of silicon oxide was as shown in FIG.
Changes continuously in the thickness direction. That is, the surface 1a of the plate 1
Is 0% in the mixing ratio with silicon oxide,
ol%. This mixture ratio continuously increases from the surface 1a to the surface 1b. Instead of silicon oxide, ThO ₂ , Al ₂ O ₃ , Y ₂ O
₃ , oxides such as Zr ₂ O ₃ and carbides such as SiC and TiC, or
A nitride such as Si ₃ N ₄ can be used.

The manufacture of this plate is performed as follows. First, copper is prepared as a powder having an average particle diameter of 1 μm. Further, as the silicon oxide, a powder having an average particle diameter of 0.1 μm is prepared. The silicon oxide need not be in the form of a powder, and for example, a fibrous form can be used. These raw material powders are charged into a mold 4 while controlling the mixing ratio using a quantitative mixer 2 schematically shown in FIG. That is, the quantitative mixer 2 is supplied with a mixture obtained by mixing a raw material powder with a volatile binder to make it flowable. The quantitative mixer 2 is controlled by the computer 3 so that the mixing ratio is continuously changed in the thickness direction of the plate. After filling, the binder mixed in the raw material is removed by evaporation.

Next, the mold 4 is placed on a press and pressurized at a pressure of about 2000 kg / cm ² to obtain a mixture, that is, a forming raw material. The pressurized material is transferred to another mold such as a glass capsule. The plurality of molding raw materials 5 thus obtained are placed in a cartridge 6 shown in FIG. 4 with the ceramic wool 7 interposed therebetween, while being contained in the glass capsule. The cartridge 6 on which the molding raw material 5 is arranged is mounted in a spacecraft and launched into space, and the spacecraft 1200
Heat to 0 ° C and hold at this temperature for about 1 hour. The heating rate is about 10 ° C / min. This heating causes the copper powder to melt. The cartridge 6 has an internal pressure of about 10 kg / cm ² when melting.
Clamp so that it is maintained. Next, the cartridge 6 is cooled to room temperature at a temperature decreasing rate of about 10 ° C./min, and
A plate 1 of a functionally graded material as shown in the figure is obtained.

(Effect)

As is clear from the above description, according to the method of the present invention, a mixture obtained by mixing a material having excellent heat conductivity and a material having excellent heat resistance so that the mixing ratio continuously changes is mixed in a weightless environment. Since it is initially melted and cooled and solidified, the functionally gradient material can be produced by a melting method without causing gravity segregation.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a plate of a functionally graded material obtained by the method of the present invention, FIG. 2 is a chart showing the change of the mixing ratio in the plate of FIG. 1, and FIG. FIG. 4 is a cross-sectional view showing a state in which the mixture obtained by mixing and molding is sealed in a cartridge. 1 ... plate, 1a, 1b ... surface, 2 ... quantitative mixer, 3 ... computer, 4 ... mold.

Continuing from the front page (72) Inventor Shunichi Minami 1-1, Kawasaki-cho, Akashi-shi, Hyogo Prefecture Inside the Akashi Plant of Kawasaki Heavy Industries, Ltd. (72) Inventor Junzo Fujioka 1-1-1, Kawasaki-cho, Akashi-shi, Hyogo Prefecture Inside the Akashi Factory (72) Inventor Haruki Hino 1-1, Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries, Ltd. Inside the Akashi Factory, Ltd. (72) Inventor Hiroyuki Matsumura 1, Kawasaki-cho, Kakamigahara-shi, Gifu Kawasaki Heavy Industries Gifu factory

Claims (4)

(57) [Claims] 1. A first material powder having a high thermal conductivity and a second material powder having an excellent heat resistance, wherein one surface is composed only of the first material powder and the other surface is composed of the second material powder. The mixing ratio of the second material becomes maximum between the one surface and the opposite surface so that the mixing ratio gradually increases toward the opposite surface. A method for producing a functionally graded material, wherein the mixture is melted under a zero-gravity environment while the mixture is held in a mold, and then cooled and solidified. 2. A first material powder having a high thermal conductivity and a second material fiber having an excellent heat resistance. One surface of the first material powder is composed only of the first material powder, and the other surface is composed of the second material fiber. The mixing ratio of the second material fiber becomes maximum between the one surface and the opposite surface so that the mixing ratio of the second material fiber gradually increases toward the opposite surface. Mixing to form a mixture, while holding the mixture in a mold,
A method for producing a functionally graded material, characterized by melting under a gravity-free environment and then solidifying by cooling. 3. The method according to claim 1, wherein said first material powder is Cu or Ti, and said second material is an oxide, carbide or nitride. 4. The method according to claim 1, wherein the melting and solidification by cooling are 1 to 100 kg / day.
A method characterized in that it is performed under a pressure of cm ² .