JPH0437655A - Production of ceramic sintered body - Google Patents

Abstract

PURPOSE:To obtain the ceramics sintered body in a short period of time without requiring a pressure reducing device and a reducing gaseous atmosphere furnace by packing ceramic powder having an electrical conductivity into a nonconductive sintering mold, and electrically sintering the powder while pressurizing the powder. CONSTITUTION:The ceramic powder 1 having the electrical conductivity is packed into the nonconductive sintering mold 3 and is electrically sintered (5: a special power source, 6: switch) under the pressurization P (e.g.; pressurized and energized by punch electrodes 4, 4). The adoption of the following method is possible as well: Composite powder 9 which consists of the nonconductive ceramics 7 as a nuclear body and is coated with the conductive ceramics 8 around this ceramics is molded, and such composite powder 9 is packed into the nonconductive sintering mold 3 and is electrically sintered under the pressurization P. The conductive ceramics is exemplified by, for example, SiC, MoSi2, TiN, etc., and the nonconductive ceramics is exemplified by Al2O3, etc.

Description

[Detailed description of the invention] “Industrial Application Field 1 The present invention relates to a method for manufacturing a ceramic sintered body.

:Prior Art] Ceramic sintered bodies are generally manufactured by the method described below.

First, a binder is mixed with ceramic powder such as alumina or silicon carbide to form a clay-like plastic matrix. Next, this base material is molded into a desired shape by a mold press, a rubber press, a hollow press, an injection molding, a doctor play method, etc. (molding step). The obtained molded body is then subjected to pressureless sintering, dregs pressure sintering, hot pressing,
Sintered by HIP etc. (sintering process), ceramic
It was manufacturing Socsu sintered bodies.

[Problem to be solved by the invention] By the way, one of the factors that reduces the strength of the ceramic sintered body produced in this way is the problem of oxidation of the ceramic powder during the above-mentioned forming and sintering processes. That is, if the ceramic powder is oxidized during the forming process and sintering process, the strength of the produced ceramic sintered body will decrease.

In particular, in order to obtain a high-strength ceramic sintered body with high heat resistance, it is necessary to subject the above ceramic powder to the following conditions ■ to ■. The conditions are such that it is easy to do so.

0. Small particle size. 0. Grain shape and grain size. - It is a compound with strong covalent bonding. - High purity. - Crystal phase is controlled. - Oxygen content is low. Therefore, when manufacturing a high-strength ceramic sintered body with high heat resistance, the above ceramic powder is sintered under reduced pressure or in an atmosphere of reducing scum (82, etc.), and during the sintering process, It is necessary to prevent oxidation of ceramic powder. The time for this sintering treatment is approximately 2 to 4 hours.

However, in this case, special equipment such as a pressure reducing device and a reducing gas atmosphere furnace is required, which increases the cost. Furthermore, since the sintering process time is long, approximately 2 to 4 hours, it has been desired to shorten the time.

In addition, as a related technology, Japanese Patent Application Laid-Open No. 60-21883 “
"Method for Manufacturing Porous Ceramics" is known, but this technique is for manufacturing porous ceramics and is different from the present invention in its structure and purpose.

The object of the present invention, which was created in consideration of the above circumstances, is to provide a method for producing a ceramic sintered body that does not require a pressure reduction device or a reducing gas atmosphere furnace, and can produce a ceramic sintered body in a short time. It is something.

[Means for Solving the Problems] In order to achieve the above object, a method for manufacturing a ceramic sintered body according to the present invention includes filling a non-conductive sintering mold with conductive ceramic powder and pressurizing the ceramic powder. 6 In addition, a composite powder is formed by using a non-conductive ceramic as a core and a conductive ceramic is coated around it, and the composite powder is sintered with a non-conductive ceramic. It may be filled into a mold and sintered with electricity while being pressurized.

[Function] When conductive ceramic powder filled in a non-conductive sintering mold is sintered under pressure, a microdischarge phenomenon occurs between the conductive ceramic powder particles and the particle surface becomes active. The ceramic sintered body is sintered in a short time.

In addition, when a composite powder consisting of a non-conductive ceramic core and a conductive ceramic coated around it is used as the sintered material filled in the sintering mold, the surface of the adjacent composite powder A microdischarge phenomenon occurs between the conductive ceramics of the parts, and a ceramic sintered body is sintered in a similar short time. In this case, the ceramic powder to be used is not limited to only four-electroconductive ones (SiC, MoSi2, etc.), but also non-conductive ones (A A 20 s, etc.), which widens the selection range.

[Example] An embodiment of the present invention will be described with reference to the accompanying drawings.

First, SiC, MoSi2. Ceramic powder having conductivity such as TiN, the particle size of which is 10 μm to 100 μm
Shape to the desired degree. Then, as shown in FIG. 1, this ceramic powder 1 is filled as a sintering material into a sintering mold 3 of an electric sintering device 2. The above sintering mold 3 is A
It is a non-conductive sintered mold 3 made of I203 or the like.

The conductive ceramic powder 1 filled in the sintering mold 3 is pressurized with a predetermined pressure P by a punch electrode 4, and is also applied with a predetermined current and voltage.

That is, this punch electrode 4 is supplied with a hydraulic pressure tFl+1! for pressurizing the ceramic powder 1 in the sintering mold 3. ! (not shown), and a special power source 5 in which a high frequency is superimposed on direct current is connected via a switch 6 6 The current, voltage and pressure P of the punch electrode 4 are appropriately changed to control operation. As a result, the conductive ceramic powder 1 filled in the sintering mold 3 undergoes a micro-discharge phenomenon between the powder particles, activating the particle surface.
A ceramic sintered body is sintered in a short time of 2 to 3 minutes. At this time, since the sintering time is extremely short, oxidation of the surface of the ceramic powder 1 during sintering can be reduced, and a pressure reducing device or reducing gas atmosphere furnace for preventing oxidation is not necessary.

Furthermore, since oxidation of the surface of the ceramic powder 1 during sintering can be reduced, the resulting ceramic sintered body has uniformity and high strength.

In addition, as a sintering material filled into the sintering mold 3 during such current sintering, a conductive material is used around the non-conductive ceramic powder 7 (A, R203, etc.) as shown in FIG. A composite powder 9 coated with ceramic powder 8 (SiCMoSi2.TiN, etc.) may also be used.

In this composite powder 9, it is desirable that the particle size ratio of the non-conductive ceramic powder 7 as a core to the conductive ceramic powder 8 coated thereon is about 10:1.

As a specific coating method, the non-conductive ceramic powder 7 and the conductive ceramic powder 8 are kneaded in an electrostatic container (not shown), and the conductive ceramic powder is coated on the surface of the non-conductive ceramic powder 7. After electrostatically depositing 8,
This was placed in a container (not shown) equipped with a rotary blade of 2000 rpm to 8000 rpm, and an impact force (centrifugal transfer) was applied by high-speed airflow for several minutes to separate the conductive ceramic powder 8 and the non-conductive ceramic powder 7. The method is to combine them using van der Waals forces.

When electrical sintering is performed using this composite powder 9, the conductive ceramic powders 8 on the surfaces of the adjacent composite powders 9 in the sintering mold 3 mutually generate micro-discharges. Similarly, the ceramic sintered body is sintered in a short time.

In this case, the ceramic powder 7.8 used is not limited to conductive ones (SiC, MoSi2, TiN, etc.), but also non-conductive ones (A, C' 203
etc.) can also be used, expanding the range of material selection. In this way, since ceramic powder with well-defined properties can be used, various ceramic sintered bodies can be manufactured depending on the purpose.

Further, the obtained ceramic sintered body has high quality in which the non-conductive ceramics 7 and the conductive ceramics 8 are uniformly dispersed.

Incidentally, when handling the composite powder 9 as shown in FIG. 2, it is conceivable that the conductive ceramic powder 8 may fall off from the surface of the non-conductive ceramic powder 7.

Therefore, in order to prevent this falling off, an auxiliary agent may be interposed between the non-conductive ceramic powder 7 and the conductive ceramic powder 8 to improve their bonding properties. That is,
As shown in FIG. 3, around the non-conductive ceramic powder 7 as a core body, stearic acid substituent or Ni is placed as an auxiliary agent 10.

A heat-resistant metal such as Mo or Cr is coated, and the conductive ceramic powder 8 is further coated around the heat-resistant metal.

The ceramic sintered body obtained by the manufacturing method as described above can be applied to hot plugs for automobile engines, ceramic glow plugs, and the like.

[Effects of the Invention] As explained above, the present invention can exhibit the following excellent effects6 (1) Since sintering can be performed in a short time, oxidation of the ceramic powder surface can be reduced and oxidation prevention can be achieved. This eliminates the need for a pressure reducing device or reducing gas atmosphere furnace.

(2) Oxidation on the surface of ceramic powder can be reduced.
A uniform, high-strength ceramic sintered body can be obtained.

(3) By using a composite powder consisting of a non-conductive ceramic coated with a conductive ceramic as the sintering material filled in the sintering mold, the non-conductive ceramic and the conductive ceramic are uniformly distributed. It is possible to obtain a ceramic sintered body in which the particles are dispersed.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an electric sintering device used in a method for manufacturing a ceramic sintered body according to an embodiment of the present invention, Fig. 2 is a schematic diagram showing a composite powder, and Fig. 3 is a schematic diagram showing another composite powder. It is a schematic diagram representing the body. In the figure, 1 is a conductive ceramic powder, 2 is an electric sintering device, 3 is a non-conductive sintering mold, 7 is a non-conductive ceramic, 8 is a conductive ceramic, and 9 is a composite powder.

Claims (2)

[Claims] 1. A method for producing a ceramic sintered body, characterized in that a non-conductive sintering mold is filled with conductive ceramic powder and sintered under pressure while being energized. 2. A composite powder is formed by using a non-conductive ceramic as a core and covering the core with a conductive ceramic, and the composite powder is filled into a non-conductive sintering mold and sintered with electricity while being pressurized. A method for producing a ceramic sintered body characterized by: