JP2643357B2 - Manufacturing method of linear high density ceramics - Google Patents

Description

The present invention relates to a method for producing a linear high-density ceramic. More specifically, the present invention relates to a method for producing a high-density linear sintered body of a non-sinterable ceramic.

[Prior Art] and [Problems to be Solved by the Invention] In the case of oxide ceramics having good low-temperature sinterability, in other words, good sinterability, densification is achieved only by firing without forming at high density. Therefore, a dense linear sintered body can be manufactured by an extrusion molding method. However, high-temperature sinterable ceramics having poor sintering properties are not densified unless they are formed at a high density, so that there is a problem that it is difficult to produce a high-density linear sintered body.

An object of the present invention is to provide a method for producing a linear sintered body sintered at high density without forming high temperature sinterable ceramics at high density.

[Means for solving the problem]

The object of the present invention is to provide, from the outside of the double annular nozzle, a polymer dope solution highly blended with ceramic powder having good low-temperature sinterability, and from the inside about 50 ° C. or higher than the low-temperature sinterable powder. The ceramic powder slurry that requires high-temperature firing at a high temperature is simultaneously extruded, and immediately immersed in a gelling bath to gel the outer layer, then the firing temperature of the outer layer ceramic powder and the inner layer This is achieved by producing a linear high-density ceramic by sequentially sintering the ceramic powder at the firing temperature and removing the outer layer portion of the obtained sintered body.

Ceramic powder that has good low-temperature sinterability and ceramic powder that requires high-temperature sintering at a temperature higher than that by about 50 ° C or more (the difference in temperature at which sintering shrinkage starts to increase significantly) are the same material and have the same particle size. The sintering temperature varies greatly depending on the diameter, surface properties, amount of structural defects, type of additive and its presence, etc., but in general, oxide ceramics such as MgO, ZrO ₂ , Al ₂ O ₃ , TiO ₂ , SiO ₂ etc. have a relatively low sintering temperature and good sinterability, and non-oxide ceramics such as Si ₃ N ₄ , AlN, NbN, TiN, ZrN, BN, SiC,
B ₄ C, TiC, etc. ZrC sintering temperature is high, it can be said that sintering-resistant ceramic.

Ceramic powder having good low-temperature sinterability is extruded from the outside of the double annular nozzle as a polymer dope solution containing the ceramic powder in a high content. These ceramic powders are generally added to an organic solvent solution of a polymer substance adjusted to a concentration of about 5 to 20% by weight, and a ceramic material of about 20 to 80% by volume with respect to the total volume of the polymer substance and the ceramic. Used in the form of adding powder.

An organic solvent solution of a polymer substance in which these ceramic powders are highly blended is formed, for example, in the following combinations.

In addition, hard-to-sinter ceramic powder that requires high-temperature sintering at a temperature about 50 ° C. or more higher than low-temperature sinterable powder is extruded from the inside of the double annular nozzle using it as a slurry. The preparation of the slurry is generally carried out using liquid paraffin, an emulsion binder such as wax or polyvinyl alcohol, methylcellulose, ethylcellulose,
The main component is a binder that exhibits high viscosity in a low-concentration aqueous solution such as starch, and a plasticizer such as glycerin, lower glycols and ethanolamine, a lubricant such as stearic acid and a wetting agent such as n-butanol if necessary. Is added to the aqueous solution to which sintering is performed, and the viscosity is adjusted to about 10 ³ poise by adding a sintering aid which is also a low-sintering ceramic powder and, if necessary, the low-temperature sintering ceramic powder.

 A composition example of such a slurry is shown as follows.

100 parts by weight of ceramic powder n-butanol 2-3 メ チ ル methyl cellulose 5 ワ ッ ク ス wax (solid content 40% emulsion) 1 ス テ stearic acid (solid content 20% emulsion) 1 〃 water 33 い ず れ All of these were mixed with ceramic powder. The polymeric dope and the slurry are simultaneously extruded from the outside and inside of the double annular nozzle and are immediately immersed in a gelling bath to gel the outer layer.

After that, firing at the firing temperature of the outer layer ceramic powder and firing temperature of the inner layer ceramic powder are sequentially performed. Prior to this, calcination is generally performed. Although the calcination temperature varies depending on the type of the polymer substance used,
Approximately 400-600 ° C. The firing temperature of the outer layer ceramic powder is about 1400 to 1600 ° C, and the firing temperature of the inner layer ceramic powder varies depending on the type and mixing ratio of the core ceramic and its sintering aid. When no sintering aid is used, the temperature is about 1700-2300 ° C., and when the sintering aid is used, the firing time is about 0.5-10 hours.

If calcination is performed at such a temperature, the polymer substance is an organic substance and has already volatilized. Therefore, the outer layer portion of the obtained sintered body is removed by polishing, crushing, or other means. Thus, a linear body made of hard-to-sinter ceramics can be obtained.

〔The invention's effect〕

Simultaneously extrude a polymer dope solution containing a high content of low-temperature sinterable ceramic powder and a slurry of hard-to-sinter ceramic powder, gel the outer layer, and fire at low temperature at the firing temperature of the outer layer ceramic powder. By
The hardly sinterable ceramic linear body of the inner layer is already densely formed by the sintering shrinkage of the outer layer ceramics, and is sintered at the firing temperature of the hardly sinterable ceramic powder to obtain a dense hard sintering. A linear body of conductive ceramics can be obtained.

As described above, since the molding density is low in the conventional extrusion molding method, the sintering density does not increase particularly in the case of a non-oxide ceramic powder such as non-oxide ceramic powder, and the strength of the molded body is low. In contrast to the fact that a product could not be formed, the method of the present invention enables the formation of a dense and high-strength linear ceramic that can be used for a conductive wire, a superconducting ceramic coil, a pin for a dot printer, and the like.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 10% by weight of a dimethylformamide solution of polysulfone blended so that Al ₂ O ₃ powder (primary particle size 5 μm) occupies 40% by volume from the outside of a double annular nozzle, and Al ₂ O ₃ as a sintering aid. Of Si ₃ N ₄ to which 5% by weight was added was simultaneously extruded from the inside of the double annular nozzle as the slurry of the above formulation example under the following conditions to gel.

Dope solution flow 10ml / min Sludge flow 10ml / min Nozzle-gel bath distance 5cm Gel bath (water) temperature 10 ℃ Winding speed 10ml / min After calcining this gel at 500 ℃, then 1500 ℃ After firing for 1 hour at 1800 ° C. for 2 hours, the outer Al ₂ O ₃ layer was polished and removed to obtain a dense linear ceramic of Si ₃ O ₄ . The obtained linear ceramics had properties of a relative density of about 99% and a bending strength of 70 kgf / mm ² .

Claims (1)

(57) [Claims] 1. A dope solution containing a high-concentration ceramic powder having good low-temperature sinterability is provided from the outside of the double annular nozzle, and a temperature higher than the low-temperature sinterable powder by about 50 ° C. or more from the inside. After simultaneously extruding the ceramic powder slurry that requires high-temperature sintering at the same time and immediately immersing it in a gelling bath to gel the outer layer, the firing temperature of the outer layer ceramic powder and the inner layer ceramic powder A method for producing a linear high-density ceramic, characterized by successively sintering at a sintering temperature and removing an outer layer portion of the obtained sintered body.