JPS63291877A - Production of nonoxide ceramic - Google Patents

Abstract

PURPOSE:To obtain the titled ceramic suitable as a heating element, having specific resistance value free from variability, excellent sintering properties and dispersibility, by adding a sediment-forming solution to a mixed solution of a Ti-containing solution and an Al-containing solution, drying the prepared coprecipitated material, nitriding, firing, blending the fired material with a fixed amount of AlN and a sintering auxiliary, molding and sintering. CONSTITUTION:A mixed solution of a Ti-containing solution such as an aqueous solution of TiCl4 and an Al-containing solution such as an aqueous solution of AlCl3 is blended with a sediment-forming solution such as NH3 ammonia water to give coprecipitated Ti hydroxide and Al hydroxide. Then the coprecipitated Ti hydroxide and Al hydroxide are filtered, separated, washed with water, dried, fired in an N2-containing atmosphere such as NH3 flow at 700-1,600 deg.C, reduced and nitrided to give fired nitride powder, which is blended with AlN and a sintering auxiliary (e.g. Y2O3) in order to give a ceramic composition having the specific resistance value. The mixed powder is molded into a desired shape and sintered in a nitrogen atmosphere at 1,500-2,100 deg.C to give the titled ceramic of TiN-AlN type.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing non-oxide ceramics, more specifically, a method for manufacturing non-oxide ceramics (TiN-AJN) for heating elements (heaters).
The present invention relates to a method for manufacturing composite ceramics.

[Conventional technology]

Conventionally, heat-resistant alloys such as nickel-chromium alloys and iron-chromium-aluminum alloys have been used as heating elements in the case of metals, and silicon carbide, molybdenum silicide, etc. have been used in the case of ceramics.

However, in the case of metal heating elements, the operating temperature is 1000
The upper limit is about 1100° C., and at higher temperatures, oxidation corrosion, fusing, etc. occur, making it unusable. In the case of silicon carbide (SiC), the temperature is 1600°C, and the temperature is 1600°C.
Although silicon carbide can be used up to about 1,800℃, silicon carbide has an extremely high resistivity, making it difficult to downsize, and molybdenum silicide starts to soften at temperatures above 1,300℃.
There are problems with high temperature strength and thermal shock resistance.

In place of these materials, in recent years, composite ceramic heaters have been attracting attention in which resistivity is adjusted by mixing a non-oxide conductive material such as TiN and a non-oxide insulating material such as AIN in an appropriate ratio. When manufacturing such a ceramic heater, for example, a sintering aid is added to TiN powder and AIN powder, these are mixed in a pot, a binder is added and granulated, and then molded and sintered. I was doing it.

[Problem that the invention seeks to solve]

Such non-oxide composite ceramics (heaters) have high heat resistance, thermal shock resistance, and high-temperature strength, but because the conductive material aggregates and sinters during firing, the conductive bus is cut. There is a problem that the specific resistance value varies when the amount of TiN component decreases.

The purpose of the present invention is to eliminate variations in resistivity values of this non-oxide composite ceramic conductive material (heater) and provide a manufacturing technology that can stably control the production of non-oxide ceramics having a wide range of resistivity values. It is something.゛ [Means for solving the problem] The above purpose is the process (a) to (e): (a) T
A step of preparing a mixed solution containing a solution containing i and a solution containing A1; (b) mixing the mixed solution and a precipitate forming solution to obtain a coprecipitate by a coprecipitation method or by a sol-gel method; Step of obtaining gel; (C) After drying the obtained coprecipitate or gel,
A step of nitriding calcination at ~1600°C; (d) a step of mixing the calcined nitride obtained by nitriding calcination with AlN and a sintering aid so as to obtain a ceramic composition with a desired resistivity value; and ( e) The obtained mixed powder is molded to 1500~
This is achieved by a method for producing TiN-AlN-based non-oxide ceramics, which is characterized by comprising the steps of sintering at 2100°C.

In the case of the coprecipitation method in the production method according to the present invention, a solution containing Ti (for example, an aqueous solution of titanium chloride (TiCl 4)) and a solution containing Aj2 (for example, an aqueous solution of aluminum chloride (TiCl 4)) are used.
A mixed solution is prepared by mixing an aqueous solution of 81ces) and optionally adding water (H2O) as a solvent. It is also possible to prepare this mixed solution as an alcohol solution instead of an aqueous solution. Next, this mixed solution and a precipitate forming liquid (for example, aqueous ammonia (NH, 0N)) are mixed to obtain a coprecipitate of titanium hydroxide and aluminum hydroxide, and this coprecipitate is separated by filtration. Wash with water and dry. This hydroxide coprecipitate is subjected to a reduction nitriding treatment in which the hydroxide coprecipitate is calcined at a temperature of 700 to 1600° C. in a nitrogen-containing atmosphere to obtain a calcined nitride (powder). In this way, the Ti component of TiN, which is a conductive material, is precipitated together with the A1 component of AIN, which is an insulating material, by the co-precipitation method, and the dispersion of Ti and Al becomes very good. The dispersibility of the calcined nitride is also very good. It should be noted that if the calcination temperature is 700°C or lower, the particles tend to aggregate, while if the calcination temperature is 1600°C or higher, the particles become coarse.

Then, in order to make ceramics (heater) with a predetermined resistivity value, the obtained calcined nitride powder and the insulating material AI
N powder and a sintering aid are mixed, formed into a predetermined shape by a known molding method, and sintered at a temperature of 1500 to 2100° C. in a nitrogen atmosphere. Yttrium oxide (Y
zOs), calcium oxide (Cab), etc. can be used. If the sintering temperature is below 1500℃, sintering will be insufficient,
On the other hand, since AIN decomposes at temperatures above 2100° C., sintering is performed within a specified temperature range. In this type of sintering, there is no agglomeration of the conductive material (TiN) and the conductive material has good dispersibility, so it is possible to control resistivity over a wider range and more stably than when using normal powder mixing. The strength of the sintered body can be improved.

In addition, in the case of the sol-gel method in the production method according to the present invention, a solution containing Ti (for example, titanium alkoxide alcohol solution) and a solution containing Al (for example, aluminum alkoxide alcohol solution) are mixed, In some cases, it is processed and mixed with alcohol as a solvent (for example, ethyl alcohol) to create a mixed solution. This mixed solution can also be made as an alcoholic solution (it is also possible to make it as an aqueous solution).Next, for example, hydrochloric acid, which is an aqueous solution of hydrogen chloride, is added to this mixed solution to form an alumina-titania sol solution by hydrolysis. It is gelled at a predetermined temperature and then dried. A calcined nitride (powder) is obtained by a reduction nitriding treatment in which the obtained alumina-titania gel is calcined at a temperature of 700 to 1600°C in a nitrogen-containing atmosphere. In this case, as in the coprecipitation method described above, the dispersibility of Ti and A1 in the gel is very good, the dispersibility of the calcined nitride is also good, and a calcined nitride equivalent to that obtained by the coprecipitation method can be obtained. In addition, the calcination temperature is 7
At temperatures below 00°C, agglomeration tends to occur, while at temperatures above 1600°C, particles become coarse. The subsequent steps for producing ceramics (heater) are the same as those for the coprecipitation method described above.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiment examples of the present invention.

On the back boat (in case of coprecipitation method) 1 mole of aluminum chloride (AIlCl, 6H, O), 1 mole of titanium chloride (TiC14), 1.51
A mixed solution was prepared with water (Hgo). Add this mixed solution to 1N of 6N-ammonia water while stirring.
Gradually add (mix) at a ratio of c, with Ti'+), j
! A hydroxide coprecipitate of 3- was obtained. After washing and drying this, a reduction nitriding treatment was performed for 10 hours in an ammonia stream at 1100° C. to obtain a calcined nitride. The grain size of this calcined nitride was 0.1 to 0.3 tna.

Next, to this calcined nitride, 1.71 mol of aluminum nitride (AIN) powder with an average particle size of 0.9 and 0.0 mol of yttrium oxide (YzOi) as a sintering aid were added.
024 mol were mixed.

This mixed powder is mixed with an organic solvent as a solvent and a binder to form a slurry, molded into a predetermined shape considering the shrinkage rate, degreased at 360°C, and then heated at 180°C.
Firing was performed at 0° C. for 4 hours in a nitrogen atmosphere. Thereafter, the surface of the sintered body was polished to obtain a ceramic heater test piece with the required dimensions.

As a result of analyzing the component ratio of TiN and AlN in the ceramic heater test piece (final sintered body) produced by the manufacturing method according to the present invention, the molar ratio was TiN: Aj! N=26.9
: It was 73.1. Therefore, for comparison, comparative test pieces were prepared using the following method so that they had almost the same composition using a conventional method.

AIN with an average particle size of 0.9-, Ti with an average particle size of 0.5-
Weigh the required amount of N, A I N 72.7n+o1%
A mixed powder having a composition of 26.7 mo1% of TiN was prepared. In addition, this mixed powder contains YzO + 0.6 mo1%
A sintering aid was also mixed. This mixed powder is mixed with an organic solvent as a solvent and a binder to form a slurry, which is molded into a predetermined shape considering the shrinkage rate and heated to 360°C.
The sample was degreased and then fired at 1800° C. for 4 hours in a nitrogen atmosphere. Thereafter, the surface of the sintered body was polished to obtain a ceramic heater comparative test piece with the required dimensions.

The characteristics of the test piece according to the present invention and the comparative test piece of the obtained ceramic heater were investigated, and the results shown in Table 1 were obtained.

Table 1 As seen from Table 1, TiN −Aj! The composition of the N ceramic heater is the same between the inventive product and the comparative product, but the inventive product has improved sintering density and bending strength compared to the conventional comparative product. These results show that the raw material powder obtained using the method of the present invention allows a more complete sintered body to be obtained than the conventional product. Furthermore, the specific resistance value of the invented product was lower than that of the conventional product despite having almost the same composition. TtN
-An! N ceramics (heater) obtains conductivity (specific resistance) through a conductive bus between TiN, and S'E
Based on the observation results by M et al., ceramic-nox sintered products using the conventional method contain Ti, which is thought to have been generated during raw material mixing and sintering.
While agglomeration of N particles is observed, TiN has very good dispersibility in the sintered body produced by the invention method. It is thought that the difference in the specific resistance values described above is the result of a smoother conductive bus being formed in the invention product due to this difference in dispersibility.

Next, the specific resistance value of the ceramic heater test piece (invented product) obtained was examined by changing the ratio of AIN added to the calcined nitride obtained in the intermediate process of the manufacturing method according to the present invention described above. is shown in Figure 1. For comparison, the resistivity values of ceramic heater test pieces (comparative products) obtained by conventional powder mixing with substantially the same composition were also investigated, and the results are shown in FIG. As you can see from Figure 1,
In general, as the TiN component decreases, it becomes difficult for the conductive bus to connect (because it becomes difficult to connect the conductive bus, so the variation becomes extremely large as the specific resistance increases, especially in comparative products (conventional products).For this reason, the variation becomes very large as the specific resistance increases. In the conventional case, it was very difficult to stably obtain a specific resistance of Ω.1 unit.On the other hand, as shown in Figure 1, with the manufacturing method of the present invention, even if the TiN component is small, the specific resistance is It is suitable for industrial production because the variation in value is small.

1LfLL (for sol-gel method) Tetraisopropoxy titanium (Ti (iso-OC3
1b) t) 1 mol and s) 1 mol of aluminum isopropoxide CA13 (iso-OC,L,),
A mixed solution was prepared with 1.21 g of ethyl alcohol (CJ, OH). While stirring this mixed solution, 70 cc of 6N hydrochloric acid was added dropwise to prepare an alumina-titania sol solution by hydrolysis. This was gelatinized at 50°C and dried for 3 days. The thus obtained alumina-titania gel was subjected to a reduction nitriding treatment for 10 hours in an ammonia stream at 1100° C. to obtain a calcined nitride. The grain size of this calcined nitride was 0.05-0.3-. Next, 1 layer of AIN powder with an average particle size of 0.9- is added to this calcined product.
．． 71 mol and 0.024 mol of sintering aids y, o, were mixed.

This mixed powder is mixed with an organic solvent as a solvent and a binder to form a slurry, which is molded into a predetermined shape considering the shrinkage rate, degreased at 360°C, and then heated at 1800°C.
Firing was performed at ℃ for 4 hours in a nitrogen atmosphere. Thereafter, the surface of the sintered body was polished to obtain a ceramic heater test piece with the required dimensions.

The results of analyzing the component ratios of TiN and AJN of the ceramic heater test piece (final sintered body) obtained in this way were almost the same as in Example 1, TtN:AffiN
-26,5: It was 73.5. The characteristics of this test piece are: sintered density 3.70g/am", three-point bending strength 44kg/w", and specific resistance 2.5X10-3Q-
am, and a good sintered body comparable to the product of the present invention in Example 1 could be obtained.

〔Effect of the invention〕

As described above, by the manufacturing method of the present invention, TiN-A
In IN ceramics (heaters), the TiN component, which is the main conductive component, is extracted from the solution raw material together with the AlN component on the base side by co-precipitation or gelation, and AβN is added to this.
By additionally mixing the sinterable and conductive component (Ti
The dispersibility of N) can be improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between TiN content and specific resistance value of a TiN-AIN ceramic heater (sintered body).

Claims (1)

[Claims] 1. The following steps (a) to (e): (a) Step of preparing a mixed solution containing a solution containing Ti and a solution containing Al; (b) The mixed solution and a precipitate forming solution (c) step of drying the obtained coprecipitate and then nitriding calcination at 700 to 1600°C; (d) calcination nitriding by the nitriding calcination. and (e) a step of molding the obtained mixed powder and sintering it at 1500 to 2100°C. A method for producing TiN-AlN-based non-oxide ceramics, characterized by comprising; 2. The method according to claim 1, wherein the mixed solution is an aqueous solution or an alcoholic solution. 3. The following steps (a) to (e): (a) Step of making a mixed solution containing a solution containing Ti and a solution containing Al; (b) Step of obtaining a gel from the mixed solution by a sol-gel method (c) A step of drying the obtained gel and then nitriding and calcining it at 700 to 1600°C; (d) Adding AlN to the calcined nitride resulting from the nitriding and calcination to obtain a ceramic composition with the desired resistivity value. and (e) molding the obtained mixed powder and sintering it at 1500 to 2100°C; TiN-AlN non-oxide ceramic characterized by comprising: manufacturing method. 4. The method according to claim 3, wherein the mixed solution is an aqueous solution or an alcoholic solution.