JPS6033787B2 - Manufacturing method of ceramic sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in ceramic sintered bodies, and more particularly to a method for obtaining dense ceramic sintered bodies with excellent heat resistance by a conventional sintering method.

Dense ceramic cords with excellent heat resistance are attracting attention in various fields as being at the forefront of horizontal construction materials.

One of the typical ceramic compacts of this type is a hot-pressed silicon nitride-based firing body.

However, compared to the hot press method, the hot press method is
It is well known that there are significant restrictions on the shape that can be obtained and that manufacturing efficiency is poor. When using the ordinary feeding method, it was difficult to densify the silicon nitride ceramic aggregates, and the heat resistance was not so good.

Recently, silicon-metal-oxygen-nitrogen compounds (8'
Ceramic silk bodies whose main constituent phase is silicon nitride-based compounds are attracting attention.

However, even in this ceramic composite body, it has not yet been possible to mass-produce a compact and sufficiently heat-resistant sintered body. The present invention provides a means for obtaining a ceramic fired striped body which is dense and has sufficiently excellent heat resistance by a conventional brazing method.

The method of the present invention is a method in which a mixture of silicon nitride, oxide, and carbon is formed and solidified.

The present invention is particularly characterized by the selection of oxides and the mixing of carbon. The configuration of the present invention is as follows.

That is, at least one kind selected from carbon or a substance that can be converted into carbon by heating as a first substance, silicon nitride as a second substance, and oxides of aluminum and titanium or oxides of aluminum and titanium as a third substance. at least one substance selected from substances that can be changed into oxides, and a fourth substance selected from oxides of yttrium, lithium, manganese, calcium, neodymium, barium, strontium, and cerium, or substances that can be changed into oxides by heating. at least 1
The mixed powder with seeds is molded and then sintered.

The present invention provides a ceramic compact that is sufficiently dense and has excellent heat resistance by mixing carbon or a substance that can be converted into carbon by heating.

This carbon or a substance that can be changed into carbon by heating is thought to work as follows. In other words, the surface of silicon nitride raw material powder is originally covered with many oxide layers, but when it is pulverized, more oxide layers are generated, and this oxide layer reacts with the mixed oxide during competitive bonding to form a glass phase. form.

This glass phase has a large difference in thermal expansion from the silicon-metal-oxygen-nitrogen compound phase, which is the main phase formed by crystallization. Therefore, thermal shock causes cracks in the sintered body due to the difference in expansion between the glass phase and the compound phase. In this case, if carbon is present, it reacts with the oxidized layer during crystallization, evaporates it, and removes it from the system, which is thought to prevent or reduce the formation of the glass phase. Examples of substances that can be converted to carbon by heating include hydrocarbons with a high carbon content and low oxygen content, such as polymethylphenylene and polyethylene.

If carbon or a substance that can be converted into carbon by heating is mixed in too large a quantity, the density will decrease, so the mixing amount may be adjusted as described below.

The oxide or substance that can be converted into an oxide by heating to be used in the mixed powder in the method of the present invention described above is selected for the following reasons. The third substance forms a silicon-metal-oxygen-nitrogen compound with silicon nitride, which is the second substance,
A dense sintered body can be obtained.

The fourth substance acts as a dawning accelerator, which makes the present invention industrially more advantageous, such as reducing the sintering time and lowering the dawning temperature.

If too many oxides or substances that can be converted into oxides by heating are mixed, the oxide phase tends to be present in large amounts in the competitive body, so it is best to adjust them as described below.

The mixed powder in the method of the present invention is preferably adjusted as follows.

The total weight of the second, third, and fourth substances is 100, and the first
The third substance is 0.2 to 1 part by weight, preferably 0.5 to 7 parts by weight, and more preferably 0.5 to 5 parts by weight.
The total amount of the fourth substance is 5 to 6 parts by weight, preferably 10 to 6 parts by weight.
5 parts by weight, more preferably 25 to 50 parts by weight,
0.2 to 10 parts by weight of the fourth substance, preferably 0.2 to 10 parts by weight
The amount is 7 parts by weight, more preferably 0.5 to 5 parts by weight, and the remainder is the second substance.

The third substance is 2. Parts by weight or more. In the present invention, substances that can be changed into oxides by heating include carbonates, oxalates, sulfates, nitrates, peroxidates, chlorides, fluorides, and hydroxides.

Sintering can normally be done competitively, ie, without pressure.

The sintering temperature is preferably 1200 to 2000q0. It is particularly desirable to sinter at 1400 to 1800 qo. If sintering is performed at too low a temperature, the density will not increase, which is not preferable. Furthermore, if the temperature is too high, decomposition and sublimation will occur, which is not preferable. The sintering atmosphere is preferably a non-oxidizing atmosphere. For example, an inert gas atmosphere or a nitrogen atmosphere can be used. After molding silicon nitride powder mixed with the additives shown in the Examples table, it was sintered in a nitrogen atmosphere at 1700 oo for 2 hours, and the relative density % based on the theoretical density and thermal shock resistance were measured.

The thermal shock resistance value was determined by rapidly cooling the bran compact in water at 2,500 °C from various temperatures, determining the temperature at which cracks occur, and determining the difference between the temperature at which cracks occur and the water temperature (ΔTc). The size of the sample was 20 mm in diameter and 5 willow in length.
From the table, it can be seen that the products produced by the manufacturing method of the present invention have thermal shock resistance of approximately 400° C. or higher and a density of 85% or higher.

table

Claims (1)

[Claims] 1 At least one kind selected from carbon or a substance that can be converted into carbon by heating as the first substance, silicon nitride as the second substance, and oxides of aluminum and titanium or oxides of aluminum and titanium as the third substance. at least one substance selected from substances that can be changed into oxides, and a fourth substance selected from oxides of yttrium, lithium, manganese, calcium, neodymium, barium, strontium, and cerium, or substances that can be changed into oxides by heating. at least 1
A method for manufacturing a ceramic sintered body in which a seed and a mixed powder are molded and then sintered, wherein the mixed powder contains the second, third, and fourth substances in terms of oxides. Assuming the total weight of the 4th substance as 100, the 1st substance is converted to carbon and is 0.
．． 2 to 10 parts by weight, and the total amount of the third and fourth substances is 5 to 10 parts by weight.
60 parts by weight, the fourth substance is 0.2 to 10 parts by weight, and the remainder is the second substance.