JPS5988374A - Manufacture of silicon nitride ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dioxynitride ceramic body and a method of manufacturing such a ceramic body.

It is known to obtain ceramic bodies of non-porous ceramic material containing reaction products by sintering of silicon, aluminum, oxygen d3 and nitrogen.

Due to the formation of an intergranular glass phase with low strength at high temperatures,
With such products, sintering under pressure or
Alternatively, it is necessary to heat treat the sintered product to obtain superior strength at high temperatures. of energy, and generally takes about a day.

The present invention (j) provides a method for manufacturing a ceramic body and a ceramic body manufactured using the method, which can be used at high temperatures at or near atmospheric pressure, and has high strength at high temperatures. .

The present invention combines silicon nitride with magnesium, yttrium, chromium, molybdenum, iron, manganese, tungsten,
A ceramic body by sintering a compact comprising one or more oxide sintering aids selected from the group comprising oxides of cobalt, vanadium, uranium, niracle, titanium, hanolaum, zirconium, niobium and tantalum. Provide manufacturing method.

The ceramic body is preferably produced by forming a compact from a mixture of silicon nitride powder and one or more of the oxide sintering aids, and sintering the compact. It will be done. Or again,
The ceramic body is formed by forming a compact from a mixture of silicon and one or more of the oxide sintering aids, by sintering a silicon nitride composite which is bonded by reaction = ÷ main. It may also be generated.

The present invention also provides silicon powder and oxides of magnesium, yttrium, chromium, molybdenum, iron, manganese, tungsten, cobalt, vanadium, uranium, nickel, titanium, hafnium, zirconium, niobium, and tantalum. or forming a compact with further oxide sintering aids, heating the compact in the presence of nitrogen to form a silicon nitride composite which is bonded by reaction, and then sintering the composite. The present invention provides a method of manufacturing a ceramic body by combining the ceramic bodies to form a ceramic body.

The sintering aid is preferably such that the total oxygen content of the sintered ceramic body or reaction-bonded composite, including any oxygen originating from impurities or other contaminants, is 3.
It is present in amounts ranging from 4 to 7% by weight, preferably from 4 to 7% by weight. The sintering aid is preferably present with m such that the total oxygen content is 4 to 7% by weight, preferably 5 to 6% by weight, most preferably 5.5% by weight.

Preferably it is at least one of the group of sintering aids comprising magnesium oxide, yttrium oxide and chromium oxide, preferably all three. Yttrium oxide is preferably present in an amount of 0.1 to 12% by weight, preferably 4 to 12% by weight, magnesium oxide is preferably present in an amount of 0.1 to 5% by weight, and yttrium oxide is present in an amount of 0.1 to 5% by weight.
．． Present in an amount of 1-3% by weight.

The sintering aid 11 is preferably 0.1 to 20% of the weight of the aid plus silicon nitride.

Sintering is carried out in a substantially oxygen-free atmosphere, e.g. 90% nitrogen by weight.
This is carried out in an atmosphere containing 10% by weight of hydrogen. This nitrogen-rich atmosphere is obtained by heating in a powder bed to which nitrogen can be supplied after the formation of the desired shaped ceramic body by compaction or some other forming method. The powder bed preferably contains silicon nitride, boron nitride and magnesium oxide, preferably substantially 50% by weight each.
:40:100 ratio.

The powder bed may advantageously be placed in an inert crucible.

Sintering is preferably carried out at between 1200 and 1800C, preferably at about 1700C.

The firing time may be from about 20 minutes to about 5 hours, and is generally about 2 hours. If the silicon nitride composite is initially formed from silicon compacts, the heating is preferably 120
From 0 to 1400'C, depending on the temperature used, from 72 to
It will last for 200 poems.

The invention also provides a sintered ceramic body produced by the method described above.

The ceramic body of the present invention is believed to contain silicon nitride, and analysis of the product's microstructure indicates the presence of a metallic phase. This is like a metal silicide, but
It is not believed to be a reaction product between lx and metal derived from the sintering aid.

Examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1 Silicon nitride A3 and oxide were thoroughly mixed by milling in an attrition mill using 2.0 mm diameter zirconia milling media and absolute ethanol as the dispersion. Milling time was 30 minutes at 1.00 Orpm.

The resulting slurry was filtered to remove the grinding media, dried, crushed, and sieved to yield 4 particles thicker than 250 μm. Uniform compression using latex rubber tools (1 sost
A test piece was obtained by calcination at 1600° C., which was submerged in a powder bed consisting of 40% boron nitride and 10% magnesium oxide and placed entirely in a boron nitride crucible. In an atmosphere of 90% nitrogen and 10% hydrogen,
A furnace with a molybdenum sheet heater was operated.

After 30 minutes of calcination at 1600° C., a relative density of 3.18 was obtained. The microstructure showed the presence of metallic phase. The strength of this composition on a machined bar is 600 at room temperature.
It was 350 Pa at 1200°C.

The oxygen content of the ceramic body was 5% by weight.

Example 2 , = (7) m acid milling medium (milling
The mixture was mixed in an attrition mill using absolute alcohol as the vehicle. A compact was produced by homogeneous compaction and calcined for 2 hours at 1700° C. in a powder bed of 50% silicon nitride, 40% boron nitride and 10% magnesia. Firing was performed in a substantially pure nitrogen atmosphere.

Mechanical properties Relative density 3.10-3.20 Modulus of rupture Room temperature 710 MPa 1250°C 4
70MPa W 1ebul l > coefficient (room temperature > 12.
The oxygen content of the zero fired ceramic body was 5.5% by weight.

(Left below) Example 3 Using absolute alcohol as a grinding medium for this composition 7
The mixture was mixed using a 1.1 helision mill.

A compact is produced by homogeneous compression, which is heated in nitrogen in a nitrogen-demanding furnace (i.e., a furnace whose heating rate is controlled to a certain extent by the reaction of silicon and nitrogen).
Heating to a temperature of 400°C produced a reactively bonded silicon nitride composite which was then sintered as in Example 2.

mechanical nature Rupture modulus (room temperature) 516MPa Uibull coefficient 17.5 The oxygen content of the composite was 5.51%.

Various modifications may be made without departing from the scope of the invention.

For example, other compounds or elements may be included in the sintering composition. The temperature, atmosphere, and opening during sintering may be selected to be suitable for the mixture to be sintered. When the ceramic body is formed from a mixture of silicon nitride powder and one or more of the aforementioned sintering aids, it is desirable, but not essential, to carry out the sintering in an oxygen-free atmosphere. However, the atmosphere does not need to contain nitrogen. If the ceramic body is produced by preheating a compact of silicon and one or more of the aforementioned sintering aids, the preheating is carried out in a nitrogen-containing or nitrogen-generating atmosphere to produce a silicon nitride M composite. Must be.

Above Patent R [Applicant: British Ceramic Research Association and 4 others Continued on page 1 Priority claim @ May 20, 1983 (33) United Kingdom (GB) ■8314003 0 Inventor Robert Swindells Penkhull Queens Road, Staffordshire, Stoke-on-Trend, United Kingdom (no address) The British Ceramic Research Association Limited

Claims (1)

[Claims] (1) Silicon nitride, magnesium, yttrium,
and one or more oxide sintering aids selected from the group including oxides of chromium, molybdenum, iron, manganese, tungsten, cobalt, vanadium, uranium, nickel, titanium, hafnium, zirconium, niobium and tantalum. A method of manufacturing ceramic bodies by sintering compacts. (2) The ceramic body is produced by forming a compact from a mixture of silicon nitride and one or more of the oxide sintering aids and sintering the compact. The method described in section. (3) The sintering aid is such that the total oxygen present in the sintered ceramic body is within the range of 3 to 7% by weight, including any oxygen derived from impurities or contaminants. A method according to claim 1 or 2, characterized in that: (4) the ceramic body forms a compact from a mixture of silicon and one or more of the above sintering aids, heating the compact in a nitrogen-containing atmosphere to form a reactively bonded silicon nitride composite; 2. The method of claim 1, wherein the composite is produced by sintering the composite. (5) The sintering aid is such that the total oxygen present in the silicon nitride composite is in the range of 3 to 7% by weight, including any oxygen derived from impurities or contaminants. The method according to claim 4, in which there is a special zone '1. (6) Magnesium oxide or 0°1-5 as a sintering aid
11. The method according to claim 11, wherein the content is present in an amount of % by weight. (7) The method according to any one of claims 1 to 6, wherein yttrium oxide is contained as a sintering aid. (9) The method according to any one of claims 1 to 8, wherein the total amount of the sintering aid is in the range of 0.1 to 20% by weight. (10) The method according to any one of claims 1 to 9, wherein the sintering is performed in a substantially oxygen-free atmosphere. (11) The method according to claim 10, wherein the sintering is carried out in an atmosphere of 90% nitrogen and 10% by weight hydrogen. (12) The sintering is carried out in a powder bed consisting of silicon nitride, boron nitride and magnesium oxide after forming the compact by compaction or molding, according to any one of claims 1 to 11. the method of. (13) A method according to any one of claims 1 to 12, wherein the sintering is carried out at a temperature between 1200°C and 1800°C. (14) The method according to any one of claims 1 to 1/1, wherein the sintering time is between 20 minutes and 5 hours. (15) The method according to any one of claims 1 to 14, wherein the heating is performed at a temperature of 1200 to 1400°C. (16) The method according to any one of claims 1 to 15, wherein the heat treatment is performed for 72 to 200 hours.