JPH09206582A - Extra-high pressure and high temperature generator and synthesis of cbn - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an extra-high pressure and high temp. generator in which stable high pressure can be generated by using a zirconia comprising cubic and/or tetragonal system and monoclinic system and having specified value or less in respect of Xm value calculated by specified formula to constitute a pressurizing plate. SOLUTION: In this extra-high pressure and high temp. generator, a cylinder body 1 is arranged between a pair of anvils 2, and a gasket 7 is inserted between the cylinder body 1 and the anvils 2 to form a reaction room in the center space between the cylinder body 1 and the anvils 2. Further, a pressurizing plate 3 is disposed between the reaction room and the anvil 2, and a pressure medium 9 is disposed between the reaction room and the cylinder body 1. The pressurizing plate 3 consists of such a zirconia that consists of a cubic or tetragonal system and a monoclinic system and has <=0.3Xm (including zero) calculated according to the formula I. Xm=Im(T11)+Im(111)/Im(T11)+Im(111)+1c(111) In the formula, Xm is the index of the amt. of the monoclinic crystal, Im(-111) is the integral intensity of the diffraction peak of-111 in the monoclinic system, Im(111) is the integral intensity of the diffraction peak of 111 in the monoclinic system, and Ic(111) is the integral intensity of the diffraction peak of 111 in the cubic system. crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrahigh pressure and high temperature generator, and more particularly to a tool for machining, a heat sink for semiconductor devices, etc., because it has high hardness, high thermal conductivity and is chemically stable. The present invention relates to an ultrahigh pressure and high temperature generator suitable for synthesizing diamond, cubic boron nitride (cBN) and the like, which are being utilized, and a method for synthesizing cBN using the same.

[0002]

2. Description of the Related Art Conventionally, cBN has been prepared by using hexagonal BN (hBN), which is a low-pressure phase BN, and turbostratic structure BN (tBN), etc. as a catalyst with nitrides, borides, and boronitrides of various metal elements.
Under thermodynamically stable conditions of BN, for example, a pressure of 5 to 6.5 GP
a, a catalyst method in which the temperature is maintained at 1400 ° C. to 1600 ° C., or a direct conversion method in which the temperature is maintained at a pressure of 7.5 GPa or more and a temperature of about 2000 ° C. without using a catalyst. There is. According to the direct conversion method, the synthesized cBN becomes a polycrystalline body composed of fine particles and has high hardness, high purity, high thermal conductivity, and high toughness. Expected to be used.

Conventionally, as a high-pressure and high-temperature generator, a cylinder body is provided between a pair of anvil bodies, and a gasket is inserted between the cylinder body and the anvil body, whereby the cylinder body and the anvil body are separated from each other. It is known that a reaction chamber is formed in the central space of the above, and a pressure increasing plate made of zirconia is inserted between the reaction chamber and the anvil body (Japanese Patent Publication No. 59-5547).

The reason why zirconia is used as a pressure intensifying plate is that zirconia has a low thermal conductivity and thus is excellent in heat insulation, and that it has a high elastic modulus and thus functions as a pressure transmitting plate. . However, even with such a high-pressure and high-temperature generator, it is difficult to stably generate a sufficiently high pressure, and it is difficult to stably synthesize high-quality diamond, cBN, or the like.

The present invention is an ultrahigh pressure and high temperature generator capable of stably producing high pressure and capable of synthesizing high quality diamond, cBN and the like, and synthesizing cBN having a high degree of conversion by a direct conversion method. It is intended to provide the law.

That is, the present invention has the following gist. (Claim 1) A cylinder body (1) is provided between a pair of anvil bodies (2), and a gasket (7) is inserted between the cylinder body and the anvil body to form a central space between the cylinder body and the anvil body. In a high-pressure high-temperature generator in which a reaction chamber is formed, a pressure increasing plate 3 is installed between the reaction chamber and the anvil body, and a pressure medium 9 is installed between the reaction chamber and the cylinder body. The pressure-increasing plate is made of cubic crystal and / or tetragonal crystal and monoclinic crystal, and the Xm value calculated by the formula (1) is 0.3 or less (including 0).
An ultrahigh pressure and high temperature generator characterized by comprising zirconia.

[Equation 2] (Claim 2) A method for synthesizing cBN, characterized in that the low-pressure phase BN is held under the thermodynamically stable condition of cBN by the ultrahigh-pressure high-temperature generator according to claim 1.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The ultrahigh pressure and high temperature generator of the present invention is provided with a cylinder body between a pair of anvil bodies, and a gasket is inserted between the cylinder body and the anvil body. A high-pressure high-temperature generator in which a reaction chamber is formed in the central space between the reaction chamber and the anvil body, and a pressure booster plate is inserted between the reaction chamber and the anvil body. There is a girdle type (for example, Japanese Patent Laid-Open No. 61-215293), but a flat belt type will be described below as an example.

FIG. 1 shows a schematic sectional view of a flat belt type high pressure and high temperature generator. In FIG. 1, 1 is a cylinder body, 2 is a pair of anvil bodies, 3 is a pressure booster plate, 4 is a current-carrying ring, 5 is a heater made of graphite, 6 is a Mo electrode plate, 7 is a gasket such as pyrophyllite, 8 Is a gasket such as paper, 9 is a pressure medium, and 10 and 11 are sample containers made of sodium chloride or the like. The pressure is generated by applying a load to the pair of anvil bodies. At that time, the load is distributed between the load applied to the reaction chamber through the booster plate and the load applied to the gasket. However, when the same load is applied, the larger the force applied to the booster plate, the higher the pressure in the reaction chamber. Will be higher. The heating is performed by applying an alternating current to the heater from the pair of anvils through the current-carrying ring and the Mo electrode plate.

The most important feature of the present invention is that the zirconia used as the pressure intensifying plate does not contain monoclinic crystals at all or is suppressed to a predetermined amount or less. The reason is as follows. Since the monoclinic crystal undergoes volume contraction when it undergoes a phase transition to a tetragonal crystal under high pressure and high temperature, the generated pressure is reduced. Therefore, in order to develop the high pressure required for stable synthesis of cBN,
This is because it is important to reduce the amount of shrinkage due to the phase transition, that is, to reduce the amount of monoclinic crystals.

The pressure-increasing plate used in the present invention has the above-mentioned (1).
The Xm value calculated by the formula is 0.3 or less (including 0), and preferably 0.15 or less (including 0). Here, having an Xm value of 0 means zirconia containing no monoclinic crystals. With zirconia having such an Xm value, stabilized zirconia consisting only of cubic crystals, partially stabilized zirconia consisting of cubic and tetragonal crystals, zirconia consisting only of tetragonal crystals, and further a small amount of monoclinic crystals to these. Any of the contained zirconia may be used.

An outline of zirconia will be given below. The microstructure of zirconia differs depending on the type and amount of stabilizer. A zirconia simple substance sintered body is a monoclinic crystal at room temperature, but when heated up to around 1000 ° C., it undergoes a phase transition to a tetragonal crystal and is destroyed by a volume change at that time. However, when an oxide of Y ₂ O ₃ , MgO, CaO, or the like is dissolved in zirconia, the cubic crystal of the highest temperature phase can exist as a stable phase up to a low temperature. This is so-called stabilized zirconia.

On the other hand, the minimum mol% of oxide necessary for stabilizing cubic zirconia is MgO: 13.8%, CaO: 11.2%, Y ₂ O ₃ : when solid-solved at 1500 ° C.
It is about 6%. If the amount added is less than this, 100%
Does not become a cubic crystal, but becomes a mixed phase such as a cubic crystal and a tetragonal crystal, a cubic crystal and a monoclinic crystal, a cubic crystal and a tetragonal crystal and a monoclinic crystal, a tetragonal crystal and a monoclinic crystal, or a tetragonal simple substance. These are called partially stabilized zirconia and show high strength and high toughness. What is generally called zirconia ceramics is this partially stabilized zirconia, which contains some monoclinic crystals for the purpose of improving mechanical properties. The Xm value of such partially stabilized zirconia is 0.5.
This is a degree, and is larger than the Xm value of zirconia used in the present invention of 0.3 or less (including 0).

In the present invention, when the Xm value of zirconia exceeds 0.3, the amount of deformation under high pressure and high temperature becomes large and it becomes impossible to generate high pressure. Also,
In the present invention, the smaller the porosity of the pressure booster plate, the smaller the amount of deformation under high pressure and high temperature and the higher the generated pressure.

The zirconia used in the present invention can be manufactured as follows. Basically, the zirconia powder and the above oxide powder are mixed in a predetermined amount so as to have a desired Xm value, and the mixed powder is molded and then fired. However, in order to reduce the porosity, It is desirable to use a mixed powder prepared by a liquid phase method such as a precipitation method. CIP molding is preferable for molding, and firing is performed at about 1700 ° C.

The case where MgO is used as the oxide powder will be described more specifically. First, cubic zirconia can be manufactured by firing and quenching in a region where ZrO ₂ containing MgO can exist in a cubic single phase. Normally, the firing is performed at a temperature of about 1700 ° C., so that the cubic Mg stable MgO amount is 9 to 13.8 at this temperature.
Mol%. In this case, the amount of MgO is 9 mol%
When the amount is less than that, cubic zirconia and tetragonal zirconia are easily obtained. In addition, zirconia containing monoclinic crystals,
The amount of MgO is set to 1.5 to 13.8 mol%, and calcined at about 1700 ° C. and then gradually cooled, or the calcining temperature is set to 1000 to 12
It can be produced by setting the temperature to about 00 ° C.

Next, the method for synthesizing cBN of the present invention will be described. The raw material hBN may be either powder or a compact, but is preferably a pyrolytic BN (P-BN) plate. Particularly, in the direct conversion method, it is preferable to use a P-BN plate. The raw material hBN is synthesized by placing it in a reaction chamber in a heater made of graphite or the like and holding it under the thermodynamically stable condition of cBN. The pressure and temperature conditions are
It may be carried out under the thermodynamic conditions of cBN, which is described in, for example, JP-B-59-5547, column 5, columns 28 to 37.
Listed on the line. In the direct conversion method, pressure 7G
It is desirable that the temperature is not less than Pa and the temperature is not less than 1800 ° C., and the pressure is 7.5 GPa or more and the temperature is about 2000 ° C. in order to increase the synthesis rate.

The synthesis of cBN of the present invention is not limited to the direct conversion method, and may be a catalytic method. The catalyst used in that case is described in JP-A-61-215203.
It is described on page 3, upper right column, line 13 to lower left column, line 4 of the publication.

In the synthesis of cBN of the present invention, heating can be performed under power control. That is, the relationship between the electric power and the temperature was calculated by comparing the platinum-platinum-rhodium
%) Thermocouple, Platinum / Rhodium (6%)-Platinum / Rhodium (30%) Thermocouple, Tungsten / Rhenium (5%)-
Insert Tungsten / Rhenium (26%) thermocouple,
It can be performed by measuring in advance. The pressure in the reaction chamber can be determined by measuring the melting temperature of silver loaded in the reaction chamber and comparing the pressure and the melting temperature of silver.

[0020]

EXAMPLES Hereinafter, examples and comparative examples will be specifically described.

Example 1 An ultrahigh-pressure high-temperature generator having an inner diameter of a cylinder body of 20 mm shown in FIG. 1 was prepared by adding MgO as a stabilizer. Porosity was 3.0%, and cubic and monoclinic crystals were mainly used. A partially stabilized zirconia having an Xm value of 0.15, which contained some tetragonal crystals as a phase, was used as a pressure increasing plate, and the reaction chamber was filled with a P-BN plate. Then, when a load of 500 tons was applied and the generated pressure was determined by the silver melting method, it was 7.5 GPa.

Under such a load of 500 tons, the temperature was raised to 2000 ° C. and the temperature was maintained for 30 minutes to synthesize cBN. For the obtained sample, c defined by Ic / (Ih + Ic) from the integrated intensity of hBN (002) plane and cBN (111) plane by X-ray diffraction
The conversion degree Fc into BN was measured to be 0.99.

Example 2 Generation in the same manner as in Example 1 except that the stabilizing agent was Y ₂ O ₃ and the pressure stabilizing plate was partially stabilized zirconia consisting only of tetragonal crystals with a porosity of 2.5%. The pressure was evaluated and cBN was synthesized. Table 1 shows the results.

Example 3 The stabilizing agent was MgO, the stabilizing plate was zirconia having a porosity of 4.0% and consisting of cubic crystals only, and the synthesis temperature was 1.
The generated pressure was evaluated and cBN was synthesized in the same manner as in Example 1 except that the temperature was set to 800 ° C. Table 1 shows the results.

Examples 4 to 5 Except that the stabilizer was MgO and the partially stabilized zirconia having the porosity, zirconia phase and monoclinic crystal content index Xm shown in Table 1 was used as the pressure plate. The generated pressure was evaluated and cBN was synthesized in the same manner as in Example 1. Table 1 shows the results.

Example 6 The same as Example 3 except that the stabilizer was MgO and the pressure booster plate was partially stabilized zirconia with a porosity of 3.0% and cubic and tetragonal with an Xm value of 0. Then, the generated pressure was evaluated and cBN was synthesized. Table 1 shows the results.

Comparative Examples 1 to 3 Except that the stabilizer was MgO and the partially stabilized zirconia having the porosity, the zirconia phase and the monoclinic crystal content index Xm shown in Table 1 was used as the pressure-increasing plate. The generated pressure was evaluated and cBN was synthesized in the same manner as in Example 1. Table 1 shows the results.

[0028]

[Table 1] Note: "C" in the zirconia phase is cubic, "M" is monoclinic,
"T" is tetragonal.

[0029]

According to the present invention, there is provided an ultrahigh pressure and high temperature generator capable of stably generating a high pressure. In addition, when cBN is synthesized by the direct conversion method, the degree of conversion is improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a flat belt type high pressure and high temperature generator.

[Explanation of symbols] 1 cylinder body 2 anvil body 3 booster plate 4 energizing ring 5 heater made of graphite 6 Mo electrode plate 7 gasket of pyrophyllite 8 gasket of paper 9 pressure medium 10 sample container of sodium chloride 11 Sample container for sodium chloride, etc.

Claims (2)

[Claims] 1. A cylinder body (1) is provided between a pair of anvil bodies (2), and a gasket (7) is inserted between the cylinder body and the anvil body to thereby form the cylinder body and the anvil. A reaction chamber is formed in a central space with the body, a pressure increasing plate (3) is provided between the reaction chamber and the anvil body, and a pressure medium (9) is provided between the reaction chamber and the cylinder body. In the high-pressure and high-temperature generator in which each is installed, the pressure-increasing plate is made of cubic crystal and / or tetragonal crystal and monoclinic crystal, and Xm value calculated by the formula (1) is 0.3 or less (including 0). An ultrahigh pressure and high temperature generator characterized by comprising zirconia. [Equation 1] 2. A method for synthesizing cBN, characterized in that the low-pressure phase BN is held under the thermodynamically stable condition of cBN by the ultrahigh-pressure high-temperature generator according to claim 1.