JPH0475767B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a high-temperature, high-pressure device comprising a cylinder, a multistage piston comprising a plurality of spacers, and a composite multilayer gasket. (Prior art and its problems) In recent years, high-pressure synthesis methods have been widely used in the production and development of inorganic materials. In particular, diamond and cubic boron nitride, which can only be produced by high-pressure synthesis, have excellent properties. Industrial applications utilizing its high hardness and high thermal conductivity are expanding. Synthesizing and sintering these materials requires high temperatures and pressures of 40 Kbor or higher and 1400°C or higher, so high-temperature, high-pressure equipment that can easily generate high temperatures and high pressures and has a long service life is extremely important. Conventional high-temperature, high-pressure equipment can be roughly divided into three types: Bridgeman type, conical type, and polyhedral anvil type. Although the Bridgeman type is a simple device, it has the disadvantage that the volume capable of generating high pressure is small. Although the polyhedral anvil type can easily obtain high hydrostatic pressure, it is not suitable for practical use because the equipment is large and complicated, and the cost required for one high-temperature and high-pressure treatment is high. Compared to these devices, the conical type has the disadvantage that the limit of the high pressure it can generate is lower than other types, but it can generate enough high pressure required for the synthesis and sintering of diamond and cubic boron nitride. The device is relatively simple and the volume for generating high pressure can be increased, so it is in practical use. However, it is possible to stably generate high pressure even in conical type equipment, increase the volume of the high-pressure part to increase the amount of treatment in one operation, and increase the number of times the equipment can be used, all of which reduce the cost of composites. Various improvements and developments regarding the device have been made so far. The inventor of the present invention has already proposed in Japanese Patent Publication No. 12261/1983 a high-pressure, high-temperature device that has a large reaction chamber volume and has no pressure drop during high-pressure and high-temperature maintenance. The inventor further conducted detailed research on the device, and as a result, by optimizing the dimensions of the first stage spacer and gasket,
We have discovered that it is possible to develop a high-temperature, high-pressure device that is even larger than the above device. In other words, the area ratio of the first spacer to the piston pressing surface of the plurality of spacers is 70 to 90%, and the thickness of the metal gasket is preferably 15 to 25% of the total gasket thickness. By using a composite gasket, we completed a high-temperature, high-pressure device that has a large volume of high-pressure generation, can stably generate 7.7GPa, the high-pressure transition point of Bi, and can perform high-pressure synthesis treatments hundreds of times. (Means for Solving the Problems) A high-temperature, high-pressure device of the present invention is a high-temperature, high-pressure device that includes a cylinder and a piston, a gasket used in the gap between the cylinder and the piston, and a plurality of disc-shaped spacers that transmit pressure from the piston. In,
It is characterized in that the area ratio of the first stage spacer in contact with the piston to the piston pressing surface is 70% to 90%. (Function) A cross section of an embodiment of the high temperature and high pressure apparatus of the present invention is composed of a cylinder 1, a piston 2, a gasket 3, a spacer 4, a holder 5, a heater 6, and a sample 7, as shown in FIG. The cylinder 1 has a multilayer structure reinforced by press fitting or shrink fitting, and the portion having a 45° taper is made of WC-Co alloy. The piston 2 is made of a frusto-conical WC-Co alloy with a cone angle of 90° based on the principle of mass support. The gasket 3 is a composite material consisting of five layers of Teflon, ceramic, metal, ceramic, and Teflon in order to have both compressibility based on the principle of sequential pressurization and sealing of generated pressure. The spacers 4-1 to 4-3 transmit the pressure of the piston to the sample 7 and concentrate the pressure on the sample, and are made of WC-Co alloy or tool steel. The holder 5 serves as a pressure medium to transmit and equalize the pressure, and is necessary for heat insulating and insulating the cylinder when heating the sample 7. Become. The heater 6 is used to heat the sample 7 by passing an electric current through it, and is made of graphitic carbon or a metal resistor. The present invention provides optimal dimensions for spacers and gaskets in large-scale high-temperature, high-pressure equipment, and the reason for this limitation is as follows. First of all, the spacer transmits the pressure of the piston to the sample and generates concentrated high pressure.If the inner diameter of the cylinder is small (φ16 mm or less), the spacer is a device that transmits the pressure of the piston to the sample and generates a concentrated high pressure. By using a spacer, we were able to generate a sufficiently high pressure. However, when the cylinder becomes large, about 24 mm in diameter, it has become clear that geometrical limitations alone are insufficient and that the high pressure limit will not be raised unless the ratio of the first-stage spacer to the piston pressing area exceeds a certain value. In other words, if the area of the first stage spacer is smaller than 70% of the piston pressing area, it will not be possible to generate a high pressure of 7.7GPa even if the press load is increased, and if you try to generate it, the cylinder and piston may be destroyed. It became clear that he would be invited. on the other hand,
The area of the first stage spacer is the piston pressing area.
When it exceeded 90%, the tensile stress applied to the cylinder in the circumferential direction increased and the cylinder was destroyed. From the above results, the optimum area ratio of the first stage spacer to the piston pressing surface was 70 to 90%. Furthermore, in order to extend the service life of a device that can stably generate high pressure, it is important to not only increase the area ratio of the spacer.
It turns out that the structure of the gasket is important.
The load of the press is applied to the piston, the upper and lower pistons are displaced, the gap between them and the cylinder becomes smaller, and the sample and holder are compressed through the spacer, generating high pressure. If there is no gasket, the holder will flow out from the gap between the piston and cylinder, and high pressure cannot be generated.If the piston and cylinder are brought into contact to prevent the holder from flowing out, and press load is applied, the cylinder or piston may be destroyed. do. Therefore, one of the roles of the gasket is to seal the generated pressure, and the gasket material must be a material with a large shearing force. On the other hand, in order to generate high pressure by displacement of the piston, the gasket material needs to be a material that is easily compressible and deformed. As shown in FIG. 2, there is a linear relationship between the displacement amount of the piston and the generated pressure, and the maximum generated pressure increases as the piston displacement amount increases. Gaskets are required to have contradictory properties: large shearing force is better for pressure sealing, and easier compressive deformation is better for generating high pressure, so gasket materials should be made of composite multilayer materials rather than single materials. Suitable gaskets are known, for example, consisting of five layers of Teflon, pyrofluorite, steel, calcined pyrofluorite and Teflon. In this five-layer gasket, Teflon does not have a pressure-sealing effect, but it uniformizes the compressive deformation of the entire gasket, and the pyrofluorite controls the amount of compressive deformation, and the steel gasket has pyrofluorite that controls the amount of compressive deformation in the initial stage of pressurization. This is to suppress large compressive deformation and maintain compressive deformation until high pressure is generated. However, compressive deformation of the gasket deforms not only the pyrofluorite but also the steel gasket, so if the steel gasket is thin, it will break due to deformation, and the gasket will deform unevenly, so the cylinder and piston must be reinforced. Unbalanced forces occurred, shortening the service life of high-temperature, high-pressure equipment. As a result of researching the wall thickness of steel gaskets, we found that if the wall thickness of the steel gasket is smaller than 15% of the total gasket, it will break easily at high pressure and damage the equipment, and if it is larger than 25%, the shearing force of the gasket will increase. It has been found that a steel gasket wall thickness of 5 to 15% of the total gasket is appropriate for large-scale high-temperature, high-pressure equipment. (Example) An actual example will be described below. Example 1 A cylinder made of WC-Co alloy with an inner diameter of 24 mm, a piston of the same material with a pressing surface diameter of 20 mm, and a first stage spacer of 17 mm x 5 mm (72%) and 18 x 5 mm.
(81%), 3 types of 1st stage spacers of φ19 x 5 mm (90%), 1st stage spacers of φ16 x 5 mm (64%) and 2nd stage spacers. A high-temperature and high-pressure apparatus was constructed with the structure shown in FIG. 1 by preparing a spacer of φ14×3 mm and a spacer of φ12×2 mm for the third stage. Note that the value in parentheses above is the area ratio of the first stage spacer to the piston pressing surface. In addition, the gasket consists of 2 sheets of Teflon with a thickness of 0.2 mm, pyrofluorite with a thickness of 1 mm, fired pyrofluorite with a thickness of 1 mm, and 5 sheets of steel with a thickness of 0.6 mm. Five layers of fluorite and Teflon were stacked in this order. The pressure generated when the piston is pressurized is determined by inserting Bi, Tl, and Ba wire rods into the AgCl block.
(3.67GPa), Ba− (5.5GPa), Bi−
(7.7 GPa) from the change in electrical resistance associated with the phase transition. Table 1 shows the relationship between phase transition pressure and press load.

[Table] As is clear from the results in Table 1, a high pressure of 7.7 GPa can be generated as the diameter of the first stage spacer becomes larger, even if the press load is lower.
It was difficult to generate a high pressure of 5.5GPa with this spacer. Example 2 Using the cylinder and piston in Example 1, 0.2 mm thick Teflon, 1 mm thick pyrofluorite, 1 mm thick calcined pyrofluorite, 0.6 mm thick,
Prepare gaskets of 0.8 mm thick steel, and 0.4 mm and 1.0 mm thick steel gaskets for comparison, and connect the cylinder and piston with 5 layers of Teflon, pyrofluorite, steel, calcined pyrofluorite, and Teflon from the cylinder side. The piston was loaded into the gap, a load was applied to the piston, and the displacement of the piston and the load at which the steel gasket broke were measured. As shown in Table 2, the results show that a 0.4 mm thick steel gasket breaks under a load of 25 tons;
A mm-thick steel gasket had a high breaking load, but the displacement of the piston was small, making it difficult to generate high pressure.

[Table] (Effects of the invention) As is clear from the detailed explanation above, according to the high temperature and high pressure device of the present invention, in a high temperature and high pressure device having a cylinder diameter of φ24 mm or more,
It can stably generate high pressures of 7.7 GPa or higher, which is the high transition pressure of Bi. In addition, it is possible to develop a large-capacity, high-temperature, high-pressure device that can produce a large amount of composite products in a single high-pressure, high-temperature operation, and the number of times it can be used can be increased. It is possible to reduce the cost of fired products.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conical type high temperature and high pressure apparatus of the present invention, and FIG. 2 is a graph showing the results of measuring the relationship between anvil displacement and generated pressure. DESCRIPTION OF SYMBOLS 1... Cylinder, 2... Piston, 3... Gasket, 4-1 to 4-3... Spacer, 5... Holder, 6... Heater, 7... Sample.

Claims (1)

[Claims] 1. In a high-temperature, high-pressure device consisting of a cylinder and a piston, a gasket used in the gap between the cylinder and the piston, and a plurality of disc-shaped spacers for transmitting pressure from the piston, a piston of a first-stage spacer in contact with the piston. The area ratio to the pressing surface is 70% ~
A high-temperature, high-pressure device characterized by a 90% 2. The high-temperature and high-pressure device according to claim 1, wherein the gasket is a composite multilayer gasket made of Teflon, ceramic, and metal, and the thickness of the metal gasket is 15 to 25% of the thickness of the entire gasket. .