SU902801A1 - Apparatus for producing high pressure and temperature - Google Patents

Description

(5) DEVICE FOR CREATING SECOND PRESSURE AND TEMPERATURE

The invention relates to a technique {high pressures, and 1 'to devices for creating high pressure and temperature used in the synthesis of diamond, cubic boron nitride and other superhard materials.

A high pressure device is known that contains two punches with recesses, between the cotors w there is a container made of heat and electrically insulating material with an opening for accommodating the SP sample.

When such a device is loaded, large pressure gradients occur in the material of the container, with a maximum of pressure near the edges, which limit the cavities in the punches. In the central part of the container, where the sample is placed, the pressure is significantly lower. The presence of a pressure peak near the edges of the depressions increases the likelihood of spontaneous release of container material under

pressure, which reduces reliability.

A more favorable pressure distribution over the volume of the container is achieved in devices equipped with steel gaskets separating 1 container into parts adjacent to the parts of the device between which the container is compressed.

The closest in technical essence is a device containing two punches, a container for a specimen and a steel core, which divides the container into two parts adjacent to the punches. The gasket is separated from the sample by a sleeve made of thermally electrically insulating material installed in the opening of the container 23.

However, in the process of compressing the container, when the pressure is created, there is a significant plastic deformation of the gasket, which is accompanied by its destruction. In laying

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annular gaps are formed, located in the area along the edges of the recesses in the punches, as well as a set of randomly arranged radial gaps. The presence of steel gasket in the container worsens the operating conditions of the device when the sample is heated to a high temperature. Due to the high thermal conductivity of the gasket material, it removes a large amount of heat from the central part of the container heated to a high temperature to its periphery. An increase in the temperature of the container, moreover uneven due to gasket breaks, leads to a change in plastic and to a decrease in the strength characteristics of the material of the container, significantly increasing the probability of spontaneous emission of the material of the container from the area of high pressures outside the device. This reduces the reliability of the device in operation. In addition, heat removal through the gasket requires additional energy to heat the sample.

The aim of the invention is to increase the reliability of the device and reduce energy consumption during heating.

The goal is achieved by the fact that in a device containing a die and / or punches, a container for a sample and a gasket, which divide the container into parts adjacent to the die and / or punches, the gaskets are made of electrically insulating material with an internal friction coefficient equal to O, 1 -0, 8 coefficient internal container material tren1.

Taking into account that the value of the coefficient of internal friction of the material depends on the pressure, the ratio of the internal friction coefficients of the gasket and container materials is determined for the range of operating pressures in which the device operates.

Due to the fact that the coefficient of internal friction of the gasket material is less than the coefficient of internal friction of the container material, when creating pressure, the container material moves along the gasket from the area with the pressure peak (area along the edges of the recesses in the punches) to the central part of the container with a lower pressure, which leads to sn14

pressure gradient. The effect of pressure equalization depends on the ratio of the coefficients of internal friction of the materials of the container and the gasket. Thus, if the coefficient of internal friction of the gasket material is no more than 0.8 of the coefficient of internal friction of the container material, the effect of pressure equalization over the volume of the container becomes statistically significant. Further reduction of the coefficient of internal friction of the gasket material up to values of the order Q, 1 from the value of the coefficient of internal friction of the material of the container leads to a more significant effect of pressure equalization over the volume of the container.

It is impractical to use gaskets with an internal friction coefficient less than 0, 1 coefficient of internal friction of the container material, since in these cases it is not possible to achieve a further decrease in the pressure gradient over the volume and increase the reliability of the device. At the same time, the gasket is squeezed out of the container area with the pressure peak and its central part at the initial load of the device and does not lead to a noticeable decrease in the pressure gradient when the device is loaded in the operating pressure range.

Since the gasket is made of a material more plastic than the container, when the device is loaded, the gasket is evenly deformed together with the plastic deformation of the container.

Considering that the thermal conductivity of electrically insulating materials is of one order, the thermal conductivity of materials used to make container and gasket is also comparable and much lower than that of metals. The execution of the strip of material with low thermal conductivity leads to a decrease in energy consumption when the sample is heated.

Thus, by uniformly deforming the gasket II and loading the device, reducing the pressure gradient throughout the container and lowering its temperature when the sample is heated, the reliability of the device increases and the energy consumption is reduced. 5. Figure 1 shows a dual punch device, a slit; figure 2 - shestipuansonny device, section; on fig.Z part of the container six-punch device. The device shown in fig.t consists of two punches 1 and 2 with recesses, between which a container of heat and electrically insulating material is mounted. The container is made detachable along the plane A-A and consists of two parts 3 and, between which a gasket 5B is placed, an opening made in the container re, sample 6 is installed. Around the container, in the gap between the punches, the coupling 7 is installed in the form of a ring of plastic material. The device shown in figure 2, consists of six equally spaced in the space of the punches 8 in the form of truncated regular tetrahedral pyramids. Between the punches 8 in the center of the device container is installed. The container is made up of six separate parts of four parts 9 with gaskets 10 and two parts of a tic gasket Q1 12. The container is formed of a cubic cavity for placing the sample 13 The device is equipped with a heater T and a sleeve 15-B 3 of the plastic material is installed between the punches 8. Parts of container 9 differ from parts 11 only in that they have no hole through which heater 1 passes in part 1 1. Traditional materials are used to make containers: pyrophyllite, lithographic stone, etc. Gaskets are made from. material with a lower coefficient of internal workout — sodium chloride, hexagonal boron nitride, fluoroplastic, etc. Couplings are made of rubber, rubber, and other plastic materials. Gaskets can be made either by pressing, for example, from sodium chloride, or by the method of casting, for example, from fluoroplastic. It is possible to use as gaskets and powder fillings, but it is less convenient to use. The gasket is recommended to be made from a few tenths to one to two millimeters thick, depending on the conditions and objectives of the experiment. It is difficult to make 1 thinner panels, and the use of gaskets with more solid material is impractical, since it does not lead to a further decrease in the pressure gradient over the volume of the container loading device. The operation of the devices is carried out in the following way. To create; 4 pressures, using a press, compress the puamsox 1, 2 or 8. Subsequently, the container 3 or container consisting of parts 9 with sample 6 and m 13 located in it (in the synthesis of superhighs x - reactionary 1) and gaskets 3 or 12, creating a high pressure. When compressing, a part of the container and gaskets | || is pressed into the gaps between the points: they form a burr, I seal (the high-pressure cavity formed by the punches. Nufts 7, 6 contribute to uniform burr formation. Gaskets S 12 benefit a gift to a low coefficient of internal friction, helps to equalize the pressure over the container volume Hz} and its compression. After the pressure is created, the sample (reaction mixture) is heated, and dp is passed an electric current either directly through the sample b when the mixture is electroconductive or heater N. A comparative test of a known and attached device was carried out in the process of synthesizing diamonds of the ASC and ACC grades. In the course of testing, devices containing punches with spherical depressions (diameter of 55 mm, depth B, 5 mm, orifice diameter for accommodating the reaction mixture — a homogeneous mixture of grated powders and soluble metal — 30 g of reaction mixture 32 g) were used. The results of the test are presented in table. The proposed device is more reliable due to the decrease in the amount of depressurization of the high-pressure cell and reduces the energy consumption during heating by 23.

Claims (2)

1. USSR author's certificate №, cl. At 01 J 3/06, 1970. 2. US patent number 29, cl. 25-77, 19ВО (prototype). J / " sixteen 12 12 ff Fchg 2