JPH0661451B2 - Ultra high pressure generator - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a facing anvil type ultrahigh pressure generator used for synthesizing diamond, cubic boron nitride and the like.

[Prior Art] Conventionally, a piston cylinder type device, a belt type device, a polyhedral anvil type device, an opposed anvil type device, etc. have been developed as an ultrahigh pressure generator. Of these, a belt type device or a polyhedral (particularly hexahedral) anvil type device is often used for industrial production of diamond and the like. This is due to the fact that these devices have the characteristics of having a relatively large reaction volume and good operability. Various improvements have been attempted in these devices, and it has become possible to generate ultrahigh pressure and high temperature of about 70 kb and 2000 ° C.

On the other hand, as a facing anvil type device, a Bridgeman anvil device is well known which uses a pair of upper and lower anvils having a truncated cone shape and a flat tip to facilitate workability. This apparatus is characterized in that an ultrahigh pressure of 100 kb or more can be generated extremely easily and stably by using a pressure medium having a simple shape, and the operability is excellent among various ultrahigh pressure generating apparatuses. As a material for the anvil, a cemented carbide having a high compressive strength is usually used. In particular, a single crystal diamond is used as the material of the anvil to further improve the pressure resistance and to generate a pressure of up to several Mb, which is used for research as a diamond anvil device.

[Problems to be Solved by the Invention] As described above, the Bridgeman anvil device is
Although it is extremely excellent in pressure resistance and operability, there are many drawbacks that limit the range of use.

FIG. 2 is a cross-sectional view showing a state in which a compressible gasket such as pyrophyllite is placed on the Bridgeman anvil and compressed. Normally, as a gasket, its shape is the same as the outer diameter of the anvil tip diameter and 10% of the anvil tip diameter.
A disc with a certain thickness is used. As will be described later, the gasket flows to the outside from the outer edge portion with the pressurization, and the super high pressure is concentrated and generated near the center of the gasket. 100
When a pressure of kb or more is generated, the gasket thickness is 3 before pressing.
Since it is about 0%, the reaction container becomes extremely small.

Further, since the gasket is thin, it is not easy to assemble the heating element inside the gasket, and it is more difficult to provide a heat insulating layer that prevents heat from flowing out to the anvil surface.

Further, when heating the pressurized sample, it is preferable to relieve the thermal stress of the anvil by cooling the frustoconical surface of the anvil. In this device, however, the cooling water gradually enters the gasket and its composition Since the flow characteristics are remarkably changed, the pressure distribution inside the gasket is changed, which causes a problem of frequent explosive ejection of the gasket during pressurization. Therefore, it is usually 100% without using cooling water.
It is considered that up to about 0 ° C is the high temperature generation limit for protecting the anvil.

As an improvement over these drawbacks of the Bridgman anvil device, for example, there is a saucer type device shown in FIG. This is a frusto-conical anvil 1a, 1b provided with a hole type 4 at the center of the tip surface, and a disk-shaped compressible gasket is arranged to pressurize the anvil 1a, 1b into a relatively thick gasket. It is possible to generate very high pressures. With this device, the thickness of the gasket increases,
Although the thermal stress load on the anvil is reduced to some extent, the hole shape in the central part of the anvil must be deepened to make the effect noticeable. There is a problem of decrease. Further, since the shape of the anvil is complicated, the anvil is easily broken. Further, the penetration of the cooling water into the gasket has the same problem as that of the Bridgman anvil device and is not improved.

Therefore, the object of the present invention is to increase the sample volume and the pressure generation efficiency without deteriorating the workability, pressure resistance, and operability similar to the conventional one, and to constantly generate a high temperature of 2000 ° C. or higher. It is to provide a facing anvil type ultra high pressure generator.

[Means for Solving the Problems] The present inventors have improved the drawbacks of the opposed anvil type device,
It has a reaction volume that can be used as an industrial production device.
The present invention has been made as a result of extensive studies to make it possible to constantly generate a high temperature of 2000 ° C. or higher at the same time as an ultrahigh pressure of 0 kb or higher.

That is, the present invention is an opposed anvil type ultra high pressure generator comprising a pair of frustoconical anvils,
An annular body made of a high molecular weight organic material exhibiting rubber-like elasticity is disposed on the tip surface of the anvil so that the center is aligned with the tip surface of the anvil, and the center of the anvil tip surface is centered inside the annular body. And a gasket disposed on the tip surface of the anvil.

[Operation] The ultrahigh pressure generator according to the present invention has a reaction volume that can be used as an industrial production apparatus by improving the drawbacks of the conventional opposed anvil type apparatus, and at the same time as the ultrahigh pressure of 100 kb or more,
It has been found that the device can constantly generate a high temperature of 00 ° C or higher.

FIG. 1 is shown below to explain the operation of the present invention. FIG. 1 is a cross-sectional view showing a state in which an object to be compressed is arranged in the ultrahigh pressure generator of the present invention. In FIG. 1, 1
a and 1b are anvils, and as the material thereof, as in the conventional case, cemented carbide, hardened steel, sintered diamond, or a combination thereof is used. 2 is a compressible gasket, which is a machined product such as pyrophyllite or talc, or a powder molded product, soft ceramics,
Ceramic fired bodies are used. Reference numeral 3 denotes a ring-shaped body made of a high molecular weight organic substance exhibiting rubber-like elasticity, and natural rubber, isoprene rubber, chloroprene rubber, nitrile rubber, silicone rubber, urethane rubber, fluororubber, chlorinated polyethylene, etc. are used. Ring 3 is anvil 1
A compressible gasket 2 is arranged on the tip surfaces of a and 1b such that their centers coincide with each other, and a compressible gasket 2 is provided inside the annular body 3 so that the center thereof also coincides with the center of the tip surfaces of the anvils 1a and 1b. Is arranged as. In FIG. 1, D ₁ is the anvil tip diameter, D ₂ is the outer diameter of the gasket, and D ₃ is the center diameter of the annular body. D ₃ needs to be less than or equal to D ₁ . h _i and d represent the initial thickness of the compressible gasket and the cross-sectional diameter of the annular body, respectively.

In FIG. 1, the cross-section of the annular body has a circular shape, but it is not always necessary to use such a shape, and it does not matter if the cross-section has an elliptical shape, a rectangular shape, or another shape. Absent. Moreover, (the thickness thereof when the cross section is other shapes) h _i and d are not necessarily match, may be in both the range of 10-20% D _1. D ₂ may be smaller than the inner diameter of the annular body 3, but if it is 30 to 70% of D ₁ , the effect is further enhanced.

Hereinafter, the operation of the ultrahigh pressure generator according to the present invention will be described in comparison with a conventional device.

The pressure generation mechanism in the simplest Bridgman anvil device among the conventional opposed anvil type devices has been analyzed by plastic mechanics, and the details are described in Japanese Journal of Applied Physics Vol. 11 No. 4 (1).
(972) pp. 578-590, "Notes for compressible gaskets and Bridgman anvil type high-pressure apparatus". That is, when a compressible gasket having the same outer diameter as the tip diameter is arranged at the tip of the Bridgman anvil for compression, the gasket is crushed from the edge portion and plastically flows out. By continuing further compression, the plastic flow region expands to the gasket center part. The pressure distribution inside the gasket when the entire gasket region is the plastic flow region is shown by the following equation.

Where dP / dr is the radial pressure gradient of the disk-shaped gasket,
τ indicates the shear strength of the gasket, and h indicates the thickness of the gasket.

When the compression is further continued, the outflow of the gasket is stopped, and the pressure increase continues due to the elastic compression. The pressure generated when the outflow stopped is about 80 kb when pyrophyllite is used for the gasket. Volume 5 of High Temperacha High Pressure (1973) 675-6
It is described on page 78.

As shown in FIG. 1, the present invention is characterized in that a compressible gasket having an outer diameter smaller than the tip diameter of the anvil and a rubber-like elastic annular body are used in combination.
In this case, the gasket gradually crushes and flows out from the outer edge portion like the conventional device, but since the initial outer diameter of the gasket is smaller than the anvil tip diameter, the diameter of the anvil that actually contributes to the compression (effective anvil). It is considered that the tip diameter) becomes relatively small, and the generated pressure efficiency increases according to the similarity rule of the apparatus shape suggested in the above-mentioned paper.
Actually, the effective anvil tip diameter also expands as the gasket flows, but at each instant in the gasket flow process, the effective anvil tip diameter is already partially plastically flown, that is, Since the gasket in the pre-compression state is pressurized, it is estimated that the generated pressure efficiency will be high. When the flowed gasket reaches the inside of the rubber-like elastic annular body in the elastically compressed state, the flow is stopped and the process moves to the elastic compression process, so that the pressure generation efficiency is further increased. The pressure sealing ability at this time is good if the above-mentioned materials are used. In addition, because the rubber-like elastic annular body also allows water to pass directly through the cooling water, which was not possible with conventional equipment, the thermal stress load on the anvil during heating is reduced and the length of the anvil is increased. The life can be extended.

[Embodiment] Embodiment 1 The ultrahigh pressure generator (D ₁ = φ100) of the present invention shown in FIG.
mm), a South African pyrophyllite disc dried at 100 ° C. (outer diameter D ₂ = φ50 mm, initial thickness h _i = 10 m
m) and neoprene rubber ring (wire diameter: d = φ8 mm, ring center diameter: D ₃ = φ92 mm) are arranged, and Bi and S
A pressure test was performed using the pressure-induced phase transition of n. For comparison, a Pyrophyllite of the same lot having an outer diameter = φ100 mm and an initial thickness = 10 mm was compressed by a Pridgeman anvil apparatus having the same shape. Along with this comparison, the resulting pressure calibration curve is shown in FIG.

From the results shown in FIG. 4, it became clear that the press load required to generate 100 kb can be reduced to about 1/3 that of the conventional case.

FIG. 5 shows the gasket thickness change in the compression process in each device. From FIG. 5, it was found that the gasket thickness at the same pressure generation was about twice that of the conventional device.

Example 2 Using the same apparatus as in Example 1, after pressurizing to 120 kb, cooling water was directly passed through the frustoconical surface of the anvil to cool it. In the device according to the present invention, the stroke change was not observed even when the cooling water was passed through while the pressure was maintained, but in the conventional device, the stroke gradually progressed, and the explosive ejection phenomenon of the gasket occurred.

Further, the apparatus according to the present invention is stable even when heated up to an estimated temperature of 2000 ° C., and it is possible to directly convert hexagonal boron nitride into cubic boron nitride to produce a strong sintered body. It was

It was possible to heat without cooling with conventional equipment, but in the above sintering experiment, cracks occurred in the anvil after repeated use several times.

[Advantages of the Invention] As described above, according to the ultrahigh pressure generator of the present invention, it is possible to generate a high pressure in the central portion of the gasket in a state where the deformation amount of the gasket is small, and a temperature that can be generated. Since the load of thermal stress on the anvil, which is one of the factors that determines the limit value of the water temperature, can be reduced by passing cooling water, 100 kb, 200
The service life is dramatically increased under the condition of 0 ° C or higher.

The present invention can be applied not only to the Bridgeman anvil device but also to a so-called saucer type device, and the same effect can be exhibited.

[Brief description of drawings]

FIG. 1 is a sectional view showing a state in which a compressible gasket is compressed by an apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a state in which a compressible gasket is compressed by a conventional Bridgman anvil device. FIG. 3 is a sectional view showing a state in which a compressible gasket is compressed by a conventional saucer type device which is an improvement of the Bridgeman anvil device. FIG. 4 is a diagram showing the relationship between the press oil pressure and the generated pressure in the first embodiment. FIG. 5 is a diagram showing the relationship between the generated pressure and the gasket thickness in Example 1 as in FIG. In the figure, 1a and 1b are anvils, 2 is a gasket,
Reference numeral 3 denotes a ring, respectively.

Claims (2)

[Claims] 1. An opposed anvil-type ultrahigh pressure generator comprising a pair of truncated cone anvils, the ultrahigh pressure generator being disposed on the tip surface of the anvil so that its center coincides with the tip surface of the anvil. A ring-shaped body made of a high molecular weight organic material exhibiting rubber-like elasticity, and a gasket arranged on the tip surface of the anvil so as to align the center with the tip surface of the anvil inside the ring-shaped body. A super high pressure generator. 2. The ultra-high pressure generation according to claim 1, wherein the gasket is a disk-shaped or disk-shaped gasket having compression deformation characteristics and friction resistance like pyrophyllite. apparatus.