JP2010254529A - Method for producing diamond and shock compression apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a diamond in which the diamond, which comprises fewer particles each having an acute portion and is larger in the primary particle diameter in comparison with the case of a cluster diamond to be obtained by an explosion method, can be obtained by subjecting the cluster diamond to shock compression treatment, and to provide a shock compression apparatus. <P>SOLUTION: The method for producing the diamond comprises: a first step of mixing the cluster diamond homogeneously with metal powder, compacting the obtained mixture 3 under pressure and housing the obtained compact in a metallic sample tube 1; a second step of subjecting the compact 3 housed in the sample tube 1 to the shock compression treatment using an explosive 10; a third step of cutting the sample tube 1 after the shock compression treatment to recover the contents; and a fourth step of chemically purifying the recovered contents to remove impurities. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a diamond capable of obtaining a diamond having a smaller primary portion and a larger primary particle diameter by impact compression treatment of cluster diamond obtained by an explosion method, and impact compression. It relates to the device.

  Conventional types of artificial diamond include single-crystal diamond produced by a static pressure method (or high-temperature and high-pressure method) and polycrystalline diamond produced by an impact compression method, which have been widely used as polishing materials and cutting materials. It was. Of these, polishing materials used in the fields of electronic materials and optical materials require high-precision precision polishing. However, single crystal diamond has a sharp edge surface, which causes scratches on the object to be polished. There is a problem that the processing speed is remarkably reduced once it wears because it is easy and there are few blade surfaces on the particle surface.

In order to solve this problem, by heating single crystal diamond in an inert gas atmosphere, the edge of the particle surface becomes obtuse to reduce scratches, and by forming fine cracks, cracks are removed from the cracks in the polishing process. A method is also disclosed in which particles break down to create a new blade surface and increase the processing speed (see Patent Document 1).
Polycrystalline diamond forms primary particles in the state that several to tens of nanometers of crystallites are sintered, and in the polishing process, the particles fall from the sintered part to produce a new blade surface. In addition, since the machining speed is high and the blade surface is relatively obtuse, the scratches are relatively few.
However, technological innovation in the electronic material field and optical material field is remarkable, and polishing of hard disks and magnetic heads, for example, requires a mirror-finished finish with extremely little scratches. Single crystal diamonds and polycrystalline diamonds that form diamonds are not suitable because the strength of the particles is too strong, and the particles that collapse during the polishing process are large and have corners, so there is a limit to reducing scratches. It was.

On the other hand, in recent years, cluster diamond has been developed that is produced by exploding a high-performance explosive having a negative oxygen balance in an explosion container filled with water or an inert gas (see, for example, Patent Document 2). In this cluster diamond, spherical primary particles of about 3 to 6 nm are aggregated to form a tuft shape, and the aggregation force is relatively weak. For this reason, there is no sharp blade surface, and the aggregates collapse relatively easily during the polishing process. Therefore, scratches are less likely to occur compared to the above-mentioned polycrystalline diamond or single crystal diamond, which is suitable for mirror finishing.
However, this cluster diamond has a problem that the processing speed is remarkably lowered when the hardness of the object to be polished is high because the primary particles are too small.

A diamond synthesis method is disclosed in which 50 to 100 μm plate-like graphite powder and 50 μm flake-like copper powder are mixed and then subjected to impact compression (see Patent Document 3).
However, what is obtained by this manufacturing method is polycrystalline diamond, and the crystallite size of the diamond obtained as Example 2 is as large as 230 nm. Moreover, it is described that the particle size is 40 to 120 μm when observed with an electron microscope, and it is only changed to 30 to 100 μm even when pulverized with a ball mill. Moreover, since the crushing strength is too strong, it is estimated that it is not suitable for precision polishing.

JP 2001-329252 A (page 6) JP 2007-269576 A (pages 8-9) Japanese Patent Publication No. 6-93995 (page 6)

  The object of the present invention is that the number of sharp corners of the particles is small, and the primary particle diameter is made larger than that of the cluster diamond before the impact compression treatment, so that scratches are hardly generated in the polishing process in the electronic material field and the optical material field. It is an object of the present invention to provide a method for producing diamond capable of obtaining a diamond having a high speed.

  In order to solve the above-mentioned problems, the present inventors have intensively studied a method for producing a diamond having a new crystalline state. As a result, the cluster diamond and the metal powder are mixed, and the mixture is pressure-molded into a metal sample tube. The present invention has been completed by finding that the problem can be solved by storing and subjecting it to impact compression treatment and then performing chemical purification after recovery.

  The first invention of the present invention is a first step of uniformly mixing cluster diamond and metal powder, press-molding the mixture and storing the mixture in a metal sample tube, and an explosive in the molded body stored in the sample tube A second step of performing an impact compression treatment using the above, a third step of recovering the contents by cutting the sample tube after the impact compression, and a fourth step of removing impurities by chemical purification of the recovered contents It is related with the manufacturing method of the diamond characterized by comprising these processes.

  The second aspect of the present invention also proposes a method for producing diamond characterized in that, in the method for producing diamond, the mixing ratio (mass ratio) of cluster diamond / metal powder is 1/99 to 20/80. To do.

  According to a third aspect of the present invention, in the diamond production method, analysis is performed using an X-ray diffractometer (scanning speed: 2.000 ° / min, sampling width: 0.020 °), and the (111) plane of the diamond crystal is analyzed. A method for producing diamond characterized in that the crystallite diameter after impact compression treatment calculated from Scherrer's equation from the peak derived from (39.0 to 48.0 °) is 30 to 200% larger than before treatment I also propose.

  According to a fourth aspect of the present invention, there is provided a metal sample which performs the impact compression treatment of the first and second steps in the diamond production method, and which is hermetically filled with a mixture of cluster diamond and metal powder. The tube is positioned in the flight tube across a circumferential space, the flight tube is installed in the center of the explosive container, and the explosive is filled so as to cover the flight tube, and a detonator is attached to the upper portion of the explosive. We also propose an impact compression device characterized by this.

  In the first invention of the present invention, since the cluster diamond obtained by the explosion method is subjected to an impact compression treatment, the number of sharp corners of the particles is small, and the primary particle diameter is larger than that of the cluster diamond before the impact compression treatment. In the polishing process in the field or optical material field, it is possible to obtain a diamond that hardly causes scratches and has a high processing speed.

  In the second aspect of the present invention, the effects as the pressure medium and the cooling medium are sufficiently exhibited, and the production efficiency is improved.

  The third invention of the present invention is more excellent in terms of the effects of the first invention.

  In the fourth invention of the present invention, the impact compression process of the first and second steps of the first invention is performed. When the detonator is detonated and the explosive is detonated, the flight tube is accompanied by a sample. Projected in the direction of the tube, the sample tube receives the shock wave, and the sample filled in the sample tube is compressed at a high pressure. Thereafter, both ends of the sample tube are cut, the sample is taken out, and subjected to chemical purification to remove impurities such as metal powder, sand, and graphite, thereby obtaining the target diamond.

It is sectional drawing which shows typically the impact compression apparatus which performs the 2nd process of the manufacturing method of the diamond of this invention. 2 is a copy of a transmission electron micrograph of a raw material cluster diamond used in Example 1. FIG. 2 is a copy of a transmission electron micrograph of diamond after shock compression treatment obtained in Example 1. FIG.

1: (Metal) Sample tube 2: Bottom plug 3: Sample (mixture, molded product)
4: Upper plug 5: Fixing ring 6: Flight tube 7: Space 8: Explosive container 9: Conical cap 10: Explosive 11: Booster explosive 12: Detonator

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing diamond according to the present invention includes a first step of uniformly mixing cluster diamond and metal powder, press-molding the mixture and storing the mixture in a metal sample tube, and an explosive in the molded body stored in the sample tube. A second step of performing an impact compression treatment using the above, a third step of recovering the contents by cutting the sample tube after the impact compression, and a fourth step of removing impurities by chemical purification of the recovered contents It consists of the process.
Below, it demonstrates for every process.

  In the first step, cluster diamond and metal powder are uniformly mixed, and the mixture is pressure-molded.

  The primary particle diameter of cluster diamond used as a starting material is usually about 3 to 6 nm. The bulk density is preferably 0.3 g / cm 3 or more. If the bulk density is lower than 0.3 g / cm 3, sufficient pressure cannot be exerted when the metal powder is mixed with the metal powder and pressure-molded, so that voids are formed in the molded body, and sufficient effects in the impact compression treatment are not exhibited. In addition, as a synthesis method of this cluster diamond, (1) the pressure vessel is filled with a gas inert to the carbon atoms in the explosive, and the explosive is exploded in that, and (2) the explosive in water. There is no particular limitation on the production method, and for example, the method of Patent Document 2 may be adopted.

  Further, the metal powder is a pressure medium at the time of impact compression, and acts as a cooling medium for preventing cluster diamond from being graphitized due to high temperature being applied at the time of impact compression. As the kind of metal powder, gold, silver, copper, iron, nickel and the like are used, but copper powder is preferable in view of easiness of chemical purification, cooling effect, cost and the like. Furthermore, in order to uniformly mix the cluster diamond and the metal powder and to exhibit the effect as a pressure medium and a cooling medium, it is desirable that the filling property is good. About 100 μm is preferable.

  The mixing ratio (mass ratio) of the cluster diamond / metal powder is preferably 1/99 to 20/80, more preferably 2/98 to 10/90. When the cluster diamond is more than 20% by mass and the metal powder is less than 80% by mass, the effect as a pressure medium and a cooling medium is not sufficiently exhibited, the cluster diamond is less than 1% by mass, and When the amount of the metal powder is more than 99% by mass, the production amount of the cluster diamond as a raw material is reduced, so that the production efficiency tends to be lowered.

  In this first step, a mixture of cluster diamond and metal powder is pressure-molded with a hydraulic press or the like and accommodated in a metal sample tube. After molding using a press mold, the molded body is sampled into a sample tube. Alternatively, the mixture may be directly placed in a sample tube and pressure-molded stepwise. In order to enhance the impact compression effect, it is preferable that the porosity of the pressure-molded sample is low. However, in order to reduce the porosity to less than 5%, it is necessary to use a special apparatus. Therefore, the porosity is preferably 5 to 50%, more preferably 5 to 30%. The material of the sample tube is preferably iron, brass, carbon steel, stainless steel, chrome steel or the like in terms of strength and cost.

Next, in the second step, the molded body accommodated in the sample tube in the first step is subjected to an impact compression treatment using an explosive.
A sample tube containing the molded body is placed in the center of another cylindrical metal container (flying tube) via an O-ring. This is arranged at the center of another cylindrical container (explosive container), and the space between the flight tube and the explosive container is filled with the explosive. The type of explosive to be used increases the impact compression effect in consideration of the mass ratio of cluster diamond / metal powder, the porosity of the molded body, the size of the space between the sample tube and the flying tube in which the molded body is embedded, etc. Should be selected. However, if the detonation pressure of the explosive is too high, the sample tube is destroyed and the internal sample leaks to reduce the recovery amount. If the detonation pressure is too low, the intended effect cannot be obtained. For this reason, dynamite, hydrous explosives, ammonium nitrate explosive (ANFO), trinitrotoluene (TNT), etc. are usually used as explosives. The material of the flight tube is preferably iron, brass, carbon steel, stainless steel, chrome steel or the like in the same manner as the sample tube in terms of strength and cost. The material of the explosive container may be selected depending on the type and amount of the explosive, but usually a metal such as iron or stainless steel, a resin, cardboard, or the like is used.

In the third step, the sample tube after impact compression is cut to recover the contents.
After the impact compression, the sample tube is cut at both ends using a cutting machine, and then the compressed contents are removed using a hydraulic press or the like.

In the fourth step, impurities are removed from the collected contents by chemical purification.
Impurities are removed from the extracted contents by chemical purification, and the target diamond is recovered. Examples of impurities include metal powder mixed with raw material cluster diamond. For example, when copper powder is used, it can be removed by dissolution treatment with nitric acid or aqua regia. Moreover, when sand etc. mix at the time of a synthesis | combination, it can melt | dissolve and remove with hydrofluoric acid. Further, when a part of diamond is phase-converted to graphite due to high heat applied in the impact compression treatment, the graphite can be removed by a sulfuric acid mixed acid treatment or heat oxidation in the presence of oxygen.

  Then, it demonstrates in detail using figures. FIG. 1 is a cross-sectional view of an impact compression processing apparatus used in the diamond manufacturing method of the present invention. A bottom plug 2 is arranged at the bottom of the metal sample tube 1, a sample 3 which is a molded product of cluster diamond and metal powder is loaded on the top of the bottom plug 2, and an upper plug 4 is mounted on the top. And seal. On the outside of the sample tube 1, a fixing ring 5 having a uniform circumferential width is attached to both the upper and lower ends, and the flying tube 6 is installed concentrically with the sample tube 1 via the fixing ring 5. Therefore, a circumferential space 7 having a certain width is held between the sample tube 1 and the flight tube by the fixing ring 5.

  The flying tube 6 containing the sample tube 1 is installed in the center of a cylindrical explosive container 8 having a bottom, and a conical cap 9 is placed on the flying tube 6. The explosive 10 is filled so as to cover the flying tube 6 and the conical cap 9. A booster explosive 11 is placed on the top of the explosive 10, and a detonator 12 is attached to the upper portion of the explosive 10 so as to be the center of the circumference of the explosive container 8. The booster explosive 11 can be omitted depending on the explosive nature of the explosive 10.

Next, the impact compression method will be described. When the detonator 12 is detonated, the explosive 10 is detonated through the booster explosive 11. With the detonation, the flight tube 6 is projected in the direction of the sample tube 1, the sample tube 1 receives the shock wave, and the sample 3 filled in the sample tube 1 is compressed at high pressure.
Further, the shock wave caused by the detonation of the explosive 10 can be applied to the sample tube 1 through the flight tube 6 or directly to the sample tube 1. In this case, the flying tube 6 is omitted, and the explosive 10 is detonated while the sample tube 1 and the explosive 10 are in direct contact.

  After the impact compression, the sample tube 1 is cut at both ends and the bottom plug 2 and the top plug 4 are removed. Then, the sample 3 is taken out and subjected to chemical purification to remove impurities such as metal powder, sand and graphite. The target diamond can be obtained.

The characteristics of the diamond obtained by the production method of the present invention will be described.
Analysis was performed using an X-ray diffractometer (scanning speed 2.000 ° / min, sampling width 0.020 °), and a peak derived from the (111) plane of the diamond crystal (39.0 to 48.0 °) was used as a Scherrer. The crystallite diameter calculated from the formula is 4 to 10 nm, preferably 5 to 8 nm.
When the crystallite diameter is within this range, the number of sharp corners of the particles is small, and the primary particle diameter is larger than that of the cluster diamond before the impact compression treatment, so that scratches are hardly generated and the processing speed is increased.

Hereinafter, the present invention will be described more specifically with reference to examples.
<Diamond primary particle diameter measurement method>
Analysis is performed with an X-ray diffractometer (RINT2000 manufactured by Rigaku Corporation) (scanning speed 2.000 ° / min, sampling width 0.020 °), and a peak (39.0 to 48) derived from the (111) plane of the diamond crystal. .0 °) was evaluated as a crystallite diameter calculated from the Scherrer equation.

[Example 1]
As a first step, after synthesizing a mixed explosive of 60% by mass of trimethylenetrinitroamine (RDX) and 40% by mass of trinitrotoluene (TNT) in a pressure vessel in a nitrogen gas atmosphere, impurities are removed by chemical purification treatment. 5% by mass of the removed cluster diamond and 95% by mass of spherical copper powder having an average particle size of 80 μm were uniformly mixed by a dry method to obtain a sample powder. The above sample powder was poured into a metal sample tube (outer diameter: 28 mm, inner diameter: 20 mm, length: 140 mm) into which a lower plug had been inserted, and then the upper plug was inserted into the upper part of the sample tube. . The lower plug was provided with a copper pipe for deaeration. After this vacuum deaeration was performed at 400 ° C. and 0.1 MPa for 2 hours using this copper pipe, the copper pipe was sealed. After the deaeration treatment, a sample tube was placed at the center of the flight tube (outer diameter 48 mm, inner diameter 42 mm, length 140 mm) via a fixing ring, and a conical cap was placed thereon. In this state, the sample tube was set at the center of the explosive container (outer diameter 114 mm, inner diameter 105 mm, length 170 mm), and dynamite (explosion speed 5,400 m / sec) was loaded between the flight tube and the explosive container. Since dynamite has good detonation sensitivity, the booster explosive was omitted, and a No. 6 electric detonator was inserted at the top of the dynamite (center position of the flight tube circumference).

As a second step, the No. 6 electric detonator was detonated to detonate dynamite, and the sample tube was subjected to impact compression treatment.
As a third step, the sample tube after the impact compression treatment was cut, the upper plug and the lower plug were removed, and the internal sample powder was taken out.
As a fourth step, impurities such as copper powder and sand were dissolved and removed with nitric acid, hydrochloric acid and hydrofluoric acid. Further, the partially graphitized carbon was oxidized and removed with sulfuric acid mixed acid, and the obtained powder was washed with water and dried.

The primary particle diameter of the raw material cluster diamond and the diamond after impact compression was evaluated as the crystallite diameter.
The crystallite diameter was 4.0 nm for the cluster diamond before impact compression and 5.5 nm for the diamond obtained after impact compression.
FIG. 2 shows a transmission electron micrograph of the raw material cluster diamond before the impact compression treatment, and FIG. 3 shows a transmission electron micrograph of the diamond after the impact compression treatment. From FIG. 2 and FIG. 3, although the raw material cluster diamond has a primary particle of several nanometers, the shape of the raw material cluster diamond remains after the impact compression, but the round particle of about 10 to 50 nm is also present. Many were recognized.

[Example 2]
A sample powder was obtained by uniformly mixing 3% by mass of cluster diamond having a crystallite size of 4.0 nm used in Example 1 and 97% by mass of spherical copper powder having an average particle size of 80 μm by a dry method. Thereafter, the same impact compression treatment and chemical purification treatment as in Example 1 were performed.
The crystallite diameter of the diamond obtained after the impact compression treatment was 6.8 nm.

(Industrial applicability)
The large crystallite diameter diamond obtained from the present invention is different in crystallinity from single crystal diamond or polycrystalline diamond, and has a larger primary particle diameter than ordinary cluster diamond. For this reason, what adjusted the particle size by the classification process is expected to show a unique performance when used as an abrasive material.

Claims (4)

  A first step of uniformly mixing the cluster diamond and the metal powder, press-molding the mixture and storing the mixture in a metal sample tube, and applying an impact compression treatment to the molded body stored in the sample tube using an explosive. And the third step of recovering the contents by cutting the sample tube after the impact compression treatment, and the fourth step of removing impurities by chemical purification of the recovered contents. A method for producing diamond.   The method for producing diamond according to claim 1, wherein the mixing ratio (mass ratio) of cluster diamond / metal powder is 1/99 to 20/80.   Analysis was performed using an X-ray diffractometer (scanning speed 2.000 ° / min, sampling width 0.020 °), and a peak derived from the (111) plane of the diamond crystal (39.0 to 48.0 °) was used as a Scherrer. 3. The method for producing diamond according to claim 1, wherein the crystallite diameter after the impact compression treatment calculated from the formula is 30 to 200% larger than that before the treatment.   A metal sample tube hermetically filled with a mixture of cluster diamond and metal powder is positioned in the flight tube across a circumferential space, and the flight tube is placed at the center of the explosive container and covers the flight tube. An impact compression device characterized in that it is filled with explosive and a detonator is attached to the top of the explosive.