JP5324556B2 - Diamond manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily and efficiently synthesizing a diamond from an organic explosive by using a simple apparatus. <P>SOLUTION: In a method for manufacturing the diamond by exploding the explosive in a pressure container, the method for manufacturing the diamond is characterized by including a process for exploding the explosive under a condition covering the explosive with ice. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a method for producing diamond that can easily and efficiently produce diamond directly from carbon atoms in the explosive by detonating the explosive using a simple device.

  Conventionally, explosives explode and generate high-temperature and high-pressure conditions of 3000 to 5000 ° C and several hundreds of thousands of atmospheres. The products obtained by the explosion are collected, foreign substances are separated, and chemicals such as nitric acid and sulfuric acid are used. There is known a method of synthesizing diamond fine particles from explosive-derived carbon by treating and purifying in an automated manner. The primary particle size of the diamond is nanometer size, and is used for precision abrasives, lubricants, lubricants, reinforcing agents, coating agents, and the like.

  As a synthesis method of the nano-sized diamond, (a) a pressure vessel is filled with a gas inert to the carbon atoms in the explosive, and the explosive is exploded therein (dry method); (b) There is a synthesis method (wet method) that explodes explosives in water.

  In the case of the dry method using an inert gas, it is necessary to use a large amount of inert gas having a cooling effect in order to cool the explosion product of the explosive. Sometimes it is necessary to increase the pressure in the pressure vessel. In addition, since the product (carbonaceous soot) generated by the explosion easily adheres to the inner wall surface of the pressure vessel, the recovery efficiency during synthesis deteriorates, and when this is continuously synthesized, The work efficiency is poor because it takes time for the soot to rise and settle in the container at the next explosion. Furthermore, the temperature of the inner wall of the pressure vessel rises due to the heat generated during the explosion, and particularly when continuously synthesized, the temperature rises further, causing pressure vessel degradation (pressure vessel body distortion, pressure due to O-ring thermal degradation). There are problems such as facilitating a decrease in the airtightness of the container and a decrease in the pressure strength. Furthermore, in order to suppress the oxidation of the produced diamond, the oxygen concentration has to be reduced to about 1.0% by volume or less, so that an operation for preparing the synthesis environment is troublesome.

  As a wet method for exploding an organic explosive in water, for example, Japanese Patent Laid-Open No. 3-271109 (Patent Document 1) has an organic explosive composition (10 g) whose oxygen balance is adjusted to be negative set inside, Disclosed is a method in which an iron cylinder with one open end is exploded while suspended in water (water depth 1.2 m), and the resulting precipitate is separated and purified to synthesize diamond. Later, it is described that about 1 to 5% of diamond is obtained with respect to the mass of the explosive. However, in the method described in Patent Document 1, since an explosive is set in an iron cylindrical container to cause an explosion, a large amount of iron impurities are contained in the recovered product, and many steps are required for purification. Since iron acts as a catalyst for promoting the oxidation of diamond, a method for producing nano-sized diamond with as few iron impurities as possible is desired.

  Japanese Patent Application Laid-Open No. 2007-269576 (Patent Document 2) stores an organic explosive having an initiation means in a bag made of a hydrocarbon-based polymer material through a coolant in approximately the center of a space in a pressure vessel. Cluster diamond by exploding the organic explosive with the detonation means under the condition that the outer space of the bag body is filled with a gas inert to the carbon atoms in the organic explosive. A method of synthesis is disclosed. By arranging both a coolant and an inert gas around the explosive in this order, cluster diamond can be synthesized easily and efficiently even in a relatively small pressure vessel. It is described. Patent Document 2 mentions water, distilled water or ice as the coolant, and when distilled water is used, it is described that it is preferable to use 3 to 20 times in mass ratio with respect to the organic explosive. . However, even in the synthesis method described in Patent Document 2, the yield is about 5% in one explosion, and a further increase in yield is desired.

JP-A-3-271109 JP 2007-269576 A

  Accordingly, an object of the present invention is to provide a method for easily and efficiently synthesizing diamond from an organic explosive using a simple apparatus.

  As a result of diligent research in view of the above object, the present inventors can form a high-temperature and high-pressure state suitable for diamond synthesis and obtain a high cooling rate by detonating the explosive while covered with ice. Therefore, the inventors have found that diamond can be easily synthesized with high yield, and have arrived at the present invention.

  That is, the method for producing diamond according to the present invention is a method for producing diamond by exploding explosives in a pressure-resistant container, characterized in that the explosives are exploded in a state covered with ice.

  The explosive is preferably exploded in a state filled in a container formed of ice.

  The explosive filled in the ice is preferably exploded in water.

  It is preferable to explode the water filled with the explosive while applying water.

  It is preferable to explode while flowing water over the entire inner wall surface in the pressure-resistant container.

  The total amount of water and ice at the time of explosion is preferably 25 to 50000 kg per kg of the explosive.

  It is preferable to perform the explosion in a state that does not contain oxygen in the container.

  The water and / or ice is preferably deoxygenated.

  The explosive is preferably a mixture of trinitrotoluene and cyclotrimethylenetrinitroamine.

The pressure-resistant container preferably has a volume of 2 to 300 m ³ with respect to 1 kg of the explosive.

  The pressure-resistant container is provided with a leak valve or a Laval nozzle, a pressure-resistant sealed container is further provided on the downstream side of the leak valve or the Laval nozzle, and the pressure generated by the explosion is passed through the leak valve or Laval nozzle. It is preferable to open the container.

  The explosion is preferably carried out twice or more continuously.

  In the method of the present invention, by exploding an explosive covered with ice, a very high pressure and high temperature can be obtained in a narrow region, and at the same time, a high cooling efficiency by ice can be obtained. It is possible to synthesize diamond with a high yield by suppressing the phase conversion to.

It is a schematic cross section which shows an example of the apparatus used with the manufacturing method of the diamond of this invention. It is a schematic diagram which shows the container of ice used with the manufacturing method of the diamond of this invention. It is a schematic cross section which shows another example of the apparatus used with the manufacturing method of the diamond of this invention. It is a schematic cross section which shows another example of the apparatus used with the manufacturing method of the diamond of this invention. It is a schematic cross section which shows another example of the apparatus used with the manufacturing method of the diamond of this invention.

  Preferred embodiments of the method for producing diamond of the present invention will be described in detail, but the present invention is not limited thereto.

(1) Synthesis of diamond The diamond production method of the present invention is a method in which an explosive is covered with ice and placed in a pressure-resistant container, and the explosive is exploded. As the explosive, an organic explosive is used. As shown in FIG. 1, an explosive 3 covered with ice 2 is suspended inside a pressure-resistant container 1 with a suspension member 4 and arranged. The position of the suspension is appropriately adjusted according to the shape of the container, the type and amount of the explosive, etc., so that the yield of the diamond obtained is as high as possible. In particular, the center of the container is preferable. It is preferable that a metal wire such as a copper wire is used as the suspension member 4 and is used as a conducting wire for supplying a current to an electric detonator attached to the explosive.

  The product obtained by the explosion is recovered as an aqueous dispersion by washing the inner wall of the pressure-resistant container with water. The product may be collected after one explosion, but it is more efficient to collect two or more explosions in succession and collect them more efficiently. improves. When explosions are carried out twice or more in succession, oxygen in the pressure-resistant container is consumed in the first explosion, so that the effect of suppressing the oxidation of diamond in the second and subsequent explosions can also be obtained.

  When carrying out two or more explosions in succession, it is necessary to carry out at least one explosion with the explosive covered with ice. It is preferable to carry out all explosions after the second time with the explosive covered with ice, and most preferred to carry out all the explosions with the explosive covered with ice. It is preferable to quickly install the explosive in the pressure resistant container in the second and subsequent explosions so that oxygen in the air does not flow into the pressure resistant container as much as possible. Further, in order to prevent air from flowing into the container when the top cover of the pressure resistant container is released, an inert gas such as nitrogen is introduced into the container from a gas inlet (not shown) provided in the pressure resistant container. It is preferable that the explosive is installed in a state where the pressure-resistant container is made to flow into a pressure higher than atmospheric pressure.

  The method of covering the explosive 3 with ice is not particularly limited. For example, a container 5a formed of ice as shown in FIG. 2 (a) is prepared, and the explosive 3 is filled in the container 5a (FIG. 2 (b) Then, the explosive 3 can be covered with ice by covering the container 5b with ice (FIG. 2 (c)). By making the explosive covered with ice in this way, the pressure generated during the explosion can be effectively increased, and rapid cooling with ice is possible, so it is generated from the carbon derived from the organic explosive. It is possible to prevent the generated diamond from phase-changing to graphite.

  The ice 2 for covering the explosive 3 is preferably formed by deoxygenated water. The method of deoxygenation is not particularly limited, but it is easy to carry out by a method such as deaeration, boiling, or replacement with an inert gas. By using ice that does not contain oxygen, it is possible to prevent the diamond synthesized by explosion from being oxidized.

  The amount of ice used is preferably 2 to 100 kg, more preferably 5 to 20 kg per kg of the explosive.

  The explosive 3 covered with the ice 2 may be exploded in a state where it is further immersed in water 6 as shown in FIG. By making it explode in water 6, a higher cooling rate can be obtained, so that diamond can be synthesized in a high yield. The amount of water used is preferably 25 to 50000 kg, more preferably 30 to 20000 kg, most preferably 50 to 10,000 kg as the total amount of ice and water. . If the amount is less than 25 kg, the effect of using water is not obtained so much. If the amount is more than 50,000 kg, it takes time to recover the product resulting from the explosion, and the yield decreases.

  Instead of immersing the explosive in the water 6 as described above, as shown in FIG. 4, the shower-like water 7 may be exploded while being put on the ice 2 filled with the explosive 3 from the upper part of the pressure-resistant container. Instead of applying shower-like water 7 from the top of the pressure-resistant container, water may be mist-like and attached to the ice 2 filled with the explosive 3 (not shown). Further, it may be sprayed from the side wall of the pressure-resistant container with a nozzle or the like and applied to the ice 2 filled with the explosive 3 (not shown). By making the explosion while applying water, a higher cooling rate can be obtained, so that diamond can be synthesized in a high yield. The amount of water supplied is preferably 10 to 5000 kg / min per kg of explosive, more preferably 20 to 2000 kg / min, and most preferably 50 to 1000 kg / min. When the method of applying water is employed, the cooling effect equivalent to the method of immersing in water with a smaller amount of water compared to the method of immersing in water is obtained, so that the efficiency when recovering the product is improved.

  It is preferable to explode while flowing water over the entire inner wall surface in the pressure-resistant container. Water may flow along the side wall surface of the container from the top of the pressure-resistant container, or water may be sprayed from the wall of the pressure-resistant container toward the inner wall surface with a nozzle or the like and applied to the inner wall surface. . Moreover, the method of making water adhere to the whole inner wall surface in a pressure-resistant container by supplying mist-like water may be used. By carrying out an explosion with water flowing through the entire inner wall surface of the pressure-resistant container or with water attached to the mist, the product generated by the explosion is less likely to adhere to the inner wall surface of the pressure vessel. The recovery efficiency of the explosion product is improved. Further, when the explosion is continuously performed, the generated carbonaceous soot can be prevented from rising in the container, and the working efficiency is improved. Furthermore, the rise in the temperature of the pressure vessel inner wall due to the heat generated during the explosion can be reduced, which contributes to the improvement of the durability of the pressure vessel.

  The water used in the method of the present invention is preferably deoxygenated. The method of deoxygenation is not particularly limited, but it is easy to carry out by a method such as deaeration, boiling, or replacement with an inert gas. By using water that does not contain oxygen, it is possible to prevent the diamond synthesized by explosion from being oxidized.

  The inside of the pressure-resistant container is preferably free from oxygen. That is, the inside of the pressure-resistant container is preferably evacuated or filled with a gas inert to carbon atoms such as carbon dioxide, nitrogen, and argon. From the viewpoint of efficiently dissipating the exploded heat, it is preferable to fill the pressure resistant container with an inert gas. When filling with an inert gas, the oxygen content is preferably 10% by volume or less, more preferably 5% by volume or less, and most preferably 2% by volume or less. As described above, when explosions are continuously performed a plurality of times, oxygen in the pressure-resistant container can be reduced by the first explosion, so that oxygen in the pressure-resistant container is not replaced with an inert gas in advance. However, the oxygen content can be reduced.

The pressure-resistant container preferably has a volume of 2 to 300 m ³ with respect to 1 kg of the explosive. If 2 m ³ less than, for too high temperature and high pressure during the explosion, may efficiently heat it is difficult to divergence, it takes time to recover the product by the explosion to be larger than 300 m ³ yield Decreases.

  In order to cool the pressure-resistant container more efficiently and recover the explosion products efficiently, as shown in FIG. 5, the pressure-resistant container 1 is provided with a leak valve 8 (or a Laval nozzle), and A pressure-resistant airtight container 9 is provided on the downstream side of the leak valve 8 (or Laval nozzle), and the pressure generated by the explosion is released to the airtight container 9 via the leak valve 8 (or Laval nozzle). Is preferred. By increasing the cooling rate in such a configuration, the yield of diamond is improved. In addition, since the explosion product released into the pressure-resistant airtight container 9 can be recovered, the yield of diamond is further improved. The pressure-resistant airtight container 9 preferably has a capacity of 1 to 30 times, more preferably 2 to 20 times the capacity of the pressure-resistant container 1, and a capacity of 3 to 15 times. Most preferably it has.

  In the present invention, known organic explosives known as high performance explosives can be used. Organic explosives include trinitrotoluene (TNT), trinitrobenzene (TNB), trimethylenetrinitramine (RDX), tetramethylenetetranitramine (HMX), tetranitromethylaniline (tetril), triaminotrinitrobenzene (TATB) ), Diaminotrinitrobenzene (DATB), hexanitrostilbene (HNS), hexanitroazobenzene (HNAB), hexanitrodiphenylamine (HNDP), picric acid, ammonium picrate, benzotriazole (TACOT), ethylenedinitramine (EDNA) , Nitroguanidine (NQ), pentaerythritol tetranitrate (pen slit), benzotrifluoroxane (BTF) and the like, and these are used alone or in combination. In particular, it is preferable to use Composition B, which is known as a mixed explosive of RDX (60%) and TNT (40%).

  These organic explosives have a carbon atom content of 15% by mass or more, preferably 20 to 35% by mass, a density of 1.5 g / cc or more, preferably 1.6 g / cc or more, and an explosion speed of 7000 m / s or more, preferably Is 7500 m / s or more, oxygen balance is negative, preferably -0.2 to -0.6, detonation pressure is 18 GPa or more, preferably 20 to 30 GPa, detonation temperature is 3000 K or more, preferably 3000 ~ 4000K. Therefore, carbon atoms in the explosive can be efficiently converted to diamond, and since the oxygen balance is negative, diamond is not oxidized during the explosion and the yield is not reduced.

  When composition B, which is a mixture of RDX and TNT, is used as the organic explosive, it can be molded into a desired shape by melting. When using an explosive in powder form (for example, one with an average particle size of about 100 μm) as an organic explosive, it can be used by molding it into a predetermined shape by using it together with an organic binder such as a polymer. Is preferred. As this organic binder, a polymer material such as polybutadiene (polybutadiene), polyurethane (polyurethane), polyether (polyethylene glycol), etc., known as a binder component of a composite propellant may be used. Alternatively, glycidyl azide polymer (GAP), polynitratomethylmethyl octacene, polyglycidyl nitrate, etc., which are known as polymers having a large combustion heat, or wax may be used. The ratio of the organic binder is preferably 1 to 40% by mass, and the ratio of the powdered organic explosive is preferably about 60 to 99% by mass.

(2) Purification of explosive product The recovered explosive product has a core / shell structure in which the surface of nano-sized diamond particles is covered with graphite-based carbon, and is colored black. This unpurified nanodiamond has a specific gravity of about 2.55 g / cm ³ and a median diameter (dynamic light scattering method) of about 200 to 250 nm. This unpurified nanodiamond is oxidized by the following method to remove the graphite-based carbon shell layer and obtain nanodiamond particles. The diamond fine particles purified by the oxidation treatment are secondary particles having a median diameter of about 150 to 250 nm made of primary particles of diamond of about 2 to 10 nm.

  Oxidation treatment of unpurified nanodiamond includes (a) high-temperature and high-pressure treatment in the presence of nitric acid (oxidation treatment A), and (b) treatment in a supercritical fluid consisting of water and / or alcohol. (Oxidation treatment B), (c) A method in which oxygen is present in a solvent consisting of water and / or alcohol, and the treatment is performed at a temperature not lower than the normal boiling point of the solvent and at a pressure not lower than 0.1 MPa (gauge pressure) ) Or (d) a method (oxidation treatment D) in which treatment is performed with a gas containing oxygen at 380 to 450 ° C. These oxidation treatments may be performed alone or in combination. When combining the oxidation treatment, it is preferable to first subject the unpurified nanodiamond obtained by the explosion method to oxidation treatment A, and then to any one of oxidation treatments B to C.

  Oxidation treatment A is applied to unpurified nanodiamond obtained by the explosion method to obtain diamond particles from which a part of the graphite phase has been removed (graphite-diamond particles). The graphite layer can be further removed by performing any one of the processes of ~ C.

The specific gravity of the oxidized nanodiamond is determined by the amount of diamond and graphite in the diamond fine particles. That is, the specific gravity of the diamond fine particles can be adjusted by changing the amount of diamond and graphite in the diamond fine particles according to the degree of oxidation treatment applied to the unpurified nanodiamond. Graphitic carbon (graphite specific gravity: 2.25 g / cm ³⁾ closer to the remaining amount is small, the more an diamonds specific gravity (3.50 g / cm ^3). Therefore, the specific gravity increases as the degree of purification increases and the remaining amount of graphite carbon decreases.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
(1) Preparation of explosive As shown in Fig. 2, 0.65 kg of explosive 3 containing TNT (trinitrotoluene) and RDX (cyclotrimethylenetrinitroamine) in a ratio of 60/40 is frozen in degassed water. The ice 2 container 5a formed in this way was filled and covered with an ice container 5b formed by freezing the degassed water 2 in the same manner. The explosive 3 was equipped with a detonation explosive and an electric detonator. The weight of ice 2 was 15 kg in total for containers 5a and 5b.

(2) Installation of explosives Ice 2 containers 5a and 5b filled with explosive 3 are suspended in a 3 m ³ pressure resistant container 1 with a suspension material 4 as shown in FIG. The air was replaced with nitrogen. A copper wire was used as the suspension member 4, and the current to the electric detonator for initiating the explosive was supplied through the copper wire. The pressure-resistant container 1 at this time was 1 atm, and the oxygen concentration was 4% by volume.

(3) Explosion As shown in FIG. 4, ice is poured over the entire inner wall of the pressure-resistant container 1 and the ice 2 containers 5a and 5b filled with explosive 3 at a supply rate of 60 kg / min. Explosive 3 filled in 2 containers 5a and 5b was exploded. The total amount of water supplied by the time of the explosion was 100 kg.

(4) Recovery of explosive products Leave after standing for 5 minutes, open the top 10 of the pressure-resistant container, and clean the inner wall of the pressure-resistant container with water. Was recovered. The yield of this unpurified nanodiamond was 10.5% by mass with respect to the amount of explosive used, the specific gravity was 2.55 g / cm ³ , and the median diameter (dynamic light scattering method) was 220 nm. This unpurified nanodiamond was estimated to be composed of 76% by volume of graphite-based carbon and 24% by volume of diamond, calculated from the specific gravity. Nanodiamonds this unpurified, a peak intensity I _a of 1,330 ± 10 cm ^-1 in the Raman spectrum, the ratio of the peak intensity I _b of 1,610 ± 100 cm ^-1 was 0.86.

(5) Purification of nanodiamond After mixing this unpurified nanodiamond with 60% by mass nitric acid aqueous solution and subjecting it to oxidative decomposition under conditions of 160 ° C, 14 atmospheres and 20 minutes, 130 ° C, 13 atmospheres, 1 Oxidative etching treatment was performed over time. Particles from which graphite was partially removed were obtained by the oxidative etching treatment. The particles were refluxed with ammonia at 210 ° C., 20 atm for 20 minutes, neutralized, then naturally settled, washed with 35% by mass nitric acid by decantation, and further washed with water three times by decantation. It was dehydrated by centrifugation and dried by heating at 120 ° C. to obtain nanodiamond powder. The yield of the nanodiamond powder was 7.1% by mass with respect to the amount of explosive used, the specific gravity was 3.38 g / cm ³ , and the median diameter was 130 nm (dynamic light scattering method). Calculated from the specific gravity, it was estimated to be composed of 90 vol% diamond and 10 vol% graphite carbon.

Example 2
In the same manner as in Example 1, (1) Preparation of explosive to (3) Explosion operation was repeated twice, (4) Explosion product recovery work, and (5) Nanodiamond purification. Were synthesized and purified in the same manner as in Example 1. The total amount of shower water supplied at the time of the explosion was 120 kg. The yield of the obtained nanodiamond powder was 7.2%.

Example 3
In the same manner as in Example 1, (1) Preparation of explosives, (2) Installation of explosives, and (3) Operation of explosion, (1) Preparation of explosives, (2) Installation of explosives, And (3) The explosion operation was repeated four times, followed by a total of five explosions. However, in the second and subsequent explosions, the operation of replacing the gas in the container with nitrogen after installing the explosive is omitted. Instead, while an inert gas is introduced from the gas inlet provided in the pressure-resistant container The explosive was quickly installed in the pressure-resistant container so that oxygen in the air could not enter the pressure-resistant container as much as possible. After the fifth explosion, in the same manner as in Example 1, (4) recovery of the explosion product and (5) purification of nanodiamond were performed. The total amount of shower water supplied at the time of the explosion was 200 kg. The yield of the obtained nanodiamond powder was 7.5%.

Example 4
Instead of showering the ice 2 containers 5a, 5b filled with explosive 3, the ice 2 containers 5a, 5b filled with explosive 3 were immersed in 100 kg of water 6 as shown in FIG. The diamond was synthesized and purified in the same manner as in Example 1 except that the explosion was carried out in the state. The yield of the obtained nanodiamond powder was 7.2%.

DESCRIPTION OF SYMBOLS 1 ... Pressure-resistant container 2 ... Ice 3 ... Explosive 4 ... Hanging material
5a, 5b ... container 6 ... water 7 ... shower-like water 8 ... leak valve 9 ... pressure-resistant sealed container
10 ... Upper lid

Claims (11)

A method for producing diamond by exploding explosives in a pressure-resistant container, in which the explosives are filled in a container formed with ice and further explode in a state of being covered with a container formed with ice. A diamond production method characterized by the above. The diamond manufacturing method according to claim 1 , wherein the explosive filled in the ice is exploded in water. The diamond manufacturing method according to claim 1 , wherein the ice filled with the explosive is exploded while applying water. The diamond manufacturing method according to any one of claims 1 to 3 , wherein the explosion is performed while flowing water over the entire inner wall surface of the pressure-resistant container. The diamond manufacturing method according to any one of claims 2 to 4 , wherein the total amount of water and ice at the time of explosion is 25 to 50000 kg per kg of the explosive. The diamond manufacturing method according to any one of claims 1 to 5 , wherein explosion is performed in a state in which the container does not contain oxygen. The diamond manufacturing method according to claim 1 , wherein the water and / or ice is deoxygenated. The diamond manufacturing method according to claim 1 , wherein the explosive is a mixture of trinitrotoluene and cyclotrimethylenetrinitroamine. The diamond manufacturing method according to claim 1 , wherein the pressure-resistant container has a volume of 2 to 300 m ³ with respect to 1 kg of the explosive. In the diamond manufacturing method according to any one of claims 1 to 9 , a leak valve or a Laval nozzle is provided in the pressure-resistant container, a pressure-resistant sealed container is further provided downstream of the leak valve or the Laval nozzle, and the explosion is performed. The method for producing diamond, wherein the generated pressure is released to the sealed container through the leak valve or a Laval nozzle. The diamond manufacturing method according to any one of claims 1 to 10 , wherein the explosion is continuously performed twice or more.

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