RU2297977C2 - Method of isolating superfine diamond from detonation charge - Google Patents

Abstract

FIELD: explosives.

SUBSTANCE: invention concerns superfine diamond, which can be used in various applications, for example to form stable coatings, in composite materials, antifriction lubricants, and the like. Method comprises treating detonation charge in a gas (air, argon, or nitrogen) flow with water steam at 340-400°C and purification with hydrochloric acid.

EFFECT: avoided necessity of using boric acid anhydride for protection of diamond surface, imparted resistance to high temperatures, and increased yield of product.

1 tbl, 3 ex

Description

The invention relates to chemical technology for producing ultrafine diamond (UDD), i.e. nanodiamond, from a carbon mixture obtained by the detonation method.

Since the middle of the last century, a large number of methods have been known for the isolation and purification of UDD from a detonation charge by treating it with oxidative mixtures of strong acids under the influence of temperature and pressure (for example, UK patents Nos. 1115649 (1968), 1154633 (1969); US No. No. 3401019 (1968), 3488163 (1970); A.S. USSR No. 1770272 (1992), 1819851 (1993), RF patents No. 19999500 (1994), 2023659 (1994 .) and etc.). Known, for example, is a method for purifying detonation diamond (US Pat. UK No. 1154633, class C01B 31/06, publ. 1969) by treating the charge with an oxidizing mixture containing up to 50% nitric acid, as well as concentrated sulfuric and phosphoric acid, heating to 250 ° C and a pressure of 280 atm for 2-60 hours. The disadvantages of such methods are the use of chemically aggressive reagents, accompanied by the release of toxic gases, and the need for special equipment to create high pressure.

The known method (Application of Japan No.2002066302, CL B01J 3/06, C01B 31/06, C04B 35/52, publ. 03/05/2002), in which the nanodiamond is obtained by heating a nanocarbon charge at 1600 ° C and a pressure of 10 GPa This method, in addition to sophisticated technology and equipment, requires high energy consumption.

A known method of separating UDD from a graphite-diamond mixture in milder conditions (US Pat. RF No. 2081821, CL 01/31, published on 06/20/97). The process is carried out in two stages: first, the initial detonation charge is washed and dried, and then it is treated with an oxidizing nitrogen-sulfur mixture at a mass ratio of dry mixture: nitrogen-sulfur mixture 1: (20 ÷ 25), while sulfuric acid is charged once per the whole process, and nitric acid is added periodically to 1 portion after the complete oxidation of each previous portion. This method also uses strong acids that emit toxic gases.

Closest to the proposed one is the method (Pat. RF No. 2004401, class СВВ 31/06, published on December 15, 1993), which consists in processing a detonation charge containing UDD by oxidizing a non-diamond form of carbon in air at at a temperature of 300-550 ° C in the presence of an aqueous solution of boric anhydride, introduced previously, by which the mixture is impregnated throughout the volume and form on the UDD particles a glassy film of boric anhydride, which protects the UDD from oxidation in air at temperatures up to 550 ° C. And the UDD particles unprotected by the film are completely oxidized already at 350-400 ° С. The product is dried and crushed. The residue is treated by boiling in hydrochloric acid to remove metal impurities, washed in water and dried. This method is more environmentally friendly in comparison with the above methods for the allocation of UDD.

The main disadvantage of this method is its complication by the need to use boric anhydride, which then needs to be removed when UDD particles are isolated. You can also note the insufficiently high yield of the finished product, not exceeding 30%.

The objective of the proposed method is to eliminate the need to use boric anhydride to protect the surface of the UDD particles and at the same time ensure their resistance to high temperatures, as well as increase the yield of the target product - UDD, in comparison with the prototype method.

The problem is solved in that when separating ultrafine diamond from the detonation charge, including the main processing of the charge using air at a temperature of 340-400 ° C, as well as additional purification with hydrochloric acid, it is proposed that the main treatment of the detonation charge be carried out with water vapor in a stream of air or inert gas - argon or nitrogen.

In this case, additional cleaning of the detonation charge with hydrochloric acid is carried out at a preliminary stage before the main processing.

The authors of the proposed method found that during oxidation by water vapor in the flow of an air carrier gas, the stability of UDD particles is manifested up to temperatures of 340-400 ° C. At higher temperatures, they are completely oxidized, and at lower temperatures, the UDD release process is ineffective. A similar resistance to the action of temperatures of the same range is also manifested when treated with water vapor in an inert gas stream. Inert gases, argon, nitrogen were used as the carrier gas. Removing the non-diamond form of carbon is based on the fact that the non-diamond phase is oxidized at lower temperatures than UDD particles.

In this case, it is preferable to clean the detonation charge with hydrochloric acid at a preliminary stage, before being treated with water vapor in a carrier gas stream, on which non-carbon impurities are removed, in order to increase the processing efficiency and yield of the finished product.

The proposed method is as follows. The initial detonation mixture containing UDD is boiled for 1-2 hours in a solution of hydrochloric acid to remove impurities. Then it is washed to neutral waters and dried at a temperature of 150-160 ° C. Get pre-purified from non-carbon impurities mixture with particles of UDD.

A portion of the purified charge (1-2 g) is placed in a quartz reactor (quartz tube), heated by two electric furnaces. Steam is supplied to the reactor (tube) with a carrier gas (air, argon or nitrogen), while the steam is first heated to operating temperature (340-400 ° C) in the zone of the first furnace, and then passes to the zone of the second furnace, containing a charge of the charge with UDD particles. During the process, the mixture is periodically mixed. At the end, the isolated and refined product - ultrafine diamond is dried in an oven at 150 ° C and its yield is determined (≈40%).

Thus, the proposed process for the allocation of UDD in milder conditions (with some reduction in processing temperatures) in an environmentally friendly way allows to obtain a higher yield of the finished product, compared with the prototype.

The conditions of the main processing of a mixture purified from non-carbon impurities of a mixture containing UDD particles are given in the examples.

Example 1. Purified by hydrochloric acid, a detonation charge with UDD particles is treated in a quartz reactor with water vapor in an air stream at a temperature of 340 ° C until the non-diamond form of carbon is completely removed. The yield of UDD was 41.2 wt.%.

Example 2. The processing of the mixture is carried out analogously to example 1, but in a stream of argon at a temperature of 340 ° C. The yield is 39.8 wt.%.

Example 3. Processing is carried out analogously to example 1, but in a stream of nitrogen at a temperature of 350 C. The yield is 38.4 wt.%.

The options for the process of UDD extraction are given in the table.

Obtaining ultrafine diamond is necessary for use in modern technologies for manufacturing thin diamond coatings with high resistance to various influences, for use in composite materials, in antifriction lubricants, as an adhesive layer for dissimilar materials, and in many other applications.

Table No. p / p Carrier gas Processing temperature, ° С Yield, wt.% Note one Air 300 0 No reaction 2 Air 340 41.2 3 Air 350 40,0 four Argon 340 39.2 5 Nitrogen 350 38.5 6 Argon 350 39.8 7 Air 400 30,0 8 Argon 420 10.0 9 Air 500 0 Complete oxidation of the charge 10 Argon 500 0 - ″ -

Claims (1)

The method of separation of ultrafine diamond from a detonation charge, including its processing in a gas stream at a temperature of 340-400 ° C, as well as cleaning with hydrochloric acid, characterized in that the detonation charge is first cleaned with hydrochloric acid, and air or inert gas is used as a gas - argon or nitrogen, and processing in a stream of the specified gas is carried out by water vapor.