The method of purification of synthetic ultradispersed diamonds

 

(57) Abstract:

The invention can be used for the recovery of diamonds from the product of detonation synthesis. 100 g diamond blend containing about 40 wt.% diamond, the rest Almazny carbon and metal impurities, place on a baking furnace. Heated to 380-440oWith a speed of 2.5-10.0 deg. /min. and maintained at the maximum temperature for 2-4 hours Exit diamond 38,5 - 39,1 wt. %, the content of non-diamond carbon 0.1 - 0.8 wt.%. The method is simple, does not require the use of toxic environments.

The invention relates to technologies for obtaining and purifying synthetic ultradispersed diamonds and can be used to extract diamonds from the products of detonation synthesis.

Known methods of chemical cleaning of synthetic diamonds is based on the oxidative effects of solutions, melts or gases (Putyatin A. A., Nikolskaya, I. C., Kalashnikov, I. N. Chemical methods of extraction of diamonds from the fusion products. - Superhard materials, 1982, No. 2, S. 20 - 28). In industrial practice, preference and affordability-oxidants.

Known purification method UDA formulations based on sulphuric, nitric acid and sulfuric aldehyde. The processing.%. The ratio of the diamond mixture : the mixture of acids is 1 : (25 - 50) (international application PCT/SU N 90/00169). The main disadvantage of this method is the use of aggressive, concentrated environments, which upon oxidation decays with emission of toxic and reactive gases (NO, NO2N2O5, SO3, CO). Disposal and decontamination waste technology requires high material costs, which leads to a rise in the cost of cleaning product - UDA.

There is a method of allocating synthetic ultra-dispersed diamonds (patent of Russia No. 2109683), in which diamond the mixture is subjected to two-stage treatment with an aqueous solution of nitric acid first 50 - 99% concentration at 80 - 180oC, followed by 10 - 40% at 220 - 280oC. Liquid-phase flow process in this way is provided by high pressure. The disadvantage of this method is the necessity of using a special acid-resistant chemical equipment working under pressure.

A known method of purification of diamonds from impurities by processing raw materials on the air for 12 - 24 hours at 300 - 550oC in the presence of 5 to 100 wt.% catalyst - lead oxide (patent England N 1115649). The disadvantages of the method are the use of highly toxic soepomo the patent of Russia No. 2004491. This method consists in processing of diamond-containing materials in air at 300 - 550oC in the presence of boric anhydride, which is added in an amount of not less than 9 wt.% content in raw diamonds. The method includes a step of mixing the raw material with a solution of boric anhydride or boric acid and the subsequent drying of the mixture at 210oC to obtain a vitreous boric aldehyde. The mixture is calcined in the pan for 4 to 5 h at 300 - 550oC with periodic stirring and cooled, treated with diluted hydrochloric acid and distilled water. The yield of diamond is 72 - 94%. A multi-stage cleaning process - mixing with boron compounds in water, drying, calcining, with stirring and subsequent removal of the residue of boric compounds makes the method inefficient and futile for industrial applications. Also used in the prototype boron oxide or boric acid have a toxic effect on the human body (maximum allowable concentrations of 5 and 10 mg/m3respectively), resulting in poor working conditions.

The task of the claimed invention is to provide a method of cleaning a synthetic tx2">

The problem is solved by the proposed method of purification of synthetic ultradispersed diamond on non-diamond carbon, which is thermooxidation diamond mixture in air at 380 - 440oC in the layer, providing the necessary conditions of the heat sink and prevent the burnout of the diamond, with a speed of 2.5 - 10.0 deg. /min, followed by isothermal aging for 2 to 4 h

Comparison of the proposed technical solution with the prototype shows that it differs from the latter in different thermal conditions of the method, with the exception of process chemical additives, other duration of the process, i.e., this solution meets the criterion of "novelty".

In the process of cleaning synthetic ultradispersed diamond from carbon impurities are not used lead compounds, boron or other catalysts, which eliminates phase shift, processing, drying, separation. In accordance with the invention, the oxidation of carbon impurities is carried out in one stage in an atmosphere of air, and heating is performed in a strictly controlled manner, ensuring the stationarity of the process. The condition of stationarity meets this heating rate oxidizable TA consists of carbon forms different patterns from amorphous and carbenoxolone to nano-sized diamond crystals. Part of the diamond particles enclosed in a quasi-spherical carbon shell, representing the transitional carbon structures.

The proposed method is based on the difference of thermal-oxidative properties of diamond and non-diamond phase of carbon and takes into account the peculiarities of the mechanisms of oxidation of crystalline and amorphous structures. The claimed mode of oxidation of the diamond charge allows you to control the specific rate of oxidation of the non-diamond carbon, at the initial stage, the temperature is increased in stages, the most oxidized active carbon forms. This process is accompanied by activation of transient surface layers of diamond particles. Isothermal oxidation for 2 - 4 h completes the process of gasification of non-diamond phases.

For better implementation of the method of the diamond mixture, it is necessary to oxidize the layer, providing the necessary conditions of the heat sink and prevent the burnout of the diamond. The temperature of oxidation over 440oC will result in the loss of the diamond more than 20%. The increasing heating rate of more than 10 deg./min violates the stationary regime of oxidation, initiating flash and ignition of the charge. Oxidation at temperatures below 380oC or increasing the heating rate is less than 2,Braz, the proposed method of purification of synthetic ultra-dispersed diamond and non-diamond carbon to declare it a set of features allows you to achieve the technical result - cleaning synthetic OUD from non-diamond carbon without the use of toxic environments while maintaining the quality of cleaning. This embodiment of the method of the prior art are not explicitly derived and it was not obvious to the experts, and the differences that directly affect the solution of the problem. It gives the basis to consider this solution as inventive.

The method does not cause problems while its industrial implementation, as described techniques and devices for its implementation is easy to reproduce. The necessity in the application of the method of purification of synthetic ultra-fine from non-diamond carbon, allowing to obtain a high quality product without the use of toxic environments, no doubt, and therefore the proposal has industrial applicability.

Example 1. 100 g diamond blend containing diamond (40,2 wt.%), Almazny carbon and metal impurities, place a layer, providing the necessary conditions of the heat sink and excluding wygu the temperature of the support in the interval (410 10)oC for 4 h, the Yield of diamond is 38.5, the residual Content of non-diamond carbon of 0.2% (according to x-ray analysis).

Example 2. 100 g of the diamond mixture (content of UDA - 39.5 wt.%) layer, providing the necessary conditions of the heat sink and prevent the burnout of the diamond, spread on a baking furnace and heated at a rate of 10 deg. /min to 430oC. After which the specified temperature is maintained within the interval (430 10)oC for 2 h, the Yield of diamond is 38,7, the residual Content of non-diamond carbon of 0.1% (according to x-ray analysis).

Example 3. 100 g of detonation diamond mixture (content of UDA - to 42.5 wt. %) layer, providing the necessary conditions of the heat sink and prevent the burnout of the diamond, spread on a baking furnace and heated at a speed of 5 deg./min to 380oC. the Specified temperature stabilize in the range (380 20)oC for 4 h, the Yield of diamond is 39,1, the Content of non-diamond carbon of 0.8% (according to x-ray analysis).

The method of purification of synthetic ultra-dispersed diamond and non-diamond carbon by thermal oxidation in air at 380 - 440oC, characterized in that termoeconomia 2 - 4 o'clock

 

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