DD259147A1 - METHOD FOR PRODUCING HIGH PRESSURE MODIFICATIONS OF THE CARBON - Google Patents

Abstract

The invention relates to the field of substance representation. Their goal is to run reactions to produce high pressure carbon modifications at lower temperatures and lower pressures. The invention has for its object to reduce the activation energy. According to the invention, the object is achieved by reacting exothermically reacting mixtures of metal carbides with metal oxides and / or metal halides, oxyhalides, metallates or halometalates at a temperature of 300 ° C. and a pressure of 10 kbar and separating the carbon modifications in a known manner. The field of application of the invention is the production of high-pressure modifications of the carbon, in particular of diamond or diamond-like carbon.

Description

Field of application of the invention

The invention relates to the field of fabric presentation. Their application is possible and expedient for the production of high-pressure modifications of carbon, in particular of diamond or diamond-like carbon.

Characteristic of the known technical solutions

It is generally known (for example, Ullmann's Encyclopedia of Industrial Chemistry 1955 Bd.6, p.228) that graphite proceeds at a temperature above 2500 ⁰ C and at a pressure of 80kbar in diamond. The high temperature is necessary to apply the required activation energy. Due to the course of the coexistence line of graphite and diamond, the high temperature but also high pressure. To avoid the technological difficulties involved in producing such high pressures, there have been no lack of attempts to reduce the pressure required. Thus, it is known from US-PS 4254091 to convert transition metal carbonates and oxalates with reducing agents to diamond. Temperature and pressure must be above the coexistence range given by Simon-Berman. The reducing agent used is preferably chromium or iron. The disadvantage of this method is that due to the high activation energy required here high temperatures of> 1 200 ° C and thus high pressures are necessary, which also the effective working volume is significantly limited.

Object of the invention

The aim of the invention is to allow reactions to be carried out to produce high-pressure modifications of the carbon at lower temperatures and lower pressures.

Explanation of the essence of the invention

The invention has for its object to reduce the activation energy. According to the invention the object is achieved in that exothermally reacting mixtures of metal carbides with metal oxides and / or metal halides, oxyhalides, metallates or halometallates at a temperature> 300 ° C and a pressure> 10kbar implemented and the carbon modifications are separated in a known manner. It is expedient that metal carbides are used with diamond-like carbon substructure. This favors the formation of diamond seeds. It is advantageous that carbon-rich metal carbides or mixtures thereof with oxygen-rich oxides or mixtures thereof and / or halogen-rich halide and / or oxygen- and halogen-rich oxide halides are used. As a result, high relative mass conversions to diamond or diamond-like carbon are achieved. A variant of the invention provides that

r

are used as exothermic mixtures oxide, oxyhalide or halogen mixtures with melting points below 800 ° C. The reaction then takes place at lower temperatures and thus at lower bridges. It is advantageous if the exothermically reacting mixtures are used in highly dispersed form and tabletted. Another variant of the invention is that the pressure is generated by shock waves. Preferably, the reaction is carried out at temperatures between 400 and 1000 ° C.

 Advantageously, the exothermic mixtures are reacted according to the relationships I to III.

embodiments Example 1:

From PbC> 2 and SnO ₂ in the ratio 1: 1 and CaC ₂ , a mixture in a molar ratio of 2: 1 is prepared. This mixture is exposed to a static pressure of 25kbar and a temperature of 600 ⁰ C. The temperature is maintained for 3 minutes and then passively cooled. From the product of the reaction, the calcium oxide and Pb-Sn alloy are separated to leave fine-grained diamond powder

Example 2:

Aluminum carbide is mixed with molybdenum dioxide dichloride in a ratio of 1: 2. The mixture is pressed into tablets. The tablets are exposed to a static pressure of 15kbar and a temperature of 400 ⁰ C. The aluminum oxide chloride and the molybdenum carbide are removed from the product and the diamond powder is thus recovered.

formulas

a Me C _x + Me'Xy = a Me X _y + Me ⁷ C ₂ + (ax - z) C _dia . (I)

a. '

X = O, F, Cl, Br (II)

O <Z <ax '' (III)

Claims (8)

1. A process for the preparation of high pressure modifications of the carbon, in particular diamond or diamond-like carbon, under pressure and temperature, characterized in that exothermically reacting mixtures of metal carbides with metal oxides and / or metal halides ^ oxyhalide, metadata or halometalates at a temperature> 300 ° C. and a pressure> 10kbar reacted and the carbon modifications are separated in a known manner. 2. The method according to item 1, characterized in that metal carbides are used with diamond-like carbon substructure. 3. The method according to item 1, characterized in that carbon-rich metal carbides or mixtures thereof with oxygen-rich oxides or mixtures thereof and / or halogen-rich halides and / or oxygen and halogen-rich oxide halides are used. 4. The method according to item 1 to 3, characterized in that are used as exothermic mixtures of mixtures, oxide halide or halide mixtures having melting points below 800 ⁰ C. 5. The method according to item 1 to 4, characterized in that the exothermically reacting mixtures are used in highly dispersed form and tabletted. 6. The method according to item 1, characterized in that the pressure is generated by shock waves. 7. The method according to item 1, characterized in that the reaction is carried out at temperatures between 400 and 1 000 ⁰ C. 8. The method according to item 1, characterized in that the exothermic mixtures are reacted according to the relationships (I) to (III).