Method for preparing of nanodiamond powders for producing of stable suspensions

FIELD: production of nanodiamond suspensions in various media for conducting of plating processes.

SUBSTANCE: method involves providing thermal processing of nanodiamond powder in air at temperature of 440-600 C until powder weight losses reach 5-85%. Thermally processed powder forms stable suspensions in water, ethyl alcohol and other solvents upon common mixing. Sediment stability of nanodiamond suspensions thermally processed in accordance with invention and produced using supersonic treatment is at least 1.5 times as high as similar parameter of nanodiamond suspensions produced by prior art processes.

EFFECT: simplified method allowing stability of nanodiamond suspension in various media to be improved.

3 ex

 

The invention relates to the field of production almatadema materials, namely suspensions diamond in different environments.

In recent years, methods of dynamic synthesis obtained new diamond products, called nanodiamonds (in the literature there are also names: ultradispersed diamonds of detonation diamonds, ultrananocrystalline diamonds) [1,2]. Such products are diamond particles with a size of 4-6 nm (sometimes up to 15 nm) with high surface area. Dry particles of nanodiamond aggregate in units larger than 1 μm. Nanodiamonds are used in a number of areas, it is often used in the form of aqueous and non-aqueous suspensions, for example in electroplating processes [1]. When used in the form of suspensions it is necessary to ensure their sustainability over time, however, a tendency inherent to the aggregation prevents this. Especially difficult is the preparation of suspensions of dry powder of nd in aqueous and nonaqueous media, not containing added surfactants.

The known method described in [3], which consists in drying of ultradispersed diamond in oxygen-containing atmosphere that allows you to simplify the process of obtaining suspensions of nanodiamonds. However, the suspension of nanodiamond obtained by a known method, do not have high sediment is sure stability.

The objective of the invention is to develop a method of preparing powders of nd to obtain stable suspensions allows to simplify the method of preparation of the suspensions and to improve their stability in different environments.

The objective of the invention is solved in the proposed method by oxidation of nanodiamond powders in oxygen-containing atmosphere to weight loss 5-85%. As oxygen-containing environment is preferable to use air as an available source of oxygen. The process of oxidation is expediently carried out at temperatures 440-600°C.

The invention consists in the following. The complexity of making the suspension of nanodiamond lies in the ability of particles to aggregation and formation of relatively large aggregates. The units are fairly stable. The oxidation of the nanodiamond powder is the interaction of the surface of the individual particles of nanodiamond with oxygen with the formation of gaseous oxides of carbon. Thus, with the surface of the particles gradually removed layers of carbon atoms. The oxidation process affects the contact area ("passages") between the particles, resulting in the formation of aggregates. Thereby a considerably weakened. When placing the treated nanodiamond powder in water or selected organic solvents unit easily raspugaet the I portions of which greatly simplifies the preparation of the suspension.

Oxidant in the described process is oxygen, which, of course, can be applied in mixture with other inert gases, for example nitrogen. More convenient and easier to carry out the process using air. The temperature oxidation, it is advisable to choose in the range of 440-600°C. At lower temperatures, the process may take a long time, and at temperatures above 600°on the contrary, to proceed too quickly, which complicates its control. However, the choice of temperature range depends on the processed powder of nd and used gas environment.

It should be emphasized that the proposed solution provides not just a surface treatment with oxygen, and the implementation of deep oxidation of nanodiamond particles with a large change in its mass. This is the main essence of the invention provides the solution of the invention and fundamentally distinguishes it from other methods.

The following examples describe the invention.

Example 1. The nanodiamond powder is placed in a quartz Cup. Cup with nanodiamond placed in a muffle furnace and heated in air (oxidized) at a temperature of 460°C for 1 hour. After that, the Cup is removed from the muffle furnace and cooled. The decrease in the mass of nanodiamond is 22%. According to the scientists the sample readily forms a stable suspension in water, even in mild stirring. Whereas the original powder nd very quickly falls to the bottom of the vessel.

Example 2. Carried out analogously to example 1. The oxidation is carried out at a temperature of 520°C for 6 hours. Reducing the mass of sample nd - 82%. The resulting nanodiamond easily forms a stable suspension in ethanol under mild stirring. Source material does not form stable suspensions in similar conditions.

Example 3. To implement the example was selected powder nd ADCS (made by "Center of the diamond technology" gsneric). The powder is divided into 2 parts. The first part of the powder was dried in air at 120°as specified in the prototype (sample 1). The second part of the powder was processed similarly to example 1. The oxidation was carried out at a temperature 480°C for 3 hours (sample 2). Reducing the mass of sample nd - 77%. From powders of sample 1 and sample 2 were prepared suspension: 1 mg nd in 10 ml of water. The suspension was subjected to ultrasonic treatment at a frequency of 22 kHz for 30 seconds After it was determined the change in optical density of the suspension through a 100 hours on the instrument FEC-56 (at a wavelength of 440 nm). For suspension based on a sample of 1 optical density was 20% of the initial optical density (measured immediately after preparation of the suspension). The optical density when spencie based on the sample 2, measured after 100 hours, amounted to 55% of the initial optical density. Thus shows a large sedimentation stability of the suspension, obtained using the proposed method.

Thus, the proposed solution allows the preparation of nano-diamond powders to obtain stable suspensions. The implementation of the method greatly simplifies the process of obtaining suspensions, and the method is relatively simple.

The sources used in the preparation of the description

1. Dolmatov VY Ultradispersed diamonds of detonation synthesis. Production, properties, application. St. Petersburg: Izd. SPb GPU, 2003. 344 S.

2. V.V. Danilenko Synthesis and sintering of the diamond explosion. Moscow: Energoatomizdat, 2003, 272 S.

3. Dolmatov VY Ultradispersed diamonds of detonation synthesis: properties and application. USP, 2001, t, No. 7, s-708.

The method of preparing powders of nd to obtain stable suspensions, including heat treatment in air at elevated temperatures, characterized in that the heat treatment is carried out at a temperature of 440-600°With the loss of the mass of powder on 5-85%.



 

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25 cl, 6 ex, 2 dwg

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