Diamond nanopowder

For many years the studies of surface modifications of synthetic diamond nanopowders have been conducted at the Institute for Superhard Materials. Our findings show that highly dispersed modified diamond powders hold a considerable promise in applications as adsorbents and catalysts of the oxidation and electrochemical catalysis [1-4], This promise is based on the following special features of the material ... 

The aim of the present work has been to study catalytic properties of detonation-synthesized diamond nanopowders and to extend their applications. The catalytic activity of diamond was studied in reactions electrochemical catalysis. 

The subjects of investigations were diamond catalysts produced by various methods of modification of the initial diamond nanopowders synthesized by the ALIT Company using the detonation of oxygen-deficient explosives. 

The development of diamond catalysts involved special two-stage treatment of the diamond nanopowder surface, the so-called modifications. Figure 1 gives the schematic of the reception of electrode materials. As is seen from the schematic, the hydrogen electrode was make from special heat-treated treatment in the hydrogen environment [6]. 

Figure 3 compares the exchange current densities on the initial nanodispersed diamond (4), modified nanodispersed diamond (after heat - treated treatment)(5), acetylene black AD-100 (1) and on the known catalysts tungsten (2) and vanadium (3) carbides. The specific surfaces of all samples of the powders were about 140 rrr/g. The exchange current density on modified diamond nanopowders is higher than that on tungsten or vanadium carbides by a factor of 1.6. 

Figure 6 compares the current exchange densities on the AD-100 hydrophobic carbon- black (1), the initial diamond nanopowders (2), diamond powders of 0,7 pm (3), nanopowders with palladium precipication (4). It is seen that the exchange current density after the promotion with palladium to be increased by a factor of 3 and 1.3 as compared with the initial diamond nanopowders and AD-100 carbon-black. 

Thus, palladium-promoted diamond nanopowders are efectifive catalists for oxygen electrodes. 

The exchange current density on modified diamond nanopowders is higher than that on tungsten or vanadium carbides by a factor of 1.6. 

Percification palladium diamond nanopowders has been high quantity of atomic oxygen. The atomic oxygen are formed at dissociations of chemical connected OH groups. 

The spectral features d d transform into broad peculiarity tf after diamond nanopowder Alit treatment in hydrogen. As a result, after diamond nanopowder Alit treatment, its CXa-emission band becomes similar to reference refined diamond powder (Fig. le). So far as nanodiamond powders CKa-bands investigation was carry out at minimum anode current densities (1 mA), the unrefined diamond powder surface remained chemisorbed atoms and molecules. However, owing to electron bombardment in sample emission focus, some of chemisorbed atoms disappeared. Therefore it was important to obtain CA -spectra... 

Abrasives Abrasive waste made from diamond nanopowders are being used for high precision polishing of lenses and mirrors in optical instruments. 

Lubricants The lubricating properties of oils are being improved by the addition of diamond nanopowders. 

In Chapter 2, the development of composite materials based on improved nanodiamonds is reported by P. Ya Detkov, V. A. Popov, V. G. Kuhchikhin and S. I. Chukhaeva. The authors describe methods for improving the quality of diamond nanopowders obtained by detonation synthesis, as well as some commercial applications of nanodiamonds. The authors prove that the synthetic detonation diamond is a promising material that can be used in many fields. Of special interest are its applications in compos ite materials both with a metal and polymer matrix. Commercial production of ultradisperse diamonds (or nanodiamonds) has been developed, and it is synthesized on a scale sufficient for particular industries. 

This chapter describes the methods of improving the quality of diamond nanopowders obtained by detonation synthesis, and some commercial applications of nanodiamonds that have been developed. 

Description of the Existing and Improved Techniques of Diamond Nanopowder Synthesis... 

To date, four types of diamond nanopowders are produced depending on how they are separated from the mixture standard, ozone, pure type 1, and pure type 2. 

The essence of the purification method used in the production of diamond nanopowders is to dissolve impurities of metals and their compounds and oxidize nondiamond forms of carbon by chromic anhydride in the presence of sulfuric acid. The use of such a strong oxidant in the presence of a strong acid makes it possible to combine in one stage the purification of diamonds both from nondiamond carbon forms and from metal impurities. The suspension of the nanodiamond-containing mixture is filtered through a set of sieves to remove mechanical impurities, the metal part is removed by magnetic treatment, and the solid phase is concentrated by nutsch filters. Dissolution of impurities of metals and their compounds and oxidation of nondiamond forms of carbon is carried out in a reactor (further on, this operation is called oxidation ). One run of oxidation to purify 3.3-3.7-kg solid phase of the mixture requires 24-27-kg sulfuric acid and 6.9-7.5-kg chromic anhydride. In the oxidation, when a solution of chromic anhydride is added, the temperature in the reactor reaches 125-130°C the mixture is kept in the reactor with sulfuric acid and chromic anhydride for 3-4 h. Following the oxidation, the reaction mixture is washed with water to remove chromium and sulfuric-acid salts. The yield is a nanodiamond suspension that contains 2.3-2.5-kg solid phase. 

Of significant interest is the use of nanodiamond powders for strengthening polymer materials. Nanopowders of oxides obtained from clay are used for these purposes at present. In commercial production of nanopowders by detonation the cost of nanodiamond powders and nanooxides obtained from clay becomes commensurate. That is, there are almost no obstacles of economic character for broad introduction of diamond nanopowders. 

These results show that small additions of diamond nanopowders to thermoplastics can be useful for solving the essential problem of increasing the elasticity modulus of polymers. 

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