1070-4272/03/7603-0428$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 3, 2003, pp. 428! 430. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 3,
2003, pp. 443! 445.
Original Russian Text Copyright + 2003 by Obraztsova, Eremenko.
Chemical Purification of Ultrafine Cutting Diamonds
I. I. Obraztsova and A. N. Eremenko
Institute of Coal and Coal Fuel Chemistry, Siberian Division, Russian Academy of Sciences,
Received June 13, 2002
Abstract-A procedure was developed for recovery and purification of ultrafine diamonds.
Superdispersed systems based on clusters or ultra-
fine diamonds (UFD) are actively studied today,
because of theoretical interest and wide possibilities of
their practical use.
Ultrafine diamonds are widely used in preparation
of abrasive materials, tools, and pastes, in composite
and electrochemical plating, in production of mech-
anical rubber goods, and as additives to diesel oils and
lubricants. Diamonds show much promise in systems
of magnetic recording, in superfine surface finishing,
when the surface quality is a decisive factor, and in
preparation of new cutting ceramic materials. At the
same time, growth of diamond films and composites
based on them is also urgent.
One of the main problems in chemical processing
of coal is the low selectivity of catalysts, because coal
contains compounds of various structures (C3C, C3N,
C3S bonds, etc.), whose selective conversion occurs
under different conditions. Therefore, development
of versatile catalysts is hardly possible, and it seems
necessary to search and study catalysts selective with
respect to separate types of compounds. In this con-
nection, it is interesting to study the reactivity of
the C3C bonds using cluster diamonds as a model.
Explosion method is the main procedure for UFD
synthesis; it is based on the detonation conversion of
carbon-containing explosives with a negative oxygen
balance [1, 2]. This process yields a carbon blend con-
taining UFD (203 60%) and non-diamond impurities
(micrographite, carbon black). The detonation blend
has a developed and active surface (~400 m
exhibits specific adsorption and colloidal properties
due to elevated reactivity of superdispersed carbon
structures characterized by high density of defects.
The explosion synthesis procedure is well developed,
and several modes of its process are patented. How-
ever, relatively low efficiency of purification and
recovery of diamonds from the carbon- and metal-
containing reaction blend hinders the growth of the
cluster diamond production.
The reactivity of diamonds and composition of
impurities determine selection of the treatment and
purification procedures. The aim of the process is
the recovery of the target product with minimal losses,
and relatively high chemical stability of the diamond
phase allows this process to be performed fairly ef-
As seen from published data , in the first stage
of the diamond recovery the catalyst and carbide
phase are dissolved in acids or their mixtures . In
the second stage, the non-diamond carbon phases are
selectively oxidized with various reagents. In the third
stage, the compounds insoluble in water and acid
solutions (except hydrofluoric acid) are removed if
their content is greater than 1%. Then, the purified
diamond crystals are washed with water and dried.
It should be noted that the separation of diamond
from graphite, which can be performed by physical
and chemical methods , is the most difficult stage
of the process. In the chemical procedure, graphite is
selectively oxidized to carbon oxides. In contrast to
physical procedures, chemical treatment provides
higher purification and, in some cases, smaller loss of
the target product.
However, the main disadvantages of physical and
chemical purification procedures are rather complex
equipment, large losses of the diamond powder, and
use of extremely aggressive compounds with release
of environmentally hazardous components.
We developed chemical procedures for recovery
and purification of UFDs from the carbon3diamond
blend providing a high yield of the diamond phase
with a high quality of the target product. These proce-
dures can be performed without additional equipment
under milder conditions as compared to the known