| United States Patent |
5,861,349
|
|
Vereschagin
, et al.
| January 19, 1999
|
Synthetic diamond-containing material and method of obtaining it
Abstract
A diamond-containing material having the following element content ratio in
per cent by weight: carbon 75-90, hydrogen 0.6-1.5, nitrogen 1.0-4.5,
oxygen the balance, the following phase content ratio in per cent by
weight: roentgen amorphous diamond-like phase 10-30, diamond of cubic
modification the balance, and having a porous structure. 10-20% of the
surface of the material consists of methyl, nitryl and hydroxyl groups of
two types, as well as functional oxycarbonic groups of the general formula
O.dbd.R where R represents .dbd.COH, .dbd.COOH, .dbd.CO, .dbd.C.sub.6
H.sub.4 O or any of their combinations, and 1-2% of the surface consists
of carbon atoms with non-compensated links. A method for obtaining said
material consists in detonation of a carbon-containing explosive substance
with negative oxygen balance, or a mixture of explosive substances, in a
closed volume in the atmosphere of gases inert to carbon, with an oxygen
content of 0.1-6.0% by volume, at a temperature of 303-363 K and in the
presence of ultradispersed carbon phase with concentration of 0.01-0.15
kg/m.
| Inventors:
|
Vereschagin; Alexandr Leonidovich (Biisk, RU);
Petrov; Evgeny Anatolievich (Biisk, RU);
Sakovich; Gennady Viktorovich (Biisk, RU);
Komarov; Vitaly Fedorovich (Biisk, RU);
Klimov; Anatoly Valentinovich (Altaisky krai, RU);
Kozyrev; Nikolai Vladimirovich (Biisk, RU)
|
| Assignee:
|
Nauchno-Proizvodstvennoe Obiedinenie "Altai" (Biisk, Ulitsa Sotsialisticheskaya, RU)
|
| Appl. No.:
|
108568 |
| Filed:
|
November 18, 1993 |
| U.S. Class: |
501/86; 423/446 |
| Intern'l Class: |
C01B 031/06 |
| Field of Search: |
423/446
156/DIG. 68
264/84
428/408
501/86
|
publications Cited
U.S. Patent Documents
| 3749760 | Jul., 1973 | Deryagin | 423/446.
|
| 4377565 | Mar., 1983 | Setaka | 423/446.
|
| 4483836 | Nov., 1984 | Adadurov et al. | 423/446.
|
| 4617181 | Oct., 1986 | Yazu et al. | 423/446.
|
| Foreign Patent Documents |
| 2479174 | Feb., 1981 | FR.
| |
| 072655 | Mar., 1990 | JP.
| |
| 271109 | Dec., 1991 | JP | 423/446.
|
| 1687761 | Oct., 1991 | SU.
| |
| 1154633 | Jun., 1969 | GB.
| |
Other publications
Savvakin, G. I. et al. "Possibilities of Phase . . . " Proceedings of the
USSR Academy of Sciences, vol. 282, No. 5, 1985. Nauka Publishers pp.
1128-1131.
Volkov, K. V. et al. "Synthesis of Diamond . . . "
The Physics of Combustion and Explosion. 1990, pp. 1128-1131.
Staver, A.M. "Ultradispersive Diamond . . . " The Physics of Combustion and
Explosion 1984, pp. 100-104.
Adaurov, G. A. et al. "Diamonds Obtained Obtained . . . " The Physics of
Pulse Pressures Proceedings, Research Institute of Physical and Radio
Engineering Measurements, Moscow, 1979, pp. 157-161.
Properties of . . . Synthesis: A.L. Vereschagin et al: 1993: pp. 160-162,
no month.
Soot Derived . . . Charge: vol. 22: No. 2, pp. 189-191, 1984, no month.
Nature: Diamonds in . . . Soot: N.Roy Greiner et al: vol. 333, 2 Jun. 1988:
pp. 22-25.
Journal of Applied Physics: vol. 62: 1 Sep. 1987: pp. 1553-2159: Mathias
Van Thiel et al.
Diamond & Related Materials: vol. 1, No. 1, Aug. 15, 1991: pp. 3-7B.
The Journal of Organic Chemistry: vol. 50: Dec. 27, 1985: No. 26: pp. 8-9A.
|
Primary Examiner: Straub; Gary P.
Assistant Examiner: Hendrickson; Stuart L.
Attorney, Agent or Firm: Ladas & Parry
Claims
1. In a synthetic diamond-bearing material consisting essentially of
aggregates of particles of a round or irregular shape, with an average
diameter of the particles not exceeding 0.1.mu., the improvement wherein
the material comprises:
a) elemental composition (% by mass):
______________________________________
carbon 75 to 90,
hydrogen 0.8 to 1.5,
nitrogen 0.6 to 4.5,
oxygen the balance;
______________________________________
b) phase composition (% by mass):
amorphous carbon 10 to 30, diamond of cubic crystal structure the balance;
c) a porous structure said material having pores with a volume of the pores
being within about 0.6 to 1.0 cm.sup.3 /g;
d) a material surface with 10 to 20% of the material surface being methyl,
nitrile, first and second hydroxyl groups having different chemical shifts
in an NMR spectrum and one or more oxycarboxylic functional groups
selected from the group consisting of carbonyl groups, carboxyl groups,
guinone groups, hydroperoxide groups and lactone groups 1 to 2% of the
material surface being occupied by carbon atoms with uncompensated bonds;
and
e) a specific surface area in a range of from 200 to 450 gM.sup.2 /g.
2. A synthetic diamond bearing material according to claim 1, wherein a
diameter of the pores is within 7.5 to 12.5 nm.
3. A synthetic diamond-bearing material according to claim 1, wherein the
material has a crystal lattice parameter of 0.3562.+-.0.0004 nm.
4. A diamond-bearing material as claimed in claim 1 prepared by a process
consisting essentially of detonating in a closed space a charge consisting
essentially of a carbon-containing explosive or mixture of explosives
having a negative oxygen balance, the detonation of the charge being
initiated in the presence of carbon particles in a concentration of about
0.01 to 0.15 kg/m.sup.3 in a medium consisting essentially of about 0.1 to
6% by volume oxygen and a balance of gases inert to carbon at a
temperature of about 303 to 363 K.
5. A diamond-bearing material as claimed in claim 3 prepared by a process
consisting essentially of detonating, in a closed space, a charge
consisting essentially of a carbon-containing explosive or mixture of
explosives having a negative oxygen balance the detonation of the charge
being initiated in the presence of carbon particles in a concentration of
about 0.01 to 0.15 kg/m.sup.3 in a medium consisting essentially of about
0.1 to 6% by volume oxygen and a balance of gases inert to carbon at a
temperature of about 303.degree. to 363.degree. K.
6. A process for preparing a synthetic diamond-bearing material consisting
essentially of:
(a) providing a pressure vessel with (i) a charge consisting essentially of
at least one carbon-containing solid explosive or mixture of
carbon-containing solid explosives, said charge having a negative oxygen
balance, and (ii) a medium consisting essentially of gases and carbon
particles ultra dispersed as a suspension in the gases in a concentration
of about 0.01 to 0.15 kg/m.sup.3, said gases consisting essentially of
oxygen in an amount of about 0.1 to 6% by volume and a balance of nitrogen
or gases inert to carbon;
(b) closing the pressure vessel and detonating the charge, the detonating
of the charge being initiated at a temperature of about 303.degree. to
363.degree. K in the absence from the charge of a carbon material other
than the carbon-containing explosive or mixture of explosives to form the
synthetic diamond-bearing material from decomposition products of the
explosive or mixture of explosives and not from the carbon particles in
the medium; and
(c) recovering the synthetic diamond-bearing material.
7. A process as claimed in claim 6, wherein the explosive or explosives are
selected from the group consisting of HMX, trinitrotriaminebenzene, RDX
and mixtures of RDX and trotyl.
Description
FIELD OF THE INVENTION
The present invention relates to the field of inorganic chemistry of
carbon, and more specifically, to the cubic modification of carbon
featuring the properties of a superhard material, and to the process for
preparing the material which comprises detonation synthesis of a
diamond-bearing burden with subsequent extraction by chemical methods.
When some explosives detonate under the conditions making it possible to
preserve the condensed carbon products of the explosion ultradispersive
diamond-bearing powders are formed, which possess such specific properties
as high dispersivity, presence of defects of carbon structure, developed
active surface. These characteristics are varied within wide limits
depending on the conditions of preparing the diamond-bearing materials.
The particular properties of the diamond-bearing detonation materials
define the spheres of the practical application, such as in composite
materials and coatings, abrasive or lubricating compositions and the like.
BACKGROUND ART
The properties of diamond-bearing materials, obtained with the use of
explosion energy, and also the conditions of their synthesis and
separation from impurities are known in the art.
A paper (G. A. Adadurov et al, "The physics of Pulse Pressures" pp 44 (74),
1979, No. 4, Papers of All-Union Science-Research Institute of Physical
and Radio Engineering Measurements, p. 157) discloses the characteristics
of the product obtained in detonation of a mixture of RDX with a carbon
material (black or graphite) in a blasting chamber in inert atmosphere.
The purified product is a powder with the average particle size 0.05 to
5.0 mom, the average particle size calculated for the unit surface values
is 0.04 to 0.08 mcm. The unit surface area is 20 to 42 m.sup.2 /g. The
pycnometric density is 3.20 to 3.40 g/cm.sup.3. By the phase composition,
the product is a mixture of diamond of a cubic (the lattice parameter
a=0.357 nm) and a hexagonal modification (lonsdalite). The size of the
coherent scattering region (CSR) of crystallites (i.e. the linear distance
between the adjacent defects) is 10 to 12 nm, and the value of
microdistortions of the second kind, characterizing the presence of
defects, is within the limits 1 to 2.multidot.10.sup.-3. After annealing at
1073 K, the size of CSR was 12 nm, and the value of microdistortions of
the second kind was reduced to 0.35.multidot.10.sup.-3. The temperature of
the beginning of graphitization is over 1073K. About one fourth of the
surface is occupied by carboxyl groups. When heated in vacuum, specimens
lose some. 8% of the mass owing to liberation of oxygen, carbon monoxide
and carbon dioxide molecules.
The properties of the diamond obtained from the carbon of explosives are
described by K. V. Volkov with co-authors (The Physics of Combustion and
Explosion, v. 26, No. 3, p, 123, 1990). Synthesis is effected when charges
are set off in a blasting chamber in the atmosphere of carbon dioxide and
in a water jacket. The particle size of the obtained diamond is 0.3 to
0.06 nm, the CSR size is 4 to 6 nm, the particle shape is round. The
pycnometric density is 3.2 g/cm.sup.3. The product contains about 90%
diamond, the balance, adsorbed gases. The product start oxidizing at 623
K. After five hour holding at. 1173K, the degree of graphitization of the
diamond is 10%.
Other versions of the method (A. M. Staver et al, The Physics of Combustion
and Explosion, V. 20, No. 5, p. 100, 1984 and G. I. Savvakin et al,
Proceedings of the USSR Academy of Sciences, V. 282, No. 5, 1985) are
based of other or the same explosives in various kinds of atmospheres. The
products resulting in this case feature properties similar to those
described by K. V. Vollcov with co-authors.
For isolating the end diamond-bearing product, use is made of a complex of
chemical operations directed at either dissolving or gasifying the
impurities present in the material. The impurities, as a rule, are of the
two kinds: non-carbon (metal, oxides, salts, etc.) and nondiamond forms of
carbon (graphite, black, amorphous carbon).
The diamond-bearing material most close by the technical properties to the
material of the present invention is that disclosed in British Patent No.
1154633.
According to this reference, the material is obtained by impact reduction
of graphite. The resulting primary product of the synthesis contains, as a
rule, less than 15% diamond of the total amount of carbon and a
considerable quantity or inorganic impurities.
The purified diamond-bearing material consists of individual diamond
particles having the average diameter no more than 0.1 mkm, the unit
surface area from 40 to 400 m.sup.2 /g, hydroxyl, carboxyl and carbonyl
groups comprise from 10 to 30% of the surface area. The diamond particles
feature no external crystalline cut. Individual diamond crystallites;
feature wide spread over the diameter: 7 10.sup.-4 to 1 10.sup.-2 mcm (7 to
100 A). The material contains 87 to 92% by mass carbon, in addition it
contains 0.1 to 2.0% hydrogen, 0.1 to 2.5% nitrogen and up to 10% oxygen.
When heating from 1123 to 1273 K for four hours in an inert atmosphere, the
material loses no more than 5% of the mass in the form of carbon monoxide,
carbon dioxide, water and hydrogen. From the results of radiographic
analysis, the material contains only carbon, possible impurities of
graphite do not exceed 0.2%, inorganic impurities neither exceed 0.2%.
The diamond-bearing material features abrasive and specific adsorption
properties, which made it possible to surmise its application in polishing
hard materials, strengthening metal coatings, and also in chromatography.
Thus, the publications disclosing the know diamond-bearing materials
synthesized with the use of the energy of explosion decomposition of
explosives and also the specific processes for obtaining these materials
fail to disclose the technical solutions to the problem which would make
the basis for the effective, economically efficient and ecologically safe
technology of industrial production of a diamond-bearing material with the
present combination of properties.
DISCLOSURE OF THE INVENTION
The invention is based on the problem of producing a diamond-bearing
material with the preset combination of properties, featuring, due to
this, a universal capacity of being included in various composite
materials and coatings and being obtained following a simple process
characterized by safety, reliability, improved technical, economical and
ecological parameters and making it possible to organize, on its basis,
large-scale industrial production of the diamond-bearing material of the
present invention.
This problem is solved by that the material of the present invention is a
man-made diamond-bearing material consisting of the aggregates of
particles of a round or irregular shape, with the average diameter not
exceeding 0.1 mcm, and part of the material surface containing functional
groups, said material being characterized by the following elemental
composition (% by mass):
______________________________________
carbon 75 to 90
hydrogen
0.6 to 1.5
nitrogen
1.0 to 4.5
oxygen the balance,
______________________________________
by a porous structure, by the following phase composition (mass %):
roentgenoamorphous diamond-like phase 10 to 30 diamond of cubic
modification the balance 10 to 20% of the material surface being methyl,
nitrile, hydroxy groups of two kinds, and also oxycarboxylic functional
groups of the general formula O.dbd.R, where R is .dbd.COH, .dbd.COOH,
.dbd.CO, .dbd.C.sub.6 H.sub.4 or any mixtures thereof, besides, 1 to 2% of
the material surface being occupied by carbon atoms with uncompensated
bonds. Crystal lattice parameter is O.3562.+-.0.0004 nm. The ash content
is 0.1 to 5.0% by mass. The ash content in the product is conditioned by
the presence of inorganic impurities due to the specific features of the
method of producing the diamond-bearing substance, and also conditioned by
the presence of ferric oxides and carbides, copper and nickel salts,
calcium and silicon compounds, which fact is by no means an obstacle in
using the material of the present invention in the above-mentioned fields
of application.
The stated problem is also solved by that the diamond-bearing material of
the invention is obtained by detonating a carbon-containing, explosive
with a negative oxygen balance in a closed space in inert (to carbon)
gases with the content of oxygen 0.1 to 6.0% by volume at the temperature
303 to 363 K in the presence of are unltradispersive carbon phase (carbon
condensate) with the concentration 0.01 to 0.15 kg/m.sup.3, with the use of
the apparatuses developed by the applicant.
The diamond-bearing material of the invention is a light-grey to dark-grey
powder with the average particle size 0.02 to 0.1 mcm, preferably no more
than 0.05 mom, determined by the sedimentation method. The particles
feature a characteristic porous structure investigated by the nitrogen
adsorption and desorption isotherms at 77.5 K. The specimens were
preheated in vacuum at 300 K.
The total volume of pores in the powders of the diamond-bearing material of
the invention is 0.6 to 1.0 cm.sup.3 /g, mainly 0.7 to 0.9 cm.sup.3 /g.
Size distribution of the pores in shown in FIG. 1; the average diameter of
the pores calculated by Dollimore-Hill algorithm is 7.5 to 12.5 nm,:
mainly 8 to 10 nm. The specific porous structure of the material particles
is formed owing to the condition of synthesis.
The unit surface area determined by Brunauer-Emmet-Teller isotherms from
the thermal desorption of argon is in the range from 200 to 450 m.sup.2
/g.
The particle size is within the limits 1 to 10 nm, mainly 4 to 7 nm.
Electron-microscopic investigations have shown that the aggregates of
particles consist of individual grains of a round or irregular shape of 2
to 10-nm diameter. Crystal faces have not been found on the surface of the
particles.
The average size of coherent scattering regions calculated by the method of
the fourth moments from the reflection profile (220) amounted to 2 to 10
nm, mainly 4 to 7 nm, which is close to the size of diamond particles,
determined from adsorption data. Concurrent with this, the value of
microdistortions of second kind was calculated from the analysis of
profile line (220), which was measured as .DELTA. a/a, where .DELTA. a is
the mean deviation of the crystal lattice parameter. For the specimens of
the material of the present invention, this value is 0.01 which is by an
order of magnitude greater than for other known forms of detonation
diamonds. The value of microstresses in GPa was calculated from the
formula:
.sigma.=.DELTA.a/aE
where E is Young's modulus equal to 1000 GPa.
It follows that the particles are compressed by a pressure of 10 GPa. The
crystal lattice parameter of the claimed material was calculated from the
analysis of reflection (220) using cobalt radiation. For this, the
position of the center of gravity of the line was found. It was revealed
that the crystal lattice parameter of the material of the present
invention is 0.3562.+-.0.0004 nm, whereas in the rest of the diamond
varieties it is 0.3567 nm. The revealed highly deformed condition of the
crystal lattice is thermally stable up to the temperature of the beginning
of graphitization, which was not observed before in any type of diamond
obtained using the energy of explosion. This results from that the forces
of surface tension of the particles compress the crystal lattice owing to
their ultradispersive condition. Thus, the compressed highly deformed
crystal lattice is specific only for the diamond-bearing material claimed
and, among other things, define the unique combination of its properties.
According to the X-ray pattern (FIG. 2), the material claimed contains the
diamond of a cubic modification and a roentgenoamorphous phase (the
reflection region corresponding to d=0.127 nm). The amount of the
amorphous phase was estimated by the decrease in the intensity of
reflection (220) of the cubic diamond as against the specimen containing
pure cubic diamond. The value obtained is 10 to 30% by mass.
Combination of the diamond cubic and amorphous phases is specific for the
diamond-bearing material of the present invention and is the result of its
cluster organization. The roentgenoamorphous phase contains no graphite.
This is proved by the studies of the specimens of the material using the
method of nuclear magnetic resonance and X-ray photoelectron spectroscopy.
Thus, in the NMR spectrum C13 (FIG. 3), there is present only one line
with a chemical shift of -34.5 parts by million (ppm), characteristic of
the diamond phase. The X-ray photoelectron spectrum of carbon in C T s
region has the absorption band in the region of 286 eV, after bombardment
of the specimen with argon ions its surface being charged to the value of
3.3 eV, which testifies to the dielectric properties of the surface carbon
structures. In the presence of conductive modifications of carbon
(graphite), charging of the surface would not be observed.
Thus, the amorphous phase is close, by the nature of the chemical bonds, to
cubic diamond and is an extremely disordered and defect-saturated
periphery of diamond clasters.
The presence of the amorphous phase defines an increased reactivity of the
claimed material as compared with other man-made diamonds. This shows up
in the following reactions. Thus, the temperature of the beginning of
oxidation in the air of the diamond-bearing material of the invention,
measured at the heating rate 10 degree/min, is 703 to 723 K, whereas for
man-made diamonds it is 843 to 923 W. In addition, when heating specimens
of the claimed material at a temperature of 443 to 753 K in carbon dioxide
at atmospheric pressure, its adsorption takes place, causing an increase
in the specimen mass by around 5%, which was-not observed before for any
of the forms of man-made diamonds.
Practically, increased activity of the material of the present invention
manifests itself in compaction processes. In particular, in hot pressing
the powders of the present material, strong low porosity compacts are
obtained at the temperatures by 100 to 500 degrees lower than it is
adopted in sintering other diamond powders. From the data of radiographic
studies, the compacted specimen lacks the amorphous phase, and the
intensity of reflections in the cubic diamond increases. It seems that
just the amorphous phase, featuring a labile structure, is the activator
of sintering diamond grains under comparatively mild conditions.
The carbon atoms with uncompensated bonds present on the surface of the
material specimens also stipulate their affinity to molecular nitrogen. As
a result of this, the material specimens, after holding in the air or in
nitrogen, chemisorb nitrogen with the formation of nitrile groups.
Ultradispersive condition of the material of the present invention
contributes to its energy characteristics. Thus, the enthalpy of its
formation, determined from the heat of combustion, amounts to 2563 to 2959
kJ/kg, whereas for the natural diamond its value is 209.16 kJ/kg. Such
energy capacity is defined by the contribution of the surface energy of
the diamond-bearing material of the present invention. So, high energy
saturation is specific to the claimed diamond-bearing material.
As distinct from the cited prior-art publications that disclose
oxygen-containing functional groups (carboxyl, hydroxyl, carbonyl and
others) directly linked with the surface atoms of the diamond
crystallites, the diamond-bearing material of the invention, featuring
inhomogeneous phase composition, is characterized by a specific way of
surface relaxation. In our case, the oxygen-containing functional groups
are, as a rule, derivatives of more diverse surface carbon structures,
aliphatic, alicyclic and aromatic included.
The qualitative and quantitative composition of the surface functional
groups was determined using several analysis methods.
Studying the gases evolved in thermodesorption of the claimed material,
liberation of carbon oxides, hydrogen, hydrogen cyanide and methane was
observed. Based on these data, it was calculated that the quantity of the
surface carbon atoms comprises no less than 2% of the total number. In
studying the IR-spectrum of absorption of specimens, the absorption bands
were revealed characteristic of carbonyl .dbd.CO, carboxyl .dbd.COOH,
hydroxyl --OH and methyl CH.sub.3 -groups. In the analysis of the spectrum
of proton magnetic resonance, it was found that two varieties of hydroxyl
groups differing in the value of the chemical shift were observed. It is
supposed that one of these varieties ire isolated groups and the other and
interacting groups. In conducting polarographic investigation, there were
identified lactone .dbd.COOCO--, quinone O.dbd.C.sub.6 H.sub.4 .dbd.O and
hydroperoxide .dbd.COOOH groups. The total amount of oxygen-containing
surface groups was determined from the reaction of metal potassium, as it
is recited in British Patent No. 1154633, and it amounted from 10 to 20%
of the specimen surface.
The surface of the material is thus a wide spectrum of both functional
groups, mainly oxygen-containing, and carbon structures to which these
groups are directly linked and which influence, to a considerable extent,
the chemical properties and reactivity of the surface. This opens up
greater possibilities to conduct various chemical reactions on the surface
the claimed diamond-bearing material than are those issuing from the
description of the surface properties of the known materials.
Thus, the diamond-bearing material of the present invention features the
following advantages as compared with the material of British Patent No.
1154633 which is the closest prior-art material, the advantages making it
possible to use it most effectively in producing composite materials:
1. Porous structure of the aggregates of diamond particles with the volume
of the pores from 0.6 to 1.0 cm.sup.3 /g and pore diameter 7.5 to 12.5 nm
which permits of using lees mass of the claimed material with the same
volume proportion of the diamond-bearing material as against that of the
prior-art material.
2. The presence of the amorphous-phase up to 30% by mass, which facilitates
the conditions of compaction of composite materials.
3. The presence of a wide spectrum of functional derivatives on the surface
with the result that the claimed material can be used for a wide range of
composite compositions without preliminary modification of the surface.
It is to be noted that the new characteristics of the substance are
stipulated by 1he method of preparing thereof. As distinct from the
closest prior art, where the diamond-bearing material is obtained by
impact loading of graphite, the material of the invention is obtained in
detonation decomposition of explosives, that is, the material is not the
product of recrystallization of one allotrope form of carbon to another,
but the product of carbon condensation through plasma (gas) and, probably,
liquid into a solid with a specific crystal structure, chemical
composition and properties.
Moreover, the diamond-bearing material of the present invention is obtained
by detonation in a blasting chamber of carbon-containing explosive with a
negative oxygen balance, with the following requisite conditions being
observed:
(a) the chamber temperature at detonation is 303 to 363 K,
(b) the oxygen content in the chamber is 0.1 to 6.0% by volume,
(c) the presence in the chamber of suspended ultradispersive particles with
the concentration 0.01 to 0.15 kg/m.sup.3.
These conditions ensure.
(a) formation of a diamond cubic phase with the size of undisturbed crystal
blocks 1 to 10 nm,
(b) condensation of a definite amount of carbon in the form of a
diamond-like roentgenoamorphous phase,
(c) formation of an ordered superstructure of the diamond, diamond-like and
other highly dispersive carbon phases, the reactive peripheral formations
included,
(d) inclusion in the condensed diamond-bearing carbon material at the
synthesis stage of a certain proportion of non-carbon (inorganic)
additives.
The presence of oxygen in the blasting chamber atmosphere in the amount 0.1
to 6.0% by volume ensures a complex macrokinetic balance between the
processes of surface and volumetric oxidation of carbon. This, in turn,
forms, at the synthesis stage, the basis of the specific porous structure
of the claimed diamond-bearing material. The rate of gasification is known
to be restricted in active media by the reverse diffusion of the reaction
products. In the set of the above-listed conditions of synthesis, the
above-mentioned content of oxygen in combination with a definite
concentration of carbon condensed phase makes it possible to block, to a
considerable degree, the surface of carbon. This favours its preservation
on the condition that the oxygen concentration does not exceed 8% by
volume. At the same time, development of topochemical reactions of
oxidation of non-diamond carbon in the reflected impact waves owing to the
catalytic influence of the above-mentioned non-carbon additives is
possible, which results in the destruction of the originally ordered
carbon structures, in the partial graphitization and amorphization of
diamond particles, in the development of defects in the diamond
macrocrystallites.
In the suspension of ultradispersive carbon particles in the synthesis
atmosphere, the carbon particles serve as the centers of crystallization
of the diamond particles and they scatter the energy of explosion because
if they are absent the output of the condensed products of explosion in
the oxygen-containing atmosphere is reduced. Because of instability of the
suspension, concentrations greater than 0.15 kg/m.sup.3 cannot be achieved
despite the ultradispersive condition of carbon.
Given below are examples illustrating the influence of the conditions of
synthesis on the properties of the diamond-bearing material obtained.
EXAMPLE 1
Placed in the center of a blasting chamber, commonly used in explosion
technologies, of 2 m.sup.3 volume is a charge of an explosive, such as
trotyl/hexogen (cyclotrimethylenetrinitramine ("RDX")) 60/40 of 0.5-kg
with an electric detonator in an atmosphere containing 4 vol. % oxygen
(the balance is nitrogen), and 0.1 kg/m.sup.3 ultradispersive carbon
particles at the atmosphere temperature 303K. The chamber is closed and
the charge is blasted. After ten minutes holding, the chamber is opened
and powder is taken off the chamber walls. Then the powder is sieved
through a screen with a mesh size of 160 mcm, is placed in a glass and
boiled with 200 ml of 468 hydrochloric acid for dissolving metal
impurities. For removing oxidized and non-diamond forms of carbon, the
product is additionally treated with a mixture of concentrated nitric and
sulfuric acids at a temperature of 523 K for 2 hours. Then the product is
washed with distilled water from the acids till pH aqueous extract equal
to 7 and is dries in the air at a temperature of 423 K for four hours. In
studying the powder, the following data are obtained.
a dark-grey powder has a picnometric density of 3.1 g/cm.sup.3, the surface
unit area being 285 m.sup.2 /g. The average particle diameter of the
specimen, calculated on the basis of the above data, is 6.6 nm.
By the data of radiographic investigation, the product consists of two
phases: a cubic carbon phase (diamond) (75%) and its amorphous phase
(25%).
The cubic lattice parameter measured by cobalt radiation from the profile
of reflection (220) is 0.3563 nm.
Studies into the elemental composition gave the following results: (C) is
88.5%, (N) is 2.2%, (H) is 1.1%, (O) is 8.2%. The yield (Y) of the end
product comprises 3.5% of the explosive and the content of diamond in the
condensed products of explosion (C) is 55.4%. The ash content (Z) is 2.1%,
the pore volume (V.sub.pore) is 0.7 cm.sup.3 /g, the average diameter
(d.sub.pore) is 8.4 nm.
The composition of the surface oxygen-containing functional groups is
determined polarographically. Quinone, lactone, carbonyl, carboxyl and
hydrogen peroxide groups are identified by the value of reduction
potential. Nitrile and methyl groups are identified by the composition of
gases evolved in heating. Hydroxyl groups are determined from the data of
IR-spectroscopy.
Other examples of conducting the process with the claimed ranges of the
method parameters are tabulated in Table 1 (hydroxyl, lactone, carbonyl,
carboxyl, hydroperoxide, nitrile, methyl groups and surface carbon atoms
with uncompensated links have been found in all the specimens prepared by
the process according to the present invention).
The table also includes comparative examples with the method conditions
different from those claimed, for a graphic comparison with the properties
of the obtained products.
TABLE 1
______________________________________
Con-
cent-
Con- rat-
tent ion
of of
oxy- sus-
gen pen-
Cham- vol. %
ded
ber (inert
par-
t, K at gas the
ti- The properties of
Examp- deto- balan-
cles, the product obtain-
le No.
Explosive
nation ce) C, kg/m.sup.3
ed
1 2 3 4 5 6
______________________________________
1 Trotyl 303 4.0 0.1 (C) = 88.55%
/RDX (H) = 1.1%
60/40 (N) = 2.2%
(O) = 8.2%
(Z) = 2.1%
(B) = 3.5%
(C) = 55.4%
a = 0.3563 nm
CRS = 6.6 nm
S = 285 m.sup.2 /g
V.sub.pore = 0.7 cm.sup.3 /g
d.sub.pore = 8.4 nm
25% of amorphous
phase and
75% of diamond
phase
2 Trotyl 303 0.0 0.1 (C) = 88.5%
/RDX (H) = 1.0%
60/40 (N) = 3.4%
(compara- (O) = 6.2%
tive (Z) = 0.9%
example (B) = 5.1%
without (C) = 45.3%
oxygen) a = 0.3567 nm
CSR = 6.0 nm
S = 240 m.sup.2 /g
V.sub.pore = 0.85 cm.sup.3 /g
d.sub.pore = 7.8 nm
5% of amorphous
phase and
95% of diamond
phase
3 Trotyl 304 0.2 0.15 (C) = 86.0%
/RDX (H) = 0.8%
60/40 (N) = 3.5%
(O) = 5.8%
(Z) = 3.5%
(B) = 5.0%
(C) = 53.4%
a = 0.3564 nm
CSR = 6.0 nm
S = 242 m.sup.2 /g
V.sub.pore = 0.92 cm.sup.3 /g
d.sub.pore = 8.9 nm
12% of amorphous
pahse and
88% of diamond
phase
4 Trotyl 305 6.2 0.5 There is no diamond
/RDX phase in the
60/40 products.
(compara-
tive
example
with
excess
oxygen)
5 Trotyl 303 0.1 0.15 (C) = 85.2%
/RDX (H) = 1.1%
60/40 (N) = 5.7%
(O) = 5.7%
(Z) = 2.1%
(B) = 5.0%
(C) = 49.2%
a = 0.3564 nm
CSR = 4.6
S = 307 m.sup.2 /g
V.sub.pore = 0.87 cm.sup.3 /g
d.sub.pore = 11.5 nm
18% of amorphous
phase and
82% of diamond
phase
6 Trotyl 303 10.1 0.15 There is no carbon
/RDX phase in the
60/40 products.
(compara-
tive
example
with
excess
oxygen)
7 Trotyl 333 0.1 0.1 (C) = 88.6%
/RDX (H) = 0.8%
60/40 (N) = 2.1%
(O) = 5.4%
(Z) = 3.1%
(B) = 5.1%
(C) = 50.3%
a = 0.3564 nm
CSR = 4.8 nm
S = 315 m.sup.2 /g
V.sub.pore = 0.99 cm.sup.3 /g
d.sub.pore = 11.2 nm
25% of amorphous
phase and
75% of diamond
phase
8 Trotyl 335 1.0 0.14 (C) = 89.0%
/RDX (H) = 0.9%
60/40 (N) = 1.5%
(O) = 3.8%
(Z) = 4.8%
(B) = 4.9%
(C) = 52.7%
a = 0.3562 nm
CSR = 3.8 nm
S = 378 m.sup.2 /g
V.sub.pore = 0.65 cm.sup.3 /g
d.sub.pore = 12.3 nm
22% of amorphous
phase and
78% of diamond
phase
9 Trotyl 332 5.8 0.12 (C) = 87.5%
/RDX (H) = 1.2%
60/40 (N) = 2.5%
(O) = 6.5%
(Z) = 2.3%
(B) = 0.5%
(C) = 9.1%
a = 0.3565 nm
CSR = 4.1 nm
S = 329 m.sup.2 /g
V.sub.pore = 0.76 cm.sup.3 /g
d.sub.pore = 8.7 nm
29% of amorphous
phase and
71% of diamond
phase
10 Trotyl 338 6.2 0.1 There is no diamond
/RDX in the products.
60/40
(compara-
tive
example
with
excess
oxygen)
11 Trotyl 363 0.1 0.1 (C) = 87.1%
/RDX (H) = 0.8%
60/40 (N) = 2.9%
(O) = 8.0%
(Z) = 1.2%
(B) = 5.1%
(C) = 53.6%
a = 0.3564 nm
CSR = 2.8 nm
S = 420 m.sup.2 /g
V.sub.pore = 0.09 cm.sup.3 /g
d.sub.pore = 11.6 nm
30% amorphous
phase and 70% of
diamond phase
12 Trotyl 361 1.0 0.15 (C) = 88.1%
/RDX (H) = 0.9%
60/40 (N) = 2.9%
(O) = 5.6%
(Z) = 1.9%
(B) = 4.8%
(C) = 58.4%
a = 0.3582 nm
CSR = 2.9 nm
S = 415 m.sup.2 /g
V.sub.pore = 0.83 cm.sup.3 /g
d.sub.pore = 12.4 nm
25% of amorphous
phase and
75% of diamond
phase
13 Trotyl 362 3.0 0.15 (C) = 88.1%
/RDX (H) = 1.1%
60/40 (N) = 1.8%
(O) = 7.4%
(Z) = 1.6%
(B) = 3.9%
(C) = 38.6%
a = 0.3563 nm
CSR = 3.0 nm
S = 398 m.sup.2 /g
V.sub.pore = 0.64 cm.sup.3 /g
d.sub.pore = 9.8 nm
25% of amorphous
phase and
75% of diamond
phase
14 Trotyl 363 6.5 0.1 There is no diamond
/RDX in the explosion
60/40 products.
(compara-
tive
example
with
excess
oxygen)
15 Trotyl 363 6.0 0.05 (C) = 87.3%
/RDX (H) = 0.9%
60/40 (N) = 1.5%
(O) = 10.3%
(Z) = 2.5%
(B) = 3.1%
(C) = 25.1%
a = 0.3564 nm
CSR = 3.5 nm
S = 408 m.sup.2 /g
V.sub.pore = 1.0 cm.sup.3 /g
d.sub.pore = 11.2 nm
12% of amorphous
phase and 88%
of diamond phase
16 Trotyl 361 4.5 0.02 (C) = 89.7%
/RDX (H) = 1.4%
60/40 (N) = 1.8%
(O) = 7.1%
(Z) = 2.1%
(B) = 3.6%
(C) = 32.1%
a = 0.3565 nm
CSR = 4.6 nm
S = 423 m.sup.2 /g
V.sub.pore = 0.98 cm.sup.3 /g
d.sub.pore = 12.4 nm
10% of amorphous
phase and 90%
of diamond phase
17 Trotyl 303 0.006 0.01 (C) = 88.9%
/RDX (Z) = 1.4%
60/40 (N) = 3.5%
(compara- (O) = 6.2%
tive (Z) = 3.0%
example (B) = 4.5%
with (C) = 43.7%
deficient a = 0.3568 nm
oxygen) CSR = 5.2 nm
S = 358 m.sup.2 /g
V.sub.pore = 1.0 cm.sup.3 /g
d.sub.pore = 11.4 nm
25% of amorphous
phase and 75%
of a diamond phase
18 Trotyl 305 2.5 0.005 (C) = 90.1%
/RDX (H) = 1.1%
60/40 (N) = 2.1%
(O) = 6.7%
(Z) = 2.5%
(B) = 2.5%
(C) = 34.6%
a = 0.3567 nm
CSR = 3.9 nm
S = 401 m.sup.2 /g
V.sub.pore = 0.95 cm.sup.3 /g
d.sub.pore = 10.5 nm
5% of amorphous
phase and 95%
of diamond phase
______________________________________
Practically any carbon-containing explosive with a negative oxygen balance,
such as octogen (cyclotetramethylene-tetranitramine ("HMX")),
trinitrotriaminebenzene, mixtures of trotyl/RDX SG/50 and trotyl/RDX 70/30
and the like, can be used as an explosive in the process of the present
invention with the same result as to the properties of the end product and
under the same conditions.
The present diamond-bearing material is suggested for use as a component of
composite materials in the form of an additive considerably improving the
wear-resistance of assemblies, their reliability and life time, and also
as a material for gas-liquid chromatography.
Thus, for example, introduction of the claimed material into lubricating
oil I-40A in the amount 0.1% by mass makes it possible to reduce the
coefficient of friction in plain s bearings by a factor of 1.5 . . . 1.8,
the rate of wear of friction pairs by a factor of 6 to 10, allows
increasing the ultimate loads on a friction assembly by a factor of 1.5 to
7.0 and decreasing the volume temperature in the zone of friction as
against the lubricating oils containing no such additive.
Introduction of the material according to the present invention into a
universal chromium electrolyte with the concentration 8 to 15 g/l and
conducting chromium deposition at the bath temperature 323 to 328 K and
current density 40 to 60 A/dm.sup.2 give chromium coating applied on to a
tool for material working, featuring the following efficiency.
TABLE 2
______________________________________
Increase in durability, times
(as compared with tools and
machine parts having no coat-
ing based on the material of
Tool the invention)
______________________________________
Dies for cold drawings of
2 . . . 5
metals
Press-tool for powder
10
metallurgy
Die tool 1.5 . . . 4.0
Dental drills 8 . . . 12
Cutting tools for glass-
3 . . . 10
reinforced plastic
Shafts, machine and
2 . . . 3
mechanism gear wheel
______________________________________
The particular increase in durability values of a tool depends on the
properties of the material being processed and the conditions of
processing.
The material of the present invention can also be used in chromatography.
The process of production of ultradispersive diamond is carried out on
commercial scale.
* * * * *
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