U.S. patent application number 14/713005 was filed with the patent office on 2015-09-17 for diamond unit cell and diamond mass by combinatorial synthesis.
This patent application is currently assigned to Unit Cell Diamond LLC. The applicant listed for this patent is Daniel HODES, Arnold L. Newman. Invention is credited to Daniel HODES, Arnold L. Newman.
Application Number | 20150259213 14/713005 |
Document ID | / |
Family ID | 51569278 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150259213 |
Kind Code |
A1 |
HODES; Daniel ; et
al. |
September 17, 2015 |
Diamond Unit Cell and Diamond Mass by Combinatorial Synthesis
Abstract
Diamond unit cell produced by a combinatorial synthesis from a
tetrahedranoidal compound and a carbon atom, and diamond mass
produced therefrom, are described. Diamond mass produced is
spectroscopically-free of graphitic impurities, and free of
observable defects.
Inventors: |
HODES; Daniel; (Bethesda,
MD) ; Newman; Arnold L.; (Bethesda, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HODES; Daniel
Newman; Arnold L. |
Bethesda
Bethesda |
MD
MD |
US
US |
|
|
Assignee: |
Unit Cell Diamond LLC
Bethesda
MD
|
Family ID: |
51569278 |
Appl. No.: |
14/713005 |
Filed: |
May 15, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14120508 |
May 28, 2014 |
9061917 |
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14713005 |
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13204218 |
Aug 5, 2011 |
8778295 |
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14120508 |
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61344510 |
Aug 11, 2010 |
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Current U.S.
Class: |
423/446 |
Current CPC
Class: |
C01B 32/25 20170801;
B01J 2203/0655 20130101; B01J 19/126 20130101; C30B 29/04 20130101;
C01B 32/26 20170801 |
International
Class: |
C01B 31/06 20060101
C01B031/06; C30B 29/04 20060101 C30B029/04 |
Claims
1. A diamond unit cell.
2. The diamond unit cell of claim 1, which is produced in a
combinatorial reaction between a tetrahedranoidal compound and a
carbon atom.
3. A diamond mass, which comprises diamond unit cells.
4. The diamond mass of claim 3, having no detectable impurities,
wherein said no detectable impurities are selected from the group
consisting of amorphous carbon, non-diamond allotropes of carbon,
hydrocarbenoids, heteroatoms, and heteroatom-bearing materials.
5. The diamond mass of claim 3, which is spectroscopically-free of
graphitic impurities.
6. The diamond mass of claim 3, which is free of discoloration from
nitrogen oxide inclusions.
7. The diamond mass of claim 3, which is free of discoloration by
inclusions of species comprising oxides of nitrogen.
8. The diamond mass of claim 3, which is contains no nitrogen
getter-contaminants.
9. The diamond mass of claim 3, which exhibits a homogeneous
crystal morphology.
10. The diamond mass of claim 3, which contains no color
zonation.
11. The diamond mass of claim 3, which contains no crystal
zonation.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains to the combinatorial
synthesis of the diamond unit cell and man-made diamond masses
produced therefrom.
BACKGROUND OF THE INVENTION
[0002] Diamond is a valuable material due its properties of
hardness (10 on the Mohs hardness scale), heat stability, high room
temperature thermal conductivity (about 2000 W/mK), very low rms
vibration at room temperature (0.002 nm), a high index of
refraction (2.4), optical transparency from infrared through
visible, and UV fluorescence. Because of its high band gap (5.45
eV) it is a superb electrical insulator (10.sup.16 ohms).
Boron-doped (blue) diamond has been found to be p-type
semiconductor having a high hole mobility and electrical breakdown
strength. Such properties may afford diamond utility with respect
to substrates for micro-electronic devices, ultraviolet light
protective coatings, high energy laser device windows, and even
diamond semiconductor devices. Such applications require that
diamond be ultra-pure.
[0003] Many synthetic methods for diamond are known. These methods
produce diamond either from elemental carbon or from elemental
carbon obtained from a compound or compounds of carbon, which
methods subject elemental carbon to conditions under which the
carbon will form the crystalline species known as diamond.
Typically, these methods involve high pressure, high temperatures,
or high energy discharges. Moreover, post treatments are frequently
necessary for purification. Most of these methods do not produce
ultra-pure diamond, however.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide the
diamond unit cell.
[0005] It is further an object of the present invention to provide
the diamond unit cell produced from combinatorial synthesis of a
tetrahedranoidal compound and a carbon atom.
[0006] Moreover, it is a further object of the present invention to
provide diamond masses made from diamond unit cells.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0007] The present invention provides diamond unit cells and
diamond masses made therefrom.
TERM DEFINITIONS
[0008] Combinatorial Synthesis: as used herein means the reaction
of a tetrahedranoidal compound with a carbon atom to produce the
diamond unit cell. In the present specification, the words
"tetrahedranoidal" and "tetrahedranoid" are used interchangeably.
No diamond seed: as used herein means that no seed of either
diamond or other mineral is used to produce either the diamond unit
cell or diamond mass. No diamond seed or other mineral seed is
provided to the product diamond mass. Homogeneous morphology: as
used herein means that the product diamond mass is at least a
contiguous, non-particulate solid in structure and appearance. No
coloration as a result of formation: means that the present diamond
mass does not incur discoloration simply as a consequence of
formation by combinatorial synthesis. Conventional synthetic
diamonds usually exhibit a yellow or yellow-brown discoloration as
a result of nitrogen oxide inclusions in the diamond crystal due to
the extreme high pressure/high pressure temperature (HP/HT)
conditions used in conventional diamond forming processes in the
presence of atmospheric air. The present diamond mass does not
suffer from this disadvantage as HP/HT conditions are avoided as is
atmospheric air. No nitrogen getters: means that no compounds or
metals are added to the present diamond mass during growth to
prevent formation of nitrogen oxide inclusions. In conventional
synthetic diamond forming reactions using HP/HT conditions under
atmospheric air, nitrogen getters must be added to absorb or react
with nitrogen in the air to prevent reaction of nitrogen and oxygen
forming nitrogen oxides. Conventionally, aluminum or titanium have
been used to remove nitrogen from growing diamond crystal. In
contrast, the present diamond mass is free of nitrogen. Thus, no
color zonation is present in the diamond mass produced by the
combinatorial synthesis of the diamond unit cell. No color
zonation: means that the present diamond mass contains no
differential color zones due to impurities in contrast to natural
and conventional synthetic diamond.
[0009] "Combinatorial Synthesis of Diamond" (Hodes, U.S.
application Ser. No. 13/204,218, filed Aug. 5, 2011, which claims
priority to 61/344,510, filed Aug. 11, 2010 herein incorporated by
reference) is directed to a vapor phase synthesis of diamond
wherein a carbon atom (C) free of meta-stable radical impurities
(methyl radical-CH.sub.3., di-radical methylene-CH.sub.2:,
tri-radical methyne-.CH:) is obtained from a hydrocarbon source.
This carbon atom so obtained is reacted with a species produced by
catalytic treatment of acetylene. The combinatorial reaction of
these two reactants yields diamond, which precipitates from the
vapor phase. While not being bound by theory, it is believed that
the species derived by catalytic treatment of acetylene is
tetrahedrane, albeit transient and in low concentration. One
skilled in the art will understand from the present specification
that the product of this reaction is the diamond unit cell. A 2D
representation of the 3D structure of the diamond unit cell is
shown below.
##STR00001##
[0010] The present disclosure is directed to the diamond unit cell
produced by combinatorial synthesis. Formation of diamond by a
synthesis of its unit cell as disclosed in this disclosure and my
previous disclosure proceeds by a method altogether different from
the typical methods of diamond formation. Synthesis of the diamond
unit cell relies upon chemical modification of molecules having
structures similar to that of the diamond unit cell. That is, they
are tetrahedral or nearly tetrahedral, structurally, and have
chemical reactivity that can be exploited to alter their structure
to produce the diamond unit cell. Stable, isolable tetrahedranes
are known. Their stability is an artifact of the four bulky
substituents on the four carbon atoms comprising the molecules.
However, it is this very large steric bulk that makes them
unsuitable for use as reactants in a diamond unit cell forming
reaction.
##STR00002##
[0011] The diamond unit cell forming reaction of this disclosure
proceeds by the reaction of a carbon atom free of meta-stable
radical impurities, which is derived from a source hydrocarbon,
with a second chemical species whose structure is closely related
to tetrahedrane--a tetrahedranoidal structure. In fact, for
purposes of the present invention, tetrahedrane, itself, is
considered to be a tetrahedranoidal structure. These
tetrahedranoidal compounds are generally understood, however, as
tetrahedranes having the 3,4 C--C bond replaced by an "insert"
species.
[0012] Examples of three known tetrahedranoidal compounds useful in
this diamond unit cell forming reaction are shown below (NON-IUPAC
naming for simplicity).
[0013] Compound I--Benzvalene (C.sub.6H.sub.6) bp=77.558.degree. C.
(760 mm Hg) vapor pressure 106.123 mmHg at 25.degree. C. The
"inserted" species is --CH.dbd.CH-- (ethylene).
##STR00003##
[0014] Compound II--2,3,4-methynyl-cyclobutanone ("Tetrahedranone",
"Carbonyl tetrahedrane") (C.sub.6H.sub.4O) bp=-37.degree. C. (some
decomposition). The inserted species is CO (carbonyl, carbon
monoxide).
##STR00004##
[0015] Compound III--3,4,5-methynyl-dihydro-1,2-pyrazole
(3,4-Diazabenvalene) (C.sub.4H.sub.4N.sub.2); decomposes at about
-60 degrees C. The inserted species is --N.dbd.N-- (dinitrogen),
i.e., an azide group.
##STR00005##
[0016] The three tetrahedranoidal compounds detailed above have
sufficient thermodynamic stability to be used as a reactant in the
diamond unit cell forming reactions detailed below providing that
appropriate manpulative care is used with respect to their
individual pecularities. However, one should not consider these
compounds to be thermodynamically stable, overall. In fact, it is
the very instability of these compounds that is exploited by the
diamond unit cell syntheses of this disclosure. Diazabenzvalene and
2,3,4-methynylcyclobutanone ("tetrahedranone") both decompose by
ejection of a leaving group (N.sub.2 and CO, respectively) to a
C.sub.4H.sub.4 transient species, which may be seen
spectroscopically as the dimer C.sub.8H.sub.8 indicative of the
initial formation of cyclobutadiene. The presence of
dicyclobutadiene in the environment of the diamond unit cell
forming reaction is highly undesriable because it is also highly
reactive and will produce condensation products, which will
inevitably contaminate the diamond mass under formation. Thus, the
use of these compounds in diamond unit cell syntheses requires
rigorous manipulative technique. By contrast, benzvalene
(C.sub.6H.sub.6) does not decompose per se; rather, it rearranges
to benzene (C.sub.6H.sub.6) under the conditions of the diamond
unit cell syntheses disclosed herein. Despite benzvalene's more
advantageous properties, as compared to diazabenzvalene or
"tetrahedranone" in the diamond unit cell syntheses of this
disclosure, one skilled in the art will recognize that relaxation
of rigorous manipulative care can result in an impurity which is
highly undesirable and must be prevented from contacting the
diamond mass under formation.
[0017] Compounds I and II are reasonably stable in the presence of
oxygen, and these compounds have good stability at ambient
temperatures. Compound III decomposes at about -60.degree. C. and
is unstable in the presence of oxygen. Compounds I and II decompose
rapidly and even violently if they contact sharp surfaces.
Compounds I and II are sensitive to rapid heating, and the rate of
heating must not exceed 5.degree. C. per minute. Compounds I, II,
and III are stored and used in inert atmospheres such as helium or
argon, which gases should be of research purity having no more than
10 ppm impurities which impurities are identifiable by gc/ms.
Reactant manipulation within an anaerobic environment eliminates
the formation of O.sub.2-induced radicals leading to impurities in
the reactants, which deleteriously effect the product of the
diamond unit cell forming reactions in which they are used. Thus, a
similar level of purity of inert gases used in the diamond unit
cell forming reactions is maintained. In one embodiment, purity is
maintained using Schlenck (double manifold) techniques.
[0018] All three compounds react with a "clean" carbon atom to
create the diamond unit cell along with concomitant ejection of 4
hydrogen atoms and the "inserted" species (HC.dbd.CH, CO, N.sub.2
for compounds I, II, and III, respectively).
##STR00006##
[0019] Diamond unit cells assemble to form a diamond mass. Thus,
the diamond mass is formed by the assembly of a plurality of
diamond unit cells, i.e., diamond molecules.
[0020] Spectral examination of diamond formed by this method using
Raman or Infrared reflectance reveals only peaks associated with
diamond. For example, C--H stretching bands at 2800-3000 cm.sup.-1
typically observed for CVD diamond using methane gas are not
observed. Graphitic impurities (sp.sup.2 carbon) at 1580 cm.sup.-1,
which are frequently observed in CVD diamond, are not observed. The
sharp peak at 1328-1332 cm.sup.-1 characteristic of diamond is
observed.
[0021] Sources of atomic carbon may include saturated hydrocarbons
such as methane, ethane, and cycloalkanes. In one embodiment, the
carbon atom source is cubane.
[0022] Cubane (C.sub.8H.sub.8) MW=104.1491 mp=131.degree. C.
bp=133.degree. C. vapor pressure=1.1 mm @25.degree. C.
##STR00007##
[0023] Cubane, which has a strain energy of 166 kcal/mol,
decomposes cleanly in a high energy discharge environment to yield
carbon and hydrogen free of meta-stable radical impurities. In one
embodiment, cubane is decomposed to hydrogen and carbon free of
meta-stable radical impurities using a microwave discharge (1 kW at
12 GHz being adequate).
##STR00008##
[0024] Other sources such as methane, ethane, and cycloalkanes do
not decompose to atomic carbon free of meta-stable radical
impurities but can be used as such sources in vapor phase diamond
unit cell forming reactions if the complications of meta-stable
radical impurities are overcome. Unsaturated hydrocarbons are
unsuitable as sources of carbon atoms free of meta-stable radical
impurities.
[0025] In one embodiment, the diamond unit cell forming reaction is
conducted in the vapor phase. In another embodiment, the diamond
unit cell forming reaction is conducted in the solid state. In one
embodiment of the solid state diamond unit cell forming reaction, a
high degree of stoichiometric precision is employed to ensure a
high degree of purity for the diamond product. An excess of cubane
(the carbon atom source) introduces graphitic and amorphous carbon
impurities into the diamond product. Excess tetrahedranoid can
introduce C--H, graphitic, and even heteroatom impurities into the
diamond product. The tetrahedranoid-to-cubane stoichiometry is 8:1.
In one embodiment, the tetrahedranoid-to-cubane stoichiometry is
precisely 8:1.
[0026] Thus, in one embodiment, stock solutions of cubane and
tetrahedranoid compounds to be used are prepared and analyzed by
liquid chromatography for concentration and for the presence of
impurities. The impurities differ depending on the tetrahedranoid
used. For example, the principal impurity in benzvalene is benzene,
which is notorious for imparting graphitic impurities into diamond.
"Tetrahedranone" decomposes emitting carbon monoxide and
rearranging to cyclobutadiene, seen spectroscopically as the dimer,
dicyclobutadiene. "Tetrahedranone" can be separated from this
impurity by slow and careful sublimation onto a -78.degree. C. cold
finger and recovered under inert atmosphere. The practitioner will
understand that manipulative care must be exercised for these
tetrahedranoidal compounds based upon their previously disclosed
properties: benzvalene and "tetrahedranone" must be heated gently
as previously described, and diazabenzvalene must be used below
about -60.degree. C., entirely under anaerobic conditions.
Commercially available liquid chromatography instruments are
available for the quantitative and qualitative analyses required
for stock solutions of reactants. Further, computer databases are
available with such instruments for qualitative analyses of
impurities (if any), and such instruments can provide the four
place precision (and even higher) for quantitative analyses in
these reactions. This allows preferred levels of precision for the
diamond unit cell forming reactions to be obtained.
[0027] The purity of the diamond produced by the solid phase
diamond unit cell forming reaction is an artifact of the purity of
the reactants used. Thus, the process begins with the use of
purified reactants. More specifically, the carbon atom source and
the tetrahedronoidal compounds are purified. In one embodiment, the
solutions of the individual reactants are prepared for analysis and
standardization by liquid chromatography or by spectroscopic
analysis. If the analysis verifies the requisite purity for the
reaction, standardized stock solutions of precisely determined
concentrations are prepared.
[0028] In one embodiment, the tetrahedranoidal compound
(benzvalene, in this example) is adequately purified by placing it
in a Schlenck (double manifold) vessel having a threaded wide mouth
port, a septum port, and valved gas/vacuum arms operatively
connected to the double manifold apparatus with a flow of inert gas
(argon). The vessel is chilled to between -20.degree. C. and
-45.degree. C. and then evacuated to remove benzene (if any). Inert
sweep gas is admitted, and an aliquot of the sweep is sampled by
gc/ms to determine the presence of impurities. When no impurities
are detected, a solvent, such as dichloromethane (in one embodiment
at least research grade) distilled under argon from CaH.sub.2 is
added to prepare a stock solution, an aliquot of which is analyzed
by liquid chromatography for standardizing the concentration of the
solution. Stock solutions of "tetrahedranone" and of cubane are
prepared similarly. Cubane may also be purified by sublimation in
vacuum. Repeated sublimations of cubane are known to provide a
product of very high purity with very small mass loss, overall.
[0029] In another embodiment, Schlenck (multiple manifolds) line
solution transfer techniques are used to deliver reactants to their
respective reaction receivers. The solutions are chilled and then
freed of solvent under vacuum. Confirmation of complete solvent
removal is done by gc/ms analysis of inert sweep gas.
Alternatively, the tetrahedronoidal compounds I and II are purified
using commercially available quantitative liquid chromatography
apparatus.
[0030] Solutions of the carbon atom source (e.g. cubane) and the
tetrahedronoidal compound are then combined and transferred to a
reaction vessel. This solution is freed of solvent under reduced
pressure and temperature. More specifically, the solutions are
chilled and solvent is evaporated under reduced pressure slowly to
prevent bumping. Once the solvent appears to be completely removed,
a flow of inert gas is passed over the remaining solid residue and
sampled by gc/ms to verify that no residual solvent remains. If any
solvent remains, the process is repeated (pumping and sampling)
until no residual solvent remains. Thereupon, the vessel is filled
with inert gas, sealed, and transferred to a dry box for transfer
of the reaction vessel to a high energy discharge cell. In one
embodiment the high energy discharge cell is a microwave, an
electrostatic discharge device, or other high-energy discharge
known in the bond cleavage art. The cell is sealed, removed from
the dry box, connected to the double manifold apparatus, fitted
with refrigerant lines to circulate refrigerant through the cold
plate, and the exit port is connected to a gc/ms instrument as well
as any additional ports as needed. Upon adequate chilling of the
solid reaction mixture within the reaction vessel placed upon the
cold plate, the discharge is energized to initiate the diamond unit
cell forming reaction while the effluent is monitored by gc/ms. In
one embodiment, this process is conducted under vacuum. In another
embodiment, this process is conducted in an inert gas. When no more
ejection products are observed spectroscopically, energy to the
discharge cell is discontinued and the reaction vessel is
transferred to a spectrometer for product analysis.
[0031] In one embodiment, the reaction vessel containing the solid
reaction is placed on a cold plate and chilled to between
-20.degree. C. and -45.degree. C. within a microwave discharge cell
under an inert atmosphere. At higher temperatures the
tetrahedroidal compound(s) have sufficient vapor pressure to alter
the precision of the stoichiometry.
[0032] In another embodiment, the cell is energized to effect the
reaction, which is complete in about three to five seconds for a 1
mmol scale reaction. In one embodiment, the reaction is conducted
under vacuum. In another embodiment, the reaction is monitored by
gc/ms at the effluent port to determine when no more ejection
products are detected. In an embodiment wherein diazabenzvalene is
the tetrahedranoidal reactant, the cold plate is kept at about
-60.degree. C. to -78.degree. C. or even lower.
[0033] Having described the present invention, reference is made
below to certain examples that are provided solely for purposes of
illustration and are not intended to be limitative.
Example 1
[0034] A solid state diamond unit cell forming reaction was
performed as follows.
[0035] A teflon lined glass receiver cylinder having a 2 cm
diameter and 5 cm wall height was placed in a Schlenck vessel
having a threaded wide mouth, gas/vacuum valve port, and septum
port to which was attached an electronically controlled syringe
pump. The vessel was sealed and evacuated followed by admission of
argon and chilling in a dry ice/chlorobenzene bath (-45.degree.
C.). Using the syringe pump a first precisely standardized solution
of 1 mmol of benzvalene in dry dichloromethane was delivered into
the contained cylinder. A second precisely standardized solution of
0.125 mmol of cubane in dry dichloromethane was delivered to the
contained cylinder to afford an 8:1 (molar) mixture of benzvalene
and cubane in dichloromethane. The syringe tube (needle) was
removed, and argon flow was stopped. Vacuum was applied slowly to
minimize bumping, and the solvent was removed under complete vacuum
(about 10 minutes). Argon was readmitted when visual observation of
the cylinder indicated that it contained a dry (solvent free)
solid. A portion of the argon flow was sampled by gc/ms to confirm
complete removal of dichloromethane and absence of benzene. The
cold bath was removed. The vessel was transferred to the load-lock
of a glove box having an argon atmosphere, and the cylinder bearing
the homogeneous mixture of solid cubane and benzvalene was removed
from the Schlenck vessel and transferred to a microwave discharge
cell. The cell was sealed, removed from the glove box, fitted with
refrigerant lines to the cold plate on which the contained reaction
cylinder was mounted, attached to the Schlenck line, attached to a
gc/ms instrument at the cell effluent port, and refrigerant was
circulated through the cold plate to maintain the reactant mixture
at -45.degree. C. Argon flow through the cell was initiated with
commencement of gc/ms effluent monitoring. The cell was then
energized to initiate the diamond forming reaction. When gc/ms
effluent monitoring indicated the effluent to be free of hydrogen
or acetylene (about 5 seconds), energy to the discharge cell was
ceased, refrigerant circulation was ceased, and the cell was opened
to recover the reaction vessel. The glassy disc within the cell was
brought to an FT-IR reflectance instrument, which confirmed diamond
(1328-1332 cm.sup.-1) No graphite, amorphous carbon, or C--H peaks
were observed. The weight of the disk was 59.12 mg (98.4% of
theoretical).
Example 2
[0036] A vapor phase diamond unit cell forming reaction was
performed as follows.
[0037] A teflon lined glass receiver cylinder having a 2 cm
diameter and 5 cm wall height was placed in a Schlenck vessel
having a threaded wide mouth, gas/vacuum valve port, and septum
port to which was attached an electronically controlled syringe
pump. The vessel was sealed and evacuated followed by admission of
argon and chilling in a dry ice/chlorobenzene bath (-45.degree.
C.). Using the syringe pump a solution of 2 mmol of benzvalene in
dichloromethane was delivered into the container cylinder. A second
teflon lined glass receiver cylinder having a 2 cm diameter and 5
cm wall height was placed in a a second Schlenck vessel having a
threaded wide mouth, gas/vacuum valve port, and septum port to
which was attached an electronically controlled syringe pump. The
vessel was sealed and evacuated followed by admission of argon and
chilling in a dry ice-chlorobenzene bath (-45.degree. C.). Using
the syringe pump a solution of 0.125 mmol of cubane in
dichloromethane was delivered into the contained cylinder. The
syringe lines (needles) were removed from both vessels. The flow of
argon was ceased to both vessels. Vacuum was applied slowly to both
vessels to minimize bumping, and the solvent was removed under
complete vacuum (about 10 minutes). Argon was readmitted to both
vessels when visual observation of the cylinders indicated that
both contain a dry (solvent free) solid. A portion of the argon
flow was sampled by gc/ms to confirm complete removal of
dichloromethane and absence of benzene. The cold bath was removed.
The vessels were transferred to the load-lock of a glove box having
an argon atmosphere, and the cylinder bearing cubane was
transferred to the evaporator contained within the microwave
discharge cell and sealed. The benzvalene-containing cylinder was
transferred to an evaporation cell having gas/vacuum valved
fittings, which were closed. Both cells were transferred to a CVD
reactor, attached to gas/vacuum fittings, and configured for the
diamond forming reaction by CVD.
[0038] A silicon foil disk deposition target was heated to
85.degree. C. Then, using pre-programmed values, gas flow, heating
of both evaporators, and application of energy to the microwave
discharge were initiated with monitoring of the effluent by gc/ms.
When no more reaction by products were detected by gc/ms, the
reaction is terminated, and the substrate is allowed to come to
ambient temperature, whereupon it was removed and weighed. Yield
was 59.77 mg (99.5% of theoretical). FTIR reflectance confirmed the
glassy film deposited upon the substrate to be diamond showing no
graphite, amorphous carbon, or C--H peaks.
[0039] Additional Considerations for Vapor Phase Reactions
[0040] For the vapor phase reaction, precise stoichiometry is not
required. Rather, an excess of tetrahedranoidal compound is
favored. That is, a tetrahedranoidal compound-to-cubane of ratio
equal to or greater than 8:1 is used. Preferably, the ratio is 16:1
(or greater) to ensure that all atomic carbon is reacted in the
vapor phase to precipitate the diamond unit cell onto the
substrate. The tetrahedranoidal compounds that may be used for this
are benzvalene and 2,3,4-methynyl-cyclobutanone ("tetrahedranone").
Benzvalene is advantageous over tetrahedranone because it is more
stable and more readily and economically obtained. The impurity due
to autogenous rearrangement for benzvalene is benzene while the
impurity obtained by autogenous decomposition of tetrahedranone is
dicyclobutadiene, which is far more difficult to maintain in the
vapor phase than benzene. Benzene can introduce graphitic
impurities into diamond obtained by its deposition during the
diamond unit cell forming reaction if allowed to come into contact
with the deposition substrate. Benzene, if it is present, can be
prevented from contaminating the diamond deposited upon the
substrate by the diamond unit cell forming reaction (vapor phase)
by two means. First, one need only heat the substrate holder (hence
the substrate) to about 80-85.degree. C. transferring sufficient
heat to the vapor phase reaction zone vicinal the deposition
substrate to "drive off" any benzene that may be present.
Alternatively, a second flow of heated carrier gas may be provided
along the surface of the deposition substrate to maintain a
"thermal barrier zone" against benzene if it is present. Such
measures against benzene contamination may not necessarily be
needed if benzvalene is properly handled, particularly during its
vaporization. Thus, if rapid heating of benzvalene to its
vaporization temperature is avoided, benzene formation can be
avoided.
[0041] Additional Considerations for Solid State Reactions
[0042] The diamond unit cell forming reaction can be conducted in
the solid state using a homogeneous mixture of cubane and any of
the above-cited tetrahedranoidal compounds. This homogeneous blend
is a molar ratio of 8:1, tetrahedranoid-to-cubane. A cubane
molecule decomposes to provide eight carbon atoms and eight
hydrogen atoms. The skilled practitioner will recognize that a high
degree of stoichiometric precision is required when preparing the
homogeneous blend of cubane and tetrahedranoid if a diamond product
of high purity is to be obtained by the diamond unit cell forming
reaction. An excess of cubane (the carbon atom source) introduces
graphitic and amorphous carbon impurities into the diamond product.
Excess tetrahedranoid can introduce graphitic, carbenoid, and even
heteroatom impurities into the diamond product.
[0043] Gravimetric methods are unlikely to achieve this level of
precision and are difficult to perform with contact-sensitive
materials such as benzvalene and 2,3,4-methynylcyclobutanone;
3,4-diazabenzvalene is unstable above -60.degree. C.
[0044] Forming stock solutions of the individual reactants (cubane
and tetrahedranoid) can achieve this precision with the use of
liquid chromatographic equipment in tandem with mass spectrometric
instrumentation (hplc-ms). Such equipment is commercially available
and can attain five decimal place precision (and even higher for
some research specification models). This equipment can readily
identify and separate impurities common to tetrahedranoidal
molecules. For benzvalene, the impurity that is observed is
benzene. For 3,4-diazabenvalene and 2,3,4-methynlcyclobutanone
("tetrahedranone"), the impurity is dicyclobutadiene, which arises
from the ejection of dinitrogen or carbon monoxide, respectively,
from these tetrahedranoidal compounds. These are four-carbon units
that probably form butadiene, which dimerizes to the final
impurity, dicyclobutadiene. Thus, it is advantageous to use
benzvalene as the tetrahedranoidal reactant for the solid-state
diamond unit cell forming reaction. It is the most stable of the
three tetrahedranoidal compounds, and it is fairly economical to
use being readily prepared by standard organic synthesis methods
from inexpensive reagents.
[0045] The use of precisely calibrated stock solutions of the
individual reactants using hplc-ms instrumentation also provides a
means for maintaining the stoichiometric precision necessary for
producing diamond by the solid state diamond unit cell forming
reaction. The two solutions are combined and freed of solvent
carefully at reduced pressure and at reduced temperature in the
reaction vessel in which the diamond unit cell reaction occurs. The
solid blend is held at low temperature in an inert atmosphere
because the vapor pressures of the individual reactants are
sufficient at ambient temperature (benzvalene: 106.12 mm Hg;
cubane: 1.1 mm Hg) to alter the stoichiometric precision of the
homogeneous blend by evaporative loss. The combination of double
manifold line manipulations and hplc-ms instrumentation simplifies
the task of preparing a stoichiometrically precise blend of
purified reactants as well as maintaining their purity and
stoichiometry.
[0046] The diamond masses produced by the present invention have no
detectable impurities, including amorphous carbon, non-diamond
allotropes of carbon, hydrocarbenoids, heteroatoms and
heteroatom-bearing materials. For example, the diamond masses of
the present invention are spectroscopically-free of graphitic
impurities, and free of discoloration from nitrogen oxide
inclusions or free of discoloration by inclusions of species
including oxides of nitrogen. The present diamond masses also
contain no nitrogen getter-contaminants.
[0047] Further, the present diamond masses contain neither color
nor crystal zonation, and exhibit a homogeneous crystal
morphology.
[0048] Hydrocarbenoids are hydrocarbon-carbene-type reactive
intermediates. Heteroatom means atoms other than carbon.
[0049] While various embodiments of the present disclosure have
been described above, it should be understood that they have been
presented by way of example only, and not limitation. It will be
apparent to persons skilled in the relevant art that various
changes in form and detail can be made therein without departing
from the spirit and scope of the disclosure. Thus, the breadth and
scope of the present disclosure should not be limited by any of the
above-described exemplary embodiments.
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