JPH0483797A - Synthesis of diamond in vapor phase method - Google Patents

Abstract

PURPOSE:To further increase separating out speed of diamond and improve uniformity of quality by introducing an organic compound having a different composition from a burning flame-forming gas or a mixed gas of an organic compound and argon or hydrogen into inner flame part of a burning flame in a box body independently of a burning flame-forming gas. CONSTITUTION:A raw material compound for separating out diamond containing carbon or a mixed gas of said compound and oxygen is burned so as to generate incomplete burning region in a box atmosphere containing oxygen or not containing oxygen to synthesize diamond in a vapor phase method. In said method, the following means is adopted in this invention: namely, an organic compound containing carbon having a composition different from a raw material for burning (jetting hole: 3) or a mixed gas of said organic compound and argon or hydrogen is directly supplied (jetting hole: 2) to an inner flame part 6 to separate out granular or filmy diamond in the box body.

Description

[Detailed description of the invention] [Industrial application field] The present invention has characteristics such as wear resistance, corrosion resistance, high thermal conductivity, and high specific elasticity, and is useful for abrasive materials, optical materials, cemented carbide tool materials, sliding materials, etc. wood,
This paper relates to the vapor phase synthesis of film-like and granular diamonds useful for corrosion-resistant materials, acoustic vibration materials, cutting edge materials, etc.

[Conventional technology]

Conventional methods for synthesizing diamond include a synthesis method using an iron- or nickel-based catalyst under ultra-high pressure conditions, and a direct conversion method of graphite using an explosive method.

In recent years, low-pressure CVD has been used to synthesize diamond in an excited state using a mixed gas of hydrogen and hydrocarbons or organic compounds containing nitrogen, oxygen, etc., using hot filaments, microwave plasma, high-frequency plasma, DC discharge plasma, DC arc discharge, etc. A method has been developed to do so. The inventors of the present application have improved the CVD method by burning a raw material compound for diamond precipitation in such a way that it has an incomplete combustion region, and depositing diamond on a base material provided in or near the incomplete combustion region. We developed a diamond synthesis method using the combustion flame method, and presented it at the 35th Japan Society of Applied Physics Association Conference (Kl Proceedings Vol. 2, Volume 2, p. 29a-T-1).
It was disclosed as JP-A-1-282193. Furthermore, in Japanese Patent Application No. 1-98058, an application was filed for a method of synthesizing diamond in a box in a method of synthesizing diamond in a vapor phase using a combustion flame.

Furthermore, Japanese Patent Application No. 1-343229 discloses a method of increasing the rate of precipitation of high-quality diamond by introducing an organic compound or a mixed gas of an organic compound and argon into the inner flame portion of the combustion flame.

[Problem to be solved by the invention]

The invention disclosed in JP-A-1-282193 is a vapor phase synthesis method that is simpler than conventional methods and can produce a large area of diamond film. This is a method in which combustion is performed so as to have a combustion zone, and diamond is precipitated in a non-oxidizing atmosphere in or near the incomplete combustion zone. This method allows diamond to be deposited on a substrate simply by forming a combustion flame from a raw material compound containing carbon, and is a revolutionary method superior to the conventional CVD method. However, in this method, it is not easy to control the quality or quantity of the precipitate due to the influence of gas in the atmosphere.

On the other hand, in Japanese Patent Application No. 1-98058, by synthesizing vapor-phase diamond using combustion flame inside a box, the precipitation rate was increased by increasing the incomplete combustion region, and the possibility of mass production was opened. It was written.

However, by depositing a large amount of film or granular diamond using these simple methods, it is possible to form diamond films of various shapes, such as coating films on various substrates, or free-standing bodies including large areas or three-dimensional shapes. In order to put the product into practical use, there remained the challenges of further increasing the diamond precipitation rate and improving the uniformity of the quality of the precipitated diamonds.

The purpose of the present invention is to solve the above *g by improving the control technology of radical reactions within combustion flames.
It provides the means for that purpose.

[Means to solve the problem]

As a result of intensive research to achieve the above object, the present inventors controlled the atmosphere and pressure in the box when burning the raw material compound for diamond precipitation, and the organic compound or organic The present invention was completed after confirming that the object could be achieved by introducing a mixed gas of the compound and argon or hydrogen separately from the combustion flame forming gas.

That is, the present invention provides an organic compound having a composition different from that of the combustion flame-forming gas or an organic compound having a composition different from that of the combustion flame-forming gas from the outside into the IA part of the combustion flame, that is, the high-temperature plasma part near the already formed core (white core) in the case. The present invention relates to a combustion flame method for synthesizing rapidly precipitated diamond, which is characterized in that a mixed gas of an organic compound and argon or hydrogen is directly introduced separately from the combustion flame forming gas.

Carbon sources for diamond synthesis used in the present invention include saturated hydrocarbons such as methane, ethane, propane, and butane; unsaturated hydrocarbons such as ethylene, propylene, butylene, and acetylene; aromatic hydrocarbons such as benzene and styrene; Alcohols such as alcohol, compounds containing a ketone group such as acetone, ethers such as diethyl ether, other aldehyde compounds, nitrogen-containing compounds, and carbon oxide can all be used.

In the present invention, the above raw material gas for diamond synthesis,
or (and) it is necessary to have a diamond-precipitating substrate present in the region of incomplete combustion of the gas mixture or in a region that is non-oxidizing and is excited to allow diamond precipitation in the vicinity of the flame. In addition, when burning a carbon-containing raw material compound for diamond precipitation so as to have an incomplete combustion region, by carrying out the combustion in a box in an oxygen-free atmosphere,
In the present invention, it is necessary to easily control the pressure, and also to qualitatively control the combustion flame by increasing the incomplete combustion region and adjusting the mixing ratio of the introduced gas.

In the gas phase synthesis of these diamonds, organic raw material compounds are separated and dissociated by heating and reaction with oxygen in a combustion flame, and further react to form radicalized active species, such as C, H, C.
2, CH, CH2, CH3, etc. are generated. In the method of the present invention, by injecting an organic compound into the inner flame part of a combustion flame, it is decomposed and dissociated by high heat, clustered or radicalized, and C radical, C2 radical, C
Through repeated collisions with active species such as H radicals, the momentum of the radicals is increased, resulting in an overall atmosphere favorable for diamond production. The properties of the precipitated diamond in this atmosphere are significantly improved, and at the same time the precipitation rate is also greatly increased.

In the normal combustion flame method, oxygen is added to raw material gas such as acetylene, styrene, allene, propane, etc. to form a combustion flame inside the box, and the volume of the incomplete combustion zone can be adjusted by adjusting the amount of oxygen added. It is.

To give an example, in the case of oxygen-acetylene system, 02
/C2H2 ratio is preferably 0.5 to 2, more preferably 0.7 to 1.2. If it is less than 0.7, soot is likely to be generated. In these cases, the temperature of the inner flame, which is the incomplete combustion region, is 2000 to 3000°C, and no auxiliary excitation means is required.

Generally, it is desirable that the diamond synthesis temperature be 1500°C or higher. The temperature of the substrate for precipitation is 500 to 1200°C, more preferably 800 to 1100°C, and can be controlled within this range by cooling.

As the base material for diamond precipitation, those commonly used in CVD methods can be used. That is, S1 wafer, S1C sintered body, S
In addition to iC granules, W, WC, Mo, TiC, TiN
, cermet, cemented carbide steel, high-speed steel, etc., and granular materials can be exemplified.

The region where diamonds are deposited is an oxygen-deficient region of the combustion flame, commonly referred to as the inner flame. Generally, an oxygen-excessive region is at a high temperature, and even if diamond is formed, for example, the excess oxygen turns into CO and CO2 and disappears. That is, it is considered that diamond does not precipitate in this region. Note that the diamond precipitation region is oxygen deficient and has a relatively low temperature. In this region, it is necessary to excite the raw material gas to conditions that produce hydrocarbon radicals (active species).

In the casing, the generation and diffusion region of radicalized active species and hydrogen atoms and oxygen atoms formed in the incomplete combustion region can be adjusted, resulting in a reduction or disappearance of the outer flame zone, i.e., the incomplete combustion region. As the combustion area expands, it becomes possible to increase the diamond precipitation area, speed, and homogenization.

Furthermore, the method of introducing additives such as organic compounds according to the present invention that adjust the combustion state in this way will be explained based on the drawings, taking the case of an oxygen-acetylene system as an example.

Figure 1 (a) (bHc) shows an example of a burner for carrying out the method of the present invention, a crater 1, in which there is a spout 2 for additives made of organic compounds etc. in the center, and acetylene etc. A combustion flame forming gas outlet 3 is arranged. Second
The figure shows a combustion flame in the atmosphere from a burner with the above-mentioned crater 1. The combustion flame is composed of an inner flame 6, an outer flame 7, a white core 4, and a radical flame (tentative name) 5 in the center. It is shown.

Radical flame formation requires that the composition of the additive be different from the combustion flame-forming gas. In particular, it is preferable that the amount of oxygen is non-oxygen or very low. FIG. 3 shows the state of the combustion flame when the combustion flame is blown from the burner nozzle 1 inside the box toward the deposition base material 9 supported on the water-cooled support stand 10. As the flame collides with the material, the combustion flame flows as shown in the figure, and the excited additives become C2
A radical flame 5 sealed inside the inner flame 6 together with carbon-containing active species such as radicals and CH radicals.
becomes.

It is thought that a reaction of (H-C) radical C2H2→(diamond precursor) radical + H2 occurs in the radical flame. In addition, in a mixed flame in which a radical flame and an inner flame intersect, activity increases due to contact between (C-H) radicals, various carbon-containing radicals, and atomic hydrogen, and more diamond precursor radicals reach the base material. arrive. Figure 4 shows the shape of the flame controlled inside the box and compares it with that in the atmosphere. In the case of (,), the core is large and completely forms an outer flame in the atmosphere, and a third component flame appears in the inner flame.This is because the core stretches inside the box and the outer flame becomes wider, and the inner flame becomes wider. A part of it diffuses into the outer flame. In this form, high-speed precipitation of diamond can be expected in the mixing zone. (In case b, the oxygen content of the combustion flame was slightly higher than in condition (a). With this composition, a slight outer flame remains in the atmosphere, but the core also stretches a little inside the box, causing a mixture of outer flame and inner flame. As the combustion progresses and becomes more uniform, it becomes possible to deposit homogeneous and large-area diamonds.Also, in (c), the oxygen content of the combustion flame was slightly higher than that in (b).With this composition, In this case, the boundary between the inner and outer flames of the combustion flame disappears, the white core also extends a little inside the box, and although the outer flame remains faint, the flame is concentrated in the center, and within this flame, fine, high-quality diamonds are obtained. In addition,
When carrying out the method of the present invention, the installation position of the substrate is 0 to 20 m from the tip of the white center in the case of oxygen-acetylene type.
m, and in the case of other systems, it is preferable to set it at a position of 2 to 20 mm from the crater.

Furthermore, when carrying out the present invention, the diamond-forming raw material for addition to be supplied is an organic compound/
C2H2 is preferably 3 vol% to 130 vol%.

When the amount of organic compounds is low, the amount of diamond precipitation decreases,
If it is too large, it will become graphitized and diamonds will not be obtained. Furthermore, when Ar gas is mixed into the raw material for addition, a high-quality diamond with a well-developed automorphic shape can be obtained. The mixing rate of Ar gas is Ar/organic compound of 5 to 70 vol%, preferably 15 to 50 vol%.

The pressure inside the box is 0. ITorr - 10,000 Torr
r, preferably 10Torr-760Torr
r, more preferably 100 Torr to 750 Torr
It is. As the pressure inside the box decreases, the flame volume increases, and the diamond synthesis area expands accordingly.

On the other hand, if the pressure is reduced too much, the flame will go out and the temperature will drop at the same time.

[Example 1] As shown in FIG. 2, the acetylene burner nozzle 1 was fixed downward. In addition, Burnaro has a slit inner diameter of 3
．． 4 mm, the slit inner diameter is 2.9 mm, and the central additive spout has a diameter of 0.9 mm.

Next, acetylene 3. Oxygen 7 t/min, oxygen 2.
8 lifter/m1n (oxygen/acetylene ratio 0.93),
Methane as an additive was supplied to the burner at a flow rate of 5 Q cc/mi, and hydrogen as a carrier gas was supplied to the burner at a flow rate of 100 cc/min, and a combustion flame was first formed in the atmosphere as shown in FIG. At this time, the outer flame disappeared and the inner flame in the center remained, as shown in Figure 4 (C'). After this, 20 m as shown in Figure 3.
An MO base material 9 of m square and 0.5 mm thickness was fixed on a water-cooled support, moved to a distance of 8 mm from the white center, and fixed.

At this time, the pressure inside the box was adjusted to 450 torr, and the substrate temperature was adjusted to 900°C. After 20 minutes of reaction, the substrate deposit was observed using an optical microscope, and it was confirmed that fine, high-quality diamond crystals with well-developed euhedral shapes were precipitated in the center of the substrate. Furthermore, as a result of microscopic Raman spectroscopy analysis of this diamond, the Raman shift was 1333.
Only one sharp peak due to diamond crystals was shown at cm-'.

When the particle size was measured, it was found that the particles were partially transparent and had an average size of 2 to 5 μm, and the yield was 0.5 μm.
It was 012g.

[Example 2] Acetylene was used at the same burner and substrate position as in Example 1.
0 lifter/min, lI! Basic 2. 75 lifter/m1n (#element/acetylene ratio 0.917), methane as an additive was supplied to the burner at a flow rate of 50 cc/min, hydrogen as a carrier gas was supplied to the burner at a flow rate of lOOcc/m1n,
A combustion flame was formed in the atmosphere as shown in Figure 2. At this time, a slight external flame remained as shown in Figure 4(b). Thereafter, synthesis was carried out for 20 minutes under the same production conditions as in Example 1. As a result, a thin film of euhedral diamonds with an average size of 5 to 10 μm was obtained over a wide area on the substrate, and the yield was 0.023 g.

[Example 3] Acetylene was used at the same burner and substrate position as in Example 1.
0 lifter/min, I! Basic 2. 7 lifter/mln (oxygen/acetylene ratio 0.90), methane additive at 50cc/min, hydrogen carrier gas at 100cc/min
It was supplied to the burner at a flow rate of cc/min, and a combustion flame was formed in the atmosphere as shown in FIG. At this time, Figure 4(a)
A complete external inflammation was formed. Thereafter, synthesis was performed for 20 minutes under the same production conditions as in Example 1.

As a result, a self-shaped diamond was deposited in the center of the base material, and diamond-like carbon (hereinafter referred to as DLC) was deposited on the outer periphery in a raised manner. Yield was 0.048g.

[Example 4] Acetylene 3.
0 lifter/min, oxygen 2. 8 lifter/m1n (oxygen/acetylene ratio 0.93), propane as additive at 50 cc/min, hydrogen as carrier gas at 10 cc/min
The mixture was supplied to the burner at a flow rate of 0 cc/min, and synthesis was performed for 20 minutes.

As a result, precipitation occurred over a wide range on the substrate.

The yield was 0.052 g, mainly consisting of euhedral diamonds with some DLC mixed in.

〔Effect of the invention〕

According to the present invention, the problems of the combustion flame method, which allows diamond to be deposited on a base material by a simple means, are solved, and a uniform diamond film with a larger area can be stably deposited on the base material. It became possible.

Furthermore, it has become possible to control the precipitate particle size and the quality of the precipitate, that is, the mixing ratio of diamond and DLC.

[Brief explanation of drawings]

FIG. 1 shows some of the vents 1 of a burner for carrying out the method of the invention, FIG. 2 shows the combustion flame in the atmosphere from a burner with vents 1, and FIG. teeth,
Figure 4 shows the state of the combustion flame when the combustion flame is blown onto the deposition base material supported on the water-cooled support from the burner vent 1 inside the box, and the state of the combustion flame when the conditions are changed. It is. 1, Burner crater 2, Additive jet port 3, Combustion flame forming gas jet port

Claims (1)

[Claims] Vapor-phase diamond is produced by burning a carbon-containing raw material compound for diamond precipitation or a mixed gas of the compound and oxygen in a box atmosphere containing or not containing oxygen so as to have an incomplete combustion region. In the synthesis method, granular or thin film diamonds are produced inside the box by directly supplying an organic compound containing carbon with a composition different from that of the combustion raw material, or a mixed gas of this compound and argon or hydrogen to the inner flame. A method for synthesizing diamond by vapor phase precipitation.