JP2680676B2 - Synthesis method of vapor phase diamond - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention has characteristics such as wear resistance, corrosion resistance, high thermal conductivity, and high specific elasticity, and is used as an abrasive, an optical material, a cemented carbide tool material, and a sliding member. The present invention relates to vapor-phase synthesis of film-like and granular diamond useful for materials, food materials, acoustic vibration materials, cutting edge materials, and the like.

[Prior Art] As a method for synthesizing diamond, under ultrahigh pressure conditions,
Conventionally, a synthesis method using an iron or nickel-based catalyst or a direct conversion method of graphite using an explosive method has been practiced.

In recent years, as a low-pressure CVD method, hydrocarbon or a mixed gas of hydrogen and an organic compound containing nitrogen, oxygen, etc. and hydrogen are synthesized by hot filament, microwave plasma, high-frequency plasma, direct current discharge plasma, direct current arc discharge, etc. to excite diamond. The way to do is being developed.

More recently, the applicant of the present invention has developed a method for synthesizing diamond in the non-oxidizing region in a combustion flame, and has filed an application as Japanese Patent Application No. 63-71758 (Japanese Patent Application Laid-Open No. 1-282193). It corresponds to the improvement method.

[Problems to be Solved by the Invention] The invention of Japanese Patent Application No. 63-71758 (Japanese Patent Laid-Open No. 1-282193) is a simpler method than the conventional method, and is capable of producing a large area of film-like diamond. A synthesis method, the main point of which is to combust a raw material compound for diamond precipitation containing carbon so as to have an incomplete combustion region, and to deposit diamond in the incomplete combustion region or in a non-oxidizing atmosphere near the region. It is a method of depositing diamond on the substrate by setting a substrate for use and maintaining the substrate temperature at the diamond deposition temperature.

This method is capable of depositing diamond on the substrate only by forming a combustion flame with a raw material compound containing carbon, and is a method that is epoch-making superior to the conventional CVD method, but for practical use It is strongly desired to further increase the diamond deposition rate, improve the homogeneity, and control the properties of the diamond.

An object of the present invention is to increase the deposition rate and deposition area of diamond, and promote homogenization and mass production of the deposit.

[Means for Solving the Problem] The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, when burning the raw material compound for diamond precipitation, the atmosphere and the pressure were controlled in the box, resulting in incompleteness. Mass production by increasing the combustion area and homogeneity increases the deposition rate of diamond in a wider deposition area, depositing more homogenized and high-quality diamond, and the flow of the base material, which is a granule or powder. The present invention has been completed and the present invention has been completed.

That is, the gist of the present invention is a method of synthesizing a vapor-phase method diamond by burning a diamond-precipitating raw material compound containing carbon so as to have an incomplete combustion region. It is a method for synthesizing a vapor-phase-process diamond, which is characterized by fluidizing a substrate for use.

 Hereinafter, the present invention will be described in detail.

As the carbon source for diamond synthesis used in the present invention, methane, ethane, propane, saturated hydrocarbons such as butane,
Unsaturated hydrocarbons such as ethylene, propylene, butylene, and acetylene; aromatic hydrocarbons such as benzene and styrene;
Alcohols such as ethyl alcohol, compounds containing a ketone group such as acetone, ethers such as diethyl ether,
Other aldehyde compounds, nitrogen-containing compounds, carbon monoxide and the like can all be used. The above compounds may be used alone or in combination of two or more.

Further, it is also possible to use solid carbon, graphite or the like as a carbon source as a carbon source through a reaction such as vaporization, combustion or hydrogenation in a combustion flame of a mixed gas of the above compound and hydrogen, oxygen or the like. At that time, a non-oxidizing gas can be mixed.

These carbon-containing raw material compounds are decomposed by combustion heat in a combustion flame and decomposed and dissociated by further reaction with oxygen, from active species radicalized by combustion, for example, C, C ₂ , CH, CH ₂ , CH ₃
It is presumed that such abundance is abundant in the incomplete combustion region, making it suitable for forming a diamond phase. Further, hydrogen atoms and oxygen atoms are also formed, which seems to be involved in the diamond precipitation reaction. In this way, the active species and hydrogen atoms radicalized and the generation and diffusion regions of oxygen atoms can be adjusted such as the reduction of the oxygen concentration in the atmosphere by the combustion in the box, and the reduction or disappearance of the outer flame part occurs, That is, this leads to the expansion of the incomplete combustion region, which enables the diamond deposition area, the velocity to be increased, and the homogenization.

In the present invention, mass production of diamond is possible by further flowing the substrate in the box. When the substrate is particles or powder, the jetting force of the flame itself of the combustion flame forms a fluidized bed, and diamond can be deposited on this substrate.

In the present invention, for example, by adding oxygen to a raw material gas such as acetylene, styrene, propane, ethyl alcohol, methyl alcohol, and benzene, a combustion flame is formed, and the oxygen content in the atmosphere in the box is adjusted by adjusting the oxygen addition amount. It is possible to reduce and control the volume of the incomplete combustion region. The incomplete combustion zone of the acetylene-oxygen flame in this case is called acetylene feather, and its volume can be controlled by changing with the oxygen / acetylene ratio, the total gas amount, the pressure of the atmosphere in the box, and the oxygen content. Is. In particular, the oxygen / acetylene ratio may be in the range of 0.5 to 2, but is preferably 0.75 to 1.

The pressure in the box can be used at 0.1 Torr to 10,000 Torr, preferably 10 Torr to 760 Torr, more preferably 100 Torr to 75 Torr.
0 Torr. As the pressure inside the box decreases, the flame volume increases, and the diamond synthesis region expands accordingly. On the other hand, if the pressure is reduced too much, the flame will be extinguished and the temperature will be decreased. Also, the oxygen content in the box is an important factor because it causes the volume of the incomplete combustion region to decrease due to the diffused oxygen from the flame periphery of the combustion flame. The number cannot be determined unconditionally because it depends on the number and the state of the substrate to be fluidized.
However, the volume of the incomplete combustion region can be controlled by controlling the amount of oxygen because it can be easily determined by an experiment by using the box of the present invention.

Generally, the temperature in the acetylene feather region under combustion conditions where an external flame is present is 2000 to 3000 ° C., and no auxiliary excitation means is required. Therefore, the preferred diamond synthesis temperature of 1500 ° C. or higher is easily achieved. Base temperature is 60
A temperature of 0 to 1200 ° C. is suitable, and it is possible to control within this substrate temperature range by cooling, heat dissipation or the like.

Excitation energy shortage may occur due to radical generation necessary for diamond generation when combustion such that the outer flame part disappears due to control of the amount of oxygen in the atmosphere inside the box or when the pressure inside the box is low. In this case, auxiliary excitation means can be used if necessary. As an auxiliary heating source, heating element by electric heating, high frequency induction heating, heating method by laser light,
There are infrared heating, heating by arc discharge, etc.

As the substrate for diamond deposition, a substrate usually used in a low pressure CVD method can be used. That is, Si wafer, SiC sintered body, SiC
In addition to the granular material, W, WC, Mo, TiC, TiN, cermet, cemented carbide tool steel, alloy tool steel, high speed steel, and other shapes and granular materials can be exemplified.

An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of a diamond synthesizing apparatus having a flow device in a box 1. At the same time as the combustion flame of the combustion burner 2 is formed, the granules 3 charged at the bottom are fluidized by the jetting force thereof. Deposition of diamond occurs while the substrate particles are retained in the diamond synthesis zone within the combustion flame. Since the base particles are fluidized, the diamond precipitation surface area of 3 to 7 times the diamond precipitation surface area in the stationary state is exposed to the diamond synthesis region and participates in the diamond precipitation. After the synthesis for a certain period of time, the bottom plate-shaped portion (powder discharge hatch) 8 is raised to form a gap, and synthetic powder can be collected. Further, new base material particles are charged by a base material inlet (not shown) near the crater 9 of the combustion burner.

In FIG. 1, 4 is a combustion gas control system, 5 is a pressure detector, 6 is the pressure inside the box, an atmosphere exhaust system, and 7 is a fluidized granule container (made of Mo) water cooling system (not shown).

The fluidized granule container 7 shown in FIG. 1 has an inner diameter of about 100 mm and an upper part of 1
The opening diameter is 80 mmφ. In this fluidization container, if the total combustion gas flow rate is in the range of 2 / min to 10 / min, the number of base particles is μ
Fluidization is possible from m to several 1000 μm.

[Examples] The acetylene-oxygen burner 2 was set vertically from the center in the box device 1 (SUS water-cooled box, 50) shown in FIG. SiC particles, 2.5 g of average particle size of about 300 μm, are placed in the fluidized particle container 7 as the granular substrate 3 for diamond precipitation and 500 To
The whole box was replaced with Ar at rr, and then acetylene gas 3.5 / min and oxygen gas 3.15 / min were supplied to the burner with the crater 9 set at a height of 15 mm from the bottom of the fluidization vessel to burn flame. Then, the SiC particles were fluidized and diamond was synthesized for about 90 minutes.

After that, the particles were collected from the inside of the reaction apparatus and observed under an optical microscope, and it was confirmed that crystallites having a diamond self-shape of several μm covered the entire particles. The coated grains were measured by microscopic Raman spectroscopy and
SiC grains by very showed a broad low i- carbon in the range of sharp peaks and 1500～1550Cm ^-1 to 33cm ^-1 was found to be coated on the diamond crystals having a euhedral. The coating thickness was about 28 μm on average when the cross section of the grain was measured by a microscope.

[Effects of the Invention] By the method of the present invention, diamond synthesis can be performed in a large area and at a high speed, and can contribute to homogenization of diamond synthesis.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a diamond synthesizing apparatus showing an example of the method according to the present invention. 1 ... Box, 2 ... Combustion burner 3 ... Base particle, 7 ... Fluidized particle container

Claims (1)

(57) [Claims] 1. A method for synthesizing a vapor grown diamond by burning a diamond-containing starting material compound containing carbon so as to have an incomplete combustion region, wherein the diamond-depositing base is a particle or powder in a box. A method for synthesizing a vapor-phase method diamond characterized by flowing a material.