JPH02279593A - Method for synthesizing diamond by vapor method - Google Patents

Abstract

PURPOSE:To accelerate the homogenization and mass production of a diamond deposit by fluidizing a base material for diamond deposition which is grains or powder in a box body and burning raw materials for diamond deposition so as to have an incomplete combustion region. CONSTITUTION:The base material for diamond deposition which is the grains or powder in the box body is fluidized in the method for synthesizing the vapor method diamond by burning the raw material compd. for diamond deposition contg. carbon so as to have the incomplete combustion region. The carbon source for synthesizing diamond to be used is exemplified by satd. hydrocarbon (e.g.; methane), unsatd. hydrocarbon (e.g.: propylene), arom. hydrocarbon (e.g.: styrene), alcohols (ethyl alcohol) on the like. In the case the base body is grains or powder, the fluidized bed is formed by the ejection force of the flame itself of the combustion flame, by which the diamond is deposited on this base 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 suitable for use in abrasive materials, optical materials, cemented carbide tool materials, This article relates to the vapor phase synthesis of film-like and granular diamonds useful for sliding materials, corrosion-resistant materials, acoustic vibration materials, keys for cutting edge materials, etc.

[Conventional technology] Diamond synthesis methods involve using iron, iron, etc. under ultra-high pressure conditions.
Synthesis methods using nickel-based catalysts and direct conversion methods of graphite using explosive methods have been practiced in the past.

In recent years, as a low-pressure CVD method, a mixed gas of hydrogen and hydrocarbons or H organic compounds containing nitrogen, oxygen, etc. is excited using a hot filament, microwave plasma, high-frequency plasma, DC discharge plasma, DC arc discharge, etc. to produce diamonds. A synthesis method has been developed.

More recently, the applicant has developed a method for synthesizing diamond in the non-oxidizing region of combustion flame, and filed a patent application No. 83-7175
No. 8 has been filed, and the present invention corresponds to this improvement method.

[Problem to be solved by the invention] The invention of Japanese Patent Application No. 83-71758 is a vapor phase synthesis method that is simpler than conventional methods and can also produce a large area of film-like diamond. burns a carbon-containing raw material compound for diamond precipitation so as to have an incomplete combustion region, and places a diamond precipitation substrate in a non-oxidizing atmosphere in or near the incomplete combustion region; This is a method in which diamond is deposited on a base material by maintaining the base material temperature at a diamond precipitation temperature.

This method allows diamond to be deposited on a substrate simply by forming a combustion flame using a raw material compound containing carbon, and is a revolutionary method compared to the conventional CVD method, but it is difficult to put it into practical use. There is a strong desire to further increase the diamond precipitation rate, improve homogeneity, and control the properties of the precipitates.

The present invention aims to increase the precipitation rate and precipitation area of diamond, and to promote homogenization of the precipitate and mass production.

[Means for Solving the Problems] As a result of intensive research to achieve the above object, the inventor of the present invention controlled the atmosphere and pressure in a box when burning the raw material compound for diamond precipitation. The increased combustion area and increased homogeneity increase the deposition rate of diamond over a wider deposition area, resulting in more homogeneous and better quality diamond deposits, and the flow of the substrate, which may be granules or powder. The inventors discovered that mass production is possible and completed the present invention.

That is, the gist of the present invention is a method for synthesizing diamond using a vapor phase method by burning a carbon-containing raw material compound for diamond precipitation so as to have an incomplete combustion region, in which diamond precipitation in the form of granules or powder is performed in a box. The present invention relates to a method for synthesizing diamond using a vapor phase method, which is characterized by fluidizing the base material.

The present invention will be explained in detail below.

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. Moreover, the above-mentioned compounds can be used alone or in combination of two or more.

Furthermore, solid carbon, graphite, etc. as a carbon source is vaporized, combusted, etc. in a combustion flame of a mixed gas of the above compound and hydrogen, oxygen, etc.
It is also possible to use it as a carbon source through reactions such as hydrogenation. Moreover, at that time, a non-oxidizing gas can also be mixed.

These carbon-containing raw material compounds are decomposed by combustion heat in a combustion flame, further decomposed and dissociated by reaction with # element, and are converted into radicals by active species, such as C, CCH, CH2.
, CH3, etc. are abundant in the incompletely twisted 2'' firing region and are presumed to be suitable for forming a diamond phase.Hydrogen atoms and oxygen atoms are also formed and are involved in the diamond precipitation reaction. The generation and diffusion region of radicalized active species, hydrogen atoms, and oxygen atoms can be controlled to reduce the oxygen concentration in the atmosphere through combustion in the box, and the outer flame area can be reduced or Dissipation occurs, which leads to an expansion of the incomplete combustion region, an increase in diamond precipitation area, velocity,
Homogenization becomes possible.

The present invention also allows mass production of diamonds by allowing the substrate to flow inside the box. When the substrate is a granule or powder, a fluidized bed is formed by the ejection force of the combustion flame from the nozzle, and diamond can be deposited on the substrate.

In the present invention, for example, oxygen is added to a raw material gas such as acetylene, styrene, propane, ethyl alcohol, methyl alcohol, benzene, etc. to form a combustion flame, and by adjusting the amount of oxygen added, the amount of oxygen contained in the atmosphere in the box is reduced. It is possible to reduce and control the volume of the incomplete combustion region. In this case, the incomplete combustion region of the acetylene-oxygen flame is called the acetylene feather, and this volume changes depending on the oxygen/acetylene ratio, the total gas amount, the pressure of the atmosphere in the box, and the amount of oxygen content, and can be controlled. It is possible. In particular, the oxygen/acetylene ratio can range from 0.5 to 2, but is preferably from 0.75 to 1.

The pressure inside the box is 0. ITorr ~10,000 Torr
r, preferably 1OTorr to 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 becomes diluted and the flame goes out, at the same time causing a drop in temperature. In addition, the oxygen content in the box is an important factor because oxygen diffused from the outer periphery of the combustion flame causes a volume reduction in the incomplete combustion region, but the shape and size of the box, and the volume of the combustion flame are also important factors. It cannot be determined unambiguously because it depends on the flow rate, number, and condition of the substrate to be flowed. However, by using the box of the present invention, the volume of the incomplete combustion region can be controlled by controlling the amount of oxygen, since the container can be determined by experiment.

Generally, the temperature in the acetylene feather region under combustion conditions in the presence of an external flame is between 2000 DEG and 3000 DEG C., and no auxiliary excitation means are required. Therefore, a preferable diamond synthesis temperature of 1500° C. or higher can be easily achieved. The substrate temperature is suitably 600 to 1200° C., and can be controlled within this range by cooling, heat dissipation, etc.

By controlling the amount of oxygen in the atmosphere of the box, there may be a lack of excitation energy to generate the radicals necessary for diamond formation when combustion causes the outer flame to disappear or when the pressure inside the box is low. In such cases, auxiliary excitation means may be used as necessary. Examples of auxiliary heating sources include a heating element using electrical heating, high-frequency induction heating, a heating method using laser light, infrared heating, and heating using arc discharge.

As the substrate for diamond deposition, those commonly used in low pressure CVD methods can be used. That is, Sl wafer StC sintered body,
W, WC outside the SiC granules.

Mo, Tic, TiN, cermet, cemented carbide tool steel 1
Examples include shaped objects and granular objects such as alloy tool steel and high-speed steel.

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

FIG. 1 is a schematic diagram of a diamond synthesis apparatus having a flow device inside a box 1. As shown in FIG. The granules 3 charged at the bottom are fluidized by the ejection force at the same time as the combustion flame of the combustion burner 2 is formed. Diamond precipitation occurs while the substrate particles remain within the diamond synthesis zone within the combustion flame. Since the base particles are fluidized, a diamond precipitation surface area that is 3 to 7 times the diamond precipitation surface area in a stationary state is exposed to the diamond synthesis region and participates in diamond precipitation. Further, after synthesis for a certain period of time, the plate-like part (batch for carrying out powder) 8 at the bottom is raised to form a gap, and the synthesized powder can be collected. Furthermore, new base material particles are charged through a base material inlet (not shown) located 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 a pressure inside the box, an atmosphere exhaust system, and 7 is a fluidized granule container (made of Mo) with a water cooling system (not shown).

The fluidized granule container 7 shown in FIG. 1 has an inner diameter of approximately 100 mmφ and an opening diameter of 180 mmφ at the top. In this fluidization vessel, the total flow rate of combustion gas is 24) /ffiin-10g/s1n
Within this range, it is possible to fluidize up to several thousand base particles.

[Example] Box device 1 shown in Fig. 1 (SUS water-cooled box, 50I)
The acetylene-oxygen burner 2 was set vertically from the center. SiC grains as the granular substrate 3 for diamond precipitation;
2.5 g of particles with an average diameter of about 300 m were placed in a fluidized granule container 7 and the entire inside of the box was replaced with Ar at 500 Torr, and then a crater 9 was set at a distance of 15 mm from the bottom of the fluidized container. Acetylene gas 3.51/sin in burner
A combustion flame was formed by supplying s oxygen gas (3.15j)/sin, and fluidization of SEC grains and diamond synthesis were performed for about 90 minutes.

Thereafter, the particles were collected from inside the reactor and observed under an optical microscope, and it was confirmed that the entire particle was covered with several crystallites having a diamond euhedral shape. Δp1 of this coated grain was determined by micro-Raman spectroscopy, and 1 of the diamond beak was determined.
Sharp peak at 333c+n-1 and 1500-1550c
The observation of very broad low i-carbon in the m-' range revealed that the SiC grains were covered with eye-shaped diamond crystals. Further, the coating thickness was about 28 mm on average when the cross section of the grain was added to the microscopic m11 FI.

[Effects of the Invention] According to the method of the present invention, diamond synthesis can be performed over a wide area and at high speed, and it can also contribute to homogenization of diamond synthesis.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a diamond synthesis apparatus showing an example of the method according to the present invention.

Claims (1)

[Claims] 1. In a method of synthesizing diamond using a vapor phase method by burning a carbon-containing raw material compound for diamond precipitation so as to have an incomplete combustion region, a diamond precipitation base material in the form of granules or powder is fluidized in a box. A vapor phase diamond synthesis method characterized by: