JP3388599B2 - Diamond-like particle formation method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for fine particles of diamond or diamond-like carbon (hereinafter collectively referred to simply as "diamond") produced by a vapor phase deposition method, particularly suitable as an abrasive for precision finishing. A method for producing fine diamond particles.

[0002]

2. Description of the Related Art In recent years, the demand for precision polishing has increased remarkably and the demand for it has also become strict. Accordingly
There is a demand for micron-class abrasive fine particles that have a large polishing ability and do not cause polishing scratches. For this purpose, it is necessary to develop a technique for producing an abrasive, especially a diamond powder, which has a narrow particle size distribution and has no coarse particles at all. Generally, micron-sized (particle diameter 50 μm or less) abrasive particles are manufactured by crushing larger particles and subjecting them to a classification step, but it becomes difficult to meet these requirements as the particle diameter becomes finer. On the other hand, since particles having good crystallinity exhibit sufficient crushing strength, it is said that such particles are preferable as the abrasive particles, but since the particles obtained in the above step are crushed pieces, There is no crystal. Therefore, it cannot be said that the inherent strength of the particles is exerted when used as crushed abrasive particles.

On the other hand, researches for synthesizing diamond by a vapor deposition method have been extensively conducted. This method is particularly applicable to coating relatively large area substrates,
It is expected to be used as a tool material, a hard protective film, an optical material, and an electronic material, and some of them are already in practical use. This technology is also being developed in consideration of its application as an abrasive material. At this time, in order to reduce costs, SiC, S
Non-diamond crushed particles such as i and alumina are used as the base particles. Such a method is described in, for example, JP-A-63-15609 and JP-A-1-305808.

A technique for obtaining automorphic diamond by using a method of vapor phase synthesis using a crushed piece of diamond as a substrate has been established.
It is known from Japanese Patent Publication No. 304. According to this method,
By growing the generated particles to twice or more the diameter of the base particles, it is possible to obtain agglomerated particles having a biaxial ratio (a long / short axis ratio in a particle pattern projected on a plane) of 1.3 or less. . However, even with this method, crushing and
Since the particles that have undergone the classification process are used, it is unavoidable that the particle size width of the substrate widens, and it is difficult to narrow the particle size width to improve accuracy unless the growth ratio is set to a large value, and it is also coarse. It is not possible to completely eliminate particle contamination.

In addition to the above, ultrafine diamond powder prepared by the so-called explosive synthesis method using impact pressure is also expected as a substrate for producing diamond particles by the vapor deposition method. Because it easily aggregates,
Special measures are required to disperse the particles in a state close to isolated particles.

In many vapor deposition processes, silicon has been used as a substrate for depositing diamond films. At this time, silicon is used as a thin plate having a side length of 1 to several cm. There is no literature describing its use as a finely powdered substrate.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention eliminates the above-mentioned difficulties, has a narrow particle size width and almost completely eliminates the inclusion of coarse particles, and is highly accurate and reliable.
An object of the present invention is to provide an efficient method for producing a micron-class diamond abrasive.

[0008]

SUMMARY OF THE INVENTION The gist of the present invention is to produce amorphous silicon fine particles by decomposing a gaseous silicon compound, and to form diamond on the fine particles by a vapor deposition method from a carbonaceous raw material gas. A diamond-like particle forming method is characterized in that diamond or diamond-like carbonaceous particles are formed by depositing carbonaceous particles.

As the silicon compound in the present invention, silicon hydrides (silanes such as SiH ₄ , Si ₂ H ₆ ) and chlorosilanes (SiH _m Cl _n : m, n = 0 to 4, m +) are used.
n = 4) is available. These gases, as are often experienced in the process of silicon production from silane,
Pyrolysis readily yields amorphous submicron silicon powder. The formation of the amorphous powder becomes more severe as the concentration of silane is higher and the decomposition temperature is higher. Especially in the case of silicon hydride, the decomposition reaction proceeds in a chain due to the exothermicity.

As a raw material gas, CH ₄ as a carbon source or a mixed gas of CO and H ₂ as a main component, to which O ₂ , H ₂ O and CO ₂ as product modifiers are added is used. it can.

The above silicon compound and carbonaceous gas are simultaneously introduced into the reaction chamber at the beginning of the reaction, and then only the carbonaceous gas is supplied together with hydrogen. Alternatively, as a first step of the reaction, a mixed gas of a silicon compound and hydrogen is introduced into the reaction vessel for nucleation, and then a mixed gas of a carbonaceous gas and hydrogen is introduced to form the nuclei formed in the first step. It is also possible to grow diamonds on top.

As an exciting method for making these gases into plasma, a method using a non-polar discharge using microwaves or high frequencies is particularly preferable, but in addition, an exciting method using a hot filament method or a direct current discharge, and other methods. Various methods can be used which are carried out in a system that is shielded from the atmosphere. In the former case, it can be carried out as a process using a fluidized bed, but in other cases, it is preferable to vibrate the deposit tray so that uniform growth can be achieved throughout the particles.

As is well known, in the diamond precipitation reaction on the substrate particles, if the process parameters are constant,
The smaller the grain size, the higher the relative growth rate with respect to the grain size. For example, according to the knowledge of the present inventors, in the precipitation step from a certain gas system, the starting seed crystal having a particle diameter of 120 nm was 5 μm (growth ratio 4
The seed crystal of 10 nm is about 3 μm (30
However, after 5 hours from the start of the reaction in which precipitation has proceeded, both become crystals of about 5 μm, and there is almost no difference. This indicates that, if other process parameters are constant, the diameter of the obtained grown particles finally almost exclusively depends on the reaction time. Therefore, by adjusting the deposition time, it is possible to obtain the abrasive particles having a desired particle size.

The silicon particles produced are initially kept in suspension by the feed gas stream. Diamond is deposited,
Since it grows and settles as the weight increases, it is received in a saucer or the like having an appropriate shape, and finally, an aqueous solution of NaOH is used to dissolve and remove Si to recover diamond particles or diamond-coated particles.

The biaxial ratio of the formed diamond particles approaches 1 as the growth rate increases. Therefore, by controlling the growth rate, it is possible to obtain a crystal product having a preferable biaxial ratio and eventually a preferable shape. As a general tendency, this ratio is 1.3 or less when the growth rate is 2 or more, 1.2 or less when 5 or more, and 1.1 or less when 10 or more.

The method of the present invention was developed with the intention of producing fine abrasive particles, particularly abrasives of 20 μm or less as described above, and is suitable for this purpose. However, it is possible to produce diamond particles of various particle sizes other than this by using starting particles of various sizes. In this case, the time for making the particle diameter uniform becomes longer as the starting particle diameter increases and as the radius growth rate increases. When the seed crystal is silicon particles of 1 μm or less, when the radius growth rate is about 2 μm / hour, it is remarkably maintained up to 8 μm for 4 hours.

[0017]

Example 1 A vapor phase deposition apparatus as schematically shown in FIG. 1 was used. The reaction tube, designated as a whole by 1, is essentially made of quartz and has a flow section 2 with an inner diameter of 44 mm, an enlarged section 3 with a diameter of 100 mm,
It has a connecting portion 4 between the two. The flow section 2 is connected to a 2.45 GHz magnetron 6 via a waveguide 5. A glass straightening plate 7 is provided at the bottom of the reaction tube 1. The inside of the reaction cylinder 1 is decompressed by the vacuum pump 8 while H ₂
Was introduced into the H ₂ atmosphere of 2.3 KPa, the microwave output was set to 160 W, and then as a substrate forming gas,
A mixed gas of 50 ml of H ₂ and 1 ml of SiH ₄ per minute was introduced through the flow controller 9 from the bottom of the reaction tube 1 for 2 minutes to form amorphous Si. After that, the gas was switched to a mixed gas of H ₂ : CH ₄ = 100: 1 for the diamond deposition reaction while keeping Si in a floating state with H ₂ gas. This mixed gas was continuously flowed at a rate of 5 minutes per minute for 3 hours, at which time the feed rate finally increased to 50 ml / minute as the process progressed. The reaction product recovered from the rectifying plate 7 was treated with an aqueous NaOH solution to obtain diamond particles. The average particle diameter was 5 μm, the maximum and minimum diameters were 8 and 3 μm, respectively, and the biaxial ratio was 1.2.

[0018]

Example 2 The operation was repeated using the same apparatus as in the above example. H ₂ : C is used as the deposition reaction gas.
A ternary mixed gas of H ₄ : O ₂ = 100: 3: 2 was used.
As in the above example, a mixed gas of SiH ₄ and H ₂ was used as the substrate forming gas. In the precipitation step for 30 minutes, the average particle size was 0.5 μm, and the maximum and minimum sizes were 0.7 and 0.
Diamond particles having a diameter of 3 μm and a biaxial ratio of 1.3 were obtained.

[0019]

Example 3 The operation was repeated using the same apparatus as in Examples 1 and 2 above. As a deposition reaction gas, H ₂ : CO:
The ternary mixed gas of CO ₂ = 100: 50: 6 was used, and the mixed gas of Si ₂ H ₆ and H ₂ was used as the substrate forming gas. Four
Diamond particles having an average particle diameter of 8 μm and a maximum and minimum diameter of 10 and 5 μm, respectively, and a biaxial ratio of 1.1 were obtained in the precipitation step of time.

[0020]

As described above, according to the present invention, since growth starts from fine nanometer-sized seeds, coarse particles are not mixed and the particle size distribution width is narrow. Further, by growing an automorphic crystal having a small biaxial ratio, sufficient strength can be obtained, so that ideal fine abrasive particles can be achieved.

[Brief description of drawings]

[Figure 1]

[Explanation of symbols]

1 reaction tube 2 Flow section 3 Expansion section 4 connection 5 Waveguide 6 magnetron 7 Current plate 8 vacuum pump 9 Flow controller

Claims (5)

(57) [Claims] 1. A fluidized portion formed in a tubular shape, and above the fluidized portion.
The enlarged part, which is located at the center and has a larger diameter than the flowing part, and the flowing part
Of the vapor phase deposition apparatus containing a connecting portion for connecting the
From the bottom into the vapor-phase deposition apparatus into a gaseous state together with hydrogen gas
Leads to silicon compounds and is indefinite due to decomposition of the silicon compounds
Generate fine particles of silicon-shaped silicon to make it float and flow, then hydrogen
Silicon compound in the state of floating flow with gas
The material gas is switched to carbonaceous raw material gas,
Diamond or diamond-like charcoal on fine silicon particles
A method for forming diamond particles, which comprises vapor-depositing and growing an element to a desired particle size . 2. The average particle size of the amorphous silicon fine particles is 1
The method for forming a diamond-like particle according to claim 1, which has a diameter of not more than μm. 3. The silicon compound is SiH ₄ or Si
_The method for forming diamond particles according to claim 1, wherein the method is ₂ H ₆ . 4. The silicon compound is SiH _m Cl _n (m,
The method for forming diamond particles according to claim 1, wherein n = 0 to 4 and m + n = 4). 5. The carbonaceous raw material gas is mainly CH ₄ , C ₂
The method for forming diamond particles according to claim 1, which contains H ₂ or CO.