JPS6344719B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of depositing diamond in the form of particles or films using a vapor phase synthesis method. Diamond is the hardest material in existence and has excellent thermal conductivity and electrical insulation, so it is used in a wide range of fields as an industrially useful material. In addition to naturally occurring diamonds, we also use an ultra-high-pressure synthesis device to produce diamonds by placing graphite powder together with a catalyst in an ultra-high-pressure generating container at a temperature of 1600°C.
Above, the reaction is carried out under high temperature and high pressure of pressure: 60 kb or above,
There are artificial diamonds produced by phase transformation of graphite into diamond. This artificial diamond can be obtained with various particle sizes by controlling the particle size of the raw material powder and the reaction time.
Not only is the device itself large-sized, but there is also a limit to the amount of production per batch, which poses a problem in terms of productivity, and it is impossible to avoid high costs. Another method for synthesizing diamonds is to convert graphite into diamond by using the impact force from the explosion of gunpowder, but the artificial diamonds produced by this method are different from the ultra-high pressure synthesis method described above. Although it is somewhat cheaper than those produced by the method, it is difficult to obtain one with perfect crystallinity, and therefore there are problems in terms of properties. Therefore, from the above-mentioned viewpoint, the present inventors have conducted research in order to manufacture perfectly crystalline artificial diamonds with high productivity and at low cost without using large press equipment etc. ,
The substrate on which diamond is deposited is an alloy whose main component is an iron group metal, that is, an Fe-based alloy, a Ni-based alloy, a Co-based alloy, and a cermet or ceramic.
Using a surface coating member formed with a coating layer made of Nb, W, Ta, Mo,
Alternatively, with a filament made of graphite positioned, the capacity ratio of CH ₄ and H ₂ , i.e.
While flowing a mixed reaction gas with CH ₄ /H ₂ adjusted to 0.001 to 0.05 so as to pass through the filament and hit the surface of the surface coating member, the surface temperature of the surface coating member: 500 to 1200°C, and the temperature of the filament were adjusted. It has been found that when the reaction is carried out at a temperature of 1800 to 2500°C, diamond with perfect crystallinity is formed in the form of particles or a film on the surface of the surface coating member. In addition, in the method of this invention, the distance between the surface of the surface coating member and the filament is 0.5 to 3.
When the diamond is relatively small within the cm range, the density of diamond precipitation nuclei becomes high, and the precipitation nuclei are arranged side by side densely, resulting in a film-like shape.On the other hand, as the separation distance increases, the diamond becomes granular. In addition, the above-mentioned coating layer is essential for precipitating a large number of diamond nuclei. Therefore, if this coating layer does not exist, the precipitation of diamond will be extremely small, and the desired precipitation of diamond nuclei will be prevented.
and its growth cannot be measured. Next, the reason why the manufacturing conditions are limited as described above in the method of the present invention will be explained. (a) Filament temperature It is thought that the filament decomposes methane (CH ₄ ) and at the same time activates the C and H ₂ formed as a result, contributing to diamond formation. However, if the temperature is below 1800°C, The reaction gas is not activated sufficiently, and its temperature is
If the temperature exceeds 2500℃, thermal radiation becomes too large, and in either case, diamond formation will be insufficient, so the filament temperature should be set at 1800 to 2500℃.
It was determined that (b) Surface temperature of the surface-coated member This surface temperature is determined by the radiant heat from the filament and the heating temperature of the member itself. If the surface temperature is less than 500°C, the precipitation rate of diamond will be slow, while if the surface temperature exceeds 1200°C Since diamond does not precipitate at this temperature, the surface temperature was set at 500 to 1200°C. (c) Ratio of CH ₄ /H ₂ in the mixed reaction gas If this ratio is less than 0.001, the rate of diamond formation is extremely slow, while if this ratio exceeds 0.05, graphite will be mixed in the diamond. , CH ₄ /H ₂ ratio from 0.001 to
It was set at 0.05. (d) Distance between the surface of the surface-coated member and the filament If this distance is less than 0.5 cm, the surface temperature of the member will exceed 1200℃ due to the radiant heat of the filament, and diamond precipitation will not occur. On the other hand, when this distance becomes larger than 3 cm, the density of diamond nucleus formation decreases rapidly, so the distance was set at 0.5 to 3 cm. Furthermore, when carrying out the method of the present invention, the reaction atmosphere should be at a pressure within the range of 5 to 100 torr using a Pirani vacuum gauge (this pressure corresponds to 0.1 to 10 torr when measured using a diaphragm vacuum gauge; It is preferable to use a vacuum atmosphere (as indicated by the pressure measured with a Pirani vacuum gauge), because at pressures below 5 torr, the rate of diamond precipitation is extremely slow, while at pressures above 100 torr, graphite will be present. This is for the reason.
Further, the above-mentioned coating layer can be formed using a conventional chemical vapor deposition method, physical vapor deposition method, thermal spraying method, or the like, depending on the base member. The diamond synthesized by the method of this invention contains 1 to 10% of filament constituents such as W, Mo, or Ta as unavoidable impurities.
Although the impurity content may be in the range of atomic %, this level of impurity content does not have any adverse effect on the properties of diamond. Next, the method of the present invention will be specifically explained using examples. Example A base member having the component composition shown in Table 1 and having dimensions of 10 mm x thickness: 2 mm is prepared, and a coating layer also shown in Table 1 is coated on the surface of this base member. Formation methods, namely chemical vapor deposition method (denoted by CVD), magnetron sputtering method (denoted by PVD-MS), which is a type of physical vapor deposition method,
or plasma spraying method (indicated by PS) under normal conditions to form a coating layer made of Nb with an average layer thickness also shown in Table 1, and then,
On the surface of the surface coating member prepared in this way,
Similarly, under the conditions shown in Table 1, methods 1 to 7 of the present invention and comparative methods 1 to 7 were carried out by performing a gas phase synthesis reaction for diamond formation, and after the implementation, no formation was observed on the surface. The average layer thickness of the synthesized diamond was measured and its condition was observed. These results are also shown in Table 1. In addition, Comparative Methods 1 to 7 are all conducted under conditions where the vapor phase synthesis conditions for diamond formation are outside the scope of this invention (the conditions marked with * in Table 1 are outside the scope of this invention). This was carried out at From the results shown in Table 1, it can be seen that in all methods 1 to 7 of the present invention, diamonds were synthesized in good condition, whereas in comparative methods 1 to 7, diamonds were synthesized in a satisfactory manner in all cases. It is clear that this will not be done. The diamonds synthesized by Methods 1 to 7 of the present invention all exhibited hardness and electrical resistance equivalent to those of natural diamond.

【table】

[Table] As described above, according to the method of the present invention, perfectly crystalline artificial diamond can be applied to the surface of a surface-coated member in the form of granules or a film without using large-scale equipment and with high productivity. Therefore, when diamond is synthesized in the form of granules, it can be mechanically scraped off the surface of the component to form a powder, and used as a grinding wheel, abrasive, or raw material powder for powder metallurgy. When forming a film, the base member can be used for various tool parts that require wear resistance and weather resistance, or those that require thermal conductivity and electrical insulation.
It can be used as an IC, LSI, etc., and can also be used as an insulating film,
In combination with doping with components such as B, P, and Al, it brings about industrially useful effects such as being able to be applied to applications such as semiconductor films.

Claims (1)

[Claims] 1. A surface-coated member made of a base member made of Fe-based alloy, Ni-based alloy, Co-based alloy, cermet, or ceramic, with a coating layer made of Nb formed on the surface thereof, is charged into a reactor, and the surface-coated member is While maintaining the distance between the surface and the filament made of W, Ta, Mo, or graphite at 0.5 to 3 cm,
While flowing a mixed reaction gas with a CH ₄ /H ₂ ratio adjusted within the range of 0.001 to 0.05 into the reactor, the surface temperature of the surface coating member: 500 to 1200 °C, and the filament temperature: 1800 to 2500 °C. A method for vapor phase synthesis of diamond, characterized in that diamond is deposited in the form of particles or a film on the surface of the surface coating member by carrying out a vapor phase synthesis reaction.