JPH0691954B2 - Method for producing cubic B-C-N crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a high hardness, insulating cubic B-C-N (hereinafter referred to as cB-N).
Abbreviated as C-N). cB-C-N
The crystals are diamond and cubic boron nitride (hereinafter cBN
Similar to the above), since it has high hardness and wear resistance, it is attracting attention as a substance having suitable characteristics as a grinding abrasive grain, a cutting tool material, and the like.

PRIOR ART AND ITS PROBLEMS Diamond is among the best known materials for hardness today. However, there are problems with stability when used at high temperatures. On the other hand, cBN is a hard material next to diamond. Moreover, its high temperature stability is
Remarkably superior to diamond. However, the hardness of cBN crystal is about half that of diamond crystal. On the other hand, the cB-C-N crystal is close to the hardness of diamond crystal and excellent in high temperature stability, and is a very promising substance as a high hardness and abrasion resistant substance.

As a conventional method for producing a cB-CN solid solution, (1) Andrzej R. Badzian, Material Research Bulletin (Mat.Res.Bull.), Vol.16, pp1385-1393,
In 1981, the synthesis of cB-CN solid solution was reported. According to the article, a hexagonal B-C-N solid solution (hB-C-N solid solution) synthesized by a chemical vapor deposition method was used at a static high temperature and high pressure apparatus at a very high pressure of 14 GPa and about 3600 K, It is reported that a cB-CN solid solution could be synthesized under temperature conditions. Also, in the same paper, they were synthesized in the same manner.
hB-C-N solid solution, diamond synthesis catalyst (Co, Ni)
And cBN synthesis catalyst (Li ₃ N, Mg ₃ N ₂ ) coexisted and treated under the same high temperature and high pressure conditions as those for synthesizing ordinary diamond and cBN, but a cB-CN solid solution is synthesized. It was not possible to report.

(2) By Nobuo Setaka, Research Report No. 39, Institute for Inorganic Materials, Chemical Agency (Research on Diamond, pp59-61, 19
(1984), the possibility of synthesizing a cB-CN solid solution by using high impact pressure was reported. The method is as follows: carbon precursor synthesized from furan resin (600 ° C treatment) and NaBH ₄ -NH ₄ Cl
The more synthesized hexagonal BN (hBN) is mixed at a ratio of 0.7: 1,
High impact pressure of 60 GPa is applied to synthesize a cB-CN solid solution.

Regardless of static or dynamic high pressure, the above-mentioned two methods that can synthesize a cB-CN solid solution are synthesis methods under extremely high pressure conditions, and therefore, as industrial processes,
Practical application is difficult. Further, as a basis for synthesizing a cB-CN solid solution, both of the above two methods are based on the fact that the lattice constants of these solid solutions are between the lattice constants of diamond and cBN.

OBJECT OF THE INVENTION The present invention eliminates the drawbacks of the conventional methods for producing cB-C-N solid solutions, does not require very high pressure conditions, and provides a method for producing cB-C-N crystals under mild high temperature and high pressure conditions. The purpose is to provide.

As a result of earnest research to achieve the above-mentioned object, the present inventors have used BCl ₃ , CCl ₄ , N ₂ , and H ₂ gas to produce the hB—C—N solid solution in the AR Badzian report. The chemical vapor deposition method (hereinafter referred to as the CVD method) is used.

However, since this method uses different source gases for the B, C, N raw materials, hBN or a heterogeneous mixture of B, N, C is selectively formed rather than a homogeneous B-C-N solid solution. It is easy and it is difficult to control the composition ratio of B, N and C.

The inventors of the present invention used both boron trichloride (BCl ₃ ) and acetonitrile (CH ₃ CN) gas and utilized the CVD reaction to obtain 750 to 900
A solid solution was prepared at ° C.

As a result, black film-like deposits were observed on the substrate at 750 ° C. As a result of electron diffraction and powder X-ray diffraction of the deposit, the lattice constants were a = 2.44Å and c = 3.40Å.
These values are very close to the lattice constants of graphite and hBN. From these, it is considered that the product has a layered structure very similar to both. The crystallinity of the product was better as the gas partial pressure was lower and the CVD reaction temperature was higher.

The chemical composition of the synthesized deposits was investigated by measuring the electron energy loss spectra and Auger electron spectroscopy. As a result, it was revealed that it had a chemical composition of BC ₂ N. Thus, a stoichiometric hB-CN solid solution can be synthesized by supplying a C, N source from acetonitrile,
It is considered that since the source of B is supplied from boron trichloride, selective hBN formation is suppressed and a deposit in which B, C and N are uniformly distributed can be obtained. In this respect, existing hB-C-N
It was found to be very different from the solid solution. The reaction is as follows.

BCl ₃ (g) + CH ₃ CN (g) → BC ₂ N (s) + 3HCl (g) The electrical resistance of the film-form hB-C-N solid solution obtained by the CVD reaction of BCl ₃ and CH ₃ CN is determined by the four-terminal method. As a result, the specific resistance was 0.
It was from 05 to 0.1 Ωcm. This value belongs to the semiconductor region,
It is located between the semi-metallic behaviour, graphite and hBN, which is an insulator. As an electrical property, film-like hB-CN solid solution is
It was found that the substance has properties closer to that of graphite rather than N.

The hB-CN solid solution synthesized by the CVD reaction of BCl ₃ and CH ₃ CN was treated at 7.7 GPa and 2000 ° C.
The presence of -CN solid solution was also not observed by X-ray diffraction. Since the temperature of the above synthesis conditions was low, it was considered that the formation of the cB-C-N solid solution was not observed, and the hB-C-N solid solution was treated under the higher synthesis conditions of 7.7 GPa and 2200 ° C. As a result of X-ray diffraction of the obtained sample, it was partially converted into a cubic crystal substance. Judging from the values of these lattice constants, it is considered that cBN was partially formed, not the cB-CN solid solution. It is considered that under high temperature and high pressure conditions of 7.7 GPa and 2200 ° C, the hB-C-N solid solution was not directly converted to the cB-C-N solid solution but was decomposed and a part thereof was converted to cBN.

Under the above pressure and temperature conditions, it is very difficult to synthesize a cB-C-N solid solution.

Therefore, it is well known as a diamond synthesis catalyst.
Metals or alloys of Co, Ni, Fe and hB-C-N solid solution were laminated and treated under the conditions of about 6 GPa and 1500 ° C. The obtained sample was treated with hot concentrated hydrochloric acid, washed with water and dried, and then examined by X-ray diffraction. As a result, the lattice constant of the sample was clearly smaller than that of cBN and larger than that of diamond. These results strongly suggest the possibility of cB-CN solid solution synthesis. As a result of examining the sample using the scanning Auger electron spectroscopy (SAM), it was possible to clearly detect the three elements B, C, and N. In addition, as a result of SEM observation of the sample, cB-C
It was also clarified that the -N solid solution was fine crystals having an automorphic surface.

It was also found that when this treatment temperature was lower than 1360 ° C., a cB-C-N crystal could not be obtained. The present invention has been completed based on these findings.

The gist of the present invention is a hexagonal BC ₂ N film or powder having a stoichiometric composition synthesized by a chemical vapor deposition method of boron trichloride and acetonitol, and selected from cobalt, iron, nickel and alloys thereof. A method for producing a cubic B-C-N crystal is characterized in that one or more metals are brought into contact with each other and heat-treated at a temperature of 1360 ° C. or higher in the diamond stable region.

A schematic diagram of a CVD reactor used in the method of the present invention is shown in FIG. 1 is a helium cylinder, 2 is a boron trichloride cylinder, 3 is a boron trichloride bubbler, 4 is an acetonitrile distillation device, 5 is an acetonitrile bubbler, 6 is an electric furnace, 7 is a trap, 8 is a vacuum line, 9 is Indicates a mercury bubbler.

Example Using the CVD reactor shown in FIG. 1, using helium gas as a carrier gas, the gas partial pressure of BCl ₃ is 60 Torr, CH ₃ CN
The reaction was carried out at a reaction temperature of 850 ° C. for 12 hours under the condition of partial pressure of 20 Torr. As a result, a black film with a thickness of about 0.1 mm could be synthesized on the SiO ₂ substrate.

As a result of X-ray diffraction of the obtained film, the sample belonged to the hexagonal system and the lattice constants were a = 2.44Å and c = 3.40Å. Second
Figure shows a SEM image of the cross section of the sample. As a result of X-ray diffraction pattern and SEM observation, the laminated state of the product was composed of homogeneous particles having a disordered turbostratic structure.

The electron beam energy loss spectrum (EELS) of the product is shown in FIG. Three peaks appeared in the energy loss range of 180 to 450 eV. These peaks are due to the excitation of K-shell electrons and were assigned to B, C and N, respectively. Since no other peaks are observed, it is clear that the product is composed of the three elements B, C and N. By comparing the area of each peak with the calculated ionization cross-section of each element, the mol% of B, C, and N are 24.7 ± 4.1% and 52.6 ±, respectively.
It was 5.8% and 22.7 ± 3.6%. From these results, the chemical composition of the product was found to be BC ₂ N. The chemical composition was also confirmed to be the same by Auger electron spectroscopy.

The obtained hB-C-N solid solution was laminated on a metal Co plate to give 5.8 GPa,
It was treated at 1500 ° C. for 1 hour. The obtained sample was treated with hot concentrated hydrochloric acid and hot concentrated sulfuric acid, washed with water, dried and examined by X-ray diffraction. The X-ray diffraction pattern (Fig. 4) showed a cubic crystal pattern and the lattice constant was a = 3.60Å. This value was between the lattice constants of cBN and diamond. The SEM image of the sample is shown in FIG. It is clear that this sample consists of sub-micron to a few micron crystallites with an automorphic surface.

SAM was used to clarify the constituent elements of this sample (Fig. 6). Since this sample is an insulator, the apparent energy values are shifted, but B, C, and N are clearly detected. We investigated Auger spectra at many points, and obtained spectra consisting of B, C, and N at all points. When the composition is estimated from the intensity of each peak, it is clear that it is a B, C, N crystal containing about 15% carbon.

From the results of X-ray diffraction, SEM image observation, and Auger electron spectrum measurement, hB-CN solid solution was laminated on a metal Co plate to give 5.8GP.
a, cB of several microns as a result of processing at 1500 ℃
It was found that a -C-N crystal was obtained.

EFFECTS OF THE INVENTION According to the method of the present invention, the cB-C-N crystal can be easily produced under mild pressure and temperature conditions without requiring the extremely high pressure in the conventional method for producing a cB-C-N crystal. can get. Therefore, the apparatus is simple and industrial production can be easily performed.

[Brief description of drawings]

FIG. 1 is a schematic view of a CVD reactor, and FIG. 2 is an SEM showing a particle structure of a hB-CN solid solution cross section obtained by the method of the present invention.
Image, Fig. 3 shows electron beam energy loss spectrum of BC ₂ N,
FIG. 4 is a powder X-ray diffraction diagram of the cB-CN crystal obtained by the method of the present invention, FIG. 5 is a SEM image showing the structure of the crystal, and FIG. 6 is Auger electron showing the structure of the crystal. The spectrum is shown. 1: Helium cylinder, 2: Boron trichloride cylinder, 3: Boron trichloride bubbler, 4: Acetonitrile distillation device, 5: Acetonitrile bubbler, 6: Electric furnace, 7: Trap, 8: Vacuum line, 9: Mercury bubbler.

Claims (1)

[Claims] 1. A hexagonal BC ₂ N film or powder having a stoichiometric composition synthesized by a chemical vapor deposition method of boron trichloride and acetonitrile, and one selected from cobalt, iron, nickel and alloys thereof. Alternatively, a method for producing a cubic B-C-N crystal is characterized in that two or more kinds of metals are brought into contact with each other and heat-treated at a temperature of 1360 ° C. or higher in a diamond stable region.