JPS61191505A - Production of boron nitride - Google Patents

Abstract

PURPOSE:To produce easily homogeneous BN without causing the scattering, bubbling or blackening of starting materials during heating by bringing a mixture of B2O3 or B with melamine into a reaction in the presence of water, drying the resulting mixed reaction product, and calcining it. CONSTITUTION:B2O3 or B is mixed with melamine in 1/3-2/1 atomic ratio of B/N, water is added to the mixture by 1.2-2g per 1g melamine, and they are brought into a reaction. The resulting mixed reaction product is dried and calcined at 600-1,000 deg.C. It is further heated to 700-2,300 deg.C in an atmosphere of a nonoxidizing gas as required.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for producing boron nitride.

BACKGROUND ART Conventionally, as an industrial method for producing boron nitride, a method has been carried out in which boric acid or borax is reduced and nitrided with a nitrogen-containing organic substance such as urea, dicyandiamide, melamine, etc.

These methods are superior in terms of efficiency because reduction and nitridation are performed using the same substance. However, the object of the invention is to solve the drawbacks of the conventional method.
The purpose is to provide a method for easily producing homogeneous boron nitride using boron oxide or boric acid and melamine as raw materials, without scattering or bubbling of the raw materials during heating, and without blackening.

Structure of the Invention In order to achieve the above object, the present inventor investigated the causes of problems in the conventional method when using boron oxide and melamine as raw materials, and found that when a mixed powder of both is heated, melamine is removed during heating. It was found that this is due to decomposition and sublimation of melamine, and melting of boron oxide (in the case of boric acid, dehydration and further melting of boric acid) before reaching the melting point of melamine (374°C). Ta.

Thus, a combination of boric acid or boron oxide and melamine is obtained. In addition, this was further treated in a non-oxidizing gas atmosphere for 7
It has been found that crystalline boron nitride can be obtained by heating at 00 to 2300°C. The present invention was completed based on this knowledge.

The gist of the present invention is that a mixture of boron oxide or boric acid and melamine at a B/N atomic ratio of 1/3 to V1 is mixed with water and reacted, and this is dried or further A method for producing boron nitride, which comprises calcining or heating at 700 to 2300°C in a non-oxidizing gas atmosphere after drying or calcining.

Figure 1 shows that after changing the mixing ratio of B2O3 and melamine and adding about 109 parts of water per 1f of melamine and stirring and mixing,
The X-ray diffraction pattern of powder dried at 0°C and the X-ray diffraction pattern of melamine are shown.

As the figure shows, in the presence of water B20. and melamine (
05N6) Since the atomic ratio of B/N with I6) is 1/3 or more, it is necessary that the atomic ratio of B/N is 1/3 or more.

When the proportion of B is high, hBN formation is promoted. In order to obtain hBN with good crystallinity, it is desirable that B/N = 171 or more.Up to approximately B/N = 2/1, improvement in crystallinity can be seen depending on the amount of boric acid; It remains uselessly in the product as a raw material. -Force amorphous BN
In order to obtain this, it is preferable that melamine be in excess, usually B/N = 1/2 or more. Therefore, the preferred range of B/N ratio is 1/3 to 2/1. The amount of water mixed differs depending on whether boric acid or boron oxide is used as a raw material, but it is appropriate that the amount of boron oxide is at least 1.2 parts water. Menu. If the amount of water is too large, it will take a long time to dry, and a large capacity container is required, so it is sufficient that it does not interfere with stirring. Usually, 2Qt dry powder is white crystalline. . When calcined, as shown in Figure 2, (
The dehydration peaks at 180°C and is completed at 300°C. This dehydration process reduces the weight by about 1/2 to 1/3 and provides a powder that exhibits an X-ray diffraction pattern similar to amorphous BN. Since this step generates water vapor and also involves degassing, it is preferable to perform it separately from the subsequent steps. 700
℃, resulting in a weight loss of 1.1 to 1.3 times that of the final product.

There is almost no weight loss up to 700-1000°C, and no noticeable progress of crystallization is observed.

What was obtained in this way was a BN crude raw material and colored powder, which contained 99% or more of BN at B/N = A to 1. The X-ray diffraction diagram differs depending on the B/IJ ratio of the starting material; when B/N = T, hBN is observed at 1200°C, and when B/N = 1/2 or less, amorphous BN is observed. .

The heating temperature is up to 2300°C, and heating above this temperature is B.
Decompose N.

Example 1゜B2O335? and melamine 21f, about 200
The mixture was gradually added to the water in Step 2 with stirring, and thoroughly stirred with a ball mill. This was dried at 80°C to obtain a white crystalline powder. Further, the mixture was heated to 300°C in a nitrogen gas stream to obtain a product with an amorphous structure.

This was further heated to 800°C to obtain boron nitride powder. This powder is white and shows an X-ray diffraction pattern of turbostratic boron nitride, with a yield of 106% of the theoretical value by weight, and is not yet completely boron nitride. The final product was made into a final product. The yield was about 95% by weight, and the BN content was over 99.8% by weight. The X-ray diffraction pattern at each heating stage was as shown in FIG.

Example 2゜B20.16.2 f, melamine 19.6 f about 2
After adding 002 to water and stirring and mixing with a ball mill, 8
Drying at 0°C gave a white powder. 20 minutes in the air
After heating at 0°C, further heated to 1200° in a nitrogen gas stream.
C. to obtain a slightly brownish boron nitride powder. The yield was about 98% by weight, and the X-ray diffraction pattern was broad as shown in Figure 4, indicating boron nitride with a turbostratic structure.

Effects of the Invention The method of the present invention eliminates the scattering and foaming of raw materials due to rapid gas generation during the heating process as in the conventional method.

[Brief explanation of drawings]

Figure 1 shows that after changing the mixing ratio of B2O3 and melamine and reacting by adding about 1 Or of water per 1f of melamine, the mixture was heated to 80°C.
The X-ray diffraction pattern of the powder obtained by drying with
．． A mixture of 3 moles of melamine and 1 mole of melamine was added to water and reacted, and the mixture was dried at 80°C. FIG. 4 is an X-ray diffraction diagram of the boron nitride obtained in Example 2.

Claims (1)

[Claims] 1) A mixture of boron oxide or boric acid and melamine at a B/N atomic ratio of 1/3 to 2/1 is mixed with water and reacted, and then dried. A method for producing boron nitride, which comprises calcining at 300 to 1000°C. 2) A mixture of boron oxide or boric acid and melamine at a B/N atomic ratio of 1/3 to 2/1 is mixed with water and reacted, and then dried or further calcined. A method for producing boron nitride, which comprises heating at 700 to 2,300°C in a non-oxidizing gas atmosphere.