RU1838233C - Charge for producing silicium nitride in nitrogen-containing gas - Google Patents

Abstract

Using; obtaining structural ceramics and cutting tools. SUMMARY OF THE INVENTION: 60-82 wt.% Of silicon powder and May 18-40.% Of zinc or zinc chloride are mixed for 15-30 minutes and nitrided in a closed volume at 1200-1400 ° C for 2-4 hours. Yield / -Sl2N j 100%, of which with a spherical particle shape - 98.7-98.9%. 1 tab.

Description

The invention relates to the field of production of refractory inorganic nitrides, and in particular, production of silicon nitride of ft modification with a particle shape close to spherical, suitable for sintering in the manufacture of structural ceramics and cutting tools.

The purpose of the invention is to increase the yield of SiaN / modification with a spherical particle shape.

The goal is achieved in that the mixture as an inorganic additive contains 60-82 wt.% Silicon and 18-40 wt.% Zinc or zinc chloride having a low boiling point.

The mixture is prepared as follows.

They take elemental silicon powder KRO GOST 2106-69 with a particle size of less than 10 microns and a powder of metallic zinc or zinc chloride having low boiling points, in the amount of 18-40% by weight

flint and mix for 15-30 minutes.

In the case when zinc or zinc chloride is added in an amount of 18-25%, the synthesis process / J-Si3N4 is preferable to carry out by heating the mixture in a closed volume at a temperature of 1200-1400 ° C and a pressure of nitrogen-containing gas (N2: NHa) at 0 -10 atm for 2-4 hours

When 25-40% Zn or ZnCIa is introduced into the mixture, it is preferable to conduct the heat treatment in the combustion mode. In the first case, the synthesis is as follows. The prepared mixture is placed in a reaction vessel, filled with nitrogen or ammonia to a pressure of 4-10 atm and placed in a furnace, heated to a synthesis temperature of 1200-1400 ° C and held at this temperature for 4 hours. After nitriding, the reaction mixture is cooled, the pressure is the reaction vessel is dropped to

with

with

00

go

iOJ CJ

ICO

atmospheric. The reaction product is analyzed and subjected to x-ray phase analysis.

In the second case, the prepared charge is loaded onto a graphite substrate and placed in a SHS reactor, filled with nitrogen or ammonia to a pressure of 100 atm. The mixture is ignited locally by a spiral. Due to the large exotherm, the reaction front propagates spontaneously throughout the load. After the end of the process, the reaction mass is cooled, the pressure is released to atmospheric. The product is subjected to x-ray and chemical analyzes.

The addition of zinc or zinc chloride provides: loosening of the load, which facilitates the access of nitrogen to the volume of the load and the complete nitriding of silicon; increasing the yield of the / phase and the formation of 51zM4 particles into a spherical shape (Ksfvr. 0.95-0.98),

The sphericity of the particles is determined by the ratio of the length to their width K l / d when viewing the powder under a microscope in an amount of at least 1000.

Example 1. Take the silicon powder, mix it with zinc in an amount of 18% by weight of silicon for 30 minutes 20 g of the mixture are loaded into the reaction vessel, filled with nitrogen until 4 atm is added, placed in a tube furnace and high temperature nitriding is carried out at temperature of 1200 ° C for 4 hours, and then cooled. After cooling the reaction mass, the nitrogen pressure is reduced to atmospheric. The product is washed with hydrochloric acid to remove zinc, dried at 100 ° C and analyzed by x-ray, chemical and microscopic analyzes. .... Silicon nitride powder is a phase-pure silicon nitride.

Chemical analysis: Siceoe 0.1%, 0 0.8%, N - 38.7%, Fe - 0.01, Zn - 0.055 wt.%.

The yield of spherical particles is 98.9%. The sphericity coefficient KSf is -0.98.

Example 2, Take a silicon powder, mixed with zinc chloride in an amount of 40 wt.% By weight of silicon for 30

min, loaded onto a graphite substrate and placed in a reactor. Fill the reactor with nitrogen to a pressure of 100 atm and ignite the mixture using a tungsten helix; the reaction proceeds spontaneously. After the end of the process, the reaction mass is cooled and analyzed chemically, radiographically and microscopically,

The powder is phase pure silicon nitride / 3 modification.

Chemical analysis: - 0.08%,, 08%, N - 38.8%. Fe - 0.01%, Zn - 0.04 wt.%.

The yield of spherical particles is 98.9%. The coefficient of sphericity, 97.

The table shows the data of chemical and x-ray phase analysis of silicon nitride powder obtained from the mixture according to the invention.

Thus, as can be seen from the examples cited, the invention makes it possible to obtain SI3N4 in / modification with the yield of spherical particles equal to 98.6-98.7% in one step.

The proposed method makes it possible to obtain 51g # / 3 modifications in a single step.

From a powder of silicon nitride / 3-modification obtained according to any of the examples by hot pressing, products were prepared to obtain physical and mechanical properties.

Sintering mode 1850 ° C. The loading time is 20 min, Rdav 30 MPa. The product has a density of d 3.6 g / cm3, otg 90 kg / mm2.

Therefore, the mixture according to the invention is suitable for producing high-density products with high physical and mechanical characteristics,

Claims (1)

The claims A mixture for producing silicon nitride in a nitrogen-containing gas, including silicon powder and an inorganic additive, characterized in that, in order to increase the yield of silicon nitride / 5-modification with a spherical particle shape, it contains zinc or zinc chloride as an inorganic additive with the following content of components, wt.%: Silicon 60-82 Zinc or Zinc Chloride 18-40