KR20020004129A - Preparation Method of High Toughened Silicon Carbide with Sialon Grain Boundary - Google Patents

Abstract

PURPOSE: Provided is a preparation method of toughened silicon carbide forming sialon in the grain boundary phase by hot pressing sialon-added raw materials and thermal treating. Therefore, the resultant silicon carbide has improved creep-resistance and high temperature strength compared with conventional silicon carbide. CONSTITUTION: The preparation method is as follows: preparing granulated silicon carbide powder by adding 2mol% of sialon composition powder(9wt.% of y2O3 + 16wt.% of AlN + 75wt.% of Si3N4) to SiC powder(alpha-phase + beta-phase) with 0.45 micrometer of size, and mixing for 5hrs.; hot-pressing at 1850deg.C for 30min. under 50MPa of pressure; thermal treating at 1950deg.C for 5hrs.

Description

Preparation Method of High Toughened Silicon Carbide with Sialon Grain Boundary

▲ Field of invention

-This technology is a tough silicon carbide sintered body in which the sintering aid in the manufacture of bulk silicon carbide is mixed with sintering composition (silicon nitride, aluminum nitride, yttria) in the starting powder, pressurized and sintered, and then transferred the grain boundary phase to sialon. .

▲ Prior art in the field

① Conventional example

A case study of sintering by adding boron, aluminum, and carbon to silicon carbide has been reported.

② Other conventional example

Case studies have been reported to improve the sintered density and toughness by adding oxides such as yttria and alumina to silicon carbide.

▲ Describe the problem of existing technology

① Silicon carbide sintered by adding boron, carbon, aluminum, etc. to silicon carbide has a high sintering temperature, resulting in a large particle size, which causes inferior toughness.

(2) Silicon carbide sintered by adding oxides such as yttria and alumina to silicon carbide forms an oxide glass phase at grain boundaries, resulting in poor toughness and strength.

① This technique is for producing silicon carbide with increased toughness by forming sialon phase with high strength at grain boundary of silicon carbide.

② It is a technology to provide a sintered body with excellent high temperature strength by forming sialon phase at the grain boundary, which has excellent creep resistance at the grain boundary, compared to conventional silicon carbide.

1 is an x-ray diffraction diagram of a sialon grained silicon carbide sintered body having 6H and 4H phases as the main phase, respectively, (a) using α-phase silicon carbide as the starting material, and (b) using β-phase silicon carbide as the starting material. If it is.

Figure 2 is an electron micrograph and EDS analysis showing the sialon grain boundary image

3 is an electron micrograph of a sialon grain boundary reinforced silicon carbide sintered body using α-SiC and β-SiC as starting materials.

Figure 4 shows the microstructural factors and fracture toughness of sialon grain boundary silicon carbide sintered body

Fig. 5 is a photograph of silicon carbide sintered body in which crack deflection, crack refraction, and grain bridging occur during crack propagation in tough silicon carbide;

① Composition

-Sialon composition; 9 wt% Y ₂ O ₃ + 16 wt% AIN + 75 wt% Si ₃ N ₄

-Silicon carbide composition: 0.45 ㎛ α phase + 2 mol% Sialon composition

Β phase + 2 mol% Sialon composition of 0.45 μm

② Manufacturing Method

-2 mol% of sialon composition powder is added to α- and β-phase SiC powders, and then mixed for 5 hours to prepare granule powder.

Sintering for 30 minutes in an argon atmosphere at a temperature of 1850 ° C. at a pressure of 50 MPa using a Hot Press.

-Heated at 1950 ° C. for 5 hours to prepare final sintered body.

③ Test result

-A sintered density of more than 99% and a sialon grain-based silicon carbide sintered body having 6H and 4H phases as main phases, respectively (FIGS. 1 and 2)

-When α-SiC is used as a starting material, a dense sintered body having isotropic particles is produced.

-When β-SiC is used as a starting material, a dense sintered body having rod-shaped and plate-shaped particles is produced (Fig. 3)

-A tough silicon carbide sintered body having a short-to-short ratio of 3.1, 4.2 and fracture toughness of 5,0, 6.0 was produced (Fig. 4).

-A tough silicon carbide sintered body is produced in which crack deflection, crack refraction, and grain bridging occur (FIG. 5).

-Improves fracture toughness and strength of silicon carbide.

-Improves creep resistance and high temperature strength of silicon carbide.

-Applicable to silicon carbide grinding balls, nozzles and bearings.

-Applicable to heat exchanger, reaction tube, heat treatment jig, etc.

Claims (1)

In producing silicon carbide sintered body with sialon composition as grain boundary Method of adding sialon composition (silicon nitride, aluminum nitride, yttria) as sintering aid Method of obtaining high density sintered body by forming sialon phase at interface during sintering and heat treatment Method for producing highly tough silicon carbide by sialon grain boundary and high density formation Method of controlling microstructure of silicon carbide by controlling sintering condition and heat treatment condition