CN102659414A - Easy-sintering AlN polytype-Sialon complex phase material and preparation method thereof - Google Patents

Abstract

The invention relates to an easily sinterable AlN polytype-Sialon composite material and a preparation method thereof, belonging to the technical field of ceramic materials and sintering. The present invention uses rare earth oxides Ln ₂ O ₃ , Si ₃ N ₄ , AlN and Al ₂ O ₃ etc. Under the condition of 12 hours, a kind of AlN polytype, β-Sialon is Si _6-z Al _z O _z N _8-z , and U phase Sialon is Ln ₃ Si _3-x Al _3+x O ₁₂ AlN polytype-Sialon composite material with _+x N _2-x as the main phase. The mass ratio of the rare earth oxide Ln ₂ O ₃ to the total ingredients is 4% to 15%, wherein the rare earth element Ln can be La, Ce, Pr, Nd, Sm and Gd, and the mass ratio of Si ₃ N ₄ to the total ingredients The mass ratio of AlN to the total ingredients is 25% to 55%, and the mass ratio of Al ₂ O ₃ to the total ingredients is 10% to 45%. The raw material formula involved has excellent sintering performance, and the prepared Sialon polytype composite material has high density, good thermal expansion/shrinkage performance and excellent mechanical properties, and can be used for high temperature resistant materials, ceramic parts welding and repairing , ceramic components with complex shapes and functionally graded materials.

Description

An easy-sintering AlN polytype-Sialon composite material and its preparation method

technical field

The invention relates to an easily sinterable AlN polytype-Sialon composite material and a preparation method thereof, belonging to the technical field of ceramic materials and sintering.

Background technique

Silicon nitride (Si ₃ N ₄ ) is an engineering material with excellent performance, which has been widely used in various industrial fields. Due to its high nitrogen content, pure silicon nitride ceramics are difficult to sinter, and sintering aids must be added to obtain a denser sintered body. In the early 1970s, people discovered a solid solution containing Si-Al-ON, that is, Sialon material, when studying the influence of sintering aids. As a new type of engineering material with excellent performance, Sialon has broad application prospects in the fields of abrasive tools and mold materials, metal cutting tools, thermal equipment, iron and steel smelting and chemical machinery. Sialon materials include a variety of phases with different crystal structures, such as α-Sialon, β-Sialon, O'-Sialon, X-Sialon, AlN polytype, JEM phase Sialon, S phase Sialon, M phase Sialon, U phase Sialon etc. (see Non-Patent Document 1). Due to their different structures, there are also differences in their mechanical properties, physical properties and sintering properties.

In the Si-Al-ON system, there are several Sialons whose components are located between β-Sialon and AlN, which have a tetrahedral layered AlN wurtzite structure, called AlN polytypes (or Sialon polytypes) model). The composition of the AlN polytype can be represented by M _m X _m+1 , wherein M represents the metal atom Si/Al, X represents the non-metal atom O/N, and m is an integer (4≤m≤13). Several common AlN polytypes can be expressed as 8H, 15R, 12H, 21R, 27R and 2H ^δ with Ramsdell symbols. Since the AlN polytype has a fibrous or plate-like morphology, and most AlN polytypes can coexist with α-Sialon and β-Sialon phases, it is generally introduced into the matrix of the above materials to strengthen or toughen effect. Different from other Sialon phase properties, although the room temperature flexural strength of the AlN polytype is low (313-366 MPa), it has the special property that the flexural strength increases significantly with the increase of temperature, and can be used as a high-temperature structure. parts etc. Especially in the range of 1000-1300° C., their high-temperature flexural strength exceeds 500 MPa (see Non-Patent Document 2).

Although the AlN polytype has superior high-temperature mechanical properties, its composition is very close to that of AlN, and its high nitrogen content makes it very difficult to sinter. Previous studies all used hot-pressing sintering process at higher temperature (1750-2100°C) and the addition of sintering aids to densify AlN polytypes. Complex process conditions and ultra-high sintering temperatures make it difficult for AlN polytype materials to achieve industrial applications.

The invention patent obtains an AlN polytype-Sialon composite material with easy sintering and its preparation method through raw material formula and process design. The invention has low requirements on sintering equipment, sintering process, etc., can greatly reduce the sintering temperature, and easily realizes the industrial production of AlN polytype body-based Sialon composite phase material.

Non-Patent Document 1: S.F.Huang, et al., Dalton Tran., 40(2011) 1261-1266.

Non-Patent Document 2: H.X.Li, et al., J. Eur. Ceram. Soc., 15(1995) 697-701.

Contents of the invention

The purpose of the present invention is to prepare an easily sinterable AlN polytype-Sialon composite material, so that it meets the requirements of simple sintering process equipment conditions, and can greatly reduce the sintering temperature, and it is easy to realize AlN polytype-based Sialon Industrial production of composite materials.

A method for preparing an easily sinterable AlN polytype-Sialon composite material proposed by the present invention is characterized in that: rare earth oxides Ln ₂ O ₃ , Si ₃ N ₄ , AlN and Al ₂ O ₃ are used as raw materials, Under the conditions of oxidizing atmosphere, atmosphere pressure 1Pa～10MPa, temperature 1400℃～2000℃, reaction time 0.1 hour～12 hours, a kind of AlN polytype, β-Sialon, namely Si _6-z Al _z O _z was prepared. N _8-z , and U-phase Sialon, namely Ln ₃ Si _3-x Al _3+x O _12+x N _2-x are the main phases of Sialon composite material.

In the preparation method of the above-mentioned Ln-Sialon single crystal, the mass ratio of the rare earth oxide Ln ₂ O ₃ to the total ingredients is 4% to 15%, the mass ratio of Si3N4 to the total ingredients is 27% to 45%, and AlN accounts for the total The mass ratio of the ingredients is 25%-55%, and the mass ratio of Al ₂ O ₃ to the total ingredients is 10%-45%.

1. The preparation method according to claim 1, characterized in that: in the rare earth oxide Ln ₂ O ₃ , the rare earth element Ln is selected from La, Ce, Pr, Nd, Sm and Gd.

2. The preparation method according to any one of claims 1-3, characterized in that the non-oxidizing atmosphere can be a nitrogen atmosphere, an inert gas atmosphere, or a mixed gas atmosphere of an inert gas and nitrogen.

3. The preparation method according to claim 4, characterized in that the atmospheric pressure is 1Pa-10MPa.

4. An easily sinterable AlN polytype-Sialon composite material, characterized in that: AlN polytype, β-Sialon is Si _6-z Al _z O _z N _8-z , and U-phase Sialon is Ln ₃ Si _3-x Al _3+x O _12+x N _2-x is the main phase.

5. The AlN polytype-Sialon composite material according to claim 4, characterized in that: AlN polytypes can be 8H, 15R, 12H, 21R, 27R and 2H6, and their chemical compositions are SiAl ₃ O ₂ N ₃ , SiAl ₄ O ₂ N ₄ , SiAl ₅ O ₂ N ₅ , SiAl ₆ O ₂ N ₆ , SiAl ₈ O ₂ N ₈ , and SiAl ₁₀ O ₂ N ₁₀ .

6. The AlN polytype-Sialon composite material according to claim 4, characterized in that: the AlN polytype has a twin structure.

7. The AlN polytype-Sialon composite material according to claim 4, characterized in that: U-phase Sialon is filled around AlN polytype phase and β-Sialon phase grains.

Description of drawings

Fig. 1 is to represent the scanning electron micrograph of Nd-doped AlN polytype-Sialon composite phase material (embodiment 1) of the present invention;

Fig. 2 is a scanning electron micrograph showing the Pr-doped AlN polytype-Sialon composite material (Example 2) of the present invention.

Detailed ways

In the present invention, the raw materials are first batched according to the ratio, and then the raw materials are mixed uniformly by mechanical ball milling, taken out and dried in an oven, and then the dried powder is machine-pressed and placed in a graphite crucible and put it into a high-temperature atmosphere furnace, and react according to the temperature, holding time and reaction atmosphere conditions; after completing the predetermined reaction time, cool down to room temperature, disconnect the power supply, and take out the sample.

The present invention will be described in more detail below through specific examples, but these examples are only used to help understand the present invention easily, and the present invention is not limited to these examples.

Example 1

Select Nd ₂ O ₃ , Si ₃ N ₄ , AlN and Al ₂ O ₃ as raw materials, the addition of Nd ₂ O ₃ accounts for 9% of the mass percentage of the total ingredients, and the addition of Si ₃ N ₄ accounts for the mass percentage of the total ingredients is 35%, the amount of AlN added accounts for 37% of the total mass percentage of the total ingredients and the total amount of Al ₂ O ₃ added accounts for 19% of the total mass percent of the ingredients, the molding pressure is 200MPa, in a nitrogen atmosphere, the atmospheric pressure is 0.9 Under the conditions of MPa, temperature ¹⁶⁵⁰ ℃, and holding for 3 hours, the Nd-doped AlN polytype-Sialon composite material was prepared. The bending strength is 335MPa.

Example 2

Select Pr ₂ O ₃ , Si ₃ N ₄ , AlN and Al ₂ O ₃ as raw materials, the addition of Pr ₂ O ₃ accounts for 11% of the mass percentage of the total ingredients, and the addition of Si ₃ N ₄ accounts for the mass percentage of the total ingredients is 34%, the addition of AlN accounts for 38% of the mass percentage of the total batching, the total addition of _Al2O3 accounts for 17% of the mass percentage of the total _batching , and the molding pressure is 30MPa. In an argon atmosphere, the atmospheric pressure is Under the conditions of 0.12MPa, temperature of 1600℃, and heat preservation for 6 hours, a Pr-doped AlN polytype-Sialon composite material was prepared, with a bulk density of 3.35g·cm ^-3 and an apparent porosity of 0.8%. The point bending strength is 306MPa.

Claims (8)

1. A method for preparing an easily sinterable AlN polytype-Sialon composite material, characterized in that: using rare earth oxides Ln ₂ O ₃ , Si ₃ N ₄ , AlN and Al ₂ O ₃ as raw materials, in non-oxidizing Under the conditions of neutral atmosphere, atmospheric pressure 1Pa～10MPa, temperature 1400℃～2000℃, and reaction time 0.1 hour～12 hours, a kind of AlN polytype, β-Sialon is Si _6-z Al _z O _z N _8-z , and U-phase Sialon, that is, Ln ₃ Si _3-x Al _3+x O _12+x N _2-x as the main phase of the Sialon composite material. 2. The preparation method according to claim 1, characterized in that: the mass ratio of the rare earth oxide _Ln2O3 to the total ingredients is 4% to 15%, and _the mass ratio of Si3N4 to the total ingredients is 27% to 45%. %, the mass ratio of AlN to the total ingredients is 25% to 55%, and the mass ratio of Al ₂ O ₃ to the total ingredients is 10% to 45%. 3. The preparation method according to claim 1, characterized in that: in the rare earth oxide Ln ₂ O ₃ , the rare earth element Ln is selected from La, Ce, Pr, Nd, Sm and Gd. 4. The preparation method according to claim 1, 2 or 3, characterized in that: the non-oxidizing atmosphere is nitrogen atmosphere or inert gas atmosphere or a mixed gas atmosphere of inert gas and nitrogen; the atmosphere pressure is 1Pa～10MPa. 5. An easily sinterable AlN polytype-Sialon composite material, characterized in that: AlN polytype, β-Sialon is Si _6-z Al _z O _z N _8-z , and U-phase Sialon is Ln ₃ Si _3-x Al _3+x O _12+x N _2-x is the main phase. 6. The AlN polytype-Sialon composite material according to claim 6, characterized in that: AlN polytypes are 8H, 15R, 12H, 21R, 27R and 2H ⁶ , and their chemical compositions are SiAl ₃ O ₂ N ₃ , SiAl ₄ O ₂ N ₄ , SiAl ₅ O ₂ N ₅ , SiAl ₆ O ₂ N ₆ , SiAl ₈ O ₂ N ₈ , and SiAl ₁₀ O ₂ N ₁₀ . 7. The AlN polytype-Sialon composite material according to claim 6, characterized in that: the AlN polytype has a twin structure. 8 . The AlN polytype-Sialon composite material according to claim 6 , wherein the U-phase Sialon is filled around the grains of the AlN polytype phase and the β-Sialon phase.

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