CN101255058B - Superplastic nano Si3N4 ceramic material and preparation method thereof - Google Patents

Abstract

The invention discloses a superplastic nano-Si3N4-based ceramic material. The Superplastic nano-Si3N4-based ceramic material is produced by mixing amorphous or crystalline nanometer silicon nitride powder, nanometer aluminum nitride powder, nanometer silicon carbide powder and sintering additive powders of nanometer aluminum oxide and nanometer yttrium oxide. The preparation method includes: adopting hot-pressing or spark plasma sintering; the sintering process being the same as the general silicon carbide sintering which needs filling nitrogen for protection after vacuum dumping. The sintering process parameter are as follows: (a) hot pressing: sintering temperature: 1500-1800 DEG C; sintering pressure: higher than 15MPa; holding time: 20min-120min; (b) spark plasma sintering: sintering temperature: 900-1300 DEG C; sintering pressure: higher than 10MPa; holding time: 5s-10min. The Superplastic nano-Si3N4-based ceramic material has a grain diameter between 50nm-200nm and can be shapedby hot press molding or superplastic forming, solving the problem that ceramic parts of complex shape are difficult in forming.

Description

A kind of superplastic nano Si 3N 4Base ceramic material and preparation method thereof

Technical field

The present invention relates to a kind of process of preparing of superplastic nano pottery, particularly relate to a kind of superplastic nano Si ₃N ₄Base ceramic material and preparation method thereof.

Background technology

Japan Nagoya Industrial Technology Research Institute in 1986 have reported the stretching superplasticity of polycrystalline ceramics, and they have found 3Y-TZP (3mol%Y ₂O ₃Stablize ZrO ₂Polycrystal) can produce＞120% Uniform Tension deformation.This piece report has caused the interior broad research about ceramic superplasticity of world wide.Except the Y-TZP material, Al ₂O ₃, Al ₂O ₃-ZrO ₂Composite, mullite, Si ₃N ₄, Si ₃N ₄The ceramic materials such as-SiC composite also are found to have superplasticity to a certain degree.

Silicon-nitride-based ceramic is very rapidly high-temperature structural material of development owing to have the excellent mechanicals behavior under high temperature such as elevated temperature strength height, wearability and corrosion resistance are good.Yet the covalent bond of silicon nitride ceramics and the high temperature of nitrogen hang down diffusion coefficient, cause Si ₃N ₄Pottery manufacturing cost height, and intrinsic fragility is unfavorable for Complex Parts processing and manufacturing.Studies show that of past, although the covalent bond pottery can show certain high temperature compressed ductility, stretching ductility is very limited, such as Si ₃N ₄The stretcher strain amount only have 3%.Up to nineteen ninety, Wakai etc. are at 1600 ℃, and strain rate is 4 * 10 ^-5s ^-1Condition under, to Si ₃N ₄/ SiC matrix material carries out tension test, and its elongation reaches 150%, has confirmed that the covalent linkage pottery also has the superplastic deformation ability.Subsequently, people are to Si ₃N ₄The superplasticity of/SiC composite and Sailon pottery has been carried out careful deep research, and the result shows that thin brilliant silicon nitride ceramics at high temperature also can show superelastic characteristics.1997, the people such as Mitomo adopted the method for reaction in-situ sintering, the β-Si take particle diameter as 200nm ₃N ₄Powder is parent material, with cordierite (2MgO2Al ₂O ₃5SiO ₂) be sintering aid, prepared Si ₃N ₄-Si ₂N ₂The O complex phase ceramic, 2000, they studied the superplasticity of pottery again, and the pottery of sintering has preferably superplasticity property.1999, the people such as Wakai also adopted special sintering process, had prepared the β-Si of pure thin crystalline substance ₃N ₄, by its superplasticity is studied discovery, having good superplasticity property, the superplasticity percentage elongation reaches 300%.2003, the Chinese of Stockholm Univ Sweden adopted discharge plasma sintering technique to prepare average crystal grain diameter at the Sialon of 200～400nm pottery, and had studied at 1600 ℃ the Sialon ceramic part has been carried out extrusion molding research.

At present, Si ₃N ₄The weak point of the preparation technology of base ceramic material and superplasticity process technology has two: one, and crystallite dimension is grown up and is difficult to control in the sintering process, the average grain size of prepared material is bigger, generally between the hundreds of nanometer is to several microns, affected the superplasticity property of material; The 2nd, Si ₃N ₄The superplasticity processing temperature height of ceramic material, rate of deformation is low, and processing conditions is relatively harsher.

The superplasticity of silicon nitride ceramics is relevant with crystal grain diameter, and crystallite dimension is more little, and its superplasticity property is more good.

Summary of the invention

In order to solve Si ₃N ₄The base ceramic material average grain size is big, superplasticity processing temperature height, rate of deformation is low and the deficiency such as processing conditions harshness, the invention provides a kind of superplastic nano Si ₃N ₄The material average crystal grain diameter that base ceramic material and preparation method thereof, this invention are prepared can between 50nm-200nm, can be realized the high strain rate superplasticity distortion of material and the Quick-forming of ceramic part.

The technical solution adopted for the present invention to solve the technical problems is:

(1) powder mixes: with amorphous or crystalline state nanometer Si ₃N ₄Powder, nanometer AlN powder, nano SiC powder and nanometer Al ₂O ₃, Y ₂O ₃The sintering aid powder mixes; Each powder average crystal grain diameter is 10～100nm, and shared mass percent is:

Nanometer Si ₃N ₄: 50%～80%;

Nanometer AlN:5%～15%;

Nano SiC: 5%～15%;

Nanometer Al ₂O ₃: 5～10%;

Nanometer Y ₂O ₃: 5～10%;

(2) sintering process:

Above-mentioned mixed powder is adopted hot pressed sintering or discharge plasma sintering; Sintering process is the same with common silicon nitride sintering, is filled with nitrogen protection after need vacuumizing.

Sintering process parameter is:

(2.1) hot pressed sintering: sintering temperature is 1500～1800 ℃, sintering pressure＞15MPa, soaking time 20min～120min;

(2.2) discharge plasma sintering: sintering temperature is 900～1300 ℃, sintering pressure＞10MPa, soaking time 5s～10min.

The invention has the beneficial effects as follows the superplastic nano Si for preparing ₃N ₄Base ceramic material comprehensive mechanical property excellence has excellent superplasticity property simultaneously, and deformation strain speed can reach 1～10 ^-3/ s can adopt superplastic forming process forming ceramic part, has solved the problem that the complicated shape ceramic part is difficult to be shaped.

Embodiment

Embodiment

(1) with nanometer Si ₃N ₄(amorphous or crystalline state) powder, nanometer AlN powder, nano SiC powder and nanometer Al ₂O ₃, Y ₂O ₃The sintering aid powder is 6: 1.5: 1.5 in mass ratio: mix at 0.5: 0.5, each powder average crystal grain diameter is 10～100nm;

(2) precompressed of mixed powder being packed in the graphite jig is put into hot-pressed sintering furnace with mould once then;

(3) be loaded into 30MPa, vacuumize, the inflated with nitrogen protection;

(4) be warmed up to 1600 ℃, soaking time is 60min;

(5) with the stove cooling, take out sample;

(6) sample is detected, sample average grain size 80nm is 1650 ℃ of tensile deformation strain rates 10 ^-2/ s.

Superplastic nano Si ₃N ₄Base ceramic material can adopt hot-forming or superplastic forming, and for example: the direct heat of various parts is molded; The pull and stretch of various sheet materials, bending forming; The bulging of tubing; The extruding of various block materials parts (turbine, blade etc.), forging and molding etc.

Claims (2)

1. superplastic nano Si ₃N ₄Base ceramic material is characterized in that: described superplastic nano Si ₃N ₄Base ceramic material is for amorphous or crystalline state Nano powder of silicon nitride, nano aluminum nitride powder, nano silicon carbide powder, nano aluminium oxide and nano yttrium oxide sintering aid powder mix; The average crystal grain diameter of each powder is 10～100nm, and shared mass percent is:

Nanometer Si ₃N ₄: 50%～80%;

Nanometer AlN:5%～15%;

Nano SiC: 5%～15%;

Nanometer Al ₂O ₃: 5～10%;

Nanometer Y ₂O ₃: 5～10%.

2. one kind prepares superplastic nano Si as claimed in claim 1 ₃N ₄The method of base ceramic material is characterized in that: adopt hot pressed sintering or discharge plasma sintering; Sintering process is the same with common silicon nitride sintering, is filled with nitrogen protection after need vacuumizing;

Sintering process parameter is:

(2.1) hot pressed sintering: sintering temperature is 1500～1800 ℃, sintering pressure＞15MPa, soaking time 20min～120min;

(2.2) discharge plasma sintering: sintering temperature is 900～1300 ℃, sintering pressure＞10MPa, soaking time 5s～10min.