CN102807389B - Preparation method for Si3N4-Si2N2O porous complex phase ceramic - Google Patents

Preparation method for Si3N4-Si2N2O porous complex phase ceramic Download PDF

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CN102807389B
CN102807389B CN 201210315790 CN201210315790A CN102807389B CN 102807389 B CN102807389 B CN 102807389B CN 201210315790 CN201210315790 CN 201210315790 CN 201210315790 A CN201210315790 A CN 201210315790A CN 102807389 B CN102807389 B CN 102807389B
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CN102807389A (en
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贾德昌
王胜金
杨治华
段小明
周玉
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Harbin Institute of Technology
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Abstract

The invention provides a preparation method for Si3N4-Si2N2O porous complex phase ceramic and relates to a preparation method for porous complex phase ceramic. The invention solves the technical problems that the conventional preparation method for the Si3N4-Si2N2O porous complex phase ceramic is complex and SiO2 is remained in the final product easily. The preparation method comprises the following steps: 1, preparing raw materials; 2, preparing block materials; 3, preparing green bodies; 4, preparing porous structure green bodies; and 5, preparing the Si3N4-Si2N2O porous complex phase ceramic. The Si3N4-Si2N2O porous complex phase ceramic prepared by the method has bending strength of 132 to 267 MPa, breaking tenacity of 1.8 to 4.3 MPa.m1/2, actual density of 1.8 to 2.7 g/cm<3> and dielectric constant of 4.0 to 6.7, and can serve as a thermal protection material and a wave-transparent material applied in the fields of aerospace, mechanical industry and the like.

Description

A kind of Si 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic
Technical field
The present invention relates to the preparation method of porous complex phase ceramic.
Background technology
Porous ceramics is a kind of novel texture and ceramic material, have that volume density is little, specific surface area reaches greatly unique physical surface properties, to the selective perviousness of liquids and gases medium, there is energy absorption or damping characteristic, and there is distinctive high temperature resistant, corrosion-resistant, the high chemical stability of pottery and dimensional stability, it is used widely in filtration, purification separation, chemical industry catalytic carrier, the many-sides such as sound absorption damping, high-quality thermal insulating material and sensing material.
Si 3n 4pottery has a series of good character, as high strength, high tenacity, anticorrosive, wear-resisting, thermal shock resistance is good, Properties of High Temperature Creep is good etc.With respect to Si 3n 4pottery, Si 2n 2the O pottery possesses more excellent high temperature oxidation resistance characteristics.Consider Si from thermodynamics 2n 2o is unique stable compound in the Si-N-O ternary system, can with Si 3n 4coexist.Si 3n 4-Si 2n 2the O complex phase ceramic can be in conjunction with Si on performance 3n 4mechanical property and Si that pottery is excellent 2n 2the excellent antioxidant property of O pottery.Therefore, Si 3n 4-Si 2n 2the O complex phase ceramic is subject to extensive concern as the structure unit be applied under high temperature, severe working conditions.
Si 3n 4-Si 2n 2traditional preparation method of O porous complex phase ceramic is: the Chinese invention patent that for example publication number is CN102229498 and CN101531538 is all with Si 3n 4and SiO 2for raw material, by adding a small amount of M xo y(M=Al, Y, Li etc.), M under hot conditions xo ywith part SiO 2the reaction solution phase, Si 3n 4in liquid phase, dissolve and with SiO wherein 2reaction generates Si 2n 2o, the hole in material is introduced by the preparation method of common porous ceramics.Q.F.Tong, et al. (J.Eur.Ceram.Soc., 27 (16), 2007,4767-72), S.Q.Li, et al. (Ceram.Int., 35 (5), 2009,1851-4), R.K.Paul, et al. (J.Mater.Sci., 42 (12), 2007,4701-6) etc. the people has also done similar report in the literature.Traditional with Si 3n 4for raw material prepares Si 3n 4-Si 2n 2there is following problem in the method for O porous complex phase ceramic: need the extra SiO of interpolation 2, preparation method's complexity, and easy residual Si O in final product 2.
Summary of the invention
The present invention will solve existing preparation Si 3n 4-Si 2n 2preparation method's complexity that the method for O porous complex phase ceramic exists, and easy residual Si O in final product 2technical problem, thereby a kind of Si is provided 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic.
A kind of Si of the present invention 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic carries out according to the following steps:
One, take Si 3n 4, Y 2o 3, Al 2o 3(NH 4) 2hPO 4, Si wherein 3n 4: Y 2o 3: Al 2o 3mass ratio be (92～95): 4: 2, (NH 4) 2hPO 4account for Si 3n 4, Y 2o 3and Al 2o 310～60vol.% of cumulative volume, to Si 3n 4, Y 2o 3and Al 2o 3in add (NH 4) 2hPO 4, adopting dehydrated alcohol is that dispersion medium carries out ball mill mixing 5～24h, obtains slurry;
Two, by slurry, in temperature, be to dry under 40～80 ℃ of fluidizing air conditions, the mixed powder after drying sieves, and under the pressure of 20～30MPa, pressurize 1～2min carries out premolding, obtains block materials;
Three, take out block materials and put into rubber mold, bleed and encapsulated, under the pressure of 100～300MPa, pressurize 1～2min cold isostatic compaction, obtain green compact;
Four, by the green compact after moulding in air furnace in 500～800 ℃ the calcining 1～2h, obtain the vesicular structure green compact;
Five, the vesicular structure green compact after finally calcining are at the N of 0.1～0.2MPa 2carry out sintering 1～3h in 1500～1800 ℃ under protective atmosphere in hot-pressed sintering furnace, obtain Si 3n 4-Si 2n 2o porous complex phase ceramic.
Si prepared by the present invention 3n 4-Si 2n 2o porous complex phase ceramic has following advantage:
(1) utilize (NH 4) 2hPO 4decomposition, original position forms the hole in green compact, after sintering, is retained, and forms Si 3n 4-Si 2n 2pore texture in the O complex phase ceramic, by controlling (NH in raw material 4) 2hPO 4size, shape and add-on, can regulate and control Si 3n 4-Si 2n 2the porosity of O complex phase ceramic and the size and dimension of hole;
(2) Si that prepared by the present invention 3n 4-Si 2n 2the O porous ceramics is by waiting axle shape α-Si 3n 4, long bar-shaped β-Si 3n 4with tabular Si 2n 2o tri-phase composites, mean pore size is 5～8 μ m;
(3) (NH 4) 2hPO 4degradation production be Si in complex phase ceramic 2n 2the generation of O provides O, Si 2n 2the growing amount of O phase is with (NH in raw material 4) 2hPO 4the increase of addition and increasing, thereby can be by controlling (NH in raw material 4) 2hPO 4introduction volume and control Si 3n 4-Si 2n 2si in the O complex phase ceramic 2n 2the content of O phase;
(4) the present invention is without the extra SiO that adds 2, make Si 2n 2the formation proceed step by step of O phase and material mesoporosity, the preparation method is simple, and noresidue SiO in final product 2, be applicable to the actual production of large-scale;
(5) Si that prepared by the present invention 3n 4-Si 2n 2bending strength 132～the 267MPa of O porous complex phase ceramic, fracture toughness property 1.8～4.3MPam 1/2, actual density 1.8～2.7g/cm 3, specific inductivity 4.0～6.7, can be used for thermally protective materials and the electromagnetic wave transparent material in the fields such as aerospace, mechanical industry.
The accompanying drawing explanation
Fig. 1 is different (NH in prepared raw material 4) 2hPO 4si during addition 3n 4-Si 2n 2the XRD figure of O porous complex phase ceramic: Fig. 1 is a) to add (NH in the prepared raw material of test one 4) 2hPO 4the time Si 3n 4porous complex phase ceramic XRD figure, Fig. 1 b) be (NH in the prepared raw material of test two 4) 2hPO 4addition accounts for Si 3n 4, Y 2o 3and Al 2o 3the Si during 10vol.% of cumulative volume 3n 4-Si 2n 2o porous complex phase ceramic XRD figure, Fig. 1 c) be (NH in the prepared raw material of test three 4) 2hPO 4addition accounts for Si 3n 4, Y 2o 3and Al 2o 3prepared Si during the 20vol.% of cumulative volume 3n 4-Si 2n 2o porous complex phase ceramic XRD figure, Fig. 1 d) be (NH in the prepared raw material of test four 4) 2hPO 4addition accounts for Si 3n 4, Y 2o 3and Al 2o 3the Si during 30vol.% of cumulative volume 3n 4-Si 2n 2o porous complex phase ceramic XRD figure, Fig. 1 e) be (NH in the prepared raw material of test five 4) 2hPO 4addition accounts for Si 3n 4, Y 2o 3and Al 2o 3the Si during 40vol.% of cumulative volume 3n 4-Si 2n 2o porous complex phase ceramic XRD figure, wherein,
Figure GDA00003171720400031
represent α-Si 3n 4, zero represents Si 2n 2o,
Figure GDA00003171720400032
represent β-Si 3n 4;
Fig. 2 is the prepared Si of experiment three 3n 4-Si 2n 2the low power SEM figure of O porous complex phase ceramic;
Fig. 3 is the prepared Si of experiment three 3n 4-Si 2n 2the high power SEM figure of O porous complex phase ceramic;
Fig. 4 is the prepared Si of experiment three 3n 4-Si 2n 2the TEM photo of O porous complex phase ceramic.
Embodiment
Embodiment one: a kind of Si in present embodiment 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic carries out according to the following steps:
One, take Si 3n 4, Y 2o 3, Al 2o 3(NH 4) 2hPO 4, Si wherein 3n 4: Y 2o 3: Al 2o 3mass ratio be (92～95): 4: 2, (NH 4) 2hPO 4account for Si 3n 4, Y 2o 3and Al 2o 310～60vol.% of cumulative volume, to Si 3n 4, Y 2o 3and Al 2o 3in add (NH 4) 2hPO 4, adopting dehydrated alcohol is that dispersion medium carries out ball mill mixing 5～24h, obtains slurry;
Two, by slurry, in temperature, be to dry under 40～80 ℃ of fluidizing air conditions, the mixed powder after drying sieves, and under the pressure of 20～30MPa, pressurize 1～2min carries out premolding, obtains block materials;
Three, take out block materials and put into rubber mold, bleed and encapsulated, under the pressure of 100～300MPa, pressurize 1～2min cold isostatic compaction, obtain green compact;
Four, by the green compact after moulding in air furnace in 500～800 ℃ the calcining 1～2h, obtain the vesicular structure green compact;
Five, the vesicular structure green compact after finally calcining are at the N of 0.1～0.2MPa 2carry out sintering 1～3h in 1500～1800 ℃ under protective atmosphere in hot-pressed sintering furnace, obtain Si 3n 4-Si 2n 2o porous complex phase ceramic.
Si prepared by present embodiment 3n 4-Si 2n 2o porous complex phase ceramic has following advantage:
(1) utilize (NH 4) 2hPO 4decomposition, original position forms the hole in green compact, after sintering, is retained, and forms Si 3n 4-Si 2n 2pore texture in the O complex phase ceramic, by controlling (NH in raw material 4) 2hPO 4size, shape and add-on, can regulate and control Si 3n 4-Si 2n 2the porosity of O complex phase ceramic and the size and dimension of hole;
(2) Si that prepared by present embodiment 3n 4-Si 2n 2the O porous ceramics is by waiting axle shape α-Si 3n 4, long bar-shaped β-Si 3n 4with tabular Si 2n 2o tri-phase composites, mean pore size is 5～8 μ m;
(3) (NH 4) 2hPO 4degradation production be Si in complex phase ceramic 2n 2the generation of O provides O, Si 2n 2the growing amount of O phase is with (NH in raw material 4) 2hPO 4the increase of addition and increasing, thereby can be by controlling (NH in raw material 4) 2hPO 4introduction volume and control Si 3n 4-Si 2n 2si in the O complex phase ceramic 2n 2the content of O phase;
(4) present embodiment is without the extra SiO that adds 2, make Si 2n 2the formation proceed step by step of O phase and material mesoporosity, the preparation method is simple, and noresidue SiO in final product 2, be applicable to the actual production of large-scale;
(5) Si that prepared by present embodiment 3n 4-Si 2n 2bending strength 132～the 267MPa of O porous complex phase ceramic, fracture toughness property 1.8～4.3MPam 1/2, actual density 1.8～2.7g/cm 3, specific inductivity 4.0～6.7, can be used for thermally protective materials and the electromagnetic wave transparent material in the fields such as aerospace, mechanical industry.
Embodiment two: present embodiment is different from embodiment one: Si in step 1 3n 4powder is the α type, and purity is 86～98%, and median size is 0.2～0.8 μ m.Other is identical with embodiment one.
Embodiment three: present embodiment is different from one of embodiment one or two: (NH in step 1 4) 2hPO 4particle diameter is 60～120 orders.Other is identical with one of embodiment one or two.
Embodiment four: present embodiment is different from one of embodiment one to three: the dispersion medium adopted during batch mixing in step 1 is dehydrated alcohol, and Ball-milling Time is 24h, ball material mass ratio (1～1.5): 1.Other is identical with one of embodiment one to three.
Embodiment five: present embodiment is different from one of embodiment one to four: the temperature rise rate of calcining in step 4 is lower than 2.5 ℃/min.Other is identical with one of embodiment one to four.
Embodiment six: present embodiment is different from one of embodiment one to five: the temperature rise rate of calcining in step 4 is 2 ℃/min.Other is identical with one of embodiment one to five.
Embodiment seven: present embodiment is different from one of embodiment one to six: in step 5, the temperature rise rate of sintering is 10～30 ℃/min.Other is identical with one of embodiment one to six.
Embodiment eight: present embodiment is different from one of embodiment one to seven: in step 5, the temperature rise rate of sintering is 20 ℃/min.Other is identical with one of embodiment one to seven.
By following verification experimental verification beneficial effect of the present invention:
Test one: this test is tested as a comparison, does not add (NH in raw material 4) 2hPO 4, preparation Si 3n 4the porous complex phase ceramic, the preparation method realizes by the following method:
One, take the Si that 94g purity is 95%, median size is 0.6 μ m 3n 4powder, 4g Y 2o 3powder and 2gAl 2o 3powder, do not add (NH 4) 2hPO 4, adopting dehydrated alcohol is that dispersion medium carries out ball mill mixing 24h, ball material mass ratio 1.5: 1, obtain slurry;
Two, by slurry, in temperature, be to dry under 60 ℃ of fluidizing air conditions, the mixed powder after drying sieves, and under the pressure of 20MPa, pressurize 90s carries out premolding, obtains block materials;
Three, take out block materials and put into rubber mold, bleed and encapsulated, under the pressure of 200MPa, pressurize 1min cold isostatic compaction, obtain green compact;
Four, by the vesicular structure green compact after moulding in air furnace, in 2 ℃/min of temperature rise rate be warming up to 500 ℃ the calcining 1h, obtain the vesicular structure green compact;
Five, the green compact after finally calcining are at the N of 0.1MPa 2in hot-pressed sintering furnace, be warming up to 1700 ℃ in 20 ℃/min of temperature rise rate and carry out sintering 2h under protective atmosphere, obtain Si 3n 4the porous complex phase ceramic.
In this testing sequence four, the real density of resulting vesicular structure green compact is 1.78g/cm 3.
This is tested in a prepared raw material and adds (NH 4) 2hPO 4si 3n 4porous complex phase ceramic XRD figure as Fig. 1 a) as shown in, a) can find out Si from Fig. 1 3n 4the porous complex phase ceramic is by α-Si 3n 4and β-Si 3n 4form, without Si 2n 2the O phase.The sintering linear shrinkage is 12.3%, and real density is 2.67g/cm 3, the ventilate rate is 13.3%, and bending strength is 433.2MPa, and fracture toughness property is 4.29MPam 1/2, the specific inductivity under 20GHz is 6.76.
Test two: a kind of Si of this test 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic realizes by the following method:
One, take the Si that 94g purity is 95%, median size is 0.6 μ m 3n 4powder, 4g Y 2o 3powder and 2gAl 2o 3powder, adding wherein the 10g particle diameter is 100 purpose (NH 4) 2hPO 4, adopting dehydrated alcohol is that dispersion medium carries out ball mill mixing 24h, ball material mass ratio 1.5: 1, obtain slurry;
Two, by slurry, in temperature, be to dry under 60 ℃ of fluidizing air conditions, the mixed powder after drying sieves, and under the pressure of 20MPa, pressurize 90s carries out premolding, obtains block materials;
Three, take out block materials and put into rubber mold, bleed and encapsulated, under the pressure of 200MPa, pressurize 1min cold isostatic compaction, obtain green compact;
Four, by the vesicular structure green compact after moulding in air furnace, in 2 ℃/min of temperature rise rate be warming up to 500 ℃ the calcining 1h, obtain the vesicular structure green compact;
Five, the green compact after finally calcining are at the N of 0.1MPa 2in hot-pressed sintering furnace, be warming up to 1700 ℃ in 20 ℃/min of temperature rise rate and carry out sintering 2h under protective atmosphere, obtain Si 3n 4-Si 2n 2o porous complex phase ceramic.
In this testing sequence four, the real density of resulting vesicular structure green compact is 1.75g/cm 3.
(the NH added in this test two 4) 2hPO 4through calcining and decomposing, at the green compact situ, form hole, then (NH 4) 2hPO 4degradation production can promote Si in sintering process 2n 2the formation of O phase, by adding (NH 4) 2hPO 4just can make Si 2n 2the formation proceed step by step of O phase and material mesoporosity, without the extra SiO that adds 2, the preparation method is simple, and noresidue SiO in final product 2.
This tests two prepared (NH 4) 2hPO 4addition accounts for Si 3n 4, Y 2o 3and Al 2o 3the Si of cumulative volume 10vol.% 3n 4-Si 2n 2o porous complex phase ceramic XRD figure is as Fig. 1 b) as shown in, from Fig. 1 b) can find out Si 3n 4-Si 2n 2o porous complex phase ceramic is by α-Si 3n 4, β-Si 3n 4and Si 2n 2o tri-phase composites, wherein Si 2n 2the content of O accounts for 20.3% of total molar content; The sintering linear shrinkage is 11.6%, and real density is 2.51g/cm 3, the ventilate rate is 15.5%, and bending strength is 266.2MPa, and fracture toughness property is 3.08MPam 1/2, the specific inductivity under 20GHz is 6.08.
Test three: a kind of Si of this test 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic realizes by the following method:
One, take the Si that 94g purity is 95%, median size is 0.6 μ m 3n 4powder, 4g Y 2o 3powder and 2gAl 2o 3powder, adding wherein the 20g particle diameter is 100 purpose (NH 4) 2hPO 4, adopting dehydrated alcohol is that dispersion medium carries out ball mill mixing 24h, ball material mass ratio 1.5: 1, obtain slurry;
Two, by slurry, in temperature, be to dry under 60 ℃ of fluidizing air conditions, the mixed powder after drying sieves, and under the pressure of 20MPa, pressurize 90s carries out premolding, obtains block materials;
Three, take out block materials and put into rubber mold, bleed and encapsulated, under the pressure of 200MPa, pressurize 1min cold isostatic compaction, obtain green compact;
Four, by the green compact after moulding in air furnace, in 2 ℃/min of temperature rise rate be warming up to 500 ℃ the calcining 1h, obtain the vesicular structure green compact;
Five, the vesicular structure green compact after finally calcining are at the N of 0.1MPa 2in hot-pressed sintering furnace, be warming up to 1700 ℃ in 20 ℃/min of temperature rise rate and carry out sintering 2h under protective atmosphere, obtain Si 3n 4-Si 2n 2o porous complex phase ceramic.
In this testing sequence four, the real density of resulting vesicular structure green compact is 1.69g/cm 3.
(the NH added in this test three 4) 2hPO 4through calcining and decomposing, at the green compact situ, form hole, then (NH 4) 2hPO 4degradation production can promote Si in sintering process 2n 2the formation of O phase, by adding (NH 4) 2hPO 4just can make Si 2n 2the formation proceed step by step of O phase and material mesoporosity, without the extra SiO that adds 2, the preparation method is simple, and noresidue SiO in final product 2.
This tests three prepared (NH 4) 2hPO 4addition accounts for Si 3n 4, Y 2o 3and Al 2o 3the Si of cumulative volume 20vol.% 3n 4-Si 2n 2o porous complex phase ceramic XRD figure is as Fig. 1 c) as shown in, from Fig. 1 c) can find out Si 3n 4-Si 2n 2o porous complex phase ceramic is by α-Si 3n 4, β-Si 3n 4and Si 2n 2o tri-phase composites, wherein Si 2n 2the content of O accounts for 34.7% of total molar content; The sintering linear shrinkage is 10.3%, and real density is 2.25g/cm 3, the ventilate rate is 20.7%, and bending strength is 246.9MPa, and fracture toughness property is 2.72MPam 1/2, the specific inductivity under 20GHz is 5.34.
This tests three prepared Si 3n 4-Si 2n 2the low power SEM of O porous complex phase ceramic schemes as shown in Figure 2, as can be seen from Figure 2, and Si 3n 4-Si 2n 2pore in O porous complex phase ceramic distributes more even in matrix, and hole becomes random shape, and pore dimension is about 5～8 μ m.
This tests three prepared Si 3n 4-Si 2n 2the high power SEM of O porous complex phase ceramic schemes as shown in Figure 3, as can be seen from Figure 3, and Si 3n 4-Si 2n 2si in O porous complex phase ceramic 2n 2o crystal grain presents very regular plate-like structure, and thickness is about 0.7～1 μ m.
This tests three prepared Si 3n 4-Si 2n 2the TEM photo of O porous complex phase ceramic as shown in Figure 4, as can be seen from Figure 4, Si 2n 2o crystal grain middle part exists piling up dislocation.
Test four: a kind of Si of this test 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic realizes by the following method:
One, take the Si that 94g purity is 95%, median size is 0.6 μ m 3n 4powder, 4g Y 2o 3powder and 2gAl 2o 3powder, adding wherein the 30g particle diameter is 100 purpose (NH 4) 2hPO 4, adopting dehydrated alcohol is that dispersion medium carries out ball mill mixing 24h, ball material mass ratio 1.5: 1, obtain slurry;
Two, by slurry, in temperature, be to dry under 60 ℃ of fluidizing air conditions, the mixed powder after drying sieves, and under the pressure of 20MPa, pressurize 90s carries out premolding, obtains block materials;
Three, take out block materials and put into rubber mold, bleed and encapsulated, under the pressure of 200MPa, pressurize 1min cold isostatic compaction, obtain green compact;
Four, by the green compact after moulding in air furnace, in 2 ℃/min of temperature rise rate be warming up to 500 ℃ the calcining 1h, obtain the vesicular structure green compact;
Five, the vesicular structure green compact after finally calcining are at the N of 0.1MPa 2in hot-pressed sintering furnace, be warming up to 1700 ℃ in 20 ℃/min of temperature rise rate and carry out sintering 2h under protective atmosphere, obtain Si 3n 4-Si 2n 2o porous complex phase ceramic.
In this testing sequence four, the real density of resulting vesicular structure green compact is 1.65g/cm 3.
(the NH added in this test four 4) 2hPO 4through calcining and decomposing, at the green compact situ, form hole, then (NH 4) 2hPO 4degradation production can promote Si in sintering process 2n 2the formation of O phase, by adding (NH 4) 2hPO 4just can make Si 2n 2the formation proceed step by step of O phase and material mesoporosity, without the extra SiO that adds 2, the preparation method is simple, and noresidue SiO in final product 2.
This tests four prepared (NH 4) 2hPO 4addition accounts for Si 3n 4, Y 2o 3and Al 2o 3the Si of the 30vol.% of cumulative volume 3n 4-Si 2n 2o porous complex phase ceramic XRD figure is as Fig. 1 d) as shown in, from Fig. 1 d) can find out Si 3n 4-Si 2n 2o porous complex phase ceramic is by α-Si 3n 4, β-Si 3n 4and Si 2n 2o tri-phase composites, wherein Si 2n 2the content of O accounts for 43.1% of total molar content; The sintering linear shrinkage is 7.5%, and real density is 2.02g/cm 3, the ventilate rate is 28.5%, and bending strength is 175.8MPa, and fracture toughness property is 2.10MPam 1/2, the specific inductivity under 20GHz is 4.61.
Test five: a kind of Si of this test 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic realizes by the following method:
One, take the Si that 94g purity is 95%, median size is 0.6 μ m 3n 4powder, 4g Y 2o 3powder and 2gAl 2o 3powder, adding wherein the 40g particle diameter is 100 purpose (NH 4) 2hPO 4, adopting dehydrated alcohol is that dispersion medium carries out ball mill mixing 24h, ball material mass ratio 1.5: 1, obtain slurry;
Two, by slurry, in temperature, be to dry under 60 ℃ of fluidizing air conditions, the mixed powder after drying sieves, and under the pressure of 20MPa, pressurize 90s carries out premolding, obtains block materials;
Three, take out block materials and put into rubber mold, bleed and encapsulated, under the pressure of 200MPa, pressurize 1min cold isostatic compaction, obtain green compact;
Four, by the green compact after moulding in air furnace, in 2 ℃/min of temperature rise rate be warming up to 500 ℃ the calcining 1h, obtain the vesicular structure green compact;
Five, the vesicular structure green compact after finally calcining are at the N of 0.1MPa 2in hot-pressed sintering furnace, be warming up to 1700 ℃ in 20 ℃/min of temperature rise rate and carry out sintering 2h under protective atmosphere, obtain Si 3n 4-Si 2n 2o porous complex phase ceramic.
In this testing sequence four, the real density of resulting vesicular structure green compact is 1.62g/cm 3.
(the NH added in this test five 4) 2hPO 4through calcining and decomposing, at the green compact situ, form hole, then (NH 4) 2hPO 4degradation production can promote Si in sintering process 2n 2the formation of O phase, by adding (NH 4) 2hPO 4just can make Si 2n 2the formation proceed step by step of O phase and material mesoporosity, without the extra SiO that adds 2, the preparation method is simple, and noresidue SiO in final product 2.
This tests five prepared (NH 4) 2hPO 4addition accounts for Si 3n 4, Y 2o 3and Al 2o 3the Si of the 40vol.% of cumulative volume 3n 4-Si 2n 2o porous complex phase ceramic XRD figure is as Fig. 1 e) as shown in, from Fig. 1 e) can find out Si 3n 4-Si 2n 2o porous complex phase ceramic is by α-Si 3n 4, β-Si 3n 4and Si 2n 2o tri-phase composites, wherein Si 2n 2the content of O accounts for 57.6% of total molar content; The sintering linear shrinkage is 6.0%, and real density is 1.84g/cm 3, the ventilate rate is 34.2%, and bending strength is 132.1MPa, and fracture toughness property is 1.81MPam 1/2, the specific inductivity under 20GHz is 4.08.
Known by above-mentioned test: (NH 4) 2hPO 4whether add and determining in final product whether to have Si 2n 2the generation of O phase.Nothing (NH in raw material 4) 2hPO 4add in fashionable, prepared material without Si 2n 2the generation of O phase, along with (NH in raw material 4) 2hPO 4add-on increase, Si in reaction product 2n 2the content of O phase is also increasing, and makes the density of material reduce simultaneously, and the ventilate rate raises.Therefore by regulating (NH in raw material 4) 2hPO 4addition, can make prepared Si 3n 4-Si 2n 2density, the ventilate rate of O porous complex phase ceramic are controlled, Si 3n 4-Si 2n 2si in O porous complex phase ceramic 2n 2the content of O phase is adjustable.

Claims (6)

1. a Si 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic, is characterized in that Si 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic carries out according to the following steps:
One, take Si 3n 4, Y 2o 3, Al 2o 3(NH 4) 2hPO 4, Si wherein 3n 4: Y 2o 3: Al 2o 3mass ratio be (92～95): 4: 2, (NH 4) 2hPO 4account for Si 3n 4, Y 2o 3and Al 2o 310～60vol.% of cumulative volume, to Si 3n 4, Y 2o 3and Al 2o 3in add (NH 4) 2hPO 4, adopting dehydrated alcohol is that dispersion medium carries out ball mill mixing 5～24h, obtains slurry;
Two, by slurry, in temperature, be to dry under 40～80 ℃ of fluidizing air conditions, the mixed powder after drying sieves, and under the pressure of 20～30MPa, pressurize 1～2min carries out premolding, obtains block materials;
Three, take out block materials and put into rubber mold, bleed and encapsulated, under the pressure of 100～300MPa, pressurize 1～2min cold isostatic compaction, obtain green compact;
Four, by the green compact after moulding in air furnace in 500～800 ℃ the calcining 1～2h, obtain the vesicular structure green compact;
Five, the vesicular structure green compact after finally calcining are at the N of 0.1～0.2MPa 2carry out sintering 1～3h in 1500～1800 ℃ under protective atmosphere in hot-pressed sintering furnace, obtain Si 3n 4-Si 2n 2o porous complex phase ceramic.
2. a kind of Si according to claim 1 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic, is characterized in that Si in step 1 3n 4powder is the α type, and purity is 86～98%, and median size is 0.2～0.8 μ m.
3. a kind of Si according to claim 1 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic, is characterized in that (NH in step 1 4) 2hPO 4particle diameter is 60～120 orders.
4. a kind of Si according to claim 1 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic, while it is characterized in that in step 1 batch mixing, Ball-milling Time is 24h, ball material mass ratio (1～1.5): 1.
5. a kind of Si according to claim 1 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic, is characterized in that the temperature rise rate of calcining in step 4 is lower than 2.5 ℃/min.
6. a kind of Si according to claim 1 3n 4-Si 2n 2the preparation method of O porous complex phase ceramic, the temperature rise rate that it is characterized in that sintering in step 5 is 10～30 ℃/min.
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