CN102557640A - High thermal conductivity multi-layer SiC monocrystal microwave attenuating material and preparation method thereof - Google Patents
High thermal conductivity multi-layer SiC monocrystal microwave attenuating material and preparation method thereof Download PDFInfo
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- CN102557640A CN102557640A CN2010105972919A CN201010597291A CN102557640A CN 102557640 A CN102557640 A CN 102557640A CN 2010105972919 A CN2010105972919 A CN 2010105972919A CN 201010597291 A CN201010597291 A CN 201010597291A CN 102557640 A CN102557640 A CN 102557640A
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Abstract
The invention discloses a high thermal conductivity multi-layer SiC monocrystal microwave attenuating material. The attenuating material comprises a plurality of SiC layers with high resistivity and SiC layers with high loss, which are alternatively compounded. The SiC layers with high resistivity are arranged on the outermost layer and the resistivity of the SiC layers with high resistivity ranges from 104 Omega m to 108 Omega m. The SiC layers with high loss are SiC layers doped with N and the resistivity of the SiC layers ranges from 10-3 Omega m to 101 Omega m. The thermal conductivity of the SiC layers with high resistivity ranges from 250 W/m.K to 410 W/m.K. According to the high thermal conductivity multi-layer SiC monocrystal microwave attenuating material, a PVT (Pressure-Volume-Temperature) method is adopted. The alternately compounded SiC layers with high resistivity and SiC layers with high loss are formed by periodically introducing different atmospheres into a crystal growing process. The SiC layers with high resistivity can be used as the heat conducting layers for passing the heat generated by the SiC layers with high loss from absorbing microwaves to the outside rapidly. The SiC layers with high loss can adjust the resistance value of the SiC monocrystal by controlling the proportion of N2 in carrier gas during the growing process so as to fulfill the purpose of attenuating electromagnetic waves in microwave frequency bands.
Description
Technical field
The present invention relates to a kind of high heat conductance multilayer SiC monocrystalline microwave attenuation material and preparation method thereof, this material can be applied in the microwave vacuum device, plays the effect that suppresses concussion, eliminates non-Design Mode ripple.
Background technology
Microwave attenuative ceramics plays a part to suppress concussion, eliminates non-Design Mode ripple in the microwave vacuum pipe.Along with microwave tube develops to high-power, high-level efficiency, high gain, broadband, long lifetime direction; To microwave absorbing property and the heat conductivility of the pottery of decaying require increasingly highly, its performance is directly connected to the stability, output rating, safety of microwave vacuum device etc.
The decay pottery is composited with loss by insulation usually mutually mutually, and the decay pottery of high heat conductance commonly used mainly comprises: AlN/Mo (W) composite ceramics, AlN/SiC composite ceramics, BeO base composite ceramic etc.Though these ceramic thermal conductivity theoretical values are very high; Like the theoretical thermal conductivity of AlN and SiC respectively at 320W/mK with more than the 490W/mK; But SiC, AlN all belong to phonon heat conduction, because the scattering process at interface makes the thermal conductivity decline of matrix material a lot, thermal conductivities of these decay potteries are generally less than 100W/mK with the compound back of other material; AlN/SiC matrix material particularly; In high-temperature sintering process, can produce serious surface reaction, cause the remarkable decline of thermal conductivity, the thermal conductivity of matrix material has only about 50W/mK usually.
Summary of the invention
The object of the present invention is to provide a kind of high heat conductance multilayer SiC monocrystalline composite microwave attenuating material, to solve composite attenuation pottery thermal conductivity problem of lower in the prior art.
Another object of the present invention is to provide a kind of preparation method of high heat conductance multilayer SiC monocrystalline composite microwave attenuating material.
For achieving the above object, the present invention adopts following technical scheme:
A kind of high heat conductance multilayer SiC monocrystalline composite microwave attenuating material has high resistivity SiC layer and high loss SiC layer alternately is composited by several layers, is in the outermost high resistivity SiC layer that is, its resistivity is 10
4Ω m～10
8Ω m; High loss SiC layer is the SiC layer of doping N, and its resistivity is 10
-3Ω m～10
1Ω m.
The resistivity of said high resistivity SiC layer is preferably 10
5Ω m～10
8Ω m, it can pass the high loss SiC layer absorption heat that microwave produced rapidly as heat-conducting layer, and its thermal conductivity is 250-410W/mK.And high loss SiC layer is through N in the carrier gas in the control growing process
2Ratio adjust the resistance value of SiC monocrystalline, reach in the microwave frequency band electromagnetic purpose that decays, its resistivity is 10
-3Ω m～10
1Ω m, its thermal conductivity is 120～250W/mK.
In the high heat conductance multilayer SiC monocrystalline composite microwave attenuating material of the present invention, high resistivity SiC layer and high loss SiC layer are alternately compound, can adjust the total thickness of the two thickness in monolayer and composite microwave attenuating material according to actual needs.Wherein, the thickness in monolayer of high resistivity SiC layer is 0.01～0.3mm, is preferably 0.05～0.1mm; The thickness in monolayer of high loss SiC layer is 0.01～0.3mm, is preferably 0.05～0.2mm.
SiC in the above-mentioned composite microwave attenuating material is the monocrystalline attitude, and the SiC monocrystalline has very high thermal conductivity, relative composite ceramics, because perfection of lattice is higher, its thermal conductivity far is higher than polycrystalline material.Physical vapor transport method (PVT) preparation is adopted in the growth of SiC monocrystalline usually.This method is under suitable carrier gas atmosphere, and formation temperature gradient between SiC powder source and seed crystal at high temperature makes the powder source decompose and on seed crystal, deposit and grows up.
A kind of preparation method of high heat conductance multilayer SiC monocrystalline composite microwave attenuating material may further comprise the steps:
1) preparation high resistivity SiC layer
Adopting purity is that the above SiC powder of 6N is as the powder source; The SiC sheet that uses insulating or conduction is carrier gas as seed crystal with the high-purity argon gas, makes powder come from 2000 ℃ of-2400 ℃ of growths and is deposited on the seed crystal; Growth air pressure is 1000～3000Pa; Thermograde between SiC powder source and the seed crystal is 5～30 ℃/cm, and the speed of growth is 0.01～1mm/h, and forming thickness is the high resistivity SiC layer of 0.01～0.3mm;
2) the high loss SiC layer of preparation
Processing condition such as the growth temperature in the maintenance step 1), air pressure, thermograde are constant; Mixed gas with high-purity argon gas and high pure nitrogen is carrier gas; Wherein, Nitrogen accounts for the 3Vol.%～99Vol.% of mixed gas, and growth thickness is the high loss SiC layer of 0.01～0.3mm on the high resistivity SiC layer that step 1) forms;
3) hocket step 1) and step 2), form the multilayer SiC monocrystalline composite material that alternately is composited by high resistivity SiC layer and high loss SiC layer, after being ground off, seed crystal can be processed into high heat conductance multilayer SiC monocrystalline composite microwave attenuating material sample.
Among the above-mentioned preparation method, set-up procedure 1 according to actual needs) and step 2) multiplicity adjust the total thickness of high heat conductance multilayer SiC monocrystalline composite microwave attenuating material.
The invention has the beneficial effects as follows:
The present invention adopts the PVT legal system to be equipped with multilayer SiC monocrystalline composite microwave attenuating material; Through in crystal growing process, periodically feeding different atmosphere; Form alternately compound high resistivity SiC layer and high loss SiC layer; High resistivity SiC layer can absorb the heat that microwave produced with high loss SiC layer as heat-conducting layer and pass rapidly; Wherein the thermal conductivity of high resistivity SiC layer is 250-410W/mK, and high loss SiC layer can be adjusted the resistance value of SiC monocrystalline through the content of control N, reaches in the microwave frequency band electromagnetic purpose that decays.
Description of drawings
Fig. 1 is equipped with the synoptic diagram of SiC monocrystalline for the PVT legal system.
Fig. 2 is the structural representation of high heat conductance multilayer SiC monocrystalline composite microwave attenuating material of the present invention.
Fig. 3 is the structural representation of high heat conductance multilayer SiC monocrystalline composite microwave attenuating material of the present invention.
Embodiment
Be illustrated in figure 1 as the synoptic diagram that the PVT legal system is equipped with the SiC monocrystalline, this method is under suitable carrier gas 3 atmosphere, and formation temperature gradient between SiC powder source 1 and seed crystal 2 at high temperature makes powder source 1 decompose and on seed crystal 2, deposit and grows up.
Like Fig. 2, the structural representation for the high heat conductance multilayer SiC monocrystalline composite microwave attenuating material of the present invention that utilizes PVT method preparation shown in Figure 3; 5 adjacent in twos by high resistivity SiC layer 4 and high loss SiC layer, alternately be composited, can adjust high resistivity SiC layer 4 and the thickness in monolayer of high loss SiC layer 5 and the total thickness of high heat conductance multilayer SiC monocrystalline composite microwave attenuating material according to actual needs.
The SiC sheet of insulating or conduction is placed in the plumbago crucible as seed crystal; Use purity as the above SiC powder of 6N (99.9999%) as the powder source, be carrier gas with the high-purity argon gas, growth thickness is the high resistivity SiC layer of 0.01mm on seed crystal; Growth air pressure is 1000Pa; Thermograde between SiC powder source and the seed crystal is 5 ℃/cm, and growth temperature is 2200 ℃, and the speed of growth is about 0.01mm/h.Keeping the processing condition of above growth constant then, is carrier gas with the mixed gas of high-purity argon gas and high pure nitrogen, and nitrogen accounts for the 3vol.% of mixed gas, the high loss SiC layer of on high resistivity SiC layer, growing, and growth thickness stops to feed nitrogen to 0.01mm.So repeat above process 100 times, the high resistivity SiC layer of last one deck under argon gas atmosphere, growing.
Can be processed into multilayer SiC monocrystalline composite microwave attenuating material sample after seed crystal ground off, structure is as shown in Figure 2, and the sample total thickness is 2mm.Wherein the thermal conductivity of high resistivity SiC layer is 350W/mK, and resistivity is 10
4More than the Ω m, the thermal conductivity of high loss SiC layer is 210W/mK, and resistivity is 10
-1-10
1Ω m.
The SiC sheet of insulating or conduction is placed in the plumbago crucible as seed crystal; Use purity as the above SiC powder of 6N (99.9999%) as the powder source, be carrier gas with the high-purity argon gas, growth thickness is the high resistivity SiC layer of 0.1mm on seed crystal; Growth air pressure is 1000Pa; Thermograde between SiC powder source and the seed crystal is 30 ℃/cm, and growth temperature is 2300 ℃, and the speed of growth is about 0.1mm/h.Regulation and control control growing speed through growth air pressure, temperature, thermograde.Keeping the processing condition of above growth constant then, is carrier gas with the mixed gas of high-purity argon gas and high pure nitrogen, and nitrogen accounts for the 30vol.% of mixed gas, the high loss SiC layer of on high resistivity SiC layer, growing, and growth thickness stops to feed nitrogen to 0.2mm.So repeat above process 10 times, the high resistivity SiC layer of last one deck under argon gas atmosphere, growing.
Can be processed into the SiC monocrystalline composite microwave attenuating material sample of MULTILAYER COMPOSITE after seed crystal ground off, structure is as shown in Figure 3, and the sample total thickness is 3.1mm.Wherein the thermal conductivity of high resistivity SiC layer is 380W/mK, and resistivity is 10
5More than the Ω m, the thermal conductivity of high loss SiC layer is 200W/mK, and resistivity is 10
-1-10
1Ω m.
The SiC sheet of insulating or conduction is placed in the plumbago crucible as seed crystal; Use purity as the above SiC powder of 6N (99.9999%) as the powder source, be carrier gas with the high-purity argon gas, growth thickness is the high resistivity SiC layer of 0.1mm on seed crystal; Growth air pressure is 3000Pa; Thermograde between SiC powder source and the seed crystal is 10 ℃/cm, and growth temperature is 2200 ℃, and the speed of growth is about 0.05mm/h.Keeping the processing condition of above growth constant then, is carrier gas with the mixed gas of high-purity argon gas and high pure nitrogen, and nitrogen accounts for the 99vol.% of mixed gas, the high loss SiC layer of on high resistivity SiC layer, growing, and growth thickness stops to feed N to 0.1mm
2So repeat above process 20 times, the high resistivity SiC layer of last one deck under argon gas atmosphere, growing.
Can be processed into the SiC monocrystalline composite microwave attenuating material sample of MULTILAYER COMPOSITE after seed crystal ground off, structure is as shown in Figure 2, and the sample total thickness is 4mm.Wherein the thermal conductivity of high resistivity SiC layer is 320W/mK, and resistivity is 10
4More than the Ω m, the thermal conductivity of high loss SiC layer is 180W/mK, and resistivity is 10
-2-10
0Between the Ω m.
The SiC sheet of insulating or conduction is placed in the plumbago crucible as seed crystal; Use purity as the above SiC powder of 6N (99.9999%) as the powder source; Growth thickness is the high resistivity SiC layer of 0.3mm on seed crystal, and growth air pressure is 1000Pa, and the thermograde between SiC powder source and the seed crystal is 5 ℃/cm; Growth temperature is 2400 ℃, and the speed of growth is about 0.2mm/h.Keeping the processing condition of above growth constant then, is carrier gas with the mixed gas of high-purity argon gas and high pure nitrogen, and nitrogen accounts for the 50vol.% of mixed gas, the high loss SiC layer of on high resistivity SiC layer, growing, and growth thickness stops to feed N to 0.3mm
2So repeat above process 3 times, the high resistivity SiC layer of last one deck under argon gas atmosphere, growing.
Can be processed into the SiC monocrystalline composite microwave attenuating material sample of MULTILAYER COMPOSITE after seed crystal ground off, its structure is as shown in Figure 2, and the sample total thickness is 2.1mm, and wherein the thermal conductivity of high resistivity SiC layer is 410W/mK, and resistivity is 10
5More than the Ω m, the thermal conductivity of depletion layer is 120W/mK, and resistivity is 10
-3-10
-1Ω m.
Claims (6)
1. a high heat conductance multilayer SiC monocrystalline composite microwave attenuating material is characterized in that, has high resistivity SiC layer and high loss SiC layer alternately is composited by several layers, is in the outermost high resistivity SiC layer that is, its resistivity is 10
4Ω m～10
8Ω m; High loss SiC layer is the SiC layer of doping N, and its resistivity is 10
-3Ω m～10
1Ω m.
2. high heat conductance multilayer SiC monocrystalline composite microwave attenuating material according to claim 1 is characterized in that the thermal conductivity of said high resistivity SiC layer is 250-410W/mK; The thermal conductivity of said high loss SiC layer is 120～250W/mK.
3. high heat conductance multilayer SiC monocrystalline composite microwave attenuating material according to claim 1 is characterized in that the resistivity of said high resistivity SiC layer is 10
5Ω m～10
8Ω m.
4. high heat conductance multilayer SiC monocrystalline composite microwave attenuating material according to claim 1 is characterized in that the thickness in monolayer of said high resistivity SiC layer is 0.01～0.3mm; The thickness in monolayer of said high loss SiC layer is 0.01～0.3mm.
5. high heat conductance multilayer SiC monocrystalline composite microwave attenuating material according to claim 4 is characterized in that the thickness in monolayer of said high resistivity SiC layer is 0.05～0.1mm; The thickness in monolayer of said high loss SiC layer is 0.05～0.2mm.
6. the preparation method of a high heat conductance multilayer SiC monocrystalline composite microwave attenuating material is characterized in that, may further comprise the steps:
1) preparation high resistivity SiC layer
Adopting purity is that the above SiC powder of 6N is as the powder source; The SiC sheet that uses insulating or conduction is carrier gas as seed crystal with the high-purity argon gas, makes powder come from 2000 ℃ of-2400 ℃ of growths and is deposited on the seed crystal; Growth air pressure is 1000～3000Pa; Thermograde between SiC powder source and the seed crystal is 5～30 ℃/cm, and the speed of growth is 0.01～1mm/h, and forming thickness is the high resistivity SiC layer of 0.01～0.3mm;
2) the high loss SiC layer of preparation
Processing condition such as the growth temperature in the maintenance step 1), air pressure, thermograde are constant; Mixed gas with high-purity argon gas and high pure nitrogen is carrier gas; Wherein, Nitrogen accounts for the 3Vol.%～99Vol.% of mixed gas, and growth thickness is the high loss SiC layer of 0.01～0.3mm on the high resistivity SiC layer that step 1) forms;
3) hocket step 1) and step 2), form the multilayer SiC monocrystalline composite material that alternately is composited by high resistivity SiC layer and high loss SiC layer, after being ground off, seed crystal can be processed into high heat conductance multilayer SiC monocrystalline composite microwave attenuating material sample.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113664204A (en) * | 2021-08-25 | 2021-11-19 | 中国核动力研究设计院 | Alloy plate with controllable axial resistivity gradient and preparation method thereof |
Citations (2)
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|---|---|---|---|---|
| US6328796B1 (en) * | 1999-02-01 | 2001-12-11 | The United States Of America As Represented By The Secretary Of The Navy | Single-crystal material on non-single-crystalline substrate |
| CN101501836A (en) * | 2006-08-30 | 2009-08-05 | 硅电子股份公司 | Multilayered semiconductor wafer and process for manufacturing the same |
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- 2010-12-20 CN CN2010105972919A patent/CN102557640A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6328796B1 (en) * | 1999-02-01 | 2001-12-11 | The United States Of America As Represented By The Secretary Of The Navy | Single-crystal material on non-single-crystalline substrate |
| CN101501836A (en) * | 2006-08-30 | 2009-08-05 | 硅电子股份公司 | Multilayered semiconductor wafer and process for manufacturing the same |
Non-Patent Citations (1)
| Title |
|---|
| MATTEO PAVESE ET.AL.: "Potential of SiC multilayer ceramics for high temperature applications in oxidising environment", 《CERAMICS INTERNATIONAL》, vol. 34, no. 1, 2 November 2006 (2006-11-02), pages 197 - 203, XP022318868, DOI: doi:10.1016/j.ceramint.2006.09.008 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113664204A (en) * | 2021-08-25 | 2021-11-19 | 中国核动力研究设计院 | Alloy plate with controllable axial resistivity gradient and preparation method thereof |
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Application publication date: 20120711 |