CN112159233B

CN112159233B - Silicon carbide-based composite ceramic material with high electric field strength resistance and preparation method thereof

Info

Publication number: CN112159233B
Application number: CN202010953557.2A
Authority: CN
Inventors: 陈健; 陈文辉; 黄政仁; 祝明; 郑嘉棋; 马宁宁
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2020-09-11
Filing date: 2020-09-11
Publication date: 2022-03-08
Anticipated expiration: 2040-09-11
Also published as: CN112159233A

Abstract

The invention relates to a silicon carbide-based composite ceramic material with high electric field resistance and a preparation method thereof. The preparation method comprises: weighing SiC, AlN, a sintering aid, a binder, ball milling and mixing, molding and debonding to obtain Silicon carbide ceramic body; and sintering the obtained silicon carbide ceramic body at 1900-2200 DEG C in a nitrogen atmosphere to obtain a high electric field strength silicon carbide-based composite ceramic material.

Description

Silicon carbide-based composite ceramic material with high electric field strength resistance and preparation method thereof

Technical Field

The invention relates to a silicon carbide-based composite ceramic material with high electric field strength resistance and a preparation method thereof, belonging to the field of silicon carbide ceramics.

Background

The silicon carbide material has excellent performances of corrosion resistance, neutron radiation resistance, high thermal conductivity, easy doping and adjustment of electrical property and the like, and can be used as an electronic component operating in a harsh environment. The silicon carbide ceramic resistor has the characteristics of a piezoresistor, is a material with typical non-volt-ampere characteristics, has the function of inhibiting transient overvoltage, has almost zero current flowing through the silicon carbide ceramic device when the terminal voltage is lower than a certain value, and has unique advantages as a surge protection device when the current value is sharply increased along with the increase of the terminal voltage when the terminal voltage is higher than the certain value. However, transient overvoltage of surge caused by lightning strike or the like may reach several kilovolts to several tens kilovolts, which requires a high electric field strength resistance of the surge protection device. Therefore, it is important to improve the electric field strength of silicon carbide to have high critical breakdown strength.

In the Chinese patent CN 104926310B, AlN is doped in SiC powder to modify the SiC powder to prepare silicon carbide ceramic, and the silicon carbide ceramic is applied to the field of structural ceramics. However, AlN is only used as a sintering aid and is introduced by a chemical method, the process is complex, the industrial production is not facilitated, and the electrical properties of the material are not researched. Based on the above, the non-linear resistance characteristics of the complex phase ceramic are studied by adding the AlN second phase into the SiC powder and changing the sintering atmosphere, and the electric field strength resistance of the material is improved. The Chinese patent application CN 104478438A is a previous application of the applicant, although the resistivity of the silicon carbide ceramic is also mentioned, but the electric field resistance of the silicon carbide ceramic is not mentioned, the inventor further researches to find that the voltage-sensitive voltage of the silicon carbide ceramic prepared by the patent application is extremely low and is less than 1V.mm^-1And the method cannot be practically applied to surge protection devices.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a silicon carbide-based composite ceramic material with high electric field strength resistance and a preparation method thereof.

In one aspect, the invention provides a preparation method of a silicon carbide-based composite ceramic material with high electric field strength, which comprises the following steps: weighing SiC, AlN, a sintering aid and a binder, ball-milling and mixing, molding and de-bonding to obtain a ceramic blank; and sintering the obtained silicon carbide ceramic blank at 1900-2200 ℃ in a nitrogen atmosphere to obtain the silicon carbide-based composite ceramic material with high electric field strength resistance.

Hair brushIn the Ming, nitrogen replaces argon to be used as sintering atmosphere, and the surprisingly found that the prepared silicon carbide-based composite ceramic material has extremely high electric field strength, namely, the voltage-dependent voltage of the obtained silicon carbide-based composite ceramic material with high electric field strength is 15-120 V.mm^-1The nonlinear coefficient alpha is 2.0 to 3.5. Can tolerate up to 100V.mm^-1Without being broken down. The inventors further studied the mechanism and considered that in the silicon carbide lattice, a position where Al doping easily substitutes for Si forms an acceptor level and a position where N doping easily substitutes for C forms a donor level. Concentration n ═ n of carriers in SiC crystal grains_D-n_AL, where n_AIs acceptor concentration, n_DIs the donor concentration. When the donor concentration is the same as the acceptor concentration, the donor and acceptor are compensated, so that carriers in the SiC are depleted, and the resistivity of the material is improved. In a high-temperature environment, the loss of nitrogen atoms can cause redundant Al acceptor levels in crystal lattices, so that hole conduction is facilitated, the resistivity of the material is reduced, and sintering in a nitrogen atmosphere can inhibit the loss of the nitrogen atoms and keep an acceptor equilibrium state, so that the material has higher electric field strength resistance.

Preferably, the total mass of SiC and AlN is 100%, and the content of aluminum nitride is more than or equal to 1 wt%, preferably 3-5%. With the increase of the content of the aluminum nitride, the electric field strength of the silicon carbide ceramic is improved. However, when AlN is excessively added, the electric field strength of the material is improved, but the performance of the material is degraded, the nonlinear resistance characteristics are degraded, and the surge absorption performance is also degraded.

Preferably, the sintering aid is B₄C、B、B₂O₃And C, the addition amount is 0.2-2 wt% of the total mass of SiC and AlN, and preferably 0.2-1.5 wt%.

Preferably, the binder is at least one of phenolic resin, PVA and PVB, and the adding amount is not more than 10wt% of the total mass of SiC and AlN.

The molding is dry pressing molding and then cold isostatic pressing, and the dry pressing molding pressure is 15 MPa-40 MPa; the cold isostatic pressure is 180-250 MPa, and the pressure maintaining time is 1-5 minutes.

Preferably, the temperature for debonding is 900-1100 ℃, and the heat preservation time is 0.5-1 hour.

Preferably, the sintering is normal pressure sintering, hot pressing sintering or SPS sintering.

On the other hand, the invention provides the silicon carbide-based composite ceramic material with high electric field strength, which is prepared by the method, wherein the voltage-sensitive voltage of the silicon carbide-based composite ceramic material with high electric field strength is 15-120 V.mm^-1The nonlinear coefficient alpha is 2.0 to 3.5.

Drawings

FIG. 1 shows the voltammetry characteristics of silicon carbide ceramics sintered under normal pressure in nitrogen atmosphere and with different aluminum nitride contents (1-5 wt%).

FIG. 2 shows the voltammetry characteristics of silicon carbide ceramics sintered under normal pressure in argon atmosphere and with different aluminum nitride contents (1-5 wt%).

Detailed Description

The present invention is described in further detail below by way of specific examples, it being understood that the following examples are illustrative of the present invention only and are not intended to limit the present invention.

The invention aims to provide a method for improving the electric field strength resistance of a silicon carbide ceramic material. In particular, the invention can prepare the voltage-sensitive voltage of 100V.mm by doping aluminum nitride and matching with the subsequent nitrogen sintering atmosphere^-1The silicon carbide ceramic is expected to be used as a surge protection device.

The preparation method of the silicon carbide-based composite ceramic with high electric field strength resistance is exemplarily described below.

Material preparation and ball milling and mixing: and weighing SiC, AlN, a sintering aid and a binder according to the calculated mass ratio, and performing ball milling and mixing. For example, the mixture is added into a ball mill pot to be mixed, wet ball milling is adopted, ethanol and SiC balls are used as ball milling media, and ball milling is carried out by a planetary ball mill. Wherein, the purity of the SiC powder is more than or equal to 99 percent, and the grain size is less than or equal to 0.5 mu m. The AlN powder has a purity of more than or equal to 99 percent and a particle size of less than or equal to 0.5 mu m. The total mass of SiC and AlN is 100%, and the content of aluminum nitride is more than or equal to 1 wt%, preferably 3-5%. The sintering aid can be B₄C、B、B₂O₃And C, the sintering aidThe amount of the agent added can be 0.2-2 wt%, preferably 0.2-1.5 wt%. The binder can be one or more of phenolic resin, PVA and PVB, and the addition amount is not more than 10wt% of the total weight of SiC and AlN powder. The proportion of the powder material to the ethanol and SiC balls can be controlled to be 1 (1.0-1.2): 1, and preferably 1 (1.1-1.2): 1.

Drying and sieving or granulating by spraying: and drying and sieving the obtained mixed slurry directly or granulating by spraying to obtain the silicon carbide-based ceramic powder. Wherein the drying temperature can be 60-80 ℃, and the mixture is sieved by a 100-200 mesh sieve.

Molding: dry pressing may be used to match the cold isostatic pressing. In one example, the dry pressing pressure is 15-40 MPa, the cold isostatic pressure is 180-250 MPa, and the pressure maintaining time is 1-5 min.

And (3) debonding: the de-bonding temperature can be 900-1100 ℃, and the heat preservation time is 0.5-1 h.

And (3) high-temperature sintering: the sintering atmosphere is nitrogen atmosphere, the sintering temperature is 1900-2200 ℃, and the sintering can be carried out by adopting pressure sintering, hot-pressing sintering or SPS sintering, and the heat preservation time can be 1-3 h. In a silicon carbide lattice, a position where Al doping easily substitutes for Si forms an acceptor level, and a position where N doping easily substitutes for C forms a donor level. Concentration n ═ n of carriers in SiC crystal grains_D-n_AL, where n_AIs acceptor concentration, n_DIs the donor concentration. When the donor concentration is the same as the acceptor concentration, the donor and acceptor are compensated, so that carriers in the SiC are depleted, and the resistivity of the material is improved. In a high-temperature environment, the loss of nitrogen atoms can cause redundant Al acceptor levels in crystal lattices, so that hole conduction is facilitated, the resistivity of the material is reduced, and sintering in a nitrogen atmosphere can inhibit the loss of the nitrogen atoms and keep an acceptor equilibrium state, so that the material has higher electric field strength resistance.

The density is measured by adopting an Archimedes drainage method, and the density of the obtained silicon carbide ceramic is 3.10-3.13 g-cm^-3The bending strength of the steel sheet is 390 to 440MPa measured by a three-point bending method.

And (3) grinding two surfaces of the obtained silicon carbide ceramic, processing the silicon carbide ceramic into a wafer with the thickness of 2mm, uniformly coating silver paste electrodes on the two surfaces of the wafer, and placing the wafer in a muffle furnace for heat preservation at 750 ℃ for 15 min. The obtained silicon carbide ceramic wafer was tested by using a Keithley2450 multi-channel test system, and it was found that the electric field resistance of the silicon carbide ceramic was continuously improved with the increase of the aluminum nitride content, as shown in FIG. 1.

The present invention will be described in further detail with reference to examples. It should be understood that the following examples are intended to further illustrate the present invention and should not be construed as limiting the scope of the present invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art based on the foregoing description are intended to be covered by the present invention. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

Weighing 99g of SiC powder and 1g of AlN powder in a ball milling tank, and adding a sintering aid B₄0.5g of C powder and 2g of phenolic resin serving as a binder, wherein the addition amount of ethanol is 110g, SiC balls are used as a ball milling medium, the use amount is 100g, and the mixture is ball milled in a planetary ball mill for 24 hours. And drying the obtained slurry in an oven at 70 ℃, and then sieving the dried slurry by a 200-mesh sieve to obtain the silicon carbide-based ceramic powder. The obtained powder was molded on a press vulcanizer at a pressure of 16MPa, and then subjected to cold isostatic pressing at a pressure of 200 MPa. After the de-bonding treatment, the ceramic material is sintered at normal pressure, wherein the sintering atmosphere is nitrogen atmosphere, the sintering temperature is 2150 ℃, the heat preservation time is 1h, and the density of the obtained ceramic material is 3.13g.cm^-3The bending strength is 393 MPa. Making the obtained material into small round pieces with diameter of 10mm and thickness of 2mm, uniformly coating both surfaces with silver paste electrode, placing in muffle furnace, maintaining at 750 deg.C for 15min, and testing with Keithley2450 multichannel test system to obtain voltage-sensitive voltage U_1mAAt 17.3V.mm^-1The nonlinear coefficient α is 2.03.

Example 2

Weighing 97g of SiC powder and 3g of AlN powder in a ball milling tank, and adding a sintering aid B₄0.5g of C powder and 2g of phenolic resin serving as a binder, wherein the addition amount of ethanol is 110g, SiC balls are used as a ball milling medium, the use amount is 100g, and the mixture is ball milled in a planetary ball mill for 24 hours. Will be provided withAnd drying the obtained slurry in an oven at 70 ℃, and then sieving the dried slurry by a 200-mesh sieve to obtain the silicon carbide-based ceramic powder. The obtained powder was molded on a press vulcanizer at a pressure of 16MPa, and then subjected to cold isostatic pressing at a pressure of 200 MPa. After the de-bonding treatment, the ceramic material is sintered at normal pressure, wherein the sintering atmosphere is nitrogen atmosphere, the sintering temperature is 2150 ℃, the heat preservation time is 1h, and the density of the obtained ceramic material is 3.10g.cm^-3The flexural strength was 428 MPa. Making the obtained material into small round pieces with diameter of 10mm and thickness of 2mm, uniformly coating both surfaces with silver paste electrode, placing in muffle furnace, maintaining at 750 deg.C for 15min, and testing with Keithley2450 multichannel test system to obtain voltage-sensitive voltage U_1mAIs 32.7V.mm^-1The nonlinear coefficient α is 2.70.

Example 3

Weighing 95g of SiC powder and 5g of AlN powder in a ball milling tank, and adding a sintering aid B₄0.5g of C powder and 2g of phenolic resin serving as a binder, wherein the addition amount of ethanol is 110g, SiC balls are used as a ball milling medium, the use amount is 100g, and the mixture is ball milled in a planetary ball mill for 24 hours. And drying the obtained slurry in an oven at 70 ℃, and then sieving the dried slurry by a 200-mesh sieve to obtain the silicon carbide-based ceramic powder. The obtained powder was molded on a press vulcanizer at a pressure of 16MPa, and then subjected to cold isostatic pressing at a pressure of 200 MPa. After the de-bonding treatment, the ceramic material is sintered at normal pressure, wherein the sintering atmosphere is nitrogen atmosphere, the sintering temperature is 2150 ℃, the heat preservation time is 1h, and the density of the obtained ceramic material is 3.11g.cm^-3The bending strength is 440 MPa. Making the obtained material into small round pieces with diameter of 10mm and thickness of 2mm, uniformly coating both surfaces with silver paste electrode, placing in muffle furnace, maintaining at 750 deg.C for 15min, and testing with Keithley2450 multichannel test system to obtain voltage-sensitive voltage U_1mAOver 100V.mm^-1The nonlinear coefficient α is 3.01.

Comparative example 1

Weighing 99g of SiC powder and 1g of AlN powder in a ball milling tank, and adding a sintering aid B₄0.5g of C powder and 2g of phenolic resin serving as a binder, wherein the addition amount of ethanol is 110g, SiC balls are used as a ball milling medium, the use amount is 100g, and the mixture is ball milled in a planetary ball mill for 24 hours. Drying the obtained slurry in an oven at 70 ℃, and then sieving the dried slurry by a 200-mesh sieve to obtain silicon carbide-based ceramic powder. The obtained powder was molded on a press vulcanizer at a pressure of 16MPa, and then subjected to cold isostatic pressing at a pressure of 200 MPa. After the de-bonding treatment, normal pressure sintering is adopted, the sintering atmosphere is argon atmosphere, the sintering temperature is 2150 ℃, the heat preservation time is 1h, and the density of the obtained ceramic material is 3.16g.cm^-3The bending strength is 303 MPa. Making the obtained material into small round pieces with diameter of 10mm and thickness of 2mm, uniformly coating both surfaces with silver paste electrode, placing in muffle furnace, maintaining at 750 deg.C for 15min, and testing with Keithley2450 multichannel test system to obtain voltage-sensitive voltage U_1mAAt 0.124V.mm^-1The nonlinear coefficient α is 1.86.

Comparative example 2

Weighing 97g of SiC powder and 3g of AlN powder in a ball milling tank, and adding a sintering aid B₄0.5g of C powder and 2g of phenolic resin serving as a binder, wherein the addition amount of ethanol is 110g, SiC balls are used as a ball milling medium, the use amount is 100g, and the mixture is ball milled in a planetary ball mill for 24 hours. And drying the obtained slurry in an oven at 70 ℃, and then sieving the dried slurry by a 200-mesh sieve to obtain the silicon carbide-based ceramic powder. The obtained powder was molded on a press vulcanizer at a pressure of 16MPa, and then subjected to cold isostatic pressing at a pressure of 200 MPa. After the de-bonding treatment, normal pressure sintering is adopted, the sintering atmosphere is argon atmosphere, the sintering temperature is 2150 ℃, the heat preservation time is 1h, and the density of the obtained ceramic material is 3.15g.cm^-3The bending strength is 327 MPa. Making the obtained material into small round pieces with diameter of 10mm and thickness of 2mm, uniformly coating both surfaces with silver paste electrode, placing in muffle furnace, maintaining at 750 deg.C for 15min, and testing with Keithley2450 multichannel test system to obtain voltage-sensitive voltage U_1mAAt 0.312V.mm^-1The nonlinear coefficient α is 1.56.

Comparative example 3

Weighing 95g of SiC powder and 5g of AlN powder in a ball milling tank, and adding a sintering aid B₄0.5g of C powder and 2g of phenolic resin serving as a binder, wherein the addition amount of ethanol is 110g, SiC balls are used as a ball milling medium, the use amount is 100g, and the mixture is ball milled in a planetary ball mill for 24 hours. And drying the obtained slurry in an oven at 70 ℃, and then sieving the dried slurry by a 200-mesh sieve to obtain the silicon carbide-based ceramic powder. Molding the obtained powder on a flat vulcanizing machine under the pressure of 16MPa and then under the pressure of 200MPaAnd carrying out cold isostatic pressing. After the de-bonding treatment, normal pressure sintering is adopted, the sintering atmosphere is argon atmosphere, the sintering temperature is 2150 ℃, the heat preservation time is 1h, and the density of the obtained ceramic material is 3.16g.cm^-3The bending strength was 338 MPa. Making the obtained material into small round pieces with diameter of 10mm and thickness of 2mm, uniformly coating both surfaces with silver paste electrode, placing in muffle furnace, maintaining at 750 deg.C for 15min, and testing with Keithley2450 multichannel test system to obtain voltage-sensitive voltage U_1mAAt 0.539V.mm^-1The nonlinear coefficient α is 1.29.

Claims

1. The application of the silicon carbide-based composite ceramic material with high field strength resistance in surge protection devices is characterized in that the preparation method of the silicon carbide-based composite ceramic material with high field strength resistance comprises the following steps:

weighing SiC, AlN, a sintering aid and a binder, ball-milling and mixing, molding and de-bonding to obtain a silicon carbide ceramic blank; and

sintering the obtained silicon carbide ceramic blank at 1900-2200 ℃ in a nitrogen atmosphere to obtain the silicon carbide-based composite ceramic material with high electric field strength resistance;

the voltage-sensitive voltage of the obtained silicon carbide-based composite ceramic material with high electric field strength is 15-120 V.mm^-1The nonlinear coefficient alpha is 2.0-3.5;

the total mass of SiC and AlN is 100%, and the content of aluminum nitride is 3-5 wt%.

2. Use according to claim 1, characterized in that: the sintering aid is B₄C、B、B₂O₃And C, the addition amount is 0.2-2 wt% of the total mass of SiC and AlN.

3. Use according to claim 1, characterized in that: the sintering aid is B₄C、B、B₂O₃And C, the addition amount is 0.2-1.5 wt% of the total mass of SiC and AlN.

4. The use of claim 1, wherein the binder is at least one of phenolic resin, PVA and PVB, and is added in an amount of no more than 10wt% of the total mass of SiC and AlN.

5. Use according to claim 1, wherein the forming is dry pressing followed by cold isostatic pressing; the pressure of the dry pressing molding is 15-40 MPa, the pressure of the cold isostatic pressing is 180-250 MPa, and the pressure maintaining time is 1-5 minutes.

6. The use according to claim 1, wherein the temperature for debonding is 900 to 1100 ℃ and the holding time is 0.5 to 1 hour.

7. Use according to claim 1, wherein the sintering is atmospheric sintering, hot-press sintering or SPS sintering.