Disclosure of Invention
The invention aims to provide a preparation method of an alumina ceramic flake with high toughness and high impact resistance.
The invention is realized by the following technical scheme:
a preparation method of an alumina ceramic flake comprises the following steps:
mixing zirconia powder, alumina powder, an adhesive and aluminum nickel zirconium alloy powder, and performing dry pressing to obtain a green body;
and (3) discharging glue from the green body in an inert atmosphere, heating to 700-750 ℃ in the inert atmosphere, heating to 1450-1520 ℃ in an oxidizing atmosphere, and preserving heat to obtain the finished product.
The purity of the alumina powder is greater than or equal to 96%;
the alumina powder has an average particle diameter D50 of 1-2 mu m.
The adding amount of the zirconia powder is 0.15-0.2wt% of the adding amount of the alumina powder.
The average particle diameter D50 of the zirconia powder is 0.1-0.2 mu m.
The addition amount of the aluminum nickel zirconium alloy powder is 1.5-2wt% of the addition amount of the alumina powder.
The average grain diameter D50 of the aluminum nickel zirconium alloy powder is 0.1-0.2 mu m.
The heat preservation time is 30-60min.
The adhesive comprises at least one of polyvinyl alcohol, hydroxymethyl cellulose and hydroxyethyl cellulose;
the addition amount of the adhesive is 5-10% of the mass of the alumina;
the aluminum nickel zirconium alloy powder comprises 5-6wt% of nickel, 4-6wt% of zirconium and the balance of aluminum.
The inert atmosphere comprises argon or helium;
the oxidizing atmosphere comprises air.
The pressure of the dry pressure is 10-30MPa;
the temperature of the adhesive discharge is 300-350 ℃;
the time for discharging the glue is 1-2h.
The volume density of the alumina ceramic flake is more than or equal to 3.75g/cm 3 ;
The elastic modulus of the alumina ceramic flake is more than or equal to 320GPa;
the flexural strength of the alumina ceramic flake is more than or equal to 370MPa;
the volume resistivity of the alumina ceramic flake is more than or equal to 9.4X10 14 Ω.cm。
Compared with the prior art, the invention has the following beneficial effects:
the method provided by the invention is simple, and zirconium oxide is reinforced at the grain boundary junction of the prepared aluminum oxide ceramic, so that the aluminum oxide ceramic has high impact resistance and high toughness.
Detailed Description
The invention provides a preparation method of an alumina ceramic flake, which comprises the following steps: mixing zirconia powder, alumina powder, an adhesive and aluminum nickel zirconium alloy powder, and performing dry pressing to obtain a green body; and (3) discharging the adhesive of the green body in an inert atmosphere, and then heating to 700-750 ℃ in the inert atmosphere to liquefy the aluminum-nickel-zirconium alloy powder. Because of poor wettability between metal and ceramic, the liquid aluminum nickel zirconium alloy moves to gaps among alumina powder, then an oxidizing atmosphere is introduced to oxidize the metal, the temperature is raised to 1450-1520 ℃, and then the heat is preserved, so that the raw materials are sintered, and zirconium oxide exists at the junction of grain boundaries of the sintered alumina flakes. It is known that when a ceramic is broken along a grain boundary by impact, a crack propagates along the grain boundary, and this is mainly because a large amount of brittle phases or impurity particles having high hardness are present at the grain boundary, and defects are formed at the grain boundary, and the strength of the defects is lowered to form cracks, and the cracks propagate along the direction of lower strength. And the strength at the junction of the ceramic grain boundaries is the weakest. As zirconia exists at the grain boundary junction of the alumina flake prepared by the method, the zirconia can limit the occurrence of alumina grain boundary sliding, holes and creep when the alumina flake is impacted, so that the alumina grain boundary is enhanced and the impact resistance is improved.
Specifically, the purity of the alumina powder is greater than or equal to 96%. When the purity of the alumina powder is too low, the strength of the prepared oxidized flake is poor. Preferably, the alumina powder has an average particle diameter D50 of 1 to 2 μm. The smaller the particle size of the alumina powder raw material is, the better the mechanical property is. In general, when the particle size of the alumina powder raw material is in the nanometer order, alumina flakes having a flexural strength of more than 400MPa can be obtained. In the method provided by the invention, the grain boundary is reinforced, so that when the average grain diameter of the alumina powder is in the micron level, the alumina flake with the bending strength of more than 400MPa can be obtained.
Specifically, the adding amount of the zirconia powder is 0.15-0.2wt% of the adding amount of the alumina powder. Preferably, the average particle diameter D50 of the zirconia powder is 0.1-0.2 μm.
Specifically, the addition amount of the aluminum nickel zirconium alloy powder is 1.5-2wt% of the addition amount of the alumina powder. The alloy can play a better role in strengthening when the addition amount of the alloy is more than 1.5 weight percent. The alloy is excessively added, and the alloy liquid phase can be separated out from the green body in the sintering process. Meanwhile, if only the aluminum-zirconium alloy is adopted singly, the wettability of the aluminum-zirconium alloy is poorer than that of the aluminum-nickel-zirconium alloy, so that the aluminum-zirconium alloy is easier to separate out from a blank. Meanwhile, the liquefying temperature of the aluminum-zirconium alloy is higher, so that the production cost is also higher. Preferably, the average particle diameter D50 of the aluminum nickel zirconium alloy powder is 0.1-0.2 mu m. The aluminum nickel zirconium alloy with the too large particle size is difficult to be uniformly mixed with the alumina powder, and the too small particle size is easy to agglomerate, so that the production cost is increased.
Specifically, during sintering, the heat preservation time is 30-60min.
Specifically, the adhesive comprises at least one of polyvinyl alcohol, hydroxymethyl cellulose and hydroxyethyl cellulose; other types of adhesives may also be used. The addition amount of the adhesive is 5-10% of the mass of the alumina.
Specifically, the aluminum-nickel-zirconium alloy powder comprises 5-6wt% of nickel, 4-6wt% of zirconium and the balance of aluminum. Too high a nickel content reduces the strength of the alumina flake. When the nickel content is too low, the liquefying temperature of the alloy can be increased, and meanwhile, the wettability of the alloy and aluminum oxide is poor, so that the alloy is easy to separate out from a blank.
Specifically, the inert atmosphere is argon or helium which does not react with the raw material, and may be other group 0 gases.
Specifically, the oxidizing atmosphere includes air and also includes a gas such as oxygen that oxidizes a metal to form an oxide.
Specifically, the pressure of the dry pressure is 10-30MPa; the temperature of the adhesive discharge is 300-350 ℃; the time for discharging the glue is 1-2h.
The volume density of the alumina ceramic flake prepared by the invention is more than or equal to 3.75g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The elastic modulus is more than or equal to 320GPa, the flexural strength is more than or equal to 370MPa, and the volume resistivity is more than or equal to 9.4X10 14 Ω.cm。
The invention will be further described with reference to specific examples.
Example 1
The embodiment provides a preparation method of alumina ceramic, which adopts the raw materials of alumina powder, zirconia powder, aluminum nickel zirconium alloy powder and polyvinyl alcohol with the purity. Wherein the purity of the alumina powder is 96.5%, and the D50 is 1 micron. The D50 of the zirconia powder was 0.1 microns. The D50 of the alnico alloy powder was 0.1 microns. The polyvinyl alcohol is polyvinyl alcohol 400. The addition amount of the zirconia powder was 0.15wt% of the alumina powder. The addition amount of the aluminum nickel zirconium alloy powder is 1.5wt% of the alumina powder. The amount of polyvinyl alcohol added was 5wt% of the alumina powder. In the aluminum nickel zirconium alloy powder, the content of zirconium is 6wt percent, and the content of nickel is 5wt percent.
The above raw materials were put in a planetary ball mill for ball milling at a rotation speed of 400rpm for 40min to obtain a mixture powder.
And (3) placing the mixture powder into a grinding tool for dry pressing, wherein the pressure of the dry pressing is controlled to be 10MPa, and the pressure maintaining time is 30s, so that a ceramic blank body is obtained.
Placing the ceramic blank on a ceramic flat plate, then placing the ceramic flat plate in a tube furnace, introducing argon, heating to 300 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then introducing air after heating to 700 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, heating to 1450 ℃ at a heating rate of 5 ℃/min, preserving heat for 30min, and cooling after the heat preservation is finished to obtain the aluminum oxide sheet.
Example 2
The embodiment provides a preparation method of alumina ceramic, which adopts the raw materials of alumina powder, zirconia powder, aluminum nickel zirconium alloy powder and hydroxymethyl cellulose with the purity. Wherein the purity of the alumina powder is 96.5%, and the D50 is 2 microns. The D50 of the zirconia powder was 0.2 microns. The D50 of the alnico alloy powder was 0.2 microns. The addition amount of the zirconia powder was 0.15wt% of the alumina powder. The addition amount of the aluminum nickel zirconium alloy powder is 2wt% of the alumina powder. The addition amount of the hydroxymethyl cellulose is 8wt% of the alumina powder. In the aluminum nickel zirconium alloy powder, the content of zirconium is 6wt percent, and the content of nickel is 6wt percent.
The above raw materials were put in a planetary ball mill for ball milling at a rotation speed of 400rpm for 40min to obtain a mixture powder.
And (3) placing the mixture powder into a grinding tool for dry pressing, wherein the pressure of the dry pressing is controlled to be 15MPa, and the pressure maintaining time is 30s, so that a ceramic blank body is obtained.
Placing the ceramic blank on a ceramic flat plate, then placing the ceramic flat plate in a tube furnace, introducing argon, heating to 300 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then introducing air after heating to 730 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, heating to 1500 ℃ at a heating rate of 5 ℃/min, preserving heat for 30min, and cooling after the heat preservation is finished to obtain the aluminum oxide sheet.
Example 3
The embodiment provides a preparation method of alumina ceramic, which adopts alumina powder, zirconia powder, aluminum nickel zirconium alloy powder and hydroxyethyl cellulose as raw materials with purity. Wherein the purity of the alumina powder is 96.5%, and the D50 is 1 micron. The D50 of the zirconia powder was 0.2 microns. The D50 of the alnico alloy powder was 0.1 microns. The addition amount of the zirconia powder was 0.15wt% of the alumina powder. The addition amount of the aluminum nickel zirconium alloy powder is 1.5wt% of the alumina powder. The amount of hydroxyethyl cellulose added was 10wt% of the alumina powder. In the aluminum nickel zirconium alloy powder, the content of zirconium is 4wt percent, and the content of nickel is 5wt percent.
The above raw materials were put in a planetary ball mill for ball milling at a rotation speed of 400rpm for 40min to obtain a mixture powder.
And (3) placing the mixture powder into a grinding tool for dry pressing, wherein the pressure of the dry pressing is controlled to be 10MPa, and the pressure maintaining time is 30s, so that a ceramic blank body is obtained.
Placing the ceramic blank on a ceramic flat plate, then placing the ceramic flat plate in a tube furnace, introducing argon, heating to 350 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then introducing air after heating to 750 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, heating to 1450 ℃ at a heating rate of 5 ℃/min, preserving heat for 30min, and cooling after the heat preservation is finished to obtain the aluminum oxide sheet.
Example 4
The embodiment provides a preparation method of alumina ceramic, which adopts the raw materials of alumina powder, zirconia powder, aluminum nickel zirconium alloy powder and polyvinyl alcohol with the purity. Wherein the purity of the alumina powder is 96.5% and the D50 is 1.5 μm. The D50 of the zirconia powder was 0.1 microns. The D50 of the alnico alloy powder was 0.1 microns. The polyvinyl alcohol is polyvinyl alcohol 400. The addition amount of the zirconia powder was 0.15wt% of the alumina powder. The addition amount of the aluminum nickel zirconium alloy powder is 2wt% of the alumina powder. The amount of polyvinyl alcohol added was 5wt% of the alumina powder. In the aluminum nickel zirconium alloy powder, the content of zirconium is 6wt percent, and the content of nickel is 5wt percent.
The above raw materials were put in a planetary ball mill for ball milling at a rotation speed of 400rpm for 40min to obtain a mixture powder.
And (3) placing the mixture powder into a grinding tool for dry pressing, wherein the pressure of the dry pressing is controlled to be 30MPa, and the pressure maintaining time is 30s, so that a ceramic blank body is obtained.
Placing the ceramic blank on a ceramic flat plate, then placing the ceramic flat plate in a tube furnace, introducing argon, heating to 320 ℃ at a heating rate of 5 ℃/min, preserving heat for 2 hours, then introducing air after heating to 720 ℃ at a heating rate of 5 ℃/min, preserving heat for 10 minutes, heating to 1520 ℃ at a heating rate of 5 ℃/min, preserving heat for 30 minutes, and cooling after the heat preservation is finished to obtain the aluminum oxide sheet.
Comparative example 1
The embodiment provides a preparation method of alumina ceramic, which adopts the raw materials of alumina powder, zirconia powder, aluminum zirconium alloy powder and polyvinyl alcohol with the purity. Wherein the purity of the alumina powder is 96.5%, and the D50 is 1 micron. The D50 of the zirconia powder was 0.1 microns. The D50 of the alnico alloy powder was 0.1 microns. The polyvinyl alcohol is polyvinyl alcohol 400. The addition amount of the zirconia powder was 0.15wt% of the alumina powder. The addition amount of the aluminum nickel zirconium alloy powder is 1.5wt% of the alumina powder. The amount of polyvinyl alcohol added was 5wt% of the alumina powder. The content of zirconium in the aluminum zirconium alloy powder was 6wt%.
The above raw materials were put in a planetary ball mill for ball milling at a rotation speed of 400rpm for 40min to obtain a mixture powder.
And (3) placing the mixture powder into a grinding tool for dry pressing, wherein the pressure of the dry pressing is controlled to be 10MPa, and the pressure maintaining time is 30s, so that a ceramic blank body is obtained.
Placing the ceramic blank on a ceramic flat plate, then placing the ceramic flat plate in a tube furnace, introducing argon, heating to 300 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then introducing air after heating to 1000 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, heating to 1450 ℃ at a heating rate of 5 ℃/min, preserving heat for 30min, and cooling after the heat preservation is finished to obtain the aluminum oxide sheet.
Comparative example 2
The embodiment provides a preparation method of alumina ceramic, which adopts alumina powder, zirconia powder and polyvinyl alcohol as raw materials with purity. Wherein the purity of the alumina powder is 96.5%, and the D50 is 1 micron. The D50 of the zirconia powder was 0.1 microns. The polyvinyl alcohol is polyvinyl alcohol 400. The addition amount of the zirconia powder was 0.15wt% of the alumina powder. The amount of polyvinyl alcohol added was 5wt% of the alumina powder.
The above raw materials were put in a planetary ball mill for ball milling at a rotation speed of 400rpm for 40min to obtain a mixture powder.
And (3) placing the mixture powder into a grinding tool for dry pressing, wherein the pressure of the dry pressing is controlled to be 10MPa, and the pressure maintaining time is 30s, so that a ceramic blank body is obtained.
Placing the ceramic blank on a ceramic flat plate, then placing the ceramic flat plate in a tube furnace, introducing air, heating to 300 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, heating to 1450 ℃ at a heating rate of 5 ℃/min, preserving heat for 30min, and cooling after the heat preservation is finished to obtain the aluminum oxide sheet.
The following table shows the results of mechanical and electrical property tests of the alumina flakes prepared in examples and comparative examples.
|
Bulk density g/cm 3 |
Elastic modulus GPa
|
Flexural strength MPa
|
Resistor 10 14 Ω∙cm
|
Example 1
|
3.77
|
375
|
386
|
9.63
|
Example 2
|
3.75
|
372
|
375
|
9.43
|
Example 3
|
3.78
|
367
|
376
|
9.87
|
Example 4
|
3.79
|
378
|
370
|
10.06
|
Comparative example 1
|
3.74
|
301
|
357
|
9.02
|
Comparative example 2
|
3.72
|
303
|
321
|
9.03 |
From the above table, it is clear that after the addition of the alloy powder, the flexural strength of the alumina flakes was significantly improved due to the presence of the grain boundary reinforcing effect. The improvement in flexural strength also demonstrates the improvement in impact resistance and toughness of the alumina flakes. Meanwhile, the resistivity of the zirconia is higher, and the zirconia at the grain boundary can obviously improve the resistivity of the alumina flake.