CN116283243B - A kind of preparation method of high-toughness aluminum oxide sheet - Google Patents

Abstract

The invention provides a method for preparing high-toughness alumina flakes, which comprises the following steps: dry pressing zirconia powder, alumina powder, an adhesive and aluminum-nickel-zirconium alloy powder to obtain a green body; debinding the green body in an inert atmosphere, raising the temperature to 700-750°C in an inert atmosphere, then raising the temperature to 1450-1520°C in an oxidizing atmosphere, and then keeping it warm. The method provided by the invention is simple, and there is zirconia reinforcement at the junction of the grain boundaries of the prepared alumina ceramics, so the impact resistance is high and the toughness is high.

Description

A kind of preparation method of high-toughness aluminum oxide sheet

technical field

The invention relates to a method for preparing an alumina ceramic sheet, belonging to the field of ceramic sensors.

Background technique

A pressure transducer (Pressure Transducer) is a device or device that can sense pressure signals and convert the pressure signals into usable output electrical signals according to certain rules. Pressure sensor is the most commonly used sensor in industrial practice. It is widely used in various industrial automatic control environments, such as water conservancy and hydropower, railway transportation, intelligent buildings, production automatic control, aerospace, military industry, petrochemical, oil wells, electric power, ships, machine tools, pipelines and many other industries.

A pressure sensor usually consists of a pressure sensitive element and a signal processing unit. Since the pressure sensor needs to be able to withstand a certain pressure, the pressure sensitive element in the pressure sensor needs to have a certain impact resistance.

At present, aluminum oxide flakes are often used to prepare pressure sensitive elements in pressure sensors. However, conventional 96 alumina ceramics have a large elastic modulus and low toughness, and their impact resistance is poor when they encounter a sudden high pressure, which will have a negative impact on the sensitivity and life of the sensor. Therefore, how to improve the impact resistance of alumina ceramics is an urgent problem to be solved.

Contents of the invention

The purpose of the present invention is to provide a method for preparing alumina ceramic flakes with high toughness and high impact resistance.

The present invention realizes through following technical scheme:

A preparation method of alumina ceramic flakes, comprising the steps of:

Mixing zirconia powder, alumina powder, binder and Al-Ni-Zr alloy powder and performing dry pressing to obtain a green body;

The green body is degummed under an inert atmosphere, then heated to 700-750°C under an inert atmosphere, and then heated to 1450-1520°C under an oxidizing atmosphere, and then kept at a constant temperature to obtain the product.

The purity of the alumina powder is greater than or equal to 96%;

The average particle diameter D50 of the alumina powder is 1-2 μm.

The added amount of the zirconia powder is 0.15-0.2wt% of the added amount of the alumina powder.

The average particle diameter D50 of the zirconia powder is 0.1-0.2 μm.

The added amount of the aluminum-nickel-zirconium alloy powder is 1.5-2wt% of the added amount of the alumina powder.

The average particle diameter D50 of the Al-Ni-Zr alloy powder is 0.1-0.2 μm.

The time of the heat preservation is 30-60min.

The binder includes at least one of polyvinyl alcohol, hydroxymethyl cellulose, and hydroxyethyl cellulose;

The amount of the adhesive added is 5-10% of the mass of alumina;

The aluminum-nickel-zirconium alloy powder includes 5-6wt% nickel and 4-6wt% zirconium, and the rest is aluminum.

The inert atmosphere includes argon or helium;

The oxidizing atmosphere includes air.

The pressure of the dry pressure is 10-30MPa;

The temperature of the debinding is 300-350°C;

The time for degumming is 1-2h.

The bulk density of the alumina ceramic flakes is greater than or equal to 3.75g/cm ³ ;

The elastic modulus of the alumina ceramic sheet is greater than or equal to 320GPa;

The flexural strength of the alumina ceramic sheet is greater than or equal to 370MPa;

The volume resistivity of the alumina ceramic sheet is greater than or equal to 9.4×10 ¹⁴ Ω.cm.

Compared with the prior art, the beneficial effects of the present invention are as follows:

The method provided by the invention adopts a simple method, and there is zirconia reinforcement at the intersection of the grain boundaries of the prepared alumina ceramics, so the impact resistance and toughness are high.

Description of drawings

Fig. 1 shows the SEM photo of the aluminum oxide ceramic flakes that embodiment 1 prepares;

FIG. 2 shows an enlarged SEM photo of the grain boundaries of the alumina ceramic flakes prepared in Example 1.

Detailed ways

The invention provides a method for preparing alumina ceramic flakes, which specifically comprises the following steps: dry pressing after mixing zirconia powder, alumina powder, a binder and AlNiZr alloy powder to obtain a green body; debinding the green body in an inert atmosphere, and raising the temperature to 700-750° C. in an inert atmosphere to liquefy the AlNiZr alloy powder. Due to the poor wettability between the metal and the ceramic, the liquid AlNiZr alloy will move to the gap between the alumina powders, and then an oxidizing atmosphere will be introduced to oxidize the metal and raise the temperature to 1450-1520°C, then keep it warm to sinter the raw materials, so that zirconia will exist at the intersection of the grain boundaries of the sintered alumina flakes. It is well known that when ceramics are impacted and fracture intergranularly, the path of crack propagation is along the direction of the grain boundary. This is mainly because there are a large number of brittle phases or impurity particles with high hardness at the grain boundary, which will form defects at the grain boundary, reduce its strength, form cracks, and expand along the direction of lower strength. The intersection of ceramic grain boundaries is the weakest. Zirconia will exist at the intersection of the grain boundaries of the alumina flakes prepared by the method provided by the present invention, and the zirconia will limit the slippage of the alumina grain boundaries and the occurrence of holes and creep when the alumina flakes are impacted, thereby strengthening the alumina grain boundaries and improving impact resistance.

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 oxide flakes is poor. Preferably, the average particle diameter D50 of the alumina powder is 1-2 μm. The smaller the particle size of the alumina powder raw material, the better its mechanical properties. Generally, when the particle size of the alumina powder raw material is at the nanoscale, alumina flakes with a bending strength greater than 400MPa can be obtained. However, because the method provided by the present invention strengthens the grain boundaries, when the average particle size of the alumina powder is in the micron range, alumina flakes with a bending strength greater than 400 MPa can also be obtained.

Specifically, the added amount of the zirconia powder is 0.15-0.2 wt% of the added amount of the alumina powder. Preferably, the average particle diameter D50 of the zirconia powder is 0.1-0.2 μm.

Specifically, the added amount of the aluminum-nickel-zirconium alloy powder is 1.5-2wt% of the added amount of the alumina powder. When the alloy addition amount is greater than 1.5wt%, it can have a better strengthening effect. If the alloy is added too much, the alloy liquid phase will be precipitated from the green body during the sintering process. At the same time, if only aluminum-zirconium alloy is used alone, it is easier to precipitate from the green body because its wettability is worse than that of aluminum-nickel-zirconium alloy. At the same time, the liquefaction temperature of aluminum-zirconium alloy is higher, so the production cost will be higher. Preferably, the average particle diameter D50 of the AlNiZr alloy powder is 0.1-0.2 μm. If the particle size is too large, the AlNiZr alloy is difficult to mix evenly with the alumina powder, and if the particle size is too small, it is easy to agglomerate, which will increase the production cost.

Specifically, during sintering, the heat preservation time is 30-60 minutes.

Specifically, the binder includes at least one of polyvinyl alcohol, hydroxymethyl cellulose, and hydroxyethyl cellulose; other types of binders may also be used. The additive amount of the binder is 5-10% of the alumina mass.

Specifically, the aluminum-nickel-zirconium alloy powder includes 5-6wt% nickel and 4-6wt% zirconium, and the rest is aluminum. Excessive nickel content reduces the strength of the alumina flakes. If the nickel content is too low, the liquefaction temperature of the alloy will increase, and at the same time, the wettability of the alloy and alumina will become poor, and it is easy to precipitate from the green body.

Specifically, the inert atmosphere is argon or helium that does not react with the raw materials, or other Group 0 gases.

Specifically, the oxidative atmosphere includes air and oxygen and other gases that can oxidize metals to form oxides.

Specifically, the dry pressing pressure is 10-30 MPa; the debinding temperature is 300-350° C.; the debinding time is 1-2 hours.

The bulk density of the alumina ceramic sheet prepared by the present invention is greater than or equal to 3.75g/cm ³ ; the elastic modulus is greater than or equal to 320GPa, the flexural strength is greater than or equal to 370MPa, and the volume resistivity is greater than or equal to 9.4×10 ¹⁴ Ω.cm.

The present invention will be further described below in combination with specific embodiments.

Example 1

This embodiment provides a method for preparing alumina ceramics. The raw materials used in the method are alumina powder, zirconia powder, aluminum-nickel-zirconium alloy powder and polyvinyl alcohol. Among them, the purity of alumina powder is 96.5%, and the D50 is 1 micron. The D50 of zirconia powder is 0.1 micron. The D50 of AlNiZr alloy powder is 0.1 micron. The polyvinyl alcohol is polyvinyl alcohol 400. The addition amount of zirconia powder is 0.15wt% of alumina powder. The addition amount of AlNiZr alloy powder is 1.5wt% of alumina powder. The addition amount of polyvinyl alcohol is 5wt% of alumina powder. In the aluminum-nickel-zirconium alloy powder, the content of zirconium is 6wt%, and the content of nickel is 5wt%.

The above raw materials were placed in a planetary ball mill for ball milling at a speed of 400 rpm for 40 minutes to obtain a mixture powder.

The mixture powder was placed in a grinding tool for dry pressing, the pressure of the dry pressing was controlled at 10 MPa, and the holding time was 30 s to obtain a ceramic green body.

Put the ceramic body on a ceramic plate, then place it in a tube furnace, pass in argon, raise the temperature to 300°C at a heating rate of 5°C/min, then keep it warm for 1 hour, then raise the temperature to 700°C at a heating rate of 5°C/min, then pass in air, keep it warm for 10 minutes, then raise the temperature to 1450°C at a heating rate of 5°C/min, and hold it for 30 minutes.

Example 2

This embodiment provides a method for preparing alumina ceramics. The raw materials used in the method are alumina powder, zirconia powder, aluminum-nickel-zirconium alloy powder and hydroxymethyl cellulose. Among them, the purity of alumina powder is 96.5%, and the D50 is 2 microns. The D50 of zirconia powder is 0.2 microns. The D50 of AlNiZr alloy powder is 0.2 microns. The addition amount of zirconia powder is 0.15wt% of alumina powder. The addition amount of AlNiZr alloy powder is 2wt% of alumina powder. The addition amount of hydroxymethyl cellulose is 8wt% of alumina powder. In the aluminum-nickel-zirconium alloy powder, the content of zirconium is 6wt%, and the content of nickel is 6wt%.

The above raw materials were placed in a planetary ball mill for ball milling at a speed of 400 rpm for 40 minutes to obtain a mixture powder.

The mixture powder was placed in a grinding tool for dry pressing, the pressure of the dry pressing was controlled at 15 MPa, and the holding time was 30 s to obtain a ceramic green body.

Put the ceramic body on a ceramic flat plate, then place it in a tube furnace, pass in argon gas, raise the temperature to 300°C at a rate of 5°C/min, then keep it warm for 1 hour, then raise the temperature to 730°C at a rate of 5°C/min, then pass in air, keep it warm for 10 minutes, then raise the temperature to 1500°C at a rate of 5°C/min, and hold it for 30 minutes.

Example 3

This embodiment provides a method for preparing alumina ceramics. The raw materials used in the method are alumina powder, zirconia powder, aluminum-nickel-zirconium alloy powder and hydroxyethyl cellulose. Among them, the purity of alumina powder is 96.5%, and the D50 is 1 micron. The D50 of zirconia powder is 0.2 microns. The D50 of AlNiZr alloy powder is 0.1 micron. The addition amount of zirconia powder is 0.15wt% of alumina powder. The addition amount of AlNiZr alloy powder is 1.5wt% of alumina powder. The addition amount of hydroxyethyl cellulose is 10wt% of alumina powder. In the aluminum-nickel-zirconium alloy powder, the content of zirconium is 4wt%, and the content of nickel is 5wt%.

The above raw materials were placed in a planetary ball mill for ball milling at a speed of 400 rpm for 40 minutes to obtain a mixture powder.

The mixture powder was placed in a grinding tool for dry pressing, the pressure of the dry pressing was controlled at 10 MPa, and the holding time was 30 s to obtain a ceramic green body.

Put the ceramic body on a ceramic flat plate, then place it in a tube furnace, pass in argon gas, raise the temperature to 350°C at a rate of 5°C/min, then keep it warm for 1 hour, then raise the temperature to 750°C at a rate of 5°C/min, then pass in air, keep it warm for 10 minutes, then raise the temperature to 1450°C at a rate of 5°C/min, and hold it for 30 minutes.

Example 4

This embodiment provides a method for preparing alumina ceramics. The raw materials used in the method are alumina powder, zirconia powder, aluminum-nickel-zirconium alloy powder and polyvinyl alcohol. Among them, the purity of alumina powder is 96.5%, and the D50 is 1.5 microns. The D50 of zirconia powder is 0.1 micron. The D50 of AlNiZr alloy powder is 0.1 micron. The polyvinyl alcohol is polyvinyl alcohol 400. The addition amount of zirconia powder is 0.15wt% of alumina powder. The addition amount of AlNiZr alloy powder is 2wt% of alumina powder. The addition amount of polyvinyl alcohol is 5wt% of alumina powder. In the aluminum-nickel-zirconium alloy powder, the content of zirconium is 6wt%, and the content of nickel is 5wt%.

The above raw materials were placed in a planetary ball mill for ball milling at a speed of 400 rpm for 40 minutes to obtain a mixture powder.

The mixture powder was placed in a grinding tool for dry pressing, the pressure of the dry pressing was controlled at 30 MPa, and the holding time was 30 s to obtain a ceramic green body.

Put the ceramic body on a ceramic flat plate, then place it in a tube furnace, pass in argon gas, raise the temperature to 320°C at a rate of 5°C/min, then keep it warm for 2 hours, then raise it to 720°C at a rate of 5°C/min, then pass in air, keep it warm for 10 minutes, then raise it to 1520°C at a rate of 5°C/min, and hold it for 30 minutes.

Comparative example 1

This embodiment provides a method for preparing alumina ceramics. The raw materials used in the method are alumina powder, zirconia powder, aluminum-zirconium alloy powder and polyvinyl alcohol. Among them, the purity of alumina powder is 96.5%, and the D50 is 1 micron. The D50 of zirconia powder is 0.1 micron. The D50 of AlNiZr alloy powder is 0.1 micron. The polyvinyl alcohol is polyvinyl alcohol 400. The addition amount of zirconia powder is 0.15wt% of alumina powder. The addition amount of AlNiZr alloy powder is 1.5wt% of alumina powder. The addition amount of polyvinyl alcohol is 5wt% of alumina powder. In the aluminum-zirconium alloy powder, the content of zirconium is 6wt%.

The above raw materials were placed in a planetary ball mill for ball milling at a speed of 400 rpm for 40 minutes to obtain a mixture powder.

The mixture powder was placed in a grinding tool for dry pressing, the pressure of the dry pressing was controlled at 10 MPa, and the holding time was 30 s to obtain a ceramic green body.

Put the ceramic body on a ceramic flat plate, then place it in a tube furnace, pass in argon gas, raise the temperature to 300°C at a rate of 5°C/min, then keep it warm for 1 hour, then raise the temperature to 1000°C at a rate of 5°C/min, then pass in air, keep it warm for 10 minutes, then raise the temperature to 1450°C at a rate of 5°C/min, and hold it for 30 minutes.

Comparative example 2

This embodiment provides a method for preparing alumina ceramics. The raw materials used in the method are alumina powder, zirconia powder and polyvinyl alcohol. Among them, the purity of alumina powder is 96.5%, and the D50 is 1 micron. The D50 of zirconia powder is 0.1 micron. The polyvinyl alcohol is polyvinyl alcohol 400. The addition amount of zirconia powder is 0.15wt% of alumina powder. The addition amount of polyvinyl alcohol is 5wt% of alumina powder.

The above raw materials were placed in a planetary ball mill for ball milling at a speed of 400 rpm for 40 minutes to obtain a mixture powder.

The mixture powder was placed in a grinding tool for dry pressing, the pressure of the dry pressing was controlled at 10 MPa, and the holding time was 30 s to obtain a ceramic green body.

Put the ceramic body on a ceramic flat plate, then place it in a tube furnace, pass in air, raise the temperature to 300°C at a rate of 5°C/min, and then keep it for 1 hour, then raise the temperature to 1450°C at a rate of 5°C/min, and keep it for 30 minutes.

The table below shows the test results of the mechanical properties and electrical properties of the aluminum oxide flakes prepared in the examples and comparative examples.

Bulk density g/cm ³ Elastic modulus GPa Flexural strength MPa Resistance 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

It can be seen from the above table that after adding alloy powder, the flexural strength of alumina flakes has been significantly improved due to the existence of grain boundary reinforcement. The improvement of the flexural strength also indicates the improvement of the impact resistance and toughness of the alumina flakes. At the same time, due to the higher resistivity of zirconia, zirconia at the grain boundary can significantly increase the resistivity of alumina flakes.

Claims (9)

1. A method for preparing a high-toughness alumina flake, which is characterized by comprising 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;

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 final product;

the addition amount of the aluminum nickel zirconium alloy powder is 1.5-2wt% of the addition amount of the alumina powder;

the aluminum nickel zirconium alloy powder comprises 5-6wt% of nickel, 4-6wt% of zirconium and the balance of aluminum.

2. The method for producing a high-toughness alumina flake according to claim 1, wherein:

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.

3. The method for producing a high-toughness alumina flake according to claim 1, wherein:

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.

4. The method for producing a high-toughness alumina flake according to claim 1, wherein:

the average grain diameter D50 of the aluminum nickel zirconium alloy powder is 0.1-0.2 mu m.

5. The method for producing a high-toughness alumina flake according to claim 1, wherein:

the heat preservation time is 30-60min.

6. The method for producing a high-toughness alumina flake according to claim 1, wherein:

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.

7. The method for producing an alumina flake according to claim 1, wherein:

the inert atmosphere comprises argon or helium;

the oxidizing atmosphere comprises air.

8. The method for producing a high-toughness alumina flake according to claim 1, wherein:

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.

9. The method for producing a high-toughness alumina flake according to claim 1, wherein:

the volume density of the alumina flake is greater than or equal to 3.75g/cm ³ ；

The elastic modulus of the alumina flake is more than or equal to 320GPa;

the flexural strength of the alumina flake is more than or equal to 370MPa;

the volume resistivity of the alumina flake is greater than or equal to 1.0X10 ¹⁴ Ω.cm。