CN116003125B - Preparation method of zirconia ceramic material for automobile exhaust sensor - Google Patents

Abstract

A preparation method of a zirconia ceramic material for an automobile exhaust sensor comprises the steps of adding a montmorillonite-chitosan compound into yttria-stabilized zirconia powder, ball milling, and then carrying out sectional calcination, wherein the sectional calcination is divided into three sections of sequentially increasing temperatures for calcination, the first section of temperature is 400-450 ℃, the calcination time is 50-70min, the second section of temperature is 550-650 ℃, the calcination time is 30-60min, the third section of temperature is 850-900 ℃, and the calcination time is 5-7h. According to the invention, the zirconia ceramic material is prepared by adding the montmorillonite-chitosan composite, so that the conductivity of the zirconia ceramic material is improved, the conductivity stability under high temperature change is excellent, the temperature change is effectively adapted, the conductivity of the zirconia ceramic material is kept at 93.75% of the initial conductivity of 0.033S/cm after the zirconia ceramic material is recycled 20000 times, the zirconia ceramic material has excellent circulation stability, and long-time stable operation under a high-temperature environment can be ensured.

Description

A preparation method of zirconia ceramic material for automobile exhaust gas sensor

technical field

The invention relates to the technical field of sensing material preparation, in particular to a preparation method of a zirconia ceramic material used for an automobile exhaust sensor.

Background technique

Oxygen sensor is a measurement element that uses zirconia ceramic sensitive elements to measure the oxygen potential in various heating furnaces or exhaust pipes, and calculates the corresponding oxygen concentration based on the principle of chemical balance, so as to monitor and control the air-fuel ratio of the combustion process, and ensure product quality and exhaust emissions. It is widely used in the atmosphere control of various combustion processes such as coal combustion, oil combustion, and gas combustion. In terms of automotive sensor applications, yttria-stabilized zirconia is very common. Oxygen sensors can only fully reflect their characteristics at high temperatures (above 300°C) and output voltage. At about 800°C, they respond fastest to changes in mixed gases. Therefore, zirconia sensors are effectively used in measuring gasoline vehicle emissions. It is currently the best way to measure the combustion atmosphere, and has the advantages of simple structure, quick response, easy maintenance, and convenient use.

However, the zirconia sensor has a short lifespan. For yttria-stabilized zirconia, due to the high operating temperature of the oxygen sensor, zirconia cannot adapt to temperature changes and long-term work in a high-temperature environment. As the temperature changes, its conductivity will also change, and the stability is poor, which affects the sensitivity and accuracy of the sensor. In addition, in the process of repeated cycles, as the number of cycles increases, its electrical conductivity decreases, resulting in attenuation of its life.

Therefore, it is extremely important for oxygen sensors to ensure that the conductivity of zirconia is stable and does not change under high temperature changes. At the same time, the conductivity is stable and does not decay under multiple cycles of work.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a zirconia ceramic material used in an automobile exhaust sensor. The prepared zirconia ceramic material has excellent conductivity stability as the temperature changes and the number of cycles increases.

The object of the invention is achieved through the following technical solutions:

A method for preparing a zirconia ceramic material for an automobile exhaust sensor, characterized in that: adding a montmorillonite-chitosan compound to yttria-stabilized zirconia, and performing segmental calcination after ball milling, the segmental calcination is divided into three stages for calcination at successively increasing temperatures, wherein the temperature of the first stage is 400-450°C, the calcination time is 50-70min, the temperature of the second stage is 550-650°C, the calcination time is 30-60min, and the temperature of the third stage is 850-90°C 0°C, the calcination time is 5-7h.

Further, the temperature in the first stage is raised at 5-8°C/min, the temperature in the second stage is raised at 4-6°C/min, and the temperature in the third stage is raised at 5-8°C/min.

Further, the mass ratio of the montmorillonite-chitosan composite to the yttria-stabilized zirconia is 3-8:75-85.

Further, the ball milling speed of the ball mill is 300-400rpm, and the ball milling time is 15-18h.

Further, the montmorillonite-chitosan composite is prepared by adding deionized water to the montmorillonite powder prepared by montmorillonite pretreatment to prepare a montmorillonite suspension, adding dilute hydrochloric acid to the chitosan to obtain a chitosan solution, adding the montmorillonite suspension to it, stirring and raising the temperature to 90-100° C., keeping the temperature for 10-12 hours, then centrifuging to collect solids, washing and drying, crushing and sieving to obtain the montmorillonite-chitosan composite.

Further, the mass ratio of the montmorillonite suspension to the chitosan solution is 1:0.2-0.4.

Further, the mass ratio of chitosan and dilute hydrochloric acid in the chitosan solution is 1:120-150, stirred and dissolved at 80-100 rpm, and the mass fraction of dilute hydrochloric acid is 5%.

Further, the above-mentioned centrifugal speed is 10000-20000rpm.

Further, the drying temperature is 100-110° C., and the drying time is 15-18 hours.

Further, the montmorillonite powder is obtained by adding deionized water in two steps after drying the crushed and sieved montmorillonite, then adding EDTA-2Na and NaHCO ₃ , stirring and standing still to obtain a suspension, adding edible salt, centrifuging to collect the precipitate after standing, washing and drying the precipitate, then ball milling, adding dilute hydrochloric acid, drying in a water bath to obtain montmorillonite powder.

Further, the mass ratio of the precipitate after ball milling to the dilute hydrochloric acid is 1:30-40, and the mass fraction of the dilute hydrochloric acid is 5%.

Further, the two-step addition of deionized water is to add deionized water to montmorillonite, soak for 36-40h, then stir at 150-200rpm for 20-30h, and then add deionized water, wherein the mass ratio of montmorillonite and deionized water added twice is 1:20-30:200-250.

Further, the mass ratio of the montmorillonite, EDTA-2Na and NaHCO ₃ is 1:0.05-0.08:0.12-0.15.

Further, the edible salt is 10-15% of the mass of the suspension.

Further, the crushing and sieving montmorillonite drying is to crush the montmorillonite through a 100-mesh sieve, and then dry it at 90-100° C. for 24-36 hours.

Further, the yttria-stabilized zirconia is obtained by mixing zirconium oxychloride (ZrOCl ₂ .8H ₂ O) and yttrium nitrate (Y(NO ₃ ) ₃ ) and dissolving them in deionized water, then adding polyethylene glycol 200, raising the temperature to 40-50°C, adding hydrochloric acid within 5-8 minutes to adjust the pH to 2.0-3.5, and then adding sodium hydroxide to adjust the pH to 9.5-10.0, and standing to form a gel. Calcined at 0°C for 2-3h.

Further, the mass ratio of ZrOCl ₂ .8H ₂ O, Y(NO ₃ ) ₃ , polyethylene glycol 200 and deionized water is: 2.48:0.054:0.027:7.8.

Further, the volume fraction of the hydrochloric acid is 5-8%, and the concentration of the sodium hydroxide is 0.5mol/L.

Most specifically, a method for preparing a zirconia ceramic material used for an automobile exhaust sensor, is characterized in that the steps are as follows:

Step 1: Preparation of yttria stabilized zirconia

Zirconium oxychloride (ZrOCl₂.8H₂O) and yttrium nitrate (Y(NO₃)₃) mixed with deionized water, stirred for 10-15min, then added polyethylene glycol 200, heated to 40-50°C, added hydrochloric acid with a volume fraction of 5-8% within 5-8min to adjust the pH to 2.0-3.5, then added sodium hydroxide with a concentration of 0.5mol/L to adjust the pH to 9.5-10.0, and stood for 8-12h to form a gel. Dried at ~80°C for 2-3 hours, then calcined at 450-500°C for 2-3 hours to obtain yttria-stabilized zirconia, ZrOCl₂.8H₂O, Y (NO₃)₃, The mass ratio of polyethylene glycol 200 to deionized water is: 2.48:0.054:0.027:7.8;

Step 2: Prepare montmorillonite-chitosan composite material

(1) Pretreatment of montmorillonite

Dry the montmorillonite crushed through a 100-mesh sieve at 90-100°C for 24-36h, add deionized water to soak for 36-40h at 150-200rpm, then add deionized water, EDTA-2Na and NaHCO in sequence₃, wherein the mass ratio of montmorillonite and twice added deionized water is 1:20-30:200-250, montmorillonite, EDTA-2Na and NaHCO₃The mass ratio of the solution is 1:0.05-0.08:0.12-0.15, stirred and left still to obtain a suspension, adding edible salt, which is 10-15% of the mass of the suspension, centrifuged at 8000-10000rpm after standing for 1-2h to collect the precipitate, repeated washing of the precipitate with deionized water 3-5 times, and then dried at 90-100°C until the water content is lower than 0.2%, then ball milled, and then added with a mass fraction of 5 % of dilute hydrochloric acid, the mass ratio of the precipitate to the dilute hydrochloric acid is 1:30-40, put it in a water bath at 85-90° C., stir at 80-100 rpm for 10-12 hours while in the water bath, filter and collect the precipitate after cooling, wash it with deionized water, dry it at a vacuum degree of -0.05 to -0.08 MPa and a drying temperature of 70 to 80° C., and pass through a 200-mesh sieve to obtain montmorillonite powder;

(2) Composite montmorillonite chitosan

Add montmorillonite powder to deionized water, stir at 60-80rpm for 10-15min to form montmorillonite suspension, the mass ratio of montmorillonite powder and deionized water is 1:80-100, add dilute hydrochloric acid with a mass fraction of 5% to chitosan to obtain a chitosan solution, the mass ratio of chitosan to dilute hydrochloric acid is 1:120-150, add montmorillonite suspension to it, stir and heat up to 90-100°C, and keep warm for 10- 12h, the mass ratio of montmorillonite suspension and chitosan solution is 1:0.2～0.4, then centrifuge at 10000-12000rpm to collect the solid, wash 3-5 times with deionized water, dry at 100-110°C for 15-18h, then pulverize and pass through a 200-mesh sieve to obtain the montmorillonite-chitosan composite;

Step 3: Preparation of zirconia ceramic powder

Add montmorillonite-chitosan compound to the yttria-stabilized zirconia prepared in step 1, and perform segmental calcination after ball milling. The segmental calcination is divided into three stages of increasing temperature for calcination, wherein the first stage temperature is raised to 400-450°C at 5-8°C/min, and calcined for 50-70 minutes; the second stage temperature is raised to 550-650°C at 4-6°C/min, and calcined for 30-60 minutes; the third stage temperature is raised at 5-8°C/min Temperature to 850-900°C, calcining for 5-7h, wherein the mass ratio of montmorillonite-chitosan compound to yttria-stabilized zirconia is 3-8:75-85.

In the prior art, the montmorillonite-chitosan composite is usually used as an adsorption material, and its adsorption performance is studied. However, in the present invention, the addition of the montmorillonite-chitosan composite, combined with three-stage heating and calcination treatment, can effectively improve the stability of the zirconia ceramic material, so that the property stability of the zirconia ceramic material is enhanced in a high-temperature working environment, and the deformation is small, thereby improving the stability of its electrical conductivity and other properties under high-temperature changes, and the performance stability of multiple cycles.

The present invention has following technical effect:

In the present invention, the zirconia ceramic material is prepared by adding the montmorillonite-chitosan compound, which improves the electrical conductivity of the zirconia ceramic material, and has excellent electrical conductivity stability under high-temperature changes, and effectively adapts to temperature changes. After 20,000 cycles of use, its electrical conductivity remains at 93.75% of the initial electrical conductivity of 0.033S/cm, has excellent cycle stability, and can ensure long-term stable work in a high-temperature environment.

Description of drawings

Figure 1: Curve of electrical conductivity of zirconia ceramic materials as a function of temperature.

Figure 2: The change curve of electrical conductivity of zirconia ceramic materials after 20,000 cycles.

Detailed ways

The present invention is specifically described below by the examples. It is necessary to point out that the following examples are only used to further illustrate the present invention, and can not be interpreted as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above-mentioned content of the present invention.

Example 1

A preparation method for a zirconia ceramic material used for an automobile exhaust sensor, the steps are as follows:

Step 1: Preparation of yttria stabilized zirconia

Zirconium oxychloride (ZrOCl₂.8H₂O) and yttrium nitrate (Y(NO₃)₃) Mix and add ionic water, stir for 10min, then add polyethylene glycol 200, increase the temperature to 40 ° C, add 5 % hydrochloric acid to pH to 3.5 within 5min, and then add sodium hydroxide with a concentration of 0.5mol/L to adjust pH to 9.5, and static 8h to form gel. PA, dried for 3 hours at 60 ° C, burned 3h at 450 ° C, ZROCL₂.8H₂O, Y (NO₃)₃, The mass ratio of polyethylene glycol 200 to deionized water is: 2.48:0.054:0.027:7.8;

Step 2: Prepare montmorillonite-chitosan composite material

(1) Pretreatment of montmorillonite

Dry the montmorillonite crushed through a 100-mesh sieve at 100°C for 24 hours, add deionized water to soak for 40 hours, and add deionized water, EDTA-2Na and NaHCO in sequence at 200 rpm₃And keep stirring for 15-20h, wherein the mass ratio of montmorillonite and deionized water added twice is 1:30:250, montmorillonite, EDTA-2Na and NaHCO₃The mass ratio of the solution is 1:0.08:0.15. Stir and stand still to obtain a suspension. Add edible salt, which is 15% of the mass of the suspension. After standing for 1 hour, centrifuge at 10,000 rpm to collect the precipitate, wash the precipitate repeatedly with deionized water for 5 times, then dry at 90°C until the water content is lower than 0.2%, then ball mill, and then add dilute hydrochloric acid. The mass ratio of the precipitate to dilute hydrochloric acid is 1:30. Stir at 0 rpm for 10 hours, filter and collect the precipitate after cooling, wash with deionized water, dry at a vacuum degree of -0.05 to -0.08MPa, and a drying temperature of 80°C, and then pass through a 200-mesh sieve to obtain montmorillonite powder;

(2) Composite montmorillonite chitosan

Add montmorillonite powder to deionized water, stir at 60rpm for 15min to form montmorillonite suspension, the mass ratio of montmorillonite powder and deionized water is 1:80, add dilute hydrochloric acid with a mass fraction of 5% to chitosan to obtain chitosan solution, the mass ratio of chitosan to dilute hydrochloric acid is 1:150, add montmorillonite suspension to it, stir and heat up to 90°C, keep warm for 12h, the mass ratio of montmorillonite suspension and chitosan solution is 1:0 .4, then collect the solid by centrifugation at 10000rpm, wash it 5 times with deionized water, dry it at 100°C for 18h, and then pulverize it through a 200-mesh sieve to obtain a montmorillonite-chitosan compound;

Step 3: Preparation of zirconia ceramic powder

Add montmorillonite-chitosan compound to the yttrium oxide-stabilized zirconia prepared in step 1, and perform segmental calcination after ball milling. The segmental calcination is divided into three stages of increasing temperature for calcination, wherein the first stage temperature is raised to 400°C at 5°C/min and calcined for 70 minutes; the second stage temperature is raised to 550°C at 4°C/min and calcined for 60 minutes; the third stage temperature is raised to 900°C at 5°C/min and calcined for 5 hours. The mass ratio of the compound to the yttria-stabilized zirconia is 3:85.

The electrical conductivity of the sensor prepared from the zirconia ceramic material prepared in this example is 0.031S/cm, and the electrical conductivity stability is excellent at 400-900°C. After 20,000 cycles, the electrical conductivity remains basically unchanged, and the electrical conductivity is still maintained at 93.16% of the initial electrical conductivity, which has excellent cycle stability.

Example 2

A preparation method for a zirconia ceramic material used for an automobile exhaust sensor, the steps are as follows:

Step 1: Preparation of yttria stabilized zirconia

Zirconium oxychloride (ZrOCl₂.8H₂O) and yttrium nitrate (Y(NO₃)₃) mixed with deionized water, stirred for 15 minutes, then added polyethylene glycol 200, heated to 50°C, added 8% hydrochloric acid to adjust the pH to 2.0 within 8 minutes, then added 0.5mol/L sodium hydroxide to adjust the pH to 10.0, stood still for 12 hours to form a gel, dried at a vacuum of -0.05 to -0.08MPa, and a temperature of 80°C for 2 hours, and then calcined at 500°C for 2 hours, Zr OCl₂.8H₂O, Y (NO₃)₃, The mass ratio of polyethylene glycol 200 to deionized water is: 2.48:0.054:0.027:7.8;

Step 2: Prepare montmorillonite-chitosan composite material

(1) Pretreatment of montmorillonite

Dry the montmorillonite crushed through a 100-mesh sieve at 90°C for 36 hours, add deionized water to soak for 36 hours, and add deionized water, EDTA-2Na and NaHCO in sequence at 150 rpm₃And keep stirring for 20h, wherein the mass ratio of montmorillonite and deionized water added twice is 1:20:200, montmorillonite, EDTA-2Na and NaHCO₃The mass ratio of the solution is 1:0.05:0.12. Stir and stand still to obtain a suspension. Add edible salt, which is 10% of the mass of the suspension. After standing for 2 hours, centrifuge at 8000rpm and collect the precipitate. Repeat washing the precipitate with deionized water for 3 times, then dry at 100°C until the water content is lower than 0.2%, and then ball mill, then add dilute hydrochloric acid with a mass fraction of 5%. bath, and stirred at 80rpm for 12h at the same time, filtered to collect the precipitate after cooling, washed with deionized water, dried at a vacuum degree of -0.05 to -0.08MPa, and a drying temperature of 70°C, crushed and passed through a 200-mesh sieve to obtain montmorillonite powder;

(2) Composite montmorillonite chitosan

Add montmorillonite powder to deionized water, stir 10min under 80rpm to form montmorillonite suspension, the mass ratio of montmorillonite powder and deionized water is 1:100, add the dilute hydrochloric acid that mass fraction is 5% in chitosan to obtain chitosan solution, the mass ratio of chitosan and dilute hydrochloric acid is 1:150, then add montmorillonite suspension to it, stir and heat up to 100 ℃, insulation 10h, the mass ratio of montmorillonite suspension and chitosan solution is 1:0.2, and then centrifuged at 12000rpm to collect the solid, washed 3 times with deionized water, dried at 110°C for 15h, and then pulverized through a 200-mesh sieve to obtain a montmorillonite-chitosan complex;

Step 3: Preparation of zirconia ceramic powder

Add montmorillonite-chitosan compound to the yttria-stabilized zirconia prepared in Step 1, and perform segmental calcination after ball milling. The segmental calcination is divided into three stages of increasing temperature for calcination, wherein the first stage temperature is raised to 450°C at 8°C/min and calcined for 50 minutes; the second stage temperature is raised to 650°C at 6°C/min and calcined for 30 minutes; the third stage temperature is raised to 850°C at 8°C/min and calcined for 5 hours. The mass ratio of the compound to the yttria-stabilized zirconia is 8:75.

The electrical conductivity of the sensor prepared from the zirconia ceramic material prepared in this example is 0.032S/cm, and has excellent stability at 400-900°C. After 20,000 cycles, the electrical conductivity remains basically unchanged, and the electrical conductivity remains at 92.49% of the initial electrical conductivity, which has excellent cycle stability.

Example 3

A preparation method for a zirconia ceramic material used for an automobile exhaust sensor, the steps are as follows:

Step 1: Preparation of yttria stabilized zirconia

Zirconium oxychloride (ZrOCl₂.8H₂O) and yttrium nitrate (Y(NO₃)₃) mixed with deionized water, stirred for 12 minutes, then added polyethylene glycol 200, heated to 45°C, added hydrochloric acid with a volume fraction of 6% within 5-8 minutes to adjust the pH to 3.0, then added sodium hydroxide with a concentration of 0.5mol/L to adjust the pH to 9.8, left to stand for 10 hours to form a gel, dried at a vacuum of -0.05 to -0.08MPa, and a temperature of 70°C for 2.5 hours, and then calcined at 480°C for 2.5 hours. 5h, ZrOCl₂.8H₂O, Y (NO₃)₃, The mass ratio of polyethylene glycol 200 to deionized water is: 2.48:0.054:0.027:7.8;

Step 2: Prepare montmorillonite-chitosan composite material

(1) Pretreatment of montmorillonite

Dry the montmorillonite crushed through a 100-mesh sieve at 95°C for 28 hours, add deionized water to soak for 38 hours, and add deionized water, EDTA-2Na and NaHCO in sequence at 180 rpm₃And keep stirring for 18h, wherein the mass ratio of montmorillonite and deionized water added twice is 1:25:230, montmorillonite, EDTA-2Na and NaHCO₃The mass ratio of the solution is 1:0.06:0.14. Stir and stand still to obtain a suspension, add edible salt, which is 12% of the mass of the suspension, centrifuge at 9000rpm after standing for 1.5h and collect the precipitate, wash the precipitate repeatedly with deionized water 4 times, then dry at 95°C until the water content is lower than 0.2%, then ball mill, then add dilute hydrochloric acid with a mass fraction of 5%. The mass ratio of the precipitate and dilute hydrochloric acid is 1:35, and the Water bath, stirring at 90rpm for 11h at the same time, after cooling, filter to collect the precipitate, wash with deionized water, dry at a vacuum degree of -0.05～-0.08MPa, and a drying temperature of 75°C, and after crushing, pass through a 200-mesh sieve to obtain montmorillonite powder;

(2) Composite montmorillonite chitosan

Add montmorillonite powder to deionized water, stir at 70rpm for 12min to form montmorillonite suspension, the mass ratio of montmorillonite powder and deionized water is 1:90, add mass fraction in chitosan and be 5% dilute hydrochloric acid to obtain chitosan solution, the mass ratio of chitosan and dilute hydrochloric acid is 1:130, then add montmorillonite suspension to it, stir and heat up to 95 ° C, insulation 11h, the mass ratio of montmorillonite suspension and chitosan solution is 1: 0.3, and then centrifuged at 11000rpm to collect the solid, washed 4 times with deionized water, dried at 105°C for 16h, and then pulverized through a 200-mesh sieve to obtain a montmorillonite-chitosan complex;

Step 3: Preparation of zirconia ceramic powder

Add montmorillonite-chitosan compound to the yttrium oxide-stabilized zirconia prepared in step 1, and perform segmental calcination after ball milling. The segmental calcination is divided into three stages of increasing temperature for calcination, wherein the temperature of the first stage is raised to 420°C at 6°C/min and calcined for 60 minutes; the temperature of the second stage is raised to 600°C at 5°C/min and calcined for 50 minutes; the temperature of the third stage is raised to 880°C at 6°C/min and calcined for 6 hours. The mass ratio of the compound to the yttria-stabilized zirconia is 5:80.

Comparative example 1:

The difference from Example 3 is that after the preparation of yttria-stabilized zirconia in Step 1, the three-stage heating and calcination treatment in Step 3 is directly carried out, that is, no montmorillonite-chitosan compound is added. All the other steps and parameters are consistent with Example 3.

Comparative example 2:

Compared with Example 3, Step 3 adopts one-stage temperature calcination treatment, specifically calcination at 850-900° C. for 10 h, and obtains zirconia ceramic powder after cooling.

Performance Testing:

The zirconia ceramic powders prepared in Example 3, Comparative Example 1 and Comparative Example 2 were processed into electrodes, and performance tests were performed. details as follows:

Remove zirconia ceramic powder, add PVA solution with a mass fraction of 25%, prepare granules, pass through a 200-mesh sieve, the mass ratio of zirconia powder to PVA is 1:0.2; press it into a green sheet at 25MPa, the pressing density is 3.6g/cm2; sinter the green sheet, and use screen printing to form an electrode.

(1) The electrodes prepared from the zirconia ceramic powders prepared in Example 3, Comparative Example 1 and Comparative Example 2 were tested for conductivity at 300-900°C, and the changes in conductivity were recorded every 100°C. The experimental results are shown in Table 1.

Table 1: Changes in conductivity at different temperatures

From the above results and Figure 1, it can be seen that at different temperatures, the zirconia ceramic materials prepared by the present invention have higher electrical conductivity and excellent stability, while the zirconia ceramic materials prepared in Comparative Example 1 and Comparative Example 2 have lower initial electrical conductivity, and as the temperature increases, a greater electrical conductivity shows a sharp upward trend, and the temperature stability is poor.

(2) The electrode prepared by the zirconia ceramic material prepared in Example 3, Comparative Example 1 and Comparative Example 2 was recycled at 800°C for 20,000 times, and the change in conductivity was shown in Figure 2. It can be seen that the electrical conductivity of the sensor prepared by the present invention prepared by the zirconia ceramic material remained basically unchanged after 20,000 cycles, and the electrical conductivity was still maintained at 93.75% of the initial electrical conductivity, which had excellent cycle stability; All of them showed obvious attenuation. After 20,000 cycles, the conductivity was 26.7% and 26.3% of the initial value respectively, and the cycle stability was poor.

Claims (7)

1. A preparation method for a zirconia ceramic material for an automobile exhaust sensor, characterized in that: add montmorillonite-chitosan compound in yttria-stabilized zirconia, carry out segmental calcination after ball milling, and the segmental calcination is divided into three sections and calcined at successively increasing temperatures, wherein the first section temperature is 400-450°C, the calcination time is 50-70min, the second section temperature is 550-650°C, the calcination time is 30-60min, and the third section temperature is 850°C -900°C, the calcination time is 5-7h, the mass ratio of the montmorillonite-chitosan compound to yttria-stabilized zirconia is 3-8:75-85, the montmorillonite-chitosan compound is prepared by adding deionized water to the montmorillonite powder prepared by montmorillonite pretreatment to prepare a montmorillonite suspension, adding dilute hydrochloric acid to the chitosan to obtain a chitosan solution, adding the montmorillonite suspension, stirring to raise the temperature to 90-100°C, and keeping the temperature for 10-12h. Then the solid is collected by centrifugation, washed and dried, and then crushed and sieved to obtain the montmorillonite-chitosan compound; the montmorillonite powder is dried by adding deionized water in two steps after the crushed and sieved montmorillonite, and then adding EDTA-2Na and NaHCO₃, stir and stand still to obtain a suspension, add edible salt, centrifuge to collect the precipitate after standing, wash and dry the precipitate, then ball mill, add dilute hydrochloric acid, and dry to obtain montmorillonite powder after water bath treatment; the two steps of adding deionized water are adding deionized water to the montmorillonite, soaking for 36-40h, then stirring at 150-200rpm for 20-30h, and then adding deionized water, wherein the mass ratio of montmorillonite to twice deionized water is 1:20-30:200- 250. 2. a kind of preparation method for the zirconia ceramic material of automobile exhaust gas sensor as claimed in claim 1, is characterized in that: in described chitosan solution, the mass ratio of chitosan and dilute hydrochloric acid is 1:120-150, stirring and dissolving under 80-100rpm, the massfraction of dilute hydrochloric acid is 5%. 3. a kind of preparation method for the zirconia ceramic material of automobile exhaust gas sensor as claimed in claim 1 or 2, is characterized in that: the mass ratio of described montmorillonite, EDTA-2Na and _NaHCO3 is 1:0.05-0.08:0.12-0.15. 4. A method for preparing a zirconia ceramic material for an automobile exhaust sensor as claimed in claim 3, wherein the edible salt is 10-15% of the mass of the suspension. 5. The preparation method of a zirconia ceramic material used for automobile exhaust gas sensors as claimed in claim 4, characterized in that: the yttria-stabilized zirconia is mixed with ZrOCl ₂ 8H ₂ O and Y(NO ₃ ) ₃ , then added polyethylene glycol 200, heated to 40-50°C, added hydrochloric acid within 5-8min to adjust the pH to 2.0-3.5, then added sodium hydroxide to adjust the pH to 9.5-10.0, left to form a gel, and dried Then calcined at 450-500°C for 2-3h. 6. A method for preparing a zirconia ceramic material for an automobile exhaust gas sensor as claimed in claim 5, wherein the mass ratio of said ZrOCl ₂ .8H ₂ O, Y(NO ₃ ) ₃ , polyethylene glycol 200 and deionized water is: 2.48:0.054:0.027:7.8. 7. A preparation method for a zirconia ceramic material for an automobile exhaust sensor, characterized in that, proceed as follows: Step 1: Preparation of yttria stabilized zirconia Using ZrOCl₂·8H₂O and Y (NO₃)₃Mix and add deionized water, stir for 10-15min, then add polyethylene glycol 200, heat up to 40-50°C, add hydrochloric acid with a volume fraction of 5-8% within 5-8min to adjust the pH to 2.0-3.5, then add sodium hydroxide with a concentration of 0.5mol/L to adjust the pH to 9.5-10.0, and let it stand for 8-12h to form a gel. Dry at 80°C for 2-3 hours, then calcinate at 450-500°C for 2-3h, ZrOCl₂·8H₂O, Y (NO₃)₃, The mass ratio of polyethylene glycol 200 to deionized water is: 2.48:0.054:0.027:7.8; Step 2: Prepare montmorillonite-chitosan composite material (1) Pretreatment of montmorillonite Dry the montmorillonite crushed through a 100-mesh sieve at 90-100°C for 24-36 hours, add deionized water to soak for 36-40 hours, and add deionized water, EDTA-2Na and NaHCO in sequence at 150-200rpm₃And keep stirring for 15-20h, wherein the mass ratio of montmorillonite and deionized water added twice is 1:20-30:200-250, montmorillonite, EDTA-2Na and NaHCO₃The mass ratio of the mixture is 1:0.05-0.08:0.12-0.15, stirred and left still to obtain a suspension, adding edible salt, which is 10-15% of the mass of the suspension, centrifuged at 8000-10000rpm after standing for 1-2h to collect the precipitate, repeatedly washed the precipitate with deionized water for 3-5 times, then dried at 90-100°C until the water content is lower than 0.2%, then ball milled, and then added dilute hydrochloric acid, The mass ratio of chitosan and hydrochloric acid is 1:30-40, in a water bath at 85-90°C, stirring at 80-100rpm while in the water bath for 10-12h, after cooling, filter and collect the precipitate, wash with deionized water, dry at a vacuum degree of -0.05～-0.08MPa, and a drying temperature of 70～80°C, and pass through a 200-mesh sieve to obtain montmorillonite powder; (2) Composite montmorillonite chitosan Add montmorillonite powder to deionized water, stir at 60-80rpm for 10-15min to form montmorillonite suspension, the mass ratio of montmorillonite powder and deionized water is 1:80-100, add dilute hydrochloric acid with a mass fraction of 5% to chitosan to obtain a chitosan solution, the mass ratio of chitosan to dilute hydrochloric acid is 1:120-150, add montmorillonite suspension to it, stir and heat up to 90-100°C, and keep warm for 10- 12h, the mass ratio of montmorillonite suspension and chitosan solution is 1:0.2～0.4, then centrifuge at 10000-12000rpm to collect the solid, wash 3-5 times with deionized water, dry at 100-110°C for 15-18h, then pulverize and pass through a 200-mesh sieve to obtain the montmorillonite-chitosan composite; Step 3: Preparation of zirconia ceramic powder Add montmorillonite-chitosan compound to the yttria-stabilized zirconia prepared in step 1, and perform segmental calcination after ball milling. The segmental calcination is divided into three stages of successively increasing temperatures for calcination, wherein the first stage temperature is 400-450°C, calcined for 50-70min, the second stage temperature is 550-650°C, calcined for 30-60min, and the third stage temperature is 850-900°C, calcined for 5-7h, wherein the montmorillonite-chitosan composite and The mass ratio of yttria-stabilized zirconia is 3-8:75-85.