Compact pure-phase lanthanum zirconate ceramic with low thermal conductivity and high strength, and preparation method thereof

Abstract

The invention discloses compact pure-phase lanthanum zirconate ceramic with low thermal conductivity and high strength, and a preparation method thereof. A chemical formula of the lanthanum zirconate ceramic is La2Zr2O7, the compactness is greater than 85%, the compression strength is 310-500MPa, the thermal conductivity and the thermal diffusion coefficient at normal temperature respectively are 1.55-1.79W / (m.K) and (0.90-0.76)*10<-6>m<2> / s; the thermal conductivity and the thermal diffusion coefficient at the temperature of 1200 DEG C respectively are 0.75-0.94W / (m.K) and (0.35-0.45)*10<-6>m<2> / s; the breaking tenacity is 1.45-1.70MPa. The lanthanum zirconate ceramic prepared according to the lanthanum zirconate ceramic preparation method provided by the invention has the advantages of low thermal conductivity, high melting point, good inoxidizability, excellent mechanical property, good high temperature-phase stability and the like, and the requirements of hypersonic velocity aerospace vehicles on the performances of high-strength thermal insulation ceramic materials can be met.

Description

technical field

[0001] The invention relates to the technical field of ceramic materials, in particular to a low-thermal-conductivity, high-strength dense pure-phase lanthanum zirconate ceramic and a preparation method thereof. Background technique

[0002] With the continuous development of aerospace technology, when the aircraft is in working condition, the heat generated by aerodynamics will cause more and more serious heating effects on the airframe. For example, the temperature at the leading edge of the wing or empennage is as high as 1455°C. There will be a large temperature gradient in the thickness direction of the thermal protection system of the aircraft. Due to the large difference in material properties between the aircraft connector and the thermal protection layer, thermal bridges with uneven temperature distribution will occur in different layers. This will lead to a decrease in the stiffness of the airframe structure, and generate thermal stress in the mater...

Examples

preparation example Construction

[0027] Such as figure 1 As shown, the steps of the preparation method of low thermal conductivity, high-strength dense pure-phase lanthanum zirconate ceramics are as follows:

[0028] 1) Mix the aqueous solutions of lanthanum nitrate and zirconium oxychloride with a concentration of 0.1~1mol / L and stir for 0.5~1h to form La 3+ with Zr4+ For the mixed solution with a molar ratio of 1:1, add the mixed solution dropwise to ammonia water at a rate of 10~60ml / min, continue to stir for 0.5~2h after the dropwise addition, and then let it stand for 12~24h. After standing, the supernatant When the pH value of the solution reaches 10~13, the precipitate is washed and separated with deionized water. When the pH value of the supernatant is 7, it is washed and separated with ethanol, and dried at 80~110°C for 12~24h to obtain an amorphous powder ;

[0029] 2) Ball mill the amorphous powder for 1~3h, heat-treat at 400~1100°C for 3~6h, ball mill for 3~8h, and sieve to obtain submicron powd...

Embodiment 1

[0033] 1) Mix the aqueous solutions of lanthanum nitrate and zirconium oxychloride with a concentration of 0.1mol / L and stir for 1 hour to form La 3+ with Zr 4+ For a mixed solution with a molar ratio of 1:1, add the mixed solution dropwise to the ammonia precipitation agent at a rate of 10ml / min, continue stirring for 2 hours after the dropwise addition, and then leave it to age for 24 hours. After standing, the pH value of the supernatant reaches 10~13, wash and separate with deionized water, when the pH value of the supernatant is 7, wash and separate with ethanol, and dry at 80°C for 24 hours to obtain an amorphous powder;

[0034] 2) Ball mill the amorphous powder for 3 hours, heat treatment at 700°C for 5 hours, ball mill for 8 hours, and sieve to obtain submicron powder with an average particle size of 300nm, add 8% polyvinyl alcohol solution of submicron powder mass to granulate , the mass percentage of polyvinyl alcohol in the polyvinyl alcohol solution is 5%, and it...

Embodiment 2

[0039] 1) Mix aqueous solutions of lanthanum nitrate and zirconium oxychloride with a concentration of 0.3 mol / L and stir for 1 hour to form La 3+ with Zr 4+ For a mixed solution with a molar ratio of 1:1, add the mixed solution dropwise to the ammonia water precipitant at a rate of 20ml / min, continue to stir for 1.5h after the dropwise addition, and then leave it to age for 20h. After standing, the pH value of the supernatant is reach 10~13, wash and separate with deionized water, when the pH value of the supernatant is 7, wash and separate with ethanol, and dry at 100°C for 12 hours to obtain an amorphous powder;

[0040] 2) The amorphous powder was ball milled for 2.5 hours, heat treated at 900°C for 4 hours, ball milled for 6 hours, and sieved to obtain a submicron powder with an average particle size of 400nm. Add 7% polyvinyl alcohol solution of submicron powder mass to make Granules, dried at 90°C until the amount of polyvinyl alcohol solution accounted for 2.5% of the...

technical field

[0001] The invention relates to the technical field of ceramic materials, in particular to a low-thermal-conductivity, high-strength dense pure-phase lanthanum zirconate ceramic and a preparation method thereof. Background technique

[0002] With the continuous development of aerospace technology, when the aircraft is in working condition, the heat generated by aerodynamics will cause more and more serious heating effects on the airframe. For example, the temperature at the leading edge of the wing or empennage is as high as 1455°C. There will be a large temperature gradient in the thickness direction of the thermal protection system of the aircraft. Due to the large difference in material properties between the aircraft connector and the thermal protection layer, thermal bridges with uneven temperature distribution will occur in different layers. This will lead to a decrease in the stiffness of the airframe structure, and generate thermal stress in the mater...

Examples

preparation example Construction

[0027] Such as figure 1 As shown, the steps of the preparation method of low thermal conductivity, high-strength dense pure-phase lanthanum zirconate ceramics are as follows:

[0028] 1) Mix the aqueous solutions of lanthanum nitrate and zirconium oxychloride with a concentration of 0.1~1mol / L and stir for 0.5~1h to form La 3+ with Zr4+ For the mixed solution with a molar ratio of 1:1, add the mixed solution dropwise to ammonia water at a rate of 10~60ml / min, continue to stir for 0.5~2h after the dropwise addition, and then let it stand for 12~24h. After standing, the supernatant When the pH value of the solution reaches 10~13, the precipitate is washed and separated with deionized water. When the pH value of the supernatant is 7, it is washed and separated with ethanol, and dried at 80~110°C for 12~24h to obtain an amorphous powder ;

[0029] 2) Ball mill the amorphous powder for 1~3h, heat-treat at 400~1100°C for 3~6h, ball mill for 3~8h, and sieve to obtain submicron powd...

Embodiment 1

[0033] 1) Mix the aqueous solutions of lanthanum nitrate and zirconium oxychloride with a concentration of 0.1mol / L and stir for 1 hour to form La 3+ with Zr 4+ For a mixed solution with a molar ratio of 1:1, add the mixed solution dropwise to the ammonia precipitation agent at a rate of 10ml / min, continue stirring for 2 hours after the dropwise addition, and then leave it to age for 24 hours. After standing, the pH value of the supernatant reaches 10~13, wash and separate with deionized water, when the pH value of the supernatant is 7, wash and separate with ethanol, and dry at 80°C for 24 hours to obtain an amorphous powder;

[0034] 2) Ball mill the amorphous powder for 3 hours, heat treatment at 700°C for 5 hours, ball mill for 8 hours, and sieve to obtain submicron powder with an average particle size of 300nm, add 8% polyvinyl alcohol solution of submicron powder mass to granulate , the mass percentage of polyvinyl alcohol in the polyvinyl alcohol solution is 5%, and it...

Embodiment 2

[0039] 1) Mix aqueous solutions of lanthanum nitrate and zirconium oxychloride with a concentration of 0.3 mol / L and stir for 1 hour to form La 3+ with Zr 4+ For a mixed solution with a molar ratio of 1:1, add the mixed solution dropwise to the ammonia water precipitant at a rate of 20ml / min, continue to stir for 1.5h after the dropwise addition, and then leave it to age for 20h. After standing, the pH value of the supernatant is reach 10~13, wash and separate with deionized water, when the pH value of the supernatant is 7, wash and separate with ethanol, and dry at 100°C for 12 hours to obtain an amorphous powder;

[0040] 2) The amorphous powder was ball milled for 2.5 hours, heat treated at 900°C for 4 hours, ball milled for 6 hours, and sieved to obtain a submicron powder with an average particle size of 400nm. Add 7% polyvinyl alcohol solution of submicron powder mass to make Granules, dried at 90°C until the amount of polyvinyl alcohol solution accounted for 2.5% of the...

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