High-reflection low-thermal-conductivity ceramic material and preparation method thereof

Abstract

The invention relates to the technical field of inorganic non-metallic materials, and discloses a high-reflection low-thermal-conductivity ceramic material and a preparation method thereof, the high-reflection low-thermal-conductivity ceramic material has a chemical formula of La < 0.9 > Sr < 0.1 > Ti < 1-x > Nb < x > O < 3 + delta >, and x is 0.1-0.15. According to the preparation method, the La0. 9Sr0. 1Ti1-xNbxO3 + delta ceramic powder is directly pressed and sintered to prepare the block, and compared with powder obtained after mixing and drying, the condition of element segregation is effectively avoided, and the solid solution effect is better; the average reflectivity of the La < 0.9 > Sr < 0.1 > Ti < 1-x > Nb < x > O < 3 + delta > ceramic material in a visible light-near infrared band is as high as 94%.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic materials, and in particular to a ceramic material with high reflection and low thermal conductivity and a preparation method thereof. Background Art

[0002] Heat transfer occurs in three ways: conduction, convection, and radiation. In industrial heating scenarios such as high-temperature heat treatment and industrial metallurgical furnaces, infrared radiation is the primary form of heat transfer, typically accounting for over 70%. However, industrial insulation materials such as rock wool and fiberglass have low thermal conductivity and achieve insulation and cooling by preventing heat conduction. However, these materials cannot reflect energy in the near-infrared band and also have prominent issues such as thick insulation layers, uneven temperature fields, and low space utilization. These issues make it difficult to meet the urgent demand for more heat-resistant and efficient insulation materials in the high-temperature industrial sector, severely restricting the upgrading of related technologies and industrial equipment.

[0003] Perovskite structure La 0.9 Sr 0.1 TiO 3+δ (abbreviated as LST) ceramic material has excellent reflective performance in the infrared band. However, during the thermal spraying process of LST ceramic material, a large number of oxygen vacancies will be generated, which will reduce the reflectivity of the coating in the infrared band, affecting the application of LST material in the field of thermal protection coating. In the prior art, by doping a certain amount of niobium into the LST material, the oxygen vacancy content can be reduced and the reflectivity of the material can be improved; for example, the Chinese invention patent with publication number CN111517790A discloses "A La 0.9 Sr 0.1 Ti 0.75 Nb 0.25 O 3+δ "Block Material and Its Preparation Method" [1], by doping LSTO with a certain amount of niobium, can reduce the oxygen vacancy content and increase the near-infrared reflectivity to 92%. However, this invention patent is applied to the insulation of new environmentally friendly buildings at lower temperatures, but has not been applied to industrial heating scenarios with higher operating temperatures.

[0004] Therefore, there is an urgent need for a high-reflectivity, low-thermal-conductivity ceramic material and a preparation method thereof to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to overcome the existing technical problems and provide a ceramic material with high reflectivity and low thermal conductivity and a preparation method thereof, mainly by optimizing the addition amount of doping elements to change its crystal structure and microstructure, so that it has a new type of ceramic material with high reflectivity and low thermal conductivity at high temperatures.

[0006] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0007] A ceramic material with high reflection and low thermal conductivity, wherein the chemical formula of the ceramic material with high reflection and low thermal conductivity is La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ , where x is 0.1 to 0.15.

[0008] Preferably, the value of x is one of 0.1, 0.125, and 0.15.

[0009] The present invention also includes a method for preparing a ceramic material with high reflectivity and low thermal conductivity, comprising the following steps:

[0010] S1, according to the chemical formula La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ Weigh lanthanum oxide, titanium dioxide, strontium carbonate, and niobium pentoxide as raw materials in a stoichiometric ratio; place grinding balls, raw materials, and anhydrous ethanol into a ball milling jar for ball milling to obtain a ball milling slurry;

[0011] S2, rotary evaporating the ball mill slurry and drying it to obtain a dried powder;

[0012] S3, sintering, grinding and sieving the dried powder to obtain La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ Ceramic powder materials;

[0013] S4, La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ Ceramic powder material is pressed into green body and then sintered to obtain La 0.9 Sr 0.1 Ti 1- x Nb x O 3+δ Ceramic bulk material.

[0014] Preferably, in step S1, the ball milling speed is 500 rpm, the ball milling time is 18 h, and the mass ratio of grinding balls: raw materials: anhydrous ethanol is 3:1:1.

[0015] Specifically, step S1 includes the following steps:

[0016] S1, lanthanum oxide (La2O3), titanium dioxide (TiO2), strontium carbonate (SrCO3) and niobium pentoxide (Nb2O5) are mixed according to the chemical formula La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ The raw materials are weighed in a stoichiometric ratio to obtain raw materials; the raw materials are added into a ball mill jar, and then anhydrous ethanol and zirconium oxide grinding balls are added to obtain a uniformly mixed ball mill slurry.

[0017] Preferably, in step S2, the rotary evaporation temperature is 80° C., the drying temperature is 150° C., and the drying time is 10 to 24 hours.

[0018] Specifically, step S2 includes the following steps:

[0019] S2, transferring the ball mill slurry to a rotary evaporator for rotary evaporation to remove ethanol, and then drying to obtain a uniformly mixed dried powder.

[0020] Preferably, in step S3, the sintering process is as follows: keeping the sintering temperature at 1400° C. for 6 hours, and then cooling with the furnace.

[0021] Preferably, in step S4, the process of pressing the green body is as follows: the green body is pressed by a cold isostatic press, and the pressing pressure is maintained at 250 MPa for 10 minutes.

[0022] Preferably, in step S4, the sintering process is as follows: the temperature is increased from room temperature to 1000°C at a heating rate of 10°C / min, then the temperature is increased from 1000°C to 1500°C at a heating rate of 5°C / min, and finally the temperature is increased to 1600°C at a heating rate of 1°C / min, and kept at 1600°C for 10 hours.

[0023] Specifically, step S4 includes the following steps:

[0024] S4, La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ The ceramic powder material is placed in a rubber sleeve and pressed into a green body, which is then sintered to obtain La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ Ceramic bulk material.

[0025] Beneficial effects:

[0026] (1) The present invention directly adopts La0.9 Sr 0.1 Ti 1-x Nb x O 3+δ The ceramic powder is pressed and sintered to prepare blocks, which effectively avoids element segregation and has a better solid solution effect than the powder after mixing and drying;

[0027] (2) La prepared by the present invention 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ The ceramic material has an average reflectivity of up to 94% in the visible-near infrared band, and its thermal conductivity is only 0.961 W·(m·K) at a high temperature of 1200°C. -1 The thermal conductivity is much lower than the current thermal protection coating material YSZ (yttria-stabilized zirconia), which is 1.25-1.35 W·(m·K) -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 XRD patterns of ceramic powder materials obtained in Example 1, Example 2, Example 3, and Comparative Example 1 of the present invention;

[0029] Figure 2 These are EDS images of ceramic powder materials obtained in Examples 1, 2, and 3 of the present invention;

[0030] Figure 3 Graphs showing the reflectivity of ceramic block materials obtained in Example 1, Example 2, Example 3, and Comparative Example 1 of the present invention;

[0031] Figure 4 This is a thermal conductivity diagram of the ceramic block materials obtained in Example 1, Example 2, Example 3, and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses industrial purity or conventional purity used in the art.

[0034] The devices used in the present invention are not particularly limited and can be devices commonly used in the art.

[0035] Example 1

[0036] A method for preparing a ceramic material with high reflectivity and low thermal conductivity comprises the following steps:

[0037] (1) La2O3, SrCO3, TiO2, and Nb2O5 were prepared in a molar ratio of 9:2:18:1 and added to a ball mill. Anhydrous ethanol and zirconium oxide grinding balls were then added, with a mass ratio of balls:material:anhydrous ethanol of 3:1:1. The ball mill was placed in a planetary ball mill and milled at a speed of 500 rpm for 18 h to obtain a uniformly mixed slurry.

[0038] (2) The ball mill slurry was transferred to a rotary evaporator to remove ethanol. The rotary evaporator was heated to 80°C. The powder was then placed in a box-type drying furnace and dried at 150°C for 10 h to obtain a uniformly mixed dry powder.

[0039] (3) The dried powder was placed in a sintering furnace and kept at 1400°C for 6 hours. It was then ground and passed through a 300-mesh sieve to obtain La 0.9 Sr 0.1 Ti 0.9 Nb 0.1 O 3+δ Ceramic powder material, referred to as LSTN 0.1 Ceramic powder materials;

[0040] (4) La 0.9 Sr 0.1 Ti 0.9 Nb 0.1 O 3+δ The ceramic powder material was placed in a rubber sleeve with a diameter of 20 mm and pressed into a green body in a cold isostatic press with a pressing pressure of 250 MPa and a holding time of 10 min. It was then placed in a sintering furnace and the temperature was increased from room temperature to 1000 °C at a heating rate of 10 °C / min, then from 1000 °C to 1500 °C at a heating rate of 5 °C / min, and finally to 1600 °C at a heating rate of 1 °C / min, kept at this temperature for 10 h, and cooled in the furnace to obtain La 0.9 Sr 0.1 Ti 0.9 Nb 0.1 O 3+δ Ceramic block material, referred to as LSTN 0.1 Ceramic bulk material.

[0041] Example 2

[0042] The difference between this embodiment and embodiment 1 is that La2O3, SrCO3, TiO2 and Nb2O5 are prepared in a molar ratio of 36:8:70:5; the steps are the same as those in embodiment 1.

[0043] Prepared La 0.9 Sr 0.1 Ti 0.875 Nb0.125 O 3+δ Ceramic powder material, referred to as LSTN 0.125 Ceramic powder material; and La 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ Ceramic block material, referred to as LSTN 0.125 Ceramic bulk material.

[0044] Example 3

[0045] The difference between this embodiment and embodiment 1 is that La2O3, SrCO3, TiO2 and Nb2O5 are prepared in a molar ratio of 18:4:34:3; the steps are the same as those in embodiment 1.

[0046] Prepared La 0.9 Sr 0.1 Ti 0.85 Nb 0.15 O 3+δ Ceramic powder material, referred to as LSTN 0.15 Ceramic powder material; and La 0.9 Sr 0.1 Ti 0.85 Nb 0.15 O 3+δ Ceramic block material, referred to as LSTN 0.15 Ceramic bulk material.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Example 1 is that La2O3, SrCO3 and TiO2 are mixed in a molar ratio of 4.5:1:10; and the steps are the same as those in Example 1.

[0049] Prepared La 0.9 Sr 0.1 TiO 3+δ Ceramic powder material, referred to as LST ceramic powder material; the prepared La 0.9 Sr 0.1 TiO 3+δ Ceramic bulk material, referred to as LST ceramic bulk material.

[0050] like Figure 1 As shown in the XRD patterns of the ceramic powder materials obtained in Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention, LSTN 0.1 The La in Example 1 is shown 0.9 Sr 0.1 Ti 0.9 Nb 0.1 O3+δ Ceramic powder material; LSTN 0.125 The La in Example 2 is shown 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ Ceramic powder material; LSTN 0.15 Indicates La in Example 3 0.9 Sr 0.1 Ti 0.85 Nb 0.15 O 3+δ Ceramic powder material; LST represents La in Comparative Example 1 0.9 Sr 0.1 TiO 3+δ Ceramic powder materials.

[0051] Depend on Figure 1 It can be seen that the ceramic materials prepared in all examples are pure single solid solutions.

[0052] like Figure 2 As shown, it is the EDS graph of the ceramic powder material obtained in Example 1, Example 2, and Example 3 of the present invention; each row of graphs in the figure represents an embodiment; the row of graphs where (a) is located represents the La in Example 1 0.9 Sr 0.1 Ti 0.9 Nb 0.1 O 3+δ Ceramic powder material; the row of graphs in Figure (b) represents the La in Example 2 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ Ceramic powder material; the row of graphs in Figure (c) represents the La in Example 3 0.9 Sr 0.1 Ti 0.85 Nb 0.15 O 3+δ Ceramic powder materials.

[0053] Depend on Figure 2 It can be seen that the elements are evenly distributed and no element is segregated, indicating that a single solid solution is successfully synthesized without producing other impurities.

[0054] like Figure 3 As shown, the reflectivity graph of the ceramic block material obtained in Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention; LSTN 0.1 The La in Example 1 is shown 0.9 Sr 0.1 Ti0.9 Nb 0.1 O 3+δ Ceramic bulk material; LSTN 0.125 The La in Example 2 is shown 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ Ceramic bulk material; LSTN 0.15 Indicates La in Example 3 0.9 Sr 0.1 Ti 0.85 Nb 0.15 O 3+δ Ceramic block material; LST represents La in Comparative Example 1 0.9 Sr 0.1 TiO 3+δ Ceramic bulk material.

[0055] Depend on Figure 3 It can be seen that the LSTN of Example 1 0.1 The average reflectivity in the visible-near infrared band is 92%. 0.125 The average reflectivity of the ceramic powder is up to 94%. 0.15 The average reflectivity of the ceramic powder is 90%, which is significantly higher than the average reflectivity of the LST ceramic powder in Comparative Example 1 (88%).

[0056] like Figure 4 As shown, the thermal conductivity diagram of the ceramic block material obtained in Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention; LSTN 0.1 The La in Example 1 is shown 0.9 Sr 0.1 Ti 0.9 Nb 0.1 O 3+δ Ceramic bulk material; LSTN 0.125 The La in Example 2 is shown 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ Ceramic bulk material; LSTN 0.15 Indicates La in Example 3 0.9 Sr 0.1 Ti 0.85 Nb 0.15 O 3+δ Ceramic block material; LST represents La in Comparative Example 1 0.9 Sr 0.1 TiO 3+δ Ceramic bulk material.

[0057] Depend on Figure 4 It can be seen that the LSTN materials prepared in Examples 1 to 3 0.1 LSTN 0.125 and LSTN 0.15 The thermal conductivity is 0.583~0.961W·(m·K) in the temperature range of 100-1200℃ -1 、0.408~0.848W·(m·K) -1 and 0.754~0.953W·(m·K) -1 Significantly lower than the 0.948-1.221 W·(m·K) of LST in Comparative Example 1 -1 .

[0058] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A ceramic material with high reflectivity and low thermal conductivity, characterized by: The chemical formula of the highly reflective and low thermally conductive ceramic material is La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ , where x is 0.1 to 0.

15.

2. The high-reflection, low-thermal-conductivity ceramic material according to claim 1, characterized in that: x is one of 0.1, 0.125, and 0.

15.

3. A method for preparing a ceramic material with high reflection and low thermal conductivity according to any one of claims 1 or 2, characterized in that: The following steps are involved: S1, according to the chemical formula La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ Weigh lanthanum oxide, titanium dioxide, strontium carbonate, and niobium pentoxide as raw materials in a stoichiometric ratio; place grinding balls, raw materials, and anhydrous ethanol into a ball milling jar for ball milling to obtain a ball milling slurry; S2, rotary evaporating the ball mill slurry and drying it to obtain a dried powder; S3, sintering, grinding and sieving the dried powder to obtain La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ Ceramic powder materials; S4, La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ Ceramic powder material is pressed into green body and then sintered to obtain La 0.9 Sr 0.1 Ti 1-x Nb x O 3+δ Ceramic bulk material.

4. The method for preparing a ceramic material with high reflection and low thermal conductivity according to claim 3, characterized in that: In step S1, the ball milling speed is 500 rpm, the ball milling time is 18 h, and the mass ratio of grinding balls: raw materials: anhydrous ethanol is 3:1:

1.

5. The method for preparing a ceramic material with high reflection and low thermal conductivity according to claim 3, characterized in that: In step S2, the rotary evaporation temperature is 80° C., the drying temperature is 150° C., and the drying time is 10 to 24 hours.

6. The method for preparing a ceramic material with high reflection and low thermal conductivity according to claim 3, characterized in that: In step S3, the sintering process is as follows: the sintering temperature is kept at 1400° C. for 6 hours, and then cooled with the furnace.

7. The method for preparing a ceramic material with high reflection and low thermal conductivity according to claim 3, characterized in that: In step S4, the process of pressing the green body is as follows: the green body is pressed by a cold isostatic press, and the pressing pressure is maintained at 250 MPa for 10 minutes.

8. The method for preparing a ceramic material with high reflection and low thermal conductivity according to claim 3, characterized in that: In step S4, the sintering process is as follows: the temperature is increased from room temperature to 1000°C at a heating rate of 10°C / min, then the temperature is increased from 1000°C to 1500°C at a heating rate of 5°C / min, and finally the temperature is increased to 1600°C at a heating rate of 1°C / min, and the temperature is kept at 1600°C for 10 hours.

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