CN102390935A - Method for preparing strontium titanate film having spherical grain accumulated porous structure - Google Patents

Abstract

The invention belongs to the technical field of functional materials, and in particular relates to a method for preparing a strontium titanate thin film with a spherical particle stacked porous structure. The present invention adopts the sol-gel template method, drops a certain concentration of strontium acetate solution into the tetrabutyl titanate ethanol solution at a speed of (0.25-2) mL/min, and continuously Stir, add non-ionic surfactant 0.5-1.5h after the titration, and continue to stir until a uniform, stable and non-layered strontium titanate sol with a concentration of 0.1-0.5mol L ^-1 is obtained. After aging, use the spin-coating method Or immersion pulling method is used to coat a film on a substrate, and obtain a strontium titanate thin film with spherical particle stacked porous structure after drying and roasting. The method of the invention has the characteristics of simple production process, less investment in equipment, low cost, easy operation and good repeatability, and can obtain a three-dimensional porous film with large specific surface area, uniform distribution of pores and good interpenetration of spherical particles.

Description

A kind of preparation method of spherical particle stacked porous structure strontium titanate thin film

technical field

The invention belongs to the technical field of functional materials, and in particular relates to a method for preparing a strontium titanate thin film with a spherical particle stacked porous structure.

Background technique

SrTiO ₃ series perovskite structure composite metal oxide has the characteristics of metal-like conductivity mechanism and variable valence oxide, and has good oxidation catalytic properties. As a gas-sensing material, especially an oxygen-sensing material, it also has the characteristics of good high temperature stability. , used in gas sensors can quickly and accurately obtain information and send it out in the form of electrical signals to detect and monitor hazardous gases in real time. The gas sensing mechanism is that when the gas molecules to be tested are adsorbed on the surface or inside of the material, it will cause changes in surface charge, surface energy band, surface adsorbed oxygen, and grain boundary barrier, etc., and then transmit them in the form of electrical signals. It can be seen that the gas-sensing performance of the material is a comprehensive reflection of the catalytic performance and electrochemical performance of the material. The sensing performance of the gas-sensing sensor is not only related to the composition of the sensitive material, but also related to the pore structure of the sensitive material. If the sensitive material of the gas sensor is made into a porous structure, the particle size, porosity, pore size and distribution, specific surface area and other factors of the material will directly affect the number of adsorption sites and active sites provided by it, so that it can be greatly improved. The amplitude improves the sensitivity characteristics of the gas sensor. At present, the research on the gas-sensing properties of semiconductor metal oxides mainly focuses on ion doping, surface modification of noble metals and the development of new materials. There are few corresponding studies on dielectric materials. In order to fundamentally solve the problems of current semiconductor metal oxide gas sensors, such as poor selectivity, poor stability, insufficient response recovery, and difficulty in achieving ^10-9 level detection, it is necessary not only to strengthen the development of new gas-sensitive materials At the same time, we should strengthen the research on the preparation of high-efficiency multi-channel structure gas-sensing materials and the optimization design of their structures, so as to promote the development of gas-sensing components to high-efficiency miniature, integrated, multi-functional, and intelligent, and promote the development of multi-channel structure gas sensors. industrialization process.

At present, the methods for preparing _SrTiO3 thin film materials mainly include pulsed laser deposition, molecular beam epitaxy, chemical vapor deposition, sol-gel method, and magnetron sputtering method. Compared with other methods, the sol-gel method has the advantages of The process equipment is simple (no vacuum conditions and equipment required), low synthesis temperature, high purity, accurate chemical composition, uniform film formation, easy doping and large-area coating, etc. common concern of foreign researchers. In recent years, the preparation technology combining the sol-gel method and the host-guest template method has gradually become the main means to realize molecular assembly and synthesis of mesoporous materials, but this method has not been used to prepare perovskite-based composite metal oxides SrTiO ₃ at home and abroad. Research report on porous thin films. When the existing hard template/sol-gel method prepares ordered porous films, there are disadvantages such as difficult template synthesis, complex removal process, high cost, and poor interpenetration between channels, while the traditional soft template/sol-gel method In the preparation of porous films, there are disadvantages such as poor thermal stability, poor uniformity of pore distribution, and easy collapse of the pore structure, which affects the degree of order and the effective use area of the film. Therefore, how to improve its structural stability, thermal stability, three-dimensional pore permeability and increase the effective use area of the film is a key technical problem in this field.

Contents of the invention

Aiming at the gap in the prior art for preparing porous structure strontium titanate thin film, the invention provides a method for preparing spherical particle stacked porous structure strontium titanate thin film with good three-dimensional pore penetration, uniform pore distribution and high effective use area.

The preparation of a kind of strontium titanate film with spherical particle stacked porous structure of the present invention adopts the sol-gel templating agent method, and uses non-ionic surfactant as the pore-forming guiding template agent, and proceeds according to the following steps:

(1) Mix anhydrous ethanol, tetrabutyl titanate and complexing agent continuously in a water bath at 30-40°C and mix evenly, and let stand for 30 minutes to form tetrabutyl titanate ethanol solution;

The complexing agent is diethanolamine or acetylacetone, and the molar ratio between tetrabutyl titanate and complexing agent is 1: (1~5);

(2) The molar ratio of strontium acetate to solvent water is 1: (30~55) and the molar ratio of strontium acetate to tetrabutyl titanate is 1:1 to prepare a strontium acetate solution, and then the strontium acetate solution is mixed with (0.25- 2) Drop into tetrabutyl titanate ethanol solution at the speed of mL/min and (500-1000) rpm stirring condition, add nonionic surfactant 0.5-1.5h after titration, the added nonionic surfactant and The molar ratio of tetrabutyl titanate is (0.005~0.045):1, and then continue to stir to obtain strontium titanate sol, and control the system temperature at 25~40°C during the whole process;

Described nonionic surfactant is polyethylene glycol or nonionic polyacrylamide;

The concentration of the strontium titanate sol is 0.1~0.5mol·L ^-1 ;

(3) The above-mentioned strontium titanate sol is aged at room temperature for 2-12 hours before coating, and the substrate is coated by spin coating or dipping method, and the substrate coated with strontium titanate sol is placed at 80- Dry at 120°C;

The substrate is glass, metal, ceramic or silicon wafer;

The number of coating layers is at least one;

(4) Calcining the dried substrate coated with strontium titanate sol at 550-750° C. for 1-4 hours to finally prepare a strontium titanate porous thin film with spherical particle stacked pore structure.

The beneficial effects of the present invention are:

(1) The present invention overcomes the disadvantages of difficult template synthesis, complex removal process, high cost and poor interpenetration between channels when preparing ordered porous films by the existing hard template/sol-gel method, and overcomes the disadvantages of soft templates at the same time. / When the sol-gel method prepares porous films, the pore distribution uniformity and thermal stability are poor, and the pore structure is easy to collapse, which affects the degree of order and the effective use area of the film;

(2) The perovskite-based composite metal oxide strontium titanate porous film prepared by the method of the present invention has a three-dimensional pore structure packed with spherical particles, has a large specific surface area, uniform distribution of pores, good interpenetration, and easy gas diffusion and transportation. Thereby improving the effective utilization of the specific surface area of the porous film;

(3) The method of the present invention has the characteristics of simple production process, low equipment investment, low cost, low synthesis temperature, easy operation and good repeatability, and can coat a large area on various substrates of different shapes and materials.

Description of drawings

Fig. 1 is the scanning electron microscope picture of the spherical particle stacked strontium titanate porous film that embodiment 1 makes;

Fig. 2 is the scanning electron microscope picture of the spherical particle stacking strontium titanate porous film that embodiment 2 makes;

Fig. 3 is the N of the spherical particle stacked strontium titanate porous film that embodiment ₂ makes Adsorption/desorption isotherm;

Fig. 4 is the BJH desorption pore size distribution curve of the spherical particle stacked strontium titanate porous film prepared in Example 2.

Detailed ways

Example 1

Add 62ml of absolute ethanol, 17.02g of tetrabutyl titanate, and 7.905g of diethanolamine to a 250ml beaker, stir continuously at a water bath temperature of 30°C, and then stand still for 30min to fully complex; under the condition of constant stirring at a speed of 500rpm 27ml of strontium acetate aqueous solution (Sr(CH ₃ COO) ₂ .0.5H ₂ O, 397.6g/L) was added dropwise to the tetrabutyl titanate ethanol solution at a rate of 0.25ml/min, and 30min after the titration , add 1.0g of polyethylene glycol PEG2000, and continue to stir until a uniform and stable transparent strontium titanate sol with a concentration of 0.4mol/L is obtained; the strontium titanate sol is aged at room temperature for 4 hours and then coated by dipping and pulling method. Put the ceramic substrate with a clean surface vertically, dip it into the strontium titanate sol at a constant speed of 6cm/min, let it rest for 20s, then pull the substrate vertically and at a constant speed at a speed of 4cm/min, and put the strontium titanate coated The ceramic substrate of the sol was dried at 80° C. for 2 hours, and then put into a muffle furnace and baked at 650° C. for 3 hours to obtain a strontium titanate thin film with spherical particle stacked porous structure.

Fig. 1 is the scanning electron microscope picture of the spherical particle stacking strontium titanate porous film that embodiment 1 makes, as can be seen from Fig. 1, the strontium titanate film that the present invention prepares is made up of spherical strontium titanate particle and pore, and pore distribution Uniform, forming a three-dimensional through-hole structure.

Example 2

Add 94ml of absolute ethanol, 17.02g of tetrabutyl titanate, and 10.54g of diethanolamine into a 250ml beaker, stir evenly at a water bath temperature of 35°C, and then stand still for 30 minutes to fully complex; under the condition of constant stirring at a speed of 600rpm 36.4ml of strontium acetate aqueous solution (Sr(CH ₃ COO) ₂ .0.5H ₂ O, 294.9g/L) was added dropwise to the tetrabutyl titanate ethanol solution at a rate of 0.5ml/min, and the titration was completed 50min Finally, add 2.0g of polyethylene glycol PEG2000, and continue to stir until a uniform, stable and transparent strontium titanate sol with a concentration of 0.3mol/L is obtained; the strontium titanate sol is aged at room temperature for 8 hours and then carried out by dipping and pulling method. For coating, vertically immerse the clean glass substrate into the strontium titanate sol at a constant speed of 6cm/min, let it rest for 20s, then pull the substrate vertically and uniformly at a speed of 4cm/min, and put the titanium-coated Dry the glass substrate of strontium acid sol at 105°C for 1 hour, repeat the above coating and drying steps, coat the second layer of film, dry the glass substrate coated with two layers of film at 120°C for 4 hours, and then put it into the muffle The furnace was fired at 600° C. for 2.5 hours to finally obtain a strontium titanate thin film with spherical particle stacked porous structure.

Fig. 2 is the scanning electron microscope picture of the spherical particle stacked strontium titanate porous film that embodiment 2 makes, as can be seen from Fig. 2, the strontium titanate film that the present invention prepares is made up of spherical strontium titanate particle and pore, and pore distribution Uniform, forming a three-dimensional penetrating pore structure; Figure 3 is the N adsorption/desorption isotherm of the spherical particle stacked strontium titanate porous film prepared in Example ₂ , and the adsorption/desorption isotherm belongs to Type IV isotherm , there is an obvious hysteresis ring, which is a typical adsorption type of mesoporous porous substances. The hysteresis ring is steep and the adsorption and desorption parts in the ring are almost parallel, indicating that the pore structure is composed of pores with regular shapes. The low pressure point (P/P ₀ =0.27) begins to form until the higher P/P0 position (P/P ₀ =0.985), indicating that the porous film material has a wide pore size distribution and contains a small amount of large Pores; Figure 4 is the BJH desorption pore size distribution curve of the spherical particle stacked strontium titanate porous film prepared in Example 2; the specific surface area of the porous film calculated by BET is 186.37m ² /g. The test results show that the spherical particle stacked strontium titanate porous film prepared by the method of the invention has a large specific surface area, good interpenetration, easy gas diffusion and transportation, and high effective utilization rate of the specific surface area.

Example 3

Add 176ml of absolute ethanol, 17.02g of tetrabutyl titanate, and 15.81g of diethanolamine into a 500ml beaker, stir continuously at a water bath temperature of 35°C, and then stand still for 30 minutes to fully complex; under the condition of constant stirring at a speed of 800rpm 41ml of strontium acetate aqueous solution (Sr(CH ₃ COO) ₂ .0.5H ₂ O, 268.4g/L) was added dropwise to the tetrabutyl titanate ethanol solution at a rate of 1ml/min, and 1 hour after the titration was completed, Add 3.0g of polyethylene glycol PEG2000, and continue to stir until a uniform, stable and transparent strontium titanate sol with a concentration of 0.2mol/L is obtained; the strontium titanate sol is aged at room temperature for 10 hours and then coated by dipping and pulling method. Put the silicon wafer with clean surface upright, dip it into strontium titanate sol at a constant speed of 6cm/min, let it rest for 20s, then lift the substrate vertically and at a constant speed at a speed of 4cm/min, and put the silicon wafer coated with strontium titanate sol Dry the silicon wafer at 105°C for 1h, repeat the above coating and drying steps, coat the second and third layers of film on the silicon wafer, dry the silicon wafer coated with three layers of film at 120°C for 6h, then put Put it into a muffle furnace and bake at 700°C for 2 hours to finally obtain a strontium titanate thin film with spherical particle stacked porous structure.

Example 4

Add 285ml of absolute ethanol, 17.02g of tetrabutyl titanate, and 21.08g of diethanolamine into a 500ml beaker, stir continuously at a water bath temperature of 40°C, and then stand still for 30 minutes to fully complex; under the condition of constant stirring at a speed of 1000rpm 36.4ml of strontium acetate aqueous solution (Sr(CH ₃ COO) ₂ .0.5H ₂ O, 294.9g/L) was added dropwise to the tetrabutyl titanate ethanol solution at a rate of 1.5ml/min, and the titration was completed 1.5 After h, add 4.0g of polyethylene glycol PEG2000, and continue to stir until a uniform, stable and transparent strontium titanate sol with a concentration of 0.15mol/L is obtained; the strontium titanate sol is statically aged at room temperature for 12h and then spin-coated. For coating, drop the strontium titanate sol on the ceramic substrate with a clean surface, and shake the sol evenly with a homogenizer to form a gel film. The speed of the glue shaking is 3000 rpm. Dry for 1h, repeat the above coating and drying steps, coat the second and third layers of film on the substrate, dry the substrate coated with three layers of film at 120°C for 6h, and then put it in a muffle furnace at 650°C After firing for 2 hours, a strontium titanate thin film with spherical particle stacked porous structure was finally obtained.

Example 5

Add 125ml of absolute ethanol, 17.02g of tetrabutyl titanate, and 10.01g of acetylacetone into a 250ml beaker. After stirring continuously at a water bath temperature of 30°C, stand still for 50 minutes to fully complex; under the condition of constant stirring at a speed of 800rpm 45ml of strontium acetate aqueous solution (Sr(CH ₃ COO) ₂ .0.5H ₂ O, 238.6g/L) was added dropwise to the tetrabutyl titanate ethanol solution at a rate of 1ml/min, and 50min after the titration was completed, Add 8.5g of nonionic polyacrylamide, and continue to stir until a uniform, stable and transparent strontium titanate sol with a concentration of 0.25mol/L is obtained; the strontium titanate sol is aged at room temperature for 6 hours and then coated by spin coating. The strontium titanate sol was dropped on the metal substrate with a clean surface, and the sol was evenly shaken off by a homogenizer to form a gel film at a speed of 4000 rpm, and then the substrate and the gel film were dried at 105°C for 1 hour. Repeat the above coating and drying steps to coat the second layer of film on the substrate, dry the substrate coated with two layers of film at 120°C for 4 hours, and then put it in a muffle furnace and bake it at 550°C for 4 hours to finally obtain spherical particles. Strontium titanate thin film with porous structure.

Example 6

Add 45ml of absolute ethanol, 17.02g of tetrabutyl titanate, and 5.0g of acetylacetone into a 250ml beaker. After stirring continuously at a water bath temperature of 30°C, stand still for 30 minutes to fully complex; under the condition of constant stirring at a speed of 1000rpm 49.5ml of strontium acetate aqueous solution (Sr(CH ₃ COO) ₂ .0.5H ₂ O, 216.9g/L) was added dropwise into the tetrabutyl titanate ethanol solution at 2ml/min, and 30min after the titration was completed, 3.78 g non-ionic polyacrylamide, and continue to stir until a uniform, stable and transparent strontium titanate sol with a concentration of 0.5mol/L is obtained; the strontium titanate sol is aged at room temperature for 2 hours and then coated by spin coating. Strontium sol was dropped on a ceramic substrate with a clean surface, and the sol was evenly shaken off with a homogenizer to form a gel film at a speed of 6000 rpm. Put it into a muffle furnace and bake it at 750°C for 1.5h to finally obtain a strontium titanate thin film with spherical particle stacked porous structure.

Claims (8)

1. a spheroidal particle is piled up the preparation method of vesicular structure strontium titanate film, it is characterized in that carrying out according to following steps:

(1) with absolute ethyl alcohol, tetrabutyl titanate and complexing agent, the mixing that under 30-40 ℃ of water bath condition, constantly stirs, static 30min forms the tetrabutyl titanate ethanolic soln;

(2) prepare the strontium acetate aqueous solution in the ratio of strontium acetate and tetrabutyl titanate mol ratio 1:1; Then with strontium acetate solution with the speed of (0.25-2) mL/min with (500-1000) splash in the tetrabutyl titanate ethanolic soln under the rpm agitation condition; Titration finishes to add nonionogenic tenside behind the 0.5-1.5h; The nonionogenic tenside that adds and the mol ratio of tetrabutyl titanate are (0.005 ~ 0.045): 1; Continue to stir again, obtain strontium titanate colloidal sol, hierarchy of control temperature is 25 ~ 40 ℃ in the whole process;

(3) with carrying out plated film behind the at room temperature static ageing 2-12h of above-mentioned strontium titanate colloidal sol, adopt spin-coating method or dip-coating method plated film on substrate, the substrate that is coated with strontium titanate colloidal sol is dried down at 80-120 ℃;

(4) substrate that is coated with strontium titanate colloidal sol after will drying finally makes the strontium titanate porous membrane that spheroidal particle is piled up pore structure in 550-750 ℃ of following roasting 1 ~ 4h.

2. a kind of spheroidal particle according to claim 1 is piled up the preparation method of vesicular structure strontium titanate film, it is characterized in that described complexing agent is diethylolamine or methyl ethyl diketone, and the mol ratio of tetrabutyl titanate and complexing agent is 1: (1 ~ 5).

3. a kind of spheroidal particle according to claim 1 is piled up the preparation method of vesicular structure strontium titanate film, it is characterized in that described nonionogenic tenside is polyoxyethylene glycol or non-ionic polyacrylamide.

4. a kind of spheroidal particle according to claim 1 is piled up the preparation method of vesicular structure strontium titanate film, and the mol ratio that it is characterized in that water and tetrabutyl titanate and strontium acetate is 30 ~ 55:1:1.

5. a kind of spheroidal particle according to claim 1 is piled up the preparation method of vesicular structure strontium titanate film, and the concentration that it is characterized in that described strontium titanate colloidal sol is 0.1 ~ 0.5molL ^-1

6. a kind of spheroidal particle according to claim 1 is piled up the preparation method of vesicular structure strontium titanate film, it is characterized in that described substrate is a glass, metal, pottery or silicon chip.

7. a kind of spheroidal particle according to claim 1 is piled up the preparation method of vesicular structure strontium titanate film, it is characterized in that said on substrate plated film, coating layers is at least one deck.

8. a kind of spheroidal particle according to claim 1 is piled up the preparation method of vesicular structure strontium titanate film, it is characterized in that the strontium titanate porous membrane of prepared spheroidal particle accumulation pore structure has the pore structure that is interconnected that the spheroidal particle accumulation forms.

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