CN111484072A - Method for preparing titanate or titanium-based composite oxide material by low-temperature crystalline phase conversion - Google Patents

Abstract

The invention relates to a method for preparing titanate or titanium-based composite oxide material by low-temperature crystalline phase conversion. The method comprises the following steps: (1) mixing Ti (SO)₄)₂·9H₂Dissolving O in ethanol, and adding H₂O₂To produce TiO₂A material; (2) to prepare TiO₂Dispersing in NaOH solution, and then adding soluble salt of M element to prepare mixture suspension; (3) carrying out constant-temperature crystal phase conversion on the obtained suspension at the temperature of 25-80 ℃ for 1-24h under a closed condition, and finally cooling; to obtain the titanate or titanium-based composite oxide material. The synthesis process has the advantages of simple operation method, mild reaction conditions, energy conservation, environmental protection and good stability, and can be converted and synthesized even at room temperature. The composition proportion of the prepared material can be regulated and controlled by simply regulating and controlling the amount of the added M component, and the method is simple and easy to implement.

Description

A method for preparing titanate or titanium-based composite oxide material by low-temperature crystal phase transformation

technical field

The invention relates to a method for preparing titanate and titanium-based composite oxide materials by low-temperature crystal phase transformation, and belongs to the technical field of functional materials.

Background technique

Titanate is an oxide material with a typical perovskite ABO ₃ structure. It has the characteristics of good thermal stability, low dielectric loss and high dielectric constant. It is widely used in ceramic functional industry, electronics, and mechanical fields. The main preparation methods of titanate include high temperature solid-phase reaction synthesis method, sol-gel method, hydrothermal method and so on. In the first two methods, even if the calcination temperature of the sol-gel method is low, it needs to reach about 700 °C. High temperature not only consumes a lot of energy, high production cost, poor preparation process safety, but also easily causes serious material agglomeration. The low temperature liquid phase synthesis has the advantages of simple method and easy control of the chemical composition of the product. Although the temperature required by the hydrothermal method is relatively low, the crystallization temperature of the direct synthesis of titanate is also far above 100 °C, and it needs to be in a pressure vessel. in progress. The method of synthesizing titanate materials by TiO ₂ crystal phase transformation has been reported (Journal of Chemistry of Higher Learning Institutions, 2011, 32, 2490). Even if nano-TiO ₂ fibers are used as precursors, it needs to be treated in 1M NaOH solution for 24h at 150℃. SrTiO ₃ was obtained. This method generally accepts the "dissolution-crystallization" mechanism, so the looser the precursor _TiO2 structure is, the more favorable the conversion reaction is. In addition, most of the reported synthetic processes are relatively complex, with high production costs, and it is almost difficult to achieve large-scale production. Therefore, the development of a simple and stable method for synthesizing titanate and titanium-based composite oxide materials at low temperature or even room temperature is of great significance to the theoretical research and industrial application of perovskite oxides.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for synthesizing titanate and titanium-based composite oxide materials by low-temperature crystal phase transformation in view of the deficiencies in the current technology. In the method of the invention, the inorganic titanium salt is used as the titanium source and ethanol is thermally crystallized to synthesize TiO ₂ ; and then the titanate material is synthesized by low-temperature crystal phase transformation in an alkaline system. The titanate or titanium-based composite oxide material is prepared by controlling the amount and type of the substance added to the system of M element during the crystal phase transformation, and regulating the proportion of titanate in the prepared material. The invention is easy to operate, stable and easy to control.

The technical scheme of the present invention is:

A method for preparing titanate or titanium-based composite oxide material by low-temperature crystal phase transformation, the method comprises the following steps:

(1) Dissolve Ti(SO ₄ ) ₂ ·9H ₂ O in ethanol, then add H ₂ O ₂ , stir the mixture for 5-30 minutes, raise the temperature to 90-120° C., and crystallize for 2-24 hours to obtain _TiO2 material;

Wherein, the concentration of Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution is 5-100 g/L; the volume of H ₂ O ₂ is 5-20% of the volume of the mixed solution;

(2) disperse the prepared TiO ₂ in NaOH solution, then add the soluble salt of M element to prepare the mixture suspension;

Wherein, the molar ratio is M:Ti=0.01～2, the solubility of NaOH solution is 0.2～2mol/L, the mass ratio of TiO ₂ and NaOH solution is 2～50%; the M is Sr, Ba, Ni or La ;

(3) the obtained suspension liquid is thermostatically transformed into crystal phase under airtight conditions at 25-80° C. for 1-24 hours, and finally cooled;

(4) After cooling, the obtained particulate matter is filtered, washed and dried to obtain titanate or titanium-based composite oxide material.

Wherein, the soluble salt of the M element in step (2) is the soluble salt of one or more elements, and the soluble salt is hydrochloride or nitrate.

When M:Ti≥1, the synthesized material is titanate, and when M:Ti<1, the synthesized material is a titanium-based composite oxide material.

The beneficial effects of the present invention are:

1. In the present invention, inorganic titanium salt is used as the titanium source, and the synthesis process used is simple in operation method and mild in reaction conditions, and can be converted into synthesis even at room temperature, which is energy-saving, environmentally friendly, and has good stability.

2. The composition ratio of the material prepared by the present invention can be regulated by simply regulating the amount of the M component added, and the method is simple and easy to implement.

3. The preparation process conditions of the material of the present invention are mild, and no special environment (such as inert atmosphere protection, etc.) is required; the microstructure of the material is easier to obtain and maintain, and it is not easy to be damaged.

Description of drawings

Accompanying drawing 1 is the XRD pattern of the strontium titanate sample described in Example 1;

Accompanying drawing 2 is the XRD pattern of the barium titanate sample described in Example 2;

Accompanying drawing 3 is the XRD pattern of the strontium titanate sample described in Example 3;

Accompanying drawing 4 is the SEM photograph of the strontium titanate sample described in Example 3;

5 is the XRD pattern of the strontium titanate sample described in Example 4.

Detailed ways

The present invention will be described below through the following examples. The described examples are only used to further explain and illustrate the present invention in detail. However, the protection scope of the present invention is not limited to the following examples. Non-essential improvements and adjustments still belong to the protection scope of the present invention.

Example 1:

Under magnetic stirring, a Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution with a concentration of 10 g/L was prepared, and 7.5% of the total volume of the solution was added with H ₂ O ₂ for complexation with Ti ⁴⁺ for 20 min, followed by crystallization for 12 h , through suction filtration and washing to obtain TiO ₂ ; then disperse it in a 1 mol/L NaOH solution, so that the concentration of TiO ₂ is 5wt%, add a certain amount of SrCl ₂ to the system, so that the molar ratio Sr:Ti=50 %, after stirring for 20 min, the obtained suspension was placed in a crystallization kettle, and the crystal phase was transformed for 4 h and 12 h under airtight conditions at 25° C., respectively, and two samples were obtained. After cooling to room temperature, the resulting particles were filtered, washed and dried. The XRD characterization results of the samples are shown in Figure 1. It can be seen from the results that at room temperature, SrTiO ₃ material has been formed in the sample after the crystal phase transformation for 4h, and the amount of SrTiO ₃ formed increases with the extension of the transformation time.

Example 2:

Under magnetic stirring, a Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution with a concentration of 10 g/L was prepared, and 7.5% of the total volume of the solution was added with H ₂ O ₂ for complexation with Ti ⁴⁺ for 20 min, followed by crystallization for 12 h , through suction filtration and washing to obtain TiO ₂ ; then disperse it in a 1 mol/L NaOH solution, so that the concentration of TiO ₂ is 1wt%, and add a certain amount of SrCl ₂ to the system to make the molar ratio Sr:Ti=50 %, stirred for 20 min, and closed the crystal phase transformation at 40 °C for 4 h to obtain the material sample. The XRD characterization results of the samples are shown in Figure 2. From the results, it can be seen that the amount of SrTiO ₃ formed by slightly increasing the crystal phase transition temperature increases significantly.

Example 3:

Under magnetic stirring, a Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution with a concentration of 10 g/L was prepared, and 7.5% of the total volume of the solution was added with H ₂ O ₂ for complexation with Ti ⁴⁺ for 20 min, followed by crystallization for 12 h , through suction filtration and washing to obtain TiO ₂ ; then disperse it in a 1 mol/L NaOH solution, so that the concentration of TiO ₂ is 1wt%, and add a certain amount of SrCl ₂ to the system to make the molar ratio Sr:Ti=50 %, stirred for 20min, closed the crystal phase transformation at 60℃ for 4h, and obtained the material sample. The XRD characterization results of the samples are shown in Figure 3, and the scanning electron microscope photos are shown in Figure 4. From the results, it can be seen that the amount of SrTiO ₃ formed by continuing to increase the crystal phase transformation temperature increases significantly.

Example 4:

Under magnetic stirring, a Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution with a concentration of 10 g/L was prepared, and 7.5% of the total volume of the solution was added with H ₂ O ₂ for complexation with Ti ⁴⁺ for 20 min, followed by crystallization for 12 h , through suction filtration and washing to obtain TiO ₂ ; then disperse it in a 1 mol/L NaOH solution, so that the concentration of TiO ₂ is 1wt%, and add a certain amount of BaCl ₂ to the system to make the molar ratio Ba:Ti=50 %, stirred for 20min, closed the crystal phase transformation at 60℃ for 4h, and obtained the material sample. The XRD characterization results of the samples are shown in Figure 5. From the results, it can be seen that _BaTiO3 materials can be prepared by replacing _SrCl2 with _BaCl2 .

Example 5:

Under magnetic stirring, a Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution with a concentration of 20 g/L was prepared, and 7.5% of the total volume of the solution was added with H ₂ O ₂ for complexation with Ti ⁴⁺ for 20 minutes, followed by crystallization for 8 hours. , through suction filtration and washing to obtain TiO ₂ ; then disperse it in a 1 mol/L NaOH solution to make the concentration of TiO ₂ 10wt%, add a certain amount of Sr(NO ₃ ) ₂ to the system, so that the molar ratio of Sr : Ti=50%, after stirring for 20min, the material sample was prepared by closed crystal phase transformation at 60℃ for 4h.

Example 6:

Under magnetic stirring, a Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution with a concentration of 10 g/L was prepared, and 7.5% of the total volume of the solution was added with H ₂ O ₂ for complexation with Ti ⁴⁺ for 20 min, followed by crystallization for 12 h , through suction filtration and washing to obtain TiO ₂ ; then disperse it in a 1 mol/L NaOH solution to make the TiO ₂ concentration 5wt%, add a certain amount of SrCl ₂ to the system to make the molar ratio Sr:Ti=100 %, stirred for 20 min, and closed the crystal phase transformation at 80 °C for 8 h to obtain the material sample.

Example 7:

Under magnetic stirring, a Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution with a concentration of 40 g/L was prepared, and 7.5% of the total volume of the solution was added with H ₂ O ₂ for complexation with Ti ⁴⁺ for 20 minutes, followed by crystallization for 20 hours. , through suction filtration and washing to obtain TiO ₂ ; then disperse it in a 1 mol/L NaOH solution, so that the concentration of TiO ₂ is 1wt%, add a certain amount of SrCl ₂ and BaCl ₂ to the system, so that the molar ratio (Sr +Ba):Ti=100%, and the material samples were prepared by closed crystal phase transformation at 80℃ for 4h after stirring for 20min.

To sum up, the method for synthesizing titanate or titanate-containing composite materials by low-temperature crystal phase transformation reported in the present invention is based on the "dissolution-crystallization" mechanism, firstly using titanium ions and hydrogen peroxide to complex polyhydroxy hydrate, In the process of heat treatment to form TiO ₂ , the hydrate decomposes to generate oxygen, which makes the material structure looser; and the loose precursor structure is conducive to the interaction between Ti and NaOH, and further promotes the crystal phase transformation. The composition of the synthesized samples can be regulated by controlling the amount of M element added. For example, when the amount of Sr added is insufficient, the obtained material is a TiO ₂ -SrTiO ₃ composite material, and when a sufficient amount or excess of Sr is added to the system, it is SrTiO ₃ ; When M:Ti≥1, the synthesized material is titanate, and when M:Ti<1, the synthesized material is a titanium-based composite oxide material.

Matters not addressed in the present invention are known in the art.

Claims (3)

1. a method for preparing titanate or titanium-based composite oxide material by low-temperature crystal phase transformation, is characterized in that the method comprises the steps: (1) Dissolve Ti(SO ₄ ) ₂ ·9H ₂ O in ethanol, then add H ₂ O ₂ , stir the mixture for 5-30 minutes, raise the temperature to 90-120° C., and crystallize for 2-24 hours to obtain _TiO2 material; Wherein, the concentration of Ti(SO ₄ ) ₂ ·9H ₂ O ethanol solution is 5-100 g/L; the volume of H ₂ O ₂ is 5-20% of the volume of the mixed solution; (2) disperse the prepared TiO ₂ in NaOH solution, then add the soluble salt of M element to prepare the mixture suspension; Wherein, the molar ratio is M:Ti=0.01～2, the solubility of NaOH solution is 0.2～2mol/L, the mass ratio of TiO ₂ and NaOH solution is 2～50%; the M is Sr, Ba, Ni or La ; (3) the obtained suspension liquid is thermostatically transformed into crystal phase under airtight conditions at 25-80° C. for 1-24 hours, and finally cooled; (4) After cooling, the obtained particulate matter is filtered, washed and dried to obtain titanate or titanium-based composite oxide material. 2. The method for preparing titanate or titanium-based composite oxide material by low-temperature crystal phase transformation as claimed in claim 1, wherein the soluble salt of the M element described in step (2) is the soluble salt of one or more elements Salt, the soluble salt is hydrochloride or nitrate. 3. the method for preparing titanate or titanium-based composite oxide material by low-temperature crystal phase transformation as claimed in claim 1, it is characterized in that when M:Ti≥1, the synthesized material is titanate, M:Ti≤ 1, the synthesized material is a titanium-based composite oxide material.

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