Preparation method of Fe / Nv-PCN piezoelectric material

Abstract

The invention is suitable for the technical field of environmental governance, and particularly relates to a Fe / Nv-PCN piezoelectric material preparation method, which comprises: in-situ synthesis of a PCN material: roasting urea to obtain the PCN material; synthesis of an Nv-PCN material: in a nitrogen atmosphere, roasting the PCN material to obtain the Nv-PCN material; ferric chloride (FeCl3. 6H2O) and ferrous sulfate (Fe2SO4. 7H2O) are used as iron sources to prepare Fe3O4 nano particles; the preparation method comprises the following steps: loading Fe3O4 nanoparticles on an Nv-PCN material by an in-situ coprecipitation method, cooling to room temperature after the reaction is finished, taking out, washing with deionized water and absolute ethyl alcohol in sequence, and drying in a closed state to obtain the Fe / Nv-PCN composite material. Through the synergistic effect of iron doping and nitrogen vacancy, the piezoelectric property and the catalytic activity are remarkably improved, the electron transmission capacity and the redox activity of the material are enhanced through iron doping, the energy band structure of the material is optimized through nitrogen vacancy, and the piezoelectric effect and the free radical generation efficiency are improved; the material has dual functions of adsorption and catalytic oxidation, and can degrade pollution for a long time.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental governance, and particularly relates to a preparation method of Fe / Nv-PCN piezoelectric material. Background Art

[0002] The efficient, green and low-cost treatment of organic-polluted groundwater and wastewater is a major environmental demand currently faced. The most widely used technology for treating organic-polluted water is the advanced oxidation process. Traditional reagent oxidation technology requires adding a large amount of oxidants, catalytic materials or adopting other catalytic methods to the water body, and there are problems such as high cost and easy generation of secondary pollution as a whole. Therefore, seeking methods for low-consumable, low-cost and long-term degradation of organic pollutants has become the forefront technology and development trend for the current treatment of organic-polluted groundwater and wastewater.

[0003] Piezoelectric catalysis is a newly emerging advanced oxidation technology for water purification in recent years. It has attracted much attention because of its advantages such as no chemical addition, rapid reaction, and no secondary pollution; it has obvious advantages compared with traditional oxidation technologies. Due to its unique piezoelectric effect, piezoelectric materials can generate electrical energy when subjected to pressure, and this characteristic provides a new idea for environmental governance. However, existing piezoelectric materials have defects such as low activity and poor stability in environmental applications, and it is difficult to meet the actual needs. Developing an efficient, stable and environmentally friendly piezoelectric material has important practical significance.

[0004] Since traditional piezoelectric materials (such as PZT) contain lead and belong to high-energy-consuming preparation processes, there is a risk of heavy metal leakage when used for water treatment, and it is difficult to meet the requirements of green environmental protection. Moreover, traditional piezoelectric materials (such as BaTiO3, ZnO) have problems such as low catalytic activity, narrow response bandwidth, and poor chemical stability; existing piezoelectric catalysts (such as TiO2) require ultraviolet light excitation, with high energy consumption and poor response to visible light. Polymer-based piezoelectric materials (such as PVDF) have low catalytic activity and are difficult to work stably in complex environments (such as acidic wastewater). Porous carbon-based materials (such as g-C3N4) have adsorption properties and visible light response, but have a low piezoelectric coefficient (<5 pm / V), weak piezoelectric effect (d33<10 pC / N), and high electron-hole recombination rate, and cannot achieve high-performance synergistic conversion of mechanical energy-chemical energy, resulting in insufficient pollutant degradation efficiency. Single modification means (such as metal doping) have limited improvement in pollutant degradation efficiency (<40%), and lack a charge separation and active site synergistic mechanism. Existing nitrogen vacancy (Nv) modification methods mostly rely on high-temperature ammonia treatment, with complex processes and uneven vacancy distribution. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of Fe / Nv-PCN piezoelectric material, aiming to solve the problems of weak piezoelectric effect and lack of charge separation and active site synergistic mechanism of existing piezoelectric materials.

[0006] The present invention is implemented as follows. A preparation method of Fe / Nv-PCN piezoelectric material, the method comprising: In-situ synthesis of PCN material: Calcining urea to obtain PCN material; Synthesis of Nv-PCN material: Under a nitrogen atmosphere, calcining the PCN material to obtain Nv-PCN material; Preparation of Fe / Nv-PCN composite material: Loading Fe3O4 nanoparticles onto the Nv-PCN material by in-situ co-precipitation method. After the reaction is completed, cool to room temperature, take out, wash successively with deionized water and absolute ethanol, and then dry in a sealed manner to obtain Fe / Nv-PCN composite material, wherein the Fe3O4 nanoparticles are prepared using ferric chloride FeCl3·6H2O and ferrous sulfate Fe2SO4·7H2O as iron sources.

[0007] Preferably, in the step of calcining urea to obtain PCN material, during calcination, the heating rate is 2.5~10°C / min, heat up to 550°C, and keep warm for 2~4 h.

[0008] Preferably, after keeping warm, cool to room temperature, collect the product, grind the product into powder, wash it with deionized water multiple times. After the washing is completed, dry it in a vacuum environment at 80°C for 12 h.

[0009] Preferably, in the step of calcining the PCN material under a nitrogen atmosphere to obtain Nv-PCN material, the PCN material is calcined in a tube furnace. During calcination, keep warm for 2-4 h, and the flow rate of nitrogen is 100 ml / min.

[0010] Preferably, after calcination, cool to room temperature, wash with deionized water and ethanol, and dry in a vacuum environment at 80°C for 12 h to obtain Nv-PCN material.

[0011] Preferably, the steps for preparing the Fe / Nv-PCN composite material include: Disperse the Nv-PCN material in a mixed solution of ethanol and water, and perform ultrasonic treatment to obtain an Nv-PCN material ultrasonic suspension; Dissolve Fe2SO4·7H2O and FeCl3·6H2O in deionized water, and add it to the Nv-PCN material ultrasonic suspension; Stir at a temperature of 80°C for 10-20 min, adjust the pH to 11, and continue stirring to obtain a black mixture; Naturally cool to room temperature, wash several times, and then dry in an oven to obtain Fe / Nv-PCN composite material.

[0012] Preferably, the volume ratio of ethanol to water is 1:1, and the molar ratio of Fe2SO4·7H2O to FeCl3·6H2O is 5:3 to 5:4.

[0013] A preparation method of an Fe / Nv-PCN piezoelectric material provided by the present invention significantly improves piezoelectric performance and catalytic activity through the synergistic effect of iron doping and nitrogen vacancies. Iron doping enhances the electron transport ability and redox activity of the material, while nitrogen vacancies optimize the energy band structure of the material, improving the piezoelectric effect and free radical generation efficiency; this material has both adsorption and catalytic oxidation dual functions and can degrade pollutants for a long time. Description of the Drawings

[0014] Figure 1 It is the X-ray diffraction pattern of PCN, Nv-PCN, Fe / PCN and Fe / Nv-PCN piezoelectric materials provided by the embodiments of the present invention; Figure 2 It is the Fourier transform infrared spectrum of PCN, Nv-PCN, Fe / PCN and Fe / Nv-PCN piezoelectric materials provided by the embodiments of the present invention; Figure 3 It is the valence band X-ray photoelectron energy spectrum of PCN, Nv-PCN, Fe / PCN and Fe / Nv-PCN piezoelectric materials provided by the embodiments of the present invention; Figure 4 It is the degradation effect diagram of Fe / Nv-PCN piezoelectric materials prepared from different raw materials provided by the embodiments of the present invention; Figure 5 It is the first degradation effect diagram of Fe / Nv-PCN piezoelectric materials under different heating rates, different heat preservation times and ultrasonic conditions provided by the embodiments of the present invention; Figure 6 It is the second degradation effect diagram of Fe / Nv-PCN piezoelectric materials under different heating rates, different heat preservation times and static conditions provided by the embodiments of the present invention; Figure 7 It is the experimental result of degrading water samples containing antibiotic pollutants with different catalysts provided by the embodiments of the present invention. Detailed Embodiments

[0015] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] The embodiments of the present invention provide a preparation method of an Fe / Nv-PCN piezoelectric material, and the method includes: In-situ synthesis of PCN material: Calcining urea to obtain PCN material; Synthesis of Nv-PCN material: Under a nitrogen atmosphere, the PCN material is calcined to obtain the Nv-PCN material; Preparation of Fe / Nv-PCN composite material: Fe3O4 nanoparticles are loaded onto the Nv-PCN material by in-situ coprecipitation method. After the reaction is completed, it is cooled to room temperature, taken out, washed successively with deionized water and absolute ethanol, and then dried in a closed container to obtain the Fe / Nv-PCN composite material, wherein the Fe3O4 nanoparticles are prepared using ferric chloride FeCl3·6H2O and ferrous sulfate Fe2SO4·7H2O as iron sources.

[0017] In the embodiments of the present invention, the specific steps of the preparation method of the Fe / Nv-PCN piezoelectric material include: Step 1: In-situ synthesis of g-C3N4 (PCN) material: Urea is calcined at high temperature to obtain the PCN material; Step 2: Synthesis of Nv-PCN material: The PCN material obtained in Step 1 is calcined at high temperature under a nitrogen atmosphere; Step 3: Preparation of Fe3O4 nanoparticles: Fe3O4 nanoparticles are prepared using ferric chloride (FeCl3·6H2O) and ferrous sulfate (Fe2SO4·7H2O) as iron sources; Step 4: Preparation of Fe / Nv-PCN composite material: Fe3O4 nanoparticles are loaded onto Nv-PCN by in-situ coprecipitation method. After the reaction is completed, it is cooled to room temperature, taken out, washed successively with deionized water and absolute ethanol, and then dried in a closed container.

[0018] In order to compare the effects of different piezoelectric materials, the present invention also gives the preparation method of the Fe / PCN composite material: Fe3O4 nanoparticles are loaded onto PCN by in-situ coprecipitation method. After the reaction is completed, it is cooled to room temperature, taken out, washed successively with deionized water and absolute ethanol, and then dried in a closed container to obtain the Fe / PCN composite material; the specific steps include: Disperse 200 mg - 250 mg of PCN in 200 mL - 300 mL of ethanol / water (1:1) and ultrasonically treat for 2 h - 3 h. Then, dissolve Fe2SO4·7H2O and FeCl3·6H2O (molar ratio = 5:3 - 5:4) in 40 - 60 mL of deionized water and add it to the PCN ultrasonic suspension. Mechanically stir at 80°C for 10 - 20 min, add NaOH aqueous solution to adjust the solution pH to 11, continue to stir at 80°C for 40 - 60 min to obtain a black mixture. After naturally cooling to room temperature, wash it alternately with deionized water and ethanol several times and then place it in an oven at 60°C for drying. Finally, obtain the solid product Fe / PCN composite material.

[0019] In this embodiment, in step one, 10 g - 20 g of urea is placed in an alumina crucible with a lid and heated in air at a rate of 2.5 - 10 °C / min to 550 °C, and held for 2 - 4 h. After the crucible is cooled to room temperature, the product is collected, ground into powder with a mortar, washed multiple times with deionized water, and vacuum dried at 80 °C for 12 h to obtain the PCN material.

[0020] In this embodiment, in step two, PCN is synthesized by calcining in a tubular furnace under a nitrogen atmosphere. 250 mg - 300 mg of PCN is thoroughly ground and heated in a nitrogen atmosphere at a heating rate of 5 °C / min to 550 °C, and held for 2 - 4 h (N2 flow rate is 100 mL / min). After cooling to room temperature, the obtained powder is washed several times with deionized water and ethanol, and vacuum dried at 80 °C for 12 h to obtain the Nv-PCN material.

[0021] In this embodiment, in step four, ferric chloride (FeCl3·6H2O) and ferrous sulfate (Fe2SO4·7H2O) are used as iron sources to synthesize the Fe / Nv-PCN composite material with Nv-PCN by in-situ co-precipitation method. The specific method is as follows: 200 mg - 250 mg of Nv-PCN is dispersed in 200 mL - 300 mL of ethanol / water (1:1) and ultrasonicated for 2 h - 3 h. Then, Fe2SO4·7H2O and FeCl3·6H2O (molar ratio = 5:3 - 5:4) are dissolved in 40 - 60 mL of deionized water and added to the Nv-PCN ultrasonic suspension. Mechanically stirred at 80 °C for 10 - 20 min, NaOH aqueous solution is added to adjust the solution pH to 11, and continue to stir at 80 °C for 40 - 60 min to obtain a black mixture. After naturally cooling to room temperature, it is washed several times alternately with deionized water and ethanol and then dried in an oven at 60 °C, and finally the solid product Fe / Nv-PCN composite material is obtained.

[0022] Application of a Fe / Nv-PCN composite material in degrading organic pollutants.

[0023] Under the combined action of the piezoelectric effect of graphitic carbon nitride and the surface chemical reaction of nitrogen vacancies of the piezoelectric catalyst of the present invention, iron tetroxide is introduced to strengthen the piezoelectric effect of the material, break through the band gap and ROS yield limitations of traditional piezoelectric materials, and exhibit excellent piezoelectric catalytic performance, which can significantly improve the efficiency of pollutant degradation. This material has high activity and good stability, and can be effectively applied to the environmental field to solve the deficiencies of existing environmental treatment technologies. At the same time, a preparation method of this material is provided, which is simple, easy to operate and low in cost, and is suitable for large-scale production. In addition, the specific application of this material in the environmental field is clarified, providing a new technical means for environmental treatment.

[0024] To verify the effectiveness of the Fe / Nv-PCN composite material provided by the present invention, the following experimental process was used for analysis; Prepare different piezoelectric materials: Example 1: Prepare PCN material: Put 10 g - 20 g of urea into an alumina crucible with a lid, heat it in air at a rate of 2.5 - 10 °C / min to 550 °C, and keep it warm for 2 - 4 h. After the crucible is cooled to room temperature, collect the product, grind it into powder with a mortar, wash it with deionized water multiple times, and vacuum dry it at 80 °C for 12 h to obtain the PCN material; Example 2: Prepare Nv-PCN material: It was synthesized by calcining PCN in a tubular furnace under a nitrogen atmosphere. Grind 250 - 300 mg of PCN thoroughly, and heat it to 550 °C at a heating rate of 5 °C / min in a nitrogen atmosphere, and keep it warm for 2 - 4 h (N2 flow rate is 100 mL / min). After cooling to room temperature, wash the obtained powder with deionized water and ethanol several times, and vacuum dry it at 80 °C for 12 h to obtain the Nv-PCN material.

[0025] Example 3: Prepare Fe / PCN material: Using ferric chloride (FeCl3·6H2O) and ferrous sulfate (Fe2SO4·7H2O) as iron sources, it was synthesized with PCN by the in-situ coprecipitation method. The specific method is as follows: Disperse 200 - 250 mg of PCN in 200 - 300 mL of ethanol / water (1:1) and ultrasonically treat it for 2 h - 3 h. Then, dissolve Fe2SO4·7H2O and FeCl3·6H2O (molar ratio = 5:3 - 5:4) in 40 - 60 mL of deionized water and add it to the PCN ultrasonic suspension. Mechanically stir it at 80 °C for 10 - 20 min, add an aqueous NaOH solution to adjust the solution pH to 11, continue to stir at 80 °C for 40 - 60 min to obtain a black mixture. After naturally cooling to room temperature, wash it with deionized water and ethanol alternately several times and then dry it in an oven at 60 °C. Finally, obtain the solid product Fe / PCN material.

[0026] Example 4: Prepare Fe / Nv-PCN composite material: Synthesized by in-situ co-precipitation method using ferric chloride (FeCl3·6H2O) and ferrous sulfate (Fe2SO4·7H2O) as iron sources with Nv-PCN. The specific method is as follows: Disperse 200 - 250 mg of Nv-PCN material in 200 mL - 300 mL of ethanol / water (1:1) and ultrasonically treat for 2 - 3 h. Then, dissolve Fe2SO4·7H2O and FeCl3·6H2O (molar ratio = 5:3 - 5:4) in 40 - 60 mL of deionized water and add it to the Nv-PCN ultrasonic suspension. Mechanically stir at 80 °C for 10 - 20 min, add NaOH aqueous solution to adjust the solution pH to 11, continue to stir at 80 °C for 40 - 60 min to obtain a black mixture. After naturally cooling to room temperature, wash it several times alternately with deionized water and ethanol, and then place it in an oven at 60 °C for drying. Finally, obtain the solid product Fe / Nv-PCN.

[0027] The results are as Figure 1 , Figure 2 and Figure 3 shown, Figure 1X-ray diffraction patterns of the PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials prepared in Examples 1-4; the diffraction patterns of PCN and Nv-PCN contain a set of diffraction peaks, which are the g-C3N4 structure. The diffraction patterns of Fe / PCN and Fe / Nv-PCN contain two sets of diffraction peaks, which are the g-C3N4 structure and the Fe3O4 structure, respectively, indicating that a semiconductor composite material with Fe3O4 structure and g-C3N4 structure has been successfully prepared. The strong peak of PCN at 27.6° corresponds to the (002) diffraction plane of the layered conjugated aromatic structure, which is generated by the interlayer stacking of the conjugated aromatic system, similar to the stacking between carbon atom layers in graphite. The weaker diffraction peak at 12.8° corresponds to the (100) diffraction plane of the heptazine unit in the repeating plane. This peak represents the periodic arrangement of triazine ring structural units in the plane and reflects the in-plane order of the material. After the nitrogen heat treatment of PCN, the two characteristic peaks in Nv-PCN significantly attenuate, indicating that nitrogen thermal etching produces g-C3N4 nitrogen vacancy defect structural units and weakened layered stacking. In addition, except for the characteristic diffraction peaks of g-C3N4, there are no additional hybrid peaks, indicating that the nitrogen heat treatment process has no effect on the lattice structure and phase purity of g-C3N4. For the Fe / PCN and Fe / Nv-PCN materials, the diffraction peaks of the Fe3O4 component are located at 2θ = 30.09°, 35.42°, 43.06°, 53.38°, 56.94°, 62.54°, and 73.93°, which are attributed to the (220), (311), (400), (422), (511), (440), and (533) crystal planes of Fe3O4, respectively. Due to the addition of Fe3O4, it may have a certain impact on the crystal structure of C3N4 containing nitrogen vacancies during the composite process, resulting in a change in its crystallinity, and the two characteristic peaks (002) and (100) attributed to PCN significantly attenuate. In addition, compared with the Fe / PCN material, due to the presence of nitrogen vacancies in the Fe / Nv-PCN material, Fe3O4 interacts with PCN, making the local structure of PCN more disordered, and then the intensity of the characteristic peaks of PCN further weakens. From the XRD comparison data of PCN, Nv-PCN, Fe / PCN, Fe / Nv-PCN, and Fe3O4, it can be seen that the Fe / Nv-PCN catalytic material has been successfully synthesized, and after introducing nitrogen vacancies and Fe3O4 components into g-C3N4 respectively, there are no other impurities present and no impact on its crystal structure.

[0028] Figure 2 Fourier transform infrared spectra of the PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials prepared in Examples 1-4. In the range of 3000-3500 cm -1 、1200-1700 cm -1and 813 cm -1 Three distinct peaks were detected in the ranges of 810 cm -1 The sharp absorption peak at 810 cm -1 is attributed to the out-of-plane bending vibration mode of the triazine ring unit, while the broad absorption band in the range of 3000 - 3600 cm -1 is related to the N-H stretching vibration in the terminal amino group and the O-H stretching vibration in H2O. In addition, the infrared peaks in the range of 1200 - 1700 cm -1 are caused by the stretching vibration of the C-N heterocycle. The stretching vibration peaks of the Nv-PCN sample are basically the same as those of the raw material PCN, indicating that after nitrogen heat treatment, the basic structure and chemical bonds of the sample are well retained. It should be noted that the intensity of the absorption peaks of the Nv-PCN sample in the range of 1200 - 1700 cm -1 decreases significantly, indicating that a large number of nitrogen defects are formed inside the PCN after nitrogen heat treatment. These nitrogen defects are expected to have an impact on the piezocatalytic performance of the catalyst. Generally speaking, nitrogen defects can provide more active sites for the piezocatalytic degradation reaction, thereby enhancing the mass transfer ability of the catalyst. The stretching vibration peaks of Fe-O belonging to Fe3O4 appear between 550 - 580 cm -1 in the Fe3O4 nanoparticles and the Fe / PCN and Fe / Nv-PCN composites. The N-H stretching vibration peaks corresponding to those in the PCN between 3000 - 3500 cm -1 and the characteristic peaks caused by the skeletal vibration of the aromatic C-N heterocycle at 1200 - 1700 cm -1 can also be observed in the Fe / Nv-PCN spectrogram. In addition, the characteristic peak at 813 cm -1 is the stretching vibration peak of the triazine ring. The FT-IR test diagram further proves the successful synthesis of the Fe / Nv-PCN composite material.

[0029] Figure 3 Figures 22(a)-(d) are the valence band X-ray photoelectron spectrograms of the PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezomaterials prepared in Examples 1 - 4. Their valence band tops (Ev) are 1.68 eV, 1.36 eV, 0.74 eV, and 0.58 eV respectively. Compared with PCN, the doping of Fe3O4 and the introduction of nitrogen vacancies increase the defect energy level and reduce the band gap, thereby reducing the energy required for electrons to transition from the valence band (VB) to the conduction band (CB), improving the utilization rate of ultrasound, and being beneficial to the improvement of piezocatalytic performance.

[0030] Example 5. On the basis of Examples 1-4, in accordance with the process of the piezoelectric catalysis activity test, before the dark adsorption began, different catalysts were used for comparison: no catalyst, PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials. Weigh 5-50 mg of the above piezoelectric catalytic material sample powder and add it to 10-50 mL of the water sample containing antibiotic pollutants. Preferably, select the best catalyst. Take samples at regular intervals for ultraviolet spectrophotometer analysis. The experimental results are as Figure 7 shown. It can be seen that the Fe / Nv-PCN piezoelectric material prepared by the preparation method provided by the present invention has the fastest degradation rate and the highest degradation rate for the water sample containing antibiotic pollutants.

[0031] Example 6: On the basis of Examples 1-4, in accordance with the process of the piezoelectric catalysis synthesis experiment, explore the influence of different raw materials on the synthesis of Fe / Nv-PCN piezoelectric materials. By adding different raw materials, urea (Fe / Nv-PCN), melamine (Fe / Nv-MCN), thiourea (Fe / Nv-TCN), perform high-temperature calcination and detect the piezoelectric catalysis reaction effect. Take samples at regular intervals for ultraviolet spectrophotometer analysis.

[0032] As Figure 4 shown, the results show that Fe / Nv-PCN with urea as the raw material has the best effect on degrading tetracycline hydrochloride. Moreover, melamine (77 ¥ / 500g) > thiourea (50.5 ¥ / 500g) > urea (23 ¥ / 500g). Considering comprehensively, urea is selected as the raw material for synthesis.

[0033] Example 7: On the basis of Examples 1-4, in accordance with the process of the piezoelectric catalysis synthesis experiment, explore the influence of different heating rates on the synthesis of Fe / Nv-PCN piezoelectric materials. By controlling different heating rates: 2.5 °C / min, 5 °C / min, 10 °C / min, perform high-temperature calcination and detect the piezoelectric catalysis reaction effect. Take samples at regular intervals for ultraviolet spectrophotometer analysis.

[0034] Example 8: On the basis of Examples 1-4, in accordance with the process of the piezoelectric catalysis synthesis experiment, explore the influence of different heat preservation times on the synthesis of Fe / Nv-PCN piezoelectric materials. By controlling different heat preservation times: 2 h, 4 h, perform high-temperature calcination and detect the piezoelectric catalysis reaction effect. Take samples at regular intervals for ultraviolet spectrophotometer analysis.

[0035] Example 9: On the basis of Examples 1-4, in accordance with the experimental process of piezoelectric catalysis synthesis, the effects of different environmental states on the Fe / Nv-PCN piezoelectric material were explored. By regulating different ultrasonic powers: 0-100 Hz, the piezoelectric catalytic reaction was excited by ultrasound for 5-60 min. After filtration, the concentration of the target pollutant antibiotic was measured.

[0036] The results are as Figure 5 and Figure 6 shown. The best heating rate is 2.5 °C / min, the heat preservation time is 4 h, and the ultrasonic state has the best effect. Under these conditions, the prepared Fe / Nv-PCN piezoelectric material has the best effect.

[0037] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of Fe / Nv-PCN piezoelectric material, characterized in that, The method includes: In-situ synthesis of PCN material: Calcining urea to obtain PCN material; Synthesis of Nv-PCN material: Under a nitrogen atmosphere, calcining the PCN material to obtain Nv-PCN material; Preparation of Fe / Nv-PCN composite material: Loading Fe3O4 nanoparticles onto the Nv-PCN material by in-situ co-precipitation method. After the reaction is completed, cool to room temperature, take out, wash successively with deionized water and absolute ethanol, and then dry in a sealed manner to obtain the Fe / Nv-PCN composite material. Among them, the Fe3O4 nanoparticles are prepared using ferric chloride FeCl3·6H2O and ferrous sulfate Fe2SO4·7H2O as iron sources.

2. The preparation method of Fe / Nv-PCN piezoelectric material according to claim 1, characterized in that, In the step of calcining urea to obtain PCN material, during calcination, the heating rate is 2.5 - 10 °C / min, heat up to 550 °C, and keep warm for 2 - 4 h.

3. The preparation method of Fe / Nv-PCN piezoelectric material according to claim 2, characterized in that, After the heat preservation is completed, cool to room temperature, collect the product, grind the product into powder, wash it with deionized water multiple times. After the washing is completed, dry it in a vacuum environment at 80 °C for 12 h.

4. The preparation method of Fe / Nv-PCN piezoelectric material according to claim 1, characterized in that, In the step of calcining the PCN material under a nitrogen atmosphere to obtain Nv-PCN material, the PCN material is calcined in a tubular furnace. During calcination, keep warm for 2 - 4 h, and the flow rate of nitrogen is 100 ml / min.

5. The preparation method of Fe / Nv-PCN piezoelectric material according to claim 4, characterized in that, After the calcination is completed, cool to room temperature, wash with deionized water and ethanol, and dry in a vacuum environment at 80 °C for 12 h to obtain Nv-PCN material.

6. The preparation method of Fe / Nv-PCN piezoelectric material according to claim 1, characterized in that, The steps for preparing the Fe / Nv-PCN composite material include: Disperse the Nv-PCN material in a mixed solution of ethanol and water, and perform ultrasonic treatment to obtain an ultrasonic suspension of Nv-PCN material; Dissolve Fe2SO4·7H2O and FeCl3·6H2O in deionized water, and add it to the ultrasonic suspension of Nv-PCN material; Stir at a temperature of 80 °C for 10 - 20 min, adjust the pH to 11, and continue stirring to obtain a black mixture; Cool naturally to room temperature, wash several times, and then dry in an oven to obtain the Fe / Nv-PCN composite material.

7. The preparation method of Fe / Nv-PCN piezoelectric material according to claim 6, characterized in that, The volume ratio of ethanol to water is 1:1, and the molar ratio of Fe2SO4·7H2O to FeCl3·6H2O is 5:3 - 5:4.

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