阅读说明：本技术 一种耐疲劳铁酸钴/聚偏二氟乙烯-三氟乙烯多层复合薄膜及其制备方法 (Fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film and preparation method thereof ) 是由 徐玲芳 朱一丁 张雨 杨昌平 王瑞龙 肖海波 于 2020-04-23 设计创作，主要内容包括：本发明属于多铁性薄膜技术领域,具体涉及一种耐疲劳铁酸钴/聚偏二氟乙烯-三氟乙烯多层复合薄膜,包括PVDF-TrFE薄膜,且PVDF-TrFE薄膜上贴附有至少一层CFO/PVDF-TrFE复合薄膜；其制备方法为：将PVDF-TrFE粉末溶解得到溶液A,再向溶液A中加入CFO纳米级粉末得到混合溶液B；然后以FTO导电玻璃为衬底,利用将溶液A在FTO导电玻璃上进行旋转涂膜,制备PVDF-TrFE薄膜,烘干后,接着将混合溶液B在PVDF-TrFE薄膜上进行旋转涂膜,制备CFO/PVDF-TrFE复合薄膜；之后将湿膜置进行退火处理,得到铁酸钴/聚偏二氟乙烯-三氟乙烯多层复合薄膜,最后在其上镀铂点电极。本发明的铁酸钴/聚偏二氟乙烯-三氟乙烯多层复合薄膜不仅铁电疲劳特性优良,而且其制备条件温和,工艺过程步骤简单且可控性强。(The invention belongs to the technical field of multiferroic films, and particularly relates to a fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film which comprises a PVDF-TrFE film, wherein at least one layer of CFO/PVDF-TrFE composite film is attached to the PVDF-TrFE film; the preparation method comprises the following steps: dissolving PVDF-TrFE powder to obtain a solution A, and adding CFO nano-scale powder into the solution A to obtain a mixed solution B; then, using FTO conductive glass as a substrate, carrying out rotary coating on the FTO conductive glass by using the solution A to prepare a PVDF-TrFE film, drying, and then carrying out rotary coating on the PVDF-TrFE film by using the mixed solution B to prepare a CFO/PVDF-TrFE composite film; and then annealing the wet film to obtain the cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film, and finally plating a platinum point electrode on the cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film. The cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film disclosed by the invention has the advantages of excellent ferroelectric fatigue property, mild preparation conditions, simple process steps and strong controllability.)

1. A fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film is characterized in that: the composite film comprises a CFO/PVDF-TrFE composite film and a PVDF-TrFE film, wherein at least one layer of the CFO/PVDF-TrFE composite film is attached to the PVDF-TrFE film.

2. A preparation method of a fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film is characterized by comprising the following steps:

s1, preparing CFO nano-scale powder;

s2, preparing a cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film;

s2.1, dissolving PVDF-TrFE powder in a diethyl carbonate solvent, and fully stirring to obtain a solution A;

s2.2, adding the CFO nano-scale powder into the continuously stirred solution A, and fully stirring to obtain a mixed solution B;

s2.3, using FTO conductive glass as a substrate, and performing rotary coating on the prepared solution A on the FTO conductive glass by using a spin coater to prepare a PVDF-TrFE film;

s2.4, placing the spin-coated wet film in a drying oven for drying;

s2.5, performing rotary coating on the prepared mixed solution B on the dried PVDF-TrFE film by using a spin coater to prepare a CFO/PVDF-TrFE composite film;

s2.6, placing the spin-coated wet film in a heat treatment furnace for annealing treatment to obtain a cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film;

s2.7, manufacturing an electrode, and plating a platinum point electrode on the cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film manufactured in the step S2.6.

3. The method for preparing the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film as claimed in claim 2, wherein: the following steps are also included between step S2.5 and step S2.6: and placing the spin-coated wet film in a drying box for drying, performing spin coating on the prepared mixed solution B on the dried CFO/PVDF-TrFE composite film by using a spin coater, and preparing a layer of CFO/PVDF-TrFE composite film.

4. The method for preparing the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film as claimed in claim 2, wherein: the mass fraction of PVDF-TrFE in the solution A is 5-7%.

5. The method for preparing the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film as claimed in claim 2, wherein: the dosage ratio of CFO to PVDF-TrFE in the mixed solution B is 0.085-0.1333 g: 0.2 g.

6. The method for preparing the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film as claimed in claim 2, wherein: in step S2.4, the wet film is dried in a drying oven at 70-80 ℃ for 3-5 min.

7. The method for preparing the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film as claimed in claim 2 or 3, wherein: the treatment temperature of the annealing treatment is 130-140 ℃, and the treatment time is 1.5-2 h.

8. The method for preparing the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film as claimed in claim 2, wherein: the preparation of the CFO nanoscale powder in step S1 includes the following steps:

s1.1, mixing cobalt nitrate pentahydrate and ferric nitrate nonahydrate according to a molar ratio of 1.05: 1 in the ratio of the solution A to the solution B to obtain a solution C, wherein the concentration of the solution C is 0.75 mol/L; dissolving citric acid in a solution C which is continuously stirred, wherein the molar ratio of the citric acid to the cations in the solution is 1: 1.2, obtaining a cobalt ferrite precursor sol;

s1.2, continuously stirring the obtained cobalt ferrite precursor sol for 2 hours to obtain stable cobalt ferrite sol, and then drying in a drying box at the temperature of 80 ℃ for 5 minutes to obtain cobalt ferrite xerogel;

s1.3, placing the obtained cobalt ferrite xerogel in a heat treatment furnace, annealing at 800 ℃ and keeping the temperature for 2 hours to obtain cobalt ferrite pre-sintering powder;

and S1.4, placing the obtained cobalt ferrite presintering powder into a mortar to be ground for 30 min to obtain CFO nano-scale powder.

9. The method for preparing the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film as claimed in claim 2, wherein: the particle size of the CFO nanoscale powder prepared in step S1 is 500-800 nm.

10. The method for preparing the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film as claimed in claim 2, wherein: and step S2.2, adding the CFO nano-grade powder into the solution A, then electrically stirring, ultrasonically dispersing, and repeating for 2-3 times to uniformly disperse the CFO nano-grade powder.

Technical Field

The invention relates to a multiferroic composite film and a preparation method thereof, in particular to a fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film and a preparation method thereof, belonging to the technical field of multiferroic films.

Background

Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) is a semi-crystalline organic substance with excellent performance and an ideal membrane material. PVDF-TrFE has high elasticity and excellent piezoelectric ferroelectric property, and has wide application prospect in the fields of pressure and acceleration sensors, energy collection, ultrasonic sensors, nonvolatile memories, waveguides and the like. Particularly, with the development of the semiconductor industry in recent years, high-density storage of organic ferroelectric films is the focus of both academic and industrial fields. While the problem of ferroelectric fatigue (as the switching frequency of the ferroelectric film increases, the remanent polarization thereof gradually decreases until the ferroelectric property is lost) becomes a key factor for restricting whether the ferroelectric memory device can really go to commercial application, the fatigue property of the pure ferroelectric organic film is often inferior to that of the inorganic material.

Cobalt ferrite (CoFe)₂O₄CFO) is a spinel crystal structure, has the advantages of larger magnetocrystalline anisotropy, large coercive field, medium saturation magnetization, high magnetostriction property, high resistivity and the like, and has wide application prospect in the fields of permanent magnets, magnetic recording, wave-absorbing materials and biomedicine.

The magnetoelectric effect refers to a phenomenon that the material generates electric polarization response in an external magnetic field or magnetization changes caused by an external electric field (the latter is called inverse magnetoelectric effect). The room-temperature magnetoelectric coupling performance of single-phase magnetoelectric materials is usually weak, so that in recent years, layered composite magnetoelectric materials have been the hot point of international research. Therefore, aiming at the defect of poor ferroelectric fatigue resistance of PVDF-TrFE ferroelectric polymer, a fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film and a preparation method thereof need to be designed to overcome the defect.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film and the preparation method thereof, which have the advantages of excellent ferroelectric fatigue property, low cost of process equipment, simple process and strong controllability.

In order to achieve the purpose, the technical scheme of the invention is that the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film comprises a CFO/PVDF-TrFE composite film and a PVDF-TrFE film, wherein at least one layer of the CFO/PVDF-TrFE composite film is attached to the PVDF-TrFE film.

The invention also provides a preparation method of the fatigue-resistant cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film, which comprises the following steps:

s1, preparing CFO nano-scale powder;

s2, preparing a cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film;

s2.1, dissolving PVDF-TrFE powder in a diethyl carbonate solvent, and fully stirring to obtain a solution A;

s2.2, adding the CFO nano-scale powder into the continuously stirred solution A, and fully stirring to obtain a mixed solution B;

s2.3, using FTO conductive glass as a substrate, and performing rotary coating on the prepared solution A on the FTO conductive glass by using a spin coater to prepare a PVDF-TrFE film;

s2.4, placing the spin-coated wet film in a drying oven for drying;

s2.5, performing rotary coating on the prepared mixed solution B on the dried PVDF-TrFE film by using a spin coater to prepare a CFO/PVDF-TrFE composite film;

s2.6, placing the spin-coated wet film in a heat treatment furnace for annealing treatment to obtain a cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film;

s2.7, manufacturing an electrode, and plating a platinum point electrode on the cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film manufactured in the step S2.6.

Further, the following steps are also included between step S2.5 and step S2.6: and placing the spin-coated wet film in a drying box for drying, performing spin coating on the prepared mixed solution B on the dried CFO/PVDF-TrFE composite film by using a spin coater, and preparing a layer of CFO/PVDF-TrFE composite film.

Further, the mass fraction of PVDF-TrFE in the solution A is 5-7%.

Further, the dosage ratio of the CFO to the PVDF-TrFE in the mixed solution B is 0.085-0.1333 g: 0.2 g.

Further, in step S2.4, the wet film is dried in a drying oven at 70-80 ℃ for 3-5 min.

Further, the treatment temperature of the annealing treatment is 130-140 ℃, and the treatment time is 1.5-2 h.

Further, the preparation of the CFO nanoscale powder in step S1 includes the following steps:

s1.1, mixing cobalt nitrate pentahydrate and ferric nitrate nonahydrate according to a molar ratio of 1.05: 1 in the ratio of the solution A to the solution B to obtain a solution C, wherein the concentration of the solution C is 0.75 mol/L; dissolving citric acid in a solution C which is continuously stirred, wherein the molar ratio of the citric acid to the cations in the solution is 1: 1.2, obtaining a cobalt ferrite precursor sol;

s1.2, continuously stirring the obtained cobalt ferrite precursor sol for 2 hours to obtain stable cobalt ferrite sol, and then drying in a drying box at the temperature of 80 ℃ for 5 minutes to obtain cobalt ferrite xerogel;

s1.3, placing the obtained cobalt ferrite xerogel in a heat treatment furnace, annealing at 800 ℃ and keeping the temperature for 2 hours to obtain cobalt ferrite pre-sintering powder;

and S1.4, placing the obtained cobalt ferrite presintering powder into a mortar to be ground for 30 min to obtain CFO nano-scale powder.

Further, the particle size of the CFO nanoscale powder prepared in step S1 is 500-800 nm.

Further, in step S2.2, after the CFO nano-scale powder is added to the solution a, the solution is electrically stirred, and then ultrasonically dispersed, and the process is repeated for 2 to 3 times, so that the CFO nano-scale powder is uniformly dispersed.

Compared with the prior art, the invention has the following beneficial effects:

the preparation method of the cobalt ferrite/polyvinylidene fluoride-trifluoroethylene multilayer composite film provided by the invention is characterized in that the high-ferromagnetism nano-particle cobalt ferrite is uniformly mixed in a polyvinylidene fluoride-trifluoroethylene solution for compounding and then is subjected to spin coating to obtain the multilayer composite film with a compact structure, the high magnetostriction coefficient of the cobalt ferrite and the plasticity of PVDF-TrFE are combined to prepare the film which meets the characteristics of the magnetoelectric material such as high magnetoelectric effect, controllable shape and the like, and the two-phase material has complementary performances and simultaneously obtains a better and reliable magnetoelectric coupling effect, thereby effectively solving the defect of poor fatigue resistance of the single-phase ferroelectric polymer polyvinylidene fluoride-trifluoroethylene.

Drawings

FIG. 1 is a schematic structural diagram of a PVDF-TrFE film (a), a CFO (PVDF-TrFE)/PVDF-TrFE/PVDF-TrFE multilayer composite film (b) obtained in example 1, and a PVDF-TrFE/CFO (PVDF-TrFE)/CFO (PVDF-TrFE) multilayer composite film (c) obtained in example 2;

FIG. 2 is an XRD spectrum of PVDF-TrFE, Cobalt Ferrite (CFO), and the CFO (PVDF-TrFE)/PVDF-TrFE/PVDF-TrFE multilayer composite film obtained in example 1, and the PVDF-TrFE/CFO (PVDF-TrFE)/CFO (PVDF-TrFE) multilayer composite film obtained in example 2;

FIG. 3 is a fatigue characteristic curve of a CFO (PVDF-TrFE)/PVDF-TrFE/PVDF-TrFE multilayer composite film prepared in example 1 of the present invention;

FIG. 4 is a hysteresis loop before and after a fatigue test of a CFO (PVDF-TrFE)/PVDF-TrFE/PVDF-TrFE multilayer composite film prepared in example 1 of the present invention;

FIG. 5 is a fatigue characteristic curve of a PVDF-TrFE/CFO (PVDF-TrFE)/CFO (PVDF-TrFE) multilayer composite film prepared in example 2 of the present invention;

FIG. 6 shows the hysteresis loops before and after the fatigue test of the PVDF-TrFE/CFO (PVDF-TrFE)/CFO (PVDF-TrFE) multilayer composite film prepared in example 2 of the present invention;

FIG. 7 is a hysteresis loop of a CFO nanoscale powder prepared in accordance with the present invention;

FIG. 8 shows the fatigue properties of PVDF-TrFE thin films.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.