CN114906877A - Preparation method of cobalt ferrite capable of being compounded with LDPE (Low-Density polyethylene) to prepare magnetic nano dielectric medium - Google Patents

Abstract

A preparation method of cobalt ferrite capable of being compounded with LDPE to prepare magnetic nano dielectric belongs to the technical field of electrical insulation. The invention aims to solve the problem of the existing CoFe ₂ O ₄ The problem that the powder preparation process is difficult to have good compatibility with LDPE matrix is that CoSO is used ₄ ·7H ₂ O、FeCl ₃ ·6H ₂ Dissolving O and NaOH in deionized water respectively to obtain a solution A, B, C; mixing the solution A and the solution B, and dropwise adding the solution C under continuous stirring until the solution C becomes a suspension solution D; transferring the suspension solution D into a hydrothermal reaction kettle, and adding the suspension solution D to the surfaceReacting an active agent for 10-20h at 100-160 ℃ to obtain a reaction solution E; cooling to room temperature, centrifuging and collecting the lower-layer solid matter of the reaction solution E; sequentially washing by using distilled water and heptane to obtain the nano CoFe ₂ O ₄ Drying the granules in vacuum; and compounding the LDPE and the LDPE by a melt blending method. CoFe prepared in the invention ₂ O ₄ Can be well compatible with an LDPE matrix under the action of the coated surfactant, and is applied to the field of electrical insulation.

Description

A preparation method of cobalt ferrite that can be compounded with LDPE to prepare magnetic nano-dielectric

technical field

The invention belongs to the technical field of electrical insulation, and in particular relates to a preparation method of cobalt ferrite which can be compounded with LDPE to prepare a magnetic nanometer dielectric.

Background technique

Low-density polyethylene (LDPE) is one of the main materials used in the industry and has been widely used in the field of electrical insulation due to its excellent dielectric and mechanical properties. Space charge is an important factor affecting LDPE insulated cables, damaging the LDPE matrix by distorting the local electric field and affecting high-field conduction and breakdown phenomena. Space charge accumulation is generally considered to be the main factor that accelerates the degradation of HVDC polymer insulation. It is found that the addition of a small amount of polar groups can greatly reduce the formation of space charges in polyolefin compounds, thereby improving the performance of LDPE-based insulating materials. Currently, inorganic fillers commonly used in LDPE-based composite dielectrics used in insulated power cables include montmorillonite (MMT), TiO ₂ , MgO, ZnO, SiO ₂ , BaTiO ₃ , nanotubes, and graphene. However, there are few studies on magnetic nanodielectrics prepared by composites of LDPE and magnetic nanoparticles. The magnetic nanocomposite medium possesses the small size effect peculiar to the nanomagnetic particles themselves and the inherent properties of the original polymer. Generally, in addition to electrical, magnetic and optical properties, magnetic nanocomposite media also exhibit some new properties, such as good film-forming and processing properties, so they can be used in cell separation, medical diagnosis, high-density information storage media, electromagnetic wave adsorption Potential applications in materials, electromagnetic devices and electromagnetic interference suppression. In addition, since the introduced magnetic nanoparticles can reduce the electrical conductivity and polarization effect of the material, the dielectric properties of the material can be affected. On the basis of the above considerations, the dispersion of magnetic nanoparticles in LDPE may reduce the formation of space charges in LDPE, and at the same time bring magnetism to the LDPE-based composite dielectric, thereby suppressing the influence of the magnetic field caused by the high-voltage DC electric field, and even possibly Broaden its applications in the fields of electromagnetic wave absorption, electromagnetic devices and electromagnetic interference suppression.

Spinel-type cobalt ferrite (CoFe ₂ O ₄ ) has high saturation magnetization, high magnetocrystalline anisotropy, good chemical stability and wear resistance, and is widely used in the fields of magnetic recording media and magnetostrictive materials. It has attracted much attention due to its broad application prospects. The key to the synthesis of cobalt ferrite is to control the particle size. At present, the synthesis methods of ferrites include physical and chemical methods. Physically, there are low temperature pulverization method, ultrasonic pulverization method, high-energy ball milling method, shock wave crushing method, steam rapid cooling method, thermal plasma method, etc. There are many impurities in the products obtained by physical synthesis. Therefore, chemical methods are often used to synthesize ferrites at present. Chemical methods include gel method, hydrothermal method, chemical co-precipitation method, vapor deposition method, etc. For example, Wu Juan prepared a composite medium of nano-cobalt ferrite and body-centered cubic cobalt-iron alloy by hydrothermal method. The samples were analyzed by X-ray diffraction and their morphology and structure were observed. The results show that the obtained nanoparticles have uniform particle size distribution and spherical shape of cubic crystal system. Mössbauer spectroscopy (MS) showed that the synthesized product was composed of nano-cobalt ferrite and body-centered cubic cobalt-iron alloy. Using VSM to measure the hysteresis loop of the composite medium, it is shown that the composite medium of nano-cobalt ferrite and body-centered cubic cobalt-iron alloy has a higher saturation magnetization. The addition of body-centered cubic cobalt-iron alloy in cobalt ferrite effectively improves its magnetic properties. Chen Xiaoyun prepared nano-cobalt ferrite particles by hydrothermal method. By changing the reaction temperature and the cobalt content, the magnetic properties of the cobalt ferrite particles were changed. XRD results show that the higher the temperature, the larger the cobalt ferrite grain size. SEM and TEM analysis results show that the nano-cobalt ferrite has a spherical structure. MD JOSEPHSEBASTIAN et al. prepared cobalt ferrite (CoxFe ₃ -xO ₄ ) by thermal decomposition, and used X-ray diffraction and Mossbauer spectroscopy to study the Mossbauer parameters, lattice parameters and crystallites of the products caused by Fe/Co changes Variation in size. It is verified that it is nano-cobalt ferrite particles with defect structure, and it is found that Fe/Co=3:2 in the initial precursor oxide is optimal. Chinese patent "A hydrothermal preparation method of spinel-type ferrite CoFe ₂ O ₄ nano-powder" (publication number: CN112408498A) uses cobalt salt, iron salt and ethanolamine as raw materials to prepare CoFe ₂ O by hydrothermal method ₄ Materials; Chinese patent "A CoFe ₂ O ₄ /gC ₃ N ₄ Magnetic Nanomaterial and Its Preparation Method" (Publication No.: CN106582772A) used cobalt salt, iron salt and sodium acetate as raw materials to prepare CoFe ₂ by high temperature calcination O ₄ material; "A preparation method of CoFe ₂ O ₄ nanoparticles" (Publication number: CN109264792A) CoFe ₂ O ₄ materials etc. were prepared by high temperature calcination with cobalt salt, iron salt and oxalate as raw materials; These methods do not involve the problem of compound compatibility with LDPE when preparing CoFe ₂ O ₄ , so they are not coated with appropriate surfactants, and it is difficult to disperse them uniformly in the LDPE matrix. At present, there is no research on the preparation and modification method of CoFe ₂ O ₄ that can be well compounded with LDPE to prepare magnetic nano-dielectrics. Therefore, for this application, a nano-CoFe that can be well compounded with LDPE to prepare magnetic nano-dielectrics is needed. Preparation method of _{2O4 .}

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problem that the existing CoFe ₂ O ₄ powder preparation process is difficult to have good compatibility with LDPE matrix, and to provide a preparation method of cobalt ferrite that can be compounded with LDPE to prepare magnetic nano-dielectric. In the present invention, cobalt sulfate, ferric chloride and sodium hydroxide are used as raw materials, and liquid water is used as a reaction solution, and nano-sized CoFe ₂ O ₄ particles are prepared by a hydrothermal method, and then surface-modified with different surfactants to select suitable surfactant to improve its compatibility with LDPE matrix, which is beneficial to its application in nanodielectrics.

To achieve the above object, the technical scheme adopted by the present invention is as follows:

A preparation method of cobalt ferrite that can be compounded with LDPE to prepare magnetic nano-dielectric, the method is specifically:

Step 1: Dissolving CoSO ₄ ·7H ₂ O, FeCl ₃ ·6H ₂ O and NaOH into deionized water respectively to obtain solutions A, B and C;

Step 2, mix solution A and B, drip solution C under constant stirring, until it becomes a suspension, obtain suspension solution D;

Step 3: Transfer the suspension solution D to a hydrothermal reaction kettle, add a surfactant, and react at 100-160° C. for 10-20 hours to obtain a reaction solution E;

Step 4: Cooling the reaction solution E to room temperature, and collecting the lower layer solid matter of the reaction solution E by centrifugation; using distilled water and heptane to clean the lower layer solid matter 2 to 5 times in turn to obtain nano-CoFe ₂ O ₄ particles, which are vacuum-dried; The size of the nano CoFe ₂ O ₄ particles is 8-20 nm.

Step 5. Using a torque rheometer, the LDPE and nano-CoFe ₂ O ₄ particles are compounded by a melt blending method to obtain a CoFe ₂ O ₄ /LDPE composite material.

In the present invention, LDPE is a non-polar high polymer, which has poor compatibility with nanoparticles, and the nanoparticles are easily agglomerated into large clusters during the compounding process, so that the nanoparticles in the prepared compound medium are not uniform in small sizes. Dispersion, after the surfactant we added during the preparation of nanoparticles is coated on the surface of the nanoparticles, it can simultaneously play the dual effect of reducing the surface energy of the nanoparticles and increasing its compatibility with LDPE, so that the blending process can be achieved. Not only can the nanoparticles be uniformly dispersed without large-scale agglomeration, it is easier for practical industrial production.

Further, in step 1, the mass fractions of CoSO ₄ in solution A, FeCl ₃ in solution B and NaOH in solution C are all 1% to 20%.

Further, in step 2, the mass ratio of the solutions A, B, and C is 1:2-2.5:6-10.

Further, in step 3, the mass fraction of the surfactant is 0.1% to 3%.

Further, in step 3, the surfactant is one or both of oleic acid diethanolamide, oleylamine, castor oil polyoxyethylene ether, sorbitan fatty acid ester, polyvinyl alcohol, and oleic acid. .

Further, in step 4, the centrifugal rotation speed is 5000r/min～10000r/min, and the time is 5min～20min.

Further, in step 5, the temperature of the vacuum drying is room temperature, and the time is 5～20min.

Further, in step 5, the mass percentage of CoFe ₂ O ₄ in the CoFe ₂ O ₄ /LDPE composite material is 1% to 5%.

Further, in step 5, the composite temperature of the torque rheometer is 100-150° C., and the rotational speed is set at 20-200 r/min.

The beneficial effects of the present invention relative to the prior art are:

1. The CoFe ₂ O ₄ prepared in the present invention has good compatibility with the LDPE matrix under the action of the coated surfactant, and is used in the field of electrical insulation, and its dispersed particle size is between 100nm and 150nm.

2. The method of the invention is simple, the particle size and crystallinity of the generated particles are easy to control, the raw materials are easily obtained, the operation is simple, the cost is low, and it is suitable for large-scale production;

3. The particle size of CoFe ₂ O ₄ prepared by the present invention is uniform, and its particle size can be controlled according to the needs of use.

4. The size of CoFe ₂ O ₄ prepared by the present invention is 8nm-20nm, and has good crystallinity and dispersibility.

5. Using CoSO ₄ ·7H ₂ O, FeCl ₃ ·6H ₂ O and NaOH as raw materials, using hydrothermal method to obtain nano CoFe ₂ O ₄ particles with good compatibility with LDPE matrix;

6. In the hydrothermal reaction, adding suitable surfactants can simultaneously achieve the dual effect of controlling the size of CoFe ₂ O ₄ nanoparticles and improving its compatibility with the LDPE matrix, expanding its application in the field of electrical insulation.

Description of drawings

1 is a transmission electron microscope image of CoFe ₂ O ₄ nanoparticles prepared in Example 1;

Fig. 2 is the XRD pattern of CoFe ₂ O ₄ nanoparticles prepared in Example 1;

3 is a SEM image of the CoFe ₂ O ₄ /LDPE composite dielectric prepared in Example 1;

FIG. 4 is a transmission electron microscope image of CoFe ₂ O ₄ nanoparticles prepared in Comparative Example 2. FIG.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the embodiments and the accompanying drawings, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention should be included in the within the protection scope of the present invention.

Example 1:

A preparation method of CoFe ₂ O ₄ with good compatibility with LDPE matrix, which is specifically completed according to the following steps:

1. Dissolve CoSO ₄ ·7H ₂ O, FeCl ₃ ·6H ₂ O and NaOH into deionized water respectively to obtain solutions CoSO ₄ , FeCl ₃ and NaOH solutions; in the CoSO ₄ solution, CoSO ₄ and FeCl ₃ solutions The mass fraction of NaOH in FeCl ₃ and NaOH solution is 5%～20%;

2. After mixing the solution CoSO ₄ and FeCl ₃ solution, add NaOH solution dropwise under constant stirring until it becomes a suspension to obtain Co(OH) ₂ and Fe(OH) ₃ mixed suspension solution; CoSO ₄ solution, FeCl ₃ The mass ratio of the solution and the NaOH solution is 1:2~2.5:6~10

3. Transfer the mixed suspension solution of Co(OH) ₂ and Fe(OH) ₃ to the hydrothermal reactor, add surfactant, and react at 100～160℃ for 10～20h to obtain CoFe ₂ O ₄ suspension The mass fraction of the surfactant is 0.5% to 3%; the surfactant is oleic acid diethanolamide, oleylamine, castor oil polyoxyethylene ether, sorbitan fatty acid ester, polyethylene One or both of alcohol and oleic acid; with the prolongation of reaction time, the grain shape is more uniform, but the size is larger.

4. Cool the CoFe ₂ O ₄ suspension to room temperature, centrifuge for 5 min to 20 min at a centrifugal speed of 5000 r/min to 10000 r/min, pour out the supernatant, discard it, and collect the lower solid matter; use distilled water, Heptane sequentially washes the collected lower layer solid matter for 3 to 5 times to obtain nano CoFe ₂ O ₄ particles, which are placed in a vacuum oven for vacuum drying at room temperature for 8 to 20 hours;

5. Using a torque rheometer, the low-density polyethylene (LDPE) and nano-CoFe ₂ O ₄ particles were compounded at 110-130 ℃ by melt blending method to obtain CoFe ₂ O ₄ /LDPE with good compatibility composite material. The mass percentage of CoFe ₂ O ₄ in the CoFe ₂ O ₄ /LDPE composite material is 1% to 5%. The rotational speed of the torque rheometer is set at 100-200 r/min.

As shown in Fig. 1, the prepared CoFe ₂ O ₄ nanoparticles are quasi-spherical, and the size is basically around 10 nm. As shown in Figure 2, which is the XRD pattern, it can be seen that 17.51°, 30.03°, 35.57°, 43.75°, 53.54°, 57.48° and 62.06° correspond to (111), (220), (311), (400 ), (433), (511) and (440) peaks, which are in agreement with the CoFe ₂ O ₄ (JCPDS-22-1086) standard card, which proves that the prepared material is CoFe ₂ O ₄ . It can be seen from the half-peak width that the prepared material is about 8-12 nm. After compounding the CoFe ₂ O ₄ nanoparticles prepared in Example 1 with LDPE at 1 wt%, the SEM of the tablet embrittlement test shows Figure 3. It can be seen from Figure 3 that the CoFe ₂ O ₄ particles are uniformly dispersed in the LDPE matrix at about 100 nm.

Comparative Example 1:

The difference between this comparative example and Example 1 is: in step 1, the NaOH solution is replaced with NH ₃ ·H ₂ O of equal mass fraction; in step 2, after mixing the solution CoSO ₄ and FeCl ₃ solution, NH ₃ ·H ₂ O was added dropwise under constant stirring; as shown in FIG. 4 , the particle size of the obtained CoFe ₂ O ₄ was about 50 nm, and the morphology was not uniform. Other steps and parameters are the same as in Example 1.

Claims (9)

1. A preparation method of cobalt ferrite capable of being compounded with LDPE to prepare magnetic nano dielectric medium is characterized by comprising the following steps: the method specifically comprises the following steps:

step one, CoSO ₄ ·7H ₂ O、FeCl ₃ ·6H ₂ Dissolving O and NaOH in deionized water respectively to obtain a solution A, B, C;

step two, mixing the solution A and the solution B, and dripping the solution C under continuous stirring until the solution C becomes a suspension to obtain a suspension solution D;

transferring the suspension solution D into a hydrothermal reaction kettle, adding a surfactant, and reacting at 100-160 ℃ for 10-20h to obtain a reaction solution E;

step four, cooling the reaction liquid E to room temperature, and centrifuging to collect solid substances at the lower layer of the reaction liquid E; washing the solid matter at the lower layer by using distilled water and heptane in sequence to obtain the nano CoFe ₂ O ₄ Drying the granules in vacuum;

step five, LDPE and nano CoFe are mixed by a melt blending method by using a torque rheometer ₂ O ₄ The particles are compounded to obtain CoFe ₂ O ₄ a/LDPE composite material.

2. The preparation method of the cobalt ferrite capable of being compounded with LDPE to prepare the magnetic nano dielectric according to claim 1, which is characterized in that: in the first step, theCoSO in solution A ₄ FeCl in solution B ₃ And the mass fraction of NaOH in the solution C is 1-20%.

3. The method for preparing the cobalt ferrite capable of being compounded with the LDPE for preparing the magnetic nano dielectric according to the claim 1 or 2, which is characterized in that: in the second step, the mass ratio of the solution A, B, C is 1: 2-2.5: 6 to 10.

4. The preparation method of the cobalt ferrite capable of being compounded with LDPE to prepare the magnetic nano dielectric according to claim 1, which is characterized in that: in the third step, the mass fraction of the surfactant is 0.1-3%.

5. The preparation method of the cobalt ferrite capable of being compounded with the LDPE to prepare the magnetic nano dielectric according to claim 1, characterized in that: in the third step, the surfactant is one or two of oleic acid diethanolamide, oleylamine, castor oil polyoxyethylene ether, sorbitan fatty acid ester, polyvinyl alcohol and oleic acid.

6. The preparation method of the cobalt ferrite capable of being compounded with LDPE to prepare the magnetic nano dielectric according to claim 1, which is characterized in that: in the fourth step, the centrifugal rotating speed is 5000r/min to 10000r/min, and the time is 5min to 20 min.

7. The preparation method of the cobalt ferrite capable of being compounded with the LDPE to prepare the magnetic nano dielectric according to claim 1, characterized in that: and fifthly, the temperature of the vacuum drying is room temperature, and the time is 5-20 min.

8. The preparation method of the cobalt ferrite capable of being compounded with the LDPE to prepare the magnetic nano dielectric according to claim 1, characterized in that: in step five, the CoFe ₂ O ₄ CoFe in/LDPE composite material ₂ O ₄ The mass percentage of (A) is 1% -5%.

9. The preparation method of the cobalt ferrite capable of being compounded with the LDPE to prepare the magnetic nano dielectric according to claim 1, characterized in that: in the fifth step, the composite temperature of the torque rheometer is 100-150 ℃, and the rotating speed is set to be 20-200 r/min.

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