CN106683813B - A kind of graphene coated can be changed phase nano magnetic composite materials and preparation method thereof - Google Patents

Abstract

The invention provides a graphene-coated variable-phase nano-magnetic composite material, which has a core-shell structure, and the shell is a graphene shell, which is composed of multi-layer graphene sheets, and the thickness of the shell layer is 5-50nm; the core is a magnetic core , is a nano-magnetic particle with a particle diameter of 10-90nm and a variable phase state. The invention also proposes a preparation method of the graphene-coated nano-magnetic composite material with a variable phase state. The method proposed by the invention uses ferrocene powder as an iron source and a carbon source, uses plasma as a synthesis environment, reduces toxicity and environmental pollution caused by reactants, and is beneficial to mass production. The phase of the obtained magnetic nanoparticles can be controlled by adjusting the nitrogen content ratio of the plasma during the preparation process. The graphene-coated nano-magnetic powder prepared by this method has fine particle size, uniform distribution, good sphericity, and a short preparation process.

Description

A kind of graphene-coated variable phase nano-magnetic composite material and preparation method thereof

technical field

The invention belongs to the technical field of nano functional powder materials and powder preparation, and in particular relates to a composite graphene functional material and a preparation method thereof.

Background technique

Graphene is a two-dimensional carbon material with a hexagonal honeycomb lattice composed of carbon atoms in sp2 hybridized orbitals and a thickness of only one carbon atom. Graphene has strong toughness, electrical conductivity and thermal conductivity. Iron and iron nitrogen compounds have excellent magnetic properties, but their chemical stability is poor, especially the iron phase. The use of graphene as a coating material can well improve the chemical stability and poor electrical conductivity of magnetic particles, so that this composite material can be well applied in magnetic fluids, targeted drugs, electromagnetic wave absorbing materials, electromagnetic shielding materials, oxidation Reduction catalysts, fine ceramic materials and lithium batteries and other fields.

In the current published patents and documents, most of the reports are the preparation methods of carbon-coated metal nanoparticles, such as pyrolysis, arc method, impregnation method, CVD method, etc. to obtain carbon-coated iron nanoparticles; for graphene-coated There is no one way to obtain iron nitrogen compound nanoparticles directly.

The application publication number is CN101347455A, and the publication date is January 21, 2009. The patent name is a carbon-coated iron nanoparticle and its application as a drug carrier for the treatment of liver cancer. It has invented a carbon-coated iron nanoparticle, especially It is prepared by direct current arc method.

The application publication number is CN102623696A, the publication date is August 1, 2012, the patent name: a preparation method and application of core-shell type coated iron nitride nanocomposite particles, which invented a core-shell type carbon-coated nitriding The preparation process of iron nanocomposite particles, especially carbon-coated iron nanoparticles synthesized in situ by DC plasma as a precursor, and then obtained carbon-coated iron nitride nanocomposite particles through a nitriding process.

The application publication number is CN101710512A, and the publication date is May 19, 2010. The patent name is graphene and carbon-coated ferromagnetic nano-metal composite material and its preparation method. It invented a ferromagnetic nanoparticle coated with graphene and carbon, and provided a special CVD method to prepare the composite powder material.

These methods have their own advantages, but also have many shortcomings, such as complex test equipment, strict preparation conditions, cumbersome process, etc., resulting in high preparation costs, which affect the production of graphene/carbon-coated iron and iron-nitrogen compound powders. development and application.

Contents of the invention

In view of the above-mentioned current situation in the art, the object of the present invention is to provide a graphene-coated nano-magnetic composite material with a variable phase state.

The object of the present invention is also to provide a preparation method of graphene-coated nano-magnetic composite material with variable phase state, and the method can regulate the phase type of magnetic core by regulating the nitrogen content ratio of plasma during the preparation process.

The technical scheme that realizes the above-mentioned purpose of the present invention is:

A graphene-coated variable-phase nano-magnetic composite material, which has a core-shell structure, and the shell is a graphene shell, which is composed of multi-layer graphene sheets, and the thickness of the shell layer is 5-50nm; the core is a magnetic core, which is a particle Nano magnetic particles with a diameter of 10-90nm and phase change.

Wherein, the phase state of the nano-magnetic particles is iron phase α-Fe, γ-Fe, and γ-Fe(N), γ'-Fe ₄ N, ε-Fe ₃ N, α”-Fe ₁₆ N ₂ One or more of the iron-nitrogen compounds in phase.

The present invention also proposes the preparation method of the graphene-coated variable-phase nano-magnetic composite material, comprising the following steps:

(1) After cleaning the reaction chamber of the plasma generating device with inert gas continuously and multiple times, the entire reaction chamber is filled with inert gas to isolate the air;

(2) After a stable inert gas plasma flow is obtained by exciting the plasma power supply, a mixed plasma flow is formed by inputting a reaction gas source, and then the ferrocene powder is thermally evaporated, and the ferrocene vapor is sent into the plasma in the form of carrier gas body center area;

(3) Using the high plasma enthalpy and chemical activation effect, ferrocene is rapidly pyrolyzed and undergoes a chemical reaction, then the nano-magnetic particles are obtained by nucleation and growth at the tail of the plasma plume and coated with graphene on the surface of the particles;

(4) The reaction chamber is lowered to room temperature under the protection of inert gas, and the obtained composite powder is collected, which is the graphene-coated nano-magnetic particle composite material.

The plasma method prepares graphene-coated phase-changeable nano-magnetic particles. Compared with other methods, the prepared particle size is smaller, the particle size distribution is uniform, and the magnetic core of different phases can be obtained by controlling the nitrogen content ratio in the plasma. . The invention adopts ferrocene (C ₁₀ H ₁₀ Fe) as a reaction raw material, promotes the reaction through plasma, and directly obtains graphene-coated variable-phase nano-magnetic particle composite powder.

Wherein, ferrocene (C ₁₀ H ₁₀ Fe) is used as the iron source and carbon source, and the evaporating bed temperature of the ferrocene powder is set at 100-400°C; the carrier gas is a combination of argon, nitrogen, and ammonia. one or more species.

Further, the plasma flow is one of the inductively coupled plasma flow, the capacitively coupled plasma flow and the microwave coupled plasma flow, all of which are formed by mixing an inert gas and a reactive gas source, and the reactive gas source and the inert gas The molar ratio is 0-5:1; the inert gas is one or more of argon, helium, and neon, and the reactant gas source is one or more of hydrogen, nitrogen, and ammonia.

Among them, the nitrogen content ratio of the plasma is controlled by adjusting the flow rate of the reaction gas source, inert gas and carrier gas, thereby controlling the phase composition of the nano-magnetic particles, so that the phase states of the nano-magnetic particles are α-Fe, γ-Fe, One or more of γ-Fe(N), γ'-Fe ₄ N, ε-Fe ₃ N, α"-Fe ₁₆ N ₂ .

One of the preferred technical solutions of the present invention is: when the nitrogen-containing ratio of the plasma (the molar ratio of nitrogen atoms to the total atomic weight of the plasma) is 0, the phase state of the nano-magnetic particles in the obtained composite material is α of the iron phase. One or both of -Fe and γ-Fe.

Another preferred technical solution of the present invention is: when the nitrogen-containing ratio of the plasma is 5-80%, the phase state of the nano-magnetic particles in the obtained composite material is γ-Fe(N), γ'-Fe ₄ N , ε-Fe ₃ N or one or more.

The advantages of the present invention are:

(1) The method proposed by the present invention utilizes ferrocene powder as an iron source and a carbon source, and uses plasma as a synthetic environment to reduce toxicity and environmental pollution caused by reactants, which is beneficial to mass production.

(2) The phase of the obtained magnetic nanoparticles can be controlled by adjusting the nitrogen content ratio of the plasma during the preparation process.

(3) The carbon-coated nano-magnetic powder prepared by this method has a fine particle size, uniform distribution, good sphericity, and a short preparation process.

The graphene-coated phase changeable nano-magnetic composite material prepared by the method of the present invention has good chemical stability, magnetic properties and electrical properties at the same time, so it is used in targeted drugs, magnetic fluids, wave-absorbing materials, lithium battery materials and catalysts, etc. It has broad application potential in multiple fields.

Description of drawings

Fig. 1 is the XRD spectrum of the graphene-coated phase transition nano-magnetic composite material prepared in Example 1, Example 2 and Example 3.

Fig. 2 is the particle size distribution and TEM figure of the graphene-coated variable-phase nanoparticle composite material prepared in Example 1

3 is a TEM image of the graphene-coated nanoparticle composite material with variable phase state prepared in Example 2.

4 is a TEM image of the graphene-coated nanoparticle composite material with variable phase state prepared in Example 3.

Detailed ways

The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention.

The preparation method of the graphene-coated phase-changeable nano-magnetic composite material proposed by the present invention comprises the following steps:

(1) After cleaning the reaction chamber of the plasma generating device with inert gas continuously and multiple times, the entire reaction chamber is filled with inert gas to isolate the air;

(2) After a stable inert gas plasma flow is obtained by exciting the plasma power supply, a mixed plasma flow is formed by inputting a reaction gas source, and then the ferrocene powder is thermally evaporated, and the ferrocene vapor is sent into the plasma in the form of carrier gas body center area;

(3) Using the high plasma enthalpy and chemical activation effect, ferrocene is rapidly pyrolyzed and undergoes a chemical reaction, then the nano-magnetic particles are obtained by nucleation and growth at the tail of the plasma plume and coated with graphene on the surface of the particles;

(4) The reaction chamber is lowered to room temperature under the protection of inert gas, and the obtained composite powder is collected, which is the graphene-coated nano-magnetic particle composite material.

The equipment used may be an existing plasma generating equipment. In the embodiment, the equipment disclosed in the patent CN104851548A is specifically used.

Unless otherwise specified, the means adopted in the examples are conventional technical means in the art.

The specific process for the preparation of graphene-coated variable-phase nano-magnetic composite material in the embodiment is as follows:

Example 1:

Using commercially available ferrocene powder as the raw material, after cleaning the reaction chamber with argon for many times, argon plasma is used as the plasma forming gas to establish a stable argon plasma. 5 slpm. The temperature of the constant temperature fluidized bed was set at 120°C, and the ferrocene vapor was sent into the plasma flame flow through the argon gas with a flow rate of 3 slpm. After plasma pyrolysis and activation reaction, graphene-coated phase-changeable nano-magnetic particles were obtained. The product The XRD pattern of the compound is shown in Figure 1, and the TEM pattern and particle size distribution are shown in Figure 2.

It can be seen from Figure 1 that the phase composition of Example 1 is α-Fe, γ-Fe and C. It can be seen from FIG. 2 that the particle size distribution of the obtained graphene-coated variable-phase nano-magnetic composite material is between 10 and 90 nm, and the average particle size is 26.3 nm. The particles are basically spherical or ellipsoidal and covered by a shell, and the measured core diameter and shell thickness are about 20nm and 5nm, respectively. After measuring the interlayer spacing of the core-shell, it is found that the interplanar spacing of the shell layer is about 0.35nm, which is close to the interplanar spacing of the (002) plane of graphene, which indicates that the shell layer is composed of multi-layer graphene sheets; The interplanar spacing of the core is 0.203 nm, which is close to the (110) interplanar spacing of α-Fe and/or the (111) interplanar spacing of γ-Fe, which is consistent with the XRD data. The particle size distribution of the composite material is uniform and the sphericity is good.

Example 2:

Using commercially available ferrocene powder as raw material, after cleaning the reaction chamber with argon several times, argon and nitrogen are used as the plasma forming gas to jointly establish argon-nitrogen plasma with stable operation, in which the flow rate of argon gas is 5 slpm, and the flow rate of nitrogen gas is 1slpm, side protection gas argon flow rate is 10slpm. The constant temperature fluidized bed was set at 160° C., the carrier gas flow rate was 1 slpm argon, and other operations were the same as in Example 1. The XRD pattern of the obtained graphene-coated iron nitride nano-magnetic particles is shown in FIG. 1 , and the TEM image is shown in FIG. 3 .

It can be seen from FIG. 1 that the phase composition of the product prepared in Example 2 is γ-Fe(N), γ′-Fe ₄ N, and ε-Fe ₃ N. It can be seen from Fig. 3 that the particle size distribution of the obtained graphene-coated variable-phase nano-magnetic composite material is between 10 and 90 nm, and it has an obvious core-shell structure, and the core is covered with multiple layers of graphene sheets. The distribution of the composite material is uniform and the sphericity is good.

Example 3:

Using commercially available ferrocene powder as the raw material, after cleaning the reaction chamber with argon several times, argon and nitrogen are used as the plasma forming gas to jointly establish argon-nitrogen radio frequency plasma with stable operation. The flow rate of argon gas is 5 slpm, and the flow rate of nitrogen gas 3slpm, side shielding gas argon flow rate is 10slpm. The constant temperature fluidized bed is set to 180° C., and other operations are the same as in Example 2. The XRD pattern of the obtained graphene-coated iron nitride nano-magnetic particles is shown in FIG. 1 , and the TEM image is shown in FIG. 4 .

As shown in Fig. 1, the phase composition of Example 3 is γ-Fe(N), ε-Fe ₃ N. It can be seen from Fig. 4 that the particle size distribution of the obtained graphene-coated variable-phase nano-magnetic composite material is between 10 and 110 nm, and has an obvious core-shell structure, and the core core is covered with multiple layers of graphene sheets. The distribution of the composite material is uniform and the sphericity is good.

Although, the present invention has been described in detail with general description, specific implementation and test above, but on the basis of the present invention, some modifications or improvements can be made to it, which will be obvious to those skilled in the art . Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (7)

1. a preparation method of graphene-coated variable-phase nano-magnetic composite material, characterized in that, described graphene-coated variable-phase nano-magnetic composite material has a core-shell structure, and the shell is a graphene shell, composed of Composed of multi-layer graphene sheets, the thickness of the shell layer is 5-50nm; the core is a magnetic core, which is a nano-magnetic particle with a particle diameter of 10-90nm and a variable phase state; Described preparation method comprises the following steps: (1) After cleaning the reaction chamber of the plasma generating device with inert gas continuously and multiple times, the entire reaction chamber is filled with inert gas to isolate the air; (2) After a stable inert gas plasma flow is obtained by exciting the plasma power supply, a mixed plasma flow is formed by inputting a reaction gas source, and then the ferrocene powder is thermally evaporated, and the ferrocene vapor is sent into the plasma in the form of carrier gas body center area; (3) Using the high plasma enthalpy and chemical activation effect, ferrocene is rapidly pyrolyzed and undergoes a chemical reaction, then the nano-magnetic particles are obtained by nucleation and growth at the tail of the plasma plume and coated with graphene on the surface of the particles; (4) The reaction chamber is lowered to room temperature under the protection of inert gas, and the obtained composite powder is collected, which is the graphene-coated nano-magnetic particle composite material. 2. The preparation method according to claim 1, characterized in that, the phase states of the magnetic nanoparticles are α-Fe, γ-Fe of the iron phase, and γ-Fe(N), γ'-Fe ₄ N , ε-Fe ₃ N, α''-Fe ₁₆ N ₂ phase iron nitrogen compound or one or more. 3. The preparation method according to claim 1, characterized in that ferrocene (C ₁₀ H ₁₀ Fe) is used as the iron source and carbon source, and the evaporating bed temperature of the ferrocene powder is set at 100-400°C; The carrier gas is one or more of argon, nitrogen and ammonia. 4. The preparation method according to claim 1, characterized in that, the plasma flow is one of inductively coupled plasma flow, capacitively coupled plasma flow, and microwave coupled plasma flow, all composed of inert gas and The reaction gas source is mixed and formed, and the molar ratio of the reaction gas source and the inert gas is 0 to 5:1; the inert gas is one or more of argon, helium, neon, and the reaction gas source is hydrogen, One or more of nitrogen and ammonia. 5. The preparation method according to claim 1, characterized in that, the nitrogen-containing ratio of the plasma is controlled by adjusting the flow rate of the reaction gas source, the inert gas and the carrier gas, thereby controlling the phase composition of the nano-magnetic particles, so that the nano-magnetic particles The phase state of the magnetic particles is one or more of α-Fe, γ-Fe, γ-Fe(N), γ'-Fe ₄ N, ε-Fe ₃ N, α''-Fe ₁₆ N ₂ . 6. preparation method according to claim 5, is characterized in that, when the nitrogen-containing ratio of described plasma is 0, the phase state of the magnetic nanoparticle in the gained composite material is α-Fe of iron phase, γ-Fe one or both of them. 7. preparation method according to claim 5, is characterized in that, when the nitrogen-containing ratio of described plasma is 5 ~ 80%, the phase state of the nano-magnetic particle in the gained composite material is γ-Fe (N), One or more of γ'-Fe ₄ N and ε-Fe ₃ N.