CN110172668B - Preparation method of metal/oxide core-shell structure nanoparticles and nanoparticles thereof - Google Patents

Abstract

The invention belongs to the field of nano material preparation, and particularly relates to a method for preparing metal/oxide core-shell structure nano particles and nano particles thereof. The invention carries out the following sputtering on the required target material: forming plasma nano beam current of metal or alloy kernel on the target material in the sputtering chamber; then the particles enter a transition chamber, oxygen with adjustable flow is introduced into the transition chamber to oxidize the particle surface layer of the plasma nano beam to form an oxide shell layer, and the core-shell structure nano particles with uniform size are obtained. The method is suitable for preparing the core-shell structure nano particles coated by the oxides of various sputterable easily-oxidized metals or alloys; the thickness of the coated oxide layer can be controlled by controlling the oxygen flow; the sputtering environment cooling system ensures that the prepared nano particles have uniform size.

Description

Preparation method of metal/oxide core-shell structure nanoparticles and nanoparticles thereof

Technical Field

The invention belongs to the field of nano material preparation, and particularly relates to a method for preparing metal/oxide core-shell structure nano particles and nano particles thereof.

Background

The core-shell structure nano-particles are prepared by combining two materials with different properties in the form of a core and a coating shell, so that the properties of the core and the coating shell are compounded. The structure can improve the performance of the nano particles so as to meet the application in special environment, and the nano particles are widely concerned by scholars in various fields. The core-shell structure nano-particles formed by the metal or alloy and the oxide of the core-shell structure nano-particles embody various special properties, and have good application prospects in the fields of optical devices, biology, medicines, information and the like.

At present, the core-shell structure nano particles coated by the oxides are mostly prepared by a chemical method, and metal or alloy nano particles are generally prepared by a reduction method and then subjected to oxidation reaction to obtain an oxidation shell layer. For example, Inderhees and Borchers et al treated Co in a mixture of oleic acid and trioctylphosphine oxide₂(Co)₈And carrying out thermal reduction to obtain Co nanoparticles, and oxidizing the Co nanoparticles in an air or oxygen environment to obtain Co/CoO core-shell structure nanoparticles with different thicknesses. (indexes S E, Borchers J A, Green K S, et al. manipulating the magnetic Structure of Co Core/CoO Shell nanoparticules: electrolytes for Controlling the exchange Bias [ J]Physical Review L meters, 2008, 101(11):117202.) this class of method is complicated and has a long production cycle Zeng and L i et al propose a method for producing Core-Shell structured nanoparticles with an oxide Shell layer by laser ablation of a metal target immersed in an aqueous solution of sodium dodecyl sulfate (Haibo Zeng, L i Z, Weiping Cai, et al microstucture Control of Zn/ZnO Core/Shell Nanoparticlesand thermal reaction-Dependent Blue emission J Blue]Journal of physical chemistry B,2007,111(51): 14311-7.). This method is relatively simple in procedure, but it is difficult to ensure uniform size of the prepared nanoparticles. In addition, the methods all need chemical reagents as assistance, and waste liquid generated in the preparation process causes pollution.

The physical methods of the prior art, generally do not involve the preparation of oxide-coated core-shell structured nanoparticles, such as:

the applicant of the present application previously developed a device and a technique for preparing a uniform high-density nanoparticle film by a physical method, which is referred to in chinese patent No.20140279632.3 entitled 'a method for preparing a uniform high-density nanoparticle film', and the structure thereof includes a sputtering chamber provided with a target gun, a deposition chamber for nanoparticle deposition, and a transition chamber connecting the two chambers. In operation, the ion beam sputtered by the target gun flows from the sputtering chamber to the deposition chamber through the transition chamber due to the air pressure of the sputtering chamber and the deposition chamber. The outlet of the sputtering chamber and the inlet of the deposition chamber are two conical screening openings, so that particles can be screened, and the size of a deposition product is uniform.

The applicant of the present application also applied chinese utility model patent No. 201720755090.4, 'a cooling device for nanoparticle preparation under vacuum' (publication No. CN 207035643U). The device can maintain the temperature of the working area to be constant in vacuum, and the uniformity of the particle size of the nano particles is improved. In addition, the size of the particle diameter of the nano particles can be changed by adjusting the temperature; however, the oxide-coated core-shell structure nanoparticles cannot be obtained by the physical methods in the prior art.

Disclosure of Invention

The invention aims to overcome the defects of chemical and physical preparation methods in the prior art, and the method for preparing the core-shell structure nano particles with the oxidation shell layers and the particles thereof, which are uniform in size, simple in preparation process and free of pollution, are obtained in vacuum by improving process parameters and adopting a magnetron sputtering device in the prior art.

In order to achieve the purpose, the invention provides the following technical scheme:

a preparation method of metal/oxide core-shell structure nano-particles, the core-shell structure nano-particles take metal or alloy as a core, the oxide of the metal or alloy is a shell, and the core and the oxide shell of the nano-particles are continuously formed in the same preparation process;

the method comprises the following steps:

a) starting the transition chamber vacuum system and the deposition chamber vacuum system to a vacuum degree higher than 5 × 10^-4Pa；

b) Adjusting the temperature of the sputtering chamber;

c) introducing gas required by sputtering into the sputtering chamber;

d) introducing oxygen into the transition chamber;

e) adjusting an air inlet plate valve of a molecular pump of the transition chamber to form a step pressure difference of sputtering chamber air pressure, transition chamber air pressure and deposition chamber air pressure;

f) the air pressure is stable, and after the air mixing is sufficient, the required target material is sputtered as follows: forming plasma nano beam current of metal or alloy kernel on the target material in the sputtering chamber; then the particles enter a transition chamber, oxygen with adjustable flow is introduced into the transition chamber to oxidize the particle surface layer of the plasma nano beam to form an oxide shell layer, and the core-shell structure nano particles with uniform size are obtained.

In step f), the sputtering comprises: and the first sputtering and the second sputtering are carried out, after a stable plasma nanoparticle beam current is formed by the first sputtering, a baffle (5) is opened to start the second sputtering, and the formed core-shell structure nanoparticles enter a deposition chamber (2).

The prepared core-shell structure nano-particles are core-shell structure nano-particles with Co as a core and CoO as a shell, or core-shell structure nano-particles with CoFe as a core and Co and Fe oxides as shells.

The gas introduced during sputtering is divided into gas required by sputtering and oxygen gas which are respectively introduced into the sputtering chamber and the transition chamber.

In the step b), the temperature of the sputtering chamber is adjusted by starting a cooling system of the sputtering chamber and adjusting the temperature of the cooling liquid in the interlayer of the cavity of the sputtering chamber, wherein the temperature of the sputtering chamber is-50 ℃ to 30 ℃.

The gas required by sputtering in the step c) comprises a mixed gas of a cooling gas and a sputtering gas, and comprises one or more of nitrogen, argon and helium.

The flow rate of the introduced gas in the step c) is 40-100 SCCM.

The flow of the introduced oxygen in the step d) is 0.3-5 SCCM.

The target material in the step f) is one of the following target materials made of oxidizable metals and alloys: co, Fe, Al, Cu, Zn, Ni, Ag, Mo, Mn and alloys thereof.

The difference between the transition chamber pressure and the deposition chamber pressure in step f) is maintained at 10^-2Of the order of Pa.

The thickness of the oxide shell layer is regulated and controlled by regulating the oxygen flow.

The nano-particles are obtained by the preparation method of the metal/oxide nano-particles with the core-shell structure, the metal or alloy is used as an inner core of the nano-particles with the core-shell structure, and the oxide of the metal or alloy is used as a shell layer;

the nano-particles are prepared by adopting a magnetron sputtering process as follows: forming plasma nano beam current of metal or alloy kernel on the target material in the sputtering chamber; then the plasma nano beam enters a transition chamber, and oxygen with adjustable flow is introduced into the transition chamber to oxidize the particle surface of the plasma nano beam to form an oxide shell.

The diameter of the nano-particles is 7.54-22.6 nm, and the thickness of the oxide shell layer is 1.96-4.5 nm.

The thickness of the oxide shell layer is regulated and controlled by regulating the flow of oxygen introduced into the transition chamber.

The nano-particles are of a core-shell structure with Co as an inner core and CoO as a shell layer.

When the nano-particles are used for magnetic materials, the coercive force is 20.68-24.5 Oe, the saturation magnetization is 269.78-388.65 emu/g, and the remanence magnetization is 227.61-325.59 emu/g.

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

proper oxygen is introduced into plasma nano beam current formed during sputtering of a target material of a corresponding inner core to oxidize the surface layer of the nano particles to generate a core-shell structure, so that the generation processes of the core and the oxidation shell of the nano particles are continuously generated in one system, and the operation flow is simpler; the thickness of the oxidation shell layer can be directly regulated and controlled only by controlling the oxygen flow; the cooling system ensures the constant temperature of the sputtering working environment, so that the prepared particles are uniform in size; the preparation process has no pollution or side product. By replacing different targets, the method is suitable for various easily oxidized metals and alloys.

Drawings

FIG. 1 is a schematic view of the production process of the present production method.

FIG. 2a is TEM morphology and particle size distribution statistics of nanoparticles prepared in example 1;

FIG. 2b is TEM morphology and particle size distribution statistics of nanoparticles prepared in example 2;

FIG. 2c is TEM morphology and particle size distribution statistics of nanoparticles prepared in example 3;

FIG. 2d is TEM morphology and particle size distribution statistics of nanoparticles prepared in example 4;

FIG. 3a is the HTEM morphology of the nanoparticles prepared in example 1;

FIG. 3b is the HTEM morphology of the nanoparticles prepared in example 2;

FIG. 3c is the HTEM morphology of the nanoparticles prepared in example 3;

FIG. 3d is the HTEM morphology of the nanoparticles prepared in example 4;

FIG. 4a is a schematic hysteresis loop of the nanoparticles prepared in examples 1, 2 and 3;

FIG. 4b shows the coercive force, saturation magnetization and remanence magnetization of the nanoparticles prepared in examples 1, 2 and 3.

Reference numerals:

1 transition chamber 2 deposition chamber 3 target gun

4 transition chamber vacuum system 5 baffle 6 deposition chamber vacuum system

7 sputtering chamber

Detailed Description

The invention is further illustrated below with reference to the accompanying drawings:

as shown in fig. 1, the present invention uses a magnetron sputtering apparatus to prepare core-shell structured nanoparticles, and the apparatus includes a transition chamber 1, a deposition chamber 2, a target gun 3, a transition chamber vacuum system 4, a baffle plate 5, a deposition chamber vacuum system 6, and a sputtering chamber 7.

A method for preparing core-shell structure nanoparticles comprises the following steps:

(1) the transition chamber vacuum system 4 and the deposition chamber vacuum system 6 are started to make the vacuum degree better than 5 × 10^-4Pa；

(2) Starting a cooling system of the sputtering chamber 7 to adjust the temperature of the cooling liquid, wherein the temperature of the cooling liquid is-50 ℃ to 30 ℃;

(3) introducing gas required for sputtering into the sputtering chamber 7, wherein the gas required for sputtering comprises mixed gas of cooling gas and sputtering gas, including one or more of nitrogen, argon and helium, and the introduced flow is 40-100 SCCM;

(4) introducing oxygen into the transition chamber 1, wherein the flow of the introduced oxygen is 1SCCM-5 SCCM; the thickness of the oxide shell is regulated and controlled by adjusting the oxygen flow, and the larger the oxygen flow is, the larger the thickness of the oxide shell is increased.

(5) Adjusting the gas inlet plate valve (not shown) of the vacuum system of the transition chamber to form the gas pressure of the sputtering chamber 7>Transition chamber 1 atmosphere>The pressure difference of the deposition chamber 2 is kept at 10^-2Pa is about;

(6) after the air pressure is stable, mixing the air uniformly, and pre-sputtering (first sputtering) the required target to form a stable plasma nanoparticle beam, wherein the target comprises one of targets made of easily-oxidized metals and alloys; core-shell structure nano particles with oxide shell layers and uniform size can be generated after the pre-sputtering is finished;

(7) then, opening the baffle (5) to start second sputtering, and enabling the formed core-shell structure nanoparticles to enter the deposition chamber (2).

Example 1:

(1) a Co target is arranged on the sputtering target gun 3;

(2) starting the vacuum system of the transition chamber and the vacuum system of the deposition chamber until the vacuum degree is better than 5 × 10^-4Pa；

(3) Starting a cooling system of the sputtering chamber to adjust the temperature of the cooling liquid to be 20 ℃;

(4) introducing argon gas flow of 82SCCM into the sputtering chamber;

(5) introducing oxygen into the transition chamber at a flow rate of 1 SCCM;

(6) adjusting the gas inlet plate valve of the molecular pump in the transition chamber to form the gas pressure in the sputtering chamber>Transition chamber gas pressure>A step pressure difference of the deposition chamber air pressure; wherein the transition chamber pressure is 2pa, the deposition chamber pressure is 1 x 10^-2Pa。

(7) After the air pressure is stable, uniformly mixing the air and performing pre-sputtering (first sputtering) to form a stable plasma nanoparticle beam; then, the baffle 5 is opened to start the second sputtering, so that the formed core-shell structure nano particles enter the deposition chamber 2. The prepared Co @ CoO core-shell structure nano-particles have the particle size range of 7.49-22.6 nm and the average particle size of 10-15 nm. TEM topography and particle size statistics are shown in fig. 2a and HTEM topography is shown in fig. 3 a.

Example 2:

the same procedure as in example 1 was used, wherein the oxygen flow rate in step (5) was 3 SCCM. TEM morphology and particle size statistics are shown in fig. 2b and HTEM morphology is shown in fig. 3 b.

Example 3:

the same procedure as in example 1 was used, wherein the oxygen flow rate in step (5) was 5 SCCM. TEM morphology and particle size statistics are shown in fig. 2c and HTEM morphology is shown in fig. 3 c.

Example 4:

wherein, the step (1) is that a CoFe alloy target is arranged on a sputtering target gun 3; wherein the flow rate of the oxygen introduced in the step (5) is 0.3 SCCM. After the air pressure is stable, uniformly mixing the air, and performing pre-sputtering (first sputtering) to form a stable plasma nano particle beam; then, the baffle 5 is opened to start the second sputtering, so that the formed core-shell structure nano particles enter the deposition chamber 2. Preparing CoFe as kernel₂O₄The oxide of (2) is a shell layer of the core-shell structured nanoparticle, the TEM morphology and the particle size statistics result are shown in FIG. 2d, and the HTEM morphology is shown in FIG. 3 d.

As can be seen from FIGS. 2a to 2c, the nanoparticles prepared under different parameters have good uniformity, and the average particle size is 11nm to 12 nm.

The shell thicknesses of the nano-particles prepared in the examples 1, 2 and 3 are 1.96nm, 2.75nm and 4.5nm respectively; it can be seen from FIGS. 3a to 3c that the oxide coating increases with increasing oxygen flow.

Fig. 2d and 3d show that core-shell structure nanoparticles with uniform particle size can be obtained by introducing oxygen into targets of other metals or alloys.

Fig. 4 shows the hysteresis loop (fig. 4a), the coercivity, the saturation magnetization and the remanence magnetization (fig. 4b) of the nanoparticles prepared in examples 1, 2 and 3. The coercive force of the nano-particles prepared by oxygen flux of 1SCCM, 3SCCM and 5SCCM is 20.68Oe, 23.66Oe and 24.54Oe respectively; the saturation magnetization is 269.78emu/g, 301.24emu/g and 388.65emu/g respectively; the remanent magnetization is 227.61emu/g, 246.90emu/g and 325.59emu/g respectively.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All changes and modifications of the equivalent structures and processes that come within the spirit of the invention are to be embraced within the scope of the invention.

Claims (15)

1. A preparation method of metal/oxide core-shell structure nano-particles is characterized in that,

the core-shell structure nano-particles take metal or alloy as a core, the oxide of the metal or alloy as a shell, and the core and the oxide shell of the nano-particles are continuously formed in the same preparation process; the diameter of the nano-particles is 7.54-22.6 nm, and the thickness of an oxide shell layer is 1.96-4.5 nm;

the method comprises the following steps:

a) starting the transition chamber vacuum system and the deposition chamber vacuum system to a vacuum degree higher than 5 × 10^-4Pa；

b) Adjusting the temperature of the sputtering chamber;

c) introducing gas required by sputtering into the sputtering chamber;

d) introducing oxygen into the transition chamber;

e) adjusting an air inlet plate valve of a molecular pump of the transition chamber to form a step pressure difference of sputtering chamber air pressure, transition chamber air pressure and deposition chamber air pressure;

f) the air pressure is stable, and after the air mixing is sufficient, the required target material is sputtered as follows: forming plasma nano beam current of metal or alloy kernel on the target material in the sputtering chamber; then the particles enter a transition chamber, oxygen with adjustable flow is introduced into the transition chamber to oxidize the particle surface layer of the plasma nano beam to form an oxide shell layer, and the core-shell structure nano particles with uniform size are obtained.

2. The method of claim 1,

in step f), the sputtering comprises: and the first sputtering and the second sputtering are carried out, after a stable plasma nanoparticle beam current is formed by the first sputtering, a baffle (5) is opened to start the second sputtering, and the formed core-shell structure nanoparticles enter a deposition chamber (2).

3. The method of claim 1,

the prepared core-shell structure nano-particles are core-shell structure nano-particles with Co as a core and CoO as a shell, or core-shell structure nano-particles with CoFe as a core and Co and Fe oxides as shells.

4. The method of claim 1,

the gas introduced during sputtering is divided into gas required by sputtering and oxygen gas which are respectively introduced into the sputtering chamber and the transition chamber.

5. The method of claim 1,

in the step b), the temperature of the sputtering chamber is adjusted by starting a cooling system of the sputtering chamber and adjusting the temperature of the cooling liquid in the interlayer of the cavity of the sputtering chamber, wherein the temperature of the sputtering chamber is-50 ℃ to 30 ℃.

6. The method of claim 1,

the gas required by sputtering in the step c) comprises a mixed gas of a cooling gas and a sputtering gas, and comprises several of nitrogen, argon and helium.

7. The method of claim 1,

the flow rate of the introduced gas in the step c) is 40-100 SCCM.

8. The method of claim 1,

the flow of the introduced oxygen in the step d) is 0.3-5 SCCM.

9. The method of claim 1,

the target material in the step f) is one of the following target materials made of oxidizable metals and alloys: co, Fe, Al, Cu, Zn, Ni, Ag, Mo, Mn and alloys thereof.

10. The method of claim 1,

the difference between the transition chamber pressure and the deposition chamber pressure in step f) is maintained at 10^-2Of the order of Pa.

11. The method of claim 1,

the thickness of the oxide shell layer is regulated and controlled by regulating the oxygen flow.

12. A nanoparticle obtained by the method for producing a metal/oxide core-shell structured nanoparticle according to claim 1,

the core-shell structure nano-particles take metal or alloy as an inner core, and oxide of the metal or alloy as a shell layer; the diameter of the nano-particles is 7.54-22.6 nm, and the thickness of an oxide shell layer is 1.96-4.5 nm;

the nano-particles are prepared by adopting a magnetron sputtering process as follows: forming plasma nano beam current of metal or alloy kernel on the target material in the sputtering chamber; then the plasma nano beam enters a transition chamber, and oxygen with adjustable flow is introduced into the transition chamber to oxidize the particle surface of the plasma nano beam to form an oxide shell.

13. The nanoparticle of claim 12,

the thickness of the oxide shell layer is regulated and controlled by regulating the flow of oxygen introduced into the transition chamber.

14. The nanoparticle of claim 12,

the nano-particles are of a core-shell structure with Co as an inner core and CoO as a shell layer.

15. The nanoparticle of claim 14,

when the nano-particles are used for magnetic materials, the coercive force is 20.68-24.5 Oe, the saturation magnetization is 269.78-388.65 emu/g, and the remanence magnetization is 227.61-325.59 emu/g.

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