CN101032754B - Method for preparing nanometer metal by low temperature plasma reduction - Google Patents

Abstract

The invention relates to a method for preparing nanometer metal by low-temperature plasma reduction in the technical field of material science. The production method is to put the metal salt directly into the vacuum chamber of the plasma discharger, evacuate the vacuum chamber, and then pass in the plasma discharge gas. The gas pressure is kept at 30-200 Pa, and 200 Pa is applied to both ends of the electrode by a high-voltage power supply. ~5000V DC or AC discharges the discharge gas to form plasma to reduce the metal salt. The reduction time is 5~120min, thereby preparing nanometer metal particles. The invention has the advantages of simple device, convenient operation, energy saving, large amount of processed metal, no chemical reducing agent, and environmental friendliness; the prepared nano-metal particles have high purity, small particle size, narrow particle size distribution range, and good dispersibility. It has excellent performance and unique performance when combined with other materials, and has broad application prospects in many fields such as molecular devices, chemical/biological sensors, catalysis, and optoelectronic materials.

Description

Method for preparing nanometer metal by low temperature plasma reduction

technical field

The invention relates to the technical field of material science, in particular to a method for preparing nanometer metal by low-temperature plasma reduction.

Background technique

Nanomaterials, also known as ultrafine particle materials, are composed of nanoparticles. Nanoparticles, also called ultrafine particles, generally refer to particles with a size between 1 and 100 nm. Nanoparticles have many advantages: small particle size, large specific surface area, and high catalytic efficiency. In addition, their optical, thermal, electrical, magnetic, mechanical, and chemical properties are significantly different from those of bulk solids; Metal particles have a single magnetic domain structure and high coercive force, and can be made into conductive coatings, conductive adhesives, etc. by using the conductivity of nano-metal particles. There are many potential applications of nano-metal particles, such as rocket boosters, microporous gas separation membranes, structural materials, and bioengineering materials. Nano-metal particles have excellent properties and unique properties when combined with other materials, and have broad application prospects in many fields such as molecular devices, chemical/biological sensors, catalysis, and optoelectronic materials.

The current methods for preparing metal nanoparticles are mainly chemical reduction method and sol-gel method, both of which need to use strong reducing chemical reagents in the solution, such as using strong reducing agent NaBH ₄ to reduce metal compounds into metal particles. The disadvantages of this method are: the preparation process is cumbersome, the operation is complicated, the conditions are harsh, and it is not easy to control, and the above-mentioned reducing agent is harmful to the environment; wherein the gel method needs to be sintered to obtain nanoparticles at the end, and the obtained nanoparticles are easy to obtain. Agglomeration, larger particle size.

The closest published technique to the present invention is: In Langmuir (2006, 11388-11394), Liu et al. disclosed a new method for the reduction of supported metal catalysts. The method uses glow discharge plasma to reduce noble metals loaded on titanium dioxide and other carriers in an argon atmosphere without using a chemical reducing agent. The device is simple, easy to operate, energy saving, and environmentally friendly. It has wide application prospect in the field of catalyst preparation. But there are also certain defects, such as long time-consuming, small amount of processed metal, and uneven distribution of obtained nano-metal particles.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for preparing nano-metals by low-temperature plasma reduction; the method is easy to operate and environmentally friendly, and the prepared nano-metal particles have high purity, small particle size, and a particle size distribution range Narrow and good dispersion.

The present invention is achieved through the following technical solutions:

A method for preparing nano-metal by low-temperature plasma reduction, the production method comprising the following steps:

(1). The metal salt is directly loaded into the vacuum chamber of the plasma discharger;

(2). Vacuumize the vacuum chamber, and then pass in the plasma discharge gas, and keep the gas pressure at 30-200Pa;

(3).Using a high-voltage power supply to apply 200-5000V DC or AC at both ends of the electrodes to discharge the discharge gas, and the formed plasma reduces the metal salt. The reduction time is 5-120 minutes, thereby preparing nano-metal particles.

Moreover, the metal salt is a salt formed by platinum or palladium or gold or silver or ruthenium or rhodium or rhenium or iridium.

Moreover, the metal salt is chloride or nitrate.

Moreover, the plasma discharge gas is an inert gas or air or oxygen, or a mixture of the above gases.

Moreover, the inert gas is argon or nitrogen or helium.

Moreover, the gas discharge is in the form of glow discharge or dielectric barrier discharge or corona discharge.

Moreover, the particle size of the prepared nano-metal particles is in the range of 2.5-20nm.

Advantage and beneficial effect of the present invention are:

1. The plasma method that the present invention relates to produces nano-metal is to utilize a large amount of high-energy electrons in the plasma produced by high-voltage direct current or alternating current power discharge to arrive near the metal particle at first, and wherein a part of electrons can be captured, and metal is promptly reduced by electrostatic, thereby Generate nanometals. The nanometer metal prepared by the plasma method has the advantages of large output, easy control of particle size and good performance.

2. The low-temperature plasma reduction method used in the present invention to prepare nano-metals can quickly and effectively prepare nano-metal particles, which can be carried out at room temperature, avoiding adverse thermal effects at high temperatures, and is simple to operate, saves energy consumption, and the amount of metal processed is large , does not use chemical reducing agents, and is environmentally friendly.

3. The plasma used in the present invention contains a large number of electrons, so that the metal compound is easily reduced; and the electrons are attached to the metal particles and repel each other, which can effectively prevent the aggregation and growth of the metal particles, thereby forming a fine and uniform distribution Crystal grains, so that the prepared nano-metal particles have high purity, small particle size, narrow particle size distribution range, and good dispersion. The particle size of the nano-metal particles is in the range of 2.5-20nm.

Description of drawings

Fig. 1 is the photoelectron energy spectrogram of chloroauric acid after low-temperature plasma treatment reduction;

Fig. 2 is the electron diffraction spectrogram of chloroauric acid after low-temperature plasma treatment reduction;

Fig. 3 is a high-magnification transmission electron microscope image of chloroauric acid reduced by low-temperature plasma treatment.

Detailed ways

The present invention is further described in detail through the following embodiments in conjunction with the accompanying drawings, but the technical content described in this embodiment is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

Example 1

Put chloroauric acid (HAuCl ₄ ) between the two electrode plates of the discharge tube in the vacuum chamber, seal it, evacuate the vacuum chamber, then fill it with argon as the discharge gas, maintain the pressure of 30Pa, and apply 800V on the electrode DC voltage, using glow discharge plasma to reduce chloroauric acid (HAuCl ₄ ), the reduction time is 100min, and prepare nano-gold particles with a particle size of 2.5-7nm.

The prepared nano-gold particles are analyzed by photoelectron energy spectrum, electron diffraction and transmission electron microscope, and the following analysis results can be obtained:

As shown in Figure 1, the photoelectron energy spectrogram shows that only the characteristic peaks of gold elements appear in the spectrum, showing that chloroauric acid is reduced to zero-valent gold by the low-temperature plasma method;

Electron diffraction figure as shown in Figure 2, only has the diffraction peak of simple gold in the figure, does not have other impurity diffraction peak to exist, shows that chloroauric acid is completely reduced;

As shown in Fig. 3, it is a high-power transmission electron microscope image, from which it can be seen that the prepared nano-gold particles are fine and uniform, and the particle size is 2.5-7nm.

Example 2:

Put H ₂ PtCl ₆ between the two electrode plates of the discharge tube in the vacuum chamber, seal it tightly, evacuate the vacuum chamber, then fill it with helium as the discharge gas, maintain the pressure of 50Pa, and apply a DC voltage of 200V on the electrodes, Using corona discharge plasma to reduce H ₂ PtCl ₆ , the reduction time is 120 min, and prepare nano-platinum particles. It was confirmed by photoelectron spectroscopy, electron diffraction and transmission electron microscopy that H ₂ PtCl ₆ was completely reduced to elemental platinum with a particle size of 2.5-10nm.

Example 3:

Place PdCl ₂ between the two electrode plates of the discharge tube in the vacuum chamber, seal it tightly, evacuate the vacuum chamber, then fill it with oxygen as the discharge gas, maintain the pressure of 90Pa, apply an AC voltage of 1000V on the electrode, and use a dielectric barrier The PdCl ₂ was reduced by the discharge plasma, and the reduction time was 40 minutes to prepare nano-lead particles. It was confirmed by photoelectron spectroscopy, electron diffraction and transmission electron microscopy that PdCl ₂ was completely reduced to elemental lead with a particle size of 3.0-15nm.

Example 4:

Put AgNO ₃ between the two electrode plates of the discharge tube in the vacuum chamber, seal it tightly, evacuate the vacuum chamber, then fill it with nitrogen as the discharge gas, maintain the pressure of 120Pa, apply an AC voltage of 1500V on the electrodes, and use glow AgNO ₃ was reduced by discharge plasma, and the reduction time was 60 minutes to prepare nano-silver particles. It was confirmed by photoelectron spectroscopy, electron diffraction and transmission electron microscopy that AgNO ₃ was completely reduced to elemental silver with a particle size of 3.0-20nm.

Example 5:

Place H ₂ IrCl ₆ between the two electrode plates of the discharge tube in the vacuum chamber, seal it, evacuate the vacuum chamber, then fill it with air as the discharge gas, maintain the pressure of 150Pa, apply an AC voltage of 2000V on the electrodes, and use The glow discharge plasma reduces H ₂ IrCl ₆ , and the reduction time is 80 minutes, and the nanometer iridium particles are prepared. It was confirmed by photoelectron spectroscopy, electron diffraction and transmission electron microscopy that H ₂ IrCl ₆ was completely reduced to elemental iridium with a particle size of 4.0-18nm.

Embodiment 6:

Place ReCl ₅ between the two electrode plates of the discharge tube in the vacuum chamber, seal it tightly, evacuate the vacuum chamber, then fill it with argon as the discharge gas, maintain a pressure of 180Pa, apply a DC voltage of 3000V to the electrodes, and use a glow Photodischarge plasma reduces ReCl ₅ , the reduction time is 20min, and prepares nano-rhenium particles. It was confirmed by photoelectron spectroscopy, electron diffraction and transmission electron microscopy that ReCl ₅ was completely reduced to elemental rhenium with a particle size of 3.5-20nm.

Embodiment 7:

Place H ₃ RhCl ₆ between the two electrode plates of the discharge tube in the vacuum chamber, seal it tightly, evacuate the vacuum chamber, then fill it with helium as the discharge gas, maintain the pressure of 200Pa, and apply a DC voltage of 4000V on the electrodes, Using glow discharge plasma to reduce H ₃ RhCl ₆ , the reduction time is 10 minutes, and prepare nanometer rhodium particles. Photoelectron spectroscopy, electron diffraction and transmission electron microscopy confirmed that ReCl ₅ was completely reduced to elemental rhodium with a particle size of 2.5-20nm.

Embodiment 8:

Put _RuCl3 between the two electrode plates of the discharge tube in the vacuum chamber, seal it tightly, evacuate the vacuum chamber, then fill it with air as the discharge gas, maintain the pressure of 90Pa, apply an AC voltage of 5000V on the electrodes, and use corona RuCl ₃ was reduced by discharge plasma, and the reduction time was 5 minutes, to prepare nanometer ruthenium particles. It was confirmed by photoelectron spectroscopy, electron diffraction and transmission electron microscopy that RuCl ₃ was completely reduced to elemental ruthenium with a particle size of 2.5-20nm.

Claims (7)

1. the method for a producing nanometer metal by plasma deoxidization in low termprature, it is characterized in that: this production method may further comprise the steps:

(1). slaine is directly packed in the vacuum chamber of plasma discharger;

(2). vacuum chamber is vacuumized, feed plasma discharge gas then, gas pressure remains on 30～200Pa;

(3). the direct current or the alternating current that utilize high voltage source to apply 200～5000V at the electrode two ends make the discharge gas discharge, and the plasma of formation reduces slaine, and the recovery time is 5～120min, prepares nano metal particles thus.

2. the method for producing nanometer metal by plasma deoxidization in low termprature according to claim 1, it is characterized in that: described slaine is platinum or palladium or gold or silver or ruthenium or rhodium or rhenium or the formed salt of iridium.

3. the method for producing nanometer metal by plasma deoxidization in low termprature according to claim 2, it is characterized in that: described slaine is chloride or nitrate.

4. the method for producing nanometer metal by plasma deoxidization in low termprature according to claim 1, it is characterized in that: described plasma discharge gas is inert gas or air or oxygen, perhaps the mixture of above-mentioned gas.

5. the method for producing nanometer metal by plasma deoxidization in low termprature according to claim 4, it is characterized in that: described inert gas is argon gas or nitrogen or helium.

6. the method for producing nanometer metal by plasma deoxidization in low termprature according to claim 1, it is characterized in that: the form of described gas discharge is glow discharge or dielectric barrier discharge or corona discharge.

7. the method for producing nanometer metal by plasma deoxidization in low termprature according to claim 1, it is characterized in that: the particle diameter of the described nano metal particles of preparing is in 2.5～20nm scope.

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