A device and method for generating monodisperse spherical metal aerosol particles

Abstract

The present invention relates to a device and method for generating monodisperse spherical metal aerosol particles, the device comprising a high temperature tube furnace, a differential electric mobility analyzer, a flow and voltage control box, a low temperature plasma, and a plasma power supply. Compared with the prior art, the present invention can generate multiple types of monodisperse metal aerosol particles, and the size of the particles can be adjusted in real time: the chemical composition of the particles can be changed by replacing the metal element in the tube furnace, and the size of the generated metal particles can be adjusted in real time by adjusting the voltage of the electric mobility analyzer.

Description

Technical Field

[0001] The invention belongs to the technical field of monodisperse aerosol particle preparation, and relates to a device and a method for generating monodisperse spherical metal aerosol particles. Background Art

[0002] Monodisperse aerosol particles refer to particles of uniform size suspended in a gas, and have many applications in scientific research and engineering involving the environment, chemistry, and materials. For example, monodisperse aerosols can be used to calibrate particle size measuring instruments, particle optical detectors, etc. In addition, since the chemical, optical, and mechanical properties of particles are closely related to their particle size, the generation of monodisperse particles is a necessary condition for conducting size-dependent studies. Currently, a variety of methods for generating gas-phase monodisperse particles have been developed, and the main methods are briefly described as follows:

[0003] (1) Electrospray or mechanical spray method. This method first synthesizes a dispersion of monodisperse particles in the liquid phase by chemical methods. The size of the particles can be adjusted by controlling the concentration of the particle precursor and the reaction time. After the dispersion is synthesized, it is introduced into the electrospray device. By applying an electric field, the solution forms fine charged droplets at the outlet of the electrospray needle. Through the volatilization of solutes and the rupture of droplets due to the electrostatic repulsion of the electric field, monodisperse particles are finally formed. The size is consistent with the basic size of the particles in the dispersion. Unlike the electrospray device, the mechanical spray method uses the interaction between gas and liquid to generate droplets. The solutes in these droplets evaporate during the transmission process (such as through a drying tube), and finally form monodisperse aerosol particles.

[0004] (2) Vibrating hole generator. This method suspends a non-volatile solute in a volatile solute, and then uses a syringe pump to pass the solution through a small hole connected to a piezoelectric ceramic at a certain flow rate. By applying a high-frequency voltage to the piezoelectric ceramic, the piezoelectric effect is used to make the small hole vibrate periodically, thereby breaking the salt solution flowing through the small hole into droplets of uniform particle size. After the solvent in the droplets evaporates, the remaining solute generates monodisperse aerosol particles.

[0005] (3) Combining a polydisperse aerosol generator with a particle size selection device to generate a monodisperse aerosol. This method first uses a method such as evaporation condensation or atomization to generate a polydisperse aerosol, and then screens out particles with uniform particle size through particle charging and particle size selection devices.

[0006] The above methods can be used to generate various types of monodisperse aerosols, but all of the above methods have significant drawbacks for generating monodisperse spherical metal particles, which are described in detail as follows:

[0007] (1) The use of electrospray or mechanical spray to prepare monodisperse metal aerosol particles requires first preparing a dispersion of the particles by liquid phase chemistry. The process of preparing the dispersion is generally complicated, and the types of metals that can be prepared are mostly limited to precious metals. In addition, commercial metal particle dispersions are expensive. In addition, in order to prevent the particles from agglomerating in the liquid, it is necessary to add "surfactants" to the particles. After spraying, these surfactants will remain on the surface of the particles, changing the particle size and surface properties of the particles. In addition, the monodispersity of the aerosol particles generated by this method depends on the monodispersity of the liquid phase particles.

[0008] (2) The vibration hole generator method can only generate particles composed of species that are micron-sized and soluble in water or organic solvents, and is generally not suitable for generating metal particles.

[0009] (3) Metal particles generated using the 'particle size selection device + polydisperse aerosol generator' method, but their structure is affected by the collision of particles to form a condensed state rather than a single sphere.

[0010] In summary, although there are some methods that can generate monodisperse aerosol particles, these methods are not suitable for the ability to generate a variety of spherical metal particles with controllable sizes. Summary of the invention

[0011] The purpose of the present invention is to provide a device and method for generating monodisperse spherical metal aerosol particles.

[0012] The present invention can generate multiple types of monodisperse metal aerosol particles, and the size of the particles can be adjusted in real time: the chemical composition of the particles can be changed by replacing the metal element in the tube furnace, and the size of the generated metal particles can be adjusted in real time by adjusting the voltage of the electric mobility analyzer.

[0013] The purpose of the present invention can be achieved by the following technical solutions:

[0014] One of the technical solutions of the present invention provides a device for generating monodisperse spherical metal aerosol particles, comprising:

[0015] A high temperature tube furnace, inside which is provided a sample boat loaded with metal elements;

[0016] A differential mobility analyzer, which has an aerosol flow inlet, an aerosol flow outlet, a sheath gas inlet, a sheath gas outlet and a central cylindrical electrode, wherein the aerosol flow inlet is connected to the outlet of the high-temperature tube furnace;

[0017] A flow voltage control box, comprising a sheath gas flow pipeline with two ends respectively connected to a sheath gas outlet and the sheath gas inlet and with a controllable flow rate, and a high-voltage electric module with a controllable output voltage, the high-voltage electric module being connected to the central cylindrical electrode;

[0018] A plasma generator comprises a quartz tube, a tube electrode extending into the interior of the quartz tube and sealedly connected to the tube mouth of the quartz tube, and an annular electrode arranged outside the quartz tube, wherein the tube electrode and the annular electrode are respectively connected to the positive and negative electrodes of a plasma power supply, the tube electrode is hollow inside, and one end thereof away from the quartz tube is also connected to the aerosol outlet, and the annular electrode is grounded.

[0019] Furthermore, the sample boat is a quartz boat or a corundum boat.

[0020] Furthermore, the sheath gas flow pipeline is provided with a flow meter, a flow control valve, and a blower in sequence, and a filter is provided at the front and rear ends of the blower respectively.

[0021] Furthermore, the flow control valve is a needle valve.

[0022] Furthermore, the tube electrode is connected to the aerosol outlet through an insulating tube.

[0023] Furthermore, the tube electrode is connected to the quartz tube via a sealed adapter.

[0024] Furthermore, the quartz tube is also connected to an outlet tube.

[0025] Furthermore, the output voltage range of the high voltage electric module is -10kV to 10kV.

[0026] Furthermore, the plasma power supply is an AC power supply or a high-voltage DC power supply.

[0027] A second technical solution of the present invention provides a method for generating monodisperse spherical metal aerosol particles, which is based on any of the above-described devices for generating monodisperse spherical metal aerosol particles, and the method comprises the following steps:

[0028] (1) taking a metal sample and placing it in a sample boat, introducing an inert carrier gas into a high-temperature tube furnace, and heating the high-temperature tube furnace to a preset temperature;

[0029] (2) Open the sheath gas flow line, adjust the sheath gas flow rate to a preset value, and set the output voltage of the flow voltage control box;

[0030] (3) Turn on the plasma power supply, adjust to the preset output voltage and frequency, and excite plasma between the tube electrode and the ring electrode;

[0031] (4) After the temperature of the high-temperature tube furnace and the plasma generator are stabilized, highly monodispersed metal spherical particles with stable concentration are obtained at the outlet of the quartz tube.

[0032] The working principle of the present invention is briefly described as follows: in a high-temperature tube furnace, a metal element is heated and converted into a gaseous state and enters a carrier gas. The gas temperature is reduced in the downstream of the temperature tube furnace, and the gaseous metal generates particles through a nucleation process. These particles further collide and form multi-dispersed condensed metal particles. After the condensed metal particles enter the differential mobility analyzer, they are subjected to the combined action of the electric field and air resistance, and only particles of a certain size can pass through the analyzer and enter the plasma of the next level. There is a one-to-one correspondence between the voltage of the mobility analyzer and the size of the particles entering the plasma, that is, the size of the particles can be changed by changing the voltage. The flow voltage control box provides the necessary working airflow and voltage for the differential mobility analyzer. After the particles enter the plasma, they will be selectively heated due to the electrical neutralization and heat release of electrons and ions on the surface, so that their temperature is higher than the surrounding carrier gas temperature. The heated particles will be converted into spherical particles due to heating, and their monodispersity will also be improved in this process due to the morphology conversion into a sphere.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1) This device uses a tube furnace to generate polydisperse metal particles as a precursor to monodisperse particles, is applicable to many types of metals, and is not limited by the availability of monodisperse nanoparticle dispersions.

[0035] 2) The use of the device does not involve complicated liquid phase chemical synthesis steps.

[0036] 3) This device utilizes the property of selective heating of particles by atmospheric-pressure low-temperature plasma to transform condensed metal particles into highly monodisperse (geometric standard deviation as low as 1.04) spherical nanoparticles.

[0037] 4) The device can adjust the particle size of the obtained metal particles in real time by changing the sheath gas flow rate and voltage of the differential mobility analyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a structural schematic diagram of the present invention;

[0039] Figure 2 is a process flow chart of the present invention;

[0040] Figure 3 is a graph showing the change in the particle size distribution of silver particles at different positions in the device in Example 2;

[0041] Figure 4 is the particle image obtained in Example 3;

[0042] Description of the markings in the figure:

[0043] 1-high temperature tube furnace, 101-tube furnace entrance, 102-sample boat;

[0044] 2-differential mobility analyzer, 201-aerosol flow inlet, 202-aerosol flow outlet, 203-sheath gas inlet, 204-sheath gas outlet, 205-central cylindrical electrode;

[0045] 3- flow voltage control box, 301- high voltage electric module, 302- fan, 303- filter, 304- flow control valve, 305- flow meter;

[0046] 4-plasma generator, 401-insulating tube, 402-tube electrode, 403-sealed adapter, 404-quartz tube, 405-ring electrode, 406-export tube;

[0047] 5- Plasma power supply. DETAILED DESCRIPTION

[0048] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0049] In the following implementation manners or examples, unless otherwise specified, functional components or structures are conventional components or conventional structures used in the art to achieve corresponding functions.

[0050] See also Figure 1 As shown, the present invention provides a device for generating monodisperse spherical metal aerosol particles, comprising:

[0051] A high temperature tube furnace 1, inside which is provided a sample boat 102 loaded with a metal element;

[0052] A differential mobility analyzer 2, which has an aerosol flow inlet 201, an aerosol flow outlet 202, a sheath gas inlet 203, a sheath gas outlet 204 and a central cylindrical electrode 205, wherein the aerosol flow inlet 201 is connected to the outlet of the high-temperature tube furnace 1;

[0053] A flow voltage control box 3, which includes a sheath gas flow pipeline with two ends respectively connected to the sheath gas outlet 204 and the sheath gas inlet 203 and with a controllable flow rate, and a high-voltage electric module 301 with a controllable output voltage, and the high-voltage electric module 301 is connected to the central cylindrical electrode 205;

[0054] The plasma generator 4 includes a quartz tube 404, a tube electrode 402 extending into the quartz tube 404 and sealed to the tube mouth of the quartz tube 404, and an annular electrode 405 arranged outside the quartz tube 404. The tube electrode 402 and the annular electrode 405 are respectively connected to the positive and negative electrodes of the plasma power supply 5. The tube electrode 402 is hollow inside, and the end thereof away from the quartz tube 404 is also connected to the aerosol outlet 202. The annular electrode 405 is grounded.

[0055] In some specific embodiments, the sample boat 102 is a quartz boat or a corundum boat.

[0056] In some specific implementations, the sheath gas flow pipeline is provided with a flow meter 305 , a flow control valve 304 , and a fan 302 in sequence, and a filter 303 is provided at the front and rear ends of the fan 302 , respectively.

[0057] Furthermore, the flow control valve 304 is a needle valve.

[0058] In some specific implementations, the tube electrode 402 is connected to the aerosol outlet 202 via an insulating tube 401 .

[0059] In some specific implementations, the tube electrode 402 is connected to the quartz tube 404 via a sealed adapter 403 .

[0060] In some specific implementations, the quartz tube 404 is further connected to an outlet tube 406 .

[0061] In some specific implementations, the output voltage range of the high voltage electrical module 301 is -10 kV to 10 kV.

[0062] In some specific embodiments, the plasma power supply 5 is an AC power supply or a high-voltage DC power supply.

[0063] Based on the above device, the present invention also provides a method for generating monodisperse spherical metal aerosol particles, see Figure 2 As shown, the method comprises the following steps:

[0064] (1) a metal sample is loaded into a sample boat 102, an inert carrier gas is introduced into the high-temperature tube furnace 1 through the tube furnace inlet 101, and the high-temperature tube furnace 1 is heated to a preset temperature;

[0065] (2) Open the sheath gas flow pipeline, adjust the sheath gas flow rate to a preset value, and set the output voltage of the flow voltage control box 3;

[0066] (3) Turn on the plasma power supply 5 and adjust it to a preset output voltage and frequency to excite plasma between the tube electrode 402 and the ring electrode 405;

[0067] (4) After the temperature of the high-temperature tube furnace 1 and the plasma generator 4 are stabilized, highly monodispersed metal spherical particles with a stable concentration are obtained at the outlet of the quartz tube 404 .

[0068] The above embodiments may be implemented individually or in any combination of two or more.

[0069] The above implementation is described in more detail below in conjunction with specific examples.

[0070] Embodiment 1:

[0071] See also Figure 1 As shown, this embodiment provides a device for generating monodisperse spherical metal aerosol particles, comprising:

[0072] A high-temperature tube furnace 1 is provided with a sample boat 102 loaded with metal elements, and an inlet 101 of the tube furnace is an inlet of an inert carrier gas (such as argon, nitrogen, etc.) at a flow rate of 0.5-2 liters / minute at normal pressure;

[0073] A differential mobility analyzer 2, which has an aerosol flow inlet 201, an aerosol flow outlet 202, a sheath gas inlet 203, a sheath gas outlet 204 and a central cylindrical electrode 205, wherein the aerosol flow inlet 201 is connected to the outlet of the high-temperature tube furnace 1;

[0074] A flow voltage control box 3, which includes a sheath gas flow pipeline with two ends respectively connected to the sheath gas outlet 204 and the sheath gas inlet 203 and with a controllable flow rate, and a high-voltage electric module 301 with a controllable output voltage, and the high-voltage electric module 301 is connected to the central cylindrical electrode 205;

[0075] The plasma generator 4 includes a quartz tube 404, a tube electrode 402 extending into the interior of the quartz tube 404 and sealedly connected to the tube mouth of the quartz tube 404, and an annular electrode 405 arranged outside the quartz tube 404. The tube electrode 402 and the annular electrode 405 are respectively connected to the positive and negative electrodes of the plasma power supply 5. The tube electrode 402 is hollow inside, and the particles generated by the differential mobility analyzer 2 enter the interior of the quartz tube 404 through the tube electrode 402, and the end away from the quartz tube 404 is also connected to the aerosol outlet 202, and the annular electrode 405 is grounded.

[0076] The sample boat 102 may be a quartz boat or a corundum boat.

[0077] Please see again Figure 1As shown, the sheath gas flow pipeline is provided with a flow meter 305, a flow control valve 304, and a fan 302 in sequence, and a filter 303 is provided at both ends of the fan 302. The flow control valve 304 may be a needle valve.

[0078] Please see again Figure 1 As shown, the tube electrode 402 is connected to the aerosol outlet 202 via an insulating tube 401, and the tube electrode 402 is connected to the quartz tube 404 via a sealed adapter 403. The quartz tube 404 is also connected to an outlet tube 406.

[0079] The output voltage range of the high voltage module 301 is -10 kV to 10 kV, and can be remotely controlled by a computer. The plasma power supply 5 is an AC power supply or a high voltage DC power supply.

[0080] The device was used to carry out two examples (respectively referred to as Example 2 and Example 3, wherein Example 2: generating 60nm and 16nm metallic silver particles; Example 3: generating 60nm metallic bismuth particles), respectively generating monodisperse silver particles and monodisperse bismuth particles. The device operating parameters are listed in Table 1.

[0081] Table 1. Operating parameters of two embodiments (the flow rates in this table are all measured at normal temperature and pressure)

[0082]

[0083] Figure 3 and Figure 4 The particle size distribution of silver particles and the electron microscope image of bismuth particles are shown respectively. Figure 3 The graph shows the change in the particle size distribution of silver particles at different locations in the device during the generation of 60 nm monodisperse silver particles in Example 2. The distribution is measured using a scanning mobility particle size spectrometer.

[0084] Figure 4 The images of particles obtained in Example 3 are shown. (a) Transmission electron microscope image of (nearly) spherical bismuth particles obtained at the plasma outlet. (b) Transmission electron microscope image of particles obtained at the high-temperature furnace outlet. The comparison of the two images shows the transformation effect of plasma on the morphology of particles.

[0085] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A device for generating monodisperse spherical metal aerosol particles, characterized in that: include: A high temperature tube furnace, inside which is provided a sample boat loaded with metal elements; A differential mobility analyzer, which has an aerosol flow inlet, an aerosol flow outlet, a sheath gas inlet, a sheath gas outlet and a central cylindrical electrode, wherein the aerosol flow inlet is connected to the outlet of the high-temperature tube furnace; A flow voltage control box, comprising a sheath gas flow pipeline with two ends respectively connected to a sheath gas outlet and the sheath gas inlet and with a controllable flow rate, and a high-voltage electric module with a controllable output voltage, the high-voltage electric module being connected to the central cylindrical electrode; A plasma generator, comprising a quartz tube, a tube electrode extending into the quartz tube and sealedly connected to the tube mouth of the quartz tube, and an annular electrode arranged outside the quartz tube, wherein the tube electrode and the annular electrode are respectively connected to the positive and negative electrodes of a plasma power supply, the tube electrode is hollow inside, and one end thereof away from the quartz tube is also connected to the aerosol outlet, and the annular electrode is grounded; The sheath gas flow pipeline is also provided with a flow meter, a flow control valve, and a blower in sequence, and a filter is respectively provided at the front and rear ends of the blower.

2. The device for generating monodisperse spherical metal aerosol particles according to claim 1, characterized in that: The sample boat is a quartz boat or a corundum boat.

3. The device for generating monodisperse spherical metal aerosol particles according to claim 1, characterized in that: The flow control valve is a needle valve.

4. The device for generating monodisperse spherical metal aerosol particles according to claim 1, characterized in that: The tube electrode is connected to the aerosol outlet through an insulating tube.

5. The device for generating monodisperse spherical metal aerosol particles according to claim 1, characterized in that: The tube electrode is connected to the quartz tube through a sealed adapter.

6. The device for generating monodisperse spherical metal aerosol particles according to claim 1, characterized in that: The quartz tube is also connected to an outlet tube.

7. The device for generating monodisperse spherical metal aerosol particles according to claim 1, characterized in that: The output voltage range of the high voltage electric module is -10kV to 10kV.

8. The device for generating monodisperse spherical metal aerosol particles according to claim 1, characterized in that: The plasma power supply is an AC power supply or a high-voltage DC power supply.

9. A method for generating monodisperse spherical metal aerosol particles, based on the device for generating monodisperse spherical metal aerosol particles according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: (1) taking a metal sample and placing it in a sample boat, introducing an inert carrier gas into a high-temperature tube furnace, and heating the high-temperature tube furnace to a preset temperature; (2) Open the sheath gas flow line, adjust the sheath gas flow rate to a preset value, and set the output voltage of the flow voltage control box; (3) Turn on the plasma power supply, adjust to the preset output voltage and frequency, and excite plasma between the tube electrode and the ring electrode; (4) After the temperature of the high-temperature tube furnace and the plasma generator are stabilized, highly monodispersed metal spherical particles with stable concentration are obtained at the outlet of the quartz tube.

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