CN103432976A - Atmospheric sliding arc discharge plasma reactor for synthesizing completely crystallized nano powder - Google Patents

Abstract

An atmospheric pressure sliding arc discharge plasma reactor for synthesizing fully crystallized nanopowder, including an upper electrode and a lower electrode in a ring or cylindrical structure, DC or AC high voltage is applied to one of the electrodes, and the other electrode is grounded; The precursor enters the reactor through the tangential inlet to form a vortex; the precursor is introduced from the center of the upper cover of the reactor with the carrier gas and flows into the sliding arc discharge area together with the vortex; the sliding arc discharge area is equipped with a powder collection tube to obtain fully crystallized Nano powder, after the reaction, the gas is discharged from the gas outlet. The titanium dioxide nanometer powder obtained by the invention is completely crystallized, and the particles are mainly nanometer balls of 20-90nm, and the crystal phase composition thereof can be adjusted through input power and gas flow rate. The method does not need a vacuum device and a cooling system, and a fully crystallized nanopowder is synthesized in one step. The invention has simple process, low energy consumption, continuous operation and is suitable for large-scale industrialization.

Description

Atmospheric pressure sliding arc discharge plasma reactor for the synthesis of fully crystallized nanopowders

technical field

The invention belongs to the technical field of nano material preparation, and relates to an atmospheric pressure sliding arc discharge plasma for synthesizing fully crystallized nano powder. The device does not need a vacuum device and a cooling system, and directly uses air as a discharge gas under atmospheric pressure to synthesize fully crystallized nanopowder in one step.

Background technique

Nano-powder materials have specific properties and a wide range of applications. For example, titanium dioxide (TiO ₂ ) powder is an ideal semiconductor photocatalytic material due to its advantages of high photocatalytic activity, light corrosion resistance, stable chemical properties, insoluble and non-toxic, and wide application range. It has self-cleaning, Eliminate environmental pollutants, antibacterial and deodorizing and other functions. The photocatalytic performance of _TiO2 mainly depends on factors such as its crystallinity, phase composition and specific surface area (particle size and morphology), which are inseparable from its synthesis method or technology. The preparation methods of nano titanium dioxide are mainly divided into two categories: liquid phase method and gas phase method. The disadvantage of the liquid phase method is that it is operated intermittently, the process is time-consuming and cumbersome, a large amount of waste liquid is produced, and the pollution is serious. The gas phase method usually adopts a chemical vapor deposition technique using flame combustion or thermal plasma as a heat source. The gas phase method is usually completed in one step, which has the advantages of short process flow and high degree of automation. However, the current gas-phase method is mostly a high-temperature process, so there are disadvantages such as high energy consumption, high requirements on the material of the equipment (such as oxidation resistance and corrosion resistance), and the need for a complex rapid cooling system. Chinese invention patent ZL200710010884.9 uses atmospheric pressure dielectric barrier discharge cold plasma (Cold plasma) to synthesize anatase phase titanium dioxide nanopowder in one step, which overcomes the shortcomings caused by the above high temperature process, but has low crystallinity and photocatalysis. The disadvantage of low activity.

The warm plasma (Warm plasma) generated by sliding arc discharge automatically and rapidly changes from the initial quasi-thermal equilibrium stage to the non-thermal equilibrium stage, which has the advantages of both hot plasma and cold plasma. In the quasi-thermal equilibrium discharge stage, its electron density is usually as high as 10 ¹³ -10 ¹⁴ cm ^-3 ; in the non-thermal equilibrium discharge stage, it has a high degree of non-equilibrium, that is, the electron temperature is much higher than the gas temperature. At present, in the domestic and foreign literature, there is no research report on the one-step synthesis of nano-powders using sliding arc discharge plasma technology.

Contents of the invention

The object of the present invention is to provide an atmospheric pressure sliding arc discharge plasma reactor for synthesizing fully crystallized nanopowders for the deficiencies of the prior art. It does not require vacuum devices and cooling systems, and can directly use air as the discharge gas under atmospheric pressure to synthesize fully crystallized nanopowders in one step.

Technical scheme of the present invention is:

An atmospheric pressure sliding arc discharge plasma reactor for synthesizing fully crystallized nanometer powder, the atmospheric pressure sliding arc discharge plasma reactor includes an upper electrode and a lower electrode, and the electrodes adopt a ring or cylindrical structure. DC or AC high voltage is applied to one of the electrodes, and the other electrode is grounded. Oxygen-containing gas enters the reactor through the tangential inlet of the reactor to form a vortex, and the rotating vortex pushes the arc channel between the two electrodes to rotate and slide. The precursor is introduced from the center of the upper cover of the reactor along with the carrier gas, and flows into the sliding arc discharge area together with the rotating eddy current in the insulating cylinder; the sliding arc discharge area is equipped with a powder collection cylinder, and the powder collection cylinder obtains crystallized nano-powder. After the reaction, the gas is discharged from the gas outlet.

The precursor may be titanium precursor, and the nano-powder is titanium dioxide nano-powder; wherein, the titanium precursor may be tetraisopropyl titanate or titanium tetrachloride.

The optimal distance between the upper electrode and the lower electrode is 5-100mm.

The carrier gas can be argon, helium or nitrogen and other gases.

The titanium dioxide nanometer powder obtained by the invention is completely crystallized, and the particles are mainly nanospheres of 20-90nm. Most of the titanium dioxide nanopowder crystal phase structure is anatase phase, a small part is rutile phase, and the crystal phase composition can be adjusted by input power and gas flow.

The invention does not need a vacuum device and a cooling system, and can directly use air as a discharge gas under atmospheric pressure to synthesize fully crystallized nanometer powder in one step. It is operated under atmospheric pressure, completed in one step, low energy consumption, continuous operation, and easy to realize industrialized large-scale production.

Description of drawings

Figure 1 is a schematic diagram of a sliding arc discharge plasma reactor for synthesizing nanopowders.

Fig. 2 is the X-ray diffraction pattern of the sample obtained in embodiment 1.

3 is a transmission electron micrograph of the sample obtained in Example 1.

In the figure: 1 upper electrode, 2 lower electrode, 3 tangential inlet, 4 reactor cover, 5 insulating cylinder, 6 powder collection cylinder, 7 gas outlet;

A precursor/carrier gas, B oxygen-containing gas.

Detailed ways

The specific embodiments of the present invention will be described in detail below in conjunction with the technical solutions and accompanying drawings.

Example 1.

The sliding arc discharge plasma reactor adopts a stainless steel ring with an outer diameter of 14 mm and an inner diameter of 10 mm as the upper electrode 1, and a stainless steel cylinder with an outer diameter of 30 mm, an inner diameter of 13 mm and a length of 20 mm as the lower electrode 2. The distance between the upper and lower electrodes is 14mm. Air with a flow rate of 1.5SLM enters the reactor through the tangential inlet 3 at normal temperature to form a vortex. AC high voltage with a frequency of 4.8kHz is applied to the lower electrode 2 (input power is 70W, 100W and 140W respectively), and sliding arc discharge plasma is generated under atmospheric pressure. The _N2 gas with a flow rate of 100SCCM carries atomized tetraisopropyl titanate (TTIP) into the center of the upper cover 4 of the reactor, and flows into the sliding arc discharge area together with the rotating air flow in the insulating cylinder 5, and the powder The nanocrystalline titanium dioxide powder is obtained in one step in the collecting cylinder 6 . Figure 2 is the X-ray diffraction pattern of nanocrystalline TiO ₂ powder obtained under three input power conditions, and Figure 3 is the transmission electron microscope photo of the sample obtained with the input power of 140W. The test results show that the particles of the obtained nano TiO ₂ powder are 20-90nm nanospheres, most of the crystal phase structure is anatase phase, and a small part is rutile phase. The content of anatase phase in the sample prepared under the condition of 140W input power is up to 96%, and the content of anatase phase in the sample prepared under 70W input power is 60%.

Claims (6)

1. the atmospheric pressure slip circle discharging plasma reactor of a synthetic complete crystallization nano-powder, it is characterized in that: this atmospheric pressure slip circle discharging plasma reactor comprises top electrode (1) and the bottom electrode (2) of annular or tubular structure, direct current or ac high-voltage put on one of them electrode, another electrode grounding; Oxygen-containing gas enters reactor formation eddy current by the tangential inlet (3) of reactor, and this rotating vortex promotes two interelectrode arc passage rotational slides; Predecessor is introduced by the center of reactor upper cover (4) with carrying gas, in the insulating cylinder (5) of reactor together with rotating vortex the slip circle region of discharge of inflow reactor; The slip circle region of discharge is provided with powder surge drum (6) for obtaining the nano-powder of crystallization, and after reaction, gas is discharged by gas vent (7).

2. atmospheric pressure slip circle discharging plasma reactor according to claim 1, it is characterized in that: described predecessor is the titanium precursor thing, described nano-powder is nano-titanium dioxide powder.

3. atmospheric pressure slip circle discharging plasma reactor according to claim 2, it is characterized in that: described titanium precursor thing is tetraisopropyl titanate or titanium tetrachloride.

4. according to claim 1,2 or 3 described atmospheric pressure slip circle discharging plasma reactors, it is characterized in that: between described top electrode and bottom electrode at a distance of 5 – 100mm.

5. according to claim 1,2 or 3 described atmospheric pressure slip circle discharging plasma reactors, it is characterized in that: the described gas that carries is argon gas, helium or nitrogen.

6. atmospheric pressure slip circle discharging plasma reactor according to claim 4, it is characterized in that: the described gas that carries is argon gas, helium or nitrogen.

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