JP2007305498A - Discharge electrode pair for ion generation / release, ion generator using the same, and ion generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus capable of efficiently generating gas ions for a long time.
An ion generator (1) includes a gas introduction part (3) and an ion discharge port (5) in a casing, and a discharge electrode (11) and a ground electrode (13) in the casing. The ion generator 7 has a chamber 9 connected to the ion emission port 5 of the ion generator 1. The discharge electrode 11 discharges a high voltage to the gas introduced from the gas introduction part 3, one end is supported by the upper part in a housing | casing, and the other end is orient | assigned to the perpendicular downward direction. The ground electrode 13 is disposed in the ion emission port 5 so as to face the discharge electrode 11 in the housing. The ground electrode 13 is a stainless steel disk-like electrode having copper formed on the ground-side surface 15, and an orifice 19 serving as an ion emission port is formed at the center.
[Selection] Figure 1

Description

  The present invention relates to an ion generator for generating gas ions, an ion generation / discharge discharge electrode pair used therein, and an ion generation apparatus for charging an aerosol or the like with gas ions from the ion generator. Such an ion generator can be used not only as a device for supplying charged aerosol to a DMA (Differential Mobility Analyzer), but also as an ion source for a mass spectrometer. .

In order to supply negative ions in a residence and charged aerosol for use in various analyzers, a device that efficiently generates gas ions is required.
As methods for generating gas ions, there are a corona discharge method, an electrospray ionization method (ESI), and an atmospheric pressure chemical ionization method (APCI). A corona discharge method is often used to charge an aerosol.

Aerosol refers to a colloid in which the dispersion medium is a gas and the dispersoid is a liquid or a solid. When the dispersoid is a liquid, the aerosol becomes fog, haze, clouds, or the like, and when the dispersoid is a solid, dust becomes smoke or the like. The measurement of the constituents of the aerosol fine particles is important in research fields such as evaluation of environmental conditions and health effects (see Patent Document 1).

In the DMA, the aerosol composed of the fine particles and the gas of the dispersion medium is charged and introduced into the DMA. It is a measuring device that classifies and measures the particle size of fine particles in an air environment efficiently and over a wide range by using (see Patent Document 2).
In order to charge the aerosol used for DMA, methods such as a cluster ion generator by corona discharge (see Patent Document 3), a radiation source such as ²⁴¹ Am, and soft X-rays (see Patent Document 4) are used. .

JP 09-184808 A JP 2000-46720 A JP 2003-326192 A JP 2004-53298 A

  The above cluster ion generator ionizes the compressed gas flowing in the casing by generating an alternating current corona discharge between the electrodes in the casing using tungsten as the discharge electrode and stainless steel as the ground electrode. The object is charged by bringing the compressed ionized gas into contact with the charged object in the chamber.

However, when ions are continuously generated, a phenomenon occurs in which an object (for example, a gas containing silver particles) cannot be charged suddenly.
In such a state, the device was not restored even when the discharge was repeatedly turned on and off, and it was no longer possible to charge the silver particles. Since the ground electrode is grounded through the chamber, the contact failure between the ground electrode and the chamber was improved, or the ground electrode was washed with alcohol to improve conductivity, but the device did not recover. It was.
Then, an object of this invention is to provide the apparatus which can produce | generate a gas ion efficiently for a long time.

The discharge electrode pair for ion generation / discharge of the present invention includes a discharge electrode to which a high voltage is applied, and a ground electrode made of a metal material disposed opposite to the discharge electrode and having an ion discharge port at the center. The ground electrode is made of an etching-resistant metal material on the side facing the discharge electrode, and the surface opposite to the opposing surface is made of a metal material having better conductivity than the facing surface. .
Here, stainless steel is exemplified as one having high etching resistance, and aluminum is exemplified as one having low etching resistance.

  As the metal material having good etching resistance, Ti, Ti alloy, Ni / Cr alloy or the like can be used in addition to stainless steel. In the examples, stainless steel that is resistant to etching and economical is used.

  The metal material on the ground side of the ground electrode can be formed on the metal material on the opposite surface side by plating, vapor deposition, sputtering or bonding.

  In the ion generator of the present invention, an ion generation / discharge discharge electrode pair and a gas introduction part are arranged in a casing, and a discharge is generated between the ion generation / discharge discharge electrode pair to thereby remove the gas introduction part from the gas introduction part. The introduced gas is ionized and discharged from the ion discharge port. The ion generation / discharge discharge electrode pair is of the present invention, and an orifice is formed by the ion discharge port of the ion generation / discharge discharge electrode pair.

  An ion generator according to the present invention includes an ion generator according to the present invention, a gas ion introduction unit that introduces gas ions discharged from an ion emission port of the ion generator, and an object introduction that introduces a particulate charged object. And a chamber provided with a discharge unit for discharging particle ions generated by ionizing the charged object with gas ions inside.

  Further, when the chamber is made of a conductive metal, the ground electrode can be grounded through the chamber by integrating the ground side of the ground electrode of the ion generator by contacting the chamber.

  The surface on the ground side is made of a material that is more conductive than the opposite surface on the opposite side, and a ground electrode made of a metal material with an orifice serving as an ion emission port at the center is used to make time Even after the lapse of time, the discharge capability does not decrease, and ions can be generated stably.

  If an ion generator is provided with the ion generator and chamber of the present invention, for example, a gas containing silver particles can be stably charged.

Hereinafter, an embodiment of the present invention will be described in detail.
FIG. 1 is a schematic cross-sectional view of an ion generator, which includes an ion generator and a discharge electrode pair for ion generation / release as a part thereof.
The ion generator 1 includes a gas introduction part 3 and an ion discharge port 5 in a casing, and includes a discharge electrode 11 and a ground electrode 13 as a pair of discharge electrodes for generating and discharging ions in the casing. The ion generator 7 is formed by connecting a chamber 9 made of a conductive metal to the ion emission port 5 of the ion generator 1 and integrating them.

The gas introduction part 3 is provided on the upper side surface in the housing, and the ion emission port 5 is provided on the bottom surface in the housing.
The discharge electrode 11 discharges the electric charge of the gas introduced from the gas introduction part 3 and charges it, and one end is supported by the upper part in the housing and the other end is directed vertically downward. The discharge electrode 11 is preferably a needle-like electrode, and Inconel or titanium alloy can be used as the metal material, but tungsten is particularly preferable. The ground electrode 13 is disposed on the bottom surface of the casing having the ion emission port 5 facing the discharge electrode 11 in the casing.

FIG. 2 is a schematic perspective view of the ground electrode 13.
The ground electrode 13 is a stainless steel disk-like electrode, and the opposing surface side 17 facing the discharge electrode 11 is made of an etching-resistant and oxidative conductive metal material. Here, stainless steel is used.
The ground-side surface 15 opposite to the facing surface side 17 is made of a metal material that is more conductive than the facing surface side 17, and copper, for example, is attached thereto. Gold or aluminum can also be used in addition to copper, and may be formed by plating.
In the center of the ground electrode 13, an orifice 19 serving as an ion emission port is formed.

The dimensions of the ground electrode 13 are not particularly limited. For example, the outer diameter is 2.1 cm, the thickness is 2 mm, and the inner diameter of the orifice 19 provided at the center is 0.1 to 0.3 mm. The thickness of copper was formed to about 0.036 to 0.11 mm.
Further, it is sufficient if the thickness of the ground-side surface 15 is about 1.8 to 5.5% of the thickness of the ground electrode 13.

  The ion generator 7 includes an ion generator 1 and a chamber 9 as shown in FIG. The chamber 9 is integrated in contact with the ground side of the ground electrode 13 of the ion generator 1, a gas ion introduction part 21 for introducing gas ions ionized in the internal space of the ion generator 1, and particulate charging. An object introduction part 23 for introducing an object and a discharge part 25 for discharging a reaction product introduced from both introduction parts 21 and 23 and reacted inside to the outside are provided.

A charged object supply device 27 for introducing a charged object is connected to the object introducing unit 23, and a discharge unit 25 is connected to a DMA or the like for classifying a sample.
Further, the ion generator 1 and the chamber 9 are connected to a common ground, and the apparatus is miniaturized by integrating the ion generator 1 and the chamber 9.

Next, the operation of this embodiment will be described.
Compressed air was introduced from the gas introduction unit 3, and a DC or AC electric field of 5000 to 10000 V was applied between the discharge electrode 11 and the ground electrode 13 by a high voltage power source.
The compressed air is ionized by corona discharge generated in a region between the discharge electrode 11 and the ground electrode 13 and then jetted from the ion discharge port 5 (gas ion introduction portion 21) as a high-speed jet. The discharge flow rate of the compressed air at the ground electrode outlet at this time was 0.14 to 3.0 L / min. The introduction of the compressed air into the ion generator 1 was set to 0.05 MPa to 0.30 MPa with a regulator.

The molecular ions of the high-speed jet ejected from the ion emission port 5 (gas ion introduction part 21) are mixed in the chamber 9 with the gas containing the silver particles supplied from the charged object supply device 27, and are mixed on the surface of the silver particles. Charges adhere and give the silver particles a charge. Silver particles having an average particle diameter of 10 nm or less were used, but larger particle diameters may be used. The flow rate of the gas containing silver particles was 1.0 to 2.0 L / min.
When the silver particles were continuously charged under the above conditions, the charging ability did not decrease even after 800 hours.

If the discharge unit 25 is connected to a DMA that measures electric mobility or the like, the charged object can be classified or analyzed using the intensity of the charged electric field.
Therefore, when the ion generator of the present invention is used as an aerosol charging device, it is possible to stably measure components of aerosol fine particles and evaluate environmental conditions even when measuring for a long time.

  In the above embodiment, a needle-like discharge electrode is used as the discharge electrode and a disk-like electrode is used as the ground electrode. However, the shape of the electrode is not limited to these.

Next, another embodiment of the present invention will be described.
In FIG. 3, the ion generator 1 and the chamber 9 are not integrated, and the ion emission port 5 and the gas ion introduction part 21 are connected using a flange pipe (made of metal such as stainless steel). Includes a gas introduction part 3 and an ion emission port 5 in a casing, and a discharge electrode 11 and a ground electrode 13 in the casing. The ion generator 7 has a chamber 9 connected to the lower part of the ion generator 1.

The chamber 9 is a horizontally long type, and is provided with a gas ion introduction part 21 at the upper part, an object introduction part 23 at the lower part, and a discharge part 25 at the side surface.
In this embodiment, the gas ion introduction part 21 and the object introduction part 23 are arranged to face each other, and the object can be efficiently charged in the chamber 9. The ion generator 1 and the chamber 9 are each connected to ground.

Further, when impedance measurement was performed between the acicular discharge electrode 11 and the ground electrode 13 using an LCR meter, copper was attached to the surface 15 on the ground side of the stainless steel when the stainless steel itself was used for the ground electrode 13. Sometimes no difference was seen.
This is because the current used for impedance measurement is not as short as that of ions, and if a current flows through stainless steel (the ground electrode 13), the value is used for impedance measurement.

  The present invention can be used not only as an apparatus for charging an aerosol for DMA but also as an ion source for a mass spectrometer.

The schematic sectional drawing of the ion generator of one Example and an ion generator is shown. The schematic perspective view of a ground electrode is shown. The schematic sectional drawing of the ion generator and ion generator of another Example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ion generator 3 Gas introduction part 5 Ion discharge port 7 Ion generator 9, 9a Chamber 11 Discharge electrode 13 Ground electrode 15 Ground side surface 17 Discharge side surface 19 Orifice 21 Gas ion introduction part 23 Target object introduction part 25 Exhaust Part 27 Charged object supply device

Claims (6)

A discharge electrode to which a high voltage is applied, and a ground electrode made of a metal material disposed opposite to the discharge electrode and having an ion emission port formed at the center thereof;
The ground electrode is formed of an etching-resistant metal material on the side facing the discharge electrode, and the surface opposite to the opposing surface is formed of a metal material having higher conductivity than the facing surface side. A discharge electrode pair for generating and releasing ions.   The discharge electrode pair for ion generation / emission according to claim 1, wherein the metal material on the opposite surface side of the ground electrode is any one of stainless steel, Ti, Ti alloy or Ni / Cr alloy.   3. The ion generation / emission discharge electrode pair according to claim 1, wherein the metal material on the ground side of the ground electrode is formed by plating, vapor deposition, sputtering or bonding to the metal material on the opposite surface side. A discharge electrode pair for ion generation / release and a gas introduction part are arranged in a casing, and the gas introduced from the gas introduction part is ionized by generating a discharge between the discharge electrode pair for ion generation / release. In the ion generator that discharges from the ion discharge port,
4. The ion generation / discharge discharge electrode pair according to claim 1, wherein an orifice is formed by an ion discharge port of the ion generation / discharge discharge electrode pair. Ion generator. An ion generator according to claim 4;
A gas ion introduction part that introduces gas ions emitted from the ion emission port of the ion generator, an object introduction part that introduces a particulate charged object, and a charged object that is ionized and generated inside by a gas ion A chamber having a discharge part for discharging the discharged particle ions to the outside;
An ion generator characterized by comprising:   6. The chamber according to claim 5, wherein the chamber is made of a conductive metal, and a grounding side of the ion generator is brought into contact with the chamber to be integrated so that the ground electrode is at a ground potential through the chamber. Ion generator.

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