JP4863915B2 - Static neutralizer - Google Patents

Description

The present invention is generated in an electric machine, an OA machine, an electric machine for clothes, an ionizer, an electric machine for food industry equipment, an electric machine equipment for chemical industry, an electric machine for pharmaceutical manufacturing equipment, an emitter assembly, etc. Static electricity neutralizers that remove static electricity

  Static electricity is generated by contact, peeling, friction, etc. between objects, but when accumulated static electricity is released, a large voltage is momentarily generated. Therefore, in electronic components and electronic devices and devices that manufacture them, It may cause failure or malfunction. In the painting booth, uneven painting occurs due to the generation of static electricity.

In an apparatus formed of a member coated with an electrically insulating material such as glass, for example, a stirring reaction device, charging occurs between the solvent and the coating layer, and the glass liner layer is damaged, liquid is altered, and is loaded. There is a risk of explosion and combustion.

In order to prevent such static electricity, electrostatic neutralizers such as stainless steel that are not easily corroded have been used for ionizers, etc., but materials such as stainless steel made of various metallic substances have been used. However, there is a drawback that the quality of the apparatus, gas, and liquid is impaired by various metal ions being dissolved in the liquid and the air. In addition, it has been pointed out that stainless steel and the like are altered and ions diffuse into the air when used in a high-temperature atmosphere exceeding 200 ° C.

Patent Document 1 discloses a technique having a sharp tip made of TiC, SiC, ZrO ₂ , lanthanum boride, tungsten carbide or the like as an electrostatic charge remover. These materials are less likely to be corroded and have fewer impurity elements than iron-type materials such as stainless steel. On the other hand, when these electrical resistivities are compared with each other, since they are higher than those of stainless steel materials, the static elimination action is equal to or less than that of stainless steel neutralizers.
The electrical resistivity of stainless steel is a typical value of about 7 × 10 ⁻⁵ Ω · cm. TiC is 5 × 10 ⁻⁴ Ω · cm, SiC varies greatly depending on the auxiliaries, but 10 ² Ω · cm to 10 ⁹ Ω · cm, ZrO ₂ is an insulator, and tungsten carbide is about 5 × 10 ⁻⁵ Ω · cm. is there.

Patent Document 2 discloses a portable electric discharger that uses tungsten or a tungsten alloy as a material for a discharge electrode. The electrical resistivity of tungsten is preferably about 5 × 10 ⁻⁶ Ω · cm. However, metallic tungsten, tungsten commonly called tungsten alloys, tungsten doped with metal rhenium, tungsten doped with oxides such as ceria and yttria, etc. are all used in air and in liquids. Oxidation is likely to occur, the tungsten surface layer is peeled off by the oxide and the static elimination member is worn out, and the liquid and air are contaminated with dust and debris, so that a satisfactory result cannot be obtained. As an example of this, when an ionizer used in an air atmosphere was subjected to static elimination for 24 hours continuously at 300 ° C., the surface turned yellow and corrosion as shown in FIG. 4B occurred.

Japanese Utility Model Publication No. 2001-233396 JP 09-120896 A

An object of the present invention is to obtain a static eliminator in an apparatus used for static eliminator that does not corrode the static eliminator itself and does not contaminate a gas or liquid to be neutralized.

  By producing an electrostatic charge eliminator with tungsten or molybdenum obtained by carbonizing only the surface layer of tungsten or molybdenum base material, the previous problem can be solved.

The carbonized tungsten or molybdenum layer is suitably 0.01 to 20 μm from the surface, and it is preferable to use a rod-like material for many applications.

It is possible to obtain a static neutralizing material that can quickly perform static neutralization and can perform static neutralization without leaving impurities in the air or liquid, and has an extremely long replacement life.

The present invention according to claim 1 is an electrostatic charge remover having a tungsten carbide layer having a thickness of 0.01 μm or more and 20 μm or less on the surface of a tungsten substrate. Tungsten has a low electrical resistivity of about 5 × 10 ⁻⁶ Ω · cm, which is suitable for static neutralization applications, but has a problem that tungsten is easily oxidized. Tungsten is particularly susceptible to oxidation in the atmosphere and in liquids that are also electrically affected. For this reason, even when used as a static eliminator, surface oxidation proceeds to change to WO, W ₂ O, WO ₃ or the like, discolor to yellow, and cause peeling. Therefore, tungsten oxide is diffused in the air or in the liquid, causing contamination. Even when contamination is not particularly a problem, tungsten itself wears out and the electrical resistivity is greatly increased, so it cannot be used without replacement for a long time.

The electrostatic neutralizing material of the present invention is characterized by having a carbonized layer having a depth of 0.01 to 20 μm from the tungsten substrate surface. By providing a carbonized layer on the surface, the oxidation of tungsten is extremely small and can be improved to be almost negligible. The carbonized layer needs to be at least 0.01 μm in order to exert its oxidation resistance effect. Moreover, when exceeding 20 micrometers, since the electrical performance (conductivity) which original tungsten has is lost, it is unpreferable. Tungsten carbide has an electrical resistivity that is about 10 times higher than that of tungsten. However, if the thickness does not exceed 20 μm, the electrical resistivity does not change compared to metallic tungsten. If the thickness exceeds 20 μm, the electrical resistivity rapidly increases, which is not desirable as an electrostatic charge eliminating material. For these reasons, when the static eliminator is used for removing static electricity, for example, in the air, a thickness of ~ several μm is sufficient. In this case, the thickness of the carbide layer may be made relatively thick (˜20 μm). Surface carbide layer is _{WC, W} 2 _C, and consisting of a composite material.

The present invention according to claim 2 is an electrostatic neutralizer having a molybdenum carbide layer having a thickness of 0.01 μm or more and 20 μm or less on the surface of a molybdenum substrate. Molybdenum also tends to oxidize in an oxygen-containing atmosphere. The reason for limiting the thickness of the carbide layer is the same as that of the first aspect. The electric resistance of molybdenum is 5.2 × 10 ⁻⁶ Ω · cm, and molybdenum carbide is 1.0 × 10 ⁻⁴ Ω · cm.

The present invention according to claim 3 is the static electricity neutralizer according to claim 1, which has a cylindrical shape. In the air or liquid, a rod-shaped one is particularly efficient. The rod-shaped static electricity removing body of the present invention includes a cylinder whose chamfered portion is mechanically chamfered, and one whose surface and both portions are smoothed by a method such as barrel treatment. As a result, the specific surface area can be kept to a minimum, and a slight dropout can be prevented without disturbing the fluid flow. Depending on the application, the tip of the cylinder can be a weight.
The present invention according to claim 4 is characterized in that the tungsten substrate is made of tungsten having a purity of 99.9% or more or potassium-doped tungsten containing 1 to 300 ppm of potassium. Static neutralizer. When tungsten is added with metal rhenium or rare earth oxides, chemical resistance and oxidation resistance may be impaired, and undesirable factors such as an increase in manufacturing costs are added.
Potassium as a doping material exists in a spherical shape at the grain boundary of tungsten, and since the amount is small, it is hardly exposed on the surface. Potassium is the most commonly used metal for tungsten doping, but is almost negligible because of this property and can be used in the same way as pure tungsten. Further, since potassium in the surface layer is preferentially discharged from the surface at the stage of carbonization, the influence is almost negligible.

The present invention according to claim 5 is characterized in that the molybdenum substrate is made of either molybdenum having a purity of 99.9% or more or potassium-doped molybdenum containing 1 to 300 ppm of potassium. Static neutralizer. The reason for adding potassium is the same as in claim 4.

  In order to obtain the static electricity eliminating material of the present invention, it is most reliable and inexpensive to use the following production method.

  First, a tungsten-based material, particularly a rod-like tungsten sintered body doped with pure tungsten or potassium, and a rod-like molybdenum sintered body (base material) doped with pure molybdenum or potassium are obtained. This can be done by any known means such as a method of performing hot forging after electric current sintering or a method of sintering a green body in a non-oxidizing atmosphere.

  When necessary, this base material is subjected to chamfering processing on the ridges and barrel processing (polishing with a liquid in which hard abrasive grains such as alumina and zirconia are dispersed). It is easy to prevent tungsten and its impurities from flowing out into the air or liquid from burrs formed during cutting of the tungsten sintered body.

Thereafter, the surface is carbonized. Using a furnace, heat treatment is performed at 1000 ° to 2500 ° C. for about 0.1 to 5 hours in a non-oxidizing atmosphere such as carbon, methane, carbon monoxide, hydrogen atmosphere, etc. It can be carbonized to a depth of 01-20 μm. If it cools after that, the target electrostatic static elimination body will be obtained.

Hereinafter, embodiments of the present invention will be described by way of examples.

As an example, the following 10 types of samples were prepared as an electrostatic charge remover for use in an ionizer used for removing high-temperature air.

Sample 1 (Invention) The surface of a tungsten substrate having a purity of 99.9% is carbonized, and Sample Sample 2 (invention) is provided with a 10 μm carbonized layer. Sample sample 3 (invention) carbonized and provided with a carbonized layer of 10 μm (invention) Sample sample 4 in which the surface of a molybdenum substrate with a purity of 99.95% was carbonized and provided with a carbonized layer of 0.1 μm (invention) Molybdenum Sample sample 5 (comparative example) having a purity of 99.9% was prepared by carbonizing the surface of a doped molybdenum base material doped with 5 ppm of potassium and providing a 0.1 μm carbonized layer. Purity 99 .95% molybdenum sample sample 7 (comparative example) tungsten sample sample 8 containing 1% thorium oxide sample (comparative example) stainless steel (SUS304) sample sample 9 (comparative example) part Samples of the sample specimen 10 in the stabilized zirconia (Comparative Example) tungsten carbide (WC-5 wt% Co)

Each sample had a cylindrical shape of φ2 (mm) × 50 (mm), and barrel processing was performed as shown in FIG. 2 to smooth the surface and round the crest.

A manufacturing method of Sample 1 and Sample 2 is shown below.
A tungsten linear material doped with 99.9% pure tungsten and 10 ppm potassium was cut into a length of 50 mm with a cutting apparatus. After cutting, barrel processing was carried out for 1 hour using zirconium oxide having an average particle diameter of φ1 μm as an abrasive. As a result, the crest was rounded to form a smooth cylinder (FIG. 2).
Next, the obtained cylindrical tungsten was put into a carbon container in a state of being mixed with carbon powder, and heat treatment (carbonization treatment) was performed in an argon gas atmosphere. The heat treatment conditions were a maximum temperature of 1500 ° C. and a cooling after holding for 2 hours.

When the tungsten cylinder treated after cooling was cut and the cross section was observed, a carbide layer of about 10 μm from the surface could be observed as shown in FIG. As a result of analysis by EPMA, it was confirmed that it was a tungsten carbide and carbonized layer (W ₂ C and / or WC).

A method for producing Sample 3 and Sample 4 will be described below.
A molybdenum linear material doped with 99.95% pure molybdenum and 5 ppm potassium was cut into a length of 50 mm with a cutting apparatus. After cutting, barrel processing was performed for 1 hour using zirconium oxide having an average particle diameter of φ1 μm as an abrasive, and the ridge was rounded to form a smooth cylinder as a whole.
Next, the obtained cylindrical tungsten was put into a carbon container in a state of being mixed with carbon powder, and heat treatment (carbonization treatment) was performed in an argon gas atmosphere. The heat treatment conditions were a maximum temperature of 1200 ° C. and a cooling after holding for 10 minutes.

When the molybdenum cylinder treated after cooling was cut and the cross section was observed, a carbide layer of about 0.1 μm was observed from the surface. As a result of analysis by EPMA, it was confirmed that the layer was a carbide of molybdenum and a layer carbonized (Mo ₂ C and / or MoC).

Example (Sample 1 to Sample 4) and Comparative Example ( ^* Sample 5 to ^* Sample 10)
In the fixing method shown in FIG. 3, using the sample 1 ^* sample 10 as a rod-like Xu collector for ionizer. The object is to eliminate the charged air by using it as a protrusion on the air passage of the ionizer. The air is used at a high temperature of about 500 ° C. The test was conducted by operating for 240 hours in this atmosphere.

About the sample 1-sample ^* 10, the result used for the said ionizer is shown below. Samples with “ ^* ” are comparative examples outside the scope of the present invention.

Sample 1, Sample 2, Sample 3 and Sample 4 had no change in state even after the sample, and no impure ion diffusion was observed in the ionizer. It was successfully used as a static eliminator.

^* Sample 5 was rapidly oxidized during use, and the surface was discolored to yellow. The surface was partially peeled off and diffused as dust in the ionizer, which was not suitable as an electrostatic charge remover. When yellow dust was investigated, it was confirmed to be tungsten oxide.

^* Sample 6 had a rapid oxidation of the surface during use, and the surface turned brown. The surface was partially peeled off and diffused as dust in the ionizer, which was not suitable as an electrostatic charge remover. An investigation of brown dust confirmed that it was molybdenum oxide.

^* Sample 7 ^* Sample 5 has occurred discoloration and peeling similarly surface and was not suitable as the electrostatic charge removing member.

^* Sample 8 had a slight discoloration after use, but a considerable amount of Fe and Ni ions were detected in the ionizer. It was unsuitable as a static neutralizer in an ionizer. In addition, since the electrical resistance was as high as about 5 × 10 ⁵ (Ω · cm), the static elimination effect was slightly lower than that of Samples 1 to 4.

^* Sample 9 was not discolored during and after use. The detected ions did not have a Zr component. However, since it is an insulator, the effect of air neutralization is not improved, and it is not suitable as an electrostatic neutralizer.

^* Sample 10 was not visually altered during and after use, but Co ions as a binder were detected in the treated air. Moreover, since the electrical resistance value is about 1.5 × 10 ^5, which is higher than those of Samples 1 to 4, it was not preferable as an electrostatic charge remover.

In addition, WC manufactured without adding a metal binder such as Co is difficult to sinter, and a large cost and equipment are required to manufacture it in a rod shape.

As a similar experiment of Sample 1, the experiment was performed using a sample having a carbide layer of less than 0.01 μm on the surface of tungsten and a sample thicker than 20 μm. As a result, a sample of less than 0.01μm is a Comparative Sample ^* Sample 3, as with ^* Sample 4, occur discoloration of the surface, it was also occurred partially peeled. In addition, when the carbide layer was thicker than 20 μm, the electrical resistivity increased about 10 times that of tungsten (5 × 10 ⁻⁶ Ω · cm), and the effect of static elimination was inferior to that of Samples 1 to 4.

1 shows a cross section of a tungsten static neutralizer having a carbonized layer about 10 μm from the surface of the present invention. Bar-shaped tungsten static neutralizer after barrel processing It is an example in which the electrostatic neutralizer of the present invention is used as an electrostatic neutralizer for an ionizer. (A) Electrostatic discharger of the present invention, after use (b) Tungsten electrostatic discharger of comparative example with surface peeling, after use

Explanation of symbols

1 Tungsten (molybdenum) carbide layer from the surface 2 Tungsten (molybdenum) substrate 3 Electrostatic charge remover of the present invention (bar-shaped)
4 Gas 5 Gas traveling direction
6 conductor
7 Earth

Claims (5)

An electrostatic neutralizer having a tungsten carbide layer having a thickness of 0.01 μm or more and 20 μm or less on the surface of a tungsten substrate. An electrostatic neutralizer having a molybdenum carbide layer having a thickness of 0.01 μm or more and 20 μm or less on the surface of a molybdenum substrate. 3. The static eliminator according to claim 1 or 2, wherein the shape is cylindrical. 2. The electrostatic neutralizer according to claim 1, wherein the tungsten substrate is made of tungsten having a purity of 99.9% or more or potassium-doped tungsten containing 1 to 300 ppm of potassium. The electrostatic neutralizer according to claim 2, wherein the molybdenum substrate is made of either molybdenum having a purity of 99.9% or more or potassium-doped molybdenum containing 1 to 300 ppm of potassium.

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