JPH0131933B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a plasma processing apparatus for powder, and particularly to an apparatus that can uniformly and efficiently process powder with plasma. Various powders such as fluorescent powder, zinc oxide powder for varistors, manganese dioxide powder for dry batteries, toner powder for dry copying machines, silica powder, plastic powder, magnetic powder for magnetic recording, etc., are processed by plasma or its active species. It has been found that the properties required of the powder can be improved by processing the powder with heat.
That is, for example, in the case of a phosphor powder such as calcium halophosphate, luminous efficiency can be improved by treating it with active species of plasma, and by plasma treatment of magnetic powder, solubility magnetization and coercive force can be improved. can be increased. In addition, in the case of manganese dioxide powder for dry batteries, the electromotive force is improved;
In the case of toner powder for dry copying machines, silica powder, and plastic powder, improvements in fluidity (dispersibility) can be made; in the case of zinc oxide powder for varistors, it is possible to improve the properties of each, such as reducing voids. However, conventionally, there have been few apparatuses capable of efficiently and uniformly plasma-treating these powders. Therefore, an object of the present invention is to provide an apparatus that can efficiently and uniformly plasma-treat powder. The apparatus developed by the present inventors includes a microwave generation system and a powder plasma processing system airtightly separated from the microwave generation system, and a microwave transmission antenna is connected to the microwave generation system. a rotating container-type powder stirring means protruding into the interior; a means for supplying discharge gas to the powder plasma processing system; and a means for exhausting the powder plasma processing system. ,
A plasma processing apparatus for powder is characterized by comprising: The present invention will be described in detail with reference to a preferred embodiment of the apparatus of the present invention shown in FIG. Figure 1 is a vertical cross-sectional view of the main parts of this device, and Figures 2, 3, and 4 are
They are - sectional view, - sectional view, and - sectional view in the figure. The parts surrounded by broken lines in Fig. 1 are the main components of this device, respectively: 1 is a microwave generation system, 2 is a powder plasma processing system, 3 is a discharge gas supply means, and 4 is an exhaust gas. It is a means. The microwave generation system 1 includes a microwave oscillator (a magnetron in this example) 11 and a waveguide 12 connected to the oscillator for transmitting microwaves. 13 is a three-stub tuber, and 14 is a plunger. The powder plasma processing system 2 consists of a cylindrical container (made of stainless steel in this example) 203 equipped with a discharge gas inlet 201 and an exhaust port 202, and the inside of the container becomes a powder plasma processing chamber 204. ing. This container 203 is airtightly sealed except for having the gas inlet 201 and the exhaust port 202. However, from the inside of the waveguide 12, a conductive material (stainless steel tube in this example, aluminum tube, copper tube, etc.) is used. An antenna 205 made of a quartz tube (or a quartz tube with a metal film deposited on it) protrudes toward the center of the container cylinder. Container 20 of this antenna 205
The protruding portion into 3 is hermetically surrounded by a cylindrical body 206 made of a microwave transparent material (quartz in this case). The diameter of the base 206a of the cylindrical body 206 is increased to increase its strength, and the base 206a is fixed to the lid of the container 203 by a flange 206b. A conductive film (in this case
The conductive film is coated with an Au (gold) deposited film (not shown), and this conductive film is grounded to provide a shielding effect against microwaves. The left end of the container in FIG. 1 is a disk 207 with a hole in the center.
A cooling water jacket 208 is provided adjacent to the cylindrical body so as to surround the base 206a of the cylindrical body, and a flange portion 206b of the cylindrical body is fixed to the jacket by a member 209. Disc 207 and jacket 20
8 and between the jacket 208 and the flange portion 206b of the cylindrical body, O-rings 210 and 211 are installed, respectively, to keep the inside of the container 203 airtight. Cooling water jacket 208
is provided to prevent O-rings 210 and 211 from deteriorating due to overheating. The antenna 205 is made of a hollow pipe, and its fixing base 205a is made of an insulating material (in this example, it is a quartz tube, but an alumina tube, a Teflon tube, etc. may also be used), but the antenna body is made of an insulating material as described above. Made of conductive material. A cooling gas such as N ₂ gas is fed into the antenna pipe from the outside, and the gas flowing out from the tip of the antenna is discharged to the outside through a gap 212 provided at the base of the antenna. The antenna 205 transmits microwaves from the inside of the waveguide 12 to the inside of the processing container 203 and generates plasma around it, but inside the horizontally arranged container 203, the powder to be processed is almost cylindrical. Since it is located below, the upper half surface of the cylinder 206 is coated with a gold vapor deposition film (not shown) so that the microwaves are reflected and high-concentration plasma is generated below the cylinder 206. There is. This coating may be made of any conductive material, such as forming a vapor deposited film of another metal, applying a metal curved plate, or even SnO ₂ , In ₂ O ₃
It may be coated with materials such as. The cylindrical container 203 is equipped with a capacitance manometer 213 in a part thereof, and is further equipped with a stirring means for uniform treatment. That is, a cylindrical stirring tool 214 is provided at the center of the processing container 203 and coaxially therewith. This cylindrical stirring tool 21
4 has an open end 215 and is fixed to a rotary drive shaft 218 at the other end by a stop plate 217 having a perforation 216. The other end of the container 203 has a recess 219 that accommodates the rotational drive shaft 218.
(Drive shaft storage housing 222) is fitted with a disc-shaped lid 220 provided in the center, and the space between the container 203 and the lid 220 is hermetically sealed by a sealing member 221 such as an O-ring. . This airtightness can be achieved by operating the exhaust means 4
When the inside is reduced in pressure, a suction force acts on the lid body 220, so this is naturally achieved during operation. The recess 219 of the lid 220 is comprised of a cylindrical housing 222 with a closed end, into which one end of the rotary drive shaft 218 is inserted. The rotation drive shaft 218 is rotatably supported by a bearing 223 provided in the lid 220 and a bearing 224 provided in the drive shaft storage housing 222.
There is no contact with either the lid body 220 or the drive shaft housing housing 222 at all. Rotary drive shaft end 218a
is made of a ferromagnetic material such as steel, and is rotated using magnetic force as described below. Around the drive shaft storage housing 222, a rotating body 226 in which a plurality of electromagnets or permanent magnets, four permanent magnets 225 in this embodiment are arranged at equal intervals, is installed in the gap 2.
27. The rotating body is rotatably supported (supporting means, not shown) around the drive shaft storage housing in a separate state.
228 is a drive motor, and the power of this motor is transmitted to the rotating body 226 by a belt 229, so that the rotating body 226 can be rotated around the drive shaft storage housing 222. When the rotating body 226 rotates, the magnetic field formed by the four permanent magnets of the rotating body 226 also rotates, which causes the rotary drive shaft 218 to also rotate. That is, in this device, the cylindrical stirring tool 214 is rotated while the inside of the processing chamber is hermetically closed from the outside, thereby stirring the powder. Cylindrical stirring tool 21
4. The inner surface is provided with protrusions 230 in some places and has an uneven shape so as to increase the stirring efficiency. The discharge gas supply means 3 includes a gas storage cylinder 3
1. A pipe 32 connected to the on-off valve 31a of the cylinder 31, and a gas flow meter 3 provided on the pipe 32.
3 and a needle valve 34. Piping 32 is connected to gas inlet 201 of container 203. Various gases are used as the discharge gas depending on the purpose of plasma processing. For example, N ₂ , N ₂ +H ₂ , NH ₃ for nitriding; H _{2 , NH 3} for reduction
N ₂ + H ₂ , CH ₄ , NH ₃ ; For oxidation treatment, use O ₂ , rare gas + O ₂ ; For etching the powder surface, use halogenated methane, halogenated methane + O ₂ , halogenated methane + rare gas, etc. As the gas used for modifying the powder other than the above, CO ₂ , CO, etc. may be used. Further, the exhaust means 4 connected to the exhaust port 202 of the container 203 includes a pipe 41, a valve 42, and a trap 43.
and an oil rotary pump 44. A cylinder 206 surrounding the antenna 205 of this device generates high-density microwave discharge plasma around it. In the preferred embodiment described above, the upper half of the cylinder is coated with a conductive material (in the above example, a gold evaporated film) so that the active species of the plasma have a higher concentration below the cylinder. Similar effects can also be obtained by the embodiments shown in FIGS. 5 to 7 below. In these drawings, only the cylindrical body is shown as a longitudinal cross-sectional view a and a cross-sectional view b. In FIG. 5, a semi-cylindrical conductive material (for example, stainless steel, aluminum, or quartz with a metal film deposited on it) covers the upper half of the cylinder 51.
A roof 52 is provided to protrude from the base. In FIG. 6, the cylindrical body has a double tube structure made of a microwave transparent material such as quartz, and the outer cylinder 53 has a hole 54 at the bottom. In this case, plasma is generated at the highest concentration between the outer cylinder and the inner cylinder, and the generated active species flow downward through the holes 54. In the embodiment shown in FIG. 7, the cylindrical body has a double tube structure as in FIG. 6, and the upper half of the outer cylinder 55 is further provided with a coating of a conductive material, such as a metal vapor deposition layer 56. The roof 52 in FIG. 5 and the coating 56 in FIG. 7 have the effect of reflecting microwaves downward, which is advantageous for generating plasma at a high density below. The apparatus of the present invention has been described above in detail with reference to embodiments, and its operating method will now be described using plasma treatment of magnetic powder as an example. First, the oil rotary pump 44 is operated to exhaust the inside of the processing container 203 to a pressure of 10 ^-3 Torr or less. Next, the discharge gas is passed through the flow meter 33 and the needle valve 3.
4, the gas is supplied from the gas storage cylinder 31 to the processing chamber 204 through the discharge gas inlet 201. At this time, the oil rotary pump 44 continues evacuation, and the pressure in the processing chamber 204 is kept at about 10 ^-1 to 5 Torr.
It is best to adjust the gas flow rate to about 30 to 300 c.c./min. The pressure and gas flow rate are adjusted using the needle valve 34 while observing the capacitance manometer 213 and flow meter 33. Next, the microwave oscillator 11 is operated to oscillate microwaves with a frequency of 2450 MHz and a power of 100 to 500 W, impedance matching is performed using the three-stub tuner 13 and plunger 14 of the waveguide 12, and the microwave is transmitted to the antenna 11. It is transmitted into the processing chamber 204 by. Then, plasma is generated around the cylindrical body 206 due to the discharge. At this time, plasma is generated almost entirely within the processing chamber 204, but a particularly high-density plasma is generated near the bottom of the cylinder 206 due to the Au vapor deposited film covering the upper half of the cylinder 206. The active species in the plasma thus generated in the processing chamber 204 come into contact with the powder 231 placed in the stirring tool 214, and the powder is subjected to plasma treatment. At this time, the cylindrical powder stirring tool 2
14 is rotated by the power of a motor 228 to stir the powder. At this time, the powder 231 to be treated
It is preferable to carry out stirring by placing a stirring piece 232 made of quartz or metal inside the stirring tool, since higher stirring efficiency can be obtained. Example of use: Using the device shown in Fig. 1,
57.5 emu/g barium ferrite powder (BaOFe _10.4 Co _0.8 Ti _10.8 O ₁₈ ) was plasma treated.
Discharge gas used, discharge power and processing time,
The saturation magnetization after treatment is shown in the table below. The input/output characteristics and frequency characteristics of the magnetic recording device are
This is largely due to the saturation magnetization of the magnetic powder used in magnetic tape. Barium ferrite is usually used with some of its Fe components replaced with Co and Ti in order to control the coercive force, but the maximum saturation magnetization is estimated to be 63 ± 1 emu/g. (Journal of Applied Physics, 35 , 3482
(1964)), however, the saturation magnetization of normally produced barium ferrite is 57-58. According to the results in the table below, it can be seen that the value of saturation magnetization can be considerably improved by plasma treatment using the apparatus of the present invention. As described above, the apparatus of the present invention is extremely useful for uniformly and efficiently plasma-treating powder.

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【table】 [Brief explanation of drawings]

FIG. 1 shows an embodiment of the plasma processing apparatus for powder according to the present invention, and is a longitudinal cross-sectional view of the main parts. FIG. 2, FIG. 3, and FIG. 4 are -, -, and - cross-sectional views of FIG. 1, respectively. And, Figures 5, 6, and 7 are
FIG. 3 is a diagram illustrating one embodiment of a cylinder body provided to surround each antenna. DESCRIPTION OF SYMBOLS 1...Microwave generation system, 2...Powder plasma treatment system, 3...Discharge gas supply means, 4...Exhaust means, 203...Cylindrical container, 205...Antenna, 206...Cylindrical body , 214... Cylindrical stirrer, 225... Magnet, 226... Rotating body, 228
...Electric motor, 229...Belt, 231...Powder, 232...Stirring piece.

Claims (1)

[Scope of Claims] 1. A microwave generation system, and a powder plasma processing system airtightly separated from the microwave generation system, wherein a microwave transmission antenna projects into the inside of the microwave generation system. a rotating container type powder stirring means; a means for supplying discharge gas to the powder plasma processing system; and a means for exhausting the powder plasma processing system. A plasma processing device for powder, which is characterized by: