JPS61101420A - Preparation of tin oxide fine particle - Google Patents

Abstract

PURPOSE:To obtain tin oxide fine powder having particle diameter of <=0.1mu, by placing an evaporation source of tin, an ionizing electrode and a thermionic emission filament in oxygen gas or gaseous mixture of oxygen and argon, and generating arc discharge at a low voltage. CONSTITUTION:The evaporation source 1 of tin, the ionizing electrode 2, the thermionic emission filament 3 and the collection plate 4 are arranged in the vacuum chamber 6. The vacuum chamber 6 is evacuated with the vacuum pump 7, and oxygen gas or a gaseous mixture of oxygen and argon is introduced into the vacuum chamber through the valve 10 furnished with oxygen flow meter and the valve 11 furnished with argon flow meter to a pressure of 0.001-0.1Torr. Tin is evaporated by electrifying the tin-evaporation source 1, and at the same time, thermions are emitted from the thermionic emission filament 3 to generate an arc discharge between the ionizing electrode 2 and the evaporation source 1. The evaporated in reacts with oxygen in the arc discharge, and the produced fine particles of tin oxide are attached to the collection plate 4.

Description

DETAILED DESCRIPTION OF THE INVENTION 1 = Industrial Application Field The present invention relates to a method for forming tin oxide particles having a particle size of 0.1 μm or less.

[Conventional technology]

Tin oxide is widely used in transparent electrodes, catalysts, gas sensor materials, etc.
Although it is an industrial material with many uses, in particular those with small particle sizes exhibit high catalytic activity due to their extremely large specific surface area, and are attracting attention as materials for high-sensitivity gas stations.

As a method for producing tin oxide fine particles, a chemical method of hydrolyzing tin tetrainopropoxide to precipitate tin oxide and drying it [for example, Keiko Suwa et al., "Material J31
, 955 (1982)), and a physical method to obtain fine tin oxide particles by attaching fine particulate metal tin to a substrate using the ion blating method and leaving it in the atmosphere to naturally oxidize [for example, Koyokura-1 et al., “IEICE Technical Research Report JE
D78-14.35 (1978)) is located here.

The former method makes it possible to obtain small tin oxide with uniform particle size, but the starting material, tin tetrahinopropoxide, is expensive and the operating conditions for hydrolysis are severe, so highly specialized technology is required. It has disadvantages such as. The latter method uses the ion plating method, which is a method of vacuum evaporation, so tin oxide with small particle size can be obtained through a simple manufacturing process. Because a high voltage of several hundred units or more is used for this purpose, there is a high operational risk, and the metal tin particles attached to the substrate must be left in the air for a week to naturally oxidize. It has the disadvantage of requiring a long period of time.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is to eliminate the drawbacks of the conventional method, use a safe device that does not use high voltage, and reduce the particle size to 0. ] The object of the present invention is to obtain a method capable of producing a large amount of tin oxide fine particles having a size of .mu.m or less in a short period of time.

Means for Solving Problem C] According to the present invention, the above problem can be solved by arranging a tin evaporation source, an ionization electrode, and a thermionic emission filament in oxygen or a mixed gas of oxygen and argon, This problem can be solved by generating an arc discharge at low voltage and causing the tin vaporized from the evaporation source to react with oxygen.

The pressure of the mixed gas of oxygen or acid and argon used has a lower limit of α001 Torr and an upper limit of 0 to 1 Torr.
Preferably, a range of Torr is used.

[Effect]

Although the details of the production mechanism of tin oxide fine particles by the method of the present invention are not necessarily clear, it can be considered as follows. In other words, the tin atoms evaporated from the evaporation source are ionized by the arc discharge between the evaporation source and the ionization electrode, making them active and highly reactive.Similarly, the oxygen in the atmosphere is also ionized and activated, so the tin atoms Reacts easily with oxygen and oxygen. Which reaction between tin and oxygen is an exothermic reaction.

Since this is a thermal sintering reaction under low pressure, the tin oxide produced becomes fine particles.

Also usually evaporation sources and ionization! A high voltage of several hundred or more is required to generate an arc discharge between the pole and the ionizing electrode. When thermionic electrons of about 0.5 mA are emitted, stable arc discharge can be generated at a low voltage of 80 V or less. Stability of this arc discharge is a necessary condition for continuous reaction of tin and oxygen. Note that arc discharge becomes more stable in a mixed gas of oxygen and argon, and argon does not interfere with the production of tin oxide.

The pressure of oxygen or a mixed gas of oxygen and argon may be sufficient to cause arc discharge to occur stably and to cause an oxidation reaction between the powder and evaporated tin. As the pressure of the mixed gas of oxygen or tR element and argon increases, the voltage required for arc discharge increases, and as the gas pressure decreases, the production rate of tin oxide fine particles slows down.

Therefore, it is preferable to set the upper and lower limits of the pressure of oxygen or a mixed gas of oxygen and argon to the above-mentioned values so as to perform stable arc discharge at a low voltage of 80 V or less.

When using a mixed gas of oxygen and argon, the γ-consolidation ratio is not particularly limited, but as the proportion of oxygen decreases, the production rate of tin oxide fine particles also decreases.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

The figure shows an apparatus for carrying out the method of the present invention, in which 1 is a tin evaporation source consisting of a resistance-heated tungsten boat, 2 is a molybdenum ion ratio electrode, and 3 is a thermionic emission filament with a diameter of 1 mm. When a tungsten tube with a length of 10 mm is heated by passing an alternating current of 50 A, thermoelectrons are generated.

Evaporation source 1, ionization electrode 2) Thermionic emission filament 3
Although not clearly shown in the drawings, power is supplied to each from the electric M4 port provided on the base plate 5.

44 Ionization'aff12) Thermionic emission filament 3
6 is a stainless steel vacuum chamber, 7 is a collection plate placed above the
is a vacuum pump connected to the vacuum chamber 6, 8 is a vacuum gauge, 9 is a squeezed pulp inserted between the vacuum pump 7 and the vacuum gauge 8,
10 and 11 are a pulp with an oxygen flow meter and a pulp with an argon flow meter connected to the vacuum 46, respectively.

The vacuum chamber 6 is first pumped with a vacuum pump 7 to l x 10 Torr.
After being evacuated to below r, oxygen or a mixed gas of oxygen and argon is introduced through the pulp 10 with a flow meter for oxygen, the pulp 11 with an albo/nitrogen meter, and the pulp 11 with a quantity meter, and the pressure is maintained at a predetermined pressure value. Ru. Next, a current is passed through the tin evaporation source 1 to heat it and evaporate the tin, while emitting thermoelectrons from the thermionic emission filament 3.
When an arc discharge is generated between them, the evaporated tin and oxygen react with each other in the arc discharge, and the generated tin oxide fine particles adhere to the lower side of the collection plate 4.

Implementation row 1 Oxygen pressure α02 Torr, arc discharge voltage 75V.

Tin oxide was produced at a tin evaporation rate of 0.08 ji/min. As a result of observation with a scanning electron microscope, the particle size of the tin oxide microspores was found to be less than α1 μm.

Example 2 Pressure of mixed gas of oxygen and argon f102Torr,
Arc failure 1 electric current 8E73V, tin evaporation rate 0.055'
/min produced tin. As a result of observation with a scanning electron microscope, the particle size of the tin oxide particles was 0.1 μm or less.

〔Effect of the invention〕

According to the present invention, tin oxide fine particles with a particle size of 01 μm or less can be obtained by arc discharge at a low voltage of 80 V or less with an extremely simple device, and unlike conventional methods, dangerous high voltages are used. This method has the advantage that tin oxide # particles can be produced in a I4a manner without the need for this process and in a short time.

[Brief explanation of the drawing]

The figure is a block diagram of an apparatus for carrying out the method of the present invention. l...Tin evaporation source, 2...Ionization electrode, 3...
Thermionic emission filament, 4. Collection plate, 6. Vacuum chamber, 7. Vacuum pump, 10. Oxygen flow meter included.
(Pulp, 11...Pulp with flow meter for argon.

Claims (1)

[Claims] 1) A tin evaporation source, an ionization electrode, and a thermionic emission filament are placed in oxygen or a mixed gas of oxygen and argon, and an arc discharge is generated at a low voltage to cause evaporation from the evaporation source. A method for producing tin oxide fine particles, the method comprising reacting tin and oxygen. 2) The method for producing tin oxide fine particles according to claim 1, characterized in that the pressure of oxygen or a mixed gas of oxygen and argon is in the range of 0.001 Torr to 0.1 Torr. Method for producing tin fine particles.