JP2009161800A - Gadolinium oxide thermally sprayed film, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive method for obtaining a thermally sprayed film having excellent fluorescence and cleanability by a photocatalyst satisfying requirements by performing thermal spraying because a flame temperature rises to 15,000 to 30,000°C when plasma thermal spraying is used in the case of manufacturing of a ceramic film by thermal spraying using gadolinium oxide powder, and anatase type titania powder, and also the flame temperature in the conventional flame thermal spraying, the flame temperature rises to 2,200 to 3,400°C, and therefore, the powder easily melts, sublimates, decomposes, and, therefore, the transformed film different from the thermally sprayed powder and the film having the changed composition are obtained. <P>SOLUTION: Unlike the conventional flame thermal spraying, the film having the required fluorescent characteristics and adhesion at a high temperature is formed by supplying thermal spraying powder and a combustion gas from behind a combustion chamber of a gun, and jetting the combustion gas and slurry-form thermal spraying fine powder toward the axis of the flame from the supply nozzle, regulating the amount of oxygen introduced into the combustion chamber, and the volume of the combustion gas to be introduced from the supply nozzle to control the temperature of the ceramic fine powder existing in the flame, and accelerating the combustion by the gas generated by the combustion to obtain the film having required fluorescence and high temperature adhesion and cleanability by the photocatalyst. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gadonium oxide film having functions such as phosphor, heat resistance, and photocatalytic property, and a manufacturing method using thermal spraying.

Metals / alloys and ceramics change their properties due to changes in temperature. In a surface modification process where the treatment temperature is high, the material properties at room temperature are transformed by the high temperature treatment and changed to other properties. In particular, in the thermal spraying process, it is difficult to perform thermal spraying by controlling the temperature below 4000 ° C to 30000 ° C and gas spraying method 2200 ° C to 3400 ° C in the plasma spraying of the electric spraying method. There is a strong demand for a method of spraying by changing the coating composition with high accuracy at a temperature at which the material does not transform.
Since the phosphor is mixed with the paint and applied, the paint is not used because it burns above the use temperature of the paint, for example, 350 ° C. or more. Further, when the phosphor is exposed to the atmosphere, dust, dust and the like adhere to it and impair the fluorescent function. Photocatalytic anatase TiO2 has a cleaning effect, but it transforms to rutile TiO2 due to high temperature spraying and does not satisfy its function.

JP 10-60617 Flame temperature 2200 to 3400 ° C, powder supplied from inside JP 2006-108178 Al2O3 particle plasma sprayed unmelted

Thermal spray process
Plasma spraying using working gases such as Ar + hydrogen, Ar + nitrogen, and He + hydrogen increases the flame temperature from 15000 ° C to 30000 ° C. On the other hand, in conventional flame spraying using fuel and oxygen, oxygen / kerosene, air / kerosene, oxygen / hydrogen, oxygen / propylene, oxygen / propane, oxygen / ethylene, oxygen / acetylene, oxygen / natural gas mixed gas To generate heat. Since the flame temperature is 2200 ° C to 3400 ° C and is a continuous combustion reaction, it is very difficult to control the temperature below that.

Powder supply device When a material with low thermal conductivity such as ceramics is instantaneously heated and melted, the finer the powder, the better. Further, if the thermal spray powder is fine, the surface roughness of the coating is fine, and there is an advantage that the subsequent surface finishing step can be omitted. However, fine powder with a particle size of 0.1 μm to 10 μm tends to agglomerate and is difficult to feed.

Thermal spraying materials Thermal spray materials Material systems that melt at relatively low temperatures, material systems that transform, and material systems that sublime need to be aware of the flame temperature. The melting point of Gd2O3 is 2310 ° C. Anatase TiO2 transforms to rutile TiO2 at 700-800 ° C. Its melting point is 1840 ° C.

  In order to emit a fluorescent color and increase its durability, a photocatalyst is added and coated to provide a cleaning effect and prevent adhesion of dust.

Thermal spraying process Gd2O3 and anatase TiO2 are melted and difficult to coat at a flame temperature of plasma spraying from 15000 ℃ to 30000 ℃. On the other hand, even in the flame temperature range of 2500 ° C to 3400 ° C in the conventional flame spraying, the film melts in the same manner and the fluorescence and photocatalytic properties of the film are impaired.

Thermal spray coating configuration A dense coating is good for the coating configuration to give fluorescence. In conventional flame spraying, it is difficult to stably coat the dense film by lowering the frame temperature to below 2200 ° C or finely controlling the ambient temperature at the part where the ceramic fine powder is put into the frame. It is.
[Means for solving problems]

  The thermal spraying method according to the present invention includes a gun tip tube in a flame spray gun using oxygen / kerosene, air / kerosene, oxygen / hydrogen, oxygen / propylene, oxygen / propane, oxygen / ethylene, oxygen / acetylene, oxygen / natural gas. Attached to the tip of the gun, powder supply nozzles are installed at two positions at a 180 ° target or four positions at a 90 ° position toward the cylindrical axis of the tip cylinder.

  Since the sprayed fine powder forms a bridge in a narrow transport tube and cannot be stably supplied, the fine powder is transported in the form of a slurry. A ceramic fine powder with a particle size of 0.1 μm to 10 μm is stirred in ethyl alcohol, methyl alcohol or kerosene as a solvent to form a slurry. Even if powder having a particle size of 10 μm or more is present, it can be made into a slurry. Pump to tube and send C2H2 gas from tube Y union to mix. A mixture of slurry-like powder and C2H2 gas is conveyed to a powder supply nozzle.

  By using ethyl alcohol, methyl alcohol, kerosene as a solvent to make the thermal spray fine powder into a slurry, and using C2H2 as a combustible gas, all of them burn and generate heat when the amount of oxygen is large, and when it is small Has the characteristic of cooling without burning, and this balance adjusts the temperature by melting or heating the fine powder.

When the amount of oxygen in the fuel is greater than the theoretical amount of oxygen, the combustion gas contains oxygen and reacts with the C2H2 (acetylene) gas and alcohol conveyed from the powder supply nozzle to generate heat. On the other hand, if the amount of oxygen relative to the fuel is less than the theoretical amount of oxygen, non-combustible fuel is contained and the temperature is lowered. Further, the frame is cooled without burning C2H2 (acetylene) gas and alcohols conveyed from the powder supply nozzle. Accordingly, when the oxygen amount is equal to or higher than the theoretical oxygen amount, the thermal spray material is heated at a high temperature. Conversely, when the oxygen amount is equal to or lower than the theoretical oxygen amount, the thermal spray material is heated at a low temperature.
Reference: C12H26 + 37 / 2O2 → 12CO2 + 13H2O

  Thermal spraying condition factors include kerosene or combustion gas and oxygen ratio, total amount, spray distance, distance from gun of powder supply nozzle at gun tip tube, C2H2 supply amount, slurry supply amount Alternatively, the atmosphere temperature of the flame of the molten particles, the sprayed heating particles, or the speed of the molten particles are controlled, and the film configuration is made to meet the target.

  For example, when using kerosene / oxygen mixture as fuel, the thermal spraying conditions are oxygen gas pressure 0.5-1.5 MPa, flow rate 400-1400 liters / minute, kerosene pressure 0.4-1.4 MPa, flow rate 0.2-0.5 liters / minute. Min, compressed air pressure to 0.2-1.5MPa, 500-1000L / min, slurry powder feed rate. 100-900g / min, C2H2 (acetylene) pressure 0.1-1.5MPa, 20-600L / min . The spraying distance should be 70mm to 400mm from the tip of the gun tip.

When using acetylene / oxygen mixture as fuel, the thermal spraying conditions are oxygen gas pressure 0.15 to 0.3 MPa, flow rate
Acetylene pressure 0.10-0.24MPa to 30-70L / min, flow rate 15-55L / min, compressed air pressure 0.2-1.5MPa, slurry powder supply amount to 100-1500L / min. 100-900g / min Min, C2H2 (acetylene) pressure 0.3-1.5 MPa, 60-600 liters / min. The spraying distance should be 50mm to 300mm from the tip of the gun tip.

  The flame temperature was lowered and the temperature was precisely controlled, enabling thermal spraying of oxide Gd2O3, oxide Gd2O3 + anatase TiO2. Due to the composite, a clean phosphor can always be developed with a cleaning effect.

A simple powder supply system, solvent and gas used enable fine powder supply. A thermal spray coating using fine powder was made, and the surface finishing process could be omitted by reducing the surface roughness. Therefore, it was possible to suppress the increase in cost.

  Lowering the frame temperature and controlling the temperature accurately, enabling the formation of dense, pores, lamellar, or spherical unmelted particles + molten mixed coatings with a spray coating composition that has previously been impossible. Can now be obtained.

As shown in the schematic diagram of FIG. 1, the flame spray gun 1 has a combustion chamber 2, introduces oxygen gas from the oxygen passage 2,
Combustion gas and fuel liquid such as kerosene, acetylene, propylene, propane, ethylene and natural gas are introduced from the fuel passage 4. Fuel and oxygen are mixed in the combustion chamber 2, guided to the gun nozzle 5, and burned when ignited. The gun nozzle has a compressed air passage 6 therein, and the compressed air flows in a laminar flow on the inner surface of the gun tip tube 9 so that the sprayed powder does not adhere to the inner surface of the gun tip tube 9.

  A powder supply nozzle 7 is installed on the gun tip tube 9 toward the axis of the gun tip tube 9. The powder supply nozzle 7 has a gas / sprayed powder passage 8. A mixture of the slurry-like powder and C2H2 gas is introduced into the powder supply nozzle 7 and injected into the combustion gas flame.

  When the theoretical oxygen amount is large with respect to the fuel, the combustion gas contains oxygen, the flame temperature rises on the inner surface of the gun tip tube 9 portion, and the sprayed powder is heated to a high temperature. When the theoretical oxygen amount is small relative to the fuel, the C2H2 gas is cooled without burning on the inner surface of the gun tip tube 9 portion, and the sprayed powder is heated at a low temperature. Since the inner diameters of the gun nozzle 5 and the gun tip tube 9 are narrow, the speed of the combustion gas is increased, and the heated particles or the molten particles are accelerated and collide with the base material 11 to form the film 10.

It is desirable to make a dense film structure composed of the lamellar layer of FIG. 2 using Gd2O3 and anatase TiO2 fine powders that require fluorescence, heat resistance and photocatalytic properties. Since anatase TiO2 is transformed into rutile TiO2 at 700 ° C to 800 ° C, it is necessary to keep the flame temperature as low as possible and accelerate the coating.
The present invention will be described in detail with reference to examples.

  A specimen of SUS304 having a size of 100 mm × 100 mm × plate thickness 2 mm was used. Before forming the film, it is washed in advance and a grit blast treatment is performed as a roughening treatment. Alumina grit 60 mesh is used and sprayed onto the specimen substrate at a pressure of about 0.5 Mpa. The surface roughness after blasting was Ra10-15 μm.

  The powder and acetylene gas were stopped using the thermal spray gun shown in FIG. 1 and combusted, and the test piece was heated from 50 ° C. to 150 ° C. and preheated. This treatment removed moisture, water, and water vapor.

Mix with ethyl alcohol using Gd2O3 fine powder particle size 1μm to 5μm. For a bulk volume of Gd2O3, a volume of ethyl alcohol of 1.5 is placed in a container and stirred to form a slurry. These mixtures are introduced into the gas / powder passage 8 by mixing acetylene from the Y-shaped union of the tube through the slurry carrying tube.
The distance from the tip of the gun tip to the specimen substrate is kept at 150 mm, and the gun axis and specimen surface are held vertically. That is, the spraying distance is 150 mm. The thermal spraying conditions are summarized below.
[Spraying conditions]

Fuel kerosene: Pressure 0.8MPa, Flow rate 0.4L / min Oxygen gas: Pressure 1.0MPa, Flow rate 700L / min Compressed air: Pressure 0.5MPa, Flow rate 600L / min Powder supply rate: Gd2O3 + Ethyl alcohol: 500g / min Acetylene gas: Pressure 0.3 MPa, Flow rate 60 liter / min

The thickness of the thermal spray coating on the test piece substrate thus obtained was 80 μm, and the surface roughness was Ra1 to 4 μm. The structure of this film cross section is shown in FIG. It is a structure having a lamellar layer slightly containing pores.
The results of examining this film with an X-ray diffractometer are shown in FIG. Gd2O3 was detected.
An appearance photograph of the Gd2O3 film is shown in FIG. The test piece was illuminated with black light to confirm the fluorescent color as shown in FIG. Moreover, it cut out from the test piece which has the said film | membrane in air | atmosphere, heated up from room temperature to 900 degreeC, hold | maintained for 5 minutes, and air-cooled. If the result was 900 ° C. or lower, peeling did not occur. It was confirmed that the fluorescence of the Gd2O3 film was maintained even in an environment exposed to 350 ° C or higher and 900 ° C or lower. Further, FIG. 8 shows a test piece which is cut out from the test piece having the above-mentioned film, heated at 600 ° C., kept for 5 minutes, and air-cooled to emit a fluorescent color by irradiating light with a black light.

  A specimen of SUS304 having a size of 100 mm × 100 mm × plate thickness 2 mm was used. Before forming the film, it is washed in advance and a grit blast treatment is performed as a roughening treatment. Alumina grit 60 mesh is used and sprayed onto the specimen substrate at a pressure of about 0.5 Mpa. The surface roughness after blasting was Ra10-15 μm. The powder and acetylene gas were stopped using the spray gun shown in FIG. 1, and the test piece was heated from 50 ° C. to 150 ° C. for pre-heat treatment. This treatment removed moisture, water, and water vapor.

  Mix with methyl alcohol using a 30% powder bulk volume mixture of 1 μm to 5 μm anatase TiO2 fine powder to a powder bulk volume 1 of Gd2O3 particle size 1 μm to 5 μm. For the mixed powder bulk volume 1 of Gd2O3 and anatase TiO2, the volume 1 of methyl alcohol is put in a container and stirred to form a slurry. These mixtures are introduced into the gas / powder passage 8 by mixing acetylene from the Y-shaped union of the tube through the slurry carrying tube.

The distance from the tip of the gun tip to the specimen substrate is kept at 150 mm, and the gun axis and specimen surface are held vertically. That is, the spraying distance is 150 mm. The thermal spraying conditions are summarized below.
[Spraying conditions]

Fuel kerosene: Pressure 0.9MPa, Flow rate 0.45L / min Oxygen gas: Pressure 1.0MPa, Flow rate 700L / min Compressed air: Pressure 0.4MPa, Flow rate 480L / min Powder supply rate Gd2O3 and anatase TiO2 + methyl alcohol: 450g / min acetylene : Pressure 0.4MPa, Flow rate 80l / min

The thickness of the sprayed coating on the test piece base material thus obtained was 100 μm, and the surface roughness was Ra1 to 4 μm. Although the structure of the cross section of the film is not shown in the drawing, it is a structure having a lamellar layer containing a few pores.
As a result of examining this film with an X-ray diffractometer, Gd2O3 and anatase TiO2 were detected.
The Gd2O3 film was illuminated with black light to confirm the fluorescent color. The cleaning effect of anatase TiO2 was confirmed after exposure to the atmosphere for a long time.

Schematic diagram of a spray gun for carrying out the flame spraying method of the present invention Schematic diagram of lamellar layer in cross section of thermal spray coating Schematic diagram of lamellar layer containing pores in the spray coating cross section X-ray diffraction chart of Gd2O3 Gd2O3 film cross section Gd2O3 spray coating appearance photo Fluorescent appearance photo of sprayed Gd2O3 coating Appearance photo showing fluorescence after holding Gd2O3 film at 600 ℃ for 5 minutes

Explanation of symbols

1 Flame spray gun 2 Combustion chamber 3 Oxygen passage 4 Fuel passage 5 Gun nozzle 6 Compressed air passage 7 Powder supply nozzle 8 Slurry spray powder + C2H2: Gas / powder passage 9 Gun tip tube 10 Spray coating 11 Base material 12 Lamellar 13 Pore 14 Spherical shape Unmelted particles

Claims (5)

In flame spraying using fuel and oxygen, oxygen / kerosene, air / kerosene, oxygen / hydrogen, oxygen / propylene, oxygen / propane, oxygen / ethylene, oxygen / acetylene, oxygen / natural gas mixed gas Generate a frame.
A powder supply nozzle is installed behind the frame. From the nozzle, a fine powder spray powder or a mixture of acetylene is sprayed as a slurry spray powder and combustion gas. At that time, a thermal spraying method in which the amount of oxygen in the combustion chamber and the amount of acetylene from the nozzle are adjusted to control the temperature of the thermal spray powder to coat. Ethyl alcohol, methyl alcohol, and kerosene are used as a medium for making the sprayed fine powder of the above claims into a slurry. In the ceramics composed of a mixture of Gd2O3 and anatase TiO2 as the thermal spraying material of the above claims, anatase TiO2 contains 0 to 70% in terms of powder bulk capacity with respect to Gd2O3 powder bulk capacity. It consists of a Gd2O3 and anatase TiO2 mixture film formed according to the above claims, and is characterized by a single layer or a combined two layer structure in a dense, pore, lamellar, or spherical + melt mixed structure. Film. The film formed according to the above claims has fluorescent, heat-resistant, and photocatalytic functions.