JPS61256962A - Light permeable alumina pipe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] 1 above This invention relates to a translucent alumina tube.

The translucent alumina tube is fired in a batch-type H2 atmosphere furnace.For example, the conventional translucent alumina tube
It has the characteristics of an average particle size of 50 μm and a radial crushing strength of 20 kgf/mi2 for a diffused (total) transmittance of 5%.

However, conventionally, in order to obtain a diffuse transmittance of 95% or more, an average grain size of 50μ or more is required, so such a crystal structure has a low radial crushing strength and is weak in strength. .

For this reason, when a translucent alumina tube is used as an arc tube for a high-pressure Na lamp, it may crack or burst, resulting in a short service life. Therefore, it is desired to develop a translucent alumina tube with high strength and diffused transmittance.

This invention was made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a translucent alumina tube having high strength and high diffused transmittance.

To 11 11 This invention has a total transmittance of 95% or more and an average particle size of 20 to 40%.
The gist is a translucent alumina tube with μ- and particle variation set to 4.0 or less.

1 - Total transmittance (diffuse transmittance) is 95% or more and average particle size is 2
The grain size is 0 to 40 μm, and the particle variation is set to 4.0 or less.

By the way, the average particle diameter (μm) is defined as follows.

The average particle size is 100 to 5 on the inner and outer surfaces of the translucent alumina tube.
Randomly take 10 micrographs of a region containing 00 particles at a magnification of 100 to 300 times, count the number of particles in this photo, calculate the average occupied area of one particle from the photo area and magnification, This is the diameter calculated assuming that this is a circular particle.

The average particle size is expressed as 1120/MX, J"Efu1. However, M is the magnification on the photograph, and S is the area of the photographic paper (mm2).
, n indicates the number of particles.

Further, the particle dispersion is the ratio between the conical sieve diameter of the largest particle within the photographic field of view under the same conditions and the average particle diameter. The light transmittance is controlled by the dispersion of particles, and the larger the dispersion, the more
Even if the average particle size remains the same, the transmittance decreases.

JL As the average particle size increases, the light transmittance increases.

Instead, the strength decreases. The translucent alumina tube of the present invention has high strength and high diffuse transmittance.

The reasons for limiting the diffuse transmittance, average particle size, and particle variation are as follows.

In order to ensure a diffused transmittance of 95% or more, increasing the average particle size increases the light transmittance, but reduces the strength. If the average particle size is small, the strength will be high but the light transmittance will be low.

Therefore, a diffused transmittance of 95% or more is ensured. As a result of various experiments, the average particle size range is 20 to 4.
It can be limited to 0 μm, and the particle variation can be limited to 4.0 or less.

Support 11 FIG. 1 shows a firing device.

First, the structure of this firing apparatus will be explained.

A heating furnace 1 (Z one S 1nter furnace), an upper setting section 2, and a lower setting section 3 are arranged in series.

The heating furnace 1 has a heat insulating layer 4. This insulation layer 4 is
It is constructed by connecting each of the segmented layers 58 to 5e in the axial direction. This heat insulating layer 4 may have a cylindrical shape, for example. A heating element 6 is set inside each of the divided layers 5a to 5e. This heating element 6 may be made of a heat generating material such as tungsten.

The partition layer 5b indicated by hatching in FIG. 1 functions as a high temperature region. That is, the heat generation temperature in the segmented layer 5b is
The heat generation temperature is set higher than that in the other partitioned layers 5a, 5c, 5d, and 5e. The maximum heat generation temperature of the section 115b is set to at least 1400°C or more, for example 1900°C.

The heat insulating layer 4 is provided vertically within the heating furnace 1 . The atmosphere inside the furnace is made of reducing gas or inert gas. The atmosphere inside the furnace can be composed of hydrogen, for example.

The space of the upper setting part 2 has sufficient space for the integral object to be fired 7 to move in the vertical direction. Upper setting section 2
An upper opening 8 is provided on the side surface of the housing. This upper opening 8 can be opened and closed.

An upper shutter 9 is provided between the upper setting section 2 and the heating furnace 1. The upper shutter 9 is configured such that a pair of left and right shielding portions 9a can be closed or opened by an actuator 9b.

A moving device 10 for moving the object to be fired 7 is provided above the upper setting section 2 . The moving device 10 has a drive roller 11 and a contact roller 12.

The lower end of the high melting point metal wire 13 is attached to the upper end of the object to be fired 7 . Therefore, the object to be fired 7 can be moved in the vertical direction by operating the moving device 10.

The lower end of the lower setting section 3 is closed. A lower opening 14 is provided on the side of the lower setting portion 3 as required. This lower opening 14 can be opened and closed.

Either the lower opening 14 or the upper opening 8 can be omitted depending on the application.

A lower shutter 15 is provided between the lower setting section 3 and the heating furnace 1. This lower shutter 15 has the same configuration as the upper shutter 9.

The upper shutter 9 and the lower shutter 15 may be of the same type, or may be of different types.

Next, the processing procedure for the integrated object to be fired 7 will be explained.

100 parts of high-purity alumina powder (purity 99.9%), 0.5 part of magnesium sulfate heptahydrate, PVA as a binder
Mix 1 part (polyvinyl alcohol) and make a slip.

(Magnesium 5A acid heptahydrate is a grain growth inhibitor.

) The raw material made into a slip is dried with a spray dryer and granulated.

This granulated powder is formed into a tube shape using an isostatic press at a pressure of, for example, 1 ton/Ca+2, and then ground into a predetermined shape. Approximately 30 mm x 27 parts m x 130
It is 0mm.

This is pre-fired at 1100°C to scatter the binder, and then fired in a hydrogen atmosphere using the above-mentioned firing apparatus.

The segmented layer 5b of the heating furnace 1 has an axial length of, for example, 30 mm.
It is set to 011m. This axial length is smaller than the axial length of the object 7 to be fired. The segmented layer 5b has a high temperature region in which the object to be fired 7 can be fired.

The object to be fired 7 is fired in the following manner.

The object to be fired 7 is held in the lower setting part 3 by a moving device 10.

The lower shutter 15 is closed. High melting point metal wire 1
3 is inserted into the lower shutter 15. In this case, the lower setting part 3 is the setting zone 16 of the object 7 to be fired. The lower setting part 3 is sealed and its atmosphere is replaced with air, N2, and H2 in this order.

Both the atmosphere in the lower setting part 3 and the atmosphere in the heating furnace 1 are composed of hydrogen.

The lower shutter 15 is opened, the moving device 10 is activated,
The object to be fired 7 is pulled upward from the setting zone 16. The object to be fired 7 is pulled upward within the heat insulating layer 4 .

The object to be fired 7 passes through the partition layer 5b of the heating zone 17, as shown in FIGS. 2 to 4.

As shown in FIG. 2, the upper end 7a of the object to be fired 7 passes through the partition layer 5b at a passing rate of 500 cm/hour, for example. Next, as shown in FIG. 3, the intermediate portion 7b of the object to be fired 7 is
It passes through the partitioned layer 5b at a passing rate of 1001111/hour, for example. Furthermore, the lower end 7C of the object to be fired 7 is divided into a section 11
5b at a passing speed of 500 ms+/hour.

In this way, the passing speed of the object 7 to be fired is changed, and the object 7 is sintered within the partitioned layer 5b.

Next, the upper shutter 9 is opened and the object to be fired 7 enters the main setting section 2. The main setting section 2 includes a take-out section 18 for the object to be fired 7.
functions as

When the upper shutter 9 is closed, the atmosphere in the main setting section 2 is as follows.
-12, N2, and air are exchanged in this order. The object to be fired 7 is taken out from the main setting section 2 .

Note that the flow direction of H2 in the heating zone 17 is opposite to the direction in which the object to be fired 7 passes.

In this way, a monolithic ceramic sintered body, for example a translucent alumina tube, is obtained. The resulting tube has the particle size dependent properties shown in FIG.

In FIG. 5, the horizontal axis indicates the position from the top of the ceramic sintered body. Moreover, the average particle size, radial crushing strength, and diffused (total) transmittance are plotted on the vertical axis.

As already mentioned, the passing speed at the upper end 7a and lower end 7C of the object to be fired 7 is set to be faster than the passing speed at the intermediate section 7b.

From this, as shown in FIG. 5, the average particle diameter of the translucent alumina tube is 20 to 40 microns higher, and is set smaller at the upper and lower ends, but larger at the middle part.

Properties that depend on this average particle size include light transmittance and intensity.

The diffuse transmittance is small at the upper and lower ends of the translucent alumina tube, and is 95% or more at the middle. Conversely, the radial crushing strength is large at the upper and lower end portions of the translucent alumina tube, and is small at the middle portion.

On the other hand, FIG. 6 shows the properties of a translucent alumina tube sintered by a conventional manufacturing method.

As is clear from this, conventionally it is not possible to arbitrarily set the diffused (total) transmittance and radial crushing strength by changing the average particle diameter.

By the way, the object to be fired 7 passes through the lower setting section 3 and the heating furnace 1 and is taken out from the main setting section 2.

However, the object to be fired 7 may be fired as follows.

For example, the object to be fired 7 is introduced from the upper opening 8 of the main setting part 2, passes through the heating zone 17, and then
It can also be taken out from the lower opening 14.

In this case, the main setting section 2 functions as a setting zone. The lower setting section 3 functions as a take-out section.

Alternatively, the object to be fired 7 may be introduced from the lower setting part 3, passed through the heating zone 17, raised to the main setting part 2, and lowered again to the lower setting part 3 and taken out from the lower opening 14. good. In this case, the lower setting section 3 functions as a setting and removal section. Furthermore, put the object to be fired 7 from the main setting part 2 and lower it to the lower setting part 3, and then return to the main setting part 2.
You can return it and take it out.

FIG. 7 shows another embodiment of the firing device.

Above and below the heating furnace 41, there are a main setting section 42 and a lower setting section 43.
is the provision. The heating furnace 41 has insulation FIj (firebrick) 30, 31, 32. The heat insulating layer 30 is provided with a tungsten heater 30a. The heat insulating layer 31 is provided with an auxiliary heater 31a. The insulation 1132 is provided with an auxiliary heater 32a.

Further, an upper shutter 49 is provided between the heating furnace 41 and the main setting section 42. A lower shutter 45 is provided between the heating furnace 41 and the lower setting part 43.

Above the ten setting section 42, there is a moving device 40.

Further, another example of the object to be fired will be explained.

High purity alumina powder with an average particle size of 1μ or more (purity 99.9
%) 100 parts, 0.5 part of magnesium sulfate heptahydrate,
PVA (polyvinyl alcohol) as binder1
Mix the parts and make a slip. It is then dried with a spray dryer and granulated.

The granulated powder is molded into a tube-pipe shape using a rubber press at a pressure of 1 ton/Cl12.

This is ground into a predetermined shape.

This processed body is pre-fired at 1100° C. for 1 hour to scatter the PVA, thereby obtaining a fired object 37.

The object to be fired 37 is fired as shown in FIGS. 8 to 10. The heating zone 57 is maintained in a hydrogen atmosphere at 1850°C.

The object to be fired 37 is suspended from a high melting point metal jig 33. The damaged fired product 37 is within the setting zone 56 (lower setting portion 43).

The lower shutter 45 is closed and the lower setting section 43 is sealed. The atmosphere inside the lower setting section 43 is replaced with air, N2, and N2 in this order. The material to be fired is pulled up by the lifting device 40.
The lower shutter 45 is audible when raised at a travel speed of 00 ■/hour.

The object to be fired 37 is fired in the heating zone 57 . When the object 37 to be fired approaches the upper shutter 49, the shutter opens and the object 37 to be fired moves into the upper setting section 42. After that, the upper shutter 49 is closed.

Inside the upper setting section 42, the atmosphere is replaced with N2, N2, and air in this order. The object to be fired is then taken out from the take-out section 58.

The translucent alumina tube thus obtained had, for example, an average crystal grain size of 30 μm and a diffused transmittance of 95.5%.

When the radial crushing strength of this translucent alumina tube was measured, it was found to be 2.
8 kgf /n+m2 T-atsuta.

In the same manner, by changing the pulling rate of the material to be fired, fired products with various particle sizes were obtained. The measurement results are shown in Table-1.

Table 1 compares the embodiments of the present invention and the embodiments produced by the conventional method. The conventional example was fired in a batch furnace. Note that the composition of the embodiment of the present invention and the conventional example are the same.

As is clear from Table 1, the average particle size is 20 to 40 μl.
In this case, the diffused transmittance was 95% or more, and the radial crushing strength was at least 24 kof/■2. In addition, the table -
Although not shown in Figure 1, the particle dispersion is 4.0 or less. Also, in the characteristics shown in FIG. 5, the particle variation is 4.0 or less.

In the present invention, a heating furnace using a small amount of bricks is used in an N2 atmosphere. Therefore, it is possible to shorten the residence time of the material to be fired in the furnace during firing.

11 Hiimaru 1 As is clear from the above explanation, even if the average grain size of the crystals is as small as 20 to 40 μm, a diffused transmittance of 95% or more can be obtained and the strength can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a firing apparatus for producing a translucent alumina tube of the present invention, FIGS. 2 to 4 are diagrams showing the firing process of the object to be fired, and FIG. Figure 6 is a diagram showing an example of the characteristics of a conventional translucent alumina tube, and Figure 7 is a diagram showing an example of the characteristics of a conventional translucent alumina tube. Figures 8 to 10 showing another example of the apparatus are diagrams showing the firing process of the object to be fired. 1...Heating furnace 7.37...Object to be fired

Claims (1)

[Claims] A translucent alumina tube having a diffused transmittance of 95% or more, an average particle diameter of 20 to 40 μm, and a particle variation of 4.0 or less.