JPS6034202B2 - High frequency power absorption element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new type of high frequency power absorption element (or power concentration heating element, hereinafter the same).

In microwave circuits, there are many opportunities to use high-frequency power absorption elements as non-reflection terminators, pseudo loads, or attenuation elements.

In this case, if the power to be absorbed is small, a metal film resistor is used, but as the power increases, carbon, ferrite, etc. are used to increase the withstand power. In the microwave band, as the frequency increases, the cross-sectional dimensions of the waveguide and coaxial tube that serve as the transmission path become smaller, so if the absorbed power increases, it is inevitable that materials with higher power resistance within a unit volume will be used. will have to use. Therefore, such a material has a large loss at high frequencies,
It is desirable to have a material that can withstand high temperatures, has good thermal conductivity, and has high mechanical strength. FIG. 1 shows an example of a waveguide-type pseudo load, in which a metal lachet 2 for heat radiation is installed on the outside of a waveguide 1, and is attached to a transmission circuit by a flange 3.

Inside the waveguide 1, a bifurcated force absorbing element 4 as shown in FIG. 2 is firmly attached to the tube wall with a high-temperature adhesive having good thermal conductivity. As such a power absorption element 4,
When ferrite is used, its ability as a high frequency power absorbing element is extremely reduced at temperatures of around 200° C. or higher, making it unusable.

In the case of carbon, oxidative combustion occurs when heated to high temperatures in an oxidizing atmosphere. In addition, a molded product made by mixing an appropriate amount of carbon powder and cement, which is commonly used, has a diameter of 200 oo
It becomes extremely mechanically brittle. In view of the above, it is an object of the present invention to provide a new type of high-frequency power absorption element that can be used stably up to about 1500 qC even at high power and in an oxidizing atmosphere, and has good thermal shock resistance and thermal conductivity against sudden load changes. purpose.

That is, silicon carbide powder (Q-SIC) with a particle size of about 24 to 3000 mesh is treated with a single particle size or mixed with various particle sizes, and with respect to 100 parts by weight of this powder, the general formula R'20
・Oxide and Si represented by R′○・R′''203
One or more substances selected from each group of 02 (
1200 by adding 3 to 30 parts by weight (approximately 3 to 23 weight % in terms of weight %) of vitreous or ceramic) as a binder.
This is a high frequency power absorbing element using a ceramic composition fired at a temperature of ~150,000 as a power absorber. Here, R' is Na, K, Li, R'' is Ca, Mg, Europe, Sr.
, R river represents a member selected from each element of AI and Cr. In addition, to improve the oxidation prevention of silicon carbide at high temperatures, heavy metal oxides such as cobalt oxide, manganese oxide, steel oxide, and lead oxide, or heavy metal powders such as copper, manganese, nickel, and cobalt are added to the additive amount of the above binder. It was also effective to add a small amount in the range of .5 to 10% by weight.

In addition, if it is necessary to strengthen the bonding strength of the ceramic composition, silicon oxide (Si02) in the binder may be used.
Phosphorus oxide (P2Q) or chlorine oxide (&0
3) can also be used.

The above ceramic composition can be used as a power absorption element for high power and
It was confirmed through physical property tests that it can be used stably up to about 1500 oo even in an oxidizing atmosphere, and has extremely good thermal shock resistance and thermal conductivity against sudden load changes. Therefore, if this material is installed in the waveguide 1 as shown in FIG. 1 as an element 4 having a shape as shown in FIG. 2, a good high-power pseudo load can be obtained. Furthermore, by attaching a large number of strip-shaped thin pieces to the waveguide wall and cooling them appropriately, it is possible to manufacture a high-power attenuator. It is also used as a high-frequency power absorption element in coaxial tubes, high-frequency heating furnaces, etc. Furthermore, in a microwave heating furnace such as a microwave oven, heat is generated essentially from within the object to be heated, so that the object to be heated does not usually have a focal point.

Therefore, depending on the object, it is necessary to focus in some way, and for this purpose, ferrite silk, lattice, plate shape, etc. are used as pyrostatic spontaneous heating elements (heating elements), but as mentioned above, ferrite Since the ceramic composition of the present invention has poor heat resistance, it is better to use the ceramic composition according to the present invention. In this case, since the ceramic composition according to the present invention has a large dielectric constant, the microwave power is concentrated, and a good focus can be created on the part of the object to be heated that comes into contact with the microwave power. Furthermore, it is extremely effective because it can withstand higher temperatures than ferrite and is mechanically robust. The reason for limiting the binder to 3 to 3 parts by weight in the above is that if the binder is less than 3 parts by weight, the mechanical strength of the product will be weakened, and if it is more than 3 parts by weight, the silicon carbide content will increase. This is because the function as a high-frequency power absorbing element is lowered, and the electrical performance is deteriorated.

In addition, heavy metal powder mixed in as an antioxidant for silicon carbide at high temperatures will not be effective in preventing oxidation if it is less than 0.5% by weight of the binder, and if it is more than 1% by weight, it will lower the melting point of the binder. This weakens the oxidation prevention effect and deteriorates the high-temperature characteristics of the high-frequency power absorption element.

The reason why the suitable firing temperature is set in the range of 1200 to 1500o0 is that if the temperature is less than 1200o0, the mechanical strength of the fired product will be weak, and if it is more than 150000000, the oxidation of silicon carbide will become intense and Si02 will be generated. This is because the electrical performance as a high frequency power absorption element deteriorates.

In the composition table of Example Table 1, a ceramic composition obtained by firing the mixed powder of composition A at about 1400 ° C. was installed as a high frequency power absorption element in a WRJ-2 rectangular waveguide with a length of 500 ribs. When a high power waveguide type pseudo load is a forced air cooling type and a high power of 5 volts is applied, the output voltage is 1.7 to 2.6
VSWR (voltage standing wave ratio,
Volta bagSondingWaveRatio)1.
Good results were obtained in Sajinai.

In addition, Table 1 shows the high frequency power absorbing element in the above pseudo load.
When other ceramic compositions of compositions B to G (composition temperature of about 1400 qo) are installed and used, in each case, VS is the same as when using the ceramic composition of composition A above.
WRI. A good score of 2 or less was obtained. The main powder SIC used in each composition in Table 1 was a mixture of about 6% by weight of particles with a particle size of about 150 microns or more and about 4% by weight of fine particles with a particle size of about 60 microns or less. It is.

When an appropriate amount of fine particles are mixed, the voids within the flesh of the fired ceramic composition are filled, thereby improving various properties. The appropriate amount varies depending on the type of binder used and the blending ratio, so it is determined through preliminary tests. When the high temperature characteristics of the device are important, as mentioned above, the amount of binder powder mixed with heavy metal oxide or heavy metal powder as an antioxidant may be 0.5 to 1.
It is effective to prevent oxidation at high temperatures by adding % by weight of oxidation inhibitors (Co oxide, Mn oxide, ) is added only in small quantities.

Table 1 Composition table (weight scale) Also, for all the elements of the above compositions A to G, the blending ratio of the binder powder to the main powder 10 parts by weight is 9.9 to 15 parts within the range of 3 to 30 parts by weight specified in the present invention. Therefore, the mechanical strength was sufficient for practical use.

As mentioned above, if the blending ratio of the binder is less than 3 parts by weight, the mechanical strength of the device will be significantly insufficient. Furthermore, if the proportion is too large, exceeding 3 parts by weight, the electrical performance will deteriorate. When the elements are loaded in the waveguide in an appropriate shape, the ratio of elements with compositions A, C, and D is within the range of 1 to 5, and the VSWR is 1 over the entire frequency band used by the waveguide. I was able to keep it within .2.

In the case of elements with compositions B and E, the electrical performance is slightly degraded, and the frequency band is VSWRI. It was within 2.
In the case of an element with composition F/G, VSWRI.
It was in the sand.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional plan view of an example of a waveguide type pseudo load, and FIG. 2 is a perspective view of an example of a power absorber element for the pseudo load installed in the waveguide. 1 is a rectangular waveguide, 2 is a heat dissipation radiator, 3 is a mounting flange, and 4 is a high frequency power absorption element. Figure l *Figure Z

Claims (1)

[Scope of Claims] 1 Mainly composed of silicon carbide powder with a single particle size or a particle size combination, and based on 100 parts by weight of this powder, the following general formula (a
), (b), (c) and SiO_2
12. A mixed powder obtained by adding 3 to 30 parts by weight of one or more substances selected from each group as a binder.
A high frequency power absorption element using a ceramic composition fired at a temperature of 00 to 1500°C as a power absorber. (a) R′_2O, (b) R″O, (c) R′″_2O
_3 However, R' is Na, K, Li, R'' is Ca, M
g, Ba, Sr, and R'' represent a member selected from each element of Al and Cr. Formula (a)
・Add 3 to 30 parts by weight of one or more substances selected from the groups of oxides and SiO_2 represented by (b) and (c) as a binder, and further add heavy metal oxides or heavy metals to this. A mixed powder obtained by adding powder of 0.5 to 10% by weight of the amount of the binder added is
A high frequency power absorption element using a ceramic composition fired at a temperature of 0.000C as a power absorption body. (a) R′_2O, (b) R″O, (c) R′″_2O
_3 However, R' is Na, K, Li, R'' is Ca, M
g, Ba, Sr, and R''' represent members selected from each element of Al and Cr.