JPH0678171B2 - How to observe soot - Google Patents

Description

The present invention relates to a soot observing method for observing a soot in a reaction chamber formed by a vapor phase axis method from outside the reaction chamber.

The temperature distribution on the deposition surface of the soot formed by the vapor phase axis method is an important factor in determining the refractive index,
Therefore, in the soot manufacturing process, the temperature of the soot deposition surface inside the reaction chamber is measured by an infrared radiation thermometer, etc., and the measured value is fed back to the manufacturing conditions to control the temperature of the soot deposition surface. I am trying.

FIG. 1 shows a conventional soot temperature measuring method, in which a target rod (not shown) arranged in a reaction chamber a is raised while being rotated, and a raw material is supplied to the target rod from below by a gas burner b. Although the soot c is formed, in order to measure the temperature of the deposition surface of the soot c, an observation window portion d is opened at the bottom of the reaction chamber a to prevent the internal gas from leaking at the opening surface. A crystal plate e such as a calcium fluoride plate having a good infrared transmittance is provided, and the temperature of the soot c is measured by the infrared radiation thermometer f through the crystal plate e.

However, on the crystal plate e, oxide fine particles such as soot that could not be exhausted from the exhaust port g adhere to the crystal plate e, and the crystal plate e is fogged, so that the infrared ray transmittance is lowered, so that the temperature of the soot c is reduced. Since the measurement cannot be performed accurately, the temperature of the soot c cannot be controlled sufficiently even if a feedback mechanism is provided.

The present invention provides a receiving plate portion in the observation window portion so as not to interfere with observation from the outside, introduces gas into the receiving plate portion to flow into the room, and observes the soot from the inflow passage of the gas. Therefore, the above problem will be solved by referring to the embodiment shown in the drawing. In FIG. 2, (1) is a reaction chamber, which is supplied from the gas burner (2) as described above. The soot (3) is formed by the deposition of the vapor phase raw material.

In the figure, (4) is the soot (3) in the reaction chamber (1).
An observation window portion (4) for observing the bottom of the reaction chamber (1) is extended to an external force, and a tip end thereof is cut and opened to form a window flange (5). ), One or more partition plates (6) a, (6) b are installed, and a calcium fluoride plate (7) having a high infrared transmittance is provided at the tip of the flange (5). 6) a,
(6) b has a receiving plate portion (9) formed by forming through holes (8) a and (8) b at substantially central portions thereof.

The side walls of the window flange (5) have partition plates (6) a, (6).
b and between the partition plate (6) b and the calcium fluoride plate (7), the gas introduction holes (11) a, (11) b communicating with the gaps (10) a, (10) b, respectively. A gas G such as air, nitrogen, argon or helium can be introduced through the gas introduction holes (11) a and (11) b.

The amount of gas introduced is set to such an extent that the deposition of the vapor phase raw material is not affected.

The size of the through holes (8) a, (8) b is set to be slightly larger than the spot size of the infrared radiation thermometer (12) for measuring the temperature at the deposition surface of the soot (3). .

The number of the partition plates (6) a and (6) b is not limited to two as shown in the drawing, and may be one or three or more. The larger the number, the more through holes ( The sizes of 8) a and (8) b can be increased, and the spot size of the infrared radiation thermometer (12) can be increased accordingly.

Further, the number of partition plates (6) a, (6) b and the through holes (8)
By adjusting the size of a and (8) b and the amount of gas introduced, it is possible to prevent the outflow of gas in the reaction chamber (1) without using the calcium fluoride plate (7), It becomes possible to measure the temperature of the soot (3).

Here, the method of measuring the temperature on the deposition surface of the soot (3) will be described. While supplying the gas phase raw material from the gas burner (2), the gas introduction holes (11) a, (11) b to the inside of the window flange (5). If the gas G is introduced into, the gas G will pass through the hole (8).
a, (8) b will flow into the reaction chamber (1), so that fine particles such as soot will pass through the holes (8) a, (8).
It will adhere to the partition plate (6) a without reaching the calcium fluoride plate (7) through b, and even if it enters the through hole (8) a of the partition plate (6) a. However, it will be deposited on the lower partition plate (6) b.

The temperature of the soot (3) is measured by the thermometer (12) through the through holes (8) a and (8) b, but the gas from the through holes (8) a and (8) b is measured. Since the soot is blown out, the soot does not block the through holes (8) a and (8) b, and therefore the temperature measurement is not hindered.

Here, a more specific example will be described. The reaction chamber (1)
As a reaction ball with a diameter of 230 mm, a diameter of 50 mm at the bottom
The cylindrical window flange (5) is attached, and a calcium fluoride plate (7) with a thickness of 5 mm is attached to the lower end surface of the flange (5).
Is installed and two partition plates (6) a and (6) b are provided above the plate (7), the distance between both plates (6) a and (6) b is set to 20 mm, and the through hole ( The diameter of 8) a and (8) b is 2m when the spot size of the infrared radiation thermometer (12) is 2m.
Since it is m, it is set to 5 mm and 3 l / m from the gas introduction hole (11) a.
in nitrogen gas from the other gas introduction hole (11) b
2 l / min of nitrogen gas was introduced to keep the pressure of the window flange (5) slightly higher than that in the reaction chamber (1).

For comparison, a temperature measurement experiment of soot (3) was performed using the apparatus shown in FIG.

Soot production was carried out for 10 hours in each of the above specific examples and comparative examples, and after the soot production was completed, the calcium fluoride plate (7) was inspected for stains. In the specific examples, no soot adhesion was observed. On the other hand, in the comparative example, soot was attached and it was stained white.

Further, through these calcium fluoride plates, the temperature of a blackbody furnace at a temperature of 500 ° C. was measured, and in the case of the specific example, the thermometer showed exactly 500 ° C.
It was found that the temperature was 80 ° C and the temperature could not be measured accurately.

As described above, in the present invention, the receiving plate portion is provided in the observation window portion, the gas is introduced into the receiving plate portion to flow into the reaction chamber, and the soot is observed from the inflow passage of the gas. The deposition of fine particles, etc., does not hinder the observation of soot from outside the reaction chamber, and therefore the infrared transmittance is also measured when the temperature at the deposition surface of the soot is measured using an infrared radiation thermometer. Therefore, it is possible to accurately measure the temperature even during the soot manufacturing process for a long time.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus used in a conventional example, and FIG. 2 is a schematic view of an apparatus used in the method according to the present invention. (1) ... Reaction chamber (3) ... Soot (4) ... Observation window G ... Gas

Claims (3)

[Claims] 1. A method of observing a soot through an observation window portion provided in a reaction chamber in which a soot is to be formed by a vapor axis method, wherein the observation window portion has a plurality of plate shapes for receiving fine particles such as soot. A soot observing method, characterized in that a receiving plate portion made of a member is provided, and gas is introduced into the receiving plate portion to flow into the reaction chamber while observing the soot through the inflow path. 2. The receiving plate part is composed of one or more partition plates having through holes and a sealing plate which is located outside the partition plate and seals the observation window part, and the gas is the partition plate. The soot observing method according to claim 1, wherein the soot is introduced into the lower part of the chamber, flows into the reaction chamber from the through hole, and the soot can be observed through the through hole and the sealing plate. 3. The receiving plate portion is composed of a large number of partition plates having through holes, and gas is introduced between the partition plates and soot can be observed through the through holes. The soot observing method according to claim 1.