WO2002096564A1

WO2002096564A1 - Method and device for stabilizing length of engineering material using thermophysical characteristic of gallium

Info

Publication number: WO2002096564A1
Application number: PCT/KR2002/000954
Authority: WO
Inventors: Seung-Woo Kim; Taeho Keem
Original assignee: Korea Advanced Institute Of Science And Technology
Priority date: 2001-05-22
Filing date: 2002-05-21
Publication date: 2002-12-05
Also published as: KR20020088910A; KR100400100B1

Abstract

Disclosed are a device and a method for making an experiment on temperature characteristic of material. The device includes a small volume thermostat for maintaining temperature uniformly and an interferometer for measuring a length change according to a temperature change of a measured fragment. Material, which maintains inside temperature of the thermostat uniformly, is disposed around the thermostat. The material maintains temperature uniformly for a long time when phase is changed. A hole is formed in a front surface of the thermostat to allow beam to be transmitted, thereby measuring the length change of the measured fragment inside the thermostat. By measuring the length change in a noncontact way when beam is transmitted through the hole, the temperature characteristic of the material is tested according to temperature.

Description

METHOD AND DEVICE FOR STABILIZING LENGTH OF

ENGINEERING MATERIAL USING THERMOPHYSICAL

CHARACTERISTIC OF GALLIUM

Technical Field

The present invention relates to a device and a method for stabilizing length of engineering material using therrnophysical characteristic of gallium. The device includes a small volume thermostat for maintaining temperature uniformly and an interferometer for measuring a length change according to a temperature change of a test sample(measured fragment). Material, which maintains inside temperature of the thermostat uniformly, is disposed around the thermostat. The material maintains temperature uniformly for a long time when phase is changed. A hole for allowing transmission of beam is formed in the front surface of the thermostat to measure the length change of the test sample inside the thermostat. When beam is transmitted through the hole, the length change of the test sample is measured in a noncontact way.

Background Art

In general, in a laboratory or a research institute requiring precise measurement, a method for stabilizing a length change of engineering material by maintaining room temperature using an electronic thermostat or the likes has been used. However, such a method requires lots of expenses for installing and maintaining the laboratory. Moreover, the method is greatly influenced by temperature change due to movement of people inside the laboratory or the research institute and opening and shutting of an entrance, and temperature change due to operation of experimental apparatuses. Additionally, it is very difficult to maintain temperature of the thermostat constantly in spite of the temperature change, and lots of costs are needed to maintain uniform temperature of the thermostat. Furthermore, the thermostat must be maintained at uniform temperature even in case of a simple constant temperature experiment requiring small-scale constant temperature. However, also in this case, it is very difficult to maintain constant temperature, and a constant temperature effect is deteriorated.

Disclosure of Invention

Accordingly, it is an object of the present invention to provide a thermostat structure capable of easily maintaining temperature of a thermostat.

It is another object of the present invention to provide a thermostat structure capable of checking a length change according to a temperature change after desired material is put in the small-sized thermostat.

To realize reliability and convenience in research and experiment, the desired material is put into the small-sized thermostat without directly exposing the material to the air, so that a length of the material can be stabilized during the experiment without any influence by a temperature change of the outside, and that laboratories and researches requiring highly precise measurement according to the temperature change can easily possess the small-sized thermostat at a low price.

Brief Description of the Drawings

FIG. 1 is a graph showing a phase change of gallium from a solid phase to a liquid phase in relation with temperature.

FIG. 2 is a graph showing a phase change of gallium from the liquid phase to the solid phase in relation with temperature.

FIG. 3 is a sectional view of a device according to the present invention.

FIG. 3 a is a front view of a simplified differential plane mirror interferometer for measuring a length change in the present invention.

FIG. 4 is a graph for changing the outdoor temperature to 0.5°C.

FIG. 5 is a graph of a temperature change of gallium in connection with the change of outdoor temperature to 0. 5°C.

FIG. 6 is a graph of a length change of alumina in connection with the change of outdoor temperature.

Best Mode for Carrying Out the Invention

The present invention relates to manufacture and maintenance of a small- sized thermostat for observing a length change in connection with temperature of material. Material, in which there occurs little temperature change during a phase change of the material, is arranged around the small-sized thermostat, and the phase change is controlled to be maintained in a temperature stabilizing phase for a long time. Furthermore, the present invention can measure the length of the material in a noncontact way by transmitting beam through a part of the thermostat to measure the length change of the material arranged in the thermostat.

For your understanding, characteristics of the material according to temperature will be described as follows.

All materials are changed in length according to the characteristic of the material and a change of outdoor temperature. The change of the material is obtained from the following formula.

ΔL = L x α x ΔT Formula 1

In the above formula 1 , the changed length(ΔL) of material is obtained by multiplying an original length(L), a material constant(α), and a temperature change(ΔT). Because the material constant is intrinsic characteristic of the material, low material constant is used to contribute to stabilization of length. However, even though the material of low material constant is used, the length change of the material depending on the change of outdoor temperature is caused. As the result, it is natural to reduce the temperature change(ΔT) of the outside to stabilize the length of the material.

Material capable of maintaining the uniform temperature for a long time is suitable for the material arranged around the thermostat. In the present invention, gallium is selected, but it is only a preferred embodiment and it would be appreciated that selection of other materials besides gallium is also within the scope of the present invention. Hereinafter, properties of gallium will be described in brief.

All materials have specific freezing point and melting point. So, at the freezing point or melting point of the material, the material requires energy for converting a solid phase into a liquid phase or the liquid phase into the solid phase. At this time, the material has latent heat of fusion preventing a temperature change of the material during the phase change. The latent heat of fusion is formed at temperature higher or lower than room temperature. However, gallium has the latent heat of fusion at room temperature(29.77°C), and the melting point of gallium is insensitive to an environment change, such as an atmospheric change and a humidity change so that gallium has excellent temperature stability even when being changed from the solid phase to the liquid phase. As the result, gallium can maintain uniform temperature for a long time without any exterior device. At the room temperature(29.77°C), if the outside of the thermostat is covered with gallium to seal the outside of the thermostat and temperature of gallium is maintained at temperature of 29°C ~30°C, temperature of the thermostat can be also maintained its temperature because temperature of gallium is maintained at the temperature of 29.77°C. As described above, because constant temperature can be maintained using a simple device, characteristics of the material can be studied in a phase that there is little influence by the temperature change.

Referring to FIGS. 1 and 2, melting feature and freezing feature of gallium will be described in brief.

FIG. 1 shows a graph that gallium, which has an area where the solid phase and the liquid phase coexist with each other, exists in the liquid phase when heat is continuously applied to gallium. FIG. 2 shows a graph that gallium passes a super cooling point and has an area where the solid phase and the liquid phase coexist with each other when heat is reduced in the liquid phase, and exists in the solid phase when heat is reduced more. In the graphs of FIGS. 1 and 2, it is shown that gallium maintains uniform temperature for a long time even during the phase change. In a difference between the melting phase(refer to FIG. 1) and the freezing phase(refer to FIG. 2), gallium has a difference of whether the super cooling point exists or not. However, because gallium can maintain constant temperature of a level requiring in the industrial world, the skilled in the relevant art can use gallium of a desired phase(freezing phase or melting phase). Hereinafter, a device for maintaining temperature of the thermostat using gallium and an embodiment for testing the length change according to the temperature change using the thermostat will be described.

FIG. 3 shows a sectional view of the thermostat of the present invention and the device for making experiment on the length change according to the temperature change using the thermostat.

First, a structure of the thermostat and a control method for maintaining constant temperature will be described. The thermostat of the present invention is manufactured for making experiment on the length change according to the temperature change of a cylindrical alumina 200 and surrounds the cylindrical alumina 200.

The thermostat includes a copper chamber 10, which has a larger outer diameter than a test sample, a temperature sensor 50, and a heating plate 40.

Hereinafter, a process for maintaining constant temperature will be described.

First, gallium of the liquid phase is injected through a gallium inlet 11, and temperature of the whole thermostat is lowered until gallium is changed into the solid phase. After that, when heat is applied from the outside of the copper chamber 10 through the heating plate 40, temperature of the copper chamber 10 rises, and when temperature of the phase change of gallium is 29.77°C, the phase change of gallium is started. It is possible to check a phase change area by measuring temperature using the temperature sensor 50. The temperature sensed from the temperature sensor is transmitted to a central control unit 400, and the central control unit 400 checks the transmitted temperature and determines whether or not to apply voltage to the heating plate. FIG. 1 shows the graph of temperature change sensed from the temperature sensor according to heat applied through the heating plate 40. If temperature around the thermostat is less than

29°C, gallium inside the thermostat tends to return to the solid phase. It can be confirmed by checking the temperature change of the temperature sensor. At this time, if heat is applied to the heating plate again, the indoor temperature of the thermostat can maintain constant temperature without difficulty.

The process for maintaining constant temperature includes the steps of: 1. injecting gallium of liquid phase into the thermostat; 2. changing the phase of gallium to the solid phase by maintaining temperature of the whole thermostat less than 28°C;

3. sensing indoor temperature of the thermostat using the temperature sensor 50 while applying heat to the copper chamber through the heating plate 40;

4. checking whether or not gallium is changed from the solid phase to the liquid phase when the sensed temperature is about 29.80°C, and stopping heat supply through the heating plate; 5. supplying heat through the heating plate when temperature drop to less than 29.70°C is sensed through the temperature sensor; and

6. maintaining the temperature of the thermostat between 29.70°C and 29.80°C while repeating the steps 4 and 5.

The skilled in the relevant art can determine the form and size of the copper chamber according to the form and size of the test sample, and the form and size of the copper chamber do not restrict the scope of the present invention.

Hereinafter, a device and a process for testing the length change according to the temperature change of alumina using the thermostat will be described.

The thermostat of this test device is surrounded with gallium as described above, and the cylindrical alumina 200 to be measured in this experiment is disposed between a target mirror 30 and a reference mirror 20 inside the copper chamber 10. The temperature sensor is attached on the outer circumference of the cylindrical alumina, gallium is injected through the gallium inlet 11, and then, the heating plate 30 is installed on the outer circumference of the copper chamber 10.

In this experiment, a differential plane mirror interferometer 1 is used for measuring only a length change of the material, which stabilizes the length. In the plane mirror interferometer 1, beam emitted from a laser beam outlet 2 (refer to FIG. 3a) of through a half wave plat and a quarter wave plat passes a hole 21 and is reflected by the target mirror 30. The reflected beam is incident on the outlet 2, passes through an outlet 4 and through another hole 22, is reflected by the target mirror 30, and then enters the outlet 4. The above beam is called measuring beam. The beam emitted from a hole(refer to FIG. 3 a) of the plane mirror interferometer 1 is reflected from the surface of the reference mirror 20, incident on the hole, emitted through an outlet 5, reflected by the reference mirror 20 again, and enters an inlet 5. The beam entering the inlet 5 is called reference beam. In the above process, holes 21 and 22 located in the reference mirror are located diagonally to each other. The detailed description of the plane mirror interferometer is omitted as being well-known technique and device.

An initial value of each material used at an initial step in this test is as follows. The length of the measured alumina 200 was 300mm, the target mirror 30 was not restricted in its length because the thickness did hot have any influence on the alumina 200, and the total length measured in this test was 312.5mm including the thickness of the reflection mirror of 12.5mm. In the above process, the length of the alumina 200 measured by the reflection mirror 20 can be influenced according to the temperature change, but it can be ignored because the percentage of the reflection mirror to the changed amount of the alumina was 0.073%, in which the changed mount of the reflection mirror and the alumina corresponding to the temperature change of 1°C were 0.006125μm and 8.4μm respectively. An amount of gallium was 800g. That is, because the length measured in this experiment was the sum of the thickness of the reflection mirror and the length of the alumina, the length change of the alumina subtracting the thickness of the reflection mirror from the sum was the length change of the alumina.

Two experiments that gallium was changed from the solid phase to the liquid phase and that gallium was changed from the liquid phase to the solid phase were carried out.

The process for making experiment on the phase change of gallium from the solid phase to the liquid phase was as the follows. Gallium of the liquid phase was injected into the gallium inlet 11, and temperature was lowered to the room temperature. After that, gallium seed was inserted, and then, gallium was changed into the solid phase. After that, temperature of the copper chamber 10 was maintained at about 30 °C using the value of the temperature sensor 50 while gallium was gradually heated by the heating plate. At this time, the length of the alumina was measured while the outdoor temperature was changed by 1°C.

FIGS. 4, 5 and 6 are graphs of the above test results.

FIG. 4 is a graph of the outdoor temperature, FIG. 5 is a graph of temperature of the alumina, which is material to be measured, and the temperature change of the alumina is the same as gallium. FIG. 6 is a graph of the length change of the alumina at the same time point in the above two graphs. For measured time, a sampling of one area from an area measured for two hours was taken. The outdoor temperature change of FIG. 4 was 0.6°C as being changed from 25.4°C to 24. °C, and at this time, the temperature change of the alumina inside the copper chamber in FIG. 5 was within 1/1000°C as being 29.769°C to 29.770°C. In FIG. 6, the length change of the alumina to the above temperature change was within 0.030μm as being 5.435μm to 5.465μm. As the experiment result, in consideration of that the length change to the temperature change of 0.6°C in connection with the alumina of the length of 300mm was 1.512μm, the length change of the alumina was 0.030μm. As the result, the length change to the temperature change can be stabilized within about 2%, and so, the present invention could increase reliability in stabilization of the length change.

Claims

What Is Claimed Is;

1. A device for stabilizing length of engineering material using fhermophysical characteristic of gallium, the device comprising: a thermostat for maintaining temperature uniformly; and an interferometer for measuring a length change of a test sample according to a temperature change, wherein the thermostat is surrounded with a predetermined material, and includes: a heating plate(40) disposed to apply heat to the material; a temperature sensor(50) for measuring temperature of the material; and a central control unit(400) for determining whether or not the temperature sensed by the temperature sensor is less than a predetermined temperature and giving order to supply power source to the heating plate.

2. The device according to claim 1, wherein the material surrounding the thermostat is material capable of maintaining uniform temperature during a phase change of the material.

3. The device according to claim 1 or 2, wherein the material surrounding the thermostat is gallium.

4. The device according to claim 1, wherein the interferometer for measuring the length change of the test sample includes: a target mirror(30) disposed at a side of the test sample located inside the thermostat; a reference mirror(20) disposed at the other side of the test sample: and a transparent window formed in front of the thermostat for making laser enter, the laser, which enters through the transparent window, being reflected by the reference mirror and the target mirror respectively, and acquiring the reflected beam and detecting the length change of the test sample.

5. A method for stabilizing length of engineering material using thermophysical characteristic of gallium, the method carrying out the experiment using a device, which includes a thermostat surrounded with a predetermined material at the outer circumference, a heating plate(40) for applying heat to the material, a temperature sensor(50) for measuring temperature of the material, an interferometer for measuring a length change of a test sample inside the thermostat, and a central control unit(400), the method comprising the steps of: sensing temperature of the material surrounding the outside of the thermostat; comparing and determining whether or not the sensed temperature is less than a predetermined temperature; applying heat to the material surrounding the thermostat by supplying voltage to the heating plate if the sensed temperature is less than the predeteπnined temperature; and intercepting the supply of heat to the material surrounding the thermostat by intercepting voltage applied to the heating plate if the sensed temperature is more than the predetermined temperature, wherein the comparing step and the voltage supplying step are performed by the central control unit.