Method and apparatus for measuring thermal diffusivity by ac joule-heating
First Claim
1. A method for measuring the thermal diffusivity in the thickness direction of a thin sample plate of relatively non-conductive material which comprises the steps of:
- forming a conductive thin layer on at least one surface of said thin sample plate to allow the thin layer to function as an ac heater generating joule heat;
applying an ac current modulated with a given modulation frequency to the ac heater so as to produce ac joule-heating;
generating an oscillation response corresponding to said ac joule-heating on the opposite surface of the ac heater; and
measuring the phase shift between said oscillation response and the ac joule-heating, thereby obtaining the thermal diffusivity in the thickness direction of said sample plate.
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Abstract
Disclosed is a method for measuring the thermal diffusivity in the thickness direction of a thin sample plate, which has the steps of forming a conductive thin layer on at least one surface of said thin sample plate to allow the thin film to function as an ac heater generating joule heat, applying an ac current modulated with a given modulation frequency to the ac heater (conductive thin layer) so as to produce ac joule-heating, generating an oscillation response corresponding to said ac joule-heating on the opposite surface of the ac heater, and measuring the phase shift between said oscillation response, and the ac joule-heating, thereby obtaining the thermal diffusivity in the thickness direction of said sample plate. Apparatus useful for the method are also disclosed.
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Citations
32 Claims
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1. A method for measuring the thermal diffusivity in the thickness direction of a thin sample plate of relatively non-conductive material which comprises the steps of:
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forming a conductive thin layer on at least one surface of said thin sample plate to allow the thin layer to function as an ac heater generating joule heat; applying an ac current modulated with a given modulation frequency to the ac heater so as to produce ac joule-heating; generating an oscillation response corresponding to said ac joule-heating on the opposite surface of the ac heater; and measuring the phase shift between said oscillation response and the ac joule-heating, thereby obtaining the thermal diffusivity in the thickness direction of said sample plate. - View Dependent Claims (2, 3, 4, 5, 6, 11, 13, 18, 19, 20, 21, 23, 24, 25, 26, 27, 29, 30, 31, 32)
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7. A method for measuring thermal conductivity of a thin sample plate comprising measuring the thermal diffusivity of the sample plate according to the method described in claim 7 and obtaining thermal conductivity using a specific heat and density of said sample plate.
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8. An apparatus for measuring thermal diffusivity in the thickness direction of a thin sample plate provided with conductive thin layers on both surfaces which comprises:
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an ac current generation means for applying an ac current with a given amplitude of modulation to one of the conductive thin layers; a dc current supplying means for applying a given dc current to the other conductive thin film which is temperature dependent; and a lock-in amplifier for amplifying a voltage which varies in accordance with changes in resistance of said temperature dependent conductive thin layer. - View Dependent Claims (9, 10)
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- 12. The method for measuring thermal diffusivity according to claim 12 wherein the sample plate is a plate fabricated from a relatively non-conductive material selected from high molecular compounds (polymers), organic dyestuffs, mineral ores, glasses and ceramics.
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16. An apparatus for measuring thermal diffusivity in the thickness direction of a thin sample plate, on one surface of which is formed a conductive thin layer functioning as an ac heater and an opposite surface of which serves as a measurement surface, which comprises:
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an ac current generation means for applying an ac current with a given amplitude of modulation to the conductive thin layer; a cell having a sound signal detector in an interior thereof which outputs output signals, said cell having inner walls and being capable of incorporating the sample plate in such a way that the measurement surface of said sample plate comprises a part of the inner walls of the cell; and a lock-in amplifier for amplifying the output signals of said sound signal detector. - View Dependent Claims (17)
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Specification