Thermal measuring and testing – Differential thermal analysis – Detail of electrical heating control
Reexamination Certificate
1998-11-25
2001-04-03
Bennett, G. Bradley (Department: 2859)
Thermal measuring and testing
Differential thermal analysis
Detail of electrical heating control
C374S010000, C374S029000, C374S030000, C374S039000
Reexamination Certificate
active
06210035
ABSTRACT:
BACKGROUND OR THE INVENTION
The present invention relates to a thermal analyzer for measuring a signal indicating variations in the physical or chemical nature of a sample as a function of temperature or time. More particularly, the invention relates to a novel thermal analyzer which permits the interchange of thermal analysis data arising from different heating rates of a sample and which, at the same time, allows a thermal analysis of the sample to be performed in a greatly shortened time.
Thermal analysis is a powerful means for investigating how a physical property of a material or sample varies with temperature.
Typical thermal analyzers include the differential scanning calorimeter (DSC), differential calorimeter (DTA), thermogravimetry instrument (TG), and thermomechanical analyzer (TMA). These instruments measure enthalpic balance of samples, differential temperatures (qualitative enthalpic balance), weights, and the dependence of various lengths on temperature (variations in physical or chemical properties of samples), respectively.
In thermal analysis, a physical property of a sample and temperature variations are continuously measured while heating the sample at a given rate. At this time, the dependence of the physical property of the sample on temperature can be derived from the relation between the temperature signal and the physical property signal. Various thermal analyzers for performing analysis of this kind are commercially available and used industrially for research and quality control purposes.
In the prior art thermal analysis described above, it is customary to heat a sample at a rate of 5 to 20 degrees/min. For example, if a temperature range of about 1000 degrees is scanned, it takes 1 to 3 hours to complete the scan. In view of this, the prior art analysis has disadvantage in that the time efficiency is low.
An ordinary thermal analyzer can perform a measurement operation at a heating rate of 50 to 100 degrees/sin. This shortens the measuring time. In spite of this, relatively low heating rates of 5 to 20 degrees/min are often used for the following primary reason. If a sample inducing plural reactions during scanning of the temperature is heated at a high rate, these reactions tend to overlap. The resulting data is inevitably cumbersome to analyze.
Thermal analysis is intended to investigate the dependence of a physical property of a sample on temperature. Detailed investigation of the measured signal indicating the physical property has shown that the physical property signal is observed to depend on time as well as on temperature in practice. The two main reasons for this are:
1) A detector for detecting variations in the physical property of the sample has intrinsic time constant.
2) The function of temperature is not the total amount of reactions induced in the sample but the reaction rate (i.e., the reaction ratio per unit time).
After thermal analysis of a sample is conducted at a varying heating rate, it measured data are simply taken as physical property values that are functions of temperature, and if they are compared, then results of the measurement are that the same sample shows different decomposition and reaction temperatures reflecting the time dependence effects of the physical property.
SUMMARY OF THE INVENTION
To quickly solve the problems with the prior art technique described above, the present invention provides: means for heating a sample at an experimental heating rate and producing a thermal analysis signal indicating how the physical property of the sample varies with temperature; an analyzer for analyzing variations in the thermal analysis signal by dividing the signal into plural overlapping fundamental elements; an activation energy-calculating unit for calculating activation energies corresponding to the fundamental elements analyzed by the analyzer; and a heating rate conversion and output device for estimating a thermal analysis signal that should be obtained when a measurement is made at a desired heating rate, based on the experimental heating rate and from the activation energy values obtained by the activation energy-calculating unit, and for producing the thermal analysis signal.
With the aforementioned structure, the sample is heated at an experimental heating rate. A thermal analysis signal is obtained by actual measurement. Then, a thermal analysis signal that should be obtained at a desired heating rate is estimated from the obtained thermal analysis signal and produced. In this manner, thermal analysis results are obtained under desired heating rate conditions. As a result, the measurement time is shortened. The reaction temperature can be compared among different data arising from different heating, rates.
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Adams & Wilks
Bennett G. Bradley
Seiko Instruments Inc.
Verbitsky G.
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