Power compensation differential scanning calorimeter
AssigneeTA Instruments, Inc.
InventorRobert L. Danley
Life of this patent
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Abstract
A power compensation differential scanning calorimeter that uses one absolute temperature measurement, two differential temperature measurements, a differential power measurement, and a five-term heat flow equation to measure the sample heat flow. The calorimeter is calibrated by running two sequential calibration experiments. In a preferred embodiment, the first calibration experiment uses empty sample and reference pans, and the second calibration experiment uses sapphire specimens in the sample and reference holders. In an alternate embodiment, sapphire calibration specimens are used in both the first and second calibration experiments.
Claims66
A power compensation differential scanning calorimeter comprising:
- (a) an absolute temperature detector which measures one of a sample temperature, a reference temperature, and an isothermal enclosure temperature;
- (b) a first differential temperature detector which measures one of the difference between the sample temperature and the isothermal enclosure temperature, the difference between the reference temperature and the isothermal enclosure temperature, and the difference between the sample temperature and the reference temperature;
- (c) a second differential temperature detector which measures another one of the difference between the sample temperature and the reference temperature, the difference between the sample temperature and the isothermal enclosure temperature, and the difference between the reference temperature and the isothermal enclosure temperature;
- and
- (d) meters for measuring a differential power to the sample with respect to the reference,
- wherein the power compensation calorimeter is calibrated by running a first experiment with an empty cell according to a pre-selected temperature program, and running a second experiment, with a sample calibration specimen in a sample holder and a reference calibration specimen in a reference holder, according to the same pre-selected temperature program.
A power compensation differential scanning calorimeter comprising:
- (a) an absolute temperature detector which measures one of a sample temperature, a reference temperature, and an isothermal enclosure temperature;
- (b) a first differential temperature detector which measures one of the difference between the sample temperature and the isothermal enclosure temperature, the difference between the reference temperature and the isothermal enclosure temperature, and the difference between the sample temperature and the reference temperature;
- (c) a second differential temperature detector which measures another one of the difference between the sample temperature and the reference temperature, the difference between the sample temperature and the isothermal enclosure temperature, and the difference between the reference temperature and the isothermal enclosure temperature;
- and
- (d) meters for measuring a differential power to the sample with respect to the reference,
- wherein the power compensation calorimeter is calibrated by running a first experiment with a first sample calibration specimen in a sample holder and a first reference calibration specimen in a reference holder according to a pre-selected temperature program, and running a second experiment, with a second sample calibration specimen in the sample holder and a second reference calibration specimen in the reference holder, according to the same pre- selected temperature program, wherein the first sample calibration specimen has a mass that is substantially different from the mass of the second sample calibration specimen.
A method for determining differential heat flow to a sample with respect to a reference in a power compensation differential scanning calorimeter comprising:
- (a) calibrating the calorimeter by measuring a sample thermal resistance, a sample thermal capacitance, a reference thermal resistance and a reference thermal capacitance;
- and
- (b) using a five-term heat flow equation to determine the differential heat flow to the sample with respect to the reference.
A method for determining differential heat flow to a sample with respect to a reference using a power compensation differential scanning calorimeter comprising:
- (a) calibrating the power compensation differential scanning calorimeter by measuring a sample thermal resistance, a sample thermal capacitance, a reference thermal resistance, and a reference thermal capacitance over a first range of temperatures;
- (b) placing a sample on a sample holder in the power compensation differential scanning calorimeter;
- (c) increasing the temperature of the sample over a second range of temperatures, wherein the second range of temperatures does not exceed the first range of temperatures;
- (d) measuring differential power to the sample with respect to the reference, differential temperature between the sample holder and a reference holder, differential temperature between the sample holder and an isothermal enclosure, and a sample temperature;
- and
- (e) determining the differential heat flow to the sample with respect to the reference using a five-term heat flow equation as follows:
- q = Δ p + Δ T o · ( R r - R s R r · R s ) - Δ T R r + ( C r - C s ) · ⅆ T s d τ - C r · ⅆ Δ T d τ
- at temperatures within the second range of temperatures.
A method for measuring the differential heat flow to a sample with respect to a reference using a power compensation differential scanning calorimeter comprising:
- (a) calibrating the calorimeter by measuring a sample thermal resistance, a sample thermal capacitance, a reference thermal resistance, and a reference thermal capacitance;
- (b) measuring individually a power supplied to a sample holder, a power supplied to a reference holder, an isothermal enclosure temperature, a sample holder temperature, and a reference holder temperature;
- and
- (c) calculating the differential heat flow to the sample with respect to the reference using a six-term equation as follows:
- q = p s - p r + T o - T s R s - T o - T r R r - C s · ⅆ T s d τ + C r · ⅆ T r d τ .
A power compensation differential scanning calorimeter comprising:
- (a) an isothermal enclosure;
- (b) a sample holder installed in the isothermal enclosure and supported by a sample thermal resistor having a small cross-sectional area in the direction normal to the heat flow to the sample holder, wherein the sample holder has a sample temperature detector and a sample heating element, and is adapted to receive a sample;
- (c) a reference holder installed in the isothermal enclosure and supported by a reference thermal resistor having a small cross-sectional area in the direction normal to the heat flow to the reference holder, wherein the reference holder has a reference temperature detector and a reference heating element, and is adapted to at receive a reference;
- and
- (d) an isothermal enclosure temperature detector for measuring the isothermal temperature.
A method for calibrating a power compensation differential scanning calorimeter having an isothermal enclosure containing a sample holder holding a sample and a reference holder holding a reference, the method comprising the steps of:
- (a) running a first experiment with the differential scanning calorimeter empty, using a thermal program comprising a first isothermal segment, a second constant heating rate segment, and a third isothermal segment;
- (b) running a second experiment with specimens loaded in the sample holder and the reference holder, using the thermal program of the first experiment;
- and
- (c) calculating a sample thermal capacitance, a reference thermal capacitance, a sample thermal resistance, and a reference thermal resistances,
- wherein the differential scanning calorimeter is calibrated by calculating the sample thermal capacitance, the reference thermal capacitance, the sample thermal resistance, and the reference thermal resistance.
A method for calibrating a power compensation differential scanning calorimeter having an isothermal enclosure containing a sample holder holding a sample and a reference holder holding a reference, the method comprising the steps of:
- (a) running a first experiment with a first sample specimen in the sample holder and a first reference specimen in the reference holder, using a thermal program comprising a first isothermal segment, a second constant heating rate segment, and a third isothermal segment;
- (b) running a second experiment with a second sample specimen in the sample holder and a second reference sample in the reference holder, using the thermal program of the first experiment;
- and
- (c) calculating a sample thermal capacitance, a reference thermal capacitance, a sample thermal resistance, and a reference thermal resistance.
A power compensation differential scanning calorimeter comprising:
- (a) an isothermal enclosure;
- (b) a sample holder contained in the isothermal enclosure, the sample holder holding a sample;
- (c) a reference holder contained in the isothermal enclosure, the reference holder holding a reference;
- (d) temperature detectors for measuring an isothermal enclosure temperature, a sample holder temperature, and a reference holder temperature;
- and
- (e) power meters for measuring individually a power supplied to the sample holder and a power supplied to the reference holder,
- wherein differential heat flow to the sample with respect to the reference is calculated using a six-term equation as follows:
- q = p s - p r + T o - T s R s - T o - T r R r - C s · ⅆ T s d τ + C r · ⅆ T r d τ .
Dependencies are inferred from the claim text.