Differential scanning calorimeter

Abstract

A differential scanning calorimeter (DSC) includes a chamber including a platform having at least a first reference material base and a first sample material base. The first calorimetric probe is configured to determine at least one thermochemical reaction of a first material in the first reference mount, and the second calorimetric probe is configured to determine at least one thermochemical reaction of a second material in the second reference mount. A rapid cooling system is at least partially disposed in the chamber. A controller is controllably coupled to at least the rapid heating system and the rapid cooling system. The controller is configured to rapidly heat the chamber and to record at least one thermochemical reaction of the second material as the second material drops in temperature.

Description

TECHNICAL FIELD

[0001] The present invention relates to a differential scanning calorimeter (DSC) tool, and more particularly, to a DSC tool including an enhanced cooling system. BACKGROUND

[0002] Differential scanning calorimetry is a thermal analysis technique in which the difference in heat required to raise the temperature of a sample and a reference is measured as a function of temperature. Throughout the experiment, both the sample and the reference are kept at nearly the same temperature. The key parameters of a conventional experiment are the heating rate (in °C / min) and the final temperature. Typically, the temperature program for a differential scanning calorimetry analysis is designed such that the sample holder temperature increases linearly as a function of time (i.e., constant heating rate). DSC spectra are measured for different heating rates, and the progression of DSC spectral features as a function of heating rate provides information about the thermal chemical reactions in the sample. The reference sample should have a well-defined heat capacity over the temperature range to be scanned. In addition, the reference sample should be stable, high purity, and cannot change too much during the temperature scan. Typically, the reference standards are metals such as indium, tin, bismuth, and lead, but other standards such as polyethylene and fatty acids have also been proposed to study polymers and organic compounds, respectively.

[0003] A differential scanning calorimeter (DSC) is a tool used to perform differential scanning calorimetry experiments. Existing DSCs are constructed using hardware components capable of heating a material at various rates and sensors that measure the heat power required to reach predefined temperatures (following a heating protocol). Changes in heat power at different temperatures (i.e., peaks in the DSC spectrum) are typically related to individual thermal chemical reactions that can have different time scales and exo / endo thermal effects. It is often unclear whether each DSC peak corresponds to one or multiple overlapping thermal chemical reactions. To resolve the DSC spectrum, in addition to conventional heating, fast cooling is needed, and the faster the cooling rate applied, the higher the resolution of the DSC spectrum that can be achieved. However, current DSCs are not configured to provide active cooling at a rate fast enough to perform cooling experiments. The maximum cooling rate achievable by conventional systems is about 80 °C / min.

[0004] Accordingly, it would be desirable to provide a DSC including the capability to perform controlled and fast heating as well as faster cooling operations. SUMMARY

[0005] In an example embodiment, a differential scanning calorimeter (DSC) includes a chamber including a platform having at least a first reference material pedestal and a first sample material pedestal. A first calorimetric probe is configured to determine at least one thermochemical reaction of a first material in the first reference pedestal, and a second calorimetric probe is configured to determine at least one thermochemical reaction of a second material in the second reference pedestal. A rapid cooling system is disposed at least partially in the chamber. A controller is controllably coupled to at least the rapid heating system and the rapid cooling system. The controller is configured to rapidly heat the chamber and record the at least one thermochemical reaction of the second material as the second material temperature decreases.

[0006] In addition to one or more of the features described herein, the rapid cooling system includes a fluid chiller disposed directly below and in thermal communication with the platform.

[0007] In addition to one or more of the features described herein, the fluid chiller contains a water-based coolant, and wherein the water-based coolant has less than 20% water.

[0008] In addition to one or more of the features described herein, the water-based coolant is a combination of water and ethylene glycol.

[0009] In addition to one or more of the features described herein, the water-based coolant is between 80% and 90% of a non-water coolant, and wherein the non-water coolant is one of ethylene glycol and propylene glycol.

[0010] In addition to one or more of the features described herein, the controller is configured to pulse a cooling fluid through the fluid chiller during the rapid cooling process.

[0011] In addition to one or more of the features described herein, the rapid cooling system includes a semiconductor chiller and a convection air chiller.

[0012] In addition to one or more of the features described herein, the semiconductor chiller includes a thermoelectric cooler disposed immediately adjacent to and in thermal communication with the platform, the semiconductor chiller including a first surface contacting the second platform and a second surface opposite the first surface, a heat sink channel extending outward from the second surface and into a cooling air flow, and a fan configured to generate the cooling air flow.

[0013] In addition to one or more of the features described herein, the semiconductor chiller is a Peltier chiller.

[0014] In addition to one or more of the features described herein, the semiconductor chiller includes a first positive current lead and a first negative current lead, and wherein the semiconductor chiller is operational when current is applied to the first positive current lead and the first negative current lead, and wherein the fan includes a second positive current lead and a second negative current lead, and wherein the fan is turned on when current is applied to the second positive current lead and the second negative current lead, and wherein the controller includes a chiller system positive control current lead and a chiller system negative control current lead, and wherein each of the first negative current lead and the second negative current lead is connected to the chiller system negative control current lead, and each of the first positive current lead and the second positive current lead is connected to the chiller system positive control current lead.

[0015] In addition to one or more of the features described herein, the heat sink channel is a thermally conductive rod.

[0016] In addition to one or more of the features described herein, the at least one thermal chemical reaction of the second material is a heat flux.

[0017] In another example embodiment, a method for measuring at least one thermal electrical property of a first material includes placing a reference material in a reference material base of a differential scanning calorimeter (DSC) and placing the first material in a sample material base, reducing a temperature of the DSC at a rate of at least 80 °C / minute using a rapid chiller until a second target temperature is reached, and measuring a thermal chemical reaction of the sample material as the temperature of the DSC is reduced, and synthesizing the measured thermal chemical reaction of the sample material into a single output plot using a controller.

[0018] In addition to one or more of the features described herein, reducing the temperature of the DSC includes activating a semiconductor chiller and an airflow fan.

[0019] In addition to one or more of the features described herein, the semiconductor chiller and the airflow fan are operated simultaneously.

[0020] In addition to one or more of the features described herein, the chiller controller outputs a single control signal to the semiconductor chiller and the airflow fan.

[0021] In addition to one or more of the features described herein, reducing the temperature of the DSC includes pulsing a coolant through a fluid chiller using a fluid pump, and wherein the coolant is a water-based coolant having less than 20% water.

[0022] In addition to one or more of the features described herein, the water-based coolant is a combination of water and ethylene glycol.

[0023] In addition to one or more of the features described herein, the percentage of water in the water-based coolant is a minimum percentage of water that the fluid pump can pump.

[0024] In addition to one or more of the features described herein, reducing the temperature of the DSC at a rate of at least 80 °C / minute includes reducing the temperature at a rate of 160 °C / minute.

[0025] The above features and advantages of the present disclosure, and other features and advantages, will become apparent to those skilled in the art from the following detailed description, which, when taken in conjunction with the drawings, discloses various embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0026] Other features, aspects, and details will become apparent only from the following detailed description, examples of which are illustrated in the accompanying drawings and described in the claims.

[0027] Figure 1 is a schematic illustration of a differential scanning calorimeter (DSC);

[0028] Figure 2A depicts a hypothetical thermo-mechanical reaction using conventional DSC cooling;

[0029] Figure 2B depicts a hypothetical thermo-mechanical reaction using Figure 1 a controlled rapid heating and cooling system of the DSC of Figure 2A ;

[0030] Figure 3 depicts a process of the DSC of Figure 1 ;

[0031] Figure 4 depicts an exemplary embodiment of the DSC of Figure 1 ; and

[0032] Figure 5 depicts another exemplary embodiment of the DSC of Figure 1 . DETAILED DESCRIPTION

[0033] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0034] As used herein, “rapid heating” and “rapid cooling” refer to a heating or cooling process that causes a change in temperature at a rate of at least 80 °C / minute. In some examples, the rate of change can be an increase or decrease of at least 100 °C / minute. In further examples, the rate of change can include an increase or decrease of about 160 °C / minute.

[0035] According to example embodiments, methods, apparatuses, and systems are provided for implementing a controlled cooling system within a differential scanning calorimeter (DSC) tool. The controlled cooling system is configured to use a fast liquid cooling control scheme and either or both of a combination of a primary cooler and a semiconductor cooler (e.g., a Peltier device) to increase the cooling rate.

[0036] The embodiments described herein present a number of advantages and technical effects. These advantages and technical effects include the ability to rapidly cool samples at rates up to 120 °C / minute, as well as providing cooling to target temperatures, allowing for more controlled experiments. Some thermochemical reactions can become determinable during the cooling process, but not during the heating process, and thus cannot be determined in a differential scanning calorimetry experiment using existing DSCs.

[0037] Figure 1 An example DSC 10 is shown that includes a chamber 20. Within the chamber 20 are a reference material base 22 and a sample material base 24 (collectively, material bases 22, 24). Connected to each material base 22, 24 is a respective calorimetric probe 28, each of which is in communication with a controller 50 such that the calorimetric probe 28 communicates at least temperature measurements of the material in the material bases 22, 24 to the controller 50. In some examples, the calorimetric probe 28 is capable of measuring one or more additional thermochemical properties of the material in the material bases 22, 24 and communicating them to the controller 50. The material bases 22, 24 are located on a platform 26, below which is a cooling system component 30. The cooling system component 30 is interconnected with a cooling system 40, and can be an electrical cooler, a liquid cooling component, or any other cooler capable of effecting rapid cooling of the chamber 20 in which the material bases 22, 24 are located.

[0038] The controller 50 is connected to the cooling system 40 and a heating system 60. The heating system 60 can be any known heating system type, and is controlled using known control techniques by the controller 50 to raise the temperature within the chamber 20 to a target temperature. Due to the temperature in the chamber 20, the temperature of the material in the material bases 22, 24 rises or falls, and the thermochemical properties of the material can be monitored. The controller 50 also controls the cooling system 40 according to a process 200 (shown in FIG. 2) that provides for fast target cooling to a particular temperature, and provides for a controlled cooling rate.

[0039] With continued reference to the DSC 10 of Figure 1 Figure 2A ​A graph 200 is shown that illustrates the specific heat flux (mW / mg) versus temperature T (°C) for a hypothetical material as observed from a conventional DSC. The conventional DSC measures the thermo-chemical reactions of the material during a rapid heating process. After the rapid heating process, a conventional cooling process is used to cool the sample. Once cooled to a sufficiently low temperature for handling, the material is removed from the chamber 20 and the next experiment can be performed. The specific heat flux shown in graph 200 includes a first region 210 that shows a downward but changing slope of the specific heat flux. In addition, at region 220, the specific heat flux appears to be a smooth curve.

[0040] In contrast, Figure 2B A graph 250 is shown that illustrates the specific heat flux (mW / mg) versus temperature T (°C) for the same hypothetical material as measured by a DSC 10 that measures the thermo-mechanical reactions during a rapid heating process and a rapid cooling process. By monitoring the thermo-mechanical reactions during a controlled rapid cooling process as well as during a controlled rapid heating process, additional fidelity is provided for graph 250. Similar additional fidelity can be determined for any thermo-chemical reactions being measured, and the specific heat flux is exemplary in nature. Figure 1

[0041] In particular, at region 210, as graph 200 progresses to higher temperatures, Figure 2B ), what appears to be only a smooth downward slope transitions into local valleys and peaks on graph 250 when measured during a rapid cooling process as well as a rapid heating process. Figure 2A

[0042] Similarly, what appears to be a smooth slope transition on region 220 transitions into a downward transition with a continuously changing slope (e.g., the downward slope change appears smooth) when measured during heating. However, when measuring rapid heating and cooling Figure 2B ), the changes in slope are not consistent (e.g., the downward slope appears "rough").

[0043] The additional resolution of the illustration provided by the controlled rapid heating and cooling shown in graph 250 of Figure 2B is exemplary and hypothetical. Figure 1 Actual use of the rapid heating and cooling of the DSC 10 of will demonstrate any number of similar additional peaks, valleys, and perturbations depending on the particular material and thermo-chemical reactions being measured. This allows for the identification and resolution of additional thermo-chemical reactions.

[0044] Figure 1 Continuing with 2A and 2B, Figure 3 A method for operating Figure 1 ​​the process 300 of the DSC 10. Initially, in a heat sample to Th step 310, the controller 50 uses the heating system 60 to rapidly increase the heat in the sample 20 to a target high temperature (Th). As the temperature of the sample 20 increases to the target temperature, the calorimetric probe 28 provides measurements to the controller 60 of the reference material (through the probe 28A) and the sample material being measured (through the probe 28B). The measurements are recorded in a first record measurements step 320.

[0045] Once the material has reached the target temperature, the controller 50 uses the cooling system 40 to rapidly decrease the temperature of the sample 20 to a low temperature target T1 in a rapidly cool sample to T1 step 330. As the temperature of the sample 20 decreases to the target low temperature, the calorimetric probe 28 provides measurements to the controller 60 of the reference material (through the probe 28A) and the sample material being measured (through the probe 28B). The measurements are recorded in a second record measurements step 340.

[0046] Once the two sets of measurements are recorded, in a combine data step 350, the outputs from the heat flow and temperature sensors are translated and converted into calibrated temperature and heat flux values at a user-defined acquisition rate (seconds). The data points are then plotted as shown in Figure 2A 、 2B and the plot 250 is output for analysis in an output plot step 360.

[0047] In the combine data step 350, the controller 50 combines and integrates the measurements into a single thermo-chemical signature plot (i.e. the plot 250) and in the output plot step 360, the plot 250 is output for analysis. Figure 2B

[0048] In addition to the extra resolution provided by the rapid cooling measurements, the use of the rapid cooling process allows for faster testing of samples, increasing the number of tests that can be performed in a shortened time period.

[0049] The DSC 10 includes a rapid cooling system or combination, including a rapid liquid cooling system and / or a combination of air cooling and semiconductor cooler cooling systems. Figure 4 An example DSC 410 is shown, which uses a combination of air cooling via a fan 412 or compressed air and semiconductor cooling via a semiconductor-based thermoelectric cooler 414 (e.g. a Peltier device) to achieve rapid cooling. Figure 5 An example DSC 510 is shown, which uses a water-based cooling system to achieve rapid cooling. While shown separately for ease of explanation, in alternative examples, the air / thermoelectric cooling system of the DSC 410 and the water cooling system of the DSC 510 can be used together in a single implementation, achieving even faster cooling. Figure 4 Figure 5 The air / thermoelectric cooling system of the DSC 410 and the water cooling system of the DSC 510 can be used together in a single implementation, achieving even faster cooling.

[0050] Reference is now made to​​Figure 4 The DSC 410 includes a chamber 420. Within the chamber 420 are a reference material seat 422 and a sample material seat 424 (collectively, the seats 422, 424). Connected to each material seat 422, 424 is a respective calorimetric probe 428, each calorimetric probe 428 in communication with a controller 450 such that the calorimetric probe 428 communicates temperature measurements of the material in the respective material seat 422, 424 to the controller 450. The material seats 422, 424 are positioned on a platform 426, beneath which is a thermoelectric cooler 414. The thermoelectric cooler 414 is a semiconductor that includes a positive lead C and a negative lead D. When an electrical current is applied to the leads C, D and through the thermoelectric cooler 414, a first surface 416 of the thermoelectric cooler 414 approaches a freezing temperature, and a second surface 417 of the thermoelectric cooler 414 is at a counterbalancing high temperature.

[0051] The thermoelectric cooler 414 is positioned with the first surface 416 in contact with the thermally conductive plate 426, which thermally couples the thermoelectric cooler 414 to the material seats 422, 424, thereby cooling the material positioned in the material seats 422, 424. A thermally conductive heat sink channel 419 provides a thermal conduit from the hot side 417 of the thermoelectric cooler 414 to the airflow channel 470. In an example, the heat sink channel 419 is a thermally conductive rod, such as a copper rod. In other examples, any other similar thermally conductive material capable of withstanding the temperature inside the chamber 420 can also be used.

[0052] In addition to the thermoelectric cooling provided by the thermoelectric cooler 414, the DSC 410 includes a fan 412 (or a coordinated set of fans) to drive an airflow 446 through the chamber 420. The airflow 446 provides convective cooling to the material in the material seat 424. The fan 412 is controlled by applying a control current from the controller 450 to the positive terminal C and the negative terminal D. Since the thermoelectric cooler 414 and the fan 412 utilize the same control current, the controller 450 outputs a control signal to the terminals C and D, and the control signal is provided to the thermoelectric cooler 414 and the fan 412. This, in turn, causes Figure 4 both cooling devices in the cooling system of FIG. 1 to be driven simultaneously.

[0053] Reference is made to Figure 5The DSC 510 includes a chamber 520. Within the chamber 520 are a reference material seat 522 and a sample material seat 524 (collectively, material seats 522, 524). Connected to each material seat 522, 524 is a respective calorimetric probe 528, each of which is in communication with a controller 550, such that the calorimetric probe 528 communicates temperature measurements of the material in the respective material seat 522, 524 to the controller 550. The material seats 522, 524 are located on a platform 526, below which is a liquid chiller 542. The liquid chiller 542 is configured to receive a cooling liquid from a first port 543, pass the cooling liquid through the liquid chiller 542, and output the cooling liquid through a second port 545. The cooling liquid is driven along this flow path via a cooling fluid pump 546, and is stored in a fluid reservoir 547. When outside of the chamber 520, the cooling liquid is cooled and returned to the chiller loop through any known cooling system.

[0054] The platform 526 is thermally conductive, and heat from the materials in the material seats 522, 524 is transferred to the cooling fluid in the liquid chiller 542. By passing the cooling fluid in a flow, the heat is carried away.

[0055] The pump 546 is controlled by the controller 550, which utilizes a pulsed operation to move a volume of fluid into the liquid chiller 542. The fluid is allowed to remain in the liquid chiller 542, and heat is transferred to the fluid through the plate 542. The pump then pulses again, driving a new volume of cooling fluid to replace the fluid in the liquid chiller 542, and the cycle repeats, allowing for rapid and controlled cooling.

[0056] Existing liquid cooling systems typically utilize a mixture of coolant and water, with the mixture having about 50% water and 50% coolant. The ratio of water to coolant is chosen to ensure that the viscosity of the combined water and coolant is low enough that the pump 546 has no difficulty moving the fluid through the cooling system 540.

[0057] To further increase the rate of cooling provided by the liquid chiller 542, Figure 5 The cooling fluid contained in the DSC 510 is a mixture of water and ethylene or propylene glycol, with the mixture limited to between 10% and 20% water, with the specific percentage of water being the minimum percentage at which the pump 546 can drive the fluid without damaging the pump 546. This results in a more viscous fluid with a much higher heat capacity than existing systems. The higher heat capacity in turn allows more heat to be carried away with each pulse, further increasing the rate of cooling applied.

[0058] The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The term “or” means “and / or” unless clearly indicated otherwise. The reference herein to “one aspect” means that a particular element described in connection with the aspect is included in at least one aspect described herein and can or can not be present in other aspects. In addition, it should be understood that the described elements can be combined in any suitable manner in the various aspects.

[0059] When an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements can also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

[0060] Unless otherwise indicated herein, all test standards are the most recent standard in effect as of the filing date of the present application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0062] While the foregoing disclosure has been described in reference to exemplary embodiments, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from the central scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope of the disclosure.

Claims

1. A differential scanning calorimeter (DSC), comprising: A chamber containing a platform, the platform having at least a first reference material base and a first sample material base; A first calorimetric probe configured to determine at least one thermochemical reaction of a first material in a first reference material base, and a second calorimetric probe configured to determine at least one thermochemical property of a second material in a second reference material base; A rapid cooling system, which is at least partially located in the room; as well as A controller, controllably coupled to at least a rapid heating system and a rapid cooling system, the controller being configured to rapidly cool a chamber and record at least one thermochemical property of the second material as the temperature of the second material decreases.

2. The DSC according to claim 1, wherein, The rapid cooling system includes a fluid cooler located directly below the platform and in thermal communication with the platform.

3. The DSC according to claim 2, wherein, The fluid cooler contains a water-based coolant, wherein the water-based coolant contains less than 20% water.

4. The DSC according to claim 3, wherein, The water-based coolant is a combination of water and ethylene glycol.

5. The DSC according to claim 4, wherein, The water-based coolant is between 80% and 90% non-water coolant, and the non-water coolant is one of ethylene glycol and propylene glycol.

6. The DSC according to claim 1, wherein, The rapid cooling system includes a semiconductor cooler and a convection air cooler.

7. The DSC according to claim 6, wherein, The semiconductor cooler includes a thermoelectric cooler disposed adjacent to the platform and in thermal communication with the platform; The semiconductor cooler includes a first surface of a contact platform and a second surface opposite to the first surface; The hot channel extends outward from the second surface and enters the cooling airflow; and A fan, configured to generate a cooling airflow.

8. The DSC according to claim 7, wherein, The semiconductor cooler is a Peltier cooler, and the heat sink channel is a heat-conducting rod.

9. The DSC according to claim 7, wherein, The semiconductor cooler includes a first positive current lead and a first negative current lead, and wherein the semiconductor cooler is operated when current is applied to the first positive current lead and the first negative current lead, and wherein the fan includes a second positive current lead and a second negative current lead, and wherein the fan is turned on when current is applied to the second positive current lead and the second negative current lead, and wherein the controller includes a cooling system positive control current lead and a cooling system negative control current lead, and wherein each of the first negative current lead and the second negative current lead is connected to the cooling system negative control current lead, and each of the first positive current lead and the second positive current lead is connected to the cooling system positive control current lead.

10. The DSC according to claim 1, wherein, At least one thermochemical reaction of the second material is specific heat flux.

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