A STAGE-TYPE FAST SCANNING CALORIMETRY WHICH CAN BE INTEGRATED WITH OTHER STRUCTURE CHARACTERIZATION APPROACHES

Abstract

A stage-type fast scanning calorimetry which can be integrated with other structure characterization approaches is provided. It relates to the field of phase and microstructure analysis. The stage-type fast scanning calorimetry comprises a sample chamber with reflection window and transmission window, a thermal stage with heating elements and coolant channels inside for temperature controlling and a transmission hole, a temperature control system for sample chamber, a fast calorimetric system. It provides the following advantages. Firstly, the fast calorimetric system is miniaturized in a thermal stage chamber, it allows the integration of fast calorimetry and structure characterization through the reflection, transmission windows and hole. Secondly, the temperature of sample can be compensated in real time by program controlling, in order to stable the sample temperature and study some metastable state conveniently.

Description

TECHNOLOGICAL FIELD

Certain examples of the technology described herein relates to the field of phase and microstructure analysis. Specifically, it is a stage-type fast scanning calorimetry which can be integrated with other structure characterization approaches, in order to perform in-situ microstructure detection to the sample after fast heat treatment.

BACKGROUND

Metastable or transient state materials usually exhibit fantastic physical chemical properties, and many materials with excellent performance are in special metastable states. For example, we usually quench the steels to transit it from austenite to metastable martensite, in order to improve the functional performance Research on metastable materials have been one of the hotspots, it involves various field including materials science, physics, chemistry, biology, power, medicine, food, environment, etc. The simplest and most direct way to obtain metastable states is heat treatment. As a result, thermal analysis, especially fast thermal analysis has been the most effective and reliable approach to study metastable materials.

In recent years, Christoph Schick and co-workers built the first fast scanning calorimeter (FSC, Patent Number: US20100046573A1) using commercial thin film vacuum sensor (thermal conductivity gauge, TCG-3880, Xensor Integration, NL), the controlled heating and cooling rate was 1 to 10000 K/s (Kelvin per second) or even higher. Specifically, the sample is cut into nanogram to microgram and transferred onto the film sensor. By which means the thermal capacities of the sample and addenda are significantly reduced, so that the heating and cooling rate could be increased. Using this method, they successfully studied the melting-recrystallizing-remelting processes of many polymers such as poly(dimethyl phthalate), polypropylene, polyamide blends, isotactic polystyrene and so on. Under such high heating and cooling rate, some structural transition could be restrained. Fast scanning calorimetry, therefore, can be applied in studying the thermal properties of some metastable materials. And besides, we can obtain the metastable states by fast heat treatment using FSC. However, the information provided only by FSC cannot meet the requirements of research on the structures and properties of metastable materials. As a results, it is necessary to develop a technique to integrate fast thermal analysis with structure characterization approaches in order to obtain the structural information of sample under metastable states.

There are two difficulties, though, to realize the technique above: 1. The working space of most structure characterization equipment are relatively small, while the available FSC takes tube-dewar method to control the temperature of sample chamber, which is difficult to in-situ integrate with other equipment. We have to transfer the sample into other equipment if we want to perform structural characterization of the metastable sample after fast heat treatment. But the structure of the sample has probably changed after this process. 2. As the heat capacities of the sample and addenda are small for FSC, the illumination of incoming light will cause great effect to the sample temperature. Unfortunately, the available FSC controls the temperature of sample by power compensation. Which means, if the effect of light illumination to the sample temperature exceeds the limit of power compensation, FSC will lose control of the sample temperature and the sample's structure may change, as well.

SUMMARY

In order to overcome these difficulties, a stage-type fast scanning calorimetry (ST-FSC) is invented. Besides the FSC's capability, it has the following characteristics: 1. There are transmission and reflection windows on the opposite sides of the sealed sample chamber, and a thermal stage in the chamber containing heating components, pipes for coolant and a hole for light transmission inside the stage. 2. The ST-FSC can perform fast response and adjustment to the temperature change of sample. The way to control the temperature of sample is changed to fast monitoring it directly by computer program, in order to guarantee the temperature of sample at the setpoint, and prevent the effect of light illumination from structure characterization equipment. 3. The ST-FSC can meet the requirements to detect both transmission and reflection signals, therefore it can be integrated with various structure characterization equipment.

A stage-type fast scanning calorimetry is provided. In certain examples, it comprises sample chamber (100), temperature control system (400) of sample chamber and fast calorimetric system (200).

The sample chamber (100) comprises: a thermal stage (110) with heating components, pipes for coolant and transmission hole (109) inside, reflection window (107), transmission window (108), wiring terminals (101) for film sensors, signal plug (102) for film sensors, inlet (103) for coolant, outlet (104) for coolant, signal plug (105) for temperature control of the thermal stage, and atmosphere channel (106). The refection and transmission windows are on the opposite sides of the sealed sample chamber.

The reflection window (107) allows the incidence light to illuminate onto the sample and the reflected light to exit the chamber. Transmission window (108) allows the incidence light to illuminate onto the sample through the transmission hole (109), and to exit through the reflection window (107). The selection of reflection window (107) and transmission window (108)'s transparent materials are according to the application, calcium fluoride lenses, for example, are recommended to use in ultraviolet, visible and infrared optical detection, while for the detection relative to X-ray the polyimide film lenses may be a good choice.

The thermal stage (110) provides the ambient temperature for the sample. The surface of the stage is made of silver or other materials with good heat conduction, in order to keep the temperature uniformity of the surface. There are temperature sensors, heating elements and pipes for coolant (like liquid nitrogen or so) inside the thermal stage (110). The inlet (103) and outlet (104) for the coolant allow the coolant enter into the inner loop of the thermal stage. The transmission hole (109) is throughout the thermal stage, facing the reflection (107) and transmission (108) windows, so that the light can pass though the stage and illuminate onto the sample. The wiring terminals (101) for film sensors connect the signal wires of the sensors to the signal plug (102). The signal plug (105) for temperature control of the thermal stage connect to temperature control system (400) of sample chamber, in order to make the temperature of the stage under control. The atmosphere channel (106) allows the atmosphere connection inside and outside of the chamber.

The temperature control system (400) of sample chamber can heat as well as cool the thermal stage, so that the temperature of stage's surface could be hold to a very setpoint.

The fast calorimetric system (200) comprises: reference film sensor (220), film sensor for loading sample (210), fast temperature control and measurement system (300) and computer for program control and data processing (500).

The reference film sensor (220) and film sensor for loading sample (210) should include thermocouples or thermopiles and heating resistance to measure and control the temperature. In certain embodiments, the commercial thermal conductivity gauge model XEN-39391, XEN-39392, XEN-39394, XEN-39395 or so loading on the XEN-014 ceramic substrates from Xensor Integration could be used as the sensors.

The fast temperature control and measurement system (300) comprises: PID controller (310) to receive temperature signals from reference film sensor (220) and produce control signals, differential amplifier (320) to receive temperature signals from both reference sensor (220) and sample sensor (210) in order to produce control signals, and fast digital-analog converter to output and gathering signals (not marked in figures, integrated with the computer). The controller (310) provides an average power for sample sensor (210) and reference sensor (220) according to the received temperature signals. The differential amplifier (320) provides compensation power for the sample sensor (210) according to the received temperature signals of sample sensor (210) and reference sensor (220). In certain embodiments, the fast digital-analog converter has 1 digital to analog conversion interface and 8 analog to digital conversion interfaces. And different sampling rate and precision are adopted to the requirement. In certain embodiments, the sampling rate of asynchronous 1.25 MS/s and accuracy of 16 bit or above are preferred. Besides, the converter should have appropriate input and output buffer to match the sampling rate. According to the heating and cooling rates, the computer (500) write the temperature program into output buffer, and provide the signal to the setpoint interface of controller (310) after digital-analog conversion. The measuring interface of controller (310) is connected to the thermopiles of reference sensor (220). The controller (310) provides an average heating power to both reference sensor (220) and sample sensor (210) according to the signals from setpoint and measuring interfaces. In certain embodiments, the differential amplifier (320) is an integrated operational amplifier circuit of adder or subtractor, also can be a PID controller. It provides compensation power to sample sensor (210) according to the temperature signals from thermopiles of sample sensor (210) and reference sensor (220).

The certain examples described herein could perform thermal analysis at the heating and cooling rates up to 200,000 K/s. The metastable states of most samples, especially the polymers, can be captured at this scanning rates. The ST-FSC can perform in situ spectroscopic detection to obtain the microstructural information of the sample through the transmission window (107), reflection window (108) and transmission hole (109), after the metastable states are captured. Meanwhile, the temperature of sample is stable at the setpoint by millisecond-time-period program control loop, to prevent the structural transition induced by the illumination of light. The above work cannot be accomplished in other similar equipment (such as the fast scanning calorimetry described in patent US20100046573A1).

Additional features, aspects, examples and embodiments are described in more detail below.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is the block diagram of the stage-type fast scanning calorimetry, in which: 100 is the sample chamber, 107 is the reflection window located on the upper surface of sample chamber (100), 108 is the transmission window located on the lower surface of sample chamber (100), 200 is the fast calorimetric system, 210 is the film sensor for loading samples, 220 is the film sensor for reference, 300 is the fast temperature control and measurement system, 301 is the cable connected to film sensors, 400 is the temperature control system controlling the temperature of thermal stage in the sample chamber, 401 is the signal cable controlling the temperature of sample chamber, 500 is the computer (for program control and data processing, with a digital-analog converter), 501 is the signal cable between the computer (500) and the temperature control system (400), 502 is the signal cable between the computer (500) and the fast temperature control and measurement system (300).

Additionally in FIG. 1, for the case reflected light is acquired, 610 is the light source and detector of structure characterization equipment that can be integrated with ST-FSC, and 611 is the light path. For the case transmitted light is acquired, 620 is the light source of structure characterization equipment, and 621 is the light path. The light transmits from the bottom of sample through the film sensor, and illuminates on the sample. Then the transmitted light is acquired by the detector (610). It is necessary to note that the light source and detector (610), light source (620), and light paths (611) and (621) are excluded from the example described here, they are used for illustrating it only.

FIG. 2 is the profile of the ST-FSC's sample chamber from overhead, the profile position is shown in FIG. 3 with dash line. In FIG. 2, 100 is the sample chamber, 110 is the thermal stage in the sample chamber, 101 is the terminals for thin film sensors, 102 is the interfaces for thin film sensors' signals, 103 is the inlet for coolant, 104 is the outlet for coolant, 105 is the interface for signals controlling the temperature of thermal stage, 106 is the channel for the atmosphere in sample chamber, 210 is the film sensor loading the sample, 214 is the flat cable for sample sensor (210), 220 is the film sensor for reference, 224 is the flat cable for reference sensor (220), 107 is the reflection window. Note that the reflection window (107) here is located above the profile showed in FIG. 2.

FIG. 3 is the profile of the ST-FSC's sample chamber from lateral, the profile position is shown in FIG. 2 with dash line. In FIG. 3, 100 is the sample chamber, 101 is the terminals for thin film sensors, 107 is the reflection window, 108 is the transmission window, 110 is the thermal stage, 109 is the transmission hole throughout the thermal stage, 210 is the sample sensor, 214 is the flat cable for sample sensor (210).

FIG. 4 is a block diagram of the fast temperature control and measurement system (300), in which: 110 is the thermal stage, 210 is the sample sensor, 220 is the reference sensor, 310 is the PID controller, 320 is a differential amplifier, 211 is the signal wire of thermopiles in sample sensor (210), 212 is the signal wire of average power provided by PID controller (310) to applied on sample sensor (210), 213 is the signal wire of compensation power provided by the differential amplifier (320), 221 is the signal wire of thermopiles in reference sensor (220), 222 is the signal wire of average power provided by PID controller (310) to applied on reference sensor (220).

FIG. 5 is the change temperature of sample when turn on and off the Raman laser illuminated on the sample, and the following adjustment by the ST-FSC described herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The block diagram of certain embodiments described herein is shown in FIG. 1. The sample sensor (210) and reference sensor (220) are placed on the surface of thermal stage (110). The ambient temperature of the two sensors (210 and 220) is controlled by the temperature control system of sample chamber (400). Based on the ambient temperature provided by the thermal stage (110), the fast temperature control and measurement system (300) monitors and controls the temperature of the heating areas in the two film sensors (210 and 220) according to the setpoint of temperature program calculated by computer (500). And it returns relative signals to the computer (500) for further calculation and processing, including the thermodynamic information of the sample.

There are built-in measuring and heating elements in the thermal stage (110). The temperature control system of sample chamber (400) acquires the temperature of the thermal stage (110) through the interface (105), and provides heating and cooling signals, accordingly. The heating signals applies on the heating elements in thermal stage through the interface (105), while the cooling signals control the external liquid nitrogen pump or magnetic valve to import the coolant into the thermal stage through inlet (103), and drained from outlet (104) after the circulation inside the thermal stage. By this means, the temperature of thermal stage (110) can be controlled by the temperature control system (400). In addition, 106 is a channel to control the atmosphere in the sample chamber in case the atmosphere affects the sample.

Each of the film sensors (210 or 220, shown in FIG. 2) have a heating area, and there are heat resistances and thermopiles settled around the area. The temperature of the heating area can be calculated from the temperature difference of the heating area (hot junction) and ambient temperature (cold junction), and the temperature of the thermal stage's surface (generally considering, the sensors' ambient temperature is equal to the thermal stage's). The temperature and heating signals are connected to the wiring terminals (101) by the flat cables (214 and 224), and then output from interface (102).

The PID controller (310, shown in FIG. 4) provides average power for both sample and reference sensors (210 and 220) according to the setpoint of temperature program and the temperature of the heating area on the reference sensor (220), while the differential amplifier (320) provides a compensation power for sample sensor (210) according to the temperature of the heating areas on the sample and reference sensors (210 and 220), so as to maintain the equivalence of the temperature between the heating areas of the two sensors. In the processes above, the temperature on the surface of the thermal stage (110) is hold to a constant value, which means the cold junctions of the thermopiles in the sensors are constant.

As shown in FIG. 3, the reflection window (107), transmission window (108) and transmission hole (109) are directly facing the heating area of sample sensor (210). The selection of reflection window (107) and transmission window (108)'s transparent materials are according to the application, calcium fluoride lenses, for example, are recommended to use in ultraviolet, visible and infrared optical detection, while for the detection relative to X-ray the polyimide film lenses may be a good choice. Integrated with spectroscopic equipment, if it is necessary to detect the reflected light, the incident light enters through reflection window (107) and illuminates onto the sample then the reflection light could be detected through the same light path. If it is necessary to detect the transmission light, the incident light goes through the transmission windows (108) and hole (109) and illuminates onto the sample, then the transmission light exits through the reflection window (107).

According to the arrangement shown in FIG. 2 and FIG. 3, the sample chamber (100) can be designed to a size of 170 mm×108 mm×30.34 mm or even smaller. Therefore, the ST-FSC can be conveniently and effectively integrated with various microstructure characterization equipment, including optical microscopy, micro-Raman spectroscopy and X-ray scattering, etc.

In order to avoid the incident light affecting the temperature of sample, the computer (500) detects the sample temperature in real time, which can be calculated from the signals obtained by fast temperature control and measurement system (300). And meanwhile, the temperature of sample is stable at the setpoint by millisecond-time-period program control loop. An experiment was performed to verify effect of this method. A small piece of polyethylene terephthalate was taken as sample, and illuminated by a laser source with a power of 6 mW and wavelength of 785 nm. The temperature of sample was detected during turning on and off the laser source, as shown in FIG. 5. The result reveals that the fluctuation of temperature is controlled in ±0.8 K, and the adjusting time is within 0.6 s.

In addition, in order to ensure the reliability of results when the ST-FSC is integrated with microstructure characterization equipment, the following experimental scheme is suggested. First, to obtain the desired state of samples by thermal treatment of ST-FSC using a specific temperature program. Second, to quench the sample to the temperature far below the one that may induce the structural transition of the sample and hold, the cooling rate should be high enough to suppress any structural transition. Third, to characterize the samples structure by the integrated equipment.

The detailed description above is not the limitations, but only used to illustrate a certain example of this invention. Ordinary technicists in relative technical fields can also make various changes under this description. So all the equivalent technical proposals also belong to the scope of the invention.

Claims

1. A stage-type fast scanning calorimetry comprising: a sample chamber (100) with reflection window (107) and transmission window (108);a thermal stage (110) with heating elements and coolant channels inside for temperature controlling, and a transmission hole (109) through the stage;a temperature control system for sample chamber (400);a fast calorimetric system (200).

2. The stage-type fast scanning calorimetry of claim 1, in which the sample chamber comprises: thermal stage with a transmission hole (109), reflection window (107), transmission window (108), wiring terminals (101) for thin film sensors, signal plug (102) for thin film sensors, coolant inlet (103), coolant outlet (104), signal plug (105) for temperature control of the thermal stage, atmosphere channel (106). The reflection window and transmission window are located on the two opposite sides of the chamber.

3. The stage-type fast scanning calorimetry of claim 1, in which the temperature control system for sample chamber (400) can heat as well as cool the thermal stage, so that the temperature of stage's surface could be hold to a very setpoint.

4. The stage-type fast scanning calorimetry of claim 1, in which the fast calorimetric system (200) comprises: a thin film reference sensor (220), a thin film sample sensor (210), a fast temperature control and measurement system (300) and a computer for program control and data processing (500).

5. The stage-type fast scanning calorimetry of claim 2, in which the thermal stage (110) provides ambient temperature for the sample, the surface of the stage is made of silver or other materials with good heat conduction, in order to keep the temperature uniformity of the surface. The thermal stage (110) is with temperature sensors, heating elements and channels for coolant. The coolant inlet (103) and outlet (104) are used to circulate the coolant inside the stage. The transmission hole (109) is throughout the thermal stage, facing the reflection (107) and transmission (108) windows, so that the light can pass though the stage and illuminate onto the sample. The wiring terminals (101) for film sensors connect the signal wires of the sensors to the signal plug (102). The signal plug (105) for temperature control of the thermal stage connect to temperature control system (400) of sample chamber, in order to make the temperature of the stage under control. The atmosphere channel (106) allows the atmosphere connection inside and outside of the chamber.

6. The stage-type fast scanning calorimetry of claim 4, in which the thin film reference sensor (220) and sample sensor (210) should include thermocouples or thermopiles and heating resistance to measure and control the temperature.

7. The stage-type fast scanning calorimetry of claim 4, in which the fast temperature control and measurement system (300) comprises: PID controller (310) to receive temperature signals from reference film sensor (220) and produce control signals, differential amplifier (320) to receive temperature signals from both reference sensor (220) and sample sensor (210) in order to produce control signals, and fast digital-analog converter to output and gathering signals.