JPH0372944B2 - - Google Patents

Description

Detailed Description of the Invention Conventionally, a device that combines a differential scanning calorimeter and a thermobalance is known as a device for simultaneously measuring changes in heat capacity and thermogravimetry. Since the standard sample container must be supported, the overall volume of the sample section becomes large.
Therefore, there was a problem in that it was not possible to accurately measure changes in thermogravimetry due to the influence of changes in buoyancy and convection due to changes in temperature.

The purpose of the present invention is to eliminate such inconveniences, and to perform heat capacity measurement with higher temperature distribution ability than a differential scanning calorimeter and with high precision. The tip of the optical fiber of the AC calorimeter that guides the light for alternating current heating of the sample is placed opposite to the bottom surface of the sample placed in the heat bath, and the sample support member is fixed to one end of the beam of the thermobalance device. It is characterized by being supported by a rod that is

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along the line shown in FIG. 1.

In the figure, 1 is a thermobalance device, and the thermobalance device 1 consists of a slit plate at the fulcrum of a beam 2 that moves in conjunction with the inclination of the beam 2, and a beam angle consisting of a lamp and a photocell arranged opposite to each other through the slit plate. a change reading device 3; a solenoid 5 for driving a magnet 4 attached to one end of the beam 2;
A weighing circuit 7 that outputs a beam angle restoration signal to the solenoid 5 in response to a beam angle change detection signal from the photocell and outputs a weighing signal to the recorder 6; and a weight pan 8 attached to the other end of the beam 2. A conventionally known one was used.

Reference numeral 9 denotes an AC calorimeter, which measures thermogravimetry and has a device 11 for supplying an intermittent heat flow to a sample 10 whose heat capacity is to be measured, and a DC amplifier 12 that amplifies a signal corresponding to the temperature of the sample 10. and a lock-in amplifier 13 for amplifying a signal corresponding to an alternating current temperature change of the sample, as is known in the art.

The device 11 for supplying the intermittent heat flow to the sample includes a light source 16 comprising a lamp 15 etc. energized by a DC power source 14 and a motor 1 connected to a power source 17.
It consists of a light intermittent chopper 19 which is rotated by 8, and an optical fiber 20 which guides the intermittent light to the sample section.

The sample 10 is placed on a sample holder 21 made of a thermally conductive thin plate having a very small heat capacity compared to the sample 10, with a silver paste 22 interposed therebetween. As clearly shown in FIGS. 3 and 4, the sample holder 21 is supported by two pairs of thermocouples 24 and 25 with a small heat capacity, which are stretched over a fixing ring 23 made of ceramic or the like and serving as a sample support member. is,
The fixing ring 23 is a pair of rods, for example, an insulating tube 2.
6, 26 so as to be placed on one end of the beam 2 of the thermobalance device 1.

In this AC calorimeter, as is known, the total thickness of the sample 10 and sample holder 21 is made extremely thin compared to the wavelength of the intermittent light, and the sample 10 is attached to the sample holder 21, thermocouples 24, 25, and fixing ring 23. The sample 10 is thermally connected to the heat bath via the heat leak resistance formed in this way, and the magnitude of the heat leak resistance is such that the temperature of the sample 10 does not rise over time due to the heat wave and The value changed in response to changes in . Since selecting the thermal leakage resistance to such a value is a well-known technique for AC calorimeters, a detailed explanation will be omitted.

The optical fiber 20 is connected to the pair of insulating tubes 26, 2.
6, and its tip faced the lower surface of the sample holder 21, so that the sample holder 21 was irradiated with intermittent light from the lower surface.

The thermocouples 24 and 25 are connected to insulating tubes 26 and 2, respectively.
6 and connected to the DC amplifier 12 and lock-in amplifier 13.

In FIG. 1, 27 is an electric furnace serving as a heat bath;
8 is a temperature controller. Next, to explain its operation, the sample 10 is heated to a predetermined temperature in an electric furnace 27 controlled by a temperature controller 28, and is also heated by intermittent light emitted from a light source 16 via a chopper 19 and an optical fiber 20. Ru.

Thus, the weight of the sample 10 at that temperature is measured by the thermobalance device 1 and recorded on the recorder 6. The temperature of the sample 10 at this time is detected by the thermocouple 24, and its output is amplified by the DC amplifier 12 via the cold junction 29 and recorded on the recorder 6. Further, an AC temperature change component of the sample 10 is detected by a thermocouple 25, and its output is amplified by a lock-in amplifier 13 and recorded in a recorder 6.

The lock-in amplifier 13 includes a phototransistor 30 that is irradiated with intermittent light obtained from a chopper 19.
The output of the chipper is used as a reference signal, and only input signals with the same frequency and phase as the chopper frequency are accepted, so there is little error. Temperature changes of 1/100°C can be measured with an accuracy of 1%, and the temperature resolution is 1. It's 1 in 10,000.

Since only the sample 10 is supported by one end of the beam 2 of the thermobalance device 1, thermogravimetry measurement is less likely to be affected by the buoyancy or convection of the sample 10.

In this way, according to the present invention, a thermobalance device and an AC calorimeter are installed together, and the tip of the optical fiber of the AC calorimeter that guides light for AC-heating the sample is connected to the sample placed in the heat bath. Since the sample support member was placed opposite to the bottom surface and supported by a rod fixed to one end of the beam of the thermobalance device,
It has a higher temperature distribution resolution when measuring heat capacity than a differential scanning calorimeter, and can measure heat capacity with high precision without the baseline drift due to the temperature difference between the sample and standard sample, unlike a differential scanning calorimeter. Of course,
This has the advantage of not impairing the accuracy of the thermogravimetry of the samples simultaneously measured.

[Brief explanation of drawings]

FIG. 1 is a diagram of an apparatus according to one embodiment of the present invention, and FIG.
The figure shows a sectional view taken along the line -- in Fig. 1, Fig. 3 shows a plan view of the sample section, and Fig. 4 shows a surface survey thereof. 1...Thermobalance device, 9...AC calorimeter, 10
... sample, 16... light source, 19... tipper, 20... optical fiber, 21... sample holder, 22... silver paste, 23... fixing ring, 24, 25... fixing ring, 26... insulating tube, 27... electric furnace.

Claims (1)

[Claims] 1 Equipped with a thermobalance device and an AC calorimeter,
The tip of the optical fiber of the AC calorimeter that guides light for AC heating the sample is placed opposite to the lower surface of the sample placed in the heat bath, and the sample support member is
A device for simultaneously measuring heat capacity changes and thermogravimetric changes, characterized in that it is supported by a rod fixed to one end of a beam of a thermobalance device.