FEATURES

• The developed equipment is meant to measure specific heat of solid materials from 10 to 300 K.
• The equipment is useful for refrigeration industry since low temperature specific heat information allows selection of proper refrigerating (low specific heat) and insulating (higher specific heat) materials.
• The equipment can be used for characterization of advanced alloys and composites meant to be used in cryogenic liquid fueled rocket propulsion engines.
• It is useful in condensed matter research where specific heat information as a function of temperature provides direct correlation with structural model identified for a material.
• Further, important physical constants like Debye temperature (θD), shape of phonon dispersion curve, etc. can be evaluated from low temperature specific heat data.
• It is useful in identifying phase transitions (magnetic, electric, elastic, order-disorder, structural, etc.) in a material as a function of temperature.

 SPECIFICATIONS

• Temperature range of operation : 10 - 300 K
• Overall system accuracy : Â±2%
• Overall system precision : Â±2%
• Sample size range : 6-9 mm diameter; 1-2 mm thickness
• Sample mass range : 500 mg - 2 g

Material characterization at cryogenic temperatures is essential to (i) obtain fundamental understanding of material behavior and (ii) qualify them for applications where sub-ambient (cryogenic) temperatures are encountered. Specific heat data of a material at cryogenic temperatures is very useful information in this regard. Researchers and technologists require this data while developing cryogenic systems. The present technology pertains to indigenous development of a automated low temperature (10 - 300 K) semi-adiabatic heat pulse calorimeter for measurement of specific heat of small solid samples (sample mass ~ 500 mg to 2 g). Complete design, fabrication, testing and performance assessment of the calorimeter has been established. This equipment is an excellent import substitute to commercial cryogenic calorimeters, which are comparatively very costly and delicate to operate and maintain.

SALIENT FEATURES

Developed calorimeter is based on absolute method of specific heat measurement. In this method, a thermally isolated specimen (having temperature T₁) is given a small and finite quantity of heat energy input (ΔQ). Specimen temperature reaches to a modified equilibrium at higher temperature (T₂). Resulting temperature increment (ΔT = T₂ - T₁) is measured using sensitive thermometry. Heat energy normalized to net temperature increment (ΔQ/ΔT) gives the specific heat of specimen at average temperature (T_avg = {T₁+T₂}/2). Sample temperature is varied from 10 to 300 K and similar heat pulse cycle at pre-defined temperature interval gives the specific heat as a function of temperature. The system has an overall accuracy of ± 2% with similar precision. It can measure small samples (mass ~ 500 mg) and calorimeter operation is fully automated. It is developed with user friendly data acquisition software, which enables the user to optimize experimental parameters as per the need. The system is easy to maintain and is excellent cost effective research equipment for universities, research institutes and research wing of industries.

APPLICATION

• The developed equipment is meant to measure specific heat of solid materials from 10 to 300 K.
• The equipment is useful for refrigeration industry since low temperature specific heat information allows selection of proper refrigerating (low specific heat) and insulating (higher specific heat) materials.
• The equipment can be used for characterization of advanced alloys and composites meant to be used in cryogenic liquid fueled rocket propulsion engines.
• It is useful in condensed matter research where specific heat information as a function of temperature provides direct correlation with structural model identified for a material.
• Further, important physical constants like Debye temperature (θD), shape of phonon dispersion curve, etc. can be evaluated from low temperature specific heat data.
• It is useful in identifying phase transitions (magnetic, electric, elastic, order-disorder, structural, etc.) in a material as a function of temperature.

DETAILED SPECIFICATIONS

• Temperature range of operation : 10 - 300 K
• Overall system accuracy : Â±2%
• Overall system precision : Â±2%
• Sample size range : 6-9 mm diameter; 1-2 mm thickness
• Sample mass range : 500 mg - 2 g
• Data collection Interval : 0.3 to 1 K
• Temperature sensor : DT-470 Silicon diode
• Sample Holder : Oxygen free high conductivity copper
• Sample Heater : Strain gauge
• Shield Heater : 25 W Manganin resistive wire
• Hardware : Standard precision instruments
• Software : Window based, LabWindows/CVI
• Communication : GPIB
• Power requirement : 220-230 VAC, 50 Hz, single phase
• System dimensions (L x W x H) : 9 feet x 3 feet x 8 feet

REQUIREMENTS

a. Infrastructure Requirements

• For fabrication of complete calorimeter probe and peripheral assemblies, access to mechanical workshop is needed. The manufacturer may have this facility (heavy duty lathe machine, metal drilling, precision welding & brazing) at his disposal. Alternatively, fabrication may be outsourced since engineering design of the probe and peripheral components has been established. Apart from this, for fine tuning small components, assembling and testing, a room (20 feet x 20 feet x 10 feet) is required that house common furniture, small lathe machine (jeweler?s lathe), electrical solder ion, multi-meter, etc. For testing the system under cryogenic conditions, access to liquid helium and liquid nitrogen as well as experience in handling these cryogenic liquids is needed.

b. Space requirements

• ~400 square meter

c. Raw Materials

• Most of the raw materials (metals, alloys, sensors and heaters) are locally available from Indian manufacturers. Few precision instruments (current source, nano voltmeters, temperature controllers, etc.) may be procured from manufacturers abroad. However, all these components are easily available.

d. Manpower requirements

• One engineering graduate/diploma (electronics)
• One engineering graduate/diploma (mechanical)
• One science graduate (B.Sc. Physics, Chemistry)
• Two technicians (turner/welder/fitter trade) (if mechanical workshop is available)