Applicability of Infrared Thermography for the Detection of Phase Transitions in Metal Alloys

This work aims at assessing the applicability of a screening-oriented device dedicated to the establishment of increasingly complex phase diagrams of phase change materials. A thermography-based method has recently been proven to allow the detection of phase transitions of organic materials for multiple samples at a time. The phase transition detection capability of the infrared thermography method is here evaluated for metal systems based on well-referenced materials commonly employed in DSC calibration (pure sample of Gallium and a mixture of Gallium and Indium). The detected transitions are compared to literature data and DSC measurements. All transitions documented in the literature could be retrieved by thermography, and liquidus transitions are validated with DSC measurements. The encouraging nature of the results is discussed, and avenues for improving the method are considered

On the Use of Infrared Thermography for the Estimation of Melting Enthalpy

A calorimetry method based on infrared thermography is showing promise for material screening, allowing the simultaneous detection of phase transitions of multiple samples at a time, hence enabling the establishment of phase diagrams in a record time. The working principle of this method is similar to the one of Differential Thermal Analysis. Therefore, this work aims at identifying if the melting enthalpy of materials could be estimated on the same basis using infrared thermography. In this work, the melting of six eutectic mixtures of fatty acids is estimated under three considerations. The results are compared to Differential Scanning Calorimetry measurements and literature data. The accuracy of the method is discussed and improvements are proposed

Characterization of Fatty Acids as Biobased Organic Materials for Latent Heat Storage

This work aims to characterize phase change materials (PCM) for thermal energy storage in buildings (thermal comfort). Fatty acids, biobased organic PCM, are attractive candidates for integration into active or passive storage systems for targeted application. Three pure fatty acids (capric, myristic and palmitic acids) and two eutectic mixtures (capric-myristic and capric-palmitic acids) are studied in this paper. Although the main storage properties of pure fatty acids have already been investigated and reported in the literature, the information available on the eutectic mixtures is very limited (only melting temperature and enthalpy). This paper presents a complete experimental characterization of these pure and mixed fatty acids, including measurements of their main thermophysical properties (melting temperature and enthalpy, specific heats and densities in solid and liquid states, thermal conductivity, thermal diffusivity as well as viscosity) and the properties of interest regarding the system integrating the PCM (energy density, volume expansion). The storage performances of the studied mixtures are also compared to those of most commonly used PCM (salt hydrates and paraffins).This research work was developed in the framework of SUDOKET project (Interreg Sudoe SOE2/P1/E0677). The authors are grateful to the European Regional Development Fund (ERDF) to co-fund the project through the Interreg Sudoe Programme and the Region Nouvelle Aquitaine for subsidizing BioMCP project (Project-2017-1R10209-13023). The authors would also like to extend their thanks to CNRS for promoting the I2M Bordeaux-CICenergiGUNE exchanges in the framework of the IEA PHASE-IR project

Performance analysis of the infrared thermography method for complex phase diagrams estimation

An infrared thermography method for the fast estimation of phase diagrams is progressively being challenged to assess the extent of its potential. Being simple, fast and at relatively low cost, it has successfully been applied to binary systems of organic materials of increasing complexity. A test campaign is now undergoing, aiming at evaluating the influence of experimental parameters on the efficiency of the method. In this work, the impact of the acquisition frequency and the heating rate on the accuracy of the estimated phase diagrams is assessed. Based on the estimation of the phase diagrams of three binary systems of fatty alcohols and fatty acids, the accuracy deviation for phase transitions detection is evaluated in comparison with measurements made by differential scanning calorimetry. Optimized parameters both in terms of heating and acquisition rates are determined to further improve the method

High-throughput experiment for the rapid screening of organic phase change materials

An emerging dynamic calorimetry method based on infrared thermography (IRT method) has recently proven to be of great interest for the fast establishment of the phase diagrams of binary systems of organic materials (sugar alcohols, fatty acids, fatty alcohols). The methods allowed for their determination in a single 2-h experiment when standard techniques require weeks of measurements hence enabling a significant improvement of the efficiency of material screening processes. As adding a component to the system greatly increases the number of compositions to be studied (21 for binary, 231 for ternary assuming a 5 mol% increment between compositions), the IRT method may be of even greater use with increasing system complexity. This work then aims at studying the applicability of IRT for the fast establishment of phase diagrams of ternary systems with the lauric (LA), myristic (MA), and palmitic (PA) fatty acids ternary system as an illustrative case. A phase diagram in agreement with the results of the literature and with DSC measurements is established using IRT in a few hours-experiments instead of weeks to months with standard methods. The obtained results (e.g.67 mol%LA + 23 mol%MA + 10 mol%PA for the eutectic composition, occurrence of a ternary eutectic reaction at 32 °C) are promising. This technique also successfully allows for rapid exploration of the phase diagram: reconstruction of the liquidus surface, identification of the eutectic transition, 4-phase equilibrium. IRT is a particularly interesting high-throughput characterization method for the establishment of the phase diagrams of ternary (or higher-order) systems

Phase Diagrams of Fatty Acids as Biosourced Phase Change Materials for Thermal Energy Storage

Thermal energy storage is known as a key element to optimize the use of renewable energies and to improve building performances. Phase change materials (PCMs) derived from wastes or by-products of plant or animal oil origins are low-cost biosourced PCMs and are composed of more than 75% of fatty acids. They present paraffin-like storage properties and melting temperatures ranging from −23 °C to 78 °C. Therefore, they could be appropriate for latent heat storage technologies for building applications. Although already studied, a more detailed exploration of this class of PCMs is still required. In this frame, a screening of fatty acids and of their related binary systems must be performed. The infrared thermography method (IRT), already used for the fast estimation of simple phase diagrams (~2 h), appears to be best suited to achieve this goal. IRT method applicability to the more complex fatty acids phase diagrams is hence studied in this work. A phase diagram comprising more than a hundred data sets was obtained for the palmitic acid–stearic acid binary system. The reliability of the results is assessed by comparison to differential scanning calorimetry (DSC) measurements or results from other standard methods presented in literature and to a solid–liquid equilibrium thermodynamic model