Effects of Neglecting PCM Hysteresis While Making Simulation Calculations of a Building Located in Polish Climatic Conditions

The use of phase change materials (PCM) in different building applications is a hot topic in today’s research and development activities. Numerous experimental tests confirmed that the hysteresis of the phase change process has a noticeable effect on heat accumulation in PCM. The authors are trying to answer the question of whether the neglecting of hysteresis or the impact of the speed of phase transformation processes reduce the accuracy of the simulation. The analysis was performed for a model building, created to validate the energy calculations. It was also important to conduct simulations for the polish climatic conditions. The calculations were conducted for three variants of materials. In addition, in the case of models containing layers with PCM, calculations were made both taking into account, as well as excluding material hysteresis in the calculations. In the analyzed examples, after taking into account hysteresis in the calculations, the period of time when surface temperature is below the phase change temperature of the materials decreased by 10.6% and 29.4% between 01 June to 30 September, for the options with PCM boards and Dupont boards, respectively. Significant differences in surface temperature were also observed. The effects of neglecting, even relatively small hysteresis, in the calculations are noticeable and can lead to significant errors in the calculation.

Poplar-based thermochromic composites that change colour at 38 °C to 46 °C

The red thermochromic dye (R-TD) is the tetradecanoic acid tetradecyl ester (C28H56O2) and methyl red (C15H15N3O2) mixture that has better permeability enabling its infiltration into wood and better thermochromic properties changing its colour at above 30 °C after about 0.5 min. Thicker poplar-based thermochromic composite specimens (R-PTC, thickness: 5.0 mm) were prepared by filling the R-TD into pre-treated poplar veneer (thickness: 5.0 mm) thus allowing better penetration after pre-treatment. After R-TD infiltration, the R-PTC samples were covered by polypropylene wax for preventing R-TD from overflowing from R-PTC under the action of phase-change temperature. This R-PTC, whose colour can change from light-red to dark-red at 38 °C to 46 °C, can recover to light-red at below 38 °C after about 14 h, and the peak of colour change is at about 42 °C. R-PTC will be suitable for materials used in thermochromic furniture that can indicate the surface temperature to potential users, thus allowing assessment of likely scalded pain when used the furniture.

Phase Change Temperature Sensor for High Radiation Environment

Performance of any sensor in a nuclear reactor involves reliable operation under a harsh environment (i.e., high temperature, neutron irradiation, and a high dose of ionizing radiation). In this environment, accurate and continuous monitoring of temperature is critical for the reactor's stability and proper functionality. Furthermore, during the development and testing stages of new materials and structural components for these systems, it is imperative to collect in-situ measurement data about the exact test conditions for real-time analysis of their performance. To meet the compelling need of such sensing devices, we propose radiation-hard temperature sensors based on the phase change phenomenon of chalcogenide glasses. The primary goal is to resolve the monitoring of the cladding temperature of light water and metallic or ceramic sodium-cooled fast reactors within a temperature range of 400°C to 600°C. This work is focused on studies of Ge-Se(S) chalcogenide glasses that have crystallization temperatures in this range. Each chalcogenide glass transforms and becomes crystalline at a specific heating rate at a definite temperature. As a result of this, both the electrical resistance and optical properties of the materials change. As this is the first time such devices have been fabricated, this work submits new data regarding materials research, various device structures, fabrication, performance, and testing under irradiation. The application of these materials in devices usually involves the formation of a thin film that works as an active layer. Traditionally, thin films are prepared by thermal evaporation, sputtering or chemical vapor deposition and they require high vacuum machinery and patterning applying photolithography. To avoid using such heavy machinery and costly fabrication processes, we investigate the formulation of nanoparticle inks of chalcogenide glasses, the formation of printed thin films using the inks, low-cost sintering and demonstrate their application in electronic and photonic sensors utilizing their phase transition effects. The printed chalcogenide glass films showed similar structural, electronic and optical properties as the thermally evaporated films. The newly developed process steps reported in this work describe chalcogenide glasses nanoparticle inks formulation, their application by inkjet printing and dip-coating methods and sintering to fabricate phase change temperature sensors. To interpret and predict the printed films' performance, Raman spectroscopy, X-ray Diffraction Spectroscopy, Energy Dispersion Spectroscopy, Atom Force Microscopy, temperature dependent Ellipsometry, and other methods are used. An essential part of materials' behavior is related to the materials' and devices' response to ion beam irradiation. Both experimental data and simulation are analyzed to study the effect of irradiation. Based on the different working principles, electrical, optical and plasmonic temperature sensors are investigated. An array of optical fiber devices fabricated with different chalcogenide glasses is shown to perform a real-time temperature reading. This work could be used as a paradigm for sensor fabrication and testing for high radiation environments and nanoparticle inks of chalcogenide glasses formulation and their application by inkjet printing and dip-coating. The most novel outcome of this work adds chalcogenide glasses to the list of inkjet printable materials, thus opening up an opportunity to achieve arbitrary structures for optical and electronic applications without photolithography.

Thermal Properties and the Prospects of Thermal Energy Storage of Mg–25%Cu–15%Zn Eutectic Alloy as Phase Change Material

This study focuses on the characterization of eutectic alloy, Mg–25%Cu–15%Zn with a phase change temperature of 452.6 °C, as a phase change material (PCM) for thermal energy storage (TES). The phase composition, microstructure, phase change temperature and enthalpy of the alloy were investigated after 100, 200, 400 and 500 thermal cycles. The results indicate that no considerable phase transformation and structural change occurred, and only a small decrease in phase transition temperature and enthalpy appeared in the alloy after 500 thermal cycles, which implied that the Mg–25%Cu–15%Zn eutectic alloy had thermal reliability with respect to repeated thermal cycling, which can provide a theoretical basis for industrial application. Thermal expansion and thermal conductivity of the alloy between room temperature and melting temperature were also determined. The thermophysical properties demonstrated that the Mg–25%Cu–15%Zn eutectic alloy can be considered a potential PCM for TES.

Ultrahigh Piezoelectricity After Field Cooling AC Poling in Ferroelectric Crystals Manufactured by Continuous-feeding Bridgman

We investigated the dielectric and piezoelectric properties of [001]-oriented 0.24Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PIMN-0.30PT) single crystals (SCs) manufactured by continuous-feeding Bridgman (CF BM) within morphotropic phase boundary (MPB) region after field cooling alternating current poling (FC ACP). By optimized the FC ACP conditions of 4 kVrms/cm from 100 to 70 oC, the PIMN-0.30PT SC process attained ultrahigh dielectric permittivity (εT 33/ε0) of 8330 and piezoelectric coefficient (d33) of 2750 pC/N, and bar mode electromechanical coupling factor k33 of 0.96 with higher phase change temperature (Tpc) of 103 oC, respectively. These values are the highest ever reported as PIMN-xPT system SCs with Tpc > 100 oC. The enhancement of these properties of the PIMN-0.30PT SC is attributed to the induced low symmetry multi-phase supported by phase analysis. This work indicates that FC ACP is a smart and promising method to enhance piezoelectric properties of relaxor-PT ferroelectric SCs including PIMNT, which provide a route to a wide range of piezoelectric device applications.