Peak Temperature Research Articles

Extending a Multi-Physics Li-Ion Battery Model from Normal Operation to Short Circuit and Venting

Abstract Mitigation of Li-ion battery system fires consists of reliable fault detection and proactive, fast discharge control. Both require modeling of failure modes due to high temperatures and currents between normal operation and thermal runaway. In this work, we present a control-oriented, reduced-order, multi-physics model that captures the electrochemical, thermal, gas generation, mechanical expansion, and venting behavior of NMC pouch cells undergoing an external short circuit (ESC) from different initial state-of-charge (SOC). The model is parameterized through experiments by fitting the solid-electrolyte interphase (SEI) decomposition rate, the cell's thermal parameters, and the particle solid-phase diffusion parameters to capture the first venting timing, peak temperature, and diffusion-limited electrical behavior at high currents. Using a single parameter set, the multi-physics model can capture behavior during an ESC to predict whether a cell will generate gas and vent, predict the vent timing within 10 seconds of it occurring in the experiment, and maximum cell expansion pressure within 10 kPa for cells that did not vent. The model can also predict the SOC trajectory for cells with a high initial SOC within 6% SOC for the 15-minute discharge or until the cell vents.

Mice with deficiency in Pcdh15, a gene associated with bipolar disorders, exhibit significantly elevated diurnal amplitudes of locomotion and body temperature

Genetic factors significantly affect the pathogenesis of psychiatric disorders. However, the specific pathogenic mechanisms underlying these effects are not fully understood. Recent extensive genomic studies have implicated the protocadherin-related 15 (PCDH15) gene in the onset of psychiatric disorders, such as bipolar disorder (BD). To further investigate the pathogenesis of these psychiatric disorders, we developed a mouse model lacking Pcdh15. Notably, although PCDH15 is primarily identified as the causative gene of Usher syndrome, which presents with visual and auditory impairments, our mice with Pcdh15 homozygous deletion (Pcdh15-null) did not exhibit observable structural abnormalities in either the retina or the inner ear. The Pcdh15-null mice showed very high levels of spontaneous motor activity which was too disturbed to perform standard behavioral testing. However, the Pcdh15 heterozygous deletion mice (Pcdh15-het) exhibited enhanced spontaneous locomotor activity, reduced prepulse inhibition, and diminished cliff avoidance behavior. These observations agreed with the symptoms observed in patients with various psychiatric disorders and several mouse models of psychiatric diseases. Specifically, the hyperactivity may mirror the manic episodes in BD. To obtain a more physiological, long-term quantification of the hyperactive phenotype, we implanted nano tag® sensor chips in the animals, to enable the continuous monitoring of both activity and body temperature. During the light-off period, Pcdh15-null exhibited elevated activity and body temperature compared with wild-type (WT) mice. However, we observed a decreased body temperature during the light-on period. Comprehensive brain activity was visualized using c-Fos mapping, which was assessed during the activity and temperature peak and trough. There was a stark contrast between the distribution of c-Fos expression in Pcdh15-null and WT brains during both the light-on and light-off periods. These results provide valuable insights into the neural basis of the behavioral and thermal characteristics of Pcdh15-deletion mice. Therefore, Pcdh15-deletion mice can be a novel model for BD with mania and other psychiatric disorders, with a strong genetic component that satisfies both construct and surface validity.

Effect of Cubic Crystal Morphology on Thermal Characteristics and Mechanical Sensitivity of PYX

To investigate the influence of the cubic crystal morphology on the thermal properties and sensitivity of 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX), cubic PYX (CPYX) crystals were prepared using the antisolvent method. Scanning electron microscopy (SEM), laser particle size analysis, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the morphology, particle size and structure of the prepared products. The thermal behavior, thermal decomposition kinetics, thermal safety parameters and thermal decomposition mechanism of CPYX were investigated by differential scanning calorimetry–thermogravimetry–mass spectrometry–Fourier transform infrared spectrometry (DSC-TG-MS-FT-IR) and in situ FT-IR experiments. Meanwhile, the mechanical sensitivity of CPYX was determined by means of the explosion probability method. The results showed that the product had a smooth cubic morphology and small crystal aspect ratio with an average particle size (d50) of 10.65 μm, but it had no distinct differences from the crystal structure of raw PYX (RPYX). The thermal decomposition peak temperature, the self-accelerating decomposition temperature and the critical temperature of the thermal explosion of CPYX increased by 7.2 °C, 6.1 °C and 10.4 °C, respectively, compared to RPYX. Similarly, the apparent activation energy increased by 15%. Besides these, the impact sensitivity and friction sensitivity of CPYX decreased by 36% and 20%, respectively, compared to RPYX. The decomposition process of CPYX contains two stages. The first stage involves the breakage of N-H bonds and -NO2 groups with the release of CO2, N2O, NO, HCN and H2O, followed by the thermal decomposition of the resulting intermediate and the release of CO2, N2O and HCN in the second stage.

Efficient Synthesis, Characterization, and DFT Calculation of 4,4’-Azo-1,2,4-triazole

ABSTRACT 4,4’-Azo-1,2,4-triazole (atrz) is a new high nitrogen energetic material with high energy density, high gas yield and wide application prospects, but the low synthesis temperature and long time are the main reasons limiting its application. To achieve efficient synthesis of atrz, the double drop synthesis method was designed to solve the problem of unstable concentration of oxidant (HClO) due to batch feeding. The reaction temperature, reaction time, and molar ratio of reactants of n(4-amino-1,2,4-triazole):n(ClO−) were studied and optimized using the single factor variable method; Characterization and analysis of atrz using theoretical calculations with elemental analysis, infrared spectroscopy, crystal morphology, and nuclear magnetic resonance; The thermal properties and stability of atrz were tested and analyzed using TG-DTA. The results showed that the reaction time of the double drop synthesis method was shortened from 5 hours to 1.5 hours under the conditions of similar yield, and the efficiency was increased by 2.3 times. The optimized process was a reaction temperature of 5°C-10°C, reaction time of 1.5 hours, n(4-amino-1,2,4-triazole):n(ClO−) of 1:2, and the yield reached 73%. The product was white, needle-like crystals, which were determined to be atrz by means of characterization and theoretical calculations. Atrz’s decomposition peak temperature is 309.0°C, and when the temperature is below 271.7°C, atrz is thermally stable. The activation energies of atrz calculated by Kissinger and Flynn-Wall-Ozawa methods were 195.0 kJ·mol−1 and 194.6 kJ·mol−1.

Feasibility study of friction stir joining of aluminium with carbon fibre reinforced thermoplastic composite

During the last decades, environmental concerns and limited resources have set focus of research on lightweight, mechanically high-performing structures for the transportation industry, in order to reduce fuel consumptions and CO2 emissions. Friction Stir Joining (FSJ), as a variant of the Friction Stir Welding (FSW), is an innovative friction-based joining technique for metal-composite hybrid structures. Joining in the plasticized state below the melting temperature of the metal leads to a comparatively small heat-affected zone, so that only minor metallurgical changes occur. Additionally, only a short processing time and no additional weight in form of fasteners is needed. The main objective of this study is to evaluate the feasibility of metal-composite structures via FSJ, intending to enable a macro-mechanical interlocking bonding mechanism. Main focus was given to the integration of an aluminium nub inserted in a carbon fiber-reinforced polyphenylene sulfide (CF-PPS) sheet, to ensure sufficient plasticization of the aluminium part and no degradation in the polymer part. Residual stress arising from the friction stir joining process was also characterised using the Contour method. In this study, aluminium alloy 6082-T6 and CF-PPS composite sheets were used to produce long lap joints. Results have shown that the joints were created at almost constant peak temperature slightly above the melting temperature of the PPS but no physical-chemical changes were detected in the PPS. In addition, the influence of a PPS film as interlayer between the sheets was investigated in order to explore a method for preventing galvanic corrosion. Preliminary results indicate that it is not possible to integrate a metal nub to the CF-PPS without interrupting the PPS film. However, it is possible to create a nub within the PPS film.

Modeling heat and mass transfer in metal hydride hydrogen storage systems: Impact of operating parameters and reactor geometry

This work introduces a transient 2D axis-symmetrical model for hydrogen absorption in a cylindrical LaNi5 reactor employing finite volume method with a fully implicit Euler's time integration scheme, coupling equations for heat, mass, and momentum transport. The validated model is used to investigate the impacts of pressure, cooling fluid temperature, and variations in reactor geometry and size on temperature and reacted fraction profiles. The findings reveal that the charging pressure affects both peak temperature and reaction kinetics, whereas cooling fluid temperature predominantly impacts the absorption kinetics. A comparative analysis of two models, one incorporating Darcy's velocity and one without, demonstrates that while Darcy's law introduces numerical instability in the coupled equations, its impact on the model outcomes is negligible. The effect of changing the non-homogeneous Neumann to Dirichlet boundary condition is also demonstrated to anticipate the utilization of phase change materials (PCM) instead of the cooling fluid.

Effects of the ice formation and its content on viscoelastic characteristics of wood exposure to low temperatures ranging from −125°C to 25°C

ABSTRACT The influence of ice formation and its content on the viscoelastic characteristics of wood were investigated in the temperature range between −125°C and 25°C. The stiffness and damping properties of the longitudinal (L), radial (R) and tangential (T) specimens were determined for different moisture content (MC) levels at or above the fiber saturation point (FSP) ranging from 25% to 300%. Results showed that the E′ value was correlated negatively with temperature for all specimens. Accompanied by the frozen free water inside the wood, the order of magnitude in E′ for specimens in the different anatomical directions trend toward an accord. The increment in E′ (ΔE′) of specimens was correlated positively with the ice content, and ΔE′ in the L direction was lower than those in the R and T directions at each MC level. The γ-relaxation ranged from −112.9°C to −94.8°C was observed for all orthotropic directions at 10 Hz, which was assigned to the reorientation of methylol groups and adsorbed water molecules in the wood cell walls. At each MC level, a lower peak temperature of γ-relaxation was observed in the L specimens compared to the transverse specimens. Notably, the γ-relaxation peak temperature in the E″ and tanδ spectrum showed obvious frequency-dependence, and the apparent activation energy (ΔH) of γ-relaxation over the measured MC range was about 38.08∼69.57 KJ/mol. The ΔH value was close for specimens in orthotropic grain orientations, indicating that this γ-relaxation phenomenon was not affected by its orthotropic structure and also related closely with the formation of ice in the wood cell lumens.

Sodium alanate in-situ doped with Ti2C MXene with enhanced hydrogen storage properties

NaAlH4 is a reversible hydrogen storage material and has attracted great attention recently. However, the application of NaAlH4 in hydrogen storage still has great difficulties. In this study, 2D MXene Ti2C-doped NaAlH4 samples were prepared in-situ by reaction ball milling of NaH under moderate condition. TPD measurement results show that all the as-prepared samples exhibit good thermodynamic performance except for the sample doped with 1 wt% Ti2C. And DSC analysis results show that at the heating rate of 5 K/min, the first and second dehydrogenation peak temperatures of the sample doped with 7 wt% Ti2C were 127.1 °C and 150.6 °C respectively, which are 57.4 °C and 123.6 °C lower than those of pure NaAlH4 (after ball milling), respectively. Meanwhile, NaH/Al-7 wt.% Ti2C sample displays a superior kinetics behavior. Isothermal hydrogen evolution curves show that NaH/Al-7 wt.%Ti2C released 5.21 wt% H2 within 30 min at 150 °C and then absorbs 5.2 wt% H2 in 90 s at 120 °C. Even at a lower temperature of 80 °C, the sample still absorbed 4.71 wt% H2 within 60 min. In addition, almost no release capacity attenuation was observed for NaH/Al-7 wt.%Ti2C after 10 hydrogen absorption/desorption cycles. The improvement of the hydrogen storage properties can be ascribed to the high reactivity of NaAlH4 produced in situ and catalysis of lamellar Ti3+/0 species formed by the reduction of high valent Ti in Ti2C during ball milling.

Nanoscale-precipitate-strengthened (Ni,Cu)-rich TiNiCu shape memory alloy with stable superelasticity and elastocaloric performance

This study aimed to enhance the stability of the superelastic and elastocaloric properties of a Ti49Ni41Cu10 shape memory alloy through a synergistic approach combining compositional design and precipitation hardening. The alloy was subjected to a 168-h aging treatment at 400 °C. The aging treatment increased the hardness of the alloy due to the formation of nano-scale C11b Ti(Ni,Cu)2 precipitates. The C11b Ti(Ni,Cu)2 precipitates exhibited a coherent interface with the matrix, contributing to the significant strengthening effect. The thickness of the precipitates was measured to be approximately 2 nm. Additionally, the lattice compatibility between the B2 parent and B19 martensite phases, determined to be 0.997 after aging, indicated a high level of compatibility between the two phases. The high compatibility and precipitate strengthening further contributed to the functional stability of the alloy. The 168-h aged Ti49Ni41Cu10 shape memory alloy showed excellent functional stability during thermal and deformation cycles. The peak temperature of B2 to B19 transformation only decreased by 0.2 °C after 10 thermal cycles and showed limited changes with a decrement of 3.2 °C after 10,000 superelastic cycles. The Ti49Ni41Cu10 SMA showed a large elastocaloric temperature drop of 18 °C at the 1st superelastic cycle and maintained a large temperature drop of 17 °C after 1000 cycles. These findings contribute to a deeper understanding of the microstructural changes and their impact on the functional properties of the Ti49Ni41Cu10 shape memory alloy. This study has demonstrated the potential for developing shape memory alloys with improved stability and performance by utilizing compositional design and precipitation hardening techniques.

Ultrasound and pulsed electric field treatment effect on the thermal properties, oxidative stability and fatty acid profile of oils extracted from berry seeds

AbstractThe seeds of berry fruits which are considered as a by-product may be valorized by recovering the oil they content. Nevertheless, the conventional extraction methods are time, energy and organic solvents consuming. In order to make extraction more environmental-friendly, alternative methods, like ultrasound-assisted and pulsed electric field-assisted processes, are being developed. The procedure of extraction may however influence the quality of obtained oil. The following study aims to define the effects of ultrasound and pulsed electric field application in the extraction process on the thermal properties, i.e., oxidative stability, melting and cyclic heating/cooling profiles, thermal decomposition characteristics. Additionally, fatty acid profile assessment was included in the study. Seeds of blackberries, blackcurrants, chokeberries, raspberries and redcurrants were used to extract oil. Based on the results, it can be summarized that extraction method influenced the resistance of oils to oxidation. Ultrasound-assisted process resulted in oils with the highest oxidation induction times. Melting profile was slightly influenced by extraction method, with peak temperatures indicating the presence of low-melting and middle-melting triacylglycerol fractions. Differential scanning calorimetry with heat/cool/heat procedure let determine crystallization peak temperatures around − 60 °C, which could be associated with the specific triacylglycerol profile of berry seed oils. The courses of thermogravimetric analysis curves were comparable for all the tested samples. The fatty acid profile study revealed that all the studied thermal properties were affected by the unique fatty acid percentage share, with a great predominance of polyunsaturated fatty acids. Obtained results allowed to conclude that extraction method influenced oxidative stability, thermal properties and fatty acid profile only to some extent. The most promising extraction method among analyzed seems to be ultrasound-assisted extraction as it provided oil with high oxidative stability, typical thermal properties and unchanged fatty acid profile, without being harmful to natural environment due to possible reduction in solvent and time consumption.

Experimental investigation of spray cooling heat transfer with microcapsule phase change suspension

This paper reveals the spray cooling heat transfer mechanism with the microencapsulated phase change suspension as the working fluid based on an experimental investigation. The heat transfer performances between the spray cooling and jet impinging with suspension are compared. A series of key parameters affecting the heat transfer are analyzed, including suspension concentration, nozzle diameter, spray height, inlet temperature, and spray inclined angle. It concludes that the spray cooling of suspension has a stronger heat transfer capability relative to the jet impinging, but the pressure loss is correspondingly larger. Compared with the water, the spray cooling heat transfer of phase change suspension is superior owing to the latent heat ability of particle core, and the maximum improvement in the current tests is 33.9 %. However, excessive suspension concentration can result in the deterioration of heat transfer because of the larger viscosity. There is an optimal volumetric flow rate and an optimal spray height for the spray cooling, where a suitable spray cone angle is present so that the heating surface may be exactly covered by the liquid-film. The latent heat absorption characteristic of phase change core leads to the existence of an optimal spray inlet temperature, which is about 10 °C lower than the melting peak temperature of the particle core. For the cases of incomplete-coverage, the decrease of the spray inclined angle may enlarge the liquid-film covering area and thence improve the heat transfer. A theoretical analysis indicates that the suspension in current tests has a high complete-melting rate (σ ≥ 93.7 %) when using in the spray cooling. The results may provide the beneficial support for the potential application of spray with phase change suspension for the cooling of electronic devices.

Kinetic and combustion characteristics of oil palm empty fruit bunch biochar using thermogravimetric analysis

The usage of renewable energy is a mitigation phenomenon majorly impacting the power sectors, with biomass being one of the sources directly replacing coal in various applications. This leads to the portrayal of biomass having the potential to be a carbonaceous material, namely the Empty Fruit Bunch (EFB) of oil palm. To increase the characteristics of EFB, it can be converted into carbon-based products through thermochemical processes, such as hydrothermal carbonization. Therefore, this study aimed to compare the characteristics of feedstock and biochar EFB using the TGA method. The heating rate used in this study is 10 – 30°C/min at five °C/min intervals. The effect of heating rate on kinetic parameters and thermal (DTG, TGA) and combustion (T ignition, T burn out) characteristics was also determined. This study carried out the HTC process at temperatures of 210ᵒC and 230ᵒC. The results showed that biochar EFB had a higher ignition, burnout temperature, and activation energy than raw EFB. Ignition temperatures for EFB-HT210°C and EFB-HT230°C were 297°C and 298°C; burnout temperatures for EFB-HT210°C, EFB-HT230°C were 407°C and 450°C; and the activation energy for EFB-HT210°C, EFB-HT230°C were 58.84 kJ/mol and 62.16 kJ/mol. Besides the characteristics of biomass, the heating rate also affects combustion. This proved that increased heating rate caused higher ignition and burnout temperature and decreased activation energy. The results also indicated that the difference in heating rate influenced the peak temperature in DTG.

Self-heating and spontaneous ignition of biomass storage piles: Towards a reliable prediction tool

Large-scale biomass storage for modern bioenergy introduces potential safety concerns due to the intrinsic self-heating of biomass. Despite this, very limited research has been conducted in this area. This project fills a critical gap by developing a comprehensive modelling framework for self-heating in biomass piles and conducting a series of experimental studies to explore the intricate sub-processes within these piles. This paper presents only a small portion of the modelling and testing work. It successfully demonstrates the model's usefulness in predicting self-heating in coal piles, guiding safety measures for coal storage. Among various storage parameters, the pile height, particle size and ambient wind velocity have been identified as having substantial impacts on self-heating and self-ignition within the coal pile. This paper also illustrates the pronounced effects of initial biomass moisture content on microbial reactivity and oxygen consumption rate. An increase in initial moisture content significantly enhances the overall microbial reactivity and oxygen consumption rate. Wheat straw, compared to rice straw, is more prone to self-heating under identical storage conditions, as evidenced by higher heat generation, faster oxygen consumption, and a shorter time to peak temperature. Moreover, microbial activity is found to play a critical role in biomass self-heating, particularly in the temperature range of 0–75 °C, during the initial stages of heat accumulation. For the modelling discussed here, the flow within the porous pile must be considered laminar, despite the highly turbulent flow around the pile. This is based on the Reynolds number, calculated from the in-pile volume average of the velocity and the mean diameter of the fuel particles, which is significantly below the critical threshold (Recr=200). The insights and sub-models to be derived from the relevant sub-processes in biomass pile can be integrated into the model framework. This integration will create a more comprehensive and robust model for predicting self-heating and self-ignition in biomass storage piles, enhancing both theoretical and practical management of these phenomena.

Combustion Characteristics, Kinetics and Thermodynamics of Peanut Shell for Its Bioenergy Valorization

To realize the utilization of peanut shell, this study investigates the combustion behavior, chemical kinetics and thermodynamic parameters of peanut shell using TGA under atmospheric air at the heating rates of 10, 20, and 30 K/min. Results indicate that increasing the heating rate leads to higher ignition, burnout, and peak temperatures, as observed in the TG/DTG curves shifting to the right. Analysis of combustion performance parameters suggest that higher heating rates can enhance combustion performances. Kinetic analysis using two model-free methods, KAS and FWO, shows that the activation energy (Eα) ranges from 93.30 to 109.65 kJ/mol for FWO and 89.72 to 103.88 kJ/mol for KAS. The data fit well with coefficient of determination values (R2) close to 1 and the mean squared error values (MSE) less than 0.006. Pre-exponential factors using FWO range from 2.19 × 106 to 8.08 × 107 s–1, and for KAS range from 9.72 × 105 to 2.25 × 107 s–1. Thermodynamic analysis indicates a low-energy barrier (≤±6 kJ/mol) between activation energy and enthalpy changes, suggesting easy reaction initiation. Furthermore, variations in enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS) upon conversion (α) suggest that peanut shell combustion is endothermic and non-spontaneous, with the generation of more homogeneous or well-ordered products as combustion progresses. These findings offer a theoretical basis and data support for the further utilization of agricultural biomass.

Effects of Laser Scanning Strategy on Bending Behavior and Microstructure of DP980 Steel

Laser bending is a kind of cumulative forming technology and bending efficiency is one of its most important indexes. This study investigates the bending behavior and the microstructure of DP980 steel plates under different laser scanning strategies, using an IPG laser system. Two sets of experiments varied the accumulated line energy density (AED) by altering the laser scanning velocity and number of scans. The results show that, for the single laser scanning process, the bending angle of the plate increases with AED, due to a larger temperature gradient through the thickness direction; however, this relationship is nonlinear. A higher AED led to a sharper initial increase in bending angle, which then plateaued. Under the same AED conditions, the bending angle of the plate undergoing multiple laser scans increases by at least 26% compared to the single one, due to the microstructure changes. It is revealed that the bending efficiency is affected by both the AED and the resultant microstructure evolution in the DP980 steel. Higher AED values and appropriate peak temperatures facilitate better bending behavior due to the formation of uniform martensite and grain refinement. Conversely, excessive peak temperatures can hinder bending due to grain growth.

Geometry-induced process and part characteristics in support-free powder bed fusion of polypropylene at room temperature

AbstractLaser-based powder bed fusion (LPBF) of semi-crystalline polymers enables the support-free layer-wise manufacturing of geometrically diverse, complex components. In contrast to the established quasi-isothermal powder bed fusion of polymers at elevated temperatures, non-isothermal, cold processing strategies allow to significantly extend the range of applicable material systems. Relying on the superposition of discretized, fractal exposure strategies and the implicit mesoscopic compensation of crystallization shrinkage, the support-free LPBF of polypropylene at room temperature is demonstrated. The present paper displays the temporally and spatially discrete exposure of superposed fractal, space-filling curves that enable the support-free LPBF of polypropylene through combining the mesoscopic compensation of crystallization shrinkage and the laser-induced minimization of thermal shrinkage through the implementation of pre-exposure scans. The non-isothermal processing regime was observed to exhibit an intrinsic robustness towards the influence of processing parameters on emerging peak temperatures while showing a significant extent of accumulated heat within manufactured parts. Complementary mechanical characterizations showed an orientation-dependent influence of the applied energy density on emerging mechanical properties, correlated with geometry-dependent temporal process characteristics that implicitly influence the available coalescence time and the timespan available for the thermal homogenization.

Rapid low-temperature densification of Ag2Se bulk material: mass transfer through the dissociative adsorption reaction of Ag protrusions and Se saturated vapor

In materials science, the impact of density on a material’s capabilities is profound. Conventional sintering requires high temperatures and is energy-demanding, propelling the pursuit of less intensive, low-temperature densification methods. Electric field-assisted sintering has recently gained attention for its simplicity and effectiveness, offering a new frontier in low-temperature densification. In this study, dense bulk materials were produced by subjecting monophasic Ag2Se powders to electric field-assisted sintering, where a direct current with an average value of 4 A was applied, achieving a peak temperature of 344 K. The novel low-temperature densification mechanism unfolds thus: nanoscale silver protrusions, stimulated by electrical current, engage in a dissociative adsorption reaction with the ambient saturated selenium vapor. This process swiftly engenders the formation of fresh silver selenide (Ag2Se) compounds, initiating nucleation and subsequent growth. Consecutively, these compounds seamlessly occupy and expand, perpetually bridging the interstices amidst the powders. In a scant 8 s, the density swiftly surpassed 99%, yielding a bulk material that exhibited a ZT value of 1.07 at 390 K. This investigation not only attains an unparalleled density at low temperatures but also charts a pioneering course for material densification in such conditions.

Influence of drought stress and growth temperature during kernel development on physical and chemical starch characteristics of malting barley

AbstractBackground and ObjectivesStarch is the main component of malting barley (Hordeum vulgare L.), and its physical and chemical characteristics are particularly important in further processing in the beverage industry. This study investigates how the parameters (i) growing temperature (high/low) and (ii) water deficit (drought stress) during grain filling affect starch characteristics by cultivating nine different commonly used malting barley varieties in greenhouses under defined conditions. Particle size distribution of the starch granules, their phase transition characteristics (DSC), the pasting temperature (RVA), and the amylose/amylopectin (AM/AP) ratio were examined to assess starch characteristics.FindingsTwo‐way ANOVA analyses revealed that drought stress during the grain‐filling phase resulted in significantly smaller starch granules, lower onset, peak, and endset temperatures (DSC), and increased pasting temperature (PT) while not affecting the AM/AP ratio. High growth temperature during grain filling resulted in significantly higher onset, peak, and endset temperatures (DSC), lower phase transition enthalpies, significantly higher PTs, and lower AM/AP ratios.ConclusionsGrowth temperature during kernel development affected starch phase transition characteristics the most, while water availability was significantly associated with starch granule sizes.Significance and NoveltyClimate change is increasing the events and severity of heat and drought in Europe. Agricultural practices and modern barley varieties must be adapted to these requirements to maintain processability for food production.

Characteristics of rice husk biochar briquettes with municipal solid waste cassava, sweet potato and matooke peelings as binders

AbstractRice husks are not readily biodegradable making their disposal challenging due to the common disposal method of open burning which has negative environmental effects. Additionally, banana, sweet potato and cassava peelings form a large percentage of organic municipal solid waste. Therefore, this study developed rice husk biochar briquettes with organic municipal peelings waste as binders. Rice husks biochar was formed via carbonization processes in a step-down kiln at temperatures ranging between 400 and 500 °C. Organic binders were mixed with the rice husk biochar at different ratios of 10% and 15% before being compacted at a pressure ≤ 7 MPa into briquettes. Thermogravimetric results showed that the developed briquettes had high ash contents ranging from 44% to 47%. Rice husk biochar briquettes with the highest particle density were observed for briquettes with 15% cassava peel binder at 427.1 kg/m3. The highest HHV and maximum attainable flame temperature of 21.75 MJ/kg and 828.7 °C were obtained for rice husk biochar briquettes with 15% matooke peeling organic binder. For all rice husk biochar briquettes, increasing the organic peeling binder had a positive impact of reducing the ash content, while at the same time increasing the peak temperatures, thus contributing to their enhanced thermal stability.

Expanded Graphite (EG) Stabilization of Stearic and Palmitic Acid Mixture for Thermal Management of Photovoltaic Cells

In this work, passive cooling systems for the revamping of existent silicon photovoltaic (PV) cells were developed and analysed in order to mitigate the efficiency loss caused by temperature rise in the hot season. For this purpose, expanded graphite (EG) was used to stabilize a phase change material (PCM) with a melting temperature close to 53 °C in order to realize thermal management systems (TMSs) able to store heat at constant temperature during melting and releasing it in crystallization. In particular, stearic and palmitic acid mixture (PA-SA) was shape-stabilized in EG at different concentrations (10, 12 and 14 part per hundred ratio) under vacuum into a rotary evaporation apparatus followed by cold compaction; PA-SA leakage was reduced due to its intercalation between the graphite lamellae, and the thermal conductivity necessary to maximize the heat transfer to a bulk TMS was improved via powder cold compaction, which minimizes voids and creates preferential thermal conductive patterns. The composite materials, stable till 150 °C, were tested by differential scanning calorimetry (DSC) at 1 °C/min to precisely determine the phase transition temperatures and the enthalpic content, which was only slightly reduced from 196 J/g of the neat PCM to 169 J/g due to the very low EG fraction necessary for the stabilization. Despite only the 14:100 EG-to-PA-SA ratio, the system’s thermal conductivity was enhanced 40 times with respect to the neat PCM (from 0.2 to 8.3 W/(m K), value never reached in works present in the literature), with a good convergence of the values evaluated through hot disk tests and laser flash analysis (LFA), finding correlation with both graphitic content and density. In order to completely avoid leaking with the consequent dispersion of PCM in the environment during the final application, all the samples were encapsulated in a PE-made film. The mechanical properties were evaluated with compression tests at 30 °C and 80 °C simulating a possible compressive stress deriving from the contact needed to maintain the TMS position on the rear of the PV cells. Finally, the material response was simulated by imposing thermal cycles into a climatic chamber and reproducing the three hottest and coldest days of summer 2022 of two Italian locations, Verona (Veneto, 45° N, 11° E) and Gela (Sicily, 37° N, 14° E), thus highlighting the thermal management effects with delays in temperature increase and daily peak temperature smoothing. The role of EG is strategic for the processing and the properties of the resulting composites in order to realize a proper compromise between the melting enthalpy of PCM and the thermal conductivity enhancement given by EG.