Extended Temperature Research Articles

Hierarchical Porous Bi2Te3@C for Wide-Temperature-Range Aqueous Zn-Based Batteries with Air-Recharging Capability.

Air-rechargeable batteries integrating energy harvesting, conversion, and storage provide the most portable and popular approach to self-charging power systems. However, air-rechargeable batteries are currently mostly aqueous Zn-based battery systems in which it has remained a significant challenge to solve the low discharge capacities and poor cycling stability of chemical self-charging due to continuous insertion/extraction of large-size hydrated Zn2+. Herein, efficient Bi2Te3@C cathodes with an active carbon paper substrate are developed. Further ex situ characterization analysis confirms the energy storage mechanism regarding the coexistence of H+/Zn2+ coinsertion and conversion reaction in the aqueous Zn||Bi2Te3@C battery. Benefiting from the fast dynamics process attributed to the unique mechanism, a reliable energy supply is provided even in an extended temperature range from -10 to 45 °C. More importantly, Bi2Te3@C cathodes boost the superior and repeatable air-rechargeability. A discharge capacity of up to 264.20 mA h g-1 at 0.30 A g-1 is manifested after self-charging for 11.00 h. In addition, two quasi-solid-state battery devices are connected in series to continuously power a timer. After the device is discharged and then air self-charged for just a few seconds, an LED is lit.

Optimized magnetic properties of a Terfenol-D alloy in an extended temperature range using a high magnetic field

Tb–Dy–Fe alloys are among the most suitable magnetostrictive materials for high-power transducers. Optimizing magnetic properties in an extended temperature range could ensure the stable operation of transducers. In this work, a high magnetic field is applied to the directional solidification of Tb–Dy–Fe alloys. We study the microstructure, crystallographic orientation, magnetic susceptibility, crystal structure, and magnetic domain of samples. When the content and alignment of the magnetic phase along with crystallographic orientation remain basically invariant, the magnetic susceptibility of samples increases with the magnetic flux density of the high magnetic field throughout the temperature range from 273 K to Curie temperature (T C). At 4 T, the maximum magnetic susceptibility is increased by ∼ 40% compared with the sample without a high magnetic field applied, and the advantage is maintained in the range ∼ 300 K. Analysis shows that the enhancement of magnetic susceptibility is not due to the change in crystal structure, as commonly believed, but to the highly ordered alignment of magnetic domains. This research provides a new method for improving the temperature properties of magnetic materials using a high magnetic field.

Grain boundary diffusion in additively manufactured CoCrFeMnNi high-entropy alloys: Impact of non-equilibrium state, temperature and relaxation

Grain boundary diffusion of Ni in the equiatomic CoCrFeMnNi high-entropy alloy, produced by additive manufacturing, is measured using a radiotracer technique in an extended temperature interval of 350 to 703 K. A strongly non-monotonic temperature dependence of the Ni grain boundary diffusion coefficients (with a spectacular intermittent retardation of the diffusion rates with increasing temperature) is seen and explained by relaxation of a non-equilibrium state induced by rapid solidification during fabrication. The grain boundary excess energy of the non-equilibrium state of these grain boundaries, as estimated from the diffusion data, is found to be larger than 0.3 J/m2. This corresponds to an increase of about 30% of the interface energy compared to relaxed general high-angle grain boundaries. The temperature-induced evolution of the grain boundary state is analyzed in terms of the concomitant structure evolution, segregation, phase stability and precipitation in the multi-component alloy.

Fast and low power SiPM amplifier operating in a wide temperature range

The next generation of Ring Imaging CHerenkov detectors in high energy physics experiments may use SiPMs as photon sensing elements. This upgrade is necessary to achieve greater detector granularity and speed, however SiPMs need to be cooled down to cryogenic temperatures to detect single photons in high-radiation environments and avoid being overwhelmed by the presence of “dark signals”. It is therefore necessary to study and characterize SiPM models in dedicated campaigns, using a custom-built amplifying chain that can also operate in an extended temperature range, between 80 K and 300 K, for detector characterization purposes. The proposed amplifier configuration consists of two amplifying stages and achieves low jitter values (<10−20psRMS) thanks to the low electronic noise and the high amplifier bandwidth. The circuit achieves a signal bandwidth of 500MHz<BW<1GHz, a phase margin of approximately 45° and a power consumption of about 65−135mW. The amplifier prototype unit can be adjusted to cover the considered temperature range and still achieve low jitter values.

Arylazo-3,5-diphenylpyrazole Derivatives: Molecular Probes Exhibiting Reversible Light-induced Phase Transitions for Energy Storage and Direct Photolithographic Patterning.

We report azopyrazole photoswitches decorated with variable N-alkyl and alkoxy chains (for hydrophobic interactions) and phenyl substituents on the pyrazoles (enabling π-π stacking), showing efficient bidirectional photoswitching and reversible light-induced phase transition (LIPT). Extensive spectroscopic, microscopic, and diffraction studies and computations confirmed the manifestation of molecular-level interactions and photoisomerization into macroscopic changes leading to the LIPT phenomena. Using differential scanning calorimetric (DSC) studies, the energetics associated with those accompanying processes were estimated. The long half-lives of Z isomers, high energy contents for isomerization and phase transitions, and the stability of phases over an extended temperature range (-60 to 80 °C) make them excellent candidates for energy storage and release applications. Remarkably, the difference in the solubility of the distinct phases in one of the derivatives allowed us to utilize it as a photoresist in photolithography applications on diverse substrates.

The anchoring effect and cooperative interactions in 5CB/CNC molecular films

ABSTRACT The advances in nanotechnology allow for the creation of hybrid materials (HMs) composed of LCs (LC) and cellulose nanocrystals (CNC). Cellulose is a natural polymer whose structural properties are used for designing new LC composite materials. The properties of CNC strongly depend on the origin and technological processes used. The LCs are materials displaying different structural properties in function of temperature or concentration that find applications mainly in electronics. The combination of LC and CNC results in enhanced properties, like an extended temperature range of mesophases, higher stability and mechanical strength of LC films. The CNC obtained through transition metal catalysed oxidative process allows obtaining hydroxyl groups active for interactions with LC molecules. By synergic combination and cooperative interaction between components, we have stabilised the 5CB molecules at the air-water interface by the anchoring effect, creating stable and compressible 5CB/CNC molecular films. The π-A isotherms, compressibility modules, Gibbs free energy of spreading, lift-of area, collapse pressure and surface pressure increment for investigated systems at different stages of the formation process are determined. We have demonstrated that creating a hybrid 5CB/CNC Langmuir film is a two-stage process. Obtained films display enhanced stability, strength and ability to form multilayers.

Electrically‐Triggered Oblique Helicoidal Cholesterics with a Single‐Layer Architecture for Next‐Generation Full‐Color Reflective Displays

AbstractElectrically‐induced oblique helicoidal cholesterics (ChOH) are attractive for use in reflective displays due to tunable photonic band gap (PBG) in a broad spectral range and natural eye‐friendly feature. However, the lack of a stable liquid crystal (LC) material system with a wide temperature range and unknown driver architecture hinder the implementation of the ChOH‐based reflective displays. Here, a prototype for a full‐color reflective display device based on electrically‐tunable ChOH‐LC is demonstrated. In the comparison of ChOH‐S1, S2 and S3 samples, the electric‐field‐induced ChOH in the ChOH‐S3 exhibits intense Bragg reflection and a tunable PBG in the extended temperature range from 19.5 °C to 30 °C. Particularly, the resulting device exhibits a lower driving voltage and a relatively larger color gamut for the full‐color reflective displays. On this basis, the display patterns with variable colors are demonstrated via the direct addressing mode. Furthermore, a proof‐of‐concept of the full‐color reflective display is demonstrated with red‐green‐blue pixeled images serving as the active panels. Ultimately, by regulating the electric field strength dependent on the ambient temperature, a stable and vivid effect of the ChOH device on the actual environment is shown. This work provides valuable insight for the development of ChOH‐based reflective displays.

Exceptionally Slow, Long-Range, and Non-Gaussian Critical Fluctuations Dominate the Charge Density Wave Transition.

(TaSe_{4})_{2}I is a well-studied quasi-one-dimensional compound long-known to have a charge-density wave (CDW) transition around 263K. We argue that the critical fluctuations of the pinned CDW order parameter near the transition can be inferred from the resistance noise on account of their coupling to the dissipative normal carriers. Remarkably, the critical fluctuations of the CDW order parameter are slow enough to survive the thermodynamic limit and dominate the low-frequency resistance noise. The noise variance and relaxation time show rapid growth (critical opalescence and critical slowing down) within a temperature window of ϵ≈±0.1, where ϵ is the reduced temperature. This is very wide but consistent with the Ginzburg criterion. We further show that this resistance noise can be quantitatively used to extract the associated critical exponents. Below |ϵ|≲0.02, we observe a crossover from mean-field to a fluctuation-dominated regime with the critical exponents taking anomalously low values. The distribution of fluctuations in the critical transition region is skewed and strongly non-Gaussian. This non-Gaussianity is interpreted as the breakdown of the validity of the central limit theorem as the diverging coherence volume becomes comparable to the macroscopic sample size. The large magnitude critical fluctuations observed over an extended temperature range, as well as the crossover from the mean-field to the fluctuation-dominated regime highlight the role of the quasi-one-dimensional character in controlling the phase transition.

Reactions dynamics for X + H2 insertion reactions (X = C(1D), N(2D), O(1D), S(1D)) with Cayley propagator ring-polymer molecular dynamics.

In this work, rate coefficients of four prototypical insertion reactions, X + H2 → H + XH (X = C(1D), N(2D), O(1D), S(1D)), and associated isotope reactions are calculated based on ring polymer molecular dynamics (RPMD) with Cayley propagator (Cayley-RPMD). The associated kinetic isotope effects are systematically studied too. The Cayley propagator used in this work increases the stability of numerical integration in RPMD calculations and also supports a larger evolution time interval, allowing us to reach both high accuracy and efficiency. So, our results do not only provide chemical kinetic data for the title reactions in an extended temperature range but also consist of experimental results, standard RPMD, and other theoretical methods. The results in this work also reflect that Cayley-RPMD has strong consistency and high reliability in its investigations of chemical dynamics for insertion reactions.

Energy-information trade-off induces continuous and discontinuous phase transitions in lateral predictive coding

Lateral predictive coding is a recurrent neural network that creates energy-efficient internal representations by exploiting statistical regularity in sensory inputs. Here, we analytically investigate the trade-off between information robustness and energy in a linear model of lateral predictive coding and numerically minimize a free energy quantity. We observed several phase transitions in the synaptic weight matrix, particularly a continuous transition that breaks reciprocity and permutation symmetry and builds cyclic dominance and a discontinuous transition with the associated sudden emergence of tight balance between excitatory and inhibitory interactions. The optimal network follows an ideal gas law over an extended temperature range and saturates the efficiency upper bound of energy use. These results provide theoretical insights into the emergence and evolution of complex internal models in predictive processing systems.

Controlling magnetically induced shape memory behavior through volume proportions in Heusler-type Fe47-xMn24+xGa29 structures

Here we demonstrate that a ferromagnetic shape memory can be tuned conveniently by volume proportions within Heusler-type Fe47-xMn24+xGa29 (x = 8, 6, 4, 2, and 0 at%) alloys over an extended temperature range. Preliminary X-ray diffraction experiments indicate that the Fe47-xMn24+xGa29 alloys crystallize into a B2 cubic structure with space group Pm3¯m for all compositions. Samples with compositions of x = 0–4 at% show the co-existence of two cubic structures (B2 and L21). The temperature dependence of magnetization M(T) measurements on Fe47-xMn24+xGa29 alloys under cooling-heating processes showed a moderate to an exceptionally large temperature hysteresis in a wider temperature range of 70–340 K, corresponding to the first-order diffusionless martensitic-to-austenite phase transformations. The M(T) curves obtained at various magnetic fields demonstrated that the magnitude and direction of temperature hysteresis is modified by volume proportions of Fe-Mn constituents. At 5, 150 and 300 K, hysteresis loop shows ferromagnetic (FM) behavior and the coercivity and remanence values vary with temperature and Mn content due to large exchange bias effects. Further ac magnetic susceptibility of Fe47-xMn24+xGa29 measurements show a cusp with a maximum below 70 K corresponding to an antiferromagnetic (AFM) transition. Thermal shift of the AFM transition is attributed to the dominant AFM-FM interactions pertaining to the pinning efficiency at the interface between Fe and Mn. These findings provide a comprehensive understanding of AFM spin structure and ferromagnetic shape memory behavior in Fe47-xMn24+xGa29 across cryogenic to 350 K temperatures.

Design and demonstration of a prototype thermally active student desk in a modern landmark for personalized cooling retrofits

This paper presents the design and evaluation of a prototype thermally active student desk (TASD) for personalized cooling retrofits using computational fluid dynamics (CFD) and field experiments. The study first developed an initial conceptual design for a TASD prototype made to esthetically match the desks in an architecture studio in a historic building that is frequently subject to comfort complaints. CFD simulations were used to validate the conceptual design and determine some component and system features. Four functional prototype TASDs for cooling were constructed and tested in the studio space with university students while the rest of the building was maintained at an extended temperature set point. CFD simulations predicted that the percent people of dissatisfied (PPD) would be ≤6% under all simulated scenarios. Surveys of 11 occupants who used the TASD revealed PPD of 9% (1/11), while PPD was 14% (17/120) among participants seated elsewhere in the building. The mean level of satisfaction (LOS) was similar among the two groups and thermal sensation vote (TSV) was slightly lower for the TASD users. This study demonstrates how a personalized conditioning system could be designed and integrated into the existing esthetics of buildings to provide cooling retrofits and potentially save energy.

Assembly of Large Flip Chip Die in Ceramic Packages

Hermetic packaging is required to ensure the reliability of processors and application specific integrated circuit (ASIC) chips that are used in strategic systems, whose operating lifetimes typically exceed thirty years. Performance requirements for emerging system applications are dictating the need for one thousand or more I/O, which precludes the use of wire bonded devices. These packaging requirements can be met by flip chip bonding die onto multilayer, high temperature cofired ceramic substrates. The hermetic environment is provided by a Kovar metal ring that is brazed onto the ceramic and sealed in the final assembly step, by welding on a metal cover. Several process and design requirements must be met to achieve high reliability flip chip assemblies. Reflowed devices must be free of flux residues because they are corrosive, provide a path for ion diffusion, are a source of moisture and degrade the adhesion of underfill to chip and substrate. Removal of flux residues by cleaning is problematic because the gap between chip and substrate is very small relative to chip area. A better approach is to bond chips without flux, as we do, by reflowing them in a formic acid environment. An important reliability requirement for strategic hardware is the ability to sustain many cycles over extended temperature ranges. Temperature cycles induce plastic deformation in the solder connections as a result of stresses generated by the mismatch in thermal expansion coefficients of the chip and package. These stresses can be reduced significantly by underfilling the bonded chip with a filled adhesive. Choice of material as well as process execution impact the effectiveness of underfill enhancement of reliability. Optimization of both the physical design and composition of the solder connections is essential to producing reliable flip chip assemblies. We make extensive use of finite element analyses (FEA) in which we track the accumulation of plastic strain energy in the solder connections as they are subjected to temperature cycle induced stresses. Good correlations between the energy accumulated per cycle and the number of cycles to failure can be achieved if accurate state models of the solder are used. We have a catalog of Anand models for the solder compositions that we use in our FEA simulations. One of the more challenging aspects of designing high performance flip chip packages is matching the size and pitch of the bond pads on the ceramic with those on the chip. Current devices use 90 micron diameter pads on 200 micron pitch, but newer designs are migrating towards 80 micron diameter pads on 180 micron pitch. It challenging to maintain tight tolerances on pad geometries in these higher density packages and to route all the additional signals. Thermal management is also an important component of the package design. Thermal vias and thermally conductive underfills are used to remove heat from the front side of the chip. On the backside of the chip, the gap between chip and cover is minimized and filled with a high thermal conductivity interface material. High fidelity FEA modeling is necessary to ensure that the chip can be adequately cooled in its hermetic environment. This paper discusses the impact of these design and assembly factors on the reliability of high performance, hermetically packaged flip chip assemblies.

Investigation of decomposition and partial oxidation of mixed acid gas and methane for syngas production

Reaction processes of decomposition and partial oxidation of a mixture of acid gas (H2S and CO2) and methane (CH4) could enable the efficient production of valuable syngas resource (H2 and CO). In this work, the decomposition and partial oxidation of H2S–CH4–CO2 system was experimentally studied in a tube furnace. Effects of temperature, CH4 and CO2 addition, equivalence ratio and residence time were studied for syngas production and H2/CO variation. Extended temperature and pressure were then studied by equilibrium calculation for thermodynamic analysis in Aspen Plus software. The results showed the increasing temperature favored reactant conversion and syngas production. H2S decomposition was the dominant reaction at temperature below 1050 °C while threshold temperature for CH4 conversion over H2S was about 1100 °C. H2 was formed mainly via H2S decomposition at low temperatures. CH4 addition promoted H2 formation and conversely restrained H2S conversion. The introduction of O2 brought partial oxidation, favored the reaction rate, balanced H2/CO but reduced syngas production. H2/CO ratio also remained at an appropriate level at high CO2 addition since CO2 evidently adjusted the ratio via CO2+H2↔CO + H2O. However, this CO2 reactivity was only adequately expressed under high temperature and extended residence time. Equilibrium calculation confirmed experimental variation trends and revealed reducing pressure favored the syngas production. It could be inferred that extended residence time, higher temperature, suitable equivalence ratio, CH4 and CO2 addition and low pressure could enable improvement in both syngas production and H2/CO. This study revealed high syngas production and adjustment of H2/CO could be realized in H2S–CH4–CO2 system and this might be of great practical in industry.

An Extended Temperature Model Based on the Trapping Effect for Drain‐Source Current in GaN HEMTs

In this work, an extended temperature current–voltage (I–V) model for AlGaN/GaN high electron mobility transistors (HEMTs) is proposed. Since there is no carrier freeze‐out effect in GaN HEMTs, the current density, switching characteristics, and heat dissipation performance are significantly improved with the decrease in temperature. The threshold voltage drift phenomenon can be accurately described at various temperatures by the trapping effect control potential model. Based on Matthiessen's law, the applicable temperature range of the mobility model is further extended. At cryogenic temperatures, the saturation current, saturation velocity, and sub‐threshold swing of the device tend to saturate as well as be temperature‐independent, which can be accurately modeled by using the equivalent temperature and applying the crucial temperature to quantify the turning point. Furthermore, the SHE modeling incorporates the temperature dependence of the material's thermal conductivity. The accuracy of the model is verified by experimental data at low (4.2–300 K) and high (298–773 K) temperatures. The proposed model overcomes the limitations of existing models applied at wide ambient temperatures.

Thermoplastic film materials for damping in mechanical engineering

An effective way of damping engineering structures is to use elements formed by a combination of hard and soft alternating layers. The outer rigid layers, made of structural materials, take up force infl uences, while the soft layers of viscoelastic polymers provide energy dissipation of the layered structure. The paper summarizes the results of research on the development of thin thermoplastic fi lms of plasticized polyvinyl acetate, polybutylmethacrylate and polymethylmethacrylate which have ultra-high dissipative properties and are used as a vibration-absorbing component of composite structures. It is shown that high damping properties are realized in fi lms with thickness of 0.1 –0.05 mm, which makes it possible to obtain two- and three-layer vibration-absorbing films with an extended temperature interval of effective damping in the metal-polymer-metal structures.

Temperature sensing technique across a wide range using phosphorescence intensity ratio of Dy3+-Doped YAG/YAP

To address the need for precise temperature measurement across an extended temperature range, we successfully synthesized a temperature-sensitive phosphorescent material using a high-temperature solid-state method. This material involves the incorporation of dysprosium dopant into the yttrium aluminum garnet/yttrium aluminum perovskite (YAG/YAP) phosphor matrix. Our primary objective was to leverage the phosphorescence intensity ratio of Dy3+ energy level transitions (4F9/2 → 6H15/2, 4I15/2 → 6H15/2) in response to temperature fluctuations, enabling temperature measurements within the 100–1300 °C range. Throughout our investigation, we observed shifts in the peak wavelengths “a” and “b” attributable to thermally coupled energy level transitions as temperature increased. Specifically, at 1000 °C, the peak wavelength “a” shifted from 457.4 nm to 457.8 nm, while at 750 °C, peak wavelength “b” shifted from 497.6 nm to 497.2 nm. Subsequently, we assessed the temperature sensitivity and measurement error of the sample. Impressively, the temperature sensitivity remained consistent across various single-pulse excitation powers and even after 50 h of continuous operation. The maximum absolute sensitivity exceeded 11.21 × 10−4 °C−1, and the relative sensitivity surpassed 2.78 × 10−2 %°C−1. The minimum temperature measurement error was approximately ±2 °C. As a result, the phosphorescent YAG/YAP: Dy3+ powder demonstrates significant potential for applications within the 100–1300 °C temperature range.

Temperature dependent rate constant for the reaction of H‐atoms with carbonyl sulfide

AbstractThe kinetics of the reaction of H‐atom with carbonyl sulfide (OCS) has been investigated at nearly 2 Torr total pressure of helium over a wide temperature range, T = 255–960 K, using a low‐pressure discharge flow reactor combined with an electron impact ionization quadrupole mass spectrometer. The rate constant of the reaction H + OCS → SH + CO (1) was determined under pseudo‐first order conditions, monitoring the kinetics of H‐atom consumption in excess of OCS, k1 = 6.6 × 10−13 × (T/298)3 × exp(−1150/T) cm3 molecule−1 s−1 (with estimated total uncertainty on k1 of 15% at all temperatures). Current measurements of k1 at intermediate temperatures (520–960 K) appear to reconcile previous high and low temperature data and allow the above expression for k1 to be recommended for use in the extended temperature range between 255 and 1830 K with a conservative uncertainty of 20%.

Resonantly enhanced lumped-element O-band Mach-Zehnder modulator with an ultra-wide operating wavelength range.

We demonstrate an O-band resonantly enhanced Mach-Zehnder modulator utilizing highly overcoupled resonators with staggered resonance wavelengths that achieves an operating range of 6.6 nm (7.1 nm) with a 1 dB (3 dB) optical modulation amplitude penalty. It can be operated in a power-efficient lumped-element configuration without any tuning of the resonators in an extended temperature range of 80°C.

Convective drying of pumpkin: Brief literature review and new data for organically produced indigenous pumpkin (Cucurbita pepo L.) over an expanded temperature range

Selected cultivars form part of the neglected and underutilized species (NUS), which can contribute to building sustainable and resilient food systems, particularly for food-insecure households. Advances in the drying of pumpkin cultivars are briefly reviewed. Background on drying, including pretreatment techniques, is discussed. It emerged that convective air drying remains the most used dehydration technique, while most pretreatment and drying approaches, although innovative and promising, have not yet been investigated for pumpkin species. Areas for future scientific investigations are also suggested. A closer look at the literature data revealed notable inconsistencies for pumpkin diffusivity data even for the same species. For this reason, independently of the review, new data are reported in this study for the Cucurbita Pepo cultivar in a quest for more accuracy and a wider temperature validity range. A convective dryer using hot air was used to determine the drying characteristics of pumpkin (Cucurbita pepo L.) slices at four different temperatures (40, 45, 50, 55 and 65) °C at a constant velocity of 1.5 m/s. The extended temperature range and the large number of experimental temperatures were meant to increase the newly reported properties’ accuracy and validity range. The Page model stood out as the most accurate approach to describe the investigated dehydration process. Pumpkin effective diffusivity was calculated as 3.74–7.30 × 10−9 m2/s while the activation energy was 21.07 kJ/mol based on experiments undertaken in the present study. The newly obtained data did not solve the problem associated with inconsistencies between the two data sets found in the literature for drying the same pumpkin cultivar. The reported data would be helpful in the accurate determination of diffusivity data instrumental for convective drying process modelling and optimization.