Thermal Instability Research Articles

Die level thermal management of microelectronics using phase change materials

Phase change materials (PCMs) are a promising passive thermal management approach for electronic devices, offering the potential to extend device operational times and mitigate thermal instability by leveraging phase transition processes. However, the effectiveness of PCM-laden designs is hindered by numerous interfacial thermal resistances between the heat source and sink, particularly for high power levels and heat fluxes. Furthermore, space constraints for mobile devices make such a macroscale strategy impractical. In this work, we evaluate an alternate microscale integration strategy where we embed the PCM within the silicon die to both minimize the thermal resistance between the heat source and the PCM, and make them a viable solution for mobile devices. We fabricate thermal test vehicles (TTVs) of realistic mobile-chip form-factors with embedded metallic PCM, and experimentally evaluate them against an all-silicon counterpart. Notably, this work presents the first successful fabrication and transient thermal evaluation of a silicon device with fully-encapsulated PCM thermal energy storage. Experimental results demonstrate that embedding the PCM within the silicon die improves thermal performance, suppressing the maximum hotspot temperature rise by up to 14% and significantly reducing transient fluctuations by up to 65%. This integration strategy proves effective even under high heat flux conditions. Specifically, with an embedded square-shaped PCM reservoir, thermal stability increases by an average of 40% for a hotspot heat flux of 65 W cm-2. Additionally, an embedded-PCM TTV demonstrates stable performance for 10,000 continuous temperature cycles (total run-time of 34 h). The choices of a duty cycle time period and power level are crucial to embedded PCM effectiveness. An optimum combination of both ensures that all the embedded PCM is effectively utilized through consistent phase changes with minimal sensible heating. The substantial reduction in temperature fluctuations across multiple operational scenarios highlights the success of a PCM-based die-level thermal management approach.

Spatiotemporal characteristics and associated circulation patterns of warm-season precipitation in a complex terrain region of Southwest China

Southwest China frequently witnesses heavy precipitation during warm seasons (May–October) under the joint influence of complex topography and diverse circulation patterns. Based on the objective classification method of spectral clustering, this study identifies three dominant circulation backgrounds and investigates their pivotal roles in determining the warm-season precipitation around Cang Mountain, a complex terrain region in southwest China. Results show that the precipitation characteristics under the three typical circulation patterns are modulated by different dynamic and thermodynamic processes, and each of which has its own seasonality and diurnal variations. Cluster 1 reveals that the northeasterly winds generated by the low-level shear line and vortex on the east side of the Tibetan Plateau provide favorable dynamic conditions for the southwestward evolution of precipitation. As the zonal (meridional) components of northeasterly winds are intensified in the nighttime (daytime), the diurnal cycle of precipitation is manifested with a major (secondary) peak in the early morning (late afternoon). Cluster 2 is featured by the northward advance of the Western Pacific Subtropical High (WPSH) and the monsoon trough over the tropical region. Moreover, there is a high frequency of intense precipitation influenced by the relatively strong thermal instability. With the low-level southeasterly winds strengthening upstream of Cang Mountain at night, the diurnal cycle of precipitation exhibits a pronounced early-morning peak. In Cluster 3, southwesterly winds prevail around Cang Mountain under the configuration of the Indian-Myanmar trough and the strengthened WPSH. The precipitation shows a high percentage of weak intensity due to the relatively weak unstable stratification. These findings offer valuable insights into how circulation patterns impact the fine-scale precipitation processes over complex terrains.

MATHEMATICAL ANALYSIS AND EMPIRICAL VALIDATION OF THERMAL DENATURATION OF GLUCOKINASE

Glucokinase (GK), an enzyme critical to glucose metabolism, exhibits thermal instability, which can affect its enzymatic activity under physiological and pathological conditions. This study aims to mathematically model the thermal denaturation kinetics of GK and empirically validate the model using experimental data. To establish a mathematical model on thermal denaturation of glucokinase (E.C.2.7.1.2) and its experimental validation, the enzyme glucokinase was investigated in a 0.075[Formula: see text]M Tris HCl buffer with pH 9.0 at 30∘C and 0.6[Formula: see text]M MgCl2. A first-order kinetic model was developed to describe the enzyme’s denaturation, incorporating temperature-dependent reaction rates based on the Arrehenius equation. Empirical data were collected through Spectrophotometer across a temperature range of 20∘–60∘C. Experimental validation revealed that GK undergoes irreversible denaturation above 60∘ with a significant reduction as temperature increases. Moreover, the thermal denaturation of GK in the presence of osmolyte Urea is a critical process affecting enzyme stability and function. This study also aims to mathematically model and empirically validate the impact of Urea on GK’s thermal denaturation behavior. Results demonstrated that Urea significantly reduces the thermal stability of GK, lowering its denaturation temperature. The results are simulated graphically using the Wolfram MATHEMATICA software. The mathematical predictions closely matched experimental data, confirming the model’s accuracy.

Drug Delivery Systems Utilizing Essential Oils and Their Compounds—A Promising Approach to Fight Pathogens

Essential oils (EOs) and their compounds are becoming a growing interest in medical sciences. Despite their potential as antimicrobial, anxiolytic, cytotoxic, and immunosuppressive drugs, their chemical characteristics make them difficult to use in direct treatment. This article intends to summarize the current body of knowledge regarding drug delivery systems that can overcome obstacles, such as low water solubility, volatility, oxidation potential, photodegradation, and thermal instability of EO compounds. Various materials like zeolites, alginate, chitosan, cellulose nanomaterials, zein, poly (D,L-lactic-co-glycolic) acid, liposomes, nanoemulsions, and their modifications can help to mitigate these problems, but their utilization in medical settings is still lacking. The biggest issue in the utilization of natural compounds seems to be the very low number of clinical trials, which seriously impedes their usage despite favorable outcomes in/of in vitro experiments.

Optimization of metal polymer friction pair composition for hydrogen wear reduction through thermal stabilization analysis

The composition of the metal-polymer friction pair is carefully considered for interacting with water and hydrogen, ensuring the metals electrode process potential remains below waters in a neutral medium. Simultaneously, adherence to defined chemical composition ratios for the metal-polymer materials is crucial. This analysis is conducted under conditions of thermal stabilization, characterized by a minimal temperature gradient across the rim thickness within an equivalent thermal field. Using the quasi-chemical approximation, the paper derives a concentration-dependent diffusion coefficient of hydrogen (H) in iron (Fe) across a broad spectrum. This derivation includes electronic and vibrational contributions to the chemical potential. The research establishes a correlation between the equivalent diffusion coefficient and the concentration of diffusing hydrogen atoms from the metal, such as the pulley or drum rim. These findings offer novel insights into optimizing hydrogen wear behaviour in brake friction couples, contributing to advancements in materials and design considerations in the automotive field.

Contrasting the Intraseasonal Precipitation in the Western and Eastern North Pacific During Boreal Winter

AbstractThe wintertime North Pacific exhibits two types of intraseasonal periodicity in daily precipitation, with a period of 10–20 and 30–90 days in the western and eastern North Pacific. This study aims to identify and compare characteristics and mechanisms of intraseasonal precipitation in these two regions using daily observational data. Our results indicate their notable differences in atmospheric circulations and dynamical processes, despite similarities in moisture sources. A wave train associated with the intraseasonal precipitation in the western North Pacific characterized by anomalous cyclones and anticyclones from West Siberia into the North Pacific is observed, accompanied by anomalous wave activity. By diagnosing local finite‐amplitude wave activity (LWA) budget, we demonstrate that the baroclinic eddy generation initiates the upstream growth of wave activity, whereas its downstream development is primarily attributed to the zonal advection of wave train. The upstream wave train induces barotropic and baroclinic instabilities in Kuroshio‐Oyashio extension (KOE). In contrast, the anomalous atmospheric circulations related to intraseasonal precipitation in the eastern North Pacific feature a tripolar structure, with downstream propagation of wave activity from the eastern North Pacific to the North American continent. Diabatic heating, along with local eddy generation, contributes to the upstream growth of wave activity. Residual term, possibly linked to the wave activity dissipation associated with wave breaking, extends the wave activity downstream. Thermal and baroclinic instabilities, associated with the diabatic heating and local eddy generation, create favorable conditions for the precipitation. This study may contribute to the improvement of intraseasonal precipitation prediction over the pan‐North Pacific region.

Frequency-Modulated Antipodal Chaos Shift Keying Chaotic Communication on Field Program Gate Array: Prototype Design and Performance Insights

Using chaos for communication can provide more robust channel security, covert transmission, and inherent support for spread-spectrum modulation. Although numerous studies have explored this technology, its practical deployment remains limited due to substantial hardware demands, complex signal processing, and a lack of efficient modulation methods for chaotic signals. In this study, a novel chaotic digital communication system is proposed and studied. A prototype of a frequency-modulated antipodal chaos shift keying (FM-ACSK) system is implemented on an Intel Cyclone V field-programmable gate array (FPGA) along with a complete mathematical model using Matlab R2022a Simulink software. Using FPGAs to implement chaotic oscillators avoids analog system problems such as component drift and high thermal instability while providing determined system parameters, rapid prototyping, and high throughput. The employment of FM over a chaotic modulation layer provides a passband operation (currently at an intermediate frequency of 10.7 MHz) while adding the benefits of carrier frequency offset robustness and constant signal envelope. Within this study, the robustness of FM-ACSK to white noise in the channel was evaluated using bit error rate, which was tested through hardware experiments and simulations. The results show the feasibility and potential performance limitations of this approach to chaotic communication system design.

Development and synthesis of anti‐zinc burn and antibacterial Schiff base zinc complexes as multi‐functional thermal stabilizers for PVC formulations

AbstractPolyvinyl chloride (PVC) thermal stabilizers are evolving toward greater efficiency and multifunctionality. This study aims to develop a multifunctional thermal stabilizer to meet the diverse application requirements. A Schiff base, VanHis, was synthesized by condensing histidine with vanillin, and its zinc salt derivative, VanHis‐Zn, was prepared by reacting VanHis with anhydrous zinc acetate. Infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and thermogravimetric analysis confirmed the successful synthesis. Thermal stability tests, including oven aging, thermogravimetric, conductivity, and Congo red tests, were conducted. Results showed that VanHis‐Zn delayed zinc burn, with complete discoloration occurring after 120 min. Compared to commercially available calcium/zinc stearate stabilizers, VanHis‐Zn exhibited the lowest weight loss rates in both the first (72.26%) and second (17.21%) stages. Additionally, dynamic mechanical analysis (DMA) and UV‐absorption spectroscopy confirmed that VanHis‐Zn suppressed the formation of conjugated double bonds during PVC thermal degradation. When blended with varying proportions of Ca(acac)2, the initial whiteness and long‐term thermal stability of PVC samples improved significantly, doubling the stability time compared to conventional systems. Antibacterial tests also demonstrated that both VanHis‐Zn and the blended PVC samples exhibited antibacterial properties. Quantum chemical calculations were performed to analyze the thermal stabilization mechanism using NPA charge distribution analysis.Highlights VanHis‐Zn from biomass enhances PVC stability under heat and delays zinc burning. VanHis‐Zn imparts antibacterial properties and inhibits PVC conjugated bond formation. Thermal stability mechanism analyzed via quantum chemical and NPA charge analysis.

A Study on Structural Changes During the Thermal Stabilization Stage of Hemp Fibers Impregnated with Phosphoric Acid Before Carbonization and Activation

Abstract After being wet treated with 4% phosphoric acid (H3PO4) aqueous solution, industrial hemp fiber was subjected to thermal stabilization processes at temperatures of 160, 180, 200, 220, 240 and finally 250 °C and holding times of 30 min. Some basic analyses were used to determine the structural and characteristic changes of all samples for the thermal stabilization of hemp fibers in an oxygen environment before the carbonization and activation processes. These included linear density, fiber thickness, flame testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (IR), X-ray diffraction, and Scanning Electron Microscopy (SEM) measurements. DSC analysis showed that impregnation of the phosphoric acid (PA) mixture increased thermal stabilization and prevented the formation of volatile products by blocking the hydroxyl groups in the cellulose structure. TGA thermograms showed an increase in carbon yield at increasing stabilization temperature values. The results from XRD indicated that the cellulose II crystal structure disappears with the increase of the stabilization temperature and an amorphous structure appears. IR spectra show that the partial loss of intramolecular and intermolecular hydrogen bonds continues as a result of the simultaneous removal of hydroxyl groups and water removal reactions. After a 250 °C stabilization, the carbon yield at 900 °C was 42%. These findings highlight the importance of H3PO4 in accelerating the formation of an aromatic structure, which is critical for withstanding the high temperatures of subsequent carbonization and activation stages. Graphical abstract

Engineering of an Alkaline Feruloyl Esterase PhFAE for Enhanced Thermal Stability and Catalytic Efficiency Through Molecular Dynamics and FireProt

Feruloyl esterases (FAEs) play critical roles in industrial applications such as food processing, pharmaceuticals, and paper production by breaking down plant cell walls and releasing ferulic acid. However, most bacterial FAEs function optimally in acidic environments, limiting their use in alkaline industrial processes. Additionally, FAEs with alkaline activity often lack the thermal stability required for demanding industrial conditions. In this study, an alkaline feruloyl esterase, PhFAE, from Pandoraea horticolens was identified that exhibits high catalytic activity but suffers from thermal instability, restricting its broader industrial applications. To address this limitation, molecular dynamics simulations were used to analyze enzyme stability, and FireProt, an automated computational tool, was employed to design stabilizing mutations. The engineered S155F mutant demonstrated a 7.8-fold increase in half-life at 60 °C and a 1.72-fold improvement in catalytic efficiency (Kcat/Km), corresponding to 680% and 72% enhancements, respectively, compared to the wild-type enzyme. Molecular docking and dynamics simulations revealed that these enhancements were likely due to increased hydrophobic interactions and altered surface charge, which stabilized the enzyme’s structure. This study provides an effective strategy for improving the functional properties of FAEs and other industrial enzymes, broadening their applicability in diverse industrial processes.

Exploiting latent microbial potentials for producing polyhydroxyalkanoates: A holistic approach.

Plastics are versatile, however, nonbiodegradable polymers that are primarily derived from fossil fuels and pose notable environmental challenges. However, biopolymers, such as polyhydroxyalkanoates (PHAs), poly(lactic acid), starch, and cellulose have emerged as sustainable alternatives to conventional plastics. Among these, PHAs stand out as strong contenders as they are completely bio-based and biodegradable and are synthesized by microbes as an energy reserve under stress conditions. Despite their limitations, including low mechanical strength, susceptibility to degradation, a restricted scope of application, and high production costs, biopolymers have promising potential. This review explores strategies for enhancing PHA production to address these challenges, emphasizing the need for sustainable PHA production. These strategies include selecting robust microbial strains and feedstock combinations, optimizing cell biomass and biopolymer yields, genetically engineering biosynthetic pathways, and improving downstream processing techniques. Additives such as plasticizers, thermal stabilizers, and antioxidants are crucial for modifying PHA characteristics, and its processing for achieving the desired balance between processability and end-use performance. By overcoming these complications, biopolymers have become more viable, versatile, and eco-friendly alternatives to conventional plastics, offering hope for a more sustainable future.

First-principles predictions of two-dimensional Ce-based ferromagnetic semiconductors: CeF2 and CeFCl monolayers.

Two-dimensional (2D) ferromagnetic (FM) semiconductors hold great promise for the next generation spintronics devices. By performing density functional theory first-principles calculations, both CeF2 and CeFCl monolayers are studied, our calculation results show that CeF2 is a FM semiconductor with sizable magneto-crystalline anisotropy energy (MAE) and high Curie temperature (290 K), but a smaller band gap and thermal instability indicate that it is not applicable at higher temperature. Its isoelectronic analogue, the CeFCl monolayer, is a bipolar FM semiconductor, its dynamics, elastic, and thermal stability are confirmed, our results demonstrate promising applications of the CeFCl monolayer for next-generation spintronic devices owing to its high Curie temperature (200 K), stable semiconducting features, and stability. Under biaxial strain from -5% to 5%, the CeFCl monolayer is a semiconductor with sizable MAE, its Curie temperature can increase to 240 K, the easy magnetization axes for CeFCl monolayer are still along the out-of-plane directions because the couplings between Cef y(3x 2-y 2) and f x(x 2-3y 2) orbitals in the different spin channels contribute most to the MAE according to second-order perturbation theory.

Review of: "Investigating and Analyzing The Process of Thermal instability (Nanoparticles) in The Change Structure of The Structure and Structure of Nanomaterials"

Review of: "Investigating and Analyzing The Process of Thermal instability (Nanoparticles) in The Change Structure of The Structure and Structure of Nanomaterials"

Review of: "structure of nanomaterials, one of the thermal phenomena caused by the shrinking of the material structure is the thermal instability of nanoparticles"

Review of: "structure of nanomaterials, one of the thermal phenomena caused by the shrinking of the material structure is the thermal instability of nanoparticles"

Copper Tantalate by a Sodium-Driven Flux-Mediated Synthesis for Photoelectrochemical CO2 Reduction.

Copper-tantalate, Cu2Ta4O11 (CTO), shows significant promise as an efficient photocathode for multi-carbon compounds (C2+) production through photoelectrochemical (PEC) CO2 reduction, owing to its suitable energy bands and catalytic surface. However, synthesizing CTO poses a significant challenge due to its metastable nature and thermal instability. In this study, this challenge is addressed by employing a flux-mediated synthesis technique using a sodium-based flux to create sodium-doped CTO (Na-CTO) thin films, providing enhanced nucleation and stabilization for the CTO phase. To evaluate the PEC performance and catalytic properties of the films, copper(II) oxide (CuO) at the Na-CTO surface is selectively etched. The etched Na-CTO shows a lower dark current, with decreased contribution from photocorrosion, unlike the non-etched Na-CTO which has remaining CuO on the surface. Furthermore, Na-CTO exhibits 7.3-fold ethylene selectivity over hydrogen, thus highlighting its promising potential as a photocathode for C2+ production through PEC CO2 reduction.

Thermodynamic aspects of higher-dimensional black holes in Einstein–Gauss–Bonnet gravity through exponential entropy

Abstract We assume exponential corrections to the entropy of $5D$ charged AdS
black hole solutions, which are derived within the framework of
Einstein Gauss-Bonnet gravity and nonlinear electrodynamics.
Additionally, we consider two distinct versions of $5D$ charged AdS
black holes by setting the parameters $q\rightarrow0$ and
$k\rightarrow0$ (where $q$ represents charge, $k$ is the non-linear
parameter). We investigate these black holes in the extended phase
space, where the cosmological constant is interpreted as pressure,
and demonstrate the first law of black hole thermodynamics. The
focus extends to understanding the thermal stability or instability,
as well as identifying first and second-order phase transitions.
This exploration is carried out through the analysis of various
thermodynamic quantities, including heat capacity at constant
pressure, Gibbs free energy, Helmholtz free energy, and the trace of
the Hessian matrix. In order to visualize phase transitions,
identify critical points, analyzing stability and provide
comprehensive analysis, we have made the contour plot of the
mentioned thermodynamic quantities and observed that our results are
very much consistent. These investigations are conducted within the
context of exponentially corrected entropies, providing valuable
insights into the intricate thermodynamic behavior of these $5D$
charged AdS black holes under different parameter limits.

Enhanced Ion Solvation and Conductivity in Lithium-Ion Electrolytes via Tailored EMC-TMS Solvent Mixtures: A Molecular Dynamics Study.

The development of stable, high-performance electrolytes is essential to addressing the safety concerns and limited lifespan caused by the thermal and chemical instability of traditional organic carbonate-based electrolytes in lithium-ion batteries (LIBs). This study examined the potential of mixed solvent systems, specifically ethyl methyl carbonate (EMC) and tetramethylene sulfone (TMS), to modify ion solvation and improve ionic conductivity in LIB electrolytes. Through molecular dynamics simulations, we investigated the solvation structure and transport properties of lithium ions (Li+) in these solvent environments. The inclusion of TMS altered the solvation structure, with TMS molecules preferentially coordinating with Li+ ions, displacing PF6 - anions and reducing their electrostatic interference. Our results demonstrated a synergistic interaction between EMC and TMS, where an EMC/TMS ratio of 1:2 led to a significant improvement in ionic conductivity, reaching 0.91 mS/cm, with a corresponding Li+ transference number of 0.40. These findings provide key insights into the molecular-level interaction governing electrolyte behavior, offering guidance for the design of future solvent mixtures to improve the safety and efficiency of LIBs.

Peptide-Scaffolded Detergents for Membrane Protein Studies.

Detergents are essential for preserving the structural integrity and functionality of membrane proteins (MPs) outside the biological membrane or in aqueous solution, and thus ensuring accurate biochemical and structural analyses. Here, we introduce peptide-scaffolded detergents, a novel class of hybrid molecules formed by preassembling detergent monomers with peptides of varying lengths, mediated via Click chemistry. These detergents are characterized by scalable, straightforward synthesis and enhanced solubility. Among the variants, A4B2 emerged as the optimal detergent, demonstrating superior thermal stabilization across a range of G protein-coupled receptors, including A2AAR, SMO and GLP-1R. Additionally, A4B2 exhibits a low critical micelle concentration and small micelle size, together making it particularly effective for electron microscopy studies of A2AAR. This innovative design leverages the benefits of peptide-based and traditional detergents, offering new insights for the development of advanced detergents in MP research.

Unveiling the potential of pullulan in enhancing ketoprofen release from PHBV filaments.

In this study, sustainable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and pullulan (PUL)/PHBV filaments were prepared with ketoprofen for scaffold preparation. The research aimed evaluate the influence of pullulan in the filament properties, such as thermal, morphological, and biological behavior. Hansen parameters demonstrated the difference in the miscibility of the polymers and drug in the blend. This difference in solubility contributed to thermal stabilization, and reduced the crystallinity of the blend, observing a reduction in crystalline peak at 30.82° (002). The morphology change was observed by SEM images, in which ketoprofen appears to smooth and homogenize the filament surface. Cytotoxicity tests on osteoblast cells confirmed that all samples were biocompatible, and the presence of ketoprofen was comparable to the control group. Importantly, the in vitro release of ketoprofen revealed that the presence of pullulan increased the cumulative release of ketoprofen, from 0.1% to 36%, within 240min of the dissolution test. This highlights the crucial role of pullulan in fine-tuning drug release. These findings underscore the potential of these materials for bone regeneration applications, combining the cytotoxic and cell adhesion properties of PHBV with the osteoblasts, and offering precise control over the degradation process and drug release through the incorporation of pullulan.

THE EFFECTS OF SEPIOLITE LOADINGS ON MECHANICAL, THERMAL, AND MORPHOLOGICAL CHARACTERISTICS OF NATURAL RUBBER/EPOXIDISED NATURAL RUBBER (NR/ENR-25) BLENDS

Sepiolite has been used widely as nanofillers to improve the properties and compatibility of rubber blends, and due to its magnesium silicate hydrates contents, the sepiolite may also function as a thermal stabilizer. These works investigate the effects of sepiolite loadings on curing, mechanical, thermal, and morphological characteristics of natural rubber/epoxidized natural rubber (NR/ENR-25) blends. The blends were made using a two-roll mill technique using standard vulcanization reagents of sulfur and carbon black as the main filler, and their vulcanization characteristics were investigated using the rheometry technique. Furthermore, the thermal, mechanical, and morphological characteristics of the blends were evaluated using thermogravimetry, tensile tests, and electron microscopy, respectively. It was found that an increase in the sepiolite loadings decreased scorch times (ts2 and t90), whereas optimum sepiolite loading with higher tensile strength was 3 phr, which lowered down when the sepiolite loading was increased up to 9 phr. The thermogram of blend specimen with 3 phr sepiolite loading also exhibited superior thermal stability, that is, has higher degradation temperature at 5% weight loss. Fracture surface SEM photographs of the blend specimens showed finely distributed sepiolite particles at optimum sepiolite loading 3 phr and exhibited agglomerations when the loadings were increased up to 9 phr.