Thermal Instability Research Articles

Significant Lifetime Improvement of Negative Bias Thermal Instability by Plasma Enhanced Atomic Layer Deposition SiN in Stress Memorization Technique

Significant Lifetime Improvement of Negative Bias Thermal Instability by Plasma Enhanced Atomic Layer Deposition SiN in Stress Memorization Technique

Ferrocene-Modified Polyacrylonitrile-Containing Block Copolymers as Preceramic Materials.

In the pursuit of fabricating functional ceramic nanostructures, the design of preceramic functional polymers has garnered significant interest. With their easily adaptable chemical composition, molecular structure, and processing versatility, these polymers hold immense potential in this field. Our study succeeded in focusing on synthesizing ferrocene-containing block copolymers (BCPs) based on polyacrylonitrile (PAN). The synthesis is accomplished via different poly(acrylonitrile-block-methacrylate)s via atom transfer radical polymerization (ATRP) and activators regenerated by electron transfer ATRP (ARGET ATRP) for the PAN macroinitiators. The molecular weights of the BCPs range from 44 to 82 kDa with dispersities between 1.19 and 1.5 as determined by SEC measurements. The volume fraction of the PMMA block ranges from 0.16 to 0.75 as determined by NMR. The post-modification of the BCPs using 3-ferrocenyl propylamine has led to the creation of redox-responsive preceramic polymers. The thermal stabilization of the polymer film has resulted in stabilized morphologies based on the oxidative PAN chemistry. The final pyrolysis of the sacrificial block segment and conversion of the metallopolymer has led to the formation of a porous carbon network with an iron oxide functionalized surface, investigated by scanning electron microscopy (SEM), energy dispersive X-ray mapping (EDX), and powder X-ray diffraction (PXRD). These findings could have significant implications in various applications, demonstrating the practical value of our research in convenient ceramic material design.

Experimental Investigation of Thermal Performancefor Novel Integrated Collector Storage

To lower the expenses of manufacturing traditional solar collectors and perfect use of water tanks in developing countries, a new design of integrated water heaters has been presented in a rhombus shape. This new design consists of a cube whose upper surface was cut into two directions at a 45o angle. This system's initial expenses can be kept to a minimum by using inexpensive commercial materials and little manufacturing skills. In cases of thermal instability, the MUE curve is typically employed to calculate the maximum efficiency that the system can attain. The MUE curve, which saves time and computer approaches in calculations of this kind, is the basis for this study. This experiment was studied during November and March to compare the system behavior under different climate conditions. The study included three cases per month. The first case was without any load, which reached a maximum useful efficiency of 59% for both November and March. In the case of continual loading, the system shows a maximum useful efficiency of 59% in March. When dealing with intermittent load, the maximum useful efficiency of 58% in March.

Structure and Properties of Thermally Stabilized and Ecologically Friendly Organic Cotton Fibers as a New Activated Carbon Fiber Precursor

Organic cotton precursor yarn was impregnated in an aqueous solution consisting of diammonium hydrogen phosphate (DAP), boric acid (BA), and urea (U) mixtures before the thermal stabilization stage and then subjected to heat treatments in an air environment at 245 °C. The effect of chemical pretreatment on organic cotton yarn was examined using methods such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy. The XRD analysis revealed a gradual decrease in the crystalline structure, attributed to the disruption of intermolecular hydrogen bonds. DSC and TGA measurements showed an improved thermal stability due to the formation of pre-graphitic structures with aromatic entities at higher temperatures. For samples chemically impregnated and then stabilized, the char yield values increased from 25% to 68% at 500 °C and 23% to 53% at 1000 °C. Analysis of IR spectra indicated a gradual reduction in both intermolecular and intramolecular hydrogen bonds associated with dehydration and dehydrogenation reactions. The IR spectra also confirmed a decrease in crystallinity with increasing oxidation time, which is consistent with the findings from X-ray diffraction. In addition, the IR spectra showed the presence of C = C bonds, indicating the formation of a crosslinked ladder-like structure. The results showed that DAP-BA-U integration increased the thermal stability of organic cotton fibers and the obtained samples were ready for the next stage, carbonization.Graphical

Accelerated multistep thermal stabilization of polyacrylonitrile fibers using an ethylenediamine pretreatment

The polyacrylonitrile multifilament yarn underwent a multistep heat treatment process including stabilization times ranging from 5 to 75 min following impregnation with a 30% ethylenediamine (EDA) aqueous solution. A series of measurements were employed to determine the structure and properties of thermally stabilized PAN samples. These included fiber thickness, fiber density, flame testing, tensile testing, X-ray diffraction, thermal analysis (differential scanning calorimetry and thermogravimetric analysis), and infrared spectroscopy. The results from XRD and IR spectroscopy indicated that the rate of aromatization reactions increased with longer stabilization times. A detailed examination of the XRD curves obtained through curve-fitting procedures suggested a rapid transformation of the original structure into a disordered amorphous phase containing pre-graphitic domains, evidenced by a gradual reduction in the degree of apparent crystallinity of the original PAN sample. The integration of EDA before the thermal stabilization stage significantly reduced the cyclization time of nitrile groups in the PAN polymer structure, thereby accelerating the stabilization reactions. This chemical pretreatment also improved the thermal stability of the samples by promoting oxidative cross-linking of the PAN polymer chains. After a 75 min multistep stabilization, the carbon yield at 1000 °C was 70.5%. Conversion index values, calculated using IR, XRD, and DSC methods, were 98.3%, 94.8%, and 89.5% respectively for the 75 min sample. These findings highlight the importance of EDA in accelerating the formation of an aromatic structure, which is critical for withstanding the high temperatures of subsequent carbonization stages.Graphical abstract

Techno-economic analysis of cleaner alternatives for recovering ammonium chloride from wastewater generated by polyvinyl chloride thermal stabilizer plants

The current conventional process for recovering NH4Cl from wastewater generated by organotin mercaptide-based polyvinyl chloride thermal stabilizer plants through evaporative crystallization is energy intensive and has not yet been discussed. Three energy-saving process variants, namely mechanical vapor recompression (MVR), double-effect evaporation (DEE), and thermal vapor recompression (TVR) processes, have been proposed and evaluated in terms of both technical and economic feasibility, treating the case as a cost-cutting project aimed to avoid off-site wastewater treatment costs. Comparative evaluation has also been carried out with the conventional (CON) process used as a reference. Under the studied conditions, the MVR, DEE, and TVR processes provided energy savings in the ranges of 60%–76%, 35%–43%, and 26%–37%, respectively, confirming that applying the three alternative processes for recovering NH4Cl results in a significantly cleaner and more sustainable recovery process. Under typical conditions and with a plant capacity of 5000 kg/h, the MVR, DEE, and TVR processes required an additional investment of 2.3, 1.0, and 0.2 million USD, respectively, compared to the CON process. The revenue was primarily driven by cost savings due to the elimination of off-site wastewater treatment, which accounted for 86.9% of the total revenue. Sensitivity analysis showed that the off-site wastewater treatment cost was found to be the most influential factor on economic feasibility. When economic targets can be traded off, MVR process is highly recommended as an alternative to the conventional energy-intensive process. If economic feasibility comparable to the conventional process is still targeted, DEE and TVR are recommended. The results of this study dismiss concerns that cleaner processes would have a negative economic impact.

Thermal instability in an inclined fluid layer subjected to Couette–Poiseuille flow

The present work deals with the onset of thermal instability in an inclined fluid layer subjected to Couette–Poiseuille flow. We consider the configuration in which one boundary is maintained at a constant temperature and the other boundary is imposed with a constant heat flux. The collocation method, based on Chebyshev polynomials, is used to discuss the instability of the flow with respect to the thermal Rayleigh number. It is found that there exists a value of the angle of inclination below which the instability sets in as longitudinal rolls, and the critical value of the Rayleigh number remains unaffected by superimposed Couette–Poiseuille flow. However, for angles of inclination greater than this threshold value, the critical mode of instability is transverse mode, and the critical value of the Rayleigh number is significantly affected by the superposition of Couette–Poiseuille flow. Further, the onset of instability also depends upon the Prandtl number of the fluid.

The CUPID neutrinoless double-beta decay experiment

Neutrinoless double-beta decay (0νββ) is a key process to address some of the major outstanding issues in particle physics, such as the lepton number conservation and the Majorana nature of the neutrino. The next-generation of experiments aims at covering the Inverted-Ordering region of the neutrino mass spectrum, with sensitivities on the half-lives greater than 1027 years. Among the exploited techniques, low-temperature calorimetry has proved to be a very promising one, and will keep its leading role in the future thanks to the CUPID experiment. CUPID will search for the neutrinoless double-beta decay of 100Mo. By deploying Li2MoO4 scintillating crystals enriched in 100Mo and cryogenic light detectors, CUPID will perform simultaneous readout of heat and light signals, allowing for particle identification, and thus a powerful rejection technique for α background. To meet the new sensitivity target, the CUORE readout system must be upgraded. The readout system for each channel will consist of a pre-amplifier, a Programmable Gain Amplifier (PGA), a low-pass filter (Bessel filter) and a Digital AcQuisition System (DAQ). Finally, there is a pulser to generate thermal stabilization energy in the crystals. The motivation and expected performance of the technical upgrades are described in the context of the goals of the CUPID experiment.

Directly Suppressing MYC Function with Novel Alkynyl-Substituted Phenylpyrazole Derivatives that Induce Protein Degradation and Perturb MYC/MAX Interaction.

Despite being a highly sought-after therapeutic target for human malignancies, myelocytomatosis viral oncogene homologue (MYC) has been considered intractable due to its intrinsically disordered nature, making the discovery of in vivo effective inhibitors that directly block its function challenging. Herein, we report structurally novel alkynyl-substituted phenylpyrazole derivatives directly perturbing MYC function. Among them, compound 37 exhibited superior antiproliferative activities to those of MYCi975 against multiple malignant cell lines. It induced dose-dependent MYC degradation in cells with degradation observed at the concentration as low as 1.0 μM. Meanwhile, its direct suppression of MYC function was confirmed by the capability to inhibit the binding of MYC/MYC-associated protein X (MAX) heterodimer to DNA consensus sequence, induce MYC thermal instability, and disturb MYC/MAX interaction. Moreover, 37 demonstrated enhanced therapeutic efficacy over MYCi975 in a mouse allograft model of prostate cancer. Overall, 37 deserves further development for exploring MYC-targeting cancer therapeutics.

New insights into the resistance of silica aerogel to temperature up to 1200 °C

Silica aerogel (SA) with high specific surface area (903 m2/g) and pore volume (6.81 cm3/g) was synthesized via base-catalyzed one-step sol–gel process. Thermal stability of SA under high temperature was estimated from structure evolution with temperature and time. The results demonstrate that the SA is thermally stabile at 1000 °C within 120 min (leaving specific surface area of 286 m2/g and pore volume of 1.46 cm3/g) and 1200 °C within 30 min (leaving specific surface area of 129 m2/g and pore volume of 0.59 cm3/g). The research provides new insights into the resistance of silica aerogels to high temperature, which is significant for application under harsh conditions.

Effect of temperature gradient on the chemical structure and physical morphology of polyacrylonitrile fibers during thermal stabilization process

The thermal stabilization process is a crucial stage for microstructure transformation and quality of carbon fibers, which is determined by the stabilization temperature gradient. In this work, the effect of the temperature gradient on the evolution of both chemical structures and physical morphology of polyacrylonitrile (PAN) fibers at multistage of thermal stabilization process was investigated. Combined with functional groups, oxygen element content, and aromatization index, increasing temperature reasonably shifted oxidation and cyclization reaction into early stage and the corresponding samples possessed relatively large degree of cyclization. It was worth noting that high stabilization temperature gradient could accelerate the formation of the conjugated structures at early stage and facilitate the cyclization reaction in the stabilized fibers. As for morphologies, there were aligned microfibrils and transvers lamellae in stabilized fibers. Their radial structure difference increased firstly and then decreased in the later stage. The tensile strength and tensile modulus decreased during the thermal stabilization process. Moreover, increasing temperature resulted in reduction of tensile strength and tensile modulus, which was mainly resulted by the high degree of cyclization instead of structural defects. These results guide the design and optimization of temperature program and adjusting the processing parameters for all commercially PAN fibers without any additional conditions.

Enhanced L-theanine production through semi-rational design of γ-glutamylmethylamide synthetase from Methylovorus mays

The thermal instability of γ-glutamylmethylamide synthetase (GMAS) from Methylovorus mays has imposed limitations on its industrial applications, affecting both stability and activity at reaction temperatures. In this study, disulfide bridges were introduced through a combination of directed evolution and rational design to enhance GMAS stability. Among the variants that we generated, M12 exhibited a 1.46-fold improvement in relative enzyme activity and a 6.23-fold increase in half-life at 40℃ compared to the wild-type GMAS. Employing variant M12 under optimal conditions, we achieved the production of 645.7 mM (112.49 g/L) L-theanine with a productivity of 29.3 mM/h, from 800 mM substrate in an ATP regeneration system. Our strategy significantly enhances the biosynthesis efficiency of L-theanine by preserving the structural stability of the enzyme during the catalysis process.

Gold-Thiolate Nanocluster Dynamics and Intercluster Reactions Enabled by a Machine Learned Interatomic Potential.

Monolayer protected metal clusters comprise a rich class of molecular systems and are promising candidate materials for a variety of applications. While a growing number of protected nanoclusters have been synthesized and characterized in crystalline forms, their dynamical behavior in solution, including prenucleation cluster formation, is not well understood due to limitations both in characterization and first-principles modeling techniques. Recent advancements in machine-learned interatomic potentials are rapidly enabling the study of complex interactions such as dynamical behavior and reactivity on the nanoscale. Here, we develop an Au-S-C-H atomic cluster expansion (ACE) interatomic potential for efficient and accurate molecular dynamics simulations of thiolate-protected gold nanoclusters (Aun(SCH3)m). Trained on more than 30,000 density functional theory calculations of gold nanoclusters, the interatomic potential exhibits ab initio level accuracy in energies and forces and replicates nanocluster dynamics including thermal vibration and chiral inversion. Long dynamics simulations (up to 0.1 μs time scale) reveal a mechanism explaining the thermal instability of neutral Au25(SR)18 clusters. Specifically, we observe multiple stages of isomerization of the Au25(SR)18 cluster, including a chiral isomer. Additionally, we simulate coalescence of two Au25(SR)18 clusters and observe series of clusters where the formation mechanisms are critically mediated by ligand exchange in the form of [Au-S]n rings.

Interdiffusion mechanism of hybrid interfacial layers for enhanced electrical resistivity and ultralow loss in Fe-based nanocrystalline soft magnetic composites

Soft magnetic composites (SMCs) composed of ferromagnetic particles and insulating binder are highly desired in energy-saving and high-efficiency devices for their high electrical resistivity and softer saturation characteristics. However, traditional insulation coatings are facing thermal instability, inhomogeneous distribution, and magnetic dilution, presenting a major challenge for the trade-off relationship between power loss and permeability. Here, the phosphate-coated FeSiBCuNb/SiO2 SMC is successfully fabricated by a unique interdiffusion effect in hybrid interfacial layers, which shows a combination of ultralow power loss of 135.8 kW/m3 (50 kHz/100 mT), high effective permeability of 80.6, and good temperature stability. The interdiffusion behavior between Si/O and Fe/P/O elements promotes the formation of ultrathin, uniform, and multilayer interface structure, which alleviates the magnetic dilution. Penetrating oxidation at the edge interface and elements interdiffusion effect contribute to a higher electrical resistivity induced by hot isostatic pressing with rapid quenching, leading to a low eddy current loss. Synergistic effect of isostatic pressures and rapid quenching facilitates the formation of high-density Cu clusters corresponding to ultrafine microstructure, which is beneficial for low coercivity and low hysteresis loss. This study involves the interdiffusion mechanism of hybrid interfacial layers and nanocrystalline behavior, providing a new strategy for the next-generation of high-performance SMCs.

Impacts of neutral collisions and finite electron inertia on longitudinal thermal instability of two-component radiative plasma for star formation in interstellar medium (ISM)

The impact of neutral friction, finite electron inertia and radiative heat-loss function on the thermal instability of viscous two-component plasma has been explored, integrating the impacts of thermal conductivity. A general dispersion relation is gained by means of the normal mode analysis scheme with the assist of appropriate linearized perturbation equations of the problem, and an amended circumstance of thermal instability is acquired. For the case of longitudinal propagation, it is obvious that the circumstance of thermal instability is independent of the finite electron inertia, magnetic field strength and viscosity of two components but relies on the radiative heat-loss function, thermal conductivity and neutral particle. From the curves, it is clear that the temperature-dependent heat-loss function, thermal conductivity and viscosity of two components represent stabilizing impact, while finite electron inertia and neutral collision depict destabilizing impact. Results discussed in this problem are helpful for star formation in ISM.

Emergent Antiferroelectric Ordering and the Coupling of Liquid Crystalline and Polar Order

Polar liquid crystals possess 3D orientational order coupled with unidirectional electric polarity, yielding fluid ferroelectrics. Such polar phases are generated by rod‐like molecules with large electric dipole moments. 2,5‐Disubstituted 1,3‐dioxane is commonly employed as a polar motif in said systems, and herein it is shown to suffer from thermal instability as a consequence of equatorial‐trans to axial‐trans isomerism at elevated temperatures. Isosteric building blocks are utilized as potential replacements for the 1,3‐dioxane unit, and in doing so new examples of fluid ferroelectric systems are obtained. For binary mixtures of certain composition, the emergence of a new fluid antiferroelectric phase, a finding not observed for either of the parent molecules, is observed. This study also reveals a critical tipping point for the emergence of polar order in otherwise apolar systems. These results hint at the possibility for uncovering new highly ordered polar liquid‐crystalline phases and delineate distinct transition mechanisms in orientational and polar ordering.

A demethylated lignin improved PVA-based supramolecular plastic with tough, degradable, and water-resistant performances

Poly (vinyl alcohol) (PVA), as an excellent degradable plastic feedstock, is limited by its diminishing stability in wet environment, low strength, thermal instability and nonopaque properties. In response to these concerns, a PVA/demethylated lignin-based supramolecular plastic (DPVA-HA-Fe-5) was designed and produced from PVA, demethylated lignin (DL), humic acid (HA) and Fe3+ ions via a simple casting method. As compared with pure PVA plastic, the tensile strength of DPVA-HA-Fe-5 were increased by 411 % to 410.61 MPa, and the breaking strain was increased by 149 % to 239.47 %. Notably, the hydrophobicity of DPVA-HA-Fe-5 was also significantly improved. Although in highly humid environment (stored in RH = 100 % for 10 days) or in alkaline organic solvent (stored in pyridine for 3 h), DPVA-HA-Fe-5 also showed excellent mechanical strengths of 302.9 and 222.99 MPa, respectively, which are equivalent or even superior to the most of commercial petroleum-based plastics. Moreover, the prepared plastics showed an outstanding UV resistance and shading performance, and about 98.3 % protection against ultraviolet radiation B rays and 90.7 % protection against visible light were obtained. In short, the introduction of lignin to improve the performance of PVA-based plastic is a feasible method, and it could facilitate the development of high-value utilization of lignin.

Thermal runaway and combustion of lithium-ion batteries in engine room fires on oil/electric-powered ships

The thermal characteristics of traditional fuel fires can be altered by the thermal instability of lithium-ion batteries (LIBs) in–oil-electric hybrid ships. The thermal runaway (TR) and combustion of 18,650 LiFePO4 LIBs with 0 %, 50 %, and 100 % states of charge (SOC) in pool fires were studied with different annular n-heptane pools. The goal is to simulate the thermal safety of LIBs in hybrid ships within the thermal environment of pool fires. The flame morphologies resulting from the combustion of the battery and pool fires, temperatures of the battery surface and flame, exhaust characteristics of the battery, heat radiated from the pool fire to the battery, and mass losses were analyzed. The results showed that the risks of thermal runaway and combustion with LIBs were significantly higher in a thermal fire environment. Lithium batteries produce jet fires that increase the width and height of the flame during pool fires. Moreover, the battery with a 0 % SOC doesn’t experience thermal runaway during the fire, but thermal runaway of the battery with a 100 % SOC is more severe than that of the battery with a 50 % SOC, and the maximum rates for their temperature increases are 12.98 °C/s and 7.12 °C/s, respectively. In addition, the energy balance method showed that the pressure relief by the battery safety valve during a fire was not dependent on the SOC. An equivalent network diagram was constructed for the radiative heat transfer between the lithium battery and the pool fire. It is proposed that the total heats required to induce thermal runaway of batteries with the same SOCs are almost the same in different thermal environments, but the energy required for the 50 % SOC battery is greater than that required for the 100 % SOC battery, 10,161 ± 59 J and 9724 ± 43 J, respectively. Moreover, the combustion rates were proportional to the height of the flame during the mixed combustion of a lithium battery jet fire and pool fire. A dimensionless model was developed for the relationship between flame height and mixed combustion rate.

Present day mantle structure from global mantle convection models since the Cretaceous

SUMMARY Using forward mantle convection models starting at 140 Ma, and assimilating plate reconstructions as surface velocity boundary condition, we predict present-day mantle structure and compare them with tomography models, using geoid as an additional constraint. We explore a wide model parameter space, such as different values of Clapeyron slope and density change across 660 km, density and viscosity of the thermochemical piles at the core–mantle boundary (CMB), internal heat generation rate, and model initiation age. We also investigate the effects of different strengths of a weak layer below 660 km and weaker asthenosphere and slabs. Our results suggest that slab structures at different subduction zones are sensitive to the viscosity of the asthenosphere, strength of slabs, values of Clapeyron slope and the density and viscosity of the thermochemical piles, while different internal heat generation rates do not affect the slab structures. We find that with a moderately weak asthenosphere ($10^{20}$ Pa·s) and strong slabs, the predicted slab structures are consistent with the tomography models, and the observed geoid is also matched well. Moreover, our models successfully reproduce the degree-2 structure of the lower mantle beneath Africa and the Pacific, also known as Large Low Shear Velocity provinces (LLSVPs). A moderate Clapeyron slope of −2.5 MPa K−1 at 660 km aids in slab stagnation while higher values result in massive slab accumulation at that depth, ultimately leading to slab avalanches. We also find that the convective patterns in the thermal and thermochemical cases with slightly denser LLSVPs are similar, although the geoid amplitudes are lower for the latter. However, with more dense LLSVPs, the slabs cannot perturb them and no plumes are generated. Plumes arise as thermal instabilities from the edges of the LLSVPs, when cold and viscous slabs perturb them. While our predicted plume locations are consistent with the observed hotspot locations, matching the plume structures in tomography models is difficult. These plumes are essential in fitting the finer features of the observed geoid. In longer-duration models, more voluminous subducted material reaches the CMB, which tends to erode the LLSVPs significantly, and yields a poor fit to the observed geoid. Our results suggest that with the presence of a thin, moderately weak layer below 660 km, a slightly dense LLSVP, and Clapeyron slope of −2.5 MPa K−1, the velocity anomalies in seismic tomography and the long-wavelength geoid can be matched well. One of the limitations of our models is that the assimilated plate motion history may be too short to overcome arbitrary initial conditions effects. Also, assimilated true plate velocities in our models may not represent the true convective vigour of the Earth.

Contribution of sequential pretreatments and enzyme-assisted extraction to rice bran protein yield improvement

Alcalase is commonly used in enzyme-assisted extraction of rice bran protein. However, broad handling of rice bran can affect proteins before proteolysis. Various pretreatments, including thermal stabilization, washing, defatting, alkaline extraction, and enzymatic cellulosic degradation, and combinations were identified regarding the present and possible handling processes of rice bran protein extraction to investigate their effects on the proteolysis of the protein afterward. Then, the protein extraction yield and proteolytic abilities were compared. The thermal stabilization of the rice bran strongly affects enzymatic protein extraction, which more elaborate extraction protocols can mitigate. Rice bran oil can be extracted earlier without seriously affecting the protein extraction. Washing removes native protease inhibitors and hence speeds up the protein extraction. Alkaline extraction is highly efficient but can cause protein denaturation, generating a challenging protein separation from the gel-like structure. The protein extraction with enzymatic (Ultimase) pretreatment is an efficient method that allows high hydrolysis of intact rice bran protein during the protein extraction step.