Thermal Activation Research Articles

Lemon peel activated carbon: A sustainable solution for lead ion removal from E-waste bioleachate

In the investigation of sustainable materials, this study explores the viability of employing Lemon Activated Carbon (LAC) for the bio-adsorption of lead ions from e-waste bio-leachate. The novelty of this work lies in the comprehensive analyses of LAC characteristics, including particle size, surface area, zeta potential, and surface morphology. The morphology and adsorption capacity were measured using scanning electron microscope (SEM) and atomic absorption spectroscopy (AAS), confirming the efficacy of LAC in removing lead ions from the bio-leachate solutions. The surface area analysis unveiled that LAC, with a surface area of 603.7 m²/g achieved through thermal activation, exhibited competitive lead ion adsorption capacity despite its lower surface area compared to commercial-activated carbon (990 m²/g). Additionally, both LAC and CAC displayed pseudo-second-order kinetics for adsorption, with the Langmuir isotherm model fitting well (R2 = 0.9879) for LAC. The amorphous nature of LAC confirmed by X-ray diffraction (XRD) analysis and FTIR spectroscopy revealed functional surface groups, highlighting their suitability for lead ion adsorption. LAC comprised 75.82% carbon and exhibited maximum lead ion adsorption at pH 6. The optimized operating parameters achieved 89.16% lead ion removal from bio-leachate. These findings highlight the innovative utilization of lemon peel-derived activated carbon as a sustainable and environmentally friendly solution for mitigating the impacts of e-waste bio-leachate, thus contributing to the advancement of environmental remediation techniques.

Effect of internal phase particle size on properties of site mixed emulsion explosive at plateau environment

To study the effect of internal particle size on the microstructure properties and thermal decomposition characteristics of site mixed emulsion explosive at different altitudes. Site mixed emulsion explosive was prepared with different shear rate. The particle size, viscosity, sensitized bubbles, detonation velocity and peak pressure of the emulsion explosive were tested after stored at different simulated altitudes. The thermal decomposition characteristics of emulsion matrix prepared at three different rotational speeds were measured by thermogravimetric analyzer and kinetic analysis was performed by non-isothermal model Kissinger–Akah–Sunose (KAS) method. The results show that with the increase in altitude, the internal phase size showed a trend of first increasing and then decreasing, and the number of sensitized bubbles within the emulsion explosive decreases. At an altitude of 0 m, the detonation velocity and peak overpressure of the emulsion explosive prepared by 1600 r min−1 increased 4.78% and 29.09%, respectively compared with 1200 r min−1, and at an altitude of 4500 m, the detonation velocity increased 11.87%, the peak overpressure increased 43.98%. The thermal decomposition activation energy of the emulsion matrix at 1600 r min−1 increased 13.14% compared to 1200 r min−1. It shows that in the production of site mixed emulsion explosive at high altitude, reducing the particle size of the internal phase of emulsion explosives in a certain range can effectively improve the performance of emulsion explosives.

Enhancement in interfacial bonding quality of CoCrFeMnNi high-entropy alloy vacuum hot-compression bonding via surface shot peening

Vacuum hot-compression bonding (VHCB) is an advanced solid-state bonding technique. To expand its application in high-entropy alloys (HEAs), a new strategy to enhance the interfacial bonding quality of CoCrFeMnNi HEA VHCB joints by surface shot peening (SP) was proposed, and the effects of SP treatment on the interfacial bonding behavior and mechanical properties of VHCB joints were investigated. The results revealed that SP treatment introduced a nanocrystalline layer and plastic deformation layer with non-uniform strain on the specimen bonding surface, and a hierarchical grain size gradient fine microstructure was formed by a static recrystallization process under the thermal activation condition before VHCB. During the bonding process, the fine microstructure of the SP-treated layer was retained and provided a large number of grain boundaries and dislocations, which facilitated atomic diffusion and plastic flow in the interfacial region and promoted the closure of interfacial voids and the dissolution of interfacial oxide particles. Additionally, interfacial crystallographic and tensile test analyses indicated that the SP treatment induced a multiple interfacial grain boundary (IGB) migration mechanism in the VHCB joints, which dramatically improved the IGB migration level and ultimately led to a complete recovery of the mechanical properties of the CoCrFeMnNi HEA VHCB joints.

Simultaneous Enhancement of the Thermostability and Catalytic Activity of D-Allulose 3-Epimerase from Clostridium bolteae ATTC BAA-613 Based on the "Back to Consensus Mutations" Hypothesis.

D-Allulose is a high value rare sugar with multiple physiological functions and commercial potential that can be enzymatically synthesized from D-fructose by D-allulose 3-epimerase (DAEase). Poor catalytic activity and thermostability of DAEase prevent the industrial production of D-allulose. In this work, rational design was applied to a previously identified DAEase from Clostridium bolteae ATCC BAA-613 based on the "back to consensus mutations" hypothesis, and the catalytic activity of the Cb-I265 V variant was enhanced 2.5-fold. Furthermore, the Cb-I265 V/E268D double-site variant displayed 2.0-fold higher specific catalytic activity and 1.4-fold higher thermostability than the wild-type enzyme. Molecular docking and kinetic simulation results indicated increased hydrogen bonds between the active pocket and substrate, possibly contributing to the improved thermal stability and catalytic activity of the double-site mutant. The findings outlined a feasible approach for the rational design of multiple preset functions of target enzymes simultaneously.

Influence of Technological Factors on the Formation and Transformation of Iron-Containing Phases in the Process of Ferritization of Exhausted Etching Solutions

Every year, metallurgical enterprises generate a massive amount of toxic exhausted high-concentration etching solutions. Application of the ferritization process to recycle exhausted etching solutions can help to prevent environmental pollution. It enables a cost-efficient use of water at an industrial plant and allows the plant to obtain products from toxic industrial waste and utilize it. The aim of the study was to analyze the qualitative and quantitative composition of the formed sediment and its grain size composition. Variable study parameters were the initial pH values of the solutions, the initial concentrations of total iron, and the duration of the aeration process of the reaction mixture. Thermal activation and alternating magnetic fields were used to activate the ferritization. The XRD showed that the formed sediments contained phases of γ-FeOOH, δ-FeOOH, Fe3O4, and γ-Fe2O3. Granulometry analysis showed that these sediments were highly dispersed and heterogeneous. Chemically stable phases of magnetite were obtained in the composition of sediments, with an initial concentration of iron in the reaction mixture of 16.6 g/dm3, a pH of 11.5, and a process duration of 15 min. The study results demonstrated the feasibility of further study and possible use of such sediments with a high magnetite content for the production of materials with ferromagnetic and sorption properties.

Study of Thermal Behavior and Activation Energy of Various Polymer Nanocomposite Blend Membranes

Study of Thermal Behavior and Activation Energy of Various Polymer Nanocomposite Blend Membranes

Nanoindentation responses of NiCoFe medium-entropy alloys from cryogenic to elevated temperatures

NiCoFe alloy, a medium-entropy alloy, shows potential for applications in extreme environments. However, there is a theoretical barrier concerning the unclear understanding of its high-temperature dislocation motion mechanism. The load response exhibits distinct signatures relevant to thermal activation, most notably a decrease in critical force (i.e., softening) from cryogenic to elevated temperatures, e.g., from 200 to 1000 K. The onset of plasticity is characterized by the nucleation of stacking faults and prismatic loops at low temperatures, whereas the surface nucleation of Shockley partial dislocations dominates plasticity at elevated temperatures. We show that thermal effects lead to non-uniform atom pile-ups and control the rate of phase transformation with increasing indentation depth. The findings in this work extend the understanding of the mechanical response of NiCoFe alloys under indentation at different temperatures, shedding light on the underlying dislocation motion mechanisms and surface deformation characteristics. The observed transformation-induced plasticity mechanism has implications for the properties of medium-entropy alloys and their potential applications in extreme environments.

Preparation of geopolymers from thermally activated lithium slag: Activity enhancement and microstructure

As an industrial by-product of the lithium extraction process from spodumene, lithium slag (LS) is less reactive, rendering it a chemically infeasible binder. In this study, a thermal activation approach was employed to enhance the reactivity of LS. The underlying mechanisms of LS's thermal activation at various temperatures were thoroughly explored through XRD and ICP. The results indicated that alterations in the aluminosilicate composition of LS occurred during calcination between 500 °C and 900 °C, leading to the transformation of spodumene into amorphous forms. Particularly noteworthy was the initial increase in the LS amorphous phase content with increasing temperature, followed by a subsequent decline. Building upon these findings, a lithium slag geopolymer (LSG) was prepared via alkali activation, using the activated LS as the exclusive precursor. It was observed that elevating the content of active components in LS enhanced the geopolymerization reactions, resulting in an improved mechanical strength of LSG. Remarkably, after 28 days of aging, geopolymer specimens prepared from LS calcined at 700 °C exhibited a compressive strength of 36.0 MPa. Combining these results with FTIR and SEM-EDS analyses, it becomes evident that suitable calcination temperatures empower LS to release a higher quantity of silicon and aluminum ions. These ions play a significant role in the geopolymerization process, leading to the formation of an amorphous sodium (calcium) aluminosilicate hydrate (N(C)-A-S-H) gel. This gel acts as a binder, tightly binding the residual solid particles, and thus forming a denser microstructure.

Reduction of heavy metal emissions by adding modified attapulgite to sludge in bubbling fluidized bed incineration process

The utilization of natural mineral adsorbents to adsorb heavy metals generated from sludge incineration was currently a research hotspot. To enhance the adsorption capacity of the adsorbent, a combination of thermal activation and acid-washing modification methods was designed to modify natural attapulgite. The effects of adding the adsorbent on the distribution of heavy metals (Cr, Cu, Ni, Zn, Pb, and Cd) were tested in a laboratory-scale bubbling fluidized bed reactor. The results indicated that increasing the incineration temperature could promote the transformation of heavy metals into the stable state in the incineration ash (bottom slag and fly ash), while facilitating the volatilization and enrichment of semi-volatile heavy metals (Zn, Pb, and Cd) in the fly ash. The addition of modified attapulgite during the sludge incineration process was superior to raw attapulgite, as it enhanced the capacity of unit adsorbents to adsorb and immobilize heavy metals in flue gaseous, thus reducing the emission of heavy metals. BCR and TCLP experiments indicated that a greater proportion of heavy metals in the incineration ash were transformed into the residual fraction, thereby reducing environmental risks. Characterization revealed that the composite modification approach promoted the adsorbent to expose more active sites and increase the active amorphous components, which improved the adsorption and immobilization of heavy metals.

Pseudogap in Sr2−xLaxIrO4: Gor'kov-Teitel'baum thermal activation model

Recently, Hall effect measurements are done on Lanthanum doped Strontium Iridate Sr2−xLaxIrO4 which is 5d analogue of cuprates [1]. Hall effect measurements show that the effective carrier density nH exhibits a crossover from nH∼x to nH∼1+x near x≃0.16. This is very similar to that found in cuprates around p≃0.19. It is proposed that a pseudogap (PG) state in Sr2−xLaxIrO4 exists and is ending at x≃0.16[1]. However, PG boundary (in doping-temperature phase diagram) remains unknown. In this work, we apply a very successfull the Gor'kov-Teitel'baum Thermal Activation (GTTA) model to Sr2−xLaxIrO4 and obtain its PG phase boundary and draw an updated phase diagram. Our results agree with previously known signatures of PG phase in this system [2–4]. Using results from GTTA model we also obtain the evolution of “Fermi arcs” in this system as a function temperature for doping concentration x≃0.08 which are in qualitative agreement with the reported results.

Origin and Recovery of Negative VTH Shift on 4H–SiC MOS Capacitors: An Analysis Based on Inverse Laplace Transform and Temperature-Dependent Measurements

SiC power MOSFETs are reported to suffer from both positive and negative threshold voltage shifts. Positive shift is well understood in the literature and attributed to electron trapping in near interface oxide traps (NIOTs). Negative shift is explained by hole generation and trapping in the oxide via impact ionization favored by the strong oxide field. However, studies on negative shift are still ongoing, and the origin and nature of the process are not fully understood. This study advances the comprehension of negative threshold voltage shift by investigating MOS capacitors subject to positive bias stress.We demonstrate that: a) a significant negative threshold shift is observed when the electric field is greater than 7.5 MV/cm; b) the detected shift is not recoverable at zero bias. Recovery can be obtained only by applying a positive gate voltage indicating a field-driven detrapping process. c) Trap-state mapping measurements were carried out to extract the activation energy of the detrapping processes, and a weak thermal activation was observed.Results collected within this paper indicate that holes are trapped at deep centers, and thermal detrapping is not possible. Hole release is only possible when a high field is applied to the insulator, possibly due to the recombination between leaking electrons and trapped holes.

Emerging universality classes in thermally assisted activation of interacting diffusive systems: A perturbative hydrodynamic approach.

Thermal activation of a particle from a deep potential trap follows the Arrhenius law. Recently, this result has been generalized for interacting diffusive particles in the trap, revealing two universality classes-the Arrhenius class and the excluded volume class. The result was demonstrated with the aid of numerical analysis. Here, we present a perturbative hydrodynamic approach to analytically validate the existence and range of validity for the two universality classes.

Improvement of the antifreeze activity of tilapia skin collagen peptides through enzymatic supramolecular assembly approach

SummaryEnzymatic supramolecular assembly was applied to increase the thermal hysteresis activity (THA) of tilapia skin collagen peptides and their applicability as cryoprotectants. The THA value of the glutamine‐assembled product increased by 61.5% and its ice crystal content dropped by 33.93% compared to the collagen peptides. Following initial separation and purification, the THA of Gln‐AFPs was further elevated by 28.6%. After five freeze–thaw cycles, tilapia surimi treated with 8% Gln‐AFPs had high levels of salt‐soluble protein, total sulfhydryl content, Ca2+‐ATPase activity, and water‐holding capacity. Additionally, the cryoprotective effect of Gln‐AFPs on the surimi was found to be superior to that of commercial antifreeze. The majority of the Gln‐AFPs turns folded, according to FTIR analysis, and ‐helices were produced. After supramolecular assembly, the Gln‐AFPs structure also smoothed out. As a result, the enzymatic supramolecular assembly drastically increased the antifreeze activity of the tilapia skin‐collagen peptides, which could eventually be developed into a novel antifreeze additive in the food industry.

A re-activation model for 169Yb intensity modulated brachytherapy sources accounting for spatiotemporal isotopic composition.

Intensity modulated brachytherapy based on partially shielded intracavitary and interstitial applicators is possible with a cost-effective 169Yb production method. 169Yb is a traditionally expensive isotope suitable for this purpose, with an average γ-ray energy of 93keV. Re-activating a single 169Yb source multiple times in a nuclear reactor between clinical uses was shown to theoretically reduce cost by approximately 75% relative to conventional single-activation sources. With re-activation, substantial spatiotemporal variation in isotopic source composition is expected between activations via 168Yb burnup and 169Yb decay, resulting in time dependent neutron transmission, precursor usage, and reactor time needed per re-activation. To introduce a generalized model of radioactive source production that accounts for spatiotemporal variation in isotopic source composition to improve the efficiency estimate of the 169Yb production process, with and without re-activation. A time-dependent thermal neutron transport, isotope transmutation, and decay model was developed. Thermal neutron flux within partitioned sub-volumes of a cylindrical active source was calculated by raytracing through the spatiotemporal dependent isotopic composition throughout the source, accounting for thermal neutron attenuation along each ray. The model was benchmarked, generalized, and applied to a variety of active source dimensions with radii ranging from 0.4 to 1.0mm, lengths from 2.5 to 10.5mm, and volumes from 0.31 to 7.85 mm3, at thermal neutron fluxes from 1×1014to1×1015 n cm-2 s-1. The 168Yb-Yb2O3 density was 8.5g cm-3 with 82% 168Yb-enrichment. As an example, a reference re-activatable 169Yb active source (RRS) constructed of 82%-enriched 168Yb-Yb2O3 precursor was modeled, with 0.6mm diameter, 10.5mm length, 3 mm3 volume, 8.5g cm-3 density, and a thermal neutron activation flux of 4 × 1014 neutronscm-2s-1. The average clinical 169Yb activity for a 0.99 versus 0.31 mm3 source dropped from 20.1 to 7.5Ci for a 4×1014ncm-2s-1 activation flux and from 20.9 to 8.7Ci for a 1×1015ncm-2s-1 activation flux. For thermal neutron fluxes ≥2×1014ncm-2s-1, total precursor and reactor time per clinic-year were maximized at a source volume of 0.99 mm3 and reached a near minimum at 3mm3. When the spatiotemporal isotopic composition effect was accounted for, average thermal neutron transmission increased over RRS lifetime from 23.6% to 55.9%. A 28% reduction (42.5 days to 30.6 days) in the reactor time needed per clinic-year for the RRS is predicted relative to a model that does not account for spatiotemporal isotopic composition effects. Accounting for spatiotemporal isotopic composition effects within the RRS results in a 28% reduction in the reactor time per clinic-year relative to the case in which such changes are not accounted for. Smaller volume sources had a disadvantage in that average clinical 169Yb activity decreased substantially below 20Ci for source volumes under 1mm3. Increasing source volume above 3 mm3 adds little value in precursor and reactor time savings and has a geometric disadvantage.

Analysis of Thermal Mixing and Entropy Generation during Natural Convection Flows in Arbitrary Eccentric Annulus

The present study presents a computational investigation into the thermal mixing along with entropy generation throughout the natural convection flow within an arbitrarily eccentric annulus. Salt water is filled inside the eccentric annulus, in which the outer and inner cylinders have Tc and Th constant temperatures. The Boussinesq approximation is used to develop the governing equations for the natural convection flow, which are then solved on a structured quadrilateral mesh using the OpenFOAM software package (FOAM-Extend 4.0). The computational simulations are performed for Rayleigh numbers (Ra=103–105), eccentricity (ϵ=0,0.4,0.8), angular positions (φ=0∘,45∘,90∘), and Prandtl number (Pr=10, salt water). The computational results are visualized in terms of streamlines, isotherms, and entropy generation caused by fluid friction and heat transfer. Additionally, a thorough examination of the variations in the average and local Nusselt numbers, circulation intensity with eccentricities, and angular positions is provided. The optimal state of heat transfer is shown to be influenced by the eccentricity, angular positions, uniform temperature sources, and Boussinesq state. Moreover, the rate of thermal mixing and the production of total entropy increase as Ra increases. It is found that, compared to a concentric annulus, an eccentric annulus has a higher rate of thermal mixing and entropy generation. The findings show which configurations and types of eccentric annulus are ideal and could be used in any thermal processing activity where a salt fluid (Pr=10) is involved.

Preparation of High-Labeled Graphene Oxide by Tritium Thermal Activation Method for Application in the Betavoltaic Cell of a Nuclear Battery

The possibility of tritium introduction into graphene oxide (GO) by tritium thermal activation method was demonstrated. It was established that, in order to produce the highest possible specific radioactivity, thin films of GO with a thickness of 5.6 mg/m2 must be treated with tritium atoms. The experiment conducted at 77 K showed a number of advantages. GO was processed with tritium atoms, the resulting specific activity of [3H]GO reached 2.6 Ci/mg in term of the weight of the initial GO (0.7 Ci/mg after removal of the labile tritium). Specific energy release of [3H]GO with this specific activity is 22.3 W/kg, which is quite sufficient for its application as a component of a nuclear battery.

The influence of γ′ morphology and size on stress rupture properties in Ni-base superalloy IN738LC

This study investigates the influence of γ′ precipitate morphology and size on the creep deformation of the cast superalloy IN738LC under conditions of 760–982 °C and 78–674 MPa. Two microstructures were obtained by different heat treatments. The analysis of the experiments show that, according to the applied stress at 760 °C and 871 °C, the S1A material, with a bimodal distribution with large cuboidal γ′ and small spherical γ′, exhibited the longer creep life compared to those with a monomodal distribution with spherical γ′ precipitates. In the creep test at 760 °C, the S1A material exhibited a stacking fault within the primary cuboidal-shaped γ′ phase. The main deformation mechanism observed was isolated stacking fault (ISF) formation. Conversely, for the S2A material, an extended stacking fault (ESF) was observed, where dislocations continuously traversed several γ′ and γ phases. At 871 °C in low-stress creep tests, the S1A alloy displayed a dislocation network resulting from thermal activation, with localized stacking faults. In the S2A alloy, three-dimensional dislocations generated by climb were primarily observed around spherical γ′ precipitates, accompanied by localized stacking faults. At 982 °C, both S1A and S2A alloys exhibited rafting under lower stress, displaying similar lifetimes. The formation of a regular dislocation network at the interface between γ′ and γ matrix and rafting of γ′ precipitate proved beneficial in improved creep resistance of the alloy.

Temperature-Dependent Mechanical Anisotropy in Textured Zircaloy Cladding

This work evaluates deformation activity in textured zircaloy-4 cladding with the aim of elucidating the mechanisms that govern mechanical behavior across a temperature range anticipated in reactor service. In particular, the dependence of mechanical anisotropy on temperature and stress state (ratio of applied stresses) is examined via uniaxial and biaxial tensile experiments at room temperature and 400 °C. The mechanical behavior is interpreted based on micro-texture and dominant slip system activity. Thermal activation of basal systems is found as a key mechanism affecting mechanical behavior across the temperature range. The biaxial stress states produce resolved shear stresses contrasting to uniaxial stress states. Mechanical testing and implications for reactor pellet-cladding mechanical interaction stress conditions are discussed.

Identification of the Thermal Activation Network in Human 15-Lipoxygenase-2: Divergence from Plant Orthologs and Its Relationship to Hydrogen Tunneling Activation Barriers.

The oxidation of polyunsaturated fatty acids by lipoxygenases (LOXs) is initiated by a C-H cleavage step in which the hydrogen atom is transferred quantum mechanically (i.e., via tunneling). In these reactions, protein thermal motions facilitate the conversion of ground-state enzyme-substrate complexes to tunneling-ready configurations and are thus important for transferring energy from the solvent to the active site for the activation of catalysis. In this report, we employed temperature-dependent hydrogen-deuterium exchange mass spectrometry (TDHDX-MS) to identify catalytically linked, thermally activated peptides in a representative animal LOX, human epithelial 15-LOX-2. TDHDX-MS of wild-type 15-LOX-2 was compared to two active site mutations that retain structural stability but have increased activation energies (Ea) of catalysis. The Ea value of one variant, V427L, is implicated to arise from suboptimal substrate positioning by increased active-site side chain rotamer dynamics, as determined by X-ray crystallography and ensemble refinement. The resolved thermal network from the comparative Eas of TDHDX-MS between wild-type and V426A is localized along the front face of the 15-LOX-2 catalytic domain. The network contains a clustering of isoleucine, leucine, and valine side chains within the helical peptides. This thermal network of 15-LOX-2 is different in location, area, and backbone structure compared to a model plant lipoxygenase from soybean that exhibits a low Ea value of catalysis compared to the human ortholog. The presented data provide insights into the divergence of thermally activated protein motions in plant and animal LOXs and their relationships to the enthalpic barriers for facilitating hydrogen tunneling.

Edge dislocation depinning from hydrogen atmosphere in α-iron

Understanding the dislocation motion in hydrogen atmosphere is essential for revealing the hydrogen-related degradation in metallic materials. Atomic simulations were adopted to investigate the interaction between dislocations and hydrogen atoms, where the realistic hydrogen distribution in the vicinity of the dislocation core was emulated from the Grand Canonical Monte Carlo computations. The depinning of edge dislocations in α-Fe at different temperatures and hydrogen concentrations was then studied using Molecular Dynamics simulations. The results revealed that an increase in bulk hydrogen concentration increases the flow stress due to the pinning effect of solute hydrogen. The depinning stress was found to decrease due to the thermal activation of the edge dislocation at higher temperatures. In addition, prediction of the obtained results was performed by an elastic model that can correlate the bulk hydrogen concentration to depinning stress.