Activation Energy Values Research Articles

The effects of 1D multi‐wall carbon nanotubes and 2D graphene nanoplatelets on curing behavior of epoxy/vinyl ester interpenetrating polymer network nanocomposites

AbstractThis study meticulously investigated the effect of two carbon allotrope nanofillers, two‐dimensional graphene nanoplatelets (GnPs) and one‐dimensional multi‐wall carbon nanotubes (MWCNTs) individually, at various loadings on the kinetics of curing of the epoxy (EP)/vinyl ester (VE) based interpenetrating polymer network (IPN) system, with a mass ratio of 1:1. The IPN system is including a liquid epoxy resin based on bisphenol A which has been cured by methyltetrahydrophthalic anhydride (MTHPA) in the presence of 1‐methyl imidazole (Mi) as an accelerator and a vinyl ester resin based on bisphenol A which has been cured by methyl ethyl ketone peroxide (MEKP). The curing behavior of all prepared nanocomposites under non‐isothermal conditions was studied using DSC at four heating rates. Two different isoconversional approaches were applied to evaluate the reaction kinetics, that is, the Friedman and the advanced Vyazovkin methods. The obtained activation energy curves for all samples revealed a complex curing behavior involving three stages: early IPN stage, IPN growth stage, and late IPN stage. Then, the activation energy values for each reaction step were determined based on the Friedman method. The presence of GnPs showed no catalytic effect on the reaction of VE with MEKP. In contrast, incorporating MWCNT nanoparticles considerably decreases the activation energy values of the reaction of ring opening of epoxides with MTHPA‐Mi and the reaction of esterification of the hydroxyl groups of VE with MTHPA.Highlights MWCNTs reduce activation energy in curing reactions for EP/MTHPA‐Mi and VE/MTHPA. GnPs do not catalyze VE/MEKP reaction unlike MWCNTs. Combining MWCNTs and GnPs enhances properties of IPN nanocomposites. Curing process includes early, growth, and late IPN stages impacting activation energy. SEM analysis reveals better dispersion of GnPs in IPN nanocomposites with MWCNTs.

Effect of Temperature and Initiator Concentration on the Curing Reaction of an Epoxy/Amine System

AbstractEpoxy blends of diglycidyl ether of bisphenol A (DGEBA) and 2‐[2‐(dimethylamino) ethoxy] ethanol (DMAEE) were prepared. The effect of DMAEE concentration on the rheological properties of the epoxy blends were investigated through oscillatory rheometry under isothermal conditions. A novel technique was developed to study the rheological behavior of the epoxy blends by using a Rubber Process Analyzer (RPA). The rheological study enabled analyzing the variations in the storage modulus (G’), loss modulus (G’’) and torque during the progress of the curing reaction. Additionally, the theoretical cross‐linking density (νe) and the degree of conversión of the curing reaction (α). The gel time (tgel) was determined at different temperatures, and the activation energy (Ea) was calculated by using Arrhenius‐type equation based on the gel time results. The activation energy values found are 24.79 kJ/mol and 23.01 kJ/mol. The results obtained are consistent with the values described in the literature. It was demonstrated that the proposed methodology is valid and, the use of the tertiary amine DMAEE curing agent for epoxy resins was confirmed.

Kinetic analysis and calculation correction methods for moisture evaporation rate in pine lignocellulosic biomass

This study investigates the kinetics of moisture evaporation in pine wood during the drying stage, focusing on analyzing thermogravimetric (TG) curves. The research is based on the kinetic rate model and TG curves obtained at various heating rates, specifically 5, 10, 15, and 20 K/min for the heat release rate, within a temperature range from room temperature to 473 K. Utilizing thermogravimetric experiments and the kinetic rate model, the apparent activation energy and pre-exponential factor are calculated. Further refinement of these calculations is achieved using the Nelder-Mead algorithm. The results show good agreement between the average values of the apparent activation energy (37.88 kJ/mol) and pre-exponential factor (4458.20 s−1) and experimental measurements in the initial and later drying stages, with discrepancies noted in the middle stage. Establishing a relationship between the correction coefficients of these parameters and the heating rate leads to a reduction in calculation errors. Notably, the pre-exponential factor is found to be influenced by heating rates, while the apparent activation energy remains relatively stable. Moreover, the errors are significantly reduced after correction, and the error curve of 10 K/min is the most significant. Overall, the proposed correction method holds promise for accurately calculating moisture evaporation rates in lignocellulosic biomass, offering valuable insights for biomass drying applications.

Enhanced creep resistance and microstructure in 7055 Al alloy by in-situ (Al2O3 + ZrB2) nanoparticles and Al3(Er, Zr)

This work put forward a novel approach to enhancing high-temperature creep resistance of 7055 Al alloy via inducing reinforcements including in-situ (Al2O3 + ZrB2) nanoparticles and Al3(Er, Zr). Creep steady-state rates of the (Al2O3 + ZrB2)/7055 Al composites enhanced by synergistic Er, Zr were lower than the (Al2O3 + ZrB2)/7055 Al composites, indicating the values of stress component (n) and apparent activation energy (Q) were 1.05–1.15 and 1.06–1.08 times of (Al2O3 + ZrB2)/7055 Al composites. The dislocation climb mechanism was considered as the dominative creep mechanism because the suitable true stress exponent was 5. The uniform distribution of Al2O3 and Al3(Er, Zr) and their influence on improving the distribution of ZrB2 aggregates gave rise to relative uniform deformation during creep process. The built interface models that induce Al3(Er, Zr) between the nanoparticle/Al interface could lead to a more thermodynamically stable and well-bonded interface. The coupling effect of attachments containing Al2O3, ZrB2 and Al3(Er, Zr) played an enhanced role in terms of vacancy-trapping, precipitate-nucleation, dislocation motion during creep process. The nanoparticles and Al3(Er, Zr) together with nuclear sites containing solute atoms, vacancies and misfits nearby, caused an expansion-inhibiting effect on the helical dislocations. The in-grain misorientation axes (IGMA) concentration of some deformed grains associated with Schmid factor (SF) analysis were related to 〈001〉, 〈111〉 and 〈101〉 direction. The calculation of creep resistance mechanisms was quantified. Additionally, typical intergranular fracture appeared within the composites due to the relatively uniform reinforcements, resulting in the complex crack path.

La3+ doped CaCu3Ti4O12 ceramics: Investigation of its microstructural and dielectric properties against varying sintering durations

This article reports the relationship between microstructure and dielectric properties of the title material were prepared through combination of solid-state and sol–gel methods and then sintered by varying durations. XRD indicates Im-3 space group with a body centred cubic structure, and Rietveld refinement analysis showed good fits for all samples, with R-factors below 10 % and GoF less than 2. The XPS analysis revealed the existence of Ca 2p, La 3d, Cu 2p, Ti 2p, O 1s, and C 1s retained their correct oxidation states. SEM results show grain sizes of 1.10 (±0.25) μm, 1.24 (±0.10) μm, and 1.75 (±0.31) μm for 8, 12, and 16 h of sintering, respectively. EDS analysis confirms the presence of Ca, Cu, Ti, La, and O, indicating the purity of the ceramics. As the sintering duration increases, grain enlargement consistently leads to higher εr values with very low tanδ. At a low frequency of 50 Hz, εr increases with sintering duration, reaching values of 5.65 × 103, 5.90 × 103 and 9.94 × 103. Meanwhile, tanδ remains significantly low (<0.1) at 1 kHz. The Nyquist plots demonstrate deviation from Debye type relaxation with NTCR behaviour. The frequency-dependent AC conductivity follows Jonscher’s power law, with activation energy values of 0.44 eV, 0.46 eV, and 0.49 eV for ceramics sintered for 8, 12, and 16 h, respectively.

Chlorine Dioxide Delays Enzymatic Browning in Postharvest Cherimoya and Enables Establishment of Kinetics Substrate Model

Cherimoya (Annona squamosa L.) is a nutrient-rich fruit. However, it is not easy to store because of its susceptibility to browning. In order to prolong the storage period of cherimoya, the fruit was treated with chlorine dioxide (ClO2) at different concentrations (20, 40, 60, 80, and 100 mg L−1) and stored at 15 °C for 8 days. The quality and biochemical indexes of the fruit were investigated using a chromameter, high-performance liquid chromatography and scanning electron microscopy, etc. The results showed that all the treatments with various concentrations of ClO2 could delay the increase in the browning index, loss of weight, and decrease in hardness. Meanwhile, ClO2 treatment effectively reduced the consumption of starch, titratable acids, and phenolics as well as inhibited the polyphenol oxidase (PPO) activity and enzymatic oxidation. It can be seen from the Fourier transform infrared spectrum (FTIR) that the C=O stretching peak at 1731 cm−1 disappeared at a ClO2 concentration of 60 mg L−1. We think the ClO2 treatment may inhibit the oxidation of phenol to quinone. According to the Arrhenius formula, the values of the apparent activation energy (Ea) for enzymatic browning reaction were estimated. The Ea with catechol in cherimoya pericarp and flesh were 67.00 and 47.83 kJ mol−1, respectively. It was found that the phenolic enzyme reaction with catechol has a much smaller Ea and a higher affinity for PPO. Therefore, treatment with ClO2 at a suitable concentration for cherimoya stored at 15 °C could effectively maintain fruit quality and prolong the storage period; the most appropriate concentration is 60 mg L−1.

Kinetics of formation, microstructure, and properties of monolithic forsterite (Mg2SiO4) produced through solid-state reaction of nano-powders of MgO and SiO2

The synthesis of forsterite can be challenging because the initial oxides react slowly and undesirable compounds like enstatite (MgSiO3) can form instead of forsterite (Mg2SiO4). Although several methods have been developed to overcome these challenges, the synthesis of forsterite using the solid-state reaction of nanopowders has not been investigated. This study aims to explore the possibility of producing forsterite by reacting MgO and SiO2 nano-powder. The initial oxides were wet ball milled, dried, and reaction sintered. Spectroscopy and microscopy methods were used to analyze the formed phases and study the formation kinetics. The density, coefficient of thermal expansion (CTE), and hardness of sintered samples were measured using a densimeter, a dilatometer, and a hardness tester, respectively. The results demonstrated that it is possible to synthesize forsterite by solid state reaction of pure MgO and SiO2 nano-powders. The reaction between the two compounds begins at a temperature as low as 860 °C and leads to the formation of forsterite by a two-step formation mechanism. The first reaction involves the reaction of MgO and SiO2 to form enstatite, and the second one produces forsterite as a result of enstatite reacting further with MgO. The activation energy values ranged from 1028.89 to 1105.655 kJ/mol for the formation of forsterite, and from 456.316 to 488.08 kJ/mol for the formation of enstatite. Monolithic forsterite was completely formed at a low temperature of 1200 °C for a relatively short duration of 2 h. The sample sintered at 1400 °C for 2 h, had a density of 2.96 g/cm3, a Vickers hardness of 7.64 GPa, and a coefficient of thermal expansion of 10.24 × 10−6/K measured in the temperature range of 200–1300 °C.

Kinetic study on the thermal decomposition of iron (II) sulfate using a global optimization approach

The thermal decomposition of sulfates is a major intermediate reaction in oxidizing roasting processes associated with metal sulfides. The optimization of iron (II) sulfate could contribute to lowering processes’ temperatures in complex systems. The present work presents the experimental and modeling results of the thermal decomposition of iron (II) sulfate heptahydrate. The investigation was first based on thermodynamic simulations followed by non-isothermal thermogravimetric analysis. The modeling technique consisted of differential equations formulated to describe each decomposition step individually, with the kinetic parameters estimated using particle swarm optimization (PSO). Using this modeling methodology over a graphical method is advantageous as it can simulate reactions that may occur simultaneously. The modeling succeeded in dehydration and desulfation steps, with an overall R2 value of 0.99. The activation energies and apparent reaction order associated with the dehydration steps were 53.3kJ.mol−1/n=1.65, 88.8kJ.mol−1/n=1.12, and 124kJ.mol−1/n=2.0 for FeSO4.7H2O, FeSO4.4H2O, and FeSO4.H2O, respectively. The desulfation steps were associated with higher activation energy values. In that case, 184kJ.mol−1 and 264kJ.mol−1 for FeSO4 and Fe2(SO4)3, respectively. Regarding the apparent reaction order, both desulfation steps showed to be first-order reactions.

Copper stearate-coated DAP-4 core–shell composites for enhanced safety and thermal decomposition performance

In this study, DAP-4@copper stearate (CS) core–shell composites were fabricated by an in situ synthesis and liquid deposition using CS as the catalyst. In addition, a comprehensive characterization was conducted on the morphology, structure, thermal decomposition, and safety performance of the acquired samples. The results revealed that DAP-4@CS composites with a complete, compact core–shell structure. During thermal analysis experiments, DAP-4@CS (5, 10, 15, and 20 wt%) resulted in a reduction in the thermal decomposition peak temperatures (Tp) by 35.22, 55.02, 68.22 and 73.76 °C respectively when compared with DAP-4, and their corresponding activation energy values decreased by 61.22, 87.3, 63.62, and 69.54 kJ/mol. Notably, the DAP-4@CS composites with 5 wt% and 10 wt% CS exhibited increased heat release by 1291.03 and 1546.8 J/g, respectively. The H50 value for DAP-4 increased from an initial value of 44.67 cm to an improved value of 64.57 cm, while its friction sensitivity increased from 30 N to 40 N during safety experiments. Moreover, we propose the principle of thermal decomposition catalysis and desensitization of CS for DAP-4. The above research results provide a new solution to the contradictions and obstacles in the application of DAP-4 as an oxidizer in fuel.

Spectral and conductivity measurements insights on loading mechanisms of DMSO/water-kaolin complexes

Kaolin, a naturally occurring clay mineral renowned for its distinctive properties, holds significant importance across various industries. The integration of dimethyl sulfoxide (DMSO) into kaolin matrices, both in the presence and absence of water, has been extensively explored for its potential to enhance material characteristics. Addressing debates surrounding the proposed adsorption mechanism for the type I structure of DMSO, this study undertook a comprehensive physicochemical characterization of DMSO-kaolin complexes (DMSO-KCs) derived from untreated (UnK) and HCl-treated (HK) Egyptian ore, with a focus on elucidating the loading mechanism facilitated by water.Key insights gleaned from electrical conductivity, dielectric constant, and Fine Testing Technology – Fourier-transform infrared (FTT-FTIR) measurements, shedding light on the bonding nature of DMSO-KCs. FTT-FTIR analysis revealed two stages of water departure at 180 °C, with the final stage coinciding with the release of pyrolysis gases, confirming the catalytic degradation of DMSO. Through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), two distinct bonding types of DMSO molecules with kaolinite were identified: amorphous adsorbed (type I) and lattice-oriented intercalated (type II).Electrical characteristic evaluations within the temperature range of room temperature (RT) to 260 °C and frequency range of 42 Hz–1 MHz revealed that DMSO intercalation enhances the electrical properties of kaolin. Hydrated DMSO-KCs exhibited higher values of σac and ɛʹ compared to non-hydrated samples. The activation energy (Ea) values for HCl-treated samples were smaller than those of untreated ones. Alternating current (AC) conductivity analysis indicated predominantly ionic behavior with frequency and temperature dependency in both HCl-treated and untreated kaolin. Our findings substantiate the adsorption mechanism of Type I DMSO, highlighting its amorphous nature, instability, and catalytic degradation over time, in contrast to the intercalated type II. This elucidation is pivotal for understanding the behavior of DMSO-KCs across diverse applications, including electronics, ceramics, and materialsscience.

Stage development characteristics of oxygen-lean combustion of coal in fire zone: Leap-migration mechanism, kinetic transition mechanism, and critical oxygen concentration

Effectively preventing the re-ignition of fire zones and safely unsealing enclosed fire zones are challenging. To address these issues, a thermogravimetric analysis technique was used to explore the leap-migration mechanism of the characteristic parameters (burnout index (H), comprehensive combustion performance parameters (Cb, S, and HF), and maximum combustion mass loss rate (dWmax))/temperatures (maximum pyrolysis mass loss rate point temperature (TVmax), pyrolysis endpoint temperature (Td), thermal polycondensation endpoint temperature (Tp), maximum combustion mass loss rate point temperature (TWmax), burnout temperature (Th), and combustion half-peak width (ΔT1/2)) of low-rank coal oxygen-lean combustion under different time-scale effects (TSEs). The sensitivity of characteristic parameters/temperatures to changes in oxygen concentration under coal rank transition was analyzed. Simultaneously, the kinetic real-time transformation mechanism during the oxygen-lean combustion stage progression was investigated. The results revealed that because of the competition between oxidation and pyrolysis, the leap-migration interval of characteristic parameters/temperatures for oxygen-lean combustion of low-rank coals is in the range of 5 %–3% oxygen concentration. This feature was less affected by the coal rank but is not affected by the TSE. In the low oxygen-lean range (5 %-1%), a change of oxygen concentration was more sensitive to the coal rank, and the high sensitivity of the oxygen concentration change reduced the influence of the coal rank on coal combustion performance. In addition, the apparent activation energy (Eα) curves during the early stage of combustion were relatively concentrated with the change of oxygen concentration, but relatively dispersed during the late stage of combustion. At 3 % oxygen concentration, the Eα values of different coals began to continuously decrease with increasing conversion rate, approaching the spontaneous reaction activation energy value of 40 kJ/mol. At oxygen concentration of 1 % reflected the complete limitation of the oxidation consumption reaction. Therefore, the critical oxygen concentration of typical low-rank coal oxygen-lean combustion was determined below 3 % oxygen concentration. The results of this study can provide scientific guidance for the unsealing of fire zones, and the effective prevention and control of the formation of new fire zone disasters.

Tuning β-Si3Al3O3N5 phosphors by Eu or Ce doping for white light-emitting diodes (wLEDs)

SiAlON-based phosphors have garnered considerable attention in the field of white lighting owing to their excellent thermal stability, and rare earth doped SiAlON-based phosphors are expected to be used in a new generation of lighting sources. In this work, Eu2+ or Ce3+ doped Si3Al3O3N5 phosphors were synthesized by high temperature solid phase method. The microstructure of the phosphors exhibited irregular grain. The two phosphors exhibit green and cyan luminescence under 365 nm excitation, which are derived from the 5d-4f transitions of Eu2+ and Ce3+, respectively. The quenching concentrations are 3 % and 4 % for Eu2+ and Ce3+doped phosphors, respectively. The fluorescence intensity of Eu2+ and Ce3+ activated SiAlON powders decreased to 50 % of the room temperature intensity at 179 °C and 170 °C, respectively. The thermal activation energy values of the two phosphors were 0.35 eV, and the coordinate configuration diagram was constructed to comprehensively analyze the thermal quenching behavior of phosphors. Finally, the two phosphors powders were mixed with red and blue fluorophore to obtain white LEDs, showing low color temperature, high color rendering, high power unsaturation and long half-life. The SiAlON-based phosphors with excellent thermal stability obtained in this work achieve different wavelengths of luminescence in the green region. The results show that the β-Si3Al3O3N5 phosphor can be used as a candidate material for high-quality green light supplement for wLEDs.

Influence of Temperature on Creep Resistance, Structural and Electrical Characteristics of S9Z1 Eutectic Alloys

In the present study, the structural and creep resistance properties of S9Z1 alloys with Cu-addition in concentrations (0.1 and 0.3% Wt.) have been investigated using x-ray diffractions (XRD) and Creep testing machine respectively. The three samples were prepared from high purity 99.99% by melting technique in the Pyrex tubs with CaCl&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; to invaded the oxidation. The obtained samples were rolled drawn (cold rolling) into two groups. The first group was as wires for the creep resistance testing. The second group was as small sheets for structural investigations. Patterns of XRD showed that the S9Z1 alloy was primarily composed of two phases; a body centered tetragonal β-Sn matrix phase, and a secondary phase of hexagonal Zn. while with addition Cu (0.1 and 0.3% Wt.) to S9Z1 Alloys the results showed new peaks in the ternary compositions, such as Cu&amp;lt;sub&amp;gt;6&amp;lt;/sub&amp;gt;Sn&amp;lt;sub&amp;gt;5&amp;lt;/sub&amp;gt;, Cu&amp;lt;sub&amp;gt;5&amp;lt;/sub&amp;gt;Zn&amp;lt;sub&amp;gt;8&amp;lt;/sub&amp;gt;, phases respectively. The average of particle size (D) of β-Sn matrix was decreased with increasing Cu -adding, whereas the dislocation density (δ) increased with increasing addition. Creep properties of S9Z1, S9Z2 and 3 Alloys were examined at different temperatures (25, 40 and 80°C) under two constant loads (σ= 18.7 and 24.94 MPa). The creep behaviors of ternary alloys were higher than the S9Z1 alloys with all different temperatures under two constant loads. Also, the S9Z3 alloy with all different temperatures and two loads exhibited greatest creep resistance, due to the refinement structure and formation of new IMCs. Values of stress exponent (n) were found to be in the range of 1 to 10.55, for all S9Z2 and 3 alloys respectively. Values of activation energy (Q) of alloys were found to be in the range of 36.48 to 37.49 kJ/mol, for σ = 18.7 Mpa and 27 to 34.8 kJ/mol for σ = 24.94 Mpa for the S9Z1 alloys with Cu addition respectively. At room temperature (25°C), the electrical conductivity of the samples was calculated, and its values increased with Cu additions.

Exploration of the structural and electrical characteristics and solar cell applications of an electrolyte membrane derived from acacia gum

The natural and eco-friendly solid-state electrolytes were prepared using varying concentrations (wt%) of ZnSO4.7H2O salt and pure acacia gum through the solution cast method. Multiple analytical methods were employed to characterize the resulting acacia gum electrolyte samples. XRD analysis confirmed the increased presence of the amorphous phase with the introduction of salt. FTIR analysis explored the formation of interlinking bands and their complex nature upon salt incorporation. The ionic conductivity was found from room temperature (RT) to 100 °C range. The optimized high ionic conductivity value was found to be 1.11 × 10−4 S/cm at 100 °C for the electrolyte composed of 70 wt% acacia gum and 30 wt% ZnSO4.7H2O, while at RT it was 1.06 × 10−5 S/cm for the same composition. Activation energy values fell within the 0.6–0.92 eV range for all samples. Complex dielectric (real and imaginary) and complex electric modulus analyses were conducted. Dielectric permittivity and electrical modulus analyses revealed a significant interaction between the segmental movements of acacia gum and salt ions. Ionic relaxation processes were explored in terms of conductivity relaxation time using the electrical modulus. The presence of a long tail in the complex dielectric modulus study indicated that the acacia-based solid electrolyte displayed favorable capacitance properties. Further, the Solar Cell (dye-sensitized solar cell) device was fabricated with (Acacia gum + ZnSO4.7H2O) electrolyte. The current density-voltage (J-V) characteristics of the prepared device were investigated. The outstanding results were optimized in the present work, Voc = 0.81 V, Jsc = 9.56 mA/cm2, Fill Factor of 0.67, and optimum power conversion efficiency ƞ = 5.17 % for the electrolyte composed of 70 wt% acacia gum and 30 wt% ZnSO4.7H2O device.

Crystallization Kinetics and Melting Behavior of Novel Biobased Poly(butylene 2,5‐thiophenedicarboxylate)

AbstractPoly(butylene 2,5‐thiophenedicarboxylate) (PBTh) is a novel biobased semicrystalline polyester with superior thermal, mechanical, and gas barrier properties; however, the crystallization kinetics and melting behavior of PBTh have not been studied in detail so far. The crystallization kinetics of PBTh was first studied in this research. The Ozawa equation failed to describe the nonisothermal melt crystallization kinetics of PBTh due to the secondary crystallization. The crystallization activation energy value was calculated by the Friedman method, which was negative and exhibited the conversion dependence. The isothermal melt crystallization kinetics of PBTh was well described by the Avrami equation in a wide range of crystallization temperature from 84 to 120 °C. PBTh showed the fastest crystallization rate at 104 °C; moreover, the Avrami exponent value slightly varied between 2.2 and 2.7, suggesting the same crystallization mechanism within the investigated temperature range. PBTh displayed one or two melting endotherms depending on crystallization temperature, which was well explained by the melting, recrystallization, and remelting mechanism. In addition, the equilibrium melting point of PBTh was estimated to be 163.1 °C with the Hoffmann−Weeks equation.

Regulating the Electrochemical Performance of Simple Halogen-Free Electrolyte Using Ammonium Bromide Additive for Magnesium-Sulfur Battery Applications

Magnesium-sulfur (Mg-S) batteries are a promising energy storage system; however, the short cycle life, low coulombic efficiency, and the shuttle effect of polysulfide hinder its practical application. Applying electrolyte additives is a powerful technique to optimize the electrochemical performance of Mg-S electrolytes. Herein, ammonium bromide (NH4Br) is used as an inorganic electrolyte additive in the halogen-free electrolyte (HFE) to guide homogeneous Mg deposition. It can be noticed that the addition of NH4Br decreases the activation energy values from 0.14 eV to 0.10 eV and reduces the value of Mg2+ stripping/plating overpotential. It is found that the introduction of NH4Br to HFE enhances the cycle life and the initial discharge capacity (~1662 mAhg-1) of the Mg-S cells compared with the cells using free NH4Br that deliver initial discharge capacity of ~ 184 mAh g-1, low coulombic efficiency, and short cycle life. Further efforts have been devoted by implementing a BaTiO3 (BTO) as a modified separator to overcome the polysulfide dissolution issue in the cell. The surface of the cell's anode applying a modified separator shows half wt.% S content compared with the bare cell after cycling. This study opens further research for developing novel electrolyte schemes for magnesium-sulfur battery applications.

Exploring the optical and electric features of PMMA/PVAc blended polymers doped with TBAI/MWCNTs fillers for different applications

The present study focuses on the production of poly (methyl methacrylate)/poly (vinyl acetate)/tetrabutylammonium iodide/multi-walled carbon nanotubes (PMMA/PVAc/TBAI/x wt %MWCNTs) blended polymers. These blends show great potential for use in advanced optical, energy storage and electronics applications. X-ray diffraction (XRD) and scanning electron microscopy techniques was used to explore the structure and morphology of PMMA/PVAc/TBAI with x wt% MWCNTs blended polymers. The optical transmittance lowered to a minimum value of 53–63 % within the specific wavelength range as the blend contained 0.55 wt % multi-walled carbon nanotubes (MWCNTs). The sample containing 0.11 wt% MWCNTs demonstrated the highest reflectance (R) values, whereas the sample with 0.55 wt% MWCNTs showed the lowest R values. As the concentration of MWCNTs increased, these values consistently decreased. The smallest direct (4.55 eV) and indirect (4.45 eV and 2.48 eV) optical band gap (Eg) values were achieved when wt% of MWCNTs were 0.44 % and 0.55 %, respectively. The doped blend with wt% of 0.11 exhibited the highest refractive index values. Blend with x = 0.55 wt % MWCNTs has the highest dielectric constant. The energy density (U) increased non-uniformly as the blend was infused with MWCNTs. Elevating the temperature enhances the values of U for all blends. All blends adhered to the correlated barrier hopping (CBH) model. The effects of MWCNTs doping amount and temperature on the impedance and electric modulus of the host blend were investigated. The dc conductivity of the doped samples was observed to be greater than that of the undoped blend, except for the blend with x = 0.44, where it diminished. The undoped blend displayed activation energy (Ea) values of 1.71 eV and 0.6 eV, depending on the temperature range. When the host blend is doped with MWCNTs, the Ea values either rise or fall depending on the quantity of MWCNTs. All samples have non-ohmic characteristics.

Rheological Property Modification of a Molten-State Polyamide through the Addition of an α-Olefin-Maleic Anhydride Copolymer.

The rheological properties of a polyamide (PA) resin with low crystallinity were modified by melt-mixing it with a small amount of an alternative α-olefin-maleic anhydride copolymer as a reactive compound. Because PA has a low melting point, rheological characterization was performed over a wide temperature range. Owing to the reaction between PA and the alternative α-olefin-maleic anhydride copolymer, the blend sample behaved as a long-chain branched polymer in the molten state. The thermo-rheological complexity was obvious owing to large flow activation energy values in the low modulus region, i.e., the rheological time-temperature superposition principle was not applicable. The primary normal stress difference under steady shear was greatly increased in the wide shear rate range, leading to a large swell ratio at the capillary extrusion. Furthermore, strain hardening in the transient elongational viscosity, which is responsible for favorable processability, was clear. Because this is a simple modification method, it will be widely employed to modify the rheological properties of various polyamide resins.

Synergistic effect of TiO2 nanoparticles and poly (ethylene-co-vinyl acetate) on the morphology and crystallization behavior of polylactic acid

The impact of adding ethylene vinyl acetate copolymer (EVA 80) and 1 wt% TiO2 nanoparticles on the morphology and crystallization behavior of poly(lactic acid) blends was investigated using DSC, SEM, and POM. Thermal analysis revealed the enhancement of crystallinity of PLA in the presence of TiO2 and higher EVA 80 content in the blend. The PLA and EVA 80 components showed compatibility, as evidenced by the shift of the glass transition temperatures of the PLA phase in the blend to lower values compared to neat PLA. The lower temperature shift of the cold crystallization of the PLA and the formation of the small spherulites of the PLA in the blends indicated that the EVA 80 and TiO2 act as a nucleating agent for crystallization. The non-isothermal crystallization parameters of the composites were evaluated using Avrami's modified model, the MO approach, and Friedman’s isoconversional method. The Avrami’s modified rate constant (K) and the effective activation energy values significantly increased with the incorporation of EVA 80 and TiO2 nanoparticles. Furthermore, the thermogravimetric analysis (TGA) showed improved thermal stability of PLA by adding EVA 80 and TiO2.

Cobalt Nanoparticles Supported Active Carbon from Chitosan Biopolymer Using Thermal Method: Synthesis, Characterization, and Hydrogen Production

AbstractActivated carbon based Cobalt nanoparticles (Co@AC NPs), considered in the context of hydrogen energy, which is a renewable and sustainable energy, were synthesized by the hydrothermal method, and their catalytic activities were tested. For this, hydrogen production tests were carried out with the help of sodium borohydride (NaBH4) methanolysis of Co@AC NPs synthesized by the thermal method. Ultraviolet–visible spectroscopy (UV–Vis), Fourier transmission spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray diffraction (XRD) characterization tests were performed. According to the TEM characterization result, it has been observed that the NPs have a spherical shape and an average size of 2.52 ± 0.92 nm. Then, using the catalytic studies, it was observed that hydrogen production’s reusability is found to be 86% . The activation energy (Ea), enthalpy (∆H), and entropy (∆S) values were found to be 20.28 kJ⋅mol−1, 17.74 kJ⋅mol−1, and −125.97 J⋅mol−1 K−1, respectively. The obtained values have yielded excellent results and guide future sustainable and renewable hydrogen energy studies by reducing costs, ensuring environmental sustainability by avoiding the formation of undesirable by-products, and producing hydrogen from NaBH4 through its high catalytic properties.