Decrease In Activation Energy Research Articles

INFLUENCE OF STABILIZED ZIRCONIUM DIOXIDE AND HIGH HYDROSTATIC PRESSURE ON THE KINETICS OF SINTERING NANOPOWDERS OF METASTABLE ALUMINUM OXIDE

The paper presents an analysis of the effect of processing powders with high hydrostatic pressure (HHP) (300, 500, 700 MPa) and stabilized zirconium dioxide (ZrO2 + 3 mol.% Y2O3, (YSZ)) doping on the compaction of metastable nanopowders mixture with γ+θ-Al2O3 + n% YSZ (n = 0, 1, 5, 10, 15wt.%) composition during sintering. The behavior of nanopowders at the initial stage of sintering was studied by dilatometry at a constant heating rate of 5 °C/min, in temperature range from 20 °C to 1500 °C. It has been determined that sintering of compacts occurs in two stages: compaction of γ + θ-Al2O3 (Ⅰ-st stage metastable phases), compaction of the stable α-Al2O3 (ⅠⅠ-nd stage), accompanied by inhibition between them. An “effect of mutual protection against crystallization” of powder mixtures was determined using the X-ray diffraction method. This is characteristic of systems obtained by co-precipitation. A connection between the above mentioned inhibition and an increase in the YSZ additive was found. That, also, correlates to the effect of “mutual protection against crystallization” of Al2O3 – YSZ powder mixtures. A study of the mechanisms and activation energies of γ+θ-Al2O3 + n% YSZ systems’ (n = 0, 1, 5, 10, 15 wt.%) sintering depending on the YSZ additive amount and the HHP value showed that a dopant and pressure increase leads to activation energy decrease of the initial sintering stage, and the prevailing sintering mechanism is volumetric diffusion in corundum grains. Also, the work shows that for γ+θ-Al2O3 + ≥5wt.% YSZ systems, the optimal compaction pressure is HHP ≥ 500 MPa, which corresponds to the transition of the sintering mechanism from grain-boundary diffusion to volumetric diffusion.

The effect of ethane on the chain reaction characteristics of methane–air mixtures explosions

In order to study the effect of ethane on gas explosions, the macroscopic properties, thermodynamics and kinetics of gas explosions were investigated using Chemkin numerical simulation software with the GRI-Mech 3.0 mechanism. Ethane was added to methane-air mixtures at seven different concentrations, such as 0%, 0.1%, 0.3% and so on, at constant initial temperature (1200 K) and pressure(0.9atm), respectively. The results show that the maximum explosion pressure, explosive power and ·H content was all maximized when the volume fraction of ethane was 3%, which was the most effective volume addition to promote gas explosion. Ethane reduced the time to peak energy of key radical reactions from 0.049s to 0.003s and reduced the sensitivity factors for reactions such as R155 and R158. When the added ethane was 8%, R158 and R98 shifted from inhibiting methane consumption to promoting methane consumption. Calculated by Arrhenius and Lindemann formulae found that ethane can act as the third molecule in unimolecular reactions, increasing the reaction rate constant and decreasing the activation energy, so accelerating the reaction. Due to the low addition of ethane, there was still a large amount of N2 acting as the third molecule, so the decrease in activation energy was small.

Relationship between structural, electrical properties and positron annihilation parameters of V2O5–Cu2O–P2O5 glasses

The structural and electrical properties of vanadium-copper-phosphate glasses with compositions of xV2O5–(40—x)Cu2O–60P2O5 (where x = 10, 20, 30, and 40 mol%) have been thoroughly investigated. As the amount of V2O5 increases, the density falls, and the molar volume rises. This effect may be attributed to the polarizing power strength, which reflects the ratio of the cation's charge to its diameter. As the concentration of V2O5 increases, the DC conductivity shows an upward trend while the activation energy decreases. Additionally, the microstructure—more specifically, the dimensions of vacancy-type defects-studied utilizing using positron annihilation lifetime (PAL) spectroscopy. A correlation was established between the sample characteristics and the PAL results. By computing the distribution of the long lifetime inferred from the PAL, the magnitude of the vacancy-type flaws was verified. The findings offer insightful information about how the PAL and sample characteristics relate to one another.

Effect of acidity of solid acid catalysts during non-oxidative thermal decomposition of LDPE

AbstractThermal decomposition of low-density polyethylene (LDPE) was monitored by thermogravimetry under N2 atmosphere in the presence of solid acid catalysts such as alumina (α-Al2O3, γ-Al2O3), crystalline silica-alumina (SA, molar ratio of Si/Al = 0.19) and amorphous silica-alumina catalysts (ASA, molar ratio of Si/Al = 4.9). Crystal structure and surface area of solid acid catalysts were measured by XRD and BET, respectively. The strength and distribution of acid sites of solid acid catalysts were estimated by NH3-TPD. It was observed that total acidity strength is in the order of ASA (1.77 μmmol NH3/g) > AS (1.42 μmol NH3/g) > γ-Al2O3 (1.06 μmol NH3/g) > α-Al2O3 (0.06 μmol NH3/g). Thermal degradation behavior of LDPE with and without solid acid catalyst was monitored by TGA, where heating rates (β) of 5, 10, and 20 °C/min were employed under an inert atmosphere, and their activation energies (Ea), onset temperatures (Tinitial), decomposition temperatures (Tdecomp) were calculated and compared. The activation energy (Ea) was evaluated using the Coats-Redfern method. Solid acid catalysts with stronger acidity and higher surface area showed a decrease in activation energy and onset temperature. Activation energy of LDPE over ASA catalyst is decreased to 97.3 kJ/mol from thermal decomposition of LDPE without catalyst of 117.2 kJ/mol under heating rate of 10 °C/min. The isothermal decomposition of LDPE was monitored at 300 °C for 3 h with a heating rate of 10 °C/min, where 13.1% and 24.2% wt. loss were observed over SA and ASA, respectively, while only 0.7% wt. loss was observed for LDPE without a solid acid catalyst. Graphical abstract Single step decomposition of LDPE Thermal degradation behavior of LDPE monitored by TGA, with different heating rates (β) of 5, 10, 20 °C/min.

Optimization of d-p band centers as efficient active sites for solar energy conversion into H2 by tuning surface atomic arrangement

The lowered reaction energy barrier and accelerated dynamic behavior for photocatalytic H2O overall splitting (HOS) involving oriented chemisorption, activation and conversion of *H and oxyhydrogen intermediates are crucial for solar energy conversion into H2 (STH). Herein, the localized heterojunction (Cd-S-Ni) composed of NiS and CdS via. tuning surface atomic arrangement with S atoms as the shared ligands has been constructed to synchronously elevate and optimize Ni 3d (Ni ε3d) and S 2p (S ε2p) band centers as efficient active sites for chemisorption of oxyhydrogen and *H intermediates with a declined Cd 4d band center (Cd ε4d) to suppress reverse reaction. A sustainable STH of 3.21 % under AM 1.5 G has been completed over Cd-S-Ni with a decreased activation energy for H2 evolution, verified by fs-TAS, in situ DRIFTS and dynamic DFT. These results devote to solving the reaction energy barrier and dynamical bottleneck for HOS by optimizing εd and εp.

Effective rare-earth doping on semiconductor behavior for BaTiO3-based automotive MLCCs

Highly accelerated lifetime test (HALT) for lifetime evaluation was performed on the state-of-art automotive MLCC prototypes by varying Dy/Mg (donor/acceptor) ratio added to BaTiO3. The results clearly showed that the mean time to failure (MTTF) more than 280 times as the Dy/Mg ratio increased from 1.0 to 10.0. Since oxygen vacancies typically form in-gap state/defect at the donor level, the activation energy value under thermal activation process as a function of voltage was calculated and compared by non-destructive testing (I–V curve) for an accurate evaluation of the extrinsic behavior. It was found that barrier height at the Ni/BT interface decreases as the voltage increases, resulting in a decrease in activation energy. As the Dy/Mg ratio increases, the density of defects/in-gap states formed at the donor level in the bandgap by oxygen vacancies decreases, which may lead to a decrease in the number of electrons excited by the external voltage. Furthermore, it was verified that the calculated Schottky barrier height of the 10.0 Dy/Mg ratio under voltage has higher value than that of the 2.6 Dy/Mg ratio. Based on the results of this study, we propose a new indicator for the design of automotive MLCCs with high lifetime reliability that can be used for comparative analysis of additive compositions through non-destructive test (I–V curve) with low evaluation time/cost.

On the"Staple" Effect in the d-Glucose Acetylation by Choline-Chloride Ethylene Glycol and Choline-Chloride Urea Deep Eutectic Solvents.

This work employs hybrid quantum mechanics molecular mechanics simulations coupled with an umbrella sampling technique to investigate the acetylation of d-glucose with acetic anhydride in two deep eutectic solvents (DESs): choline-chloride ethylene glycol (ChCl/Etg) and choline-chloride urea (ChCl/U). The reaction proceeds spontaneously, with activation free energy barriers of 18.19 ± 0.15 and 19.83 ± 0.15 kcal/mol for ChCl/Etg and ChCl/U, respectively. These values align with literature data for similar reactions in ionic liquids, highlighting the potential of DESs as green reaction media for wood modifications, while minimizing lignocellulosic matrix degradation. Energy pair distribution analysis, radial distribution functions, and noncovalent interactions reveal a more solvated transition state compared to the initial reactant state within ChCl/Etg, facilitating the acetylation reaction. Interestingly, combined distribution function analysis unveils a "staple" effect in both solvents, potentially hindering efficient product separation. The work further explores hydrogen bond networks and Kamlet-Taft solvatochromic parameters to elucidate the role of solvents in the reaction mechanism. It was observed that a notable decrease in activation energy is accompanied by increasing net basicity, along with a reduction in the "staple" effect. This suggests that solvent parameters could serve as an effective screening tool for identifying novel and efficient DESs for wood modifications.

Exploring the Impact of Elements on the Reactivity of a Straightforward Procedure for Generating Vinyl-Carbazole Derivatives via a Frustrated Lewis Pair Mechanism.

The effect of chemical element on the reactivity for carbazolation reaction of phenylacetylene utilizing G13(C6F5)3 (Lewis acid) and G15-carbazole (Lewis base) was theoretically investigated using density functional theory (M06-2X-D3/def2-TZVP), where G13 represents Group 13 elements and G15 represents Group 15 elements. Through activation strain model (ASM) analysis, it is apparent that the reactivity of the entire carbazolation reaction is chiefly governed by the structural strain energy of the alkyne fragment. In other words, if G13(C6F5)3 or G15-carbazole features an atomic radius that is either too small (e.g., B atom) or too large (e.g., Tl or Bi atom), it results in inadequate orbital overlap between the reactants due to the impact of steric effects. This, in turn, results in an elevation of the activation energy for such reactions, thereby impeding the alkyne from undergoing the carbazole catalytic reaction. In light of the above analyses, our theoretical findings suggest that, except for Tl(C6F5)3, the other four Lewis acid catalysts (B(C6F5)3, Al(C6F5)3, Ga((C6F5)3, and In((C6F5)3) demonstrate effectiveness in catalyzing the carbazolation reaction of alkyne alongside with N-carbazole. Additionally, it is anticipated that, among the five categories of G15-carbazole molecules studied, only N-carbazole can participate in the carbazolation reaction with alkyne catalyzed by B(C6F5)3, considering both kinetic and thermodynamic factors at room temperature. Our theoretical investigations, as outlined in this study, indicate that the carbazolation reaction of the alkyne, catalyzed by G13(C6F5)3 and G15-carbazole, follows Hammond's postulate. To put it more plainly, when the transition state of the chemical reaction occurs earlier, it results in a decrease in activation energy.

Introducing the sulfone group as a cellulose-binding site to improve the hydrolysis performance of the solid acid

To clarify the role of the specific sulfur-containing functional groups of solid acids in the hydrolysis of cellulose, it is necessary to prepare a solid acid bearing relatively single sulfur-containing functional groups apart from the –SO3H group. However, diphenylsulfone cannot be polymerized through Friedel-Crafts alkylation, limiting the possibility of preparing sulfone-based solid acids. Therefore, diphenyl sulfide was crosslinked through Friedel-Crafts alkylation, followed by sulfonation and oxidation. The results showed that the sulfone group was successfully introduced onto the solid acid, and the density of –SO3H groups increased by 80.88 % through this strategy. The sulfone group is a strong adsorption site for cellulose, and its introduction leads to a decrease in apparent activation energy. Cellulose conversion and glucose selectivity are as high as 77.54 % and 97.13 %, respectively. Unexpectedly, the stability of the functional groups and carbon skeleton is significantly improved due to the conjugation effect of the sulfone group.

Electrochemical Doping of Two-Dimensional Superatomic Materials.

We report an electrochemical method for doping two-dimensional (2D) superatomic semiconductor Re6Se8Cl2 that significantly improves the material's electrical transport while retaining the in-plane and stacking structures. The electrochemical reduction induces the complete dissociation of chloride anions from the surface of each superatomic nanosheet. After the material is dehalogenated, we observe the electrical conductivity (σ) increases by two orders of magnitude while the 3D electron carrier density (n3D) increases by three orders of magnitude. In addition, the thermal activation energy (Ea) and electron mobility (μe) decrease. We conclude that we have achieved effective electron-doping in 2D superatomic Re6Se8Cl2, which significantly improves the electrical transport properties. Our work sets the foundation for electrochemically doping and tuning the transport properties of other 2D superatomic materials.

Effect of the accelerated aging process on the thermal decomposition of LiAlH4-based composite solid propellants

In the present work, a study was carried out on the effect of the accelerated aging process on the thermal decomposition of two composite solid propellants based on ammonium perchlorate (AP) and hydroxy-terminated polybutadiene (HTPB). The first one (CP1) was enriched with aluminum (Al) powders, while the second (CP2) contained a mixture of aluminum and lithium alanate (LiAlH4) as a high-energy fuel additive. The thermal properties of the investigated propellant samples were determined using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The obtained results clearly demonstrated the effect of the aging process on the thermal degradation of the aged samples compared to the unaged ones, by shifting the temperature peaks of their main decomposition step to lower temperatures with a decrease in their DSC heat release. In addition, the residual unburnt propellant was increased, particularly for the complex metal hydride-based propellant. Kinetic modeling of the main thermal degradation phase, applying two advanced isoconversional methods, revealed a significant decrease in activation energy for the aged samples. Furthermore, the three-dimensional diffusion model involved during the investigated decomposition phase of the unaged samples was changed to a random nucleation model after 60 days of aging time.

Comprehensive study of alkali lignin pyrolysis catalyzed by composite metal-modified molecular sieves for the preparation of hydrocarbon liquid fuels

Catalytic lignin pyrolysis for hydrocarbon liquid fuel production offers a viable alternative to fossil fuels. This study investigated the effects of transition metal (Fe, Co, Ni, Cu) modified composite molecular sieve catalysts on the pyrolysis product distribution and behavior of alkali lignin (AL). AL pyrolysis achieved the highest liquid product yield of 24.50 % at 600 °C, with high temperatures favoring hydrocarbon product formation. Volatile gaseous products from AL pyrolysis included H2, CO, CO2, phenolic compounds, heteroatomic compounds, and hydrocarbons. Molecular sieve catalyst additions were all favorable to the increase in hydrocarbon content. Compared with ZSM-5 and SBA-15, catalysts processed through acid etching and metal modification exhibited optimized pore structure, acid site distribution, and catalytic performance. Metal-modified composite molecular sieve catalysts (FeZS, CoZS, NiZS, and CuZS) generated more liquid products and promoted hydrocarbon formation. Notably, Cu-modified ZS catalysts exhibited superior acid site distribution and specific surface area, considerably reducing oxygenated compounds in the products. A higher catalyst-to-feedstock ratio increased the number of catalytically active sites, facilitating the cracking and deoxygenation of oxygenated components and generating more hydrocarbon products. The highest hydrocarbon yield for AL with a catalyst-to-biomass ratio of 10:1 under CuZS was 92.25 %, with 66.07 % being monocyclic aromatic hydrocarbons (MAHs) and 61.72 % benzene, toluene, ethylbenzene, and xylenes (BTEX). Additionally, kinetic and thermodynamic analyses revealed a substantial decrease in the average activation energy (Eα) of AL and a reduction in entropy value with the CuZS catalyst, indicating enhanced pyrolytic reactivity of AL. Therefore, the proposed method is highly effective for producing highly selective hydrocarbons through catalytic pyrolysis of AL.

Phosphorous Vacancy and Built-In Electric Field Effect of Co-Doped MoP@MXene Heterostructures to Tune Catalytic Activity for Efficient Overall Water Splitting.

Developing cost-effective, durable bifunctional electrocatalysts is crucial but remains challenging due to slow hydrogen/oxygen evolution reaction (HER/OER) kinetics in water electrolysis. Herein, a combined engineering strategy of phosphorous vacancy (Vp) and spontaneous built-in electric field (BIEF) is proposed to design novel highly-conductive Co-doped MoP@MXene heterostructures with phosphorous vacancy (Vp-Co-MoP@MXene). Wherein, Co doping regulates the surface electronic structure and charge re-distribution of MoP, Vp induces more defects and active sites, while BIEF accelerates the interfacial charge transfer rate between Vp-Co-MoP and MXene. Therefore, the synergistic integration of Vp-Co-MoP/MXene efficiently decreases activation energy and kinetic barrier, thus promoting its intrinsically catalytic activity and structural stability. Consequently, the Vp-Co-MoP@MXene catalyst displays low overpotentials of 102.3/196.5 and 265.0/320.0mV at 10/50mA cm-2 for HER and OER, respectively. Notably, two-electrode electrolyzers with the Vp-Co-MoP@MXene bifunctional catalysts to achieve 10/50mA cm-2, only need low-cell voltages of 1.57/1.64V in alkaline media. Besides, experimental and theoretical results confirm that the hetero-structure effectively reduces hydrogen adsorption free energy and rate-determining-step energy barrier of OER intermediates, thereby greatly boosting its intrinsically catalytic activity. This work verifies an effective strategy to fabricate efficient non-precious bifunctional electro-catalysts for water splitting via combination engineering of phosphorous vacancy, cation doping, and BIEF.

Phosphate/Silicate Ratio Allows for Fine-Tuning of Bioactive Glass Crystallisation and Glass-Ceramic Microstructure

A combination of XRD, solid-state NMR and state-of-the-art imaging techniques were used to investigate how the calcium orthophosphate/calcium silicate ratio affects the crystallisation of bioactive glasses in the system SiO2-P2O5-CaO-CaF2. In the phosphate-free glass, xonotlite, wollastonite and cuspidine crystallised. From 2.4 mol% P2O5, fluorapatite also formed, while the amount of wollastonite decreased. Crystallisation tendency was low for low phosphate contents, while above 3 mol% P2O5 it increased. The phosphate-free glass showed a volume crystallisation mechanism with constant activation energy. By contrast, the glass with the largest phosphate to silicate ratio showed both volume and surface crystallisation, causing a pronounced decrease in activation energy with crystallisation degree. This work shows that by changing the phosphate/silicate ratio we can determine which crystal phases form, obtaining for example fluorapatite-free or wollastonite-free glass-ceramics, depending on the desired application and properties such as mechanical strength or activity in contact with physiological solutions.

Hydrolysis rate constants of ATP up to 120 °C and 1.6 GPa: Implications for life at extreme conditions

Extreme environments are habitats for a diverse array of microorganisms, namely extremophiles, that have evolved unique biochemical adaptations to their geological setting. Some examples of extremophiles can be found in the subseafloor or near hydrothermal vents on the ocean floor. Cultivated strains of extremophiles have demonstrated the ability to tolerate temperatures (T) up to 122 °C and pressures (P) up to 125 MPa. Organisms depend on the stability of key metabolites, such as adenosine triphosphate (ATP), to survive and reproduce under these conditions. In order to maintain their intracellular ATP levels, living cells must compensate for the abiotic hydrolysis of ATP, which occurs at a particularly rapid rate at high temperatures. The role of high pressures and high temperatures in abiotic hydrolysis of ATP has been rarely investigated despite the potential for this phenomenon to contribute to limit the adaptation of microorganisms to simultaneous extreme temperatures and pressures. This study presents new data on the effect of pressure on the abiotic hydrolysis of ATP to adenosine diphosphate (ADP) at elevated temperatures. In situ Raman spectra were measured at high pressure and high temperature of the hydrolysis of aqueous disodium ATP solutions in two experimental systems: a hydrothermal diamond anvil cell (HDAC) and a gas-pressurized autoclave. These two systems permitted the determination of hydrolysis rate constants of ATP into ADP up to 1670 MPa at 80 °C, 100 °C, and 120 °C. The data exhibited Arrhenian behavior with a slight decrease in activation energy from 0.5 MPa to 140 MPa. The effect of pressure on ATP hydrolysis rate constants was found to be vanishingly low in the so far known vital range up to 125 MPa. Abiotic hydrolysis rates of ATP showed a pronounced increase at higher pressures. For example, at 100 °C, a rise in pressure from 365 MPa to approximately 1670 MPa results in a nearly tenfold increase in the ATP hydrolysis rate constant. When compared with the typical ATP turnover times reported in living cells, the abiotic ATP hydrolysis rates determined in this study provide insights into the pressure and temperature conditions that could be consistent with living microorganisms.

Examining the impact of nano‐sized Litharge, Tenorite, and Hematite on the thermal decomposition of ammonium perchlorate‐based cross‐linked composite modified double base propellant

AbstractThis study aims to compare the catalytic effects of three nano‐metal oxides (nMOs); Litharge (α‐PbO), Tenorite (CuO), and Hematite (α‐Fe2O3) on the thermal decomposition of an ammonium perchlorate based cross‐linked composite modified double base propellant (AP‐XLCMDBP). The three nMOs are synthesized via a chemical precipitation method and then characterized using XRD, FTIR, and SEM. Their effect on the thermal decomposition of AP‐XLCMDBP is studied using thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). The results indicate that Litharge has no significant effect on the thermal decomposition of AP‐XLCMDBP. However, both Tenorite and Hematite nanocatalysts accelerate the thermolysis process and enhance the total heat released from AP‐XLCMDBP. Moreover, compared to Tenorite, Hematite nanoparticles are found to be a more efficient catalyst, where their presence in AP‐XLCMDBP leads to a significant decrease in activation energies of the first and the second decomposition stages by 13.67 kJ/mol and 17.57 kJ/mol, respectively. An increase of the total decomposition heat by 153.73 J/g is also attained in the presence of Hematite, displaying its high catalytic action on the thermal decomposition of AP‐XLCMDBP.

High cyclic stability and low plateau of Ti2V2Zr/NaH/Al hydrogen storage composite system prepared by ultrasound-assisted ball milling

NaH/Al doped with Ti2V2Zr with the aim of lowering the rehydrogenation pressure, lowering the dehydrogenation temperature, and improving the hydrogenation/dehydrogenation kinetics of NaAlH4. It was found that moderate ultrasonic-assisted wet grinding was beneficial to fine particles efficiently, improved uniformity of particle size, and reduced lattice distortion because its crystalline phase can converge more active hydrogen atoms and reduce the energy barrier of H exchange between the alloy and the matrix, thus improving the comprehensive hydrogen storage performance of the composite systems. It could reversibly store 4.81 wt% of hydrogen and completely hydrogenation under a low hydrogen pressure of 55 atm, its starting and ending dehydrogenation temperatures decrease by 81 and 89 °C, respectively, and the activation energies of the two-step dehydrogenation decrease by 26.7 and 52.7 kJ mol−1 respectively, with a dehydrogenation capacity retention of up to 99.58% over five cycles.

Kinetic and combustion characteristics of oil palm empty fruit bunch biochar using thermogravimetric analysis

The usage of renewable energy is a mitigation phenomenon majorly impacting the power sectors, with biomass being one of the sources directly replacing coal in various applications. This leads to the portrayal of biomass having the potential to be a carbonaceous material, namely the Empty Fruit Bunch (EFB) of oil palm. To increase the characteristics of EFB, it can be converted into carbon-based products through thermochemical processes, such as hydrothermal carbonization. Therefore, this study aimed to compare the characteristics of feedstock and biochar EFB using the TGA method. The heating rate used in this study is 10 – 30°C/min at five °C/min intervals. The effect of heating rate on kinetic parameters and thermal (DTG, TGA) and combustion (T ignition, T burn out) characteristics was also determined. This study carried out the HTC process at temperatures of 210ᵒC and 230ᵒC. The results showed that biochar EFB had a higher ignition, burnout temperature, and activation energy than raw EFB. Ignition temperatures for EFB-HT210°C and EFB-HT230°C were 297°C and 298°C; burnout temperatures for EFB-HT210°C, EFB-HT230°C were 407°C and 450°C; and the activation energy for EFB-HT210°C, EFB-HT230°C were 58.84 kJ/mol and 62.16 kJ/mol. Besides the characteristics of biomass, the heating rate also affects combustion. This proved that increased heating rate caused higher ignition and burnout temperature and decreased activation energy. The results also indicated that the difference in heating rate influenced the peak temperature in DTG.

Correlation between structural, morphological, and electrical transport properties of nano-dimensional Tellurium thin film by low energy ion beam irradiation

Tellurium (Te), an emerging semiconductor material, exhibits intriguing physical properties in low-dimensional forms. This study investigates the structural, morphological, and transport properties of low-dimensional Te thin film deposited by physical vapor deposition after 400 keV Kr2+ ion irradiation with varying fluences of 1 × 1013, 5 × 1013, and1 × 1014 ions-cm−2. The X-ray diffraction (XRD) pattern reveals the hexagonal phase of pristine Te. As ion fluence increases, intensity of the XRD peaks decreases and the full-width half maxima (FWHM) increases, indicating a reduction in crystallinity. The intensity of the Raman peak decreases upon irradiation, resulting in a red shift in the spectra of the irradiated sample. The evolution of morphology at different fluences has been examined with atomic force microscopy (AFM) measurements. The results indicate the segregation of grains and an increase in root mean square (RMS) roughness from 2.59 pm to 5.11 pm with ion fluence up to 5 × 1013 ions-cm−2. At the highest fluence, i.e., 1 × 1014 ions-cm−2, there is an agglomeration of grains, and hence a decrease in RMS roughness to 3.92 pm is observed. The DC resistivity measurement indicates the semiconducting nature of all films. Additionally, this measurement signifies the rapid decrease in activation energy at both band-to-band conduction and nearest neighbour hopping (NNH) conduction. Following irradiation, Hall measurement demonstrates a decrease in the concentration of charge carriers and an increase in resistivity due to scattering originating from grain boundaries. However, when the fluence is increased to 1 × 1014 ions-cm−2, there is a reduction in resistivity and an increase in carrier concentration with enhanced Hall mobility in comparison to pristine Te. Therefore, this study showcases that low-energy ion irradiation has a significant impact on the modification of the structure, morphology, and electrical transport properties of semiconducting Te thin film.

Preparation and Reactivity of Core-Shell Al@CL-20 Composites Embedded with Graphene-Based Complexes as Catalysts.

Incomplete combustion of Al in solid propellants can be effectively resolved by coating of an oxidizer at the microscale. In this paper, Al@CL-20 composites with polydopamine as the interfacial layer were prepared using this strategy. The structure, heat of reaction, thermal decomposition properties, and combustion performances of these composites under the effects of graphene oxide (GO) and graphene-based carbohydrazide complexes (GO-CHZ-M, M = Co2+, Ni2+) have been comprehensively investigated. The experimental results show that the heat of reaction of Al@CL-20 is 6482 J g-1, which is 561 J g-1 higher than that of the corresponding mechanical mixture. The presence of GO-CHZ-Co can further increase the heat of reaction of Al@CL-20 to 6729 J g-1 with a decreased activation energy by about 54.8%. Under the synergistic effect of interfacial control and GO-CHZ-M, the ignition delay time of Al@CL-20-Co decreases from 5.1 to 4.2 ms. Besides, the D50 of the combustion condensed products (CCPs) decreased from 5.62 to 4.33 μm, indicating the combustion efficiency of Al is greatly improved.