Ea Values Research Articles

Non‐Isothermal Decomposition Kinetics of Hafnium and Zirconyl Hydrogentellurates

ABSTRACTThe thermal characteristics of zirconyl and hafnium hydrogentellurates, ZrO(HTeO4)2 × 4H2O (ZrOTe) and Hf(HTeO4)4 × 8H2O (HfTe), were investigated via non‐isothermal decomposition kinetics in this paper for the first time. Important kinetic parameters such as activation energy (EA), pre‐exponential factor (A) and g(α) function were determined using Coats‐Redfern integral method. The latter was verified by means of z(α) master plots. In addition, plausible decomposition mechanisms for the title compounds were offered. Based on the EA values, less thermal stability for ZrOTe (633.69 kJ/mol) with respect to HfTe (872.24 kJ/mol) was observed. Thermodynamic functions (ΔS≠, ΔH≠, and ΔG≠) of the activated complexes generated during the thermal decomposition steps were studied as well. A high positive ΔH≠ value (855.70 kJ/mol) for the thermal decomposition of HfTe indicated formation of high‐ordered activated complexes. In contrast, lower ΔH≠ (612.50 kJ/mol) for ZrOTe suggested easier formation the transition states in that case.

A New Approach for Predicting Strength Based on Temperature-Time History Using Two-Parameter Maturity ANN Models

One widely used method to predict concrete strength development based on temperature variations during curing is the equivalent maturity time (te) method. This method uses the activation energy (Ea) as its key parameter, which reflects the cement’s sensitivity to temperature. However, research shows that the Ea value varies depending on factors such as cement type, water/cement ratio, temperature, and additives. The permanent subject of discussion is the question of what value of the Ea parameter should be assumed. In this paper, a new approach is proposed by using a neural network analysis method to develop a strength–temperature history model. It was assumed that the ANN-fc% = f(Q, E, T, t) model would have 4 inputs: hydration heat (Q), activation energy (Ea), temperature (T), and time (t). The research was conducted on mortars using 6 cements, at curing temperatures ranging from 5 to 35 °C, assessing strength over a 90 day period. The results showed that the ANN analysis method allows for estimating the relative compressive strength with sufficient accuracy. Analysis of the input nodes indicated that Q influences early strength gain, while Ea affects later strength development. The application of the ANN model for calculating strength based on temperature changes during maturation was illustrated.

Catalysts review for hydrogen generation from sodium borohydride solutions and surviving ability of living beings in the long-time space flights

Hydrogen (H2), environmentally friendly effective energy carrier with the most advantageous combustion by-products, readily attained from borohydride (NaBH4) with higher hydrogen (H2) generation rates (HGRs) as safer than e other hydrates necessitating the use of various catalysts. The catalysts' performances are major factors in high HGR from NaBH4 regardless of hydrolysis or methanolysis reactions. The HGR is influenced by NaBH4 concentrations, reaction temperature, and the catalyst amounts. Nobel metals e.g., ruthenium (Ru), platinum (Pt), Rhodium (Rh) etc reported as highly effective catalysts for fast H2 production from NaBH4 solutions including ethanol, methanol, and ethylene glycol. Due to shortage and cost considerations of noble metals, transition metal-based catalysts e.g., cobalt (Co), nickel (Ni), and manganese (Mn) have gained great interest for H2 production from NaBH4 hydrolysis/alcoholysis. Metal nanoparticle-based catalysts, and their synthetic and natural polymer composites along with non-metallic catalyst including micro/nanogels, bulk hydrogels, cryogels, and polymeric ionic liquids (PILs) have been employed as catalysts in methanolysis/hydrolysis of NaBH4 to attain lower Ea and high HGR values. Therefore, in this review catalysts whether metal or non-metal used in H2 generation reactions will be surveyed, Moreover, space application of H2 energy systems with their commercial application for future use will be assessed.

Kinetic and thermodynamic study of maize stalk biomass using thermogravimetric analysis

Abstract Investigating thermodynamic and kinetic aspects is crucial for assessing efficiency of converting biomass into energy. This study presents kinetic and thermodynamic characteristics of maize stalk using thermogravimetric analysis. The novelty of this research stems from the combination of kinetic and thermodynamic analysis, the application of multiple kinetic models and understanding of pyrolysis-based bioenergy production process from maize stalk. Analysis was performed using a temperature range of 25–650 °C employing 5, 10, 15 and 20 °C/min heating rate. The temperature range of 250–650 °C was selected to analyze the complete decomposition of the three main components of maize stalk i.e. hemicellulose, cellulose and lignin and to prevent the decomposition of inorganic substances such as CaCO3 which decompose at high temperature. The apparent activation energy values were evaluated using Kissinger-Akahira-Sunose (KAS), Friedman and Ozawa-Flynn-Wall (OFW) models. The resulting mean apparent Ea values calculated for KAS, Friedman and OFW were 167.86, 177.34 and 162.96 kJ/mol, accordingly. Additionally, Gibbs free energy (ΔG) values were 164.17 kJ/mol, enthalpy (ΔH) −178.31 J/molK and entropy (ΔS) 285.59 kJ/mol, respectively. These findings suggest that maize stalk holds promise as a potential bioenergy source, aligning with sustainable goals and waste-to-energy strategies.

Kinetic and Chemical Analysis of Pyrolysis in Bambusa vulgaris Leaves and Derived Fibers

Bamboo, a perennial and monocarpic plant, holds immense potential beyond its commonly recognized applications. In this study, fiber was extracted from bamboo leaves. Pyrolytic kinetic studies were done on leaves and the extracted fibers, utilizing thermogravimetry and derivative thermogravimetry (TG/DTG) data obtained at heating rates 10, 20, and 30 K/min within the temperature range of 298–1093 K. Model-free methods such as Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS), and Friedman were employed to calculate the activation energy (Ea) and the pre-exponential factor (A). For leaves, the calculated Ea values were found to be 283 kJ/mol (KAS), 279 kJ/mol (OFW), and 318 kJ/mol (Friedman), while the A values were determined as 7.2 × 1043 s−1 (KAS), 1.07 × 1043 s−1 (OFW), and 5.7 × 1045 s−1 (Friedman). In the case of fiber, the Ea values were found to be 162 kJ/mol (KAS), 164 kJ/mol (OFW), and 165 kJ/mol (Friedman), with corresponding A of 4.6 × 1015 s−1 (KAS), 5.6 × 1013 s−1 (OFW), and 348 × 1013 s−1 (Friedman). Additionally, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) analyses were conducted on both leaves and fiber.

On the Activation Energy of Termination in Radical Polymerization, as Studied at Low Conversion.

The chain-length-dependent nature of the termination reaction in radical polymerization (RP) renders the overall termination rate coefficient, <kt>, a complex parameter in the usual situation where the radical chain-length distribution is non-uniform. This applies also for the activation energy of termination, Ea(<kt>), which we subject to detailed mechanistic investigation for the first time. The experimental side of this work measures Ea(<kt>) for the dilute-solution, low-conversion, chemically initiated homopolymerization of styrene (ST), methyl methacrylate (MMA), butyl methacrylate, and dodecyl methacrylate. Values of 25-39 kJ mol-1 are obtained, consistent with strong chain-length-dependent termination (CLDT) for short chains. On other hand, the reanalysis of analogous bulk polymerization data for ST and MMA finds Ea(<kt>) values of 18-24 kJ mol-1, consistent with weak CLDT for long chains. Both these results are as expected from the so-called composite model for CLDT. A simple analytic framework for understanding and predicting Ea(<kt>) values is presented for the standard RP situation of continuous initiation. All the results of this work can be rationalized via this framework, which clearly establishes that Ea(<kt>) is determined by far more than just the Ea of radical diffusion. This framework is extended to activation energy for the number-average degree of polymerization, Ea(DPn), which we measure and successfully scrutinize via our CLDT model. In the final section of this work, we make interesting, testable predictions about Ea(<kt>) and/or Ea(DPn) in various RP systems of different natures to those studied here, most notably, systems involving acrylates, continuous photoinitiation, or dominant chain transfer.

Kinetic study of the combustion process in internal combustion engines: A new methodological approach employing an artificial neural network

The comprehension of combustion mechanisms enables supervision of reaction rates. By adjusting factors such as heat transfer rates, combustion duration, self-ignition propensity, ignition delay and laminar flame speeds, it is possible to minimize emissions and enhance fuel conversion efficiency in internal combustion engines (ICE). The present study aims to develop and explore a methodology employing an Artificial Neural Network that uses Mass Burned Fraction data as a function of crankshaft angular position to determine combustion kinetics in ICE. The Artificial Neural Network was programmed in this work as a home-made code and produced accurate results. The kinetic triplet consisting of Activation Energy (Ea), Frequency Factor (A) and Reaction Model throughout the combustion process was determined to explore the combustion characteristics of different gasoline formulations and ICE operation conditions. The experimental data were obtained in a Single Cylinder Research Engine (SCRE) operating with gasoline formulations commercialized in Brazil. The methodology determines the kinetics of combustion along the process and recovers the values of Ea and A without resorting to mechanisms that describe each reaction individually, describing, instead, the global contribution of physical models. Because the kinetic models activate the neurons in the hidden layer, they accurately reproduce the experimental Mass Burned Fraction data and bring physical information to the network about the combustion process. The kinetic study showed that the samples with higher values of Ea also had higher ignition delay. The rate constant was also related to the consumption and combustion efficiency during the combustion process, i.e., the fuel with a higher rate constant presents greater combustion efficiency and smaller consumption.

Construction and Comparative Research of Two MOFs Proton Conducting Materials Containing Nitro Groups.

In field of electrochemistry, there has been a growing interest in the potential applications of proton-conducting metal-organic frameworks (MOFs). Therefore, how to design and synthesize MOFs with high proton conductivity is considered crucial. In this study, two examples of nitro-containing Cd-based MOFs, MOF-1 {[Cd3(TIPE)1.5(NO3)5Cl(H2O)2]·17H2O}n and MOF-2 {[Cd(TIPE)0.5(nip)]·10H2O}n (TIPE=1,1,2,2-tetrakis(4-(1H-imidazole-1-yl)phenyl)ethene, H2nip=5-Nitroisophthalic Acid), had been successfully designed and synthesized, and their proton-conducting properties were thoroughly investigated. Notably, both materials displayed peak proton conductivity at 98% RH and 90 °C, exhibiting values of 9.13 × 10-3 and 3.00 × 10-3 S∙cm-1 for MOF-1 and MOF-2, respectively. The plausible proton conduction pathways and mechanisms were elucidated through structural analyses, water vapor adsorption studies, and the determination of activation energy (Ea) values. It was found that the difference in proton conductivity between MOF-1 and MOF-2 was mainly associated with the different water absorption rates of the samples. The uniqueness of this study was that for the first time conducted an in-depth study of the role of nitrate in proton conduction, providing new ideas for designing materials with excellent proton conductivity.

Highly efficient CO2 capture by a non-aqueous amine-based absorbent of 3 aminopropanol/polyethylene glycol 200: Experimental and computational simulation

In the present work, a novel non-aqueous 3-aminopropanol/polyethylene glycol 200 (3AP/PEG200) absorbent for efficient carbon dioxide (CO2) capture was designed using environment-benign and non-toxic polyethylene glycol 200 (PEG200) as an alternative to water. The mechanism, physical, thermodynamic, and kinetic properties of absorption process was investigated through a combination of experimental and multi-scale computational simulation approaches including molecular dynamics (MD) simulation and quantum chemical (QC) calculations. It was found that the addition of PEG200 not only enhanced the thermal stability of the absorbent, but also did not significantly increase the viscosity. In addition, kinetic studies revealed that the absorption process conforms to a pseudo-first-order equation, with the activation energy (Ea) value of 20.40 kJ/mol, significantly lower than that of the benchmark 30 % monoethanolamine (MEA) aqueous solution used in industrial CO2 capture. Furthermore, the enthalpy change (ΔH) and entropy change (ΔS) values were found to be more negative than those of other liquid absorption systems, indicating that the 3AP/PEG200 absorbent is favorable for CO2 absorption even at low partial pressures. Most importantly, the absorption system exhibited good regeneration capability, as demonstrated by five absorption–desorption cycle experiments. In conclusion, the non-aqueous 3AP/PEG200 absorbent exhibits low viscosity, high thermal stability, enhanced absorption capacity, and excellent cyclic performance, positioning it as a promising candidate for CO2 absorption in industrial applications.

Corrosion Inhibition and Adsorption Behaviour of Centrosema pubescens Leaf Extract for Copper in HCl Solution

Study’s Excerpt In this study, Centrosema pubescens leaf extract (CPE) has been confirmed as eco-friendly and efficient green inhibitor for copper corrosion in hydrochloric acid. Detailed thermodynamic analysis, revealed that CPE adsorption follows a Freundlich isotherm model. SEM-EDX and FTIR characterizations confirmed the formation of a protective layer confirming the potentials of the plant extracts in sustainable corrosion prevention. Full Abstract The anti-corrosion behaviour of Centrosema pubescens leaf extract (CPE) on copper in 1.5 M hydrochloric acid was investigated using weight loss method at different temperatures, followed with scanning electron microscopy (SEM) surface characterization connected with energy dispersive X-ray spectroscopy (EDX). The Fourier transform infrared spectrum of CPE was obtained. CPE inhibition effectiveness depends on the temperature and its concentration. CPE restrains the copper corrosion with 94.26 % inhibition efficiency at 1.0 g/L of CPE and at 303 K. For the CPE-inhibited system, a higher activation energy (Ea) value (range of 31.09 to 38.70 kJmol-1) compared to 20.34 kJmol-1 of the blank solution was obtained. The reaction process is spontaneous and endo thermic, as indicated by the ΔH, ΔS and ΔG values calculated. CPE adsorption behaviour fitted best into Freundlich isotherm.

Energy Recovery from Municipal Sewage Sludge: Combustion Kinetics in a Varied Oxygen–Carbon Dioxide Atmosphere

Energy from municipal sewage sludge can be obtained by applying a thermal conversion method. In this study, the combustion kinetics of municipal sewage sludge were analyzed in an O2/CO2 atmosphere. Studies were conducted in different gaseous atmospheres consisting of varying proportions of oxygen and carbon dioxide. The participation of oxygen was as follows: 20, 40, 60, 80 and 100% vol. The experimental temperatures varied from 873 to 1273 K. The experimentally obtained results helped establish the basic kinetic parameters, such as the reaction order n, factor Ko and activation energy Ea of sludge grains. The values of the activation energy Ea and Ko were, respectively, 46 kJ/mol and 0.0127 mg/m2sPa. They show that the limiting factor of combustion is the diffusion of oxygen and that combustion reactions take place in the outer layer of the unreacted core. Therefore, sludge is promising for energy recovery because it has quite a high net calorific value (NCV) and a high gross calorific value (GCV). The GCV was 14.1 MJ/kg and the NCV was 12.8 MJ/kg. The experimental studies with a wide range of process parameters helped to create an array of apparent reaction rates as a function of the temperature and oxygen concentration, showing the significant effect of oxygen on the apparent reaction rate, in contrast to the effect of temperature.

Endoxylanase Immobilized Nanoporous Silica for the Production of Xylooligosaccharides: Equilibrium Kinetics, Thermodynamic Studies, and Enzyme Characteristics

AbstractNanoporous structured silica materials, namely f‐SiO2, SBA‐15, IITM‐41, and MCM‐41 were employed as the matrices for immobilizing endoxylanase by adsorption method. The equilibrium kinetics, activation energy, and thermodynamic parameters associated with endoxylanase adsorption were investigated. Our findings revealed a two‐phase adsorption mechanism: an initial phase featuring rapid adsorption rates, succeeded by a slower phase wherein adsorption gradually progressed until equilibrium was attained. Analysis of the adsorption kinetic data indicated a better fit with the pseudo‐second‐order model, suggesting chemisorption and highlighting its temperature dependency. The calculated activation energy (Ea) values fell within the range of physisorption, indicating the involvement of both types of adsorption processes. Thermodynamic assessments confirmed that the adsorption reactions were spontaneous, feasible, and endothermic. Notably, the immobilization process did not change the optimum pH of the enzyme, while the optimum temperature shifted slightly. Furthermore, immobilized enzymes show a higher reaction rate (Vmax) than the soluble XynC. All immobilized xylanases produced xylobiose (X2) to xylohexose (X6) by hydrolyzing the xylan substrate. Recycling studies showed that up to 80 % of the yield was retained after seven cycles of reuse. Our study demonstrates the potential of nanostructured silica as an effective immobilization matrix for enzymes of industrial significance.

Adsorption Performance of Fe-Mn Polymer Nanocomposites for Arsenic Removal: Insights from Kinetic and Isotherm Models.

Global concern over arsenic contamination in drinking water necessitates innovative and sustainable remediation technologies. This study evaluates the adsorption performance of Fe-Mn binary oxide (FMBO) nanocomposites developed by coating polyethylene (PE) and polyethylene terephthalate (PET) with FMBO for the removal of As(III) and As(V) from water. Adsorption kinetics were rapid, with equilibrium achieved within 1-4 h depending on the material and pH. PET-FMBO and FMBO exhibited faster rates and higher arsenic removal (up to 96%) than PE-FMBO. Maximum As(III) adsorption capacities ranged from 4.76 to 5.75 mg/g for PE-FMBO, 7.2 to 12.0 mg/g for PET-FMBO, and up to 20.8 mg/g for FMBO, while capacities for As(V) ranged from 5.20 to 5.60 mg/g, 7.63 to 18.4 mg/g, and up to 46.2 mg/g, respectively. The results of the Dubinin-Radushkevich isotherm model, with free energy (Ea) values exceeding 16 kJ/mol, suggest chemisorption is the dominant mechanism, which is supported by the kinetics data. Given the effective removal of As(III), chemisorption likely proceeds through ligand exchange during the Mn oxide-mediated oxidation of As(III) and complexation with hydroxyl groups on the nanocomposite. These findings highlight the strong potential of Fe-Mn polymer nanocomposites, particularly PET-FMBO, for efficient arsenic removal during practical water treatment applications.

Effect of fullerene (C70) on the structural, morphological optical and thermal properties of poly(butyl methacrylate) (PBMA)

Poly(butyl methacrylate) (PBMA)/Fullerene (C70) nanocomposites were successfully prepared by solvent removal method and characterized by different techniques. Structural characterization showed an interaction between PBMA and C70 nanofiller. Morphological features showed that C70 was homogeneously distributed in the PBMA matrix. Optical analysis confirmed the formation of nanocomposites with wavelength shift in PBMA/C70 nanocomposites compared to pure PBMA. Photoluminescence spectra showed that the emission bands of PBMA/C70 nanocomposites shifted from blue to red and the presence of new emission spectra in the red region. The data obtained from thermal analysis showed that the Tg of the nanocomposites increased by about 10 °C compared to pure PBMA and the maximum decomposition temperatures improved by about 65–70 °C, confirming the increased thermal stability. The data obtained from thermogravimetric analyses performed at different heating rates were analyzed by Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) equations to calculate the activation energy values. According to the regression coefficient values, the experimental results were in good agreement with the FWO method (R2 PBMA=0.937 and R2 PBMA/C70 (5 wt%)=0.953). The activation energy of PBMA and fullerene doped nanocomposite were calculated as 48 kJ/mol and 104 kJ/mol, respectively and the results showed that the Ea value of nanocomposite was higher than PBMA.

Methane Production Is More Sensitive to Temperature Increase than Aerobic and Anaerobic Methane Oxidation in Chinese Paddy Soils.

Methane emissions from paddy fields can increase under future warming scenarios. Nevertheless, a comprehensive comparison of the temperature sensitivity of methane-related microbial processes remains elusive. Here, we revealed that the temperature sensitivity of methane production (activation energy (Ea) = 0.94 eV; 95% confidence interval (CI), 0.78-1.10 eV) and aerobic (Ea = 0.49 eV; 95% CI, 0.34-0.65 eV) and anaerobic (Ea = 0.46 eV; 95% CI, 0.30-0.62 eV) methane oxidation exhibited notable spatial heterogeneity across 12 Chinese paddy fields spanning 35° longitude and 18° latitude. In addition, the Ea values of aerobic and anaerobic methane oxidation were significantly positively and negatively correlated to the latitude, respectively, while there was no significant correlation between the Ea of methane production and the latitude. Overall, there were no soil factors that had a significant effect on the Ea of methane production. The Ea of aerobic methane oxidation was primarily influenced by the contents of ammonium and clay, whereas the Ea of anaerobic methane oxidation was mainly influenced by the conductivity. Despite the variation, the overall temperature sensitivity of methane production was significantly higher than that of oxidation at a continental scale; therefore, an increase in the emission of methane from paddy fields will be predicted under future warming. Taken together, our study revealed the characteristics of temperature sensitivity of methane production and aerobic and anaerobic methane oxidation simultaneously in Chinese paddy fields, highlighting the potential roles of soil factors in influencing temperature sensitivity.

Theoretical screening of single-atom catalysts (SACs) on Mo2TiC2O2 MXene for methane activation

Producing value-added chemicals and fuels from methane (CH4) under mild conditions efficiently utilizes this cheap and abundant feedstock, promoting economic growth, energy security, and environmental sustainability. However, the first CH bond activation is a significant challenge and requires high energy. Efficient catalysts have been sought for utilizing CH4 at low temperatures including emerging single-atom catalysts (SACs). In this work, we screened fourteen transition metals (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt) doped at a single oxygen vacancy in Mo2TiC2O2 (TMSA-Mo2TiC2O2 SACs) for methane activation using density functional theory (DFT) calculations. Our results reveal that methane adsorption is thermodynamically stable on all simulated TMSA-Mo2TiC2O2 SACs, with the adsorption energies (Eads) ranging from −0.92 to −0.40 eV. For the CH activation process, Ru-SAC exhibits the lowest activation barrier (Ea) of 0.22 eV. In summary, Ru-, Rh-, Co-, V-, Cr-, Ti-, and Pt-SACs demonstrate promising catalytic properties for methane activation, with Ea values below 1.0 eV and an exothermic nature. Our findings pave the way for the design and development of novel single-atom catalysts in MXene materials, applicable not only for methane activation but also for other alkane dehydrogenation processes.

On the effect of energy input on microstructure evolution and mechanical properties of laser beam powder bed fusion processed Ti-27Nb-6Ta biomedical alloy

Additive manufacturing of pre-alloyed Ti-27Nb-6Ta powder by laser beam powder bed fusion (PBF-LB/M) employing a wide range of processing parameters is reported. An in-depth microstructure analysis along the whole process chain from powder feedstock material to additively manufactured bulk structures was conducted employing scanning electron microscopy (SEM) as well as X-ray and high-energy synchrotron diffraction. It is shown that near-fully dense parts (≥99.96 %) with β+α’’ dual-phase microstructure and very homogenous element distribution are obtained in a large process window. In particular, a considerable influence of the energy input during PBF-LB/M on the solidification microstructure, i.e. phase composition and texture, is found. With increasing energy per unit area (EA) both an increase in the volume fraction of the bcc β-phase and more pronounced texture components are seen. Furthermore, the mechanical behavior was evaluated under monotonic tensile loading. The PBF-LB/M processed Ti-27Nb-6Ta structures feature good mechanical properties with ultimate tensile strength (UTS) and strain to failure values of up to 768 MPa and 33.8 %, respectively. Due to the strong impact of the energy input during additive manufacturing on the microstructure evolution, however, an inverse strength-ductility behavior is observed. While UTS clearly decreases with increasing EA values, strain to failure increases at the same time. The underlying relationships between processing (energy input), microstructure and mechanical properties are explored and rationalized.

Kinetics study of pyrolysis of petroleum sludge and characterization of char

Thermochemical conversion (or pyrolysis) has emerged as an effective technique for the disposal of sludge generated in process industries. This paper reports physicochemical characterization and kinetic analysis of pyrolysis of sludge from a petroleum refinery and characterization of resultant char. The sludge had high volatile matter (>70 wt%) and low ash content (15 wt%). Pyrolysis of sludge was studied using a thermo-gravimetric analyzer (TGA). The TGA data was analyzed using two isoconversional models, viz. KAS and Vyazovkin AIC are used for the deduction of kinetic triplets, viz. activation energy, pre-exponential factor, and reaction mechanism. The activation energy (Ea ) of sludge pyrolysis varied in the 64.79–190.37 kJ/mol range. The pre-exponential factor varied from 1.18E + 07 to 4.29E + 12 s−1. The predominant solid-state mechanism of thermal conversion was an order-based reaction (F2/F3). The thermodynamic factors (viz. ΔH, ΔS, ΔG) of sludge pyrolysis were also determined. Relatively small values of (Ea – ΔH) ∼ 5 kJ/mol revealed high susceptibility of sludge for thermal conversion. Residual char after pyrolysis was characterized for physicochemical properties. The char properties were fixed carbon = 54.37%, calorific value = 22.48 MJ/kg, and BET surface area = 18.35 m2/g. These properties make char suitable for numerous applications.

Reactivity of polyaniline composites with attractive cyclic nitramines

Composite microcrystals of the nitramines (NAs) RDX, HMX, BCHMX and CL-20 with electrically conductive polyaniline (PANi) are a charge transfer complexes in composite crystals (CACs). The activation energies of thermolysis, Ea, of the pure NAs and their PANi-composites were determined using the Kissinger method, and decomposition processes are discussed. Except for the RDX/PANi CAC, all the other CACs show higher Ea values for decomposition compared to their pure NA counterparts. For all CACs, relationships are specified between the Ea values, on the one hand, and the squares of the detonation velocities, enthalpies of formation, spark energy and impact sensitivities, on the other. The relationships between their low-temperature heats of decomposition, ΔH, from DSC, and their enthalpy of formation, logarithm of impact sensitivity, electric spark energy, as well as detonation energy, are described. The PANi favorably influences the density of the corresponding CAC; surprisingly close linear correlations were found, and explained, between these densities and the Ea values. This presence of PANi strongly increased the electrical spark sensitivity of the CACs in comparison to the base NAs. Based on the results obtained, it can be noted in particular the exceptional desensitization of HMX to impact and the increased sensitivity to electrical spark by coating its crystals with polyaniline.

Synthesis of a new quaternary ammonium salt for efficient inhibition of mild steel corrosion in 15 % HCl: Experimental and theoretical studies

The corrosion phenomenon and its economic impacts can hardly be ignored in any application. This study synthesized a quaternary ammonium salt (3) containing hydrophobic dodecyl and electron-rich diallylbenzyl amine moieties to be used in 15 % HCl as a corrosion inhibitor of mild steel. Several techniques, such as 1H and 13C NMR, IR, TGA, and elemental analysis, have been used to characterize inhibitor 3. Popular corrosion measurement techniques, namely weight loss, potentiodynamic polarization techniques, and electrochemical impedance spectroscopy, have been used to determine the efficiency of inhibitor 3. At 303 K and a moderately low concentration of 50 ppm, the quaternary ammonium salt-based inhibitor demonstrated a maximum efficiency of ≈95.0 %. At elevated temperatures of 313, 323, and 333 K, the inhibition efficacy values were recorded as 91.3, 82.8, and 75.0 %, respectively. Adsorption isotherm study revealed that the adsorption of inhibitor 3 followed Langmuir adsorption isotherm. The value of ΔGads° was found to be – 40.19 kJ mol−1, indicating that inhibitor 3 became adsorbed via a mixed physi-chemisorption mechanism. A very high adsorption constant (Kads) of 1.53 × 105 L mol−1 suggested strong adsorption of inhibitor 3. The difference in activation energy (Ea) value of 42.4 kJ mol−1 between the control and the inhibited solution indicated an efficient adsorption of inhibitor 3. The ability of inhibitor 3 to retard both anodic and cathodic half-cell reactions was proved via open circuit potential and Tafel curves studies. Detailed discussions on the change in corrosion current densities (icorr), polarization (Rp) and charge transfer (Rct) resistances have been offered to discuss the inhibition efficiency. Water contact angle measurement showed a drastic increase in mild steel surface hydrophobicity following inhibitor 3 adsorption. SEM-EDX and XPS studies confirmed the definitive presence of inhibitor 3 on the mild steel surface. Density functional theory (DFT) studies revealed the frontier molecular orbitals with which the metal surface interacts. A detailed corrosion inhibition mechanism has been offered in the context of adsorption isotherm and DFT studies.