Calculated Activation Energy Research Articles

Preparation, crystal structure and proton conductive properties of a water-stable ferrocenyl carboxylate framework

Recently, solid-state materials with high crystallinity characteristics have received considerable attention for applications in the field of proton conductivity, but relevant studies on ferrocene-based carboxylate frameworks are still very rare. Herein, a ferrocene-based hydrogen-bonded organic framework, [FcC(CH3) ​= ​CHCOOH] (namely FHOF 1), (Fc = (η5-C5H5)Fe(η5-C5H4)) bearing both ferrocenyl and carboxylate units has been successfully prepared and structurally characterized. Further experiments have confirmed that introducing ferrocene groups greatly improves the thermal and water stability of 1; in addition, the presence of free carboxyl groups within the framework will enable high proton conductivity to be guaranteed. Proton conductivity was studied for 1 ​at variable relative humidities (68–98% RHs) and temperatures (30–100 ​°C) and was discovered to increase with humidity and temperature. The optimum proton conductivity of 1.58 ​× ​10−3 ​S ​cm−1 was reached at 100 ​°C and 98% RH. Subsequently, activation energy calculations and structural analysis were used to explore the proton conductive mechanism. Finally, we corroborated the structural and electrochemical stability of 1 after completing the AC impedance test by means of PXRD and SEM tests.

Generalized Brønsted‐Evans‐Polanyi Relationships for Reactions on Metal Surfaces from Machine Learning

AbstractBrønsted‐Evans‐Polanyi (BEP) relationships, i. e., a linear scaling between reaction and activation energies, lie at the core of computational design of heterogeneous catalysts. However, BEPs are not general and often require reparameterization for each class of reactions. Here we construct generalized BEPs (gBEPs), which can predict activation energies for a diverse dataset of reactions of C, O, N and H containing molecules on metal surfaces. In a first step we develop a set of descriptors based on scaling relationships that can capture the change in chemical identity of reactants during the reaction. Subsequently, we use the reaction energy, these descriptors and a single descriptor for the surface structure to parameterize machine learning based regression approaches for the prediction of activation energies. The best approach we developed shows a Mean Absolute Error (MAE) of 0.11 eV for the training set (80 % of the data set) and 0.23 eV for the test set (20 % of the data set). The methodology presented here allows to calculate activation energies within fractions of seconds on a typical personal computer and due to its generality, accuracy and simplicity in application it might prove to be useful in transition metal catalyst design.

Theoretical and Experimental Insights of Benzimidazole Catalyzed by the Epoxy-Acrylic Acid Reaction.

This study focuses on the experimental and molecular-level investigation of epoxy acrylate formation. Epoxy acrylate vinyl ester resin was prepared by a reaction of diglycidyl ether of bisphenol-A-based epoxy resin and acrylic acid, using benzimidazole as a catalyst. It was confirmed that benzimidazole can effectively catalyze this reaction. FTIR analysis of the product revealed a simple addition esterification reaction between the epoxide group and carboxylic group of acrylic acid excluding the side reactions (e.g., etherification). DFT computational studies were performed to theoretically explore the insights of reaction mechanisms. The calculations revealed that the benzimidazole-catalyzed reaction dominates the uncatalyzed reaction. A comparison of calculated activation energies showed that concerted mechanisms are less significant in such reactions owing to their high activation barriers.

Electrical characteristics of multiferroic BiFeO3 electronic system

The structural, dielectric and conductivity properties of bismuth ferrite oxide (BiFeO3) electronic system which was synthesized by means of a solid-state reaction route are explained in this literature. For material fabrication, the exact proportion of 99.9 % pure Fe2O3 and Bi2O3 was taken and processed. The resulting material is extremely pure and stable in nature. The X-ray Diffraction (XRD) on calcined powder confirms the prepared material's structure as a single-phase rhombohedral crystal system. To understand the electronic behavior in the frequency range of 1 kHz-1 MHz with a temperature range of 35–450 °C, the prepared material was characterized in the form of dielectric and conductivity properties. The synthesized material's normal dielectric behavior has been described. It has a high dielectric constant at high temperatures and a low tangent loss at low temperatures. The tangent loss exhibits lower value at lower temperatures, but as the temperature rises, the plot rises abruptly and reaches a peak around 380 °C. This dielectric loss characteristic is caused by inadequate thermal carriers and oxygen vacancies. The significant grain and grain boundary effect of resistive characteristics of synthesized BFO has been observed at this higher temperature. The frequency-dependent dielectric plots show that the dielectric constant and dielectric loss of the composed material decrease with increasing frequency, regardless of temperature variation. The AC conductivity value decreases with increasing frequency at low temperatures. With the increase in frequency up to 10 kHz, the calculated activation energy of synthesized BFO at a specific temperature region rises. The Fourier transform infrared spectroscopy (FTIR) analysis of the processed material reveals the formation of octahedral FeO6 properties in perovskites mode and many other intriguing results regarding BFO structure. Electronic material may act as a budding contender for designing electronic devices for many useful applications due to all these intriguing characteristics and findings.

Ceria and gold co-decorated porous MoS2@graphene nanocomposite electrochemical electrode integrated with smartphone-controlled microstation for simultaneous dual metal ions detection

Continuous increase in release of toxic metals into ecosystem posed a threat to public ecology, leading to demand for the portable monitoring system to control contamination source and monitor disease progression. Herein, ceria and gold co-decorated porous MoS2@graphene nanocomposite was synthesized to construct electrochemical chip and integrate with smartphone-controlled hand-held microstation for simultaneous detecting Zn(II) and Cu(II). Concretely, MoS2 nanosheets coated polyimide were firstly laser-induced into 3D frame-structured MoS2/graphene with abundant oxygen-containing groups and active breaking edges, thereby accelerating the electron transfer and improving the absorptivity and reductive affinity for divalent ions. Double electro-deposition of ceria and gold provide vast oxygen vacancies for sensing, and Ce(III)/Ce(IV) cycle inhibit the recombination of electrons and holes, prolonging the life of carriers to enhance its electro-conductibility. The hydroxylation of ceria under acidic conditions is favorable for ions adsorption. Benefitting from synergetic effect among materials, the smartphone-controlled sensing system exhibits high sensitivity and low detection limit for Cu(II) of 2.8 ppt and Zn(II) of 103.6 ppt. Low energy barrier of target plating/stripping kinetics were also substantiated via calculating activation energy upon composite using Arrhenius formula. Furthermore, its outstanding flexibility, reusability, and anti-interference performance was verified, indicating the potential implementation possibilities in complex environment.

APPLICATION OF MATHEMATICAL MODELING AND PHYSICO-CHEMICAL ANALYSIS METHODS IN THE PREDICTION OF BIOLOGICAL ACTIVITY AND QUALITY CONTROL OF GOSSYPOL DERIVATIVES

Objective: The purpose of this work was to evaluate in silico biological activity profiles of real and virtual molecular structures of gossypol derivatives and to develop methods of Physico-chemical analysis to control their quality. Methods: Substance of gossypol-acetic acid (GAA) and 14 virtual derivatives; PASS and ChemicDescript QSAR methods; low angle and dynamic laser light scattering (LALLS, DLS) methods; IR Spectroscopy–Cary 630 Fourier Transform IR Spectrometer, UV spectrometry–Cary-60 spectrophotometer, Optical microscopy (Altami BIO 2 microscope); Spirotox method for a sample’s biological activity. Results: A distance-based topological Balaban index (J) was successfully selected by ChemicDescript analysis; the Pa meaning by PASS Online program showed maximum (from 0.8 to 0.9) variations of antitumor and antiandrogenic and minimum of antiviral activities of GAA derivatives (Pa<0.5) despite the existing literature data. Microscopy and DLS methods demonstrated the values of high powder dispersion d=0.8 nm and weak stability of colloidal particles =-0.9 mV. According to UV data =42.4±0.8 (100 ml·g-1·cm-1) at λmax=380 nm. The LALLS method determined the GAA dissolution rate constant in ethanol: k=0.041±0.004 s-1. The calculated activation energy values of cell biosensor death process in 1 mmol solution of GAA in N,N-DMF: °bsEa=174.36±0.45 kJ·mol-1 in comparison with the solvent medium: °bsEa=213±1.55 kJ·mol-1 Conclusion: The developed approach of chemometric, laser and biotesting methods can be used for the identification of biologically active properties, as well as for qualitative analysis within the development of the standard for the pharmaceutical substance of natural polyphenols.

New Dy3+-activated KCa2Nb3O10 yellow-emitting phosphors for w-LEDs application: Preparation and optical properties

A novel single-phase KCa 2 Nb 3 O 10 :Dy 3+ yellow-emitting phosphor can be efficiently excited under 388 nm irradiation. • KCa 2 Nb 3 O 10 :Dy 3+ phosphors have been firstly synthesized using the molten-salt method. • The KCa 2 Nb 3 O 10 :Dy 3+ product shows excellent thermal stability with high temperature quenching temperature. • The KCa 2 Nb 3 O 10 :Dy 3+ product shows rich UV excitation band and yellow light emission. • The CIE color coordinates of prepared KCa 2 Nb 3 O 10 :Dy 3+ phosphors change slightly. A series of Dy 3+ doped KCa 2 Nb 3 O 10 niobate phosphors that generated yellow emission was prepared using the molten-salt method. The crystal structure, X-ray diffraction (XRD), optimal concentration, photoluminescence excitation/emission (PLE/PL), and luminescent stability of the prepared phosphors were exhaustively studied. The KCa 2 Nb 3 O 10 lattice has a perovskite-like structure, which possesses the Cmcm (No.63) space group. The KCa 2 Nb 3 O 10 :Dy 3+ phosphors can be efficiently excited by n -ultraviolet ( n -UV) excitation of 388 nm. Besides, KCa 2 Nb 3 O 10 :Dy 3+ phosphors can emit three dominant peaks centered at 486, 577, and 662 nm, which are ascribed to the 6 H J /2 ( J = 15/2, 13/2, and 11/2) transitions, respectively. The optimum doping concentrations of Dy 3+ ions in the KCa 2 Nb 3 O 10 host are determined to be 0.02 mol. The thermal-quenching temperature ( T 0.5 ) for the KCa 2 Nb 3 O 10 :0.20Dy 3+ sample is estimated to be above 500 K, and the calculated activation energy ( E a ) is 0.29 eV. Furthermore, the Commission International de I'Eclairage (CIE) color coordinates of prepared KCa 2 Nb 3 O 10 :Dy 3+ phosphors change slightly. KCa 2 Nb 3 O 10 :Dy 3+ phosphors possess good color purity, color stability, and low correlated color temperature (CCT). All results indicate that the KCa 2 Nb 3 O 10 :Dy 3+ phosphors are suitable for white light-emitting diodes (w-LEDs) applications.

Iron Extraction from South African Ilmenite Concentrate Leaching by Hydrochloric Acid (HCl) in the Presence of Reductant (Metallic Fe) and Additive (MgSO4)

The high content of iron in ilmenite ore poses a great challenge, particularly in the synthesis of titanium-containing products due to high susceptibility of iron (Fe) to corrosion. Direct leaching of ilmenite ore in hydrochloric acid (HCl) encouraging Fe dissolution was investigated. The influence of variable parameters, the use of additives, and the addition of metallic iron powder were studied to establish the optimum leaching parameters. The results showed that ilmenite with the particle size distribution of +150 µm yielded better efficiencies when leaching was performed with an acid concentration of 7.5 M and a solid-to-acid ratio of 1:10 at 90 °C. An agitation speed of 450 rpm yielded a superior Fe extraction of about 92.32% and a 2.40% titanium (Ti) loss. The addition of both metallic Fe and the MgSO4 additive significantly enhanced Fe dissolution and decreased Ti recovery in a leach solution. It was found that leaching under optimum conditions produced a solid residue with 1.37% Fe impurity while 98.63% was extracted. The leached residue was comprised of 91.4% TiO2 rutile phase and contained a high content of the ilmenite FeTiO3 (4.37%) and SiO2 (2.23%) impurities, while Al2O3, MgO, MnO2, CaO, V2O5, MnO2, and Cr2O3 were below 0.13%. The high TiO2 content in the leached residue makes it suitable for use as feed in the production of synthetic rutile. The leaching kinetics of Fe dissolution was found to conform to the shrinking core model, where diffusion through the product layer is rate controlling. The calculated activation energy according to the Arrhenius equation was 19.13 kJ/mol.

Catalytic hydrolysis of sodium borohydride for hydrogen production using phosphorylated silica particles.

Hydrolysis of sodium borohydride (NaBH4) offers substantial applications in the production of hydrogen but requires an inexpensive catalyst. Herein, silica (SP) and phosphorylated silica (SP-PA) are used as a catalyst for the generation of hydrogen from NaBH4 hydrolysis. The catalyst is prepared by sol-gel route synthesis by taking tetraethyl orthosilicate as the precursor of silica whereas phosphoric acid served as the gelation and phosphorylating agent. The prepared catalyst is characterized by FT-IR spectroscopy, XRD, SEM, and EDAX. The hydrogen generation rate at SP-PA particles (762.4mLmin-1g-1) is higher than that of silica particles (133mLmin-1g-1 of catalyst). The higher catalytic activity of SP-PA particles might be due to the acidic functionalities that enhance the hydrogen production rate. The kinetic parameters(activation energy and pre-exponential factor) are calculated from the Arrhenius plot and the thermodynamic parameters (enthalpy, entropy, and free energy change) are evaluated using the Erying plot. The calculated activation energy for NaBH4hydrolysis at SP-PA catalyst is 29.92kJ.mol-1 suggesting the high catalytic activity of SP-PA particles. The obtained entropy of activation (ΔS‡ = - 97.75 JK-1) suggested the Langmuir-Hinshelwood type associative mechanism for the hydrolysis of NaBH4at SP-PA particles.

A Service Life Prediction Method of Stranded Carbon Fiber Composite Core Conductor for Overhead Transmission Lines.

The effect of temperature on the service life of stranded carbon fiber composite core conductors was studied based on the kinetic theory of material pyrolysis. The thermal decomposition activation energy calculation for stranded carbon fiber composite cores was carried out by thermogravimetric analysis (TGA). The activation energy E of stranded carbon fiber composites was calculated according to the Flynn–Wall–Ozawa, Kissinger, and Coast–Redfern methods, which were 168.76 kJ/mol, 166.79 kJ/mol, and 160.35 kJ/mol, respectively. The results from these different treatments were within 10% or less, and thus the thermochemical reactions of stranded carbon fiber composite cores were considered to be effective. The life prediction model of the carbon fiber composite core was developed based on the kinetic equation of thermal decomposition. The service life is related to the reaction mechanism function G(α) and the reaction rate parameter k(t). The reaction mechanism function G(α) = ((1 − α)−3.3 − 1)/3.3 and the reaction rate parameter k(t) = 2.14 × 1012exp(E/RT) were obtained by fitting the thermal weight loss data of stranded carbon fiber composite cores. Based on the 5% mass loss criterion for the end of life of stranded carbon fiber composites, the service life of the carbon fiber composite core is given at various operating temperatures.

Structural-enhanced bacterial cellulose based alkaline exchange membranes for highly selective CO2 electrochemical reduction and excellent conductive performance in flexible zinc-air batteries

Through the combinations of layer-by-layer method and double cross-linking process, OH– conducting membrane based on bacterial cellulose (BC) had been synthesized with the modification by Poly (diallyldimethyl-ammonium chloride) (PDDA) and Poly (vinyl alcohol) (PVA) of different molecular weights. Under the help of PVA, an enhanced internal three-dimensional network could be easily constructed to overcome the disadvantage of excessively loosely binding in the BC membrane. Charge carrier PDDA were confirmed by FTIR and SEM to be firmly embedded into the network while studies on XRD and DSC indicated that amorphous content which was beneficial to ionic transfer and ions hopping held the large proportion in the membrane. Stability measurements such as thermogravimetric analysis, mechanical properties, alkaline and oxygen resistance were carried out, showing that the prepared membranes possessed excellent durable performance under various extreme conditions. Moreover, OH– conductivity and water uptake were intensively investigated by changing crosslinking conditions, KOH concentrations and PVA molecular weights. Achieving the maximum σOH− of 72.95 mS cm−1 at room temperature, the LPVA-PDDA-BC-OH– membrane showed the lowest calculated activation energy value of 10.211 KJ mol−1, indicating that both Grotthus and vehicle mechanisms played an important role on ionic transportation. When as-prepared LPVA-PDDA-BC-OH– membrane was applied for CO2 electrochemical reduction (CO2ER) in 0.5 M KHCO3, current density could reach up to 47.44 mA cm−2 at −1.06 VRHE. Meanwhile, Faradaic efficiency for formate (FEHCOO−) could achieve the maximum value of 67.89 % that dampened only 7.09 % after 20 h electrolysis. Furthermore, when as-prepared LPVA-PDDA-BC-OH– membrane was assembled into the flexible zinc-air batteries (F-ZAB), excellent power density of 130.3 mW cm−2 could be obtained at room temperature.

Enhanced manganese leaching from electrolytic manganese residue by electrochemical process and Na2SO3

Electrolytic manganese residue (EMR) is a general industrial solid waste containing manganese (Mn) and heavy metals that is produced in the process of electrolytic metal manganese. In this study, the leaching efficiency of Mn from EMR was improved by using Na2SO3 and electric field. The results showed that Mn leaching efficiency reached 96.63 % (333 K, 8 wt% H2SO4, 60 mA/cm2 current density and 0.16 mol/L Na2SO3), which was 30.56 % higher than leaching with H2SO4 and 12.76 % higher than leaching by using electric field. The kinetic results based on the unreacted contraction nucleus model showed that the process is controlled by a mixture of external diffusion interfaces and chemical reactions, with a calculated activation energy of 19.68 kJ/mol. Na2SO3 and electric field enhanced the leaching of Mn by removing the compound salts layer wrapped around the outside of Mn and reducing the release of high-valent Mn to divalent Mn. This study provide a novel approach for the utilisation of EMR.

A comprehensive study on the extraction of transition metals from waste random access memory using acetic acid as a chelating solvent

The reduced lifespan of electrical and electronic equipment results in the generation of electronic waste (e-waste), one of the fastest-growing solid waste streams. A systematic and practical approach is needed for the sound management of e-waste and metal recovery. We report an effective and comprehensive study for metal extraction from waste random access memory using acetic acid as a chelating solvent. Under the optimized conditions, Cu, Pb, Zn, and Ni extraction was 97.5%, 88.2%, 79.3%, and 83.7%, respectively. Subsequently, the kinetic study revealed that the diffusion-controlled mechanism governs the metal extraction. The calculated activation energy for Cu, Pb, Zn, and Ni are 11.3, 12.6, 17.6, and 13.3 kJ/mol, respectively, which indicates Cu-extraction could be more favourable than the rest of the metals. Furthermore, the metal leached salt was recovered from the leached solution and was thoroughly characterized to understand the nature of the compound formed and the corresponding leaching mechanism. It was observed that the leached salt could be comparable with standard copper acetate, revealing the acetic acid's ligation property. Finally, the Cu-content in the cathode was recovered as 92.7 wt% from the leached solution using the electrowinning process. We believe, our contribution can be a paradigm for promoting the effective extraction of transition metals from waste random access memory.

Correlation between Ion Transport and Structural Heterogeneity in Triazole-Based Polymerized Ionic Liquids

In this study, the relationship between chemical structure, nanoscale organization, and ion transport in 1,2,3-triazolium polymerized ionic liquids (PILs) was investigated by wide-angle X-ray scattering (WAXS) and broadband dielectric spectroscopy (BDS). Analyzing the WAXS and BDS results indicated that mobile ion types and chemical structure of the pendant groups controlled structural heterogeneity and ion conduction of the PILs below Tg. The normalized heterogeneity length extracted from WAXS data was used to correlate the structural heterogeneity and ion conduction activation energy. For the polycation samples, larger TFSI– mobile anion results in a higher packed structure than small Cl– while in the polyanion samples inverse trend was observed. The calculated activation energy of the dc conductivity below Tg is quantitatively correlated to the structural heterogeneity obtained from nano structure analysis using WAXS. This suggested increasing the spatial heterogeneity of the PILs results in the reduction of the activation energy of long-range ion motions. These results highlight the role of spatial heterogeneity in designing efficient polymerized ionic liquids

Theoretical calculations of formation and reactivity of o-quinomethide derivatives of resorcin[4]arene with reference to empirical data.

This paper describes theoretical reaction pathways of alkoxybenzyl derivatives of resorcin[4]arene leading to the formation of o-quinomethide derivatives of resorcin[4]arene (o-QMR[4]A). For each case, the activation energies for the formation of one o-QMR[4]A unit and the activation energies for the backward reaction were calculated. Based on the calculated reaction pathways, the reaction mechanism of o-QMR[4]A formation was proposed. Using the example of o-QMR[4]A generated from a methoxy derivative of resorcin[4]arene, the activation energies with selected nucleophiles were calculated and the reaction mechanisms discussed. Reaction path calculations were performed using the nudged elastic band method and semiempirical extended tight-binding method (GFN2-xTB). Using hydroxybenzyl derivatives of resorcin[4]arene as an example, a comparison of calculated activation energies by selected density-functional theory methods with GFN2-xTB and B97-3c geometries was performed. B97-3c and wB97XD methods were used to calculate the energies of the reactants (R), transition states (TS) and products (P) of the analysed reactions. Theoretical reaction mechanisms were discussed with respect to the orbital-weighted Fukui dual descriptor (Δfw) and experimental data.

Deep understanding of structural and physical properties of BaTiO3 over a broad temperature range

BaTiO3 (BT) ceramic has been prepared by the solid-state reaction method. The Rietveld refinement and the Raman spectroscopy have been employed to characterize the structural information of the BT ceramic based on the analysis of dielectric at room temperature (RT). Detailed microstructure has been observed by scanning electron microscopy. The dielectric properties of our ceramic have been investigated over wide frequency (102-106 Hz) and temperature (−100–600 °C) ranges. At high temperature region (250–600 °C), a dielectric relaxation phenomenon has been observed. To better understand the physical mechanisms at high temperature, a macroscopic and phenomenological statistical model has been used. The calculated activation energy for relaxation and conduction was approximated to 1 eV. This suggests that relaxation in our studied sample at high temperature region is associated with the short-range hopping of ions. This is caused by oxygen vacancies in the bulk of the material. The BT ceramic demonstrated optimum electrical properties: εr = 1105, tanδ = 0.079, TC = 130 °C, εmax = 4050, Pmax = 18.35 μC/cm2, Pr = 7.93 μC/cm2, EC = 2.65 kV/cm, |Y| = 1.86*1011 N/m2, d33 = 197 pC/N, kp = 14%, and Qm = 196. In addition, the evolution of energy storage performance with an increase in the applied electric field has been investigated. The energy storage efficiently has achieved 40 % at RT, under an electrical field of 30 kV/cm.

Dissolution of β-C2S Cement Clinker: Part 2 Atomistic Kinetic Monte Carlo (KMC) Upscaling Approach.

Cement clinkers containing mainly belite (β-C2S as a model crystal), replacing alite, offer a promising solution for the development of environmentally friendly solutions to reduce the high level of CO2 emissions in the production of Portland cement. However, the much lower reactivity of belite compared to alite limits the widespread use of belite cements. Therefore, this work presents a fundamental atomistic computational approach for comprehending and quantifying the mesoscopic forward dissolution rate of β-C2S, applied to two reactive crystal facets of (100) and (). For this, an atomistic kinetic Monte Carlo (KMC) upscaling approach for cement clinker was developed. It was based on the calculated activation energies (ΔG*) under far-from-equilibrium conditions obtained by a molecular dynamic simulation using the combined approach of ReaxFF and metadynamics, as described in the Part 1 paper in this Special Issue. Thus, the individual atomistic dissolution rates were used as input parameters for implementing the KMC upscaling approach coded in MATLAB to study the dissolution time and morphology changes at the mesoscopic scale. Four different cases and 21 event scenarios were considered for the dissolution of calcium atoms (Ca) and silicate monomers. For this purpose, the (100) and () facets of a β-C2S crystal were considered using periodic boundary conditions (PBCs). In order to demonstrate the statistical nature of the KMC approach, 40 numerical realizations were presented. The major findings showed a striking layer-by-layer dissolution mechanism in the case of an ideal crystal, where the total dissolution rate was limited by the much slower dissolution of the silicate monomer compared to Ca. The introduction of crystal defects, namely cutting the edges at two crystal boundaries, increased the overall average dissolution rate by a factor of 519.

Pyrolysis of sewage sludge under conditions relevant to applied smouldering combustion

Pyrolysis of sewage sludge under conditions relevant to applied smouldering combustion was carried out in this study to investigate the influences of gas flow rate, oxidative atmosphere, and inert porous medium involvement on the properties of products. The experiments were carried out at 300–600 °C under atmospheres of N2, 5% O2/95% N2, 10% O2/90% N2, and 15% O2/85% N2, with Darcy flow rates of 1.0 and 3.5 cm/s, respectively, with dried sewage sludge loaded individually or as a mixture with sand. As a result, both the increment of gas flow rate and involvement of sand leaded to lower yields of char and higher yields of bio-oil and gas under N2 at temperature of ≤500 °C, due to the enhanced efficiency of pyrolysis reaction and gas transportation. However, when temperature increased to 600 °C, the influencing trends on product distributions changed due to the mechanisms of secondary cracking reaction and volatile-char interaction. The involvement of oxygen in fraction of ≤15 vol% at temperatures of 400–500 °C would lead to the intense decreasing yields of char and bio-oil, and increasing yield of the gaseous (dominated by CO2 and CO), due to the involved oxidation reaction during pyrolysis. Both increment of temperature and oxygen fraction would lead to the delay of ignition and the increase of activation energy of the produced char, except for that of char produced at 400 °C under 5% O2/95% N2, whose calculated activation energy was lower and volatile content was higher compared to that of char produced from pyrolysis at 400 °C under N2. The bio-oil from pyrolysis under N2 was dominated by aliphatic acids, phenols, steroids, amides, and indoles, etc., and the involvement of partial oxidation would lead to the weakened formation of aromatics, phenols, and S/Cl/F-containing compounds in bio-oil.

HR MAS NMR, dielectric impedance and XRD characterization of polyethylene oxide films for structural phase transitions

The amorphous/crystalline phase transition behavior of PEO films prepared by spin casting method was studied. According to X-ray diffraction (DELTA) analysis, PEO film has a semicrystalline nature at room temperature. The amorphous to crystalline nature of PEO increases with temperature until reaching an amorphous state at 333 K. 1H NMR spectra of PEO in the temperatures between 298 K and 323 K exhibit two main peaks at around 1.132 ppm and 3.174 ppm with very different widths, where the narrow component can be assigned to the mobile polymer chains in the amorphous phase, whereas the broad component is assigned to the more rigid molecules in the crystalline phase. The calculated activation energies from the Arrhenius fit of the Γ1 data of the crystalline and amorphous phases are comparable and found to be 0.252 eV and 0.221 eV, respectively. Form fitting dielectric loss (ε″) and the electrical modulus (M″) data with the Havriliak-Negami model with addition of the electrical conductivity term in the case of ε″, it was deduced that the inverse relaxation time (τ−1), dielectric strength (Δε) and electrical conductivity (σ) follow an Arrhenius-like behavior plot versus reciprocal temperature.

Comparison Study of Hot Deformation Behavior and Microstructure Evolution of Rack Steels with and without Segregation

In order to compare the hot deformation behavior and microstructure evolution of the rack steels with and without segregation, hot compression tests are carried out in the temperature range of 1173–1423 K and the strain rate range of 0.01–10 s−1 on a DIL805A/D quenching and deformation dilatometer. The flow stress, constitutive relation, processing map, and microstructure characterization are investigated. The results show that the flow stress increases with the increase of strain rate and the decrease of deformation temperature. The calculated activation energy (Q) and stress exponent (n) for the segregated samples are 395.245 kJ mol−1 and 6.046, which are higher than segregated samples, showing 376.815 kJ mol−1 and 5.930. The processing maps show that the workability of the nonsegregated steel is significantly more excellent than segregated steel. The segregated steel shows a higher kernel average misorientation angle and local strain. Complete dynamic recrystallization occurs at a high strain rate, and high deformation temperature can refine the grains.