Apparent Activation Energy Research Articles

The effects of the contents of modified‐diatomite on the properties of modified‐diatomite/epoxy resin composites

AbstractExternal plasticization is one of the effective ways to toughen epoxy resins. In this study, an inorganic filler (EMD) was prepared by chemical modification of diatomite and was used to fill epoxy resin matrix. The effects of different amounts (5%, 10%, 15%, and 20%) of raw diatomite (RD) and modified‐diatomite (EMD) on the mechanical and thermal properties of epoxy resin composites were studied. The mechanical results showed that the impact strength, tensile strength, and bending strength of EMD/EP were higher than those of RD/EP. The impact strength of EMD‐15/EP reached 5.39 KJ/m2, which was 36.8% higher than that of RD‐15/EP. Thermogravimetric analysis showed that the thermal stability of EMD/EP was better than that of RD/EP. The results of DMA show that the glass transition temperature of EMD/EP was lower than that of RD/EP. Non‐isothermal differential scanning calorimetry study showed that the apparent activation energy of EMD‐15/EP was much lower than that of RD‐15/EP, which proved that EMD could promote the curing of epoxy resin. The Malek method was used to determine that both the RD‐15/EP and EMD‐15/EP curing systems were autocatalytic (Šesták–Berggren) models.

Coupling geometric and electronic engineering over RuNi ultrafine alloys for fast boosting hydrolytic dehydrogenation of NH3BH3

Developing a suitable catalyst for ammonia borane (AB, NH3BH3) hydrolysis and clarifying the catalytic mechanism are essential and challenging at present. In this work, RuNi nanoalloys are supported on an N/O co-coped glucose-derived carbon (g-C) with the adsorption-NaBH4 reduction method. Attributed to the particular geometric and anchoring effects, as well as the improved hydrophilicity of the multi-level porous support, the RuNi alloys are highly and firmly confined in the framework of g-C. Specifically, the optimal Ru0.25Ni0.75@g-C with an average alloy particle size of 1.4 nm exhibits pleasurable specific hydrogen evolution rate (437,990 mL min−1 gRu−1) and turnover frequency (1612.37 min−1) in NaOH aqueous solution (1.5 M) at 303 K, superior to the corresponding monometallic counterparts (i.e., Ni@g-C and Ru@g-C) and many previous results. In addition, apart from satisfactory durability, the optimal alloy catalyst delivers an encouraging apparent activation energy (28.1 kJ mol−1). Our work not only explains the geometric and electronic effects on the catalytic performance but also offers a promising catalyst for hydrogen release from liquid-phase AB.

Well-designed flame retardants for epoxy resin composites that simultaneously improve heat resistance, mechanical properties and fire safety

Epoxy resin (EP) flammability severely limits its application in some industrial fields, while flame retardant epoxy resin (FREP) often suffers from the problem of not being able to balance flame retardant properties with mechanical properties. To solve the problem, in this work, HDP, a reactive flame retardant was succeeded in synthesizing by the one-pot method using protocatechuic aldehyde (PH), 2,4-diamino-6-phenyl-1,3,5-triazine (DPT), and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as reactive monomers, was used to improve the flame retardancy of EP. And evaluated the effect of HDP on the curing reaction, heat resistance and mechanical property of EP. The introduced of four phenolic hydroxyl groups and two secondary amine groups enhanced the compatibility of the flame retardant HDP in EP and improved process performance. The apparent activation energy (Ec) was reduced by 8.1 %, facilitating the curing of EP/DDM. When 5 wt% of HDP (with only 0.36 wt% phosphorus content) was added to EP, the flexural strength and modulus of FREP increased by 21.0 % and 14.9 %, respectively, and the Tg increased by 9.0 % compared to EP. Cone calorimeter test (CCT) data showed that compared to EP, samples of EP/HDP-5 showed a 14.5 % and 21.6 % reduction in total heat release (THR) and total smoke production (TSP), respectively, and a 13.7 % increase in coke yield (CY). EP/HDP-5 has a high limited oxygen index (32.5 %) and passes the UL-94 V-0 classification. The excellent char formation and flame retardancy was owed to the dual role of the condensed and gas phases of FREP in the combustion process.

Microwave-assisted atmospheric alkaline leaching process and leaching kinetics of rare earth melt electrolysis slag

This study focuses on the difficulty of converting fluorinated rare earth elements into hydroxylated rare earth elements in rare earth melt electrolysis slag (RMES) and proposes the use of a microwave-assisted atmospheric alkaline leaching method for the treatment of RMES. The leaching behavior of RMES under microwave-assisted atmospheric alkaline leaching was studied, and the optimal reaction conditions were determined. Under the conditions of a reaction temperature of 150 °C, initial NaOH concentration of 60 %, NaOH-to-slag mass ratio of 4:1, microwave power of 700 W, reaction time of 120 min, and stirring speed of 300 r/min, the conversion rate of fluorinated rare earths reached 99.17 %. The apparent rate equation of the microwave-assisted atmospheric alkaline leaching process was obtained by leaching kinetic analysis, and the apparent activation energy under this process was calculated to be 54.872 kJ/mol, which was 12.458 kJ/mol lower than that achieved when conventional heating was used for leaching (67.33 kJ/mol).

Carbon dots decorated cadmium sulfide nanomaterials for boosting photocatalytic activity for ciprofloxacin degradation

This study investigates the utilization of carbon dots (CDs) from neem leaves (Azadirachta indica) decorated onto cadmium sulfide (CdS) for the photocatalytic degradation of ciprofloxacin. A comparative study of ciprofloxacin degradation with pristine CdS and CD decorated CdS demonstrated high degradation of ∼ 75 % with CD/CdS when compared to bare CdS (∼68 %). Process optimization studies were further carried out with CD/CdS catalysts at different solution pH (4–10), feed concentrations (10–50 mg/L), catalyst loadings (25–125 mg/L), temperatures (10 – 30 °C), and lamp power (25, 50, 250 W and sunlight). Higher temperatures, combined with a solution pH of 7 and catalyst loading of 100 mg/L favored the enhanced degradation of 20 mg/L of ciprofloxacin. The ciprofloxacin degradation rate increased linearly with temperature with an apparent activation energy of 27 kJ mol−1. The CD/CdS photocatalyst demonstrated maximum degradation rates with higher lamp powers while it also showed remarkable performance under natural sunlight achieving the same degradation within 3 h.

Sustainable strategies for recovering metallic copper from waste printed circuit boards: Clean leaching and micro-nano copper powder preparation

Recovery and utilization of valuable metals from waste printed circuit boards (WPCBs) have the dual significance of alleviating resource shortages and protecting the ecological environment. This study focuses on the feasibility analysis of copper in WPCBs for preparing micro-nano copper powders by clean leaching and chemical reduction processes. Firstly, the effect of temperature and other parameters on copper leaching rate in glycine-hydrogen peroxide (Gly-H2O2), ammonia-ammonium chloride (NH3·H2O-NH4Cl) leaching systems with sulfuric acid-hydrogen peroxide (H2SO4-H2O2) system as control group were emphasized. Subsequently, the leaching characteristics of copper concentrate particles were analyzed by leaching kinetics to elucidate the leaching mechanism and apparent activation energy of copper. Finally, the micro-nano copper powders were prepared using ascorbic acid and sodium borohydride reduction system with different copper leach solutions as precursors. The micro-nano copper morphology and phase compositions were analyzed by SEM and XRD. The results show that both the Gly-H2O2 and NH3·H2O-NH4Cl system can replace the H2SO4-H2O2 system to achieve efficient leaching of copper. Increasing temperature can significantly enhance the copper leaching rate. When the temperature was increased from 15 °C to 45 °C, the maximum copper leaching rate in the three systems increased from 58.13 %,71.26 %,78.26 % to 90.36 %,91.21 %,92.87 %, at − 0.074 mm for 40 min. The Avrami model accurately describes the leaching behavior of copper concentrate particles, and the copper leaching process is dominated by chemical reaction control. SEM and XRD results show that micro-nano copper particles of hundreds of nanometers are successfully prepared by both reduction systems.

Influence of composite chloride salt retardant on the characteristics of coal spontaneous combustion and comprehensive evaluation methodology

ABSTRACT In this study, we aimed to improve the efficacy and longevity of single inhibitors. NaCl, CaCl2, MgCl2, and layered double hydroxides (LDHs) were selected as the inhibitory components for experimental study. The impact of the composite inhibitors on the spontaneous combustion characteristics of the coal was studied through temperature programmed experiment, thermal analysis experiments, thermogravimetric mass spectrometry and entropy weight method, and the optimal inhibitor was determined. The findings indicate that the apparent activation energy (E a ) of the coal sample, with the addition of inhibitors during the oxidation stage, was improved. E a of MgCl2 +1.0 LDHs + Coal was the highest (127.28 kJ/mol), i.e. 35.99 kJ/mol higher than that of the original coal. The inclusion of the inhibitor increased the characteristic ignition temperatures of the coal samples compared with the original coal. The highest ignition temperature was observed for MgCl2 +0.5 LDHs + Coal, reaching (323.98°C), i.e. 11.42°C higher than that of the original coal. The addition of inhibitors significantly inhibited the production of CO. Among the three chloride salts, MgCl2 exhibited the strongest inhibitory effect on CO production. According to the entropy weight method, MgCl2 +0.5 LDHs showed the best inhibitory effect. The results show that the composite halogen inhibitor can effectively inhibit the spontaneous combustion of coal.

Thermal Decomposition Mechanism of P(DAC-AM) with Serial Cationicity and Intrinsic Viscosity.

The thermal decomposition of the thermodynamic, kinetic and mechanisms of copolymer P(DAC-AM) samples with serial cationicity and intrinsic viscosity ([η]), and the control samples of homopolymer PAM and PDAC, were studied and analyzed using TG, DSC, FTIR. The results of the thermal decomposition thermodynamics confirmed that the thermal decomposition processes of the serial P(DAC-AM) samples and the two control samples could be divided into two stages. It was found that the processes of the copolymer P(DAC-AM) samples were not a simple superposition of those of homopolymers, whose monomers had composed the unit structures of the copolymer, but there were interactions between the two suspension groups. The results of thermal decomposition kinetics showed that the apparent activation energy (E) of the thermal decomposition process of all polymer samples had different varying trends in the terms of weight-loss rate (α). The reaction order (n) of the thermal decomposition of P(DAC-AM) in Stage I and II was close to 1, but in the former and the latter it tended to be 2 and 0.5, respectively. Finally, the thermal decomposition mechanism of copolymer P(DAC-AM) samples was discussed. The above research could not only fill in the knowledge vacancy of the thermal decomposition of the thermodynamic, kinetic and mechanisms of P(DAC-AM), but could also lay a foundation for the study of thermal decomposition mechanisms of the other types of polymers, including cationic polymers.

Efficient calcium sulfite oxidation treatment by a highly active iron-manganese bimetallic metal-organic frameworks (MOFs)

Calcium sulfite (CaSO3) oxidation is the key step in the resource utilization of flue gas desulfurization (FGD) ash waste. However, under natural conditions the oxidation rate of CaSO3 is very low, limiting its conversion into calcium sulfate, an acceptable product for construction material. This study was devoted to the investigation of the synthesis and performance of a bimetallic MOFs with potential catalytic activity, namely, Fe/Mn(BDC)(DMF,F) catalysts. A combination of techniques including SEM, EDS, XRD, FT-IR, etc. were used to characterize the catalysts. The excellent catalytic performance examined in a gas-liquid-solid three-phase oxidation system are due to the special flexible respiratory architecture and homogeneous distribution of active sites, which allows the reactants to fully contact with the catalyst. Mn incorporated in the backbone of the metal-organic framework significantly enriches the catalytic active species that participate in a radical chain reaction with activated SO32- as ·SO3-, which in turn generates the key radical ·SO5- that reacts with SO32- to form SO42-. In the presence of Fe/Mn(BDC)(DMF, F)-13, the oxidation ratio of CaSO3 could reach 90.71%, which is more than 30-fold compared to non-catalytic oxidation and almost 5 times the effects of the single metal Fe(BDC)(DMF, F) catalyst. In addition, the study of kinetics shows that the oxidation rate of Fe/Mn(BDC)(DMF,F)-13 can reach 0.042 mmol·L-1·s-1 with an apparent activation energy of 10.86 kJ/mol. The oxidation rate is mainly affected by reaction temperature, pH value, catalyst concentration, and air flow rate. This study provides a potentially sustainable way for utilization of CaSO3-containing desulfurization ash.

Synergistic effect of Ru single atom and nanoparticle on photothermal methane dry reforming reaction

Dry reforming of methane is indeed an attractive pathway for converting greenhouse gases into syngas. However, owing to the strong-endothermic nature of this reaction, high reaction temperature is commonly involved which causes high energy consumption, catalytic deactivation by sintering of active species, and/or coke formation. Herein, a RuSA+NP/TiO2 composite catalyst consisting of uniformly dispersed Ru nanoparticles (RuNP) and Ru single atoms (RuSA) on TiO2 sheet is fabricated. This catalyst demonstrates remarkable syngas generation rates of 1380 mmol g-1h−1 for CO and 933 mmol g-1h−1 for H2 at 500 °C under light irradiation. It is concluded that the presence of Ru single atoms modulates the electronic structure of catalyst, reducing energy barrier in the DRM process. Additionally, the electron-deficient Ru nanoparticles provide effective sites for CH4 dissociation. Light irradiation is found to reduce the apparent activation energy (Ea) of DRM and enhance durability of catalyst by retarding coking process.

Effect of Cubic Crystal Morphology on Thermal Characteristics and Mechanical Sensitivity of PYX

To investigate the influence of the cubic crystal morphology on the thermal properties and sensitivity of 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX), cubic PYX (CPYX) crystals were prepared using the antisolvent method. Scanning electron microscopy (SEM), laser particle size analysis, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the morphology, particle size and structure of the prepared products. The thermal behavior, thermal decomposition kinetics, thermal safety parameters and thermal decomposition mechanism of CPYX were investigated by differential scanning calorimetry–thermogravimetry–mass spectrometry–Fourier transform infrared spectrometry (DSC-TG-MS-FT-IR) and in situ FT-IR experiments. Meanwhile, the mechanical sensitivity of CPYX was determined by means of the explosion probability method. The results showed that the product had a smooth cubic morphology and small crystal aspect ratio with an average particle size (d50) of 10.65 μm, but it had no distinct differences from the crystal structure of raw PYX (RPYX). The thermal decomposition peak temperature, the self-accelerating decomposition temperature and the critical temperature of the thermal explosion of CPYX increased by 7.2 °C, 6.1 °C and 10.4 °C, respectively, compared to RPYX. Similarly, the apparent activation energy increased by 15%. Besides these, the impact sensitivity and friction sensitivity of CPYX decreased by 36% and 20%, respectively, compared to RPYX. The decomposition process of CPYX contains two stages. The first stage involves the breakage of N-H bonds and -NO2 groups with the release of CO2, N2O, NO, HCN and H2O, followed by the thermal decomposition of the resulting intermediate and the release of CO2, N2O and HCN in the second stage.

Temperature effects on ion migration and energy consumption during brackish water electrodialysis desalination

Electrodialysis (ED) is a well-established brackish water (BW) desalination technology based on the selective electro-transfer mechanism of ions for meeting freshwater demands in scarce water regions. While the influence laws of water temperature difference caused by changing seasons on the performance of BWED need to be clarified further. This study examined the effect of temperature on the desalination efficiency and energy consumption of BWED by controlling the water temperature with a constant temperature tank. Results showed that higher temperature significantly increased the current density and salt flux of BWED, but also caused a decrease and then an increase in energy consumption. The apparent activation energy of BWED system in low temperature range is about 40 % higher than that in high temperature range, indicating that higher temperature is contributed to reduce the ion transport resistance. While higher temperature increased ion diffusivity and membrane pore size, with a corresponding rise in LCD of ∼0.41 mA/cm2 and an increase in desalination ratio of ∼7.75 % for increment of every 10 °C, thus enhanced reverse salt diffusion. The running parameters of BWED system should be regularly regulated with the seasonal temperature based on the trade-off between desalination efficiency and energy consumption to ensure an efficient operation.

Potential-dependent photo-electro-catalysis coupling mechanism for methanol oxidation: A case study over Pt/Cu-Nb2O5 nanorod arrays

The sluggish methanol oxidation kinetics has seriously hindered the development of direct methanol fuel cells. Photo-electro-catalysis is expected to accelerate reaction rates, yet suffers from lack of efficient photoelectrocatalysts and more importantly, less understanding on photo-electro-catalysis mechanism. Herein, a unique Cu-Nb2O5 nanorod array with excellent light adsorption and charge transfer ability, on which supports Pt nanoparticles, is constructed for photo-electrocatalytic methanol oxidation reaction (MOR). Systematical investigation discovers a potential-dependent photo-electro-catalysis coupling mechanism, i.e., at lower potential bias where the Fermi level of semiconductor (Ef,s) is beyond the Fermi level of Pt (Ef,Pt), electrons transferring from Pt to semiconductor is switched off, so semiconductor Cu-Nb2O5 alone takes a dominant role for both methanol and water activation; at higher potential bias where Ef,s is below Ef, Pt, electrons flowing from Pt to semiconductor is switched on, so methanol dehydrogenation on Pt surface is allowed energetically. Further investigation on the MOR processes prompts us to propose a MOR pathway that methanol dehydrogenates on Pt surface, with the aid of *OH from the photo-activated water on Cu-Nb2O5 to proceed via formaldehyde, formic acid to carbon dioxide, resulting to a low apparent activation energy and fast kinetics of MOR as compared to its counterpart Pt/Nb2O5. This work not only provides an efficient photoelectrocatalyst for methanol oxidation, but also sheds lights on the underlying photo-electro-catalysis coupling mechanism over semiconductor–metal catalysts.

Investigation of the properties of alumophosphate solutions and products crystallized from them

The physicochemical properties of freshly prepared alumophosphate solutions obtained in the Al(OH)3 – H3PO4 – H2O system with the molar ratio n(Al2O3) : n(P2O5) = 1.0 : 2.75 have been investigated. The density and temperature dependence of the dynamic viscosity of the studied solutions with a concentration of P2O5 300–485 g/l were studied. The values of the apparent activation energy of the viscous flow (Eη) of alumophosphate solutions are calculated and the concentration range (390–420 g/l P2O5) is established, in which Eη is practically constant and is 15.0 kJ/mol. It is suggested that the change in the activation energy of the viscous flow of alumophosphate solutions is due to their structure determined by the composition of aluminum phosphate complexes. The influence of the viscosity properties of alumophosphate solutions and their concentration on the crystallization process of hydrated alumophosphate, in particular, the duration of the induction period and the rate of phase formation, is shown.

Atomized Mg-Li spherical alloys: A new strategy for promoting reactivity of Mg

In this study, to improve the reactivity Mg, which is a frequently used fuel, Li was incorporated into it. Mg-Li alloys with 3 and 5 wt% Li, prepared via centrifugal atomization, displayed a high degree of sphericity and consisted of αMg. Thermal behaviors indicated that the initiation oxidization temperature of Mg-Li powders was ∼170–200°C lower than that of pure Mg, owing to the lower melting point of soluble Li than that of Mg. Li passes through oxide shells and initiates the oxidization of metals in the core. The apparent activation energy of Mg decreased significantly from ∼361.2 kJ/mol to ∼141.1 kJ/mol with the incorporation of Li. For combustion in air, the Li content should be 5 wt% to achieve increased combustion intensity compared to Mg powders. When Mg-Li alloys and Mg powders were composited with polytetrafluorethylene (PTFE) serving as an oxidizer, the burn rates of MgLi3/PTFE and MgLi5/PTFE were ∼7.1 and 12.1 m/s, respectively, which were ∼1.8 and 6.8 m/s higher than that of Mg/PTFE. The flame temperature of Mg-Li/PTFE (∼1537–1552℃) of 3–5 µm was slightly lower than that of Mg/PTFE (∼1637℃). Therefore, the prepared Mg-Li alloys are promising candidates for use as fuels for energetic materials.

“Acid + Oxidant” Treatment Enables Selective Extraction of Lithium from Spent NCM523 Positive Electrode

With the rapid development of new energy vehicles and energy storage industries, the demand for lithium-ion batteries has surged, and the number of spent LIBs has also increased. Therefore, a new method for lithium selective extraction from spent lithium-ion battery cathode materials is proposed, aiming at more efficient recovery of valuable metals. The acid + oxidant leaching system was proposed for spent ternary positive electrode materials, which can achieve the selective and efficient extraction of lithium. In this study, 0.1 mol L−1 H2SO4 and 0.2 mol L−1 (NH4)2S2O8 were used as leaching acid and oxidant. The leaching efficiencies of Li, Ni, Co, and Mn were 98.7, 30, 3.5, and 0.1%, respectively. The lithium solution was obtained by adjusting the pH of the solution. Thermodynamic and kinetic studies of the lithium leaching process revealed that the apparent activation energy of the lithium leaching process is 46 kJ mol−1 and the rate step is the chemical reaction process. The leaching residue can be used as a ternary precursor to prepare regenerated positive electrode materials by solid-phase sintering. Electrochemical tests of the regenerated material proved that the material has good electrochemical properties. The highest discharge capacity exceeds 150 mAh g−1 at 0.2 C, and the capacity retention rate after 100 cycles exceeds 90%. The proposed new method can extract lithium from the ternary material with high selectivity and high efficiency, reducing its loss in the lengthy process. Lithium replenishment of the delithiation material can also restore its activity and realize the comprehensive utilization of elements such as nickel, cobalt, and manganese. The method combines the lithium recovery process and the material preparation process, simplifying the process and saving costs, thus providing new ideas for future method development.

Isothermal reduction and comparative analysis of reaction kinetics of sponge iron produced from hematite-charcoal reaction using non-contact direct reduction method

The challenge of making sponge iron, or direct reduced iron (DRI), is hard to overstate. These are a key feed for metallurgical operations while iron extraction sets these limits, which include scarcity of metallurgical coke, poor environmental impact, and high production cost. Thus, the non-contact direct reduction process of DRIs has the potential to significantly reduce carbon deposition and CO2 emission from the ironmaking process. This work produced sponge iron from commercially acquired hematite ore using an alternative reducing agent (i.e. charcoal) under specified isothermal conditions. Comparative analysis of reaction kinetics models including Ginstein−Brounshtein and Shrinking core models was also performed to ascertain the resistances that control the reaction rate for reduction degree up to 98.1%. The reduction kinetics were found to be described by reaction control time and activation energies based on a shrinking core model as the reduction time lasted for 120 min at temperatures 843–1273 K. At temperatures above 973–1073 K, the rate-limiting step was found to be solely an interfacial chemical reaction process, with an apparent activation energy of 196.1 kJ/mol. In addition, a slowing trend was observed for iron ore sample sizes 10–20 mm as a result of ash layer infiltration around the inner-core structure of the DRI metal matrix. The DRI morphological characteristics were performed using Scanning Electron Microscopy (SEM) and Electron Dispersive Spectrometry (EDS) to ascertain the mineralogical and morphological properties of the DRI samples. The XRF analysis confirms that the raw iron ore sample is hematite. Its iron content is 70.04% metallic iron (TFe) which has 83.59% Fe2O3 The SEM/EDS image also revealed the presence of micropores on the DRI morphology. This indicates that the reduction ratio and swelling extent rise with the temperature and time. This happens for all DRI sizes. However, the EDS result confirms the presence of gangue elements within the DRI metal matrix and mineralogical structure. The DRI contains very high silicon content up to 33.90%. So, a fluxing experiment is needed using limestone (CaCO3) or quicklime (CaO) quicklime to remove gangue (silicate, aluminate) from the DRI matrix. At the set reduction temperatures, the largest metallization degree of 93.05% at 1273 K for a reduction time of 120 min was achieved. This showed that the overall reduction process still follows the expected chronological order since the NDR process uses CO gas from preheated charcoal. This makes DRI be produced from raw hematite under non-contact reduction bases. Therefore, the NDR technique offers a viable option for sponge iron production in modern-day iron and steelmaking processes.

Effects of the ice formation and its content on viscoelastic characteristics of wood exposure to low temperatures ranging from −125°C to 25°C

ABSTRACT The influence of ice formation and its content on the viscoelastic characteristics of wood were investigated in the temperature range between −125°C and 25°C. The stiffness and damping properties of the longitudinal (L), radial (R) and tangential (T) specimens were determined for different moisture content (MC) levels at or above the fiber saturation point (FSP) ranging from 25% to 300%. Results showed that the E′ value was correlated negatively with temperature for all specimens. Accompanied by the frozen free water inside the wood, the order of magnitude in E′ for specimens in the different anatomical directions trend toward an accord. The increment in E′ (ΔE′) of specimens was correlated positively with the ice content, and ΔE′ in the L direction was lower than those in the R and T directions at each MC level. The γ-relaxation ranged from −112.9°C to −94.8°C was observed for all orthotropic directions at 10 Hz, which was assigned to the reorientation of methylol groups and adsorbed water molecules in the wood cell walls. At each MC level, a lower peak temperature of γ-relaxation was observed in the L specimens compared to the transverse specimens. Notably, the γ-relaxation peak temperature in the E″ and tanδ spectrum showed obvious frequency-dependence, and the apparent activation energy (ΔH) of γ-relaxation over the measured MC range was about 38.08∼69.57 KJ/mol. The ΔH value was close for specimens in orthotropic grain orientations, indicating that this γ-relaxation phenomenon was not affected by its orthotropic structure and also related closely with the formation of ice in the wood cell lumens.

Defects engineering of nickel tellurium electrocatalyst to boost urea oxidation reaction: Electrodeposition mechanism and performance

The urea oxidation reaction (UOR) offers an attractive strategy to replace the oxygen evolution reaction (OER) for energy-saving hydrogen production due to its favorable thermodynamic property, but its development is hindered by the lack of efficient and cost-effective electrocatalysts. In this study, nickel-tellurium (Ni-Te) grown on 3D nickel foam was successfully synthesized using a simple and facile electrodeposition method. The electrodeposition process of Ni-Te follows the three-dimensional instantaneous nucleation/growth mechanism controlled by diffusion. The apparent activation energy (Ea) of Ni-Te in the electrodeposition process is as low as 36.5 kJ∙mol-1. Lattice distortion structure obtained by electrodeposition modifies the intrinsic electronic structure and optimizes the adsorption energy of intermediates. Thanks to the synergistic effects of fast electron transport, superhydrophilic surface and nanoflake structure, the prepared Ni-Te electrocatalyst shows excellent activity toward UOR with a low potential of 1.503 V vs. RHE at 100 mA·cm-2 and a small Tafel slope (63.6 mV·dec-1) in 1.0 M KOH containing 0.33 M urea solution.

Chemical recycling of post-consumer poly(ethylene terephthalate) (PET) driven by the protic ionic liquid 2-HEAA: Performance, kinetics and mechanism

The circular economy is a paradigm for the upcoming industrial era, in which plastic wastes must be focused on as new resources. Chemical valorisation permits deepening into waste-to-gate schemes by obtaining new chemical platforms to be reintroduced in the production market. In this context, the potential of the protic ionic liquid 2-hydroxyethyl ammonium acetate (2-HEAA) to be used as a homogeneous catalytic co-solvent for the glycolytic conversion of post-consumer poly(ethylene terephthalate) (PET) was validated from different perspectives. Studies were performed for the reaction triplet framed under the experimental conditions (i) temperature T [160,170,180 ºC], (ii) plastic-to-solvent mass ratio P/S [1:3, 1:4,1:5] and (iii) plastic-to-ionic liquid mass ratio P/IL [2:1, 2:2, 2:3]. The reaction was confirmed in terms of the transformation of PET into BHET (bis(2-hydroxyethyl terephthalate) and a proposal of mechanism induced by the amine group of the 2-HEAA is given. The thermal kinetics were modelled and a first-order equation and an apparent activation energy of 60.5 kJ·mol-1 were obtained. A statistical Box-Behnken design of experiments explained the relationship between the factors of the glycolysis triplet by a response surface, with a maximum around {T = 170 ºC, P/S = 1:3.75 and P/IL = 2:1.75}, being T and P/S statistically relevant, whereas only the presence of 2-HEAA and not its amount P/IL was significant. Finally, the reusability of 2-HEAA after 90-min glycolytic chemical valorisations was confirmed up to 4 cycles. The results position 2-HEAA as a promising catalytic co-solvent for the scale-up of chemical valorisation of PET.