Sonochemical synthesis of CeVO4 nanoparticles for electrochemical hydrogen storage

In this study, the synthesis of cerium vanadate (CeVO₄) nanoparticles using ammonium metavanadate, cerium (III) nitrate hexahydrate as the primary reactant and hydrazine as the source of OH^? was presented in the absence and presence of ultrasonic waves. Reaction control was performed using OH^? and ethylenediamine sources. Other parameters such as solvent, surfactant, power, and time were also examined. Nanostructures were analyzed by XRD, FESEM, FTIR, DLS, BET, and EDS. FESEM results showed that using ultrasonic irradiation, relatively fine spherical nanoparticles were formed in one step while uniform spherical nanostructures were formed in a two-step path. The obtained product was used for electrochemical storage of hydrogen. The discharge capacity of spherical nanoparticles of CeVO₄ with high uniformity was recorded at about 4299 mAh/g.     

Effect of carbon nanotube on PA6/ECO composites: Morphology development,rheological, and thermal properties

Thermoplastic elastomer (TPE) nanocomposites based on polyamide‐6 (PA6)/poly(epichlorohydrin‐co‐ethylene oxide) (ECO)/multiwall carbon nanotube (MWCNTs) were prepared by melt compounding process. Different weight ratios of ECO (20, 40, and 60 wt %) and two kinds of functionalized and non‐functionalized MWCNTs were employed to fabricate the nanocomposites. The morphological, rheological, and mechanical properties of MWCNTs‐filled PA6/ECO blends were studied. The scanning electron microscopy of PA6/ECO blends showed that the elastomer particles, ECO, are well‐dispersed within the PA6 matrix. The significant improvement in the dispersibility of the carboxylated carbon nanotubes (COOH‐MWCNTs) compared to that of non‐functionalized MWCNTs (non‐MWCNTs) was confirmed by transmission electron microscopy images. The tensile modulus of samples improved with the addition of both types of MWCNTs. However, the effect of COOH‐MWCNTs was much more pronounced in improving mechanical properties of PA6/ECO TPE nanocomposites. Crystallization results demonstrated that the MWCNTs act as a nucleation agent of the crystallization process resulted in increased crystallization temperature (T_c) in nanocomposites. Rheological characterization in the linear viscoelastic region showed that complex viscosity and a non‐terminal storage modulus significantly increased with incorporation of both types of MWCNTs particularly at low frequency region. The increase of rheological properties was more pronounced in the presence of carboxylic (COOH) functional groups, in the other words by addition of COOH‐MWCNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45977.     

Shear deformation and micromechanics of woven fabrics

This paper includes an experimental study and a mathematical analysis of the shear deformation of woven fabrics by using picture-frame type shear testing. Four types of weaves were tested and compared: a loose plain weave, a tight plain weave, a twill and a satin weave. The locking shear angle was determined both in picture-frame tests and manual shear tests. The experimental data presented for each fabric include curves of shear load–shear stress as a function of either the shear angle or the shear rate, and measured locking shear angles. The shear deformation data were analysed by following elasticity principles and taking into account the effects of fibre inextensibility. A microstructural analysis was carried out in all four fabrics to investigate the shear locking on the basis of a geometrical approach and the maximum packing fibre fraction.     

Physicochemical properties and electrochemical hydrogen storage performance of Li2M(WO4)2 (M = Co,Ni and Cu)

In this work, new materials of the Li₂M(WO₄)₂ type with (M = Co, Ni and Cu) have been studied for the first time as electrodes for electrochemical hydrogen storage. The three double tungstates compounds, have been synthesized by a one-step solid-state reaction and carefully characterized, using X-ray diffraction, scanning electron microscopy, UV–visible and FTIR spectroscopy. The presence of a pure and single phase is confirmed by XRD with the Rietveld refinement for all the studied materials, while SEM observation reveals the granular microstructure of these compounds (1-10 μm). Very close energy gaps of 1.60 eV, 1.62 eV and 1.64 eV are respectively attributed to Li₂Cu(WO₄)₂, Li₂Co(WO₄)₂ and Li₂Ni(WO₄)₂. Cyclic voltametry shows the characteristic redox peaks of these samples and clearly elucidates the redox behavior of the battery type. EIS results show good contact between the surface of the studied materials and the H₂SO₄ electrolyte, with a surface resistance of (~2 Ω/cm²). The charge-discharge galvanostatic cycling gives a specific storage capacity of 120.1 mA h.g⁻¹ Li₂Ni(WO₄)₂, 98.88 mA h.g⁻¹ Li₂Co(WO₄)₂ and 84.44 mA h.g⁻¹ Li₂Cu(WO₄)₂ at 1 A g⁻¹. They also exhibit a good life cycle stability that exceeds 84%–90% of the retention capacity of Li₂Ni(WO₄)₂ after 50 cycles at 1 A g⁻¹.     

Stability and bonding nature of tin borohydride

Hydrogen in borohydrides M(BH₄)_n form BH₄⁻ unit and the binding strength is dominated by the B–H bonds. The M−H interactions regulate the B–H bonds and the stabilities depend on the electron donor properties of metal atoms M. The crystal structures of Sn(BH₄)₄ are determined by using global optimization algorithm combined with density functional theories, and the stabilities, electronic properties and bonding natures are systematically compared with other borohydrides of Zr, Al, Mg, Na. Sn transfers 41% of its valence electrons while Na/Mg transfers 84%/82%. The Sn–H bond is of covalent nature with strong polarities, and the covalent Sn–H interaction weakens the B–H bonds. The covalent interactions of different bonds are evaluated using crystal orbital Hamilton populations (COHPs). The results show that both the ionic and covalent interactions of the B–H bonds are obviously weaker in Sn(BH₄)₄ than in other borohydrides. With hydrogen content of 9.0 wt%, Sn(BH₄)₄ may be a promising hydrogen storage material working at moderate temperatures.     

Green synthesis of Ln2Zr2O7 (Ln = Nd,Pr) ceramic nanostructures using extract of green tea via a facile route and their efficient application on propane-selective catalytic reduction of NOx process

In this paper, we present the fabrication of Ln₂Zr₂O₇ (Ln = Nd, Pr) ceramic nanostructures with green tea extract (GrTeEx) as novel and efficacious fuel through easy and repeatable route as well as their application in propane-selective catalytic reduction of NO_x process (propane-SCR-NO_x), for the first time. As-fabricated samples with green tea extract have been examined via diverse kind of techniques. Our outcomes represented the successful production of the pure nanostructured Ln₂Zr₂O₇ (Ln = Nd, Pr) in presence of green tea extract as novel and efficacious fuel. Moreover, the nanostructured samples can be utilized as a potential novel kind of catalysts with desirable efficiency for propane-SCR- NO_x. It was found that Pr₂Zr₂O₇ denoted better performance than Nd₂Zr₂O₇ for NO_x abatement so that the conversion of NO_x in to N₂ for Pr₂Zr₂O₇ was 67% and for Nd₂Zr₂O₇ was 56%. Also the concentration of CO production for Pr₂Zr₂O₇ which is inevitable and undesirable product in SCR-NOx process with hydrocarbons such as propane was lower than Nd₂Zr₂O₇.     

Effect of coagulation treatment on antifouling properties of PVC nanocomposite membrane in a submerged membrane system for water treatment

A submerged membrane system was used in this work to investigate the effect of the polyaluminum chloride (PAC) coagulant on the antifouling performance of the polyvinyl chloride/alumina (PVC/Al₂O₃) nanocomposite membrane. The prepared nanocomposite membranes were characterized with field emission scanning electron microscopy (FE-SEM), atomic force microscopy, contact angle, porosity measurement, and pure water flux. The results revealed that the membrane containing Al₂O₃ nanoparticles (the mass ratio of PVC to Al₂O₃ was 98.5/1.5) had a higher hydrophilicity, porosity, and pure water flux than other membranes. The FE-SEM images showed that when Al₂O₃ nanoparticles were present in the PVC membrane, large pores and macrovoids formed on the surface and cross-section of the membrane. The fouling behavior of membranes was investigated through the filtration of humic acid (HA) solution with and without the PAC coagulant. Without PAC addition, the PVC/Al₂O₃ membrane significantly decreased the irreversible fouling ratio from 60.7% to 19.4% and showed a high HA removal efficiency of approximately 90.5%. The Hermia model confirmed that the cake formation mechanism best described the experimental data for the neat PVC and nanocomposite membranes with the presence and absence of the PAC coagulant. This confirms that the PAC coagulant can significantly mitigate fouling and improve HA removal in the submerged membrane system.     

Investigations of BaFe0.5Nb0.5O3 nano powders prepared by a low temperature aqueous synthesis and resulting ceramics

A facile method to prepare nanoscaled BaFe_0.5Nb_0.5O₃ via synthesis in boiling NaOH solution is described herein. The nano-crystalline powder has a high specific surface area of 55 m² g⁻¹ and a crystallite size of 15 nm. The as-prepared powder does not show any significant crystallite growth up to 700 °C. The activation energy of the crystallite growth process was calculated as 590 kJ mol⁻¹. Dense ceramics can be obtained either after sintering at 1200 °C for 1 h or after two-step sintering at 1000 °C for 10 h. The average grain sizes of ceramic bodies can be tuned between 0.23 μm and 12 μm. The thermal expansion coefficient was determined as 11.4(3)·10⁻⁶ K⁻¹. The optical band gap varies between 2.90(5) and 2.63(3) eV. Magnetic measurements gave a Néel temperature of 20 K. Depending on the sintering regime, the ceramic samples reach permittivity values between 2800 and 137,000 at RT and 1 kHz.     

An internal variable approach for anomalous yield phenomena of β-CuZn alloy

A new interpretation for the anomalous yield phenomena of β-CuZn alloy (B2 ordered structure) has been made using an internal variable approach. The high temperature deformation behavior of β-CuZn alloy has been examined through a series of load relaxation tests (28–430 °C) and analyzed. The deformation behavior has been well described by the internal variable theory of inelastic deformation, consisting of three deformation modes; plastic, inelastic, and dislocation creep deformation modes. Among these, the inelastic deformation mode has proved to be most important in affecting the anomalous phenomena. Microstructural factors related to the inelastic deformation mode characteristics in B2 ordered alloys are discussed. It has also been proposed that the anomalous phenomena can occur only when the reference strain rate ($\text{ε}\text{̇}{}_{\mathrm{<mtext>o</mtext>}}$) falls into the region of lower strain rate and lower stress with increasing temperature. The decrease of yield stress above anomalous peak temperature (T_p) in tensile results can be attributed to the dislocation creep process. The activation energy of the process is obtained as 159 kJ/mol, similar to that for the self-diffusion of Cu or Zn.     

Facile fabrication of efficient Pr2Ce2O7 ceramic nanostructure for enhanced photocatalytic performances under solar light

The design and synthesis of high-performance catalytic compounds for the decomposition and removal of wastewater containing hazardous contaminants are substantial for water remediation. Here, we report the efficient preparation of A₂Ce₂O₇ (A = Bi, Dy, and Pr) nanostructures and cerium dioxide nanoparticles utilizing barberry extract as an environmentally friendly reactant and their application as natural-based nanocatalysts to decompose and eliminate hazardous contaminants in an aqueous medium. The features of the produced oxide nanostructures were checked utilizing various techniques. The activity of the fabricated photocatalytic nanostructures was evaluated in the decomposition of Acid Red 14 contaminants under visible light. The outcomes revealed that the kind of trivalent element introduced meaningfully affects the dimension, architecture, optical properties, porosity, and catalytic performance of the ceria sample. Compared to other nanocatalysts, porous Pr₂Ce₂O₇ nanostructures exhibited enhanced photodegradation yield for decomposing Acid Red 14 (99.2%). The porous Pr₂Ce₂O₇ sample also demonstrated stable performance after ten cycles. Photo-generated holes and hydroxyls are the leading species accounting for Acid Red 14 decomposition. Furthermore, the decomposition kinetics of Acid Red 14 followed the pseudo-first-order kinetics.