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Deformation under the combined action of external stress and cyclic hydrogen charging/discharging is studied in a model material, titanium. Cyclic charging with hydrogen is carried out at 860 °C, which repeatedly triggers the transformation between hydrogen-lean α-Ti and hydrogen-rich β-Ti. Due to bias from the externally applied tensile stress, the internal mismatch strains produced by this isothermal α-β transformation accumulate preferentially along the loading axis. These strain increments are linearly proportional to the applied stress, i.e., flow is ideally Newtonian, at small stress levels (below ∼2 MPa). Therefore, after multiple chemical cycles, a tensile engineering strain of 100% is achieved without fracture, with an average strain rate of 10-5 s-1, which demonstrates for the first time that superplastic elongations can be achieved by chemical cycling. The effect of hydrogen partial pressure, cycle time, and external stress on the value of the superplastic strain increments is experimentally measured and discussed in light of a diffusional phase transformation model. Special attention is paid to understanding the two contributions to the internal mismatch strains from the phase transformation and lattice swelling. [ABSTRACT FROM AUTHOR]

Abstract: Composites consisting of a Ti–W solid-solution-strengthened matrix reinforced with TiC particles are produced by powder metallurgy. TiC additions increase strength but reduce ductility and matrix microhardness. Composites with 7.5wt.% TiC show some tensile ductility (3–7%) but those with 15wt.% TiC are brittle in tension. They are however strong and ductile in compression: Ti–15W/15TiC (wt.%) has a compressive yield strength exceeding 1200MPa. This composite also shows tensile crack growth rates which are considerably faster than for pure titanium (by a factor 2) or Ti–15W (by a factor 2–6) and a fracture toughness which remains relatively high as compared to Ti–15W (21 vs. ). [Copyright &y& Elsevier]

Abstract: The alloy Ti-6Al-4V was modified by addition of 10wt.% tungsten through powder metallurgy. Depending on the initial W powder size, different materials were formed after powder densification: (i) “alloys” for fine (0.7 and 2μm) W powders which were almost completely dissolved in the Ti-6Al-4V matrix; (ii) “alloyed composites” for intermediate (12 and <45μm) W powders which were partially dissolved; (iii) and “composites” for coarse (<250μm) W powders which were nearly un-dissolved. In all cases, tungsten strengthens Ti-6Al-4V, but much more so when dissolved in the matrix than as a second phase. Ductility was not affected by W additions for the fully-dissolved alloys, but was reduced in the case of composites with W particles, which exhibited fracture or pull-out from the matrix. Flaw sensitivity was apparent from strain hardening being much lower in tension than in compression, and from a much reduced ductility exhibited by one specimen with residual porosity. [Copyright &y& Elsevier]

Abstract: Blends of 90wt.% Ti and 10wt.% W powders were consolidated by powder metallurgy, using an initial W powder size that was very fine (0.7 and 2μm) or very coarse (<250μm). Dissolution of W powders in the Ti matrix during consolidation was almost complete for the former blends (thus forming Ti–10W “alloys”) but very limited for the latter blend (thus forming a Ti–10W “composite”). The Ti–10W alloys exhibit much higher yield and tensile strengths than the Ti–10W composite, indicating that tungsten strengthens titanium more efficiently as a solute atom (solid-solution strengthening) than as a second phase (composite strengthening by load transfer). The Ti–10W alloys also exhibit much higher ductility than the Ti–10W composite, whose brittle W particles exhibit fracture or pull-out from the matrix. [Copyright &y& Elsevier]

Reticulated nickel foams were alloyed with chromium by pack-chromizing, resulting in Ni–Cr foams with 9–32wt.% Cr and 2.6–3.5% relative density. The oxidation resistance at 1000°C of the Ni–Cr foams and the corresponding bulk Ni–Cr alloys is the same, provided the foam’s higher surface area is taken into account. The foam compressive yield stress at ambient temperature is in agreement with model predictions. The foam creep behavior, measured between 725 and 825°C in the stress range of 0.1–0.2MPa, is compared to two models assuming strut compression or strut bending as creep deformation modes. These models, which originally consider dislocation creep as the sole deformation mechanism, are modified to incorporate diffusional creep, due to the relatively fine grain size of the Ni–Cr struts. Good agreement is then found between data and the strut creep compression model. [Copyright &y& Elsevier]

Reticulated nickel foams were alloyed with 8–9 wt% Al or 14–18 wt% Cr and 5–9 wt% Al in a three-step method consisting of (i) gas-phase deposition of Cr and/or Al onto the struts of a pure Ni foam by pack-cementation at 1000 °C; (ii) homogenization at 1200 °C to remove concentration gradients and to solutionize the alloyed struts; (iii) aging at 900 °C to form γ′ precipitates within the struts. The resulting alloyed foams retain the low relative densities (less than 3%) and open-cell structure with hollow struts of the original pure Ni foams, and they exhibit struts with the γ/γ′ structure typical of nickel-base superalloys. The compressive behavior of the superalloy foams, measured at ambient temperature, is compared to model predictions. The creep behavior of the superalloy foams, measured between 680 and 825 °C in the stress range of 0.1–0.3 MPa, is discussed using two models assuming strut compression or strut bending as deformation modes. [Copyright &y& Elsevier]

Cobalt-based superalloy microlattices with γ/γ′ microstructure are manufactured by combining two additive methods: ink-extrusion 3D-printing and pack-cementation surface alloying. First, a microlattice green structure is 3D-printed at ambient temperature from inks comprised of Co 3 O 4 , NiO, and WO 3 powders, an elastomeric binder and solvents. Organic removal followed by oxide reduction under Ar-5% H 2 , sintering and homogenization at 1250 °C lead to a metallic microlattice with dense struts with uniform γ (fcc)-Co–22Ni–8W (at.%) composition. Second, aluminum is deposited on the strut surfaces via pack-cementation at 1000 °C, diffused at 1300 °C through the strut volume to achieve a uniform composition (Co–20Ni–6W–10Al or Co–18Ni–5W–13Al, at.%), and precipitated during aging at 900 °C as γ′ precipitates within the γ matrix. The compressive strength, ductility and energy absorption of these γ/γ′ Co-based precipitation-strengthened microlattices is measured at ambient temperatures for two aging time (16 and 65 h) and found to be much superior to those of an unalloyed Co microlattice. [ABSTRACT FROM AUTHOR]

Abstract Current research on the application of nanoferrites as an electrode material for Li-ion batteries (LIBs) has reached a tremendously high level. The structural, electrical, and optical properties of nanoferrite materials for LIBs have been characterized in several studies. The intention in the present study was to introduce new ferrite materials for improving the cyclic property and efficiency of Li batteries and to provide further characterization of the optical and electrical properties of these CoLi x Fe 1-x O 4 nanoferrites synthesized using a sol-gel combustion technique. Moreover, the synthesized CoLi x Fe 1-x O 4 ferrite samples were characterized by identifying their structural, electrical, and optical properties. A UV analysis illustrated a decrease in the bandgap energy values with increasing Li concentration, while a Fourier transform-infrared spectroscopy study confirmed a spinel ferrite structure. Electrochemical performance of the synthesized CoLi x Fe 1-x O 4 nanoferrites showed an initial coulombic efficiency of 80% and an initial discharge capacity of 1258 mAh g−1. Highlights • The crystalline nature of the synthesized nanoparticles decreased with increasing Li content. • SEM analysis reveals cubic structure. • The calculated bandgap energies tended to decrease with increasing Li concentration. • The discharge (charge) capacity and coulombic efficiency shows 1258 mAhg−1 (1010 mAh g−1) and 80%. [ABSTRACT FROM AUTHOR]

Copper foams are fabricated by directional freezing of aqueous suspensions of nanometric CuO powders followed by ice sublimation, reduction to Cu in Ar–5% H 2 gas and sintering. During slurry solidification, parallel, lamellar, centimeter-long ice dendrites grow, pushing the CuO powders into lamellar interdendritic spaces. Upon subsequent ice sublimation, the ice dendrites create lamellar pores surrounded by CuO walls that are subsequently reduced to copper and sintered; these ice-templated walls display surface micropores and, depending on the reduction/sintering parameters, internal micropores. Varying the main processing parameters – powder fraction in the slurry (from 13 to 19 vol%) and casting temperature (from −10 to −30 °C) – has a strong effect on the foam microstructure: (i) porosity (varying from 45% to 73%) is inversely related to slurry powder fraction, (ii) oriented lamellar macropores width increases from 15 to 64 µm with decreasing slurry fraction and increasing freezing temperature and (iii) oriented lamellar Cu wall width increases from 19 to 63 µm with increasing slurry fraction and freezing temperature. The resulting Cu foams show oriented, lamellar macropores (beneficial to permeability) and walls micropores (which increase the surface area) and are promising for use in electrochemical cells given the simplicity, scalability, low cost, and microstructure tunability associated with the ice-templating process. The ice-templated Cu foams, with pore directions parallel and perpendicular to the direction of compressive loading, show ductile compressive behavior with high yield stress, ductility and energy absorption; they are compared to model predictions and literature data of Cu lotus foams with elongated, cylindrical pores. [ABSTRACT FROM AUTHOR]

Nitroquinolines are an important toxic element in ecosystems and have great significance for monitoring the environmental system with appropriate tools for safety assessments. In this work, we developed a sensitive method for accurate and low-level detection of 5-nitroquinoline (5-NQ) using 1T-molybdenum disulfide core shells unified with nitrogen-rich amorphous carbon nanotube (1T-MoS 2 /NCNT). The 1T-MoS 2 /NCNT core-shells composite is prepared using a hydrothermal method to fabricate a ratiometric low-level detection of a 5-NQ sensor. The screen-printed carbon electrode (SPCE) modified with 1T-MoS 2 /NCNT reveals superior electrochemical performance for the detection of 5-NQ with a wide dual linear range of 0.03–258.58 µM and 274.91–604.25 µM, low-level detection limit (LOD) of 0.0089 µM, and a higher sensitivity of 1.83 µA µM−1 cm−2 due to its higher electrochemical active surface area, superior conductivity, and excellent stability. The π-delocalized electrons in 5-NQ facilitate the rapid electron transfer at the electrode-electrolyte interface, allowing easy conjugation with 1T-MoS 2 /NCNT. The operational stability of the sensor retains 98.7 % after 40 consecutive cycles. In addition, the achieved recovery rates are 96.80–99.76 % and 97.93–99.75 % for 5-NQ detection in various soils and water samples, signifying its feasibility for real-time industrial waste monitoring. [Display omitted] • The core-shell 1 T-MoS 2 /NCNT is constructed for low-level and accurate detection of 5-NQ in environmental samples. • 1 T-MoS 2 /NCNT exhibits excellent conductivity, enlarged interlayer distance, and higher active surface area. • It displays a dual linear range of 0.03–258.58 µM and 274.91–604.25 µM and a lower detection limit of 0.0089 µM. • Real-time analysis of the sensor retains the high-level recovery in soil and water samples. [ABSTRACT FROM AUTHOR]

Innovative and efficient electrocatalysts using selenide based composites are essential for electrochemical analyses and could significantly impact various modern technologies. This paper prepared a flake-like architecture comprising SnSe 2 grafted N-doped carbon (NC) (SnSe 2 -NC) through a simple hydrothermal method and successfully applied the material for electrochemical sensing of carbendazim (CBZ). We investigated impacts from calcination temperature on prepared SnSe 2 materials using various characterization methods, including XRD, XPS, BET, TGA, HR FE-SEM and FE-TEM. Nanocomposite electrochemical activity toward CBZ detection was ascribed to synergy between NC providing a conductive matrix and SnSe 2 agglomeration providing large active surface area, superior conductivity, and abundant active surface sites. The fabricated sensor detected CBZ across a wide linear concentration range 0.002–139.38 μM under ideal conditions, with limit of detection = 0.67 nM. The propound sensor was effectively applied to detect CBZ in pure water and vegetable extracts, with reasonable recovery rates. [ABSTRACT FROM AUTHOR]

Abstract: Y0.2CoFe1.8O4 nanopowders were prepared using a sol–gel combustion method. Metal nitrates, such as yttrium nitrate, cobalt nitrate and ferric nitrate, were used as the source materials. Citric acid and polyvinyl alcohol were used as the burning agent and agglomeration reducing agent, respectively. The pH of the precursor was maintained at 7. The mean crystallite size of the prepared ferrite was in the range of ∼20–70nm. The inverse spinel structure, cubic morphology, and the identification of functional groups of the yttrium-doped cobalt ferrite were analyzed systematically using several analytical tools. [Copyright &y& Elsevier]

Abstract: Commercially-pure zirconium is alloyed and dealloyed repeatedly with hydrogen at 810 °C, thereby cyclically triggering phase transformations between hydrogen-free α-Zr and hydrogen-alloyed β-Zr. Under an externally applied tensile stress, the internal mismatch stresses produced by the α-β transformations are biased, resulting in the accumulation of strain increments after each chemical cycle in the direction of the applied stress. Two key parameters, i.e., half-cycle time and applied stress, are examined to determine their effects on the strain increments. A tensile strain of 133% is achieved without fracture after multiple chemical cycles, demonstrating for the first time transformation superplasticity in zirconium induced by isothermal hydrogen cycling. [Copyright &y& Elsevier]

A set of strontium (Sr)-doped cobalt (Co) nanoferrites Co 1-x Sr x Fe 2 O 4 (x = 0.1 and 0.2) was synthesized using a sol-gel combustion method. The phase, nanocrystallinity, and optical properties of as-prepared and annealed samples were investigated. The average crystallite sizes obtained were 36, 40, and 30 nm for the nanoferrites with lattice parameters of 8.25, 8.30, and 8.30 Å, respectively. Raman spectroscopy confirmed the spinel structure of the ferrite crystals. The existence of cations at the octahedral and tetrahedral sites in the nanoparticles was also confirmed by X-ray photoelectron spectroscopy. Direct bandgap energy values of 1.29, 1.32, and 1.35 eV were determined and an applied temperature of 680 °C ensured the complete decomposition of precursors. The correlation between the Sr substitution in Co ferrite and the structural and optical changes is discussed. [Display omitted] • Sr doped cobalt ferrite is less investigated for functional properties. • Spinel cubic structure from the Co2+ and Fe3+ states was confirmed. • XPS confirms the existence of cations at the octahedral and tetrahedral sites. • Prepared sample may be useful as an electrode material. [ABSTRACT FROM AUTHOR]

Solid-oxide iron-air batteries have potential for applications in large-scale energy storage systems, but their storage materials, iron and iron oxides, have limited cycle life due to powder sintering and choking of gas flow. To address this issue, Fe foams are synthesized with either equiaxed or directional dendritic pore structures by camphene-based freeze casting of Fe 2 O 3 powders, followed by H 2 reduction to Fe and sintering. For each pore architecture, Fe foams are created with three different initial porosities, ranging from 47 to 63 vol %, and are then cycled at 800 °C under alternating oxidation (via H 2 O) and reduction (via H 2) conditions. The redox-cycled foams are examined by optical microscopy, scanning electron microscopy, and synchrotron X-ray tomography to assess the evolution of their porosity driven by the redox volume changes, sintering, and micropore formation via the Kirkendall effect. After 5 redox cycles, the Fe foams have lost the majority (39 ± 2 vol %) of their initial porosity. • Solid-oxide iron-air batteries have potential for large-scale energy storage systems. • Fe foams are synthesized by camphene-based freeze casting. • 3D microstructural analysis is used to determine degradation mechanism. [ABSTRACT FROM AUTHOR]

Cobalt-based superalloy microlattices were created via (i) three-dimensional-extrusion printing of inks containing a suspension of Co-, Ni- and W-oxide particles, (ii) H 2 -reduction of the oxides and sintering to a homogenous Co-Ni-W alloy, (iii) Al pack-cementation to deposit Al on the microlattice struts, followed by Al-homogenization. The resulting Co-(18–20)Ni-(5–6)W-(10–13)Al (at.%) microlattices, with 27–30% relative density and 350 μm diameter struts, display a peak in yield strength at 750°C, consistent with their γ/γ′ aged microstructure. Oxidation resistance is strongly improved compared to Al-free printed Co-Ni-W lattices, via the formation of an Al 2 O 3 surface layer. However, the resulting Al depletion within the struts reduces creep resistance at 850°C, which nevertheless remains similar to Ni-based superalloy foam, with 35% relative density. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The effect of cubic-phase stabilizing dopant (Al, Ga, Ta) on the mechanical and electrochemical properties of Li garnet solid electrolyte was studied. Dense Li 6.25 La 3 Al 0.25 Zr 2 O 12 , Li 6.50 La 3 Ta 0.50 Zr 1.5 O 12 , Li 6.25 La 3 Ga 0.25 Zr 2 O 12 were prepared by conventional solid-state synthesis of powder and densified using hot pressing. Ga-LLZO exhibited the highest fracture stress (∼143 MPa), fracture toughness (∼1.22 MPa m1/2) and total conductivity (∼1 mS/cm) of the three materials; however, the bulk conductivity was about 1.5 mS/cm. We believe that the weak grain-boundaries, as evidenced by a predominately intergranular fracture, correlates with a relatively high grain-boundary impedance, thus reducing the value of the total conductivity by about 30 % lower than that for the bulk. Based on the combined mechanical and electrical properties, overall, Li 6.25 La 3 Ga 0.25 Zr 2 O 12 exhibits the most favorable combination of some of the most salient properties of the three dopants. We believe the results of this study will facilitate the commercialization of Li metal batteries using Li-garnet ceramic electrolyte. [ABSTRACT FROM AUTHOR]

Abstract Most previously proposed methods for the manufacture of dealloyed nanoporous copper (Cu) could not be realized for practical applications, due to their poor mechanical properties caused by the use of metal 'powders' to create a precursor alloy prior to dealloying. Therefore, a new facile synthesis is proposed based on a pack-cementation process using Cu foil instead of Cu powder. Depending on the pack-cementation time and the amount of Al, a hierarchical micro/nanoporous Cu was also created and coated with tin. The coin-cell test exhibited a four-fold higher areal capacity (7.4 mAh/cm2 without performance degradation up to 20 cycles) than graphite. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract We synthesized Fe foams using water suspensions of micrometric Fe 2 O 3 powder by reducing and sintering the sublimated Fe oxide green body to Fe under 5% H 2 /Ar gas. The resultant Fe foam showed aligned lamellar macropores replicating the ice dendrites. The compressive behavior and deformation mechanism of the synthesized Fe foam were studied using an acoustic emission (AE) method, with which we detected sudden localized structural changes in the Fe foam material. The evolution of the deformation mechanism was elucidated using the adaptive sequential k -means (ASK) algorithm; specifically, the plastic deformation of the cell struts was followed by localized cell collapse, which eventually led to fracturing of the cell walls. For potential biomedical applications, the corrosion and biocompatibility characteristics of the two synthesized Fe foams with different porosities (50% vs. 44%) were examined and compared. Despite its larger porosity, the superior corrosion behavior of the Fe foam with 50% porosity can be attributed to its larger pore size and smaller microscopic surface area. Based on the cytotoxicity tests for the extracts of the foams, the Fe foam with 44% porosity showed better cytocompatibility than that with 50% porosity. Graphical abstract Unlabelled Image Highlights • Iron foam synthesized from water suspension of Fe 2 O 3 powder under 5% H 2 /Ar gas. • Compressive deformation mechanism of iron foam is analyzed using an acoustic emission. • Not porosity but pore size is a dominant factor for corrosion behavior of iron foams. • Concentration released Fen+ controls cytotoxicity of iron foam extracts. [ABSTRACT FROM AUTHOR]

Abstract The effects of hydrogen charging on the evolution of strain-induced lattice defects and phase transformation were investigated in 316L stainless steel. The initial material was obtained by cold rolling to a thickness reduction of 20%. The surfaces of some of the initial samples were cathodically charged with hydrogen. Afterward, both the charged and uncharged samples were subjected to tension until failure. The dislocation density and twin-fault probability in the charged and uncharged specimens during tension were compared. We found that hydrogen charging reduced the degree of increase in the dislocation density and twin-fault probability during the application of tension to the same strain level. Significant martensitic phase transformation was observed in the uncharged samples tested to the strain of 10% or higher. In the hydrogen-charged samples, only a slight increase in the martensite phase fraction was detected. A correlation between the α′-martensite fraction and the dislocation density was found for the studied samples, suggesting that the lower degree of martensitic phase transformation in the charged 316L steel was caused by the smaller amount of stress developed due to the lower dislocation density. In accordance with the differences observed in the phase composition and defect densities, the hydrogen-charged material exhibited lower surface hardness. [ABSTRACT FROM AUTHOR]

Metal oxides are widely used as electrode materials due to their high potential for various applications. Specifically, spinel-structured cobalt ferrite is employed in various energy applications. Among the available conventional techniques to synthesize nano-ferrites, the sol-gel combustion approach is one of the simplest and most effective. In this work, strontium-doped cobalt ferrite nanoparticles are synthesized using the sol-gel combustion technique and annealed at various temperatures. Further, the prepared samples are characterized using XRD to identify the phase and crystallinity of the materials. It shows the average crystallite sizes of 33, 36, and 35 nm for various temperatures of 200 °C, 300 °C, and 500 °C, respectively. FESEM illustrated the clustered and homogeneous structure of the sample. From UV-Vis-NIR absorption spectroscopy, direct bandgap energy values are calculated using Tauc's plot as 1.24, 1.21, and 1.20 eV. To examine electrochemical properties, galvanostatic measurements are used. The observed sample (Co 0.8 Sr 0.2 Fe 2 O 4 at 300 °C) shows a supercapacitance value of 637 Fg−1 at 0.5 Ag−1 and retained 85.5 % after 1000 cycles at 5 Ag−1, showing 98.79 % coulombic efficiency after 5000 cycles at 15 Ag−1. The result indicates that doped nanoferrites are a promising electrode material for supercapacitor applications. • Enhanced electrochemical performance of Co 0.8 Sr 0.2 Fe 2 O 4 were discussed. • It achieves the specific capacitance value of about 637 Fg−1 at 0.5 Ag−1 in 300 °C. • It shows 98.79 % coulombic efficiency after 5000 cycles at 15 Ag−1. • Co 0.8 Sr 0.2 Fe 2 O 4 is suitable electrode for enhanced supercapacitor applications. [ABSTRACT FROM AUTHOR]

Experiments were conducted to study the compression behavior of Cu-Ni foams prepared using freeze casting. The struts of the foam samples were solid-solutioned with differing Cu/Ni ratios, after which the grain size in the struts was measured using scanning electron microscopy. The compression performance of the samples was studied in both parallel and perpendicular directions to the temperature gradient, and compared with model calculations. It was confirmed that alloying increased the yield strength of the struts. The experimentally determined yield strength and elastic modulus were compared with model calculations, which revealed that the elastic modulus of the foams was lower than the values calculated from the classical compression and Gibson-Ashby models due to variation in the thickness of the struts. It was also found that the alloying of Cu and Ni improved the mechanical performance of the alloy foams because the absorbed energy for the alloys was considerably higher than that for the pure foams. [ABSTRACT FROM AUTHOR]

The use of aluminum nitride (AlN) has recently begun to be explored for advanced functional applications. For some particular applications, it is more advantageous to use porous-structured AlN, simply because it can provide a greater surface area and higher permeability. However, porous or bulk AlN is very difficult to achieve due mainly to its high melting point (2200 °C). This study proposes a new novel processing method to synthesize porous AlN through a complete transformation from porous aluminum (Al) using a remarkably low nitriding/sintering temperature (620 °C) as opposed to only the surface nitride AlN-Al core composite systems reportedly at or above 1000 °C in the literature. A uniform microporous bead structure of porous AlN with a mean pore size of 74.0 ± 27.7 μm was obtained that also contained nanoparticles ranging from 80 to 230 nm that covered the surface. [ABSTRACT FROM AUTHOR]

With increasing demand for porous materials with their popular use in functional applications, there is a strong need to develop a decent strength prediction method for porous materials. The Gibson-Ashby (G-A) model, which is the most common prediction method, has served this purpose. This model is constructed upon a weakly-structured open-cell porous material, thus providing a ‘lower bound’ of yield strength. This study considers ‘contiguity’ as a governing parameter to predict the strength of porous materials and proposes a modified G-A model by incorporating the concept of contiguity. This paper supports preliminary evidence that the new model better describes the strength of selected porous materials. [ABSTRACT FROM AUTHOR]

Twin roll casting (TRC), with a relatively fast solidification rate, is an excellent production method with promising potential for producing wrought semi or final Mg alloy products that can often suffer from poor formability. We investigate in this study the effect of the TRC method and the subsequent heat treatment on the microstructure and deformation mechanisms in Mg-Zn-Zr-Nd alloy deformed at room temperature using the in-situ neutron diffraction and acoustic emission techniques and ex-situ texture measurement and microscopy, respectively. Although a higher work hardening is observed in the rolling direction due to the more intensive -type dislocation activity, the difference in the mechanical properties of the specimens deformed in the RD and TD directions is small in the as-rolled condition. An additional heat treatment results in recrystallization and significant anisotropy in the deformation. Due to the easier activation of the extension twinning in the TD given by texture, the yield stress in the TD is approximately 40% lower than that in the RD. [ABSTRACT FROM AUTHOR]

Cobalt with anisotropic open porosity is fabricated by directional solidification of aqueous slurries of nanometric Co 3 O 4 powder where ice dendrites push powders into aligned interdendritic spaces, followed by ice sublimation, reduction of the oxide to metallic Co powders, and sintering of these Co powders into parallel lamellae. As the Co 3 O 4 powder slurry fraction decreases (from 10 to 4 vol%), Co lamellae width in the final foam also decreases (from 93 to 8 μm) while foam porosity increases (from 66 to 85%). A drop in solidification temperature (from −10 to −50 °C) decreases porosity (from 77 to 63%) and lamellae width (from 11 to 5 μm) at a constant 8 vol% slurry fraction. Finally, with increasing sintering time (for −10 °C solidification temperature and 8% slurry fraction), Co foam porosity decreases (from 77 to 68%) and lamella width strongly increases (from 10 to 59 μm), consistent with sintering-induced coalescence of lamellae. The Co foams exhibit high strength but relatively low stiffness as compared to simple theoretical models, consistent with internal Co lamella buckling. A uniform Co oxide layer is grown by oxidation to create an active coating on the Co lamellae useful for lithium-ion storage. A coin-cell test carried out on the oxidized Co foam demonstrates a capacity (1283 mAhg −1 ) almost twice that of a control oxidized Co foil anode, owing to its considerably larger surface area. Finite-element analysis is used to compute stresses and plastic strain evolutions during the lithiation process to understand the effect of oxide layer thickness and roughness, and micropores within the Co lamellae. [ABSTRACT FROM AUTHOR]

Abstract: Demands for sustainable production of hydrogen are rapidly increasing because of environmental considerations for fossil fuel consumption and development of fuel cell technologies. Thus, the development of high‐performance and economical catalysts has been extensively investigated. In this study, a nanoporous Mo carbide electrode is prepared using a top‐down electrochemical process and it is applied as an electrocatalyst for the hydrogen evolution reaction (HER). Anodic oxidation of Mo foil followed by heat treatment in a carbon monoxide (CO) atmosphere forms a nanostructured Mo carbide with excellent interconnections, and these structural characteristics lead to high activity and durability when applied to the HER. Additionally, characteristic behavior of Mo is observed; metallic Mo nanosheets form during electrochemical anodization by exfoliation along the (110) planes. These nanosheets are viable for chemical modification, indicating their feasibility in various applications. Moreover, the role of carbon shells is investigated on the surface of the electrocatalysts, whereby it is suggested that carbon shells serve as a mechanical barrier against the oxidative degradation of catalysts that accompanies unavoidable volume expansion. [ABSTRACT FROM AUTHOR]

Despite the importance of tin oxide (SnO 2 ) in diverse functional applications, little information is available on the mechanical properties of bulk or porous SnO 2 . In this study, porous SnO 2 was synthesized using an ice-templating method to produce a “dual” pore structure that comprises large wall pores (on the order of several micrometers) with small micropores (~2 µm) on their surfaces. The Vickers hardness decreased with increasing porosity and increased with increasing contiguity of struts. The compressive stress–strain curves of porous SnO 2 samples with porosity ranging from 48% to 73% were compared with both the Gibson–Ashby and the cellular-lattice-structure-in-square-orientation models, which generally represent the “lower” and “upper” bounds of yield strength for porous materials, respectively. As expected, the yield strength of the porous SnO 2 samples decreased with increasing porosity, and all the yield-strength values of porous SnO 2 fell between the two extreme prediction models. The sample with the lowest porosity of 48% exhibited sharply increasing elastic behavior followed by sudden rupture, as generally reported for bulk ceramics; however, the other samples with higher porosities ranging from 50% to 73% exhibited “porous-metal-like” behavior at strains of 15% or greater as a result of the fracturing of the solid walls between the pores. [ABSTRACT FROM AUTHOR]

A range of morphology-controlled hematite superstructures, including two-dimensional sheet assembly, microspheres with a vein-like network, hollow urchin with tapered nanorods, and flowers with porous branch-like structures, were obtained from different solvents via the solvothermal approach. The results showed that the variation of the solvent from protic to aprotic facilitated morphological modifications, with the solvent playing a key role in determining the overall architecture of the oxide particles under different polar conditions. A porous microsphere grown from water solvent delivered a reversible capacity of 880 mAh g −1 over 60 cycles at 200 mA g −1 with good rate stability. Here, the bicontinuous nanoporous structure, with well-developed mesoporosity in the microsphere, reduced the severity of volume changes during the cycling process and stabilized passivation layer growth. The hematite nanostructure grown from water/dimethylformamide solvent exhibited the highest photocurrent density of 190 μA/cm −2 vs. Ag/AgCl, which was attributed to the rapid transport of charge carriers in the porous nanostructure. Thus, solvent-mediated synthesis can be used to prepare a range of hematite porous nanostructures for use as an anode in lithium-ion batteries and as a photoanode in photoelectrochemical cells, as well as for water splitting, gas sensors, and catalytic applications. [ABSTRACT FROM AUTHOR]

Lithium Nickel Manganese Cobalt Oxide (NMC) is one of the most common oxide cathode materials for Li-ion batteries. NMC is also under consideration for use in all solid-state batteries. However, differences in the coefficients of thermal expansion (CTE) between NMC and the solid electrolyte during composite electrode fabrication and differential expansion and contraction during electrochemical cycling will cause stresses possibly resulting in electrode fracture and battery capacity fade. As a consequence, we hot-pressed phase-pure polycrystalline NMC with controlled density and accurately measured the mechanical (elastic modulus, shear modulus, Poisson’s ratio and nanoindentation hardness) and physical properties (CTE and thermal conductivity). We believe that this is the first report of the mechanical and physical properties of commercially available NMC and these experimental data are important to predict or increase the cycle life of NMC as a cathode material for state-of-the-art Li-ion and advanced solid-state batteries. [ABSTRACT FROM AUTHOR]

This study investigates the processing and potential application of Ti foams to the anode of lithium-ion batteries (LIBs). Ti foam is successfully synthesized using a water-based freeze-casting process, and anatase titanium dioxide (TiO 2 ) is formed on the surface of the Ti foam for application to the anode of LIB. The metallic Ti foam acts as a current collector “platform” with increased surface area and the TiO 2 surface coating acts as an active anode material. Coin-cell test results show that the unique combination of the Ti foam and the TiO 2 coating anode has highly stable cycling properties and can thus be considered promising for use as an advanced anode for LIBs that require high safety and stability. It is anticipated that the use of the unique Ti-foam-based electrode design will not only be limited to LIBs but also will be applied to other energy and environmental areas as a catalyst or filter. [ABSTRACT FROM AUTHOR]

Nanostructured metal oxide semiconductors have shown outstanding performances in photoelectrochemical (PEC) water splitting, but limitations in light harvesting and charge collection have necessitated further advances in photoelectrode design. Herein, we propose anodized Fe foams (AFFs) with multidimensional nano/micro-architectures as a highly efficient photoelectrode for PEC water splitting. Fe foams fabricated by freeze-casting and sintering were electrochemically anodized and directly used as photoanodes. We verified the superiority of our design concept by achieving an unprecedented photocurrent density in PEC water splitting over 5 mA cm−2 before the dark current onset, which originated from the large surface area and low electrical resistance of the AFFs. A photocurrent of over 6.8 mA cm−2 and an accordingly high incident photon-to-current efficiency of over 50 % at 400 nm were achieved with incorporation of Co oxygen evolution catalysts. In addition, research opportunities for further advances by structual and compositional modifications are discussed, which can resolve the low fill factoring behavior and improve the overall performance. [ABSTRACT FROM AUTHOR]

Nanostructured metal oxide semiconductors have shown outstanding performances in photoelectrochemical (PEC) water splitting, but limitations in light harvesting and charge collection have necessitated further advances in photoelectrode design. Herein, we propose anodized Fe foams (AFFs) with multidimensional nano/micro-architectures as a highly efficient photoelectrode for PEC water splitting. Fe foams fabricated by freeze-casting and sintering were electrochemically anodized and directly used as photoanodes. We verified the superiority of our design concept by achieving an unprecedented photocurrent density in PEC water splitting over 5 mA cm−2 before the dark current onset, which originated from the large surface area and low electrical resistance of the AFFs. A photocurrent of over 6.8 mA cm−2 and an accordingly high incident photon-to-current efficiency of over 50 % at 400 nm were achieved with incorporation of Co oxygen evolution catalysts. In addition, research opportunities for further advances by structual and compositional modifications are discussed, which can resolve the low fill factoring behavior and improve the overall performance. [ABSTRACT FROM AUTHOR]

A Novel 3D porous Sn-Cu architecture is prepared as an anode material for use in an advanced lithium-ion battery. Micro-lamellar-structured 3D porous Cu foam, which is electroless-plated with Sn as an active material, is used as anode current collector. Compared to Sn-coated Cu foil, the 3D Sn-Cu foam exhibits superior Li-ion capacity and stable capacity retention, demonstrating the advantage of 3D porous architecture by preserving its structural integrity. In addition, the effect of heat-treatment after Sn plating is investigated. Sn/Sn 6 Cu 5 and SnO 2 /Cu 10 Sn 3 were formed on and in the 3D Sn-Cu foam under the heat-treatment at 150 °C and 500 °C, respectively. The development of Cu 10 Sn 3 in the 3D Sn-Cu foam heat-treated at 500 °C can be a key factor for the enhanced cyclic stability because the Cu 10 Sn 3 inactively reacts with Li-ion and alleviates the volume expansion of SnO 2 as an inactive matrix. [ABSTRACT FROM AUTHOR]

Differential scanning calorimetry (DSC) was used to study the thermal stability of the microstructure and the phase composition in nanocrystalline 316L stainless steel processed by high-pressure torsion (HPT) for ¼ and 10 turns. The DSC thermograms showed two characteristic peaks which were investigated by examining the dislocation densities, grain sizes and phase compositions after annealing at different temperatures. The first DSC peak was exothermic and was related to recovery of the dislocation structure without changing the phase composition and grain size. The activation energies for recovery after processing by ¼ and 10 turns were ~163 and ~106 kJ/mol., respectively, suggesting control by diffusion along grain boundaries and dislocations. The second DSC peak was endothermic and was caused by a reverse transformation of α’-martensite to γ-austenite. The hardness of annealed samples was determined primarily by the grain size and followed the Hall–Petch relationship. Nanocrystalline 316L steel processed by HPT exhibited good thermal stability with a grain size of ~200 nm after annealing at 1000 K and a very high hardness of ~4900 MPa. [ABSTRACT FROM AUTHOR]

The effect of relative density on the hardness and fracture toughness of Al-substituted cubic garnet Li6.19 Al0.27 La3 Zr2 O12 ( LLZO) was investigated. Polycrystalline LLZO was made using solid-state synthesis and hot-pressing. The relative density was controlled by varying the densification time at fixed temperature (1050°C) and pressure (62 MPa). After hot-pressing, the average grain size varied from approximately 2.7-3.7 μm for the 85% and 98% relative density samples, respectively. Examination of fracture surfaces revealed a transition from inter- to intragranular fracture as the relative density increased. The Vickers hardness increased with relative density up to 96%, above which the hardness was constant. At 98% relative density, the Vickers hardness was equal to the hardness measured by nanoindentation 9.1 GPa, which is estimated as the single-crystal hardness value. An inverse correlation between relative density and fracture toughness was observed. The fracture toughness increased linearly from 0.97 to 2.37 MPa√m for the 98% and 85% relative density samples, respectively. It is suggested that crack deflection along grain boundaries can explain the increase in fracture toughness with decreasing relative density. It was also observed that the total ionic conductivity increased from 0.0094 to 0.34 mS/cm for the 85%-98% relative density samples, respectively. The results of this study suggest that the microstructure of LLZO must be optimized to maximize mechanical integrity and ionic conductivity. [ABSTRACT FROM AUTHOR]

A 316L stainless steel was processed by high-pressure torsion (HPT) to evaluate the grain refinement and phase transformation. The initial material was essentially a single phase γ-austenite with a coarse-grained microstructure of ∼42 µm but the grain size was reduced to ∼45 nm after 10 turns of HPT. In addition, there was a phase transformation and the initial γ-austenite transformed initially to ε-martensite and finally to α′-martensite with increasing strain. The dislocation density increased to an exceptionally high value, of the order of ∼10 16 m −2 , in the main α′-martensite phase after 10 HPT revolutions. The formation of the multiphase nanocrystalline microstructure yielded a four-fold increase in hardness to reach an ultimate value of ∼6000 MPa. The Hall–Petch behaviour of the HPT-processed alloy is compared directly with coarse-grained materials. [ABSTRACT FROM AUTHOR]

An investigation was conducted to evaluate the effect of annealing at different temperatures on the tensile properties of ultrafine-grained 316L stainless steel processed by high-pressure torsion (HPT). A “moderate-temperature” annealing at 740 K resulted in reduced strength and elongation due to the annihilation of mobile dislocations. A “high-temperature” annealing at 1000 K yielded a remarkably good combination of yield strength (∼1330 MPa) and elongation to failure (∼43%) which can be attributed to the almost full reversion of α′-martensite formed during HPT into γ-austenite while the grain size remained very fine with a value of about 200 nm. [ABSTRACT FROM AUTHOR]

Titanium (Ti) foams with relative densities of 0.32, 0.37, and 0.49 were processed via freeze casting. The mechanical characteristics of samples with different porosities were studied in uniaxial compression tests at initial strain rates between 0.001 and 0.5 s−1. According to the results, the stress–strain response does not significantly depend on the strain rate, at least up to the applied maximum stress, which corresponds to 0.1–0.3 engineering strain. In-situ acoustic emission (AE) experiments have revealed that the stress drop beyond the maximum stress corresponds to the formation and propagation of macrocracks. However, cracks were also initiated below the maximum stress, particularly, in samples with higher relative densities. The analysis of the Young's modulus and yield strength versus the porosity exhibits a power law relationship with a high exponent (approximately 4–5). This high exponent is reasonable if the decrease in the porosity level is associated with a change in the deformation mechanism from the compression model to the Gibson–Ashby (GA) model between 0.37 and 0.49 relative density. [ABSTRACT FROM AUTHOR]

Antibiotics are essential medications for human and animal health, as they are used to battle urinary infections and bacterial diseases. Therefore, the rapid determination of antibiotic drugs in biological samples is necessary to address the current clinical challenge. Here, we developed a heterojunction ternary composite of BiOCl/BiVO 4 nanosheets enriched with graphene oxide (BiOCl/BiVO 4 @GO) for accurate and minimal-level detection of an antihistamine (promethazine hydrochloride, PMZ) in urine samples. The BiOCl/BiVO 4 nanosheets were prepared by a wet chemical approach using a deep eutectic green solvent. The spectroscopic and analytical methods verified the formation and interaction of the BiOCl/BiVO 4 @GO composite. Our results showed that the thoroughly exfoliated BiOCl/BiVO 4 @GO composite retained good electrical conductivity and fast charge transfer toward the electrode–electrolyte interface in neutral aqueous media. In addition, the experimental conditions were accurately optimized, and the BiOCl/BiVO 4 @GO composite showed excellent electrocatalytic activity toward the oxidation of PMZ. Indeed, the BiOCl/BiVO 4 @GO composite demonstrated a good linear response range (0.01–124.7 μM) and a detection level of 3.3 nM with a sensitivity of 1.586 μA μM−1 cm−2. In addition, the BiOCl/BiVO 4 @GO composite had excellent storage stability, good reproducibility, and reliable selectivity. Finally, the BiOCl/BiVO 4 @GO displayed a desirable recovery level of PMZ in urine samples for real-time monitoring. • A heterojunction composite of BiOCl/BiVO 4 @GO was prepared via green synthesis. • BiOCl/BiVO 4 @GO showed excellent electrocatalytic activity towards PMZ detection. • BiOCl/BiVO 4 @GO showed much lower detection limit of PMZ with good stability. • BiOCl/BiVO 4 @GO was applied to real time analysis of PMZ in urine samples. [ABSTRACT FROM AUTHOR]

This study employs for the first time surface-nitrided Ni foam as a counter-electrode free of Pt and transparent conducting oxides (TCOs) to realize a cost-effective counter electrode for dye-sensitized solar cells (DSSCs). This electrode simultaneously features high catalytic activity for triiodide reduction and high conductivity in a single layer. The nitrided Ni foam is synthesized by nitridation treatment of open-cell Ni foam in an ammonia atmosphere. This electrode presents high catalytic activity on the nitrided surface and easy electron transport ability in the three-dimensional, interconnected metallic structure. This study provides a preliminary design concept for utilizing the nitrided Ni foam as a promising cost-effective counter electrode that does not require expensive Pt and TCO. [ABSTRACT FROM AUTHOR]

Abstract: Nanoporous metallic foams with an exceptionally high specific surface area can be a perfect solution for advanced energy applications. There have been an increasing number of recent efforts to achieve nanoporous metallic foams, but the latest research has paid much attention to the processing and characterization of noble nanoporous metallic foams (Pt and Au) through the conventional dealloying technique. This study proposes a new and innovative method of processing non-noble nanoporous (sub-micrometer-scale) metallic foams: a technique that combines the conventional electroless plating and three-dimensional proximity-field nanopatterning. Copper and nickel foams with sub-micrometer-scale pores are processed and characterized in this study. [Copyright &y& Elsevier]

Highlights: [•] Methanol tolerable PtPdCo/C ternary electrocatalysts were prepared. [•] PtPdCo/C showed enhanced activity in the half-cell and the actual DMFC single-cell. [•] Long-term single-cell operation test was performed successfully. [•] PtPdCo/C can be used as a replacement for the cathode catalyst in DMFCs. [Copyright &y& Elsevier]

This paper discusses a new method of powder-metallurgy processing to produce regular-structured Cu nanofoams or irregular-structured Cu foams containing both micropores and nanopores. Coarser Cu nanofoam struts (approximately 2.5 times larger) formed in the ribbon samples of the foams subjected to additional sintering at 900 °C after initial lower-temperature sintering at 450 °C than those formed in the ribbon samples of the foams subjected to additional sintering at 700 °C. Furthermore, a much higher degree of strut continuity was observed in the Cu nanofoam sintered at 900 °C, which should improve the ductility and structural integrity of the Cu nanofoam. This study can be considered as a framework for using a simple method of powder-based dealloying to produce nanoporous and micro/nanoporous metallic foams for a variety of energy-based applications requiring metallic foam materials with a high density of specific surface area. Although the dealloying process of achieving Cu nanofoams is not new, this powder-based method has significant implications because often a difficult and expensive material shaping process can be avoided by forming the precursor alloy with a near-net shape geometry in the method. [ABSTRACT FROM AUTHOR]

Abstract: We examined the high-temperature tensile properties of 316L austenite stainless steel (SS) cathodically charged with hydrogen (H) and discussed how the H distribution, strain rate, and temperature range affected the mechanical properties of 316L SS at elevated temperatures, with particular focus on dynamic strain aging (DSA). A preheat treatment was applied prior to each high-temperature tensile test to lessen the H gradient on the outer surface of the specimen. DSA, manifested by serrations in the stress–strain curve, was observed at temperatures between 400 and 500°C and was analyzed using strain-rate sensitivity, dynamic strain–hardening stress, and the temperature dependence of critical serration strain. In particular, this study confined its scope to the influence of H in the range of a few tens of parts per million. [Copyright &y& Elsevier]

Althoughdifferent kinds of metal oxide nanoparticles continueto be proposed as anode materials for lithium ion batteries (LIBs),their cycle life and power density are still not suitable for commercialapplications. Metal oxide nanoparticles have a large storage capacity,but they suffer from the excessive generation of solid–electrolyteinterphase (SEI) on the surface, low electrical conductivity, andmechanical degradation and pulverization resulted from severe volumeexpansion during cycling. Herein we present the preparation of mesoporousiron oxide nanoparticle clusters (MIONCs) by a bottom-up self-assemblyapproach and demonstrate that they exhibit excellent cyclic stabilityand rate capability derived from their three-dimensional mesoporousnanostructure. By controlling the geometric configuration, we canachieve stable interfaces between the electrolyte and active materials,resulting in SEI formation confined on the outer surface of the MIONCs. [ABSTRACT FROM AUTHOR]

The thin-plate specimen of 316L austenite stainless steel was charged with hydrogen using a cathodic charging technique. Despite the short diffusion distance of hydrogen predicted by the diffusion-controlled model for a semi-infinite sheet, the Vickers hardness measurements revealed the full effect of hydrogen in the center of the cross-sections of thin-plate specimens as well as in the vicinity of the outer surfaces, which appears to be due to the short-circuit diffusion mechanism along the grain boundaries. The room-temperature tensile properties of both undeformed and deformed (20, 40%) samples were examined and compared. Hydrogen softening was apparent in both types of samples. For example, the 40% deformed sample showed an approximately 17 and 7% lower yield and tensile strength, respectively, after H charging at a strain rate of 2 × 10−4 s−1 with a concomitant decrease in ductility compared to that without H. [ABSTRACT FROM AUTHOR]

Abstract: The acoustic emission (AE) method has been used for the in-situ investigations of the mechanical properties of an AJ51 magnesium alloy, reinforced with short Saffil® fibers, in compression mode and at room temperature. It is shown that the frequency analysis of the AE signals could reveal changes in the deformation processes caused by the presence of reinforcing fibers, as well as by the onset of cracks in them. [Copyright &y& Elsevier]

Abstract: This is the first report of fracture toughness analysis of a new ceramic electrolyte (Li7La3Zr2O12). The fracture toughness was measured using an indentation technique and subsurface crack propagation was analyzed using a novel focused ion beam/scanning electron microscope (FIB–SEM) technique. The fracture toughness of polycrystalline Li7La3Zr2O12 was between 0.86–1.63MPa√m. FIB–SEM analysis of the indentation cracks suggested that both half-penny and Palmquist cracks were present. The fracture toughness of Li7La3Zr2O12 is comparable to other state of the art ceramic electrolytes such as Li0.33La0.57TiO3 and Li1.3Al0.3Ti1.7(PO4)3. [Copyright &y& Elsevier]

The cathode catalyst layer in direct methanol fuel cells (DMFCs) was prepared using polystyrene beads as a pore former. Field emission scanning electron microscopy showed that the catalyst layer with the pore former contained pores with a uniform shape and size. Mercury intrusion porosimetry showed that the pore former increased the volume of secondary pores in the catalyst layer. The electrochemical properties of the membrane electrode assembly (MEA) were evaluated by current–voltage polarization measurements, electrochemical impedance spectroscopy and cyclic voltammetry. These results suggest that the catalyst layer with the pore former reduces the mass transfer resistance and improves the cell performance by approximately 50% through modification of its morphology. [ABSTRACT FROM AUTHOR]