Cu and Cu–Al alloys with different stacking fault energies (SFEs) were processed using rolling and the Split Hopkinson pressure bar followed by rolling. The effect of strain rate on the microstructures and mechanical properties of the alloys were investigated using x-ray diffraction analyses, transmission electron microscopy, and tensile tests. Tensile testing results demonstrated that the strength and ductility of the samples increased simultaneously with decreasing SFE. Microstructural observations indicated that the average grain size of the samples decreased with decreasing SFE, but the twin and dislocation densities increased. With decreasing SFE, twinning becomes the dominant deformation mechanism. Our findings indicated that the SFEs significantly affect the strength and ductility of the materials because they play a key role in determining the deformation mechanism. Decreasing the SFE of Cu alloys has proved to be the optimum method to improve the ductility without compromising the strength of the material.

An in situ redox reaction was developed to synthesize bundled tungsten oxide (WO3@W18O49) ultrafine nanowires (BUNs) loaded with Ag nanoparticles using weakly reductive W18O49 and oxidative silver nitrate as precursor. However, due to the weak activation between the two reactants, redox just happened on the surface of W18O49, resulting in the formation of W18O49 coated with WO3 (here, we refer this structure to WOx simply), and the bulk phase of the composites retained the same pattern. Ag nanoparticles (<5 nm) with a narrow size distribution were obtained and immobilized onto WOx BUNs without any aggregation. The paper presented a systematic investigation on the Ag-WOx nanocomposite used as a catalyst for the reduction of p-nitrophenol and as an antibacterial agent against Escherichia coli. The remarkably enhanced performance may be ascribed to the moderate interaction of the small Ag-NPs and WOx BUNs with high specific surface area.

Heusler Ni–Mn–(Ga, In, Sn, Sb) materials can provide large magnetic-field-induced strain, giant magnetocaloric and magnetoresistance effects based on their first-order solid-state martensitic transformation. In the present work, effects of Co doping on martensitic transformation behavior in melt-spun Ni–Mn–Sn ribbons were studied by x-ray diffraction, scanning/transmission electron microscopy, and thermal analysis. Experimental results showed that both martensitic transition and austenite Curie temperatures increased linearly with Co addition to Ni49Mn39Sn12; and meanwhile, crystal structures of the martensite evolved from four-layered orthorhombic (4O) to five-layered orthorhombic (10M), and then seven-layered monoclinic (14M). The compositional dependence of the martensitic transition temperatures was well correlated with changes of valence electron concentration (e/a) and unit-cell volume of high-temperature austenite. It was proposed that both increase of valence electron concentration and shrinkage of austenite unit-cell volume with Co addition are favorable to the occurrence of martensitic transformation. In addition, the Curie temperature of austenite increases with Co addition, which was ascribed to the enhancement of ferromagnetic exchange interaction.

Understanding solvent transport in polymers is of practical importance for the applications of polymers in the fields of food packaging, biomedical bandages, materials engineering, etc. We studied one-side desorption in poly(methyl methacrylate) (PMMA). Experimental results showed that methanol desorption in PMMA depended on temperature and the initial distribution of concentration. The diffusion coefficient in PMMA and the evaporation rate of methanol across the PMMA surface followed the Arrhenius relation. The activation energies for the diffusion and the evaporation of methanol are 18.3, 42.6 and 8.6, 18.3 kJ/mol for the specimens with the ratio of initial mass to the equilibrium saturated absorbed mass, Mi/M∞, being 14.6% and 35.3%, respectively. The partial molal volume increased with the increase of the desorption temperature for Mi/M∞ = 14.6%, while it had an opposite trend for Mi/M∞ = 35.5%. The chemical stresses developed in PMMA during the desorption were also studied.

This paper discusses tensile testing of small samples of nanocrystalline Al6061-T6 alloy obtained from an unusual application of machining as a severe plastic deformation process. Ultrafine grained (UFG) shavings obtained from plane-strain cutting show higher hardness than the bulk material in agreement with existing literature. Application of restricted contact tools and extrusion-machining was explored to obtain shavings with minimum curvature to aid in tensile test specimen preparation. A novel method to prepare small tensile test specimens from these shavings has been described. During the tensile testing of UFG material, strains were measured using digital image correlation of natural speckles on the specimen. Specimens made from the UFG material had higher tensile strength and yield stress than the bulk, while ductility was lower. Lower values of Young's modulus were observed during the tensile testing of small specimens made from UFG as well as bulk material.

Besides graphene and hexagonal boron nitride, transition metal dichalcogenides (TMDs) also exhibit a layered structure in which the layers weakly interact via van der Waals forces. Semiconducting TMDs in bulk are indirect band gap materials. However, an isolated sheet exhibits a direct gap. This particular behavior makes them very attractive in terms of optical properties. Moreover, NbS2 and NbSe2 in bulk and their monolayers are metallic. Density functional theory calculations were carried out to study different TMD bilayer systems. First, different bilayer geometries with different stackings were considered. It was found that the indirect and direct band gaps compete; however, the indirect band gap always dominates. Surprisingly, bilayer heterostructures of different TMDs have been found to possess direct band gaps. Finally, heterobilayers composed of one metallic monolayer and a semiconducting layer are predicted as novel metallic van der Waals solids that might find applications in new two-dimensional nanodevices.

The effects of film thickness and surface orientation on melting behaviors of copper nanofilms were investigated by molecular dynamics simulations. A stepwise heating scheme was adopted to make sure that the nanofilms reached thermal equilibrium before further temperature increase. Melting of the nanofilms was monitored by examining the equilibrium potential energy, radial distribution function, and mean square displacement of the simulated nanofilms. From the simulation, the melting was observed to occur at a specific temperature within 1 K error, unlike the progressive melting process reported in the literature. The melted temperature and the latent heat of fusion of the nanofilms were found to increase with film thickness and approach the bulk value. The nanofilms with (111) surface have the highest melted temperature and the largest latent heat of fusion as compared to the ones with (001) and (011) surfaces, which could be explained by the lowest surface energy of (111) surface.

In this study, a simple, facile, green, and versatile strategy was developed for the synthesis of water-soluble and well-dispersed fluorescent gold nanoclusters (Au NCs) with wave length-tunable emissions using protein as capping agent and template. The resultant Au NCs exhibited excellent characteristics such as large Stokes shift, good stability, and high resistance to photobleaching. They showed strong emission at 680 nm, with a quantum yield of 4.5%. Heavy metal ion (Hg2+) could quench the fluorescence of Au NCs efficiently and thus the as-prepared Au NCs were successfully developed as “turn-off” fluorescent probes for the detection of Hg2+ sensitively and selectively. The lowest concentration to quantify mercuric ions could be as low as 1 nM and the fluorescence intensity of the Au NCs was proportional to the concentrations of Hg2+ over the range 8 × 10−8 M to 1 × 10−5 M (R = 0.9982). To validate the practicality of this probe, real water samples spiked with Hg2+ were determined with RSD values less than 3%. And the results demonstrated that the developed probes worked well in environmental samples. The action mechanism between the Au NCs and Hg2+ was explored as well.

In this paper, we report the structural, electrical, and magnetic properties of polycrystalline La0.85–xSmxNa0.15MnO3 (x = 0.05, 0.1, 0.15) manganites. Rietveld refinement of x-ray data infers that doped manganite compounds possess a rhombohedrally distorted structure (space group $R\bar 3C$). Both lattice parameter and unit cell volume decrease and a systematic change in both Mn–O–Mn bond angle and tolerance factor is observed with Sm content. Resistivity measurements discern metal–insulator transition (TP). For x = 0.15 sample, a double metal–insulator transition with a single ferromagnetic transition is depicted. All samples exhibit extrinsic magnetoresistance (MR) effect. A large value of MR of 65% (253 K, 8 T) is associated with grain and grain boundary formation. The highest low-field MR of 23% (12 K, 2 T) and 35.2% (23 K, 2 T) for x = 0.05 and 0.1 is observed. The electronic and magnetic inhomogeneities induced by Sm and nonmagnetic metal Na phases account for MR properties.

Three-dimensional (3D) morphological evolution and growth mechanisms of primary I-phase particles have been investigated in directionally solidified Al–6Mn–2.5Be (wt%) alloy at a wide range of growth rates (100–1500 μm/s). At relatively low growth rates (100–600 μm/s), the I-phase particles exhibit faceted growth with strong anisotropy, forming a hierarchical flower-like aggregate with icosahedral morphological symmetry composed of several attached irregular polyhedrons or pentagonal dodecahedrons. At higher growth rates (e.g., 1000 μm/s), the interface of the I-phases becomes unstable along the edges and corners of the pentagonal dodecahedron, thereby arousing growth perturbations. Correspondingly, a transition from faceted to nonfaceted growth occurs with increasing growth rate. Further increase of the growth rate leads to the formation of I-phase columnar dendrites' preferential growth along the 3-fold axis. The configurations of the flower-like aggregates can be adequately illustrated by a geometrical model in terms of the perfect and elongated pentagonal dodecahedrons. A growth mechanism for the flower-like aggregates has been proposed based on the clear understanding of the 3D morphological evolution of the I-phase particles.

We report on the occurrence of sinter-hardening with concurrent improved plasticity in fine-grained Fe79.3Mo4.5P8.1C6.75B1.35 bulk alloys fabricated by spark plasma sintering (SPS) of metallic glass composite powder. When the sintering temperature is higher than the austenite transformation temperature, the as-fabricated bulk alloys are composed of expected wattle martensite plus Fe3P, Fe7C3, and Fe3Mo3C. Meanwhile, the martensite-containing bulk alloys exhibit increased hardness, fracture strength as well as concurrent improved plasticity. The fracture stress and strain of the martensite-containing bulk alloys are as high as 2573 MPa and 8.6%, respectively. The formation of the martensite microstructure is attributed to that high sintering temperature leads to the austenitization transformation and consequently formed austenite partially transforms into martensite under rapid cooling rate provided by SPS system. The results obtained provide insight into fabrication of iron alloys with good mechanical property by powder metallurgy.

A novel series of binuclear transition metal phthalocyanines M2Pc2HnC (M = Mn(II), Fe(II), Co(II), Ni(II), and Cu(II)) were developed for highly efficient electrocatalysts to lithium/thionyl chloride (Li/SOCl2) battery. The capacity of the battery can increase approximately by 40–65% when the binuclear compounds are present in the electrolyte of the battery. To investigate the effect of the binuclear metal phthalocyanines on Li/SOCl2 battery further, this work studied the electrocatalytic reaction of the binuclear compounds to the battery by electrochemical methods (cyclic voltammetry) and other characterization means. The results demonstrate that the order of the electrocatalytic activity of the binuclear compounds with diverse center metal ions is: Fe(II) > Co(II) > Mn(II) > Ni(II) > Cu(II).

Conjugated polymer films are of considerable current interest for functionalizing the surfaces of a wide variety of devices including implantable biomedical electronics. Toward these ends, copolymer films of 3,4-ethylenedioxythiophene (EDOT) with a carboxylic acid functional EDOT (EDOTacid) were electrochemically deposited and characterized as a systematic function of the EDOTacid content (0, 25, 50, 75, and 100%). Chemical surface characterization of the films confirmed the presence of both EDOT and EDOTacid units. Toluidene blue assays showed that the surface concentration of the carboxylic acid groups increased to a maximum of 2.75 nmoles/mm2, and the contact angle measurements confirmed the increased hydrophilicity of the films with increasing EDOTacid content (decreasing from 52.6 to 32.5 degrees). Cyclic voltammetry showed that the films had comparable charge storage capacities regardless of their composition. The morphology of the films varied depending on the monomer feed ratio. The addition of EDOTacid induced a transition from a nodular, porous surface to a more dense, pleated surface structure. These methods provide a facile means for synthesizing electrically active carboxylic acid functional poly(3,4-ethylenedioxythiophene) copolymer films with tunable hydrophilicity and surface morphologies.

The effects of magnetic field on the austenite formation and grain size were studied by applying high magnetic field during the different stages. Optical microscopy and scanning electron microscopy were used to characterize the microstructure evolution for the samples treated without and with magnetic field. Magnetic field dramatically retards the austenite formation kinetics including pearlite to austenite transformation and cementite dissolution. The austenite grain size is enlarged by the magnetic field applied during austenite formation and not affected by the magnetic field applied only during austenite grain coarsening. The austenite treated with magnetic field during the whole austenitization process also has a larger grain size. The changes in austenite formation kinetics and grain size are related to lower nucleation rate of austenite caused by magnetic field.

Material extrusion 3D printing (ME3DP) based on fused deposition modeling (FDM) technology is currently the most commonly used additive manufacturing method. However, ME3DP suffers from a limitation of compatible materials and typically relies upon amorphous thermoplastics, such as acrylonitrile butadiene styrene (ABS). The work presented here demonstrates the development and implementation of binary and ternary polymeric blends for ME3DP. Multiple blends of acrylonitrile butadiene styrene (ABS), styrene ethylene butadiene styrene (SEBS), and ultrahigh molecular weight polyethylene (UHMWPE) were created through a twin screw compounding process to produce novel polymer blends compatible with ME3DP platforms. Mechanical testing and fractography were used to characterize the different physical properties of these new blends. Though the new blends possessed different physical properties, compatibility with ME3DP platforms was maintained. Also, a decrease in surface roughness of a standard test piece was observed for some blends as compared with ABS.

A new physical model of plastic deformation in nanocrystalline (NC) materials with finest grains (whose grain size is 2–4 nm) is suggested and theoretically described. The model represents the effect of the finest grains located at triple junctions on the fracture toughness of NC materials in the case that there are multiple dislocations pile-up at grain boundaries (GBs). The maximum number n of the pile-up dislocations is determined by both the capacity of dislocations emitting associated with the crack propagation and the capacity of dislocations pile-up due to the existence of the finest grains. The calculation indicates that the parameter n increases with increment of the grain size and decreases with the finest grain size increasing. The results theoretically reveal that the triple junctions with finest grains can significantly improve the fracture toughness of NC materials compared with the normal triple junctions in wide ranges of their structural parameters.

Modified MMT clay-doped PMMA composites have been prepared by solvent casting method for different weight percentages. The prepared composite films were characterized by FTIR and SEM. Also, the DC conductivity was carried out for PMMA and PMMA composite films. Among all composites, it was found that 30 wt% shows highest conductivity of 1.59 × 10−3 S/cm. The negative thermal coefficient behavior of these polymer composite films confirms that the increase in conductivity is due to the elongation of polymer chain which helps in charge transport mechanism. Dielectric study also shows that 30 wt% has the lowest dielectric constant and dielectric loss of 2.5 and 3.3, respectively, resulting in an increase in conductivity of 5 × 10−3 S/cm. The isotropic nature of 30 wt% composite film shows a high quality factor of 0.005 because of overdamping of electron at 104 Hz. Cole–cole plots show that the semi arc originated from a single point and its area decreases with filler concentration up to 30 wt% due to drop in the electrical resistance. Tensile modulus increases because of high MMT aspect ratio and distribution ratio. The 30 wt% of the composite shows high tensile strength at 55 MPa which induces 8% of strain in the PMMA–MMT clay composite films. Therefore, these composite films can be used in many sensor and solar technologies as encapsulation materials.

When properly designed at ultra-low density, hollow metallic microlattices can fully recover from compressive strains in excess of 50%, while dissipating a considerable portion of the elastic strain energy. This article investigates the physical mechanisms responsible for energy loss upon compressive cycling, and attributes the most significant contribution to a unique form of structural damping, whereby elastic local buckling of individual bars releases energy upon loading. Subsequently, a simple mechanical model is presented to capture the relationship between lattice geometry and structural damping. The model is used to optimize the microlattice geometry for maximum damping performance. The conclusions show that hollow metallic microlattices exhibit exceptionally large values of the damping figure of merit, (Young's modulus)1/3(loss coefficient)/(density), but this performance requires very low relative densities (<1%), thus limiting the amount of energy that can be dissipated.

Various heat treatments and thermal simulation with different austenitizing temperatures and austenite deformation were applied on a bearing steel to obtain various austenitic state. The effect of austenitic state on microstructure of martensite/bainite (M/B) dual phase steel and its mechanical property has been investigated via microstructure observation and kinetic analysis. The results show that the M/B steels austenitized at 900 and 950 °C have better comprehensive performance compared with the steels austenitized at 850 and 1050 °C. The refined microstructure can be obtained after deformation, and the heavy deformation and low deformation temperature are useful for refining the microstructure. The bainite lath is longer and has well-directional arrangement at high austenitizing temperature with the same deformation. Furthermore, austenite deformation can improve the nucleation ratio, reduce incubation process, and affect the kinetics of bainite transformation significantly.

Doping of a heteroatom such as nitrogen in carbon nanomaterials provides a means to tailor their electronic properties and chemical reactivities. In this article, we present simple methods to synthesize carbon quantum dots (CQDs) with high nitrogen doping content (18–22%), involving the reaction of glucose in the presence of urea under hydrothermal conditions or by microwave irradiation. The N-doped carbon quantum dots (N-CQDs) show high aqueous solubility and tunable photoluminescence (PL). Interaction of N-CQDs with exfoliated graphene or dimethylaniline quenches PL. Interaction of N-doped as well as undoped C-dots with electron-donating tetrathiafulvalene and electron-withdrawing tetracyanoethylene has been examined. The intense blue PL of CQDs has been exploited to produce white light by mixing the CQDs with yellow light emitting ZnO nanoparticles or graphene oxide. The N-doped CQDs exhibit superior photocatalytic activity compared to pristine CQDs.