Herein is described the preparation and characterization of conductive materials for application in energy storage devices, such as fuel cells. The synthetic approach uses commercially available materials and simple experimental procedures to decorate multi-walled carbon nanotubes (MWCNTs) with plain and thiolated gold nanoparticles (Au NPs). The compositional characterization data (x-ray photoelectron spectroscopy) and the electrical conductivity data (cyclic voltammetry (CV) and oxygen reduction reaction (ORR)) for the MWCNT-Au NP composites, both pre- and post-anneal, is reported.

Ti–47Al–1.0W–0.5Si (at.%) alloy was directionally solidified in the range of growth rate (V) (V = 3–100 μm/s) at a constant temperature gradient (G = 18 K/mm). It was found that α phase was the primary phase of the alloy. Both primary dendritic arm spacing (λ) and interlamellar spacing (λs) decreased with increase of the growth rate (V) according to the relationship of λ ∝ V −0.356 and λs ∝ V −0.49, respectively. The Solidification segregation occurred since the enrichment of the solute element W in primary α phase during solidification. The degree of the segregation increased with the increase of the growth rate (V). The results also revealed that the lamellar orientation was not always perpendicular to the growth direction (GD) because the GD of primary α dendritic deviated from the preferred $\left\langle {0001} \right\rangle$ direction. The microhardness increased with increasing growth rate (V) according to H V ∝ 289.5V 0.12 because of the microstructure refinement.

The effects of boron and zirconium contents from 0 to 0.049 wt% on the casting fluidity, as-cast microstructure and mechanical properties of IN718C superalloy are systematically investigated. The results show that as the B or Zr content increases, the fluidity firstly increases and then decreases. The optimum fluidity is obtained at the pouring temperature of 1470 °C when the content of B is 0.0059 wt% or Zr is 0.042 wt%, respectively. The addition of Zr can lead to the formation of blocky laves phase, but B has no influence on microstructure morphology. Furthermore, the addition of B or Zr can effectively improve the tensile and stress life properties as well as casting fluidity of IN718C superalloy. As compared with IN718C master alloys, the tensile strength can increase 6.2–8.6% and stress life can be improved by 1.3 times when B content is 0.0059 wt%. In addition, when the alloy contains 0.042 wt% Zr, the tensile strength can increase 5.6–7% and stress life can increase 1.076 times than that of the master alloy.

The corrosion resistance behavior of age-treated at 250 °C, 150 °C and solution-treated at 540 °C Al–4.2 wt%Ag alloys were investigated in a 3.5 wt% NaCl solution using cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy measurements. Furthermore, the Vickers microhardness, microstructure, and phase analysis were studied by Vickers microhardness test, scanning electron microscopy (SEM), and x-ray diffraction. The Vickers microhardness test indicated significant increase in the hardness of the aged samples due to precipitation formation in the Al matrix. SEM images of all samples after corrosion tests showed pitting corrosion. Furthermore, it is found that the presence of ageing precipitates (Ag2Al plates) in the age-treated samples created local galvanic cells and can led to the formation of the anodic and cathodic sites. Hence, the corrosion resistance decreased compared to the solution-treated sample without any precipitates. In addition, for more ageing temperature at 250 °C in comparison with 150 °C, was made more anodic and cathodic sites due to more Ag2Al precipitates formation, and decreased resistance to pitting corrosion. Besides, the aluminum and silver oxides were corrosion products. The major phase was aluminum oxide because the Al was the main element of the alloy.

In semiconductor system for solar-energy utilization by photoelectrochemical (PEC) water splitting, the effective absorption of visible light and the efficient separation and transfer of photogenerated charge carriers are still of key importance. In this manuscript, composite photoanodes of PbO sensitized ZnO nanorod arrays were prepared by a two-step hydrothermal process and used as anodes for PEC test under visible-light irradiation. The photocurrent achieved the highest value of 94 μA cm−2 at 0.8 V (versus Ag/AgCl electrode) when the amount of Pb source was optimized to form only a thin layer (a few nanometers) of PbO nanoparticles on the surfaces of ZnO nanorods. Such a nanostructure enabled the visible-light absorption, and also ensured the sufficient contact of PbO with ZnO to form junction with a type II band alignment and the sufficient contact with aqueous solution to form interfaces, thus facilitating the excitation, separation, and transfer of charge carriers to generate photocurrent and finally enhancing the PEC activity.

Hot compression tests on pure Ni and Ni–30Cu at 950–1150 °C and strain rates of 0.001–1 s−1 were performed to identify the physical interpretation of the apparent activation energy (Qd). For pure Ni, Qd was constant and identical to that of the self-diffusion. However, for Ni–30Cu, it decreased steadily with strain. The value of Qd was separated into thermal and mechanical parts. The thermal part was necessary to propel diffusion. For pure Ni, the mechanical part was zero at low and medium strain rates of 0.001–0.1 s−1 and the self-diffusion was the controlling mechanism. However, at 1 s−1, both the thermal and mechanical parts were needed to provide Qd. For Ni–30Cu, Qd was greater than that for the interdiffusion of Ni and Cu. The value of mechanical part decreased with increasing temperature and strain rate. Although the thermal parts for pure Ni and Ni–30Cu were nearly identical, the mechanical part for the latter was considerably higher. The difference was attributed to the strengthening effect of Cu atoms and the sluggish dynamic softening with respect to pure Ni.

Hydrophobic functionalized SBA-15 has been developed via postsynthesis modification with trimethylchlorosilane (TMCS) and used for volatile organic compounds (VOCs) removal. The adsorption and desorption performance of different SBA-15-TMCS under static and dynamic conditions were investigated. Experimental results indicated that all samples showed a highly ordered two dimensional hexagonal mesostructure, and the organic groups were chemically incorporated into the pore surface of SBA-15 substrate. Comparing with commercial silica gel and activated carbon, SBA-15-TMCS shows higher static adsorption capacities of n-hexane and 93# gasoline, good recyclability, lower water vapor adsorption capacity, higher dynamic adsorption capacity, and longer breakthrough time. The high adsorption efficiency and stability of SBA-15-TMCS are associated with their hydrophobic surface, uniform and large pore size, high surface area and pore volume. The designed SBA-15-TMCS with high VOC adsorption capacity and recyclability shows great potential for VOC removal.

Nanocomposites of 2024 aluminum–MoSi2 were prepared using mechanical alloying method followed by cold and hot pressing. Influences of volume fraction and distribution of nanosized MoSi2 reinforcement on mechanical properties of the composites were investigated. Microstructural characterization was carried out by scanning electron microscopy and energy dispersive spectroscopy. Mechanical properties of the nanocomposites were evaluated via hardness, wear, and also room and high temperature compression tests. The results showed that although the distribution of low content of MoSi2 nanoparticles in the matrix is homogeneous, with increasing the reinforcement fraction, the tendency of agglomeration is gradually intensified. The addition of reinforcing particles continuously brings a considerable enhancement in the mechanical properties of the matrix alloy but by exceeding a certain amount of the reinforcement fraction, this improvement reduces mainly because of the microstructure inhomogeneity. In addition, the nanocomposite with 3 vol% MoSi2 exhibits the optimum mechanical properties at ambient temperature.

A series of characterization tests were performed to elucidate the high-cycle fatigue (HCF) behavior in SAE 1050 steel subjected to tensile elastic pre-deformation at different strain rates. In the pre-strained stage, the deformation was maintained constant at 0.16%, which was close to the low yield point at strain rates ranging from 10−5 s−1 to 10−2 s−1. Although pre-deformation occurred entirely in the elastic regime, using different pre-straining rates resulted in the occurrence of heterogeneous microscopic strain at different sites and locations during subsequent fatigue tests. It was found that the effect of pre-straining rate on crack initiation and crack propagation was not monotonous and was influenced by the homogeneity of deformation within grain boundaries, the integrity of the boundary structure, and the fracture toughness. In addition, the rough set theory model was introduced for the attribute reduction of characteristic parameters and provided a scientific basis to establish the fatigue model. The model was able to effectively predict the lifetime of the process of HCF in pre-strained steel. Hence, the pre-straining rate should be an important boundary condition in further studies.

The microstructural evolution during spark plasma sintering of ultrafine WC–1 wt% Si (n-WC–Si) is presented. At 1323 K (T < TmSi), extensive stacking faults on the $\left\{ {10\bar 10} \right\}$ prismatic planes are observed. The defect microstructure can be described as a combined shear of $1/6\left\langle {\bar 12\bar 13} \right\rangle$ on the prism planes and simultaneous out-diffusion of carbon through the faults to the interparticle boundaries. At temperatures near TmSi (1673 K), a large fraction of abnormally grown platelets is observed. These platelets contain a single planar defect on their basal planes, described by a ${1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}\left\langle {10\bar 10} \right\rangle$ translation of the carbon atoms across a Σ1 grain boundary (GB). Three factors contribute to the abnormally high density of platelets: (i) the low-temperature prismatic dislocations interact to form facet-roughening steps/kinks that act as nucleation sites, (ii) a liquid phase triggers an increased growth rate in the vicinity of the Si inclusions, and (c) the basal twin produces a re-entrant edge for 2D nucleation.

Van der Waals (vdW) heterojunctions consisting of vertically-stacked individual or multiple layers of two-dimensional layered semiconductors, especially the transition metal dichalcogenides (TMDs), show novel optoelectronic functionalities due to the sensitivity of their electronic and optical properties to strong quantum confinement and interfacial interactions. Here, monolayers of n-type MoSe2 and p-type Mo1−x W x Se2 are grown by vapor transport methods, then transferred and stamped to form artificial vdW heterostructures with strong interlayer coupling as proven in photoluminescence and low-frequency Raman spectroscopy measurements. Remarkably, the heterojunctions exhibit an unprecedented photoconductivity effect that persists at room temperature for several days. This persistent photoconductivity is shown to be tunable by applying a gate bias that equilibrates the charge distribution. These measurements indicate that such ultrathin vdW heterojunctions can function as rewritable optoelectronic switches or memory elements under time-dependent photo-illumination, an effect which appears promising for new monolayer TMDs-based optoelectronic devices applications.

The microstructural evolution of spray-formed high speed steel during hot deformation was investigated as well as the effects of spray forming parameters on the porosity formation. Four distinct zones are identified in the as-deposited material, and interstitial porosity is present in the bottom and peripheral zones, while gas-related porosity is mainly found in the central zone. It can keep the porosity at a minimum value by using the optimum parameters, e.g., the average porosity of central zone is 3.7% for a superheat of 170 °C and a gas-to-metal flow rate of 0.7. During hot deformation at 1150 °C, the amount of porosity can be obviously decreased by increasing the height reduction which also plays a key role in breaking up eutectic carbides. The critical height reduction for the breakdown of the eutectic carbides is 50%, the dominant mechanism being mechanical fragmentation.

The oxidation behavior of three types of stainless steels, namely AISI 321, AISI 316, and AISI 409, was compared. In all stainless steels, oxide layers were formed and their masses and thicknesses increased with oxidation time. Among them, AISI 409 ferritic stainless steel demonstrated higher oxidation rate. According to the kinetical oxidation behavior of them at elevated temperatures, the oxidation mechanism was determined. Among them, the AISI 409 ferritic stainless steel showed the lowest and AISI 321 austenitic stainless steel demonstrated the highest oxidation resistance. Based on the experimental results, it was suggested that the kinetic of oxide growth in stainless steels was followed by a parabolic relationship. In all cases, a well-known Cr-rich internal oxidation zone (IOZ) was observed. The formation of IOZ was suggested by the Gibbs free energy expression and confirmed by following up the formed oxide layers at different holding times. Furthermore, the formation of thicker oxide layers in ferritic stainless steel was explained by using solid-state diffusion relations and supported by quasi-steady-state approximation of Fick's first law.

The characterization of nanostructured samples with at least one restricted dimension like thin films or nanowires is challenging but important to understand their structure and transport mechanism and to improve current industrial products and production processes. We report on the development of a chip-based platform to simultaneously measure the in-plane electrical and thermal conductivity, the Seebeck coefficient as well as the Hall constant of a thin film in the temperature range from 120 K up to 450 K and in a magnetic field of up to 1 T. Due to the design of the setup, time consuming preparation steps can be omitted and a nearly simultaneous measurement of the sample properties is achieved. Typical errors caused by different sample compositions, varying sample geometries, and different heat profiles are avoided with the presented measurement method. As a showcase study displaying the validity and accuracy of our system, we present measurements of the thermoelectric properties of a 110 nm Bi87Sb13 thin film in the temperature range from 120 K up to 450 K.

Hot deformation and dynamic recrystallization (DRX) behavior of the Cu–Cr–Zr–Ag alloy were studied by hot compressive tests in the 650–950 °C temperature and 0.001–10 s−1 strain rate ranges using Gleeble-1500D thermomechanical simulator. The activation energy of deformation was determined as Q = 343.23 kJ/mol by the regression analysis. The critical conditions, including the critical strain and stress, for the occurrence of DRX were determined based on the alloy strain hardening rate. The critical strain related to the onset of DRX decreases with temperature. The ratios of the critical to peak stress and critical to peak strain were also identified as 0.91 and 0.49, respectively. The evolution of DRX microstructure strongly depends on the deformation conditions in terms of temperature and strain rate. Dislocation generation and multiplication are the main hot deformation mechanisms for the alloy. The addition of Ag can refine the grain and effectively improve the DRX of the Cu–Cr–Zr alloy. It can also inhibit the growth of the DRX grains at 950 °C deformation temperature, making the microstructure much more stable.

Highly oriented Ni–Mn–Ga thin film with multiple variants and room temperature orthorhombic martensite structure were prepared on a single crystalline Al2O3$\left( {11\bar 20} \right)$ substrate by DC magnetron sputtering. X-ray diffraction and rocking curve measurements reveal the film as (202)7M oriented with an excellent crystal quality (Δω = 1.8°). Spot-like pole figures indicate that the Ni–Mn–Ga film grows with a strong in-plane preferred orientation. An in-depth analysis of the measured pole figure reveals the presence of a retained austenite phase in the film. Two phase transformations, MS ∼345 K and TC ∼385 K, are observed and are attributed to first order structural transformation from cubic to orthorhombic, and second order phase transformation from ferromagnetic to paramagnetic, respectively. In situ high temperature x-ray diffraction measurements provide a clear indication of a thermally-induced martensite ↔ austenite reversible structural phase transformation in the film. The presence of martensite plates with seven modulated orthorhombic structure and adaptive nano-twins are some of the important microscopic features observed in the film with transmission electron microscopy investigations.

Electroreduction of solid V2O3 pellets (∼0.7 g) to V in molten CaCl2 at 900 °C has been studied by cyclic voltammetry and potentiostatic electrolysis, together with scanning electron microscopy, energy dispersive x-ray, and elemental analyses. The intermediate products of the potentiostatic electrolysis are various, forming some lower valence state compounds (VO, V16O3, V7O3, VO0.2) and higher valence state which are likely VO2, CaVO3, or CaV2O5. At potentials more negative than −0.6 V versus Ag/AgCl, fine vanadium powder (aggregates of nodular ∼500 nm particles) can be prepared by electrolysis of porous solid of the V2O3 pellets. The current efficiency and energy consumption were satisfactory, about 53.4% and 2.5 kW h/(kg V) at −0.6 V versus Ag/AgCl, respectively. Moreover, V–20Ti alloys were electrochemically synthesized by constant voltage electrolysis at the indicated potentials, the control of composition as well as the reduction optimization of the mixtures were demonstrated. This electrochemical route is efficient and offers a product with controlled stoichiometry, with particular advantage of manufacturing of low cost alloys and intermetallics directly from mixed oxide precursors, and has potential to produce functional vanadium alloys.

Al–Sn binary alloys are fabricated by powder consolidation using high-pressure torsion (HPT). The HPT-processed samples are immersed in pure water and hydrogen generation behavior is investigated with respect to the imposed strain through the HPT processing at a selected temperature in the range of 297–333 K. Microstructures of HPT-processed alloys are analyzed by x-ray diffraction, transmission electron microscopy (TEM), electron probe microanalysis (EPMA) and electron back scattered diffraction (EBSD) analysis. Results show that it is important to add more than 60 wt% of Sn to activate hydrogen generation from the Al–Sn alloys in pure water. TEM and EBSD images reveal significant grain refinement while EPMA results exhibit homogenous distribution of elements achieved by HPT. The grain refinement and distribution of elements attained by HPT processing influence greatly the hydrogen generation rate and yield of the alloys. An Al–80 wt% Sn alloy with an average grain size of ∼270 nm exhibits the highest hydrogen yield and generation rate in pure water at 333 K.

The influence of hydrostatic compression on the charge transport properties of an excellent 2,6-diphenylanthracene (2,6-DPA) semiconducting single crystal was investigated up to 10 GPa by performing density-functional calculations together with the tight binding approximation. In this pressure region the lattice constants a, b and c decrease by up to 0.948 Å (5.23%), 1.30 Å (17.26%), and 0.711 Å (11.34%), respectively, while the monoclinic angle β increases by 3.4°. The unit-cell volume decreases by increasing pressure, and the volume decreases by 30.5% at 10 GPa. In comparison, the C–C and C–H intermolecular distances within and between the herringbone layers reduced by 16–19% and 16–24%, respectively, in the same pressure ranges. The results indicate that under high pressure, the molecular planes of the crystal become more and more parallel to each other due to molecular rearrangement in the 2,6-DPA crystal. The band gap decreases with increasing pressure due to decreasing intermolecular separation between neighboring molecules. Finally, the results indicate an improvement of the hole mobility of 2,6-DPA single crystals under hydrostatic pressure.

Magnesium based nanocomposites containing 0.66 vol% of different types of oxide (i.e., Al2O3, Y2O3, and ZrO2) nano particles. The nano oxide particles were dispersed using melt processing. Microstructural characterization reveled that Y2O3 and ZrO2 nano particles were relatively better magnesium matrix grain refiner compared to nano-size Al2O3 particles. Mechanical characterization revealed that the oxides used in this study as reinforcement have strong strengthening effect on the magnesium matrix, where Y2O3 particles were most effective and Al2O3 particles were least effective. Ductility and resistance to fracture of magnesium was significantly improved by Al2O3 nano particles, unaffected by Y2O3 nano particles, and adversely affected by ZrO2 nano particles.