To investigate the effects of cold rolling on the microstructure, the precipitation behavior and the morphology of δ-phase, Inconel 718 alloy samples with different cold rolling reductions were aged for different periods at temperatures range from 850 °C to 1000 °C. Detailed microstructural observations and quantitative measurements were conducted to characterize the evolution of the δ-phase during aging. The results show that the microstructure consists of large deformed grains as a result of a slow static recovery at the low aging temperatures (850 and 900 °C); whereas the austenite matrix is fully recrystallized at the high aging temperatures (950 and 1000 °C). It is also found that the amount of δ-phase and the number density of spherical δ-phase particles increase with the increase in the degree of cold rolling both at low and high aging temperatures. With respect to different microstructural changes for the cold-rolled samples at the low or the high aging temperatures, two distinct mechanisms have been, respectively, introduced to interpret the changes in the precipitation behavior and the appearance of δ-phase.

Hematite (α-Fe2O3) photoanodes are widely studied as candidates for water splitting photoelectrochemical (PEC) cells. To speed up the development of high efficiency hematite photoanodes, systematic investigations of the effect of material properties such as dopants and microstructure on PEC properties that determine the photoanode performance are crucial. Toward this end, this work presents a route for reproducible fabrication of thin film hematite photoanodes with reproducible microstructure and PEC properties. Hematite thin (50 nm) films are deposited by pulsed laser deposition from a Ti-doped (1 cation%) Fe2O3 target onto cleaned transparent conducting substrates (fluorinated tin oxide, FTO, coated glass substrates). Special attention is paid to rigorous cleaning of the substrates prior to the hematite deposition, which is found to be crucial for achieving highly reproducible results. Specimens prepared by this route display homogenous conformal coating with very little spread in PEC properties between different specimens, meeting the necessary prerequisite for systematic investigation of hematite photoanodes.

2D materials play a special role in the race to make smaller and smaller devices. Their unique and strong in-plane bonding makes them impervious to diffusion into other layers and provides excellent thickness control. Their van der Waal's bonding with other monolayers or substrates allows for heterostructures unattainable by any other technique. This is reflected by the abundant popularity of research into graphene and other 2D materials. In this review article, we will describe the out-of-plane properties of graphene and functionalized graphene. We will use three specific examples to illustrate how these out-of-plane properties can be used in spintronic devices, in section “Graphene as a Tunnel Barrier” we will describe a magnetic tunnel junction (MTJ) based on graphene. Section “Graphene Based MTJs” will describe the spin injecting properties of a graphene tunnel barrier on silicon. Section “Graphene in Semiconductor Spintronic Devices” describes how you can use functionalized graphene to make a homoepitaxial graphene device. The second part of this article reviews monolayer transition-metal dichalcogenides (TMDs). First, we will show how TMDs are grown and specifically how we can grow large-area TMDs by chemical vapor deposition. Secondly, we will describe the optical properties of several TMDs and compare the results from several authors. Finally, we choose a chemical sensor as a specific example to show how TMDs can be used in a device.

A magnesium–lithium (Mg–Li) hybrid battery consists of an Mg metal anode, a Li+ intercalation cathode, and a dual-salt electrolyte with both Mg2+ and Li+ ions. The demonstration of this technology has appeared in literature for few years and great advances have been achieved in terms of electrolytes, various Li cathodes, and cell architectures. Despite excellent battery performances including long cycle life, fast charge/discharge rate, and high Coulombic efficiency, the overall research of Mg–Li hybrid battery technology is still in its early stage, and also raised some debates on its practical applications. In this regard, we focus on a comprehensive overview of Mg–Li hybrid battery technologies developed in recent years. Detailed discussion of Mg–Li hybrid operating mechanism based on experimental results from literature helps to identify the current status and technical challenges for further improving the performance of Mg–Li hybrid batteries. Finally, a perspective for Mg–Li hybrid battery technologies is presented to address strategic approaches for existing technical barriers that need to be overcome in future research direction.

(1 − x) (Bi1/2Na1/2)TiO3–xBiFeO3 (x = 0–0.9) ceramics were prepared and the ferroelectric and piezoelectric properties along with the crystal structure were investigated. The crystal system of the ceramics was rhombohedral with the R3c symmetry throughout the compositions. The rhombohedral distortion (90° − α), where α was the rhombohedral angle based on a pseudocubic perovskite cell, was minimized at x = 0.1, while the lattice constant increased linearly with x. Saturated ferroelectric polarization-electric field hysteresis loops were observed at x = 0–0.6. The coercive field was reduced at x = 0.05–0.2 and the high remanent polarization of 30–35 µC/cm2 was obtained at x = 0–0.4. The piezoelectric constants d33 and d33* (which was calculated from a unipolar strain–electric field curve) were maximized to 93 pC/N at x = 0.1 and 183 pm/V at x = 0.05, respectively. These results suggested that the increase in the piezoelectric properties was associated with the reduction in the rhombohedral distortion, which could be useful in development of high performance lead-free piezoelectric materials.

Indentation method has been widely used in the measurement of material mechanical properties and residual stress for its simple, fast and nondestructive characteristics. In the indentation test, because of the plastic deformation of the material, the material accumulation and subsidence occurs around the indentation. It is found that the deformation amount of the indentation, especially the maximum pile-up around the indentation after unloading, is related to the magnitude and direction of the residual stress. In this paper, an experimental study on the pile-up morphology around an indentation for determining the direction and magnitude of residual stress is reported. Nonsymmetrical morphology of spherical indenting deformation on artificially strained steel specimen was measured with a laser scanning confocal system. A unique relationship between pile-up after unloading and biaxial residual stress was set up based on the experimental results. The direction and components of nonequibiaxial residual stress can be determined by the proposed method.

In this study, the MnOx–FeOy hollow nanospheres with solid solution structure were prepared by supercritical antisolvent (SAS) process. The average particle size was about 50 nm, and average pore diameter was 7 nm. By applying the SAS method, novel nonsupported MnOx–FeOy catalysts with a Mn/Fe mass ratio of 1:1 showed rather high selective catalytic reduction activity and broad active temperature window. The NOx conversion rate reached 97% at 220 °C, and maintained above 92% from 180 to 260 °C. The experiment results showed that iron doping could cause the apparent change of MnOx morphology and structure, which enhanced the oxidative ability of manganese species and increased surface active oxygen species. Meanwhile, compared with traditional methods, the SAS process could efficiently enhance the interaction between manganese and iron, and produce smaller size and larger pore volume nanoparticles with more active sites on the surface.

Density modulated tungsten (W) thin films with nanoscale porosity contents of 7% to 40% by volume were grown on Si substrates through magnetron sputter deposition. Process parameters were selected according to the structure zone model, which resulted in film thicknesses between 105 nm and 520 nm. Nanomechanical properties of samples were investigated by means of instrumented nanoindentation. Reduced-χ2 analysis was carried out to assess four models formulated through differential effective medium approach. The model that factored in both the crowding effect and the maximum random packing of pores successfully captured the experimental trends. Attempts to breach the auxetic barrier resulted in large-scale pulverization or spontaneous conversion into WO3. Porosity corrected yield strength calculations underlined the possibility of defining a porosity threshold beyond which the compressive yield strength of density modulated nanoporous metallic thin films would drop abruptly due to aggravated geometric slenderness effects in agreement with earlier hypotheses.

The charge transport properties of anthra-tetrathiophene (ATT) and its brominated and cyanated derivatives (TBATT and TCATT) were investigated by the density functional theory (DFT) coupled with incoherent charge-hopping model. The crystal structure of TCATT is predicted by the dispersion-corrected DFT (DFT-D) method, and those of ATT and TBATT are retrieved from the Cambridge Crystallographic Data Center. The introduction of electron-withdrawing substituents of bromine and cyano decreases the frontier molecular orbital energies but increases the electron affinities, which is beneficial to electron injection and guarantees charge carrier stabilization. The π–π stacking of neighbor molecules with a short distance and large coupling area contributes to the largest transfer integral. The predicted electron mobility of TCATT reaches up to 1.851 cm2/(V·s), indicating that the cyanation of ATT is favorable for improving the electron transport. The angular dependent simulation for electron mobility shows that the electron transport is remarkably anisotropic.

In this study, a system of triple liquid phases was developed using Li2CO3, Na2CO3, and K2CO3 to improve the densification of the akermanite scaffolds fabricated by selective laser sintering (SLS). The system formed a ternary liquid phase (Li2CO3–Na2CO3–K2CO3) at 399 °C, a binary liquid phase (Na2CO3–K2CO3) at 695 °C, and a unitary liquid phase (K2CO3) at 891 °C during sintering process. The effects of the liquid phases on the sinterability and mechanical properties of the scaffolds were investigated. The fracture toughness and compressive strength is increased by 43 and 152% with liquid phases increasing from 0 to 4 wt%, respectively. This was explained that liquid phases enhanced densification via improving diffusion kinetics and inducing particle rearrangement. In addition, the scaffolds maintained favorable hydroxyapatite (HA) formation ability and cell proliferation ability, which was proved by simulated body fluid (SBF) test and microculture tetrazolium test (MTT), respectively.

MnOx –CeO2/t-ZrO2 catalyst was prepared by impregnation of nanotetragonal zirconia. The NO conversion of 5 wt% MnOx –CeO2/t-ZrO2 catalyst was 68.1% at 100 °C while that of 30 wt% MnOx –CeO2/t-ZrO2 catalyst was 97.4%. The x-ray diffraction, Brunner–Emmet–Teller measurements (BET), and H2-TPR showed surface properties of the prepared catalysts were good for selective catalytic reduction reactions. X-ray photoelectron spectroscopy analysis indicated that Mn4+ and Ce4+ oxidation states were predominant on the surface of the catalyst and so was lattice oxygen which was conducive to Lewis acid sites. NH3-TPD test results demonstrated that Lewis acid sites are predominant on the surface of catalyst. The presence of SO2 reduced the catalyst activity. The realized conversion dramatically decreased to 47% from nearly 100% after 8 h. Characterization of fresh and spent catalysts indicated the deterioration of active component and deposition of NH4HSO4 or (NH4)2SO4 contribute to SO2 poisoning.

Thermoluminescence (TL) and radioluminescence (RL) spectra of the long-lasting phosphorescence of SrA12O4:Eu2+,Dy3+ with A1N addition and commercially used SrA12O4:Eu2+,Dy3+ were compared. Their spectra were slowly recorded over the temperature range from 25 to 673 K (400 °C). A1N offers a higher temperature TL peak, which should lengthen the phosphor lifetime. However, both TL and RL, especially that below room temperature, reveal that there are additional decay paths for the samples of SrA12O4:Eu2+,Dy3+ with A1N additions. These new defect sites reduce the phosphor efficiency. Some speculative models of potential sites are proposed and discussed. In addition, discontinuous intensity changes have been observed for both sample types in TL and RL spectra, which are assigned to the transitions of embedded impurity phases. The justification for this model is explained. Suggestions for future experimentation are also considered.

The slip systems in ZrB2 flexural tested at 1000 °C and 1500 °C have been quantified. The dislocations in both samples were long and straight with a dislocation density of approximately 1013 m−2. The structure of the dislocations as well as the low density is in agreement with a ceramic that is hard and brittle and dislocation nucleation and motion is restricted. The low temperature slip systems were found to include c-prismatic slip— ${1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}\left[ {0001} \right]\left( {\bar 1010} \right)$ —and a-pyramidal slip— ${1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}\left[ {11\bar 20} \right]\left( {\bar 1101} \right)$ whereas the elevated temperature sample revealed a-basal slip— ${1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}\left[ {11\bar 20} \right]\left( {0001} \right)$ . Density functional theory Generalized Stacking Fault Energy curves for perfect slip were calculated and agreed well with geometric considerations for slip, including interplanar spacing and planar packing. Though basal slip has the lowest fault energy, the presence of the other dislocation types is suggestive that the activation barrier is not a hindrance for the temperatures studied and is likely activated to increase the number of plastic degrees of freedom.

Graphene nanoribbons as a quasi-one-dimensional form of graphene has attracted intensive attention in energy related devices. Upon oxidation and cutting of multiwall carbon nanotubes (MWCNTs), highly dispersive graphene oxide nanoribbons (GONRs) were obtained, on which Zn2+ and Sn4+ can be homogenously deposited. The reduced graphene oxide nanoribbons (rGONRs)/Zn2SnO4 composite with a homogeneous distribution of nanoparticles on the nanoribbons have been prepared through facile in situ chemical co-reduction process. It is worth noting that the size of Zn2SnO4 particles tightly dispersed on rGONRs is about 15 nm. Benefit from the introduction of rGONRs, the specific surface area and electrode conductivity of rGONRs/Zn2SnO4 can both be effectively enhanced. The as-prepared rGONRs/Zn2SnO4 as anode material for lithium-ion batteries displays desirable electrochemical performance (727.2 mA h/g after 50 cycles at the current density of 100 mA/g), which is mainly attributed to the uniformly distributed Zn2SnO4 nanoparticles and the immobilizing and conducting effects of rGONRs.

The ground state properties of γ-Fe4X (X = B, C, N, and O) were studied by means of the density functional theory. The calculations were performed using the linearized augmented plane wave method as implemented in the Wien2k code. From the equilibrium cohesive energy point of view, all the compounds are ferromagnetic and the stability increases in the following sequence: γ-Fe4O, γ-Fe4N, γ-Fe4B, γ-Fe4C. The electron density suggests that the chemical bonding in γ-Fe4X (X = B, C, N, and O) is a mixture of covalent and ionic character that vary in intensity with the X atom. The magnetic moments and hyperfine interactions are clearly and differently affected by the nature of the X atom. The results indicated that there is not a linear relation between the 2p electron number of the X atom and the magnetic properties of the compounds.

The Al–50Si alloy, as a kind of potential electronic packaging material, is manufactured by different methods, such as casting and spray deposition. The possible influences of the P refiner on the microstructure of the Al–50Si alloy are investigated at different cooling rates. The refinement mechanism of primary Si phase is discussed in view of the P refiner addition, and the variation of the cooling rates. The thermal conductivity (TC), as a key parameter for electronic materials, is measured. The coupled effects of the cooling rate and the addition of the P refiner during the solidification of the Al–50Si alloy on the TC are elucidated based on structural observations. Furthermore, the porosity in the Al–50Si alloy is treated as a second phase influencing the TC.

The effects of annealing temperatures on the structure and photocurrent response of nanoporous iron oxide film prepared by anodization of iron foil in an ethylene glycol, NH4F, and H2O electrolyte were studied. The as-anodized anodic film was found to be rather amorphous and crystallized to predominantly α-Fe2O3 upon annealing in nitrogen. Nitrogen was used as to reduce the thickening of the barrier layer which affects the photocurrent response of the oxide. However, annealing must be done above 300 °C to produce crystalline oxide but must be kept lower than 500 °C since high temperature promotes grain growth, destroying the nanoporous structure and also thickens the barrier layer, which significantly reduce the photocurrent of the film. Sample annealed at 450 °C in nitrogen has the highest photocurrent of 1.04 mA/cm2 (0.5 V versus Ag/AgCl in 1 M NaOH) compared to 0.13 mA/cm2 at 0.5 V for air-annealed sample.

Effect of a transverse magnetic field on macrosegregation and growth of primary Al2Cu dendrites in directionally solidified Al–40 wt% Cu alloys was investigated experimentally. The experimental results indicated that the magnetic field caused the formation of channel-like and freckle segregations. It was also found that the application of the magnetic field benefited the growth of primary Al2Cu dendrites and the axial segregation. Moreover, the magnetic field decreased the primary dendrite spacing and the mushy zone length; however these effects weakened with the increase of the magnetic field intensity. The above experimental results should be attributed to the formation of the thermoelectric magnetic convection during directional solidification under the transverse magnetic field.

Single- and multi-layer amorphous carbon (a-C) films of varying thickness were deposited on Si(100) substrates by radio-frequency sputtering in a pure Ar atmosphere. The thickness, roughness, coefficient of friction, and residual stress of the a-C films were measured by profilometry, atomic force microscopy, surface force microscopy, and curvature method, respectively. The through-thickness nanostructure and elemental composition of the films were examined by cross-sectional transmission electron microscopy and electron energy loss spectroscopy. The multi-layer a-C films, consisting of alternating ∼10-nm-thick hard and soft a-C layers deposited under 0 and −200 V substrate bias, respectively, were found to exhibit lower roughness, coefficient of friction, and residual stress and slightly higher tetrahedral carbon atom hybridization than single-layer a-C films of similar thickness. The results of this study reveal a strong correlation of the friction characteristics with the surface roughness and nanostructure of single- and multi-layer a-C films.

Density functional theory computations were performed to investigate the adsorption and diffusion properties of lithium (Li) on tin disulfides nanosheets and its derived nanoribbons (NRs), in comparison with SnS2 bulk in 1T phase. The Li adsorption energies and migration barriers are comparable in SnS2 bulk and bilayer, and Li adsorbed at the octahedral sites has the highest binding energy in both SnS2 bulk and bilayer. Reducing the dimension of SnS2 to monolayer significantly lowers the Li diffusion barrier while keeping a considerable binding energy, and lithium favors the hollow sites which corresponding to the octahedral sites in bulk phase. Due to the edge effect, SnS2NRs gain an enhanced Li binding strength, increased Li mobility, and improved Li capacity. Thus, SnS2 NRs are a promising candidate for anode materials of Li-ion batteries with a high power density and fast charge/discharge rates.