Active research is ongoing in logic devices beyond complementary metal–oxide–semiconductor electronics. One of the most promising classes of such devices is spintronic/nanomagnetic devices. Switching of magnetization by spin torque (ST) demonstrated in spintronic devices results in relatively high switching energy. An attractive option for lowering switching energy is magnetoelectric (ME) switching achieved by placing other materials (mostly oxides) adjacent to ferromagnets. We review recent experiments on ME switching, classify them according to the ME phenomena into surface anisotropy, exchange bias, and magnetostrictive, and compare switching parameters for these classes. Then, we perform micromagnetic simulations of switching by the effective ME field of both stand-alone nanomagnets and spintronic interconnects. We determine the threshold values of ME field for switching and the resulting switching time. These switching requirements are incorporated into the previously developed benchmarking framework for spintronic logic devices and circuits. We conclude that ME switching results in 1 to 2 orders of magnitude improvement of switching energy and several time improvement of switching delay compared with ST switching across various schemes of spin logic devices.

Gradient plasticity provides an effective theoretical framework to interpretheterogeneous and irreversible deformation processes on micron and submicronscales. By incorporating internal length scales into a plasticity framework,gradient plasticity gives access to size effects, strain heterogeneities atinterfaces, and characteristic lengths of strain localization. To relate themagnitude of the internal length scale to parameters of the dislocationmicrostructure of the material, 3D discrete dislocation dynamics (DDD)simulations were performed for tricrystals of different dislocation sourcelengths (100, 200, and 300 nm). Comparing the strain profiles deduced from DDDwith gradient plasticity predictions demonstrated that the internal length scaledepends on the flow-stress-controlling mechanism. Different dislocationmechanisms produce different internal lengths. Furthermore, by comparing agradient plasticity framework with interfacial yielding to the simulations itwas found that, even though in the DDD simulations grain boundaries (GBs) werephysically impenetrable to dislocations, on the continuum scale the assumptionof plastically deformable GBs produces a better match of the DDD data than theassumption of rigid GBs. The associated effective GB strength again depends onthe dislocation microstructure in the grain interior.

For a better understanding of the local fracture behavior of semi-brittle materials, we carried out bending experiments on notched microcantilevers of varying sizes in the micrometer range using NiAl single crystals. Smaller and larger beams were milled with a focused ion beam in the so-called “soft” <110> and “hard” <100> orientation and were tested in situ in a scanning electron microscope and ex situ with a nanoindenter, respectively. The measurements were evaluated using both linear-elastic fracture mechanics and elastic–plastic fracture mechanics. The results show that (i) the fracture toughness is in the same range as the macroscopically determined one which is around 3.5 MPa$\sqrt {\rm{m}}$ for the soft orientation and around 8.5 MPa$\sqrt {\rm{m}}$ for the hard orientation, that (ii) there is a strong influence of the anisotropic behavior of NiAl on the fracture toughness values, and that (iii) the J-integral technique is the most accurate quantification method.

In this study, the precipitation behavior of the pretwinned extruded Mg–6Al–1Zn alloy was investigated. It was observed that the precipitates preferentially nucleated at the twin boundaries or within the preexistent twins. This distribution of the precipitates led to the distinguishing influences on subsequent compression and tension process, which were dominated by twinning and detwinning of the preexistent twins, respectively. The compressive yield strength after aging was a little lower than the stress when the precompression was interrupted, which meant that the impeding effect of precipitation on twin expansion was relatively smaller than that of dislocations induced by precompression. However, the tensile yield strength of aged samples was extremely higher than that of non-aged samples as the migration of the twin boundaries during detwinning was considerably hindered because of the preferential precipitation within the preexistent {10-12} twins.

To thoroughly understand the relationship between heat treatments and characteristics of both microstructure and corrosion behavior of Ni–Fe–Cr alloy 028, a series of heat treatments were carried out. The area fraction of precipitates increases with increasing duration of aging treatment at 900 °C. The precipitation rate is higher at 900 °C than at 850 and 950 °C. The precipitates are formed both in grains and at grain boundaries, this behavior enhances the hardness. The corrosion behavior was evaluated by potentiodynamic polarization test and electrochemical impedance spectroscopy measurement under sodium chloride solution. The results indicate that the variation of morphology, amount, and distribution of precipitates attributed to the heat treatment strongly influences the corrosion behavior of alloy 028 in the sodium chloride solution. There is a galvanic effect of Cr-rich phase in the corrosion process. The increase of corrosion rate with the aging time is attributed to the acceleration of the microgalvanic corrosion.

Single-walled carbon nanotubes (SWCNTs), which have a unique electronic structure, nanoscale diameter, high curvature, and extra-large surface area, are ideal for making a new class of nanocomposites. In this study, under the condensed phase optimized molecular potentials for atomistic simulation studies force field, classical molecular dynamics simulation is used to study the molecular interactions between SWCNTs and the molecules of binaphthyl core-based chiral phenylene dendrimers (G0–G2). The simulation results revealed that both G2 and G1 molecules have obvious attractive interactions with SWCNTs, and theoretically demonstrated the possibility of noncovalent functionalization of SWCNTs with chiral dendrimers. The influence of temperature on composites was also studied, and the results indicate that the interaction decreases strongly for SWCNTs@G1 and SWCNTs@G2 with increasing temperature. The possibility during real-world composite processing would create the desired structure bridges between nanotubes and chiral dendrimers, which can be used to produce nanocomposites such as highly sensitive as well as enantioselective fluorescent sensors.

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.

Plasmonic Ag nanoparticles (AgNPs) with narrow distribution were successfully loaded on graphitic carbon nitride (g-C3N4) sheet by thermal polymerization of melamine precursor and a simple wet-chemical pathway in the presence of polyvinylpyrrolidone (PVP). N,N-dimethylformamide (DMF) was used as an efficient reducing agent as well as a solvent and its presence facilitated homogeneous distribution of AgNPs under mild reaction condition and easy control of its particle growth under different precursor amounts. Ag/g-C3N4 composites of different Ag content were prepared, and the phase, chemical structure, morphologies, electronic and optical properties of Ag/g-C3N4 heterostructures were well characterized, respectively. The photocatalytic activity of Ag/g-C3N4 composites was evaluated by the decolorization of methyl orange (MO), and they exhibited superior photocatalytic activity to bulk g-C3N4 under visible-light irradiation. Influence of Ag content to photocatalytic activity was also discussed and possible mechanism was explored based on the analysis of photoluminescence spectra (PL) and photodecoloration activity.

We investigated how changes in the method of supplying Sn and Fe carbon nanocoil (CNC) catalysts affected the results of chemical vapor deposition. The Sn/Fe catalysts were supplied using the following four materials: a thin Sn film, a drop-coated solution of Fe2O3, tetramethyltin (TMT) vapor, and ferrocene vapor. The CNC purity was evaluated using scanning electron microscopy. The CNC purity in the overall carbon deposit was also evaluated by analyzing the cross-section of the deposit. The CNC purity averaged over the overall carbon deposit was increased 1.5-fold by the TMT supply. We obtained a maximum CNC purity of 72% using a combination of TMT and ferrocene vapors, with Sn/Fe deposition on the substrate. Energy-dispersive x-ray spectroscopy analysis of the catalyst nanoparticles in the tips of the CNCs and carbon nanofibers (CNFs) revealed that there was a large difference in the Sn/Fe molar ratios for the angular- and round-type CNFs.

A series of MnOx–CeO2 binary oxide catalysts were synthesized by polyvinylpyrrolidone -assisted supercritical antisolvent precipitation and the effects of the manganese (Mn)/cerium (Ce) molar ratio and calcination temperature on the structure and properties of MnOx–CeO2 were investigated. A solid solution was obtained at each experimental condition and the highest surface area of 107.6 m2/g was obtained at the Mn/Ce molar ratio of 3:5 and the calcination temperature of 400 °C. Low-temperature selective catalytic reduction of emissions of nitrogen oxides, namely NO, NO2, and N2O (deNOx) with ammonia (NH3) to convert them into nitrogen and water, was used as model reaction to evaluate MnOx–CeO2 catalytic performance. It is found that the activity first increased and then decreased with increasing Mn content and decreased with increasing calcination temperature. The highest catalytic activity (93.3% NO conversion and 100% N2 selectivity) was obtained at the Mn/Ce molar ratio of 1/1 and the calcination temperature of 400 °C, which was attributed to the combination of high surface area and high redox performance of the catalyst.

TiO2 has attracted tremendous research interest for photocatalytic water splitting, solar hydrogen generation, environmental pollution removal, dye-sensitized solar cells, lithium-ion batteries, supercapacitors, and field emission. Microwave absorption materials (MAMs) play important roles in many military (e.g., the stealth coating on the B-2 bomber) and civil (e.g., telecommunications, noise reduction, information security, signal, and data protection) applications. However, TiO2 is not a good MAM due to its poor absorption in the microwave region. Here, we report that via hydrogenation excellent and tunable microwave absorption is achieved with hydrogenated TiO2 nanocrystals. After hydrogenation, 4.3x and 103x improvements have been obtained in storing and dissipating the electric energy of the microwave electromagnetic field. Their permittivity values are higher than those of the current carbonaceous MAMs. Instead of relying on the dipole rotation or ferromagnetic resonance mechanisms for traditional MAMs, the hydrogenated TiO2 nanocrystals work as good MAMs based on a newly proposed collective-movement-of-interfacial-dipole (CMID) mechanism. Although there is still no direct physical evidence of the interface effects of the CMID mechanism, the CMID as a hypothesis at this point successfully explained the origin of the enhanced microwave absorption of the hydrogenated TiO2 nanoparticles. This study thus may open new applications for TiO2 nanocrystals and also stimulate new approaches for new MAM development.

Reduced graphene oxide–nickel ferrite (RGO–NiFe2O4) has been successfully synthesized by the hydrothermal method in the presence of poly(diallyldimethylammonium chloride) (PDDA). PDDA is used both as a reducing agent and as a stabilizer. The prepared RGO–NiFe2O4 nanocomposites have been thoroughly characterized by spectroscopic (Fourier-transform infrared spectroscopy, Raman spectroscopy, and x-ray diffraction) and thermogravimetric analysis. Microscopy techniques (scanning electron microscopy, atomic force microscopy, and transmission electron microscopy) were used to probe the morphological structures as well as to investigate the exfoliation of RGO sheets. It is interesting to find that RGO–NiFe2O4 nanocomposites exhibited much better electrochemical capability than NiFe2O4. In addition, the as-prepared RGO–NiFe2O4 nanocomposites can effectively remove methyl orange from water under ultraviolet light irradiation, which can be used as novel photocatalysts for environmental protection.

Ta2O5 added MgCuZn ferrites are prepared by the microwave-hydrothermal (M-H) processing. The nanocrystalline ferrites are sintered to a temperature of 900 °C using conventional sintering (CS) and microwave sintering (MW) methods. The effect of Ta2O5 addition on the microstructure, d.c. resistivity, and Curie temperature of the ferrites has been studied. By the addition of Ta2O5 to MgCuZn ferrites, resistivity decreases without grain growth. The complex permittivity and complex permeability of the prepared samples were measured in the frequency range from 10 kHz to 1.8 GHz. The value of ε′ and tan δ for all the samples decreases from 10 to 100 kHz and almost remains constant up to 300 MHz and increases further by increasing the frequency up to 1 GHz. The µ* spectra are analyzed into two magnetization processes with a focus on the grain size of the ferrite samples. The present ferrites exhibited high values of permeability (>1000) in the frequency range of 10 kHz to 50 MHz. Then the values of permeability are found to decrease with an increase in frequency up to 180 MHz and finally, frequency dispersion occurred at 200 MHz.

Nanostructured Al1−xMnx/Al1−yMny multilayers were deposited from room temperature ionic liquid using galvanostatic control at various current densities and electrolyte compositions. By tuning the deposition parameters, multilayers with both micrometer and nanometer layer thicknesses were synthesized, with modulation of the elastic modulus and hardness between Mn-lean and Mn-rich layers. Surface morphology, composition, and microstructure of the films were characterized using x-ray diffraction and electron microanalysis tools. Nanoindentation and nanoscratch tests were performed to evaluate the mechanical and tribological properties of selected multilayers. Finally, the effects of deposition parameters on the microstructure evolution and mechanical properties of the multilayers were discussed.

Periodic, highly uniform arrays of dome-like Ge quantum dots (QDs) with 50 nm interdot pitch have been achieved on Si (001). The Si surface was patterned using ultra-low-dose focused ion beam and defect-selective etching, resulting in a continuously height-modulated, “egg-carton” morphology. The directed self-assembly process is robust, occurring across a range of ion doses, growth temperatures, and deposition rates. By selectively etching off the Ge dots to reveal the underlying Si surface just prior to Ge growth, we showed that Ge QDs preferentially formed on crowns (regions of negative curvature) rather than pits (regions of positive curvature) as is mostly seen in the literature. The width of the QD size distribution mimics that of the underlying substrate pattern, indicative of a complete lack of coarsening during the Ge growth, despite the small length scales, and extensive mass transport leading to QD formation.