We have investigated the equilibrium conformation of Pt2Ru3 nanoparticles in the presence of H2 and CO mixture gas using density functional theory (DFT) and Monte Carlo (MC) simulation. A multiple linear regression equation was prepared using DFT results to calculate adsorption energy from the structural descriptors. Using the regression equation, MC simulations were employed to elucidate the equilibrated conformation of Pt2Ru3 particles at a finite temperature of H2/CO where CO concentration in the range 100–500 ppm. MC results indicate that CO/H2 coadsorption induced the rearrangement of alloying atoms and Pt/Ru ratio exposed to the surface decreases with the increase of CO concentration.

The use of zinc nitride (Zn3N2) films as a transparent electrode in various electronic devices has attracted much attention owing to its high-carrier mobility. In this study, we investigate the influence of the sputtering process on structural, optical, and electrical properties of a Zn3N2 film deposited by reactive magnetron sputtering. The reactivity of nitrogen species can be improved by changing the type of sputtering gas. Compared with Ar or Ne sputtering gas, polycrystalline Zn3N2 films deposited using He sputtering gas have a larger grain size. The optical band gap of the Zn3N2 films varied from ~1.2 to 1.5 eV depending on the N2 flow ratio and type of sputtering gas. The maximum mobility was 91.1 cm2/Vs when the Zn3N2 film was deposited using Ar sputtering gas with an N2 flow ratio of 40%. The carrier density of Zn3N2 films deposited using Ar sputtering gas was notably higher than those deposited using Ne or He sputtering gas, and more oxygen atoms are considered to substitute into nitrogen sites, where oxygen is considered to be from the residual water vapor in the sputtering chamber.

The present work demonstrates controllable directive radiation of a dipolar emitter coupled to a substrate-supported dielectric nanowire antenna. Nanoactuators, transparent-conducting oxides, and graphene are integrated into the substrate, respectively, to establish tunable antenna platforms in visible, near-infrared (IR), and far-IR frequency regimes. We exploit the substrate-induced interference effects and tunability mechanisms in each antenna system to achieve directive radiation with real-time steering capability. The design and modeling are rigorously carried out using an efficient and accurate semi-analytical framework based on transition matrix formulation. Each configuration is optimized to achieve maximal steering range while attaining a proper gain. Owing to subwavelength footprint, enhanced directionality, real-time tunability, and fairly simple geometry, the proposed platforms are ideal candidates for nanoantenna synthesis.

Biologic neural networks are immersed in common electrolyte environment, and homeoplasticity or global factors of this environment are forcing specific normalization functions that regulate the overall network behavior. In this work, a common electrolyte is used to gate a grid of organic electrochemical devices. The electrolyte functions as a global parameter that controls collectively the device grid. Statistical analysis of the grid and the subsequent definition of global metrics reveal that the grid behaves similarly to a single device. This global control modulates the gain of the device grid, a phenomenon analog to multiplicative scaling in biologic networks. This work demonstrates the potential use of electrolytes as homeostatic media in neuromorphic device architectures.

In the present work, the effect of cooling rate on the evolution of the microstructure and mechanical properties of an α + β titanium alloy has been systematically investigated. Titanium alloy samples were heated to 1066 °C (above the β transus), 930 °C (just below the β transus), and 850 °C (well below the β transus) followed by oil quenching, air cooling, and furnace cooling, respectively. Primary alpha (αp), lamellar alpha (αL), and martensite (α′) were the dominant features of the microstructures for all the samples heated below the β transus. Furnace-cooled samples showed variation in the size and shape of the αp and fraction of αL according to the heating temperature. At slower cooling rates, the thickness of the αL increased with the increase in temperature. Transmission electron microscopy and X-ray diffraction confirmed the presence of α′ in all the quenched samples. The volume fraction and size of the αp decreased with the increase in temperature but was independent of the cooling rate. The microhardness was relatively unaffected by the cooling rate for heating just below the β transus, i.e., 930 °C. The modulus of elasticity was found to be extremely sensitive to the microstructure.

Carbon-doped titania was fabricated via carbothermal treatment in nitrogen–acetylene gas flow and further used as a precursor for multiwalled titanate nanotube (TNT) synthesis via alkaline hydrothermal route. Investigation of the reaction products after hydrothermal treatment of carbon-doped titania using Transmission electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller method shows the successful formation of TNTs. The presence of carbon was proved although the type of incorporation could not be certified. All samples show approximately the same carbon content before and after hydrothermal treatment. An increasing pretreatment temperature of titania precursor powders yields more secondary products in the nanotube samples, indicating lower reactivity of the titanium oxycarbide phase during hydrothermal treatment. In this study, TNTs with 6 wt% carbon and with the highest specific surface area of 340 m2/g were formed via hydrothermal treatment of carbon-doped titania precursor powder exposed to 700 °C during carbothermal pretreatment.

Significant progress in nanoscience was achieved through the development of methods and instruments to better comprehend nanoscale properties. We present here a methodology and automated setup to measure layer-by-layer films capacitance in the air immediately after polyelectrolytes adsorption. It presents high accuracy (~0.01 pF) to check the capacitance stabilization during spontaneous drying process in the air, with sensitivity to show electrical signal alternation accordingly to the outermost polyelectrolyte layer. Besides, a linear trend in capacitance was observed similar to UV–vis measurements. This method allows analyzing films electrical properties, affording better choice of materials, thickness, and molecular architecture.

Elastocaloric materials exhibit extraordinary cooling potential, but the repetition of cyclic mechanical loadings during long-term operation of cooling systems requires the refrigerant material to have long fatigue life. This article reviews the fundamental cause of fatigue from aspects of initiation and propagation of fatigue cracks in shape-memory alloys (SMAs) that are used as elastocaloric materials, and highlights recent advances in using compression to overcome fatigue by curtailing the generation of surfaces associated with crack propagation. Compression is identified as a key means to extend fatigue lifetime in engineering design of elastocaloric cooling drive mechanisms. We summarize the state-of-the-art performance of different SMAs as elastocaloric materials and discuss the influence of low cyclic strains and high resistance to transformation. We present integration of compression-based material assemblies into a cooling system prototype and optimization of the system efficiency using work recovery and related measures.

For more than a century, humankind has achieved refrigeration by exploiting volatile gases that harm the environment when released to the atmosphere. More recently, the observation of electrocaloric effects in commercial multilayer capacitors has inspired the possibility of environmentally friendly cooling. In this article, we describe electrocaloric effects in multilayer capacitors for cooling applications, compare the electrocaloric performance of existing multilayer capacitors, and discuss the improvements required for practical cooling devices.

Magnetocaloric heat pumps (MHPs) use the solid-state magnetocaloric effect (MCE) to move heat from cold to hot using an intermediate heat-transfer fluid. Work input is required to drive the MCE via a change in a magnetic field. Work input is also required to drive the heat-transfer fluid flow. Thus design of a MHP involves the coupling of materials, magnetics, heat transfer, and fluid flow. We discuss design principles and operational devices that have brought this technology toward technical feasibility, and the approaches to overcome remaining hurdles to commercial feasibility.

The fundamentals and applications of ferroic materials—ferromagnetic, ferroelectric, and ferroelastic—are common subjects discussed in just about every graduate course related to functional materials. Looking beyond today’s traditional uses, such as in permanent magnets, capacitors, and shape-memory alloys, there are worthwhile and interesting questions common to the caloric properties of these ferroic materials. Can ferroic materials be used in a cooling cycle? Why are these materials susceptible to external fields? Which combination of properties is required to make some of them suitable for efficient cooling and heat pumping? We address these questions in this introduction to ferroic cooling, which comprises magnetocaloric, electrocaloric, elastocaloric and barocaloric approaches and combinations thereof (i.e., multicalorics). These are addressed in greater detail in the articles in this issue.

Pseudoelastic NiTi-based shape-memory alloys (SMAs) have recently received attention as candidate materials for solid-state refrigeration. The elastocaloric effect in SMAs exploits stress-induced martensitic transformation, which is associated with large latent heat. Most importantly, cyclic mechanical loading/unloading provides large adiabatic temperature drops exceeding 25 K at high process efficiencies. This article summarizes the underlying principles, important material parameters and process requirements, and reviews recent progress in the development of pseudoelastic SMAs with large coefficients of performance, as well as very good functional fatigue resistance. The application potential of SMA film and bulk materials is demonstrated for the case of cyclic tensile loading/unloading in prototypes ranging from miniature-scale devices to large-scale cooling units.

Multicaloric materials show thermal changes that can be driven simultaneously or sequentially by more than one type of external field. The use of more than one driving field can induce larger thermal changes, with smaller field magnitudes, over wider ranges of operating temperature, and can also eliminate hysteresis in one control parameter by transferring it to another. The thermodynamics behind multicaloric effects is well established, but only a small number of multicaloric materials have been experimentally studied to date. Here, we describe the fundamentals of multicaloric effects and discuss the performance of representative multicaloric materials. Exploiting multicaloric effects could aid the future development of cooling devices, where key challenges include energy efficiency and the span of the operating temperature.

This article overviews the current status of magnetocaloric materials for room-temperature refrigeration. We discuss the underlying mechanism of the magnetocaloric effect and illustrate differences between first- and second-order type materials starting with gadolinium as a reference system. Beyond the key functional properties of magnetocaloric materials, the adiabatic temperature, and entropy change, we briefly address the criticality of the most promising materials in terms of their supply risk. Looking at practical applications, suitable geometries and processing routes for magnetocaloric heat exchangers for device implementation are introduced.