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Yttria-stabilized zirconia (YSZ) nanospheres were synthesized by calcination at 900 °C after the adsorption of Y3+ ions into the pores of a zirconium-based metal–organic framework (MOF). The synthesized 3YSZ (zirconia doped with 3 mol% Y2O3), 8YSZ (8 mol% Y2O3), and 30YSZ (30 mol% Y2O3) nanospheres were found to exhibit uniform sizes and shapes. Complex permittivity and complex permeability were carried out in K-band (i.e., 18–26.5 GHz) to determine their suitability for use as low-k materials in 5G communications. The real and imaginary parts of the permittivity of the sintered 3YSZ were determined to be 21.24 and 0.12, respectively, while those of 8YSZ were 22.80 and 0.16, and those of 30YSZ were 7.16 and 0.38. Control of the real part of the permittivity in the sintered YSZ was facilitated by modifying the Y2O3 content, thereby rendering this material an electronic ceramic with potential for use in high-frequency 5G communications due to its excellent mechanical properties, high chemical resistance, and good thermal stability. In particular, it could be employed as an exterior material for electronic communication products requiring the minimization of information loss.

Low-temperature fuel cells have attracted significant attention owing to their low cost and high performance. Herein, uniform Ru nanoparticles (NPs) with various size distributions were synthesized as a non-Pt catalyst on a carbon support by fluidized bed reactor-atomic layer deposition (FBR-ALD) as a function of ALD cycles for the hydrogen oxidation reaction (HOR) in alkaline medium. With an increase in the number of ALD cycles from 5 to 30 cycles, the wt% of the Ru NPs increased from ∼5 to ∼32 wt%. In addition, the structural characterization of the Ru NPs revealed the formation of Ru NPs with a uniform, dense, and controllable size (∼2–4 nm) and crystallinity depending on the growth cycle of ALD. However, the 10 cycled Ru catalyst with a NP size of ∼2 nm possessed a highly electrochemically active roughened surface (amorphous moiety covered the crystallite), which enhanced its HOR and mass activity. Remarkably, the ALD-synthesized Ru catalyst outperformed a commercial Ru/C catalyst with a similar wt%. Hydrogen binding energy (HBE) calculations revealed that the specific activity of the catalyst increased with decreasing HBE. The mechanistic pathway for the HOR indeed illustrates that enhanced activity under alkaline conditions was found owing to the weakening of the metal–H interaction influenced by the Ru NP crystallinity and size. The findings of this study indicate that the FBR-ALD technique is an effective, scalable approach for the synthesis of active non-Pt metal catalysts.

The structural and electrical properties of PtRu bimetallic alloy (BA) thin films prepared via atomic layer deposition (ALD) were systemically investigated according to the film composition, which was controlled at a deposition temperature of 340 °C by changing the numbers of Pt and Ru subcycles of a supercycle. As-deposited PtRu BA thin films exhibited weaker crystallinity than Pt36Ru64 when the Ru content was high. However, crystallinity improved, and the peak shifts became clearer after Ar heat treatment at 700 °C, reflecting the formation of well-mixed solid solutions. The electrical resistivity and work function also improved. The work function of PtRu BA thin films can be controlled between the work functions of Pt and Ru, and is only weakly dependent on the film composition in the single solid solution region.

We demonstrated highly efficient oxygen reduction catalysts composed of uniform Pt nanoparticles on small, reduced graphene oxides (srGO). The reduced graphene oxide (rGO) size was controlled by applying ultrasonication, and the resultant srGO enabled the morphological control of the Pt nanoparticles. The prepared catalysts provided efficient surface reactions and exhibited large surface areas and high metal dispersions. The resulting Pt/srGO samples exhibited excellent oxygen reduction performance and high stability over 1000 cycles of accelerated durability tests, especially the sample treated with 2 h of sonication. Detailed investigations of the structural and electrochemical properties of the resulting catalysts suggested that both the chemical functionality and electrical conductivity of these samples greatly influence their enhanced oxygen reduction efficiency.

Seawater splitting represents an inexpensive and attractive route for producing hydrogen, which does not require a desalination process. Highly active and durable electrocatalysts are required to sustain seawater splitting. Herein we report the phosphidation-based synthesis of a cobalt–iron–phosphate ((Co,Fe)PO4) electrocatalyst for hydrogen evolution reaction (HER) toward alkaline seawater splitting. (Co,Fe)PO4 demonstrates high HER activity and durability in alkaline natural seawater (1 M KOH + seawater), delivering a current density of 10 mA/cm2 at an overpotential of 137 mV. Furthermore, the measured potential of the electrocatalyst ((Co,Fe)PO4) at a constant current density of −100 mA/cm2 remains very stable without noticeable degradation for 72 h during the continuous operation in alkaline natural seawater, demonstrating its suitability for seawater applications. Furthermore, an alkaline seawater electrolyzer employing the non-precious-metal catalysts demonstrates better performance (1.625 V at 10 mA/cm2) than one employing precious metal ones (1.653 V at 10 mA/cm2). The non-precious-metal-based alkaline seawater electrolyzer exhibits a high solar-to-hydrogen (STH) efficiency (12.8%) in a commercial silicon solar cell.

Atomic Layer Deposition (ALD) is a unique vapor-phase non-line-of-sight deposition process, it can provide excellent control over the wall thickness of nanostructures at the sub-angstrom scale and can be used to create highly conformal coatings of dense inorganic film even on the nano-sized templates with high aspect ratios. Due to these inherent merits, it has become an inevitable process in current semiconductor industries. Following the success of ALD in the semiconductor industries, ALD is recently focused because it can efficiently enhance the performance of energy conversion and storage devices. As a representative example, electrochemical supercapacitors, as one type of novel power device, have attracted universal research interest because of their great potential to be applied in many fields. In particular, pseudocapacitor is recently focused due to its larger capacitance. The electrochemical energy conversion and storage performance of pseudocapacitors depends strongly on the intrinsic properties of the active electrode materials and their surface area. To maximize these performance, various nano-morphologies and transition metal oxides/hydroxides, such as NiO, Co3O4, MnO2, Ni(OH)2 and etc., having a large theoretical capacitance has been extensively investigated. Those psuedocapacitor materials, however, generally showed a high electrical resistivity and it remain unable to achieve high theoretical capacitance in practical applications. To solve these drawbacks, ultrathin conductive ALD coatings can be considered. As a representative example, we design and fabricate a novel hybrid 3D Ni(OH)2@ZnO nanostructured electrode material with a high surface area and high conductivity using a hydrothermal method and ALD. ALD-ZnO thin films were deposited on the surface of a 3D porous Ni(OH)2 nanostructure. The optimization of ALD-ZnO was performed to achieve a high conductivity and electrochemical performance. And, it was exhibited that this hybrid 3D core-shell structure, which benefits from the synergistic effects of both Ni(OH)2 and ZnO, can result in a much improved supercapacitor performance.

Proton exchange membrane fuel cell (PEMFC) is an efficient electrochemical energy conversion device that directly generates electricity from the chemical energy of fuels without the emission of greenhouse gases. The most reliable catalyst in PEMFC is Platinum (Pt) metal nanoparticles (NPs) that exhibit excellent electrochemical activity and stability compared to other catalysts. However, using of Pt catalyst is limited due to its very high cost and low abundance on Earth. Therefore, it is important to use Pt catalyst efficiently for making the PEMFC economically viable. In this regard, several synthesis techniques have been developed to reduce the loading and uniform distribution of Pt NPs on carbon support with high electrochemically active surface area (ECSA). One of the most efficient techniques to uniformly deposit Pt NPs with a controllable size on carbon support is to use a fluidized bed reactor (FBR) atomic layer deposition (ALD). Our group recently demonstrated that FBR-ALD Pt/C catalysts can exhibit high fuel cell performance and high endurance even with low Pt NPs loading by optimizing the surface of carbon supports combined with proper ALD process parameters [1]. However, it is still challenging to further improve the fuel cell performance by rational designing the Pt NPs surfaces in order to make FBR-ALD into a viable commercial production. In this study, a unique way to improve the fuel cell performance was suggested to design and optimize atomic scale surface textures of Pt NPs. During the FBR-ALD of Pt NPs, in-situ surface modulation of Pt NPs was applied via a proper protective oxide deposition and etching. A careful surface studies was performed to analyze the surface morphology, distribution and uniformity of Pt NPs. Electrochemical performances were evaluated and optimized by measuring cyclic voltammetry (CV) and oxygen reduction reaction (ORR). Finally, a fuel cell performance was studied through membrane electrode assembly (MEA) characteristics. References W. J. Lee, S. Bera, H. C. Shin, W. P. Hong, S. J. Oh, Z. wan, S. H. Kwon, Adv. Mater. Interfaces 6, 1901210 (2019).

Rapid, accurate, and intuitive detection of unknown liquids is greatly important for various fields such as food and drink safety, management of chemical hazards, manufacturing process monitoring, and so on. Here, we demonstrate a highly responsive and selective transparency-switching medium for on-site, visual identification of various liquids. The light scattering–based sensing medium, which is designed to be composed of polymeric interphase voids and hollow nanoparticles, provides an extremely large transmittance window (95%) with outstanding selectivity and versatility. This sensing medium features ternary transparency states (transparent, semitransparent, and opaque) when immersed in liquids depending on liquid-polymer interactions and diffusion kinetics. Several different types of these transparency-changing media can be configured into an arrayed platform to discriminate a wide variety of liquids and also quantify their mixing ratios. The outstanding versatility and user friendliness of the sensing platform allow the development of a practical tool for discrimination of diverse organic liquids.

The work function (WF) of Pt-Ru bimetallic alloy (BA) films prepared by atomic layer deposition (ALD) was systemically investigated depending on the thickness. Pt-Ru BA films were deposited using a supercycle consisted of 10 subcycles for Pt and 1 subcycle for Ru. And, the thicknesses of Pt-Ru BA films were carefully controlled from 2.9 to 35.7 nm through changing the number of supercycles. Although a fixed ALD supercycle was used, the composition of Pt-Ru BA films was gradually changed and then saturated to Pt: ∼92 at.% and Ru: ∼8 at.% with increasing the film thickness. In addition, the microstructural evolution of Pt-Ru BA films happened from island-like nuclei to continuous film at an initial growth stage. As a result, the WF and electrical resistivity of ALD Pt-Ru BA films exhibited saturated values of ∼5.36 eV and ∼19.95 µΩ·cm, respectively at higher than 8.7 nm thickness.

In this study, Al2O3/CrAlSiN multilayer coatings with various periods were prepared using a hybrid process involving overlapping magnetron sputtering of CrAlSiN and atomic layer deposition (ALD) of Al2O3. The influence of the number of Al2O3 layers on the mechanical properties, corrosion behavior and oxidation characteristics of the coatings was studied using nano/micro indentation, electrochemical corrosion, and high temperature static oxidation tests. The results show that the multilayer structure can effectively prevent crack propagation during the coating and subsequently increase the coating toughness. A substantial improvement in the resistance to electrochemical and oxidation corrosion was observed in the Al2O3/CrAlSiN multilayer coatings and increasing the number of Al2O3 layers dramatically increases the corrosion durability. The Al2O3 ALD layers are expected to inhibit the diffusion of corrosive substances such as ions and oxygen and the increase of the Al2O3 layer number decreases the diffusion fluxes of the coating elements to the surface and limit the oxide growth, resulting in the evolution of the oxidation produces from irregular particles to nano-walls/fibers. It is supposed that the PVD/ALD hybrid process may open a new hard coating design concept by providing a superior toughness and corrosion/oxidation resistance.

Pt-decorated In2O3 nanofibers with tailored size and morphology were synthesized as sensing materials for a highly sensitive toluene gas sensor. The bridge-type micro-platforms, including micro-heaters and micro-electrodes for the integration of In2O3 nanofibers-based sensing materials, were designed to demonstrate the sensing at high temperature with low power consumption. The gas sensing properties of the fabricated toluene gas sensor were systematically investigated by controlling the power of the micro-heater and the concentration of the toluene gas. Additionally, the enhanced sensing properties for various gas concentrations of toluene were investigated for Pt-nanoparticle-decorated In2O3 nanofibers.

Recently, porous ceramics have received much attention from researchers because of their excellent thermal and chemical stabilities compared to their counterparts (such as porous polymers and metals), despite their inferior mechanical instability. Among the various types of porous ceramics, reticulated porous ceramics have significant industrial potential because of their synergistic high porosity and permeability. However, to the best of our knowledge, there is insufficient data on the processing conditions or preparing optimal reticulated porous alumina. Therefore, we prepared and characterized reticulated porous alumina specimens by controlling various processing conditions, namely average particle size, solid loading, binder, and dispersant. The data obtained were used to assess whether the compressive strength of the reticulated porous alumina could be enhanced and to discuss the potential of these materials for various applications.

Nanostructuring is considered one of the key approaches to achieve highly efficient thermoelectric alloys by reducing thermal conductivity. In this study, we investigated the effect of oxide (ZnO and SnO2) nanolayers at the grain boundaries of polycrystalline In0.2Yb0.1Co4Sb12 skutterudites on their electrical and thermal transport properties. Skutterudite powders with oxide nanolayers were prepared by atomic layer deposition method, and the number of deposition cycles was varied to control the coating thickness. The coated powders were consolidated by spark plasma sintering. With increasing number of deposition cycle, the electrical conductivity gradually decreased, while the Seebeck coefficient changed insignificantly, this indicates that the carrier mobility decreased due to the oxide nanolayers. In contrast, the lattice thermal conductivity increased with an increase in the number of deposition cycles, demonstrating the reduction in phonon scattering by grain boundaries owing to the oxide nanolayers. Thus, we could easily control the thermoelectric properties of skutterudite materials through adjusting the oxide nanolayer by atomic layer deposition method.

A dataset in this report is regarding an article “Ultrathin Effective TiN Protective Films Prepared by Plasma-Enhanced Atomic Layer Deposition for High Performance Metallic Bipolar Plates of Polymer Electrolyte Membrane Fuel Cells” [1] . TiN (Titanium Nitride) thin films were deposited by Plasma-Enhanced Atomic Layer Deposition (PEALD) method using well known two types of precursor: using tetrakis(dimethylamino)titanium (TDMAT) and titanium tetrachloride (TiCl4), and plasma. Summarized reports, growth characteristics (growth rate as a function of each precursor pulse time, plasma power, precursor and plasma purge time, thickness depending on the number of PEALD cycles), each precursor structural information and the atomic force micrographs (AFM) data are herein demonstrated. For TDMAT-TiN, N2 plasma was used as a reactant whereas, H2+N2 plasma was used as TiCl4-TiN reactant. To apply the bipolar plate substrate, two types of TiN thin films were introduced into Stainless steel (SUS) 316L.

Thermally assisted nanotransfer printing process enables nanopattern formation at an 8-inch wafer., Nanotransfer printing (nTP) has attracted considerable attention due to its good pattern resolution, process simplicity, and cost-effectiveness. However, the development of a large-area nTP process has been hampered by critical reliability issues related to the uniform replication and regular transfer printing of functional nanomaterials. Here, we present a very practical thermally assisted nanotransfer printing (T-nTP) process that can easily produce well-ordered nanostructures on an 8-inch wafer via the use of a heat-rolling press system that provides both uniform pressure and heat. We also demonstrate various complex pattern geometries, such as wave, square, nut, zigzag, and elliptical nanostructures, on diverse substrates via T-nTP. Furthermore, we demonstrate how to obtain a high-density crossbar metal-insulator-metal memristive array using a combined method of T-nTP and directed self-assembly. We expect that the state-of-the-art T-nTP process presented here combined with other emerging patterning techniques will be especially useful for the large-area nanofabrication of various devices.

The performance of proton exchange membrane fuel cells (PEMFCs) depends on the controlled size, dispersion and density of Pt nanoparticles (NPs) on carbon supports, which are strongly affected by the carbon characteristics and fabrication methods. Here, we demonstrated a high-performance Pt/carbon catalyst for PEMFCs using fluidized bed reactor atomic layer deposition (FBR-ALD) that was realized by an effective matching of the carbon supports for the FBR-ALD process and an optimization of the ionomer content during the preparation of the membrane electrode assembly (MEA). For this, the synthesis of Pt NPs was conducted on two porous supports (Vulcan XC-72R and functionalized carbon) by FBR-ALD. The functionalized carbon possessed a higher surface area with a large pore volume, abundant defects in a disordered structure and a large number of oxygen functional groups compared to those of the well-known Vulcan carbon. The favorable surface characteristics of the functionalized carbon for nucleation produced Pt particles with an increased uniformity and density and a narrow size range, which led to a higher electrochemical surface area (ECSA) than that of Pt/Vulcan carbon and commercial Pt/carbon. The PEMFC test of the respective Pt/carbon samples was investigated, and highly dense and uniform Pt/functionalized-carbon showed the highest performance through optimization of the higher ionomer content compared to that for the ALD Pt growth on Vulcan carbon and commercial Pt/carbon. In addition, the Pt catalyst using ALD demonstrated a significant long-term stability for the PEMFC. This finding demonstrates the remarkable advantages of FBR-ALD for the fabrication of Pt/carbon and the ability of functionalized carbon supports to achieve a high PEMFC efficiency and an enhanced durability. Small tweaks to techniques used to manufacture platinum catalysts can have a big impact on the long-term stability of fuel cells. Platinum nanoparticle catalysts help fuel cells turn hydrogen and oxygen into water and electricity, but their small size makes them tricky to manipulate. Se-Hun Kwon from Pusan National University in Busan, South Korea, and colleagues have now optimized a high-tech procedure for attaching these tiny nanocatalysts to large, porous materials known as carbon supports. Their process coats various supports with platinum nanoparticles, less than one monolayer at a time, until the desired thicknesses are reached. Various factors including the physical textures of the supports and leftover chemical impurities were shown to significantly affect coating uniformity. Adjusting these factors enabled the team to generate supports with greater durability than commercial platinum–carbon composites. Very efficient, fast and scalable Fluidized Bed Reactor Atomic Layer Deposition (FBR-ALD) of highly dense and uniform Pt nanoparticles (NPs) on the functionalized carbon were successfully demonstrated for the proton exchange membrane fuel cell (PEMFC) application. The textural properties, functional groups and structural defects of the carbon supports significantly influenced Pt NPs deposition. A proper carbon supporter matching for FBR-ALD of Pt resulted in excellent electrochemical properties, long-term durability and fuel cell performance.

Recently, research has been conducted on nanocomposite thin films containing new additive elements in ZrN. In this paper, a method for depositing ZrCuSiN nanocomposite coatings using a ZrCuSi single target is presented. The ZrCuSi target that was used to easily deposit a ZrCuSiN coating in a mixed gas atmosphere (Ar + N2) was produced by a simple arc melting method (casting process). The effect of the nitrogen content was investigated by depositing a ZrCuSiN coating using alloy targets at various nitrogen gas flow rates (2, 4, 6, and 8 sccm). X-ray diffraction analysis of the ZrCuSiN coatings revealed a ZrN structure with a preferable orientation (200). As the nitrogen flow rate increased, the formation of o-Zr3N4 was dominant in the ZrN formation. A nitrogen gas flow rate of 4 sccm produced a coating with optimal ZrN and a-Si3N4 coordination and maximum hardness (41 GPa). Reciprocal friction tests of all coatings and uncoated carburized SCM415 steel in a 5W30 lubrication atmosphere demonstrated that the 4 sccm coating had the lowest friction coefficient (0.002). Therefore, our method has the potential to be an alternative surface coating technique for materials used in automotive engine parts and various other wear protection applications.

Generally, thin-film metal glass (TFMG) is deposited using two or more elemental targets. Thus, achievement of a homogeneous coating during mass production is difficult. As a new method of TFMG deposition, a single target with high glass-forming ability (GFA) has been used to improve the sputtering process, facilitating easy processing and broad application of sputtering targets. In this study, three kinds of targets (i.e., cast, amorphous, and crystalline targets) are prepared via casting and powder processes. The thermal and mechanical properties of the three targets prepared using the various methods are investigated, and the crystalline target is found to be the most thermodynamically and mechanically stable of the three alternatives. In addition, for TFMG deposited using the microcrystalline target, excellent compositional uniformity between the target and coating is achieved. Therefore, this study experimentally demonstrates that a fine crystalline target is most suitable for use as a multi-component single target in GFA manufacturing methods. These findings are expected to facilitate commercial use of TFMGs.

Amorphous carbon films containing a wide-range content of Mo and a small amount of Cu (MoCu:a-C films) were prepared by a hybrid sputtering system. The influences of the doping contents of MoCu on the microstructure and properties of the films were studied. The results show that the doped Cu atoms tend to dissolve in the a-C matrix while the doped Mo atoms exist as solid solution and carbide nanoparticles embedding in the a-C matrix. It is found that the size of the carbide nanoparticles shows an influence on the formation of the sp2-C. Increasing the nanoparticle size will decrease the sp2-C fraction and thus increase the sp3/sp2 in the films. The high sp3/sp2 and hard carbide nanoparticles contribute to the high hardness of the films. However, the hard carbide nanoparticles cause serious abrasive wear performances.

The mechanism of hardness improvement of a TiZrN coating by carbon doping was investigated in terms of the residual stress and the lattice deformation. Carbon was doped using laser carburization to improve the hardness of TiZrN, which was increased from 3025 HV to 3388 HV. The lattice parameter was calculated through Rietveld refinement in order to analyze the behavior inside the lattice due to carbon doping, which showed that the parameter increased from 4.21 A to 4.44 A after the carbon doping process. The diffraction pattern was analyzed using an electron beam to identify the lattice state of the coating layer, and lattice distortion was revealed through a diffused ring pattern. The compressive residual stress was increased by 48%, which was identified through the sin2Ψ method using the lattice constant change due to carburization. After the carbon doping, the hardness of the TiZrN was increased by 10%, which was attributed to the expansion distortion generated in the TiZrN lattice and the increase of the compressive residual stress.

The formation of thin amorphous cobalt titanium nitride (CoTiN) layers was investigated using a supercycle method of atomic layer deposition (ALD). The stoichiometry of the resultant ALD CoTiN films was controlled by changing the ratio of Co and TiN thicknesses. X-ray diffraction analysis and transmission electron microscopy observations showed that the microstructure of the ALD Co and TiN was transformed from polycrystalline to amorphous CoTiN. The stoichiometry of the CoTiN layer was affected by the growth characteristics of ALD Co and TiN on each surface. The results revealed that ALD TiN undergoes nucleation incubation on the ALD Co surface, whereas ALD Co does not undergo nucleation incubation on the ALD TiN surface. The properties of the amorphous CoTiN layers were evaluated by diffusion experiments and mechanical tests. Because of the lack of grain boundaries, the CoTiN efficiently blocks the diffusion of Cu at elevated temperatures and exhibits higher hardness compared with ALD Co.