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In this study, a high-entropy approach was employed to design a new single-phase A2B2O7 oxide for thermal insulation applications. Multicomponent high-entropy oxides, containing up to seven different cations, were successfully synthesized in a single defective fluorite structure. We observed that the incorporation of the functional cation, Zn2+, effectively blocked the heat radiation phenomenon by reducing the photon mean free path, and further reduced the high-temperature thermal conductivity owing to the larger free carrier concentration originated from the large number of oxygen vacancies. Although a large concentration of Zn2+ caused a slight reduction in thermal expansion, this study suggests that functional cations can be easily incorporated; thus, expanding the material diversity beyond the typical doping levels to develop new thermal barrier materials.

The development of efficient, low-cost, and stable bifunctional catalysts is necessary for renewable energy storage and conversion, but it remains a challenge. Herein, we first report a novel strat...

Heterogeneous structured-metal sulfides are widely used in various applications due to their excellent electrochemical activity. We report a facile synthesis of Cu1.75S/Cu1.8S microspheres assemble...

The development of cost-effective and high-performance electrocatalysts for water oxidation has attracted intense research interest. It was reported recently that the interface between the amorphous and crystalline phases plays a significant role in the electrocatalytic activity of transition metal compounds. It was reckoned therefore that an increase in the density of the crystalline–amorphous phase boundary would enhance the electrochemical water oxidation on the catalyst. In this work we develop a new and facile strategy for inducing high density crystalline–amorphous phase boundaries via selective fluorination surface doping. This resulted in excellent characteristics of the engineered material for electrochemical water splitting. An initial computational simulation is carried out to design the crystalline–amorphous phase boundary material and an experimental verification follows for demonstration and optimization of the impact of surface doping. We conclude that the engineering of the interface using this facile and cost-effective strategy maximizes the crystalline and amorphous phases of metal–metalloids, which can be used to fabricate low-cost and efficient electrocatalysts for water oxidation.

Beyond graphene, two-dimensional (2D) atomic layered materials have drawn considerable attention as promising semiconductors for future ultrathin layered nano-electronic device applications, transparent/flexible devices and chemical sensors. But, they exhibit high levels of low-frequency due to interfacial scattering (small thickness) and interlayer coupling (large thickness). The sources and mechanisms of low frequency noise should be comprehensive and controlled to fulfill practical applications of two-dimensional transistors. This work seeks to understand the fundamental noise mechanisms of 2D transistors to find ways to reduce the noise level. It also verifies how noise can provide a spectroscopy for analysis of device quality. Most noise analysis tend to apply classical MOSFET models to the noise and electrical transport of 2D transistors, which put together all possible independent noise sources in 2D transistors, ignoring the contact effects. So this could lead to wrong estimation of the noise analysis in 2D transistors. This work demonstrates how the noise components can come from the channel and contact/access regions, all independently adding to the total noise. Each noise source can contribute and may dominate the total noise behavior under the specific gate voltage bias. Herein, the measured noise amplitude in our MoS2 and MoSe2 FETs shows a direct crossover from channel- to contact-dominated noise as the gate voltage is increased. The results can be interpreted in terms of a Hooge relationship associated with the channel noise, a transition region, and a saturated high-gate voltage regime whose characteristics are determined by a voltage-independent conductance and noise source associated with the metallurgical contact and the interlayer resistance. The approach for separating channel contributions from those contact/access region allows clear evaluation of the channel noise mechanism and also can be used to explain the qualitative differences in the transition regions between contact- and channel-dominated regimes for various devices.

Development of efficient and durable electrocatalysts for the oxygen evolution reaction (OER) is essential for sustainable hydrogen production by water splitting. The physicochemical properties of the electrocatalyst can be tailored by defect engineering. Herein, we report the fabrication of [Fe(CN)6]3− coordination sphere vacancies via the rapid coprecipitation in Ni3Ⅱ[FeIII (CN)6]2-x (x ≤ 0.12) electrocatalyst anchored on reduced graphene oxide (v-NiFe PBA@rGO) for OER. The formation of [Fe(CN)6]3− coordination sphere vacancies (VFeCN) via the rapid coprecipitation during the synthesis under the absence of chelating agents enables the regulation of electronic states of Ni active site, leading to the improvement in OER. Reduced graphene oxide (rGO) is employed as a substrate to maximize the concentration of VFeCN and exposed active sites by the uniform formation of nano-sized Ni3Ⅱ[FeIII (CN)6]2-x. The presence of VFeCN and hybridization with rGO effectively suppress Fe leaching behavior. The v-NiFe PBA@rGO shows a low overpotential of 251 mV at 10 mA cm−2 in alkaline condition and the long-term stability for 200 h.

Li dendrite growth and poor Coulombic efficiency still prevent the practical use of Li metal anodes. Here, we report a stable solid electrolyte interphase (SEI) layer consisting of Li3N and LiF by employing lithium nitrate (LiNO3) in carbonate electrolytes for the improved cycle performance with dendrite-free Li deposition for Li metal anodes. We demonstrate that the lower charge transfer activation energy is realized with the Li3N-rich SEI layer and LiF-rich SEI layer in carbonate electrolytes. With the Li3N and LiF composite SEI layer, outstanding improvements are achieved in that the very low charge transfer activation energy of 46.64 KJ mol−1 and stable electrochemical performances with dendrite-free Li deposition. With those benefits, the Li || Cu cell shows stable cyclability with high Coulombic efficiency of ∼ 97% at a current density of 0.5 mA cm−2 with a capacity of 0.5 mAh cm−2 over 200 cycles, and Li can be densely plated with lower porosity of 10.1 % with a plated Li of 2 mAh cm−2. Finally, the outstanding cyclability is demonstrated in full cells consisting of LiNi0.8Co0.1Mn0.1O2 as a cathode and thin Li metal electrode with a thickness of 20 μm in lean electrolytes of 8 μL mAh−1.

The electrocatalytic performance of transition metal sulfide (TMS)–graphene composites has been simply regarded as the results of high conductivity and the large surface/volume ratio. However, unavoidable factors such as degree of oxidation of TMSs have been hardly considered for the origin of this catalytic activity of TMS–graphene composites. To accomplish the reliable application of TMS-based electrocatalytic materials, a clear understanding of the thermodynamic stability of TMS and effects of oxidation on catalytic activity is necessary. In addition, the mechanism of charge transfer at the TMS–graphene interface must be studied in depth to properly design composite materials. Herein, we report a comprehensive study of the physical chemistry at the junction of a Co1–xNixS2–graphene composite, which is a prototype designed to unravel the mechanisms of charge transfer between TMS and graphene. Specifically, the thermodynamic stability and the effects of oxidation of TMSs during the oxygen evolution react...

A key issue with Na-ion batteries is the development of active materials with stable electrochemical reversibility through the understanding of their sodium storage mechanisms. We report a sodium storage mechanism and properties of a new anode material, digenite Cu1.8S, based on its crystallographic study. It is revealed that copper sulfides (CuxS) can have metal-rich formulas (x ≥ 1.6), due to the unique oxidation state of +1 found in group 11 elements. These phases enable the unit cell to consist of all strong Cu–S bonds and no direct S–S bonds, which are vulnerable to external stress/strain that could result in bond cleavage as well as decomposition. Because of its structural rigidness, the Cu1.8S shows an intercalation/deintercalation reaction mechanism even in a low potential window of 0.1–2.2 V versus Na/Na+ without irreversible phase transformation, which most of the metal sulfides experience through a conversion reaction mechanism. It uptakes, on average, 1.4 Na+ ions per unit cell (∼250 mAh g–1) and exhibits ∼100% retention over 1000 cycles at 2C in a tuned voltage range of 0.5–2.2 V through an overall solid solution reaction with negligible phase separation.

We report a polylactic acid (PLA)-polyethylene glycol (PEG) mixture as a thermoplastic binder to prepare shape-machinable ceramic green bodies. During the mixing process, the high viscosity of the PLA binder impedes effective mixing with ceramic powders. To address this issue, PEG was introduced as a plasticizer into ceramic/PLA composites to diminish the overall viscosity of the feedstock, which resulted in effective mixing with ceramic powders. After sintering green bodies composed of PLA-PEG binders and ceramic compounds, the mechanical properties (flexural strength and porosity) of the sintered specimens were investigated and compared with those of sintered specimens made from wax-based green bodies. The sintered specimens made from ceramic/PLA-PEG composites showed comparable mechanical properties and porosities with the sintered specimens made from ceramic/wax composites. In addition, the shape-machinable characteristic of the green bodies made from ceramic/PLA-PEG composites was demonstrated by deforming the entire structure of the green bodies via simple heat treatment.

Alkaline electrolysis is one of the most powerful technologies to produce hydrogen energy, where the electrocatalysts play an important role. The cathode electrocatalysts often suffer from undesirable oxidation due to the oxygen gas crossover through the porous separator during electrolysis. This leads to oxygen reduction reaction (ORR) on the cathode electrocatalysts, resulting in the loss of activity for hydrogen evolution reaction (HER). Here, we report a highly efficient and durable HER and ORR bifunctional electrocatalyst derived from Ni metal-organic frameworks to address the above problem. Decoupled active sites for ORR and HER are induced in a hybrid material, NiFeP@Ni_NC, where an ORR catalytic N-doped nanocarbon layer can protect a HER catalytic Niδ+ from the undesired ORR. Therefore, excellent bifunctional stability is secured for NiFeP@Ni_NC. The strategy to enhance HER stability presented herein can be widely extended to design bifunctional electrocatalysts with improved stability in alkaline electrolysis.

We demonstrate the dual advantages of graded photoabsorbers in mesoporous metal oxide-based hetero interfacial photoanodes in improving photogenerated charge carrier (e−/h+) separation for the solar light-driven water-oxidation process. The pre-deposition of sol–gel-derived, tungsten-doped bismuth vanadate (W:BiVO4) onto a primary BiVO4 water oxidation layer forms graded interfaces, which facilitate charge transfer from the primary photoabsorber to the charge transport layer, thereby superseding the thickness-controlled charge recombination at the BiVO4 water oxidation catalyst. As a result, the WO3/BiVO4 hetero photoanode containing the photoactive W:BiVO4 interfacial layer showed 130% higher photocurrent than that of the interfacial layer-free hetero photoelectrode owing to the enhanced charge separation led water oxidation process.

The practical implementation of the lithium metal anode is hindered by obstacles such as Li dendrite growth, large volume changes, and poor lifespan. Here, copper nitride nanowires (Cu3 N NWs) printed Li by a facile and low-cost roll-press method is reported, to operate in carbonate electrolytes for high-voltage cathode materials. Through one-step roll pressing, Cu3 N NWs can be conformally printed onto the Li metal surface, and form a Li3 N@Cu NWs layer on the Li metal. The Li3 N@Cu NWs layer can assist homogeneous Li-ion flux with the 3D channel structure, as well as the high Li-ion conductivity of the Li3 N. With those beneficial effects, the Li3 N@Cu NWs layer can guide Li to deposit into a dense and planar structure without Li-dendrite growth. Li metal with Li3 N@Cu NWs protection layer exhibits outstanding cycling performances even at a high current density of 5.0 mA cm-2 with low overpotentials in Li symmetric cells. Furthermore, the stable cyclability and improved rate capability can be realized in a full cell using LiCoO2 over 300 cycles. When decoupling the irreversible reactions of the cathode using Li4 Ti5 O12 , stable cycling performance over 1000 cycles can be achieved at a practical current density of ≈2 mA cm-2 .

We first demonstrate a facile and effective strategy to directly deposit a Nafion nanoweb onto a sulfur cathode to address the challenges underlying in Li–S batteries. The Nafion nanoweb not only blocks the diffusion of polysulfides by electrostatic repulsion but also allows fast Li-ion exchange with the sulfur cathode through the selective protection layer. The Nafion nanoweb-sulfur cathode retained an excellent cycle performance over 200 cycles and delivered an improved rate capability, as compared to a sulfur cathode and a Nafion layer-sulfur cathode.

The development of bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has recently attracted significant attention. Transition metal-based electrocatalysts have demonstrated a highly promising catalytic performance in electrochemical HER or OER. Moreover, their electrocatalytic performance can be further improved using a self-supported structure of the electrocatalyst, owing to strong physicochemical contact between the catalyst and current collector. In this context, we propose vanadium-incorporated cobalt phosphide (CoVP) self-supported catalysts on carbon cloth (CoVP@CC) as highly efficient bifunctional electrocatalysts for alkaline HER and OER. In CoVP@CC, V plays a crucial role in modulating the surface electronic structure of the self-supported CoP nanosheets, leading to excellent catalytic activity in both HER and OER. The self-supported CoVP@CC demonstrates a promising overall water-splitting performance, requiring only 1.61 V to afford a current density of 10 mA cm−2.

Metal-based frameworks are developed for lithium metal batteries due to their effective suppression of the lithium dendritic growth. However, the use of appealing metals such as copper (Cu), the best current collector in batteries, are still limited owing to lithiophobicity. Here, we report a facile lithiophilic surface treatment of metal- and metallic compound-based scaffolds via gas nitriding. Due to nitride anion (N3−) from ammonia (NH3) gas that can bond to almost all elements and form lithiophilic binary nitrides, the gas nitriding on a pristine Cu foam and a Cu(OH)2 nanorods grown Cu foam results in a formation of lithiophilic Cu3N film on the surface without a noticeable structural change. After lithium melt infusion, symmetric cells assembled with two types of lithium hosts show stable structural stability and a smooth Li plating/stripping behavior without a dendritic growth of lithium. Particularly, a full cell test demonstrates that lithiated Cu3N nanorods grown Cu foam exhibits enhanced electrochemical performances including capacity, rate capability, and cycle performance compared to a bare Li foil. Our findings demonstrate the gas nitriding is a powerful tool for lithiophilic surface treatment of metals and metallic compounds with various dimensions and sizes from micro to nanoscale.

In field-effect transistors (FETs) with two-dimensional (2D) transition metal dichalcogenide channels, the dependence of field-effect mobility on atomic layer thickness has been studied and interpreted in terms of interface scattering and interlayer coupling resistance (Rint). However, a model for 1/f noise, such as in MoS2 and in MoSe2 FETs, for various contact metals and layer number thicknesses has not been reported. In this work, we have experimentally studied current–voltage and 1/f noise on MoS2 and MoSe2 FETs with source and drain contacts of high and low work function metals to understand both the mobility and the noise behavior. We have developed a noise model incorporating layer number dependent Hooge parameters and Rint. The noise and mobility models utilize screening lengths for charge, mobility, and Hooge parameter to describe the variation of these quantities with a layer number. Using our single model topology with appropriate fitting parameters for each material and each contact metal, the model captures the experimentally observed layer thickness dependence of the Hooge parameter. Our noise analysis is fully comprehensive and, hence, could be applied to any 2D layered systems.

Transition metal layered double hydroxides (LDHs) have received much attention as high-performance oxygen evolution reaction (OER) catalysts due to their large number of active sites with favorable adsorption/desorption energies for intermittent reactants. However, the relatively sluggish charge transfer kinetics of transition metal LDHs due to their intrinsically low conductivity often hinders their use in practical applications as high-performance water oxidation catalysts. Here, we disclose a novel strategy of metalloid incorporation into transition metal LDHs, allowing us to simultaneously optimize surface electronic configuration and charge transfer between adsorbed reactants and catalyst surface. Importantly, incorporated metalloid can enhance the density of states (DOS) near the Fermi level and alter the nature of the chemical bonds in the catalytically active atoms, resulting in fast reaction kinetics. Thus, metalloid incorporation into transition metal LDHs can substantially improve the overall reaction kinetics and thermodynamics for water oxidation due to a large number of active sites and high conductivity, boosting OER performance of transition metal LDHs. The metalloid-incorporated transition metal LDHs far outperform their counterpart transition metal LDHs and even the noble metal catalyst RuO2.

Herein, holey, thin, conductive nickel substituted cobalt molybdenum boride (Ni-CMB) nanosheets have been designed to obtain superior electrochemical HER performance with small overpotential of 69 mV at 10 mA cm-2 current density and lower Tafel slope of 76.3 mV dec-1 in alkaline medium. Incorporation of Ni leads to improved conductivity and favorable hydrogen adsorption on Mo sites, which collectively yield efficient electrocatalytic H2 production from Ni-CMB catalyst. The ultrathin nature (thickness = 5.0 nm) of the designed material expectedly helps to attain high exposure of active sites and facile charge transportation through the nanosheets. Additionally, the decorated mesopores (average size = 3.86 nm) on nanosheets have benefitted towards faster electrolyte diffusion, easy gas escape from catalyst surface to support high electrocatalytic performance. Finally, well-maintained morphology of the sample and evolution of HER active sites in the material have guaranteed long-term, sustainable hydrogen production even at high current densities, which clearly demonstrate its superiority over an expensive electrolyzer (Pt-C) in alkaline water.

Citation: Kwon, J., Prakash, A., Das, S. R., & Janes, D. B. (2018). Correlating Electronic Transport and 1/f Noise in MoSe2 Field-Effect Transistors. Physical Review Applied, 10(6), 064029. https://doi.org/10.1103/PhysRevApplied.10.064029

A key issue with Na-ion batteries is the development of active materials with stable electrochemical reversibility through the understanding of their sodium storage mechanisms. We report a sodium storage mechanism and properties of a new anode material, digenite Cu

Producing clean fuel (O2 and H2) using semiconductors through solar driven water splitting process has been considered as a promising technology to mitigate the existing environmental issues. Unlike the conventional single photoabsorbers, heterostructured semiconductors exhibit the merits of improved solar light photon harvesting and rapid charge separation, which are anticipated to result in high quantum yield of solar fuel generation in photoelectrochemical (PEC) cells. In this report, we demonstrate the electrospun derived WO3 backbone fibrous channel as heteropartner to the primary photoabsorber (Fe2O3 and BiVO4) for promoting the electron transport from charge injection point to charge collector as well as photoholes to the electrolyte. We examine structure, optical, photoelectrochemical and charge transfer property of Fe2O3/WO3 and BiVO4/WO3 electrodes. These results were compared with directly coated Fe2O3 and BiVO4 photoabsorber onto conducting substrate without WO3 backbone. The optical results showed that the absorbance and visible light activity of Fe2O3 and BiVO4 is significantly improved by WO3 backbone fibers due to high amount of photo absorber loading. In addition, one dimensional (1-D) WO3 fibers beneficially enhance the optical path length to the photoanode through light scattering mechanism. The electrochemical impedance analysis exhibits WO3 nanofiber backbone reduces charge transfer resistance at Fe2O3 and BiVO4 by rapid charge collection and charge separation compare to backbone-free Fe2O3 and BiVO4. As a result, Fe2O3/WO3 and BiVO4/WO3 fibrous hetero interface structures showed fourfold higher photocurrent generation from PEC cell.

Objectives: We investigated mutation profiles of CALR , JAK2 , and MPL in 199 Korean patients with myeloproliferative neoplasms (MPNs). Methods: In total, 199 patients with MPN (54 primary myelofibrosis [PMF], 79 essential thrombocythemia [ET], 58 polycythemia vera [PV], and eight MPN-unclassifiable [MPN-U]) and 4 patients with acute panmyelosis with myelofibrosis (APMF) were retrospectively subjected to Sanger sequencing for CALR , JAK2 , and MPL . Results: The overall frequency of CALR mutations was 12.6% (type 1 mutation, 16 patients; type 2 mutation, nine patients): most frequent in MPN-U (37.5%), followed by ET (17.7%) and PMF (14.8%). CALR mutations were not found in PV or APMF. CALR and JAK2 or MPL mutations were mutually exclusive. In PMF, the CALR mutations were associated with lower levels of leukocytes, lower bone marrow cellularity, and higher number of megakaryocytes. Patients with CALR -mutated ET more frequently progressed to the accelerated or blast phases compared with patients with JAK2 mutations. CALR mutations were frequently observed in the JAK2 -negative MPNs, most frequently in MPN-U. Conclusions: The prognostic significance of CALR mutations likely differs among the MPN subtypes.

H0.43Ti0.93Nb1.07O5 engineered with large d-spacing of ~8.3 Å and two-dimensional ionic channels enables easy Na+ ion uptake., Key issues for Na-ion batteries are the development of promising electrode materials with favorable sites for Na+ ion intercalation/deintercalation and an understanding of the reaction mechanisms due to its high activation energy and poor electrochemical reversibility. We first report a layered H0.43Ti0.93Nb1.07O5 as a new anode material. This anode material is engineered to have dominant (200) and (020) planes with both a sufficiently large d-spacing of ~8.3 Å and two-dimensional ionic channels for easy Na+ ion uptake, which leads to a small volume expansion of ~0.6 Å along the c direction upon Na insertion (discharging) and the lowest energy barrier of 0.19 eV in the [020] plane among titanium oxide–based materials ever reported. The material intercalates and deintercalates reversibly 1.7 Na ions (~200 mAh g−1) without a capacity fading in a potential window of 0.01 to 3.0 V versus Na/Na+. Na insertion/deinsertion takes place through a solid-solution reaction without a phase separation, which prevents coherent strain or stress in the microstructure during cycling and ensures promising sodium storage properties. These findings demonstrate a great potential of H0.43Ti0.93Nb1.07O5 as the anode, and our strategy can be applied to other layered metal oxides for promising sodium storage properties.

We demonstrate the dual advantages of graded photoabsorbers in mesoporous metal oxide-based hetero interfacial photoanodes in improving photogenerated charge carrier (e

Here we report the fabrication of a novel three-dimensional conjugated porous polymer (CPP–P1) developed by a palladium-catalysed Sonogashira poly-condensation reaction. The solid polymer was thoroughly characterized by 13C cross-polarization solid-state NMR and X-ray photoelectron spectroscopy (XPS). The pristine nitrogen-containing CPP was explored as an electrocatalyst for the oxygen reduction reaction (ORR) in alkaline media 0.1 M KOH. We observed that in the case of pristine polymer CPP-P1 oxygen reduction occurs through four electron transfer pathway with excellent stability and good tolerance to methanol. The detailed molecular-level structure for oxygen reduction and mode of oxygen binding site to the polymer was explained by density functional theory (DFT) calculation.

In spite of the promising future of the Sodium (Na)-ion batteries (NIBs), it still suffers with low specific capacity and stability mostly owing to the slow kinetics associated with Na ion. In this regard, transition metal sulfides (TMSs) are considered to be one of the best anode materials that can efficiently store Na ions not only owing to their graphite-like layered structure but also through conversion reactions facilitated by their multi-oxidation states. However, the poor cyclic stability of these TMSs attributed to the low electronic conductivity of the TMSs hinders the practical use. Therefore, understanding on an optimized mass loading (or physical dimensions) and configuration of such active electrode material are essential to improve the kinetics associated with Na-ion and electron pathway. To study this, plasma-enhanced atomic layer deposition (PEALD) is employed to grow WS2 using tungsten hexacarbonyl [W(CO)6] and H2S plasma as a precursor and reactant, respectively. The thin films of WS2 deposited directly on stainless steel coin with varying ALD cycles (200–600) are then tested as anode in NIBs without any binder or conducting carbon. Two-stage growth mode is observed with increasing number of ALD cycles which leads to WS2 nano-flakes formation on top of a two-dimensional film of the same. Reversible conversion and intercalation reactions from the cyclic voltammetry measurements are evident for the electrochemical stability of these pristine-WS2 films. While the highest areal capacity of ∼58.8 μAh/cm2 at a current density of 50 μA/cm2, after 50 charge-discharge cycles, is achieved with 400 ALD cycles, the highest capacity retention (∼72.5%) is observed for the film deposited with minimum (200) ALD cycles under same conditions. However, the capacity as well as its retention degrades drastically when the number of ALD cycles is further increased beyond 400. In this study, we address a critical issue associated with WS2 as an anode material for NIBs which should be similarly true for other TMSs as well.

Low-frequency noise studies in transition metal dichalcogenides have considered the layer-thickness dependence but generally do not separate channel contributions from those of contact/access regions. Here, we study the voltage-dependent 1/f noise and the resistance correlation in MoS2 FETs with an ∼142 atomic layer-thickness channel and three different lengths. The gate-voltage dependence of noise can be separated into a channel contribution, with a comparable Hooge parameter for the three devices and a contact/access region contribution. Separation of these contributions allows the evaluation of the channel noise mechanism and can be used to explain the length-dependence of the transition region between contact- and channel-dominated regimes.

A new method of fabricating translucent alumina brackets using powder injection molding (PIM) is reported. Alumina powder was mixed with MgO, La 2 O 3 , and Y 2 O 3 to control grain size and porosity. The powders were mixed with a binder consisting of a mixture of paraffin wax and polyethylene in a 1:1 ratio to make feedstock for injection molding. The total amount of binder was limited to 14 wt% to minimize shrinkage and cracking after sintering. After injection molding, debinding was performed using the wicking method and samples were sintered in a vacuum at 1700 °C to achieve high density. Ultimately, translucent corundum was fabricated. The sintering additives resulted in a decrease in porosity and an improvement in translucency by promoting grain growth during pressure-less sintering. After sintering, Vickers hardness, bending strength, density, and transmittance of the fabricated parts were measured to show that those values were comparable to those of the commercially available dental brackets. Therefore, the translucent alumina block was successfully fabricated using PIM method to be potentially used as a dental bracket.

Porosity of transition metal oxides makes their unique physicochemical properties for using energy storage. However, synthesizing active materials by a simple method is still hard to develop without sacrificial templates. In this regard, we report a synthesis of hollow TiNb2O7 nanotubes through dual nozzle electrospinning as a high power anode material for LIBs. The porosity of hollow TiNb2O7 nanotube was controlled by molar ratios of acetic acid to Ti/Nb alkoxide precursors and degree of Ti/Nb metal hydroxides formation in electrospun fibers. The TiNb2O7 nanotubes have the average diameter of 260 nm and a surface area in the range of 52–151 m2g-1. Moreover, the porous nanotubes consist of micropores below 2 nm and mesopores in the range of 5–60 nm in their walls that are connected to the inner hole with a diameter of 150 nm. Particularly, the unique structure of the nanotubes shows a high discharge capacity of 294 mAh g-1, stable cycle performance of 86% capacity retention over 700 cycles, and superior rate capability of 230 mAh g-1 at high 50C. Our strategy confirmed a facile synthesis of porous TiNb2O7 nanotubes without templates and the potential to use of high power anode material for LIBs.

Lithium sulfur (Li-S) batteries have drawn much attention as next-generation batteries because of their high theoretical capacity (1672 mAh g−1), environmental friendliness and low cost. However, several critical issues, which are mainly associated with the polysulfide shuttling effect, result in their poor electrochemical performance. Carbon-modified separators have been introduced to attempt to address these systemic challenges. However, this approach focused only on the suppression of dissolved polysulfides on the cathodic side without considering the further entrapment of polysulfides on the anodic side. In this study, we first designed a multifunctional trilayer membrane comprising a carbon layer and a boron nitride (BN) layer to facilitate the electrochemical performance of Li-S batteries and protect the Li anode from unexpected side reactions. When a BN-carbon separator was employed, the sulfur cathode delivered stable capacity retention over 250 cycles and an excellent specific capacity (702 mAh g−1) at a high current density (4 C). The BN-carbon separator also facilitated the uniform plating/striping of Li and, thus, suppressed the severe growth of dendritic Li on the electrode; this led to the stable operation of the Li anode with a high Coulombic efficiency and improved cycling performance. A membrane that enhances the performance of high-capacity lithium–sulfur batteries has been developed by a team in Korea and the USA. Adding sulfur to lithium-ion batteries is predicted to improve their storage capacity, but in practice the number of times a battery can be charged and discharged is limited by the formation of compounds called polysulfides, which corrode the lithium anode. Now, Ungyu Paik from Hanyang University and co-workers have shown that using a three-layer membrane made of carbon, a polymer and boron nitride can limit this problem. Unlike previous carbon-modified separators, the trilayer membrane both suppresses dissolution of polysulfides on the cathode side and protects the anode from unwanted side reactions. The separator enabled the sulfur cathode to maintain a stable capacity over 250 cycles. The BN-carbon separator was first demonstrated as a multifunctional trilayer membrane to facilitate the better electrochemical performances of Li-S batteries and protect a Li anode from unexpected side reactions. Unlike the previous approach to block the polysulfides only within the cathodic side, the concept of placing a BN interlayer on anodic side showed promising results in achieving high electrochemical performances of Li-S batteries and stable operations of lithium metal at a high current density.