Transmission Electron Microscopy-energy Dispersive Spectroscopy Research Articles

Titanium Silicon Nitride Films With Low Silicon Content Deposited via Reactive High-Power Pulsed Sputtering Penning Discharge

Reactive high-power pulsed sputtering Penning discharge at a total pressure of 0.7 Pa and an N2 fraction of 20% in gas phase was used to synthesize titanium silicon nitride (TiSiN) films. The content ratio ( $R_{\mathrm {TS}}$ ) of Si in a target containing a Ti component and an Si component was varied from 0% to 15%. The properties of the as-deposited films were compared with those of the films deposited on high-temperature substrates. The chemical compositions and bonding states of the films were investigated via X-ray photoelectron spectroscopy (XPS). Film structure was evaluated via X-ray diffraction (XRD) and transmission electron microscopy-energy dispersive X-ray spectroscopy. Through XPS, the relative content ratio of Si to Ti was found to increase from 0% to ~25% with increasing $R_{\mathrm {TS}}$ , and the nitrogen content ranged between 47.5% and 50% for all films. The grain size of the films deposited at an $R_{\mathrm {TS}}$ lower than 10% was estimated using the XRD peak of the (111) orientation and found to be ~10 nm. The hardness and elastic modulus of the films deposited on high-temperature substrate at an $R_{\mathrm {TS}}$ value of 8% had the highest values of 43 and 360 GPa, respectively.

Improved analysis methods to study the behavior of potassium ions in the interlayer of montmorillonite

The behavior of potassium chloride (KCl) as a main mud shale inhibitor remains poorly defined in the interlayer of montmorillonite (Mt). In this paper, a new analysis method of transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) was established. The distribution of K+ in the interlayer of Mt and the processes surrounding d-spacing shifts in Mt were investigated through X-ray diffraction and TEM-EDS. The experimental results revealed shoulder peaks in the diffraction patterns at KCl concentrations between 11% and 19%. The distribution of K+ varied in the inner and outer layers of Mt with different KCl concentrations. It could be concluded that the distribution of K+ and the changes in d-spacing of Na are determined by two factors: negative charge sites and concentration difference. When the KCl concentration was below 8%, both factors cause the outer layer of Mt to adsorb more K+ than the inner layer, with all layers exhibiting d-spacings within the 1.50nm state. At an 8% KCl concentration, all negative charge sites were occupied by K+. As the KCl concentration rose above 8%, the outer layer of Mt adsorbed more K+ than the inner layer due to the concentration difference. With a further increase in the KCl concentration, the d-spacing shifted linearly to 1.30nm from the outer to the inner layer of Mt. All layers of Mt exhibited a d-spacing of 1.30nm at KCl concentrations of up to 23%. These results demonstrate the benefits and capabilities of the proposed method in investigating the intercalating mechanisms of Mt.

Study on the cross-sectional microstructure of a thin ceramic coating on stainless steel surface fabricated by the application and calcination of an aqueous clay mineral paste

In this study a technique is described that enables the ceramic coating on stainless steel with good adhesion via a simple application, drying, and calcination process using an aqueous paste based on clay mineral dispersion. On the basis of this technique, the cross-sectional microstructure of the interfacial area between the clay-derived ceramic coating and stainless steel was analyzed in detail, and the mechanism behind the coating of the ceramic layer with good adhesion was investigated. From the results of elemental mapping using transmission electron microscopy, scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, it was discovered that iron from the stainless steel diffuses into the ceramic coat, and the specific passivation film of the stainless steel integrates with the clay mineral-derived ceramic coating during the calcination, revealing that such chemical reactions are effective in promoting strong adhesion between the coat and stainless steel surface. In addition, a unique advantage of using this coating method was discovered in that even if there are small natural scratches on the raw stainless steel, the clay mineral paste can be used to cover these, resulting in a good, flat surface.

Preparation and characterization of selenized Astragalus polysaccharide and its inhibitory effect on kidney stones.

Astragalus polysaccharide (APS) was modified using the Na2SeO3/HNO3 method to obtain selenized APS (Se-APS) with a selenium content of 1.75mg/g. The structure and physicochemical properties of APS and Se-APS were investigated through transmission electron microscopy-energy dispersive spectroscopy mapping, fourier transform infrared spectroscopy, nuclear magnetic resonance, nano-zetasizer analysis, atomic force microscopy, and scanning electron microscopy. APS and Se-APS did not exhibit toxic effects on human kidney proximal tubular epithelial (HK-2) cells and were able to remove hydroxyl and DPPH radicals, alleviate the damage caused by calcium oxalate (CaOx) monohydrate (COM) crystals to HK-2 cells, reduce intracellular reactive oxygen species levels, and restore cell viability and morphology. Both APS and Se-APS could inhibit COM growth, induce calcium oxalate dihydrate formation, and increase the absolute zeta potential of the crystals to inhibit crystal aggregation. However, the ability of Se-APS to regulate CaOx crystals and protect the cells from COM-induced damage was better than that of APS. These results suggested that Se-APS might be a candidate drug for the treatment and prevention of kidney stones.

Insight into the Correlations Between Fiber Dispersion and Physical Properties of Chrome Tanned Leather

The correlations between fiber dispersion and physical properties of chrome tanned leather were investigated to provide new insights into improving leather quality and designing tanning agents and tannages. Wet blues were prepared by tanning pickled pelts with different amounts of chrome powder, and their pore structures in the range of 5.48 nm–120 ?m were measured using a mercury intrusion porosimetry (MIP). The porosity and total pore area of wet blue increased with increasing amount of chrome powder from 2% to 8%. These MIP data combined with the images observed using a field emission scanning electron microscopy and a scanning transmission electron microscopy–energy dispersive spectroscopy indicated that chrome tanning agent opened up the microfibrils, fibrils, elementary fibers and fiber bundles of wet blue. The sufficient fiber dispersion of wet blue was attributed to the fact that chrome tanning agent penetrated into the microfibrils and fixed collagen fibers from microfibril level to fiber bundle level. The wet blues were then fatliquored to prepare crust leathers. The tensile strength, tear strength, elongation at break, softness, fullness and water vapor permeability of the leathers improved with increasing chrome powder. These results implied that there is a positive correlation between fiber dispersion and physical properties of chrome tanned leather.

Pitting Corrosion and Passive Behavior of Type AISI 304-based Borated Stainless Steels in a Boric Acid Solution

Pitting corrosion resistance and passive films of Febalance-18Cr-12Ni-1.5Mn-0.07C-based alloys containing 0.19, 0.78, and 1.76 wt% B were investigated through potentiodynamic polarization tests and scanning transmission electron microscopy—energy dispersive spectroscopy analyses, respectively, in NaCl and H3BO3 solutions. The addition of B lowered the resistance to pitting corrosion due to the increase in the volume fraction of (Cr,Fe)2B. For the alloy with a large volume fraction of (Cr,Fe)2B, the resistance to pitting corrosion in the NaCl solution was improved due to the addition of H3BO3, as H3BO3 assisted passivation and raised the Cr fraction in the passive film.

The formation kinetics of Cr2O3dispersed Cu synthesized by Cryo-milling

AbstractNano-crystalline (nc) Cu with Cr2O3dispersoid (~4 vol.%) was successfully made by reactive-milling at 210 K with a mixture of pure Cu, Cu2O, and Cr powder. The vacuum hot pressing (HP) was performed at 1123 K and 50 MPa for 2h to consolidate the milled powder for further analysis. TEM (Transmission Electron Microscopy) work revealed that the HPed materials were comprised with a mixture of the nc-Cu and a homogeneous distribution of Cr2O3dispersoids. The microstructure and Vickers hardness of the as-milled powder and the HPed materials were characterized by standard metallographic techniques. The grain size of the Cu was measured using Scherrer’s formula (XRD) and TEM observation; the Cr2O3dispersoid size was estimated from the HADDF (High Angle Annular Dark Field) images and element mapping by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy) works. The formation kinetics and coarsening of the Cr2O3dispersoids in Cu matrix were discussed based on the calculations with thermodynamic parameters in comparison with those of Al2O3.

Improved Catalytic Performance of Ethane Dehydrogenation in the Presence of CO2 over Zr-Promoted Cr/SiO2.

The Zr-, Ce-, Sr-, and Sn-promoted Cr/SiO2 catalysts were prepared by the incipient wetness impregnation method, then characterized by N2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, H2-TPR, CO2-TPD, UV–vis, high-angle annular dark-field imaging–scanning transmission electron microscopy—energy dispersive X-ray spectroscopy elemental mapping, Raman, and thermogravimetric techniques to study the structural evolution under the preparation/reaction conditions, and applied to catalyze ethane oxidative dehydrogenation with CO2. The results suggested that the Cr6+ species were indispensable for activating the dehydrogenation reaction thanks to the oxidation–reduction cycle between Cr6+ and Cr3+. The type of the promotor also affected significantly the ability of replenishing the lattice oxygen through the disassociation of CO2, leading to the different catalytic performances. The Zr-promoted sample had the best performance in converting the reactants as well as the catalytic stability.

Rapid and Eco-Friendly Synthesis of Red Fluorescent Gold Nanoclusters for Sensing and Anti-Counterfeiting Applications

A rapid and eco-friendly synthesis method for the preparation of gold nanoclusters (Au NCs) with strong red emission has been developed. A one-pot microwave (MW) irradiation method yields bright red-emitting Au NCs, providing an easy route for the synthesis of fluorescent Au NCs without the need for a tedious operation, time-consuming procedure, or the use of toxic/corrosive agents and harsh conditions. The as-prepared Au NCs show a small-sized distribution, good dispersibility and a broad excitation band (from UV light to visible light). The optimal experimental conditions, including concentrations and order of addition of Na2CO3, bovine serum albumin (BSA), and HAuCl4and the time of MW irradiation, were investigated in detail. The as-synthesized Au NCs were well characterized by fluorescence spectroscopy, UV-Vis spectroscopy, infrared spectroscopy, high-resolution transmission electron microscopy-energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Due to favorable photoluminescence features as well as minimal toxicity, the Au NCs could be applied to sensing, patterning and anti-counterfeiting. The Au NCs displayed strong red emission that was efficiently quenched by hydrogen peroxide (H2O[Formula: see text]. More strikingly, the obtained Au NCs were used as a fluorescent ink for producing luminescent handwriting and patterns, which may expand the potential applications of Au NCs in the fabrication of security inks.

Characterization of stoker ash from the combustion of high-lanthanide coal at a Kentucky bourbon distillery

Lanthanide- and yttrium-bearing minerals were examined by transmission electron microscopy - energy-dispersive spectroscopy (TEM-EDS) and related diffraction techniques in the combustion ash produced from the burning of an eastern Kentucky coal in a stoker boiler. The feed coal has nearly 2000 ppm and the stoker ash has over 1400-ppm lanthanides + Y + Sc In one section, zircon with trace amounts of Y was noted. Hafnium was noted in the preliminary scanning electron microscopy - EDS examination of a zircon. In the TEM procedure, the Hf peaks overlap with other peaks and, thus, the presence of Hf could not be confirmed. Both La-, Ce-, Nd-monazite and a La-, Ce-bearing Ti-Fe mineral were observed in the ash. The latter mineral corresponds both in composition and in aspects of the diffraction pattern to crichtonite or davidite or loveringite, all minerals within the Dana-class crichtonite group.

Evaluation of potential reaction between BaZr0.8Y0.2O3-δ ceramics and Pt at high temperatures

BaZr0.8Y0.2O3-δ (BZY20) is found to react with Pt at high temperatures, although Pt is generally regarded as an inert material that prevents its reaction with many materials even at high temperatures. The reaction between BZY20 with Pt is difficult to be confirmed by X-ray diffraction (XRD) analysis as no observable secondary phase can be detected even after high-temperature treatment. However, the obvious color change of the fired BZY20 powder implies the potential reaction. Therefore, transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) and X-ray photoelectron spectroscopy (XPS) techniques are used to have an insightful analysis of the material. TEM-EDS result indicates that there is an existence of Pt element in the BZY20 powder after firing, suggesting a Pt diffusion into the BZY20 lattice. XPS analysis results further confirm the content of Pt4+ and Pt2+ in the BZY20 powder after firing and the content of Pt4+ increases with the increase of firing temperatures, and the increase of Pt4+ content lowers the O1s binding energy, which might be beneficial for the proton migration.

Kinetics of interfacial microstructural variation across insulator-thermoelectric semiconductor interface and its effects on thermoelectric properties of magnesium silicide thin films

Thermoelectric semiconductor magnesium silicide epitaxial films were fabricated on insulating (001) alumina (Al2O3) and (111) magnesium oxide (MgO) substrates using low temperature (220 °C) RF magnetic sputtering followed by high temperature (500 °C) annealing. Cross sectional studies of interfaces by bright field transmission electron microscopy reveals the formation of an interfacial region over a length scale of ∼30 to 120 nm for films deposited on MgO substrate and magnesia buffered Al2O3 substrates. A more detailed analysis using scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) studies clearly showed that Mg2Si film grown on magnesia buffer and MgO substrate indicate the formation of O and Si rich interfacial layer over a range of length scales (30–120 nm), while there is no such formation for the film deposited on Al2O3 substrate. The electrical conductivity of the film deposited on alumina substrate shows ∼60% higher value than the film on magnesia substrate. Further, the Seebeck coefficient measurement showed almost similar magnitude, at the same time of opposite polarity between film on alumina substrate (positive) and the film on magnesia substrate (negative). Changes in the carrier concentration arising due to the formation of an interfacial layer can be primary influence for the observed anomaly between two films. The theoretical modeling based on standard space charge kinetics across the multi-layer structures comprising alumina substrate-magnesia buffer-Mg2Si thin film, clearly indicates the possibility of oxygen migration from magnesia buffer layer when annealing temperature is increased above ∼750 °C.

Modulating Ferroelectric Response in Colloidal Semiconductor Nanocrystals through Cation Exchange

We report the appearance of ferroelectric behavior in CdSSe nanocrystals arising from a room-temperature cation exchange of semiconductor nanoparticles. Cation exchange reactions were performed on colloidal CdSSe nanocrystals using antimony, tin, and gold salts. The degree of exchange was determined using scanning transmission electron microscopy–energy-dispersive spectroscopy and the ferroelectric response was measured using a Sawyer-Tower circuit. As the percent exchange of tin(IV) was varied, the ferroelectric properties were optimized at ∼30 and 70% as a result of intracrystal atomic displacements. The amount of disorder can be minimized by selecting the exchange cation that exhibits the largest change in saturation polarization with the least amount of exchange. The ability to tune the structure and ferroelectric response of nanostructures could offer new routes toward the development of ferroelectric random-access memory devices as well as lower the cost of energy-harvesting applications.

Highly Uniform Resistive Switching in HfO2 Films Embedded with Ordered Metal Nanoisland Arrays

AbstractMemristors enter a critical developmental stage where emerging large‐scale integration methods face major challenges with severe switching instabilities in the oxide layer. Here, the superior uniformity is achieved within HfO2 films by embedding highly ordered metal nanoisland (NI) arrays. Embedded films exhibit a significant reduction in both SET and RESET while displaying enhanced uniformity in operating voltages and resistance states. This behavior is attributed to the concentration of electric fields along Pt and Ti NIs and their interactions with the surrounding oxide film matrix environment, which induce separate and distinct filamentary formation mechanisms that affect the stability. A method is reported to further optimize the uniformity of the SET voltage by translating the NI array position down the film‐thickness dimension towards the bottom electrode. A comparison of the density and distribution of the oxygen vacancies responsible for the formation/dissolution of conducting filaments is made via combined electrostatic force microscopy and conductive atomic force microscopy (c‐AFM) studies. Finally, complete observation of the morphological evolution of conducting filaments produced by Pt and Ti is enabled by 3D c‐AFM nanotomography and cross‐sectional scanning transmission electron microscopy–energy dispersive spectroscopy to provide direct correlations between NI‐oxide interactions and overall switching performance.

Nanoconfined Hydrated Zirconium Oxide for Selective Removal of Cu(II)-Carboxyl Complexes from High-Salinity Water via Ternary Complex Formation.

Toxic metals are usually present as organic complexes in high-salinity effluents from various industries. The efficient removal of such metal complexes is an imperative but still challenging task due to their stable structure and high mobility. Herein, we propose a new strategy to remove Cu-carboxyl complexes from high-salinity water by using a commercially available nanocomposite HZO-201, i.e., nanohydrated zirconium oxide (HZO) confined inside anion exchanger D201. In contrast to D201 and a cation exchanger D001, which both adsorb Cu-citrate negligibly, HZO-201 exhibits preferable adsorption toward Cu-citrate (∼130 mg Cu/g-Zr) at high salinity (1.5 wt % NaCl). On the basis of scanning transmission electron microscopy energy-dispersive spectrometry (STEM-EDS), attenuated total reflection Fourier transform infrared (ATR-FTIR), and X-ray photoelectron spectrometry (XPS) analysis, the formation of ternary complex among Cu(II), citrate, and the embedded nano-HZO is evidenced to be responsible for the removal of Cu-citrate. The exhausted HZO-201 can be regenerated with a binary HCl-NaCl solution for repeated use for 5 cycles without capacity loss. Fixed-bed adsorption demonstrates that HZO-201 column is capable of producing ∼1150 bed volume (BV) clean water (<0.5 mg Cu/L) from simulated high-salinity wastewater, whereas only ∼10 BV and ∼60 BV was produced for the D001 and D201 columns, respectively. Furthermore, HZO-201 shows excellent removal of Cu(II) complexes with three other carboxyl ligands (oxalate, tartrate, and succinate).

Mechanochemical synthesis and characterisation of niobium silicide nanoparticles

Mechanochemical synthesis (MCS) investigations of niobium silicide powders in Nb2O5SiO2Mg powder mixtures were conducted via high-energy ball milling and leaching by means of process parameters such as the milling duration, initial Nb2O5 crystal structure, and excess Mg amount. The compositional, thermal, and microstructural properties of the products were characterised using X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), particle size analysis (PSA), stereomicroscopy (SM), scanning electron microscopy (SEM), and transmission electron microscopy/energy-dispersive spectrometry (TEM/EDS). After the 5 h milling of the stoichiometric mixtures, an instantaneous ignition occurred and NbSi2, Nb5Si3, Nb, and MgO phases formed with some residual Mg. In addition, the use of excess Mg inhibited the formation of Nb5Si3. Afterwards, leaching treatments (in a 4 M HCl solution) completely removed the Mg-based phases from the synthesised products. The XRD calculations revealed that the resultant product consisted of 97 wt% NbSi2 and 3 wt% Nb5Si3 phases. The TEM analyses indicated that each Nb silicide nanoparticle was coated with a SiO2 layer. According to random measurements, the average particle size of the Nb silicide cores and average thickness of the SiO2 layer were approximately 61 and 7.5 nm, respectively.

Mesoporous SiO2/BiVO4/CuOx nanospheres for Z-scheme, visible light aerobic C–N coupling and dehydrogenation

In light of the growing demand to use renewable energy, we have synthesized a mesoporous bismuth vanadate-copper oxide-silica photocatalyst (SiO2/BiVO4/CuOx) to act as a chromophore in a Z-scheme system. These photocatalysts are intended for effective light harvesting and charge separation in the synthesis of solar chemicals, using air as an environmentally benign oxidant. Full characterization of the SiO2/BiVO4/CuOx was conducted, including X-ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS), and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), which confirm the presence of CuOx at the heterojunction of the nanostructures. The other characterization methods that were employed included powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), elemental mapping, UV–vis diffuse reflectance spectroscopy (UV–vis DRS), N2 sorption experiments, photoluminescence spectroscopy (PL), electrochemical impedance spectroscopy (EIS), and photocurrent measurements. Notably, the SiO2/BiVO4/CuOx nanospheres perform seven times faster than bulk BiVO4 and provide higher yields for the oxidative coupling of amines to imines, which are valuable precursors for agrochemicals and active pharmaceutical ingredients. The superior photocatalysis of SiO2/BiVO4/CuOx is attributed to the surface CuOx nanoparticles that increase the average PL lifetime from 2.3 to 4.5ns, which improved the charge separation and decreased the unproductive recombinations of electron–hole pairs. In addition, the photocurrent density of the SiO2/BiVO4/CuOx electrode was about 3.5 times higher than that of SiO2/BiVO4, while lower charge transfer resistance was observed by EIS. Meanwhile, chemical scavenging experiments revealed that holes and superoxide radicals were the main reactive oxygen species in the photocatalytic reaction. The nanospheres also show broad functional group tolerance, good recyclability with high conversions, and high to moderate yields for the oxidatively coupled imine products after eight runs. Thus, we demonstrate that an effective and green approach in artificial photosynthesis is applicable for organic synthesis as well.

Synthesis, characterisation and water-gas shift activity of nano-particulate mixed-metal (Al, Ti) cobalt oxides.

The formation of mixed-metal cobalt oxides, representing potential metal-support compounds for cobalt-based catalysts, has been observed at high conversion levels in the Fischer-Tropsch synthesis over metal oxide-supported cobalt catalysts. An often observed increase in the carbon dioxide selectivity at Fischer-Tropsch conversion levels above 80% has been suggested to be associated to the formation of water-gas shift active oxidic cobalt species. Mixed-metal cobalt oxides, namely cobalt aluminate and cobalt titanate, were therefore synthesised and tested for potential catalytic activity in the water-gas shift reaction. We present a preparation route for amorphous mixed-metal oxides via thermal treatment of metal precursors in benzyl alcohol. Calcination of the as prepared nanoparticles results in highly crystalline phases. The nano-particulate mixed-metal cobalt oxides were thoroughly analysed by means of X-ray diffraction, Raman spectroscopy, temperature-programmed reduction, X-ray absorption near edge structure spectroscopy, extended X-ray absorption fine structure, and high-resolution scanning transmission electron microscopy. This complementary characterisation of the synthesised materials allows for a distinct identification of the phases and their properties. The cobalt aluminate prepared has a cobalt-rich composition (Co1+xAl2-xO4) with a homogeneous atomic distribution throughout the nano-particulate structures, while the perovskite-type cobalt titanate (CoTiO3) features cobalt-lean smaller particles associated with larger ones with an increased concentration of cobalt. The cobalt aluminate prepared showed no water-gas shift activity in the medium-shift temperature range, while the cobalt titanate sample catalysed the conversion of water and carbon monoxide to hydrogen and carbon dioxide after an extended activation period. However, this perovskite underwent vast restructuring forming metallic cobalt, a known catalyst for the water-gas shift reaction at temperatures exceeding typical conditions for the cobalt-based Fischer-Tropsch synthesis, and anatase-TiO2. The partial reduction of the mixed-metal oxide and segregation was identified by means of post-run characterisation using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy energy-dispersive spectrometry.

Phase stability of single phase Al0.12CrNiFeCo high entropy alloy upon irradiation

Phase stability of NiCoFeCr and Al0.12NiCoFeCr single phase high entropy alloys (HEAs) was studied under 3 MeV Ni2+ irradiation at 500 °C to a fluence of 1 × 1017/cm2 reaching a peak dose of ~100 displacements per atom (dpa). Transmission electron microscopy (TEM) diffraction pattern and scanning transmission electron microscopy-energy dispersive X-Ray spectroscopy (STEM-EDS) were utilized to detect any second phases that formed in the irradiated regions of the specimens. While the single phase of NiCoFeCr alloy has remained stable under the irradiation, the phase in Al0.12NiCoFeCr alloy decomposed into FCC matrix phase, and Ni3Al type nanoprecipitates with L12 ordered structure. On the other hand, in Al0.12NiCoFeCr alloy, the non-irradiated region of the TEM specimen (annealed for 10 h at 500 °C) and the as-cast alloy annealed for 490 h at 500 °C exhibited no such precipitates similar to those observed in the irradiated region. Based upon the thermodynamic stability of these alloys, we propose that radiation-enhanced diffusion under the irradiation accelerated the formation of the Ni3Al type equilibrium phase. Our study clearly demonstrates that the phase stability of HEAs under irradiation should be considered as one of the deciding factors in the materials design and selection for nuclear applications.

Catalytic Activities of Mono- and Bimetallic (Gold/Silver) Nanoshell-Coated Gold Nanocubes toward Catalytic Reduction of Nitroaromatics.

A new class of core-shell metallic nanostructures with tunable near-surface composition and surface morphology with excellent catalytic activity is reported. Very thin shells of metal nanoassemblies such as monolayer (Ag and Au), bilayer of Ag or Au, and AgAu alloy layer with controlled size and morphology were deposited onto a gold nanocube (AuNC) core. UV-vis absorption spectroscopy and high-resolution transmission electron microscopy analyses along with selected-area electron diffraction, energy dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometer, and X-ray diffraction techniques were used to characterize the prepared core-shell nanocubes. High-angle annular dark field scanning transmission electron microscopy-energy dispersive X-ray spectroscopy mapping images were recorded for the bilayer shell and alloy layer shell in the core-shell nanostructures. Reduction of 4-nitroaniline in the presence of sodium borohydride was chosen to validate the catalytic activity of the prepared core-shell metal nanocubes. Interestingly, the AgAu alloy shell layer over the AuNC (AuNC1@Ag0.25Au0.25) showed excellent catalytic activity compared with the pristine AuNC and monolayer and bilayer core-shell nanostructures.