Search

This study investigates the surface functionalization of plastic substrates through dip‐coating in azide‐functionalized polymer solutions, followed by a click reaction (i.e., strain‐promoted azide–alkyne cycloaddition). Acrylic, poly(ethylene terephthalate) (PET), and nylon substrates are dip‐coated with a series of polymers containing various azide groups grafted onto the poly(methyl methacrylate‐co‐hydroxyethyl methacrylate) backbone to examine structural effects on the surface density of clickable azide groups. X‐ray photoelectron spectroscopy and fluorescence spectroscopy confirm the subsequent click‐immobilization of cycloalkyne‐tagged fluorescein, which is quantified to calculate the surface density of clickable azide groups. Further investigations demonstrate that the surface density of azide groups can be controlled by manipulating the polymer ratio during dip‐coating, thus enabling the preparation of a linear surface gradient in terms of azide group density. Finally, the microcontact printing (µCP) method is employed to pattern the functionalized surfaces and quantify the functional molecules immobilized on the surface by µCP. This study highlights the adaptability of click chemistry and polymer coating techniques for the advanced functionalization of plastic surfaces for materials science and engineering applications. [ABSTRACT FROM AUTHOR]

Durable functionalization on polypropylene (PP) surfaces is always a key problem to besolved. Coatings with low surface energy peel off easily especially under extreme conditions, owing to their weak adhesion. In this paper, side groups of both polyhedral oligomeric silsesquioxane (POSS) and alkane are grafted to polypentafluorophenyl methacrylate (PFP), and then PP blends with these side‐group modified PFP are obtained through a melt‐blending process. It is found that POSS can result in surface segregation and provide hydrophobicity in blends. Microfibers are formed because of the orientation effect during the tensile testing, which furtherly promotes mechanical strength. Significantly, alkaneside‐groups can be entangled with PP segments, which brings about cross linking. Therefore, with crosslinking and synchronous orientation of POSS, the elongation at the break of blends is greatly increased up to 974%. The final blend demonstrates quite durable hydrophobicity under many extreme conditions, such as repeated tape peeling, ultrasonic washing, strong friction, and soaking in strong acid (pH = 1), strong alkali (pH = 14) and alcohol. The heat and UV resistance of the blend are also obviously improved. This study will develop anovel and facile strategy to endow PP with durable hydrophobicity as well as greatly enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

To study the influence of the surface roughness and eutectic silicon segregation on the anodising of diecast Al-Si-Cu alloys, an AlSi11Cu2(Fe) alloy was high-pressure diecast and hard anodised. The microstructure and surface topography of milled and grit-blasted regions were investigated to analyse their effect on the growth of the anodic layer. The surface mechanical properties of the anodised surfaces were also studied. The results showed how high surface roughness and silicon segregation present in the grit-blasted surface hindered the thickening of the oxide layer. After anodising, the milled surface exhibited better mechanical properties than the grit-blasted one. The wear resistance was enhanced by a thicker anodic layer, while the scratch resistance was positively affected by a lower surface roughness. [ABSTRACT FROM AUTHOR]

We present a study of Ge segregation at the surface of highly germanium-doped gallium oxide (2.5 × 1020 cm−3 nominal doping level) grown by molecular beam epitaxy. We probed the dopant concentration as a function of depth by hard x-ray photoelectron spectroscopy and standard laboratory photoemission spectroscopy. We notably found that there is germanium segregation within the top 2 nm where its concentration is 3 times the nominal doping level. This increased dopant concentration leads to a threefold enhancement of surface conductivity. The results suggest a reliable method for delta doping for power electronics applications. [ABSTRACT FROM AUTHOR]

Despite decades of research, the fundamental question of structure and morphology of the poly(3,‐4‐ethylenedioxythiophene):poly(styrene sulfonate) complex (PEDT: PSS) electrically conducting polymer remains open. Here, through a systematic study of the polymerization of 3,4‐ethylenedioxythiophene (EDT) on two series of sulfonated polystyrenes, i.e., PS‐co‐SSH and PS‐co‐SSNa, with per cent sulfonation 24 ≲ x ≲ 100, this study shows that the substrate polyelectrolyte not only affords charge compensation and processability, but also templates the morphology of the growing PEDT chain—whether extended, coiled or collapsed. This determines the electrical, electronic and optical properties of the resultant PEDT: PSS interpolyelectrolyte complexes, including their work function. This study calls this the Polyelectrolyte Template model. The PEDT: PSS complex retains memory of its polymerization morphology even after subsequent ion‐exchange, for example, to the same acid form. Electrical conductivity decreases sharply with decreasing x, and depends on whether the polymerization is templated with the H+ or Na+ form of the polyelectrolyte. The work function is less sensitive to x, but exhibits a transition from low to high work function (5.2–5.3 eV) when x exceeds a threshold, which indicates formation of a polar surface driven by molecular‐scale segregation of the PSS counteranion. This surface segregation also affects the ability of these complexes to inject holes into very large‐ionization‐energy semiconductors. [ABSTRACT FROM AUTHOR]

Surface segregation method, as an in situ method for simultaneous modification of membrane external surfaces and inner pore surfaces, has been more commonly employed to fabricate antifouling membranes. In this study, dopamine (DA) with self‐polymerization and bio‐adhesion ability is chosen as a surface segregation agent to fabricate antifouling polyvinylidene fluoride (PVDF) membrane for oil‐in‐water emulsions separation through synergistically regulating phase inversion, self‐polymerization of DA, and surface segregation of poly‐dopamine (PDA). During the phase inversion process, DA contacts with an alkaline coagulation bath to trigger self‐polymerization of DA, then the surface segregation of PDA proceeds spontaneously. The addition and self‐polymerization of DA can regulate the phase inversion process to acquire membranes with high porosity, as a result, the water permeance is increased from 134 to 538 L m−2 h−1 bar−1 with the oil rejection higher than 99.8%. Because the hydrophilic PDA layer on membrane and pore surfaces leads to a robust hydration layer, the membrane exhibits super‐oleophobicity underwater and excellent antifouling properties with water recovery ratio of more than 99.4%. This study may open a new route to preparing antifouling membranes by using small molecules as surface segregation agents. [ABSTRACT FROM AUTHOR]

Solid oxide electrolysis cell (SOEC) is a promising solid-state electrochemical device that can convert CO 2 into CO with high efficiency. However, the poor catalytic activity and Sr segregation of the cathode diminish the electrode reaction, hindering the large-scale application. Herein, a medium-entropy strategy is proposed to suppress the Sr enrichment while enhancing the catalytic activity for CO 2. The surface Sr content on Sr 2 Fe 1.2 Ni 0.1 Cu 0.1 Co 0.1 Mo 0.5 O 6-δ (SFNCCM) is significantly reduced after the Ni, Cu, and Co co-doping at Fe-site. Moreover, the oxygen surface exchange and bulk diffusion coefficient at 800 °C for SFNCCM oxide reach 2.42 × 10−4 cm2 s−1 and 2.28 × 10−5 cm2 s−1, which are 1.35 and 1.39 times higher than parent Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM) oxide. At 850 °C and 1.5 V, single with SFNCCM-Sm 0.2 Ce 0.8 O 6-δ (SDC) composite exhibits a current density of 2.22 A cm−2 with good stability for up to 100 h. The results suggest that the medium-entropy strategy is a promising method to inhibit Sr segregation and enhance the performance of CO 2 direct electrolysis. • The stability of SFM in CO 2 is significantly improved by medium-entropy strategy. • Surface Sr segregation is dramatically suppressed on SFNCCM oxide. • The catalytic activity for CO 2 RR is enhanced by the low-valent elements co-doping. • The current density of the SFNCCM electrode reaches 2.2 A cm−2 at 850 °C, 1.5 V. [ABSTRACT FROM AUTHOR]

The oxidation of the (100) surface of Au‐Si‐Ho quasicrystalline approximant was studied using low‐energy electron diffraction and X‐ray photoelectron spectroscopy. The combination of these two techniques provides evidence for a Ho and Si surface segregation induced by O2 adsorption, resulting in the loss of surface long‐range order. [ABSTRACT FROM AUTHOR]

The segregation of solute elements to defects in metals plays a fundamental role for microstructure evolution and the material performance. However, the available computational data are scattered and inconsistent due to the use of different simulation parameters and methods. A high‐throughput study is presented on grain boundary and surface segregation together with their effect on grain boundary embrittlement using a consistent first‐principles methodology. The data are evaluated for most technologically relevant metals including Al, Cu, Fe, Mg, Mo, Nb, Ni, Ta, Ti, and W with the majority of the elements from the periodic table treated as segregating elements. Trends among the solute elements are analyzed and explained in terms of phenomenological models and the computed data are compared to the available literature data. The computed first‐principles data are used for a machine learning investigation, showing the capabilities for extrapolation from first‐principles calculation to the whole periodic table of solutes. The present work allows for comprehensive screening of new alloys with improved interface properties. [ABSTRACT FROM AUTHOR]

We report abrupt Te doping of GaInP solar cells grown by molecular beam epitaxy (MBE) through the use of a low substrate temperature of 420 °C and subsequent elimination of surface segregation. First, a Te surface pre-dose layer and reduced substrate temperature were required to achieve abrupt profiles at doping >1 × 1018 cm−3 in calibration samples, while reduced doping of 5.7 × 1017 cm−3 did not require the surface layer. Next, we demonstrate front-junction n+/p GaInP cells with an improved internal quantum efficiency (IQE) after Te doping of the n-type emitter directly attributable to an ∼2.5× higher carrier diffusion length, with IQE-derived short-circuit current density increasing from 13.2 to 14.1 mA/cm2. Rapid thermal annealing further boosted the performance through improvements in the minority carrier lifetime of the p-GaInP base. The use of low substrate temperature in MBE-grown GaInP enables abrupt Te doping profiles to be attained in a straightforward manner and is promising for both solar cells and tunnel junctions. [ABSTRACT FROM AUTHOR]

Experimental and simulation studies were conducted for surface segregation-limited kinetics of nitrogen incorporation into a 4H-SiC crystal during physical vapor transport (PVT) crystal growth. It was revealed that the nitrogen incorporation is kinetically limited by the step-flow velocity on the growing crystal surface of a 4H-SiC crystal; in this study, the surface step-flow velocity at the growth front was deduced from the local inclination angle of the growth front measured from the (000 1 ¯) plane, assuming a uniform growth rate along the c-axis (crystal growth direction) across the growth front, and the nitrogen concentration across the growth front was measured using Raman scattering microscopy. The step-flow velocity dependence of nitrogen incorporation was theoretically analyzed using a two-site-exchange model, and the simulated dependence using the model was in good agreement with the experimental data. On the basis of these experimental and simulation results, kinematical and energetical aspects of nitrogen incorporation at the growth front of a 4H-SiC crystal during PVT growth are discussed. [ABSTRACT FROM AUTHOR]

We discuss the electrical properties of molecular beam epitaxy (MBE) grown, modulation doped, Ge1− x Sn x quantum well devices. A consequence of the epitaxial growth process is that electronic disorder is introduced even in modulation doped quantum well structures and electrical transport properties that are characteristic of a high level of disorder are apparent. MBE growth of this material also results in the surface segregation of elemental β -Sn in the way that has been observed utilizing other epitaxial growth methods. A thermally activated, p-type mobility is a clear feature of the electrical properties with generally temperature independent hole densities ∼1012 cm−2 from the measured Hall effect and coming from the modulation doping. We present a discussion of Hall effect measurements in this disordered regime. The percolation carrier density in MBE modulation doped GeSn is in the region of ∼1 × 1012 cm−2 although Hall measurements in this regime are difficult to quantify when the resistivity >(h / e 2). In this notation h is Planck's constant and e is the unit of charge. Conductivities (σ) as low as ∼0.028 × (e 2/ h) × square can be measured in the four-contact ac configuration and the temperature dependence indicates a mobility edge in these p-type devices below ∼2 × 1012 cm−2. At lower temperatures (<∼1 K) the presence of a Coulomb gap can be determined using dc transport, constant voltage measurements where small ac current excitation is not available experimentally. This two-contact configuration can determine σ down to ∼10−6 × (e 2/ h), deep into the localization regime, revealing a hopping conductivity dominated system. We discuss the relevance of these electrical properties for MBE grown GeSn devices. [ABSTRACT FROM AUTHOR]

Nickel‐rich LiNi0.8Co0.1Mn0.1O2 (NMC 811) cathode offers high voltage and high specific capacity, making it promising for high energy density batteries. However, large‐scale manufacturing of aqueous‐processed NMC 811 electrodes remains challenging due to proton exchange causing material decomposition and capacity loss. This work addresses this issue by constructing an in situ nanocellulose protective layer for NMC 811 particles via electrostatic interactions during the slurry preparation. For the first time, the interatomic spacing between inter‐chains of nanocellulose is measured through wide‐angle X‐ray scattering and demonstrate the ability to effectively confine interlayer water using atomistic simulations. Moreover, this nanocellulose coverage simultaneously minimizes Li+ surface segregation and mitigates water infiltration. Owing to less material decomposition during the aqueous processing, nanocellulose‐protected NMC electrodes exhibit higher initial coulombic efficiency (83% vs 62% at 0.1C) and capacity (133 vs 59 mAh g−1 at 6C) than unprotected electrodes. Additionally, optimized aqueous‐processed NMC electrodes offer comparable or even superior electrochemical properties compared to the electrodes fabricated using the conventional toxic organic solvent, N‐methyl‐2‐pyrrolidone. Consequently, the developed approach enables affordable, sustainable aqueous processing for Nickel‐rich NMC 811 cathodes with excellent electrochemical performances. [ABSTRACT FROM AUTHOR]

Perfluorosulfonic acid (PFSA) polymers are used as electrolyte membranes in polymer electrolyte fuel cells. To investigate the effect on proton conductivity through structural orientation control, we added 1,2,4-triazole to PFSA films during casting to impart anisotropy to the ion-cluster structure of the films. The proton conductivities of the films were found to be high in the film-surface direction and low in the film-thickness direction. Structural analysis using small-angle X-ray scattering suggested that the anisotropy in proton conductivity was due to anisotropy in the ion-cluster structure, which in turn was attributed to the formation of a phase-separated structure via strong bonding between sulfonic acid groups and 1,2,4-triazole during cast film formation and the surface segregation of fluorine. We expect the findings of this study to aid in the fabrication of PFSA films with controlled ion clusters. [ABSTRACT FROM AUTHOR]

To addresses the limitations in electrode performance observed at temperatures ≤700 °C, attributed to the low oxygen surface exchange coefficient primarily caused by high Sr surface segregation, we developed an electrode performance enhancement strategy involving A-site alkali metal doping to SrTi 1-x Fe x O 3-δ (STF)-based perovskite. Here, we present the symmetrical electrode material for solid oxide electrochemical cells (SOCs), Sr 0.95 Mg 0.05 Ti 0.3 Fe 0.7 O 3-δ (SMTF), demonstrating a unique combination of excellent symmetrical electrode performance and long-term stability. A-site Mg doping reduces the Sr surface segregation and improves the conductivity but also significantly enhances its electrochemical performance. At 700 °C, the performance of SMTF symmetric cell in both fuel cell and electrolysis modes is 1.5 times higher than that of STF. Moreover, under air atmosphere, SMTF demonstrates stable performance (>1000 h) at 1 A cm−2, with no degradation observed after 400 h testing under humidified hydrogen conditions. Additionally, SMTF exhibits excellent CO 2 tolerance in CO 2 -rich atmospheres. • SMTF exhibits excellent ORR and OER activity as a symmetrical electrode material. • R p of SMTF electrode at 700 °C is 1/4 of STF in the air and 1/2 of STF in H 2. • S–SOCs with SMTF electrodes achieved peak power density of 1.12 W cm−2 at 800 °C. • SMTF exhibits excellent stability in both air and H 2. • SMTF demonstrated excellent CO 2 tolerance and reversibility. [ABSTRACT FROM AUTHOR]

The nitrogen doping (N‐doping) treatment for niobium superconducting radio‐frequency (SRF) cavities is one of the key enabling technologies that support the development of more efficient future large accelerators. However, the N‐doping results have diverged due to a complex chemical profile under the nitrogen‐doped surface. Particularly, under industrial‐scale production conditions, it is difficult to understand the underlying mechanism thus hindering performance improvement. Herein, a combination of spatially resolved and surface‐sensitive approaches is employed to establish the detailed near‐surface phase composition of thermally processed niobium. The results show that intermediate phase segregations, particularly the nanometric carbon‐rich phase, can impede the nitridation process and limit the interactions between nitrogen and the niobium sub‐surface. In comparison, the removal of the carbon‐rich layer at the Nb surface leads to enhanced nitrogen binding at the Nb surface. Combining the RF test results, it is shown that the complex uniformity and grain boundary penetrations of impurity elements have a direct correlation with the mid‐field quench behavior in the N‐doped Nb cavities. Therefore, proper control of the nanometric intermediate phase formation in discrete thermal steps is critical in improving the ultimate performance and production yield of the Nb cavities. [ABSTRACT FROM AUTHOR]

The orderings of atoms in bimetallic 1.6–2.1 nm-large CuCo nanoparticles, important as catalytic and magnetic materials, were studied using a combination of DFT calculations with a topological approach. The structure and magnetism of Cu50Co151, Cu101Co100, Cu151Co50, and Cu303Co102 nanoparticles; their resistance to disintegrating into separate Cu and Co species; as well as the exposed surface sites, were quantified and analyzed, showing a clear preference for Cu atoms to occupy surface positions while the Co atoms tended to form a compact cluster in the interior of the nanoparticles. The surface segregation of Co atoms that are encapsulated by less-active Cu atoms, induced by the adsorption of CO molecules, was already enabled at a low coverage of adsorbed CO, providing the energy required to displace the entire compact Co species inside the Cu matrices due to a notable adsorption preference of CO for the Co sites over the Cu ones. The calculated adsorption energies and vibrational frequencies of adsorbed CO should be helpful indicators for experimentally monitoring the nature of the surface sites of CuCo nanoparticles, especially in the case of active Co surface sites emerging in the presence of CO. [ABSTRACT FROM AUTHOR]

This review delineates the mechanisms of pit nucleation and growth, establishes the foundational principles of etching technology, and presents the findings from investigations on the behavior of anodic dissolution and anodic film formation on high-purity aluminum foils for electrolytic capacitors based on electrochemical analyses and surface electron microscopic observations of etched surfaces. To elucidate pit nucleation and growth mechanisms, the effects of crystalline oxide and small amounts of lead on etching behavior were investigated. Pits initiate at cracks surrounding MgAl2O4 spinel or γ-Al2O3, resulting from the crystallization of the oxide film at metal ridges on the aluminum substrate. Using ultra-high-resolution field-emission scanning electron microscope (FE-SEM), high-angle backscattered electron (BSE) images revealed the presence of lead as the bright nanoparticles, approximately 10 nm in size, at the surface oxidation layer along rolling lines attributable to pick-up inclusions during hot rolling. Pitting attacks predominantly occur in the oxidation layer owing to the less noble potential for tunnel dissolution in the initial DC etching phase. Increased titanium content within the aluminum foil accelerated hydrogen evolution in the pit and hydrous oxide formation during the cathodic half-cycle of alternating current etching. The crystallization of anodic oxide films around MgAl2O4 spinel crystals, formed in a boric acid solution, was observed using transmission electron microscopy (TEM). Round-shaped γA-Al2O3 formed around the MgAl2O4 crystals and expanded across the surface as the formation voltage increased. [ABSTRACT FROM AUTHOR]

The hydrogen evolution and nitrite reduction reactions are key to producing green hydrogen and ammonia. Antenna–reactor nanoparticles hold promise to improve the performances of these transformations under visible‐light excitation, by combining plasmonic and catalytic materials. However, current materials involve compromising either on the catalytic activity or the plasmonic enhancement and also lack control of reaction selectivity. Here, we demonstrate that ultralow loadings and non‐uniform surface segregation of the catalytic component optimize catalytic activity and selectivity under visible‐light irradiation. Taking Pt−Au as an example we find that fine‐tuning the Pt content produces a 6‐fold increase in the hydrogen evolution compared to commercial Pt/C as well as a 6.5‐fold increase in the nitrite reduction and a 2.5‐fold increase in the selectivity for producing ammonia under visible light excitation relative to dark conditions. Density functional theory suggests that the catalytic reactions are accelerated by the intimate contact between nanoscale Pt‐rich and Au‐rich regions at the surface, which facilitates the formation of electron‐rich hot‐carrier puddles associated with the Pt‐based active sites. The results provide exciting opportunities to design new materials with improved photocatalytic performance for sustainable energy applications. [ABSTRACT FROM AUTHOR]

The performance of bifunctional hybrid catalysts based on phosphotungstic acid (H3PW12O40, HPW) supported on TiO2 combined with a Cu-ZnO(Al) catalyst in the direct synthesis of dimethyl ether (DME) from syngas has been investigated. In this work, different types of TiO2 were used as a support to study the effect of changes in the structure of the TiO2 support on the acidity and dispersion of HPW. Various TiO2 supports with different structural and surface characteristics have been studied and the results indicate that: (i) the crystallinity and crystallite size of the primary particles of the HPW units depend on the TiO2 support; (ii) the pore size distribution of the TiO2 support affects the surface segregation of the heteropolyacids; and (iii) changes in the supported HPW acid catalysts do not significantly alter the crystal structure of the CuO and ZnO phases after contact with CZA in bifunctional catalysts. The activity results indicate that the variation in the intrinsic activity of the Cu-ZnOx centers in the bifunctional catalysts for direct DME synthesis is minimal due to the limited alteration of the crystal structure of the centers. [ABSTRACT FROM AUTHOR]

The effect of gases on the surface composition of Cu–Pt bimetallic catalysts has been tested by in situ infrared (IR) and x-ray absorption spectroscopies. Diffusion of Pt atoms within the Cu–Pt nanoparticles was observed both in vacuum and under gaseous atmospheres. Vacuum IR spectra of CO adsorbed on CuPtx/SBA-15 catalysts (x = 0–∞) at 125 K showed no bonding on Pt regardless of Pt content, but reversible Pt segregation to the surface was seen with the high-Pt-content (x ≥ 0.2) samples upon heating to 225 K. In situ IR spectra in CO atmospheres also highlighted the reversible segregation of Pt to the surface and its diffusion back into the bulk when cycling the temperature from 295 to 495 K and back, most evidently for diluted single-atom alloy catalysts (x ≤ 0.01). Similar behavior was possibly observed under H2 using small amounts of CO as a probe molecule. In situ x-ray absorption near-edge structure data obtained for CuPt0.2/SBA-15 under both CO and He pointed to the metallic nature of the Pt atoms irrespective of gas or temperature, but analysis of the extended x-ray absorption fine structure identified a change in coordination environment around the Pt atoms, from a (Pt–Cu):(Pt–Pt) coordination number ratio of ∼6:6 at or below 445 K to 8:4 at 495 K. The main conclusion is that Cu–Pt bimetallic catalysts are dynamic, with the composition of their surfaces being dependent on temperature in gaseous environments. [ABSTRACT FROM AUTHOR]

A challenge hindering the development of durable solid oxide fuel cells (SOFCs) is the significant performance degradation of cathodes owing to poisoning by volatile Cr originating from the Fe─Cr alloy interconnect. Herein, a heterogeneous catalyst coating, composed of Ba1−xCe0.8Gd0.2O3–δ and BaCO3, remarkably improves the oxygen adsorption, dissociation capability, and Cr resistance of a La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) cathode is demonstrated. The coherent heterointerface interactions formed between the catalyst coating and LSCF result in varied levels of surface strain and electrostatic interactions, significantly suppressing Sr surface segregation on LSCF. A single cell with the catalyst coating‐decorated LSCF (CC‐LSCF) achieves a peak power density of 1.73 W cm−2 at 750 °C, with no noticeable performance degradation for 100 h. The CC‐LSCF cathode also exhibits outstanding durability under accelerated Cr poisoning conditions, compared with the tremendous degradation rate of 0.42% h−1 for the bare LSCF cathode. The enhanced Cr resistance is attributed to synergy induced by the stabilization of the lattice Sr cations by heterointerface interactions and the remarkable structural stability of the catalyst coating under Cr poisoning conditions. The novel heterointerface engineering strategy in this study provides insight into the design and development of active and Cr‐tolerant cathodes. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3) represents a carbon-free hydrogen carrier that can be used as a zero-emission fuel in the maritime and heavy transport sector with hydrogen fuel cells. To use ammonia as feedstock, the hydrogen must be recovered through NH 3 decomposition into H 2 and N 2. Ammonia decomposition by a membrane-enhanced reactor would inherently produce high-purity H 2 through the membrane avoiding the need for a costly hydrogen separation/purification unit. Pd-based membrane reactors can obtain full ammonia decomposition and show significantly higher conversion than conventional reactors. However, the H 2 permeability is found to be inhibited in the presence of NH 3. A further fundamental understanding of the long-term stability and performance of the Pd-based membranes under exposure to NH 3 is therefore required. In the current work, the adsorbate-adsorbate interactions during co-adsorption, the influence the presence of NH 3 has on the hydrogen dissociation kinetics, and surface segregation effects in the presence of NH 3 and/or hydrogen on the surface of Pd and Pd 3 Ag are investigated in detail using density functional theory calculations. We find that both the hydrogen surface coverage and dissociation kinetics are hindered by the presence of NH 3 on the surface, and possible segregation of Ag towards the surface in the presence of NH 3 , which could explain the reduced hydrogen permeation in NH 3. [Display omitted] • Hydrogen and NH3 co-adsorption on Pd–Ag membranes has been investigated using density functional theory calculations. • Adsorbate-adsorbate interactions and segregation effects in the presence of NH 3 are assessed. • Both the hydrogen surface coverage and dissociation kinetics are hindered by the presence of NH 3. • The results work can be used to explain the reduced permeation performance in presence of NH 3. [ABSTRACT FROM AUTHOR]

Indoor photovoltaics (IPV) is a promising technology to power the rapidly developing Internet of Things (IoT) devices, offering advantages of distributed power source and reduced maintenance cost. Wide‐bandgap perovskite solar cells (PSCs), with the features of easy bandgap tuning and low‐cost solution process, hold significant potential for powering indoor IoT devices. However, the efficiency and stability of wide‐bandgap PSCs suffers from severe phase segregation and surface defects. Herein, a novel bromide‐rich 2D passivation strategy targeting both bulk and surface passivation of wide‐bandgap PSCs for IPV application is introduced. Ammonium salts with optimized alkyl chain length is confirmed to suppress the phase segregation in the bulk. Bromide‐rich 2D perovskite exhibit superior performance compared to their iodide counterparts, effectively suppressing nonradiative recombination and forming favorable energy band alignment with the electron transport layer (ETL). The wide‐bandgap PSCs achieved an impressive power conversion efficiency (PCE) up to 41.58% under 1000 lux light emitting diode (LED) illumination. Furthermore, the wide‐bandgap perovskite module efficiently powers a Bluetooth IoT sensor at 400 lux indoor illumination, which can sense and broadcast the environmental information. This work highlights the remarkable potential of wide‐bandgap PSCs for indoor IoT devices and provides valuable insights into enhancing the efficiency and stability of PSCs for future IoT applications. [ABSTRACT FROM AUTHOR]

Surface structure and relevant oxygen vacancy play an important role in the application of RE2Si2O7 for environmental barrier coatings, in which the oxygen vacancies in RE2Si2O7 may influence their thermal and optical properties. In this work, the structure and thermodynamics of (0 0 1) and (1 1 0) surfaces of RE2Si2O7 (RE = Yb, Lu) are studied via first‐principles calculations to reveal the underlying mechanism of the surface formation and the associated oxygen vacancy behavior. The (1 1 0) surface is preferred energetically, being in good agreement with the experiential results. It is uncovered that the weak chemical bond broken dominates the decrease of the surface energy, together with the contribution from the polyhedral distortion. Furthermore, the [O3Si–O–SiO3] site is found to be the preferred site for oxygen vacancies on (1 1 0) surface. The formation energies of oxygen vacancies on the (1 1 0) surfaces are lower than those in the bulk, suggesting their segregation on the surfaces. These findings provide essential insights into the surface excitation and oxygen vacancy behaviors of RE2Si2O7, which could shield light on the experimental improvement of the thermal, mechanical, and corrosion properties for RE2Si2O7‐based environmental barrier coating materials. [ABSTRACT FROM AUTHOR]

High-entropy (HE) oxides have attracted a lot of research, because it has the advantages of adjustable structure and excellent catalytic performance. However, the lack of a better understanding for the thermal stability impedes its wider application in solid oxide cells (SOCs). Here, a B site HE layered perovskite, PrBa 0.5 Sr 0.5 (Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 Cu 0.2) 2 O 5+ δ (HE-PBSC), with low Co content, exceptional resistance to thermal shock is surprisingly obtained. Additionally, the surface cation segregations on the HE-PBSC and its relationship with annealing stability are reported. The polarized impedance (Rp) of symmetrical cell with HE-PBSC electrode increases 14.77%, from 3.771 Ω cm2 to 4.328 Ω cm2, after 200 h of annealing. With respect to improving the stability, efforts need to be made in the future to mitigate cation segregations on surface. • A novel B-site high entropy layered perovskite oxygen electrode (PrBa 0.5 Sr 0.5 (Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 Cu 0.2) 2 O 5+δ). • The B-site high entropy electrode has excellent thermal shock resistance performance. • The mechanism of segregation on the surface of electrode materials is revealed. [ABSTRACT FROM AUTHOR]

Significances of the work function in the field of surface science need knowledge of how electrons are transported out of the Fermi surface to the vacuum as well as ways the energy needed can be accurately estimated. Full knowledge of work functions as well as the surface energy of the metallic surface enhances understanding of the formation of grain boundaries and surface segregation. Statistical significance of differences in modeling approaches requires studies that can reliably distinguish between systematic approach effects and errors resulting from modeling approach variation. In this work, researchers introduced analysis of variance and correlation analysis to assess the statistical significance of differences in modeling approach variation. Comparisons of obtained results with estimating the work function of semiconductor variation data of support vector machine (SVM) and linear regression with natural logarithm transformation (LRNLT) were presented. [ABSTRACT FROM AUTHOR]

The increasing use of iron scrap to reduce greenhouse gas emissions results in the enrichment of steel with the tramp element Sn. However, the effect of Sn on phosphatase activity remains unclear. Therefore, this study aims to investigate the effect of the Sn content on the phosphatase activity of cold‐rolled steel plates. The phosphatability of the cold‐rolled steel sheets is evaluated by adding several tens of ppm of Sn. The surface characteristics of the materials are analyzed using X‐Ray photoelectron spectroscopy and transmission electron microscopy. Additionally, the reactivities of the materials in the phosphate treatment solution are assessed using an electrochemical evaluation method. Notably, a significant decrease in phosphatase activity is observed, which is attributed to the inhibition of the phosphate reaction by the Sn oxide layers formed on the steel sheet surface, with a layer thickness of a few nanometers. These Sn surface oxides can be removed by pickling with HCl, and the initial phosphate reaction occurs rapidly in areas where the oxides are removed. [ABSTRACT FROM AUTHOR]

The stability of solid oxide fuel cells (SOFCs) cathodes is often severely damaged by impurity poisonings from Cr vapors. Here we report a medium entropy GdBa(Mn 0.2 Fe 0.2 Co 1.2 Ni 0.2 Cu 0.2)O 5+δ (ME-GBCO) double perovskite cathode, which exhibits remarkably improved Cr-tolerant ability. The polarization resistance (R p) of GBCO increases from ∼0.44 to ∼0.70 Ω cm2 after 20 h exposure to Cr in air at 700 °C. In contrast, R p value of ME-GBCO cathode increases from ∼0.16 to ∼0.24 Ω cm2 under the same condition. The enhanced operational stability is attributed to the in situ formed BaCoO 3-δ (BCO) nanoparticles on ME-GBCO surface, which is very inactive to Cr vapors. This work highlights that the configuration entropy modulation is an effective avenue for surface engineering and for the development of robust cathode materials for SOFCs. [ABSTRACT FROM AUTHOR]

The results of molecular dynamics and atomistic simulations demonstrated the segregation of Pd atoms to the surface of binary Pt–Pd nanoparticles and the surface segregation of Cr in Ni–Cr nanoparticles. At the same time, molecular dynamics results predicted a transition from the surface segregation of Cr to the surface segregation of Ni at low Cr contents in Ni–Cr nanoparticles. [ABSTRACT FROM AUTHOR]

Chalcogenide-based nonvolatile phase change materials (PCMs) have a long history of usage, from bulk disk memory to all-optic neuromorphic computing circuits. Being able to perform uniform phase transitions over a subwavelength scale makes PCMs particularly suitable for photonic applications. For switching between nonvolatile states, the conventional chalcogenide phase change materials are brought to a melting temperature to break the covalent bonds. The cooling rate determines the final state. Reversible polymorphic layered materials provide an alternative atomic transition mechanism for low-energy electronic (small domain size) and photonic nonvolatile memories (which require a large effective tuning area). The small energy barrier of breaking van der Waals force facilitates low energy, fast-reset, and melting-free phase transitions, which reduces the chance of element segregation-associated device failure. The search for such material families starts with polymorphic In2Se3, which has two layered structures that are topologically similar and stable at room temperature. In this perspective, we first review the history of different memory schemes, compare the thermal dynamics of phase transitions in amorphous-crystalline and In2Se3, detail the device implementations for all-optical memory, and discuss the challenges and opportunities associated with polymorphic memory. [ABSTRACT FROM AUTHOR]

In this study, the effect of 3 mass%Cu additions on microstructure formation and Cu segregation in 800 MPa grade ductile cast iron during solidification was investigated. The calculated phase diagram showed that after the addition of 3 mass%Cu, the Cu phase with a negligible amount appeared below 1000°C, and most Cu was included in the matrix. Based on optical microstructure, after the addition of 3 mass%Cu, the size of graphite nodules became finer, and the microstructure rarely had an area with a-ferrite. Image analysis showed that the fraction of pearlite increased significantly, indicating that Cu greatly promoted the formation of pearlite. Compositional analysis by scanning electron microscopy indicated that the pearlitic area also contained approximately 3 mass%Cu, which corresponds to those of primary and secondary austenite calculated. A small and bright phase particle containing a large amount of Cu was observed at the interface of graphite and matrix. [ABSTRACT FROM AUTHOR]

CdZnTe crystals are widely used as epitaxial substrates for HgCdTe thin films for infrared detectors and in the fabrication of room temperature nuclear radiation detectors. During crystal growth, the interface shape is closely related to the heat state. Combined with the numerical simulation technique to control the temperature field distribution during CdZnTe crystal growth, the crystal growth procedure of micro-convex solidification interface by vertical Bridgman method and vertical gradient freeze method were designed, and the single crystal rate of CdZnTe crystals was analyzed according to the actual crystal growth experiments. The distribution spectrum of Zn components in the longitudinal section of CdZnTe crystals with equal diameters was obtained by photoluminescence spectroscopy for compositional testing in order to investigate the relationship between the temperature field distribution at the solid-liquid interface and the macroscopic segregation behavior of Zn components. It is found that the temperature gradient distribution on both sides of the solid-liquid interface significantly influences the shape selection and stability of the solidification interface during the crystal growth process, and a larger temperature gradient on the solid-phase side contributes helps to achieve stable crystal growth at the convex interface, thereby increasing the likelihood of growing single crystals. [ABSTRACT FROM AUTHOR]

Solutes segregating at the grain boundary (GB) have a significant influence on the mechanical and chemical properties of steel. In this study, the segregation effects of Si, P, and S on γ-Fe ∑5 (210)[001] GB were systematically analyzed with solution energy, segregation energy, and tensile tests by using a first principles calculation. Si, P, and S are preferred to segregate at substitutional sites in the first layer near the GB. The variation in atomic configuration and electron distribution were investigated by the analysis of bond lengths, charge density, charge density difference, and density of states (DOS), which is caused by the atomic size and electronegativity of solute atoms. Through tensile tests, it was found that Si has a strengthening effect on GB, while P and S exhibit embrittlement effects at low concentration. As the concentration of solutes increase, the segregation sites of P are different from the others owing to the tendency to form Fe3P. The exhibited embrittlement effect is mitigated at first and then aggravated. However, in both cases Si and S show aggravating embrittlement effects on GB cohesion, while the effect of Si changes from strengthening to embrittlement. This work provides comprehensive insights into the effects of Si, P, and S, which will be a useful guidance in steel design. [ABSTRACT FROM AUTHOR]

Metal oxide supported metal catalysts show promising catalytic performance in many industry-relevant reactions. However, the enhancement of performance is often limited by the insufficient metal/metal oxide interface. In this work, we demonstrate a general synthesis of Pt-early transition metal oxide (Pt-MOx, M = Ti, Zr, V, and Y) catalysts with rich interfacial sites, which is based on the air-induced surface segregation and oxidation of M in the supported Pt-M alloy catalysts. Systematic characterizations verify the dynamic structural response of Pt-M alloy catalysts to air and the formation of Pt-MOx catalysts with abundant interfacial sites. The prepared Pt-TiOx interfacial catalysts exhibit improved performance in hydrogenation reactions of benzaldehyde, nitrobenzene, styrene, and furfural, as a result of the heterolytic dissociation of H2 at Pt-metal oxide interfacial sites. [ABSTRACT FROM AUTHOR]

The interaction between mechanics and chemistry plays an essential and critical role in the surface segregation and relaxation in nanoscale alloys. Following the thermodynamics analysis based on surface eigenstress, the present study takes the free-standing nanometer thick films of Ni1–xCux solid solutions with face-centered cubic (fcc) crystalline structures as an example to investigate surface segregation of Cu and relaxation of the films. Hybrid Monte Carlo and Molecular Dynamics (MCMD) simulations are conducted on free-standing Ni1–xCux alloys of (100) and (111) nanofilms. The MCMD simulations verify the theoretical analytic results and determine the values of parameters involved in the theoretical analysis. Especially, the parameter of the differentiation in reference chemical potential behaves like the molar free energy of segregation in the McLean adsorption isotherm, and the differentiation in chemical composition induced eigenstrain plays also an important role in surface segregation and relaxation. The integrated theoretical and numerical study exhibits that both surface excess Cu concentration and apparent biaxial Young's modulus of Ni1–xCux nanofilms depend on the nominal Cu concentration and the film thickness. [ABSTRACT FROM AUTHOR]

We examine athermal binary blends composed of conformationally asymmetric polymers of equal molecular volume next to a surface of width ξ. The self-consistent field theory (SCFT) of Gaussian chains predicts that the more compact polymer with the shorter average end-to-end length, R0, is entropically favored at the surface. Here, we extend the SCFT to worm-like chains with small persistence lengths, ℓp, relative to their contour lengths, ℓc, for which R 0 ≈ 2 ℓ p ℓ c . In the limit of ℓp ≪ ξ, we recover the Gaussian-chain prediction where the segregation depends only on the product ℓpℓc, but for realistic polymer/air surfaces with ξ ∼ ℓp, the segregation depends separately on the two quantities. Although the surface continues to favor flexible polymers with smaller ℓp and bulky polymers with shorter ℓc, the effect of bulkiness is more pronounced. This imbalance can, under specific conditions, lead to anomalous surface segregation of the more extended polymer. For this to happen, the polymer must be bulkier and stiffer, with a stiffness that is sufficient to produce a larger R0 yet not so rigid as to reverse the surface affinity that favors bulky polymers. [ABSTRACT FROM AUTHOR]

A thorough study of the phosphorus (P) heavy doping of thin Silicon-On-Insulator (SOI) layers by UV nanosecond Laser Thermal Annealing (LTA) is presented in this work. As a function of the implant dose and laser annealing conditions, the melting regimes and regrowth processes, as well as the redistribution and activation of P in the top-Si amorphized layer, were investigated. The findings emphasize the critical role of the thin crystalline silicon layer that remains after the top-Si layer amorphizes, as it provides nucleation seeds for liquid phase recrystallization. The effect of the implant dose on the recrystallization process is thoroughly investigated in terms of melt energy thresholds, crystallographic nature of the resolidified layer, defect formation, surface roughness, and the formation of hillocks on the silicon surface. Optimized laser annealing conditions, corresponding to the laser energies just preceding the onset of the full melt, were identified for all implanted doses. Such optimized layers have perfect crystallinity, negligible P out-diffusion, a nearly perfectly flat P depth profile located below the segregation-induced surface pileup peak, and dopant active concentrations well above 1021 cm−3, which is close to the highest reported values for phosphorus in bulk Si substrates. [ABSTRACT FROM AUTHOR]

The effect of Mn on interfacial Sn segregation during the selective oxidation of Fe-(0–10)Mn-0.03Sn (at.%) alloys was determined for annealing conditions compatible with continuous galvanizing. Significant Sn enrichment was observed at the substrate free surface and metal/oxide interface for all annealing conditions and Mn levels. Sn enrichment at the free surface was insensitive to the Mn alloy concentration, which was partially attributed to the opposing effects of Mn on segregation thermodynamics and kinetics: Mn increases the driving force for Sn segregation via reducing Sn solubility in Fe but also reduces the effective Sn diffusivity by increasing the austenite volume fraction. This insensitivity was exacerbated by the depletion of solute Mn near the surface due to the selective oxidation of Mn. Thus, Sn segregation occurred in regions with a local Mn concentration lower than the nominal bulk composition of the alloys suggested. Sn enrichment at the metal/external oxide interface was reduced compared to the free surface and decreased with increasing bulk Mn content, which was attributed to changes in the external oxide morphology and metal/internal oxide interfaces acting as Sn sinks. [ABSTRACT FROM AUTHOR]

The Boltzmann kinetic theory for a model of a confined quasi-two dimensional granular mixture derived previously [Garzó et al., "Navier–Stokes transport coefficients for a model of a confined quasi-two dimensional granular binary mixture," Phys. Fluids 33, 023310 (2021)] is considered further to analyze two different problems. First, a linear stability analysis of the hydrodynamic equations with respect to the homogeneous steady state (HSS) is carried out to identify the conditions for stability as functions of the wave vector, the coefficients of restitution, and the parameters of the mixture. The analysis, which is based on the results obtained by solving the Boltzmann equation by means of the Chapman–Enskog method to first order in spatial gradients, takes into account the (nonlinear) dependence of the transport coefficients and the cooling rate on the coefficients of restitution and applies in principle to arbitrary values of the concentration, and the mass and diameter ratios. In contrast to the results obtained in the conventional inelastic hard sphere (IHS) model, the results show that all the hydrodynamic modes are stable so that the HSS is linearly stable with respect to long enough wavelength excitations. On the other hand, this conclusion agrees with previous stability analysis performed in earlier studies for monocomponent granular gases. As a second application, segregation induced by both a thermal gradient and gravity is studied. A segregation criterion based on the dependence of the thermal diffusion factor Λ on the parameter space of the mixture is derived. In the absence of gravity, the results indicate that Λ is always positive, and hence, the larger particles tend to accumulate near the cold plate. However, when gravity is present, our results show the transition between Λ > 0 (larger particles tend to move toward the cold plate) to Λ < 0 (larger particles tend to move toward the hot plate) by varying the parameters of the system (masses, sizes, composition, and coefficients of restitution). Comparison with previous results derived from the IHS model is carried out. [ABSTRACT FROM AUTHOR]

Cu-cored solder interconnects have been demonstrated to increase the performance of interconnect structures, while the quantitative understanding of the effect of the Cu-cored structure on microstructure evolution and atomic migration in solder interconnects is still limited. In this work, the effect of the Cu-cored structure on phase migration and segregation behavior of Sn-58Bi solder interconnects under electric current stressing is quantitatively studied using a developed phase field model. Severe phase segregation and redistribution of Bi-rich phase are observed in the Cu-cored Sn-58Bi interconnects due to the more pronounced current crowding effect near the Cu core periphery. The average current density and temperature gradient in Sn-rich phase and Bi-rich phase decrease with an increase in the diameter of the Cu core. The temperature gradient caused by Joule heating is significantly reduced owing to the presence of the Cu core. Embedding of the Cu core in the solder matrix could weaken the directional diffusion flux of Bi atoms, so that the enrichment and segregation of the Bi phase towards the anode side are significantly reduced. Furthermore, the voltage across the solder interconnects is correspondingly changed due to the phase migration and redistribution. [ABSTRACT FROM AUTHOR]

This paper uses physical experiments to investigate the segregation behavior of binary granular mixtures in a quasi-two-dimensional rotating drum. Spherical polyformaldehyde (POM) beads and cylindrical red beans constitute the granular mixtures. The effects of particle size, particle density, and particle shape interplay during the segregation process in the spherical/non-spherical particulate system. A long-axis ratio (LAR), the ratio of the spherical POM beads' diameter to the red beans' primary dimension, was defined to explore the particle shape effect. The experimental results show that the long-axis ratio and the rotation speed play substantial roles in the granular segregation behavior. As the long-axis ratio increases, the steady-state segregation intensity decreases. An increase in the rotation speed enhances the segregation of the binary granular mixtures for each long-axis ratio studied here. In addition, the average velocity and granular temperature of spherical POM beads increase as the long-axis ratio increases. Both properties also increase as the rotation speed increases. The dynamic angle of repose for the binary mixtures increases with the increase in the long-axis ratio. Most interestingly, reverse granular segregation does occur at a long-axis ratio of 0.70 with the cylindrical red beans in the core and the spherical POM beads at the periphery for each rotation speed studied here. This reverse segregation has not been observed in previous studies. This highlights the substantial impact of particle shape on the granular segregation in binary granular mixtures. [ABSTRACT FROM AUTHOR]

The Ni-stanogermanides were formed via an interfacial reaction between Ni film and a Ge1−xSnx (x = 0.083) epilayer grown on a Si substrate driven by thermal treatment, and their microstructural and chemical features were investigated as a function of a rapid thermal annealing (RTA) temperature. The Ni3(Ge1−xSnx) phase was formed at the RTA temperature of 300 °C, above which Ni(Ge1−xSnx) was the only phase formed. The fairly uniform Ni(Ge1−xSnx) film was formed without unreactive Ni remaining after annealing at 400 °C. However, the Ni(Ge1−xSnx) film formed at 500 °C exhibited large surface and interface roughening, followed by the formation of Ni(Ge1−xSnx) islands eventually at 600 °C. The Sn concentration in Ni(Ge1−xSnx) gradually decreased with increasing RTA temperature, implying the enhancement of Sn out-diffusion from Ni(Ge1−xSnx) grains during the Ni-stanogermanidation process at higher temperature. The out-diffused Sn atoms were accumulated on the surface of Ni(Ge1−xSnx), which could be associated with the low melting temperature of Sn. On the other hand, the out-diffusion of Sn atoms from Ni(Ge1−xSnx) along its interface was dominant during the Ni/Ge1−xSnx interfacial reaction, which could be responsible for the segregation of metallic Sn grains that were spatially confined near the edge of Ni(Ge1−xSnx) islands. [ABSTRACT FROM AUTHOR]

Focusing on hydrophilic surface modification of poly(methyl methacrylate)/poly(methyl methacrylate‐co‐acrylic acid) (PMMA/PMMA‐co‐PAA) composite film, a copolymer is synthesized to improve the hydrophilicity and compatibility with PMMA matrix, and the composite film is subjected to surface activation using a sodium hydroxide solution. The infrared absorption peaks corresponding to –OH and –C═O functional groups become progressively weaker with the increase of copolymer content, indicating the formation of intermolecular hydrogen bonds. The hydroxyl absorption peak is significant and two new absorption peaks corresponding to the symmetric contraction and antisymmetric contraction of –COO– appear, indicating that sodium hydroxide solution can disrupt the intermolecular hydrogen bond and react with acrylic acid to form sodium acrylate to make the surface contain sodium elements. The elemental sodium content on the composite film can reach 1.9% and the nanostructures contain 20 times more sodium than the smooth parts, indicating the sodium acrylate can induce surface segregation of PMMA and form nanoparticle‐like structures to improve surface roughness. The hydrophilic component combined with the surface structure makes the contact angle less than 10°. Furthermore, thermostability can be slightly promoted by introducing the copolymer which is closely related to the intermolecular hydrogen bonding formed directly between the copolymer and the PMMA matrix. [ABSTRACT FROM AUTHOR]

An as-cast aluminum billet with a diameter of 100 mm has been successfully prepared from aluminum scrap by using direct chill (DC) casting method. This study aims to investigate the microstructure and mechanical properties of such as-cast billets. Four locations along a cross-section of the as-cast billet radius were evaluated. The results show that the structures of the as-cast billet are a thin layer of coarse columnar grains at the solidified shell, feathery grains at the half radius of the billet, and coarse equiaxed grains at the billet center. The grain size tends to decrease from the center to the surface of the as-cast billet. The ultimate tensile strength (UTS) and the hardness values obtained from this research slightly increase from the center to the surface of the as-cast billet. The distribution of Mg, Fe, and Si elements over the cross-section of the as-cast billet is inhomogeneous. The segregation analysis shows that Si has negative segregation towards the surface, positive segregation at the middle, and negative segregation at the center of the as-cast billet. On the other hand, the Mg element is distributed uniformly in small quantities in the cross-section of the as-cast billet. [ABSTRACT FROM AUTHOR]

In the automotive industry, there is a drive to reduce environmental impact, energy consumption, and costs related to the manufacturing of forged aluminum suspension components. The replacement of extruded stock with cast forging stock is one option that offers substantial potential for such savings. The casting technology, low-pressure casting (LPC), allows for production of high-quality cast forging stock with minimal surface segregation and smaller diameters than those achieved with traditional casting technologies. This study is a proof-of-principle, conducted to directly compare the microstructure and mechanical properties of LPC and extruded material after forging, through both generic and full-scale industrial forging trials. The results show the advantages of the cast material, including higher robustness against surface grain growth after forging and a positive correlation between mechanical properties, both strength and ductility and the introduction of plastic deformation. Overall, the work demonstrates how forged aluminum components produced from LPC forging stock can achieve mechanical properties and performance, on par with extruded forging stock, showcasing industrial relevance through the production of a safety-critical automotive component. [ABSTRACT FROM AUTHOR]

AlGaN self-assembled superlattices (SASLs) and their customization were investigated via metal modulated epitaxy. Using the dynamics of metal accumulation, surface strain, and surface segregation, coherent SASL structures were demonstrated with high repeatability over 910 nm (63 periods) with no growth interrupts at rates as high as 2.8 μm/h. High customizability was shown with control over period thickness as well as the thickness of the individual layers. Factors effecting the thickness and composition of each layer are discussed and methods of customization are presented. Transmission electron microscopy shows abrupt interfaces between individual layers of the SASL and good coherency throughout the structure and strong wavelength tunable ultraviolet photoluminescence was observed. Such a method of SASL fabrication offers promise for the growth of multi-quantum well structures, distributed Bragg reflectors, strain relaxation buffers, and beyond without the need for growth interrupts, and thus unintentional contaminant incorporation, between layers. [ABSTRACT FROM AUTHOR]

In this work, we study the oxygen reduction reaction (ORR) properties of Pt-containing 3d transition-metal high-entropy alloy (Pt-HEA) surfaces, focusing on the constituent alloying elements. The surface Pt and underlying Cr-Mn-Co-Ni(111) (Pt/Cr-Mn-Co-Ni(111)) stacked lattice layers, which are synthesized through the vacuum deposition of the underlying alloy and surface Pt stacking layers on Pt(111) substrate, exhibit high pristine ORR activity and structural stability under potential-cycle loading, compared to Pt/Cr-Co-Ni, Pt/Mn-Co-Ni, and Pt/Co-Ni(111) surfaces. The outperformed ORR properties are attributed to the effective suppression of the surface segregation of Cr. This study demonstrates that not only the “high-entropy” effect induced by increasing the numbers of constituent elements but also the “chemical affinity” of Pt and the individual HEA constituent elements determine the ORR performances of Pt-HEA.

Exsolution is one of the most successful functionalization techniques to improve the catalytic activity of electrodes in solid oxide fuel and electrolyzer cells (SOFC/SOEC). The objective of this technique is to produce the highest possible number of metallic nanoparticles on the surface of a host-oxide, without significantly altering its structure. In this work, we compare three similar SOFC electrodes: STF (SrTi 0.3 Fe 0.7 O 3), STFN (Sr 0.93 Ti 0.3 Fe 0.63 Ni 0.07 O 3), and STFNC (Sr 0.93 Ti 0.3 Fe 0.56 Ni 0.07 Co 0.07 O 3), revealing that there is a significant difference between Ni–Fe/Ni–Co–Fe nanoparticle formation in STFN/STFNC and pure Fe0 particle formation in STF, which is evidenced by the size and amount of produced nanoparticles, but also by their anchoring to the host-oxide. The terms exsolution and particle segregation will be used, respectively, to distinguish these phenomena. Next, we explore two different reduction methods and observe that the characteristics of exsolution do not only depend on temperature, atmosphere and reduction times, but also on the reduction path taken to reach such conditions. [Display omitted] • Exsolution differs from particle segregation in the NP distribution, density, size and anchorage. • The characteristics of exsolved NPs are influenced by the hydrogen reduction path. • In-situ absorption spectroscopy is used to determine the exsolution temperature threshold. [ABSTRACT FROM AUTHOR]