Red-emitting phosphor of Ca0.8Zn0.2TiO3:0.2 mol% Pr3+ was synthesized by the hydrothermal method with urea as a mineralizer. The crystalline structure, micromorphology, and luminescent properties of the resultant phosphor were investigated. Results show that elevated calcination temperature does not change the shape of particles that are hollow spheres with a shell thickness of 210–480 nm, and smaller particles are in the middle of the larger ones. The emission intensity at 612 nm originated from 1D2 → 3H4 transition of Pr3+ ions increases with the elevated calcination temperature due to a higher crystallinity. Excitation curves consist of two strong broad bands centered at about 330 and 380 nm and a weaker broad band range from 450 to 500 nm. The sample prepared by the hydrothermal method has better luminescent properties than that of its counterpart prepared by the solid-state method, especially the improvement of near-UV region (380 nm) excitation intensity.

The fabrication of bimetallic magnetic nanoparticles (NPs) smaller than the size of single magnetic domain is very challenging because of the agglomeration, non-uniform size, and possible complex chemistry at nanoscale. In this paper, we present an alloyed ferromagnetic 4 ± 1 nm thiolated Au/Co magnetic NPs with decahedral and icosahedral shape. The NPs were characterized by Cs-corrected scanning transmission electron microscopy (STEM) and weretheoretically studied by Grand Canonical Monte Carlo simulations. Comparison of Z-contrast imaging and energy dispersive x-ray spectroscopy used jointly with STEM simulated images from theoretical models uniquely showed an inhomogeneous alloying with minor segregation. The magnetic measurements obtained from superconducting quantum interference device magnetometer exhibited ferromagnetic behavior. This magnetic nanoalloy in the range of single domain is fully magnetized and carries significance as a promising candidate for magnetic data recording, permanent magnetization, and biomedical applications.

We report that an electron beam focused for high-resolution imaging rapidly initiates observable crystallization of amorphous Me–Si–C films. For 200-keV electron irradiation of Nb–Si–C and Zr–Si–C films, crystallization is observed at doses of ~2.8 × 109 and ~4.7 × 109 e−/nm2, respectively. The crystallization process is driven by atomic displacement events, rather than heating from the electron beam as in situ annealing (400–600 °C) retains the amorphous state. Our findings demand a critical analysis of alleged amorphous and nanocrystalline ceramics including reassessing previous reports on nanocrystalline Me–Si–C films for possible electron-beam-induced crystallization effects.

Fine-sized powders of BaSi3Al3O4N5:Eu2+ phosphors with high stability and improved photoluminescence properties were successfully synthesized by the traditional solid-state reaction method under a reductive atmosphere using BaF2-fluxing additives in the raw powder mixture. The produced phosphors had strong blue emission under excitation in ultraviolet (UV) and vacuum ultraviolet (VUV) light, due to the 4f 5d–4f7 transition of Eu2+ ions. X-ray diffraction, scanning electron microscopy, XANES, and the photoluminescence (PL) spectra under UV and VUV were used to characterize the as-received samples. The experimental results showed that the addition of BaF2 flux improved the crystalline regime and the PL properties of the produced phosphors. Most significantly, it allowed control of the particle size and particle size distribution in the final powders but did not jeopardize the high thermal and chemical stability of the phosphors produced. With the modification of the BaF2 flux, the blue-emitting BaSi3Al3O4N5:Eu2+ phosphors will show excellent packing and coating properties and could be a good candidate for the light-emitting diodes and plasma display panels.

Fully dense (Ti,Mo)2AlC/Al2O3 in situ composites with high purity were successfully synthesized at 1350 °C by reactive hot pressing of the Ti, Al, TiC, and MoO3 powder mixtures. The effect of MoO3 content on the phase composition, microstructure, and mechanical properties was investigated in detail. The introduction of the Al–MoO3 displacement reaction into the Ti–Al–TiC system resulted in a submicron grain size and a homogeneously distributed matrix phase of (Ti,Mo)2AlC with a secondary Al2O3 phase. The matrix grain size was significantly refined with increasing the Al2O3 content. Compared with the sample without MoO3 addition, the addition of 13.81 wt% MoO3 (corresponding to 10 wt% Al2O3 formation) evidently enhanced the hardness, flexural strength, and fracture toughness by 25%, 69%, and 146%, respectively. The strengthening and toughening mechanisms for the (Ti,Mo)2AlC/Al2O3 composites were also investigated.

The considerable potential of model-type thin film electrodes for the investigation of oxygen exchange pathways is demonstrated for different electrode materials on yttria-stabilized zirconia (YSZ). In particular, a correlation of voltage-driven 18O tracer experiments and electrical ac and dc measurements has proven to be helpful when aiming at mechanistic conclusions. For Pt electrodes, two different parallel reaction pathways can be identified under equilibrium conditions. At lower temperatures, a diffusion limited path through the electrode is dominant, whereas at higher temperatures, an electrode surface path with oxygen incorporation at the three-phase boundary determines the electrochemical activity. In addition, for high cathodic polarization, an electrolyte surface path with electron transfer via YSZ outperforms both other pathways. The oxygen incorporation zones of the bulk path as well as the electrolyte surface path can be visualized by 18O tracer incorporation experiments in combination with time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis. A successful separation of surface and bulk path can also be obtained for La0.8Sr0.2MnO3−δ (LSM) electrodes by means of 18O tracer incorporation at different cathodic overpotentials. Under lower polarization, a surface path with oxygen incorporation at the three-phase boundary is dominant, whereas at higher cathodic overpotential, the bulk path becomes significantly more pronounced. These changes are discussed in terms of polarization-induced changes of the ionic conductivity in the LSM electrode. Measurements on the acceptor-doped perovskite-type materials La0.6Sr0.4CoO3−δ (LSC) and La0.6Sr0.4FeO3−δ (LSF) illustrate the limitations of the tracer incorporation method. In the case of highly active LSC electrodes with low polarization resistances, the tracer distribution is determined by the electrolyte, and thus the active sites of the electrodes can no longer be visualized. The effect of polarization-induced changes of the electrode's electronic conductivity is demonstrated for LSF. Only a region close to the current collector remains electrochemically active owing to limited lateral electron transport.

A new acentric protonated garnet Li6−xHxCaLa2Nb2O12 has been synthesized and structurally characterized from Rietveld refinement of high-resolution neutron diffraction data. This phase can be prepared by Li+/H+ exchange on the mother garnet Li6CaLa2Nb2O12 in acetic acid heated at reflux for 4 days, conditions determined after several tests varying acid solution, time, and temperature. Li6−xHxCaLa2Nb2O12 crystallizes in the noncentrosymmetric cubic space group I$\overline 4$3d (no. 220) with the cell parameter a = 12.8040(3) Å. The noncentrosymmetry has been confirmed from unambiguous results obtained by second harmonic generation test as well as from transmission electron microscopy study (selected area electron diffraction). The Li+/H+ exchange corresponds to a topotactic reaction since this new protonated phase is built from the garnet framework [CaLa2Nb2O12]6− like its mother form Li6CaLa2Nb2O12 with lithium and proton cations distributed on different sites.

Core–shell nickel oxide/carbon nanotube (CNT) microwires, with interconnected nickel oxide nanoflakes (∼10 nm in thickness) vertically oriented on polymer-based CNTs, were synthesized by using low-cost starting materials and a scalable growth route. As revealed by morphological characterization, sheet–sheet and wire–wire interwoven of the composite constructed a porous structure. The composite as lithium ion battery anode exhibited high reversible capacity of 752 mAh/g at a current density of 100 mA/g over 30 cycles with 82% capacity retention. Even at high rate (1000 mA/g), the composite still delivered a high charge capacity (304 mAh/g) over 25 cycles. When the rate was reset to its initial value, 87.7% of the initial charge capacity was recovered. The composite showed remarkably enhanced performance compared to pure NiO, which was presumably due to the advantages of porous structure, oriented attachment, and attractive synergetic effect.

Confining light metal hydrides in micro- or mesoporous scaffolds is considered to be a promising way to overcome the existing challenges for these materials, e.g. their application in hydrogen storage. Different techniques exist which allow us to homogeneously fill pores of a host matrix with the respective hydride, thus yielding well defined composite materials. For this report, the ordered mesoporous carbon CMK-3 was taken as a support for LiAlH4 realized by a solution impregnation method to improve the hydrogen desorption behavior of LiAlH4 by nanoconfinement effects. It is shown that upon heating, LiAlH4 is unusually oxidized by coordinated tetrahydrofuran solvent molecules. The important result of the herein described work is the finding of a final composite containing nanoscale aluminum oxide inside the pores of the CMK-3 carbon host instead of a metal or alloy. This newly observed unusual oxidation behavior has major implications when applying these compounds for the targeted synthesis of homogeneous metal–carbon composite materials.

Electronic devices made from single crystal thin films attached to inexpensive support substrates offer reduced material costs compared to wafer-based devices; however, scalable and inexpensive processes for producing these single crystal film structures have remained elusive. In this work, we describe a new approach for fabricating these structures. In our approach, an epitaxial film is grown on a single crystal template and is then separated from its growth surface via fracture along a weak heteroepitaxial interface between the single crystal film and its growth substrate. We show that epitaxial films of Si, Ge, and GaAs, with thicknesses ranging from 100 nm to 1 μm, grown on epitaxial CaF2 overlayers on Si <111> substrates, can be transferred to glass substrates by inducing fracture along the heteroepitaxial interface between the semiconductor film and CaF2, or between CaF2 and the Si wafer, assisted by the presence of water as in moisture-assisted cracking.

Compositional patterning in two-phase immiscible alloys during severe plastic deformation at elevated temperatures has been investigated. Kinetic Monte Carlo computer simulations were used to test the proposed idea that patterning derives from a dynamic competition between homogenization by forced chemical mixing and phase separation by thermally activated diffusion [P. Bellon and R.S. Averback, Phys. Rev. Lett.74, 1819 (1995) and F. Wu et al., Acta Mater.54, 2605 (2006)]. We utilize the concept of pair diffusion coefficients to compare thermal diffusion with forced chemical mixing and discuss the fundamentally different behavior with respect to pair separation distance in both mechanisms. While the general ideas of this model are verified and are in good quantitative agreement with our simulations, it is found that the dynamic processes of alloys under high-temperature shear are very complex, even in highly idealized systems, making experimental verification of this model very difficult. We illustrate our findings for a model AB alloy with properties similar to Cu–Ag by showing how alloy morphology and solubility depend on shear rate, temperature, and composition.

Among the different porous materials, bulk metallic glass (BMG) foams are of special interest due to their high strength combined with large elastic limit. Large surface areas and, therefore, high reactivity in chemical applications can be achieved by properly adjusting the pore characteristics. Pore size and pore size distribution are the key factors for determining the overall performance of open-cell porous materials used for functional applications, such as filtration or catalysis. As a result, the control of these factors is a necessary requirement for material design and application. In this work, BMG foams are produced by powder metallurgy through the selective dissolution of a fugitive phase. The work is focused on the manufacturing processes needed to properly control pore size and pore size distribution. The results reveal that customized hybrid BMG porous structures can be produced through the controlled milling of the BMG-composite powders.

Mn-doped bismuth oxide bromide microspheres have been prepared by the hydrothermal method. The resultant composite microspheres exhibited higher photocatalytic activity under visible light irradiation, attributing to the improvement of the photo-absorption property and the separation efficiency of photogenerated electrons and holes. The holes and O2•− are the main active species in aqueous solution under visible light irradiation, rather than •OH.

Solid oxide fuel cells (SOFCs) are attractive for clean and efficient electricity generation, but high operating temperatures (Top > 800 °C) limit their widespread usage. Oxygen ion conducting cathode materials (mixed ion-electron conductors, MIECs), such as La1−xSrxCo1−yFeyO3 (LSCF), enable lower Top by reducing cathode polarization losses. Understanding how composition affects oxygen diffusion in LaFeO3 is vitally important for designing high-performance LSCF cathodes. To do this, we employ first-principles density functional theory plus U (DFT+U) calculations to show how lanthanum vacancies in LaFeO3 dramatically change the oxygen diffusion coefficient. Our ab initio results show that A-site substoichiometry is a viable route to increased oxygen diffusion and higher SOFC performance.

Grain refinement strengthening in low carbon ferrite–cementite steel was investigated using the estimated true stress (σ)–true strain (ε) relationship up to the plastic deformation limit, i.e., just before fracture. Static and stepwise tensile tests were performed using ferrite–cementite (FC) steels with ferrite grain sizes in the range 0.5–34 μm, and the σ–ε relationships up to the plastic deformation limit were estimated by using the Bridgman equation. In the nominal stress–strain curves, the lower yield stress and tensile strength increased and the uniform and total elongations decreased with a decrease in the ferrite grain size. It was found from the σ–ε relationships of the FC steels that grain refinement strengthening up to 0.8 μm can improve σ and ε at the plastic deformation limit. From the scanning electron microscopy observations of the cross-sectional planes parallel to the tensile direction for the FC steels, voids were observed at the interface between ferrite and cementite in the case where the thickness of elongated ferrite came close to the size of the dispersed cementite.

The development and characterization of pressure sensing porous nanocomposites are reported here. A thermoplastic polyurethane (TPU) was chosen as an elastomeric matrix, which was reinforced with multiwall carbon nanotubes (MWNTs) by high shear twin screw extrusion mixing. Porosity was introduced to the composites through the phase separation of a single TPU-carbon-dioxide gas solution. Interactions between MWNT and TPU were elucidated through calorimetry, gravimetric decomposition, conductivity measurements, and microstructure imaging. The piezoresistance (pressure–resistance) behavior of the nanocomposites was investigated and found to be dependent on MWNT concentration and nanocomposite microstructure. Mechanisms of piezoresistance in solid and porous nanocomposites are proposed.

Tissue engineering principles suggest the formation of 3D scaffolds based on polymer fibers and adhesive proteins. These scaffolds aim to mimic the native extracellular matrix and thus providing a favorable environment for cell attachment and proliferation. The application of an electric field (EF) can influence the quantity and the spatial orientation/conformation of adsorbed proteins, which could lead to changes in their functions. We study the influence of alternating current (AC) EF on the adsorption of fibronectin onto poly(etherimide) (PEI) electrospun fiber materials in 3D structures and subsequent cell adhesion. The results are compared with 2D PEI material and glass surface. 3D scaffolds adsorbed a lower amount of fibronectin than 2D film or glass. Application of AC EF with a frequency of 1 Hz decreased the adsorption of fibronectin. Cell adhesion on 3D materials was reduced compared with 2D film and glass. The application of EF with frequencies between 1 and 10 Hz improved cell adhesion on both 2D and 3D materials.

An in situ redox reaction was developed to synthesize bundled tungsten oxide (WO3@W18O49) ultrafine nanowires (BUNs) loaded with Ag nanoparticles using weakly reductive W18O49 and oxidative silver nitrate as precursor. However, due to the weak activation between the two reactants, redox just happened on the surface of W18O49, resulting in the formation of W18O49 coated with WO3 (here, we refer this structure to WOx simply), and the bulk phase of the composites retained the same pattern. Ag nanoparticles (<5 nm) with a narrow size distribution were obtained and immobilized onto WOx BUNs without any aggregation. The paper presented a systematic investigation on the Ag-WOx nanocomposite used as a catalyst for the reduction of p-nitrophenol and as an antibacterial agent against Escherichia coli. The remarkably enhanced performance may be ascribed to the moderate interaction of the small Ag-NPs and WOx BUNs with high specific surface area.