Metal oxide optoelectronics is an emerging field that exploits the intriguing properties of the ns orbital-derived isotropic band structure as a replacement for traditional silicon-based electronics in advanced active-matrix information displays. Although the device performance of metal oxide thin film transistors (TFTs) has been substantially improved, the device reliability against external light and gate bias stress remains a critical issue. This paper provides a literature review of light-induced gate bias stress instability in metal oxide TFTs and explain the importance of photo-bias instability in the applications of metal oxide TFTs to optoelectronic device. The rationale of threshold voltage (Vth) instability under the negative bias illumination stress (NBIS) condition is discussed in detail. The charge trapping/injection model, oxygen vacancy photoionization model, and ambient interaction model are described as plausible degradation mechanisms. Finally, the possible approaches to prevent NBIS-induced Vth instability are proposed based on an understanding of the NBIS instability.

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.

The intermetallic materials digold bismuthide, gold diantimonide, and gold ditelluride were chemically synthesized with a bottom-up wet chemical approach, which has not been achieved before. These gold-based materials display a nano- to microparticle grain size and a well-defined composition-based structure. True intermetallic nanoparticle-based materials have traditionally proven challenging to obtain via wet chemical approaches, making the materials created here significant from a fundamental synthesis standpoint. The knowledge gained by developing reliable synthesis approaches toward intermetallic nanoparticles may be used to develop new materials and enhance the understanding of how to refine the characteristics and enhanced properties of emerging nanoparticle semiconductor materials in advanced applications such as for thermoelectrics.

A novel surface enhanced Raman scattering (SERS) substrate was produced by combining Ag nanoparticles (AgNPs) and carbon nanocoils (CNCs). Three different methods were developed for loading AgNPs on CNCs, which include (i) direct deposition of AgNPs on CNCs by radio-frequency magnetron sputtering (RFMS) to form an Ag–CNC hybrid, (ii) deposition of a TiO2 film on CNCs by RFMS, followed by photoinduced growth of AgNPs to form an Ag–TiO2–CNC hybrid (called A-substrate), and (iii) deposition of a TiO2 film on CNCs by spin coating and then photoinduced growth of AgNPs to form an Ag–TiO2–CNC hybrid (called B-substrate). Experimental SERS results showed that B-substrates exhibited the highest SERS enhancement with an enhancement factor of over 107 for rhodamine 6G. The as-prepared Ag–TiO2–CNC substrates also showed much higher Raman signal enhancement than ordinary planar SERS substrates in our system. This was mainly due to the unique three-dimensional structure where the large surface area was available for loading more densely packed AgNPs which contribute to abundant Raman hot spots.

The structure of ultrathin amorphous carbon (a-C) films synthesized by filtered cathodic vacuum arc (FCVA) deposition was investigated by high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy. Results of the plasmon excitation energy shift and through-thickness elemental concentration show a multilayered a-C film structure comprising an interface layer consisting of C, Si, and, possibly, SiC, a buffer layer with continuously increasing sp3 fraction, a relatively thicker layer (bulk film) of constant sp3 content, and an ultrathin surface layer rich in sp2 hybridization. A detailed study of the C K-edge spectrum indicates that the buffer layer between the interface layer and the bulk film is due to the partial backscattering of C+ ions interacting with the heavy atoms of the silicon substrate. The results of this study provide insight into the minimum thickness of a-C films deposited by FCVA under optimum substrate bias conditions.

Hyperbranched polyurethane/Fe3O4 nanoparticles decorated multiwalled carbon nanotube (Fe3O4-MWCNT) nanocomposites were prepared by the in situ polymerization technique. The presence of Fe3O4 nanoparticles on the surface of the MWCNTs was confirmed by x-ray diffraction and transmission electron microscopic studies. The saturation magnetization value of Fe3O4-MWCNT was 0.23 emu/g. The glycidyl ether of bisphenol-A epoxy cured thermosetting nanocomposites exhibited enhanced tensile strength (6.4–38.5 MPa), scratch hardness (3.0–8.5 kg), and thermal stability (241–292 °C) with the increase of loading of Fe3O4-MWCNT (0–2 wt%). The nanocomposites possess good shape fixity over the repeated cycles of test. The nanocomposites also showed good shape recovery under the application of microwave irradiation. The shape recovery speed was found to be increased with the increase of the content of Fe3O4-MWCNT. Thus, the studied thermosetting nanocomposites have potential to be used as noncontact shape memory materials.

Natural fiber composites are becoming more attractive for applications as energy absorbers in the automotive industry despite their high moisture absorption characteristics. The main objective of this paper is to study the impact strength and moisture absorption properties of long fiber and short fiber hybrid composites using a kenaf/polyethylene terephthalate fiber reinforced in the polyoxymethylene matrix. The results obtained from the impact test gave 10.8 J/cm for the longer fiber hybrid composites, which is higher compared to 8.0 J/cm obtained for the short fiber hybrid composites due to less fiber pullout from the matrix. A moisture content of 0.92% and percentage water absorption of 6.77% were obtained for the long fiber composite due to poor interfacial adhesion between the fiber and the matrix. A high void content of 0.52% and porosity of 1.21% also accounted for high water and moisture absorption of the long fiber hybrid composite.

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.

Grain boundary segregation provides a method for stabilization of nanocrystalline metals—an alloying element that will segregate to the boundaries can lower the grain boundary energy, attenuating the driving force for grain growth. The segregation strength relative to the mixing enthalpy of a binary system determines the propensity for segregation stabilization. This relationship has been codified for the design space of positive enthalpy alloys; unfortunately, quantitative values for the grain boundary segregation enthalpy exist in only very few material systems, hampering the prospect of nanocrystalline alloy design. Here we present a Miedema-type model for estimation of grain boundary segregation enthalpy, with which potential nanocrystalline phase-forming alloys can be rapidly screened. Calculations of the necessary enthalpies are made for ∼2500 alloys and used to make predictions about nanocrystalline stability.

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.

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.

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.