Elemental enrichment behavior on the surface of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) was investigated in order to understand potential degradation mechanism of solid oxide fuel cell cathodes. Surface morphological changes were examined using scanning electron microscopy after heat treatment in the temperature range of 600–900 °C. Submicron-sized precipitates were formed on grain surfaces after heat treatment. Their shapes appeared to be aligned along the surface orientations of the underlying grains. Auger electron spectroscopy and transmission electron microscopy characterization revealed that the precipitate was strontium (Sr)-oxygen (O) based. The formation of Sr–O precipitates was found to increase with increasing temperature and oxygen partial pressure. A defect chemistry model is presented based on the observed phenomena.

Cu6Sn5 is a critical intermetallic compound in soldering operations. Conventional equilibrium phase diagrams show that this compound is of either a hexagonal or monoclinic structure at temperatures above and below 186 °C, respectively. Under nonequilibrium conditions, the crystal structure is dependent on composition, temperature, and processing history. The effect of Zn, Au, and In on the hexagonal to monoclinic polymorphic transformation in Cu6Sn5 intermetallics is investigated using variable temperature synchrotron powder x-ray diffraction and differential scanning calorimetry. It is revealed that, as in the case of trace Ni additions, the alloying elements Zn and Au completely stabilize the hexagonal Cu6Sn5 and prevent the phase transformation. In contrast, In additions only partially stabilize the hexagonal Cu6Sn5.

Calcium vanadate nanorods with Ca10V6O25 phase have been synthesized by a hydrothermal process without any surfactants. Hydrothermal temperature, reaction time and calcium (Ca) raw materials play important roles in the formation and size of the calcium vanadate nanorods. The nucleation and crystal growth combined with crystal splitting process have been proposed to explain the formation and growth of calcium vanadate nanorods. The calcium vanadate nanorods are used as glassy carbon electrode-modified materials to analyze the electrochemical behaviors of tartaric acid. The calcium vanadate nanorod-modified glassy carbon electrode exhibits good performance for the electrochemical detection of tartaric acid with a detection limit of 2.4 μM and linear range of 0.005–2 mM. The analytical performance and straightforward fabrication method make the calcium vanadate nanorods promising for the development of electrochemical sensors for tartaric acid.

High purity anatase titanium dioxide (TiO2) and iron (Fe)-doped TiO2 nanocrystals were prepared by a continuous flow synthesis method using isopropanol-water mixtures as solvent in supercritical or near-critical conditions. The method allows complete control of size (5–20 nm) and crystallinity (10–100%) of the nanoparticles and provides quick synthesis with a residence time of ∼10 s that can be scaled up to commercial production. It is found that the average crystallite size can be easily controlled by adjusting the ratio between isopropanol and water in the solvent, whereas the crystallinity is mainly controlled by the reaction temperature. As-prepared Fe-doped TiO2 nanoparticles appear to be single phase, but Fe3+ ions most likely do not occupy the Ti4+ sites in the anatase TiO2 crystal structure.

Exceptionally dense titanium dioxide (TiO2) films were prepared via dip coating from a sol containing poly(hexafluorobutyl methacrylate) as the structure-directing agent. The films were grown on glass, F-doped SnO2, and crystalline silicon (111) faces, either pure or with a thin layer of SiO2. The TiO2 films cover perfectly even rough surfaces, which was ascribed to thixotropic properties of the precursor gel. The films provide antireflection function to crystalline Si wafers for photovoltaic applications. The optical reflectance in visible to near-infrared (NIR) wave lengths region is considerably smaller for Si wafers covered by TiO2/SiO2 film compared with that of SiO2/Si. The dense TiO2 films are amorphous with small amount of anatase and monoclinic TiO2(B). These two phases withstand calcination at 900 °C in films deposited on Si. For comparison, porous TiO2 films were grown by the same dip-coating protocol, but with alternative organic additives, either polymers or ionic liquids.

The epitaxial growth of graphene on hexagonal silicon carbide polytypes on both the silicon-terminated (0001) and carbon-terminated ($000\bar 1$) faces has shown promise in the development of large area graphene production. It is important during these growth procedures to ensure that the underlying silicon carbide substrate is well ordered before the graphene growth. Regularly, this involves the use of a hydrogen etching procedure before graphene growth to remove polishing scratches and other defects from the substrate surface. Here, we present evidence that annealing silicon carbide substrates in argon gas at atmospheric pressure suppresses the onset of graphitization up to a temperature of 1500 °C and allows for regularly stepped terraces and removes surface defects. This allows substrate preparation and subsequent graphitization (by increasing the annealing temperature) to be carried out within a single process under an inert gas atmosphere.

X-ray photoemission spectroscopy using synchrotron radiation from 100 to 1486.6 eV was used to investigate polarity-dependent differences between the Zn-polar (0001) and the O-polar () faces of ultrahigh vacuum cleaved hydrothermally grown ZnO single crystals. The cleaved polar surfaces showed a characteristic polarity effect in that the intensity of emission from the lowest binding energy O 2p related valence band states was significantly stronger on the Zn-polar face, even when the cleaved surfaces were imperfect with irregular nonatomically flat features. A residual submonolayer hydroxyl termination of approximately 0.5 ML was observed on both the Zn-polar and O-polar surfaces immediately after cleaving. The near-surface downward band bending on the O-polar face was removed by the cleaving process leaving almost flat bands, while on the cleaved Zn-polar face, emission from states above the valence band edge was observed.

Piezoresponse force microscopy (PFM) has emerged as a powerful tool to characterize piezoelectric, ferroelectric, and multiferroic materials on the nanometer level. Much of the driving force for the broad adoption of PFM has been the intense research into piezoelectric properties of thin films, nanoparticles, and nanowires of materials as dissimilar as perovskites, nitrides, and polymers. Recent recognition of limitations of single-frequency PFM, notably topography-related cross-talk, has led to development of novel solutions such band-excitation (BE) methods. In parallel, the need for quantitative probing of polarization dynamics has led to emergence of complex time- and voltage spectroscopies, often based on acquisition and analysis of multidimensional datasets. In this perspective, we discuss the recent developments in multidimensional PFM, and offer several examples of spectroscopic techniques that provide new insight into polarization dynamics in ferroelectrics and multiferroics. We further discuss potential extension of PFM for probing ionic phenomena in energy generation and storage materials and devices.

Titanium dioxide (TiO2) nanomaterials, as important photocatalysis materials, have been synthesized with many approaches. In this study, we reported the synthesis of TiO2 nanomaterials by reacting titanium isopropoxide with ethylene glycol under basic condition followed by calcination at high temperatures. The structural, optical, and photocatalytic properties of the TiO2 nanomaterials were studied with x-ray diffraction, Raman spectroscopy, transmission electron microscopy, differential scanning calorimetry, Fourier-transformed infrared spectroscopy, x-ray and ultraviolet (UV) photoemission spectroscopy, UV–vis diffusive reflectance, and photocatalytic decomposition of methylene blue. We found that the titanium ethylene glycolide decomposes at 330 °C and transforms into pure anatase TiO2 around 400 °C. The anatase phase further transforms into core/shell rutile/anatase TiO2 composite at 550 °C and displays the highest photocatalytic activity among the samples prepared. The high photocatalytic activity can be attributed to the improved charge separation at the rutile/anatase n/n junction interface and the high crystallinity of the sample after calcination.

Nanocomposite piezoelectric powders comprising polyvinylidene fluoride (PVDF) and carbon nanotubes (CNTs) were synthesized using a novel process, which combines ultrasonication and solvent-nonsolvent mixture-induced crystallization at very low temperatures ≤10 °C. The morphological and thermal properties of these composite powders were extensively studied. Scanning electron microscopy characterization showed that these composite powders have polymer particles with an average diameter of 150 nm. Fourier transform infrared spectroscopy, differential scanning calorimetry and wide-angle x-ray scattering analyses confirmed that at CNT concentrations of 0.05–20 wt% this process introduces the β-phase in both PVDF/single-walled CNT (SWCNT) and PVDF/multiwalled CNT (MWCNT) composite powders. Both types of composite powders (PVDF-multiwalled and PVDF-single-walled nanotubes) have shown piezoelectric response at different voltages up to 1% loading of multiwalled nanotubes (MWCNTs) and 0.5% loading of single-walled nanotubes (SWCNTs) in composites.