Doped ceria (CeO2) compounds are fluorite related oxides which show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, considerable interest has been shown in application of these materials for 'intermediate temperature (300- 500°C)' operation of solid oxide fuel cells (SOFCs). In this review paper, our experimental data was re-introduced to propose a new design paradigm for development of high quality doped CeO2 electrolytes. Based on our experimental data, our original idea a control of nano-inhomogeity of doped CeO2 electrolytes was proposed. In our work, the nano-sized powders and dense sintered bodies of M doped CeO2 (M: Sm, Gd, Y, Yb, Dy, Ho, Tb and La) specimens were fabricated using ammonium carbonate co-precipitation method, conventional sintering method and pulsed electric current sintering method. Also nano-structural features of those specimens were carefully observed for conclusion of relationship between electrolytic properties and microstructure in doped CeO2. It is essential that the electrolytic properties of doped CeO2 reflect in changes of microstructure even down to the atomic scale. Accordingly, a combined approach of ultimate analysis, simulation and processing route design is required to develop the superior quality doped CeO2 electrolytes for the intermediate temperature operation of SOFCs.
This review paper describes some of our recent topics on surface functionalization of IV semiconductors. Well-designed surfaces of the semiconductors create exciting opportunities for technological applications. To meet such exciting functionality, we use a monolayer system in which the reactive monolayer attaches to the semiconductor surface via covalent linkage. Most importantly, this molecular system enables chemists to manipulate the non-oxidized surfaces of the semiconductors even under ambient conditions. A variety of organic approaches is available to modify the surface chemical property in a lab environment without surrounding environmental control using glove box. The covalent attachment of organic mono layers leads to the appearance of unique property. For example, (i) The surface organic passivation leads to the highly efficient luminescence from silicon nanoparticles. Interestingly, the monomolecular density can controls the optical transition process of photoexcited careers in the nanostructured silicon. (ii) A multifunctional microarray, in which different types of self-assembled monolayers (SAMs) are respectively positioned on predefined surface sites, allows the parallel detection of different bimolecular interactions under the same buffer condition. (iii) The successful formation of reactive moieties on the IV semiconductors has provided unique chemical template for subsequent biomolecular attachment. The industrial use of IV semiconductors provides the unsurpassed compatibility with microelectronics. Furthermore, these semiconductors with a high chemical affinity for carbon, oxygen, and nitrogen have a potential to produce a variety of its organic derivatives hybridized at the molecular level.
For alleviating both of the environmental and resource-depletion problems related to heavy metals, the authors examined the heavy-metal adsorption and desorption functionalities of some hydrogels. It was found that the functional hydrogels can capture the heavy metals more efficiently than other adsorbents, and besides, some of them can desorb the adsorbed heavy metal with the efficiency of ～100%. From these experimental results, the authors have proposed a new heavy-metal recycling system in which the hydrogel adsorbent is also recycled repeatedly.
Control of microstructure during processing is necessary to produce materials with optimum properties. Grain growth behaviour in both two-phase (solid/liquid) and single phase materials is strongly dependant on interface structure, either rough (atomically disordered) or faceted (atomically ordered). Materials with disordered interfaces show normal grain growth behaviour, whereas materials with ordered interfaces can show different types of non-normal grain growth, which are system and time-dependant: pseudo-normal, abnormal, stagnant and delayed abnormal. Examples of the different types of grain growth are given from ceramic and metallic systems, and general principles of microstructure evolution with respect to interface structure are presented.
This paper is the review for the authors' works on Free Electron Laser (FEL) irradiation effects aiming at syntheses of 3-dimensional C60 polymers. The used pristine was 99.5% C60 powder or the mixtnre with iodine, and also C60 precipitates prepared by a liquid-liquid interfacial precipitation (LLIP) method. The pristine was set in the vacuum and was compressed in the anvil with the pressure of 600 MPa～7 GPa. The third harmonics (@400-500 nm) FEL was irradiated with a macro-pulse (@20 μs) containing very short micro-pulses (@200 fs). The Raman Ag(2) peak of C60 molecules in the vicinity of 1469 cm-1 becomes broad and shifts to the lower energy side as proceeding of polymerization. Under higher pressure the larger red-shift and the increment of the half width of the Raman peak were observed. The irradiated mixture with iodine revealed the more distinctive red-shift, above 10cm-1. Also the large peak red-shift ca. 10cm-1 was observed in the LLIP specimen probably because of highly packing of C60 molecules. The obtained results suggested that the C60 molecular accession and/or the photon-assisted hole-doping from iodine were decisively effective to promote photo-polymerization.
Fuel-based and incandescent lamps convert ≤ 5% of the energy they consume into visible light; the remaining energy is given off as heat. The conversion efficiency of fluorescent lamps is approximately 20%. These very common sources of light convert the earth's energy sources mostly into waste heat and greenhouse gases. The increasingly precious energy resources and the increasing evidence of pollution-driven climate change demand that we reduce the energy and environmental costs of these forms of artificial lighting both by improving these sources and the employment of new forms of lighting. Light-emitting diodes (LEDs) convert electricity into light using semiconductor materials and, at present, represent the energy efficient technology of the future. Currently, LEDs are primarily used for interior and display lighting, as the efficiency of the diodes “droops” rapidly with an increase in the injected current that is necessary to achieve high-brightness. Exterior solid-state lighting within cities is being tested; however, much research, engineering and technological development remain necessary to achieve increased efficiency, low heat generation and the color temperatures and color rendering that are acceptable to human visual perception.
One of the most important factors for advanced ceramics preparation is nature of the powders. There are many methods to prepare powders for ceramics, namely, mechanical, thermal decomposition, precipitation, hydrolysis, hydrothermal, melt and quenching, etc. This is a review of powder preparation for advanced ceramics. Characteristics of these methods are described. And also ideal powder for advanced ceramics is described.
The results of x-ray diffraction, the size of lattice parameter, and the values of oxygen diffusion coefficient in YO1.5-CeO2, GdO1.5-CeO2, and NdO1.5-CeO2 systems were reviewed. In YO1.5-CeO2 system, the lattice parameter decreases as the concentration of YO1.5 increases. In GdO1.5-CeO2 system, the lattice parameter does not change very much. And in NdO1.5-CeO2 system, it increases as the concentration of NdO1.5 increases. When the oxygen diffusion coefficient was plotted as a function of lattice parameter, there was no correlation between them. However, when the oxygen diffusion coefficient was plotted as a function of the concentration of trivalent cation additives, there was very good correlation between them. Consequently, the diffusion coefficient does not depend on the size of crystal lattice in ceria solid solutions, but it depends on the concentration of trivalent cation additives.
In this article it is reviewed on enigmatic electrical and magnetic properties of La(Ba)MnO3 thin films, useful for tunable microwave filters. As-grown films have well separated insulating to metallic (Tp) and paramagnetic to ferromagnetic (Tc) transition temperatures, which can be understood from the phase separation model. The film shows negative magnetoresistance (MR) caused by normal double exchange coupling effect, and positive MR which is interpreted by a magnetostriction effect. The phase separation is caused by crystal strain in the film. By annealing these two temperatures, Tp and Tc, become more separated, implying a size reduction of ferromagnetic grains. The phase separation scenario can be confirmed by ferromagnetic resonance (FMR) showing doublet signals. The FMR indicates anisotropic phase transition which supports the magnetostriction model. Moreover, the narrow FMR signals suggest high spin ordering and good crystallinity.
Recently, long coated conductors, in which superconducting YBa2Cu3O7 (YBCO) thin films are deposited on oriented metallic tapes, have been developed, and high critical current densities Jc are required for their application to various power devices. In this review we present our recent investigations on the flux pinning mechanisms in YBCO thin films that determines Jc.
Top quality thin films for different applications are always of interest. However, it is not easy to grow such films and many criteria have to be fulfilled. The degree of complexity enhances significantly for muticomponent materials such as high-Tc superconductors, giant magnetoresistive materials, heterostructures, others. This translates into a lower growth control level. Solution resides in identification of the specific details as well as of the general principles of growth and their personalized application towards preparation of optimized thin films of top quality. This is our approach and goal. Examples in this regard will be introduced with a strong emphasis on HTS cuprates for sensor applications such as those working in the terahertz domain and currently considered for construction of future “safe and secure society”.