Development of a wide range-operable,rich-lean low-NOx combustor for NH3 fuel gas-turbine power generation

Low-NOx NH₃-air combustion power generation technology was developed by using a 50-kWe class micro gas-turbine system at the National Institute of Advanced Industrial Science and Technology (AIST), Japan, for the first time. Based on the global demand for carbon-free power generation as well as recent advances involving gas-turbine technologies, such as heat-regenerative cycles, rapid fuel mixing using strong swirling flows, and two-stage combustion with equivalence ratio control, we developed a low-NOx NH₃-air non-premixed combustor for the gas-turbine system. Considering a previously performed numerical analysis, which proved that the NO reduction level depends on the equivalence ratio of the primary combustion zone in a NH₃-air swirl burner, an experimental study using a combustor test rig was carried out. Results showed that eliminating air flow through primary dilution holes moves the point of the lowest NO emissions to the lesser fuel flow rate. Based on findings derived by using a test rig, a rich-lean low NOx combustor was newly manufactured for actual gas-turbine operations. As a result, the NH₃ single fueled low-NOx combustion gas-turbine power generation using the rich-lean combustion concept succeeded over a wide range of power and rotational speeds, i.e., below 10–40 kWe and 75,000–80,000?rpm, respectively. The NO emissions were reduced to 337?ppm (16% O₂), which was about one-third of that of the base system. Simultaneously, unburnt NH₃ was reduced significantly, especially at the low electrical power output, which was indicative of the wider operating range with high combustion efficiency. In addition, N₂O emissions, which have a large Global Warming Potential (GWP) of 298, were reduced significantly, thus demonstrating the potential of NH₃ gas-turbine power generation with low environmental impacts.     

Tip-enhanced Raman spectroscopy for nanoscale strain characterization

Tip-enhanced Raman spectroscopy (TERS), which utilizes the strong localized optical field generated at the apex of a metallic tip when illuminated, has been shown to successfully probe the vibrational spectrum of today’s and tomorrow’s state-of-the-art silicon and next-generation semiconductor devices, such as quantum dots. Collecting and analyzing the vibrational spectrum not only aids in material identification but also provides insight into strain distributions in semiconductors. Here, the potential of TERS for nanoscale characterization of strain in silicon devices is reviewed. Emphasis will be placed on the key challenges of obtaining spectroscopic images of strain in actual strained silicon devices. Figure Figure Concept of Tip Enhanced Raman Spectroscopy (TERS), which utilizes the strong localized optical field generated at the apex of a metallic tip when illuminated. TERS has been demonstrated to successfully probe the vibrational spectrum of today’s and tomorrow’s state-of-the-art silicon and next generation semiconductor devices     

High-Tc ferromagnetic semiconductor-like behavior and unusual electrical properties in compounds with a 2×2×2 superstructure of the half-Heusler phase

Heusler phases, including the full- and half-Heusler families, represent an outstanding class of multifunctional materials on account of their great tunability in compositions, valence electron counts (VEC), and properties. Here we demonstrate a systematic design of a series of new compounds with a 2×2×2 superstructure of the half-Heusler unit cell in X-Y-Z (X=Fe, Ru, Co, Rh, Ir; Y=Zn, Mn; Z=Sn, Sb) systems. Their structures were solved by using both powder and single-crystal X-ray diffraction, and also directly observed by using high-angle annular dark-field imaging in a scanning transmission electron microscope (HAADF-STEM). The VEC values of these new compounds span a wide and continuous range comparable to those for the full- and half-Heusler families, thereby implying tunability in compositions and physical properties in the superstructure. In fact, we observed abnormal electrical properties and a ferromagnetic semiconductor-like behavior with a high and tunable Curie temperature in these superstructures.     

The effect of annealing on the proton conductivity of Mg-doped α-Al2O3

In order to evaluate the effect of annealing treatment on the proton conductivity of ??-alumina, the electrical conductivity of Mg-doped polycrystalline ??-alumina kept at 1,873?K under various conditions of the surrounding atmosphere and then cooled in the furnace was measured in the temperature range 1,173?C1,473?K. The H⁺/D⁺ isotope effect on the electrical conductivity was also examined under a hydrogen atmosphere at 1,273?K. The protonic conductivity measured at 1,273?K increased with the increase in the activity of oxygen and water vapor in the annealing atmosphere at 1,873?K. It is considered that the solubility limit of magnesium ions in ??-alumina in equilibrium with the small amount of the spinel phase increased with the increase in the activity of oxygen and water vapor at 1,873?K. This enhanced amount of magnesium ions is frozen in a non-equilibrium state to 1,273?K and works as the enriched acceptor dopant for the incorporation of protons.     

An estimation of the distribution functions of doped Tb and Nd in glasses by fluorescence measurements

The distribution functions of doped Tb³⁺ and Nd³⁺ in silicate, germanate, borate and phosphate glasses, in which cross-relaxation among active ions plays an important role, have been estimated by fluorescence measurements. In order to analyze both the steady state and the transient fluorescence characteristics, a non-linear model for the resonant energy transfer has recently been developed. The experimental fluorescence intensity and decay curves, measured as a function of acceptor concentration, suggested a modified distribution function, which included the effect of the segregation of donors and acceptors. The number of segregated Tb³⁺ ions at the second nearest neighbor position around a Tb³⁺ ion was estimated to be 0.1–3.4, depending on the host glass.     

Passive Transport of Ionic Drugs through Membranes with pH-Dependent Fixed Charges

We have studied both theoretically and experimentally the passive transport of ionic drugs through membranes with pH-dependent fixed charge. The system considered constitutes a simplified model for pH-controlled drug delivery through membranes of biochemical and pharmaceutical interest. The theoretical approach employed is based on the Nernst-Planck flux equations and all of the species present in the system (the neutral or ionic drug and the hydrogen and hydroxide ions) have been taken into account together with a Langmuir-type isotherm for the adsorption of the ionic drug onto the membrane surface. The membrane permeabilities of cationic, anionic, and neutral drugs through porous membranes with graft-polymerized weak polyelectrolytes have been measured as a function of the external pH. According to the nature of the grafted polyelectrolyte, the ionized membrane fixed groups can be negative or positive. For the amphoteric membrane, both fixed charge groups are present in the grafted chains. In all cases, the ionization state of the weak polyelectrolyte fixed groups changes with the local pH within the membrane. A comparison of the theoretical results with the experimental data allows one to explain qualitatively the changes of the membrane flux with the external pH and gives new physical insights into the transport problem. Copyright 2000 Academic Press.     

Potentiometric Cr(VI) selective electrode based on novel ionophore-immobilized PVC membranes

For the determination of Cr(VI) concentrations with a potentiometric ion-selective electrode (ISE), ionophore-immobilized membranes were prepared by ultraviolet (UV)-induced graft polymerization followed by chemical treatment. Novel ionophores comprising various amine structures were immobilized onto poly(vinyl chloride) (PVC) matrixes, and these were examined to determine Cr(VI) selectively. Of the three ionophores examined in this study, the membranes with N,N,N,N-tetrakis(3-aminopropyl)-1,4-butanediamine (DABAm4) exhibited the highest Cr(VI) ion selectivity in both extraction and potentiometry experiments. The plasticizer in the membrane was optimized as 1.0 ml o-nitrophenyl octyl ether (NPOE)/g PVC to form diffusible channels. The potentiometric studies revealed that the performance of DABAm4-immobilized PVC was equivalent to that of mobile ionophores in supported liquid membranes (SLMs). A reproducible response of Cr(VI) was attained within a response time of 1 s in the range of 2.16 × 10⁻⁶ to 0.1 M, using the membrane prepared in this study. The selectivity for the Cr(VI) ion against the other interfering ions was compared reasonably between a solvent extraction and potentiometry. The long-term response of the Cr(VI) ISE showed slight deterioration over a continuous operation for 6 months, while the detection limit slightly decreased due to the leaching-out of the plasticizer. The ISE along with the DABAm4 immobilized membrane showed a higher Cr(VI) ion selectivity and more stable response under long-term usage than ISEs with typical SLMs.     

Advances in the preparation of organofluorine compounds involving iodine and/or iodo-compounds

The intriguing properties of iodine have drawn the attention of organic chemists. In this paper, we will describe the recent development of stereo- and/or regioselective synthesis of fluorine-containing organic compounds employing hypervalent iodine fluorides such as ArIF₂ (1), IF₅ (22), and (E)-2-fluoro-alk-1-enyl-4-aryl iodonium salts R(F)C=C(H)IF-Ar (12). The electrochemical fluorination procedures involving iodo-compounds will also be presented to prepare fluoro-organic compounds.     

Structural relation properties of hydrothermally stable functionalized mesoporous organosilicas and catalysis

The surfactant assistant syntheses of sulfonic acid functionalized periodic mesoporous organosilicas with large pores are reported. A one-step condensation of tetramethoxysilane (TMOS) with 1,2-bis(trimethoxysilyl)ethane (BTME) and 3-mercaptopropyltrimethoxysilane (MPTMS) in highly acidic medium was performed in the presence of triblock copolymer Pluronic P123 and inorganic salt as additive. During the condensation process, thiol (-SH) group was in situ oxidized to sulfonic acid (-SO(3)H) by hydrogen peroxide (30 wt % H(2)O(2)). X-ray diffraction studies along with nitrogen and water sorption analyses reveal the formation of stable, highly hydrophobic, and well-ordered hexagonal mesoscopic structures in a wide range of -CH(2)CH(2)- concentrations in the mesoporous framework. The resultant materials were also investigated by (29)Si MAS and (13)C CP MAS NMR, thermogravimetric analyses, UV-Raman spectroscopy, and FT-IR spectroscopy. The role of the bridged organic group on the hydrothermal stability of the mesoporous materials was established, which revealed an enhancement in hydrothermal stability of the materials with incorporation of the bridged organic groups in the network. The catalytic performance of -SO(3)H functionalized mesoporous materials was investigated in the esterification of ethanol with acetic acid, and the results demonstrate that the ethane groups incorporated in the mesoporous framework have a positive influence on the catalytic behavior of the materials.     

Radiation-induced precipitation of nickel ion in aqueous solution saturated with hydrogen gas

Ni²⁺ ion is proved to precipitate in a solution saturated with H₂ by the aid of ⁶⁰Co γ-ray irradiation. The amount of Ni precipitated increases in proportion to the total dose, where the G(Ni) is accounted for as 0.29. A log–log plot has revealed that precipitation increases linearly with dose rate under less than 1 kGy/h, followed by a subsequent levelling off. In regard to the effect of initial [Ni²⁺], the increase in [Ni²⁺] has incurred a reduction of precipitation rate of Ni.