Ammonia production using iron nitride and water as hydrogen source under mild temperature and pressure

Ammonia generation was studied in the reaction between water and nitrogen-containing iron at 323 K and atmospheric pressure. Similar to metallic Fe, the interstitial compound Fe₃N reduced water through Fe oxidation to produce hydrogen gas, while the N combined with atomic hydrogen to produce ammonia as a byproduct. The addition of carbon dioxide to this system accelerated the reaction with concomitant consumption of carbon dioxide. The promoted ammonia production upon addition of carbon dioxide can be attributed to the generation of atomic hydrogen from the redox reaction of carbonic acid and Fe, as well as removal of used Fe from the reaction system through the formation of a soluble carbonato complex. When carbonate was added to the reaction system, the production rates of ammonia and hydrogen increased further. The results here confirmed that ammonia can be synthesized from iron nitride under mild conditions by utilizing carbon dioxide.     

Design and fabrication of RESURF MOSFETs on 4H-SiC(0001), (112~0), and 6H-SiC(0001)

Design and fabrication of lateral SiC reduced surface field (RESURF) MOSFETs have been investigated. The doping concentration (dose) of the RESURF and lightly doped drain regions has been optimized to reduce the electric field crowding at the drain edge or in the gate oxide by using device simulation. The optimum oxidation condition depends on the polytype: N/sub 2/O oxidation at 1300/spl deg/C seems to be suitable for 4H-SiC, and dry O/sub 2/ oxidation at 1250/spl deg/C for 6H-SiC. The average inversion-channel mobility is 22, 78, and 68 cm/sup 2//Vs for 4H-SiC(0001), (112~0), and 6H-SiC(0001) MOSFETs, respectively. RESURF MOSFETs have been fabricated on 10-/spl mu/m-thick p-type 4H-SiC(0001), (112~0), and 6H-SiC(0001) epilayers with an acceptor concentration of 1/spl times/10/sup 16/ cm/sup -3/. A 6H-SiC(0001) RESURF MOSFET with a 3-/spl mu/m channel length exhibits a high breakdown voltage of 1620 V and an on-resistance of 234 m/spl Omega//spl middot/cm/sup 2/. A 4H-SiC(112~0) RESURF MOSFET shows the characteristics of 1230 V-138 m/spl Omega//spl middot/cm/sup 2/.     

Noncontact Material Identification and Distance Measurement Using Effective Capacitance With CdS Cells

We propose a novel noncontact sensing method for material identification and for detection of the distance between the sensor and the surface of a material by using its electrical and optical properties. In the proposed method, capacitance between the terminals of a pair of CdS cells, called the effective capacitance, is measured, and several capacitance values are obtained by changing the emission strength of the light emitting diode, thus changing the resistance value of the CdS cells. From these values, it is possible to identify the materials and to detect the distance between the CdS cells and the material. In this paper, we compare four kinds of effective capacitance measurement methods using a pair of CdS cells and describe the proposed measurement method. In addition, this paper discusses the measurement accuracy of effective capacitance values in the proposed method and demonstrates its ability to identify six material samples-clear, white, and black acrylic, clear vinyl chloride, brown bakelite, and aluminum-and to detect the distance between the CdS cells and the material.     

Correlates and prognosis in relation to intellectual dysfunction in a community-residing elderly population

To estimate the risk factors for intellectual dysfunction and examine its prognosis in a community-residing (non-institutionalized) elderly population, a randomly selected sample of 1,473 elderly people aged 65 years and over living in S city, Osaka Prefecture, was studied in October 1992, and data were obtained from 1,383, a response rate of 93.9%. A cohort of 1,383 was followed for 42 months and follow-up was completed for 1,300 (94.0%). The main results were as follows: 1) The prevalence of intellectual dysfunction did not differ significantly between sexes, and there was an increasing prevalence of intellectual dysfunction with age in both sexes. The prevalence of severe intellectual dysfunction was found to increase highly at age 85 and over. 2) By univariate analysis, odds ratios for age older than 75 years, low Activities of Daily Living (ADL), urinary and fecal incontinence, and no participation in social activities were significantly higher than 1 in any level of mild, moderate, and severe intellectual dysfunction. In the multivariate analysis using logistic regression, age older than 75 years and urinary and fecal incontinence showed significant higher odds ratios than 1 for severe intellectual dysfunction, and low ADL and treatment for hypertension also showed significant higher odds ratios than 1 for moderate intellectual dysfunction. 3) From analysis using the Kaplan-Meier method, the cumulative survival rates decreased with a decline in intellectual functioning in both age groups of 65-74 and 75 years and older. 4) Application of the Cox proportional hazards model resulted in adjusted hazard ratio for severe intellectual dysfunction of 1.79 (95% confidence interval, 1.02-3.12), controlling for other factors such as sex, age, general health status, incontinence and social activities.     

Monocarbonyl compounds from catalytic decomposition of autoxidized unsaturated fatty acid esters

Monocarbonyl compounds formed by the decomposition of autoxidized triolein, methyl linolenate, and methyl arachidonate were converted into their 2,4-dinitrophenylhydrazone derivatives and analyzed by thin layer and paper chromatographies. From decomposition of autoxidized triolein with acid-washed Fuller’s earth alkanals were the only monocarbonyl products found, whereas, with metal catalysts or heat, 2-alkenals were the primary products. Autoxidized methyl linolenate and methyl arachidonate decomposed with metal catalysts or heat yielded 23–55% of 2,4-alkadienals but minor amounts with acid-washed Fuller’s earth. The differences in distribution of monocarbonyl products were attributed to a selective course of scission of the hydroperoxides that depended upon the conditions of decomposition.     

Synthesis and properties of bismaleimide resins containing ether bonds

New bismaleimides containing ether bonds were prepared. The thermal properties of the bismaleimides were investigated by differential scanning calorimetry (DSC). The effects of structure of the bismaleimides and curing conditions on the thermal and mechanical properties of the cured resins such as initial decomposition temperature (T_d), glass transition temperature (T_g), and flexural strength were studied. The introduction of ether bonds to bismaleimide resins decreased the brittleness of the resins without reductions in their heat-resistant properties.     

Thermal Behavior of BaTiO3 Particles Synthesized by Plasma Chemical Vapor Deposition

The thermal behavior of nanoparticles BaTiO₃, prepared by a radio-frequency plasma chemical vapor deposition (RF-plasma CVD) method, was characterized by various analysis methods. The BaCO₃ phase was included in the powder as byproducts, which is also observed in hydrothermal BaTiO₃ powder. The BaCO₃ phase decomposed and disappeared by annealing at 873 K for 30 min. H₂O, N₂, CO₂ and H₂, were detected by a thermal desorption spectra measurement from BaTiO₃ powder. The annealed powder became well-crystallized particles without grain growth, although as-prepared powder included polycrystalline particles. We successfully observed in-situ grain growth for BaTiO₃ nanoparticles by thermal transmission electron microscope. At the initial step of normal grain growth, very fine particles with 40–60 nm diameters started to merge into the larger grains around 1083 K. The migration rate was measured by video images and a grain boundary diffusion coefficient D_gb was calculated.     

Effect of Grain Boundaries on Thermal Conductivity of Silicon Carbide Ceramic at 5 to 1300 K

The thermal conductivity of a SiC ceramic was measured as 270 W·m⁻¹·K⁻¹ at room temperature. At low temperatures ( T < 25 K), the decrease in the conductivity was proportional to T ³ on a logarithmic scale, which indicated that the conductivity was controlled by boundaries. The calculated phonon mean free path in the ceramic increased with decreased temperature, but was limited to ∼4 μm, a length almost equal to the grain size, at temperatures below 30 K. We concluded that the thermal conductivity of the ceramic below 30 K was influenced significantly by grain boundaries and grain junctions.     

Barium Carbonate Phase on the Surfaces of Barium Titanate Particles and in Situ Transmission Electron Microscopy Observation of Its Decomposition

A BaCO₃ phase is found on the surfaces of hydrothermally synthesized BaTiO₃ particles; it occurs as aggregates or small protuberances. A small proportion of the phase decomposes to BaO crystallites when heated by a convergent electron beam in a transmission electron microscope. The BaO and BaCO₃ crystallites disappear when they are irradiated successively by the convergent electron beam. The BaO crystallites and the BaCO₃ phase sublimate and/or react with BaTiO₃ crystals whose surface layers are deficient in Ba²⁺ ions.