Microstructure and yield strength of UDIMET 720LI alloyed with Co-16.9 Wt Pct Ti

We proposed a new method for developing Ni-base turbine disc alloy for application at temperatures above 700 °C by mixing a Ni-base superalloy U720LI with a two-phase alloy Co-16.9 wt pct Ti in various contents. The microstructure and phase stability of the alloys were analyzed using an optical microscope, a scanning electron microscope, energy-dispersive spectroscopy, and an X-ray diffractometer. The yield strength was studied by compression tests at temperatures ranging from 25 °C to 1200 °C. The results show that all the alloys had a dendritic structure. Ni₃Ti (η) phase was formed in the interdendritic region in the alloys with the addition of Co-16.9 wt pct Ti, and its volume fraction increased with the increase in the addition of Co-16.9 wt pct Ti. The results of exposure at 750 °C show that the addition of Co-16.9 wt pct Ti to U720LI had a great effect on suppressing the formation of σ phase due to the reduced Cr content in the γ matrix. Compared to U720LI, the alloys with the addition of Co-16.9 wt pct Ti possessed higher yield strength. The solid-solution strengthening of γ and γ′ and higher volume fraction of γ′ were assumed to cause this strength increase.     

Using selective precipitant for uranyl ions — Fundamental studies for evaluating the precipitant performance

We have developed a simple reprocessing process for spent FBR fuels using N-cyclohexyl-2-pyrrolidone (NCP) which has selective precipitation ability for UO₂²⁺ ions. It was confirmed that NCP has sufficient precipitation ability for UO₂²⁺ ions, decontamination capability (separation of UO₂²⁺ from simulated fission products), and resistance to γ-ray radiation in nitric acid solutions. These findings indicate that NCP is applicable to our reprocessing process. We have also evaluated performances of other precipitants such as N-n-propyl-2-pyrrolidone (NProP), N-n-butyl-2-pyrrolidone (NBP), and N-n-butyl-2-pyridone (NBPyr). It was found that higher decontamination factors (DFs) are obtained by using NProP and NBP. This can be interpreted that the hydrophobicity of NProP and NBP is lower than that of NCP. Furthermore, we have obtained an experimental result that the resistance of NBPyr to γ-ray radiation is superior to that of NCP.     

Low temperature synthesis of silver-palladium alloy powders internal electrodes for multilayer ceramic devices

Physical and electrical properties of three types of Ag-Pd pastes, which consist of different metal fine powders, i.e., a coprecipitated powder, an agglomerated alloy powder made by heat treatment and a pulverized alloy powder produced by improved pulverization method, have been studied. The paste prepared from pulverized alloy powder showed a higher film packing density (6.3 g/cm³) than those made of the other powders. The film consisting of pulverized alloy powder showed a lower expansion at around 500 °C, a lower shrinkage from 700 °C to 1100 °C and a lower electric resistivity. The results indicated that the paste which consists of an pulverized Ag-Pd alloy powder was superior in performance to the other two pastes for an internal electrode material of multilayer ceramic device.     

Highly efficient electrochemical valence control of uranium using microfluidic chip equipped with microelectrodes

We have developed a novel microchip equipped with a microchannel and Pt microelectrode array for electrochemically controlling valences of actinide (An) species. The square wave voltammograms of the redox reaction of potassium hexacyanoferrate(II) in the microchannel were measured. We found that the fabricated Pt microelectrode array has superior performances for the detection of the electrochemically active species in the microchannel. Therefore, the potentiostatic electrolysis experiments of uranium ions were carried out in the microchannel, and the concentration changes of uranium ions accompanied by the potentiostatic electrolysis were examined using thermal lens microscope. The results showed that the redox reactions between U(VI) and U(IV) can be performed completely in a microchannel in a few minutes, that is, the microscale reaction is accelerated by a factor of more than 10 compared with the bulk solution reactions taking hours mostly. The developed microchip was found to have enough performances for realizing rapid and highly efficient redox reactions for An species, which are impossible in the bulk reactions.     

Construction of an extremal self-dual code of length 62

We construct an extremal singly-even self-dual [62, 31, 12] code. The existence of such a self-dual code was not previously known. Combined with known results, the above code also determines all lengths for which there are self-dual codes with minimum weight 12     

Quantum flux parametron: a single quantum flux device for Josephsonsupercomputer

A quantum flux parametron (QFP), a single quantum flux superconductive device that has a potential of up to 100-GHz switching with nW-order power dissipation, is considered. The potential of the QFP and key technologies when QFPs are applied to a Josephson supercomputer are described. Switching speed, stability, and power dissipation of a QFP are discussed. QFP gates, circuits, and systems are next described. Then, ultra-fast clock distribution using a standing wave is explained. High-speed operation at more than 10 GHz and 10¹⁴ error-free operations per QFP have been demonstrated. Finally described is a high-density packaging scheme by three-dimensional integration, which is very important for ultra-high speed circuits because the propagation delay becomes dominant in such circuits     

Twin-electron biprism

In order to obtain a large deflection angle without increasing the applied voltage to an electron biprism, we have developed a 'twin-electron biprism' (TBP), which is composed of two filament electrodes and a pair of ground plates. The observed interference-fringe spacing revealed that the deflection angle created by a TBP was about twice larger than that by a 'conventional electron biprism'. Also, we have suggested, in a double-electron biprism interferometry, the optimal disposition of a TBP for reducing the intensity of Fresnel fringes recorded in an electron hologram.     

Effects of base layer thickness on reliability of CVD Si3N4 stack gate dielectrics

Effects of the base layer in Si₃N₄/SiON stack gate dielectrics, in particular, the physical thickness of the base layer, on the dielectric reliability, MOSFET performance and process controllability are investigated. It is found that the electrical characteristics such as TDDB lifetime as well as the Si₃N₄ film property in Si₃N₄/SiON stack dielectrics with the same capacitance oxide equivalent thickness strongly depend on the SiON-base layer thickness. From the TDDB measurements for both stress polarities and from the Si₃N₄ stoichiometry by the X-ray photoelectron spectroscopy analysis, the optimum SiON-base layer thickness is determined to be approximately 1 nm, in order to obtain longer TDDB lifetime and surperior n-ch MOSFET performance. The obtained results are considered to attribute to the nitrogen profile in the Si₃N₄/SiON stack dielectrics and the strained layer thickness near SiON/Si interface.     

A unified analysis of resonant converters

The general method of analysis for resonant power converters is presented. This analytical method generalizes the idea of state-space-averaging technique to overcome the limitations of the conventional state-space-averaging method. As the result, the characteristics of resonant power converters are clarified so that transfer functions and stability conditions are revealed. In addition, a computer program of analysis based on the proposed method is developed. The program can be applied to various resonant power converters, even when they have parasitic losses and higher-order resonant circuits