Recent developments of high-performance NEOMAX magnets

For further improvement in achieving extremely high magnetic properties of Nd- Fe- B sintered magnets, extensive investigation has been done to densify the magnet up to the theoretical value, to increase the volume fraction of the Nd ₂Fe₁₄B matrix phase, and to achieve a high degree of alignment. By controlling chemical composition and the amount of constituent phases,improving particle size distribution, and adopting the isostatic pressing method to get better alignment of fine particles, we have succeeded in obtaining a high-performance magnet having residual flux density (B_r) of 1.495 T (14.95 kG), maximum energy product [(BH)_max] of 431 kj/m³ (54.2 MGOe), and intrinsic coercivity (iH_c) of 845 kA/m (10.62 kOe).     

A 7 ns 1 Mb BiCMOS ECL SRAM with shift redundancy

A 7-Mb BiCMOS ECL (emitter coupled logic) SRAM was fabricated in a 0.8 μm BiCMOS process. An improved buffer with a high-level output of nearly V_CC is adopted to eliminate the DC current in the level converter circuit, and the PMOS transistor has a wide operating margin in the level converter. The configurable bit organization is realized by using a sense-amplifier switch circuit with no access degradation. A wired-OR demultiplexer for the ×1 output, having the same critical path as the ×4 output circuit, allows for the same access time between the two modes. The ×1 or ×4 mode is electrically selected by the external signal. A simplified programming redundancy technology, shift redundancy, is utilized. Address programming is performed by cutting only one fuse in the shift redundancy. The RAM operates at the ECL-10K level with an access time of 7 ns. and the power dissipation at 50 MHz is 600 mW for the × mode     

Principle and operation of a new type motor consisting of piezoelectric device and strain wave gearing

The authors have developed a new type of motor consisting of a piezoelectric device and strain wave gearing, and is called a piezoelectric motor. This is a first step in realizing a low-speed, small-size and lightweight motor. The principle of the motor is that the traveling wave is produced by piezoelectric devices and displacement conversion devices without mechanical resonance, and the torque to rotate the motor is generated by a mechanism of strain wave gearing (circular spline and flexspline) without using friction. The motor is operated at variable frequency and its rotational position (angle) is controlled in open-loop because it is basically a synchronous motor. In this paper, the structure and principle of the proposed motor are explained and the driving method and the mechanical characteristics of an experimental motor also are described. The results are as follows:

• 1 The realizability of the proposed piezoelectric motor is verified experimentally. The experimental motor operates at 2920 steps per revolution, and its speed range is 0 to 960 pps [or 0 to 20 (rpms)].
• 2 The torque characteristics are clarified qualitatively.
• 3 The generated torque of the experimental motor is small (less than 0.03 Nm) and therefore the improvement of the torque is an important subject hereafter.
• 4 It is possible to construct the motor with nonmetallic material. This fact is considered to facilitate obtaining a means to lighten the weight of the motor in the future.

     

Radiation grafting of α,β,β-trifluoroethylenesulfonyl fluoride onto low-density polyethylene film by simultaneous irradiation method. I. Kinetic study of simultaneous-irradiation grafting

α,β,β-Trifluoroethylenesulfonyl fluoride (TFESF) was grafted onto polyethylene (PE) film by a simultaneous-irradiation method. The influences of the grafting conditions were analyzed kinetically. The dependencies of the grafting rate on the dose rates and monomer concentrations ranging from 10 to 75% were found to be of 1 and 0 order, respectively. The overall activation energy for the graft polymerization was 2.05 × 10⁴ J/mol. The grafting rate was found to be independent of the film thicknesses ranging from 25 to 100 μm.     

Synthesis of cationic flocculant by radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide in aqueous solution

The radiation-induced copolymerization of the methyl chloride salt of N,N-dimethylaminoethyl methacrylate (DMAEM·MC) with acrylamide (AAm) was used to prepare a cationic polymer flocculant. The polymerization rate increased with increasing dose rate, polymerization temperature, monomer concentration and mole fraction of AAm in the monomer mixture. The molecular weight of the copolymer was also found to increase with monomer concentration and mole fraction of AAm, but at high concentration and fraction of AAm, intermolecular crosslinking tends to occur during the polymerization to form water-insoluble copolymer. A water-soluble copolymer having various molecular weights and cationic strengths can be synthesized by selecting suitable reaction conditions; i.e., this radiation process can provide a much higher molecular weight copolymer with a wide range of cationic strength. The flocculation effect was evaluated using sludge from wastewater of sugar manufacture. It was found that the radiation-polymerized copolymer DMAEM·MC–AAm has an excellent flocculation effect.     

Phase Formation and Microstructure of Titanium Oxides and Composites Produced by Thermal Plasma Oxidation of Titanium Carbide

The phase formation and microstructure of titanium oxides and composites produced by Ar–O₂ thermal plasma oxidation of titanium carbide powders were investigated in detail by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Relationships between the phase compositions and microstructures of the oxides were established by combined structural and phase analyses, in correlation with synthesis conditions and phase formation mechanisms. It is revealed that vapor condensation favored the formation of anatase, which existed as smaller particles, while liquid/solid oxidation favored the formation of rutile, which appeared as larger particles or composites. A higher oxygen input in the plasma gases (Ar + O₂) enhanced the formation of anatase due to impeded oxidation and evaporation. A small amount of Ti₄O₇ and Ti₃O₅ was detected in the larger particles coexisting with rutile or TiC. These suboxides were formed as intermediates in solid oxidation of TiC or precipitated from the Ti–C–O melt during cooling. Furthermore, extensive cracks, dislocations and stresses were observed in the monolithic rutile and composites, in association with the rapid quenching in this high-temperature in-flight oxidation process.     

Control of Oxidation State of Eu Ions in Na2O–Al2O3–SiO2 Glasses

Glasses doped with well‐controlled Eu³⁺ and Eu²⁺ ions have attracted considerable interest due to the possibility of tuning the wavelength range of the emitted light from violet to red by using their ⁵D₀→⁷F_j and 5d–4f electron transitions. Glasses were prepared to dope Eu³⁺ ions in a Na₂O–Al₂O₃–SiO₂ system, and the changes in the valence state of Eu³⁺ ions and the glass structure surrounding the Eu atoms during heating under H₂ atmosphere were investigated using fluorescence spectroscopy, X‐ray absorption fine‐structure spectroscopy, and ²⁷Al magic‐angle spinning solid‐state nuclear magnetic resonance spectroscopy. The reduction behavior of Eu³⁺ ions was dependent on the Al/Na molar ratio of the glass. For Al/Na < 1, the Al³⁺ ions formed the AlO₄ network structure accompanied by the Na⁺ ions as charge compensators; the Eu³⁺ ions occupied the interstitial positions in the SiO₄ network structure and were not reduced even under heating in H₂ gas. On the other hand, in the glasses containing Al₂O₃ with the Al/Na ratio exceeding unity, the Eu³⁺ ions commenced to be coordinated by the AlO₄ units in addition to the SiO₄ network structure. When heated in H₂ gas, H₂ gas molecules reacted with the AlO₄ units surrounding Eu³⁺ ions to form AlO₆ units terminated with OH bonds, and reduced Eu³⁺ ions to Eu²⁺ via the extracted electrons.     

Decomposition Characteristics of an Artificial Biogas in a Low‐Pressure DC Glow Discharge

The decomposition characteristics of an artificial biogas, which is a mixture of CH ₄, CO ₂, and H ₂ S, using a low‐pressure DC glow discharge have been investigated. It is found that H ₂, CO, C ₂ H ₂, H ₂ O, CS ₂, and COS are produced from the artificial biogas in the glow discharge. About 65% of the hydrogen atoms in CH ₄ are converted into H ₂ at an input energy of 800 J, at which CH ₄ is completely decomposed, and the decomposition characteristics of the artificial biogas are minimally dependent on the H ₂ S additive. Further, H ₂ S has a tendency to be decomposed earlier than the other components of the artificial biogas. When the glow discharge is generated in the artificial biogas with H ₂ S, some of the carbon atoms are found to deposit on the electrodes and the wall of the discharge chamber. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(1): 26–33, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22304