Kiyoshi Terayama

Controlled-rate thermal analysis

Binder burnout has been carried out by a controlled heating programme which depends on the composition of the binder system used. The present paper gives the principle of constant decomposition rate thermogravimetry, which falls within controlled-rate thermal analysis, and the advantage of this technique when evolved gas analysis is used in discriminating the process of super hard material burnout by comparison with the conventional linear heating method is described. In this technique, the sample temperature is varied to maintain a constant rate of mass loss by control of the heating of the infrared image furnace. Since the constant decomposition rate control (CDRC) allows a much better control of the sample environment, which generally depends on the rate of gas evolution, it is possible for uniform conditions to exist throughout the sample, and the total burnout time can be reduced considerably without crack formation. The efficiency of this CDRC was proved by the obtained temperaturevs. time curve and SEM observations of the heat-treated sample after the debinding process.

Investigation of double oxides in the system of Pr2O3–WO3

Powdered samples composed of Pr2O3 and WO3 in various mixing mole ratios were heat-treated in an air flow or in an N2 gas flow at 1000°C. The phases formed in the samples were investigated by XRD. Single phases of the five double oxides of the mole ratios Pr2O3:WO3 of 1:4.4, 1:3, 1:2, 1:1, and 5:2 were obtained at the respective mixing mole ratios by a reaction in air. The single phase of 3:1 oxide, which was reported to be obtained in a vacuum or an Ar atmosphere, was not obtained by a heat treatment in air but rather by a reaction in an N2 atmosphere. Furthermore, the crystal system and the lattice parameters were determined for the double oxides with the mole ratios of 1:4.4, 1:3, 1:1, and 5:2.

Deposition of novel nanocomposite films by a newly developed differential pumping co-sputtering system

A differential pumping co-sputtering system was developed to facilitate a controlled, but flexible fabrication of multifunctional nanocomposite films with compositions not limited by thermodynamic restrictions. This system features a multichamber design with a differential pumping system. Dividing atmospheres with this set up greatly reduced the cross-contamination between chambers, and each material could be co-deposited by rapid rotation of the substrate. The clearance between the substrate holder and the chamber was set at 1–2 mm, and the conductance of the clearance was examined roughly using conductance equations for typical types of orifices. It was found that the potential difference (PD) value of the clearance between the two chambers was less than 0.01; the gas flow between the two chambers through the clearance thus appears to be a practical molecular flow. The PD value, where P is a pressure (Pa) and D is a diameter of an orifice or a pipe (m), is a gas flow indicator or parameter obtained from an equation of Knudsen number. The changes in the oxygen partial pressure and glow discharge plasma in the left chamber were investigated using a process gas monitor (PGM) and optical emission spectroscope (OES) by introducing different gases to each chamber. The PGM results revealed that the cross-contamination of oxygen from the other chamber was suppressed to 10 ± 3% of the original. In addition, the OES measurement for glow discharge plasma did not detect substantial oxygen contamination from the other chamber. Using the newly developed system, an AlN/SiOx nanocomposite film consisting of B4-type AlN and amorphous SiOx was obtained successfully.A differential pumping co-sputtering system was developed to facilitate a controlled, but flexible fabrication of multifunctional nanocomposite films with compositions not limited by thermodynamic restrictions. This system features a multichamber design with a differential pumping system. Dividing atmospheres with this set up greatly reduced the cross-contamination between chambers, and each material could be co-deposited by rapid rotation of the substrate. The clearance between the substrate holder and the chamber was set at 1–2 mm, and the conductance of the clearance was examined roughly using conductance equations for typical types of orifices. It was found that the potential difference (PD) value of the clearance between the two chambers was less than 0.01; the gas flow between the two chambers through the clearance thus appears to be a practical molecular flow. The PD value, where P is a pressure (Pa) and D is a diameter of an orifice or a pipe (m), is a gas flow indicator or parameter obtained from...

Reduction of MnFe2O4 without and with carbon

We succeeded in studying the mechanism of hydrogen added carbothermic reduction process of iron-manganese oxide by means of the new technique, simultaneous measurement of evolved gas analysis (EGA) and humidity sensor (HS). Water vapor evolved by the reduction with hydrogen can be detected by HS. Other gas was detected by TCD. Without carbon, the hydrogen reduction process was followed to the formation of the intermediate product between MnO and FeO and finally reduction to the mixture of MnO and Fe. With carbon, the intermediate products between MnO and FeO was formed at about 780 K. The methane was formed in higher temperature than 1073 K and the reduction with carbon proceeded mainly. At higher temperatures, methane decomposed to yield nascent carbon that tended to result in the acceleration of the reduction rate with carbon. The study is concerned with the mechanism of the hydrogen reduction of MnFe2O4 and the effect of without and with carbon on this reduction by means of combining EGA and HS.

Impurity-Doped GaSe Radiation Detector Evaluated at 100°C

The pulse height distribution for 5.5 MeV α particles from 241Am was measured using a GaSe detector doped with 0.1 at.% Sn at 100°C and compared with that measured at room temperature. It was found that the energy resolution at 100°C was 8.3% which was as good as that at room temperature. The temperature dependence of the leakage current of the detector was also measured for the applied voltage of 50 V and found to have a small value of 60 nA at 100°C.

Pattern Formation of Sputtered Films by Deposition through Mask

The thickness of the film near the edge of a film pattern formed by sputter deposition through a mask is not uniform, because of the shadowing effect of the side wall of the mask edge. When the effect is large, a sharp pattern can not be obtained. In order to clarify the precision or the sharpness of the film pattern, the distribution of the film thickness near the pattern edge was measured. It was found that the sharpness depended on the position of the pattern edge and the attitude of the side wall of the mask. A mask with bridges was contrived for the formation of an isolated space in a film, and the film deposition under the bridge was observed. It was found that the ratio of the gap between the substrate and the bridge to the bridge width must be larger than 1.0 for the thickness under the bridge to be greater than half the full thickness.

Fabrication of Tantalum nitride thin film using the low vacuum magnetron sputtering system

Tantalum nitride (TaN) thin film is attractive material as a diffusion barrier coating and used in electronics industry. TaN thin film is fabricated by some method such as DC sputtering, CVD and pulse laser deposition. In this study, TaN thin film was deposited on Si (111) wafer, soda glass substrates by reactive sputtering at low vacuum conditions for reducing energy costs. N2/Ar gas mass flow rate was ranged from 9 to 23% at N2 gas. At lower N2 gas flow, crystalline TaN thin films were obtained. Amorphous like TaN thin films were observed at other rate range using XRD. Ta oxide layer was observed between the crystalline TaN film and both of Si wafer and glass substrates by GDS depth profiling. Film thickness was 200- 400 nm. The TaN layer deposited on Si and glass substrate in 9 % N2 flow having columnar structure was observed in these films by FE-SEM.

Mechanical Properties of Al-10 Mass % Si-Mg High-Pressure Die-Casting Alloy with Different Mg Content

The influence of Mg content on Al-10 mass % Si-0.05, 0.30 and 0.60 mass % Mg alloys castings were produced by high-pressure die-casting process, used by microstructure observation and evaluation of mechanical properties. With increasing Mg content, the main constituent phases (primary α-Al phase and eutectic phase) were not changed, but a small amount of phases crystallized at last stage of solidification (β-Al5FeSi, π-Al8Si6Mg3Fe and Mg2Si) were changed in the kind and the volume. In the mechanical property, 0.2%PS and UTS were increased, elongation and absorbed energy were decreased with increasing Mg content or difference of heat treatment. Because the fracture mode in primary α-Al phase was changed from ductile to brittle by precipitation strengthening.

Age-Hardening Behavior of Mg-Al-Zn Alloys Produced by Sand Mold Casting

In recent years, Mg-Al-Zn system alloy has been used for the parts in the automobile for weight reductions. The age-hardening behavior of Mg-6mass%Al (-1mass%Zn)-0.3mass%Mn alloys sand mold castings were investigated by Vickers hardness measurement and optical microscopic observation. Both alloys were solution-treated and then isothermal-aged at 473, 498 and 523K. For each aging temperature, both alloys were indicated age-hardening obviously, and decreased the value of maximum hardness and shorten time to maximum hardness with heighten aging temperature. Age-hardening curves for both alloys approximately showed the same change of hardness. However, these optical micrographs after aging treatment are observed different microstructure. In case of AM60 magnesium alloy, discontinuous precipitation preferentially occurred in aged sample. The volume fraction of discontinuous precipitation was larger than that of continuous precipitation. On the other hand, in case of AZ61 magnesium alloy, the volume fraction of continuous precipitation was larger than that of discontinuous precipitation. Furthermore, over-aged sample of both alloys were consisted of discontinuous precipitation, continuous precipitation and pre-precipitation area.

Room Temperature Screw Form Rolling of AZ91D Magnesium Alloy through Processing by Extrusion-Torsion Simultaneous Working

Extrusion-torsion simultaneous processing is a very attractive technique for fabricating a rod-shape material with fine grain and random texture. We have proposed a new screw form rolling process combined with preliminary extrusion-torsion simultaneous working. Microstructure evolution and mechanical property change of AZ91D magnesium alloy during extrusion-torsion simultaneous processing was examined through microstructure observation, X-ray diffraction analysis and micro-Vickers hardness measurement. By the addition of torsion, the crystal orientation of AZ91D magnesium alloy workpiece was drastically changed from basal crystalline orientation to the random orientation. Crystal grain occurred through the dynamic recrystallization and tended to coarsen with an increase of extrusion-torsion temperature. Grain refinement under 2 um was achieved at the lowest extrusion-torsion temperature of 523 K. M8 gauge AZ91D magnesium alloy screw was successfully formed at room temperature using the extrusion-twisted workpiece preliminary solution treating at 678 K for 345.6 ks. It was found that the extrusion-torsion temperature of 678 K must be selected to fabricate the good screw without any defects.