Kenzo Tanaka

Phase Transformation and Deformation Processes in Oriented Polyethylene

Plastic deformation processes in oriented polyethylene are investigated by the X-ray method, and changes in texture produced by transverse compression are interpreted in terms of twinning, slip and phase transformation. The crystal structure of the new form produced by the phase transformation is determined, and the unit cell is a monoclinic one with a=8.09, b=2.53, c=4.79 A and β=107.9°. The phase transformation is considered to be of diffusion-less type and a transition mechanism similar to that of twinning is proposed.

Growth and Evaporation of Tungsten Oxide Crystals

Growth and evaporation processes of tungsten oxide crystals formed on a surface of metallic tungsten filament at elevated temperature were observed continuously by an electron microscope. In the temperature ranges of 700∼1300°C, 1300∼1600°C and 1600∼1800°C, needle crystals, lump-like crystals and thin films were grown up respectively, but they soon disappeared by evaporation, and above 2000°C, no crystals were grown. The effect of preliminary heating of the specimen filament in air on the crystal growth was also ascertained. It became clear that the material needed for crystal growth was supplied from the vapour phase, and a simple relation between growth rate and needle diameter was obtained.

Crystal Structures and Electrical Properties of Alkali Antimonides

Both X-ray study and electrical measurement were simultaneously carried out keeping the specimen in vacuum. In K–Sb and Na–Sb, the crystallization into the hexagonal structure from amorphous state and the transition from p -type semiconductor to n -type one occur simultaneously with successive activation by alkali metal. But Cs–Sb keeps constantly p -type in spite of the crystallization into the cubic structure from amorphous state. In Rb–Sb, the transition of the structure occurs, i.e., amorphous→cubic→hexagonal, and n -type conduction appears in the hexagonal structure. In order to explain these facts, the relation between the excess alkali atoms and the crystal structure was considered. The cubic phase of Rb 3 Sb was found to be the same as the structure of Cs 3 Sb. The unit cell ( a =884±0.02A) is described by the space group F d 3 m – O h 7 with eight rubidium atoms at (0, 0, 0; 0, \(\frac{1}{2}\), \(\frac{1}{2}\); \(\frac{1}{2}\), 0, \(\frac{1}{2}\); \(\frac{1}{2}\), \(\frac{1}{2}\), 0)+0, 0, 0 and ...

Effects of Impurities on the Charged Dislocations in Sodium Chloride Single Crystals

The dependence of the electric charge of the edge dislocations in sodium chloride on impurity atoms was investigated at room temperature. It was found that the edge dislocations are negatively charged when the crystal contains positive divalent impurities (Mg ++ , Ca ++ ) and are positively charged when the crystal contains negative divalent impurity (S - ). Measurements have been done on the decay of the electric potential on the surfaces of the crystal when the crystal is suffering a cyclic plastic bending of 120 c/s of a finite amplitude. The electric potential on the surfaces decays through two stages and the decay depends on the kind and the concentration of the divalent impurity atoms contained in the crystal. This decay aspect was discussed in terms of the dislocation multiplication and the decrease of the electric charge of the dislocations during the cyclic plastic deformation.

Effect of the Diffraction Condition on the Mean Free Path of 50 kV Electron for Plasmon Excitation in Aluminium

The mean free path of high energy electrons for the plasmon excitation has been measured in a single crystal of aluminium by a Mollenstedt type energy analyser combined with an electron microscope. The mean free path of 50 kV electron is 1000±100A when the crystal is far away from the exact Bragg condition to the incident electrons. When the crystal is near the exact Bragg condition to the incident electrons, an anomaly in the mean free path was observed. The mean free path was 900±100A and 1100±100A when W >0 and W <0 respectively, where W is a parameter showing the deviation from the exact Bragg condition. This result indicates that there are two mean free paths corresponding to the two Bloch waves, i. e. The Bloch wave on the branch-1 has the shorter mean free path than that on the branch-2.

Defect-Clusters in Electron and in Neutron Irradiated Lithium Fluoride

The defect-clusters in LiF irradiated by thermal neutrons and by 100 KeV electrons have been studied by transmission electron microscopy. The defect-clusters in the electron-irradiated crystals are formed after exposure to about 1014 electrons/cm2 and they are some 30 A in diameter having no crystallographic orientation relationship to the matrix. They grow larger under subsequent electron irradiation and stop growing when they are about 500 A in diameter. The defect-clusters in the crystals exposed to 1013~1018 nvt of neutrons are platelets parallel to one of the {100} planes. They are less than 200 A in diameter and less than 50 A in thickness. Their density, about 5×1015/cm3, is almost independent of exposure. It is probable that the defect-clusters in electron- and neutron-irradiated crystals are of same nature, since the defect-clusters in neutron irradiated crystals grow as a result of electron irradiation during observation in the electron microscope. No inhomogeneous line defects have been observed.

Construction of a Universal Electron Diffraction Microscope and its Optical Features

A universal electron diffraction microscope, as we call it, consists of three stage electron lens and two specimen chambers and functions both as an electron microscope and as an electron diffraction unit. This instrument can be used in the following seven ways:(1) Electron microscope; range of magnification between 800 and 20 000 times can be covered continuously.(2) Electron microdiffraction unit; electron diffraction pattern characteristic of any small area of a specimen under microscopic observation can be revealed by a switch.(3) Dark‐field electron microscopic image.(4) High‐resolution electron diffraction unit.(5) Effective camera length of electron diffraction is variable from 0 to 250 cm.(6) Shadow micrographs of the specimen used in (4) can be directly obtained.(7) Shadow microdiffraction (probe diffraction); dark‐field microscopic image appears in each diffraction spot.The specimen in the second chamber can be heated at any temperature up to about 800°C and on which two kinds of substances can ...

Lattice Defects in Zinc Sulphide Whiskers

An electron microscope investigation was made on lattice defects in zinc sulphide whiskers. Axial screw dislocations were observed in whiskers parallel to . This supports the screw dislocation mechanism of whisker growth. Bicrystal structures were also found in whiskers parallel to , and plane defects on (0001) in whiskers parallel to . It is concluded that an alternative mechanism of growth must be considered for whiskers having a bicrystal structure.

Use of Balanced Filters for Automatic Recording X‐Ray Diffractometer

Using balanced filters with an automatic recording x‐ray diffractometer, almost the same effect of monochromatization as with a crystal monochromator was achieved. The detection efficiency of the balanced filters method was about 30, taking the value as 100 when no filter was used. The effective resolving time of the system involving the electronic circuits was about 5 μsec using a NaI scintillation counter as a detector. The Cu‐target x‐ray tube was operated on full‐wave rectified 60 cps 40 kvp. The comparison with the other monochromatization methods is discussed.

Cinematographic study of the growth process of oxide crystals in the electron microscope

Improving our specimen heating device (1), we developed a new specimen holder for continuous observation at high temperatures up to 3000° C. The specimen to be observed is placed on a fine metal wire of high melting point such as tungsten and platinum so that the specimen can be heated by passing electric current through the wire, as has been done by Yamaguchi (2) and v. Ardenne (3). This heating device is inserted in a specially designed chamber in which gases of pressures of 10−3 mm Hg ~ 10−1 mm Hg can be introduced on to the heated specimen, as has been done by Ito and Hiziya (4). The vacuum in the specimen chamber was measured by a MacLeod gauge and an ionization gauge. The temperature was measured by an optical pyrometer and a thermocouple.