Keinosuke Kobayashi

Crystallization of sheared polymer melts

Abstract The Crystallization kinetics of molten polyethylene subjected to a constant shear stress were investigated theoretically and experimentally. The rate of crystallization depends on the difference of entropy (Δs) between the crystalline and molten state. The constant shear stress in the melt decreases Δs causing an abrupt increase in the rate of crystallization and a decrease of the thickness of the folded-chain lamellar crystals.

Setting angle of molecular chains in polyethylene crystals

Abstract The setting angles of chains in solution-grown crystals of paraffins were measured from optical transforms of their electron diffraction patterns. Those of solution-grown, melt-crystallized, and drawn polyethylenes were determined by the x-ray diffraction method. The cell dimensions, paracrystalline disorder, and thickness and size of crystallites of these specimens were measured. From these data, factors increasing the setting angle were found as follows; (1) folding of molecular chains, (2) imperfections of crystal lattice, (3) expansion of cell dimensions and (4) smallness of thickness and lateral size of crystallites. The temperature dependence of the setting angle is also discussed; the higher the temperature, the larger the setting angle. At low temperatures, the setting angle also increases, and the values are compared with those predicted theoretically from the minimization of lattice energy. The temperature dependence of the setting angle is interpreted in terms of a conformational chang...

Paracrystalline Structure of Polymer‐Crystal Lattice Distortion Induced by Electron Irradiation

The melting temperature of polyethylene crystals decreases and the lattice constants (both a and b) and lattice distortion increase, but the macroscopic volume of the specimen does not change with electron irradiation. From these results a model of a deformed lattice structure with point defects produced by irradiation is proposed. Calculations indicate that the anisotropy of a polymer crystal (difference between the elastic modulus along the molecular axis and perpendicular to the axis) increases the range of the distortion in a crystal caused by a defect. The presence of lattice distortion in electron irradiated polymer single crystals produces observable features in the Moire patterns obtained from the crystals.

Construction of 300 KV Electron Microscope and Its Electronmicroscopy

The three stage voltage supply and three stage electron gun for a 300 KV electron microscope are described. Each stage of the high voltage supply is operated at 100 KV with a ripple stability of about 1×10-4 and is connected to corresponding electrode of the gun. 300 KV is applied to the top electrode directly through an insulated cable whose exterior surface is kept at 200 KV so that 300 KV is not exposed to the air. The stability when operated at about 300 KV is within 4×10-4/min. The resolving power of the electron microscope measured at 300 KV is 20 A. Transmissive powers of electron waves accelerated at 100 KV, 200 KV and 300 KV have been estimated for an aluminium single crystal from the contrast of the electron micrographs. Energy dependence of inelastic scattering in organic specimens is also shown. Electron micrographs of Mgo smoke crystals, stainless steel and polyoxy-methylene single crystals taken at 300 KV are presented.

Changes in the fold content due to drawing and annealing of polyethylene

Abstract The fold content of polyethylene, which varies with drawing and/or annealing, was evaluated by an IR method. Solution-grown n-paraffin single crystals are assumed as a standard material containing no folds, while solution-grown single crystals of polyethylene are assumed to contain one unit of fold content. In preparing mixtures of these two standard materials, the following equation is obtained: A1304—0.49A1350 = 0.14Cf A1304 and 0.49A1350 are the absorbances of the IR band at 1304 and 1350 cm-1, respectively. The fold contents (Cf of polyethylene specimens prepared under various conditions are estimated in terms of this equation. In the drawing process of polyethylene films, Cf decreases abruptly in the region of draw ratio of 2 ∼ 3 and gradually decreases with further drawing when drawn along the machine direction. The content of remaining folds are quite different between specimens drawn along the machine direction and those drawn transversely to this direction. This fact reflects the differe...

Fabrication of nano-gap electrodes using ultrathin metal film

Organic molecules have attracted a great deal of attention because of their promising applications to electronics. Many researchers have recently studied electrical properties of ultrathin molecular films for the developments of molecular electronic devices (MEDs). Since electrical junctions between the metallic electrode and the molecular film are directly related to the carrier injection in the device, the nanoscale investigations of molecular structures and electrical properties at the metal/molecular film interface is indispensable. Scanning probe microscopy techniques are remarkably suitable methods for such investigations. However, it is often difficult to bring the probe tip in the close proximity of the electrode edge because of a large difference in height between the electrode and the ultrathin molecular film with the typical thickness of a few nm, which prevents us from the nanoscale investigations of the metal/molecular-film interface. In this study, for overcoming the difficulty we fabricated Pt nano-gap electrodes having a molecular-scale thickness and atomical flatness. We investigated the structures and the electrical properties of the molecular films at the electrode edge using atomic force microscopy (AFM) and Kelvin force microscopy.

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.

A new high voltage (350 kV) universal electron microscope and its applications

A research electron microscope with an accelerating voltage up to 350 kV was developed. High tension is generated by means of step-up transformers, and fed to the three-stage accelerators through a coaxial cable which avoids exposing the highest tension. Thus the corona and leakage loss are minimized and the fluctuation of voltage is kept in the order of 10−5. The electron beam from the gun is adjusted by both static and magnetic deflectors. The intermediate and projector lenses are adjustable to the optical axis of the objective lens merely by moving their pole pieces. All lenses can be replaced or removed from the side without disassembling the microscope body. This microscope, thus designed, can be adapted to any electron diffraction studies. Even heat-sensitive organic specimens keep their original structures in this microscope, and it is possible to obtain distinct diffraction patterns from any selected area. Solid materials can be investigated more extensively; the transitions of crystals and phases are also easily followed by applying the heating or cooling devices. The most interesting application of this instrument is stereoscopy, that is, the three-dimensional observation of inner structures, which otherwise are attainable only by laborious observations of successive ultra thin sections.