In these days, boriding of metals and alloys has been studied for improving their wear, corrosion, and oxidation resistances.
There are four methods of boriding; solid, liquid, gaseus, and electrolytic boridings. The elect-rolytic boriding is mainly researched among them, because it gives a thick and dense borided layer at lower temperatures in a shorter period, as compared with other methods. The electrolytic boriding of tungsten was studied in order to improve its wear and oxidation resistances.
This paper describes the relation between the boriding conditions and borided layer in electrolytic boriding of tungsten using a molten borax bath.
The results of studies were as follows:
(1) The borided layer consisted of two borides, W₂B₅ and WB. The latter layer was thicker than that of the former in these experiments.
(2) The preferable conditions of the boriding were as follows: the current density was 0.2-0.3Amp/cm² and the addition of B₂O₃ to the borax bath was 20-25%.
A layer of about 50μ in thickness was obtained at 900°C for 2hrs. under the above conditions.
(3) The effects of contamination on the borided layer by dissolution of Fe, Cr, Ni, etc. from the crucible and anode materials were remarkable; care must be taken to prevent it from these contaminations.

抄録全体を表示

The ESR spectra of anodized alumina films, which had been formed in various electrolytes, were studied and the oxide films were classified into the following two groups:
(1) Strong ESR spectrum
This type of film was obtained in organic acid electrolytes such as oxalic acid and NMF-boric acid system.
(2) Weak ESR spectrum
This type of film was obtained in electrolytes containing sulfur such as sulfuric and sulfamic acids.
When the films of Type (II), which had been formed in sulfuric acid, sulfamic acid, and sulfosalicylic acid+sulfuric acid were irradiated by γ-ray from ⁶⁰Co source, a new ESR spectrum appeared, the color of which was at a certain time deepened.
At the results of these studies, it will partially be explained that the built-in color of anodized alumina films would be caused by the fact that electrons are trapped by the crystalline defects or other places corresponding to vacancies of glassy alumina.

抄録全体を表示

Sulfiding treatment of sintered iron has recently been practised in the technical field. Various methods of treatment have their merits and demerits, but most of them cause the public pollution. The packing method was selected for our experiments, because it causes little pollution in practical use. The study was made for the specimens treated by this method on their mechanical properties (mainly wear resistance) and the properties of the treated layers.
The results of the experiments were as follows:
(1) When NH₄Cl and K₄Fe(CN)₆ were added to the sulfiding agent, the wieght of specimen increased with the increases in the amount of additives and heating time and the rise in heating temperature.
(2) When KCNS was added, the weight of specimen increased with the increases in the amount of the additive and heating time; but the increase in the weight of specimen was maximum at the heating temperature of 500-600°C.
(3) As the results of X-ray diffraction analysis of the treated layers, α-Fe and FeO were identified when NH₄Cl was added; Fe₄N, Fe₃N, Fe₂N, α-Fe, and Fe₃C were identified when K₄Fe(CN)₆ was added; and Fe₄N, Fe₃N, Fe₂N, Fe_1-xS, and Fe₃C were identified when KCNS was added.
(4) The highest wear resistance within the range of these experiments was obtained by the addition of KCNS. The wear resistance after treating the specimen under the optimum condition (with 5% of KCNS at 550°C for 3hrs.) was as high as that of the specimen treated by the salt bath method.
(5) After treatment of specimen with the addition of KCNS, the hardness and tensile strength increased; but surface roughness, impact value, and elongation decreased; and the dimensional change was about 0.2%.

抄録全体を表示

Thick anodic oxide films were formed in 15wt% H₂SO₄ bath and their electrical properties were investigated in order to clarify the effects of electrical and structural imperfections such as impurities, vacancies, and micro-pores.
The following results were obtained:
(1) Absorption currents having long relaxation times were observed, which suggested the presence of many traps in the films.
(2) The presence of traps was confirmed by measuring the detrapping currents by light irradiation during discharging process.
(3) The I-V characteristics of the films were expressed by the equation I=kVⁿ (n=2), which indicates that the electrical conduction mechanism of the films is controlled by only one kind of carrier current limited by the space charge in the case of shallow trap states.
(4) The photo-quenched currents as well as the photo-induced currents were also found by measuring the photo-electric effects of the films.

抄録全体を表示

The effects of protection potentials for aluminum in 0.5N NaCl solutions as functions of the potential turning from anode to cathode and all values of pH of the solutions were reported in the preceding paper.
The protection potentials of aluminum were always constant independent of pH values when the border potentials turning from anode to cathode were constantly regulated in 0.5N NaCl solution of pH=4-6, at which an oxide film was produced on the surface of aluminum.
The protection potentials in 0.5N NaCl solutions of pH=4, 5.5, and 6 at the up-down border potentials of+50mV (vs. SCE) were -1.45V (vs. SCE), -1.47V (vs. SCE), and -1.39V (vs. SCE), respectively; and the potentials of these solutions at the up-down border potentials of about -500mV (vs. SCE) were -1.20V (vs. SCE), -1.37V (vs. SCE), and -1.20V (vs. SCE), respectively.
In the same way, the protection potentials of aluminum in 0.5N NaCl solutions of pH=8 and 10 were affected by the border potentials, but were independent of pH values when the up-down border potentials were regulated, on the assumption that Al₂O₃⋅H₂O was formed on the surface of aluminum at the time when the aluminum was put in the solutions.
The protection potentials in 0.5N NaCl solutions of pH=8 at the up-down border potential of+50mV (vs. SCE) and about -500mV (vs. SCE) were -1.36V (vs. SCE) and -1.16V (vs. SCE), respectively; and the potentials in these solutions of pH=10 at the above border potentials were -1.35V (vs. SCE) and -1.16V (vs. SCE), respectively.
The approximate flowing currents of aluminum at the above up-down border potentials were nearly constant independent of pH values.
In 0.5N NaCl solutions of pH=12, the protection potentials of aluminum were nearly constant, about -1.8V (vs. SCE), independent of the up-down border potentials.

抄録全体を表示

The crystallographic morphology of the gold film electrodeposited for less than 40min. on iron was examined by scanning and transmission electron microscopes and electron diffraction.
The results obtained were as follows:
(1) The morphology of the gold film electrodeposited for a long period much varied according to the effects of iron substrate orientation, but it usually formed step structures widely exposing {111} planes.
(2) Needle and dendritic crystals and other crystals of complicated shape grew on the step structure. The growth directions of the needle and dendritic crystals seemed to be ‹110› directions.
(3) Pyramidal and roof-like crystals grew on (001) orientated gold plate crystals formed on (001) iron substrate. These crystals grew in ‹001› direction and thier slant faces consisted of {111} planes.
(4) Two types of roof-like crystals were observed and each of them developed in ‹110› direction.

抄録全体を表示