The molten aluminum resistance of arc-ion plated TiN coating was evaluated in pure molten aluminum by immersion tests at 715, 765 and 800°C. The interfacial reaction between TiN and molten aluminum was studied by micro beam x-ray diffraction and cross-sectional TEM. After immersion tests, a compound layer containing hexagonal wruzite AlN and Al3Ti was observed at the interface. We assume that a TiN+4Al→AlN+Al3Ti reaction took place. The compound layer thickness was increased as the testing temperature and time was increased. The compound layer growth ratio at 765°C was 2.5μm/ks significantly larger than that of CrN coating previously reported. This difference in reactivity may depend on the protectivity of the AlN compound layer formed at the interface. The microstructure of the compound layer is discussed in connection with that of the CrN and TiN coating.
High-density RF induction plasma having a density of 1013cm-3 was generated using 13.56MHz 350W RF power Anticipating the effect of high-density ions, we applied the high-density nitrogen plasma to surface nitriding of iron A nitrided layer consisting of Fe3N and Fe4N was obtained at 550°C without applying a bias voltage When -200V of bias voltage was applied to the iron substrate, the main product at the surface was Fe3N having a higher nitrogen content than Fe3N obtained without bias voltage This bias voltage enabled us to nitride the iron surface even at 350°C The Vickers hardness of the surface obtained by conventional low-density plasma at 550°C was 360Hv Using high-density plasma, we obtained 980Hv Vickers hardness increased to 1390Hv when we applied a bias voltage of -100V The maximum hardness, 1410Hv, was obtained at 550°C by applying -200V The Vickers hardness of the surface prepared at 350°C with -200V bias voltage was 970Hv, comparable to that prepared at 550°C with no bias voltage The thickness of the nitriding layer obtained at 550°C with a bias voltage of -200V was 1.9μm, thinner than that obtained by conventional plasma under the same nitriding conditions We concluded that a large amount of nitrogen ion species in the high-density plasma significantly affects iron nitriding, especially surface hardness
Our study of the influence of different lignins on the anomalous growth of metallic Pb on negative electrodes in lead-acid batteries showed that the cell voltage during charging is increased by adding lignin to the electrolyte, while growth is suppressed The higher the cell voltage, the lower the x-ray intensity ratio of Pb(111)/PbSO4(211) for the negative electrode This makes the cell voltage during charging a useful criterion of lignin quality for suppressing the anomalous growth of metallic Pb Partially desulfonized lignin (PD-lignin) suppresses growth more effectively than standard lignin The arrangement of functional groups such as carboxyl and alcoholic hydroxide is more important to the effect than molecular weight During charging, lignin obstructs the movement of Pb2+ ions to the site where charge-transfer is progressing We deduced from a rotating ring-disk experiment that lignin suppresses the onset of the solid-state reaction in favor of dissolution-precipitation during discharge
A study of the effects of chromium (III) ion added as CrK(SO4)2 on average internal tensile stress in nickel deposits electroplated from a Watts bath of pH3.0 enabled us to detect variations in elastic deformation in deposits in situ using a resistance wire strain gauge on the reverse side of a copper electrode. Chromium (III) ions close to the electrode surface changed to chromium hydroxide due to increased solution pH during nickel electroplating with hydrogen evolution. This is included in deposits as chromium oxide and chromium hydroxide. With increasing CrK(SO4)2 concentration, total chromium oxide and chromium hydroxide in deposits increased and average internal tensile stress in deposits also rose. Internal tensile stress rose markedly at 1.5mM CrK(SO4)2, causing numerous cracks on the surface of nickel deposits at a concentration of 2.0 to 10.0mM CrK(SO4)2. The dependence of chromium oxide and chromium hydroxide content on CrK(SO4)2 concentration showed that these two compounds greatly enhance internal tensile stress in nickel deposits.
Cu/Ni multilayers were deposited on a rotating disk electrode by galvanostatic pulse electrolysis in a bath containing 1mol/L nickel sulfamate, 0.005mol/L copper sulfamate, and 0.49mol/L boric acid at pH4.0 and 50°C. The Cu deposition current density was 0.8 times the limiting one to avoid dendritic growth. Ni was deposited at a current density of 15A/dm2. Cu/Ni multilayers were deposited with (111) preferred orientation on the stainless steel substrate with (110) preferred orientation.
The effect of the current waveform on etch morphology and surface film of aluminum produced in 3.6% HCl solution at 323K was studied using scanning electron microscopy (SEM) and Auger spectroscopy (AES). Current forms used for etching were asymmetrical triangular anodic pulses having a maximum current density of 0.5A/cm2 at tm within an on time of 10-2s, and the off time between pulses was varied from 0 to 0.1s. The change of the etched surface depended on tm, and off time was found due to the amount of etch products composed of an anodic film of Al2O3 shown by AES analysis and a small quantity of aluminum hydroxide observed by SEM. The etched morphology was classified into three stages by current sweep rate. Above 200A/cm2s (tm<2.5×10-3s), it remained partly unattached area. Fine pits were produced at 125∼200A/cm2s (tm=2.5∼4×10-3s) where an anodic film several nm thick developed. Large pits having a diameter of ≥30μm yielded to the thicker anodic film at less than 100A/cm2s (tm>5×10-3s). The anodic film thickness increased with increasing tm and off time.
Organic composite coated steel sheets (OCC) show excellent corrosion resistance during cyclic corrosion tests (CCT). To clarify the mechanism behind this corrosion resistance, we studied changes in corrosion products and elements of plating, chromate, and organic resin layers of OCC with different organic resin layer weights. Larger amounts of corrosion products were detected on OCC with a smaller weight organic resin layer. Larger amounts of basic zinc chloride [ZnCl2·4Zn(OH)2] forming under the organic resin layer were detected by X-ray diffraction and electron probe microanalysis (EPMA) on OCC with a larger weight organic resin layer. Chromium remained in the chromate layer longer in OCC having the larger weight organic resin layer. The contribution of the corrosion products on the organic resin layer, the organic resin layer, the basic zinc chloride under the organic resin layer and the chromate layer to resistance was estimated by AC impedance measurements. That of the basic zinc chloride under the organic resin layer and the chromate layer was largest, followed by that of the organic resin layer. The excellent corrosion resistance of OCC therefore depends on the high barrier of the corrosion products on the organic resin layer and the ability to maintain the chromate layer and the basic zinc chloride under the organic resin layer in a corrosive environment.
Ferricyanide ion ([Fe(CN)6]3-) reduction by cyanide ions (CN-) in an aqueous solution was markedly enhanced in freezing, in which ferricyanide ions were reduced to ferrocyanide ion ([Fe(CN)6]4-). When the concentration of potassium hexacyanoferrate (III) (K3[Fe(CN)6]) was fixed at 1.21×10-3mol dm-3, the yield of the redox reaction for potasium cyanide (KCN) concentration added increased monotonically until a 1.53×10-3 mol dm-3 concentration. The redox reaction was found to strongly depend on initial solution pH, in which the yield for pH=9∼11 was 85% and pH=11∼13 was 100%. Comparing several freezing speeds showed that the rate of reaction was enhanced with increasing freezing speed. The rate and yield were enhanced to be come strongly dependent on the concentration of sodium chloride (NaCl) added. These results suggest that the redox reaction in freezing strongly depended growing ice crystal.