Magnetic field effects on plating and etching were discussed in terms of the magnetohydrodynamic (MHD) and micro-MHD effects. These effects result from the Lorentz forces induced by the interaction between the electrolytic current and the magnetic field; however, the scales of length are quite different. The MHD effect emerges in macroscopic scales in the electroplating or electroetching, whereas the micro-MHD effect prevails in the scale of the order of .Em. Therefore, the micro-MHD effect is effective in electroless plating or chemical etching since the electrochemical local cells with a.Em scale of length play important roles. All the effects enhance the mass transfer process through the MHD flow and the micro-MHD flow generated by the Lorentz forces. However, when the mass-transfer process is not ratedetermining, they suppress the rate of plating or etching to level the surface irregularities.
In recent years high temperature superconducting materials and the refrigerating machine technology have advanced so extensively, that the helium free superconducting magnet can provide strong magnetic fields of about 10 T easily. Magnetic substances in a strong magnetic field is expected to produce a high gradient magnetic field near their surfaces. A study has been made on the magnetic field effect on the behavior of oxygen and water near a steel surface submerged in water in strong magnetic field. We have found differences in corrosion of the steel surface along the gradient magnetic field, and the shape change of water surface has been observed. Further, the relation between the corrosion pattern and magnetic field gradient has been made clear from the analysis of the magnetic field distribution around the steel.
Effects of magnetic exposure on aqueous systems have been investigated employing colloidal particles, an atomic force microscope (AFM), fluorescent probes and others. A series of quantitative and reproducible data on the magnetic effects has been obtained by well controlled experiments. The followings were found: (1) the magnetic exposure reduces the rapid coagulation rate, the zeta potential and diffusivity of colloids, (2) the exposure affects the formation of CaC03 crystals, (3) the exposure thickens the adsorbed layer on the surface in electrolyte solution and reduces the potential of solid surface, which are clarified by AFM measurements, (4) the exposure increases the emission intensity of fluorescent probes with a long carbon chain in solutions, (5) there exists a memory in the magnetic effects. It is postulated from these results that the magnetic effects are attributable to the stabilization of the water molecules adsorbed on the solid surface and those hydrated around structure-disordering ions.
The bottleneck of a three-dimensional structural analysis of protein molecules is the crystallization of large (>0.1μm) and suitable high quality crystals. To overcome this difficulty, magnetic field effects have been studied intensively in recent years. Here, we outline the magnetic field effects on the crystallization of protein. Crystallization of hen eggwhite lysozyme was carried out under a static and homogeneous magnetic field of 0-11 T. It is clearly demonstrated that a magnetic field decreased the number of nuclei that appeared and not only oriented the crystals but also changed the crystal habit. The magnetic field effects on the orientation and growth rate of the crystals were further investigated. The degree of orientation of the crystals depends on crystal growth rate and container geometry, in addition to magnetic field strength. The magnetic field decreases the growth rate of the crystals and also the flow rate of the buoyancy convection in an electrolyte solution.
Two examples of steady magnetic field effects (MFE) on inhomogeneous systems are reported: (1) The molecular adsorption was affected by steady magnetic fields (MF), depending on adsorbed amounts, pore structure, and MF intensity. It inferred that such magnetoadsorption should be accompanied with magnetization changes of the system in adsorbing under MF. Another MFE on adsorption, magnetic-field-gradient-induced adsorption, is shown by mixing an oxide superconductor with a zeolite, which leads to make O2 in micropores desorb under MFs. Moreover, a kind of magnetosensitized adsorption is referred to: magnetic photoadsorption and the electron spin resonance adsorption. (2) The great MFE on membrane potential (Ψ) of black lipid membranes (BLM) of dipalmitoylphosphatidylcholin (DPPC) was observed. |Ψ| markedly decreased up to -50% by MFs less than 0.15 T and increased in higher MFs. The MFE seems to occur not via the Lorentz force on ion flux but via cooperative orientation of lipid molecules. The addition of molecules having different magnetic anisotropy to a BLM modified the magnetic responses of BLM. The changes in Ψ due to aramethicin bound to a BLM and to photoexitation of an azo-dye in a BLM were enhanced under MF, which may be a kind of magnetosensitization.
Time-of-flight mass spectrometric and optical emission spectroscopic studies have been carried out on ablation plumes produced by laser ablation of graphite at 266nm in vacuum with or without a magnetic filed of about 0.1 T. Some processes including ionization, cluster formation, and deexcitation were found to be enhanced by the magnetic field. We have also examined the influence of the magnetic filed on the deposition of carbon nitride films using laser ablation of graphite in a nitrogen atmosphere. Corresponding to an intense CN emission, a magnetic field induced enhancement of N incorporation and the formation of sp3 C-N bonding were both observed in the films. These results suggest a possible reaction control in ablation plumes of carbon and related materials by a magnetic filed.
Unintended degradation of specimens during X-ray irradiation is a very important phenomenon in quantifying the surfaces using X-ray photoelectron spectroscopy. However, there has been no practical method for quantitative evaluation of the degradation during the measurement. There are some prospective samples to be used for this purpose. We have tried to test a nitrocellulose-celluloseacetate specimen as a reference to evaluate the relative X-ray dose to the specimen using the surface chemical change of it. This sample is stable against the exposed vacuum, and also against the neutralizing flood electrons during the period of measurements. The nitrogen 1s photoelectron peaks of nitrocellulose-celluloseacetate specimen show that two stages of first order reactions occur. At first, N 1s shows the highest binding energy (408 eV) equal to that of -ONO2 state. Next state shows 405 eV-binding energy of -ONO state (represented using -NO2), and finally goes to 400 eV, binding energy of -NO, -CN etc. This experiment clarified the two stages of first order photo-reactions of nitrogen atoms in the nitrocellulose-celluloseacetate specimen. N 1s peak of -ONO2 state decreases its intensity exponentially according to the first order reaction with photons, and this means that this samples can be used to evaluate the amount of X-ray irradiation, and this quantitative relationship between speci-men degradation and X-ray dose can standardize the XPS measurement. The rate constant of dissociation is 7.5×10-5 min-1 W-1 (0.0225 min-1 at 300 W) when using the focused X-ray source on the XPS system at 75 degrees of X-ray in-cident angle. And yields are approximately 29% for the first photo-reaction (-ONO2 → -ONO), and 85% for the fol-lowing (-ONO → -NO, -CN etc.). According to the nature of these reactions, the nitrocellulose-celluloseacetate sample can be used as a good reference material to evaluate the amount of X-ray irradiation.
The structure of sulfuric acid species adsorbed on a Pt(111) electrode has been successfully determined by using ultrahigh vacuum modeling tactics. This review concerns modeling of the electrochemical double layers in ultrahigh vacuum. An electrode potential change induces an interconversion between a bisulfate anion/hydronium cation coadsor-bate and a sulfuric acid neutral molecule on Pt(111). The solvation structure of the adsorbed ions indicates that single hydration water molecule per bisulfate anion/hydronium cation pair stabilizes the ion pair. The water molecules in the overlayers are subjected to a preferential orientation that is induced by the presence of the adsorbed anions in the first layer. These microscopic informations about the structure of an adsorbed electrolyte anion and water as a solvent would be indispensable to a true molecular level understanding of the electrochemical double layers and chemical reaction at the electrode surfaces.
This article describes a series of demonstration experiments, which were exhibited to general visitors in open days of our research institute. The intention is to provide the people with an opportunity to actually experience by themselves why and how atoms assemble to form various types of materials. At the same time, these experiments are designed to be an enjoyable introduction to our research activity.