Er-doped Al₂O₃ films and Er-doped SiO_x films have been synthesized by using ion beam assisted deposition (IBAD) methods. The microstructures of films and their annealing behaviors have been studied by using transmission electron microscopy (TEM) and x-ray diffraction (XRD). According to the results of TEM and XRD, Er-doped Al₂O₃ films are dominantly amorphous when deposited below 500°C. The films became polycrystalline γ-Al₂O₃ after annealing at 800°C and 1000°C for 6 hours and unique α-Al₂O₃ after annealing at 1200°C for 2 hours. The refractive index of Al₂O₃ films is in the range of 1.65 to 1.70 at the substrate temperature of 70-500°C. High substrate temperature can improve the distribution of refractive index and optical loss of the Al₂O₃ films. Er-doped SiO_x films as deposited below 500°C are amorphous and change into nano-crystalline after 800°C annealing and polycrystalline after 1100°C annealing. The photoluminescence (PL) of Er-doped SiO_x can be detected after the films annealed at 700°C and PL intensity increases with the increase of annealing temperature in the range of 700°C to 1100°C.

View full abstract

The bombardment of intense pulsed ion beam has been shown leading many physical and chemical effects. As a flash heating source, it produced a fast heating and cooling process in the region near the surface of target. Besides the evidence of formation of amorphous layer and phase transformation, there were many craters of various kinds found on the surface of target.
In this paper, we studied the distributions of these craters according to the beam parameters such as ion energy (accelerating voltage), beam current density, pulse number, etc.. These beam parameters are 250 keV of ion energy, 72∼200 A/cm² of beam current density, 60 ns of pulse duration and 2∼24 of pulse number, respectively. The surface morphology was observed with SEM and the compositions were determined by EDS methods. Also statistical comparisons of crater distributions at different beam parameters were given in the paper. Through our experiments and analysis, we obtained that there are several kinds of craters appeared in our experiment. The size and number of crater varies according the beam parameters. The discussion about the reason of formation of those craters was also given in this paper. And the main factors to form craters on melted surface were the surface energy state distributions and eroded particles from ion sources.

View full abstract

Various ion species including C, N, O and Ar are implanted into WC-6.5%Co cermet samples to study surface modification of tribological properties for industrial applications of the cermet tools. Ultra low friction coefficient down to 0.04 is found under high-load WC-self wearing for low-beam-current high-dose C-ion implanted samples. In order to achieve an excellent compromise of a combination of low friction, high hardness and high wear resistance for WC-Co tooling applications with superior performance of tooling harder materials, C-ion implantation using low beam currents and to higher doses is found to be the best choice. The C-ion-implantation induced modifications of the mechanical properties of the cermet have been attributed to physical interactions such as microstructural fining.

View full abstract

Titanium dioxide (TiO₂) thin films as a photocatalyst were prepared using the pulsed laser deposition (PLD) method. The structural and compositional properties of the films are described. Electron binding energy peaks of (a) Ti 2p3/2 and (b) O1s can be observed on films prepared by the PLD method. The crystallinity of the prepared TiO₂ film was measured by X-ray diffraction as a parameter of substrate temperature (Ts). XRD measurements revealed that the substrate temperature affected the phase formation, the crystalline structure and the preferred orientation of the TiO₂ films. The structure of the films as measured by an atomic force microscopy (AFM) suggests that the films prepared at Ts≤400°C are composed of particles of two sizes : small particles of ∼10 nm in diameter and large particles of ∼100 nm in diameter. The films prepared at Ts=600°C were composed entirely of large particles.

View full abstract

The chemical reactivity of a hydrogenated diamond surface with carboxylic acid in benzoyl peroxide containing an organic solution was investigated. Stearic acid, which has a long alkyl chain in its chemical structure, was reacted with a hydrogenated diamond surface by using benzoyl peroxide. The surface condition treated with stearic acid was shown to be stable against chemical solvents. By increasing the amount of the addition of stearic acid added, the functional group derived from the stearic acid was introduced on the diamond surface more preferentially than the functional group derived from the benzoyl peroxide.

View full abstract

We investigated the reactivity of the carbonyl group on a diamond surface. When the oxygenated surface of a diamond powder was treated with LiAlH₄, the intensity of the peak assigned to the C=O bond in the IR spectrum decreased, while that of the peak assigned to the O-H bond increased. Reactivity of the C=O bonds on the oxygenated diamond surface depended on the amount of LiAlH₄ and the reaction time. However, the peak assigned to the C=O group did not disappear completely. It was found that carbonyl groups on the diamond surface had a lower reactivity toward LiAlH₄ than those found in organic compounds. The oxygenated diamond surface could be controlled through organic chemistry.

View full abstract

Reasonable peak assignments of N 1s and C 1s X-ray photoelectron spectra in amorphous carbon nitrides (a-CN) were determined by ab-initio molecular orbital (MO) calculations. We calculated the binding energies of model molecules representing the components in a-CN. N 1s and C 1s spectra were deconvoluted into four and five peaks, respectively. We propose the following assignment for these peaks in N 1s and C 1s spectra. Peaks of N 1s spectra located at around (N-1) 398.5, (N-2) 399.9, (N-3) 400.2 and (N-4) 402.2eV were assigned, respectively, to (N-1) pyridine structure and β-C₃N₄, (N-2) nitril groups, (N-3) sp³N in graphite structure and sp²N in aliphatic structure, and (N-4) nitroso groups. Peaks of C 1s spectra located at around (C-1) 284.5, (C-2) 285.5, (C-3) 286.6, (C-4) 287.0 and (C-5) 288.0eV were assigned, respectively, to (C-1) sp³C, sp²C and sp³C in bonds between carbon and carbon, (C-2) spC, sp²C and sp³C in bonds between carbon and nitrogen or oxygen, (C-3) sp²C and sp³C in bonds between carbon and nitrogen or oxygen (C-4) ketone groups and β-C₃N₄, and (C-5) carboxyl groups. We monitored the changes in spectra induced by vacuum ultraviolet (VUV) irradiation on a-CN. Only our peak assignments provided a reasonable interpretation of the spectral changes.

View full abstract

A thin film prepared from trimethylmethoxysilane by means of microwave plasma chemical vapor deposition have been applied to chemical sensors for organic substances. The film with a proper nanotexture and a hydrophobic surface terminated with methyl groups, and which consequently showed ultra water-repellency, was deposited on a quartz crystal microbalance (QCM) sensor. We evaluated changes in resonance frequency, that is, mass changes, of the QCM sensor due to adsorption of organic molecules. Organic substances, for example, formaldehyde, methanol, ethanol, acetone, toluene and hexane, preferentially adsorbed on the film, while the adsorption of water vapor was restricted due to the hydrophobic nature of the film. The amount of the adsorbed organic molecules seemed to depend on the polarity of each organic molecule. That is a less polar organic molecule adsorbed more preferentially to the film surface. The nanotexture of the film was crucial in order to enhance sensitivity of the chemical sensors through the increase in effective surface areas for the adsorption of organic molecules. Our chemical sensor is expected find applications in environmental sensors. This sensor selectively detects toxic organic substances that are not easily influenced.

View full abstract

Mechanical properties, such as fracture strength and Young’s modulus, of the anodic oxide films formed on aluminum specimens in sulfuric acid, oxalic acid and chromic acid baths were measured by means of a tensile testing machine. Experimental results show that the shapes of stress-strain curves of aluminum specimens with the anodic oxide films varied according to the kinds of the anodizing baths used for the formation of the films. Based on theoretical analysis of the above curves of the specimens, Young’s modulus and the fracture strength of the oxide films obtained by various baths were calculated. These results revealed that the values of fracture strength of the anodic oxide films formed in the above baths were between 140-220 MPa, while the values of Young’s modulus of the anodic oxide films were more different according to the baths used for anodizing. The values were around 36 GPa for the film formed in oxalic acid bath, around 28 GPa in the sulfuric acid bath, and around 15 GPa in the chromic acid bath. Elongation of the oxide film formed in the chromic acid bath was greater than those of the films formed in the other baths. The formation of the anodic oxide films on aluminum alloys resulted in a great decrease of the fatigue strength of aluminum specimens.

View full abstract

An Al deposit layer on a SUS 304 stainless steel substrate was formed by electrodepositing Al and alloying it with SUS 304 steel in molten salt. Electrolysis of Al was conducted using a potentiostatic polarization method in an equimolar NaCl-KCl melt containing 3.5mol%AlF₃ at 1023K. Deposits formed at −1.3∼−1.6V[vs. Ag/Ag⁺(0.1)] built up a homogeneous layer, which was adhesive to the SUS 304 substrate. These deposits consisted mainly of Fe aluminides. The thickness of the deposit layer and the aluminum concentration in the deposit layer increased with a decrease in polarization potential. The SUS 304 steel covered by the electrodeposited layer was more resistant than bare SUS 304 steel to high temperature oxidation.

View full abstract

Colloidal silica films were produced on zinc-electroplated steel using a new chemical conversion treatment, which provides an alternative to chromate conversion coating. The treatment solution consisted of colloidal silica, titanium sulfate, cobalt sulfate and nitrate ions at 298K, pH2. The corrosion resistance of the film coated specimens was estimated by impedance measurement in a sodium chloride solution for 8 days.
The effects of colloidal silica concentration, treatment time and additive ions on corrosion resistance and adhesion of the film were investigated. The addition of titanium sulfate to the colloidal silica solution changed the surface potential of silica particles from negative to positive and improved the film characteristics. The addition of cobalt sulfate enhanced the adhesion between the zinc on the steel and the silica film. The film was not formed without nitride ions. Chemical conversion for 90s in a solution containing 200mM colloidal silica, 4.2mM titanium sulfate, 1.8mM cobalt sulfate, 4.2mM succinic acid and ajusted pH2 by nitric acid at 298K showed excellent film characteristics.

View full abstract

Now, the development of lead-free solder alloys and soldering technology using them is pushed forward by global scale. Among them, the examination for the Sn-Ag-Cu solder is pushed forward mainly for the reason of being superior in joint reliability although the melting point is higher. And products using this solder are already on the market partly. However, in flow soldering with Sn-Ag-Cu solder, peculiar defects called shrinkage cavity, fillet-lifting and land-lifting occur at solder joints. And these defects become one of a problem toward full-scale practical use. In this study, we investigated the influence that shrinkage cavities occurred on the solder joint surface in flow soldering with Sn-3.5 mass%Ag-0.75 mass%Cu lead-free solder on reliability. Furthermore, we added examination about prevention of shrinkage cavity. As a result, the shrinkage cavity understood not to become a fatal defect and not to largely decrease reliability of solder joints. We understood also, that shrinkage cavities are prevented by water cooling just after soldering or increasing the silver content.

View full abstract

Electrolyzed alkaline water, obtained by the electrolysis of a dilute NaCl solution in a cathode compartment shows high pH (alkalinity), low ORP (Oxidation Reduction Potential), and moderate reducibility and oil-emulsification. By utilizing the characteristics of the alkalinity and the oil-emulsification of the electrolyzed alkaline water, metals and lead frames stamped with oil were washed and cleaned, then the cleanness of metals and lead frames for electronic products was evaluated. The surface analysis and quantitative data on remaining residual oils and ionic contamination, AES (Auger Electron Spectroscopy) analysis on metals, and wire-bond pull strength on the lead frames which were washed and cleaned by the electrolyzed alkaline water, showed the same level of cleanness compared to that of the conventional cleaning method by chemicals.

View full abstract

Titanium dioxide/titanium electrodes were prepared by anodic oxidation in sulfuric acid solution followed by thermal oxidation in air. X-ray diffraction revealed that both anatase and rutile phases appeared and the ratio was dependent on the oxidation temperature. The photoanodic oxidation of Pb²⁺ in nitric acid solution occurred more effectively on electrodes treated at high temperature.

View full abstract