Takao Araki

High temperature oxidation behavior of laser clad NiCrAlY layer

Abstract The oxidation behavior of laser clad NiCrAlY layers with different aluminum content and the influence of heat treatment were investigated. The oxidation behavior was found to obey the parabolic rate law. The parabolic rate constant of the clad layer with low aluminum content was approximately the same order with that of the bulk material. The oxides formed on the clad layers was mainly α -Al 2 O 3 , regardless of the aluminum content. However, θ -Al 2 O 3 was also formed on the clad layer with high aluminum content and this increased the growth rate of the oxide. The heat treatment made the distribution of aluminum in the clad layer more homogeneous and enhanced the nucleation of Al 2 O 3 denser at the initial stage of the oxidation, resulting in the lower growth rate.

The PLD of BaTiO3 target produced by SPS and its electrical properties for MLCC application

Abstract The pulsed laser deposition (PLD) of barium titanate (BaTiO 3 ) target produced by spark plasma sintering (SPS) has been carried out by using excimer laser. The effects of sintering conditions of SPS on the BaTiO 3 target, the influence of PLD conditions and oxygen pressure on thin film were investigated. Furthermore, the effects of the post-deposition annealing and the oxygen pressure on the dielectric properties were also studied. At a mixing ratio of 2:5 with diameter powder of 0.1 and 0.5 μm and at sintering temperature of 1423 K, the relative density of a sintered compact was 99.6%. At an oxygen pressure of 5 Pa, the ratio of Ba/Ti of thin film was approximately 1, making it ideal as dielectric materials. However, the crystalline of film as deposited was still not obtained. The crystalline BaTiO 3 film with a tetragonal and cubic structure was obtained by annealing at 873 K in the atmosphere for 10 min. At the oxygen pressure below 10 Pa, the relative permittivity increased with the increase of oxygen pressure. The highest relative permittivity was obtained at 5 Pa; the relative permittivity reached 300 at the BaTiO 3 ratio of about 1.0. The surface form of thin film as deposited and after crystallization did not change; it was flat and smooth.

Fabrication of NiTi intermetallic compound by a reactive gas laser atomization process

Abstract We attempted to synthesize NiTi intermetallic compound from two types of stranded wires, pure Ti wire (with a diameter of 300 μm) and pure Ni wire (with diameters of 300 and 250 μm). The stranded wire was melted and reacted using a laser, and the melted metal was gas-atomized using high-pressure Ar gas or coated on an aluminum base material. The particle size of the obtained powder ranged from 10 to 125 μm. Thickness of the coating layer was 3 mm. The compositions of the powders and coating layer could be adjusted by changing the wire diameter of Ni of the stranded wire. In other words, the compositions of the powders and coating layer could be controlled by adjusting the Ti to Ni ratio of the stranded wire. Consequently, we produced NiTi intermetallic compound with the purposive composition. Sintered compact with a relative density of 99.9% or more could be produced by sintering the powders by pulsed electric-current sintering device. The defects of the coating layer were reduced to 0.1% or less by the hot press treatment. The sintered compact of the powders with a Ti–Ni composition ratio of one to one and the molding compact of the coating layer produced in a similar manner were a single NiTi martensite phase. By this manufacturing method, NiTi intermetallic compound with an M f temperature of 320 K and A f temperature of 365 K could be produced.

Reduction of droplet of tantalum oxide using double slit in pulsed laser deposition

Abstract We developed a double slit method in order to reduce droplets that were a problem in pulsed laser deposition (PLD) of tantalum oxide. The tantalum oxide films were deposited using KrF excimer laser ablation of a Ta target in 5xa0mass% O 3 at a pressure of 10xa0Pa. Stoichiometric and dense films with few droplets were obtained at a pressure of 10xa0Pa. Without double slit, as the laser pulses increased, the number of droplets containing rich metal on the film gets increased and its size became larger, and the surface morphology of the target also became more and more rugged. It was found that the number of droplet could be controlled by changing the initial roughness of the target. The number of droplets with a diameter size of under 1xa0μm was decreased to 1/10 of their sizes. Droplets larger than 3xa0μm, which mostly affect the corrosion resistance and hardly increase even beyond the laser pulses of 100xa0000. It is evident from this study that the double slit is a very effective method for reducing the droplets, which are otherwise a problem often seen in film production by PLD.

The effect of 5 mass% O3 gas on PLD of tantalum oxide

Abstract Tantalum oxide films were deposited using KrF excimer laser ablation of a Ta target and a Ta2O5 target in 5xa0mass% O3 gas. The 5xa0mass% O3 gas was used to improve the O/Ta ratio of the films. The tantalum oxide film properties such as transparency and corrosion resistance were then evaluated. The O/Ta ratio of the films deposited using Ta target were much improved by using 5xa0mass% O3 gas at pressure lower than 1xa0Pa. There was no difference in the O/Ta atomic ratio of the film deposited in 5xa0mass% O3 gas, although the Ta target as well as Ta2O5 target was used. The XPS spectrum of the oxidized layer of Ta surface at 5xa0mass% O3 gas pressure of 5xa0Pa shifted to a higher binding energy than that in O2 gas. The transparency of the films deposited in both 5xa0mass% O3 gas and O2 gas increased steeply at a O/Ta ratio of 2. The transparency of the stoichiometric films became as high as 90%. The corrosion resistance of the stoichiometric film was as high as the passive film of the Ta plate in the 3.5xa0mass% NaCl solution.

Crystalization of sol-gel derived precursor zinc oxide file during KrF excimer laser irradiation

The present paper describes a study on the crystallization of a sol-gel derived precursor ZnO film during and after the irradiation of an excimer laser. The temporal change of the structure of ZnO films was discussed based on the time-resolved signal of a reflected and a transmitted laser beam during the excimer laser irradiation. The surface morphology of the films was analyzed by atomic force microscope (AFM). The pulse-to-pulse changes of integrated signals reflected the surface conditions of the ZnO film. In time-resolved measurement, significant changes of both signals were observed during the first pulse.

Interfacial structure of multi-layered thin-films produced by pulsed laser deposition for use in small-scale ceramic capacitors

The aim of this study was to develop thin film capacitors with superior properties that could provide an alternative to materials currently used in conventional multi-layer ceramic capacitors fabricated by sintering. To this end, an artificial dielectric super lattice technique, incorporating pulsed laser deposition, was applied to improving the dielectric properties of thin film capacitors. This method permits the A-site atoms of a perovskite ABO3 structure to be selected layer by layer at a nanoscopic scale; consequently, multi-layer BaTiO3- SrTiO3 thin films were produced on Pt(111)/Ti/SiO2/Si(100) and SrTiO3(111) substrates. Hetero-epitaxial grain growth was observed between BaTiO3 and SrTiO3, with the lattice mismatch between them introducing a compressive residual strain at the interface. The dielectric properties of these multi-layer thin-film capacitors were found to be superior to those of conventional solid-solution thin films once the thickness of the layers and the ratio of the two oxides were optimized.

Vibration Property of a Rubber Crawler System when Traveling Over Bumps

Abstract This study analyzed the vibration of a transporter with rubber crawlers caused by road surfaces, and compared of the performance of rubber crawlers with and without iron cores to assess the human response to vibration (vibration perceptible to human body) and the reduction of vibration. The human response to vibration was measured using an ISO standard device. Using a walking transporter traveling on an uneven road surface model, three different laden weights, four different road surface bumps dimensions, and four levels of vehicle speed were examined. The frequency-weighted r.m.s acceleration was measured at three locations — the center of gravity of the chassis, the handlebar and the carrying platform. The results revealed that the acceleration properties at each measurement point could be explained using a basic movement model.

Surface activated bonding for copper plate by excimer laser irradiation

When a pair of clean solid surface are brought close to the atoms distance in the vacuum, the solids were bonded by the gravitation and binding force. Such a way of bonding is called a surface activated bonding. In this work, a laser irradiated to a couple of copper plates surface under various conditions of laser irradiation. The surface oxidation layer and organic layer were removed by laser ablation. After the irradiation, a couple of copper plates surface get close to each other. The possibility of the bonding was examined by AFM.

Effect of laser power on clad metal in laser-TIG combined metal cladding

TIG arc welding has been used to date as a method for clad welding of white metal as bearing material. We propose a new clad welding process that combines a CO2 laser and a TIG arc, as a method for cladding at high speed. We hypothesized that this method would permit appropriate control of the melted quantity of base metal by varying the laser power. We carried out cladding while varying the laser power, and investigated the structure near the boundary between the clad layer and the base metal. Using the laser-TIG combined cladding, we found we were able to control appropriately the degree of dilution with the base metal. By applying this result to subsequent cladding, we were able to obtain a clad layer of high quality, which was slightly diluted with the base metal.