Yoshihisa Uchida

Spectroscopical Measurements of Ablation Plasma Generated by an Excimer Laser from Functionally Graded Materials

Functionally graded materials (FGMs) are drawing attention in the fields of industrial applications. For industrial applications, FGMs require reprocessing, such as cutting and drilling. It is generally difficult to reprocess FGMs. Therefore, excimer laser processing that enables microprocessing has been made available. When the FGM is exposed to a laser beam, ablation plasma is generated. The mechanism of generating the ablation plasma, which differs for each material, influences the accuracy of production, but this has not been investigated sufficiently. The purpose of this study is to analyze the mechanism of ablation plasma generation and to achieve precise microprocessing and surface treatment methods for FGMs by controlling the plasma generation. This paper reports on the characteristics of the electron temperature in ablation plasma. The laser used in this experiment was an ultraviolet pulse excimer laser with a wavelength of 308 nm, a maximum pulse energy of 500 mJ and a pulse duration of 30 ns. The electron temperature dependence of the ablation plasma plumes on the ceramic-metal content of FGMs is observed.

Spectroscopic Measurement of High-Pressure Argon Plasma Produced by Excimer Laser

When a XeCl excirner laser beam was focused in a high-pressure gas of up to 100 atm, a hot and dense plasma was produced at the focal spot. The plasma developed not only backward but also forward. The forward plasma developed by means of a forward breakdown wave. The radius of the forward plasma becomes smaller further from the focal spot because the laser beam transmitted through the plasma was further focused by the plasma. The radiation intensity from plasma produced by an ultraviolet laser was observed using a spectrometer. The temporal spectral intensity signal had two peaks. The first peak was a signal from the plasma produced at the observed point, but the second peak was that diffused from the back. The electron temperature was measured from the ratio of the spectral intensity of Ar II lines. The electron temperature on the order of 10 5 K was obtained.

Blue spectral shift of P3HT organic film by KrF excimer laser ablation

A technique for morphology control of self-assembled organic films based on laser ablation is presented. The regioregular poly 3-hexylthiophene (RR-P3HT) films prepared by using drop casting method and spin coating method are irradiated and ablated by the ultraviolet KrF excimer laser. Absorption spectra and XRD profiles of the films are investigated. For spin coated films, Blue absorption spectral shift is observed; For drop cast films, Blue shift in the absorption spectra, accompanied with the disappearance of the peak intensity of XRD profiles, are observed. The results indicate that molecular structure has been changed due to photo-thermal effect and molecule cutting effect of laser ablation.

Characteristics of Electron Density in Ablation Plasma Generated from Functionally Graded Material in Excimer Laser Processing

Functionally graded materials (FGMs), which possess the dual characteristics of two materials, are expected to be useful in industry in the near future. It is important to find a process of laser ablation when laser is used in the reprocessing of FGM such as cutting and drilling. The electron density is one of the important parameters needed to analyze the mechanism of the ablation plasma. The characteristics of electron density in ablation plasma were estimated. A XeCl excimer laser with a wavelength of 308 nm, a maximum pulse energy of 500 mJ and a pulse duration of 30 ns was used. A Mach-Zehnder interferometer was used to measure the electron density. The electron density dependence of the ablation plasma plumes on the ceramic-metal content of FGMs was observed. The temporal and spatial profiles of the electron density were also observed.

An experiment to purify diesel exhaust gas using an electric trap and three types of catalysers

Abstract Diesel engine exhaust gas is known to be one cause of photochemical smog, which is so damaging to city environments. However, because of its high thermal efficiency and economic advantages, the diesel engine is not easily dispensable. The authors have previously conducted a series of experiments to assess the purifying effects of a diesel gas purification device employing an electric trap. It has been confirmed that an extraction rate of 60 ∼ 75 % for black smoke can be achieved using this apparatus, but the extraction effect for nitrogen oxides (NOx) is insufficient if the electro-trap device is used on its own. To improve its performance, experiments have now been undertaken using the same device in combination with various types of attached catalysers to oxidise and remove the nitrogen in the exhaust gas. Utilising a commercial 3-way catalyser, it proved difficult to maintain the gas at a suitable temperature, so that no outstanding result could be obtained. Nor was any significant result observed from the use of an ozoniser. However, with a zeolyte catalyser, it was possible to achieve a NOx reduction of 20 ∼ 30 %. This latter experiment is reported in the present paper.

Computer Controlled Mask Aligner Using Modified Moire Technique

The operation of mask alignment is one of the most important steps in the process of fabrication of integrated circuits. In this paper we report a computer controlled mask alignment system using modified moire’ technique. In this technique the alignment is controlled in high slope region of the moire’ signal by using a single pair of grating alignment marks. Two methods have been proposed to obtain alignment. The error signal for alignment is taken as the difference of moire’ signal and a secondary signal computed from the moire’ signal. In one method this secondary signal is the inverted moire’ signal while in other it is the average value calculated from the maximal and minimal value of moire’ signal. Experiments were conducted using He-Ne laser of 0.633 μm wavelength and 25μm grating pitch. The alignment accuracy of 0.06μm has been achieved.

Characteristics of a Mower Robot with Swing Mower Mechanism by Simulation.

This study proposes a new mower robot with a swing mower mechanism for advantages such as a string trimmer and a wide swath. The proposed swing mower mechanism is designed for installation in the main body of a four-wheel drive mower robot AMR-D01. The AMR-D01 had overall dimensions as follows: 0.60 m length, 0.50 m width, and 0.30 m height; it weighs 28 kg and maximum velocity is 1.29 m/s. The swing mower mechanism is based on the lever-crank mechanism and translates motor rotation into swing of the rotary blade. We model the mechanism and simulate the characteristics of the centroid movement, sideslip, energy consumption, and operation time to evaluate the swing mower mechanism. The robot velocity is controlled to prevent the occurrence of the unmown spot. Swath is increased from 0.24 m to 0.62 m by 2.58 using the mechanism. The operation time is also decreased by 1/2.58. The swing mower mechanism does not have much influence on the robot movement. The change of the static friction coefficient and the slope angle also does not have much influence on the sideslip of the robot under the present conditions. The energy consumption increases with the increasing robot velocity.

Three-dimensional whole circumference shape measurement system using optical patterns projection technique

An automatic three-dimensional whole circumference shapes measurement system using an optical patterns projection technique has been developed. The system is composed of an optical spatial modulator from which grating patterns are projected on the surface of the object set on a turntable stage, a CCD camera controlled by a robot arm, and a computer. The patterns on the surface of the object are taken into the computer by the CCD camera, and the three-dimensional coordinates of the patterns on the surface of the object are calculated according to a principle of a trigonometry measurement. The patterns faced to the CCD camera are taken into the computer by the CCD camera, four photographs at each turntable angle of 0, 90, 180, and 270 degrees are processed and the image processing data are composed as whole circumference shapes. This improved system using mechanical and optical method and data analysis has the following advantages. (1) It is possible to capture the surface topography without any contact. (2) The time required for the measurements is shorter than the light-section method. (3) The optical spatial modulator using a liquid crystal projector enables to control the striped patterns accurately by the computer. (4) It is possible to measure precisely and to expand the measurement area using a zoom camera. (5) The improved system has whole circumference shapes measurement area as well as high resolution.

Mechanical Properties of TiO2-Kaolin FGM Produced by Progressive Lamination Method for NOx Reduction

Mechanical properties of TiO2-Kaolin Functionally Graded Materials (FGMs) that combined TiO2 and Korean kaolin (Al2Si2O5(OH)4) in a graded distribution were experimentally investigated. TiO2 is an excellent photocatalysis material, however, it does not have the mechanical strength sufficiently. Therefore, FGMs were used as the photocatalysis materials with mechanical strength. To improve the mechanical properties, Korean kaolin was selected as a binder. Bulk FGMs were produced by vacuum filtration and compression involving wet filtration, mechanical compression and sintering. By this process, it is easy to control the thickness of FGMs. The porosity in FGM depends on the content of TiO2. The porosity in FGM decreases with increasing pressure of the compressor. The shrinkage decreases with increasing compression pressure at all ratios of TiO2 and kaolin. The materials have almost no shrinkage at 10 MPa. The bending strength and the Young’ modulus depends on content of TiO2. The bending strength of material was found to be approximately 2.5 MPa for 10 MPa compression pressure at TiO2 side. The bending strength and the Young’ modulus increases with increasing compression pressure. These results indicate that kaolin particles are useful to improve the strength of FGM. These properties of FGM, such as porosity, shrinkage, mechanical strength, etc., can be controlled by content of TiO2 and compression pressure. Based on an optimal design of production conditions, FGMs were developed for the nitrogen oxides (NOx) removal. The NOx reduction increases with increasing compression pressure. NO of 11.7 mg/m2h was removed under present conditions. The sintering temperature ensured the optimal removal of NOx was 800 oC. After NOx removal test, the FGMs were found to be free from erosion due to photocatalysis. And kaolin particles do not interfere in photocatalysis effect of TiO2. It can be concluded that TiO2-Kaolin FGM have a possibility for application to the air purification.

Three-dimensional shape measurement system using optical spatial modulator and zoom camera

An automatic measurement system of three-dimensional shapes by a projection method with striped patterns from an optical spatial modulator has been developed. Patterns on the surface of the object were taken into a computer by a CCD camera, and the 3D cocordinate of the surface of the object was calculated according to a principle of a trigonometry measurement. This system has the following advantages. (1) It is possible to capture the surface topography without any contact. (2) The time required for the measurements is shorter than the light-section method. (3) The optical spatial modulator using a liquid crystal projector is possible to control the striped patterns accurately by the computer. (4) It is possible to measure precisely and to expand the measurement area using a zoom camera. In this study, we developed the method with using zooming of a CCD camera image. By using zooming of a CCD camera image, the measurement accuracy improved and the measurement range was expandable.