A new procedure of in-process monitoring and adaptive control for stable formation of laser spot lap welds has been developed with the objectives of producing sound partial- and full-penetration welds without through-holes and swell in A3003 aluminum alloy sheets, respectively. In the case of the formation of partial-penetration welds, the reflected laser beam and the radiated heat from the welding area were effectively utilized as in-process monitoring signals in detecting melting and though-hole formation in the upper sheet during laser irradiation. Laser pulse duration and peak power were controlled at every 0.15 ms interval during spot welding on the basis of the heat radiation signal detecting the though-hole. In the full-penetration welds, spot welding was performed at low laser power density to reduce the swell of joint part. Then the concavity level of a weld fusion zone increased remarkably with an increase in the pulse duration. Therefore, the laser pulse duration was controlled at 0.15 ms intervals on the basis of the total intensity of heat radiation so as to produce a satisfactory spot weld fusion zone. As a result, fully penetrated welds of desirable sizes with the reduced swells were consistently produced in all 20 samples. These results proved the effectiveness of in-process monitoring and the availability of adaptive control.
Diamond films were synthesized on a Mo substrate using combustion flame. During cooling process, the most diamond films delaminated between the diamond film and the Mo substrate. It was caused by the thermal stresses due to a mismatch of thermal expansion between the diamond film and Mo substrate. In the previous study, a three-step synthesis method was proposed. According to the results, the delamination could be prevented to some extent, but it was not able to protect completely. Scratching treatments on the surface of the substrate and distances from inner cone to the surface of the substrate were remarked as influence factors of the delamination. Experiments were performed with changed parameters of its influence factors, and effects of influence for the delamination were discussed from experimental results. Optimal conditions of diamond film synthesized using combustion flame were discussed in terms of prevention of the delamination.
The powders called IZC(Itomuka Zinc Calcine) that are obtained from waste dry battery by roast processing mainly consist of oxides of zinc and manganese. Part of IZC is used as a raw material of the ferrite but the majority is unused. Authors considered its application to the thermal spray material. Thermal sprayed coating made by IZC powders possesses excellent light absorption, heat absorption, electromagnetic wave absorption and hydrophilicity characteristics. Hydrophilicity characteristic of IZC coating is especially remarkable, and IZC coating is expected to be applied for various heat exchangers such as evaporators. In this study, control test was done on two kinds of thermal sprayed coatings made by IZC powders decreased in zinc oxide and manganese dioxide powders without containing zinc oxide, and hydrophilicity characteristic of the IZC coatings were experimentally considered from the viewpoint of structure of coating and chemical composition. As a result of this study, the following useful findings were acquired to the clarification of the hydrophilicity appearance mechanism. Contact angle as an evaluation indicator of hydrophilicity characteristic is effected by manganese oxide stronger than zinc oxide, while not strongly effected by the roughness of the structure. The diameter of waterdrop spread is not necessarily the same even if the contact angle is the same as θ=0°.
In this paper, the three dimensional laser fabrication of aluminum alloy is investigated. While the processed bead of pure aluminum powders by laser irradiation is ordinarily discontinuous in the shape of balls and is not welded to the base plate, the continuous bead suitable for a fabrication unit can be processed using aluminum powders compounded with alloy elements. A smooth bead with deviation of the maximum height of less than 0.1mm is obtained on the titanium base plate under the optimum processing conditions. The bead of the aluminum powders compounded with 5-7.5wt% the silicon and 5wt% the titanium can be laminated to the plate of smooth top without cracks or detachment from the base plate by the change of melting and solidifying process. In this processed bead the eutectic microstructures are observed containing aluminum-silicon alloy and Al3Ti distributed minutely with the grain size under 20 micrometer. The average tensile strength of this processed plate is equivalent to pure aluminum at 82 MPa. Three dimensional shapes of aluminum alloy, for example quadrangular pyramids, are fabricated easily with smooth appearance of the surface.
Feature of field emission current and electrical breakdown was experimentally investigated for very short gap in the range of 0.1μm to 3μm between a pointed cathode coated with Carbon-Nano-Tube (CNT) and a plane anode in vacuum environment. The experimental setup, which consists of the CNT coated cathode, the stainless steel anode and the precise positioning mechanisms actuated by piezoelectric devices, was installed in scanning electron microscope (SEM). The pointed cathode coated with CNT was confirmed to emit electrons by field emission through F-N plots of voltage and current between both electrodes. The minimum voltage required for detecting field emission current decreases with decrease of gap length. The breakdown voltage was higher than the minimum voltage for emission current when the gap length was kept constant.