Interactions of ions, radicals and photons in VUV-UV regions from Ar plasmas and Ar-O2 mixture plasmas with polymer surfaces were investigated on the basis of surface morphological changes and depth analyses of chemical bonding states in the nano-surface layer of polyethylene terephthalate (PET) films. The depth analyses of chemical bonding states were carried out with hard x-ray photoelectron spectroscopy (HXPES) and conventional x-ray photoelectron spectroscopy (XPS). The AFM images indicated that oxygen ions and/or radicals have a significant effect on the surface morphology. The HXPES results indicated that the degradation of the chemical bonding states due to the plasma exposure was insignificant in deeper regions up to about 50 nm from the surface. Whereas, the conventional XPS analysis showed that C-O bond and O=C-O bond decreased after exposure to the Ar plasmas which have high energy ion (over 7 eV). Furthermore, the C-O bond and the O=C-O bond increased after exposure to the Ar-O2 mixture plasma and VUV-UV photons from the plasma. These results suggest that it is possible to prevent the decomposition of functional groups via controlling the plasma to suppress the ion energy less than 6eV. Moreover, it is important to control reactive species and VUV-UV photons for development low-temperature and low-damage plasma processes.
The microstructure of plasma sprayed ceramic coatings is characterized by the existence of splats along with other morphological features such as interlamellar and globular pores, intrasplat microcracks and splat boundaries. These various process-dependant micro- defects extremely influence physical and mechanical properties such as thermal conductivity and elastic modulus and then influence coating behavior. In this approach, the process involved in the cavitation erosion of plasma sprayed ceramic coatings have been studied using the ultrasonic vibratory technique. The weight loss occurring during fifteen minute intervals of exposure to cavitational erosion was determined, the surface of specimens and the wear debris were examined by Scanning electron microscopy (SEM). The results suggest that the improvement in coating performance could be achieved by controlling the effective contact between lamellae of which the coating is made up using the plasma spray conditions, such as sufficient preheat, short standoff distance and slow gun traversing movement.
Laser cladding has many advantages compared to alternative surface treatment processes. However, the utilization of the laser energy should be improved in order to increase the efficiency of the laser cladding process. The Ni-base self-fusing alloys can produce layers by means of laser processing techniques. The diode laser is more compact and the electro-optical-efficiency is higher about one order of magnitude. This is an advantage in both the small-size manufacturing field and large-size construction out door field. Another advantage is the wavelength. The shorter wavelength output of the diode laser is better absorbed by cladding materials than the light of the YAG and especially the mid-infrared CO2 laser. For laser power exceeding 191W, the Vickers hardness of Ni-base self-fusing alloy layer increases with increasing laser power. The layer clad thickness decreased up to higher scan velocities. The layers formed at laser power of 262W and overlap rate of 66% had a high hardness of HV1177.
Titanium dioxide (TiO2) is functional ceramics and shows the photocatalytic function by ultraviolet light illumination. This photocatalytic function enables decomposition of organic matter such as bacteria, mold and odors. In our previous study, the TiO2 film was darkened by the femtosecond laser irradiation and electrical resistance of the darkened film was decreased. In this study, we investigated variation of the photocatalytic function of the darkened TiO2 films. The TiO2 film was produced by aerosol beam irradiation. The wavelength, the pulse width and the repetition rate of the femtosecond laser were 775 nm, 150 fs and 1 kHz, respectively. The laser spot was scanned on the whole area of the TiO2 film surface and the laser fluence was changed within the laser fluence regime in which the laser ablation was not caused and topography of the film surface was not varied. The photocatalytic function of the darkened TiO2 films was evaluated in the acetaldehyde decomposition test. In the test, the films in acetaldehyde were illuminated with the UV and visible light sources, respectively. The acetaldehyde concentration was measured every hour during the illumination. The results of the test shows that the film had photocatalytic function by visible light illumination.
Blast processing is a substrate processing technique during which spherical or granular materials are jetted against the substrate surface using compressed air. Blasting techniques is widely used for various mechanical parts as a surface reforming technique. When performing blast processing to a complicated-shaped substrate for the purpose of thermal spraying method, it is difficult to set blasting angle to a constant value and it is necessary to clarify the effect of state of substrate on blast processing. In present paper, the effect of blasting angle to removal processing effect and the modification state of substrate is investigated. Results from this investigation are summarized as follows: When blasting angle θ was 30º, the removal quantity ● showed the maximum. The removal quantity became large as cylindrical diameter D was larger. Removal quantity of particle diameter a =100 μm is bigger than that of a =700 μm. As a nozzle movement rate v increased, removal quantity ● became small. As blasting angle θ became small, removal quantity ● became large even though nozzle movement rate v was changed. As blasting pressure P increases, removal quantity ● became big.
The synthesis kinetics of Mg2Si intermetallic compounds (IMC) from the elemental mixture of Mg-Si powders was studied by using differential thermal analysis (DTA). The exothermic peaks were at 818 K, which indicated the synthesis reaction of 2Mg+Si → Mg2Si. The synthesis kinetics of Mg2Si was evaluated by the Ozawa method and KAS method. The activation energy of Mg2Si was calculated as 376.0 kJ/mol by using the data from DTA curves. The bulky materials of Mg-Mg2Si composite were prepared through solid-state reaction by using SPS consolidation process. From the results of XRD and SEM-EDS analysis, it was known that Mg and Si powders never react completely at low temperatures of 813 K and 833 K, and the suitable temperature of solid-state synthesis by SPS should be about 853 K.
Titanium (Ti) and titanium alloys have been interested as an engineering material because they are widely used across various industrial applications, for example, motorcycle, automotive and aerospace industries, due to their light weight, high specific strength and superior corrosion resistance. Ti materials are particularly significant for the aircraft using carbon/carbon (C/C) composites, for example, carbon fiber reinforced plastics (CFRP), because Ti materials are free from the problem of contact corrosion between C/C composites. However, the applications of Ti materials are limited because of their high cost. From a viewpoint of cost reduction, cost effective process to fabricate Ti materials is strongly required. In the present study, the direct consolidation of titanium hydride (TiH2) raw powders in solid-state was employed to fabricate pure Ti bulk materials by using thermal decomposition of TiH2. In general, the production cost of Ti components is expensive due to using commercially pure (CP) Ti powders after dehydrogenation. On the other hand, the novel process using TiH2 powders as starting materials is a promising low cost approach for powder metallurgy (P/M) Ti products. Furthermore, this new process is also attractive from a viewpoint of energy saving because the dehydrogenation is integrated into the sintering process. In this study, TiH2 raw powders were directly consolidated by conventional press technique at 600 MPa to prepare TiH2 powder compacted billets. To thermally decompose TiH2 and obtain sintered pure Ti billets, the TiH2 powder billets were heated in the integrated sintering process including dehydrogenation. The hot-extruded pure Ti material, which was heat treated at 1273 K for 180 min in argon gas atmosphere, showed tensile strength of 701.8 MPa and elongation of 27.1%. These tensile properties satisfied the requirements for JIS Ti Grade 4. The relationship between microstructures, mechanical properties response and heat treatment temperature is discussed in detail.
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