Cherng Yuh Su

Fabrication and optical properties of Ti-doped W18O49 nanorods using a modified plasma-arc gas-condensation techniquea)

In this study, Ti-doped W18O49 nanorods were prepared without any templates or catalysts using a modified plasma-arc gas-condensation technique. Structure investigations were conducted and the optical properties of the as-prepared nanorods were characterized by field emission gun scanning electron microscope, high-resolution transmission electron microscope, x-ray diffractometer, x-ray photoelectron spectroscope, micro-Raman, and ultraviolet (UV)-visible spectrometers. The experimental results showed that the diameter and the length of the as-prepared nanorods were approximately 20nm and 3μm, respectively. The as-prepared nanorods exhibited W18O49 structures and characteristic Raman peaks could be observed. UV-visible absorption investigations revealed that Ti-doped W18O49 nanorods exhibited a redshift phenomenon when compared with the pure TiO2 and WO3.

Study of micro-lens array by reflow process

In this study, different diameters of photoresist AZ4620 are defined using lithography. According to the specification of the back light module (BLM) for a liquid crystal display (LCD), the diameters of micro-lenses are divided into two groups. The first group includes lenses with diameters of 90, 95, 100, 105, 110 and 150 µm at a 100 µm pitch; the reflow temperatures for this first group range from 175–300°C with heating times of 6–24 h. The second group includes lenses with diameters of 10, 20, 30, 40, and 50 µm at pitches of 40, 30, 20, 10, and 25 µm, respectively; the reflow temperatures are the same as for the first group with heating times of 1–12 h. In this study, the parametric effects of reflow time and temperature on micro-opticals are characterized and discussed, and optical properties such as the focal length of micro-lenses are measured and analyzed. Then, each micro-lens is sputtered with a conductive seed layer of silver (Ag) for the subsequent eletroforming process, which is the mold for hot embossing. The mold is further incorporated with hot embossing materials and hot embossing techniques to produce the micro-lens required.

Formation of tungsten oxide encapsulated in titanium oxide nanocages by modified plasma arc gas condensation

Non-stoichiometric tungsten oxide (W18O49) nanoparticles encapsulated in titanium oxide (TiO2) nanocages were successfully prepared by a modified plasma arc gas condensation technique. The morphology and structure of these core?shell nanoparticles, as well as the growth mechanism, were investigated using transmission electron microscopy (TEM) and x-ray diffraction (XRD). The results demonstrate that the demands associated with mass production and the choice of materials can be addressed by utilizing this synthesis method.

Evaluation of hillock-like deposition behaviour of HVOF thermal spray coatings using rotary shutter procedure

Abstract Evaluation of hillock-like deposition behaviour of WC/Co coatings was performed using a rotary shutter procedure coupled with 100 passes of high velocity oxy fuel thermal spraying. During the spraying procedure, a DPV 2000 in situ diagnostic instrument was used to monitor the temperature and velocity of inflight particles. The microstructure of the coatings was analysed using an optical microscope to monitor the porosity and thickness distributions at various positions of the hillock-like coatings. A 7·1% porosity was observed at the centre of the hillock-like coatings, and a 10% porosity was observed at the edge, each at a spraying distance of 200 mm. The centre area of hillock-like coatings exhibited almost a 30% decrease in porosity compared to the edge area. The results indicate a higher quality structure at the centre area of the hillock-like coatings.

A Splats Obtaining System for Thermal Spray Deposits

The image of thermal spray splats is difficult to collect due to its high velocity of droplets. Especial in High Velocity Oxy-Fuel (HVOF) process, the process present higher velocity of flame jet correlated to other thermal spray process. The system presents at this article describes a useful splats catching method to obtaining splats during thermal spray deposited. Capabilities and advantages of using this instrument are declared at this theme. The final result presented the instrument caught the single spot of HVOF sprayed splats at sub-micro second. Splats of spot were dispersed well on the glass substrate at the obtaining system, and presented various information of droplets impact at different location on the substrate.

Characterization and Modification of Nanocrystalline Iron Oxide Powders Prepared by an Inert Gas Condensation Technique

Nanocrystalline iron oxide powders were prepared by an inert gas condensation technique under various oxygen partial pressures. The as-prepared nanocrystalline iron oxide powders were further modified by electroless nickel plating. The as-prepared and modified nanocrystalline powders were characterized by X-ray diffraction, transmission electron microscopy, and synchrotron X-ray absorption techniques. In addition, magnetic properties of the iron oxide nanoparticles before and after electroless nickel plating were evaluated by vibrating sample magnetometer. The experimental results show that the as-prepared nanocrystalline iron oxide powders exhibited a mixture of iron and γ-Fe2O3 phases. TEM observations revealed that oxidation started from the surface of the gas-condensed iron nanoparticles. The amount of iron oxide increased with increasing oxygen partial pressure and was confirmed by synchrotron x-ray absorption examination. A decrease in saturated magnetization and coercivity of the nanocrystalline iron oxide powders was observed after electroless nickel plating.