C.Y. Hsu

Use of the grey-Taguchi method to optimise the micro-electrical discharge machining micro-EDM of Ti-6Al-4V alloy

This article demonstrates the effectiveness of optimising multiple quality characteristics (electrode depletion (ED), material removal rate (MRR) and overcut) to achieve a better finish quality for micro-electrical discharge machining (micro-EDM) of Ti-6Al-4V alloy, using the grey-Taguchi method. The effect of various cutting factors (peak current, pulse on-time, pulse off-time and gap) on the ED, MRR and overcut for micro-EDM of Ti-6Al-4V alloy is analysed. The experimental results show that the peak current and pulse on-time are the most important factors in the micro-EDM of Ti-6Al-4V alloy. The optimum conditions for good multiple performance characteristics for the micro-EDM of Ti-6Al-4V alloy, A1B1C3D3, are a peak current of 0.3 A, a pulse on-time of 6 μs, a pulse off-time of 13 μs and a gap of 40 V. The ED is decreased from 129.1 to 70.6 μm, the MRR is decreased from 8.58 to 4.05 × 10−4 mm3/min and the overcut is decreased from 20.00 to 16.23 μm. The use of the grey-Taguchi method results in clear improvements in ED and overcut.

Electrical and optical studies of Ga-doped ZnO thin films

Nanostructure Ga-doped zinc oxide (GZO) thin films with highly (0 0 2) preferred orientation were fabricated on glass substrates, using radio frequency magnetron sputtering with an GZO ceramic target (The Ga2O3 contents was about 3 wt%) and different deposition conditions. The structural features, surface morphology and electrical and optical properties of the GZO thin films were studied, in terms of the deposition parameters. A Grey-based Taguchi method was used to determine the optimal deposition parameters for GZO thin films by considering multiple performance characteristics. The response graph and table for each level of the deposition parameters forms the Grey relational grade and the optimal levels of the deposition parameters were chosen. The experimental results show that the process pressure and the thickness make the most significant contribution to the overall performance. In the confirmation runs, Grey relational analysis showed that the improvement in deposition rate is 14.2xa0%, the improvement in electrical resistivity 38.1xa0% and the improvement in optical transmittance is 1.2xa0%. Annealing in a vacuum further improved the crystalline quality and optoelectronic performances of the GZO thin films.

Properties of the Mo Back Contact for the Formationof a Thin-Film Photovoltaic Absorber

A Taguchi experimental design was used to find which deposition parameter has the most dominant effect on the electrical resistivity of molybdenum (Mo) films. Based on the most important parameter, the Mo films were further characterized by structural, electrical, and adhesive methods. Then, a copper indium gallium selenide (CIGS) thin film was fabricated by a two-stage process on the obtained Mo layer. The results show that working pressure had a dominant effect on electrical resistivity. The Mo films deposited at 1xa0mTorr and 2xa0mTorr exhibited compressive strain and dense polycrystalline microstructure, whereas those deposited at 3xa0mTorr and 4xa0mTorr exhibited tensile strain and an elongated grain with open boundaries. A Mo film with open porous structure, tensile strain, and lower resistivity was suitable for the formation of CIGS films. After selenization at 560°C, a single-phase chalcopyrite CIGS film with a layer of MoSe2 at the Mo/CIGS interface was obtained.

The characteristics of transparent conducting Al-doped zinc oxide thin films deposited on polymer substrates

Al-doped zinc oxide (AZO) transparent, conductive thin films were deposited on inexpensive polyethylene terephthalate substrates, using radio frequency (rf) magnetron sputtering, with an AZO ceramic target (the Al2O3 content is approximately 2 wt%). This paper presents an effective method for the optimization of the parameters for the deposition process for AZO thin films with multiple performance characteristics, using the Taguchi method, combined with grey relational analysis. Using the Taguchi quality design concept, an L9 orthogonal array was chosen for the experiments. The effects of various process parameters (rf power, substrate-to-target distance, substrate temperature and deposition time) on the electrical, structural, morphological and optical properties of AZO films were investigated. In the confirmation runs, using grey relational analysis, the electrical resistivity of the AZO films was found to have decreased from 5.0xa0×xa010−3 to 1.6xa0×xa010−3xa0Ω-cm and the optical transmittance was found to have increased from 74.39 to 79.40%. The results demonstrate that the Taguchi method combined with grey relational analysis is an economical way to obtain the multiple performance characteristics of AZO films with the fewest experimental data. Additionally, by applying an Al buffer layer, of thickness 10xa0nm, the results show that the electrical resistivity was 3.1xa0×xa010−4xa0Ω-cm and the average optical transmittance, in the visible part of the spectrum, was approximately 79.12%.

Using metallic resin and aluminum alloy molds to manufacture propellers with RP/RT technique

Purpose – This purpose of this study is to investigate an effective method to manufacture propellers.Design/methodology/approach – The investment casting process and injection molding process have been applied separately to the rapid prototyping/rapid tooling (RP/RT) to obtain metal (Al‐Si alloy) propellers and plastic (Acrylonitrile butadiene styrene – ABS) propellers. The two different manufacturing processes were compared following the same master model (MM). The Moldflow software is used to optimize the experimental parameters of the molding. Furthermore, a gypsum type of powder is used to produce the RP MM of the propeller according to the Pro‐E software. The RP MM then is filled with a metallic resin material (at room temperature) to obtain a wax mold. Then, this wax mold was coating by dipping the ZrO2 slurry to improve heat resistant ability, and following solidification, and then filled with metal alloy to obtain metal (Al‐Si alloy) propellers. Another process, the RP MM by dipping the ZrO2 slurr...

Induced NH2 bonding of carbon nanotubes using NH3 plasma-enhanced chemical vapor deposition

Plasma-enhanced chemical vapor deposition was used to modify the multiwall carbon nanotubes (MWCNTs) using ammonia (NH3) plasma. For various durations of NH3 plasma treatment, a scanning electron microscope, X-ray, Raman spectroscopy and contact angle measurement were used to ascertain several characteristics of the MWCNTs. The experimental results show that: (1) the length of the MWCNTs is reduced, if the duration of the plasma treatment is increased; (2) the NH3 plasma treatment can incorporate amine (NH2−) or amino (NH−) functional groups onto the MWCNT surface; (3) the plasma treated carbon nanotubes become more hydrophilic.

Effects of TiN, CrN and TiAlN coatings using reactive sputtering on the fatigue behaviour of AA2024 and medium carbon steel specimens

ABSTRACT The effects of ceramic coatings (TiN, CrN and TiAlN films) on the fatigue behaviour of 2024 aluminium alloy (AA2024) and medium carbon steel (MCS) specimens under cyclic loading have been investigated in this study. These ceramic thin films of about 2 μm thickness were deposited on the substrates using radio frequency reactive magnetron sputtering, with metallic Ti, Cr and Al targets in an Ar/N2 gas environment. The (111), (200) and (220) and (311) peaks of a face centre cubic (fcc) structure in CrN films, and the (111), (200) and (220) peaks in TiN/TiAlN films were observed using X-ray diffraction method, respectively. Fatigue tests were performed using rotational bending conditions at a speed of 3000 rpm with five stress levels (115, 173, 231, 288 and 346 MPa for AA2024; 288, 346, 404, 462 and 519 MPa for MCS) in air. Scanning electron microscopy was used for the analysis of surface morphologies and initial failure stage. The results show that the fatigue life of coated specimens is significantly increased under lower cyclic loading, for example, from 42% at 288 MPa, to 98% at 230 MPa and up to 434% at 173 MPa, for AA2024 with TiN coatings. The improvements of mean fatigue life for MCS coated with TiN films are 88% at 519 MPa, 197% at 462 MPa and up to 597% at 404 MPa, respectively. The experimental results also depict that the coated specimens with higher surface hardness (TiAlN) tended to increase in fatigue strength and fatigue life over uncoated and TiN/CrN specimens.

Influence of oxygen flow rate on photocatalytic TiO2 films deposited by rf magnetron sputtering

Titanium dioxide (TiO2) thin films having anatase (1 0 1) crystal structure were prepared on non-alkali glass substrates by rf (13.56xa0MHz) magnetron sputtering using a TiO2 ceramic target under various oxygen partial pressures. At a fixed substrate temperature of 400xa0°C and total gas pressure of 1xa0Pa after 3xa0h deposition. Effects of oxygen partial pressure on the structural, surface morphology, and photocatalytic activities of the TiO2 thin films were investigated. We performed both photoinduced decomposition of methylene blue (MB) and photoinduced hydrophilicity under UV light illumination. The XRD patterns exhibited a broad-hump shape indicating the amorphous structure of TiO2 thin films. The results showed that when the [O2/(Arxa0+xa0O2)] flow rate increased to 50%, the photoinduced decomposition of MB and photoinduced hydrophilicity were enhanced. The water contact angle after 9xa0min UV illumination was approximately 4.5°, and the methylene blue (MB) solution decomposition from 12 down to 3.34xa0μxa0mol/L for 240xa0min UV irradiation.

Effect of selenization and sulfurization on the structure and performance of CIGS solar cell

This study prepares a Cu (In, Ga) Se2 (CIGS) thin film by sputtering metal precursors and subsequent selenization/sulfurization. The quality of the Mo bilayers/CIGS samples that are selenized at 550xa0°C is confirmed by SEM. The XRD patterns for the CIGS absorber film show a chalcopyrite crystal structure with a preferred orientation of (112), (204)/(220) and (312)/(116). The Raman scattering results for the CIGS thin films show a mean peak at ~u2009174xa0cm−1 and weak signals at ~u2009215xa0cm−1. The high resolution TEM micrograph shows the corresponding (112) peak for the chalcopyrite structure, which is in agreement with the XRD and Raman results. Sulfurization uses sulfur powder (without toxic H2S gas) in a tube type resistance furnace. After sulfurization, S atoms substitute Se atoms to form a Cu (In, Ga) (Se,S)2 (CIGSS) mixed crystal at the surface regions and an additional CIGSS diffraction peak appears at 2θu2009~u200927.40°. The SEM images show that the films’ surface becomes smooth and densely uniform. The main structure of the CIGS films remains unchanged and the grain size increases slightly after sulfurization. The SIMS scan shows that S atoms diffuse into the surface regions of the CIGS layer to a depth of ~u2009300xa0nm, after sulfurization at 530xa0°C for 5xa0min. The CIGS solar cell devices that are prepared using sulfurization exhibit improved photo-conversion efficiency.

Best compromise for photocatalytic activity and hydrophilicity: N-doped TiO2 films under UV light

AbstractThis study seeks to determine the best compromised parameters for photoluminescence performance and hydrophilicity of nitrogen-doped titanium dioxide coatings deposited on glass substrates using radio frequency reactive magnetron sputtering. Rf power (W), process pressure (mtorr), Ar/O2/N2 flow ratios and substrate temperature (°C) were optimized with reference to the structure and photocatalytic characteristics of TiO2. An L9 (34) orthogonal array, the signal-to-noise ratio and analysis of variance were employed for determination of the compromise deposition settings of nitrogen-doped titanium dioxide thin films, annealed in Ar ambient (10u2009mtorr) at temperatures of 250, 350 and 450u2009°C, for a period of 30u2009min. The results demonstrate that for Ar/O2/N2 flow ratios of 80/20/0, 75/20/5, 70/20/10, and 65/20/15, the respective corresponding methylene blue absorbance is 0.412, 0.406, 0.385, and 0.355, which depicts a greater photocatalytic activity with a larger N2 flow ratio. For the morphological properties, the nitrogen-doped titanium dioxide films with a larger N2 flow ratio show a homogenous structure, smaller grain sizes and more spherical particles with Ra roughness of 1.394–0.362u2009nm. The effects of annealing temperature, duration of ultraviolet and visible light irradiation were also analyzed. The films annealed at higher temperature (450u2009°C) under ultraviolet and visible light irradiation of 240u2009min exhibit coexistence of the anatase (101) and rutile (004) structures, which appears to imbue the nitrogen-doped titanium dioxide film with greater photocatalytic activity and photo-induced hydrophilicity.Graphical AbstractNovelty Statement1. This study seeks to determine the best compromised parameters for photoluminescence performance and hydrophilicity.2. The ANOVA results show that the rf power has the major effect on methylene blue (MB) absorbance and the process pressure ranks the second.3. This study determines the effect of Ar/O2/N2 flow ratios and post annealing treatment on the morphology, hydrophilicity and photocatalytic activity of N-TiO2 thin films. The results demonstrate that a greater photocatalytic activity for N-TiO2 thin films can be achieved by using a greater N2 flow ratio.4. The film that is annealed at 450u2009°C exhibits the coexistence of the anatase (101) and rutile (004) structures, which appears to imbue the N-doped TiO2 film with greater photocatalytic activity and photoinduced hydrophilicity under UV and visible light illumination.n