Effects of CF4 plasma treatment on the moisture uptake,diffusion, and WVTR of poly(ethylene terephthalate) flexible films

We studied the effects of CF₄ plasma surface treatment on moisture uptake, diffusion, and the water-vapor-transmission-rate (WVTR) of poly(ethylene terephthalate) (PET) films using a CF₄ plasma generated by a radio-frequency (13.56 MHz) reactive ion etcher at 60 W. After CF₄ plasma treatment, moisture uptake in PET film was reduced with increasing treatment time due to (1) lower adsorption of water molecules onto the hydrophobic surface, as confirmed by contact angle measurement and XPS analysis, and (2) reduced diffusion coefficient through the denser fluorinated top-layer as detected by XRR. In addition, the WVTR of untreated PET is found to be 2.7 g/m²/day, while a significant reduction (84%) of WVTR to 0.43 g/m²/day, is achieved for CF₄ plasma-treated PET film (60 W, 15 min), which alters the surface hydrophobicity (~ 107°) and simultaneously builds a denser, fluorinated top-layer (47 nm). The surface fluorinated layer has a diffusivity of to 8.7 × 10^?12 m²/s and a WVTR of ~ 1.0 × 10^?4 g/m²/day based on a series resistance model.     

Crystallization mechanisms of (In15Sb85)100−xBix phase change recording thin film

The (In₁₅Sb₈₅)_100−xBi_x films (x = 0–18.3) were deposited on nature oxidized Si wafer and glass substrate at room temperature by magnetron co-sputtering of Sb target and InBi composite target. The optical and thermal properties of the films were examined by reflectivity thermal analyzer. Microstructures of the films were analyzed by X-ray diffraction and transmission electron microscope. The crystallization activation energy of the (In₁₅Sb₈₅)_100−xBi_x film (x = 0–18.3) was decreased with increasing Bi content, this indicated that the crystallization speed was improved by doping Bi. The structure of as-deposited (In₁₅Sb₈₅)_100−xBi_x films was amorphous and it would transform to Sb, InSb, Bi, and BiIn₂ coexisting phases after annealing at 250 °C for 30 min.     

3D Printing of Ceramics with Controllable Green-Body Configuration Assisted by the Polyvinyl Alcohol-Based Physical Gels

Additive manufacturing of ceramics has received intense attention. In particular, 3D-printed ceramics with customized shapes are highly desirable in the chemical industry, aerospace, and biomedical engineering. Nevertheless, developing a simple and cost-effective process that shapes dense ceramics to complex geometries remains challenging because of the high hardness and low ductility of ceramic materials. Extrusion-based printing, such as direct ink writing (DIW), often requires supporting materials that pose additional difficulties during printing. Herein, a simple approach is developed to produce stretchable ceramic green bodies of zirconia and alumina for DIW. The ink is composed of polyvinyl alcohol (PVA) and an aqueous suspension of ceramic powders. Besides the colloidal network formed by the ceramic particles, PVA plays an important role in tuning the printability of the aqueous ink. Through a freeze-thaw process, PVA crystallizes to form physical networks. This strategy provides highly stretchable hydrogel green bodies that can be reprogrammed to complex geometries difficult for common DIW printing. The subsequent drying, debinding, and sintering processes produce ceramics with dense structures and fine mechanical properties. In short, this work demonstrates an efficient method for the DIW of ceramic parts that can be reprogrammed to complex geometries.     

Chemical characterization of melt-textured YBCO produced by hybrid powder metallurgy

Monolithic YBCO samples were made by traditional top-seeded melt-texturing processes from cold-milled mixtures of Y123 (YBa₂Cu₃O_7−δ) and elemental Y. The bulk composition does not lie on the Y211 (Y₂BaCuO₅)–Y123 join so, formation of Y123 from liquid and Y211 is not an essentially isothermal process on cooling. The reaction liquid + Y211 = Y123 is a ternary reaction and occurs over several tens of degrees. The Y123 thus produced has a range in compositions – particularly in Cu:(Y + Ba) – which may reflect crystallization over the thermal interval. The liquid migrates to an invariant point at which CuO also crystallizes with complete loss of liquid. The presence of trains of CuO grains in the YBCO indicates the locations of the last liquids to be preserved in the sample. These trains are dominantly in an annulus 1–3 mm from the edge of the 20-mm diameter sample. Mapping the compositional variation in Y123 may allow mapping the path of crystallization of these monolithic YBCO samples.     

Optimal sun-shading design for enhanced daylight illumination of subtropical classrooms

This study investigates the feasibility of fitting windows with sun-shadings in order to minimize the lighting power costs in daylight-illuminated classrooms lit from a single side in subtropical regions. An IES-CPC model is created of a representative classroom in Taiwan, and a series of simulations is performed to determine the average illuminance value and the uniformity of the illuminance distribution in the classroom under various lighting conditions with no sun-shadings fitted to the window. The numerical results are found to be in good agreement with the experimental measurements obtained using an array of nine-channel photometers. Having confirmed the validity of the simulation scheme, the illumination properties of four different sun-shading designs are considered. The results show that a double-layered sun-shading represents the optimal sun-shading design in terms of achieving a uniform illumination distribution within the classroom. Given appropriate physical dimensions, this daylight access device achieves the minimum illuminance requirement of 500 lx and improves the lighting uniformity ratio from 0.25–0.35 to 0.40–0.42. Furthermore, using this sun-shading device, the required illuminance ratio of 0.5 can be obtained simply by switching on one of the three rows of lights in the classroom. Accordingly, the daylight access device not only improves the illuminance conditions within the classroom, but also reduces the lighting power cost by 71.5% compared to the case where all of the lights are turned on.     

Temperature-dependent properties of Pd/GaN Schottky type hydrogen sensors with Cl2 plasma surface treatments

Temperature-dependent hydrogen sensing properties of Pd/GaN Schottky type sensors with different Cl₂ plasma surface treated times are studied and demonstrated. The sensing behaviors are studied in terms of Schottky barrier height variation Δφ_B, sensing response S_r, and transient-state response times. The highest sensing response (S_r) values of 7.1 × 10⁴ and 2.12 × 10⁵ are obtained in forward- and reverse-bias voltages, respectively, upon exposure to a 10,000 ppm H₂/air gas at 30 °C. In addition, a correspondingly large Schottky barrier height variation Δφ_B of 0.38 eV is found. This could be attributed to the effective dissociation of hydrogen molecules due to a rougher Pd surface and lower baseline current. Moreover, the studied devices with Cl₂ plasma surface treatment have a stable and widespread reverse voltage operation regime. From transient-state behaviors measurement, the studied device with a 30 s plasma surface treatment shows the overshooting phenomenon and fast response (recovery) time of 4 (5) s.     

Measuring the influence of the greening design of the building environment on the urban real estate market in Taiwan

To address the worsening problems of global warming and the urban heat island effect, ecological cities and building environment greening are being promoted in population-dense urban areas domestically and abroad. For example, the Japanese Ministry of Land, Infrastructure, Transport, and Tourism announced the CASBEE-HI (Heat Island) assessment system in 2008 as a response to worsening urban warming and urban heat island effects. The Ministry implemented “Building Space Greening Plans” in Tokyo, Osaka, and other cities, enforcing by law the effective reduction of urban temperatures and improving urban living environments and alleviating the threat of urban ecological disasters. Therefore, this study integrates Taiwan domestic and foreign building space greening design, derived greening benefits, implementation promotion methods, and greening design policies as measurement constructs to examine the mutual influence between different constructs and to analyze the degree of influence on the urban real estate market.     

A microcantilever-based gas flow sensor for flow rate and direction detection

Utilizing conventional micro-electro-mechanical systems techniques, this study fabricates and characterizes a novel micro gas flow sensor comprising four silicon nitride/silicon wafer cantilever beams arranged in a cross-form configuration. The residual stresses induced within the beams during their fabrication cause the tip of each beam to curve slightly in the upward direction. However, as air travels over the surface of the sensor, the upstream cantilevers are deflected in the downward direction, while the downstream cantilevers are deflected in the upward direction. The velocity of the air flow is then determined by measuring the corresponding change in resistance of the piezoresistors patterned on the upper surface of each cantilever beam. It is shown that by measuring the change in resistance of all four cantilever beams, the proposed sensor can detect not only the velocity of the air flow, but also its direction.     

Gold nanoparticle-aluminum oxide adsorbent for efficient removal of mercury species from natural waters

We report a new adsorbent for removal of mercury species. By mixing Au nanoparticles (NPs) 13 nm in diameter with aluminum oxide (Al(2)O(3)) particles 50-200 μm in diameter, Au NP-Al(2)O(3) adsorbents are easily prepared. Three adsorbents, Al(2)O(3), Au NPs, and Au NP-Al(2)O(3), were tested for removal of mercury species [Hg(2+), methylmercury (MeHg(+)), ethylmercury (EtHg(+)), and phenylmercury (PhHg(+))]. The Au NP adsorbent has a higher binding affinity (dissociation constant; K(d) = 0.3 nM) for Hg(2+) ions than the Al(2)O(3) adsorbent (K(d) = 52.9 nM). The Au NP-Al(2)O(3) adsorbent has a higher affinity for mercury species and other tested metal ions than the Al(2)O(3) and Au NP adsorbents. The Au NP-Al(2)O(3) adsorbent provides a synergic effect and, thus, is effective for removal of most tested metal ions and organic mercury species. After preconcentration of mercury ions by an Au NP-Al(2)O(3) adsorbent, analysis of mercury ions down to the subppq level in aqueous solution was performed by inductively coupled plasma mass spectrometry (ICP-MS). The Au NP-Al(2)O(3) adsorbent allows effective removal of mercury species spiked in lake water, groundwater, and seawater with efficiencies greater than 97%. We also used Al(2)O(3) and Au NP-Al(2)O(3) adsorbents sequentially for selectively removing Hg(2+) and MeHg(+) ions from water. The low-cost, effective, and stable Au NP-Al(2)O(3) adsorbent shows great potential for economical removal of various mercury species.