Precursor Decomposition,Microstructure, and Porosity of Yttria Stabilized Zirconia Thin Films Prepared by Aerosol‐Assisted Chemical Vapor Deposition

Microstructures of yttria stabilized zirconia thin films deposited by aerosol assisted chemical vapor deposition (AA‐CVD) are correlated with the thermal decomposition behavior of the corresponding metal precursors, zirconium and yttrium 2,4‐pentanedionate. Process conditions of AA‐CVD are investigated with the aim of producing dense and compact YSZ thin films for applications as gas‐tight electrolyte. Based on systematic cross sectional scanning transmission electron microscopy (STEM) investigations and conductivity measurements, the development of percolating nanoporosity is observed in samples prepared at temperatures between 350 °C and 600 °C at standard solution throughput. Compact columnar thin films with bulk conductivity are obtained at 600 °C by reducing the metal content of the precursor solution and at 450 °C by reducing the solution throughput.     

Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application

In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 ^oC. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 ^oC. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance.For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 ^oC by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application.     

Environmental Synthesis of Few Layers Graphene Sheets Using Ultrasonic Exfoliation with Enhanced Electrical and Thermal Properties

In this paper, we report how few layers graphene that can be produced in large quantity with low defect ratio from exfoliation of graphite by using a high intensity probe sonication in water containing liquid hand soap and PVP. It was founded that the graphene powder obtained by this simple exfoliation method after the heat treatment had an excellent exfoliation into a single or layered graphene sheets. The UV-visible spectroscopy, FESEM, TEM, X-ray powder diffraction and Raman spectroscopy was used to analyse the graphene product. The thermal diffusivity of the samples was analysed using a highly accurate thermal-wave cavity photothermal technique. The data obtained showed excellent enhancement in the thermal diffusivity of the graphene dispersion. This well-dispersed graphene was then used to fabricate an electrically conductive polymer-graphene film composite. The results demonstrated that this low cost and environmental friendly technique allowed to the production of high quality layered graphene sheets, improved the thermal and electrical properties. This may find use in the wide range of applications based on graphene.     

Mechanical,Optical, Thermal,and Barrier Properties of Poly (Lactic Acid)/Curcumin Composite Films Prepared Using Twin-Screw Extruder

In this present work, we synthesized poly (lactic acid) (PLA)/curcumin composite films using a twin-screw extruder and evaluated their mechanical, optical, thermal, and barrier properties. The composite films were characterized using Fourier transform infrared spectroscopy (FTIR), Universal testing machine (UTM), thermogravimetric analysis (TGA), ultraviolet-visible spectrometry (UV-visible), colorimetry, goniometry, and oxygen permeation analysis. The results confirmed that, the composite films exhibited better ultraviolet radiation-blocking properties and hydrophobicities than did the reference PLA film. The oxygen and water vapor permeabilities of the composite films were also lower than those of the reference PLA film.

     

Physicochemical,Thermal, Pasting and Microstructure Properties of Hydroxypropylated Jackfruit Seed Starch Prepared by Etherification with Propylene Oxide

The jackfruit seed starch was subjected to the hydroxypropylation process by using various volumes of propylene oxide in the range of 5–50 ml (HP₅-HP₅₀). It was found that the molecular substitution (MS) increased with the volume of propylene oxide used. The shape of the native starch appeared irregular, round to bell or semi-oval with an average size of 7.66 μm. The modified granules were still intact in granular form without fragmentation. However, the presence of traces of degradation was observed on some starch granules, particularly the treatment of HP₄₀-HP₅₀. No marked differences in the XRD pattern were observed between the native starch and the hydroxypropyl derivatives. However, a decrease in the degree of crystallinity was found as the volume of propylene oxide in the reaction mixture increased. The swelling power and solubility of the hydroxypropylated starches were higher than in the native starch. Progressive increases in swelling power and solubility were observed as the MS increased among the hydroxypropylated starches. The pasting properties revealed that decreases in the pasting temperature, final viscosity and setback was found with increasing MS while the breakdown increased. Hydroxypropylated starches had lower gelatinization parameters (To, Tp, Tc and ?H) compared with the native starch. During refrigerated storage of the starch gel, the native starch showed syneresis from the first cycle while no syneresis was found during seven cycles for the treatment of HP₁₀-HP₅₀.