an-Hsiang Yu

Preparation and properties of poly(vinyl alcohol)–clay nanocomposite materials

Abstract A series of polymer–clay nanocomposite (PCN) materials that consist of poly(vinyl alcohol) (PVA) and layered montmorillonite (MMT) clay are prepared by effectively dispersing the inorganic nanolayers of MMT clay in organic PVA matrix via an in situ free radical polymerization with AIBN as initiator. Organic vinyl acetate monomers are first intercalated into the interlayer regions of organophilic clay hosts and followed by a one-step free radical polymerization. The prepared poly(vinyl acetate)–clay (PVAc–clay) solution are then saponified via direct-hydrolysis with NaOH solution to form PVA–clay nanocomposite materials. The as-synthesized PCN materials are typically characterized by Fourier-Transformation infrared (FTIR) spectroscopy, wide-angle X-ray diffraction and transmission electron microscopy. The molecular weights of poly(vinyl alcohol) (PVA) extracted from polymer-clay nanocomposite (PCN) materials and bulk PVA are determined by gel permeation chromatography (GPC) analysis with THF as eluant. The viscosity property of PCN materials with different feeding amount of MMT clay is studied by an ubbelohode capillary viscometer. The morphological image of as-synthesized materials is studied by scanning electron microscopy (SEM) and optical polarizing microscope (OPM). Effects of the material composition on the thermal stability, mechanical strength, optical clarity of PVA along with a series of PCN materials, in the form of fine powder and free-standing film, are also studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA) and UV–visible transmission spectra, respectively.

Reduced graphene oxide/macrocyclic iron complex hybrid materials as counter electrodes for dye-sensitized solar cells

A novel series of reduced graphene oxide (RGO)/macrocyclic iron (Fe) complex hybrid materials were synthesized and then used in the production of counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The electrode properties of various CEs were comprehensively analyzed using scanning electron microscopy, transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, and cyclic voltammetry analyses. DSSCs, based on various CEs, were characterized using current density-voltage, incident monochromatic photon-to-current conversion efficiency, and electrochemical impedance spectroscopy measurements. DSSCs fabricated using the RGO/macrocyclic Fe nanocomposite CEs yielded an efficiency of 6.75%. The RGO/Fe CEs exhibited efficient electrocatalytic capability because catalytic Fe particles were uniformly distributed on the surface of RGO. The results indicated that a DSSC with a RGO/Fe CE can exhibit an efficiency comparable to that of a platinum (Pt) CE DSSC and can therefore replace conventional Pt CE DSSCs to lower the cost of solar cells.

19.2: Spray‐Coating Process for Preparing CNT‐FED Cathode

A novel process for fabricating field emission display (FED) devices with spray-coating method is proposed. Spray-coating method can be applied to cathode and even possible for anode fabrication process. It is a fast and low cost process that is easily scaling up for large size panel. Mixing MWNT, which is synthesized by arc-discharge, some conductive materials, and binding with solvent makes CNT mixture for spraying. Cathode is coated with CNT film by the spray process. After sintering process, it is evaluated by electron emission. This diode type CNT-FED with spray-coating process possessed good electron emission properties.