Nurdan Demirci Sankir

Selective deposition of PEDOT/PSS on to flexible substrates and tailoring the electrical resistivity by post treatment

Purpose – This paper aims to describe two manufacturing techniques for selective patterning of Poly‐3‐4‐ethyleneoxythiophene/poly‐4‐sytrensulfonate (PEDOT/PSS) for flexible electronic applications. The paper also includes methods to tailor the electrical conductivity of the patterned polymeric films.Design/methodology/approach – Line patterning and inkjet printing methods were used to pattern PEDOT/PSS onto mechanically flexible substrates including polyethylene terephthalate, polyimide and paper.Findings – PEDOT/PSS thin films with controlled spatial resolution and strong adhesion passing a laboratory Scotch‐tape test were patterned onto flexible substrates using both line patterning and inkjet printing techniques. After annealing, the sheet resistivities of patterned PEDOT/PSS lines increased slightly. Treating the electrodes with ethylene glycol dramatically increased the electrical conductivity.Research limitations/implications – There has been extensive work on selective deposition of solution proces...

Synthesis and Characterization of 2-Hydroxyethyl Methacrylate (HEMA) and Methyl Methacrylate (MMA) Copolymer Used as Biomaterial

A series of poly(methyl methacrylate-co-hydroxyethyl methacrylate) (PMMA-co-PHEMA), copolymers were synthesized by an emulsion polymerization technique. Copolymer compositions were determined by FT-IR and 1H-NMR spectroscopy. It was found that comonomer ratios used in the recipes were comparable within the actual copolymers. Glass transition temperatures (Tg) of PMMA-co-PHEMA copolymers were varied from 119°C to 100°C by increasing HEMA content. Thermogravimetric analysis showed that the copolymers were stable up to 330°C. High intrinsic viscosity values of copolymer resulted in ductile solution-cast films. The hydrophilicity of the films was analyzed by water uptake measurements.

Hydrogen Production Technologies

Hydrogen is viewed as a clean and efficient fuel for future energy generation, with an enormous amount of research being pursued to study the various routes for the production, storage, and application of hydrogen fuel. To date, diverse approaches have been employed for the production of hydrogen-rich fuel through catalytic processes using nonrenewable materials as well as sustainable feedstocks. This review of the recent literature, is intended to provide an outlook on the catalyst development, reaction mechanism and reactor modeling studies of hydrogen production using catalytic steam reforming of oxygenated hydrocarbons with focus on methanol, ethanol, and glycerol feedstocks. Various attempts to optimize the catalyst performance, including the utilization of various noble and transition active metals as well as oxide support materials, are extensively discussed. Tremendous effort has been dedicated to develop a reaction mechanism for the reforming of oxygenated hydrocarbons, with no consensus to date on the exact reaction pathway due to the complex nature of the reforming process. This review provides insights into the fundamental understanding of the reaction mechanism and the contribution of the active metals and support on the observed kinetics. Moreover, the previous literature on the modeling and simulation of the hydrogen production process is also reviewed.

Chemical hydride powered and air breathing PEMFC for UAVs

In this study, hydrogen gas generation for Proton Exchange Membrane Fuel Cells (PEMFC) was provided using precious catalysts. The critical catalyst concentration value and the effects of the catalyst amount and the sodium borohydride concentration on the hydrogen production rate were analyzed. PEMFC are one of the good candidates for powering unmanned air vehicles due to their low weight and high durability. They can provide longer flying times than lithium ion batteries. Our group manufactured a PEMFC producing 150 W power for unmanned air vehicles and optimized its performance. Moreover, the influence of the compression and the purge valve on and off time on fuel cell performance was investigated.

Spray pyrolized copper indium gallium sulfide abosrober layers for thin film solar cells

In this study, copper indium gallium sulfide (CuIn1-xGaxS2) films was deposited on glass substrates using ultrasonic spray pyrolysis technique (USP). The Ga/(In+Ga) molar ratio in the precursor solutions has been tailored to obtain the stoichiometric films. Chalcopyrite structure of the films was confirmed by XRD analysis. High absorption coefficient values have been obtained for all samples. It has been observed that the optimum Ga/(In+Ga) ratio in precursor was 0.5 for the best-performed CuInGaS2 thin films.

Nano Heterojunctions of Cadmium Sulfide and Cadmium Telluride for Photoelectrocemical Cell Applications

This study presents a very cost effective template-based electrochemical technique to synthesize the nano heterojunctions of cadmium sulfide (CdS) and cadmium telluride (CdTe). SEM analysis revealed that the average length of CdS nanowires varied from 500 nm to 4 μm depending on the deposition time and voltage. Also, average diameter of the CdS nanowires ranged between 100 and 200 nm. The structures of CdS nanowires have been confirmed by XRD and EDX analysis. Photoelectrochemical performances of CdS nanowires revealed that there is a dramatic change in the photoelectrochemical performances with the change in deposition time and voltage. The maximum fill factor (FF) and power efficiency (η) of the CdS nanowires has been calculated as 45 % and 1.36 %, respectively. After the optimization of the CdS nanowire deposition conditions based on the PEC performance, CdTe nanostructures have been deposited on CdS nanowires at various deposition time. SEM analysis showed that CdTe nanostructures have a tendency to grow as nanoclusters. It was observed that the density and the average diameter of the clusters was a strong function of the deposition time. The average diameter of the CdTe nanoclusters after 9-hour deposition reached about 260 nm. The successful heterojunction of CdS nanowires with CdTe nanoclusters have been observed in the SEM analysis. It has been concluded that the PEC performances of the CdS nanowires improved significantly after CdTe deposition. The maximum η, obtained in this study is about 8.04 %. This is one of the highest efficiencies reported in the literature for the nanowire array photoelectrochemical cells.