Mehmet Sankir

Highly Chlorine‐Tolerant Polymers for Desalination

Consequently, membrane manufacturers recommend thatfeed-water chlorine concentration to such membranes belimitedtoconcentrationslowerthan0.1ppm.Tomeettheseconflicting requirements, water to be purified is oftenchlorinated,todisinfectitandultimatelyinhibitbiofoulingof the membranes, then dechlorinated before being fed tomembrane desalination units. After passing through themembranes, the water is then rechlorinated before beingsenttothedistributionnetwork.

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.

Influence of Electrical and Ionic Conductivities of Organic Electronic Ion Pump on Acetylcholine Exchange Performance

By using an easy and effective method of depositing conjugated polymers (PEDOT:PSS) on flexible substrates, a new design for organic bioelectronic devices has been developed. The purpose was to build up a system that mimics the motion of neurotransmitters in the synaptic cleft by obtaining an electrical to chemical signal transport. Fourier transform infrared (FTIR) spectroscopy and Raman measurements have demonstrated that electrochemical overoxidation region which separates the pristine PEDOT:PSS electrodes and allows ionic conduction has been achieved successfully. The influence of both electrical and ionic conductivities on organic electronic ion pump (OEIP) performances has been studied. The ultimate goal was to achieve the highest equilibrium current density at the lowest applied voltage via enhancing the electrical conductivity of PEDOT:PSS and ionic conductivity of electrochemically overoxidized region. The highest equilibrium current density, which corresponds to 4.81 × 1017 number of ions of acetylcholine was about 41 μA cm−2 observed for the OEIP with the electrical conductivities of 54 S cm−1. This was a threshold electrical conductivity beyond which the OEIP performances were not changed much. Once Nafion™ has been applied for enhancing the ionic conductivity, the equilibrium current density increased about ten times and reached up to 408 μA cm−2. Therefore, it has been demonstrated that the OEIP performance mainly scales with the ionic conductivity. A straightforward method of producing organic bioelectronics is proposed here may provide a clue for their effortless mass production in the near future.

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.

Dealloyed Ruthenium Film Catalysts for Hydrogen Generation from Chemical Hydrides

Thin-film ruthenium (Ru) and copper (Cu) binary alloys have been prepared on a Teflon™ backing layer by cosputtering of the precious and nonprecious metals, respectively. Alloys were then selectively dealloyed by sulfuric acid as an etchant, and their hydrogen generation catalysts performances were evaluated. Sputtering time and power of Cu atoms have been varied in order to tailor the hydrogen generation performances. Similarly, dealloying time and the sulfuric acid concentration have also been altered to tune the morphologies of the resulted films. A maximum hydrogen generation rate of 35 mL min−1 was achieved when Cu sputtering power and time were 200 W and 60 min and while acid concentration and dealloying time were 18 M and 90 min, respectively. It has also been demonstrated that the Ru content in the alloy after dealloying gradually increased with the increasing the sputtering power of Cu. After 90 min dealloying, the Ru to Cu ratio increased to about 190 times that of bare alloy. This is the key issue for observing higher catalytic activity. Interestingly, we have also presented template-free nanoforest-like structure formation within the context of one-step alloying and dealloying used in this study. Last but not least, the long-time hydrogen generation performances of the catalysts system have also been evaluated along 3600 min. During the first 600 min, the catalytic activity was quite stable, while about 24% of the catalytic activity decayed after 3000 min, which still makes these systems available for the development of robust catalyst systems in the area of hydrogen generation.

Effect of LiClO4 Salt on Dielectric Properties of Acrylonitrile-Methyl Methacrylate and Acrylonitrile-Isobutyl Methacrylate Copolymers

Poly(acrylonitrile-co-isobutyl methacrylate), PAN-co-PIBMA, and poly(acrylonitrile-co-methyl methacrylate), PAN-co-MMA copolymers are synthesized by emulsion polymerization. The structural characterization is done by FTIR and 1H-NMR spectroscopy and thermal analyses are performed by thermogravimetric analysis (TGA). After various amounts of LiClO4 salt loading into copolymer films, the dielectric properties of these films at different temperatures and frequencies are determined. The effects of different methacrylate groups and salt content on the dielectric properties of copolymers are investigated. It is found that the dielectric constant increases systematically with increasing MMA and IBMA content in the copolymer. The samples with higher salt content show higher ac-conductivities.

PEM TİPİ YAKIT PİLLERİ İÇİN ÇİFT KUTUPLU AKIŞ PLAKALARININ MODELLENMESİ

Yakit pili teknolojisi, hidrojen enerjisini en ekonomik ve verimli kullanan teknolojilerden bir tanesidir.Kullandigi yakit ve uretebildigi guc miktari bakimindan cesitli yakit pilleri mevcuttur. Bu yakit pilleri icerisindeen cok polimer elektrolit membranli yakit pillerinin (PEMYP) gelecek vaad ettigi ongorulmektedir. Bucalismada tek hucreli bir polimer elektrolit membranli yakit pili Comsol Multiphysics programi kullanilarak ikiboyutlu olarak modellenmistir. Akisa paralel kesitte model olusturulmustur. Akis kanalina farkli geometrilerdeengeller konularak daha fazla yakiti reaksiyona zorlamak hedeflenmistir. Bu sekilde ideal performansdegerlerine yakin akim ve guc yogunluklari olusturulmaya ve kayiplar en aza indirilmeye calisilmistir. Sinirkosullari olarak degisik hiz degerleri girilmistir. Ayrica cikis sinir sartlari icin farkli basinc degerleri verilerekperformans etkisi arastirilmistir. Yapilan calismalar sonucu gorulmustur ki; giris hizinin artmasi, cikis basincininartmasi, katot tarafindaki sinir sartlarina anoda gore daha fazla oksidant beslenmesi ve kanal boyunca bulunanengellerin derinliginin artmasi sonrasinda yakit hucresi performansi artmistir.