Cost-Effective Control of Molecular Weight in Ultrasound-Assisted Emulsion Polymerization of Styrene

This paper focuses on the determination of economically most feasible conditions to obtain polystyrene with various target molecular weights through ultrasound-assisted emulsion polymerization. Briefly, batch polymerizations of styrene have been performed by ultrasound-assisted emulsion polymerization process using different reaction feed compositions. Polymerization rates were calculated using the monomer conversions at various reaction times. Also, molecular weights of the synthesized polymers, as well as the Mark-Houwink constants, were determined by intrinsic viscosity and gel permeation chromatography measurements. It was found that the polydispersity index of the polymers is ranging from 1.2 to 1.5, and the viscosity average molecular weights are in between 100000-1500000 g/mol depending on the reaction conditions. Finally, model equations were also developed for response variables, and the most economical ways of reaching various target molecular weights were interpreted by response surface methodology based multi objective optimization

Graphene Oxide/Cholesterol-Substituted Zinc Phthalocyanine Composites with Enhanced Photodynamic Therapy Properties

In the present work, cholesterol (Chol)-substituted zinc phthalocyanine (Chol-ZnPc) and its composite with graphene oxide (GO) were prepared for photodynamic therapy (PDT) applications. Briefly, Chol-substituted phthalonitrile (Chol-phthalonitrile) was synthesized first through the substitution of Chol to the phthalonitrile group over the oxygen bridge. Then, Chol-ZnPc was synthesized by a tetramerization reaction of Chol-phthalonitrile with ZnCl2 in a basic medium. Following this, GO was introduced to Chol-ZnPc, and the successful preparation of the samples was verified through FT-IR, UV–Vis, 1H-NMR, MALDI-TOF MS, SEM, and elemental analysis. Regarding PDT properties, we report that Chol-ZnPc exhibited a singlet oxygen quantum yield (Φ∆) of 0.54, which is slightly lower than unsubstituted ZnPc. Upon introduction of GO, the GO/Chol-ZnPc composite exhibited a higher Φ∆, about 0.78, than that of unsubstituted ZnPc. Moreover, this enhancement was realized with a simultaneous improvement in fluorescence quantum yield (ΦF) to 0.36. In addition, DPPH results suggest low antioxidant activity in the composite despite the presence of GO. Overall, GO/Chol-ZnPc might provide combined benefits for PDT, particularly in terms of image guidance and singlet oxygen generation

POLYANILINE COMPOSITES AS THERMOELECTRIC MATERIALS

Ph.DDOCTOR OF PHILOSOPH

Mg-Ni Metaller Arası Bileşiklerinin Erimiş Tuz İçerisinde Üretilmesi

Mg2Ni, hidrojen depolama kapasitesi yüksek olan (3.4 ağ.%- 3.6 ağ. %) önemli bir metaller arası bileşiktir. Yapısında hidrojen ile kolay bağ kurabilen Mg bulunması depolamanın kolay olmasına, hidrojen ile kolay bağ kuramayan Ni bulunması da hidrojen ayrışımının kolaylaşmasına yardımcı olmaktadır. Literatür taraması yapıldığında Mg2Ni’nin bir çok çeşitli yöntemle üretilebildiği fakat bu yöntemlerin her birinde Mg ve Ni metallerinin üretim öncesinde hazır bulunması gerekliliği gözlemlenmiştir. Fakat magnezyum’un kolay oksitlenebilen bir metal olması, ayrı olarak tutulmasının da zor olmasına neden olmaktadır. Bu araştırma; Mg2Ni üretimi için yeni bir metodun uygulanabilirliğinin incelenmesini amaçlamaktadır. Bilindiği gibi Ni, NiO’in elektrodeoksidasyonu ile, Mg ise MgCl2’nin erimiş tuz içerisinde elektrolizi ile üretilebilmektedir. Bu iki metalin ayrı ayrı hücrelerde elde edilip daha sonra başka prosesler ile Mg2Ni bileşiği üretilmesi yerine tüm işlemin tek bir hücrede tamamlanması daha faydalı olacaktır. Bileşiminde MgCl2 bulunan bir elektrolit içerisinde, NiO elektrodeoksidasyonunu takiben uygulanacak yüksek potansiyellerin katotta Mg2Ni oluşumuna imkan verebileceği düşünülmüştür. Bu çalışmada temel amaç NiO elektrodeoksidasyonunu takiben yerinde Mg2Ni oluşturarak, önceki yöntemlere alternatif daha düşük maliyetli Mg2Ni metaller arası bileşiği oluşturmaktır. Sıcaklık, elektrik potansiyeli, erimiş tuz elektroliti kompozisyonu, NiO peletin porozitesi ve sinterleme süresi gibi değişkenlerin Mg-Ni metallerarası bileşiklerin oluşmasına etkilerinin incelenmesini kapsamaktadır. Sonuçta Mg2Ni oluşumuna yukarıdaki parametrelerin etkileri belirlenecektir

On the Preparation of Mg2Ni by Combining Electrodeoxidation and Electrolysis Techniques

Mg2Ni is a well-known hydrogen storage alloy. Most of the preparative methods for this alloy require high temperature processing of pure magnesium and nickel. The proposed method, studied in this work, involves the production of Mg2Ni alloy directly from NiO and MgCl2 in an electrochemical cell. This method can eliminate the difficulties that may arise, during handling due to the reactive nature of metallic components, especially Mg. XRD patterns of reduced samples indicated the partial formation of Mg2Ni. Experimental results also showed that sintering of NiO, which resulted in the decrease of porosities, adversely affects the formation of Mg-Ni intermetallic compounds. Such an observation was thought to be the result of higher molar volume of Mg2Ni as compared to that of NiO

Elektrodeoksidasyon ve erimiş tuz elektrolizi metotlarının intermetalik ve/veya alaşım üretmek için birleştirilmesi

Bu buluş, erimiş tuz elektrolizi ve elektrodeoksidasyon tekniklerini birleştirerek, intermetalik (metaller arası) bileşik ve/veya alaşım oluşturmayla ilgilidir. Daha özelde; intermetalik ve/veya alaşımın en az bir bileşeni, oksidinden veya başka bir bileşiğinden, oksijen veya başka bir metalik olmayan safsızlığın atılmasıyla elde edilmelidir. Benzer şekilde; intermetalik ve/veya alaşımın en az bir bileşeni, hedeflenen intermetalik bileşik ya da alaşımı oluşturmak üzere, erimiş tuz elektrolitlerinden, klasik erimiş tuz elektrolizi yöntemiyle oluşturulmalıdır

AN INVESTIGATION INTO THE ELECTROCHEMICAL PRODUCTION OF Si BY THE FFC CAMBRIDGE PROCESS

The FFC Cambridge process was suggested as a promising Si production technique for the expanding solar energy industry. Direct electrochemical reduction of bulk SiO2 plates and porous SiO2 pellets in molten CaCl2-NaCl salt mixture were investigated at 750 degrees C by applying 2.8 V potential difference. The produced Si powder was brown and found to be contaminated by the Ni and stainless steel plates used as the cathode contacting materials. The reduction rates of the bulk SiO2 plates and porous SiO2 pellets were compared from variations of current and accumulative electrical charge that passed through the cell during the electrochemical reduction. The amorphous bulk SiO2 plates were reduced slightly faster than porous pellets of crystalline SiO2. The overall reduction potential of SiO2 pellets against the graphite anode at 750 degrees C in molten CaCl2- NaCl salt mixture was determined as 2.3 V by cyclic voltammetry. This potential was supported by calculations

A Novel and Eco-friendly Approach for the Simultaneous Recovery of Copper and Diamond from Waste Cutting Segments via Electrodissolution/Deposition

A new approach is brought to diamond recovery from waste cutting segments. Unlike the commonly used hydrometallurgical processes, this approach offers the simultaneous recovery of copper with diamond. Besides, instead of strong acids, this work involves use of a dilute acid solution, reducing the evolution of toxic vapors. Copper base segments of waste diamond tools were used as anode, which were dissolved by applying potentials above the dissociation voltage of Cu. Simultaneously, the diamond grits detached from the segments and gathered at the bottom of the cell. Then, the dissolved Cu2+ cations were reduced, and Cu powders were electrodeposited at cathode without affecting the accumulated diamond particles. Eventually, the diamond particles could be collected from the bottom of the cell, providing the simultaneous recovery. In this work, the effect of individual process parameters on the outcome of presented approach is studied. The process parameters were then optimized, and mathematical models were developed for response variables by response surface methodology. Also, a mini-prototype was designed and operated at the optimized conditions to check the possibility of converging the proposed approach to industrial applications. Prototype tests show that all detached diamond could be recovered in 3 h and simultaneously with Cu powders