Production and characterization of nano struc-tured RuO2/Ti coatings

Bu &ccedil;alışmada titanyum altlık malzeme &uuml;zerine termal dekompozisyon y&ouml;ntemi kullanılarak rutenyum klor&uuml;r tuzlarından y&uuml;zeyde okside par&ccedil;alama işlemi ile DSA&reg; (boyutsal kararlı anot) elektrotlar &uuml;retilmiştir. Farklı dekompozisyon sıcaklıkları kullanılarak (400-450-500 &deg;C) elde edilen elektrotların y&uuml;zey morfolojileri ve faz bileşimleri FESEM ve X-ışınları difraksiyon analizleri ve elektrotların elektrokimyasal &ouml;zellikleri ise kronopotansiyometri ve doğrusal tarama voltametrisi y&ouml;ntemleriyle incelenmiştir. Elde edilen elektrotların 100 nm&rsquo;den k&uuml;&ccedil;&uuml;k RuO2 nano-kristallerden oluştuğu bulunmuştur. Dekompozisyon sıcaklığının artışıyla tane b&uuml;y&uuml;mesi ve efektif y&uuml;zey alanı k&uuml;&ccedil;&uuml;lmesi tespit edilmiştir. Buna paralel olarak, elektrodun elektrokimyasal &ouml;zellikleri de (Tafel denkleminin a ve b katsayıları) değişmiştir. D&uuml;ş&uuml;k dekompozisyon sıcaklıklarında &uuml;retilen elektrotların y&uuml;ksek elektroaktivite ve d&uuml;ş&uuml;k anot potansiyel değerine sahip olduğu g&ouml;r&uuml;lm&uuml;şt&uuml;r. T&uuml;m elektrotların d&uuml;ş&uuml;k akım yoğunluğu b&ouml;lgesinde elektroaktif reaksiyonu temsil eden d&uuml;ş&uuml;k Tafel eğimlerine (b =~59 mV/dec) sahip olduğu ancak anodik polarizasyon değerinin artışına bağlı olarak Tafel doğrularının kırılma g&ouml;sterdiği ve oksijen deşarjının ~118 mV/dec eğimli reaksiyon &uuml;zerinden ger&ccedil;ekleştiği tespit edilmiştir. Bu temel b&uuml;y&uuml;kl&uuml;klerden hareketle, asidik &ccedil;&ouml;zeltilerde elektroaktif ve elektroaktif olmayan elektrotlar i&ccedil;in ge&ccedil;erli oksijen deşarj reaksiyon mekanizması &ouml;nerilmiştir. Elektrokatalitik aktiviteyi dolaylı yollardan etkileyen diğer bir parametre olan malzeme sabiti (a) ise artan dekompozisyon sıcaklığı ile artmıştır. Bu durumun, sıcaklığa bağlı morfolojik yapının değişmesiyle orantılı olduğu g&ouml;r&uuml;lm&uuml;şt&uuml;r.&nbsp;Anahtar Kelimeler: DSA&reg;, RuO2, oksijen deşarjı, elektroaktivite, titanyum elektrot, termal dekompozisyon.Dimensionally stable anodes (DSA®) are widely used as electrode materials in several electrochemical applications. In the production of these types of electrodes thermal decomposition method is successfully applied. This method is based on thermal decomposition of precious metal chloride precursor solutions on titanium surface to give metal oxide. Production conditions, namely; substrate treatment, type of precursor solution, application procedure of precursor solution and heat treatment have great influence on the morphological and electrochemical properties of these electrodes. Most of these pretreatment steps have been standardized: titanium substrates are generally sandblasted to obtain high roughness (high surface area); precursor solutions are prepared in aliphatic mono-alcohols to ease the evaporation of the solvents; painting, spraying or dip-withdrawal techniques are generally used. Among these parameters heat treatment is the key parameter affecting the behavior of both physical and electrochemical properties of DSA®. In this study, various decomposition temperatures (400-450-500 °C) were used to prepare RuO2 coated titanium electrodes by utilizing thermal decomposition method. The effect of decomposition temperature on morphology was examined by field emission scanning electron microscope (FESEM) and the phase determination was done by thin film-X ray diffraction analysis (XRD). Electrochemical behavior and characteristics of the coatings prepared at different decomposition temperatures were investigated by chronopotentiometry (CP), and linear sweep voltammetry (LSV). Correlation between the physical and electrochemical properties of the electrodes was scrutinized by means of morphology and electrocatalytical activity. In the morphological investigations, it was found that the surfaces obtained at all decomposition temperatures were alike with roughened heterogeneous morphology. The surfaces consisted of flat areas (sub-surfaces) and nano-crystals (particularly on the hills of the rough surface). Nano structured RuO2 crystals (< 100 nm) were formed in the shape of columnar base with a rutile type tetragonal structure. Crystallinity and the size of nano-structures were found to increase with increasing decomposition temperature and agglomeration occurred locally on the hills of the surface. It was seen that an increment of 50 °C in the decomposition temperature results in ~37% increase in particle size. Although particle coarsening was occurred by the increase of decomposition temperature, it was found that particle growth was also in nano-scale. Moreover, the flat areas were found to form of nano crystals which could only be detected at higher magnifications. Nano-structured crystals indicated that the real surface area of the electrodes was high, nevertheless higher decomposition temperature resulted in smaller real surface area. The results obtained from morphological investigations made us to examine their influence on the electrochemical properties of the electrodes. Chronopotentiometric tests showed that lower anode potentials could be obtained for the electrodes prepared at lower decomposition temperatures. This was due to the higher real surface area providing excess active sites being involved in the electrochemical reactions. When the decomposition temperature was higher, electrodes were found to possess higher anode potentials. This was caused by the better crystallinity and particle coarsening with increasing temperature that resulted in smaller real surface area. The electrocatalytical activities of the electrodes were investigated by current density - potential (j - E) curves. Results showed that higher current flow could be achieved for the electrode prepared at 400 °C. This indicates that surface active sites - being involved in the electrochemical reaction - were much higher than the others. Similarly, for a given current density value, the anode potentials were lower for the electrodes prepared at lower decomposition temperatures. Tafel plots were done in order to define the electrocatalytical activity of the electrodes. Break in the Tafel lines was occurred which indicates that the reaction mechanism was changed. It was observed that at lower current density region, all electrodes have the same Tafel slope (~59 mV/dec) which showed that the same reaction mechanism took place on the electrodes. At higher current densities, Tafel slope for oxygen depolarization was found to be 118 mV/dec. The materials coefficient, a, was found to increase with the increasing decomposition temperature. It is concluded that lower decomposition temperatures in the preparation of DSA® electrodes are beneficial. Keywords: DSA®, RuO2, oxygen depolarisation, electroactivity, titanium electrode, thermal decomposition

Bio-functionalized (Ag-Ser) nanoparticle synthesis and characterization for biomedical platforms

[No abstrack available

PyNanospacing: TEM image processing tool for strain analysis and visualization

The diverse spectrum of material characteristics including band gap, mechanical moduli, color, phonon and electronic density of states, along with catalytic and surface properties are intricately intertwined with the atomic structure and the corresponding interatomic bond-lengths. This interconnection extends to the manifestation of interplanar spacings within a crystalline lattice. Analysis of these interplanar spacings and the comprehension of any deviations, whether it be lattice compression or expansion, commonly referred to as strain, hold paramount significance in unraveling various unknowns within the field. Transmission Electron Microscopy (TEM) is widely used to capture atomic-scale ordering, facilitating direct investigation of interplanar spacings. However, creating critical contour maps for visualizing and interpreting lattice stresses in TEM images remains a challenging task. Here we developed a Python code for TEM image processing that can handle a wide range of materials including nanoparticles, 2D materials, pure crystals and solid solutions. This algorithm converts local differences in interplanar spacings into contour maps allowing for a visual representation of lattice expansion and compression. The tool is very generic and can significantly aid in analyzing material properties using TEM images, allowing for a more in-depth exploration of the underlying science behind strain engineering via strain contour maps at the atomic level.Comment: Preprint, 13 pages, 9 figure