Surface and porous recast layer analysis in µ-EDM of MWCNT-Al2O3 composites

Machining of ceramic materials has been a major challenge owing to high hardness and brittleness. The reinforcement of a conducting filler allows permissible machining in electrical discharge machining (EDM) process. The current effort analyses the impact of multi-walled carbon nanotubes (MWCNT) of concentrations of 2.5 and 5 vol. %, as conducting filler towards machinability of alumina composites in µ-EDM process. The influence of tool materials and its rotation are closely analyzed. A successful machining process is observed in both the two composites, with a higher material removal rate (MRR) in 5 vol. % MWCNTs. When the tool starts to rotate at 750 rpm, an increment of around 60–65% is observed in MRR for both the two composites. Similarly, the surface roughness (R_a) decreases by a factor of 20?25%. The brass tool is observed to yield better machining capabilities due to the frequent initiation of sparks. A highly porous machined surface is observed in both the two composites. This scenario depicts the spalling effect as more dominant than melting-evaporation effect. The extent of porous recast layer on the drilled edges is found to reduce with increasing the speed of tool rotation.     

Photovoltaic effect in single-layer organic solar cell devices fabricated with two new imidazolin-5-one molecules

Organic solar cells were fabricated with two new imidazolin-5-one molecules as active layers. The use of imidazolin-5-ones, derivatives of a biomolecule chromophore, for photovoltaic applications is particularly attractive due to its biodegradable nature and tunable properties. Single-layer devices with two analogues of imidazolin-5-ones were prepared and characterized. Devices fabricated with one of the molecules as the active layer showed a maximum J_sc of 0.52 μA cm⁻² and V_oc of 0.68 V at an incident power of 20.32 mW cm⁻², while the other set of devices showed a maximum J_sc of 0.63 μA cm⁻² and V_oc of 0.57 V at the same incident power.     

Direct electrochemistry of dinuclear CuA fragment from cytochrome c oxidase of Thermus thermophilus at surfactant modified glassy carbon electrode

Cytochrome c oxidase is ubiquitous enzyme involved in the terminal step of respiratory electron transfer process. The unique binuclear copper center containing bis-dithiolato bridges form a valance delocalized [Cu^1.5+-Cu^1.5+] state of the metal center located at the subunit II of cytochrome c oxidase. This metal center acts as the electron entry site of the enzyme and accepts electrons from cytochrome c. Direct electrochemistry of this binuclear copper center containing the water soluble protein obtained by genetically truncating the membrane bound part of the subunit II from Thermus thermophilus was achieved by favorable orientation of the protein on glassy carbon electrode surface promoting efficient electron transfer in the presence of various surfactants. Very reproducible, Nernstian responses are obtained with Cu_A. The redox potential and the electrochemical response were enhanced prominently in case of cationic surfactant CTAB indicating that the nature of the surfactant has a significant effect on the microenvironment of the protein-electrode interface. The results have been used to understand the mechanism of electron transfer from cytochrome c to the copper center during the enzymatic reaction.     

Titanium carbide: An emerging electrocatalyst for fuel cell and electrolyser

Development of cost-effective, high-performance and non-precious electrocatalyst for Polymer Electrolyte Membrane Fuel Cell (PEMFC) is an essential requirement to replace Pt-group metal catalyst. Nanostructured transition metal carbides have attracted vast interest in fuel cell and electrolyser as electrocatalyst or support, due to its high conductivity and thermo-chemical stability. This paper provides a review in the recent experimental and theoretical studies on Titanium Carbides (TiC) as electro-catalyst and support for fuel cell and electrolyser. The morphologies of TiC show strong impact on the performance of the electrocatalyst in different oxidation and reduction reactions. This study discusses the electrochemical properties and synthesis processes for the development of different TiC nanostructure. The critical issues, challenges and the future perspective for TiC as electrocatalyst as well as electrocatalyst support in fuel cell and electrolyzer with desired activity and stability are also discussed.     

Synthesis and characterization of plasmonic visible active Ag/ZnO photocatalyst

Ag deposited ZnO nanoparticles (NPs) have been synthesized by simple sol–gel method for visible light active photocatalytic application. X-ray diffraction (XRD), TEM, UV–DRS and PL studies have been used to characterize the photocatalyst. The results show that Ag/ZnO NPs are wurtzite phase (WZ) of ZnO with Ag NPs in the surface region forming a hetero-interface of Ag–WZ (ZnO). Visible light activity of the material has been studied using photocatalytic degradation kinetics of methylene blue as a probe pollutant. Ag/ZnO NPs exhibit five times higher visible-light driven photocatalytic activity than pristine ZnO and four times than the reference Degussa P-25, under identical conditions. The high visible activity of Ag/ZnO may be attributed to the surface plasmon effect complemented sensitization in the presence of metallic Ag and effective charge separation through Ag–WZ hetero-interfaces.