Kazi Md. Shorowordi

Effects of molybdenum additions on the structure, depth, and austenite grain size of the case of carburized 0.13% carbon steels

Carbon (0.13%) steel samples containing about 0.48% molybdenum (Mo) singly and in combination with nickel (Ni) were carburized in a natural Titas gas atmosphere at a temperature of 1223 K (950 °C) and at a pressure of about 0.10 MPa (15 psia) for time periods ranging from 1–4 h followed by slow cooling in the furnace. Their microstructure was studied by optical microscopy. The austenite grain size of the case and the case depths were determined. It was found that Mo and Ni alone and in combination decrease the thickness of the cementite network near the surface of the carburized case of the steels. However, Ni is found to be more effective than Mo in decreasing the thickness of cementite network. Both Mo and Ni enhance the formation of Widmanstätten cementite plates at the grain boundary and within the grains near the surface of the carburized steels. However, Ni alone is more effective than Mo in the formation of Widmanstätten cementite plates. In the presence of Ni, Mo is much more effective in the formation of Widmanstätten cementite plates than Mo in absence of Ni. It was also revealed that both Mo and Ni increased the case depth. Ni is more effective than Mo in increasing the case depth. The combined effect of Mo and Ni is much greater than that of either Mo or Ni alone in increasing case depth. Mo as Mo carbide (Mo2C) particles refined the austenite grain size of the carburized case. Ni in solution was not found to have any effect in restricting grain growth of austenite, but the presence of Ni enhances the austenite grain size refining effect of Mo in the carburized case.

Electrodeposition and dependency of optical properties on operating voltage and bath temperature of Copper oxide (II) thin films for photovoltaic applications

In our current research, thin films of Copper oxide (CuO) were deposited on copper plate in an electrolytic bath containing CuSO4.5H2O, 3M lactic acid and NaOH by electrodeposition process. CuO thin films were electrodeposited at different voltage and different temperature whereas bath concentration, pH and time were kept constant. The characterization of the CuO thin films deposited at different electrodeposition conditions were conducted by Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS). The SEM study showed the grain sizes of CuO thin films decreased at more negative potentials. Film thickness with regards to voltage and temperature are analysed. Absorption spectrum was obtained from UV-Vis absorption spectroscopy. Subsequently, the optical band gap was determined from their absorption spectrum by using Taucs equation. It was found that CuO thin films deposited at low voltage have lower band gap than that of films deposited at higher voltage due to crystalline, uniform and compact grains. The band gap decreases with increasing operating temperature.