Journal of Advanced Materials in Engineering (Esteghlal)

Preliminary results of a research on the effects of microstructure and surface roughness of a hypoeutectic cast iron on its wetting angle are presented in this article. For this purpose, molten cast iron was solidified at different cooling rates to produce two samples of the same composition, i.e. a gray cast iron with A type flake graphite and a white cast iron. Two samples were then prepared in polished, electroetched (four different stages) and mechanically abraded (four different stages) conditions and their wetting angles were measured after evaluating their roughness profile. Maximum and minimum wetting angles were observed on white cast iron surfaces roughened with 80 and 800 sand papers which were equal to 42 and 13 degrees, respectively.Wetting angles of electroetched white cast iron surfaces varied between 25 and 31 degrees by varying surface roughness. Maximum and minimum wetting angles on the surface of gray cast iron were obtained in stage one (40 degree) and stage three (25 degree) of electroetching, respectively. Wetting angles on mechanically abraded surfaces of this sample varied between 27 and 31 degrees. Then, the surface roughness factor and the solid fraction in contact with water were calculated using Wenzel equation and Cassie Baxter equation, respectively, and Wenzel and Cassie-Baxter wetting angles of the surfaces were calculated and were compared with their corresponding measured wetting angles. The results indicated that the surface microstructure and the type of constituents present at the surface, surface-roughening method and surface-roughness value influence the cast iron surface wettability, and it is possible to modify metal wetting angle by modification of its structure, surface-roughness method and surface-roughness value. It was also shown that in gray cast iron, the wetting behavior of the electroetched surfaces followed Cassie-Baxter equation in the first and second stages of electroetching and followed Wenzel equation at higher surface roughness (third and fourth stages of electroetching). In all stages of mechanically abrading, the surface of this sample followed Wenzel equation. The wetting behavior of the white cast iron followed Wenzel equation in all electroetching stages. In mechanically abraded conditions, the white cast iron wettability was variable and depended on the surface roughness.

In this study, the parameters affecting the synthesis of silver nanoparticles were optimized by green chemical reduction method to make a conductive pattern. The raw materials used in this study, include silver nitrate as a source of
silver ions, polyvinylpyrrolidone as surface stabilizer, and glucose as the reducing agent. Effective parameters were investigated
by Taguchi statistical design, to determine the optimum conditions and achieve the smallest average particle size. Silver nanoparticles were characterized by X-ray diffraction and field emission scanning electron microscopy. The smallest particle size can be applied by solution adding rate of 0.1 ml/min, temperature 90 ^°C, weight ratio of glucose to silver nitrate 3 g/g and weight ratio of Polyvinylpyrrolidone to silver nitrate 3.2 g/g. According to.our expectation 20 nm silver nanoparticles were obtained in this condition. FE-SEM confirmed the above results and showed nanoparticles with a size of 25 nm. Finally, A conductive pattern was printed on a glass substrate with synthesized powder. The electrical resistance of the printed pattern was 0.088× 10 ^-4 Ω.cm.