Fikret Yılmaz

Effect of variation in voltage on the synthesis of Ag nanopowder by pulsed wire evaporation

Nanosized Ag particles were obtained in liquid medium, which is composed of deionized water and sodium hexametaphosphate, using pulsed wire evaporation within hundreds of microseconds from pure initial Ag wire (99.98%), with varying voltage. Changes in powder morphology and microstructure due to change in supply voltage was observed by FE-SEM and HR-TEM, and phase structure of powders was analyzed by XRD. The results revealed that average particle size slightly increased with increasing supply voltage without any impurity and oxide phase, which was explained in terms of addition of stabilizer into the coolant liquid. The experimental results also suggest that addition of sodium hexametaphosphate into the coolant liquid is good for enhancing the dispersibility property of silver nanopowders.

Effect of acid pretreatment on the dyeing performance of walnut ( Juglans regia ) leaves on wool fibers

In this study, dyeability of wool fabrics with walnut leaves extract have been investigated in presence of various acids including acetic acid, citric acid, maleic acid, oxalic acid, and formic acid. Each wool fabric was pretreated with 1 M of acid solution, separately. The pretreated fabrics were dyed with walnut leaves extract using various mordants by metamordanting method. Color strength values of the dyed fabrics were evaluated by measuring K/S values. Fastness properties (washing, rubbing, and light fastness) were also determined. The pretreated fiber sample surfaces were observed using a scanning electron microscope (SEM). The present study showed that citric acid pretreatment plays an important role for improving the dyeability of wool fabrics with walnut leaves extract.

Determination of the Dyeing Potential of Mint and Sage Crops Wastes on Wool and Cotton Fibers

ABSTRACT In the present study, dyeing potential of waste water from distillation process was investigated for fresh and dried herbs of Menthaspicata (MS), Menthapiperita (MP), and Salvia officinalis (SO) species. Meta-mordanting method was used in the dyeing of wool and cotton fabrics in the presence of FeSO4·7H2O (iron) and AlK(SO4)2·12H2O (alum) mordants. The color of each dyed material was investigated in terms of the CIELab (L*, a*, b*, C, and h°) and K/S values. The surfaces of the samples were observed using a scanning electron microscope. It was observed that the color strength of fresh and dried plant is depended on the plant species, mordant, and fabric type. Best color intensity (K/S = 16.68) was obtained with iron mordant using fresh SO on cotton fabric. For wool fabric, the highest color strength (K/S = 9.62) was obtained with fresh SO in the presence of alum mordant. Presence of metal mordant for natural dyeing process of cotton with MS, MP, and SO extract has shown remarkable improvement in terms of dye adherence and fastness properties thus metal mordanting could be suitable alternative dyeing method for ecofriendly industrial application.

Nanoindentation study on Gd-deposited YBaCuO superconductor

Nanoindentation technique was used to characterize the mechanical properties of Gd-deposited bulk YBaCuO superconductors fabricated by solid-state reaction method. In order to determine the hardness and reduced modulus of the samples, load-displacement data were analysed by using the Oliver–Pharr method. The hardness values exhibited significant peak load-dependence especially at lower peak loads, while the reduced modulus values were found to be nearly constant at studied loading range. In order to find true hardness of the samples, the peak load-dependency of hardness was analysed by using Meyer’s law, minimum resistance model, elastic/plastic deformation model, energy balance model, Nix–Gao model and Mukhopadhyay approach. Of the aforementioned models, energy balance model and Mukhopadhyay approach were found to be the most effective models to explain the load-dependency of hardness.

Effects of Substitution of Al and Bi for Ni on Structure and Hydrogen Storage Properties of LaNi4.7-xAl0.3Bix (x=0.1, 0.2, 0.3) Alloy

In this research, the effects of Al and Bi substitution for Ni on the microstructure and hydrogen absorption/desorption properties of LaNi4.7-xAl0.3Bix (x=0.1, 0.2, 0.3) alloys were investigated. The results showed that substituting Ni with Al led to a desirable decrease in absorption/desorption plateau pressure as well as to hysteresis without a reduction in hydrogen capacity. However, Bi substitution reduced the hydrogen capacity and increased the absorption/desorption plateau pressure of the samples. The formation of the (Al,Ni) intermetallic and Bi phases at grain boundaries was found to be the main reason for the changes in hydrogen storage properties.