Ercan Karaköse

Influences of high temperature on the microstructural, electrical and mechanical properties of Ni-23 wt.% Al alloy

Abstract The microstructural, electrical and mechanical characteristics of conventionally and rapidly solidified Ni-23 wt.% Al alloys after heat treatments were investigated. The microstructures of Ni-23Al alloys were examined by means of scanning electron microscopy and the phase composition was identified using X-ray diffraction analysis. The phase transitions during the solidification process were investigated using differential thermal analysis under an Ar atmosphere. X-ray diffraction analysis indicated that the Ni-23Al samples showed an intermetallic γ′-Ni3Al phase, and we observed the intermetallic γ′-Ni3Al phase together with the β-NiAl phase after heat treatment at 700–900°C for 24 h. We performed electrical resistivity measurements by using the four-point probe technique in the temperature range 100–900°C. The resistivity of Ni-23 wt.% Al samples increases linearly with temperature. Vickers microindentation tests were carried out on the heat-treated samples with loads ranging from 392.26 mN to 1174.86 mN at room temperature. We found that the microhardness and effective elastic modulus values increased with increasing temperature and these values showed peak load dependence. The tensile and compressive stress values of the Ni–Al alloys also decreased with increasing temperature.

Microstructure properties and microhardness of rapidly solidified Al64Cu20Fe12Si4 quasicrystal alloy

This paper presents differences in the microstructure and microhardness properties of conventional casting (ingot) and rapidly solidified Al64Cu20Fe12Si4 quasicrystal (QC) alloys. The phases present in the Al64Cu20Fe12Si4 ingot alloy were determined to be icosahedral quasicrystalline (IQC) Ψ-Al65Cu20Fe15, cubic β-AlFe, tetragonal θ-Al2Cu, and monoclinic λ-A13Fe4 phases, whereas only IQC Ψ-Al65Cu20Fe15 and cubic β-AlFe phases were identified in the rapidly solidified alloy. The microhardness value of the melt spun alloy was measured to be approximately 790 kg/mm2. Microhardness increases with increasing solidification rates.

Green synthesis and antimicrobial activity of ZnO nanostructures Punica granatum shell extract

Abstract The manufacture of nanoparticles (NPs) is a new area of investigation due to potential applications related to the improvement of new technologies; in particular, environmentally safe manufactured nanomaterials have become a growing area within nanoscience. In this research, we synthesized zinc oxide (ZnO)-NPs using an aqueous extract of Punica granatum shell prepared using the green synthesis method. The ZnO-NPs were examined by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and UV-visible spectroscopy. The XRD patterns illustrated a single phase hexagonal (wurtzite) structure. The FE-SEM micrographs revealed the formation of erythrocyte-like structures and the average particle sizes were found to be 30–180 nm. The UV-visible measurements showed that the average optical transparency is over 85% in the visible range. The electrical conductivity values of the nanostructured ZnO-NPs were between 7.07×10−7 and 3.31×10−4 Ω−1 cm−1 in the temperature range 25–650°C. In addition, the ZnO-NPs did not show any antimicrobial affect against a Gram-positive bacterium (Bacillus thuringiensis).

Microstructural evolutions and hardness during heat treatment of Al64Cu20Fe12Si4 quasicrystal alloy

The microhardness and microstructural characteristics and subsequent heat treatment of conventionally solidified Al64Cu20Fe12Si4 quasicrystal were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) together with energy dispersive spectroscopy (EDS), differential thermal analysis (DTA), and Vickers microhardness tester. XRD analysis indicated that the conventionally solidified samples showed a quasicrystalline icosahedral phase (i-phase) together with cubic β-AlFe, tetragonal θ-Al2Cu, and monoclinic λ-A13Fe4 crystal phases. However, the i-phase together with cubic β-AlFe and monoclinic λ-A13Fe4 phases observed heat threaded samples. As-cast and subsequently heat-treated quasicrystal samples were measured using a microhardness test device. Vickers microindentation tests were carried out on the heat-treated quasicrystal samples with the load ranging from 1 to 500 mN at room temperature. The melting point of the i-phase was determined as 900°C by DTA examinations.

Structure and mechanical properties of Al‐3Fe rapidly solidified alloy

The Al based Al‐3 wt%Fe alloy was prepared by conventionally casting (ingot) and further processed the melt‐spinning technique and characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM) together with energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC) and the Vickers microhardness tester. The rapidly solidified (RS) binary alloys were composed of supersaturated α‐Al solid solution and finely dispersed intermetallic phases. Experimental results showed that the mechanical properties of RS alloys were enhanced, which can be attributed to significant changes in the microstructure. The dependence of microhardness HV on the solidification rate (V) was analysed. These results showed that with the increasing values of V, the values of HV increased.