Y. Aydogdu

Effects of thermal treatments on transformation behaviour in shape memory Cu–Al–Ni alloys

Abstract The martensitic transformation behaviour, morphology and transition temperatures in copper-based shape memory alloys are strongly influenced by heat treatments. The effects of various quenching, up-quenching and step-quenching in a water bath 100 °C and in an oil bath at 200 °C have been studied on two shape memory Cu–Al–Ni alloys. The changes at entropy and enthalpy at the martensitic transition have been determined by means of differential scanning calorimeter (DSC) measurements. It was observed that quenching has a marked influence on the transformation temperatures.

Electrical and optical properties of newly synthesized glyoxime complexes

Abstract In this study, the electrical and optical properties of newly prepared Ni(L 1 H 2 ) and Ni(L 2 H 2 ) complexes have been investigated and the results obtained were analyzed. It is seen that these complexes have inorganic semiconductor properties. The activation energies ( E a ) for the complexes were calculated by using Arrhenius plots and their optical band gaps have been determined through the optical spectra. Thermal probe measurements indicated that these samples have n -type of electrical conductivity.

Solid state electrical conductivity properties of copper complexes of novel oxime compounds containing oxolane ring

Abstract In this study, a novel dioxime having the 1,3-oxolane group, 1,2-dihydroxyimino-3,7-diaza-9,10-O-cyclohexylidenedecane (L1H2) and 9,10,bis(hydroxyimino)-4-8,11,15-tetraaza-1,2,17,18-O-dibenzaloctadecane (L2H2), were synthesised from 1,2-O-benzal-4-aza-7-aminoheptane, which was prepared from a reaction of 1-choloro-2,3-O-benzalpropane and dichlorogloxime. The electrical properties of complexes of those ligands with Cu(II) salts were investigated and obtained results were analyzed. It was seen that these complexes had semiconducting properties. The activation energies (Ea) were calculated for the complexes by using the Arrhenius plot. Thermal probe measurement indicated that these complexes had an n-type electrical conductivity.

X-ray diffraction studies, electrical and optical properties of some metal complexes of the ligand including 1-amino-3-(N-benzylamino) propane

Abstract Metal complexes containing Cu +2 , Ni +2 and Cd +2 of the ligand including 1-amino-3-( N -benzylamino propane) named M2 — [CdL 1 ](Cl 2 ), M3 — [CuL 2 ](NO 3 ) 2 , M4 — [CuL 2 ](Cl 2 ) and M5 — [NiL 2 ](Cl 2 ) were investigated structurally by X-ray diffraction (XRD), electrically by two probe and optically by optical methods. From the XRD data, the unit cells of the samples were found as M2, monoclinic, and M3, M4 and M5, triclinic. Hot probe and thermoelectric power measurements indicated that the complexes M2, M3, M4 and M5 have n-type of electrical conductivity and optical band gaps of the complexes are 1.66, 1.31, 1.25 and 1.29 eV, respectively.

The influence of ageing on martensite ordering and stabilization in shape memory Cu-Al-Ni alloys

Abstract The martensitic transformation and the associated mechanical shape reversibility in copper-based shape memory alloys is strongly influenced by quenching and ageing treatments. Ageing of martensite in as-quenched Cu-Al-Ni alloys can result in loss of memory behavior. Structural studies have been carried out to measure the changes in the degree of order that develop during martensitic ageing of two Cu-Al-Ni alloys. Stabilization is directly related to disordering in martensitic state and the spacing differences (Δd) between selected pairs of diffraction planes reflect the degree of ordering in martensite. The changes in degree of order are shown to be similar in asquenched and post-quenched β-phase annealed alloys, thereby leading to the conclusion that loss of memory in as-quenched alloys is not solely attributable to any extra changes in degree of order brought about by excess vacancies during martensitic ageing.

Effect of composition on the thermal behavior of NiMnGa alloys

The methods to determine martensitic transformation temperature, enthalpy and entropy change, specific heat capacity change with temperature, and transformation activation energies of Ni–%29.5Mn–%21Ga, Ni–%29Mn–%21Ga, Ni–%29.5Mn–%20Ga, and Ni–%28.5Mn–%20.5Ga (atomic percentage) alloys were investigated by differential scanning calorimetry. It was observed that the transformation temperature increased with an increase in atomic nickel ratio. Meanwhile, it was detected that the change in enthalpy increases with the amount of nickel. The highest values of entropy change and the heat capacity at room temperature were observed in the alloy having the least amount of nickel in it.

Electrical and optical properties of [poly[2-(3-1,2,3,4-tetrahydronaphtyl-3-methylcyclobutyl)-2-hydroxyethylmethacrylate]

Abstract The electrical and optical properties of newly synthesized polymer, poly[2-(3-1,2,3,4-tetrahydronaphtyl-3-methylcyclobutyl)-2-hydroxyethylmethacrylate (PTCHEMA), have been investigated. The results show that the sample has semiconducting behavior as its conductivity increases with increased temperature and the value of conductivity is order of magnitude (10 −6 S/cm). In addition, the thermal conductivity is measured in the investigated temperature range. Optical energy band gap and activation energy of the sample have been determined by means of optical spectra and electrical measurements, respectively. The study of the surface appearance of the sample is done by means of electron scanning (SEM).

XRD, SEM studies and electrical properties of metal complexes, including sodium oxalate ligand (Na2C2O4)

Abstract The crystal structure, microstructure, and electrical properties of inorganic semiconductors were based on metal complexes, including sodium oxalate ligand. The crystal structure of samples at room temperature was examined using X-ray diffraction (XRD). X-ray diffraction showed that the three samples have different crystal structures. The microstructures of the samples have also been investigated by scanning electron microscopy (SEM). These samples have been found to be inorganic semiconductors having moderate conductivities and activation energies. Room temperature conductivities of O–Co, O–Ni, and O–Cu samples were 6.43×10−9, 3.85×10−7, and 2.10×10−6 S/cm, respectively. The mobility and concentration of the carriers were calculated by means of current–voltage curve samples in the space charge limited region (SCLC).

Electrical and optical properties of inorganic complexes C36H76N2O9ClNa and C14H12N2O4TeBr2

Abstract The electrical properties of some inorganic samples were studied as functions of temperature and the results were analyzed. These samples activation energies were calculated from the electrical conductivity measurements. Also, a detailed study of optical absorption is presented. The optical absorption spectra are measured in the UV+invisible wavelength range 200–1100 nm. The absorption coefficient and value optical energy gaps were determined from the absorption spectra. The complex C 36 H 76 N 2 O 9 ClNa is characterized by direct optical absorption with an optical edge at 4.49 eV. However, the complex C 14 H 12 N 2 O 4 TeBr 2 is characterized by indirect optical absorption with an optical edge at 1.45 eV, and a nearby direct one at hν =1.80 eV.

Electrical and optical properties of semiconducting metal complexes

Abstract The electrical conductivity, crystal structure, thermoelectric power, thermal conductivity and optical properties of newly synthesized Cu(II), Ni(II) and Co(II) complexes have been investigated. The crystal structure of the complexes was carried out by powder X-ray diffraction (XRD). XRD show that samples are polycrystalline. The conduction mechanism was determined by activation energy process. The electronic parameters of the complexes were calculated, such as, activation energy E for dc conductivity and the density of localized states at the Fermi level N ( E F ). The electrical conductivity measurements exhibit three-dimensional variable hopping conduction. The mechanism of the optical absorption follows the rule of direct transition. As a result, it is interpreted that the samples show semiconducting behavior as their conductivity increases with increasing temperature and they have direct optical band gap.