Kadir Esmer

Electrical conductivity of modified bentonites and FT-IR spectroscopic investigations of some aromatic molecules adsorbed by bentonites

Abstract Electrical conductivity of natural and ion-exchanged Anatolian bentonites (Ag–, Cu–) and of different organic molecules (benzidine–, pyrazine– and 1,4-diamino benzene–) adsorbed by bentonites were investigated. Dc and ac measurement techniques were applied to ribbon and sandwich type samples. Measurements were made under standard pressure, humidity and room temperature. It was observed that conductivity of ion exchanged Ag–, Cu–bentonite and benzidine–bentonite complexes has increased. In addition, FT-IR spectrometry was used to assign complex pattern and composition in clay–organic molecule complexes. Spectroscopic investigations suggest that organic molecules intercalate the interlayers of bentonite with a monolayer arrangement.

Electrical conductivity and dielectric behaviour of modified sepiolite clay

Electrical and dielectric properties of modified sepiolite mineral taken from the Anatolia region have been investigated at room temperature. Sepiolite mineral dispersed by ultrasonic methods and saturated with Fe2+ by ion exchange has been oriented in a 10-K Gauss magnetic field. It has been observed that sepiolite shows a paramagnetic property in the EPR spectrum. Then, the current–voltage changes have been investigated in parallel and perpendicular directions to the magnetic field. It has been observed that while the conductivity in magnetic field direction being increases, it decreases slightly in the perpendicular direction. The capacitive measurements have been done between 10 kHz and 10 MHz, and the dielectric permittivities and the loss tangent and dielectric conductivity have been calculated. The dielectric conductivity of Fe-sepiolite is found to increase having a permanent orientation polarization due to the magnetic field. In the natural sepiolite, relaxation of O→H dipole moment polarization depending on insufficient amounts of Fe2+ and Fe3+ has increased with the effect of the electric field. Thus, overall polarization at high frequencies has been observed a very rapid decrease. The changes for both samples have been observed at 100 kHz.

Current–voltage characteristics and aging of sepiolite oriented by magnetic field

Abstract Current–voltage characteristics and aging properties of modified sepiolite taken from Anatolia have been studied. Sepiolite mineral dispersed by ultrasonic methods and saturated with Fe2+ by ion-exchange has been oriented in an 11 kG magnetic field. DC measurement techniques have been applied to ribbon type samples oriented in a magnetic field. Whereas, application of these techniques to samples that have not been oriented in a magnetic field was possible because of very small and unstable current, samples oriented in a magnetic field have shown a linear change. The current–voltage studies done at different time periods have shown that sample resistance has risen in time approximately 100 times, and aging has begun. This has been evaluated as being the result of sepiolite interaction with water vapor in the medium, rather than the oxidization of the contacts.

THE ADSORPTION OF ANIONIC AND CATIONIC SURFACTANTS BY THE DIFFERENT CLAY MINERALS: FTIR SPECTROSCOPIC STUDY

The adsorption of an anionic surfactant LABS (Linear alkyl benzene-sulphonate) and a cationic surfactant DDAC (Distearly dimethyl ammonium chloride) by kaolinite, bentonite and sepiolite clays was investigated by vibrational spectroscopy. The samples prepared at different concentrations, and clay-surfactant spectra in the natural state, were recorded. The spectroscopic results indicate that the LABS and DDAC adsorbed on sepiolite and kaolinite. Bentonites are coordinated to either surface hydroxyls by H-bonding interacti on (sepiolite) or to exchangeable catoins (kaolinite, bentonite) through both sulphur and nitrogen atoms as ligands. Interactions of both surfactants showed similarities, in that LABS was coordinated on clay surfaces with broken ends, and the DDAC molecule was adsorbed on the clay surface.

Molecular Structure, Vibrational Spectra and Chemical Shift Properties of C12H9ClO4 and C12H9BrO4 Crystals by Density Functional Theory and ab initio Hartree-Fock Calculations

The molecular geometry, vibrational spectra, and gauge including atomic orbital (GIAO), individual gauges for atoms in molecules (IGAIM), and continuous set of gauge transformations (CSGT) 1H and 13C chemical shift values of ethyl 6-chloro-2-oxo-2H-chromene-3-carboxylate (C12H9ClO4-(I)) and ethyl 6-bromo-2-oxo-2H-chromene-3-carboxylate (C12H9BrO4-(II)) in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (B3LYP) with 6- 31G+(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The computed vibrational frequencies were used to determine the types of molecular motions associated with the spectra of the experimental bands observed. Also, calculated 1H and 13C chemical shift values were compared with the experimental ones.

Dielectrical Properties of a Novel Porcelain Produced from Natural Clay, Waste Glass and Fly Ash

A novel porcelain was obtained by sintering 50% kaolinite clay, 25% waste glass and 25% fly ash (a byproduct of Turkey thermal power plant) at different temperatures of 1373-1523 Κ (ΠΟΟ-1250 °C). The microstructure and phase changes on heating were studied using SliM and XRD techniques. Fly ash used in this study contributed towards development of anorthite (CaO.Al2O3.2SiO2) phase by crystallization of melted glassy phase. In samples exposed to sintering for 5 hours in 1523 K, viscosity and porosity in the structure decreased when the glassy phase melted. Dielectric permittivity (real and imaginary), conductivity and tan8 as a function of temperature were analyzed at 10 KHz frequency. Samples exposed to sintering for 5 hours exhibit increased conductivity in the 200-260 °C temperature range. This observation corresponds to the settlement of changeable cations in more stable octahedral sites during sintering. These results are significant in terms of usability of waste materials like waste glass and fly ash in obtaining new generation materials and in electric-electronic industry.

The Photoluminescence Quenching of Porous Silicon

In this study, time‐depended photoluminescence (PL) quenching of porous silicon (PS) produced in different solutions by electro‐chemical method under UV light was investigated. A two‐time‐constant exponential function characterizing the quenching of PL intensity was developed and found to be in good agreement with experimental results. Spectra were performed in millisecond intervals since the intensity and wavelength of maximum peak of tile PL spectra were affected by excitation light of PL. It was observed that spectroscopic results of UV and FTIR were coherent and especially Si–O‐Si bonds, Si‐Hx stretch and deformation bonds in the PL quenching played a crucial role.