Senay Taşcıoğlu

A novel alternative to the additives in investment casting pattern wax compositions

Abstract In this research, modifying effects of some soybeans on the properties of an investment casting sprue wax (B97) have been studied. For this purpose, soybeans of Wilken-3480, NS-6, RHS-6592 and SGI-3308 varieties have been used as the additives. The effects of these soybeans on the surface roughness, solidification shrinkage, viscosity, hardness, tensile strength and wettability of B97 have been investigated. It has been conclusively shown that these soybeans improve the properties of B97 to such an extent that it converts into a pattern wax having properties superior to those of a commercial investment casting pattern wax (B140).

Conversion of an Investment Casting Sprue Wax to a Pattern Wax by Chemical Agents

Abstract In this research, the properties of a commercial investment casting sprue wax (B97) were modified to improve its properties so it can be used as a pattern wax in investment casting. For this purpose, some colloids (gum arabic, pectin, agar, polyvinylpyrrolidone-40, polyvinylpolypyrrolidone, alginic acid, cellulose, carboxymethyl cellulose, silicon, tannic acid, saponin), some surface active agents (sodium dodecyl sulfate, sorbitane oleostearate, glycerine), and activated charcoal and palmitic acid were used as additives or fillers. The effect of these chemicals on the surface roughness, solidification shrinkage, apparent viscosity, hardness, tensile strength, and wettability of B97 wax were investigated. These additives modified the properties of B97 sprue wax to such an extent that it had properties superior to those of a commercial investment casting pattern wax (B140).

Elucidation of the mechanism of an aromatic substitution reaction by the utilization of micelles as mechanistic probes

Abstract A mechanistic study has been performed in order to elucidate the mechanism of the iodination of aniline and the iodination species in this reaction. For this purpose, the reaction has been performed in the presence of cationic and anionic surfactants in order to utilize from micellar charge effect. The results of this study provided evidence to support the hyphothesis that the iodination reagent in this reaction is hypoiodous acid.

Preparation of stable Sb2S3 sols labeled with 99mTc for use in the detection of malignant tumors

Abstract In this study a radiocolloid has been prepared for use in the detection of malignant tumors by scintigraphy. The radiocolloid is of lower toxicity than those proposed previously. Its ability to enable the detection of malignant tumors has been confirmed by its application to rabbit and human thyroids. Electron microscopic studies have also been performed to characterize Sb 2 S 3 particles in the solution and to elucidate their interaction with a protective colloid.

Micelle nano-reactors as mediators of water-insoluble ligand complexation with Cu(II) ions in aqueous medium

Complexation reactions between water-soluble and -insoluble reactants were shown to occur in aqueous media in the presence of normal or reverse surfactant micelles, in significantly higher yields at lower temperatures compared to those achieved in neat organic solvents. The highest yield enhancement in the complexation of novel water-insoluble bis(2-amino-1,3,4-thiadiazolyl)methane and 1,4-bis(2-amino-1,3,4-thiadiazolyl)benzene ligands with Cu(II) ions was achieved in the sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-heptane-water reverse micellar system at the hydration ratio of 15. The results revealed that AOT normal micelles cause a change in the reaction mechanism together with the enhancement of the complex formation. The observed micellar effects were rationalized on basis of the properties of bulk solvents, surfactants and ligands, considering the solvation and hydration ratios of reverse micelles. The results have proved the dependence of complex yield on the amount and accordingly also on the properties of water in the micellar core, indicating that the yield can be maximized by the optimization of the hydration ratio.

Syntheses of some Terpolymer Resins and Studies on Their Structure and use as Cation Exchangers

Abstract Terpolymer resins have been synthesized by the condensation of various phenols, aldehydes, and amino acids. The dependence of Ca2+ and Mg2+ exchange capacities on the natures of the monomers, pH, and regeneration has been studied and is discussed. Studies have been made to elucidate the structures.

Removal of Pb(II) ions from aqueous solution using complexation-ultrafiltration

Abstract Ligand-modified micellar-enhanced ultrafiltration (LM-MEUF) is a membrane technique based on a separation process which can be used for removal of target metals from an aqueous solution. This method involves adding both a metal complexing ligand and surfactant molecule to the aqueous solution under conditions where most of the molecules are present as micelles. This ligand can be attached to the surface of micelles by solubilization and forms the ligand complexes with the metal ion. The aqueous solution is then treated through a membrane which has to be smaller pore sizes than those of the complexes. Hence, permeate water is then purified from the heavy metals. In this study, divalent lead is the target ion in a solution. Filtration experiments were performed with ultrafiltration membrane system, equipped with a regenerated cellulose membrane with a 5000 Daltons cutoff. The pressure was fixed at 4.0 bar with a permeate flow rate of 500 mL min−1. Complexes of Pb2+ ions with three ligands were investigated in micellar medium of different surfactants at different pH values to determine the ligands which could provide separation. Different parameters affecting the percentage rejection of the Pb2+, such as pH and surfactant concentration were also discussed. Results have shown that the maximum percentage of the Pb2+ ions rejection were obtained using sodium dodecyl sulfate (SDS) as a surfactant and dithizone (DZ) as the lead-specific ligand. A waste stream sample from a battery plant was subjected to LM-MEUF process in the optimum conditions determined in this study and it was shown that Pb2+ ions in a waste stream could be removed by LM-MEUF effectively.

A novel reagent for spectroscopic determination of Mo(VI)

A new reagent for spectrophotometric determination of Mo(VI) was developed utilizing micellar effects. For this purpose, differences in the ultraviolet and visible spectral properties of Mo(VI), gallic acid, L-serine, and their binary and ternary solutions were studied in the presence and absence of cationic, anionic, and non-ionic surface active agents. L-serine was observed to form binary complexes and a ternary complex with Mo(VI) and gallic acid below its isoelectric point. The maximum Mo(VI) sensitivity was exerted by the Mo(VI) + gallic acid + L-serine + hexadecyltrimethylammonium bromide system at pH of 4.5. This system was proposed for use in the spectrophotometric determination of Mo(VI) as a superior alternative to the Mo(VI) + gallic acid + hexadecyltrimethylammonium bromide system and to most of the instrumental analysis methods referred to in the literature. The mechanism of micellar effects was discussed on the basis of the spectral data obtained above and below the isoelectric point of L-serine and explained in terms of the molecular charge of the substrates and the surfactants.