Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Effects of Span 60 Template and Freeze Drying on Zinc Borate Produced From Zinc Nitrate Hexahydrate and Borax Decahydrate(Taylor and Francis Ltd., 2022) Alp, Burcu; Gönen, Mehmet; Atakul Savrık, Sevdiye; Balköse, DevrimZinc borate is an important additive to polymers and lubricants. The process variables such as reactant concentration, presence of template in precipitating medium and drying method determine the composition and particle size of zinc borates. In the present study, zinc borate precipitate obtained by mixing aqueous zinc nitrate and borax decahydrate solutions was dried either by conventional method or by freeze drying. The products were well characterized by advanced methods. Zinc borate from 1 mol dm(-3) reactants had (2.1 +/- 0.5)x(2.5 +/- 0.5)x(1.3 +/- 0.2) mu m and (0.5 +/- 0.1)x(1.3 +/- 0.1)x(0.028 +/- 0.01) mu m dimensions by conventional and freeze drying respectively. Individual particles smaller in size is obtained since the particles are not agglomerated due to absence of surface tension of liquid water for case of freeze drying. Planar particles agglomerated into 20 to 60 mu m crystals in the presence of template Span 60 in 1 mol dm(-3) reactants for conventional drying. Nano zinc borate particles with primary particle size of (46 +/- 9) nm were obtained by decreasing the reactant concentration to 0.1 mol dm(-3). The primary particle size was decreased to (40 +/- 3) nm by addition of Span 60 to dilute solutions. However zinc borate nanoparticles obtained from dilute solutions adhered to each other forming agglomerates during conventional drying. Their freeze drying would allow formation of a freely flowing nano powder.Article Citation - WoS: 15Citation - Scopus: 18Preparation and Characterization of Magnesium Stearate, Cobalt Stearate, and Copper Stearate and Their Effects on Poly(vinyl Chloride) Dehydrochlorination(John Wiley and Sons Inc., 2015) Gönen, Mehmet; Egbuchunam, Theresa Obuajulu; Balköse, Devrim; İnal, Fikret; Ülkü, SemraPreparation and characterization of pure metal soaps and investigation of their effects on poly(vinyl chloride) (PVC) dehydrochlorination were the objectives of the present study. Magnesium stearate (MgSt2), cobalt stearate (CoSt2), and copper stearate (CuSt2) were prepared by a precipitation method. An aqueous sodium stearate (NaSt) solution was mixed at 500 rpm with respective metal salt solutions at 75oC. The precipitates that formed were collected by filtration, washed with water, and ultimately dried at 105oC under reduced pressure. Lamellar crystals that melted on heating were obtained. Solid-liquid phase transitions were observed by optical microscopy at 160oC, 159oC, and 117oC for MgSt2, CoSt2, and CuSt2, respectively. However, the melting points of MgSt2, CoSt2, and CuSt2 were determined as 115oC, 159oC, and 111oC, respectively, by analysis by differential scanning calorimetry. The onset temperature of the mass loss was the lowest at 255oC for CuSt2 and the lowest activation energy for thermal decomposition was 18 kJ/mol for CuSt2. CoSt2 was effective in extending the induction time of PVC dehydrochlorination at both 140oC and 160oC. The activation energy calculated from stability time decreased from 175 kJ/mol for a blank PVC sample to 114, 105, and 107 kJ/mol for MgSt2, CoSt2, and CuSt2-containing PVC samples, respectively. All three metal soaps accelerated the dehydrochlorination of PVC. J. VINYL ADDIT. TECHNOL., 21:235-244, 2015.Article Citation - WoS: 6Citation - Scopus: 8Dehydration, Water Vapor Adsorption and Desorption Behavior of Zn[b3o3(oh)5] · H2o and Zn[b3o4(oh)3](Taylor and Francis Ltd., 2012) Alp, Burcu; Gönen, Mehmet; Atakul Savrık, Sevdiye; Balköse, Devrim; Ülkü, SemraThe dehydration behaviors of two different hydrated zinc borate species, Zn[B3O3(OH)5] · H2O and Zn[B3O4(OH)3], which are industrially important flame retardants, were studied by thermal gravimetric(TG) analysis and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Dehydration onset temperatures of Zn[B3O3(OH)5] · H2O and Zn[B3O4(OH)3] were 129 and 320°C, respectively, at a 10°C/min ramp rate. A very small amount of boric acid was volatilized in addition to water vapor when both samples were heated at 250°C. A significant amount of water vapor was adsorbed by Zn[B3O3(OH)5] · H2O from air at 25°C. However, Zn[B3O4(OH)3] adsorbed a very small amount of water under the same conditions. Both zinc borates did not have a tendency to cake during storage.Article Citation - WoS: 11Citation - Scopus: 15Supercritical Carbon Dioxide Drying of Methanol-Zinc Borate Mixtures(American Chemical Society, 2009) Gönen, Mehmet; Balköse, Devrim; Gupta, Ram B.; Ülkü, SemraSupercritical carbon dioxide (CO 2) drying of zinc borate species was investigated to evaluate possible chemical alterations in the product during the drying. Methanol-wetted zinc borates produced either from borax decahydrate and zinc nitrate hexahydrate (2ZnO · 3B 2O 3 ·7H 2O) or from zinc oxide and boric acid (2ZnO · 3B 2O 3 ·3H 2O) were dried by both conventional and supercritical carbon dioxide drying methods. Zinc borate samples dried by both techniques were characterized using analytical titration, X-ray powder diffraction (XRD), thermo gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, and scanning electron microscopy (SEM). It was found that while zinc borate obtained from zinc oxide and boric acid did not have any chemical interaction with CO 2, carbonates were formed on the surface of zinc borate obtained from borax decahydrate and zinc nitrate hexahydrate. The main factor for the carbonate formation during supercritical CO 2 drying is anticipated as the structural differences of zinc borate species. CO 2 is a nonpolar solvent, and it does not usually react with polar substances unless water is present in the medium. While 2ZnO · 3B 2O 3 ·3H 2O had three bound OH groups, 2ZnO · 3B 2O 3 ·7H 2O had five bound OH groups and one mole of water of crystallization. It is proposed that the water of crystallization reacts with CO 2 forming carbonic acid. Then, carbonic acid, which is stronger than boric acid, substitutes borate ions from their zinc salts.Article Citation - WoS: 34Citation - Scopus: 43Zinc Stearate Production by Precipitation and Fusion Processes(American Chemical Society, 2005) Gönen, Mehmet; Balköse, Devrim; İnal, Fikret; Ülkü, SemraIn this study, the production of ZnSt2 using sodium stearate and zinc sulfate in a precipitation process, and stearic acid and zinc oxide in a fusion process, was investigated with regard to product purity. In the fusion process, an increase in mixing rate decreased the induction time occurring at the beginning of the reaction. While the melting point of the zinc stearate prepared by the precipitation process was found to be about 122°C by optical microscopy, it was slightly lower than 122°C for zinc stearate produced by the fusion process. Differential scanning calorimetry (DSC) indicated onset of melting at 120°C and 118°C for samples prepared by precipitation and fusion processes, respectively. Characteristic peaks of ZnSt2 were present in XRD patterns of the products obtained by both processes. From SEM micrographs, it was seen that zinc stearate obtained by both processes had lamellar structure.