WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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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: 14Supercritical Ethanol Drying of Zinc Borates of 2zno Center Dot 3b(2)o(3)center Dot 3h(2)o and Zno Center Dot B2o3 Center Dot 2h(2)o(Elsevier Ltd., 2011) Gönen, Mehmet; Balköse, Devrim; Ülkü, SemraSupercritical ethanol (SCE) drying of zinc borates was investigated to obtain dry zinc borate nanoparticles and to elucidate possible chemical interactions between zinc borates and ethanol. Commercial and synthesized 2ZnO center dot 3B(2)O(3)center dot 3H(2)O and ZnO center dot B2O3 center dot 2H(2)O samples were dried by both conventional and SCE drying methods and the products were compared. Zinc borates were characterized using X-ray powder diffraction (XRD), thermo gravimetric analysis (TGA), Fourier transform infrared (FTIR) analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and helium pycnometer. Zn and B contents of samples were also determined by analytical titration. It was found that zinc borate of ZnO center dot B2O3 center dot 2H(2)O decomposed completely into zinc oxide and boric acid. However, zinc borate having oxide formula of 2ZnO center dot 3B(2)O(3)center dot 3H(2)O decomposed partially to form anhydrous zinc borate, zinc oxide, water and boric acid during the SCE drying carried out at 250 degrees C and 6.5 MPa. Boric acid and water were extracted from both of zinc borates by supercritical ethanol. The extraction of boric acid by ethanol in the SCE drying of zinc borates is an important result which can be utilized in the production of boric acid from water insoluble natural minerals, e.g. colemanite. The boric acid-ethanol solution could be directly utilized in the synthesis of ethyl borate. (C) 2011 Elsevier B.V. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 6Use, Preparation, and Characterization of Copper-Containing Silica Gel(American Chemical Society, 2020) Ulutan, Sevgi; Tüzüm Demir, Ayşe Pınar; Balköse, DevrimThe preparation and characterization of humidity-indicating silica gel containing copper sulfate were aimed at in the present study. The equilibrium and kinetics of Cu(II) sorption were investigated by contacting 200-1600 mg dm(-3) Cu ion-containing solutions with silica hydrogel slabs having 10% silica. The diffusion coefficient of Cu(II) in silica hydrogel was determined to be on the order of 10(-10) m(2) s(-1). X-ray diffraction indicated that the gels contained mainly CuSO4 center dot 3H(2)O, CuSO4 center dot H2O, and small amounts of CuSO4 and CuSiO3 center dot 2H(2)O. The silica gel with Cu(II) can be used as a humidity indicator since its color changes from light blue to dark blue upon moisture adsorption.Article Citation - WoS: 6Citation - Scopus: 9Preparation and Characterization of Flexible Polyvinylchloride-Copper Composite Films(Smithers Rapra Technology, 2013) Kurt, Emrah; Özçelik, Cenk Yağız; Yetgin, Senem; Özmıhçı Ömürlü, Filiz; Balköse, DevrimFlexible PVC films are statically charged due to their low electrical conductivity. This creates fire threat during its handling. Conductive materials are added to films to prevent this. In the present study it was aimed to prepare PVC- copper composite films by sol gel technique and characterize the prepared films. It was aimed to increase the electrical conductivity of the films by adding copper powder. However, the copper particles settled down to bottom instead of forming a conductive network that covers the whole cross section. Thus at the film crosssection a plastic upper phase and a copper rich lower phase were present. The film did not conduct electricity due to this uneven distribution. The minimum volumetric and surface resistivities of the films were at the order of 109 ohm-cm and 1010 ohm square respectively.Article Citation - WoS: 2Citation - Scopus: 2Morphology of Sodium Salt of Calf Thymus Dna on Mica, Alumina, and Silica Surfaces: Effect of Solvent and Drying Method(Taylor and Francis Ltd., 2017) Yetgin, Senem; Balköse, DevrimInvestigation of morphology of deoxyribonucleotide triphosphate (DNA) dried on different surfaces by atomic force microscopy (AFM) is important in DNA research that is focused on subjects of condensation for gene therapy, sizing, DNA mapping, and cancer examination. The solvent, the surface type, and the method of drying effect the morphology of DNA on solid surfaces. Ethanol and water were used as solvents, flat mica, silica, and alumina surfaces were used as the substrates in the present study. Different methods such as ambient air-drying, N2-forced flow regime drying, and freeze-drying have been applied to droplets of DNA solutions in water or ethanol on the substrates. Forced flow drying regime causes nonlinear DNA attachment on the surface and self-assembly. DNA vertical distance on mica surface was found to be 6 and 1.4 nm for DNA dried in ambient air from ethanol and water solutions, respectively. It was 1.6 nm for N2 flow drying of aqueous DNA solution on mica surface. It was 4.6, 4.6, and 1.99 nm for ambient, N2 flow, and freeze-dried aqueous DNA on alumina surfaces, respectively. Aqueous solution of DNA dried under N2 flow on silica surface had 0.8 nm vertical distance. The smallest standard deviation of 0.05 nm was observed for DNA dried under N2 flow on alumina surface.Article Citation - WoS: 60Citation - Scopus: 66Preparation and Characterization of Calcium Stearate Powders and Films Prepared by Precipitation and Langmuir-Blodgett Techniques(American Chemical Society, 2010) Gönen, Mehmet; Öztürk, Serdar; Balköse, Devrim; Okur, Salih; Ülkü, SemraThe preparation of calcium stearate (CaSt2) using precipitation and Langmuir-Blodgett techniques was investigated in this study. While sodium stearate and calcium chloride were used in the precipitation process, calcium stearate nanofilms were produced from stearic acid and calcium chloride in sodium borate buffer with the Langmuir-Blodgett technique. Fourier transform infrared (FTIR) spectroscopy indicated carboxylate bands at 1577 and 1543 cm-1 in equal intensity in the powder form, but the films had a higher intensity 1577 cm-1 band than the 1543 cm-1 band. This showed the calcium ions associated with the COO- ions in the monodendate and bidendate structures in powders, and it was mainly in the bidendate structure in films. While characteristic peaks of CaSt2 at 2θ values of 6.40° and 19.58° were obtained in the X-ray diffraction (XRD) pattern of the dried powdered product, no sharp peaks were present in the 13 layer CaSt2 film. From scanning electron microscopy (SEM) micrographs, it was seen that calcium stearate powder had lamellar structure and the average particle size was 600 nm. The AFM picture of the CaSt2 film indicated the surface was not smooth with a peak to valley distance of 6 nm. © 2010 American Chemical Society.Article Citation - WoS: 11Citation - Scopus: 12Calf Thymus Dna Characterization and Its Adsorption on Different Silica Surfaces(Royal Society of Chemistry, 2015) Yetgin, Senem; Balköse, DevrimDNA adsorption is the initial stage of gene therapy for drug delivery systems and solid phase extraction methods of DNA purification. High pore volume and high adsorption capacity are simple requirements not only for producing 'smart' drug delivery systems but also the development of purification kits. Silica is the most used material for this purpose. The present study aimed at elucidating the calf thymus DNA biosorption process by the characterization of calf thymus DNA and silica to increase the efficiency of the currently used silica material. Mesoporous silica has long been used for DNA adsorption and silica aerogel is the new adsorbent investigated in the present study. When DNA solution was freeze dried on a silica wafer, self-assembled super helices formed as shown by atomic microscopy (AFM). Thus DNA existed not as single molecules but as large sized agglomerates in water. Thus it could be adsorbed in the macropores and on the external surface of adsorbents. Adsorption of calf thymus DNA to a silica aerogel, a mesoporous silica gel and a silica wafer was investigated in the present study. Silica aerogel was synthesized from TEOS by a supercritical ethanol drying process. The DNA adsorption capacity of the silica aerogel was nearly two times that of the mesoporous silica gel due to its macroporous structure and its higher silanol content. Silica aerogel was found to be a very promising material for DNA adsorption. Therefore silica aerogel can be considered as a good candidate for the delivery of DNA.Article Citation - WoS: 1Citation - Scopus: 1Flexible Pvc-Silica Composites as an Adsorptive Material for Water Soluble Dyes(Smithers Rapra Technology, 2013) Ulutan, Sevgi; Yetgin, Senem; Balköse, DevrimMethylene Blue (MB) adsorption studies were performed on flexible Polyvinyl Chloride/Silica composites which were obtained by using plastisol-plastigel technology. Change of MB concentration in aqueous phase as the adsorption process advanced was followed by using visible spectroscopy. The diffusion of MB through the composites exhibited non-Fickian behavior with a diffusivity of 10-11 m2s-1. Making use of such PVC-silica composite sheets as column packing, the packing time will be reduced and the surface available for diffusion will be increased. © 2013 Smithers Rapra Technology.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: 13Citation - Scopus: 14Characterization and Dehydration Behavior of a Natural, Ammonium Hydroxide, and Thermally Treated Zeolitic Tuff(Taylor and Francis Ltd., 2011) Narin, Güler; Balköse, Devrim; Ülkü, SemraAqueous NH4OH-treated and subsequently calcined forms of local natural zeolitic tuff were characterized by different techniques including scanning electron microscopy (SEM), X-ray powder diffraction, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), volumetric N2 adsorption at -196°C, thermogravimetry (TG), differential scanning calorimetry (DSC), and transmittance infrared spectroscopy. The dehydration behavior of the samples was investigated using an in situ temperature-programmed diffuse reflectance Fourier transform infrared spectroscopy (TP-DRIFTS) method under vacuum. The DRIFTS spectra recorded yielded information about the effect of the NH4OH treatment and subsequent calcination on the dehydration behavior of the natural zeolite.Changes in the infrared bands corresponding to vibrations of the O-H and N-H bonds upon in situ heating under vacuum were analyzed.
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