Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
Browse
3 results
Search Results
Now showing 1 - 3 of 3
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.Book Part High-Performance Materials and Engineered Chemistry(CRC Press, 2018) Türk, Merve; Gümüş, Barış; Ustun, Fatma; Balköse, DevrimNano-sized nickel borate hydrate were precipitated from equimolar mixtures of dilute nickel nitrate and borax solutions at 25°C. Produced nickel borate samples were characterized by TGA, DSC, FTIR spectroscopy, X-ray diffraction, SEM, Elemental Analysis (EDX), Titration (nickel determination by EDTA, B<inf>2</inf>O<inf>3</inf> determination by NaOH), Particle Size Distribution, and Dehydration. The particles with 55 nm, 80 nm and 70 nm sizes were obtained for the cases without template, with span 60 and PEG 4000 in the reaction mixture respectively. The empirical formula of the vacuum dried precipitates were NiO.1.3B<inf>2</inf>O<inf>3</inf>.5.6 H<inf>2</inf>O, NiO.1.2B<inf>2</inf>O<inf>3</inf>.5.6 H<inf>2</inf>O and NiO.1.0B<inf>2</inf>O<inf>3</inf>.5.4 H<inf>2</inf>O for the cases without template, with span 60 and PEG 4000. The density of the nickel borate hydrates was around 2 g/ml and they had a color described by 157, 199 and 158 in RGB color scale. The nickel borate hydrates were amorphous in structure and no sharp peaks related to a crystal structure was present in their x-ray diffraction diagram. The effect of presence of span 60 and PEG 4000 were not significant on the particle size and chemical composition of the nanoparticles. © 2019 Elsevier B.V., All rights reserved.Article Citation - Scopus: 1Optical and Surface Properties of Zinc Oxide Nanoparticles Dried by Conventional and Supercritical Ethanol Drying Techniques(Research India Publications, 2014) Egbuchunam, Theresa Obuajulu; Yetgin, Senem; Özmıhçı Ömürlü, Filiz; Balköse, DevrimZinc oxide (ZnO) nanoparticles were synthesized by conventional (ZnO-A) and supercritical ethanol drying (ZnO-B). Nitrogen adsorption/desorption analyses were performed to determine the surface areas of the powders. The specific surface area was 28.30m2/g and 10.61 m2/g for ZnO-A and ZnO-B respectively. The powders adsorbed very small amount of CO2with the conventionally dried powder adsorbing more CO2. Supercritical ethanol dried ZnO had ethanol on its surface which was eliminated by vacuum application at room temperature. Both powders had OH groups which were eliminated on heating up to 500°C under vacuum. However, OH groups were present in lower amounts in supercritical ethanol dried ZnO. The powders were characterized by UV-VIS optical absorption and room temperature photoluminescence spectroscopic analyses. The UV-VIS absorption spectrum showed an absorption band at 375nm due to ZnO nanoparticles. The photoluminescence spectrum of ZnO excited at 380nm exhibited three emission peaks: one at 424nm and 490nm corresponding to band gap excitonic emission and another located at 520nm due to the presence of singly ionized oxygen vacancies.