GCRIS

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Nanosized zing borate production
(Izmir Institute of Technology, 2009) Gönen, Mehmet; Balköse, Devrim
The present study covers both zinc borate synthesis from boric acid-zinc oxide and borax decahydrate-zinc nitrate hexahydrate pairs; treatment of those samples by supercritical carbon dioxide drying, supercritical ethanol drying, and freeze drying techniques to obtain nanosized products. Zinc borate samples before and after supercritical drying were characterized by analytical titration, SEM, XRD, TGA, DSC, FTIR, and N2 adsorption at 77 K.The use of oleic acid as a modifying agent, ultrasonic treatment and nanosized zinc oxide in the reaction of zinc oxide and boric acid did not make significant effect in controlling the particle size. However, particle size of zinc borate produced from borax and zinc nitrate has increased with reaction time. Interaction of zinc borates with CO2 or ethanol at supercritical conditions or compression of crystals by high pressure created by the expansion of water during freezing are possible side effects of the nanoparticle producing processes. Zinc borate (2ZnO.3B2O3.7H2O) having water of crystallization in its structure reacted partially with CO2 to produce zinc carbonate, however zinc borate (2ZnO.3B2O3.3H2O) containing only hydroxyl groups did not react with CO2 in supercritical CO2 drying. While zinc borate (2ZnO.3B2O3.3H2O) decomposed partially and formed anhydrous zinc borate and zinc oxide, zinc borate (ZnO.B2O3.2H2O) decomposed completely and formed only zinc oxide in the supercritical ethanol drying that was carried out at 6.5 MPa and 250aC. Boric acid formed from the decomposition of both zinc borates was separated by ethanol extraction. If the initial particle size of zinc borate sample was at nano level, it would be possible to obtain nano particles by freeze drying.
Enhancement of Tribological Properties of Mineral Oil by Addition of Sorbitan Monostearate and Borate
(Izmir Institute of Technology, 2010) Atakul Savrık, Sevdiye; Çiftçioğlu, Muhsin
The development of modern automobile and engine industries requires lubricants that can withstand high temperatures and pressures. Recent advances made in the chemistry provide the use of inorganic particles as lubricant additives. Therefore inorganic boron-based additives have been the focus of much attention, as they posses a good combination of properties, such as wear resistance, friction-reducing ability. In this study, the state of art in the field of inorganic particle, zinc borate synthesis and its employment in tribology were investigated. The synthesis of zinc borate was achieved not just by precipitation, but also production methods such as inverse emulsions. The products were characterized by SEM, FTIR, TGA, DSC, EDX. In lubrication part, the friction reducing and antiwear ability of the particles as an additive in the mineral oil was focused. Sorbitan monostearate was used to cover the surfaces of inorganic particles in order to provide better dispersion of additives in the oil. Friction and wear behavior of the lubricants were measured by four-ball wear test machine. The effects of dispersing agent, zinc borate type as well as surfactant concentration on the tribological properties of the lubricants were investigated. Sorbitan monostearate not only outperformed as a dispersing agent of inorganic particles, but also it proved to be an efficient antiwear agent. The lowest wear scar diameter was obtained by the lubricant containing zinc borate synthesized via coordination precipitation method. The addition of this sample with the surfactant in the oil reduced the wear scar diameter from 1.402 mm to 0.550 mm.

Phd Degree / Doktora

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