338 *Corresponding author: devrimbalkose@iyte.edu.tr AbstrAct Nano particles of zinc borate were obtained by homogeneous precipitation method which is based on dissolving zinc borate in ammonia and precipitating it as nano particles by slow evaporation of ammonia. The synthesized zinc borates were characterized by advanced analytical techniques. Zinc borate nano particles were used as a lubricant additive to spindle oil having Span 60 dispersant. The particles were well dispersed in spindle oil as shown by optical microscopy of the oils. Four ball tests of the lubricants indicated zinc borate lowered (61.8%) the wear scar diameter signifcantly. The hardness of wear surfaces of test balls was reduced from 688 HV to 618 HV and presence of zinc borate particles embedded on the surface indicated a fexible skin was formed. Therefore the pressure was decreased due to increase of the contact area of the balls. The surface roughness was also decreased from 35.63 nm to 27.60 nm by the addition of zinc borate to spindle oil having Span 60. Zinc borate prepared by homogeneous precipitation technique lowered the wear of the surfaces that rub to each other. 1. Introduction Nano particles of zinc borate hydrates can be obtained using diferent methods. 4ZnO·B 2 O 3 ·H 2 O nanopar- ticles can be synthesized by dissolving the precipitate obtained from borax decahydrate and zinc nitrate so- lution [1] or by dissolving 2ZnO·3B 2 O 3 ·3.0-3.5H 2 O [2] in ammonia and then reprecipitating it with the help of evaporation of ammonia by heating the solution. Form- ing zinc borate nano particles in mineral oil allows the use of the mixture as lubricating oil [3]. Hydrophobic zinc borate nanoparticles could be obtained from zinc oxide, boric acid and oleic acid in water [4]. Safari et al. prepared nano-sized zinc borates at 200°C and 15 bar pressure from aqueous borax and zinc nitrate so- lutions [5]. The surfactants are added to the mixture in order to obtain nano zinc borate particles with diferent geometries [6-9]. Agglomerates of nano zinc borate platelets were obtained from nano zinc oxide and bo- ric acid at 85°C with surfactants or without surfactants. Either 2ZnO·3B 2 O 3 ·7H 2 O, 2ZnO·3B 2 O 3 ·3.5H 2 O or 3ZnO·3B 2 O 3 ·5H 2 O were obtained by mixing aqueous borax and sodium nitrate solutions in diferent propor- tions by controlling the temperature (80°C-90°C) and pH [10]. The efects of temperature (45°C-85°C), mix- ing rate (400-500 rpm) and reactant feed rate (300- 900 cm 3 hr -1 ) on zinc borate particle size were investi- gated by Polat and Sayan [11]. Zinc sulfate hydroxide (Zn 4 SO 4 (OH) 6 ) and boric acid in aqueous solution were used in zinc borate preparation [12]. The mor- phology of zinc borates (2ZnO·3B 2 O 3 ·3H 2 O) changed from platelet to polyhedron at the reaction temperature of 90°C with increasing the water content in the reac- tion solution [12]. Zinc borates had fame retarding efect in epoxy resin [1], polyvinyl chloride [2], polyethylene [4], polyure- thane [10], polyvinyl alcohol [12] and cellulose [13]. Cotton fabric that was dried after immersing in a sus- pension of nano particles of zinc borate had fame re- tardant properties [13]. Many studies were made using zinc borate nanopar- ticles as lubricant additives [3]. Zinc borate nanopar- ticles by inverse emulsion method in mineral oil us- ing Span 60 lowered friction coefcient and wear scar diameter in four ball tests compared to that of pristine mineral oil [3]. Nano zinc borate with 40 nm size dis- persed in mineral oil lowered the wear scar diameter by 50% and friction coefcient by 20% [14]. Nano zinc BORON 6(3), 338 - 347, 2021 ArtIcLE INFO Article history: Received June 12, 2021 Accepted August 11, 2021 Available online September 30, 2021 Research Article DOI: 10.30728/boron.951463 Keywords: Four ball tests Homogeneous precipitation Lubricants Span 60 Zinc borate Lubricants having zinc borate by homogeneous precipitation and Span 60 in spindle oil Sevdiye Atakul Savrik 1 , Burcu Alp 2 , Mehmet Gönen 3 , Devrim Balkose 4,* 1 Akzo Nobel, Izmir, 35410 Turkey, ORCID orcid.org/0000-0002-1402-0569 2 Süleyman Demirel University, Department of Chemical Engineering, Isparta, 32260, Turkey ORCID orcid.org/0000-0002-0380-2020 3 Süleyman Demirel University, Department of Chemical Engineering, Isparta, 32260, Turkey ORCID orcid.org/0000-0001-5780-4622 4 Izmir Institute of Technology, Department of Chemical Engineering, Izmir, 35430, Turkey ORCID orcid.org/0000-0002-1117-9486 BOR JOURNAL OF BORON DERGİSİ 21 20 03 06 bOr DERGİSİ JOURNAL OF BORON https://dergipark.org.tr/boron