hrvatski

Tekućine za obradu metala na osnovi nanofluida

U ovome radu istraženi su priprava i svojstva nanofluida s ugljikovim nanocijevima na osnovi mineralnih baznih ulja SN150 i SN200 i biljnog repičinog ulja sa i bez dodatka površinski aktivnih tvari. Cilj je bio pripraviti stabilne nanofluide s poboljšanim svojstvima podmazivanja i prijenosa topline. Ultrazvučnim mješanjem priređene su tri vrste nanofluida: (1) mineralno bazno ulje SN200 / višestjenčane ugljikove nanocijevi (MWCNT) / površinski aktivna tvar (PAT, šest različitih spojeva, komercijalnih i priređenih u laboratoriju), (2) mineralno bazno ulje SN150 / MWCNT / PAT, (3) repičino ulje / MWCNT / PAT. Karakterizacija stabilnosti i svojstava pripravljenih nanofluida provedena je različitim metodama. Raspršenost ugljikovih nanocijevi u baznom fluidu mjerena je primjenom UV- Vis spektrofotometrije i izračunata primjenom Beer – Lambertove jednadžbe, a dobiveni podaci su uspoređeni s onima dobivenima iz baždarnih dijagrama. Raspršenost nanocijevi je praćena i vizualnim opažanjima. Najveću stabilnost pokazali su nanofluidi s dodanim površinski aktivim tvarima na temelju polimera s disperznim svojstvima. Takvim nanofluidima s različitom koncentracijom ugljikovih nanocijevi određena su svojstva mazivosti testom s četiri kuglice, toplinska vodljivost, viskoznost i kontaktni kut na teflonskoj i metalnoj podlozi. Neki od nanofluida su pokazali poboljšana svojstva mazivosti i toplinske vodljivosti, dok općenito, do pogoršanja svojstava dodavanjem MWCNT u usporedbi s baznim fluidom nije došlo. In this master's thesis the subject of the research was the preparation and characterization of nanofluids with carbon nanotubes based on SN150 and SN200 mineral base oils and vegetable rapeseed oil with or without the addition of surfactants (surface active agents). The goal was to produce stable nanofluids with enhanced lubricating and thermal conductivity capabilities. Three types of nanofluids were made by using ultrasonic mixing: (1) mineral base oil SN200 / multiwall carbon nanotubes (MWCNT) / surfactant (six different chemical compounds, commercial and laboratory made), (2) mineral base oil SN150 / MWCNT / surfactant, (3) rapeseed oil / MWCNT / surfactant. The assessment of the dispersion stability and properties of the produced nanofliuds was made by using various methods. The dispersion stability of the carbon nanotubes in the base fluid was measured using UV – Vis spectrophotometry and calculated via the Beer – Lambert equation. Results were compared with the one received from the calibration diagrams. The dispersion stability was also observed by visual inspection. The highest stability was shown by the nanofluids with added surface active agents based on polymers with dispersive capabilities. The lubrication properties of such nanofluids with different concentrations of carbon nanotubes were measured using the four ball wear test. Apart from that, the thermal conductivity, viscosity and the contact angle on teflon and metal surfaces were also measured. Some of the measured nanofluids showed increased lubrication properties and thermal conductivity while, in general, there was no degradation of characteristics when adding MWCNT compared to the base fluid.

nanofluidi; mineralno bazno ulje; biljno repičino ulje; ugljikove nanocijevi; maziva; trošenje; toplinska vodljivost

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