LEE- Polimer Bilim ve Teknolojisi-Doktora
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Konu "Nanoparticles" ile LEE- Polimer Bilim ve Teknolojisi-Doktora'a göz atma
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ÖgeStudies on suspension of some inorganic nanoparticles as additive in motor engine/lubrication oils(Lisansüstü Eğitim Enstitüsü, 2021) Tanrıseven, Zulhice ; Gül, Ahmet ; 709893 ; Polimer Bilim ve TeknolojisiNanoparticles have very wide range applications. They are used for in almost every field, from medicine to coatings. Nanomaterials have very large surface area and very small particle sizes. Since they have very larger surface area than macroscale materials, nanomaterials are choosen to achieve desired properties with less amount of substances. There are nanomaterials which is known with their intrinsic lubrication efficiencies. Some of these materials, like graphene or hexagonal boron nitride or boric acid, have lamelar structure. These platelets, the layers, slide over each other when they are squeezed into two sliding surfaces to help reducing the friction between these two surfaces. There is another type of nanomaterials that have lubrication effect like titanium dioxide; these types of nanomaterials have spherical geometrical shapes. These nanomaterials act like marble and third body substance between two sliding surfaces. All nanomaterials have huge tendencies to agglomerate to form aggregates. In order to dispers them into targeted media, they should have gone certain stages before introducing into the targeted media. The aim of this study is to suspend nanomaterials that have lubrication properties in nonpolar media. In this study, multiwall carbon nanotubes, expandable graphene, graphene oxide, hexagonal boron nitride, boric acid, zinc oxide and titanium dioxide were used. All nanoparticles' morphologies were characterized by SEM or TEM and other proper characterization methods were used to characterize them; for instance, RAMAN for carbon based nanomaterials and XRD for crystal structure analyses. In order to suspend these seven nanomaterials in nonpolar media, two different methods were used through the study. One of these methods is called two step method which indicates first synthesizing the material then suspend it into targeted media. All seven nanoparticles were tried to be kept suspended in nonpolar media by two step method first. In order to prepare nanoparticles by two step method, nanoparticles were supplied and dispersed in different amphiphilic several base fluids by ultrasonic horn to have nanofluids. Diisononyl adipate (DiNA), diisodecyladipate (DiDA), nonylphenol etoxylate (NP), diisononyl phthalate (DiNP) and nonanol were examined to be base fluid. Nonanol is determined as the most appropriate base fluid to have stable suspension of nanoparticles in nonpolar media. It is a liquid fatty alcohol. It has both lipophilic long hydrocarbon chain and a hydrophilic hydroxy group at the end of this chain. It helps nanoparticles remain suspended in a nonpolar medium. In order to model nonpolar media, fully formulated commercial engine oils and poly alpha olefin oils were used. Prepared nanofluids were added to oils and added oils were examined by their suspension stability by two methods, turbidimetry and sedimentation photography. Turbiscan instrument was used to perform turbidimetry characterization method. This instrument sends a light (880 nm) to the sample by varying time and records the transmittance and backscattering intensities comes from different height levels of sample holder. Changes of transmittance or backscattering intensities over time indicates the unstability of the suspension. Furthermore, viscosity effects of nanofluid addition were examined by viscosimeter. All seven nanoparticles were examined to suspend in nonpolar media by two step method. MWCNT, expandable graphene, GO, boric acid had low TSI values that indicates stable suspention in nonpolar media. Other three nanoparticles did not have low TSI values; so, they were encapsulated by liposome structure to have stable suspension in nonpolar media. Characterization methods mentioned above were also implemented to nanofluids that have been prepared by liposoming method. Liposomes are spherical structures made by PC (Phosphotidyl Choline). These structures are biomimetic structures; thus, they are used as drug delivery agents. They have difficult and expensive preparation steps; so, they have not been used for suspending a nanoparticle in an engine oil. However, as the liposome preparation technology is developing, more practical agents and ways are developed to prepare liposomes; therefore, today it is easier and cheaper to prepare these liposomes. In this study, one-step and easy way is used to prepare liposomes of nanoparticles. In addition, unlike to previous liposome preparation methods in literature, chosen base fluid is used as preparation medium in liposome method, nonanol. Fatty alcohols were used as stabilizing agents for liposomes. Using a stabilizing agent as preparation medium enables us to have very stable liposomes (more than three months). Hexagonal boron nitride, titanium dioxide and zinc oxide were encapsulated by liposome structure. First time in the literature, in this study, these nanoparticles were encapsulated by liposome structure with proposed method and these liposomes were photographed by TEM. These liposomes were also characterized by zeta sizer instrument for their particle sizes and their polydispersity indexes. TEM and particle size analyses conducted showed results confirming each other and demonstrating the stability of liposomes. It was observed the fact that the proposed liposome preparation method facilitates to dispers and suspend any nanoparticle in the lipophilic medium. Suspending nanoparticles with chemicals that have not been used for this purpose and by encapsulating them by liposome structure by proposed one-step and easy method is a new and alternative way for literature. Nanoparticles have very wide usage areas. These easy-prepared suspendable nanofluids can also be implemented to other areas.