Yüzeyi Fonksiyonelize Edilmiş Nanoparçacıklar ile Kararlı Nanoakışkan Hazırlanması ve Isıl İletkenlik Değişiminin Belirlenmesi

TÜBİTAK MAG Proje01.04.2019Çok çesitli uygulama alanına sahip olan nanoakıskanlar, ısı transferi sistemlerinde, kullanılanakıskanların ısıl iletkenlik katsayısını arttırmak amacıyla baz akıskanın içerisine, ısıl iletkenligiyüksek nano boyutlarda parçacıklar katılmasıyla üretilirler. Nanoakıskanların hazırlanması,hazırlanan nanoakıskanın ısıl iletkenliginin arttırılması her ne kadar basit görünse de çokkarmasık bir sistemdir. Nanoakıskanların ısıl iletkenliginin artması ve ısı transferiuygulamalarında kullanılabilirligi, hazırlanan nanoakıskanın kararlılıgından, viskozitesinekadar birçok önemli parametre ile baglantılıdır. Isıl iletim katsayısı ne kadar artmıs olursaolsun, kararlı olmayan nanoakıskanların kısa sürede çökmesi ve viskozitesinin baz akıskanagöre fazlaca artıs göstermesi, ısı transferi sistemlerinde basınç düsüsüne, korozyona vetıkanıklıklara neden olmaktadır. Tüm bunlar göz önüne alındıgında, hazırlanannanoakıskanların pratikte kullanımı için bu parametrelerin incelenmesi ve birbiri ile olanbaglantılarının ortaya konulması gerekmektedir. Bu projede kararlı nanoakıskanlarınhazırlanması ve ısıl iletkenliklerinin belirlenmesinin yanı sıra bu parametrelerin birbiri ilebaglantısının aydınlatılması hedeflenmistir.Baz akıskan olarak su, etilen glikol (EG) ve kompresör yagı kullanılan bu projede,nanoparçacık olarak farklı yüzey alanlarına sahip grafen nanoplateletler (GNP) ve tek duvarlıkarbon nanotüpler (SWCNT) kullanılmıstır. Nanoakıskan kararlılıgının saglanması amacıyla,polietilen glikol türevi polihedral oligomerik silseskuokzan (PEG-POSS) nanoakıskanlarda ilkkez yüzey aktif madde olarak bu projede kullanılmıstır. Ayrıca hazırlanan akıskanlarınkararlılıgının artması için pH ayarlaması yapılmıstır. SWCNT içeren su bazlı nanoakıskanlarınhazırlanmasında 50 dk ve 100 dk olmak üzere iki farklı ultrasonikasyon süresi kullanılarak ısıliletkenlige etkisi incelenmistir. Kararlılık degerlendirmesi için UV-Vis Spektrofotometrisi veZeta Potansiyeli ölçümleri yapılmıstır. Bu projede örneklerin santrifüj edilmesi gibi farklıislemler sayesinde nanoparçacık konsantrasyonunun zeta potansiyeline etkisi basarıylaincelenmistir. Isıl iletkenlik ölçümleri 3-omega yöntemiyle gerçeklestirilmistir. Ayrıca farklıyüzey alanlarına sahip nanoparçacıkların kullanılması, farklı konsantrasyonlarda yüzey aktifmadde kullanımı ve farklı baz akıskanlarla çalısılması; bu örneklerin reolojik davranısı, ısıliletkenlik ve yüzey gerilimi ile temas açısı gibi ısı transferi sistemlerinde önem tasıyanözelliklerinin belirlenmesi ve bu özellikleri etkileyen parametrelerin incelenmesi, bu projeyi çokyönlü ve basarılı bir çalısma haline getirmistir.Nanofluids, which have a wide range of applications, are produced by the addition of nanosizedparticles having high thermal conductivity to the base fluid to increase the thermalconductivity of the fluids used in heat transfer systems. Preparing the nanofluids andincreasing the thermal conductivity of the nanofluid are very complex process. The increase ofthermal conductivity of nanofluids and its usage in heat transfer applications are related withmany important parameters from the stability of the nanofluids to their viscosity. No matter howmuch the thermal conductivity is increased, the rapid sedimentation of unstable nanofluids andthe increase in viscosity of nanofluids over that of the base fluid lead to pressure drop,corrosion, and clogging in heat transfer systems. Considering all these, it is necessary toexamine these parameters and to make connections with each other for the practical use ofprepared nanofluids. In this project, it is aimed to prepare stable nanofluids and determine theirthermal conductivity and to clarify the connection of these parameters.Distilled water, ethylene glycol (EG), and compressor oil were used as base fluid. Graphenenanoplatelets (GNP) with different surface areas and single walled carbon nanotubes(SWCNT) were used as nanoparticles. Polyethylene glycol-derived polyhedral oligomericsilsesquioxane (PEG-POSS) was used for the first time in literature, as a surface active agentin nanofluids in order to ensure their stability. In addition, pH value was adjusted to increasethe stability of the nanofluids. In the preparation of water-based nanofluids containing SWCNT,the effect of two different ultrasonication times, 50 min and 100 min, on thermal conductivitywas investigated. UV-Vis Spectrophotometry and Zeta Potential analyses were performed forstability assessment. In this project, the effect of nanoparticle concentration on zeta potentialhas been studied successfully through different processes such as centrifugation and dilutionof samples. Thermal conductivity measurements were carried out by 3ω method. In additionto the usage of different carbon based nanoparticles, various concentrations of surface activeagent, and 3 different base fluids; studying the other factors (e.g. pH, ultrasonication time etc.)affecting the thermal, rheological, and surface properties of nanofluids in heat transfer systemhas made this project a multi-faceted and successful work.Key Words: GNP, SWCNT, nanofluids, 3ω thermal conductivity, viscosity

Darbe dayanımı iyilerştirilmiş polietilen tereftalat-organik kilnanokompozitleri.

This study was conducted to investigate the effects of component concentrations and addition order of the components, on the final properties of ternary nanocomposites composed of poly(ethylene terephthalate), organoclay, and an ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA) terpolymer acting as an impact modifier for PET. In this context, first, the optimum amount of the impact modifier was determined by melt compounding binary PET-terpolymer blends in a corotating twin-screw extruder. The amount of the impact modifier (5 wt. %) resulting in the highest Young̕s modulus and reasonable elongation at break was selected owing to its balanced mechanical properties. Thereafter, by using 5 wt. % terpolymer content, the effects of organically modified clay concentration and addition order of the components on ternary nanocomposites were systematically investigated. Mechanical testing revealed that different addition orders of the materials significantly affected mechanical properties. Among the investigated addition orders, the best sequence of component addition (PI-C) was the one in which poly(ethylene terephthalate) was first compounded with E-MA-GMA. Later, this mixture was compounded with the organoclay in the subsequent run. Young's modulus of not extruded pure PET increased by 67% in samples with 5 wt. % E-MA-GMA plus 5 wt. % clay loading. The highest percent elongation at break was obtained as 300%, for the addition order of PI-C, with 1 wt. % clay content, which is nearly 50 fold higher than that obtained for pure PET. In X-ray diffraction analysis, extensive layer separation associated with delamination of the original clay structure occurred in PI-C and CI-P sequences with both 1 and 3 wt. % clay contents. X-ray diffraction patterns showed that, at these conditions exfoliated structures resulted as indicated by the disappearence of any peaks due to theM.S. - Master of Scienc

Characterization of perlite powders from Izmir, Türkiye region

Perlite is an amorphous volcanic glass-type rock which is collected in open mines in various parts of the world. In this study, eight different perlite samples, supplied from the mines located in the Bergama, Izmir region, were used. The perlite samples were structurally, morphologically, and mineralogically characterized via a wide range of analytical techniques such as Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) Surface Area Analysis, Optical Microscopy, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and a liquid pycnometer. Platelet shaped-like structures were observed in the SEM analysis of the expanded perlites in contrast to the images of spongy or cracked expanded perlites reported in literature. The O-H bending and Si-O-Si vibrations (both asymmetric and symmetric stretching) of perlite structures were confirmed by FTIR. Highly amorphous phases with a rather low percentage of crystalline phases were observed by XRD. In the BET surface area analysis, expanded perlite materials exhibited higher surface area compared to unexpanded ones. A detailed characterization of perlite structures is essential as there is a significant potential to use these minerals in various biocomposite applications and it is useful to explain structure-property relationships in this class of materials

Review on Hybrid Reinforced Polymer Matrix Composites with Nanocellulose, Nanomaterials, and Other Fibers

The use of composite materials has seen many new innovations for a large variety of applications. The area of reinforcement in composites is also rapidly evolving with many new discoveries, including the use of hybrid fibers, sustainable materials, and nanocellulose. In this review, studies on hybrid fiber reinforcement, the use of nanocellulose, the use of nanocellulose in hybrid forms, the use of nanocellulose with other nanomaterials, the applications of these materials, and finally, the challenges and opportunities (including safety issues) of their use are thoroughly discussed. This review will point out new prospects for the composite materials world, enabling the use of nano- and micron-sized materials together and creating value-added products at the industrial scale. Furthermore, the use of hybrid structures consisting of two different nano-materials creates many novel solutions for applications in electronics and sensors.US Department of Energy DEAC05-00OR22725 funding was used.US Department of Energy [DEAC05-00OR22725

Review on Hybrid Reinforced Polymer Matrix Composites with Nanocellulose, Nanomaterials, and Other Fibers

The use of composite materials has seen many new innovations for a large variety of applications. The area of reinforcement in composites is also rapidly evolving with many new discoveries, including the use of hybrid fibers, sustainable materials, and nanocellulose. In this review, studies on hybrid fiber reinforcement, the use of nanocellulose, the use of nanocellulose in hybrid forms, the use of nanocellulose with other nanomaterials, the applications of these materials, and finally, the challenges and opportunities (including safety issues) of their use are thoroughly discussed. This review will point out new prospects for the composite materials world, enabling the use of nano- and micron-sized materials together and creating value-added products at the industrial scale. Furthermore, the use of hybrid structures consisting of two different nano-materials creates many novel solutions for applications in electronics and sensors