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Experimental and Computational Investigation of Transport Phenomena in Initiated Chemical Vapor Deposition (icvd) Process
(Izmir Institute of Technology, 2017) Ateş, Selcan; Ebil, Özgenç; Ebil, Özgenç
As a polymer thin-film deposition technique, initiated CVD (iCVD) is a heterogeneous process involving gas phase precursors and solid film formation on a solid/liquid substrates at different temperature regions. Obtaining fine-tuned film properties over different substrate geometries at different process conditions is a challenging tasks and requires experimental trials. The major goal of this study is to develop a computational model which describes all relevant transport phenomena occurring in iCVD process, and which is capable to predict the polymer film thickness at different deposition conditions for flat and/or non-flat substrates in a 3D reactor geometry. A Finite Element Analysis (FEA)-based 3D computational model, which can be applied to a variety number of iCVD reactor and substrate geometries, has been developed in the study. To validate the model, reported experimental conditions of 1H,1H,2H,2Hperfluorodecyl acrylate (PFDA) deposition with t-butyl peroxide (TBPO) initiator, and butyl acrylate (BA) deposition with t-amyl peroxide (TAPO) initiator, are applied to the model, respectively. The simulation results of both deposition processes show good agreement with experimental results reported in literature. Presented model successfully describes the relevant transport phenomena, and provides a priori predictions on polymerization rate, and film thickness on complex substrate geometries for a polymerization reaction with known kinetic data. For further studies, presented model can be modified or used as an approach for modeling of other types of CVD systems as well as facilitating process scale-up. The model can also extract valuable polymerization kinetics data provided that a sufficient number of experiments are performed at a specified substrate temperature, and process parameters and measured final film thicknesses are entered to the model.
Preparation of Nanosized Ceo2 Particles and Their Incorporation Into Transparent Acrylate Polymers
(Izmir Institute of Technology, 2014) Tunusoğlu, Özge; Demir, Mustafa Muammer; Tanoğlu, Metin
Nanoparticles having a size smaller than 100 nm are important building blocks of nanomaterials. Organically functionalized CeO2 nanoparticles were prepared by colloidal synthesis in this work. The particles were nucleated by mixing aqueous solutions of Ce(NO3)3·6H2O and ammonia at room temperature. Different small organic molecules were chosen as capping agents and injected into the reaction medium at the beginning of the synthesis: 3- (mercaptopropyl) trimethoxy silane (MPS), hexadecyltrimethyl ammonium bromide (CTAB), 3-mercapto propionic acid (3-MPA), and thioglycolic acid (TGA). The resulting nanocrystals were quasi-spherical and has a narrow mean size distribution with an average size smaller than 10 nm. Polymerization of monomer/nanoparticle dispersion, namely in situ polymerization, has been frequently used for the fabrication of polymer nanocomposites. Both in situ and ex situ approaches were applied for surface functionalization. The particles were dispersed into methyl methacrylate and free radical polymerization was carried out. The process of nanocomposite formation was examined in terms of conversion, molecular weight, and molecular weight distribution. The polymerization responds merely to the in situ functionalized particles. Regardless of the capping agents used, the particles function as a retarder and inhibitor. Their interaction with polymerization medium shows many complexities such that molecular weight is found to be strongly dependent on the capping agent employed.

Phd Degree / Doktora

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