Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Türkiye
Tezin Onay Tarihi: 2009
Öğrenci: ALİ ARDA ÖZKENTER
Danışman: NACİ SEVİNÇ
Özet:Hexagonal boron nitride (h-BN) formation by carbothermic reduction of B2O3 under nitrogen atmosphere at 1500°C and effect of CaO addition into the initial B2O3 – active C mixture were investigated during this study. Reaction products were characterized by powder X-ray diffraction, scanning electron microscopy (SEM) and quantitative chemical analysis. Main aim of this study was to investigate the presence of a second reaction mechanism that catalytically affects h-BN formation during CaO or CaCO3 addition into the initial mixture. It was found that similar to CaCO3 addition, CaO addition has a catalytic effect on carbothermic formation h-BN. In order to investigate the reaction mechanism experiments with B2O3 – CaO mixtures without active carbon addition into the mixture were conducted. Furthermore nucleation of h-BN from calcium borate melts had been investigated and experiments were conducted with h-BN addition into CaO – B2O3 mixtures. It was concluded that nucleation of h-BN in calcium borate slags under experimental conditions is not possible. Hexagonal BN should be present in the system in order to activate the second nitrogen dissolution followed by h-BN precipitation mechanism. Highest efficiency was achieved in the experiment conducted with CaCO3 addition and largest particle size was observed during the experiment conducted to investigate the effect of nucleation.