Investigation of Boro/Carbothermic and Carbothermic Reduction Synthesized Calcium Hexaborides

Abstract

In this study, crystal structure and powder morphologies of CaB₆ synthesized via different synthesis methods were investigated via Rietveld method and TEM studies. CaB₆ powders were synthesized via two different methods and to investigate the effect of the synthesis method on the crystal structure, synthesis temperature and dwell time were kept as constant for both method. In the first method, CaB₆ was synthesized via boro/carbothermal reduction of calcium carbonate by in-situ synthesized boron carbide. In the second method, CaB₆ powders were formed by carbothermal reduction of calcium hexaborate penthydrate by carbon obtained from pyrolysis of PVA in PVA-Borate gels. Phase analysis of powders were studied via X-Ray Diffraction (XRD) and crystal structure refinement was done using Rietveld method via Maud^TM software. Particle morphologies and size were studied with Transmission Electron Microscope (TEM) and crystal structure were analyzed via Selected Area Electron Diffraction (SAED). 

Keywords

• CaB6,Hexaboride,Hexaborate,Borocarbothermic Reduction

Boro/Karbotermik ve Karbotermik İndirgeme Yöntemiyle Sentezlenen Kalsiyum Hekzaborürlerin İncelenmesi

Abstract

Bu çalışmada, iki farklı yöntemle sentezlenen CaB₆ kristal yapısı ve toz morfolojisi incelenmiş ve sentez yönteminin, yapı üzerindeki etkisi Rietveld metodu ve TEM yardımıyla incelenmiştir. CaB₆ tozları iki farklı yöntem kullanılarak sentezlenmiş ve üretim yönteminin kristal yapı üzerindeki etkisinin incelenmesi için sentez sıcaklığı ve süresi her iki yöntem için sabit tutulmuştur. İlk yöntemde, CaB₆ tozları, kalsiyum karbonatın (CaCO₃) boro/karbotermik olarak yerinde indirgenmesiyle sentezlenmiştir. Diğer yöntemde ise kalsiyum pentaborat hekzahidrat (CaB₆O₁₀.5H₂O) tozları, PVA-Borat içeren jelin pirolizinden elde edilen karbonun indirgeyici olarak rol oynamasıyla ve boratın yerinde indirgenmesiyle sentezlenmiştir. Tozların faz analizi X-Işını Kırınım (XRD) tekniği ile, kristal yapıya ait detayların belirlenmesi ise Maud^TM yazılımı kullanılarak Rietveld analizi ve Elektron Kırınımı (SAED) yöntemi ile gerçekleştirilmiştir. Parçacık morfolojisi ve boyutu, geçirimli elektron mikroskobu (GEM) kullanılarak incelenmiştir.  

Keywords

• CaB6,Hekzaborür,Hekzaborat,Borokarbotermik İndirgeme

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