اصفهان: دانشگاه صنعتي اصفهان، دانشكده ‎‎مهندسي مواد

1394

چهارده، 97ص.: مصور

مسعود پنجه پور، محمود مرآتيان

حسن حدادزاده

1394/09/03

‎‎مهندسي مواد

ID9859

Boron carbide synthesis by magnesiothermic and aluminothermic reduction using a new process design of boron oxide production Siavash Aghili s aghili@ma iut ac ir August 22 2015 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Dr M Panjepour Assoc Prof E Mail panjepour@cc iut ac irDr M Meratian Assoc Prof E Mail panjepour@cc iut ac irAbstractIn this research at first B4C synthesis was performed in magnesiothermic reaction with commercialboron oxide High hygroscopic nature and also lack of desired particle size of commercial boronoxide caused problems such as formation of HBO2 and Mg OH 2 compounds in the initial mixtureduring milling On the other hand explosion and severe fragmentation of sample duringcombustion synthesis process was caused that the combustion wave during synthesis was notobserved and not examined Also increasing magnesium borate phase in combustion synthesisproduct caused difficult acidic leaching condition and thus remaining this phase in the product Therefore according to the results and ensuring failure of commercial boron oxide due to theextreme hygroscopic nature in relation to the production of B4C with good efficiency duringmagnesiothermic process production issue of B2O3 from boric acid were examined for achievingits key properties to compensate for the boron oxide inefficiency particle size surfacemorphology hygroscopic nature For this purpose three methods including methods of fusion non fusion and chemo thermal method were examined The results of fusion and non fusionmethods showed that due to the failure to remove hygroscopic nature and also the lack of access toappropriate particle size and morphology the product of these two methods have similar behaviorwith commercial B2O3 and therefore it is not efficient Thus according to the third method toachieve the required properties a new method that is a combination of chemical and heat treatmentprocesses were designed for the first time Therefore boron oxide dry powder is obtained bydehydrating boric acid in two stages In the first stage metaboric acid HBO2 was produced by areflux process coupled with distillation performed at 64 C for 1 5 hours In the second themetaboric acid obtained in the previous stage is subjected to heat treatment using a specifiedthermal profile of up to 240 C for less than 150 minutes and boron oxide was produced X raydiffraction patterns XRD and Fourier transform infrared analysis FT IR reveal the crystallinephase of metaboric acid produced in the first stage and the amorphous boron oxide produced in thesecond Moreover thermal gravimetric analysis TGA and scanning electron microscopy SEM images are used to show the presence of dehydrated boron oxide powder as well as porousmetaboric acid powder with a particle size of less than 1 5 After obtaining produced boronoxide combustion synthesis operation was carried out during magnesiothermic andaluminothermic processes The results of this two processes indicated that magnesiothermicprocess after acidic leaching with a solution of HCl is associated with high interest of boroncarbide production But in the aluminothermic process due to formation of alumina compoundduring the process and the inability to wash it with solution of sodium hydroxide due tounavailable the optimum condition temperature and pressure to obtain boron carbide is difficultwith the high production As a result magnesiothermic process for production of boron carbideenjoys higher efficiency relative to aluminothermic process Based on the results obtained it maybe claimed that the proposed reflux process coupled with distillation and followed by heattreatment offers an easy method for producing B2O3 with a very fine particle size over far lowerdehydration times than is commonly achieved by other methods and it can be concluded that thenew method of boron oxide production have had an effective role in the process of B4C synthesis especia

مسعود پنجه پور، محمود مرآتيان

حسن حدادزاده