Surface Properties and Morphology of Boron Carbide Nanopowders Obtained by Lyophilization of Saccharide Precursors.

Dawid Kozień,Zbigniew Olejniczak,Joanna Stępień,Zbigniew Pędzich,Piotr Jeleń,Maciej Sitarz

doi:10.3390/ma14123419

Dawid Kozień, Zbigniew Olejniczak + Show 4 more

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https://doi.org/10.3390/ma14123419

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Abstract

The powders of boron carbide are usually synthesized by the carbothermal reduction of boron oxide. As an alternative to high-temperature reactions, the development of the carbothermal reduction of organic precursors to produce B4C is receiving considerable interest. The aim of this work was to compare two methods of preparing different saccharide precursors mixed with boric acid with a molar ratio of boron to carbon of 1:9 for the synthesis of B4C. In the first method, aqueous solutions of saccharides and boric acid were dried overnight at 90 °C and pyrolyzed at 850 °C for 1 h under argon flow. In the second method, aqueous solutions of different saccharides and boric acid were freeze-dried and prepared in the same way as in the first method. Precursors from both methods were heat-treated at temperatures of 1300 to 1700 °C. The amount of boron carbide in the powders depends on the saccharides, the temperature of synthesis, and the method of precursor preparation.

Highlights

IntroductionBoron carbide (B4 C), due to its specific properties (high hardness, low density, high melting point, high elastic modulus, etc.) [1,2], has been widely used in many applications such as in polishing as an abrasive, in ball mills as a neutron absorber and as a neutron shield, and in boron neutron capture therapy (BNCT)
Our work led us to conclude that the morphology and size of boron carbide strongly depend on the saccharide precursor and the temperature of synthesis
Lyophilization of saccharide precursors reduces the size of the particles and allows to obtain fine boron carbide, but the lyophilization process itself causes, for most compositions, a decrease in the percentage of B13 C2 phase in the obtained powders, compared to recrystallized powders

Summary

Introduction

Boron carbide (B4 C), due to its specific properties (high hardness, low density, high melting point, high elastic modulus, etc.) [1,2], has been widely used in many applications such as in polishing as an abrasive, in ball mills as a neutron absorber and as a neutron shield, and in boron neutron capture therapy (BNCT). In BNCT research, nuclear reactors or accelerators generate thermal neutrons, which are captured by a variety of nuclei, but the probability of capture by an isotope of boron (10 B) is much higher than that of the capture of another isotope. The first studies of synthesized boron carbide (B4 C) started when Henri Moissan obtained boron carbide from the reduction of diboron trioxide (B2 O3 )

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