Synthesis and Characterization of a Carborane-containing Precursor for B<sub>4</sub>C Ceramics

Abstract

B 4 C ceramic is one of widely used ceramics with properties of low density, high hardness, high thermal-stability and high neutron absorption cross-section. However, the high melting point and high hardness of B 4 C make it difficult to be prepared as materials with complex shape. Precursor derived method is an effective approach to prepare special-shaped ceramics. In the early research of B 4 C ceramic precursors, highly toxic and unstable decaborane was generally used as the boron source material, and precursors were also unstable and difficult to synthesize. In this work, a new B 4 C precursor is designed and synthesized, and m-carborane, which has stable chemical properties and high thermal stability, is used as the boron source. Firstly, m-carborane is converted into lithium salt after removing active hydrogen by n-butyllithium. Then, catalyzed by Cu(I), the lithium salt reacts with m-chloroiodobenzene so that monomer, bis(3-chlorophenyl)-m-carborane, is prepared. The monomer is polymerized through Ullmann Coupling reaction at the present of Ni(0) catalyst and Zinc powder, and precursor poly[bis(3-chlorophenyl)-m-carborane] is finally synthesized. The precursor is stable at room temperature in air and soluble in Tetrahydrofuran, with Mw of 1013g/mol, and ceramic yield of 62.20% at 900°C in N 2 . The precursor pyrolytic product is composed of B 4 C and graphite after heat treated at 1600°C in inert atmosphere.

Composites and Materials Prepared from Boron Cluster Anions and Carboranes

“…The preparation of boron carbide through the pyrolysis of various carborane-containing polymers has been described [ 137 , 138 , 139 , 140 ]. The Ni-catalyzed polymerization of 1,2-bis(4-chloro-phenyl)- ortho -carborane leads to poly(phenylene- ortho -carborane).…”

“…It was found that the heating of the polymer at 1000–1200 °C resulted in the crystallization of boron carbide, according to the X-ray powder diffraction studies [ 139 ]. The Ni-catalyzed polymerization of 1,7-bis(4-chlorophenyl)- meta -carborane produces poly(phenylene- meta -carborane), which can be used as a novel boron carbide precursor [ 140 ]. Due to its high ceramic yield, it can be used to prepare boron carbide ceramics with different shapes [ 141 ].…”

Performance of glucose, sucrose and cellulose as carbonaceous precursors for the synthesis of B4C powders

“…Therefore, acquiring the technical knowledge of B4C production, achieving its manufacturing technology from available raw materials, as well as using cost-effective fabrication methods are of special importance [8][9][10]. There are various techniques for synthesis of B4C ceramics including carbothermal reduction [11,12], synthesis from its elemental constituents [13,14], magnesiothermal reduction [15,16], chemical vapor deposition (CVD) [17][18][19], and synthesis from polymeric raw materials [20][21][22]. Among the above methods, the synthesis using constituent elements is not cost-effective due to the expensive pure raw materials required and is merely a research-based methodology for synthesis in the laboratory [23].…”

Effects of glucose pretreatment and boric acid content on the synthesizability of B4C ceramics

“…Boron carbide is widely employed in strategic industrial applications due to its fascinating characteristics such as low density (2.5 g/cm 3 ), high hardness and wear resistance, high melting temperature (2445 °C), and inertness against chemicals [1][2][3][4][5][6]. Synthesis from its elemental constituents [7,8] or polymeric raw materials [9][10][11], magnesiothermal [12,13] or carbothermal reduction [14,15], and chemical vapor deposition [16][17][18] are the main manufacturing processes for the production of B 4 C ceramics. Although the B 4 C is usually synthesized through the high temperature carbothermal reduction of B 2 O 3 , the evolution of the carbothermal reduction for organic precursors to synthesize B 4 C is receiving considerable curiosity [19].…”