On the preparation of some chromium, molybdenum and tungsten borides

Chromium and chromium-based alloys: Problems and possibilities for high-temperature service

“…15,26,43,44 Boron addition can modify the nitride impurity after heat treatment and reduce the DBTT of impure cast chromium. 45 Some researchers attempted to correlate properties of the alloying element with its effect on the DBTT and their work indicated that the effect of alloying on the DBTT of chromium is not directly related to the atomic size of the solute atoms. 46 However, Carlson et al indicated that the DBTT of chromium-based alloys is dependent primarily on the atomic size of the alloying elements and concluded that the DBTT of iodide chromium is decreased by the addition of solute atoms that form solid-solution alloys and have atomic diameters larger than chromium but not exceeding the 15% size limit.…”

Preparation of tungsten borides by combustion synthesis involving borothermic reduction of WO3

“…According to previous studies on the preparation of metal borides [16,25,26], an excess amount of boron was suggested to account for the loss of boron through evaporation during the high-temperature synthesis process. Therefore, two initial reactant compositions modified from Reactions (1) and (2) are adopted in this study to consider additional boron and variable tungsten.…”

“…Itoh et al [25] prepared various tungsten borides by solid state reactions between tungsten and boron powers at 800-1550 8C, and indicated that optimum production of WB and W 2 B 5 was attained in the samples with a nearly 10 at.% excess of boron. Peshev et al [26,27] performed a series of experiments on the borothermic reduction of different metal www.elsevier.com/locate/ceramint oxides between 1000 and 1750 8C to prepare the corresponding metal borides, including CrB 2 , Mo 2 B 5 , W 2 B 5 , VB 2 , NbB 2 , and TaB 2 .…”

Preparation of borides in Nb–B and Cr–B systems by combustion synthesis involving borothermic reduction of Nb2O5 and Cr2O3

“…Yeh). NbB 2 by heating amorphous boron and niobium powders of their equivalent compositions at 1000 • C for 60 min and obtained Nb 3 B 4 under a higher temperature of 1800 • C. According to Iizumi et al [12,13], both CrB and CrB 2 have been synthesized in pure form by milling chromium and boron powders in a planetary ball mill for 20-40 h, followed by annealing at 900-1000 • C. Peshev et al [14,15] performed a series of experiments on the borothermic reduction of metal oxides between 1000 and 1750 • C to prepare the corresponding metal borides, including CrB 2 , Mo 2 B 5 , W 2 B 5 , VB 2 , NbB 2 , and TaB 2 . In addition, Sonber et al [16] fabricated CrB 2 through the reaction of Cr 2 O 3 with boron carbide at 1500-1700 • C in the presence of carbon.…”

“…Many transition metal borides have been fabricated by the solidstate reaction between boron and metal powders [10][11][12][13], and by the reduction of metal oxides with boron [14,15] or boron carbide [16] as the reducing agent. Matsudaira et al [10] produced NbB and * Corresponding author.…”