A study of the mechanically milled h-BN-H system

Defective nanostructured h-BN, with different structural characteristics, can be prepared by mechanical milling under hydrogen and argon atmospheres. When h-BN was mechanically milled under a hydrogen atmosphere, hydrogen could be trapped by the B - and N-dangling bonds formed; the amount of which reached up to 2.6 mass% after 80 h milling. The absorbed hydrogen can be released only as molecular hydrogen starting from about 570 K. As is clarified by a combination of TDS and IR measurements, the hydrogen detrapped from B-H and N-H bonds dominates the desorption at the lower and higher temperature ranges, respectively. After the nanostructured h-BN was heated to 1173 K, some of the hydrogen was still trapped by N-H bonds where, correspondingly, no recrystallization was detected.