Laser ignition and combustion characteristics of B-Al compound powder without and with HMX: A comparative study.

A micro-sized B-Al alloy has application potential to be an energetic material for metal fuel. To understand the combustion mechanism of micro-sized B-Al compound powder and explosives containing B-Al (30 wt.%), the ignition and combustion characteristics of B-Al compound powder without and with HMX (cyclotetramethylenetetranitramine) under different pressures (0.4, 0.8, 1.2, 1.5 and 1.8 MPa) and atmospheres (60% O + 2 40 % N 2 , 80% O + 2 20 % N 2 and 100% O 2) were studied via a laser ignition experimental system. The images and characteristic parameters of the ignition and combustion process with different conditions for the B-Al compound powder without and with HMX were obtained. The effects of atmosphere and pressure on the ignition and combustion characteristics of the B-Al compound powder without and with HMX were discussed through a comparative analysis. For the condensed combustion products (CCPs), the phase crystal structures were analysed with X-ray diffraction (XRD), the micro-morphology of the surface was observed with scanning electron microscopy (SEM), and the micro-area elementary composition was analysed with X-ray energy dispersive spectrum (EDS). The results show that whether the increase in pressure or oxygen concentration, the ignition delay time (t id) and combustion time (t ct) of samples without and with HMX decrease, while the maximum spectral intensity (I max) and the maximum combustion temperature (T max) increase. According to the flame morphology, the combustion of the B-Al compound powder is weaker, while that of the B-Al powder with HMX is more intense, and the flame area is larger, which produces a large amount of smoke and presents a deflagration phenomenon. Specially, for various B-Al powder (B/Al = 3/7, 1/1 and 7/3) with HMX under high pressures (1.2, 1.5 and 1.8 MPa), the higher ratio of B leads to shorter combustion time and stronger spectral intensity. Unreacted B, Al and their final oxides, B 2 O 3 and Al 2 O 3 , were detected in the CCPs of both samples without and with HMX. In addition, the CCPs like BN, AlN and Al 5 O 6 N were also detected. The experimental results can help us better understand the chemical reaction mechanism and energy release characteristics of HMX-based explosives containing B-Al. [ABSTRACT FROM AUTHOR]