Ignition, combustion, and oxidation of mixtures of amorphous and crystalline boron powders

Ignition, combustion, and oxidation characteristics of mixtures of amorphous and crystalline boron powders are studied by using a laser ignition system and a thermogravimetric analyzer. Yellow, green, and white-glow flames are observed. When the weight ratio of the amorphous boron powder $(K)$ is lower than $0.33$, burning of the mixtures is found to be at the ignition stage, while the combustion stage gradually appears with increasing $K$. The emission spectrum intensity is weakened by $3/4$ as $K$ decreases from $1$ to $0.75$. No obvious emission spectrum is detected at $K<0.33$. The ignition delay time is found to decrease significantly with increasing $K$, but it does not change much at $K<0.8$. Mixtures with larger values of $K$ have a lower peak temperature of differential thermal gravity and a greater weight gain and maximum reaction rate. The Satava–Sestak method is applied to study the kinetics of the oxidation reaction of the mixtures. The calculated apparent activation energy decreases from $297$ to $191$ kJ/mol as $K$ increases from $0$ to $1$. For mixtures with $K$ ranging from $0.23$ to $0.75$, the apparent activation energy mainly stays constant at a value of $280$ kJ/mol.