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Ignition, combustion, and oxidation of mixtures of amorphous and crystalline boron powders
W. Aoab,
J. Zhoub,
W. Yangb,
J. Liub,
Ya. Wangb,
K. Cenb a Science and Technology on Combustion, Internal Flow and Thermal-structure Laboratory, Northwestern Polytechnical University, Xi’an, 710072, China
b Zhejiang University, Hangzhou, 310027, China
Abstract:
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.
Keywords:
boron, solid propellant, oxidation, ignition, combustion, kinetics.
UDC:
536.36
Received: 01.12.2013