Thermal Reaction Characteristics And Kinetic Of Coated Nano-aluminum In CO₂

Nano-aluminum powder?nAl? has become the first choice for the metal combustion agent because of larger specific surface area, lower ignition temperature and faster burning rate. However, nAl is very easily oxidized due to its high activity and the formed oxide film leads to difficult ignition and low combustion efficiency.Therefore, it is necessary to coat nAl. Firstly, different concentrations of TMP, AP and SiO₂ have been used to coat nAl whose average particle size is 100 nm and coated samples are characterized by SEM, EDS and FTIR. Secondly, the effects of TMP, AP and SiO₂ on thermal reaction and kinetic characteristics of nAl/CO₂ are analyzed.Finally, the effects of TMP, AP and SiO₂ on the ignition and combustion characteristics of coated nAl/CO₂ are studied by tubular furnace. The main results in this paper are as follows:1. TMP coating nAl and AP coating nAl are prepared by recrystallization method and SiO₂ coating nAl is prepared by sol-gel method. The results show that nAl particles are coated successfully.2. The gross gain rate and the oxidation degree of nAl coated TMP and AP are increased and TMP and AP promote the oxidation of nAl in low temperature stage in carbon dioxide atmosphere. NAl coated SiO₂ has one weight increase stage, and the oxygen reaction is more concentrated.3. The kinetics of analysis shows the activation energy of nAl coated TMP is decreased by 111.04 kJ/mol in the first weight increase stage and 34.56 kJ/mol in the second weight increase stage, respectively. The activation energy of nAl coated AP is decreases by 196.83 kJ/mol in the first weight increase stage and 124.09 kJ/mol in the second weight increase stage, respectively. However,the activation energy of nAl coated SiO₂ is increased by 7.72 kJ/mol. The results show that TMP and AP promote the oxidation of nAl in CO₂ atmosphere while SiO₂ is unfavorable for the reaction of Al/CO₂.4. The reaction of both weight increase stages of nAl and CO₂ correspond to F2 model and the mechanism functions are G???=?1-??-1-1. The first weight increasestage is R3 model for nAl coated TMP, and mechanism function is G???=1-?1-??1/3.The first and the second weight increase stages of AP/nAl correspond to R2 and R3 model, and the mechanism functions are G???=1-?1-??1/2 and G???=1-?1-??1/3,respectively. SiO₂/nAl corresponds to R3 model.5. The effects of TMP, AP and SiO₂ on ignition and combustion characteristics of nAl are studied by tubular furnace. Results show that the ignition temperature of nAl is decreased by TMP or AP, especially for AP. NAl coated SiO₂ is unfavorable for ignition and combustion.