Kinetics of the Synthesis of Aluminum Boride by the Self-Propagating High-Temperature Synthesis Method

Abstract

The influence of certain factors on the kinetics of the process of obtaining aluminum borides (burning rate, ingot formation, and phase separation) was investigated. In this study, we report the registration of diboride using the SHS protocol. The synthesis of aluminum diboride from boric anhydride occurred by the aluminothermic method. The initial components were boron trioxide and aluminum in the form of powders. Researchers paid special attention to the degree of grinding of the charge fluxing substances. The influence this had on the rate of development of the degree of charge concentration was studied. To calculate the degree of charge, a composition was chosen according to the speed obtained from a number of experiments where melting was carried out with the following charge densities in g/cm3: 0.80; 1.08; 1.18; 1.74. The method of melting was ignition from above. The experimental results allowed us to conclude that the nature of the change in the combustion rate of the system, where there was an excess of the reducing agent in the charge, is the same. An increase in the combustion rate, where there was an excess of aluminum of up to 20%, was likely due to the fact that the reaction area of the charge components increased. In addition, an increase in speed can be explained by a decrease in heat losses due to a reduction in the melting time. With an increase in excess aluminum above 20% of the stoichiometry, the observed decrease in the combustion rate can be explained by a decrease in the specific heat of the process due to the melting of the excess aluminum, which played the role of a ballast.

Optimization of Aluminum Boride Synthesis in the Self-Propagating High-Temperature Synthesis Mode to Create Waste-Free Technology

“…The synthesis of aluminum boride was carried out by the aluminothermic method in the SHS mode [2,12,13].…”

Investigation of the Effect of Aluminum Powder on the Combustion Rate of the Composite

“…), as well as their hydrides. Metal fuel in its pure form cannot be a source of reactive energy, but if it is mixed with an oxidizing fuel, then the heat generated during the combustion of the metal fuel significantly increases the temperature of the resulting gas and, consequently, its outflow rate increases, which increases the specific jet thrust [1,2].…”

Influence of fluxing additives on aluminothermic synthesis of aluminum borides

“…Құйманың түзілу процесі мен қорытпаның толық алынуына балқымалардың тығыздығы да әсер етеді. Кейбір алюминотермиялық қорытпалардың және кальций, барий, бор, титан, кремний сияқты элементтері бар негізгі қорытпалардың тығыздығы алынған қождың тығыздығына жақын болуы мүмкін, г/см 3 : Ba -3.57; Са -1.44; Ti -4.11; B -2.3 [9]; Al2O3 -3.0 [10]; алюминий боридтері -2.8-3.19 [11], бұл құйма түзілудің қалыпты процесінің бұзылуына әкеледі. Алюминий тотығы қожының тығыздығының төмендеуі бүкіл балқыма температурасының жоғарылауымен мүмкін болады, 200°С жоғарылау қож тығыздығын 0.05-0.07 г/см 3 төмендетеді [13].…”