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Formation of Nanosized Aluminum and Its Applications in Condensed Phase Reactions
Published in Claudia Altavilla, Enrico Ciliberto, Inorganic Nanoparticles: Synthesis, Applications, and Perspectives, 2017
Jan A. Puszynski, Lori J. Groven
An investigation of the melting behavior of nanosized aluminum was conducted by Trunov et al. for 44, 80, and 121 nm under argon atmosphere and a heating rate of 5°C/min and indicated a reduction in the melting endotherm to 570°C for all three sizes of aluminum powder (Trunov et al. 2006). However, as shown in Figure 6.18, for powders with 50 nm, 80 nm, 100 nm, 2 μm, and 44 μm, no significant shift in the melting endotherm was observed, and therefore no significant reduction in the melting point (<6°C) was recorded. Therefore, the depression of the melting temperature of aluminum nanopowders cannot solely explain the decrease of the ignition temperature for nanosized aluminum–nickel system. The generation of internal stresses within a single nanoparticle of aluminum, coated with a nanolayer of alumina, during the heating process followed by crack formations might be another reason for the ignition to occur at lower temperatures (Levitas et al. 2007).
Pyrometallurgy
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
The particle size of the aluminum powder used plays an interesting role in the aluminothermic process. The viscosity of molten high alumina slags does not vary linearly with temperature; it decreases sharply with a relatively small increase in temperature. For instance, the viscosity of an 85Al2O3−7CaO slag drops from about 40 poise at 1750°C to about 10 poise at 1800°C and to around 3 poise at 1850°C. This feature underlines the fact that during aluminothermic reduction the peak temperature reached may not be as critical as the residence time above the temperature at which the slag becomes fluid. With a fine-sized aluminum powder, the reaction is the most rapid and is completed before the conduction of heat to the cooler reactor makes itself felt. A high peak temperature is developed, but since no additional heat is liberated after all the aluminum is consumed by oxidation, the temperature drops rapidly and the residence time above the temperature required for the obtainment of a highly fluid slag is short. With a medium-sized aluminum powder, on the other hand, the rate of the reaction is somewhat slower and the generation of heat and the dissipation of heat take place simultaneously. The overall result is that a reduced peak temperature is arrived at, but the residence time above the temperature required for a highly fluid slag is longer. With a coarse aluminum powder, the reaction is the slowest so that the temperature reached is not much higher than the required temperature, and slag-metal separation is not as good as with a medium-sized powder. Generally, aluminum powder should not be smaller than 3 to 5 μm or greater than 500 μm for achieving good slag-metal separation.
Nanomaterial-Based Energy Storage and Supply System in Aircraft Systems
Published in Keka Talukdar, Nanomaterials-Based Composites for Energy Applications, 2019
Turbo engines can be protected using zirconia-based nanocomposites. Polymer nanocomposites have a great future for special design and other applications related to aerospace. Nano-chromium is used for the protection of the aluminum structure, and it also resists corrosion. Nano aluminum powder is used as a component of propellants and also modifies the burning rate of fuel. Nano copper serves as conductive plastic, lubricant, etc. Iron and iron oxide NPs may be used for conductive plastic
Mechanism of the organic fluoride effect on the formation of agglomerates and condensed products in the combustion of aluminised solid propellants
Published in Combustion Theory and Modelling, 2020
Xuyuan Zhou, Li Gong, Fenglei Huang, Rongjie Yang, Jianmin Li
Aluminum powder is widely used in solid rocket propellants as a metal fuel. It is characterised by high density, low oxygen consumption, and high heat of combustion, which brings many benefits to the energy performance of propellants, such as increased energy density, improved specific impulse, and suppressed unstable combustion. However, a high Al content often causes the Al particles to burn relatively slowly after leaving the burning surface, resulting in significant agglomeration. Such agglomerates often lead to incomplete combustion, potentially resulting in serious deposition in the combustion chamber. It has been reported that such agglomerates formed during the combustion process would lower the specific impulse by 2–10% [1]. Moreover, a concentrated agglomerate particle flow in the chamber could cause severe erosion and ablation of the insulating layer, and even block the rocket nozzle. The abovementioned shortcomings have partly restricted the application of Al powder in solid rocket propellants [2,3].
Effect of Organic Fluoride on Combustion Performance of HTPB Propellants with Different Aluminum Content
Published in Combustion Science and Technology, 2021
Yanpei Guo, Jianmin Li, Li Gong, Fei Xiao, Rongjie Yang, Lingchao Meng
Aluminum powder is one of the most widely used high-energy fuels in solid propellants due to its high density, high combustion heat, low oxygen consumption and low cost (Lv et al. 2017; Pokhil et al. 1971). In addition, the alumina formed by the combustion can effectively inhibit the unstable combustion of solid propellant (Atwood et al. 1998). However, it is worth noting that the agglomerates formed by the combustion of aluminum powder in the propellant may cause two-phase flow loss, slag deposition and increased ablation of the protective insulation layer in the rocket chamber under the action of flow of particle-laden gases. The presence of agglomerates undoubtedly results in a reduced combustion efficiency of the aluminum powder.
Recovery of Al2O3/Al powder from aluminum dross to utilize as reinforcement along with graphene in the synthesis of aluminum-based composite
Published in Particulate Science and Technology, 2023
Shashi Prakash Dwivedi, Shubham Sharma
Figure 4 shows the line diagram of an in-house developed experimental set-up by using a domestic microwave of 25 L capacity (1400 W, 2.45 Hz) for a rapid microwave sintering process. Matrix material (Al powder) and reinforcement particles (Aluminum dross powder and Graphene) have been taken in stoichiometric amounts. The matrix and reinforcement particles were weighed suspiciously as per the selected composition (Table 2) using an analytical balance. The matrix (Al powder) and reinforcement particles (Aluminum dross powder and Graphene) were alloyed mechanically using a ball-milling process. The ball milling process parameters were ball milling atmosphere, grinding medium, ball milling time, milling vial, ball milling speed, and ball-to-powder weight ratio (BPR). Though, the ball-milling time affected more significantly on the particle size of the powder in this study. The average particle size of aluminum powder and ball-milled (aluminum dross powder and grapheme) powder was 20 µm and 5 µm respectively. The ball-milling milling speed and BPR were fixed 200 rpm at 5:1 during the milling process. Mechanical alloying of aluminum powder and ball-milled (aluminum dross powder and grapheme) powder was carried out for 25, 50, 75, and 100 hours by placing compositions amount (0.90 Kg of Al + 0.05 Kg of aluminum dross powder + 0.05 Kg of Graphene) as shown in Table 2. The average particle size was found to be 15 ± 2 µm after the ball milling for 25 h. In the same manner, when aluminum powder and ball-milled (aluminum dross powder and grapheme) powder were ball-milled for 50 h, the average particle size was 12 ± 2 µm. The average particle size came to 10 ± 2 µm after ball-milling to aluminum powder and ball-milled (aluminum dross powder and grapheme) powder for 75 h. However, when both the powders were ball milled up to 100 h, then the average particle size was found to be 9 ± 2 µm. Though, many undesirable phases were produced when the milling time was increased by more than 100 h. Therefore, the milling of reinforcement particles was kept for 100 h. The same course of action was conducted for the other compositions shown in Table 2.