Aluminum Powder Particles Research Articles

Investigation on the Effect of Energy Release Rate of Aluminized Explosive on the Damage of Underwater Targets

AbstractAs a type of high‐energy explosive, aluminized explosives are extensively used in underwater weapons and ammunition. This study aims to investigate the energy release rate on the damage of underwater targets caused by aluminized explosives (RDX/Al). The ship was selected as a target, and numerical simulations were conducted using AUTODYN software to study the energy release rate corresponding to different particle sizes of aluminum powder (25 nm −300 μm) in the underwater explosion process of RDX/Al, as well as its destructive effect on targets in the water. The research quantitatively evaluates the whole ship′s destruction results, including longitudinal bending deformations and crevasse. In addition, typical cabins were selected in this study to assess the local damage effects by analyzing stress, shock wave pressure, displacement, and acceleration shock response. Based on the damage results, it was revealed that RDX/Al with aluminum powder particle sizes ranging from 54 nm to 145 nm exhibited the most optimal damaging effects on ships after underwater explosions. These findings provide a basis for improving the destructive power of aluminized explosives against underwater targets, simultaneously, they can be utilized by ship designers to guide research and development of improved protective measures, aiming to reduce the vulnerability of ships to explosive attacks.

Underwater explosion energy output characteristics of hexanitrohexaazaisowurtzitane (CL-20)-based aluminized explosives with different aluminum powder particle sizes

Underwater explosion energy output characteristics of hexanitrohexaazaisowurtzitane (CL-20)-based aluminized explosives with different aluminum powder particle sizes

Combustion and micro-explosion characteristics of biodiesel–ethanol–aluminum powder particles droplet under simulated air nitrogen–oxygen

Compared with aviation fuel, biodiesel has a smaller energy density, so the flight range of aircraft using biodiesel as aviation fuel is relatively short. Adding aluminum powder particles can significantly improve the energy density of fuel and then improve the flight range of aircraft, but the combustion characteristics of fuel will change after adding aluminum powder particles to fuel. In this experiment, a tubular furnace was used to simulate the ratio of nitrogen to oxygen in air, and the micro-explosion and combustion characteristics of BD60E40 droplet and BD60E40 droplet 10%AP (8 μm) under 700 and 750 °C were compared and studied by using moving droplet tracking technology. It is found that the greater the steam pressure inside the droplet, the greater the intensity of micro-explosion, and the greater the initial velocity of the secondary droplet after micro-explosion. In addition, it is found that the proportion of aluminum powder in droplets increases gradually during the combustion cycle, and the frequency and intensity of micro-explosion of droplets increase gradually. The instantaneous combustion micro-explosion intensity model and the average combustion intensity model were established. It was found that the average combustion micro-explosion intensity of droplets increased gradually with the increase in temperature through calculation.

Foaming Behavior of Microsized Aluminum Foam Using Hot Rolling Precursor

Aluminum foam that is lightweight with high specific strength, high energy absorption and other characteristics can be used in aerospace, transportation, machinery manufacturing and other fields. The PCM method is usually used to prepare closed-cell aluminum foams. The microsized aluminum foams made by this process can solve the non-uniform pore structures caused by liquid drainage during the foaming process of large aluminum foams. The surface morphology and internal pore structure of microsized aluminum foams are affected by the quality of the precursor used for foaming. In this paper, foamable precursors were obtained via either hot rolling or hot extrusion and subsequently foamed. By analyzing the micromorphology and foaming process of the precursor, the influence of the technological method on the macroscopic pore structure of the final aluminum foam was studied. The results show that the aluminum powder particles in the precursor prepared with the hot rolling method had metallurgical bonding, and the outer surface was dense, with almost no porosity and holes in the interior. The microsized aluminum foam obtained after foaming was smooth in appearance, and the internal pore structure was round and uniform. The reason is that during the foaming process of microsize aluminum foam, the foaming agent was evenly distributed in the precursor of the hot rolling process because of its compact structure. During the foaming process, the decomposed gas of the foaming agent will not escape, and the evenly distributed foaming agent tends to nucleate in situ. In the process of rapid foaming, the pressure in the bubble is enough to resist the liquid drainage phenomenon caused by gravity, and the growth direction of the gas core is isotropic, which promotes the foam structure to be more rounded and uniform.

Research on the quasi-isentropic driving model of aluminized explosives in the detonation wave propagation direction

Taking CL-20 (Hexanitrohexaazaisowurtzitane)-based aluminized explosives with high gurney energy as the research object, this research experimentally investigates the work capability of different aluminized explosive formulations when driving metal flyer plates in the denotation wave propagation direction. The research results showed that the formulations with 43 μm aluminum (Al) powder particles (The particle sizes of Al powder were in the range of 2∼43 μm) exhibited the optimal performance in driving flyer plates along the denotation wave propagation direction. Compared to the formulations with Al powder 13 μm, the formulations with Al powder 2 μm delivered better performance in accelerating metal flyer plates in the early stage, which, however, turned to be poor in the later stage. The CL-20-based explosives containing 25% Al far under-performed those containing 15% Al. Based on the proposed quasi-isentropic hypothesis, relevant isentropy theories, and the functional relationship between detonation parameters and entropy as well as Al reaction degree, the characteristic lines of aluminized explosives in accelerating flyer plates were theoretically studied, a quasi-isentropic theoretical model for the aluminized explosive driving the flyer plate was built and the calculation methods for the variations of flyer plate velocity, Al reaction degree, and detonation product parameters with time and axial positions were developed. The theoretical model built is verified by the experimental results of the CL-20-based aluminized explosive driving flyer plate. It was found that the model built could accurately calculate the variations of flyer plate velocity and Al reaction degree over time. In addition, how physical parameters including detonation product pressure and temperature varied with time and axial positions was identified. The action time of the positive pressure after the detonation of aluminized explosives was found prolonged and the downtrend of the temperature was slowed down and even reversed to a slight rise due to the aftereffect reaction between the Al powder and the detonation products.

Unraveling the dispersion mechanism of carbon nanotubes in aluminum powder particles during high energy ball milling by FIB-TEM study

For the development of high-performance aluminum (Al) matrix composites reinforced with carbon nanotubes (CNTs), high energy ball milling (HEBM) is the most prevalent method to disperse CNTs in Al powder. However, the dispersion mechanism of CNTs in Al powder is still unclear, mainly because it is difficult to characterize CNTs when they are buried inside Al powder particles. Herein, focused-ion-beam-assisted transmission electron microscopy observation of CNTs in Al powder via HEBM with various milling times was conducted. Results showed that with increasing HEBM time, CNTs clusters were firstly broken up to be dispersed shorter-lengthed CNTs on the surface of Al flakes with gradually reduced thickness. Afterward, cold-welding of Al flakes was the predominant phenomenon, which resulted in re-spheroidization of Al powders and homogeneously dispersed CNTs. This study may provide guidance for controlling and optimizing the HEBM process to disperse CNTs in Al matrix towards the development of high-performance CNTs/Al composites.

FLAKE POWDER METALLURGY APPROACH FOR PRODUCTION OF Al–Al2O3COMPOSITES WITH ENHANCED PROPERTIES

Flake Powder Metallurgy (FPM) is utilized for the processing of Al–Al2O3composites. The effects of contents of 1-[Formula: see text]m-sized alumina (0, 3, 6 and 9 vol.%) on the microstructure, hardness, porosity and wear behavior of these composites are investigated. The as-received aluminum powder particles are milled in a planetary ball mill for different time durations (0.5, 1, 1.5 and 2 h), and the resultant flake powders are characterized by sieving, SEM, optical microscopy and XRD to determine their particle size, morphology and grain size. Al flakes and different amounts of Al2O3powders are stacked into the mold cavity using a floating column filled with alcohol. Then the compacts are cold pressed at 750 MPa and sintered in a tube furnace at 655∘C for 60[Formula: see text]min. For comparison, reference samples from as-received aluminum powders are also fabricated. SEM studies showed a uniform distribution of alumina particles within the matrix of FPM-processed composites. These composites, despite their higher porosity, exhibited higher hardness levels and improved wear properties in comparison with the conventionally produced powder metallurgy (PM) counterparts. This is due to: (i) the special morphology of the flake powders that contributed to a more uniform distribution of alumina within the matrix and (ii) their smaller grain size due to work hardening that occurred during milling, which resulted in higher hardness values.

Fabrication and characterization of aluminum-based powders multi-reinforced with nano- and microparticles

Multi-reinforced powders were obtained by high-energy ball milling in a planetary mill. The process of obtaining heterogeneous powders consisted of two stages. At the first stage, a nanocomposite powder of AlMg6 + 0.3 wt.% C60 was obtained. In the second stage, 10, 30, 50, and 70 wt.% Al2O3 were added to the obtained nanocomposite powder and processing continued. Methods such as scanning electron microscopy, X-ray diffraction, and particle size analysis were used to characterize the obtained powders. It is shown that after the first stage of processing, the particles of the composite powder are characterized by an irregular shape. C60 reinforcing particles in the form of nanosized agglomerates were fixed on the surface of aluminum powder particles. After the second stage of processing, the particle size of the powder mixture decreased from 17.8 to 12.3 μm, while the proportion of Al2O3 particles increased from 10% to 70% by weight. It is shown that the synthesized heterogeneous powders were a mechanical mixture consisting of complex composition agglomerates and micro-sized ceramic particles. Complex composition agglomerates were formed from nanocrystalline matrix material particles and C60, and also with Al2O3 microparticles embedded in them, as well as located on the surface. The concentration of Al2O3 particles on the surface and inside the agglomerates increased with increasing weight fraction of ceramic particles in the mixture. It has been found that the introduction of 10-70 wt. % Al2O3 into the powder mixture increases the microhardness of the powder particles by approximately 16-23%. The resulting multi-reinforced powder mixtures can be utilized for coating deposition using the cold gas dynamic spraying method.

Influence of micron-sized aluminum particles on micro-explosion and combustion characteristics of ethanol-biodiesel droplets under co-heat flow

As a high-energy metal fuel, aluminum powder particles (AP) have long been used as fuel propellants and combustion-supporting additives in explosives to meet the design requirements of a new generation of high-energy–density fuels. In this experiment, the micro-explosion and combustion characteristics of ethanol-biodiesel mixed droplets with different aluminum powder particle contents and particle sizes were studied under high temperature and pure oxygen environment. In order to better control the experimental variables, a more accurate single-droplet suspension method was adopted in this experiment. The entire evaporation and combustion process of the mixed fuel was completely recorded and analyzed by using high-speed photography technology, binarization imaging technology and droplet optimization algorithms. The experimental results show that when the content of aluminum powder particles remains unchanged, increasing the particle size of aluminum powder in the mixed droplets will promote the micro-explosion phenomenon. When the particle size of the aluminum powder contained in the mixed fuel is different, the increase of the particle content will have a completely different effect on the heating time of the droplet. When the particle size of aluminum powder particles is small, the combustion duration of the mixed droplets increases with the increase of aluminum powder content, while the opposite results are shown when the aluminum powder particles are larger. Increasing the amount of aluminum powder also extends the full life of the droplets. In addition, this study introduces the microburst intensity (MI), which provides a new idea and method for laterally comparing the microburst phenomena of fuel droplets with different initial diameters. For mixed fuel containing micron-sized aluminum particles, the particle content that produces the best micro-explosion intensity is about 20%.

Synthesizing AlN Coatings Using Suspension Plasma Spraying: Effect of Promotional Additives and Aluminum Powder Particle Size

Synthesizing AlN Coatings Using Suspension Plasma Spraying: Effect of Promotional Additives and Aluminum Powder Particle Size

Deformation and cracking phenomena in cold sprayed 6061 Al alloy powders with nanoscale aluminum oxide films

This paper presents deformation and cracking phenomena associated with the cold spray of nanoscale surface oxide layers associated with the cold spray of 6061 Al alloy powders. The structure of the top surface oxide film was revealed via Focused Ion Beam (FIB), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). The observations show the oxide layer characteristics most likely matches crystalline γ-Al2O3. Phenomena associated with surface contacts, contact-induced elastic-plastic deformation, heating, and cracking are then studied using a combination of analytical models, Finite Element Analysis (FEA) and Molecular Dynamics (MD) simulations. MD simulations are also used to obtain estimates of oxide film young's moduli, strains to failure, and the fracture energies of oxide films. The results from the MD simulations and microscopy observations are incorporated into a bi-linear Johnson- Cook finite element simulations of cold spray contact-induced deformation and cracking due to the impact of aluminum powder particles with nanoscale oxide layers and similar substrates with nanoscale oxide layers. The powder impacts are shown to result in localized splat deformation and heating, along with the cracking of the oxide layers that expose fresh metallic surfaces to high temperature surface contacts (at temperatures above the recrystallization temperature for aluminum/6061 Al) that can give rise to bonding and mechanical interlocking. The implications of the results are then discussed for the design of cold spray processes for the fabrication and repair of 6061 Al structures.

Effects of aluminum and silicon carbide on morphological and mechanical properties of epoxy hybrid composites

The present research focuses on the effects of aluminum (Al) and silicon carbide (SiC) hybridization on mechanical and morphological properties of Al and SiC particles reinforced hybrid epoxy composites. Composites were prepared by hand lay-up technique at five levels of reinforcement loading (10, 20, 30, 40, and 50 wt%). Aluminum powder and silicon carbide particles were utilized as reinforcement at a ratio of (1:1) during composite preparation. Microstructural analysis using a scanning electronic microscope and optical microscope was performed to observe the adhesiveness between the matrix and reinforcement. For mechanical characterization, tensile, flexural, impact, and hardness tests were performed. Tensile and flexural strength decreased, while Young’s modulus, flexural modulus, impact strength, and hardness increased with increase in aluminum and silicon carbide particle loading. Based on the particle loading, 50 wt% of particle-reinforced composite had the best set of mechanical properties among all prepared composites.

The Effect of Adding Sodium Carbonate on the Electrical Conductivity of Aluminum Paste

Base metal pastes have been widely used in the preparation of ZnO varistor electrodes, and it is important to accurately grasp the relevant mechanisms affecting the conductivity of aluminum electrodes. In this paper, the effect of adding sodium carbonate on the conductive property of aluminum paste was assessed, and the microscopic mechanism during aluminum electrode sintering explored. The results show that adding sodium carbonate can reduce the softening point of glass powder and enhance its fluidity. Sodium carbonate, glass, and aluminum oxide film react together; consequently, the aluminum oxide film is partially dissolved by reaction to produce defects, and there is tight contact at the interface between the aluminum powder particles. The sodium ions will displace the aluminum ions in the alumina, conferring the alumina film with a certain ionic conductivity. At the same time, sodium ions are doped into the aluminum lattice, which causes the aluminum lattice to swell. After sintering, the structure of aluminum electrode is compact and its electrical conductivity is significantly improved. This study is a valuable reference for the theoretical research and the potential applications of aluminum paste.

Sintering mechanism of electronic aluminum paste and its effect on electrical conductivity of aluminum electrode

In view of the wide application of aluminum paste in the manufacture of electronic devices, it is important to thorough understanding and accurate control of the factors affecting electrical conductivity of aluminum electrodes and the related mechanisms. In this paper, we investigate the microstructural evolution of aluminum paste during sintering and analyze the effects of process parameters such as glass type and temperature on electrical conductivity of aluminum electrodes. The results demonstrate that differences in sintering temperature, glass type and content cause significant changes in the structural compactness and electrical conductivity of aluminum electrodes. At a certain temperature, part of the aluminum oxide film will break or peel off due to the difference in thermal expansion between aluminum particles and oxide film. At the same time, the melt glass has a certain fusion effect on the aluminum oxide film on the surface of the aluminum powder. The combined effect of these two factors can cause damage, thinning, peeling or removal of the oxide film on the surface of the aluminum powder, so that more conductive contact points (surfaces) are formed at the interface between the aluminum powder particles, and as a consequence, a coherent conductive network microstructure is formed at the aluminum electrode. With the increase of glass content in aluminum paste, the square resistance of aluminum electrode first decreases and then increases. Results of the study will provide reference for further study and application of electronic aluminum paste.

Compressive Properties and Failure Mechanisms of Gradient Aluminum Foams Prepared by a Powder Metallurgy Method

A layered gradient aluminum foam was prepared by powder sintering with sodium thiosulfate (Na2S2O3) particles as the cell-forming agent. By cutting, polishing and observing under a microscope, it was found that the aluminum powder particles were not completely melted after sintering but were only combined by surface melting. Based on the quasi-static compression test and the macroscopic diagram of the sample during deformation, the mechanical properties of gradient aluminum foam were studied, and their deformation characteristics and mechanism were analyzed and discussed.

Effect of sintering path on the microstructural and mechanical behavior of aluminum matrix composite reinforced with pre-synthesized Al/Cu core-shell particles

The effect of different sintering techniques (vacuum sintering, hot-pressing, spark plasma sintering) on microstructure and mechanical properties were investigated for pre-synthesized core-shell (Al/Cu) particles reinforced Al matrix composites (AMC). In the first step, copper was deposited on aluminum powder particles by galvanic replacement method to synthesize Al/Cu particulates. In the next step, green compacts of Al/Cu core-shell particles reinforced AMCs were prepared by using vacuum sintering (VS), hot-pressing (HP) and spark plasma sintering (SPS). The microstructure and phase analysis of the prepared composites were performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) while their mechanical properties were evaluated by performing compression test and microhardness test. The results revealed that the sintering path has a pronounced impact on the properties of prepared composites. Depending on the consolidation technique, the deposited Cu in the core-shell structure is transformed in-situ into various types of intermetallic. This results in specially tailored microstructures with improved strength along with varying toughness depending upon the sintering technique. Mechanical characterization showed that the spark plasma sintered composite has the highest microhardness and compressive strength. To meet the current industrial requirements for structural and functional applications, this study provides a methodology to obtain tailor-made microstructure of AMCs with much improved mechanical characteristics.

Preparation and properties of controllable aluminum foam

As an important method for preparing aluminum foam, space holders have the advantages of simple preparation process, controllable porosity, high operation safety, easy to realize the large-scale production and so on. In this paper, sodium thiosulfate (Na2S2O3) is selected as the new raw material for spacer to replace the traditional spacer (such as urea and salt), which is prepared by melting, injecting into the mold and solidifying. Three kinds of spherical spacer with different diameters were modified, and aluminum foams with three porosity (65%, 70% and 75%) and three pore sizes (Ø2mm, Ø3mm and Ø4mm) were prepared by compaction, dissolution and sintering. The results of metallographic analysis of aluminum foam sintered sample show that the aluminum powder particles bond closely above 600 °C. The quasi-static compression results show that the interaction between aluminum matrix materials and pore structure affects the mechanical properties of foamed aluminum, and the interaction between porosity and pore size affects the mechanical properties of foamed aluminum.

Study on Electrical Explosion Mechanism and Ignition Characteristics of Copper and Aluminum Powder Under Ignition Solid Propellant

In order to study the characteristic of the electrical explosion of copper and aluminum powders, a multilayer generator was designed, an experimental system was set up, and the parameters of metal powder electrical explosion were measured and analyzed. The results show that the duration of the electrical explosion process increases significantly due to the addition of metal powder. The duration of aluminum powder electrical explosion jet flow is ~86.36 ms due to its self-sustained combustion, which releases a large amount of energy, and a small fraction of aluminum powder particles is not burned. The duration of copper powder electrical explosion jet flow is ~15.84 ms, and most of the copper powder particles are in the solid state. The current pause process is absent; instead, the first discharge process is connected to the second discharge process. The effect of copper powder on the first discharge process is greater than that of aluminum powder. Furthermore, the ignition ability of copper powder electrical explosion to solid propellant is stronger than that of aluminum powder in a closed bomb experiment. These results are indubitably meaningful for the application of metal powder electrical explosion and ignition of solid propellant in an electrothermal chemical gun.

Preparation and Study of the Properties of Aluminum Powders, Suitable for the Manufacture of Powder Electrodes

The results of the study of the shape, morphology and elemental composition of aluminum powder particles obtained in distilled water with the following electrical parameters of the electroerosive dispersion unit are presented: the capacity of discharge capacitors is 65 μF, voltage 100 V, pulse frequency 50 Hz. It is established that the powder consists of particles of regular spherical shape (or elliptical), irregular shape (conglomerates) and fragmentation, and the main elements of the powder are aluminum and oxygen. The obtained powder materials can be used for the manufacture of powder electrodes used in welding and surfacing of a wide range of parts.

Spheroidization of low-cost alumina powders for the preparation of high-flux flat-sheet ceramic membranes

Two kinds of low-cost alumina powders with irregular morphology were pretreated by spheroidization and the two spherical powders were used to prepare high-flux flat-sheet support and microfiltration (MF) membrane with high separation accuracy, respectively. It was found that the spheroidization pretreatment not only unified the morphology of alumina powder particles into spherical shape, but also narrowed the particle size distribution of the powders, which both were conducive to optimizing the performance of the as-prepared ceramic membranes. After sintering at 1350 °C, the open porosity, bending strength, average pore diameter and pure water permeability of alumina flat-sheet support from spheroidized alumina coarse powder were 44.3%, 36.3 MPa, 3.3 μm and 3240 L/h m2 bar, respectively. The slurry derived from spheroidized alumina fine powder was dip-coated on the flat-sheet support to prepare MF membrane. The crack-free MF membrane with a thickness of 23.5 μm had a pore diameter of 0.12 μm and pure water permeability of 850 L/h m2 bar. Additionally, the elaborated MF membrane was used to clarify aqueous suspension of carbon black with the maximum rejection rate of up to 99.7%, exhibiting excellent cleaning performance at the same time by completely restore the virgin permeate flux after backwash.