Ultrafine Aluminum Research Articles

Incidence of cardiovascular disease in a cohort of mine workers exposed to ultrafine aluminum powder in Ontario, Canada.

A retrospective cohort study was conducted to estimate associations between an ultrafine aluminum powder, McIntyre Powder (MP), and cardiovascular disease incidence in a cohort of mine workers from Ontario, Canada. Disease outcomes included ischemic heart disease (IHD), acute myocardial infarction (AMI), congestive heart failure (CHF), and strokes and transient ischemic attacks (STIA). Using work history records from the Ontario Mining Master File (MMF) mine workers were followed for disease incidence in administrative health records. The analysis included 25,813 mine workers who were exposed to MP between 1943 and 1979 and followed for cardiovascular disease (CVD) diagnoses between 2006 and 2018. Cardiovascular disease cases were ascertained using physician, hospital, and ambulatory care records. Poisson regression models were used to estimate age and birth-year adjusted incidence rate ratios (RR) and 95% confidence intervals (CI) for associations between MP exposure and CVD outcomes. Ever-exposure to MP was positively associated with modest increases in the incidence rate of IHD, AMI, and CHF, but not STIA, using both assessment approaches. Duration of self-reported MP exposure was positively associated with monotonically increasing rates of IHD and AMI compared to never-exposed miners, with the greatest association observed among miners with >20 years of exposure (for IHD: RR 1.24, 95% CI: 0.91-1.68; and for AMI: RR 1.52, 95% CI 1.01-2.28). Mine workers ever-exposed to MP had modestly elevated rates of CVD. The rate of CVD diagnoses appeared to increase with longer duration of exposure when assessed by both self-reported exposure and through historical records.

A model for the combustion behavior of AP/HTPB propellant containing ultrafine aluminum

AbstractNano‐aluminum, renowned for its remarkable efficacy in augmenting propulsion efficiency and regressive velocity, stands out as a compelling choice for incorporation into heterogeneous propellant compositions. Nevertheless, the considerable expense of this ultrafine aluminum variant, coupled with the inherent hazards associated with conducting propellant trials, may deter extensive allocation of resources and efforts towards the intricate processes of amalgamation, molding, and comprehensive analysis of the combustion characteristics of freshly devised propellant blends. To provide theoretical support for predicting the chemical properties of nano‐Al composite propellant, we establish a numerical framework to study the combustion characteristics under the working environment of a solid rocket motor. A new five‐step kinetic mechanism is developed in this model to describe the reaction process in the gas phase while accounting for heat conduction, radiative effects, and non‐planar moving surfaces. The comparison between our theoretical work and experimental results confirms that making no distinction among Al particle sizes below 3 μm is reasonable. Finally, the effects of nano‐Al on combustion, burning rate variation, and temperature sensitivity are analyzed in detail.

Efficient production of kilometer-scale ultrafine aluminum wire with superior strength and electrical conductivity

The rapid development of new energy vehicles has generated considerable interest in the efficient production of ultrafine aluminum electronic wiring harnesses with superior strength and electrical conductivity (EC). However, achieving a balance between strength and EC/ductility remains a challenge. To overcome the trade-off relation, we precisely controlled the grain size and grain boundary structure by using ultrafine aluminum powders (∼1 μm) as the starting material, and introduced dislocations into the as-sintered sample to enhance the strain rate sensitivity via cold deformation. In the cold-deformed sample, a unique mechanical response was observed: the elongation increased with deformation. Meanwhile, the strength and EC maintained to be a high level. Based on the unique properties, we successfully fabricated kilometer-scale ultrafine aluminum wire (0.2 mm in diameter) by cold deformation without any intermediate annealing, realizing high strength (206 MPa) and high EC (59.1%IACS, International Annealed Copper Standard) simultaneously. Our work provides a new concept and a new processing route to efficiently produce ultrafine aluminum electronic wiring harness with excellent properties.

Research on explosion hazard and prevention of ultrafine aluminium powder based on orthogonal matrix analysis

This study investigated the coupled effects of multiple factors, namely dust mass concentration, dust particle size, and oxygen volume concentration, on the explosion intensity of ultrafine aluminium powder (UAP); the study determined the weight of each factor by using an orthogonal experimental design. Explosion intensity was evaluated using the maximum explosion pressure (MEP) and MEP rise rate (MEPR) of UAP. Explosion tests were performed using a 20 L standard spherical explosive device. A weight matrix for the explosion intensity was calculated. The results revealed that the MEP and MEPR increased most with the oxygen volume concentration. They also increased with the dust mass concentration to a lesser extent. The dust particle size had the smallest effect; the MEP and MEPR initially increased and then decreased as the particle size increased. The weights for oxygen volume concentration, dust mass concentration, and dust particle size were 69.191%, 18.761%, and 13.038%, respectively. The optimal factor combination for minimizing intensity was a dust mass concentration of 500 g/m3, an oxygen volume concentration of 9 vol%, and a dust particle size of 0.172 µm. On the basis of these findings, the study proposes industrial explosion-proofing countermeasures to increase the safety of production in aluminium-related enterprises.

Detoxification of chromium slag using corn stalk for the hierarchical preparation of ultrafine aluminum hydroxide and iron hydroxide

The harmless treatment and resource utilization of chromite ore processing residue (COPR), a consequential byproduct of chromate production, carry profound significance. In this study, corn stalk, an agricultural waste, was used to generate reducing substances through high-temperature and vacuum treatments and was successfully used to detoxify COPR. The acid leaching method combined with multi-step purification was employed to extract iron and aluminum, two crucial metallic elements, from COPR. The successful preparation of iron hydroxide and ultrafine aluminum hydroxide (ATH) was achieved. The prepared ATH has an average particle size of 8.124 μm, with a highly uniform distribution, enabling it to be a promising environmentally friendly inorganic flame retardant. This study not only effectively addresses the issue of pollution caused by COPR but also presents a novel approach to utilizing industrial and agricultural wastes, thereby promoting the maximization of resource utilization.

AP assembled on ultrafine aluminum particle and its application to NEPE propellant

Coating modification is an important way to enhance the reactivity of aluminum powder. In this paper, ammonium perchlorate and aluminum powder were assembled into energetic microunits by liquid deposition method. Spherical particles with AP as shell and ultrafine aluminum powder as the core (Al@AP) were gained. The micromorphology results show that the coated particles are about 5 μm, and the coating layer is evenly distributed on the outer surface of aluminum powder, indicating a complete coating. The energetic microunits were implanted into the nitrate ester plasticizing adhesive system (NEPE) as solid phase fillers. The effect of filler on the rheological properties, safety, mechanical properties, thermal reaction and energy properties of the system was analyzed by comparing with the raw aluminum filler. The test results show that the rheological properties, mechanical properties and pressure index of NEPE containing system Al@AP meets the requirements of solid propellant charging. Compared with Al based propellant, the mechanical sensitivity and thermal sensitivity are decreased, the safety is better, and the explosion heat of the propellant is increased by 7.8%. The engine test shows that the specific impulse is increased by 1.2 s. Al@AP can improve the energy output and safety of NEPE propellant, and has potential application prospects in high-energy propellants.

Synergistic inhibitory effect of sodium bicarbonate and melamine cyanurate on the thermal reaction of ultrafine aluminium powder

In this study, the thermal reaction characteristics of ultrafine aluminium powder (UAP) and its composites containing different mass proportions of sodium bicarbonate (SBC), melamine cyanurate (MCA), or SBC and MCA were investigated through synchronous thermal analysis. The results indicated that SBC and MCA remarkably inhibited the thermal reaction of UAP. With an increase in the mass proportion of the inhibitor (i.e., SBC, MCA, or SBC and MCA), the thermogravimetry and differential thermogravimetry increased, and the heat release decreased, which strengthened the inhibition of a UAP explosion. For UAP + SBC + MCA powder with a mass proportion of 1:1:1, SBC and MCA had a strong explosion inhibition effect on UAP explosion near 660 °C. Finally, the synergistic inhibition effect of SBC and MCA on the thermal reaction of UAP was clarified, and physical and chemical inhibitory effects were observed. Inhibitor pyrolysis resulted in the absorption of the heat released through UAP oxidation and the generation of inert gas, which diluted the oxygen concentration; thus, the thermal reaction of UAP was inhibited.

Investigation of the wear resistance of in-situ Al-Ti composites fabricated by mechanical alloying and hot extrusion

ABSTRACT In this research, the wear behaviour of Al-20%Ti composites, fabricated by mechanical alloying and hot extrusion at different conditions, was investigated using the pin-on-disc method. A high-energy vibratory mill was applied to produce the nanocomposite (Al-20Ti-4hrV) and nanocrystalline (NC) Al samples, while a low-energy planetary mill was used to produce the other composites (Al-20Ti-20hrP and Al-20Ti-60hrP). To examine the microstructure and worn surface of specimens, optical microscopy and scanning electron microscopy were performed. To estimate the mechanical properties of the samples, their density and Brinell hardness were measured. The use of a high-energy vibratory mill caused the formation of an ultrafine aluminium matrix with in-situ nanometric intermetallic particles in the Al-20Ti-4hrV sample. As a result, the highest relative density and hardness and the best wear resistance were obtained in the Al-20Ti-4hrV sample. The application of the low-energy planetary mill led to the formation of flaky particles; accordingly, low relative density, poor mechanical properties and wear resistance in Al-20Ti-20hrP and Al-20Ti-60hrP samples were observed. The dominant wear mechanisms for Al-20Ti-4hrV and NC Al samples were identified as microploughing, adhesion and oxidation in the mild wear regime, whereas those of the Al-20Ti-20hrP and Al-20Ti-60hrP samples were mainly adhesion wear mechanism and inconsiderable delamination in the mild wear regime. The highest hardness and wear resistance were obtained for the nanocomposite sample owing to nanometric Al3Ti reinforcement, nanocrystalline Al matrix and good adhesion between particles and the matrix. This study confirmed that the nanocomposite production method presented in this research is suitable for wear-resistance applications.

The mechanism of nano-network structure formed by friction-induced pozzolanic silicate

Friction transfer film is one of the influencing factors in the evolution of the subsurface microstructure of frictional contact materials. An iron-poor friction transfer film of aluminum-based composites with silicon carbide and pozzolanic silicate particles as the reinforcing phase was investigated utilizing scanning electron microscope, focused ion beams, transmission electron microscopy and energy dispersive X-ray analysis. The results showed that the friction transfer film contained ultra-fine aluminum, nano-aluminum, broken silicon carbide and silicate particles, as well as in-situ generated andradite and gismondine, which self-assemble into a nano-network structure to support the formation of the friction transfer film. Thermodynamic calculations and high-resolution transmission electron microscopy clarified the formation mechanism of andradite and gismondine.

Ultrafine aluminum sulfide nanocrystals anchored on two-dimensional carbon sheets for high-performance lithium-ion batteries.

Aluminum sulfide is a novel light metal sulfide, which possesses multiple advantages for lithium storage, including high theoretical capacity, proper discharge potential and good conductivity. However, much research has not been done in areas related to light metal sulfide materials. Herein, we synthesized Al2S3/C nanocomposite by a facile one-step ball milling method. This simple method not only effectively achieves the uniform composite of Al2S3 nanoparticles and carbon sheets, but also controls Al2S3 into ultrafine nanocrystals. Al2S3/C electrode demonstrates very outstanding lithium storage performance with large reversible specific capacity (1249 mAh g-1 at 100mAg-1), remarkable rate capability (670 mAh g-1 at 5000mAg-1) and superior long-cycling stability (retaining 850 mAh g-1 even after 1000 cycles at 1000mAg-1). Moreover, the reversible lithium storage behavior and excellent diffusion kinetics of Al2S3/C are unveiled deeply. This work provides an inspiration to develop new light metal sulfide materials for the next-generation high-performance lithium ion battery.

Activated Sintering of Cr2O3-Based Composites by Hot Pressing

The paper presents and discusses questions on structure formation during the sintering process of Cr2O3-based composites using the hot pressing method, when a chemical reaction between the components takes place. The task was difficult because Cr2O3 decomposes when sintered at temperatures above 1300 °C. The proposed novel method allowed for interaction between aluminum and chromia, thus avoiding the decomposition of the latter. Here, ultrafine aluminum powder played the role of the active agent forming a liquid phase and reacting with Cr2O3. The appearance of the solid solutions of (Cr,Al)2O3 with different stoichiometry of Cr and Al depended on the aluminum content in the initial mixture. The solid solution significantly strengthened boundaries between composite phases, resulting in the composite material of high fracture toughness between 5 and 7 MPa m½ and bending strength of ca. 500 MPa. The best mechanical properties exhibited the cermet with 22 wt.% of the restored chromium.

Study of the nano-network structure in the friction transfer film of the hybrid reinforced aluminum-based composite

Hybrid reinforced aluminum-based composites with a silicate component with pozzolanic activity and silicon carbide ceramic particles as reinforcement phases can form an iron-poor friction transfer film during the friction process, thereby making the aluminum-based composites exhibit a high friction coefficient and a low wear rate characteristics. The phase composition in the friction transfer film was investigated utilizing focused ion beams, transmission electron microscopy, and energy-dispersive X-ray analysis. The results showed that the friction transfer film was mainly composed of nanosized aluminum, ultra-fine aluminum, and crushed silicate particles, which interwove into a nano-network structure to protect the matrix and improve the friction performance.

A novel green process for the synthesis of high-whiteness and ultrafine aluminum hydroxide powder from secondary aluminum dross

Secondary aluminum dross (SAD) is a dangerous pollutant as well as a valuable resource. About 95% SAD is disposed by stockpiling on the spot due to its complex composition and technical limitations, causing severe ecological damage and public health threat. A novel green process was developed herein for the preparation of high-whiteness and ultrafine Al(OH) 3 from SAD. The SAD mixed with Na 2 CO 3 and CaO was dry molded and roasted, then the Al and Na elements were efficiently extracted to produce a high-value product. The phase transition path and toxic element transfer behavior of the roasting and leaching processes were investigated by thermodynamic analysis, X-ray diffraction analysis, X-ray fluorescence spectroscopy, scanning electron microscopy, and chemical analysis. The recovery of Al and Na reached 95.12% and 97.33%, respectively, under the optimum conditions (roasting temperature of 1150 °C, Na 2 CO 3 /SAD mass ratio of 80%, CaO/SAD mass ratio of 24%, and roasting time of 1 h). The removal rates of Cl, N, and soluble F in the roasting product were 95.38%, 98.68%, and 98.57%, respectively. The test results showed a purity of 99.17%, a whiteness of 98.1 and an average volume particle size D(4, 3) of 2.053 μm for the prepared high-whiteness and ultrafine Al(OH) 3 powder with uniform powder morphology. A cost analysis based on laboratory-scale data and market price indicates that a net profit of $431.6 can be obtained by recycling one ton SAD. The detoxification of SAD and the valuable Al element extraction can be achieved effectively by the green process. • A green and economic process for recycling secondary aluminum dross is proposed. • Dry molded roasting achieves both detoxification and recycling of aluminum dross. • Various factors affecting Al and Na recovery are evaluated and optimized. • Migration behavior of toxic elements in roasting process is investigated. • High-whiteness and ultrafine Al(OH) 3 product shows excellent physical properties.

Preparation of hydrotalcite crystals using impinging jet mixers

The active pharmaceutical ingredient hydrotalcite (aluminium magnesium carbonate hydroxide hydrate) is an antacid marketed either as suspensions or tablets. It is necessary to have stringent control on multiple crystal properties not only due to the demand on high quality of the medicine but also as a result of the need to improving the efficiency of down-stream processing e.g. of filtration of crystals. This work investigated impinging jet mixers integrated with a stirred tank for the preparation of hydrotalcite crystals, using aluminum sulfate, sodium carbonate and porous magnesium hydroxide as the raw materials. The new process design has shown superior performance to the commonly used stirred tanks. The hydrotalcite crystals were of narrow particle size distribution, large size and high bulk density, high purity, and uniform morphology. An attempt was also made at trying to develop mechanistic understanding of the reactive crystallization processes taking place inside the integrated impinging jet mixers - stirred tank equipment. Firstly the impinging jet mixers enabled generation of ultrafine aluminum hydroxide particles during the reactive precipitation between sodium carbonate and aluminum sulfate aqueous solutions. Then, the ultrafine aluminum hydroxide accumulated in the shallow layer of the porous magnesium hydroxide particles and gradually filled the porous particles under the stirring effect of the tank reactor. Meanwhile, the magnesium hydroxide gradually reacted with aluminum hydroxide to generate hydrotalcite from the surface towards the inside of the particles, and finally produced the high quality hydrotalcite crystals.

Sustainable manufacturing of ultra-fine aluminium alloy 6101 wires using controlled high levels of mechanical strain and finite element modeling

The evolution of grain size and component mechanical behaviour are fundamental aspects to analyse and control when manufacturing processes are considered. In this context, severe plastic deformation (SPD) processes, in which a high shear strain is imposed on the material, are recognized as the main techniques to achieve microstructural changes and material strengthening by the recrystallization, attracting both academic and industrial investigation activities. At the same time, nowadays, sustainable manufacturing design is one of the main responsibilities of the researchers looking at UN2030 agenda and the modern industrial paradigms. In this paper a new severe SPD process is proposed with the aim to steer manufacturing to fourth industrial revolution using some of Industry 4.0 pillars. In particular, additive manufacturing (AM) and numerical simulations were setup as controlling and monitoring techniques in manufacturing process of wires. Strengthening effect (yield and ultimate tensile strength, plasticity and hardness) and microstructural evolution (continuous dynamic recrystallization -CDRX-) due to severe plastic deformation were experimentally analysed and numerically investigated by an innovative finite element (FE) model able to validate the effectiveness of a properly modified process for ultra-fine aluminium alloy AA6101 wires production designed with the aim to avoid any post manufacturing costly thermal treatment. The study provides an accurate experimental study and numerical prediction of the thermo-mechanical and microstructural phenomena that occur during an advanced large plastic deformation process; it shows how the combination of smart manufacturing and simulations control represents the key to renew the traditional manufacturing methods in the perspective of the Industry 4.0, connecting and integrating the manufacturing process for the industrial evolution in production.

Combustion Characteristics of Nanoaluminium-Based Composite Solid Propellants: An Overview

The nanosized powders have gained attention to produce materials exhibiting novel properties and for developing advanced technologies as well. Nanosized materials exhibit substantially favourable qualities such as improved catalytic activity, augmentation in reactivity, and reduction in melting temperature. Several researchers have pointed out the influence of ultrafine aluminium (∼100 nm) and nanoaluminium (<100 nm) on burning rates of the composite solid propellants comprising AP as the oxidizer. The inclusion of ultrafine aluminium augments the burning rate of the composite propellants by means of aluminium particle’s ignition through the leading edge flames (LEFs) anchoring above the interfaces of coarse AP/binder and the binder/fine AP matrix flames as well. The sandwiches containing 15% of nanoaluminium solid loading in the binder lamina exhibit the burning rate increment of about 20–30%. It was noticed that the burning rate increment with nanoaluminium is around 1.6–2 times with respect to the propellant compositions without aluminium for various pressure ranges and also for different micron-sized aluminium particles in the composition. The addition of nano-Al in the composite propellants washes out the plateaus in burning rate trends that are perceived from non-Al and microaluminized propellants; however, the burning rates of nanoaluminized propellants demonstrate low-pressure exponents at the higher pressure level. The contribution of catalysts towards the burning rate in the nanoaluminized propellants is reduced and is apparent only with nanosized catalysts. The near-surface nanoaluminium ignition and diffusion-limited nano-Al particle combustion contribute heat to the propellant-regressing surface that dominates the burning rate. Quench-collected nanoaluminized propellant residues display notable agglomeration, although a minor percentage of the agglomerates are in the 1–3 µm range; however, these are within 5 µm in size. Percentage of elongation and initial modulus of the propellant are decreased when the coarse AP particles are replaced by aluminium in the propellant composition.

Insight into ultra-refined grains of aluminum matrix composites via deformation-driven metallurgy

Ultra-refined grains were obtained in few-layer graphene nanoplatelets reinforced aluminum matrix composites via deformation-driven metallurgy under coupled thermo-mechanical effect. Fragmentation, thinning and re-dispersion of the reinforcements accelerated the nucleation of recrystallized grains and inhibited the migration of grain boundaries. The synergy grain refinement mechanism led to a greatly refined microstructure with an average grain size of 267.0 nm, which was much smaller than the grain size of conventional aluminum matrix composites to realize high strengthening-toughening efficiency. This novel preparation route showed the capacity of developing ultra-fine aluminum matrix composites with the exceptional grain refinement towards ultra-lightweight design.

Regimes and critical conditions of detonation propagation in expanding channels in gas suspensions of ultrafine aluminum particles

Under study are the regimes of detonation propagation in channels with linear expansion filled with monodisperse mixtures of oxygen and ultrafine aluminum particles of various loading; the methods of numerical simulations are used. The detonation combustion of submicron aluminum particles is described within the semi-empirical model of reduced kinetics with due regard to the transition from the diffusion-limited regime of combustion to the kinetic one. Waves of both planar and developed cellular detonation are considered as initial conditions. The characteristics of the main flow regimes are obtained and described: the subcritical (detonation failure), critical (detonation failure in some part of the channel) and supercritical (continuous detonation propagation). The maps of flow regimes in suspensions of 200-nm – 400-nm particles are presented in the plane of parameters: the channel width, expansion angle. The obtained critical conditions are similar to those observed in the gas detonation. The critical channel width linearly depends on the expansion angle up to a first critical value (35°–38°). Behind the second critical value (50°), the channel width is independent on the expansion angle. Between these values, there is an interval of nonmonotonicity similar to the detonation of micro-sized suspensions of aluminum particles. The effect of particle loading on the critical conditions in poor mixtures appears in the form of a sharp increase in the critical channel width, if the mass concentration falls below 0.25.

Effect of Ultrafine Grains on the Coating Reaction and Anticorrosion Performance of Anodized Pure Aluminum

This work analyzes the effects of ultrafine aluminum (Al) grains on the anodizing coating reaction and anticorrosion performance of anodized industrial pure Al. Equal-channel angular pressing (ECAP) was applied to cast pure Al continuously for 16 passes at room temperature, and its average grain size was dramatically refined to about 1.5 μm. The ultrafine-grain (UFG) pure Al was further anodized with a cast sample via a parallel anodizing circuit at a constant total input current. Benefited by the higher volume fraction of grain boundaries and higher internal energy of the UFG substrate, the anodizing process of the ECAP-processed pure Al was significantly accelerated, showing a more intense initial anodizing reaction, a faster initial coating thickening, and much earlier porous-layer formation compared to the cast sample. As the anodizing reaction continued, the newly formed thicker coating of the ECAP-coated sample significantly hindered the diffusion process, weakening the thermodynamic advantage and decreasing the anodizing current of the ECAP-processed sample. During the entire anodizing duration, the ECAP-processed pure Al experienced gradually decreased anodizing current, while the cast sample experienced increased anodizing current. Because of the more total reaction, the ECAP-coated sample always maintained a relatively thicker coating and better anticorrosion performance during the entire anodizing duration.

Ultra‐Fine Aluminium Characterization and its Agglomeration Features in Solid Propellant Combustion for Various Quenched Distance and Pressure

AbstractAddition of micrometer‐sized aluminium powder in solid propellant increases the specific impulse whereas it also contributes to thrust loss due to two‐phase flow. Aluminium particles form large sized agglomerates during propellant burning. In this context, agglomeration feature of ultra‐fine aluminium (UFAL) in solid propellant combustion is investigated using experimental study. The synthesized UFAL powder is used with the intensity weighted harmonic mean size of 438 nm which is produced by RF induction plasma method. The morphology and purity of the UFAL is verified using SEM and EDAX studies respectively. The ultra‐fine particles are also characterized using gas volumetric method, surface area measurement and XRD analysis. Quench particle collection technique is adopted to estimate the aluminium agglomerate measurement over the pressure ranges from 2 MPa to 8 MPa. The flame quenching distance from the propellant burning surface is varied from 5 mm to 71 mm to estimate the effect on agglomerate size. The inherited residual forces of UFAL strongly influences the agglomeration process, and also the aluminium agglomerate sizes vary from propellant burning surface towards the complete aluminium combustion. The XRD and XPS results of the agglomerates show that the aluminium content decreases and alumina content increases far away from the burning surface, invariably represents the initiation of combustion process over the considered quenching distances. UFAL powder exhibits significant agglomeration with the size ranging from 11–21 μm. This will substantially benefit from exhaust signature point of view and also reduction in two‐phase flow losses to thrust in contrast to micron sized‐aluminium particles in propellant which displays large sized aluminium agglomerates.