Al Nanoparticles Research Articles

Phase transition behaviors of Al nanoparticles with low oxidation degree: A molecular dynamics study

In this study, the ReaxFF reactive force field is applied to simulate the melting and annealing behaviors of aluminum (Al) nanoparticles (ANP) by molecular dynamics (MD) simulations. Potential energy, specific heat and FCC lattice number are used to study the thermal behavior of the entire phase transition process. First, the melting and solidification process of 3[Formula: see text]nm cubic Al and Al2O3 models under constant-pressure/temperature ensemble (NPT) system was simulated without boundary, and the steady-state simulation was discussed at specific temperature points. The non-boundary simulation proved the effectiveness of the Reaxff reactive force field for ANP phase transition simulations. It is confirmed that the physical properties of Al and Al2O3 could be effectively reflected in the MD simulations. ANP with low oxidation degree cannot be completely ignored in engineering applications. The existence of oxide layer hinders the annealing behavior. Therefore, this study also carried out an additional simulation process of 6 nm ANP and its oxide particles in canonical ensemble (NVT). Those obtained results show that a small amount of oxide layer can greatly change the thermal properties of ANP. If the surface of ANP is isolated, then its melting point could be increased by at least 30[Formula: see text]K.

Study on the Combustion Characteristics of Ethanol Nanofuel

This study investigates the thermophysical and combustion characteristics of ethanol-based nanofuels incorporating aluminum (Al) and nickel-coated aluminum (Ni-Al). The nanofuels are prepared with varying concentrations of Al and Ni-Al nanoparticles. The results reveal that, despite the non-uniform deposition of nickel on Al particles, a sintering reaction occurs between the two materials. Nanofuels containing Al exhibit unburned Al residues after combustion, while nanofuels containing Ni-Al show intense AlO radical emission during combustion termination, indicating enhanced combustion. However, nanofuels containing Ni-Al demonstrate a lower burning rate compared to Al nanofuels, attributed to the lower thermal conductivity of nickel. Overall, the findings suggest that nanofuels containing Ni-Al possess higher energy potential but extended combustion duration.

Single-Particle ICP-MS/MS Application for Routine Screening of Nanoparticles Present in Powder-Based Facial Cosmetics.

The short- and long-term impacts of nanoparticles (NPs) in consumer products are not fully understood. Current European Union (EU) regulations enforce transparency on products containing NPs in cosmetic formulations; however, those set by the U.S. Food and Drug Administration are lacking. This study demonstrates the potential of single-particle inductively coupled plasma tandem mass spectrometry (spICP-MS/MS) as a screening method for NPs present in powder-based facial cosmetics (herein referred to as FCs). A proposed spICP-MS/MS method is presented along with recommended criteria to confirm particle presence and particle detection thresholds in seven FCs. FC products of varying colors, market values, and applications were analyzed for the presence of Bi, Cr, Mg, Mn, Pb, Sn, Ag, Al, and Zn NPs based on their ingredient lists as well as those commonly used in cosmetic formulations. The presence of NPs smaller than 100 nm was observed in all FC samples, and no correlations with their presence and market value were observed. Here, we report qualitative and semi-quantitative results for seven FC samples ranging in color, brand, and shimmer.

Mechanistic study of the influence of aluminum nanoparticles on the pressure sensitivity of 1,3,5-trinitro1,3,5-triazinane (RDX) thermal decomposition

The incorporation of Al nanoparticles (Al NPs) into 1,3,5-trinitro1,3,5-triazinane (RDX) can catalyze its thermal decomposition and reduce the pressure exponent (n) of solid propellants. However, the underlying reaction mechanism at a deeper level remains unclear. In this study, the reaction processes of Al NPs catalyzing the thermal decomposition of RDX under different initial pressures were investigated by utilizing the ReaxFF molecular dynamics (ReaxFF-MD) simulations combined with DFT calculations, and the influence mechanism of Al NPs on the pressure sensitivity of RDX thermal decomposition was revealed from various perspectives. In the initial stage of the reaction, unlike the nitro group dissociation observed in pure RDX, the incorporation of Al NPs alters the initial decomposition pathway of RDX, making it more easily adsorbed on the surface of Al and enhancing the early-stage decomposition rate. Furthermore, Al NPs exhibit higher catalytic activity in low-pressure systems. In the later stage, because of the massive adsorption of free radicals generated from RDX decomposition on the surface of Al NPs, the decomposition rate of RDX decreases significantly, especially in high-pressure systems. Consequently, Al NPs synergistically reduce the pressure sensitivity of the RDX thermal decomposition from two different perspectives. Compared to traditional experimental research or single RDX simulation studies, this work further explores the interaction between Al and RDX from a microscopic perspective, addressing the gap in the field of the influence mechanisms of Al NPs on the pressure sensitivity of RDX thermal decomposition. It also establishes a theoretical foundation for the practical application of Al@RDX fuels.

Combustion Behavior of Ethanol/Ether Molecules-Coated Al Nanoparticles with H2O Vapor by Non-equilibrium Molecular Dynamics Simulations.

Al nanoparticles (ANPs) have high reactivity and can improve the system's combustion performance. However, ANPs are susceptible to inactivation by external oxidants. Here, we use ethanol and ether molecules to coat ANPs and then compare and discuss the combustion process between coated ANPs and bare ANPs. Our results show that the ethanol/ether coating can adsorb more H2O molecules and increase the active Al atom number and the Al core area in the ignition stage. The combustion phase can be divided into four stages according to the rate of the combustion temperature. The ethanol/ether coating can enable ANPs to deliver a better combustion performance, reducing the ignition delay time of particles, greatly increasing the combustion temperature, and making the whole system enter the gas phase combustion stage. These will enable the ethanol/ether-ANPs systems to release more energy and improve the combustion efficiency of the system.

Preparation and Superhydrophobicity of Nano-Al-Coated Wood by Magnetron Sputtering Based on Glow-Discharge Plasma

A superhydrophobic coating on wood can effectively improve the hydrophobicity and service life of wood. In this study, an Al superhydrophobic nano-coating was constructed on the transversal section of poplar wood by magnetron sputtering based on glow-discharge plasma. The structure, microscopic morphology, surface elements, and hydrophobic properties were characterized and tested. When coated for 20 s, the water contact angle on the sample surface can reach 148.9°. When coated for 30 min, the Al-coated wood had a contact angle of 157.3°, which could maintain excellent superhydrophobic properties for 300 s. The sputtered Al nanoparticles were uniformly distributed on the wood surface and formed nanoclusters. Plenty of voids between the clusters can trap air and block contact between water droplets and the coating, making the coating obtain superhydrophobic properties. When the coating time was 60 min, the characteristic peak of the Al (111) crystal plane appeared at 38.4°, while the intensities of (101), (002), and (040) peaks of cellulose were reduced. In conclusion, magnetron sputtering was used to deposit a superhydrophobic coating on wood without low surface free energy agents. Furthermore, this research provides new inspirations for the physical modification of wood and the construction of superhydrophobic coatings on wood.

Combustion of Al Nanoparticles Coated with Nitrocellulose/Ethanol/Ether Molecules by Equilibrium Molecular Dynamics Simulations.

Al nanoparticles (ANPs) have high reactivity, but they are easily inactivated by external oxidants. To improve their surface properties, we coat ANPs with a nitrocellulose (NC)/ethanol/ether solution. Comparative discussions are raised from the coating to the combustion process. Our results show that NC/ethanol/ether forms a dense coating layer on the surface of annealed ANPs and passivates ANPs through physical and chemical adsorption. The coating layer can block the contact between the active Al atoms and O2 molecules at low temperatures. In the ignition phase, the NC/ethanol/ether coating layer can increase the density of the O2 molecules around the ANPs and the surface temperature of ANPs. At the end of the ignition phase, the number of O atoms adsorbed on the surface of NC/ethanol/ether coating-passivated ANPs (csANPs) and NC/ethanol/ether coating-annealed ANPs (cANPs) increased by about 60 and 50%, respectively, compared with passivated ANPs (sANPs). Since the desorption and diffusion of the coating layer will expose more reaction sites, ANPs have a shorter ignition delay and a lower ignition temperature. According to the change in atomic displacement, the combustion stage can be divided into three stages: surface oxidation/core melting diffusion, combustion inward propagation, and uniform combustion. The decomposition of NC molecules can increase the combustion speed, combustion time, and efficiency of ANPs. Such improvement will enable ANPs to obtain better storage and combustion performance and play a stronger role in the field of energetic materials.

Efficiency enhancement of GaAs nanowire array-based solar cell by plasmonic Al nanoparticles

Gallium arsenide (GaAs) nanowire (NW) solar cells (SCs) have piqued the interest of researchers because they exhibit superior light-harvesting and anti-reflection properties along with reduced material consumption compared to their planar counterparts. However, the high surface-to-volume ratio associated with these NWs degrades their performance in practical applications. Light trapping is considered one of the most crucial parameters for producing low-cost high-efficiency NW-SCs. Thus, numerous light-trapping strategies have been explored, among which surface plasmon resonance (SPR) based optical absorption enhancement using metal nanoparticles (NPs) has emerged as a potential method. The role of plasmonic aluminum (Al) NPs in the efficiency enhancement of GaAs NW SC has not yet been explored. Therefore, in this study, a vertically aligned GaAs NW SC structure incorporated with Al NPs has been investigated using the finite-difference time-domain (FDTD) method. The sidewalls of GaAs NWs are embellished with uniformly arranged Al NPs with diameters ranging from 30 to 60 nm. The excitation of localized surface plasmon resonance in metal NPs results in significant light absorption enhancement at the GaAs near-band of the proposed structure. The results demonstrate that even with a low aspect ratio (D/P) of 0.3, optimizing the geometrical parameters of the NPs results in a 41.96 % increase in power conversion efficiency (PCE) and a 45 % increase in absorption efficiency at 800 nm for the proposed structure when compared to the bare structure. Hence, our suggested structure which utilizes the light-trapping mechanism of Al NPs proves to be a cost-effective and promising material combination for high-efficiency nanoscale SCs.

Atmospheric Microplasma Treatment Based on Magnetically Controlled Fe–Al Dynamic Platform for Organic and Biomaterials Surface Modification

By exploiting the physical effect of the electron emission from a thermionic source in combination with a magnetically controlled Fe–Al dynamic platform to assist electrical discharge, we generated atmospheric microplasma (AM). The electrical characteristics of microplasma discharge-induced cold atmospheric plasma in combination with a magnetically controlled Fe–Al dynamic platform in open air were evaluated. The surface analysis of organic wheat seeds was investigated at two steps: (1) the coating effect of an Al nanoparticle with an electrons drift toward the seed surface along the direction of an electric field and (2) inelastic collision with secondary electrons moving from the cathode in the presence of an electric field. Using SEM microscopy analysis, it was found that plasma affects seed surface topography and apparent contact angle (ACA). The effect of atmospheric microplasma treatment leads to seed surface modification by the manifestation of fine mesh structures on the seed surface. Well-established AM technology will garner interest in agriculture and biomaterials coatings applications.

Molecular dynamics study on the thermal decomposition of 1,3,5-trinitro-1,3,5-triazinane (RDX) catalyzed by aluminum nanoparticles with different contents

The mechanism of thermal decomposition of 1,3,5-trinitro-1,3,5-triazinane (RDX) catalyzed by nano-sized aluminum powder remains unclarified. In the present study, reactive molecular dynamics simulations using the parameterized reactive force field with low gradient correction (ReaxFF-lg) were conducted to study the microscale process of the RDX thermal decomposition catalyzed by different Al contents, and the density functional theory calculations were used to analyze the initial decomposition pathways of RDX on the Al surface. The thermal disintegration and the released energy of RDX are significantly facilitated by an increase in Al concentration at a lower level and the optimal value is around 35 wt%, while a higher concentration of Al will lead to an opposite effect. The dissociation of nitro group is the most probable initial reaction pathway for RDX decomposition on the Al surface. In addition, the evolutions of Al-containing clusters, key intermediates, and final products were analyzed, providing more information about this reaction. The findings suggest that the addition of Al nanoparticles improves the properties of RDX-based explosives, but the optimal amount of Al is critical for achieving the desired effects. The detailed analysis of the reaction mechanism and intermediate products provides valuable insights into the underlying mechanisms of the Al/RDX system.

Microstructure evolution and mechanical properties of Al doped ta-C films prepared by filtered cathodic vacuum arc

Al-doped tetrahedral amorphous carbon (ta-C) films were prepared by filtered cathodic vacuum arc technique. Effect of Al content on the structure and properties of the ta-C film were systematically investigated. Results showed that Al content in films increased from 0 to 39.5 at. % as the Al target current altered from 0 to 2 A. Without Al doping, ta-C film mainly presented amorphous characteristic with disordered arrangement and compact structure. With a small amount of Al doping, the film maintained the amorphous phase structure, and Al atoms mainly existed in the carbon tetrahedral interstitial space in the form of solid solution. At high Al doping content, the formed Al nanoparticles embedded in the carbon matrix network. Meanwhile, the addition of Al could promote the graphitization of films. The residual stress of ta-C films decreased gradually with increase of Al content. Furthermore, the hardness and elastic modulus of films also decreased with increasing Al content. That's ascribed to the reduction of residual stress and graphitization of the carbon structure. In addition, the ta-C film with Al addition could effectively improve the friction and wear properties of films at both room and high temperature. The friction coefficient decreased with the increase of Al content at room temperature (RT). At 400 °C, the film containing 7.6 at. % Al obtained the lowest friction coefficient and wear rate, corresponding to the values of 0.29 and 12.3 × 10−8 mm3/N⋅m, respectively.

Effect of self-interaction corrections (SIC) on physical properties of small Al, Ag and Ni nanoparticles

The density functional method with self-interaction corrections (SIC) has been used to calculate the static dipole polarizations and surface plasmons of small metallic nanoparticles. It turns out that SIC lower the static dipole polarization per atom in the case of Al clusters when decreasing the number of atoms. In the case of silver, the dipole plasmon like excitation energies increase on going to smaller nanoparticles. The comparison with experiments has been shown to be in good agreement. Also, the static dipole polarizabilities of the Ni nanoparticles have been considered.

Localized surface plasmon enhanced carbon dots based solar-blind ultraviolet photodetectors by Al nanoparticles

Localized surface plasmon enhanced carbon dots based solar-blind ultraviolet photodetectors by Al nanoparticles

Excellent Dielectric Properties and Finite Element Simulation of Al-Epoxy Composites with Constructed Ultrathin Al2O3 Parallel-Plate Microcapacitors.

Metal-polymer dielectric composites show promising potential as embedded capacitors, whereas it remains a great challenge to achieve a high dielectric constant (εr) and low dielectric loss (tan δ) simultaneously. This work demonstrates a strategy for overcoming this challenge. Al nanoparticles with self-passivated ultrathin Al2O3 shells are compacted under the uniaxial pressure (P), and Al-epoxy composites are prepared by curing the liquid epoxy monomer that infiltrates into Al compacts. The contacting regions between adjacent Al nanoparticles are flattened and enlarged during the compacting process, so that the ultrathin Al2O3 parallel-plate microcapacitors are constructed by the insulating Al2O3 shells and conductive Al cores. The composite with P of 100 MPa and Al volume fraction (υAl) of 53.7% exhibits the εr of 189 at 10 kHz, which is much higher than the εr (48-102) of 0-3 type Al-polymer composites with similar υAl and even higher than the highest εr (160) reported in the Al-polymer composite with υAl > 80%. Furthermore, the present composites show low tan δ (<0.03) and good frequency and temperature stability of εr. The finite element simulation proves that the construction and enlargement of ultrathin Al2O3 parallel-plate microcapacitors dramatically increase the electric energy stored in Al2O3 and therefore greatly improve the εr.

The Influence of Surface Processing on the Surface Plasmonic Enhancement of an Al-Nanoparticles-Enhanced ZnO UV Photodectector.

Surface Plasmonic Resonance (SPR) induced by metallic nanoparticles can be exploited to enhance the response of photodetectors (PD) to a large degree. Since the interface between metallic nanoparticles and semiconductors plays an important role in SPR, the magnitude of the enhancement is highly dependent on the morphology and roughness of the surface where the nanoparticles are distributed. In this work, we used mechanical polishing to produce different surface roughnesses for the ZnO film. Then, we exploited sputtering to fabricate Al nanoparticles on the ZnO film. The size and spacing of the Al nanoparticles were adjusted by sputtering power and time. Finally, we made a comparison among the PD with surface processing only, the Al-nanoparticles-enhanced PD, and the Al-nanoparticles-enhanced PD with surface processing. The results showed that increasing the surface roughness could enhance the photo response due to the augmentation of light scattering. More interestingly, the SPR induced by the Al nanoparticles could be strengthened by increasing the roughness. The responsivity could be enlarged by three orders of magnitude after we introduced surface roughness to boost the SPR. This work revealed the mechanism behind how surface roughness influences SPR enhancement. This provides new means for improving the photo responses of SPR-enhanced photodetectors.

The cognitive deficit induced by Al nanoparticle ingestion is associated with hippocampal inflammation in mice

AbstractBackgroundAlthough, both environmental and genetic factors are known as the predispositions to AD development, each of these factors are suggested to acts via increasing the Al content of brain tissue. Al nanoparticles are newer nanomaterials that have been significantly exposed to the human body. When Al reaches the nanosize, it may display different characteristics from natural Al, and its potential influence on body function is an interesting aspect of research as these particles might have more negative impact on human health. Activation of microglia and expression of the inflammatory cytokine IL‐1 (interleukin‐1) in the brain have been used as hallmarks of brain inflammation. Our recent findings suggest that administration of nano‐Al for a short period of 5 days can cause memory impairment. Given the importance of neuroinflammation in Alzheimer’s pathology, the question was whether 5‐day nano‐Al intake could lead to inflammatory changes in the hippocampus.MethodAdult male NMRI mice were treated with nano‐Al in doses 5 and 10 mg/kg/oral gavage for 5 days. The test session of novel object recognition (NOR) task was performed on day 5. Following the NOR test, the hippocampi were isolated. Considering the key roles of microglia activation and IL‐1β in neuroinflammation, the levels of hippocampal iba‐1 (as the speciefic marker of microglial activation) and IL‐1β were determined using western blot studies.ResultThe results showed that nano‐Al oral gavage in doses of 5 and 10 mg/kg impairs NOR memory in mice. Moreover, the memory impairing effect of nano‐Al coincided with a dose dependent increase in hippocampal iba‐1. It also increased the content of IL‐1 in the hippocampus.ConclusionThis study showed that nano‐Al in doses as low as 5 and 10 mg/ kg ingested for 5 days impairs memory and induces neuroinflammation in the hippocampus.

Preparation and characterization of strained Al nanoparticles by ball milling method

The objective of this investigation is to assess the grain size and lattice strain of pure strained Al nanopowder synthesized through the ball milling method. The evaluation is performed using the Williamson-Hall method. Lattice strain is induced in the powder through repetitive grinding. In this study, a notable finding is that the Debye-Waller factor exhibits a positive correlation with the lattice strain. The effective Debye-Waller factor (DWF) for zero strain has been precisely calculated in this research, taking into account the relationship between strain and DWF. Moreover, the researchers have investigated the influence of lattice strain on the energy required for vacancy generation.

Interactions of alumina and polystyrene nanoparticles with the innate immune system of Galleria mellonella

Nowadays, particularly metallic, and polymeric nanoparticles (NPs) are widely produced and used in many fields. Due to the increase in both their usage and diversity, their release and accumulation in the environment are also accelerating. Therefore, their interactions with cells, especially immune cells, and their health risks are not fully understood. The impacts of metallic alumina (Al) NPs and polystyrene (PS) NPs obtained after the polymerization of carcinogenic styrene on living organisms have not yet been elucidated. Galleria mellonella larvae can biodegrade plastics. While biodegradation and solving the waste problem have attracted much attention, the interactions of this distinctive property of G. mellonella larvae in the immune system and ecosystem are not yet completely understood. Al and PS NPs were applied to G. mellonella separately. Al NPs were purchased and PS NPs were prepared from PS by single-emulsion technique and characterized. Then LC50 values of these NPs on G. mellonella were determined. The interactions of these NPs with encapsulation, melanization, and phenoloxidase activity, which express innate immune responses in G. mellonella larvae, were revealed. NP exposure resulted in suppression of the immune response, probably because it affects the functions of hemocytes such as enzymatic activation, hemocyte division, and populations. In this context, our data suggest that Al and PS NPs induce toxic impacts and negatively alter the physiological status of G. mellonella. It is also shown that G. mellonella has the potential to be an impactful alternative model for biosafety and nanotoxicology studies.

Zero-valent metal incorporated cellulose acetate oxygen scavenging system for packaging of liquid food

Preserving packaged food from oxidative degradation is essential to improve the food quality and shelf life. This work focuses on synthesizing inexpensive zero-valent metal-incorporated polymeric films with a high oxygen scavenging rate, thus decreasing dissolved oxygen and bacterial growth. The optimal solvent for film synthesis was determined, with CADMSO films demonstrating the highest scavenging rate of 0.028 day−1. Next, zero-valent Fe, Cu, and Al nanoparticles were synthesized and incorporated into cellulose acetate films for use in active packaging. The resulting ZFe films showed the highest scavenging rate of 0.994 day−1 followed by ZCu and ZAl films with rates of 0.604 day−1, and 0.3516 day−1, respectively. Both ZFe and ZCu films exhibited potent antibacterial effects against gram-positive and gram-negative bacteria after 24 h, with reductions exceeding 99%. ZAl films showed a 99% reduction in bacterial colonies for gram-positive and a 97.5% reduction for gram-negative after 24 h. When tested with fruit juice, ZFe films exhibited the greatest scavenging capacity, achieving a 100% reduction in dissolved oxygen within 5 days. The films exhibited stability, as observed from FTIR and TGA analysis. The films' potent oxygen scavenging and bactericidal properties suggest that they may have applications as packaging agents.

The reaction mechanism and interfacial crystallization of Al nanoparticle-embedded Ni under shock loading

The shock-induced reaction mechanism and characteristics of Ni/Al system, considering an Al nanoparticle-embedded Ni single crystal, are investigated through molecular dynamics simulation. For the shock melting of Al nanoparticle, interfacial crystallization and dissolution are the main characteristics. The reaction degree of Al particle first increases linearly and then logarithmically with time driven by rapid mechanical mixing and following dissolution. The reaction rate increases with the decrease of particle diameter, however, the reaction is seriously hindered by interfacial crystallization when the diameter is lower than 9 nm in our simulations. Meanwhile, we found a negative exponential growth in the fraction of crystallized Al atoms, and the crystallinity of B2–NiAl (up to 20%) is positively correlated with the specific surface area of Al particle. This can be attributed to the formation mechanism of B2–NiAl by structural evolution of finite mixing layer near the collapsed interface. For shock melting of both Al particle and Ni matrix, the liquid-liquid phase inter-diffusion is the main reaction mechanism that can be enhanced by the formation of internal jet. In addition, the enhanced diffusion is manifested in the logarithmic growth law of mean square displacement, which results in an almost constant reaction rate similar to the mechanical mixing process.