Enhancing the Combustion of Magnesium Nanoparticles via Low-Temperature Plasma-Induced Hydrogenation.

The hydrogenation of metal nanoparticles provides a pathway toward tuning their combustion characteristics. Metal hydrides have been employed as solid-fuel additives for rocket propellants, pyrotechnics, and explosives. Gas generation during combustion is beneficial to prevent aggregation and sintering of particles, enabling a more complete fuel utilization.

Microscopic Studies on the Interaction of Multi-Principal Element Nanoparticles and Bacteria.

Multi-principal element nanoparticles are an emerging class of materials with potential applications in medicine and biology. However, it is not known how such nanoparticles interact with bacteria at nanoscale. In the present work, we evaluated the interaction of multi-principal elemental alloy (FeNiCu) nanoparticles with () bacteria using the graphene liquid cell (GLC) scanning transmission electron microscopy (STEM) approach.

In-Situ Thermochemical Shock-Induced Stress at the Metal/Oxide Interface Enhances Reactivity of Aluminum Nanoparticles.

Although aluminum (Al) nanoparticles have been widely explored as fuels in energetic applications, researchers are still exploring approaches for tuning their energy release profile via microstructural alteration. In this study, we show that a nanocomposite (∼70 nm) of a metal ammine complex, such as tetraamine copper nitrate (Cu(NH)(NO)/TACN), coated Al nanoparticles containing only 10 wt. % TACN, demonstrates a ∼200 K lower reaction initiation temperature coupled with an order of magnitude enhancement in the reaction rate.

Vaporization-Controlled Energy Release Mechanisms Underlying the Exceptional Reactivity of Magnesium Nanoparticles.

Magnesium nanoparticles (NPs) offer the potential of high-performance reactive materials from both thermodynamic and kinetic perspectives. However, the fundamental energy release mechanisms and kinetics have not been explored due to the lack of facile synthetic routes to high-purity Mg NPs. Here, a vapor-phase route to surface-pure, core-shell nanoscale Mg particles is presented, whereby controlled evaporation and growth are utilized to tune particle sizes (40-500 nm), and their size-dependent reactivity and energetic characteristics are evaluated.

High-Temperature Interactions of Metal Oxides and a PVDF Binder.

Interactions between energetic material relevant nanoscale metal oxides (SiO, TiO, MgO, AlO, CuO, BiO) and poly(vinylidene fluoride) (PVDF) at high temperature were investigated by temperature-jump/time-of-flight mass spectrometry (T-jump/TOFMS) and thermogravimetric-differential scanning calorimetry (TGA-DSC). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the morphology of the compositions, while X-ray diffraction (XRD) was utilized to analyze the condensed phase crystalline species at temperatures of interest. The exergonicity and exothermicity of HF gas with hydroxyl-terminated metal oxide surfaces make HF the likely fluorine-bearing moiety and primary mode of the fluorinating reactions, where terminal OH configurations are replaced by F in the formation of a stronger metal-fluorine bond.

Magnetic-Field Directed Vapor-Phase Assembly of Low Fractal Dimension Metal Nanostructures: Experiment and Theory.

While gas-phase synthesis techniques offer a scalable approach to production of metal nanoparticles, directed assembly is challenging due to fast particle diffusion rates that lead to random Brownian aggregation. This work explores an electromagnetic-levitation technique to generate metal nanoparticle aggregates with fractal dimension () below that of diffusion limited assembly. We demonstrate that in addition to levitation and induction heating, the external magnetic field is sufficient to compete with random Brownian forces, which enables the formation of altered fractals.

Modelling and simulation of field directed linear assembly of aerosol particles.

Unlike liquid phase colloidal assembly, significantly changing the structure of fractal aggregates in the aerosol phase, is considered impractical. In this study, we discuss the possibility of applying external magnetic and electric fields, to tune the structure and fractal dimension (D) of aggregates grown in the aerosol phase. We show that external fields can be used to induce dipole moments in primary nanoparticles.

Silicon Nanoparticles for the Reactivity and Energetic Density Enhancement of Energetic-Biocidal Mesoparticle Composites.

Biocidal nanothermite composites show great potential in combating biological warfare threats because of their high-energy-release rates and rapid biocidal agent release. Despite their high reactivity and combustion performance, these composites suffer from low-energy density because of the voids formed due to inefficient packing of fuel and oxidizer particles. In this study, we explore the potential of plasma-synthesized ultrafine Si nanoparticles (nSi, ∼5 nm) as an energetic filler fuel to increase the energy density of Al/Ca(IO) energetic-biocidal composites by filling in the voids in the microstructure.

Oxidation Studies of High-Entropy Alloy Nanoparticles.

Although high-entropy alloys (HEAs) have shown tremendous potential for elevated temperature, anticorrosion, and catalysis applications, little is known on how HEA materials behave under complex service environments. Herein, we studied the high-temperature oxidation behavior of FeCoNiCuPtHEA nanoparticles (NPs) in an atmospheric pressure dry air environment by gas-cell transmission electron microscopy. It is found that the oxidation of HEA NPs is governed by Kirkendall effects with logarithmic oxidation rates rather than parabolic as predicted by Wagner's theory.

Ultrafast, scalable laser photothermal synthesis and writing of uniformly dispersed metal nanoclusters in polymer films.

This paper presents a fast CO laser synthesis and writing technique - laser photothermal synthesis and writing (LPSW) - to generate and write a high concentration of unaggregated, spherical sub-10 nm metal nanoparticles (sMNPs). The method is generic, and we demonstrate the fabrication of Ni, Cu, and Ag directly in polymer thin films. A partly IR-absorbing thin polymer film can be heated by the laser to high temperatures in a short time, triggering metal-reduction, nucleation, and growth.

Thermal Shock Synthesis of Metal Nanoclusters within On-the-Fly Graphene Particles.

Metal nanoclusters (1-10 nm) have drawn great attention because of their potential applications including energy storage, catalysis, nanomedicine, and electronic devices. However, manufacturing ultrasmall metal nanoparticles at high concentrations in an unaggregated state is not a solved problem. Here, we report an aerosol-based thermal shock technique for in situ synthesis of well-dispersed metal nanoclusters in on-the-fly graphene aerosols.