Aerosol Measurement Principles Techniques And Applications

The oxides of copper (CuxO) are fascinating materials due to their remarkable optical, electrical, thermal and magnetic properties. Nanostructuring of CuxO can further enhance the performance of this important functional material and provide it with unique properties that do not exist in its bulk form. Three distinctly different phases of CuxO, mainly CuO, Cu2O and Cu4O3, can be prepared by numerous synthesis techniques including, vapour deposition and liquid phase chemical methods. In this article, we present a review of nanostructured CuxO focusing on their material properties, methods of synthesis and an overview of various applications that have been associated with nanostructured CuxO.

Nanostructured copper oxide semiconductors : a perspective on materials, synthesis methods and applications

Electrohydrodynamic atomization: A two-decade effort to produce and process micro-/nanoparticulate materials.

Nanotechnology has stimulated revolutionary advances in many scientific and industrial fields, particularly in energetic materials. Powder mixing is the simplest and most traditional method to prepare nanoenergetic composites, and preliminary findings have shown that these composites perform more effectively than their micro- or macro-sized counterparts in terms of energy release, ignition, and combustion. Powder mixing technology represents only the minimum capability of nanotechnology to boost the development of energetic material research, and it has intrinsic limitations, namely, random distribution of fuel and oxidizer particles, inevitable fuel pre-oxidation, and non-intimate contact between reactants. As an alternative, nanostructured energetic composites can be prepared through a delicately designed process. These composites outperform powder-mixed nanocomposites in numerous ways; therefore, we comprehensively discuss the preparation strategies adopted for nanostructured energetic composites and t...

Nanostructured energetic composites: synthesis, ignition/combustion modeling, and applications.

3D printing technology is now frequently employed in many areas of research and development. However, a relatively narrow range of 3D printable materials with a limited spectrum of physico-chemical properties still restricts the true potential of this potentially disruptive technology. There is rapidly increasing interest in the improvement and diversification of properties of generic printing materials via the introduction of fillers with unique properties, and/or by blending materials exhibiting different properties to generate high performance composites. 3D printed composites have already been utilised in a wide range of applications, including biomedical, mechanical, electrical, thermal and optically enhanced products. The increasing popularity of 3D printed composites can be attributed to the ability to fabricate complex geometries, low cost production, and other advantages associated with rapid prototyping. This review covers all the recent reports in which the properties of generic 3D printable materials have been modified either by adding nanoparticles, fibers, other polymers, or by a chemical reaction for fabrication of composites with enhanced biomaterial, mechanical, electrical, thermal, optical and other properties.

Recent developments in 3D printable composite materials

Energetic thin films with high mass loadings of nanosized components have been recently fabricated using electrospray deposition. These films are composed of aluminum nanoparticles (nAl) homogeneously dispersed in an energetic fluoropolymer binder, poly(vinylidene fluoride) (PVDF). The nascent oxide shell of the nAl has been previously shown to undergo a preignition reaction (PIR) with fluoropolymers such as polytetrafluoroethylene (PTFE). This work examines the PIR between alumina and PVDF to further explain the reaction mechanism of the Al/PVDF system. Temperature jump (T-jump) ignition experiments in air, argon, and vacuum environments showed that the nAl is fluorinated by gas phase species due to a decrease in reactivity in a vacuum. Thermogravimetric analysis coupled with differential scanning calorimetry (TGA/DSC) was used to confirm the occurrence of a PIR, and gas phase products during the PIR and fluorination of nAl were investigated with temperature jump time-of-flight mass spectrometry (T-jump ...

Probing the Reaction Mechanism of Aluminum/Poly(vinylidene fluoride) Composites.

One of the challenges in the use of energetic nanoparticles within a polymer matrix is the difficulty in processing by traditional mixing methods. In this paper, electrospray deposition is employed to create high loadings of aluminum nanoparticles (Al-NPs) in polyvinylidene fluoride (PVDF) reactive composite films. The deposited films containing up to 50 wt% Al are found to be crack free and mechanically flexible. Thermochemical behavior characterized by thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis shows that the addition of Al-NPs sharply reduces the onset decomposition temperature due to a pre-ignition reaction occurring in the film. The combustion propagation velocity in air at three different mass loading of Al-NPs shows burning rates of 5, 16, and 23 cm s−1 for loadings of 16.7, 30, and 50 wt% Al-NPs. The results suggest electrospray deposition as a direct approach to make bulk polymer composites containing high metal particle mass loading and may be a prelude to 3D printing of rocket motors.

Electrospray Deposition of Energetic Polymer Nanocomposites with High Mass Particle Loadings: A Prelude to 3D Printing of Rocket Motors**

Nanometallic fuels with high combustion enthalpy, such as aluminum, have been proposed as a potential fuel replacement for conventional metallic fuel to improve propellant performance in a variety of propulsive systems. Nevertheless, nanometallic fuels suffer from the processing challenges in polymer formulations such as increased viscosity and large agglomeration, which hinder their implementation. In this letter, we employ electrospray as a means to create a gel within a droplet, via a rapid, solvent evaporation-induced aggregation of aluminum nanoparticles, containing a small mass fraction of an energetic binder. The gelled aluminum microspheres were characterized and tested for their burning behavior by rapid wire heating ignition experiments. The gelled aluminum microspheres show enhanced combustion behavior compared to nanoaluminum, which possibly benefits from the nitrocellulose coating and the gelled microstructure, and is far superior to the corresponding dense micrometer-sized aluminum.

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Electrospray formation of gelled nano-aluminum microspheres with superior reactivity.

The biological agents that can be weaponized, such as Bacillus anthracis, pose a considerable potential public threat. Bacterial spores, in particular, are highly stress resistant and cannot be completely neutralized by common bactericides. This paper reports on synthesis of metal iodate-based aluminized electrospray-assembled nanocomposites which neutralize spores through a combined thermal and chemical mechanism. Here metal iodates (Bi(IO3)3, Cu(IO3)2, and Fe(IO3)3) act as a strong oxidizer to nanoaluminum to yield a very exothermic and violent reaction, and simultaneously generate iodine as a long-lived bactericide. These microparticle-assembled nanocomposites when characterized in terms of reaction times and temporal pressure release show significantly improved reactivity. Furthermore, sporicidal performance superior to conventional metal-oxide-based thermites clearly shows the advantages of combining both a thermal and biocidal mechanism in spore neutralization.

Jeffery B. DeLisio

Papers

Probing the Reaction Mechanism of Aluminum/Poly(vinylidene fluoride) Composites.

Electrospray Deposition of Energetic Polymer Nanocomposites with High Mass Particle Loadings: A Prelude to 3D Printing of Rocket Motors**

Electrospray formation of gelled nano-aluminum microspheres with superior reactivity.

Metal Iodate-Based Energetic Composites and Their Combustion and Biocidal Performance.

Assembly and encapsulation of aluminum NP's within AP/NC matrix and their reactive properties