In the present work, the nano-Al2O3 powder was produced by the wire explosion technique. The shape and size of the particles were measured using Transmission Electron Microscope (TEM) studies. The Scanning Electron Microscope (SEM) studies were carried out to confirm that the particles are of sub-micron size. The compositions of the material were characterized through the Energy Dispersive Angle X-ray Analysis (EDAX) results. The Wide Angle X-ray Diffraction (WAXD) and the Fourier Transform Infra-Red (FTIR) results confirmed the nanosize powder formed by the process as crystalline γ-Al2O3 powder. It is identified that the local temperature of the medium at the time of formation of nanopowder decides the phase characteristics of the powder material. The mechanism of formation of nanopowder by wire explosion technique was explained in detail. © 2003 Elsevier B.V. All rights reserved.

Ramanujam Sarathi

Department of Electrical Engineering

Satyanarayanan R. Chakravarthy

Department of Aerospace Engineering

V. Sabari Giri

C. Venkataseshaiah

Alumina

Ceramic materials

Composition

current density

Electric potential

Energy dispersive spectroscopy

EXPLODING WIRES

Fourier transform infrared spectroscopy

oxidation

Particle size analysis

Powder metals

Scanning electron microscopy

Transmission electron microscopy

Nanopowders

WIDE ANGLE X-RAY DIFFRACTION (WAXD)

Nanostructured materials

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Materials Letters

Single-step synthesis of γ-Alumina (γ-Al2O3), by wire-explosion process (WEP), is described in this work. Molecular oxygen is used as ambient gas with different levels of pressure to obtain the corresponding oxide nanoparticles (NPs). The energy (E) deposited to the capacitor, used for the explosion is in multiples of the sublimation energy. XRD and TEM techniques are used to characterise the synthesized nanoparticles. The content of γ-Al2O3 increases with increase in E and/or oxygen pressure (P). The average particle size of the nanoparticles reduces with the increase in E and/or decrease in P. The Born-Haber cycle is used to calculate the lattice energy (LE) of the bulk Al2O3. The dependence of LE and the formation enthalpy of alumina nanoparticles with size are evaluated. A classical homogenous nucleation theory is used to see the effect of saturation ratio and temperature on the activation energy and the nucleation rate of the NPs correlating it with size dependence on E and P used in the WEP. © 2017 IEEE.

International Conference on High Voltage Engineering and Power Systems, ICHVEPS 2017 - Proceeding

Synthesis of γ-Alumina nanoparticles by wire-explosion process: Characterisation and formation mechanism

Aluminum (Al) nanoparticles are synthesized by wire explosion process (WEP) in an inert ambience of argon. Thermodynamic analysis and structural characterization of nano Al particles are made in the present work. Transmission electron microscopy (TEM) characterization has shown that the Al nanoparticles produced are spherical in shape and it follows a lognormal distribution. A unimodal size dependent thermodynamic model is formulated to understand the size dependent thermal behavior of aluminum nanoparticles. Three different melting modes such as, homogeneous melting mode (HMM), liquid skin melting (LSM) and liquid nucleation and growth (LNG) are assumed to understand the melting behavior of aluminum nanoparticles synthesized by the WEP process. The effect of saturation ratio on the nucleation rate and the impingement factor is also discussed. The size dependent melting and enthalpy of fusion of Al nanoparticles predicted by thermodynamic model are in tandem with the DSC results. © Materials Research Society 2017.

Journal of Materials Research

Thermodynamic modeling and characterizations of Al nanoparticles produced by electrical wire explosion process

This paper reports the production of nanoaluminum particles using the wire explosion process at our laboratory. Electrical energy is applied to the aluminum wire in an argon atmosphere to yield spherical particles around 50 nm in size. The material is also characterized by a number of methods. The nano-Al is included in bimodal ammonium Perchlorate composite solid propellants, and their burning rates are compared with those containing normal micron- sized aluminum and nonaluminized propellants in a total of 21 formulations in the 1-12 MPa pressure range. Nanoaluminized propellants show ∼100% increase in burning rate relative to nonaluminized or microaluminized ones, but only when large-sized coarse ammonium Perchlorate particles are used. Burning-rate plateaus observed in non- and microaluminized propellants are washed out with the addition of nano-Al, but the burning rates of nanoaluminized propellants register low pressure exponents in the elevated pressure range. The results suggest that the heat feedback from the diffusion-limited combustion of nano-Al particles near the propellant burning surface controls the propellant burning rate when sufficiently large parts of the burning surface are made up of the nanoaluminized fine ammonium-perchlorate/binder matrix.

Journal of Propulsion and Power

Production, characterization, and combustion of nanoaluminum in composite solid propellants

Organic-inorganic hybridization technique is the recent trend to increase the performance of conventional organic coatings. In this work inorganic nano-Al2O3 was incorporated in organic waterborne polyurethane conventional coating (PUA) and applied on mild steel. The problem of lack of interfacial interaction between inorganic nanoreinforcement (nano-Al2O3) and organic matrix, agglomeration of high surface energetic nano-Al2O3 within the coating need to be solved. In order to obtain stable hybrid coating the organic bi-functional polymers, methyltrimethoxysilane (MTMS) and 3-glycidoxy-propyltriethoxysilane (GPTMS) were grafted on the surface of nano-Al2O3 and dispersed in PU coating by ultrasonication which were designated as PUM and PUG respectively. AFM analysis indicates that the grafting of nano-Al 2O3 significantly reduces the agglomeration problems as well as root mean square surfaces roughness (Rq) of coating. Immersion studies conducted in 3.5 wt.% NaCl solution showed that the dielectric properties (polarization resistance) increases and corrosion rate decreases significantly with grafted coatings as measured by electrochemical technique. The mechanical properties of PUG and PUM hybrid coating showed the much better performance than waterborne Polyurethane (PU) coating. © 2011 World Scientific Publishing Company.

International Journal of Nanoscience

High-performance nano-alumina-grafted waterborne polyurethane coating

Studies on production and characterization of nano-Al2O 3 powder using wire explosion technique

Journal	Materials Letters
ISSN	0167577X
Open Access	No