In this work, nanocrystalline tungsten oxide (WO3) powder was obtained by high energy ball milling (HEBM) followed by heat treatment of tungsten (W) powder. HEBM significantly influenced the oxidation behavior by reducing the crystallite size and inducing lattice strain in W powder. The resultant nanocrystalline WO3 shows variation in the optical bandgap with respect to the bulk counterparts. The alteration in the bandgap of WO3 is ascribed to the changes in crystallite size and the unit cell volume. In the end, a thorough correlation between fundamental interactions of these changes was succinctly highlighted. © 2019 Acta Materialia Inc.

Shaik Adil

Ball milling

Chromium compounds

Energy gap

Mechanical Alloying

Milling (machining)

Nanocrystalline materials

Nanocrystalline powders

Nanocrystals

Tungsten compounds

X ray diffraction

BAND-GAP TUNING

BULK COUNTERPART

CRYSTALLINE OXIDES

HIGH-ENERGY BALL MILLING

MECHANICAL MILLING

Nanocrystallines

Oxidation behaviors

UNIT-CELL VOLUME

Crystallite size

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

Scripta Materialia

The present paper reports the growth and branching mechanism of W18O49 nanowires grown on nanocrystalline tungsten (W) surfaces. Nanocrystalline W powder was prepared using high energy ball milling. The nanopowder was non-isothermally heat-treated up to 1400 °C in argon atmosphere. The nanowires of 30-50 nm diameter were observed on nanopowder surfaces after the heat-treatment. A model based on crystallographic shear phase formation to accommodate the oxygen deficiency during the reduction of WO3 is discussed to explain the growth and branching mechanism of these nanowires which correlates well with the observed angle for the branching. © 2016 Elsevier B.V.

Crystallographic-shear-phase-driven W18O49 nanowires growth on nanocrystalline W surfaces

The grain size dependency of lattice parameter during high-energy ball milling of W has been investigated. The lattice parameter varies non-monotonically with grain size during milling with a lattice contraction initially followed by an expansion. The lattice parameters were calculated in view of the non-equilibrium grain boundary structure that evolved during milling using excess free volume and the interfacial stresses at the grain boundaries. The calculated lattice parameters closely match the experimentally observed values. © 2014 Acta Materialia Inc.

Grain-size-dependent non-monotonic lattice parameter variation in nanocrystalline W: The role of non-equilibrium grain boundary structure

Nanocrystalline ZnO particles were prepared using the high-energy ball milling technique and investigated with electron paramagnetic resonance (EPR), impedance, and Raman spectroscopy to reveal the origin of surface and core defects. We observed two distinct EPR signals with different g-factors, g ∼ 2.0 and ∼1.96, indicating EPR-active defects on the surface and core, respectively. Using the semi-empirical core-shell model, we identified that sufficiently small nanocrystals (below 30 nm) can show p-type character. The model can also explain the origin of the non-linearity of the U-I behaviour in nanocrystalline ZnO. © 2012 American Institute of Physics.

Fulltext

Journal of Applied Physics

Investigation of intrinsic defects in core-shell structured ZnO nanocrystals

Journal of the American Chemical Society

Band Gap Tuning via Lattice Contraction and Octahedral Tilting in Perovskite Materials for Photovoltaics

Journal of Materials Chemistry C

Effective band gap tuning by foreign metal doping in hybrid tin iodide perovskites

Crystallite size induced bandgap tuning in WO3 derived from nanocrystalline tungsten

Journal	Scripta Materialia
Publisher	Acta Materialia Inc
ISSN	13596462
Open Access	No