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

Aluminum oxide nanocomposites reinforced with multiwalled carbon nanotubes (MWNT) were prepared by atmospheric plasma spraying of blended and spray-dried powders. Thermal conductivity was measured using the laser flash technique for temperatures between 25° and 300°C. An aluminum oxide - 4 wt% MWNT nanocomposite prepared from the blended powder showed the highest conductivity, followed by aluminum oxide without nanotubes, 8 and 4 wt% MWNT composite prepared from spray-dried powder in that order. The thermal conductivity values obtained are rationalized taking into account the crystallite size, porosity, MWNT content, microstructure, and the interfaces and metastable γ-Al 2O3 content present in the nanocomposite. © 2007 The American Ceramic Society.

Department of Metallurgical and Materials Engineering

World University root node

Journal of the American Ceramic Society

Thermal conductivity of plasma-sprayed aluminum oxide - Multiwalled carbon nanotube composites

Deformation behavior and damage mechanisms of multiwalled carbon nanotubes have been studied under the high strain rate impact during cold spraying. Rippling is suggested as the mechanism for breakdown of nanotubes into smaller nanotubes and possible formation of carbon onions. Necking and cup-and-cone fracture with 70% reduction in area are observed that are comparable to mild steel fracture. Peeling off of outer walls of multiwalled carbon nanotubes is also seen due to shearing action between particles. © 2008 Acta Materialia Inc.

Scripta Materialia

Deformation and damage mechanisms of multiwalled carbon nanotubes under high-velocity impact

Multiwalled carbon nanotube (CNT) reinforced aluminum nanocomposite coatings were prepared using cold gas kinetic spraying. Spray drying was used to obtain a good dispersion of the nanotubes in micron-sized gas atomized Al–Si eutectic powders. Spray dried powders containing 5&nbsp;wt.% CNT were blended with pure aluminum powder to give overall nominal CNT compositions of 0.5&nbsp;wt.% and 1&nbsp;wt.% respectively. Cold spraying resulted in coatings of the order of 500&nbsp;μm in thickness. Fracture surfaces of deposits show that the nanotubes were uniformly distributed in the matrix. Nanotubes were shorter in length as they fractured due to impact and shearing between Al–Si particles and the Al matrix during the deposition process. Nanoindentation shows a distribution in the elastic modulus values from 40–229&nbsp;GPa which is attributed to microstructural heterogeneity of the coatings that comprise the following: pure Al, Al–Si eutectic, porosity and CNTs.

Surface and Coatings Technology

Carbon nanotube reinforced aluminum composite coating via cold spraying

In the present work, multiwalled carbon nanotube (MWNT) reinforced UHMWPE composite films were prepared by electrostatic spraying followed by consolidation. X-ray diffraction and differential scanning calorimetry studies showed a decrease in the crystallinity of UHMWPE due to the nature of the fabrication process as well as addition of MWNT. Tensile test showed an 82% increase in the Young’s modulus, decrease in stress to failure from 14.3 to 12.4&nbsp;MPa and strain to failure from 3.9% to 1.4% due to 5% addition of MWNT. Raman spectra showed the presence of compressive stresses in the nanotubes. Fracture surface showed presence of pullout like phenomena in the MWNT reinforced film.

Composites Part A: Applied Science and Manufacturing

Synthesis and characterization of multiwalled carbon nanotube reinforced ultra high molecular weight polyethylene composite by electrostatic spraying technique

Two different coatings of 1100 aluminium were cold sprayed onto similar substrates, using He and He-20N2 (vol.-%) mixture as carrier gases. Three point bend testing was carried out. The elastic moduli of the coatings were found to be close to each other and the substrate. The He processed coating showed higher fracture strength which was attributed to the higher degree of strain hardening. The He-20N2 processed coating failed at lower stress owing to its strain relaxed structure. The mode 1 fracture of the coating substrate system was found to be higher for the helium processed coating. The toughness was correlated to the microstructure. The delaminated coating showed a higher degree of brittle failure of the interface for the He processed coating. © 2007 Institute of Materials, Minerals and Mining.

Surface Engineering

Effect of carrier gas on mechanical properties and fracture behaviour of cold sprayed aluminium coatings

Al 2O 3 ceramic reinforced with 4-wt% multiwalled carbon nanotube (CNT) is plasma sprayed for improving the fracture toughness of the nanocomposite coating. Two different methodologies of CNT addition have been adopted in the powder feedstock to assist CNT dispersion in the nano-Al 2O 3 matrix. First, spray-dried nano-Al 2O 3 agglomerates are blended with 4 wt% CNT as powder-feedstock, which is subsequently plasma sprayed resulting in the fracture toughness improvement of 19.9%. Secondly, spray dried composite nano-Al 2O 3 and 4 wt% CNT powder was used as feedstock for attaining improved dispersion of CNTs. Plasma sprayed coating of composite spray dried powder resulted in increase of 42.9% in the fracture toughness. Coating synthesized from the blended powder displayed impact alignment of CNTs along splat interface, and CNTs chain loop structure anchoring the fused Al 2O 3 melt whereas coating synthesized from composite spray dried powder evinced anchoring of CNTs in the solid state sintered region and CNT mesh formation. Enhanced fracture toughness is attributed to significance of CNT dispersion. Copyright © 2007 American Scientific Publishers All rights reserved.

Journal of Nanoscience and Nanotechnology

Role of powder treatment and carbon nanotube dispersion in the fracture toughening of plasma-sprayed aluminum oxide - carbon nanotube nanocomposite

Compositions with easy bulk metallic glass formation have been identified in quinary systems with the Gibbs-energy change between the amorphous and solid solution phases as the thermodynamic parameter. The Gibbs-energy change has been calculated with the help of Miedema, Miracle, mismatch entropy, and configurational entropy models. The best glass forming composition has been identified by drawing iso-Gibbs-energy change contours by representing quinary systems as pseudo-ternary ones. Attempts have been made to correlate the Gibbs-energy change with different existing glass forming criteria and it is found that the present thermodynamic parameter has good correlation with the reduced glass transition temperature. Further, encouraging correlations have been obtained between the energy required for amorphization during mechanical alloying to the Gibbs-energy change between the amorphous and solid solutions. © 2006 Elsevier B.V. All rights reserved.

Materials Science and Engineering A

Identification of compositions with highest glass forming ability in multicomponent systems by thermodynamic and topological approaches

Ultrahigh-molecular-weightpolyethylene (UHMWPE) and 5 wt.% multiwalled-carbon-nanotube-(MWNT) reinforced UHMWPE coatings were prepared on a steel substrate by electrostatic spraying. Nanoindentation and nanoscratch tests were performed on the coatings to evaluate the mechanical and wear properties at small length scales. The mean values of elastic modulus and hardness were higher for the MWNT-reinforced coating, while the plasticity index of the coatings was unaffected. The lateral force and coefficient of friction was considerably higher in the case of the MWNT-reinforced coating, indicating an increase in resistance to wear due to the addition of MWNT.

Functional Coatings

The nanomechanical and nanoscratch properties of MWNT-reinforced ultrahigh-molecular-weight polyethylene coatings

Torsional wave motion when displacements over the cross section of a circular cylinder involve nodal circles has been studied in the case of piezoelectric (622) crystal class. Solutions are obtained in the following cases: (a) when initial motion is prescribed; and (b) when external stresses are prescribed. © 1969.