The review renders a short background on the research work carried out on epoxy clay nanocomposites Clays are one of the ideal nano reinforcements for polymers because of their high intercalation chemistry and aspect ratio Epoxy clay nanocomposites are finding vast applications in various industries like aerospace, defense, automobile, etc The physical and chemical properties of the epoxy systems are influenced by the processing techniques, clay modifier and curing agents used for the preparation of nanocomposites The clay morphology (intercalation/exfoliation) of the nanocomposites is also depended on the above parameters So the emphasis of the present work is to highlight these parameters on morphology and the final mechanical, thermal and barrier properties of the nanocomposites The proposed applications of the epoxy clay nanocomposites are also discussed

Epoxy clay nanocomposites ― processing, properties and applications: A review

Energy harvesting technologies have been explored by researchers for more than two decades as an alternative to conventional power sources (e.g. batteries) for small-sized and low-power electronic devices. The limited life-time and necessity for periodic recharging or replacement of batteries has been a consistent issue in portable, remote, and implantable devices. Ambient energy can usually be found in the form of solar energy, thermal energy, and vibration energy. Amongst these energy sources, vibration energy presents a persistent presence in nature and manmade structures. Various materials and transduction mechanisms have the ability to convert vibratory energy to useful electrical energy, such as piezoelectric, electromagnetic, and electrostatic generators. Piezoelectric transducers, with their inherent electromechanical coupling and high power density compared to electromagnetic and electrostatic transducers, have been widely explored to generate power from vibration energy sources. A topical review of piezoelectric energy harvesting methods was carried out and published in this journal by the authors in 2007. Since 2007, countless researchers have introduced novel materials, transduction mechanisms, electrical circuits, and analytical models to improve various aspects of piezoelectric energy harvesting devices. Additionally, many researchers have also reported novel applications of piezoelectric energy harvesting technology in the past decade. While the body of literature in the field of piezoelectric energy harvesting has grown significantly since 2007, this paper presents an update to the authors' previous review paper by summarizing the notable developments in the field of piezoelectric energy harvesting through the past decade.

https://iopscience.iop.org/article/10.1088/1361-665X/ab36e4/pdf

A review of energy harvesting using piezoelectric materials: state-of-the-art a decade later (2008–2018)

Polymer nanocomposites from modified clays: Recent advances and challenges

Polymeric microcomponents are widely used in microelectromechanical systems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control To address these needs, we fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy Spatially modulated photopatterning was applied in a shape-independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix By freely programming the rotational axis of each component, we demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three-dimensional motion

Programming magnetic anisotropy in polymeric microactuators.

Nanoindentation in polymer nanocomposites

b A contact fatigue phenomenon is most common failure seen in the structural components, which are under high-cyclic fatigue loads. Rail wheels, mating gears, ball bearing and wherever the formal contact between the two structural elements, are affected by contact fatigue failure, is commonly referred as pitting of surface. It can be seen that those structural elements are manufactured by powder metallurgy technology since it has more technical as well as commercial advantages over the conventionally made structural parts. Development in powder metallurgy manufacturing technologies, will give us confident to use of more powder metallurgy structural parts in place of conventional parts. Rolling-sliding contact fatigue (RSCF) experiments on powder metallurgy (PM) steels have been carried out in the laboratories with available experimental set-up. The lubrication oil is collected for regular interval and ferrography test is involved to predict the wear rate of the powder metallurgy steels. Wear morphology of porous steel is predicted.

/pdf/ferrography-a-procedure-for-measuring-wear-rate-1c5vfho2v9.pdf

Ferrography — A procedure for measuring wear rate

Introduction of compressive residual stress on the surface of dynamically loaded structural members improves the fatigue life. Oil jet peening is a new surface modification technique that can be potentially applied to introduce compressive residual stresses. Effect of oil jet peening on the surface modification and fatigue behavior of medium carbon steel, AISI 1040, is reported. The compressive residual stress on the surface of oil jet peened specimen was in the order of 332 MPa and the depth of compressive stress induced was about 50 μm. The surface hardness increased due to the oil jet peening. Oil jet peening improved the fatigue strength under cantilever-bending conditions to about 19% compared to unpeened specimens.

Effect of oil jet peening duration on surface modification and fatigue behavior of medium carbon steel, AISI 1040

Relative performance of hydrogenated, argon-incorporated and nitrogen-incorporated diamond-like carbon coated Ti–6Al–4V samples under fretting wear loading

Compressive residual stresses that improve fatigue strength of material are obtained by peening the surface. Unlike traditional processes, a novel process of oil cavitation jet peening was developed. The process is based on implosion generated by the oil cavitation jet that plastically deforms the surface, imparting compressive residual stresses. The process developed involves injection of a high-speed oil jet (∼230 m/s) through a suitably designed nozzle, into an oil-filled chamber containing the specimen to be peened. The region of cavitation generation, growth, and collapse, at the various cavitation numbers, was recorded using high-speed photography. To optimize the process parameters, a simple erosion test was performed in aluminum alloy, AA 6063-T6, specimens. The impact pressure generated during the implosion of cavitation bubbles causes plastic deformation and erosion of the surface. The surface deformation and cavitation jet erosion in the exposed specimens were characterized using optical and scanning electron microscopies. The standoff distance, which measures jet impact zone of the specimen from nozzle, was optimized at 15 mm in a cavitation number (which is a measure of pressure ratio across the nozzle) of 0.0017. The surface deformation produced by collapse of the oil bubble was similar to impact of oil droplet on the surface. The material removal mechanism during implosion of the bubble is predominately by ductile shear deformation.

Development of a Novel Oil Cavitation Jet Peening System and Cavitation Jet Erosion in Aluminum Alloy, AA 6063-T6

The influences of microstructure, alloying additions and processing method on the flexural strength and fracture behavior of gamma base titanium aluminides were investigated at room and elevated temperatures. The flexural strength strongly depends on the microstructure, alloying addition and processing method. The lamellar microstructure material exhibited high strength and ternary chromium or niobium addition improved the strength. Isothermal forging resulted in a fine grain microstructure and influenced the bend properties. The flexural strength increased up to a ‘critical temperature’ and thereafter it decreased. This ‘critical temperature’ seemed to depend on the chemical composition. The room-temperature fracture was mostly transgranular cleavage and intergranular fracture regions were dominant with increasing temperature. At high temperatures ductile tearing was observed, irrespective of the microstructure.

R. Gnanamoorthy

Papers

Ferrography — A procedure for measuring wear rate

Effect of oil jet peening duration on surface modification and fatigue behavior of medium carbon steel, AISI 1040

Relative performance of hydrogenated, argon-incorporated and nitrogen-incorporated diamond-like carbon coated Ti–6Al–4V samples under fretting wear loading

Development of a Novel Oil Cavitation Jet Peening System and Cavitation Jet Erosion in Aluminum Alloy, AA 6063-T6

Flexural strength of gamma base titanium aluminides at room and elevated temperatures