Our highly industrialized society is always in search of ways to reduce or control friction and wear of materials. Diamond coatings can provide an efficient solution for these problems. The focus of this research work is to study the potential of diamond coatings to improve the tribological properties of steel components. Although chemical vapour deposition (CVD) of diamond is well researched and well established on various non-diamond substrates, deposition on ferrous materials is difficult to obtain and not yet up to the stage of commercial realization. One of the main challenges associated is that iron comes under the group VIII transition metals and due to their partially filled 3d orbital, Fe atoms are highly reactive towards carbon. On the other hand, carbon also has a high coefficient of diffusion in the iron matrix. As a result, the incubation time to reach the critical carbon concentration is very long for steel substrates. Another major drawback is the thermal expansion coefficient mismatch between steel and diamond, which results in high thermal stresses upon cooling, leading to poor adhesion. Using various interlayer and surface pretreatment techniques, we have overcome the above mentioned problems and successfully obtained diamond coatings on steel substrates by hot filament chemical vapour deposition (HFCVD) technique. Tribological characterization of the diamond coated steel substrates was performed under small amplitude oscillatory motions, known as fretting. In this talk, an overview of the diamond CVD mechanism, challenges, interlayer systems and the fretting wear behaviour of the diamond coatings will be presented.

Pine, Chaikin and collaborators [Nature (2005), Nature Physics (2008)]have recently studied the transition between reversible andirreversiblebehavior in a simple experiment. The experiment consists of observingand studying the trajectories of a large number of particles suspendedina fluid sheared between two coaxial cylinders. These experimentsillustrate a novel way in which a driven many-particle system canself-organize (termed“random organization” by these authors). They also illuminateseveral problems which lie at the foundations of statisticalmechanics, such as theconnection between irreversible behaviour at the macroscopic scale andmicroscopic reversibility at the microscale.I will first describe these experiments and then present a simplemodel for the underlying physics. Predicting universal features of thereversible-irreversibletransition seen in these experiments then becomes possible. Thesepredictions are in reasonable agreement with what is seen in theexperiments. I will also brieflydescribe the connection to recent ideas concerning the “jamming”transition in granular materials, ideas that may have broaderimplications for theories of the glasstransition.

Driven diffusive systems are generically out of equilibrium. Iwill consider two paradigmatic examples, the asymmetric simple exclusionprocess and the zero-range process. I will discuss size effects on thebehavior of fluctuations in the nonequilibrium stationary state of these twoprocesses on a one-dimensional periodic lattice of finite size. Theexclusion process involves hard core particles executing biased diffusionwith a constant rate. In the zero-range process, particles perform biasedhopping between sites with a rate which depends on the occupancy at thedeparture site. In the stationary state, this process shows a phasetransition as a function of the particle density, from a low-densitydisordered phase to a high-density condensed phase. In both these processes,size effects interplay with the nonequilibrium dynamics to bring in richdynamical phenomena otherwise absent in equilibrium.

Conducting polymer is a very interesting and scientifically as well astechnologically important class of polymer. This research work aims togain an insight into the monomer level processes and mechanism ofelectropolymerization of conducting polymer (CP) so as to control theporosity and morphology and standardize various parameters for obtainingbetter quality CP films. Another objective is to study the effects ofheavy ion irradiation on CP electrodes and to understand the interactionof the fast ions with the polymer film. Polyaniline, polypyrrole andpoly(3-methylthiophene) CP films doped with different dopants have beeninvestigated. Electrochemical synthesis of CP films was carried out in three electrodesingle compartment electrochemical cell on indium doped tin oxide (ITO)coated glass substrates. These CP films were irradiated with swift heavyion (SHI) beam of 160 MeV Ni12+ and 120 MeV Si9+ to investigate theeffect of irradiation on CP electrodes. Cyclic voltammetry, dcconductivity, XRD, SEM, UV-Vis and FTIR studies were carried out forcharacterization of the CP films before and after irradiation. Theperformance of the CP films as electrodes has also been investigated byfabricating supercapacitors with unirradiated and irradiated CP films aselectrodes.The electrochemical polymerization of CP produces better quality films inthe potentiodynamic mode as compared to potentiostatic mode. The dcconductivity of the conducting polymer films has been observed to bedependent on the type of dopant ions. The scanning electron microscopy ofthe conducting polymer films shows that the potentiodynamic polymerizationmethod produced films with better surface morphology as compared to thoseby the potentiostatic method. Grain growth and densification of thepolymer film surface have been observed upon SHI irradiation. The UV-Visstudy showed that the polymer absorbing at higher wavelength exhibitsbetter conductivity. Increase in carrier absorption intensities with shiftof absorption peaks towards higher wavelength were observed in the UV-Visspectra of the irradiated CP films indicating lowering of band gap andincrease in electrical conductivity. The dopant ion interaction absorptionpeaks in the FTIR spectra confirmed the presence of the dopants in the CPfilms deposited by electrochemical polymerization and also afterirradiation. The XRD patterns of the unirradiated CP films showedsemi-crystalline nature of the films with increase in degree ofcrystallinity upon SHI irradiation.Solid state all-polymer redox supercapacitors fabricated using CP films aselectrodes and PVDF-HFP-PMMA gel polymer electrolyte showed goodcapacitive behaviour with capacitance on the order of 200-250 F/gm andCoulombic efficiency of about 90-96%. Stability tests up to 10,000charge-discharge cycles showed that the supercapacitors fabricated byusing SHI irradiated CP films exhibit slightly less capacitance andCoulombic efficiency but markedly improved electrochemical stability. Avery small decrease in internal resistance of the supercapacitors is foundafter SHI irradiation. A decrease in total charge-discharge time has alsobeen observed for supercapacitors with SHI irradiated electrodes.