Effect of organic modifiers on dynamic and static nanomechanical properties and crystallinity of intercalated clay–polycaprolactam nanocomposites

Polymer clay nanocomposites (PCN) of Polyamide6 and sodium montmorillonite are prepared using different organic modifiers (12‐aminolauric acid, n‐dodecylamine, and 1,12‐diaminododecane) to study effect of organic modifiers on structure and nanomechanical properties of PCN. Using X‐ray diffraction and differential scanning calorimetry, crystalline nature of PCNs are evaluated. Nanoscale viscoelastic properties of PCNs are evaluated using nanodynamic mechanical analyzer (NanoDMA). Nanoscale elastic modulus and hardness of PCNs are evaluated using nanoindenter. PCNs show enhancement in elastic modulus, storage modulus, loss modulus, and loss factor by maximum amount of 62.88%, 56.38%, 145.74%, and 71.43%, respectively, and decrease in percentage crystallinity by 16.52% compared to pure polymer. This result indicates that organic modifiers have effect on crystallinity and nanomechanical properties of PCN. To evaluate effect of clay loading on nanomechanical properties of PCN, PCN containing 12‐aminolauric acid is synthesized with different weight percent (3, 6, and 9% of weight of polymer) of organically modified montmorillonite (OMMT), which shows that nanomechanical properties of PCN improves with increase in clay loading. Our study reveals that change in crystallinity of polymer in PCN may have role in the enhancement of nanomechanical properties of PCNs in comparison to pristine polymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical behaviour of an austempered ductile iron

Austempering of a ferrite-pearlitic grade of ductile iron was carried out to assess the potential use of the material for crank shaft application reported. A commercial material was austempered at 340°C to realize the properties. The austempered ductile iron gave good strength although the ductility values were lower. The material developed had complete ausferritric structure free of pearlite. The various phase constitution and phase transformation associated with the treatment and during mechanical deformation was examined. Using XRD analysis the volume fraction of the austenite in the matrix was estimated. The various aspects of processing a commercial cast iron during ausetmpering, the phase transformation, microstructural evolution have been examined along with the property of the material. The mechanical behaviour of the material and the scope for further improvement is discussed.     

Wear behavior of alloyed hypereutectic gray cast iron

Alloyed gray cast iron of varying compositions was studied for their wear behavior. In general, the alloyed gray irons studied have higher graphite volume fraction (∼20%) with Type-A graphite flake morphology. Base cast iron showed two to three times higher wear rates than the alloyed gray irons. Tensile strength and wear rates show decreasing trend with increase in graphite and carbide volume fraction. Wear track analysis shows three body abrasive wear mode resulting in debris generation and smudging along the wear tracks. The graphite gets released during sliding to form films along the wear tracks and then forms irregular debris.     

Wear and friction behavior of alloyed gray cast iron with solid lubricants under boundary lubrication

Friction and wear behavior of MoS₂, boric acid, graphite and TiO₂ has been compared under extreme boundary lubrication condition. Boundary lubrication was simulated for the study. Results show that MoS₂ and graphite were 30-50% more effective than other two lubricants. Friction coefficient shows a decreasing trend with increase in sliding speed due to increasing temperature and higher shear force. High friction coefficient values were recorded for all the lubricants (0.2-0.5). This is due to predominating solid interactions during boundary lubrication condition. Boric acid and TiO₂ were not much effective in lubrication.     

Honeycomb solar pond collector and storage system

An analysis of a honeycomb-stabilized, saltless solar pond as a solar energy collector and long term (spanning seasons) storage system is presented. The solar pond is considered with a nonconvective zone made up of an oil layer and air honeycomb configuration. A heat flow model is developed using the two loss mechanisms (conduction and radiation). The efficiency of heat collection and the storage characteristics of the system are excellent for hot water production and process heat applications.     

Fretting fatigue studies of titanium nitride-coated biomedical titanium alloys

Fretting fatigue is an adhesive wear mechanism caused by repetitive tangential micro-oscillation between two contacting materials pressed together under cyclic load. Bioimplants, such as hip joints and bone plates, are prone to undergo fretting fatigue failures during their service within the body. This article presents the fretting fatigue damage characterization of physical vapor deposition (PVD) TiN-coated biomedical titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) subjected to cyclic loads. The PVD TiN layer delayed the damage because of superior tribological properties compared with uncoated alloys. Delamination and abrasive wear damage of TiN at contact caused failure of the alloy. Friction coefficient curves of the PVD TiN-coated pair showed an irregular pattern caused by the influence of wear particulates and Ringer fluid at the contact.     

Molecular interactions in intercalated organically modified clay and clay-polycaprolactam nanocomposites: Experiments and modeling

In this work we have evaluated molecular interactions in organically modified clay and polymer clay nanocomposite using a combination of experimental (photoacoustic FTIR, XRD) and computational (molecular dynamics (MD)) techniques. The FTIR data reveals hydrogen bond and ionic bond interaction between functional end groups of organic modifier and surface oxygen of interlayer clay sheet lying in the organically modified clay; and, the hydrogen bond formation between intercalated polymer and organic modifier and surface oxygen of clay sheet lying in the interlayer clay gallery in the polymer clay nanocomposite. In this work we report the nature of interactions between clay and polymer, clay and organic modifier in polymer-clay nanocomposites through experiments and molecular dynamics simulations.