Biofouling and Marine Materials

Any solid surface exposed to marine waters immediately gets covered by a thin layer of organic material which attracts micro-organisms like bacteria and diatoms. This is called biofilm and it attracts the larvae of macro-fouling creatures like algae, sponges, anemones, tunicates, hydroids, barnacles, mussels and tube worms. Surfaces of ships and offshore platforms are welcoming surfaces for such attachments and this undesirable accumulation is termed as biofouling. Among the different fouling species barnacles, tubeworms and mussels are referred to as hard foulers as they develop calcareous shells around their body and adhere firmly. The consequence of biofouling is that the roughness of ship surface increases thereby reducing its maneuverability. To maintain the speed more fuel is consumed adding to the emission of greenhouse gases. Continuous requirement of hull cleaning, paint removal and repainting has made biofouling as an expense factor for marine industry.

Since biofouling is an age-old problem, there has always been a requirement for an antifouling surfaces. Tri-butyl tin containing copolymer paints were used as a method to fight against fouling, as the tin ions leaking from these paints kill the adhering larvae. But due to the severe ecological impacts of tin ions on non-target species too, the usage of these paints has been banned in recent times. Current research is into developing a low surface energy, foul-releasing surface, which lowers the adhesion strength of the foulers such that these are removed as the vessel moves through water.

The current project aims in understanding the adhesion mechanism, characterizing the adhesive secreted by the barnacles and the development of a technological solution for this problem and this requires an interdisciplinary approach involving biology, biochemistry, materials science and materials engineering.

Polymer Derived Ceramics

The polymer derived ceramics are ultrahigh temperature materials which can be tailor-made to obtain any specific property by altering the final chemical composition of the ceramic by chosing a suitable polymer precursor and by heat treating it to higher temperatures to evaporate the organic components present in it. Thus the ceramic with desired microstructure can be produced.

Unlike the conventional sintering routes of producing highly covalent ceramic materials using oxidic sintering additives, the polymer derived ceramics can be produced absolutely without any use of sintering additives and hence it is a sintering-free production process. These polymer derived ceramics can not only form strong covalent structures but also exhibit extraordinarily high thermal stability, better mechanical properties compared to many of the known covalent ceramics such as silicon carbide and silicon nitride.

In general, the processing of ceramic materials through organometallic precursors involves the synthesis of preceramic thermosetting polymers or oligomers from monomeric units, followed by cross linking these polymers in order to obtain an unmeltable preceramic network, enabling high ceramic yields and shape stability. Transformation of the cross linked precursors into amorphous covalent ceramic materials is performed by heat treatment in inert atmospheres. It should be emphasized that the polymeric network is locally reconstructed during the organic-inorganic transition forming new bonds. Amorphous covalent ceramic materials are crystallized by post-annealing at higher temperatures. Out of the many precursors, organosilicon precursors are of interest which can be used for silicon containing ceramics.

Group members: Sujith Ravindran, Eranezhuth Wasan Awin, S.Soumya, Vinothkumar

Spray Atomization and Deposition

Spray atomization and deposition (also known as “Spray forming” or “Spray casting”) is a novel idea where sufficiently superheated melt is made to atomize with the help of an inert gas and the resultant droplet cloud (which may be a mixture of liquid, semi solid and solid) is collected onto a substrate. The end product will be a coherent, dense billet with limited porosity which could be eliminated by a secondary processing.  The shape of the product can be affected by suitably designing the substrate so that one can achieve the so called near-net-shape for the final product.

Group members: Devaraj Sonnappa and Raghukiran Nadimpalli 

Syntactic foams

Syntactic foams are composites consisting of hollow microspheres based on inorganic and polymeric materials dispersed in a resinous matrix which could be thermosetting or thermoplastic. They are excellent candidate materials for light-weight structural applications since they exhibit isotropic physical properties, high specific compressive strength & stiffness, low moisture absorption, and high thermal stability. Concomitantly, these materials also possess low effective dielectric constants that can show great potential for specific electric/dielectric applications as exemplified below.

Group members: Kousaalya A. Baktavachalam