Vol . 8 No. 5 & 6 October/December 2000
Naval Materials Technology
Any technological advancement is always linked with matching development in materials. DRDO has developed protective coating for ships, speciality polymers, stealth materials, structural steels and ceramic materials and also caters to the need of the Navy for material testing, like failure analysis, quality assurance of POL used and other fuel samples testing. Some of the present areas of work relate to protective measures against marine corrosion and bio-fouling, high strength alloys, stealth materials, environmental studies on enclosed space in submarines, pollution in harbours, and fuel cells. Some of the major systems developed are: dual purpose anode system for submarine, impressed current cathodic protective (ICCP) systems for ships, high build chlorinated rubber-coal tar, anticorrosive paint for underwater hull and boot trap areas of ships and pontoons, heavy duty non-skid paint for decks and engine room floors, solvent-free anticorrosive paint for interior compartments and storage tanks for petroleum products, and fuel cell.
Carbon Dioxide Control System
The system comprises carbon dioxide monitor, molecular sieve for carbon
dioxide absorption and a microprocessor for
automatic control. The carbon dioxide absorbent is inert, safe and regenerative in nature.
The operation does not disturb the RH level of the atmosphere. This is an essential system
Fuel cells are alternative source of power and may well be in use for propulsion of underwater vehicles. Phosphoric acid fuel cell has been developed. It generates electricity when hydrogen and air are passed into phosphoric acid and a contact established in catalyst-incorporated electrode matrix. Methanol reformer has been developed to generate hydrogen for fuel cell operation.
Cathodic Protection System (ICCP)
Platinised titanium .anode-based ICCP has been developed for prevention of hulls from underwater corrosion. The system consists of auto control unit, reference electrode, and anodes. The Ag-AgCl reference electrodes have been developed to meet the requirement of the Navy for the existing ICCP system onboard ships. Also, electroless antifouling device based on cuprious oxide and polyvinyl alcohol/resin/teflon binders has been developed. The system starts leaching of copper as soon as it comes in contact with sea water and prevents fouling.
Fire Retardant Intumescent Paint
This paint on coming in contact with fire produces char of about 100 times its original thickness thereby insulating the surface on which it is applied and protecting it. The paint consists of special polymer emulsion pigmented with titanium dioxide and intumescent materials to be applied by brush. The fumes generated during burning of paint are non-toxic. The paint has civil usage also in high rise building interiors, train compartments, etc.
A heavy duty epoxy non-skid paint has been developed to prevent skidding of personnel and aircraft on flight deck, helo and weather decks. The paint, after application, provides niform rough texture. It also possesses resistance to thermal stresses due to intermittent heating up to 250oC.
High Performance Exterior Paint
The paint developed for superstructure of ship and other structures in marine environment has excellent corrosion resistance, chalking resistance and gloss-retention properties. Silicone modified soya alkyd is used as binder and rutile titanium dioxide as pigment.
Vibration Damping Material
This is an elastomeric material. A large number of polymer blends and interpenetrating polymer networks have been developed and incorporated in the product range. The materials have excellent damping capabilities, in wide frequency and temperature range. These find use as shock vibration mount for machines, constrained layer damper for plates for structures, and bush/washers for sonar transducer array. The materials, made from elastomers and vinyl polymers, are under trial.
Ion Exchange-cum-Indicator Resin
The material is a cation exchange resin used for purification of water and as acid-base indicator. It is based on crosslinked polymers containing acid groups. The material is superior to conventional cation exchange resin and its indicator property is unique in nature as it can indicate the regeneration time of the exchange column. In other areas, the indicator can be used as reusable solid phase acid-base indicator. The material is under trial.
The material is used for sealing gaps between rubber-to-rubber and rubber-to-metal articles. It is a two-component system and has excellent sea water, marine atmosphere resistance and ageing characteristics.
PZT Polymer Composites & Hydrophones
PZT polymer composites are the state-of-the art materials for high
efficiency hydrophones and are made from high purity submicron size chemically homogenous
PZT powder and matrix polymer. The material is used for sonars and seismic sensing,
ultrasonic imaging and smart structures.
A process for dispersion of oil in sea water has been developed by employing a technique using bio-emulsifier, nutrient mixture and oil degrading bacteria (ODB). The isolation and culture techniques of ODB have been developed. A protection process for bioemulsifiers has been established and the unjoint action of emulsifier, bacteria and nutrient has been proven for speedy dispersion of floating oil.
High Strength Materials
High Strength low Alloy Steel
Research on the development of ultrafine bainitic steel through new alloy design concept and thermomechanical-controlled processing has resulted in B and Cu containing steel having high strength coupled with high toughness and good weld ability. This CuBx steel offers considerable cost benefits taking into account overall economics, productivity and infrastructure available in Indian steel industry. In addition to its possible use in defence it has also promise for use in other areas, such as bridges, pipelines, offshore platforms, etc. As a spin off, an ultra high strength steel has been developed with minor addition of alloying elements and can be considered for possible armour application. Patents for this technology have already been filed.
Fe-TiC Metal Matrix Composite
The material is iron-based TiC particulate metal matrix composite. It has been synthesised by aluminothermic reduction of oxide. The product can be cast into required shapes and can be used to make wear/corrosion-resistant coating .