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EVOLUTION OF POLYMERS Evolution of advanced ceramics from preceramic precursors

Aug 24, 2022

There has been a significant rise in the use of Precursor-Derived Ceramics (PDCs) in recent years. The article explains the rise of polymer/precursor-derived ceramics from theory to translational research and highlights its application benefits and business potential. - Prof Ravi Kumar, HoD, Department of Metallurgical and Materials Engineering, & Professor of Ceramics, Laboratory for High Performance Ceramics, Indian Institute of Technology- Madras (IIT-Madras); Raghunath Sharma, MVSS, Research Scholar (PhD), Laboratory for High Performance Ceramics, Department of Metallurgical and Materials Engineering, Indian Institute of Technology-Madras (IIT Madras)

The technology of Precursor-Derived Ceramics (PDCs) is a fantastic way to design advanced technical ceramics at different length scales. The methodology usually involves the selective use of monomers that are polymerised and subjected to atmospheric pyrolysis resulting in a conversion of a polymer precursor into an amorphous ceramic.

These thermally stable amorphous ceramics can be heated further to produce crystalline phases that are thermodynamically stable. In addition to solid-state thermolysis, which can result in ceramic powders, structural and functional ceramic coatings, fibres and highly porous materials can also be produced using conventional polymer processing techniques. Pre-ceramic polymers can be utilised to produce amorphous materials with distinctive compositions that are not attainable with traditional ceramic powder-based processes.

These materials can withstand extremely high temperatures. The main advantages of making ceramics from polymeric precursors include pressure-free sintering, machinability, development of nanoceramics with the desired composition, kinetic stabilisation of less stable phases, adaptability of diverse manufacturing capabilities of polymer process engineering, and development of the desired composition of nanoceramics. By carefully controlling the precursor chemistry and the processing parameters, the microstructure of these synthesised ceramics may be modified to create products specifically tailored to the needs of a given application.

Application areas

Aerospace applications, such as scramjet propulsion, hypersonic travel, re-entry vehicles, and advanced rocket motors, require new materials that can operate in oxidising or corrosive atmospheres at temperatures greater than 2000°C and occasionally throughout a long working life. These applications are where the preceramic precursor technology & the derived ceramics are of particular interest.

External parts like the nose, vertical fins, wing leading edges or flaps, divert/attitude control thrusters, nozzle throats, combustor liners, and panels, where higher thermal and mechanical loads are encountered, can be made of these ceramic materials for re-entry vehicles, hypersonic aircraft, missiles, and rockets. The uses of such materials are not restricted to the mentioned examples or fields and can be expanded to other potential arenas such as environmental, functional, structural, automotive (petrol/diesel-powered vehicles as well as electric vehicles), and energy applications such as in solar cell, fuel cell, supercapacitor, and battery, chemical and gas nanosensor, piezoelectric sensors, actuators, dielectric material, and other emerging fields.

Business potential

The history of such a niche technology dates to the 1970’s with the advent of SiC fibres involving pyrolysis of polycarbosilane by Yajima. To date, such fibres can be developed only through the precursor-derived route. SiC, SiCN, and SiBCN are examples of high-performance nonoxide ceramic fibres that display outstanding thermomechanical properties. These fibres maintain their high tensile strength (>2 GPa) and stiffness (>200 GPa) even at temperatures exceeding 1500°C.

These fibres are primarily utilised in ceramic matrix composites (CMCs) and metal matrix composites (MMCs) as reinforcement. To satisfy the rising demands in the automotive, energy, aerospace, and military industries, these lightweight thermo-structural composite materials are being developed. Ceramic fibre filaments are essential for the aerospace and defence industries, making them one of the most important materials for advancing both technology and national security.

The only five businesses that commercially produce nonoxide Si-based ceramic fibre filaments are Nippon Carbon (Japan), Ube Industries (Japan), Dow Corning (USA), COI ceramic (USA), and BJS Ceramics (Germany). It is important to note that despite our readiness to pay the expensive price, these fibres are on an embargo list and hence cannot be imported into India. India has yet to establish indigenous technology for the mass manufacture of ceramic filaments based on silicon and non-silicon-based ceramic fibres.

With a compound annual growth rate (CAGR) of 10.2% over five years, the global market for precursor-derived ceramics expanded from $437.6 million in 2017 to $712.4 million by 2022. Additionally, there are numerous private companies with annual revenues of more than $100 million throughout the world, such as Starfire Inc, USA, which have been extensively explored over the past 40 years.

Towards advanced ceramics

Originally, PDCs were marketed as structural ceramics for high-temperature applications. In recent times, adding more transitional elements to silicon oxycarbide and silicon carbonitride ceramic systems has demonstrated intriguing possibilities in terms of increased mechanical capabilities and thermal stability at a lower processing cost than its non-oxide ceramic equivalents. Also, the flexibility to tailor non-silicon containing molecular precursors is an added advantage, single source precursor derived advanced non-oxide ceramics such as B4C, BCN,ZrC have exceptional oxidation stability that maybe maintained even at very high temperatures (>1600oC) and have a wide range of thermo-structural uses.

This approach can be used to incorporate transition metals such as Ti, V, Hf, Ta, and Nb-based carbide, carbonitride, borocarbide, and borocarbonitride ceramic systems. It is not just restricted to the synthesis of B4C, BCN, ZrC, ZrC, ZrCN, ZrBC, and ZrBCN based ceramic. The possibility to obtain HfCN based ceramic- material with the highest melting point is the icing of the cake further. The fabrication of high phase purity and complicated shaped ceramic components, such as dense monolithic ceramic, fibres, coatings, and composites, is possible using this new type of cost-effective precursor technology.

The inception of CeraTattva InnoTech

The growing impetus towards Aatmanirbhar Bharat and India’s strategic self-reliance can be envisaged only when entrepreneurial ventures come up based on such niche materials that can accelerate India’s space and defence capabilities even further. In this context, the inception of private ventures that can collaboratively work with various government organisations in terms of technology development, and upscaling is the need of the hour.

CeraTattva InnoTech (CTIT) is a specialty material innovative technology-based start-up focused on the indigenous development of non-oxide ceramic precursors or polymers, advanced ceramic materials, and ceramic processing technologies at cost-competitive pricing. CTIT is the first private venture in the country concentrated on the development of novel preceramic/precursor technologies which will assist the core strategic sectors of aerospace defence, and energy along with significant applications in the automobile industry as well. CTIT incorporates a unique amalgamation of remarkable non-oxide ceramic products and solutions as well as extraordinary manufacturing/production capabilities in their operational backbone.

Highlighting the key benefits to the country from this technology, Prof Ravi Kumar, Head, Department of Metallurgical and Materials Engineering, IIT Madras, said, “Ceratattva is India’s first of its kind company based on novel polymer-derived ceramics with capabilities to manufacture highly tailorable ceramic precursors. It is dedicated to the indigenous development of strategic non-oxide ceramics which are mostly on the embargo list and are not commercially available in India.”

Image Gallery

  • Potential application arenas of the recursor derived ceramics: pushing the limits of India’s strategic self reliance further in defence and aerospace sectors

  • Precursor derived ceramics ranging from tailorable precursors, to specialised fibre manufacturing technologies

  • Prof Ravi Kumar

    HoD - Department of Metallurgical and Materials Engineering

    Professor of Ceramics, Laboratory for High Performance Ceramics

    Indian Institute of Technology- Madras (IIT-Madras)

  • Raghunath Sharma

    MVSS, Research Scholar (PhD), Laboratory for High Performance Ceramics

    Department of Metallurgical and Materials Engineering

    Indian Institute of Technology-Madras (IIT Madras)

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