RESEARCH PROJECTS
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Design of new type of polymer-derived ultrahigh temperature materials:
This project focuses on design and development of novel polymeric precursors for synthesis of multifunctional ceramics, such as Si-C-N, Si-O-C, and Si-B-C-N/HfC systems. These materials are of immense technological significant because of their unique high temperature mechanical, optical, and electrical properties. They are being actively explored for applications in environments that require materials to withstand extreme conditions, such as those experienced in gas turbines, jet engines, modular reactors, and space applications. More specifically, we study the chemistry of polymer-to ceramic transformation, optimization of the precursor structure with the goal to enhance final ceramic's physical properties. By combining novel materials with advanced synthesis techniques, the research aims to push the boundaries of what can be achieved with precursor derived ceramics, ensuring reliable performance in next-generation high temperature applications.
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Advanced thermal and optical coatings:
This project involves design of advanced thermal and optical coatings utilizing carbon nanotube and graphene modified ceramic composites. These coatings are engineered for applications that require materials to withstand extreme thermal conditions and yet exhibit excellent absorption across a broad range of wavelengths, from UV to far IR. Such coatings may enhance the performance and durability of devices used in aerospace and fundamental scientific research applications, where precision and reliable working of the device (for example, a power meter) under extreme conditions is essential.
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Manufacture of bulk powders of 2-D materials for use in energy storage devices:
This project investigates preparation and use of 2-D materials, particularly those comprising of exfoliated sheets of transition metal dichalcogenides (TMDs) and TMD-alloys, in energy storage devices. Atomically thin layers of TMDs (MoS2, WS2 etc. including alloy TMDs such as MoWS2), exhibit unique chemical and physical properties such as high surface area, thickness dependent tunable optical/electrical properties that arise from their 2-D structure. These materials are being studied for a range of applications including high-capacity, lightweight, and flexible electrodes for next generation batteries, capacitors and other electrochemical devices including sensor devices. The project aims to scale up synthesis of powders of nano sheets of TMDs and incorporate them into hybrid composites, leading to significant advancements in energy storage systems.
TMDs are 2-D materials similar to graphene with unique chemical and physical properties.
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Fundamental understanding of charge storage and degradation mechanisms in 2-D electrodes:
Goal here is to gain deeper insights into charge storage mechanisms in high surface area 2-D materials, especially electrodes made from graphene derivatives and TMDs. A significant challenge in the field of nano materials for energy storage is the low charge capacity and voltage hysteresis that often occurs in the first cycles of Li-ion battery use. By investigating fundamental issues that lead to these problems, the project aims to uncover the origins of irreversibility and develop approaches (for example, voltage cut-off, nano structuring, conformal coatings to prevent degradation with electrolyte) to mitigate the first-cycle loss and energy inefficiency. Overall objective is to explore new strategies for optimizing electrode materials, enhancing their chemical stability, and enabling faster charging and longer lifetimes.
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Impact Publications
1. L. David, R. Bhandavat, and G. Singh*. Large Area MoS2/graphene Composite Paper Based Electrode for
Room Temperature Na-ion Batteries: Electrochemical and Mechanical Characterization. ACS Nano, 8 (2), pp 1759–1770 (2014). Citations: 1312
Prof. Singh and students were the first to report on mechanical and electrochemical testing of a new kind of composite consisting of layered graphene and molybdenum disulfide for sodium ion batteries. Flexible paper-like material made from graphene and molybdenum disulfide fixed swelling of electrodes in sodium-ion batteries. This work was later patented by Prof. Singh and student [U.S. Patent No. 10,950,850. The work was highlighted in IEEE Spectrum Magazine:
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2. R. Bhandavat, L. David and G. Singh*. Synthesis of Surface Functionalized WS2 Nanosheets and Performance as Li-Ion Battery Anode. Journal of Physical Chemistry Letters 3 (11), 1523–1530 (2012). Citations: 431
Highlighted in Science Daily, PhysOrg, Azo-Nano, ChemViews, and IEEE Spectrum magazine.
3. L. David, R. Bhandavat, U. Barrera, and G. Singh*. Silicon Oxycarbide Glass-Graphene Composite Paper
Electrode for Long-Cycle Lithium-ion Batteries. Nature Communications, 7, Article number: 10998 doi:10.1038/ncomms10998 (2016). Citations: 380
Silicon electrodes when used in Li-ion batteries tend to crack and break after just a short number of charge/discharge cycles. Meanwhile, the use of graphene on electrodes is limited because graphene’s attractive surface area is only possible in single stand-alone sheets, which don’t provide enough volumetric capacitance. Layer the graphene sheets on top of each other to gain that volumetric capacity, and you begin to lose that attractive surface area. Prof. Singh and student developed a technique that uses a new type of silicon-based ceramic material--silicon oxycarbide that makes the combination of silicon and graphene achieve its expected greatness as an electrode material. Stable cycling in Li-ion batteries up to 1000 cycles was demonstrated without capacity degradation. This work is considered among this most significant works on bendable electrodes for Li-ion batteries. Prof. Singh also have patent on this material [U.S. Patent No. 10,950,850]. News media: http://spectrum.ieee.org/nanoclast/semiconductors/materials/potential-of-silicon-and-graphene-together-for-liion-electrodes-realized
4. L. David, and G. Singh*. Reduced Graphene Oxide Paper Electrode: Opposing Effect of Thermal Annealing on Li and Na Cyclability. Journal of Physical Chemistry-C, 118 (49), pp 28401–28408 (2014). Citations: 194
5. R. Bhandavat and G. Singh*. Stable and Efficient Li-Ion Battery Anodes Prepared from Polymer-Derived
Silicon Oxycarbide–Carbon Nanotube Shell/Core Composites. The Journal of Physical Chemistry C, 117 (23), 11899–11905 (2013). Citations: 118
6. R. Bhandavat, A. Feldman, C. Cromer, J. Lehman, and G. Singh. Very High Laser-damage Threshold of Polymer-Derived Si (B) CN-Carbon Nanotube Composite Coatings. ACS-Applied Materials & Interfaces, 5 (7),
2354–2359 (2013). Citations: 67
During the last 100 years, thermal detector coatings based on carbon-based paints, diffuse metals (gold black, silver black), oxidized metals and other materials have been investigated about spectral uniformity and resistance to damage and aging. Such coatings, however, are vulnerable to damage at high optical powers from forced air, as well as aging and hardening at UV wavelengths. To address this challenge, Prof. Singh and colleagues demonstrated synthesis of a silicon-based ceramic/carbon nanotube shell/core composite. Such coatings show high optical absorbance (98 % from UV for IR) and an unprecedented thermal damage resistance of more than 15 kW.cm-2 at 10.6 μm, highest reported value for any material to date. This material has been patented by Singh and student [U. S. Patent No. 9,453,111]. It was also highlighted in NIST Technical Beat, http://www.nist.gov/pml/div686/nanotubes-041713.cfm
7. L. David, A. Feldman, E. Mansfield, J. Lehman, and G. Singh*. Evaluating Thermal Damage Resistance of
Graphene/Carbon Nanotube Hybrid Composite Coatings. Scientific Reports (Nature Publishing Group) 4, Article number: 4311 (2014). Citations: 46
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8. L. David, D. Asok, and G. Singh*. Synthesis and Extreme Rate Capability of Si–Al–C–N Functionalized
Carbon Nanotube Spray-on Coatings as Li-Ion Battery Electrode. ACS-Applied Materials & Interfaces, DOI: 10.1021/am5052729 (2014). Citations: 36
A new kind of liquid polymer was developed that can be transformed into ultrahigh temperature ceramic upon heating. The liquid polymer may also be used in 3-D printing of ceramics. The waterlike polymer, which becomes a ceramic when heated, also can be mass-produced. This work was later patented by Prof. Singh and student [U.S. Patent No. 9,908,905].
9. G. Singh*, P. Rice, R.L. Mahajan, and J.R. McIntosh. Fabrication and Characterization of a CNT Based Nano-Knife. Nanotechnology, 20, 095701 (2009). Citations: 24
This work, performed by Professor Singh as PhD student was the first demonstration of fabrication and mechanical testing of a carbon nanotube-based compression cutting tool for biological applications.
This work was highlighted in Nanowerks and Singh interviewed for History Channel Modern Marvels—World’s Sharpest: https://www.nanowerk.com/spotlight/spotid=9315.php
10. G. Singh*, P. Rice, R.L. Mahajan, and J.R. McIntosh. Fabrication and Mechanical Characterization of a Force Sensor Based on an Individual Carbon Nanotube. Nanotechnology, 18, 475501 (2007). Citations: 33