Mohan Manoharan

Self-assembly of an organic–inorganic block copolymer for nano-ordered ceramics

Self-assembly is a promising approach for achieving controlled nanoscale architectures in ceramics. The addition of ceramic-forming precursors to templating agents such as self-assembled surfactants or organic block copolymers (BCPs) has thus far been the primary route to forming ordered nanoporous oxides1,2,3,4,5 and nanostructured non-oxide ceramics6,7,8,9. In spite of its viability, however, this approach has several intrinsic shortcomings, including: (1) stringent requirements for amphiphilicity between template and precursor, lack of which may lead to macro-phase separation and loss of nano-scale order; (2) morphologies that can change uncontrollably with varying amounts of added ceramic precursor. Here we report a novel single-source ceramic precursor, based on a hybrid organic–inorganic BCP of polynorbornene–decaborane, that enables the formation of ordered ceramic nanostructures with tunable morphology and composition. In particular, we describe the synthesis of nanostructured boron carbonitride and mesoporous boron nitride, the latter of which exhibits the highest reported surface area for this material to date.

Finite Element Analysis of Crack-Path Selection in a Brick and Mortar Structure

Many natural composite materials rely on organized architectures that span several length scales. The structures of natural shells such as nacre (mother-of-pearl) and conch are prominent examples of such organizations where the calcium carbonate platelets, the main constituent of natural shells, are held together in an organized fashion within an organic matrix. At one or multiple length scales, these organized arrangements often resemble a brick-and-mortar structure, with calcium carbonate platelets acting as bricks connected through the organic mortar phase.

Hierarchical Nanoceramics for Industrial Process Sensors

This project developed a robust, tunable, hierarchical nanoceramics materials platform for industrial process sensors in harsh-environments. Control of material structure at multiple length scales from nano to macro increased the sensing response of the materials to combustion gases. These materials operated at relatively high temperatures, enabling detection close to the source of combustion. It is anticipated that these materials can form the basis for a new class of sensors enabling widespread use of efficient combustion processes with closed loop feedback control in the energy-intensive industries. The first phase of the project focused on materials selection and process development, leading to hierarchical nanoceramics that were evaluated for sensing performance. The second phase focused on optimizing the materials processes and microstructures, followed by validation of performance of a prototype sensor in a laboratory combustion environment. The objectives of this project were achieved by: (1) synthesizing and optimizing hierarchical nanostructures; (2) synthesizing and optimizing sensing nanomaterials; (3) integrating sensing functionality into hierarchical nanostructures; (4) demonstrating material performance in a sensing element; and (5) validating material performance in a simulated service environment. The project developed hierarchical nanoceramic electrodes for mixed potential zirconia gas sensors with increased surface area and demonstrated tailored electrocatalytic activity operable at high temperatures enabling detection of products of combustion such as NOx close to the source of combustion. Methods were developed for synthesis of hierarchical nanostructures with high, stable surface area, integrated catalytic functionality within the structures for gas sensing, and demonstrated materials performance in harsh lab and combustion gas environments.