The proposed research, funded by the Solid State and Materials Chemistry program, is aimed at synthesizing mesostructures of diamond at high pressure using periodic mesostructured carbons produced by soft self-assembly with surfactant templates. For the synthesis, the carbons will be infiltrated by polycarbosilanes until the pore space is filled. Heat-treatment of the so-infiltrated carbons will produce periodic mesostructured silicon carbide/carbon composite materials. Subsequently, these composites will be treated at high pressure and temperature to transform the carbon phase into periodic mesostructures of diamond. The synthesis will be performed in multi-anvil assemblies which allow for pressures of up to 27 GPa and temperatures above 2000°C. The produced mesostructured silicon carbide/diamond composites will be structurally characterized and tested for their mechanical properties. By selective removal of the silicon carbide phase from the SiC/diamond composites mesoporous forms of diamond will be produced. In addition, we will explore the mechanisms and kinetics of the phase transitions within mesostructures at high pressure by in-situ Raman, SAXS, and IR spectroscopic experiments. The in-situ experiments will be done in diamond anvil cells. It is expected that the realization of these aims will create seminal knowledge across the different fields of high-pressure science and periodic mesostructures, and produce potentially useful new materials.
NON TECHNICAL SUMMARY Mesoporous materials belong to the most important classes of materials due to their wide structural diversity and broad range of applications including catalysis, separation, microelectronics, and drug-delivery. Pressure and temperatures are the two major thermodynamic variables in synthesis. The emphasis of this work is to explore the role of high pressure in synthesis to produce mesostructures of diamond and investigate the mechanisms of phase transformations at high-pressure inside a mesostructure. Thereby, the project will advance the understanding of the chemical high-pressure behavior of periodic mesostructures and make a broad impact on synthetic high-pressure chemistry which is currently an underrepresented field. Diamond is the arguably the most technologically important high-pressure phase. Mesostructured composites of diamond, which are the expected products in this research, could find applications as ultrahard materials. Diamond is known as biocompatible material and thus mesoporous forms of diamond could have potential in drug-delivery. Commercially relevant outcomes of the work will be communicated to industry via the Lehigh Nanotechnology Network and Lehigh's Industrial Liaison Program. Leading companies for the production of diamond materials will be involved in materials testing, which will catalyze technology transfer. The project will be done in collaboration between a degree-granting University (Lehigh University) and a non-degree granting research institution (Carnegie Institution of Washington) thereby building a close tie between these institutions. The involved students and post-docs will learn an unusual combination of synthetic (synthesis of mesostructured materials, high pressure syntheses) and analytical techniques (electron microscopy, X-ray diffraction, gas sorption etc.). Results from the work will be integrated into "Advanced Inorganic Chemistry", and "Solid State Chemistry" courses.
