Michael R. Zachariah - US grants

Award Abstract
CTS-0500008

Principal Investigator: Michael R. Zachariah

Institution: University of Maryland - College Park

Proposal Title: Collaborative Research: GOALI: Nanocrystal Formation and Morphology in Nonthermal Plasmas


Crystalline nanoparticles are intensely studied as building blocks for a wide variety of novel nanoscale systems and devices. Among nanoparticle materials silicon plays an important role due to its excellent electronic properties, its wide use in microelectronics manufacturing, its low toxicity, and the absence of environmental hazards. Low-pressure plasmas-partly ionized gases created at only a fraction of the atmospheric pressure-offer several unique properties that are highly beneficial for the synthesis of crystalline silicon nanoparticles. Plasmas allow for high processing rates based on the efficiency of direct gas-to-particle conversion. Compared to other gas phase processes, plasmas offer the advantage that particles are unipolarly negatively charged, which strongly suppresses or completely avoids detrimental agglomeration of nanoparticles.
This Collaborative Research/GOALI project focuses on the study of a plasma process that was shown to yield high-quality silicon nanoparticles with highly unique virtually perfect cubic shapes. Particles are highly uniform in size and exhibit virtually no detectable crystal defects. Nanocrystals of this kind appear to be ideal building blocks for nanoscale devices such as novel vertical Schottky barrier transistors or light emitting devices. While the research will focus on a particular plasma process, the studies will help to answer much broader unresolved questions. Among those are how crystalline particles can be formed in a plasma environment that is close to room temperature, and why silicon particles would assume the highly unusual cubic shape, which is ideal for device applications but is not the equilibrium shape for pure silicon particles.
The technical studies aim at finding the currently unknown relations between plasma proper-ties and the properties of the synthesized particles. The project pursues four goals: (1) the ex-perimental characterization of the plasma properties in the synthesis process; (2) the experimen-tal study of particle properties including their size distribution, particle crystallinity, and mor-phology; (3) the numerical study of the plasma properties and plasma dynamics caused by the presence of particles; and (4) the atomic simulation study of the relation between the process plasma conditions and the particle crystallinity and morphology. Tasks (1)-(3) will be pursued by the group at the University of Minnesota, task (4) by the group at the University of Maryland. The GOALI industrial partner is InnovaLight, Inc., based in St. Paul, MN, a company that pur-sues the development of solid state light sources based on silicon nanocrystals.
The leverage provided by an NSF-IGERT project for "Nanoparticle Science and Engineer-ing" will enhance the broader impact of this project. The involvement of at least three graduate students and minority undergraduate students will foster the integration of research and training and the involvement of underrepresented groups. The close collaboration with InnovaLight will ensure rapid knowledge transfer to industry. This will enable and accelerate the development of potential commercial applications such as more energy-efficient light sources as well as elec-tronic devices and biomedical diagnostics. This project is co-funded by NSF and the U.S. De-partment of Energy under the NSF/DOE Partnership for Basic Plasma Science and Engineering.

0730963 Probing and Manipulating Heat Transfer in Nanofluids and Nanoemulsion Fluids

There has been enormous interest in using nanofluids and nanoemulsion fluids to meet new challenges in various technologies because of the observed superior thermal properties. However, the fundamental mechanisms of heat transfer in these fluids are currently not well understood. There exists a great need for research to investigate the underlying physical phenomena of energy transport in these fluids. The proposed research aims to explore the fundamental relation between the macroscopic thermal properties and the microscopic structure and dynamics of nanofluids and nanoemulsions. Model nanofluid systems with controlled microstructure and dynamics will be developed. These model systems, combined with a multi-pronged experimental characterization, will be used to resolve the existing controversy in understanding the energy transport process in nanofluids and nanoemulsion fluids. A thorough understanding of physical phenomena of thermal transport in nanofluids and nanoemulsion fluids allows for the development and optimization of critically important fluids with significantly enhanced thermophysical properties.
The proposed research also seeks to integrate research and education by involving students as research partners, and by participating in outreach activities for local high school educators and students. Apart from the education and training opportunities for the students directly supported in this project, underrepresented undergraduate students will be involved in this research through the NIST Summer Undergraduate Research Fellowship Program (www.surf.nist.gov). Additionally, hands-on demonstrations of nanofluids and nanoemulsion fluids will be given to students in an undergraduate course (ENME332). The proposed research will also utilize the outreach program ESTEEM (www.eng.umd.edu/k12/k12_summer-programs.html) to motivate high school students with hands-on experiments and real life examples, to become scientists and engineers.

The conversion of solar energy into solar fuels provides long-term storage and transport of the world?s most abundant but intermittent source of energy. In the transition from fossil fuels to hydrogen as an energy carrier, materials science will play an unprecedented role. Significant materials challenges exist in the production and storage of hydrogen related to development of renewable hydrogen energy based technologies. This joint effort between the University of Maryland and the Dayalbagh Educational Institute in Agra, India, implements a systematic study focusing on design, synthesis and evaluation of inexpensive, abundant and stable transition metal oxide semiconductor materials, hematite, titania and copper oxide, with end applications in photoelectrochemical production of hydrogen. The team brings together expertise in nanomaterials synthesis and characterization (US/India), and photoelectrochemistry (India). The objective is to improve the state-of-the-art for this class of photoactive materials through careful integration of synthesis, characterization, and simulation, and to use this basis for substantial fundamental advances in materials design.

Through scientific exchange, as well as exchanges of personnel, the team develops significant intellectual infrastructure for materials research, as well as optimizes use of instruments and facilities at each of the partner institutions in this international collaboration. Beyond the laboratory, recognizing that advances in materials science will not be translated into improved quality of life without a well-trained scientific and engineering workforce, the multidisciplinary and multinational team and the timely topic of materials for hydrogen generation will attract and retain more students in the science, technology, engineering and mathematics (STEM) pipeline.

This award is co-funded by the NSF Office of International Science and Engineering.

The project is an exploratory study aimed at confirming and extending a report published in Science (Guo et al. 2014) of an iron-silica catalyst and reaction conditions leading to direct, non-oxidative, methane conversion (DNMC) to higher-value chemical feedstocks including ethylene, benzene, and naphthalene. The technology, if proven, represents a significant technological breakthrough with transformative potential for converting the large quantities of shale gas derived methane to transportable, high-value chemical feedstocks rather than the current practice of flaring with associated emissions of the greenhouse gas, carbon dioxide.

The underlying challenge in methane chemistry is active and selective catalytic conversion to form fuels and chemicals in an economical approach without deactivating the catalyst via thermal processes or coke formation. The PIs will elucidate the reaction pathways and mechanisms in the DNMC reactions over Fe©SiO2 catalyst by ex-situ analysis of catalyst fine structures and using Molecular Beam Mass Spectroscopy (MBMS)to analyze both stable and radical gas phase reaction intermediates and products. The study will also evaluate the effects of hydrogen and hydrocarbon species on catalysis as a parameter to control DNMC and demonstrate its applicability in context of the following specific aims: (i) Successfully synthesize the catalyst and understand its activation mechanism; (ii) Systematically tune the product selectivity and methane conversion by controlling the feed stream compositions; (iii) Rigorously describe the kinetic effects of feed composition on methane reaction pathways and catalyst deactivation. The proposed research will provide specific guidance for the development of catalysts and processes useful in manufacturing value-added products from low cost methane gas resources. To this end the broader impact of a practical DNMC process would transform the fuels and chemicals industry while reducing the atmospheric burden of CO2 and the impact of fossil resources on global warming. The technology could also have potential application in other areas such as processing of pyrolysis gases from biorenewable sources. The study will create a unique opportunity for graduate and undergraduate students to experience cross-cutting education in aspects of catalysis, reaction engineering, gas analysis, and chemical kinetics.

This award is co-funded by the Engineering Directorate Office of Emerging Frontiers and Multidisciplinary Activities.

Nanoparticles (NPs) hosted in a conductive matrix are important for a range of applications from electrochemical energy storage, to catalysis to energetic devices. However, manufacturing NPs in high quality and at high efficiency remains as a challenge. Aiming to address this challenge, this Scalable NanoManufacturing (SNM) award plans to investigate a scalable nanomanufacturing and stabilization method for NPs embedded within a conductive matrix through a unique thermal shock process. This project can lead to an ultra-fast and facile NP nanomanufacturing approach in a carbon matrix based on high-temperature (up to 3000 K) thermal shock within 10 milliseconds. The relatively simple approach to manufacturing NPs in a conductive matrix by heating provides an ideal teaching tool for high school and undergraduate students. Involving these students in this project helps increase their interests in science and technology and offering training opportunities to gain research experience. Cyber-based outreach activities via iMechanica.org will also further broaden the impacts of the proposed research and educational activities.

The project originates from the team's recent demonstration of ultra-fast (<0.01 s) synthesis of uniformly distributed metal NPs within a conductive matrix by Joule heating, followed by subsequent rapidly quenching. In this project, the fundamentals of ultra-fast, in situ NP formation in conductive matrices using aluminum NP and reduced-graphene oxide or carbon nanofiber matrix as a model system will be investigated. The fundamental understanding of the process will be applied to investigate the scale-up synthesis of the NPs in a conductive matrix, focusing on overcoming major scale-up roadblocks, such as uniform distribution throughout the thickness direction, and low cost, followed by designing and benchmarking scalability with a lab-scale roll-to-roll processing setup. The team will also demonstrate, evaluate and optimize the roll-to-roll system to fabricate aluminum NP composites, and investigate the key nanomanufacturing-related issues, such as fabrication rate, throughput, product quality, reproducibility, yield, efficiency and cost.