Low-Pressure Plasma Process for Nanoparticle Coating Investigators: Farzad Mashayek, MIE/UIC; Themis Matsoukas, ChE/Penn State Prime Grant Support: NSF Simulated flow of ions over a nanoparticle Problem Statement and Motivation Nanoparticles of various materials are building blocks and important constituents of ceramics and metal composites, pharmaceutical and food products, energy related products such as solid fuels and batteries, and electronics related products. The ability to manipulate the surface properties of nanoparticles through deposition of one or more materials can greatly enhance their applicability. Nanolayer coating on a silica particle Technical Approach Key Achievements and Future Goals A low-pressure, non-equilibrium plasma process is developed using experimental and computational approaches. Two types of reactors are being considered. The first reactor operates in “batch” mode by trapping the nanoparticles in the plasma sheath. Agglomeration of the particles is prevented due to the negative charges on the particles. The second reactor is being designed to operate in a “continuous” mode where the rate of production may be significantly increased. This reactor will also provide a more uniform coating by keeping the nanoparticles outside the plasma sheath. The batch reactor is already operational and has been used to demonstrate the possibility of coating nanoparticles. A reaction model has been developed to predict the deposition rate on the nanoparticle surface. The possibility of using an external magnetic field to control the trapping of the particles has been investigated computationally. The experimental effort is now focused on the design of the “continuous” mode reactor. The computational effort is focused on development of a comprehensive code for simulation of the plasma reactor, nanoparticle dynamics, and surface deposition. The goal of this project is to design, analyze and optimize a continuous, low-pressure plasma process for the deposition of nanocoatings on nano- and micron-sized particles, by conducting concurrent computational and experimental studies. Low-pressure plasmas are unique in their ability to handle a broad variety of substrate materials, particle sizes and shapes, and gas-phase precursors. They offer the advantage of low temperature processing (300 K to 600 K), wide range of chemistries that can be conducted, excellent purity control compared to liquid-phase processing, and ability to produce surface features in the nanometer range. Further, the non-equilibrium nature of these plasmas produces a population of highly energetic electrons and results in negatively charged dust particles. A consequence of the high degree of charging is the resistance of such particles against aggregation, a problem that usually plagues both liquid and gas-phase processing. Charge stabilization in the plasma is effective for particles as small as 50 nm thus making it possible to process sizes well below the limits of traditional fluidization without the detrimental effects of aggregation. The Penn State group has recently demonstrated the feasibility of low-pressure plasma process for depositing films with thickness of the order of a few to several hundred nanometers on micron and sub-micron particles. The existing setup, however, has certain shortcomings: (a) it is characterized by non-uniformities of the deposited film that arise from the immobilization of particles in areas of low reactivity, (b) it is limited in the amount of particulate matter that it can process, and (c) it is not easily amenable to optimization because of the asymmetric electrode design needed to provide stable particle confinement. Here, we propose to use a radially symmetric plasma for continuous film deposition that does not require particles to become trapped in the sheath. In this configuration, the decoupling of gravity from other trapping forces prevents trapping, allowing particles to move continuously through the reactor. The numerical study considers the solution to the Lagrangian equations for plasma (ions and electrons) and dust particles in conjunction with the Eulerian equations for electromagnetic fields, fluid motion, and transport of the precursor and other species in the plasma. The chemical reaction process, leading to particle surface coating, is also modeled and included in the simulations. To adequately address the issue of coating nonuniformity, the plasma particles will be simulated using both the direct method of particle-in-cell (PIC) as well as a more general method involving the solution of the Eulerian equations for ions and electrons in conjunction with a stochastic approach for dust particle charging.

Nanostructured Sensors for Detecting Low Levels of Hydrogen at Low Temperatures Investigators: J. Ernesto Indacochea & Ming L. Wang, Materials Engineering Department Prime Grant Support: National Science Foundation Problem Statement and Motivation Self-sustained membrane oxide material p - Semiconductor Pd imbedded nanotubes Recent research thrusts for alternate methods of power generation has turn to production and storage of H2 as alternative fuel, as it is the most environmental friendly fuel. It is foreseen that H2 will become a basic energy infrastructure to power future generations; however it is also recognized that if it is not handled properly (e.g. transportation, storage), it is as dangerous as any other fuel available. Ultra sensitive hydrogen sensors are urgently needed for fast detection of hydrogen leakage at any level, such as the H2 leaks in solid oxide fuel cells (SOFC). Technical Approach Key Achievements and Future Goals This investigation is being performed in collaboration with the Materials Science Division of Argonne National Laboratory. Nanotubes have been selected because their high surface-to-volume ratio will lower requirements for critical volumes of H2 to be detected without compromising the sensitivity of the sensor. Pd-nanotube assemblies will be processed by ANL and initial hydrogen sensing tests will be conducted at their facilities. The nanostructured MOS sensor will be assembled at UIC-Microfabrication Laboratory; this will be tested first in H2 atmospheres, where the H2 levels and temperature will be adjusted. The final stage of the study will involve field testing in SOFC’s and detect hydrogen evolution in acidic corrosion of metals. Pd nanotube assemblies have been fabricated successfully at the Argonne National Laboratory. Pd nanotubes excel in high sensitivity, low detection limit, and fast response times in hydrogen sensing. These nanotubes show an expanded surface area and granular nature, in addition to the high capability for dissociation of molecular hydrogen. Electrochemical techniques will be used to monitor H2 evolution with time. These nanotubes will be incorporated into the design and fabrication of a nanostructured MOS sensor which will be evaluated for H2 detection. <Add some notes to help explain in simple terms the slide. This can be one or two paragraphs.>

Molecular Simulation of Gas Separations Sohail Murad, Chemical Engineering Department Prime Grant Support: US National Science Foundation Problem Statement and Motivation Understand The Molecular Basis For Membrane Based Gas Separations Explain At The Fundamental Molecular Level Why Membranes Allow Certain Gases To Permeate Faster than Others Use This Information To Develop Strategies For Better Design Of Membrane Based Gas Separation Processes For New Applications. Technical Approach Key Achievements and Future Goals Advanced gas separation techniques such as those based on membranes offer significant potential advantages over conventional cryogenic methods based on liquefaction. These benefits include considerable cost improvement due to higher process efficiencies, as well as fewer environmental consequences. However, despite such processes being commercially available for over a decade, they have been unable to replace traditional methods significantly, which clearly points to some deficiencies in these newer technologies. One aspect that requires improvement is a better understanding of the molecular level forces between the competing gas molecules and the membrane surfaces, which are ultimately responsible for these separations. Our present study is an attempt to address this deficiency. In our studies we have modeled the membrane as a faujasite (FAU) zeolite. The unique properties of zeolites have led to their widespread application in many scientific and technological fields and show considerable potential for gas separations. Zeolites are widely used as molecular sieves for the separation of gases, liquids, etc. The remarkable chemical properties of zeolites arise from their complex porous crystalline aluminosilicate structure, in which the pore sizes are comparable to molecular dimensions of many chemical substances. Therefore, they show peculiar mechanisms of diffusion in which the zeolite framework plays a major role. Recent progress in the manufacture of thin zeolite membranes adds to the promise of zeolite membranes for gas separations Determine The Key Parameters/Properties Of The Membrane That Influence The Separation Efficiency Use Molecular Simulations To Model The Transport Of Gases –i.e. Diffusion or Adsorption Focus All Design Efforts On These Key Specifications To Improve The Design Of Membranes. Use Molecular Simulations As A Quick Screening Tool For Determining The Suitability Of A Membrane For A Proposed New Separation Problem Explained The Molecular Basis Of Separation of N2/O2 and N2/CO2 Mixtures Using a Range of Zeolite Membranes. Used This Improved Understanding To Predict Which Membranes Would Be Effective In Separating a Given Mixture Used Molecular Simulation to Explain the Separation Mechanism in Zeolite Membranes. .

NER: Integrating Nanowires into Microstructures Investigators: Carmen Lilley, ME, Thomas Royston, ME, Michael McNallan, CE Prime Grant Support: NSF (Pending) Problem Statement and Motivation Design and reliability of nanostructures is an important research area that is in its infancy and the proposed research into integration of nanowires into microstuctures would provide an improved fundamental understanding of the salient mechanisms in this area. The research will also contribute to new methods for improving reliability of MEMS devices by developing nanocomposites for MEMS structural material. Figure 2. FEM models for 1st Resonance Mode shape for a free standing thin film with a defect at the lower left corner. Figure 1. Silicon die with nanolines embedded between two metal layers for fabricating composite films. Technical Approach Key Achievements and Future Goals Design and optimize fabrication processes for composites. Microfabrication will mostly take place at the MAL in UIC. Characterize composite materials using techniques based on transmission electron microscopy (TEM). Characterize mechanical properties of the samples using the bulge test, resonance testing, and photo-acoustics (laser ultrasonics) Model samples under mechanical test loads using FEM to extract mechanical properties from experimental data The completed research will be used as a basis for studying long term effects of dynamic and static loads on failure mechanisms, aging effects, and reliability of nanostructures integrated into larger scale systems. Additionally, the proposed exploratory research will enable optimization of a fabrication process for integrating periodic nanowires into microstructures. These composite materials will be used for designing new and more reliable microdevices, such as RF switches. The proposed research is relevant to the Micro- and Nano- Technology Cluster of the MIE Dept. and COE The proposed research focuses on design and reliability of Micro- and Nanostructures. In particular, failure mechanisms of nanowires integrated into microstructures will be studied. The findings will make a significant contribution in the relatively new area of design and reliability of nanostructures. Thin films of gold and aluminum are commonly used as structural materials for Microelectromechanical Systems (MEMS) and their failure mechanisms have been studied extensively. The prevalent modes of failure are fatigue and creep, which affect the lifetime for MEMS devices that are cyclically loaded (e.g. switches) or statically loaded (e.g. pressure sensors). Therefore, aligned nanowires of materials with a greater modulus and fracture strength will be embedded in thin film structures to improve their lifetime by changing the creep behavior of the metal film. In addition, the effects of fabrication on the fatigue and fracture properties of these integrated structures will be studied for design and reliability. Figure 1 shows a schematic of a composite film with nanowires in the middle layer that will be fabricated and tested as part of this exploratory research. Figure 2 is the image of the first resonance mode of a gold/silicon nitride layered film as measured by resonance testing. By fitting measured resonance to FEM models of the resonance modes, elastic properties of the nanocomposite films can be extracted.

Nano-magnetism and high-density magnetic memory Vitali Metlushko, Department of Electrical & Computer Engineering, UIC Prime Grant Support: NSF ECS grant # ECS-0202780, Antidot and Ring Arrays for Magnetic Storage Applications and   NSF NIRT grant # DMR-0210519 : Formation and Properties of Spin-Polarized Quantum Dots in Magnetic Semiconductors by Controlled Variation of Magnetic Fields on the Nanoscale, B. Janko (P.I.), J. K. Furdyna (co-P.I.), M. Dobrowolska (co-P.I.), University of Notre Dame is leading organization, A. M. Chang (Purdue) and V. Metlushko, (UIC) Problem Statement and Motivation Fig. 1a. In circular magnetic elements the magnetization flux forms a vortex. Fig. 1b. Lorentz TEM image of the vortex in 750 nm permalloy dot. Fig. 1c. SEM image of 750 nm permalloy dot with non-magnetic Au con-tacts. The field of nanoelectronics is overwhelmingly dedicated to the exploitation of the behavior of electrons in electric fields. Materials employed are nearly always semiconductor-based, such as Si or GaAs, and other related dielectric and conducting materials. An emerging basis for nanoelectronic systems is that of magnetic materials. In the form of magnetic random access memories (MRAM), nanoscale magnetic structures offer fascinating opportunities for the development of low-power and nonvolatile memory elements. Technical Approach Key Achievements and Future Goals In past few years, the interest in nano-magnetism has encreased rapidly because they offer potential application in MRAM. Modern fabrication techniques allow us to place the magnetic elements so close together that element-element interactions compete with single-element energies and can lead to totally different switching dynamics. To visualize the magnetization reversal process in individual nano-magnets as well as in high-density arrays, Metlushko and his co-authors employed several different imaging techniques- magnetic force microscopy (MFM), scanning Hall microscopy, magneto-optical (MO) microscopy, SEMPA and Lorentz microscopy (LM). This project has led to collaboration with MSD and APS ANL, Los Alamos NL, Katholieke Univesiteit Leuven, Belgium, University of Notre Dame, NIST, Universita` di Ferrara, Italy, Inter-University Micro-Electronics Center (IMEC), Belgium, Cornell University, McGill University and University of Alberta, Canada During the past 3 years this NSF-supported work resulted in 21 articles in refereed journals already published and 10 invited talks in the US, Europe and Japan .

Nanocrystalline Carbide Derived Carbon for Tribological Applications Investigators: Michael McNallan, Civil and Materials Engineering, UIC; Ali Erdemir, Argonne National Laboratory Prime Grant Support: U.S. Department of Energy Problem Statement and Motivation max. safe temperature Mechanical Seals and bearings fail due to frictional heating and wear Materials used are hard ceramics, such as SiC or WC Friction can be reduced by coating with carbon as graphite or diamond Graphitic coatings are not wear resistant Diamond coatings are wear resistant, but fail by spallation or delamination from the underlying ceramic SiC-SiC SiC-CDC Pump seal face temperature during dry running at 4000 rpm With and without CDC coating Technical Approach Key Achievements and Future Goals Produce a low friction carbon layer by chemical conversion of the surface of the carbide SiC(s) + 2Cl2(g)  SiCl4(g) + C(s) At temperatures < 1000oC, carbon cannot relax into equilibrium graphitic state and remains as Carbide Derived Carbon (CDC) CDC coating contains nano-porous amorphous C, fullerenes, and nanocrystalline diamond CDC is low friction, wear resistant, and resistant to spallation and delamination CDC has been produced in the laboratory It’s structure and conversion kinetics have been characterized Tribological performance was verified in laboratory and industrial scale pump tests with water CDC was patented and selected for an R&D 100 Award in 2003 CDC was Licensed to Carbide Derivative Technologies, Inc.in 2006 Scale up to industrial production rates, characterization of process reliability and testing in specific industrial environments is the next goal. <Add some notes to help explain in simple terms the slide. This can be one or two paragraphs.>

Carbon Nanopipes for Nanofluidic Devices Investigators: C. M. Megaridis, Mechanical and Industrial Eng., UIC; Y. Gogotsi, J.C. Bradley, Drexel Univ.; H. Bau, Univ. Pennsylvania; A. Yarin, Technion-Israel Prime Grant Support: National Science Foundation Problem Statement and Motivation Investigate the physical and chemical properties of aqueous fluids contained in multiwall carbon nanotubes Determine the continuum limit for fluid behavior under extreme confinement Provide experimental data for parallel modeling efforts Evaluate the feasibility of fabricating devices using carbon nanotubes as building blocks Technical Approach Key Achievements and Future Goals Multiwall carbon nanotubes filled by high-pressure high-temperature processing in autoclaves Nanotube diameter in the range 5nm-200nm, and lengths 500nm-10μm Gas/liquid interfaces used as markers of fluid transport High-resolution electron microscopy and chemical analysis techniques used to resolve behavior of fluids stimulated thermally in the electron microscope Model simulations used to interpret experimental observations Gas/Liquid interfaces in carbon nanotubes resemble interfaces in macroscopic capillaries when nanotube diameter is above 10nm Non-continuum behavior observed in nanotubes with diameter below 10nm Wettability of carbon walls by water observed; important property for adsorption applications Future applications include drug delivery systems, lab-on-a-chip manufacturing, electrochemical cells, etc. This research examines carbon nanotubes (nanopipes) as a platform for fundamental studies of fluid transport in the spatial regime between molecular and macroscopic (a.k.a. continuum) behavior. The work seeks fundamental understanding of fluid behavior under extreme confinement, as needed for the design and fabrication of a new generation of nanofluidic devices and nano-analytical systems. The methodology includes: (a) fabrication, characterization, and modification of carbon nanopipes, (b) performance of chemical and fluidic experiments, and (c) fabrication of experimental setups that allow transport and measurements of various liquid flows in a controlled fashion. Fluid behavior is investigated by following the dynamic response of visualized fluid interfaces to external thermal stimuli. The experimental work is supplemented by modeling based on parallel molecular dynamic simulations, as well as a theoretical model using a continuum approach, which combines temperature-dependent diffusion with intermolecular interactions. The breakthrough result of this work so far is displayed in the slide figure, which shows a liquid inclusion inside a multiwall, closed carbon nanotube.

A Simple, Scientific Way to Optimize Catalyst Preparation John R. Regalbuto, Dept. of Chemical Engineering Prime Grant Support: NSF 2) Finding optimum pH H2 3) Optimized Pt/SiO2 catalyst 1) Electrostatic adsorption mechanism Problem Statement and Motivation Technical Approach supported metal catalysts like the automobile catalytic converter are immensely important for environmental cleanup chemical and pharmaceutical synthesis energy production catalyst preparation is thought of as a “black art” industry has successful recipes but little fundamental understanding; development is laborious and expensive our lab is a world leader at fundamental studies of catalyst preparation method of “strong electrostatic adsorption:” locate pH of optimal electrostatic interaction reduce metal coordination complex at conditions which retain the high dispersion of the precursor extremely small nanocrystals result (sub-nanometer) metal utilization is optimized method is generalizeable About one third of the country's GDP passes over a catalyst at some point. 90 percent of all industrial reactions are catalyzed. The catalyst usually contain small metal or metal oxide particles anchored onto a stable, high surface area oxide or carbon material, called a “support.” the challenge is to make the smallest metal particles possible on the support; the smaller the metal particle, the more metal atoms are exposed to the gaseous reactants which can only react on metal particle surfaces. Less metal is wasted/inaccessible inside metal particles. You can start with the metal atomically dissolved in liquid solution, but this is only a start. We exploit the chemistry of the hydroxyl groups which populate the surface of oxide and carbon materials. These OH groups are neutral at the oxide’s point of zero charge (PZC), which is different for every oxide. At pH values below the PZC, the OH groups protonate and the surface becomes positively charged and capable to adsorbing metal anions. Above the PZC, the OH groups deprotonate, the surface charges negatively, and cations can be adsorbed. Our work is a matter of measuring PZCs, and selecting a metal coordination complex such as platinum hexachloride or platinum tetraammine (shown above) which best matches an oxide’s tendency to charge negatively or positively (oxides or carbons with low PZCs like to deprotonate and charge negatively at high pH, and vice versa). We then measure metal uptake versus pH to determine the pH at which the strongest interaction occurs. We then make catalyst at this pH, and once contacted and dried, it is a matter of converting the coordination complexes to elemental Pt; that is, to the catalytically active metal. To remove the Cl or NH3 ligands, a combination of heat and reactive gases is normally employed. This results in the reduction of the Pt+4 or Pt+2 precursor to the elemental metal phase (Pt0). The Pt particles shown on a silica support in the figure are less than 1 nm in diameter. These truly are nanoparticles…. We are trying to get the most out of common, relatively cheap catalyst precursor by understanding them better…. Key Applications fuel cell electrocatalysts automobile catalytic converters petroleum refining catalysts