Multi-scale Sensors and Systems

For this overall objective: two separate goals are defined. The first goal is the fundamental understanding of the relation between cell performance and pressure drop using a single-channel fuel cell, and the second goal is more practical study with a multiple, parallel channel segmented fuel cell. In both cases the operation at low current density with low stoichiometric ratio will be focused, because the water drainage is significantly reduced at such operating conditions.

Project Description

Quenching, rapid cooling, has been used to improve hardness and reduce crystallinity by preventing low temperature processes of phase transformations. So cooling alloys and steels in an extremely rapid manner produces martensitic microstructure in their surfaces. Conventional quenching methods use oil, polymer, air, and water. In this proposal, intensive quenching using high velocity water flows is proposed to improve heat-extraction rate by increasing 3-5 times greater heat fluxes from the heated surface of metals. This method is highly efficient and ecofriendly because it uses water and provides greater heat-extraction rates resulting in greater temperature gradient in the sample. This temperature gradient forms compressive stresses from the surface that mainly eliminates cracking. So the intensive quenching keeps the residual surface stresses compressive, while the conventional quenching normally produces tensile or neutral residual surface stresses. The main goal of this project is to establish fundamental and practical technology on intensive quenching heat treatment.

Michigan Tech will do survey on intensive heat treatment technologies available and/or practical in the world and also do corresponding analytical studies for Year I. For the second year, Michigan Tech will continue doing market survey and analyzing recent research trends for intensive quenching and traditional heat treatment technologies. For Year III, Michigan Tech will provide future market trends and comprehensive technology analysis on heat treatment.

Confidential

Confidential

This project encompasses three separate projects that are a part of a NSF I/UCRC that is centered at the University of Denver. The three projects are:

• B3: Physical and Chemical Aging of Carbon/Epoxy Composites

• Cl: Development of Advanced Aluminum Alloys for High Conductivity, Elevated Temperature Strength, and Low Galanic Corrosion

• C2: Thermo-Mechanical-Electrical Properties of Carbon Fiber /Nanoparticle/Epoxy Composites

Project Goal of B3

This project has three objectives: (1) Develop simple and accurate structure­ property relationships relating exposure conditions and nanoparticle content to expected thermo-mechanical performance; (2) Fabricate, characterize, and test polymer and polymer composite materials exposed to long durations of sub-Tg and elevated temperatures, moisture, UV radiation, and oxidative environments; and (3) Use molecular modeling techniques to provide physical insight into observed behavior.

Project Goal of C1

Potential aluminum alloys will be identified and examined for their conductivity through Vienna Ab-initio-Simulation Package (VASP) Density Functional Theory (DFT). Precipitation kinetics will be simulated with Prisma using the MOBA13 database. Using VASP DFT calculations and ThermoCalc, a computational survey will be utilized to select promising alloy compositions and heat treatments. Once this computational survey has been performed, select alloys will be fabricated and assessed experimentally for conductivity and hardness amongst other properties.

Project Goal of C2

This project has two objectives: (1) Develop molecular models to efficiently determine nanoparticle/epoxy combinations that enhance stress & heat transfer and (2) Fabricate and test graphite fiber/nanoparticle/epoxy hybrid composite panels for thermal conductivity, impact & compression strength, and electrical conductivity and shielding

Introduction/Synopsis

Polymer-matrix nanocomposites have the potential to become one of the primary structural materials used in future aircraft and spacecraft. High specific-stiffness and specific-strength properties of these materials can be established by using the right combination of polymer matrices, nanostructured reinforcement, matrix/reinforcement interfacial conditions, reinforcement weight fraction, and reinforcement orientation.

This large combination of nanostructural/microstructural material parameters renders the experimental development of these materials to be expensive and time consuming if a trial-and-error approach is used. Fortunately, multiscale computational modeling can be used to facilitate material development through the prediction of structure-property relationships that are efficient and accurate.

While a significant effort has been put forth by numerous researchers to predict bulk-level mechanical properties of crystalline materials (e.g. metals, ceramics) and other highly-ordered systems (e.g. carbon nanotubes) based on molecular structure, very little attention has been paid to amorphous polymer systems. However, an equivalent-continuum modeling method has been established to predict the macroscopic Young's modulus of polymers and polymer nanocomposites based on polymer type, reinforcement geometry, and polymer/reinforcement conditions using a simple, efficient, and accurate modeling approach. Recently, this approach was improved by placing it within a thermodynamic framework. As a result, the equivalent-continuum modeling method can now predict bulk mechanical properties, such as strength and Young's modulus, of polymer nanocomposites as a function of molecular structure in a manner that is thermodynamically consistent and accurate.

Objectives

The overall goal of the research is to use multiscale modeling to establish structure-property relationships for polyimide nanocomposites. Molecular- and rnicrostructural characteristics of these materials will be related to tl1e predicted mechanical properties. Specifically, the following nanocomposite materials systems will be studied:

• Polymer matrix materials

3. ULTEM
4. sp; LaRC-8515

• Reinforcement materials

2. SWNTs
3. Graphene oxide sheets

The structure-property relationships will relate the following structures and mechanical properties:

• Molecular- and micro-structural parameters

0. Polymer matrix material type
1. Reinforcement material type
2. Matrix/reinforcement interface conditions
3. Reinforcement weight fraction
4. Reinforcement orientation
5. Reinforcement size

• Bulk-level mechanical properties

1. Young's modulus
2. Strength (onset of microvoid formation)

The overall objective of establishing the structure-property relationships will be achieved with the following series of tasks:

• Task 1: Establish a series of equilibrated molecular structures for different combinations of matrix and polymer materials and a range of interfacial conditions using MD-based techniques

• Task 2: Predict the molecular-level Young's modulus and the onset of mechanical failure for these materials systems using MD-based techniques

• Task 3: Construct a series of micromechanical models that incorporate the results of Task 2 and predicts the bulk-level stiffness and strength for a range of reinforcement weight fractions, orientations (randomly dispersed, aligned), and size (length, diameter)

Scope of Work

The Environmental Molecular Sciences Laboratory (EMSL), a national US Department of Energy (DOE) User Facility located at the Pacific Northwest National Laboratory (PNNL), requires services to work in collaboration with EMSL staff for the deployment of in-situ TEM and correlative microscopy of biological systems in support of the BER Mesoscale Pilot Project.

The second year of this study will take place from October 1, 2015–September 30, 2016 with potential extension into FY2017. MTU will provide expertise and labor for operating electron and optical based imaging platforms at EMSL, collecting and analyzing data, maintaining scientific records and presenting and publishing research results.

Overview:

Nano-sized transition metal oxides (TMO) are promising materials for lithium-ion batteries. These materials operate through conversion reactions and are associated with much higher energy densities than intercalation reactions. Extensive research is ongoing on the electrochemical characterization of TMO-based electrodes; however, many fundamental questions remained to be addressed. For instance, TMOs exhibit a mysterious extra capacity beyond their theoretical capacity through mechanisms that are still poorly understood. In addition, nano-sized TMOs are highly vulnerable to structural defects produced during synthesis that can alter lithium ion pathways by perturbing the local electronic and lattice strains. No experimental work has been reported to reveal the underlying mechanisms that can correlate structural defects to the electrochemical lithiation in TMOs owing to the difficulty in characterizing structure at the nanoscale, particularly at buried interfaces. This research aims to fill this gap.

The objective is to understand the underlying atomistic mechanisms by which structural defects such as hetrointerfaces, heteroatoms, dislocations, twining, and grain boundaries affect the lithiation behavior of TMOs. In order to meet this objective, single TMO nanowires (NWs) will be subjected to in situ electrochemical lithiation inside high-resolution transmission electron microscope (HRTEM) and aberration-corrected scanning transmission electron microscope (CsSTEM). The in situ electrochemical lithiation will be conducted using state-of-the art scanning tunneling microscope (STM-TEM) and conductive atomic force microscope (cAFM-TEM) holders. This unique combination enables the study of evolution of local lattice strains and electronic perturbations at the vicinity of defects with unprecedented spatial resolutions better than 0.7 A and chemical sensitivity down to 0.35eV.

Intellectual Merit:

The in situ studies will enable research in three poorly understood fields: (I) the effect of structural defects (twins, dislocations, grain boundaries, and hetrointerfaces) on the nucleation of Li₂0 and TM particles due to conversion reactions in TMOs; (II) the pinning/unpinning effect of impurities or dopants during grain boundary movement associated with the nucleation of Li₂0 and TM phases; and (III) the evolution of localized strain and electronic structure at the vicinity of structural defects and their effect on Li-ion pathways The new understanding can facilitate the design of structurally-tailored TMOs for Li-ion battery applications. Furthermore, the experimental methodology and protocols to analyze the in situ data can be extended to other nanomaterials to enable high performance batteries.

Abstract

The research aims to understand the mechanisms by which (1) doping elements and chemistry defects; and (2) structural properties of nanowires (length, diameter, shape, and orientation) affect the piezoelectric-driven electrical output in semiconductor nanowires for energy harvesting systems. This understanding will shed light and provide solid experimental evidence on one of the most important on-going research debates related to the ability to obtain electrical output from semiconducting-piezoelectric nanowires. Currently, the underlying nanoscale mechanisms by which doping elements, defects, and structure affect the piezoelectric-driven electrical output in nanowires are unknown. The electro-mechanical coupling of ZnO nanotubes will be studied by straining the nanotubes specimens using a first of its kind in-situ force and electrical measurement system (AFM/STM) inside the transmission electron microscope {TEM) where the microstructure of ZnO nanowires can be simultaneously imaged in high resolution. The proposed research provides a unique opportunity to advance scientific knowledge on the mechanisms of mechanical energy harvesting in nanowires, and the ability to clear up existing uncertainties in the field.

Intellectual Merit

The in-situ electrical-mechanical probing of ZnO nanowires inside the TEM will enable research in two unexplored areas: (i) the role of doping elements and defect chemistry; and (ii) the role of structural properties of nanowires (diameter, length, shape, orientation) on the piezoelectric-driven electrical output, for which data is not yet available in the literature. The new understanding on the coupling phenomenon is not limited to ZnO nanotubes, and will pave the roadmap for experimental studies on other semiconductorpiezoelectric nanowires (for instance ZnS, GaN, BaTiQ,, AIN). The PI has several years of research experience in the area of electron microscopy of materials, and the Co-PI is a well-established researcher in the area of nanomaterials synthesis and in particular ZnO nanowires.

Abstract

The goal of this research is to improve the current Lithium-Sulfur Batteries. Li-ion batteries have improved in performance, reliability and safety. Lithium-sulfur batteries have a high theoretical capacity (1672 mAh/g) and energy density (2500 Wh/kg), which, along with low cost and toxicity, makes them an excellent candidate for applications ranging from consumer electronics to electric vehicles. This has created opportunities for new applications such as in electric and hybrid vehicles. These applications to such a large-sized device require larger capacity and better durability, and an increase in the capacity of the anode material could be very effective in raising the specific energy of Li-ion batteries. Thereafter, improving the lithium sulfur battery cycling performance could double the current LIB technology.

In order to understand the causes of Lithium-Sulfur Batteries failure when it is cycled for hundreds of cycles, investigation will focus on lithium insertion in sulfur with in situ transmission electron microscopy (TEM). This will help identify small modification in a local area of the cathode before its generation. To date no in situ (TEM) or in situ atomic force microscopy (AFM) studies on Li-S batteries have been reported in the literature. The only in situ structural characterization experiments on Li-S batteries that are reported are based on X-ray experiments.

Objective and Method: The objective of this research is to understand the electrochemically induced polysulfide phase formations and degradation mechanisms in cathode electrodes for Li-S batteries. In order to meet this objective, novel cathode materials (carbon fibers with encapsulated sulfur) subjected to in situ electrochemical testing inside high-resolution TEM (HRTEM), aberration-corrected scanning transmission electron microscope (Cs-STEM), and AFM. This unique combination enables the study of evolution of local lattice strains and electronic perturbations in the cathode materials with sensitivity to single atoms. This fundamental research yield new understandings on the electrochemical performance of cathode materials in Li-S batteries and will pave the roadmap for developing batteries that surpass current Li-ion batteries.

Polymer composite materials have become a staple in the design, development, and manufacturing of commercial, military, and research aircraft. Because of their relatively high mechanical properties {per unit mass) they are used as the main structural components in fuselages and control surfaces in many subsonic fixed-wing aircraft. In order to continue to make improvements in aircraft safety, efficiency, and comfort; composites with increased functionality must be developed. Traditionally, a time-consuming trial-and-error approach has been employed 'with the development of polymer composite materials until an acceptable material that meets the design requirements has been found. The development process is further complicated 'with the inclusion of nanoparticles into traditional composite materials {either as a matrix-doping agent or as the primary reinforcement). Because of the small size of nano-reinforcements, the physical basis for observed material behavior cannot always be ascertained through experimental means. Multiscale modeling approaches, which have gained considerable interest in the last decade, can be used to facilitate traditional research by removing these barriers. Thus, coupling multiscale modeling and experiments can increase the rate of materials development and provide physical insight into observed material behavior.

The objective of this research is to develop a multiscale modeling approach to predict the mechanical and acoustic absorption properties of nanocomposite materials as a function of material structure. The model will be validated using experimental tests on the modeled material. The modeled material will be a hybrid composite composed of graphene nanoplatelets, traditional carbon fibers, and a Polyetherimide polymer (ULTEM). The graphene nanoplatelets will be dispersed into the ULTEM polymer to form a nanocomposite material. This nanocomposite will be used as the matrix component of a traditional 'woven fabric composite with curb on fiber. Because graphene has been shown to exhibit sound-absorbing capabilities and improved mechanical properties when used in composite materials, it is anticipated that the hybrid composite will have good overall mechanical and acoustic damping properties. This material could potentially be used in aircraft structures, included the fuselage, for mechanical durability and reduced cabin noise.

The research is broken up into three specific tasks. For the first task, a multiscale modeling technique will be established to predict the bulk-level 1nechanical and acoustic absorption properties of carbon fiber/graphene/ULTEM composites. This modeling strategy will incorporate molecular dynamics simulation, micromechanics analysis, and the Fiber Undulation Model to relate molecular structure to bulk-level properties of the composite. For the second task, composite test specimens will be fabricated and tested to determine the elastic and acoustic absorption properties of the material. This data will be used to validate the modeling strategy. The third task will focus on the development of simple structure-property relationships using the validated modeling approach. The resulting structure-property maps will serve as design guides materials researchers and engineers involved in materials selection.

As a result of this study, an efficient and accurate multiscale modeling approach will be developed 'which can be easily adapted by other researchers to continue the development of materials used for aerospace structures. Also, the model \Viii be experimentally validated and used to establish structure-property relationships for a hybrid carbon fiber/graphene/UL TEM composite which have the potential to improve mechanical properties and noise-reduction capabilities for aerospace structures.

Interpretation of data that is computationally-generated at Colorado State University (CSU) and Mayo Clinic as part of the newly-funded NIH program for the development and testing of the intramuscular pressure sensor. Consultation and direct interaction with researchers participating in the computational simulation of skeletal muscle. Dr. Odegard has a unique set of skills in continuum mechanics modeling of materials that will be useful for the successful completion of the overall project.

Abstract

For shear driven flows, a comparison of the traditional boiler and condenser operations with those of the proposed innovative boiler and condenser operations. The innovative devices are introduced for functionality and high heat capability for shear dominated situations that arise in milli-meter scale operations, certain gravityinsensitive operations (on aircrafts), and zero-gravity operations. These devices therefore facilitate the development of thermal management applications which employ boilers and condensers under these conditions. The operational methodologies that exploit ways to significantly enhance heat-flux (e.g. > 1 kW/cm2) within the context of the proposed operations are also presented. These benefits are realized at acceptably low mass-fluxes, pressure drops, and inlet temperatures close to saturation temperatures (i.e. without subcooling requirements).

The experimental realizations for innovative devices are reported for flows within horizontal channels. Results for these flows of FC-72 vapor in a horizontal rectangular cross-section duct (2 or 6 mm gap and 15 mm width) of 1 m length. The experiments demonstrate the ability to restrict the boiling and condensing flows to annular flows where a thin film flows (< 0.5 mm) over the entire heat exchange surface of the device.

Introduction and utilization of controlled pulsations (in 5-20 Hz range) in the mass flow rate show an ability to maintain thin film flows with significant additional enhancements ( >300 %) in heat-transfer rates over those obtained in the absence of controlled pulsations. The reported enhancements are associated with asymmetric reduction in the timeaveraged mean film thickness (associated with high heat-flux values) appears to be related to the larger “dwell” time (relative to the characteristic time period of the pulsation) of wave-troughs when the instantaneous film thicknesses (at the wave troughs) become less than tens of micro-meters. The demands of this “dwelling/sticking” nature of micro-scale flows on top of a wetting heat-exchange surface are believed to be met by interactions with (and destabilization of) the adjacent solid-like adsorbed layer (whose thickness may be <200 nm) on the heat-exchange surface. The presence of adsorbed layer under these conditions (three phases being close to one another) allows for the presence of phenomena that govern film dynamics – e.g. a range of positive to negative disjoining pressures and the ability to withstand shear stresses. In nucleate pool boiling, similar phenomena (very high heat-flux values) under similar conditions are known to be present at the contact line of growing and departing bubbles.

Abstract

Advancement in electronic-cooling, avionics-cooling, and spaced based operations have posed enormous engineering challenges of low heat removal rates, high pressure drops, and device-and-system level instabilities. The need, to meet these challenges, is innovations for the critically needed shear dominated boiler and condenser operations. This is to allow efficient removal of large amounts of heat. Even large industrial-scale gravity-driven boiler operations need to be innovated for the next generation combined cycle (or related) electric power plant technologies – towards producing electricity in more efficient and sustainable ways. These innovations need a combined breakthrough in boiler and air-side flow technologies - to meet global energy challenges.

To meet the challenges, on-going research on enabling breakthroughs. These are based on fundamental fluid-physics based experimental discoveries for boiler and condenser operations. For developing scientific knowledge and engineering design tools, these discoveries are also supported by breakthroughs in associated modeling and simulations research.

A key innovative operation procedure introduces passive recirculating vapor flows within the devices. This controls the flows and ensures that very stable boiling and condensing flows occur in a manner where a thin liquid film flow, typically within 0.5 mm thickness, covers the entire heat-exchange surface. A second innovation is introduction of large amplitude waves through controlled resonant pulsations in the liquid film - leading to a 200-1000% enhancement of the heat removal rates. Analysis suggests the underlying physics. As the troughs of the waves on the liquid film approach the wetting heat-exchange surface to within 30-50 μm, the specific location starts exhibiting solid-liquid-vapor interactions phenomena similar to the high heat-flux contact line locations associated with nucleate boiling or drop-wise condensation. Retaining this physics and changing the working fluid to water, ongoing research plans to demonstrate very high heat removal (> 1 kW/cm2) values over the entire length of the innovative devices.

Abstract

Cellulose nanocrystals (CNCs) are highly crystalline organic polymers that can be extracted from natural materials. They are stiffer than aluminum and theoretical calculations place their tensile strength at 7500 MPa, higher than glass fibers or steel. Considering that these crystals are biocompatible, lightweight, low cost, and sustainable they offer tremendous potential for applications in biomedical materials, energy technologies, electronics, and microelectromechanical systems (MEMS) devices. However, this potential has not yet been fully realized, primarily because little is known about the parameters that affect the CNC's mechanical properties including: (i) variations between different natural resources of cellulose (e.g. bacteria, plants, and agricultural products), (ii) the size-scale effect, and (iii) crystallographic anisotropy. To date, no experimental tests have been utilized to measure the strength properties of CNCs. In order to evaluate such properties the underlying mechanisms responsible for nanoscale mechanics should be determined. In-situ experiments and multiscale models for deformations in small-scale components could open possibilities for improved design and applications of CNCs. This research aims to fill that gap.

The objectives of this research are (i) to explore the nanoscale mechanics of individual CNCs as a function of the cellulose resource; (ii) to determine the dependency of CNC's mechanical properties to cellulose dimensions; and (iii) to fully characterize the elastic modulus of CNCs as function of their crystallographic orientations. To meet these objectives, nanomechanical properties will be investigated through the use of a novel in-situ characterization technique that enables atomic force microscopy (AFM) experiments inside the chamber of a transmission electron microscope. The in-situ data will then be used to develop and validate the continuum mechanics and molecular dynamics models of CNCs.

These in-situ studies will enable research in two relatively unexplored fields: (i) the effect of cellulose resources on the strength properties of individual CNCs will be directly measured, and (ii) the strength properties of individual CNCs as a function of length-scales, load-modes, and crystallographic orientations. These areas have not been accounted in the literature, but clearly have a large effect on the mechanical properties. The use of AFM allows for the unprecedented material characterization of individual CNCs as compared to other methods that can characterize only aggregate properties.

CNC-based materials are expected to have great impacts on the biomedical field (e.g. as bone scaffolds, hip and cartilage replacements), automotive components (e.g. interior and, potentially, exterior components), and high performance textiles and nonwovens.

Overview:

Mobility is a key factor to well-being, both emotionally (through increased independence and decreased depression and anxiety) and physically {through reduced disease risk, bone maintenance, muscle strength, and weight control). Over a million US citizens are limb amputees, primarily lower leg amputees. This program will 1) work to improve the mobility of lower extremity amputees through research in design and control of powered ankle-foot prostheses, which mimic the steering mechanism of human gait by having two controllable degrees of freedom (DOF) and 2) integrate research with education and outreach to inspire and equip a diverse next generation of engineers. To work toward these long-term goals, this program will develop – and use in education and outreach - a lightweight, cable-driven, powered ankle-foot prosthesis capable of steering and traversing slopes by learning from human ankle impedance in the sagittal and frontal planes during gait.

This research is based on the hypothesis that an ankle-foot prosthesis capable of applying torques and impedance modulation in both the sagittal and frontal planes, similar to the human ankle, will improve maneuverability and increase mobility by lowering the metabolic cost of gait - both when walking straight and turning. Advances in powered prostheses have shown the ability to reduce metabolic cost and increase the preferred speed of gait for unilateral transtibial amputees during straight walking by providing sufficient power during push-off. Powered prostheses can also reduce asymmetrical gait patterns and thus may lower risk of secondary complications. However, studies show that turning steps account for 8-50% of steps, depending on activity, and thus may account for 25% of daily steps. Modulation of ankle impedance in the sagittal and frontal planes plays a major role in controlling lateral and propulsive ground reaction forces. While a non-amputee relies on hip movement in the coronal plane and the moment generated in the ankle joint, an amputee using a passive prosthesis uses the hip extension in the sagittal plane as a gait strategy. The hypothesis is supported by preliminary results which show a large inversion of the ankle during the stance period of step turns, indicating a significant deviation of ankle rotations from the straight-step pattern.

Understanding the role of the ankle in locomotion and developing a platform for design and control of new ankle-foot prostheses will allow exploratory research and education. Research includes: Thrust 1: Estimate ankle impedance in the sagittal and frontal planes during the stance period of gait; Thrust 2: Develop a powered ankle-foot prosthesis with two controllable DOF; Thrust 3: Evaluate the design and control of the prosthesis using an evaluation platform and with below-knee amputees through collaboration with Mayo Clinic; and Thrust 4: Education/Outreach: Utilize the steerable ankle-foot prosthesis for education, outreach, and research experiences to impact diverse K-12, community college, undergraduate, and graduate students.

The work is significant in that it will contribute 1) new knowledge about multivariable impedance modulation of the human ankle during the stance period of gait, an area not yet fully explored, and 2) a unique framework for developing and evaluating powered ankle-foot prostheses. The steerable ankle-foot prosthesis is innovative because it will enable amputees to walk with a more natural gait by using the ankle joint, rather than merely the hip and knee. Development of this novel platform will be a substantial step toward the long-term goal of improving design and maneuverability in lower extremity assistive prostheses and robots.

Robotics is a high-impact way to attract the attention of future engineers. Outreach activities are included to that spark and sustain STEM interest in pre-college students, especially underrepresented minorities. Development of an inexpensive powered ankle-foot prosthesis will improve well-being of Wounded Warriors and civilian amputees, while at the same time inspiring and training the future STEM workforce. In addition, a newly developed a low-cost EMG-controlled manipulator will be included as an educational platform that will be used in outreach programs to teach fundamentals of mechatronics, robotics, and biomechanics to K-12, community college, undergraduate, and graduate students.

Abstract

Overview: Apoferritin is an organic cage that captures the toxic free ferrous ions and transforms them into a ferrihydrite and iron oxide crystalline nanoparticle through a complex biomineralization process (the resulting structural protein is called ferritin). Any dysfunction of ferritin protein can result in iron toxicity, serious illness, chronic diseases, and especially neurological diseases. Dysfunction in ferritin results in the alterations in the biomineralization of the ferritin cores, and therefore, understanding the process of biomineralization within ferritin, is of great importance in the study of neurodegeneration and other chronic diseases. While these unique proteins have been the subject of intense research in biology and chemistry fields due to their importance in many chronic diseases, little effort has been made to unveil the dynamics of such biomineralization processes in liquid conditions. To the Pl's knowledge, there has been no direct evidence at atomic level on how the biomineralization or demineralization inside a ferritin protein progresses over time. This research aims to fill this gap.

The objective of this project is to investigate the in situ crystallization of ferrous ions into crystalline ferrihydrite and iron oxide nanoparticles as well as the demineralization of crystalline core in healthy and dysfunction ferritins in unprecedented resolutions within liquids. In-situ studies conducted inside an atomic resolution aberration-corrected scanning transmission electron microscope (STEM) enabling imaging at resolutions better than 1A. A miniaturized graphene-based electron transparent bio/nano reactor compatible with the microscope chamber is utilized to preserve the liquid environment inside the electron microscope. In this graphene bio/nano reactor, ferrous ions delivered to apoferritins through break down of liposomes acting as reservoirs of irons to trigger the biomineralization within apoferritins cores.

The research is the first atomic resolution study of proteinmediated biomineralization and demineralization within a liquid media and inside a transmission electron microscope. This CAREER research unfolds: (I) The nucleation and growth mechanisms of mineral core (ferrihydrite and iron oxide crystals), (II) the existence and evolution of atomic defects (vacancy, twinning, misorientation boundaries, amorphous regions, etc) during the crystallization, (Ill) the evolution of chemical gradient from surface to core of crystals during the biomineralization, (IV) the mechanisms of demineralization due to iron release, and (V) The atomic-scale morphological and structural differences between a healthy and dysfunctional ferritins.

This research probes the ground rules for ferritin biomineralization with the goal to unveil the fundamental differences with dysfunctional ferritins responsible for neurological diseases. In addition, a new research field for the utilization of bio/nano reactors to image complex biochemical reactions at atomic resolutions will be developed. The CAREER plan will impact the society by integrating multi-disciplinary research with education at all levels while promoting diversity. Graduate and undergraduate students involved with the project will be trained in cross-cutting areas.

The research is focused on two of the three key microgravity challenges;

(i) Evaporation and condensation processes and (ii) Efficient use of detailed models to simulate cryogenic propellant behavior.

The research objectives are:

I. Develop a standard method for measuring accommodation coefficients for evaporating hydrogenated cryogenic propellants using neutron imaging. The experiments addressing this objective will utilize the NIST Neutron Imaging Facility (Gaithersburg, MD). The accommodation coefficients for liquid hydrogen and liquid methane will be obtained in both a pure vapor environment and a two-component (vapor and gaseous helium) environment.

II. Develop a numerical simulation of liquid films of hydrogen and methane using a modified version of an evolution equation that couples the vapor phase to the liquid film via a kinetic model for evaporation and condensation.

The research addresses the solicitation goal of supporting future space science and exploration needs of NASA by providing fundamental knowledge on evaporation and condensation of cryogenic propellants. Long-duration, microgravity storage and transfer of cryogenic propellants are mission critical technology. A variety of passive and active technologies have been used to control boil-off, but the current state of understanding of cryogenic evaporation/condensation in microgravity is insufficient and at TRL-1. The proposed effort would increase the state of understanding to TRL-3 through the development of a novel experiment utilizing the Neutron Imaging Facility located at NIST.

The experiments and accompanying modeling will enable determination of the accommodation coefficients necessary for the development of zero boil-off technologies and methodologies. Currently, there are no experimental methods for determining accommodation coefficients for cryogenic propellants. The proposed experiments will enable determination of these coefficients and could become a standard method for measuring accommodation coefficients of hydrogenated cryogenic propellants.

In addition, simulations of evaporation and condensation from liquid films will provide data to address the uncertainty in how kinetic expressions of phase change should be modified in the presence of two-component mixtures in the tank ul1age. The thin film simulations directly address the need for a simplified model to predict instantaneous thermodynamic conditions of cryogenic liquid films in the propellant tank ullage.

The outcomes will be a new standard method for obtaining fundamental data for hydrogenated cryogenic propellants, a more thorough understanding of underlying physics of cryogenic evaporation and condensation, and a foundation for establishing the minimum size of system-level technology demonstrations.