Investigators: Drs. J.A. Puszynski and J.J. Swiatkiewicz, Department of Chemical and Biological Engineering, SDSM&T
Research Topic: Investigation of Ignition Characteristics of Heterogeneous Strongly Exothermic Reactions.
In recent years researchers have found that energetic materials, which are produced on nanoscale have shown significantly improved performance, especially in the area of impact sensitivity, mechanical properties, and energy release rate. Metastable Intermolecular Composites (MICs) also call superthermites represent one example of such materials. These systems consist of metal (e.g. aluminum) and oxidizer nanopowders. The MIC formulations are based on intimate mixing of reactants on the nanometer length scale. As the specific surface area increases, the number of contact points between the reactants also increases and therefore the reaction rate increases. Review of the recent literature on the combustion of pyrotechnic materials shows the relation between the reaction rate and an average particle size of reactants is significant. The experimental studies have also shown that the reaction rate depends on other factors, including particle size distribution and degree of intermixing. Reaction rates between nanosize aluminum and metal oxides can be significantly greater than those observed with traditional micron-size thermite powders. Reactions occurring between metal and metal oxide powders are accompanied by the generation of high temperatures (>3000 K). Super-thermites, formed by mixing of aluminum and metal oxide nanopowders result in energy release rate by two orders of magnitude higher than similar mixtures consisting of micronsize reactants. These super-thermites may find an application in formulations of environmentally benign percussion primers, air bag initiators and inflators, parts of weapon systems as well as components of thermal batteries. The same idea of reacting nanopowders e.g., aluminum and nickel with addition of carbon nanotubes can be used to form in-situ intermetallic nano-composites for structural applications. This novel process is called combustion synthesis.
During the past few years, a significant research effort has been made in the formation of reactive nanometer size powders (nanopowders), including reactive elements, such as aluminum, boron, nickel, and silicon. These powders are characterized by very high specific surface area (20 - 150 m2/g). The average particle size of such powders is below 100 nm. Due to a large specific surface area, these nanopowders might be pyrophoric when exposed to air or another oxidizing atmosphere. They can be handled in air environment only if a proper passivation layer is applied. In 1999-2000, Dr. Puszynski spent his sabbatical leave working at the Naval Surface Warfare Center (NSWC) at Indian Head, MD. During his one-year sabbatical leave he designed a pilot plant installation and assisted NSWC to produce nanosize aluminum powder with various average particle sizes. At that time, this was only reliable source of aluminum nanopowders in the United States. The aluminum nanopowders produced by NSWC were further subjected to passivation with oxygen in order to make them suitable for processing in air. A typical TEM photograph of aluminum nanopowder generated in the installation designed by Dr. Puszynski is shown in Figure 1. The oxygen-passivated aluminum nanopowders are covered with a thin layer of aluminum oxide having a thickness between 2-3 nm. This thickness of aluminum oxide layer is sufficient to prevent the powder from further oxidation by molecular oxygen. The rate of diffusion is sufficiently low to see any effect of oxidation in dry air over the period of several years.
Figure 1. TEM photograph of Al nanopowder generated in NSWC pilot plant installation.
The current research study of new nanothermites at the South Dakota School of Mines and Technology (SDSM&T) is supported by the Defense University Research Initiative (DURINT) multi-university grant from the Army Research Office. As a result of this prestigious award, a new National NanoEnergetic Materials Center was established and SDSM&T participates as one of five universities in activities of that center. This research initiative and the formation of the new center led to a very active cooperation and exchange of information among center's researchers and DoD and DoE employees. In addition, Dr. Puszynski's research group is supported by two NSF grants, one DEPSCoR grant, and two research contracts with the Armament Research Development Engineering Center at Picatinny Arsenal, NJ. Dr. Puszynski's research group has also a close cooperation with the Naval Surface Warfare Center at Indian Head, MD.
The goal of this RET sponsored research is to investigate the kinetics of heterogeneous exothermic reactions involving nanoreactants. A selected participant will conduct measurements of reaction kinetics using differential scanning calorimetry and ignition characteristics of in-situ formed pyrophoric iron or nickel nanopowders. It is expected that the participant will get also involved in characterization of nanopowders using scanning electron microscopy (SEM) and determination of thermal conductivity of mixtures consisting of nanopowders. Thermal conductivity of reactive systems effects the ignition and combustion reaction propagation in condensed phases. This property is typically estimated for heterogeneous mixtures of reactant particles and the experimental data are scarce or non-existing for newly assembled reactive systems based on nanopowders. Thermal diffusion in solid samples can be measured using photothermal spectroscopy methods, specifically, the thermal deflection method. This method is a non-contact technique based on so called mirage effect, where a laser probe beam is changing path crossing refractive index gradient set within a thin layer of air above the heated sample. Using sensitive detection of the probe beam position in relation to known thermal stimulation of the solid sample one can evaluate thermal properties of the solid. Thermal deflection method can be applied to various materials, like highly conductive single crystals (diamond, GaAs) and porous materials with poor thermal conductivity (paper). Thermal deflection apparatus build in laser application laboratory in the Department of Chemical and Biological Engineering at SDSM&T was constructed specifically for sampling porous pellets of the reactant materials prepared for combustion reactions.
Investigator: Dr. S. S. Bang, Department of Chemical and Biological Engineering
Research Topics: The major research topics that RET awardees may participate in include: 1) isolation of thermophilic microbes from DUSEL samples and 2) extraction of DNA from DUSEL thermophiles for genomic analysis.
One of my ongoing research projects deals with the development of improved biocatalysts for hydrolyzing agricultural and forestry biomass utilizing thermophilic microbial processes. The main source of these extremophiles will be the Homestake Gold Mine, Lead, South Dakota. This deepest mine in North America is currently being transformed into a Deep Underground Science and Engineering Laboratory (DUSEL) for the National Science Foundation. During the active mining period, the surface microorganisms were introduced into the subsurface environments (often extreme temperature and pH) that provided unique opportunities for genetically distinct microbes to develop novel enzymes and other metabolic products.
Investigators: D.J. Medlin, PhD, PE, Department of Materials and Metallurgical Engineering, SDSM&T and D. Mitchell, Department of Humanities, Director of APEX Gallery, SDSM&T
Research Topic: Alloy Development and Microstructural Characterization of Artistic Damascus Steel and Mokume-Gane Composites by Traditional Blacksmithing Techniques
Damascus steel and Mokume-Gane have legendary mechanical properties when used to make weaponry, such as swords and knives, and also have artistic allure due to numerous myths about their processing histories. This project will involve replicating some of the ancient processing methods for these composite metals in a blacksmithing laboratory and heat treating these materials by several historic and modern day methods in an effort to replicate the ancient macroscopic decorative designs. The microstructures of the composite metals will be etched with a variety of chemicals to reveal the microstructures specific to each composite metal and heat treatment process. The microstructures will be analyzed, characterized and documented with modern day metallographic techniques and compared to standard alloy steels. Some of the metallographic techniques include optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and microhardness testing. The results of this investigation will be submitted for publication and/or a conference presentation associated with the topic of archeometallurgy.
Investigator: Dr. Myung-Keun Yoon, Department of Chemical and Biological Engineering, SDSM&T
Research Topic: Distributed Health Monitoring Sensors with Time Domain Reflectometry
1. Background of TDR System
TDR is a method of sending a fast pulse down a transmission line, and then monitoring the reflection signal returning back from impedance changes along the line. Figure 1 shows a schematic diagram of a typical TDR configuration. The transmission line typically consists of a co-axial cable and two parallel conductors. The two conductors are embedded within a structure or surface-mounted on the structure as a sensor to monitor local changes in the material properties. Changes in material spatial properties can be related to changes in local impedances in the vicinity of the sensor, which result in attenuation/increase in the reflection signal as well as propagation delay. Therefore investigating reflection signals provides useful information on the local material properties since material properties or structural status (such as moisture contents, resin curing, density, crack size, chemical adsorption, and failure locations) can be correlated with dielectric, magnetic, and electric properties as well as geometry changes (or discontinuities) in the vicinity of the sensor.
Figure 1 Configuration of a typical TDR system.
Typical TDR applications include detecting groundwater levels in soil layers that cause changes in permittivity values and detecting faults in networking and cable-TV. Recently, TDR sensors have been developed for composite material applications including resin flow, resin curing, and structural-health monitoring.
2. Significance of the Research
Existing sensors are mostly point sensors that monitor responses from a few discrete locations, while TDR sensors can interrogate distributed changes along their entire length of the sensor line. The present research will develop a TDR health monitoring system to identify the locations and size of local defects such as cracks, corrosion, fatigue damage, water/ice contaminations, and degradation in material properties in a structure. Since the developed TDR system provides real time monitoring capability, it can detect even the initiation and propagation of damage as well as existing defects. Adequately designing TDR sensors will improve the sensitivity and coverage of monitoring areas and provide reliable input data to a structural health monitoring system for proactive structural maintenance.
3. Technical Objectives and Research Plan
The objective of this research is to develop a structural health monitoring system using advanced TDR sensors for critical structural components in aircraft/aerospace structures or civil infrastructures. To achieve this objective, a few monitoring methods will be developed and tested with laboratory-scale samples. During the laboratory tests, the feasibility tests will be performed and the design of the sensors will continuously be improved to achieve appropriate performance and reliability levels. TDR sensors will be made/improved by using the Direct Writing Machine in conjunction with researchers at the South Dakota School of Mines and Technology. The next step will be developing mathematical models to estimate the relationship between the damage types and measured TDR signals, so as to inversely identify the changes in local physical or chemical properties quantitatively from measured TDR signals. The final step will be to apply the TDR sensors to various real world structural components.
4. Qualification of Research Assistants
RET RA applicants are expected to have basic knowledge in physics and electrical circuits to perform this project effectively.
Investigator: Dr. R.K. Sani, Department of Chemical and Biological Engineering, SDSM&T
Research Topic: Biodegradation of cellulose using thermophiles isolated from the deep underground mine, Homestake Gold Mine in South Dakota
Cellulosic materials are among the Earth's most abundant renewable resources. Recently the National Resources Defense Council and the Union of Concerned Scientists in a joint statement said that cellulosic fermentative bioproducts (such as ethanol) have the potential to substantially reduce our consumption of gasoline. For example, Shell Oil has predicted "the global market for biofuels such as cellulosic ethanol will grow to exceed $10 billion by 2012." Therefore the degradation of cellulosic waste materials at greater rates by high potential microbes is very important. It has been shown that degradation rates of cellulosic materials by mesophilic microbes (that grow best at temperatures of 20 - 45 °C) are typically low, and it is believed that the kinetics of degradation is controlled by cellulosic materials solubility and mass transfer rates. The cellulosic materials solubility and mass transfer rates thus degradation rates may increase at increased temperature accompanied by the use of thermophilic microorganisms (that grow at relatively high temperatures >50°C with optimum growth temperatures of 60 - 70°C).
We recently found that thermophilic aerobic cellulose-degrading bacteria were present in the deep subsurface of Homestake Gold Mine in South Dakota. One pure deep mine isolate growing on cellulose was analyzed using Scanning Electron Microscope (SEM) and found to be coccus shape (Figure). In this project, RET participant will identify pure isolates using nucleic acid sequence-based techniques (16S rRNA amplification); and determined cellulose degradation kinetics using pure thermophilic cultures of new isolates. The RET researcher involved in the project will receive training in interdisciplinary fields including microbiology, molecular biology, and microbial degradation kinetics. The broader impacts of this project include the education/training of participants on issues of "energy generation".
Investigator: Umesh A. Korde, Department of Mechanical Engineering, James W. Sears, Additive Manufacturing, SDSM&T
Research Topic: Smart Structures with Tunable Impedance
Technical Description: Deployable, lightweight, flexible space structures may encounter large dynamic loads when they are deployed out of their stowed configurations. Post deployment, such structures may experience large dynamic/vibratory loads due to nearby flywheels, momentum wheels, or cryo coolers. In order to minimize the destructive effects of possible resonances, the energy in these vibrations needs to be dissipated. Since this must be accomplished without sacrificing design economy and overall reliability, and without exceeding the weight and power budgets, passive damping solutions are generally preferred. However, the broad range of dynamic load frequencies and the existence of multiple structural resonances also require that the energy dissipation system be tunable.
The method investigated in this work includes the use of piezoelectric films distributed over the membrane or thin plate lightweight structure. Each film is connected in parallel with an electronic circuit designed to provide a "negative capacitance". Because of the inverse piezoelectric effect, each film forms an electromechanical system together with the circuit, and the overall impedance of this system can be controlled by suitably varying a gain parameter in the circuit. It is not difficult to envisage a lightweight space structure with piezoelectric polymer strips or sheets and direct-written resistors and capacitors along the structure boundaries, which also carry integrated circuits and conductor buses to the circuit power supplies.
The goal of this RET project will be to fabricate a test specimen of specified dimensions using material available in our Adaptive Dynamics lab, which includes Kapton membranes, piezoelectric polymer strips and piezoelectric polymer sheets. The researcher will work with the Additive Manufacturing Laboratory to deposit on the test specimen resistors and inductors conforming to supplied values, and test the specimen using the instrumentation provided. The researcher will work closely with our group through all stages, including evaluation and validation of the test results. This project is being carried out in collaboration with the Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, NM.
Figure 1: (Left): A piezoelectric polymer strip element undergoing tests; (Right): Measurement set up highlighting a laser vibrometer used to validate measurements in this project.
Knowledge/Skill Outcomes for RET RA: Light weight space vehicles technology, Fundamentals of mechanical vibrations, fundamentals of piezoelectricity; experience with direct-write manufacturing, experimental test techniques and laboratory instrumentation.
Investigator: Dr. Todd Menkhaus, Department of Chemical and Biological Engineering, SDSM&T
Research Topic: Tangential Flow Ultrafiltration for Recovery of Biopharmaceutical Products from Agricultural Plant Extracts
Biopharmaceuticals (i.e. enzymes, antibodies, plasmid DNA, and viral vectors), as opposed to small-molecule organic drugs, are quickly becoming the products of choice in the fights against cancer, auto-immune disorders, and other debilitating diseases. These "new-age" pharmaceuticals offer great hope to inflicted patients. However, the large scale production and purification of these products presents a unique challenge. One promising production alternative is the use of transgenic corn to act as a "bioreactor" for these high value biopharmaceuticals. While agricultural crops are capable of producing recombinant proteins (biopharmaceuticals) at a fraction of the cost that traditional fermentors do, the purification of product is less understood and can often amount to over 80% of the overall costs. Thus, understanding and improving the separation processes of biopharmaceuticals from corn and other plant agriculture will allow for much more affordable drugs to patients.
For decades ultrafiltration (a size-based separation) has been a common unit operation used for concentration and purification of proteins produced in bacterial and mammalian cultures. Today, with the emergence of transgenic agriculture and biorefineries, there are newly recognized sources (i.e. plant agriculture extracts) for recovering valuable biological products. The matrix of components within a plant extract (proteins, nucleic acids, carbohydrates, phenolic compounds, etc.) is complex, and is vastly different than bacterial or mammalian cultures. These differences have caused unforeseen difficulties when applying traditional bioseparation techniques to plant agricultural systems. Therefore, an investigation into the selective recovery of a recombinant protein from different plant extracts (i.e. corn kernel, corn stover, soy, and soybean) with different membrane chemistries (i.e. cellulosic and polyethersulfone) is needed. Fouling of the membrane, selectivity, and recovery would all be assessed along with microscopic visualization of pore clogging. In addition to planning, conducting, and analyzing results for a laboratory research project, the RET participant will have an opportunity to learn about the rapidly growing biopharmaceutical industry. Specific instruments to be used will include bench-scale bioseparations equipment (tangential flow ultrafiltration and control systems) and microscopic evaluation of filtration membranes (i.e. light microscope and Scanning Electron Microscope - SEM). Depending on the background and experience of the participant, time may be available for analyses by gel electrophoresis, high performance liquid chromatography and enzyme activity.
Figure 1: Purification of an antibody pharmaceutical from transgenic corn using tangential flow ultrafiltration.
Investigators: Naveen Vaduri, MES PhD Candidate, Dr. Robb Winter, Department of Chemical and Biological Engineering, SDSM&T
Research Topic: Designing of an optical assembly to capture crack propagation in the bi-axial loading device coupled with interfacial force microscope
Interphase is a three dimensional region formed between the polymeric resin and the reinforcement in polymer composite materials. The interphase's properties are proven to be critical in determining the properties of the composite. Bi-axial loading device (BLD) is an instrument which is capable of measuring interfacial fracture toughness of polymer composite materials by controlled crack propagation at interphase under combination of tensile and shear loads. Figure 1 shows the BLD along with its electronic controls. Interfacial force microscope (IFM) is capable of measuring viscoelastic properties of polymeric materials to nanometer resolution. IFM in Figure 1 is shown as a sub-picture.
Figure 1: Picture showing the BLD, electronic controls of the BLD and the IFM.
By combining the BLD and the IFM, it is possible to measure interfacial fracture toughness and viscoelastic properties simultaneously while the crack is propagating at desired interphase. Figure 2 shows the coupled BLD and IFM.
Figure 2: Picture of the coupled BLD and IFM.
In order to make the desired measurements calculation of the velocity of the crack is required. To measure the velocity of the crack, the crack propagation is to be recorded in computer and velocity is to be calculated. The challenge in this project is that on top of the BLD, the IFM is placed, as shown in Figure 2, and crack recording should be performed through the clearance between the bottom of the BLD and the table. The intended plan is to design an optical assembly using Solid Works whose capabilities are enhanced by an opto-mechanical plug-in. Solid Works is the state of the art computer aided design (CAD) software used in design of products ranging from shoes to aircrafts. Opto-mechanical plug-in is software which is used in industry and research to check the optical accuracy of a mechanical design before fabrication. Figure 3 shows an image of simulation of light passing through a mechanical design.
Figure 3: Simulation of light rays traveling through a mechanical design developed using Solid Works.