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Sauti, Godfrey

Publications and source records attributed to Sauti, Godfrey.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Toward Ultralight High Strength Structural Materials via Collapsed Carbon Nanotube Bonding

The growing commercial availability of carbon nanotube (CNT) macro-assemblies such as sheet and yarn is making their use in structural composite components increasingly feasible. However, the mechanical properties of these materials continue to trail those of state-of-the-art carbon fiber composites due to relatively weak inter-tube load transfer. Forming covalent links between adjacent CNTs promises to mitigate this problem, but it has proven difficult in practice to introduce them chemically within densified and aligned CNT materials due to their low permeability. To avoid this limitation, this work explores the combination of pulsed electrical current, temperature, and pressure to introduce inter-CNT bonds. Reactive molecular dynamics simulations identify the most probable locations, configurations, and conditions for inter-nanotube bonds to form. This process is shown to introduce covalent linkages within the CNT material that manifest as improved macroscale mechanical properties. The magnitude of this effect increases with increasing levels of prealignment of the CNT material, promising a new synthesis pathway to ultralight structural materials with specific strengths and stiffnesses exceeding 1 and 100 GPa/(g/cu.cm), respectively.

Jensen, Benjamin D.↗
NASA NTRS2019

NtGCM User's Manual: 1.1 (High Pressure High Temperature Laser based) Nanotube Growth Chamber Monitor

This manual describes the installation and use of NtGCM software. NtGCM is software designed for monitoring the growth of nanotubes in a high temperature and high pressure chamber using a laser*. NtGCM software monitors a dozen dierent parameters that are important to understanding the growth of the nanomaterials including the laser input power, the temperature at eight separate locations inside and outside the growth chamber, as well as the pressure and ow rate of the gaseous media that control the environment in the chamber. The measurements are all made in real time. The program features a robust user account management layer and a rich data display manager that allows plotted data, displayed units and other parameters to be changed on the y for the operator's convenience.

Sauti, Godfrey↗
NASA NTRS2018

Undirectional Carbon Nanotube Yarn/Polymer Composites

Carbon nanotubes (CNTs) are one-dimensional nanomaterials with outstanding electrical and thermal conductivities and mechanical properties at the nanoscale. With these superior physical properties, CNTs are very attractive materials for future light weight structural aerospace applications. Recent manufacturing advances have led to the availability of bulk formats of CNTs such as yarns, tapes, and sheets in commercial quantities, thus enabling the development of macroscale composite processing methods for aerospace applications. The fabrication of unidirectional CNT yarn/polymer composites and the effect of processing parameters such as resin type, number of CNT yarn layers, CNT yarn/resin ratio, consolidation method, and tension applied during CNT yarn winding on the mechanical properties of unidirectional CNT yarn composites are reported herein. Structural morphologies, electrical and thermal conductivities, and mechanical performance of unidirectional CNT yarn/polymer composites under tensile and short beam shear loads are presented and discussed. The application of higher tension during the winding process and elevated cure pressure during the press molding step afforded a compact structural morphology and reduced void content in the composite. However, the composite tensile strength was negligibly impacted by the fabrication parameters, such as cure pressure, winding tension, and resin chemistry, excepting resin content and number of CNT yarn layers. The tension winding method produced better quality and lower resin content CNT yarn composites compared to conventional prepregging methods, resulting in higher specific strength and modulus of the composites. The specific tensile strength of the CNT composite was approximately 69 % of the starting CNT yarn. Electrical and thermal conductivities of unidirectional CNT yarn/polymer composites were in the range of 1000 to 12000 S/cm and 22 to 45 W/mK, respectively.

Kim, Jae-Woo↗
NASA NTRS2018

High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nontubes (CNTs), graphites, or their combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mates of BNNTs are uses as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also uses as reinforcing inclusions combining with other polymer matrices to create composite layer like typical reinforcing fibers such as Kevlar (Registered Trademark), Spectra (Registered Trademark) ceramics and metals. Enhanced wear resistance and prolonged usage time, even under harsh conditions, are achieved by adding boron nitride nanomaterials because both hardness and toughness are increased. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800 C in air. Boron nitride based composite materials are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear for the human body as well as for vehicles, helmets, shields and safety suits/helmets for industry.

Kang, Jin Ho↗
NASA NTRS2018

Solar Radiation Control and Energy Harvesting Film

Some implementations provide a device (e.g., solar panel) that includes an active layer and a solar absorbance layer. The active layer includes a first N-type layer and a first P-type layer. The solar absorbance layer is coupled to a first surface of the active layer. The solar absorbance layer includes a polymer composite. In some implementations, the polymer composite includes one of at least metal salts and/or carbon nanotubes. In some implementations, the active layer is configured to provide the photovoltaic effect. In some implementations, the active layer further includes a second N-type layer and a second P-type layer. In some implementations, the active layer is configured to provide the thermoelectric effect. In some implementations, the device further includes a cooling layer coupled to a second surface of the active layer. In some implementations, the cooling layer includes one of at least zinc oxides, indium oxides, and/or carbon nanotubes.

Kang, Jin Ho↗
NASA NTRS2017

Multi-Functional BN-BN Composite

Multifunctional Boron Nitride nanotube-Boron Nitride (BN-BN) nanocomposites for energy transducers, thermal conductors, anti-penetrator/wear resistance coatings, and radiation hardened materials for harsh environments. An all boron-nitride structured BN-BN composite is synthesized. A boron nitride containing precursor is synthesized, then mixed with boron nitride nanotubes (BNNTs) to produce a composite solution which is used to make green bodies of different forms including, for example, fibers, mats, films, and plates. The green bodies are pyrolized to facilitate transformation into BN-BN composite ceramics. The pyrolysis temperature, pressure, atmosphere and time are controlled to produce a desired BN crystalline structure. The wholly BN structured materials exhibit excellent thermal stability, high thermal conductivity, piezoelectricity as well as enhanced toughness, hardness, and radiation shielding properties. By substituting with other elements into the original structure of the nanotubes and/or matrix, new nanocomposites (i.e., BCN, BCSiN ceramics) which possess excellent hardness, tailored photonic bandgap and photoluminescence, result.

Kang, Jin Ho↗
NASA NTRS2017

Sucrose Treated Carbon Nanotube and Graphene Yarns and Sheets

Consolidated carbon nanotube or graphene yarns and woven sheets are consolidated through the formation of a carbon binder formed from the dehydration of sucrose. The resulting materials, on a macro-scale are lightweight and of a high specific modulus and/or strength. Sucrose is relatively inexpensive and readily available, and the process is therefore cost-effective.

Sauti, Godfrey↗
NASA NTRS2017

Metallized Nanotube Polymer Composite (MNPC) and Methods for Making Same

A novel method to develop highly conductive functional materials which can effectively shield various electromagnetic effects (EMEs) and harmful radiations. Metallized nanotube polymer composites (MNPC) are composed of a lightweight polymer matrix, superstrong nanotubes (NT), and functional nanoparticle inclusions. MNPC is prepared by supercritical fluid infusion of various metal precursors (Au, Pt, Fe, and Ni salts), incorporated simultaneously or sequentially, into a solid NT-polymer composite followed by thermal reduction. The infused metal precursor tends to diffuse toward the nanotube surface preferentially as well as the surfaces of the NT-polymer matrix, and is reduced to form nanometer-scale metal particles or metal coatings. The conductivity of the MNPC increases with the metallization, which provides better shielding capabilities against various EMEs and radiations by reflecting and absorbing EM waves more efficiently. Furthermore, the supercritical fluid infusion process aids to improve the toughness of the composite films significantly regardless of the existence of metal.

Park, Cheol↗
NASA NTRS2017

Doped Chiral Polymer Metamaterials

Some implementations provide a composite material that includes a first material and a second material. In some implementations, the composite material is a metamaterial. The first material includes a chiral polymer (e.g., crystalline chiral helical polymer, poly-.gamma.-benzyl-L-glutamate (PBLG), poly-L-lactic acid (PLA), polypeptide, and/or polyacetylene). The second material is within the chiral polymer. The first material and the second material are configured to provide an effective index of refraction value for the composite material of 1 or less. In some implementations, the effective index of refraction value for the composite material is negative. In some implementations, the effective index of refraction value for the composite material of 1 or less is at least in a wavelength of one of at least a visible spectrum, an infrared spectrum, a microwave spectrum, and/or an ultraviolet spectrum.

Park, Cheol↗
NASA NTRS2016

Nanostructure Neutron Converter Layer Development

Methods for making a neutron converter layer are provided. The various embodiment methods enable the formation of a single layer neutron converter material. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross section, tailored resistivity providing a good electric field penetration with submicron particles, and a high secondary electron emission coefficient. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development.

Park, Cheol↗
NASA NTRS2016

Effect of Nanofiller Characteristics on Nanocomposite Properties

This report surveys the effect of nanofiller characteristics on nanocomposites fabricated with two polyimide matrices. Mechanical and electrical properties were determined. Microscopy results showed that matrix chemistry, nanofiller characteristics and processing conditions had significant impact on nanocomposite quality.

Working, Dennis C.↗
NASA NTRS2016

Additive Manufacturing of Multifunctional Components Using High Density Carbon Nanotube Yarn Filaments

Additive manufacturing allows for design freedom and part complexity not currently attainable using traditional manufacturing technologies. Fused Filament Fabrication (FFF), for example, can yield novel component geometries and functionalities because the method provides a high level of control over material placement and processing conditions. This is achievable by extrusion of a preprocessed filament feedstock material along a predetermined path. However if fabrication of a multifunctional part relies only on conventional filament materials, it will require a different material for each unique functionality printed into the part. Carbon nanotubes (CNTs) are an attractive material for many applications due to their high specific strength as well as good electrical and thermal conductivity. The presence of this set of properties in a single material presents an opportunity to use one material to achieve multifunctionality in an additively manufactured part. This paper describes a recently developed method for processing continuous CNT yarn filaments into three-dimensional articles, and summarizes the mechanical, electrical, and sensing performance of the components fabricated in this way.

Gardner, John M.↗
NASA NTRS2015

Multifunctional Electroactive Nanocomposites Based on Piezoelectric Boron Nitride Nanotubes

Space exploration missions require sensors and devices capable of stable operation in harsh environments such as those that include high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation. However, conventional or state-of-the-art electroactive materials like lead zirconate titanate, poly(vinylidene fluoride), and carbon nanotube (CNT)-doped polyimides have limitations on use in those extreme applications. Theoretical studies have shown that boron nitride nanotubes (BNNTs) have strength-to-weight ratios comparable to those of CNTs, excellent high-temperature stability (to 800 C in air), large electroactive characteristics, and excellent neutron radiation shielding capability. In this study, we demonstrated the experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites. Upon application of an external electric field, the 2 wt % BNNT/polyimide composite was found to exhibit electroactive strain composed of a superposition of linear piezoelectric and nonlinear electrostrictive components. When the BNNTs were aligned by stretching the 2 wt % BNNT/polyimide composite, electroactive characteristics increased by about 460% compared to the nonstretched sample. An all-nanotube actuator consisting of a BNNT buckypaper layer between two single-walled carbon nanotube buck-paper electrode layers was found to have much larger electroactive properties. The additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions. utilizing the unique characteristics of BNNTs.

Kang, Jin Ho↗
NASA NTRS2015

High Volume Fraction Carbon Nanotube Composites for Aerospace Applications

Reported nanoscale mechanical properties of carbon nanotubes (CNTs) suggest that their use may enable the fabrication of significantly lighter structures for use in space applications. To be useful in the fabrication of large structures, however, their attractive nanoscale properties must be retained as they are scaled up to bulk materials and converted into practically useful forms. Advances in CNT production have significantly increased the quantities available for use in manufacturing processes, but challenges remain with the retention of nanoscale properties in larger assemblies of CNTs. This work summarizes recent progress in producing carbon nanotube composites with tensile properties approaching those of carbon fiber reinforced polymer composites. These advances were achieved in nanocomposites with CNT content of ~70% by weight. The processing methods explored to yield these CNT composite properties will be discussed, as will the characterization and test methods that were developed to provide insight into the factors that contribute to the enhanced tensile properties. Technology maturation was guided by parallel advancements in computational modeling tools that aided in the interpretation of experimental data.

Siochi, Emilie J.↗
NASA NTRS2015

Structural CNT Composites Part II: Assessment of CNT Yarns as Reinforcement for Composite Overwrapped Pressure Vessels

Carbon nanotubes (CNTs) are one-dimensional nanomaterials with outstanding electrical and thermal conductivities and mechanical properties. This combination of properties offers routes to enable lightweight structural aerospace components. Recent advances in the manufacturing of CNTs have made bulk forms such as yarns, tapes and sheets available in commercial quantities to permit the evaluation of these materials for aerospace use, where the superior tensile properties of CNT composites can be exploited in tension dominated applications such as composite overwrapped pressure vessels (COPVs). To investigate their utility in this application, aluminum rings were overwrapped with thermoset/CNT yarn composite and their mechanical properties measured. CNT composite overwrap characteristics such as processing method, CNT/resin ratio, and applied tension during CNT yarn winding were varied to determine their effects on the mechanical performance of the CNT composite overwrapped Al rings (CCOARs). Mechanical properties of the CCOARs were measured under static and cyclic loads at room, elevated, and cryogenic temperatures to evaluate their mechanical performance relative to bare Al rings. At room temperature, the breaking load of CCOARs with a 10.8% additional weight due to the CNT yarn/thermoset overwrap increased by over 200% compared to the bare Al ring. The quality of the wound CNT composites was also investigated using x-ray computed tomography.

Kim, Jae-Woo↗
NASA NTRS2015

Structural CNT Composites: Developing a Carbon Nanotube Filament Winder - Part I

Carbon nanotube (CNT) based materials promise advances in the production of high strength and multifunctional components for aerospace and other applications. Specifically, in tension dominated applications, the latest CNT based filaments are yielding composite properties comparable to or exceeding composites from more established fibers such as Kevlar and carbon fiber. However, for the properties of these materials to be fully realized at the component level, suitable manufacturing processes have to be developed. These materials handle differently from conventional fibers, with different wetting characteristics and behavior under load. The limited availability of bulk forms also requires that the equipment be scaled down accordingly to tailor the process development approach to material availability. Here, the development of hardware and software for filament winding of carbon nanotube based tapes and yarns is described. This hardware features precision guidance of the CNT material and control of the winding tension over a wide range in an open architecture that allows for effective process control and troubleshooting during winding. Use of the filament winder to develop CNT based Composite Overwrapped Pressure Vessels (COPVs) shall also be discussed.

Sauti, Godfrey↗
NASA NTRS2015

Robust, Flexible and Lightweight Dielectric Barrier Discharge Actuators Using Nanofoams/Aerogels

Robust, flexible, lightweight, low profile enhanced performance dielectric barrier discharge actuators (plasma actuators) based on aerogels/nanofoams with controlled pore size and size distribution as well as pore shape. The plasma actuators offer high body force as well as high force to weight ratios (thrust density). The flexibility and mechanical robustness of the actuators allows them to be shaped to conform to the surface to which they are applied. Carbon nanotube (CNT) based electrodes serve to further decrease the weight and profile of the actuators while maintaining flexibility while insulating nano-inclusions in the matrix enable tailoring of the mechanical properties. Such actuators are required for flow control in aeronautics and moving machinery such as wind turbines, noise abatement in landing gear and rotary wing aircraft and other applications.

Sauti, Godfrey↗