Godfrey Sauti's research while affiliated with Hampton VA Medical Center and other places
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Publications (42)
An expansion of the high-temperature/high-performance polymer 3D printing feedstock palette is critical for the adoption of the technology in more aerospace applications. Open-source printers are a potential platform for the insertion of new materials to the printing palette. However, as-purchased, they are not capable of printing high-temperature...
A framework using peridynamic theory is developed and demonstrated for deformation and failure analysis of carbon nanotube (CNT) yarn-based structural composites. Experimental work involved tension testing of a CNT yarn/polymer composite resulting in stress–strain response up to and including failure. The as-prepared specimen was characterized usin...
Fused filament fabrication (FFF), a form of filament-based material extrusion additive manufacturing (AM), is an extremely useful technique for the rapid production of highly customized products; however, empirical evidence is heavily relied upon for understanding of the process. Initial modeling attempts have traditionally focused on predicting he...
Various nanofillers have been adopted to enhance the thermal conductivity of polymer nanocomposites. While it is widely believed that the contact thermal resistance between adjacent nanofillers can play an important role in limiting thermal conductivity enhancement of composite materials, lack of direct experimental data poses a significant challen...
Achieving high strength in fiber reinforced structural composites requires effective load transfer between the high-performance fiber reinforcement, e.g., carbon nanotube (CNT) yarn, and the matrix. Various processing approaches to enhance the interaction between CNT fiber and the matrix were investigated. The apparent interfacial shear strengths (...
Silver nanowires have been widely adopted as nanofillers in composite materials used for various applications. Electrical and thermal properties of these composites are critical for proper device operation, and highly depend on transport through the nanowires and their contacts, yet studies on silver nanowires have been limited to one or two sample...
We report on electrical insulating materials that not only have sufficient mechanical toughness to survive use conditions, but also possess the ability to undergo thermally induced self-repair when damaged. By controlling the cross-link density, a modified ethylene-octene copolymer (EOC) is able to retain its self-healing abilities while also being...
The growing commercial availability of carbon nanotube (CNT) macro-assemblages 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....
We report the thermal properties of boron nitride nanotube (BNNT) reinforced ceramic composites using the polymer derived ceramic (PDC) processing route. The nano‐composites had a BNNT loading of up to 35.4 vol.%. TGA results showed that the nano‐composites have good thermal stability up to 900 °C in air. BNNTs in the nano‐composites survived in an...
Graphene, the first discovered and most studied two-dimensional material, has gained increasing interest in the research community due to a combination of unique optical, electronic transport, and structural properties. Single layer graphene is transparent, conductive, strong and flexible. In this work the mechanical flexibility, conductivity, and...
Quality control and repeatability of 3D printing must be enhanced to fully unlock its utility beyond prototyping and noncritical applications. Machine learning is a potential solution to improving 3D printing performance and is explored for areas including flaw identification and property prediction. However, critical problems must be resolved befo...
Experimental results of the complex magnetic permeability (µ) and the electrical conductivity (σ) of a granular paramagnetic Gadolinium Gallium Garnet (GGG: 0.3 to 26 Vol. %) and Teflon (PTFE) system are presented, and discussed in relation to previously published (conductivity) and unpublished (permeability) studies on granular Fe3O4 – talc and Ni...
Molecular dynamics simulations of carbon nanotube (CNT) composites, in which the CNTs are continuous across the periodic boundary, overestimate the experimentally measured mechanical properties of CNT composites along the fiber direction. Since the CNTs in these composites are much shorter than the composite dimensions, load must be transferred eit...
Continuous carbon nanotube (CNT) yarn filaments can be employed as an inherently multifunctional feedstock for additive manufacturing (AM). With this material, it becomes possible to use a single material to impart multiple functionalities in components and take advantage of the tailorability offered by fused filament fabrication (FFF) over convent...
Carbon nanotubes (CNTs) are one-dimensional nanomaterials with outstanding electrical and thermal conductivities and mechanical properties. Recent advances in CNT manufacturing have made bulk forms such as yarns, tapes and sheets available in commercial quantities to permit the evaluation of these materials for aerospace use. The high tensile prope...
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 (PZT), poly(vinylidene fluoride) (PVDF) and ca...
This article reviews the application of nanomaterials for radiation shielding to protect humans from the hazards of radiation in space. The focus is on protection from space radiation, including galactic cosmic radiation (GCR), solar particle events (SPEs), and neutrons generated from the interactions of the GCR and SPEs with the intervening matter...
Recently, multiple commercial vendors have developed capability for the production of large-scale quantities of high-quality carbon nanotube sheets and yarns [1]. While the materials have found use in electrical shielding applications, development of structural systems composed of a high volume fraction of carbon nanotubes is still lacking [2]. A r...
Thermoset/carbon nanotube (CNT) sheet nanocomposites were successfully fabricated by resistive heating assisted infiltration and cure (RHAIC) of the polymer matrix resin. Resistive heating takes advantage of the electrical and thermal conductivity of CNTs to rapidly and uniformly introduce heat into the CNT sheet. Heating the CNT sheet reduces the...
A key, enabling element of a dielectric barrier discharge (DBD) actuator is the dielectric substrate material. While various investigators have studied the performance of different homogeneous materials, most often in the context of related DBD experiments, fundamental studies focused solely on the dielectric materials have received less attention....
Scientists have predicted that carbon’s immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990’s, the boron nitride nanotube (BNNT) has proven very difficult to make until now. H...
Tailoring the solar absorptivity (αs) and thermal emissivity
(ɛT) of materials constitutes an innovative approach to solar
energy control and energy conversion. Numerous ceramic and metallic
materials are currently available for solar absorbance/thermal emittance
control. However, conventional metal oxides and
dielectric/metal/dielectric multi-coat...
The key objectives of this study are to investigate, both computationally and experimentally, which forms, compositions, and layerings of hydrogen, boron, and nitrogen containing materials will offer the greatest shielding in the most structurally robust combination against galactic cosmic radiation (GCR), secondary neutrons, and solar energetic pa...
Although many metal decorated nanotubes and nanowires appear in the literature, well-dispersed metal decorated nanotube polymer composites have rarely been reported because of the excessive density mismatch between the decorated nanotubes and polymer matrix. Here, we report a novel method to prepare well-dispersed, highly functional, metallized nan...
AC conductivity experiments, or Impedance Spectroscopy, at temperatures between 100 and 400°C, made on 8 mole % Yttria Stabilized Zirconia (8YSZ) with different grain sizes, are presented. The results are analyzed using Effective Media Theories, the Brick Layer Model and percolation theory. The results obtained are satisfactory, only if the measure...
Single-wall carbon nanotubes (SWCNTs) have been added to high molecular weight poly(-benzyl-L-glutamate), or PBLG, to evaluate their effects on the polymer's shear piezoelectricity. While the addition of SWCNTs increased various PBLG physical properties such as electrical conductivity, dielectric constant, several mechanical properties, and electro...
A range of liquid-phase sintered silicon carbide (LPS SiC) materials were produced, using hot pressing and gas pressure sintering. The densified materials were further heat-treated at the sintering temperature, 1925 °C. The ac electrical properties were measured and impedance spectroscopy used between room temperature and 330 °C. The investigated L...
The ac conductivity of silicon–polyester resin composites is found to be best fitted using the two exponent phenomenological
percolation equation (TEPPE) (formerly known as the general effective media (GEM) equation). The results show that, with the
actual experimentally measured components’ electrical properties as input, the TEPPE can be used to...
Experimental results and simulations of scaled plots of the normalized conductivity [log(σmr(ϕ,ω,T)∕σmr(ϕ,0,T))] against the scaled frequency [log(ω∕ωce) or log(ω∕ωcp)], for different conductor volume fractions ϕ, for various percolation systems are examined and analyzed. Here, ωce is the critical scaling frequency obtained from superimposing exper...
Analysis of the AC conductivity, complex dielectric constant, and the resulting immittance spectra of liquid-phase-sintered silicon carbide (SiC) ceramics showed that for this system, the dominant experimental observations are due to a multicomponent grain-boundary phase and not due to SiC grains. This is confirmed by noting that the temperature de...
ac and dc conductivity results for a percolating system, which consists of a conducting powder (magnetite) combined with an “insulating” powder (cellulose acetate), are presented. Impedance and modulus spectra are obtained in a percolation system. The temperature dependence of the resistivity of the cellulose acetate is such that at 170 °C, it is e...
While high shear alignment has been shown to improve the mechanical properties of single-wall carbon nanotube (SWNT)-polymer composites, this method does not allow for control over the electrical and dielectric properties of the composite and often results in degradation of these properties. Here, we report a novel method to actively align SWNTs in...
An AlN ceramic sample was prepared using a reaction-bonding technique with Al and AlN powders, together with a very small amount of CaO (a sintering aid), as the starting materials. The effects of annealing at 1800 °C for 10 h in one atmosphere of Ar on the thermal and electrical properties of the ceramic were investigated. After annealing the ther...
Liquid-Phase Sintered Silicon Carbide (LPSSiC) materials were produced with different Y2O3:Al2O3 sintering additive ratios. Different densification techniques were employed (hot pressing (HP) and gas pressure sintering (GPS)) and densification kinetics studied. The results show significant increase in densification with decreasing Y 2O3: Al2O3 rati...
Liquid‐Phase Sintered
Silicon
Carbide (LPSSiC) materials were produced with different Y2O3: Al2O3 and Y2O3: SiO2
sintering additive ratios. Densification was achieved by hot pressing (HP). The ratio of the polytypes and the amount and crystalline composition of the grain boundary phases was determined using Rietveld analysis. Microstructures of...
The microstructures, upon which the widely used Maxwell–Wagner (MW) and the Bruggeman symmetric (BS) and anti-symmetric (BA) effective media (EM) theories applications are based, are presented and the limitations of these methods are discussed. The microstructures characterizing percolation systems and the resultant critical volume fractions are pr...
Citations
... Unlike the MsM, these NsM, at proper replacement of fiber-bridging effect with nanoscale bridging, do not compromise in-plane properties and, depending on the modification type, show improvement in fracture toughness. Additionally, these NsM adds multiscale hierarchical toughening mechanisms [24,25] which is not noted in case of MsM. Compared to MsM, a NsM offers a higher surface-tovolume ratio, which presents the possibility of increasing the amount of energy dissipated during fracture. ...
... One of the most popular AM methods, based on the principle of material extrusion, is called fused filament fabrication (FFF), or fused deposition modelling (FDM). This process makes use of thermoplastics to manufacture products by depositing melted material layer-by-layer [1][2][3][4][5][6]. The systems working on the principle of FFF/FDM are termed as 3D printers [7,8]. ...
... They presented that the tensile strength of CNT composites is 69% of that of CNT yarn itself. Also, Barber et al. [26] analyzed the deformation as well as the failure strength of composites made with CNT yarns and polymer. They utilized X-ray to characterize the specimens and showed that sharp gradients and the accumulation of the resin are two major reasons for failure. ...
... Interlayer bond quality depends on the degree of polymer chain interpenetration between coincident rasters in the MEX part (De Gennes, 1971;Hart et al., 2018;Wool & O'Connor, 1981). The degree of polymer chain interpenetration during Young et al. (2018) the build process is driven by thermal factors such as time the polymer spends above its glass transition temperature (Sun et al., 2008), thermal gradients in the part (Das et al., 2020), and temperature cycling, among others (Gilmer et al., 2021). MEX process parameters influence these thermal factors, which influence the interlayer bond strength (Abbott et al., 2018;Rodriguez et al., 1999;Spoerk et al., 2017). ...
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... In nanodevices, the contact/interfacial thermal resistance (inverse of contact thermal conductance) plays a major part in the transfer of thermal energy. Integration of nanoelectronics requires a comprehensive knowledge of nanoscale interfacial heat transport phenomena 109,122,123 . To probe the impact of contact thermal conductance between the metallic seamless NWN and the substrate on sheet resistance and network average temperature, we varied this quantity as depicted in Figure 14. ...
... Carbon nanotubes (CNTs) have become an attractive reinforcement in polymer composites due to their outstanding thermal, electrical, and mechanical properties [1][2][3][4][5][6]. New structural forms of CNTs, such as yarns, tapes, and sheets [1], have permitted the development of lightweight macroscale components used in many multifunctional structures [1,3,6,7]. ...
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... In the sample preparation, we performed a wetting treatment to enhance the contact between the nanowire and the membranes 24 . After placing each sample on the measurement device, a drop of reagent alcohol was locally delivered to each suspended membrane and evaporated at about 80 °C, which led to tight binding between the wire and the membrane. ...
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... The interaction area between nanotubes can be maximized by collapsing the nanotube structure, similar to stacked ribbons. Flattened tube surfaces from collapsed CNT (C-CNT) structures may also enhance the intertube shear strength (12). Theoretically, collapsed tube structures experience extended pairwise Lennard-Jones interactions, which provide an advantage for dislocation stacking over regular and dislocation dipole stacking (13). ...
... CNTs have high absorption for a large portion of the light spectrum. They also have high thermal conductivity [11][12][13]. Hence, adding CNTs could increase the absorption of electromagnetic radiation, as well as create a more uniform temperature distribution due to their high thermal conductivity. ...
Reference: Laser Sintering of CNT/PZT Composite Film
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... High strength and ductility are made possible by setting the parameters at their ideal values. In [47], a technique that forecasts the ideal parameters to produce free-flaw geometries is suggested. A CNN model for object detection is employed to find errors in already printed components. ...
