19 results on '"Kristopher D. Behler"'
Search Results
2. Observations of grain boundary chemistry variations in a boron carbide processed with oxide additives
- Author
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Martin P. Harmer, Kristopher D. Behler, Scott D. Walck, Jerry C. LaSalvia, and Christopher J. Marvel
- Subjects
010302 applied physics ,Materials science ,Mechanical Engineering ,Fracture (mineralogy) ,Metallurgy ,Metals and Alloys ,Oxide ,02 engineering and technology ,Boron carbide ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,chemistry.chemical_compound ,Analytical electron microscopy ,Annular dark-field imaging ,chemistry ,Mechanics of Materials ,0103 physical sciences ,General Materials Science ,Grain boundary ,Composite material ,0210 nano-technology ,Spectroscopy - Abstract
Analytical electron microscopy was used to examine the grain boundary chemistry in boron carbide containing Al-O-rich phases at triple junctions. In this study, SiO2, Al2O3, and B2O3 additives were used to synthesize an aluminoborosilicate glass on the grain boundaries with the long-term goal to enhance fracture resistance. Nanolayer films were not observed using high-angle annular dark field imaging; however, energy-dispersive spectroscopy quantification revealed grain boundaries with varying excess of Si and Al. Overall, it was concluded variations in grain boundary chemistry depend upon the intrinsic grain boundary character and spatial heterogeneity of the oxide additives.
- Published
- 2018
3. Extending ζ-factor microanalysis to boron-rich ceramics: Quantification of bulk stoichiometry and grain boundary composition
- Author
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Richard A. Haber, Christopher J. Marvel, Kristopher D. Behler, Masashi Watanabe, Jerry C. LaSalvia, Martin P. Harmer, and Vladislav Domnich
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010302 applied physics ,Materials science ,Silicon ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,Boron carbide ,021001 nanoscience & nanotechnology ,01 natural sciences ,Microanalysis ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Boron nitride ,0103 physical sciences ,Silicon carbide ,Grain boundary ,Boron suboxide ,0210 nano-technology ,Boron ,Instrumentation - Abstract
Accurate quantification of light elements which produce only soft X-ray lines via X-ray energy dispersive spectrometry (XEDS) has been traditionally difficult due to poor X-ray emission and detector efficiencies at low energies and significant X-ray absorption effects. The ζ-factor microanalysis method enables one to correct for these shortcomings; however, ζ-factor microanalysis has not yet been thoroughly applied to inorganic materials which are entirely or mostly composed of light elements such as boron carbide, boron nitride, or boron suboxide. This work successfully extended ζ-factor microanalysis to boron-rich ceramics and accurately determined stoichiometries of multiple boron carbides and measured grain boundary compositions of a boron carbide mixed with additives consisting of rare-earth ions. Various strategies were employed to experimentally determine a full range of ζ-factors and measurements were validated using materials of known composition including silicon hexaboride and silicon carbide. Overall, this work has shown that XEDS is a viable technique for light element quantification in (scanning) transmission electron microscopy, in terms of both the accuracy and precision, which is comparable or superior to the complementary electron energy loss spectrometry.
- Published
- 2019
4. Challenges of Engineering Grain Boundaries in Boron-Based Armor Ceramics
- Author
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Efraín Hernández-Rivera, Jennifer Synowczynski-Dunn, Shawn P. Coleman, Mark A. Tschopp, and Kristopher D. Behler
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010302 applied physics ,Toughness ,Materials science ,Metallurgy ,General Engineering ,chemistry.chemical_element ,02 engineering and technology ,Boron carbide ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,chemistry.chemical_compound ,Fracture toughness ,chemistry ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,General Materials Science ,Grain boundary ,Ceramic ,Boron suboxide ,0210 nano-technology ,Boron - Abstract
Boron-based ceramics are appealing for lightweight applications in both vehicle and personnel protection, stemming from their combination of high hardness, high elastic modulus, and low density as compared to other ceramics and metal alloys. However, the performance of these ceramics and ceramic composites is lacking because of their inherent low fracture toughness and reduced strength under high-velocity threats. The objective of the present article is to briefly discuss both the challenges and the state of the art in experimental and computational approaches for engineering grain boundaries in boron-based armor ceramics, focusing mainly on boron carbide (B4C) and boron suboxide (B6O). The experimental challenges involve processing these ceramics at full density while trying to promote microstructure features such as intergranular films to improve toughness during shock. Many of the computational challenges for boron-based ceramics stem from their complex crystal structure which has hitherto complicated the exploration of grain boundaries and interfaces. However, bridging the gaps between experimental and computational studies at multiple scales to engineer grain boundaries in these boron-based ceramics may hold the key to maturing these material systems for lightweight defense applications.
- Published
- 2016
5. Locating Si atoms in Si-Doped Boron Carbide: a Route to Understand Amorphization Mitigation Mechanism
- Author
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Richard A. Haber, Kevin J. Hemker, Kristopher D. Behler, Atta U. Khan, Chawon Hwang, Kelvin Y. Xie, Mingwei Chen, Jerry C. LaSalvia, Anthony Etzold, Xiaokun Yang, Vladislav Domnich, William A. Goddard, and Qi An
- Subjects
Materials science ,Polymers and Plastics ,Rietveld refinement ,Metals and Alloys ,02 engineering and technology ,Crystal structure ,Boron carbide ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,chemistry.chemical_compound ,Crystallography ,chemistry ,visual_art ,0103 physical sciences ,Atom ,Scanning transmission electron microscopy ,Ceramics and Composites ,visual_art.visual_art_medium ,Ceramic ,010306 general physics ,0210 nano-technology ,Powder mixture - Abstract
The well-documented formation of amorphous bands in boron carbide (B4C) under contact loading has been identified in the literature as one of the possible mechanisms for its catastrophic failure. To mitigate amorphization, Si-doping was suggested by an earlier computational work, which was further substantiated by an experimental study. However, there have been discrepancies between theoretical and experimental studies, about Si replacing atom/s in B12 icosahedra or the C-B-C chain. Dense single phase Si-doped boron carbide was produced through a conventional scalable route. A powder mixture of SiB6, B4C, and amorphous boron was reactively sintered, yielding a dense single phase Si-doped boron carbide material. A combined analysis of Rietveld refinement on XRD pattern coupled with electron density difference Fourier maps and DFT simulations were performed in order to investigate the location of Si atoms in the boron carbide lattice. Si atoms occupy an interstitial position, between the icosahedra and the chain. These Si atoms are bonded to the chain end C atoms, which result in a kinked chain. Additionally, these Si atoms are also bonded to the neighboring equatorial B atom of the icosahedra, which is already bonded to the C atom of the chain, forming a bridge like structure. Owing to this bonding, Si is anticipated to stabilize the icosahedra through electron donation, which is expected to help in mitigating stress-induced amorphization. Possible supercell structures are suggested along with the most plausible structure for Si-doped boron carbide.
- Published
- 2018
6. Graphene non-covalently tethered with magnetic nanoparticles
- Author
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M. N. F. Hoque, Kristopher D. Behler, Sriya Das, Micah J. Green, Daniel P. Cole, Zhaoyang Fan, Dorsa Parviz, Robert J. Fullerton, and Fahmida Irin
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Materials science ,Polyvinylpyrrolidone ,Graphene ,Iron oxide ,Nanoparticle ,Nanotechnology ,General Chemistry ,Coercivity ,equipment and supplies ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,medicine ,Magnetic nanoparticles ,Surface modification ,General Materials Science ,human activities ,medicine.drug ,Superparamagnetism - Abstract
We describe a novel approach for coupling pristine graphene with superparamagnetic iron oxide nanoparticles to create dispersed, magnetically responsive hybrids. The magnetic iron oxide (Fe3O4) nanoparticles are synthesized by a co-precipitation method using ferric (Fe3+) and ferrous (Fe2+) salts and then grafted with polyvinylpyrrolidone (PVP). These PVP-grafted Fe3O4 nanoparticles are then used to stabilize colloidal graphene in water. The PVP branches non-covalently attach to the surface of the pristine graphene sheets without functionalization or defect creation. These Fe3O4–graphene hybrids are stable against aggregation and are highly responsive to external magnetic fields. These hybrids can be freeze-dried to a powder or magnetically separated from solution and still easily redisperse while retaining magnetic functionality. At all stages of synthesis, the Fe3O4–graphene hybrids display no coercivity after being brought to magnetic saturation, confirming superparamagnetic properties. Microscopy and light scattering data confirm the presence of pristine graphene sheets decorated with Fe3O4 nanoparticles. These materials show promise for multifunctional polymer composites as well as biomedical applications and environmental remediation.
- Published
- 2014
7. ζ–Factor Development and Quantification of a Boron Carbide and Silicon Hexaboride Diffusion Couple
- Author
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Richard A. Haber, Jerry C. LaSalvia, Masashi Watanabe, Vladislav Domnich, Christopher J. Marvel, Martin P. Harmer, Kristopher D. Behler, and Anthony Etzold
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010302 applied physics ,Materials science ,Silicon ,chemistry.chemical_element ,02 engineering and technology ,Boron carbide ,021001 nanoscience & nanotechnology ,01 natural sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,0103 physical sciences ,Diffusion (business) ,0210 nano-technology ,Instrumentation - Published
- 2018
8. Infrared spectroscopy and Density Functional Theory of crystalline β-2,4,6,8,10,12-hexanitrohexaaziosowurtzitane (β CL-20) in the region of its C–H stretching vibrations
- Author
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Rosario C. Sausa, J. Cabalo, R. Pesce-Rodriguez, and Kristopher D. Behler
- Subjects
Bridged-Ring Compounds ,Models, Molecular ,Chemistry ,Overtone ,Anharmonicity ,Analytical chemistry ,Infrared spectroscopy ,Spectrum Analysis, Raman ,Atomic and Molecular Physics, and Optics ,Analytical Chemistry ,symbols.namesake ,Spectroscopy, Fourier Transform Infrared ,symbols ,Quantum Theory ,Density functional theory ,Bond energy ,Fourier transform infrared spectroscopy ,Crystallization ,Raman spectroscopy ,Spectroscopy ,Instrumentation - Abstract
Molecular vibrational spectroscopy provides a useful tool for material characterization and model verification. We examine the CH stretching fundamental and overtones of energetic material β-2,4,6,8,10,12-hexanitrohexaaziosowurtzitane (β-CL-20) by Raman spectroscopy, Fourier Transform Infrared Spectroscopy, and Laser Photoacoustic Overtone Spectroscopy, and utilize Density Functional Theory to calculate the C-H bond energy of β-CL-20 in a crystal. The spectra reveal four intense and distinct features, whose analysis yields C-H stretching fundamental frequencies and anharmonicity values that range from 3137 to 3170 cm(-1) and 53.8 to 58.8 cm(-1), respectively. From these data, we estimate an average value of 42,700 cm(-1) (5.29 eV) for the C-H bond energy, a value that agrees with our quantum mechanical calculations.
- Published
- 2013
9. High-Pressure Characterization of Nitrogen-Rich Bis-triaminoguanidinium Azotetrazolate (TAGzT) by In Situ Raman Spectroscopy
- Author
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Kristopher D. Behler, Rosario C. Sausa, and Jennifer A. Ciezak-Jenkins
- Subjects
Nitrogen rich ,chemistry ,High pressure ,In situ raman spectroscopy ,Analytical chemistry ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Compression (physics) ,Nitrogen ,Intensity (heat transfer) ,Isothermal process ,Characterization (materials science) - Abstract
Compounds rich in nitrogen are attracting significant interest not only because of their high energy content but also because they are potentially more environmentally benign in comparison to conventional energetic materials. Given this interest, it is desirable to understand their molecular composition and structural variations with pressure to derive their stability and determine the conditions in which they transform physically or chemically. In this study, we examine the room-temperature isothermal compression behavior of bis-triaminoguanidinium azotetrazolate (TAGzT) by in situ Raman spectroscopy to pressures near 17 GPa. We assign the characteristic vibrational bands and report the effects of pressure on band intensity, line width, and frequency shift. Two prominent peaks near 1370 and 1470 cm(-1) arise from the C-N and N═N symmetric stretches, respectively. Overall, the intensity of these bands and others diminishes with pressure, and their spectral linewidths increase monotonically upon compression. The vibrational frequency modes blue shift linearly upon compression, indicating a generalized stiffening of the bonds as the pressure increases. These results, together with micro Raman spectroscopic analyses of the recovered, decompressed samples, suggest that TAGzT does not undergo any phase transitions within this pressure range. We estimate and report the C-N and N═N intermolecular bond lengths under compression.
- Published
- 2013
10. Directional amorphization of boron carbide subjected to laser shock compression
- Author
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Bimal K. Kad, Marc A. Meyers, Jerry C. LaSalvia, Christopher Wehrenberg, Bruce Remington, Kristopher D. Behler, and Shiteng Zhao
- Subjects
Materials science ,Non-equilibrium thermodynamics ,02 engineering and technology ,Boron carbide ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Planar ,law ,0103 physical sciences ,Composite material ,010306 general physics ,Multidisciplinary ,business.industry ,021001 nanoscience & nanotechnology ,Laser ,Crystallography ,chemistry ,Shear (geology) ,Transmission electron microscopy ,Heat transfer ,Physical Sciences ,0210 nano-technology ,business ,Thermal energy - Abstract
Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45∼50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C.
- Published
- 2016
11. Nanodiamond-Polymer Composite Fibers and Coatings
- Author
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Vadym Mochalin, Guzeliya Korneva, Antonella Stravato, Kristopher D. Behler, Yury Gogotsi, and Gleb Yushin
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business.product_category ,Materials science ,Polymers ,Acrylic Resins ,General Physics and Astronomy ,engineering.material ,Nanocomposites ,Nanomaterials ,chemistry.chemical_compound ,Microscopy, Electron, Transmission ,Microfiber ,General Materials Science ,Composite material ,Nanodiamond ,chemistry.chemical_classification ,General Engineering ,Polyacrylonitrile ,Diamond ,Polymer ,Electrospinning ,Nylons ,chemistry ,Nanofiber ,Microscopy, Electron, Scanning ,engineering ,Feasibility Studies ,Spectrophotometry, Ultraviolet ,business - Abstract
While nanocrystalline diamond is quickly becoming one of the most widely studied nanomaterials, achieving a large fraction of diamond nanoparticles in a polymer coating has been an unresolved problem. In this work, polymer nano- and microfibers containing high loadings of 5 nm diamond particles (up to 80 wt % in polyacrylonitrile and 40% in polyamide 11) have been demonstrated using electrospun nanofibers as a delivery vehicle. The electrospun nanofibers with a high load of nanodiamond in the polymers were fused into thin transparent films, which had high mechanical properties; an improvement of 4 times for the Young's modulus and 2 times for the hardness was observed already at 20% nanodiamond in polyamide 11. These films can provide UV protection and scratch resistance to a variety of surfaces, especially in applications where a combination of mechanical, thermal, and dielectric properties is required.
- Published
- 2009
12. Microstructure and multifunctional properties of liquid + polymer bicomponent structural electrolytes: Epoxy gels and porous monoliths
- Author
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Kristopher D. Behler, Eric D. Wetzel, Phuong-Anh T. Nguyen, Edwin B. Gienger, James F. Snyder, and Wai Chin
- Subjects
Supercapacitor ,Materials science ,Polymers and Plastics ,technology, industry, and agriculture ,General Chemistry ,Electrolyte ,Epoxy ,Microstructure ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,chemistry ,Percolation ,visual_art ,Propylene carbonate ,Materials Chemistry ,visual_art.visual_art_medium ,Ionic conductivity ,Composite material ,Porosity - Abstract
Multifunctional structural batteries and supercapacitors have the potential to improve performance and efficiency in advanced lightweight systems. A critical requirement is a structural electrolyte with superior multifunctional performance. We present here structural electrolytes prepared by the integration of liquid electrolytes with structural epoxy networks. Two distinct approaches were investigated: direct blending of an epoxy resin with a poly(ethylene-glycol) (PEG)- or propylene carbonate (PC)-based liquid electrolyte followed by in-situ cure of the resin; and formation of a porous neat epoxy sample followed by backfill with a PC-based electrolyte. The results show that in situ cure of the electrolytes within the epoxy network does not lead to good multifunctional performance due to a combination of plasticization of the structural network and limited percolation of the liquid network. In contrast, addition of a liquid electrolyte to a porous monolith results in both good stiffness and high ionic conductivity that approach multifunctional goals. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42681.
- Published
- 2015
13. The Effect of SiO2 and B2 O3 Additives on the Microstructure and Hardness of Hot-Pressed Boron Carbide
- Author
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Kristopher D. Behler, Jerry C. LaSalvia, and A. Z. Hutchinson
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Diffraction ,chemistry.chemical_compound ,Materials science ,chemistry ,Metallurgy ,X-ray ,Boron carbide ,Microstructure - Published
- 2015
14. TEM Characterization of the Deformed Region Beneath Knoop Indents in Boron Carbide
- Author
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Scott D. Walck, Jerry C. LaSalvia, and Kristopher D. Behler
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010302 applied physics ,Materials science ,Metallurgy ,02 engineering and technology ,Boron carbide ,021001 nanoscience & nanotechnology ,01 natural sciences ,Characterization (materials science) ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Knoop hardness test ,0210 nano-technology ,Instrumentation - Published
- 2016
15. Laser- and Filament-Induced Multi-scale Surface Structures on Solid Target Materials
- Author
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Andrew Porwitzky, Kristopher D. Behler, Matthew Weidman, Martin Richardson, Anthony Valenzuela, and Chase A. Munson
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chemistry.chemical_classification ,Surface (mathematics) ,Materials science ,Scale (ratio) ,business.industry ,Scanning electron microscope ,macromolecular substances ,Polymer ,Laser ,law.invention ,Protein filament ,Optics ,chemistry ,law ,visual_art ,visual_art.visual_art_medium ,Ceramic ,business ,Material properties - Abstract
Laser-induced filaments can ablate solid material at distances greater than that practicably achieved through linear optics. We observed multi-scale structures on metals, polymers, and ceramics from filaments and compared to those from short-focused laser pulses.
- Published
- 2014
16. Carbon Nanotube Assisted Electrical Treeing for Vascular Network Synthesis
- Author
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Kristopher D. Behler and Eric D. Wetzel
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chemistry.chemical_classification ,Materials science ,Dielectric strength ,Electrical treeing ,Polymer ,Dielectric ,Carbon nanotube ,law.invention ,chemistry ,law ,Electric field ,Electrode ,Fluidics ,Composite material - Abstract
Electrical treeing (ET) is a stepwise dielectric breakdown process that generates a branched, hollow network of tubules in the dielectric between the electrode and ground. In this study, the controlled growth of electrical trees (ETs) in epoxies is demonstrated as a technique for fabricating synthetic vascular systems in engineering materials. A number of experimental conditions are explored, including AC versus DC voltage and geometric arrangement of the electrode and ground. AC growth tends to induce highly branched, “bush-like” trees while DC growth tends to produce lower-order branched structures. In addition, treating electrode surfaces with multi-walled carbon nanotubes (MWCNTs) is shown to promote ET initiation, most likely due to enhancements in the local electric field intensity. The utility of these structures for vascular applications is demonstrated by filling the channels with dyed liquids.
- Published
- 2009
17. Laser-induced light emission from carbon nanoparticles
- Author
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Yury Gogotsi, Kristopher D. Behler, and Sebastian Osswald
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Materials science ,Photoluminescence ,business.industry ,General Physics and Astronomy ,chemistry.chemical_element ,Carbon black ,Laser ,law.invention ,Nanomaterials ,Optical properties of carbon nanotubes ,symbols.namesake ,chemistry ,law ,symbols ,Optoelectronics ,Light emission ,Raman spectroscopy ,business ,Carbon - Abstract
Strong absorption of light in a broad wavelength range and poor thermal conductance between particles of carbon nanomaterials, such as nanotubes, onions, nanodiamond, and carbon black, lead to strong thermal emission (blackbody radiation) upon laser excitation, even at a very low (milliwatts) power. The lasers commonly used during Raman spectroscopy characterization of carbon can cause sample heating to very high temperatures. While conventional thermometry is difficult in the case of nanomaterials, Raman spectral features, such as the G band of graphitic carbon and thermal emission spectra were used to estimate the temperature during light emission that led to extensive graphitization and evaporation of carbon nanomaterials, indicating local temperatures exceeding 3500 °C.
- Published
- 2008
18. Self-assembled multi-walled carbon nanotube coatings
- Author
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Yury Gogotsi, Mickael Havel, Kristopher D. Behler, and Davide Mattia
- Subjects
chemistry.chemical_classification ,Nanotube ,Materials science ,business.product_category ,Layer by layer ,Polymer ,Carbon nanotube ,Polyelectrolyte ,law.invention ,chemistry ,Chemical engineering ,law ,Nanofiber ,Polyamide ,Microfiber ,business - Abstract
Multi-walled carbon nanotube (MWCNT) grafting onto electrospun poly(acrylonitrile) (PAN) nanofibers yields a layer by layer deposition of self assembled (LBL-SA) nanotube filaments or nanowires. PAN fibers were first functionalized with carboxylic groups through a sodium hydroxide treatment. Then, poly(diallyldimethylammonium chloride) (PDDAC), a positively charged polyelectrolyte was adsorbed onto the fibers via electrostatic interaction. When placed in contact with the modified fibers, acid treated MWCNT (ac-MWCNT) self-assemble, producing a dense and continuous layer onto the polymer nanofibers, while the inherent structure and morphology of the polymer nanofibers are retained. This method is being investigated as a universal approach applicable to a variety of materials. By producing layers of nanotubes, the electrical conductivity of polymers may be improved due to formation of a continuous MWCNT monolayer on the surface as opposed to traditional incorporation of large amounts of nanotubes into the bulk of the polymer. This method can further be implemented on polymer systems that promote a positively charged surface for COOH functionalized MWCNT to attach. Polyamides offer a perfect scenario in which they do not need to be modified to allow hydrogen bonding between the polymer and the ac-MWCNTs. Electrospun polyamide 11 (PA 11) provides a network of 100 nm and greater, fibers for deposition of ac-MWCNTs. These MWCNT coated nanofibers possess high electrical conductivity, about 0.1 S/cm, resulting from a dense coverage of MWCNTs on the polymer surface.
19. First principles model of yttrium adsorption on boron suboxide (0001) surface
- Author
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Christopher J. Marvel, Martin P. Harmer, Kristopher D. Behler, Jerry C. LaSalvia, and J. Synowczynski-Dunn
- Subjects
Surface (mathematics) ,chemistry.chemical_compound ,Adsorption ,Materials science ,chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Yttrium ,Boron suboxide
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