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Articles 1 - 30 of 60
Full-Text Articles in Engineering
Electrospun Nanofibers For Potential Space-Based Applications, G. Zhang, W. Kataphinan, R. Teye-Mensah, P. Katta, L. Khatri, E. Evans, George Chase, R. Ramsier, Darrell Reneker
Electrospun Nanofibers For Potential Space-Based Applications, G. Zhang, W. Kataphinan, R. Teye-Mensah, P. Katta, L. Khatri, E. Evans, George Chase, R. Ramsier, Darrell Reneker
Darrell Hyson Reneker
SiO2 nanofibers have been produced by the electrospinning method by two different approaches: direct spinning of silica precursor-containing nanofibers and spinning of polymer nanofibers followed by sol–gel silica coating. After pyrolysis of the resulting materials, both methods yield silica nanofibers. We extend this work by coating the silica nanofibers with AlN films using a reactive magnetron sputtering technique. Substrate temperature, input gas composition and radio frequency (rf) power are the critical operating parameters for the formation of different crystal structures of the AlN shells. The AlN/SiO2 core-shell heterostructures demonstrate that electrospinning has the potential to produce low-mass, high-surface-area flexible nanofibers …
Polymeric Nanofibers: Introduction, Darrell Reneker, Hao Fong
Polymeric Nanofibers: Introduction, Darrell Reneker, Hao Fong
Darrell Hyson Reneker
Polymeric nanofibers are rapidly finding their place in nanomaterials technology. Electrospinning makes it easy to produce many kinds of nanofibers for many purposes.
Synthetically Spun Silk Nanofibers And A Process For Making The Same, Shahrzad Zarkoob, Darrell Reneker, Dale Ertley, R. Eby, Steven Hudson
Synthetically Spun Silk Nanofibers And A Process For Making The Same, Shahrzad Zarkoob, Darrell Reneker, Dale Ertley, R. Eby, Steven Hudson
Darrell Hyson Reneker
A silk nanofiber composite network produced by forming a solution of silk fiber and hexafluroisopropanol, wherein the step of forming is devoid of any acid treatment, where the silk solution has a concentration of about 0.2 to about 1.5 weight percent silk in hexafluroisopropanol, and where the silk is selected from Bombyx mori silk and Nephila clavipes silk; and electrospinning the solution, thereby forming a non-woven network of nanofibers having a diameter in the range from about 2 to about 2000 nanometers.
Development Of Carbon Nanofibers From Aligned Electrospun Polyacrylonitrile Nanofiber Bundles And Characterization Of Their Microstructural, Electrical, And Mechanical Properties, Zhengping Zhou, Chuilin Lai, Lifeng Zhang, Yong Qian, Haoqing Hou, Darrell Reneker, Hao Fong
Development Of Carbon Nanofibers From Aligned Electrospun Polyacrylonitrile Nanofiber Bundles And Characterization Of Their Microstructural, Electrical, And Mechanical Properties, Zhengping Zhou, Chuilin Lai, Lifeng Zhang, Yong Qian, Haoqing Hou, Darrell Reneker, Hao Fong
Darrell Hyson Reneker
Carbon nanofibers with diameters of 200–300 nm were developed through stabilization and carbonization of aligned electrospun polyacrylonitrile (PAN) nanofiber bundles. Prior to the oxidative stabilization in air, the electrospun PAN nanofiber bundle was tightly wrapped onto a glass rod, so that tension existed during the stabilization. We also investigated several carbonization procedures by varying final carbonization temperatures in the range from 1000 to 2200 °C. The study revealed that: (1) with increase of the final carbonization temperature, the carbon nanofibers became more graphitic and structurally ordered; (2) the carbon nanofiber bundles possessed anisotropic electrical conductivities, and the differences between the …
Liquid Drop Growth On A Fiber, A. Yarin, George Chase, W. Liu, S. Doiphode, Darrell Reneker
Liquid Drop Growth On A Fiber, A. Yarin, George Chase, W. Liu, S. Doiphode, Darrell Reneker
Darrell Hyson Reneker
A quantitative model is described and verified to predict the growth of oil droplets by coalescence on a single nanofiber. The model considers a stream of fluid carrying many tiny droplets of a different fluid. The mechanisms by which the tiny droplets are captured by a drop growing on a fiber are considered. Different capture mechanisms are examined, including interception, Brownian motion of droplets, and vapor deposition by diffusion. It is shown that droplet interception and Brownian diffusion contribute to drop growth on nanofibers for airborne oil droplets in the size range from 100 to 1000 nm. Merging of growing …
Nanofiber Manufacturing: Toward Better Process Control, Darrell Reneker, Alexander Yarin, Eyal Zussman, Sureeporn Koombhongse, Woraphon Kataphinan
Nanofiber Manufacturing: Toward Better Process Control, Darrell Reneker, Alexander Yarin, Eyal Zussman, Sureeporn Koombhongse, Woraphon Kataphinan
Darrell Hyson Reneker
This paper considers the development of a comprehensive model of the electrospinning process. All stages of the electrospinning process, from the preparation of the solution to the collection of the nanofibers are discussed together from the point of view of manufacturing. Experimental observations of the three-dimensional path of the jet can be compared with the path calculated from the model.
Growth Of Carbon Nanostructures On Carbonized Electrospun Nanofibers With Palladium Nanoparticles, Chuilin Lai, Qiaohui Guo, Xiang-Fa Wu, Darrell Reneker, Haoqing Hou
Growth Of Carbon Nanostructures On Carbonized Electrospun Nanofibers With Palladium Nanoparticles, Chuilin Lai, Qiaohui Guo, Xiang-Fa Wu, Darrell Reneker, Haoqing Hou
Darrell Hyson Reneker
This paper studies the mechanism of the formation of carbon nanostructures on carbon nanofibers with Pd nanoparticles by using different carbon sources. The carbon nanofibers with Pd nanoparticles were produced by carbonizing electrospun polyacrylonitrile (PAN) nanofibers including Pd(Ac)2. Such PAN-based carbon nanofibers were then used as substrates to grow hierarchical carbon nanostructures. Toluene, pyridine and chlorobenzine were employed as carbon sources for the carbon nanostructures. With the Pd nanoparticles embedded in the carbonized PAN nanofibers acting as catalysts, molecules of toluene, pyridine or chlorobenzine were decomposed into carbon species which were dissolved into the Pd nanoparticles and consequently grew into …
Electrospun Jets Launched From Polymeric Bubbles, Darrell Reneker, George Chase, Jackapon Sunthornvarabhas
Electrospun Jets Launched From Polymeric Bubbles, Darrell Reneker, George Chase, Jackapon Sunthornvarabhas
Darrell Hyson Reneker
The invention relates to a novel method for electrospinning fibers wherein the fiber-spinning solution is infused with gas bubbles which travel through the electrospinning fluid, causing the bubbles to be coated with electrospinning solution. The coated bubbles, in turn, in response to an applied electrical force, generate jets of the electrospinning fluid that travel away from the bubble surface. The invention further relates to the fibers formed by this bubble-jet process and to products made therefrom.
Selective Emitters For Thermophotovoltaics: Erbia-Modified Electrospun Titania Nanofibers, V. Tomer, R. Teye-Mensah, J. Tokash, N. Stojilovic, W. Kataphinan, Edward Evans, George Chase, R. Ramsier, D. Smith, Darrell Reneker
Selective Emitters For Thermophotovoltaics: Erbia-Modified Electrospun Titania Nanofibers, V. Tomer, R. Teye-Mensah, J. Tokash, N. Stojilovic, W. Kataphinan, Edward Evans, George Chase, R. Ramsier, D. Smith, Darrell Reneker
Darrell Hyson Reneker
Titania nanofibers were synthesized by electrospinning and characterized with scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The nanofibers were annealed to 773 K to achieve the anatase titania crystal structure, and to 1173 K to obtain the rutile phase. In order to create erbia-containing titania nanofibers, erbium (III) oxide particles were added to the pre-cursor solution before electrospinning. After pyrolysis the titania nanofibers supported and encapsulated the erbia particles. Temperature-dependent near-infrared emission spectra demonstrate that the erbia-containing nanofibers emit selectively in the range 6000–7000 cm−1. Because of their large surface to volume ratios and narrow-band optical emission, these …
Erbia-Modified Electrospun Titania Nanofibres For Selective Infrared Emitters, R. Teye-Mensah, V. Tomer, W. Kataphinan, J. Tokash, N. Stojilovic, George Chase, Edward Evans, R. Ramsier, D. Smith, Darrell Reneker
Erbia-Modified Electrospun Titania Nanofibres For Selective Infrared Emitters, R. Teye-Mensah, V. Tomer, W. Kataphinan, J. Tokash, N. Stojilovic, George Chase, Edward Evans, R. Ramsier, D. Smith, Darrell Reneker
Darrell Hyson Reneker
Tetraisopropyl titanate (TPT) was mixed with a solution of polyvinylpyrrolidone (PVP) and the solution electrospun into nanofibres. Thermal annealing at 900 °C was used to pyrolyse the PVP, leaving nanofibres of rutile-phase titania. Erbium (III) oxide particles were also added into the solution before electrospinning, and selectively modified the near-infrared optical properties of the titania nanofibres as verified by both absorption and emission spectra. We thereby demonstrate the production of high-temperature optically functionalized nanostructures that can be used in a thermophotovoltaic energy conversion system.
Structure And Morphology Of Electrospun Silk Nanofibers, Shahrzad Zarkoob, R. Eby, Darrell Reneker, Steven Hudson, Dale Ertley, Wade Adams
Structure And Morphology Of Electrospun Silk Nanofibers, Shahrzad Zarkoob, R. Eby, Darrell Reneker, Steven Hudson, Dale Ertley, Wade Adams
Darrell Hyson Reneker
Nanoscale fibers of natural silks of Bombyx mori and Nephila clavipes were produced from solutions in hexafluoro-2-propanol. The electrospun fibers were observed by optical, scanning electron, and transmission electron microscopy. These nanofibers showed optical retardation, appeared to have a circular cross-section, and were thermally stable under nitrogen to 280 °C (N. clavipes) and to 245 °C (B. mori). The diameter of the fibers ranged from approximately 6.5–200 nm making them orders of magnitudes smaller than the natural silks spun by most silkworms and spiders. The smallest fiber diameters correspond to 200 molecules in the cross section of the N. clavipes …
Nanofibers And Spheres By Polymerization Of Cyanoacrylate Monomer, Sphurti Doiphode, Darrell Reneker, George Chase
Nanofibers And Spheres By Polymerization Of Cyanoacrylate Monomer, Sphurti Doiphode, Darrell Reneker, George Chase
Darrell Hyson Reneker
A unique method for creating polymer nanofibers and spheres on a variety of substrates is described. Cyanoacrylate monomer vapor was collected on a solid surface and polymerized to form nanofibers. Tiny spots of initiator on the surface of a substrate and small monomer droplets in a monomer vapor appear to be required for the growth of the polycyanoacrylate nanofibers. The polycyanoacrylate nanofibers create a network and increase the specific surface area significantly.
Nitric Oxide-Modified Linear Poly(Ethylenimine) Fibers And Uses Therefor, Daniel Smith, Darrell Reneker
Nitric Oxide-Modified Linear Poly(Ethylenimine) Fibers And Uses Therefor, Daniel Smith, Darrell Reneker
Darrell Hyson Reneker
A novel coating for medical devices provides nitric oxide delivery using nanofibers of linear poly(ethylenimine)diazeniumdiolate. Linear poly(ethylenimine)diazeniumdiolate releases nitric oxide (NO) in a controlled manner to tissues and organs to aid the healing process and to prevent injury to tissues at risk of injury. Electrospun nanofibers of linear poly(ethylenimine)diazeniumdiolate deliver therapeutic levels of NO to the tissues surrounding a medical device while minimizing the alteration of the properties of the device. A nanofiber coating, because of the small size and large surface area per unit mass of the nanofibers, provides a much larger surface area per unit mass while minimizing …
Polybenzimidazole Nanofiber Produced By Electrospinning, Jong-Sang Kim, Darrell Reneker
Polybenzimidazole Nanofiber Produced By Electrospinning, Jong-Sang Kim, Darrell Reneker
Darrell Hyson Reneker
Nanofibers of aromatic heterocyclic PBI (poly(2,2′(m-phenylene)-5,5′ bibenzimidazole)) polymer were made by an electrospinning process. The diameter of the fibers was around 300 nanometers. A liquid jet of a polymer solution, formed when electrical force overcame surface tension, stretched and dried as the solvent evaporated. The resulting electrically charged nanofibers were attracted to and collected on a rotating cylinder covered with aluminum foil that was electrically grounded. The fibers were collected in non-woven sheets about 20 centimeters wide and 100 centimeters long, with a compressed thickness of a few tens of microns. The mass per unit area of the nonwoven sheets …
Fibrous Media Utilizing Temperature Gradient And Methods Of Use Thereof, Darrell Reneker, Alexander Yarin, Wenxia Liu
Fibrous Media Utilizing Temperature Gradient And Methods Of Use Thereof, Darrell Reneker, Alexander Yarin, Wenxia Liu
Darrell Hyson Reneker
A method for removing a liquid from a gas, comprises passing the gas and the liquid through a network of fibers containing at least one fiber in which a temperature gradient has been induced along at least a portion of the length of the fiber, thereby permitting droplets of the liquid to be captured by the at least one fiber, and wherein the temperature gradient causes migration of the droplets. A method of preventing the fouling of a coalescence filter is also disclosed. The method comprises inducing a temperature gradient along at least a portion of a length of at …
Highly Hydrophobic Electrospun Fiber Mats From Polyisobutylene-Based Thermoplastic Elastomers, Goy Lim, Judit Puskas, Darrell Reneker, Antal Jakli, Walter Horton
Highly Hydrophobic Electrospun Fiber Mats From Polyisobutylene-Based Thermoplastic Elastomers, Goy Lim, Judit Puskas, Darrell Reneker, Antal Jakli, Walter Horton
Darrell Hyson Reneker
This paper is the first report of electrospinning neat polyisobutylene-based thermoplastic elastomers. Two generations of these materials are investigated: a linear poly(styrene-b-isobutylene-b-styrene) (L_SIBS) triblock copolymer and a dendritic poly(isobutylene-b-p-methylstyrene) (D_IB-MS), also a candidate for biomedical applications. Cross-polarized optical microscopy shows birefringence, indicating orientation in the electrospun fibers, which undergo large elongation and shear during electrospinning. In contrast to the circular cross section of L_SIBS fibers, D_IB-MS yields dumbbell-shaped fiber cross sections for the combination of processing conditions, molecular weight, and architecture. Hydrophobic surfaces with a water contact angle as high as 146 ± 3° were obtained with D_IB-MS that had …
Interpretation And Use Of Glints From An Electrospinning Jet Of Polymer Solutions, Kaiyi Liu, Camden Ertley, Darrell Reneker
Interpretation And Use Of Glints From An Electrospinning Jet Of Polymer Solutions, Kaiyi Liu, Camden Ertley, Darrell Reneker
Darrell Hyson Reneker
Optical observations of jets provide information useful for control of electrospinning of polymer solutions. Combinations of videography, stereography, and methods for illumination of the multiple coils of an electrospinning jet path, that depend on bright glints of reflected light from the jet, recorded quantitative information about the location, vector velocity, and rotation of selected segments of the jet. New bending coils were observed to form at rates of 200–1560 turns per second. This bending frequency decreased as the capillary number of the solutions increased. The polarization of light, in glints reflected at Brewster's angle, allows measurement of the index of …
Carbon Nanotubes On Carbon Nanofibers: A Novel Structure Based On Electrospun Polymer Nanofibers, H. Hou, Darrell Reneker
Carbon Nanotubes On Carbon Nanofibers: A Novel Structure Based On Electrospun Polymer Nanofibers, H. Hou, Darrell Reneker
Darrell Hyson Reneker
No abstract provided.
Characterization Of Electrospinning Jet Using Interference Color Technique, Han Xu, Darrell Reneker
Characterization Of Electrospinning Jet Using Interference Color Technique, Han Xu, Darrell Reneker
Darrell Hyson Reneker
A comprehensive model combining electromagnetic theory of light and quantitative science of color perception was developed and experimentally validated to characterize the diameter of a fluid electrospinning jet from the interference colors shown on the jet. One light source and one camera provide real-time micron scale information about the jet diameter. The jet segments may be moving during the measurements. This method provides continuous measurements of jets with diameters from 15 to 0.5 microns. Observation of color patterns also provides information about the taper of the jet.
Delamination Resistant Composites Prepared By Small Diameter Fiber Reinforcement At Ply Interfaces, Yuris Dzenis, Darrell Reneker
Delamination Resistant Composites Prepared By Small Diameter Fiber Reinforcement At Ply Interfaces, Yuris Dzenis, Darrell Reneker
Darrell Hyson Reneker
A fiber reinforced composite material comprising a resin matrix and primary reinforcement fibers and further comprising secondary, smaller diameter, reinforcement fibers at one or more ply interfaces, or portion thereof, provides improved interlaminar toughness, strength, and delamination resistance without substantial reduction of in-plane properties and without substantial increase in weight. In one embodiment, the small fibers are attached to one side of a conventional prepreg prior to lamination. The small fibers are flexible and are expected to conform to the shape and distribution of the primary reinforcing fibers at the interface.
Electrospun Polymer Nanofibres With Small Diameters, Chaobo Huang, Shuiliang Chen, Chuilin Lai, Darrell Reneker, Haiyan Qiu, Ying Ye, Haoqing Hou
Electrospun Polymer Nanofibres With Small Diameters, Chaobo Huang, Shuiliang Chen, Chuilin Lai, Darrell Reneker, Haiyan Qiu, Ying Ye, Haoqing Hou
Darrell Hyson Reneker
Nylon-4,6 nanofibres with diameters ranging from about 1 µm down to 1 nm were prepared by electrospinning. The fibre diameter was varied by adjusting the concentration of the polymer solution. Electrospinning of a concentrated solution of as high as 20% nylon-4,6 by weight in formic acid produced a ribbon-like electrospun fibre with a ribbon width of about 850 nm. A semi-dilute concentration of 2% nylon-4,6 by weight produced the thinnest nylon-4,6 nanofibres with diameters of 1.6 nm or less. A small amount of pyridine was added to the electrospinning solution to avoid the formation of beaded nanofibres in the course …
Electrospun Fibers And An Apparatus Therefor, Daniel Smith, Darrell Reneker, Albert Mcmanus, Heidi Schreuder-Gibson, Charlene Mello, Michael Sennett
Electrospun Fibers And An Apparatus Therefor, Daniel Smith, Darrell Reneker, Albert Mcmanus, Heidi Schreuder-Gibson, Charlene Mello, Michael Sennett
Darrell Hyson Reneker
A novel fiber comprising a substantially homogeneous mixture of a hydrophilic polymer and a polymer which is at least weakly hydrophobic is disclosed. The fiber optionally contains a pH adjusting compound. A method of making the fiber comprises electrospinning fibers of the substantially homogeneous polymer solution. A method of treating a wound or other area of a patient requiring protection from contamination comprises electrospinning the substantially homogeneous polymer solution to form a dressing. An apparatus for electrospinning a wound dressing is discosed.
Electrospinning For Tissue Engineering Scaffolds, J. Lannutti, Darrell Reneker, T. Ma, D. Tomasko, D. Farson
Electrospinning For Tissue Engineering Scaffolds, J. Lannutti, Darrell Reneker, T. Ma, D. Tomasko, D. Farson
Darrell Hyson Reneker
Tissue engineering involves fabrication of three-dimensional scaffolds to support cellular in-growth and proliferation. The goal: generation of ‘neotissues’ that the body can adapt to carry out physiological function. To achieve this generation of scaffolds having tailored, biomimetic (across multiple scales) geometries has become important. The functional complexity of electrospun scaffolds provides significant advantages over other techniques; however, improvements are required before optimal utilization in vivo becomes routine. Cells on such surfaces are sensitive to topography. Electrospinning can be altered to influence either (1) the surface topography of the fibers themselves or (2) the larger topography of the ‘web’ of spun …
Electrospinning Jets And Polymer Nanofibers, Darrell Reneker, Alexander Yarin
Electrospinning Jets And Polymer Nanofibers, Darrell Reneker, Alexander Yarin
Darrell Hyson Reneker
In electrospinning, polymer nanofibers are formed by the creation and elongation of an electrified fluid jet. The path of the jet is from a fluid surface that is often, but not necessarily constrained by an orifice, through a straight segment of a tapering cone, then through a series of successively smaller electrically driven bending coils, with each bending coil having turns of increasing radius, and finally solidifying into a continuous thin fiber. Control of the process produces fibers with nanometer scale diameters, along with various cross-sectional shapes, beads, branches and buckling coils or zigzags. Additions to the fluid being spun, …
Corona Discharge From Electrospinning Jet Of Poly (Ethylene Oxide) Solution, Sureeporn Tripatanasuwan, Darrell Reneker
Corona Discharge From Electrospinning Jet Of Poly (Ethylene Oxide) Solution, Sureeporn Tripatanasuwan, Darrell Reneker
Darrell Hyson Reneker
Corona discharges from electrospinning jets were observed and photographed at the tip of the Taylor cone, and in a cylindrical region around the jet, a few millimeters below the tip. The corona discharge was also faintly visible to a dark adapted eye. At the position at which the cylindrical corona discharge became apparent, typical conditions were a jet diameter of 30 μm, an applied potential of 12 kV, and a calculated radial electric field of 400 kV/cm, The calculated electric field required to create a corona in air around a metal wire of the same diameter, calculated from Peek's empirical …
Process And Apparatus For The Production Of Nanofibers, Darrell Reneker
Process And Apparatus For The Production Of Nanofibers, Darrell Reneker
Darrell Hyson Reneker
A nozzle for forming nanofibers by using a pressurized gas stream comprises a center tube, a first supply tube that is positioned concentrically around and apart from the center tube, a middle gas tube positioned concentrically around and apart from the first supply tube, and a second supply rube positioned concentrically around and apart from the middle gas tube. The center tube and first supply tube form a first annular column. The middle gas tube and the first supply tube form a second annular column. The middle gas tube and second supply tube form a third annular column. The tubes …
Assembly Of Well-Aligned Multiwalled Carbon Nanotubes In Confined Polyacrylonitrile Environments: Electrospun Composite Nanofiber Sheets, Jason Ge, Haoqing Hou, Qing Li, Matthew Graham, Andreas Greiner, Darrell Reneker, Frank Harris, Stephen Cheng
Assembly Of Well-Aligned Multiwalled Carbon Nanotubes In Confined Polyacrylonitrile Environments: Electrospun Composite Nanofiber Sheets, Jason Ge, Haoqing Hou, Qing Li, Matthew Graham, Andreas Greiner, Darrell Reneker, Frank Harris, Stephen Cheng
Darrell Hyson Reneker
Highly oriented, large area continuous composite nanofiber sheets made from surface-oxidized multiwalled carbon nanotubes (MWNTs) and polyacrylonitrile (PAN) were successfully developed using electrospinning. The preferred orientation of surface-oxidized MWNTs along the fiber axis was determined with transmission electron microscopy and electron diffraction. The surface morphology and height profile of the composite nanofibers were also investigated using an atomic force microscope in tapping mode. For the first time, it was observed that the orientation of the carbon nanotubes within the nanofibers was much higher than that of the PAN polymer crystal matrix as detected by two-dimensional wide-angle X-ray diffraction experiments. This …
High-Strength And High-Toughness Polyimide Nanofibers: Synthesis And Characterization, Chuyun Cheng, Juan Chen, Fei Chen, Ping Hu, Xiang-Fa Wu, Darrell Reneker, Haoqing Hou
High-Strength And High-Toughness Polyimide Nanofibers: Synthesis And Characterization, Chuyun Cheng, Juan Chen, Fei Chen, Ping Hu, Xiang-Fa Wu, Darrell Reneker, Haoqing Hou
Darrell Hyson Reneker
High-strength and high-toughness nanofibers were made from polyimide 6F-PI through electrospinning. The 6F-PI had a backbone made up with 3,3′,4, 4′-biphenyl-tetracarboxylic dianhydride and 2,2-bis[4-(4-aminophenoxy)phenyl]-hexafluoro-propane residues. Electrospun 6F-PI precursor nanofibers were collected in the form of aligned fiber sheet on the rim of a rotating disc. Heating process converted the precursor fiber sheets to 6F-PI nanofiber sheets. Gel permeation chromatography and Ostwald Viscometer were used to determine the molecular weight and the molecular weight distribution of the 6F-PI precursor, i.e., the 6F-polyamic acid. Scanning electron microscopy, infrared spectroscopy, X-ray scattering, tensile testing, dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry …
Buckling Of Jets In Electrospinning, Tao Han, Darrell Reneker, Alexander Yarin
Buckling Of Jets In Electrospinning, Tao Han, Darrell Reneker, Alexander Yarin
Darrell Hyson Reneker
Various buckling instabilities of electrospinning jets were observed and compared with the buckling instabilities of uncharged fluid jets. Buckling instability arises due to jet compression at impingement on a collector surface and occurs independently of the electrical bending instability. The velocity, diameter, density and viscosity of the electrospinning jets are the key factors that determine the buckling frequency. The electrically charged jets impinging onto grounded, horizontal or inclined (wedge-like) electrodes moving laterally at a constant velocity are studied experimentally. Straight and bending (electrospinning) jets emerge at short and sufficiently long inter-electrode distances, respectively. The experiments show that both straight segment …
Investigation Of The Formation Of Carbon And Graphite Nanofiber From Mesophase Pitch Nanofiber Precursor, Hao Fong, Darrell Reneker
Investigation Of The Formation Of Carbon And Graphite Nanofiber From Mesophase Pitch Nanofiber Precursor, Hao Fong, Darrell Reneker
Darrell Hyson Reneker
Mesophase pitch nanofibers, made by a recently patented nanofiber processing technology, were stabilized, carbonized and graphitized to study the formation of novel carbon and graphite nanofibers. These pitch nanofibers were birefringent, and had diameters as small as 100 nm. Thermogravimetric analysis showed the pitch nanofibers could be stabilized in air, and the air stabilization resulted in ca. 6 % weight gain, due to the absorption of oxygen. Air stabilization eliminated aromatic and aliphatic C—H structures, and created carbonyl and aryl/alkyl ether structures. After stabilization, the pitch molecules were crosslinked which prevented the nanofibers from melting during subsequent carbonization. Carbonization of …