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Centrifugally spun polyacrylonitrile (PAN) microfibers surface-coated with Co3O4 nanoparticles were prepared as precursors to produce coated Co3O4 carbon-fiber (CCF) composites for lithium-ion battery anodes. The Co3O4/C composite-fiber anodes were obtained after the stabilization of surface-coated Co3O4/PAN fibers at 200 °C for four hours, and subsequent carbonization at 600 °C for 6 hours. The electrochemical performance of the Co3O4/C composite-fiber anode with different active material loading was evaluated by using galvanostatic charge/discharge, rate performance, cyclic voltammetry, and electrochemical impedance spectroscopy experiments. The CCF anode delivered a specific charge capacity of 632 and 420 mAh g−1 after 100 cycles at 100 and 200 mA g−1, respectively, and exhibited good rate capability. An improved electrochemical performance of the CCF was observed compared to the carbon-fiber (CF) anode (300 mAh g−1), which was attributed to the interaction between CFs and Co3O4 nanoparticles. The synthesis method presented in this work can provide an effective avenue for the fabrication of surface coated-fiber materials, including free-standing anode materials for lithium-ion batteries with increased specific capacity and improved electrochemical performance compared to carbon-fiber electrodes.

α-Fe2O3 hollow nanofibers with wall thicknesses of 45 ± 16 nm were fabricated via centrifugal spinning of a solution containing Fe(NO3)3·9H2O and polyvinylpyrrolidone. These fibers were subjected to mechanical milling and mixed in ethanol. Polyacrylonitrile (PAN) fiber mats were also fabricated by centrifugal spinning from dimethylformamide-based solutions. The as-prepared PAN fibrous mats were dipped in the iron-oxide suspension. The coated PAN membranes were then subjected to a heat treatment which yielded carbon fibers coated with Fe3O4 nanoparticles. Both pure carbon fibers (carbonized PAN fibers) and Fe3O4/C composite fibers were used as anode materials in Li-ion batteries. The Fe3O4/C composite anode exhibited high specific capacity and good cycle stability when compared to that of the carbon-fiber electrode. An initial discharge capacity (Li insertion) of 882 mAh g−1 was obtained for the Fe3O4/C composite fibers with promising cycle performance and rate capability. These composite fibers show promising applications as electrode materials in high-performance rechargeable lithium-ion batteries.

In recent years, there has been growing concern regarding the use of petroleum-based lubricants. This concern has generated interest in readily biodegradable fluids such as vegetable oils. The present work evaluated the rheological and tribological characteristics of sunflower oil modified with silicon dioxide (SiO2) and titanium dioxide (TiO2) nanoparticles as lubricant additives at different concentrations. A parallel plate rheometer was used to evaluate the effects of concentration and shear rate on the shear viscosity, and the experimental data was compared with conventional models. The wear protection and friction characteristics of the oil-formulations were evaluated by conducting block-on-ring sliding tests. Surface analysis-based instruments, including scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and profilometry, were used to characterize the morphology and structure of the worn surfaces. The experimental results showed that the coefficient of friction decreased with the addition of SiO2 and TiO2 nanoparticles by 77.7% and 93.7%, respectively when compared to base sunflower oil. Furthermore, the volume loss was lowered by 74.1% and 70.1%, with the addition of SiO2 and TiO2 nanoparticles, respectively. Based on the experimental results, the authors conclude that modified sunflower oil enhanced with nanoparticles has the potential for use as a good biodegradable lubricant.

Nanocrystalline complex oxide scintillators have emerged for use in X-ray and gamma-ray detection in recent years. Here the doping concentration dependence of europium-doped lanthanum zirconate (La2Zr2O7:xmol%Eu3+, x = 1 to 35) nanoparticles (NPs) were investigated by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), and optically and X-ray excited luminescence. Spectroscopic methods revealed a gradual increase in disorder from the ordered pyrochlore structure to the defect fluorite structure as the Eu3+ concentration increases. They showed red luminescence under charge transfer band (258 nm), and Eu3+ 4f-4f bands (322, 394 and 465 nm) excitation with optical intensity dependent on the Eu3+ doping concentration and not quenching up to 5% Eu3+ doping concentration. The quantum yield of the red emission was found to depend on the Eu3+ doping concentration and excitation wavelength. Moreover, these La2Zr2O7:x%Eu3+ NPs demonstrated an atypical Eu3+ related scintillating response with a red emission under high-energy X-ray excitation with the scintillation intensity also depending on the Eu3+ doping concentration. Finally, the irradiation damage behavior induced by the excitation source was representatively examined for the La2Zr2O7:5%Eu3+ NPs. It is expected that the current study will pave the way for future research of nanoscintillators.

The development of alternative anode materials out of flexible composite nanofibers has seen a growing interest. In this paper, binary carbon nanofiber electrodes of SnO 2 /NiO and Sn nanoparticles are produced using a scalable technique, Forcespinning (FS), and subsequent thermal treatment (carbonization). The Sn/C composite nanofibers were porous and flexible, while the SnO 2 /NiO composite nanofibers had “hairy-like” particles and pores on the fiber strands. The nanofiber preparation process involved the FS of Sn/PAN and SnO 2 /NiO/PAN solution precursors into nanofibers and subsequent stabilization in air at 280 ° C and calcination at 800 °C under an inert atmosphere. The flexible composite nanofibers were directly used as working electrodes in lithium-ion batteries without a current collector, conducting additives, or binder. The electrochemical performance of the SnO 2 /NiO/C and Sn/C composite fiber anodes showed a comparable cycle performance of about 675 mAhg −1 after 100 cycles. However, the SnO 2 /NiO/C electrode exhibited a better rate performance than the Sn/C composite anode and was able to recover its capacity after charging with a higher current density. A postmortem analysis of the composite nanofiber electrode after the aging process revealed a heavily passivated electrode from the electrolyte decomposition by-products. The synthesis and processing methods used to produce these composite nanofibers clearly were a factor for the high rate capability and excellent cycle performance of these binary composite electrodes, largely on the account of the unique structure and properties of the composite nanofibers.

With nanofibers receiving much attention in the application of lithium ion batteries (LIBs), we herein report the use of multichannel hollow nanofibers composed of TiO 2 and Carbon as a binder-free anode for LIBs. The nanofibers were produced by the Forcespinning ® of an emulsion precursor solution composed of Polyvinylpyrrolidone (PVP), Titanium (IV) butoxide, ethanol, acetic acid, and mineral oil. The as-prepared precursor nanofibers were subjected to a thermal treatment by first stabilizing in air at 280 °C followed by carbonizing at 550 °C under an argon atmosphere to form TiO 2 /C composite multichannel hollow nanofibers without the need for a sacrificial polymer to produce this morphology. This fibers’ hollow structure resulted in improved electrochemical performance when compared to non-hollow fibers. These hollow fibers also showed excellent cycling performance with a specific capacity of 228.9 mAhg −1 at a current density of 100 mAg −1 while maintaining a Coulombic efficiency of ∼98% after 100 cycles compared to the TiO 2 /C non-hollow fibers which showed a capacity of 61.4 mAhg −1 . These composite hollow nanofibers show a great promise as alternative anode materials for next generation LIBs.

The development of nanostructured anode materials for rechargeable Lithium-ion Batteries has seen a growing interest. We herein report the use of a new scalable technique, Forcespinning (FS) to produce binder-free porous Sn/C composite nanofibers with different Sn particle size loading. The preparation process involves the FS of Sn/PAN precursor nanofibers and subsequently stabilizing in air at 280 °C followed by carbonization at 800 °C under an inert atmosphere. The Sn/C composite nanofibers are highly flexible and were directly used as binder-free anodes for lithium-ion batteries. The produced Sn/C composite nanofibers showed an improved discharge capacity of about 724 mA h g− 1 at a current density of 100 mA g− 1 for over 50 cycles compared to most nanofiber electrodes prepared by electrospinning and centrifugal spinning. The FS method clearly produces Sn/C nanofiber composite electrodes that have a high specific capacity and excellent cyclic performance, owing to the unique structure and properties of the nanofibers. The FS technology is thus a viable method for the large scale production of nano/micro fibers for battery electrodes, separators, and other applications. To the best of our knowledge, this is the first time to report results on the use of Forcespinning technology to produce composite nanofiber anodes for lithium-ion batteries.

TiO2/carbon composite-fiber anodes for lithium ion batteries were prepared through the centrifugal spinning of TiS2/polyacrylonitrile (PAN) precursor fibers and subsequent thermal treatment. The TiS2/PAN precursor solutions were prepared by mixing TiS2 nanoparticles (a 2-D layered structure) with PAN in N, N-dimethylformamide (DMF). The thermal treatment of the TiS2 in the centrifugally spun PAN fibers resulted in TiO2/carbon composite fibers. The structure of TiO2 nanoparticles embedded in the carbon-fiber matrix synthesized from the TiS2 starting material may accommodate high amounts of Li ions. The TiO2/C structure may lead to increased specific capacity, improved stability, and enhanced electrochemical performance of the TiO2/C composite electrode after prolonged charge/discharge cycles. The TiO2/C composite-fiber anode delivered discharge and charge capacities at the first cycle of 683 mAhg−1 and 356 mAhg−1, respectively, with a reversible charge capacity of 290 mAhg−1 after 100 cycles at a current density of 100 mAg−1. The TiO2/C composite fibers showed an improvement in the rate performance at higher current densities compared to the graphite anode alone.

In the present study, catalytic systems based on La-doping were developed to improve the activity and performance of CoMoS2 hydrodesulfurization catalysts. Lanthanum-doped at 5, 10, or 25% of the Co content in CoMoS2 hydrodesulfurization catalysts were synthesized through a solvothermal process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses confirmed the catalysts were triphasic consisting of Co9S8, MoS2, and La2S3. The La doped catalysts showed enhanced catalytic activity compared with CoMoS2 synthesized under the same conditions. The CoMoS2 prepared under solvothermal synthesis conditions showed a catalytic activity of 6.80 mol g-1 s-1, however, the La0.05Co0.95MoS2 doping showed a catalytic activity of 6.51 mol g -1 s-1 whereas the La0.1Co0.9MoS2 and La0.25Co0.75MoS2 samples showed catalytic activities of 10.7 mol g-1 s-1. The reaction products indicated the major reaction pathway was direct desulfurization. The La0.25Co0.75MoS2 catalyst after one reaction cycle showed a lower amount of carbon, than the undoped CoMoS2 catalyst.

The photocatalytic degradation of simazine (SIM) was investigated using zinc oxide/graphene oxide (ZnO/GO) composite materials under visible light irradiation. The reaction kinetics was studied to optimize the reaction parameters for efficient degradation of SIM. Batch studies were performed to investigate the effects of initial reaction pH, the loading of the ZnO onto GO, and mass of catalyst on the removal of SIM from aqueous solution. A pH of 2 was determined to be the optimal reaction pH for the different ZnO-loaded GO catalysts. In addition, a mass of 40 mg of catalyst in the reaction was observed to be the most effective for the catalysts synthesized using 20 and 30 mmol of Zn2+ ions; whereas a mass of 10 mg was most effective for the ZnO/GO composite material synthesized using 10 mmol Zn2+ ions. The reaction was observed to follow a second-order kinetics for the degradation process. Furthermore, the synthesized ZnO/GO composite catalysts resulted in higher reaction rates than those observed for pure ZnO. The 30 mmol ZnO/GO composite expressed a rate of SIM degradation ten times greater than the rate observed for pure ZnO, and sixty-two times greater than the rate of photolysis. In addition, the catalyst cycling exhibited a constant photocatalytic activity for the ZnO/GO composite over three reaction cycles without the need of a conditioning cycle.

We present results of centrifugally spun carbon fibers (CFs) made from aqueous Polyvinylpyrrolidone (PVP) solution. In the production of these fibers, the centrifugal spinning technique was used due to its high production rate of fibers. Subsequent heat treatment was conducted using a novel three step process that resulted in reduced residual stresses in the fibers after the centrifugal spinning process and subsequent thermal treatment. Moreover, this process increases the fibers’ resistance to degradation during carbonization at higher temperatures. Electrochemical performance tests were conducted on Li-ion half cells using the CFs as binder-free anodes. The carbon-fiber anode delivered a discharge capacity of Capacities of 618.7, 222.7 and 214.5 mAh g-1 at the 1st, 50th, and 100th cycles at a current density of 100 mAg-1. This work provides a novel and feasible pathway for designing and developing carbon fibers from water soluble polymer solution for use as anodes in high-performance lithium ion and sodium-ion batteries.

In this study, polyacrylonitrile (PAN) nanofibers are produced through a novel technique known as Hybrid-Spinning (HS) and used as a precursor for anodes in lithium ion batteries (LIBs). HS is a combination of two fiber-producing technologies: Centrifugal spinning (CS) and Electrospinning (ES). The use of HS for nanofiber production is promising due the limitations of both CS and ES. CS produces a high yield of nanofibers through centrifugal forces but is unable to account for the control of the fiber morphology, which limits the potential of the nanofibers-production through this technology. ES, on the other hand, produces nanofibers through electrical forces, allowing for a high degree of fiber morphology control by alternating the electrical field and process parameters. However, the high cost, safety concerns, and low yield of ES makes it unsuitable for the mass production of nanofibers in industry. Therefore, Hybrid Spinning has a high potential in changing the nanofiber industry by removing the limitations of both ES and FS while also minimizing safety-concerns, cost, and environmental impact. This work documents the morphology and characteristics of PAN nanofibers produced through HS and compares them to nanofibers made through FS and ES. The PAN fibrous mats obtained by HS are then converted into carbon nanofibers by calcination and directly used as free-binder anodes in lithium-ion batteries. The electrochemical performance of the HS carbon-fiber anodes is then compared with that prepared by ES and CS to determine the viability of HS technology with respect to Lithium-ion battery applications.

The quest to increase the energy density and improve the cycle life performance of lithium ion batteries (LIBs) and beyond has led to the development of various suitable and alternative materials for energy storage and conversion. The morphology and electrode architecture in advanced battery materials have been re-designed into nanofibers and composite nanofibers. Nanofiber-based separators and electrodes have demonstrated to improve the energy density and cycling performance of LIBs. The improvement in the structure and morphology of nanofibers in LIBs such as LiSi and LiSn, have once again ignited the interest in these Li:M alloy anodes as alternative anode and cathode materials. The major challenges that confront this new frontier have the lack of scalable method among the various techniques and designing nanofibers with good structure and morphology that could prevent dendrite penetrations. However, there seems to be a solution in sight with the advent of mass production techniques such as electrospinning and Forcespinning® that have recently been developed. In this paper, the use of nanofibers and composite nanofibers as electrode and separator materials for lithium ion, Li-O2 and Li-S batteries is reviewed. The discussion focuses on the performance characteristics of these nanostructured electrode and separator materials and methods used to improve their performances.

Nanofiber-based membranes were prepared by two different methods for use as separators for Lithium-ion batteries (LIBs). In the first method, Electrospinning was used for the fabrication of Polyvinylidene fluoride PVDF nanofiber coatings on polyolefin microporous membrane separators to improve their electrolyte uptake and electrochemical performance. The nanofiber-coated membrane separators show better electrolyte uptake and ionic conductivity than that for the uncoated membranes. In the second method, Forcespinning® (FS) was used to fabricate fibrous cellulose membranes as separators for LIBs. The cellulose fibrous membranes were made by the Forcespinning® of a cellulose acetate solution precursor followed by a subsequent alkaline hydrolysis treatment. The results show that the fibrous cellulose membrane-based separator exhibits high electrolyte uptake and good electrolyte/electrode wettability and therefore can be a good candidate for high performance and high safety LIB separators.

In the present study, titanium (IV) sulfide (TiS(2)) was synthesized and investigated for the removal of Cu(2+) and Pb(2+) ions from aqueous solutions. TiS(2) nanoparticles synthesized through a solvothermal synthesis were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The average particle size for the TiS(2) material was determined to be 8.03 ± 0.98 nm from the diffraction pattern. Studies were performed to examine the effects of pH, temperature, time, and interfering ions on the binding of Cu(2+) and Pb(2+) to the TiS(2). As well isotherm studies were performed to determine the binding capacity of TiS(2) for both Cu(2+) and Pb(2+) ions. The pH profile studies showed optimal binding occurred at pH 2 for the sorption of both Cu(2+) and Pb(2+) to the TiS(2). The isotherm studies showed the adsorption capacities at temperatures of 4, 22, and 45°C for Cu(2+) were 243, 222, and 153 mg/g, respectively. An opposite trend in the adsorption was observed for Pb(2+) binding to the TiS(2). The observed binding capacities for Pb(2+) were 32, 166, and 357 mg/g, at temperatures of 4, 22, and 45°C, respectively. The thermodynamic parameters for binding showed a non-spontaneous process for the sorption of Cu(2+) whereas a spontaneous binding process was observed for the sorption of Pb(2+). Additionally, the binding of Cu(2+) on TiS(2) in the presence of interfering ions (Na(+), K(+), Mg(2+), and/or Ca(2+)) was observed to decrease at high concentrations; however, the binding of Pb(2+) was unaffected by the presence of the same cations.

With the invention of the electric cars and the exponential growth in portable electronics over the last decade, energy storage systems that can supply and store more power are of utmost importance. Li-ion batteries (LIBs) entered the market less than a decade ago to keep up with market demands and have since become the most efficient way to store energy due to their reversible nature. Graphite is currently the most widely used material in (LIB) anodes due to its long cycle life and low manufacturing cost, its main drawback being its low theoretical capacity of 372 mAg-1. Metal oxides have been of interest as electrode materials for (LIBs) due to their inherently high theoretical capacities and low cost. However, the main drawback of metal oxide-based anodes includes high volume expansion, particle agglomeration, and dendrite formation. Developments in composites and novel micro/nano-structures that withstand large temperature ranges and maintain structural stability have attracted interest for their use as electrode materials in LIBs. Here, we explore the performance of Iron Oxide (Fe2O3), Tin Oxide (SnO2), Zinc Oxide (ZnO), and Cobalt Oxide (Co3O4), coated on carbon fibers as hosts for lithium ion insertion/de-insertion during charge/discharge process. The synthesis and design of Fe2O3/Carbon and SnO2/C composite fibers were reiliazed by the centrifugal spinning of metal-oxides precursors in polyacrylonitrile (PAN)/ dimethylformamide (DMF) solutions and followed by calcination at 600 °C in an inert gas. The characterization of Fe2O3/C, ZnO/C, Co3O4/C and SnO2/C composite fibers was conducted using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and energy dispersive X-ray analysis (EDAX). The pre-coated carbon fibers with metal-oxide nanoparticle precursors showed improved electrochemical performance compared to the pristine composite carbon-fibers anodes.

We present results on the centrifugal spinning of Metal-oxides (MOx)/PAN and Metal-Sulfides (MS)/PAN precursors for the mass production of MOx /C and MS/C composite fibers as anode materials for Lithium-ion batteries. MOx and MS such as NiO, TiO2, and SnO2, SnS2 and MoS2 were chosen with carbon as the active materials for the composite-fibers anodes. The microfiber preparation process involved the centrifugal spinning of MOx/MS/PAN precursors into microfibers and subsequent stabilization in air at 280ºC and calcination at 700ºC under Argon atmosphere. The MOx/C and MS/C composite-fibers anodes exhibited a specific capacity between 300 and 1200 mAhg-1 at the first cycle with a high irreversible capacity. The initial high irreversible capacity was attributed to the formation of the SEI layer and the high surface area of the centrifugally spun composite microfibers. In the subsequent cycles, the MOx/C and MS/C composite-fibers anodes exhibited a much stable cycling performance, i.e. 150-600 mAhg-1 was maintained after 100 cycles. The effect of pre-lithiation of the electrode after the first discharge cycle and coating the composite fibers-anode with active materials, prior to cycling, was systematically investigated. The pre-lithiation of carbon composite-fibers anodes after the first cycle exhibited higher charge/discharge capacities and higher coulombic efficiency up to 98% than the pristine carbon composite fibers.

Prelithiation is a good method used to mitigate the loss of lithium caused by the formation of the solid electrolyte interface (SEI) layer and by the irreversible reactions at the first discharge cycle. The main goal of this work is to systematically study the effect of prelithiation and thermal treatment on the electrochemical performance of carbon fiber anodes for LIBs. We present results on the centrifugal spinning of Polyacrylonitrile (PAN) fibers and PAN/ceramic composite fibers subjected to thermal treatment under different temperature and environmental conditions. The carbon composite-fibers anodes treated under a nitrogen atmosphere showed better electrochemical performance than that treated under argon atmosphere. The pre-lithiation of carbon fiber anodes after the first cycle exhibited higher charge/discharge capacities and higher coulombic efficiency up to 98% than the pristine carbon fibers. The results show that the pre-lithiation and the creation of defects onto the carbon-fibers surface are the detrimental keys of achieving and designing anode materials with enhanced electrochemical performance.

Poly(vinyl) butyral (PVB) nanofibers (NFs) and carbon nanotube (CNT) reinforced PVB NF composites were developed by using the Forcespinning® technology. PVB was dissolved in a mixture of ethanol and methanol (7:3 wt/wt) at various concentrations, and the solutions were spun at rotational speeds varying between 3,000 and 9,000 rpm. The CNT/PVB solutions were prepared using the same solvent ratio with varying the concentration of CNTs. The results show that the diameter of the PVB fibers increased with increasing rotational speed; however the standard deviation of the fiber diameter distribution decreased. The morphology and thermal properties of the developed fiber systems were studied by DSC, TGA, Raman, and FTIR. The effect of CNT on the mechanical properties of the developed fibers was investigated by carrying out tensile tests at different strain rates. Raman and FTIR analyses indicate a noncovalent π–π stacking interactions and hydrogen bonding between CNT and the PVB NFs. Adding CNT to the PVB NF matrix resulted in improved tensile strength by 150%. POLYM. ENG. SCI., 55:81–87, 2015. © 2014 Society of Plastics Engineers

Polycaprolactone (PCL) fibers were produced using Forcespinning® (FS). The effects of PCL concentration, solvent mixture, and the spinneret rotational speed on fiber formation were evaluated. The concentration of the polymer in the solvents was a critical determinant of the solution viscosity. Lower PCL concentrations resulted in low solution viscosities with a correspondingly low fiber production rate with many beads. Bead-free fibers with high production rate and uniform fiber diameter distribution were obtained from the optimum PCL concentration (i.e., 12.5 wt%) with tetrahydrofuran (THF) as the solvent. The addition of N, N-dimethylformamide (DMF) to the THF solvent promoted the gradual formation of beads, split fibers, and generally affected the distribution of fiber diameters. The crystallinity of PCL fibers was also affected by the processing conditions, spinning speed, and solvent mixture.

An electrospun nanofiber-coated Celgard® 2400 polypropylene microporous battery separator was prepared using polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-co-chlorotrifluoroethylene (PVDF-co-CTFE). The coating of PVDF and PVDF-co-CTFE nanofibers was carried out using single nozzle and nozzle-less electrospinning methods. The nanofiber coating prepared by the nozzle-less electrospinning method was found to have better adhesion to the microporous separator membrane than the nanofiber coating prepared by single nozzle electrospinning. The PVDF and PVDF-co-CTFE nanofiber coatings increased the electrolyte uptake capacity in a secondary lithium-ion battery, with PVDF-co-CTFE co-polymer nanofiber-coated microporous membrane showing higher electrolyte uptake capacity than PVDF homopolymer-coated microporous membrane. In addition, the PVDF and PVDF-co-CTFE nanofiber coatings improved the adhesion of the porous microporous membrane to a battery electrode. It was also found that nanofiber coatings prepared by the nozzle-less electrospinning method have better adhesion properties and higher electrolyte uptake capacity than those by single nozzle electrospinning.

Carbon nanofibers decorated with various amounts of electrochemically-inert metallic nickel nanoparticles are synthesized through electrospinning and carbonization processes. The morphology and composition of Ni nanoparticles in carbon nanofibers are controlled by preparing different nanofiber precursors. The lithium-ion battery performance evaluations indicated that the content of electrochemically-inert Ni nanoparticles in carbon nanofibers has a great influence on the final electrochemical performance. For example, at certain Ni contents, these composite nanofibers display excellent electrochemical performance, such as high reversible capacities, good capacity retention, and excellent rate performance, when directly used as binder-free anodes for rechargeable lithium-ion batteries. However, when the Ni content is too low or too high, the corresponding electrodes show low reversible capacities although they still have good reversibility and rate performance.

Novel conductive inorganic fiber/polymer hybrid proton exchange membranes (PEMs) were obtained by taking advantage of sulfated zirconia (S-ZrO2) fibers made by electrospinning and post-electrospinning processes. Induced by electrospun inorganic fibers, long-range ionic channels were formed by agglomerating functional groups, which served as continuous hopping pathways for protons and significantly improved the proton conductivity of PEMs. Keywords: Proton exchange membranes, Electrospun fibers, Functional polymers, Ionic channels, Proton conductivity

Lithium lanthanum titanate oxide (LLTO)/polyacrylonitrile (PAN) submicron composite fiber-based membranes were prepared by electrospinning dispersions of LLTO ceramic particles in PAN solutions. These ionic-conducting LLTO/PAN composite fiber-based membranes can be directly used as lithium-ion battery separators due to their unique porous structure. Ionic conductivities were evaluated after soaking the electrospun LLTO/PAN composite fiber-based membranes in a liquid electrolyte, 1 M lithium hexafluorophosphate (LiPF 6 ) in ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (1:1 vol). It was found that, among membranes with various LLTO contents, 15 wt.% LLTO/PAN composite fiber-based membranes provided the highest ionic conductivity, 1.95 × 10 −3 S cm −1 . Compared with pure PAN fiber membranes, LLTO/PAN composite fiber-based membranes had greater liquid electrolyte uptake, higher electrochemical stability window, and lower interfacial resistance with lithium. In addition, lithium//1 M LiPF 6 /EC/EMC//lithium iron phosphate cells containing LLTO/PAN composite fiber-based membranes as the separator exhibited high discharge specific capacity of 162 mAh g −1 and good cycling performance at 0.2 C rate at room temperature.

We present results on the Forcespinning (FS) of PVP solution precursors for the mass production of porous carbon microfibers as anode materials for Lithium-ion batteries. The porous microfiber carbon anodes are produced using a scalable technique (FS) and subsequent thermal treatment (carbonization). The carbon fiber anodes were porous and flexible. The flexible microfibers were directly used as working electrode in lithium-ion batteries without a current collector, conducting additives, or binder. Mixed organic/ionic liquid electrolytes (MOILEs) were employed in Lithium ion cell cycling studies with the porous carbon anode and commercial cathodes to investigate the electrochemical and cycling performance of the Li-ion cells. A temperature range of 25 to 60 °C and different current rates were used to study the effects of temperature on the ionic conductivity of MOILEs and on the electrochemical performance of LIB cells. 1-Ethyl-3-Methyl-imidazolium Lithium bis(trifluoromethanesulfonyl) imide (EMI-TFSI) ionic liquid was synthesized in our laboratory by reacting the EMI cation and TFSI ion in a 1:1 mole ratio. The EMI-TFSI ionic liquid and LiTFSI salt were mixed with organic liquids (Ethylene carbonate (EC) dimethyl carbonate (DMC) and Succinonitril (SCN) to improve the ionic transport of the electrolyte during the charge/discharge cycles. The carbon microfiber electrodes delivered a good electrochemical performance and Coulombic efficiency when used half and full cells. This study provides a novel and feasible pathway for designing and developing promising anodes with mixed organic/ionic liquid electrolytes for high-performance lithium ion batteries.

A novel rheometer plate was used to measure radial pressure profiles during cone-and-plate and parallel-plate shearing flows of a concentrated colloidal dispersion of poly(methyl methacryalate) spheres suspended in dioctyl phthalate. There is a long history of using suspensions of this type as a model rheological system. The measured pressure profile can be used to calculate N1 and N2, and also provides a check on the flow field in the rheometer. At shear rates just below onset of shear thickening, our measurements show that N1 is positive as predicted by Stokesian dynamics simulations of model Brownian hard spheres, but we are unable to determine the sign of N2. After the onset of thickening, we find that in both flow geometries the pressure increases sharply with radial position. This is in striking contrast to the pressure profiles ordinarily observed for viscoelastic liquids (with the exception of certain liquid crystal polymers), for which the pressure decreases with radial position. Under these cond...

We report the results from tensile creep tests performed on an epoxy resin in the presence of carbon dioxide at different pressures (Pco2) and at a constant temperature below the glass-transition temperature. Time-Pco2 superposition was applied to the data to account for the plasticization effect because of the interaction between the carbon dioxide molecules and the polymer. In addition, physical aging of the epoxy films was investigated with sequential creep tests after carbon dioxide pressure down-jumps at constant temperature and after temperature down-jumps at constant carbon dioxide pressure. The isothermal pressure down-jump experiments showed physical aging responses similar to the isobaric temperature down-jump experiments. However, the aging rate for the CO2 jump was slightly lower than that for the temperature-jump (T-jump) experiments, and the retardation time for the Pco2-jump experiments was up to 6.3 times longer than for the T-jump conditions. The results are discussed in terms of classical physical aging and structural recovery frameworks, and speculation about the differences in the energy landscape resulting from the Pco2-jump and T-jump experiments is also made. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2050–2064, 2002

We present results on the Forcespinning (FS) of SnS2/SnO2/PAN and MoS2/PAN precursors for the mass production of SnS2/SnO2 /carbon and MoS2/C as anode materials for Lithium-ion and Sodium-ion batteries. The binary composite nanofiber electrodes of SnS2/SnO2/C and MoS2/C are produced using a scalable technique (FS) and subsequent thermal treatment (calcination). The composite nanofiber anodes were porous and flexible. The nanofiber preparation process involved the FS of SnS2/SnO2/PAN and MoS2/PAN precursors into nanofibers and subsequent stabilization in air at 280oC and calcination at 800oC under an inert atmosphere. The flexible composite nanofibers were directly used as working electrode in lithium-ion and sodium-ion batteries without a current collector, conducting additives, or binder. The SnS2/C and SnS2/SnO2/C electrodes delivered a specific capacity of 556 mAhg-1 and 965 mAhg-1 respectively during the first sodiation cycle. This initial high capacity is attributed to the irreversible formation of a stable SEI layer and to the porous structure of the Forcespun composite nanofibers. In the subsequent cycles, the SnS2/C electrode exhibited a much stable cycling performance compared to SnS2/SnO2/C i.e. 145 mAhg-1 was maintained after 50 cycles. The MoS2/C composite nanofiber electrodes delivered a good electrochemical performance and Coulombic efficiency when used for Lithium-ion batteries. This study provides a novel and feasible pathway for designing and developing promising anodes and cathodes for high-performance lithium ion and sodium-ion batteries.

Empirical models corresponding to a constitutive equation with fractional derivatives are proposed for linear viscoelastic polymers. For these models, the relaxation modulus, the dynamic moduli, the relaxation time spectra, and other material functions can be calculated as a function of a few parameters that characterise the behaviour of a viscoelastic polymer. The fractional calculus approach allows us to calculate the relaxation time spectrum H(τ) via the Stieltjes inversion in the linear viscoelastic zone. Polymethylmethacrylate (PMMA) is chosen as a model amorphous polymer in a temperature range from Tg + 90°C to Tg + 25°C. This polymer is characterised by a non-equilibrium state between at least the β and α relaxations. The structural recovery of PMMA has been investigated using dynamic mechanical thermal analysis (DMTA) by varying the preparational history. The effect of time and temperature on the model parameters and on the relaxation time spectra are also investigated in the neighbourhood of the glass transition.

The development of alternative anode materials out of flexible nanofibers has seen a growing interest. In this paper, binary carbon nanofiber electrodes of SnO2/NiO and Tin nanoparticles are produced using a scalable technique, Forcespinning (FS) and subsequent thermal treatment (calcination). The Sn/C nanofibers were porous and flexible, while the SnO2-NiO nanofibers had “hairy-like” particles and pores on the fiber strands. The nanofiber preparation process involved FS the Sn/PAN and SnO2/NiO/PAN precursors into nanofibers and subsequently stabilizing in air at 280oC and calcination at 800oC under an inert atmosphere. The flexible composite nanofibers were directly used as working electrode in lithium-ion batteries without a current collector, conducting additives, or binder. The electrochemical performance of the SnO2/NiO/C and Sn/C electrodes showed a comparable cycle performance of about 675 mAhg-1 after 100 cycles. However, the SnO2/NiO/C electrode exhibited a better rate performance than Sn/C anode and was able to recover its capacity after charging with a higher current density. The synthesis and processing methods used to produce these nanofibers clearly was a factor for the high rate capability and excellent cyclic performance of these binary composite electrodes, largely on the account of the unique structure and properties of the composite nanofibers.

The osmotic and scattering properties of hyaluronan-based composite hydrogels composed of stiff biopolymer chains (carboxymethylated thiolated hyaluronan (CMHA-S)) crosslinked by a flexible polymer (polyethylene glycol diacrylate (PEGDA)) are investigated and analyzed in terms of the scaling theory. The total pre-gel polymer weight concentration is varied between 0.5 wt.% and 3.2 wt.%, while the mole ratio between the reactive PEG chain ends and the thiolated HA moieties is changed between 0.15 and 1.0. The shear modulus G of the fully swollen gels exhibits a stronger dependence on pre-gel concentration than on the crosslink density. Osmotic deswelling measurements reveal that the osmotic mixing pressure depends on the weight ratio CMHA-S/PEGDA, and is practically unaffected by the pre-gel concentration. Small-angle neutron scattering observations indicate that the thermodynamic properties of these composite gels are governed by total polymer concentration, i.e., specific interactions between the two polymeric components do not play a significant role.