The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
John M. Torkelson - One of the best experts on this subject based on the ideXlab platform.
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polypropylene graphite nanocomposites made by solid state shear Pulverization effects of significantly exfoliated unmodified graphite content on physical mechanical and electrical properties
Polymer, 2010Co-Authors: Katsuyuki Wakabayashi, Philip J Brunner, Junichi Masuda, Sheldon Hewlett, John M. TorkelsonAbstract:Abstract Nanocomposites made from polypropylene and as-received graphite were prepared by solid-state shear Pulverization (SSSP) as a function of graphite loading (0.3–8.4 wt%). X-ray diffraction indicates that SSSP employing harsh Pulverization conditions yields substantial graphite exfoliation at 0.3–2.7 wt% graphite content with less exfoliation being achieved at higher graphite content. With increasing graphite content, thermal degradation temperature and non-isothermal onset crystallization temperature increase substantially (by as much as 35 and 23 °C relative to neat polypropylene) while isothermal crystallization half-time decreases dramatically. In contrast, Young’s modulus and tensile yield strength exhibit maxima (∼100% and ∼60% increases, respectively, relative to neat polypropylene) at 2.7 wt% graphite content, with all nanocomposites retaining high elongation at break values except at the highest filler loading. Electrical conductivity measurements indicate percolation of graphite at 2.7 wt% and higher graphite content, consistent with rheology measurements showing the presence of a solid-like response of melt-state shear storage modulus as a function of frequency. Significant tunability of graphite exfoliation and property enhancements is demonstrated as a function of SSSP processing.
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preparation and characterization of multiwalled carbon nanotube dispersions in polypropylene melt mixing versus solid state shear Pulverization
Journal of Polymer Science Part B, 2009Co-Authors: Saswati Pujari, John M. Torkelson, Junichi Masuda, T Ramanathan, Kosmas Kasimatis, Rodney Andrews, Catherine L Brinson, Wesley Roth BurghardtAbstract:Dispersions of multiwalled carbon nanotubes (MWNT) in polypropylene (PP) were prepared via conventional melt batch mixing and solid-state shear Pulverization. The properties and structure of each system were assessed via linear viscoelasticity, electrical conductivity, PP crystallization kinetics, dynamic mechanical analysis, scanning electron microscopy, and small angle X-ray scattering. Increasing either the duration or the intensity of melt mixing leads to higher degrees of dispersion of MWNT in PP, although at the cost of substantial melt degradation of PP for long mixing times. Samples prepared by Pulverization exhibit faster crystallization kinetics and higher mechanical stiffness than the melt blended samples, but in contrast show no measurable low frequency elastic plateau in melt rheology, and lower electrical conductivity than melt-mixed samples. X-ray scattering demonstrates that neither sample has uniform dispersion down to the single MWNT level. The results illustrate that subtle differences in the size and distribution of nanotube clusters lead to differences in the nanotube networks with strong impact on bulk properties. The results also highlight distinctions between conductive networks and load transfer networks and demonstrate that a complete and comparative picture of dispersion cannot be determined by simple indirect property measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1426–1436, 2009
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compatibilizing effects of block copolymer mixed with immiscible polymer blends by solid state shear Pulverization stabilizing the dispersed phase to static coarsening
Polymer, 2005Co-Authors: Andrew H Lebovitz, John M. TorkelsonAbstract:Abstract A continuous, industrially scalable process called solid-state shear Pulverization (SSSP) leads to compatibilization of polystyrene (PS)/high-density polyethylene (HDPE) blends by addition of a commercially available styrene/ethylene–butylene/styrene (SEBS) triblock copolymer. Partial or full compatibilization is characterized by a reduction or elimination of coarsening of the dispersed-phase domains during high-temperature (190 °C), static annealing. In the case of a 90/10 wt% PS/HDPE blend, processing with 3.5 wt% SEBS block copolymer by SSSP yields a coarsening rate that is reduced by a factor of 10 (six) relative to a melt-mixed blend without copolymer (with 3.5 wt% SEBS block copolymer). Addition of 5.0 wt% SEBS block copolymer to the 90/10 wt% PS/HDPE blend during SSSP yields a reduction in coarsening rate by a factor of thirty relative to a melt-mixed blend without copolymer. With an 80/20 wt% PS/HDPE blend, Pulverization with 10 wt% SEBS block copolymer yields cessation of coarsening when the average dispersed-phase domain diameter reaches 1.6–1.7 μm. The implications of these results for developing a new, technologically attractive method for achieving compatibilization of immiscible polymer blends are discussed.
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Trace levels of mechanochemical effects in pulverized polyolefins
Journal of Applied Polymer Science, 2001Co-Authors: Manisha Ganglani, John M. Torkelson, Stephen Howard Carr, Klementina KhaitAbstract:This research investigated the structural changes that occur on different polyethylene polymer systems as a result of a novel Pulverization process called solid-state shear Pulverization (S3P). High-density polyethylene, low-density polyethylene, and two forms of linear low-density polyethylene were run through a pulverizer under high shear conditions as well as low shear conditions. The physical properties were examined before and after the Pulverization via melt index, melt rheology, GPC, and DSC, techniques. The low shear Pulverization did not noticeably alter the physical properties of the polymers. In contrast, high shear Pulverization did result in an increase in viscosity as observed by melt index and oscillatory shear experiments, although solid-state and bulk properties as observed by DSC and GPC were not affected. These results indicate that a small amount of mechanochemically induced changes occur as a result of the Pulverization process, including incorporation of a small amount of long-chain branches randomly placed on a few of the polymer chains. No evidence of short-chain branching resulting from S3P processing was found in these systems. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 671–679, 2001
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solid state shear Pulverization of plastics a green recycling process
Polymer-plastics Technology and Engineering, 1999Co-Authors: Klementina Khait, John M. TorkelsonAbstract:Abstract A novel process called solid-state shear Pulverization (S3P) has been developed at Northwestern University to recycle single or commingled postconsumer or preconsumer polymeric waste without sorting by type or color. This continuous, one-step process converts shredded plastic or rubber waste into controlled-particle-size powder ranging from coarse (10 and 20 mesh) to fine (80 mesh) or ultrafine (200 mesh). As a result, the Pulverization product is usable in applications ranging from direct injection molding without prior pelletization, to rotational molding, to use in protective and decorative powder coatings, as well as to blending with virgin resins and compounding with additives. Scanning electron microscopy reveals that the fine particles have a unique elongated shape that is attributed to the high shear conditions occurring during the Pulverization process. Injection-molded parts made from the powder product of the S3P process have mechanical and physical properties comparable to or better t...
Hui Shen - One of the best experts on this subject based on the ideXlab platform.
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Reconstructing ZnO quantum dot assembled tubular structures from nanotubes within graphene matrix via ongoing Pulverization towards high-performance lithium storage
Journal of Materials Chemistry A, 2016Co-Authors: Zihua Li, Ruimei Xu, Wenxia Zhao, Yong Liu, Donghai Wang, Xiao Yu, Hao Zhang, Hui ShenAbstract:The electrode Pulverization can be a blessing in disguise for improving Li-ion storage by rationally designing graphene-wrapped ZnO nanotubes. Transition metal oxides are very promising anode materials for high-performance lithium-ion batteries (LIBs). However, they experience large volume expansion upon cycling, resulting in electrode Pulverization and poor cycling stability. Here, we demonstrate a rational design and synthesis of graphene-wrapped ZnO nanotubes, and graphene oxide nanosheets in the reaction form a “soft” sealing layer to confine the crystal growth within a small space, which enables the nanotubes to be tightly bound with the graphene matrix. It is interesting to find that electrode Pulverization upon cycling is not so much a drawback but a blessing in disguise, which reconstructs the starting nanotubes into quantum dots with an average size of ∼2.3 nm within the graphene matrix in the form of a tubular structure. The formed quantum dots not only provide a high contact area with the electrolyte but also shorten the solid-phase ion diffusion. Meanwhile, the graphene nanosheets are still tightly bound with the quantum dot assembled tubular structure, which can accommodate volume change and facilitate efficient electron transport and lithium-ion diffusion in electrodes. When used as an anode in LIBs, they demonstrate excellent cycling stability with a high reversible specific capacity of 891 mA h g −1 over 1000 cycles at 2000 mA g −1 .
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Controlled synthesis of series NixCo3-xO4 products: Morphological evolution towards quasi-single-crystal structure for high-performance and stable lithium-ion batteries
Scientific Reports, 2015Co-Authors: Yu Zhou, Wenxia Zhao, Yong Liu, Baojun Li, Xiang Zhou, Hai Wang, Hui ShenAbstract:Transition metal oxides are very promising alternative anode materials for high-performance lithium-ion batteries (LIBs). However, their conversion reactions and concomitant volume expansion cause the Pulverization, leading to poor cycling stability, which limit their applications. Here, we present the quasi-single-crystal NixCo3-xO4 hexagonal microtube (QNHM) composed of continuously twinned single crystal submicron-cubes as anode materials for LIBs with high energy density and long cycle life. At the current density of 0.8 A g(-1), it can deliver a high discharge capacities of 1470 mAh g(-1) over 100 cycles (105% of the 2nd cycle) and 590 mAh g(-1) even after 1000 cycles. To better understand what underlying factors lead our QNHMs to achieve excellent electrochemical performance, a series of NixCo3-xO4 products with systematic shape evolution from spherical to polyhedral, and cubic particles as well as circular microtubes consisted of spheres and square microtubes composed of polyhedra have been synthesized. The excellent electrochemical performance of QNHMs is attributed to the unique stable quasi-single-crystal structure, which can both provide efficient electrical transport pathway and suppress the electrode Pulverization. It is important to note that such quasi-single-crystal structure would be helpful to explore other high-energy lithium storage materials based on alloying or conversion reactions.
Yi Cui - One of the best experts on this subject based on the ideXlab platform.
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Inorganic Glue Enabling High Performance of Silicon Particles as Lithium Ion Battery Anode
Journal of The Electrochemical Society, 2011Co-Authors: Li Feng Cui, Jang Wook Choi, Liangbing Hu, Hui Wu, Yi CuiAbstract:Silicon, as an alloy-type anode material, has recently attracted lots of attention because of its highest known Li+ storage capacity (4200 mAh/g). But lithium insertion into and extraction from silicon are accompanied by a huge volume change, up to 300%, which induces a strong strain on silicon and causes Pulverization and rapid capacity fading due to the loss of the electrical contact between part of silicon and current collector. Silicon nanostructures such as nanowires and nanotubes can overcome the Pulverization problem, however these nano-engineered silicon anodes usually involve very expensive processes and have difficulty being applied in commercial lithium ion batteries. In this study, we report a novel method using amorphous silicon as inorganic glue replacing conventional polymer binder. This inorganic glue method can solve the loss of contact issue in conventional silicon particle anode and enables successful cycling of various sizes of silicon particles, both nano-particles and micron particles. With a limited capacity of 800 mAh/g, relatively large silicon micron-particles can be stably cycled over 200 cycles. The very cheap production of these silicon particle anodes makes our method promising and competitive in lithium ion battery industry.
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Interconnected silicon hollow nanospheres for lithium-ion battery anodes with long cycle life
Nano Letters, 2011Co-Authors: Yan Yao, William D. Nix, Ill Ryu, Matthew T. Mcdowell, Nian Liu, Liangbing Hu, Hui Wu, Yi CuiAbstract:Silicon is a promising candidate for the anode material in lithium-ion batteries due to its high theoretical specific capacity. However, volume changes during cycling cause Pulverization and capacity fade, and improving cycle life is a major research challenge. Here, we report a novel interconnected Si hollow nanosphere electrode that is capable of accommodating large volume changes without Pulverization during cycling. We achieved the high initial discharge capacity of 2725 mAh g–1 with less than 8% capacity degradation every hundred cycles for 700 total cycles. Si hollow sphere electrodes also show a Coulombic efficiency of 99.5% in later cycles. Superior rate capability is demonstrated and attributed to fast lithium diffusion in the interconnected Si hollow structure.
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High-Performance Lithium Battery Anodes using Silicon Nanowires.
Nature nanotechnology, 2008Co-Authors: Candace K. Chan, Kevin McIlwrath, Kevin Mc Ilwrath, Gao Liu, Robert A Huggins, Xiao-feng Zhang, Hailin Peng, Xiaohong Zhang, Yi CuiAbstract:There is great interest in developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices. Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh g(-1); ref. 2). Although this is more than ten times higher than existing graphite anodes and much larger than various nitride and oxide materials, silicon anodes have limited applications because silicon's volume changes by 400% upon insertion and extraction of lithium which results in Pulverization and capacity fading. Here, we show that silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without Pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. We achieved the theoretical charge capacity for silicon anodes and maintained a discharge capacity close to 75% of this maximum, with little fading during cycling.
Z Sofiani - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the nonlinear optical properties and luminescence for thin films based on Sn doped In2O3 prepared by the reactive chemical Pulverization
2012 14th International Conference on Transparent Optical Networks (ICTON), 2012Co-Authors: Z Sofiani, Malika Addou, El M. Jouad, K Bahedi, S Bayoud, M. Makha, N. Fellahi, B. Sahraoui, J. EbotheAbstract:Summary form only given. Nonlinear optical properties and photoluminescence behavior of Tin-doped indium oxide (In2O3:Sn) thin films layers were investigate in detail. On heated glass substrates, we deposited these layers at different temperatures 400°C, 450°C and 500°C and different doping agent percentage, by the so called Spray Pyrolysis Technique, the reactive chemical Pulverization.
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effects of deposition temperature on the surface roughness and the nonlinear optical susceptibility of sprayed deposited zno zr thin films
Applied Surface Science, 2009Co-Authors: K Bahedi, Malika Addou, El M. Jouad, S Bayoud, Z SofianiAbstract:Abstract Zirconium doped zinc oxide thin films were deposited by reactive chemical Pulverization spray pyrolysis technique on heated glass substrates at 400 °C, 450 °C and 500 °C using zinc and zirconium chlorides as precursors. The effect of zirconium dopant and surface roughness on the nonlinear optical properties was investigated using atomic force microscopy (AFM) and third harmonic generation (THG). The best value of susceptibility χ(3) was obtained from the doped films with less roughness. A strong third order nonlinear optical susceptibility χ(3) = 20.49 × 10−12 (esu) of the studied films was found for the 5% doped sample at 450 °C.
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Third order non linear optical properties of ZnO:Al thin films prepared by spray pyrolysis
2009 11th International Conference on Transparent Optical Networks, 2009Co-Authors: K Bahedi, Malika Addou, El M. Jouad, S Bayoud, Z Sofiani, B. Sahraoui, M. Bouaouda, Z. EssaidiAbstract:In this study, zinc oxide (ZnO) and aluminium doped zinc oxide (ZnO:Al) thin films were deposited by reactive chemical Pulverization spray pyrolysis technique on heated glass substrates at 450degC. X-ray diffraction (XRD), scanning electron microscopy (SEM) and third harmonic generation (THG) are used to characterize their structure , morphology and nonlinear optical properties as a function of Al concentration (0, 3, 5, 7 at %). The intensity of third order non linear optical susceptibility increase by incorporation of aluminium. A strong value of susceptibility chi(3) was found for films with a good crystallinity.
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Study of Nonlinear-Optical Properties and Roughness Surface of ZnO:Zr Thin Films
2008 2nd ICTON Mediterranean Winter, 2008Co-Authors: K Bahedi, Malika Addou, El M. Jouad, S Bayoud, Z Sofiani, B. Sahraoui, Z. EssaidiAbstract:Zinc oxide (ZnO) and zirconium doped zinc oxide (ZnO:Zr) thin films were deposited by reactive chemical Pulverization spray pyrolysis technique on heated glass substrates at 450degC using zinc and zirconium chlorides as precursors. Effect of zirconium dopant and surface roughness on the nonlinear optical properties was investigated using atomic force microscopy (AFM) and third harmonic generation (THG).The best value of susceptibility chi(3) was obtained from the doped films with less roughness. A strong third order nonlinear optical susceptibility chi(3) = 20,49 times10-12 (esu) of the studied films was found for the 5% doped sample at 450degC.
K Bahedi - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the nonlinear optical properties and luminescence for thin films based on Sn doped In2O3 prepared by the reactive chemical Pulverization
2012 14th International Conference on Transparent Optical Networks (ICTON), 2012Co-Authors: Z Sofiani, Malika Addou, El M. Jouad, K Bahedi, S Bayoud, M. Makha, N. Fellahi, B. Sahraoui, J. EbotheAbstract:Summary form only given. Nonlinear optical properties and photoluminescence behavior of Tin-doped indium oxide (In2O3:Sn) thin films layers were investigate in detail. On heated glass substrates, we deposited these layers at different temperatures 400°C, 450°C and 500°C and different doping agent percentage, by the so called Spray Pyrolysis Technique, the reactive chemical Pulverization.
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effects of deposition temperature on the surface roughness and the nonlinear optical susceptibility of sprayed deposited zno zr thin films
Applied Surface Science, 2009Co-Authors: K Bahedi, Malika Addou, El M. Jouad, S Bayoud, Z SofianiAbstract:Abstract Zirconium doped zinc oxide thin films were deposited by reactive chemical Pulverization spray pyrolysis technique on heated glass substrates at 400 °C, 450 °C and 500 °C using zinc and zirconium chlorides as precursors. The effect of zirconium dopant and surface roughness on the nonlinear optical properties was investigated using atomic force microscopy (AFM) and third harmonic generation (THG). The best value of susceptibility χ(3) was obtained from the doped films with less roughness. A strong third order nonlinear optical susceptibility χ(3) = 20.49 × 10−12 (esu) of the studied films was found for the 5% doped sample at 450 °C.
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Third order non linear optical properties of ZnO:Al thin films prepared by spray pyrolysis
2009 11th International Conference on Transparent Optical Networks, 2009Co-Authors: K Bahedi, Malika Addou, El M. Jouad, S Bayoud, Z Sofiani, B. Sahraoui, M. Bouaouda, Z. EssaidiAbstract:In this study, zinc oxide (ZnO) and aluminium doped zinc oxide (ZnO:Al) thin films were deposited by reactive chemical Pulverization spray pyrolysis technique on heated glass substrates at 450degC. X-ray diffraction (XRD), scanning electron microscopy (SEM) and third harmonic generation (THG) are used to characterize their structure , morphology and nonlinear optical properties as a function of Al concentration (0, 3, 5, 7 at %). The intensity of third order non linear optical susceptibility increase by incorporation of aluminium. A strong value of susceptibility chi(3) was found for films with a good crystallinity.
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Study of Nonlinear-Optical Properties and Roughness Surface of ZnO:Zr Thin Films
2008 2nd ICTON Mediterranean Winter, 2008Co-Authors: K Bahedi, Malika Addou, El M. Jouad, S Bayoud, Z Sofiani, B. Sahraoui, Z. EssaidiAbstract:Zinc oxide (ZnO) and zirconium doped zinc oxide (ZnO:Zr) thin films were deposited by reactive chemical Pulverization spray pyrolysis technique on heated glass substrates at 450degC using zinc and zirconium chlorides as precursors. Effect of zirconium dopant and surface roughness on the nonlinear optical properties was investigated using atomic force microscopy (AFM) and third harmonic generation (THG).The best value of susceptibility chi(3) was obtained from the doped films with less roughness. A strong third order nonlinear optical susceptibility chi(3) = 20,49 times10-12 (esu) of the studied films was found for the 5% doped sample at 450degC.
