129 research outputs found

    Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries

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    The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about 15/kgwhereasthecosttomanufacturecarbonsootasaby‚ąíproductfromlarge‚ąíscalemillingofabundantgraphiteisabout15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about 1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization. √ā¬© 2014 Badi et al.; licensee Springer

    Percolation phenomena for new magnetic composites and TIM nanocomposites materials

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    This paper presents a theoretical investigation in order to obtain new composite and nanocomposite magnetic industrial materials. The effective conductivity and thermal effective conductivity have been predicted by adding various types and percentages of conductive particles (Al2O3, MgO, ZnO, Graphite etc.) to the main matrices of Epoxy, Iron and Silicon for formulating new composite and nanocomposite industrial materials. The characterization of effective conductivity of new polymeric composites has been investigated with various applied forces, inclusion types and their concentrations. In addition, the effect of inclusion types and their concentrations on the effective thermal conductivities of thermal interface nanocomposite industrial materials has been explained and discussed

    0D-1D hybrid silicon nanocomposite as lithium-ion batteries anodes

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    Lithium ion batteries (LIBs) are the enabling technology for many of the societal changes that are expected to happen in the following years. Among all the challenges for which LIBs are the key, vehicle electrification is one of the most crucial. Current battery materials cannot provide the required power densities for such applications and therefore, it makes necessary to develop new materials. Silicon is one of the proposed as next generation battery materials, but still there are challenges to overcome. Poor capacity retention is one of those drawbacks, and because it is tightly related with its high capacity, it is a problem rather difficult to address with common and scalable fabrication processes. Here we show that combining 0D and 1D silicon nanostructures, high capacity and stability can be achieved even using standard electrode fabrication processes. Capacities as high as 1200 mAh/g for more than 500 cycles at high current densities (2 A/g) were achieved with the produced hybrid 0D/1D electrodes. In this research, it was shown that while 0D nanostructures provide good strain relaxation capabilities, 1D nanomaterials contribute with enhanced cohesion and conductive matrix integrityThis research was funded by the European Union‚Äôs Horizon 2020 research and innovation programme under the Marie SkŇāodowska-Curie grant agreement No 713567 and Science Foundation Irelands Research Centre award 12/RC/2278_P2. This work was supported by the Ministerio de Econom√≠a y Competitividad (MINECO) of Spain, under Grant ENE2014-57977-C2-1-R and ‚ÄúEstancias de Movilidad Salvador Madariaga‚ÄĚ. Financial support from the U.S. Department of Defense (grant W911NF-14-1-0046), and from the U.S. Department of Energy, through the Consortium for Integrating Energy Systems in Engineering and Science Education, CIESESE (DE-NA0003330) is also acknowledge

    Fabrication and characterization of porous Si and embedded porous Si for photonics application / Rihana Yusuf and Alhan Farhanah Abd Rahim

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    The development of nanoelectronics demands the implementation of new materials that should be Si-compatible but with enhanced electric and photonic properties for further device scaling. Si/Ge can be considered as a useful and promising material for this purpose. However in photonics, Si and Ge suffer from their poor optical properties and cannot compete with the direct bandgap semiconductors^, g GaAs). Si/SiGe nanostructures need to offer new solutions for improving the optical efficiency of the materials. Ge nanostructures have attracted world-wide attention due to their interesting quantum effects both in electronics and photonics application[l]. A variety of techniques have been employed to grow such structures, the most popular one is self-assembled growth nanometer islands in highly strained system using sophisticated Molecular Beam Epitaxy (MBE) or Low Pressure Chemical Vapor Deposition(LPCVD) techniques[2-5]. However these techniques require sophisticated machine and the cost is very high. In addition, the discovery of room temperature photoluminescence in porous silicon (PS)[6], presents a great interest in optoelectronic studies of this material. Covering or filling the pore network of a PS layer to produce a silicon nanocomposite is a promising process for new potential optoelectronics applications. Hence, there is a need to find a cost effective technique to grow a quality Ge nanostructures for photonics application. In this work, an effective and low cost method of thermal evaporation is used to fabricate the Ge nanostructure while low cost porous silicon will be utilized as the patterned substrate for the Ge nanostructure inclusion. Although there is still lack of commercially valuable Si-based active photonic devices, efficient light sources and detectors based on Si/SiGe would be a breakthrough that will open possibilities for the new systemon- a-chip to incorporate photonic devices with Si nanoelectronics. Si and Ge -based photodetectors are probably the most attractive candidate for this purpose due to possibility of integration into the logic IC chips.Hence, it is therefore of high interest to study the structural and optical characteristics of Ge nanostructure embedded inside porous silicon for effective light emission and detection

    The impact of nanostructured silicon and hybrid materials on the thermoelectric performance of thermoelectric devices: review

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    Nanostructured materials remarkably improve the overall properties of thermoelectric devices, mainly due to the increase in the surface-to-volume ratio. This behavior is attributed to an increased number of scattered phonons at the interfaces and boundaries of the nanostructures. Among many other materials, nanostructured Si was used to expand the power generation compared to bulk crystalline Si, which leads to a reduction in thermal conductivity. However, the use of nanostructured Si leads to a reduction in the electrical conductivity due to the formation of low dimensional features in the heavily doped Si regions. Accordingly, the fabrication of hybrid nanostructures based on nanostructured Si and other different nanostructured materials constitutes another strategy to combine a reduction in the thermal conductivity while keeping the good electrical conduction properties. This review deals with the properties of Si-based thermoelectric devices modified by different nanostructures and hybrid nanostructured material

    Luminescence properties and ROS generation of magnetic porous silicon nanoparticles

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    Magnetite‚ÄíPorous Silicon 100‚ąí150 nm size nanoparticles (MPSi) were obtained combining luminescent and magnetic properties from silicon and magnetite, respectively. MPSi hybrids were characterized by high-resolution transmission electron microscopy, atomic and magnetic force microscopy and X-ray photoelectron spectroscopy. The presence of magnetite quenches statically visible luminescence of Porous Silicon toluene suspensions. Whereas MPSi, maintain the luminescence in the 300‚ąí450 nm spectral region. Particles retained the capacity for singlet oxygen and superoxide radical ion generation (Reactive Oxygen Species, ROS). However quantum yield singlet oxygen generation is much lower than the PSi analogues and superoxide radical ion concentration dismiss when magnetite is incorporated in the PSi matrix. Silanization of Porous Silicon and MPSi yield nanoparticles with ‚ąí SH terminal groups with unique luminescence properties.Fil: Caregnato, Paula. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Centro Cient√≠fico Tecnol√≥gico Conicet - La Plata. Instituto de Investigaciones Fisicoqu√≠micas Te√≥ricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoqu√≠micas Te√≥ricas y Aplicadas; ArgentinaFil: David Gara, Pedro Maximiliano. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Centro Cient√≠fico Tecnol√≥gico Conicet - La Plata. Centro de Investigaciones √ďpticas. Provincia de Buenos Aires. Gobernaci√≥n. Comisi√≥n de Investigaciones Cient√≠ficas. Centro de Investigaciones √ďpticas. Universidad Nacional de La Plata. Centro de Investigaciones √ďpticas; ArgentinaFil: Prieto, Eduardo Daniel. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Centro Cient√≠fico Tecnol√≥gico Conicet - La Plata. Instituto de Investigaciones Fisicoqu√≠micas Te√≥ricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoqu√≠micas Te√≥ricas y Aplicadas; ArgentinaFil: Gonzalez, Monica Cristina. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Centro Cient√≠fico Tecnol√≥gico Conicet - La Plata. Instituto de Investigaciones Fisicoqu√≠micas Te√≥ricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoqu√≠micas Te√≥ricas y Aplicadas; Argentin
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