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See detailPreparation and characterization of Silicon-carbon composite powders using recycled Silicon from solar cells as anode material in Li-ion batteries
Eshraghi, Nicolas ULiege; Mahmoud, Abdelfattah ULiege; Berardo, Loris ULiege et al

Poster (2017, September)

Currently, silicon (Si) coming from the recycling of solar cells is a non-valued fraction. The principal aim of this work is the development of silicon recovered during the dismantling of solar panels as ... [more ▼]

Currently, silicon (Si) coming from the recycling of solar cells is a non-valued fraction. The principal aim of this work is the development of silicon recovered during the dismantling of solar panels as electrode material for Li-ion batteries. The main technological challenge associated with the use of silicon in this type of application is to control the volume expansion during charge/discharge cycles. This drawback could be avoided through the formation of Silicon/carbon composites in which the size of the silicon particles and their dispersion must be controlled. In this research, we develop a carbon matrix consisting of graphene or carbon nanotubes (CNT) that allow the incorporation of silicon particles coated with a carbon layer (Si@C/C). The process is divided in two main steps : I) the grinding of leached Si wafer pieces in order to extract pure Si powder and then a mixed aqueous suspension of this recycled Si and an organic carbon source (Acetic acid, Ascorbic acid or Lactose) is spray-dried followed by heat treatment to generate the coating of silicon particles with carbon (Si@C). Then, II) aqueous suspension of Si@C and graphene/CNT is spray dried and calcined to obtain the final composite structure (Si@C/C). The morphology of composite materials is analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical performance of Si@C/C composites are characterized by galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy (EIS). [less ▲]

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See detailRecycling of silicon used in solar cells to prepare silicon-carbon composite powders as anode material in li-ion batteries
Eshraghi, Nicolas ULiege; Mahmoud, Abdelfattah ULiege; Berardo, Loris ULiege et al

Poster (2017, September)

Currently, silicon (Si) coming from the recycling of solar cells is a non-valued fraction. The principal aim of this work is the development of silicon recovered during the dismantling of solar panels as ... [more ▼]

Currently, silicon (Si) coming from the recycling of solar cells is a non-valued fraction. The principal aim of this work is the development of silicon recovered during the dismantling of solar panels as an electrode material for lithium or sodium batteries. The main technological challenge associated with the use of silicon in this type of application is to control the volume expansion during charge/discharge cycles. This problem could be solved through the synthesis of Silicon/carbon composites in which the size of the silicon particles and their dispersion must be controlled [1–4]. We develop a carbon matrix consisting of graphene or carbon nanotubes (CNT) that allow the incorporation of silicon particles coated with a carbon layer (Si@C/C). The process is divided in two main steps. In the first step, Si wafer pieces are ground to prepare Si powder and then a mixed suspension of Si and an organic carbon source (Acetic acid, Ascorbic acid or Lactose) is spray-dried followed by heat treatment to generate the coverage of silicon particles with carbon (Si@C). In the second step, aqueous suspension of Si@C and graphene/CNT is spray dried and heat treated to obtain the final composite structure. The morphology of composite materials is analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical performance of Si@C/C composites are characterized by galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy (EIS). [less ▲]

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See detailSpray-drying as a tool to disperse conductive carbon inside Na2FePO4F particles by addition of carbon black or carbon nanotubes to the precursor solution
Mahmoud, Abdelfattah ULiege; Caes, Sebastien; Brisbois, Magali et al

in Journal of Solid State Electrochemistry (2017)

In this work, Na2FePO4F-carbon composite powders were prepared by spray-drying a solution of inorganic precursors with 10 and 20 wt% added carbon black (CB) or carbon nanotubes (CNTs). In order to compare ... [more ▼]

In this work, Na2FePO4F-carbon composite powders were prepared by spray-drying a solution of inorganic precursors with 10 and 20 wt% added carbon black (CB) or carbon nanotubes (CNTs). In order to compare the effect of CB and CNTwhen added to the precursor solutions, the structural, electrochemical, and morphological properties of the synthesized Na2FePO4F-xCB and Na2FePO4F-xCNT samples were systematically investigated. In both cases, X-ray diffraction shows that calcination at 600 °C in argon leads to the formation of Na2FePO4F as the major inorganic phase. 57Fe Mössbauer spectroscopy was used as complementary technique to probe the oxidation states, local environment, and identify the composition of the iron-containing phases. The electrochemical performance is markedly better in the case of Na2FePO4F-CNT (20 wt%), with specific capacities of about 100 mAh/g (Na2FePO4F-CNT) at C/4 rate vs. 50 mAh/g for Na2FePO4F-CB (20 wt%). SEM characterization of Na2FePO4F-CB particles revealed different particle morphologies for the Na2FePO4F-CNT and Na2FePO4F-CB powders. The carbon-poor surface observed for Na2FePO4FCB could be due to a slow diffusion of carbon in the droplets during drying. On the contrary, Na2FePO4F-CNT shows a better CNT dispersion inside and at the surface of the NFPF particles that improves the electrochemical performance. [less ▲]

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See detailSpray Drying-­Assisted Synthesis of Na2FePO4F/CB and Na2FePO4F/CNT Composite Cathodes for Lithium Ion Battery
Mahmoud, Abdelfattah ULiege; Brisbois; Caes, sebastien et al

Conference (2017, May 08)

Fluorophosphates are considered among the most interesting series of cathode materials for Li/Na-ion batteries. Na2FePO4F, with layered structure and two-dimensional pathways for facile Na+/Li+ transport ... [more ▼]

Fluorophosphates are considered among the most interesting series of cathode materials for Li/Na-ion batteries. Na2FePO4F, with layered structure and two-dimensional pathways for facile Na+/Li+ transport [1], exhibits minimal structural changes (3.7%) upon reduction/oxidation. The average working voltage is 3.3 V versus Li+/Li. However, one of the key drawbacks of Na2FePO4F electrodes is their low intrinsic electronic conductivity. In this work, we report on the synthesis of Na2FePO4F by spray-drying, a technique which is easily scaled-up from the lab- to the industrial-scale and ensures a good homogeneity of all precursors. We are investigating the replacement of the grinding step by the addition of conductive carbon (carbon black and carbon nanotubes) to the solution containing the inorganic precursors of the Na2FePO4F phase in order to prepare Na2FePO4F/CB and Na2FePO4F/CNT with different ratios of CB and CNT (10 and 20%) and enhanced conductivity. The electrochemical performance shows that the addition of CNT improves remarkably the capacity of the NFPF electrode material thanks to better CNT dispersion inside and at the surface of the NFPF particles which enhances the electronic conductivity. Acknowledgements: The authors thank the Walloon Region for support under the “PE Plan Marshall 2.vert” program (BATWAL -1318146). A. Mahmoud is grateful to the Walloon region for a Beware Fellowship Academia 2015-1, RESIBAT n° 1510399. References [1] M. Brisbois, S. Caes, M-T. Sougrati, B. Vertruyen, A. Schrijnemakers, R. Cloots, N. Eshraghi, R-P. Hermann, A. Mahmoud, F. Boschini, Solar Energy Materials & Solar Cells 148 (2015) 11-19. [less ▲]

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See detailNa2FePO4F/multi-walled carbon nanotubes for lithium-ion batteries: Operando Mössbauer study of spray-dried composites
Brisbois, Magali; Caes, Sébastien ULiege; Sougrati, M.T. et al

in Solar Energy Materials & Solar Cells (2016), 148

In order to favor electronic conductivity in sodium iron fluorophosphate electrodes for lithium- or sodium-ion batteries, composites of Na2FePO4F with multi-walled carbon nanotubes (CNTs) were prepared by ... [more ▼]

In order to favor electronic conductivity in sodium iron fluorophosphate electrodes for lithium- or sodium-ion batteries, composites of Na2FePO4F with multi-walled carbon nanotubes (CNTs) were prepared by pilot-scale spray drying. Addition of multi-walled CNTs in the solution results in an excellent dispersion of the CNTs within the volume of Na2FePO4F and not only at the surface of the particles. Following a heat treatment at 600°C in argon in order to reach crystallization, X-ray diffraction and ex situ Mössbauer spectroscopy revealed the presence of significant amounts of Fe(III) and maghemite (γ-Fe2O3) in the powder. However, Na2FePO4F/CNTs composites exhibit good electrochemical performance when cycling against lithium, with a discharge capacity of 104mAhg-1 at C/10 rate and 90mAhg-1 at 1C rate. Therefore, operando 57Fe transmission Mössbauer spectroscopy analyses were carried out in order to investigate the evolution of the iron oxidation state during cycling. During the first discharge, all the Fe(III) is reduced to Fe(II), explaining the good electrochemical performance. [less ▲]

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See detailInnovative materials improving energy efficiency of buildings
Dewalque, Jennifer ULiege; Denayer, Jessica ULiege; Schrijnemakers, Audrey ULiege et al

Conference (2014, July 01)

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See detailSpray-drying synthesis of Na2FePO4F/carbon powders for lithium-ion batteries
Brisbois, Magali ULiege; Krins, Natacha ULiege; Hermann, Raphael et al

in Materials Letters (2014), 130

Sodium iron fluorophosphate Na2FePO4F is a candidate positive electrode material for both lithium-ion batteries and sodium-ion batteries. We report the synthesis of Na2FePO4F/carbon powders by the simple ... [more ▼]

Sodium iron fluorophosphate Na2FePO4F is a candidate positive electrode material for both lithium-ion batteries and sodium-ion batteries. We report the synthesis of Na2FePO4F/carbon powders by the simple and easily up-scalable technique of spray-drying. An aqueous solution containing citric acid as a carbon source was sprayed in a pilot-scale spray-dryer. Heat treatment at 600°C in argon for 12 hours was found appropriate to obtain single-phase Na2FePO4F; only 1.8% of Fe (III) were detected by iron-57 Mössbauer spectroscopy. When cycled against lithium, the discharge capacity reached 110 mAh g-1 at C/15 rate. (C) 2014 Elsevier B.V. All rights reserved. [less ▲]

Detailed reference viewed: 175 (30 ULiège)
See detailHigh Performance DSSC Based on Semiconducting Oxides Prepared Through Soft Chemistry Processes
Dewalque, Jennifer ULiege; Schrijnemakers, Audrey ULiege; Thalluri, Venkata Visveswara Gopala Kris ULiege et al

Conference (2013, July)

DSSCs have been reported by O’Regan and Grätzel in the early nineties as a very promising alternative to conventional photovoltaic silicon devices. Main benefits of these cells are their low cost as well ... [more ▼]

DSSCs have been reported by O’Regan and Grätzel in the early nineties as a very promising alternative to conventional photovoltaic silicon devices. Main benefits of these cells are their low cost as well as their mild manufacturing process. In most of the specific literature, DSSCs are made of TiO2 films prepared by doctor-blade or screen-printing of anatase nanoparticles paste. However, due to the random organization of the nanoparticles, pore accessibility by the dye and electrolyte could be incomplete. Moreover, some anatase crystallites could suffer from a lack of connectivity, leading to electron transfer issues. The strategy adopted by our group to improve photovoltaic efficiencies involves a templating-assisted process allowing the preparation of highly porous layers with well-ordered and accessible pores as well as improved crystallites connectivity. The main goal is to increase the film surface area and to perfectly control the mesostructure in order to maximize the adsorption of active dye and the electrolyte infiltration inside the porous network. This talk especially focuses on the templating-assisted synthesis of TiO2 and ZnO semiconducting layers used as photoelectrode in DSSCs. Besides, due to the surface area improvement as well as the perfect control of the pore organization and the pore size, the templating strategy can be an effective solution to overcome light harvesting and solid electrolyte filling limitations encountered in solid-state DSSCs. Special effort is paid to the tuning of the TiO2 and ZnO semiconducting layers mesostructure in order to match with solid-state DSSC applications. [less ▲]

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See detailMullite plasma spraying for in situ repair of cracks in mullite refractories: Simultaneous optimization of porosity and thickness by statistical design of experiments
Schrijnemakers, Audrey ULiege; Francq, B. G.; Cloots, Rudi ULiege et al

in Journal of Thermal Spray Technology (2013), 22(7), 1133-1139

We report a laboratory-scale study about the suitability of the plasma spraying process for "in situ" repair of cracks in mullite refractories of industrial furnaces. The "design of experiments" approach ... [more ▼]

We report a laboratory-scale study about the suitability of the plasma spraying process for "in situ" repair of cracks in mullite refractories of industrial furnaces. The "design of experiments" approach is used to investigate how the coating porosity and thickness are influenced by six experimental parameters. Arc current, secondary gas (H 2) flow rate, and stand-off distance are the most significant parameters for both responses. Several interaction terms also affect significantly the thickness response. The validity of the model equations is discussed both from a statistical point of view and regarding the physical credibility of the main model terms. Additional experiments confirm that the measured properties lie into the prediction intervals provided by the model. Using a set of parameters optimized for minimal porosity and high thickness (relevant for the crack repair application), coatings with 6% porosity and 1070 μm thickness can be prepared reproducibly. © 2013 ASM International. [less ▲]

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See detailNanosphere Lithography and Hydrothermal Growth : How to Increase Surface Area and Control Reversible Wetting Properties of ZnO Nanowire Arrays ?
Colson, Pierre ULiege; Schrijnemakers, Audrey ULiege; Vertruyen, Bénédicte ULiege et al

in Journal of Materials Chemistry (2012), 22(33), 17086-17093

Due to their large surface-area-to-volume ratio as well as their interesting intrinsic optical and electronic properties, ZnO 1D nanostructures are part of the few dominant materials for nanotechnology ... [more ▼]

Due to their large surface-area-to-volume ratio as well as their interesting intrinsic optical and electronic properties, ZnO 1D nanostructures are part of the few dominant materials for nanotechnology. In this article, we compare two different routes of using the nanosphere lithography for the manufacturing of well-aligned, density-controlled ZnO nanowires by low-temperature hydrothermal growth. The first route uses the colloidal mask as a template for the patterned growth of the nanowires, while in the second route, the nanospheres act as a mask to pattern the seed layer. SEM and XRD characterizations are performed on samples manufactured by both routes and evidence patterned well-aligned nanowires with high c-axis texturing in the first synthetic route. Oriented growth is less pronounced in the second route, as well as the ability to adsorb dye. However, for the first route the dye loading measurements reveal that the amount of N-719 adsorbed is higher than on unpatterned ZnO nanowires films, highlighting an increased interface area. Reversible hydrophobicity to superhydrophilicity transition was observed and intelligently controlled by alternation of UV illumination and dark storage. This promising synthetic route opens exciting perspectives for the production of ZnO nanowire arrays with tunable density, wetting properties and enhanced adsorption properties. [less ▲]

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See detailMullite coatings on ceramic substrates: Stabilisation of Al2O3-SiO2 suspensions for spray drying of composite granules suitable for reactive plasma spraying
Schrijnemakers, Audrey ULiege; Andre, Sophie; Lumay, Geoffroy ULiege et al

in Journal of the European Ceramic Society (2009), 29(11), 2169-2175

The present work deals with the preparation of stable alumina + silica suspensions with high solid loading for the production of spray-dried composite powders. These composite powders are to be used for ... [more ▼]

The present work deals with the preparation of stable alumina + silica suspensions with high solid loading for the production of spray-dried composite powders. These composite powders are to be used for reactive plasma spraying whereby the formation of mullite and the coating on a ceramic substrate are achieved in a single step process. Electrostatic stabilisation of alumina and silica suspensions has been studied as a function of pH. Silica suspensions are most stable at basic pH whereas alumina suspensions are stable at acidic pH. The addition of ammonium polymethacrylate (APMA) makes it possible to stabilise alumina and prepare a stable 50 wt% alumina + silica suspension at pH 10. The optimum amounts of dispersant and binder have been determined by zeta potential, viscosity and sedimentation measurements. Spray drying of the suspension yields composite powders whose morphology, size distribution and flowability have been characterized before realizing reactive plasma spraying tests. (C) 2009 Elsevier Ltd. All fights reserved. [less ▲]

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