Showing results 1 to 20 of 28
   Lithium transition metal (Ti, Nb, V) oxide mesoporous thin films: contrasting results when attempting direct synthesis by evaporation-induced self assemblyCaes, Sébastien  ; Malherbe, Cédric ; Krins, Natacha et alin Microporous & Mesoporous Materials (2013), 172 This work investigates the possibility to prepare mesoporous thin films of Li-Ti, Li-Nb, Li-Nb-V and Li-V oxides through a direct sol-gel EISA route by dissolving a lithium salt in the precursor solution ... [more ▼] This work investigates the possibility to prepare mesoporous thin films of Li-Ti, Li-Nb, Li-Nb-V and Li-V oxides through a direct sol-gel EISA route by dissolving a lithium salt in the precursor solution. Experimental conditions involve a hydrolysis molar ratio H2O/TM ~10 (TM = Ti,Nb,V) and the common Pluronic structuring agent P123 (EO20-PO70-EO20). Systematic formation of lithium-containing oxides as first-crystallizing phases points to a significant intermixture of lithium and transition metal ions in the inorganic network. In the case of Ti-based and Nb-based oxide films, addition of lithium to the precursor solution is compatible with the formation of amorphous mesoporous films at 350°C. On the contrary, addition of lithium has a detrimental effect on the notoriously difficult formation of vanadium-based mesostructured films: even when replacing half of the vanadium by niobium as a stabilizer, formation of mesostructured films has not been possible in the investigated range of experimental conditions. [less ▲] Detailed reference viewed: 32 (19 ULg)Use colloidal nanocrystals for Li ion battery on the way to 3D architectured electrodesKrins, Natacha ; ; et alConference (2012) Detailed reference viewed: 1 (0 ULg)Assessing the role of pore structure and porosity in composite electrodes through model thin film electrode studiesKrins, Natacha ; ; et alPoster (2012) Detailed reference viewed: 1 (0 ULg)Assessing the role of porosity in composite electrodes through model thin film electrode studiesKrins, Natacha ; ; et alPoster (2012) Detailed reference viewed: 3 (0 ULg)Assessing the role of porosity in composite electrodes through model thin film electrode studiesKrins, Natacha ; ; et alPoster (2012) Detailed reference viewed: 1 (0 ULg)Precisely controlled mesoporous films to assess the role of architecture in Li‐ion batteriesKrins, Natacha ; ; et alPoster (2012) Detailed reference viewed: 4 (0 ULg)TiO2 Mesoporous Thin Film :model phase to assess the role of porosity in composite electrode for Li batteryKrins, Natacha ; Cloots, Rudi ; et alConference (2012) Detailed reference viewed: 8 (3 ULg)Assembly of Ligand-Stripped Nanocrystals into Precisely Controlled Mesoporous Architectures; ; Krins, Natacha et alin Nano Letters (2012), 12 Detailed reference viewed: 8 (0 ULg)Microstructural evolution of a TiO2 mesoporous single layer film under calcination: Effect of stabilization and repeated thermal treatments on the film crystallization and surface areaDewalque, Jennifer ; Cloots, Rudi ; et alin Thin Solid Films (2012), 520 This study quantifies the highest perturbation encountered by the first layer of a TiO2 12 layers-mesoporous coating, which is submitted to a multistep calcination process. Besides, we propose an ... [more ▼] This study quantifies the highest perturbation encountered by the first layer of a TiO2 12 layers-mesoporous coating, which is submitted to a multistep calcination process. Besides, we propose an alternative thermal treatment in order to limit the degradation induced by repeated calcinations. This paper reports and compares the modifications in film thickness, surface area, anatase crystallite size and global crystallinity of films obtained from different thermal treatments. It defines the maximum crystal size compatible with the preservation of the mesoarchitecture initially induced by templating. Differences in microporosity and rate of crystallization are also discussed. [less ▲] Detailed reference viewed: 47 (15 ULg)Thick and crack-free nanocrystalline mesoporous TiO2 films obtained by capillary coating from aqueous solutionsKrins, Natacha ; ; et alPoster (2011) Detailed reference viewed: 2 (0 ULg)Thick and crack-free nanocrystalline mesoporous TiO2 films obtained by capillary coating from aqueous solutionsKrins, Natacha ; ; et alPoster (2011) Detailed reference viewed: 2 (0 ULg)Mesoporous SiO2 thin films containing ZnO photoluminescent nanoparticles. Simultaneous SAXS / WAXS / Ellipsometry investigationsKrins, Natacha ; ; et alin Journal of Materials Chemistry (2011), 21 Detailed reference viewed: 1 (0 ULg)Direct nano-in-micropatterning of TiO2 thin layers and TiO2/Pt nanoelectrode arrays by deep X-ray lithography; ; et al in Journal of Materials Chemistry (2011), 21 Detailed reference viewed: 2 (0 ULg)Understanding Crystallization of Anatase into Binary SiO2/TiO2 Sol-Gel Optical Thin Films: An in Situ Thermal Ellipsometry Analysis; Krins, Natacha ; et alin Journal of Physical Chemistry C: Nanomaterials, Interfaces, and Hard Matter (2011), 115 Detailed reference viewed: 1 (1 ULg)TiO2 multilayer thick films (up to 4 μm) with ordered mesoporosity: Influence of template on the film mesostructure and use as high efficiency photoelectrode in DSSCsDewalque, Jennifer ; Cloots, Rudi ; Mathis, François et alin Journal of Materials Chemistry (2011), 21(20), 7356-7363 Mesoporous templated anatase thin films are very promising materials to act as photoelectrode in dye-sensitized solar cell. Templated-assisted dip-coating techniques are used to obtain thin films with ... [more ▼] Mesoporous templated anatase thin films are very promising materials to act as photoelectrode in dye-sensitized solar cell. Templated-assisted dip-coating techniques are used to obtain thin films with ordered porosity. However, monolayer films are very thin and suffer from a low quantity of active material, leading to poor photovoltaic performances. In this paper, a dip-coating-based multilayer deposition technique is reported. First, we have studied the influence of the template on the film organization and porosity in terms of long-range order, percentage of porosity, pore size and pores connectivity. Different techniques such as transmission electron microscopy (TEM), atmospheric poroellipsometry (AEP) and UV-visible absorption spectroscopy (UV-vis.) have been used to describe the microstructural features of the films with a thickness of 1 µm. The film exhibiting the highest dye loading was selected and its thickness gradually increased up to 4 µm. Finally, the photovoltaic performances of the thick films (1 to 4 µm) have been evaluated in combination with the N-719 dye and show excellent efficiency (6.1%) when compared to values reported in the literature. Such mesostructured films are compared in terms of photovoltaic performance with TiO2 nanoparticles films, generally used in DSSC. [less ▲] Detailed reference viewed: 69 (29 ULg)NbVO5 Mesoporous Thin Films by Evaporation Induced Micelles Packing: Pore Size Dependence of the Mechanical Stability upon Thermal Treatment and Li Insertion/ExtractionKrins, Natacha ; ; et alin Chemistry Of Materials (2011), 23(18), 4124-4131 Mesoporous thin films (MTFs) appear as an interesting architecture for positive electrodes in Li-ion energy storage systems because they offer high specific area and interconnected porosity presenting ... [more ▼] Mesoporous thin films (MTFs) appear as an interesting architecture for positive electrodes in Li-ion energy storage systems because they offer high specific area and interconnected porosity presenting homogeneous pore size and wall thickness. However, it must be ascertained that the mesostructure survives template removal or/and crystallization and is retained on electrochemical cycling. In order to investigate the potentialities and limits of the soft-templating approach in the case of complex transition metal oxide networks, we deliberately selected a "difficult" compound: NbVO5 was chosen because it combines a challenging synthesis with reported severe structural distortions during the first lithium insertion in the bulk material. In this work, NbVO5 MTFs with different pore sizes were synthesized using the evaporation induced micelles packing (EIMP) method. PS-b-PEO diblock copolymers of different molar weights were used as structure directing agent in order to obtain wormlike porous networks with pore size and wall thickness ranging from 15 to 100 nm. Thermal ellipsometry analysis, used to track surfactant removal and crystallization of the layer, reveals that partial crystallization is possible while retaining the mesoporous architecture. Electron tomography complements result from environmental ellipsometric porosimetry, atomic force microscopy, and transmission electron microscopy to provide a comprehensive description of the structure. A multilayer process is also proposed to build crack-free thick mesoporous films. The mechanical stability of MTFs presenting three different pore sizes is tested by inserting Li(+) in amorphous NbVO5 MTFs using cyclic voltammetry. Capacity retention data show that the mechanical stresses associated with Li+ insertion are better accommodated by MTFs compared to nonporous films, and this ability is enhanced as the pore size decreases. [less ▲] Detailed reference viewed: 38 (9 ULg) TiO2 thin films (1 µm) with ordered porosity used as high performance photoelectrode in DSSCDewalque, Jennifer ; Cloots, Rudi ; et alPoster (2010, July 06) Mesoporous anatase thin films are very promising materials to act as electrode in dye-sensitized solar cells. Randomly oriented nanocrystalline TiO2 particles are usually used to prepare photoelectrodes ... [more ▼] Mesoporous anatase thin films are very promising materials to act as electrode in dye-sensitized solar cells. Randomly oriented nanocrystalline TiO2 particles are usually used to prepare photoelectrodes with a thickness of 10-15 µm. Templated-assisted dip-coating techniques are used to obtain thin films with ordered porosity. The use of different templates influences the film porosity in terms of long-range order, percentage of porosity, pore size and pores connectivity. The photovoltaic performances of the samples have been evaluated. Such mesostructured films are compared in terms of photovoltaic performance with TiO2 nanoparticles films, generally used in DSSC. [less ▲] Detailed reference viewed: 14 (4 ULg)Repeated thermal treatments applied to ordered TiO2 mesoporous thin film: Effect on the film crystallization and surface areaHenrist, Catherine ; ; Krins, Natacha et alConference (2010, July 06) Ordered, mesoporous films are prepared by template-assisted sol-gel techniques such as dip-coating from a precursors solution. However, monolayer films are only a few hundred nanometers thick and present ... [more ▼] Ordered, mesoporous films are prepared by template-assisted sol-gel techniques such as dip-coating from a precursors solution. However, monolayer films are only a few hundred nanometers thick and present a limited surface area of active material resulting in poor photovoltaic performances. Therefore it is needed to increase the film thickness. A multilayer deposition process for anatase mesoporous film has been reported in the literature in 2005 by Zukalova and all. Unfortunately, later researches have shown a surface area limitation despite the increase of film thickness due to the repeated thermal treatments applied to the layers. In this study, we have investigated the microstructural evolution of a single mesoporous TiO2 layer submitted to repeated thermal treatments. The modifications are discussed in terms of film thickness, surface area, anatase crystals size and global crystallinity. Besides, we propose an alternative thermal treatment designed in an attempt to overcome the limitations induced by repeated calcinations. We have followed and compared the properties of mesoporous films submitted to both thermal treatments by X-ray diffraction (XRD), transmission electron microscopy (TEM) and environmental poroellipsometry (EEP). Those results show the importance of the tuning of thermal treatment when multilayers films are envisaged for DSSC applications. Indeed, this study quantifies the maximum perturbation encountered by the first layer during the preparation of a multilayer (up to 12) coating, which is submitted to a multistep calcination. Finally, the photovoltaic performances of assembled cells have been evaluated. [less ▲] Detailed reference viewed: 15 (4 ULg)Vanadium oxide-based mesoporous films as positive electrode material in Li-ion batteriesKrins, Natacha ; Caes, Sébastien ; et alConference (2010) Detailed reference viewed: 6 (2 ULg)Thick and crack-free nanocrystalline mesoporous TiO2 films obtained by capillary coating from aqueous solutionsKrins, Natacha ; ; et alin Chemistry of Materials (2010), 22 Detailed reference viewed: 2 (0 ULg)
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