17 research outputs found
Phase formation, hydration behavior, and pressure response of sulfide and thiophosphate solid electrolytes
Rechargeable lithium ion batteries (LIB) have become an essential part of our daily lives in recent decades, powering mobile phones, laptops, cordless power tools, and even automobiles. While LIB technology currently dominates the battery market for these mobile applications, its physicochemical power and energy density limit will be reached soon. The use of a solid electrolyte instead of a liquid electrolyte in LIBs promises higher energy density, safer operation, and faster charging. Although the benefits of an all-solid-state battery (ASSB) are enormous, certain prerequisites for solid electrolyte application must be met in order for ASSBs to be technologically and commercially competitive. Ionic conductivity is arguably the most important performance indicator of a solid electrolyte. This thesis introduces the concept of LIBs and ASSBs, as well as fundamentals of battery performance and ion conduction in solids, an overview of material classes with a focus on sulfide- and thiophosphate-based solid electrolytes. Furthermore, the techniques used to characterize the solid electrolytes presented in this thesis are introduced. This work presents several design strategies for improving the ionic conductivity of solid electrolytes based on sulfides and thiophosphates. Bottom-up and top-down post-synthetic modification approaches, thermally and chemically induced phase transitions, and microstructure modifications cover a wide range of length scales
Carbon-Based Materials
New carbon materials with improved mechanical, electrical, chemical, and optical properties are predicted and considered to be very promising for practical application. Carbon-based materials in the form of films, fabrics, aerogels, or microstructural materials are known for their large surface areas and pore volumes, light weight, and a great variety of structural morphology. Such unique structures can then be employed for a variety of purposes, for example, the production of new electronic devices, energy storage, and the fabrication of new materials. Nowadays, clear understanding of carbon materials via several examples of synthesis/processing methodologies and properties characterization is required. This Special Issue, “Carbon-Based Materials”, addresses the current state regarding the production and investigation of carbon-based materials. It consists of 13 peer-reviewed papers that cover both theoretical and experimental works in a wide a range of subjects on carbon structures
Light in correlated disordered media
The optics of correlated disordered media is a fascinating research topic
emerging at the interface between the physics of waves in complex media and
nanophotonics. Inspired by photonic structures in nature and enabled by
advances in nanofabrication processes, recent investigations have unveiled how
the design of structural correlations down to the subwavelength scale could be
exploited to control the scattering, transport and localization of light in
matter. From optical transparency to superdiffusive light transport to photonic
gaps, the optics of correlated disordered media challenges our physical
intuition and offers new perspectives for applications. This article reviews
the theoretical foundations, state-of-the-art experimental techniques and major
achievements in the study of light interaction with correlated disorder,
covering a wide range of systems -- from short-range correlated photonic
liquids, to L\'evy glasses containing fractal heterogeneities, to hyperuniform
disordered photonic materials. The mechanisms underlying light scattering and
transport phenomena are elucidated on the basis of rigorous theoretical
arguments. We overview the exciting ongoing research on mesoscopic phenomena,
such as transport phase transitions and speckle statistics, and the current
development of disorder engineering for applications such as light-energy
management and visual appearance design. Special efforts are finally made to
identify the main theoretical and experimental challenges to address in the
near future.Comment: Submitted to Reviews of Modern Physics. Feedbacks are welcom
The Transmission Electron Microscope
The book "The Transmission Electron Microscope" contains a collection of research articles submitted by engineers and scientists to present an overview of different aspects of TEM from the basic mechanisms and diagnosis to the latest advancements in the field. The book presents descriptions of electron microscopy, models for improved sample sizing and handling, new methods of image projection, and experimental methodologies for nanomaterials studies. The selection of chapters focuses on transmission electron microscopy used in material characterization, with special emphasis on both the theoretical and experimental aspect of modern electron microscopy techniques. I believe that a broad range of readers, such as students, scientists and engineers will benefit from this book
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Fabrication and application of structured graphene/polymer based composites
Despite there being a significant development in polymer composites for multiple applications over the past few decades, there are still many difficulties relating to the effective distribution of nanoparticles such as Graphene and other 2D materials in preparing structure and minimising aggregation. To overcome these obstacles a simple method for modulating the properties of the composites by controlling the organization of the fillers, using an ordered lattice of polymer particles as a template, is described. This technique can facilitate the self-assembly of nanomaterials while preserving their useful properties and allows well-defined interface between the polymer and the nanomaterial resulting in a honeycomb-like arrangement. The ideal case would be to obtain a segregated percolating network whereby low loadings of nanoparticles are added to obtain high performance systems and thus reduce the cost for possible industrial applications. The enhancement of the mechanical and electrical properties of the composites suggests the use of these materials for different applications such as transport applications, where the combination of high strength and lightweight is required. Moreover, to reinforce systems that are very delicate such as membranes or fibres or for possible applications in sensor technology, molecular electronics, supercapacitors, electrochromic devices and pressure sensitive adhesives materials. The physical properties of these composites can be tailored using different matrices such as natural rubber, or a bimodal particle system, to create materials with high density and low void fractions, and hence very low percolation threshold. Furthermore, the combination of excellent monolayer fraction and homogenous dispersion of the GO within the polymer dispersion leads to highly uniform films, with good distribution of the filler throughout, in a segregated network. A reduction in situ proceeds to improve the innate properties of the GO, but also to modify the polymer in close proximity through and exothermic process, thus providing a much improved interface between filler and matrix, improving both the electrical and mechanical properties. The advantage of this method to organize the graphene nanoparticles in a segregated pathway does not require the use of expensive equipment or materials, and it is a promising way to open up pathways to tunable electronic composite materials on a large scale
Carbones mésoporeux fonctionnalisés pour l'extraction sélective des terres rares
Les allotropes de carbone sont des matériaux très polyvalents qui sont étudiés par la communauté scientifique depuis plusieurs décennies. Depuis la découverte des fullerènes, des nanotubes et du graphène, une grande part de la recherche scientifique s’est concentrée sur ces matériaux à cause de leurs caractéristiques uniques. En effet, le carbone a le potentiel d’être utilisé dans une foule d’applications. Sa stabilité chimique et sa conductivité thermique, de même que sa conductivité électrique, expliquent le grand intérêt de la communauté scientifique pour ce type de matériaux. La silice structurée est intéressante pour l’adsorption de divers produits puisqu’il est possible d’en modifier simplement la surface avec des ligands adaptés pour l’application voulue. Au cours des dernières années, des recherches ont été réalisées pour la séparation et l’extraction des terres rares (TRs). En effet, il a été démontré que l’utilisation de silice modifiée avec un ligand de type amide diglycolic mène à de meilleurs résultats qu’une résine commerciale pour la séparation des terres rares. En revanche, la silice ne possède pas la stabilité chimique à des pH acide (<4) nécessaire pour les applications industrielles. Le carbone mésoporeux est une bonne alternative pour obtenir un adsorbant solide pour l’extraction des TRs. Cette forme de carbone nanostructurée est un matériau intéressant pour l’adsorption de composé puisqu’elle possède à la fois une grande surface spécifique et une excellente stabilité chimique. Ces caractéristiques en font un matériau qui pourrait être bien adapté pour les extractions au niveau industriel. Ce mémoire porte sur la modification de surface de carbone mésoporeux pour l’extraction sélective des TRs et leur application à des pH acides. Les différentes structures de carbone poreux (CMK-3, CMK-5, CMK-8, etc…) ont été synthétisées, modifiées par des ligands sélectifs pour les TRs et leurs comportements pour la sélectivité et l’extraction des TRs. Le développement de ces supports est intéressant dans la perspective du développement durable et des technologies vertes en milieu industriel. En effet, ce type de matériaux très stables offre un grand potentiel industriel. En effet, il serait théoriquement possible de les réutiliser de nombreuses fois, ce qui entrainerait une diminution des quantités de matières premières et de déchets associés requises pour leurs synthèses.Carbons allotropes have been under constant study for more than two decades. Ever since the discovery of fullerene, nanotube and graphene, the number of papers showing different synthesis route for their surface modification has been steadily increasing. Indeed, carbon has the potential to be a great support for a lot of applications. Carbon’s unique attributes for chemical resistance, thermal stability, thermal conductivity and high electrical conductivity explain the high interest of the scientific community for this material. Structured silica is useful for adsorption of various products since it is possible to simply modify its surface with ligands suitable for the desired application. Over the last few years, research has been conducted for the separation and extraction of rare earth elements (REEs). Indeed, it has been demonstrated that the modified silica with a diglycolic amide-type ligand obtained better results than the current commercial resin for the separation of rare earth elements. However, silica lack of chemical resistance to acidic pH (˂4) required for industrial applications is a major drawback for this material. The mesoporous carbon is a good alternative to be used as a solid adsorbent for extraction of REEs. This allotrope of carbon presents a large surface area as well as a greater chemical resistance which makes it better suited for industrial extractions. This research therefore focuses on the surface modification of mesoporous carbon for the selective extraction of REEs and their application to acidic pH. Different porous carbon structures (CMK-3, 5-CMK, CMK-8, etc.) were synthesized, modified by selective ligands for the REEs and behaviours for selectivity and extraction of REEs. The development of these materials is interesting in the context of sustainable development and green technologies in an industrial environmen
Electron Microscopy Characterization of Pentacene and Perfluoropentacene Grown on Different Substrates
This thesis deals with the study of the morphology, arrangement and orientation
of organic semiconductor films by (scanning) transmission electron microscopy
((S)TEM) techniques. The organic semiconductor perfluoropentacene (PFP) as well
as the organic heterostructures of pentacene (PEN) and PFP have been investigated.
PFP has been grown on graphene substrate, while the organic mixtures formed by
PEN and PFP have been deposited with different mixing ratios on two different
substrates, i.e. SiO2 and KCl.
PFP deposited on graphene exhibits an epitaxial growth in island shapes where
the molecules lie flat and parallel to the substrate adopting the so called ‘π-stacked
polymorph’. Within this work, the lateral alignment of the PFP molecules with respect
to the graphene substrate has been determined. It was found that the long molecular
axis of PFP is aligned along the zig-zag direction of the graphene. However, this
alignment is not exactly parallel, but exhibits a small offset.
Furthermore, the morphology of the PFP islands has been investigated. A
characteristic angle around 68° was found between confining edges of PFP islands.
The combination of TEM micrographs and electron diffraction patterns has enabled
the determination of the planes that run parallel to the confining edges of the islands
‘as seen’ by the electron beam in the two-dimensional projection. From that the
possible side facets associated with each confining edge have been suggested. Finally,
electron tomography experiments were used to gain insight into the shape of the PFP
islands, allowing the 3D reconstruction of them.
PEN:PFP blends have been prepared with mixing ratios of [2:1], [1:1] and [1:2]
on an inert substrate such as SiO2. Although different phases and morphologies have
been observed for each mixture, a mixed phase made out of PEN and PFP which
exhibits similar lattice parameters in all cases has been found independently of the
mixing ratio. The monocrystalline SAED pattern of the mixed phase has been shown
for the first time on this substrate. The diffraction pattern is rather similar to the one
of the pure PEN in �0 0 1� direction, suggesting that the crystal structure of the mixed
phase is similar to the one of pure PEN. For non-equimolecular blends, the respective
pure phase in excess is present apart from the mixed phase.
A different morphology was observed for the different PEN:PFP mixing ratios.
The equimolecular mixture of PEN and PFP exhibits fiber-like structures consisting
of the mixed phase. For the mixture with PFP in excess, some fibers are formed on a
background layer. The PFP is contained in the fibers, while the background layer is
made out of the mixed phase. For the mixture with PEN in excess, a grainy structure
(grain size of 10 nm-60 nm) with contributions of pure PEN and of the mixed phase
is detected.
PEN:PFP blends with mixing ratios of [2:1] and [1:2] grown on KCl substrates
have been investigated too. The mixed phase formed by PEN and PFP is also present
and both blends reveal a quite different morphology. The composition, orientation and
crystalline details of each phase have been inspected.
In the blend with PEN in excess, the mixed phase together with the pure PEN
phase are found in a uniform layer formed with domains that are rotated in-plane by
90° towards each other. In contrast, the blend with excess of PFP presents two
different arrangements. The majority of the sample exhibits some spicular fibers made
out of PFP on a background layer composed by the mixed phase. The other
arrangement present to a lesser extent consists of a film of pure PFP lying in direct
contact with the KCl substrate.
The importance of PFP grown on graphene lies in the relevance of the graphene
substrate together with the π-stacked arrangement exhibited by PFP on this substrate.
This motif enhances charge carrier mobility along the stacking direction. The
knowledge of the relative alignment as well as the faceting are a key information since
the physical properties depend on these parameters. Furthermore, considering the role
of the organic heterostructures in the development of organic electronic devices, a
detailed understanding of the basic arrangement of the organic molecules in the
organic blend is a requirement for the development of new organic devices