63 research outputs found
Ion Beam Fabrication of Graphitic Structures in Single-Crystal Diamond for Electrically-Stimulated Luminescence
Tragacanth gum as green binder for sustainable water-processable electrochemical capacitor
9Enabling green fabrication processes for energy storage devices is becoming a key aspect in order to achieve a sustainable fabrication cycle. Here we focus on the exploitation of the tragacanth gum, an exudated gum like arabic and karaya gums, as green binder for the preparation of carbon-based for electrochemical capacitors. The electrochemical performance of tragacanth (TRGC)-based electrodes are thoroughly investigated and compared with another water-soluble binder largely used in this field, i.e. sodium-carboxymethyl cellulose (CMC). Apart from the higher sustainability both in production and processing, TRGC exhibits a lower impact on the obstruction of pores in the final active material film with respect to CMC, allowing for more available surface area. This directly impacts on the electrochemical performances resulting in a higher specific capacitance and better rate capability. Moreover, the TRGC-based supercapacitor shows a superior thermal stability than CMC with a capacity retention of about 80 % after 10.000 cycles at 70 °C.partially_openopenScalia, Alberto; Zaccagnini, Pietro; Armandi, Marco; Latini, Giulio; Versaci, Daniele; Lanzio, Vittorino; Varzi, Alberto; Passerini, Stefano; Lamberti, AndreaScalia, Alberto; Zaccagnini, Pietro; Armandi, Marco; Latini, Giulio; Versaci, Daniele; Lanzio, Vittorino; Varzi, Alberto; Passerini, Stefano; Lamberti, Andre
Interaction of nanodiamonds with water: Impact of surface chemistry on hydrophilicity, aggregation and electrical properties
In recent decades, nanodiamonds (NDs) have earned increasing interest in a wide variety of research fields, thanks to their excellent mechanical, chemical, and optical properties, together with the possibility of easily tuning their surface chemistry for the desired purpose. According to the application context, it is essential to acquire an extensive understanding of their interaction with water in terms of hydrophilicity, environmental adsorption, stability in solution, and impact on electrical properties. In this paper, we report on a systematic study of the effects of reducing and oxidizing thermal processes on ND surface water adsorption. Both detonation and milled NDs were analyzed by combining different techniques. Temperature-dependent infrared spectroscopy was employed to study ND surface chemistry and water adsorption, while dynamic light scattering allowed the evaluation of their behavior in solution. The influence of water adsorption on their electrical properties was also investigated and correlated with structural and optical information obtained via Raman/photoluminescence spectroscopy. In general, higher oxygen-containing surfaces exhibited higher hydrophilicity, better stability in solution, and higher electrical conduction, although for the latter the surface graphitic contribution was also crucial. Our results provide in-depth information on the hydrophilicity of NDs in relation to their surface chemical and physical properties, by also evaluating the impacts on their aggregation and electrical conductance
Tragacanth Gum as Green Binder for Sustainable Water-Processable Electrochemical Capacitor
Enabling green fabrication processes for energy storage devices is becoming a key aspect in order to achieve a sustainable fabrication cycle. Here, the focus was on the exploitation of the tragacanth gum, an exudated gum like arabic and karaya gums, as green binder for the preparation of carbonâbased materials for electrochemical capacitors. The electrochemical performance of tragacanth (TRGC)âbased electrodes was thoroughly investigated and compared with another waterâsoluble binder largely used in this field, sodiumâcarboxymethyl cellulose (CMC). Apart from the higher sustainability both in production and processing, TRGC exhibited a lower impact on the obstruction of pores in the final active material film with respect to CMC, allowing for more available surface area. This directly impacted the electrochemical performance, resulting in a higher specific capacitance and better rate capability. Moreover, the TRGCâbased supercapacitor showed a superior thermal stability compared with CMC, with a capacity retention of about 80â% after 10000 cycles at 70â°C
Drawing Boundaries
In âOn Drawing Lines on a Mapâ (1995), I suggested that the different ways we have of drawing lines on maps open up a new perspective on ontology, resting on a distinction between two sorts of boundaries: fiat and bona fide. âFiatâ means, roughly: human-demarcation-induced. âBona fideâ means, again roughly: a boundary constituted by some real physical discontinuity. I presented a general typology of boundaries based on this opposition and showed how it generates a corresponding typology of the different sorts of objects which boundaries determine or demarcate. In this paper, I describe how the theory of fiat boundaries has evolved since 1995, how it has been applied in areas such as property law and political geography, and how it is being used in contemporary work in formal and applied ontology, especially within the framework of Basic Formal Ontology
Efficient fabrication of high-density ensembles of color centers via ion implantation on a hot diamond substrate
Nitrogen-Vacancy (NV) centers in diamond are promising systems for quantum
technologies, including quantum metrology and sensing. A promising strategy for
the achievement of high sensitivity to external fields relies on the
exploitation of large ensembles of NV centers, whose fabrication by ion
implantation is upper limited by the amount of radiation damage introduced in
the diamond lattice. In this works we demonstrate an approach to increase the
density of NV centers upon the high-fluence implantation of MeV N2+ ions on a
hot target substrate (>550 {\deg}C). Our results show that, with respect to
room-temperature implantation, the high-temperature process increases the
vacancy density threshold required for the irreversible conversion of diamond
to a graphitic phase, thus enabling to achieve higher density ensembles.
Furthermore, the formation efficiency of color centers was investigated on
diamond substrates implanted at varying temperatures with MeV N2+ and Mg+ ions
revealing that the formation efficiency of both NV centers and
magnesium-vacancy (MgV) centers increases with the implantation temperature.Comment: 12 pages, 5 figure
How much does size really matter? Exploring the limits of graphene as Li ion battery anode material
Abstract We unravel the role of flake dimensionality on the lithiation/de-lithiation processes and electrochemical performance of anodes based on few-(FLG) and multi-layer graphene (MLG) flakes prepared by liquid phase exfoliation (LPE) of pristine graphite. The flakes are sorted by lateral size (from 380 to 75 nm) and thickness from 20 (MLG) to 2 nm (FLG) exploiting a sedimentation-based separation in centrifugal field and, finally, deposited onto Cu disks for the realization of four binder-free anodes. The electrochemical results show that decreasing lateral size and thickness leads to an increase of the initial specific capacity from â590 to â1270mAhg â1 . However, an increasing irreversible capacity is also associated to the reduction of flakes' size. We find, in addition, that the preferential Li ions storage by adsorption rather than intercalation in small lateral size
The Structure of Spatial Localization
Material objects, such as tables and chairs, have an intimate relationship with space. They have to be somewhere. They must possess an address at which they are found. Under this aspect, they are in good company. Events, too, such as Caesarâs death and Johnâs buttering of the toast, and more elusive entities, such as the surface of the table, have an address, difficult as it may be to specify. A stronger notion presents itself, though. Some entities may not only be located at an address; they may also own (as it were) the place at which they are located, so as to exclude other entities from being located at the same address. Thus, for certain kinds of entities, no two
tokens of the same kind can be located at the same place at the same time. This is typically the case with material objects. Likewise, no two particularized properties of the same level or degree of determinacy can be located at the same place at the same time (although particularized properties of different degree, such as the red of this table and the color of this table, can). Other entities seem to evade the restriction. Two events can be perfectly co-located without competing for their address. Or, to use a different terminology, events do not occupy the spatial region at which they are located, and can therefore share it with other events. The rotation of the Earth and the cooling down of the Earth take place at exactly the same regio
Li1.5La1.5MO6 (Mâ=âW6+, Te6+) as a new series of lithium-rich double perovskites for all-solid-state lithium-ion batteries
Solid-state batteries are a proposed route to safely achieving high energy densities, yet this architecture faces challenges arising from interfacial issues between the electrode and solid electrolyte. Here we develop a novel family of double perovskites, Li1.5La1.5MO6 (Mâ=âW6+, Te6+), where an uncommon lithium-ion distribution enables macroscopic ion diffusion and tailored design of the composition allows us to switch functionality to either a negative electrode or a solid electrolyte. Introduction of tungsten allows reversible lithium-ion intercalation below 1âV, enabling application as an anode (initial specific capacity >200 mAh g-1 with remarkably low volume change of âŒ0.2%). By contrast, substitution of tungsten with tellurium induces redox stability, directing the functionality of the perovskite towards a solid-state electrolyte with electrochemical stability up to 5âV and a low activation energy barrier (<0.2âeV) for microscopic lithium-ion diffusion. Characterisation across multiple length- and time-scales allows interrogation of the structure-property relationships in these materials and preliminary examination of a solid-state cell employing both compositions suggests lattice-matching avenues show promise for all-solid-state batteries
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