Search results for "Lithium"
showing 10 items of 680 documents
Z+/Z− lithium niobate optical waveguide sensitivity related to pyroelectric effect
2020
Lithium niobate crystal is widely used for the design and fabrication of integrated electro-optic modulators. As a ferroelectric material, one sees its spontaneous polarization change with temperature variations. This phenomenon, known as the pyroelectric effect, induces strong waveguide transmission variations for waveguides realized on Z -cut wafers. Waveguides made by titanium in-diffusion either on the Z + or Z − side of the crystal show a significant difference in temperature behavior. Experimental data, enlightened by numerical simulations, help to show why Z − waveguides are more immune to temperature changes than Z + ones.
The Joining of LiNbO3, Quartz, TlBr-TlI and Other Optical Materials by the Use of Thin Metal Films as Bonding Agents
2000
A method of joining ferroelectric, optical and other non-metallic materials, such as lithium niobate, quartz, TlBr-TlI, glass, etc., at room temperature under a pressure of 0.1÷0.5 MPa is described. The surfaces to be joined are prepared to optical flatness, and indium or lead coatings as bonding agents are used. To obtain clean surfaces, procedures of the coating deposition and sample joining are performed in situ in a vacuum of l0-4 Pa. The strength of the obtained joints is about 20MPa for indium coatings and about 30MPa for lead coatings. It is supposed that attractive surface forces play a decisive role in the contact formation and bonding of the wafers. The method has been applied for…
Electrophoretically deposited α-Fe2O3 and TiO2 composite anchored on rGO with excellent cycle performance as anode for lithium ion batteries
2018
Abstract Two nanostructured oxides, α-Fe2O3 and TiO2 with a particle diameters 50 nm and 21 nm, were mixed with graphene oxide (GO). Composite thin films on a stainless steel substrate were obtained by electrophoretic deposition (EPD) procedure from water suspensions: α-Fe2O3/GO, TiO2/GO and α-Fe2O3/TiO2/GO. Subsequently reduction of as-prepared thin films was performed. Thicknesses of acquired films were evaluated in the range of 2–6 μm. Structure and morphology were investigated as well as electrochemical properties of all samples were studied. The results revealed that α-Fe2O3/TiO2/rGO (in this article denoted as FTGO) exhibited the specific discharge capacity of 790 mAh·g−1 after 150 cy…
Electrophoretic Nanocrystalline Graphene Film Electrode for Lithium Ion Battery
2015
Graphene sheets were fabricated by electrophoretic deposition method from water suspension of graphene oxide followed by thermal reduction. The formation of nanocrystalline graphene sheets has been confirmed by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The electrochemical performance of graphene sheets as anode material for lithium ion batteries was evaluated by cycling voltammetry, galvanostatic charge-discharge cycling, and electrochemical impedance spectroscopy. Fabricated graphene sheets exhibited high discharge capacity of about 1120 mAhg−1 and demonstrated good reversibility of lithium intercalation and deintercalation in graphene sheet film with capacity…
The synthesis of a hybrid graphene–nickel/manganese mixed oxide and its performance in lithium-ion batteries
2012
Abstract Mixing of aqueous suspensions of delaminated NiMn layered double hydroxide (LDH) and graphene oxide leads to the instantaneous precipitation of a hybrid material that after calcination under inert atmosphere at 450 °C leads to Ni6MnO8 nanoparticles deposited on larger reconstituted graphene sheets. This material exhibits electrical conductivity similar to graphite, superparamagnetism and can be used as an anode for Li-ion batteries. A maximum capacity value of 1030 mA h g−1 was found during the first discharge, and capacity values higher than 400 mA h g−1 were still achieved after 10 cycles. The methodology used here should allow the preparation of a large variety of hybrid graphen…
Facile hybridization of Ni@Fe2O3 superparticles with functionalized reduced graphene oxide and its application as anode material in lithium-ion batte…
2015
Abstract In our present work we developed a novel graphene wrapping approach of Ni@Fe2O3 superparticles, which can be extended as a concept approach for other nanomaterials as well. It uses sulfonated reduced graphene oxide, but avoids thermal treatments and use of toxic agents like hydrazine for its reduction. The modification of graphene oxide is achieved by the introduction of sulfate groups accompanied with reduction and elimination reactions, due to the treatment with oleum. The successful wrapping of nanoparticles is proven by energy dispersive X-ray spectroscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The developed composite material shows strongly i…
Energy leaks through the optical barrier created by H+ implantation in BaTiO3 and LiNbO3 planar waveguides
1998
Abstract The energy leaks through the index barrier created by the proton implantation process are put in evidence in planar optical waveguides made in BaTiO 3 and LiNbO 3 substrates. The selective detection of the light emerging from the guiding region permits to measure the optical attenuation of the guided wave. The results obtained on mono or twice implanted LiNbO 3 and BaTiO 3 waveguides are presented and discussed. It is shown that the light confinement is better in BaTiO 3 than in LiNbO 3 .
Neutronic and photonic analysis of the single box water-cooled lithium lead blanket for a DEMO reactor
1998
Abstract The water-cooled Pb–17Li demonstration plant (DEMO) breeding blanket line was selected in 1995 as one of the two EU lines to be further developed in the next decade. In this paper the results of a neutronic and photonic analysis of the `single box' concept is presented. A full three-dimensional model, including the whole assembly and many of the DEMO reactor components, has been developed, together with a three-dimensional neutron source. A tritium breeding ratio (TBR) value of 1.16, with no ports and a Li6 enrichment of 90%, has been obtained and a further analysis has been performed to determine Li6 enrichment that would still ensure tritium breeding self-sufficiency. Selected po…
<title>Effects of light polarization and crystal orientation on the holographic recording efficiency in doped LiNbO<formula><inf>&l…
2008
The holographic recording efficiency in doped LiNbO3 crystals has been studied both experimentally and theoretically depending on the type of dope, on the recording geometry and on the polarizations of the recording and readout light.. The studied crystals can be arranged in the following order by their efficiency: LiNbO3:Cu, LiNbO3:Fe (yet having a smaller thickness and donor concentration than LiNbO3:Cu), LiNbO3:Fe+Cu, LiNbO3:Fe+Ti, LiNbO3:Ti. It was found that the recording geometry with the holographic grating vector along the optical axis is much more efficient than in the perpendicular configuration.This fact is in accordance with the photorefraction theory based on photogalvanic and …
Iron and lithium-iron alkyl phosphates as nanostructured material for rechargeable batteries
2018
Abstract Inorganic/organic hybrid materials composed by iron atoms bonded to an alkyl phosphate can be easily synthesized by mixing at 110 °C iron chlorides with tri-alkyl phosphates. Since structural information on these products are lacking and taking into account that lithium/iron organic hybrid materials are important in lithium ion battery technology we report here the physico-chemical characterization of different hybrid lithium/iron butylphosphates. These materials are characterized by the presence of elongated hexagonal crystals stable up to 315 °C. The insertion of lithium does not affect the local structure. Thanks to such structures the material can be electrochemically-cycled an…