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- 2019
- Mach Zehnder Interferometer
- Convolution code
- Lithium Niobate
- Parity
- Electro-optic
- Optoelectronic Information Science and Engineering
- DIT University
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End-pump high efficiency 355 nm laser with a convex–concave cavity and optically-uncoated Brewster angle-cut LiB <sub/>3</sub> O <sub/>5</sub> crystal
摘要： Porous organic polymers (POPs), with features of permanent nanopores and designable frameworks, show great promise as sulfur host materials to restrain the shuttling of polysulfides, one of the main obstacles in the development of lithium–sulfur batteries. However, the simple physical entrapment from weak intermolecular interactions via a typical melt-diffusion method results in the diffusive loss of polysulfides that has thus far restricted their potential. Herein, a facile strategy for introducing chemical covalent interactions between POPs and sulfur via the regulation of sulfur infiltration temperature is reported. The results show that increasing the temperature to a suitable value, e.g., 400 °C, for a fluorinated triazine-based framework (FCTF), enables chemical bonding between the sulfur and aromatic FCTF backbone. Benefitting from the synergetic chemical and physical confinement effect, the shuttling of polysulfides can be efficiently restrained. As a result, the sample features superior sulfur utilization, high-rate performances, and good cycle stability, as compared with the sample with only physical confinement. The proposed strategy can also be extended to other POPs, such as the boroxine-linked covalent organic framework, by judiciously tailoring the infiltration temperatures. The findings disclose the important role of infiltration temperatures in developing efficient cathode host materials for lithium–sulfur batteries.
关键词： porous organic polymers,electrochemical performance,covalent chemical interactions,lithium–sulfur batteries,elevated sulfur infiltration temperature
更新于2025-09-11 14:15:04
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Electro-optic sensor for static fields
摘要： A sensor has been developed for low frequency and DC electric fields E. The device is capable of measuring fields with ??E = 4 (1) V/cm resolution. It is based on a Y-cut Z-propagation lithium niobate electro-optic crystal. For a particular commercially available bare crystal, we achieved an in air time constant ?? c(air) =6.4(1.8) h for the decay of the electro-optic signal. This enables field monitoring for several hours. As an application, we demonstrated that a constant electric field Eext = 640 V/cm applied via external electrodes to a particular spherical glass container holding an Xe/He gas mixture decays inside this cell with a time constant ??glass E = 2.5(5) h. This is sufficient for the needs of experiments searching for a permanent electric dipole moment in Xe. An integrated electric field sensor has been constructed which is coupled to a light source and light detectors via optical fibers. The sensor head does not contain any electrically conducting material.
关键词： Electric field monitoring,Static fields,Electro-optic sensor,Lithium niobate
更新于2025-09-11 14:15:04
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Facile fabrication of hierarchical micro-meso-macro porous metal oxide with high photochemical and electrochemical performances
摘要： A feasible route with a dual-templating method including both ice and SiO2 hard templates to fabricate hierarchical porous TiO2 with micro-, meso-, and macro-pores from inorganic/organic metal oxo cluster precursors is proposed. As-prepared TiO2 shows high photocatalytic activity and excellent electrochemical performances. The current strategy can be applied to fabrication of a broad range of metal oxide materials for catalysis and energy related applications.
关键词： Metal oxide,Lithium-ion batteries (LIBs),Photocatalytic,Hierarchical porous,TiO2
更新于2025-09-11 14:15:04
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Determination of the phase relation of a Li La(1?)/3NbO3 system by the slow cooling floating zone method
摘要： The phase relation during cooling of molten LixLa(1?x)/3NbO3 (LLN) was investigated by the slow cooling ?oating zone (SCFZ) method. It was found that LLN melts incongruently into LaNbO4 and a liquid. From the results of an electron probe microanalysis (EPMA) of the SCFZ samples, the solubility limit of Li into LLN was estimated to be x = 0.29, and the distribution coe?cient of Li into LLN appeared to be 0.54. The melting temperatures of LLN with various Li content were determined by di?erential thermal analysis. The results of the present work could be valuable for the growth of high-quality LLN single crystals.
关键词： Lithium compounds,Solubility,Oxides,Slow cooling ?oating zone,Phase diagrams,Lanthanum lithium niobate
更新于2025-09-10 09:29:36
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One-step hydrothermal synthesis of Fe<sub>2</sub>O<sub>3</sub>@TiO<sub>2</sub> microspheres with high lithium storage performance
摘要： The precursor of Fe(OH)3, C and TiO2 was synthesized by a simple one-step hydrothermal method. Then, the of C in the composite was eliminated by calcination at 500 ℃ for 5h in an air atmosphere. Thereby, a Fe2O3@TiO2 microspheres composite material is synthesized. The incorporation of Fe2O3 helps provide high specific capacity, high speed cycling and stable life performance. The first discharge capacity is 688mAh/g, with higher discharge capacity of Fe2O3@TiO2 microspheres (372mAh/g), and with the insertion/extraction of Li+ during charge and discharge, a dense SEI (Solid Electrolyte Interface) film is formed on the surface of the material to cause actual discharge of the graphite carbon material. The capacity is relatively low since the graphite carbon material has a lower theoretical specific capacity. The 2nd to 50th charge and discharge of Fe2O3@TiO2 microspheres, the capacitance retention rate exceeds 90%. The outstanding stable cycling and well rate performance suggest that Fe2O3@TiO2 microspheres have great potential to be applied as anode material for lithium ion batteries.
关键词： Anode,Carbon,Titanium dioxide,Ferric oxide,Lithium ion battery
更新于2025-09-10 09:29:36
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Life cycle assessment of PV-battery systems for a cloakroom and club building in Zurich
摘要： The Office for Building Engineering of the City of Zurich plans the construction of a cloakroom and club building. The building and the floodlights of the surrounding soccer fields use electricity mainly in the evening. That is why the installation of a photovoltaic (PV) system in combination with a battery storage system is evaluated in the pre‐project phase. The environmental footprint of the PV system with multi‐crystalline silicon modules and of current, future, and second‐life lithium‐ion batteries is quantified within the life cycle assessment of the building. The self‐consumption share of PV electricity increases from 31% to 62% if a 60 kWp PV system is complemented by a 100 kWh battery storage. The complementary grid electricity mix strongly influences the environmental impacts of electricity consumed by the cloakroom and club building. The installation of a PV system and a battery storage leads to a 10% to 17% reduction in greenhouse gas emissions compared with the full coverage of the electricity demand by the average Swiss supply mix. The addition of a current battery system does not yield any further reduction compared with the “PV only” option. With the renewable electricity mix of the City of Zurich, the installation of a PV system and a battery storage leads to higher environmental impacts of the electricity consumed by the cloakroom and club building, irrespective of the type of battery used. A future increase in energy density, production optimisations, and second‐life batteries bear a significant potential to reduce the environmental impacts of battery storage systems.
关键词： lithium‐ion,life cycle assessment,building,battery,photovoltaics,self‐consumption
更新于2025-09-10 09:29:36
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A Tunable Low-Power Oscillator Based on High-Q Lithium Niobate MEMS Resonators and 65-nm CMOS
摘要： This paper presents a comprehensive guide to co-design piezoelectric RF-micro-electromechanical system (MEMS) resonators and CMOS for enabling voltage-controlled MEMS oscillators (VCMOs) that harness the best benefits out of both platforms. The analysis, focusing on understanding different tradeoffs among the tuning range, power consumption, gain, and phase noise, is generic to any kind of piezoelectric resonators and specific for Colpitts VCMOs. As a result of this paper, the first VCMO based on the heterogeneous integration of a high-Q lithium niobate (LiNbO3) micromechanical resonator and CMOS has been demonstrated. A LiNbO3 resonator array with a series resonance at 171.1 MHz, a Q of 410, and an electromechanically coupling factor of 12.7% is adopted, while the TSMC 65-nm RF LP CMOS technology is used to implement the feedback and tuning circuitry with an active area of 220 × 70 μm2. The frequency tuning of the VCMO is achieved by programming a binary weighted digital capacitor bank and a varactor that are both connected in series to the resonator. The best measured phase noise performance of the VCMO is ?72 and ?153 dBc/Hz at 1 kHz and 10-MHz offsets from 178.23- and 175.83-MHz carriers, respectively. The VCMO consumes a dc current of 60 μA from a 1.2-V supply while realizing a tuning range of 2.4 MHz (～1.4% fractional tuning range). Such VCMOs can be applied to enable ultralow power, low phase noise, and wideband RF signal synthesis for emerging applications in Internet of Things.
关键词： RF-micro-electromechanical system (MEMS),lithium niobate (LiNbO3),phase noise,oscillator,Internet of Things (IoT)
更新于2025-09-10 09:29:36
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5 GHz laterally-excited bulk-wave resonators (XBARs) based on thin platelets of Lithium Niobate
摘要： In a free-standing 400-nm-thick platelet of crystalline ZY-LiNbO3, narrow electrodes (500nm) placed periodically with a pitch of a few microns can eXcite standing shear-wave Bulk Acoustic Resonances (XBARs), by utilizing lateral electric fields oriented parallel to the crystalline Y axis and parallel to the plane of the platelet. The resonance frequency of ~4800MHz is determined mainly by the platelet thickness and only weakly depends on the electrode width and the pitch. Simulations show Quality-factors (Q) at resonance and anti-resonance higher than 1000. Measurements of the first fabricated devices show a resonance Q-factor ~300, strong piezoelectric coupling ~25%, (indicated by the large Resonance-antiResonance (RaR) frequency spacing, ~11%) and an impedance at resonance of a few Ohms. The static capacitance of the devices, corresponding to the imaginary part of the impedance, is ~100 Ohms. This device opens the possibility for the development of low-loss, wide band, RF filters in the 3-6 GHz range for 4th and 5th generation (4G/5G) mobile phones. XBARs can be produced using standard optical photolithography and MEMS processes. The 3rd, 5th, 7th, and 9th harmonics were observed, up to 38 GHz, and are also promising for high frequency filter design.
关键词： Lithium Niobate,MEMS,RF filters,XBARs,5G
更新于2025-09-10 09:29:36
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Robust Pitch on Silicon Nanolayer-Embedded Graphite for Suppressing Undesirable Volume Expansion
摘要： A significant volume expansion exhibited by high-capacity active materials upon lithiation has hindered their application as Li-ion battery anode materials. Although tremendous progress has been made in the development of coating methods that improve the stability of high-capacity active materials, suitable coating sources that are both strong and economical to use are yet to be discovered. Pitch is reported here as a promising coating source for high-capacity anodes owing to the high mechanical strength and low-cost process. Using in situ transmission electron microscopy, it is found that pitch can withstand the severe volume expansion that occurs upon Si lithiation owing to its high mechanical strength, originating from the long-range graphitic ordering. Notably, pitch-coated silicon nanolayer–embedded graphite (SG) exhibits superior capacity retention (81.9%) compared to that of acetylene-coated SG (66%) over 200 cycles in a full-cell by effectively mitigating volume expansion, even under industrial electrode density conditions (1.6 g cc?1). Thus, this work presents new possibilities for the development of high-capacity anodes for industrial implementation.
关键词： volume expansion,Si anodes,lithium ion batteries,pitch,solid electrolyte interphase
更新于2025-09-10 09:29:36
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Li2SnO3 branched nano- and microstructures with intense and broadband white-light emission
摘要： Exploiting the synergy between microstructure, morphology and dimensions by suitable nanomaterial engineering, can effectively upgrade the physical properties and material performances. Li2SnO3 elongated nano- and microstructures in form of belts, wires, rods and branched structures have been fabricated by a vapor-solid method at temperatures ranging from 700 to 900 °C using metallic Sn and Li2CO3 as precursors. The achievement of these new morphologies can face challenging applications for Li2SnO3, not only in the field of energy storage, but also as building blocks in optoelectronic devices. The micro- and nanostructures grown at 700 and 800 °C correspond to monoclinic Li2SnO3, while at 900 °C complex Li2SnO3/SnO2 core-shell microstructures are grown, as confirmed by X-ray diffraction and Raman spectroscopy. Transmission electron microscopy reveals structural disorder related to stacking faults in some of the branched structures, which is associated with the presence of the low-temperature phase of Li2SnO3. The luminescent response of these structures is dominated by intense emissions at 2, 2.5 and 3 eV, almost completely covering the whole range of the visible light spectrum. As a result, white-light emission is obtained without the need of phosphors or complex quantum well heterostructures. Enhanced functionality in applications such as in light-emitting devices could be exploited based on the high luminescence intensity observed in some of the analysed Li2SnO3 structures.
关键词： white light emitters,luminescence,nanostructures,lithium oxides
更新于2025-09-10 09:29:36