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Direct Synthesis of Fluorinated Carbon Materials via a Solid-State Mechanochemical Reaction Between Graphite and PTFE
No full textFluorinated carbon materials (FCMs) have received significant attention, because of their exceptional stability, which is associated with the strong C-F bonding, the strongest among carbon single bonds. However, the fluorination of carbon materials requires extremely toxic and moisture-sensitive reagents, which makes it inapplicable for practical uses. Here, a straightforward and relatively safe method are reported for the scalable synthesis of FCMs, by mechanochemical depolymerization of polytetrafluoroethylene (PTFE) and fragmentation of graphite. The resultant FCMs are evaluated as anode materials for lithium-ion batteries (LIBs). An optimized FCM delivered capacities as high as 951.6 and 329.3 mAh g (-1) at 0.05 and 10 A g (-1), respectively. It also demonstrated capacity retention as high as 76.6% even after 1000 cycles at 2.0 A g (-1)
Cobalt???Porphyrin???Based Covalent Organic Frameworks with Donor???Acceptor Units as Photocatalysts for Carbon Dioxide Reduction
No full textCovalent organic frameworks (COFs) have emerged as a promising platform for photocatalysts. Their crystalline porous nature allows comprehensive mechanistic studies of photocatalysis, which have revealed that their general photophysical parameters, such as light absorption ability, electronic band structure, and charge separation efficiency, can be conveniently tailored by structural modifications. However, further understanding of the relationship between structure-property-activity is required from the viewpoint of charge-carrier transport, because the charge-carrier property is closely related to alleviation of the excitonic effect. In the present study, COFs composed of a fixed cobalt (Co) porphyrin (Por) centered tetraamine as an acceptor unit with differently conjugated di-carbaldehyde based donor units, such as benzodithiophene (BDT), thienothiophene (TT), or phenyl (TA), were synthesized to form Co-Por-BDT, Co-Por-TT, or Co-Por-TA, respectively. Their photocatalytic activity for reducing carbon dioxide into carbon monoxide was in the order of Co-Por-BDT>Co-Por-TT>Co-Por-TA. The results indicated that the excitonic effect, associated with their charge-carrier densities and ??-conjugation lengths, was a significant factor in photocatalysis performance
On the Featutrs of Double-Wire Vibrating Wire Monitor
No full textThe vibrating wire monitors are used for measuring transverse pro-files of radiation beams of different nature. For increasing the accuracy of scanning, and in some cases escaping the scanning procedure (measurement of the beam profile using a matrix of wires), it is proposed to use several vibrating wires. A monitor of this kind with two vibrating wires spaced apart at some distance formed the measuring unit of the laboratory stand, developed by us for training students in accelerator technology. The features of such a two-wire monitor and, in particular, the problem of laser radiation power redistribution between the wires are discussed
Recent Advances in Triboelectric Nanogenerators: From Technological Progress to Commercial Applications
No full textSerious climate changes and energy-related environmentalproblemsare currently critical issues in the world. In order to reduce carbonemissions and save our environment, renewable energy harvesting technologieswill serve as a key solution in the near future. Among them, triboelectricnanogenerators (TENGs), which is one of the most promising mechanicalenergy harvesters by means of contact electrification phenomenon,are explosively developing due to abundant wasting mechanical energysources and a number of superior advantages in a wide availabilityand selection of materials, relatively simple device configurations,and low-cost processing. Significant experimental and theoreticalefforts have been achieved toward understanding fundamental behaviorsand a wide range of demonstrations since its report in 2012. As aresult, considerable technological advancement has been exhibitedand it advances the timeline of achievement in the proposed roadmap.Now, the technology has reached the stage of prototype developmentwith verification of performance beyond the lab scale environmenttoward its commercialization. In this review, distinguished authorsin the world worked together to summarize the state of the art intheory, materials, devices, systems, circuits, and applications inTENG fields. The great research achievements of researchers in thisfield around the world over the past decade are expected to play amajor role in coming to fruition of unexpectedly accelerated technologicaladvances over the next decade
Tuning orbital-selective phase transitions in a two-dimensional Hund's correlated system
No full textHund's rule coupling (J) has attracted much attention recently for its role in the description of the novel quantum phases of multi-orbital materials. Depending on the orbital occupancy, J can lead to various intriguing phases. However, experimental confirmation of the orbital occupancy dependency has been difficult as controlling the orbital degrees of freedom normally accompanies chemical inhomogeneities. Here, we demonstrate a method to investigate the role of orbital occupancy in J related phenomena without inducing inhomogeneities. By growing SrRuO3 monolayers on various substrates with symmetry-preserving interlayers, we gradually tune the crystal field splitting and thus the orbital degeneracy of the Ru t(2g) orbitals. It effectively varies the orbital occupancies of two-dimensional (2D) ruthenates. Via in-situ angle-resolved photoemission spectroscopy, we observe a progressive metal-insulator transition (MIT). It is found that the MIT occurs with orbital differentiation: concurrent opening of a band insulating gap in the d(xy) band and a Mott gap in the d(xz/yz) bands. Our study provides an effective experimental method for investigation of orbital-selective phenomena in multi-orbital materials. Hund's coupling, or the intra-atomic exchange, can drive novel quantum phases in multi-orbital systems, but this requires precise control of orbital occupancy. Ko et al. report an orbital-selective metal-to-insulator transition driven by Hund & PRIME;s physics via symmetry-preserving strain tuning in monolayer SrRuO3
DeepVehicleSense: An Energy-Efficient Transportation Mode Recognition Leveraging Staged Deep Learning Over Sound Samples
No full textIn this paper, we present a new transportation mode recognition system for smartphones called DeepVehicleSense, which is widely applicable to mobile context-aware services. DeepVehicleSense aims at achieving three performance objectives: high accuracy, low latency, and low power consumption at once by exploiting sound characteristics captured from the built-in microphone while being on candidate transportations. To attain high energy efficiency, DeepVehicleSense adopts hierarchical accelerometer-based triggers that minimize the activation of the microphone of smartphones. Further, to achieve high accuracy and low latency, DeepVehicleSense makes use of non-linear filters that can best extract the transportation sound samples. For recognition of five different transportation modes, we design a deep learning based sound classifier using a novel deep neural network architecture with multiple branches. Our staged inference technique can significantly reduce runtime and energy consumption while maintaining high accuracy for the majority of samples. Through 263-hour datasets collected by seven different Android phone models, we demonstrate that DeepVehicleSense achieves the recognition accuracy of 97.44% with only sound samples of 2 seconds at the power consumption of 35.08 mW on average for all-day monitoring
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No full textHierarchically designed 3-D printed porous nylon fabric-based personal thermoregulatory for radiative and directional wick-evaporative cooling
No full textEnergy consumption is increasing with global warming which remains a great challenge towards sustainable growth. Radiative cooling is an emergent technology towards personalized thermoregulation that radiates heat to outer space to attain self-cooling providing thermal comfort to humans while outdoors through economical way without any energy consumption. Herein a hydrophobic-hydrophilic porous nylon fabric (PNF) composite having unique pores across the composite with hierarchical silver nanoparticles decorated zinc stannate nanorods (Ag@ZTO) synthesized directly over the PNF. We designed the composite by novel and quick threedimensional (3D) printing technique for the first time that utilizes synergistic innovative integration of radiative and wick-evaporation cooling. The high reflectance of solar irradiance (89.5%) and high emissivity of human body thermal radiation (91.8%) permitted the textile to reduce the temperature of simulated skin by 19.3 degrees C under direct sunlight demonstrating its superior passive cooling capability. An excellent water vapor transmission rate, water-wicking, washability, durability, tensile strength (70.8% compared to bare PNF) is demonstrated for the composite and a high one-way transport index R (1368 %) shows its unidirectional liquid transport behavior. This approach of designing fabric through tailoring the properties by cost-effective techniques offers new routes for personal thermoregulatory and moisture management towards advanced functional textiles introducing a pioneering direction to sustainable energy
A cutting-edge solution for adhesives
No full textMetamaterial adhesives with nonlinear cut architectures provide strong and reversible adhesion, directionality and spatially programmable adhesive strength
