Lithium Sulfide–Carbon Composites via Aerosol Spray Pyrolysis as Cathode Materials for Lithium–Sulfur Batteries

We demonstrate a new technique to produce lithium sulfide-carbon composite (Li2S-C) cathodes for lithium-sulfur batteries via aerosol spray pyrolysis (ASP) followed by sulfurization. Specifically, lithium carbonate-carbon (Li2CO3-C) composite nanoparticles are first synthesized via ASP from aqueous solutions of sucrose and lithium salts including nitrate (LiNO3), acetate (CH3COOLi), and Li2CO3, respectively. The obtained Li2CO3-C composites are subsequently converted to Li2S-C through sulfurization by reaction to H2S. Electrochemical characterizations show excellent overall capacity and cycle stability of the Li2S-C composites with relatively high areal loading of Li2S and low electrolyte/Li2S ratio. The Li2S-C nanocomposites also demonstrate clear structure-property relationships

Electrochemical Lithiation of Covalently Bonded Sulfur in Vulcanized Polyisoprene

We report the synthesis of vulcanized polyisoprene (SPIP) nanowires and an investigation of the electrochemical lithiation mechanism of the covalently bonded sulfur bridges in SPIP. Electrochemical analysis demonstrates that the sulfur chains in SPIP have distinct electrochemical signatures from those that are characteristic of bulk elemental sulfur. The cyclic voltammetry and galvanostatic cycling data show a distinct multistep charge-transfer process and solid-state lithium–sulfur reaction behavior, and it is clear that this new material provides a promising basis for the development of cathodes for rechargeable batteries. Chemical changes due to the lithiation process are studied using Raman and X-ray photoelectron spectroscopy, on the basis of which new lithiation mechanisms of covalently bonded sulfur are proposed

Photonic Crystal Properties of Self-Assembled Kagome Lattices

47 pagesBinary colloidal mixtures are at the frontier for the creation of new photonic crystals (PhCs) because they spontaneously undergo complex ordering at the mesoscale and have the potential to vastly increase the range of structures that can be self-assembled. It is now known that binary mixtures of sub-micrometer shapes form colloidal alloys, i.e., analogous to metalic alloys, determined by the size ratio of the particle populations, the relative concentrations, and the total packing fraction. What is currently unknown is how the multicomponent basis and particle composition in binary colloidal crystals effect photonic dispersion relations. This gap in our understanding of structure-optocal property relationships in colloidal alloys is an important problem because this knowledge will aid in establishing a new paradigm in the colloid-based photonics field and will guide experimentalists to high payoff targets. Inspired by recent studies showing that binary mixtures of (shape-anisotropic) patchy particles are predicted to self-assemble into a range of Archimedian tilings (ATs), we investigate the photonic properties of the Kagome lattice, i.e., Schläfli symbol (3 ∙ 6)2, using electromagnetic calculations (MIT photonic bands package, MPB) and simulations (MIT Electromagnetic Equation Propagation package, MEEP). The Schläfli symbol represents the cyclic order of triangular- and hexagonal cross-section rods surrounding the vertices, with repeated elements collected as the exponent. We expected that this strucure would support strong light-matter interactions because it meets the structure factor criteria for large photonic bandgaps, i.e., the static structure factor approaches zero as the wavevector magnitude approaches zero. In this thesis, we find large bandgaps up to 30% (TM, gap-to-midgap ratio) in the direct (3 ∙ 6)2 structure. The dielectric constants for non-close-packed hexagonal- and triangular rods are varied independently, between 2 and 16, consistent with binary compositions. Mode field distributions indicate that the bandgaps originate from Lorenz-Mie scattering. For inverse structures, bandgaps arise due to dielectric band-air band transitions. Equifrequency contour analysis and finite difference time domain (FDTD) simulations show that negative refraction occurs over all angles of incidence (AANR) for normalized frequencies of 0.27-0.28 (ε(hexagon) = 16, ε(triangle) = 2), 0.32-0.34 (ε(triangle) = 16, ε(hexagon) = 2), and 0.32-0.34 (ε(matrix) = 12). The effective refractive indices reach negative one within these ranges. Sub-wavelength imaging and self-collimation are demonstrated for flatlenses having the (3 ∙ 6)2 structure. These dielectic PhCs provide an alternative to lossy metallic materials for realizing negative refraction in the optical and near-IR region. The photonic properties predicted here are important for applications in waveguides, solid state lighting, nonlinear optics, and superlenses, i.e., imaging beyond the diffraction limit

Fabrication of Ceramic Matrix Composites via Cold Sintering Process

Integrating polymers into ceramics is very intriguing since many new interesting characteristics can be introduced into the system while modifying the flaws of ceramic materials. However, the fabrication of ceramic-polymer composites, particularly polymer-in-ceramic matrix composites, has always been a problem due to the substantial temperature disparity between the melting points of polymers and ceramics. Cold sintering is an emerging technology that applies uniaxial pressure and a transient solvent to reduce the ceramic sintering temperature by approximately an order magnitude, down to about 100-200oC, which is significantly lower than typical sintering temperatures (e.g., 1000-1500oC) by using traditional sintering methods, making it very ideal for combining ceramics and polymers. This review delves into the current status, understanding, and application of cold co-sintering, examining various examples of ceramics and polymers employed. By adjusting the polymer types and percentages in the composite, quality control and surface engineering can be achieved. Moreover, the potential of cold sintering remains largely unexplored, and we discuss its outlooks and future implications for ceramic-polymer composites, including considerations for scale-up possibilities and recycling capabilities for an eco-manufacturing process. As our understanding of the cold sintering process continues to advance, it promises to unlock significant breakthroughs in producing ceramic-polymer composites in the future

Microstructure and Mechanical Properties of High-Specific-Strength (TiVCrZr)_{100<i>−x</i>}W<i>_x</i> (<i>x</i> = 5, 10, 15 and 20) Refractory High-Entropy Alloys

With the increasing demand for high-specific-strength materials for high-temperature applications, particularly in the aerospace field, novel (TiVCrZr)100−xWx (x = 5, 10, 15 and 20) refractory high-entropy alloys (RHEAs) were developed. The phase formation, microstructure, and mechanical properties were studied. The (TiVCrZr)100−xWx RHEAs exhibit a relatively high specific strength and low density compared with the W-containing RHEAs and most of the W-free RHEAs. In (TiVCrZr)100−xWx RHEAs, Laves, BCC and Ti-rich phases are formed, where the Laves phase is the major phase, and the volume fraction of the BCC phase increases with increasing W content. (TiVCrZr)100−xWx RHEAs exhibit dendrite structures, where W is enriched in the dendrite region, and increasing W-rich precipitations corresponding to the BCC phase are observed. The improvement of the strength and hardness of RHEAs is mainly attributed to the evolution of the microstructure and corresponding strengthening effect of W. The empirical parameters and calculated phase diagram were investigated, which further explain and verify the formation and variation of phases. The present findings give more insights into the formation of multi phases in (TiVCrZr)100−xWx RHEAs, and explore their application potential in the aerospace industry and nuclear reactors due to their high specific strength and low-activation constituent elements

Data Acquisition Network Configuration and Real-Time Energy Consumption Characteristic Analysis in Intelligent Workshops for Social Manufacturing

To achieve energy-saving production, one critical step is to calculate and analyze the energy consumption and energy efficiency of machining processes. However, considering the complexity and uncertainty of discrete manufacturing job shops, it is a significant challenge to conduct data acquisition and energy consumption data processing of manufacturing systems. Meanwhile, under the growing trend of personalization, social manufacturing is an emerging technical practice that allows prosumers to build individualized services with their partners, which produces new requirements for energy data processing. Thus, a real-time energy consumption characteristic analysis method in intelligent workshops for social manufacturing is established to realize data processing and energy efficiency evaluation automatically. First, an energy-conservation production architecture for intelligent manufacturing processes is introduced, and the configuration of a data acquisition network is described to create a ubiquitous manufacturing environment. Then, an energy consumption characteristic analysis method is proposed based on the process time window. Finally, a case study of coupling-part manufacturing verifies the feasibility and applicability of the proposed method. This method realizes a combination of social manufacturing and real-time energy characteristic analysis. Meanwhile, the energy consumption characteristics provide a decision basis for the energy-saving control of intelligent manufacturing workshops

Data Acquisition Network Configuration and Real-Time Energy Consumption Characteristic Analysis in Intelligent Workshops for Social Manufacturing

To achieve energy-saving production, one critical step is to calculate and analyze the energy consumption and energy efficiency of machining processes. However, considering the complexity and uncertainty of discrete manufacturing job shops, it is a significant challenge to conduct data acquisition and energy consumption data processing of manufacturing systems. Meanwhile, under the growing trend of personalization, social manufacturing is an emerging technical practice that allows prosumers to build individualized services with their partners, which produces new requirements for energy data processing. Thus, a real-time energy consumption characteristic analysis method in intelligent workshops for social manufacturing is established to realize data processing and energy efficiency evaluation automatically. First, an energy-conservation production architecture for intelligent manufacturing processes is introduced, and the configuration of a data acquisition network is described to create a ubiquitous manufacturing environment. Then, an energy consumption characteristic analysis method is proposed based on the process time window. Finally, a case study of coupling-part manufacturing verifies the feasibility and applicability of the proposed method. This method realizes a combination of social manufacturing and real-time energy characteristic analysis. Meanwhile, the energy consumption characteristics provide a decision basis for the energy-saving control of intelligent manufacturing workshops

Analysing Urban Tourism Accessibility Using Real-Time Travel Data: A Case Study in Nanjing, China

This study aimed to evaluate the spatial accessibility of tourism attractions in the urban destination city. An analytical framework for assessing urban tourism accessibility at different spatial scales was proposed to provide references on the interaction of urban transport and tourism systems. In addition to the travel time-based measure, a modified gravity model integrating the tourism destination attractiveness, urban transport system characteristics, and tourist demand distribution was developed to evaluate tourism accessibility in this study. Real-time travel data obtained from the Web Maps service were used to take the actual road network operation conditions into consideration and improve the accuracy of estimation results. Taking Nanjing as an example, the analysis results revealed the spatial heterogeneity of tourism accessibility and inequality in tourism resource availability at different levels. Road transport service improvement plays a dominant role in increasing tourism accessibility in areas with insufficient tourism resources, such as the outskirts of the destination city. As for areas with abundant attractions, authorities could pay attention to destination attractiveness construction and demand management in addition to the organization and management of road network operations around attractions during holidays. The results of this study provide a potentially valuable source of information for urban tourism destination management and transport management departments

Analysing Urban Tourism Accessibility Using Real-Time Travel Data: A Case Study in Nanjing, China

This study aimed to evaluate the spatial accessibility of tourism attractions in the urban destination city. An analytical framework for assessing urban tourism accessibility at different spatial scales was proposed to provide references on the interaction of urban transport and tourism systems. In addition to the travel time-based measure, a modified gravity model integrating the tourism destination attractiveness, urban transport system characteristics, and tourist demand distribution was developed to evaluate tourism accessibility in this study. Real-time travel data obtained from the Web Maps service were used to take the actual road network operation conditions into consideration and improve the accuracy of estimation results. Taking Nanjing as an example, the analysis results revealed the spatial heterogeneity of tourism accessibility and inequality in tourism resource availability at different levels. Road transport service improvement plays a dominant role in increasing tourism accessibility in areas with insufficient tourism resources, such as the outskirts of the destination city. As for areas with abundant attractions, authorities could pay attention to destination attractiveness construction and demand management in addition to the organization and management of road network operations around attractions during holidays. The results of this study provide a potentially valuable source of information for urban tourism destination management and transport management departments