High Performance Power Research Articles

Improving Manganese Hexacyanoferrate’s Performance by Optimizing Processing Conditions and Adding Minuscule Amount of Ni

Intermittent energy generation from solar and wind demands a large deployment of energy storage systems (ESS), with 850 GWh expected by 2040 [1], in order to move away from fossil fuels. Na-ion cells are a fairly mature technology that could meet ESS demands. Among Na-ion cathode materials, Prussian Blue Analogs (PBAs) are promising because of their low cost, facile syntheses, long cycle life, and high-power performance associated with their open-framework structure. A high discharge voltage of ~3.5 V allows manganese hexacyanoferrate (MnHCF) to compete with LiFePO4-based Li-ion cells in Wh/kg and cost, but lacks in Wh/l. The latter may be acceptable for stationary ESS. However, PBAs’ open-framework structure enables them to absorb water rather easily, jeopardizing the longevity of the cell’s performance in organic electrolytes [2]. Moreover, rudimentary co-precipitation synthesis introduces vacancies in the structure, causing capacity loss due to limited redox sites [3].In this study, we explore and optimize the synthesis and processing conditions of PBAs that lead to excellent calendar life performance of >2000 hours (~400 cycles) in Na half-cells. First, MnHCF and nickel hexacyanoferrate (NiHCF) were synthesized using a chelating agent-aided route to obtain the monoclinic phase, as shown by XRD, which indicates high Na content and minimal vacancies, showing cubic morphology. We also show that the water content of PBAs can be significantly reduced (<0.40 wt.% for MnHCF) with thorough drying at 170 °C as verified by TGA. Both analogs demonstrated their own distinctive characteristics, i.e., high specific capacity for MnHCF and stable capacity retention in the case of NiHCF (Figure 1). MnHCF’s lower cost and higher energy density make it a more viable candidate, but the Jahn-Teller distortion of Mn is suggested to cause performance decay over time. This prompted us to add a minuscule amount of Ni to MnHCF in order to alleviate some strain in the structure, as reported in other literature reports [4,5]. The resulting NiMnHCF showed a synergetic effect of both transition metals, outperforming MnHCF in terms of normalized capacity retention, as shown in Figure 1. We also validated the C-rate performance of these PBAs, showing > 80% capacity at 10C rate and compared their performance to our previously reported Na0.96Ca0.02Ni1/3Fe1/3Mn1/3O2 cathode [6] and vendor supplied LiFePO4 and PBA commercial active materials. We also saw that choice of carbon diluents is crucial in augmenting PBAs’ performance due to their relatively lower electronic conductivity than oxide-based cathodes.

Simulation of Stack-Integrated Autothermal Reformer and Solid Oxide Fuel Cells for Operation in Aircraft Engines

Renewable liquified natural gas provides a potential sustainable aviation fuel, but with a volumetric energy density around 70% of conventional jet fuel. As such, alternative aircraft power plants such as hybrid gas turbine (GT) / solid oxide fuel cells (SOFCs) have been proposed to increase fuel conversion efficiency and support hybrid electric propulsion concepts. To enable reliable SOFC operation within aircraft gas turbine flow paths, stack architectures must be identified that sustain very high-power densities with direct inline air feeds from the gas turbine compressor outlet. Typical aircraft compressor outlet temperatures are below SOFC operating temperatures but high enough to light-off a catalytic autothermal reformer (ATR). The ATR combined with an air heat exchanger (HX) can preheat anode and cathode streams to desirable inlet temperatures above 500 °C for intermediate-temperature SOFCs that utilize gadolinia-doped ceria (GDC) electrolytes or thin-film, yttria-stabilized zirconia (YSZ) electrolytes. By packaging the inline ATR/HX within the SOFC stack and mixing partial anode exhaust recycle and bleed air with the ATR fuel stream, a volumetrically efficient inline stack architecture is being designed for demonstration at conditions simulating an aircraft gas-turbine compressor outlet. The combination of the ATR/HX and the high-power-density SOFC imposes significant temperature gradients within the stack that can impact performance. To assess suitable operating conditions and preferred designs for the ATR/HX/SOFC operating on renewable natural gas, a 3-D multi-physics CFD model has been developed. Simulation results for SOFCs with thin-film YSZ or GDC electrolytes show the challenge maintaining high-power densities while maintaining the full stack within expected temperature limits for expected cell materials.The ATR/HX/SOFC stack design includes the upstream ATR/HX, 3.6 cm in length. The ATR flow path is filled by a porous mesh with a washcoat-supported Pt catalyst for light off of CH4/bleed air/H2O inlet mixtures. The air-side flow paths in the ATR/HX are etched parallel channels that extract heat from the exothermic ATR reactions. The ATR/HX outlets feed the SOFC anode and cathode flow paths respectively. For this study, the SOFC membrane electrode assembly (MEA) 10 cm in length, consists of a porous Ni-YSZ anode-support (400 mm thick), dense YSZ or GDC electrolytes (≤ 20 mm thick), and a perovskite-YSZ composite cathode (35 mm thick). The anode flow passages over the support involve a high-porosity mesh that enables current collection. The cathode flow channels are etched ribs that enable high air flow rates to support high power density with adequate SOFC stack cooling. The ATR/HX/SOFC design has been incorporated into an ANSYS Fluent model to explore how integration of the ATR/HX in the stack can enable high-power performance of the SOFC while supporting light-off of the ATR fuel stream at aircraft compressor outlet conditions. The ANSYS Fluent model uses customized user-defined functions to handle the heterogeneous catalytic CH4oxidation surface chemistry for the ATR (supported Pt catalyst [1]) and for internal CH4 reforming in the Ni/cermet anode support in the SOFC [2]. The model simulates non-isothermal operation of a single ATR/HX/SOFC cell, representative of a full stack, at various inlet flow temperatures, pressures, flow rates, and fuel stream compositions, which are set by anode exhaust recycle fraction.CFD model results for thin-film YSZ-electrolyte MEAs illustrate a strong dependence of SOFC power density on the anode recycle fraction and cathode bleed air splits into the ATR fuel stream. For a 400 °C air inlet, the short ATR/HX is capable of achieving near-equilibrium CH4 conversion to an H2-rich reformate while preheating the cathode inlet up to 500 °C. Simulations over a range of anode recycle fractions show that lower recycle fractions increase ATR outlet temperatures and H2 mole fractions with SOFC power densities reaching 2.0 W cm-2, but at the risk of excessive anode temperatures and large temperature gradients across the length of the MEA. Increased cathode excess air ratios can lower the temperatures at the expense of stack power density. Higher anode recycle fractions decrease the temperature rise across the length of the MEA, but also at the expense power density. Further studies with GDC electrolytes based on recent GDC SOFC model developments [3] will explore how high-power densities of GDC can be supported within its operating temperature constraints.

Design and research of high voltage β-Ga2O3/4H-SiC heterojunction LDMOS

Abstract In recent years, gallium oxide (Ga2O3), one of the ultra-wide band-gap semiconductor materials, has been regarded as one of the most promising materials in the field of high-voltage and high-power electronic devices in the future because of its unique electrical properties and low preparation cost. However, it is difficult for β-Ga2O3 materials to form effective P-type doping, so the PN junction is not formed in most of its power devices, which greatly limits the improvement of its voltage resistance. A novel lateral double-diffused metal-oxide-semiconductor field-effect transistor (LDMOS) is proposed to realize a junction β-Ga2O3 power device and improve the voltage resistance performance of β-Ga2O3 power devices. In this device, a β-Ga2O3 power device with a junction is realized by using P-type 4H-SiC to form a PN junction with N-type β-Ga2O3, and the voltage resistance of the β-Ga2O3 power device is improved. Sentaurus TCAD software was used to simulate the device structure and electrical performance. The device is optimized by adjusting the length of the drift zone, drift zone concentration, SiC channel concentration, and gate oxide thickness. Optimized, the device exhibits a positive threshold voltage of 3.42 V, a breakdown voltage of 2203 V, a specific on-resistance of 7.80 mΩ·cm2, and a power figure of merit of 622 MW cm−2. The results show that the heterojunction device is significant for realizing high-performance junction β-Ga2O3 power devices.

Orientation-dependent strain and dislocation in HVPE-grown α -Ga2O3 epilayers on sapphire substrates

Orientation-dependent substrates provide effective platforms for achieving α-Ga2O3 with low dislocation densities, whereas the associated strain and dislocation dynamics have not been fully explored. Herein, we investigated the evolution of growth mode, interfacial strain, and dislocation propagation in the α-Ga2O3 epitaxial layer with various orientations, grown by the halide vapor-phase epitaxy. Strain tensor theory and geometric phase analysis indicate that the m-plane α-Ga2O3 epitaxial layer exhibits the lowest misfit tensile strain, measured at εxx = 1.46% and εyy = 1.81%, resulting in the lowest edge dislocation density. The m-plane lattice exhibits an inclination of 33.60°, while the c-plane lattice is horizontally aligned and the a-plane lattice oriented perpendicularly. The orientation-dependent growth significantly influences stress relaxation through the generation of misfit dislocations, originating from either basal or prismatic slip. Edge dislocations, induced by misfit dislocations, favor the c-axis, remaining well confined within the in-plane interfacial layer of the m-plane α-Ga2O3, leading to reduced low edge dislocation density in the subsequent thick epitaxial layer. These findings shed light on the epitaxial dynamics of α-Ga2O3 heteroepitaxy, paving the way for the development of high-performance power devices.

Compact Carbon-Based Ultra-High-Power Electrodes: A Sodium Alginate-Induced Self-Shrinkage and Densification Approach.

The trade-off between compact energy storage and high-power performance presents a significant challenge in device development. While densifying carbon materials enhances volumetric energy density by optimizing the balance between porosity and packing density, it often disrupts electronic conductivity due to random physical contact between nanomodules, limiting the power performance. This work presents a sodium alginate (SA)-induced self-shrinkage densification strategy that overcomes this limitation by incorporating nanometer-sized "spacers," namely carbon quantum dots (CQDs), into graphene nanosheets and crosslinking them by carbonizing SA accompanying with the shrinkage. These CQDs and SA-derived carbon enhance specific surface area, electronic conductivity, and ion transport rate due to the CQDs' spacer function and the formation of welded junction between the reduced graphene oxide (rGO)/CQDs nanosheets. Subsequently, the rGO/CQDs/SA-derived carbon film exhibits an extraordinary volumetric power density of 12307.7W cm-3 in an aqueous electrolyte under a mass loading of 0.12mg cm-2. Notably, the assembled aqueous supercapacitors achieve a high volumetric power density of 349.5W cm-3 under a higher mass loading of 0.49mg cm-2. This paves the way for developing compact, highly conductive carbon-based electrodes without compromising high porosity, offering a significant advancement in ultra-high-power energy storage devices.

From biomass to power: High-performance reactor design for coking-resistant operation

Biomass gasification coupled with solid oxide fuel cell (SOFC) technology utilizes the gas generated from biomass gasification directly as fuel for SOFC, thereby realizing power generation from solid waste. This technology combines the carbon–neutral feature of biomass with the high efficiency and low emissions of SOFC, making it a promising route for clean energy generation. However, biomass gasification syngas possesses a complex composition, including a high concentration of inert gases, which imposes higher requirements on SOFC. This study developed a multi-channel, hierarchical structural design based on the commercial NiO-yttria-stabilized zirconia (YSZ) material system, realizing high-performance power generation using biomass gasification syngas. The results showed that the combination of a unique structural design and an enhanced interface electrochemical reaction effectively mitigates the influence from inert composition dilution. When operating in gasification syngas with nearly 60 % inert components, the power density can reach 2.07 W·cm−2 (750 °C). In addition, due to the spatial separation of the inert support region and the electrochemically active region, the effect of controlling the position of carbon deposits was achieved, demonstrating 100 h stable operation with dry biomass gasification syngas. Hence, the combination of micro-tubular SOFC with distinctive structural regulation and biomass gasification exhibits promising prospects for further development.

Application of prelithiated nanoporous carbon anode for high-power lithium-ion capacitor

Abstract Prelithiated nanoporous carbons were applied as an anode material in lithium-ion capacitors to achieve high-power performance. Nanoporous carbon anodes with different pore structures, graphitization degrees, and prelithiation conditions were comparatively investigated for their rate performance, self-discharge property, and full-cell performance. Prelithiated nanoporous carbon anode prepared under optimized condition exhibited high power and energy densities.

Spin-Tunneling Magnetoresistive Effects in Bottom-Up-Grown Ni/Graphene/Ni Nanojunctions.

Two-dimensional (2D) materials embedded in magnetic tunnel junctions (MTJs) provide a platform to increase the control over spin transport properties by the proximity spin-filtering effect. This could be harnessed to craft spintronic devices with low power consumption and high performance. We explore the spin transport in the 2D MTJs based on graphene, which is uniformly grown on Ni(111) substrates using the chemical vapor deposition technique. After the Ni thin film is deposited bottom-up on the well-grown Ni(111)/graphene surface in an e-beam evaporation system by the physical vapor deposition method, the Ni/graphene/Ni nanojunction array devices are successfully prepared by using nanography technology. Evidence of the emergence of tunneling magnetoresistance (TMR) effects with ultrasmall resistance × area products in graphene-based nanojunctions is observed by the exclusion of anisotropic magnetoresistance. The theoretical analysis shows that this TMR is mainly attributed to the strong spin-filtering effect at the perfect Ni(111)/graphene interface. Besides, earlier findings indicate that the TMR would be promoted more effectively if the short-circuit effect formed in the process of nanographic etching by an ion beam can be further eliminated. Overall, this study provides a path to harness the full potential of graphene-based MTJ array devices with a high efficiency and performance.

RISC-V Leads the Future: Evolution and Outlook of CPU Architecture

This essay mainly talked the development of CPU and some instruction set architecture based on RISCV. CPU is known as the Central Processing Unit, the main appliment is RISCV, Also the ARM architecture is characterized by a focus on the balance between low power consumption and high performance. Then X86, its significant advantage is its complex instruction set and excellent performance, so it can handle complex computational tasks. We also explore the Pipeline technology, it is a widely used parallel processing technology today. The design principle is to divide complex, multilevel combinational logic circuits into multiple levels. Then, we find some experiment data to explore our conclusion. We find that each has its own advantages and is better suited to different scenarios. In terms of performance, x86 offers superior capabilities but consumes more power, making it ideal for high-performance computing and server applications. ARM, on the other hand, excels in power efficiency and finds its primary use in mobile devices and embedded systems. RISC-V, known for its flexibility, allows for a balance between performance and power consumption based on specific requirements, making it suitable for highly customizable applications, IoT devices, and emerging high-performance computing markets. The advantages of each architecture in different fields depend on the specific application environment and demands placed on them.

Robust and broadband tap couplers using misaligned waveguides based on thin-film lithium niobate.

Robust and high-performance power splitters with an ability to partition the input light power into different proportions are vital for various on-chip optical systems. Here we propose and experimentally demonstrate several tap couplers with unbalanced power splitting ratios (PSRs) from 4%: 96% to 40%: 60% using misaligned waveguides on thin-film lithium niobate (TFLN). The device utilizes misaligned waveguide width differences to obtain a flat power splitting ratio over a broadband optical wavelength. The measured results indicate that all the proposed devices exhibit less than 2% PSR variation over a 120 nm optical bandwidth from 1500 nm to 1620 nm and over ±100 nm planar fabrication tolerance. The demonstrated tap couplers offer a promising application prospect in high-density photonic integrated circuits.

Origin of Reliable High-Power Performances of PbZr0.5Ti0.5O3-Pb(Mn1/3Nb2/3)O3-Based Piezoelectric Ceramics.

High-power piezoelectric ceramics typically operate under severe conditions. This makes the accurate evaluation of their high-power performances through pure quasi-static parameters challenging. The 0.94PbZr0.5Ti0.5O3 - 0.06Pb(Mn1/3Nb2/3)O3 + 0.005Fe2O3 + 0.002Sc2O3 (PZT-1) ceramic exhibits exceptional and reliable high-power performances at elevated temperatures and under loading conditions. While numerous PZT-based ceramics demonstrate excellent quasi-static parameters, only the PZT-1 ceramic displays superior high-field parameters, such as a low tan δ of 0.97% at 566 V/mm (1 kHz) and a large Qm of 1164 at 50 V/mm (100 kHz). Therefore, the PZT-1 ceramic demonstrates remarkably slow heat generation and the highest surface temperatures are only 41.8 °C at 50 V/mm (100 kHz). Moreover, the PZT-1 ceramic shows a minimal resonance frequency variation of -0.04% in the temperature range of 25-120 °C at 50 V/mm. Consequently, the PZT-1 ceramic maintains a high and reliable vibration velocity of 0.90 m/s at 120 °C for 30 min, and the ceramic cantilever sustains a high amplitude of 7 μm, significantly outperforming other ceramics. This study conclusively demonstrates that high-field parameters, rather than quasi-static parameters, are more effective in accurately estimating the high-power performances of ceramics.

X-law operation for energy-efficient time-of-arrival positioning to achieve higher accuracy with lower bandwidth: A game-changer for UWB localization devices

Ultra-wideband (UWB) technology is a good candidate for low-latency high-resolution localization. This paper proposes the x-law operation (XLO) to boost the positioning accuracy of UWB localization systems. The proposed scheme significantly reduces the contribution of low-SNR samples and increases the time resolution of the pulse. Thus, the XLO achieves a time-of-arrival (ToA) positioning accuracy that existing methods require more energy and bandwidth to attain. The significant performance gain of the XLO for localization makes the XLO a good candidate for simultaneous positioning and communication with low complexity, high performance, and low power consumption suited for Internet of Things (IoT) devices.

Warfare and wind tunnel: engineers, physicists, and the evolution of combat aircraft 1914-1918

Abstract The British aircraft industry was transformed across the course of the First World War. Annual output grew exponentially, while by 1917-1918 the intensity of wartime research and development saw technologically advanced machines seeking air supremacy in all theatres of operation, most notably the Western Front. Capability had been inhibited by the absence of reliable, high performance power units, but ultimately production and procurement problems were resolved. This heroic narrative warrants qualification given the high ratio of poor to outstanding aircraft and the reality that in August 1914 Britain was by no means wholly unequipped to wage war in the air: the development programmes of the National Physical Laboratory and Royal Aircraft Factory, and the Royal Naval Air Service’s collaboration with science-based companies such as Short Brothers run counter to a popular belief that machines were still crudely built and militarily ineffective. There existed a working partnership between pioneer engineers and designers, schooled in applied science at metropolitan technical colleges, and graduate physicists and mathematicians encouraged by far-sighted dons to join a fledgling but fast-growing industry. That fusion of theory and practice, academic and industrial, was consolidated once British science’s human assets were mobilised to wage ‘industrial war’. Yes, aviation saw huge changes across the War, but the continuity is striking: before 1914 designers and air frame manufacturers were drawn from both the shop floor and the varsity, a wartime infusion of research scientists generated remarkable advances in aeronautics and in consequence a vital extension of Allied air power; and after 1918 companies survived retrenchment thanks to a durable combination of the entrepreneurial engineer and the experimental analyst.

A V-band injection locking tripler with 26.8% locking range and 7.3-dBm output power in 65 nm CMOS

With a 65-nm CMOS process, a V-band wideband injection locking (IL) frequency tripler is proposed by cascading a multiplier and a driver amplifier stage. Concerning high output power and efficiency performance over a wideband locking range (LR), two transformer-based IL topologies are analyzed in the multiplier and driver stages, in which the cross-coupled pair is connected at the input and output ports of the transformer, respectively. Moreover, the active device is carefully designed in terms of the operating point of the harmonic generator and device sizing in the driver amplifier stage. With measurements, the proposed tripler achieves a maximum measured output power of 7.3 dBm with 22.4% output-to-DC power efficiency and 26.8% LR from 50.4 to 66 GHz. Including the output driver amplifier, the IL tripler consumes 24 mW DC power. The measured fundamental and 2nd-harmonic rejection ratios (HRR) are both better than 30 dBc, while the measured phase noise (PN) degradation is in close agreement with the theoretical value.

Auxotonic training in muscle strength and power performance of professional young volleyball players

Auxotonic training unexplained on isotonic and isometric muscular contraction combination to develop strength and power gain. The study aimed to investigate muscle strength and power changes of professional young volleyball players on the auxotonic training effect. Volleyball players divided in AUT (auxotonic group: 16.32 y, 1.72 m, 63.63 kg) trained over 8 week and per week 2 day performing isotonic + isometric contraction combination periodization and IKT (isokinetic group: 16.23 y, 1.69 m, 60.22 kg) performed only isokinetic contraction periodization. The linear muscle strength and power processes of training periodization preferred for maximize performance. The strength changes of this study resulted on AUT and IKT for 1RM strength test and activforce isometric muscular strength adaptation test were similar, however, AUT obtained high improvement power performance (p &lt; .05). Auxotonic training developed on strength and power for AUT. Additionally, showing of comparison between AUT and IKT concluded CMJ (90°) ES = 1.09 very large, vertical jump ES = 1.31 very large and handgrip right ES = 0.05 small effect size. Based on the results we obtained, current auxotonic contraction was determined on resistance training applied to young volleyball players effective in strength and power development. Auxotonic training performed on young volleyball players will bring a perspective to the coaches and athletes work in this field as a resistance training model. The auxotonic training strategy for long term performance changes on outcomes of using aimed potential muscle isotonic + isometric contraction combination may be effective maximize strength and power performance.

Enhancing the piezoelectric performance of novel PZT-PMS-PSN piezoelectric ceramics by fine-tuning the monoclinic phase

The enhanced high-power performance of 0.93 Pb(Zr1-xTix)O3-0.05 Pb(Mn1/3Sb2/3)O3-0.02 Pb(Sc1/2Nb1/2)O3 (x = 0.48, 0.50, 0.52, 0.54, 0.56) piezoelectric ceramics (PZT-PMS-PSN) has been achieved with notable improvement in the piezoelectric coefficient (d33). The presence of the monoclinic phase (Cc) has led to an increase in d33 from 214 pC N−1 to 315 pC N−1. Therefore, the composition 0.93 Pb(Zr0.48Ti0.52)O3-0.05 Pb(Mn1/3Sb2/3)O3-0.02 Pb(Sc1/2Nb1/2)O3 exhibits excellent mechanical and electrical parameters: a d33 value of 315 pC N−1, a high mechanical quality factor of 1578, an electromechanical coupling factor kp of 52 %, and a low dielectric loss tanδ of only 0.288 %. Additionally, this ceramic exhibits a significantly high Curie temperature (Tc), reaching up to 328 °C which stabilizes its ferroelectric phase. Moreover, the phase transition of PZT-PMS-PSN ceramics from rhombohedral to tetragonal phase was investigated by X-ray diffraction, Raman scattering, Piezo-response force microscopy.

Application of high-performance computing in sustainable energy campus building design

In high-performance computing (HPC) systems, energy and power considerations play an increasingly important role. This work aims to ensure the implementation of China’s green and ecological concepts, respond to China’s strategy of building an environment-friendly and resource-saving society, and actively promote the construction of sustainable development campuses. First, the theoretical basis of sustainable energy campus architecture is described. Next, the teaching feedback model under HPC is constructed. Finally, with the evaluation results of students’ task completion processes and students’ task works as measurement indexes, the corresponding data is collected and comprehensively evaluated and analyzed to verify the effectiveness of the model. The analysis results indicate that most students are able to complete tasks within two hours; however, their proficiency with multimedia technology is inadequate, and they lack initiative in the learning process. There is a correlation between the overall evaluation of task performance and the students’ level of understanding of the tasks. By implementing a teaching feedback model, students’ learning enthusiasm and the quality of their work improved, providing effective educational support for promoting sustainable development on campus. Overall, the awareness of using computers and other multimedia technologies among students is not strong, and their learning process is relatively closed, with insufficient enthusiasm and initiative. This model can achieve the acquisition, integration, and statistical analysis of teacher feedback information. The model can realize the acquisition, integration, and statistical analysis of teachers’ feedback information. This work hopes to use this learning and feedback mode in practical teaching to address specific problems in computer multimedia courses.

Terahertz Modulation Properties Based on ReS2/Si Heterojunction Films

Low cost, low power consumption and high performance are urgent needs for the application of terahertz modulation devices in the 6G field. Rhenium disulfide (ReS2) is one of the ideal candidate materials due to its unique direct band gap, but it lacks in-depth research. In this work, a highly stable ReS2 nanodispersion was prepared by liquid-phase exfoliation, and a uniform, dense and well-crystallized ReS2 film was prepared on high-resistivity silicon by drop casting. The morphological, optical and structural properties of the ReS2/Si heterojunction film were characterized by OM, SEM, AFM, XRD, RS and PL. The terahertz performance was tested by using a homemade THz-TDS instrument, and the influence of different laser wavelengths and powers on the terahertz modulation performance of the sample was analyzed. The modulation depth of the sample was calculated based on the transmission curve, and the changes in the refractive index and conductivity of the sample with frequency at the corresponding laser power were calculated. The results show that the fabricated ReS2/Si heterojunction terahertz modulator can stably achieve 30% broadband modulation in the range of 0.3~1.5 THz under the low-power pumping of 1555 mW/cm2, and the maximum conductivity is 3.8 Ω−1m−1.

A Flexible Multifunctional Cyanoethyl-Modified Bacterial Cellulose Nanofiber Framework for High-Energy and High-Power Density Aqueous Li-Ion Batteries.

Aqueous rechargeable lithium-ion batteries (ARLIBs) are extensively researched due to their inherent safety, typical affordability, and potential high energy density. However, fabricating ARLIBs with both high energy density and power performance remains challenging. Herein, based on cyanoethyl-modified bacterial cellulose nanofibers (CBCNs), a multifunctional fast ion transport framework is developed to construct the flexible free-standing ARLIBs with high areal loading and excellent rate performance. Benefiting from the unique merits of CBCNs, such as ultra-high aspect ratio, excellent toughness, superior adhesion, good lithiophilicity and ideal stability, the flexible free-standing and highly robust electrodes are fabricated and exhibit a long-term stable cycling of 1200 cycles with a high specific capacity of 117 mAh∙g-1 at 15 C. Remarkably, the corresponding full cell with the free-standing high mass loading (45.5 mg∙cm-2) electrodes under the condition of ultra-low addition of battery binder demonstrates a cycle lifespan of over 1000 cycles with a specific capacity of 120 mAh∙g-1 and a capacity decay as low as 0.03% per cycle, which is far superior to those of almost all previous reports. This work provides a strategy for constructing ARLIBs with high energy density and power performance by introducing a unique fast ion transport nanofiber framework.

Short-side-chain perfluorinated polymeric membranes annealed at high temperature: Structure, conductivity, and fuel cell performance

The relationship between the mechanical, electrical, and morphological properties of annealed films based on short-side-chain perfluorinated sulfonic acid ionomer (SSCI) with an Aquivion structure was systematically investigated using dynamic mechanical analysis (DMA), small-angle X-ray scattering (SAXS), and impedance spectroscopy. Annealing the membranes at temperatures of 140, 150, and 160 °C—above the glass transition temperature of SSCI—and the nature of the liquid phase in the polymer dispersion significantly influence the structural parameters of the membranes, specifically the size of the conductive channels formed by hydrophilic sulfonic acid groups. SAXS and AFM analyses revealed that membranes cast from N,N-dimethylacetamide (DMAA) exhibit a denser, less structured morphology, resulting in lower hydrogen permeability (φ = 4.6 ± 0.7 nmol/m/s/MPa), comparable to the commercial Nafion 211 membrane (φ = 6.5 nmol/m/s/MPa), but with significantly lower proton conductivity (35 ± 5 mS/cm) than Nafion 211 (95 mS/cm). In contrast, membranes obtained from a water-alcohol mixture showed a well-defined structure (SAXS, AFM), with proton conductivity values ranging from 70 to 103 mS/cm, comparable to Nafion 211. However, the hydrogen permeability of these membranes varied significantly depending on the annealing conditions (φ = 5.5–65.3 nmol/m/s/MPa). SAXS data indicated that the membranes had a similar degree of crystallinity (11–13%) but differed in the positions of the ionomer peak and matrix knee, which are associated with variations in the size of the conductive channels and account for the observed differences in ionic conductivity. Membranes annealed at 150 °C, which exhibited hydrogen permeability and ionic conductivity values close to those of the commercial Nafion 211 membrane, were used to fabricate membrane electrode assemblies (MEA). The electrochemical characteristics of these MEAs were investigated at 30 and 60 °C, 100% relative humidity, at both atmospheric pressure and 200 kPa overpressure. At a current density of 1.75 A/cm2, the fabricated membranes demonstrated power outputs of up to 550 and 950 mW/cm2, which are comparable to, and even exceed, those of the commercial Nafion 211 membrane (700 mW/cm2). However, despite the high-power performance, significant membrane degradation was observed after 10,000 cycles in durability tests. These findings contribute to a better understanding of the relationship between the electrochemical properties and the structure of short-side-chain perfluorinated sulfonic acid ionomers with an Aquivion-type structure and are expected to enhance their application in fuel cells.