Rapid Energy Conversion Research Articles

Ti3C2Tx MXene/Graphene hybrid frameworks for constructing thermally conductive phase change composites with solar-thermal conversion ability

Application of three-dimensional (3D) carbon framework in phase change material (PCM) has aroused a tremendous interest. However, implementing a high alignment carbon framework with low interfacial thermal resistance (ITR) remain challenging. Herein, we demonstrated a synergetic effect strategy by Ti3C2Tx MXene and graphene nanoplate (GNP) to achieve a 3D thermally conductive framework with high alignment skeleton and low filler-to-filler ITR. Typically, the 3D anisotropic carbon framework is fabricated by unidirectional ice template freezing cellulose nanofibers (CNF)/GNP solution with the assistance of MXene. The abundant functional groups of MXene and the similar layered structure promote the dispersion stability of GNP in CNF aqueous solution, resulting in the significant improvement in GNP alignment and the filler-to-filler ITR. Therefore, the final phase change composites obtained by impregnating polyethylene glycol (PEG) into the framework achieves a satisfactory thermal conductivity (TC) of up to 3.49 W/m K at only 6.25 vol% filler loading. Combining the solar-thermal conversion ability of graphene and MXene, the PCM reveals a rapid energy conversion, transfer and storage capability. More importantly, the phase change enthalpy of the PCM can be as high as 164.3 J/g, with little change even after 50 heating-cooling cycles, and the existence of carbon framework can effectively prevent the leakage phenomenon in solid-liquid conversion process, ensuring its shape stability.

A Thermosalient and Mechanically Compliant Organic Crystalline Optical Waveguide Switcher

AbstractThe dense and ordered molecular arrangements endow dynamic molecular crystals with fast response, rapid energy conversion, low energy dissipation, and strong coupling between heat/light and mechanical energy. Most of the known dynamic crystals can only respond to a single stimulus, and materials that can respond to multiple stimuli are rare. Here, we report an organic crystalline material that can be bent plastically and is also thermosalient, as its crystals can move when they undergo a reversible phase transition. The crystals transmit light regardless of their shape or crystalline phase. The combination of light transduction and reversible thermomechanical deformation provides an opportunity to switch the waveguiding capability of the material in a narrow temperature range, which holds a tremendous potential for applications in heat‐averse electronic components, such as central processing units. Unlike existing electronics, the material we report here is completely organic and therefore much lighter, potentially reducing the overall weight of electronic circuits.

A Thermosalient and Mechanically Compliant Organic Crystalline Optical Waveguide Switcher.

The dense and ordered molecular arrangements endow dynamic molecular crystals with fast response, rapid energy conversion, low energy dissipation, and strong coupling between heat/light and mechanical energy. Most of the known dynamic crystals can only respond to a single stimulus, and materials that can respond to multiple stimuli are rare. Here, we report an organic crystalline material that can be bent plastically and is also thermosalient, as its crystals can move when they undergo a reversible phase transition. The crystals transmit light regardless of their shape or crystalline phase. The combination of light transduction and reversible thermomechanical deformation provides an opportunity to switch the waveguiding capability of the material in a narrow temperature range, which holds a tremendous potential for applications in heat-averse electronic components, such as central processing units. Unlike existing electronics, the material we report here is completely organic and therefore much lighter, potentially reducing the overall weight of electronic circuits.

Multidimensional Interactive Cascading Nanochips for Detection of Multiple Liver Diseases via Precise Metabolite Profiling.

It is challenging to detect and differentiate multiple diseases with high complexity/similarity from the same organ. Metabolic analysis based on nanomatrix-assisted laser desorption/ionization mass spectrometry (NMALDI-MS) is a promising platform for disease diagnosis, while the enhanced property of its core nanomatrix materials has plenty of room for improvement. Herein, a multidimensional interactive cascade nanochip composed of iron oxide nanoparticles (FeNPs)/MXene/gold nanoparticles (AuNPs), IMG, is reported for serum metabolic profiling to achieve high-throughput detection of multiple liver diseases. MXene serves as a multi-binding site and an electron-hole source for ionization during NMALDI-MS analysis. Introduction of AuNPs with surface plasmon resonance (SPR) properties facilitates surface charge accumulation and rapid energy conversion. FeNPs are integrated into the MXene/Au nanocomposite to sharply reduce the thermal conductivity of the nanochip with negligible heat loss for strong thermally-driven desorption, and construct a multi-interaction proton transport pathway with MXene and AuNPs for strong ionization. Analysis of these enhanced serum fingerprint signals detected from the IMG nanochip through a neural network model results in differentiation of multiple liver diseases via a single pass and revelation of potential metabolic biomarkers. The promising method can rapidly and accurately screen various liver diseases, thus allowing timely treatment of liver diseases.

ДОСЛІДЖЕННЯ ДВОНАПРЯМНОГО ПЕРЕТВОРЮВАЧА ПОСТІЙНОЇ НАПРУГИ ДЛЯ ЗАСТОСУВАННЯ В СИСТЕМАХ НАКОПИЧЕННЯ ЕНЕРГІЇ

Electromagnetic processes in a bidirectional DC converter with the possibility of increasing and decreasing output voltage levels using an asymmetric inverter for a battery energy storage system when operating in difficult conditions with a short conversion period and determining its parameters are considered. Bidirectional DC converters are widely used in hybrid energy storage systems and in DC distribution power systems. This non-isolated bidirectional boost-buck converter is designed to control the flow of energy between sources with different voltage levels due to the use of low-voltage batteries in these systems. Thanks to the ability of these converters to quickly redirect electrical energy both in one and the other direction, it became possible not only to charge the battery from stationary sources of electricity, but also to charge the battery during the operation of the generator from the internal combustion engine and regenerative braking. The results of calculations of the prototype of a bidirectional DC converter with a 14 V battery, a 200 V DC bus and an output power of 3500 W are given. A prototype was made to confirm the possibility of rapid energy conversion. Ref. 9, fig. 6. Keywords: electric power storage systems, bidirectional DC voltage converter, fast energy conversion, hybrid electric vehicle.

Recent Advances in Common Transition Metal‐Based Single‐Atom Nanozymes and Their Applications in Pollutant Detection and Degradation

AbstractNanozymes can be used as favorable substitutes for natural enzymes because of their strong catalytic activity and good stability. At the same time, research on single‐atom catalysts (SACs) with isolated metal atoms as active centers is also in full swing, showing excellent performance in a variety of catalytic reactions. With the in‐depth study of SACs, people have a comprehensive understanding of them and put forward the concept of single‐atom nanozymes (SAzymes) by combining nanozymes with SACs. As a new type of nanomaterial, SAzymes have attracted great interest due to their remarkable catalytic activity and rapid energy conversion. However, most applications of SAzymes are mainly in the fields of biomedicine and biosensing, and less research has been done in the field of the environment. Based on the amazing ability of nanozymes to detect and degrade pollutants, SAzymes are also used in the environmental field, and even they will show better capabilities. This review mainly analyses common transition metal‐based SAzymes and describes their applications in the field of environmental pollutants.

Vacancy engineering in Co-doped CuS1-x with fast Electronic/Ionic migration kinetics for efficient Lithium-Ion batteries

Slow Li ion diffusion kinetics and disordered migration of electrons are two most crucial obstacles to be resolved in electrode material design for higher rate capability of Li-ion batteries. Herein, the Co-doped CuS1-x with abundant high active S vacancies is proposed to accelerate the electronic and ionic diffusion during the energy conversion process, because contraction of Co-S bond can cause the expansion of atomic layer spacing, thus promoting the Li ion diffusion and directional electron migration parallel to the Cu2S2 plane, and also induce the increasing of active sites to improve the Li+ adsorption and electrocatalytic conversion kinetics. Especially, the electrocatalytic studies and plane charge density difference simulations demonstrate that electron transfer near the Co site is more frequent, which is conducive to more rapid energy conversion and storage. Those S vacancies formed by Co-S contraction in CuS1-x structure obviously increase Li ion adsorption energy in Co-doped CuS1-x to 2.21 eV, higher than the 2.1 eV for CuS1-x and 1.88 eV for CuS. Taking these advantages, the Co-doped CuS1-x as anode of Li-ion batterie shows an impressive rate capability of 1309 mAh·g−1 at 1A g−1, and long cycling stability (retaining 1064 mAh·g−1 capacity after 500 cycles). This work provides new opportunities for the design of high-performance electrode material for rechargeable metal-ion batteries.

Development of a Bidirectional DC–DC Converter with Rapid Energy Bidirectional Transition Technology

Bidirectional DC–DC converters are key devices in the DC distribution system and the energy storage system (ESS). It is important to consider the safety of the elements in the converter for rapid conversion of the power direction. Damages may occur to the power-related components in the circuit if the direction of the inductor current or the capacitor voltage changes instantaneously. To make the power flow change smoothly and quickly, this research proposed a bidirectional DC–DC converter with rapid energy transition technology implemented in the circuit architecture. The rapid energy bidirectional transition technology added a resonance path based on the LC resonant circuit, allowing rapid energy conversion through the resonance path. Therefore, the energy in the energy storage element could be quickly converted without causing circuit surges. Analyses of the converter operating in the step-up mode, the step-down mode, and the transition operation mode are presented. The proposed circuit architecture had a high voltage-conversion ratio and a simple architecture. A prototype bidirectional DC–DC converter with a full load of 500 W, a low side voltage of 24 V, and a high side voltage of 200 V was developed to prove the concept. The feasibility of the rapid energy bidirectional transition technology was verified by the simulation results and experimental results using the prototype converter. The maximum efficiencies in the step-up mode and the step-down mode were 95.3% and 93.8% respectively. Under full-load conditions, the transient time of the energy transition from the step-up mode to the step-down mode was 17.7 μs, and the transient time of the energy transition from the step-down mode to the step-up mode was 19.3 μs.

Design and Implementation of the Bidirectional DC-DC Converter with Rapid Energy Conversion

The bidirectional DC-DC converters are widely used in the energy storage system (ESS) and DC distribution system. The power capacity is limited when the converter is operated with smooth power transfer. In addition, the directions of the inductor current and the capacitor voltage cannot change instantaneously. In this study, a rapid energy conversion technique for smoothing and accelerating the energy transfer under the same specification of the main components in steady state is proposed. Moreover, a bidirectional DC-DC converter with a high conversion ratio is proposed to overcome the commonly low voltage input from renewable energy sources. The operating principles of the proposed converter’s step-down and step-up modes are discussed in this study. Furthermore, to achieve rapid energy conversion, digital control is a crucial component in the converter system. A digital signal processor is used as the control platform, and a control strategy is formulated to achieve rapid energy conversion. The bidirectional DC-DC prototype converter with a 24 V battery, a DC bus of 200 V, and an output power of 500 W is constructed to confirm the feasibility of rapid energy conversion. The proposed converter can be operated in CCM, BCM, and DCM conditions. The transfer period can be completed within one switching cycle when the proposed converter is operated in BCM or DCM. The energy is freewheeled before energy conversion when the proposed converter is operated in CCM condition. In the experiment, the minimum transfer period is 6.29 µs on the DCM stage.

Prospectus on electron acceleration via magnetic reconnection

Many explosive plasma phenomena are powered by magnetic reconnection. Striking evidence of such events is found in short bursts of radiation from energetic electrons with energies much larger than what is typical of the ambient medium. Reconnection is a fundamentally multi-scale process that couples the global scale over which energy accumulates with small-scale dissipation. These macro- and micro-scales are bridged by a mesoscale of coherent magnetic structures that facilitate rapid energy conversion. Although there are many channels by which reconnection may release magnetic energy, a guiding-center approach distills electron energy gain into three basic mechanisms: parallel electric fields, Fermi reflection, and betatron acceleration. An efficient mechanism must scale strongly with the particle energy and operate over a globally significant region. These criteria favor the Fermi mechanism, which operates in volume-filling plasmoids. The guide field plays a critical role, facilitating three-dimensional transport that enables high-energy particles to continuously access acceleration sites, yet suppressing acceleration if the guide field is much larger than the reconnecting field. Open issues include the conditions necessary for power-law formation, the roles of scattering and plasma compression, and differences between the relativistic and nonrelativistic regimes. New high-resolution observations in the earth's magnetosphere offer a timely opportunity to test the predictions of numerical studies. On the other hand, understanding solar flares, where the global and dissipative scales are separated by many orders of magnitude, requires hybrid models that incorporate both the global evolution of the magnetic field and the self-consistent acceleration and feedback of energetic particles.

An open holey structure enhanced rate capability in a NaTi2(PO4)3/C nanocomposite and provided ultralong-life sodium-ion storage.

Sodium-ion battery (SIB) technology is competitive in the fields of transportation and grid storage, which require electrode materials showing rapid energy conversion (high rate capability) and long cycle life. In this work, a NaTi2(PO4)3/C (NTP/C) nanocomposite with an open holey-structured framework was successfully prepared for the first time using a solvothermal reaction followed by pyrolysis. The nanocomposite realized fast sodium-ion transport and thus preferable battery performances. Within the wide rate range of 0.5-50C, only a very small decrease in capacity from 124 to 120 mA h g-1 was observed. A high discharge capacity of 103 mA h g-1 (88.3% retention of the 1st cycle) was delivered even after 10 000 cycles at an ultrahigh rate of 50C without any obvious morphological change and without structural pulverization. Forming open channels for ion transport proved to contribute to such performance enhancement and therefore has the potential to become a universal model for the development of sustainable electrode materials in SIBs and other battery systems.

Plasmoid Instability in Forming Current Sheets

Abstract The plasmoid instability has revolutionized our understanding of magnetic reconnection in astrophysical environments. By preventing the formation of highly elongated reconnection layers, it is crucial in enabling the rapid energy conversion rates that are characteristic of many astrophysical phenomena. Most previous studies have focused on Sweet–Parker current sheets, which are unattainable in typical astrophysical systems. Here we derive a general set of scaling laws for the plasmoid instability in resistive and visco-resistive current sheets that evolve over time. Our method relies on a principle of least time that enables us to determine the properties of the reconnecting current sheet (aspect ratio and elapsed time) and the plasmoid instability (growth rate, wavenumber, inner layer width) at the end of the linear phase. After this phase the reconnecting current sheet is disrupted and fast reconnection can occur. The scaling laws of the plasmoid instability are not simple power laws, and they depend on the Lundquist number (S), the magnetic Prandtl number (P m ), the noise of the system ( ), the characteristic rate of current sheet evolution ( ), and the thinning process. We also demonstrate that previous scalings are inapplicable to the vast majority of astrophysical systems. We explore the implications of the new scaling relations in astrophysical systems such as the solar corona and the interstellar medium. In both of these systems, we show that our scaling laws yield values for the growth rate, wavenumber, and aspect ratio that are much smaller than the Sweet–Parker–based scalings.

Efficient acceleration of relativistic magnetohydrodynamic jets

Relativistic jets in active galactic nuclei, galactic microquasars, and gamma-ray bursts are widely considered to be magnetohydrodynamically driven by black hole accretion systems, although conversion mechanism from Poynting into particle kinetic energy flux is still open. Recent detailed numerical and analytical studies of global structures of steady, axisymmetric magnetohydrodynamic (MHD) flows with specific boundary conditions have not reproduced as rapid an energy conversion as required by observations. In order to find more suitable boundary conditions, we focus on the flow along a poloidal magnetic field line just inside the external boundary, without treating transfield force balance in detail. We find some examples of the poloidal field structure and corresponding external pressure profile for an efficient and rapid energy conversion as required by observations, and that the rapid acceleration requires a rapid decrease of the external pressure above the accretion disk. We also clarify the differences between the fast magnetosonic point of the MHD flow and the sonic point of de Laval nozzle.

High‐Oil‐Load Encapsulation of Medium‐Chain Triglycerides and d‐Limonene Mixture in Modified Starch by Spray Drying

Oil mixtures of medium-chain triglycerides (MCT) and D-limonene in mixing ratios from 10 to 100 wt% were encapsulated in modified starch (wall material) by spray drying to produce oil-rich powders. The oil load (mass ratio of oil mixture to wall material) of the infeed emulsion markedly influenced the properties of the infeed liquid and the characteristics of the resulting powder. The viscosity of the infeed liquid and the particle size of the powder exponentially decreased with increasing oil load, while the emulsion droplet size in the infeed liquid increased. In addition, retention of D-limonene during spray drying also decreased markedly with increasing oil load. Irrespective of the different oil loads and concentrations of the wall material, D-limonene retention was well correlated with the emulsion droplet diameter of the infeed liquid. The encapsulation efficiency of the oil mixture exhibited a maximum value (almost 100%) at an oil load between 0.5 and 1.0, before decreasing at higher oil loads. At an oil load of 2.0, the encapsulation efficiency of D-limonene was reduced to almost zero, while around 40% of the initial MCT was encapsulated in the powder. The increase in oil load also led to increased amounts of surface oil of MCT and D-limonene in the resulting powder due to the increasing emulsion droplet diameter of the infeed liquids. This study proposes the microencapsulation of medium-chain triglycerides under high-oil-load conditions by spray drying. The powders prepared by this process provide significant benefits in terms of rapid energy conversion after consumption without accumulation in the body. Important quality factors of the powder products such as the encapsulation efficiency and the amount of surface oil were examined to understand the optimum process conditions for spray drying.

Magnetic Energy Release in Relativistic Plasma

AbstractThe efficiency of the energy conversion rate in the relativistic magnetic reconnection is investigated by means of Relativistic Resistive Magnetohydrodynamic (R2MHD) simulations. We confirmed that the simple Sweet-Parker type magnetic reconnection is a slow process for the energy conversion as theoretically predicted by Lyubarsky (2005). After the Sweet-Parker regime, we found a growth of the secondary tearing instability in the elongated current sheet. Then the energy conversion rate and the outflow velocity of reconnection jet increase rapidly. Such a rapid energy conversion would explain the time variations observed in many astrophysical flaring events.To construct a more realistic model of relativistic reconnection, we extend our R2MHD code to R3MHD code by including the radiation effects (Relativistic Resistive Radiation Magnetohydrodynamics R3MHD). The radiation field is described by the 0th and 1st moments of the radiation intensity (Farris et al. 2008, Shibata et al. 2011). The code has already passed some one-dimensional and multi-dimensional numerical problems. We demonstrate the first results of magnetic reconnection in the radiation dominated current sheet.