Thermal Reduction Research Articles

Extracting zinc from ironworking dust having a high zinc content by vacuum silicothermic reduction

Zinc dust having a high ZnO content can be obtained after the preliminary treatment of zinc-bearing dust generated by the iron and steel industry by using a rotary kiln. However, this material has a high concentration of chloride salts that can affect the hydro-metallurgical extraction of metallic zinc. The present study used a vacuum distillation-vacuum thermal reduction process to recover zinc metal from this dust. This process first separated chloride and PbO by vacuum distillation and then extracted metallic zinc via the vacuum silicothermic reduction of ZnO. The results show that high-purity ZnO was prepared by vacuum distillation using the original zinc dust as a raw material. Both alkali metal chlorides and PbO in the dust could be removed with greater than 99 % efficiency by vacuum distillation at 1000 °C. Following this step, the slag contained more than 80 wt% Zn but less than 0.01 wt% chlorine and PbO. The vacuum thermal reduction process used the slag obtained from distillation as the raw material together with ferrosilicon alloy as a reducing agent. ZnO was reduced above 1000 °C and the recovery of this oxide exceeded 99 % using a reduction temperature of 1200 °C, reduction time of 2 h, and ferrosilicon mass ratio of 0.27. The main phase in the slag after reduction was SiO2 and the ZnO concentration was below 1 wt%, indicating a purity greater than 99 %. This method can realize the separation, recovery, and reuse of zinc-bearing dust to maximize the value-added utilization of this resource.

Effects of high-temperature thermal reduction on thermal conductivity of reduced graphene oxide polymer composites

The graphitic crystalline structure of reduced graphene oxide (rGO) can be improved by high-temperature thermal reduction at various heat-treatment temperatures ranging from 1000 to 2500 °C. The crystallinity significantly increased with increasing heat-treatment temperature. The electrical conductivities of the rGOs heat-treated at 2000 and 2500 °C (h-rGO-2000 and h-rGO-2500, respectively) were similar to those of commercial graphite. The isotropic thermal conductivity of rGO/epoxy composite with 10 wt% h-rGO-2500 (2.56 W/mK) was 11.6 times higher than that of pristine rGO (p-rGO; 0.22 W/mK) and significantly superior to those of epoxy composites with commercial graphite (0.82 W/mK) and mesophase pitch-based carbon fibers (MPCFs; 1.29 W/mK). Moreover, owing to the synergistic effect operating in the MPCF–h-rGO hybrid filler in epoxy composites, this combination of fillers increased the thermal conductivity to a greater extent than the MPCF–p-rGO hybrid filler. Optimum synergistic effects on the isotropic and in-plane thermal conductivities were achieved with an MPCF:h-rGO-2000 weight ratio of 49:1 (11.90 and 17.93 W/mK, 1.48 and 1.85 times higher than 8.02 and 9.69 W/mK for MPCF–p-rGO, respectively). Finally, a machine learning method that could predict and optimize the properties of rGOs based on their heat-treatment temperatures and material compositions was developed.

Enhanced Electrochemical Performance of Ca-Doped Na3V2(PO4)2F3/C Cathode Materials for Sodium-Ion Batteries.

Na3V2(PO4)2F3 (NVPF) with a NASICON structure has garnered attention as a cathode material owing to its stable 3D structure, rapid ion diffusion channels, high operating voltage, and impressive cycling stability. Nevertheless, the low intrinsic electronic conductivity of the material leading to a poor rate capability presents a significant challenge for practical application. Herein, we develop a series of Ca-doped NVPF/C cathode materials with various Ca2+ doping levels using a simple sol-gel and carbon thermal reduction approach. X-ray diffraction analysis confirmed that the inclusion of Ca2+ does not alter the crystal structure of the parent material but instead expands the lattice spacing. Density functional theory calculations depict that substituting Ca2+ ions at the V3+ site reduces the band gap, leading to increased electronic conductivity. This substitution also enhanced the structural stability, preventing lattice distortion during the charge/discharge cycles. Furthermore, the presence of the Ca2+ ion introduces two localized states within the band gap, resulting in enhanced electrochemical performance compared to that of Mg-doped NVPF/C. The optimal NVPF-Ca-0.05/C cathode exhibits superior specific capacities of 124 and 86 mAh g-1 at 0.1 and 10 C, respectively. Additionally, the NVPF-Ca-0.05/C demonstrates satisfactory capacity retention of 70% after 1000 charge/discharge cycles at 10 C. These remarkable results can be attributed to the optimized particle size, excellent structural stability, and enhanced ionic and electronic conductivity induced by the Ca doping. Our findings provide valuable insight into the development of cathode material with desirable electrochemical properties.

Simultaneous preparation of ZnO/rGO composites through Zn(OH)2 decomposition and graphite oxide reduction and their photocatalytic properties.

ZnO/reduced graphite oxide (rGO) composites were simultaneously prepared by the thermal reduction of graphite oxide (GO) and the decomposition of Zn(OH)2. The samples were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence, and DRS. Results indicate that Zn(OH)2 was heated and decomposed into ZnO at a low temperature (200 ℃), while GO was reduced to graphene. The synthesized ZnO particles were small and loaded on graphene layers. The ZnO/rGO photocatalysts exhibited excellent photocatalytic activity against methylene blue (MB) under simulated sunlight irradiation. The ZnO/50% rGO photocatalyst showed the best MB photodegradation rate of up to 99.7% within 3min. Synchronous reaction provided an efficient, simple, and fast preparation method for ZnO/rGO composites, with an excellent solar photocatalytic degradation ability.

Comparative Effects of Hydrazine and Thermal Reduction Methods on Electromagnetic Interference Shielding Characteristics in Foamed Titanium Carbonitride MXene Films.

The urgent need for the development of micro-thin shields against electromagnetic interference (EMI) has sparked interest in MXene materials owing to their metallic electrical conductivity and ease of film processing. Meanwhile, postprocessing treatments can potentially exert profound impacts on their shielding effectiveness (SE). This work comprehensively compares two reduction methods, hydrazine versus thermal, to fabricate foamed titanium carbonitride (Ti3CNTx) MXene films for efficient EMI shielding. Upon treatment of ≈ 100µm-thick MXene films, gaseous transformations of oxygen-containing surface groups induce highly porous structures (up to ≈ 74.0% porosity). The controlled application of hydrazine and heat allows precise regulation of the reduction processes, enabling tailored control over the morphology, thickness, chemistry, and electrical properties of the MXene films. Accordingly, the EMI SE values are theoretically and experimentally determined. The treated MXene films exhibit significantly enhanced SE values compared to the pristine MXene film (≈ 52.2dB), with ≈ 38% and ≈ 83% maximum improvements for the hydrazine and heat-treated samples, respectively. Particularly, heat treatment is more effective in terms of this enhancement such that an SE of 118.4dB is achieved at 14.3GHz, unprecedented for synthetic materials. Overall, the findings of this work hold significant practical implications for advancing high-performance, non-metallic EMI shielding materials.

Facile preparation of high-strength SiC/C aerogels from pre-reacted resorcinol–formaldehyde and siloxane

Carbon aerogels are ideal thermal insulation materials in the field of aerospace. However, their poor oxidative resistance at high temperatures is a significant drawback. Therefore, there is considerable interest in developing SiC/C aerogels. In this study, using pre-reacted resorcinol–formaldehyde gel (RF) as the carbon source, homogeneous silica/phenolic resin (SiO2/RF) hybrid aerogels were prepared via atmospheric pressure drying using a simple process. The SiC/C aerogels were subsequently obtained via carbon thermal reduction. As the C/Si ratio decreased (from 6 to 4.5 and 3), the density, thermal conductivity, and compressive strength of the aerogels decreased from 0.19 to 0.26 g·cm−3, 0.0330 to 0.0983 W/(m·K), and 0.57 to 4.83 MPa, respectively. The linear shrinkage rate was 16.4–18.3 %, which is lower than those of most reported SiC/C aerogels. Here, the carbon improved the strength of the SiC-based aerogels while maintaining their thermal insulation characteristics. A composite material prepared using the relatively low-strength aerogels and mullite fibre felt could achieve long-term insulation at 1400 °C in an air environment. This study lays the foundation and outlines various options for achieving an optimal balance between the strength and thermal conductivity of SiC/C aerogels for industrial applications.

Self‐Sacrificing Reductive Interphase for Robust and High‐Performance Sulfide‐Based All‐Solid‐State Lithium Batteries

AbstractAll‐solid‐state lithium‐ion batteries (ASSLIBs) based on sulfide solid‐state electrolytes (S‐SSEs) are considered as one of the most promising choices to address the safety hazards of traditional lithium‐ion batteries. However, the high‐voltage cathodes, such as LiCoO2 (LCO) with high‐valence Co (+3), tend to spontaneously oxidize S‐SSEs, causing polarization increase and rapid degradation. Herein, a self‐sacrificing reductive interphase consisting of CoO/Li2CO3/C, is in situ constructed on LCO surface via a simple carbon‐induced thermal reduction of LCO. With such a design, the Co valence of LCO surface is reduced to +2, reducing the oxidative nature of LCO to avoid reactions with S‐SSEs. As a result, ASSLIBs using Li10GeP2S12 (LGPS) S‐SSEs achieve a high initial capacity of 144.9 mAh g‒1 at 0.2 C and retard 93.1% of initial capacity after 100 cycles. Additionally, excellent rate cyclability of 109.2 mAh g‒1 at 1.0 C with 81.5% retentive capacity for 200 cycles is attained as well. Comprehensive evidence strongly demonstrates the effectiveness of this self‐sacrificing reductive interphase in inhibiting the interfacial reactions and ensuring long‐term cyclability. The proposed concept of a self‐sacrificing reductive interface in this study paves the way for stabilizing the cathode/SSEs interface and offers a novel approach for the design of high‐performance sulfide‐based ASSLIBs.

Efficient reduction of spent cathode materials via in-situ thermal reduction by defect-rich petroleum coke

Based on the dual attributes of environmental risk and resource value of spent Lithium-ion batteries (LIBs), low-cost and high-efficiency recovery methods of valuable metals from spent LIBs have been widely studied. Here, a strategy to efficiently recover valuable metals from spent cathode materials using defect-rich petroleum coke (PC) is proposed. The results show that only 5.8 % PC is required to reduce the spent cathode materials at 700 °C for 60 min, which shows strong reducibility. Meanwhile, thermodynamic and DFT calculations explore the mechanism of strong reducibility of defect-rich PC in the recovery of spent cathode materials. Based on the strong reduction effect of PC and the synergistic effect of gas–solid reaction and solid–solid reaction, the spent cathode materials are converted to soluble Li2CO3 as well as insoluble Ni, Co and MnO. The CO2 produced in the PC-assisted roasting process can participate in the Boudoureau reaction and the formation of Li2CO3 in situ, accelerating the efficient reduction of spent cathode materials and realizing the high value-added utilization of the roasting byproducts—CO2. The regenerated cathode materials show excellent electrochemical properties. This closed‐loop recovery process uses PC instead of expensive graphite, with a profit of around 6.67 $∙kg−1 cell, which reduces the cost.

Submicroscopic iron-rich grains throughout impact glasses in Chang'E-5 regolith

In lunar regolith returned by Chang'E-5, Apollo and Luna missions, submicron-sized iron-rich grains that are dominated by reduced iron and with sizes of about 10 s to 100 s nanometers are widespread on surfaces of impact glasses, such as glass spherules and glass that welds agglutinates. With flat or mound-like tops, such submicroscopic iron-rich grains typically occur in chains, nets and/or mists, and they were interpreted to be surface adherents that are mainly composed of native iron. Processes such as cooling of iron melt veneer, condensation of iron vapor, and in situ thermal reduction of regolith particles have been separately invoked to explain their origin. Meanwhile, some iron-rich grains have lower hemispheres being embedded in their host glasses, and spherical iron-rich grains with similar sizes, compositions and spatial distributions are also widespread in interiors of their host glasses. It is possible that both the surface and interior iron-rich grains were formed simultaneously during cooling of the host impact melt. However, the precise composition and crystallography of the surface and interior iron-rich grains have not been adequately constrained. In this study, we prepared focused ion beam (FIB) sections for chains of iron-rich mounds that occur on surfaces of impact glasses in the Chang'E-5 lunar regolith. Several FIB sections also exposed interior iron-rich grains that exhibit similar sizes and regular distribution patterns. High-resolution elemental mapping shows that both the surface and interior iron-rich grains are mainly composed of iron and sulfur, and crystallographic inspections reveal that the grains are similarly composed of α-Fe and troilite with varying volume proportions. As the glass spherules and agglutinate glasses are mainly melt products of local regolith materials, both the surface and interior iron-rich grains are most consistent with being formed due to liquid immiscibility between FeS and silicate melt. Troilite preferentially occurs along margins of the iron-rich grains due to heterogeneous distribution of S in the iron-rich melt and the relatively greater compatibility between troilite and silicate melt. The varying morphology of the surface iron-rich grains (e.g., flat tops, mounds) is likely caused by different surface tensions of FeS melt droplets and different wettability between the solidifying Fe-dominating melt and FeS melt with silicate melt. This interpretation predicts that iron-rich grains formed during cooling of impact melt may be dispersed in melt strips and even detached from the melt body during ejecta motion, and they could be subsequently adhered to surfaces of other lunar regolith particles. For reflectance spectra of lunar regolith at visible to near-infrared wavelength, the long-noticed darkening effect caused by submicron-sized iron may be caused by such two-phase iron-rich grains (i.e., α-Fe plus troilite).

Bifunctional Cu-incorporated carbon nanospheres via in-situ complexation strategy as efficient toluene adsorbents and antibacterial agents

Carbon adsorbents have been widely used to remove indoor volatile organic compounds (VOCs), however, the proliferation of bacteria on the carbon adsorbents may deteriorate the indoor air quality and thus pose a serious threat to human health. Herein, we report the synthesis of antibacterial porous carbon spheres (carbonized aminophenol-formaldehyde resin, CAF) with well-dispersed Cu species via an in situ incorporation of Cu2+ during the polymerization of 3-aminophenol-formaldehyde resin followed by a thermal carbonization and reduction process. Compared with CAF, the Cu/CAF-x nanocomposites with Cu loading show a much higher specific surface area (>700 m2 g−1vs. 569 m2 g−1 for CAF). In addition, the pore size of Cu/CAF-x is ranging from 0.7 to 1.68 nm, which is exactly conducive to adsorb the toluene molecules. As a result, the toluene adsorption capacity is improved from 123.50 mg g−1 for CAF to >170 mg g−1 for Cu/CAF-x. More importantly, such adsorbents possess excellent antibacterial performance, the Cu/CAF-10 (10 wt% of Cu loading) with a concentration of 50 μg mL−1 can completely kill the E. coli within 30 min. Our work paves the way to the development of bifunctional adsorbents with both efficient VOCs adsorption and excellent antibacterial performance.

Microstructure and thermoelectric properties of pristine and Al-doped ZnO ceramics fabricated by cost-effective and eco-friendly wet chemistry methods

ZnO has potential as a thermoelectric material for high-temperature applications, but its performance is limited by the strong interconnection between electrical and thermal transportation. In this study we proved that ZnO bulk samples produced from cost-effective and environmentally friendly nitrates via ultrasonic spray pyrolysis and modified chemical precipitation methods followed by spark plasma sintering, demonstrate significantly higher thermoelectric performance than those fabricated from commercially available ZnO powder. To further explore the potential of the developed chemical precipitation technique, we synthesized a series of Al-doped samples with a nominal composition of Zn1–xAlxO (x = 0.02, 0.04, 0.06). The substitutuion of Al into the ZnO structure led to two significant effects: (i) a partial substitution of Zn with Al boosts the power factor; (ii) the formation of the ZnAl2O4 spinel phase acting as scattering center for phonons in addition to the mass and strain fluctuations induced by the partial Zn-Al substitution, both leading to the thermal conductivity reduction. As a result, Al doping led to a threefold enhancement of the thermoelectric performance with zT value of ∼0.12 achieved at 1100 K for the Zn0.94Al0.06O sample.

Regulation of interlayer channels of graphene oxide nanosheets in ultra-thin Pebax mixed-matrix membranes for CO2 capture

For the application of carbon capture by membrane process, it is crucial to develop a highly permeable CO2-selective membrane. In this work, we reported an ultra-thin polyether-block-amide (Pebax) mixed-matrix membranes (MMMs) incorporated by graphene oxide (GO), in which the interlayer channels were regulated to optimize the CO2/N2 separation performance. Various membrane preparation conditions were systematically investigated on the influence of the membrane structure and separation performance, including the lateral size of GO nanosheets, GO loading, thermal reduction temperature and time. The results demonstrated that the precisely regulated interlayer channel of GO nanosheets can provide rapidly CO2-selective transport channels due to the synergetic effects of size sieving and preferential adsorption. The GO/Pebax ultra-thin MMMs exhibited CO2/N2 selectivity of 72 and CO2 permeance of 400 GPU (1 GPU = 10–6 cm3(STP)·cm–2·s–1·cmHg–1), providing a promising candidate for CO2 capture.

Study on reaction mechanism for the synthesis of vanadium nitride by carbothermic reduction nitridation method

Vanadium nitride (VN), as a typical transition metal nitride, has widespread applications in various fields due to its high melting point, high hardness, and excellent thermal and chemical stability. In this study, VN was synthesized through the carbon thermal reduction nitridation method using V2O3 as the main material, and the reaction mechanism was thoroughly examined. Thermodynamic analysis, coupled with thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), revealed that the reaction mechanism was not simply a direct nitridation process nor a two-step coupling of reduction and carburization. Instead, it was the result of multiple reaction mechanisms working in conjunction. Direct nitridation of V2O3 occurred throughout the entire reaction process, while indirect nitridation of VO and VC also occurred with the variation of temperature. A kinetic model was constructed based on the material thermal weight loss curve and revealed that in the carbothermal reduction nitridation system of V2O3, the solid phase reaction followed a three-dimensional diffusion model, with an activation energy of 160.244 kJ/mol, while the gas phase reaction with the solid phase followed a one-dimensional interface model, with an activation energy of 169.015 kJ/mol.

Development of a novel ternary FeWO4/CoP/Mn0.5Cd0.5S composite photocatalyst for photocatalytic hydrogen evolution in watersplitting

The construction of a non-homogeneous photocatalyst system with the advantages of both efficient photogenerated charge separation efficiency and abundant number of active sites remains a major challenge in the field of photocatalysis. A new ternary MnCdS-based photocatalyst combined with FeWO4 and CoP modifications was successfully prepared by chemical precipitation and thermal reduction methods. The ternary FeWO4/CoP/Mn0.5Cd0.5S photocatalyst exhibited a maximum hydrogen evolution activity of 30.45 mmol⋅g−1⋅h−1, which was 6.86 times higher than that of pureMn0.5Cd0.5S. The enhancement of the hydrogen production performance of the FeWO4/CoP/Mn0.5Cd0.5Sphotocatalyst was attributed to the p-n heterojunction constructed at the interface of FeWO4 and Mn0.5Cd0.5S, which strengthened the charge separation ability of the system. On the other hand, the decoration of CoP remarkably diminishes the hydrogen evolution potential of the system and supplies richer active sites for the catalytic reaction.

N2O Consumption by Thermal Decomposition and Reduction with CH4, C2H6 and NH3

ABSTRACTConsumption of nitrous oxide (N2O) by thermal decomposition and reduction with methane (CH4), ethane (C2H6), and ammonia (NH3) were investigated using a micro-flow reactor with controlled temperature profile. N2O mole fractions were measured using a gas chromatograph and mass spectrometers at the maximum wall temperatures from 900 to 1400 K. For N2O thermal decomposition, the measured N2O mole fraction was in good agreement with the prediction using the model proposed by Mulvihill, et al. The low-pressure limit of N2O (+M) = N2 + O (+M) was dominant and H2O showed the largest impact on N2O consumption as a third-body, followed by CO2 and Ar. New third-body coefficients were proposed from the comparison of measured N2O mole fractions with model predictions. For N2O reduction with respective fuels, experiments showed that N2O consumption became greater in the order of C2H6/N2O/Ar ≈ NH3/N2O/Ar > CH4/N2O/Ar > N2O/Ar mixtures. Chemical reaction analyses showed that N2O + H = N2 + OH is the dominant reaction for N2O consumption in all fuel/N2O cases. In the C2H6/N2O case, high rates of H radical production from the fuel radical (C2H5) at a low temperature was identified, resulting in a greater N2O consumption than the CH4/N2O case. In the NH3/N2O case, a reaction of N2O and the fuel radical (NH2) showed high contribution to N2O consumption. Additionally, NNH and H2, the products in N2H2 + H = NNH + H2, produce H radicals through subsequent reactions. These reactions create a cycle of production/consumption of H and OH radicals and promote consumption of NH3 and N2O.

Thermodynamic analysis on CSP integrated cerium oxide (CeO2 − CeO1.72/1.83) water splitting cycle for hydrogen production

Solar thermochemical CeO2-based H2O splitting cycle was thermodynamically analyzed to ascertain the optimal thermal reduction (TH) and re-oxidation (TL) temperatures and evaluate the solar-to-fuel conversion efficiency (ηsolar−to−fuel) of the cycle. The equilibrium composition of CeO2, CeO1.72,CeO1.83 and O2 exhibited that the thermal reduction initiated at 1400 K thereby attaining 100 % TR at 2734 K. The observed variations in Gibbs free energy (ΔG) correspond to the feasibility of the re-oxidation step of CeO1.83 and CeO1.72 at 1050 K and 1200 K respectively. It was reported that the absorption efficiency of solar reactor (ηabs−solar−reactor−WS) decreases from 95.6 % to 37 %, as the TH increases from 1400 K to 2734 K. The results show that ηsolar−to−fuel reached the maximum value of 7.45 % for CeO1.72 and 7.69 % for CeO1.83 at 61.72 % TR of CeO2 without heat recuperation. Further, the ηsolar−to−fuel attained the maximum value of 14.92 % and 13.54 % for CeO1.83 and CeO1.72, respectively at the %TR of CeO2 of 80 % with 50 % heat recuperation. The solar-to-fuel conversion efficiency (ηsolar−to−fuel) further can be increased with the optimization of oxygen partial pressure (PO2) and molar flow rate of reduction regents (Ar or N2).

Phonon thermal transport in ferroelectric α-In2Se3 via first-principles calculations

Two-dimensional (2D) ferroelectrics are promising candidates in the field of microelectronics due to their unique properties such as excellent photoelectric responsiveness. However, the thermal properties of 2D ferroelectrics are less investigated. Here, the thickness dependent thermal conductivity in ferroelectric α-In2Se3 is systematically investigated by the first-principles method combined with the phonon Boltzmann transport equation. On this basis, the strain and oxidation effects on the thermal conductivity of monolayer α-In2Se3 is further studied. The calculation results show that the thermal conductivity has a significant reduction with decreasing film thickness or increasing tensile strain, and the anharmonic phonon–phonon scattering rate is the intrinsic mechanism for the reduction in thermal conductivity. On the other hand, the replacement of Se atoms by O atoms can achieve a bidirectional and wide-range (12×) tuning of thermal conductivity. The increase in specific heat and phonon group velocity is responsible for the thermal conductivity enhancement at high doping levels while that in phonon–phonon scattering rate is responsible for the thermal conductivity reduction at low doping levels. In all cases, acoustic phonons dominate the in-plane thermal transport behavior. These findings broaden our understanding of phonon transport and its control in ferroelectric semiconductor α-In2Se3.

Mott-Schottky heterojunction formation between Co and MoSe2 on carbon nanotubes for superior hydrogen evolution

Molybdenum selenide (MoSe2) has been regarded as an advanced electrocatalyst for the hydrogen evolution reaction (HER). However, its electrocatalytic performance is far inferior to platinum (Pt). Combining semiconductors with metals to construct Mott-Schottky heterojunctions has been considered as an effective method to enhance HER activity. In this work, we report a typical Mott-Schottky heterojunction composed of metal Co and semiconductor MoSe2 on carbon nanotubes (Co/MoSe2@CNT), prepared by a sol-gel process followed by thermal reduction. The characterization and theoretical calculations show that a Co/MoSe2 Mott-Schottky heterojunction can cause electron redistribution at the interface and form a built-in electric field, which not only optimizes the free energy of hydrogen atom adsorption, but also improves the charge transfer efficiency during hydrogen evolution. Thus, the Co/MoSe2@CNT has excellent catalytic activity with a low overpotential of 185 mV at 10 mA cm−2 and a small Tafel slope of 69 mV dec−1. This work provides a new strategy for constructing Co/MoSe2 Mott-Schottky heterojunctions and highlights the Mott-Schottky effect, which may inspire the future development of more attractive Mott-Schottky electrocatalysts for H2 production.

Thermal Constrained Energy Optimization of Railway Cophase Systems With ESS Integration—An FRA-Pruned DQN Approach

This paper investigates the railway co-phase traction power supply system (TPSS) with a power flow controller (PFC) to address the power quality and neutral section issues. To collect the regenerative energy and achieve a more flexible power flow, the energy storage system (ESS) is integrated into the co-phase system. As the key components, the reliability of power electronics modules in PFC and battery cells in ESS is highly related to their thermal performance. It is therefore vital to consider their operational thermal dynamics, leading to the proposal of a deep Q network (DQN) based thermal constrained energy management strategy in this paper. Firstly, the system power flow model and electrothermal models for power electronics modules and battery cells are all established. Then, a DQN method is adopted to learn an optimized policy for peak power shaving while meetings thermal constraints. Finally, an FRA-based pruning method is proposed to reshape the agent to become more compact without sacrificing its performance. Case studies confirm that the proposed strategy can effectively reduce the peak traction power supply by up to 42.0%, and achieve up to 94.1% thermal reduction. The FRA-based pruning can achieve up to 89.9% agent size reduction and 87.2% computation savings.

Optimization of operating conditions in the steam turbine blade cascade using the black-box method

Water droplets cause corrosion and erosion, condensation loss, and thermal efficiency reduction in low-pressure steam turbines. In this study, multi-objective optimization was carried out using the black-box method through the automatic linking of a genetic algorithm (GA) and a computational fluid dynamics (CFD) code to find the optimal values of two design variables (inlet stagnation temperature and cascade pressure ratio) to reduce wetness in the last stages of turbines. The wet steam flow numerical model was used to calculate the optimization parameters, including wetness fraction rate, mean droplet radius, erosion rate, condensation loss rate, kinetic energy rate, and mass flow rate. Examining the validation results showed a good agreement between the experimental data and the numerical outcomes. According to the optimization results, the inlet stagnation temperature and the cascade pressure ratio were proposed to be 388.67 (K) and 0.55 (−), respectively. In particular, the suggested optimal temperature and pressure ratio improved the liquid mass fraction and mean droplet radius by about 32% and 29%, respectively. Also, in the identified optimal operating state, the ratios of erosion, condensation loss, and kinetic energy fell by 76%, 32.7%, and 15.85%, respectively, while the mass flow rate ratio rose by 0.68%.