High Temperature Thermal Process Research Articles

Optimizing thermal performance in internal passage cooling with extended rib: Applying response surface method with artificial neural networks

Efficient cooling technology is crucial for high-temperature gas turbines which are significant applications in thermal processes particularly in industries such as power generation aerospace and marine propulsion. Enhancing cooling efficiency in these systems not only improves energy utilization but also plays a critical role in reducing fuel consumption increasing operational reliability and minimizing environmental impacts. This research focuses on optimizing the thermal performance of internal passage cooling channels with extended ribs using a combination of the response surface method and artificial neural networks. By varying the extended rib length and rib width the study aims to enhance heat transfer and minimize flow loss leading to improvements in overall system efficiency. Latin Hypercube Sampling is employed to strategically select variables and automated numerical simulations are conducted to perform a thorough parametric analysis. A steady-state k-ω shear stress transport turbulence model is applied in the simulations and the numerical results are validated against experimental data ensuring accuracy. The combined response surface method–artificial neural network approach integrated with TensorFlow-based modeling allows for the prediction of heat transfer and friction factor ultimately generating a comprehensive response surface to identify the optimal design point. Applying the optimized design leads to a 23.99 % improvement in the thermal performance factor compared to the reference case. The findings of this study highlight a significant enhancement in the thermal performance of the cooling channel structure particularly in high heat flux environments. This research provides valuable insights into the design of more efficient thermal management systems for gas turbines and has broader implications for other high-temperature thermal processes. The proposed optimization methodology offers a reliable approach for improving cooling technologies contributing to the development of the next generation of energy-efficient high-performance gas turbines and other industrial applications where effective thermal management is essential.

Optimization of high-temperature thermal pretreatment conditions for maximum enrichment of lithium and cobalt from spent lithium-ion polymer batteries

Due to their increasingly high demand, lithium-ion batteries (LIBs) will encounter a scarcity of essential resources if recycling is not prioritized. The current pretreatment methods for spent LIBs used in industrial production are inefficient, costly, and hazardous. The study aimed to maximize the yield of lithium and cobalt from the black mass of spent Lithium-ion batteries through an optimized high-temperature thermal pretreatment process, which combined mechanical (direct crushing) and thermal treatments to facilitate the subsequent recovery of these valuable metals. Sieve analysis showed that direct crushing for 2 min resulted in 40.81 % of the anode material in the 4750 + 2500 μm size range, while 5 min of crushing led to a more even distribution, with 28.57 % in the smallest size range (−75 μm). Heat treatment followed by 2 min of crushing concentrated 52.38 % of the anode material in the 4750 + 2500 μm range. For the cathode material, 2 min of direct crushing distributed 24.49 % in the −2500 + 1250 μm range, while 5 min of crushing accumulated 38.80 % in the −75 μm range. Heat treatment and 2 min of crushing resulted in 56.05 % of the cathode material in the −75 μm range, indicating improved liberation. The combination of heat treatment and mechanical treatment effectively liberates and reduces the size of the active materials, resulting in a higher cumulative mass fraction of finer particles (≤630 μm). Heat treatment at 600 °C for 15 min, followed by 2 min of crushing, dissociated current collectors (Al) from the cathode material, minimized the harmful gas emissions and produced fine particles (630 μm) with minimal Al content (0.8 wt%). The optimal heat treatment condition of 600 °C for 35 min achieved complete decomposition of PVDF and enriched 73.49 wt% cobalt and 5.41 wt% lithium in the black mass, superior to previous studies.

A Planar-Cavity Receiver Configuration for High-Temperature Solar Thermal Processes

Next-generation concentrating solar thermal power (CSP) technologies target a wide spectrum of applications including electricity generation, thermochemical processes, and industrial process heat for broad decarbonization potential. Many of these applications require higher temperatures than those of current commercial nitrate salt systems. Particulate materials are promising candidates for next-generation high-temperature heat transfer and low-cost storage media and can facilitate operation over a wide temperature range. However these materials necessitate novel receiver configurations to accept the high incident flux concentrations that enable high solar-to-thermal receiver efficiency. One option is a novel light-trapping planar cavity receiver configuration in which small cavity-like structures are formed from opaque planar surfaces such that a high incident flux concentration at the cavity aperture is reduced to a wall-absorbed solar flux concentration that is manageable within limited wall-to-particle heat transfer rates. The paper introduces the receiver configuration and provides calculated optical performance for a preliminary 50 MWt receiver design.

Applicability of Non-PGM Bi-Functional Electrocatalyst in a Scaled-up Anion Exchange Membrane Water Electrolysis

While non-precious metal catalyst materials are crucial for AEMWE systems, catalyst substances possessing both adequate hydrogen molecule adsorption ability and suitable electrical conductivity and hydrophilicity are still in the developmental stage.Ni-Mo alloy metals are known as those that have appropriate hydrogen molecule adsorption binding energy, making them excellent electrochemical catalysts for the cathode. However, they suffer from a high content of oxide, which hampers electrical conductivity, and the formation of a high oxidation state of Ni molecules, making hydrogen molecule detachment challenging.On the other hand, Ni-Fe alloys are recognized for their excellent -OOH group adsorption ability and high electrical conductivity, and that has a low oxidation state Ni phase for high hydrogen desorption ability.Therefore, in this study, we aimed to synthesize NiMoFe-based alloy catalysts to enhance the hydrogen evolution reaction (HER) activity of Ni-Mo group catalysts while simultaneously increasing the oxygen evolution reaction (OER) activity. Using a hydrothermal synthesis method for NiMoFe catalysts we employed a high-temperature thermal reduction process to minimize the oxide layer that has poor conductivity.Evaluation of the catalyst activity through half-cell experiments demonstrated low overpotentials in both Overall water electrolysis reactions. Furthermore, an MEA-type experiment was conducted to evaluate the applicability of single-cell.Furthermore, Stability tests confirmed a stable voltage.Finally, when compared to the combination of precious metal catalysts, this exhibited superior performance. Therefore, this study suggests that non-noble catalysts could serve as a crucial stepping stone, surpassing PGM metal catalysts in alkaline media.

Deterioration Mechanism and Status Prediction of Hydrocarbon Lubricants under High Temperatures and Humid Environments

In practical engineering applications, high temperatures and water ingress seriously affect the service life of hydrocarbon lubricants. In this study, the deterioration process of hydrocarbon lubricants under high temperatures and humid environments was investigated, and a new health state prediction model was proposed. Simulation of hydrocarbon lubricant Polyalpha−olefin (PAO) molecules used the ReaxFF force field to analyse the high temperature thermal oxidation process of lubricants. The rheological properties of oil−water emulsions were determined by observing the morphology of oil−water two−phase mixtures with different water contents. A multiparameter fusion viscosity prediction model was proposed using a linear model of the viscosity of aqueous fluids, as affected by temperature and water content, and was fitted with the Andrade viscosity−temperature equation to predict lubricant viscosity changes under multiple parameters. Online validation tests were carried out on a compound planetary transmission system, and the surface topographical parameters of the transmission components were further discussed. Experimental results show that the linear correlation with the improved lubricant viscosity prediction model is 0.966, and the surface wear of transmission components is consistent with the trend of lubricant quality change. These findings provide a fundamental basis for the assessment of lubricant service life in high temperatures and humid environments.

Update on the ASTRI High-Temperature Solar Sodium Facility

The Australian Solar Thermal Research Institute (ASTRI) has been developing technologies designed to collect and store solar energy at high-temperature to drive more efficient power cycles, or for providing heat to high-temperature thermal industrial processes. ASTRI is pursuing two alternative pathways: one is based on the use of liquid sodium as a heat transfer fluid, and the other is based on the use of solid fluidous particles. The current work describes ASTRI’s completion of the design and construction of a nominal 1MW high-temperature solar sodium test facility, which will be operational at CSIRO’s solar field at the National Energy Centre in Newcastle, Australia, by 2024.

Fate of perfluoroalkyl and polyfluoroalkyl substances (PFAS) through two full-scale wastewater sludge incinerators.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are an emerging issue in wastewater treatment. High-temperature thermal processes, incineration being time-tested, offer the opportunity to destroy and change the composition of PFAS. The fate of PFAS has been documented through wastewater sludge incinerators, including a multiple hearth furnace (MHF) and a fluidized bed furnace (FBF). The dewatered wastewater sludge feedstock averaged 247- and 1280-μmol targeted PFAS per sample run in MHF and FBF feed, respectively. Stack emissions (reportable for all targeted PFAS from MHF only) averaged 5% of that value with shorter alkyl chain compounds comprising the majority of the targeted PFAS. Wet scrubber water streams accumulated nonpolar fluorinated organics from the furnace exhaust with an average of 0.740- and 0.114-mol F- per sample run, for the MHF and FBF, respectively. Simple alkane PFAS measured at the stack represented 0.5%-4.5% of the total estimated facility greenhouse gas emissions. PRACTITIONER POINTS: The MHF emitted six short chain PFAS from the stack, which were shorter alkyl chain compounds compared with sludge PFAS. The FBF did not consistently emit reportable PFAS from the stack, but contamination complicated the assessment. Five percent of the MHF sludge molar PFAS load was reported in the stack. MHF and FBF wet scrubber water streams accumulated nonpolar fluorinated organics from the furnace exhaust. Ultra-short volatile alkane PFAS measured at the stack represented 0.5%-4.5% of the estimated facility greenhouse gas emissions.

Facile interfacial defect healing in solution-processed In-Ga-Zn-O thin film transistor through rapid intense pulsed light annealing

We introduce intense pulsed light (IPL) annealing as a versatile and cost-effective interface treatment approach for solution-processed In-Ga-Zn-O thin film transistor, focusing on its potential to improve its operational stability. We fabricate solution-processed IGZO-based thin film transistors (IGZO-TFTs) and systematically investigate the dependence of IPL shot numbers on key parameters that dictate the electrical characteristics of the devices. Under identical positive bias stress (PBS) conditions, we compare the operational stability of IGZO-TFTs treated with IPL annealing during ∼5 min to those subjected to conventional high-temperature thermal processes during 2 h, and reveal that IPL-annealed IGZO-TFTs exhibit superior stability as well as significantly suppressed threshold voltage shifts by ∼22 % (from 3.31 to 2.58 V). To gain deeper insights, we employ photo-excited charge collection spectroscopy analysis, which provides quantitative evidence of the rapid recovery of oxygen vacancies and hydrogen-related interfacial defect states (located at 2.1 ∼ 2.5 eV and near 2.79 eV below conduction band minimum) affecting operational device stability. Our findings underscore the technical advantages of IPL annealing over time-consuming thermal processes, positioning it as a promising method for optimizing IGZO-TFT performance.

Z-scheme WOx/Cu-g-C3N4 heterojunction nanoarchitectonics with promoted charge separation and transfer towards efficient full solar-spectrum photocatalysis

Construction of Z-scheme heterojunctions has been considered one superb method in promoting solar-assisted charge carrier separation of carbon-based materials to achieve efficient utilization of solar energy in hydrogen production and CO2 reduction. One interesting concept in nanofabrication that has become trend recent years is nanoarchitectonics. A heterostructure photocatalyst constructed based on the idea of nanoarchitectonics using the combination of g-C3N4, metal and an additional semiconducting nanocomposite is investigated in this paper. Z-scheme tungsten oxide incorporated copper modified graphitic carbon nitride (WOx/Cu-g-C3N4) heterostructures are fabricated via immobilization of WOx on Cu nanoparticles modified superior thin g-C3N4 nanosheets. Mechano-chemical pre-reaction and a two-step high-temperature thermal polymerization process are the keys in attaining homogeneous distribution of Cu nanoparticles in g-C3N4 nanosheets. The horizontal growth of homogeneously distributed WOx nanobelts on Cu modified g-C3N4 (Cu-g-C3N4) base via solvothermal synthesis is achieved. The photocatalytic performances of the heterostructures are evaluated through water splitting and CO2 photoreduction measurements in full solar spectrum irradiation condition. The presence of Cu nanoparticles in the composite system improves charge transport between g-C3N4 and WOx and thus enhances the photocatalytic performances (H2 generation and CO2 photoreduction) of the composite material, while the presence of WOx nanocomposites enhances light absorption of the composite material in the near infrared range. The synthesized heterostructure with optimized WOx to Cu-g-C3N4 ratio and in case of no co-catalyst addition exhibits enhanced photocatalytic H2 evolution (4560 μmolg-1h−1) as well as excellent CO2 reduction rate (5.89 μmolg-1h−1 for CO generation).

선택적 레이저 소결을 이용한 유연인쇄전자소자 제작

It is necessary to develop a low temperature process that can deposit and pattern metal on a heat sensitive substrate because most flexible printed electronics use high temperature sensitive materials such as plastic. The most commonly used photolithography process is not suitable for flexible printed electronics because the high temperature thermal treatment process and chemicals are not compatible with plastic. Recently research has been actively conducted on a method of minimizing thermal damage to plastic and high-resolution metal patterning by using selective laser sintering after forming a liquid metal nanoparticle thin film without using existing photolithography and vacuum deposition. In this review paper, we explore flexible printed electronics such as flexible thin film transistors and flexible transparent conductors using selective laser sintering of nanomaterials and discuss future development directions.

Excellent HZO ferroelectric thin films on flexible PET substrate

The development of flexible memory devices has been attracting more and more interests to advance next-generation lightweight and wearable electronics. Though HfO2-based ferroelectric thin film has shown promising future for the mass-production of low-cost ferroelectric memory, the fabrication of HfO2-based ferroelectric devices on thermosensitive flexible substrates has been a practical challenge due to the necessity of a high temperature thermal process to reach its potential of ferroelectric high-performance. In this work, a flexible Pt/W/Hf0.5Zr0.5O2/W/Pt multilayer stack with excellent ferroelectric properties is fabricated on PET by a controlled spalling technology, which is simple, reliable and cost-efficient. AFM characterizations proved that multilayer film exhibited a smooth surface after spalling process, and the e-testing results showed that Hf0.5Zr0.5O2 film did not show obvious deterioration in ferroelectric properties during spalling and transfer. Furthermore, the flexible Hf0.5Zr0.5O2 ferroelectric films maintained superior polarization, retention, and endurance performance under a series of bending deformations and cycling tests, indicating its outstanding mechanical resilience. This work is of great significance for the practical application of new HfO2-based thin film flexible ferroelectric memory in wearable electronics.

Metal Ion Cutting-Assisted Synthesis of Defect-Rich MoS2 Nanosheets for High-Rate and Ultrastable Li2S Catalytic Deposition.

Active metal ions often show a strong cutting effect on the chemical bonds during high-temperature thermal processes. Herein, a one-pot metal ion cutting-assisted method was adopted to design defect-rich MoS2-x nanosheet (NS)/ZnS nanoparticle (NP) heterojunction composites on carbon nanofiber skeletons (CNF@MoS2-x/ZnS) via a simple Ar-ambience annealing. Results show that Zn2+ ions capture S2- ions from MoS2 and form into ZnS NPs, and the MoS2 NSs lose S2- ions and become MoS2-x ones. As sulfur hosts for lithium-sulfur batteries (LSBs), the CNF@MoS2-x/ZnS-S cathodes deliver a high reversible capacity of 1233 mA h g-1 at 0.1 C and keep 944 mA h g-1 at 3 C. Moreover, the cathodes also show an extremely low decay rate of 0.012% for 900 cycles at 2 C. Series of analysis indicate that the MoS2-x NSs significantly improve the chemisorption and catalyze the kinetic process of redox reactions of lithium polysulfides, and the heterojunctions between MoS2-x NSs and ZnS NPs further accelerate the transport of electrons and the diffusion of Li+ ions. Besides, the CNF@MoS2-x/ZnS-S LSBs also show an ultralow self-discharge rate of 1.1% in voltage. This research would give some new insights for the design of defect-rich electrode materials for high-performance energy storage devices.

Pollution Characteristics and Emission Factors of PCDD/Fs from Iron and Steel Industry

The pollution level, emission characteristics, and emission factors of PCDD/Fs from a number of steel plants were investigated in a particular province of China. The results showed that the concentration of PCDD/Fs was at a low level and decreased by 1-2 orders of magnitude compared with that in 2005-2019. In detail, the concentrations of PCDD/Fs ranged from 0.003-0.557 ng·m-3(I-TEQ), and the mean value was 0.165 ng·m-3 for the sintering process. Moreover, the concentrations of PCDD/Fs ranged from 0.006 to 0.057 ng·m-3, and the mean value was 0.025 ng·m-3 for the electric furnace process. In addition, the concentration of PCDD/Fs in the iron and steel industry from 2005 to 2020 increased first and then decreased, especially after the implementation of the new emission standard and the ultra-low emission control of conventional pollutants such as smoke, showing a significant decline. The results of fingerprint analysis showed that 2,3,7,8-TCDF was the largest congener contributing to the mass concentration, and lower chlorinated PCDFs were increased. This result differed from those of previous studies in which highly chlorinated PCDFs and PCDDs dominated, indicating that the generation source of PCDD/Fs had changed. The congener and isomer profiles of PCDD/Fs in flue gas from the sintering process were similar to those in the flue gas from the electric furnace process. Additionally, showing the characteristics of the typical high-temperature thermal process, the de novo synthesis may be the dominant mechanism of formation of PCDD/Fs in the sintering process and electric furnace process. The emission factor was 0.003-0.5 μg·t-1 (I-TEQ), and the average emission factor was (0.18±0.22) μg·t-1 for the sintering process. The emission factor was 0.04-0.5 μg·t-1, and the average emission factor was (0.27±0.23) μg·t-1 for the electric furnace process. These values were far lower than those of the standard toolkit for identification and quantification of dioxin and furan emissions released by UNEP in 2013 and the emission factors in the dioxin emission inventory of China in 2004. It is suggested that the emission factors of PCDD/Fs in the iron and steel industry of China should be studied and updated.

N-doped graphene film prepared by rapid thermal shock for ultra-sensitive temperature reading

Graphene is restricted by its zero-band gap when applying in functional components. However, its band structure can be adjusted appropriately through nitrogen doping. At present, many nitrogen doping processes have been developed such as chemical vapor deposition, thermal annealing and plasma sputtering, but in general these methods are time-consuming and difficult to control the type of nitrogen atom doped. In this work, an in situ high-temperature thermal shock process, with an extremely fast rate of temperature change of more than 104 K/s, is developed and used to prepare the nitrogen doped graphene (NG) films. This novel N-doped process enables the preparation of NG films within 10 s, which is the fastest to the best of our knowledge. Moreover, the type and content of doped nitrogen atoms can be effectively regulated by controlling the composition of precursor films. Optimally, the nitrogen content of NG film reaches 2.26 %, and the proportion of graphite nitrogen is more than 60 %. The electrical conductivity and the average Seebeck coefficient of the NG film are 13,870 S·m−1 and −46.5 μV/K, respectively. Its thermoelectric power factor reaches 30 μW·m−1·K−1, indicating that the NG film has a good prospect of functional application. Furtherly, A NG film-based temperature reading device is developed, which shows ultra-high accuracy and sensitivity in temperature reading within a rather wide temperature range.

Ultra-high temperature oxidation resistance of a novel (Mo, Hf, W, Ti)Si2 ceramic coating with Nb interlayer on Ta substrate

In order to solve the challenge of recyclability of tantalum substrates in high temperature oxidation environments, a novel MoSi2-WSi2-HfSi2-TiSi2 composite ceramic coating containing an Nb interlayer was prepared on the surface of tantalum substrate by a three-step method. The mix ceramic silicide coating exhibited superior performance and effective protection for 10.2 h at 1800 °C, possibly due to the formation of an outer SiO2-HfO2-HfSiO4 composite oxide film with low oxygen permeability, moderate viscosity and thermal expansion coefficient, as well as good self-healing ability. Furthermore, the coating successfully passed 537 thermal cycles from room temperature to 1800 °C. The presence of Nb interlayer significantly mitigated the thermal mismatch between the ceramic coating and the tantalum substrate, and the bidirectional diffusion of Nb element during the high temperature oxidation and thermal shock process further reduced the tendency of the coating to crack.

Hard Carbons for Use as Electrodes in Li-S and Li-ion Batteries.

Activated hard carbons, obtained from the pyrolysis of various waste biomasses, were prepared and characterized for use as the active material for the fabrication of battery electrodes. The preparation consisted of a pyrolysis process, followed by an activation with KOH and a further high-temperature thermal process. TG and DTA were used to discriminate the steps of the activation process, while SEM, XRD, and Raman characterization were employed to evaluate the effects of activation. The activated carbons were tested as electrodes in lithium-sulfur and lithium-ion batteries. The carbonaceous materials coming from cherry stones and walnut shells have proved to be particularly suitable as electrode components. When used as anodes in lithium-ion batteries, both carbons exhibited a high first cycle discharge capacity, which was not restored during the next charge. After the first two cycles, in which there was a marked loss of capacity, both electrodes showed good reversibility. When used as cathodes in lithium-sulfur batteries, both carbons exhibited good catalytic activity against the redox reaction involving sulfur species with good cycle stability and satisfactory Coulombic efficiency.

Effect of surface brittle-to-ductile transition on high-temperature thermal shock resistance of Al2O3 ceramics

The effect of surface brittle-to-ductile transition (BDT) on the high-temperature thermal shock resistance (TSR) of Al2O3 ceramics was investigated by quenching in a cold compressed-air flow. The brittle-to-ductile transition (BDT) and transition temperature were determined from the transformation in fracture mechanism via measuring flexural strength at elevated temperatures. Effects of cooling rate on the residual strength and microstructural evolution of Al2O3 ceramics were systematically studied. Results showed that the BDT temperature in Al2O3 ceramics was around 1000 °C. The BDT mechanism is associated with the softening of the grain boundary glass phase, which permits a certain degree of crack passivation to reduce thermal stress concentration. Compared with the original strength of 375 MPa, the residual strength of the specimen decreased rapidly to 190 MPa at a final temperature of 700 °C, while the residual strength of the specimen was maintained to 352 MPa at a final temperature of 1000 °C. The appearance of surface BDT in Al2O3 ceramics during the high-temperature thermal shock process produces a favorable impact on improving the residual strength of specimens by blunting the crack tip and reducing the surface thermal stress. Therefore, the surface BDT in Al2O3 ceramics is beneficial to the improvement of the high-temperature TSR of Al2O3 ceramics.

Introduction of high tensile strain into Ge-on-Insulator structures by oxidation and annealing at high temperature

It is demonstrated in this work that a high-temperature thermal process including oxidation and N2 annealing at 850 °C can provide a tensile strain of ∼0.58% at maximum into Ge-on-Insulator (GOI) structures without any special patterning or external stressors. The different impacts of oxidation and annealing on tensile strain generation, surface roughness, and crystal qualities in the GOI structures fabricated by Ge condensation and wafer bonding are systematically examined. A tensile strain of 0.47% is achieved without severe thermal damages under the optimal thermal process condition, which indicates the high potential of the present method for improving the performance of GOI n-channel metal-oxide-semiconductor field-effect transistors. The influence of thermal expansion mismatch between Ge and SiO2 is suggested as a possible physical origin of the high amount of tensile strain into GOI structures.

The Spin Modulation Stimulated Efficient Electrocatalytic Oxygen Evolution Reaction over LaCoO3 Perovskite.

Perovskite is a promising non-noble catalyst and has been widely investigated for the electrochemical oxygen evolution reaction (OER). However, there is still serious lack of valid approaches to further enhance their catalytic performance. Herein, we propose a spin state modulation strategy to improve the OER electrocatalytic activity of typical perovskite material of LaCoO3 . Specifically, the electronic configuration transition was realized by a simple high temperature thermal reduction process. M-H hysteresis loop results reveal that the reduction treatment can produce more unpaired electrons in 3d orbit by promoting the electron transitions of Co from low spin state to high spin state, and thus lead to the increase of the spin polarization. Electrochemical measurements show that the catalytic performance of LaCoO3 is strongly dependent on its electronic configuration. With the optimized reduction treatment, the overpotential for the OER process in 0.5 M KOH electrolyte solution at 10 mA cm-2 current density was 396 mV, significantly lower than that of the original state. Furthermore, it can mediate efficient OER with an overpotential of 383 mV under an external magnetic field, which is attributed to the appropriate electron filling. Our results show that electron spin state regulation is a new way to boost the OER electrocatalytic activity.

Novel High-Flux Indoor Solar Simulator for High Temperature Thermal Processes

Novel High-Flux Indoor Solar Simulator for High Temperature Thermal Processes