High-temperature Characteristics Research Articles

Influence of Water Immersion Time on Re-Ignition Characteristics of High Temperature Oxidized Coal

ABSTRACT After a coal seam is mined, the oxidized coal left in its goaf is prone to water immersion, and spontaneous combustion accidents involving water-immersed coal may easily occur when mining the underlying coal seam. Using scanning electron microscopy and nitrogen adsorption experimental methods, the physical structure of high-temperature pre-oxidized water-immersed coal samples was characterized. By means of infrared spectroscopy, electron spin resonance (ESR) and simultaneous thermal analysis, the microscopic characteristics of the coal samples and the endothermic and exothermic characteristics of the oxidative combustion process were studied. The results showed that a specific pre-oxidation soaking time generated more oxidation pores in the coal sample, causing more water to become trapped in the pores and increasing the secondary oxidation heat absorption. High-temperature oxidation promoted the conversion of coal sample functional groups (FG) and free radical active sites, Water immersion led to the formation and loss of FG, and the longer the water immersion time was, the greater the loss. The larger average pore size of the pre-oxidized water-immersed coal sample provided more coal-oxygen contact sites, and the breaking of chemical bonds in the FG during the secondary oxidation process accelerated the heat release and promoted the oxidative re-ignition of the coal sample. The spontaneous combustion of water-immersed coal in the goaf can be prevented by controlling the high oxidation temperature and water immersion time.

Study on high-temperature and high-voltage insulation characteristics of polypropylene blend with highly packed elastomeric domains for power cable applications

In this paper, we report the high-temperature and high-voltage (HV) insulation characteristics of the polypropylene (PP) blend with highly packed elastomeric domains that showed excellent mechanical toughness in our previous study to find its suitability as insulation material for power cable applications. The main focus lies on tensile properties with thermal aging, thermomechanical behavior corresponding to the thermal transition, high-temperature volume resistivity and DC dielectric strength, and space charge accumulation behavior of the PP blend in comparison to the crosslinked polyethylene (XLPE). Our PP blend having low elastic modulus of approximately 266.9 MPa exhibited high tensile strength and elongation at break, and high-temperature stability as well. Using this PP blend, not only good HV insulating performances in volume resistivity and DC breakdown strength (BDS) were obtained similar to XLPE, but also adequate values were obtained at high temperature, even at 110 °C, which was not possible with XLPE. However, there was space charge accumulation and electric field distortion in the PP blend like XLPE, which needs to be suppressed. Therefore, our PP blend is expected to have the potential to replace existing XLPE as insulation materials for future HV power cables.

Experimental investigation of performance properties of asphalt binder and stone matrix asphalt mixture using waste material and warm mix additive

Many distresses occur in the pavement due to the increase in traffic and changes in weather conditions through the year (hot to cold). Asphalt binder modification is the best way to control these stresses. On the other hand, utilization of warm mix asphalt additives has significant environmental benefits. This research investigates the influence of simultaneous usage of two waste material (ground tire rubber (5%, 10% 15%, and 20% by weight of asphalt binder) and natural bitumen (10%, 20%, 30%, and 40% by weight of asphalt binder)) on performance behavior of asphalt binders and mixtures containing warm mix asphalt additive. Performance behavior of binders and mixtures were evaluated by several tests such as; conventional asphalt binder tests, linear Amplitude Sweep (LAS), Multiple Stress Creep Recovery (MSCR), Bending Beam Rheometer (BBR), Dynamic Shear Rheometer (DSR), storage stability, resilient modulus, indirect tensile strength, dynamic creep, hamburg wheel track, and four point beam fatigue (FPB) tests. The statistical analysis was performed to investigate the additives have significant effect or not. Results revealed that fatigue and rutting performance of samples were improved by combination of waste materials. Addition of waste natural bitumen led to decreases the low-temperature behavior of asphalt binder, while addition of waste ground tire rubber improves the resistance against low-temperature cracking. Addition of natural bitumen up to 10% has positive impact on storage stability of binder and by adding more content of additive, phase separation occurred. Warm mix additives improve the fatigue and rutting resistance of mixtures containing waste materials. Adding 20% CR to 30% Gilsonite -modified binder causes an enhanced the high temperature characteristics of about 34%. Based on outcomes, waste ground tire rubber enhances the fatigue resistance of mixtures containing natural bitumen. In general, utilization of waste materials in combination with warm mix additives improve the performance properties of asphalt binder and mixture. Mr of mixtures, containing 40% Gilsonite, was 52% greater compared to base mixture. Nonetheless, 30% Gilsonite as well as 5% CR had Mr values nearly 44% higher compared to base mixture. Also, based on statistical analysis, addition of mentioned additives has significant effect on improving the performance of specimens.

Effect of High-Sintering-Temperature Reduction Behavior on Coke Solution Loss Reaction with Different Thermal Properties

With the shortage of high-quality coking coal resources and the pursuit of low-cost smelting, the types and sources of coal have changed. Therefore, it is difficult to establish an effective correlation between the existing evaluation indexes of coke thermal performance and the production indexes of the blast furnace. The dissolution deterioration of coke directly affects the production benefits of the blast furnace, and the dissolution deterioration of blast furnace coke is the result of ore–coke coupling. To better understand the mechanism of the coupling reaction relative to the thermal properties of coke, this paper experimentally studies ore–coke coupling between two kinds of coke and one kind of blast furnace standing sinter which have different reactivities but are used in practical applications. This method adopts a matched thermogravimetric device. By analyzing and calculating the high-temperature reduction behavior and characteristics of the sinter and the dissolution loss behavior and characteristics of coke in the gas–solid coupling reaction test of coke and sinter, and comparing and fitting the coupling reaction factors of the coupling reaction and the thermal properties of coke, it was revealed that the real degradation behavior of coke was affected by the reduction reaction of the sinter. The results show that the temperature range with the best matching degree between the reduction reaction of oxygen supply from sinter and the gasification reaction of oxygen consumption from coke is at a position where the coupling factor is closest to 1. In the gas–solid coupling reaction between low-reactivity coke and sinter, the strongest dissolution rate, RCSL, is approximately 1200 °C, while in the gas–solid coupling reaction between high-reactivity coke and sinter, the RCSL is approximately 1100 °C. The minimum strength, CSCSL, of high-active coke and sinter after dissolution is approximately 1100 °C, while that of low-active coke and sinter after dissolution is approximately 1200 °C. It is shown that there is a good linear relationship between the RCSL of high- and low-reactive coke and strength after dissolution loss CSCSL.

High-temperature deformation characteristics of 3D printing of nano-ceramic materials

In order to improve the application effect of three-dimensional printing of nano ceramic materials, the high-temperature deformation characteristics of three-dimensional printing of nano ceramic materials were studied. First, the main raw materials and experimental instruments for preparing nano ceramic materials were selected. Then, high-temperature nano ceramic materials were prepared by using 8%, 12%, and 15% polyester modified silicone resins respectively; And put it into the storage box of the direct writing 3D printer to print the 3D ceramic sample with the 3D printer. At last, the high temperature deformation characteristics under different high temperature environments are analysed. The results show that the adhesive force and salt spray resistance of 12% polyester modified silicone resin 3D ceramic specimens are good, and the bending strength of 12% polyester modified silicone resin 3D ceramic specimen is high, its structural stability is good, and the deformation value is small under the same high temperature environment.

A new method of parameter identification for proton exchange membrane fuel cell based on hybrid particle swarm optimization with differential evolution algorithm

With the characteristics of high energy conversion efficiency, high energy den?sity and low operating temperature, the proton exchange membrane fuel cells (PEMFC) have become one of the green energy sources with broad prospects. The establishment of accurate mathematical model of the PEMFC is the basis of simulation and control strategy. At present, some intelligent algorithms have certain drawbacks, and can hardly find the balanced point between precision and computational time. In this study, a novel parameter identification approach com?bining the hybrid particle swarm optimization (PSO) algorithm with differential evolution, i.e. hybrid DEPSO, is proposed to obtain the unknown parameters in the PEMFC mathematical model and solve the problems of premature convergence of PSO and poor global search ability of differential evolution. Six benchmark functions are applied to verify the performance of the algorithm. The results prove that the hybrid DEPSO can evade local optimum preferably while having swifter convergence rate. Two PEMFC stacks are investigated and modeled. In order to evaluate the accuracy of model, the sum of squared errors between the measured voltage and the estimated output voltage are examined. Numerical results show higher accuracy of the hybrid DEPSO-based model comparing with other recently published optimization approaches. Furthermore, the simulation results indicate that the accuracy of the PEMFC model optimized by the hybrid DEPSO algorithm improves 0.19-1.86%, which can provide a new solution the multi-objective opti?mization problem and promote the practical application of the PEMFC.

Spatial and Temporal Characteristics of Extreme High Temperature in Altay Prefecture of Xinjiang in Recent 40 Years

Spatial and Temporal Characteristics of Extreme High Temperature in Altay Prefecture of Xinjiang in Recent 40 Years

Evaluation of the Applicability of Three Methods for Climatic Spatial Interpolation in the Hengduan Mountains Region

Abstract An ideal spatial interpolation approach is indispensable for obtaining high-quality gridded climatic data in mountainous regions with scarce observations, particularly for the Hengduan Mountains Region (HMR) with dense longitudinal ranges and gorges. However, there is much controversy about the applicability of thin plate smooth spline (TPSS), cokriging, and inverse distance weighting (IDW) in mountainous regions. Here, we use the daily observations of temperature and precipitation at 125 stations in HMR and its surroundings from 1961 to 2018 and adopt three interpolation methods to map the annual average temperature and precipitation at a resolution of 500 m in HMR. Then, we assess the applicability of three interpolation methods in HMR from the perspectives of interpolation accuracy and effects. The evaluation implies a satisfactory interpolation accuracy of TPSS with the highest correlation and lowest error, whether for temperature (R2 = 0.92, RMSE = 1.2°C) or precipitation (R2 = 0.54, RMSE = 165.9 mm). In addition, the TPSS could better display the temperature (precipitation) gradient along elevation and depict dry valleys’ high-temperature and low-precipitation characteristics. Moreover, the satisfactory interpolation performance of TPSS mainly benefits from the screening of optimal TPSS model that varied primarily with the regional topography feature and meteorological observation density. The uncertainty of gridded climate datasets has become an urgent problem to solve in the complex terrain. This research illustrates the satisfactory applicability of TPSS for climatic spatial interpolation in HMR, providing theoretical support for high-precision interpolation in complex terrain, hopefully improving the regional weather forecasts and disaster warnings.

Resource utilization of High-Ti vanadium titanomagnetite: Preparation and properties of sinter

In order to achieve the goal of resource utilization of High-Ti vanadium titanomagnetite (High-Ti VTM), the high-temperature sintering characteristics of High-Ti VTM were investigated by micro-sintering experiments, while the effects of different ordinary iron ore dosage and basicity on the sintering process parameters and sinter quality were investigated by sintering pot experiments. The results showed that the TiO2 and SiO2 contents increased gradually with increasing dosage of High-Ti VTM, and the liquid phase fluidity index and binder phase strength increased gradually, while the assimilation temperature and intergranular consolidation strength showed a decreasing trend. With the increase of the dosage of ordinary iron ore, the vertical sintering speed was reduced, while the sinter yield and tumble index gradually increased. As the basicity of the sinter gradually increased, the sintering time and the pulverization degree of the sinter gradually increased and the sinter yield gradually decreased, while the vertical sintering speed and the tumble index both showed a trend of first increasing and then decreasing. The results of the study provide data to support the preparation of sinter with High-Ti VTM.

Numerical Study of High-Temperature Gas Transport Characteristics During the Continuous Welding Process

Numerical Study of High-Temperature Gas Transport Characteristics During the Continuous Welding Process

Study on the high and low temperature performance of nano alumina modified asphalt mixture

To improve the high and low temperature performance of asphalt mixture, nano alumina was used as additive in this study. Firstly, the high temperature characteristics of asphalt mixture with different content of nano alumina were studied by rutting test and dynamic creep test. Secondly, the fatigue properties of modified asphalt mixture at different temperature were tested by indirect tensile fatigue test. Finally, the low temperature bending test and indirect tensile test were used to evaluate the low temperature performance. The results show that nano alumina can improve the high temperature and fatigue properties of asphalt mixture to some extent, while the low temperature performance decreases slightly.

ŁUKASIEWICZ RESEARCH NETWORK – INSTITUTE FOR FERROUS METALLURGY – CURRENT AND FUTURE RESEARCH ACTIVITIES

At the beginning of 2023, Łukasiewicz Research Network – Institute for Ferrous Metallurgy (Łukasiewicz – IMŻ) begins its activity in the structure of a new institute under the name of Łukasiewicz Research Network – Upper Silesian Institute of Technology, after consolidation with Łukasiewicz – Institute of Welding and Łukasiewicz – Institute of Electrical Drives and Machines KOMEL. On the eve of this change, this study presents the research achievements of Łukasiewicz – IMŻ in 2022 and the topics planned to be undertaken in 2023. It takes into account projects financed from the national and EU budget for science, as well as the significant involvement of the Institute in the implementation of applied projects that contribute to increasing the innovativeness of the domestic industry, including the energy and defence sectors. Attention was paid to the dynamically developing new hydrogen technologies in metallurgy, additive technologies and high-temperature material characteristics, important for the aerospace industry. At the same time, we would like to announce that the current issue of “Journal of Metallic Materials” is the last issue of our quarterly, publishing original research results in the field of metallurgy, materials engineering, chemistry, environmental protection and management in the iron and steel industry. Its traditions date back to 1949, when the first issue of the journal was published under the title “Prace Badawcze Głównego Instytutu Metalurgii i Odlewnictwa (Research Works of the Central Institute of Metallurgy and Casting)”. In 1976-2018, the quarterly was published under the title “Prace Instytutu Metalurgii Żelaza (Works of the Institute for Ferrous Metallurgy)”. The title changed to the current one in 2019. On behalf of the entire editorial team, we would like to thank all readers and authors of articles and reviewers for their cooperation. The establishment of the new Institute will certainly create conditions for the continuation of publishing activities in a broader substantive scope.

Study on Friction and Wear Properties and Mechanism at Different Temperatures of Friction Stir Lap Welding Joint of SiCp/ZL101 and ZL101

In order to achieve the goal of lightening the braking system of urban rail trains, SiCp/ZL101 and ZL101 plates were welded by friction stir lap welding (FSLW) to prepare a new type of brake disc material. The friction and wear properties of the friction-stir-processed composite material were studied at different temperatures (30 °C, 100 °C, 150 °C, 200 °C, 250 °C, 300 °C) to provide a theoretical basis for the evaluation of braking performance. The experimental results showed that the sliding friction processes at each temperature were relatively stable, the friction coefficients did not vary much and the average friction coefficients changed slightly, stabilizing at about 0.4. The wear extent and the depth of wear scars increased with the increase in the temperature, reaching the highest at 150 °C and then began to decrease. At room temperature, the wear forms were mainly oxidative wear and abrasive wear; as the temperature rose, under the cyclic shearing action of the grinding ball, the abrasive debris fell off under the expansion of fatigue cracks and fatigue wear was the main form at this stage. When the temperature reached 200 °C, it began to show the characteristics of adhesive wear; after 250 °C, due to the gradual formation of a mechanical mixed layer containing more SiC particles and oxides on the wear surface, it exhibited high-temperature lubrication characteristics, and the wear extent was equivalent to 35% of the wear extent at normal temperature, indicating that the composite material had good high-temperature friction and wear properties.

Systematic study of radiation-induced segregation in neutron-irradiated FeCrAl alloys

This work systematically reports grain boundary radiation-induced segregation (RIS), and insights into RIS mechanisms, in FeCrAl alloys. Recently, FeCrAl alloys have received significant attention as direct replacement accident tolerant fuel (ATF) claddings for light water cooled nuclear reactors, because of their corrosion and high-temperature oxidation resistance characteristics. One degradation method not studied in detail is RIS, which could sufficiently alter grain boundary chemistry, potentially compromising the superior aqueous corrosion resistance. This study focuses on candidate ATF FeCrAl alloys C06M, C35M, C36M, and C37M that are neutron irradiated to 1.8 displacements per atom (dpa) at 357°C. Grain boundary Cr enrichment and Al depletion are observed in all irradiated alloys that span the 10-13 wt.% Cr and 5-6 wt.% Al composition space. Fe will either enrich or deplete at grain boundaries to balance the grain boundary composition. The Cr enrichment is attributed to interstitial diffusion, consistent with that in body centric cubic 9-12 wt.% Cr steels. The depletion of Al occurs through the same mechanisms as α−α′ phase partitioning previously observed in FeCrAl alloys. This study underscores the need for FeCrAl alloy design to consider RIS implications on corrosion and oxidation susceptibility.

Evaluation of the field-aged performance of foamed warm mix asphalt: Comparisons with hot mix asphalt

The foamed warm mix asphalt (FWMA) has been widely used as a sustainable construction technique in pavement engineering, yet has not yet been fully studied for its aging performance or durability. Here we aim to examine and evaluate the performance variation characteristic of FWMA compared with conventional hot mix asphalt (HMA) under long-term service conditions. The performance evolution of FWMA core samples drilled from four highways was compared to that of ordinary HMA, which was simultaneously constructed. Fourier transform infrared (FTIR), dynamic shear rheology (DSR), and bending beam rheometer (BBR) tests were respectively performed to evaluate the aging degree, high-temperature, and low-temperature rheological characteristics. The results demonstrated that the aging resistance of foamed WMA was slightly diminished under construction conditions with no temperature reduction. With increased service time, the rheological characteristics of FWMA were enhanced at high temperatures, while deteriorated at low temperatures. The foaming water and service time were primary determinants of the aging as well as high and low-temperature rheological properties of FWMA without temperature construction reduction. Additionally, the aging degree of FWMA under short-term and long-term service was smaller than HMA when the construction temperature decreased. The rheological characteristics of FWMA were inferior to those of HMA during both short-term and long-term service stages. Under conditions of temperature reduction, foaming water and mixing temperature exhibited a considerable influence on the aging and rheological properties of FWMA at high and low temperatures. Therefore, the amount of water used for foaming and the temperature of production should be strictly control in the foamed warm mix asphalt technology.

Microstructure and high-temperature tribological characteristics of self-lubricating TiAlSiN/VSiN multilayer nitride coatings

In recent years, self-lubricating hard protective coatings operated at elevated temperature have drawn great amount of attentions. It has been found that alloying certain elements such as vanadium is an effective method to reduce the friction coefficient, since the Magnéli phase formed at elevated temperature provides a self-lubricious surface during the wear process. However, the formation kinetics of the Magnéli phase should be appropriately controlled. Insufficient or excessive amount of Magnéli phase formation may result in high friction coefficient or severe oxidation of coatings. This study reports an architectural design strategy to engineer the mechanical and high temperature tribological properties of TiAlSiN/VSiN multilayer.In this study, the multilayer system exhibited a low friction coefficient of 0.28 and the lowest wear rate of 7.01 × 10−6mm3N−1m−1 was revealed at multilayer with bilayer period of 16 nm during the wear test at 700 °C. The existence of the Magnéli phase, V2O5, was observed by XPS and its high-temperature lubricating effect was revealed as compared to the wear test at room temperature. It is demonstrated that a particular architectural design of TiAlSiN/VSiN multilayer coating provides a potential candidate for high-speed cutting tools due to their mechanical and lubricious properties.

Effects of in-situ temperature in deep reservoirs on shale fracture properties

The development of deep shale reservoirs is a major strategic demand to meet national energy requirements. However, the high-temperature characteristics of in-situ reservoirs make it difficult to understand the fracture properties of deep shale clearly, which restricts the development of reservoir stimulation technologies. Based on digital image correlation method and fracture mechanics theory, this study investigates the issue of rock fracture parameters testing in high-temperature environments. This study builds an in-situ high-temperature environment rock fracture visualization test system that can dynamically capture crack-tip initiation and propagation. Further, the influence law of temperature on shale fracture behaviour has been analysed. The results have shown that, under the condition of no confining pressure, with increases in the temperature, the macroscopic material stiffness and fracture toughness of shale increase; this shows that high temperatures inhibit crack initiation and propagation. Further, with increases in the temperature, the temperature-dependent CTOD is positively correlated with the fracture toughness, the simultaneous increase of these two factors leads to the increase of local plasticity in the crack tip region. When considering high-temperature conditions alone, the fracture tip still experiences a small-scale yield state; the research conclusions can provide a reference for studies on deep reservoir fractures.

Optimal operation of RSOC integrated energy systems considering multi-state transitions

Reversible solid oxide fuel cells (RSOC) can realize energy storage and power generation in a compact structure, and their high-temperature operation characteristics provide the possibility for combined heat and power generation. Therefore, RSOC can be used as the node of the multi-energy flow intersection of the integrated energy system. The flexible operation mode of RSOC will greatly reduce the operation cost. However, the optimal operation of an integrated energy system including RSOC is very rare at present, so this paper establishes an integrated energy system of the electric gas network including RSOC. On this basis, this paper constructs an RSOC model, a DC power flow model and a linearized gas power flow model considering multiple operating states. Then, based on GAMS, the economic cost of a 24-20 electric gas composite network is optimized. After verifying the reliability of the model, the optimization results considering two working conditions and four working conditions are compared. It is concluded that the model considering multiple operating states of RSOC will reduce the operating cost of the system by 24%.

Heat transfer performance of high temperature and high velocity hydrogen flow and analysis of blockage characteristics

In the current situation of increasing demand for nuclear heat propulsion in various countries, the heat transfer characteristics of high temperature and high velocity fluid in the flow channel are particularly important for safe core operation and efficient heat transfer. In order to obtain the flow and heat transfer characteristics of the coolant channel of nuclear thermal propulsion reactor under normal and blocked flow conditions, the numerical method based on commercial CFD software is adopted. Researches by changing the inlet velocity of the coolant channel and the blocking forms of the circular pipe are carried out. The SST k-omega viscous model together with the pressure-based coupling algorithm, which have extraordinary applicability to the model, are adopted. The impulse which are vital to the performance of nuclear heat propulsion is analyzed.The calculation results indicate that with the increase of the inlet velocity, the coolant outlet impulse increases significantly; The heat transfer deteriorated gradually, and the wall temperature slightly increased; The closer to the center of the pipe the blockage occurred, the higher the pipe temperature became. The research methods and results can provide a reference for the study of the heat transfer characteristics of high temperature and high velocity hydrogen flow, and the heat transfer characteristics and transient simulation initiated by the blockage of the nuclear thermal propulsion reactor.

High-temperature characteristics of GaN/InGaN multiple-quantum-well UV photodetectors fabricated on sapphire substrate: Analysis of photovoltaic and carrier transit time properties

To accomplish a high-temperature operation of GaN/InGaN multiple-quantum-well (MQW) UV photodetectors (UV-PDs), the investigation of device performances at high-temperature regimes is truly essential. Therefore, in the present work, GaN/InGaN MQW-based UV-PDs on sapphire are fabricated and their photovoltaic and carrier transit time characteristics are investigated at different temperatures. Our results suggest that the temperature has a strong impact on various photovoltaic properties: we noticed an increase in short circuit current density and a significant lowering in open circuit voltage and power conversion efficiency when the ambient temperature increases from 25 to 300 °C. The time-dependent photo-response characteristics at different temperatures suggest that both the rise time and fall time are reduced at high temperatures, indicating the thermal activation of localized charges at an exacerbated temperature.