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In this study, the heat transfer characteristics of nanofluids used in spray cooling systems were examined. Three nanofluids, i.e., Cu, CuO, and Al2O3, respectively, with volume fractions ranging from 0.1% to 0.5%, as well as different volume fractions of a surfactant Tween 20, were used. In addition, their contact angles were measured to examine the heat-transfer characteristics. Under the same experimental conditions, with the increase in the volume fraction of the Cu nanoparticles from 0.1% to 0.5%, the maximum heat flux qmax increased from 3.36 MW/m2 to 3.48 MW/m2 from the impinging central point to r = 30 mm (r is the distance from the impingement point), and the corresponding temperature of qmax increased from 400°C to 420°C. Results revealed that with increasing Tween 20 concentrations, the contact angle decreased because of the decrease in the surface tension of nanofluids and improvement of the wetting ability, and the corresponding qmax increased from 3.48 MW/m2 to 3.94 MW/m2 at the impact central point.

Wastewater containing quinoline has become a common pollutant in water and soil environments, which poses a threat to human health due to its carcinogenicity, teratogenicity, and mutagenicity. Quinoline's stability and toxicity hinders its degradation by conventional physicochemical and biological methods. In this contribution, Fe-Co-Bi/kaolin particle electrodes were prepared for the efficient degradation of quinoline in wastewater, and characterized by using scanning electron microscope, X-ray diffraction, pyridine-IR, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, and four-probe resistivity test. Parameters affecting the degradation efficiency were optimized to be the particle electrode dosage of 40 g/L, pH 3.5, H

The influence of cooling models and moving velocity on the temperature variation and cooling rate through the thickness of a metal plate is experimentally investigated. In this investigation, the cooling process is divided into four stages: a starting stage (I), a rapid cooling stage (II), a slow cooling stage (III) and a stopping stage (IV). Based on the curves, cooling rate, temperature difference, the heat transfer coefficient and center temperature curves are discussed. The results indicate that the cooling model and moving velocity influence the heat transfer on the surface, and affects the cooling rate through the thickness by changing the temperature difference. When the flow rates of nozzles 1, 2 and 3 are set to be V1, V2 and V3 respectively, the highest heat transfer is observed when V1 > V2 > V3. Under this cooling model, the maximum temperature difference occurs at the time of transition from the rapid cooling stage (II) to the slow cooling stage (III). In the slow cooling stage (III), increased moving velocity improves the synchronization of the heat transfer and decreases the maximum heat flux. As well, the speed of motion affects the internal heat conduction and cooling rate by affecting surface heat transfer.

Modern products are usually designed with high reliability and have complex structures, and degradation analysis of the complex systems with two or multiple performance characteristics is still a challenge. In this paper, we propose a new bivariate degradation model based on the Wiener process. There are three main merits of the proposed model: it can describe the common factor affecting the degradation of the two performance characteristics and unit-to-unit variation simultaneously, the reliability functions of the system and the remaining useful life of the system have analytic forms, and the model parameters and the missing values can be estimated by the Bayesian method and data augmentation. The simulation study and data analysis show that the Bayesian method and the proposed model have satisfactory performance.

The combined influence of Mg and Ca treatment on the properties of heat-affected zone (HAZ) of low-carbon steel after high heat input welding was systematically studied. Experimental steels deoxidized with different elements were prepared, i.e., C–Mn steel with Al, Ti–Ca steel with Ti and Ca, Ti–Mg–Ca steel with Ti, Mg and Ca. Results showed that the inclusions in C–Mn steel were mainly Al2O3 and MnS with low density and large size. However, the average size was refined to only ~ 0.34 μm in Ti–Mg–Ca steel and the amount increased remarkably. Microstructure of simulated HAZ for 200 kJ/cm changed from ferrite side plates or upper bainite to acicular ferrite after treatment with Ti, Mg and Ca. Ca addition decreased the strain field around inclusions and enhanced the ability of acicular ferrite nucleation. In situ observation of Ti–Mg–Ca steel showed that the movement of austenite grain boundaries was retarded and nucleation sites of acicular ferrite were greater than Ti–Ca steel because of Mg addition. Impact energy of HAZ at − 40 °C was increased from 7 to 232 J and showed excellent stability because of Ti–Mg–Ca treatment. High volume fraction of acicular ferrite acted as obstacles toward cleavage cracks.

To improve the superplasticity of Inconel 718, cold rolling with 84% reduction, followed by two-stage annealing, was designed to refine and homogenize the grains. Compared with cold rolling and single-stage annealing, a finer grain size of 1.21 μm was obtained and provided better superplasticity (up to 657% elongation) at 950 °C with a strain rate range of 6 × 10-4 to 1 × 10-2 s-1. Sizeable plastic deformation introduces plenty of crystal defects and storage energy, which contributes to the dense and fine distribution of δ phase in the first stage annealing and enhances the driving force for static recrystallization (SRX) in the subsequent high-temperature annealing. The pre-existing δ phase stimulates the nucleation of SRX and hinders the growth of grains. In addition, the second phase particles form a uniform distribution due to dissolution, thereby controlling the difference in grain size. The sufficient pre-precipitation and subsequent uniform dispersion of δ phase achieve a significant grain refinement effect. This paper is expected to serve as a reference for the industrial production of superplastic Inconel 718 sheets.

The microstructure and mechanical properties of low carbon bainite high strength steel plate were studied via different cooling paths at the pilot scale. There was a significant increase in mechanical properties, and notably, the yield strength, tensile strength, and toughness at -40 °C for the tested steel processed by ultra-fast cooling were 126 MPa, 98 MPa and 69 J, respectively, in relation to steel processed by accelerated cooling. The ultra-fast cooling rate not only refined the microstructure, precipitates, and martensiteaustenite (M/A) islands, but also contributed to the refinement of microstructure in thick plates. The large size M/A constituents formed at lower cooling rate experienced stress concentration and were potential sites for crack initiation, which led to deterioration of low-temperature impact toughness. In contrast, the acicular ferrite and lath bainite with high fraction of high-angle grain boundaries were formed in steel processed by ultra-fast cooling, which retarded cleavage crack propagation.

We revisit the photoelectron spectroscopy of aqueous phenol in an effort to improve our understanding of the impact of inhomogeneous broadening and inelastic scattering on solution-phase photoelectron spectra. Following resonance-enhanced multiphoton ionisation via the 11ππ* and 11πσ* states of phenol, we observe 11ππ*–D0/D1 ionisation and competing direct S0–D0/D1 ionisation. Following resonance-enhanced multiphoton ionisation via the 21ππ* state, we observe the signature of solvated electrons. By comparing the photoelectron spectra of aqueous phenol with those of gas-phase phenol, we find that inelastic scattering results in peak shifts with similar values to those that have been observed in photoelectron spectra of solvated electrons, highlighting the need for a robust way of deconvoluting the effect of inelastic scattering from liquid-phase photoelectron spectra. We also present a computational strategy for calculating vertical ionisation energies using a quantum-mechanics/effective fragmentation potential (QM/EFP) approach, in which we find that optimising the configurations obtained from molecular dynamics simulations and using the [phenol·(H2O)5]QM[(H2O)n≥250]EFP (B3LYP/aug-cc-pvdz) method gives good agreement with experiment.

Herein, the influence of inter-pass cooling (IC) and conventional two-stage rolling (CTR), on microstructural evolution and plastic deformation behavior of ultra-heavy EH47 plates, is demonstrated. It is reported that the deformation amount and deformation rate, in every deformation pass during rough rolling, at 1/4- and 1/2-thickness of IC steel were higher than the CTR steel. The volume fraction of ferrite and acicular ferrite was 45% and 18%, at 1/4-thickness, and 35% and 50% at 1/2-thickness of IC steel, respectively, whereas the sum of both ferrite phases was smaller than 25% in the CTR steel. The austenite grain boundary area and high-angle grain boundary fraction in the IC steel were higher than the CTR steel. The high density of fine and shapeless pearlite has been observed in IC steel, whereas large-size carbides, with hexagonal structure, have been observed in CTR steel. Compared to the CTR steel, the density of precipitates was apparently lower in IC steel. Two kinds of Nb containing precipitates, such as (Ti, Nb)(C, N) and (Nb, Ti)C, were observed in the tested steels. Total ductility and uniform elongation of the IC steel were higher than the CTR steel. During the tensile process, the crack initiation energy and crack propagation energy of the IC steel were higher than the CTR steel. Moreover, the volume fraction of retained austenite (FCC) was reduced from 7.71% to 0.42% near the tensile fracture in IC steel at 1/4-thickness. In additon, the strain of synergetic plastic deformation of the IC steel was higher than the CTR steel. Meanwhile, compared to the CTR steel, the synergetic plastic deformation of the IC steel occurred at low stress after the yield point, which can be ascribed to the presence of fewer microcracks in the IC steel. Hence, a delayed fracture has been observed in the IC steel plate.

Recently, the impinging jet has been widely used in the controlled cooling process following hot rolling as a key technology to develop an ultra-fast cooling system. The hot plate/strip undergoes a symmetrically cooling process on the top and bottom surface. Under this consideration, a laboratory apparatus was established to investigate the heat transfer characteristics of a single circular jet impinging on the top or bottom surface of the plate. The results demonstrate that the differences in the heat transfer performance and the wetting front propagation phenomena are noticeable. The top-surface heat flux is slightly higher than the bottom one in the measured cooling region. The heat flux increases with the water flow rate, and decreases with the nozzle-to-surface distance. However, with the increase of radial distance, the top-surface wetting front expanding speed is significantly lower than that of the bottom-surface, especially when the water flow rate is higher than 2 l/min. The results indicate that jet velocity is the critical factor to generate higher cooling performance during both impinging processes. The present study is useful for designing an ultra-fast cooling device and the optimized cooling parameters will enhance the cooling efficiency and cooling uniformity of the industrial ultra-fast cooling equipment.

The heat transfer ability and cooling uniformity in ultra-fast cooling technology played a critical role in improving the microstructure and mechanical properties of hot rolling steel. However, the heat transfer characteristics and boiling phenomena during the cooling process of a water jet impinging on a hot plate surface approximate to the industrial conditions were rarely reported. Herein, we investigated the effect of the initial surface temperature, water temperature, and jet velocity on the heat transfer characteristics for the industrial applications. The results revealed that the rewetting front propagation was considerably affected by the growth and detachment of the bubbles in the rewetting front region. The wetting delay time was extended by the superheat increase, and the sub-cooling and jet velocity decrease, because the ability to condense the bubbles was weakened in the front rewetting region. Meanwhile, the wetting velocity varied with the distance from the stagnant point. Moreover, the maximum heat flux, qmax, was influenced by the initial surface temperature, water temperature, and jet velocity; finally, a regression equation was established to predict the qmax value. The information provided in this work would be beneficial for predicting and optimizing the industrial applications of ultra-fast cooling technology.

Plate cooling is a complex process so that it cannot be described by a fixed model. So, the mathematical model requires self-adaptive ability to comply with the various parameters such as gauges and temperatures of plates. Considering the effect of influence factors on cooling process, an online variable scale grid (VSG) model for cooling is developed. VSG model builds a multi-dimension space system where each dimension is determined by the effect of each factor on heat transfer. Every plate can find a corresponding point in the space, according to its own process conditions. To guarantee the higher precision of temperature control, it adopts dimensionless treatment for all the factors to avoid the errors caused by different physical units. In order to reduce the computational cost, the technologies of finite element meshing and centroid calculation have been applied. When a new plate comes, the correlations between the new one and historical samples, centroids are described by Euclidean distance. Finally, the target value is estimated through the distance-weighted average method. The results of experiments and applications with real industrial data show that the proposed VSG is effective in the plate cooling control and has a wide application prospect.

To elucidate the hot deformation characteristics of TiAl alloys, flow stress prediction, microstructural evolution and deformation mechanisms were investigated in Ti-44Al-5Nb-1Mo-2V-0.2B alloy by isothermal compression tests. A constitutive relationship using the Arrhenius model involving strain compensation and back propagation artificial neural network (BP-ANN) model were developed. A comparison of two models suggested that the BP-ANN model had excellent capabilities and was more accurate in predicting flow stress. Based on the microstructural analysis, bending and elongation of colonies, γ and B2 grains were the main microstructural constituents at low temperature and high strain rate. Dynamic recrystallization (DRX) of γ and dynamic recovery (DRY) of β/B2 were the main deformation mechanisms. With the increase of temperature and decrease of strain rate, phase transformation played an important role. The flake-like γ precipitates in B2 grains, and a coarsening of γ lamellae via α lath dissolution during compression were observed. Additionally, the flow softening process commenced with dislocation pile-up and formation of sub-grain boundaries, followed by grain refinement, twins and nano-lamellar nucleation. Continuous DRX and phase transformation promoted the formability of Ti-44Al-5Nb-1Mo-2V-0.2B alloy.

Water is the predominant medium for chemistry and biology, yet its role in determining how molecules respond to ultraviolet light is not well understood at the molecular level. Here, we combine gas-phase and liquid-microjet photoelectron spectroscopy to investigate how an aqueous environment influences the electronic structure and relaxation dynamics of phenol, a ubiquitous motif in many biologically relevant chromophores. The vertical ionization energies of electronically excited states are important quantities that govern the rates of charge-transfer reactions, and, in phenol, the vertical ionization energy of the first electronically excited state is found to be lowered by around 0.8 eV in aqueous solution. The initial relaxation dynamics following photoexcitation with ultraviolet light appear to be remarkably similar in the gas-phase and aqueous solution; however, in aqueous solution, we find evidence to suggest that solvated electrons are formed on an ultrafast time scale following photoexcitation just above the conical intersection between the first two excited electronic states.

The tensile properties, high-cycle fatigue properties, and microstructure evolutions during fatigue process of as-received and pre-strained Fe-30Mn-0.9C twinning-induced plasticity (TWIP) steel were investigated. It is found that the fatigue lives of the TWIP steel can be effectively improved through pre-straining, since the deformation twins induced by pre-straining could effectively lead to the improved yield strength and the homogenized deformation. This study may provide possible ways for improving the high-cycle fatigue properties of TWIP steels.

Thermo-mechanical control process (TMCP) technology is widely used for processing steels, where an important aspect is controlled cooling, Recently, the ultra-fast cooling (UFC) method, which has high flow speed, adjustable inclination angle, and stagger arranged nozzles is gradually replacing the traditional cooling practice. This paper focuses on the flow field and heat transfer mechanism in high temperature plates during the cooling process. Next, the effect of different initial temperatures (600 and 750°C) and inclination angles (0°, 30°, and 60°) were studied. The surface temperature and heat flux were calculated using finite difference method. The data suggests that with the initial temperature increasing from 600 to 700°C, and the inclination angle increasing from 0° to 60°, the maximum heat flux and its corresponding temperature increases in the major part of the cooling region. Given that the experimental conditions were similar to the industry, the new findings are expected to effectively guide the development of UFC in the near future.

Taking the element specific-heat interpolation function into account, a one-dimensional (1-D) finite element temperature field model for the on-line control of the ultra fast cooling process was developed based on the heat transfer theory. This 1-D model was successfully implemented in one 4300 mm plate production line. To improve the calculation accuracy of this model, the temperature-dependent material properties inside an element were considered during the modeling process. Furthermore, in order to satisfy the real-time requirements of the on-line model, the variable bandwidth storage method and the Cholesky decomposition method were used in the programming to storage the data and carry out the numerical solution. The on-line application of the proposed model indicated that the deviation between the calculated cooling stop temperature and the measured one was less than ±15 °C.

A new recirculating liquid-microjet photoelectron spectrometer for multiphoton ultraviolet photoelectron spectroscopy is described. A recirculating system is essential for studying samples that are only available in relatively small quantities. The reduction in background pressure when using the recirculating system compared to a liquid-nitrogen cold-trap results in a significant improvement in the quality of the photoelectron spectra. Moreover, the recirculating system results in a negligible streaming potential. The instrument design, operation, and characterization are described in detail, and its performance is illustrated by comparing a photoelectron spectrum of aqueous phenol recorded using the recirculating system with one recorded using a liquid nitrogen cold-trap.

Dual-level electronic structure calculation has been performed to investigate the mechanism and all possible channels of OH radical reaction with CH3CH2F. Geometries and frequencies are computed at the B3LYP/6-311G(d,p) level of theory for all stationary points and complexes and transition states are located. Potential energy surfaces are constructed at the PMP2/cc-pVTZ//B3LYP/6-311G(d,p) level + ZPE correction. Four types of reaction channels are identified: hydrogen abstraction, fluorine abstraction and attack on carbon atom along or perpendicular to the C–C bond axis. Hydrogen abstraction channels have lower barriers and are more exothermic, while out-of-plane β–H abstraction with the lowest barrier is competitive with a–H abstraction. Due to the high energy barrier, contributions of non-H abstraction channels are excluded. The influence of hydrogen bonding interaction is clearly observed in the barrier heights.