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Table of Content
05 December 2022, Volume 73 Issue 12
    Reviews and monographs
    Advances on continuous synthesis of topological polymers in microreactors
    Liang XIANG, Zihao ZHONG, Yuanhai SU
    2022, 73(12):  5275-5288.  doi:10.11949/0438-1157.20221283
    Abstract ( 865 )   HTML ( 71)   PDF (1939KB) ( 413 )  
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    The development of polymers with complex topological chain structures has greatly enriched the varieties and properties of polymeric materials, and microreactor technology provides a powerful platform for the regulation of polymer topology structures. This paper first briefly introduces the background of the structure and properties of topological polymers, synthesis methods and the theoretical basis of micro-reaction technology. Then, the applications of microreactor technology in polymer synthesis are systematically expounded, focusing on the research progress on the continuous synthesis of branched polymers and the advantages of continuous-flow operation with microreactors over the batch process. Moreover, the technical difficulties and improvement schemes of synthesizing complex topological polymers with the use of microreactors are analyzed. Finally, the research directions about basic research, engineering scale-up, and product applications are prospected.

    Recent progress on anode for sulfide-based all-solid-state lithium batteries
    Linan JIA, Yibo DU, Bangjun GUO, Xi ZHANG
    2022, 73(12):  5289-5304.  doi:10.11949/0438-1157.20221033
    Abstract ( 975 )   HTML ( 62)   PDF (3008KB) ( 567 )  
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    All-solid-state lithium batteries (ASSLBs) exhibit higher energy density and more safety than current liquid lithium batteries, which are the main research direction for next-generation energy storage devices. Compared with other solid-state electrolytes, sulfide solid-state electrolytes (SSEs) have the characteristics of ultra-high ionic conductivity, low hardness, easy processing, and good interfacial contact, which are one of the most promising routes to realize all-solid-state batteries. However, there are some interfacial issues between anodes and SSEs that limit their applications such as interfacial side reactions, poor rigid contact, and lithium dendrite. This study outlines the current progress in anode materials used for sulfide-based ASSLBs, summarizes the development status, application advantages, interface problems and mainstream solution strategies of the main anode materials including lithium metal, lithium alloys, silicon anode for sulfide-based ASSLBs, and provides guiding suggestions for the next development of anode materials and the solution of interfacial issues.

    Thermodynamics
    COSMO-RS based solvent screening and H2/CO separation experiments for CO absorption by ionic liquids
    Meng HUO, Xiaowan PENG, Jin ZHAO, Qiuwei MA, Chun DENG, Bei LIU, Guangjin CHEN
    2022, 73(12):  5305-5313.  doi:10.11949/0438-1157.20221230
    Abstract ( 528 )   HTML ( 25)   PDF (2024KB) ( 192 )  
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    Among the currently available CO absorption methods, ionic liquid absorption has attracted much attention due to its unique advantages. In this study, 350 ionic liquids were screened as solvents by the COSMO-RS, using the selectivity of CO at 293.15 K and viscosity of ionic liquids as indicators. The effect of the anionic and cationic configurations of the ionic liquids on the selectivity of CO was analyzed. The ionic liquids were synthesized in the laboratory, and their viscosity-temperature curve was measured. Subsequently, Fourier transform infrared spectroscopic analysis showed that there existed intermolecular hydrogen bond force in the proton-type ionic liquid. Phase equilibrium experiments were carried out by using a high-pressure transparent sapphire kettle, solubility curves were determined, and the effect of the gas-to-liquid ratio on the separation factor was analyzed. The results showed that the separation factor of CO/H2 could reach 109.29 at 293.15 K, 2.1 MPa, and a gas-liquid ratio of 77.75. Finally, the stability of the ionic liquid was demonstrated by FTIR, which implies that the solvent has potential for industrial applications.

    Solvents selection for separation of biphenyl from FCC diesel: experimental and computational thermodynamics
    Tengfei GAO, Guoxuan LI, Zhigang LEI
    2022, 73(12):  5314-5323.  doi:10.11949/0438-1157.20221304
    Abstract ( 284 )   HTML ( 16)   PDF (2284KB) ( 211 )  
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    For the biphenyl-dodecane system, the COSMO-RS model was used to predict the infinite dilution activity coefficients of biphenyl and dodecane in different ionic liquids. The separation performance of ionic liquids was evaluated and screened by several indicators, and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) was considered as the most potential extractant. The ternary liquid-liquid equilibrium data of biphenyl-dodecane-extractant systems at atmospheric pressure and 303.2 K were measured by liquid-liquid equilibrium experiment. With dimethyl sulfoxide and furfural as benchmark extractants, the separation performance of [BMIM][BF4] as extractants was evaluated. Finally, the computational chemistry theory was used to explore the separation mechanism of different extractants for biphenyl-dodecane system. The C—H…π interaction, π-π interaction and hydrogen bond interaction are considered to be the most important interactions between the extractant and biphenyl.

    Fluid dynamics and transport phenomena
    Calculation model of flow and heat transfer characteristics of printed microchannel heat exchanger
    Zhiqiang YU, Jianze WU, Yatao REN, Mingjian HE, Xikui YU, Hong QI
    2022, 73(12):  5324-5342.  doi:10.11949/0438-1157.20220942
    Abstract ( 284 )   HTML ( 21)   PDF (3875KB) ( 200 )  
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    As the energy problem becomes more and more prominent, it is urgent to develop high-efficient energy equipment. Microchannel heat exchanger has attracted much attention in thermal management system due to its excellent performance. In this paper, a calculation model is proposed for the theoretical calculation of flow and heat transfer characteristics of microchannel heat exchanger. Based on the establishment of experimental database of literature, 10 and 6 kinds of heat transfer and flow calculation correlation formulas are compared and analyzed respectively. And numerical simulation and model solving research are carried out for a heat exchanger structure. The empirical solution of heat transfer characteristics obtained by using the correlation formula proposed by Stephan et al. and Sarmiento et al. is in good agreement with experimental solutions. The empirical solution of flow characteristics obtained by using the correlation formula, which are proposed by Kim et al., Muzychka et al., is in good agreement with the experimental solution. The numerical simulation and model calculation of the heat exchange unit are carried out, and the error of most points in the numerical solution and the empirical solution is within 10% , which verifies the accuracy and reliability of the calculation model proposed in this paper in the theoretical solution.

    Evolution mechanism of water freezing phase interface in porous media at mesoscale
    Wensong WANG, Yingying YANG, Zhoulin CHEN, Qingyu YANG, Shuaihua LI, Weidong WU
    2022, 73(12):  5343-5354.  doi:10.11949/0438-1157.20221233
    Abstract ( 275 )   HTML ( 24)   PDF (4425KB) ( 241 )  
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    Heat and mass transfer problems in the freezing process of water in porous media generally exist in the fields of engineering in cold region, food freezing and preservation, construction, and pavement freeze-thaw damage. In this study, the evolution mechanism of water freezing phase interface in porous media is studied at the mesoscale by experiments and simulations. Firstly, the evolution of phase interface and temperature field during water freezing in microchannels with pore radius of 500 μm was studied by unidirectional freezing experiment. Then, the effects of boundary temperature, pore space and pore structure on the evolution of phase interface and water freezing rate were studied through numerical simulation. The results show that the relative curvature of the phase interface decreases with the decrease of pore radius. In the channel, the relative curvature decreases firstly and then increases, making the phase change from concave to convex. The temperature in the channel decreases quickly and then slowly with time, and the rate is related to the temperature gradient. Supercooling causes the formation of supercooled zone between 0℃ isotherm and phase interface. The smaller the pore space is, the stronger the sudden temperature gradient in the pore channel is, which hinders heat transfer. Among the four pore structures studied in this paper, the circular straight-row has the highest freezing rate.

    Influence of lift model on gas-liquid-solid flow field in polyethylene fluidized bed reactor
    Yongshuai LI, Yi ZHENG, Lan LI, Xinshuang LI, Xinyi ZHAO, Hui PAN, Hao LING
    2022, 73(12):  5355-5366.  doi:10.11949/0438-1157.20221147
    Abstract ( 264 )   HTML ( 24)   PDF (2556KB) ( 143 )  
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    When the gas-phase polyethylene process is operated in the condensation mode, the liquid phase evaporates in the bed and the fluid flow pattern changes to the rotary type, and the effect of lift force can't be ignored. In this paper, the CFD model of the gas-liquid-solid three-phase flow polyethylene fluidized bed reactor was established, and the effects of three different lift models of Saffman-Mei, Legendre-Magnaudet and Moraga on the multiphase fluid flow of the polyethylene fluidized bed reactor were explored. The simulation results show that the lift model has no significant effect on the average bed height and the average reactor temperature after fluidization stabilization, but there are differences in the particle phase distribution in different height regions of the bed and the temperature distribution in the low region. The different particle sizes of solid phase particles have different fluidization processes under the influence of lift, small particles tend to produce larger bubbles in the fluidization process, and the aggregation phenomenon of large particles at the wall is more obvious. The Saffman-Mei and Moraga models have similar evaporation rates of the liquid phase. The Moraga model has the most intense particle and bubble motion. The bed pressure drop predicted by the Legendre-Magnaudet model is the most accurate, and the phase distribution and temperature distribution during the fluidization process are more uniform.

    Effect of desiccant adsorption isotherm on dehumidification performance of desiccant coated heat exchanger
    Tianyu YANG, Tianshu GE
    2022, 73(12):  5367-5375.  doi:10.11949/0438-1157.20221248
    Abstract ( 223 )   HTML ( 18)   PDF (1662KB) ( 116 )  
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    Compared with the traditional air compression air conditioning system, the adsorption dehumidification air conditioning system based on desiccant coated heat exchanger uses solid desiccant to deal with the latent heat load in the air, which effectively improves the evaporation temperature and greatly improves the energy efficiency of the air conditioning system. The choice of desiccant coating is very important to the performance of desiccant coated heat exchanger system. It is difficult to effectively select desiccant materials suitable for dehumidification heat exchanger system by using existing experimental and simulation methods. Based on the adsorption isotherm of desiccant, the applicability of desiccant material for dehumidification heat exchanger is discussed in this paper. Starting from the adsorption isotherm curve of desiccant, this paper discusses the dehumidification performance of desiccant with different types of adsorption isotherm curves firstly, and concludes that the desiccant with“S”type adsorption isotherm curve has the best dehumidification ability. The step pressure of“S”type adsorption isotherm is also analyzed and discussed, and the calculation method of the optimal step pressure under specific working conditions is determined. The above conclusions are consistent with the simulation results. The feasibility of obtaining desiccant with ideal adsorption isotherm by compounding hygroscopic salts and synthesizing materials with specific pore structure was also discussed.

    Velocity/pressure field analysis of a single-bubble boiling on a diversion-enhanced microstructure surface
    Xiang GAO, Yiran WANG, Chaoyang GUAN, Zhihua GE, Hongxia CHEN
    2022, 73(12):  5376-5383.  doi:10.11949/0438-1157.20221067
    Abstract ( 208 )   HTML ( 11)   PDF (4709KB) ( 85 )  
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    Compared with the smooth surface, micro-pillar structured surfaces can enhance nucleate boiling significantly. The enhancement mechanism mainly includes increasing heat transfer area, increasing nucleation site density, reducing bubble departure diameter, etc. Few in-depth studies have been done on the diversion effect of microstructure gaps. In this paper, the three-dimensional multiphase fluid integral model is used to define the important geometric and time dimensionless parameters of single-bubble boiling on the microstructure surface. Through the analysis of velocity field and pressure field, the interaction of bubbles, micro-columns and surrounding liquid during the boiling process is discussed. The results show that the gap of the microstructure promotes the liquid backflow. Furthermore, the diversion effect in the channels established between the liquid-vapor interface at the bubble bottom and the substrate is the most obvious, which leads to an increased liquid flow rate, an accelerated bubble departure and the heat transfer enchancement of the single bubble-boiling. At the same time, the diversion effect of the microstructure promotes the formation of a high pressure thin film at the bottom and the sidewall of micropillar structures, in which the thin liquid film at the bottom has a capillary drainage capability and can maintain the liquid heat transfer area at the micropillar root in the bubble. The thin liquid film on the sidewall of the micropillars replaces the original dryout region, the heat transfer area is correspongdingly increased and the heat transfer efficiency is improved significantly.

    Study on anti-fouling characteristics of particulate fouling using built-in self-rotating rotors
    Guangshuo XIE, Siliang ZHANG, Jiarui WANG, Juan XIAO, Simin WANG
    2022, 73(12):  5384-5393.  doi:10.11949/0438-1157.20221419
    Abstract ( 240 )   HTML ( 9)   PDF (1994KB) ( 112 )  
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    Dirt on the surface of heat transfer tubes not only hinders heat transfer, but also increases fluid flow resistance, resulting in reduced service life of heat transfer tubes and economic losses. By inserting the rotor into a heat transfer tube, the heat transfer enhancement, antifouling and descaling can be realized simultaneously. In this paper, the flow field and particle fouling characteristics in the heat transfer tube with built-in rotors were studied under different inlet velocities. Using multiple reference frame model (MRF) to show the rotation of rotors, particle fouling characteristics were obtained based on Euler-Euler liquid-solid two-phase flow model and user defined functions (UDF) plug-in program. The results show that the spiral flow appears by installing a rotor to the heat transfer tube, and the circumferential velocity and radial velocity of the fluid can be increased, so the heat transfer performance of the tube wall is enhanced. With the flow rate increasing from 0.15 m/s to 0.35 m/s, the stable value of particle deposition rate in the tube with the self-rotating rotor increases by 136.5%, and the increasement gradually becomes larger. However, the asymptotic value of fouling resistance decreases by 48.3%, and the time required to reach asymptotic value decreases with increasing inlet velocity. On this basis, compared with the fixed rotor, it is found that when the flow rate is 0.15—0.25 m/s, the fouling resistance is smaller when the rotor is fixed, and when the flow rate is 0.30—0.35 m/s, the fouling resistance is smaller when the rotor is rotating. Therefore, the study of particle fouling characteristics at different inlet velocities provides an important basis for the selection and design of the built-in rotor.

    Experimental study on the effect of initial quenching temperature on the boiling heat transfer characteristics of hydrophobic surfaces
    Wenxiang LI, Junhe WANG, Yijing HAO, Leping ZHOU
    2022, 73(12):  5394-5404.  doi:10.11949/0438-1157.20221222
    Abstract ( 193 )   HTML ( 7)   PDF (3116KB) ( 70 )  
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    The effect of initial quenching temperature on the transient boiling has been little discussed in depth, especially the mechanism of its effect on the quenching on surfaces with different wettability is still lacking. In this paper, nanoparticle deposition was used to prepare hydrophobic surfaces, and the influence of initial quenching temperature on the boiling heat transfer characteristics of hydrophobic surfaces was investigated experimentally. The evolution of critical heat flux (CHF), minimum heat flux (MHF), and transition heat flux (THF) as well as the corresponding temperature and time were quantitatively analyzed. The results show that the enhanced hydrophobicity shifts the quenching curve to the right, the boiling curve shifts to the left, the CHF and MHF and corresponding temperature decrease, and the quenching time increases. The above trends became less pronounced when the initial quenching temperature increased. This indicates that the increase of hydrophobicity deteriorates the heat transfer in general, while the increase of initial quenching temperature can relatively enhance the heat transfer. At the same time, it was found that the sub-regimes of the transition boiling stage increased with increasing initial quenching temperature, and the critical transition point (CTP) was also affected accordingly. The heat transfer coefficient exhibits a similar change to the boiling curve, with its maximum value occurring near the deviation from nucleation boiling (DNB) point.

    Influence of solutal Marangoni effect on the stability of falling film flows
    Chengzhi LIU, Chunxi LI, Jingyi ZHOU, Xuemin YE
    2022, 73(12):  5405-5413.  doi:10.11949/0438-1157.20220973
    Abstract ( 190 )   HTML ( 2)   PDF (2775KB) ( 61 )  
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    The stability of falling film flows is one of the significant factors in improving coating quality, guaranteeing the heat transfer performance of falling film heat exchangers and promoting drug absorption. Based on the two-dimensional nonlinear evolution equation of liquid film thickness and surfactant concentration, the stability of a falling film flow with an insoluble surfactant on an inclined plane is investigated. The critical Reynolds number is presented, including inclination angle θ, Marangoni number M, Weber number S and Peclet number Pe. The impact of solutal Marangoni effect, inclination angle and perturbation wave number on the linear stability of film flow is examined. The spatial and temporal perturbation characteristics of surface waves are inspected. The results show that the initial small perturbation is separated into fast waves and slow waves under the solutal Marangoni effect and the slow wave develops into a surface wave with multi-peak wave structure in the later stage of evolution. Enhancing solutal Manangoni effect is effectively to raise the critical Reynolds number, which expands the stability region, decreases the perturbation growth of the instability region and reduces the dispersion of the surface waves. Both increasing S and decreasing Pe can suppress the evolution of slow waves, but have little effect on the evolution of fast waves.

    Catalysis, kinetics and reactors
    Research on chemical looping reforming of CH4 by CeO2 doped CuFe2O4 oxygen carrier coupled with CO2 thermocatalytic reduction
    Baowen WANG, Gang ZHANG, Tongqing LIU, Weiguang LI, Mengjia WANG, Deshun LIN, Jingjing MA
    2022, 73(12):  5414-5426.  doi:10.11949/0438-1157.20221139
    Abstract ( 240 )   HTML ( 28)   PDF (8920KB) ( 129 )  
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    The CH4 chemical chain reforming coupled with CO2 thermal catalytic reduction can not only flexibly adjust the H2/CO ratio of the prepared syngas, but also realize the high-value utilization of the two greenhouse gases, which has great application prospects. Mixed oxygen carriers of CuFe2O4 doped with CeO2 of different mass contents were prepared by using a sol-gel combustion synthesis (SGCS) method. In a self-made multifunctional fixed-bed reactor, the thermal catalytic reduction performance of modified oxygen carrier and CH4 for partial oxidation and reduced oxygen carrier for CO2 was systematically investigated. And through continuous redox experiments, it was found that the CuFe2O4 composite oxygen carrier enhanced by CeO2 doping has higher reactivity towards CH4 and CO2 than the single oxide component. Furthermore, CuFe2O4 doped with 30%(mass) CeO2 was found to have the highest CH4 conversion, and during the cyclic reaction processes, high conversions of both CH4 and CO2 were sustained, as thus demonstrating its desired reaction performance and cyclic stability.

    Effect of oxygen concentration on homogeneous/heterogeneous coupled reaction characteristics of methane in microchannel
    Xiao YANG, Rui DING, Mohan LI, Zhengchang SONG
    2022, 73(12):  5427-5437.  doi:10.11949/0438-1157.20221301
    Abstract ( 215 )   HTML ( 16)   PDF (3114KB) ( 99 )  
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    Based on the detailed homogeneous and heterogeneous reaction mechanisms of methane, the catalytic combustion process of methane in a planar microchannel was simulated, and the effect of inlet oxygen concentration on the coupled reaction characteristics and its regulation mechanism were analyzed. The results show that the increase of oxygen concentration causes the exothermic position of the homogeneous and heterogeneous reactions of methane to move to the inlet side, shortening the homogeneous ignition distance and broadening the stable combustion range. At a fixed methane concentration at the inlet, increasing O2 concentration lowers the equivalence ratio of mixture and changes the competition mechanism between homogeneous and heterogeneous reactions for reactant O2; the combined effect of O2 concentration and equivalence ratio changes the adsorption and desorption behavior of gas radicals. The increase of O2 concentration promotes the homogeneous reaction consumption of CH4 and H radicals and also inhibits the heterogeneous reaction rate of CH4 and H on the catalytic surface. With the increase of O2 concentration, the rates of O2, and intermediate gas phase products CO and H2 participating in the heterogeneous reaction first increase and then decrease.

    Separation engineering
    Microporous Noria polymer for selective adsorption and separation of xylene isomers
    Qingling QIAN, Qing ZHU, Zhengjin YANG, Tongwen XU
    2022, 73(12):  5438-5448.  doi:10.11949/0438-1157.20221303
    Abstract ( 182 )   HTML ( 6)   PDF (2834KB) ( 173 )  
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    The separation of xylene isomers is an important but challenging industrial process, and the development of novel adsorbent materials is the key to achieving efficient separation. Herein,microporous Noria polymer (MNP) with network structure was synthesized by reacting Noria with 2, 3, 5, 6-tetrafluoroterephthalonitrile and explored for the separation of xylene isomers. MNP is microporous and shows high specific surface area, as revealed by nitrogen adsorption and desorption isotherms. The adsorption of xylene isomers on MNP was investigated. The adsorption isotherms fit well to the Langmuir isotherm model and the adsorption kinetics of three xylene isomers can be described by the pseudo second-order kinetics model. We found that MNP shows a selective interaction with o-xylene, with a maximum adsorption capacity of up to 344 mg·g-1 for o-xylene according to Langmuir adsorption isotherm fitting. The selectivity of o-xylene over p-xylene is about 1.9 in competitive adsorption experiments, while that of o-xylene over m-xylene can reach as high as 2.4. Dynamic breakthrough experiments verify that MNP can effectively separate o-xylene from xylene isomer mixtures. In addition, MNP has an extremely short adsorption equilibrium time and excellent thermal stability, and is a potential adsorbent for the separation of o-xylene.

    Process system engineering
    Lumping gasoline with molecular properties and density peak clustering
    Huaixu LI, Xiaoyan SUN, Shaohui TAO, Li XIA, Shuguang XIANG
    2022, 73(12):  5449-5460.  doi:10.11949/0438-1157.20221231
    Abstract ( 192 )   HTML ( 12)   PDF (3031KB) ( 80 )  
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    With advancement in petroleum molecular management technology, oil and its downstream products like gasoline are characterized by their real molecular composition. While the molecular characterization of oil products brings more detailed information, it also leads to a sharp increase in the scale and computational complexity of oil refining process simulation and optimization models. To solve this problem, a density peak clustering technique, which does not require a predetermined number of categories, is applied and the oil is lumped by thermodynamic properties of the real components, thus the oil product is fully characterized by a small number of pseudo-components. Taking a desulfurized gasoline feed in a certain process as an example, the density peak clustering lumping method was applied to the lumping of this gasoline. The results indicated that the number of components of gasoline products is greatly reduced by the proposed approach, and the simulation efficiency of the gasoline fractionator is effectively improved while the simulation accuracy is guaranteed.

    A deep learning-based model for predicting the stability constants of metal ions with organic ligands
    Shuping QI, Wenlong WANG, Lei ZHANG, Jian DU
    2022, 73(12):  5461-5468.  doi:10.11949/0438-1157.20221081
    Abstract ( 424 )   HTML ( 29)   PDF (1651KB) ( 253 )  
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    The stability of metal ion-organic ligand complexes is determined by three factors: metal ion species, organic ligand structure and experimental conditions. Obtaining the stability constants of complexes using traditional methods is time-consuming and labor-intensive, which is not conducive to high-throughput screening of specific metal chelators. Therefore, based on multi-head graph attention network (multi-head GAT), a high-throughput prediction model of complex stability constant is proposed in this paper. Firstly, molecular attribute diagrams were generated for 1371 organic molecules out of 7127 complexes extracted from mini stability constant database. Second, the multi-head graph attention network is used to extract the features of the attributed molecular graph. The extracted molecular features are spliced with the metal ions and the experimental conditions encoded by one-hot encoding. Finally, all feature codes are sent to the fully connected layer to predict the stability constants of the complexes. The determination coefficient (R2) and root mean square error (RMSE) of the model on the test set are 0.956 and 1.251, respectively, indicating that the model has good generalization ability. In addition, using the model to predict the stability constants of chelates in the literature, the model proposed in this paper is more reliable and efficient than the results based on density functional theory (DFT) calculations.

    Full-cycle slow-lift limited optimization analysis of multi-effect distillation heat transfer temperature difference in seawater desalination system
    Dehong WANG, Lin SUN, Xionglin LUO
    2022, 73(12):  5469-5482.  doi:10.11949/0438-1157.20221212
    Abstract ( 154 )   HTML ( 10)   PDF (3102KB) ( 78 )  
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    Multi-effect evaporative seawater desalination technology is the mainstream seawater desalination method at this stage. In the actual production process, the process designer will redundantly design the evaporator heat exchange area to deal with the scaling and safety problems of the system. On the another hand, the secondary steam valve in the conventional method does not play an appropriate role in the distillation process, which leading to lower anti-jamming capability of the system. Based on the temperature characteristics of the seawater desalination multi-effect system, it was found that the full-cycle operation of the secondary steam valve can not only improve the utilization rate of the heat exchange area and the operating efficiency of the system, but also avoid the occurrence of the problem of internal consumption. Therefore, a slow-lift limited full-cycle optimization method of the evaporative heat transfer temperature difference is proposed. This method increases the operating efficiency of the margin slow-release optimization model, controls the secondary steam valve and considers the full-cycle operating characteristics. Therefore, this new method realizes the effective monitoring of the heat exchange area of the system. At the end of this essay, the full-cycle slow-lift limited optimization of heat transfer temperature difference is verified in the eight-effect seawater desalination device. The results show that this method takes into account the long-term and short-term goals of system operation, enhances the system's adjustment ability during full-cycle operation, reduces the coupling phenomenon between various effect evaporators, decreases internal margin consumption and external driving steam consumption, and realizes slow release of margin of the slow time-varying system.

    Integrating physics-informed neural networks with partitioned coupling strategy for modeling conjugate heat transfer
    Zhibin LU, Yimeng LI, Chang HE, Bingjian ZHANG, Qinglin CHEN, Ming PAN
    2022, 73(12):  5483-5493.  doi:10.11949/0438-1157.20221174
    Abstract ( 361 )   HTML ( 14)   PDF (2948KB) ( 250 )  
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    Physics-informed neural network (PINN) realizes deep learning with embedded physical knowledge by mathematically encoding partial differential equations, and has been successfully applied in the fields of fluid mechanics and heat transfer. However, due to the strong coupling of heat transfer in fluids and heat conduction in solids, regular PINN methods are difficult to effectively solve the conjugate heat transfer problems that commonly exist in the aforesaid fields. As a widely-used partitioned coupling strategy, the heat transfer coefficient forward temperature backward (hFTB) can feasibly deal with complex coupling relation in the interface by solving the fluid and solid domains separately. In this work, based on real physical property systems, a modeling strategy that combines partitioned coupling and PINN is proposed by using hFTB approach. Taking 2-D and 3-D conjugate heat transfer models as examples, the results of multi-physics fields obtained by the proposed strategy are compared with those by using conventional CFD simulation. The resulting maximum absolute errors of the solid temperature of the 2-D and 3-D models are only 0.19 K and 2.12 K, respectively, which reflects the effectiveness of the proposed strategy in modeling conjugate heat transfer under the real physical property systems.

    Energy system integration and catalyst regeneration cycle optimization of benzene hydrogenation to cyclohexene process
    Liwen ZHAO, Guilian LIU
    2022, 73(12):  5494-5503.  doi:10.11949/0438-1157.20221213
    Abstract ( 256 )   HTML ( 13)   PDF (1300KB) ( 98 )  
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    The selective hydrogenation of benzene to cyclohexene is the best way for industrial large-scale production of cyclohexene. The key to this reaction is the selection of catalysts with high activity and selectivity. Under the influence of various factors, the catalyst activity deteriorates with time, affecting reactor parameters and the integration of the heat exchanger network (HEN). A coupling model of the reactor-HEN system is established based on the material balance, the energy balance, and the analysis of the temperature-enthalpy diagram, revealing the influence of catalyst deactivation on energy system integration. This model is applied to analyze the hydrogenation process of benzene to cyclohexene, and correlations among the catalyst activity, the parameters of reactor, and energy consumption of the HEN are deduced. Based on these equations, the reactor-HEN coupling performance diagram is constructed with catalyst activity as the independent variable. It can directly reflect the variation trend of conversion, inlet and outlet temperatures of reactor, heat load of reactor, system energy consumption, system running time, and unit product cost with catalyst deactivation. The optimal regeneration activity of the Ru-Zn-B/ZrO2 catalyst is determined to be 0.5, and the optimal regeneration cycle is 0.92 a by taking the unit product cost as an evaluation index. After the optimization, the average production cost per unit product can be reduced by 19.9%.

    Surface and interface engineering
    Study on the occurrence and development mechanism of pipeline corrosion behind butterfly valve
    Guoqing SU, Jianwen ZHANG, Yan LI
    2022, 73(12):  5504-5516.  doi:10.11949/0438-1157.20221209
    Abstract ( 178 )   HTML ( 9)   PDF (5892KB) ( 141 )  
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    Aiming at the abnormal thinning of the pipeline behind the butterfly valve in a petrochemical plant, combined with corrosion analysis, corrosion test and numerical simulation, the causes of abnormal thinning of the pipeline were analyzed, and the occurrence and development mechanism of corrosion were studied. The structure and composition of the samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), energy spectrometer (EDS) and metallographic microscope. The influence of flow field parameters on corrosion process was calculated and analyzed based on computational fluid dynamics (CFD). The results show that the main failure reason is flow accelerated corrosion. In addition, the pipeline behind the butterfly valve is divided into three different areas based on the relationship between velocity boundary layer and wall roughness, and the occurrence and development mechanism of corrosion in different areas are explained by schematic diagrams.

    Influence of wall charge on ice adhesion on copper surface
    Wenhao CAI, Xiongwen XU
    2022, 73(12):  5517-5525.  doi:10.11949/0438-1157.20221169
    Abstract ( 162 )   HTML ( 9)   PDF (3714KB) ( 101 )  
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    In the dynamic ice storage of supercooled water, the ice adhesion on the low temperature heat exchange surface is the main threat to the stable operation of the system. Studies have shown that the interfacial region of ice and heat exchange surface has a quasi-liquid layer whose thickness is the main factor affecting the adhesion strength. The wall charging may increase the thickness of the quasi-liquid layer of ice and reduce the adhesion strength. Therefore, the molecular dynamics simulation of the equilibrium and stripping of the adhering ice on the copper wall was carried out under different wall charging conditions at the same water molecular system temperature (T=255 K), and the thickness of the quasi-liquid layer of adhering ice and adhesion strength was obtained. The results show that, compared with the case where the wall is uncharged, when the wall charge density Qstatic=±0.1123 e/nm2 and remains constant, the thickness of the quasi-liquid layer changes little, and the adhesion strength of ice increases due to the enhanced Coulomb interaction between the wall surface and water molecules. When the copper wall is charged with pulse Qperiod=±0.1123 e/nm2, the thickness of the quasi-liquid layer of ice increases significantly, and the adhesion strength decreases by 31.9% within the range that can be reduced. Therefore, wall pulse charging is an effective way to reduce the strength of ice adhesion.

    Fractal wear prediction model and numerical analysis of floating ring seal face
    Zhimin ZHANG, Xuexing DING, Lanxia ZHANG, Ning LI, Jiaxin SI
    2022, 73(12):  5526-5536.  doi:10.11949/0438-1157.20221175
    Abstract ( 177 )   HTML ( 10)   PDF (2084KB) ( 74 )  
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    Aiming at the end face wear of graphite floating ring seal of aero-engine, based on the modified fractal contact theory and Archard wear theory, the fractal wear prediction model of graphite floating ring seal end face is derived from the microscopic point of view, and the test data of literature is used to verify the rationality of the model. Next, numerical simulations were then adopted to analytically study the influence of surface contour parameters and working conditions on the rate of surface wear. The results show that the rate of surface wear first increased before decreasing with fractal dimension, reaching its minimum when the fractal dimension lies between 1.45 and 1.65. Moreover, keeping the fractal dimension constant proves to raise the rate of surface wear with increasing magnitudes of surface feature parameters, friction coefficient and sliding speed of floating ring. The rate of surface wear is mainly related to the smallest level of the frequency component and the seven successive levels of asperities thereafter. By contrast, the influence of the remaining asperities on the overall surface wear rate is negligible.

    Study on evaporation characteristics of sessile droplet on a convex substrate at constant temperature
    Shulei ZHANG, Bingjie LI, Jian JIANG, Xinyu DONG, Lu LIU
    2022, 73(12):  5537-5546.  doi:10.11949/0438-1157.20221227
    Abstract ( 199 )   HTML ( 5)   PDF (2143KB) ( 87 )  
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    In this paper, experimental and theoretical studies on the evaporation process of sessile droplets on a convex constant temperature substrate were carried out. In the aspect of experimental research, a visual experimental system for evaporation of distilled water droplets on a convex constant temperature substrate was developed to capture the morphological changes during droplet evaporation process, and the temperature distribution on the droplet surface was obtained by using an infrared thermal imager. In terms of theoretical research, a heat and mass transfer model for the sessile droplet evaporation on a convex constant temperature substrate was established based on an annular coordinate system, and analytical solutions of the temperature distribution inside the droplets and the concentration distribution of the surrounding vapor were derived. The model results are compared with the experimental data to verify the reliability of the calculation model. The results show that the evaporative cooling effect should be considered in the model calculation. Increasing the substrate temperature and decreasing the substrate curvature diameter can increase droplet evaporation rate. Compared with the plane substrate, the spreading radius of the droplets on the convex substrate is larger, the pinning time is longer, and the total evaporation time is reduced. The droplet evaporation mainly follows the constant contact radius evaporation mode. In addition, the excess temperature at the droplet/air interface increases monotonously along the direction from the center of the droplet surface to the contact line, and the overall temperature distribution of the droplet tends to be uniform as the evaporation process proceeds. The results help to understand the heat and mass transfer mechanism of sessile droplet evaporation on a convex substrate.

    Energy and environmental engineering
    Dissolution reactivity and kinetic model of low-grade limestone
    Shuaiwei GU, Wei ZHANG, Zhen CHEN, Haiming WANG, Changfu YOU
    2022, 73(12):  5547-5554.  doi:10.11949/0438-1157.20220864
    Abstract ( 223 )   HTML ( 4)   PDF (1993KB) ( 59 )  
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    The non-creation and non-regeneration of limestone resources lead to the shortage of high-grade limestone and the continuous decline of limestone grades. The application of low-grade limestone leads to a decrease in the efficiency of the desulfurization system, which has gradually become a frequent accident in the industry. In order to study the dissolution kinetics of low-grade limestone in acidic environment, the effects of experimental variables including reaction temperature, slurry pH and initial particle size are investigated, respectively. The results show that the dolomite [CaMg(CO3)2] is the main impurity in low-grade limestone which has a much lower dissolution rate than that of CaCO3 in acidic environment. The dissolution process of low-grade limestone is mainly controlled by the internal diffusion. In addition, a semi empirical dissolution kinetic equation of low-grade limestone is established based on the shrinkage model of unreacted core.

    Safety differences of LiFePO4 batteries at the beginning of life and end of life
    Bozheng LIU, Jingbo WANG, Tao ZENG, Yaxia YIN, Yuguo GUO
    2022, 73(12):  5555-5563.  doi:10.11949/0438-1157.20221339
    Abstract ( 526 )   HTML ( 12)   PDF (1814KB) ( 235 )  
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    Compared with fresh batteries, the safety research of lithium-ion batteries in the whole life cycle is more worthy of attention. The large-size prismatic aluminum-shell lithium iron phosphate power batteries in two states, i.e., beginning of life (BOL) and end of life (EOL) were selected as the research objects. The specific heat capacity, thermal conductivity, material's thermal stability and direct current internal resistance of BOL and EOL batteries were analyzed firstly. The safety differences of BOL and EOL batteries were compared in detail, such as over-discharge, over-charge, external short-circuit, heating, nail penetration, and crush, etc. The results show that compared to BOL battery, the specific heat capacity of the EOL battery decreases from 1.088 J/(g·℃) to 1.065 J/(g·℃). The thermal conductivity in the height, width, and thickness directions of the battery decreased from 25.84, 21.21, 1.05 W/(m·K) to 22.20, 18.44, 1.00 W/(m·K). The exothermic peaks shifted to low temperature, and the exothermic peak of solid electrolyte interface film decomposition appeared near 121℃, and the exothermic enthalpy of the reaction between the intercalated lithium-graphite compounds, electrolyte, and binder decreased from 1019 J/g to 841 J/g. In terms of safety, the EOL battery after over-discharge generated more gas, leading to a larger thickness swelling. Over-charge produced more gas with EOL battery, and the vent opened ahead of 7% state of charge. The external short-circuit current cannot fuse the connecting structure, and the battery would discharge continually to over-discharge state, giving more gas production and serious swelling. The nail penetration did not release smoke, the vent was not broke, and the safety was greatly improved. The temperature of thermal runaway caused by heating was close, and the differences of other safety test items were little. The research results enriched the research on the safety performance of lithium-ion batteries in the whole life cycle, and contributed to the thermal runaway protection design of batteries, modules and systems.

    Characterization and reactivity of soot from biomass pyrolysis in a fixed bed reactor
    Yan LI, Jinhui CAO, Yuanyi LIU, Houzhang TAN
    2022, 73(12):  5564-5571.  doi:10.11949/0438-1157.20221152
    Abstract ( 211 )   HTML ( 5)   PDF (4122KB) ( 78 )  
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    The pyrolysis experiments of two biomasses, wheat straw and wood chips, were carried out on a fixed bed. The physicochemical properties of the pyrolysis soot were characterized, and their oxidation/gasification characteristics were determined on a thermobalance. The yield, particle size distribution and internal nanostructure of the two biomass soots were studied at different pyrolysis temperatures. On this basis, the influencing factors of the soot reactivity were analyzed, and the results were compared with the adopted comparison of soot obtained by one-dimensional settling furnace pyrolysis. The results show that soot obtained by fixed bed pyrolysis has higher purity. With the increase of the generation temperature, the structure of soot becomes more ordered, which indicates the increases of graphitization. Besides, the geometric average particle size of the single soot particle becomes smaller. However, the reactivity of soot becomes worse at elevated temperature, indicating the change of the internal structure of soot plays a major role in its oxidative activity. The fuel concentration of biomass in a limited space affects the yield, inter-structure and particle size of soot. High feedstock spatial concentrations tend to generate more soot with larger particle size. Compared with wheat straw soot, sawdust soot has higher graphitization degree, thus showing poor reactivity.

    Numerical simulation of novel SOFC interconnector with thermoelectric co-enhancement
    Keqing ZHENG, Ya SUN, Yangtian YAN, Li LI, Jun YANG
    2022, 73(12):  5572-5580.  doi:10.11949/0438-1157.20220933
    Abstract ( 186 )   HTML ( 4)   PDF (1530KB) ( 67 )  
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    The development of thermal management technology is of great significance to the industrialization of solid oxide fuel cell (SOFC). At present, the main method of SOFC thermal management is to supply excess air into the cathode to take away the waste heat. However, this method results in high extra power consumption due to the small specific heat capacity of air. Therefore, in this paper, a novel interconnector is proposed for SOFC thermal management, in which the in-site heat production of the cell is balanced by the heat absorption of NH3 cracking reaction. The results show that compared with the excess air thermal management method, the novel interconnector reduces the maximum temperature difference in the cell by 80.2% and improves the cell performance by 23.1%. The numerical results demonstrate the potential of the novel interconnector for thermo-electric synergistic enhancement.

    Investigation on cofiring high-alkali coal with coal gangues: SO2, NO reduction and ash slagging inhibition
    Shunjin HUANG, Li ZHANG, Jingchong YAN, Zhigang WANG, Zhiping LEI, Zhanku LI, Shibiao REN, Zhicai WANG, Hengfu SHUI
    2022, 73(12):  5581-5591.  doi:10.11949/0438-1157.20221221
    Abstract ( 260 )   HTML ( 5)   PDF (2746KB) ( 110 )  
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    Slagging and fouling are common problems in high-alkali coal-fired boilers. Meanwhile, a large amount of solid waste coal gangue from coal mining and coal washing needs to be reduced and utilized for economical and ecological considerations. Given this, cofiring high-alkali coal (HAC) with coal gangues (CG) was performed to verify the possibility of inhibiting ash-related problems of HAC meanwhile achieving resource utilization of CG. Besides, the evolution behaviors of pollution gases (SO2 and NO) were examined. The results show that cofiring reaction follows a three dimensional diffusion model, and at proper ratios the activation energy of cofiring can be lower than that of mono-combustion. NO can be efficiently reduced during cofiring with the enhanced catalytic components in the blended fuels, while the reduction of SO2 is largely determined by the blending ratio and ash compositions. Alkali metals are effectively retained in ashes thus lowering the fouling and slagging propensity, while alkaline metals participate the competitive reaction with silica and alumina components and that of SO2 fixation reactions. The ash fusion temperatures can be adjusted through cofiring with CG with various inherent minerals, thus providing the opportunity to alleviate the ash-related problems for burning HAC in commercial boilers.

    Material science and engineering, nanotechnology
    Effect of Co on the pre-reduction process of WO3-Co3O4 and carbonization performance of its product
    Huijun SHANG, Hengli LI, Jiayi LIU, Feng PAN, Zhan DU, Linbing SUN
    2022, 73(12):  5592-5604.  doi:10.11949/0438-1157.20221018
    Abstract ( 155 )   HTML ( 8)   PDF (3819KB) ( 67 )  
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    In order to avoid the formation of η phase (Co6W6C or Co3W3C) that adversely affect the sintering process and its products in the preparation process ultra-fine WC-Co powder, we propose a technical route of pre-reduction of WO3-Co3O4 to WO2-Co and then deep reduction carbonization to WC-Co. The influence of Co content and cobalt source particle size on the pre-reduction process of WO3-Co3O4 was investigated at 600℃ H2-C2H4-Ar atmosphere in a fluidized-bed reactor, and the deep reduction and carbonization properties of the pre-reduced products were tested. The results show that the presence of Co can catalyze the splitting of C2H4 to separate H2 and C, significantly accelerate the pre-reduction rate of WO3, and the pre-reduction rate increases significantly with the increase of Co content. The carbon evolution rate and carbon evolution amount of ethylene also increase with the increase of Co content. Cobalt source particle size has a significant effect on the pre-reduction rate of WO3 and carbon evolution rate of C2H4. In this experimental system, the carbon evolution rate of C2H4 in nano cobalt source system is about twice that of micron cobalt source system. Meanwhile, WO3 in nano cobalt source system also has faster reduction rate. The pre-reduced product was calcined with methane partial pressure of 1.25% at 950℃ for 60 min, and fine WC-Co composite powder without η could be obtained.

    Preparation and analysis of carbon aerogel microspheres based on coal tar pitch
    Huifang NIU, Lunjing YAN, Peng LYU, Xufeng ZHANG, Meijun WANG, Jiao KONG, Weiren BAO, Liping CHANG
    2022, 73(12):  5605-5614.  doi:10.11949/0438-1157.20221095
    Abstract ( 217 )   HTML ( 23)   PDF (2648KB) ( 228 )  
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    Coal tar pitch is a complex mixture composed of highly condensed aromatic compounds, which has the advantages of high carbon content, widely availability, and low price. It is regarded as one of the promising precursors in the synthesis of various functional carbon materials. Using coal tar pitch as raw material and furfural as a cross-linking agent, pitch-furfural gel is formed by the cross-linking reaction under the catalysis of sulfuric acid, then, the carbon aerogel microspheres were obtained after ambient-pressure drying and carbonization. The effects of the coal tar pitch to solvent, crosslinking agent, and catalyst ratios on the gel degree of carbon gel and carbon aerogel microspheres density were discussed. It was found that the optimal ratio of pitch to solvent was 0.5 g/ml, pitch to crosslinking agent was 0.10 g/ml, and pitch to catalyst was 5 g/ml. The density of carbon aerogel spheres was 0.24 g/cm3 after carbonization. The microstructure of carbon aerogel microspheres is generated by the accumulation of spherical particles, according scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyzer (TG) were used to examine the structure evolution of pitch-furfural gel during the gelation process, as well as the production mechanism of pitch-furfural aerogel.The pore structure of the carbon aerogel spheres was dramatically improved after CO2 activation. With the increase of activation temperature and activation time, the specific surface area and pore diameter of the obtained samples were continuously increased, and mesopores with pore diameter of 2—3 nm were gradually formed. The samples activated in a CO2 atmosphere at 900℃ for 4 h and 950℃ for 2 h has specific surface areas of 2540 and 2852 m2/g, respectively. The microstructure of the carbon aerogel microspheres was unaffected, and the micromorphology of spherical particles was preserved, the particle shape was regular and the surface was smooth.

    Influence of cobalt-manganese ratio adjustment on the properties of LiNi0.8Co0.10-y Mn0.05+y Al0.05O2 materials
    Wei YANG, Yujie WANG, Kaibin FANG, Hanbo ZOU, Shengzhou CHEN, Zili LIU
    2022, 73(12):  5615-5624.  doi:10.11949/0438-1157.20220692
    Abstract ( 182 )   HTML ( 8)   PDF (3305KB) ( 198 )  
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    A series of LiNi0.8Co0.10-y Mn0.05+y Al0.05O2 (y=0.01,0.02,0.03,0.04) materials with different cobalt-manganese ratios were prepared by co-precipitation method with oxalic acid as precipitant and transition metal manganese as cobalt replacement element, and the effect of gradual substitution of manganese for cobalt on the properties of Ni-rich quaternary materials was studied. The experimental results show that the LiNi0.8Co0.08Mn0.07Al0.05O2 material had the best morphology, structural development and electrochemical performance. The co-doping of cobalt and manganese has a synergistic effect on the synthesized LiNi0.8Co0.10-y Mn0.05+y Al0.05O2 material, and the electrochemical capacity can be improved when the ratio of manganese doping is lower than that of cobalt. When the doping ratio of manganese exceeds that of cobalt, the capacity begins to decrease, indicating that the excessive doping ratio of manganese is not helpful for the improvement of the electrochemical performance of the synthesized high-nickel quaternary materials.

    Preparation and lithium storage performance of K+-doped spinel (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4 high-entropy oxide anode materials
    Pengpeng WANG, Yanggang JIA, Xia SHAO, Jie CHENG, Aiqin MAO, Jie TAN, Daolai FANG
    2022, 73(12):  5625-5637.  doi:10.11949/0438-1157.20221116
    Abstract ( 216 )   HTML ( 10)   PDF (4383KB) ( 253 )  
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    A series of inactive K+-doped spinel-type (K x CoCrFeMnNi)3/(5+x)O4 (x=0, 0.5, 1, 1.5) high-entropy oxides lithium-ion battery anode materials were successfully synthesized by solution combustion method, and the effects of K+ doping on the structure and lithium storage performance were systematically investigated. The results show that all the synthesized nanocrystalline powders are crystallized as single spinel structure with the increase of K+ doping. Among them, the equimolar K+-doped (K1/6Co1/6Cr1/6Fe1/6Mn1/6Ni1/6)3O4 high-entropy oxide anode material has the highest specific capacity, excellent cycling stability and rate capability. The initial specific discharge capacity of (K1/6Co1/6Cr1/6Fe1/6Mn1/6Ni1/6)3O4 is 1295 mA·h·g-1 at the current density of 200 mA·g-1 with columbic efficiency of 78%. The specific capacity decreases first and then increases as the cycle proceeds, and after 150 cycles the reversible specific capacity increases to 1505 mA·h·g-1. Even at a high current density of 1000 mA·g-1, it still has a reversible specific capacity of 1402 mA·h·g-1 after 500 cycles, which is much higher than the theoretical specific capacity of 898 mA·h·g-1. Although the doping of low-valent inactive K+ decreases the lattice constant due to the charge compensation effect, entropy-stabilized crystal structure improves the cycling stability, and the abundant surface oxygen vacancies, small grain size and mesoporous structure are beneficial to improve the pseudocapacitive contribution and electron/ion diffusion ability, which significantly improve the specific capacity and rate performance of the as-synthesized (K1/6Co1/6Cr1/6Fe1/6Mn1/6Ni1/6)3O4 anode material.

    Quantum chemistry study on gas reaction path in InN MOCVD growth
    Xiaokun HE, Yuan XUE, Ran ZUO
    2022, 73(12):  5638-5647.  doi:10.11949/0438-1157.20221276
    Abstract ( 205 )   HTML ( 5)   PDF (1386KB) ( 210 )  
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    By performing density functional theory (DFT) calculations of quantum chemistry, the gas-phase reaction paths in the InN MOCVD process are systematically investigated. By calculating the changes of Gibbs energy (ΔG) and the energy barrier (ΔG*/RT) of all proposed steps at different temperatures, the main gas reaction paths in InN growth from TMIn/NH3 are determined. According to computational results, when N2 is used as the carrier gas, the TMIn pyrolysis path competes with the adduct path could for the main reaction. The TMIn pyrolysis dominates the gas reaction path at high temperatures(T>873.0 K), whereas at low temperature (T<602.4 K), the adduct reaction to form TMIn:NH3 is favored, and the decomposition of TMIn:NH3 is predominant at medium temperature (602.4 K <T <873.0 K).When H2 is used as the carrier gas, the H and NH2 radicals can be generated through gas pyrolysis as well as surface reactions. Because H radicals can accelerate the TMIn pyrolysis and NH2 radicals canreact with TMIn and DMIn to generate DMInNH2, both radicals can disrupt InN MOCVD process. The formed amides can further react with H radicals and generate InNH2 near the high temperature substrate, and hence swaps the surface reaction precursors from MMIn and In to InNH2. Additionally, this study also illustrate how changing reaction temperature could affect InN MOCVD gas-phase pathways, and reveals novel reaction pathways with the interferences from H and NH2 radicals.

    Efficient solar interfacial evaporation using laser-induced graphene
    Xuemei CHEN, Tong WANG, Yubo GAO, Dingcheng PENG, Yuting LUO
    2022, 73(12):  5648-5659.  doi:10.11949/0438-1157.20220604
    Abstract ( 321 )   HTML ( 14)   PDF (4379KB) ( 143 )  
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    The traditional graphene preparation process is complicated and the environment is harsh. In this paper, laser induced method is used to prepare graphene, and its application in the field of solar-driven interfacial evaporation is explored. The commercial thermal insulation cork board (ICB board) is utilized as the substrate, and laser-induced graphene (LIG) is generated on its surface as a photothermal membrane (ICB-LIG membrane). With the aid of thermal insulation devices and water transportation channels, a new solar evaporator is constructed. The evaporation performance test results show that the solar evaporator can achieve an evaporation rate of up to 1.33 kg·m-2·h-1 under 1 sunlight irradiation, and the corresponding photothermal conversion efficiency is 86.0%. In addition, the solar evaporator has good durability, and the evaporation rate drops only 3.0% in 7 cyclic experiments.

    Preparation of highly thermally conductive and shape-stabilized polyethylene glycol-based phase change material
    Wenqi CUI, Shuguang YANG, Hongzhou LI, Fubin LUO
    2022, 73(12):  5660-5671.  doi:10.11949/0438-1157.20221141
    Abstract ( 238 )   HTML ( 11)   PDF (4575KB) ( 112 )  
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    Shape-stabilized and highly thermally conductive phase change materials (PCMs) have been prepared based on polyethylene glycol (PEG) and boron nitride (BN). The PCMs are obtained by two-step blending assisted by the complexation of polyacrylic acid (PAA). The thermal conductivity and the stabilization mechanism of the PCMs have been investigated. The results show that the flake-like BN can significant improve the thermal conductivity of the composites. The thermal conductivity of the prepared PCMs can reach to 6.437 W/(m·K) when the mass fraction of BN is 60%. It is also confirmed that when one-third and one-sixth of flake-like BN is replaced by the spherical BN, the composites show an increased thermal conductivity, which suggests that the hybrid fillers has positive effect on the enhancement of thermal conductivity. The experimental results demonstrate that PAA can form hydrogen bond with PEG, which contributes to preventing the leakage of PEG from the matrix when enduring heating. In addition, abundant flake-like BN can act as a solid physical barriers to restrict the molten PEG being escaped from the matrix, resulting the excellent shape preserving property.

    Process safety
    Effect of ignition delay time on explosion suppression characteristics of CO2-ultra-fine water mist
    Bei PEI, Yaxiang KANG, Minggao YU, Jiaqi GUO, Shuangming WEI, Liwei CHEN
    2022, 73(12):  5672-5684.  doi:10.11949/0438-1157.20221224
    Abstract ( 181 )   HTML ( 8)   PDF (7224KB) ( 52 )  
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    In order to study the influence of ignition delay time on the characteristics of CO2-ultra-fine water mist suppression of gas/coal dust explosion, different concentrations of ultra-fine water mist and CO2 were introduced into 20 L ball through a self-made ultra-fine water mist generator, and the explosion pressure, flame propagation velocity, flame structure and explosion flow field turbulence images of gas/coal dust under different ignition delay time were obtained. The research results show that compared with single explosion suppression, under the action of CO2-ultra-fine water mist, with the extension of ignition delay time and the increase of water mist concentration, the explosion intensity of gas/coal dust is weakened and the flame propagation speed is reduced. For 10%CO2 and 306 g/m3 ultra-fine water mist, the maximum explosion pressure and pressure rise rate at 1500 ms ignition delay are reduced by 6.79% and 16.14% respectively compared with those without water mist, and the arrival time of maximum explosion pressure is extended by 24.47%. Under 10%CO2 and 204 g/m3 ultra-fine water mist, the maximum explosion pressure and average flame speed at 2000 ms ignition delay are reduced by 5.22% and 37.5% respectively compared with 1000 ms ignition delay, and the arrival time of maximum explosion pressure is extended by 24.66%. It can be seen from the explosion flame schlieren image and PIV test that with the increase of water mist concentration and the extension of ignition delay time, the flame brightness decreases and sinks, and the motion state of coal dust particles in the flame changes from centripetal motion to rotational motion. This is because the initial intensity of gas explosion under the action of CO2 inerting decreases, while the concentration of water mist increases, the energy consumed by water mist endothermic evaporation increases during the explosion process, and the generated water vapor dilutes the oxygen concentration around the flame, further inhibiting the explosion reaction. Prolonging the ignition delay time strengthens the influence of water mist on the movement of pulverized coal, reduces the agglomeration and dispersion of coal dust, weakens the turbulent effect of coal dust cloud, suppresses the combustion and explosion of coal dust clouds, and finally reduces the explosion intensity of gas/coal dust. The research results provide technical guidance for the determination of control parameters of gas/coal dust explosion suppression by gas-liquid two-phase detonation inhibitor.