As the dual carbon goals and the energy revolution continue to advance, hydrogen energy has received widespread attention as an important clean energy source. Among the various hydrogen production pathways, electrolysis of water into hydrogen by solid oxide electrolytic cell (SOEC) is considered as one of the most promising pathways. In order to better serve the industrialization of SOEC, the current research status and challenges of SOEC need to be sorted out systematically. In this paper, the composition and basic principles of SOEC are introduced firstly. Then, the existing systems and bottlenecks of key materials are summarized based on domestic and international research. Meanwhile, the current research status and development direction of the stack and system are analyzed. Finally, the industrialization process are sorted out. Although electrolysis of water by SOEC has the advantages of high hydrogen production efficiency, low environmental pollution and efficient utilization of waste heat, there are still many difficulties in long-term stable operation and large-scale integration. And a certain gap exists in the industrialization of SOEC in China compared to foreign countries. Improving the stability of materials and optimizing control strategy are the key development directions of SOEC. In addition, accelerating the industrialization process of SOEC also needs to cooperate with the development of upstream and downstream industrial to reduce production costs. With the maturity of technology, electrolysis of water by SOEC is expected to be widely used in chemical industry, distributed energy resources and other fields.

Solid electrolyte interphase (SEI) is a passivation film formed on the surface of the lithium metal anode when the lithium metal battery is first charged and discharged. This interphase has a crucial impact on the cycle performance and safety of lithium metal batteries. A good understanding of SEI will help researchers develop lithium metal batteries with longer cycle life and higher safety. This paper reviews the research progress on solid electrolyte interphase in lithium metal batteries. It introduces the composition and structure of SEI, organizes the formation conditions and roles of various common components. Two main models used to describe the structure of SEI, namely the mosaic model and the laminar model, are demonstrated. Additionally, it summarizes key factors that affect the composition and structure of SEI such as electrolyte additives, electrode potentials, temperature, and current density etc. We also introduced the latest research progress in achieving interface stability control by introducing electrolyte additives and constructing artificial SEI membranes, and finally looked forward to the future research directions of SEI membranes.

With the rapid development and wide application of power battery vehicles, the demand for lithium resources has increased sharply. How to realize the efficient utilization and development of lithium resources in salt lakes, which has international resource advantages in China, is a key issue that the salt lake chemical industry needs to solve urgently in recent decades. Compared with the salt lakes that have been developed and utilized abroad, except for some salt lakes in Xizang, the lithium resources in China's salt lakes are mostly low-grade resources with lithium concentrations as low as tens of mg/L and extremely high magnesium lithium ratio (about 500 or even higher). Up to now, based on the characteristics of lithium resources in salt lakes, several methods have been developed to extract lithium from salt lakes, such as membrane method, adsorption method, solar pool method, solvent extraction method and electrochemical method, some of which have been successfully applied in the actual industrial production of lithium extraction from salt lake brines. Especially, adsorption method has attracted much attention due to its characteristics of high Li⁺ selectivity, good applicability, simple process, green efficiency and recyclability. Layer-structured aluminum-based adsorbents (Li/Al-LDHs) have been successfully industrialized due to their high selectivity, green environmental protection and other advantages. However, there are still some problems such as extremely low dynamic adsorption capacity and serious pulverization in the large-scale application of this kind of adsorbent, which need further study and discussion. Therefore, based on the structure-activity relationship between the adsorption properties of Li/Al-LDHs and the crystal structure, this paper summarized the reasons for the short cycle period and poor application performance of Li/Al-LDHs adsorbent, and proposed the performance improvement scheme from the perspective of structural stability.

In recent years, industries such as energy-saving, environmental protection, intelligent manufacturing and green low-carbon continue to develop, with the gradual implementation of the “14th Five-Year Plan” policy, carbon materials have played a crucial irreplaceable role. Soft and hard carbons have attracted wide attention from the scientific and industrial communities owing to their belongings to an important carbon material like graphite, graphene and nanocarbon. Thus, there is a vigorous growth in the development and utilization of soft and hard carbons in numerous fields such as new energy, new technology and ecological environment. First, the importance, research hotspots and historical development (in terms of professional terminology) of soft and hard carbons are introduced. The structure characteristics and classic structure models of soft and hard carbons are systematically summarized. Then, a comprehensive overview is focused on the preparation methods (e.g., gas-phase, liquid-phase and solid-phase carbonizations) and control means (including the rational selection of carbonaceous precursors), as well as regulating measures, thermal evolution laws and mutual transformation of microcrystalline structure. While giving a brief overview of the applications of soft/hard carbon in traditional fields, it also focuses on its applications in emerging fields such as energy storage and conversion, advanced catalytic materials, and efficient adsorption and environmental protection. Finally, a summary and outlook is presented on the research prospects and development trends of soft and hard carbons, offering an overall perspective for the design and development of soft and hard carbons with low-cost production, controllable fine-structure, adjustable excellent-performance, and high value-added and high-end applications.

The organic Rankine cycle (ORC) has important applications in the field of low and medium-temperature heat utilization. The control strategy exploration is a necessary process for the commercialization of this technology. In this paper, an ORC unit is designed based on the hot-dry-rock geothermal parameters through thermodynamic calculation and equipment selection. Then, the dynamic models of this unit and equipment were developed. The effect of four strategies on the performance of the ORC unit was investigated: constant superheat operation, constant evaporating pressure operation, constant load operation, and variable load operation. The results show that adjusting the flow rate of the working fluid pump can satisfy the dynamic control of the ORC system and achieve efficient and stable operation of the system. The constant superheat operation not only ensures the safe operation of the system when the heat source temperature fluctuates but also shows the best output performance. The constant evaporation pressure operation, constant load operation, and variable load operation can be applied in their required stable pressure, stable load, and variable load scenarios, but they all have a great influence on the superheat level, which limits their scope of application. Therefore, different operation modes should be combined in the control strategy according to the specific operating scenarios in practical applications.

Spiral wound tube heat exchangers (SWHE) are widely used in the chemical industry due to their compact structure and high heat transfer efficiency. However, their complexity also brings difficulties to research. In this article, a three-dimensional numerical model of SWHE is established by the mixture model and phase transition model to investigate flow and heat transfer characteristics in both shell side and tube side. To achieve this goal, an overall geometric model with the same size as the experimental equipment is constructed. Then, a whole physical model of the phase-change heat transfer process is developed by employing the mixture model and interface mass transfer model. The proposed model is validated by the experimental data. The validation results show that the simulation data can agree with the experimental data with a deviation of 4.98%. The influences of operating conditions on heat transfer characteristics and phase change are investigated by using this model. The effects of the heat exchanger length and the number of layers are also analyzed. The paper provides numerical methods and data for the design purpose of SWHE.

The evaporation of sessile droplets plays an important role in various applications. However, numerical simulation methods still need to be explored to investigate the influence of electric fields on the internal flow and heat transfer of droplets. A multi-relaxation lattice Boltzmann model was proposed by combining the phase change and leakage dielectric models, and was compared and verified with experimental results. This model was used to study the influence of electric field on the morphological changes, electric field force distribution, flow and heat transfer during the evaporation process of droplets. The results showed that the droplets were stretched along the direction of the electric field, and their height increased with the electric capillary number (Ca_E) while the contact diameter of the droplet decreased. The electric field expanded the range of the internal flow of the droplets to render their flow more uniform. When Ca_E=0.4, the value of Peclet number was 3.3 times that in the absence of the electric field, but the internal flow of the droplets had no significant effect on the temperature distribution of the system. As the electric field stretches the droplets, the thermal resistance to heat transfer increases and therefore the time required for evaporation increases. The effect of electric field is to change the geometric characteristics of droplets, and the increase of contact line densityis the main reason affecting the average heat flux.

Since there are many factors that influence the heat transfer coefficient in the horizontal tube falling film evaporation process, it is difficult to describe its complex nonlinear relationship by relying on traditional correlations. Hence, a BP neural network is proposed to construct a predictive model due to its exceptional capability in fitting functions. Additionally, a GA-BP model is developed to further refine the neural network through genetic algorithms. The parameters fed into the neural network include spray density, evaporation temperature, tube diameter, tube spacing, and salinity. To assess the models' efficacy, predicted values are compared with actual values while also introducing heat transfer correlations as a reference. The results indicate that the GA-BP model exhibits a mean absolute percentage error (MAPE) of only 8.10%, marking a 31.93% reduction compared to the original BP neural network and leading to an approximate 70% improvement in predictive accuracy over traditional heat transfer correlations. It appears that neural network methods hold a distinct advantage in modeling nonlinear systems, effectively predicting the heat transfer coefficient of horizontal tube falling film evaporation. This lays a reliable foundation for further optimizing operational parameters and enhancing the evaporator's heat transfer performance.

Wall shear stress is a key parameter in the near wall transfer process of gas-liquid two-phase flow. Based on the limit diffusion current method, the wall shear stress characteristics of gas-liquid two-phase slug flow in an upward tube under rolling condition were experimentally studied, and the radial distribution and axial evolution of the wall shear stress were obtained. The test section is 2.3 m in height, the rolling amplitude and frequency are in the ranges of 10 mm to 30 mm and 1 Hz to 2.5 Hz, respectively. The results show that the intermittent flow of Taylor bubbles and liquid plugs under slug flow causes the transient wall shear stress to have pulsating characteristics. The radial distribution of the wall shear stress under static conditions is relatively uniform and slightly increases along the flow direction. As the rolling amplitude and frequency increase, the length of Taylor bubbles tends to be shorter, resulting in decrease in the peak region of transient wall shear stress.

It is very important to construct the temperature field of blast furnace wall for field operators to master the heat load state and fuel combustion in the furnace, find out the abnormal working conditions of blast furnace in time and ensure the stable and smooth operation of blast furnace. Aiming at the problems of difficult acquisition and visualization of the existing furnace wall temperature field, and the phenomenon of slag peel off and formation is not considered in the process of modeling and temperature measurement, this paper proposes a modeling method of blast furnace wall temperature field based on steady-state heat transfer analysis. First, taking the specific structure of blast furnace as the research object, the physical structure and heat transfer characteristics are analyzed in detail, and the three-dimensional simulation model of furnace wall is built by COMSOL simulation software. Secondly, fully considering the influence of slag skin on the temperature change of furnace wall, the physical and chemical changes of slag skin formation and shedding process are analyzed, and a steady-state heat transfer model including slag skin heat source term is established to obtain the initial temperature field of the inner surface of the furnace wall. Then, in order to improve the accuracy of the temperature field model, based on the inverse problem theory of heat conduction and taking the measured temperature of the thermocouple in the cooling wall as a reference, a furnace wall temperature field correction model was constructed to achieve iterative correction of the furnace wall temperature field data. The experiment shows that the calculation error of the heat transfer model can be controlled within 5% after the correction of the temperature field correction model, which indicates that the proposed method can meet the requirements of on-site detection accuracy and has obvious feasibility and great social value. Finally, through visual display, it provides reliable furnace wall temperature field data for the stable and smooth operation of blast furnace and the regulation and operation of staff, which is helpful to improve the production efficiency of blast furnace and the level of energy saving and emission reduction, and promote the intelligent transformation and upgrading.

The sizes, the distances between the bubbles, and the coalescence time of chlorine gas bubbles were experimentally measured in brine under electric field conditions in this article. A two-phase flow and the phase field models were used to numerically simulate the coalescence process of chlorine gas bubbles under electric field conditions. The results showed that the deviation of the bubble coalescence time obtained by experimental and numerical methods was 11.0%, indicating a good agreement between them. On this basis, the coalescence process of bubbles under different voltages was analyzed, and the effects of bubble diameter, liquid surface tension, and viscosity on the coalescence process of chlorine gas bubbles were investigated, and their influencing laws were obtained. The results show that within the voltage range of 0—200 V, the larger the voltage, bubble diameter, and liquid viscosity, the larger the bubble spacing, and the longer the coalescence time. The greater the surface tension of the liquid, the smaller the spacing between bubbles, and the shorter the coalescence time.

As a high-efficiency heat exchange element, pulsating heat pipes (PHP) can play an important role in the cold transfer process of cryogenic refrigerators. Visualization on the flow patterns enables a comprehensive understanding of the fluid dynamic and heat transfer mechanism involved in the PHP. However, due to the complexity of conducting visual experiments in cryogenic environments, there has been a scarcity of experimental studies on flow patterns in cryogenic PHPs. In this study, we developed a visualization setup utilizing a cryocooler as the heat sink to systematically investigate the effects of condenser temperature on heat transfer performance. The results show that higher condenser temperatures decrease the required heat load for startup at low filling ratio, but the heat transfer limit occurs. At the medium filling ratio, the partial operation, which is not fully activated, leads to an increment in the thermal resistance at low condenser temperatures. The fully activated operation can decrease the thermal resistance. With a high filling ratio, the regular gas-liquid motion occurs inside the PHP. As the heat load increases, the thermal resistance initially decreases and then stabilizes at a constant value. For the three kinds of filling ratios, the condenser temperature increases, which can benefit for the fully activated operation inside the PHP, consequently resulting in lower thermal resistances.

Electrocatalytic water splitting is one of the most effective strategies for hydrogen production. Oxygen evolution reaction (OER) is the decisive step for water splitting. In view of the slow kinetics for OER, developing electrocatalysts that can effectively accelerate OER kinetics has become the research hots. Here, carbon paper (CP) was firstly chosen as the self-supporting substrate, and zinc oxide nanoneedles (ZnO) was in situ hydrothermally grown onto it. After that, NiCoMo-layered hydroxide (NiCoMo-LDH) nanosheets were further generated on it by the hydrothermal treatment to obtain the NiCoMo-LDH/ZnO/CP composite. Finally, NiCoMo-LDH/ZnO/CP was annealed in the presence of dicyandiamide (DCDA) as the carbon and nitrogen sources for 2 h in nitrogen atmosphere, preparing the MoC and NiCo-encapsulated N-doped carbon nanotubes (NCNT) constructed on CP (i.e. MoC-NiCo@NCNT/CP). Due to the synergistic effect between MoC and NiCo, high electrical conductivity, and binder-free electrode configuration, the self-supported MoC-NiCo@NCNT/CP electrode exhibited the excellent activities in 1 mol·L^-1 KOH solution with only 243 mV overpotential to drive a current density of 50 mA·cm^-2. Moreover, MoC-NiCo@NCNT/CP still showed good stability for 20 h at 20 mA·cm^-2.

Fluorine-doping of TiO₂ (F-TiO₂) was prepared by using solvothermal method and subsequent soaking in KF solution, and hierarchical porous carbon foam (CCF) was prepared by using coal loose medium component as raw material. A composite photocatalyst F-TiO₂/CCF was then prepared by impregnating F-TiO₂ onto CCF. With phenol as the target pollution, the effects of F ion concentration, soaking time and activation time of CCF on the catalytic performance of the catalysts were studied. The samples were characterized by using XRD, XPS, SEM, N₂ adsorption, UV-Vis-DRS, etc. The results showed that the optimized preparation conditions of F-TiO₂/CCF were 0.1 mol/L of KF concentration, 24 h of soaking time, and 1 h of steam activation of CCF. The prepared composite catalyst had a photodegradation rate of 76% for phenol under 6 h of simulated sunlight which was 2.7 times higher than that of F-TiO₂ nanoparticles, and a total removal rate of 89%. After four consecutive degradation cycles, the removal rate of phenol remained around 84%. The strong electronegativity of doped fluorine atoms make the Ti in F-TiO₂ more positive, which is more conducive to coordinate with oxygen atoms in phenol. While the CCF support not only promotes the separation of photoexcited carriers, but also ensures the effective use of light and the rapid adsorption and diffusion of phenol due to its macro/meso/micro porous structure. All these factors contribute to the significant improvement of the photocatalytic performance of F-TiO₂/CCF.

The separation of aromatic and aliphatic hydrocarbons from straight-run naphtha is an important prerequisite for the optimal utilization of resources in the petrochemical industry. Solvent extraction and extractive distillation are commonly used separation methods. But traditional solvents usually have an upper limit of extraction capacity and the separation performance of low concentration aromatics is not ideal. Based on reversible π-complexation reaction, π-complexation extraction can realize the separation of mixtures. Bimetallic halides can directionally complex with aromatics, which breaks the limit of extraction capacity and achieves the purpose of highly selective separation of aromatics. The aromatics complexation extraction performance of a variety of bimetallic halides was investigated. It was found that CuAlCl₄ showed good complexation extraction performance for aromatics. The aromatics selectivity could reach 88.15, which was significantly better than the traditional solvents. The interaction forms and interaction energy between bimetallic halides and hydrocarbons were explored using molecular simulation based on the density functional theory. The results showed that π-complexation is the essential reason for the separation of aromatics. The study indicates that bimetallic halides can separate aromatics from naphtha with high selectivity.

A six-bed PSA oxygen production process was designed by using 13X zeolite as adsorbent, which can be used in medium-sized medical oxygen concentrators. The adsorption isotherms of nitrogen and oxygen on 13X zeolite were measured by the static volumetric method. A mathematical model of the pressure swing adsorption process was developed, including the mathematical model of adsorption bed and auxiliary equipment. The process was simulated by using Aspen Adsorption software, and the pressure, temperature and solids concentration distribution within the column were analyzed. The simulations demonstrated that the purity of oxygen is as high as 93% with a recovery rate of 46.85%, and the production capacity is 3.42×10^-2 m³·h^-1·kg^-1 under 6 bar (1 bar=0.1 MPa), 8 s step duration and 6 m³·h^-1 product flow rate. Compared with the existing two-bed and four-bed processes, the recovery of this process has been improved. The effects of step duration, adsorption pressure, and product flow rate on oxygen concentration, recovery, and productivity were investigated. Moreover, as the product flow range expands to 4.5 m³·h^-1to 7.5 m³·h^-1, this process can produce oxygen with a purity of more than 90% and can be applied to scenarios with different oxygen purity requirements.

A reactive distillation process with component recycling is proposed to address the challenging operational issues for unfavorable volatility sequence in the reaction system. Taking the esterification of excess n-propanol with propionic acid to produce n-propyl propionate as an example, a reactive distillation process with n-propanol circulation was constructed. The pinch point of the binary vapor-liquid equilibrium of n-propyl propiate and n-propanol was determined by thermodynamic analysis, and the integrated process of reactive distillation was systematically studied to determine the purity of recycled n-propanol (X_ProOH). Using sequential optimization method, the operating parameters and structural parameters of the reactive distillation column and recovery column were determined with the minimum annual total cost (TAC) as the optimization objective. The results show that when X_ProOH=0.80, a trade-off between the reaction process of the reactive distillation tower and the separation process of the recovery tower is achieved, and the process parameters with minimum TAC are obtained. In addition, a composition/temperature-proportional control scheme is proposed to study the dynamic response performance of the closed-loop system when the disturbance of ±10% propionic acid feed flow is introduced.

To address the increased seal leakage caused by wear on the sealing end face due to the high-frequency fluctuations during the operation of floating ring seals, a fractal wear prediction model for the end face of the floating ring seal based on fractal theory was established. ABAQUS's UMESHMOTION subroutine and ALE adaptive grid technology were employed to simulate the wear process of the sealing end face. The wear depth in the contact area was calculated by using the modified Archard wear theory, and the intrinsic laws of wear on the floating ring end face were studied. The accuracy of the finite element model was validated experimentally. The research further analyzed the impact of surface morphology and operating conditions on wear depth, in order to guidance for the design and wear protection of the floating ring end face seals. The results show that the wear depth of the floating ring end face decreases with the increase of fractal dimension D but increases with the increase of characteristic scale G. When D≤1.65, the change of G has a particularly significant impact on wear depth. As the load on the floating ring end face increases, its wear depth shows an approximately linear upward trend related to the increase in fractal dimension D and characteristic scale G, especially when G value is larger. Different wear cycle times will result in different wear depth distributions, and as the cycle times increase, the wear depth of graphite floating rings gradually rises, especially reaching a peak at the edge of the contact area, and obvious dents appear at both ends of the wear area.

Natural fibers can replace synthetic fibers in many fields, particularly in reinforced composite materials. They ensure a certain strength and stiffness while having the advantages of low cost, light mass, and easy degradation. However, there is currently a lack of research on pyrolysis recycling of natural composite materials. To address this gap, this study investigates the thermal decomposition kinetics and product characteristics of natural fiber-reinforced epoxy resin composites using thermal gravimetric analyzer (TGA) and pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) experimental methods. The results indicate that the synergistic effect of cellulose and epoxy resin in the composite reduces its thermal stability and significantly decreases the residual char content, ultimately leading to a substantial reduction in the activation energy for the composite. On the other hand, the synergistic effect has a less noticeable impact on the types of products during rapid pyrolysis but significantly influences the yield and distribution of products.

Electrochemical impedance spectroscopy (EIS) has a wide range of applications in the research of fuel cells and secondary batteries. Distribution of relaxation times (DRT) is a novel and efficient EIS analysis technique, which has the advantages of not relying on prior knowledge and high resolution. However, the reconstruction process of the DRT function is an inverse problem solving process, and there are ill-posed problems. In response to the above challenges, an innovative DRT function reconstruction method combining elastic network regularization and quantum-behaved particle swarm optimization algorithm is proposed. The ill-posed problem can be effectively solved by the elastic network regularization, while the regularization parameters (regularization factor and mixing coefficient) of the elastic net regularization can be reasonably selected by the quantum particle swarm algorithm, avoiding the problem of manual parameter selection. The reliability of the developed DRT reconstruction method was evaluated by using EIS of equivalent circuits, EIS of equivalent circuits containing noise, and EIS of experimental measurements. The results indicate that the developed DRT reconstruction method can reconstruct high-quality DRT functions in all three cases.

Graphite fibers were prepared by rapid high-power laser irradiation heat conduction of polyacrylonitrile based carbon fibers under argon pressure of 0—0.3 MPa. The effect of argon pressure on the graphitization properties of carbon fibers was studied. The results show that when the gas field pressure is 0 MPa, the carbon fiber undergoes inflation under rapid irradiation with high-power laser: a large amount of non-carbon elements in the carbon fiber rapidly escape in the form of gas, the diameter of the carbon fiber increases, and at the same time, part of the surface layer falls off. Further increasing the gas field environmental pressure during high-power laser irradiation, when the gas field pressure is 0.2—0.3 MPa, the diameter of the carbon fiber decreases and gradually stabilizes, and the surface detachment disappears. The degree of graphitization of the carbon fiber and the size of graphite microcrystals further increased, at the same time, the tensile strength loss of graphite fibers decreased and the Young's modulus increased after pressurized laser irradiation. Therefore, applying 0.2—0.3 MPa argon gas pressure is an effective method to improve the performance of graphite fibers prepared by high-power laser irradiation.

Polymer films often experience complex temperature fields and tensile fields during processing. Stretching affects the aggregated structure by inducing molecular chain orientation, thereby affecting various properties of the film. Compared to other crystal modifications, βcrystal isotactic polypropylene (iPP) has much better mechanical properties. In this work, we used WBG to improve the βcrystal content of iPP and investigated its structural evolution during casting and post-stretching. With the increase of draw ratio and the decrease of temperature, the crystallinity and tensile strength of iPP casting film increase, however, the βcrystal content decreases. During the post stretching process, increasing the stretch temperature and strain accelerates the transition of iPP from βcrystal to αcrystal. Meanwhile, cavitation occurs at the late stage of post-stretching, which provides the foundation of iPP microporous membrane preparation.

Graphene quantum dots (GQDs), as an emerging 0D graphene derivative, have the advantages of smaller size, larger specific surface area and stronger hydrophilicity than 2D graphene oxide, which have attracted much attention as membrane separation materials in recent years. Three different serials of GQDs and assembling GQDs composite membranes were successfully prepared by one-step hydrothermal method with three different precursors: citric acid, sodium lignosulfonate and glucose. The influence of these three precursors on the microstructure and pervaporation desalination performance of GQDs composite membranes was systematically investigated. The particle sizes and d-spacing of GQDs were confirmed to be affected with these three precursors by various characterizations of UV-Vis, FTIR, XRD, and TEM, which could significantly influence surface microstructure and their desalination performance of these GQDs composite membranes. Among these three serials membranes, CA-GQDs composite membranes prepared with citric acid as the precursor exhibited the highest desalination performance. The CA-GQDs composite membrane optimized and prepared in 3.5% (mass) NaCl solution at 30℃ has a permeation flux of up to 37.36 kg·m^-2·h^-1 (permeance is as high as 1.2×10^-4 mol·m^-2·s^-1·Pa^-1), and the salt rejection rate is nearly 100%. In addition, the composite membrane has good acid and alkali resistance in the range of feed liquid pH=2 to 12, especially when the salt rejection rate remains above 99.95% at pH=8—11.

Graphyne is an emerging two-dimensional layered material with promising applications in the field of thermoelectricity. An objective of this paper is to profoundly investigate the thermoelectric transport properties of γ, δ, and α structured graphyne using first principles calculations. This paper mainly discussed the effect regularities of the three different structures on phonon thermal transport, electronic conductivity, and thermoelectric figure of merit. The results show that graphdiyne with γ, δ and α structures have low thermal conductivity at room temperature, which are 31.19947, 13.44974 and 5.87009 W·m^-1·K^-1, respectively, and the thermal conductivity gradually decreases as the temperature increases. In terms of electrical transport, the three different structures of graphyne demonstrate high power factors under appropriate carrier doping, which are 0.135, 0.045, and 0.011 W·m^-1·K^-2, respectively. Consequently, the maximum thermoelectric figure of merit (ZT_max) was obtained to be about 2.93, 2.22, and 1.67 for each respective structure. The graphyne materials with different atomic structures have their own advantages in the fields of heat and electricity. Under the rational distribution of sp-hybridized carbon atoms, these materials can form Dirac cones or tunable small band gaps, and obtain lower thermal conductivity. The maximum thermoelectric figure of merit can reach 2.93. The thermoelectric performance of graphyne materials with different structures will contribute to their application in the field of thermoelectric, and provide reference and inspiration for the application of two-dimensional layered carbon nanomaterials in the field of thermoelectric.

To reduce the popularization and application cost of the photovoltaic/thermal (PV/T) collector, using nanofluids as the spectral-beam splitter (SBS), low-cost water-ZnO nanofluid is prepared by the two-step method as the SBS, and its preparation parameters are optimized to enhance its stability, including the dispersant type, dispersion ratio, and ultrasonic duration. On this basis, the effects of mass fraction, nanoparticle size, and optical path on the spectral transmittance of water-ZnO nanofluid are first tested experimentally; secondly, the effects of the above parameters on the regulation performance of heat-to-electricity of the SBS-PV/T collector are simulated and analyzed; finally, the sensitivity of the above parameters to four evaluation indexes is evaluated. The results show that adding sodium hexametaphosphate as a dispersant with the dispersion ratio of 1∶5 and ultrasonic treatment for 1.5 hours can maximize the stability of water-based ZnO nanofluid. Secondly, the mass fraction, particle size, and optical path have a linear influence on the thermal and electric performances of the SBS-PV/T collector; concretely, the photothermal efficiency, heat-to-electric ratio, overall efficiency, and merit function of the SBS-PV/T collector increase with the mass fraction, particle size, and optical path; while the photovoltaic efficiency is the opposite. Of which, the heat-to-electric ratio is most sensitive to the change of nanofluid parameters, with an average sensitivity coefficient of 0.45; on the other hand, the performance of the SBS-PV/T collector is most sensitive to the optical path, and its sensitivity coefficients to photothermal efficiency, photovoltaic efficiency, heat-to-electric ratio, and merit function of the collector are 0.53, -0.27, 0.76, and 0.09, respectively.

Based on the method of characteristics and combined with the S-W equation describing the CO₂ state, a propagation model of decompression wave was constructed. The simulation results of decompression wave velocity were compared with the industrial-scale experimental results to verify the reliability of the model. Using the constructed decompression wave model and the HLP model proposed by the Japan High Strength Pipeline Research Committee (HLP), the decompression wave velocity and crack propagation velocity of X65 and X70 pipe steel during one-dimensional supercritical CO₂ pipeline leakage under different initial pressures or temperatures were simulated and compared to explore the impact of initial pressure or temperature changes on the initial decompression wave velocity and the minimum wall thickness for crack arrest. The results show that the velocity of the decompression wave is approximately equal to the sound velocity under the initial conditions, so an increase in initial pressure and a decrease in temperature (increase in sound velocity) will increase the propagation speed of the decompression wave. When the initial pressure increased from 7.5 MPa to 9.5 MPa, the initial decompression wave velocity (0.01 s) increased by 53%, and the minimum wall thickness of X65 and X70 pipe steel for minimum wall thickness for crack arrest decreased by 13% and 14%, respectively. When the initial temperature decreased from 45℃ to 35℃, the velocity of the decompression wave increased by 56%, and the minimum wall thickness of X65 and X70 tube steels for minimum wall thickness for crack arrest decreased by 20% and 19%, respectively. When the working pressure is both lower than 8.0 MPa (working temperature is 35℃), or the working temperature is higher than 41℃ and 39℃ (working pressure is 9.0 MPa), the X65 and X70 pipe steel wall thickness calculated by GB 150—2011 does not have the ability to stop cracking.

In order to develop a novel explosion suppression material with excellent performance, low cost, and environmental friendliness, zeolite was chosen as the base material. Based on the elementary reaction of ethylene explosion, two types of silane coupling agents, namely, amino propyl trimethoxy silane and vinyl trimethoxy silane, were selected to modify the surface of zeolite. The modified zeolite's ability to suppress ethylene explosion overpressure and flame propagation was studied by using a 20 L spherical explosive apparatus and a 5 L pipeline explosive apparatus. The experimental results showed that the silane coupling agents were successfully grafted onto the zeolite surface by using a hydrolysis method, resulting in the synthesis of amino propyl-modified zeolite and vinyl-modified zeolite. Under the same conditions, the zeolite, aminopropyl zeolite, and vinyl zeolite dust with concentration of 1500 g·m^-3 can make the explosion pressure of ethylene with concentration of 6.5%(vol) reduce 31.40%, 42.05%, and 43.43%, respectively, and make the explosion pressure rise rate reduce 63.36%, 91.22%, and 92.40%, respectively. The zeolite, aminopropyl zeolite, and vinyl zeolite dust with concentration of 900 g·m^-3 can significantly reduce the 6.5% ethylene explosion flame brightness and flame structure continuity, and reduce the average flame propagation speed by 60.46%, 92.23%, and 93.16%, respectively. In contrast, modified zeolite has a more significant inhibitory effect on ethylene explosion overpressure and flame, that is, modified zeolite has better ethylene explosion suppression performance, and vinyl zeolite has better suppression performance than aminopropyl zeolite. Finally, based on the thermolysis characteristics of zeolite and modified zeolites, as well as the elementary reaction of ethylene explosion, the inhibitory mechanism of the modified zeolites on ethylene explosion was analyzed from both physical and chemical perspectives.