- Ei，ESCI收录期刊
- 中国科学引文数据库(CSCD)核心期刊
- 中文核心期刊
- 文摘与引文数据库(Scopus)
- 剑桥科学文摘(CSA)
By dissecting DZ125 turbine blades that have been in actual service for 499 h and integrating an artificial neural network model to assess the service temperature and stress in various blade components， the normal and overtemperature service tissues of the turbine blades have been identified. Focusing on DZ125 alloy for turbine blades， simulations of normal and overtemperature service conditions are conducted through variable cross-section experiments at 925 ℃/32-200 MPa/500 h and 1075 ℃/10-60 MPa/100 h， respectively. Both service structures undergo sub-solvus recovery heat treatment at a solid solution temperature of 1200 ℃， and the impacts of this treatment on both service structures are observed. The results reveal that the most severely damaged part of the DZ125 turbine blade is the leading edge in the middle of the blade， with a maximum service temperature of 1075 ℃. The microstructure degradation of DZ125 alloy is more pronounced at 1075 ℃ compared to 925 ℃. Following sub-solvus recovery heat treatment， the normal service structure simulated at 925 ℃ with variable cross sections exhibits degradation， whereas the overtemperature service structure simulated at 1075 ℃ with variable cross sections shows precipitation of cubic secondary γ′ phase. Notably， after sub-solvus recovery heat treatment， the creep life of DZ125 alloy in a specific overtemperature service damage state increases from 16 h to 25 h under conditions of 980 ℃/220 MPa. The sub-solvus recovery heat treatment proves detrimental to the normal temperature service microstructure but has a beneficial recovery effect on the overtemperature service microstructure.
In view of the microstructure damage and property degradation of directionally solidified DSM11 service turbine blades， it is urgent to study the partial-solution rejuvenation heat treatment. In this study， the effects of different recovery heat treatments on the microstructure and mechanical properties of DSM11 superalloy are studied by using alloys after thermal exposure at 980 ℃ for 500 h with reference to the microstructure of DSM11 blade in real service condition. The results show that bimodal microstructures of 23% secondary γ' phase with the size of approximately 270 nm and 17% coarse degraded γ' phase can be obtained by 1180 ℃/2 h solution combined with 1120 ℃/2 h/AC+850 ℃/24 h/AC recovery heat treatment. Meanwhile， the M 23C6 carbides at the grain boundary， which are formed during the thermal exposure， are also dissolved. And γ' films on the grain boundary are also partially dissolved. Although the M 23C6 carbides at the grain boundary can also be dissolved by direct aging at 1120 ℃ without solution heat treatment， the γ' film on the grain boundary changes slightly. The size and volume fraction of the secondary γ' phase are closely related to the solution temperature and the cooling rate after the solution. The secondary γ' phase size obtained by furnace cooling is larger than that obtained by air cooling. The secondary γ' phase obtained at 1160 ℃ solution treatment is completely dissolved in the subsequent aging process and will not be retained in the final. After 1180 ℃/2 h/AC+1120 ℃/2 h/AC+850 ℃/24 h/AC rejuvenation heat treatment， the creep life of degraded DSM11 superalloy is recovered from 18 h to 24 h， which is about 86% of that in standard heat treatment. A certain amount of the reprecipitated secondary γ' phases play an important role in the recovery of mechanical properties.
The phase composition and structure play an important role in the high-temperature oxidation resistance of the bonding layer alloy. Furthermore， the high-temperature oxidation resistance of the alloy strongly affects the working life of the thermal barrier coating prepared. In this paper， the effects of different Hf contents on the phase composition， structure， and isothermal oxidation process at 1150 ℃ are investigated by Thermo-Calc， X ray diffraction， and field emission scanning electron microscopy. The results of theoretical calculations and microstructure observations indicate that the phase composition of NiCoCrAlY alloy containing 0.5% （mass fraction， the same below） and 1%Hf are mainly composed of the γ'-Ni3Al phase and the β-NiAl phase. As the Hf content increases from 0.5% to 1%， the liquidus temperature of the alloys decreases from 1422 ℃ to 1418 ℃， the solidus temperature decreases from 1297 ℃ to 1287 ℃， and the solidification temperature range increases. Furthermore， the precipitation temperature of the α-Cr phase increases from 860 ℃ to 880 ℃ with increasing Hf content. The β-NiAl phase content of the bonding alloy with 0.5%Hf in the temperature range of 1000-1250 ℃ is higher than that of the alloy with 1.0%Hf. The isothermal oxidation analysis for 200 h shows that the mass gain versus oxidation time curves follow the typical parabolic oxidation kinetics. As the Hf content increases from 0.5% to 1.0% in alloys， the average oxidation rate increases from （0.15±0.008） g·m-2·h-1 to （0.32±0.006） g·m-2·h-1， and the parabolic oxidation rate constant k p increases from 4.163 g2∙m-4∙h-1 to 9.337 g2∙m-4∙h-1. According to the phase analysis and morphology observation of the oxide layer， it is found that the oxide layer is mainly a dense Al2O3 layer； the white contrast HfO2 phase is also distributed in the oxide film. With the increase of Hf content， the distribution of the HfO2 phase in the oxide layer changes from discontinuity to continuousness， and the number and area of HfO2 particles increase. Meanwhile， the internal oxidation degree is aggravated and the thickness of the lean Al layer is improved.
The phase constitution and properties of MCrAlY bond coating material are essential to improve the service stability and life of thermal barrier coatings for turbine blades. In this work， the microstructure characteristics， thermal expansion and high-temperature oxidation resistance of the Re-modified NiCoCrAlY bond coating alloy are systematically investigated using Thermo-Calc software， X-ray diffraction， field emission scanning electron microscopy， transmission electron microscopy， and thermal dilatometer， etc. The results show that the microstructure is primarily composed of β-NiAl coupled with some σ-CoCr， α-Cr and Ni5Y. Meanwhile， the rare earth element Y binding Ni forms Ni5Y， while the modification element Re is mostly solid dissolved in the α-Cr and σ-CoCr phases. Moreover， when the temperature increases from room temperature to 1200 ℃， the coefficient of thermal expansion reaches （18.1±0.1）×10-6 K-1. As the isothermal oxidation time at 1100 ℃ extends to 100 h， the thickness of the oxidation layer and Al depletion layer is （2.44±0.09） μm and （2.53±0.33） μm， respectively. The oxidation rate is （0.06±0.01） g·m-2·h-1， achieving the oxidation rate of a complete antioxidant level. Compared with the properties of the conventional MCrAlY bond coating alloy， the coefficient of thermal expansion at 1200 ℃ and the oxidation rate at 1100 ℃ for 100 h decrease by 12% and 25%， respectively. Namely， the Re-modified NiCoCrAlY bond coating alloy processes lower thermal expansion and higher oxidation resistance， which can provide design strategy for developing a high-property bond coating material.
NiCoCrAlYSiHf coatings are deposited on the DSM11 Ni-based superalloy substrate using arc ion plating （AIP） technology， followed by complete removal of the coatings through a chemical method. The effects of coating removal and subsequent recoating on the mechanical properties of the substrate alloy are evaluated through high-temperature creep， instantaneous tensile tests， and other mechanical testing. Scanning electron microscopy （SEM） is employed to observe and analyze the cross-sectional morphology of the substrate before and after coating removal.Results show that solution 1# effectively removes the NiCoCrAlYSiHf coating， with a mass loss of 0.1078 g after 180 minutes， achieving near-complete coating removal. After complete coating removal， the coating/substrate alloy interface and the microstructural morphology of the substrate alloy remain essentially unchanged from the original state， indicating that the removal process has no impact on the substrate alloy. During coating degradation， the coating layers detach progressively， and the mass loss of the coating correlates with reaction time， confirming this observation. Test results show that the NiCoCrAlYSiHf coating has no significant impact on the mechanical properties of the DSM11 alloy， and the coating removal has minimal effect on the high-temperature creep and instantaneous tensile performance of the substrate alloy.
In recent years， with the rapid development of aerospace technology， the requirements for engine thermal efficiency and light weight are getting higher and higher， resulting in the continuous reduction of the wall thickness of turbine blades. However， the reduction in wall thickness leads to decreased properties of the alloy material for blades， i.e.， the thin-wall effect. Therefore， the study of the thin-wall effect is of great significance to the safe and stable operation of turbine engines. However， the reasons and laws of the thin-wall effect are very complicated. Based on this， this paper reviews the influence of experimental conditions， surface states of materials， coatings， polycrystals， single crystals， and anisotropy of alloys on the thin-wall effect of alloy materials for blades， and summarizes three typical cases according to the mechanism and model of the thin-wall effect： the oxidative damage model， the oxidation-creep damage model and an analysis based on crack growth. Due to oxidation and the presence of hard and brittle phases， cracks are inevitably generated in the workpiece during service. Based on the crack growth analysis， it is shown that there is a significant correlation between crack growth and thin-wall effect， providing new insights for future research on thin-wall effects.
The Ti/Al dissimilar welded structure combines the high strength and corrosion resistance of titanium alloys with the lightweight and formability advantages of aluminum alloys， providing a broader range of options for product design and manufacturing. Meanwhile， this structure helps reduce component mass and cost， achieving lightweight design and structural-functional integration. Friction stir welding （FSW）， as a solid-state welding method， is one of the most suitable techniques for Ti/Al dissimilar joining. However， conventional Ti/Al FSW still faces challenges such as severe tool wear， non-uniform mechanical properties along the weld thickness， potential lack of penetration at the weld root， and difficulty in precisely controlling intermetallic compounds （IMCs）. This paper reviews the improvements proposed by researchers worldwide to address these issues， exploring various innovative processes to overcome the limitations of conventional Ti/Al FSW and achieve high-quality joints. It analyzes and compares the characteristics and applicability of different modified FSW techniques， including interlayer addition at the interface， application of auxiliary external fields， modification of joint configurations， and stationary shoulder FSW. The study further explores their roles and mechanisms in enhancing weld quality and optimizing interface properties， while systematically summarizing future research directions for Ti/Al dissimilar FSW. Finally， it is pointed out that future research should focus on further optimizing modified welding processes， improving process stability， and enhancing industrial feasibility to promote the engineering application of Ti/Al dissimilar welded structures.
MXene， as a new class of two-dimensional（2D）materials， has garnered extensive research interest due to its excellent electrical conductivity， efficient photo-thermal conversion ability， and rich terminal functional groups. However， the susceptibility of MXene to oxidation and its relatively weak mechanical properties have limited its widespread use in various application fields. MXene-based shape memory composites not only enhance the anti-oxidation and mechanical properties of MXene but also endow the material with intelligent response characteristics in macroscopic 3D structures. These properties open new avenues for MXene applications in information transmission， energy conversion， electromagnetic shielding， and fire safety protection. This study aims to review the research progress in MXene-based shape memory composites comprehensively and deeply analyzes their preparation methods， shape memory mechanisms， and application potential， offering valuable references for further research and development， and application of these composites. Meanwhile， the future direction of MXene-based shape memory composites in terms of efficient preparation， performance optimisation， multifunctional development， and their potential stability enhancement and commercialisation challenges are analysed to effectively promote technological advancement and innovation in this field.
Polytetrafluoroethylene （PTFE）， as a special engineering plastic， has many advantages such as excellent self-lubricating properties， good chemical stability， and a wide range of operating temperatures. However， its core disadvantages are poor wear resistance and easy wear， which seriously shorten its service life. Starting from the structural characteristics of PTFE molecules， this article takes the transfer film theory as the main thread to deeply analyze the friction and wear mechanism of PTFE and the research and development process. It summarizes the tribological modification methods of PTFE， analyzes the common methods of surface modification， filling modification， and blending modification， compares the internal mechanisms of these three types of modification methods， and summarizes the development trend of composite modification. Finally， based on recent research achievements and existing problems in the research process， the research direction of PTFE tribological modification is discussed， some suggestions on the quantitative study of transfer film， the industrial feasibility of multimode type collaborative composite modification， the selection and application of modification system under actual working conditions are given.
Radiation thermal protection coating based on rigid ceramic fiber insulation tile is a thermal protection system widely used in spacecraft， and improving its reusable performance such as emissivity， impact resistance， and thermal shock resistance has always been a research focus. This article reviews the research progress on the structural design and material improvement of radiation thermal protective coatings for rigid ceramic fiber insulation tiles under the background of diversified performance optimization. The structural design approach and composition adjustment ideas of radiation thermal protective coatings are analyzed， from single-layer dense structure to multi-layer gradient structure and scaly structure，and the advantages and existing problems of radiant thermal protection coatings with different structures are summarized. Finally， it is pointed out that multilayer gradient structure coatings， due to their comprehensive advantages of dense top layer and porous gradient structures and their adjustability， are still the mainstream of current research. In the future， radiant thermal protection coatings should further optimize the integrated design of thermal insulation， and conduct research on the impact of structure and composition on performance in service simulation environments.
To investigate the solidification behavior and microstructure characteristics of Incoloy825 alloy pipe by using the vacuum centrifugal casting （VCC） process， a simulation model of VCC is established using ProCAST software to simulate and calculate the filling and solidification process of the alloy. The results show that the metal liquid exhibits good forming effects at pouring temperatures between 1480 ℃ and 1520 ℃. When the mold rotation speed exceeds 800 r/min， the metal liquid can be uniformly distributed along the mold wall. The pouring temperature above 1480 ℃ reduces the shrinkage rate to 0%-1.33%. At the pouring temperature of 1520 ℃ and the mold rotation speed of 800 r/min， the initial solidification time for the lower， middle， and upper parts of the casting is 9.61， 12.53 s， and 14.32 s， respectively. Based on the simulation results， optimal process parameters are determined and casting experiments are conducted. Microstructure analysis of the castings reveals that the average length of dendrites from the center to the outer layer of the casting gradually decreases from 271 μm to 121 μm， indicating a significant grain size gradient along the cooling direction of the microstructure.
TiC/Ti6Al4V composites are prepared by synchronous ultrasonic energy field-assisted laser melting deposition. The effects of synchronous ultrasonic energy field treatment on the microstructure and properties of the composites with TiC volume fraction of 5% and 20%， respectively， are studied. The results show that the as-built composites contain inhomogeneous distributed undissolved TiC particles and in-situ TiC particles， among which 5%TiC/Ti6Al4V （volume fraction，the same below）composites contain chain shaped eutectic TiC with larger size， and 20%TiC/Ti6Al4V composites contain dendritic primary TiC with larger size. With the application of synchronous ultrasonic energy field treatment， the distribution uniformity of undissolved TiC particles in the composite is improved. Moreover， the in-situ TiC reinforcing phase is refined， where the chain shaped eutectic TiC transforms to granular eutectic TiC， and the size of dendritic primary TiC decreases. Due to the effect of synchronous ultrasonic energy field treatment， the microhardness of 5%TiC/Ti6Al4V and 20%TiC/Ti6Al4V increases from 406.5HV0.2 and 498.4HV0.2 to 414.2HV0.2 and 539.1HV0.2， respectively. The wear rates reduce from 1.82 × 10-6 mm3·m-1·N-1 and 1.04×10-6 mm3·m-1·N-1 to 1.78×10-6 mm3·m-1·N-1 and 9.48×10-7 mm3·m-1·N-1， respectively. The tensile strength of the 5%TiC/Ti6Al4V increases from 1075.23 MPa to 1116.31 MPa， the yield strength increases from 1021.51 MPa to 1043.12 MPa， and the fracture strain increases from 1.27 % to 1.45 %， which realizes the simultaneous improvement of strength and plasticity.
SiO2， TiO2， NaCl， and KCl are chosen as activating fluxes for laser welding of 5 mm thick TC4 titanium alloy to increase the laser absorptivity of base material and improve weld formation. Based on the influence of activating fluxes on weld formation， the mechanism of action of activating fluxes and their impact on the microstructure and properties of welded joints are analyzed. The experimental results show that the activating fluxes have no significant effect on the macro formation of the weld， and the four activating fluxes can affect the shape size of the weld by increasing the laser absorptivity related to welding heat input. Besides， SiO2 mainly reduces the absorption and scattering of laser beam by reducing photoinduced plasma， and TiO2 primarily reflects and propagates laser beam among the fine particles， NaCl and KCl have both. The tensile strength of the joint coated with SiO2 and TiO2 has descended by 14% and 10% respectively. It is related to the change of weld microstructure by activating fluxes. The tensile properties of the welded joints coated with NaCl and KCl are not lower than that of uncoated welded joints. They can be used as an effective activating flux for TC4 titanium alloy laser welding.
Metal phase-change materials （PCMs） show great potential in improving energy efficiency and conservation. In this study， A30， H30， A50 and H50 alloy particles are successfully synthesized using the pulsated orifice ejection method （POEM） as high-temperature thermal storage PCMs. The results show that the POEM-fabricated particles exhibit mono-sized， high sphericity， high purity， smooth and dense surfaces， and uniform particle size distribution. Moreover， thermal performance analysis reveals that these particles possess excellent thermal stability and high latent heat values. The melting latent heats of A30， H30， A50 and H50 particles are 347.54， 359.67， 262.63， 284.82 J/g， respectively， with corresponding solidification latent heats of 366.24， 377.50， 256.82， 296.47 J/g. After multiple thermal cycles， these particles maintain high energy storage density and good structural stability. Al-Si alloy particles prepared via POEM demonstrate significant application potential in the field of phase-change energy storage， providing important evidence for the development of novel and high-efficiency energy storage materials.
Defects are the main factors affecting fracture behavior of casting materials. The fracture behavior of high pressure casting aluminium alloy is predicted using Gurson-Tvergaard-Needleman （GTN） damage model combined with finite element simulation software. The results show that damage parameters suitable for high pressure casting aluminum alloy materials are obtained through finite element reverse fitting， with a nucleated void volume fraction ， critical void volume fraction ， and fracture void volume fraction . At the same time， fracture behavior prediction based on microscopic features is carried out by simplifying the pore morphology as ellipsoids and ignoring pores with volumes less than 0.001 mm3， to avoid low efficiency and non convergence in finite simulation calculations. The applicability of the two models in predicting the fracture behavior of casting materials is compared， and it is concluded that the finite element simulation combined with damage mechanics has higher computational efficiency， but the finite element simulation based on microscopic characteristics has higher prediction accuracy.
Based on two kinds of SiC particles with the median particle size of 76 μm and 14 μm， six SiC particle grading schemes are designed according to different proportions， and the SiCP/2024Al composites with 55% volume fraction are prepared by hot isostatic pressing sintering， and then two kinds of stabilization heat treatment strategies， which are “thermal-cold cycle” and “solid solution + thermal-cold cycle”， are designe. The effects of particle grading and heat treatment on the microstructure and dimensional stability of 55%SiCP/2024Al composites are studied. The results show that the particle grading has a significant effect on the content of Al2Cu phases in the aluminum alloy matrix. When the proportion of small SiC particles is 40%， it is conducive to the precipitation of Al2Cu phases. The solid solution + thermal-cold cycle stabilization heat treatment improves the size and distribution uniformity of Al2Cu phases and the phase stability. In the real and standard models， the thermal mismatch stress level generated by the stabilization heat treatment process shows a trend of first increasing and then decreasing with the increase of the proportion of fine SiC particles. Furthermore， the Mises stress reaches the maximum value （7.95 MPa and 3.52 MPa， respectively） when the proportion is 40%， which is conducive to releasing of the residual stress in the composites and improving the stability of the stress state. After adopting the particle grading scheme of small particle SiC accounting for 40% and carrying out the stabilization heat treatment of “solid solution + thermal-cold cycle”， 55%SiCP/2024Al composite has the best dimensional stability， with dimensional change rate remaining within ±0.07% for 5 cycles thermal load at 180 ℃.
The crystal internal stress and texture evolution of six-pass hot rolled ZK61 magnesium alloy plate are studied by means of combining macroscopic finite element simulation and microscopic crystal plasticity analysis. According to the rolling experiment and tensile test， the corresponding synchronous hot rolling model is established and simulated， and the simulation results are entered as boundary conditions in the polycrystalline plasticity model based on Voronoi diagram. Then the crystal plasticity finite element method is used to simulate the synchronous hot rolling of the polycrystalline model， and the plastic parameters and texture pole figures of the hot-rolled ZK61 magnesium alloy in each pass are obtained. Compared with the tensile test results and the texture pole figures derived from the electron backscatter diffraction experiment， the crystal plastic deformation and texture evolution mechanism of the hot-rolled ZK61 magnesium alloy under different passes are summarized. The results show that there are a large number of twins and dynamic recrystallization in the ZK61 plate after multi-pass hot rolling， the grain homogenization and refinement effect is obvious. The pole intensity of basal texture is correlated with the whole rolling passes， the peak misorientation angle of the alloy under different passes has a quite diversity （8°， 28°， and 88°）， and the mechanical properties of the alloy are improved. The alloy strength is increased by 7.55%， and the elongation is achieved by 19.5%. The results can provide reference for improving the plastic processing ability of magnesium alloy.
Using two-dimensional transition metal carbides/nitrides （MXene） and carbonized zeolitic imidazolate frameworks （CZIF） as functional fillers， MXene-CZIF/PI composite films with both conductivity and magnetic properties are successfully prepared by in-situ polymerization and thermal imidization processes. The electrical conductivity， magnetic properties， mechanical properties， flame retardant properties and thermal stability of the composite films are also systematically studied. The results show that as the content of MXene and CZIF fillers increases， the electrical conductivity and saturation magnetization of the composite films significantly improve. When the content of MXene and CZIF reaches 40%（mass fraction）， the electrical conductivity reaches 0.33 S/cm， and the saturation magnetization reaches 6.95 A·m2·kg-1. The PMCo-40 film exhibits excellent comprehensive performance with the tensile strength of 47.83 MPa， the limiting oxygen index （LOI） as high as 37.7% （volume fraction）， and the film being virtually unchanged after 60 s of combustion under an alcohol lamp， demonstrating outstanding flame retardancy. The carbon residue at 800 ℃ under nitrogen atmosphere reaches 80.76%， indicating exceptional thermal stability.
The effect of Pt catalysts with varied carbon supports on the performance of membrane electrode assembly （MEA） in proton exchange membrane fuel cell is different. In this study， graphene and Vulcan XC-72 supported Pt catalysts （Pt/G and Pt/C） are prepared respectively， and their morphology and physical properties are characterized. As cathode catalysts of MEA， the effects of Pt/G and Pt/C on the performance of MEA at varied I/C ratios are investigated by polarization curve performance test and electrochemical impedance spectroscopy test. The cyclic voltammetry curve test and accelerated stress test are carried out to further evaluate the influence of Pt catalysts with different carbon supports on the stability of MEA in the fuel cell operating environment through the changes in the electrochemical active surface area and polarization curve. The results show that the optimal I/C ratios of Pt/G and Pt/C are 0.5 and 0.6， respectively. With the increase of Pt loadings， the polarization curves show a trend of first increasing and then decreasing， and the maximum value is 0.8 mgPt/cm2. After 30000 triangular wave cycles， the ECSA loss rate of Pt/G is 63%， and the peak power retention rate is as high as 60%. Compared with Pt/C， graphene is a MEA catalyst carrier with better stability than amorphous carbon Vulcan XC-72.
Graphite composite bipolar plates have received widespread attention in the field of fuel cells due to their excellent conductivity and corrosion resistance. The traditional method of molding graphite composite bipolar plates has problems such as low efficiency and complex operation. Therefore， this study proposes a preform process scheme that simplifies the process operation and improves efficiency by rolling graphite/resin mixed powder into a pre-compress plate through a rolling machine and then rapidly molding it. By optimizing the rolling parameters and adding auxiliary binders， the problems of insufficient compaction and structural defects in the pre-compress plate are solved， improving the reliability of the process and material utilization rate. The results show that increasing the temperature and reducing the roll distance can both improve the compaction density of the pre-compress plate. Adding PTFE as an auxiliary binder can effectively improve the defects during the rolling process， but excessive addition can have a negative impact on conductivity and airtightness. The optimal addition ratio is 5% （mass fraction）. Compared with traditional direct compression molding， the bipolar plate prepared by this scheme has a slight decrease in in-plane conductivity， but its bending strength is increased by 14.2% and the preparation cycle is shortened to 42.9%， significantly improving production efficiency.
Proton exchange membrane fuel cells （PEMFC） have the advantages of high energy conversion efficiency， low impact of load changes on power generation efficiency， and low harmful substances and carbon emissions. The bipolar plate is one of the key structural components of PEMFC and undertakes the functions of electron transfer， gas distribution， internal water management， and supporting membrane electrode components. Composite bipolar plates have advantages such as light weight， corrosion resistance， and low cost， and have received more attention. However， to maintain the stable operation of fuel cells， it is necessary that water accumulated in the flow channel can be smoothly discharged while ensuring membrane wetting. This poses new requirements for the surface characteristics of bipolar plates. For composite graphite plates， they can adjust the contact angle and regulate the water and gas conditions of PEMFCs by changing their composition and preparation process. This article introduces the addition of carbon nanofibers prepared by chemical vapor deposition （CF-CVD） in the flake graphite-resin composite materials to regulate the hydrophilicity of composite bipolar plates. Additionally， the impact of varying flake graphite particle sizes on the hydrophilicity regulation of these plates is examined. The results reveal that increased carbon fiber content enhances the surface hydrophilicity of bipolar plates， with the smallest contact angle achieving 10.28°. The particle size of flake graphite affects the contact angle of composite bipolar plates. To optimize the hydrophilicity of bipolar plates with CF-CVD， 500-1500 mesh graphite is recommended as the conductive substrate. Specifically， a CF-CVD content of 3%， combined with 1000 mesh flake graphite， yields a hydrophilic composite bipolar plate with superior comprehensive performance， exhibiting a conductivity of 239.33 S/cm and a bending strength of 73.47 MPa.
Carbon/carbon （C/C） composites are prone to oxidation above 370 ℃， which restricts their further utilization in aerospace and military applications. Hence， enhancing the ablation resistance of C/C composites holds paramount significance. This research utilized citric acid， ethylene glycol， and metal salt solutions as precursors to fabricate C/C-Hf x Zr1- x C composite materials with a density ranging from 2.00 g/cm3 to 2.10 g/cm3 employing the precursor impregnation and pyrolysis （PIP） and ceramicization. The effect of different Hf/Zr ratios on the ablation resistance of C/C-Hf x Zr1- x C composites is investigated. The results indicate that Hf x Zr1- x C manifests as a solid solution ceramic. With the increase in Hf proportion， the ablation rate of C/C-Hf x Zr1- x C composites first decreases and then increases. Among them， C/C-Hf0.5Zr0.5C shows superior ablation resistance. When ablated for 120 s at a heat flux density of 3.5 MW/m2， the mass ablation rate and linear ablation rate of C/C-Hf0.5Zr0.5C are 1.39×10-2 g/s and 7.49×10-3 mm/s， respectively. This superiority can be attributed to the strong adhesion of the oxidation product HfO2-ZrO2 to the fiber and matrix in C/C-Hf0.5Zr0.5C， thereby mitigating mechanical erosion on the fiber and matrix. Simultaneously， the lower melting point of the HfO2-ZrO2 mixture facilitates the formation of a molten mixture of HfO2-ZrO2， consequently reducing the oxygen permeability of the oxide layer.
Ta0.8Hf0.2C exhibits excellent thermal protection properties， making it well-suited for high-temperature ablation environments. MoSi2， an outstanding sintering agent， is frequently employed in anti-ablation coatings. To investigate the impact of MoSi2 content on the ablative performance of Ta0.8Hf0.2C-SiC-MoSi2 coatings， we employ the slurry-sintering method to prepare coatings with varying MoSi2 concentrations on C/C composites， which are pre-coated with SiC transition layers. We conduct a comprehensive analysis of the phase composition， micromorphology， and ablation behavior of these coatings. The findings reveal that， at a MoSi2 content of 10% （mass fraction）， the coating exhibits optimal ablative properties， with a mass ablation rate of 1.24 mg·s-1 and a line ablation rate of 0.02 μm·s-1. This superior performance is attributed to MoSi2 ability to hinder the active oxidation of SiC， thereby reducing its consumption. Additionally， the high-viscosity liquid layer formed during ablation effectively resists the erosion of high-temperature flames， further preventing the diffusion of oxygen.
Copper molybdate （Cu3Mo2O9） with nanosheet structure is synthesized by a hydrothermal method. The morphology， structure， and specific surface area of the sample are characterized by techniques such as SEM， XRD， and EDS. Two gas sensors are fabricated with Cu3Mo2O9 nanosheets and MoO3 nanorods as sensing materials. The sensing performances of the two sensors for volatile organic gases are tested. It is found that when the sensors are exposed to 100×10-6 acetone， the Cu3Mo2O9 sensor shows an ultra-high response of 145.4 at 210 ℃. This response is about 2.1 times that of the MoO3 sensor （67.8）. The response/recovery time are 29.7 s/21.2 s， respectively. The excellent cycling stability of the Cu3Mo2O9 sensor is demonstrated by 10-cycle tests exposed to 100×10-6 acetone. Its excellent sensing properties are attributed to its porous nanosheet structure and the synergistic interaction between the two metal elements copper and molybdenum. The structure has a large specific surface area， providing a large number of surface active sites for the adsorption of gas molecules， promoting the redox reaction between gases. Cu3Mo2O9 nanosheet sensor shows excellent sensing properties for acetone， indicating that it has great potential in the practical detection of acetone gas in the future.
This study endeavors to fabricate and comprehensively characterize electrospun nanofibers derived from walnut shells. Utilizing walnut shells as the primary raw material， the electrospinning technique is employed to generate the nanofibers. The study delves into the impact of various spinning parameters on the morphology and diameter of the resultant nanofibers， employing SEM for detailed examination. Furthermore， FT-IR， XRD， TGA， and resistivity measurements are conducted to elucidate the structure and properties of the walnut shell nanofibers. The findings reveal that under optimized conditions—specifically， a spinning solution concentration of 55%， a spinning voltage of 16 kV， an injection rate of 0.75 mL/h， and a collector distance of 14 cm，smooth-surfaced nanofibers with a uniform diameter distribution and an average diameter of 0.38 μm are successfully produced. Notably， the structural orderliness of these nanofibers is substantially enhanced， and their thermal stability at 500 ℃ exhibits a 1.29-fold improvement compared to the initial state. Additionally， the electrical conductivity of the nanofibers also undergoes a favorable enhancement.
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