- 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)
Solid oxide fuel cell (SOFC) is a clean and efficient energy conversion device that can directly convert chemical energy to electricity.The state-of-the-art cermet anodes face various issues such as carbon deposition, sulfur poisoning and poor redox stabilities, which limit the application of SOFC. In order to avoid the problems of the cermet anodes, the perovskite anode materials with mixed electronic-ionic conductivities have drawn considerable attention in recent years.Among them, Sr2Fe1.5Mo0.5O6-δ perovskite has good stability, high conductivity, suitable thermal expansion coefficient and excellent electrochemical performance, and thus has been widely studied, especially element doping.The element doping was discussed at A-site, B-site and O-site of Sr2Fe1.5Mo0.5O6-δ perovskite, and the effects of doping elements and doping content on crystal structure, stability, electronic conductivity, thermal expansion and electrochemical performance were summarized.These doping strategies provide some novel ideas for modifying Sr2Fe1.5Mo0.5O6-δ perovskite anode, which can also be used to modify other similar perovskite anode materials.Finally, the development direction of Sr2Fe1.5Mo0.5O6-δ and typical ceramic anode materials was prospected. On one hand, the strategies of anion doping and co-doping could be adopted to improve the performance of ceramic anode materials. On the other hand, the mechanism of element doping will be further clarified through the combination of doping strategy and theoretical calculation.
MXene, very recently emerging family of two-dimensional (2D) transition metal carbides and/or nitrides, have attracted a wide range of attention due to unique layered structure, hydrophilicity, high conductivity and catalytic activity.First, synthesis and various applications of MXene in adsorption, photocatalysis and membrane separation were summarized in this review.Then, the effects of structure control, surface modification and composite of MXene on the adsorption performance of MXene and the formation of effective heterojunction, the exposure of active crystal face and the deposition of precious metals on the catalytic performance of MXene based photocatalysts were discussed.The approaches of constructing MXene based separation membrane for separating pollutants and desalinating seawater were described in detail.Finally, the existing problems in the applications of MXene in the field of water treatment were summarized and analyzed, and the prospects of designing MXene based water treatment materials with excellent performance were put forward.
Carbon nanotubes(CNTs), as an important discovery in the research of nanomaterials, have become a research hotspot in the field of carbon materials since their birth. With its unique porous structure, metal-organic frameworks (MOFs) has been developed into one of the frontiers of research in recent years. With the continuous development of materials science in recent years, the research on composite technology of materials with different functional characteristics has become one of the main methods to solve key problems in the field of materials applications.CNTs and MOFs are two very important types of nanomaterials in the current material field. Combining the high electrical conductivity of CNTs with the high specific surface area and rich pore distribution characteristics of MOFs through composite technology is an inevitable trend for future research and application in the field of materials. In this paper, the main composite forms and preparation methods of MOFs and CNTs in recent years were reviewed, and the latest research progress of composites in the fields of supercapacitors, lithium battery electrodes, catalysis, adsorption, etc. was summarized. The synergistic improvement of the performance of the two materials was discussed and analyzed, and it was pointed out that the composite of CNTs and MOFs materials and the growth and distribution of CNTs have a high degree of randomness, and further control of them is the focus of future technical research.
Aluminum and aluminum alloys are widely utilized metal materials. When they are used as surfaces working below 0℃, the anti-icing protection is of great importance for the operation safety of facilities. Two types of aluminum-based anti-icing surfaces were introduced, including superhydrophobic surfaces and organic lubricating layers. First, methods of preparation of micro/nanostructures and surface energy lowering for aluminum-based anti-icing surfaces were discussed, followed by the summarization of their advantages and disadvantages. Then, the characterization of anti-icing performances for aluminum-based surfaces was introduced, including delay of droplets freezing and ice adhesion strength, by which the difference of the anti-icing performance of aluminum-based surfaces can be evaluated. In the end, it was put forward that the future research should be focused on the durability and sustainability of aluminum-based anti-icing surfaces during icing/de-icing cycles.
Taking the preparation of electrode materials of supercapacitors, the study of properties and the performance of assembled asymmetric supercapacitors as the core contents, and improving the electrochemical performance of supercapacitors as the main purpose, the in-situ polymerization method was used to prepare carboxylated multi-walled carbon nanotubes (PI-MWCNTs) grafted polyimide solution, which is used as the precursor of nitrogen-doped carbon to realize the growth of composites on the surface of carbon cloth and as electrode material.Manganese dioxide-carbon cloth (MnO2-CC) as the positive electrode, Polyimide-carbon cloth grafted with multi-walled carbon nanotubes as negative electrode (PI-MWCNTs-CC), build asymmetric supercapacitors. The structure and electrochemical properties of the electrode materials were characterized by scanning electron microscopy, raman spectroscopy, surface area and pore size testing, X line photoelectron spectroscopy, cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. According to the study, when the scan rate is 20 mV/s, asymmetric capacitor potential window can be increased to 1.3 V and its volume specific capacity is 1.80 F/cm3.When the power density is 14.08 mW/cm3, the energy density can reach up to 0.423 mWh/cm3.
In order to make full use of the porous structure and overcome the shortcoming of low mechanical strength of nanofiber-based separators, polyacrylonitrile (PAN) separator was prepared directly on the surface of graphite anode by the electrospinning method. And an integrated separator/anode assembly (SAA) was formed. The microstructure, mechanical strength, electrolyte wettability, thermal resistance and battery performance were systematically investigated. The results show that the nanofibers in PAN separator are tightly bonded to the rough surface of graphite anode, resulting in a well-integrated interface structure (tensile strength higher than 200 MPa). Compared with polyolefin separators, SAA exhibits better electrolyte affinity and higher ion conductivity (1.9 mS/cm). The above advantages endow the LiCoO2/SAA full cell with better C-rate (capacity retention 44.3% at 32 C compared with that at 0.5 C) and cycling performances (capacity retention 98% after 200 cycles at 0.2 C) compared with those of LiCoO2/polyolefin separator/graphite battery. Consequently, this work provides an advanced separator/anode assembly and the corresponding fabrication method, which may be a new strategy for improving the charge-discharge performance and assembly efficiency of lithium-ion batteries.
Lithium-rich manganese-based cathode material is a promising next-generation lithium-ion battery cathode material, however, it exhibits significant differences in electrochemical performance at different temperatures, which severely limits the application in practical environments. A variety of electrochemical measures were used to characterize the difference in electrochemical performance of lithium-rich material within the temperature range of 5-45℃. The influencing factors of material properties and temperature dependence were analyzed from the perspective of polarization. The results show that the charge/discharge capacity of lithium-rich material decreases with decreasing temperature, which is mainly due to the significant increase in the polarization of the oxygen/manganese ion reaction in the high-voltage and low-voltage ranges with decreasing temperature, resulting in a severe decrease in its capacity contribution.The significantly increased polarization is mainly caused by the poor intrinsic kinetic performance of oxygen/manganese ions, which leading to high apparent activation energy of the charge transfer process. In addition, the participation of oxygen and manganese ions in the charge compensation reaction changes the structure of the material seriously.It induces changes in the composition of the interface film, which increases the apparent activation energy of lithium ion transmission at the interface in the low voltage interval. Moreover, it causes bulk diffusion of lithium ions at the end of the charge and discharge process having higher apparent activation energy. Therefore, improving the oxygen/manganese ion reaction kinetics of lithium-rich material is the main method to enhance its environmental adaptability.
Perovskite solar cells(PSCs) are paid much attention due to simple preparation and high photoelectric conversion efficiency. Carbon nanofiber films(CNFs) prepared by electrospinning have high specific surface area, electrical properties and chemical stability, but the application in PSCs is limited due to their brittleness. The flexible and conductive Ag/ZrO2/C composite nanofiber films were prepared by electrospinning and hydrothermal method. After that, it was applied as the counter electrode of flexible PSCs and the effect of Ag nanoparticles with different concentrations on the performance of the composite nanofiber films and the PSCs were studied. The results show that when the concentration of precursor solution rises from 0 g/mL to 0.030 g/mL, the coating effect of Ag nanoparticles on the Ag/ZrO2/C composite nanofiber improves obviously and all the composite nanofiber films display the excellent flexibility and modulus of elasticity (0.479 MPa), meanwhile, the conductivity of the films increases from 866 S/m to 4862 S/m, so as to enhance the hole-electron transport capacity of the films and the performance of flexible PSCs. When the solution concentration is 0.030 g/mL, the PSCs have best photoelectric conversion efficiency(PCE) of 6.05% and optimal current density (18.44 mA/cm2). It is of great significance to further improve the performance of flexible PSCs and the application of flexible carbon nanofiber films.
TiAl/Ti2AlNb dissimilar alloys were successfully bonded together by spark plasma diffusion bonding. The joints were subjected to post-weld heat treatment at different temperatures. The microstructure of the welded joint was analyzed and the tensile strength and microhardness of the joint were tested. The results indicate that after heat treatment, the microstructure of Ti2AlNb base metal, TiAl base metal and interface has no obvious change. In the Ti2AlNb heat affected zone(HAZ), most B2 phase gradually turns into O phase, due to the precipitation of acicular O phase, the microhardness increases significantly compared to as welded condition. With the increase of heat treatment temperature, the microhardness of the Ti2AlNb HAZ gradually decreases, meanwhile, the tensile strength of the joint at room temperature shows an evident increase compared to as welded. The maximum tensile strength of the joint reaches 376 MPa at heat treatment temperature of 900℃. After heat treatment, the fracture mode of the joint is brittle fracture.
Near β titanium alloy is widely used in automotive and aerospace industries due to their high strength-to-weight ratio and high corrosion resistance. The near β titanium alloy can precipitate ω phase and α phase after solution and ageing treatment, the strength of which can be remarkably increased, usually at the expense of ductility. It is one of the most important structural components of load-bearing that usually as aircraft skin, shell plating, main frame, linker and special fastener. The alloy used in this paper is a self-developed Ti-Al-V-Mo-Cr-Zr-Fe-Nb ultra-high-strength β titanium alloy, which is a typical near β titanium alloy. The characteristic of isothermal phase transformation of near β titanium alloys is diversity and complexity, which is sensitive to temperature and directly affects the mechanical properties after ageing. In this paper, the microstructural evolution and mechanical properties of a Ti-Al-V-Mo-Cr-Zr-Fe-Nb ultra-high strength β titanium alloy after isothermal treatment were investigated by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and micro-hardness tester. The results show that only the isothermal ω precipitates are formed during ageing at 300℃, and the size of isothermal ω phases increase with the ageing time. The isothermal ω precipitates are first precipitated during ageing at 400℃. With the extension of the ageing time, the α phase nucleation occurs near the ω/β interface. No α precipitates are obtained in the alloy aged at 500℃, and needle-like α precipitates are directly precipitated from the β matrix, which is evenly distributed in the β matrix in a "V" shape. Tensile test shows that the tensile strength of the alloy is 1716.1 MPa and the elongation is 2% after ageing at 400℃ for 12 h. The tensile strength of the alloy is 1439.8 MPa and the elongation is 9.84% after ageing at 500℃ for 12 h, and has a good combination of strength and toughness.
The volume fractions of γ (austenite), ε-M (hcp martensite) and α'-M (bcc martensite) in static and high speed compressed high manganese transformation induced plasticity (TRIP) steel were calculated by the XRD technique to investigate the effect of strain rate on the kinetic characteristics of γ→ε-M and ε-M→α'-M transformation. Orientation dependence of γ→ε-M and ε-M→α'-M transformation in high speed compressed specimen was analyzed by the EBSD technique and the calculation of martensitic transformation crystallography. The results show that the effects of strain rate on γ→ε-M and ε-M→α'-M transformation are different. Compared to static compression, the γ→ε-M transformation is inhibited due to the higher stacking fault energy, and ε-M→α'-M transformation is promoted because higher stress during high speed compression. Compared to static compressed specimen, martensitic transformation is accelerated at the early stage of high speed compression. High speed compressed specimen shows orientation dependence of martensitic transformation, which is related to the mechanical work of martensitic transformation in differently orientated γ grains. γ→ε-M phase transformation is only related to the mechanical work of ε-M; ε-M→α'-M phase transformation depends on the mechanical work of both ε-M and α'-M.
The creep rupture strength data of Grade 91 steel specimens with various hardness values were used to study the correlation of hardness with creep rupture strengths and maximum allowable stresses of the steel. The results show that creep rupture tests at a certain temperature and stress applied to the specimens with a series of hardness values receive the results in both overestimation and underestimation of rupture properties, leading to some unrealistic effect on 105h creep rupture strengths determined in this way. An approach was thus proposed to determine the lower limits of hardness satisfying the maximum allowable stresses at given temperatures. It was found with this method that a hardness level of ≥ 201(205) HBW of any of the Type 1- and Type 2-Grade 91 components running at a temperature of ≤ 575(600)℃ can satisfy the requirement of the maximum allowable stresses at the corresponding temperature specified by ASME BPVC 2019, and a hardness value of ≥ 204HBW is effective for the grade 91 components with a wall-thickness of ≥ 75 mm running at a temperature of ≤ 575℃ to satisfy the requirement of the maximum allowable stresses at the corresponding temperature specified by ASME BPVC 2017. Therefore, the most recently modified specification brings, to some extent, about difficulty in continuously practicing the application of the lower limit of hardness values (190-250HBW) specified by ASME BPVC 2017-2019 because it is not satisfied with the requirement on the maximum allowable stress at some given temperatures. Thus, there is a need to raise the lower limit of hardness values to settle this issue in the future. In addition, the optimization of the function fitting the creep-rupture data currently used in the estimation calculation of service/remaining lives was studied, showing that the tendency of overestimation of rupture properties can be reduced by replacing the current power function with the logarithm one. Quite good fitness of the practical data with the logarithm function curves is contributed to separating the whole data group with a series of hardness values into the higher and lower hardness level groups in calculation. On this basis, the relationship of thickness, hardness and service life of the components with variable dimensions and hardness values can be obtained by integrating the technical parameters of the safety assessment, which is able to reflect the applicability, reliability and intuitiveness of this combination. The above results can be used as reference for both the revisions of the relevant technical standards and the practical applications of industry.
Ti3SiC2 ceramic bulk with a relative density greater than 99% was prepared by hot pressing sintering (HP) using Ti3SiC2 powder as raw material, and the hardness, flexural strength and fracture toughness of HP Ti3SiC2 bulk were 775HV, 520.46 MPa and 7.62 MPa·m1/2, respectively. To evaluate its oxidation-resistance and thermal shock resistance, ultra-high temperature ablation tests were conducted under oxyacetylene flame without cooling. The results show that the Ti3SiC2 ceramics remain flat within 10 s of the ablation, no macrocracks within 25 s.SEM and XRD analysis reveal that Ti3SiC2 samples are decomposed and oxidized during the ultra-high temperature ablation, elements Si and C are oxidized into gaseous Si-O and C-O compounds, TiO2 (rutile) with a loose structure remains on the surface of the sample. To analyze the internal oxide layer, a dense layer composed of rutile TiO2 and Al2TiO5 is observed, under which an Al2O3 particle-enriched layer is found covering the substrate. The dense internal oxide layer can effectively prevent O2 from diffusing inward, thereby reducing the oxidation rate of Ti3SiC2. The high melting point and high viscosity Al2O3 particle layer can absorb a large amount of heat and then reduce the transfer of heat flow to the Ti3SiC2 substrate, thus improving the anti-ablation of the Ti3SiC2 material.
The three-dimensional carbon fiber fabric was densified by chemical vapor infiltration and precursor impregnation cracking composite process, and the high thermal conductivity 3D C/C composite material with density of 1.95 g/cm3 was obtained. Using SEM, XRD, thermal conductivity test, linear expansion coefficient test and three-point bending experiment to study the effect of different heat treatment temperatures of 2350, 2550, 2850℃ on the microscopic morphology, structure, thermal conductivity, linear expansion coefficient and bending performance of 3D C/C composites. The results show that with the increase of the heat treatment temperature, the mesophase pitch-based carbon fiber graphite sheet structure becomes more obvious, the order of the pyrolytic carbon sheets evenly wrapped around the carbon fiber increases, and the arrangement between the sheets becomes more dense; the graphitization and thermal conductivity of 3D C/C composite materials improve; in the test temperature range of 250-1400℃, the linear expansion coefficient increases slightly with the increase of the test temperature, and the 3D C/C composite after different heat treatment temperatures. The linear expansion coefficient of the materials is -1×10-6-2×10-6℃-1, showing good "zero expansion". In addition, when the heat treatment temperature increases, the bonding of the carbon fiber and the matrix of the 3D C/C composite materials are weakened, resulting in the decrease in the bending strength and flexural modulus of the materials. A large number of long fibers are pulled out on the bending fracture surface of the materials after the high temperature heat treatment at 2850℃. In general, the fracture after three different heat treatment temperatures shows "pseudoplastic" fracture characteristics.
The carbon fiber reinforced Si-C-N ceramic matrix composite with a mullite interlayer(C/mullite/Si-C-N) was fabricated with the matrix fabricated by CVI and the interphase fabricated by PIP. The thermal expansion and heat diffusion were measured by using thermal dilatometer and laser heat conductometer, respectively. SEM and XRD were used to analyze the structure and morphology of the material, and the structural changes in the matrix material were analyzed by DSC/TG simultaneous analyzer. The results indicates that the average coefficient of thermal expansion and line expansion rate of C/mullite/Si-C-N between 25-1200℃ is 1.58×10-6℃-1 and 0.18%, respectively. The thermal diffusivity decreases exponentially with temperature, which results from the amorphous structure of the matrix. As compared to the unheat-treated sample, the thermal diffusivity of the heat-treated C/mullite/Si-C-N is significantly reduced at room temperature, while slightly increased above 300℃. The structure of the composite is stable below 1000℃, which can meet the needs of engineering applications.
The temperature profile is an important process parameter for the autoclave curing of composite, which has an important influence on the curing time and the quality of the cured composite part. The curing period and curing quality of autoclave processed composite can be simultaneously controlled by the optimal design of the temperature profile. The numerical simulation of the curing process of a C-shaped composite part was carried out. The prediction results are in good agreement with the experimental test results, which verify the capability of the simulation method. Then, the temperature profile was optimized by using the design of experiment (DOE) method and particle swarm algorithm to achieve the simultaneous control of curing period and curing quality. Experiments were also carried out to verify the optimization results. The results show that the optimal design of temperature profile can effectively reduce the curing period and satisfy the constraints of curing uniformity, curing degree and curing deformation. The curing periods of the optimization cases are reduced by 64% and 45%, respectively.
Phosphated hydrotalcite (P-LDHs) was synthesized from steel slag and modified hydrotalcite (SDS-P-LDHs) was obtained by intercalation of P-LDHs with sodium dodecyl sulfate (SDS). P-LDHs and SDS-P-LDHs were blended with expanded graphite and ethylene vinyl acetate copolymer (EVA), to prepare EVA foam composites, respectively. The surface morphology and structure of P-LDHs and SDS-P-LDHs were characterized by XRD, XRF, FT-IR, SEM and TEM. Combined with limited oxygen index(LOI), UL-94, SEM, TG, tensile strength and elongation at break, the effects of P-LDHs and SDS-P-LDHs on the flame retardancy and mechanical properties of EVA foam composites were discussed. The results show that the addition of P-LDHs and SDS-P-LDHs significantly improves the flame retardant properties of EVA foam composites and can play a good role in charring formation. Compared with P-LDHs, SDS-P-LDHs have better compatibility with EVA matrix. When the addition amount of SDS-P-LDHs is 30%(mass fraction), the LOI reaches 27.5%, UL-94 reaches V-0 level, tensile strength and elongation at break are 2.27 MPa and 251%, respectively. The comprehensive properties of the system are optimal.
A mesoporous material of Fe-Zr(P) was synthesized by modifying the bimetallic material of Fe-Zr with polyether P123. Then, TEPA(n)/Fe-Zr(P) was prepared by modifying Fe-Zr(P) with tetraethylenepentamine (TEPA). X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption-desorption and thermogravimetric analysis were used to analyze the structure and thermal stability of the synthesized materials. The results show that P123 is remained in the pore channels of the support. Besides, TEPA was introduced to the surface of Fe-Zr(P) through the coordination between N and Zr species. The adsorbents filled with P123 and TEPA keep stable when the temperature is less than 182℃. In addition, the adsorbents exhibit good CO2 adsorption performance in a stream of 5% CO2 concentration. Over TEPA(n)/Fe-Zr(P), both of the hydroxyl and amine groups react with CO2, leading to the occurrence of CO2 chemical adsorption and the enhancement of adsorption capacity and N utilization. When the mass fraction of TEPA is 30%, a remarkable adsorption capacity of 211.3 mg/g and the utilization of N species of 62.7% are achieved at 75℃ in a stream of 10 mL/min. After 20 cycles of adsorption-desorption, the adsorption capacity keeps stable.
The application of materials with special wettability is a hot research topic in recent years. It is reported that Bi2O3 coating with hydrophobic modification could achieve the reversible conversion of superhydrophobicity to superhydrophilicity under UV-visible light irradiation and dark storage. Based on this finding, the application of Bi2O3 coating in antibacterial and oil-water separation under different wettability was studied. The results show that superhydrophobic surface exhibits good bacterial anti-adhesion effect against E.coli and S.aureus, while superhydrophilic surface shows selectively antibacterial activity. In terms of oil-water separation, the superhydrophobic surface can block water and allow oil pass through the filter with the separation efficiency more than 93%, while the superhydrophilic surface can block oil and allow water pass through the filter after pre-wetting treatment. Therefore, Bi2O3 coating with reversible wettability can be used as an intelligent antibacterial membrane material for oil-water separation, which has potential application in the field of oil-water separation.
|
Founded in 1956 (monthly) ISSN 1001-4381 CN 11-1800/TB Sponsored by AECC Beijing Institute of Aeronautical Materials |
