- 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)
To meet the development needs of advanced aeroengines, the structure of aeroengine turbine blades is becoming increasingly complex, and the content of refractory elements is increasing in single crystal superalloys, which are the preferred materials for turbine blades. As a result, the tendency to form the grain defects increases during the preparation of single crystal turbine blades, which directly affects the quality of single crystal turbine blades. In this paper, a kind of grain defect that appears in the directional solidification process of single crystal superalloys—freckle was discussed. The research works on the formation mechanism, the criterion model and the control method of freckles formation during the directional solidification of single crystal superalloys in recent years was reviewed. The influence of the alloy composition, blade structure, directional solidification process and crystal orientation of single crystal castings on the formation of freckles was analyzed. Considering the influence of the alloying elements in different alloy systems and the parameters of the directional solidification process on the freckle formation, further studying the freckle formation mechanism of the single crystal turbine blade with complex structures, establishing an effective method for prediction and control of freckles are the future research directions.
Nanoporous materials have attracted great attention in the fields of adsorption and membrane separation due to their remarkable nanoscale spatial effects. As an extension of inorganic porous materials, metal organic framework (MOF) has been widely used in gas-phase storage and separation, liquid-phase adsorption separation and catalytic reaction due to its large specific surface area, high porosity and adjustable pore structure. In this paper, the types of MOF are classified, and the synthesis methods and particle size control mechanism of MOF materials were compared. Among them, the advantages of solvothermal synthesis were emphatically introduced. At the same time, the problems and limitations of MOF materials in adsorption separation research were summarized systematically, and the advanced preparation technology of composite membrane based on MOF materials was prospected; the application of MOF in gas storage separation, liquid adsorption separation and membrane separation was summarized. Finally, for the preparation of composite membrane, the idea of improving the compatibility of MOF material and organic membrane by changing the synthesis method of MOF was proposed.
The rapid development of new energy vehicles places a more and more urgent demand for high-performance lithium-ion batteries. As an important part of lithium-ion battery, the electrode performance has a significant impact on the overall performance of lithium-ion battery. In the electrode, the uniformity and stability of the slurry, which is a multi-component mixture, own a great influence on the performance of the electrode sheet. However, most of the current researchers' interests are usually placed after the slurry process, that is, only focus on the performance of the electrode, but ignore the slurry which is the preconditions of the performance of the electrode. Uniformity of the electrode is determined by the uniformity and stability of slurries. However, as a complicated mixture of multicomponent suspended particles, it's hard to measure the uniformity and stability of the slurry directly. At present, the rheological property test of the slurry is the most effective method to characterize the uniformity and stability of the slurry. In this paper, the effects of active materials, binders, conductive agents, solvents, dispersing additives, pH value, temperature, mixing steps on the rheological properties of the slurry during the manufacturing of lithium ion battery electrode pastes were reviewed. The influence of these factors on the rheological properties of the slurry was summarized, which provides a certain guiding role for fabricating slurries with higher uniformity and stability and developing high performance Li-ion batteries.
Lithium metal batteries have been considered as one of the most promising high-energy-density energy storage devices, however, the low Coulombic efficiency and uncontrolled dendrite growth seriously hinder their commercialization. In lithium metal batteries, the electrolytes would directly participate in the formation of solid electrolyte interface (SEI), which play important roles in affecting the lithium metal anode Coulombic efficiency and inhibiting the growth of lithium dendrites.In the traditional LiPF6 based ester electrolyte, lithium metal anode exhibits low Coulomb efficiency and serious lithium dendrites.In recent years, significant improvement has been achieved for the protection of lithium anode through manipulating the electrolyte additive, solvents, lithium salt and lithium salt concentration, etc. For examples, ether solvent presenting better compatibility with lithium metal was selected to reduce the side reactivity of electrolyte with lithium metal; varieties of additives were adopted to suppress the formation of lithium dendrites; high concentration electrolytes were employed to form stable SEI.In this paper, the growth principles of lithium dendrites, the research status of electrolytes chemistries for protection of lithium metal anode by means of solvents, lithium salts, additives and high concentration electrolytes strategies were reviewed and the advantages and limitations of various approaches were summarized.New insights on the development of electrolytes chemistries were also put forward to stimulate new strategies to face the subsequent challenges of lithium-metal batteries.
Carbon/Carbon(C/C) composites are widely used in aerospace industry due to their diverse advantages such as low density, reliable thermal shock resistance and excellent mechanical properties at elevated temperatures. However, their awful oxidation resistance, especially at higher temperatures, has greatly limited their further applications. Ultra-high temperature ceramics(UHTCs) are ceramics whose melting points are higher than 3000 ℃. Some advanced performances like high strength, high hardness and outstanding thermal stabilities have given the UHTCs huge potential in ultra-high temperature applications. Using UHTCs to modify the matrix of C/C composites is a commonly applied method to improve the oxidation resistance of the C/C composites. There are numerous methods to fabricate UHTCs modified C/C composites(C/C-UHTCs), yet none of them could assure low cost, high efficiency and uniform bulk density simultaneously. Compared to C/C composites, C/C-UHTCs possess better performances both in anti-oxidation ablation and mechanical properties. But, the long-term(over 120 s) anti-oxidation ablation properties and anti-oxidation ablation properties of prototype structures are waiting to be improved to meet the updated requirements of modern sharp-edged aerospace vehicles. Meanwhile, reducing the brittleness of the modified composites and improving the reliability of the structure should be considered in order to avoid the hazard brittle fracture of the composites. In order to provide references to future studies, the state of the arts of the C/C-UHTCs were reviewed from four perspectives, which were manufacture processes, microstructure morphologies, anti-oxidation ablation properties and mechanical performances. Moreover, the future research tendency of this kind of composites was also predicted in this work.
With the rapid development of packaging industry and the improvement of environmental protection requirements of human society, biodegradable functional packaging film materials have attracted great attention. However, commercial biodegradable functional package film materials have been constrained by its high cost, low mechanical properties and water resistance. The lignin microspheres were firstly prepared by self-assembling and were adhered to the surface of cellulose film via self-depositing, resulting in fabrication of novel cellulose-based UV-blocking film materials. Subsequently, the surface morphology, ultraviolet resistance and mechanical properties of the obtained functional film materials were studied. The surface properties of films were investigated by scanning microscopy (SEM), infrared spectroscopy (FTIR) and confocal laser scanning microscopy.The mechanical properties and UV resistance of cellulose based films were characterized by tensile test and UV transmittance test.It is noteworthy that the lignin microspheres with 1-2 μm in size are uniformly distributed on cellulose films and hydrophobic modification of cellulose-based films facilitated the deposition of lignin. Moreover, the deposited contents of lignin microspheres increase with the increase of the lignin concentration in solution. Due to the introduction of lignin microspheres, the strength of cellulose composites film increases by 22% and the UVB-shielding capacity reaches 94% as compared with the controlled cellulose films.
By using 4, 7-dibromo-2, 1, 3-benzothiadiazole as photoactive group, the Sonogashira coupling between 4, 7-dibromo-2, 1, 3-benzothiadiazole and 1, 3, 5-triethynylbenzene results in benzothiadiazole functionalized conjugated microporous polymer (CMP), named CMP-3-BT. The obtained CMP-3-BT shows hierarchical structures, which consists of microspheres and curved nanobelts. Moreover, CMP-3-BT is semiconductive porous materials with band gap of 2.24 eV. By using 425 nm LED (3 W) as light source, assisted by H2O2, CMP-3-BT enables the oxidation of thioanisole bearing various substituents to their corresponding sulfoxides under O2 atmospheres at room temperature with high efficiency and excellent selectivity. EPR spectra indicate that the 1O2 and O2·- are the active oxygen species for the photo-oxidation of thioanisole. Importantly, the catalytic activity of CMP-3-BT remains unchanged after 6 cycles, indicating the excellent structural stability and catalytic activity of CMP-3-BT serving as a reusable green catalyst.
BN and BN/SiC interphases were prepared on the surface of SiC tows by chemical vapor infiltration (CVI).The tows were furthered deposited a thick SiC layer to form mini SiC composites, whose tensile properties were tested.The surface and cross-section of interphase and mini-composites were observed by SEM.The surface roughness of the interphase was evaluated by AFM.The crystal structure of interphase was characterized by XRD and TEM.The results show that the BN interphase prepared by the CVI method follows Stranski-Krastanov growth mode, possessing smooth surface and weak bonds with the matrix.After heat treatment, the crystallinity and the surface roughness of BN interphase increase, and the bond with the matrix is also slightly enhanced.The BN/SiC interphase follows V-W growth mode, possessing rough surface and weak bonds with the matrix.The tensile strength of mini-composites with BN, HBN and BN/SiC interphases are 970, 1050 MPa, and 1720 MPa, respectively.
In order to solve the forming difficulty of the ceramic matrix composites used as the aeroengine complex components, carbon fiber fabric was used as the reinforcement, two different slurries, with or without powder additives, were taken to form the carbon fiber fabric reinforced silicon carbide composites via slurry-casting and melt infiltration technology. The process adaptability of the two slurries in the slurry-casting and melt infiltration process were explored, and corresponding basic properties of the composites were investigated. The results show that the viscosity of the two slurries is moderate during the slurry-casting process, and they could keep the station for more than 3-5 hours at the setting temperatures, which could obtain dense and uniform polymer matrix composites. After being carbonized at 900 ℃, the porosity of the solidified sample synthesized via slurries with or without powder is 39.6% and 31.3%, the residual carbon ratio is 24% and 76%, and the average diameter of pore is 0.068 μm and 0.069 μm, respectively. The carbon fiber fabric-reinforced silicon carbide composite prepared with powder-added slurry has lower porosity of 3.54% and higher bending strength of 162 MPa, which meets the application requirements of aeroengine static components.
By aid of aluminium trichloride (AlCl3), an effective fabrication of the preform of carbon/carbon silicon carbide (C/C-SiC) composites via catalytic carbonization was developed, using coal tar as precursor at a low temperature. C/C-SiC composites were obtained by two different approaches, one combining catalytic carbonization and in-situ reacted (CC-ISR) method, the other combining catalytic carbonization and reactive melt infiltration (CC-RMI) method. Furthermore, the microstructure and mechanical properties of the resulted C/C-SiC composites were characterized. SiC nanowires distributed in the voids of interbundle and intrabundle of carbon fibers in as-prepared samples with CC-ISR process. The CC-ISR sample exhibits a pseudo-plastic fracture mode and its flexural strength is about (158±12) MPa. By contrast, the SiC morphology of composites fabricated in CC-RMI process contains cube and hexagonal grains. The fracture behavior of CC-RMI sample shows a brittle fracture mode and its flexural strength was about (150±10) MPa. Compared with the CC-RMI method, the C/C-SiC composites obtained by the CC-ISR method has many advantages such as simple technology, low cost and excellent mechanical properties.
(FeNiCo)-(AlCrSiTi) multicomponent alloy coatings with different contents of alloying components (Al, Cr, Si, Ti) were manufactured by laser deposition. The effect of the alloying components content on the microstructure and mechanical properties of the coatings was investigated. The results show that the content of face-centered cubic (FCC) phase in the coatings decreases gradually and the microstructure is changed from FCC phase+body-centered cubic (BCC) phase to BCC phase dominated with the increase of alloying components (Al, Cr, Si, Ti) content. Moreover, the density of nano-precipitation particles in the BCC phase increases significantly and the average size of the nano-precipitation particles decreases from 97 nm to 36 nm. Meanwhile, with the increase of alloying components content, the area of equiaxed grain microstructure in the coatings increases and the equiaxed grains become much finer, with the minimum average grain size of only 10.8 μm. Furthermore, the microhardness of the coating cross section increases from 271HV0.1 to 718HV0.1. However, the bending strength of the coating decreases from 2208 MPa to 1374 MPa and the maximum bending strain also decreases from 7.3% to 0.47%.
Inorganic Bi-based double perovskite oxide, Bi2FeCrO6 (BFCO), has offered new opportunities for applications in burgeoning fields of optoelectronic and photovoltaic, due to its unique multiferroic properties at room temperature. The P-type direct-bandgap semiconductor Cu2ZnSnS4 (CZTS) was adopted to couple with BFCO as hole transport layer, in order to construct BFCO/CZTS heterostructure. Pulsed laser deposition (PLD) technique was used to deposit above-mentioned polynary compound films on different substrates (i.e. FTO conductive glass, Nb-doped SrTiO3 and Si/SiO2/Ti/Pt). For the preparation of heterojunctions, the interfacial defects and impurities could be effectively restrained by in-situ layer-by-layer deposition technique. The systematical analysis according to SEM, AFM, EDS and XRD measurements verified that the morphology of the achieved stoichiometric films was basically uniform and dense. The impacts of deposition temperature on the product performance were emphatically investigated. The bandgap of obtained BFCO and CZTS films (i.e. 2.23 eV and 1.49 eV, respectively) was estimated by using Tauc method based on visible absorption spectroscopy measurements. The results show that BFCO/CZTS heterojunction has a favorable rectifying characteristic; the leakage current mechanism is consistent with Schottky emission model when the electric field intensity spans from 0.5 kV/cm to 2.0 kV/cm.
The core-shell structured CoNiCrAlY-Al2O3 powders were well-designed and fabricated with the Al2O3 as the shell. The ball milling preparation process of core-shell structured powders was optimized by orthogonal experiment design. The phase structure and microstructure evolution of the high velocity oxy-fuel sprayed(HVOF) CoNiCrAlY-Al2O3 coatings caused by using of core-shell structured powders were discussed. The oxidation behavior of HVOF CoNiCrAlY coating and CoNiCrAlY-Al2O3 composite coating at 800 ℃ was comparatively studied.The results show that the influence of the process parameters on the average coating rate of the core-shell structured powders in descending order are: ball milling rotation speed, mass ratio of ball to powder and ball milling time.The optimal ball milling parameters for preparing CoNiCrAlY-Al2O3 core-shell structured powders are: ball milling rotation speed of 180 r/min, mass ratio of ball to powder of 10∶1, and ball milling for 6 h. The HVOF CoNiCrAlY coating is mainly composed of γ-Co-Ni-Cr phase.The oxidation behavior of CoNiCrAlY alloy during spraying process is significantly inhibited by the using of core-shell structured raw powders. Due to the existence of the high melting point Al2O3 shell in the raw powders, the CoNiCrAlY-Al2O3 composite coating contains a high content of β-NiAl phase. In addition, the coating has high porosity and high content of un-melted particles.Compared with CoNiCrAlY coating, CoNiCrAlY-Al2O3 composite coating has excellent high temperature oxidation resistance. The high content of β-NiAl and Al2O3 in the composite coating leads to the formation of a dense Al2O3 rich protective layer on the surface of the coating during high temperature oxidation. The oxide film significantly inhibits the growth of non-protective oxides.
In order to improve the performance of tungsten copper infiltration materials to adapt to the development of advanced propulsion technology, ZrC powder and W powder were adopted as raw materials to prepare ZrC-W framework by pressureless sintering process and the pressure infiltration of ZrC-W framework was conducted by pressure infiltration to prepare ZrC-W-Cu composites. The effect of ZrC content(volume fraction, the same below) on the porosity, compression strength, and microstructure as well as mechanical properties of ZrC-W-Cu composites were investigated. The results show that with the increase of ZrC content, the open porosity of ZrC-W framework increases first and then decreases, reaching the maximum value(29.77%) when ZrC content is 4%. The compressive strength of ZrC-W framework decreases with the increase of ZrC content, for which the compressive strength is lower than that of W framework. With the increase of ZrC content, the Vickers hardness of ZrC-W-Cu composites gradually increases and reaches 3.26 GPa when ZrC content is 15%. The elastic modulus remains unchanged basically, while the fracture toughness first increases and then decreases with the increase of ZrC content. The flexural strength reaches the maximum value up to 1243 MPa when ZrC content is 4%.
20 kHz ultrasounds were applied in the process of 390 ℃ hot dip galvanization of 1050 aluminum alloy. The evolution of the cavitation bubbles were solved numerically from the Keller-Miksis and Mettin equations. The growth of the cavitation bubbles of 0-800 W ultrasonic cavitation and their effects in the ZnAl8 molten pool were described. The effects of the ultrasonic power on the alloy structure of the coating and the removal of the oxide film on the surface of the 1050 aluminum alloy were analyzed. The results show that cavitational effects display nonlinear relation with the ultrasonic power. For ultrasonic power in the range of 0-500 W, stable cavitation dominates. The dendritic structure of the coating ZnAl8 alloy and the aluminium oxide film remain mostly unchanged. When the power is 600-800 W, transient cavitation bubbles release energy in the form of violent collapse. The high cavitation pressure and temperature, respectively, crush and melt the oxide film on the surface of the aluminum alloy, which facilitates spreading, wetting and transfer of the elements between the aluminum substrate and the coating. Therefore, under the action of power ultrasonic waves of 700-800 W, good metallurgical bond is formed between the coating alloy and the aluminum alloy substrate, and the coating alloy displays fine and uniform rosette-like microstructure.
The interface reaction between directionally solidified alloy IC10 and Al2O3 ceramic mold was investigated by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that the interface reaction between Al2O3 ceramic mold and alloy IC10 occurs, and severe sand-burning of the alloy surface is observed. Due to the high content of 1.5% (mass fraction) Hf, the activity of alloy IC10 obviously increases. The reaction zone with thickness about 5-8 μm can be divided into inner layer and outer layer. The outer layer is mainly HfO2, and the inner layer is rich in (Al, Ta, Nb) oxides, Al content is 80%. Hf and Al are the main elements induced the reactions.
The surface damage resistance of chemically strengthened aluminosilicate glass is very important. The surface hardness and modulus are closely related to the damage resistance of glass. The micromechanical behaviors such as surface hardness and modulus of chemically strengthened aluminosilicate glass were analyzed by finite element method, and compared with the results of nanoindentation experiment. The results show that the load displacement curve of nanoindentation calculated by finite element method is in good agreement with the experimental results. According to the load displacement curve obtained by finite element simulation, Oliver and Pharr method was used to calculate the hardness and Young's modulus. The calculated results are very close to the experimental values. The relationship between the yield strength of aluminosilicate glass and the stress-strain in the plastic region calculated by Larsson's plastic formula is used in the simulation process. The simulation results are in good agreement with the experimental results, which indicates that the accuracy of the plastic parameters of aluminosilicate glass obtained by Larsson's plastic formula is high. Finally, according to the stress distribution obtained by finite element simulation, the elastic-plastic deformation behavior of aluminosilicate glass before and after chemical strengthening was analyzed. The results show that the surface compressive stress layer produced by chemical strengthening has more influence on the elastic zone of aluminosilicate glass, but has less influence on the plastic zone.
The single-lap joints with different overlap lengths were bonded by carbon fiber reinforced plastics (CFRP) laminate, and their failure load, fracture process and strain fields were characterized by digital image correlation (DIC) and universal testing machine. The effects of overlap length on the tensile properties, fracture process, strain distribution and failure characteristics of single lap joints were studied. The results show that with the development of overlap length, the average shear strength of joints is decreased firstly and then tends to be stable. The secondary bending effect of joints caused by the eccentric load during the stretching process becomes more significant with the increase of overlap length, the end deformation of the lap area is increased, and the initial failure position of joints changes from one end to both ends of the lap area. The strain concentration area at the end of the front and side of joints transitions from asymmetric to symmetric. The peeling stress of joints gradually is increased, and the main failure mode between layers is changed from shear to peeling failure. The failure mode of joints go through the process from interface and slight fiber tearing to mixed failure and then to delamination.
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