- 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)
In recent years, carbon-ceramic matrix composite materials have become a hot topic due to their high temperature resistance, low density, good corrosion resistance, low thermal expansion coefficient, and strong performance design. Biomorphic carbon-ceramic composites have been prepared by introducing the wood-derived pore structure into ceramic matrix.The pore structure, preparation process, properties and application prospects of biomorphic carbon-ceramic matrix composites were reviewed. The importance of designing the microstructure of materials was emphasized, and the key technology in the preparation process of carbon-ceramic matrix composites-infiltration technology were specified, including: chemical vapor infiltration, melt infiltration, sol-gel infiltration, slurry infiltration, polymer precursor infiltration, and molten salt infiltration. The solutions to the existing problems of each technology were proposed. Composite strength and fracture strength of biomass carbon-ceramic matrix composites were reviewed. Suggestions for future research directions on the performance were put forward. It was pointed out that the mechanical properties of materials should be tested under high temperature, strong acid and strong alkali, and alternating cold and heat environments. The potential applications of biomorphic carbon-ceramic matrix composites were discussed in three aspects, including aero-engine blades, automobile exhaust gas purifiers, and catalyst carriers. Existing challenges and practical limitations such as complex molding, strong mechanical properties and thermal stability were outlined. Finally, the improvement of the preparation process and the study of mechanical properties of biomorphic carbon-ceramic matrix composites were prospected, which provides theoretical basis and guidance for the development and application of biomorphic carbon-ceramic matrix composites.
Hypersonic flight technology is an important direction in the development of aerospace field and plays an important role in national defense security. The thermal protection materials and structures are the key to the safe service of hypersonic vehicles in extreme environments. On one hand, the thermal protection materials and structures must be able to withstand the harsh aerodynamic thermal environment, and on the other hand, they also must reduce its mass to increase the vehicle payload. Therefore, it is necessary to develop thermal protection structures that can combine high temperature resistance, light weight, and load-bearing characteristics at the same time. The manufacturing methods of lightweight C/SiC ceramic matrix composite structures were firstly introduced in this review, then the research on the room temperature and high temperature mechanical behavior, heat transfer mechanism and behavior of the lightweight C/SiC ceramic matrix composite structures were summarized. At last, integrated thermal protection structures with high temperature resistance and lightweight load-bearing were reviewed based on the lightweight C/SiC ceramic matrix composite structures. Finally, the future challenges of the lightweight ceramic matrix composite structures towards thermal protection application were also forecasted in four aspects: new design theory and method, new manufacturing technology, service characteristics and multi-functional integrated design and realization. This review provides some guidance for the research and development of novel thermal protection structures for the next generation hypersonic flight.
In order to obtain a nitride ceramic material with good flexural and dielectric properties, using silicon nitride whiskers (Si3N4w) as raw material, three kinds of Si3N4w spherical particle powders with different particle size distributions were prepared by spray drying process at first in this work, and the effect of the rotating speed of the atomizing disc on the particle size distribution of Si3N4w spherical particles was studied. Then, using the Si3N4w spherical particles obtained by spray drying as raw materials, three kinds of Si3N4w preforms with different particle gradations were prepared by dry pressing method, and the pore size distribution of the particle gradation Si3N4w preforms was studied. Si3N4 matrices were further prepared in three kinds of particle gradation Si3N4w preforms by chemical vapor infiltration (CVI) and precursor impregnation and pyrolysis (PIP) methods, and the phase and microstructure evolution of Si3N4w/Si3N4 composites during the preparation process were investigated. Finally, the effect of particle gradation on the microstructure, density, flexural and dielectric property of Si3N4w/Si3N4 composites was studied. The results show that the three kinds of particle gradation Si3N4w preforms all have bimodal pore structure characteristics, in which the pore sizes of small pores are all about 0.7 μm, and the pore sizes of large pores are 45.2, 30.1 μm and 21.3 μm, respectively. Among the as-prepared three types of Si3N4w/Si3N4 composites with particle gradation, the flexural strength of the S13 composites reaches 81.59 MPa since it has the best particle gradation effect. In addition, the dielectric constant and dielectric loss of this sample are 5.08 and 0.018, respectively. Good flexural strength and dielectric properties indicate that the as-prepared Si3N4w/Si3N4 composites are expected to be used in the field of missile radomes.
To meet the requirements of high energy density and fast charge for energy storage systems and electric vehicles, the high-energy and high-power density lithium-ion batteries have attracted numerous attentions.Designing thick-electrode can significantly increase energy density and reduce cost, and is also compatible with various electrode materials, which makes it one of hottest researches for the development of high-energy density lithium-ion batteries.Thick electrodes usually suffer from poor mechanical properties and sluggish reaction kinetics. Therefore, it is very important to construct a thick electrode with good mechanical properties and fast transport network for lithium ion and electron.The electrochemical behavior and key scientific issues of thick electrodes were firstly analyzed in this review, the current strategies for constructing thick electrodes and their advantages were then introduced, and finally the design principles and the development direction of thick electrodes were pointed out.
The recycled copper alloy powders prepared by physical method were further alloyed, and therefore four medium entropy alloys (MEAs), (Fe40Ni40Mn20)50Cu50, (Fe38Ni38Mn19Al5)50Cu50, (Fe36Ni36Mn18Al10)50Cu50 and (Fe32Ni32Mn16Al20)50Cu50were successfully prepared via mechanical alloying (MA) and spark plasma sintering (SPS). The influence of Al content on the microstructure and mechanical properties of the MEAs were systematically studied. Following 60 h of MA, the mechanical alloyed powders of the four MEAs consist of a primary supersaturated FCC solid solution along with a trace amount of WC contaminants. Following SPS, the (Fe40Ni40Mn20)50Cu50, (Fe38Ni38Mn19Al5)50Cu50 and (Fe36Ni36Mn18Al10)50Cu50 show a dual-phase structure consisting of a Cu-rich phase (FCC1) and a Fe-Ni-rich phase (FCC2), displaying a multiscale grain structure of ultrafine grains and micron grains. However, the (Fe32Ni32Mn16Al20)50Cu50 alloy shows a primary Cu-rich phase (FCC1) with a small amount of Fe-Mn rich phase (FCC2) and Ni-Al rich B2 phase. The plasticity of the four MEAs is gradually decreased, while the strength and hardness are gradually increased with the increase of Al content. The compressive yield strength, compressive strength and Vickers hardness of (Fe40Ni40Mn20)50Cu50 MEAs are 878 MPa, 1257 MPa and 248.5HV, respectively. Compared with (Fe40Ni40Mn20)50Cu50, the compressive yield strength and hardness of (Fe32Ni32Mn16Al20)50Cu50 are increased by 50.1% and 50.4%, respectively, whereas the fracture strain is decreased from 19.55% to 8.31%.
GH3536 superalloy samples were made by selective laser melting (SLM) with a parameter combination of laser power and scanning speed. The porosity and defect characteristics within the samples were characterized by μCT technique, and the defect types as well as the morphologies of molten pool were analyzed using optical microscope and scanning electron microscope. The results show that process parameters are closely related with defect characteristics and the morphologies of molten pool. As the laser power and scanning speed are optimized, continuous molten pool with a higher aspect ratio overlaps well with each other. The porosity in the fabricated samples is far less than 0.01%, and with randomly distributed small pores. When the deviation from the optimized process parameters occurs, not only larger voids are formed at the interface of discontinuous molten pool, but also the process instability are increased, resulting in the formation of minor amounts of lamellar lack of fusion. The latter two types of defects present a certain anisotropy. Additionally, smaller micropores and microcracks are beyond the μCT detection ability.
A split Hopkinson pressure bar was used to perform dynamic compression experiments on HS-Q&P steel at the strain rates of 0-12000 s-1. The deformation behavior of the specimen during dynamic compression was studied by SEM, EBSD, XRD characterization methods. The results show that the deformation behavior of the experimental steel at different rates is similar and is divided into three stages. First, there is a slight increase in stress at the platform, but the increase is more reflected in the strain. The adiabatic heating effect that occurs during the compression process will bring a softening effect. The strength and plastic deformation ability of the experimental steel can be improved by the retained austenite. The volume fraction of retained austenite in steel reduced by the transformation induced plasticity (TRIP) effect is the same as the volume fraction of martensite increased and proves the TRIP effect is the main strengthening mechanism in the steel. At the same time, it is observed by SEM that the retained austenite is transformed into acicular martensite by the TRIP effect. As the strain rate increases, the lattice distortion becomes more and more serious, and some deformation twins can be observed in the EBSD maps. At different strain rates, 〈001〉oriented grains are more likely to produce deformation twins.
The effect of solid solution cooling rate on mechanical properties and the morphology of strip α phase of TB17 titanium alloy was studied by Gleeble thermal simulation compression testing machine, microhardness tester, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that after solid solution of TB17 titanium alloy with basket-weave microstructure in α+β phase region, when the solid solution cooling rate is 200℃/min, the microhardness of the titanium alloy is 250HV. With the decrease of solid solution cooling rate, the microhardness increases gradually. When the solid solution cooling rate is reduced to 1℃/min (furnace cooling), the microhardness increases to 320HV. And TB17 titanium alloy occurs β→α phase transformation during cooling process, and secondary α phase precipitates on β matrix, and the strip-shaped α phase transforms into "fork-like" structure. As the solid solution cooling rate decreases, the "fork-like" structure gradually becomes thicker and larger. When the rate is 40℃/min, the width of the "fork-like" structure is about 14 nm. When the rate is 10℃/min, the width is about 100 nm. When the rate is 1℃/min (furnace cooling), the width is about 300 nm. When the solid solution cooling rate is greater than 10℃/min, the side and end faces of the strip-shaped α phase are wrapped with the rhombohedral martensite α″ phase, and the existence of the martensite phase promotes the transformation of α phase and the formation of the "fork-like" structure. When the solid solution cooling rate is gradually reduced to about 1℃/min which is equivalent to the furnace cooling rate, the "fork-like" structure becomes thicker, the orthorhombic martensite phase on the end and side faces of the strip-shaped α phase disappears, and α″→α phase transformation occurs.
Fe-NiAlMn and Fe-CuNiAlMn alloys were aged at 500℃ for different time after solution treatment at 900℃ for 2 h and water quenching. The influence of Cu-addition on the precipitation strengthening in Fe-CuNiAlMn alloy was studied using hardness testing and atom probe tomography(APT). The results show that the addition of Cu effectively enhances the effect of precipitation strengthening in the early stage of aging and accelerates the whole process of precipitation strengthening. Cu elements first segregate to form Cu-rich phase, which promotes Ni, Al and Mn elements to segregate and nucleate at the interface between Cu-rich phase and matrix to form Ni(Al, Mn) phase resulting in core-shell structure during aging. With the extension of aging time, Cu-rich phase changes from BCC to FCC and separates from Ni(Al, Mn) phase.
With the development of electric vehicles, higher requirements for battery energy density are put forward. High nickel/SiOx-C batteries with high energy density have become the first choice for long-range electric vehicles. However, high nickel/SiOx-C batteries have the problem of rapid capacity decay in practical use. Non-destructive electrochemical analysis and post-mortem analysis were used to detect the changes in battery capacity and internal resistance during the cycle. The changes in the structure, material morphology and surface composition of positive and negative electrodes before and after the battery cycle were compared, revealing the mechanism of cycling failure of high nickel/SiOx-C batteries. The results show that the capacity decay of the battery presents three stages: the stationary period, the rapid decay period and the extreme decay period. After cycling, the polarization of the battery is more serious, and the polarization internal resistance of the battery, the surface film resistance of the negative electrode and the charge transfer resistance increase significantly. Through differential curve analysis combined with disassembly analysis, it is found that the high nickel cathode material has less attenuation, and the silica carbon anode material has more attenuation and active lithium-ion loss. The expansion and cracking of silicon oxide particles, the loss of negative electrode active material, and the continuous growth of solid electrolyte interface film on the negative electrode surface consuming too much active lithium are the main reasons for the rapid decline of battery capacity.
Li4Ti5-xYxO12 (x=0, 0.05, 0.10, 0.15, 0.20) anode materials were synthesized by ball milling assisted solid-state method used Li2CO3 and anatase TiO2 as raw materials and yttrium nitrate (Y(NO3)3·6H2O) as yttrium source. The phase and morphology of the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), respectively. The electrochemical performance and transport characteristics of the materials were tested and analyzed by an electrochemical workstation. The results show that there is no effect of Y3+ doping on the spinel structure of LTO material. When x=0.15, the ion and electronic conductivities of the Li4Ti4.85Y0.15O12 sample are 2.68×10-7 S·cm-1 and 1.49×10-9 S·cm-1, respectively, which are an order of magnitude higher than that of the intrinsic LTO, and present good transport characteristics. Electrochemical tests show that a first discharge capacity of Li4Ti4.85Y0.15O12 sample can reach 171 mAh·g-1 at 0.1 C rate. The sample still has a higher specific capacity of 102 mAh·g-1 and 79 mAh·g-1 at a high rate of 10 C and 20 C, respectively.After 200 cycles, the capacity retention rates are 92.6% and 89.1% respectively, showing good magnification characteristics.
Core-shell Al2O3@carbonyl iron powders (CIPs) were prepared by ball-milling-in-situ oxidation method. The phase composition, mass change and micromorphology of Al2O3@CIPs were analyzed by X-ray diffraction, thermogravimetric analyzer and scanning electron microscopy. The effects of various oxidation temperature on electromagnetic properties and absorbing performance of Al2O3@CIPs were studied. The results show that, as the oxidation temperature increases, the shell of Al2O3@CIPs is damaged to some extent and accompanied by the formation of iron oxides, its permittivity rises first and then declines, while permeability shows a downward trend. Compared with CIPs, Al2O3@CIPs obtained by in-situ oxidation at 400℃ achieve excellent electromagnetic wave absorption performance.The real part of the permittivity is about 15, and the imaginary part is 2.8-4.3. The effective absorption band (< -10 dB) of 3.4 GHz can be obtained under the thickness of 1.8 mm in the X-band, while the Al2O3@CIPs obtained by in-situ oxidation at 450℃ achieve the maximum reflection loss of -30 dB at 11.1 GHz.
To improve the mechanical properties of carbon fiber reinforced polymer (CFRP) bonding interface, the surface treatment of CFRP was performed using low-temperature oxygen plasma treatment equipment. The surface physico-chemical properties including surface wettability, surface energy, surface morphology and surface chemical components of CFRP were characterized by contact angle measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) test equipment, as well as the mechanical properties of CFRP bonding interface was tested by double cantilever beam (DCB) test. The results show that the water contact angle of surface decreases from 97° to 29° with the increase of oxygen plasma treatment time from 0 s to 30 s, as well as the surface wettability of CFRP is the best and the percentage of polar components increases significantly. As the increase of treatment time, the surface roughness and the maximum height difference of CFRP decrease significantly, and more nanoscale grooves with valley distribution are formed and thus the surface area of substrate increases. Meanwhile, the content of oxygen-containing polar functional groups including C—O and C＝O on the surface are increased obviously, the content of C—C/C—H and Si—C functional groups are decreased, and the surface contaminants are effectively removed or transformed. In comparison with the untreated specimens, the maximum peeling load and mode Ⅰ fracture toughness of CFRP adhesive interface are improved by 1.01 times (62.73 N) and 1.92 times (649.21 J/m2) after oxygen plasma treatment for 20 s, respectively. The study reveals that oxygen plasma treatment can significantly improve the physico-chemical properties of CFRP surface, which is conducive to better bonding between CFRP and adhesive, and improve the peel strength and toughness of the adhesive interface.
Surface modification of poly(benzoxazole-imide) (PI) film was carried out by means of oxygen plasma treatment. A flexible copper clad laminate (FCCL) was fabricated using Ni-Cr ion implantation and electro-Cu plating process. Controlling the constant pressure, the effects of such treatment conditions as power and time were systematically investigated on the surface roughness, chemical composition and interface adhesion with Cu. It is found that the optical parameters for production of FCCL with excellent adhesion and solder resistance are 50 W/5 min and 100 W/10 min, respectively. Suitable roughness, reactive radical with high content pendent oxygen group, and metal-oxazole complex help to endow exceptional adhesive property to the interface of PI/Cu. And the peel strength of FCCL prepared from PI film with such modified surface rises by 60%.
Poly(aryl ether ketone) (PAEK) thermoplastic composites can replace some traditional thermosetting composites because of their outstanding toughness, aging resistance, fatigue resistance, low cost, high manufacturing efficiency and recyclability. Thus, PAEK composites have been successfully applied in foreign aviation and other high-end industrial fields. PAEK is a kind of semi-crystalline polymer. Hence, different molding process conditions of PAEK composites lead to different aggregation structures of resin matrix, which have significant influence on mechanical properties and aging resistance of the composites. Crystallization kinetics of domestic PAEK resin was studied. Then, continuous carbon fiber reinforced PAEK composites with different crystallinities were prepared by mold pressing at different cooling conditions. The composites were subjected to hydrothermal aging treatment. Flexural properties of the composites were evaluated. The results show that higher cooling rates can improve the crystallization rates but reduce the crystallinity of PAEK resin. The crystallinity of PAEK resins of the composites prepared at furnace cooling, air cooling and water cooling are about 36.3%, 29.7% and 26.5%, respectively. Thus, the decrease of PAEK crystallinity leads to the decrease of flexural strength of its composites. Moreover, flexural strength retention rates of composites with different crystallinities after hydrothermal aging treatment for 240 h are 88.8%, 86.7% and 86.6%, respectively. Therefore, higher crystallinity can better resist the damage of water on the interface and improve the hydrothermal aging resistance of the composite.
PEO-based solid polymer electrolytes are considered as a promising solid electrolyte in the field of solid-state lithium batteries.PEO/LiClO4 solid polymer electrolyte(SPE) was prepared through electrostatic spinning technology, in order to meet the demand of industrial production. The effects of spinning voltage, spinning solution concentration and lithium salt content on the morphology and diameter of the fiber were studied.The morphology of SPE fiber was observed by scanning electron microscope and the diameter of SPE fiber was analysed by Image J.Furthermore, the composition, structure and properties of solid polymer electrolyte fiber membranes prepared by electrospinning were studied by DSC, XRD, FTIR-ATR and tensile testing.The results show that the PEO/LiClO4 solid polymer electrolyte membrane prepared by electrostatic spinning method has good fiber morphology, when the spinning voltage is 15 kV, and the concentration of PEO/LiClO4 spinning solution is 6%, and the molar ratio ([EO]: [Li+]) is 10:1.Meanwhile, the average diameter of the fibers is 557 nm, giving relatively uniform distribution.When[EO]: [Li+]=10:1, the melting point of PEO in the SPE fiber membrane is only 53.8℃, with the crystallinity as low as 18.9%. And the ionic conductivity of the prepared SPE exhibits as high as 5.16×10-5 S·cm-1 at 30℃.Moreover, the prepared electrospun SPE has good electrochemical stability and interfacial stability.
Based on ZnO and melamine, the ZnO/g-C3N4 for photocatalytic U(Ⅵ) reduction was pre-pared by thermal polymerization methods. The surface morphology, lattice structure, element composition and photocatalytic efficiency were analyzed by SEM, XRD, XPS, PL and UV-Vis methods.The results show that the doping of ZnO reduces the recombination rate of photogenerated electrons and holes, expands the response range of the material to visible light, makes ZnO/g-C3N4 have higher photocatalytic activity. When pH=5 and dosage is 0.5 g/L, the highest U(Ⅵ) removal rate can reach 97% after dark reaction for 30 min and light reaction for 30 min. The U(Ⅵ) on the surface of the photocatalyst can be reduced to U(Ⅳ). The photoelectron e- is the main factor for reducing U(Ⅵ) to U(Ⅳ).
Natural attapulgite was used as silicon source, butyl titanate as titanium source, tetrapropyl ammonium hydroxide as template for one-step hydrothermal synthesis of titanium silicon molecular sieve, the effect of titanium silicon ratio on the structure and performance of synthetic products was studied. XRD, SEM, UV-Vis and N2 adsorption-desorption were used to characterize the crystal structure, morphology, titanium form and pore characteristics of Ti-Si molecular sieves. The results show when the Ti-Si ratio is 1:30, the XRD characteristic peak strength of Ti-Si is high, the grain size is uniform in a regular six-prism shape, titanium exists in the form of skeleton titanium and anatase TiO2, and the pore structure is both microporous and mesoporous. The molecular sieve has photocatalysis, photocatalytic reaction follows quasi-first order kinetics. The optimal experimental conditions of pH=7.8 methylene blue solution for optimizing the model established by response surface method are as follows: the initial concentration is 10.0 g/mL, the photocatalytic time is 48 min, the dosage is 0.05 g, and the decolorization rate of the photocatalytic degradation solution is 98.75%.
Nondestructive evaluation on fatigue damage of metallic materials with ultrasound is important to ensure the load-bearing capability and in-service reliability of high-performance components.The fatigue damage of industrial pure iron was studied, and a nondestructive testing method which combined the critically refracted longitudinal (LCR) wave and recurrence quantification analysis (RQA) was proposed. Results show that with the increasing loading cycles and hardening during the tensile-compressive cyclic loading until 1000 cycles, the amplitude of LCR wave and the corresponding normalized amplitude difference Adifboth evolve monotonically. The sensitivity of 5 MHz testing frequency is significantly higher than that of 2.25 MHz. A further analysis of LCR wave with RQA presents that the resulting recurrence plot possesses higher sensitivity. The normalized recurrence rate difference RRdif is extracted. The sensitivity indicates an obvious increase up to 44% compared with the maximum amplitude indexes in time domain, frequency domain, and time-frequency domain. It proves that the proposed method would be a new solution to the nondestructive evaluation on early-stage fatigue damage of metallic materials.
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