- 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)
The historical evolution, the latest research progress and the related industrial status of equipment development of the three major photopolymerization-based ceramic 3D printing technologies were reviewed, i.e. stereolithography (SL), digital light processing (DLP) and two-photon polymerization (TPP). The characteristics of feedstock materials, printing process, post-treatments and final ceramic properties were summarized and discussed.Meanwhile, some of the issues and challenges such as incapability of mass production and low efficiency persist, and high-end industrial application scenarios of printed parts still need to be excavated. Therefore, new materials, new theories and new technologies regarding ceramic photopolymerization-based 3D printing should be further developed in order to seek for efficiency and application breakthroughs. Finally, it was suggested that structural-functional integral/gradient manufacturing and multi-material/multi-process comprehensive and efficient manufacturing are the important development directions of ceramic 3D printing technology in the future.
Among the manufacturing methods of high performance gradient functional materials, laser additive manufacturing technology can achieve the materials with gradient microstructure and property through precisely controlling the powder feeding and corresponding process adjustment, providing a new way to prepare high performance gradient functional materials more conveniently and efficiently. The basic principles and classification of laser additive manufacturing technology for high performance gradient functional materials were introduced in this paper, and the research progress in manufacturing high performance gradient functional materials by laser additive manufacturing technology at home and abroad was summarized. Furthermore, the shortcomings of this research field in material selection, process optimization and process monitoring were proposed, and its future research directions, such as the establishment of standard systems, in-depth theoretical research and the development of new manufacturing systems, were prospected, which provide guidance for the research of laser additive manufacturing technology for high performance gradient functional materials.
As one of the core hot components of aeroengines, the safe service of turbine blades is crucial to the operation of aeroengines.When the aeroengines encounter some emergency conditions, the turbine blades may suffer overheating, the temperature of which is much higher than the highest normal operating temperature. Overheating can lead to serious microstructural degradation and even premature failure of turbine blades. In this paper, the methods of overheat inspection and failure analysis were introduced, as well asthe effects of overheating on the microstructural degradation and mechanical propertiesof aeroenginesturbine blades. In addition, the damage assessment, life prediction and microstructure rejuvenation of superalloys after overheating were prospected in this paper, which provide a guidance and theoretical basis for the degradation evaluation and failure analysis of turbine blades as well as the development of new superalloys.
The metallic molybdenum disulfide exhibits large interlayer spacing, high electrical conductivity and abundant active sites, which shows wildly application prospects in the field of energy storage and conversion. The recent progress of metallic molybdenum disulfide in energy storage and conversion was reviewed. Firstly, the crystal and electronic structure of the metallic molybdenum disulfide were introduced, and the synthesis methods such as top-down (lithium intercalation stripping) and bottom-up (solvent/hydrothermal) were included. Then, the progress of metallic molybdenum disulfide and its composites in the fields such as hydrogen evolution reaction, lithium (sodium) ion batteries and supercapacitors were summarized. Finally, it is pointed out that the current challenges of metallic molybdenum disulfide are uncontrollable synthesis process and poor structural stability. The in-depth study on the structure and properties of metallic molybdenum disulfide is expected to fundamentally improve its performance and practical application in the field of energy storage and conversion.
Supercapacitors are power-type energy storage devices with high power density and long cycle life. However, the low energy density limits wider applications. In this paper, the working principle of supercapacitors was first introduced, and the characteristics of electrode materials needed and current progress were summarized. Then, the characteristics and related progress of aqueous, organic and ionic liquid electrolytes were introduced. Finally, the principle and the factors of energy density limitation of supercapacitors were pointed out, and the improvement methods were discussed from the aspects of electrode materials, electrolytes and the structure of supercapacitors, respectively.
Surgery, radiotherapy, and chemotherapy are inevitable for most cancer patients, but these treatments also cause great damage to the body of humans.However fluorescent nanomaterials have the advantages of high fluorescence stability, low biotoxicity, and good biocompatibility, the most important thing is that it can perform non-invasive targeted therapy through its own peculiarity to avoid the harm of the above therapy to the human body. Therefore, fluorescent materials will be particularly important in biological applications. As a new type of carbon nanomaterial, carbon dot has excellent light stability and fluorescence performance, good biocompatibility, low toxicity and so on, which can be applied to biosensors, bioimaging and biomedical applications. This review will express the preparation of carbon dots, the mechanism of luminescence and the application of biology, and focus on the application of carbon dots in biological diagnosis and treatment, and discusses the combination of carbon dots with specific targeting molecules to form carbons that detect fluorescent signals, by means of advanced optical imaging technology, which can perform real-time dynamic monitoring of intracellular and biological molecules, perform rapid immunofluorescence analysis of major infectious disease sources, and provide new technologies and methods for disease occurrence, diagnosis, and treatment research.
CeO2 mesoporous microspheres were synthesized by hydrothermal method and loaded with AgBr nanoparticles(NPs)on their surface. A small amount of Ag nanoparticles were obtained by in-situ reduction by photo deposition method to prepare CeO2-Ag/AgBr heterostructure catalyst. CeO2-Ag/AgBr samples were characterized by scanning electron microscopy (SEM), ultraviolet diffuse reflection (DRS), transmission electron microscopy (TEM), fluorescence spectroscopy (PL) and X-ray photoelectron spectroscopy(XPS).The photocatalytic performance of CeO2-Ag/AgBr(CAAB) was investigated with Rhodamine B(RhB) as the target degradation material and xenon lamp (500 W). The results show that the photocatalytic activity of CAAB-3 (36.03%AgBr) is the highest. When the concentration of CAAB-3 is 5 mg/L, the degradation rate of RhB reaches 94.84% within 80 min, which is 22.3 times of the degradation capacity of CeO2. After multiple cycles of experiments, the degradation rate of CAAB-3 remains stable at 88.55%. The plasma on resonance effect of Ag NPs reduces the recombination of electron holes and photogenic carriers and enhances the photocatalytic performance.
Cellulose graphene composite aerogels (CMC/GA) were prepared by one-step hydrothermal reaction based on graphite oxidation with the addition of low cost carboxymethyl cellulose. The functional group structure and microstructure of CMC/GA were characterized. The mechanism and capacity of the adsorption of Methylene Blue (MB) were investigated by CMC/GA in water. The results show that the higher temperature and higher initial concentration of MB are beneficial to the adsorption of CMC/GA. The adsorption isotherm is fitted with Langmuir model, the adsorption activation energy of the system is 57.951 kJ·mol-1, indicating that the adsorption of MB by CMC/GA is monolayer and belongs to chemical adsorption. The adsorption kinetics of MB is fitted with pseudo-second-order kinetics model. The intrapartical diffusion model of MB with different concentration shows that the adsorption process of CMC/GA for MB can be divided into two stages:macroporous diffusion and microporous diffusion, and the diffusion rate of macroporous diffusion is obviously higher than that of microporous diffusion.
Calcium silicate/calcium alginate (PET-s-CaAlg/CaSiO3@SiO2) composites supported by polyethylene terephthalate fibers were prepared by chemical crosslinking. The PET-s-CaAlg/CaSiO3@SiO2 was characterized by optical microscope, Scanning Electron Microscopy (SEM), Fourier Transform infrared spectroscopy (FTIR) and BET.As can be seen in SEM, mesoporous SiO2 with the size of 150-200 nm appears on the surface of the material. FTIR shows that Si-OH structure has been formed on the surface of PET non-woven fabric.BET analysis showed that the specific surface area of the material increases significantly. The factors affecting the adsorption properties of Pb2+ were simultaneously discussed, such as the initial Pb2+ concentration, adsorption contact time, temperature and pH value. The results show excellent adsorption properties of PET-s-CaAlg/CaSiO3@SiO2for Pb2+ is obtained and the saturated adsorption amount is 58.33 mg/g. Its adsorption kinetics for Pb2+ is in accordance with the quasi second-order kinetic model. Low temperature is conducive to adsorption. The adsorption capacities of Pb2+on PET-s-CaAlg/CaSiO3@SiO2are affected by the pH of the solution through the ionization of surface functional groups and the degree of hydrolysis of Pb2+. It shows that the best adsorption capacities of Pb2+ is at the pH of 4.0-6.0.
Bismuth layer structured piezoelectric ceramics, Na0.5Bi4.5TaxTi4-xO15+0.5x (NBT-Ta-x)(x=0-0.20), were fabricated via a solid state sintering process. The effect of Ta5+ doping for B site on the microstructure, electrical conductivity, dielectric and piezoelectric properties of NBT-Ta-x ceramics was investigated by means of XRD, SEM and an automatic temperature control testing system. The results show that Ta doping brings about the decrease in grain size and aspect ratio of grain with a preferable orientation growth along c-axis. Meanwhile, both theoretical density and measured density of the ceramics is increased with increasing tantalum doping content, with the highest relative density of 96.1% at x=0.05, showing that the solid solution limit of tantalum in NBT lattice is in the proximity of x=0.10. The Curie temperature is decreased slightly from 680℃ to 658℃ with the increase of Ta5+ doping content x to 0.20. The electrical resistivity of NBT-Ta-x ceramics is increased as much as about two orders of magnitude by Ta5+ modification and the piezoelectric constant d33 values is increased significantly from 13.8 pC/N to 23 pC/N. The x=0.04-0.05 samples exhibit the optimal electrical performance:Tc=670-672℃, d33=21.8-23 pC/N, kp=7.9%-8.3%.
The Mg2Ni-type hydrogen storage alloy with the addition of a little Y and Cu was prepared by medium frequency induction melting. The phase composition and microstructure were characterized by X-ray diffractometer, scanning electron microscope, energy dispersive spectrum analyzer and transmission electron microscope. Hydrogen desorption performances of the alloy were measured by hydrogen absorption/desorption equipment based on the Sieverts method and high pressure differential scanning calorimeter. The activation energy and corresponding mechanism of dehydrogenation under isothermal and continuous heating conditions were investigated. The results show that the as-cast alloy presents lamellar-shaped structures which are composed of Mg2Ni and YMgNi4 as the main phase and small amount of Mg. The alloy exhibits good activation properties in which the time taken to reach 90% of the maximum dehydrogenation content is 446, 418, 360, 354, 342 s and 336 s in the first six isothermal hydrogen desorption cycles respectively. The fitting results of the hydrogen desorption kinetics indicate that the dehydrogenation is governed by random nucleation and subsequent growth mechanism. The activation energy of the isothermal hydrogen desorption of the alloy is Ea=67.6 kJ/mol. Comparatively, the activation energy of hydrogen evolution at continuous heating is Ea=69.5 kJ/mol. At the same time, it is found that crystal transitions of Mg2NiH4 are identified to be triggered at 505 K and 512 K. Furthermore, dehydrogenation of Mg2NiH4 starts more easily than that of MgH2.
TEM, DSC and other techniques were used to characterize the heating aging precipitation behavior of 7050 aluminum alloy under compression pre-deformation conditions, and the influence law and mechanism of pre-deformation on heating aging precipitation were investigated. The results show that 7050 aluminum alloy can obtain excellent strength and corrosion resistance after pre-deformation heating aging, which can significantly shorten time and reduce energy consumption compared with traditional aging process. The pre-deformation greatly promotes the aging precipitation of 7050 aluminum alloy. The precipitate size increases rapidly as the increase of deformation during the same heating aging process, and its size distribution range increases rapidly too. The pre-deformation during heating aging process not only reduces the phase transformation activation energy of η' and η phases of 7050 aluminum alloy, but also accelerates the diffusion of solute atoms, which intensifies the Ostwald ripening and promotes the growth of precipitates. The calculation results show that the phase transformation activation energy of 7050 aluminum alloy gradually decreases with the increase of deformation. When the deformation amount increases from 0% to 18%, the phase transition activ-ation energy of η' and η phases decreases from 116.0 kJ/mol to 101.7 kJ/mol and 120.8 kJ/mol to 107.5 kJ/mol, respectively.
Isothermal compression tests were carried out on a Gleeble-3500D thermal simulation machine. The hot compression deformation behavior of a new hot-extruded Ni-Co-Cr-based powder metallurgy(P/M) superalloy at the temperatures from 1020℃ to 1110℃ with the strain rates from 10-3 s-1 to 1 s-1was systematically investigated. The flow stress curves were corrected by friction. Using the friction-corrected data, the constitutive equation for hot compression of the alloy and the flow stress model considering the strain compensation were established, respectively. At the same time, the hot processing map was built, and the hot deformation parameters of the alloy were optimized by combining with the analysis of the microstructure. The results show that apparently dynamic recrystallization occurs in the process of hot compression of the alloy, and the flow stress decreases with the decrease of strain rate or the increase of deformation temperature. The predicted values obtained from the developed flow stress model considering the strain compensation agree well with the experimentally friction-corrected data. According to the hot processing map and microstructural analysis, the reasonable hot working parameters of the alloy were suggested to be at the deformation temperatures of about 1076-1103℃ and the strain rates of about 10-3-10-2.77s-1.
A novel hybrid method for the production of spherical fine metal powders by centrifugal atomization based on mono-sized droplets was proposed. In this method, the mono-sized droplets were prepared by pulsated orifice ejected system, and then the droplets were atomized by centrifugal atomization. The powders with smooth surface, small particle size, narrow particle size distribution, high spherical degree and no satellite powders were prepared by this method. Fine Sn63Pb37, Sn0.3AgCu powders were prepared by this method. The effects of heated treatment on rotation disk and different disk materials Cu, Ni, 304 stainless steel on the preparation of the powders were studied, the difference between the experimental value and the theoretical value of particle size was analyzed, and the disintegration mode of liquid film in atomization process was discussed. The results show that the liquid film on the rotation disk tends to be thin and the average particle size of powders can be refined by heating the rotation disk. The better the wettability between the rotation disk and the metal material, the smaller the average particle size of the powders obtained, and the theoretical value of powders is higher than the experimental value, the smallest average particle size of the powders is 21.0 μm prepared by copper rotation disk. The mode of liquid disintegration in this method is related to the wettability between the rotation disk and the metal material, the copper rotation disk shows direct droplets disintegration, the nickel rotation disk shows film disintegration, the 304 steel rotation disk does not show liquid disintegration.
A ternary alloy strengthened by the phase with long period stacking ordered (LPSO) structure with composition of Mg97.5Gd1.9Zn0.6 (atom fraction/%) was prepared by conventional permanent mold casting. The microstructure evolution and mechanical properties in as-cast, as-annealed, as-extruded and extruded-T5 alloy were systematically investigated by OM, SEM, TEM and electronic universal testing machine. The results show that the as-cast microstructure of the alloy consists of the α-Mg matrix, (Mg, Zn)3Gd eutectic and lamellar 14H-LPSO phase. Annealing at 510℃ results in the transformation of (Mg, Zn)3Gd into the block-shaped 14H-LPSO phase. According to the distribution and morphology of the 14H-LPSO phase observed in the microstructure after annealing, the peritectoid transformation (Mg, Zn)3Gd +α-Mg→14H-LPSO possibly occurs during annealing. The lamellar 14H-LPSO and β' p precipitates have also been observed in the alloy during extruded-T5 treatment. Under the combined action of 14H-LPSO toughening and precipitation strengthening, the aged sample shows the best tensile properties at room temperature:ultimate tensile strength of 361 MPa, yield strength of 216 MPa and elongation of 6.9%.
TC4 titanium alloy was shot-peened by multiple kinds of intensity and surface coverage. Surface roughness and topography, residual stress profile were compared. Moreover room-temperature rotating-bending fatigue property was tested. The results show when the intensity is raised, the surface roughness, the depth of residual compressive stress depth and the location of the maximum residual stress are increased and the surface residual stress is decreased. The enfoldment appears on the surface with the increase of surface coverage. Rotating-bending fatigue property is enhanced by shot-peening. Compared with median fatigue life estimated value of 5.06×104 cycles at grinding state, the fatigue cycles ranges are raised to 5.12×106-5.28×106 cycles after shot-peened at the intensity 0.12 mmA and 3.28×106-4.23×106 cycles at 0.25 mmA, indicating that the fatigue property is decreased with the increase of the intensity. By comparison, when the intensity is low (0.12 mmA), the coverage has no impact on the fatigue property. However, fatigue cycles decline from 4.23×106 cycles to 3.28×106 cycles when the coverage is inclined from 125% to 600% and the intensity is relatively high (0.25 mmA). Furthermore, on the premise of considering the surface stress concentration of the external load and the residual stress of shot peening, the position of the dangerous section with large actual stress after shot peening is calculated and verified by the fracture analysis.
In order to explore the influence of cold-pressing and constant-volume sintering molding process on the friction and mechanical properties of porous polyimide (PI) materials, the effects of density, sintering temperature and holding time on the oil content, friction coefficient, tensile strength and impact strength of porous PI materials were studied by orthogonal experimental design method.By comprehensively considering the friction coefficient and impact strength after centrifuging oil, the molding process of the porous PI material was optimized. The experimental results show that as the density decreases, the surface holes of the material increase, the internal hole brackets become rarefied, and the oil content significantly increases, but the oil retention becomes lower, the friction coefficient becomes relatively high, the tensile strength and impact strength are significantly reduced.When the sintering temperature is 350℃, the impact strength is high; the strength of porous PI materials with different densities can be guaranteed by holding for 60 minutes. After optimizing the preparation process, the oil content of the material is 12.0%, and the friction coefficient is 0.092 after centrifuging oil for two hours.The impact strength is 105.9 kJ/m2 and the tensile strength is 74.2 MPa.
In order to obtain the curing reaction temperature parameters of E-glass fiber/epoxy resin prepreg, DSC was carried out. Kissinger and Crane equations were used to obtain the phenomenological nth-order reaction curing kinetic parameters of the prepreg. The optimal curing temperature of the prepreg was obtained by T-β extrapolation method, and the phenomenological curing kinetic model of the prepreg was established. Monolayer board and laminate of[0]10 were prepared by molding process. The dynamic thermodynamic properties of the prepreg were studied by dynamic mechanical analysis (DMA). The results show that the apparent activation energy and the reaction order of the prepreg are 87.8 kJ/mol and 0.93, respectively. The glass transition temperature Tg of the laminates is 130-133℃. The loss factor tanδ of[0]10 laminate is higher than that of monolayer board.
Aiming at the problem of accurate identification of delamination defects of composite laminates, an optimization method of activation aperture of phased array ultrasonic testing was proposed by simulation and experiment, and the effects of the activation aperture on the acoustic field characteristics and detection results at different focusing depths were studied and analyzed. Firstly, for the phase array ultrasonic contact testing method, the multipoint source 3D acoustic field model under the solid-solid interface was deduced. Then, the phase array ultrasonic sound field was simulated, and the characteristics of sound field under different activation apertures were analyzed. Finally, the carbon fiber reinforced polymer (CFRP) laminate with delamination defects was prepared using autoclave process, and a phased array ultrasonic testing system was built to test the CFRP laminate test block. The experimental results show that the accurate identification of CFRP lamination defects can be achieved by optimizing the activation aperture of phased array ultrasound, and the defect detection accuracy can be improved effectively.
50℃ and 80℃ high temperature aging environments were selected and the quasi-static tensile strength and shear strength of the aluminum alloy-BFRP (basalt fiber reinforced polymer composite) bonded joints aged for 0, 10, 20 and 30 days under high-temperature were measured at the loading rate of 1 mm/min with the designed testing fixture.The failure section of the joint was analyzed by macroscopical analysis.After 80℃ high temperature aging, post curing occurs in adhesive, the mechanical properties are enhanced. Chemical bond fracture occurs in BFRP, and glass transition temperature (Tg) is decreased. After aging for 30 days, the tensile strength of the joint is decreased and the shear strength is increased. After 30 days, the failure section of tensile joint appears to be stratified. Mixed failure of adhesive layer cohesion and fiber tear appears in the shear joint. After 50℃ high temperature aging, the mechanical properties of adhesive are slightly increased. The failure strength of the tensile joint changes little, and the failure mode is dominated by fiber tearing and delamination.The failure strength of shear joint is increased slightly, and the failure mode is mainly adhesive cohesive. According to the secondary stress criterion, the curves of tensile strength and shear strength were fitted.According to the response surface principle, the response surface equation of failure criterion with aging time was established to predict the crack generation and propagation of the adhesive layer of aluminum alloy-BFRP bonded structures.
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