- 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 7YSZ thermal barrier coating was prepared with three different process parameters by plasma spraying-physical vapor deposition(PS-PVD). The phase structure and microstructure of the coating were analyzed using XRD and SEM methods, and the thermal conductivity of coating was measured under different temperatures using laser pulse method. The results show that PS-PVD technology can prepare YSZ thermal barrier coating with different structures of columnar section, dense lamellar and column-particle mixed structure with surface "cauliflower" shape or undulating peaks by adjusting the process parameters, such as the current and plasma gas composition.Phase structure of 7YSZ coating is transformed from m-ZrO2 powder to t-ZrO2 coating in the process of preparation and stays in room temperature. The thermal conductivity of 7YSZ coating increases with the rising of temperature between 700-1100℃, the columnar crystal coating with higher porosity can effectively reduce the thermal conductivity of coating and the thermal conductivity is 1.0-1.2W·m-1·K-1; while layered crystal coating is dense with relatively higher thermal conductivity.
The anisotropy and microstructures during aging treatment for 2A66 Al-Li alloy were studied by Brinell hardness, tensile testing, optical microscope(OM), scanning electron microscope(SEM) and transmission electron microscope (TEM). The main factors which influence the anisotropy of mechanical properties were discussed. The results indicate that, before 165℃ peak-aged, the anisotropy of the mechanical properties of the 2A66 Al-Li alloy decreases gradually with the extension of aging time. When the alloy is over-aged, the anisotropy of the alloy increases; the anisotropy of ductility is more serious than that of strength. The IPA values of σb, σ0.2 and δ of the alloy reach the lowest value at 3.0%, 3.0% and 12.2% respectively at the time of peak aging (64h), and the alloy is also obtained with good plasticity and axial tensile properties. σb, σ0.2 and δ of the alloy are 526.5, 448.9MPa, 10.1% respectively. Under different heat treatment conditions, the general behavior of the anisotropy of 2A66 Al-Li alloy is as follows: longitudinal (0°) and transverse (90°) have the highest strength, 45° direction is the lowest strength; 45° direction specimen has the highest elongation, vertical and horizontal direction has the minimum elongation.
The microstructure and interface diffusion behaviour of SiCP/Al composites prepared by high-pressure torsion under different turning numbers were investigated by OM and EDS, and the effect of turning numbers on the tensile properties and fracture mechanism was analysed combined with microstructure and interface characteristics. The results show that increasing the turns can improves the uniformity of the particles and reduces the porosity, with the Al diffusion ability enhanced and the diffusion distance increased, and the diffusion coefficient of Al is enhanced by about 1017 times in comparison with the theoretical value, leading to tensile strength and elongation of composites improved continuously and the fracture is mainly based on the ductile fracture of matrix, with a small amount of SiC particles distributed uniformly in the dimple of the fracture. When the turns come to bigger, SiC particles are broken severely by the shearing deformation, particles "regeneration and agglomeration" leads to increased porosity and more potential crack sources, forming a large quantity of new fracture interfaces with low bond strength. The tensile strength and elongation of the sample decrease greatly, and it is easy to form larger deep dimples in the agglomeration, composite fracture exhibits the mixed mode of ductile fracture and brittle fracture.
Alclad and unclad 2E12 aerospace aluminum alloy were treated by sulfuric acid anodic oxidation. The effects of alclad layer and anodizing time on the anodization behaviour and corrosion resistance of anodic oxide layer on 2E12 aluminum alloy were studied. Surface and cross-section morphology of anodic oxide films were observed by scanning electron microscopy. The electrochemical properties of anodic oxide films were analyzed by potentiodynamic polarization curve and electrochemical impedance spectroscopy. The results show that the protective anodic oxide layers are formed on alclad and unclad 2E12 aluminum alloy. The film thickness increases with anodizing time extending. The copper rich second phase particles lead to more cavity defects and even micro cracks on anodic oxide films of unclad 2E12 aluminum alloy. The anodic oxide films on alclad 2E12 aluminum alloy are thicker and have fewer cavity defects, resulting in better corrosion resistance. The films obtained after 30min and 45min anodic oxidation treatment exhibit lower corrosion current and higher impedance of the porous layer than other anodizing time.
By establishing the intra-granular ferrite nucleation model and conducting a series mathematical calculation, it was found that the nucleation energy of inclusion in irregular shape is lower than that in spherical shape, which is easier to induce the ferrite nucleation. Moreover, the influence factors of intra-granular ferrite nucleation induced by spherical inclusions were also analyzed. The results show that it is adverse to the nucleation of ferrite when the inclusion size is too small, while it has little effect when the size is larger than 0.15μm. Besides, the smaller of the wetting angle, the easier of the nucleation. When the wetting angle is between 70° and 90°, the ferrite is easily induced by spherical inclusions in the form of normal triangular pyramid. However, when the wetting angle is less than 70°, the ferrite is precipitated in the form of spherical. The precipitation rate of ferrite in the form of triangular pyramid is higher than that of spherical. A group of experiments were also verified that irregular inclusions could induce the nucleation of ferrite, while it had little effect when the size is larger than 0.15μm.
In order to enhance the capability of resistant to protein adsorption of the copolymer membrane of polyacryloylmorpholine-graft-acryloylmorpholine(PVDF-g-PACMO), a crosslinking agent of ethylene glycoldimethacrylate(EGDMA) was added to prepare the copolymer.The copolymers with different proportions of the crosslinking agent were cast into flat membranes via a liquid-liquid phase separation technique, and then the influence of EGDMA contained in the membranes on its capability of resistant to protein adsorption was investigated. FT-IR results indicate the PVDF-g-PACMO copolymers with EGDMA are synthesized successfully. A series of tests, including XPS, SEM, the contact angle, the static protein adsorption and permeation experiments, show that PACMO is much easier to segregate to the surface with the increase of the crosslinking agent content in the system, the number of membrane pores increases, meantime, the hydrophilicity and water flux of the copolymer membranes are improved. Moreover, the adsorption amount of protein, total pollution index and irreversible pollution index decrease, and reversible pollution index increases. All results indicate the crosslinking agent of EGDMA can enhance the capability of resistant to protein adsorption of PVDF-g-PACMO membranes.
A series of expanded graphite (EG)/paraffin composites with various EG contents were prepared for Li-ion battery thermal management, in which paraffin was chosen as PCM and EG as the promoter of thermal conductivity. The thermal conductivity of the samples was measured by a thermal conductivity analyzer based on the transient hot wire method.The effect of EG content in composite on Li-ion battery thermal management was investigated. The thermal management performance of EG/PCM composites with different thermal conductivity was also discussed by software ANSYS. The results show that:EG incorporation dramatically enhances the thermal conductivity of PCM; the thermal conductivity of EG/PCM shows anisotropy, with EG content equaling to or exceeding 9%; The temperature of Li-ion battery surface decreases with an increase in EG content of composite, EG(12)/PCM(88) exhibits excellent thermal management for Li-ion battery.To adequately increase the thermal conductivity of EG/PCM in radial direction is beneficial to improve Li-ion battery thermal management.
In order to investigate mechanical properties of Y2SiO5 and Y2Si2O7 yttrium silicates coatings on Cf/SiC composites and design thermal environment barrier coatings, first-principles calculations were performed to investigate electronic and mechanical properties of X1-Y2SiO5 and γ-Y2Si2O7 using gradient generalized approximation (GGA) based on first principles. The results indicate that they are both mechanically stable structures. Bulk, shear modulus, Young's modulus of X1-Y2SiO5 and γ-Y2Si2O7 are 112GPa, 49GPa, 128GPa, 0.31 and 114GPa, 55GPa, 142GPa, 0.29, respectively. These mechanical properties of X1-Y2SiO5 are lower than those of γ-Y2Si2O7. At the same time, toughness, thermal expansion coefficient and residual stress of two ideal crystals were studied. The results show that X1-Y2SiO5 has better ductile properties than γ-Y2Si2O7 and its thermal expansion coefficient is larger than that of γ-Y2Si2O7 and while, the residual stress of Y2SiO5 is lower.
Diluted magnetic semiconductors Zn1-xMnxS with different consistency (x=0.00, 0.02, 0.05, 0.07) were synthesized by hydrothermal method, and the effects of doping concentration Mn2+ on the microstructure and optical properties of ZnS nanorods were investigated. The crystal microstructure, morphology and optical properties of the products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), corresponding selected-area electron diffraction (SAED), X-ray energy dispersive spectrometry (XEDS) and ultraviolet-visible spectrophotometer(UV-vis).The results show that all samples synthesized by this method possess wurtzite structure with good crystallization, no other impurity phase appears and generates single-phase Zn1-xMnxS nanocrystalline. The morphology of the samples is nanorods and well disperses. The doping element of Mn enters into the ZnS nanocrystals, Mn2+ replaces Zn2+, and the lattice constant decreases with the increase of Mn content. Meanwhile, the optical band gap increases and the blue shift occurs for the sample in the UV-vis spectra.
This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing the sol-gel method prepared Ni-Zn ferrite particles as insulating compound to coat iron powder, and the influence of NiZnFe2O4 content and molding pressure on the magnetic properties was studied. The morphology, magnetic properties and density of Ni-Zn ferrite insulated compacts were investigated. Scanning electron microscope, line-scan EDX analysis and distribution maps show that the iron particle surface is covered with a thin layer of uniform Ni-Zn ferrites. The existing of the insulating layer can effectively improve the electrical resistivity of soft magnetic composites. Magnetic measurements show that the real part of permeability decreases with the increase of the Ni-Zn ferrite content, and the sample with 3%(mass fraction, the same below) Ni-Zn ferrite has an acceptable real part and minimum imaginary part of permeability in comparison with other samples. Results show that the addition of NiZnFe2O4 can dramatically decrease the internal magnetic loss, the magnetic loss of coated samples decreases by 83.8% as compared with that of uncoated samples at 100kHz. The density of the Fe-3%NiZnFe2O4 compacts reaches 7.14g/cm3 and the saturation magnetization is 1.47T when the molding pressure is 1000MPa.
In order to improve the photocatalytic degradation performance and stability of nano TiO2, Dy doped TiO2 supported on high silica glass fiber was prepared by microwave-sol method combined with dip-coating method. The samples were analyzed by XRD, SEM, PL, EDS, XPS and other equipments for phase composition of films, surface topography, surface elements and the stability of films. And the effects of pretreatment solution and coating method on the high-silica fiber film were investigated.In addition, the photocatalytic performance of the sample has been investigated by degrading methylene blue. The results show that the catalytic stability of Dy doping TiO2 nanofilms supported on high silica glass fiber can be improved and the degradation of methyl orange can reach 94% in 30min after 5 times of coating treatment.
La2Ti2O7/HZSM-5 photocatalysts were prepared by sol-gel method, and its photocatalytic activity was studied. The results show that the original crystal phase of La2Ti2O7 is not changed after loading La2Ti2O7 on HZSM-5, and is still perovskite structure. La2Ti2O7 is dispersed on the surface of HZSM-5 after loading to apparent increasing specific surface area and formation of new mesoporous structure. The growth of La2Ti2O7 is constrainted by HZSM-5, resulting in the reduction of grain size. The absorption boundary has a blue shift and the band gap increases with decreasing La2Ti2O7 loading content. Binding energies of La3d and O1s electrons move to higher energy after loading La2Ti2O7 on HZSM-5. La2Ti2O7/HZSM-5 has enhanced photocatalytic activity as compared to La2Ti2O7. 91.8% of the reactive brilliant red(RBR) X-3B is decolorized on 70%La2Ti2O7/HZSM-5 after 120min of UV irradiation, while only 31.7% of the dye is removed on La2Ti2O7.
Diphenyldiphenylethynylsilane monomer (DPDPES) was synthesized with ethyl bromide, diphenyldichlorosilane and phenylacetylene by Grignard reaction. The molecular structure was characterized by FTIR and 1H-NMR spectroscopy. The polymer of polydiphenyl(diphenylethynyl)silane (PDPDPES) was also prepared by thermal polymerization. Non-isothermal thermal decomposition process of PDPDPES was studied with TG-DTG technology via model method to get thermal decomposition function and the corresponding mechanism which was further verified by model-free method. Results show that the apparent activation energy and the pre-exponential factor are about Ea=245.37kJ/mol and lgA=13.78s-1 obtained by six different kinetic methods, respectively. The mechanism of functions are
In order to quantitatively test fuzz degree of carbon fiber (CF) tow, a measuring method for fuzz mass of CF tow was developed, and the testing device was built. Fuzz mass of two kinds of domestic T800-grade CF were tested using the established method. The effects of spreading width of CF tow, tension and fuzz-adsorption material on the fuzz mass of the two fibers were investigated. Several kinds of imported, domestic T700-grade CF and T800-grade CF were tested using optimized testing conditions. The experimental results show that the testing method is easy to operate and has wide applicability. Under 1-2N tension, 0.1-0.6mm pore size of sponge and 1-4N load applied on sponge, the measured values of T800-grade CF with 12K yield are reasonable. For CF tow with high fuzz mass, certain spreading width makes fuzz inside fiber bundle expose, which is needed to ensure the accuracy of testing result.
The off-axis tensile mechanical behaviors of 2D-C/SiC composite laminates were obtained by tests under different off-axis angles, and the influence of off-axis angle on the tensile mechanical behaviors was studied. By sticking strain gauges on the surfaces of specimens, the stress-strain behaviors in the loading direction and in the fiber bundle directions of material were obtained and analyzed. Combined with the SEM (scanning electron microscope) results of fractured surfaces on specimens, the coupling effects between tensile and shear damage in the fiber bundle directions were also analyzed. Test results show that the tensile modulus and strength of material decrease significantly with increasing off-axis angle; and there exists obvious mutual effect between tensile and shear damage in fiber bundle orientation. Furthermore, based on the stress-strain data obtained from 0° and 45° tensile tests, a predictive model was built to predict the off-axis tensile stress-strain behaviors of material. The prediction has good agreement with test data.
Based on Lcr wave acoustoelastic theory, the influence mechanism of blind-hole on stress evaluation with Lcr wave was discussed. Combined with equivalent method, the blind-holes with different diameters were preset, the difference in time of flight between Lcr wave was calculated by cross correlation coefficient function, the Lcr wave acoustoelastic coefficient was determined with linear fitting function, the influence mechanism of blind-hole diameter on Lcr wave acoustoelastic coefficient was clarified based on the elastic plastic deformation theory and stress concentration theory of hole. The results show that when the diameter of blind-hole is different, the change rule of the difference in time of flight between Lcr wave is basically the same as stress increases, the difference in time of flight between Lcr wave increases linearly as stress increases, while the nonlinear feature is also gradually obvious, the maximum stress in linear stage is less than the yield strength of specimen, the Lcr wave acoustoelastic coefficient decreases gradually as blind-hole diameter increases, and it tends to be constant. The analysis shows that the stress concentration is seen as the main reason for above results, anisotropic structure of specimen and blind-hole depth are also the important reasons for that.
A series of bending fretting fatigue tests of 18CrNiMo7-6 alloy steel were carried out, the bending fretting fatigue S-N curve was built up, and an analysis was made on the test results. The results show that, the S-N curve of 18CrNiMo7-6 alloy steel presents a shape of "ε" curve, which is different from the medium carbon steel, and also different from the plain bending fatigue. With the increase of the bending fatigue stress, the fretting regime transforms from partial slip regime to mixed regime and slip regime. The wear mechanisms of fretting damage zones mainly are delaminated, abrasive wear and oxidative wear. In the mixed regime, the cracks are easy to initiate and propagate, and the cracks all originate from the subsurface of contact zone. Due to the different influence levels of the contact stress and bending fatigue stress, the initiation and propagation of the bending fretting fatigue cracks can be divided into three stages. Firstly, the cracks initiate from subsurface under the control of contact stress; then propagate to a larger angle direction under the joint control of contact stress and bending fatigue stress; lastly the cracks propagate vertically to contact surface until fracture failure under the control of bending fatigue stress.
Shape memory polymers(SMPs) are a class of functional "smart" materials that have shown bright prospects in the area of biomedical applications. The novel smart materials with multifunction of biodegradability and biocompatibility can be designed based on their general principle, composition and structure. In this review, the latest process of three typical biodegradable SMPs(poly(lactide acide), poly(ε-caprolactone), polyurethane) was summarized. These three SMPs were classified in different structures and discussed, and shape-memory mechanism, recovery rate and fixed rate, response speed was analysed in detail, also, some biomedical applications were presented. Finally, the future development and applications of SMPs are prospected: two-way SMPs and body temperature induced SMPs will be the focus attension by researchers.
The formation process of manufacturing defects in Fiber Reinforced Plastic (FRP) fabricated by automated fiber placement which involves different spatiotemporal scales, the mechanism of defects cannot be achieved by using macroscopic failure theory and experimental analysis methods. To solve these issues, this paper aimed at thermoplastic FRP, the common types of defects and reasons they formed were reported, and the present situation of bubble nucleation, thermo-mechanical coupling, theory of interface strengthening and in-situ consolidation were investigated. More importantly, the shortcomings of the current method for mechanism of defects were pointed out. According to existing multi-scale analysis method and nested relation of material design, multi-scale analysis method of anti-serial nested was presented, furthermore analysis and calculation method of microscopic mechanics parameters were discussed, such as fluidity of matrix, crystallinity, viscoelasticity, hygroscopicity. Finally, multi-scale collaborative design method for process parameters in FRP placement was put forward, based on methods of Grey Relational Analysis (GRA) and Multi-Objective Optimization (MOO). The future research will focus on analysis of the correlation characteristics of processing parameters, manufacturing defects and mechanical properties after application with AFP prototype. The mechanism of defects formation will be then revealed, and simultaneously, processing parameters will be optimized.
The application and research progress of β-type Ti-Mo base alloys were reviewed from aspects of aerospace, biomedical, offshore, new energy and other fields. The strengthening-toughening approach through the coupled deformation modes, namely martensitic phase transformation, twinning and dislocation slip was focused, and the control method of mechanical properties based on a combination of deformation microstructures and phase transformation was described. It was pointed out that high-performance and multifunctionality will be the development directions of Ti-Mo base alloys with multiple deformation modes.
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