- 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)
Graphene is a kind of two-dimensional atomic crystal with one atomic layer, which is the basic structure unit of other dimensions of graphite materials, such as zero dimensional fullerenes, one-dimensional carbon nanotubes and three-dimensional graphite. Graphene has a lot of unique electronic and mechanical properties, which have attracted high attention of many scientists in the field of chemistry, materials and other fields. Raman spectroscopy as a sensitive and convenient characterization method, has played a very important role in the study of graphene. Raman spectroscopy is an integral part of graphene research. The application of Raman spectroscopy in graphene characterization in recent years is reviewed in this paper. The characteristic peak of monolayer graphene was first intnduced. Then, through the analysis of the changes of D peak, G peak and 2D peak intensity, position and half peak width of Raman spectra, the number of graphene layers can be quickly and accurately characterized, as well as, the stacking orders, edge chirality and doping degree of graphene were defined. At the same time, the effects of substrate, doping, temperature and laser power on the intensity, position and half width of D peak, G peak and 2D peak of Raman spectra in the process of preparing graphene were also systematically analyzed.
Graphene oxide has potential application prospects in the field of environmental protection as the adsorption material of uranium-containing wastewater due to its many advantages such as its large specific surface area, high mechanical strength and good chemical stability, which has attracted much attention. The research situation and progress of uranium adsorption of graphene-oxide composite materials were summarized in this paper. The principle about effect of solution pH value, temperature, ionic strength, contact time and adsorbent dosage on uranium adsorption by graphene oxide composite materials was analyzed. The study on internal relationship between the microstructure and micromorphology of graphene oxide composite materials and uranium adsorption capacity by the methods of surface complexation model, spectral analysis and theoretical calculation was elaborated. Meanwhile, the challenges in the study of the adsorption of uranium by graphene oxide composite materials were studied, the research on the interaction mechanism of uranium and graphene oxide materials and their development and application in environmental protection were prospected.
Graphene oxide and nano-ZnO have excellent performance, but are prone to agglomeration in epoxy. To solve this problem, surface modification needs to be carried out. Using zinc sulfate heptahydrate as the raw material, the zinc oxide was loaded on the surface of graphene oxide. Nano-ZnO was dispersed evenly on GO by FT-IR, XRD, SEM, EDS, TG and contact angle measurement, and the GO-sheet structure can be retained, while the agglomeration is avoided and the hydrophilicity of GO is reduced. Then nano-ZnO/GO/epoxy composite is obtained by nano-ZnO loaded GO with epoxy resin. The results show that mechanical properties and thermal stability of GO/nano-ZnO/epoxy composite are increased significantly. When the mass fraction of ZnO/GO is 0.250%, the overall performance of the composite is the best. The tensile strength, tensile modulus, elongation at break, impact strength of the nano-ZnO/GO/epoxy composites are improved by 99.87%, 12.09%, 98.35%, 151.48% than pure epoxy. Compared with pure epoxy, the water absorption of nano-ZnO/GO/epoxy composite is decreased 81.48%.
Graphene is an ideal reinforcement for various composites for its unique physical, chemical and mechanical properties. However, the problem of graphene dispersibility and poor wettability severely limits its further development in composites application. (RE-M-GO) were prepared by impregnation method and heating modifier method. The morphology and phase structure of RE-M-GO were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The changes of functional groups of modified graphene oxide were analyzed by means of Fourier transform infrared (FTIR), optical spectra (UV) and energy dispersive spectrometer (EDS), and the modification mechanism was also discussed. The results show that the dispersibility of rare earth modified graphene oxide is obviously improved due to the reaction of rare earth elements with the oxygen-containing functional groups of graphene oxide to form coordination bonds, resulting in a new functional group, which reduces the interfacial energy of graphene oxide and surface energy, thereby the dispersion of graphene oxide is improved.
In order to further explore the potential performance of 600℃ high temperature titanium alloy blisk, the design idea and corresponding manufacturing technology of dual property blisk (DP-Blisk) have been innovated by optimizing of material technology and process technology, namely, microstructural control of blade region and disc body are respectively suitable for the actual service condition requirements of aeroengine to integrate material properties and structural design perfectly. Based on reviewing the development process and application of titanium alloy blisk, the reasons for the development from homogeneous blisk to DP-Blisk of structural design in advanced aeroengines were analyzed, the latest research progress in manufacturing technology of 600℃ high temperature titanium alloy TA29 DP-Blisk forging was introduced. Compared with separated region temperature-controlled forging (SRTCF) process, separated region temperature-controlled heat treatment (SRTCHT) process can achieve the expected dual microstructure more easily, that is, the blade region obtains uniform and fine bi-modal structure, and the disc body obtains fine lamellar structure by means of controllable SRTCHT process, the microstructure of transitional region changes gradually along the radial direction of the blisk forging. Finally, key issues need to be solved in the future in application research of DP-Blisk of 600℃ high temperature titanium alloy were proposed, including precise control of microstructure and performance of blade and disc body, position and size control of the transitional region, and key service performance evaluation and research.
Aluminum alloys have gained much attention in aerospace, military and automobile applications because of their outstanding properties such as low density, high specific strength, and good damage tolerance compared with the other commercial alloys. However, the formability of aluminum alloy is poor at room temperature, thus a further heating process is necessary to improve its formability and manufacture complex shaped products. On the other hand, this leads to the increase of manufacturing costs and the reduction of production efficiency and poorer surface quality of the product, restricts its application in complex structural components and high-end manufacturing fields. Therefore, the tailored heat treatment technology is used to address the above mentioned issues and significantly improve the formability of aluminum alloys at room temperature. In this paper, the characteristics and technical principles of tailored heat treatment technology for aluminum alloys were discussed. In addition, the influence of the tailored heat on the microstructural evolution and mechanical properties of aluminum alloys, as well as, the means to achieve tailored heat treatment, besides the heat treatment layout and the application in the actual sheet metal forming were systematically reviewed. Furthermore, the main microstructural mechanisms of tailored heat treatment on the softening and hardening behavior of aluminum alloys were introduced. Finally, the real effect of the tailored heat treatment on improving the formability of aluminum alloys sheets was analyzed and compared, in order to promote this novel technology to manufacture high-performance aluminum products in China.
Dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs) are the research focuses at present in the field of solar cells. However, the commonly used counter electrodes (CEs) in these two solar cells, such as Pt and Au, are rare and expensive, they are not suitable for mass production. Low-cost and abundant carbon-based materials can substitute Pt and Au in DSSCs and PSCs as CEs, showing gradually approaching or even higher photoelectric conversion efficiency and suggesting a bright future. The structure and electrochemical properties of carbon-based materials as well as the photovoltaic performances as CEs were reviewed in this paper. The recent advances achieved by carbon-based CEs were highlighted, and the limitations and unsettled problems in present researches were also pointed out, and finally, the possible directions for further research were discussed.
Shape memory polymer, a kind of smart material that can response to the external stimulation and produce morphology changes, has achieved a plenty of progress in recent years. More initiation methods and advanced memory effects by applying specific chemical structures and reactions to the shape memory system were found by the researchers with further understanding of the shape memory mechanism. Multiple shape memory polymer, as the morphology extension of traditional shape memory polymer, has attracted more interests for its exclusive performance in a memory circle. Polymer blending is an easier way to prepare multiple shape memory system. Recently, a new theoretic breakthrough has been made on multiple shape memory polymer that assures it complex morphological change, making it more potentially applicable in real life. In this paper, we aim to provide more information on the theory and characterization of the polymer's shape memory effect and the development of multiple shape memory polymer in recent years.
Large-sized TiAl/Ti3Al multi-layered composite thin sheet was prepared by electron beam physical vapor deposition technology (EB-PVD). The phase composition and microstructure were analyzed by XRD and SEM. After hot isostatic pressing, samples were evaluated with static tensile test. The breakdown of layered structure was investigated by the high temperature annealing according to different temperature. The results show that the prepared material with visible lamellar structure is composed of α2-Ti3Al and γ-TiAl phases. The sample after hot isostatic pressing has a higher tensile strength and a good characteristic of tensile elongation. The fracture mode is transformed from brittle fracture into a mixed mode consisting of intergranular fracture and ductile deformation fracture. Furthermore, the heat treatment temperature and the diffusion of Al play a key role in the evolution of structure and morphology.
To study the effect of heat treatment at different temperatures on microstructure and fretting wear resistance of laser clad Ti-matrix composite coatings, Ti-matrix composite coatings were fabricated by laser cladding with the powder precursor:40%Ti-25.2%TiC-34.8%WS2 (mass fraction). The coatings were heated at 300, 500℃ and 700℃ in vacuum for 1h respectively, and the microstructure and fretting wear resistance of coatings were analyzed. Results indicate that the main phase compositions of coatings are all composed of α-Ti, (Ti, W)C1-x, TiC, Ti2SC and TiS. The microhardness of coatings without heat treatment and with heat treatment at 300, 500℃ and 700℃ is 1049.8, 980.7, 1143.3HV0.5 and 1190.7HV0.5. The coating with heat treatment at 700℃ exhibits excellent fretting wear resistance and the wear mechanism is mainly adhesive wear and abrasive wear.
With the method of laser processing, the groove and grid structure were constructed on the surface of aluminum alloy which showed the properties of superhydrophobicity and corrosion resistance. The features of the material surfaces were characterized by using scanning electron microscope (SEM), laser scanning confocal microscopy (LSCM), X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), water contact angle measurements and polarization curves measurements, respectively. The results indicate that the groove and grid structure, which are formed by alternating ablation, show grooves, granular bumps and a pit texture and other composite structures and morphologies; the grid structure under the line spacing of 200μm shows excellent hydrophobic properties, and the static contact angle can reach up to 154.9° and the sliding angle is 7°. The analysis on Tafel curve and the curve's fitting results show that the method of laser processing make the groove and grid structure a better corrosion resistance, and the grid structure under the line spacing of 100μm is the best among in these structures.
In order to solve the existing problem of the poor corrosion resistance of the superhydrophobic materials, a novel type of copper mesh-based superhydrophobic materials with outstanding corrosion resistance was prepared and then was applied to the oil/water separation. The octadecylamine modified multi-walled carbon nanotubes was combined with the aminoethylaminopropyl polydimethylsiloxane(AEAPS) modified WPU and one-step spray method was adopted to prepare the copper mesh-based superhydrophobic surfaces with nest-like structure. The as-prepared mesh shows both superhydrophobic and superoleophilic properties simultaneously with a high water contact of 162° and an oil contact angle of 0°. Thus, they can be used to separate a series of oil/water mixtures, such as kerosene, toluene, tetrachloromethane, petroleum and hexane with separation efficiency above 93.79% and stable recyclability. In addition, the as-prepared mesh can maintain its superhydrophobic property after soaking in corrosive solutions (1mol/L NaOH, HCl, NaCl) for 24h.
For aluminum/steel laser brazing-welding, metal coating on the surface of steel has an important impact on the performance of aluminum/steel joint. Spreading effect of the liquid of 5A06 aluminum alloy on low carbon steel surface with the various metallic coatings was studied. Microstructure of the interface, thickness and kinds of intermetallic compound of the welding-brazing joint were analyzed by SEM, and the mechanical properties and fracture appearance of aluminum/steel joint with different metallic coatings on steel were further investigated. The results show that the spreading effect and infiltration are impaired by metal coating on the steel surface in the aluminum/steel laser welding-brazing. The spreading effect of aluminum lap with aluminized steel is the best, and the tensile property of the lap joint of aluminum alloy and aluminized zinc steel is the best, which accounted to base metal aluminum alloy for 70%. The Fe2Al5, FeAl3 and FeAl intermetallic compounds are discovered at the weld interface of aluminum/steel laser brazing-welding by using aluminum-coated steel, aluminized steel or galvanized steel, and the Fe4Al13 intermetallic compounds is existed in the interface of aluminum/steel with nickel plated steel.
The Ni60 overlay was deposited on Z2CN18-10 stainless steel substrate by plasma transferred arc (PTA) method, and the microstructure, hardness and corrosion resistance of Ni60 overlay were investigated. The results show that the overlay mainly consists of Ni-rich γ solid solution (γ-Ni), borides and carbides, and γ-Ni and borides eutectic structure. The overlay from the top to bottom shows different phase fractions, and the amount of chrysanthemum-like structure in the middle is large. The hardness of Ni60 overlay is around 500HV, which is higher than that of Z2CN18-10 stainless steel. The hardness increase is attributed to the chrysanthemum-like eutectic structure. In the borate, Ni60 exhibits higher passivation ability than that in seawater, and the corrosion potential of Ni60 alloy is similar to Z2CN18-10 stainless steel. In simulated seawater, the corrosion resistance of overlay in the middle is more superior than that in the bottom and top. Due to the large difference of corrosion potential in seawater, the galvanic corrosion is prone to occur between Ni60 overlay and Z2CN18-10 stainless steel.
Composite coatings consisting of a Ni-Co alloy matrix reinforced with ZrO2 particles(average size of 50nm) were synthesized by electrochemical deposition assisted by an external ultrasonicfield.The kinetics of electrodeposition was investigated using linear sweep voltammetry and cyclic voltammetry. Scanning electron micrographs, X-ray diffraction and energy dispersive spectrum were employed to characterize the morphology and composition of the coatings. Also in order to evaluate the mechanical properties of the coating nano-indentation and wear tests were conducted. The results indicated that the electro-crystallization of Co2+ was governed by a three-dimensional "nucleation/growth" process. The electric potentials of co-deposition of alloy and composites are -0.72V and -0.70V respectively. The results show that polarizability of the composite system is smaller with the addition of ZrO2 particles and the ZrO2 improves the electrode process. when the addition of ZrO2 is 15g/L, coating nanohardness, elastic modulus and the ratio of nanohardness to elastic modulus increase to 6.13GPa, 291GPa and 0.026 and friction coefficient and wear mass loss decrease to 0.3273 and 0.55×10-5 g/m, which is about 3/4 and 1/2 of Ni-Co alloy coating respectively.Results reveal that tribological properties of coating can be improved significantly by incorporating ZrO2 simultaneously with ultrasonic.
WC-10Co-4Cr coating was prepared on Q235 steel substrate by high velocity oxygen fuel (HVOF) spray process. The microstructure and wear properties of the WC-10Co-4Cr coating were investigated by transmission electron microscopy(TEM), scanning electron microscopy(SEM), X-ray diffraction(XRD), microhardness tester and friction-abrasion testing machine. The results show that the coating exhibits dense structure with the porosity of 0.67% and compact bonding with the substrate. The coating is mainly composed of WC, and a small amount of W2C and amorphous phases as well, and the average microhardness of the coating is 1230HV0.3. The cumulative mass loss of WC-10Co-4Cr coating is only 2/5 of the cold work die steel Cr12MoV, which indicates the WC-10Co-4Cr coating exhibits better abrasive properties. The abrasive wear is the main wear mechanism for the coating.
Bi2S3 microflowers with diameter of 4μm composing of nanorods were successfully synthesized via a mixed solvent hydrothermal method, and the influences of different reaction time and solvent ratio on the morphology were also studied. Then the Bi2S3 microflowers were deposited on patterned ITO glass substrates by dip-coating to fabricate photodetectors. The photoresponse properties using Bi2S3 microflowers as a representative system show that the photocurrent under simulated sunlight is 50 times larger than that of the dark current, the response and decay time are estimated to be 227ms and 880ms, respectively, indicating the photodetector has excellent photoelectric responsiveness; the light current is not obviously attenuated by the periodic opening and closing of the photodetector, indicating that the photodetector has good stability.
Co element was added into Gd-doped ceria (GDC) powders by two methods namely lattice solution and preferred grain boundary segregation, respectively. The 10% (mole fraction, the same below) Gd-doped ceria (10GDC) solid solution powders were co-precipitated and then doped with 1%Co by the means of the two ways. These powders were named as 10GDC-1Co (SS) and 10GDC-1Co (GBS), respectively. Then the powders above were sintered at 1000℃ for 1h to obtain 10GDC, 10GDC-1Co (SS) and 10GDC-1Co (GBS) ceramic samples. All the synthesized powders and sintered samples only consist of the CeO2 solid solution phase, and their grain sizes are 10.1-12nm and 59.8-112nm, respectively. The conductivities of 10GDC-1Co (SS) and 10GDC-1Co (GBS) samples are higher than that of 10GDC samples. When the test temperature is lower than 430℃, the conductivities of 10GDC-1Co (GBS) samples are higher than that of 10GDC-1Co (SS) samples, but as the test temperature increases, the conductivities of 10GDC-1Co (GBS) samples are lower than that of 10GDC-1Co (SS) samples.
Pb0.92Sr0.06Ba0.02(Sb2/3Mn1/3)0.05Zr0.48Ti0.47O3:xCeO2 piezoelectric ceramics were prepared by a conventional solid state reaction method. The effect of CeO2 addition on the phase transition, microstructure piezoelectric and dielectric performances of samples were systematically investigated. The results show that ceramics are pure perovskite structure when the doping amount of CeO2 is less than or equal to 0.5% (mass faction, the same below), with the CeO2 doping content increasing, the formation of pyrochlore phase will be facilitated, but the samples are still not completely transformed to rhombohedral phases; and CeO2 doping plays the role of grain refinement, when x=0.25% the sample has an even grain size, clear boundary and it also has lower porosity and higher density, the main fracture mode of the sample is intergranular fracture; when x=0.25% ceramic samples obtain the best piezoelectric and dielectric performance:d33=346pC/N, kp=0.60, Qm=1396, εr=1309, tanδ=0.474%.
The uniform experiment design and multivariate nonlinear regression equation were adopted to study the effect of Ce-La dosage (the mole ratio of Ce-La to tetrabutyl titanate), the mole ratio of Ce to La, calcination temperature, and amount of tetraethyl orthosilicate (the volume ratio of tetraethyl orthosilicate to tetrabutyl titanate) on the moisture absorption-desorption and photocatalytic properties of Ce-La/TiO2 hollow microspheres, so as to ensure the optimal preparation parameters of Ce-La/TiO2 hollow microspheres. Then, the decanoic-palmitic acid were pressed into the cavity of the optimal Ce-La/TiO2 hollow microspheres by vacuum absorption to prepare environment coordination Ce-La/TiO2 composite materials and analyze the photocatalytic-mositure-heat properties. The scanning electron microscopy and laser particle size analyzer were used to characterize the microscopic morphology and particle size distribution. The results show that the four factors all have effect on the moisture absorption-desorption and photocatalytic properties of Ce-La/TiO2 hollow microspheres, primary and secondary sequence of each factor is Ce-La dosage > amount of tetraethyl orthosilicate > the mole ratio of Ce to La > calcination temperature. The optimization program is Ce-La dosage 0.76%, the mole ratio of Ce to La is 1.0, calcination temperature 646℃, and amount of tetraethyl orthosilicate 0.63. The Ce-La/TiO2 composites have good moisture absorption-desorption, photocatalytic and phase changing temperature-adjusting properties. Under 43.16%-75.29% relative humidity, the equilibrium humidity content reaches 0.0576g/g, the degradation rate to formaldehyde reaches 56.37% after 5h, the cooling time lasting nearly 500s during 30-15℃, so the Ce-La/TiO2 composites have remarkable and sustainable phase changing platform.
Tensile behaviors at 20-600℃ and fatigue properties at room temperature of the SA508 Gr.3 Cl.1 steel were tested and analyzed. The results show that the SA508 Gr.3 Cl.1 is composed of upper bainite and carbide, the grain size is 8.0. Coarse D type ball oxide with moy level 1.0 which is distributed in the steel matrix is about 0.0325% (volume fraction) of the steel matrix. There are a large number of parallel and entangled dislocations distributing in the steel matrix, in addition to a large number of carbide particles, the precipitates are mainly Al6(Fe, Mn) particles with base-centered orthorhombic lattice. The yield strength and tensile strength decrease with the increase of temperature. The elongation remains at 20.2%-29.1%. The percentage reduction of area is relatively stable at 20-300℃, is about 70%; while it increases after 300℃, and the corresponding value reaches 90.2% at 600℃. Stretching results in the increase of microhardness of the steel matrix, but its value decreases with the increase of temperature, and the microhardness value is 225HV at 600℃. XRD analysis shows that stretching leads to no obvious phase transformation. The tensile properties meet the performance requirements of reactor internals in the large advanced PWR such as AP100 etc. The fatigue tests show that the fatigue limit of S-N curve of the steel is 268.64MPa. The average value of the JΙC is 331.2kJ/m2, and KIC is 269.07MPa·m1/2.
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