- 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)
Advanced carbon fibers reinforced polymer-based composites have been widely used in the fields of aeronautics and aerospace, due to their excellent mechanical properties. However, their poor conductivity may cause severe lightning damage and electromagnetic interference issues of composite structures, which significantly restricts large-scale applications and overall performance of the composites. In this paper, a critical review was made on the recent research progress of electrically conductive composites which may be potentially used in aeronautics structures. The different methods of conductive modification for matrix resin, reinforcing fiber and laminated plate were introduced respectively. In particular, the representative studies using new carbon nanomaterials such as carbon nanotubes and graphene were discussed in details. The combination of matrix resin modification and laminated plate modification is expected to achieve a good match between mechanical properties and electrical conductivity of composites.
The catalytic flame retardant system has the characteristics of the low addition amount, high char formation efficiency, stable carbon structure at high temperature and so on. The research on flame retardant method and mechanism of the catalytic flame retardant system has become more and more important. In this paper, the status of research and development on catalytic flame-retardant polymer systems at home and abroad was reviewed. The applications research progress on metal oxides, carbon materials, metal salts, montmorillonite, molecular sieves and boron phosphors in catalytic flame-retardant polymer systems was introduced. The catalytic mechanism in the char-forming process of condensed phase was discussed. At last, it was pointed out that the development trend of catalytic flame retardant polymer materials is to develop new carbon materials represented by graphene and to achieve superfine and organic of catalytic flame retardant.
The properties of cathode materials play an important role in the development and application for lithium ion batteries. However, their phase transition, low conductivity and side reaction with electrolyte restrict the further improvement of battery performance. Coating is one of the effective techniques to overcome these problems. This paper focuses on the influence of surface coating on the properties of cathode materials for lithium ion batteries. The research progress of various coating materials was summarized. The modification mechanism of coating materials was also elaborated. And the future development trend of coating materials was proposed, for example, exploring continuously new coating materials with excellent performance, investigating in depth coating mechanism, and optimizing further coating technologies.
CNT fibers are composed of millions of highly aligned CNTs. The mechanical properties of CNT fibers when passing through different intensities of currents were investigated experimentally. The experimental results show that the introduction of current can obviously reduce the modulus and breaking strength of the fibers. When the current passes through the fibers, an axial electro-contraction force is produced, the electro-contraction force is increased with the increase of current intensity, the electro-contraction force at 5mA is about 2.5mN. By stretching the fiber to the 2% strain axially, after 1000s of the stress relaxation, the load tends to be stable, then switch on current or increase the current intensity, it is found that the tension of the fiber is obviously decreased due to the decrease of the stress caused by the change of modulus is greater than the increase of electric-contraction force. Stretching the fiber axially to 2% strain when passing through a certain intensity of current, after the stress relaxation, the load tends to be stable, then the same intensity of AC current is passed through, the response of the electro-contraction force is very quick.When the AC current changes experience 400 cycles, electro-contraction force exhibits good change, which makes the CNT-fibers as a new type of electro-actuation material.
The highly efficient Z-scheme photocatalyst Ag2CO3/Ag/g-C3N4 with Ag nanoparticles, as an electron mediator, was fabricated by a simple calcinations-precipitation reaction. Photocatalytic experiments of the as-prepared samples were tested by the photocatalytic oxidation degradation of RhB aqueous solution. The results show that Ag2CO3/Ag/g-C3N4 composites exhibit enhanced photocatalytic activity, compared with Ag2CO3 and g-C3N4. The composites exhibit the highest photocatalytic performance, when the mass ratio of g-C3N4 to Ag2CO3/Ag is 20%, which is attributed to the formation of Z-scheme heterojunction structure between Ag2CO3 and g-C3N4, thus accelerating electron transfer rate and separating efficiently the photo-generated electron-hole pairs. Meanwhile, the Z-scheme heterojunction structures extend the wavelength range of visible light absorption (from 450nm to 670nm) due to the surface plasma resonance (SPR) of Ag nanoparticles. The trapping experiment results confirm that·O2- and h+ are main active species, ·OH plays a relatively minor role in the decomposition of RhB. A possible mechanism for enhanced photocatalytic activity of Ag2CO3/Ag/g-C3N4 heterojunction photocatalyst is proposed.
MWNTs/Fe2O3 was prepared by chemical liquid-deposition process, and unsymmetrical dimethylhydrazine (UDMH) wastewater was chosen as targets to evaluate the photocatalytic performance of MWNTs/Fe2O3. Mechanism of MWNTs in MWNTs/Fe2O3 composites was investigated by XRD, TEM, UV-vis, FTIR, TG-DSC and Raman spectra. The results demonstrate that MWNTs will influence the absorbability and the ability of photocatalysis of Fe2O3. When the mass ratio between MWNTs and Fe2O3 is 1:2, the decomposition efficiency of Fe2O3 photocatalysis for UDMH will be increased effectively. There is a quantitative relationship between the amount of MWNTs and the crystal type of Fe2O3. When the mass ratio between MWNTs and Fe2O3 is higher than 5:1, Fe2O3 will be transformed from α to γ. The introduction of MWNTs has broad the light effect of Fe2O3. The close connection between MWNTs and Fe2O3 form a positive interaction and a strong combination, during which they also produce a chemical bond of Fe-O-C. Under the light, MWNTs will work as a photosensitizer and transform electrons to the Fe2O3 through Fe-O-C, which reduce the possibility of electron-hole pairs recombination and increase the efficiency of photocatalysis.
Based on CNFs supports, a series of MnO2/CNFs catalysts were synthesized by a liquid phase coprecipitation method, and it was applied to selective catalytic reduction (SCR) of NO. The microstructure, elemental composition, and valence state of the as-obtained catalysts were characterized by BET, XRD, FESEM, EDS, XPS and TEM. The results show that MnO2 is distributed on the surface of CNFs with amorphous form equably as the active components. MnO2/CNFs catalyst shows up the best activity in the test of SCR at the testing temperature range of 80-180℃, when the loading amount is 6%. NO transformation rate is 65.25% at 80℃, and 95.25% at 180℃. Amorphous structure, favorable dispersion and higher content of surface oxide are the main cause of MnO2/CNFs's excellent catalytic activity at low temperature. MnO2 is loaded on the CNFs without any acid-treated, which makes it more environment-friendly.
Fluorine-doped tin oxide (FTO) films were deposited onto glass substrates by the sol-gel-evaporation method with SnCl4·5H2O as a tin source, and CF3COOH, HF or SnF2 as a fluorine source, respectively. The effect of different fluorine sources on the surface morphology, structure and photoelectric properties of SnO2 thin films was investigated, and the mechanism of the impact on properties of FTO film was systematically discussed. The results show that all the particles in the FTO films present a tetragonal rutile phase. The surface morphologies of the FTO films correspond to irregular polygonal shape, rod-shaped and pyramid-shaped for fluorine sources CF3COOH, HF and SnF2. For the optimized sample the values of sheet resistance and IR reflectivity are 14.7Ω/□ and 86.1%, respectively. The doping mechanism of three different fluorine sources is the different bonding forms between F ion and the growing SnO2 grains, or is different in forming tin fluorine compound. The performance of FTO films prepared by one time doping SnF2 is superior to secondary doping HF and indirect doping fluorine source CF3COOH.
Based on the sensing principle of optical fiber grating, a kind of fiber Bragg grating (FBG) sensor packaged in glass fiber/epoxy composite substrate was designed and fabricated. The glass fiber/epoxy composite laminate was used as the bottom substrate, and the glass fiber fabric was used as the covering layer. Then the FBG was encapsulated between the bottom substrate and the covering layer by means of a vacuum-assisted infusion process of liquid epoxy. The only once but fully curing and the pre-curing processes were separately adopted in the process of preparing the glass fiber/epoxy composite substrate. Through the comparison of the two kinds of experimental results, it can be concluded that when the only once but fully curing process is adopted to prepare the glass fiber/epoxy composite substrate, the linearity and repeatability of the temperature response of the packaged FBG sensor are poor, and its relative repeatability error is as high as 10.90%, while the linearity is only 0.99871; when the pre-curing process is adopted before packaging and the secondary curing process is adopted after packaging, the relative repeatability error of the temperature response of the packaged FBG sensor is only 1.87%, and the linearity is 0.99998; besides, its strain sensitivity coefficient is 0.05514nm/kg, and its temperature sensitivity coefficient is 0.02357nm/℃, which is 2.4 times of the temperature sensitivity coefficient of bare FBG sensor.
A method for preparing iron-based friction material directly from the vanadium-bearing titanomagnetite concentrates by means of in-situ carbothermic reaction and sintering was presented. Effect of Ni content (1%-4%, mass fraction, the same below)on microstructure, mechanical properties and wear performance of iron-based friction material was investigated. The results show that the sintered sample consists of iron matrix, graphite lubricating phases and hard particles (mainly TiC). The matrix is predominantly composed of laminated pearlite with higher strength and hardness than those of ferrite. Compared with the sintered sample without Ni, the microstructure and properties of iron-based friction material are improved in varying degrees with different Ni contents. Low Ni content (1%-2%) promotes sintering process, which exhibits the decreasing amount of pores and uniform distribution of lubricating graphite phases and hard particles. Besides, the hardness and wear performance are improved significantly with the increase of Ni content. However, when Ni content exceeds 2%, not only the amount of pores increases, but also graphite phases and hard particles segregate in the microstructure, which result in decreasing hardness and poor wear performance of the material. To sum up, the microstructure and properties are the best when the Ni content is 2%.
The fretting wear behavior of micro-arc oxidation (MAO) treated ZK60 magnesium alloy under simulated bone plate-screw service condition was investigated. The MAO treatments on the surface of ZK60 magnesium alloy were conducted with different duty cycles of 20%, 30%, and 40%, respectively. Results show that the surface hardness and corrosion resistance of MAO-treated magnesium alloy specimens with different duty cycles are similar and are improved significantly in comparison with the bare magnesium alloy. Under the simulated bone plate-screw fretting condition, the worn surface of the bare magnesium alloy is characterized by ploughs and corrosion pits, accompanied with a high wear volume of 13.1×106 μm3, while the wear is obviously decreased and mainly dominated by ploughs on the surface of the MAO-treated magnesium alloy. With the increase of duty cycle, the wear volume is 6.6×106, 6.1×106 μm3 and 6.5×106 μm3, respectively. There is no obvious difference in the fretting wear behavior and the worn surface morphology among the MAO-treated ZK60 magnesium alloy specimens with different duty cycles. In sum, the anti-fretting wear performance of ZK60 magnesium alloy can be improved obviously after micro-arc oxidation treatment, and the duty cycle has little influence on the microstructure and fretting wear properties of the MAO layer on ZK60 magnesium alloy under the given experimental conditions.
The ultrafine-palygorskite/copper composites(ultrafine-P/Cu) were prepared by mechanical ball milling. The extreme pressure properties and the effect of load and speed on tribological properties of ultrafine-P/Cu powders, as 150N base oil additive, were evaluated on a four ball friction wear tester. The morphologies, element distributions and micromechanical properties of the worn surface were investigated by means of scanning electron microscopy, energy dispersive spectrometry and X-ray photoelectron spectroscopy. The results indicate that ultrafine-P/Cu used as a lubricant additive can effectively improve the tribological properties of base oil. The non-seizure value PB of ultrafine-P/Cu lubricant is increased by 31.6% than the base oil and by 9.1% than the single particles. Load and speed can affect the tribological properties of ultrafine-P/Cu. Ultrafine-P/Cu exhibits the optimum friction-reducing property and anti-wear property at the load of 245N and speed of 1200r/min, respectively. The excellent tribological properties of ultrafine-P/Cu can be attributed to the porous auto-restoration film of palygorskite and extended film of Cu formed on the worn surface to compensate wear and repair friction.
Tribological properties of lubricating oil containing T307 with and without electromagnetic field affection were evaluated on a modified four-ball tribo-tester. The morphologies and chemical states of several typical elements on the worn surfaces were examined by scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS). Then the mechanisms were discussed. The results indicate that the wear scar diameters of worn surfaces lubricated with the T307-doped oils and coefficients of friction obtained from electromagnetic field were bigger than those obtained from non-electromagnetic field. It can be attributed to the negative effect of the electromagnetic field on the combination of elemental phosphorus, sulfur, oxygen and nitrogen in T307 with metal surface, which has an undesirable effect on the formation of the tribo-chemical reaction films, and resulted by the tribo-diffussion of functional elements in T307 to the subsurface induced by electromagnetism. Moreover, the influencing mechanism of electromagnetic field was analyzed considering the molecular structure and active elements.
Preparation technology of an organic high friction composite materials was optimized by RSM(response surface methodology) and Design-Expert software. The friction tests were performed by MMS-2A friction tester. The quadratic regression model was established between process parameters and friction coefficient and wear rate. The results show that the correlation between predictive value and test value of the quadratic regression models has good fitting precision which are 91.97% and 87.85% respectively. There is strong interaction between molding temperature and holding time in the hot-pressing technology. Macro and micro surface morphologies were observed by the metallurgical microscope, scanning electron microscope, 3D measuring laser microscopy and hardness tester. The interfacial properties of the composites are affected by hot pressing process, which determine the tribological properties of composites. The optimum process parameters can be optimized by response surface methodology with the analysis of the wear mechanism, and the optimum hot pressing process are 19-25MPa, 165-174℃, 18-22min.
The effect of Mg content on microstructure and properties of near-rapidly solidified Al-Zn-Mg-Cu alloys was studied by means of OM, DSC, XRD and SEM. The results show that increasing the content of Mg results in the increase of the amount of non-equilibrium eutectic phase and grain boundary area, the decrease of the dendritic arm spacing and the refinement of the grain size. As a result, the tensile strength of the alloys is increased and the plasticity is decreased. On the other hand, increasing the content of Mg gives rise to the increase of the amount of residual secondary phase increased and the reduction of the homogenizing efficiency.
The relationship between phase transformation and time of Ti5Mo5V3Al-Cr (Cr content is 1.0%, 3.0%, 5.0%, 7.0% and 9.0%, mass fraction) alloys at 420, 520, 620℃was studied by in-situ thermal expansion and XRD method. According to the Johnson-Mehl-Avrami equation and experimental results, the kinetic parameters of Ti5Mo5V3Al-Cr alloys were obtained by fitting, and the dynamic equation of the system was established. Furthermore, based on the experimental results and theoretical calculation results, the time temperature transformation (TTT) contrast curve of Ti5Mo5V3Al-Cr alloys was plotted. The results show that the calculated results are in good agreement with the experimental results. Besides, 1Cr and 3Cr alloys have a fast phase change speed in the test temperature range of 420, 520, 620℃; 5Cr and 7Cr alloys have the fastest alpha phase transition velocity at the "nose temperature zone" of 550℃. The "nose temperature zone" of 9Cr alloy is not obvious, which means that the phase transition rate is slow.
The equilibrium solidified and the vertical section phase diagrams of Fe-C pseudo-binary were drawn with different chromium content (Fe-3.0%C-10.0%V-0.8%Si-0.8%Mn-X%Cr, X=2.0, 5.0, 10.0, mass fraction) by the Thermo-Calc software. The effect of chromium on the phase diagrams and solidification microstructure was investigated by OM, SEM, EDS, XRD, DSC and wear resistance test. The results show that the changes of eutectic transition points and phase region area are tiny with the increase of chromium content. The calculated temperatures of precipitated phase are close to the DSC results. The solidification microstructure is composed with α-Fe, MC, and M7C3. Chromium is mainly distributed in α-Fe and M7C3 carbides. With the increase of chromium, the amount of MC decreases and the amount of M7C3 increases; the α-Fe has no change. The hardness of the cast alloy increases with the increase of chromium content, and the maximum value reaches to 67.0HRC when chromium content is 10.0%. The wear loss is about 15.6mg when the chromium content is 5.0%, the wear resistance is the best.
Taking 8Cr4Mo4Ni4V bearing steel as the experimental material, the effect of heating temperature and holding time on austenite grain size was studied by austenite isothermal experiment. The grain size under different heat treatment conditions was measured by using linear intercept method. The results show that with the increase of heating temperature and holding time, the austenite grain size increases gradually. When the heating temperature exceeds 1100℃ or the holding time is over 120min, grain coarsening begins to occur. When the heating temperature exceeds 1150℃, grains become coarsened completely. The mathematical model of the austenite grain growth of 8Cr4Mo4Ni4V bearing steel with the heating temperature and holding time is obtained by linear regression, which can provide a theoretical basis of forging and heat treatment process for the 8Cr4Mo4Ni4V aviation bearing steels.
The welding materials and processes of fusion welding joint for TA1-X80 explosive composite plate were designed by corresponding welding experiment. Based on the microstructure, composition and properties of the welded joints, a good welding material and process as transition layer for welding titanium-steel composite plate was obtained. The results show that Y-type groove and double-layer transition for metallurgical connection of titanium-steel composite plate are effective. The double-layer consists of nearly titanium layer of Ti-Ni-Al alloy and nearly steel layer of Ni-Cr-Fe alloy. The weld microstructure is changed from coarse equiaxed grain in the titanium layer to fine equiaxed grain or dendrite in the transition layer, and finally is interlaced with the structure of steel. The tensile and yield strength of the welded joint are 501.1MPa and 373.0MPa respectively, which reach the equal match. But the plasticity and toughness are slightly insufficient, which can be improved subsequently by reducing the thickness of the transition layer and adjusting the elements for refining grain size.
A superhydrophobic conversion film on AA6061 aluminium alloy was prepared via ultrasonication-assistant chemical etching by FeCl3/HCl aqueous solution, KMnO4 passivation, and ultrasonic deposition of trichloro (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane. Field emission scanning electron microscopy (FESEM), contact angle test and Fourier transform infrared spectrometer (FTIR) were used to investigate the morphology, hydrophobicity, and chemical compositions of superhydrophobic conversion film, respectively. The results show that superhydrophobic surface exhibits a high contact angle of 153° and endows the Al matrix promising self-cleaning ability, resistance to acid or alkali erosion, anti-friction and anti-corrosion capability. Compared with the dipping method, ultrasonic preparation of superhydrophobic film on Al alloy surface can not only improve the homogeneity of self-assembly of PFCPS, but also enhance its bonding force with Al matrix and form a superhydrophobic film with good protective performance.
Based on the problem of corrosion acceleration possibly existing in aluminum alloy sheets under the influence of both loading and brine solution, the corrosion behavior of 5A06 aluminum alloy sheets with the thickness of 1.8mm by the two-point bending method in 3.5% NaCl aqueous solution at 50℃ was discussed.It is found that stress actually can promote the speed of corrosion in these aluminum alloy sheets.Crack morphologies, metallurgical structures and elemental compositions in different corrosion periods of these samples were analyzed.The results show:firstly, large stress will cause severe corrosion, which proves that stress can accelerate the corrosion; secondly, the solid solution strengthening phase in aluminum alloy can cause the anode areas preferentially dissolve, resulting in the formation of corrosion pits.Furthermore, stress can result in tearing of oxide film on the aluminum alloy surface, and facilitate corrosion crack propagation.
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