| The composite nanofiber is a new functional composite fiber composed of two or more materials with different properties and coupled together with nano-size using various technologies. Composite nanofibers are charactered of large specific surface area, high length/diameter aspect ratio, light quality and excellent mechanical properties, which have received tremendous attention in the research of advanced material field, it has been widely applied and highly valued in the clothing, biomedical, aerospace, reinforced materials and photoelectric materials.Composite nanofibers as reinforcement for metal and ceramic matrix composites are of enormous interest to improve their mechanical properties of strength, fracture toughness, impact resistance, which due to their superior properties. Currently, the enhanced toughening nanofibers are mainly boron fiber, carbon fiber, silicon carbide fiber, alumina fiber, silicate nanometer fiber, etc. However, alumina fibers have incomparable advantage in reinforcing high temperature alloy due to the superior characteristics, one-component nanofiber lack of surface specificity, poor mechanical properties and degradation rate was difficult to remain, it have been difficult to meet the needs of application, in order to overcome the above shortcomings, the yttrium aluminum garnet/metal oxide nanofibers composite nanofiber caused wide attention as reinforcement. At present, yttrium aluminum garnet/metal oxide composite nanopowder was used the reinforcement and composite material enhanced by nanopowder have some shortcomings in mechanical performance, such as poor strength, fracture toughness, impact resistance and easily-cracked. Compared with the powder materials, yttrium aluminum garnet/metal oxide nanofibers exhibit excellent properties such as large specific surface area, high length/diameter aspect ratio, filiform molecular structure and high adhesive force. Therefor, the composite nanofibers as the reinforcing material have a good prospect of application in metal matrix and ceramic matrix composite.Yttrium aluminum Garnet(chemical formula is Y3Al5O12, YAG for short) fiber has high strength, high elastic modulus, high temperature resistance, oxidation resistance and resistance to high temperature creep features, is a good enhancement. Alumina(Al2O3) nanofiber has many excellent properties, such as high strength, high modulus, heat resistance, high tensile strength at high temperature, it also has superior high-temperature oxidation resistance, corrosion resistance. Meanwhile, the alumina nanofiber have a well invasion with metallic matrix, the interface reaction is small, which is a good reinforced material.Zirconia(Zr O2) nanofiber exhibit superior speciality of high temperature resistance, high strength, good toughness and corrosion resistance. As reinforced materials, they ere applied in some field, such as high temperature components of the space vehicle power system. There is a good chemical compatibility and similar thermal expansion coefficient exists among yttrium aluminum garnet, alumina and zirconia and all of them have high melting point and superior oxidation resistance, therefore, Al2O3/YAG/Zr O2 tri-phase composite nanofiber is a hopeful and promising high temperature enhanced toughening material.YAG, Al2O3 and Zr O2 are good reinforcements, the composite nanofiber synthesized by them has a considerable potential applications value as reinforcing material. Composite nanofibers were incorporated into metallic matrix and the influence of fiber to metal matrix mechanical properties, such as hardness, fracture toughness, impact resistance, etc. The luminescent of material is very significant to study composite nanofiber and mechanical property of fiber/metal matrix composites. Hence we adopt electrospinning to synthesize the YAG/Al2O3(Zr O2) composite nanofibers area great significance. XRD, TG-DSC, SEM and FT-IR were employed to characterize the samples. According to that, we get some valuable conclusions as follows:1. YAG/Al2O3 composite nanofibers were succesfully synthesized by electrospinning. Nanofibers with different morphology were prepared under different spinning condition. The optimal spinning parameters were obtained: the PVA content is 10%, spinning voltage of 25 k V, the distance between spinning nozzle and collecter is 16 cm. Thermal analysis showed that the temperature is 1000 ℃, the nanofiber was only YAG phase and Al2O3 and the crystallinity is well. It can be found that the nanofiber with a homogeneous diameter, an average dimeeter of about 300 nm, length/diameter aspect ratio is 80:1 and the surface is smooth. TEM analysis showed that YAG/Al2O3 nanofiber contains two sets of diffraction spots, it is the superposition of phase YAG phase and phase Al2O3 diffraction pattern.2. YAG/Zr O2 composite nanofibers were synthesized by electrospinning. Nanofibers with different morphology were prepared under different spinning technological parameters, such as PVA content, spinning voltage and curing distance. The results indicate that the diameter size of precursor fiber is uniform and the average diameter is about 1μm. It is concluded that the optimum content of PVA is 11%, the best spinning voltage is 20 k V. The curing distance is 16 cm. XRD spectrum analysis indicated that after the calcination temperature is higher than 1100 ℃, crystalline phase of composite nanofiber began to form. When the temperature reached 1200 ℃, the nanofiber contains only YAG phase and Zr O2 phase, its crystallinity is good and the diffraction peak intensity is high. At the same time, the amount of PVA content has no influence on the formation of composite nanofiber phase. The diameter of composite nanofiber is uniform, the average diameter is about 500 nm, length/diameter aspect ratio is 50:1, and the surface of fiber is more smooth when the precursor fiber after annealed at 1200 ℃ for 5 h. TEM pattern indicates that YAG/Zr O2 composite fiber contains two diffraction patterns of diffraction spot and diffraction ring two, the diffraction ring has a dispersion and broadening phenomenon, which illustrate that the nanofiber has a fine grain size. There are two kinds of crystalline in composite annofiber, including polycrystalline Zr O2 and single crystal YAG.3. Al2O3/YAG/Zr O2 composite nanofibers were prepared by electrospinning. Nanofibers with different morphology were obtained by changing the spinning parameters, such as PVA content, spinning voltage and curing distance and the optimum spinning process conditions were confirmed. The SEM analysis demonstated that the diameter of precursor fiber is uniform and average diameter is about 0.8 μm. The optimal spinning parameters are as follows: PVA content is 10%, spinning voltage is 25 k V, receiving distance is 18 cm. XRD spectrum analysis showed that that the calcination temperature is higher than 1200 ℃ and crystalline phase of composite nanofiber began to form. The annealing temperature is 1200 ℃, the composite nanofiber contains the α-Al2O3 phase, YAG phase and Zr O2 phase. Meanwhile the amount of PVA content has no influence on the formation of ternary omposite nanofiber phase. The average diameter of composite nanofiber is about 250 nm, length/diameter aspect ratio is 70:1, and the surface of fiber is more smooth when the precursor fiber after annealed at 1350 ℃ for 5 h. TEM images showed that Al2O3/ YAG/Zr O2 nanofibers have three lattice fringes distribution, the crystal lattice fringe with the spacing d values of ~0.25 m, ~0.24 nm and ~0.23 nm can be measured, which corresponds to the(110) crystal facet of Al2O3 phase,(002) crystal facet of Zr O2 phase and(420) crystal facet YAG phase. The selected area electron diffraction(SAED) pattern indicates that the ternary composite nanofibers contain three sets of diffraction spots, corresponding to the Al2O3, YAG and Zr O2 three crystal structures.4. Com The YAG/Al2O3, YAG/Zr O2, Al2O3/YAG/Zr O2 composite nanofibers and the novel aluminum bronze were used to prepare fiber/metal matrix composites, the hardness and tribological properties of composites were studied. Compared with novel aluminum bronze sintering samples without nanofibers, the composite nanofibers can improve the the hardness of Cu-14Al-X metallic powders based composites and YAG/Al2O3 nanofiber enhancement effect is best. After adding different composite fiber, nanofibers/Cu-14Al-X composites have a small friction coefficient and wear. The composite wear surface morphology of YAG/Al2O3 nanofiber and Cu-14Al-X has a slight surface scratches and less grinding. When adding YAG/Zr O2 nanofiber, the composite wear surface morphology has furrows phenomenon and large grinding. After adding Al2O3/YAG/Zr O2 nanofiber, composite wear surface morphology has a lot of scratches and furrows, and even appears adhesive wear. The Cu-14Al-X wear surface morphology produces the obvious plastic deformation, and the major wear forms is adhesive wear. |
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