Papers by Author: Feng Li

Abstract: In this paper, Ni-Co coatings on Al foil were prepared by electroplating to obtain Al/Ni-Co composite. Phase transformations and magnetic property of Al/Ni-Co composite heated at 823 K for 80 h were investigated. The results showed that obviously exchanged zone in Al matrix exited and the thickness was about 2.5μm. Ni diffused into the Al easilier than Co. β phase (AlNi and AlCo) and γ phase (Al (Ni, Co) solid solution) of Co-Ni-Al formed during the annealing. The Ms of was decreased significantly when Al diffused into the NiCo alloy film and formed Ni-Al and Co-Al intermetallic compounds.

Abstract: In this paper, Ni-Co alloy films with different composition were obtained by means of electroplating method. The morphology, structure and magnetic properties of Ni-Co alloy films with different Cobalt content are evaluated. The effect of the crystal orientation on the morphology of Ni-Co deposits with different compositon was discussed. The results showed that Ni–Co alloy films with Cobalt content decrease is composed of pyramidal, spindly, mixed pyramidal and spindly, and cellular particles respectively. To the deposits with similar composition, change of morphology is related to the preferential orientation. With the increase of the Nickel content, the saturation magnetization (Ms) value of the Ni–Co alloy films increases and then decreases sharply. The coercivety (Hc) value of the Ni–Co alloy films decreases with the Nickel content increase.

Abstract: In this paper, the silicone rubber composed of carbon fibers was prepared. The influence of different concentration of carbon fibers on the conductivity, electromagnetic shielding interference effectiveness property of the silicone rubber was discussed from the point of view of condition of carbon fiber and silicone rubber. The results showed that there existed the extreme conductivity and shielding effectiveness (SE) across the tested frequency range from 2.6 GHz to 3.95 GHz of silicone rubber composites filled with carbon fibers. When the content of the carbon fibbers was 50 parts per hundred of rubber (phr), the SE values of composites were typically above 63 dB and close to the extremum. The compact packing structure of carbon fibers does not play an important role in improved the conductivity of composite. The SE of the composite depends on the conductivity of composite.

Abstract: A sprayed MoB/CoCr cermet coating was formed on 310S stainless steel by low pressure plasma spraying (LPPS), and its durability in the molten Al-12.07wt.%Si has been investigated by SEM、EDS and XRD. The immersion test revealed that the MoB/CoCr coating has much higher durability without dissolution in the molten Al-12.07wt.%Si alloy. Little change of crystal structure, mainly composed of ternary borides of Co2MoB2 and CoMoB, suggesting that the ternary borides have much higher durability.

Abstract: Corroded behavior of 310S stainless steel by molten Al-Si eutectic alloy in high temperature thermal cycles of 495～620°C was investigated. SEM/EDX, XRD and metallographic technique were used for observing and analyzing the morphology, composition and internal microstructure of the corrosion specimens. Results showed: on the surface of 310S stainless steel, after corroded through 300 melting-solidification thermal cycles, a corrosion layer of about 3μm thick, composed mainly of Fe2Al5 phase and FeAl3 phase was formed. Besides, upon observation of internal microstructure of 310S stainless steel after corrosion, plenty intercrystalline precipitation was present, which resulted in relatively severe intercrystalline corrosion. This was considered the principal factor that compromised mechanical property of the specimen of 310S stainless steel.

Abstract: Image thinning is one of important steps of fingerprint preprocessing. Most of fingerprint recognition algorithms checked the characteristic points on thinning image. In this paper, we discover some shortages in OPTA and mathematical morphology thinning algorithm and find out the reasons for some shortages such as many glitches and snags, defective thinning, and so on. A new improved algorithm is proposed in the paper, which is an ideal algorithm because it is faster, produces less glitch, and thins completely.

Abstract: In this paper, the technology of semi-solid casting was to used are produced Sn-Bi alloy. The influence of agitating time at 125 °C on the microstructure and mechanical properties of of Sn-58Bi casting alloy were discussed. The eutectic Sn-Bi alloy was mechanically agitated during the casting solidification process. The results indicated that non-lamellar Sn-Bi structure with long plate shape, short strip, small size block and suborbicular block shape Sn phase was obtained for different stirring time. The elongation of Sn-Bi alloy with non-lamellar eutectic structure is improved prominently. Compared with the elongation of lamellar eutectic Sn-Bi alloy prepared by conventional die casting, the elongation of semi-solid Sn-Bi alloy with suborbicular block shape Sn phase is enhanced up to 45%.

Abstract: Preparation of semi-solid Sn–58Bi alloys by mechanical stirring casting method was investigated. The effect of temperature below the melting temperature on the microstructures and mechanical properties of semi-solid Sn–58Bi alloys was discussed. The experimental results showed that long plate shape, block shape and suborbicular Sn phases were formed by mechanical agitation during the casting solidification process. The non-lamellar Sn-Bi Microstructure improves prominently the elongation of Sn-Bi alloy. The elongation of semi-solid Sn-Bi alloy with suborbicular Sn phase is enhanced up to 37% compared with the elongation of lamellar eutectic Sn-Bi alloy prepared by conventional die casting. After the agigation above 130 °C, non-lamellar Sn-Bi eutectic structure is formed and lamellar Sn-Bi eutectic precipitates. When the agitating temperature was 135 °C, the elongation of semi-solid Sn-Bi alloy mixed with non-lamellar and lamellar Sn-Bi alloy microstructure is enhanced up to 24%.

Abstract: The change of thermal properties of Al-17 wt.% Si alloys in different heating-cooling cycles was studied by differential scanning calorimetry (DSC). The influence of heating-cooling cycles on the latent heat of melting was discussed in the view of microstructure of Al-Si alloy. The results showed the latent heat of as-cast Al–13 wt%Si alloy is 548.6 J/g, which Al-Si alloy possesses good thermal energy storage property. The onset of melting point of Al-Si alloy increases indistinctively and is about 577 °C. When the heating-cooling cycle was 1200 times, the latent heat increased to 526.0 J/g. With heating-cooling times increase, the grain size and shape of the primary Si decrease. The shape of eutectic Si is changed into stripe

Abstract: TiB₂ protective coating was prepared in the 310S container wall to improve the life of the container and achieve long-term protection purposes, and also studied the properties of TiB₂ coating with anti-heat shock, mechanical and anticorrosion to molten Al-12.07%Si . The results showed that the anti-heat shock properties of the coating was good, bonding strength between coating and substrate was high, the corrosion resistance was improved under certain limited temperature, and the life of container was also remarkable enhanced.