Papers by Author: Ping Hua Lin

Abstract: With the development of the ECAP technology, the corrosion behavior of the UFG materials has been investigated in some degree. Two categories of corrosion behaviors of UFG material were discussed in this paper. The large proportion of the non-equilibrium grain boundaries and high residual stress inside of the grain were regarded as the key to affect the corrosion behavior of the UFG materials. The corrosion behavior was also affected by the ECAP factors especially the press pass number and the pressing temperature. Finally some prospects of making UFG materials combined with high mechanical property and good corrosion resistance by ECAP technology were expounded.

Abstract: The influence of Mn content on the structure and magnetic permeability of Nd3Fe68-xMnxCo18B11 (x = 0, 1, 2) amorphous soft magnetic alloys was studied. The ribbons were prepared by melt-spining. The permittivity–frequency and permeability–frequency properties were determined in the microwave frequency regime of 2-18 GHz by vector network analysis. XRD spectra showed that only α-Fe diffraction peak was observed in the as-spun alloy. It is found that the acquired complex permittivity and permeability values match the microwave frequency when the 1at% Mn content doped. The results suggest a new design of microwave absorbers based on electromagnetic wave absorbing materials.

Abstract: An electrolytic sulfurization at room temperature has been introduced in the present work, which process parameters are optimized to the quenched Cr12 substrate. Morphology and microstructure of the sulfide layers are investigated deeply, and their formation mechanism is discussed in detailed. According to optimum parameter of sulfurizing process ( assistant current density of 1.8A/dm2, the saturated rare-earth-halide solution containing 300g Na2S2O3, 60g KHSO3 and 1000ml H2O, 298K/20~40min), the ferrous sulfide coating was easily obtained on the quenched Cr12 substrate with a uniform thickness of above 10μm, no matter about the treated parts with the complex geometrical shapes. The tribological experiment results of a block-on-ring tribometer indicate that the sulfide coatings on hard substrate have a very low friction coefficient and could obviously reduce the wear extent of its counterpart. Compared with the traditional low-temperature process, this sulfurizing technology has such virtues as simple process, heatless, low cost, little deformation, without pollution question, etc., which could be employed for industrial solid lubricant due to the good friction-reducing characteristic of lamellar-structure FeS phase.

Abstract: With the aim to obtain the high cavitation-erosion-resistance coating for the surface safeguard of fluid machinery, two kinds of hard coatings (WC-Cr-Co and Cr3C2-NiCr) were prepared on 1Cr18Ni9Ti substrate by high velocity oxy-fuel spraying (HVOF), which microstructure and performance were investigated respectively by optical microscope, X-ray diffraction, Vickers hardness, scanning electron microscope (SEM), and vibratory cavitation apparatus. The results indicated that these two coatings had the higher hardness and the finer structure than ZG06Cr13Ni5Mo, which is used actual in water conservancy. The results of cavitation erosion continued for 39 hours presented that the mass loss of WC-Cr-Co and Cr3C2 -NiCr coatings increased ceaselessly with time, and the cavitation erosion speeds varied with time. Compared with ZG06Cr13Ni5Mo, their cavitation erosion resistance performances were better due to their higher hardness and finer structure, and WC-Cr-Co coating was much better than Cr3C2-NiCr coating. Obviously, the higher hardness and finer structure could strengthen the cavitation erosion resistance of coating materials.

Abstract: This paper discusses the sulfate resistance and frost of mass hydraulic concrete which containing fly ash, superplasticizer and a novel MgO-bearing expansive agent (HNM), at same time, the mechanisms and processes of sulfate attack on it have been proposed. Results showed that using a water/binder ratio of 0.48 in RCC containing 50 % fly ash and 8 % HNM a durability factor of over D300 can be achieved and sulfate resistance may be improved slightly.

Abstract: The poly (L-lactic acid) (PLLA) porous scaffolds were prepared by porogen leaching combined freeze drying with the porogen particulates of ice in this paper. The ice particulates are made of distilled water sprayed into liquid nitrogen through a nozzle under a certain pressure. The pore morphology, porosity and residual porogen of the scaffolds was studied. There is no residual porogen when the ice particulate is used and the leaching mechanism of porogen is discussed. The scaffolds are composed of macro and micro pores and with a porosity of 80-90%. The macro pores are formed by ice particulate and the micro pores by thermal induced phase separation of solvent. The pore size can be changed easily by altering the size of ice particulate. The MTT assay was used to estimate cellular activity by L-929 cells culture in vitro. The results demonstrate that the scaffolds have no cytotoxicity. It could confidently be stated that the combined process seems to be a promising technique for the fabrication of porous polymer scaffold.

Abstract: Submicron hydroxyapatite powder with particle size in the range of 80-250 nm was fabricated by sol-gel process in our laboratory. To make ceramic slurry with good flowability, the powder was mixed with binder and distilled water. The binder was consisted of acid magnesium and aluminum phosphates. The polyurethane foam was impregnated in the slurry, squeezed out the excess slurry and the composite porous body gained. Green body was dried in room temperature naturally and then moved to electric furnace and sintered at high temperature. The sintered scaffolds possess interconnected open pore structure and with a porosity of 70-85% and compressive strength 10-20 MPa, and was consisted of doped HA and other phosphates. The scaffolds were co-cultured with osteoblasts in vitro. SEM analyses revealed that the cells adhere to the ceramic surface, proliferate and growth properly. Experimental results showed that the scaffold possesses good biocompatibility and could be used in bone tissue engineering.

Abstract: The addition of manganese into Nd9Fe85-xMnxB6（X=0,0.5,1） was found to enhance the magnetic properties of a -Fe/Nd2Fe14B magnets. After optimal annealed, the coercivity and remanence ratio increased from 0.34MA/m to 0.4MA/m and from 0.70 to 0.72, respectively, for the increase of x from 0 to 1. The XRD patterns indicated the addition of manganese could promote crystallization of as-spun samples. Moreover, the XRD spectra showed almost same grain sizes obtained for the optimal annealed samples. Thermomagnetic analysis (TMA) measurement indicated that the doping of Mn reduces the Tc of the Nd2Fe14B phase and raises that of a-Fe phase in the system. It is believed the exchange coupling between the Nd2Fe14B phase and a-Fe phase was partly changed by Mn addition, which is the reason for the enhanced magnetic properties and the change of Tc.