Advanced Materials Research Vols. 150-151

Abstract: We have measured photoluminescence of porous silicon which is electrochemically prepared on single crystal silicon wafer with co-implantation of Ar+ and N+ ions. The results show that the photoluminescence intensity of porous structure of co-implanted silicon was enhanced that we attribute these to the enhanced formation of porous silicon microstructure induced by ion implantation and from the analysis by scanning electron microscopy, it is demonstrated that the different density of the pores with different doses ion implantation

Abstract: The marked brittleness with low tensile strength and strain capacities of ultra high strength concrete (UHSC) with compressive strength of 100 MPa can be overcome by the addition of polyvinyl alcohol (PVA) fibers. The compressive strength and splitting tensile strength of ultra high strength concrete containing PVA fibers are investigated this paper. The PVA fibers were added at the volume fractions of 0%, 0.17%, 0.25%, 0.34% and 0.5%. The compressive strength of the PVA fiber reinforced ultra high strength concrete (PFRC) reached a maximum at 0.5% volume fraction, being an 8.2% improvement over the UHSC. The splitting tensile strength of the PFRC improved with increasing the volume fraction, achieving 46.7% improvements at 0.5% volume fraction. The splitting strength models were established to predict the compressive and splitting tensile strengths of the PFRC. The models give predictions matching the measurements.

Abstract: Al-2%Mn alloy matrix composites reinforced with Al2O3 particulates was fabricated by stir-casting, and the hardness and friction and wear behaviour of the composites were analyzed using Brinell hardness tester and ring-on-block tribometer under both dry and lubricated sliding in which the .SO4•Cl- Na•Ca• Mg corrosive alkalescent aqueous solution accompanied with SiO2 and Al2O3 grinding particles was used as lubricant. The wear mechanism and the effect of Al2O3 particulates on the friction and wear behaviour of the composites were discussed. The results showed that the friction coefficients of the samples under dry condition are generally lower than those under lubricated one. In comparison with the base aluminium and the Al-2%Mn alloy, the hardness of the composites increases~70%, the friction coefficients are lower in most cases especially at higher applied loads under lubricated condition, and the wear mass losses are much less at any applied loads whether under dry or lubricated condition. The composites possesses a good wear-resistance and antifriction due to its higher hardness.

Abstract: In order to investigate the crack resistance capacity of cross shaped steel encased ultra high-strength concrete (CSSEUHSC) column to reinforced concrete (RC) beam connection subjected to reversal cycle load, six interior joint specimens were tested with various axial load ratio nt and volumetric stirrup ratio ρv. A discussion on the crack resistance capacity was presented. Calculation methods of crack resistance capacity were deduced and calculating results were in good agreement with the experimental results. The research results indicated that parameters of CSSEUHSC column to RC beam connection with better crack resistance performance may be referred for engineering application.

Abstract: The water permeability of cementitious composites containing polyvinyl alcohol (PVA) fiber, fly ash (FA) and silica fume (SF) is studied in this paper. The parameters studied include volume fraction of PVA fiber, cement substitution with fly ash and cement substitution with both silica fume and fly ash. The research findings show that with the increase of volume fraction of PVA fiber, the penetration depth of cementitious composites is decreased. The penetration depth increases with the addition of FA and SF. Conclusions were drew that PVA fiber, FA and SF have an obvious influence on the water permeability.

Abstract: Flexural strength of cementitious composites containing polyvinyl alcohol (PVA) fiber, fly ash (FA) and silica fume (SF) is studied in this paper. The parameters studied include volume fraction of fiber, the substitution ratio of cement by fly ash and the substitution ratio of cement by both silica fume and fly ash, which have an influence on the compressive strength and flexural strength of cementitious composites. The research findings show that with the increase of volume fraction of fiber, the flexural strength of cementitious composites are improved .When the volume fraction of fiber rises from 0 to 2% ,the flexural strength increases by 51.8%. When the volume fraction of fiber remains 2%, cement substitution with fly ash reduces the flexural strength of cementitious Composites, while which is improved by cement substitution with both silica fume and fly ash.

Abstract: Antistatic Poly(ethylene terephthalate) (PET) materials had been successfully prepared through solution-blending incorporation of ethylene glycol-graft-Multi-walled carbon nanotubes (EG-g-MWCNTs). MWCNTs were first carboxylated and then esterified with EG to yield EG-g-MWCNTs. The FT-IR spectra, TEM images, Raman spectra, TGA curves and electrical conductivity were investigated, which indicated that the agglomeration degree of MWCNTs has been reduced and the conductivity keeps as high as 4.278 S/cm after the modification of EG. On the other hand, EG-g-MWCNTs dispersed well in EG, which was one of the synthetic monomers for PET, and thus ensured its good compatibility with PET. As a result, the electrical conductivity of PET/EG-g-MWCNTs nanocomposites (0.1 wt%) was seven orders of magnitude higher than pure PET and reached the antistatic level.

Abstract: The impact on curved box girder bridges due to applying prestressing force have been analyzed using finite element method. This paper presents the results of an experimental investigation and analytical studies. Based on the model experiment, the results and conclusions of shear lag in curved box girder with prestressing force are presented that prestressing force has changed shear lag distribution. The prestressing force action on box girder shall be considered comprehensively, structural force shall be analyzed accurately, optimize prestressing tendons shall be set rationally which would make force more rationally. The results highlighted that the impact factors of a curved box girder bridge have been observed to be generally very high, while those of the other responses are also relatively higher than that of corresponding straight box girder bridge.

Abstract: The effect of fly ash in improving the mechanical properties of concrete is investigated and the existing concrete strength development models are studied. Based on the chemic reactivity properties between fly ash and cement, an appropriate concrete strength model are chosen, and a new model for the fly ash strength factor combing Maturity method is built up and the factors are regressed by existing experimental datum. A total of 24 concretes, including two concretes were produced with two partial fly ash replacement ratios (23.7%, 32.7%). The cubic samples produced from ash fly concrete were demoulded after a day, and cured at standard temperature ( in GB/T 50081-2002) with 100% relative humidity until 28 days, then cured in water. The compressive strength tests were carried out on the cubic specimens at different ages. The compressive strength with time was evaluated by using the new predicted model. It was found that the calculated results by new method are fit the experimental data well.

Abstract: A new method for preparation of coatings with codeposition plating on the ordinary A3 steel and heat treatment later. Research the coatings on electrochemical corrosion behavior variation in Q-sun. Results show that corrosion potential shuffle, corrosion current density reduced nearly two number magnitudes value, polarization resistance increased, the cathode polarization effect enhanced obviously in polarization curves, and self-corrosion current reduced, impedance increased twenty times in alternating current impedance atlas than A3 steel substrate without coatings. It was indicated that the coating improve effectively the corrosion resistance of plain carbon steel.