Advanced Materials Research Vols. 538-541

Abstract: Liquid metal flowing through filter media can create a vacuum in channel. Inclusions and gases in liquid metal are adsorbed onto surface of the filter media by negative pressure so that liquid metal was purified. Theoretical discussion was carried on the use of vacuum to purify metal and a series of measures such as increasing casting speed were proposed to improve the effect of purification. Experiments show that these measures are effective.

Abstract: Abstract. The pitting corrosion behavior of two kinds (W and Cu-free; W and Cu-bearing) of supermartensitic stainless steels (SMSS) were studied in CO2-saturated chloride solution with three chloric ion concentration: 21200, 50000, 100000ppm, and four different temperatures:19, 40, 60, 80°C by potentiodynamic polarization measurement. The results indicate that the pitting potential decreased with temperature increasing, and in a logarithmic relation with the chlorine concentration in both alloys. The pitting potential of supermartensitic stainless steel is increased by together adding tungsten and copper.

Abstract: Using tetraethyl orthosilicate and anhydrous aluminum chloride as precursors, ethyl ether as oxygen donor, LiF as mineralizer, and Na2SO4-NaCl as compound molten salt, mullite whisker was synthesized in the low temperature by nonhydrolytic sol-gel process combined with molten salt method. The phase transformation of mixed powder composed of mullite xerogel and molten salt during the heat treatment and the microstructure of mullite whisker corresponding to different temperature were characterized by means of DTA-TG, XRD SEM and TEM. The results show that mullite crystal phase can be formed via non-hydrolytic sol-gel process combined with the molten salt method at 750°C. The synthetic effect of mullite get better as the temperature increased to 850°C, while NaAlSiO4 crystal phase is also detected. Mullite whisker, with diameters ranging from 300~500 nm and lengths of 3~5μm, is prepared at the temperature of 850°C.

Abstract: The electron energy loss spectroscopy (EELS) of pure Ti, TiNi, Ni3Ti and pure Ni has been acquired and d-electron occupancy of both Ti and Ni in the metals has been measured from the white-line intensity. It is found that the change of d-electron occupancy of Ni is very small in all metals, but the d-electron occupancy of Ti in Ni3Ti increases considerable large relative to pure Ti. The change of d-electron occupancy is discussed in terms of charge transfer mechanism, local charge neutrality (LCN) approximation, and hybridization.

Abstract: This investigation involves the effects of non-ionic surfactant materials on the industrial sodium oleate, sodium naphthenate and their mixtures at different temperatures by the surface tension methods. The effects on the critical micelle concentration (CMC) of sodium oleate were assessed by the Toween 80(T-80) presence, polyethylene glycol, polyether and other non-ionic surfactant. T-80 was proved more effective than other non-surfactant in increasing the sodium oleate CMC at same concentration. Using the optimal composition of sodium fatty acid and the surfactant can reduce the temperature of separation hematite from 43°C to 23°C, achieve the purpose of low carbon and energy saving.

Abstract: Based on the oxidation of acid chrome blue K (ACBK) by hydrogen peroxide in 0.002 mol/L sulfuric acid solution, while 1,10-phenanthroline (phen) acts as an activator, a simple kinetic spectrophotometric method was developed for the determination of trace amounts of Se(IV).The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of ACBK at 524 nm with a fixed-time method. The decrease in the absorbance of ACBK is proportional to the concentration of Se (IV) in the range 0.06–1.0 µg/L with a fixed time of 4–10 min from the initiation of the reaction. The limit of detection is 0.018 µg/L Se (IV). The influence of the factors such as acidity, concentration of reactants, reaction time, temperature and co-existing ions on the reaction is discussed. The optimum conditions of reaction are established and some kinetic parameters are determined. The apparent activation energy of catalytic reaction is 62.30 kJ/mol. The relative standard deviation for 11 replicate determination of 0.01 and 0.02 µg/25mL selenium (III) was calculated to be 2.3 % and 2.0 %, respectively. Combined with sulphydryl dextrane gel (SDG) separation and enriching, the method has been successfully applied to the determination of Se (IV) in foodstuff samples with the relative standard deviation of 1.1 %–3.7 % and the recovery of 99.0 %–104.0 %, the results are in good agreement with those provided by HG-AAS method.

Abstract: The dezincification corrosion resistance of complex aluminum-brass HAl72-2.5-1 was studied by weight-loss, metallographic analysis method and energy dispersive spectroscopy. The effect of processing states and Al content（2.0%、2.5%、3.0%）in brass on zinc corrosion resistant was investigated. The research result shows that corrosion resistant is affected greatly by processing state, as-cast organization is loose and with much beta phrase, the dezincification of beta phrase is easy in corrosion solution, corroded at 75°C in 1% CuCl₂ solution for 30 days. The dezincification layer of as-cast brass is over 137.3μm. Compare with the as-cast alloy, the corrosion depth of brass plate hot-rolled is only about 70.6μm, because the recrystallization process and the β phase dissolved into α phase during hot rolling process, the construction is more condense than that in as-cast state. The corrosion goes easily along the grains orientation which occurs in cold rolling, and existence of residual stress accelerates stress corrosion, which turns higher corrosion rate than that hot-rolled brass. The corrosion velocity enhances with the increase of Al content in brass.

Abstract: MgAl2O4-SiC Composites were prepared by using magnesium aluminate spinel and silicon carbide powder as starting materials and the sintering mechanism was investigated at 1600°C in reduction atmosphere. Sintered samples were analyzed using XRD, SEM and EDS. The results show that Alumina-rich spinel and SiCN are formed due to the reactions between spinel and SiC. Weight loss of samples was detected due to SiO formation and volatilization. The bulk density of samples decreases and apparent porosity increases as increasing the content of SiC.

Abstract: The extraction of tea seed oil obtained from wild camellia seed using supercritical CO2 extraction has been investigated. The extraction was carried out under operation pressures of 20, 30, 35, 40 and 50 MPas at 45°C, with a supercritical fluid flow rate of 5mL•min-1. The collected extracts were analyzed and the relative compositions of the tea oil were determined by gas chromatography-mass spectrometry(GC-MS). The purpose of this work was to investigate the effect of operation pressure on the extraction yield, extraction time, and extract composition. The results from supercritical CO2 fluid extraction (SFE) showed that the extraction pressure positively related to the extraction yield and negatively and linearly related to the extraction time. Only 5 constituents were found in the extract under the pressure of 20 MPa. However, about 20 constituents in the extract were obtained under the pressure of 35 MPa, approximately the same as those under 50 MPa. The curve of the extraction pressure versus the extraction yield demonstrated that the extractable constituents of wide camellia seeds have two states: a free state and a bound state. In the bound state, extractable constituents can only be extracted under an extraction pressure above the threshold. Taking into consideration of the extraction yield, equipment, and operation, the appropriate pressure of the SFE is between 36.4 MPa and 40 MPa.

Abstract: The thermal barrier coatings (TBC) of the yttria-stabilized zirconia (YSZ) has been deposited by the atmospheric plasma spraying (APS),followed by the irradiation of high intensity pulsed ion beam (HIPIB) with the voltage of 250 KV and the ion current density of 300 A/cm2 and pulsed times of 2, 5, 10 and 20, respectively. The X-ray diffraction (XRD) analysis reveals that the coating is characterized by the tetragonal ZrO2 phase instead of the cubic phase and the original monoclinic phase after the irradiation. The scanning electron micros cope analysis demonstrates that the HIPIB treatment leads to a smooth TBC surface, but produces micro-cracks and round grain at the surface. This implies that the plasma erupts during the ion beam interaction with the coatings with poor thermal conductivity, and the micro-cracks were produced in the cooling process. The isothermal oxidation experiment performed at 1050°C in air and suggests that the oxidation resistance of the coating can be largely enhanced after HIPIB treatment.