Materials Science Forum Vols. 610-613

Abstract: An all-thin-film glass/ITO/MoO3/LiAlO2/NiOx/ITO device was deposited by magnetron sputtering for electrochromic application. The amorphous MoO3 and LiAlO2 thin films were prepared with the substrate temperature below 0 °C and in O2 and Ar gas pressure. The structure and surface morphology of the films were characterized by x-ray diffraction (XRD) and atomic force microscopy (AFM). It has been found that the amorphous LiAlO2 thin film was a suitable ion conductor for the electrochromic device. The transmittance in the wavelength range of 400-800 nm for the ITO/MoO3/LiAlO2/NiOx/ITO device changed from 14.48 % to 57.68 % by the applied voltage of 7 V. The blue-colored electrochromic property could be observed for the all-thin-film device. The experimental results indicated that such a monolithic system had great potential to be applied in flat-panel displays and smart windows.

Abstract: Chromium-activated ZnGa2O4 nano-sized phosphor powder was prepared by the Sol-Gel technique using citric acid as chelator, and the microstructure and luminescent property were studied. The host ZnGa2O4 belongs to the spinel structure and the ZnGa2O4:Cr3+ phosphor powder exhibited bright red emission band. The excitation bands with peak of maximum height at about 250 nm, 410 nm and 560 nm were related to the charge transfer (CT) of Ga-O, 4A2-4T1 and 4A2-4T2 transitions of Cr3+, respectively. Different quenching concentrations of the CT state and intrinsic excitation were discovered originating from different energy transfer schemes. Meanwhile, with the increasing of the calcining temperature the PLE spectrum exhibited an obvious blue-shift which is attributed to the enhancement of the crystal field.

Abstract: The microstructure and property of a new high temperature surface wear-resistant chromium carbide/Ni3Al composite deposited onto IC6SX alloy by manual argon tungsten-arc welding.have been investigated The microstructures of the WL(welding layer), HAZ(heat affected zone), BM(base metal) were observed by SEM and Optical microscope and analyzed by EDS and EMPA. Since the large amount of Mo which diffused from the substrate IC6SX strongly effected the formation of hard phases in the welding layer, the microstructures of WL in this study turned out to be very different from former studies where the different materials were chosen as base metals. Due to the high welding temperature and the rapid cooling process, the microstructures in HAZ were much smaller than that in BM. And the microhardness tests results illustrated that the two materials were well metallurgically bonded.

Abstract: The evenly dispersed Cu-Ti-C composites have been synthesized successfully from the element powders by mechanical alloying (MA) and spark plasma sintering（SPS）techniques. The evolution of microstructure with different processing parameters has been investigated by XRD and SEM. The Cu-TiC and the Cu-Ti2Cu3-C composites with different hardness and density were obtained from different content of Cu, milling time and sintering temperature. The effect of Cu content in the compound powders, milling times and sintering temperatures on the solid solution and reaction process of Cu-Ti-C system was also discussed and analyzed.

Abstract: A two-dimensional mathematical model for deposition behavior of SiC coating on C/C composites in a hot-wall CVD reactor was developed. Deposition rate of SiC was calculated by finite element method and optimized by using an orthogonal L9(3)4 test. The single and coupling effects of process parameters on deposition rate of SiC, including deposition temperature, the flux of mixed gases, the volume ratio of H2 and Ar, and that of MTS and mixed gases, were calculated and discussed. The optimal deposition rate of SiC was obtained.

Abstract: Al-Cu-Cr quasicrystalline coatings were prepared by low power plasma spraying with axially-fed powder systerm. The Al65Cu20Cr15 powders were deposited on AISI 1045 steel substrate at the power ranged from 4.0 to 5.5 kW. The effects of H2/Ar flow ratio on the phase composition, microstructure and tribological properties of the as-sprayed coatings were investigated. The XRD results showed that the feedstock powders and as-sprayed coatings contained a predominant icosahedral quasicrystalline phase I-Al65Cu24Cr11 and three minor crystalline phases, including a body-centered cubic α-Al69Cu18Cr13, a monoclinic θ-Al13Cr2 (i.e. Al83Cu4Cr13) and a hexagonal ε-Al2Cu3. A qualitative analysis on the XRD patterns indicated that the volume fraction of any crystalline phase (α, ε or θ) in the coatings increased, while the quasicrystalline I-phase decreased with the rise of hydrogen (H2) content in the working gas. However, as increasing the plasma power, the friction and wear resistance of the coating were improved under the same dry sliding wear test conditions. The improvementincrease of the wear resistance may be attributed to the high hardness of quasicrystal.

Abstract: In the present paper, Cr, CrN single-layer films and Cr/CrN multilayer films were deposited on iron and silicon wafer substrates by means of unbalanced magnetron sputtering. The film thickness was measured using surface profile meter. The porosity ratio was calculated using coulometric method based on the polarization curves obtained in the 30g/L NaCl solution at room temperature. Moreover, the corrosion resistance of the sample in a 350°C water vapor atmosphere was also analyzed. The thickness of all films ranged from 1.03 to 1.54 micrometer. The porosity ratio of the Cr and CrN single-layer film were 3.72% and 5.83%, respectively. The porosity of the Cr/CrN multilayer film decreased to 0.39%. The results showed that the Cr/CrN multilayer films had better protection than the Cr and CrN single-layer films.

Abstract: Ti-doped diamond-like carbon(Ti-DLC) coatings and undoped diamond-like carbon(DLC) coatings were synthesized by unbalanced magnetron sputtering using carburized Chromium Molybdenum Steels (SCM415) as substrates. Nanocomposite structure coatings with metal carbides nanocrystals uniformly dispersing in the amorphous carbon matrix were obtained by the optimization of the kinds of doped metals and deposited parameters. This kind of nanocomposite structure permits improved hardness while maintaining a lower residual stress and getting thick coatings. The friction coefficients of Ti doping DLC coatings are relatively lower compared with undoping DLC coatings in engine oil. The analysis on the wear surface of coatings have indicated that: the surface of DLC doped with metal absorbs more elements from the engine oil, which indicates that the doping of metal can improve the affinity of the coating for the engine oil, enhance the formation of lubrication oil films, and reduce the friction coefficient thereby.

Abstract: By means of the measurement of creep curves and microstructure observation, the influence of T6 heat treatment on the microstructure and creep properties of the wrought Ti-6Al-4V the alloy has been investigated. The experimental results showed that the microstructure of the wrought alloy consists of the strip-like +  phases, which results in the alloy displaying a higher strain rate and shorter creep life under the test condition of 575 MPa and 400°C. After T6 treatment, the creep life of the alloy at same conditions enhanced to 548 h from 66 h. Microstructure of T6 treated alloy consisted of the primary  and /phases, and signification amount of the bundle-likephase precipitated along the different orientations in the grains, this is a main reason of enhancing creep life of the alloy. During forging, the denser dislocation rows were activated in the local region of the matrix in the alloy. During creep, the deformed mechanism of the alloy was the double orientations slip of and dislocations activated on the pyramidal planes in  phase.

Abstract: The intergranular corrosion and stress corrosion cracking resistance of Al-Zn-Mg-Cu alloy with trace Er addition were studied by means of such methods as stress corrosion cracking and intergranular corrosion test in GB-T7998-2005 and HB5254-83. The microstructures were observed by optical microscope and scanning electron microscope (SEM). The results show that alloys with trace Er addition have been improved on intergranular corrosion and stress corrosion cracking resistance, but corrosion resistance of alloys can be descending when Er addition exceed 0.4%.