Advanced Materials Research Vols. 602-604

Abstract: The cermet prepared by powder metallurgy method is a new structural material. In this article TiC-based cermets prepared by using the vacuum sintered was described, the influence of the different Mo content of TiC-based cermets on the flexural strength and resistivity was discussed and analyzed from its structure and wettability of the Ni. The results showed that the Mo content was 10% in TiC-Ni-Mo cermet, that is, the ratio of Ni and Mo was 1:1, TiC-based cermet had smallest resistivity and higher flexural strength.

Abstract: The effect of titanium nitride addition on the microstructure, porosity and mechanical properties of Ti(C, N)-based cermets were investigated in this work. Results show that cermets have typical core-rim microstructure, the grain size of hard phase refines and the porosity increases with the addition of titanium nitride content. The transverse rupture strength reaches maximum at about 15wt.% titanium nitride. The hardness declines with the incremental titanium nitride content.

Abstract: The effect of sintering atmosphere and nitrogen pressure on microstructure of Ti(C, N)–12WC–16Ni–4Mo₂C cermet were investigated by scanning electron microscopy (SEM) and optical microscopy (OM), the transverse rupture strength (TRS), porosities, volume fractions of phases and grain sizes were determined. Results show that nitrogen pressure has a significant impact on TRS, appropriate nitrogen pressure could improve TRS. Vacuum sintering promotes the densification of sintered body, however, nitrogen atmosphere sintering could gain maximal TRS. Nitrogen atmosphere sintering facilitates the formation of inner rim phase and reduces the dissolution of TiC and TiN, small grain size is gained.

Abstract: Ceramic materials has approximate color and translucency with natural tooth, which is unmatched by other restorative materials. Because of its beautiful appearance, good physical and chemical properties, all-ceramic crown restorations are more widely used. However, due to the brittleness of ceramics and the stress mismatch between different materials, failure phenomenon is often observed during the service period of all-ceramic crowns. The failure process and mechanism are not clear, in this paper, the force performance of all-ceramic crowns is analyzed using the RFPA (realistic failure process analysis) system. The crack initiation, propagation and failure process of all-ceramic crown can be clearly observed and the research results provide guidance for clinical application.

Abstract: Nasicon type compounds of general formula Li1..3M0.3Ti1.7 (PO4)3 (M = Al, Cr, Fe) were prepared using melt quenching method. The samples were characterized by X-ray powder diffraction and infrared spectra. Thermal stability against crystallization was evaluated by DSC curve. All the compounds crystallize in hexagonal lattice with R-3c space group. The IR spectra show the characteristic PO4 vibrations. DSC curve reveals that the Li1.3Fe0.3Ti1.7(PO4)3 glass-ceramics possesses the better thermal stability against crystallization. Conductivity studies indicate that the total conductivity is dominated by the grain boundary

Abstract: In this paper, the structural stability, adhesion and chemical bonding of the TiO2 (110)/TiAl (111) interface are investigated by the first-principles calculations. We predict the maximum adhesion energy of 1.91J/m2 of the TiO2/TiAl interface. We also calculated the Nb doped interface, and found that the doped Nb atom prefers to replace the Ti atom at the second layer of TiAl slab. The atomic geometry and density of states are analyzed. The results show that the effect of doped Nb is localized and insignificant on the TiO2 (110)/TiAl(111) interface.

Abstract: Hot compression tests of Ti40 alloy was carried out on a GLEEBLE 3500 thermo- mechanical simulator at the deformation temperatures of 950~1100°C, the strain rates of 0.01~0.1s-1 and the height reductions from 20% to 60%. The true stress/true strain curves were obtained through the tests. Through physical experiment and FEM-based microstructure modelings, the dynamic recrystallizaiton (DRX) behavior of the alloy is extensively explored. The results show that increasing true strain, raising deformation temperature and reducing strain rate are contribute to the DRX of the Ti40 alloy. The simulation results agree well with the experiment results, which prove the accuracy of the microstructure evolution models for predicting the DRX process during hot compression.

Abstract: Nickel-cobalt alloys have broad application prospect for their excellent properties (i.e. high microhardness, strength, abrasion, corrosion resistance and magnetic properties.etc). Nickel-rich Ni-Co coatings were produced on SUS304 substrates by pulse electrodeposition from sulfamate electrolytes with different average current density, pulse frequency, duty cycle and different bath temperature. It is clearly observed that the content of cobalt in the nickel-rich deposits gradually increases from 4.29 % to 25.47 % as the Co2+/Ni2+ concentration ratio increasing from 0.022 to 0.1(the current density applied was 2 A/dm2,bath temperature 25 °C). The Co content increases from 16.98 % to 25.47 % to 30.06 % when the duty cycle ranged from 20 % to 50 % to 60 %.The Co content seems to hardly change when pulse frequency changed from 500 Hz to 1000 Hz. The cobalt content decreases as the growth of the current density. The formation of good Ni-Co deposits with high cobalt content and smooth morphologies can be obtained by reducing current density, increasing bath temperature and pulse duty cycle.

Abstract: With lanthanum, magnesium and nickel chloride as the main salt, citric acid (C₃H₈O₇•H₂O) as a complexing agent, La-Mg-Ni storage materials were prepared by galvanostatic electrodeposition method in aqueous solution. The effect of additive C₆H₄SO₂NNaCO•2H₂O on the properties of electrodeposited alloy film was studied. The results showed that: adding appropriate amount of C₆H₄SO₂NNaCO•2H₂O may be effective in improving the surface morphology of the La-Mg-Ni alloy film, and be more conducive to the formation of LaMg₂Ni₉ alloy phase; when the dosage was 0.20g/L, the cathodic polarization of the bath was the strongest, and cracks and pores were the least on the alloy film surface prepared by electro-deposited, the apparent activation free energy of alloy film was 48.2 kJ/mol, electrode absorption level Q was 0.030μF/cm², the alloy film resistor Rd was 138.5Ω/cm².

Abstract: By using local spin density approximation (LSDA) scheme within the density functional theory (DFT), the structure, magnetism and electronic properties of Co-doped Heusler alloy Ti2NiAl with Hg2CuTi- and Cu2MnAl-type structure are comprehensively investigated. The results revealed that whole of the doped alloys with Hg2CuTi-type structure are ground configurations and half-metallic. With the increase of Co-doped concentration, the lattice constants and total magnetic moments in per unit are changed linearly, and the discrepancies of total energy between Hg2CuTi- and Cu2MnAl structure are also enhanced. Analysis on density of states (DOS) revealed that the Fermi level should gradually move to high-energy orientation with increasing Co content due to stronger hybridization of d-electronic atoms.