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Room temperature ferromagnetic tetragonal superstructure Sr3ErCo4O10.5+δ polycrystals were prepared by solid-state reaction method.XRD and SEM were used to characterize the structure and cross-sectional morphology of polycrystals prepared at 7 different sintering temperatures between 1025 and 1200℃. At 1 025 ℃,the polycrystalline crystallization of Sr3ErCo4O10.5 was completed and appeared heterogeneous Er2O3. With the increase of sintering temperature, the (103), (215) peak intensities of superstructure increased, the impurity phase decreased gradually; the Sr3ErCo4O10.5+δ grain grew, the porosities decreased and the lattice integrity improved.At 1160℃,the peak intensities of superstructure were the highest, the impurity phase disappeared completely, and the degree of ordering was the best.With the increase of sintering temperature, the peak intensities of superstructure decreased, the degree of ordering weakened, and Er2O3 appeared on the particle surface. TG-DSC showed that the polycrystal absorbed oxygen (δ) at 1 025-1200℃ and gradually completed the ordering. Iodine titration further confirmed that the stoichiometric ratio of polycrystal oxidation increased with the increase of sintering temperature.Polycrystal was prepared at 1160℃,which resistivity of 300 K was 0.09 Ω· cm, and the ferromagnetic-paramagnetic transition temperature (Tc) of polycrystal was 332 K, and the M-H curve further proved that the polycrystal was ferromagnetic at room temperature and underwent paramagnetic-ferromagnetic transformation at 332 K. [ABSTRACT FROM AUTHOR]

The polycrystalline Ca(1-x) YxCu3Ti4O12 (x = 0, 0.005, 0.010, 0.015, 0.020, 0.030, 0.040) ceramics samples were prepared by traditional solid-state reaction method. The microstructure and non- ohmic properties were characterized by X-ray diffraction, scanning electron microscope and the high-voltage digital source-meter. The effect mechanism of the variation in grain boundary barrier on the non-ohmic properties was also discussed. The results presented that there was no phase transition in Y3+-doped CaCu3Ti4O12 samples, while the grain growth was related to the doping content. Both the density and chemical environment in grain boundary of samples were influenced by doping. The non-ohmic properties of CaCu3Ti4O12 ceramics material were modified by Y3+ doping, and both non-linear coefficient and break down voltage were apparently enhanced by doping with the appropriate content ( x = 0.010 ~ 0. 020) . [ABSTRACT FROM AUTHOR]

A thermo-mechanical coupling atom-continuum coupled model and its efficient algorithm were studied systematically, and the formulae for calculation of thermodynamic and mechanical parameters of metallic materials in micro/nano-scale were obtained. The heterogeneous structure and deformation of polycrystalline clusters in micro- and nano-scale were studied by means of the 'structural deformation' part of the atomic motion. Then the lattice structural transformation of atomic clusters was related with the continuum deformation, and the expressions of free energy density, entropy density and internal energy density, which were dependent on the micro-structural deformation and thermal vibration, were derived under the quasi-harmonic approximation assumptions, with some transient thermodynamic and mechanical parameters given. The numerical simulation of a tensioning test on a Cu nanowire proves correctness of the proposed model and validity of the algorithm. [ABSTRACT FROM AUTHOR]

Numerical simulations on α-iron and polycrystalline iron are conducted using discrete element method (DEM) combined with undiffused two-phase transition model, thermodynamic consistent free energy function, and phase transition kinetics of relaxation equation. The phase boundary and Hugoniot relation are obtained through numerical simulation. The simulation result of polycrystalline iron shows that the shock-front irregularities rise when the propagation distance of shock wave increases; and the shock-front is more irregular in the coarse grain model than in the fine grain model; the phase transitions in the polycrystalline are heterogeneous, and the transitions are observed first along grain boundaries. The curve of local average pressure and transformed mass fraction is obtained. [ABSTRACT FROM AUTHOR]

To study the variation of cutting temperature in high-speed milling of titanium alloy with polycrystalline diamond, factorials design and uniform design were applied to the cutting temperature experiments. The main effects and interaction effect which have significant influence on cutting temperature were found out by factorials design. By using uniform design, the influence law of main effects and interaction effects on cutting temperature were investigated. Nonlinear mathematical model on the relationship between cutting parameters and cutting temperature was established. The results show that under high speed milling, the interaction effect between cutting speed and width of the uncut chip is significant. The relationship between cutting temperature and cutting parameters is nonlinear, and the effect of one cutting speed on cutting temperature changes with width of the uncut chip. [ABSTRACT FROM AUTHOR]

PURPOSE: To evaluate the interface compatibility between tooth-like yttria-stabilized tetragonal zirconia polycrystal (Y--TZP) by adding rare--earth oxide and Vita VM9 veneering porcelain. METHODS: Six kinds(Sl,S2,S3,S4,S5, S6) of tooth--like yttria stabilized tetragonal zirconia polycrystal were made by introducing internal colorating technology to detect the thermal shock resistance and interface bonding strength with Vita VM9 Bsaedentin. Statistical analysis was performed using SAS6.12 software package. RESULTS: There was no gap between the layers via hot shocking test. The shear bonding strength between Y-TZP and VitaVM9 was higher and the value was (36.03±3.82) to (37.98±4.89) MPa. CONCLUSIONS: By adding rare -earth oxide to yttria -stabilized tetragonal zirconia polycrystal, better compatibility between the layer (TZP and Vita VM9) can be formed which is of better interface integrate and available for clinical applications. Supported by Biomedical Project of Science and Technology Commission of Shanghai Municipality (09411954600)and Shanghai University Scientific Selection and Cultivation for Outstanding Young Teachers(jdy09046). [ABSTRACT FROM AUTHOR]

With polycrystalline diamond (PCD) tools, Ti-6A1-4V alloy was machined at different cutting speeds. Optical microscope and scanning electron microscopy (SEM) micrographs of chip were analyzed in order to understand the thermoplastic shear instability in PCD tools cutting titanium alloy Ti-6A1-4V. Chip segment angle reduces after the first increase with the increasing of cutting speed when the thermoplastic shear instability happens. It is proved that phase transformation of titanium alloy happens when the thermoplastic shear instability takes place through calculating shear strain in the segment, measuring microhardness and X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

PURPOSE: To develop six kinds of tooth-like yttria stabilized tetragonal zirconia polycrystal(Y-TZP) ceramic blocks. METHODS: Six kinds(Sl,S2,S3,S4,S5,S6) of tooth-like yttria stabilized tetragonal zirconia polycrystal (Y-TZP) were made by introdticing internal colorating technology, and the color gauged with shade-eye chromatometry instrument was compared between Vita classical shade selection and the 6 kinds of tooth-like ceramic blocks. RESULTS: The color of six kinds of tooth-like TZP was presented in the CIELab system. The value of L* was from 68.8-80.37,a* was from - 1.0-0.9,and b* was from 12.2-17.93, which was covered by Vita classical shade selecting and Chinese tooth color parameter. CONCLUSIONS: Rare earth and transition element as colorants can endow TZP with tooth-like color with different proportions. It is possible to develop tooth-like Y-TZP by adding minority rare earth oxides (Pr6O11,CeO2,Er2O3, MnO2). [ABSTRACT FROM AUTHOR]

In order to study the effect of nucleation mechanism on the hot working process of polycrystalline metals? the evolvement of dynamic recrystallization microstructure under three nucleation mechanisms was simulated by developing a two-dimension cellular automaton model. The variation of the mean size of recrystallization grains(R-grains) and the characteristics of growth kinetics during the hot working process were obtained. The simulated results of the three models were discussed and compared together. It is found that the variation of the mean size of recrystallization grains is decided by the nucleation mechanism and the growth mode. However, the steady mean size only depends on the total number of nuclei. The curve of the growth kinetics looks like the shape of "S" and its variation follows the JMAK theory. The Avrami exponent is decided by the spatial distribution of nuclei. [ABSTRACT FROM AUTHOR]