Advanced Materials Research Vol. 624

Abstract: NH₄F with ethylene glycol solution as the electrolyte, the anodic oxidation of titanium mesh surface in preparation of ordered TiO₂ nanotube array. The structure, morphology and absorption properties of samples were characterized by XRD, SEM and UV spectrophotometer. The results show that, in a certain time range, nanotube length and diameter will increase with the increase of oxidation time. The best oxidation time is 60min. Ultraviolet visible spectrophotometer results show that, the optical band gap of samples is from 3.26-3.42eV. The photoelectric conversion characteristics of dye sensitized solar cell assembled with prepared nanotube arrays were tested.

Abstract: To assess the color stability of different resin cements after accelerated ageing. Four different resin cements were included in the study (1mm thickness). The resin cements were bonded to ceramic disks (0.5mm thickness) built with the VITABLOCS MARK-Ⅱ ceramic (n=7). All of the samples were stored in 37°C distilled water at dark. Then color measurement were determined using spectrophotometric before and after accelerated ageing in a weathering machine with a total energy of 150kJ/m². Changes in color (ΔE) were obtained using the CIE Lab system coordinates where a ΔE data above 3 was accepted as visible discoloration. The ΔE of Superbond C&B, RelyX ARC, Variolink Veneer and Tetric Flow were 2.24±0.52, 2.47±0.28, 0.62±0.31 and 0.72±0.31 respectively. The Superbond C&B and RelyX ARC achieved significant higher ΔE than the other groups (P0.05). All of the resin cements assessed in this study show varying degrees of discoloration after accelerated ageing. However, the color change are not beyond the clinical aesthetic demand. And the Tetric Flow and Variolink Veneer demonstrate a higher color stability.

Abstract: To evaluate bond strength of veneering ceramics to a graded zirconia core. Two zirconia core ceramics (Y-TZP and graded zirconia) were fabricated and veneered with IPS e.max Ceram. A metal ceramic system (IPS d.SIGN, Ivoclar Vivadent, Liechtenstein) was used as a control group for the two all-ceramic test groups (n=20). Shear bond strength test and microtensile bond strength test were conducted by a universal testing machine. Fracture surfaces were also evaluated to determine the failure modes. Additionally, one-way ANOVA and Tukey's HSD tests were used to analyze the data. The shear bond strength test and microtensile bond strength test showed the familiar results. Graded zirconia exhibited the highest bond strength value (SBS: 31.01±2.01 MPa, MTBS: 40.95±1.95 MPa), significantly higher than that of Y-TZP (SBS: 28.14±2.28 MPa, 37.99±2.83 MPa). No significant differences were found between the metal core group and the two zirconia core groups. All test groups demonstrated cohesive failure within the veneer, as well as adhesive failure between the core and the veneer. Glass infiltration to zirconia may affect bond strength between zirconia core and veneering ceramics. A graded zirconia glass structure exhibits a benign bond to a veneering ceramics which could be similar to that of a metal ceramic system.

Abstract: The need for bone repair has increased as the population ages. However, currently, the bone grafts still have some disadvantages, such as low compressive strength and porosity, which limit their use. In order to solve these disadvantages, in this study, the porous beta-tricalcium phosphate (β-TCP) anorganic bone graft were prepared from healthy bovine cancellous bone by cell-free, defat and twice calcinations. X-ray diffraction (XRD) was used to investigate the chemical composition of the bone graft. And the morphology, porosity and mechanical strength of the bone graft were also evaluated. The results showed that most constituent of the bone graft was β-TCP. In addition, the bone graft scaffold exhibited the macro and micro porous structure and the porosity was 57.63%, just as the nature cancellous bone. The compressive strength was 4.47±0.63MPa. Above all, the porous β-TCP anorganic bone graft not only has similar chemical composites as the nature cancellous bone, but also it can effectively retain the porous structure of natural cancellous bone and provides optimal channels for the ingrowth of new bone and blood vessels.Therefore, the porous β-TCP anorganic bone graft is a potential biomaterial in bone tissue engineering.

Abstract: The purpose of this study was to compare the transmittance of four dental all-ceramic core materials at clinical recommendation thickness.Specimens with 10mm in diameter and 0.50.01mm in thickness,including IPS e.max Press,Zenostar Zirconia,Lava Zirconia and Upcera Zirconia,were fabricated.The transmittance of specimens were measured with PR2650 spectrophotometer and measurements were analysed statistically with SPSS13.0.Experimental results showed that they had significantly different transmittance.There was a decreasing order,IPS e.max Press Lava Zirconia Zenostar Zirconia Upcera Zirconia,which were 6.1136.750 for IPS e.max,1.6042.135 for Lava Zirconia,1.5782.117 for Zenostar Zirconia and 0.9951.265 for Upcera Zirconia.

Abstract: This study aimed to compare the translucency of four veneered dental all-ceramic core materials,including IPS e.max Press,Zenostar,Lava Zirconia and Upcera Zirconia.All specimens were fabricated at 10mm in diameter and 1.00.01mm in thickness.The translucency of specimens were measured with color difference meter and measurements were statistically analysed with SPSS 13.0. Experimental results showed that their translucency had significant difference,the order of relative translucency from high to low was IPS e.max PressLava ZirconiaZenostarUpcera Zirconia.IPS e.max Press which has good optical effect may be preferable for restoring anterior tooth with higher translucent. As for relatively opaque posterior tooth,Upcera Zirconia may be advisable.

Abstract: In this study, β-Sialon/Al₂O₃/TiN diphase powder was synthesized using low-grade bauxite and rutile via carbothermal reduction-nitridation. The phase transitions of low-grade bauxite and rutile in the carbothermal reduction and nitridation process were analyzed by XRD, SEM and EDS. The effects of different reaction parameters such as reaction temperature, rutile addition on the phase composition and microstructure of products were analyzed. The results showed that β-Sialon/Al₂O₃/TiN powder was prepared using low-grade bauxite and rutile as raw materials and coke as reducing agent by carbothermal reduction-nitridation reaction in flowing nitrogen atmosphere of 0.03 MPa at 1350-1375 °C, for 4 h.

Abstract: A series of Na₅La(WO₄)₄:M³⁺ (M = Eu, Sm, Bi) phosphors have been synthesized successfully by the solid-state reactions. The corresponding crystal structure and lattice parameters were refined by the Rietveld method, and the impact of doped metal ions upon the structure were also studied. The photoluminescent properties were investigated at room temperature. All the samples were observed a strong red emission under 395nm or 465 nm excitation, and the CIE chromaticity coordinates (x = 0.67, y = 0.33) was found to be close to the National Television Standard Committee (NTSC) standard red, implying high color purity. This kind of tungstate phosphor is a promising candidate as the red phosphor for white light-emitting diodes (WLED).

Abstract: Preparing amorphous alloy of Al₈₇Ce₃Ni_10-xCu_x（x=0,1,3,5）with single roller spin quenching technology, after annealing the alloy for 20 minutes at 180 degrees Celsius, 200 degrees Celsius, 220 degrees Celsius and 240 degrees Celsius, and then the nanocomposites can be obtained. he microhardness of amorphous nano-composite materials are measured .The microstructure, grain size of , thermal stability, midrohardness are related with the annealing temperature and the composition of alloy, and studying the relationship between them by X-ray diffraction (XRD) and differential scanning calorimetry (DSC).The present results indicated that with the increase of the content of Cu, the grain size of decreases, the increasing of the microhardness is due to the grain refinement: with the increase of the content of Cu, precipitation temperature of moves to low, which is helpful for the precipitation of phase.

Abstract: A retarded zirconium cross-linking agent ECA-1 was prepared by using zirconium oxychloride, lactic acid， xylitol, and so on, then we got a high-temperature delayed cross-linking acid with cross-linking agent ECA-1 added to EVA-180 gelling acid, cross-linked acid performance and its influencing factors were discussed in details, such as reaction conditions of crosslinker, concentrations of crosslinker and thickener, and so on. The results showed that the obtained cross-linked acid had good temperature-tolerate and shear-tolerate properties when the mass ratio of zirconium oxychloride, lactic acid and xylitol is 1:1.25:0.0208 , the reaction temperature is 50~55°C, the reaction time is 4 hours, the delayed cross-linking time of acid system can be adjusted by changing the dosage of crosslinker and thickener.