Papers by Keyword: Sintering Property

Abstract: In this study, a magnesium oxide partially stabilized zirconia (Mg-PSZ) sample was prepared by granulation, molding, drying, and calcining. MgO was used as stabilizer, along with chemical-and electrofusion-made zirconium dioxide (ZrO₂) powder, as well as a different mixture of the two as the raw material. The effects of material reactivity on the sintering properties of the Mg-PSZ metering nozzle were studied by analyzing the physical properties and microscopic structure of the sample. The results show that, under the same sample preparation conditions, the electrofusion-made ZrO₂ had lower reactivity, resulting in a lower percentage of stable phase, loose adhesion among particles after sintering, more than 20% porosity, and poor antierosion and antiscouring performance. However, electrofusion-made ZrO₂ only had a shrinking percentage of 6%, leading to a higher sintering yield. However, compared with the electrofusion-made ZrO₂, chemical-made ZrO₂ had a higher reactivity, better sintering properties, more stable phase component, and approximately 75% less porosity. Chemical-made ZrO₂, however, had a shrinking percentage as high as 20%, causing serious sample cracking after sintering. Therefore, both types of ZrO₂ are not ideal as the only raw material for Mg-PSZ metering nozzles. Nonetheless, when a 1:1 mixture of the two types of ZrO₂ was used as the raw material, the calcined sample showed better property parameters in porosity and volume density, as well as compressive strength, satisfying the requirements for Mg–PSZ-based metering nozzles.

Abstract: Doped ceria-based (Gd0.2Ce0.8O1.9, GDC) solid electrolytes were prepared by Solid-phase synthesis method. The effect of doping bismuth oxide and samarium oxide on the phase and microstructure of GDC was investigated. The phase composition was analyzed by the X-ray diffraction (XRD).The single cubic fluorite structure was observed after doping these oxides. Appearance and microstructure of doped ceria-based solid electrolytes were analyzed by the scanning electron microscopy (SEM) and the transmission electron microscopy (TEM). The results showed that the doped trivalent cations had entered into the ceria structure uniformly. The density, porosity rate and water absorption of GDC were measured by Archimedes principle. It indicated that the density of doped GDC solid electrolyte increased with the rising of sintering temperature.

Abstract: The influence of conductivity of supernatant of 3Y-TZP powder on the sintering properties of its ceramics is evaluated. It is found that the conductivity of supernatant is helpful for the determination of the sintering activities. The sintering properties of 3Y-TZP ceramics are improved with the increase of the conductivity of supernatant. It is attributed to a large amount of unsaturated states in the powder.

Abstract: Single phase YIG powders were synthesized successfully using Fe2O3 and Y2O3 as starting materials by solid state reaction, and YIG ceramics were prepared by pressureless sintering. The influence of synthesizing temperature and Fe2O3 content on the final production were studied The effect of Fe2O3 content on volume density and microstructure of the sintered YIG was also investigated. The results showed that single phase YIG powders were synthesized by solid state reaction at 1400°C for 3h. When Fe2O3 content was excessive 3 wt%, YIG ceramics with a density of 5.294g·cm-3 was fabricated by sintering at 1480°C for 2.5h.

Abstract: The sintering and electronic conducting properties of La0.8Ca0.2CrO3 synthesized by a glycine-nitrate process (GNP) were investigated in comparison with that synthesized by the conventional solid state reaction (SSR) method. The results demonstrate the advantage of the GNP method in producing La0.8Ca0.2CrO3 ceramic. Compared with the powder synthesized by the SSR method, that synthesized by the GNP method shows a higher sinterability due to its fine morphology. The relative densities of the ceramics made by the GNP and SSR methods attain 96.5 % and 96.0 % when sintering at 1450°C and 1550°C, respectively. In the case of similar relative densities, the ceramic made by the GNP method (sintered at 1450°C) exhibits superior electronic conducting properties to that made by the SSR method (sintered at 1550°C). This is attributed to a desired microstructure of the ceramic made by the GNP method.

Abstract: b-tricalcium phosphate(TCP, Ca3(PO4)2) ceramics are preferred as a bioceramics because of its chemical stability and reasonable degradation rate in vivo, but it is difficult to obtain b-TCP ceramics with high compressive strength at lower temperature than that of phase transition to a-TCP. In this study, the sintering behavior of TCP, Ca2P2O7-doped TCP, and CaCO3-doped TCP in the range of 2wt%~5wt% were investigated respectively. Phase transition of pure TCP took place between 1100°C to 1150°C, and pure b-TCP ceramics could achieve a compressive strength of only 3MPa. However, calcium pyrophosphate (CPP, Ca2P2O7) additive prevented the transformation of b-TCP to a-TCP, but the second phase of CPP was observed in the resultant ceramics. Phase transition of TCP ceramics by addition of both CPP and calcium carbonate (CC, CaCO3) took place between 1200°C to 1250°C and the resultant TCP ceramics had few impurity of CPP. By adding CPP and CC to TCP, final ceramics with compressive strength over 12MPa could be obtained when sintered at 1200°C for 2hrs.