Papers by Keyword: Sintering

Abstract: One of the most promising technologies for future applications of solide oxide fuel cells (SOFC)is the so-called “anode-supported” configuration: a dense yttria-stabilised zirconia (YSZ) ceramic electrolyte is deposited as a thin film over a porous Ni / YSZ cermet substrate anode, followed by a porous ceramic cathode such as La1-xSrxMnO3 (LSM). In this paper, a short review is made of the current technologies available to achieve this particular architecture, and to optimise the service behaviour. Then, alternative materials and fabrication technologies, as well as their possible impact on performance, are proposed and investigated.

Abstract: The effects of Bi3+ addition on the sintering performance and microstructural evolution of cordierite were analyzed in this paper. Cordierite powders were prepared by sol-gel processing. As nucleating agent, the Bi3+ additive was found to promote the phase transition from µ-cordierite to α-cordierite and decrease sintering temperatures. The effect of Bi3+ on the activation of cordierite can be attributed to the nucleation of cordierite. The doping of Bi3+ increased the expansion coefficient and dielectric constant. Too much Bi3+ will inhibit the cordierite crystallization and encourage anorthite crystallization.

Abstract: BaCe0.9Y0.1O3-a and SrCe0.9Y0.1O3-a powders were synthesized by both the solid-state reaction method and the liquid citrate method. The shrinkage, porosity and relative density of membranes prepared from these powders were determined, after sintering at 1550°C (BaCe0.9Y0.1O3-a membrane) or 1450°C (SrCe0.9Y0.1O3-a membranes) for 3 hours. The XRD patterns show that the crystal structures of the prepared powders and the sintered membranes are orthorhombic perovskite structures. The membranes prepared from the powders synthesized by the solid-state reaction method are denser than those from the powders synthesized by the citrate method with the same composition under the identical sintering conditions.

Abstract: Ni/BaTiO3 composite was prepared by decomposition of NiC2O4·2H2O/BaTiO3 precursor, which was prepared by precipitating of nickel in the form of oxalate into the BaTiO3 slurry. The composite must be sintered in reducing atmosphere. Otherwise NTC effect would be introduced. The prepared composite almost had no PTC effect. But PTC effect of the Ni/BaTiO3 composite can be effectively renewed by heat-treatment in air. Under a proper composition and method, the composite shows low room-temperature resistivity (ρRT=6.0 Ω·cm) and obvious PTC effect (ρmax/ρmin=102).

Abstract: To achieve improvements in the mechanical properties, fine grain size, homogeneous microstructure and high density are desirable. The poor dispersion of the powders produce difficulties in the densification and the presence of agglomerates is responsible for poor mechanical properties. Slurry casting is an important colloidal processing method for the ceramic industry and helps to prevent the agglomeration of fine particles. In the present study, the effect of processing parameters, namely solid content, dispersing agent concentration, slurry viscosity and milling time on slurry casting of 8YSCZ ceramics were investigated and optimum values were determined. The results showed that ceramic powder used was castable under limited conditions. The effect of shaping processon sintering behaviour and microstructure was also investigated for slurry-cast and die-pressed specimens. The results showed that specimen processed by slurry-casting had a faster sintering rate and lower sintering temperatures, compared to die-pressed specimen. The reason for better sintering was due to the homogeneous dispersion of the powder and elimination of agglomerates in slurry-cast specimen.

Abstract: The paper tries to prepare dense piezoceramics by way of reactive liquid phase sintering. Technique concerning a low-temperature sinterable process is developed by incorporating 4PbO×B2O3. The host system is a perovskite type piezoceramic, Pb(Ti,Zr)O3. If small amounts of 4PbO.B2O3 glass powder are added to the calcined Pb(Ti,Zr)O3 ceramics, the liquid phase is formed during sintering. Hence, the piezoelectric and dielectric properties are enhanced and the sintering temperature can be reduced. The value of the kp, KT 33 and Qm is increased and dielectric loss tangent is decreased when a small amounts of 4PbO.B2O3 dopant (i.e. 0.2 wt%) are added to the PZT system. With more 4PbO.B2O3 doping (i.e. 2 wt%), the value of the kp and KT 33 is decreased due to the glassy phase segregation at the grain boundary.

Abstract: The dielectric properties and sintering activity of nano-BaTiO3 powders synthesized by HGRP method were investigated. The starting BaTiO3 powders were calcined at different temperatures from 700 to 900°C to improve their crystallinity and the mean particle size of BaTiO3 powders obtained increased from 40nm to 80nm. After being formed by conventional dry pressing the green bodies were sintered at 1100°C and 1200°C for 2hr in air. The effects of both calcinating and sintering temperatures on the sinterability, dielectric property and microstructure of BaTiO3 ceramics were discussed. The experimental results showed that the BaTiO3 powders have high sintering activity and the highest dielectric constant of this material at room temperature may reach 2880.

Abstract: The influences of temperature and time on sintering behaviour of nanosized HAP powder were investigate in this paper. The calcium hydroxyapatite powder, with the average crystallite size of 34 ± 1 nm, was uniaxially pressed at a pressure of 500 MPa. Obtained green compacts were sintered at temperature ranging from 1000°C to 1200°C in air atmosphere at various times. According to the results of scanning electron microscopy, X-ray and FTIR analyses, it is shown that HAP compacts with dense microstructure and average grain size below 250 nm is obtained.

Abstract: Composite biomaterials of calcinated bovine bone derived hydroxyapatite (HA) doped with 5 and 10 wt% commercial inert glass (CIG) were prepared by sintering. The production of HA from natural sources satisfies economic and time-saving aims, while the use of CIGs is directed by economic and ecological aspects. The produced composites were subjected to scanning electron microscopy (SEM) and X-ray diffraction analysis. Measurements of compression strength, microhardness, and density were also carried out. The experimental results and their discussion showed that the type and the composition of incorporated glass are of crucial importance. Consequently, provided that an optimum amount of glass is incorporated, the resultant materials can exhibit good values of compression strength and microhardness and hence they can be suggested for potential use in load-bearing biomedical applications.

Abstract: fabricated by pressureless sintering process. The effect of BG on the sintering ability and mechanical strength of the ceramics, and the adhesion and proliferation of osteoblasts were investigated. The results showed that the optimum amount of BG was 20wt.% and the samples sintered at 1100oC for 5h revealed a bending strength of 172 MPa, which was approximately 2-times higher than that of the pure CaSiO3 ceramics. The cell experiments showed that BG reinforced CaSiO3 ceramics supported osteoblast adhesion and possessed higher proliferation than that of the pure CaSiO3 ceramics, which indicated excellent biocompatibility. Our results suggested that BG reinforced CaSiO3 ceramics could be potential candidates as bioactive bone implant materials.