Papers by Keyword: CaZrO₃

Abstract: Lead-free piezoelectric ceramics of (1-x)(K_0.5Na_0.5)NbO₃ - xCaZrO₃ (abbreviated as KNN-CZ, x = 0 ~ 0.04) were synthesized by the conventional solid state method. Their phase structures and piezoelectric properties were investigated with x-ray diffraction (XRD), Scanning Electron Microscope (SEM), d₃₃ meter and Impedance Analyzer. KNN-CZ samples exhibit only pure perovskite phases with a small monoclinic distortion. It was observed that the lattice parameter b has a maximum at x = 0.02 but the monoclinic distortion angle β shows a minimum at the same composition. From the dependence of the lattice parameters (a, b, c, β) and cell volume on the content of CZ, it is considered that the intermediate phase transition exists near at x = 0.02. Piezoelectric properties show the maximum value of d33 = 121 pC/N and kp = 0.35 for the sample with x = 0.02, which seems to be due to the co-existence of the two different phases.

Abstract: Through Mechanical grounding method, CaZrO₃ – 8YSZ(8% in mol yttria stabilized zirconia) electrolyte samples with different amounts of CaZrO₃ at 10wt%, 20wt%, 30wt% were sintered at different temperatures in Muffle furnace. The decomposition temperature of CaZrO₃ is 825°C-900°C under one atmosphere. At high temperature, CaZrO₃ decomposes into CaO and ZrO₂. So Y₂O₃-CaO-ZrO₂ complex is composed. The effects of the sintering temperature and the contents of the CaZrO₃ on the conductivity, porosity, flexure strength, hardness were investigated. XRD and SEM were used to analyse the compositions and microcosmic morphology.

Abstract: Aiming at flexible oxidation in the MLCC production, the surface modification of the ultrafine nickel powders has been carried out to coat Ni powders with CaZrO3 by using chemical precipitation method. CaZrO3-coated composite ultrafine nickel powders have been synthesized in methanol-water solvent by both precipitation agents solution and zirconium-calcium solution dripped into the Ni-particle-dispersed methanol solution at the meantime. Composite nickel powders obtained under the optimum conditions were characterized, It was approved that those composite nickel powders still possessed good dispersion, the resistance to oxidation and shrinkage were improved greatly.

Abstract: Eddy current as a non-destructive technique has been used for evaluation of thermal barrier coatings (TBCs) system. In this study the TBCs system which consists of substrate material of stainless steel 316, Ni-20Cr as a bond coat and top coat of CaZrO₃ was produced by air plasma spraying technique. Isothermal treatment of TBCs system was performed and its effect on the microstructures and oxide formation was investigated. The chromium oxide formation as a function of temperature and time was observed. The observed changes in microstructure and formation of chromium oxide were then correlated with variation in eddy current values.

Abstract: Thermal barrier coatings (TBCs) are multilayered coatings having the complex structure. In thermal spray coatings characteristic features of deposited molten particle and its microstructure is very important in defining coating properties. In this work stainless steel (AISI 316) was used as substrate material on which bond coat of Ni-20Cr and top coat of CaZrO₃ were deposited by air plasma spraying method. Effect of isothermal treatment on the internal microstructure structure of lamella (splat) and phase changes in CaZrO₃ coating was studied. The fractured surface of coatings was investigated to observe the splat morphology. It was observed that the nanocrystallites present within the splat grew with increase in temperature. Further, the monoclinic phase was formed as function of temperature and time.

Abstract: The synthesizing CaZrO₃ are prepared with fused zirconia powder (0.044mm), monoatomic zirconia powder (0.044mm), desilication zirconia powder (0.044mm) and calcium oxide powder (0.044mm). The effect of different moulding pressure and firing temperature on synthesizing CaZrO₃ has been studied in this paper. The test results show that: The impurity composition SiO₂ and Al₂O₃ in raw material have participated in reaction, and generated liquid, accelerated transmission quality speed of reaction. Desilication ZrO₂ is the best ZrO₂ raw material to synthesizing CaZrO₃ in above three ZrO₂ raw materials, firing temperature markedly influence the synthetic rate of CaZrO₃, but moulding pressure is not this. Desilication ZrO₂ and CaO as raw material, firing 1600°C for 3h, pressure at 160Mpa and one stage burning process are the best technical conditions to synthesize CaZrO₃.

Abstract: The mechanical behaviour of ceramic refractories formulated in the MgO-CaO-SiO2- ZrO2 system is analysed in terms of the room temperature Young´s modulus, the modulus of rupture and the work of fracture at 25 and 1100°C. The materials have been designed taking into account the phase equilibrium relationships to obtain MgO-CaZrO3-Ca2SiO4-Ca3Mg(SiO4)2 or MgO-CaZrO3-Ca3Mg(SiO4)2-c-ZrO2 as final crystalline phases. Different relationships between the proportion and sizes of the fines and the aggregates have been explored. The microstructure of the materials has been characterised in terms of density, crystalline phases and phase distribution and morphology. A combination of X-Ray diffraction (XRD) analyses and Reflected Light Optical Microscopy (RLOM) has been used. The relationships between the obtained phases and microstructures and the grain size distributions of the used raw materials have been established. The relationships between the mineralogical composition and the obtained microstructure and the mechanical behaviour are discussed.

Abstract: The CaZrO3 complex oxide ceramic was synthesized in the development of the potential refractory for melting of titanium alloy, the crucible ( 40XH40mm) was prepared by the solid sintering of mixture of powder (CaO:ZrO2 =1:1) with a small amount of TiO2 as additive at 1750°C. The melting of TiNi and Ti6Al4V was carried out in the inducting furnace under vacuum or/and Ar atmosphere. The interfacial reaction between the melts of alloys and CaZrO3 refractory was investigated by scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS). It is found that, the thickness of interfacial reaction layer between the ceramic CaZrO3 and the melt of titanium alloys (TiNi and Ti6Al4V) is approximately 30-300 μm, there are few elements such as Ca, Zr, Ti, and Ni diffused through the interfacial reaction layer. These results may provide the basement to designing a novel refractory for melting of titanium alloys.

Abstract: Fine powder of CaZrO3 (CZ) was synthesized by using ultra-fine and highly dispersed CaCO3 as a precursor. The results showed that the calcination temperature could be reduced to inhibit grain growth of CZ. Mean grain size of the CZ fine powder was 80 nm. Moreover, the CZ powder was used to synthesize a solid solution of (Ba,Ca)(Zr,Ti)O3 (BCZT) to examine the effect of the powder’s grain size on the reactivity of BT and CZ. It was found that the fine CZ powder enhanced the BT and CZ reaction.