Mass Transport and Thermodynamics at the Interface in the High-Temperature Metal/Ceramics Composites

Metals/ceramics composites are the promising materials for structure application at highTypical materials are superalloys with ceramic coatings，metallic参数dispersion ceramic matrix composites与数学相关的知识结构。and metals has chemically and mechanically different feature from each bulk material.The objectivepresent research is the interface between ceramics and metals is generalized as a basisof the thermodynamics and transport phenomena to discuss the chemical stability of the interface.两个不同的主题是通用的interfacial phenomena一个是measurements of thermodynamic properties and diffusion coefficient of the complex oxides which arethe products at the interface. Another is high temperature oxidation at the interface between oxideceramics and metals.(1) Thermodynamic properties and diffusion coefficient of the complex oxidesPe……More rovskite类型chromites (ABO - D23 - D2) are focused in the present work. They haveimportant role at the interface between Cr - D22 - D2O - D23 - D2 scale and alloy to improve the scaleadhesion With respect to the thermodynamic propertiesstandard Gibbs energy change of formation， ΔG°，on NdCrO D23 was determined by measuring the electroconductivities of the different two-phasesamples,NdCrO - D23 - D2 with Cr - D22 - D2O - D22 - D2 and D22 - D2O - D23 - D2. As compared with the reportedones of YCrO - D23 - D2 and LaCrO - D23 - D2the value of ΔG°is consistent in the relationship between ΔG°and ionic radius of A ion.Diffusioncoefficients of A ions in LaCrO D23 - D2 and NdCrO D23 - D2 was determined by the solid state反应技术。Discussed their diffusion coefficients with the reported value of Y ion inYCrO - D23 - D2，absolute values可以explained with the concentration of A site vacancy. the activation energydepends on the ionic radius of A ions.In order to compare with their chromitesdiffusion coefficient of Ba ion in BaTiO D23 D2 is same method. the values ofBaTiO D23 D2 is very similar to their chromites. Diffusion coefficient of A ion in the perovskiteoxides has little dependence of the valances of a and b ions .(2) high temperature oxidation at theoxide ceramics和metalsOxidation of Ni covered by oxide ceramicsD22 D2O D23 D23 D2-stabilized ZrO D22 D2 (YSZ) is investigated in this work. The one dimensional模型of the oxidation kinetics is established to assume that flux of O伊D12- YSZ is equalD12+ D1 in the NiO scale. in order to verify the kinetic model，the oxidation rate and oxygen partial pressure at the interface were investigated on the close cellwith YSZ thin plate including Ni in the inside. the experimental results are in agreement with thekinetic model. The life design of The interface of The ceramic coating on The metals and metalparticle dispersion ceramics matrix composite可以启用as a basis of the kinetic model. Less

Metals/ceramics composites are the promising materials for structure application at high temperatures. Typical materials are superalloys with ceramic coatings, metallic particles dispersion ceramic matrix composites, and functionally gradual materials comprised of ceramics and metals. The interface between ceramics and metals has chemically and mechanically different feature from each bulk material.The objective of the present research is that the interface between ceramics and metals is generalized as a basis of the thermodynamics and transport phenomena to discuss the chemical stability of the interface. Two different topics are carried out to generalize the interfacial phenomena. One is the measurements of thermodynamic properties and diffusion coefficient of the complex oxides which are the products at the interface. Another is high temperature oxidation at the interface between oxide ceramics and metals.(1) Thermodynamic properties and diffusion coefficient of the complex oxidesPe … More rovskite type chromites (ABOィイD23ィエD2) are focused in the present work. They have important role at the interface between CrィイD22ィエD2OィイD23ィエD2 scale and alloy to improve the scale adhesion. With respect to the thermodynamic properties, the standard Gibbs energy change of formation, ΔG°, on NdCrOィイD23ィエD2 was determined by measuring the electroconductivities of the different two-phase samples, NdCrOィイD23ィエD2 with CrィイD22ィエD2OィイD22ィエD2 and NdィイD22ィエD2OィイD23ィエD2. As compared with the reported ones of YCrOィイD23ィエD2 and LaCrOィイD23ィエD2, the value of ΔG°is consistent in the relationship between ΔG°and ionic radius of A ion.Diffusion coefficients of A ions in LaCrOィイD23ィエD2 and NdCrOィイD23ィエD2 was determined by the solid state reaction technique. Discussed their diffusion coefficients with the reported value of Y ion in YCrOィイD23ィエD2, the absolute values can be explained with the concentration of A site vacancy. The activation energy depends on the ionic radius of A ions.In order to compare with their chromites, diffusion coefficient of Ba ion in BaTiOィイD23ィエD2 is also measured by the same method. The values of BaTiOィイD23ィエD2 is very similar to their chromites. Diffusion coefficient of A ion in the perovskite oxides has little dependence of the valances of A and B ions.(2) High temperature oxidation at the interface between oxide ceramics and metalsOxidation of Ni covered by YィイD22ィエD2OィイD23ィエD2-stabilized ZrOィイD22ィエD2 (YSZ) is investigated in this work. The one dimensional model of the oxidation kinetics is established to assume that flux of OィイD12-ィエD1 in YSZ is equal to one of NiィイD12+ィエD1 in the NiO scale. In order to verify the kinetic model, the oxidation rate and oxygen partial pressure at the interface were investigated on the close cell with YSZ thin plate including Ni in the inside. The experimental results are in agreement with the kinetic model. The life design of the interface of the ceramic coating on the metals and metal particle dispersion ceramics matrix composite can be enable as a basis of the kinetic model. Less