Preparation of Functionally Gradient Ceramics by Forming a Series of Solid Solutions

通过形成一系列固溶体制备功能梯度陶瓷

• 批准号: 05650655
• 负责人: OTA Toshitaka
• 金额: $ 1.34万
• 依托单位: Nagoya Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05650655/
• 关键词: Functionally Gradient Materials; Ceramics; Thermal Expansion; Nepheline; Solid Solution; Lead Titanate; Dielectric Constant

Thermal expansions of ordinary ceramics are generally lower than those of metals. So, in composite materials composed of ceramic and metal, a stree is developed by the thermal expansion mismatch, and then the composite sometimes breaks up. In order to avoid thisfailure, there is a new technique to use functionally gradient materials (FGM), which is characterized by the material having a continuously varying property from one surface to the other. Such a material is prepared by forming a pile of composite layrs composed of ceramic and metal having the pre-determined compositional distribution. In this study, a FGM was prepared by forming a series of solid solutions in a single ceramic body. First, a FGM with respect to thermal expansion was prepared from nepheline solid solutions (Na_<1-x>M_xAlSiO_4 : M=Li and K). By sintering green-compact layrs composed of NaAlSiO_4 powder and {(1-x)NaAlSiO_4 + xMAlSiO_4 (M=Li and K)} mixed powder, they bonded together to form a gradient solid solution, which compositon continuously varied with the distance from the interface. Nepheline solid solutions had high thermal expansion coefficients equal to those of metals. The thermal expansion coefficient decreased from 1.6x10^<-5>/ﾟC for x=0 to 1.2x10^<-5>/ﾟC for x=0.15 in Na_<1-x>Li_xAlSiO_4, and increased to 1.8x10^<-5>/ﾟC for x=0.43 in Na_<1-x>K_xAlSiO_4 with increasing x. Consequently, the thermal expansion coefficient of the gradient solid solutions should gradually vary with position according to the composition of solid solution. Second, a FGM with respect to electrical properties was investigated. A series of PbZr_xTi_<1-x>O_3 solid solutions was formed in a single ceramic body by sintering layred compacts of PZT (A) and PZT (B) in contact with each other, where Zr and Ti diffused each other. The dependence of dielectric constant on temperature decreased for the sample with gradient solid solution.

普通陶瓷的热膨胀通常低于金属。因此，在由陶瓷和金属组成的复合材料中，由于热膨胀不匹配而产生应力，有时复合材料会破裂。为了避免这种失败，出现了一种使用功能梯度材料（FGM）的新技术，其特点是材料从一个表面到另一个表面具有连续变化的特性。这种材料是通过形成一堆由具有预定成分分布的陶瓷和金属组成的复合层来制备的。在这项研究中，通过在单个陶瓷体中形成一系列固溶体来制备 FGM。首先，由霞石固溶体(Na_1-xM_xAlSiO_4：M＝Li和K)制备关于热膨胀的FGM。通过烧结由NaAlSiO_4粉末和{(1-x)NaAlSiO_4 + xMAlSiO_4(M=Li和K)}混合粉末组成的生坯层，它们结合在一起形成梯度固溶体，其组成随着距界面的距离而连续变化。霞石固溶体具有与金属相同的高热膨胀系数。随着x的增加，Na_<1-x>Li_xAlSiO_4中的热膨胀系数从x=0时的1.6x10^<-5>/ﾟC降低到x=0.15时的1.2x10^<-5>/ﾟC，并且随着x的增加，Na_<1-x>K_xAlSiO_4中x=0.43时的热膨胀系数增加到1.8x10^<-5>/ﾟC。因此，梯度固溶体的热膨胀系数应根据固溶体的成分随位置逐渐变化。其次，研究了 FGM 的电性能。通过烧结相互接触的PZT(A)和PZT(B)的层状压块，在单个陶瓷体中形成一系列PbZr_xTi_<1-x>O_3固溶体，其中Zr和Ti相互扩散。对于具有梯度固溶体的样品，介电常数对温度的依赖性降低。