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首页> 外文学位 >Effect of Electric Field on the Processing and Properties of Yttria-stabilized Zirconia (YSZ).
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Effect of Electric Field on the Processing and Properties of Yttria-stabilized Zirconia (YSZ).

机译：电场对氧化钇稳定的氧化锆（YSZ）的加工和性能的影响。

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摘要

It is well-known that the processing and properties of polycrystalline ceramics are grain size dependent; the grain size is usually controlled by thermo-mechanical treatments and the addition of solutes. More recently, application of an electric field has been found to retard grain growth and in turn influence the annealing, sintering and plastic deformation rate of ceramic materials. Moreover, it is well-established that the bulk conductivity of polycrystalline ceramics decreases with decrease in grain size.;This research deals with the effect of an applied electric field on the processing and properties of 3 mole percent yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP), whereby DC and AC fields were applied during sintering and isothermal annealing of 3Y-TZP. Regarding sintering, it was found that grain growth during sintering was retarded with the application of electric field compared to without. The ratio of the grain size with field to that without d¯E/d¯ decreased with increase in field strength up to ∼ 26 V/cm and then remained constant with further increase in field strength to ∼ 60 V/cm, the transition occurred at the ratio of d¯E/d¯ = 0.4. It was further found that an AC field had a greater effect on grain growth retardation compared to DC. In the isothermal annealing study a modest DC field with an initial strength of 14 V/cm was applied during the isothermal annealing at 1300 °C and 1400 °C. It was again found that the grain growth rate was retarded by the field.;SEM micrographs showed that the grains were tetrakaidecahedral in shape and essentially isotropic both with electric field and without. The grain size distribution was consistent with the Bitti-Di Nunzio model for both fully sintered and isothermally annealed conditions, which gives that the entire size distribution shifted to a smaller grain size. The retardation of grain growth rate was attributed to a reduction in grain boundary energy by the interaction of the applied electric field with the space charge at the grain boundary.;Physical models are proposed for the magnitudes of the GB energy components, namely electrostatic (space charge) gammabe, crystallographic mismatch (bSigma) and the ionic size misfit (bs) components. It was determined that the former two components combined comprised 40% of the total grain boundary energy in 3YSZ and the electrostatic component 60%. The reduction in be by electric field is considered to result from the bias exerted by the applied field on the space charge potential that occurs with the segregation of the yttrium ions at the grain boundaries, and is proposed to be the major factor responsible for the retardation of grain growth in 3YSZ by an electric field.;The electrical conductivity of 3 Y-TZP was investigated during the sintering and annealing processes. It was found that the bulk resistivity rho O increased with applied field E to ∼ 20-25 V/cm and then becomes relatively independent of E with further increase to ∼ 65-70 V/cm. The bulk resistivity with ac field rhoO(AC) was greater than that with dc rhoO(DC) at all but the highest sintering temperatures. Employing with brick layer model, the grain boundary resistivity rho b was 131 O-cm and 114 O-cm at 1300 °C and 1400 °C, respectively, and in turn gave the ratio of rho b/rhog(resistivity of the grain interior) =257 and 124, which are in good accord with the results obtained by impedance spectroscopy (IS) and 4-probe method. The value of rho b obtained was 173O-cm and 128 O-cm at 1300 °C and 1400 °C respectively, taking that the observed increase in bulk resistivty rho O with applied field strength E results from the corresponding decrease in grain size.
机译：众所周知，多晶陶瓷的加工和性能是取决于晶粒尺寸的。通常通过热机械处理和添加溶质来控制晶粒尺寸。最近，发现施加电场会延迟晶粒的生长，进而影响陶瓷材料的退火，烧结和塑性变形速率。此外，众所周知，随着晶粒尺寸的减小，多晶陶瓷的整体电导率会降低。;本研究研究了施加电场对3摩尔％氧化钇稳定的四方氧化锆多晶（3Y -TZP），从而在3Y-TZP的烧结和等温退火过程中施加DC和AC场。关于烧结，发现与没有烧结相比，在施加电场的情况下，烧结期间的晶粒生长受到阻碍。随磁场强度的增加，晶粒尺寸与无déE/ d的比值随磁场强度的增加而降低，直至〜26 V / cm，然后随着磁场强度的增加而保持恒定，直至〜60 V / cm，过渡发生了。 d / E / d = 0.4进一步发现，与直流相比，交流电场对晶粒生长延迟的影响更大。在等温退火研究中，在1300°C和1400°C的等温退火过程中施加了初始强度为14 V / cm的适度DC场。再次发现，该场阻碍了晶粒的生长速度。SEM显微照片显示，该晶粒为四十二面体形状，并且在有电场和无电场的情况下均具有各向同性。在完全烧结和等温退火条件下，晶粒尺寸分布均与Bitti-Di Nunzio模型一致，这使整个尺寸分布移至较小的晶粒尺寸。晶粒生长速率的延迟归因于外加电场与晶界处空间电荷的相互作用而降低了晶界能量。；针对GB能量分量的大小，即静电（空间），建立了物理模型电荷）伽马射线，晶体学失配（bSigma）和离子尺寸失配（bs）成分。可以确定，前两个成分合计占3YSZ中总晶界能的40％，而静电成分占60％。电场引起的be的减少被认为是由于外加电场对晶界处钇离子的偏析而产生的空间电荷电势的影响，因此被认为是造成延迟的主要原因。通过电场对3YSZ晶粒的生长进行了研究。在烧结和退火过程中研究了3 Y-TZP的电导率。已经发现，随着施加的电场E，体电阻率rho O增大到〜20-25 V / cm，然后变得相对独立于E，并进一步增大到〜65-70 V / cm。除最高烧结温度外，交流场rhoO（AC）的体电阻率均大于直流rhoO（DC）的体电阻率。采用砖模型，在1300°C和1400°C下，晶界电阻率rho b分别为131 O-cm和114 O-cm，进而得出rho b / rhog之比（晶粒内部电阻率） ）＝ 257和124，这与通过阻抗谱（IS）和四探针法获得的结果非常吻合。假定在1300°C和1400°C下得到的rho b值分别为173O-cm和128 O-cm，这是由于观察到的随电阻场强E增大的体电阻率rho O的增加是由晶粒尺寸的相应减小引起的。

著录项

  • 作者

    Wang, Jun.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Engineering Materials Science.;Nanoscience.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 139 p.
  • 总页数 139
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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