Grain Growth Behavior of Al2O3-ZrO2 with a Small Amount of Zirconia

2007 ◽  
Vol 561-565 ◽  
pp. 535-538 ◽  
Author(s):  
M. Nagashima ◽  
Motozo Hayakawa
Keyword(s):  
Growth Inhibition ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Growth Behavior ◽  
Pinning Effect ◽  
Grain Growth Behavior ◽  
Good Agreement ◽  
Zirconia Content

Grain growth behavior in Al2O3 with a small amount of ZrO2 (< 5 vol%) was examined. Grain growth of Al2O3 was retarded by zirconia particles, despite the small amount of added zirconia. The fraction of the zirconia particles embedded within alumina grains (intragranular zirconia particles) increased with decreasing zirconia content and increasing sintering temperature. Grain growth inhibition of alumina in the Al2O3-ZrO2 showed good agreement with the prediction of modified Zener’s pinning effect by the zirconia particles on grain boundaries.

Grain growth behavior of a nanostructured 5083 Al–Mg alloy

2001 ◽  
Vol 16 (4) ◽  
pp. 938-944 ◽  
Author(s):  
V. L. Tellkamp ◽  
S. Dallek ◽  
D. Cheng ◽  
E. J. Lavernia
Keyword(s):  
Activation Energy ◽  
Stress Relaxation ◽  
Low Temperature ◽  
Grain Boundaries ◽  
Relaxation Process ◽  
Grain Growth ◽  
Alloy Powder ◽  
Growth Behavior ◽  
Mg Alloy ◽  
Grain Growth Behavior

A nanostructured 5083 Al–Mg alloy powder was subjected to various thermal heat treatments in an attempt to understand the fundamental mechanisms of recovery, recrystallization and grain growth as they apply to nanostructured materials. A low-temperature stress relaxation process associated with reordering of the grain boundaries was found to occur at 158 °C. A bimodal restructuring of the grains occurred at 307 °C for the unconstrained grains and 381 °C for the constrained grains. An approximate activation energy of 5.6 kJ/mol was found for the metastable nanostructured grains, while an approximate activation energy of 142 kJ/mol was found above the restructuring temperature.

High Barrier Effects of (0001)|(0001) Zinc Oxide Bicrystals: Implication for Varistor Ceramics with Inversion Boundaries

2005 ◽  
Vol 20 (8) ◽  
pp. 2101-2109 ◽  
Author(s):  
Jong-Sook Lee ◽  
Joachim Maier
Keyword(s):  
Zinc Oxide ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Growth Behavior ◽  
Impurity Effects ◽  
Barrier Effects ◽  
Zno Varistor ◽  
Grain Growth Behavior ◽  
Superior Property ◽  
Strong Barrier

Inversion boundaries (IBs) of a head-to-head or (0001)|(0001) (C+|C+) configuration bisect virtually every grain in typical commercial ZnO varistor ceramics. They are most often considered electrically inactive, and the effect on the grain growth behavior has been recently addressed. In this work, various configurations of ZnO bicrystals were prepared using different source crystals and strong barrier effects were observed in some (0001)|(0001) (C−|C−) bicrystals using crystals with higher impurity contents. The crystallographic polarity and impurity effects were systematically examined by doping C+|C+ and C−|C− bicrystals with single and double additives of Mn, Co, Ni, and Bi. Varying degrees of barrier effects including varistor-like behaviors were observed in C−|C− bicrystals depending on dopants, while C+|C+ bicrystals consistently exhibited negligible effects. Because the IBs in ZnO varistor ceramics preferentially expose C− surfaces in the grain boundaries, the superior property of commercial ZnO varistor ceramics is suggested to be assisted by the presence of IBs.

Grain Boundary Segregation-Induced Phase Transformation and Grain Growth in Y2O3-Stabilized ZrO2 Polycrystals

2014 ◽  
Vol 616 ◽  
pp. 8-13
Author(s):  
Koji Matsui ◽  
Hidehiro Yoshida ◽  
Yuichi Ikuhara
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Boundary Segregation ◽  
Growth Behavior ◽  
Grain Boundary Segregation ◽  
Transmission Electron ◽  
Grain Growth Behavior

We systematically investigated the phase transformation and grain-growth behaviors during sintering in 2 and 3 mol% Y2O3-stabilized tetragonal ZrO2 (2Y and 3Y) and 8 mol% Y2O3-stabilized cubic ZrO2 polycrystals (8Y). In particular, grain-boundary segregation and grain-interior distribution of Y3+ ions were examined by high-resolution transmission electron microscopy (HRTEM)- and scanning transmission electron microscopy (STEM)-nanoprobe X-ray energy dispersive spectroscopy (EDS) techniques. Above 1200°C, grain growth during sintering in 8Y was much faster than that in 2Y and 3Y. In the grain boundaries in these specimens, amorphous layers did not present; however, Y3+ ions segregated at the grain boundaries over a width of about 10 nm. The amount of segregated Y3+ ions in 8Y was significantly less than in 2Y and 3Y. This indicates that the amount of segregated Y3+ ions is related to grain growth behavior; i.e., an increase in segregated Y3+ ions retards grain growth. Therefore, grain-growth behavior during sintering can be reasonably explained by the solute-drag mechanism of Y3+ ions segregating along the grain boundary. In 2Y and 3Y, the cubic-phase regions were formed in grain interiors adjacent to the grain boundaries and/or the multiple junctions in which Y3+ ions segregated, which can be explained by a grain boundary segregation-induced phase transformation (GBSIPT) mechanism.

scholarly journals Microstructure and Magnetic Properties of La-Ca-Co Substituted M-Type Sr-Hexaferrites with Controlled Si Diffusion

2020 ◽  
Vol 10 (21) ◽  
pp. 7570
Author(s):  
Kyoung-Seok Moon ◽  
Pyeong-yeol Yu ◽  
Young-Min Kang
Keyword(s):  
Grain Growth ◽  
Sintering Temperature ◽  
Material Design ◽  
Bimodal Distribution ◽  
Growth Behavior ◽  
Diffusion Behavior ◽  
Grain Growth Behavior ◽  
Type Lattice ◽  
Cell Volumes ◽  
Microstructure And Magnetic Properties

La-Ca-Co substituted M-type Sr-hexaferrites (Sr0.3Ca0.4La0.3Fe9.8Co0.2O19-δ) were prepared by a solid-state reaction using two different procedures, where the SiO2 additive was mixed either before calcination (pre-Si) or after calcination (post-Si). At the same sintering temperature, smaller cell volumes and reduced saturation magnetization (Ms) values were obtained for samples processed with the pre-Si method than those with the post-Si method. This implied that the pre-Si method resulted in a greater degree of Si substitution into the M-type lattice and increased Fe extrusion out of the lattice. The grain growth behavior was controlled by the SiO2 amount and sintering temperature. It was found that abnormal grains occur with a bimodal distribution in the 0.5 wt% SiO2 samples sintered at 1240 °C, due to the increased critical driving force for growth caused by an increased amount of SiO2 addition. The Ms and coercivity values were altered with the control of Si diffusion and abnormal grain growth. The control of the additive diffusion behavior is one of the important keys in the material design under same materials compositions.

Development of Abnormal Grain Growth in Cold Rolled and Recrystallized AA 5182 Sheet

2006 ◽  
Vol 116-117 ◽  
pp. 316-319 ◽  
Author(s):  
Han Gil Suk ◽  
E.J. Shin ◽  
Moo Young Huh
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Growth Behavior ◽  
Abnormal Grain Growth ◽  
Annealing Temperatures ◽  
Cold Rolled ◽  
Grain Growth Behavior

Grain growth in the cold rolled and subsequently recrystallized AA 5182 sheets was investigated by means of microstructure observations and texture measurements. Grain growth behavior strongly depends on the annealing temperatures. Grain growth hardly took place at temperatures lower than 470°C, which is attributed to a low mobility of grain boundaries. Abnormal grain growth occurred at temperatures ranging from 480 to 530°C. Annealing above 560°C gave rise to the dissolution of inhibitor precipitates, which led to normal grain growth.

Grain Growth Behavior and Characteristics of Multiphase Ceramic Composites Fabricated by Organic-Inorganic Solution Technique

2007 ◽  
Vol 558-559 ◽  
pp. 1249-1253
Author(s):  
Sang Jin Lee
Keyword(s):  
Polyethylene Glycol ◽  
Flexural Strength ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Ceramic Composites ◽  
Milling Process ◽  
Growth Behavior ◽  
Solution Technique ◽  
Polymeric Carrier ◽  
Grain Growth Behavior

Multi-component ceramic composites consisting of two, three and four phases, based on duplex microstructures of zirconia and alumina, were fabricated by a polymer complexation route employing polyethylene glycol (PEG) as a polymeric carrier. The polymer complexation route provided porous and soft powders and they were sintered after a simple ball milling process. In this study, the microstructures and flexural strengths of the multi-component (Al2O3-ZrO2-Y2O3-SrO) ceramic composites were examined on the processing variations of mole ratio and sintering temperature. The composites showed various grain morphologies according to the sintering temperature, and flexural strength of 410 MPa was obtained in the Al2O3·ZrO2·0.5Y2O3·0.4SrO composite sintered at 1600 °C for 1 h. In particular, needle-shape grains were observed in the four-component composites sintered at 1500 °C.

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