Step Free Energy Change and Microstructural Development in BaTiO3-SiO2

2007 ◽  
Vol 352 ◽  
pp. 25-30 ◽  
Author(s):  
Jaem Yung Chang ◽  
Suk Joong L. Kang
Keyword(s):  
Free Energy ◽  
Grain Growth ◽  
Driving Force ◽  
Growth Behavior ◽  
Abnormal Grain Growth ◽  
Free Energy Change ◽  
Energy Change ◽  
Microstructural Development ◽  
Two Phase ◽  
Grain Growth Behavior

The effect of step free energy on the grain growth behavior in a liquid matrix is studied in a model system BaTiO3-SiO2. BaTiO3-10SiO2 (mole %) powder compacts were sintered at 1280°C under various oxygen partial pressures (PO2), 0.2, ~ 10-17 and ~ 10-24 atm. As the step free energy decreases with the reduction of PO2, it was possible to observe the change in growth behavior with the reduction of the step free energy. At PO2 = 0.2 atm, essentially no grain growth (stagnant grain growth) occurred during sintering up to 50 h. At PO2 ≈ 10-17 atm, abnormal grain growth followed stagnant grain growth during extended sintering (incubation of abnormal grain growth). At PO2 ≈ 10-24 atm, normal grain growth occurred. These changes in growth behavior with PO2 and the step free energy reduction are explained in terms of the change in the critical driving force for appreciable growth relative to the maximum driving force for grain growth. The present experimental results provide an example of microstructure control in solid-liquid two- phase systems via step free energy change.

Densification behaviors and piezoelectric properties of MnO2, SiO2-doped Pb(Ni1/3Nb2/3)O3–PbTiO3–PbZrO3 ceramics

1993 ◽  
Vol 8 (12) ◽  
pp. 3184-3191 ◽  
Author(s):  
Jong H. Moon ◽  
Hyun M. Jang ◽  
Beoung D. You
Keyword(s):  
Grain Growth ◽  
Oxygen Vacancies ◽  
Piezoelectric Properties ◽  
Mechanical Quality Factor ◽  
Growth Behavior ◽  
Microstructural Development ◽  
Relative Dielectric Permittivity ◽  
Diffusion Controlled ◽  
Mechanical Quality ◽  
Grain Growth Behavior

The roles of additives (MnO2, SiO2, and CdO) in controlling microstructural development and piezoelectric properties of Pb(Ni1/3Nb2/3)O3– PbTiO3–PbZrO3(PNN–PT–PZ) ceramics were systematically examined. The addition of SiO2 (<1 wt. %) to the pseudoternary PNN–PT-PZ system enhances densification, but suppresses grain growth significantly. On the other hand, the presence of MnO2 expedites the rate of grain growth without increasing the rate of densification appreciably. The observed difference in the grain-growth behavior was discussed in terms of the viscosity of liquid phase formed during sintering and the diffusion-controlled process for the solute-atoms transport. The rapid increase in the mechanical quality factor (Qm) and the decrease in the relative dielectric permittivity (∊r) and d33 for the MnO2-doped specimens indicate the formation of oxygen vacancies by the dissolution of Mn-atoms into the B-sites of perovskite structure. On the contrary, the presence of CdO (2 mol %) remarkably increases ∊r and d33 of PNN–PT–PZ ceramics.

Boundary Structure-Dependent Grain Growth Behavior in Polycrystals: Model and Principle

2013 ◽  
Vol 753 ◽  
pp. 377-382 ◽  
Author(s):  
Suk Joong L. Kang
Keyword(s):  
Grain Growth ◽  
Microstructural Evolution ◽  
Driving Force ◽  
Coupling Effect ◽  
Normal Growth ◽  
Growth Behavior ◽  
Boundary Structure ◽  
Mixed Control ◽  
Grain Boundary Structure ◽  
Grain Growth Behavior

This paper reviews our recent investigations on grain growth in ceramics. Grain growth behavior has been found to be governed by the grain boundary structure: normal growth with a stationary relative grain size distribution for rough boundaries and non-normal (nonstationary) growth for faceted boundaries. Based on the concept of nonlinear migration of faceted boundaries, the mixed control model of grain growth is introduced and the principle of microstructural evolution is deduced. This principle states that various types of grain growth behavior are predicted as a result of the coupling effect between the maximum driving force for growth and the critical driving force for appreciable migration of the boundary. A wealth of experimental results supports the theoretical predictions of grain growth behavior, showing the generality of the suggested principle of microstructural evolution. Application of this principle is also demonstrated for the fabrication of single crystals as well as polycrystals with desired microstructures.

scholarly journals Grain Growth Behavior of 0.95(Na0.5Bi0.5)TiO3–0.05BaTiO3 Controlled by Grain Shape and Second Phase

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1344 ◽  
Author(s):  
Sang-Chae Jeon ◽  
John G. Fisher ◽  
Suk-Joong L. Kang ◽  
Kyoung-Seok Moon
Keyword(s):  
Liquid Phase ◽  
Grain Growth ◽  
Growth Mechanism ◽  
Driving Force ◽  
Grain Shape ◽  
Growth Behavior ◽  
Second Phase ◽  
Two Dimensional ◽  
Grain Growth Behavior ◽  
Powder Compacts

The grain growth behavior of 0.95(Na0.5Bi0.5)TiO3 –0.05BaTiO3 (mole fraction, NBT–5BT) grains was investigated with excess Bi2O3 addition. The powder compacts of NBT–5BT were sintered at 1200 °C for various sintering times and with various amounts of Bi2O3 (0.1, 1.5, 4.0 and 10.0 mol%). When Bi2O3 was added to round-edged cubic NBT–5BT, the grain shape changed to a more faceted cube and the amount of liquid phase increased during sintering. A more faceted cubic grain shape indicates an increase in the critical driving force for appreciable growth of grains. However, obvious abnormal grain growth did not appear in any of the NBT–5BT samples with excess Bi2O3. The amount of liquid phase increased as the amount of Bi2O3 increased. Therefore, the rate of grain growth could be decreased by the increasing the distance for the diffusion of atoms. These observations allowed us to conclude that the growth of Bi2O3-excess NBT–5BT grains is governed by the growth of facet planes via the two-dimensional nucleation grain growth mechanism during changing grain shape and amount of liquid.

The Effects of Nb Carbo-Nitride Precipitation Conditions on Abnormal Grain Growth in Nb Added Steels

2007 ◽  
Vol 539-543 ◽  
pp. 4167-4172 ◽  
Author(s):  
Toshio Murakami ◽  
Hitoshi Hatano ◽  
Yosuke Shindo ◽  
Mutsuhiro Nagahama ◽  
Hiroshi Yaguchi
Keyword(s):  
Grain Growth ◽  
Ostwald Ripening ◽  
Growth Behavior ◽  
Abnormal Grain Growth ◽  
Pinning Force ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Ripening Rate ◽  
Grain Growth Behavior ◽  
Nitride Precipitation

In order to investigate the effects of Nb carbo-nitride precipitation conditions on abnormal grain growth behavior during high temperature carburizing, size of Nb carbo-nitride precipitates was controlled by precipitation treatment at 1173-1273K for 0.6-54ks, and the specimens were quasi-carburized at 1323K. Abnormal grain growth was enhanced when the size of Nb precipitates was fine or coarse, so there is a suitable size range in Nb precipitates to suppress abnormal grain growth. The reason why abnormal grain growth was enhanced is the lack of pinning force as the conventional theory proposed by Hillert or Gladman; however, it cannot be explained by this theory that small precipitates promote abnormal grain growth. It is considered that Ostwald ripening rate of precipitates is also an important factor in controlling abnormal grain growth in addition to the amount and size of precipitates and austenite grain size, which were parameters in the Gladman‘s theory on abnormal grain growth behavior.

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.

The Effect of Small Amounts of Yttrium Addition on Static and under Superplastic Deformation Grain Growth in Newly Developed α+β Type, Ti-4.5Al-6Nb-2Mo-2Fe Alloy

2006 ◽  
Vol 15-17 ◽  
pp. 970-975 ◽  
Author(s):  
Behrang Poorganji ◽  
S. Hotta ◽  
Taichi Murakami ◽  
Takayuki Narushima ◽  
Yasutaka Iguchi ◽  
...  
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Growth ◽  
Hot Deformation ◽  
Superplastic Deformation ◽  
Superplastic Forming ◽  
Growth Behavior ◽  
Two Phase ◽  
Yttrium Addition ◽  
Grain Growth Behavior

New α+β type titanium alloy with Ti-4.5Al-6Nb-2Mo-2Fe was developed on the basis of using biocompatible elements and eliminating the cytotoxic ones such as Vanadium, while achieving the desirable mechanical properties such as appropriate strength, cold workability and low superplastic forming (SPF) temperature. The present study was conducted to investigate the effect of yttrium addition of less than 0.05% into this alloy on static and under superplastic deformation grain growth behavior. The new alloy bar manufactured by α+β processing and annealed at 1073K yielded extremely fine two-phase microstructure with α grain size around 2μm. Specimens were heated at temperatures of 1048, 1073 and 1098K and kept for times between 3.6 to 172.8KS. Yttrium forms in-situ Y2O3 particles, and the presence of these particles yield finer two phase microstructure due to their retardation effect on β phase grain growth. Grain growth behavior during hot deformation was investigated by hot compression test in use of a hot working simulator of THERMEC-Master Z. Strain rate was varied from 2×10-2 to 2×10-4S-1 and strain was 0.69. Grain size of both α and β phases increased with a reduction of strain rate, and Y2O3 particle was also effective to retard grain growth under hot deformation. It was confirmed from comparison of grain growth during isothermal heating with and without hot deformation that grain growth was much accelerated by deformation. All of these results were discussed based on grain growth mechanism or model for two-phase microstructures as well as superplastic deformation mechanism.

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