Crack Healing, Reopening and Thermal Expansion Behavior of Al2TiO5 Ceramics at High Temperature

2007 ◽  
Vol 336-338 ◽  
pp. 2448-2450 ◽  
Author(s):  
Ik Jin Kim ◽  
Kee Sung Lee ◽  
Christos G. Aneziris
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Low Temperature ◽  
Grain Boundary ◽  
Crack Healing ◽  
Thermal Expansion Anisotropy ◽  
Low Thermal Expansion ◽  
Micro Cracks ◽  
Expansion Behavior ◽  
The Individual

The low thermal expansion (α25-1100oC = 0.05 ~ 1.6 × 10–6/K) of Al2TiO5 ceramics are apparently due to a combination of grain boundary micro cracking caused by the large thermal expansion anisotropy of the crystal axes of the Al2TiO5 phase. During the reheating run, the individual crystallites expanded at low temperature; thus, the solid volume of the specimen expanded into the micro cracks, where as the macroscopic dimensions remained almost unchanged. As a result, the material expanded very little. The micro cracks closed at higher temperatures. This result is closely related to relatively steeper thermal expansion curves.

EFFECT OF HIGH TEMPERATURE DEFORMATION ON THE LOW THERMAL EXPANSION BEHAVIOR OF FE-29%NI-17%CO ALLOY

2008 ◽  
Vol 22 (31n32) ◽  
pp. 6016-6021 ◽  
Author(s):  
K. A. LEE ◽  
J. NAMKUNG ◽  
M. C. KIM
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Strain Rate ◽  
Strain Rate Range ◽  
Theoretical Explanation ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Thermal Expansion Behavior ◽  
Low Thermal Expansion ◽  
Expansion Behavior

The effect of high temperature deformation on the low thermal expansion property of Fe -29 Ni -17 Co alloy was investigated in the compressive temperature range of 900~1300°C at a strain rate range of 25 ~ 0.01 sec. -1. The thermal expansion coefficient (α30~400) generally increased with increasing compressive temperature. In particular, α30~400 increased remarkably as the strain rate decreased at temperatures above 1100°C. Note, however, that α30~400 at low compressive temperatures (900°C and 1000°C) increased abnormally at high strain rates. Based on the investigation of various possibilities of change in low thermal expansion behavior, the experimental results indicated that both the appearance of the α phase and evolution of grain size due to hot compression clearly influenced the low thermal expansion behavior of this invar-type alloy. The correlation between the microstructural cause and invar phenomena and theoretical explanation for the low thermal expansion behavior of Fe -29% Ni -17% Co were also suggested.

Crack healing, reopening and thermal expansion behavior of Al2TiO5 ceramics at high temperature

2007 ◽  
Vol 27 (2-3) ◽  
pp. 1431-1434 ◽  
Author(s):  
Hyung Chul Kim ◽  
Kee Sung Lee ◽  
Oh Seong Kweon ◽  
Christos G. Aneziris ◽  
Ik Jin Kim
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Crack Healing ◽  
Thermal Expansion Behavior ◽  
Expansion Behavior

Negative Thermal Expansion up to 1000°C of ZrTiO4-Al2TiO5 Ceramics for High-Temperature Applications

2007 ◽  
Vol 280-283 ◽  
pp. 1179-1184 ◽  
Author(s):  
Ik Jin Kim ◽  
Hyung Chul Kim ◽  
In Sub Han ◽  
Christos G. Aneziris
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Negative Thermal Expansion ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Anisotropy ◽  
Low Thermal Expansion ◽  
Lower Thermal Expansion ◽  
Shock Resistance ◽  
Temperature Applications

High temperature structural ceramics based on Al2TiO5-ZrTiO4 (ZAT) having excellent thermal-shock-resistance were synthesized by a reaction sintering. The ZAT ceramics sintered at 1600oC had a negative thermal expansions up to 1000oC and a much lower thermal expansion coefficient (0.3 ~ 1.3 x 10-6 /K) than that of polycrystalline Al2TiO5 (1.5 x 10-6 /K). These low thermal expansion are apparently due to a combination of microcracking caused by the large thermal expansion anisotropy of the crystal axes of the Al2TiO5 phase. The microstructural degradation of the composites after various thermal treatment for high temperature applications were analyzed by scanning electron microscopy, X-ray diffraction, ultrasonic and dilatometer.

Influence of B2O3 on Dielectric, Mechanical, and Thermal Properties of MgO-Al2O3-SiO2 Glass-Ceramics

2019 ◽  
Vol 821 ◽  
pp. 435-439
Author(s):  
Bo Li ◽  
Ke Jing ◽  
Hai Bo Bian
Keyword(s):  
Activation Energy ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Low Temperature ◽  
Flexural Strength ◽  
Glass Ceramic ◽  
Glass Ceramics ◽  
Mechanical And Thermal Properties ◽  
Sintering Process ◽  
Low Thermal Expansion

Low temperature sintered MgO-Al2O3-SiO2 glass-ceramic with high mechanical and low thermal expansion was prepared for package. The remarkable influence of B2O3 addition on the electrical, mechanical, and thermal properties was fully investigated. A small amount of B2O3 promoted the sintering process and improved the densification of MAS. The kinetics via Kissinger method indicated that an appropriate B2O3 content decreased the activation energy and helped the occurrence of crystallization. Due to the increase of crystallinity and indialite phase, B2O3 addition significantly enhanced flexural strength and Young’s modulus. MAS doped with 3wt% B2O3 can be sintered at 900 °C and obtained good properties: σ = 229 MPa, φ = 86 GPa, α = 1.66×10-6 /°C, εr = 5.29, and tanδ = 5.9×10-4.

Advantages of MIS Processing on Passivated Polycrystalline Silicon

1981 ◽  
Vol 5 ◽  
Author(s):  
G. Rajeswaran ◽  
M. Thayer ◽  
V. J. Rao ◽  
W. A. Anderson
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Polycrystalline Silicon ◽  
Hydrogen Plasma ◽  
Mis Structures

ABSTRACTWacker polycrystalline silicon shows enhanced grain boundary activity after a high temperature (950° C) anneal. It is possible to passivate this effect in a hydrogen plasma. The low temperature (600° C) processing of MIS technology does not activate grain boundaries or deteriorate a passivated specimen. Activated grain boundaries with MIS structures can be used to assess the character of recombination currents. It is concluded that MIS processing is advantageous for passivated polycrystalline silicon.

Thermal expansion behavior of A- and B-type amylose crystals in the low-temperature region

2015 ◽  
Vol 131 ◽  
pp. 399-406 ◽  
Author(s):  
Kayoko Kobayashi ◽  
Satoshi Kimura ◽  
Philip-Kunio Naito ◽  
Eiji Togawa ◽  
Masahisa Wada
Keyword(s):  
Thermal Expansion ◽  
Low Temperature ◽  
Temperature Region ◽  
Thermal Expansion Behavior ◽  
Expansion Behavior
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