High temperature ultrasonic characterization of intrinsic and microstructural changes in ceramic YBa2Cu3O7−δ

1992 ◽  
Vol 7 (7) ◽  
pp. 1629-1635 ◽  
Author(s):  
S. Suasmoro ◽  
D.S. Smith ◽  
M. Lejeune ◽  
M. Huger ◽  
C. Gault

Young's modulus of ceramic YBa2Cu3O7−δ was measured between room temperature and 1000 °C, E(T), by an ultrasonic pulse-echo technique. Experimental results are presented for nonaligned ceramics with average grain sizes from 2 to 10 μm and densities from 80% to 95% of the theoretical value. Young's modulus is shown to be strongly sensitive to oxygen content with the orthorhombic phase being significantly stiffer than the tetragonal phase. In addition, the phase transition is denoted by a pronounced minimum in E(T) relating to softening of certain bonds in the unit cell. At high temperature (>900 °C) melting of the second phase gives a steep drop in E(T) while subsequent densification increases E. Finally, cooling of large-grained ceramic below 450 °C opens microcracks due to anisotropic volume changes. This results in hysteresis between the heating and cooling curves for E(T). Hence the technique is used to show that ceramic, with an average grain size of 2 μm and 85% of theoretical density, is well oxygenated and undamaged by its thermal treatment.

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2949
Author(s):  
Marzieh Rabiei ◽  
Arvydas Palevicius ◽  
Amir Dashti ◽  
Sohrab Nasiri ◽  
Ahmad Monshi ◽  
...  

Taking into account X-ray diffraction, one of the well-known methods for calculating the stress-strain of crystals is Williamson-Hall (W–H). The W-H method has three models, namely (1) Uniform deformation model (UDM); (2) Uniform stress deformation model (USDM); and (3) Uniform deformation energy density model (UDEDM). The USDM and UDEDM models are directly related to the modulus of elasticity (E). Young’s modulus is a key parameter in engineering design and materials development. Young’s modulus is considered in USDM and UDEDM models, but in all previous studies, researchers used the average values of Young’s modulus or they calculated Young’s modulus only for a sharp peak of an XRD pattern or they extracted Young’s modulus from the literature. Therefore, these values are not representative of all peaks derived from X-ray diffraction; as a result, these values are not estimated with high accuracy. Nevertheless, in the current study, the W-H method is used considering the all diffracted planes of the unit cell and super cells (2 × 2 × 2) of Hydroxyapatite (HA), and a new method with the high accuracy of the W-H method in the USDM model is presented to calculate stress (σ) and strain (ε). The accounting for the planar density of atoms is the novelty of this work. Furthermore, the ultrasonic pulse-echo test is performed for the validation of the novelty assumptions.


Author(s):  
Firmansyah Sasmita ◽  
Thea Athalia Candra ◽  
Hermawan Judawisastra ◽  
Toni Agung Priambodo

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1258
Author(s):  
Marzieh Rabiei ◽  
Arvydas Palevicius ◽  
Sohrab Nasiri ◽  
Amir Dashti ◽  
Andrius Vilkauskas ◽  
...  

Calcium titanate-CaTiO3 (perovskite) has been used in various industrial applications due to its dopant/doping mechanisms. Manipulation of defective grain boundaries in the structure of perovskite is essential to maximize mechanical properties and stability; therefore, the structure of perovskite has attracted attention, because without fully understanding the perovskite structure and diffracted planes, dopant/doping mechanisms cannot be understood. In this study, the areas and locations of atoms and diffracted planes were designed and investigated. In this research, the relationship between Young’s modulus and planar density of unit cell, super cells (2 × 2 × 2) and symmetry cells of nano CaTiO3 is investigated. Elastic constant, elastic compliance and Young’s modulus value were recorded with the ultrasonic pulse-echo technique. The results were C11 = 330.89 GPa, C12 = 93.03 GPa, C44 = 94.91 GPa and E = 153.87 GPa respectively. Young’s modulus values of CaTiO3 extracted by planar density were calculated 162.62 GPa, 151.71 GPa and 152.21 GPa for unit cell, super cells (2 × 2 × 2) and symmetry cells, respectively. Young’s modulus value extracted by planar density of symmetry cells was in good agreement with Young’s modulus value measured via ultrasonic pulse-echo.


2004 ◽  
Vol 19 (5) ◽  
pp. 1432-1438 ◽  
Author(s):  
Takafumi Kusunose ◽  
Rak-Joo Sung ◽  
Tohru Sekino ◽  
Shuji Sakaguchi ◽  
Koichi Niihara

Hexagonal graphitic BN (h-BN) is interesting as a second phase for high-temperature structural ceramics because it has the same crystal structure as graphite, for which fracture strength and Young’s modulus increase with increased temperature. In this study, high-temperature mechanical properties of Si3N4/BN nanocomposite were evaluated to clarify the effect of fine h-BN particles at elevated temperatures. As a result, we found that high-temperature strength and hardness of the nanocomposite were maintained up to high temperatures; also, its Young’s modulus increased gradually, concomitant with elevated temperatures up to 1400 °C. Finally, these properties were compared with those of monolithic Si3N4 and Si3N4/BN microcomposite.


Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 968
Author(s):  
Fumitada Iguchi ◽  
Keisuke Hinata

The elastic properties of 0, 10, 15, and 20 mol% yttrium-doped barium zirconate (BZY0, BZY10, BZY15, and BZY20) at the operating temperatures of protonic ceramic fuel cells were evaluated. The proposed measurement method for low sinterability materials could accurately determine the sonic velocities of small-pellet-type samples, and the elastic properties were determined based on these velocities. The Young’s modulus of BZY10, BZY15, and BZY20 was 224, 218, and 209 GPa at 20 °C, respectively, and the values decreased as the yttrium concentration increased. At high temperatures (>20 °C), as the temperature increased, the Young’s and shear moduli decreased, whereas the bulk modulus and Poisson’s ratio increased. The Young’s and shear moduli varied nonlinearly with the temperature: The values decreased rapidly from 100 to 300 °C and gradually at temperatures beyond 400 °C. The Young’s modulus of BZY10, BZY15, and BZY20 was 137, 159, and 122 GPa at 500 °C, respectively, 30–40% smaller than the values at 20 °C. The influence of the temperature was larger than that of the change in the yttrium concentration.


2012 ◽  
Vol 18 (7-8) ◽  
pp. 945-953 ◽  
Author(s):  
Oliver Pabst ◽  
Michael Schiffer ◽  
Ernst Obermeier ◽  
Tolga Tekin ◽  
Klaus Dieter Lang ◽  
...  

2006 ◽  
Vol 41 (22) ◽  
pp. 7663-7666 ◽  
Author(s):  
E. Yeugo Fogaing ◽  
Y. Lorgouilloux ◽  
M. Huger ◽  
C. P. Gault

Author(s):  
A. Sinha ◽  
K. Kokini ◽  
K. J. Bowman

The changes in stiffness properties for a CAS matrix-Nicalon fiber unidirectional composite resulting from cyclic heating and cooling are presented. The measurements are made using an ultrasonic pulse-echo technique. It is shown that a significant decrease in stiffness is observed after 30 cycles.


2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
J. Jakubowicz ◽  
M. Sopata ◽  
G. Adamek ◽  
P. Siwak ◽  
T. Kachlicki

The nanocrystalline tantalum-ceramic composites were made using mechanical alloying followed by pulse plasma sintering (PPS). The tantalum acts as a matrix, to which the ceramic reinforced phase in the concentration of 5, 10, 20, and 40 wt.% was introduced. Oxides (Y2O3 and ZrO2) and carbides (TaC) were used as the ceramic phase. The mechanical alloying results in the formation of nanocrystalline grains. The subsequent hot pressing in the mode of PPS results in the consolidation of powders and formation of bulk nanocomposites. All the bulk composites have the average grain size from 40 nm to 100 nm, whereas, for comparison, the bulk nanocrystalline pure tantalum has the average grain size of approximately 170 nm. The ceramic phase refines the grain size in the Ta nanocomposites. The mechanical properties were studied using the nanoindentation tests. The nanocomposites exhibit uniform load-displacement curves indicating good integrity and homogeneity of the samples. Out of the investigated components, the Ta-10 wt.% TaC one has the highest hardness and a very high Young’s modulus (1398 HV and 336 GPa, resp.). For the Ta-oxide composites, Ta-20 wt.% Y2O3 has the highest mechanical properties (1165 HV hardness and 231 GPa Young’s modulus).


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