Determination of mechanical properties of geomaterials based on nano-indentation tests and fraction order models

As a typical multi-functional single crystal material, lithium tantalate (LiTaO3 or LT) exhibits its excellent electro-optical, piezoelectric properties and has now found many applications, such as electro-optical modulators, pyroelectric detectors, optical waveguide, piezoelectric transducers and SAW (Surface Acoustic Wave) substrates. Although LT is known as a very brittle material, however, detailed summaries of its mechanical properties and machinability are not readily available yet. In order to clarify and understand the fundamental mechanical properties of LT, micro/nano indentation tests are conducted in this study to evaluate elastic modulus, hardness and fracture toughness. Other two typical single crystals of silicon and sapphire are chosen for comparison. The obtained results are analyzed and discussed to understand their behaviors in elastic, plastic (ductile) and brittle regimes, and the influences on their machinability in the machining process.

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Mechanical Properties of Micro-Tubular SOFCs

ASME 2008 6th International Conference on Fuel Cell Science, Engineering and Technology ◽

10.1115/fuelcell2008-65261 ◽

2008 ◽

Author(s):

Brycen R. Roy ◽

Nigel M. Sammes ◽

Toshio Suzuki

Keyword(s):

Mechanical Properties ◽

Wall Thickness ◽

Power Efficiency ◽

Sintering Temperature ◽

Design Parameters ◽

Pore Former ◽

Nano Indentation ◽

Indentation Tests ◽

Support Tube ◽

Ring Testing

A fundamental issue with micro-tubular Solid Oxide Fuel Cells (SOFCs) is improvement of the mechanical strength of the cell. Fabricated using extrusion and co-firing techniques, the approximately 1.7 mm diameter tubes are composed of NiO-Gd-doped ceria (GDC) as an anode (support tube), GDC as an electrolyte and La0.8Sr0.2Co0.6Fe0.4O3 (LSCF)-GDC as a cathode. The mechanical properties of SOFCs are analyzed through burst testing, c-ring testing, and micro- and nano-indentation testing; the burst test is an especially important parameter because of improved power efficiency at increased fuel pressures. Results from micro- and nano-indentation tests performed on electrolytecoated Ni-GDC anode pellets indicate that the hardness of GDC is comparable or greater than that of YSZ. To develop a trend for the mechanical behavior of micro-tubes in relation to variations in fabrication techniques, several parameters were varied. The standard tubes, used as a baseline for variations had four key design parameters as follows: they were not reduced, contained 40% pore former, were sintered at 1400 °C and had a wall thickness of approximately 0.64 mm. A variation on each of the four parameters was performed. The four variations were 1) to reduce the standard tube, 2) to increase the percent pore former to 60%, 3) to decrease sintering temperature to 1350 °C, and 4) to decrease the wall thickness to approximately 0.56 mm. An average burst strength of 9.6 ± 0.6 MPa was observed for the standard tubes, 14.6 ± 7.0 MPa for the reduced tubes, 5.4 ± 3.2 MPa for the increased pore former, 12.9 ± 4.1 MPa for the decreased sintering temperature and 11.7 ± 2.4 MPa for the thinner tubes.

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Evaluation of Mechanical Properties of SOFC Components by Nano-Indentation Tests

ASME 2010 8th International Fuel Cell Science, Engineering and Technology Conference: Volume 2 ◽

10.1115/fuelcell2010-33158 ◽

2010 ◽

Author(s):

Hideaki Ito ◽

Kazuhisa Sato ◽

Atsushi Unemoto ◽

Koji Amezawa ◽

Tatsuya Kawada

Keyword(s):

Mechanical Properties ◽

Young’S Modulus ◽

Crystal Orientation ◽

Young's Modulus ◽

Yttria Stabilized Zirconia ◽

Stabilized Zirconia ◽

Indentation Method ◽

Nano Indentation ◽

Electron Backscattering Diffraction ◽

Indentation Tests

The Young’s modulus and the hardness of single crystals and polycrystalline sintered compacts of yttria-stabilized zirconia (YSZ), (Y2O3)x(ZrO2)1−x (x = 0.08, 0.10) was investigated by using the nano-indentation method. Together with results obtained by the secondary electron microscope observation and the electron backscattering diffraction analysis, the effect of the crystal orientation on the mechanical properties was discussed. It was empirically demonstrated that the Young’s modulus of YSZ depends on the crystal orientation. The Young’s modulus of YSZ showed the highest value on the (001) surface while the lowest value on the (111) surface. However, the observed anisotropy of the Young’s modulus was rather small compared with predicted one from the single crystal elastic constants in literature. Compared with the Young’s modulus, the anisotropy of the hardness of YSZ was less significant.

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DETERMINATION OF THE MECHANICAL PROPERTIES OF TERNARY THIN FILM MEASURED BY NANO INDENTATION

International Journal of Engineering Applied Sciences and Technology ◽

10.33564/ijeast.2020.v05i01.019 ◽

2020 ◽

Vol 5 (1) ◽

pp. 139-144

Author(s):

Obasi B. Ibe ◽

Eze Joseph. O.

Keyword(s):

Thin Film ◽

Mechanical Properties ◽

Nano Indentation

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Control of Stress with Growth Conditions and Mechanical Parameters Determination of 3C-SiC Heteroepitaxial Thin Films

MRS Proceedings ◽

10.1557/proc-657-ee5.20 ◽

2000 ◽

Vol 657 ◽

Cited By ~ 1

Author(s):

C. Gourbeyre ◽

T. Chassagne ◽

M. Le Berre ◽

G. Ferro ◽

C. Malhaire ◽

...

Keyword(s):

Thin Films ◽

Mechanical Properties ◽

Residual Stress ◽

Epitaxial Growth ◽

Buffer Layer ◽

Growth Conditions ◽

Mean Value ◽

Nano Indentation ◽

Deposited Films

ABSTRACTWe report here on the influence of the epitaxial growth conditions on the residual stress of heteroepitaxial 3C-SiC grown on silicon using atmospheric-pressure chemical vapour deposition (APCVD) and on the determination of its mechanical properties. 3C-SiC films were grown on (100) Si substrates in a vertical reactor by APCVD. SiH4 and C3H8 are used as precursor gases and H2 as carrier gas. The growth procedure involves the formation of a carburization buffer layer at 1150°C under a mixture of H 2 and C3H8. The epitaxial growth occurs then at 1350°C by adding SiH 4.For as-deposited films the measurement techniques implemented are substrate curvature measurements, AFM, and nano-indentation. For micromachined self-suspended SiC membranes, load deflection measurements were used. The substrate curvature measurement leads to the determination of the residual stress in the deposited SiC film. We show that we can achieve 3C-SiC layers with a compressive or a tensile state having equivalent crystallinity. Whereas thermal mismatch just accounts for tensile stresses, we demonstrate that 3C-SiC thin films may have compressive stresses by using specific conditions for the formation of the buffer layer. The early stage of growth is indeed of major importance.Regarding the mechanical properties, the 3C-SiC Young's modulus was determined using nano-indentation. Its mean value reaches 378 GPa comparable to the calculated value of 307 GPa. As test structures, we have processed self-suspended SiC membranes. Load deflection measurements enable the determination of the Young's modulus and the residual stress of the self-suspended films. For self-suspended SiC membranes, the absolute value of the residual stress in the SiC thin films decreases compared to the as-deposited films and takes a mean value of 170 MPa in a tensile state.

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