Elastic constants of chemical-vapor-deposition diamond thin films: resonance ultrasound spectroscopy with laser-Doppler interferometry

Nakamura, Nobutomo; Ogi, Hirotsugu; Hirao, Masahiko

doi:10.1016/j.actamat.2003.10.012

Cited by 65 publications

(68 citation statements)

References 23 publications

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“…We fabricated 15 direct-conversion-sintering NPD specimens (DC-NPDs) (specimen nos 1-14 and 43), 13 monocrystal diamond specimens (specimen nos 15-27) using the temperature-gradient method 16,17 , epitaxial chemical-vapourdeposition (CVD) diamonds on monocrystal diamond substrate using a microwave-plasma CVD method (nos 28-31) and polycrystalline diamond specimens by a microwave-plasma CVD method without (CVD-micropolycrystalline diamond (CVD-MPD), nos [32][33][34][35] and with (CVD-NPD, nos 36-42) nitrogen gas. Adding nitrogen gas significantly decreases the grain size through formation of nuclei 18,19 .…”

Section: Specimensmentioning

confidence: 99%

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Observation of higher stiffness in nanopolycrystal diamond than monocrystal diamond

et al. 2013

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Diamond is the stiffest known material. Here we report that nanopolycrystal diamond synthesized by direct-conversion method from graphite is stiffer than natural and synthesized monocrystal diamonds. This observation departs from the usual thinking that nanocrystalline materials are softer than their monocrystals because of a large volume fraction of soft grainboundary region. The direct conversion causes the nondiffusional phase transformation to cubic diamond, producing many twins inside diamond grains. We give an ab initio-calculation twinned model that confirms the stiffening. We find that shorter interplane bonds along [111] are significantly strengthened near the twinned region, from which the superstiff structure originates. Our discovery provides a novel step forward in the search for superstiff materials.

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Section: Specimensmentioning

confidence: 99%

“…Considering lattice anharmonicity, such a softening is attributed to the larger free volume at the grain boundaries 7 . Also, the macroscopic stiffness decreases considerably when the material contains noncohesive intergrain bonds, because displacement increases when a softer region is stressed 8,9 . Thus, low stiffness in nanopolycrystals is well established.…”

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Observation of higher stiffness in nanopolycrystal diamond than monocrystal diamond

et al. 2013

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“…The specific microstructures of fiber texture or preferred orientation of polycrystalline thin films fabricated by many methods such as sputtering technology, pulsed-laser deposition and chemical vapor deposition [1][2][3], have attracted much attention from the research community. The out-of-plane orientations of all grains in the fiber-textured films are almost parallel to a specific crystallographic direction, while the in-plane orientations of the grains are nearly random [4].…”

Section: Introductionmentioning

confidence: 99%

Effective biaxial modulus and strain energy density of ideally (hkl)-fiber-textured hexagonal, tetragonal and orthorhombic films

Wu¹,

Wu²,

Wang³

et al. 2008

Applied Surface Science

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“…Similarly, there is no DSC peak observed at low temperatures for the GSP coating, although there is an obvious hysteretic loop on the RUS curve. In this case, the possible interpretation is that the RUS measurements can detect the changes of mechanical properties in relatively small volume fractions (RUS can be used, e.g., to detect elasticity of surface layers the volume of which is less than 1/100 of the volume of the underlying substrate [44]), which, however, do not produce/consume sufficient latent heat to be detectable by DSC.…”

Section: Combination Of the Techniques Usedmentioning

confidence: 99%

Phase stabilization in plasma sprayed BaTiO3

Ctibor

Seiner

Sedláček

et al. 2013

Ceramics International

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This paper presents a comparison of properties of BaTiO 3 ceramics prepared by two different production methods: gas-stabilized plasma spraying (GSP) and spark plasma sintering (SPS). Samples of both materials were evaluated by various techniques, the goal being to detect the Curie temperature of the ferroelectric transformation between the tetragonal and the cubic phase. All tests, resonant ultrasound spectroscopy, dielectric measurements, differential scanning calorimetry and temperature-resolved X-ray diffraction (XRD), used in combination, proved the absence of this transformation in the case of GSP coating up to 500 1C. Similarly, the tetragonal-toorthorhombic transition temperature is shifted downwards, this transition probably taking place in a small fraction of the volume of coating. The SPS samples exhibit several anomalies, such as a strong anisotropy of relative permittivity, but their phase transformations were detected in the usual temperature ranges.

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Elastic constants of chemical-vapor-deposition diamond thin films: resonance ultrasound spectroscopy with laser-Doppler interferometry

Cited by 65 publications

References 23 publications

Observation of higher stiffness in nanopolycrystal diamond than monocrystal diamond

Observation of higher stiffness in nanopolycrystal diamond than monocrystal diamond

Effective biaxial modulus and strain energy density of ideally (hkl)-fiber-textured hexagonal, tetragonal and orthorhombic films

Phase stabilization in plasma sprayed BaTiO3

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