Ceramic Coating Inspection Using Laser-Based Ultrasonics and Nanoindentation

Steen, T. L.; Basu, Sandip; Sarin, V.K.; Murray, Todd W.

doi:10.1063/1.2717976

Cited by 2 publications

(4 citation statements)

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“…Direct indentation of cross-sectioned samples has been conducted mostly on multilayer systems. ,, and to a lesser extent on graded materials. , To help improve the resolution of the measurements, some researchers have employed small-angle cross-sectional (SACS) nanoindentation. ,, However, even at small angles there is considerable influence on individual measurements by the surrounding sample volume and, additionally, sample cross-sectioning and preparation can influence the results. These limitations have hampered the wider application of this technique in the coating engineering field.…”

Section: Introductionmentioning

confidence: 99%

“…16,17,20 and to a lesser extent on graded materials. 20,23 To help improve the resolution of the measurements, some researchers have employed smallangle cross-sectional (SACS) nanoindentation. 16,17,24 However, even at small angles there is considerable influence on individual measurements by the surrounding sample volume and, additionally, sample cross-sectioning and preparation can influence the results.…”

Section: Introductionmentioning

confidence: 99%

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Direct Imaging of Mechanical and Chemical Gradients Across the Thickness of Graded Organosilicone Microwave PECVD Coatings

Hall

Murphy

Griesser

2014

ACS Appl. Mater. Interfaces

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The characterization of variations in the chemical composition and ensuing mechanical properties across the thickness of coatings with continuously varying compositions through their thickness (graded coatings) presents considerable challenges for current analytical techniques in materials science. We report here the direct imaging of nanomechanical and chemical gradients across cross-sections of an organosilicone coating fabricated via microwave plasma enhanced chemical vapor deposition (PECVD). Cross-sectional nanoindentation was used to determine the mechanical properties of uniform and graded organosilicone coatings. Both hardness and modulus across the coatings were directly measured. Additionally, "modulus mapping" on cross-sections was used to map the complex modulus. For the graded coating, it was found that variations in the complex modulus was predominantly due to varying storage modulus. It was observed that at the interface with the substrate there was a low storage modulus, which linearly increased to a relatively high storage modulus at the surface. It is proposed that the increase in stiffness, from the substrate interface to the outer surface, is due to the increasing content of a cross-linked O-Si-O network. This mechanical gradient has been linked to a change in the Si:O ratio via direct compositional mapping using ToF-SIMS. Direct mapping of the mechanical and compositional gradients across these protective coatings provides insight into the changes in properties with depth and supports optimization of the critical mechanical performance of PECVD graded coatings.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Direct Imaging of Mechanical and Chemical Gradients Across the Thickness of Graded Organosilicone Microwave PECVD Coatings

Hall

Murphy

Griesser

2014

ACS Appl. Mater. Interfaces

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“…SAW velocity measurements are made by mapping the complex displacement field over a source-to-receiver distance of approximately 500µm. The wavelength of the SAW at a given excitation frequency is extracted from this data, and the phase velocity is determined [5,6].…”

Section: Methodsmentioning

confidence: 99%

“…We have recently developed a frequency domain LBU approach that is well suited for the inspection of as-grown CVD mullite coatings [5,6]. This technique uses an intensity-modulated continuous wave laser source to generate extremely narrow-band surface acoustic waves (SAWs).…”

Section: Introductionmentioning

confidence: 99%

Measurement and Analysis of Narrow-Band Surface Acoustic Waves in Ceramic Environmental Barrier Coatings

Steen¹,

Basu²,

Sarin³

et al. 2008

AIP Conference Proceedings

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A laser-based ultrasonic system is used to measure the mechanical properties and thickness of mullite environmental barrier coatings deposited on SiC substrates. Narrow-band surface acoustic waves (SAWs) are generated with an amplitude modulated laser source, and a photorefractive crystal based interferometer coupled to a lock-in amplifier is used to detect the resulting surface displacement. The complex displacement field is mapped over a source-to-receiver distance of approximately 500µm in order to extract the wavelength of the SAW at a given excitation frequency, from which the phase velocity is determined. Dispersion curves measured over a frequency range of 100-180MHz are used to extract mean values for the elastic modulus and thickness of the coating over the measurement region. These values are compared to the mean elastic modulus and thickness of the coating measured using nanoindentation and optical microscopy, respectively. It is shown that porosity in the substrate can have a significant impact on the experimental results, particularly over short measurement distances. Experiments on SiC with 1-4% porosity show a linear increase of the mean SAW velocity with decreasing porosity. Additionally, measurements made on a sample with a given bulk porosity indicate that the SAW velocity varies locally, leading to additional error in the measurement of coating properties. This error can be reduced through spatially averaging the velocity measurements.

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Ceramic Coating Inspection Using Laser-Based Ultrasonics and Nanoindentation

Cited by 2 publications

References 1 publication

Direct Imaging of Mechanical and Chemical Gradients Across the Thickness of Graded Organosilicone Microwave PECVD Coatings

Direct Imaging of Mechanical and Chemical Gradients Across the Thickness of Graded Organosilicone Microwave PECVD Coatings

Measurement and Analysis of Narrow-Band Surface Acoustic Waves in Ceramic Environmental Barrier Coatings

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