The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates
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| Language: | English |
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Case Western Reserve University School of Graduate Studies / OhioLINK
2012
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=case1337013344 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-case1337013344 |
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NDLTD |
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English |
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Chemical Engineering Materials Science Mechanical Engineering Diamond Tension Testing Films Biomedical Electrodes Mechanical Testing Material Properties |
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Chemical Engineering Materials Science Mechanical Engineering Diamond Tension Testing Films Biomedical Electrodes Mechanical Testing Material Properties Stagon, John Thomas The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates |
| author |
Stagon, John Thomas |
| author_facet |
Stagon, John Thomas |
| author_sort |
Stagon, John Thomas |
| title |
The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates |
| title_short |
The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates |
| title_full |
The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates |
| title_fullStr |
The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates |
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The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates |
| title_sort |
mechanical property analysis of thin diamond coated metal substrates |
| publisher |
Case Western Reserve University School of Graduate Studies / OhioLINK |
| publishDate |
2012 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=case1337013344 |
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AT stagonjohnthomas themechanicalpropertyanalysisofthindiamondcoatedmetalsubstrates AT stagonjohnthomas mechanicalpropertyanalysisofthindiamondcoatedmetalsubstrates |
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1719421951248695296 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-case13370133442021-08-03T05:34:26Z The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates Stagon, John Thomas Chemical Engineering Materials Science Mechanical Engineering Diamond Tension Testing Films Biomedical Electrodes Mechanical Testing Material Properties <p>The choice of substrate material is crucial for biosensing electrodes that use thin film diamond due to material property changes that occur during the high-temperature, chemical vapor deposition (CVD) process for diamond coating. Three materials were studied in this context: tungsten, a tungsten/rhenium alloy, and a molybdenum rhenium alloy, all of which obtained as extruded wire with a 120 µm diameter. These materials were selectively coated by hot-filament CVD with boron-doped polycrystalline diamond and the material properties studied in three different states, using tensile tests and SEM imaging of corresponding fracture surfaces. First, the inherent substrate ductility before diamond coating was determined by examining stress vs. strain data from tensile tests. Then, ductility of “vertically” oriented wire substrates was determined, the substrate positioning in the CVD system during the diamond coating process similar to what has been used to selectively grow diamond micro-wire electrodes. In this case, the substrates, aligned perpendicular to the hot filaments, could be used to profile gradients in ductility along the substrate length, including in regions that would not be diamond-coated, but still exposed to the high temperature environment. Lastly, the effect of diamond growth time on ductility was studied, for a given substrate-to-filament distance; the substrates were aligned parallel to the hot filaments (“horizontally” aligned) to produce uniform coatings of diamond along the wires. The process time was varied between 2 to 20 hours to produce films of different thickness. For all three states, fractured samples were examined by SEM to identify fracture modes and suggest potential embrittlement mechanisms.</p><p> The molybdenum/rhenium alloy was the only substrate that retained sufficiently ductile properties to enable tension testing; all tungsten and tungsten/rhenium alloy samples became highly brittle, fracturing with any attempt to load them for testing. The molybdenum/rhenium’s ductility decreased with increased diamond-growth time, the ultimate tensile stress decreasing from 2200 MPa to 1000 MPa after 20 hours at a 9 mm substrate-filament distance. Its ductility gradient was large, as varying substrate-filament distance, the ultimate tensile stress increasing from 1800 MPa to the equivalent of the untreated wire at 2200 MPa, over a 3 mm length from the point where diamond coating ceased. Tungsten and tungsten/rhenium alloy fracture cross-sections showed complete and even embrittlement. The molybdenum/rhenium alloy was embrittled only around the periphery, a distinct brittle phase visible underneath the diamond film. Ductile features such as a dimpled fracture surface remained in the core of the coated molybdenum/rhenium alloy, even for growth times far exceeding those needed to produce a complete diamond coating. </p><p> Overall, these data showed an embrittlement mechanism occurring for all three metals considered. The distance that the substrate was from the heating element in the CVD reactor and the time it was exposed to high temperature conditions both had a significant impact on its resulting ductility. Overall, mechanical testing and imaging data supported that the molybdenum/rhenium alloy is the most promising candidate for substrate material to produce ductile, implantable diamond electrodes for biomedical applications.</p> 2012-06-26 English text Case Western Reserve University School of Graduate Studies / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=case1337013344 http://rave.ohiolink.edu/etdc/view?acc_num=case1337013344 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |