Testing a material claimed to be harder than diamond creates a measurement problem when the indenter is itself diamond. Krishna Choudhary and Lester Nare discuss how peer review of Bulk hexagonal diamond led the researchers to add sound-wave measurements as an independent check on mechanical properties. Those measurements probe elastic stiffness, which can inform a hardness comparison but is not the same property as indentation hardness.
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Vickers hardness is an indentation measurement, rather than a scratch test.
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Pulse-echo measurements use the travel of sound through a sample to help determine elastic properties.
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The peer-review discussion shows why a strong materials claim benefits from more than one measurement method.
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The published paper reports slightly higher hardness than cubic diamond, rather than the much larger improvement sometimes associated with theoretical predictions.
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45:57thingy without much analysis. >> Yeah, yeah. And and finally they also instead of doing the Vickers hardness scale, which is like the scratching on the diamond thing, reviewer one suggested that they should do something called pulsed echo experiments. >> Okay. >> This is a way that you can like basically send sound waves effectively through a material and the response of that material lets you calculate the elastic modulus of that material. And then there's ways to back calculate what the hardness is. So, he said, "If your scratch test and this echo experiment give you the same number, then I'll believe you." So, they did it. It did come out. It showed that the Young's modulus was bigger than
46:38diamonds. And so, finally, version three, which is the fourth version cuz you start with version zero. So, with version three, reviewer one finally says that he's happy with the version. He says, "The authors revised the paper according to the recommendations. Now the paper and supplement provide all the relevant information and the results are truly convincing at the end. And in the middle, he's saying that I believe refining all of this was worth it. So, he's kind of saying like, "I know I gave you guys a hard time, but I think it was worth it because now I think this paper is stellar." And at the end, he says, "Congratulations for this important work." And he signs his own name. Oliver um Schauviller. >> Yeah, yeah. >> He's from the University of Nevada, Las
47:20Vegas, I believe. So, he did He put his name He doesn't have to, right? But he put his own name there to show, "Okay, this is who I was." >> Yeah. >> And my >> Appreciate the work he did. >> Right, right. >> So, reviewer one turns out to be like kind of a hard-ass, but >> Right. >> the paper is quite incredible because now no one can say anything. >> this is And I think this is the key point of why I wanted to preface the cultural moment and the sort of judgment of you know, it it it it it this process really does matter. And I do think some of the feedback that was brought up makes total sense. >> yeah, yeah. >> Like very reasonable. >> like reviewer two said the same stuff. Yeah. >> And if it worked, it's e- it was easily resolvable. It didn't require a huge refactor.
48:00>> Or anything like that. >> You got the sample. Just >> Yeah. >> do a little more double-checking. >> Yeah. >> And fascinating. >> Yeah. >> I I the the And this is And again, we
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