I'm looking for a fast and facile way to quantatively measure and compare the hardness of some bulk of crystals (approx. size of each crystal is about 0.5*0.5*0.5 mm). If indentation methods, like nanoindentation which focus on single crystals, is applied, it will be necessary to perform these methods on several single crystals in a certain bulk to get an average hardness value.
Are there any (standard) methods that test a bulk of crystals at once and give an average measure for its hardness?
I use to micro-hardness testing method to Vickers. In the case of such large crystals will be good. They should of course immobilize and discoveries to measure but it is really quite simple; preparation.
Dear Javad,
I do not understand what do you means by some bulk of crystals. I suppose that you are talking of polycrystalline material with a mean grain size of 0.5 mm.
If this is the case, 0.5 mm is a big grain size and indeed (as you commented) by using nanoindentation it is required to do some statistics to obtain an average value. The grain size of 0.5 mm is even too big to apply micro-hardness method as suggeted by Dr. Marcin Nabiatek, because the indent in this case has tipically some tens of micrometers and you should again do some statistics to obtain the average value.
For such big grain size you may use directly a hardness testing method (not micro / nano) using Vickers hardness or even Rockwell or Brinell hardness methods, depending of your material. You may look for the definitions of these kind of hardness measurements in wikipedia, or in any textbook of mechanical properties.
All these methods are standard according the different international norms, ASTM, ISO, etc.
These kind of equipment are usually used in the Engineering Departments of Univ. and in the Quality Control Departments of metallurgical companies.
Best regards
Dear professor Nabiałek
Thank you very much for your simple and pithy answer. It was helpful.
As regards the study of solid polycrystalline materials with large grain, Vickers is not a good method. But when we are dealing with single grains then the Vickes is the best. Therefore, I do not quite know whether is it a test of grains or solid material. This question also asked by Professor Jose San Juan. When it comes to solid material he is right. And if that single grain I recommend Vickers.
Dear professor San Juan
I'm grateful for your precise answer. Actually, by bulk of crystals, I mean a pile of crystals, several kilograms of each sample.
We are looking for a method to measure the average hardness (or some measure for mechanical stability) of each sample without testing single crystals. For example, we separate a certain mesh of these crystals and we grind it for a certain time. Then by calculating the fraction of the resulted powders to the initial wight of crystals, a measure can be obtained.
Best regards,
Dear Javad,
If I'm correctly understood then you are dealing with particles in the form of 0.5*0.5*0.5 mm single crystalline grains (something like a pile of sugar maybe). If my assumption is correct nanoindentation or microindentation is probably the most promising tool to test your material, given that you can fix your particles in a manner that you can indent on a surface which is perfectly flat and horizontal. This will be necessary for any other hardness measurement technique but the only advantage of nano and micro indentation would be the possibility of performing a large number of indents in the same particle. However there are considerations regarding the indentation size effect that you also have to consider when using a low indentation depth for measuring the hardness.
Cheers,
Afrooz
Hi
I agree with Mr.Marcin Nabiałek
I would use a micro-hardness testing method, especially if the size of the crystal around 0.5*0.5*0.5 mm.
Dear professor Barnoush
Exactly, you cannot be right anymore about the samples.
Actually, as I mentioned earlier, we are looking for a method to measure the average hardness (or some measure for mechanical stability) of each sample without testing its single crystals.
For example, we separate a certain mesh of these crystals and we grind it for a certain time. Then by calculating the fraction of the resulted powders to the initial wight of crystals, a hardness measure can be obtained.
So, the perfect method should be like the mentioned one but with a standard procedure and some references in the literature.
Best regards,
Javad
Dear Dr. Habib
Thank you for corroborating the micro-hardness method.
Would you please mention some other methods for measuring hardness of a pile of crystals, like the one I mentioned above (grinding a certain mesh of crystals) ?
What about measuring the abrasion resulted from the a certain amount of powder on a specific surface under a controlled impact condition.
Cheers,
Afrooz
Dear Professor Barnoush,
Is there any standard procedure for the mentioned method?
Best regards,
Javad
No there is no standards for the method I proposed based on abrasion but there could be standard methods for measuring the abrasion resistance of materials using a similar technique. You have to check in standards then convert it so it fits into your specific purpose but wouldn't be a standard method.
Cheers,
Afrooz
Dear all,
I've found a suitable standard test method except it's for catalyst particles.
"Standard Test Method for Attrition and Abrasion of Catalysts and Catalyst Carriers"
"D4058 – 96"
I hope it helps you too.
- Badges
- Science topic
- Similar topics
- Mathematics
- Algebra
- Matrix