Yes and there are at least 2 methods used as nanoindentation with atomic force microscopy (AFM), and in situ compression by a force probing holder based on the observation with transmission electron microscopy (TEM).

However, in both cases the results are still under debate for it is not clear how particle size and nanoindentation depth could influence quite puzzling results especially for nanosized particles

see for instance the excellent paper by Dan Guo et al. :

‘’Mechanical properties of nanoparticles: basics and applications’’

Dan Guo, Guoxin Xie and Jianbin Luo

Published 3 December 2013 • © 2014 IOP Publishing Ltd Journal of Physics D: Applied Physics, Volume 47, Number 1

Yes may be you need to use SEM

A method was mentioned in this book chapter

https://www.sciencedirect.com/topics/engineering/particle-hardness

Yes you can use it ... but I think you will need to use SEM with it.

You can use TEM

What are the particles made off?

Nelda Antonovaite it is more made up of silica sio2 and aluminina al2o3.

Dear Mohammad Reja Amiri,

First understand the purity of powder before particle size measurement. Hertz theory is very important to understand measurement of particle hardness.

Purity of the powder can play a role in reducing compressibility as the hardness of a particle can increase due to elements in solution (green and compact density powder metallurgy). Generally, the higher the ratio between particle and surface hardness, the higher the wear rate. In the case of a spherical particle contacting a plane surface, the application of Hertz's theory leads to the conclusion that the maximum contact stress is approximately 80% of the particle hardness, which means that the particle hardness needs to be at least 125% of the surface hardness to cause significant surface deformation(this is a very important point). The hard material would scratch a softer one and that the softer one would not do the opposite inspired the creation of the Mohs hardness scale, with an integer number assigned to 10 minerals. The mechanical resistance of the particle material also can influence the wear rate and mechanism. When a hard particle contacts a surface, plastic deformation is significant when the contact pressure is higher than a certain value. If the hard particle breaks or deforms with a load smaller than that required for the surface deformation, the wear rate is greatly reduced.

The Brinell, Vickers, Meyer, Rockwell, Shore, IHRD, Knoop, Buchholz, and nanoindentation methods are commonly used to measure the indentation hardness of materials. Main issues in the hardness interpretation are like the influence of grain size in polycrystalline materials, indentation size effects at micro- and nanoscale, and the effect of the substrate when calculating thin films hardness.

(1) Particle Size Analyzer (PSI) is an on-line analyzer for mineral slurries without sampler.

(2) Laser Diffraction Particle Size Analyzer can measure micro hardness of particles.( for scratch it is quite useful)

(3) Metallographic Hardness Tester

(4) The hardness of the film was measured with a digital microhardness HXD-2000TM/LCD. The surface layer of the sample can be analyzed X-ray instrument.the morphology, uniformity, particle size, roughness of the micro arc oxide film can be analyzed using SEM.

SEM is the best instrument which withstands all constraints can be selected as it is the best method among the proposed four mentioned above. to be in more advance TEM/SEM(EDS)/AFM can characterize Influence of grain size in polycrystalline materials, indentation size effects at micro- and nanoscale, and the effect of the substrate when calculating thin films hardness.

Ashish

Dear Mohammad Reza Amiri,

You can certainly use nano-indentation to measure the hardness of a particle less than 120 um in diameter. First, minimize the mismatch between the modulus of elasticity and yield strength associated with the particle and the modulus and yield strength associated with the mounting resin. Once the material is mounted, use standard polishing and grinding procedures to minimize the surface roughness, achieve a mirror finish, and expose the cross-section of the particle. Once you've calibrated your nanoindenter frame stiffness, compliance, and tip's contact area function using a reference material such as fused silica, determine the particle-dominated depth limit using the criteria proposed by Yan et al. such that indentation depth is less than or equal to 0.02 * R, where R is the radius of a given particle. Otherwise, David Mercier et al. appear to have had success when using the guiding principal established by Constantinides et al., which advocates for a depth limit of 10% of the particle size. From my own experience, when the mismatch between a particle's stiffness and the stiffness of a given mounting material is very large, then Constantinides 10% rule no longer holds and the 2% particle radius rule from Yan et al. remains reasonable.

With the aforementioned in mind you will still face a significant challenge in so far as the indentation size effect is concerned. Depending upon the radius of your particle, when you abide by Yan et al.'s approach then you may not obtain enough values of hardness as a function of indentation depth to apply the Nix-Gao relation before surpassing the particle-dominated depth limit. Therefore, care needs to be taken in interpreting the results. In other words, the hardness will not be the "true" hardness without the Nix-Gao analysis unless your particle is 120 um in diameter, then you could potentially solve for the true hardness by fitting the hardness vs. depth data between depths of 100 nm and 1200 nm. Such a range would likely be sufficient for indentation size effect analysis.

Lastly, one could take an alternative approach. You could acquire a flat-punch indenter tip and compress the micro-particles using an indenter. See Assadi et al. for more information surrounding this alternative approach.

Best,

Bryer C. Sousa

Materials Science and Eng.

Worcester Polytechnic Institute

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