The relationship between crystal and hardness

[vinhphysics]

Hello all,
Who can tell me the ralationship between crystal and hardness of the coatings. I do XRD and measure hardness but the some coatings with high intensity of XRD peak show the low hardness. The questions are: what direction of planes is useful for hadrness? what elements affect on hardness?
Thanks so much!

 

[Astronuc]

In metals, the tensile/compressive yield strength may be correlated with hardness, so whatever element increases yeild strength would also increase hardness. Pure (unirradiated) elements have relatively low hardness, while alloying and radiation (which produces dislocation) generally increases strength and harness. Strength and hardness are greater in the direction of lowest interatomic spacing. For example, in hcp metals, the strength would be greatest paralle to the basal plan (a-direction) and lower in the direction of the c-axis (normal to basal plane). Cubic systems would be stronger along diagonals.

Ceramic materials have high strength and high hardness, and BN (http://en.wikipedia.org/wiki/Boron_nitride,http://www.azom.com/details.asp?ArticleID=78) is perhaps the hardest ceramic. Diamond is perhaps the hardest substance with a tetrahedral (A4) structure (http://cst-www.nrl.navy.mil/lattice/struk/a4.html) .

One might find this site useful - http://cst-www.nrl.navy.mil/lattice/index.html

 

[ravenprp]

The relationship between crystal and hardness can be complex and is not always a direct correlation. In general, the hardness of a material is determined by its atomic structure and the strength of the bonds between its atoms. Crystalline materials have a regular, repeating atomic structure, which can contribute to their overall hardness. However, the orientation and arrangement of the crystal planes can also play a role in determining the hardness of a material.

In terms of XRD analysis, the intensity of the peaks can indicate the degree of crystallinity of a material. A high intensity peak suggests a well-ordered crystal structure, while a low intensity peak may indicate a more disordered or amorphous structure. However, this does not necessarily directly correspond to the hardness of the coating.

The direction of planes that are useful for hardness can vary depending on the material and its crystal structure. In general, planes with tightly packed atoms and strong bonding between them tend to contribute to higher hardness. However, this can also be affected by the presence of impurities or defects in the crystal structure.

In terms of elements that affect hardness, this can also vary depending on the specific material. Generally, elements with higher atomic weights and stronger bonding tend to contribute to higher hardness. However, this can also be influenced by the crystal structure and arrangement of the atoms.

In summary, the relationship between crystal and hardness is multifaceted and can be influenced by various factors such as crystal structure, orientation of planes, and the presence of impurities or elements. Further research and analysis may be needed to fully understand and predict the hardness of a material based on its crystal structure.