Excellence in Nanomechanical Test Instrumentation

Nanoindentation

Nanoindentation using the MML NanoTestTM is a remarkably flexible and informative mechanical test. For an overview of the theory behind nanoindentation, and an overview of the values it quantifies, click here. Due to its relatively simple experimental method, nanoindentation can yield a wide range of information concerning a wide range of materials, including metals, thin films, plastics, powders and much more.

Nanoindentation using the MML NanoTestTM

The MML Pendulum System

Micro Materials Ltd use a unique pendulum design in order to effect accurate and reproducible indents. This set-up means that the platform is open, allowing large sample sizes. The user may also access the indenter easily, meaning an indenter may be changed in less than a minute.

The NanoTestTM is currently in use worldwide for both research and industrial applications. It is used extensively along the research and development stages of production right through to quality assurance of finished products. Customers include MIT, Tsinghua University, University of Cambridge, Philips, Siemens, Hong Kong University of Science and Technology and many many more.

Overview of Nanoindentation

During traditional indentation, a hard tip, typically a diamond, is pressed into a sample with a known load. After a set period of time the load is removed. The area of the residual indentation in the sample is measured and the hardness, H, is defined as:

H = P/Ar where P = Maximum Load
  Ar = Residual Indentation Area

In order to determine the indent area, a powerful microscope is needed. However, an alternative method may be used - depth sensing indentation.

Depth Sensing Indentation

In contrast to traditional hardness testers, the MML NanoTest nanoindentation system allows the application of a specified force or displacement history, such that force, P, and the displacement, h, are controlled and/or measured simultaneously and continuously over a complete loading cycle. The extremely small force and displacement resolutions possible with the MML NanoTest, which are as low as 30nN and 0.001nm, respectively, are combined with very large ranges of applied forces (0 - 500mN) and displacements (0-50µm or more). This allows the NanoTest to be used to characterize nearly all types of material systems.

 

The following properties may be measured:

What can hardness tell you about your materials?

Hardness is proportional to the strength of the material.
High hardness generally corresponds to high abrasive wear resistance.

Case Study: Coatings
The hardness of wear-resistant coatings should be optimised in order to obtain best wear resistance. High hardness values may be accompanied by brittle fracture but low values may lead to deformation and cracking. Substrates must be hard enough to support their coatings under load.

What does hardness indicate in relation to coatings?
A "hardness" test indicates surface or material consistency, which varies with microstructure, crystallographic orientation, composition, contamination, and intrinsic stress.

What can be studied using hardness measurements?
Diffusion profiles
Preferred orientation of polymers
Phase distribution
Time-dependent material changes are easily monitored
Width of welding zones can be investigated
"Hardness" tests can provide information on densification in amorphous materials
"Hardness" tests can be used to determine the bonding strength of fibres and particles in a matrix
"Hardness" tests can be used to find the fracture strength of particulates, which can be used when defining powder processing conditions

What can a modulus tell you about your materials?

Modulus is a direct property of a material (unlike hardness), so data may be easily compared between samples.

Case Study: Thin Films
Modulus is sometimes the best indicator of thin film quality. The elastic contact area may be determined by the elastic modulus. Bulk deposition materials can be easily compared with the thin film materials produced.

Modulus and stress:
Modulus is a factor in determining film intrinsic stress and thermal stress

Applications:

  1. Indentation modulus is valuable for MEMS design since materials are too thin for other methods to be used
  2. Higher film modulus tends to give higher scratch test critical loads
  3. For elastic strains in films under load, it is preferable to have a film modulus lower than the substrate modulus
End of content