Correlate Ceramic Microstructure to Mechanical Properties

Nanoindentation and scanning electron microscopy (SEM) may be used as complementary techniques to evaluate ceramic processes. A grid pattern of nanoindents can be mapped with hardness or modulus data, then correlated to the SEM image and compared to processing conditions. For example, high temperature processing of pyrolysis bonded silicon carbide (PBSC) can be characterized using nanoindentation to determine modulus and hardness. These properties may be mapped and overlaid on SEM images.

Nanoindentation and SEM Evaluation of Silicon Carbide Systems

Silicon carbide (SiC) is an attractive material for various applications due to its high melting point, corrosion resistance, high thermal conductivity and excellent mechanical properties. Some high temperature processing conditions for pyrolysis bonded silicon carbide (PBSC) have been detrimental to mechanical properties and also resulted in mass reduction. Understanding the mechanical behavior of these materials at the nanoscale is extremely important. Nanoindentation is a fast and accurate method to measure the local elastic and hardness properties of individual microstructure components. Scanning electron microscopy (SEM) analysis is used to understand the obtained results and to provide information about the correlation between the mechanical and materials properties.

Note: This work was presented at the ICACC 2016 conference. For a complete copy, please fill in the Contact Form and request ICACC poster.

Nanoindentation

Using a sophisticated constant strain rate method with a proprietary dynamic technique, four dimensional property maps of hardness, modulus, stiffness and topography are created at high speeds, with less than 3.5 seconds per indentation using an iNano nanoindenter. Two examples are shown below.

Nanoindentation hardness maps for different SiC processing temperatures

Nanoindentation hardness maps for different SiC processing temperatures

 

Scanning Electron Microscopy

A backscattered electron detector provides material contrast, with heavier elements appearing brighter in the SEM image. The larger grains in SiC are clearly pronounced in BSD images. The indentations are evident in the topography mode images.

The mechanical maps from nanoindentation are overlaid on the SEM images, showing correlation between microstructure and phase distribution with modulus (shown) and hardness. 

Ceramic SiC sample from UnivFL BSD SEM image at 1350x with modulus map overlay

Modulus map from nanoindentation shows good representation of the SiC microstructure and phase distribution correlated with the BSD scanning electron microscope image


The maps of indentations (additional maps and data presented at ICACC16) are in agreement with scanning electron images, suggesting that the weakening of the bulk samples are due to a weaker matrix. Dynamic nanoindentation measurement provides four dimensional property maps of hardness, modulus, stiffness and topography as a function of XY spatial dimension and depth.

Thanks to Mehrad Mehr and Professor Juan Nino from the University of Florida for their collaborations.  


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