An interview with Dr Alexander Karbach, Material Scientist at Currenta Analytics, conducted by Jake Wilkinson, BSc
How does Currenta Analytics work in the field of failure analysis?
Currenta is a service provider located in CHEMPARK Leverkusen. The division Currenta Analytics offers an extensive range of analytical services for research, development and production in industry such as material analytics. For example, in this field we investigate material complaints for our customers.
Is there a sample with a failure or defect? Our job is to assess what it is all about is. Is it a foreign particle? Is it a production error? Did dust get into the system?
Based on our results, we create a report including the images, diagrams, a short summary and a conclusion.
For Solid State and Surface Analytics we can fall back on a large portfolio of methods and techniques. Therefore, we have got techniques like Infrared and RAMAN Spectroscopy combined with Microscopy, Thermal Analysis, X-ray Diffraction, Atomic Force Microscopy and Optical Microscopy. In addition to this we perform SEM (scanning electron microscope) and elemental analysis as well as nanoindentation experiments.
Nanoindentation allows us to spatially test the mechanical properties of a material, such as taking measurements along a weld seam to assess where the material has failed.
What different types of materials does Currenta Analytics work with?
In Solid State and Surface Analytics department we mainly work on polymers and their raw materials, additives and fillers which can be used in almost any application. We can measure all types of materials, from very soft to hard metals, ceramics and organics. Typical areas of application for these materials are industries such as pharmaceuticals and crop protection, consumer goods and construction as well as transportation, electrical engineering/electronics.
After the analysis, we inform the customer of the cause for the error. For example, what could have caused cracks in their sample? Maybe they welded too hard, or they cooled it too quickly. As soon as we have identified the cause, we talk to the customer and make a recommendation or try to find a solution.
What different techniques do you use for failure analysis?
We use a variety of imaging and analytical techniques to help our customers tackle their problems at their roots.
We always start our analysis by taking an image of the sample. We then identify the location of the defect and examine it with an optical microscope. We can use the different contrast modes in an optical microscope to assess the defect afterwards. If the defect is metallic we can visualize it using an SEM with elemental analysis.
When analyzing coatings, we would cross section the sample and use an AFM to image all fine layers in the micro- and nanometre range to understand the problem. We can subsequently determine whether there are issues with an interpenetrating layer or an unwanted deposit in the layers of the coating.
We also offer compositional analyses using techniques such as IR Spectroscopy or Raman, and often dissolve the sample in solvent for further measurements. If the sample looks crystalline, we perform crystallographic analysis using X-ray Diffraction to observe its crystal structure and determine if it is disturbed.
Nanoindentation plays an important role when it comes to observing the intersections between materials such as the weld seam in metals or bonding polymers together. For example, we had a customer who welded polymer strips for packaging. One in a thousand strips would break and the customer asked why.
Using optical microscopy and nanoindentation, we determined the mechanical properties of the weld seam.
What are the advantages of using nanomechanical testing over more traditional testing methods?
If you carry out a large mechanical test, you only have a large piece to process. With nanoindentation, however, you concentrate directly on the area in which the sample breaks or bends.
This is becoming increasingly important as the pressure on technology to be lightweight increases. For example, laptops will soon be made of carbon fibre composites that are lightweight and aesthetically pleasing, but can also be bent or broken if they are not properly designed.
Through nanomechanical tests we can determine where bends and breaks come from then we feed this back to the designers who can then improve their design.
Why did you choose to use Hysitron nanoindentation systems?
We have been working with Hysitron for 18 years. Initially, it was a project that focused on thin layers of coatings with a thickness of several micrometres. The equipment we had back then was not suitable because we needed something precise enough to work at a nanoscale thickness and a low force. The TriboIndenter from Hysitron was exactly what we needed.
How useful is the new XPM measurement feature?
The XPM feature was very useful because at the end you get a measurement and a quantitative image much faster than before. The quantitative mapping is well received by our customers. As they say, an image says more than a thousand words (see figure 1).
Figure 1: XPM Modulus map on the cross section of 3D printed poly lactide acid (PLA) strands.
We can refer to the image above to describe whether certain areas are correct or where the failure comes from. The speed allows you to adjust the range using the optical microscope. You go to the nanoindenter stage with the sample, adjust the area and then use the indenter to adjust the procedure and measure, e.g. 20,000 indentations overnight.
Alternatively, you can use the old-fashioned standard method, which is more suitable in some cases. Measurements for each individual indentation allow you to adjust the depths, so that this instrument has some of the best features of the new and the old.
About Dr Alexander Karbach
Dr. Alexander Karbach works as Material Scientist with over 30 years’ experience in the field of materials characterization of polymers, rubber, metals, ceramics, hybrid materials and drugs.
At Currenta Analytics he is responsible for the department of surface and solid state analysis.
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