Surfaces & Coatings

In multilayer coatings the individual layers often have individual functions, e.g., protection from mechanical impacts and contamination, corrosion protection, adhesive layers, etc. Therefore, a homogeneous layer structure without defects, inclusions, etc. is essential for the quality and functionality of the product. With OCT (Optical Coherence Tomography) it is possible to measure the thickness of coatings with micrometre precision (even for most multilayer coatings).

In a research cooperation with the Institute of Biomedical Mechatronics (Johannes Kepler University, Linz), the skin structure of a Texan horned lizard was artificially recreated. With its unique skin structure, this animal can move condensed water from the whole body surface directly to the mouth. The successful application of OCT played a major role in the success of this project. As an instrument for imaging and characterization of the surface, OCT contributed to the understanding of functionality of the surface. Applications for similar “functional surfaces” are “Lab-on-chip” applications, wound compresses, textile fibers, and the distribution of lubricant on friction bearings.

Using Laser-Ultrasonics, the frequency dependent velocity of surface acoustic waves in a layer can be measured. The data can be evaluated to find the layer properties, for example its thickness. Our systems enable us to measure SAW dispersion curves up to 1 GHz, which allows us to characterize layers ranging from 500 nm up to several mm thickness. The illustrations show a core material (red) with an oscillating layer on top (blue) at increasing frequencies of a guided wave mode from case 1 to 4, whereas the penetration depth of the displacement field decreases until only the layer material influences the wave propagation (4). Thus, depending on the geometry and elastic properties of the layer material under investigation, the appropriate parameters of the measurement can be selected
The investigation of layered structures with higher complexity (e.g., multilayers or gradual layers) is possible by adapting the theoretical models for the calculation of dispersion curves.

Metallic components are often coated dielectrically in order to optimize the operating characteristics (such as tribology).
With Terahertz technology (THz) such coatings can be measured efficiently inline.

The OCT (Optical Coherence Tomography) provides insight into nearly all common polymer materials used in the industrial environment. As a tomographic measurement technique, OCT delivers information about the internal structure in order to detect and characterise cracks, defects, inclusions, pores, etc. OCT not only controls the quality and functionality of the plastic products, but also delivers relevant information to help understand and optimize the manufacturing process.

Laser-Ultrasonics allows a very efficient characterization of thin-film structures. High-frequency ultrasonic waves (SAW) are excited up to 1 GHz by laser pulses. The layer systems are characterized by analysing the dispersion behaviour of the waves. Ask our LUS experts!

With laser-based methods surfaces can be structured for different purposes. The OCT technology (Optical Coherence Tomography) is a perfect tool for imaging and measuring such structures in the micrometre range (e.g. microscopic laser drilled holes shown in the picture) and can also be measured online and in real-time during the process.

As illustrated in this image of a coin, the topography or roughness (parameters cf. ISO 25178) of a sample can easily be determined by Optical Coherence Tomography (OCT). The advantage of using OCT, compared to other methods, is the additional possibility of measuring steep edges. The accuracy in the measurement of height profiles is below 1 micron.

In lacquer coating layers (or similar coatings), embedded particles (of different materials) are very important for the functionalization of the coating or for e.g. a perfect automotive-metallic-coating.
With the low-cost OCT method we are able to monitor and characterize the partial embedding, which helps to secure and optimize the production process.

Do you want to know the exact local distribution (in micrometer range) of your chemical components? With Mid-Infrared-Microscopy we can chemically characterize and measure materials and cross-sections (e.g. residues or inclusions) with a spatial resolution as small as 5 µm.

The determination of the hardness penetration depth in thermally hardened components is essential for quality control. State-of-the-art is to cut samples and do etching and hardness measurements. Laser-Ultrasonics opens a non-destructive alternative. Thereby, zones of different microstructures at arbitrary positions can be imaged up to a tomographic representation of the hardness penetration depth.