Material Properties of Hard Coatings Developed for High Damping

Author(s):  
Peter J. Torvik ◽  
Bryan Langley
Author(s):  
Shad A. Reed ◽  
Anthony N. Palazotto ◽  
William Baker

Several researchers have shown that the material properties of hard coatings used in free layer damping treatments are dependent on the strain amplitude in the coating. This nonlinear phenomenon complicates the material characterization process and makes it difficult to find independent sets of data that are in complete agreement. During a recent in depth study of these materials, it became apparent that there were several other time and load history dependent nonlinearities present in these fascinating materials. These nonlinearities were observable because a free response based testing methodology was employed. Results indicate that the stiffness and damping of these materials change during the first several million loading cycles before finally stabilizing. Additionally, results suggest that the material properties are dependent on the initial condition of the free response, indicating a short term loading history dependency.


Author(s):  
C.L. Briant

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.


Author(s):  
R. T. Chen ◽  
R.A. Norwood

Sol-gel processing has been used to control the structure of a material on a nanometer scale in preparing advanced ceramics and glasses. Film coating using the sol-gel process was also found to be a viable process technology in applications such as optical, porous, antireflection and hard coatings. In this study, organically modified silicate (Ormosil) coatings are applied to PET films for various industrial applications. Sol-gel materials are known to exhibit nanometer scale structures which havepreviously been characterized by small-angle X-ray scattering (SAXS), neutron scattering and light scattering. Imaging of the ultrafine sol-gel structures has also been performed using an ultrahigh resolution replica/TEM technique. The objective of this study was to evaluate the ultrafine structures inthe sol gel coatings using a direct imaging technique: atomic force microscopy (AFM). In addition, correlation of microstructures with processing parameters, coating density and other physical properties will be discussed.The materials evaluated are organically modified silicate coatings on PET film substrates. Refractive index measurement by the prism coupling method was used to assess density of the sol-gel coating.AFM imaging was performed on a Nanoscope III AFM (by Digital Instruments) using constant force mode. Solgel coating samples coated with a thin layer of Ft (by ion beam sputtering) were also examined by STM in order to confirm the structures observed in the contact type AFM. In addition, to compare the previous results, sol-gel powder samples were also prepared by ultrasonication followed by Pt/Au shadowing and examined using a JEOL 100CX TEM.


Author(s):  
Brian Ralph ◽  
Barlow Claire ◽  
Nicola Ecob

This brief review seeks to summarize some of the main property changes which may be induced by altering the grain structure of materials. Where appropriate an interpretation is given of these changes in terms of current theories of grain boundary structure, and some examples from current studies are presented at the end of this paper.


2016 ◽  
Author(s):  
Frank Malgo ◽  
Neveen A T Hamdy ◽  
Alberto M Pereira ◽  
Nienke R Biermasz ◽  
Natasha M Appelman-Dijkstra

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