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Elektronenmikroskopische Untersuchung der Mikrostruktur von pseudoelastischen NiTi-Stents

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Published/Copyright: May 8, 2013
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Practical Metallography
From the journal Practical Metallography Volume 44 Issue 5

Kurzfassung

Nickel-Titan-Formgedächtnislegierungen (NiTi-FGL) werden seit einigen Jahren kommerziell erfolgreich eingesetzt. Insbesondere im Bereich der Medizintechnik gibt es zahlreiche Anwendungen, bei denen sich NiTi etabliert hat. Ein Beispiel dafür sind Gefäßprothesen (Stents). Auch wenn NiTi-Stents zur Zeit nur einen Anteil von cirka 12% der weltweit mehr als 3,5 Millionen implantierten Stents pro Jahr ausmachen, wird der Markt für endo- und kardiovaskuläre Stents 2006 ein Volumen von 5,5 Milliarden Euro überschreiten [1, 2]. Bei der Stent-Produktion entstehen Oberflächendefekte, welche unter Ermüdungsbeanspruchung zur Rissbildung beitragen können. Für die Hersteller von Stents sind daher Oberflächenqualität und Mikrostruktur mit Hinblick auf die funktionalen Eigenschaften und Ermüdungsbeständigkeit wichtige Faktoren. In der vorliegenden Arbeit wurden NiTi-Stents mit Hilfe von raster- sowie transmissionselektronenmikroskopischen (TEM) Methoden untersucht. Die Probenpräparation für TEM-Untersuchung wurde mit Hilfe einer Fokussierbaren Ionenstrahlanlage (FIB) durchgeführt, weil aufgrund der geringen Dimensionen eine andere Probenpräparation extrem schwierig ist. Dieses Verfahren wird ausführlich beschrieben und die Ergebnisse diskutiert.

Abstract

Nickel titanium shape memory alloys (NiTi-SMA) have been commercially available for a number of years. Particularly in the field of medical technology there are applications in which NiTi alloys have become established. One such example is in arterial prosthetics as stents. Even though NiTi-stents account for only about 12% of the more than 3.5 million stents implanted each year, the market for endo- and cardiovascular stents in 2006 will be worth over 5.5 billion Euros [1, 2]. In the production of stents surface defects occur which, under fatigue loading, can result in the formation of cracks. For the manufacturer of stents, microstructure and surface quality in respect of the functional properties and resistance to fatigue of the stents are thus both important factors. In the work presented here NiTi stents are examined with the aid of scanning (SEM) and transmission electron microscopic (TEM) methods. The specimen preparation for the TEM examinations was carried out with the aid of a focused ion beam unit (FIB) because due to their extremely small size, any alternative method of preparation would have been extremely difficult. The procedure used is discussed and described in detail.

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Translation: Phil Tate

Matthias Frotscher 09-10-1977 Dresden, studies of Mechanical Engineering, branch: Materials, Ruhr-University Bochum; diploma thesis Metallographic Study on the Casting Processing of TiSi by Means of Induction-Melting in Graphite Crucibles, since 2006 working on PhD thesis: Highly Flexible NiTi Shape-Memory Alloy Components for Medical Applications-Materials Scientific Studies on Microstructures and Mechanical Properties.

Andreas Kröger 21-08-1973 Bochum, studies of Mechanical Engineering, branch: Materials, Ruhr-University Bochum; diploma thesis: In-situ TEM-Investigations on the strain Induced B19’-Phase in NiTi Shape Memory Alloys structured by FIB; since 2005 working on PhD thesis: Shape Memory behaviour subject to Ni-rich precipitates in NiTi single crystals — special TEM specimen investigation for in situ experiments (heating/cooling and straining), structuring of surfaces using Focused Ion Beams (FIB) and preparing specimens for the Nano Indentation System.

Literatur/References

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Erhalten: 2006-7-11
Angenommen: 2006-10-12
Online erschienen: 2013-05-08
Erschienen im Druck: 2007-05-01

© 2007, Carl Hanser Verlag, München

Articles in the same Issue

  1. Contents/Inhalt
  2. Inhalt / Contents
  3. Editorial
  4. Editorial
  5. Technical Contributions/Fachbeiträge
  6. Elektronenmikroskopische Untersuchung der Mikrostruktur von pseudoelastischen NiTi-Stents
  7. Metallographic Studies on a Defective Plate Heat Exchanger
  8. Correlation between Crystal Orientation, Channeling Contrast and Topography during FIB Milling of Cu Studied by FIB, EBSD, SEM, and AFM
  9. Fabrication and Modification of Photonic Structures with Focused Ion Beam
  10. Novel Applications of a Focused Ion Beam Workstation for Specimen Preparation and Nanostructuring
  11. Automated X-Ray Elemental Analysis in Three Dimensions Using a Dual Beam-Focused Ion Beam System
https://doi.org/10.3139/147.100338

Articles in the same Issue

  1. Contents/Inhalt
  2. Inhalt / Contents
  3. Editorial
  4. Editorial
  5. Technical Contributions/Fachbeiträge
  6. Elektronenmikroskopische Untersuchung der Mikrostruktur von pseudoelastischen NiTi-Stents
  7. Metallographic Studies on a Defective Plate Heat Exchanger
  8. Correlation between Crystal Orientation, Channeling Contrast and Topography during FIB Milling of Cu Studied by FIB, EBSD, SEM, and AFM
  9. Fabrication and Modification of Photonic Structures with Focused Ion Beam
  10. Novel Applications of a Focused Ion Beam Workstation for Specimen Preparation and Nanostructuring
  11. Automated X-Ray Elemental Analysis in Three Dimensions Using a Dual Beam-Focused Ion Beam System
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