Von statisch zu dynamisch: In situ Experimente im ESEM

Transkript

1 Von statisch zu dynamisch: In situ Experimente im ESEM Peter Pölt FELMI, TU Graz, und ZFE Graz Workshop Mikroskopie von Polymeren und Verbundwerkstoffen Graz, 2. Februar

2 Motivation 2

3 ESEM basics SEM High vacuum in the specimen chamber necessary ( < 10-4 torr). 3

4 ESEM basics ESEM E(nvironmental) SEM High vacuum in the specimen chamber possible ( < 10-4 torr). Additional variable pressure range ( torr). 4

5 ESEM basics 0-100% rel. humidity Scattering of electrons at the gas atoms / molecules creates positive ions Those ions compensate for the negative charging by the electrons. Phase diagram of water The specimen chamber can be converted into a climate chamber, where the relative humidity can be adjusted. But also other gases like N 2 can be used, important in case of cryo-experiments. 5

6 Observation of physical and chemical processes and reactions in the microscope, with high resolution and great tdepth of ffocus: microscopic parameters. Simultaneous recording of the macroscopic changes of stress, strain, temperature, pressure macroscopic parameters. 6

7 ESEM-Quanta 600 FEG A microlab for Science and Industry 7

8 Tensile tests and the crack ktip 8

9 Cooling / heating platform for the tensile stage max 1 2 L r 42/24x10x4mm 24 x 4 (RT / cryo) crack tip stress-strain diagram A. Zankel et al., SCANNING 29, (2007) 9

10 Tensile tests: isotactic polypropylene, β-nucleated (MFI 20), v = 1 mm/min 10

11 Fracture behaviour, MFI and spherulites ipp, β-nucleated (MFI 20), tensile test with v = 1 mm/min; top: 2 images at elongations of around 2 mm (left) and 3.8 mm (right); bottom: force-elongation diagram; the red marker indicates the elongation corresponding to the centre of the area marked in the image top right P. Poelt et al., Conf. proc. PPS 24 (2008) 11

12 Fracture behaviour and particles ipp (MFI 10) / EPR (20 wt% rubber), MFI: 6.9 ipp (MFI 10) / EPR (20 wt% rubber), MFI: 2.3 Tensile e tests, v = 1 mm/min; top left: images recorded at the elongations marked in the stress-strain diagram; top right: TEM images, showing the size and the distribution of the EPR particles in the respective materials. P. Poelt et al., Conf. proc. PPS 24 (2008) 12

13 ipp, v = 1 mm/min 42 / 24 x 10 x 4 mm (RT / cryo) 13

14 Tensile tests and the specimen surface 14

15 Particles as µ extensometer ipp, with glass spheres as filler particles, polished surface to remove the utmost layer. Tensile test with v = 2 mm/min. Left: the change of the distance between the points A and B in the image top right as a function of the elongation. The blue diamond symbol gives the elongation, where the first crack was visible at the surface. Right: the images corresponding to the points given in the diagram left. 15

16 Composite materials wood and polymer 16

17 Composite materials: wood and polymer Advantages: Low weight, cheap. Specimen by courtesy of IB Steiner 17

18 Composite materials: wood and polymer Pine PP 18

19 The third dimension 19

20 Ultramicrotomy in the ESEM Left: Schematic of an ultramicrotome in the ESEM (3View TM from Gatan GmbH). Right: The ultramicrotome mounted at the door of the specimen chamber; Denk W, Horstmann H (2004): Serial block-face scanning electron microscopy to reconstruct three-dimensional tissue nanostructure, PLoS Biol 2(11): e329; t / /3 h 20

21 Ultramicrotomy in the ESEM Left: Direct view of specimen and diamond knife. Bottom: Principle of ultramicrotomy in the ESEM: cut record image of the block face cut record image of the block face cut. Contrary to conventional TEM sectioning, all images are aligned. The thickness of the slices is adjustable and can be as small as 50 nm. The maximum area is around 1 mm². 21

22 Ultramicrotomy in the ESEM ipp (MFI 10) / EPR (17 wt% rubber), MFI: 4.8 Test stopped at 25% of Yield Preparation: Embedding in resin Staining: RuO 4 Pre-cutting 22

23 Ultramicrotomy in the ESEM Preparation: Embedding in resin Staining: RuO 4 Pre-cutting Test stopped at 25% of Yield ipp (MFI 10) / EPR (17 wt% rubber), MFI: dim. representation of the cuts of the sample of the previous page; blue: EPR particles, white: PP matrix, yellow: cracks, voids. P. Poelt et al., Conf. proc. PPS 24 (2008) 23

24 Conclusion Correlations between microstructure, macroscopic parameters and characteristics can be gained Inorganic filler particles can serve as micro-extensometers, enabling the calculation of local strain fields in dependence on the overall strain. Tensile tests in dependence on the relative humidity can be performed. Combinations of in situ tensile testst with other methods like acoustic emission i analysis, e.g. for glass fibre reinforced polymers, are possible Automated ultramicrotomy in the ESEM allows to elucidate the 3-dimensional interior structure of a specimen. 24

25 Part of this work was kindly sponsored by (project ) 25

26 Thank You for Your kind attention 26