CMA Analytical Workshop Day 1 24th April 2012 XRD/ XRF. Robbie Goodhue

Transcription

1 CMA Analytical Workshop Day 1 24th April 2012 XRD/ XRF Robbie Goodhue

2 Discovery of x-rays 8 th November 1895 Wilhelm Röntgen

3 Discovery of x-ray diffraction X-ray beam Copper sulphate Photographic paper Max von Laue

4 Determining crystal structure using x-rays Lead shielding Slits Crystal Ionisation chamber Rotating tables Braggs x-ray spectrometer (1913) William Lawrence Bragg

5 Determining crystal structure using x-rays nλ = 2d Sinθ d William Henry Bragg

6 Nobel Prize in Physics Röntgen 1901 von Laue 1914 Bragg & Bragg 1915

7 Properties of x-rays 1. Able to penetrate solid matter 2. Short Wavelength Å 3. Able to cause fluorescence in certain chemical compounds 4. Able to ionize atoms

8 Philips PW1720 powder XRD

9 Diffractometer Soller slit Divergence slit At certain Bragg angles a diffracted beam reaches the detector Monochromator Shutter Sample Receiving slit Detector

10

11

12

13

14 Peaks Background

15 d = 1 x λ /(2Sinθ) λ = Å (Cu Kα) d = 3.342Å

16

17

18

19

20

21

22

23 Help is at hand The International Centre for Diffraction Data in Philadelphia holds a database of materials The ICDD 2011 Powder Diffraction File contains 715,953 unique material data sets These include organics, explosives, pigments, pharmaceuticals, zeolites, minerals, metals, polymers, ceramics.

24 XRD Example 1 Investigation of defects in houses

25 Irish Times, Wednesday 25 th February 2009 In the case, Menolly was seeking indemnity against up to 60 million in damage claims that householders are expected to bring. Lagan s testing has shown only marginal movement in the cracks, and this was due to changes in temperature. this blows out of the water the theory

26

27

28

29

30 Proposed reaction FeS 2 + 2CaCO H 2 O O 2 = FeO(OH) + 2CaSO 4.2H 2 O + 2CO 2 Pyrite + calcite + water + oxygen = goethite + gypsum + carbon dioxide EXPANSION

31 Cracks propagating Doors jamming Top and bottom Visible bulge in centre of floors Tiles cracking

32 XRD Example 2 Polymorph detection in pharmaceutical

33 Polymorphism ability of a solid material to exist in more than one form or crystal structure α β

34 Quantitative polymorph determination in tablet Excipients Tablet API

35 X-ray Diffraction (XRD) Rapid Powder sample 40 / 60 minute scan ~30 minute interpretation Cheap 50 per sample Powerful 628,155 unique material data sets in ICDD file

36 Bruker S2 Ranger ED-XRF Energy Dispersive X-ray Fluorescence George Gabriel Stokes UV

37 Generation of x-rays Characteristic radiation (of target) 1.54Å K α Intensity Continuous breaking radiation 1.39Å K ß Wavelength

38 Target material - Copper Nucleus K-shell L-shell M-shell N-shell

39 Target material - Copper Ejected Electron Incoming photon K-shell L-shell M-shell N-shell

40 Target material - Copper 1.54Å K α Kα Characteristic Radiation Cu K α Intensity 1.39Å K ß Wavelength K-shell L-shell Kß M-shell N-shell

41 Detection of fluorescent x-rays (Energy Dispersive XRF) Tube: 20 kv No filter Cps 0 30 KeV 0

42 Detection of fluorescent x-rays (Energy Dispersive XRF) Tube: 20 kv No filter Fe K α Cps Fe K ß S K α S K ß 0 30 KeV 6.4 0

43 Detection of fluorescent x-rays (Energy Dispersive XRF) Tube: 20 kv No filter 40 kv Al 500 µm filter Cps 0 30 KeV 0

44 Can we obtain quantitative XRF data? Complexities exist: Matrix effects (absorption and enhancement) Line overlaps Rayleigh and Compton scatter Macroscopic effects But modern software is very advanced

45 Sample preparation Powder and Pellet

46 Sample preparation Fused glass disc Fuse sample in glass with lithium metaborate / lithium tetraborate flux at 1000 C C

47 XRF Example 1 Distinguishing sandstones from the Mandawa Basin Wellington Hudson

48 The problem The Mandawa Basin of Southern Coastal Tanzania is under exploration for hydrocarbons and has several sandstone formations It is difficult to distinguish these sandstones in the field because they lack distinctive features Yet it is believed that the sandstones have different depositional histories and this may prove significant in terms of hydrocarbon exploration

49 Calibration 0.8 Intensity (Cps) XRF Concentration (%) The project used XRF to attempt to discriminate the sandstones For each element, a calibration curve was established, using standards Concentration (%) Int. net Int. background Conc. XRF 0

50 K 2 0 (w t % ) Miocene or younger Nangurukuru Kihuluhulu Makonde Nalwehe Mitole Rufiji fluvials Upper Kipatimu Lower Kipatimu Nondwa/Mtumbei Kandawale-Karoo XRF Results By plotting oxides of elements (K and Si) against each other discrimination of the Mitole Zone from the others is possible 4 2 Mitole Zone Upper Kipatimu Zone SiO2 (wt %) Lower Kipatimu Zone Nangurukuru Zone Kandawale Zone

51 A l 2 O 3 / C a O Miocene or younger Nangurukuru Kihuluhulu Makonde Nalwehe Mitole Rufiji fluvials Upper Kipatimu Lower Kipatimu Nondwa/Mtumbei Kandawale-Karoo XRF Results Use of other elements and their ratios or sums resolves the other sandstones Fe2O3 + MgO (wt %) Mitole Zone Upper Kipatimu Zone Lower Kipatimu Zone Nangurukuru Zone Kandawale Zone

52 XRF provides a solution At least five Geochemical Zones related to formations can be recognized With just the chemical information on a sample, it is now possible to assign it to a geological formation XRF offers an unbiased way of categorizing sandstones

53 XRF Example 2 Meteorites or Meteorwrongs?

54 Hunt for the EUR500k rock METEORITE FIREBALL LANDS IN IRELAND September 4, 2003 Pat Flanagan IRISH treasure hunters are on the lookout for a chunk of space rock that could earn them up to 500,000. The flaming meteorite was seen hurtling through the night sky and is believed to have landed in north Tipperary. Sky-watchers gathered on the Silvermines Mountains hoping to get a good look at Mars were amazed when the fireball streaked above them. They said it was a "very bright falling star" that lit up the entire area. One witness added: "We saw the fireball falling at an angle almost parallel to the horizon. "First it appeared like a falling star and then it seemed to glow white...

55 Send us your meteorites Dr Ian Sanders

56 Finds Canyon Diablo, Arizona (Iron Octahedrite Meteorite) Fell 20,000 40,000 years ago

57 Falls Bovedy, Derry Fell (through asbestos roof of RUC Stores) 25 th April 1969 $5490

58 X-ray Fluorescence (XRF) Rapid qualitative assessment Solid / powder / liquid sample 5 minute scan 5 minute interpretation Quantitative analysis possible with calibration using suitable preparation and standards Powerful Most elements from Boron (Z=5) to Uranium (Z=92) Concentrations from ppm

59 Continuous Flow Isotope Ratio Mass Spectrometry CF-IRMS

60 Global abundance 12 6 C 98.89% 14 7 N 99.64% 16 8 O % 13 6 C 1.11% 15 7 N 0.36% 17 8 O % δ ( ) = R sa - R std R std X O %

61 Thermo Delta plus Flash Elemental Analyser or EA Gas Bench Mass spec

62

63 IRMS Example 1 Reconstructing fossil ecosystem Jo Hellawell Chris Nicholas Robbie Goodhue

64 Green River lagerstatten from Wyoming, USA Hypothesis: isotopes of nitrogen and organic carbon can be used to find out information about ecosystems from much further back in time, in order to gain some quantitative trophodynamic information about food webs from extinct fossil communities

65 RHF2 Nearshore Quarry

66 Preparation of fish

67 δ 15 N vs δ 13 C 10.0 Average δ 15 N AIR ( ) D. dentatus K. eocaena K. alta Average δ 13 C org VPDB ( )

68 IRMS Example 2 Nutrient removal in domestic waste-water reed beds Niall O Luanaigh Laurence Gill Robbie Goodhue

69 1.5 g of isotopically heavy ammonium chloride spike introduced 15 NH 4 -N (98% 15 N) Effluent collected over 64 day period, filtered and dried

70