Faststof NMR studier af uorganiske materialer

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1 Faststof NMR studier af uorganiske materialer Jørgen Skibsted Instrument Centre for Solid-State NMR Spectroscopy and Interdisciplinary Nanoscience Center (inano) Department of Chemistry, University of Aarhus, Denmark Introduction to solid-state NMR Applications: Portland cements NMR interactions: Chemical shift Dipole-dipole interaction Spin-lattice relaxation Kemi-lærerdag, Institut for Kemi, 16. januar

2 NMR frequencies wavelengths 13 C 9.4 Tesla L = MHz E = 0.04 J/mol = 2.71 m Infrared = m = MHz E = 150 kj/mol Visible-UV = m = MHz E = 240 kj/mol X-rays = m = MHz E = kj/mol 2

3 87 Rb MAS NMR: Rb 2 SO 4 E L = MHz (9.4 T) R = 14.5 khz 3

4 Nuclear Magnetic Resonance Fourier transformation 4

5 Low-resolution NMR I NV γ s B0 h I(I 1) 3kT Spin-lattice relaxation (T 1 ) dmz(t) dt M z (t) M T 1 0 Spin-spin relaxation (T 2 ) 20 MHz 0.47 T 50 mm dmx(t) dt Mx(t) T 2 dm y dt (t) M y T 2 (t) McDonald, Mitchell, Mulheron, Aptaker, Korb, Monteilhet Cem. Concr. Res. 37, 303 (2007). 5

6 Magnetic Resonance Imaging Frequency Magnetic field 3 cm Beyea, Balcom, Mastikhin, Bremner, Armstrong, Grattan-Bellew, J. Magn. Reson. 144, 255 (2000) 6

7 High-resolution NMR of solids B o B 0 = 9.4 T 7 mm 4 mm B 0 : 4.7 T 23.5 T 7

8 NMR at low magnetic field L = -B 0 B gauss (Earths magnetic field) S. Appelt et al. Research Centre Jülich & Achen University of Technology (2005) 8

9 High magnetic field: 950 MHz (22.3 T) Aarhus 9

10 The NMR Periodic Table Spin I = ½ Spin I > ½ Quadrupole 10

11 Magic-Angle Spinning Heteronuclear dipolar coupling m = o 11

12 Magic-Angle Spinning m = o Ferrocene (C 5 H 5 ) 2 Fe 2000 Hz 900 Hz 400 Hz 200 Hz Static 12

13 Magic-Angle Spinning Max spinning speed: 350 m/s 4 mm 1.6 mm 13

14 In vivo 1 H MAS NMR Spectroscopy R. A. Wind, Pacific Northwest National Laboratories, Washington, USA -CH 2 -CH 2 -CH= =CH-CH 2 -CH= 14

15 Sensitivity enhancement Properties I S Spin isotope 1 H, 19 F C, 15 N, 29 Si... Abundance High Low Gyromagnetic ratio, High Low Short spin-lattice relaxation time, T 1 Short Long The cross polarization CP/MAS NMR experiment: I Enhances the signal-to-noise (S/N) ratio by I / S Reduces the spectrometer time S 15

16 Cross polarization: Spin-lock LAB-frame Double rotating frame I Z (B 0 ) Z (B 0 ) L,I = I B 0 y (/2) y x (B 1I ) L,I y cold x Boltzman distribution n n B exp k T S Z (B 0 ) Z (B 0 ) L,S = S B 0 y B 0 >> B 1 y hot x x (B 1S ) L,S 16

17 Cross polarization: Hartmann-Hahn match I S T 1 I T 1I T 1S T 1 S Lattice Matching the energy difference between - and - states I C I B 1I = S B 1S C I 17

18 Solid-state 13 C NMR: Sensitivity B o H eff = H + H D + H J Technische Universität München, November 30,

19 Portland cement composition Metal oxides: wt.% CaO wt.% SiO 2 1 5wt.% Al 2 O wt.% Fe 2 O 3 Trace elements: MgO, Na 2 O, K 2 O, SO 3, P 2 O 5, TiO 2, Mn 2 O 3 Composition of the earth s crust Composition of cement Mg K Na rest Mg S Na K rest Ca Fe Al O O Ca Si Si Fe Al 19

20 Portland cement composition Alite: Ca 3 SiO 5 = C 3 S Belite: Ca 2 SiO 4 = C 2 S Ca 2.9 Si 0.95 Mg 0.06 Al 0.04 Fe 0.03 P 0.01 Na 0.01 O 5 Ca 1.94 Si 0.9 Al 0.07 K 0.03 Fe 0.02 Mg 0.02 P 0.01 Na 0.01 O 3.93 Calcium aluminate: C 3 A Ferrite: C 4 A 1-x F x Gypsum CaSO 4 2H 2 O Cement nomenclature: C = CaO S = SiO 2 A = Al 2 O 3 F = Fe 2 O 3 H = H 2 O S SO3 20

21 Challenges for the cement industry World-wide cement production: ~ 6 % of CO 2 emission Billion Mia. tonnes tons tonne of cement ~800 kg CO 2 (modern cement plant) CaCO 3 (s) 900 o C CaO(s) + CO 2 (g) (1 tonne) (440 kg) 21

22 B 0 = 14.1 T CO S 35 Cl 17 O 2 H 29 Si 13 C 27 Al 19 F 1 H // L (MHz) Al(4) Al(5) C S H Al(6) 22

23 d dt Spin Hamiltonian > = -ih > 180 o 90 o H = H ext + H int H ext = H Z + H rf H int = H + H D + H J + H Q High B 0 : H Z >> H int 23

24 Chemical shift: H 24

25 Chemical Shielding Chemical Shift = (/2)( 1 )B 0 = ( sample ref ) (Hz) = 10 6 ( sample ref )/ ref = ( sample ref ) 10 6 (ppm) 1 H, 13 C, 29 Si: ref = TMS Si(CH 3 ) 4 1 H NMR: Chemical shift region: = 0 12 ppm 13 C NMR: - - = ppm 29 Si NMR: - - = ppm 25

26 Chemical shift Chemical shift anisotropy Single-crystal Powder H = I B = 0 iso = ⅓( xx + yy + zz ) Liquid 26

27 29 Si NMR of silicates Q 4 (0Al) Q 4 (1Al) Q 4 (2Al) Q 4 (3Al) Q 4 (4Al) SiO 4 -tetrahedron Q 0 Q 2 Q 1 Q 1 Q 4 SiO 4 units: SiO 5 : 150 ppm SiO 6 : 180 to 200 ppm 27

28 29 Si MAS NMR Wollastonite: -Ca 3 Si 3 O 9 (triclinic P1) H = I B 0 iso (14.1 T) R = Hz = iso zz xx yy R = Hz iso (ppm) (ppm) Si(3) Si(1) Si(2)

29 29 Si Chemical Shift Anisotropy = SiO 4 4- Q 2 Q 1 Q 0 iso = ⅓( xx + yy + zz ) = iso zz xx yy Hansen, Jakobsen, Skibsted, Inorg. Chem. 42, 2368 (2003) 29

30 29 Si MAS NMR of zeolites Al/Si NMR 4 n0 I Si(nAl) / 4 n0 n 4 I Si(nAl) 30

31 Zeolite MFI: Confined space synthesis Al in MFI framework Si/Al(4) ( 27 Al) 55 ppm Al( O Si) 4 Al(iPrO) 3 Al(iPrO) NaAlO 2 51 Al(iPrO) 3 83 Al(NO) 3 74 Jacobsen, Madsen, Janssens, Jakobsen, Skibsted Micropor. Mesopor. Mater. 39, 393 (2000). Al(4) Al(6) 31

32 Dipole dipole interaction: H 32

33 Dipole dipole interaction H DD jk d jk Iˆ e I ˆ e 3 Iˆ j jk k jk j Iˆ k e jk d jk 0 j k rjk 33

34 Dipole dipole interaction: Pake dublet B 0 Intermolecular dipolar coupling H DD k k j 1 H DD jk d 1/r jk 3 Intramolecular dipolar coupling jk = 90 jk = MA D 1 d 3cos 2 jk 2 jk 1 jk = 0 iso 34

35 29 Si{ 19 F} REDOR NMR S 0 29 Si 19 F Na 2 SiF 6 S 29 Si 19 F 35

36 REDOR curves for isolated 29 Si 1 H spin pair B 0 R ΔS S d n sin d cos e j k r Si-H : 3 Å r Si-H : 4 Å r Si-H : 5 Å 36

37 Fluoride Mineralization Reduction of temperature in the cement kiln (~100 o C) Controlled addition of fluoride (CaF 2, NaF, MgF 2, ) Entropy of mixing Gibbs Free Energy 19 F MAS NMR: White Portland cement 0.25 wt.% F 7.1 T, L = 282 MHz R = 12 khz 8192 scans D1 = 4 S cg = ppm FWHM = 11.2 ppm 37

38 29 Si MAS NMR Fluoride-mineralised wpc (0.77 wt.% F) Exp 29 Si Simulation Belite Alite M3 19 F 29 Si Ca 3 SiO 5 + ½xCaF 2 Ca 3 Si(O 5x F x ) x+ + ½xCaO + ½xO 38

39 29 Si{ 19 F} CP/MAS NMR 19 F 29 Si 0.77 wt.% 0.47 wt.% 0.23 wt.% 39

40 Al 3+ guest-ions in alite 27 Al MAS NMR (14.1 T, R = 13.0 khz) 19 F Al 3+ in Ca 3 SiO 5 Al 3+ in Ca 2 SiO 4 27 Al Ca 3 Al 2 O 6 27 Al MAS NMR (7.1 T, R = 5.0 khz) 27 Al{ 19 F} CP/MAS 40

41 Oxygen sites in alite Ca 27 Si 9 (O b ) 36 (O i ) 9 Average distances: Triclinic C 3 S SiO covalent = 1.63 Å SiO interstitial = 4.32 Å Monoclinic M III SiO covalent = 1.63 Å SiO interstitial = 4.28 Å 41

42 29 Si{ 19 F} CP/REDOR NMR ΔS S 0 1 cos 4 2λnsin βcosβsin α Si λn ndt r d 3 r F SiF 0 S = S S 0 Tran, Herfort, Jakobsen, Skibsted J. Am. Chem. Soc. 131, (2009) 42

43 Fluoride guest-ions in alite Ca 27 Si 4.5 Al 4.5 (O b ) 36 (O i ) 4.5 (F i ) 4.5 Si 4+ + O 2- Al 3+ + F Ca 27 (Si 9x Al x )(O b ) 36 (O i ) 9x (F i ) x Tran, Herfort, Jakobsen, Skibsted J. Am. Chem. Soc. 131, (2009) No interstitial Oxygen sites in belite 43

44 Spin-lattice relaxation 44

45 29 Si MAS NMR of anhydrous Portland cements Experimental Deconvolution Belite sub-spectrum Alite sub-spectrum Alite (Ca 3 SiO 5 ) : 68.6 wt.% Belite (Ca 2 SiO 4 ) : 17.8 wt.% 45

46 29 Si Inversion-recovery experiments 29 Si inversion-recovery spectra of cement A (white Portland cement) 180 o 90 o d1 FID A series of intensities for alite and belite as a function of the recovery time Least-squares fitting to: M z (t) = M 0 [1 (1 + )exp(- /T 1 )] Alite: T 1 = ± s Belite: T 1 = ± 0.21 s 46

47 29 Si Inversion-recovery experiments 180 o 90 o d1 FID Belite sub-spectrum ( = 0.14 s) Alite sub-spectrum ( = 2.5 s) 47

48 P 5+ ions in anhydrous cement Phosphorus in Biofuels: Meat and bone meal 31 P MAS NMR (9.4 T, ν R = 12.0 khz) Sewage sludge P 2 O 5 (wt.%)

49 31 P Inversion recovery NMR: Cement A 31 P MAS NMR (9.4 T, ν R = 12.0 khz) 180 o 90 o (s) 29 Si Inv. Rec. MAS NMR (9.4 T, ν R = 12.0 khz) Poulsen, Kocaba, Le Saoût, Jakobsen, Scrivener, Skibsted Solid-State Nucl. Magn. Reson. 36, 32 (2009). 49

50 31 P Spin-Lattice relaxation: Cement A Single-exponential relaxation M z (t) = M 0 [1 2exp( (t/t 1 )] Stretched -exponential relaxation M z (t) = M 0 [1 2exp( (t/t 1 ) ½ ] alite belite alite belite T 1 (alite) T 1 (belite) 31 P 0.26 s 2.0 s 29 Si 0.24 s 8.2 s Poulsen, Jakobsen, Skibsted Inorg. Chem. 49, 5522 (2010). 50

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