Powder Neutron Diffraction - an introduction MENA3100 March 7 2018 - PowerPoint PPT Presentation

Powder Neutron Diffraction - an introduction MENA3100 – March 7 2018 Magnus H. Sørby 13.03.2018

Scope • The advantages of neutrons vs. X-rays • Examples of neutron diffraction studies • Neutron diffraction at IFE

The glory of neutrons • There is no systematic correlation between atomic number and the scattering length. • Can get information about light and heavy elements simultaneously. Can distinguish neighboring elements in the periodic table. • The neutron interacts weakly with matter. Complicated sample environment is possible. Large samples can be studied. Scattering from bulk; not just the surface. • The neutron has a magnetic moment. Can study magnetic ordering.

Light and heavy elements Metal hydrides • Materials that contain chemical bonding between metal- and hydrogen atoms. 4 kg H 2 Mg 2 NiH 4 LaNi 5 H 6 Liquid H 2 H 2 gas (200 bar) L. Schlapbach, A. Zuttel Nature 414 (2001) 353-358 M (s) + x/2 H 2(g) ↔ MH x(s) + energy

Light and heavy elements H Alanates Al Al H AlH 4- AlH 63- 3.7wt% ~120 ° C 3 NaAlH 4 Na 3 AlH 6 + 2 Al + 3 H 2 TiCl 3 1.9wt% ~180 ° C Na 3 AlH 6 3 NaH + Al + 3/2 H 2 TiCl 3 1.9wt% 425 ° C NaH Na + ½ H 2 5.6 wt% B. Bogdanovic, J. Alloys Comp. 253-254 (1997) 1-9.

Light and heavy elements Crystal structure of alanates NaAlH 4 Na 3 AlH 6 LiAlH 4 β -LiAlH 4 Li 3 AlH 6 Al KAlH 4 PUS - high resolution diffractometer Mg(AlH 4 ) 2 Sr 2 AlH 7 BaAlH 5 Li 3 AlD 6 seen by X-rays Ba 2 AlH 7 a c Na 2 LiAlH 6 K 2 NaAlH 6 D LiMg(AlH 4 ) 2 LiMgAlH 6 Ca(AlD 4 ) 2 CaAlD 5 The JEEPII reactor Li 3 AlD 6 seen by neutrons

Light and heavy elements Crystal structure of alanates NaAlH 4 Na 3 AlH 6 LiAlH 4 β -LiAlH 4 Li 3 AlH 6 PUS - high resolution diffractometer KAlH 4 SNBL/ESRF (Grenoble, France) Mg(AlH 4 ) 2 Sr 2 AlH 7 BaAlH 5 Ba 2 AlH 7 LiAlH 4 Na 2 LiAlH 6 Li 3 AlH 6 LiMgAlH 6 K 2 NaAlH 6 Ca(AlH 4 ) 2 Na 2 LiAlH 6 K 2 NaAlH 6 LiMg(AlH 4 ) 2 LiMgAlH 6 Ca(AlD 4 ) 2 β -LiAlH 4 CaAlD 5 NaAlH 4 KAlH 4 LiMg(AlH 4 ) 3 Mg(AlH 4 ) 2 CaAlH 5

The glory of neutrons • There is no systematic correlation between atomic number and the scattering length. • Can get information about light and heavy elements simultaneously. • Can distinguish neighboring elements in the periodic table. • The neutron interacts weakly with matter. Complicated sample environment is possible. Large samples can be studied. Scattering from bulk; not just the surface. • The neutron has a magnetic moment. Can study magnetic ordering.

Neighboring elements Alloys β -Mn: Cubic, complex structure, a = 6.31 Å, Z = 20 Mn(1) 12 Mn(2) 8 What happens when a 40% of the Mn is substituted with Co?

Neighboring elements Alloys β -Mn: Cubic, complex structure, a = 6.31 Å, Z = 20 [Mn 0.6 Co 0.4 ](1) 12 [Mn 0.6 Co 0.4 ](2) 8 What happens if 40% a of the Mn is substituted with Co?

Neighboring elements Alloys β -Mn: Cubic, complex structure, a = 6.31 Å, Z = 20 Mn(1) 12 Co(2) 8 What happens if 40% a of the Mn is substituted with Co?

Neighboring elements Alloys Which model is right for Mn 0.6 Co 0.4 ? Random Co distribution X-rays: Z(Mn)=25 Ordered Co distribution Z(Co)=27

Neighboring elements Alloys Which model is right for Mn 0.6 Co 0.4 ? Random Co distribution Random Co distribution X-rays: Z(Mn)=25 Ordered Co distribution Ordered Co distribution Z(Co)=27 Neutrons: b(Mn)=-0.373 b(Co)=+0.249

Neighboring elements Alloys Which model is right for Mn 0.6 Co 0.4 ? Co selectively occupy the 8-fold position! O. B. Karlsen, et al. J. Alloys Comp., 2009, 476 (2009) 9-13

The glory of neutrons • There is no systematic correlation between atomic number and the scattering length. • Can get information about light and heavy elements simultaneously. • Can distinguish neighboring elements in the periodic table. • The neutron interacts weakly with matter. • Complicated sample environment is possible. Large samples can be studied. Scattering from bulk; not just the surface. • The neutron has a magnetic moment. Can study magnetic ordering.

Penetration depth Penetration 5 mm Al X-ray λ = 1.54 Å I/I o = 10 -29 Neutrons λ = 1.0 Å I/I o = 0.996 X-ray λ = 0.2 Å I/I o = 0.02

Penetration depth Sample environment • Neutrons can penetrate several millimeters of materials like aluminium and steel. Sample container (Inconel super-alloy) rated to 3000 bar and 600 o C.

Penetration depth Sample environment • Neutrons can penetrate several millimeters of materials like aluminium and steel. Furnace Cryostat

The glory of neutrons • There is no systematic correlation between atomic number and the scattering length. • Can get information about light and heavy elements simultaneously. • Can distinguish neighboring elements in the periodic table. • The neutron interacts weakly with matter. • Complicated sample environment is possible. • Large samples can be studied. Scattering from bulk; not just the surface. • The neutron has a magnetic moment. Can study magnetic ordering.

Penetration depth Study of large samples • How did the machining of the hole influence the material?

Penetration depth Study of large samples

Penetration depth Study of large samples 3D residual stress-field can be mapped in a non-destructive way! Planned at IFE from Loading a sample at the 2020. NRSF2 instrument at Oak Ridge National Lab (US)

The glory of neutrons • There is no systematic correlation between atomic number and the scattering length. • Can get information about light and heavy elements simultaneously. • Can distinguish neighboring elements in the periodic table. • The neutron interacts weakly with matter. • Complicated sample environment is possible. • Large samples can be studied. • Easy interpreations of scattering intensities. • The neutron has a magnetic moment. Can study magnetic ordering.

Scattering intensity 2 2 r r ∑ ∑ π ⋅ π + + = 2 = ⋅ = ⋅ 2 i ( r K ) 2 i ( hx ky lz ) I F b e b e i i i i K i i i i • Can (usually) neglect effects of multiple scattering and absorption.

The glory of neutrons • There is no systematic correlation between atomic number and the scattering length. • Can get information about light and heavy elements simultaneously. • Can distinguish neighboring elements in the periodic table. • The neutron interacts weakly with matter. • Complicated sample environment is possible. • Large samples can be studied. • Easy interpreations of scattering intensities. • The neutron has a magnetic moment. • Can study magnetic ordering.

Magnetic scattering Magnetic neutron scattering unit scattering • The neutron has a magnetic spin vector, K magnetic moment. direction, M α • This will interact with the incident beam magnetic moment of atoms diffracted beam with unpaired electrons. r r ∑ π + + = ⋅ 2 i ( hx ky lz ) F m f e i i i , magnetic hkl i i r r r r i r r = ⋅ − = α m K ( K M ) M , m sin r r r = || m 0 , K M 2 2 ∝ 2 = + r r I F F F r ⊥ hkl hkl nucl , hkl magnetic , hkl = 1 , m K M

Magnetic scattering Magnetic neutron scattering 450 100 110 400 Nuclear scattering 350 Magn. scattering Intensity (arb. units) 300 Total scattering 250 200 111 150 100 50 0 5 10 15 20 25 30 35 2 θ (deg.) Ferromagnetic

Magnetic scattering Magnetic neutron scattering 450 100 110 400 Nuclear scattering 350 Magn. scattering Intensity (arb. units) 300 Total scattering 250 200 111 150 100 ½00 ½10 ½11 50 0 5 10 15 20 25 30 35 2 θ (deg.) Antiferromagnetic

Neutron diffraction at IFE PUS – a high resolution diffractometer • In operation since 1997.

Neutron diffraction at IFE PUS – a high resolution diffractometer • In operation since 1997. Soller collimator (from Risø). 15’, 30’ and “open” (60’)

Neutron diffraction at IFE PUS – a high resolution diffractometer • In operation since 1997. Vertically focusing Ge monochromator (from Risø). 311, 511 or 711 reflection plane can be used  λ = 0.75-2.60 Å

Neutron diffraction at IFE PUS – a high resolution diffractometer • In operation since 1997. Sample temperature: 8 – 1200K Gas pressures up to 8 bar (soon 100 bar)

Neutron diffraction at IFE PUS – a high resolution diffractometer • In operation since 1997. Oscillating radial collimators (MURR).

Neutron diffraction at IFE PUS – a high resolution diffractometer • In operation since 1997.

Neutron diffraction at IFE PUS – a high resolution diffractometer • In operation since 1997. 2 detector banks with 7 vertically stacked position sensitive detectors in each. Each bank cover 20 o scattering angle.

New instruments ODIN - a brand new powder diffractometer SANS PUS 1 ODIN To Air 2 1 Lock Staircase 3 4 5 6 JEEP II R2D2 10 7 8 DIFF 9 Cold Moderator Reflectometer 10 m

New instrument ODIN - a brand new powder diffractometer • Optimized DIffractometer for Neutrons • All aspects of the design is optimized by Monte Carlo simulations • 3.5 times higher intensity at slightly better resolution than PUS. • Or 15 times higher intensity at lower resolution.