Near-surface diffraction capabilities at NECSA TP Ntsoane Diffraction Section 11 September 2015

OUTLINE Introduction D8 Advance Sample stage & holder types D8 Discover Examples: Interaction with HEI Possible areas of collaboration Conclude

Introduction Diffraction techniques are widely used in non-destructive materials characterisation. Applications ranges from Phase Identification, Crystallite size determination, lattice parameter determination, crystallinity, strain/stress and texture. Shallow penetration depth allows Near-surface region information Two Bruker AXS diffractometers (formerly Siemens X-ray division) D8 Advance D8 Discover

D8 Advance D500 

Comparison D500 NaI scintillation  -2  goniometer D8 Advance Lynx eye detector (0 & 1 D mode) Sample stages  -  Goniometer Sample rotation Goebel mirror Online status Windows based Variable measurement time NECSA-WITS Workshop

Sample stages Automatic sample changer Capillary stage XYZ stage Small angle X-ray scattering

Automatic changer 9 sample holders (x7) Allows overnight measurement Sample types: powder, liquid, thin films Allows sample rotation during meas. Reflection geometry Rotated by 90° Transmission geometry

Superposed peaks from different multisample slots indicating variation in peak position Δ2  max = 0.003° Ok for most applications Automatic changer con’t

XYZ stage Useful for localized investigation – Localized characterization – Allows large samples Top view of XYZ stage

Capillary stage Useful for small amount of sample Minimization of preferred orientation Challenges: filling the capillary with powder

Sample holders Standard Reflection  = 25 mm, 40mm  = 25 mm Si crystal Domed-shape holder Transmission  = 25 mm Capillary stage  = 50  m, 1mm, 2mm, 2.5mm wall thickness = 10  m

Superposed powder diffraction pattern of Cr2O3 on standard sample holder and dome-shaped and empty dome shaped sample holder. NECSA-WITS Workshop

Possible investigations ● Grazing angle investigations:  inc < 1  Thin films  Near-surface modifications ● Analysis of radioactive & environmentally sensitive samples

D8 Discover – 2D detector Vantec500 – Laser & Video align – Eulerian cradle – 0.8mm collimator

Applications Residual strain and stress investigation Texture analysis Micro Powder diffraction (Phase identification)

Basic principle

 = 0º  = 10º  = 20º  = 30º  = 40º  = 50º  = 60º  = 70º  = 80º  = 89.7º Q 211 C Scattering plane compressive stress

Interaction HEI

Thin films Ms P. Mudau, Univ. of Johannesburg Interaction with HEI

Dr. N. Janse van Rensburg, Univ. of Johannesburg Grit-blasted Ti alloy cylinder

Thermal sprayed Coating Ms H. Mathabatha, TUT

Micro Diffraction Phase identification in Friction Spot Stir Weld Mr P. Mubiayi, UJ

Mr M. Vhareta, WITS Influence of fatigue on residual stress

Prof R. Knutsen, Univ. of Cape Town Pole figures of rolled Aluminium Software: Multex Texture analysis

Possible areas of collaboration  Near-surface characterization of  layered structures  modified surfaces i.e. grit-blasting, polishing etc  Irradiated surfaces  Engineering components  Thin film investigation  Micro-diffraction for localized investigation

For more information: Tshepo Ntsoane Zeldah Sentsho Andrew Venter African Light Source Conference and Workshop European Synchrotron Radiation Facility, Grenoble France 16 th – 20 th November

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