ULTRASONIC FORCE MICROSCOPY (UFM) : a technique for mapping materials properties at a nanometer scale with potential applications to building materials Teresa Cuberes E. U. Politécnica de Almadén, UCLM

Introduction: - What is Ultrasonic-AFM? - Potential of ultrasonic-AFM at building materials Ultrasonic-Atomic Force Microscopies - Acoustic Atomic Force Microscopy (AFAM) - Ultrasonic Force Microscopy (UFM) - Heterodyne Force Microscopy (HFM) UFM at a construction ceramic UFM at Porland cement paste Summary Outline

Introduction Piezo Longitudinal acoustic waves v  10 3 m/s  mm Is it possible to detect ultrasonic vibration at a sample surface in the near-field regime, with a lateral resolution in the nanometer scale, using the tip of an AFM? AFM: WHAT IS ULTRASONIC - AFM?

Introduction APPLICATIONS OF ULTRASOUND Determination of elastic properties Non-destructive testing Sensor of materials internal structure Use in materials processing Metrology Mechanical machining Chemistry, biology, medicine, etc.  : from 20 kHz up to GHz

Potential of Ultrasonic-AFM at building materials Evaluation of nanoscale elasticity and/or viscoelasticity in composites or multiphase materials (differentiation of phases at the nanometer scale on the basis of their elastic and/or viscoelastic behaviour, etc.) Testing of nanostructured coatings (detection of deboding or elastic inhomogeneities at the coating/substrate interface at the nanometer scale, etc.) Characterization of micropores and/or internal stresses (study of moisture flow at individual nanopores, etc.) Rheological measurements at the nanometer scale with extreme time-sensitivity (nanoseconds) (influence of additives in the workability of fresh concrete, etc.)

Introduction: - What is Ultrasonic-AFM? - Potential of ultrasonic-AFM at building materials Ultrasonic-Atomic Force Microscopies - Acoustic Atomic Force Microscopy (AFAM) - Ultrasonic Force Microscopy (UFM) - Heterodyne Force Microscopy (HFM) UFM at a construction ceramic UFM at Porland cement paste Summary Outline

The cantilever can support high- frequency resonant modes AFAM provides information about sample elasticity with nanoscale lateral resolution. Measured magnitude: Resonance frequency of the cantilever high-order modes (the contact stiffness and the Young modulus can be evaluated) cantilever sample K* ACOUSTIC ATOMIC FORCE MICROSCOPY (AFAM) U. Rabe and W. Arnold, Appl. Phys. Lett. 64, 1493 (1993) The tip-sample interaction is kept in the linear tip-sample force regime

Linear-detection based ultrasonic-AFM techniques “Scanning local-acceleration Microscopy” N. A. Burnham, A. J. Kulik, G. Gremaud, P.J. Gallo, and F. Oulevey, J. Vac. Sci. Technol. B 14 (2) (1996) Acoustic Atomic Force Microscopy U. Rabe and W. Arnold, Appl. Phys. Lett. 64, 1493 (1993) “Ultrasonic atomic force microscopy with overtone excitation of the cantilever”, K. Yamanaka and S. Nakano, Jpn. J. Appl. Phys. 35, 3787 (1996) “Scanning microdeformation microscopy”, B. Cretin and F. Sthal, Appl. Phys. Lett. 62, 829 (1993); P. Variac and B. Cretin, Appl. Phys. Lett. 68, 461 (1996)

O. Kolosov and K. Yamanaka, Jpn. J. Appl. Phys. 32, L1095 (1993) ULTRASONIC FORCE MICROSCOPY UFM provides information about sample elasticity and adhesion with nanoscale lateral resolution. Measured magnitude: static cantilever displacement induced by the ultrasonic force. Ultrasonic force:

M. T. Cuberes et al. J. Phys. D. Appl. Phys. 33, 2347 (2000) HETERODYNE FORCE MICROSCOPY Phase-HFM makes possible to study dynamic relaxation processes in nanometre volumes with a time-sensitivity of nanoseconds SCANNING NEAR FIELD ULTRASOUND HOLOGRAPHY Phase-SNFUH provides elastic information of buried features with great sensitivity. Shekhawat and Dravid. Science 310, 90 (2005)

ADVANTAGES OF ULTRASONIC-AFM Material contrast on hard samples (in the presence of surface ultrasonic vibration a soft cantilever can indent hard materials) Material contrast on soft samples (in the presence of surface ultrasonic vibration, friction reduces or vanishes) Information from subsurface features in the image contrast Potential to provide information about dynamic surface adhesive properties, capillarity or entropic effects, etc. Potential to study dynamic viscoelastic or relaxation processes with extremely high sensitivity.

Introduction: - What is Ultrasonic-AFM? - Potential of ultrasonic-AFM at building materials Ultrasonic-Atomic Force Microscopies - Acoustic Atomic Force Microscopy (AFAM) - Ultrasonic Force Microscopy (UFM) - Heterodyne Force Microscopy (HFM) UFM at a construction ceramic UFM at Porland cement paste Summary Outline

UFM AT A CONSTRUCTION CERAMIC: ● Mixture of clays and carbonates Brick fabric “Rústicos La Mancha” Santa Cruz de Mudela, Ciudad Real ● B. Acosta, I. Iglesias, R. Yu, G. Ruiz and A. Acosta, Anales de Mecánica de Fractura, Vol. 22, 22nd Meeting of the Spanish Group of Fracture (March 2005). Description of the material:

UFM AT A CONSTRUCTION CERAMIC: AFM UFM UFM contrast at construction ceramics reveal the presence, morphology and distribution of nanometer-scale phases with different elasticity. soft hard

AFMUFM AFM UFM

UFM AT CEMENT PASTE Preparation of the cement paste: Porland cement powder is mixed with water (water/cement ratio: 0.5), stirred by hand 6 min, casted on a fresly cleaved mica surface, and aged during 28 days to complete the setting and hardenning process. After hardenning, the mica is easily detached from the sample surface, and the region below is examined under the AFM microscope. Mica Replication Method (MRM) T. Yang et al. J. Phys. D.: Appl. Phys. 35 (2002) L25; J. of Mater. Sci. 38 (2003), 1909

UFM AT CEMENT PASTE C 3 S + H C-S-H + CH C 2 S + H C-S-H + CH ● Ca(OH) 2 platelets ● thin foils of C-S-H AFM ?

UFM AT CEMENT PASTE AFM UFM

UFM AT CEMENT PASTE AFM UFM Evidence of nanopores in the UFM image?

UFM AT CEMENT PASTE AFM UFM

UFM AT CEMENT PASTE AFM UFM

UFM AT CEMENT PASTE AFM UFM

UFM AT CEMENT PASTE AFM UFM Surface layers on top of CH crystals clearly show distinct elastic and/or adhesive contrast

C. Plassard et al. Ultramicroscopy 100 (2004) 331 Elastic modulus perpendicular to the C-S-H layer plane The elastic modulus changes depending on the calcium hydroxide concentration in the solution during the formation of the C-S-H

Summary ● Ultrasonic-AFM can be applied to construction ceramics, allowing us to distinguish phases with different elasticity with lateral resolution in the nanometer scale. The obtained information can be useful for the study of the optimum composition of the mixture, or the best fabrication method to improve its macroscopic mechanical behaviour. ● Ultrasonic-AFM can be applied to cement paste. Potential applications of the technique in cement-based materials include the characterization of nanopores and the identification of phases of different elasticity. ●Ultrasonic-AFM techniques show promise of useful applications for the characterization of building materials.

Acknowledgements ● G. Ruiz is gratefully acknowledged for assistance in the preparation of the samples. ● S. Conejero is gratefully acknowledged for assistance in the AFM and UFM measurements. ● Finantial support from the Spanish MEC (project MAT ) and from the Junta de Comunidades de Castilla-La Mancha (JCCM) (projects PBI and PBI ) is gratefully acknowledged.