AGGREGATION OF NANOPARTICLES IN 1D The C-S-H gel. RAQUEL GONZALEZ Low dimensional curse 22 February 2009

Introduction - The cement based materials. C-S-H gel: - Structural models - Colloidal models Aggregation - Brownian Cluster Dynamics: -Isotropic interactions -Non-isotropic interactions Preliminar results Conclusions and perspectives OUTLINE

INTRODUCTION

Wide range of properties Improving our life NANOPARTICLES

Can it be nano??

CEMENT BASED MATERIALS

C-S-H GEL

STRUCTURAL MODEL CalciumSiliconOxygenHydrogen Silicate chain Ca-O layer

5 nm sized Rounded particles Single Basic Building Block COLLOIDAL MODELS LD C-S-H HD C-S-H Basic Building Block JENNINGS MODEL

Drawbacks: Link between structural models and colloidal models Inner and Outer product 3D 1D TEM images

AGGREGATION

Existence of Inner and Outer product Two type of forces: Isotropic: V d W Directional AGGREGATION IN C-S-H GEL a b Geometrical restrictions!!

BROWNIAN CLUSTER DYNAMICS WITH ISOTROPIC INTERACTIONS

Stochastic processes Brownian Dynamics DESPLACEMENT PROPORTIONAL TO TIME

BROWNIAN CLUSTER DYNAMICS APPROACH clusters are built by forming randomly rigid bonds between neighboring particles with a probability P = 1- exp(u/kT) monomers/clusters move with no bond breaking nor overlap clusters are rebuilt at each time step Algorithm: V(r) Square well potential r 0 1 u a b

Thermodinamic relation E1 E nl Ea ∆E=E1-Enl α β

ISOTROPIC INTERACTIONS: DLCA AND RLCA LIMITS Depending on the probability α that particles form a bond at each collision. α = 1α → 0DLCARLCA (b) [11]

BROWNIAN CLUSTER DYNAMICS WITH NON ISOTROPIC INTERACTIONS

ANISOTROPIC SYSTEM directional interaction + isotropic interaction rotational +translational diffusion

ANISOTROPIC SYSTEM θ the interaction takes place Ω Ω

PRELIMINAR RESULTS

Isotropic interactions p= 0.37 AMORFUS 3D [9]

Non isotropic interactions: α1=1 β1=0.331 α2=1 β2=0 CRYSTALINE 1D [9]

CONCLUSIONS AND PERSPECTIVES

The method allows passing from a 3D structure to a 1D structure as we can see in the results. In cementitious materials there are two types of systems, the Inner and the Outer product, which correspond with the aggregation of particles in 1D or 3D. These preliminary results point out that the Basic Building Blocks are not a unique “black” particle they must be have something inside which makes them different. Some MD calculations point out that for similar morphology there are different structures formed.

CSH aggregation My work

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