As already said, TiO2 is insoluble in water in the sense of decomposing into free ions. However, with sufficiently small particles and appropriate dispersants you can obtain relatively stable suspensions. In the case of very small particles, i.e. nanosized ones the suspension is called colloidal solution. In order to obtain a homogeneous composite you need to obtain a homogeneous and stable suspension of your TiO2 and whatever other materials are to from the composite with the aid of a dispersant (also called defloculant sometimes). However, this approach is not very adequate for achieving homogeneity on the nanoscale since the nanoparticles easily flock together even in very well defloculated suspensions. For nanocomposites there are other methods for achieving high homogeneity such as sol-gel, polymerized complex, etc. I recommend you to go to the library and find a specialized book on ceramic materials or composites processing. Also check carefully if a synthesis procedure hasn't already been developed. There is a high probability there are publications describing it.
