The answer of Mr. Kais Hbaieb might be help.

Composite materials necessary means more than one phase. A second phase is usually introduced to control some properties of the host material. Whereas doped material means that different element is introduced in the lattice structure of the host material, thus it is expected that the material maintain its structure. Here we talk about the solid solution; that is when the doping material exceeds the solubility limit it will segregate to form a second phase. This may happen during non-proper treatment.

Doping and nanocomposites are two different concepts in materials science and engineering.

Doping refers to the intentional introduction of impurities into a material, typically a semiconductor, to modify its electrical or optical properties. The impurities, known as dopants, are added in small amounts to alter the number of charge carriers in the material, which can affect its conductivity, resistivity, or other electronic properties. Doping is commonly used in the semiconductor industry to create p-type and n-type semiconductors, which are used in electronic devices such as transistors and solar cells.

On the other hand, nanocomposites refer to materials composed of two or more phases, with at least one phase having nanoscale dimensions (typically less than 100 nm). The different phases can be different materials, or the same material with different properties. Nanocomposites can exhibit unique and enhanced properties compared to their individual components, such as increased strength, stiffness, or thermal stability. Nanocomposites have a wide range of applications, including in electronics, energy, medicine, and aerospace.

In summary, doping is a method to modify the electrical or optical properties of a material by introducing impurities, while nanocomposites are materials composed of two or more phases with at least one phase having nanoscale dimensions, leading to unique and enhanced properties.