Size Dependent Properties of Reactive Materials

Abstract

The nature of the self-sustained reaction of reactive materials is dependent on the physical, thermal, and mechanical properties of the reacting materials. These properties behave differently at the nano scale. Low-dimensional nanomaterials have various unusual size dependent transport properties. In this review, we summarize the theoretical and experimental reports on the size effect on melting temperature, heat capacity, reaction enthalpy, and surface energy of the materials at nano scale because nanomaterials possess a significant change in large specific surface area and surface effect than the bulk materials. According to the theoretical analysis of size dependent thermodynamic properties, such as melting temperature, cohesive energy, thermal conductivity and specific heat capacity of metallic nanoparticles and ultra-thin layers varies linearly with the reciprocal of the critical dimension. The result of this scaling relation on the material properties can affect the self-sustained reaction behavior in reactive materials. Resultant, powder compacts show lower reaction propagation velocities than bilayer system, if the particle size of the reactants and the void density is decreased an increase of the reaction propagation velocity due to an enhanced heat transfer in reactive materials can be achieved. Standard theories describing the properties of reactive material systems do not include size effects.

Enhanced Release of Calcium Ions from Hydroxyapatite Nanoparticles with an Increase in Their Specific Surface Area

“…This ratio depends on the parameters of size and shape; the smaller the solid and the more needle-like its shape, the greater the specific surface area. In nanoparticles with dimensions of several nm, large fractions of atoms are situated on the surface and, therefore, their free energy is high compared to large particles [91,92] (Figure 11). Such properties are sought and explored in the field of nanotechnology, in which the chemical composition of the material is constant, but the size of the particles or the crystallites of the material are variable.…”

“…This ratio depends on the parameters of size and shape; the smaller the solid and the more needle-like its shape, the greater the specific surface area. In nanoparticles with dimensions of several nm, large fractions of atoms are situated on the surface and, therefore, their free energy is high compared to large particles [91,92] (Figure 11). The concentration of Ca 2+ ions in PBS depends on the SSA value, and not on time.…”

Materials Development Using High-Energy Ball Milling: A Review Dedicated to the Memory of M.A. Korchagin

“…Although significant progress has been achieved in the development of materials using HEBM, further research is still needed. Both physical and chemical properties of fine-grained materials depend on their characteristic particle size [82]. Therefore, the control over the internal structure of the particles formed by HEBM of reaction mixtures is important for the outcome of the subsequent synthesis.…”