Civil Engineering Reference
In-Depth Information
increasingly attractive, in recent years. Nanoscience, the study that deals with the
inherent functional properties of the materials or their structures at nanometre
level,
has
substantially
implanted
numerous
identifications
on
the
materials
produced at nanoscale.
The advanced nanostructured materials, whose surface-to-volume ratio are very
high when compared to the same material at its bulk state plays a vital role in
characterizing the thermophysical properties of the base material to which they are
embedded.
The active transformation of the scientific innovations on functional materials at
nanometre level into the real-time application, as referred to the nanotechnology,
has paved way for achieving improved performance of many bulk materials,
especially on the heat storage materials.
The penetration of the nanotechnology into the spectrum of TES in buildings
from the scheme inception of preparation up to the performance testing of PCMs
embedded with nanoparticles are briefly explained in the forthcoming sections.
9.1 Preparation of Nanomaterials
The preparation of the nanomaterials of size ranging from 1 to 100 nm can be
performed through two broad techniques, namely top-down and bottom-up
methods. In the top-down method, the nanoparticles are produced by subjecting
the bulk materials to undergo crushing, grinding or high-energy impact motion for
longer period of time.
The final yield obtained can be in the form of wet or dry powder depending on
the reactive materials being added during the process. This method is advanta-
geous for producing high thermal conductive materials initially in the form of
sheets (e.g. graphene oxide), metallic alloys and nanocomposite structures.
Due to the mechanical stresses and microstuctural deformation observed in the
nanomaterials being produced, this method is less pronounced for the preparation
of nanoparticles with effective size distribution.
On the other hand, in the bottom-up approach, the nanoparticles are formed by
the atomic interaction of two or more chemically reactive materials present in the
colloidal state, wherein the size, shape and dispersion of the nanoparticles can be
effectively controlled.
This method is widely preferred for the preparation of smaller size nanoparticles
in the range of 1-10 nm in colloidal solution, and so this approach is also referred to
as the sol-gel method. Numerous nanostructured materials have been prepared
using the sol-gel method so far.
Other physical methods are also available to synthesize the nanomaterials,
which include physical vapour deposition, chemical vapour deposition, laser
ablation, pulsed-vapour method, electric arc method, etc. Each method has its own
