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Thermal Analysis |
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Differential
thermal analysis (DTA) and differential
scanning calorimetry (DSC) are among thermal
analysis techniques that can provide useful
information of chemical materials. Since
various elements and compounds have a
specific heat energy and also chemical
transformations involve adsorption or the
generation of heat, unknown materials in the
sample are being identified using this
method.
In DTA the
difference of the temperature between the
sample and a reference material is monitored
over a range of varying temperature. In DSC,
the heat required for keeping the
temperature of sample and reference the same
over the range of varying temperature is
measured.
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Helium Inflow |
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Helium atoms
can be used as nanostructural probe to
detect qualitatively the existence of small
spaces that are not accessible to helium
instantly. A simple helium pycnometer,
conventionally used for solid volume
measurements, is employed for this purpose.
This pycnometer that is always kept at
constant gas pressure first measures the
true volume of the material. After that over
time helium penetrates smaller pores and
spaces. There is then a reduction in the
pressure of the helium chamber that can be
corresponded to the volume change in order
to keep the pressure constant.
This technique
has been widely used by R. F. Feldman and P.
J. Sereda in order to study the volumetric
changes associated with the structure of the
hydration products of cementitious materials
at various humidity conditions.
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X-Ray Diffraction |
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The X-ray
generated by the instrument is reflected
when it hits the lattice surfaces of a
crystalline material. This reflection is
unique for each lattice and can be detected
by the instrument in a specific angle
(usually referred to as 2q).
The intensity of the collected reflections
varies for each lattice based on the order
and arrangement of the crystal structure of
a material.
The full
spectrum of the intensities versus 2q
is the X-ray pattern and unique to each
material like a fingerprint. Usually three
or four main high intensity reflections are
used for comparison purposes.
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FTIR |
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This technique
is employed to evaluate the bonding
characteristics between polymers and C-S-H
in nanohybrid preparations. The absorption
of the IR energy by stretching or rotating
bonds in a molecule at a specific wavelength
can be detected and analyzed to study
various types of bonding between the atoms. |
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Scanning Electron Microscopy |
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Although the current SEM instruments are not
able to provide images at the nano level,
the morphology of calcium silicate hydrates
in the range of 0.5 to 1 micrometer can be
easily evaluated. Backscattered micrographs
are not very useful because of the close
atomic number of Ca and Si. |
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Nuclear Magnetic Resonace |
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The environment in which each atom is
located can be studied using NMR. This
technique provides the information on the
structural information about the bonds
between atoms in a material. In my research,
29Si MAS NMR is mainly employed in order to
investigate the silica tetrahedra
connections together at various levels of
humidity in the C-S-H. |
