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pure polymer and its nanohybrid are fabricated by irradiating with
swift heavy ions (SHI) (Ag+) having 140 MeV energy followed
by selective chemical etching of the amorphous path, caused by the
irradiation of SHI, to generate nanochannels of size ∼80 nm.
Grafting is done within the nanochannels utilizing free radicals generated
from the interaction of high-energy ions, followed by tagging of ionic
species to make the nanochannels highly ion-conducting. The uniform
dispersion of two-dimensional nanoparticles better controls the size
and number density of the nanochannels and, thereby, converts them
into an effective membrane. The nanoparticle and functionalization
induce a piezoelectric β-phase in the membrane. The functionalized
membrane removes the radioactive nuclide like 241Am+3 (α-emitting source) efficiently (∼80% or 0.35
μg/cm2) from its solution/waste. This membrane act
as a corrosion inhibitor (92% inhibition efficiency) together with
its higher proton conduction (0.13 S/m) ability. The higher ion-exchange
capacity, water uptake, ion conduction, and high sorption by the nanohybrid
membrane are explored with respect to the extent of functionalization
and control over nanochannel dimension. A membrane electrode assembly
has been fabricated to construct a complete fuel cell, which exhibits
superior power generation (power density of 45 mW/cm2 at
a current density of 298 mA/cm2) much higher than that
of the standard Nafion, measured in a similar condition. Further,
a piezoelectric matrix along with its anticorrosive property, high
sorption characteristics, and greater power generation makes this
class of material a smart membrane that can be used for many different
applications.
Studies on isotopic and ion-exchange kinetics of mercury ions in Nafion-117 membrane have been carried out with (203)Hg radiotracer in the presence of Cl(-) and NO(3)(-) in solution. The results of isotopic-exchange kinetics indicate that mercury ions diffuse into the membrane as monovalent cation from HgCl(2) solution while as divalent ion from Hg(NO(3))(2) solution. The studies on the kinetics of ion exchange of Hg(2+) with Na(+) follow the prediction of the Nernst-Planck equation when NaNO(3) is used as an external salt solution. The Nernst-Planck equation fails to predict the kinetics when NaCl is used as an external salt solution, indicating that the complexation of Cl(-) with Hg(2+) in the membrane influences the kinetics. Permeation studies using (203)Hg and (36)Cl radiotracer between two HgCl(2) solutions show that the permeability coefficients of mercury and chloride ions are the same, indicating the cotransport of mercury and chloride ions through the membrane. Ion-exchange equilibrium studies using a mixture of HgCl(2) and HNO(3) solution were carried out to ascertain the species transporting through the membrane. The equilibrium sorption of mercury in the membrane shows the uptake of an ionic species, presumably HgCl(+), not a neutral salt. The speciation diagrams, calculated as a function of pH, show wide divergence of species present in HgCl(2) and Hg(NO(3))(2) solution and explain the difference in membrane transport behavior for HgCl(2) and Hg(NO(3))(2) solution. The results show that any ion-exchange-membrane-based separation of Hg(2+) needs careful consideration regarding the anions present in the solution, as it influences the speciation of mercury and hence its transport behavior through the membrane.
Thin poly(bis[2-(methacryloyloxy)ethyl] phosphate) grafted glass has been used for selective preconcentration and source preparation for alpha spectrometry of Pu(iv) ions.
Several incidences of nuclear smuggling during the past
few decades
have raised the demand for the development of a strong “on-site”
nuclear forensic infrastructure. High-resolution γ-ray spectrometry
(HRGRS) plays an important role in nuclear forensics. However, the
existing methodologies, developed primarily for nuclear fuel cycle
applications, are relative and rely on the availability of a standard,
limiting their use for the absolute assay of special nuclear materials
in nonstandard geometry samples with an unknown matrix, which is vital
to make a quick “on-site” decision on the severity,
potential radiological threat, and intended use of an interdicted
package. In this work, a methodology has been developed using HRGRS
for quantifying fissile (235U, 239Pu) and other
radioisotopes, which is applicable to sealed packages without requiring
the knowledge of the sample geometry and the matrices. By combining
experiments and Monte Carlo simulations, an iterative methodology
has been proposed for “point” to “extended”
source absolute efficiency transformation and demonstrated further
for the absolute isotopic assay of uranium and plutonium standards,
mock-up nuclear forensic samples, and an unknown nuclear material
mixture with a nonstandard geometry, compound matrices, and a wide
variation in the elemental and isotopic compositions with a view to
imitate an “on-site” experience. The present methodology
requires an assay time of only a few minutes to an hour and thus promises
“on-site” nuclear forensic analysis of suspected flagged
packages at borders and ports using high-resolution γ-ray spectrometry.
Furthermore, the present methodology is versatile and can also be
adopted for wider applications, beyond nuclear forensics.
The conducting nanochannel is made
up of poly(vinylidene fluoride)
and its nanohybrid (NH) membrane through irradiation of high-energy
(80 MeV) lithium ions followed by chemical etching. The NH is prepared
through the solution route by dispersing 2-D-layered silicates in
a polymer matrix. Morphological studies indicate that the dimension
of the conducting nanochannel is in the range of 40–50 nm.
The nanochannels are filled with the styrene monomer and are polymerized
within the channels to use the free radicals available in the periphery
of the walls, exposed after etching the irradiated films. Polystyrene
chains are sulfonated and, thereby, converted the nanochannel ion
conduction exclusively with a proton conduction of 30 mS·cm–1 in the NH membrane. The effect of fluence has been
evaluated for the improvement of different useful parameters of the
membrane. Structural alteration of the functionalized membrane is
revealed through XRD, thermal measurements, and morphological studies.
The functionalized membranes are used to capture radionuclide 241Am3+, an alpha emitter. The studies on uptake
kinetics show more than ∼98% uptake within an hour. Alpha radiography
is carried out to map the radionuclide distribution in the nanochannels.
A comparison of Li+- and Ag+-ion-irradiated
films indicates preferential grafting at the near-surface of the membrane
in the case of Ag+-ion-irradiated films, whereas comparatively
more uniform distribution of radionuclides is observed in the Li+-irradiated membrane across the depth. Measurement of scintillation
pulse height spectra suggests relative response of the membrane depending
on the nanochannel dimension. However, Li+-ion-irradiated
films are better suited for the possible application in uptake/transport
of radionuclides, whereas Ag+-ion-irradiated films are
better suited for their applications in radionuclide sensing.
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