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Aluminum Nitride by Microwave Assisted Synthesis: Effect of Added Ammonium Chloride1
No full textHexagonal aluminum nitride (AlN) crystals were synthesized by microwave method with ammonium chloride used as an additive. Starting mixtures consisted of Al powder, NH4Cl, and urea as a fuel taken in a 1 : 3 : 1 ratio. The microwave oven operated at 630 W, the synthesis time was 10, 30, 60, and 120 min. The
results showed that the pure AlN powder with regular and fine grains could be obtained in 30 min. The synthesized powders were characterized by TGA/DTA, XRD, FTIR, UVVIS, SEM, and TEM
Synergetic effects of pulse constraints and additives in electrodeposition of nano-crystalline zinc:Corrosion,structural and textural characterization
No full textPulse electrodeposition was to produce nanocrystalline(nc) zinc from alkaline non-cyanide electrolyte with primary and secondary additives. The combined effect of pulse parameters(ON-time(TON), OFF-time (TOFF), pulse peak current density(IP)) and additives on the corrosion properties (evaluated using electrochemical techniques) of zinc electrodeposits are elucidated in terms of surface morphology(using scanning electron microscope),topography and rootmeansquare(RMS)roughness(using atomic force
microscope), crystallitesize,its orientations and relative texture co-efficient(RTC,%)were evaluated
using X-ray diffraction.The corrosion resistance of zinc electrodeposits obtained at constant TON and IP
enhanced (i.e.,low Icorr and high Rct values) with increased TOFF. Atconstant TOFF and IP, the Icorr values
increased and Rct values decreased with TON while the former decreases and latter increases with
IP at constant TON and TOFF. The inclusion of primary and secondary additives in to the electrolyte pro-
duced nc zinc electrodeposits at 5Adm−2, showed enhanced protective properties(Icorr—16-Acm−2 and
Rct—481.8-cm−2). inegrained due to high negative over potential,reduced roughness and higher per-centage of basal plane[00.2] orientation have major impact for the enhanced corrosion resistances
Corrosion Inhibition of Mild Steel by Essential Oils in an HCl Environment
No full textInhibitors are known for their specificity
of action.1 A substance, which effectively
protects a given metal under
certain conditions, may cease to be
effective under other conditions or with
other metals. The extracts of some common
plants and by-products (peels, seeds,
fruit shells, leaves, etc.) contain different
organic compounds (e.g., amino acids,
tannin, alkaloids, and most of their constituents),
which are known to have inhibitive
action.2-6 It is therefore expected
that the essential oils extracted from plants
would exhibit inhibitive action.
Vapor corrosion inhibitors (VCIs) are
chemicals that are used to protect metallic
items from atmospheric corrosion
during manufacture, storage, and transportation.
Initially, camphor was used to
protect military equipment and machinery
parts.6 In later years, the development
of organic compounds as VCIs for metals7-
10 has been important. Our previous
work11-12 revealed that the extracts of bark
oils and amine-azole-nitro compounds
are quite effective in reducing the corrosion
of mild steel in marine and industrial
environments. Jasminum grandiflorum (JG),
Jasminum auriculatum (JA), Oleum palmarosae
(OP), Ocimum basilicum (OB), and Vetiveria
zizanioides (VZ) oils were used in this work
Tunable optical features from self-organized rhodium nanostructures
No full textManipulating the surface to tune plasmonic emission is an exciting fundamental challenge and here we report on the development of unique morphology-dependant optical features of Rh nanostructures prepared by an equilibrium procedure. The emergence of surface plasmon peaks at 375 nm and 474 nm, respectively, is ascribed to truncated and smooth surface of nanospheres in contrast to the absence of surface plasmon for bulk Rh(0) in the visible range. Smaller sized, high surface area domains with well developed, faceted organization are responsible for the promising characteristics of these Rh nanospheres which might be especially useful for potential catalytic, field
emission and magnetic applications
Characterization of corrosive bacterial consortia isolated from petroleum-product-transporting pipelines
No full textMicrobiologically influenced corrosion is a problem
commonly encountered in facilities in the oil and gas
industries. The present study describes bacterial enumeration
and identification in diesel and naphtha pipelines
located in the northwest and southwest region in India,
using traditional cultivation technique and 16S rDNA gene
sequencing. Phylogenetic analysis of 16S rRNA sequences
of the isolates was carried out, and the samples obtained
from the diesel and naphtha-transporting pipelines showed
the occurrence of 11 bacterial species namely Serratia
marcescens ACE2, Bacillus subtilis AR12, Bacillus cereus
ACE4, Pseudomonas aeruginosa AI1, Klebsiella oxytoca
ACP, Pseudomonas stutzeri AP2, Bacillus litoralis AN1,
Bacillus sp., Bacillus pumilus AR2, Bacillus carboniphilus
AR3, and Bacillus megaterium AR4. Sulfate-reducing
bacteria were not detected in samples from both pipelines.
The dominant bacterial species identified in the petroleum
pipeline samples were B. cereus and S. marcescens in the
diesel and naphtha pipelines, respectively. Therefore,
several types of bacteria may be involved in biocorrosion
arising from natural biofilms that develop in industrial
facilities. In addition, localized (pitting) corrosion of the
pipeline steel in the presence of the consortia was observed
by scanning electron microscopy analysis. The potential
role of each species in biofilm formation and steel corrosion
is discussed
Solution-Combustion Synthesized Nanocrystalline Li4Ti5O12 As High-Rate Performance Li-Ion Battery Anode
No full textNanocrystalline Li4Ti5O12 (LTO) crystallizing in cubic spinel-phase has been synthesized by
single-step-solution-combustion method in less than one minute. LTO particles thus synthesized are
flaky and highly porous in nature with a surface area of 12 m2/g. Transmission electron micrographs
indicate the primary particles to be agglomerated crystallites of varying size between 20 and 50 nm
with a 3-dimensional interconnected porous network. During their galvanostatic charge-discharge
at varying rates, LTO electrodes yield a capacity value close to the theoretical value of 175 mA h/g at
C/2 rate. The electrodes also exhibit promising capacity retention with little capacity loss over
100 cycles at varying discharge rates together with attractive discharge-rate capabilities yielding
capacity values of 140 mA h/g and 70 mA h/g at 10 and 100 C discharge rates, respectively. The
ameliorated electrode-performance is ascribed to nano and highly porous morphology of the
electrodes that provide short diffusion-paths for Li in conjunction with electrolyte percolation
through the electrode pores ensuring a high flux of Li
Sodium-alginate-based proton-exchange membranes as electrolytes for DMFCs
No full textNovel mixed-matrix membranes prepared by blending sodium alginate (NaAlg) with polyvinyl alcohol
(PVA) and certain heteropolyacids (HPAs), such as phosphomolybdic acid (PMoA), phosphotungstic
acid (PWA) and silicotungstic acid (SWA), followed by ex-situ cross-linking with glutaraldehyde (GA)
to achieve the desired mechanical and chemical stability, are reported for use as electrolytes in direct
methanol fuel cells (DMFCs). NaAlg-PVA-HPA mixed matrices possess a polymeric network with
micro-domains that restrict methanol cross-over. The mixed-matrix membranes are characterised for
their mechanical and thermal properties. Methanol cross-over rates across NaAlg-PVA and NaAlg-
PVA-HPA mixed-matrix membranes are studied by measuring the mass balance of methanol using
a density meter. The DMFC using NaAlg-PVA-SWA exhibits a peak power-density of 68 mW cm�2 at
a load current-density of 225 mA cm�2, while operating at 343 K. The rheological properties of NaAlg
and NaAlg-PVA-SWA viscous solutions are studied and their behaviour validated by a non-
Newtonian power-law
Electrochemical fluorination of dimethyl glutarate and its characterization
No full textMonofluoro dimethyl glutarate has been successfully
synthesized for the first time by electrochemical
fluorination. It is done in an undivided polypropylene cell
with platinum electrodes. Initially at three different current
densities, dimethyl glutarate is subjected to electrofluorination.
Maximum yield of monofluoro product is obtained at
15 mA cm−2. Selecting this current density, electrosynthesis
is done at three different charges. Maximum yield of 71.5%
of the monofluoro product is obtained with a conversion
efficiency of 95.2% when the charge of 6 F/mol is passed.
The synthesized product is characterized using Fourier
transform infrared (FTIR), gas chromatography/mass spectrometry
(GC/MS), and nuclear magnetic resonance
(NMR). The product purity and composition are ascertained
using GC/MS. The attachment of fluorine to methylene
group is indicated using FTIR data. From NMR studies, the
environment of fluorine in the neighborhood of carbon and
hydrogen has been established. Results are discussed in the
paper
Effect of additives on electrodeposition of tin and its structural and corrosion behaviour
No full textThe present investigation deals with the electrodeposition
of tin from chloride electrolytes. Gelatin,
b-naphthol, polyethylene glycol, peptone and histidine were
used as additives in the plating bath to improve the surface
morphology, grain size, smoothness and corrosion resistance
of the tin deposits. XRD data obtained for electrodeposited
tin show polycrystalline nature with single b-phase
and tetragonal structure. A uniform and pore free surface
was observed under SEM analysis. AFM results indicate
the grain refining brought about by the additives. Corrosion
rate measurements using the Tafel extrapolation method and
electrochemical impedance spectroscopy reveal the
increased corrosion resistance from baths containing
additives
Stearic acid modified glassy carbon electrode for electrochemical sensing of parathion and methyl parathion
No full textStearic acid modified glassy carbon electrode
for the sensing of parathion and methyl parathion was
fabricated. The electrochemical responses for parathion
and methyl parathion were investigated by cyclic voltammetry,
differential pulse voltammetry and amperometry.
The results on stearic acid modified electrode and bare
glassy carbon electrode were compared. Higher sensing
current was obtained on stearic acid modified glassy carbon
electrode. Analytical characteristics of the sensor such as
sensitivity, linear dynamic range, lower detection limit and
response time were evaluated