Litty, Irimpan; Ambika, D; Kumar, V; Nampoori, V P N; Radhakrishnan, P(American Institute of Physics, 2008)
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Abstract:
The annealing effect on the spectral and nonlinear optical NLO characteristics of ZnO thin films
deposited on quartz substrates by sol-gel process is investigated. As the annealing temperature
increases from 300–1050 °C, there is a decrease in the band gap, which indicates the changes of the
interface of ZnO. ZnO is reported to show two emission bands, an ultraviolet UV emission band
and another in the green region. The intensity of the UV peak remains the same while the intensity
of the visible peak increases with increase in annealing temperature. The role of oxygen in ZnO thin
films during the annealing process is important to the change in optical properties. The mechanism
of the luminescence suggests that UV luminescence of ZnO thin films is related to the transition
from conduction band edge to valence band, and green luminescence is caused by the transition
from deep donor level to valence band due to oxygen vacancies. The NLO response of these
samples is studied using nanosecond laser pulses at off-resonance wavelengths. The nonlinear
absorption coefficient increases from 2.9 ×10−6 to 1.0 ×10−4 m/W when the annealing temperature
is increased from 300 to 1050 °C, mainly due to the enhancement of interfacial state and exciton
oscillator strength. The third order optical susceptibility x(3) increases with increase in annealing
temperature (T) within the range of our investigations. In the weak confinement regime, T2.4
dependence of x(3) is obtained for ZnO thin films. The role of annealing temperature on the optical
limiting response is also studied.
Anantharaman, M R; Al-Omari, I A(Scientific Research Publishing, May 25, 2012)
[+]
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Abstract:
The results of the investigation of the magnetic and structural properties of the alloy system Fe0.75–xSi0.25Sbx, where x = 0, 0.05, 0.1, 0.15, 0.2, and 0.25 synthesized by mechanical alloying followed by heat treatment are described. The x-ray diffraction reveals that all samples crystallize in the DO3-type cubic phase structure. Substituting Fe by Sb led to a de-crease in the lattice constant and the unit cell volume. The magnetic properties are investigated by vibrating sample magnetometer and show that all the samples are ferromagnetically ordered at room temperature. The Curie temperature is found to decrease linearly from (850 ± 5) K for the parent alloy to (620 ± 5) K for the alloyith x = 0.25. The satura-tion magnetizations at room temperature and at 100 K are found to decrease with increasing the antimony concentration. The above results indicate that Sb dissolves in the cubic structure of this alloy system.
Description:
World Journal of Condensed Matter Physics, 2012, 2, 61-65
Cashew kernels have high
nutritive value. Upon exposure
to air kernels turn rancid and
their nutritive value decreases.
From this study it is concluded
that chemical treatment using
antioxidants reduced oxidative
rancidity but failed to prevent
deterioration in organoleptic
characteristics and decrease in
protein and carbohydrate
content of stored kernels.
Rani, Joseph(Hutig & Wepf Verlag,Basel, October 5, 1987)
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Abstract:
Compounding of styrene-butadiene copolymer/polybutadiene , natural rubber/
ethylene-propylene-diene terpolymer and natural rubber/butadiene-acrylonitrile copolymer
blends was done in three different ways and their curing behaviour and the
tensile properties of the es are compared.
Anantharaman, M R; Soloman, M A; Philip, Kurian; Joy, P A(Wiley Periodicals, September 26, 2002)
[+]
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Abstract:
Fine particles of barium ferrite (BaFe12O19)
were synthesized by the conventional ceramic technique.
These materials were then characterized by the X-ray diffraction
method and incorporated in the natural rubber matrix
according to a specific receipe for various loadings of
ferrite. The rubber ferrite composites (RFC) thus obtained
have several applications, and have the advantage of molding
into complex shapes. For applications such as microwave
absorbers, these composites should have an appropriate
dielectric strength with the required mechanical and
magnetic properties. The N330 (HAF) carbon black has been
added to these RFCs for various loadings to modify the
dielectric and mechanical properties. In this article we report
the effect of carbon black on the mechanical and dielectric
properties of these RFCs. Both the mechanical and dielectric
properties can be enhanced by the addition of an appropriate
amount of carbon black
Description:
Journal of Applied Polymer Science, Vol. 89, 769–778 (2003)
James, Joseph; Ananthakrishnan, T R; Nampoori, V P N; Rudra Warier, M K; Karanjikar, N P; Kamat, M J(World Scientific Publishing Company, 1995)
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[-]
Abstract:
The effect of Ce3+ on the fluorescence emission from CaS:Ce3+ phosphor is studied using X-ray excitation. Apart from the emission in the visible region, the phosphor also shows fluorescence emission in the ultraviolet region. Variation in wavelengths and intensities of these emissions due to change in dopant concentration is also analysed.
Pillai, S M; Vallabhan, C P G(Solid State Communications, 1983)
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Abstract:
ZnS: Cu: Cl phosphor prepared under a vacuum firing process is found to
give blue electroluminescence with emission peak at 460 nm which remams
unaltered with the frequency of the excitation voltage. Addition of excess
chlorine in the phosphor gives blue, green and red emission at 460, 520
and 640 run. The intensity of the blue band decreases and It fmally
disappears as chlorine concentration is increased. A scheme involving
three energy levels attributed to Cu2+, Cu+ and Cl- centres in Zns
explains the experimental results completely.
The effect of chromium doping on methylene
blue sensitized Poly (vinyl alcohol)/Acrylamide was carried
out by varying the ratios of Ammonium dichromate
and methylene blue. In the case of films without ammonium
dichromate, the diffraction efficiency was found to
decrease on storage. On chromium doping the storage life
was improved. Interestingly, a self-enhancement in efficiency
was observed for a particular ratio of methylene
blue and ammonium dichromate.
Anantharaman, M R; Swapna, Nair S; Mercy, Mathews; Joy, P A; Kulkarni, S D(Elsevier, July 26, 2004)
[+]
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Abstract:
Superparamagnetic nanocomposites based on g-Fe2O3 and sulphonated polystyrene have been synthesized by ion
exchange process and the preparation conditions were optimized. Samples were subjected to cycling to study the effect
of cycling on the magnetic properties of these composites. The structural and magnetization studies have been carried
out. Magnetization studies show the dependence of magnetization on the number of ion exchange cycles. Doping of
cobalt at the range in to the g-Fe2O3 lattice was effected in situ and the doping was varied in the atomic percentage
range 1–10. The exact amount of cobalt dopant as well as the iron content was estimated by Atomic Absorption
Spectroscopy. The effect of cobalt in modifying the properties of the composites was then studied and the results
indicate that the coercivity can be tuned by the amount of cobalt in the composites. The tuning of both the
magnetization and the coercivity can be achieved by a combination of cycling of ion exchange and the incorporation of
cobalt
Description:
Journal of Magnetism and Magnetic Materials 283 (2004) 344–352
Sudha Kartha, C; Nimmi, K P; Sreekumar, K; Rani, Joseph; Pramitha, V(Wiley Online Library, January 7, 2012)
[+]
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Abstract:
Holographic grating with good storage
life in poly(vinyl alcohol) based photopolymer film, prepared
by gravity settling method, with reduced concentration
of the dye was found to give good diffraction
efficiency without crosslinking. The material was found
to show good diffraction efficiency and sensitivity (75%
diffraction efficiency at exposure energy of 80 mJ/cm2).
The shelf life of the photopolymer solution could be
improved by storage at a temperature 4 C in refrigerator
Description:
Journal of Applied Polymer Science, Vol. 125, 1238–1243 (2012)
Isora fibre-reinforced natural rubber (NR) composites were cured at 80, 100, 120 and
150°C using a low temperature curing accelerator system. Composites were also prepared using a
conventional accelerator system and cured at 150°C. The swelling behavior of these composites at
varying fibre loadings was studied in toluene and hexane. Results show that the uptake of solvent
and volume fraction of rubber due to swelling was lower for the low temperature cured vulcanizates
which is an indication of the better fibre/rubber adhesion. The uptake of aromatic solvent was higher
than that of aliphatic solvent, for all the composites. As the fibre content increased, the solvent
uptake decreased, due to the superior solvent resistance of the fibre and good fibre-rubber interactions.
The bonding agent improved the swelling resistance of the composites due to the strong interfacial
adhesion. Due to the improved adhesion between the fibre and rubber, the ratio of the change in
volume fraction of rubber due to swelling to the volume fraction of rubber in the dry sample (V,) was
found to decrease in the presence of bonding agent. At a fixed fibre loading, the alkali treated fibre
composite showed a lower percentage swelling than untreated one for both systems showing superior
rubber-fibre interactions.
Anantharaman, M R; Malini, K A; Sindhu, S; Chinnasamy, C N; Ponpadian, N; Narayanasamy, A; Balachandran, M; Sivasankara Pillai,V N(Kluwer Academic Publishers, February 1, 2001)
[+]
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Abstract:
Magnetic nanocomposites containing iron oxide particles embedded in a polymer matrix
have been synthesized using the method of ion exchange. They have been characterized by
using low temperature and room temperature magnetic measurements and Mo¨ ssbauer
spectroscopy. The iron content in these samples has also been determined. The results
have been analysed and explained. The physical and chemical properties of these
nanocomposite materials are different from those of the bulk. Some of the unique
properties of these materials find application in information storage, color imaging,
ferrofluids and magnetic refrigeration
Ramachandran, A; Rajendra, Badonia; Viswanathan Nair, P G(Society of fisheries Technologists (India), 1990)
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Abstract:
Effect of delayed icing on the microbial quality and shelf-life of Hilsa toll was studied
. Fish iced in rigor condition had a shelf-life of 11 days irrespective of the state
of rigor . Fish procured from the landing centre had a shelf-life of only 8 days . It
showed the presence of coagulase positive staphylococci, faecal streptococci and E. coli.
Total bacterial count was low in all the samples and it increased after spoilage
Measurements of dc conductivity and dielectric constant show that deuteration causes an upward shift of the high temperature phase transition point from 186.5 to 191°C and a downward shift of the low temperature transition point from 10 to -1.5°C in LiNH4SO4. Mechanisms of phase transitions and of electrical transport in the crystal are discussed.
Rani, Joseph(Wiley InterScience, February 18, 2006)
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Abstract:
In this paper we report the preparation and
dielectric properties of poly o-toluidine:poly vinyl chloride
composites in pellet and film forms. The composites were
prepared using ammonium persulfate initiator and HCl
dopant. The characterization is done by TGA and DSC. The
dielectric properties including dielectric loss, conductivity,
dielectric constant, dielectric heating coefficient, absorption
coefficient, and penetration depth were studied in the
microwave field. An HP8510 vector network analyzer with
rectangular cavity resonator was used for the study. Sbands (2-4 GHz), C band (5-8 GHz), and X band (8-12
GHz) frequencies were used in the microwave field. Comparisons
between the pellet and film forms of composites
were also included. The result shows that the dielectric
properties in the microwave field are dependent on the frequency
and on the method of preparation.
Rani, Joseph(Wiley lnterScience, September 4, 2006)
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Abstract:
The latex industry has expanded over the
years to meet the world demands for gloves, condoms,
latex thread etc. Because of the strict specifications for
the products and the unstable nature of the latex, as
high as 15%, of the final latex products are rejected.
Since waste latex rubber (WLR) represents a source of
high quality rubber hydrocarbon, it is a potential candidate
for generating reclaimed rubber of superior quality.
Two types of WLR with different amounts of polysulfidic
bridges are used in these experiments, which are
reclaimed with variation of the concentration of the
reclaiming agents, the reclamation temperature and time,
Di phenyldisultide, 2-aminophenyldisulfide and 2,2'-dibenzamidodiphenyldisulfide
(DBADPDS) are used as reclaiming
agents, and the effect of diphenyldisulfides (DPDS)
with different substituents, on the reclamation efficiency of WLR is investigated. A kinetic study of the reclamation
reaction with the three reclaiming agents is done.
The reaction rates and activation energies are calculated
and compared with literature values. The comparative
study of the three different reclaiming agents shows that
(DBADPDS) is able to break the crosslinks at temperature
levels 20'C below the temperature levels normally
used with DPDS. Another advantage of this reclaiming
agent is the reduced smell during the reclamation process
and of the final reclaims, one of the most important
shortcomings of other disulfides used for this purpose.
Ravisankar, M; Reghunath, A T; Sathianandan, K; Nampoori, V P N(Optical Society of America, September 15, 1988)
[+]
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Abstract:
The split-pulse laser method is used to reinvestigate the optical attenuation of distilled water in the region from 430 to 630 nm. The studies are then extended to ionic solutions of NaCl, MgCl2, and Na2SO4, these salts forming the major constituents of seawater. The effect of the concentration of these constituents on optical attenuation is investigated. Further, optical attenuation studies are carried out for the region from 430 to 630 nm for an aqueous solution prepared with all the major constituents in the same proportions as in natural seawater. These values are then compared with values obtained for natural seawater. The relative role of dissolved salts and suspended particles on optical attenuation in seawater is discussed. The lowest attenuation is observed at ~450 nm for all solutions and is found to coincide with that for distilled water.
Mohanan, T(American Institute of Physics, August 22, 2005)
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Abstract:
The effect of dopants with different valencies and ionic radii on the densification, structural
ordering, and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 (BMT) is investigated. It is
found that dopants such as Sb2O5, MnO, ZrO2, WO3, and ZnO improve the microwave dielectric
properties of BMT. Addition of trivalent dopants is detrimental to the cation ordering and dielectric
properties of BMT. A correlation between the microwave dielectric properties of BMT and ionic
radii of the dopant has been established. The variation of the dielectric properties of pure and doped
BMT at cryogenic temperatures is also discussed.
Surendran,K P; Sebastian,M T; Mohanan, P; Mohanan,Jacob V(American Institute of Physics, 2005)
[+]
[-]
Abstract:
The effect of dopants with different valencies and ionic radii on the densification, structural
ordering, and microwave dielectric properties of Ba(Mg1t3Tazt3)O3 (BMT) is investigated. It is
found that dopants such as Sb,05, MnO, ZrO,, WO1, and ZnO improve the microwave dielectric
properties of BMT. Addition of trivalent dopants is detrimental to the cation ordering and dielectric
properties of BMT. A correlation between the microwave dielectric properties of BMT and ionic
radii of the dopant has been established. The variation of the dielectric properties of pure and doped
BMT at cryogenic temperatures is also discussed