Sajan D, George; Rajesh, Komban; Warrier, K G K; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Taylor & Francis, February , 2010)
[+]
[-]
Abstract:
A laser-induced photoacoustic technique was employed to investigate
thermal transport through nanocrystalline CePO4 samples prepared via the
sol–gel route. Evaluation of thermal diffusivity was carried out using the
one-dimensional model of Rosencwaig and Gersho for the reflection
configuration of the photoacoustic method. Structural analyses of samples
revealed that they are nanoporous in nature, possessing micron-sized
grains. Analysis of results shows that thermal diffusivity value varies with
sintering temperature. Results are explained in terms of the variation in
porosity with sintering temperature and the effects of various scattering
mechanisms on the propagation of phonons through the nanoporous
ceramic matrix. Further analyses confirm that apart from porosity, grain
boundary resistance and interface thermal resistance influence the effective
value of thermal diffusivity of the samples under investigation.
Balasubramani, N; Dr. Pillai, U T S(National Institute for Interdisciplinary Science and Technology (CSIR), 2009)
[+]
[-]
Abstract:
MAGNESIUM ALLOYS have strong potential for weight reduction in a wide
range of technical applications because of their low density compared to other structural
metallic materials. Therefore, an extensive growth of magnesium alloys usage in the
automobile sector is expected in the coming years to enhance the fuel efficiency through
mass reduction. The drawback associated with the use of commercially cheaper Mg-Al
based alloys, such as AZ91, AM60 and AM50 are their inferior creep properties above
100ºC due to the presence of discontinuous Mg17A112 phases at the grain boundaries.
Although rare earth-based magnesium alloys show better mechanical properties, it is not
economically viable to use these alloys in auto industries. Recently, many new Mg-Al
based alloy systems have been developed for high temperature applications, which do not
contain the Mg17Al12 phase. It has been proved that the addition of a high percentage of
zinc (which depends upon the percentage of Al) to binary Mg-Al alloys also ensures the
complete removal of the Mg17Al12 phase and hence exhibits superior high temperature
properties.ZA84 alloy is one such system, which has 8%Zn in it (Mg-8Zn-4Al-0.2Mn, all
are in wt %) and shows superior creep resistance compared to AZ and AM series alloys.
These alloys are mostly used in die casting industries. However, there are certain large
and heavy components, made up of this alloy by sand castings that show lower
mechanical properties because of their coarse microstructure. Moreover, further
improvement in their high temperature behaviour through microstructural modification is
also an essential task to make this alloy suitable for the replacement of high strength
aluminium alloys used in automobile industry. Grain refinement is an effective way to
improve the tensile behaviour of engineering alloys. In fact, grain refinement of Mg-Al
based alloys is well documented in literature. However, there is no grain refiner
commercially available in the market for Mg-Al alloys. It is also reported in the literature
that the microstructure of AZ91 alloy is modified through the minor elemental additions
such as Sb, Si, Sr, Ca, etc., which enhance its high temperature properties because of the formation of new stable intermetallics. The same strategy can be used with the ZA84
alloy system to improve its high temperature properties further without sacrificing the
other properties. The primary objective of the present research work, “Studies on
grain refinement and alloying additions on the microstructure and
mechanical properties of Mg-8Zn-4Al alloy” is twofold:
1. To investigate the role of individual and combined additions of Sb and Ca on
the microstructure and mechanical properties of ZA84 alloy.
2. To synthesis a novel Mg-1wt%Al4C3 master alloy for grain refinement of
ZA84 alloy and investigate its effects on mechanical properties.
The present work describes the immobilization of α-amylase over well ordered mesoporous molecular sieve SBA-15 with different pore diameters synthesized by post synthesis treatment (PST) hydrothermally after reaction at 40°C. The materials were characterized by N 2 adsorption–desorption studies, small angle X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. Since α-amylase obtained from Bacillus subtilis has dimensions of 35 × 40 × 70 Å it is expected that the protein have access to the pore of SBA-15 (PST-120°C) with diameter 74 Å. The pore dimension is appropriate to prevent considerable leaching. The rate of adsorption of the enzyme on silica of various pore sizes revealed the influence of morphology, pore diameter, pore volume and pH.
Reena, T A; Dr. Prathapachandra Kurup, M R(Cochin University of Science & Technology, March , 2011)
[+]
[-]
Abstract:
The present work is concentrated on the studies of two novel
semicarbazones, di-2-pyridyl ketone-N4-phenyl-3-semicarbazone (HL1) and
quinoline-2-carboxaldehyde-N4-phenyl-3-semicarbazone (HL2). The compositions
of these semicarbazones were determined by the CHN analyses. For the
characterization of these compounds we have used IR, UV and NMR spectral
studies. The molecular structure of quinoline-2-carboxaldehyde-N4-phenyl-3-
semicarbazone (HL2) was obtained by single crystal X-ray diffraction studies.
Also, we have synthesized Zn(II), Cd(II), Cu(II), Ni(II), Co(II) and Mn(II)
complexes of these semicarbazones, HL1 and HL2. These complexes were
characterized by various spectroscopic techniques, magnetic and conductivity
studies. We could isolate single crystals of some Zn(II) and Cd(II) compounds
suitable for X-ray diffraction studies. For other complexes we could not isolate
single crystals of good quality for single crystal X-ray diffraction studies.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
Beena, P S; Dr. Chandrasekaran, M; Dr. Sarita G, Bhat(Cochin University of Science & Technology, January , 2010)
[+]
[-]
Abstract:
Marine fungi remain totally unexplored as a source of industrial enzyme
and prospective applications. Further tannase production by a marine organism has
so far not been established. The primary objective of this study included the
evaluation of the potential of Aspergillus awamori isolated from sea water as part
of an earlier study and available in the culture collection of the Microbial
technology laboratory for tannase production through different fermentation
methods, optimization of bioprocess variables by statistical methods, purification
and characterization of the enzyme, genetic study, and assessment of its potential applications.
Description:
Department of Biotechnology,
Cochin University of Science and Technology
V P N Nampoori; Senoy,Thomas; Jinesh,Mathew; Radhakrishnan,P; George,A K; Al-Harthi,R V; Ramanujan; Anantharaman,M R(Sensors and Actuators: A Physical, May 11, 2010)
[+]
[-]
Abstract:
Metallic glass alloy Metglas 2826 MB based amorphous magnetic thin films were
fabricated by the thermal evaporation technique. Transmission electron micrographs and
electron diffraction pattern showed the amorphous nature of the films. Composition of
the films was analyzed employing x-ray photoelectron spectroscopy and energy
dispersive x-ray spectroscopy techniques. The film was integrated to a long period fibre
grating. It was observed that the resonance wavelength of the fibre grating decreased with
an increase in the magnetic field. Change in the resonance wavelength was minimal at
higher magnetic fields. Field dependent magnetostriction values revealed the potential
application of these films in magnetostrictive sensor devices
V P N Nampoori; Mohammed Yusuff,K K; Arun,V; Mathew,S; Robinson,P P; Jose,M(Elsevier, Journal of Dyes and Pigments, March 20, 2010)
[+]
[-]
Abstract:
The Schiff base, 3-hydroxyquinoxaline-2-carboxalidine-4-aminoantipyrine, was synthesized by the
condensation of 3-hydroxyquinoxaline-2-carboxaldehyde with 4-aminoantipyrine. HPLC, FT-IR and NMR
spectral data revealed that the compound exists predominantly in the amide tautomeric form and
exhibits both absorption and fluorescence solvatochromism, large stokes shift, two electron quasireversible
redox behaviour and good thermal stability, with a glass transition temperature of 104oC. The
third-order non-linear optical character was studied using open aperture Z-scan methodology employing
7 ns pulses at 532 nm. The third-order non-linear absorption coefficient, b, was 1.48 x 10-6 cm W-1 and
the imaginary part of the third-order non-linear optical susceptibility, Im c(3), was 3.36 x10-10 esu. The
optical limiting threshold for the compound was found to be 340 MW cm-2.
Mohammed Yusuff, K K; V P N Nampoori; Arun,V; Mathew,S; Robinson,P; Jose,M(Elsevier, Journal of Dyes and Pigments, March 20, 2010)
[+]
[-]
Abstract:
The Schiff base, 3-hydroxyquinoxaline-2-carboxalidine-4-aminoantipyrine, was synthesized by the
condensation of 3-hydroxyquinoxaline-2-carboxaldehyde with 4-aminoantipyrine. HPLC, FT-IR and NMR
spectral data revealed that the compound exists predominantly in the amide tautomeric form and
exhibits both absorption and fluorescence solvatochromism, large stokes shift, two electron quasireversible
redox behaviour and good thermal stability, with a glass transition temperature of 104 oC. The
third-order non-linear optical character was studied using open aperture Z-scan methodology employing
7 ns pulses at 532 nm. The third-order non-linear absorption coefficient, b, was 1.48 x 10-6 cm W-1 and
the imaginary part of the third-order non-linear optical susceptibility, Im c(3), was 3.36x10-10 esu. The
optical limiting threshold for the compound was found to be 340 MW cm-2.