The microwave dielectric properties of (I -x)CaTiO3-xSm(Mg1/2Tit,2)O3(0.1 <-x< 1.0) have been investigated. The
system forms a solid solution throughout the entire compositional range. The dielectric constant decreases from 86 to 25 as x
varies from 0.1 to 1.0. The Qxf varies non-linearly and increases for composition with x> 0.6. The nonmonotonic variation
with composition x is more pronounced in Tt than in er. The microwave dielectric properties indicate the possibility of a phase
transformation for x between 0.4 and 0.5
Pazhoor Bijumon, Varghese; Mohanan, P; Mailadil, Thomas Sebastian(The Japan Society of Applied Physics, 2002)
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Abstract:
Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state
ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave
frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Q5 x f > 30000GHz) and
small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator
applications in microwave integrated circuits. [DOI: 10. 1 143/JJAP.41.3834]
Isuhak, Naseembeevi Jawahar; Narayana Iyer, Santha; Mailadil, Thomas Sebastian(Materials Reserach Society, December , 2002)
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Abstract:
Single-phase polycrystalline ceramics in the MO-La2O3-Ti02 (M = Ca, Sr, Ba)
system, such as cation-deficient hexagonal perovskites CaLa4Ti4O15, SrLa4Ti4O15,
BaLa4Ti4O15, and Ca2La4Ti5O18 and the orthorhombic phases CaLa4Ti5O17 and
CaLa8Ti9O31, were prepared through the solid-state ceramic route. The phases
and structure of the ceramics were analyzed through x-ray diffraction and scanning
electron microscopy. The microwave dielectric properties of the ceramics were studied
using a network analyzer. The investigated ceramics show high Er in the range 42 to
54, high quality factors with Q x f in the range 16,222 to 50,215 GHz, and low Tf in
the range -25 to +6 ppm3/°C. These high dielectric constant materials with high Q x f
up to 50,215 GHz are suitable for applications where narrow bandwidth and extremely
low insertion loss is necessary, especially at frequencies around 1.9 GHz
V P N Nampoori; Radhakrishnan, P; Girijavallabhan, C P; Sivsankara Pillai, V N; Suresh Kumar, P(Journal of Optics : A Pure and Applied Optics, March 8, 2002)
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Abstract:
A fibre optic technique for detecting trace amounts of nitrite compounds in
water is described. The off-line fibre optic sensor outlined here is based on
evanescent field absorption in a test solution formed by the reaction of nitrite
compounds in water with suitable chemical reagents. A short unclad portion
of a plastic clad silica fibre acts as the sensing region. The experimental
results clearly establish the usefulness of the present technique for detecting
very low concentrations of the order of 1 ppb (parts per billion) of nitrite
compounds with a large dynamic range of 1–1000 ppb. Such a high
sensitivity enables the present device to be used for measuring the nitrite
content in drinking water.
Sivasankara Pillai, V N; Radhakrishnan, P; V P N Nampoori; Girijavallabhan, C P; Suresh Kumar, P(Journal of Optics : A Pure and Applied Optics, March 8, 2002)
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Abstract:
A fibre optic technique for detecting trace amounts of nitrite compounds in
water is described. The off-line fibre optic sensor outlined here is based on
evanescent field absorption in a test solution formed by the reaction of nitrite
compounds in water with suitable chemical reagents. A short unclad portion
of a plastic clad silica fibre acts as the sensing region. The experimental
results clearly establish the usefulness of the present technique for detecting
very low concentrations of the order of 1 ppb (parts per billion) of nitrite
compounds with a large dynamic range of 1–1000 ppb. Such a high
sensitivity enables the present device to be used for measuring the nitrite
content in drinking water.
Radhakrishnan, P; Girijavallabhan, C P; V P N Nampoori; Sivsankara Pillai, V N; Suresh Kumar, P(Journal of Optics : A Pure and Applied Optics, March 8, 2002)
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Abstract:
A fibre optic technique for detecting trace amounts of nitrite compounds in
water is described. The off-line fibre optic sensor outlined here is based on
evanescent field absorption in a test solution formed by the reaction of nitrite
compounds in water with suitable chemical reagents. A short unclad portion
of a plastic clad silica fibre acts as the sensing region. The experimental
results clearly establish the usefulness of the present technique for detecting
very low concentrations of the order of 1 ppb (parts per billion) of nitrite
compounds with a large dynamic range of 1–1000 ppb. Such a high
sensitivity enables the present device to be used for measuring the nitrite
content in drinking water.
Suja, Haridas; Dr. Sugunan, S(Cochin University of Science & Technology, January , 2002)
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Abstract:
The present project was a systematic investigation of the
physico-chemical properties and catalytic activity of some transition metal promoted
sulphated zirconia systems. The characterisation and catalytic activity results were
compared with that of pure Zr02 and simple sulphated zirconia systems. Sulphated
zirconia samples were prepared by a controlled impregnation technique. In the case of
metal incorporated systems, a single step impregnation was carried out using required
amounts of sulphuric acid and metal salt solutions. As a preliminary step, optimisation of
calcination temperature and sulphate content was achieved. For further studies, the
optimised sulphate loading of 10 ml per gram of hydrous zirconium oxide and a
calcination temperature of 700°C was employed. Metal incorporation had a positive
influence on the physico-chemical properties. Vapour phase cumene conversion served as
a test reaction for acidity. Some industrially important reactions like Friedel-Crafts
reaction, phenol hydroxylation, nitration, etc. were selected to test the catalytic activity of
the prepared systems.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
Deepa, C S; Dr.Sugunan, S(Cochin University of Science & Technology, August , 2002)
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Abstract:
In the present work, we have tried to evaluate systematically the surface properties
of sulphated tin oxide systems modified with three different transition metal oxides viz. iron
oxide, tungsten oxide and molybdenum oxide. The catalytic activities of these systems are
checked and compared by carrying out some industrially important reactions such as
oxidative dehydrogenation of ethylbenzene and Friedel-Crafts reactions.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology