microwave dielectric properties of ceramics based on Ba(Mgv3Ta(2-2x)t3W,t3Tixt3)O3 is investigated as a function of x. The
15 densification as well as dielectric properties deteriorate with increase in the substitution levels of (Ti 1,3W113)333 + at (Ta213)3.33+ site
16 in Ba(Mg113Ta213)03. The rt is approaching zero between x = 0.1 and 0.15 in Ba(Mg it3Ta(2-2,,.)t3W,it3Ti,Tt3)O3 where quality factor is
17 reasonably good (Qu x f = 80,000-90,000 GHz). The Ba(Mg1,3Ta(2_,013W,13Ti,,13)03 with x = 1.0 has e, = 15.4, rf= -25.1 ppm/
18 "C, Q„ x f = 35,400 GHz
The BaO-2CeO2-nTiO2 ceramics with n = 3, 4 and 5 have been prepared with CeO2 as starting material . The ceramics have been
characterized using scanning electron microscopy , X-ray diffraction , Raman and X-ray photoelectron spectroscopy techniques. The
microwave dielectric properties have been measured using standard dielectric resonator techniques . BaO-2CeO2-3TiO2 (123),
BaO-2CeO2-4TiO2 ( 124) and BaO-2CeO2-5TiO2 ( 125) ceramics showed dielectric constants of 38, 27 and 32, respectively . All the
ceramics showed fairly good unloaded Q - factors . 124 and 125 compounds exhibited low tf values, while 123 showed a high rf value
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
Microwave dielectric ceramics based on RETiTaO6 (RE = La, Cc, Pr, Nd, Sm, Eu,
Gd, Tb, Dy, Ho, Y, Er, Yb, Al, and In) were prepared using a conventional solid-state
ceramic route. The structure and microstructure of the samples were analyzed using
x-ray diffraction and scanning electron microscopy techniques. The sintered samples
were characterized in the microwave frequency region. The ceramics based on Ce, Pr,
Nd, Sm, Eu, Gd, Tb, and Dy, which crystallize in orthorhombic aeschynite structure,
had a relatively high dielectric constant and positive T f while those based on Ho, Er,
and Yb, with orthorhombic euxenite structure, had a low dielectric constant and
negative Tf. The RETiTaO6 ceramics had a high-quality factor. The dielectric constant
and unit cell volume of the ceramics increased with an increase in ionic radius of the
rare-earth ions, but density decreased with it. The value of Tf increased with an
increase in RE ionic radii, and a change in the sign of Tf occurred when the ionic
radius was between 0.90 and 0.92 A. The results indicated that the boundary of the
aeschynite to euxenite morphotropic phase change lay between DyTiTaO6 and
HoTiTaO6. Low-loss ceramics like ErTiTaO6 (Er = 20.6, Qxf = 85,500), EuTiTaO6
(Er = 41.3, Qxf = 59,500), and YTiTaO6 (Er = 22.1, Q„xf = 51,400) are potential
candidates for dielectric resonator applications
Dielectric resonator ceramics with composition formula Ba[(D3+0.3 Bi0.2)Nb0.5]O3,where D3+=Y,Pr,Sm,Gd,Dy and Er,were prepared by the conventional ceramic preparation route
Eby Thomas, Thachil; Bindu, Sharmila T K; Ajalesh, Nair B; Beena, Abraham T; Sabura Begum, P M(Elsevier, May 22, 2014)
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Abstract:
Graphene has captured the attention of scientific community due to recently emerging high performance
applications. Hence, studying its reinforcing effects on epoxy resin is a significant step. In this study,
microwave exfoliated reduced graphene oxide (MERGO) was prepared from natural graphite for subsequent
fabrication of epoxy nanocomposites using triethylenetetramine (TETA) as a curing agent via insitu
polymerization. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman spectroscopy,
Fourier transform infrared spectroscopy (FTIR), C13 NMR spectroscopy, X-ray photoelectron spectroscopy
(XPS) and ultravioletevisible (UVevis) spectroscopy were employed to confirm the simultaneous
reduction and exfoliation of graphene oxide. The reinforcing effect of MERGO on epoxy resin was
explored by investigating its static mechanical properties and dynamic mechanical analysis (DMA) at
MERGO loadings of 0 to 0.5 phr. The micro-structure of epoxy/MERGO nanocomposites was investigated
using scanning electron microscope (SEM), transmission electron microscope (TEM) and XRD techniques.
The present work reports an enhancement of 32%, 103% and 85% in tensile, impact and flexural strength
respectively of epoxy by the addition of even 0.25 phr MERGO. At this loading elastic and flexural moduli
also increased by 10% and 65%, respectively. Single-edge-notch three-point-Bending (SEN-TPB) fracture
toughness (KIC) measurements were carried out where a 63% increase was observed by the introduction
of 0.25 phr MERGO. The interfacial interactions brought about by graphene also benefited the dynamic
mechanical properties to a large extent in the form of a significant enhancement in storage modulus and
slightly improved glass transition temperature. Considerable improvements were also detected in
dielectric properties. The epoxy nanocomposite also attained an ac conductivity of 10 5 S/m and a
remarkable increase in dielectric constant. The simple and cost effective way of graphene synthesis for
the fabrication of epoxy/MERGO nanocomposites may be extended to the preparation of other MERGO
based polymer nanocomposites. This remarkable class of materials has thrown open enormous opportunities
for developing conductive adhesives and in microelectronics
Subin Thomas; Dr. K. Rajeev Kumar(Cochin University of Science and Technology, November 11, 2015)
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Abstract:
The semiconductor industry's urge towards faster, smaller and cheaper
integrated circuits has lead the industry to smaller node devices. The integrated
circuits that are now under volume production belong to 22 nm
and 14 nm technology nodes. In 2007 the 45 nm technology came with
the revolutionary high- /metal gate structure. 22 nm technology utilizes
fully depleted tri-gate transistor structure. The 14 nm technology is a
continuation of the 22 nm technology. Intel is using second generation
tri-gate technology in 14 nm devices. After 14 nm, the semiconductor industry
is expected to continue the scaling with 10 nm devices followed by
7 nm. Recently, IBM has announced successful production of 7 nm node
test chips. This is the fashion how nanoelectronics industry is proceeding
with its scaling trend.
For the present node of technologies selective deposition and selective removal
of the materials are required. Atomic layer deposition and the
atomic layer etching are the respective techniques used for selective deposition
and selective removal. Atomic layer deposition still remains as
a futuristic manufacturing approach that deposits materials and lms in
exact places. In addition to the nano/microelectronics industry, ALD is
also widening its application areas and acceptance. The usage of ALD
equipments in industry exhibits a diversi cation trend. With this trend,
large area, batch processing, particle ALD and plasma enhanced like ALD
equipments are becoming prominent in industrial applications. In this
work, the development of an atomic layer deposition tool with microwave
plasma capability is described, which is a ordable even for lightly funded
research labs.
Bindu, G; Vinu, Thomas; Anil, Lonappan; Aanandan,C K; Mathew, K T(John Wiley & Sons, January , 2006)
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Abstract:
A phantom that exhibits complex dielectric properties similar to low-water-content biological tissues over the electromagnetic spectrum of 2000–3000 MHz has been synthesized from carbon black, graphite powder, and poly vinyl acetate (PVA)-based adhesive. The material overcomes various problems that are inherent in conventional phantoms such as decomposition and deterioration due to the invasion of bacteria or mold. The absorption coefficients of the material for various concentrations of carbon and graphite are studied. A combination of 50% poly-vinyl-acetate-based adhesive, 20% carbon, and 30% graphite exhibits a high absorption coefficient, which suggests another application of the material as a good microwave absorber for the interior lining of tomographic chamber in microwave imaging. The cavity-perturbation technique is adopted to study the dielectric properties of the material.
Terry Mechado; Dr.Seralathan, P(Cochin University Of Science And Technology, April 12, 1995)
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Abstract:
Continental shelf is of particular significance in marine geology ,
because it links the two basically different structural zones in the earth's crust; the
continents and ocean basins. The shelf area has much wider importance in many
fields of activity such as scientific, economic, social, political and strategic. The
pace of development has ultimately put pressure on mankind to look for exploitable
resources and accessibility to the continental shelf area and beyond. Added to the
above, the developmental activities in the coastal area would readily and directly
influence the innershelf sediments. This situation demands a thorough geological
knowledge of the continental shelf area. Moreover, a successful management of
the continental shelf zone requires an optimum data base on the physico-chemical
nature of the shelf sediments. Although sedimentological studies were carried out
along the western continental shelf of India, a well documented systematic study
of the inner shelf off Trivandrum coast is still found to be lacking. Considering the
physiographic settings and the vicinity of two renowned placer deposits at Chavara
and Manavalakurichi, such a sedimetological inventory has become all the more
vital.
In view of the above, a research programme has been drawn up to
account the salient sedimentological and mineralogical aspects of the innershelf
and beach sediments between Paravur and Kovalam, Trivandrum district, Kerala
(latitudes 8° 7'00" to 8° 47'45" and longitudes 76°43'00" to 77° 40'45"). The
findings are presented in six chapters formatted to address the aim of this
research.
Description:
Marine Geology Division
School of Marine Sciences
Cochin University of Science And Technology
Mi ni -trawls are operated by the artisanal fishermen from small wooden non-motorised
canoes. Shrimp, fish and crab trawls wi th head rope length rang ing from 3.5-8 m, made of
Po lyethy lene mon ofila ment (PE) twisted and Polyamide mullifilament (PA) rigged to 6-7 kll
fla t rectangular wooden otter boards are common in the lower reaches of Kariango de and
Chandrag iri rive rs. Since the trawling speed is less, ca tch is do minated by crus taceans. Less
scope ratio also may be affecting the catching efficiency of the gear. This pape r deals with
the design, operation and economics of mini traw ling carried out by a group of fisherme n
in the above rivers of Kasargod district Kerala state.
Maheswaran, P A; Revichandran, C(NATIONAL INSTITUTE OF OCEANOGRAPHY, August , 2004)
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Abstract:
In this thesis, a detailed attempt has been made to understand the general hydrography of the upper 300m of the water column, in the eastern Arabian Sea and the western Bay of Bengal, the two contrasting basins in the northern Indian Ocean, using recently collected data sets of Marine Research-Living Resources (MR-LR) assessment programme, funded by Department of Ocean Development, from various cruises, pertaining to different seasons. Initially it discuss the general hydrography of the west and east coasts of India are covered, in the context of mixed layer processes. The study describes the materials and methods . To compare the hydrography of the AS and BOB, a unique MLD(Mixed Layer Depth) definition for AS and BOB is essential, for which the 275 CTD profiles were used. A comparison has been made among the various MLD criteria with the actual MLD.
The monthly evolution of MLD, barrier layer thickness and the role of atmospheric forcing on the dynamics of the mixed layer in the AS and BOB were studied. The general hydrography along the west coast of India is described. The upwelling/downwelling, winter cooling processes, in the context of chemical and biological parameters, are also addressed. Finally the general hydrography of the Bay of Bengal is covered. The most striking feature in the hydrography are the signature of an anticyclonic subtropical gyre during spring intermonsoon and a cold core eddy during winter monsoon. The TTS(Typical Tropical Structure) of the euphotic layer was also investigated.