Abstract: | ZnO micro particles in the range 0.4-0.6 μm were synthesized by microwave irradiation method. The XRD analysis reveals that the sample is in the wurtzite phase with orientation along the (101) plane. SAED pattern of the sample reveals the single crystalline nature of the micro grains. TEM images show the formation of cylindrical shaped ZnO micro structures with hexagonal faces. The optical phonon modes were slightly shifted in the Raman spectrum,attributed to the presence of various crystalline defects and laser induced local heating at the grain boundaries. A broad transmission profile was observed in the FTIR spectrum from 1550-3400 cm-1 which falls in the atmospheric transparency window region. PL spectrum centered at 500 nm with a broad band in the region 420-570 nm comprised of different emission peaks attributed to transition between defect levels. Various emission levels in the sample were expliained with a band diagram |
Description: | Journal of Optoelectronics and Biomedical Materials Vol. 4, Issue 1, January-March 2012, p. 1 - 7 |
URI: | http://dyuthi.cusat.ac.in/purl/4563 |
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Photoluminescen ... d Zno Micro Structures.pdf | (1.592Mb) |
Abstract: | SnO2 nanocrystalline thin films were deposited on glass substrates by the spray pyrolysis technique in air atmosphere at 375, 400, 425, 450 and 500 ◦C substrate temperatures. The obtained films were characterized by using XRD. The room temperature photoluminescence (PL) spectra of these films have near band edge (NBE) and deep level emission under the excitation of 325 nm radiation. NBE PL peak intensity decreased consistently with temperatures for samples prepared at 400, 450 and 500 ◦C, while a sudden reduction in intensity is observed for the sample prepared at 425 ◦C. A similar effect was observed for the optical transmittance spectra. These effects can be explained on the basis of the change in population of oxygen vacancies as indicated by the change in a values |
Description: | J. Phys. D: Appl. Phys. 39 (2006) 4540–4543 |
URI: | http://dyuthi.cusat.ac.in/purl/4546 |
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Photoluminescen ... ms on glass substrates.pdf | (148.6Kb) |
Abstract: | Conjugated polymers in the form of thin films play an important role in the field of materials science due to their interesting properties. Polymer thin films find extensive applications in the fabrication of devices, such as light emitting devices, rechargeable batteries, super capacitors, and are used as intermetallic dielectrics and EMI shieldings. Polymer thin films prepared by plasma-polymerization are highly cross-linked, pinhole free, and their permittivity lie in the ultra low k-regime. Electronic and photonic applications of plasma-polymerized thin films attracted the attention of various researchers. Modification of polymer thin films by swift heavy ions is well established and ion irradiation of polymers can induce irreversible changes in their structural, electrical, and optical properties. Polyaniline and polyfurfural thin films prepared by RF plasmapolymerization were irradiated with 92MeV silicon ions for various fluences of 1×1011 ions cm−2, 1×1012 ions cm−2, and 1×1013 ions cm−2. FTIR have been recorded on the pristine and silicon ion irradiated polymer thin films for structural evaluation. Photoluminescence (PL) spectra were recorded for RF plasma-polymerized thin film samples before and after irradiation. In this paper the effect of swift heavy ions on the structural and photoluminescence spectra of plasma-polymerized thin films are investigated. |
Description: | Synthetic Metals 155 (2005) 311–315 |
URI: | http://dyuthi.cusat.ac.in/purl/4382 |
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Photoluminescen ... polymerized thin films.pdf | (320.2Kb) |
Description: | Plasma Science, 2002. ICOPS 2002. IEEE Conference Record-Abstracts. The 29th IEEE International Conference on |
URI: | http://dyuthi.cusat.ac.in/purl/4434 |
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Plasma Assisted ... lyanisidine Thin Films.pdf | (86.27Kb) |
Abstract: | Fine (approximately 18 nm) particles of nickel ferrite were synthesized by the sol-gel technique, and their structural properties were evaluated by X-ray diffraction. Neoprene-based rubber ferrite composites were prepared by incorporating these nickel ferrite powders in the rubber matrix according to a specific recipe. The cure characteristics were analyzed, and the samples were molded into particular shapes whose properties were determined according to ASTM standards. Magnetization studies were carried out using a Vibrating Sample Magnetometer. This study indicates that neoprene rubber-based flexible magnets with desired magnetic properties and appropriate mechanical properties can be prepared by incorporating an adequate amount of nanoscale nickel ferrite particles within the rubber matrix |
Description: | Polymer-Plastics Technology and Engineering, 47: 137–146, 2008 |
URI: | http://dyuthi.cusat.ac.in/purl/4388 |
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Physicomechanic ... ber Ferrite Composites.pdf | (827.3Kb) |
Abstract: | Spinel ferrites are commercially important because of their excellent magnetic and catalytic properties. The study by Low Energy Ion Scattering (LEIS) can reveal atomic scale information on the surface. The surface of selected spinel ferrites was investigated by LEIS. It has been found that it is the octahedral sites which are preferentially exposed on the surface of the spinel ferrites. So the probable planes which are exposed on spinel ferrite surfaces are D(110) or B(111). This prediction using LEIS gives scope for tailor-making compounds with catalytically active ions on the surface for various catalytic reactions. |
Description: | JOURNAL OF MATERIALS SCIENCE 34 (1999) 4279 – 4283 |
URI: | http://dyuthi.cusat.ac.in/purl/4404 |
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Preferential ex ... pinel ferrite surfaces.pdf | (84.33Kb) |
Abstract: | Optimum conditions for the preparation of tape recording quality Y-Fe20 s by the thermal decomposition of ferrous oxalate dihydrate have been established. Formation of the intermediate F%O~ which is most important in forming Y-FezO 3 takes place only in the presence of water vapour. Various stages of decomposition have been characterised by DTA, TG, DTG, and x-ray powder diffraction. The method for the preparation of acicular "Y-Fe208 that matches very well with the commercial tape recording material has been developed |
Description: | Bull. Mater. Sei., Vol. 3, Number 2, July 1981, pp. 201-208 |
URI: | http://dyuthi.cusat.ac.in/purl/4396 |
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Preparation and ... ape recording material.pdf | (374.1Kb) |
Abstract: | Rubber ferrite composites (RFC) are magnetic polymer composites and have a variety of applications as flexible magnets, pressure=photo sensors, and microwave absorbers. The mouldability into complex shapes is one of the advantages of these magnetic elastomers. They have the potential of replacing the conventional ceramic materials, due to theire flexible nature. In the present study, the incorporation of pre-characterized hexagonal ferrites, namely barium ferrite (BaFe12O19), into natural rubber matrix is carried out according to a suitable recipe for various loadings of the filler. The processability of these compounds was determined by evaluating the cure characteristics: scorch time, cure time, and minimum and maximum torque. It has been found that the addition of magnetic fillers does not affect the processability of the composites, whereas the physical properties are modified. The magnetic properties of these composites containing various loadings of the magnetic filler were also investigated. The magnetic properties of RFC can be controlled by the addition of appropriate amount of the ferrite filler. |
Description: | International Journal of Polymeric Materials, 53:565–575, 2004 |
URI: | http://dyuthi.cusat.ac.in/purl/4406 |
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Processability ... taining Barium Ferrite.pdf | (172.8Kb) |
Abstract: | Rubber ferrite composites have the unique advantage of mouldability, which is not easily obtainable using ceramic magnetic materials. The incorporation of mixed ferrites in appropriate weight ratios into the rubber matrix not only modi es the dielectric properties of the composite but also imparts magnetic properties to it. Mixed ferrites belonging to the series of Mn(1 – x )Znx Fe2O4 have been synthesised with diVerent values of x in steps of 0·2, using conventional ceramic processing techniques. Rubber ferrite composites were prepared by the incorporation of these pre-characterised polycrystallineMn(1 – x )Znx Fe2O4 ceramics into a natural rubber matrix at diVerent loadings according to a speci c recipe. The processability of these elastomers was determined by investigating their cure characteristics. The magnetic properties of the ceramic llers as well as of the rubber ferrite composites were evaluated and the results were correlated. Studies of the magnetic properties of these rubber ferrite composites indicate that the magnetisation increases with loading of the ller without changing the coercive eld. The hardness of these composites shows a steady increase with the loading of the magnetic llers. The evaluation of hardness andmagnetic characteristics indicates that composites with optimummagnetisation and almost minimum stiVness can be achieved with a maximum loading of 120 phr of the ller at x=0·4. From the data on the magnetisation of the composites, a simple relationship connecting the magnetisation of the rubber ferrite composite and the ller was formulated. This can be used to synthesise rubber ferrite composites with predetermined magnetic properties |
Description: | Plastics, rubber and composites,vol 31,issue 3,pp 106-113 |
URI: | http://dyuthi.cusat.ac.in/purl/4378 |
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Processability, ... anganese zinc ferrites.pdf | (295.8Kb) |
URI: | http://dyuthi.cusat.ac.in/purl/764 |
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ApplPhysLett_88_212103.pdf | (165.1Kb) |
URI: | http://dyuthi.cusat.ac.in/purl/788 |
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Pulsed laser de ... pe _-AgGaO2 thin films.pdf | (785.6Kb) |
Abstract: | Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 · 3H2O are recorded and analyzed. The observed bands are assigned on the basis of BrO3 − and H2O vibrations. Additional bands obtained in the region of 3 and 1 modes in [Cu(H2O)6](BrO3)2 are due to the lifting of degeneracy of 3 modes, since the BrO3 − ion occupies a site of lower symmetry. The appearance 1 mode of BrO3 − anion at a lower wavenumber (771 cm−1) is attributed to the attachment of hydrogen to the BrO3 − anion. The presence of three inequivalent bromate groups in the [Al(H2O)6](BrO3)3 · 3H2O structure is confirmed. The lifting of degeneracy of 4 mode indicates that the symmetry of BrO3 − anion is lowered in the above crystal from C3v to C1. The appearance of additional bands in the stretching and bonding mode regions of water indicates the presence of hydrogen bonds of different strengths in both the crystals. Temperature dependent Raman spectra of single crystal [Cu(H2O)6](BrO3)2 are recorded in the range 77–523 K for various temperatures. A small structural rearrangement takes place in BrO3 − ion in the crystal at 391 K. Hydrogen bounds in the crystal are rearranging themselves leading to the loss of one water molecule at 485 K. This is preceded by the reorientation of BrO3 − ions causing a phase transition at 447 K. Changes in intensities and wavenumbers of the bands and the narrowing down of the bands at 77 K are attributed to the settling down of protons into ordered positions in the crystal |
Description: | Spectrochimica Acta Part A 58 (2002) 899–909 |
URI: | http://dyuthi.cusat.ac.in/purl/4554 |
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Raman and FTIR ... [Cu(H2O)6](BrO3)2 and.pdf | (240.6Kb) |
Abstract: | Raman and FTIR spectra of CaFeTi(PO4)3 and CdFeTi(PO4)3 are recorded and analyzed. The observed bands are assigned in terms of vibrations of TiO6 octahedra and PO4 tetrahedra. The symmetry of TiO6 octrahedra and PO4 tetrahedra is lowered from their free ion symmetry. The presence of Fe3+ ion disrupts the Ti–O–P–O–Ti chain and leads to the distortion of TiO6 octrahedra and PO4 tetrahedra. The PO4 3 tetrahedra in both crystals are linearly distorted. The covalency bonding factor of PO4 3 polyanion of both the crystals are calculated from the Raman spectra and compared to that of other Nasicon-type systems. The numerical values of covalency bonding factor indicates that there is a reduction in redox energy and cell voltage and is attributed to strong covalency of PO4 3 polyanionin |
Description: | Journal of Physics and Chemistry of Solids 69 (2008) 1985–1989 |
URI: | http://dyuthi.cusat.ac.in/purl/4549 |
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Raman and FTIR ... eTi(PO4)3 [A ¼ Ca, Cd].pdf | (247.5Kb) |
Abstract: | Raman and infrared spectra of Tl2NbO2PO4, Tl3NaNb4O9(PO4)2 and TlNbOP2O7 are reported. The observed bands are assigned in terms of vibrations of NbO6 octahedra and PO4 tetrahedra in the first two compounds and in terms of NbO6 octahedra and P2O7 4− anion in the third compound. The NbO6 octahedra in all the title compounds are found to be corner-shared and distorted. The higher wavenumber values of the ν1 (NbO6) mode and other stretching modes indicate that the NbO6 octahedra in them are distorted in the order TlNbOP2O7 > Tl2NbO2PO4 > Tl3NaNb4O9(PO4)2. The splitting of the ν3 (PO4) mode indicates that PO4 tetrahedra is distorted more in Tl2NbO2PO4 than in Tl3NaNb4O9(PO4)2. The symmetry of P2O7 4− anion in TlNbOP2O7 is lowered. Bands indicate that the P–O–P bridge in the above compound has a bent P–O–P bridge configuration |
Description: | Materials Chemistry and Physics 73 (2002) 179–185 |
URI: | http://dyuthi.cusat.ac.in/purl/4545 |
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Raman and infra ... O9(PO4)2 and TlNbOP2O7.pdf | (106.4Kb) |
Abstract: | Raman spectra of the KTP single crystal are recorded in electric fields (dc and ac) applied along the polar axis c. Spectra with the laser beam focused near the cathode end, anode end and the centre of the crystal are recorded. The cathode end of the crystal develops a spot ‘grey track’ where the laser beam is focused after a lapse of 5 h from the application of a dc electric field of 38 V/cm. The spectra recorded at the cathode end after the application of field show variations in intensity of bands. A new band appears at 177 cm21. Changes in band intensities are explained on the basis of changes in polarizability of the crystal due to the movement of K1 ions along the polar axis. K1 ions accumulate at the cathode end, where the ‘Grey track’ formation occurs. The intensity enhancement observed for almost all bands in the ac field is attributed to the improvement of crystalline quality. |
Description: | Journal of Physics and Chemistry of Solids 60 (1999) 1983–1988 |
URI: | http://dyuthi.cusat.ac.in/purl/4548 |
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Raman spectra o ... in situ electric field.pdf | (348.1Kb) |
Abstract: | A red rain phenomenon occurred in Kerala, India starting from 25th July 2001, in which the rainwater appeared coloured in various localized places that are spread over a few hundred kilometers in Kerala. Maximum cases were reported during the first 10 days and isolated cases were found to occur for about 2 months. The striking red colouration of the rainwater was found to be due to the suspension of microscopic red particles having the appearance of biological cells. These particles have no similarity with usual desert dust. An estimated minimum quantity of 50,000 kg of red particles has fallen from the sky through red rain. An analysis of this strange phenomenon further shows that the conventional atmospheric transport processes like dust storms etc. cannot explain this phenomenon. The electron microscopic study of the red particles shows fine cell structure indicat- ing their biological cell like nature. EDAX analysis shows that the major elements present in these cell like particles are carbon and oxygen. Strangely, a test for DNA using Ethidium Bromide dye fluorescence technique indicates absence of DNA in these cells. In the context of a suspected link between a meteor airburst event and the red rain, the possibility for the extraterrestrial origin of these particles from cometary fragments is discussed. |
URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1976 |
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Red rain phenomenon of Kerala.pdf | (412.3Kb) |
Abstract: | This work projects photoluminescence (PL) as an alternative technique to estimate the order of resistivity of zinc oxide (ZnO) thin films. ZnO thin films, deposited using chemical spray pyrolysis (CSP) by varying the deposition parameters like solvent, spray rate, pH of precursor, and so forth, have been used for this study. Variation in the deposition conditions has tremendous impact on the luminescence properties as well as resistivity. Two emissions could be recorded for all samples—the near band edge emission (NBE) at 380 nm and the deep level emission (DLE) at ∼500 nm which are competing in nature. It is observed that the ratio of intensities of DLE to NBE (𝐼DLE/𝐼NBE) can be reduced by controlling oxygen incorporation in the sample. 𝐼-𝑉 measurements indicate that restricting oxygen incorporation reduces resistivity considerably. Variation of 𝐼DLE/𝐼NBE and resistivity for samples prepared under different deposition conditions is similar in nature. 𝐼DLE/𝐼NBE was always less than resistivity by an order for all samples.Thus from PL measurements alone, the order of resistivity of the samples can be estimated. |
Description: | International Journal of Photoenergy Volume 2013, Article ID 105796, 9 pages |
URI: | http://dyuthi.cusat.ac.in/purl/4723 |
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Reliable and Da ... luminescence Technique.pdf | (1.904Mb) |
Abstract: | A new photopolymerizable recording media is introduced based on poly (vinyl alcohol) and vinyl acetate sensitized with methylene blue. It is observed that this MBPVA/VAc system can be reused a number of times without significant decrease in diffraction efficiency. The PVA-VAc ratio was optimized at 2:1. Diffraction efcienc4y of 6.3% was obtained without any fixing at a dye concentration of 9.3 x 10- mol/l at an exposure of 750mJ/cm2. The material is attractive on account of its reusability. |
URI: | http://dyuthi.cusat.ac.in/purl/873 |
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Beena Mary John ... recording...,march2005.PDF | (7.043Mb) |
Abstract: | A new photopolymerizable recording media is introduced based on poly (vinyl alcohol) and vinyl acetate sensitized with methylene blue. It is observed that this MBPVA/VAc system can be reused a number of times without significant decrease in diffraction efficiency. The PVA-VAc ratio was optimized at 2:1. Diffraction efficiency of 6.3% was obtained without any fixing at a dye concentration of 9.3 10 4 mol/l at an exposure of 750 mJ/cm2. The material is attractive on account of its reusability. |
URI: | http://dyuthi.cusat.ac.in/purl/612 |
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Reusable medium MBPVA Vinyl acetate.pdf | (279.2Kb) |
Abstract: | Effect of chlorine doping on the opto-electronic properties of β-In2S3 thin film, deposited by spray pyrolysis technique is studied for the first time. Chlorine was incorporated in the spray solution, using HCl. Pristine sample prepared using In(NO3)3 and thiourea as the precursors showed very low photosensitivity. But upon adding optimum quantity of chlorine, the photosensitivity increased by 3 orders. X-ray analysis revealed that crystallinity was also increasing up to this optimum level of Cl concentration. It was also observed that samples with high photosensitivity were having higher band gap. The present study proved that doping with chlorine was beneficial as this could result in forming crystalline and photosensitive films of indium sulfide. |
Description: | Thin Solid Films 518 (2010) 1779–1783 |
URI: | http://dyuthi.cusat.ac.in/purl/4711 |
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Role of chlorin ... of β-In2S3 thin films.pdf | (681.1Kb) |
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