IOSR-JAP   Volume-12 ~ Issue-5 ~ Sep. – oct. 2020

ABSTRACT: Phosphors are materials that exhibit the phenomenon of luminescence. They emit light when excited by radiation such as ultraviolet (UV) light or electron beams. A nanophosphor is a phosphor having particles with particle sizes ranging from 1-100 nm and it exhibits striking properties. In this paper nanosilica which can serve as a nanophosphor has been synthesized from a waste material known as rice husk by simple chemical and thermal treatments. The produced sample shows an amorphous structure and has nanosized spherical morphology. The average size of the particles of the sample is 32.62 nm. The silica nanophosphor has a wide bandgap of 5.6 eV and can be excited by both far UV (275 nm) and near UV (365 nm) light sources. The photoluminescence spectrum shows blue.....

Keywords: Nanophosphor; silica; rice husk; amorphous; blue-light emission;morphology.

[1]. H. Chang, S.Q. Sun, Silicon nanoparticles: Preparation, properties, and applications, Chinese Phys. B. 23 (2014) 1–14. https://doi.org/10.1088/1674-1056/23/8/088102.
[2]. C. Mbakaan, I. Ahemen, A.N. Amah, A.D. Onojah, L. Koao, White-light-emitting Dy3+-doped amorphous SiO<inf>2</inf> nanophosphors derived from rice husk, Appl. Phys. A Mater. Sci. Process. 124 (2018). https://doi.org/10.1007/s00339-018-2156-6.
[3]. R.S. A. Birkel, K.A. Danault, N.C. George, Advanced Inorganic Materials for Solid-State Lighting, in: Funct. Inorg. Mater. From Precursors to Appl., 2012: pp. 22–25.
[4]. C. Mbakaan, I. Ahemen, A.D. Onojah, A.N. Amah, K.G. Tshabalala, F.B. Dejene, Luminescent properties of Eu 3 + -doped silica

ABSTRACT:In this work we developed a low cost potentiostat to monitor redox processes using open source software and hardware for undergraduate laboratories in the developing countries. The developed system consists of three main modules namely user interface, triangular voltage generator, and current to voltage converter. Arduino Uno, 12-bit digital to analog converter and nine operational amplifiers were used to construct the proposed hardware. It operates in voltage range -2.5 V to +2.5 V and measure current in the range of ± 25 μA -0.025 A with 10 nA resolution and 1 mV dc-potential resolution for the cyclic voltammetry measurements. The performance of this system is compared with a commercially available potentiostat using K3Fe(CN)6 solutions. The three-electrode system reported.....

Key Word: Cyclic voltammetry; Digital to analog conversion; Electrochemical measurements; Potentiostat; Three-electrode system

[1]. A. A. Rowe et al., "Cheapstat: An open-source, "do-it-yourself‟ potentiostat for analytical and educational applications," PLoS One,
vol. 6, no. 9, 2011.
[2]. Johann F Osma, "Miniaturization of Cyclic Voltammetry Electronic Systems for Remote Biosensing," Int. J. Biosens. Bioelectron.,
vol. 3, no. 3, pp. 297–299, 2018.
[3]. A. V. Gopinath and D. Russell, "An Inexpensive Field-Portable Programmable Potentiostat," Chem. Educ., vol. 6, no. 05, pp. 1–6,
2005.
[4]. M. I. Cohen and P. A. Heimann, "A Microprocessor Controlled Potentiostat for Electrochemical Measurements*."
[5]. M. D. M. Dryden and A. R. Wheeler, "DStat: A versatile, open-source potentiostat for electroanalysis and integration," PLoS One,
vol. 10, no. 10, pp. 1–17, 2015.

ABSTRACT: In medical science zinc based materials are biodegradable materials and it has possible alternative of corrosion less resistant magnesium based materials. Zinc powders with two different particle sizes (7.5μm and 150μm) were processed by the methods of powder metallurgy. The micro structure of prepared materials was evaluated in terms of light optical microscopy, and the mechanical properties were analyzed with Vickers micro hardness testing and three-point bend testing. Fractographic (study of the fracture surfaces of materials) analysis of broken samples was performed with scanning electron microscopy. Particle size was shown to have a proper effect on compacts mechanical properties.....

[1]. He, C.; Bin, S.; Wu, P.; Gao, C.; Feng, P.; Yang, Y.; Liu, L.; Zhou, Y.; Zhao, M.; Yang, S.; et al. Microstructure EvolutionandBiodegradationBehaviorofLaserRapidSolidifiedMg–Al–ZnAlloy.Metals2017,7,105. [CrossRef]
[2]. Gu, X.; Zheng, Y.; Cheng, Y.; Zhong, S.; Xi, T. In vitro corrosion and biocompatibility of binary magnesium alloys. Biomaterials 2009, 30, 484–498. [CrossRef] [PubMed]
[3]. Ilich, J.Z.; Kerstetter, J.E. Nutrition in Bone Health Revisited: A Story beyond Calcium. J. Am. Coll. Nutr. 2000, 19, 715–737. [CrossRef] [PubMed]
[4]. Xu, L.; Yu, G.; Zhang, E.; Pan, F.; Yang, K. In vivo corrosion behavior of Mg-Mn-Zn alloy for bone implant application. J. Biomed. Mater. Res. Part A 2007, 83, 703–711. [CrossRef] [PubMed]
[5]. Hänzi,A.C.;Gerber,I.;Schinhammer,M.;Löffler,J.F.;Uggowitzer,P.J.Ontheinvitroandinvivodegradation performance and biological response of new biodegradable Mg–Y–Zn alloys. Acta Biomater. 2010, 6, 1824–1833. [CrossRef] [PubMed].

ABSTRACT: Conditions under which a density gradient of wave energy can lead to particle trapping in a plasma, have been discussed. It has been shown that such trapping can give rise to a new series of side band instabilities with a frequency separation proportional to the wave field amplitude in contrast to the usual side band instabilities due to phase trapping (where the frequency gap is proportional to.....

Keywords: plasma waves and instabilities, nonlinear wave-particleinteraction, plasma turbulence

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ABSTRACT: Mode conversion (MC) process proves to be of prime importance in fusion as well as in magnetospheric plasma. However, the presence of multiple ion species, even with small concentrations, can lead to the appearance of new and modified resonance, cutoff, and crossover frequencies. Nonlinear effects such as pump self induced filamentation and parametric decays further complicate the MC physics and associated heating processes. It is generally seen that intense localized electric fields of the soliton form are generated due to the density changes (density cavities) caused by the dominant ponderomotive forces acting on the charged species. It turns out that the nonlinear fate of the mode converted electrostatic wave beyond the MC layer is still an open question. With this motivation, a nonlinear....

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Wave-particle studies in the ion cyclotron and lower hybrid ranges of frequencies in alcator c-mod. Fusion Science and Technology,
51(3):401{436, 2007.
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ABSTRACT: Background: This work is broadly motivated by the development of ferroelectric liquid crystal devices and the need to develop a basic understanding of these strategic materials' wetting properties. Materials and Methods: This article studied the surface stability and wetting properties of the smectic C* ferroelectric liquid crystal mixture using highly polarized reflected optical microscopy. We used a homemade spin-coated machine to prepare the thin-film samples of smectic C* ferroelectric liquid crystal mixture on soft silicon dioxide substrate with a thickness of 300 nm and 600 nm. Images of the film texture caught on heating and cooling processes, with a heating rate of 0.5 oC/min....

Keywords: Liquid crystal, thin-film, wetting properties, surface undulation, anchoring force, contact angle, tension surface length.

[1] P. G. De Gennes, J. Prost, The physics of liquid crystals, 2nd Ed., Oxford Science Publications; Oxford University Press, (1993), New York, N. Y., ISBN: 0-19-852024-7; xvi + 597 pages
[2] C. Khoo, Liquid crystals. 2nd Ed. Hoboken, New Jersey, USA: Wiley (2007).
[3] C. Khoo, Nonlinear optics of liquid crystalline materials, Physics Reports; (2009); 471, pp: 221- 267.
[4] K. Y. Law, H. Zhao, Surface wetting: characterization, contact angle, and fundamentals, Springer International Publishing Switzerland, (2016).
[5] J. W. Goodby, P. J. Collings, T. Kato, C. Tschierske, H. F. Gleeson, P. Raynes, Handbook of liquid crystals, edited by, Weinheim, Wiley-VCH, (2014)..

ABSTRACT: MRINDO/S-CI Calculation Completed by singly excited configuration intraction was performed on the octaazacubane, octaazapentalene and octaazacuneane. The importance of outer (Rydberg) atomic orbitals is stressed and it is found that a few singlet-singlet transitions of the higher azines lead to an excited state with considerable Rydberg character..

Keywords: MRINDO/S,octaazacubane, octaazapentalene and octaazacuneane..

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ABSTRACT:In a MOSFET device in inversion, the oxide voltage must be corrected by the experimental band bending at the oxide/semiconductor interface instead of the theoretical band bending. Following this premise,
the conduction band barrier height in n-channel 4H-SiC MOSFET device in inversion is found to reduce from 2.92 eV with the oxide voltage corrected by the theoretical band bending to 2.816 eV with the oxide voltage
corrected by the experimental band bending at 298K, close to the confirmed model value of 2.79 eV at 298 K. This example can be extended to barrier heights at other temperatures also in the device where the oxide
voltage was originally corrected by the theoretical band bending. The barrier heights with the oxide voltage corrected by the experimental band bending is expected to match with the model values at all temperatures and
thus support the model for the temperature dependence of the Fowler-Nordheim tunnelling current in a MOS device proposed by the author in an earlier study.

Keywords: Band bending, MOSFET, Silicon Carbide, Temperature, Tunnelling

[1]. O. Avino-Salvado, B. Asllani, C. Buttay, C. Raynaud, H. Morel, "Extraction of the 4H-SiC/SiO2 barrier height over temperature", IEEE Trans. On ED, 2020;67(1):63-68.
[2]. R.K.Chanana, "A simple model for temperature dependence of the Fowler-Nordheim carrier tunnelling current through the oxide in a metal-oxide-semiconductor device in accumulation or inversion", IOSR-J. Appl. Phys., 2020;12(4):29-34.
[3]. Z.A. Weinberg, "On tunneling in metal-oxide-silicon structures", J. Appl. Phys., 1982;53(7):5052-5056.
[4]. R.K. Chanana, K. McDonald, M. Di Ventra, S.T. Pantelides, L.C. Feldman, G.Y. Chung, C.C. Tin, J.R. Williams, R.A. Weller, "Fowler-Nordheim hole tunneling in p-SiC/SiO2 structures", Appl. Phys. Letts., 2000;77(16):2560-2562.
[5]. R.K. Chanana, "Determination of hole effective mass in SiO2 and SiC conduction band offset using Fowler-Nordheim tunnelling characteristics across metal-oxide-semiconductor structures after applying oxide field corrections", J. Appl. Phys., 2011;109:104508..

ABSTRACT: Tin oxide (SnO) thin films are one of the most extremely studied due to its usefulness in UV-detector. SnO is known for wide bandgap of 3.6eV which makes it a good candidate for window layers in heterjunction solar cells. Transition metal chalcogenides (TMCs): Zinc (II) Sulphide (ZnS), Chromium (II) Sulphide (CrS), and dye-extracts exhibits unique properties such as high conversion efficiency, good absorption coefficient and good bandgap energy. These properties make their thin films versatile as coating materials. Spray pyrolysis Master Airbrush Brand-model G25, G255-SET and G266-SET have been used to deposit SnO, SnO:Zn-ion, SnO:Cr-ion, and SnO:dye of tectona grandis at 0.1M and 1% concentration respectively. The deposition was done at different substrate temperature of 50oC, 100oC, 150oC and 200oC. The dye used is extract from the leaves of tectona grandis. The effect of substrate temperature on the optical properties of the SnO (core) and SnO/TMCs (biphasic) films were examined and analysed vis-a-vis the bandgap. The result showed that the optical transmittance decreased with....

Keywords:Bandgap, Dopants (Zn2+ & Cr2-), Dye of tectona grandis, and Substrate temperature.

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ABSTRACT: Carbon-based materials such as graphene, CNTs and activated carbon with macro-, micro-, meso- and nanoporous structures are the essential resources for electrochemical energy storage applications. The first commercialized activated carbon material was used energy storage devices, such as power backup systems in customer electronics, windmills, UPSs, electric and hybrid electric vehicles, airplanes, trains, buses, industrial equipment and telecommunication systems. The innovative porous electrode (cathode/anode types) materials were quickly developed. Numerous resource materials were studied for morphological structures, which are essential for improving supercapacitor performance. Important properties of electro-active materials and increasing surface area with mesoporous/hollow structures control the pore volume/size, electrical conductivity, and stability and surface functionalities.....

Keywords: Effects, Factors, Nanotechnology

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