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31.
Vaithianathan V Moon JH Chang CH Asokan K Kim SS 《Journal of nanoscience and nanotechnology》2006,6(11):3422-3425
The electronic structure of laser-deposited P-doped ZnO films was investigated by X-ray absorption near-edge structure spectroscopy (XANES) at the O K-, Zn K-, and Zn L3-edges. While the O K-edge XANES spectrum of the n-type P-doped ZnO demonstrates that the density of unoccupied states, primarily O 2p-P 3sp hybridized states, is significantly high, the O K-edge XANES spectrum of the p-type P-doped ZnO shows a sharp decrease in intensity of the corresponding feature indicating that P replaces O sites in the ZnO lattice, and thereby generating P(O). This produces holes to maintain charge neutrality that are responsible for the p-type behavior of P-doped ZnO. Both the Zn K-, and Zn L3-edge XANES spectra of the P-doped ZnO reveal that Zn plays no significant role in the p-type behavior of ZnO:P. 相似文献
32.
H S Virk G S Randhawa R Thangaraj D K Avasthi K Asokan 《Bulletin of Materials Science》1999,22(4):791-795
The samples of SR-86 polymer were irradiated with12C5+ ions of energy 5·0 MeV/u using fluences of 1011−1014 ions/cm2 at NSC Pelletron in a high vacuum scattering chamber. The optical studies show an increase in absorption of UV or IR in the
shorter wavelength region (250–500 nm). The study also reveals that the increase in radiation dose extends the optical absorption
region to longer wavelengths. It is observed that the bulk etch rate of this polymer is enhanced after heavy ion irradiation. 相似文献
33.
High field electrical switching studies on x Ag2O − (50−x) P2O5 −50V2O5 glasses have been carried out as a function of sample thickness, composition and temperature. The I–V characteristic show
that switching in these glasses is memory type. The switch voltages are found to decrease with increase of temperature, on
the other hand, the voltages increase with the thickness of the sample. The experimental findings clearly reveal that switching
in these glasses is a thermally assisted bulk effect. The results obtained are explained on the basis of formation of crystalline
conducting channels. Another notable observation is that the glass with 15 mol% Ag2O concentration only exhibits the switching property at room temperature. This aspect is examined in view of various structural
groups present in these glasses with the help of spectroscopic studies; IR and MAS–NMR measurements have been carried out.
IR studies of these glasses show characteristic absorption peaks corresponding phosphate and vanadium vibrations in the network.
31P MAS–NMR chemical shift show presence of [POO3/2]0 and [POO2/2O]− groups. 相似文献
34.
Jarosite characteristics and its utilisation potentials 总被引:2,自引:0,他引:2
During metallic zinc extraction from zinc sulphide or sulphide ore, huge quantity of jarosite is being released universally as solid residues. The jarosite mainly contains iron, sulphur, zinc, calcium, lead, cadmium and aluminium. Jarosite released from such industrial process is complex and its quality and quantity make the task more complex for safe disposal. Apart from water contamination, jarosite already accumulated and its increasing annual production is a major source of pollution for surrounding environment including soil, vegetation and aquatic life and hence its disposal leads to major concern because of the stringent environmental protection regulations. An attempt was made to evaluate the characteristics of Indian jarosite with an objectives to understand its potentials for recycling and utilising as raw materials for developing value added products. Sand and Coal Combustion Residues (CCRs) was used as an admixture to attain good workability and detoxify the toxic substance in the jarosite. Result revealed that jarosite is silty clay loam in texture having 63.48% silt sized and 32.35% clay sized particles. The particle size of jarosite (D90=16.21+/-0.20 microm) is finer than the CCRs (D90=19.72+/-0.18 microm). The jarosite is nonuniform in structure and shape as compared to the CCRs having spherical, hollow shaped and some of them are cenosphere in nature. The major mineral phase of jarosite is Potassium Iron Sulphate Hydroxide {KFe3(SO4)2(OH)6}and Iron Sulphate Hydrate {2 Fe2O3SO3 x 5 H2O}. In CCRs the dominant phases are quartz {SiO2}, mullite {3 Al2O3 x 2 SiO2} and hematite {Fe2O3}. The high electrical conductivity of jarosite (13.26+/-0.437 dS/m) indicates that the presence of cations and anions are predominant over CCRs (0.498+/-0.007 dS/m). The major portion of jarosite consists of iron (23.66+/-0.18%), sulphur (12.23+/-0.2%) and zinc (8.243+/-0.075%). But CCRs main constituents are silicon (27.41+/-0.74%), aluminium (15.167+/-0.376%) and iron (4.447+/-0.69%). The other constituents such as calcium, aluminium, silicon, lead, and manganese are also present in the range of 0.5 to 5%. Heavy metals such as copper, chromium, and cadmium are found higher in jarosite as compared to the CCRs. The statistically designed experimental trials revealed that the density, water absorption capacity and compressive strength of fired jarosite bricks are 1.51 gm/cm3, 17.46% and 43.4 kg/cm2 respectively with jarosite sand mixture in the ratio of 3:1 indicating the potentials in developing building materials. 相似文献
35.
Mayakrishnan Prabakaran Seung-Hyun Kim Asokan Sasireka Kathirvel Kalaiselvi 《Journal of Adhesion Science and Technology》2018,32(18):2054-2069
The corrosion of aluminum specimens in Polygonatum odaratum (P. odaratum) extract was studied using weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy (SEM), and electron dispersive X-ray spectroscopy (EDX) techniques. The inhibition efficiency of the aluminum specimens in the presence of inhibitor from P. odaratum plant extract at 303–333 ± 1 K was evaluated with the weight loss technique. The results indicate the inhibition efficiency of P. odaratum plant extract increased with increased concentration of the inhibitor and decreased temperature in an acidic medium. The corrosion inhibition properties of the P. odaratum plant extract for aluminum specimen corrosion in 1 M HCl were analyzed using polarization studies and electrochemical impedance studies, which clearly showed a mixed-type inhibitor. UV-visible spectroscopy, Fourier transform infrared (FT-IR), SEM, and EDX revealed the surface morphology in the presence and absence of inhibitor on the metal surface. The results indicated the feasibility of using the P. odaratum plant extract as a corrosion inhibitor in acid environments. 相似文献
36.
Shoja'eddin Chenouri Asokan Mulayath Variyath 《Quality and Reliability Engineering International》2011,27(7):857-865
Use of Hotelling's T2 charts with high breakdown robust estimates to monitor multivariate individual observations are the recent trend in the control chart methodology. Vargas (J. Qual. Tech. 2003; 35: 367‐376) introduced Hotelling's T2 charts based on the minimum volume ellipsoid (MVE) and the minimum covariance determinant (MCD) estimates to identify outliers in Phase I data. Studies carried out by Jensen et al. (Qual. Rel. Eng. Int. 2007; 23: 615‐629) indicated that the performance of these charts heavily depends on the sample size, amount of outliers and the dimensionality of the Phase I data. Chenouri et al. (J. Qual. Tech. 2009; 41: 259‐271) recently proposed robust Hotelling's T2 control charts for monitoring Phase II data based on the reweighted MCD (RMCD) estimates of the mean vector and covariance matrix from Phase I. They showed that Phase II RMCD charts have better performance compared with Phase II standard Hotelling's T2 charts based on outlier free Phase I data, where the outlier free Phase I data were obtained by applying MCD and MVE T2 charts to historical data. Reweighted MVE (RMVE) and S‐estimators are two competitors of the RMCD estimators and it is a natural question whether the performance of Phase II Hotelling's T2 charts with RMCD and RMVE estimates exhibits similar pattern observed by Jensen et al. (Qual. Rel. Eng. Int. 2007; 23: 615‐629) in the case of MCD and MVE‐based Phase I Hotelling's T2 charts. In this paper, we conduct a comparative study to assess the performance of Hotelling's T2 charts with RMCD, RMVE and S‐estimators using large number of Monte Carlo simulations by considering different data scenarios. Our results are generally in favor of the RMCD‐based charts irrespective of sample size, outliers and dimensionality of Phase I data. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
37.
Polycrystalline Ba0.7Sr0.3Ti(1?x)FexO3 (x = 0.1) (BSTF) ceramics, synthesized via solid-state reaction route were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and complex impedance spectroscopy (CIS). The Rietveld refinement of the XRD data confirmed the presence of tetragonal and cubic phases in the prepared sample. The SEM image revealed that the sample has well distributed grains along with some degree of agglomerations. The electrical behaviour of the BSTF ceramic has been studied by complex impedance spectroscopy (CIS) as a function of frequency (1 Hz to 1 MHz) at different temperatures (RT to 700 K). Two semicircular arcs observed in the Cole-Cole plot confirm the contribution from the grain and grain boundary in overall impedance. Both the electrical as well as ac conduction phenomena take place via correlated barrier hopping (CBH) authenticated by detailed complex modulus analysis and ac fitted conductivity respectively. The values of activation energies calculated from electrical impedance, modulus, and conductivity data clearly reveal that the relaxation and conduction processes in BSTF ceramic are induced by doubly ionized oxygen vacancies. 相似文献
38.
Feroz A. Mir G. M. Bhat K. Asokan K. M. Batoo Javid A. Banday 《Journal of Materials Science: Materials in Electronics》2014,25(1):431-437
The structural, optical and dielectric properties of micro-crystals of Oxypeucedanin (C16H14O5), isolated from ethyl acetate extract of the roots of the plant Prangos pabularia is presented. These isolated crystals were characterized by using X-ray diffraction (XRD), scanning electron microscopy, optical microscope, ultraviolet (UV)–visible spectroscopy and dielectric spectroscopy techniques. XRD of these crystals confirm that they have monoclinic structure (space group = P21/c). The frequency-dependent real part of the complex ac conductivity was found to follow the universal dielectric response: σac (ω)–ω s . The trend in the variation of the frequency exponent (s) with frequency (ω) supports the fact that correlated barrier hopping is the dominant charge transport mechanism for this compound. From the UV spectroscopy, the optical band gap (E g ) has been found to be around 3.76 eV and is following indirect allowed transition. The observed optical and electric properties predict these crystals as an open choice for modern flexible electronics. 相似文献
39.
M. BalajiK. Asokan D. KanjilalC. Sanjeeviraja T.R. RajasekaranD. Pathinettam Padiyan 《Thin solid films》2011,520(1):204-211
The bulk copper ferrite nanomaterials are synthesized by co-precipitation technique. The vibrating sample magnetometer measurement for bulk CuFe2O4 reveals its unsaturated superparamagnetic behavior. The crystallites of the synthesized nanomaterial are in cubic form having an average size of ~ 100 Å and are used as target to prepare thin films of various thicknesses (600, 900 and 1100 nm) by radio frequency magnetron sputtering technique. X-ray peaks arise only when films are annealed at 1200 °C and also they are found to be in tetragonal structure. The magnetic characteristics of 900 nm unirradiated CuFe2O4 thin film exhibit superparamagnetic behavior and have an unsaturated magnetic moment at high field. Magnetic force microscopy images of unirradiated CuFe2O4 thin films confirm the soft nature of the magnetic materials. The 150 MeV Ni11+ swift heavy ion irradiation on these thin films at the fluence of 1 × 1014 ions/cm2 modifies the polycrystalline nature due to electron-phonon coupling. Atomic force microscopy image shows that the swift heavy ion irradiation induces agglomeration of particles in 600 and 900 nm thin films and increases rms surface roughness from 33.43 to 39.65 and 69.7 to 102.46 nm respectively. However, in 1100 nm film, holes are created and channel-like structures are observed along with a decrease in the rms surface roughness from 75.12 to 24.46 nm. Magnetic force microscopy images of 900 nm irradiated thin film explain the formation of domains on irradiation and are also supported by the ferromagnetic hysteresis observed using vibrating sample magnetometer. 相似文献
40.
Jai Prakash A. Tripathi Sanjeev Gautam K.H. Chae Jonghan Song V. Rigato Jalaj Tripathi K. Asokan 《Materials Chemistry and Physics》2014
The present experimental work provides the phenomenological approach to understand the dewetting in thin noble metal films with subsequent formation of nanoparticles (NPs) and embedding of NPs induced by ion irradiation. Au/polyethyleneterepthlate (PET) bilayers were irradiated with 150 keV Ar ions at varying fluences and were studied using scanning electron microscopy (SEM) and cross-sectional transmission electron microscopy (X-TEM). Thin Au film begins to dewet from the substrate after irradiation and subsequent irradiation results in spherical nanoparticles on the surface that at a fluence of 5 × 1016 ions/cm2 become embedded into the substrate. In addition to dewetting in thin films, synthesis and embedding of metal NPs by ion irradiation, the present article explores fundamental thermodynamic principles that govern these events systematically under the effect of irradiation. The results are explained on the basis of ion induced sputtering, thermal spike inducing local melting and of thermodynamic driving forces by minimization of the system free energy where contributions of surface and interfacial energies are considered with subsequent ion induced viscous flow in substrate. 相似文献