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effect of synthesis conditions and surrounding medium on luminescence properties of YVO_4:eu^(3+) nanopowders

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Journal of Rare earths 2015年第2期33卷 129-134页

作者： e.V.Golyeva D.V.Tolstikova i.e.Kolesnikov M.D.Mikhailov St.Petersburg State Polytechnical University St.Petersburg 195251 Russia Scientific and Technological institute of Optical Material Science VNTs S.I.Vavilov State Optical InstituteSt.Petersburg 192171 Russia St.Petersburg State University St.Petersburg 199034 Russia

Nanocrystalline yttrium vanadate doped with europium ions powders were synthesized via sol-gel method based on decomposition of metal-polymer complex. X-ray diffraction analysis showed that samples had pure tetragonal phase without any impurities. Scanning electron microscopy and static light scattering technique were used to study morphology and size of prepared nanoparticles. Average diameter of the nanoparticles was about 40 nm. The changes in structural and luminescence properties were observed as a function of the first and second calcination temperature. The optimal conditions for synthesis of nanoparticles were determined as Т1=500℃, t1=1 h; Т2=950 ℃, t2=1.5 h. The effect of different media surrounding the nanoparticles on their luminescence properties and lifetime was investigated and discussed in terms of effective refractive index. it was found that the observed lifetime of YVO4：eu^3＋ 5 at.% nanophosphor was decreased from 0.64 ms in air（nmed=1） to 0.45 ms in chalcogenide glass As39S61（nmed=2.39）.

关键词： nanopowders rare earths luminescence effective refractive index lifetime

Rietveld refinement and optical properties of SrWO_4:eu^(3+) powders prepared by the non-hydrolytic sol-gel method

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Journal of Rare earths 2015年第2期33卷 113-128页

作者： P.F.S.Pereira i.C.Nogueira e.Longo e.J.Nassar i.L.V.Rosa L.S.Cavalcante Chemistry institute University of the State of Sao Paulo Julio de Mesquita Filho-UNESP Francisco DegniAraraquara-SP 14800-900 Brazil LieC-Chemistry Department Federal University of Sao Carlos Via Washington Luis Km 235Sao Carlos-SP 13565-905 Brazil University of Franca-UNiFRAN Via Dr.Armando Sales de OliveiraNo.201 Franca-SP 14404-600 Brazil CCN-DQ-GeRATeC University of the State of Piauí Joao Cabral 2231 P.O.Box 391Terezina PI 64002-150 Brazil

We investigated the effect of annealing time on the structure and optical properties of Sr WO4：eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 *** and differential thermal analyses revealed that Sr WO4：eu^3＋ powders were obtained at about 800 ℃.X-ray diffraction patterns and Rietveld refinement data confirmed that all powders had a scheelite-type tetragonal ***-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O-W-O bonds associated with tetrahedral[WO4]*** properties were investigated by ultraviolet-visible（UV-vis）diffuse reflectance,and photoluminescence（PL）data which provided the evolution of quantum efficiency（η）and lifetime（τ）.UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4：eu^3＋ *** properties validated that the eu^3＋ electric-dipole（^5D0→^7F2）transition in PL emission spectra was dominant which proved that eu^3＋ ions were positioned in a site without an inversion center.[（^5D0→^7F2）/（^5D0→^7F1）]band ratios showed that eu^3＋ ions were located in a low symmetry *** PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4：eu3＋powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800℃ for 8 h.

关键词： SrWO4 Rietveld refinement optical band gap eu^(3+) +-rare earth luminescence

Structural evolution, optoelectrical and corrosion properties of electrodeposited WO_3 integration on Zn-TiO_2 electrolyte for defence super application

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Defence Technology（防务技术） 2018年第5期14卷 396-402页

作者： A.A.Daniyan L.e.Umoru O.S.i.Fayomi A.P.i.Popoola Department of Materials Science and engineering Obafemi Awolowo University Department of Che.i.a. Metallurgical and Materials Engineering Tshwane University of Technology Department of Mechanical engineering Covenant University

Multifunctional nano composite coatings of Zn-TiO_2-WO_3 were deposited electrolytically on mild steel(MS) from Zn bath, having Zn^(2+) ions and uniform dispersion of TiO_2 and WO_3 nano particulates. The electrical, optical and corrosion resistance characteristics of the electrocodeposited coatings were assessed by Keithley 2400 Series Source meter with Multimeters, Newport Solar Simulator and a PGSTAT30 Autolab potentiostat respectively. The morphological characteristics of the composite coatings were characterized by scanning electron microscope(SeM) equipped with energy dispersive spectrometer(eDS). The result revealed that the electrocodeposits showed good stability and Zn-TiO_2-WO_3 nanocomposite deposits displayed enhanced microstructural qualities, good electrical conductivity and exhibited enriched corrosion resistance.

关键词： Nano-composite electrocodeposition Corrosion Conductivity and resistance

Groundwater occurrence and flow patterns in the ishiagu mining area of southeastern Nigeria

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Frontiers of earth Science 2012年第1期6卷 18-28页

作者： i.C.eZeKWe e.ODUBO G.N.CHiMA i.S.ONWUCHeKWA Department of Geography and environmental Management Niger Delta UniversityWilberforce IslandPMB 071YeneganaNigeria Department of Geography and Planning Abia State UniversityPMB 2000UtumNigeria

The ishiagu area is a water scarce region and has played host to mining activities for more than four decades. Mining-related activities have become a threat to potable water supply in the area. This paper is an attempt to show the extent of this threat and in particular, investigate the regional groundwater occurrence and flow pattem based on GPS, water well and geological data. This basin- wide model can be used for further groundwater assess- ment, pollution control and contaminant management. Groundwater occurs between 2.4 and 9 m in the Lekwesi- Lokpaukwu area; 1.5-3.7 m in the Ndi-Ugbugbor-Ayaragu axis and 1.2-4.6 m in the ishiagu area. Recharge areas include the Leru-Amaubiri-Lekwesi sandstone hills and the ihetutu-Ugwuajirija mine field. While the ultimate sink of contamiants is the ivo River system, other discharge axis is the ishiagu-Ayaragu axis and the Ogwor Ndi- Ugbugbor zone. An unconfined and a confined （〉 10） circulation groundwater system was inferred, and flow model reveals that a large part of ishiag-Ayaragu and Ndi- Ugbugbor part of the study area suffer polluted recharge from the Pb/Zn mining area. Groundwater was also subjected to hierarchical cluster analysis and the existence of 3-4 hydrological regimes, which revealed： Unpolluted recharge areas, areas affected by polluted recharge, a deep water and shallow water circulation and mine effluents.

关键词： groundwater flow mining heavy metals,pollution cluster analysis ishiagu Nigeria

Systematic experimental study of the temperature dependence of viscosity and rheological behavior of water-based drilling fluids with nano-additives

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Petroleum 2023年第4期9卷 534-544页

作者： A.V.Minakov M.i.Pryazhnikov e.i.Mikhienkova Y.O.Voronenkova Siberian Federal University KrasnoyarskRussia Kutateladze institute of Thermophysics SB RASNovosibirskRussia

The paper presents the results of a systematic study of the influence of nano-additives of various concentrations,average sizes and composition on the temperature dependence of the viscosity and rheological behavior of water-based drilling *** compositions of drilling fluids,such as water suspensions of various clay solutions and gammaxan-based polymer solutions,were *** nanoparticles of silicon and aluminum oxides were used as nano-additives at concentrations ranging from 0.25 to 3 wt%.The average nanoparticle size varied from 10 to 151 *** temperature of drilling fluids varied from 25℃ to 80℃.it is shown that the addition of nanoparticles to drilling fluids leads to a significant change in their rheological properties depending on the *** was found that with increasing temperature,the yield stress and consistency index of drilling fluids with nanoparticles increase,while the behavior index,on the contrary,*** behavior depends on the size of the *** the particle size increases,their influence on the temperature dependence of the drilling fluids’viscosity *** general,it is shown that the addition of nanoparticles makes the viscosity of drilling fluid more stable with regard to the *** is an essential fact for practical application.

关键词： Drilling fluid Nano-additive Viscosity Rheology Temperature

electron-phonon coupling and spin fluctuations in the ising superconductor NbSe_(2)

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npj Computational Materials 2023年第1期9卷 1686-1694页

作者： S.Das H.Paudyal e.R.Margine D.F.Agterberg i.i.Mazin Department of Physics and Astronomy George Mason UniversityFairfaxVA 22030USA Quantum Science and engineering Center George Mason UniversityFairfaxVA 22030USA Department of Physics Applied Physicsand AstronomyBinghamton University-SUNYBinghamtonNY 13902USA Department of Physics University of WisconsinMilwaukeeWI 53201USA

ising superconductivity,observed in NbSe2 and similar materials,has generated tremendous ***,attention was called to the possible role that spin fluctuations(SF)play in this phenomenon,in addition to the dominant electron–phonon coupling(ePC);the possibility of a predominantly triplet state was discussed and led to a conjecture of viable singlet–triplet Leggett ***,these hypotheses have not been put to a quantitative *** this paper,we report first principle calculations of the ePC and also estimate coupling with SF,including full momentum *** find that:(1)ePC is strongly anisotropic,largely coming from the K-K0 scattering,and therefore excludes triplet symmetry even as an excited state;(2)superconductivity is substantially weakened by SF,but anisotropy remains as above;and,(3)we do find the possibility of a Leggett mode,not in a singlet–triplet but in an s_(++)–s_(±)channel.

关键词： coupling phonon superconductivity

Photoluminescence properties of eu3+-doped MgAl2O4 nanoparticles in various surrounding media

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Journal of Rare earths 2019年第8期37卷 806-811,I0001页

作者： i.e.Kolesnikov e.V.Golyeva e.V.Borisov e.Yu Kolesnikov e.Lahderanta A.V.Kurochkin M.D.Mikhailov St.Petersburg State University St.PetersburgRussia Lappeenranta University of Technology LUT LappeenrantaFinland Peter the Great St.Petersburg Polytechnic University St.PetersburgRussia Scientific and Technological institute of Optical Material Science VNTs S.I.Vavilov State Optical InstituteSt.PetersburgRussia Volga State University of Technology Yoshkar-OlaRussia

eu3+-doped MgAl2O4 nanoparticles were prepared by modified Pechini method.X-ray diffraction analysis shows pure tetragonal spinel phase without any *** average size of synthesized nanoparticles was determined to be about 50-60 nm using scanning electron microscopy and static light scattering *** and excitation spectra as well as lifetimes of MgAl2O4:eu3+ nanophosphors were explored in surrounding media with different refractive *** medium does not affect luminescence bands position,whereas 5D0 lifetime monotonically decreases along with increase of medium refractive *** of surrounding media on radiative and nonradiative decay rates,which were calculated using 4f-4f intensity theory,was studied and *** factor of prepared nanoparticles is defined using both radiative and observed lifetimes.

关键词： eu3+ Nanoparticles Filling factor Luminescence Lifetime Rare earths

From blood to breath: New horizons for esophageal cancer biomarkers

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World Journal of Gastroenterology 2016年第46期22卷 10077-10083页

作者： Roger Yazbeck Simone e Jaenisch David i Watson Department of Surgery Flinders Centre for Innovation in Cancer Flinders University

esophageal cancer is a lethal cancer encompassing adenocarcinoma and squamous cell carcinoma subtypes. The global incidence of esophageal cancer is increasing world-wide, associated with the increased prevalence of associated risk factors. The asymptomatic nature of disease often leads to late diagnosis and five-year survival rates of less than 15%. Current diagnostic tools are restricted to invasive and costly endoscopy and biopsy for histopathology. Minimally and non-invasive biomarkers of esophageal cancer are needed to facilitate earlier detection and better clinical management of patients. This paper summarises recent insights into the development and clinical validation of esophageal cancer biomarkers, focussing on circulating markers in the blood, and the emerging area of breath and odorant biomarkers.

关键词： Breath analysis Cancer Micro RNA Noninvasive esophageal cancer Biomarker

High-Strength Nanostructured Cold-Resistant Steels for Continental Shelf Development

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Journal of iron and Steel Research international 2011年第S1期18卷 66-71页

作者： Oryshchenko A S Khlusova e i Orlov V V FSUe CRiSM PROMeTeY St.PetersburgRussia

The article describes principles of developing steels for maritime structures and main *** scientific approach lies in forming an ultra fine-grained and submicrocrystal structure through thermomechanical treatment of low-carbon low-alloyed steels,providing higher strength and resistance to brittle *** article presents results of assessing the operability characteristics and introducing new steels.

关键词： low-alloyed steels microstructure mechanical properties thermomechanical treatment