检索结果-南通市图书馆

Characterization and photoluminescence properties of ultrafine copper molybdate(α-CuMoO_4) powders prepared via a combustion-like process

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2016年第11期23卷 1340-1345页

作者： Mohamed Benchikhi Rachida El Ouatib Sophie Guillemet-Fritsch Lahcen Er-Rakho Bernard Durand laboratoire de Physico-Chimie des Matériaux inorganiques Faculté des Sciences Ain Chock Université Hassan Ⅱ Casablanca Institut Carnot CIRIMAT CNRS Université de Toulouse

We report a simple method for preparing copper（II） molybdate（CuMoO_4） powders via a combustion-like process. A gel was first prepared by the polymerizable complex method, where citric acid was used as a complexing and polymerizing agent and nitric acid was used as an oxidizing agent. The thermal decomposition behavior of the（CuMo）-precursor gel was studied by thermogravimetry–differential thermal analysis（TG–DTA）, Fourier transform infrared spectroscopy（FTIR）, and X-ray diffraction（XRD）. We observed that the crystallization of CuMoO_4 powder was completed at 450°C. The obtained homogeneous powder was composed of grains with sizes in the range from 150 to 500 nm and exhibited a specific surface area of approximately 5 m^2/g. The average grain size increased with increasing annealing temperature. The as-prepared CuMoO_4 crystals showed a strong green photoluminescence emission at room temperature under excitation at 290 nm, which we mainly interpreted on the basis of the Jahn-Teller effect on [MoO_4^（2-）] complex anions. We also observed that the photoluminescence intensity increased with increasing crystallite size.

关键词： copper molybdate chemical synthesis photoluminescence Jahn-Teller effect

Effect of the synthesis route on the structural and dielectric properties of SrBi1.8Y0.2Nb2O9 ceramics

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2018年第11期25卷 1304-1312页

作者： Mohamed Afqir Amina Tachafine Didier Fasquelle Mohamed Elaatmani Jean-Claude Carru Abdelouahad Zegzouti Mustapha El Hammioui laboratoire des Sciences des Matériaux inorganiques et leurs Applications Facultédes Sciences SemlaliaUniversitéCadi AyyadMarrakech 40000Maroc Unite de Dynamique et Structure des materiaux Moleculaires Universite du Littoral-Cote d’OpaleCalais 62100France laboratoire de recherche sur la réactivitédes matériaux et l’optimisation des procédés Facultédes Sciences SemlaliaUniversitéCadi Ayyad 40000MarrakechMaroc

This work is devoted to the synthesis and characterization of yttrium-doped SrBi_2Nb_2O_9 ceramics prepared by three methods: solid state reaction, co-precipitation, and hydrothermal. Multiple characterizations, specifically scanning electron microscopy(SEM), X-ray powder diffraction(XRD), and Fourier transform infrared spectroscopy(FTIR), were used to validate the structural feature. The crystallite size was estimated by Scherrer's formula and the Williamson–Hall plot. The effect of the process on the band intensities of the FTIR spectra was investigated. The crystallite size and microstructure of ceramics prepared from different synthesis processes were strongly influenced by the sinterability. SEM images revealed nanograin ceramics for materials prepared by co-precipitation and hydrothermal methods and micrograin ceramics prepared by the solid state method. The synthesized compounds underwent phase transitions at 480–465°C. The dielectric and electrical properties of these Y-doped SrBi_2Nb_2O_9 ceramics appear to be dependent on the grain size.

关键词： Aurivillius,synthesis routes crystallite size microstructure dielectric

Characterization and Photoluminescence Properties of Alumina Nanowires Elaborated by Arc-Plasma

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2006年第1期22卷 127-129页

作者： C.Arnoult X.Devaux H.Rinnert M.Vergnat laboratoire de Physique des materiaux UMR CNRS 7556Ecole des MinesCS14234F54042 Nancy cedexPrance

Ultrafine powders containing alumina nanowires are synthesized by DC arc plasma from pure aluminium metal. Nanowires grow only when reactive gases are composed of nitrogen and less than ten percent of oxygen. Nanowires have the diameters ranging from 20 to 80 nm and lengths ranging from hundreds nanometers to tens of micrometers. A first assumption of the mechanism process is proposed, in which nanowires grow starting directly from the aluminium. Photoluminescence measurements show that the powders have three emission peaks around 435, 530 and 750 nm resulting from different kinds of defects such as oxygen vacancies, aluminium interstitial ions and surface defects.

关键词： Nanowires Alumina Arc plasma Photoluminescence

X-ray and DFT Crystal Structure Determination and Conformational Analysis of a Pyrethroid Compound

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Structural Chemistry 2013年第10期32卷 1544-1552页

作者： YAHIAOUI Salem CHOUAIH Abdelkader HAMZAOUI Fodil laboratoire de Structure Elaboration et Applications des Materiaux Moleculaires(SEA2M)University of Mostaganem27000 MostaganemAlgeria

The structure of （E）-N-[（E）-3-[（lR,2R）-2-（3,4-dibromo-phenyl）-l-fluro-cyclopropyl]- allylidene]-2-0-tolyl-acetamide （C21HIsONFBrz, Mr = 479.18） has been determined by X-ray single- crystal diffraction and theoretical calculations to establish the configuration, stereochemistry and a stable conformation of the molecule. The compound crystallizes in the monoclinic space group P21/c, a = 28.3452（10）, b = 4.9311（10）, c = 14.257（2） A, fl = 102.7654（10）, V = 1943.5（5） A3 and Z = 4. The structure has been refined to the final R = 0.05 for the observed structure factors with 1 〉 30（/）. Theoretical calculations in the ground state have been carried out for the compound studied using the Hartree-Fock （HF） and density functional theory （DFT）（B3LYP） with 6-31G（d,p） basis sets. The results show that the studied compound prefers the keto form. The compound involves intra- and intermolecular hydrogen bonding of C-H.-.O and C-H-..F types, which further stabilize the structure and display a trans configuration for the C=N and C=C double bonds. The calculated results show that the predicted geometry can well reproduce the structural parameters.

关键词： X-ray diffraction crystal structure insecticide

Naked Eye and Selective Detection of Copper(II) in Mixed Aqueous Media Using a Cellulose-based Support

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2019年第4期35卷 598-603页

作者： FETTOUCHE Souad BOUKHRISS Aicha TAHIRI Mohamed CHERKAOUI Omar BAZI Fathallaah GMOUH Said laboratoire Recherche sur les materiaux Textile(REN4TEX) Ecole Supeneure des Induseries de Textile et de L'habillement(ESITH)CasablancaBP 7731Maroc laboratoire Hydrogeochimie et Bassin versant Faculte des Sciences Ain ChockUniversite Hassan IICasablancaB. P 5366Maroc Laboratore Chimie Analytique et Physico-chimie des materiaux Faculte des Sciences Ben M'sik Universitie Hassan II CasablancaBP 150Macro laboratoire d'lngeniene et materiaux(LIMAT) Faculte des Sciences Ben MsikUniv er site Hassan IICasablanceBP 150Maroc

A new colorimetric sensor based-azo dye for Cu^2+ detection was synthesized and characterized by FTIR and NMR spectroscopies. The results showed that the azo dye had a high selective and sensitive recognition toward Cu^2+. The solution containing the sensor changed color from pink to pale yellow with a hypsochromic shift in the presence of Cu^2+. The sensor selectivity and sensitivity toward Cu^2+ ions were investigated by colorimetry and UV-Vis spectroscopy. For practical applications, a cellulosic textile test strip for high-selectivity detection of Cu^2+ ions in aqueous solution was developed using the synthesized azo dye as chromogenic chemosensor molecule, while using a solid cellulose textile as a substrate. As a result, a spectacular color change of the test strip was observed do pending on the amount of copper ions in contact with the strip, which allows an estimation of Cu^2+ concentration by naked eye.

关键词： Copper(II) ions detection Azo dye Chromogenic chemosensor Cellulose-based probe

Optical Constant and Electrical Resistivity of Annealed Sn3Sb2S6 Thin Films

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2016年第3期29卷 287-294页

作者： Y.Fadhli A.Rabhi M.Kanzari laboratoire de Photovoltaique et materiaux Semi-conducteurs-ENIT BP 37 Le belvedere 1002 Tunis Tunisia laboratoire de Photovoltaiques et materiaux Semi-conducteurs-ENIT-IPEITunis Montfleury Universite de Tunis Tunis Tunisia

In this study,we report the annealing effects on the physical properties of Sn_3Sb_2S_6 thin ***_3Sb_2S_6 thin films were prepared onto non-heated glass substrates via thermal evaporation *** as-deposited films were annealed in air for 1 h in the temperature range from 100 to 300 °C.X-ray diffraction results show that the crystallinity of the thin films increased after *** microstructure parameters crystallite size,dislocation density,lattice strain and stacking fault probability were *** optical properties were obtained from the analysis of the experimental recorded transmittance and reflectance spectral data over the wavelength range 300–1800 *** absorption coefficient（10~5cm^（-1）） reached to the visible and near-IR spectral range.A decrease in optical band gap from 1.92 to 1.71 e V by increasing the air annealing temperature was *** energy E_o and dispersion energy E_d of the films after annealing were estimated according to the model of Wemple–Di Domenico single ***–Fan model was applied to determine the electron free carrier susceptibility and the ratio of carrier concentration to the effective *** layers annealed at temperatures 〉150 ℃ undergo abrupt changes in their electrical properties and exhibit a resistive hysteresis *** properties confer to the material interest perspectives for its application in diverse advanced technologies such as photovoltaic applications and optical storage.

关键词： Thin films Sn_3Sb_2S_6 Optical constants Resistivity Hysteresis

Theoretical prediction of structural,electronic and optical properties of quaternary alloy Zn_(1-x)Be_xS_ySe_(1-y)

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第3期21卷 321-327页

作者： Hacini K Meradji H Ghemid S El Haj Hassan F laboratoire LPR D'epartement de PhysiqueFaculté des SciencesUniversité de Annaba laboratoire de physique des Matériaux Faculté des SciencesUniversité Libanaise

Within density functional theory based on the full potentiM-linearized augmented plane wave method, we carry out the first-principles calculation of the structural, electronic, and optical properties of the zinc blende quaternary alloy Zn1-xBexSySe1-y. The Perdew-Burke-Ernzerhof generaized gradient approximation based on the optimization of total energy and the Engel-Vosko generalized gradient approximation based on the optimization of the corresponding potential are used. Our investigation on the effect of the composition on lattice constants, bulk modulus, band gap, optical dielectric constant, and refractive index shows a non-linear dependence. The energy gap Eg（x, y） has been determined over the entire compositions x and y. In addition, the energy band gap of the technologically important quaternary alloy Znl-xBexSySe1-y in conditions of being lattice matched to ZnS substrate has been investigated. It is noteworthy that the present work is the first theoretical study of the quaternary alloy of interest.

关键词： density functional theory full potential-linearized augmented plane wave method qua-ternary alloy lattice-matched substrate

High Temperature Stability of Platinum Nanoparticles on Few-Layer Graphene Investigated by In Situ High Resolution Transmission Electron Microscopy

在线全文

学校读者我要写书评

暂无评论

Nano Research 2011年第5期4卷 511-521页

作者： Izabela Janowska Maria-Simona Moldovan Ovidiu Ersen Herve Bulou Kambiz Chizari Marc J. Ledoux Cuong Pham-Huu laboratoire des materiaux Surfaces et ProcEdEs pour la Catalyse （LMSPC UMR 7515 CNRS） 25 rue Becquerel F-67087 Strasbourg Cedex 02 France Institut de Physique et Chimie des materiaux de Strasbourg （IPCMS UMR 7504 CNRS） 23 rue du Loess F-67037 Strasbourg Cedex 08 France

Heterogeneous catalytic reactions involve the use of highly dispersed active phases such as metal, metal oxide, or metal sulphide nanoparticIes on thermally stable supports. Fluctuations of the reaction temperature during the reactions can induce sintering of the particles. The stability of such small particles represents a crucial parameter in the development of new families of catalysts with high activity in many fields. Here we report the stability of platinum nanoparticles （2-3 nm） on a few-layer graphene （FLG） surface as studied by in situ high temperature transmission electron microscopy.

关键词： Graphene platinium nanoparticles diffusion catalysis TEM annealing

Predicting recrystallized grain size in friction stir processed 304L stainless steel

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2019年第4期35卷 491-498页

作者： M.P.Miles T.W.Nelson C.Gunter F.C.Liu L.Fourment T.Mathis Manufacturing Engineering Department Brigham Young University Centre de Mise en Forme des materiaux Mines ParisTech

A major dilemma faced in the nuclear industry is repair of stainless steel reactor components that have been exposed to neutron irradiation. When conventional fusion welding is used for repair, intergranular cracks develop in the heat-affected zone(HAZ). Friction stir processing(FSP), which operates at much lower peak temperatures than fusion welding, was studied as a crack repair method for irradiated 304 L stainless steel. A numerical simulation of the FSP process in 304 L was developed to predict temperatures and recrystallized grain size in the stir zone. The model employed an Eulerian finite element approach,where flow stresses for a large range of strain rates and temperatures inherent in FSP were used as input. Temperature predictions in three locations near the stir zone were accurate to within 4%, while prediction of welding power was accurate to within 5% of experimental measurements. The predicted recrystallized grain sizes ranged from 7.6 to 10.6 μm, while the experimentally measured grains sizes in the same locations ranged from 6.0 to 7.6 μm. The maximum error in predicted recrystallized grain size was about 39%, but the associated stir zone hardness from the predicted grain sizes was only different from the experiment by about 10%.

关键词： Stainless steel Numerical simulation Friction stir welding Recrystallized grain size