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Synthesis and M ssbauer characterization of Cu and Cr doped magnetites  [cached]
Barrero, C. A.,Morales, A. L.,Mazo-Zuloaga, J.,Jaramillo, F.
Revista de Metalurgia , 2003,
Abstract: A detailed M ssbauer investigation of magnetites prepared under different hydrothermal conditions and doped with Cu and Cr is presented. The samples were characterized by means of room temperature M ssbauer spectrometry, infrared spectroscopy, and X-ray diffraction. M ssbauer results show that the hydrothermal method produces highy stoichiometric and relatively well-crystallized magnetites. The results suggest that the best samples are obtained when the alkaline solution is added quickly to the ferrous solution. It was also found that mixing the solutions under constant ultrasonic stirring produce magnetites with slightly better crystallinity and stoichiometry than the samples produced under magnetic or nitrogen bubbling stirring. The effect of the Cu and Cr on the hyperfine parameters is also presented and discussed. Se presenta una investigación M ssbauer detallada de magnetitas preparadas bajo diferentes condiciones hidrotermales y dopadas con Cu y Cr. Las muestras fueron caracterizadas utilizando la espectrometría M ssbauer a temperatura ambiente, espectroscopia infrarroja y difracción de rayos X. Los resultados M ssbauer muestran que el método hidrotermal produce magnetitas altamente estequiométricas y relativamente bien cristalizadas. Los resultados sugieren que las mejores muestras se obtienen cuando la solución alcalina se a ade rápidamente a la solución ferrosa. Se encontró que la mezcla de las soluciones bajo agitación ultrasónica constante produce magnetitas con cristalinidad y estequiometría levemente mejores que las muestras producidas bajo agitación magnética o por burbujeo de nitrógeno. También se presentan y se discuten los efectos del Cu y del Cr en los parámetros hiperfinos.
Preparation and characterization of Nickel-and cobalt-doped magnetites
Lelis, Maria de Fátima Fontes;Fabris, José Domingos;Mussel, Wagner da Nova;Takeuchi, Armando Yoshihaki;
Materials Research , 2003, DOI: 10.1590/S1516-14392003000200006
Abstract: nickel- and cobalt-doped magnetites were prepared by a co-precipitation method and studied in some detail, in an effort to identify some effects of the doping cations on the magnetic, crystallographic and morphological properties of the resulting spinel. the synthetic samples were characterized by conventional chemical analysis, powder x-ray diffractometry, m?ssbauer spectroscopy, saturation magnetization and scanning electron microscopy. from chemical analysis, the continuous increase of ni2+ or co2+ is accompanied by a simultaneous decrease of the fe2+ contents, in the spinel structure. the magnetization values also decrease continuously with increasing doping cation contents. m?ssbauer parameters are characteristic of substituted magnetites and indicate the presence of a single phase only. based on the inverted intensities of the lines 1 (leftmost, on the negative doppler velocity scale) and 2 of m?ssbauer spectra of doped samples, relatively to the pure magnetite, it was assumed that the isomorphical substitution occurs preferentially on octahedral coordination sites of the spinel structure. the coercive field of these ferrites decrease steadily with ni2+ but increases with co2+ contents, reaching a maximum at x = 0.38, in the general formula coxfe3-xo4 .
Preparation and characterization of Nickel-and cobalt-doped magnetites
Lelis Maria de Fátima Fontes,Fabris José Domingos,Mussel Wagner da Nova,Takeuchi Armando Yoshihaki
Materials Research , 2003,
Abstract: Nickel- and cobalt-doped magnetites were prepared by a co-precipitation method and studied in some detail, in an effort to identify some effects of the doping cations on the magnetic, crystallographic and morphological properties of the resulting spinel. The synthetic samples were characterized by conventional chemical analysis, powder X-ray diffractometry, M ssbauer spectroscopy, saturation magnetization and scanning electron microscopy. From chemical analysis, the continuous increase of Ni2+ or Co2+ is accompanied by a simultaneous decrease of the Fe2+ contents, in the spinel structure. The magnetization values also decrease continuously with increasing doping cation contents. M ssbauer parameters are characteristic of substituted magnetites and indicate the presence of a single phase only. Based on the inverted intensities of the lines 1 (leftmost, on the negative Doppler velocity scale) and 2 of M ssbauer spectra of doped samples, relatively to the pure magnetite, it was assumed that the isomorphical substitution occurs preferentially on octahedral coordination sites of the spinel structure. The coercive field of these ferrites decrease steadily with Ni2+ but increases with Co2+ contents, reaching a maximum at x = 0.38, in the general formula Co xFe3-xO4 .
Y-Doped ZnO Nanorods by Hydrothermal Method and Their Acetone Gas Sensitivity  [PDF]
Peng Yu,Jing Wang,Hai-ying Du,Peng-jun Yao,Yuwen Hao,Xiao-gan Li
Journal of Nanomaterials , 2013, DOI: 10.1155/2013/751826
Abstract: Pure and yttrium- (Y-) doped (1 at%, 3 at%, and 7 at%) ZnO nanorods were synthesized using a hydrothermal process. The crystallography and microstructure of the synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Comparing with pure ZnO nanorods, Y-doped ZnO exhibited improved acetone sensing properties. The response of 1 at% Y-doped ZnO nanorods to 100?ppm acetone is larger than that of pure ZnO nanorods. The response and recovery times of 1 at% Y-doped ZnO nanorods to 100?ppm acetone are about 30?s and 90?s, respectively. The gas sensor based on Y-doped ZnO nanorods showed good selectivity to acetone in the interfere gases of ammonia, benzene, formaldehyde, toluene, and methanol. The formation mechanism of the ZnO nanorods was briefly analyzed. 1. Introduction As an important II–VI semiconducting material with a wide direct band gap ( at 300?K) and large exciton binding energy (~60?meV), ZnO has drawn much attention in the last few decades, owing to its specific electrical, catalytic, photochemical optoelectronic properties and the sensitivity to various gases, all of which make ZnO highly promising in a broad range of real-world applications [1, 2]. Recently, ZnO has shown great potentials for sensing toxic and combustible gases such as CO, H2, NH3, ethanol, and acetone [3–5]. One way to enhance gas sensing property is by doping with other elements. For example, Niu et al. [6] used Fe, Co, and Cr as dopants to improve the gas sensing property of pure ZnO, and the results showed that ZnFe2O4 had high response and good selectivity to Cl2. Au-doped ZnO enhanced acetone sensing performance [7]. Co-doped ZnO nanofibers improved selective acetone sensing properties [8]. Pd [9] is also used as dopant to improve CO gas sensing property of ZnO. There are some reports about the lanthanide elements of Y-doped ZnO and Y doping has significant effects on the luminescence, chemical, and surface modification of ZnO [10, 11]. However, the lanthanide elements of Y as a dopant to improve gas sensing property of ZnO are new challenges. Furthermore, many synthesis methods have been used to prepare zinc-oxide nanoparticles (NPs) including chemical vapor deposition [12], sol-gel method [13], spray pyrolysis method [14], solid state reaction method [15], and hydrothermal method [16]. Hydrothermal method is fairly simple and suitable for industrial production, which will pave the way for the development of a low-cost practical gas sensor for detection of probable chemical
Effect of Pressure on Synthesis of Pr-Doped Zirconia Powders Produced by Microwave-Driven Hydrothermal Reaction  [PDF]
A. Opalinska,C. Leonelli,W. Lojkowski,R. Pielaszek,E. Grzanka,T. Chudoba,H. Matysiak,T. Wejrzanowski,K. J. Kurzydlowski
Journal of Nanomaterials , 2006, DOI: 10.1155/jnm/2006/98769
Abstract: A high-pressure microwave reactor was used to study the hydrothermal synthesis of zirconia powders doped with 1 mol % Pr. The synthesis was performed in the pressure range from 2 to 8 MPa corresponding to a temperature range from 215C∘ to 305C∘. This technology permits a synthesis of nanopowders in short time not limited by thermal inertia of the vessel. Microwave heating permits to avoid contact of the reactants with heating elements, and is thus particularly well suited for synthesis of doped nanopowders in high purity conditions. A mixture of ZrO2 particles with tetragonal and monoclinic crystalline phases, about 15 nm in size, was obtained. The p/T threshold of about 5-6 MPa/265–280C∘ was necessary to obtain good quality of zirconia powder. A new method for quantitative description of grain-size distribution was applied, which is based on analysis of the fine structure of the X-ray diffraction line profiles. It permitted to follow separately the effect of synthesis conditions on the grain-size distribution of the monoclinic and tetragonal phases.
Biocompatibility and antimicrobial activity of zinc(II) doped hydroxyapatite, synthesized by hydrothermal method  [PDF]
Radovanovi? ?eljko,Veljovi? ?or?e,Joki? Bojan,Dimitrijevi? Suzana
Journal of the Serbian Chemical Society , 2012, DOI: 10.2298/jsc121019131r
Abstract: In order to obtain multifunctional materials with good biocompatibility and antimicrobial effect, hydroxyapatite (HAp) doped with Zn2+ was synthesized by hydrothermal method. Powders with different content of zinc ions were synthesized and compared with undoped HAp to investigation of Zn2+ ion influence on the antimicrobial activity of HAp. Analyses of undoped and Zn2+-doped powders before and after thermal treatment at 1200oC were performed by SEM and XRD. Antimicrobial effects of powders were examined in relation to Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans in liquid medium. The results showed that the obtained powders have good antimicrobial activity, but higher antimicrobial activities of powders doped with Zn2+ were observed after annealing at 1200°C. For powders annealed at 1200°C in vitro biocompatibility tests MTT and DET with MRC-5 fibroblast cells in liquid medium were carried out. Based on MTT and DET tests it was shown that powders do not have a significant cytotoxic effect, which was confirmed by SEM analysis of MRC-5 fibroblast cells after theirs in vitro contact with powders. [Projekat Ministarstva nauke Republike Srbije, br. III 45019 and FP7-REGPOT-2009-1 NANOTECH FTM]
Preparation and Gas-sensing Properties of Cu2+-doped ZnO Nanorods
CHEN Tong-Yun, ZHU Xiao-Hua, CHU Xiang-Feng, GE Xiu-Tao, DONG Yong-Ping, YE Ming-Fu
无机材料学报 , 2012, DOI: 10.3724/sp.j.1077.2012.11780
Abstract: Cu2+-doped ZnO nano-rod powders (0–6mol%) were prepared via solvothermal method. The crystal and micro-morphology of the doped ZnO nano-rods were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The effects of Cu2+ dopant and the thermal condition (reaction temperature and duration) on the gas sensitivities of ZnO nano-rods were studied. The gas sensing properties of pure ZnO nanorod sensor and 3mol% Cu2+-doped ZnO nano-rod sensors to formaldehyde, acetic acid, toluene, ethanol, acetone and trimethylamine were also studied. The results show that the micro-morphology of ZnO powders are nano-rods, the lengths and diameters of ZnO nanorods change with the variation of the Cu2+ concentration. The sensor based on 3mol% Cu2+-doped ZnO nano-rods exhibits high response and good selectivity to dilute ethanol, the responses to 1×10-3 ethanol and 1×10–6 ethanol reach 380.5 and 4.2 when it works at 395 respectively, and its response time and recovery time are 16 s and 40 s, respectively.
Hydrothermal Processing of Phase Pure and Doped Hydroxyapatite and its Characterization  [PDF]
Muhammad Musaddique Ali Rafique
Journal of Encapsulation and Adsorption Sciences (JEAS) , 2018, DOI: 10.4236/jeas.2018.81002
Abstract: Hydroxyapatite (HA) is a synthetic ceramic which is used in numerous biomedical applications. However, its use is restricted in load bearing applications. A novel batch hydrothermal method is indigenously developed to synthesize fine size, crystalline hydroxyapatite (HA) and titania doped hydroxyapatite (TiO2-HA) powders with distinct phase formation. Powders were characterized using XRD, FTIR and DSC-TGA. Sharp peaks in HA XRD pattern after sintering at 1000°C indicate significant crystallinity while sharp peaks in TiO2 XRD pattern at 27°, 36° and 5° after sintering indicate anatase to rutile transformation. This fact is also confirmed by FTIR and DSC-TGA Plots.
Synthesis and Characterization of Aluminum Doped Zinc Oxide Nanostructures via Hydrothermal Route  [PDF]
A. Alkahlout,N. Al Dahoudi,I. Grobelsek,M. Jilavi,P. W. de Oliveira
Journal of Materials , 2014, DOI: 10.1155/2014/235638
Abstract: Stable crystalline aluminum doped zinc oxide (AZO) nanopowders were synthesized using hydrothermal treatment processing. Three different aluminum precursors have been used. The Al-precursors were found to affect the morphology of the obtained nanopowders. AZO nanoparticles based on zinc acetate and aluminum nitrate have been prepared with different Al/Zn molar ratios. XRD investigations revealed that all the obtained powders have single phase zincite structure with purity of about 99%. The effect of aluminum doping ratio in AZO nanoparticles (based on Al-nitrate precursor) on structure, phase composition, and particle size has been investigated. The incorporation of Al in ZnO was confirmed by UV-Vis spectroscopy revealing a blue shift due to Burstein-Moss effect. 1. Introduction Zinc oxide ZnO is a wide band gap (3.4?eV) semiconductor which has broad range of potential uses in optical and electrical applications such as in solar energy conversion, thin film transistors, photocatalysis, nonlinear optics, gas sensors, pigments, cosmetic, LED, anti-UV and low-emission coatings, and photoluminescent and sensor materials [1–8]. Undoped ZnO shows n-type conductivity due to the existence of native defects such as oxygen vacancy, zinc interstitials, and hydrogen interstitials in the ZnO lattice [9–11]. Unfortunately, the conductivity of undoped ZnO is thermally unstable. The substitution of Zn2+ ions with group III ions (B3+, Al3+, Ga3+, and In3+) [8–16] generates extra electrons and improves ZnO optical, electrical, thermal, and magnetic properties. Al3+ has been the most used dopant element due to its small ionic radius and low material cost. The substitution of Zn2+ ions with Al3+ in ZnO lattice improves the electrical conductivity through the increase of charge carriers where it is reported that the electron concentration increases from 1016 to 1021/cm?3 [17, 18]. The mobility of the charge carriers is strongly influenced by scattering at the disorder locations created in the crystal structure due to doping. Therefore, well crystalline doped ZnO particles, pure in phase, are very important for obtaining good electrical conducting properties. Accordingly, structural considerations should also be included [19]. The choice of aluminum precursor used for substitution of Al3+ ions in ZnO host lattice is very important. Organic salts are recommended for successful homogenous substitution [20]. On the other hand, doping based on aluminum’s inorganic salts is reported to be not successful [21, 22]. In this work, AZO nanoparticles were synthesized using hydrothermal
Morphology and Photoluminescence of HfO2Obtained by Microwave-Hydrothermal  [cached]
Eliziário SA,Cavalcante LS,Sczancoski JC,Pizani PS
Nanoscale Research Letters , 2009,
Abstract: In this letter, we report on the obtention of hafnium oxide (HfO2) nanostructures by the microwave-hydrothermal method. These nanostructures were analyzed by X-ray diffraction (XRD), field-emission gum scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDXS), ultraviolet–visible (UV–vis) spectroscopy, and photoluminescence (PL) measurements. XRD patterns confirmed that this material crystallizes in a monoclinic structure. FEG-SEM and TEM micrographs indicated that the rice-like morphologies were formed due to an increase in the effective collisions between the nanoparticles during the MH processing. The EDXS spectrum was used to verify the chemical compositional of this oxide. UV–vis spectrum revealed that this material have an indirect optical band gap. When excited with 488 nm wavelength at room temperature, the HfO2nanostructures exhibited only one broad PL band with a maximum at around 548 nm (green emission).
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