scholarly journals Synthesis and Application of Inverse Spinel NiFe2O4 Produced by EDTA-citrate Method: Structural, Vibrational, Magnetic, and Electrochemical Properties

2021 ◽  
Author(s):  
Maitê Medeiros de Santana e Silva ◽  
Rafael A. Raimundo ◽  
Luciena S. Ferreira ◽  
Daniel A. Macedo ◽  
Marco A. Morales ◽  
...  
Keyword(s):  
Electrochemical Properties ◽  
Single Phase ◽  
Crystal Size ◽  
Band Gap Energy ◽  
Inverse Spinel ◽  
Microstructural Characteristics ◽  
Crystallite Sizes ◽  
Ph Conditions ◽  
Synthesized Materials ◽  
Discharge Curves

Abstract In this paper we studied the production of single-phase NiFe2O4 powders synthesized by the complexation method combining EDTA-citrate. The structural, optical, magnetic, and electrochemical properties of were studied as a function of the synthesis pH. Powders obtained with pH 9 showed larger crystallite sizes (73 nm) in comparison to those produced with pH 3 (21 nm). The band gap energy was found to be inversely proportional to the crystal size (1.85 and 2.0 eV for powders with crystallites of 73 nm and 21 nm, respectively). The synthesized materials presented an inverse spinel crystalline structure. The samples obtained at higher pH conditions were found to be fully magnetic saturated with a saturation magnetization of 50.5 emu g-1, while that synthesized at pH 3 is unsaturated with a maximum measured magnetization of 48.4 emu g-1. Cyclic voltammetry and charge-discharge curves indicate a battery-type behavior, with an better performance for the material obtained at pH 9 (65 C g-1 at a specific current of 3 A g-1). The remarkable performance of the associated with its by microstructural characteristics (particle size, particle agglomeration and porosity). This work offers an alternative synthesis route for obtaining spinel ferrites for magnetic and electrochemical applications.

scholarly journals The effects of varying the Eu3+ concentration on the structural and optical properties of Mg1.5Al2O4.5:x% Eu3+ (0 ≤ x ≤ 2) nanophosphors prepared by sol–gel method

2018 ◽  
Vol 8 ◽  
pp. 184798041880064 ◽  
Author(s):  
VM Maphiri ◽  
BF Dejene ◽  
TE Motaung ◽  
TT Hlatshwayo ◽  
OM Ndwandwe ◽  
...  
Keyword(s):  
Single Phase ◽  
Crystal Size ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Transmission Electron ◽  
Crystallite Sizes ◽  
The Eu

Mg1.5Al2O4.5: x% Eu3+ (0 ≤ x ≤ 2) nanopowders were successfully synthesized via sol–gel method. The X-ray diffraction (XRD) spectrum revealed that the Mg1.5Al2O4.5: x% Eu3+ matches the single phase of face-centred cubic MgAl2O4. The estimated average crystallite sizes calculated using the XRD spectra were found to be in the order of 4 nm. The estimated crystal size was confirmed by the high-resolution transmission electron microscopy. The energy dispersive X-ray spectroscopy confirmed the presence of all expected elementary composition (Mg, Al, O and Eu). The field emission gun scanning electron microscope showed that varying the Eu3+ concentration influence the morphology of the prepared nanophosphor. The photoluminescence results showed that the host emits the violet colour at around 382 nm, which was attributed to the defects within the band gap ( Eg) of host material. The Eu3+-doped samples showed the emission at around 560, 580, 593, 618, 655 and 704 nm which are, respectively, attributed to the 5D1 → 7F3, 5D0 → 7F0, 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4 characteristic transitions in Eu3+. The International Commission on Illumination colour chromaticity showed that the Eu3+ doping influences the emission colour.

Formation of synthetic analogues of double metal-hydroxy carbonate minerals under controlled pH conditions: I. The synthesis of pyroaurite and reevesite

Clay Minerals ◽  
1990 ◽  
Vol 25 (2) ◽  
pp. 161-179 ◽  
Author(s):  
H. C. B. Hansen ◽  
R. M. Taylor
Keyword(s):  
Oxidation Rate ◽  
Reasonable Agreement ◽  
Single Phase ◽  
Morphological Features ◽  
Air Oxidation ◽  
Synthetic Analogues ◽  
Synthesis Technique ◽  
Homogeneous Product ◽  
Ph Conditions ◽  
Hydroxy Carbonate

AbstractTwo-layered Fe(III)-M(II) hydroxy carbonates (M(II) = Ni or Mg) have been synthesized by induced hydrolysis using controlled air oxidation of an aqueous Fe(II)-M(II) mixture (M(II)/Fe(II) ratio >3) at a pH below which the hydroxide of the M(II) cation precipitates. The crystalline, homogeneous product can be a single phase consisting of very thin circular to hexagonal plates (0·2–0·8 µm diam.). For synthetic reevesite (Ni(II)-Fe(III) hydroxy carbonate), stable spherular aggregates are formed. The well crystallized products have an M(II)/Fe(III) ratio of about two. However, by varying the pH, the initial M(II)-Fe(III) ratio and the oxidation rate, the M(II)/Fe(III) ratio in the product and its crystallinity can be varied. The derived formulae are in reasonable agreement with the known composition of pyroaurite-type compounds. Possible synthesis pathways are discussed. The ability to control some physical and morphological features of the products indicates that the synthesis technique could prove advantageous in the preparation of certain catalyst precursors.

Multi-Phasic Ceramic Composites made by Sol-Gel Technique

1984 ◽  
Vol 32 ◽  
Author(s):  
Rustum Roy ◽  
S. Komarneni ◽  
D.M. Roy
Keyword(s):  
Single Phase ◽  
Crystal Size ◽  
Sol Gel ◽  
Ceramic Composites ◽  
Silver Halides ◽  
Metal Atoms ◽  
Metallic Salts ◽  
Second Phases ◽  
Gel Technique ◽  
Work Done

ABSTRACTInstead of aiming to prepare homogeneous gels and xerogels, this paper reports on work done to prepare deliberately diphasic materials. This has been achieved by three different paths: (1) mixing 2 sols; (2) mixing 1 sol with 1 solution; and (3) post formation diffusion of either one or two solutions.By the last named process we have made SiO2, mullite and alumina based composites, with silver halides, BaSO4, CdS, etc., as the dispersed phase. The crystal size can be confined to the initial pores by rapid diffusion giving rise to extremely fine second phases in the submicron range. Subsequent reduction of appropriate metallic salts can be used to give finely dispersed metals (e.g. Cu, Ni) in essentially any xerogel matrix. The open porosity makes these metal atoms very accessible.By the first two processes we have made both single phase and di-phasic gels of the same composition (prototype: mullite) and shown that though they cannot be distinguished by XRD, SEM, and TEM, by DTA and thermal processing, they are radically different. Such di-phasic gels store more metastable energy than any other solids.

N-rich GaNAs with High As Content Grown by Metalorganic Vapor Phase Epitaxy

2003 ◽  
Vol 798 ◽  
Author(s):  
Akitaka Kimura ◽  
H. F. Tang ◽  
C. A. Paulson ◽  
T. F. Kuech
Keyword(s):  
Vapor Phase ◽  
Single Phase ◽  
Metalorganic Vapor Phase Epitaxy ◽  
Band Gap Energy ◽  
Vapor Phase Epitaxy ◽  
Miscibility Gap ◽  
X Ray Diffraction ◽  
Specular Surfaces ◽  
Rich Side ◽  
Absorption Measurements

ABSTRACTGaN1-yAsy epitaxial alloys on the N-rich side with high As content were grown by metalorganic vapor phase epitaxy. They had specular surfaces and the single-phase epitaxial nature was confirmed by X-ray diffraction. The As incorporation increased through both a decrease in the growth temperature and V/III ratio. These trends were similar to that found in other III-V alloy systems which exhibit a large miscibility gap and the anion incorporation was considered to have been limited kinetically under the conditions of the low V/III ratio. The range of achieved As content was extended up to y=0.067, which is a composition well within the miscibility gap. The As-content dependence of the band gap energy was determined by optical absorption measurements and large bowing parameter of 16.8 ± 0.9 eV was determined.

scholarly journals Enhancing Mechanical Response of Monolithic Magnesium Using Nano-NiTi (Nitinol) Particles

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1014 ◽  
Author(s):  
Gururaj Parande ◽  
Vyasaraj Manakari ◽  
Saif Wakeel ◽  
Milli Kujur ◽  
Manoj Gupta
Keyword(s):  
Mechanical Properties ◽  
Mechanical Response ◽  
Hot Extrusion ◽  
Nickel Titanium ◽  
Structure Property ◽  
Microstructural Characteristics ◽  
Magnesium Matrix ◽  
Melt Deposition ◽  
Synthesized Materials ◽  
Minimal Adverse Effect

The present study focuses on investigating the effects of Nickel-Titanium (NiTi) nanoparticles on the microstructure and properties of pure Mg. Mg composites containing varying weight percentages (0.5, 1, 1.5, 3) of NiTi nanoparticles were fabricated using Disintegrated Melt Deposition (DMD), followed by hot extrusion. The synthesized materials were characterized in order to investigate their physical, microstructural and mechanical properties. Synthesized materials were characterized for their density and porosity levels, microstructural characteristics, and mechanical response. Superior grain refinement was realized by the presence of NiTi nanoparticles in the magnesium matrix. The addition of NiTi nanoparticles resulted in strength property enhancements of pure Mg with minimal adverse effect on the ductility. Structure-property evaluations are detailed in the current study.

Hydrothermal Synthesis and Characterization of Nanocrystalline Gd2Sn2O7:Eu3+ Phosphors

2011 ◽  
Vol 239-242 ◽  
pp. 2851-2854 ◽  
Author(s):  
Jin Yu Yang ◽  
Yu Chang Su ◽  
Zhuo Chen ◽  
Xue Ying Liu
Keyword(s):  
Single Phase ◽  
Concentration Quenching ◽  
Synthesis And Characterization ◽  
Photoluminescence Properties ◽  
Excitation Spectra ◽  
Pyrochlore Type ◽  
Co Precipitation ◽  
Synthesized Materials ◽  
Quenching Phenomenon

Phase-pure Eu3+doped Gd2Sn2O7nanocrystals have been successfully synthesized via a co-precipitation processes combined with hydrothermal treatment. The crystal structure, particle size, morphologies, composition, and photoluminescence properties of the as-synthesized products were investigated by XRD, SEM, TEM, EDS and PL. The samples were single-phase cubic pyrochlore-type nanocrystals with a typical size of about 30 - 60 nm. All the samples exhibited irregular flower like secondary nanostructure assembled by primary nanoparticles. Photoluminescence properties of Gd2Sn2O7:Eu3+were investigated, and the results revealed that the as-synthesized materials displayed intense and prevailing emission located at 580 - 630 nm. The excitation spectra indicated that an energy transfer from Gd3+to Eu3+occurred. Meanwhile, the concentration quenching phenomenon was observed in Gd2Sn2O7:Eu3+nanocrystals.

Synthesis of ZnO Nanoparticles via Simple Wet-Chemical Routes

2013 ◽  
Vol 699 ◽  
pp. 133-137 ◽  
Author(s):  
Byeong Woo Lee ◽  
Jin Heui Koo ◽  
Tae Suk Lee ◽  
Yun Hae Kim ◽  
Jae Suk Hwang
Keyword(s):  
Single Phase ◽  
Hydrothermal Process ◽  
Processing Parameters ◽  
Zinc Nitrate ◽  
Precursor Concentration ◽  
Precipitation Process ◽  
Process Conditions ◽  
Crystallite Sizes ◽  
Zno Powders ◽  
Wet Chemical

Zinc oxide (ZnO) powders were synthesized by a simple precipitation and a hydrothermal process at the temperature range RT-100°C. In precipitation process, the powders were formed by mixing aqueous solutions of zinc nitrate with NaOH aqueous solution under controlled process conditions such as precursor concentration, reaction pH and temperature. Single phase ZnO particles can be easily synthesized in lower precursor concentration, higher reaction pH and temperature. The powders synthesized at room temperature exhibited plates, rods or pointed multipod morphologies depending on the concentration and pH. ZnO crystallites synthesized by hydrothermal process consisted mostly of well developed large or elongated crystallites of plates or rods in shape. The results reveal that the ZnO crystallite sizes and shapes would be efficiently controllable by changing the processing parameters of the preparation processes.

Single phase A2B7-type La-Mg-Ni alloy with improved electrochemical properties prepared by melt-spinning and annealing

2019 ◽  
Vol 37 (12) ◽  
pp. 1305-1311 ◽  
Author(s):  
Yiming Li ◽  
Zhuocheng Liu ◽  
Guofang Zhang ◽  
Yanghuan Zhang ◽  
Huiping Ren
Keyword(s):  
Electrochemical Properties ◽  
Melt Spinning ◽  
Single Phase ◽  
Ni Alloy

Synthesis of CuO nanowires on Cu-foil using thermal oxidation method, a novel annealing process

2016 ◽  
Vol 30 (05) ◽  
pp. 1650039 ◽  
Author(s):  
Hosein Eshghi ◽  
Mehdi Torabi Goodarzi
Keyword(s):  
Electron Microscopy ◽  
Thermal Oxidation ◽  
Cupric Oxide ◽  
Band Gap Energy ◽  
Optical Investigation ◽  
Spectra Analysis ◽  
Oxidation Method ◽  
Cuo Nanowires ◽  
Air Atmosphere ◽  
Crystallite Sizes

Cupric oxide (CuO) nanowires (NWs) on Cu-foils were prepared by thermal oxidation method in air atmosphere using two annealing manners (continuous and steps) in the temperature ranges of 400–500[Formula: see text]C and 400–600[Formula: see text]C. Morphology and microstructure of the NWs was studied using field effect scanning electron microscopy (FESEM), X-ray diffractogram (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Optical reflectance spectrum was used for the optical investigation of the layers. We found the NWs formed have two different morphologies, curved and straight, with diameters between 50 nm and 200 nm and lengths between 5 [Formula: see text]m and 10 [Formula: see text]m. SAED pattern of a single NW revealed as a CuO single crystal with monoclinic structure. The reflectance spectra analysis based on Kubelka–Munk method showed that the band gap energy of the CuO NWs are varying in the range of 1.40–1.47 eV depending on the crystallite sizes of the NWs, a confirmation for the happening of the quantum confined effect in these samples.

Low Temperature Synthesis and Characterization of CaO and MgO- Stabilized Nanocrystalline Tetragonal Zirconia by Citrate Gel Process

2008 ◽  
Vol 368-372 ◽  
pp. 754-757
Author(s):  
Hasan Gocmez ◽  
Hirotaka Fujimori
Keyword(s):  
Single Phase ◽  
Tetragonal Zirconia ◽  
Xrd Analysis ◽  
Complex Method ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Heat Treated ◽  
Crystallite Sizes ◽  
Citrate Gel Process

The citrate gel method, similar to the polymerized complex method, was used to synthesize homogenous tetragonal zirconia at 800oC and 1000oC. Nanocrystalline tetragonal single phase has been fully stabilized with 3, 7, 10 mol% CaO and 10, 15 mol% MgO at 800oC, respectively. In addition, the XRD analysis showed the absence of monoclinic phase after addition of 7 and 10 mol% CaO into zirconia-based solid solutions, which have been fully stabilized both 800oC and 1000oC. The crystallite sizes of the t-ZrO2 with 3, 7 and 10 mol% CaO at 1000oC were 32, 28 and 29nm, respectively. For ZrO2- x mol% MgO (x=3, 10, 15) solid solution, the crystallite sizes of samples at 800oC were less than 29nm, however it was increased up to 69nm at 1000oC. The prepared gel and subsequent heat-treated powders were characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) to get detail information regarding to differentiation of polymorphs of zirconia as well as formation of powders.

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