Preparation of High-Purity α-Alumina by Oil-in-Water Microemulsion

2011 ◽  
Vol 399-401 ◽  
pp. 673-676 ◽  
Author(s):  
Jing Jing Ma ◽  
Bo Lin Wu
Keyword(s):  
High Purity ◽  
Average Crystallite Size ◽  
Microemulsion System ◽  
Alumina Powder ◽  
Mixed Solution ◽  
X Ray Diffraction ◽  
Step Size ◽  
Oil In Water ◽  
Diffraction Peaks ◽  
Mixed Oil

The main objective of this work was to prepare high purity α-alumina powder (α-Al2O3) by mixed oil-in-water microemulsion route. In this study α-alumina was prepared by quaternary microemulsion system (water/surfactant/co-surfactant/oil-phase). OP-10, alcohol and the mixed solution of cyclohexane and aluminium isopropoxide were used as surfactant, co-surfactant and oil-phase, respectively. After drying the amorphous precursor powder, α-alumina powder is obtained by sintering at 1200°C for 3-5h. The X-ray diffraction pattern shows the presence of alumina phase with crystal structure and the slow scan with step size 0.0170°/sec of selected diffraction peaks such as (113) has been recorded and calculated by Scherer’s formula. The average crystallite size is about 40nm.

SYNTHESIS, CHARACTERIZATION, AND SELF-CONTROLLED ORTHORHOMBIC TO TETRAGONAL POLYMORPHIC TRANSFORMATION IN BaTiO3 NANOPARTICLES

2007 ◽  
Vol 21 (25) ◽  
pp. 1697-1714
Author(s):  
S. RAM ◽  
A. JANA ◽  
T. K. KUNDU
Keyword(s):  
Composite Structure ◽  
Single Phase ◽  
Average Crystallite Size ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Volume ◽  
Proposed Model ◽  
Diffraction Peaks ◽  
Two Phases ◽  
O Phase

The phase formation and thermal-induced phase transformation are studied in BaTiO 3 nanoparticles. 2 h of heating a polymer precursor at 550°C in air formed a single phase BaTiO 3 of 15 nm average crystallite size D. The X-ray diffraction peaks are analyzed assuming a P nma orthorhombic (o) crystal structure of lattice parameters a = 0.6435 nm , b = 0.5306 nm , and c = 0.8854 nm . The lattice volume V = 0.3023 nm 3, with z = 4 formula units, yields a density ρ = 5.124 g/cm 3. This is a new polymorph in comparison to well-known P m3m tetragonal (t) structure, V = 0.0644 nm 3 or ρ = 6.016 g/cm 3 (z = 1). An o ↦ t transformation appears on heating at temperature as high as 650°C in air. A proposed model explains the transformation above a certain D value in terms of the Gibbs free energy. Unless heating above 750°C, the two phases coexist in a composite structure (D≤27 nm ), with as much residual o-phase trace as ~28 vol%. As a function of temperature both the phases decrease in the V values up to 0.2975 and 0.0643 nm3 at 750°C respectively (0.0650 nm3 at 650°C). This is an important parameter for designing useful ferroelectric and other properties in a hybrid composite structure.

Influence of Scanning Parameters on X-Ray Diffraction Peaks of Copper

2017 ◽  
Vol 751 ◽  
pp. 202-206
Author(s):  
Parinya Chakartnarodom ◽  
Nuntaporn Kongkajun ◽  
Edward A. Laitila
Keyword(s):  
Statistical Analysis ◽  
Relative Error ◽  
X Ray Diffraction ◽  
Step Size ◽  
X Ray ◽  
Integrated Intensity ◽  
Preset Time ◽  
Diffraction Peaks ◽  
Intensity Calculation ◽  
Statistical Analysis Methods

The aim of this work is to study the influence of x-ray diffractometer scanning parameters on the integrated intensity and full-width at half maximum (FWHM) of copper powder x-ray diffraction peaks by using statistical analysis methods. X-ray diffraction (XRD) analysis of the copper powder was accomplished using step scan mode with step sizes of 0.03o and 0.05o 2q, and preset time changes from 0.1-3.5 s. Integrated intensity of an x-ray peak was calculated by the numerical method. FWHM was measured as the width of Pearson VII model of the x-ray peak at the half-maximum intensity. The statistical analysis methods including linear regression and statistical hypothesis test were used to analyze the correlation between the preset time and the error on integrated intensity calculation, and the FWHM of a peak on the XRD pattern. The results from statistical analysis show that increasing the preset time from 0.1 s to 3.5 s does not affect the FWHM of an x-ray peak, but it reduces the relative error in integrated intensity calculation. Moreover, using the preset time greater than 1 s will minimize the relative error in integrated intensity calculation of an x-ray peak. While step size did not affect both the relative error in integrated intensity calculation or FWHM, the smaller step size would provide more data points for better accurate model of an x-ray peak.

scholarly journals Contribution to Analysis of Co/Cu Substituted Ni-Zn Ferrites

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
G. S. V. R. K. Choudary ◽  
P. Prameela ◽  
M. Chaitanya Varma ◽  
A. Mahesh Kumar ◽  
K. H. Rao
Keyword(s):  
Sol Gel ◽  
Chelating Agent ◽  
Average Crystallite Size ◽  
Initial Permeability ◽  
Scanning Electron Micrographs ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
Ferrite Material ◽  
Diffraction Peaks ◽  
Sol Gel Synthesis

In this communication, Co/Cu substituted Ni-Zn ferrites processed through sol-gel synthesis using polyethylene glycol (PEG) as a chelating agent are studied, intending to aid in understanding and choosing the optimum ferrite material for high frequency applications. Lattice constant and average crystallite size have been estimated from FWHM of the X-ray diffraction peaks, and these parameters are understood by considering the ionic radii of the substituted as well as the replacing ions. Observed variations in saturation magnetization and initial permeability for these ferrites have been explained on the basis of anisotropy contribution for cobalt and segregation of copper at grain boundaries evident from scanning electron micrographs.

Chemical synthesis and study of structural and optoelectronic properties of CdS thin films: Effect of SILAR growth cycles

2015 ◽  
Vol 9 (3) ◽  
pp. 2461-2469
Author(s):  
S. R. Gosavi ◽  
K. B. Chaudhari
Keyword(s):  
Thin Films ◽  
Average Crystallite Size ◽  
X Ray Diffraction ◽  
Silar Method ◽  
Growth Cycles ◽  
Glass Substrates ◽  
Layer Adsorption ◽  
Cds Thin Films ◽  
Structural And Optoelectronic Properties ◽  
Deposited Film

CdS thin films were deposited on glass substrates by using successive ionic layer adsorption and reaction (SILAR) method at room temperature. The effect of SILAR growth cycles on structural, morphological, optical and electrical properties of the films has been studied.  The thickness of the deposited film is measured by employing weight difference method. The X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) studies showed that all the films exhibit polycrystalline nature and are covered well with glass substrates. The values of average crystallite size were found to be 53 nm, 58 nm, 63 nm and 71 nm corresponding to the thin films deposited with 30, 40, 50 and 60 SILAR growth cycles respectively. From the UV–VIS spectra of the deposited thin films, it was seen that both the absorption properties and energy bandgap of the films changes with increasing number of SILAR growth cycles. A decrease of electrical resistivity has been observed with increasing SILAR growth cycle. 

Control of the phase composition of advanced calcium phosphates using an x-ray diffractometer with a curved position-sensitive detector

2020 ◽  
Vol 86 (6) ◽  
pp. 29-35
Author(s):  
V. P. Sirotinkin ◽  
O. V. Baranov ◽  
A. Yu. Fedotov ◽  
S. M. Barinov
Keyword(s):  
Phase Composition ◽  
Calcium Phosphates ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
X Ray Diffraction ◽  
X Ray ◽  
Impurity Phases ◽  
Position Sensitive ◽  
Diffraction Peaks ◽  
Diffraction Patterns

The results of studying the phase composition of advanced calcium phosphates Ca10(PO4)6(OH)2, β-Ca3(PO4)2, α-Ca3(PO4)2, CaHPO4 · 2H2O, Ca8(HPO4)2(PO4)4 · 5H2O using an x-ray diffractometer with a curved position-sensitive detector are presented. Optimal experimental conditions (angular positions of the x-ray tube and detector, size of the slits, exposure time) were determined with allowance for possible formation of the impurity phases during synthesis. The construction features of diffractometers with a position-sensitive detector affecting the profile characteristics of x-ray diffraction peaks are considered. The composition for calibration of the diffractometer (a mixture of sodium acetate and yttrium oxide) was determined. Theoretical x-ray diffraction patterns for corresponding calcium phosphates are constructed on the basis of the literature data. These x-ray diffraction patterns were used to determine the phase composition of the advanced calcium phosphates. The features of advanced calcium phosphates, which should be taken into account during the phase analysis, are indicated. The powder of high-temperature form of tricalcium phosphate strongly adsorbs water from the environment. A strong texture is observed on the x-ray diffraction spectra of dicalcium phosphate dihydrate. A rather specific x-ray diffraction pattern of octacalcium phosphate pentahydrate revealed the only one strong peak at small angles. In all cases, significant deviations are observed for the recorded angular positions and relative intensity of the diffraction peaks. The results of the study of experimentally obtained mixtures of calcium phosphate are presented. It is shown that the graphic comparison of experimental x-ray diffraction spectra and pre-recorded spectra of the reference calcium phosphates and possible impurity phases is the most effective method. In this case, there is no need for calibration. When using this method, the total time for analysis of one sample is no more than 10 min.

Structural, Morphological, Magnetic and Self-Heating Studies of One-Step Polyol Synthesized Manganese Ferrite (MnFe2O4) Nanoparticles

2019 ◽  
Vol 19 (01) ◽  
pp. 1950003
Author(s):  
P. R. Ghutepatil ◽  
S. H. Pawar
Keyword(s):  
Room Temperature ◽  
Synthesis Method ◽  
Average Crystallite Size ◽  
Superparamagnetic Nanoparticles ◽  
Polyol Synthesis ◽  
X Ray Diffraction ◽  
Self Heating ◽  
Transmission Electron ◽  
One Step ◽  
Mnfe2o4 Nanoparticles

In this paper, uniform and superparamagnetic nanoparticles have been prepared using one-step polyol synthesis method. Structural, morphological and magnetic properties of obtained MnFe2O4 nanoparticles have been investigated by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and thermogravimetric analysis (TGA) techniques. Structural investigation showed that the average crystallite size of obtained nanoparticles was about 10[Formula: see text]nm. Magnetic study revealed that the nanoparticles were superparamagnetic at room temperature with magnetization 67[Formula: see text]emu/g at room temperature. The self-heating characteristics of synthesized MnFe2O4 nanoparticles were studied by applying external AC magnetic field of 167.6 to 335.2[Formula: see text]Oe at a fixed frequency of 265[Formula: see text]kHz. The SAR values of MnFe2O4 nanoparticles were calculated for 2, 5, 10[Formula: see text]mg[Formula: see text]mL[Formula: see text] concentrations and it is observed that the threshold hyperthermia temperature is achieved for all concentrations.

scholarly journals Investigation of Polyol Process for the Synthesis of Highly Pure BiFeO3 Ovoid-Like Shape Nanostructured Powders

Nanomaterials ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 26 ◽  
Author(s):  
Manel Missaoui ◽  
Sandrine Coste ◽  
Maud Barré ◽  
Anthony Rousseau ◽  
Yaovi Gagou ◽  
...  
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
High Purity ◽  
Average Crystallite Size ◽  
Polyol Process ◽  
Pure Bifeo3 ◽  
Optimum Parameters ◽  
Mössbauer Measurements ◽  
Synthesis Protocol ◽  
Nanostructured Powders

Exclusive and unprecedented interest was accorded in this paper to the synthesis of BiFeO3 nanopowders by the polyol process. The synthesis protocol was explored and adjusted to control the purity and the grain size of the final product. The optimum parameters were carefully established and an average crystallite size of about 40 nm was obtained. XRD and Mössbauer measurements proved the high purity of the synthesized nanostructurated powders and confirmed the persistence of the rhombohedral R3c symmetry. The first studies on the magnetic properties show a noticeable widening of the hysteresis loop despite the remaining cycloidal magnetic structure, promoting the enhancement of the ferromagnetic order and consequently the magnetoelectric coupling compared to micrometric size powders.

Comparative Studies of Ultra Low-κ Porous Silica Films with 2-D Hexagonal and Disordered Pore Structures

2004 ◽  
Vol 812 ◽  
Author(s):  
Nobutoshi Fujii ◽  
Kazuhiro Yamada ◽  
Yoshiaki Oku ◽  
Nobuhiro Hata ◽  
Yutaka Seino ◽  
...  
Keyword(s):  
Pore Structure ◽  
Nonionic Surfactants ◽  
Porous Silica ◽  
Silica Film ◽  
X Ray Diffraction ◽  
Silica Films ◽  
X Ray ◽  
X Ray Scattering ◽  
Porous Silica Film ◽  
Diffraction Peaks

AbstractPeriodic 2-dimensional (2-D) hexagonal and the disordered pore structure silica films have been developed using nonionic surfactants as the templates. The pore structure was controlled by the static electrical interaction between the micelle of the surfactant and the silica oligomer. No X-ray diffraction peaks were observed for the disordered mesoporous silica films, while the pore diameters of 2.0-4.0 nm could be measured by small angle X-ray scattering spectroscopy. By comparing the properties of the 2-D hexagonal and the disordered porous silica films which have the same porosity, it is found that the disordered porous silica film has advantages in terms of the dielectric constant and Young's modulus as well as the hardness. The disordered porous silica film is more suitable for the interlayer dielectrics for ULSI.

Influence of Preparation Temperature on Performance of Ce1-xPrxO2 Ultrafine Powder Prepared by a Microemulsion Process

2008 ◽  
Vol 368-372 ◽  
pp. 784-786 ◽  
Author(s):  
Jun Yang ◽  
Zhen Feng Zhu ◽  
Jing Ping Li
Keyword(s):  
Crystallite Size ◽  
Calcination Temperature ◽  
Average Crystallite Size ◽  
Ultrafine Powder ◽  
Microemulsion System ◽  
Sem Images ◽  
Preparation Temperature ◽  
Annealing Conditions

A W/O microemulsion system composed of OP-emolsifier / water / cyclohexane / 1-Pentanol was adopted to prepare ultrafine Ce1-xPrxO2 powder via the reaction between the precipitants of cerium and praseodymium salt solved in the nano reactors. The influence of the annealing conditions on the preparation of Ce1-xPrxO2 powder was investigated. It was shown that, with the increase of calcination temperature from 400 °C to 800 °C, the average crystallite size of the particles increases from 9.5 nm to 25.8 nm. FE-SEM images showed that shape of the particles is layered and sheet-like.

The crystal chemistry of the uranyl carbonate mineral grimselite, (K, Na)3Na[(UO2)(CO3)3](H2O), from Jáchymov, Czech Republic

2012 ◽  
Vol 76 (3) ◽  
pp. 443-453 ◽  
Author(s):  
J. Plášil ◽  
K. Fejfarová ◽  
R. Skála ◽  
R. Škoda ◽  
N. Meisser ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Czech Republic ◽  
Structure Refinement ◽  
Unit Cell ◽  
Carbonate Mineral ◽  
X Ray Diffraction ◽  
The Czech Republic ◽  
Cell Parameters ◽  
Uranyl Carbonate ◽  
Diffraction Peaks

AbstractTwo crystals of the uranyl carbonate mineral grimselite, ideally K3Na[(UO2)(CO3)3](H2O), from Jáchymov in the Czech Republic were studied by single-crystal X-ray diffraction and electron-probe microanalysis. One crystal has considerably more Na than the ideal chemical composition due to substitution of Na into KO8 polyhedra; the composition of the other crystal is nearer to ideal, and similar to synthetic grimselite. The presence of Na atoms in KO8 polyhedra, which are located in channels in the crystal structure, reduces their volume, and as a result the unit-cell volume also decreases. Structure refinement shows that the formula for the sample with the anomalously high Na content is (K2.43Na0.57)Σ3.00Na[(UO2)(CO3)3](H2O). The unit-cell parameters, refined in space group P2c, are a = 9.2507(1), c = 8.1788(1) Å, V = 606.14(3) Å3 and Z = 2. The crystal structure was refined to R1 = 0.0082 and wR1 = 0.0185 with a GOF = 1.33, based on 626 observed diffraction peaks [Iobs>3σ(I)].

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