Chemical gelation of cerium (III)-doped yttrium aluminium oxide spherical particles

2006 ◽  
Vol 21 (10) ◽  
pp. 2510-2515 ◽  
Author(s):  
L.T. Su ◽  
A.I.Y. Tok ◽  
F.Y.C. Boey ◽  
J.L. Woodhead
Keyword(s):  
Electron Microscopy ◽  
Spherical Particles ◽  
Processing Temperature ◽  
X Ray Diffraction ◽  
Direct Crystallization ◽  
Yttrium Aluminum Oxide ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Crystallite Sizes ◽  
Reaction Processes

A novel low-temperature (900 °C) chemical gelation method was developed to synthesize spherical and nonagglomerated Ce3+-doped yttrium aluminum oxide particles (YAG:Ce3+). This represents a process with a much lower processing temperature than current solid-state reaction processes (1400 °C). Characterization of the particles via x-ray diffraction and thermoanalytical methods showed that calcination at 900 °C for 2 h allowed direct crystallization from the amorphous phase, inferring that this process allows homogeneous mixing and increased precursor reactivity. Electron microscopy results showed that the spherical particles (∼100 to ∼3 μm) were the flocks of crystallites. The crystallite sizes (Rietveld refinement) grew linearly from 27 nm (900 °C) to 114 nm (1300 °C). The surface area decreased from 40 m2/g (900 °C) to 5 m2/g (1300 °C) because of the coagulating and growing of crystallites to bigger grains at 1300 °C. Single-crystal nanoparticles (around 100 nm) were obtained with this process and their atomic structures were revealed via high-resolution transmission electron microscopy.

Effect of Synthesis Temperature on Particles Size and Morphology of Zirconium Oxide Nanoparticle

2017 ◽  
Vol 50 ◽  
pp. 18-31 ◽  
Author(s):  
Rudzani Sigwadi ◽  
Simon Dhlamini ◽  
Touhami Mokrani ◽  
Patrick Nonjola
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Zirconium Oxide ◽  
Thermo Gravimetric Analysis ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Crystallite Sizes ◽  
Ft Ir

The paper presents the synthesis and investigation of zirconium oxide (ZrO2) nanoparticles that were synthesised by precipitation method with the effects of the temperatures of reaction on the particles size, morphology, crystallite sizes and stability at high temperature. The reaction temperature effect on the particle size, morphology, crystallite sizes and stabilized a higher temperature (tetragonal and cubic) phases was studied. Thermal decomposition, band structure and functional groups were analyzed by Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Thermo-gravimetric analysis (TGA) and Fourier transform infrared (FT-IR). The crystal structure was determined using X-ray diffraction. The morphology and the particle size were studied using (SEM) and (TEM). The shaped particles were confirmed through the SEM analysis. The transmission electron microscopic analysis confirmed the formation of the nanoparticles with the particle size. The FT-IR spectra showed the strong presence of ZrO2 nanoparticles.

Microstructural characteristics and photoluminescence performance of nanograined thermally treated CeO2-TiO2 xerogels

2007 ◽  
Vol 22 (5) ◽  
pp. 1182-1187
Author(s):  
Amita Verma ◽  
A.K. Srivastava ◽  
N. Karar ◽  
Harish Chander ◽  
S.A. Agnihotry
Keyword(s):  
Electron Microscopy ◽  
Crystallite Size ◽  
Sol Gel ◽  
Structural Features ◽  
X Ray Diffraction ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Crystallite Sizes ◽  
Thermally Treated

Nanostructured thermally treated xerogels have been synthesized using a sol-gel process involving cerium (Ce) chloride heptahydrate and titanium (Ti) propoxide mixed in different Ce:Ti molar ratios. Structural features of the xerogels have been correlated with their photoluminescence (PL) response. The crystallite sizes in the samples lie in the nanorange. The x-ray diffraction and transmission electron microscopy results have confirmed the coexistence of CeO2 and TiO2 nanocrystallites in these xerogels. In general, a decrease in the CeO2 crystallite size and an increase in the TiO2 crystallite size are observed in the xerogels as a function of Ti content. Scanning electron microscopy results have evidenced the evolution of ordered structure in the xerogels as a function of TiO2 content. Although both of the phases (CeO2 and TiO2) have exhibited PL in ultraviolet and visible regions, the major luminescence contribution has been made by the CeO2 phase. The largest sized CeO2 crystallites in 1:1 thermally treated xerogel have led to its highest PL response. PL emission in the xerogels is assigned to their nanocrystalline nature and oxygen vacancy-related defects.

Study of the Surface Morphology and the Microstructure of PAN-Based Carbon Fibers

2011 ◽  
Vol 239-242 ◽  
pp. 1279-1282
Author(s):  
Xue Jun Zhang ◽  
Zan Han ◽  
Yan Hong Tian ◽  
Yan Feng Yang
Keyword(s):  
Electron Microscopy ◽  
Carbon Fibers ◽  
Interlayer Spacing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Graphite Crystallite ◽  
Crystallite Sizes ◽  
Degree Of Graphitization ◽  
Better Than

The microstructure of two kinds of self-made PAN-based high-modulus carbon fibers (HMCF-1, HMCF-2) was studied by scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), and was compared with that of T800 and M55J. The correlation of XRD and HRTEM in terms of graphite crystallite sizes and interlayer spacing of graphite layer was also investigated. The results show that the diameters of T800, HMCF-1 and HMCF-2 are almost the same (~5.20μm) and all of them are lager than that of M55J (~4.86μm). The crystal sizes and the degree of graphitization are in the order of HMCF-2>HMCF-1>M55J>T800, while the regularity of the lattice fringes of HMCF-2 is better than those of others.

Nanostructured CaWO4, CaWO4:Eu3+ and CaWO4:Tb3+ Particles: Sonochemical Synthesis and Luminescent Properties

2008 ◽  
Vol 8 (3) ◽  
pp. 1183-1190 ◽  
Author(s):  
Chunxia Li ◽  
Cuikun Lin ◽  
Xiaoming Liu ◽  
Jun Lin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Field Emission ◽  
Spherical Particles ◽  
X Ray Diffraction ◽  
Blue Emission Band ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Nanostructured CaWO4, CaWO4:Eu3+, and CaWO4:Tb3+ phosphor particles were synthesized via a facile sonochemical route. X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, low voltage cathodoluminescence spectra, and photoluminescence lifetimes were used to characterize the as-obtained samples. The X-ray diffraction results indicate that the samples are well crystallized with the scheelite structure of CaWO4. The transmission electron microscopy and field emission scanning electron microscopy images illustrate that the powders consist of spherical particles with sizes from 120 to 160 nm, which are the aggregates of even smaller nanoparticles ranging from 10 to 20 nm. Under UV light or electron beam excitation, the CaWO4 powder exhibited a blue emission band with a maximum at 430 nm originating from the WO2−4 groups, while the CaWO4:Eu3+ powder showed red emission dominated by 613 nm ascribed to the 5D0 → 7F2 of Eu3+, and the CaWO4:Tb3+ powders showed emission at 544 nm, ascribed to the 5D4 → 7F5 transition of Tb3+. The PL excitation and emission spectra suggest that the energy is transferred from WO2−4 to Eu3+CaWO4:Eu3+ and to Tb3+ in CaWO4:Tb3+. Moreover, the energy transfer from WO2−4 to Tb3+ in CaWO4:Tb3+ is more efficient than that from WO2−4 to Eu3+ in CaWO4:Eu3+. This novel and efficient pathway could open new opportunities for further investigating the novel properties of tungstate materials.

Study of the Reproducibility of Ni-Zn Nanoferrite Obtained by Combustion Reaction

2014 ◽  
Vol 775-776 ◽  
pp. 415-420 ◽  
Author(s):  
Débora Albuquerque Vieira ◽  
Verônica Cristina Souza Diniz ◽  
Daniel R. Cornejo ◽  
Ana Cristina Figueiredo de Melo Costa ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Electron Microscopy ◽  
Combustion Synthesis ◽  
Soft Magnetic Materials ◽  
Spherical Particles ◽  
Magnetic Characteristics ◽  
X Ray Diffraction ◽  
Soft Magnetic ◽  
X Ray ◽  
Crystallite Sizes ◽  
Scanning Electron

This work involved a study of the reproducibility of the process of combustion synthesis to produce Ni-Zn ferrites. The structural, morphological and magnetic characteristics of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetometry using an alternating gradient magnetometer (AGM). The XRD diffractograms of the samples indicated that they are monophasic, crystalline, with crystallite sizes ranging from 21 to 38 nm, and have a homogeneous morphology consisting of agglomerates of spherical particles. The samples behaved as soft magnetic materials, with magnetization levels ranging from 37 to 47 emug-1. The combustion synthesis was found to be efficient in producing Ni-Zn nanoferrites, yielding reproducible results.

scholarly journals Effect of Growth Temperature and Time on Morphology and Gas Sensitivity of Cu2O/Cu Microstructures

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Ling Wu ◽  
Lun Zhang ◽  
Zhipeng Xun ◽  
Guili Yu ◽  
Liwei Shi
Keyword(s):  
Electron Microscopy ◽  
Gas Sensors ◽  
Gas Sensing ◽  
Spherical Particles ◽  
X Ray Diffraction ◽  
Gas Sensitivity ◽  
X Ray ◽  
Transmission Electron ◽  
Wide Range ◽  
Gas Response

A facile hydrothermal synthesis with CuSO4as the copper source was used to prepare micro/nano-Cu2O. The obtained samples have been characterized by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). With increasing the reaction temperature and time, the final products were successively Cu2O octahedron microcrystals, Cu2O/Cu composite particles, and a wide range of Cu spherical particles. The gas sensitivity of products towards ethanol and acetone gases was studied. The results showed that sensors prepared with Cu2O/Cu composites synthesized at 65°C for 15 min exhibited optimal gas sensitivity. The gas sensing mechanism and the effect of Cu in the enhanced gas response were also elaborated. The excellent gas sensitivity indicates that Cu2O/Cu composites have potential application as gas sensors.

scholarly journals Relationship between Crystal Shape, Photoluminescence, and Local Structure inSrTiO3Synthesized by Microwave-Assisted Hydrothermal Method

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Luís F. da Silva ◽  
Waldir Avansi ◽  
Mário L. Moreira ◽  
Alexandre Mesquita ◽  
Lauro J. Q. Maia ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Method ◽  
Spherical Particles ◽  
Lower Amount ◽  
X Ray Diffraction ◽  
Edge Structure ◽  
X Ray ◽  
Microwave Assisted ◽  
Transmission Electron ◽  
X Ray Absorption

This paper describes the effect of using different titanium precursors on the synthesis and physical properties of SrTiO3powders obtained by microwave-assisted hydrothermal method. X-ray diffraction measurements, X-ray absorption near-edge structure (XANES) spectroscopy, field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HRTEM) were carried out to investigate the structural and optical properties of the SrTiO3spherical and cubelike-shaped particles. The appropriate choice of the titanium precursor allowed the control of morphological and photoluminescence (PL) properties of SrTiO3compound. The PL emission was more intense in SrTiO3samples composed of spherelike particles. This behavior was attributed to the existence of a lower amount of defects due to the uniformity of the spherical particles.

scholarly journals The X-ray, Raman and TEM Signatures of Cellulose-Derived Carbons Explained

2022 ◽  
Vol 8 (1) ◽  
pp. 4
Author(s):  
Petros Kasaira Mubari ◽  
Théotime Beguerie ◽  
Marc Monthioux ◽  
Elsa Weiss-Hortala ◽  
Ange Nzihou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Raman Spectroscopy ◽  
Structural Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Characterization Techniques ◽  
Transmission Electron ◽  
Crystallite Sizes ◽  
Xrd Patterns ◽  
Average Size

Structural properties of carbonized cellulose were explored to conjugate the outcomes from various characterization techniques, namely X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy. All these techniques have evidenced the formation of graphene stacks with a size distribution. Cellulose carbonized at 1000 and 1800 °C at a heating rate of 2 °C/min showed meaningful differences in Raman spectroscopy, whereas in XRD, the differences were not well pronounced, which implies that the crystallite sizes calculated by each technique have different significations. In the XRD patterns, the origin of a specific feature at a low scattering angle commonly reported in the literature but poorly explained so far, was identified. The different approaches used in this study were congruous in explaining the observations that were made on the cellulose-derived carbon samples. The remnants of the basic structural unit (BSU) are developed during primary carbonization. Small graphene-based crystallites inherited from the BSUs, which formerly developed during primary carbonization, were found to coexist with larger ones. Even if the three techniques give information on the average size of graphenic domains, they do not see the same characteristics of the domains; hence, they are not identical, nor contradictory but complementary. The arguments developed in the work to explain which characteristics are deduced from the signal obtained by each of the three characterization techniques relate to physics phenomena; hence, they are quite general and, therefore, are valid for all kind of graphenic materials.

Preparation of nanocrystalline titania powder via aerosol pyrolysis of titanium tetrabutoxide

1999 ◽  
Vol 14 (10) ◽  
pp. 3938-3948 ◽  
Author(s):  
P. P. Ahonen ◽  
E. I. Kauppinen ◽  
J. C. Joubert ◽  
J. L. Deschanvres ◽  
G. Van Tendeloo
Keyword(s):  
Electron Microscopy ◽  
Ultrafine Particles ◽  
Anatase Phase ◽  
Spherical Particles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Raman And Infrared Spectroscopy ◽  
Nanocrystalline Titanium ◽  
Titanium Tetrabutoxide

Nanocrystalline titanium dioxide was prepared via aerosol pyrolysis of titanium alkoxide precursor at 200–580 °C in air and in nitrogen atmospheres. Powders were characterized by x-ray diffraction, thermogravimetric analysis, Brunauer–Emmett–Teller analysis, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, x-ray fluorescence, Raman and infrared spectroscopy, and Berner-type low-pressure impactor. The anatase phase transition was initiated at 500 °C in nitrogen and at 580 °C in air. Under other conditions amorphous powders were observed and transformed to nanocrystalline TiO2 via thermal postannealing. In air, smooth and spherical particles with 2–4-μm diameter were formed with an as-expected tendency to convert to rutile in the thermal postannealings. In nitrogen, a fraction of the titanium tetrabutoxide precursor evaporated and formed ultrafine particles via the gas-to-particle conversion. At 500 °C thermally stable anatase phase was formed in nitrogen. A specific surface area as high as 280 m2 g−1 was observed for an as-prepared powder.

Porous LaFeO3 with High Response to Acetone Synthesized from Biotemplates

2013 ◽  
Vol 575-576 ◽  
pp. 20-23 ◽  
Author(s):  
Yu Zhen Ma ◽  
Peng Song ◽  
Qi Wang
Keyword(s):  
Electron Microscopy ◽  
Gas Sensing ◽  
Perovskite Phase ◽  
Spherical Particles ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Xrd Patterns ◽  
Microscopy Characterization

Biomorphic porous LaFeO3 samples were prepared using aspen leaves as biotemplates. The structural and microscopy characterization has been carried out with X-ray diffraction, scanning electron microscopy and transmission electron microscopy. XRD patterns confirm thatLaFeO3 shows perovskite phase with orthorhombic structure. The results of SEM and TEM revealed that the the obtained LaFeO3 with hollow and porous structure. And the porous LaFeO3 is composed of spherical particles with the size of 50-80 nm The gas sensing performance of as-prepared LaFeO3 nanocrystlas was investigated. It is found that porous LaFeO3 calcined at 700°C exhibit good sensitivity to acetone with rapid response.

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