scholarly journals Hexagonal Nanocrystals into AlGaN Powders Obtained via Pyrolysis from an Organometallic Compound

2019 ◽  
Vol 4 (3) ◽  
pp. 68-72
Author(s):  
Ana Maria Herrera ◽  
Godofredo García ◽  
Erick Gastellóu ◽  
Fabiola Nieto ◽  
Rafael García ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Organometallic Compound ◽  
Crystal Size ◽  
Average Crystal Size ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Micrographs ◽  
Transmission Electron ◽  
Visible Spectra ◽  
Diffraction Patterns ◽  
The Right

Hexagonal nanocrystals into Al0.2Ga0.8N and Al0.6Ga0.4N powders via pyrolysis from an organometallic compound, followed by a nitridation process in ammonia flow at 1000 °C for two hours were obtained. X-ray diffraction patterns demonstrated a shift towards greater angles to the right for the AlGaN powders with respect to GaN powders, this shift could indicate the formation of the AlGaN powders. Scanning electron microscopy micrographs showed the obtaining from semi-plates of porous appearance for the Al0.2Ga0.8N powders until well-defined plates for the Al0.6Ga0.4N powders. High resolution transmission electron microscopy micrographs demonstrated the presence of hexagonal nanocrystals into Al0.2Ga0.8N powders with an average crystal size of 10.3 nm, while that for the Al0.6Ga0.4N powders an average crystal size of 9.7 nm was observed. UV-visible spectra showed a transmittance cut-off for the Al0.2Ga0.8N powders of 3.71 eV (334.2 nm) and a transmittance cut-off of 4.53 eV (273.7 nm) for the Al0.6Ga0.4N powders.

scholarly journals Synthesis of Novel YbxSb2 − xTe3Hexagonal Nanoplates: Investigation of Their Physical, Structural, and Photocatalytic Properties

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Younes Hanifehpour ◽  
Sang Woo Joo
Keyword(s):  
Electron Microscopy ◽  
Emission Spectra ◽  
Hydrothermal Condition ◽  
X Ray Diffraction ◽  
Dopant Content ◽  
Transmission Electron ◽  
Intensity Changes ◽  
Diffraction Patterns ◽  
Green Solution ◽  
Microscopy Images

Yb-doped Sb2Te3nanomaterials were synthesized by a coreduction method in hydrothermal condition. Powder X-ray diffraction patterns indicate that theYbxSb2−xTe3crystals (x=0.00–0.05) are isostructural with Sb2Te3. The cell parameteradecreases forYbxSb2−xTe3compounds upon increasing the dopant content (x), whilecincreases. Scanning electron microscopy and transmission electron microscopy images show that doping of Yb3+ions in the lattice of Sb2Te3produces different morphology. The electrical conductivity of Yb-doped Sb2Te3is higher than the pure Sb2Te3and increases with temperature. By increasing concentration of the Yb3+ions, the absorption spectrum of Sb2Te3shows red shifts and some intensity changes. In addition to the characteristic red emission peaks of Sb2Te3, emission spectra of doped materials show other emission bands originating fromf-ftransitions of the Yb3+ions. The photocatalytic performance of as-synthesized nanoparticles was investigated towards the decolorization of Malachite Green solution under visible light irradiation.

Microstructural properties and formation mechanisms of GaN nanorods grown on Al2O3 (0001) substrates

2009 ◽  
Vol 24 (8) ◽  
pp. 2476-2482
Author(s):  
Kyu H. Lee ◽  
Jeong Y. Lee ◽  
Y.H. Kwon ◽  
Tae W. Kang ◽  
Dong H. Kim ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydride Vapor Phase Epitaxy ◽  
Formation Mechanisms ◽  
Gas Mixing ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Increasing Temperature ◽  
Microscopy Images

X-ray diffraction patterns, scanning electron microscopy images, and transmission electron microscopy images showed that one-dimensional GaN nanorods with [0001]-oriented single-crystalline wurtzite structures were grown on Al2O3 (0001) substrates by hydride vapor-phase epitaxy without a catalyst. The tip morphology of the GaN nanorods became flat with increasing temperature difference between the gas mixing and the substrate zones. The gas mixing temperature significantly affected the formation of the nanorods, and the substrate temperature influenced the morphology and the strain of the GaN nanorods near the GaN/Al2O3 heterointerface. The strain and the stress existing in the GaN layer near the heterointerface were decreased with increasing growth rate. The formation mechanisms of the GaN nanorods grown on the Al2O3 (0001) substrates are described on the basis of the experimental results.

Preparation and Application of Carboxyl-Functioned Magnetic Nanoparticles for Arylsulfatase Immobilization

2016 ◽  
Vol 13 (10) ◽  
pp. 7408-7415
Author(s):  
Yongxing Li ◽  
Qiong Xiao ◽  
Qin Yin ◽  
Hui Ni ◽  
Yanbing Zhu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Magnetic Nanoparticles ◽  
Vibrating Sample Magnetometry ◽  
X Ray Diffraction ◽  
Sulfate Ester ◽  
Xrd Pattern ◽  
X Ray ◽  
Transmission Electron ◽  
Mean Diameter ◽  
Diffraction Patterns

Arylsulfatase, one of a few enzymes that can enhance the gelling strength of agar by cleaving the sulfate ester bonds in agar, was covalently immobilized with carboxyl functioned magnetic nanoparticles (CMNPs). The resultant CMNPs and immobilized arylsulfatase were characterized by transmission electron microscopy (TEM), Dynamic Light scattering (DLS), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and thermogravimetric analysis (TGA). The TEM result indicated that the CMNPs and immobilized arylsulfatase had a similar mean particle size of 10 nm. The arylsulfatase-CMNPs had a mean diameter of 1200 nm in aqueous solution determined by the DLS, which was much bigger than the CMNPs (433.6 nm). The different sizes demonstrated that the arylsulfatase was coated on CMNPs successfully. XRD showed that diffraction patterns of the CMNPs and arylsulfatase-CMNPs were close to the standard XRD pattern of Fe3O4. Saturation magnetizations were 52.1 emu/g for carriers and 47.9 emu/g for immobilized arylsulfatase, which indicated that the particles had superparamagnetic characteristics. The TGA revealed that the amount of arylsulfatase bound to the surface of CMNPs was 5.65%. The arylsulfatase exhibited better thermal stability and reusability after immobilization, the immobilized arylsulfatase can retain more than 50% enzyme activity up to the 9th cycle.

Synthesis of Ni-Mo-W Sulfide Nanorods as Catalyst for Hydrodesulfurization of Dibenzothiophene

2008 ◽  
Vol 8 (12) ◽  
pp. 6406-6413 ◽  
Author(s):  
F. Paraguay-Delgado ◽  
R. García-Alamilla ◽  
J. A. Lumbreras ◽  
E. Cizniega ◽  
G. Alonso-Núñez
Keyword(s):  
Electron Microscopy ◽  
Physical Adsorption ◽  
Atomic Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxide Precursor ◽  
Transmission Electron ◽  
Adsorption Of Nitrogen ◽  
Diffraction Patterns ◽  
Scanning Electron

Two trimetallic sulfurs, MoWNiS and MoWSNi, were synthesized to be used as a catalyst in hydrodesulfurization reactions. The mixed oxide mesoporous nanostructured MoO3-WO3 with an Mo:W atomic ratio of 1:1 was used as the precursor. The first catalyst was prepared by impregnating nickel in the oxide precursor and then subsequent sulfiding with an H2S/H2 mix at 400 °C for 2 hours. The second catalyst was prepared by sulfiding the precursor and then impregnating the nickel, and finally reducing the material with a H2/N2 at 350 °C. In both catalysts the Mo:W:Ni atomic ratio was maintained at 1:1:0.5. The materials obtained were characterized by physical adsorption of nitrogen, X-ray diffraction, scanning electron microscopy, transmission electron microscopy. Furthermore, the materials obtained were evaluated by a dibenzothiophene hydrodesulfuration reaction. The diffraction patterns show that both materials are polycrystalline and mainly of MoS2 and WS2 phases.

SONOCHEMICAL SYNTHESIS OF PbWO4 NANOPARTICLES

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2734-2739 ◽  
Author(s):  
JUN GENG ◽  
JIAN-RONG ZHANG ◽  
JIAN-MIN HONG ◽  
JUN-JIE ZHU
Keyword(s):  
Crystal Size ◽  
Sodium Tungstate ◽  
Ambient Air ◽  
Complexing Agents ◽  
Average Crystal Size ◽  
X Ray Diffraction ◽  
Lead Tungstate ◽  
Sonochemical Synthesis ◽  
X Ray ◽  
Transmission Electron

Lead tungstate ( PbWO 4) an important inorganic scintillator, was synthesized via a mild sonochemical route from an aqueous solution of lead acetate and sodium tungstate in the presence of complexing agents under ambient air. X-ray diffraction (XRD), transmission electron microscope (TEM) and photoluminescence (PL) were used to characterize the products. The as-prepared PbWO 4 nanocrystals crystallize in a tetragonal structure and have an average crystal size of ca. 10 nm.

Paper 24: Dry Wear of Steel as Revealed by Electron Microscopy and X-Ray Diffraction

1967 ◽  
Vol 182 (14) ◽  
pp. 201-213
Author(s):  
T. F. J. Quinn
Keyword(s):  
Electron Microscopy ◽  
Medium Carbon Steel ◽  
X Ray Diffraction ◽  
Medium Carbon ◽  
X Ray ◽  
Ambient Temperatures ◽  
Transmission Electron ◽  
Steel Aisi ◽  
Diffraction Patterns ◽  
Fatigue Failures

Low-alloy, medium-carbon steel (AISI 4340) pins have been worn against discs of the same material at various loads under unlubricated (‘dry’) sliding conditions. Shadowed carbon replicas have been obtained from the surfaces of selected pins and discs. Transmission electron microscopy of these replicas revealed several interesting features, the most interesting being the presence of reproducible crack systems occurring in those parts of the surface at which the wear is taking place. These cracks are very similar to those obtained in fatigue failures. X-ray diffraction patterns were also obtained from these specimens, and from the corresponding wear debris. These indicated that oxidation had occurred at temperatures considerably in excess of the measured ambient temperatures. The various topographic and crystallographic features revealed by the electron microscopy and X-ray diffraction techniques are discussed in relation to a possible mechanism of ‘dry’ wear

scholarly journals Investigation of Lithiated Carbons by Transmission Electron Microscopy and X-Ray Diffraction Analysis

1998 ◽  
Vol 548 ◽  
Author(s):  
T. D. Tran ◽  
X. Y. Song ◽  
K. Kinoshita
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Carbon Black ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Lattice Image ◽  
X Ray ◽  
Storage Mechanism ◽  
Transmission Electron ◽  
Diffraction Patterns

ABSTRACTThe microstructures of lithiated synthetic graphite and carbon black were studied by high- resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. Information about the crystal structure of carbon containing various Li compositions can provide useful insights to our understanding of the Li storage mechanism in carbonaceous materials. Samples with compositions of Li0.93C6or Li0.45C6 were found to contain both stage-one and stage-two compounds. These observations are consistent with XRD data. The changes in sample microstructure as the results of lithiation and exposure to electron irradiation were observed by TEM and recorded over several minutes in the microscope environment. Selected area electron diffraction patterns indicated that the lithiated samples quickly changed composition to LiC 24, which appeared to dominate during the brief analysis period. The layer planes in the lattice image of a disordered carbon black after Li insertion are poorly defined, and changes in the microstructure of these lithiated carbons was not readily apparent. Observations on these lithium intercalation compounds as well as the limitation of the experimental procedure will be presented.

The Formation of New Periodicities after N-Implantation in 4H- and 6H-SiC Samples

2013 ◽  
Vol 740-742 ◽  
pp. 447-450
Author(s):  
Konstantinos Zekentes ◽  
Katerina Tsagaraki ◽  
Aikaterini Breza ◽  
Nikolaos Frangis
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Periodic Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Nitrogen Ions ◽  
Diffraction Patterns ◽  
Post Implantation

The purpose of the present study is to study the crystal periodicities that appear in 4H- and 6H-SiC material after the implantation with nitrogen and prior to post-implantation annealing. High Resolution X-Ray diffraction (HRXRD) and Transmission Electron Microscopy (TEM) have been employed towards this purpose. Extra peaks at smaller, than the main (00n) peak, diffraction angles in HRXRD scans and extra spots in the electron diffraction patterns have been observed due to the presence of these periodicities. Higher lattice constant periodic structures are apparently formed from the implanted nitrogen ions located at interstitial sites and disappear after the annealing and the resulting positioning of nitrogen atoms in substitutional sites.

Nanostructural characterizations of hydrogen-permselective Si–Co–O membranes by transmission electron microscopy

2009 ◽  
Vol 24 (2) ◽  
pp. 372-378 ◽  
Author(s):  
Shinji Fujisaki ◽  
Koji Hataya ◽  
Tomohiro Saito ◽  
Shigeo Arai ◽  
Yuji Iwamoto ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Gas Permeation ◽  
Hydrogen Gas ◽  
Transmission Electron Microscopy Micrographs ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Diffraction Patterns ◽  
Permeation Properties

Nanostructural characterizations of liquid metal–organic precursors-derived cobalt-doped amorphous silica (Si–Co–O) membranes supported on a mesoporous anodic alumina capillary (MAAC) tube were performed to study their unique high-temperature hydrogen gas permeation properties. Cross-sectional scanning transmission electron microscopy images and selected-area electron diffraction patterns indicated that the metal cobalt and the different oxidation states of cobalt oxides (CoO and Co3O4) nanocrystallites having a size range of 5–20 nm were in situ formed in the mesopore channels of the MAAC tube. In addition, high-resolution transmission electron microscopy micrographs and electron energy loss spectroscopy elemental mapping images indicated that the highly dense Co-doped amorphous Si–O formed within the mesopore channels of the MAAC tube. These nanostructural features could contribute to the hydrogen-selective permeation properties observed for the membranes.

Substructure Measurements by Statistical Fluctuations in X-Ray Diffraction Intensity

1965 ◽  
Vol 9 ◽  
pp. 74-90 ◽  
Author(s):  
E. F. Sturcken ◽  
W. E. Gettys ◽  
E. M. Bohn
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
X Ray Diffraction ◽  
Diffraction Intensity ◽  
Laue Diffraction ◽  
X Ray ◽  
Statistical Fluctuations ◽  
Transmission Electron ◽  
Diffraction Patterns

AbstractThe substructures of a bet a-quenched and a recrystallized form of high-purity uranium were measured by a method based on statistical fluctuations in X-ray diffraction intensity. For these measurements, Warren's statistical equation for determining grain size was modified to make the equation applicable to materials with high absorption coefficients or moderate-to-large grain size ( > 20 microns) or both, since many metals fall into this category, and to allow for defocusing of the X-ray beam which occurs as a natural consequence of the experiment.The beta-quenched uranium was found to have numerous subgrains with a range of misorientation angles that was smaller and larger than the limits of the X-ray measurements (Ω = 10−4 to 10−2 steradians). The presence of the large subgrains was corroborated by optical microscopy. The presence of very small subgrains was corroborated by transmission electron microscopy which showed 0.1- to 1-micron subgrains relatively free of dislocations bounded by dense dislocation networks, and by micro Laue diffraction patterns (30-micron beam diameter) which showed partial rings similar to a powder pattern.The recrystallized uranium had no misorientation within the grains greater than 5.5 × 10−3 steradians. In contrast to the beta-quenched case, no subgrains were found either by transmission electron microscopy (TEM) or micro Laue diffraction patterns. The TEM micrographs showed a uniform distribution of dislocation networks. Since no other substructural elements were observed, the dislocations are believed to be the cause of the misorientation within the grains for solid angles of less than 5 × 10−3 steradiflns.These preliminary experiments show that the statistical method may be used in conjunction with transmission electron microscopy and micro Laue diffraction for the study of substructure. The statistical method gives quantitative data on “bulk” specimens that can be given a meaningful interpretation with the aid of the other techniques.

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