scholarly journals Structural Changes of Mo/ZSM-5 Catalysts During the Methane Dehydroaromatization

2009 ◽  
Vol 12 (1) ◽  
pp. 9 ◽  
Author(s):  
Z.R. Ismagilov ◽  
E.V. Matus ◽  
I.Z. Ismagilov ◽  
M.A. Kerzhentsev ◽  
V.I. Zailovskii ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Atomic Ratio ◽  
X Ray ◽  
Reducing Atmosphere ◽  
Structure Changes ◽  
Transmission Electron ◽  
Methane Dehydroaromatization ◽  
Naoh Treatment ◽  
Mo Content

<p>The structure changes of Mo/ZSM-5 catalysts with different Mo content (2 and 10 wt. % Mo) and Si/Al atomic ratio (17, 30 and 45) during the methane dehydroaromatization have been investigated by X-ray powder diffractometry, N<sub>2</sub> adsorption and transmission electron microscopy. The treatment of Mo/ZSM-5 catalysts in reducing atmosphere (CH<sub>4</sub> or H<sub>2</sub>) at about 700 °C promotes development of mesoporous system. The pores are open to the exterior of the zeolite grain and have an entrance diameter of ~ 4-10 nm. It is proposed that mesopore formation in Mo/ZSM-5 catalyst is connected with the dealumination of zeolite. The mesopore formation in the parent H-ZSM-5 zeolite by NaOH treatment does not improve the activity of /ZSM-5 catalyst.</p>

Size dependent behavior of Fe3O4crystals during electrochemical (de)lithiation: an in situ X-ray diffraction, ex situ X-ray absorption spectroscopy, transmission electron microscopy and theoretical investigation

2017 ◽  
Vol 19 (31) ◽  
pp. 20867-20880 ◽  
Author(s):  
David C. Bock ◽  
Christopher J. Pelliccione ◽  
Wei Zhang ◽  
Janis Timoshenko ◽  
K. W. Knehr ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
X Ray ◽  
Size Dependent ◽  
Transmission Electron ◽  
Dependent Behavior ◽  
X Ray Absorption

Crystal and atomic structural changes of Fe3O4upon electrochemical (de)lithiation were determined.

The structural changes of polycrystalline film C60/C70: Ni caused by Ni diffusion

1996 ◽  
Vol 11 (12) ◽  
pp. 3146-3151 ◽  
Author(s):  
E. Czerwosz ◽  
P. Byszewski ◽  
R. Diduszko ◽  
H. Wronka ◽  
P. Dluźewski ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
Structural Changes ◽  
Thermal Conditions ◽  
Vacuum Deposition ◽  
X Ray Diffraction ◽  
Polycrystalline Structure ◽  
X Ray ◽  
Transmission Electron

C60/C70: Ni films with 1.5 wt. % Ni concentration obtained by vacuum deposition under different thermal conditions have been investigated. The structural changes of the layers were investigated by transmission electron microscopy, electron and x-ray diffraction, and Raman spectroscopy. The polycrystalline structure was detected for the layers grown at approximately 450 K on the substrate. At elevated temperature and maintained temperature gradient on the substrate during the process, the changes of the layer's structure and the formation of Ni microcrystals were observed. The Ni microcrystals (5–10 nm in the diameter) and the elongated shapes dimensioned 10 × 150 nm were perceived.

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.

scholarly journals Sol-Gel Derived Eu3+-Doped Gd2Ti2O7Pyrochlore Nanopowders

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Sanja Ćulubrk ◽  
Željka Antić ◽  
Vesna Lojpur ◽  
Milena Marinović-Cincović ◽  
Miroslav D. Dramićanin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Sol Gel ◽  
Pyrochlore Phase ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Sol Gel Synthesis

Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7pyrochlore nanopowders. According to Gd2Ti2O7precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ions concentration shows that Gd2Ti2O7host can accept Eu3+ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (~2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.

Nanostructure evolution and properties of two-phase nc-Ti(C, N)/a-(C, CNx) nanocomposites by high-resolution transmission electron microscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy

2007 ◽  
Vol 22 (9) ◽  
pp. 2460-2469 ◽  
Author(s):  
Y.H. Lu ◽  
Y.G. Shen
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Solid Solution ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
Photoelectron Spectroscopy ◽  
Atomic Ratio ◽  
Two Phase ◽  
X Ray ◽  
Transmission Electron

High-resolution transmission electron microscopy, x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were used to study phase configuration and nanostructure evolutions of Ti–Cx–Ny thin films with different amounts of C incorporation. It was found that the atomic ratio of (C + N)/Ti played a crucial role in phase configuration and nanostructure evolutions as well as mechanical behaviors. When the ratio was less than one unit, a nanocrystalline (nc-) Ti(C, N) solid solution was formed by way of dissolution of C into TiN lattice. When this dissolution reached saturation, precipitation of a small amount of amorphous (a-) C phase along nc-Ti(C, N) grains was followed with more C incorporation. Further increase of C content (up to ∼19 at.% C) made the amorphous phase fully wet nanocrystallites, which resulted in the formation of two-phase nanocomposite thin films with microstructures comprising of ∼5 nm nc-Ti(C,N) crystallites separated by ∼0.5 nm a-(C, CNx) phase. Thicker amorphous walls and smaller sized grains were followed when the C content was further increased, accompanying with the formation of some disorders and defects in nc-grains and amorphous matrices. When the C content was increased to ∼48 at.%, 1–3 nm nanocrystallites with an average size of ∼2 nm were embedded into amorphous matrices. Both microhardness and residual compressive stress values were increased with increase of the atomic ratio in solid solution thin films when the atomic ratio value was less than one unit. Their maximums were obtained at stiochiometry nc-Ti(C,N) solid solution. Enhancement of hardness values was attributed to solid solution effect.

Transmission electron microscopy of hexadecyltrimethylammonium-exchanged smectite

Clay Minerals ◽  
2002 ◽  
Vol 37 (3) ◽  
pp. 465-471 ◽  
Author(s):  
Seung Yeop Lee ◽  
Soo Jin Kim
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Structural Features ◽  
Morphological Features ◽  
X Ray Diffraction ◽  
X Ray ◽  
Morphological Heterogeneity ◽  
Transmission Electron ◽  
Lattice Distortions

AbstractThe morphological and structural changes in smectite caused by hexadecyltrimethylammonium (HDTMA) treatment were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The HDTMA-exchanged smectite shows not only morphological features such as irregular, wavy surface with curled edges, but also structural features such as large d-spacings (20 – 26 Å ) and lattice distortions. The surface morphological heterogeneity is assumed to be related to the inhomogeneous intercalation of HDTMA cations into the interlayer of smectite.

A study of solid-state amorphization in Zr–30 at. % Al by mechanical attrition

1996 ◽  
Vol 11 (3) ◽  
pp. 599-607 ◽  
Author(s):  
A. Biswas ◽  
G. K. Dey ◽  
A. J. Haq ◽  
D. K. Bose ◽  
S. Banerjee
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Morphological Changes ◽  
Phase Evolution ◽  
Atomic Ratio ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Transmission Electron ◽  
Mechanical Attrition ◽  
State Amorphization

Elemental powders of zirconium and aluminum in the atomic ratio of 70:30 were mechanically alloyed in an attritor under argon atmosphere using zirconia balls as milling media. Samples have been taken out for characterization after different durations of milling. The process of alloying and resultant amorphization had been studied using x-ray diffraction (XRD) and transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was carried out to study the morphological changes occurring during repeated cold welding and breaking of the particles. Samples for TEM study were prepared by dispersing the mechanically attrited particles in the nickel foil by electrochemical codeposition. TEM study of the initial stages of milling revealed that localized structural changes precede the bulk amorphization process during mechanical alloying (MA). The sequence of phase evolution has been identified as (i) the formation of nanocrystalline supersaturated solid solution of aluminum in α-zirconium, (ii) amorphization of localized regions at powder interfaces, (iii) ordering of aluminum-rich regions in the metastable Zr3Al (DO19) phase, and, finally, (iv) bulk amorphization of the powders.

Improved visible-light photocatalytic activity of sodium tantalum oxide via biomass-derived silk fibroin doping

2018 ◽  
Vol 89 (7) ◽  
pp. 1332-1339
Author(s):  
Yehua Sun ◽  
Yuzhuo Luo ◽  
Yaofeng Zhu ◽  
Yaqin Fu
Keyword(s):  
Electron Microscopy ◽  
Photocatalytic Activity ◽  
Visible Light ◽  
Silk Fibroin ◽  
Photoelectron Spectroscopy ◽  
Structural Changes ◽  
Diffuse Reflectance Spectroscopy ◽  
Hydrothermal Process ◽  
X Ray ◽  
Transmission Electron

Biomass-derived silk fibroin (SF)-doped NaTaO3 catalysts were successfully synthesized by a simple hydrothermal process using SF as the dopant. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) analyses. The samples were tested as photocatalysts in the degradation of methylene blue under UV and visible light. XRD results showed the monoclinic structure of NaTaO3 lacking significant structural changes after anion doping. SEM and TEM images revealed the nanocubic morphology of the samples, the crystal particle sizes of which were about 100–300 nm. The XPS spectrum showed the peak of Ta4p3&N1s, indicating the combination of N and Ta. The UV-vis DRS results of the samples revealed a cut-off edge that red shifted from 315 nm of the pure NaTaO3 to 324 nm of the SF-doped counterpart. SF doping helped narrow the band gap and rendered the prepared sample sensitive to visible light. Under UV and visible-light irradiation, SF-doped NaTaO3 exhibited higher photocatalytic activity than that the undoped compound. SF-doped NaTaO3 samples also exhibited excellent stability during the recycling photocatalytic process.

Transmission electron microscopy and x-ray structural investigation of La0.7Ca0.3MnO3 thin films

1998 ◽  
Vol 13 (8) ◽  
pp. 2161-2169 ◽  
Author(s):  
Y. H. Li ◽  
K. A. Thomas ◽  
P. S. I. P. N. de Silva ◽  
L. F. Cohen ◽  
A. Goyal ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Lattice Mismatch ◽  
X Ray ◽  
Cell Parameters ◽  
Transmission Electron ◽  
The Difference ◽  
Face Centered ◽  
A Minor

The structural changes and magnetoresistance (MR) properties of as-grown and post-annealed La0.7Ca0.3MnO3 films were investigated by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The data for the films were compared to that for bulk La0.7Ca0.3MnO3 post-annealed under the same conditions. The main structure of the as-grown films was face-centered pseudo-cubic with a doubled perovskite unit cell, of size ∼2ap × ∼2ap × 2ap, where ap is the single perovskite parameter. The phase showed a cube-on-cube epitaxy with the underlying LaAlO3 substrate. Upon annealing to a saturation point, a minor primitive pseudo-tetragonal structure evolved, of cell parameters . A total of four possible orientations of the two structures was observed by TEM, comprised of one orientation of the ∼ 2ap × ∼ 2ap × ∼ 2ap cell, i.e., the cube-on-cube epitaxy, giving rise to (00l) peaks in x-ray, and three orientations of the cell, giving rise to a single (00l)/(hk0) peak in x-ray. The bulk La0.7Ca0.3MnO3 sample also contains the × structure. The difference between the bulk and the film and the effects of annealing on films can be ascribed to the influence of strain between the film and substate, induced by lattice mismatch.

Electrochemical Fabrication of BixTe1-x (0.4 ≤ x ≤ 0.7) Nanowire Arrays

2007 ◽  
Vol 546-549 ◽  
pp. 2171-2174
Author(s):  
Wei Wang ◽  
J.F. Qu ◽  
X.L. Lu ◽  
G.Q. Zhang ◽  
Guang Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Large Scale ◽  
Atomic Ratio ◽  
Nanowire Arrays ◽  
X Ray Diffraction ◽  
Alumina Membrane ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Electrochemical Fabrication

Large scale and highly ordered thermoelectric BixTe1-x (0.4 ≤ x ≤ 0.7) nanowire arrays were successfully fabricated by cathodic electrolysis into porous anodic alumina membrane (AAM) templates in aqueous solution. The structure of the nanowires was characterized by X-ray diffraction and selected-area electron diffraction (SAED). Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results show that the nanowires are smooth and uniform with the diameters of about 50 nm and lengths up to tens of micrometers. Energy dispersive spectroscopy (EDS) was used to check the exact stoichiometry of as-prepared samples. The results reveal that the atomic ratio between Bi and Te can be modulated effectively by controlling the concentration of the electrolyte solution. The synthesis of high quality BixTe1-x nanowires with controllable x is significant for optimizing the thermoelectric performance.

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