Analysis of Cerium–Zirconium Mixed Metal Oxides by X-Ray Photoelectron Spectroscopy

2001 ◽  
Vol 8 (2) ◽  
pp. 126-161 ◽  
Author(s):  
Alan E. Nelson ◽  
Melissa K. Graves-Brook ◽  
Kirk H. Schulz
Keyword(s):  
Metal Oxides ◽  
Photoelectron Spectroscopy ◽  
Mixed Metal Oxides ◽  
X Ray ◽  
Mixed Metal

scholarly journals Characterization of Mixed-Metal Oxides Using Synchrotron-Based Time-Resolved x-ray Diffraction and x-ray Absorption Spectroscopy

1999 ◽  
Vol 590 ◽  
Author(s):  
José A. Rodriguez ◽  
Jonathan C. Hanson ◽  
Joaquín L. Brito ◽  
Amitesh Maiti
Keyword(s):  
Metal Oxides ◽  
Density Functional ◽  
Chemical Properties ◽  
Local Symmetry ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Mixed Metal ◽  
X Ray Absorption

ABSTRACTExperiments are described showing the utility of synchrotron-based time-resolved x-ray diffraction (TR-XRD) and x-ray absorption near-edge spectroscopy (XANES) for characterizing the physical and chemical properties of mixed-metal oxides that contain Mo and a second transition metal (Fe, Co or Ni). TR-XRD was used to study the transformations that occur during the heating of a FeMoO4/Fe2(MoO4)3 mixture and the α⇒β phase transitions in CoMoO4 and NiMoO4. The Mo LII- and O K-edges in XANES are very useful for probing the local symmetry of Mo atoms in mixed-metal oxides. The results of XANES and density-functional calculations (DMo13, DFT-GGA) show large changes in the splitting of the empty Mo 4d levels when going from tetrahedral to octahedral coordinations. XANES is very useful for studying the reaction of H2, H2S and SO2 with the mixed-metal oxides. Measurements at the S K-edge allow a clear identification of S, SO2, SO3 or SO4 on the oxide surfaces. Changes in the oxidation state of molybdenum produce substantial shifts in the position of the Mo LII- and MIII-edges.

SYNTHESIS OF NOVEL NANOSTRUCTURED LANTHANUM COBALT FERRITE MIXED METAL OXIDES BY SOL–GEL

2013 ◽  
Vol 12 (01) ◽  
pp. 1350007
Author(s):  
V. MARY TERESITA ◽  
V. JESEENTHARANI ◽  
B. AVILA JOSEPHINE ◽  
S. ARUL ANTONY
Keyword(s):  
Metal Oxides ◽  
Sol Gel ◽  
Chemical Properties ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mixed Metal ◽  
Size Dependent ◽  
Ft Ir ◽  
And Chemical Properties

Properties of nanoscale materials are very interesting and these are either comparable to or superior to those of bulk. These materials are interesting due to their exciting size dependent optical, electronic, magnetic, thermal, mechanical and chemical properties. Different mole ratios of nanostructured mixed metal oxides of LaCo x Fe 1-x O 3-δ (x = 0 to 1) were prepared by the sol–gel method by varying the mole ratios of iron and cobalt substrates. The compounds were sintered for 700°C in the tubular furnace for 8 h. The purity of the compounds was analyzed by TG-DTA. The compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) studies were employed to study the structural phases, vibrational frequencies, surface morphology of the highest humidity sensing compounds.

scholarly journals Dielectric Studies of Bi2MoO6/Graphene Oxide and La-Doped Bi2MoO6/Graphene Oxide Nanocomposites

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 559
Author(s):  
Syed Farooq Adil ◽  
Shoomaila Latif ◽  
Muhammad Waqar ◽  
Muhammad Imran ◽  
Sadia Noreen ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Graphene Oxide ◽  
Metal Oxides ◽  
Gravimetric Analysis ◽  
Mixed Metal Oxides ◽  
Impedance Analyzer ◽  
X Ray ◽  
Mixed Metal ◽  
La Doped ◽  
Precision Impedance Analyzer

The mixed metal oxides Bi2MoO6 and La-doped Bi2MoO6 were prepared by the sol–gel method. Then, varying quantities of the as-prepared mixed metal oxides were blended with graphene oxide (GO), employing sonication, to obtain Bi2MoO6/GO (BM/GO) and La-Bi2MoO6/GO (LBM/GO) nanocomposites. These prepared materials were characterized by different techniques such as thermal gravimetric analysis (TGA), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and transmission electron microscopy (TEM). Dielectric properties were studied by using a precision impedance analyzer. Dielectric constant and loss tan of the synthesized composites were studied as a function of frequency by using a precision impedance analyzer. Overall, the dielectric constant (ɛ’) observed for the LBM/GO composites was higher than that of BM/GO.

scholarly journals Synthesis and characterization of layered double hydroxides with different cations (Mg, Co, Ni, Al), decomposition and reformation of mixed metal oxides to layered structures

2011 ◽  
Vol 9 (2) ◽  
pp. 275-282 ◽  
Author(s):  
Kristina Klemkaite ◽  
Igoris Prosycevas ◽  
Ricardas Taraskevicius ◽  
Alexander Khinsky ◽  
Aivaras Kareiva
Keyword(s):  
Metal Oxides ◽  
Layered Double Hydroxides ◽  
Xrd Analysis ◽  
Layered Structures ◽  
Magnesium Nitrate ◽  
Mixed Metal Oxides ◽  
X Ray ◽  
Mixed Metal ◽  
Different Temperatures ◽  
Double Hydroxides

AbstractThree layered double hydroxides (LDH) [Mg1−xAlx(OH)2]x+(Am−)x/m]·nH2O and [MII 1−xMIII x (OH)2]x+(Am−)x/m]·nH2O (MII — Mg, Co, Ni; MIII — Al; A — CO3 2−) were successfully synthesized by the low supersaturation method. The as-synthesized LDH samples were thermally decomposed and the derived mixed metal oxides reformed back to layered structures in water and magnesium nitrate media at different temperatures. All synthesized samples were characterized by X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis, X-ray fluorescence (XRF) analysis and scanning electron microscopy (SEM). The results of XRD and XRF analyses showed that single-phase layered double hydroxides were formed during synthesis and reformation. It was demonstrated, that a partially substituted by cobalt and nickel LDH samples also show memory effect. The crystallite size of regenerated LDH depends on the regeneration media, temperature and chemical composition. The LDH samples after regeneration consist of large particles with sharp edges along with a large amount of smaller particles

Novel SrO-CaO Mixed Metal Oxides Catalyst for Ultrasonic-Assisted Transesterification of Jatropha Oil into Biodiesel

2017 ◽  
Vol 70 (3) ◽  
pp. 258 ◽  
Author(s):  
Syed Danish Ali ◽  
Isma Noreen Javed ◽  
Usman Ali Rana ◽  
Muhammad Faizan Nazar ◽  
Waqas Ahmed ◽  
...  
Keyword(s):  
Metal Oxides ◽  
Fatty Acid Methyl Esters ◽  
Methyl Esters ◽  
Mixed Metal Oxides ◽  
Jatropha Oil ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mixed Metal ◽  
Acid Methyl ◽  
Ultrasonic Assisted

The transesterification of edible and non-edible oils to produce biodiesel is traditionally carried out using homogeneous catalysts (such as NaOH, KOH, and H2SO4). However, these homogenous catalysts often suffer from multiple drawbacks including their corrosive nature and solubility in the reaction mixture, and high costs associated with their recovery. Recent studies have shown that heterogeneous catalysts based on mixed metal oxides have the potential to address the issues associated with conventional homogeneous catalysts, thereby emerging as an efficient class of catalyst materials for biodiesel production. In this study, we describe a heterogeneous strontium oxide/calcium oxide (SrO-CaO) mixed metal oxides catalyst, which displays remarkable efficiency towards the ultrasonic-assisted transesterification of Jatropha oil into biodiesel. The SrO-CaO heterogeneous catalyst was prepared by the wet impregnation method, and the structural morphology of the as-synthesized catalyst was revealed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and nitrogen sorption technique coupled with the Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods. The X-ray diffraction analysis confirmed the cubic structure of the SrO-CaO catalyst. The catalytic activity of this newly developed catalyst showed a high percentage conversion of triglyceride into the corresponding fatty acid methyl esters (98.19 %) as confirmed by 1H NMR spectroscopy. The chemical composition of the prepared biodiesel by this ultrasonic-assisted transesterification process was determined by the gas chromatography–mass spectrometry. Five major fatty acid methyl esters were identified, of which 9-octadecenoic acid methyl ester was obtained with the highest percentage ~38.22 %. Hence, the study reveals that the SrO-CaO catalyst exhibits high efficiency towards converting Jatropha oil into biodiesel by ultrasonic-assisted transesterification.

Structure and Thermo-Chemical Stability of Sr-Fe-Co-O Mixed Metal Oxides

2012 ◽  
Vol 549 ◽  
pp. 193-197
Author(s):  
Xiang Hong Huang ◽  
Jun Qiao ◽  
Qian Feng Zhang
Keyword(s):  
High Temperature ◽  
Metal Oxides ◽  
Chemical Stability ◽  
Elevated Temperatures ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
Crystalline Phases ◽  
X Ray ◽  
Mixed Metal ◽  
Two Samples

SrFexCo0.5Oδ(x=0.5, 0.75, 1.0, 1.25) mixed metal oxides were synthesized by the citrate method. The structure and thermo-chemical stability of the obtained SrFexCo0.5Oδpowders were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results show that the SrFexCo0.5Oδpowders are composed of perovskite-type cubic structure at both room temperature and high temperature. The crystalline phases of the SrFexCo0.5Oδpowders are dependent on the content of Fe and SrFe0.5Co0.5O3, SrFe0.19Co081O2.78are the main crystalline phases. The powders have good thermo-chemical stability at elevated temperatures in helium, which is confirmed by an in-situ high-temperature X-ray diffraction. The SEM images show that the product of the SrFexCo0.5Oδ(x=0.5, 1.0) is composed of single grain, while other two samples consist of layer structures and some open porosities.

scholarly journals Ceria–Zirconia Mixed Metal Oxides Prepared via Mechanochemical Grinding of Carbonates for the Total Oxidation of Propane and Naphthalene

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 475 ◽  
Author(s):  
Parag M. Shah ◽  
Joseph W. H. Burnett ◽  
David J. Morgan ◽  
Thomas E. Davies ◽  
Stuart H. Taylor
Keyword(s):  
Metal Oxides ◽  
Surface Area ◽  
Laser Raman Spectroscopy ◽  
Mixed Metal Oxides ◽  
Total Oxidation ◽  
Oxidation Activity ◽  
X Ray ◽  
Mixed Metal ◽  
Oxygen Defects ◽  
Zirconia Content

A series of ceria–zirconia mixed metal oxides with varying metal ratios were prepared by the calcination of precursors synthesized by mechanochemical grinding of the metal carbonates, and tested for catalytic naphthalene and propane total combustion. The mechanically-mixed metal oxides were more active for both propane and naphthalene total oxidation compared to the parent metal oxides. Ce0.95Zr0.05Ox was the most active catalyst for the total combustion of propane and naphthalene. Catalysts were characterized by x-ray diffraction, BET surface area, laser Raman spectroscopy, temperature programmed reduction, scanning electron microscopy with energy dispersive x-ray analysis and x-ray photoelectron spectroscopy techniques. Formation of ceria–zirconia solid solutions was observed for catalysts with a zirconia content of 10% or lower, whereas ceria and zirconia phase separation was observed when zirconia content was above 25%. Surface area increased when ceria and zirconia were mixed, and the reduction temperature of the bulk shifted to lower temperatures upon increasing zirconia content. Incorporation of zirconia was found to increase the relative concentration of surface oxygen defects compared to pure ceria, with low amounts of zirconia showing the greatest increase. The concentration of oxygen defects correlates with propane and naphthalene total oxidation activity. The enhanced total oxidation activity occurs as a result of the increased number of oxygen defects and the higher surface area. The results demonstrate that mechanochemical preparation from carbonate precursors was an effective route to make active catalysts.

scholarly journals Synthesis of Mg-Fe layered double hydroxides and its application as catalyst for Friedel-Crafts benzoylation

2016 ◽  
Vol 19 (4) ◽  
pp. 185-193
Author(s):  
Phuong Thi Minh Nguyen ◽  
Phuong Hoang Tran ◽  
Chinh Quoc Nguyen
Keyword(s):  
Metal Oxides ◽  
Layered Double Hydroxides ◽  
Coprecipitation Method ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mixed Metal ◽  
Before And After ◽  
Double Hydroxides

Mg-Fe layered double hydroxides were synthesized by the coprecipitation method with different of Mg/Fe ratio (2/1, 3/1 and 4/1) and then were thermally transformed into mixed metal oxides. The obtained materials before and after the calcination at 450 oC were characterized by X-ray diffraction (XRD), SEM, BET, TGA, ICP. The samples were used as a catalyst for Friedel-Crafts benzoylation reactions. The catalyst can be easily separated and recycled compared to the traditional one.

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