scholarly journals Alloying Effect of Silver on Zirconia Support Manipulated Palladium Catalyst for Methane Combustion

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 863
Author(s):  
Mengmeng Chu ◽  
Fan Cai ◽  
Xiaohong Cao ◽  
Li Xing ◽  
Lefu Yang ◽  
...  
Keyword(s):  
Oxidation Reaction ◽  
Methane Combustion ◽  
Active Phase ◽  
Alloying Effect ◽  
Redox Cycles ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Zirconia Support ◽  
Effect Of Support ◽  
Alloy Catalysts

PdAg/ZrO2 alloy catalysts calcined at different temperatures were employed to elucidate the effect of support-metal interaction (SMI) on methane combustion. Combustion activity was depressed when the sample was calcined at an elevated temperature from 500 °C to 700 °C. However, calcination at 850 °C enhanced the beneficial SMI, which facilitated a more active phase for the oxidation reaction. The high-resolution transmission electron microscopy experiments show that a special micro-domain structure at the interface is formed during the reduction pretreatment. H2-TPR and O2-TPD measurements illustrate that the active phase would undergo reconstruction upon redox cycles. The active phase manipulated by the support is more suitable for combustion reaction in the course of temperature altering.

scholarly journals Development of Quantum Dot (QD) Based Color Converters for Multicolor Display

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1089
Author(s):  
Muhammad T. Sajjad ◽  
Ashu K. Bansal ◽  
Francesco Antolini ◽  
Eduard Preis ◽  
Lenuta Stroea ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Cost Effective ◽  
Final Size ◽  
Force Microscopy ◽  
Morphological Studies ◽  
Color Displays ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Color Conversion ◽  
Temperature Time

Many displays involve the use of color conversion layers. QDs are attractive candidates as color converters because of their easy processability, tuneable optical properties, high photoluminescence quantum yield, and good stability. Here, we show that emissive QDs with narrow emission range can be made in-situ in a polymer matrix, with properties useful for color conversion. This was achieved by blending the blue-emitting pyridine based polymer with a cadmium selenide precursor and baking their films at different temperatures. To achieve efficient color conversion, blend ratio and baking temperature/time were varied. We found that thermal decomposition of the precursor leads to highly emissive QDs whose final size and emission can be controlled using baking temperature/time. The formation of the QDs inside the polymer matrix was confirmed through morphological studies using atomic force microscopy (AFM) and transmission electron microscopy (TEM). Hence, our approach provides a cost-effective route to making highly emissive color converters for multi-color displays.

scholarly journals Effect of calcination temperature on rare earth tailing catalysts for catalytic methane combustion

2020 ◽  
Vol 9 (1) ◽  
pp. 734-743
Author(s):  
Ran Zhao ◽  
ZiChen Tian ◽  
Zengwu Zhao
Keyword(s):  
Rare Earth ◽  
Mine Tailings ◽  
Photoelectron Spectroscopy ◽  
Methane Combustion ◽  
Space Velocity ◽  
High Catalytic Activity ◽  
Reduction Peak ◽  
X Ray ◽  
Different Temperatures ◽  
Bayan Obo

AbstractBayan Obo tailings are rich in rare earth elements (REEs), iron, and other catalytic active substances. In this study, mine tailings were calcined at different temperatures and tested for the catalytic combustion of low-concentration methane. Upon calcination at 600°C, high catalytic activity was revealed, with 50% CH4 conversion at 587°C (space velocity of 12,000 mL/g h). The physicochemical properties of catalysts were characterized using thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, hydrogen temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). Compared to the raw ore sample, the diffraction peak intensity of Fe2O3 increased post calcination, whereas that of CeCO3F decreased. A porous structure appeared after the catalyst was calcined at 600°C. Additionally, Fe, Ce, Ti, and other metal elements were more highly dispersed on the catalyst surface. H2-TPR results revealed a broadening of the reduction temperature range for the catalyst calcined at 600°C and an increase in the reduction peak. XPS analysis indicated the presence of Ce in the form of Ce3+ and Ce4+ oxidation states and the coexistence of Fe in the form of Fe2+ and Fe3+. Moreover, XPS revealed a higher surface Oads/Olatt ratio. This study provides evidence for the green reuse of Bayan Obo mine tailings in secondary resources.

scholarly journals Optical and Electrical Properties of Thin Films of CuS Nanodisks Ensembles Annealed in a Vacuum and Their Photocatalytic Activity

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
J. Santos Cruz ◽  
S. A. Mayén Hernández ◽  
F. Paraguay Delgado ◽  
O. Zelaya Angel ◽  
R. Castanedo Pérez ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Hydrogen Peroxide ◽  
Photocatalytic Activity ◽  
Electrical Properties ◽  
Absolute Temperature ◽  
Glass Substrates ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Blue Solution

Effects on the optical, electrical, and photocatalytic properties of undoped CuS thin films nanodisks vacuum annealed at different temperatures were investigated. The chemical bath prepared CuS thin films were obtained at 40°C on glass substrates. The grain size of13.5±3.5 nm was computed directly from high-resolution transmission electron microscopy (HRTEM) images. The electrical properties were measured by means of both Hall effect at room temperature and dark resistivity as a function of the absolute temperature 100–330 K. The activation energy values were calculated as 0.007, 0.013, and 0.013 eV for 100, 150, and 200°C, respectively. The energy band gap of the films varied in the range of 1.98 up to 2.34 eV. The photocatalytic activity of the CuS thin film was evaluated by employing the degradation of aqueous methylene blue solution in the presence of hydrogen peroxide. The CuS sample thin film annealed in vacuum at 150°C exhibited the highest photocatalytic activity in presence of hydrogen peroxide.

Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

2020 ◽  
Vol 98 (10) ◽  
pp. 2205-2213 ◽  
Author(s):  
Massimiliano Zanoletti ◽  
François Godard ◽  
Michel Perrier
Keyword(s):  
Methane Combustion ◽  
Palladium Oxide ◽  
Effect Of Support

scholarly journals Effect of Annealing on the ZnS Nanocrystals Prepared by Chemical Precipitation Method

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Nadana Shanmugam ◽  
Shanmugam Cholan ◽  
Natesan Kannadasan ◽  
Kannadasan Sathishkumar ◽  
G. Viruthagiri
Keyword(s):  
Chemical Precipitation ◽  
Chemical Precipitation Method ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Visible Absorption ◽  
Atomic Force ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Uv Visible ◽  
Dta Curves

Nanocrystals of ZnS have been synthesized through simple chemical precipitation method using thiourea as sulphur source. The synthesized products were annealed at different temperatures in the range of 200–800∘C. The as-synthesized and annealed samples were characterized by X-ray diffraction (XRD), UV-Visible absorption (UV-Vis), and room temperature photoluminescence (PL) measurements. The morphological features of ZnS annealed at 200 and 500∘C were studied by atomic force microscope (AFM) and transmission electron microscope (TEM) techniques. The phase transformation of ZnS and formation of ZnO were confirmed by thermogravimetric (TG) and differential thermal analysis (DTA) curves.

Structure and Properties of the Melt-Spun Fe41Ni39P10Si5B5 Alloy Heat Treated at Elevated Temperatures

2010 ◽  
Vol 163 ◽  
pp. 101-105
Author(s):  
Krzysztof Ziewiec ◽  
Krystian Prusik
Keyword(s):  
Glass Transition ◽  
Phase Transformations ◽  
Storage Modulus ◽  
Elevated Temperatures ◽  
Amorphous Structure ◽  
Transmission Electron ◽  
Melt Spun ◽  
Different Temperatures ◽  
Alloy Heat ◽  
Two Stages

The aim of the work was to provide information on structure development and change of properties at elevated temperatures in Fe41Ni39P10Si5B5 amorphous alloy. The alloy was characterized by X-ray diffraction. The changes of properties were characterized with use of dynamic mechanical thermal analysis (DMTA) and the resistivity measurements at elevated temperatures. The microstructure of the melt spun ribbon was investigated with use of transmission electron microscope (TEM) at different stages of phase transformations after heating to different temperatures. The initially amorphous structure undergoes phase transformations due to glass transition and crystallization of the alloy. The appearance of glass transition region results in decrease of storage modulus and in a reversible change of temperature coefficient of resistivity (TCR). The phases are characterized with use of TEM. The crystallization was found to have the two stages. Formation of bcc crystals and Ni12P5 is followed by transformation of the products into fcc crystals and Ni3P. Temporary changes of the storage modulus and elongation of the sample suggest formation of hard phases during crystallization.

Preparation and Characterization of Rare Earth Composite Catalytic Materials for Conversion of Exhaust from Natural Gas Automobiles

2013 ◽  
Vol 320 ◽  
pp. 413-418
Author(s):  
Yan Kun Yuan ◽  
Gang Xue ◽  
Sai Fei Wang ◽  
Xue Liang Zhang
Keyword(s):  
Rare Earth ◽  
Specific Surface ◽  
Sol Gel ◽  
Methane Combustion ◽  
Fluorite Structure ◽  
Perfect Crystal ◽  
Reduction Peak ◽  
Transmission Electron ◽  
Catalytic Material ◽  
Temperature Programmed

A series of rare-earth composite catalytic material LZ1,LZ2 and LZ3 that contains mixture of La0.9Sr0.1Co0.5Mn0.5O3and Ce0.7Zr0.3O2in different proportion (3:7, 5:5, 7:3) were prepared by a sol-gel method and characterized by X-ray diffraction (XRD), specific surface analysis (BET) , Transmission electron microscopy (TEM) and temperature programmed reduction (TPR). The results indicated that in LZ3, a perfect crystal structure of perovskite and a cubic fluorite structure were formed. Besides LZ3 presented scattered spherical granules with a particle size of about 30 nm and a specific surface area of 20.9870 m2/g. The temperature of reduction peak was lowest (490°C) and peak area was larger, so it had the best catalytic activity for methane combustion.

Structural and Chemical Properties of MBE Grown Niobium Overlayers on (110) Rutile

1996 ◽  
Vol 441 ◽  
Author(s):  
J. Marien ◽  
T. Wagner ◽  
M. Rühle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Defect Structure ◽  
Chemical Properties ◽  
High Energy ◽  
Initial Growth ◽  
High Energy Electron ◽  
Transmission Electron ◽  
Different Temperatures ◽  
And Chemical Properties

AbstractThin Nb films were grown by MBE in a UHV chamber at two different temperatures (50°C and 950°C) on the (110) surface of TiO2 (rutile).At a growth temperature of 50°C, reflection high energy electron diffraction (RHEED) revealed epitaxial growth of Nb on rutile: (110)[001] TiO2 ¦¦ (100)[001] Nb. In addition, investigations with Auger electron spectroscopy (AES) revealed that a chemical reaction took place between the Nb overlayer and the TiO2 substrate at the initial growth stage. A 2 nm thick reaction layer at the Nb/TiO2 interface has been identified by means of conventional transmission electron microscopy (CTEM) and high-resolution transmission electron microscopy (HRTEM).At a substrate temperature of 950°C, during growth, the Nb film was oxidized completely, and NbO2 grew epitaxially on TiO2. The structure and the chemical composition of the overlayers have been investigated by RHEED, AES, CTEM and HRTEM. Furthermore, it was determined that the reaction of Nb with TiO2 is governed by the defect structure of the TiO2 and the relative oxygen affinities of Nb and TiO2.

Fe–Cr/Al2O3 metal-ceramic composites: Nature and size of the metal particles formed during hydrogen reduction

1994 ◽  
Vol 9 (1) ◽  
pp. 229-235 ◽  
Author(s):  
Ch. Laurent ◽  
J.J. Demai ◽  
A. Rousset ◽  
K.R. Kannan ◽  
C.N.R. Rao
Keyword(s):  
Hydrogen Reduction ◽  
Ceramic Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Total Reduction ◽  
Transmission Electron ◽  
Combined Use ◽  
Metal Ceramic ◽  
Different Temperatures ◽  
Metallic Species

Fe-Cr/Al2O3 metal-ceramic composites prepared by hydrogen reduction at different temperatures and for different periods have been investigated by a combined use of Mössbauer spectroscopy, x-ray diffraction, transmission electron microscopy, and energy-dispersive x-ray spectroscopy in order to obtain information on the nature of the metallic species formed. Total reduction of Fe3+ does not occur by increasing the reduction time at 1320 K from 1 to 30 h, and the amount of superparamagnetic metallic species is essentially constant (about 10%). Temperatures higher than 1470 K are needed to achieve nearly total reduction of substitutional Fe3+. Interestingly, iron favors the reduction of chromium. The composition of the Fe-Cr particles is strongly dependent on their size, the Cr content being higher in particles smaller than 10 nm.

Sign in / Sign up

Export Citation Format

Share Document