Synthesis and Thermal Stability of Palladium Nanoparticles Supported on γ-Αl2O3

2020 ◽  
Vol 5 (1) ◽  
pp. 79-90
Author(s):  
Yevhen Y. Kalishyn ◽  
Vladislav V. Ordynskyi ◽  
Mykola V. Ishchenko ◽  
Igor B. Bychko ◽  
Zinaida V. Kaidanovych ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Size Distribution ◽  
Palladium Nanoparticles ◽  
Palladium Catalysts ◽  
Colloidal Solution ◽  
X Ray Diffraction ◽  
Supported Nanoparticles ◽  
Transmission Electron ◽  
Al2o3 Composite ◽  
High Temperature Processes

Background: Deposition of palladium nanoparticles from colloidal solution on various supports produces palladium catalysts with a predetermined size and concentration of the palladium nanoparticles, which allows to study the nanoparticle size effects and support influence on palladium catalytic properties. Objective: The goal of the present work was the development of a preparation method of systems supported on γ-Al2O3 palladium nanoparticles with a controlled size and determination of their thermal stability in oxidizing and reducing atmospheres. Methods: We demonstrated the preparation of Pd/γ-Al2O3 composite by precipitation of the size-controlled palladium nanoparticles with a narrow size distribution from colloidal solution. The composites were characterized by X-ray diffraction (XRD), and transmission electron microscope (TEM) methods. Result: The size and size distribution of the nanoparticles supported on γ-Al2O3 were found to be increasing upon precipitation due to strong Pd/γ-Al2O3 interaction. A significant enlargement of the supported nanoparticles occured at 300°C. The aggregation of the nanoparticles was observed at temperatures above 500°C resulting in an increase in their size. Conclusion: Our findings are not only applicable for the preparation of a model Pd supported on the γ-Al2O3 catalyst but could be applicable to the designing of the Pd-containing catalyst for important industrial high-temperature processes.

Microstructure and thermal stability of an ultrafine Al/Al2O3 composite

2003 ◽  
Vol 18 (2) ◽  
pp. 272-278 ◽  
Author(s):  
Zhiqing Yang ◽  
Lianlong He ◽  
Ji Chen ◽  
Hongtao Cong ◽  
Hengqiang Ye
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Transmission Electron Microscopy ◽  
Grain Growth ◽  
High Strength ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Al2o3 Composite ◽  
Almost All ◽  
Thermal Stability Of

Studies were carried out on the microstructure and thermal stability of an ultrafine Al/Al2O3 composite with high strength and low density. Transmission electron microscopy indicated that Al2O3 shells remained undeformed below 550 °C, which limited grain growth of Al. Both transmission electron microscopy and x-ray diffraction analysis indicated that no obvious grain growth of Al with time occurred upon annealing at 620 °C. After almost all the alumina shells were destroyed following annealing at 620 °C, the Al2O3 fragments with various morphologies distributed in the material could still limit the migration of Al grain boundaries to increase the thermal stability of the material. After Al melted and resolidified, the grain sizes of Al were still about 200 nm. The bulk composite sample showed good dimensional stability. Even if the Al grains melted, the network of Al2O3 fragments kept the sample from deforming due to the wetting of Al2O3 network with liquid Al.

Formation and Thermal Stability of Nd0.32Y0.68Si1.7 Layers Formed by Channeled Ion Beam Synthesis

1998 ◽  
Vol 514 ◽  
Author(s):  
M. F. Wu ◽  
A. Vantomne ◽  
S. Hogg ◽  
H. Pattyn ◽  
G. Langouche ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Ion Beam ◽  
Hexagonal Structure ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Good Crystalline Quality ◽  
Ion Beam Synthesis ◽  
Thermal Stability Of

ABSTRACTThe Nd-disilicide, which exists only in a tetragonal or an orthorhombic structure, cannot be grown epitaxially on a Si(111) substrate. However, by adding Y and using channeled ion beam synthesis, hexagonal Nd0.32Y0.68Si1.7 epilayers with lattice constant of aepi = 0.3915 nm and cepi = 0.4152 nm and with good crystalline quality (χmin of Nd and Y is 3.5% and 4.3 % respectively) are formed in a Si(111) substrate. This shows that the addition of Y to the Nd-Si system forces the latter into a hexagonal structure. The epilayer is stable up to 950 °C; annealing at 1000 °C results in partial transformation into other phases. The formation, the structure and the thermal stability of this ternary silicide have been studied using Rutherford backscattering/channeling, x-ray diffraction and transmission electron microscopy.

scholarly journals Low-temperature hydrothermal synthesis of hierarchical flower-like CuB2O4 superstructures

2020 ◽  
Vol 14 (2) ◽  
pp. 113-118
Author(s):  
Daniel Ursu ◽  
Anamaria Dabici ◽  
Marinela Miclau ◽  
Nicolae Miclau
Keyword(s):  
Thermal Stability ◽  
Low Temperature ◽  
Self Assembly ◽  
Hydrothermal Solution ◽  
Optical Measurements ◽  
Oriented Attachment ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
One Step

We report for the first time the fabrication of hierarchical ordered superstructure CuB2O4 with flower-like morphology via a one-step, low temperature hydrothermal method. The tetragonal structure of CuB2O4 was determined by X-ray diffraction and high-resolution transmission electron microscopy. Optical measurements attested of the quality of the fabricated CuB2O4 and high temperature X-ray diffraction confirmed its thermal stability up to 600 ?C. The oriented attachment growth and the hierarchical self-assembly of micrometer-sized platelets producing hierarchical superstructures with flower-like morphology are designed by pH of the hydrothermal solution. The excellent band gap, high thermal stability and hierarchical structure of the CuB2O4 are promising for the photovoltaic and photocatalytic applications.

scholarly journals Polystyrene/Montmorillonite Nanocomposites: Study of the Morphology and Effects of Sonication Time on Thermal Stability

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Mashael Alshabanat ◽  
Amal Al-Arrash ◽  
Waffa Mekhamer
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Solution Method ◽  
Sonication Time ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Polystyrene Matrix ◽  
Before And After ◽  
Silicate Layers ◽  
Thermal Stability Of

Polymer nanocomposites of polystyrene matrix containing 10% wt of organo-montmorillonite (organo-MMT) were prepared using the solution method with sonication times of 0.5, 1, 1.5, and 2 hours. Cetyltrimethylammonium bromide (CTAB) is used to modify the montmorillonite clay after saturating its surface with Na+ions. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the montmorillonite before and after modification by CTAB. The prepared nanocomposites were characterized using the same analysis methods. These results confirm the intercalation of PS in the interlamellar spaces of organo-MMT with a very small quantity of exfoliation of the silicate layers within the PS matrix of all samples at all studied times of sonication. The thermal stability of the nanocomposites was measured using thermogravimetric analysis (TGA). The results show clear improvement, and the effects of sonication time are noted.

Immobilization of hemoglobin on stable mesoporous multilamellar silica vesicles and their activity and stability

2005 ◽  
Vol 20 (10) ◽  
pp. 2682-2690 ◽  
Author(s):  
Yufang Zhu ◽  
Weihua Shen ◽  
Xiaoping Dong ◽  
Jianlin Shi
Keyword(s):  
Thermal Stability ◽  
Pore Size ◽  
X Ray Diffraction ◽  
X Ray ◽  
Practical Applications ◽  
Silica Material ◽  
Transmission Electron ◽  
Mesoporous Support ◽  
Adsorption Desorption ◽  
Thermal Stability Of

A stable mesoporous multilamellar silica vesicle (MSV) was developed with a gallery pore size of about 14.0 nm. A simulative enzyme, hemoglobin (Hb), was immobilized on this newly developed MSV and a conventional mesoporous silica material SBA-15. The structures and the immobilization of Hb on the mesoporous supports were characterized with x-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms, Fourier transform infrared, ultraviolet-visible spectroscopy, and so forth. MSV is a promising support for immobilizing Hb due to its large pore size and high Hb immobilization capacity (up to 522 mg/g) compared to SBA-15 (236 mg/g). Less than 5% Hb was leached from Hb/MSV at pH 6.0. The activity study indicated that the immobilized Hb retained most peroxidase activity compared to free Hb. Thermal stability of the immobilized Hb was improved by the proctetive environment of MSV and SBA-15. Such an Hb-mesoporous support with high Hb immobilization capacity, high activity, and enhanced thermal stability will be attractive for practical applications.

Thermal Stability and Failure Mechanisms of Au/Tiw(N)/Si and Au/TiW(N)/Si02/Si Systems

1996 ◽  
Vol 427 ◽  
Author(s):  
C. R. Chen ◽  
L. J. Chen
Keyword(s):  
Thermal Stability ◽  
Failure Mechanisms ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Single Face ◽  
Face Centered ◽  
The Stability ◽  
Ar Gas

AbstractThermal stability and failure mechanisms of Au/TiW(N)/Si and Au/TiW(N)/SiO2/Si systems have been studied by both conventional and high-resolution transmission electron microscopy, X- ray diffraction and Auger electron spectroscopy. For films deposited in Ar gas containing 20% N2, a single face-centered-cubic phase was the only crystalline phase detected to form. The samples were found to remain stable after annealing at 700 °C for 30 min. The stability temperature for Au/TiW(N)(Ar:N2=80:20)/SiO2/Si samples was found to be higher than those of Au/TiW(N) (Ar:N2=90:10)/SiO2/Si and Au/TiW/SiO2/Si samples.

Synthesis of Ag Nanoparticles-Clinoptilolite Composite by Homogeneous and Heterogeneous Nucleation

2013 ◽  
Vol 755 ◽  
pp. 97-103 ◽  
Author(s):  
A. Ruíz-Baltazar ◽  
R. Esparza ◽  
R. Pérez ◽  
G. Rosas
Keyword(s):  
Silver Nitrate ◽  
Sodium Borohydride ◽  
Heterogeneous Nucleation ◽  
Ag Nanoparticles ◽  
Natural Zeolite ◽  
Colloidal Solution ◽  
Chemical Reduction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

In this study, a natural zeolite clinoptilolite-type was impregnated through homogeneous and heterogeneous nucleation with silver nanoparticles. The synthesis of Ag nanoparticles was carried out by chemical reduction of silver nitrate (AgNO3) with sodium borohydride (NaBH4). In the case of homogeneous nucleation, colloidal solution of Ag nanoparticles at concentrations of 1, 2 and 4 parts per million was added and magnetically mixed with the porous material. With respect to heterogeneous nucleation, a solution of clinoptilolite and silver nitrate (0.01 M) was prepared and stirred; subsequently, the reduction of Ag was possible due to the addition of an aqueous solution of sodium borohydride. For the structural characterization, transmission electron microscopy (TEM), X-ray diffraction (XRD) and infrared spectroscopy (IR) techniques were carried out. The results were compared and discussed in both types of nucleation.

Scalable Production of Carbon Encapsulated Ni Nanoparticles by Water Arc Discharge: Structural and Magnetic Properties

2005 ◽  
Vol 23 ◽  
pp. 87-90 ◽  
Author(s):  
K.H. Ang ◽  
I. Alexandrou ◽  
N.D. Mathur ◽  
R. Lacerda ◽  
I.Y.Y. Bu ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Arc Discharge ◽  
Narrow Particle Size Distribution ◽  
Ni Nanoparticles ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Water Container

An electric arc discharge in de-ionised water between a solid graphite cathode and an anode made by compressing Ni and C containing powders in a mass ratio of Ni:C = 7:3 was used here to prepare carbon encapsulated Ni nanoparticles in the form of powder suspended in water. The morphology of the produced material was analysed using high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The magnetic properties of the samples were determined using a Princeton vibrating sample magnetometer (VSM). Collection of the powder produced from different depths in the water container has proved to be an effective method for obtaining samples with narrow particle size distribution. Further material purification by dry NH4 plasma etching was used to remove the amorphous carbon content of the samples. XRD and HRTEM analysis showed that the material synthesized is fcc Ni particles with mean particle size ranging from 14 to 30 nm encapsulated in 2 to 5 graphitic cages. The data suggests that the process reported has the ability to mass-produce carbon encapsulated ferromagnetic nanoparticles with desired particle size distribution, and hence with controlled size-dependent magnetic properties.

Polymer Stabilized Undoped and Copper Doped Cadmium Sulphide Nanoparticles: Polymer Crosslinked, Optical, and Thermal Stability

2014 ◽  
Vol 492 ◽  
pp. 291-296
Author(s):  
Arup Ratan Mandal ◽  
Sergey Volchematiev ◽  
Denis Leybo ◽  
Dmitry Muratov ◽  
Denis V. Kuznetsov
Keyword(s):  
Thermal Stability ◽  
Cadmium Sulphide ◽  
Cds Nanoparticles ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Chemical Technique ◽  
Band Transition ◽  
Wet Chemical Technique ◽  
Polymer Stabilized

Cadmium sulfide (CdS) nanoparticles synthesized by utilization of wet chemical technique are grown in polyvinyl alcohol (PVA) matrix. X-ray diffraction (XRD) pattern shows the typical inter-planar spacing corresponding to the cubic phase of CdS. High-resolution transmission electron microscopy (HRTEM) studies show the nanoparticles formation with diameter around 11 nm. Particle size is further determined by dynamic light scattering (DLS) measurement. The polymerization of PVA is confirmed by fourier transform infrared (FTIR) spectroscopy of CdS nanoparticles. UV-visible optical spectroscopy study shows that sharp excitonic bands are largely blue shifted from the absorption onset of bulk CdS and inter band transition of copper doped samples. Thermal stability of the samples is measured by thermogravimetric (TG) analysis which is also studied in details.

scholarly journals Preparation of Mesoporous Silica-Supported Palladium Catalysts for Biofuel Upgrade

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Ling Fei ◽  
Harvind Kumar Reddy ◽  
Joshua Hill ◽  
Qianglu Lin ◽  
Bin Yuan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mesoporous Silica ◽  
Palladium Catalysts ◽  
Methyl Esters ◽  
Catalyst Activity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Cnts Surface ◽  
Supported Palladium

We report the preparation of two hydrocracking catalysts Pd/CoMoO4/silica and Pd/CNTs/CoMoO4/silica (CNTs, carbon nanotubes). The structure, morphologies, composition, and thermal stability of catalysts were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and thermogravimetric analysis (TGA). The catalyst activity was measured in a Parr reactor with camelina fatty acid methyl esters (FAMEs) as the feed. The analysis shows that the palladium nanoparticles have been incorporated onto mesoporous silica in Pd/CoMoO4/silica or on the CNTs surface in Pd/CNTs/CoMoO4/silica catalysts. The different combinations of metals and supports have selective control cracking on heavy hydrocarbons.

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