scholarly journals Gamma Radiolytic Formation of Alloyed Ag-Pt Nanocolloids

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
M. K. Temgire ◽  
Jayesh Bellare ◽  
S. S. Joshi
Keyword(s):  
Cluster Structure ◽  
Colloidal Dispersions ◽  
Bimetallic Clusters ◽  
Alloy Formation ◽  
Tem Analysis ◽  
Structural Formation ◽  
Gamma Radiolysis ◽  
Reduction Methods ◽  
Sequential Reduction ◽  
Brij 97

Colloidal dispersions of Ag-Pt composite nanoparticles were prepared by gamma radiolysis technique in the presence of nonionic surfactant Brij'97. Simultaneous as well as sequential reduction methods were employed in order to study the structural formation of Ag-Pt bimetallic clusters. Similar shape and trend was observed in optical spectra for both methods. Radiolysis yielded nearly spherical Ag-Pt bimetallic clusters by use of AgNO3 instead of AgClO4. The disappearance of the silver resonance and the simultaneous growth of the 260 nm resonance are independent of cluster structure and degree of alloying. To understand formation of Ag-Pt aggregate, the optical studies were also done as a function of amount of dose absorbed, concentration of surfactant, that is, Brij'97. The shape of the absorption spectrum did not change with increase in gamma radiation dose. TEM analysis exhibited fine dispersions of Ag-Pt clusters surrounded by a mantle when capped with Brij'97. The particle size obtained was in the range of 5–9 nm. On the basis of optical, XRD, and TEM analysis, alloy formation is discussed.

APPLICATION OF PERFORMANCE REDUCTION METHODS FOR MINIMIZATION OF ANALYZED NUMBER OF PARALLEL PROGRAM VARIANTS

2019 ◽  
pp. 43-49 ◽  
Author(s):  
A. I. Dordopulo
Keyword(s):  
Computer Systems ◽  
Automatic Parallelization ◽  
Parallel Program ◽  
Parallel Applications ◽  
Performance Reduction ◽  
Reduction Methods ◽  
And Performance ◽  
Hardware Costs ◽  
Sequential Reduction ◽  
Information Graph

In this paper, we review and compare the methods of parallel applications’ development based on the automatic program parallelizing for computer systems with shared and distributed memory and on the information graph’s hardware costs and performance reduction for reconfigurable computer systems. The increase in the number of computer system’s units or in the problem’s dimension leads to the significant growth of the automatic parallelization complexity for a procedural program. As a result, the obtainment of parallelizing results in acceptable time using state-of-the-art computer systems is very problematic. In reconfigurable computer systems, the reduction of absolutely parallel information graph of a problem is applied for the parallel program creation. The information graph illustrates the parallelizing and pipelining of computations. In addition to the traditionally practiced reduction of basic subgraphs’ number, the reductions of computational operations’ quantity and of data digit capacity can be utilized for the performance or hardware costs’ scaling. We have proved that the methods of information graph hardware costs and performance reduction provide a considerable decrease in the number of steps needed for adaptation of parallel application to reconfigurable computer systems’ architectures in comparison with automatic parallelizing. We have proved the theorem of coefficient value at sequential reduction, the theorem of increase in reduction coefficient at custom value and the theorem of commutativity of various reduction transformations. The proved theorems help to find a rational sequence of reduction transformations.

Colloidal Dispersions of Palladium–Platinum Bimetallic Clusters Protected by Polymers. Preparation and Application to Catalysis

1989 ◽  
Vol 18 (10) ◽  
pp. 1769-1772 ◽  
Author(s):  
Naoki Toshima ◽  
Kakuta Kushihashi ◽  
Tetsu Yonezawa ◽  
Hidefumi Hirai
Keyword(s):  
Colloidal Dispersions ◽  
Bimetallic Clusters ◽  
Palladium Platinum

scholarly journals Synthesis and characterization of ternary Pt-alloy nano particles for hydrogen fuel cell application

2020 ◽  
Vol 12 (1) ◽  
pp. 419-425
Author(s):  
Alhassan Kabiru Usman ◽  
Kamal Danazumi
Keyword(s):  
Electron Microscope ◽  
Average Particle Size ◽  
Carbon Support ◽  
Peak Position ◽  
Reduction Reaction ◽  
Nano Particles ◽  
Alloy Formation ◽  
Average Particle ◽  
Hydrogen Fuel Cell ◽  
Tem Analysis

A novel ternary PtM2 nano structures was prepared using simple salvothermal process. The alloy formation has been ascertained using different characterizations techniques such as X-ray diffraction, Tunneling electron microscope TEM, Scanning electron microscope SEM, EDX. The XRD pattern reveals that, the peak position was shifted to higher 2𝜃 angle specifying the presence of Co and Ni into the lattice to form an ordered L10 phase with a reduced Pt-Pt distance. The thickness of the alloy was found to be ~4.3nm and interplaner distance of ~0.23nm which correlate with TEM analysis with an average particle size ~20nm and distribution of the catalyst on carbon support was also investigated by TEM images. SEM was used to obtain the surface morphology of the synthesized catalyst as well the amount of metallic loaded from EDX. Key words; Platinum, Cobalt, Nickel on Carbon Support (PCN/C), Platinum, Cobalt and Nickel for 8 hour (PCN-8h), Commercial Platinum on Carbon Support (Pt/C), Oxidation Reduction Reaction (ORR), PEMFC, SEM, EDX, TEM, XRD.  

Oncornavirus assembly at the cell surface revealed in replicas of freeze-dried cells

1978 ◽  
Vol 36 (2) ◽  
pp. 354-355
Author(s):  
Anthony Demsey ◽  
Christopher W. Stackpole
Keyword(s):  
Cell Surface ◽  
Surface Membrane ◽  
Viral Origin ◽  
Intact Cells ◽  
Structural Formation ◽  
Virus Core ◽  
Freeze Dried ◽  
Cacodylate Buffer ◽  
Surface Replica ◽  
Leukemia Viruses

The murine leukemia viruses are type-C oncornaviruses, and their release from the host cell involves a “budding” process in which the newly-forming, RNA-containing virus core becomes enveloped by modified cell surface membrane. Previous studies revealed that the released virions possess a dense array of 10 nm globular projections (“knobs”) on this envelope surface, and that these knobs contain a 70, 000 MW glycoprotein (gp70) of viral origin. Taking advantage of this distinctive structural formation, we have developed a procedure for freeze-drying and replication of intact cells which reveals surface detail superior to other surface replica techniques, and sufficient to detect even early stages of virus budding by localized aggregation of these knobs on the cell surface.Briefly, cells growing in monolayer are seeded onto round glass coverslips 10-12 mm in diameter. After a period of growth, cells are fixed in situ for one hour, usually with 1% OsO4 in 0. 1 M cacodylate buffer, and rinsed in distilled water.

TEM Analysis of Long-Period Polytypes in SiC—S

1976 ◽  
Vol 34 ◽  
pp. 630-631
Author(s):  
S. Shinozaki ◽  
J. W. Sprys
Keyword(s):  
Electron Diffraction ◽  
Isothermal Annealing ◽  
Tem Analysis ◽  
Long Period ◽  
Transmission Electron ◽  
Average Grain Size ◽  
High Resolution Tem ◽  
Structural Lattice ◽  
The Stability ◽  
Continuous Curves

In reaction sintered SiC (∽ 5um average grain size), about 15% of the grains were found to have long-period structures, which were identifiable by transmission electron microscopy (TEM). In order to investigate the stability of the long-period polytypes at high temperature, crystal structures as well as microstructural changes in the long-period polytypes were analyzed as a function of time in isothermal annealing.Each polytype was analyzed by two methods: (1) Electron diffraction, and (2) Electron micrograph analysis. Fig. 1 shows microdensitometer traces of ED patterns (continuous curves) and calculated intensities (vertical lines) along 10.l row for 6H and 84R (Ramsdell notation). Intensity distributions were calculated based on the Zhdanov notation of (33) for 6H and [ (33)3 (32)2 ]3 for 84R. Because of the dynamical effect in electron diffraction, the observed intensities do not exactly coincide with those intensities obtained by structure factor calculations. Fig. 2 shows the high resolution TEM micrographs, where the striped patterns correspond to direct resolution of the structural lattice periodicities of 6H and 84R structures and the spacings shown in the figures are as expected for those structures.

Lorentz electron microscopy of magnetic domains in rapidly solidified and annealed Pt-Co-B alloys

1991 ◽  
Vol 49 ◽  
pp. 784-785
Author(s):  
N. Qiu ◽  
J. E. Wittig
Keyword(s):  
Rapid Solidification ◽  
Ion Beam ◽  
Magnetic Behavior ◽  
High Coercivity ◽  
Magnetic Domains ◽  
Beam Angle ◽  
Tem Analysis ◽  
Intrinsic Coercivity ◽  
Hard Magnets ◽  
Rapidly Solidified

PtCo hard magnets have specialized applications owing to their relatively high coercivity combined with corrosion resistance and ductility. Increased intrinsic coercivity has been recently obtained by rapid solidification processing of PtCo alloys containing boron. After rapid solidification by double anvil splat quenching and subsequent annealing for 30 minutes at 650°C, an alloy with composition Pt42Co45B13 (at.%) exhibited intrinsic coercivity up to 14kOe. This represents a significant improvement compared to the average coercivities in conventional binary PtCo alloys of 5 to 8 kOe.Rapidly solidified specimens of Pt42Co45B13 (at.%) were annealed at 650°C and 800°C for 30 minutes. The magnetic behavior was characterized by measuring the coercive force (Hc). Samples for TEM analysis were mechanically thinned to 100 μm, dimpled to about 30 nm, and ion milled to electron transparency in a Gatan Duomill at 5 kV and 1 mA gun current. The incident ion beam angle was set at 15° and the samples were liquid nitrogen cooled during milling. These samples were analyzed with a Philips CM20T TEM/STEM operated at 200 kV.

In situ TEM studies of irradiation effects for materials improvement

1991 ◽  
Vol 49 ◽  
pp. 452-453
Author(s):  
Charles W. Allen
Keyword(s):  
Nuclear Reactor ◽  
Austenitic Stainless Steels ◽  
High Energy ◽  
Point Of View ◽  
In Situ Tem ◽  
Irradiation Effects ◽  
Tem Analysis ◽  
Radiation Induced ◽  
Analytical Tools

Irradiation effects studies employing TEMs as analytical tools have been conducted for almost as many years as materials people have done TEM, motivated largely by materials needs for nuclear reactor development. Such studies have focussed on the behavior both of nuclear fuels and of materials for other reactor components which are subjected to radiation-induced degradation. Especially in the 1950s and 60s, post-irradiation TEM analysis may have been coupled to in situ (in reactor or in pile) experiments (e.g., irradiation-induced creep experiments of austenitic stainless steels). Although necessary from a technological point of view, such experiments are difficult to instrument (measure strain dynamically, e.g.) and control (temperature, e.g.) and require months or even years to perform in a nuclear reactor or in a spallation neutron source. Consequently, methods were sought for simulation of neutroninduced radiation damage of materials, the simulations employing other forms of radiation; in the case of metals and alloys, high energy electrons and high energy ions.

Transmission Electron Microscopy of an Aluminum-Silver-Stainless Steel Solid State Bond

1985 ◽  
Vol 43 ◽  
pp. 172-173
Author(s):  
M. J. Carr ◽  
J. F. Shewbridge ◽  
T. O. Wilford
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Solid State ◽  
Specimen Preparation ◽  
Dimensional Control ◽  
Tem Analysis ◽  
Metal Parts ◽  
Dissimilar Metal ◽  
Transmission Electron ◽  
Short Time

Strong solid state bonds are routinely produced between physical vapor deposited (PVD) silver coatings deposited on sputter cleaned surfaces of two dissimilar metal parts. The low temperature (200°C) and short time (10 min) used in the bonding cycle are advantageous from the standpoint of productivity and dimensional control. These conditions unfortunately produce no microstructural changes at or near the interface that are detectable by optical, SEM, or microprobe examination. Microstructural problems arising at these interfaces could therefore easily go undetected by these techniques. TEM analysis has not been previously applied to this problem because of the difficulty in specimen preparation. The purpose of this paper is to describe our technique for preparing specimens from solid state bonds and to present our initial observations of the microstructural details of such bonds.

Sign in / Sign up

Export Citation Format

Share Document