scholarly journals Size-Dependent Alloying Ability of Immiscible W-Cu Bimetallic Nanoparticles: A Theoretical and Experimental Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1047
Author(s):  
Hongbo Zhang ◽  
Tao Liu ◽  
Siqi Zhao ◽  
Zhanyuan Xu ◽  
Yaozha Lv ◽  
...  
Keyword(s):  
Binary Systems ◽  
Bimetallic Nanoparticles ◽  
Driving Forces ◽  
Phase Particle ◽  
Phase Segregation ◽  
High Yield ◽  
Universal Method ◽  
Face Centered Cubic ◽  
Original Size ◽  
Face Centered

The preparation of alloyed bimetallic nanoparticles (BNPs) between immiscible elements is always a huge challenge due to the lack of thermodynamic driving forces. W–Cu is a typical immiscible binary system, and it is difficult to alloy them under conventional circumstances. Here, we used the bond energy model (BEM) to calculate the effect of size on the alloying ability of W–Cu systems. The prediction results show that reducing the synthesis size (the original size of W and Cu) to less than 10 nm can obtain alloyed W–Cu BNPs. Moreover, we prepared alloyed W50Cu50 BNPs with a face-centered-cubic (FCC) crystalline structure via the nano in situ composite method. Energy-dispersive X-ray spectroscopy (EDS) coupled with scan transmission electron microscopy (STEM) confirmed that W and Cu are well mixed in a single-phase particle, instead of a phase segregation into a core-shell or other heterostructures. The present results suggest that the nanoscale size effect can overcome the immiscibility in immiscible binary systems. In the meantime, this work provided a high-yield and universal method for preparing alloyed BNPs between immiscible elements.

Radiolytic Synthesis of Bimetallic Nanoparticles with High Aspect Ratio

2002 ◽  
Vol 740 ◽  
Author(s):  
C. M. Doudna ◽  
M. F. Bertino ◽  
S. Pillalamarri ◽  
F. D. Blum ◽  
A. T. Tokuhiro ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Bimetallic Nanoparticles ◽  
Water Soluble ◽  
Face Centered Cubic ◽  
Radiation Dose Rate ◽  
Water Soluble Polymer ◽  
Transmission Electron ◽  
Counter Ions ◽  
Face Centered

ABSTRACTWe present a technique to synthesize high aspect ratio metallic nanostructures based on the radiolysis method. In our experiments, we use gamma rays to irradiate aqueous solutions containing Ag and Pt ions and a water-soluble polymer. The aspect ratio of the nanoparticles is controlled by varying the radiation dose rate, the type of polymer, and the type of counter ions. Transmission electron microscopy shows that wire-like structures composed of grains with a face centered cubic (fcc) structure can be formed with a length of up to 3.5μm and typical diameters between 5 and 12nm. X-Ray absorption spectroscopy shows that Ag and Pt do not form an alloy, but remain segregated.

scholarly journals Synthesis of Bimetallic PdAg Nanoparticles and Their Electrocatalytic Activity toward Ethanol

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Fahui Gao ◽  
Yanru Yin ◽  
Zhengshuai Cao ◽  
Hongliang Li ◽  
Peizhi Guo
Keyword(s):  
Electrocatalytic Activity ◽  
Bimetallic Nanoparticles ◽  
Molar Ratio ◽  
Face Centered Cubic ◽  
Ethanol Electrooxidation ◽  
Uniform Size ◽  
Catalytic Current ◽  
The Face ◽  
Alloy Nanostructures ◽  
Face Centered

Palladium-based bimetallic nanoparticles (NPs) have been studied as important electrocatalysts for energy conversion due to their high electrocatalytic performance and the less usage of the noble metal. Herein, well-dispersed PdAg NPs with uniform size were prepared via oil bath accompanied with the hydrothermal method. The variation of the Ag content in PdAg NPs changed the lattice constant of the face-centered cubic alloy nanostructures continuously. The Pd/Ag molar ratio in the PdAg alloy NPs affected their size and catalytic activity toward ethanol electrooxidation. Experimental data showed that PdAg NPs with less Ag content exhibited better electrocatalytic activity and durability than pure Pd NPs owing to both the small size and the synergistic effect. PdAg-acac-4 with the Pd/Ag molar ratio of 4 : 1 in the start system possessed the highest catalytic current density of 2246 mA/mg for the electrooxidation of ethanol. The differences in the morphology and electrocatalytic activity of the as-made PdAg NPs have been discussed and analyzed.

Energy vs. Entropy in Superlattices of Ligand-Covered Nanoparticles

2019 ◽  
Author(s):  
Zhaochuan Fan ◽  
Michael Gruenwald
Keyword(s):  
Potential Energy ◽  
Driving Forces ◽  
Molecular Model ◽  
Configurational Entropy ◽  
Nearest Neighbors ◽  
Coarse Grained ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Core Size ◽  
Face Centered

Nanoparticles covered with short ligands tend to self-assemble into face-centered cubic (fcc) superlattices, while nanoparticles with longer ligands preferentially form body-centered cubic (bcc) superlattices. The thermodynamic driving forces for these structures are not fully understood and conflicting theories have been proposed. In this paper, we systematically study the thermodynamic stability of fcc and bcc superlattices as a function of ligand length, core size, and ligand coverage with a coarse-grained molecular model. Our simulations reveal that bcc superlattices are stabilized via two fundamentally different mechanisms, depending on ligand length. For shorter ligands, the bcc superlattice has a lower potential energy than fcc, due to additional interactions between ligands on next-nearest neighbors in the superlattice. For longer ligands, the bcc superlattice is stabilized due to a larger configurational entropy of ligands.

Energy vs. Entropy in Superlattices of Ligand-Covered Nanoparticles

2019 ◽  
Author(s):  
Zhaochuan Fan ◽  
Michael Gruenwald
Keyword(s):  
Potential Energy ◽  
Driving Forces ◽  
Molecular Model ◽  
Configurational Entropy ◽  
Nearest Neighbors ◽  
Coarse Grained ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Core Size ◽  
Face Centered

Nanoparticles covered with short ligands tend to self-assemble into face-centered cubic (fcc) superlattices, while nanoparticles with longer ligands preferentially form body-centered cubic (bcc) superlattices. The thermodynamic driving forces for these structures are not fully understood and conflicting theories have been proposed. In this paper, we systematically study the thermodynamic stability of fcc and bcc superlattices as a function of ligand length, core size, and ligand coverage with a coarse-grained molecular model. Our simulations reveal that bcc superlattices are stabilized via two fundamentally different mechanisms, depending on ligand length. For shorter ligands, the bcc superlattice has a lower potential energy than fcc, due to additional interactions between ligands on next-nearest neighbors in the superlattice. For longer ligands, the bcc superlattice is stabilized due to a larger configurational entropy of ligands.

scholarly journals Antibacterial Activity and Characteristics of Silver Nanoparticles Biosynthesized From Carduus Crispus

2021 ◽  
Author(s):  
Enerelt Urnukhsaikhan ◽  
Bum-Erdene Bold ◽  
Aminaa Gunbileg ◽  
Nominchimeg Sukhbaatar ◽  
Tsogbadrakh Mishig-Ochir
Keyword(s):  
Silver Nanoparticles ◽  
Antibacterial Activity ◽  
Functional Groups ◽  
Micrococcus Luteus ◽  
Blue Shift ◽  
High Yield ◽  
Face Centered Cubic ◽  
Average Grain Size ◽  
Medical Plant ◽  
Face Centered

Abstract Recently, synthesizing metal nanoparticles using plants has been extensively studied and recognized as a non-toxic and efficient way for biomedical field. The aim of this study is to investigate the role of different parts of Carduus crispus medical plant on synthesizing silver nanoparticles and their characteristics. Our study showed that silver nanoparticles (AgNP) synthesized via whole plant extract exhibited a blue shift in absorption spectra with increased optical density, which correlates to a high yield and smaller size. Also, the results of zeta potential, XRD, PCCS analysis showed the surface charge of -54.29 ±4.96 mV (AgNP-S), -42.64 ±3.762 mV (AgNP-F), -46.02 ±4.17 mV (AgNP-W), the crystallite size of 36 nm (AgNP-S), 13 nm (AgNP-F), 14 nm (AgNP-W) with face-centered cubic structure and average grain size of approximately 100 nm. Another important characteristic, such as elemental composition and constituent capping agent has been determined by EDX and FTIR. The silver nanoparticles were composed of ~80% Ag, ~15% K, and ~7.5% Ca (or ~2.8% P) elements. Moreover, the results of the FTIR measurement suggested that AgNP-F and AgNP-S contained distinct functional groups, on the other hand, AgNP-W contained all of the functional groups present in AgNP-F and AgNP-S. The silver nanoparticles showed antibacterial activity on both gram-negative bacterium Escherichia coli (5.5 ± 0.2 mm to 6.5 ± 0.3 mm) and gram-positive bacterium Micrococcus luteus (7 ± 0.4 mm to 7.7 ± 0.5 mm). Our study is meaningful as a first observation indicating the possibility of using special plant organs to control the characteristics of nanoparticles.

Thermodynamische Analyse der binären Systeme des Germaniums mit Kupfer, Silber und Gold

1971 ◽  
Vol 26 (4) ◽  
pp. 722-734 ◽  
Author(s):  
B. Predel ◽  
D. W. Stein
Keyword(s):  
Binary Systems ◽  
Enthalpies Of Formation ◽  
Enthalpies Of Solution ◽  
Face Centered Cubic ◽  
Enthalpies Of Mixing ◽  
Electronegativity Difference ◽  
Face Centered ◽  
The Stability ◽  
Electron Compounds ◽  
Liquid Tin

Abstract For the purpose of carrying out a thermodynamic analysis of the binary systems of germanium with copper, silver and gold, the enthalpies of mixing of liquid Cu-Ge and Au-Ge alloys were determined at 1150 °C. Further the enthalpies of mixing of Ag-Ge solid solutions and the enthalpies of formation of the ζ and ε1 phases of the Cu-Ge system were obtained from the enthalpies of solution in liquid tin. It was possible to determine the enthalpy of transformation of germanium from its stable modification into a hypothetical, face-centered cubic structure (ΔHT(Ge) = 13.0 kcal /g-atom) which has a decisive influence on the stability of the solid phases in the systems under consideration. Liquid Cu-Ge alloys show energetic pecularities similar to those existing in the solid state and leading to the formation of electron compounds. A distinct influence of the valency difference of the components can also be demonstrated. In the gold-germanium system, however, the influence of the electronegativity difference of the components is dominant.

Atomic Organization In Magnetic Bimetallic Nanoparticles: An Experimental And Theoretical Approach

2003 ◽  
Vol 789 ◽  
Author(s):  
Marie-Claire Fromen ◽  
Samuel Dennler ◽  
Marie-José Casanove ◽  
Pierre Lecante ◽  
Joseph Morillo ◽  
...  
Keyword(s):  
Surface Segregation ◽  
Bimetallic Nanoparticles ◽  
Interaction Model ◽  
Face Centered Cubic ◽  
Chemical Route ◽  
Energy Filtering ◽  
Pure Cobalt ◽  
Transmission Electron ◽  
The Face ◽  
Face Centered

ABSTRACTUltrafine bimetallic CoRh nanoparticles synthesized by a soft chemical route with compositions ranging from pure cobalt to pure rhodium are investigated using high-resolution and energy filtering transmission electron microscopy techniques as well as wide angle x-ray scattering. In parallel, they are simulated with the use of an n-body semi-empirical interaction model: quenched molecular dynamics and Monte-Carlo Metropolis simulated annealing are performed on these nanoparticles in order to find their most stable isomers as a function of composition and size. A progressive evolution from an original polytetrahedral structure to the face-centered cubic structure with increasing Rh content is observed in these particles. Strong tendency to Co surface segregation is both experimentally evidenced and confirmed by the simulations.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

Microstructure of Electro-Eroded Cemented Carbide Surfaces

1968 ◽  
Vol 26 ◽  
pp. 284-285
Author(s):  
V. N. Filimonenko ◽  
M. H. Richman ◽  
J. Gurland
Keyword(s):  
Surface Layer ◽  
Cobalt Content ◽  
Cemented Carbides ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Metallographic Examination ◽  
Standard Procedures ◽  
Face Centered ◽  
Diamond Paste ◽  
Plastic Carbon

The high temperatures and pressures that are found in a spark gap during electrical discharging lead to a sharp phase transition and structural transformation in the surface layer of cemented carbides containing WC and cobalt. By means of X-ray diffraction both W2C and a high-temperature monocarbide of tungsten (face-centered cubic) were detected after electro-erosion. The W2C forms as a result of the peritectic reaction, WC → W2C+C. The existence and amount of the phases depend on both the energy of the electro-spark discharge and the cobalt content. In the case of a low-energy discharge (i.e. C=0.01μF, V = 300v), WC(f.c.c.) is generally formed in the surface layer. However, at high energies, (e.g. C=30μF, V = 300v), W2C is formed at the surface in preference to the monocarbide. The phase transformations in the surface layer are retarded by the presence of larger percentages of cobalt.Metallographic examination of the electro-eroded surfaces of cemented carbides was carried out on samples with 5-30% cobalt content. The specimens were first metallographically polished using diamond paste and standard procedures and then subjected to various electrical discharges on a Servomet spark machining device. The samples were then repolished and etched in a 3% NH4OH electrolyte at -0.5 amp/cm2. Two stage plastic-carbon replicas were then made and shadowed with chromium at 27°.

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