scholarly journals Size-dependent non-space filling atomic packing in metallic nanoparticles

2014 ◽  
Vol 70 (a1) ◽  
pp. C867-C867
Author(s):  
Vicky Doan-Nguyen ◽  
Simon Kimber ◽  
Diego Pontoni ◽  
Danielle Reifsnyder ◽  
Benjamin Diroll ◽  
...  
Keyword(s):  
Metallic Nanoparticles ◽  
Pd Nanoparticles ◽  
Distribution Functions ◽  
Face Centered Cubic ◽  
Structure Property ◽  
Space Filling ◽  
Atomic Packing ◽  
Size Dependent ◽  
Local Ordering ◽  
Icosahedral Clusters

Ni-Pd nanoparticles synthesized for CO catalysis are characterized by transmission electron microscopy and total X-ray scattering. The sizes of these nanoparticles can be tuned to size with great control over the monodispersity of the samples. The pair distribution functions of the reveal a local ordering within the highly disordered atomic structure within the nanoparticles. The PDFs show a size-dependent deviation from typical bulk face centered cubic (fcc) structure for these materials. The long-range isotropic disorder within these non-fcc nanoparticles can be fitted using an exponentially damped single-mode sine wave. Below a diameter of 5 nm, the Ni-Pd nanoparticles exhibit local ordering of atoms as found in typical icosahedral clusters. The transition from fcc to non-space filling atomic packing of icosahedral clusters in a nanoparticle is modeled to show the structural origin of the observed PDFs. Understanding this type of disorder can give insight into structure-property relations for applications in heterogeneous catalysis.

Size-dependent Hydrogen trapping in Palladium nanoparticles

2021 ◽  
Author(s):  
Wang Liu ◽  
Yann Magnin ◽  
Georg Daniel Förster ◽  
Julie Bourgon ◽  
Thomas Len ◽  
...  
Keyword(s):  
Experimental Study ◽  
Theoretical Approach ◽  
Palladium Nanoparticles ◽  
Hydrogen Absorption ◽  
Pd Nanoparticles ◽  
Hydrogen Trapping ◽  
Size Dependent

We report an experimental study, supported by a theoretical approach based on simulations, to explore the phenomenon of H trapping in small Pd nanoparticles. Hydrogen absorption/desorption of a series of...

scholarly journals Expanding Monomers as Anti-Shrinkage Additives

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 806
Author(s):  
Philipp Marx ◽  
Frank Wiesbrock
Keyword(s):  
Ring Opening ◽  
Covalent Bond ◽  
Volumetric Shrinkage ◽  
Structure Property ◽  
Atomic Packing ◽  
Materials Properties ◽  
Volumetric Expansion ◽  
Structure Property Relationships ◽  
Ring Opening Reaction ◽  
Measuring Techniques

Commonly, volumetric shrinkage occurs during polymerizations due to the shortening of the equilibrium Van der Waals distance of two molecules to the length of a (significantly shorter) covalent bond. This volumetric shrinkage can have severe influence on the materials’ properties. One strategy to overcome this volumetric shrinkage is the use of expanding monomers that show volumetric expansion during polymerization reactions. Such monomers exhibit cyclic or even oligocyclic structural motifs with a correspondingly dense atomic packing. During the ring-opening reaction of such monomers, linear structures with atomic packing of lower density are formed, which results in volumetric expansion or at least reduced volumetric shrinkage. This review provides a concise overview of expanding monomers with a focus on the elucidation of structure-property relationships. Preceded by a brief introduction of measuring techniques for the quantification of volumetric changes, the most prominent classes of expanding monomers will be presented and discussed, namely cycloalkanes and cycloalkenes, oxacycles, benzoxazines, as well as thiocyclic compounds. Spiroorthoesters, spiroorthocarbonates, cyclic carbonates, and benzoxazines are particularly highlighted.

scholarly journals Nonlocal and Size-Dependent Dielectric Function for Plasmonic Nanoparticles

2019 ◽  
Vol 9 (15) ◽  
pp. 3083
Author(s):  
Kai-Jian Huang ◽  
Shui-Jie Qin ◽  
Zheng-Ping Zhang ◽  
Zhao Ding ◽  
Zhong-Chen Bai
Keyword(s):  
Metallic Nanoparticles ◽  
High Efficiency ◽  
Finite Size ◽  
Plasmonic Nanostructures ◽  
Accurate Analysis ◽  
Finite Size Effects ◽  
Size Dependent ◽  
Quantum Size ◽  
The Impact ◽  
Electron Energy Loss

We develop a theoretical approach to investigate the impact that nonlocal and finite-size effects have on the dielectric response of plasmonic nanostructures. Through simulations, comprehensive comparisons of the electron energy loss spectroscopy (EELS) and the optical performance are discussed for a gold spherical dimer system in terms of different dielectric models. Our study offers a paradigm of high efficiency compatible dielectric theoretical framework for accounting the metallic nanoparticles behavior combining local, nonlocal and size-dependent effects in broader energy and size ranges. The results of accurate analysis and simulation for these effects unveil the weight and the evolution of both surface and bulk plasmons vibrational mechanisms, which are important for further understanding the electrodynamics properties of structures at the nanoscale. Particularly, our method can be extended to other plasmonic nanostructures where quantum-size or strongly interacting effects are likely to play an important role.

scholarly journals Size Dependent CO2 Reduction Activity of Ag Nanoparticle Electrocatalysts

2021 ◽  
Author(s):  
Xingyi Deng ◽  
Dominic Alfonso ◽  
Thuy-Duong Nguyen-Phan ◽  
Douglas Kauffman
Keyword(s):  
Active Sites ◽  
Density Functional ◽  
Particle Diameter ◽  
Small Diameter ◽  
Co2 Reduction ◽  
High Population ◽  
Structure Property ◽  
Size Dependent ◽  
Catalyst Utilization ◽  
Ag Catalysts

Abstract Coinage metals (Au, Cu and Ag) are state-of-the-art electrocatalysts for the CO2 reduction reaction (CO2RR). Size-dependent CO2RR activity of Au and Cu has been studied, and increased H2 evolution reaction (HER) activity is expected for small catalyst particles with high population of undercoordinated corner sites. A similar consensus is still lacking for Ag catalysts because the ligands and stabilizers typically used to control particle synthesis can block specific active sites and mask inherent structure-property trends. This knowledge gap is problematic because increased performance and catalyst utilization are still needed to improve economic viability. We combined density functional theory, microkinetic modeling, and experiment to demonstrate a strong size-dependence for pristine Ag particles in the sub-10 nm range. Small diameter particles with a high population of Ag edge sites were predicted to favor HER, whereas CO2RR selectivity increased towards that of bulk Ag for larger diameter particles as the population of Ag(100) surface sites grew. Experimental results validated these predictions and we identified an optimal particle diameter of 8-10 nm that balanced selectivity and activity. Particles below this diameter suffered from poor selectivity, while larger particles demonstrated bulk-like activity and reduced catalyst utilization. These results demonstrate the size-dependent CO2RR activity of pristine Ag catalysts and will help guide future development efforts.

scholarly journals Polyether Based Thermoplastic Polyurethane Melt Blown Nonwovens

2006 ◽  
Vol 1 (1) ◽  
pp. 155892500600100 ◽  
Author(s):  
Terezie Zapletalova ◽  
Stephen Michielsen ◽  
Behnam Pourdeyhimi
Keyword(s):  
Fiber Orientation ◽  
Thermoplastic Polyurethane ◽  
Strong Relationship ◽  
Thermoplastic Elastomers ◽  
Distribution Functions ◽  
Structure Property ◽  
Melt Blowing ◽  
Polyurethane Elastomers ◽  
Fiber Orientation Distribution ◽  
The Web

A series of melt blown samples were produced from three hardness grades of ether based thermoplastic polyurethane elastomers (TPU). The fabrics were tested to investigate their structure-property relationship in a melt blown process. Solution viscosities of the web were only 20–26% of there original values indicating a large loss in polymer molecular weight during melt blowing. Fiber diameter distributions measured on melt blown samples were found comparable to those made with more conventional polymers. The fiber orientation distribution functions (ODF) suggest slight fiber orientation in machine direction. Tensile and elongation properties depended on die-to-collector distance (DCD), polymer hardness and fiber ODF. A strong relationship between the tensile strength and die-to-collector distance was identified and attributed to reduced interfiber adhesion in the web with increasing DCD. The reduction in adhesion was attributed to greater extents of solidification before reaching the forming belt for longer DCDs. This paper is the first in a series relating the influence of the melt blowing process parameters on the polymer properties and the nonwoven fabric properties for block thermoplastic elastomers.

Metallic Nanoparticles from Single Polyelectrolyte Molecules

2002 ◽  
Vol 726 ◽  
Author(s):  
Ganna Gorodyska ◽  
Anton Kiriy ◽  
Sergiy Minko ◽  
Manfred Stamm
Keyword(s):  
Metallic Nanoparticles ◽  
Flat Surface ◽  
Pd Nanoparticles ◽  
Palladium Acetate ◽  
Step Procedure ◽  
Synthetic Procedure ◽  
Metallic Palladium ◽  
Dimethylamine Borane ◽  
Pd Clusters ◽  
Si Wafer

AbstractHere we report on the metallization of poly(2-vinylpyridine) (P2VP) by coordination with palladium acetate (PA) followed by reduction with dimethylamine borane (DAB) to metallic palladium. The morphology of the resulting products deposited on a flat surface was analyzed with AFM. If P2VP, PA and DAB are mixed together, the Pd clusters up to 30 nm in diameter are obtained. A two step synthetic procedure was examined. The initially prepared complex P2VPH-1/2(PdCl4) was deposited on Si-wafer and then reduced, leading to the Pd clusters with a narrow size distribution (3 nm height by 100 nm length). Alternately, a step-by-step procedure was used wherein P2VP single molecules were deposited on Si wafers from very dilute acidic aqueous solutions then placed in PA solution and finally reduced with DAB, resulting in the 1.5-5 nm in the diameter wire-shaped Pd nanoparticles with the length of about 350 nm.

scholarly journals Theoretical Investigation on Structure-Property Relationship of Asymmetric Clusters (CH3FBN3)n (n = 1– 6)

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Deng-Xue Ma ◽  
Yao-Yao Wei ◽  
Yun-Zhi Li ◽  
Guo-Kui Liu ◽  
Qi-Ying Xia
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Dft Method ◽  
Energy Difference ◽  
Structure Property ◽  
Functional Theory ◽  
Size Dependent ◽  
Stable Clusters ◽  
Chemical Inertness ◽  
Relationship Of

The structural, relative stability, electronic, IR vibrational, and thermodynamic properties of asymmetric clusters (CH3FBN3)n (n = 1–6) are systematically investigated using density functional theory (DFT) method. Results show that clusters (CH3FBN3)n (n = 2–6) form a cyclic structure with a B atom and a Nα atom binding together. Five main characteristic regions are observed and assigned for the calculated IR spectra. The size-dependent second-order energy difference shows that clusters (CH3FBN3)3 and (CH3FBN3)5 have relatively higher stability and enhanced chemical inertness compared with the neighboring clusters. These two clusters may serve as the cluster-assembled materials. The variations of thermodynamic properties with temperature T or cluster size n are analyzed, respectively. Based on enthalpies in the range of 200–800 K, the formations of the most stable clusters (CH3FBN3)n (n = 2–6) from monomer are thermodynamically favorable. These data are helpful to design and synthesize other asymmetric boron azides.

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