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Title: Interaction Effects Witin Langmuir Layers and Three-Dimensional Arrays of E-Co Nanoparticles

Abstract

Magnetostatic interactions are studied in two types of nanoparticle assemblies. Highly ordered monolayers of {epsilon}-Co nanoparticles are prepared from Langmuir films and self-assembled three-dimensional (3D) arrays formed by slow precipitation of colloidal dispersions of same nanoparticles. The structure of assemblies is found from electron microscopy and small-angle x-ray scattering. The differences in magnetic behavior are interpreted in terms of the particle moment, interparticle separation, and coordination number. Preferential in-plane magnetization is observed due to interactions within a monolayer. 3D arrays show stronger interactions compared to monolayers due to an increased number of nearest neighbors.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914397
Report Number(s):
BNL-78965-2007-JA
Journal ID: ISSN 0021-8979; JAPIAU; TRN: US200809%%55
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Appl. Phys.; Journal Volume: 99
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; COBALT; COORDINATION NUMBER; INTERACTIONS; NANOSTRUCTURES; COLLOIDS; PRECIPITATION; MAGNETIC PROPERTIES; national synchrotron light source

Citation Formats

Sachan,M., Walrath, N., Majetich, S., Krycka, K., and Kao, C. Interaction Effects Witin Langmuir Layers and Three-Dimensional Arrays of E-Co Nanoparticles. United States: N. p., 2006. Web. doi:10.1063/1.2168438.
Sachan,M., Walrath, N., Majetich, S., Krycka, K., & Kao, C. Interaction Effects Witin Langmuir Layers and Three-Dimensional Arrays of E-Co Nanoparticles. United States. doi:10.1063/1.2168438.
Sachan,M., Walrath, N., Majetich, S., Krycka, K., and Kao, C. Sun . "Interaction Effects Witin Langmuir Layers and Three-Dimensional Arrays of E-Co Nanoparticles". United States. doi:10.1063/1.2168438.
@article{osti_914397,
title = {Interaction Effects Witin Langmuir Layers and Three-Dimensional Arrays of E-Co Nanoparticles},
author = {Sachan,M. and Walrath, N. and Majetich, S. and Krycka, K. and Kao, C.},
abstractNote = {Magnetostatic interactions are studied in two types of nanoparticle assemblies. Highly ordered monolayers of {epsilon}-Co nanoparticles are prepared from Langmuir films and self-assembled three-dimensional (3D) arrays formed by slow precipitation of colloidal dispersions of same nanoparticles. The structure of assemblies is found from electron microscopy and small-angle x-ray scattering. The differences in magnetic behavior are interpreted in terms of the particle moment, interparticle separation, and coordination number. Preferential in-plane magnetization is observed due to interactions within a monolayer. 3D arrays show stronger interactions compared to monolayers due to an increased number of nearest neighbors.},
doi = {10.1063/1.2168438},
journal = {J. Appl. Phys.},
number = ,
volume = 99,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • Magnetostatic interactions are studied in two types of nanoparticle assemblies. Highly ordered monolayers of {epsilon}-Co nanoparticles are prepared from Langmuir films and self-assembled three-dimensional (3D) arrays formed by slow precipitation of colloidal dispersions of same nanoparticles. The structure of assemblies is found from electron microscopy and small-angle x-ray scattering. The differences in magnetic behavior are interpreted in terms of the particle moment, interparticle separation, and coordination number. Preferential in-plane magnetization is observed due to interactions within a monolayer. 3D arrays show stronger interactions compared to monolayers due to an increased number of nearest neighbors.
  • Under certain conditions, numerous internal surface cracks develop in pressurized thick-walled cylinders, both in the radial and longitudinal directions. For fatigue life assessment of such vessels, the 3-D interaction effects among these cracks on the prevailing stress intensity factors (SIFs) need evaluation. In Part 1 of this paper, radial crack arrays are considered exclusively. The mode 1 SIF distribution for a wide range of semi-circular and semi-elliptical cracks are evaluated. The 3-D analysis is performed via the finite element method with the submodeling technique, employing singular elements along the crack front. SIFs are evaluated for arrays of up to nmore » = 180 cracks; for a wide range of crack depth to wall thickness ratios, a/t, from 0.05 to 0.6; and, for various ellipticities of the crack, i.e., the ratio of crack depth to semicrack length, a/c, from 0.2 to 2. Using a least-squares fit, two simple expressions for the most critical (n = 2) SIFs are obtained for sparse and dense crack arrays. The formulas, which are functions of a/t and a/c, are of very good engineering accuracy. The results clearly indicate that the SIFs are considerably affected by the interaction among the cracks in the array as well as the three-dimensionality of the problem. In Part 2 of this paper, the interaction effects between longitudinal coplanar cracks will be analyzed.« less
  • In the first part of this paper, the interaction effects among many radial, internal, semi-circular, and semi-elliptical cracks in a pressurized, thick-walled vessel were quantified. In the present paper, the mode 1 stress intensity factor (SIF) distribution for numerous longitudinal coplanar, internal, semi-circular, and semi-elliptical arrays of surface cracks in an infinite, pressurized, thick-walled cylinder are evaluated. The 3-D analysis is performed by the finite element (FE) method and the submodeling technique, employing singular elements along the crack front. The effects f dense and sparse interacting longitudinal coplanar crack arrays on the SIFs are studied for a wide range ofmore » crack depth to wall thickness ratios, a/t, from 0.05 to 0.6; and, for various ellipticities of the crack, i.e., the ratio of the crack depth to semi-crack length, a/c, from 0.2 to 2.0. An analysis is performed to determine the influence of the three major parameters--crack density, crack ellipticity, and crack depth--on the interaction effects between adjacent cracks. The results clearly indicate that crack density, and, in some cases, ellipticity have opposing effects on the SIF of longitudinal crack arrays as compared to radial crack arrays. As a result of these contrasting behaviors, thick-walled cylinders having combined longitudinal and radial crack arrays would need further study.« less
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