Daigle A.,Northeastern University |
Daigle A.,Metamagnetics, Inc. |
Modest J.,Northeastern University |
Geiler A.L.,Metamagnetics, Inc. |
And 9 more authors.
Nanotechnology | Year: 2011
The synthesis and properties of Mg(x)Zn(1 - x)Fe 2O4 spinel ferrites as a low-toxicity alternative to the technologically significant Ni(x)Zn(1 - x)Fe 2O4 ferrites are reported. Ferrite nanoparticles have been formed through both the polyol and aqueous co-precipitation methods that can be readily adapted to industrial scale synthesis to satisfy the demand of a variety of commercial applications. The structure, morphology and magnetic properties of Mg(x)Zn(1 - x)Fe2O4 were studied as a function of composition and particle size. Scanning electron microscopy images show particles synthesised by the aqueous co-precipitation method possess a broad size distribution (i.e. ∼ 80-120nm) with an average diameter of the order of 100nm 20nm and could be produced in high process yields of up to 25 gl-1. In contrast, particles synthesised by the polyol-based co-precipitation method possess a narrower size distribution with an average diameter in the 30nm 5nm range but are limited to smaller yields of ∼ 6gl-1. Furthermore, the polyol synthesis method was shown to control average particle size by varying the length of the glycol surfactant chain. Particles prepared by both methods are compared with respect to their phase purity, crystal structure, morphology, magnetic properties and microwave properties. © 2011 IOP Publishing Ltd. Source
Sarobol P.,Purdue University |
Chen W.-H.,Purdue University |
Pedigo A.E.,Naval Surface Warfare Center Crane Division |
Su P.,Cisco Systems |
And 2 more authors.
Journal of Materials Research | Year: 2013
A whisker and hillock growth model based on local film microstructure, grain misorientation, and elastic strain energy density (ESED) as the driving force for growth was developed to predict preferred sites for growth. Local grain orientations and strains measured by synchrotron microdiffraction in nine regions containing whiskers or hillocks were compared with elastic finite element analysis simulations including Sn elastic anisotropy. Whisker and hillock grains were observed to have higher crystallographic misorientations with neighboring grains than generally observed in the microstructure. While elastic simulations predicted higher local out-of-plane elastic strains and ESEDs at those locations with high misorientations before growth, synchrotron measurements of out-of-plane strains of whisker and hillock grains after growth showed relaxation, with correspondingly low ESEDs calculated from measured strains. Hence, highly localized out-of-plane elastic strains and ESEDs of grains with high relative misorientations with their neighbors determined, at least in part, which grains became whiskers or hillocks. Copyright © 2013 Materials Research Society. Source
Khatiwada R.,Indiana University |
Khatiwada R.,Indiana University - Purdue University Indianapolis |
Khatiwada R.,University of Washington |
Dennis L.,Cornell College |
And 10 more authors.
Measurement Science and Technology | Year: 2015
Materials with very low DC magnetic susceptibility have many scientific applications. To our knowledge however, relatively little research has been conducted with the goal to produce a totally nonmagnetic material. This phrase in our case means after spatially averaging over macroscopic volumes, it possesses an average zero DC magnetic susceptibility. We report measurements of the DC magnetic susceptibility of three different types of nonmagnetic materials at room temperature: (I) solutions of paramagnetic salts and diamagnetic liquids, (II) liquid gallium-indium alloys and (III) pressed powder mixtures of tungsten and bismuth. The lowest measured magnetic susceptibility among these candidate materials is in the order of 10-9 cgs volume susceptibility units, about two orders of magnitude smaller than distilled water. In all cases, the measured concentration dependence of the magnetic susceptibility is consistent with that expected for the weighted sum of the susceptibilities of the separate components within experimental error. These results verify the well-known Wiedemann additivity law for the magnetic susceptibility of inert mixtures of materials and thereby realize the ability to produce materials with small but tunable magnetic susceptibility. For our particular scientific application, we are also looking for materials with the largest possible number of neutrons and protons per unit volume. The gallium-indium alloys fabricated and measured in this work possess to our knowledge the smallest ratio of volume magnetic susceptibility to nucleon number density per unit volume for a room temperature liquid, and the tungsten-bismuth pressed powder mixtures possess to our knowledge the smallest ratio of volume magnetic susceptibility to nucleon number density per unit volume for a room temperature solid. This ratio is a figure of merit for a certain class of precision experiments that search for possible exotic spin-dependent forces of Nature. © 2016 IOP Publishing Ltd. Source
Hoyle R.,Indiana University Bloomington |
Templeman R.,Indiana University Bloomington |
Templeman R.,Naval Surface Warfare Center Crane Division |
Armes S.,Indiana University Bloomington |
And 3 more authors.
UbiComp 2014 - Proceedings of the 2014 ACM International Joint Conference on Pervasive and Ubiquitous Computing | Year: 2014
A number of wearable 'lifelogging' camera devices have been released recently, allowing consumers to capture images and other sensor data continuously from a first-person perspective. Unlike traditional cameras that are used deliberately and sporadically, lifelogging devices are always 'on' and automatically capturing images. Such features may challenge users' (and bystanders') expectations about privacy and control of image gathering and dissemination. While lifelogging cameras are growing in popularity, little is known about privacy perceptions of these devices or what kinds of privacy challenges they are likely to create.To explore how people manage privacy in the context of lifelogging cameras, as well as which kinds of first-person images people consider 'sensitive,' we conducted an in situ user study (N = 36) in which participants wore a lifelogging device for a week, answered questionnaires about the collected images, and participated in an exit interview. Our findings indicate that: 1) some people may prefer to manage privacy through in situ physical control of image collection in order to avoid later burdensome review of all collected images; 2) a combination of factors including time, location, and the objects and people appearing in the photo determines its 'sensitivity;' and 3) people are concerned about the privacy of bystanders, despite reporting almost no opposition or concerns expressed by bystanders over the course of the study. Copyright © 2014 by the Association for Computing Machinery, Inc. (ACM). Source
Balogun Y.A.,Naval Surface Warfare Center Crane Division |
Ubelhor R.,Naval Surface Warfare Center Crane Division
Materials Science and Technology Conference and Exhibition 2014, MS and T 2014 | Year: 2014
The likelihood of successful system operation following long periods of dormancy can be increased by assessing the long-term environmental effects on the performance of materials and subsystems. Because of the long experimental times often required in many accelerated aging programs, the need for faster and more reliable methods for investigating the degradative aging of polymeric materials under various environments becomes important. In this study, a micro-calorimeter was used in monitoring the heat flow as a function of time for a Nylon 6.6 polymer. Arrhenius model was used in fitting the data, following which activation energy was determined. The results obtained are consistent with published data for other sensitive measurement methods, but at a fraction of the samples and time. Implementation of technique and mitigation of weaknesses inherent in it will be presented and discussed. Copyright © 2014 MS&T14®. Source