Gas-Phase Production of Multifunctional Composite Nanoparticles by Photoinduced Chemical Vapor Deposition

2010 ◽  
Author(s):  
Adam Boies ◽  
Pingyan Lei ◽  
Jeff Roberts ◽  
Steven Girshick
Keyword(s):  
Magnetic Field ◽  
Gas Phase ◽  
Magnetic Particles ◽  
Magnetic Force ◽  
Critical Size ◽  
Chemical Vapor ◽  
Electrically Conductive ◽  
Magnetic Resonance Imaging Mri ◽  
Phase Production ◽  
Pole Orientation

Nano-scale materials and devices allow for unique interactions that are not possible at larger scales. Magnetic particles below a critical size (∼10 nm) demonstrate distinctive behavior known as superparamagnetism, where particles do not exhibit any net magnetic force outside the presence of an external magnetic field. However, within an alternating magnetic field, as in a magnetic resonance imaging (MRI) machine, superparamagnetic particles give off heat as a result of Brownian and Nee´lian relaxation. Heat produced by the shifting pole orientation can raise the temperature of the tissue sufficient to cause cell death through necrosis or apoptosis [1]. Additionally, combinations of electrically conductive and insulating materials within a single nanoparticle give rise to surface plasmon resonance. The resonance of the plasmon absorption can be tuned based on the relative thicknesses of the two layers. These particles can be used to thermally ablate cancer cells if the resonance is tuned to absorb light from an infrared laser. The penetrating ability of the nanoparticles combined with their capacity to kill cells make them excellent candidates for treatment of conditions such as brain tumors and prostate cancer.

scholarly journals High-Resolution Magnetic Force Microscopy Using Carbon Nanotube Probes Fabricated Directly by Microwave Plasma-Enhanced Chemical Vapor Deposition

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
Kei Tanaka ◽  
Masamichi Yoshimura ◽  
Kazuyuki Ueda
Keyword(s):  
Electron Microscopy ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Magnetic Force Microscopy ◽  
Magnetic Particles ◽  
Magnetic Force ◽  
Microwave Plasma ◽  
Chemical Vapor ◽  
Force Microscopy ◽  
Afm Cantilever

Carbon nanotubes (CNTs) have been successfully grown on the tip apex of an atomic force microscopy (AFM) cantilever by microwave plasma-enhanced chemical vapor deposition (MPECVD). Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations reveal that the diameter of the CNTs is∼30 nm and the magnetic particles with diameter of∼20 nm, which was used as catalyst for the CNT growth, exist on the top. This CNT probe has been applied to magnetic force microscopy (MFM) on the ultrahigh-density magnetic recording media with 1200 kilo flux change per inch (kfci).

HEATING RATE PREDICTION FOR INDUCTION WELDING MAGNETIC SUSCEPTORS

2021 ◽  
Author(s):  
ROMAIN G. MARTIN ◽  
CHRISTER JOHANSSON ◽  
JASON R. TAVARES ◽  
MARTINE DUBÉ
Keyword(s):  
Magnetic Field ◽  
Heating Rate ◽  
Surface Area ◽  
Magnetic Particles ◽  
Eddy Currents ◽  
Field Amplitude ◽  
Hysteresis Curve ◽  
Heating Rates ◽  
Electrically Conductive ◽  
Thermoplastic Matrix

Induction welding involves generating heat by applying an oscillating magnetic field, which produces eddy currents and Joule losses in an electrically-conductive material or hysteresis losses in a magnetic material. Most applications rely on eddy currents generation as composites are often made of electrically-conductive carbon fibres. However, in other applications, heat can be produced by a magnetic susceptor located at the weld interface of the parts to be joined. Composite films of magnetic particles dispersed in a thermoplastic matrix can serve as magnetic susceptors. Magnetic particles selection relies on various parameters that must be thoroughly defined beforehand. Firstly, the applied magnetic field amplitude and frequency is calculated, based on the generated current and the induction coil geometry. Secondly, the thermoplastic matrix is characterized, mainly with DSC measurements, to define its processing window. Finally, the magnetic properties of the particles are measured – for instance using a vibrating sample magnetometer (VSM) – to obtain the hysteresis curve for the applied field. The enclosed surface area of the hysteresis curve (i.e. absorbed energy density) is critical, as low hysteresis materials (i.e. soft magnets) will not dissipate enough heat, while high hysteresis materials (i.e. hard magnets) cannot be fully exploited as the saturation hysteresis is not reached within the used field amplitude. A methodology to approximate the hysteresis enclosed surface area with limited data is proposed, helping to anticipate the heating rate of a susceptor candidate material. Based on these parameters, the theoretical heating rates of three magnetic susceptor materials (magnetic particles of iron, nickel and magnetite) for induction welding are calculated. They are verified experimentally by comparing with the hysteresis analysis and by measuring the temperature evolution of samples made of polypropylene containing the magnetic particles.

Mechanism of a Magnetic Field Assisted Finishing Process Using a Magnet Tool and Magnetic Particles

2007 ◽  
Vol 339 ◽  
pp. 106-113 ◽  
Author(s):  
Yan Hua Zou ◽  
Takeo Shinmura
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Magnetic Force ◽  
Magnetic Particle ◽  
Machining Process ◽  
Finishing Process ◽  
Magnet Surface ◽  
Magnetic Abrasives ◽  
Quality Surface ◽  
Process Method

This paper describes a new efficient internal finishing process for a thick tubing (10~30mm in thickness), by the application of a magnetic field-assisted machining process using a magnet tool. Because a stronger magnetic force can be generated than conventional magnetic abrasives, it makes the internal finishing of thick non-ferromagnetic tubing possible. Moreover, in order to obtain a high-quality surface, this process method was developed using magnetic particles magnetically attracted on the magnet surface. This paper characterizes the processing principle and advantages of this process. Then, the mechanism of this finishing process was examined by a plane model experiment. It was clarified that the magnetism and shape of a magnetic particle influence realization possibility of this processing method, and it also influence the finishing characteristics.

scholarly journals Importance of Basset History Force for the Description of Magnetically Driven Motion of Magnetic Particles in Air

2020 ◽  
Vol 20 (2) ◽  
pp. 50-58 ◽  
Author(s):  
Andrej Krafcik ◽  
Peter Babinec ◽  
Melania Babincova ◽  
Ivan Frollo
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Magnetic Force ◽  
Magnetic Particle ◽  
Homogeneous Magnetic Field ◽  
Gradient Magnetic Field ◽  
Driven Systems ◽  
Long Time ◽  
History Force ◽  
Stokes Force

AbstractLungs are used as an attractive possibility for administration of different therapeutic substances for a long time. An innovative method of such administration widely studied nowadays is the application of aerosolized magnetic particles as the carriers to the lungs in the external non-homogeneous magnetic field. For these reasons we have studied dynamics of such a system on a level of particle trajectory in air in the presence of magnetic force as a driving force exerted on micrometric magnetic particle. On two typical examples of magnetically driven systems—motion of magnetic particle in a gradient magnetic field and cyclotron-like motion of a charged particle in homogeneous magnetic field in microscale, where the external accelerating forces are very large and the relevant time scale is of the order from fraction of milliseconds to seconds, we have examined the importance of these forces. As has been shown, for particles with high initial acceleration, not only the commonly used Stokes force but also the Basset history force should be used for correct description of the motion.

X-ray powder spectroscopy to determine easy axis in colloidal magnetic particles

1987 ◽  
Vol 20 (6) ◽  
pp. 530-532
Author(s):  
E. Briggs ◽  
A. C. Nunes
Keyword(s):  
Magnetic Field ◽  
Langevin Equation ◽  
Applied Field ◽  
Magnetic Particles ◽  
Easy Axis ◽  
Critical Size ◽  
Easy Magnetization ◽  
X Ray ◽  
Line Intensities ◽  
Intensity Changes

Non-interacting suspended colloidal single-domain magnetic particles can be expected to acquire a preferred orientation in a magnetic field. Their direction is determined by the easy magnetization axes of the particle and the applied field to a degree determined by the Langevin equation governing paramagnetic phenomena. The magnitudes of resulting changes in powder line intensities have been calculated and found to be of the order of 5 to 25% for ferrite particles near the critical size (where anisotropy energy ≥ kT), the larger for larger particles. The pattern of line intensity changes allows one to distinguish between (1,0,0) and (1,1,1) easy axes.

scholarly journals Investigation of Magnetic Nanoparticle Motion under a Gradient Magnetic Field by an Electromagnet

2018 ◽  
Vol 2018 ◽  
pp. 1-5 ◽  
Author(s):  
Weizhong Wei ◽  
Zhen Wang
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Electromagnetic Field ◽  
Magnetic Nanoparticles ◽  
Particle Motion ◽  
Biomedical Applications ◽  
Magnetic Nanoparticle ◽  
Magnetic Particles ◽  
Magnetic Force ◽  
Gradient Magnetic Field

Finite element numerical simulations were carried out in 2D geometry to calculate the magnetic force on magnetic nanoparticles under a specially fabricated electromagnet. The particle motion was modeled by a system of ordinary differential equations. The snapshots of trajectories of 4000 MNPs with and without magnetic field were analyzed and qualitatively found to be in agreement with camera visualizations of MNP movement in a container. The results of the analysis could be helpful for the design of electromagnetic field and motion analysis of magnetic particles for the delivery of magnetic materials in biomedical applications.

scholarly journals Compatibility of endoclips in the gastrointestinal tract with magnetic resonance imaging

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Dong Yeol Shin ◽  
Sumi Park ◽  
Ain Kim ◽  
Eung-Sam Kim ◽  
Han Ho Jeon
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Magnetic Resonance ◽  
Tissue Damage ◽  
Magnetic Force ◽  
Ex Vivo ◽  
Resonance Imaging ◽  
Gi Tract ◽  
3T Mri ◽  
Magnetic Resonance Imaging Mri

Abstract There are no clear guidelines on the compatibility between endoclips that remain in the gastrointestinal (GI) tract and magnetic resonance imaging (MRI). The purpose of this study was to investigate the effect of 3T (T) MRI on endoclips placed in excised pig tissues. Two types of endoclips were assessed: Olympus EZ (HX-610-135L) and QuickClip Pro (HZ-202LR). We assessed tissue damage or perforation and detachment of endoclips under 3T MRI magnetic field. We also evaluated the magnitude of force required to detach the endoclips from the porcine tissue. We measured the magnetic force acting on the Olympus EZ clips. QuickClip Pro clips were used as a control in this study. There was no tissue damage and no detachment of the endoclips (Olympus EZ and QuickClip Pro) during 3T MRI. The force required to detach the Olympus EZ clips ranged from 0.9 to 3.0 N. The translational magnetic force acting on the endoclips was 3.18 × 10–3 N. Ex vivo experiments showed that the magnetic field generated by 3 MRI did not cause tissue damage or perforation and did not detach the endoclips. Olympus EZ clips and QuickClip Pro clips in the GI tract appear to be safe during 3T MRI.

Analysis of magneto rheological elastomers for energy harvesting systems

2020 ◽  
Vol 64 (1-4) ◽  
pp. 439-446
Author(s):  
Gildas Diguet ◽  
Gael Sebald ◽  
Masami Nakano ◽  
Mickaël Lallart ◽  
Jean-Yves Cavaillé
Keyword(s):  
Magnetic Field ◽  
Energy Harvesting ◽  
Shear Strain ◽  
Magnetic Induction ◽  
Magnetic Particles ◽  
Homogeneous Magnetic Field ◽  
Electrical Signal ◽  
Harvesting Systems ◽  
Dc Bias ◽  
Magneto Rheological

Magneto Rheological Elastomers (MREs) are composite materials based on an elastomer filled by magnetic particles. Anisotropic MRE can be easily manufactured by curing the material under homogeneous magnetic field which creates column of particles. The magnetic and elastic properties are actually coupled making these MREs suitable for energy conversion. From these remarkable properties, an energy harvesting device is considered through the application of a DC bias magnetic induction on two MREs as a metal piece is applying an AC shear strain on them. Such strain therefore changes the permeabilities of the elastomers, hence generating an AC magnetic induction which can be converted into AC electrical signal with the help of a coil. The device is simulated with a Finite Element Method software to examine the effect of the MRE parameters, the DC bias magnetic induction and applied shear strain (amplitude and frequency) on the resulting electrical signal.

Study of MFM Application in Semiconductor Failure Analysis

2004 ◽  
Author(s):  
Way-Jam Chen ◽  
Lily Shiau ◽  
Ming-Ching Huang ◽  
Chia-Hsing Chao
Keyword(s):  
Magnetic Field ◽  
Failure Analysis ◽  
Magnetic Force Microscopy ◽  
Magnetic Force ◽  
Current Flow ◽  
Force Microscopy ◽  
The Magnetic Field ◽  
A Current

Abstract In this study we have investigated the magnetic field associated with a current flowing in a circuit using Magnetic Force Microscopy (MFM). The technique is able to identify the magnetic field associated with a current flow and has potential for failure analysis.

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