Study on the Solidification Structures of Al-Fe-Si Alloy under DC and AC Magnetic Fields

2011 ◽  
Vol 189-193 ◽  
pp. 4477-4482
Author(s):  
Chun Yan Ban ◽  
Xu Zhang ◽  
Peng Qian ◽  
Yi Han ◽  
Jian Zhong Cui
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Chinese Script ◽  
Minor Amount ◽  
Fine Needle ◽  
Ac Magnetic Field ◽  
Dc Magnetic Field ◽  
Conventional Condition ◽  
The Difference ◽  
Al Matrix

The effects of DC and AC magnetic field on the phase composition, morphology and distribution of the ternary Al-Fe-Si alloy were investigated. The solidification structures of the alloy solidified with and without the application of magnetic fields were confirmed by DSC and structural measurements. The results showed that, in this Al-Fe-Si alloy the fine needle-like Al3Fe phase dominated the microstructure at the grain boundaries with the minor amount of Chinese script-like α-AlFeSi. Distribution of Al3Fe phase was almost homogeneous in the volume of the sample when alloy was solidified in the conventional condition. When the DC magnetic field was imposed, distribution of Al3Fe phase was more homogeneous. However, the Al3Fe and α-AlFeSi phases were accumulated towards the center of the sample with the application of the AC magnetic field. This is due to the difference of Lorentz force between Al matrix and iron-containing intermetallics. Furthermore, the amount of Chinese script-like α-AlFeSi was increased remarkably under AC magnetic field.

Effect of Magnetic Fields on the Resistance and Microstructure of Al-Cu Alloy during Solidification Processing

2011 ◽  
Vol 287-290 ◽  
pp. 2916-2920
Author(s):  
Chun Yan Ban ◽  
Peng Qian ◽  
Xu Zhang ◽  
Qi Xian Ba ◽  
Jian Zhong Cui
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Turning Points ◽  
Probe Method ◽  
Solidification Processing ◽  
Ac Magnetic Field ◽  
Dc Magnetic Field ◽  
Cu Alloy ◽  
The Difference ◽  
Good Agreement

The resistance of Al-21%Cu alloy under no magnetic field, DC magnetic field and AC magnetic field from liquid to solid was measured by a four-probe method. The difference of resistance versus temperature curves (R-T curves) was analyzed. It is found that the R-T curves of Al-21%Cu alloy are monotone decreasing and have two obvious turning points. Under DC magnetic field, the liquidus and solidus temperatures of the alloy both decrease, while under AC magnetic field, the liquidus and solidus temperatures both increase. There is a good agreement between the microstructure of quenching sample and R-T curves. The mechanism of the effect of magnetic fields was discussed.

Effect of DC and AC Magnetic Fields on the Solidification Structure of Commercially Pure Aluminium

2012 ◽  
Vol 583 ◽  
pp. 387-390 ◽  
Author(s):  
Chun Yan Ban ◽  
Dan Dan Jiang ◽  
Lian Liu ◽  
Jian Zhong Cui
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Cooling Rate ◽  
Solidification Structure ◽  
Pure Aluminium ◽  
Ac Magnetic Field ◽  
Dc Magnetic Field ◽  
Commercially Pure

The effect of DC and AC magnetic fields on the macrostructure, morphology and distribution of the iron-containing intermetallics in the commercially pure Al was investigated. It is found that, at a cooling rate of 3°C/min, the grain is very coarse when the alloy solidifies both with and without magnetic fields. Comparing with the sample solidifies without magnetic field, the solidification structure has almost no change when it solidifies under DC magnetic field, while AC magnetic field changes the solidification structure obviously and makes grains show radial columnar crystals. The intermetallics is dominated by long needle-like phase when the sample solidifies under the condition of no magnetic field. Under AC magnetic field, the intermetallics is refined and accumulated towards the center of sample, and the amount of bone-like α-AlFeSi phase is increased remarkably. The mechanism of the effect of magnetic fields was discussed.

Enhanced dc Magnetic Field Sensitivity for Coupled ac Magnetic Field and Stress Driven Soft Magnetic Laminate Heterostructure

2020 ◽  
Vol 20 (24) ◽  
pp. 14756-14763
Author(s):  
Yao Wang ◽  
Ning Xiao ◽  
Rui Xiao ◽  
Yumei Wen ◽  
Ping Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Soft Magnetic ◽  
Ac Magnetic Field ◽  
Dc Magnetic Field ◽  
Field Sensitivity

scholarly journals A Wireless, Passive pH Sensor Based on Magnetic Higher-Order Harmonic Fields

2009 ◽  
Vol 3 (2) ◽  
Author(s):  
B. Horton ◽  
E. Tan ◽  
B. Pereles ◽  
K. Ong
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Human Body ◽  
Remote Monitoring ◽  
Higher Order ◽  
Sensing Element ◽  
Dc Magnetic Field ◽  
Harmonic Field ◽  
Field Shift ◽  
Detection Coil

A wireless, passive sensor was fabricated for remote monitoring of chemical analytes in the human body. The sensor was made of a magnetically soft film (sensing element) and a permanent magnetic film (biasing element) sandwiching a reversibly swelling hydrogel. When subjected to a low frequency magnetic AC field, the sensing element generated higher-order harmonic magnetic fields that were detected with a remotely located detection coil. In the presence of a DC magnetic field (biasing field), such as that generated from the biasing element, the pattern of the higher-order harmonic magnetic fields varied, and the magnitude of change (referred to as the harmonic field shift) was proportional to the strength of the biasing field. The hydrogel, which acted as a transducer that converted variations in the chemical concentration into changes in dimensions, physically varied the separation distance between the sensing and the biasing elements. This causes a change in the magnitude of biasing field experienced by the sensing element, thus changing its higher-order harmonic field shift allowing remote measurement of chemical concentrations. The novelty of this sensor was its wireless and passive nature, which allows it to be used inside a human body for long term chemical monitoring. A scaled-up prototype was fabricated and tested to demonstrate the pH monitoring capability of the sensor. The main structure of the prototype sensor was a polycarbonate substrate containing a larger rectangular well of 36mm×8mm×4mm on top of a smaller well of 30mm×5mm×2mm (see Fig. 1). The smaller well was filled with hydrogel made of (poly)vinyl alcohol and (poly)acrylic acid. A commercial magnetoelastic thick film, Metglas 2826MB from Metglas Inc., was attached to the step at the bottom of the larger well and allowed to rest on the hydrogel. The DC magnetic field was provided by an Arnokrome III film (Arnold Magnetic Technologies) of 30mm×6mm attached at the bottom of the sensor structure. The sensor was placed on the detection coil, and its response was measured with a spectrum analyzer while exposed to test solutions of varying pH. The sensor's harmonic field shift, when cycled between pH 7 and pH 3, was measured and plotted in Fig. 2. As shown in the figure, the hydrogel swelled when the sensor was exposed to pH 3, decreasing the harmonic field shift. The response and recovery times of the hydrogel were below 2 minutes. This experiment proves the feasibility of the technology for real-time, remote monitoring of pH. Further work includes improving the response time and sensitivity of the hydrogel, as well as miniaturization of the sensor.

Magneto-Spectroscopy of Two-Electron Transitions in Homoepitaxial GaN.

2001 ◽  
Vol 693 ◽  
Author(s):  
M. Wojdak ◽  
J.M. Baranowski ◽  
A. Wysmolck ◽  
K. Pakula ◽  
R. Stepnicwski ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Excited State ◽  
Magnetic Fields ◽  
Effective Mass ◽  
Electron Energy ◽  
Electron Transition ◽  
Electron Effective Mass ◽  
Neutral Donor ◽  
Electron Transitions ◽  
The Difference

AbstractTwo-electron transition occurs when the exciton bound to a neutral donor (DBE) recombines and leaves the donor in an excited state. The two-electron energy is therefore lower than that of the DBE peak by the difference in ground and excited state of the neutral donor. In a magnetic field the two-electron satellite splits into several components. These intra-donor excitations have been studied in homoepitaxial GaN up to magnetic fields reaching 23T. For Faraday (B‖c) configuration the two-electron transition splits mainly into 2s, 2p0, 2p+ and 2p- components. The total splitting between 2p+ and 2p- is equal to Landau energy. For Voigt (B???c) configuration in addition to transition to 2s, 2p0, 2p- and 2p+ there are additional lines which origin is discussed. It has been found that for two configurations of magnetic field the separation between 2p+ and 2p- is not exactly equal, what indicates the anisotropy of the electron effective mass. It has been found that m| = 0.205m0 and m??? = 0.225m0.

scholarly journals Strongly Magnetized Sources: QED and X-ray Polarization

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 76 ◽  
Author(s):  
Jeremy Heyl ◽  
Ilaria Caiazzo
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
First Principles ◽  
Quantum Electrodynamics ◽  
Polarization State ◽  
Radiative Corrections ◽  
Strong Magnetic Fields ◽  
X Ray ◽  
The Difference

Radiative corrections of quantum electrodynamics cause a vacuum threaded by a magnetic field to be birefringent. This means that radiation of different polarizations travels at different speeds. Even in the strong magnetic fields of astrophysical sources, the difference in speed is small. However, it has profound consequences for the extent of polarization expected from strongly magnetized sources. We demonstrate how the birefringence arises from first principles, show how birefringence affects the polarization state of radiation and present recent calculations for the expected polarization from magnetars and X-ray pulsars.

Analysis of Biological Effect of AC-DC Electromagnetic Fields using the Lorenz Model

2011 ◽  
pp. 31-53
Author(s):  
Malka N. Halgamuge ◽  
Chathurika D. Abeyrathne ◽  
Priyan Mendis
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Electric Field ◽  
Electromagnetic Fields ◽  
Biological Effect ◽  
Initial Velocity ◽  
Charged Particles ◽  
Initial Position ◽  
Dc Magnetic Field ◽  
Ac Electric Field

Electromagnetic fields (EMF) are essential to various applications directly involving humans. Fears about the biological effect of exposure to electromagnetic fields drive enormous research into this area. This research generates conflicting results, and consequently, uncertainty regarding possible health effects. This chapter studies a nonlinear Lorenz model describing interactions among charged particles and combined alternating (AC: alternating current) and static (DC: direct current) electromagnetic fields, for various combinations of frequencies, field strengths and relative angle (?) between the AC and DC magnetic fields. We investigate the effect on charged particles of three possible combinations of alternating and static electromagnetic fields: (i) AC electric field and DC magnetic field (ii) AC magnetic field and DC magnetic field (iii) AC electric field and AC and DC magnetic field. Then the behavior of the particle in these fields with different initial conditions and strong directional effects is observed when the angle between AC and DC magnetic fields is varied. The results show that the cyclotron resonance frequency is affected by charged particles’ initial position and initial velocity. Further, we observe strong effects of electric and magnetic fields on a charged particle in a biological cell with initial position and initial velocity.

scholarly journals Fusion and nucleosynthesis by hypervelocity impact using hybrid magnetic fields

2005 ◽  
Vol 23 (2) ◽  
pp. 219-224 ◽  
Author(s):  
ALEXANDRE POZWOLSKI
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Hypervelocity Impact ◽  
Mutual Interaction ◽  
High Current ◽  
Fusion Reactions ◽  
Dc Magnetic Field ◽  
Metallic Ring

The electromagnetic acceleration of a metallic ring carrying a high current, combined with the mutual interaction of a concentrical conductor carrying the same current, in the presence of a DC magnetic field, results in a converging beam of particles reaching a velocity above 1000 km/s. Lithium, gold, and uranium rings are considered and transient temperatures ranging from 108to 1010°K are expected. In the presence of deuterium and tritium fusion reactions will occur and the capture of the released neutrons may result in the synthesis of heavier elements. The considered device lends itself to a varied treatment allowing to consider velocities in the range of 2000 km/s.

scholarly journals Hall-Effect Sensor Technique for No Induced Voltage in AC Magnetic Field Measurements Without Current Spinning

2021 ◽  
Author(s):  
Anand Lalwani ◽  
Ananth Saran Yalamarthy ◽  
Debbie Senesky ◽  
Maximillian Holliday ◽  
Hannah Alpert
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Hall Effect ◽  
Induced Voltage ◽  
Field Frequency ◽  
Magnetic Field Frequency ◽  
Ac Magnetic Field ◽  
Hall Effect Sensor ◽  
Offset Voltage ◽  
The Magnetic Field

Accurately sensing AC magnetic field signatures poses a series of challenges to commonly used Hall-effect sensors. In particular, induced voltage and lack of high-frequency spinning methods are bottlenecks in the measurement of AC magnetic fields. We describe a magnetic field measurement technique that can be implemented in two ways: 1) the current driving the Hall-effect sensor is oscillating at the same frequency as the magnetic field, and the signal is measured at the second harmonic of the magnetic field frequency, and 2) the frequency of the driving current is preset, and the measured frequency is the magnetic field frequency plus the frequency of the current. This method has potential advantages over traditional means of measuring AC magnetic fields used in power systems (e.g., motors, inverters), as it can reduce the components needed (subsequently reducing the overall cost and size) and is not frequency bandwidth limited by current spinning. The sensing technique produces no induced voltage and results in a low offset, thus preserving accuracy and precision in measurements. Experimentally, we have shown offset voltage values between 8 and 27 μT at frequencies ranging from 100 Hz to 1 kHz, validating the potential of this technique in both cases

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