Dissertation Defense Schedule
Academic Excellence
Sharing original dissertation research is a principle to which the University of Delaware is deeply committed. It is the single most important assignment our graduate students undertake and upon completion is met with great pride.
We invite you to celebrate this milestone by attending their dissertation defense. Please review the upcoming dissertation defense schedule below and join us!
PROGRAM | Physics
Nanowire based Exchange Coupled Permanent Magnet
By: Muhammad Asif Warsi Chair: John Xiao
ABSTRACT
Permanent magnets (PMs) are found in many applications such as electrically controlled brake systems, robotics, wind power generators, magnetic relays, etc. Performance of these devises strongly depends upon the properties PMs, whose figure of merit is defined as magnetic energy product (BH)max. The efficiency of PM based devices can be increased by increasing the (BH)max of PMs. Two possible approaches exist to increase the (BH)max significantly: (1) finding new materials with higher (BH)max and (2) developing an exchange couple PM by coupling a soft phase of high magnetization with a hard phase of high coercivity.
We focused on addressing some of the challenges to developed exchange coupled PM. This includes (1) fabrication of suitable soft magnetic material and (2) low temperature synthesis to reduce the interdiffusion between soft and hard phase.
We used electrospinning method to fabricate soft magnetic Fe65Co35 nanowires with ultra-small diameter and high magnetization. The diameter and diameter distribution were controlled by the viscosity and surface tension of electrospinning solutions. Surface tension is found to plays a critical role to control diameter distribution for ultra-small (20- 50 nm) Fe65Co35 nanowires.
Hard magnetic materials generally require high annealing temperature to develop hard magnetic characteristics. High temperature treatment often induces interdiffusion between hard and soft phases, which significantly deteriorate the performance of exchange coupled PM. Interdiffusion can be reduced by decreasing the processing temperature. We developed an exchange coupled PM of Fe65Co35/L10 FePt at 400 °C. Low synthesis temperature indeed reduces the interdiffusion that leads to good magnetic properties of exchange coupled PMs.
Another approach to restrict the interdiffusion is to find chemical processes to couple soft and hard magnetic materials. In collaboration with Prof. Ren at Temple University, we have developed a room temperature solution process method to exchange couple Fe65Co35 nanowires with MnBi. The magnetic properties of the composite show that the solution process is a promising method to develop exchange coupled PM.
The Process
Step-by-Step
Visit our “Step-by-Step Graduation Guide” to take you through the graduation process.From formatting your Dissertation to Doctoral Hooding procedures.
Dissertation Manual
Wondering how to set up the format for your paper. Refer to the “UD Thesis/Dissertation Manual” for formatting requirements and more.
Defense Submission Form
This form must be completed two weeks in advance of a dissertation defense to meet the University of Delaware Graduate and Professional Education’s requirements.
