My advisor was gone for two weeks, first in Los Alamos for a workshop and then in Europe for a thesis defense. Whenever he returns from extended returns, I normally stop by his office to a) say hello and b) catch-up in terms of where I am in research. I still send reports and results during his absence, although the usual responses are silence or confusion due to miscommunication. The miscommunication coming from my part of still learning how to convey information across correctly and with the least complexity.
However, the one thing I did not expect to discuss today was the Overview. In the Material Science and Engineering Department of Carnegie Mellon University, the overview is the equivalent to a practice thesis defense. It can be either public or private, however one presents their work to a committee, who then decide what additional work is necessary to reinforce the arguments and research done during the student's graduate career. The actual thesis defense should then follow anywhere from 6-12 months after the overview, depending on the amount of research to still be performed as well as the number of revisions to be made.
Needless to say, I was not expecting that to come up, and now remained troubled and awake at 1:00 thinking of what I have accomplished, what still needs to be accomplished, and what I myself, personally want to see.
These are all important things not just in the timeline and requirements for graduation, but also how am I preparing myself for the next step after my PhD. Which led to our second discussion topic as well, what was I planning to do after CMU? My advisors intention was clearly not to scare me, but to start putting the gears into motion and thinking about what I would like to see and do.
Being caught off-gaurd on all of these though has sent my brain into a panic mode and anxious about what the future does hold. It has brought back the usual question of, why did I come for a PhD again in the first place? Do my aspirations of becoming a professor still hold or not?
Like always, I suppose all the answers will come with time...
Monday, October 7, 2013
Sunday, October 6, 2013
October 3 Simulation Work
***Being posted on October 6th after having to leave for lunch on the 3rd***
I've always been quite grateful for the breadth that my project encompasses (while the other half of the time I'm panicking about how any of the objectives will be completed within the given time frame).
As an experimentalist, I work on two very different behaving materials, polycrystalline nickel and nanocrystalline nickel. While on the characterization side the primary source of my data comes from EBSD, but the CMU Physics group has also provided an HEDM dataset which provides an immense amount of information to be found.
However, to play around with simulation work really adds another side to my research work. While we design experiments with controls and variables to investigate what we like, ultimately natural laws and physics still dictate the behavior of atoms and molecules. What we discover, helps us understand the things that were not clear before. But when one works with simulations, they dictate the laws, they make the rules, the make things that cannot happen. We, the scientist, get the opportunity to truly manipulate the experiment.
Of course, we could design anything, but in the end, we have to design simulated microstructures that behave similar to real microstructures in order to contribute to the field of science.
The model I primarily work with for microstructure evolution is the Potts model, which labels each individual grain as a spin "number", and grows or shrinks based on the number of neighbors. As a result, the model is curvature driven and aims to reduce the overall energy by eliminating the number of grains with time, thereby eliminating grain boundaries. It should be important to point out that grain boundaries are indiscrete in this model, that is, they are not defined, but exist at the points where two different spins interact. This brings about an interesting point that we assign factors such as grain boundary mobilities, energy, and so forth, based on the original spin site and the neighboring spin sites that we pick at the simulation step. As we add more factors and complexity to our model, the probability to change a spin, that results in grain growth, becomes the aggregate of several energy arguments. Because all terms considered end up in the same summation, this leads to interesting competing effects or even domination of one term over all the others.
The simplicity of the Potts model is ideal as it keeps calculations to a minimum, maximizing the simulation speed. Potts model has been thoroughly applied to grain growth and recrystallization, and in turn, I eventually hope to develop a feasible Potts model exhibiting twinning.
I've always been quite grateful for the breadth that my project encompasses (while the other half of the time I'm panicking about how any of the objectives will be completed within the given time frame).
As an experimentalist, I work on two very different behaving materials, polycrystalline nickel and nanocrystalline nickel. While on the characterization side the primary source of my data comes from EBSD, but the CMU Physics group has also provided an HEDM dataset which provides an immense amount of information to be found.
However, to play around with simulation work really adds another side to my research work. While we design experiments with controls and variables to investigate what we like, ultimately natural laws and physics still dictate the behavior of atoms and molecules. What we discover, helps us understand the things that were not clear before. But when one works with simulations, they dictate the laws, they make the rules, the make things that cannot happen. We, the scientist, get the opportunity to truly manipulate the experiment.
Of course, we could design anything, but in the end, we have to design simulated microstructures that behave similar to real microstructures in order to contribute to the field of science.
The model I primarily work with for microstructure evolution is the Potts model, which labels each individual grain as a spin "number", and grows or shrinks based on the number of neighbors. As a result, the model is curvature driven and aims to reduce the overall energy by eliminating the number of grains with time, thereby eliminating grain boundaries. It should be important to point out that grain boundaries are indiscrete in this model, that is, they are not defined, but exist at the points where two different spins interact. This brings about an interesting point that we assign factors such as grain boundary mobilities, energy, and so forth, based on the original spin site and the neighboring spin sites that we pick at the simulation step. As we add more factors and complexity to our model, the probability to change a spin, that results in grain growth, becomes the aggregate of several energy arguments. Because all terms considered end up in the same summation, this leads to interesting competing effects or even domination of one term over all the others.
The simplicity of the Potts model is ideal as it keeps calculations to a minimum, maximizing the simulation speed. Potts model has been thoroughly applied to grain growth and recrystallization, and in turn, I eventually hope to develop a feasible Potts model exhibiting twinning.
Sunday, September 22, 2013
September 22nd Sunday Reflections
Since creating this blog last year, I've only totaled 12 posts (13 including this one). That's the equivalent of writing a single post in a month. Although in reality, I wrote a series of consecutive posts, then gradually realized I didn't have that many things to discuss on a daily schedule. Then it became on and off randomly, and then non-existent. I remember initially creating this blog to help keep track of my own research on a weekly basis, so I can look and see how far I've come along, while at the same time, sharing whatever information to what readers are on here.
Ultimately, I've failed and disappointed myself. The most likely cause was the expectation of creating a daily post, in an already busy enough day as a graduate researcher. There's no individual reason as to why I'm writing again, instead it's much more an aggregation of several presentations, talks, and motivation from others. Perhaps the most influential is another Blogger, by the name of Bongi, who points out that a) we should write as a hobby and on our time and b) as long as we write about what we love and do, the readers will come. Check it out here.
I'd like to give this blog a new start, but without creating a new blog nor deleting the old posts. Therefore I feel like it is obligatory to give a wrap-up of everything that has happened between now and the last post...
In August, my adviser presented a talk for me at PRICM-8 on topology measurements of grain boundary networks during grain boundary engineering (GBE).
In July to August, my collaborator from France came for another month-long exchange to do a study of temperature vs. deformation and it's effects on the twin density in GBE pure nickel samples. This ended up being both a very busy and stressful month, but also quite enjoyable with the results.
In May, my advisor presented another talk at the PICS conference on the nanocrystalline nickel sample that I work with which exhibits grain growth. This talk also included the kinetics results based on the JMAK equations as well as the TEM interface studies by my other colleagues and collaborators.
In May I also got to go to Sydney, Australia to present my first ever talk at the 5th International Conference on Recrystallization & Grain Growth. I won't claim whether it was well received or anything, but it certainly was an experience. (I imagine the first talk for any graduate student, or student, is.)
Besides all that, I was occupied with other life priorities and team obligations. So hopefully from here on out I'll start writing on at least a weekly or bi-weekly basis.
Cheers,
Brian
Ultimately, I've failed and disappointed myself. The most likely cause was the expectation of creating a daily post, in an already busy enough day as a graduate researcher. There's no individual reason as to why I'm writing again, instead it's much more an aggregation of several presentations, talks, and motivation from others. Perhaps the most influential is another Blogger, by the name of Bongi, who points out that a) we should write as a hobby and on our time and b) as long as we write about what we love and do, the readers will come. Check it out here.
I'd like to give this blog a new start, but without creating a new blog nor deleting the old posts. Therefore I feel like it is obligatory to give a wrap-up of everything that has happened between now and the last post...
In August, my adviser presented a talk for me at PRICM-8 on topology measurements of grain boundary networks during grain boundary engineering (GBE).
In July to August, my collaborator from France came for another month-long exchange to do a study of temperature vs. deformation and it's effects on the twin density in GBE pure nickel samples. This ended up being both a very busy and stressful month, but also quite enjoyable with the results.
In May, my advisor presented another talk at the PICS conference on the nanocrystalline nickel sample that I work with which exhibits grain growth. This talk also included the kinetics results based on the JMAK equations as well as the TEM interface studies by my other colleagues and collaborators.
In May I also got to go to Sydney, Australia to present my first ever talk at the 5th International Conference on Recrystallization & Grain Growth. I won't claim whether it was well received or anything, but it certainly was an experience. (I imagine the first talk for any graduate student, or student, is.)
Besides all that, I was occupied with other life priorities and team obligations. So hopefully from here on out I'll start writing on at least a weekly or bi-weekly basis.
Cheers,
Brian
Saturday, February 2, 2013
Feb 2nd Unexpectedly Magnificent
 |
| EBSD map of a fully impinged AGG Ni sample |
This electron backscatter diffraction (EBSD) map came from an annealed nanocrystalline nickel (Ni) sample that featured abnormal grain growth (AGG). I have shown some pictures in the past where the AGG remained as individual islands from one another. This sample was annealed further such that all the abnormal grains are impinging upon one another and completely fill up the space of whatever remaining matrix grains were there. As a result, there are some extremely planar facets on certain grains, but also some interesting grain morphology not seen in your typical sample, especially the twin related grains that exist within the their parent grain.
Of major point of curiosity was how the how the twin content of this material compared to traditional FCC Ni. What we knew before from some previous scans is that some of these AGG featured bi-grain clusters, which were very often twin related. However, these twins were very often just single boundaries which could be continuous, but also sometimes jagged. We suspected that if we allowed this microstructure to grow out completely, the twin statistics should be very different because this wasn't the traditional twinning mechanism.
The interesting point was when the fraction of twin boundaries in both type of observed materials were approximately the same. That being said, one of my advisers had predicted this even though I adamantly thought it would be otherwise.
In my head I lost this little science bet, but nonetheless excited for some of the upcoming future work.
Subscribe to:
Posts (Atom)