MSE 101: Classes of Materials

"What is it made of?" Usually, not a question you need a super-specific answer for, on a daily basis. Steel is usually good enough, but maybe you need even less detail than that. Materials science has several generally agreed upon groups of materials based on certain fundamental properties that come in handy when describing properties.

Metals
This includes elemental metals, and alloys like steel and chrome. Metals typically have an ordered crystal structure of protons, with a sort of electron soup. Electrons don't tend to call any particular atom home, but atoms have well established positions relative to one another. This makes metals highly conductive, ductile (easily bent or deformed), and strong.

Ceramics
Most ceramic materials contain multiple elements, like aluminum oxide, of sodium chloride (table salt). They are largely defined by the very strong and stiff interatomic bonds, making them strong, but brittle. Ceramics have great properties at high temperatures, but can be expensive to make, and weak in tension.

Polymers
Polymers are fundamentally based on large chains of carbon and hydrogen, with other elements sometimes present, such as oxygen, sulfur, and nitrogen. There are two classes of polymers: thermoplastics and thermosets. Thermoplastics can be melted for a solid and formed at high temperature. They are usually cheaper, easier to manufacture, but can be used for a much more limited range of applications. Examples include polyethylene and polystyrene.  Thermosets are usually much strong, but once the polymer chains have formed, that's it. Attempts to melt will result in burning. However, than can be used at higher temperatures than thermoplastics. Examples include polypropylene and epoxies.

Glasses
Classically considered a subset of ceramics, with the growth of the metallic glass field, I decided to put these off in their own category. Unlike ceramics, which are highly ordered, glasses have no demonstrable long range order. Atom pairs have defined lengths, and small groups of atoms called "network units" (such as SiO4 groups in silica glasses) have a standard geometry. However, beyond that, there is no defined microstructure. As long as there are no defects, glasses can be incredibly strong, due to the interconnected networks of atoms, much like in polymers. However, even the slightest scratch can lead to failure due to the low fracture toughness.

Composites
Composites explicitly mix two or more distinct phases (form of a material) of differing properties. Natural precipitates don't count, such as silica in aluminum alloys. Example composites include fiberglass (polymer matrix composite), concrete (ceramic matrix composite) and toughened cylinder heads (metal matrix composites).

My research as a graduate student has mostly been in the last two categories, but I've dabbled in pretty much everything at some point.

Spring Break, or Where Did the Undergrads All Go?

This week is spring break, even though it's still February. One of the biggest shifts in grad school is instead of having a week off for things like spring break, you get a week with quieter halls, more parking spots, and no classes.  For TAs, it can be a chance to catch up on grading. For me, I'll just enjoy the peace and quiet in the building for awhile.

Book Recommendation

http://www.amazon.com/Why-Things-Break-Understanding-World/dp/1400048834/ref=sr_1_1?ie=UTF8&qid=1298641231&sr=8-1

I bought this book my senior year of high school, when I was applying to MSE programs. I've re-read it several times since then, and I keep finding new things. It gives a wonderful overview of some of the history of fracture mechanics, as well as great explanations of some of the fundamentals. It's largely written in an anecdotal style, so it feels a bit like having a conversation with Professor Eberhart. It does assume a certain minimum background in chemistry, but it is an enjoyable read even without one.

Eberhart mentions that he always felt materials science was about when things break, not why. On this point, I would like to argue that materials *engineering* is when, materials *science* is why. While his statement may have been true when he was a student, theory has become much more integrated in the curriculum over the years. When he was a student, quantum methods were just beginning to be applied to materials problems. Now, universities may have multiple research groups devoted to such calculations.

Eberhart does a fantastic job of relating these mechanics to objects and situations you are more likely to have encountered, though he does occasionally slip into jargon territory. All in all, a fantastic book for anyone who's ever wondered why things, in fact, break.

Little Frustrations

Dear Advisor,

I know grant proposals haven't been going well lately, and that there are a million other things you would rather be getting done right now, but you're the one who wanted one-on-one meetings. Can you at least pretend to be a little interested in what I'm doing? I still need some feedback. Thank goodness for the postdocs.

Thanks,
Alleged Advisee

On Discipline and Gender Dynamics

Lately, there's been a lot of discussion about gender and sexism in the engineering blogosphere, particularly at Engineer Blogs and FrauTech's response to some of the fallout here.

Here's the thing I've noticed, though: we may all be engineers, but different disciplines have very different gender dynamics.

My undergraduate institution was almost entirely engineering majors, with an overall 3:1 male:female ratio. In some departments (like mine), there was gender parity, and in biomedical engineering, women actually dominated. On the other hand the "big" departments, EE and MechE, were very male dominated.

Consequently, the environment I experienced was very different than my female counterparts in EE, or Computer Science. I had other women to study with, but I also never had issues where the men were trying to prove they were smarter. I attribute part of this culture in the department to our fabulous undergrad lab technician who rules with an iron fist and the best brownies on the planet. Another thing is the small class sizes. I took almost every class my junior and senior years with the same 35 people. We had a pretty good idea of who was good at what, and there was a sense of camaraderie I didn't see in the larger departments.

The ME and EE departments had more female professors, but also tended towards massive lectures without much interaction. It's very easy to go the entire semester and never learn anyone else's name in the room. The environment was also much more intensely competitive, with more professors grading on curves. In the smaller, higher level classes, many of the female students had just gotten used to never speaking up, and apparently had fallen into the habit of sitting quietly and keeping a low profile. I took a higher level Photonics class, with the only other female in the room a native EE student. At the beginning of the semester, she took the quiet route. I, on the other hand, coming out of a very different environment, had gotten used to speaking up and raising my hand. As the semester progressed, she seemed to come out of her shell and get more engage in the class.

I really believe that xkcd captured it perfectly. If there aren't many women, each one feels as if she has to represent the entire gender. When women make up almost half the room, though, it's easier to escape that mindset. This is why it's critical to get more women into engineering in the first place: to reach the threshold where women have a support network.

Hazards of Proposal Prepartation

Potential hazards of conducting thorough literature reviews include:
Paper cuts
Screen glare headaches
Back aches
Caffeine overdose
Dreams about papers (should you find time to sleep, that is)
Lost ability to hold normal conversations.


Diving back into the brain-melting goo now.

Google Alerts

Has anyone ever tried using Google Alert feeds as a way of keeping up with literature in a very specific subfield? On of the areas I'm currently investigating has some active research in journals I don't always think to check, so I'm wondering if this is a reasonable way to find papers faster.

Either way, I'm going to set up a few alerts on my favorite queries, and see how it goes. I do wish I could restrict Alerts to Google Scholar, rather than a full web search.

Scope Creep

I am rapidly approaching my preliminary defense, and facing the challenge of defining my thesis topic. My advisor has given me an initial direction, but now I need to turn that into a more specific question. The hardest part is trying to figure out what is "enough" for a thesis. I can think of a vast number of relevant systems to study, and ways to study them, but I'd rather not spend 10 years working on my thesis. Because a good deal of what I'm doing involves writing code, it can be difficult to predict how long any segment will really take.

It's also difficult to predict what my advisor will consider sufficiently substantial to be a paper. I know his standards are higher than most, and so I'm likely to end up with fewer, but more substantial papers. Unfortunately, the first project I was working on doesn't have funds or motivation to continue, so I'm switching topics midstream.

It doesn't help that I find it all fascinating... My hunting through the experimental literature keeps turning up awesome materials that are very closely related to what I was originally intending to study.

MSE Fundamentals

Somewhat uniquely among graduate program with a similar undergraduate degree, a very large fraction of MSE grad students majored in something else as an undergrad (usually physics or chemistry). However, in most programs, there's not a good review class covering the things all your other classes will assume you know already.  Taking the undergraduate overview class can be frustrating for many grad students, with a lot of overlap with material they do know, and little depth in areas they don't. Consequently, those of us with a BS in MSE often end up tutoring our peers in the major-specific basics.

I'm going to try and run two different types of posts on materials science fundamentals. MSE 101 posts will be aimed towards those with a background in general chemistry and basic calculus, but not much beyond that. MSE 501 posts will be aimed at explaining topics to someone with a BS degree in science or engineering. If nothing else, I want to have these written down somewhere I can find them later when asked.

If there's a particular aspect of materials science you'd like me to address, please free to leave it in the comments.

Epiphanies and Contributing to the Scientific Knowledgebase

I'm currently in the process of writing the proposal for my thesis work, which currently involves a vast quantity of reading. Because I do computational work, I've got even more literature to wade through. First is the computational stuff related to the kind of systems and calculations I'm interested in. However, in order to do good simulations, you need to have experimental data to compare to and validate your model. So every literature search I do, I pretty much end up doing twice.

Ultimately, you hope to find something that no one else has really done that somehow relates to your interests and preliminary work. That's really what the thesis is supposed to be: your novel contribution to science and human knowledge. You may know very early on in your research what that is. Sometimes, finding your little research niche comes about in more roundabout ways. It may be a conversation with faculty or fellow students, or an impulsive change of search terms, but when you find the gap, it feels awfully good.

Woman Scientist Profile: Professor Mildred Dresselhaus

Professor Dresselhaus may be a Condensed Matter Experimental Physicist at MIT, but as a materials scientist, I'm claiming her for our side.

I first became aware of Prof. Dresselhaus at a conference, where she was giving an invited talk on the state of thermoelectric materials research, one of several areas in which she is considered a significant innovator. She's also one of the premiere researchers in carbon science, having worked in the field since ~1973, studying superconductivity in intercalated graphite compounds, and written four books on the subject.  She was involved in critical experiments to validate the structure of of single-walled nanotubes using Raman spectroscopy.  Her most recent projects have studied bismuth nanowire fabrication.  Her list of career awards is intimidatingly impressive (including the US National Medal of Science), but my favorite thing about Professor Dresselhaus?

She never stops looking forward.

(If you haven't seen Meet The Robinsons yet, you're missing out!)

She doesn't sit on her ample scientific laurels and drift into an emeritus haze. She keeps finding what she thinks is new and interesting. To hear her give a talk is to be inspired about all of the possibilities for increasing our understanding of the universe. She asks hard questions when she sits in on a talk. She is a woman, confident in herself, and her work, and she's awesome!

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If it isn't obvious, I'm still playing around with different directions to take this blog. To some extent, I plan to talk about daily grad student life, but I'd also like to try and explain what about materials science in particular is so awesome.

Graduate Coursework

As I'm still in the early phases of my graduate education, I still have classes. In many ways, graduate classes aren't that different from some of what I did as an undergrad. Some of the key differences in my experience so far are:

More outside learning/prior knowledge is expected. You should either know it, or learn it on your own, but don't expect a lot of hand-holding. A good grad level class will cover more material in greater depth than you've likely seen before.

Less frequent, more difficult homework. Problem sets won't be every night, but they will take significantly more time, and often require you to consult resources not necessarily provided in class (see first point...) Sometimes there may not even be a "right" answer.

Less rigid structure. In the land of engineering undergraduate education, there is ABET certification, by which syllabi must meet certain criterion in order for your department to stay accredited. These requirements don't exist at the graduate level. Classes often change depending on the interests of the students, and what topics people want to explore in greater depth. Some departments have certain "core subjects" that cover topics required for the qualifying exams, and these classes will not be nearly so free-form. On the other hand, specialized topic classes are often open to student direction.

Exam Review?  What's that? See point one: your class is likely trying to cover vast quantities of material. You can review on your own time. (Note: does not seem to apply to medical or pharmaceutical courses, according to friends.)

Fewer classes at a time. Typically engineering grad student load seems to be 2-3 courses a term, instead of 5-7 at the undergrad level. Of course, it is very likely you are expected to be doing 40+ hours a week of research at the same time...

Of course, some courses will just be glorified undergrad classes. If you've been given the gift of a class with a very specific, closely followed syllabus, take advantage of that and get as far ahead as possible when you have research lulls, lest the daily homework thing catch you unaware until 30 minutes before the lecture.

On Materials Science, Steampunk and Your Grandmother

I recently attended a book signing by my favorite steam punk author, Cherie Priest (@cmpriest).  The question of how to define steampunk came up, and she raised an excellent point: "When I was a goth, I could say to my Grandma 'You know Dracula?  Like that.' Steampunk doesn't have that".

Materials science needs that too. Even other engineers aren't really sure what it is.  For half of my grandparents, it's a trivial problem, as academics with friends in the field. My other grandparents, however, are farmers. I can explain partial concepts, especially anything that can be related to tractors.  But there's not a great general description.

Part of my goal in blogging is to get better at explaining what I do without jargon, to develop metaphors so that when I end up in front of a class of undergrads, they can make the connection to the material. Or so I can explain my research to people outside of my sub-field.

The recent NOVA miniseries, Making Stuff, was an awesome first step. But most high school kids, trying to find a school, and a major, aren't going to have watched it. I originally thought I wanted to be a chemical engineer, but the more I read about it, the more it didn't describe what I wanted to do. I was lucky enough to have family members who knew what MSE was.

Any suggestions for a new MSE catchphrase?

My Favorite Equation

Earlier this week, I was asked what the most important thing I've learned in higher education, and I answered the following:

σ=Eε

In typically MSE terminology, this translate into words as stress equals stiffness times strain.  


E, Young's modulus, is one of the first ways we quantitatively characterize the way a material reacts to a stress (force/ unit area) or strain (change in net dimensions). The equation above assumes the material reacts uniformly in all direction, but even the more complete formula retains a simple elegance.


However, the real thing I've learned is this: being flexible under strain leads to less stress. If you've planned your day in 15 minute increments from the moment you wake up until bed, the extra homework assignment, or failed experiment you have to redo suddenly becomes more stressful.  The busier I get, the harder this is to remember, but it's better to be a bit flexible than break. 

Welcome!

After spending months reading, lurking, and periodically commenting on a number of blogs, I'm finally caving to the urge to create my own. This blog exists as a way for me to muse upon the challenges of graduate school, and discuss the fundamentals of materials science and engineering. After a B.S. degree and nearly two years in graduate school, I've discovered that even other scientists and engineers are often highly unaware of what we do. Probably because MSE covers a little bit of everything, from mechanical engineering to biology to physics.

So... what is MSE?


Materials science is the study of the relationships between processing, properties, structure, and performance. At some point, you will inevitably be shown "the tetrahedron", so let's get that out of the way now:

My current research is in the area of computationally characterizing structures, and analyzing the effect of structure variation on properties. I hope to spend more time later going over what is meant by all of these terms in greater detail. While most academic materials science programs have their roots in metallurgy, materials science effectively covers all solid materials, from metals to ceramics to polymers to nanotubes. (Everything is spiffier at the nanoscale!)

For those who have been paying attention, you may have noticed "and engineering" attached to the discipline. MSE covers both fundamental understanding and cutting-edge innovation (i.e., science), as well as practical things, like what to build a bridge with, or how to increase the lifespan of engine components (i.e., engineering). 

Between undergraduate research, summer internships, coursework, and graduate school, I've had a chance to dabble in a broad range of topics under the MSE umbrella. Eventually, I may even cover all of them... 

-Miss MSE