This blog is my attempt to reconnect with the world of chemistry. I have a PhD in Inorganic Chemistry and make a living doing research for a large company in Michigan. As times have changed, that company has changed its focus and I no longer have as much chance to do the basic, fundamental research which I most enjoy. Through this blog, I am hoping to recapture the magic which I felt during my graduate (and undergraduate) days in college. Expect topics on chemistry and alchemy along with some non-chemistry related items which I think might be interesting.

"The chymists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasure among smoke and vapour, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I would change places with the Persian King."

Johann Joachim Becher (phlogistonist)
Acta Laboratorii Chymica Monacensis, seu Physica Subterranea, (1669).

Tuesday, March 24, 2009

Being Flexible as a Chemist

My freshman year was almost over. Final exams would take place in about two weeks and I was already beginning to prepare myself mentally. Almost as an afterthought, the chemistry professor assigned us one last chapter to read on solid-state chemistry. It wasn’t a real assignment – the professor never mentioned the chapter again and as I correctly surmised, it wasn’t going to be covered on the final exam. It should have been a meaningless blip in my academic career, quickly forgotten, but I still remember that chapter after all these years, or at least the section which covered the concept of non-stoichiometric materials.

I remember absolutely hating it.

We had just spent the entire year having the “Law of Multiple Proportions” hammered into our brains. “Atoms combine in ratios of natural numbers,” they would say. “If you can’t grasp this basic concept, you’ll never get a job as a chemist. You’ll just have to settle for being a doctor or lawyer or telemarketer.” Frightening words indeed! But now, just weeks before the final, I was discovering that this law was more of a suggestion.

I think I even remember one of the provided examples. It was NiO1.03. WTF? 1.03? What sort of sick joke was this? It looked like something a freshman engineer would write, one who hadn’t yet grasped the concept of rounding. This deviation from stoichiometry was within the experimental error associated with an elemental analysis. I cannot begin to imagine what my thesis advisor would have done had I submitted an article discussing the properties of the V10O27.976- ion. The beatings would have been severe. The whole idea seemed stupid to me.

Fast forward to the present and my mind is now quite a bit more receptive to this concept. The field of non-stoichiometric materials is huge, incredibly huge, due to their special properties (catalytic, electronic, and optical). As a transition metal chemist, I now understand that the many oxidation states available to most transition metals can lead to mixed oxides, many of which are non-stoichiometric. I’ve also come to the realization that over half of my projects over the years have involved non-stoichiometric oxides in some fashion. Examples would include ZrO2/CeO2 solid solutions, various doped metal oxide catalysts, zeolites, and, at the present time, fuel cell cathodes. (Strictly speaking, zeolites are not really considered non-stoichiometric materials since there are no mixed oxidation states available, but with formulae such as NaxAlxSiO(2+2x), where x can be < 0.01, I’m still counting them.)

The defect sites in these non-stoichiometric oxides make them wonderful catalysts, especially for redox reactions. The vacancies left by the loss of oxygen atoms in the crystal structure can create materials with the ability for ion conduction (usually at higher temperatures). This leads to their use in gas sensors, batteries, and fuel cells. (La1-xSrx)yMnO3-z is a typical oxide used in fuel cell cathodes. Non-stoichiometric oxides are here to stay.

And I'm loving it.



The moral of the story: Don’t dismiss new concepts in chemistry until you’ve had a chance to work with them first.

2 comments:

John Fetzer said...

In my guise of guru of career management for scientists, I tell people this ofyen. Never box yourself in. Science continually changes and if you are good, you have to be ready to accept new ideas.

The examples are rife. MALDI_TOFS mass spectrometry is not new. It was a niche technique written off by most MS "experts
. The people who did and eventually tried proteins and biopolymers got tons of papers, citations, and awards.

Chemgeek said...

“If you can’t grasp this basic concept, you’ll never get a job as a chemist. You’ll just have to settle for being a doctor or lawyer or telemarketer.”

I teach my Gen Chem class in about an hour and I plan on using this quote.

During the semester (usually late in 2nd) we briefly cover materials (ceramics, conductors, zeolites, etc...). I always have to brace my students for the "weird" formulas.

John: As an Organic Chemist that exploited the hell out of MALDI-TOF during my graduate work, I can assure you, I personally appreciate those who developed it.