Monthly Archives: February 2013

NPR Materials?

The previous post was on NLC materials that expand along some (but only some!) directions under an applied pressure. NLC, of course, stands for negative linear compressibility. The expansion along some directions is more than compensated by a shrinkage along … Continue reading

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How do materials respond to hydrostatic pressure?

Thermodynamic stability demands that the compressibility, , be positive. This means that the volume should decrease with increasing pressure. For fluids (gases and liquids), the volume decrease is accomplished by an equal decrease in linear dimensions along all directions. This … Continue reading

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From tin pest to Napoleon’s disastrous war against Russia

Let’s start with a video of tin pest: From the Wikipedia entry on tin pest: At 13.2 degrees Celsius (about 56 degrees Fahrenheit) and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form white tin to brittle, … Continue reading

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Supercooling of water

Here’s a YouTube video that describes how it is done. Watch: It does a good job of explaining some of the physics behind how we can achieve cooling water to some temperature below 273 K without forming ice. Things to … Continue reading

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Mathematicians, chemists, cartoons

Reading cartoons are a great way to develop a healthy disdain for what other people do for a living. This is a great one from SMBC — the mathematics majors in our class will especially enjoy it. SMBC has something … Continue reading

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Cohesive energy

Here’s a site that lists cohesive energies. Copper, for example, is listed as having a cohesive energy of 336 kJ / mol, which also translates into 3.49 eV / atom. In the solid state, copper atoms interact with other atoms … Continue reading

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Melting point of iron at 800,000 atm!

Since we were just talking about the effect of pressure on the melting and boiling temperatures of pure materials, here’s an interesting news item. Recent research at Caltech suggests that the melting point of iron at high pressures of 10 … Continue reading

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Electronic Tattoo

An interesting NBC Learn feature on wearable electronics for medical diagnostic (and many other) purposes.

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