In addition to its lubricity, graphite has a vast number of useful properties, some of which have been exploited since antiquity. But current thinking is that graphite is slippery thanks to adjacent layers getting twisted relative to each other on an axis perpendicular to the layer lines this has the effect of unlocking the nesting between layers, allowing them to slide over each other. It was once thought that graphite’s lubricity came from fluids like air or water being trapped between these monoatomic layers, giving it some slip, or just from the fact that the individual sheets would shear away from each other. It’s formed of multiple one-atom-thick layers of carbon stacked on top of each other, which leads to graphite’s fame as a lubricant. Graphite is a very soft mineral, often as soft as talc. No matter how graphite is formed, the nearly pure crystals of carbon give it unique chemical and physical properties. The heat and pressure cooked out everything but the carbon in the coal, leaving behind almost completely pure carbon. On the other hand, amorphous graphite formed when the dead cyanobacteria formed coal deposits, which were then subsequently swallowed up into the Earth’s furnace. These metamorphic conditions produced rocks with crystals of graphite trapped inside them. The most abundant form of graphite is flake graphite, which occurred when those dead cyanobacteria formed carbon-rich shales and limestones which were then thrust into high pressure and temperature conditions by tectonic activity. While all these dead bacteria are the ultimate source of graphite (not to mention every other carbon mineral, from coal to oil to diamonds), exactly what type of graphite is formed depends on geological circumstances. The graphite layers in the anode help store charge by intercalating lithium ions between individual graphene layers. When they died, mats of their carbon-rich remains piled up on the floors of the oceans, eventually becoming entombed under thick layers of sediment, where pressure and heat could begin to work their alchemy. Having just managed the evolutionary trick of figuring out photosynthesis, these organisms sopped up the nearly unlimited carbon dioxide from the Precambrian atmosphere, turning the upper layers of the ocean into a thick bacterial soup. The story of graphite begins two billion years ago, when the oceans were teeming with cyanobacteria. So let’s take a look at what it takes to mine and refine graphite. Graphite is amazingly useful stuff and fairly common, but not all that easy to extract and purify. The stuff turns up everywhere, and it’s becoming increasingly important as the decarbonization of transportation picks up pace. The properties that made graphite great for bumper cars - slippery, electrically conductive, tenacious, and cheap - are properties that make it a fit with innumerable industrial processes. And for the first few runs of the day, before the stuff worked into the floor, the excited guests were as likely as not to get their shoes loaded up with the stuff, and since everyone invariably stepped on the seat of the car before sitting on it… well, let’s just say it was easy to spot who just rode the bumper cars from behind, especially with white shorts on. It was an impossibly messy job - get the least bit of the greasy silver-black goop on your hands, and it was there for the day. To keep the sheet steel floor of the track from rusting, every morning we had to brush on a coat of graphite “paint”. Like everything else in the park, the ride was old and worn out, and maintenance was a daily chore. One of my assignments, and the one I remember most fondly, was running the bumper cars. Looking back on it, the whole experience was a lot of fun, although with the minimum wage at $3.37 an hour and being subjected to the fickle New England weather that ranged from freezing rains to heat stroke-inducing tropical swelter, it didn’t seem like it at the time. In my teenage years I worked for a couple of summers at a small amusement park as a ride operator.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |