Category: Chemistry

Peritectic point

Peritectic point

03/23/17

“What happens when a solid phase and a liquid phase merge together?”

A material’s composition is often in multiple different phases. Sometimes, they are in a solid phase, sometimes a liquid, and sometimes a proportion of the two. So what happens when two of such compositions come together? Well, if the material is just at the right composition as well as the temperature, then the two phases will merge to forge a new phase known as a peritectic! Although peritectics are not as common as their simpler cousins eutectics and eutectoids, peritectics are just as much of a wonderful illustration of the laws of nature!

Eutectoid point

Eutectoid point

03/22/17

“Can a solid become two other solids under certain conditions?”
It is well known when a eutectic point, is reached, a material will instantly become a liquid. However, is it possible for such a reaction to occur but for the two products to become solids instead/ This is the primal idea behind a reaction in Materials Science known as the Eutectoid point, and can be found on a material’s phase diagram

Eutectic point

Eutectic point

03/20/17

“What is the lowest possible melting point for a composite material?”
Pure elements always have a fixed melting point. However, when mixed, their melting point can change drastically. Let’s say we have a crystal composed of elements A and B. If element A is predominant, then B will melt first and vice versa for element B. So is there a single point of possible element combinations in which both elements will melt? Well, after years of research, Materials Scientists have came up with the definition of the eutectic point to describe this scenario. The eutectic point is not only the point of complete melting but the point of lowest possible melting since both elements will be melted!

Recrystallization

Recrystallization

03/19/17

“How can we purify a crystal by dissolving it?”
Crystals are some of the most omnipresent structures in the universe. However, often times such crystals will have impurities to be found inside their crystal lattice, changing the properties of the material. So what is one way that we could get rid of such an impurity? Well, let’s think about it. We know that crystal lattice element and the impurities are made from different molecules, therefore having different melting and cooling points. We also know that if we were to dissolve this compound into a hot solvent, we could effectively decouple the elements from one another. So what if we were to take these two concepts, combine them, and make a system in which the crystal with the impurity would be dissolved and then cooled down to the point that the crystal reforms but the impurity does not? Well, it turns out that this is a process known as recrystallization, and is used by chemists and material scientists to purify crystal elements.

Thermal Batteries

Thermal Batteries

03/16/17

“How can we reinvent batteries using heat?”

The most widely used for of batteries are oxidation process based batteries. Even though these units are plentiful, their construction can be very destructive to the environment. However, their use as large-scale energy storage systems is most valuable, so how can we change their composition to be less intensive on our resources? Well, let’s think about it. One way to release energy from cells is to heat them up. An easy way to do this is to use a material near such cells. So what if we were to put this theory into practice and create a series of heat dependent cells between an anode and a cathode contained with a meltable electrolyte? This setup is known as a thermal battery. Thermal batteries are compact and lightweight, making them a popular application for electric vehicles, and can store energy for upwards of 50 years!

Isomorphous Binary Phase Diagrams

Isomorphous Binary Phase Diagrams

03/15/17

“Can we make a phase diagram that takes into account gradual phase transitions?”
Classical phase diagram charts treat separate phases (solid, liquid, gas, etc.) as being completely discrete from one another. However, in the real world, phases do not immediately transition from one to another but instead undergo a gradual change in which both phases will be present. So how could we take this information and use it to reinvent phase diagrams? Well, let’s take a look. First, let’s draw out the regions where the material will be completely one phase and completely another. The empty boundary in between these regions will be where more than one phase will be present. Now how can we determine the phase composition of the material at any point within this boundary? This can be accomplished as follows. First, draw the point in which the temperature and phase composition meet. Then, draw a horizontal line from this point so that it touches both phases on opposite ends. Take the mass composition reading from these points. Then, split up these lines into two discrete regions, a for the line traveling to the phase on the left and b for the one traveling to the phase on the right. The length of A and B can be found by taking the absolute difference of the composition of the intersection and the composition given as an input. Then divide these lengths by the total length C, and that will give you the respective mass composition of each phase respectively!

Solubility limit

Solubility limit

03/14/17

“How can we determine the maximum concentration of a solute without a precipitate forming?”

It is well known that a solute mixed into a solvent will form a percentage of the substance composition. However, it is also well known that if this concentration becomes too high, then precipitation will occur, inducing a solid phase to exist within the substance. So how can we determine the solubility limit for a substance? Well, to begin, let’s analyze a phase diagram with the solute percentage composition as the independent variable. We would notice that as we increase the composition, the phase of the substance will be closer to the solubility limit, or the point in which precipitation is active. However, in addition to percentage composition, the temperature of a substance also has an effect on the solubility limit.

Slip (materials science)

Slip (materials science)

03/13/17

“How does plastic deformation in a material affect the internal defects?”
All physical materials have defects within their crystal structure. Furthermore, plastic deformations can cause the internal structure of a material to shift. So what happens when a plastic deformation is applied to a material with edge dislocations? Well, let’s use our scientific mindset to think about it. We know that these edge dislocations represent an absence of atoms along a chain. We also know that applying plastic deformations will cause a plane of atoms to move in the direction of the force. So logically, wouldn’t this plastic deformation cause the edge deformation to move within the lattice? This is the fundamental idea behind a phenomenon in Materials Science and Engineering known as a slip and can be used to characterize the internal movement of atoms.

Acids and bases

Acids and bases

03/12/17

“What are Acids and bases?”

Think back to when you were younger. You were in your high school chemistry class, and you were learning about these items called acids and bases. You have heard these words many times in your everyday lives, but you had no idea what they were and what they actually did. Well, this lesson will fix that.
Before we begin everything, we must contemplate one fact, the presence of hydride[h-] ions within substances. In the case of water, there is 1 hydride molecule for every ten million water chemicals or 1*10^-7 hydride for every hydrogen! Since the scale of hydride ions in different substances are usually in orders of magnitude difference, it would be easier to take the log of the concentration level and flip the sign so we could put it on a standardized scale. Let’s use water as our example. Since water has 10^-7 hydride molecules for every of its own, we would represent this as -log(10^-7) which would output as 7. And if an element has ten times more hydride ions in its density, it would be 6, and ten times less, it would be 8. We call this standardized level a pH level (pH → power of hydrogen). This pH level is what Scientists and Engineers use to determine the level of acidity in a substance or the amount of hydroxide ions. If the pH level is below 7, then an acid is considered to be more acidic, and if it is above 7, then it is considered to be more basic. Acids taste sour and react strongly with metals, while bases taste bitter and feel slippery.