Electrons are the most common way for a current to be carried through a solid material. But since flow of charge is synonymous with flow of electrons there are other ways for charge to be transported. Superionic conductors are materials in which the ions are free to move and are also known as solid electrolytes. Being used to transfer ions between electrodes without the need for a liquid to be present is just one of superionic conductors uses. These properties are achieved through the slight cheat that the ion conductors are only partly solid, having some crystalline properties but actually being an intermediate between this and a liquid stage in which the ions can move without hindrance. One of the hopes is that a completely solid lithium battery could be created in which a solid ionic transporter would be a key component.
Over the last couple of decades the possibilities of what additive manufacture, more commonly known as 3D printing, can achieve has spread into the medical, aerospace and military industries. The most effective way of performing these processes for metals would be power bed fusion. This is where a layer of the metal powder, less than a fifth of a millimetre thick, is distributed in the correct shape. A laser fuses this powder together and second layer is applied. This continues until the design is realised. For more detail I strongly recommend looking here at this page made by Loughborough University which goes into a lot more of the details.
In 1839 the first ever hydrogen fuel cell was created. It was already well known that when enough energy was put into water it could be broken into the hydrogen and oxygen that form it. One William Robert Grove had the idea that if hydrogen and oxygen could be recombined with an electrolyte present to reproduce the water but also gain a flow of charge. Now vehicles can be fuelled with hydrogen but there is a catch. How is the least dense element going to be contained in a reasonable volume. It could be cooled into a liquid but this doesn’t seem practical for a car or perhaps out under high pressure but there are quite a lot of safety concerns about putting high pressure tanks in road vehicles. One of the suggestions that is being looked into is that of using metal hydrides as a way of chemically storing hydrogen by reacting it with a metal from which it can be extracted when used in the car.
An optical resonator can be described as just a box made of mirrors. If strong enough laser light is shone on the outside it will transmit through one of the mirrors and the photons will start bouncing back and forth inside the box, known as a cavity. As all lasers must have some divergence eventually this bouncing light is destined to spread out and fade away. It is however possible to form lasting stable reflections within the cavity and when this happens the set up is known as an optical resonator. This can be imagined as a standing wave of light in a fixed shape. If a gain medium is present then this design can be turned into a laser with the present photons generating more through stimulated emission. When an active medium is present the resonator is called active and unsurprisingly passive is the name given to when there is no contributing medium.
If you were to ask any child for a method of cleaning water then filtering is probably the answer they would give. A step up from a piece of filter paper is a membrane which only allows water or water sized particles through while resisting others. Separation by membrane is a very useful process as it is nontoxic, requires little energy input and can be easily up sized for different water quantities. Unfortunately, like with all filters, the impurities and contaminants will remain on the membrane if not treated and severely limits the practical applications of such membranes. What is required is a membrane that has some way of cleaning itself, hopefully during the process.
Carbon is known to form many different allotropes such as the nice variety shown on the right (a-diamond, b-graphite, c-Lonsdaleite, d-buckminsterfullerene, e-Fullerite, f-C70, g-amorphous carbon and h-carbon nanotube). Due to the ability to form four strong covalent bonds structures like diamond are very tough due to the tetrahedral formation. The other common arrangement, which can be seen in b, d, e, f and h, is the hexagonal ring with occasional help from the pentagonal ring. An interesting fact of 3D geometry is that any plane of regular hexagons (that are, of course, tessellating) can be bent into three dimensions and form a closed surface by adding just 12 pentagons to the structure.
Polymorphism is the ability of solids, most often ordered crystalline solids, to have different viable structures for them to exist in. A polymorphic transition is the change between two of these polymorphs which of course don’t have to have the same chemical of physical properties due to the new structural form. Normally these transitions are temperature or pressure based and one of the best examples would be carbon forming graphite or diamond based on the conditions. (It should be noted that in this case these forms of carbon are also allotropes and although polymorphs and allotropes share similarities they are distinct as polymorphism is only consistently applied to crystal rearrangement.)