Anonymous 05/31/19 (Fri) 17:58:48 No. 934
Graphene is a single layer (monolayer) of carbon atoms, tightly bound in a hexagonal honeycomb lattice. It is an allotrope of carbon in the form of a plane of sp2-bonded atoms with a molecular bond length of 0.142 nanometres. Layers of graphene stacked on top of each other form graphite, with an interplanar spacing of 0.335 nanometres. The separate layers of graphene in graphite are held together by van der Waals forces, which can be overcome during exfoliation of graphene from graphite.
Graphene is the thinnest compound known to man at one atom thick, the lightest material known (with 1 square meter weighing around 0.77 milligrams), the strongest compound discovered (between 100-300 times stronger than steel with a tensile strength of 130 GPa and a Young's modulus of 1 TPa - 150,000,000 psi), the best conductor of heat at room temperature (at (4.84±0.44) × 10^3 to (5.30±0.48) × 10^3 W·m−1·K−1) and also the best conductor of electricity known (studies have shown electron mobility at values of more than 200,000 cm2·V−1·s−1). Other notable properties of graphene are its uniform absorption of light across the visible and near-infrared parts of the spectrum (πα ≈ 2.3%), and its potential suitability for use in spin transport. Bearing this in mind, one might be surprised to know that carbon is the second most abundant mass within the human body and the fourth most abundant element in the universe (by mass), after hydrogen, helium and oxygen. This makes carbon the chemical basis for all known life on earth, making graphene potentially an eco-friendly, sustainable solution for an almost limitless number of applications. Since the discovery (or more accurately, the mechanical obtainment) of graphene, applications within different scientific disciplines have exploded, with huge gains being made particularly in high-frequency electronics, bio, chemical and magnetic sensors, ultra-wide bandwidth photodetectors, and energy storage and generation.
Anonymous 06/19/19 (Wed) 15:41:48 No. 955
Casein plastics were introduced at the beginning of the 20th century, their starting material being the protein in cows milk, precipitated by the action of the enzyme rennin.
Although casein is readily moulded to shape under moderate heat and pressure, it does not produce a stable material for manufacture until it has become hardened by soaking in formalin (5% solution of formaldehyde in water) for a long period. Unfortunately, this causes much distortion so casein plastics are almost always produced by machining stock material such as sheet, rod, tube or buttton blanks (small discs). After machining, casein may be polished either mechanically with abrasives or chemically with a ‘dip polish’. The material readily takes a surface dye, so coloured items can be quickly made from pale coloured stock items. This was especially important for the button trade which was the principal consumer of casein plastics. As well as buttons and buckles, casein was also used for knitting pins, fountain pen and propelling pencil barrels, dressing table ware and a host of other items.