Unique electrical and magnetic properties of electroceramics enable them to be used as a material in the fields of communications, electronics, and energy conversion. The properties of electroceramics depend on the complex interactions that occur at the interface between the ceramic material and metal. Techniques including X ray spectroscopy and electron microscopy are used to study the structure of atoms at the interface and spectroscopy allows for direct measurements to understand the dielectric properties of the ceramic at the interface as well. The ultimate goal is to understand these properties enough to adjust or tailor at the interface for a specific need.
Very recently research has been conducted into the mechanics and physics of very small particles. Properties such as hardness seem to be different when studied on a nanometer scale. Research has shown a four-fold increase in the hardness of silicon nanospheres as compared to bulk silicon. The increased hardness of smaller volumes of various elements and compounds may have important applications in materials science.
Recently, biological and chemical weapons have been a huge concern. Scientists have been developing a dust like particle made out of silicon that can detect the weapons before they cause any damage. Using a light laser source, the silicon crystals have the ability to identify many different harmful chemical and biological agents from a distance much like a grocery store scanner. Their ability to detect different substances is due to the photonic band gap. Research is still being done to optimize the crystals so that they can perform from at least a kilometer away.
Discovered in 1966 at General Atomics, Pyrolytic Carbon (PyC) has developed today into the premier biomaterial for mechanical artificial heart valves. Pyrolytic Carbon is a carbon material deposited from gaseous hydrocarbon compounds on suitable underlying substrates (such as carbon materials, metals and ceramics) at temperatures ranging from 1000 to 2500 K (chemical vapour deposition). Due to its low surface energy, this specially heat-treated carbon has greatly improved hemocompatibility in heart prosthesis, does not provoke blood clots and has the mechanical durability to endure for a recipient's lifetime. For heart valves, a silicon-alloyed Pyrolytic Carbon is used in the form of a thick coating on a polycrystalline graphite substrate. Silicon is added to improve mechanical properties such as stiffness, hardness, and wear resistance, without significant loss in biocompatibility. Components are made by co-depositing carbon and silicon carbide on the graphite substrate by a chemical vapor-deposition, fluidized bed process that uses a gaseous mixture of silicon-containing carrier gas with a hydrocarbon.
Kevlar is a polymer developed by Dupont in the 1960’s. Although it found limited use at first, today it has many applications. Although it is used everywhere from under the seas to outer space, perhaps its greatest use to humans is its protective function. Due to its high strength and low weight, it can be found in protective garments from helmets, to gloves to bulletproof vests. The functionality of Kevlar arises from its structure, which consists of polyamide chains. Strong intermolecular forces lead to high strength and rigidity.
Teflon is a commercial handle for polytetrafluoroethylene (PTFE), and synthetic fluoropolymer first developed by the DuPont Corporation. Its fluorinated carbon-chain structure exhibits extraordinarily low tendency toward corrosion and adhesion. These properties make PTFE desirable for a number of applications from plumbing & cooking to medical and electronic venues; they also give rise to a number of industrial-application difficulties.
Polystyrene is a very common material in most households- it is used in packing materials, toys, computer casings, styrofoam cups, etc. Polystyrene is a vinyl polymer and can be processed as a foam or a solid. Styrofoam is a common Polystyrene: it has the form of a rigid foam created through the extrusion process so it has a closed-cell structure. I will explain the structure of polystyrenes, the uses, how they are created, and how they are recycled.
There are two main components of stealth technologies. First, there is radar cross section reducing geometry. This consists of designing surfaces to scatter incident radar signals. Because the signal was scattered, the radar station will not detect the signal, and therefore cannot locate the stealth object. The other component is radar absorbent materials. These act to attenuate the radar signal, such that the signal is too weak for the radar station to detect. This can be accomplished with resonant absorbers or with graded dielectric absorbers. Resonant absorbers use wave properties to cancel out the radar signal. Graded dielectric absorbers use a gradual increase in permittivity and permeability to absorb the radar signal.
Polythiophene, a plastic polymer, has the unique ability to formulate a nearly 2-dimentional unit cell, with herringbone equatorial packing. There can be pronounced fluctuations in the axial chain to chain registry between neighboring chains so that there is appreciable paracrystallinity, and this causes gaps in where the polymer can intertwine with other similar polymers. Polythiophene can be synthesized with a fullerene polymer to form a bithiophene with pendant fullerene substituants. Ultrafast electron transfer can take place along the fullerene/thiophene polymer, but when the fullerenes cluster around various parts of the polythiophene, the void can hinder electron movement. The potential applications of polythiophene are in organic plastic conductors and semiconductors, and photovoltaics.
Bucky balls and single wall carbon nanotubes are both derived from a single sheet of graphite, with pentagons interspersed in the hexagonal structure. Bucky balls are shaped like soccer balls, with 60 Carbon atoms, and the nanotubes are long tubes of 1 nm in diameter that can be hundreds of nanometers in length. Buckyballs naturally occur in these nanotubes in a small percentage of the nanotube population. They line up in a linear fashion, and can favorably fill the tubes to the limits of van der Waals forces. However, methods have been developed to cause this situation to occur in higher percentages. Since the peapods can be fabricated to the desired quantities, they can be studied more efficiently. With high heat and lasers, the bucky balls can be fused to form round-ended tubes within the nanotubes, and these structures have interesting properties due to their hybridized electronic band.
Liquid crystal technology utilizes a substance that has both solid, and liquid characteristics. This substance could be in between, since it acts as a liquid at a certain temperature, but melts at a temperature a little higher than that. The crystals in LCD screens are in a nematic phase. These crystals in the nematic phase can be altered by electric current, which we can then predict the movements of, giving us a way to make displays.
Photochromic lenses are used in transition eyeglasses which darken in sunlight. Ag+ and Cu+ are dispersed throughout the area near the surface of the glass. In the presence of ultraviolet radiation, the Cu+ reduces the Ag+ to Ag(s). The tiny particles of solid silver block light, tinting the glasses according to the amount of UV present.
Shape memory alloys are materials that have the ability to return to a given shape after being bent, twisted, or otherwise changed. When the metal is below its given transformation temperature, it is deformed easily into a new shape. It maintains this shape until it is heated above the transformation point, where its crystal structure will return it to its original shape. If the metal receives any resistance during the transformation, there will be large forces generated.
Old abstract:
A superconductor is an element or compound that will conduct electricity without resistance below a certain temperature. High-current films using superconductors have always been deposited on single cystals. Now, scientists are able to deposite superconducting material on metal substrates. Researchers use a zirconia buffer layer to dictate the orientation of individual cystalites. Being able to deposit superconducting material on metal made it possible to have superconducting wires
in magnetic coils. Superconducting coils are used today in magnetic imaging, magnetically levitated trains, fast switches, etc.
Olestra
is a fat substitute that was developed by Proctor and Gamble starting in the
late seventies that was approved by the FDA for use in foods as a fat replacer in 1996. It is sold now under the trade name
In 1997, Advanced Tissue Sciences, Inc developed a new skin replacement for severe burn wounds. Dermagraft TC, as it was called, is produced by culturing human dermal fibroblasts (a type of cell commonly found in the dermal layer and connective tissue) onto a commercially available biosynthetic material consisting of an ultra-thin, semipermeable membrane bonded to nylon mesh. The nylon mesh forms a three-dimensional scaffold for growth of the dermal tissue and the membrame forms a synthetic (non-immunogenic) epidermis. As the fibroblasts proliferate in the nylon mesh, they secrete important structural proteins and growth factors, thereby generating a three-dimensional human dermal matrix. Dermagraft prevents fluid loss and promotes a vascularized wound bed for autograft.
A mixture of porous polymers and cells can be
injected into the body at the site of some type of damaged tissue such as
cartilage or bone. The polymers PLA-PEG-biotin
self-assemble into a scaffold with the aid of the cross-linking protein avidin. Other
components such as growth factors or other signaling molecules can be added to
the mixture as needed. The scaffold
molds to fit the area into which it was injected. At this point, the cells are trapped in
the scaffold and begin to multiply allowing the damaged tissue to be repaired.
Microscopic cracks in composite material can cause significant damage in the structure of the object. Is there any way that these objects can be “healed” instead of being replaced by a new part that may form new cracks? A material has been developed that adds microscopic capsules to the composite without compromising the material’s properties or performance. The capsules contain a dicyclopentadiene monomer that seeps out of the capsule once it has been ruptured by a crack. The monomer is then polymerized by a catalyst in the surrounding material and forms a stable polymer that seals the crack and prevents it from getting any wider.
Studies are being conducted on high molecular weight polymers that have cationic sites on them, particularly poly(vinyl-N-hexylpyridinium bromide) (hexyl-PVP). These polymers have been found to kill both Gram-positive and Gram-negative bacteria on contact. This type of polymer can be derivatized onto nearly any material making it a disinfectant. Additionally washing has no effect on the potency of the material so the bactericidal quality of the material will not diminish significantly over time. This type of material has many potential applications including as a defense against biological warfare. It is believed that the bactericidal quality of the polymer is due to the cationic sites on the polymer. Bacteria have negative charges on the surface, so when the bacteria land on the polymer, they are attracted to the surface by electrostatic interactions, and the bacteria are lysed and die on contact.