|
Aluminium Foam
Regular foamed aluminium A metal foam is a cellular structure consisting of a solid metal (frequently aluminium) with gas-filled pores comprising a large portion of the volume. The pores can be sealed (closed-cell foam) or interconnected (open-cell foam). The defining characteristic of metal foams is a high porosity: typically only 5–25% of the volume is the base metal. The strength of the material is due to the square–cube law. Metal foams typically retain some physical properties of their base material. Foam made from non-flammable metal remains non-flammable and can generally be recycled as the base material. Its coefficient of thermal expansion is similar while thermal conductivity is likely reduced. Definitions Open-cell Open-celled metal foam, also called metal sponge, can be used in heat exchangers (compact electronics cooling, cryogen tanks, PCM heat exchangers), energy absorption, flow diffusion, scrubbers, flame arrestors, and lightweight optics. The high ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminium Foam
Regular foamed aluminium A metal foam is a cellular structure consisting of a solid metal (frequently aluminium) with gas-filled pores comprising a large portion of the volume. The pores can be sealed (closed-cell foam) or interconnected (open-cell foam). The defining characteristic of metal foams is a high porosity: typically only 5–25% of the volume is the base metal. The strength of the material is due to the square–cube law. Metal foams typically retain some physical properties of their base material. Foam made from non-flammable metal remains non-flammable and can generally be recycled as the base material. Its coefficient of thermal expansion is similar while thermal conductivity is likely reduced. Definitions Open-cell Open-celled metal foam, also called metal sponge, can be used in heat exchangers (compact electronics cooling, cryogen tanks, PCM heat exchangers), energy absorption, flow diffusion, scrubbers, flame arrestors, and lightweight optics. The high ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lightweight Optics
Lightweight is a weight class in combat sports and rowing. Boxing Professional boxing The lightweight division is over 130 pounds (59 kilograms) and up to 135 pounds (61.2 kilograms) weight class in the sport of boxing. Notable lightweight boxers include Henry Armstrong, Ken Buchanan, Tony Canzoneri, Pedro Carrasco, Joel Casamayor, Al "Bummy" Davis, Oscar De La Hoya, Roberto Durán, Joe Gans, Artur Grigorian, Benny Leonard, Ray Mancini, Floyd Mayweather Jr., Juan Manuel Márquez, Sugar Shane Mosley, Miguel Ángel González, Carlos Ortiz, Katie Taylor, Edwin Valero, Len Wickwar, Pernell Whitaker, Manny Pacquiao and Ike Williams. Current world champions Current world rankings =''The Ring''= As of , . Keys: : Current '' The Ring'' world champion =BoxRec= As of , . Longest reigning world lightweight champions Below is a list of "longest reigning lightweight champions" career time as champion (for multiple time champions) does not apply. Amateur boxing Olympic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stiffness
Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a body is a measure of the resistance offered by an elastic body to deformation. For an elastic body with a single degree of freedom (DOF) (for example, stretching or compression of a rod), the stiffness is defined as k = \frac where, * F is the force on the body * \delta is the displacement produced by the force along the same degree of freedom (for instance, the change in length of a stretched spring) In the International System of Units, stiffness is typically measured in newtons per meter (N/m). In Imperial units, stiffness is typically measured in pounds (lbs) per inch. Generally speaking, deflections (or motions) of an infinitesimal element (which is viewed as a point) in an elastic body can occur along multiple DOF (maximum of s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bicycle Helmet
A bicycle helmet is a type of helmet designed to attenuate impacts to the head of a cyclist in falls while minimizing side effects such as interference with peripheral vision. There is ongoing scientific research into the degree of protection offered by bicycle helmets in the event of an accident, and the effects of helmet wearing on cyclist and motor vehicle driver behaviour. There is active debate over what can be concluded from available studies, and on whether the use of helmets by cyclists should be promoted or mandated, either just for children, or for cyclists of all ages. In particular the debate over bicycle helmet laws has been intense and occasionally bitter, often based not only on differing interpretations of the scientific and other academic literature, but also on differing assumptions and interests of various parties. History History of designs A cycle helmet should generally be light in weight and provide ample ventilation because cycling can be an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals. The term "polymer" derives from the Greek word πολύς (''polus'', meaning "many, much") and μέρος (''meros'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver and was formerly named hydrargyrum ( ) from the Greek words, ''hydor'' (water) and ''argyros'' (silver). A heavy, silvery d-block A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. The term appears to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-blo ... element, mercury is the only metallic element that is known to be liquid at standard temperature and pressure; the only other element that is liquid under these conditions is the halogen bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature. Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is obtained by Mill (grinding), grinding natural cinnabar or synthetic mercuric sulfide. Mercury is used in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blowing Agent
A blowing agent is a substance which is capable of producing a cellular structure via a foaming process in a variety of materials that undergo hardening or phase transition, such as polymers, plastics, and metals. They are typically applied when the blown material is in a liquid stage. The cellular structure in a matrix reduces density, increasing thermal and acoustic insulation, while increasing relative stiffness of the original polymer. Blowing agents (also known as 'pneumatogens') or related mechanisms to create holes in a matrix producing cellular materials, have been classified as follows: *Physical blowing agents include CFCs (however, these are ozone depletants, banned by the Montreal Protocol of 1987), HCFCs (replaced CFCs, but are still ozone depletants, therefore being phased out), hydrocarbons (e.g. pentane, isopentane, cyclopentane), and liquid CO2. The bubble/foam-making process is irreversible and endothermic, i.e. it needs heat (e.g. from a melt process or the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palladium Hydride
Palladium hydride is metallic palladium that contains a substantial quantity of hydrogen within its crystal lattice. Despite its name, it is not an ionic hydride but rather an alloy of palladium with metallic hydrogen that can be written PdHx. At room temperature, palladium hydrides may contain two crystalline phases, α and β (sometimes called α'). Pure α-phase exists at ''x'' 0.58; intermediate x values correspond to α-β mixtures. Hydrogen absorption by palladium is reversible and therefore has been investigated for hydrogen storage. Palladium electrodes have been used in some cold fusion experiments, under the hypothesis that the hydrogen could be "squeezed" between the palladium atoms to help them fuse at lower temperatures than would otherwise be required. History The absorption of hydrogen gas by palladium was first noted by T. Graham in 1866 and absorption of electrolytically produced hydrogen, where hydrogen was absorbed into a palladium cathode, was first d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osmium
Osmium (from Greek grc, ὀσμή, osme, smell, label=none) is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element. When experimentally measured using X-ray crystallography, it has a density of . Manufacturers use its alloys with platinum, iridium, and other platinum-group metals to make fountain pen nib tipping, electrical contacts, and in other applications that require extreme durability and hardness. Osmium is among the rarest elements in the Earth's crust, making up only 50 parts per trillion ( ppt). It is estimated to be about 0.6 parts per billion in the universe and is therefore the rarest precious metal. Characteristics Physical properties Osmium has a blue-gray tint and is the densest stable element; it is approximately twice as dense as lead and narrowly denser tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Platinum Black
Platinum black (Pt black) is a fine powder of platinum with good catalytic properties. The name of platinum black is due to its black color. It is used in many ways; as a thin film electrode, a fuel cell membrane catalyst, or as a catalytic ignition of flammable gases for "self-lighting' gas lamps, ovens, and stove burners. Uses Thin film electrode Platinum black is widely used as a thin film covering solid platinum metal, forming platinum electrodes for applications in electrochemistry. The process of covering platinum electrodes with such a layer of platinum black is called "platinization of platinum". The platinized platinum has a true surface area much higher than the geometrical surface area of the electrode and, therefore, exhibits action superior to that of shiny platinum. Fuel cell membrane catalyst Platinum black powder is used as a catalyst in proton-exchange membrane fuel cells. In common practice, the platinum black is either sprayed using an ultrasonic nozzle or hot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palladium Black
Palladium black is a coarse, sponge-like form of elemental palladium which offers a large surface area for catalytic activity. It is used in organic synthesis as a catalyst for hydrogenation reactions. The term palladium black is also used colloquially to refer to a black precipitate of elemental palladium, which forms via decomposition of various palladium complexes. Preparation Palladium black is typically prepared from palladium(II) chloride or palladium(II)-ammonium chloride. The palladium chloride process entails the formation of palladium hydroxide using lithium hydroxide followed by reduction under hydrogen gas while the palladium(II)-ammonium chloride route employs a solution of formic acid followed by the precipitation of the catalyst using potassium hydroxide. See also *Platinum black *Platinum dioxide *Platinum on carbon *Palladium on carbon *Rhodium-platinum oxide Rhodium-platinum oxide (Rh–Pt oxide), or Nishimura's catalyst, is an inorganic compound used as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
