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Ultra-high Temperature Ceramic
Ultra-high-temperature ceramics (UHTCs) are a type of refractory ceramics that can withstand extremely high temperatures without degrading, often above 2,000 °C. They also often have high Thermal conductivity, thermal conductivities and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking. Chemically, they are usually borides, carbides, nitrides, and oxides of early transition metals. UHTCs are used in various high-temperature applications, such as Thermal protection system, heat shields for spacecraft, Industrial furnace, furnace linings, Hypersonic flight, hypersonic aircraft components and nuclear reactor components. They can be fabricated through various methods, including hot pressing, spark plasma sintering, and chemical vapor deposition. Despite their advantages, UHTCs also have some limitations, such as their brittleness and difficulty in machining. However, ongoing research is focu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refractory Ceramic
In materials science, a refractory (or refractory material) is a material that is resistant to decomposition by heat or chemical attack and that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compounds that may be porous or non-porous, and their crystallinity varies widely: they may be crystalline, polycrystalline, amorphous, or composite. They are typically composed of oxides, carbides or nitrides of the following elements: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium. Many refractories are ceramics, but some such as graphite are not, and some ceramics such as clay pottery are not considered refractory. Refractories are distinguished from the ''refractory metals'', which are elemental metals and their alloys that have high melting temperatures. Refractories are defined by ASTM C71 as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Vapor Deposition
Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. In typical CVD, the wafer (electronics), wafer (substrate) is exposed to one or more Volatility (chemistry), volatile wikt:precursor, precursors, which chemical reaction, react and/or chemical decomposition, decompose on the substrate surface to produce the desired deposit. Frequently, volatile by-products are also produced, which are removed by gas flow through the reaction chamber. Microfabrication processes widely use CVD to deposit materials in various forms, including: Single crystal, monocrystalline, polycrystalline, amorphous, and Epitaxy, epitaxial. These materials include: silicon (Silicon dioxide, dioxide, silicon carbide, carbide, silicon nitride, nitride, silicon oxynitride, oxynitride), carbon (carbon (fiber), fiber, carbon nanofibers, nanofibers, carbon nanot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zirconium Diboride
Zirconium diboride (ZrB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB2 is an ultra-high temperature ceramic (UHTC) with a melting point of 3246 °C. This along with its relatively low density of ~6.09 g/cm3 (measured density may be higher due to hafnium impurities) and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and hafnium diboride. ZrB2 parts are usually hot pressed (pressure applied to the heated powder) and then machined to shape. Sintering of ZrB2 is hindered by the material's covalent nature and presence of surface oxides which increase grain coarsening before densification during sintering. Pressureless sintering of ZrB2 is possible with sintering additives suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grain Size
Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which refers to the size of a single crystal inside a particle or grain. A single grain can be composed of several crystals. Granular material can range from very small colloidal particles, through clay, silt, sand, gravel, and cobbles, to boulders. Krumbein phi scale Size ranges define limits of classes that are given names in the Wentworth scale (or Udden–Wentworth scale named after geologists Chester K. Wentworth and Johan A. Udden) used in the United States. The Krumbein ''phi'' (φ) scale, a modification of the Wentworth scale created by W. C. Krumbein in 1934, is a logarithmic scale computed by the equation :\varphi=-\log_2, where :\varphi is the Krumbein phi scale, :D is the diameter In geometry, a diameter of a circle i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanical Strength
Mechanical may refer to: Machine * Machine (mechanical), a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement * Mechanical calculator, a device used to perform the basic operations of arithmetic * Mechanical energy, the sum of potential energy and kinetic energy * Mechanical system, a system that manages the power of forces and movements to accomplish a task * Mechanism (engineering), a portion of a mechanical device Other * Mechanical (character), one of several characters in Shakespeare's ''A Midsummer Night's Dream'' * A kind of typeface in the VOX-ATypI classification See also * Machine, especially in opposition to an electronic item * '' Mechanical Animals'', the third full-length studio release by Marilyn Manson * Manufactured or artificial, especially in opposition to a biological or natural component * Automation, using machine decisions and processing instead of human * Mechanization, using machine labor in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxidation
Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. The oxidation and reduction processes occur simultaneously in the chemical reaction. There are two classes of redox reactions: * Electron-transfer – Only one (usually) electron flows from the atom, ion, or molecule being oxidized to the atom, ion, or molecule that is reduced. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * Atom transfer – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously, the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Conductivity
The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials such as mineral wool or Styrofoam. Metals have this high thermal conductivity due to free electrons facilitating heat transfer. Correspondingly, materials of high thermal conductivity are widely used in heat sink applications, and materials of low thermal conductivity are used as thermal insulation. The reciprocal of thermal conductivity is called thermal resistivity. The defining equation for thermal conductivity is \mathbf = - k \nabla T, where \mathbf is the heat flux, k is the thermal conductivity, and \nabla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refractory
In materials science, a refractory (or refractory material) is a material that is resistant to decomposition by heat or chemical attack and that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compounds that may be porous or non-porous, and their crystallinity varies widely: they may be crystalline, polycrystalline, amorphous, or composite. They are typically composed of oxides, carbides or nitrides of the following elements: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium. Many refractories are ceramics, but some such as graphite are not, and some ceramics such as clay pottery are not considered refractory. Refractories are distinguished from the '' refractory metals'', which are elemental metals and their alloys that have high melting temperatures. Refractories are defined by ASTM C71 as "non-metallic materials having those chemical and physical properties that make them applicable for structures, o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Shuttle
The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was the Space Transportation System (STS), taken from the 1969 plan led by U.S. vice president Spiro Agnew for a system of reusable spacecraft where it was the only item funded for development. The first (STS-1) of four orbital test flights occurred in 1981, leading to operational flights (STS-5) beginning in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011. They launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST), conducted science experiments in orbit, participated in the Shuttle–Mir program, Shuttle-''Mir'' program with Russia, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boeing X-20 Dyna-Soar
The Boeing X-20 Dyna-Soar ("Dynamic Soarer") was a United States Air Force (USAF) program to develop a spaceplane that could be used for a variety of military missions, including aerial reconnaissance, bombing, space rescue, satellite maintenance, and as a space interceptor to sabotage enemy satellites. The program ran from October 24, 1957, to December 10, 1963, cost US$660 million ($ in current dollars), and was cancelled just after spacecraft construction had begun. Other spacecraft under development at the time, such as Mercury or Vostok, were space capsules with ballistic re-entry profiles that ended in a landing under a parachute. Dyna-Soar was more like an aircraft. It could travel to distant targets at the speed of an intercontinental ballistic missile, was designed to glide to Earth like an aircraft under the control of a pilot, and could land at an airfield. Dyna-Soar could also reach Earth orbit, like conventional, crewed space capsules. These characteristics m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypersonic Technology Vehicle
In aerodynamics, a hypersonic speed is one that exceeds five times the speed of sound, often stated as starting at speeds of Mach 5 and above. The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since individual physical changes in the airflow (like molecular dissociation and ionization) occur at different speeds; these effects collectively become important around Mach 5–10. The hypersonic regime can also be alternatively defined as speeds where specific heat capacity changes with the temperature of the flow as kinetic energy of the moving object is converted into heat. Characteristics of flow While the definition of hypersonic flow can be quite vague and is generally debatable (especially because of the absence of discontinuity between supersonic and hypersonic flows), a hypersonic flow may be characterized by certain physical phenomena that can no longer be analytically discounted as in supersonic flow. The peculiarities in hy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Air Force
The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its origins to 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established by transfer of personnel from the Army Air Forces with the enactment of the National Security Act of 1947. It is the second youngest branch of the United States Armed Forces and the fourth in United States order of precedence, order of precedence. The United States Air Force articulates its core missions as air supremacy, intelligence, surveillance, target acquisition, and reconnaissance, global integrated intelligence, surveillance and reconnaissance, airlift, rapid global mobility, Strategic bombing, global strike, and command and control. The United States Department of the Air Force, Department of the Air Force, which serves as the USAF's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
