File Lava bomb 01.jpg thumb Fusiform lava bomb. Capelinhos Volcano, Faial Island , Azores . File VolcanicBombMojaveDesert.JPG thumb Volcanic bomb found in the Cinder Cones region of the Mojave National Preserve . File VulcaniaBombeVolcanique.JPG thumb Volcanic bomb at Vulcania Puy de D me A volcanic bomb is a mass of molten rock tephra larger than 65 mm 2.5 inches in diameter, formed when a volcano ejects viscosity viscous fragments of lava during an eruption. They cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they do not have Crystallite grains making them extrusive igneous rocks. Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight. Bombs can be extremely large the 1935 eruption of Mount Asama in Japan expelled bombs measuring 5 6 m in diameter up to 600 m from the vent. Volcanic bombs are a significant volcanic hazard, and can cause severe injuries and death to people in an eruption zone. One such incident occurred at Galeras volcano in Colombia in 1993 six people near the summit were killed and several seriously injured by lava bombs when the volcano erupted unexpectedly. Volcanic bombs are known to occasionally explode from internal gas pressure as they cool, but contrary to some claims in popular culture specifically, the 1997 film Volcano 1997 film Volcano , explosions are rare in most cases most of the damage they cause is from impact. Bomb explosions are most often observed in bread crust type bombs. ref http www.gc.maricopa.edu earthsci imagearchive bombs.htm Volcanic bombs, Glendale Community College ref Types of bombs Bombs are named according to their shape, which is determined by the fluidity of the magma from which they are formed. Ribbon or cylindrical bombs form from highly to moderately fluid magma, ejected as irregular strings and blobs. The strings break up into small segments which fall to the grou ... more details
wiktionary supersaturation Image KDP crystal.jpg thumb right 250px Enormous, highly pure, single crystal substances can be grown from a solution at the metastable boundary between an unsaturated and supersaturated solution. Here, a monopotassium phosphate crystal grown to create frequency doubling optics for the National Ignition Facility NIF laser. http crystals.llnl.gov KDP solution chem.html The term supersaturation refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under the solubility amount. It can also refer to a vapor of a compound that has a higher partial pressure than the vapor pressure of that compound. Condensation Small particles seed crystal seeds can trigger particle physics trigger the separation of the dissolved material from the solvent or condensation of the vapor. Seeds triggering the conversion of vapor are referred to as condensation nuclei , as in the case of water vapor . In the solid form these seeds can form to the formation of crystallite s or even large single crystal s. Supersaturation is a measure of the deviation of a dissolved salt crystal from its equilibrium state. Preparation Supersaturated solutions are prepared or result when some condition of a saturated solution is changed, for example increasing temperature , decreasing volume of the saturated Liquid as by evaporation , or increasing pressure . Examples File Rock Candy Sticks.jpg thumb right The supersaturation of sugar in water allows for rock candy to form. Carbonated water is a supersaturated solution of carbon dioxide gas in water . At the elevated pressure in the bottle , more carbon dioxide can dissolve in water than at atmospheric pressure . At atmospheric pressure, the carbon dioxide gas escapes very slowly from the supersaturated liquid . This process may be accelerated by the presence of nucleation sites within the solution, such as small bubbles, caused by shaking the bottle, or another solute, such as sugar pow ... more details
File Twinned crystals of Albite.png thumb right 300px Diagram of twinned crystals of Albite . On the more perfect cleavage, which is parallel to the basal plane P , is a system of fine striations, parallel to the second cleavage M . Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals. Crystallography Crystallographers classify twinned crystals by a number of twin laws . These twin laws are specific to the crystal system . The type of twinning can be a diagnostic tool in mineral identification. Twinning can often be a problem in X ray crystallography , as a twinned crystal does not produce a simple X ray scattering techniques diffraction pattern . Types of twinning File Pyrite 60608.jpg thumb Twinned pyrite crystal group Simple twinned crystals may be contact twins or penetration twins. Contact twins share a single composition surface often appearing as mirror images across the boundary. Plagioclase , quartz , gypsum , and spinel often exhibit contact twinning. Merohedral twinning occurs when the lattices of the contact twins superimpose in three dimensions, such as by relative rotation of one twin from the other. An example is metazeunerite . In penetration twins the individual crystals have the appearance of passing through each other in a symmetrical manner. Orthoclase , staurolite , pyrite , and fluorite often show penetration twinning. Image Galvanized spangle.jpg thumb 240px right Galvanization Galvanized surface with macroscopic crystalline features. Twin boundaries are visible as striations within each crystallite , most prominently in the bottom left and top right. If several twin crystal parts are aligned by the same twin law they are referred to as multiple or repeated twins . If these multiple twins are aligned in parallel they ... more details
Crystallization refimprove date February 2010 Image KDP crystal.jpg thumb left A huge Monopotassium phosphate KDP crystal grown from a seed crystal in a supersaturated aqueous solution at LLNL which is to be cut into slices and used on the National Ignition Facility for frequency doubling and tripling. A single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries . The absence of the defects associated with grain boundaries can give monocrystals unique properties, particularly mechanical, optical and electrical, which can also be anisotropic , depending on the type of crystallography crystallographic structure. These properties, in addition to making them precious in some gems, are industrially used in technological applications, especially in optics and electronics. Because entropy entropic effects favor the presence of some imperfections in the microstructure of solids, such as impurity impurities , inhomogeneous strain and crystallographic defect s such as dislocation s, perfect single crystals of meaningful size are exceedingly rare in nature, and are also difficult to produce in the laboratory, though they can be made under controlled conditions. On the other hand, imperfect single crystals can reach enormous sizes in nature several mineral species such as beryl , gypsum and feldspar s are known to have produced crystals several metres across. The opposite of a single crystal is an amorphous structure where the atomic position is limited to short range order only. In between the two extremes exist polycrystalline , which is made up of a number of smaller crystals known as crystallite s , and paracrystalline phases. Uses Semiconductor industry Monocrystalline silicon Single crystal silicon is used in the Fabrication semiconductor fabrication of semiconductors . On the quantum mechanics quantum scale that microprocessor s operate on, the pre ... more details
Unreferenced date July 2009 Grain growth is the increase in size of grains crystallite s in a material at high temperature. This occurs when Recovery metallurgy recovery and Recrystallization metallurgy recrystallisation are complete and further reduction in the internal energy can only be achieved by reducing the total area of grain boundary. The term is commonly used in metallurgy but is also used in reference to ceramics and minerals. Importance of grain growth Most materials exhibit the Hall Petch effect at room temperature and so display a higher yield stress when the grain size is reduced. At high temperatures the opposite is true since the open, disordered nature of grain boundaries means that vacancy chemistry vacancies can diffuse more rapidly down boundaries leading to more rapid Coble creep . Since boundaries are regions of high energy they make excellent sites for the nucleation of precipitates and other second phases e.g. Mg Si Cu phases in some aluminium alloys or martensite platlets in steel. Depending on the second phase in question this may have positive or negative effects. Rules of grain growth Grain growth has long been studied primarily by the examination of sectioned, polished and Industrial etching etched samples under the optical microscope . Although such methods enabled the collection of a great deal of empirical evidence, particular with regard to factors such as temperature or Alloy composition , the lack of crystallographic information limited the development of an understanding of the fundamental physics . Nevertheless, the following became well established features of grain growth Grain growth occurs by the movement of grain boundaries and not by coalescence i.e. like water droplets Boundary movement is discontinuous and the direction of motion may change suddenly. One grain may grow into another grain whilst being consumed from the other side The rate of consumption often increases when the grain is nearly consumed A curved boundary typically ... more details
No footnotes date February 2008 Technical date December 2009 Boninite is a mafic extrusive Rock geology rock high in both magnesium and silica, formed in fore arc environments, typically during the early stages of subduction. The rock is named for its occurrence in the Bonin Islands Izu Bonin Island arc arc south of Japan . It is characterized by extreme depletion in incompatible trace elements that are not fluid mobile e.g., the heavy rare earth elements plus Nb, Ta, Hf but variable enrichment in the fluid mobile elements e.g., Rb, Ba, K . They are found almost exclusively in the fore arc of primitive island arcs that is, closer to the trench and in ophiolite complexes thought to represent former fore arc settings. Boninite is considered to be a primitive andesite derived from melting of metasomatism metasomatised Mantle geology mantle . Similar Archean intrusives called sanukitoid s have been reported in the rocks of several early craton s. Petrology Boninite typically consists of phenocryst s of pyroxene s and olivine in a crystallite rich glassy matrix geology matrix . Geochemistry Boninite is defined by high magnesium content MgO 8 15 low titanium Titanium dioxide TiO sub 2 sub 0.5 silica content is 57 60 high Mg Mg Iron Fe 0.55 0.83 Mantle normal compatibility geochemistry compatible elements Nickel Ni 70 450 parts per million, Chromium Cr 200 1800 ppm barium Ba , strontium Sr , L Rare earth element REE enrichments compared to Tholeiitic magma series tholeiite Characteristic Ti Zirconium Zr ratios 23 63 and Lanthanum La Ytterbium Yb ratios 0.6 4.7 Genesis Boninite magma is formed by second stage melting in forearc s via mineral hydration hydration of previously depleted mantle within the mantle wedge above a subduction subducted slab , causing further melting of the already depleted peridotite . The extremely low content of titanium, which is an incompatible element within melting of peridotite is the result of previous melting events that removed most of the ... more details
No footnotes date July 2011 File Wentworth Grain Size Chart.pdf thumb 300px Wentworth grain size chart from United States Geological Survey Open File Report 2006 1195 Particle size , also called grain size , refers to the diameter of individual grains of sediment , or the lithification lithified particles in clastic rock s. The term may also be applied to other granular material s. This is different from the crystallite size, which is the size of a single crystal inside the particles or grains. A single grain can be composed of several crystal s. Granular material can range from very small colloid colloidal particles , through clay , silt , sand , and gravel , to boulder s. United States Size ranges define limits of classes that are given names in the Wentworth scale or Udden Wentworth used in the United States . The Krumbein phi scale, a modification of the Wentworth scale created by W. C. Krumbein , Krumbein & Sloss 1963 is a logarithmic scale computed by the equation math phi log 2 D Do , math where math phi math is the Krumbein phi scale, math D math is the diameter of the particle, and math Do math is a reference diameter, equal to 1 mm to make the equation Dimensional analysis dimensionally consistent . This equation can be rearranged to find diameter using math D Do times 2 phi , math class wikitable scale Size range br metric Size range br approx. inches Aggregate name br Wentworth Class Other names 8 256 mm 10.1 in Boulder 6 to 8 64 256 mm 2.5 10.1 in Cobble geology Cobble 5 to 6 32 64 mm 1.26 2.5 in Very coarse gravel Pebble 4 to 5 16 32 mm 0.63 1.26 in Coarse gravel Pebble 3 to 4 8 16 mm 0.31 0.63 in Medium gravel Pebble 2 to 3 4 8 mm 0.157 0.31 in Fine gravel Pebble 1 to 2 2 4 mm 0.079 0.157 in Very fine gravel Granule geology Granule 0 to 1 1 2 mm 0.039 0.079 in Very coarse sand 1 to 0 1 mm 0.020 0.039 in Coarse sand 2 to 1 mm 0.010 0.020 in Medium sand 3 to 2 125 250 Micrometre m 0.0049 0.010 in Fine sand 4 to 3 62.5 125 m 0.0025 0.0049 in Very ... more details
theories relating to the structure of glass included the crystallite theory whereby glass is an aggregate of crystallite s extremely small crystals . ref name Wright94JNCS Cite journal doi 10.1016 0022 ... more details
Image ShipPropellor.JPG thumb Phosphor bronze propeller salvaged from 1940s American warship. Phosphor bronze is an alloy of copper with 3.5 to 10 of tin and a significant phosphorus content of up to 1 . The phosphorus is added as deoxidizing agent during melting. These alloys are notable for their toughness , strength of materials strength , low coefficient of friction , and fine crystallite grain . The phosphorus also improves the fluidity of the molten metal and thereby improves the castability, and improves mechanical properties by cleaning up the grain boundary grain boundaries . Industrial uses Phosphor bronze is used for spring device springs , screw bolts and various other items used in situations where resistance to fatigue, wear and chemical corrosion are required e.g., a ship s propeller s in a marine ocean marine environment . The alloy is also used in some dental bridge s. Grades A, C and E C51000, 52100, 50700 are commonly used nonferrous spring alloys. The combination of good physical properties, fair electrical conductivity and moderate cost make Phosphor Bronze round, square, flat and special shaped wire desirable for many springs and electrical contacts and a wide variety of wire forms where cost of properties does not prescribe Beryllium copper . ref cite web url http www.lfa wire.com phosphor.htm title Little Falls Alloys accessdate 2009 05 08 ref Phosphor Bronze 94.8 copper , 5 tin , 0.2 phosphorus is also used in cryogenics . In this case the combination of a fair electrical conductivity , and a low thermal conductivity allows to make electrical connection to devices at ultra low temperature without adding an excessive heat load. ref cite web url http www.lakeshore.com temp acc am wirepo.html title LakeShore accessdate 2011 12 23 ref Spent nuclear fuel overpack File Loppusijoituskapseli.jpg thumb The CuOFP capsule used as overpack for spent nuclear fuel disposal in the KBS 3 concept Finnish version . Oxygen free copper can be alloyed with phosp ... more details
Image Intergranular corrosion.JPG thumb Microscope view of a polished cross section of a material attacked by intergranular corrosion Intergranular corrosion IGC , also known as intergranular attack IGA , is a form of corrosion where the boundaries of crystallite s of the material are more susceptible to corrosion than their insides. Cf. transgranular corrosion. This situation can happen in otherwise corrosion resistant alloys, when the grain boundaries are depleted, known as visible anchor grain boundary depletion , of the corrosion inhibiting elements such as chromium by some mechanism. In nickel alloys and austenitic stainless steel s, where chromium is added for corrosion resistance, the mechanism involved is precipitation of chromium carbide at the grain boundaries, resulting in the formation chromium depleted zones adjacent to the grain boundaries this process is called Sensitization effect sensitization . Around 12 chromium is minimally required to ensure passivation, mechanism by which an ultra thin invisible film, known as passive film, forms on the surface of stainless steels. This passive film protects the metal from corrosive environments. The self healing property of the passive film make the steel stainless. Selective leaching often involve grain boundary depletion mechanisms. These zones also act as local galvanic couple s, causing local galvanic corrosion . This condition happens when the material is heated to temperature around 700 C for too long time, and often happens during welding or an improper heat treatment . When zones of such material form due to welding, the resulting corrosion is termed weld decay . Stainless steels can be stabilized against this behavior by addition of titanium , niobium , or tantalum , which form titanium carbide , niobium carbide and tantalum carbide preferentially to chromium carbide, by lowering the content of carbon in the steel and in case of welding also in the filler metal under 0.02 , or by heating the entire pa ... more details
Shock metamorphism or impact metamorphism describes the effects of shock wave related deformation and heating during Impact crater impact events. The formation of similar features during supervolcano explosive volcanism is generally discounted due to the lack of Metamorphism metamorphic effects unequivocally associated with explosions and the difficulty in reaching sufficient pressures during such an event. ref http www.lpi.usra.edu meetings lpsc1992 pdf 1219.pdf A. J. Gratz, A.J., W. J. Nellis, W.J. & Hinsey, N. 1992. Laboratory Simulations of Explosive Volcanism and Implications for the K T boundary. Abstracts of the Lunar and Planetary Science Conference, volume 23, page 441. ref Effects Mineral microstructures Planar fractures Planar fractures are parallel sets of multiple planar cracks or cleavages in quartz grains they develop at the lowest pressures characteristic of shock waves 5 8 GPa and a common feature of quartz grains found associated with impact structures. Although the occurrence of planar fractures is relatively common in other deformed rocks, the development of intense, widespread, and closely spaced planar fractures is considered diagnostic of shock metamorphism. ref name French http www.lpi.usra.edu publications books CB 954 chapter4.pdf Chapter 4, Shock Metamorphic Effects in Rocks and Minerals of the online book, French, B.M. 1998. Traces of Catastrophe , A handbook of shock metamorphic effects in terrestrial meteorite impact structures, Lunar and Planetary Institute 120pp. ref Planar deformation features File Suvasvesi shocked quartz.jpg thumb 200px Shocked quartz with two sets of decorated planar deformation features in impactite impact melt rock from the Suvasvesi South impact structure, Finland thin section photomicrograph, plane polarized light . Main Planar deformation features Planar deformation features, or PDFs, are optically recognizable microscopic features in crystallite grain s of silicate minerals usually quartz or feldspar , consi ... more details
Misorientation is the difference in crystallographic orientation between two crystallites in a polycrystalline material. In crystalline materials, the orientation of a crystallite is defined by a transformation from a sample reference frame i.e. defined by the direction of a rolling or extrusion process and two orthogonal directions to the local reference frame of the crystalline lattice, as defined by the basis of the unit cell . In the same way, misorientation is the transformation necessary to move from one local crystal frame to some other crystal frame. That is, it is the distance in orientation space between two distinct orientations. If the orientations are specified in terms of matrices of direction cosines g sub A sub and g sub B sub , then the misorientation operator g sub AB sub going from A to B can be defined as follows math g B Delta g AB g A math math Delta g AB g B g A 1 math where the term g sub A sub sup 1 sup is the reverse operation of g sub A sub , that is, transformation from crystal frame A back to the sample frame. This provides an alternate description of misorientation as the successive operation of transforming from the first crystal frame A back to the sample frame and subsequently to the new crystal frame B . Various methods can be used to represent this transformation operation, such as Euler angles , Rodrigues vectors, axis angle axis angle where the axis is specified as a crystallographic direction , or Quaternions and spatial rotation unit quaternions . Symmetry and Misorientation The effect of crystal symmetry on misorientations is to reduce the fraction of the full orientation space necessary to uniquely represent all possible misorientation relationships. For example, cubic crystals i.e. FCC have 24 symmetrically related orientations. Each of these orientations is physically indistinguishable, though mathematically distinct. Therefore, the size of orientation space is reduced by a factor of 24. This defines the fundamental zone fo ... more details
orphan date May 2010 Friction stir processing is a method of changing the properties of a metal through intense, localized plastic deformation . R Sterling1 page1 7 Mahmoud1 page2 1117 This deformation is produced by forcibly inserting a non consumable tool into the workpiece, and revolving the tool in a stirring motion as it is pushed laterally through the workpiece. R Sterling1 page1 5 NTRS1 The precursor of this technique, friction stir welding , is used to join multiple pieces of metal without creating the heat affected zone typical of fusion welding . R Sterling1 page1 5, 7 When ideally implemented, this process mixes the material without phase transition changing the phase by melting or otherwise and creates a microstructure with fine, equiaxed crystallite grains . R Mahmoud1 page1 1117 NTRS1 This homogeneous grain structure, separated by high angle boundaries, allows some aluminium alloy s to take on superplasticity superplastic properties. R Sterling1 page1 7 Friction stir processing also enhances the tensile strength and fatigue strength of the metal. R Mahmoud1 page1 1117 In tests with actively cooled magnesium alloy workpieces, the microhardness was almost tripled in the area of the friction stir processed seam to 120 130 Vickers hardness . R Du1 page1 565 Applications Examples of materials successfully processed using the friction stir technique include 2519 aluminium alloy AA 2519 , 5083 aluminium alloy AA 5083 and 7075 aluminium alloy AA 7075 aluminum alloys, R Sterling1 page1 7 8 AZ61 magnesium alloy AZ61 magnesium alloy , R Du1 page1 562 nickel aluminum bronze nickel aluminium bronze R Sterling1 page1 7 and 304L stainless steel 304L stainless steel . R Sterling1 page1 33 Casting Metallic parts produced by casting are comparatively inexpensive, but are often subject to metallurgical flaws like porosity and microstructural defects. R Mishra1 Friction stir processing can be used to introduce a wrought microstructure into a cast component and eliminate m ... more details
Crystallographic defect defects sintering Pores and crystallite s tend to have straight grain boundaries ... in orientation. The term crystallite boundary is sometimes, though rarely, used. Grain boundary ... a material, so reducing crystallite size is a common way to improve strength, as described by the Hall ... more details
semicrystalline behavior, i.e. part of the material forms an ordered crystallite by folding ... between atom i and atom j . One can also use this to predict the effect of nano crystallite shape on detected ... more details
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