title: Floral emblem

text: The national flower of Antigua and Barbuda is "Agave karatto", also known as "dagger log" or "batta log".


title: Floral emblem

text: The national flower of Barbados is known locally as the Pride of Barbados ("Caesalpinia pulcherrima").


title: Floral emblem

text: The national flower of Dominica is "Sabinea carinalis", commonly known as Carib wood or "Bois Caraibe".


title: Floral emblem

text: The Dominican Republic's national flower was originally the flower of the "caoba" (mahogany tree, "Swietenia mahagoni"). In 2011, the mahogany was dubbed the national tree, vacating the national flower spot for the Bayahibe rose ("Pereskia quisqueyana") in order to bring attention to its conservation.


title: Floral emblem

text: Golden Wattle ("Acacia pycnantha") was officially proclaimed the floral emblem of Australia on 1 September 1988.


title: Floral emblem

text: The Tahitian gardenia (tiare flower) is the national flower of Tahiti, French Polynesia, and the Cook Islands.


title: Floral emblem

text: The national flower of Fiji is "tagimaucia" ("Medinilla waterhousei"), a vine with red and white flowers endemic to the highlands of the island of Taveuni.


title: Floral emblem

text: New Zealand does not have an official national flower, but the silver fern (foliage) is acknowledged as its national emblem. The Kowhai ("Sophora" spp., native trees with yellow cascading flowers) is usually regarded as the national flower. Other plant emblems are Koru (a curled fern symbol) and the crimson-flowered Pohutukawa ("Metrosideros excelsa"), also called New Zealand's Christmas tree.


title: Floral emblem

text: The "heilala" ("Garcinia sessilis") is Tonga's national flower. The name of Tonga's beauty pageant, the Heilala Festival, is taken from this flower. Resorts as well as consumer products are also often named after this flower, such as the Heilala Lodge and Heilala Vanilla. The flower is also used in Tonga for medicinal and ornamental purposes.


title: Floral emblem

text: The national flower of Argentina is the flower of the ceibo tree ("Erythrina crista-galli"), also known as "seibo" or "bucaré".


title: Floral emblem

text: Bolivia has two national flowers: the "kantuta" ("Cantua buxifolia") and "patujú" ("Heliconia rostrata").


title: Floral emblem

text: "Cattleya trianae" is the national flower of Colombia and is the orchid which flowers in May. The May flower was chosen because the colors are the same as those of the Colombian flag.


title: Floral emblem

text: The national flower of Peru is the cantuta (also spelled "kantuta" or "qantuta", from Quechua "qantu"). It can be found in the high valleys of the Andes in Peru and Bolivia.


title: Floral emblem

text: Called "faya lobi" ("fiery love") in Sranantongo, the jungle geranium ("Ixora coccinea") is commonly considered a symbol of Suriname.


title: Floral emblem

text: A county flower is a flowering plant chosen to symbolise a county. They exist primarily in the United Kingdom, but some counties in other countries also have them.


title: Floral emblem

text: One or two county flowers have a long history in England – the red rose of Lancashire dates from the Middle Ages, for instance. However, the county flower concept was only extended to cover the whole United Kingdom in 2002, as a promotional tool by a charity. In that year, the plant conservation charity Plantlife ran a competition to choose county flowers for all counties, to celebrate the Golden Jubilee of Queen Elizabeth II.


title: Floral emblem

text: Plantlife's scheme is loosely based on Britain's historic counties, and so some current local government areas are not represented by a flower, and some of the counties included no longer exist as administrative areas. Flowers were also chosen for thirteen major cities: Belfast, Birmingham, Bristol, Cardiff, Edinburgh, Glasgow, Leeds, Liverpool, London, Manchester, Newcastle upon Tyne, Nottingham and Sheffield. The Isles of Scilly was also treated as a county (distinct from Cornwall) for the purpose of the scheme. The Isle of Man was included, even though it is not a county, but a self-governing territory outside of the United Kingdom with an existing national flower: the ragwort or "cushag". The Channel Islands were not included.


title: Floral emblem

text: A total of 94 flowers was chosen in the competition. 85 of the 109 counties have a unique county flower, but several species were chosen by more than one county. Foxglove or "Digitalis purpurea" was chosen for four counties – Argyll, Birmingham, Leicestershire and Monmouthshire – more than any other species. The following species were chosen for three counties each:


title: Floral emblem

text: In addition, Sticky Catchfly "Lychnis viscaria" was chosen for both Edinburgh and Midlothian, the county containing Edinburgh.


title: Floral emblem

text: For most counties, native species were chosen, but for a small number of counties, non-natives were chosen, mainly archaeophytes.


title: Floral emblem

text: No plant or flower seems to be among the current official symbols. Some flowering plants from the area include "Althaea armeniaca", Armenian Basket, "Muscari armeniacum", Armenian Poppy, Armenian vartig (vargit), and "Tulipa armena".


title: Floral emblem

text: Azerbaijan currently has no official national flower. Traditionally, various regions have different designations where national symbols are concerned. The city of Shusha named the Khari Bulbul ("Ophrys caucasica") the floral emblem of the Nagorno-Karabakh.


title: Floral emblem

text: China currently has no official national flower. Traditionally, various regions have different designations where national symbols are concerned.


title: Floral emblem

text: In 1903, the Qing dynasty named the peony () the floral emblem of the nation. The peony has long been considered a flower of wealth and honor in China.


title: Floral emblem

text: The puppet state Manchukuo followed Japan's model of dual floral emblems: the "spring orchid" (Cymbidium goeringii) for the Emperor and the imperial household, and the sorghum blossom (Sorghum bicolor) for the state and the nation.


title: Floral emblem

text: The plum blossom, "meihua" (), has also been one of the most beloved flowers in Chinese culture. The Republic of China government named the plum blossom as the national flower in 1964. The plum blossom is symbol for resilience and perseverance in the face of adversity, because plum blossoms often bloom most vibrantly even amidst the harsh winter snow.


title: Floral emblem

text: The People's Republic of China, which has controlled mainland China since 1949, has no official floral emblem. There have been several petitions in recent years to officially adopt one. However, the government has not taken any action yet. A poll in 2005 showed that 41% of the public supports peony as the national flower while 36% supported the plum blossom. Some scholars have suggested that the peony and plum blossoms may be designated as dual national flowers. In addition, the orchid, jasmine, daffodil and chrysanthemum have also been held as possible floral symbols of China.


title: Floral emblem

text: No flower has been officially declared as a national symbol. Unofficially the rose and the orchid are claimed to hold that title.


title: Floral emblem

text: Both Blue Egyptian Lotus and White Egyptian Lotus are regarded as Egypt's national flowers, and they appear in many Ancient Egyptian paintings and monuments.


title: Floral emblem

text: In a 2018 public vote "Vernonia djalonensis" was voted as the national flower of Guinea, a decision which is currently awaiting government approval


title: Floral emblem

text: Italy doesn't have an official floral emblem, though the Lily lilium is commonly cited. Other less common options are the Rose and the White poppy.


title: Floral emblem

text: Japan's national government has never formally named a national flower, as with other symbols such as the green pheasant, which was named as national bird by a non-government body in 1947. In 1999, the national flag and anthem were standardised by law.


title: Floral emblem

text: A "de facto" national flower for Japan for many is the "sakura" (cherry blossom), while a stylised depiction of a Chrysanthemum morifolium is used as the official emblem of the imperial family (Imperial Seal of Japan). The Paulownia blossom was also used by the imperial family in the past, but has since been appropriated by the Prime Minister and the government in general (Government Seal of Japan).


title: Floral emblem

text: While the Netherlands does not have an official national flower, the tulip is widely considered to be its national flower.


title: Floral emblem

text: While France does not have an official national flower, the fleur-de-lis, which was a symbol of the royal family, as well as the cornflower (blue), marguerite (white), and red poppy, which together represent the tri-colored national flag, are also generally treated as French national flowers.


title: Floral emblem

text: While Vietnam does not have an official flower, four plants are traditional regarded as the "four graceful plants", namely: the lotus, the pine, bamboo, and the chrysanthemum. The lotus ("Nelumbo nucifera") is generally regarded as the unofficial national flower of Vietnam, as portrayed, for example, on their postage stamps. In Vietnamese tradition, the lotus is regarded as "the symbol of purity, commitment and optimism for the future."


title: Filter feeder

text: Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish (including some sharks). Some birds, such as flamingos and certain species of duck, are also filter feeders. Filter feeders can play an important role in clarifying water, and are therefore considered ecosystem engineers. They are also important in bioaccumulation and, as a result, as indicator organisms.


title: Filter feeder

text: Most forage fish are filter feeders. For example, the Atlantic menhaden, a type of herring, lives on plankton caught in midwater. Adult menhaden can filter up to four gallons of water a minute and play an important role in clarifying ocean water. They are also a natural check to the deadly red tide.


title: Filter feeder

text: In addition to these bony fish, four types of cartilaginous fishes are also filter feeders. The whale shark sucks in a mouthful of water, closes its mouth and expels the water through its gills. During the slight delay between closing the mouth and opening the gill flaps, plankton is trapped against the dermal denticles which line its gill plates and pharynx. This fine sieve-like apparatus, which is a unique modification of the gill rakers, prevents the passage of anything but fluid out through the gills (anything above 2 to 3 mm in diameter is trapped). Any material caught in the filter between the gill bars is swallowed. Whale sharks have been observed "coughing" and it is presumed that this is a method of clearing a build up of food particles in the gill rakers. The megamouth shark has luminous organs called photophores around its mouth. It is believed they may exist to lure plankton or small fish into its mouth. The basking shark is a passive filter feeder, filtering zooplankton, small fish, and invertebrates from up to 2,000 tons of water per hour. Unlike the megamouth and whale sharks, the basking shark does not appear to actively seek its quarry; but it does possess large olfactory bulbs that may guide it in the right direction. Unlike the other large filter feeders, it relies only on the water that is pushed through the gills by swimming; the megamouth shark and whale shark can suck or pump water through their gills. Manta rays can time their arrival at the spawning of large shoals of fish and feed on the free-floating eggs and sperm. This stratagem is also employed by whale sharks.


title: Filter feeder

text: Mysidacea are small crustaceans that live close to shore and hover above the sea floor, constantly collecting particles with their filter basket. They are an important food source for herring, cod, flounder, and striped bass. Mysids have a high resistance to toxins in polluted areas, and may contribute to high toxin levels in their predators.


title: Filter feeder

text: Antarctic krill manages to directly utilize the minute phytoplankton cells, which no other higher animal of krill size can do. This is accomplished through filter feeding, using the krill's developed front legs, providing for a very efficient filtering apparatus: the six thoracopods form a very effective "feeding basket" used to collect phytoplankton from the open water. In the animation at the top of this page, the krill is hovering at a 55° angle on the spot. In lower food concentrations, the feeding basket is pushed through the water for over half a meter in an opened position, and then the algae are combed to the mouth opening with special setae on the inner side of the thoracopods.


title: Filter feeder

text: Porcelain crabs have feeding appendages covered with setae to filter food particles from the flowing water.


title: Filter feeder

text: Most species of barnacles are filter feeders, using their highly modified legs to sift plankton from the water.


title: Filter feeder

text: The baleen whales (Mysticeti), one of two suborders of the Cetacea (whales, dolphins, and porpoises), are characterized by having baleen plates for filtering food from water, rather than teeth. This distinguishes them from the other suborder of cetaceans, the toothed whales (Odontoceti). The suborder contains four families and fourteen species. Baleen whales typically seek out a concentration of zooplankton, swim through it, either open-mouthed or gulping, and filter the prey from the water using their baleens. A baleen is a row of a large number of keratin plates attached to the upper jaw with a composition similar to those in human hair or fingernails. These plates are triangular in section with the largest, inward-facing side bearing fine hairs forming a filtering mat. Right whales are slow swimmers with large heads and mouths. Their baleen plates are narrow and very long — up to in bowheads — and accommodated inside the enlarged lower lip which fits onto the bowed upper jaw. As the right whale swims, a front gap between the two rows of baleen plates lets the water in together with the prey, while the baleens filter out the water. Rorquals such as the blue whale, in contrast, have smaller heads, are fast swimmers with short and broad baleen plates. To catch prey, they widely open their lower jaw — almost 90° — swim through a swarm gulping, while lowering their tongue so that the head's ventral grooves expand and vastly increase the amount of water taken in. Baleen whales typically eat krill in polar or subpolar waters during summers, but can also take schooling fish, especially in the Northern Hemisphere. All baleen whales except the gray whale feed near the water surface, rarely diving deeper than or for extended periods. Gray whales live in shallow waters feeding primarily on bottom-living organisms such as amphipods.


title: Filter feeder

text: Bivalves are aquatic molluscs which have two-part shells. Typically both shells (or valves) are symmetrical along the hinge line. The class has 30,000 species, including scallops, clams, oysters and mussels. Most bivalves are filter feeders (although some have taken up scavenging and predation), extracting organic matter from the sea in which they live. Nephridia, the shellfish version of kidneys, remove the waste material. Buried bivalves feed by extending a siphon to the surface. For example, oysters draw water in over their gills through the beating of cilia. Suspended food (phytoplankton, zooplankton, algae and other water-borne nutrients and particles) are trapped in the mucus of a gill, and from there are transported to the mouth, where they are eaten, digested and expelled as feces or pseudofeces. Each oyster filters up to five litres of water per hour. Scientists believe that the Chesapeake Bay's once-flourishing oyster population historically filtered the estuary's entire water volume of excess nutrients every three or four days. Today that process would take almost a year, and sediment, nutrients, and algae can cause problems in local waters. Oysters filter these pollutants, and either eat them or shape them into small packets that are deposited on the bottom where they are harmless.


title: Filter feeder

text: Bivalve shellfish recycle nutrients that enter waterways from human and agricultural sources. Nutrient bioextraction is "an environmental management strategy by which nutrients are removed from an aquatic ecosystem through the harvest of enhanced biological production, including the aquaculture of suspension-feeding shellfish or algae". Nutrient removal by shellfish, which are then harvested from the system, has the potential to help address environmental issues including excess inputs of nutrients (eutrophication), low dissolved oxygen, reduced light availability and impacts on eelgrass, harmful algal blooms, and increases in incidence of paralytic shellfish poisoning (PSP). For example, the average harvested mussel contains: 0.8–1.2% nitrogen and 0.06–0.08% phosphorus Removal of enhanced biomass can not only combat eutrophication and also support the local economy by providing product for animal feed or compost. In Sweden, environmental agencies utilize mussel farming as a management tool in improving water quality conditions, where mussel bioextraction efforts have been evaluated and shown to be a highly effective source of fertilizer and animal feed In the U.S., researchers are investigating potential to model the use of shellfish and seaweed for nutrient mitigation in certain areas of Long Island Sound.


title: Filter feeder

text: Bivalves are also largely used as bioindicators to monitor the health of an aquatic environment, either fresh- or seawater. Their population status or structure, physiology, behaviour, or their content of certain elements or compounds can reveal the contamination status of any aquatic ecosystem. They are useful as they are sessile, which means they are closely representative of the environment where they are sampled or placed (caging), and they breathe water all the time, exposing their gills and internal tissues: bioaccumulation. One of the most famous projects in that field is the Mussel Watch Programme in America.


title: Filter feeder

text: Sponges have no true circulatory system; instead, they create a water current which is used for circulation. Dissolved gases are brought to cells and enter the cells via simple diffusion. Metabolic wastes are also transferred to the water through diffusion. Sponges pump remarkable amounts of water. "Leuconia", for example, is a small leuconoid sponge about 10 cm tall and 1 cm in diameter. It is estimated that water enters through more than 80,000 incurrent canals at a speed of 6 cm per minute. However, because "Leuconia" has more than 2 million flagellated chambers whose combined diameter is much greater than that of the canals, water flow through chambers slows to 3.6 cm per hour. Such a flow rate allows easy food capture by the collar cells. Water is expelled through a single osculum at a velocity of about 8.5 cm/second: a jet force capable of carrying waste products some distance away from the sponge.


title: Filter feeder

text: The moon jellyfish has a grid of fibres which are slowly pulled through the water. The motion is so slow that copepods cannot sense it and do not react with an escape response.


title: Filter feeder

text: Tunicates, such as ascidians, salps and sea squirts, are chordates which form a sister group to the vertebrates. Nearly all tunicates are suspension feeders, capturing planktonic particles by filtering sea water through their bodies. Water is drawn into the body through the inhalant buccal siphon by the action of cilia lining the gill slits. The filtered water is then expelled through a separate exhalant siphon. To obtain enough food, a typical tunicate needs to process about one body-volume of water per second.


title: Filter feeder

text: Flamingos filter-feed on brine shrimp. Their oddly shaped beaks are specially adapted to separate mud and silt from the food they eat, and are uniquely used upside-down. The filtering of food items is assisted by hairy structures called lamellae which line the mandibles, and the large rough-surfaced tongue.


title: Filter feeder

text: Prions are specialised petrels with filter-feeding habits. Their name comes from their saw-like jaw edges, used to scope out small planktionic animals.


title: Filter feeder

text: The extinct swan "Annakacygna" is speculated to be a filter-feeder due to its bill proportions being similar to those of shoveler ducks. It is unique in being a large, flightless marine animal, unlike the smaller still volant flamingos and prions.


title: Filter feeder

text: Traditionally, Ctenochasmatoidea as a group has been listed as filter-feeders, due to their long, multiple slender teeth, clearly well adapted to trap prey. However, only "Pterodaustro" showcases a proper pumping mechanism, having up-turned jaws and powerful jaw and tongue musculature. Other ctenochasmatoids lack these, and are now instead thought to have been spoonbill-like catchers, using their specialised teeth simply to offer a larger surface area. Tellingly, these teeth, while small and numerous, are comparatively unspecialised to the baleen-like teeth of "Pterodaustro".


title: Filter feeder

text: Boreopterids are thought to have relied on a kind of rudimentary filter feeding, using their long, slender teeth to trap small fish, though probably lacking the pumping mechanism of "Pterodaustro". In essence, their foraging mechanism was similar to that of modern young "Platanista" "dolphins".


title: Filter feeder

text: Filter feeding habits are conspicuously rare among Mesozoic marine reptiles, the main filter feeding niche being seemingly instead occupied by pachycormid fish. However, some sauropsids have been suggested to have engaged in filter feeding. "Henodus" was a placodont with unique baleen-like denticles and features of the hyoid and jaw musculature comparable to those of flamingos. Combined with its lacustrine environment, it might have occupied a similar ecological niche. In particular, it was probably a herbivore, filtering out algae and other small-sized flora from the substrates.


title: Filter feeder

text: Stomatosuchidae is a family of freshwater crocodylomorphs with rorqual-like jaws and minuscule teeth, and the unrelated Cenozoic "Mourasuchus" shares similar adaptations.


title: Superalloy

text: A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Several key characteristics of a superalloy are excellent mechanical strength, resistance to thermal creep deformation, good surface stability, and resistance to corrosion or oxidation.


title: Superalloy

text: The crystal structure is typically face-centered cubic (FCC) austenitic. Examples of such alloys are Hastelloy, Inconel, Waspaloy, Rene alloys, Incoloy, MP98T, TMS alloys, and CMSX single crystal alloys.


title: Superalloy

text: Superalloy development has relied heavily on both chemical and process innovations. Superalloys develop high temperature strength through solid solution strengthening and precipitation strengthening from secondary phase precipitates such as gamma prime and carbides. Oxidation or corrosion resistance is provided by elements such as aluminium and chromium. Superalloys are often cast as a single crystal—while grain boundaries may provide strength at low temperatures, they decrease creep resistance.


title: Superalloy

text: The primary application for such alloys is in aerospace and marine turbine engines. Creep is typically the lifetime-limiting factor in gas turbine blades.


title: Superalloy

text: Superalloys are the materials which have made much of very-high-temperature engineering technology possible.


title: Superalloy

text: Because these alloys are intended for high temperature applications (i.e. holding their shape at temperatures near their melting point) their creep and oxidation resistance are of primary importance. Nickel (Ni)-based superalloys have emerged as the material of choice for these applications because of their unique γ' precipitates. The properties of these Ni-based superalloys can be tailored to a certain extent through the addition of many other elements, both common and exotic, including not only metals, but also metalloids and nonmetals; chromium, iron, cobalt, molybdenum, tungsten, tantalum, aluminium, titanium, zirconium, niobium, rhenium, yttrium, vanadium, carbon, boron or hafnium are some examples of the alloying additions used. Each of these additions has been chosen to serve a particular purpose in optimizing the properties for high temperature application.


title: Superalloy

text: Creep resistance is dependent, in part, on slowing the speed of dislocation motion within a crystal structure. In modern Ni-based superalloys, the γ’-Ni(Al,Ti) phase present acts as a barrier to dislocation motion. For this reason, this γ’ intermetallic phase, when present in high volume fractions, drastically increases the strength of these alloys due to its ordered nature and high coherency with the γ matrix. The chemical additions of aluminum and titanium promote the creation of the γ’ phase. The γ’ phase size can be precisely controlled by careful precipitation strengthening heat treatments. Many superalloys are produced using a two-phase heat treatment that creates a dispersion of cuboidal γ’ particles known as the primary phase, with a fine dispersion between these known as secondary γ’. In order to improve the oxidation resistance of these alloys, Al, Cr, B, and Y are added. The Al and Cr form oxide layers that passivate the surface and protect the superalloy from further oxidation while B and Y are used to improve the adhesion of this oxide scale to the substrate. Cr, Fe, Co, Mo and Re all preferentially partition to the γ matrix while Al, Ti, Nb, Ta, and V preferentially partition to the γ’ precipitates and solid solution strengthen the matrix and precipitates respectively. In addition to solid solution strengthening, if grain boundaries are present, certain elements are chosen for grain boundary strengthening. B and Zr tend to segregate to the grain boundaries which reduces the grain boundary energy and results in better grain boundary cohesion and ductility. Another form of grain boundary strengthening is achieved through the addition of C and a carbide former, such as Cr, Mo, W, Nb, Ta, Ti, or Hf, which drives precipitation of carbides at grain boundaries and thereby reduces grain boundary sliding.


title: Superalloy

text: While Ni-based superalloys are excellent high temperature materials and have proven very useful, Co-based superalloys potentially possess superior hot corrosion, oxidation, and wear resistance as compared to Ni-based superalloys. For this reason, efforts have also been put into developing Co-based superalloys over the past several years. Despite that, traditional Co-based superalloys have not found widespread usage because they have a lower strength at high temperature than Ni-based superalloys. The main reason for this is that—until recently—they appeared to lack the γ’ precipitation strengthening that is so important in the high temperature strength of Ni-based superalloys. A 2006 report on metastable γ’-Co(Al,W) intermetallic compound with the L1 structure suggests Co-based alloys as alternative to traditional Ni-based superalloys. However this class of alloys was reported in a PhD thesis by C. S. Lee in 1971. The two-phase microstructure consists of cuboidal γ’ precipitates embedded in a continuous γ matrix and is therefore morphologically identical to the microstructure observed in Ni-based superalloys. Like in the Ni-based system, there is a high degree of coherency between the two phases, which is one of the main factors resulting in the superior strength at high temperatures.


title: Superalloy

text: This provides a pathway for the development of a new class of load-bearing Co-based superalloys for application in severe environments. In these alloys, W is the crucial addition for forming the γ’ intermetallic compound; this makes them much denser (>9.6 g/cm compared to Ni-based superalloys. Recently a new class of γ - γ’ cobalt-based superalloys have been developed that are W-free and have much lower density comparable to nickel-based superalloys. In addition to the fact that many of the properties of these new Co-based superalloys could be better than those of the more traditional Ni-based ones, Co also has a higher melting temperature than Ni. Therefore, if the high temperature strength could be improved, the development of novel Co-based superalloys could allow for an increase in jet engine operation temperature resulting in an increased efficiency.


title: Superalloy

text: Adding new elements is usually good because of solid solution strengthening, but engineers need to be careful about which phases precipitate. Precipitates can be classified as geometrically close-packed (GCP), topologically close-packed (TCP), or carbides. GCP phases are usually good for mechanical properties, but TCP phases are often deleterious. Because TCP phases are not truly close packed, they have few slip systems and are very brittle. They are additionally bad because they "scavenge" elements away from GCP phases. Many elements that are good for forming γ' or have great solid solution strengthening may precipitate TCPs. Engineers need to find the balance that promotes GCPs while avoiding TCPs.


title: Superalloy

text: The main GCP phase is γ'. Almost all superalloys are Ni-based because of this phase. γ' is an ordered L1 (pronounced L-one-two), which means it has a certain atom on the face of the unit cell, and a certain atom on the corners of the unit cell. For Ni-based superalloys, that usually means Ni on the faces and Ti or Al on the corners.


title: Superalloy

text: Another "good" GCP phase is γ<nowiki>"</nowiki>. It is also coherent with γ, but it dissolves at high temperatures.


title: Superalloy

text: The United States became interested in gas turbine development around 1905. From 1910-1915, austenitic ( γ phase) stainless steels were developed for the high temperatures in gas turbines. By 1929, 80Ni-20Cr alloy was the norm, with small additions of Ti and Al. Although early metallurgists did not know it yet, they were forming small γ' precipitates in Ni-based superalloys. These alloys quickly surpassed Fe- and Co-based superalloys, which were strengthened by carbides and solid solution strengthening.


title: Superalloy

text: Although Cr was great for protecting the alloys from oxidation and corrosion up to 700 °C, metallurgists began decreasing Cr in favor of Al, which had oxidation resistance at much higher temperatures. The lack of Cr caused issues with hot corrosion, so coatings needed to be developed.


title: Superalloy

text: Around 1950, vacuum melting became commercialized, which allowed metallurgists to create higher purity alloys with more precise composition.


title: Superalloy

text: In the 60s and 70s, metallurgists changed focus from alloy chemistry to alloy processing. Directional solidification was developed to allow columnar or even single-crystal turbine blades. Oxide dispersion strengthening could obtain very fine grains and superplasticity.


title: Superalloy

text: Historically, Co-based superalloys have depended on carbide precipitation and solid solution strengthening for mechanical properties. While these strengthening mechanisms are inferior to gamma prime (γ') precipitation strengthening, cobalt has a higher melting point than currently ubiquitous nickel-based superalloys and has superior hot corrosion resistance and thermal fatigue. As a result, carbide-strengthened Co-based superalloys are used in lower stress, higher temperature applications such as stationary vanes in gas turbines.


title: Superalloy

text: However, recent research has shown that cobalt "can" exhibit the γ' phase. Actually, the first reported existence of γ' occurred in a 1971 PhD dissertation, but was never published. The γ/γ' microstructure was rediscovered and first published in 2006 by Sato et al. That γ' phase was Co(Al, W). It was furthermore found that Mo, Ti, Nb, V, and Ta partition to the γ' phase, while Fe, Mn, and Cr partition to the matrix γ.


title: Superalloy

text: The next family of Co-based superalloys was discovered in 2015 by Makineni et al. This family has a similar γ/γ' microstructure, but is tungsten-free and has a γ' phase of Co(Al,Mo,Nb). Since tungsten is a very heavy element, the elimination of tungsten makes Co-based alloys increasingly viable in turbines for aircraft, where low density is especially important.


title: Superalloy

text: The most recently discovered family of superalloys was computationally predicted in a high throughput study by Nyshadham et al. in 2017, and demonstrated in the lab by Reyes Tirado et al. in 2018. This γ' phase is again tungsten free and has the composition Co(Nb,V) and Co(Ta,V).


title: Superalloy

text: The use of steels in superalloy applications is of interest because certain steel alloys have showed creep and oxidation resistance similar to that of Ni-based superalloys, while being far less expensive to produce.


title: Superalloy

text: Gamma (γ): Like the phases found in Ni-based superalloys, Fe-based alloys feature a matrix phase of austenite iron (FCC). Alloying elements that are commonly found in these stainless steel alloys include: Al, B, C, Co, Cr, Mo, Ni, Nb, Si, Ti, W, and Y. While Al is introduced for its oxidation benefits, Al additions must be kept at low weight fractions (wt.%) because Al stabilizes a ferritic (BCC) primary phase matrix, which is an undesirable phase in superalloy microstructures, as it is inferior to the high temperature strength exhibited by an austenitic (FCC) primary phase matrix.


title: Superalloy

text: Gamma-prime (γ’): This phase is introduced as precipitates to strengthen the alloy. Like in Ni-based alloys, γ’-Ni3Al precipitates can be introduced with the proper balance of Al, Ni, Nb, and Ti additions.


title: Superalloy

text: Two major types of austenitic stainless steels exist and are characterized by the oxide layer that forms at the surface of the steel: chromia-forming or alumina-forming stainless steel. Chromia-forming stainless steel is the most common type of stainless steel produced. However, chromia-forming steels do not exhibit high creep resistance at high operating temperatures, especially in environments with water vapor, when compared to Ni-based superalloys. Exposure to water vapor at high operating temperatures can result in an increase in internal oxidation in chromia-forming alloys and rapid formation of volatile Cr (oxy)hydroxides, both of which can reduce the durability and lifetime of the alloy.


title: Superalloy

text: Alumina-forming austenitic stainless steels feature a single-phase matrix of austenite iron (FCC) with an alumina oxide at the surface of the steel. Alumina is more thermodynamically stable in oxygen than chromia. More commonly, however, precipitate phases are introduced to increase strength and creep resistance. In alumina-forming steels, NiAl precipitates are introduced to act as Al reservoirs to maintain the protective alumina layer. In addition, Nb and Cr additions help form and stabilize alumina by increasing precipitate volume fractions of NiAl.


title: Superalloy

text: Research endeavors for the development of alumina-forming, Fe-base superalloys have shown at least 5 grades of alumina-forming austenitic (AFA) alloys, with different operating temperatures at oxidation in air + 10% water vapor:


title: Superalloy

text: Operating temperatures with oxidation in air and no water vapor are expected to be higher. In addition, an AFA superalloy grade was shown to exhibit a creep strength approaching that of the nickel-based alloy UNS N06617.


title: Superalloy

text: In pure NiAl phase atoms of aluminium are placed at the vertices of the cubic cell and form the sublattice A. Atoms of nickel are located at centers of the faces and form the sublattice B. The phase is not strictly stoichiometric. There may exist an excess of vacancies in one of the sublattices, which leads to deviations from stoichiometry. Sublattices A and B of the γ'-phase can solute a considerable proportion of other elements. The alloying elements are dissolved in the γ-phase as well. The γ'-phase hardens the alloy through an unusual mechanism called the yield strength anomaly. Dislocations dissociate in the γ'-phase, leading to the formation of an anti-phase boundary. At elevated temperature, the free energy associated with the anti-phase boundary (APB) is considerably reduced if it lies on a particular plane, which by coincidence is not a permitted slip plane. One set of partial dislocations bounding the APB cross-slips so that the APB lies on the low-energy plane, and, since this low-energy plane is not a permitted slip plane, the dissociated dislocation is now effectively locked. By this mechanism, the yield strength of γ'-phase NiAl actually "increases" with temperature up to about 1000 °C, giving superalloys their currently unrivaled high-temperature strength.


title: Superalloy

text: Initial material selection for blade applications in gas turbine engines included alloys like the Nimonic series alloys in the 1940s. The early Nimonic series incorporated γ' Ni(Al,Ti) precipitates in a γ matrix, as well as various metal-carbon carbides (e.g. CrC) at the grain boundaries for additional grain boundary strength. Turbine blade components were forged until vacuum induction casting technologies were introduced in the 1950s. This process significantly improved cleanliness, reduced defects, and increased the strength and temperature capability of the material.


title: Superalloy

text: Modern superalloys were developed in the 1980s. The first generation superalloys incorporated increased aluminium, titanium, tantalum, and niobium content in order to increase the γ' volume fraction in these alloys. Examples of first generation superalloys include: PWA1480, René N4 and SRR99. Additionally, the volume fraction of the γ' precipitates increased to about 50–70% with the advent of single crystal, or monocrystal, solidification techniques (see Bridgman technique) for superalloys that enable grain boundaries to be entirely eliminated from a casting. Because the material contained no grain boundaries, carbides were unnecessary as grain boundary strengthers and were thus eliminated.


title: Superalloy

text: The second and third generation superalloys introduced about 3 and 6 weight per cent Rhenium, for increased temperature capability. Re is a slow diffuser and typically partitions to the γ matrix, decreasing the rate of diffusion (and thereby high temperature creep) and improving high temperature performance and increasing service temperatures by 30 °C and 60 °C in second and third generation superalloys, respectively. Re has also been shown to promote the formation of rafts of the γ' phase (as opposed to cuboidal precipitates). The presence of rafts can decrease creep rate in the power-law regime (controlled by dislocation climb), but can also potentially increase the creep rate if the dominant mechanism is particle shearing. Furthermore, Re tends to promote the formation of brittle TCP phases, which has led to the strategy of reducing Co, W, Mo, and particularly Cr. Younger generations of Ni-based superalloys have significantly reduced Cr content for this reason, however with the reduction in Cr comes a reduction in oxidation resistance. Advanced coating techniques are now used to offset the loss of oxidation resistance accompanying the decreased Cr contents. Examples of second generation superalloys include PWA1484, CMSX-4 and René N5. Third generation alloys include CMSX-10, and René N6. Fourth, Fifth, and even Sixth generation superalloys have been developed which incorporate ruthenium additions, making them more expensive still than the prior generation's Re-containing alloys. The effect of Ru on the promotion of TCP phases is not well-determined. Early reports determined that Ru decreased the supersaturation of Re in the matrix and thereby diminished the susceptibility to TCP phase formation. More recent studies have noted the opposite effect. Chen, et al., found that in two alloys differing significantly only in Ru content (USTB-F3 and USTB-F6) that the addition of Ru increased both the partitioning ratio as well as the supersaturation in the γ matrix of Cr and Re, and thereby promoted the formation of TCP phases.


title: Superalloy

text: The current trend is to avoid very expensive and very heavy elements. An example is Eglin steel, a budget material with compromised temperature range and chemical resistance. It does not contain rhenium or ruthenium and its nickel content is limited. To reduce fabrication costs, it was chemically designed to melt in a ladle (though with improved properties in a vacuum crucible). Also, conventional welding and casting is possible before heat-treatment. The original purpose was to produce high-performance, inexpensive bomb casings, but the material has proven widely applicable to structural applications, including armor.


title: Superalloy

text: Single-crystal superalloys (SX or SC superalloys) are formed as a single crystal using a modified version of the directional solidification technique, so there are no grain boundaries in the material. The mechanical properties of most other alloys depend on the presence of grain boundaries, but at high temperatures, they would participate in creep and must be replaced by other mechanisms. In many such alloys, islands of an ordered intermetallic phase sit in a matrix of disordered phase, all with the same crystalline lattice. This approximates the dislocation-pinning behavior of grain boundaries, without introducing any amorphous solid into the structure.


title: Superalloy

text: Single crystal (SX) superalloys have wide application in the high-pressure turbine section of aero and industrial gas turbine engines due to the unique combination of properties and performance. Since introduction of single crystal casting technology, SX alloy development has focused on increased temperature capability, and major improvements in alloy performance have been associated with the introduction of new alloying elements, including rhenium (Re) and ruthenium (Ru).


title: Superalloy

text: With increasing turbine entry temperature, it is important to gain a fundamental understanding of the physical phenomena occurring during creep deformation of single crystal superalloys under such extreme condition (i.e. high temperature and high stress). The creep deformation behavior of superalloy single crystal is strongly temperature, stress, orientation and alloy dependent. For a single-crystal superalloy, there are 3 different modes of creep deformation under regimes of different temperature and stress: Rafting, Tertiary and Primary. At low temperature (~750 °C), SX alloys exhibits mostly primary creep behavior. Matan et al. concluded that the extent of primary creep deformation depends strongly on the angle between the tensile axis and the <001>/<011> symmetry boundary. At temperature above 850 °C, tertiary creep dominates and promotes strain softening behavior. When temperature exceeds 1000 °C, the rafting effect is prevalent where cubic particles transform into flat shapes under tensile stress The rafts would also form perpendicular to the tensile axis, since γ phase was transported out of the vertical channels and into the horizontal ones. After conducting unaxial creep deformation of <001> orientated CMSX-4 single crystal superalloy at 1105 °C and 100 MPa, Reed et al. has established that rafting is beneficial to creep life since it delays evolution of creep strain. In addition, rafting would occur quickly and suppress the accumulation of creep strain until a critical strain is reached.


title: Superalloy

text: For superalloys operating at high temperatures and exposed to corrosive environments, the oxidation behavior is of paramount concern. Oxidation involves chemical reactions of the alloying elements with oxygen to form new oxide phases, generally at the surface of the metal. If unmitigated, oxidation can degrade the alloy over time in a variety of ways, including:


title: Superalloy

text: The primary strategy used to limit these deleterious processes is called selective oxidation. Simply, the alloy is designed such that the ratio of alloying elements promotes formation of a specific oxide phase that can then act as a barrier to further oxidation. Most commonly, aluminum and chromium are used in this role, because they form relatively thin and continuous oxide layers of alumina (AlO) and chromia (CrO), respectively. Furthermore, they possess low oxygen diffusivities, effectively halting further oxidation beneath this layer. In the ideal case, oxidation proceeds through two stages. First, transient oxidation involves the conversion of various elements, especially the majority elements (e.g. nickel or cobalt). Transient oxidation proceeds until the selective oxidation of the sacrificial element forms a complete barrier layer.


title: Superalloy

text: The protective effect of selective oxidation can be undermined by numerous mechanisms. The continuity of the thin sacrificial oxide layer can be compromised by mechanical disruption due to stress or may be disrupted as a result of the kinetics of oxidation (e.g. if diffusion of oxygen is too fast). If the layer is not continuous, its effectiveness as a diffusion barrier to oxygen is significantly reduced. The stability of the oxide layer is also strongly influenced by the presence of other minority elements. For example, the addition of boron, silicon, and yttrium to superalloys promotes oxide layer adhesion, reducing spalling and maintaining the integrity of the protective oxide layer.


title: Superalloy

text: Oxidation is only the most basic form of chemical degradation superalloys may experience. More complex corrosion processes are common when operating environments include salts and sulfur compounds, or under chemical conditions that change dramatically over time. These issues and those of basic oxidation are often also addressed through thin coatings.


title: Superalloy

text: The historical developments in superalloy processing have brought about considerable increases in superalloy operating temperatures. Superalloys were originally iron-based and cold wrought prior to the 1940s. In the 1940s investment casting of cobalt base alloys significantly raised operating temperatures. The development of vacuum melting in the 1950s allowed for very fine control of the chemical composition of superalloys and reduction in contamination and in turn led to a revolution in processing techniques such as directional solidification of alloys and single crystal superalloys.


title: Superalloy

text: There are many forms of superalloy present within a gas turbine engine, and processing methods vary widely depending on the necessary properties of each specific part.


title: Superalloy

text: Casting and forging are traditional metallurgical processing techniques that can be used to generate both polycrystalline and monocrystalline products. Polycrystalline casts tend to have higher fracture resistance, while monocrystalline casts have higher creep resistance.


title: Superalloy

text: Jet turbine engines employ both poly and mono crystalline components to take advantage of their individual strengths. The disks of the high-pressure turbine, which are near the central hub of the engine are polycrystalline. The turbine blades, which extend radially into the engine housing, experience a much greater centripetal force, necessitating creep resistance. As a result, turbine blades are typically monocrystalline or polycrystalline with a preferred crystal orientation.


title: Superalloy

text: Investment casting is a metallurgical processing technique in which a wax form is fabricated and used as a template for a ceramic mold. Briefly, a ceramic mold is poured around the wax form, the wax form is melted out of the ceramic mold, and molten metal is poured into the void left by the wax. This leads to a metal form in the same shape as the original wax form. Investment casting leads to a polycrystalline final product, as nucleation and growth of crystal grains occurs at numerous locations throughout the solid matrix. Generally, the polycrystalline product has no preferred grain orientation.


title: Superalloy

text: Directional solidification uses a thermal gradient to promote nucleation of metal grains on a low temperature surface, as well as to promote their growth along the temperature gradient. This leads to grains elongated along the temperature gradient, and significantly greater creep resistance parallel to the long grain direction. In polycrystalline turbine blades, directional solidification is used to orient the grains parallel to the centripetal force. It is also known as dendritic solidification.


title: Superalloy

text: Single crystal growth starts with a seed crystal which is used to template growth of a larger crystal. The overall process is lengthy, and additional processing via machining is necessary after the single crystal is grown.


title: Superalloy

text: Powder metallurgy is a class of modern processing techniques in which metals are first converted into a powdered form, and then formed into the desired shape by heating below the melting point. This is in contrast to casting, which occurs with molten metal. Superalloy manufacturing often employs powder metallurgy because of its material efficiency - typically much less waste metal must be machined away from the final product—and its ability to facilitate mechanical alloying. Mechanical alloying is a process by which reinforcing particles are incorporated into the superalloy matrix material by repeated fracture and welding.


title: Superalloy

text: Sintering and hot isostatic pressing are processing techniques used to densify materials from a loosely packed "green body" into a solid object with physically merged grains. Sintering occurs below the melting point, and causes adjacent particles to merge at their boundaries, leading to a strong bond between them. In hot isostatic pressing, a sintered material is placed in a pressure vessel and compressed from all directions (isostatically) in an inert atmosphere to affect densification.


title: Superalloy

text: Selective laser melting (also known as "powder bed fusion") is an additive manufacturing procedure used to create intricately detailed forms from a CAD file. In CAD, a shape is designed and then converted into slices. These slices are sent to a laser writer to print the final product. In brief, a bed of metal powder is prepared, and the first slice of the CAD design is formed in the powder bed by a high energy laser sintering the particles together. After this first slice is generated, the powder bed moves downwards, and a new batch of metal powder is rolled over the top of the slice. The second layer is then sintered with the laser, and the process is repeated until all the slices in the CAD file have been processed. Due to the nature of many additive manufacturing processes, porosity can be present in products made by selective laser melting. Many products will often undergo a heat treatment or hot isostatic pressing procedure to densify the product and reduce porosity which can result in cracking.


title: Superalloy

text: In modern gas turbine, the turbine entry temperature (~1750K) has exceeded the incipient melting temperature of superalloys (~1600K), with the help of surface engineering. Under such extreme working condition, the qualification of coating becomes vital.


title: Superalloy

text: Historically, three "generations" of coatings have been developed: diffusion coatings, overlay coatings and thermal barrier coatings. Diffusion coatings, mainly constituted with aluminide or platinum-aluminide, is still the most common form of surface protection. To further enhance resistance to corrosion and oxidation, MCrAlX-based overlay coatings (M=Ni or Co, X=Y, Hf, Si) are deposited to surface of superalloys. Compared to diffusion coatings, overlay coatings are less dependent on the composition of the substrate, but also more expensive, since they must be carried out by air or vacuum plasma spraying (APS/VPS) or else electron beam physical vapour deposition (EB-PVD). Thermal barrier coatings provide by far the best enhancement in working temperature and coating life. It is estimated that modern TBC of thickness 300 μm, if used in conjunction with a hollow component and cooling air, has the potential to lower metal surface temperatures by a few hundred degrees.


title: Superalloy

text: Thermal barrier coatings (TBCs) are used extensively on the surface of superalloy in both commercial and military gas turbine engines to increase component life and engine performance. A coating of about 1-200 µm can reduce the temperature at the superalloy surface by up to 200K. TBCs are really a system of coatings consisting of a bond coat, a thermally grown oxide (TGO), and a thermally insulating ceramic top coat. In most applications, the bond coat is either a MCrAlY (where M=Ni or NiCo) or a Pt modified aluminide coating. A dense bond coat is required to provide protection of the superalloy substrate from oxidation and hot corrosion attack and to form an adherent, slow growing TGO on its surface. The TGO is formed by oxidation of the aluminum that is contained in the bond coat. The current (first generation) thermal insulation layer is composed of 7wt % yttria-stabilized zirconia (7YSZ) with a typical thickness of 100–300 µm. Yttria stabilized zirconia is used due to its low thermal conductivity (2.6W/mK for fully dense material), relatively high coefficient of thermal expansion, and good high temperature stability. The electron beam directed vapor deposition (EB-DVD) process used to apply the TBC to turbine airfoils produces a columnar microstructure with several levels of porosity. The porosity between the columns is critical to providing strain tolerance (via a very low in-plane modulus), as it would otherwise spall on thermal cycling due to thermal expansion mismatch with the superalloy substrate. The porosity within the columns reduces the thermal conductivity of the coating.


title: Superalloy

text: The bond coat adheres the thermal barrier coating to the superalloy substrate. Additionally, the bond coat provides oxidation protection and functions as a diffusion barrier against the motion of substrate atoms towards the environment.


title: Superalloy

text: There are five major types of bond coats, the aluminides, the platinum-aluminides, MCrAlY, cobalt-cermets, and nickel-chromium.


title: Superalloy

text: For the aluminide bond coatings, the final composition and structure of the coating depends on the composition of the substrate. Aluminides also lack ductility below 750 °C, and exhibit a limited by thermomechanical fatigue strength. The Pt-aluminides are very similar to the aluminide bond coats except for a layer of Pt (5—10 μm) deposited on the blade. The Pt is believed to aid in oxide adhesion and contributes to hot corrosion. The cost of Pt plating is justified by the increased blade life span. The MCrAlY is the latest generation of bond coat and does not strongly interact with the substrate. Normally applied by plasma spraying, MCrAlY coatings are secondary aluminum oxide formers. This means that the coatings form an outer layer of chromium oxide (chromia), and a secondary aluminum oxide (alumina) layer underneath. These oxide formations occur at high temperatures in the range of those that superalloys usually encounter. The chromia provides oxidation and hot-corrosion resistance. The alumina controls oxidation mechanisms by limiting oxide growth by self-passivating. The yttrium enhances the oxide adherence to the substrate, and limits the growth of grain boundaries (which can lead to flaking of the coating). Investigation indicates that addition of rhenium and tantalum increases oxidation resistance. Cobalt-cermet-based coatings consisting of materials such as tungsten carbide/cobalt can be used due to excellent resistance to abrasion, corrosion, erosion, and heat. These cermet coatings perform well in situations where temperature and oxidation damage are significant concerns, such as boilers. One of the unique advantages of cobalt cermet coatings is a minimal loss of coating mass over time, due to the strength of carbides within the mixture. Overall, cermet coatings are useful in situations where mechanical demands are equal to chemical demands for superalloys. Nickel-chromium coatings are used most frequently in boilers fed by fossil fuels, electric furnaces, and waste incineration furnaces, where the danger of oxidizing agents and corrosive compounds in the vapor must be dealt with. The specific method of spray-coating depends on the composition of the coatings. Nickel-chromium coatings that also contain iron or aluminum perform much better (in terms of corrosion resistance) when they are sprayed and laser glazed, while pure nickel-chromium coatings perform better when thermally sprayed exclusively.


title: Superalloy

text: Superalloy products that are subjected to high working temperatures and corrosive atmosphere (such as high-pressure turbine region of jet engines) are coated with various kinds of coating. Several kinds of coating process are applied: pack cementation process, gas phase coating (both are a type of chemical vapor deposition (CVD)), thermal spraying, and physical vapor deposition. In most cases, after the coating process near-surface regions of parts are enriched with aluminium, the matrix of the coating being nickel aluminide.


title: Superalloy

text: Pack cementation is a widely used chemical vapor deposition technique which consists of immersing the components to be coated in a metal powder mixture and ammonium halide activators and sealing them in a retort. The entire apparatus is placed inside a furnace and heated in a protective atmosphere to a lower than normal temperature for diffusion to take place, due to the halide salts chemical reaction which causes a eutectic bond between the two metals. The new surface alloy that is formed due to thermal diffused ion migration has a metallurgical bond to the surface substrate and a true intermetallic layer found in the gamma layer of the new surface alloys.


title: Superalloy

text: Pack Cementation has had a revival in the last 10 years as it is being combined with other chemical processes to lower the temperatures of metal combinations even further and give intermetallic properties to different alloy combinations for surface treatments.


title: Superalloy

text: Thermal spraying is a process of applying coatings by heating a feedstock of precursor material and spraying it on a surface. Different specific techniques are used depending on desired particle size, coat thickness, spray speed, desired area, etc. The coatings applied by thermal spraying of any kind, however, rely on adhesion to the surface. As a result, the surface of the superalloy must be cleaned and prepared, usually polished, before application of the thermal coating.


title: Superalloy

text: Of the various thermal spray methods, one of the more ideal and commonly used techniques for coating superalloys is plasma spraying. This is due to the versatility of usable coatings, and the high-temperature performance of plasma-sprayed coatings. Plasma spraying can accommodate a very wide range of materials, much more so than other techniques. As long as the difference between melting and decomposition temperatures is greater than 300 Kelvin, a material can be melted and applied as a coating via plasma spraying.


title: Superalloy

text: This process is carried out at higher temperatures, about 1080 °C. The coating material is usually loaded onto special trays without physical contact with the parts to be coated. The coating mixture contains active coating material and activator, but usually does not contain thermal ballast. As in the pack cementation process, the gaseous aluminium chloride (or fluoride) is transferred to the surface of the part. However, in this case the diffusion is outwards. This kind of coating also requires diffusion heat treatment.


title: Superalloy

text: Failure of thermal barrier coating usually manifests as delamination, which arises from the temperature gradient during thermal cycling between ambient temperature and working conditions coupled with the difference in thermal expansion coefficient of the substrate and coating. It is rare for the coating to fail completely – some pieces of it remain intact, and significant scatter is observed in the time to failure if testing is repeated under identical conditions. There are various degradation mechanisms for thermal barrier coating, and some or all of these must operate before failure finally occurs:


title: Superalloy

text: Additionally, TBC life is very dependent upon the combination of materials (substrate, bond coat, ceramic) and processes (EB-PVD, plasma spraying) used.


title: Superalloy

text: Nickel-based superalloys are used in load-bearing structures to the highest homologous temperature of any common alloy system (Tm = 0.9, or 90% of their melting point). Among the most demanding applications for a structural material are those in the hot sections of turbine engines (e.g. turbine blade). The preeminence of superalloys is reflected in the fact that they currently comprise over 50% of the weight of advanced aircraft engines. The widespread use of superalloys in turbine engines coupled with the fact that the thermodynamic efficiency of turbine engines is increased with increasing turbine inlet temperatures has, in part, provided the motivation for increasing the maximum-use temperature of superalloys. In fact, during the past 30 years turbine airfoil temperature capability has increased on average by about 4 °F (2.2 °C) per year. Two major factors which have made this increase possible are:


title: Superalloy

text: About 60% of the use-temperature increases have occurred due to advanced cooling concepts; 40% have resulted from material improvements. State-of-the-art turbine blade surface temperatures are near ; the most severe combinations of stress and temperature corresponds to an average bulk metal temperature approaching .


title: Superalloy

text: Although Nickel-based superalloys retain significant strength to temperatures near , they tend to be susceptible to environmental attack because of the presence of reactive alloying elements (which provide their high-temperature strength). Surface attack includes oxidation, hot corrosion, and thermal fatigue. In the most demanding applications, such as turbine blade and vanes, superalloys are often coated to improve environmental resistance.


title: Superalloy

text: In general, high temperature materials are needed for energy conversion and energy production applications. Maximum energy conversion efficiency is desired in these energy applications, which can be achieved by increasing operating temperatures, as described by the Carnot cycle. Because Carnot efficiency is limited by the temperature difference between the hot and cold reservoirs, higher operating temperatures result in higher energy conversion efficiencies. Operating temperatures are limited by the performance of today’s superalloys, and currently, most applications operate at around 1000 °C-1400 °C. Energy applications and their superalloy components include:


title: Superalloy

text: Alumina-forming stainless steels can be processed via melting and ladle casting, similar to the production of more common steels. Compared to vacuum casting processes, ladle casting is much less expensive. In addition, alumina-forming stainless steel has been shown to be weldable and has potential for use in high performance automotive applications, such as for high temperature exhaust piping and in heat capture and reuse.


title: Superalloy

text: The availability of superalloys during past decades has led to a steady increase in turbine entry temperatures, and the trend is expected to continue. Sandia National Laboratories is studying a new method for making superalloys, known as radiolysis. It introduces an entirely new area of research into creating alloys and superalloys through nanoparticle synthesis. This process holds promise as a universal method of nanoparticle formation. By developing an understanding of the basic material science behind these nanoparticle formations, there is speculation that it might be possible to expand research into other aspects of superalloys.


title: Superalloy

text: There may be considerable disadvantages in making alloys by this method. About half of the use of superalloys is in applications where the service temperature is close to the melting temperature of the alloy. It is common therefore to use single crystals. The above method produces polycrystalline alloys, which suffer from an unacceptable level of creep.


title: Superalloy

text: Future paradigms in alloy development are expected to focus on weight reduction and improving oxidation and corrosion resistance while maintaining the strength of the alloy. Furthermore, with the increasing demand for turbine blades for power generation, another focus of alloy design is to reduce the cost of superalloys.


title: Superalloy

text: There has been ongoing research and development of new stainless steel alloys because of the lower costs in producing such alloys, as well as the need for an austenitic stainless steel with high-temperature corrosion resistance in environments with water vapor. Research is focusing on increasing high-temperature tensile strength, toughness, and creep resistance to compete with Ni-based superalloys.


title: Superalloy

text: A new class of alumina-forming austenitic stainless steel is actively being developed for use in high-temperature applications by Oak Ridge National Laboratory. Initial research showed similar creep and corrosion resistance at 800 °C to that of other austenitic alloys, including Ni-based superalloys.


title: Superalloy

text: Development of AFA superalloys with a 35 wt.% Ni-base have shown potential for use in operating temperatures upwards to 1,100 °C.


title: 2022 F4 Spanish Championship

text: The 2022 F4 Spanish Championship is the seventh season of the Spanish F4 Championship. It is a multi-event motor racing championship for open wheel, formula racing cars regulated according to FIA Formula 4 regulations, based in Spain. It is the first season to use the Tatuus T-021 car. It is also the first full season in which the series is partnered with the Richard Mille Young Talent Academy.


title: 2022 F4 Spanish Championship

text: The calendar was announced on 3 December 2021. The five rounds in Spain were organized by the RFEDA. The season opener at Portimão was held in support of the Deutsche Tourenwagen Masters and the second abroad event took place at Circuit de Spa-Francorchamps.


title: 2022 F4 Spanish Championship

text: Points are awarded to the top ten classified finishers in 25-minute races and for the top eight classified finishers in 18-minute races.


title: Voice change

text: A voice change or voice mutation, sometimes referred to as a voice break or voice crack, commonly refers to the deepening of the voice of people as they reach puberty. Before puberty, both sexes have roughly similar vocal pitch, but during puberty the male voice typically deepens an octave, while the female voice usually deepens only by a few tones.


title: Voice change

text: A similar effect is a "voice crack", during which a person's voice suddenly and unintentionally enters a higher register (usually falsetto) for a brief period of time. This may be caused by singing or talking at a pitch outside the person's natural vocal range, stress, fatigue, emotional tension, or the physical changes associated with puberty. An instance of a voice crack (when associated with puberty) lasts for only a moment and generally occurs less frequently as a person grows into maturity.


title: Voice change

text: Most of the voice change begins around puberty. Adult pitch is reached 2–3 years later but the voice does not stabilize until the early years of adulthood. It usually happens months or years before the development of significant facial hair. Under the influence of sex hormones, the voice box, or larynx, grows in both sexes. This growth is far more prominent in males than in females and is more easily perceived. It causes the voice to drop and deepen. Along with the larynx, the vocal folds (vocal cords) grow significantly longer and thicker.


title: Voice change

text: The facial bones begin to grow as well. Cavities in the sinuses, the nose, and the back of the throat grow bigger, thus creating more space within the head to allow the voice to resonate. Occasionally, voice change is accompanied by unsteadiness of vocalization in the early stages of untrained voices. Due to the significant drop in pitch to the vocal range, people may unintentionally speak in head voice or even strain their voices using pitches which were previously chest voice, the lowest part of the modal voice register.


title: Voice change

text: Historical changes in the average age of puberty have had profound effects on the composing of music for children's voices. The composer Joseph Haydn was known for typically singing parts in high pitches throughout his 17th year.


title: Voice change

text: Unchanged voices were in high demand for church choirs, which historically excluded women. The British cathedral choir ideal remains based on boy sopranos (or trebles), with the alto part executed by adult countertenors. In German-speaking countries, however, the alto parts are also sung by boys.


title: Voice change

text: Historically, a strategy for avoiding the shift altogether was castration. "Castrati" are first documented in Italian church records from the 1550s. Mozart's "Exultate Jubilate", Allegri's "Miserere" and parts of Handel's "Messiah" were written for this voice, whose distinctive timbre was widely exploited in Baroque opera. In 1861, the practice of castration became illegal in Italy, and in 1878 Pope Leo XIII prohibited the hiring of new castrati by the church. The last "castrato" was Alessandro Moreschi, who served in the Sistine Chapel Choir.


title: Voice change

text: Children are able to sing in the same octave as women. When the voices of male teenagers break, they are no longer able to sing in the same octave. For music sung in the same key as women, they can sing in falsetto or drop an octave.


title: Faecal calprotectin

text: Faecal calprotectin (or fecal calprotectin) is a biochemical measurement of the protein calprotectin in the stool. Elevated faecal calprotectin indicates the migration of neutrophils to the intestinal mucosa, which occurs during intestinal inflammation, including inflammation caused by inflammatory bowel disease. Under a specific clinical scenario, the test may eliminate the need for invasive colonoscopy or radio-labelled white cell scanning.


title: Faecal calprotectin

text: Calprotectin is a 24 kDa dimer of calcium binding proteins S100A8 and S100A9. The complex accounts for up to 60% of the soluble protein content of the neutrophil cytosol. "In vitro" studies show that calprotectin has bacteriostatic and fungistatic properties, that arise from its ability to sequester manganese and zinc. Calprotectin has two transition metal binding sites that form at the interface of the S100A8 and S100A9 monomers, and metal sequestration by calprotectin has been shown to be calcium dependent. The complex is resistant to enzymatic degradation, and can be easily measured in faeces.


title: Faecal calprotectin

text: The main diseases that cause an increased excretion of faecal calprotectin are inflammatory bowel diseases (IBD), coeliac disease, infectious colitis, necrotizing enterocolitis in infants, intestinal cystic fibrosis and colorectal cancer.


title: Faecal calprotectin

text: Although a relatively new test, faecal calprotectin is regularly used as indicator for IBD during treatment and as diagnostic marker. IBD are a group of conditions that cause a pathological inflammation of the bowel wall. Crohn's disease and ulcerative colitis are the principal types of inflammatory bowel disease. Inflammatory processes result in an influx of neutrophils into the bowel lumen. Since calprotectin comprises as much as 60% of the soluble protein content of the cytosol of neutrophils, it can serve as a marker for the level of intestinal inflammation. Measurement of faecal calprotectin has been shown to be strongly correlated with 111-indium-labelled leucocytes – considered the gold standard measurement of intestinal inflammation. Levels of faecal calprotectin are usually normal in patients with irritable bowel syndrome (IBS). In untreated coeliac disease, concentration levels of faecal calprotectin correlate with the degree of intestinal mucosal lesion and normalize with a gluten-free diet.


title: Faecal calprotectin

text: High fecal calprotectin is a common finding among hospitalized coronavirus disease 2019 (COVID-19) patients, especially those with SARS-CoV-2 fecal shedding.


title: Faecal calprotectin

text: Faecal calprotectin is measured using immunochemical techniques such as ELISA or immunochromatographic assays. The antibodies used in these assays target specific epitopes of the calprotectin molecule.


title: Faecal calprotectin

text: Although faecal calprotectin correlates significantly with disease activity in people with confirmed IBD, faecal calprotectin can be false-positive if the laboratory uses low calprotectin cut-off levels. Most importantly, intake of non-steroidal anti-inflammatory drugs (aspirin included) increases calprotectin values, possibly due to the associated induced enteropathy.


title: Opinion polling on the United Kingdom rejoining the European Union (2020–present)

text: Following the United Kingdom's formal exit from the European Union at the end of January 2020, polling organisations have conducted surveys to gauge public opinion on rejoining the organisation.


text: The chart below shows opinion polls conducted about whether the United Kingdom should rejoin the European Union. The trend lines are local regressions (LOESS).


text: Polling of British voters on whether the United Kingdom should rejoin the European Union. Polling includes only those that explicitly ask how the responder would vote in a hypothetical referendum on the United Kingdom rejoining the European Union, rather than repeating the remain/leave question of the 2016 referendum.


text: In 2021, for the fifth anniversary of the UK's EU membership referendum, Euronews commissioned a survey by Redfield & Wilton Strategies of attitudes to the European Union and Brexit in the EU's four largest countries. This included a question about how responders would feel about the UK re-joining the EU.


title: End SARS

text: Within a few days of protests, on 11 October 2020, the Nigerian Police Force announced that it was dissolving the unit with immediate effect. The move was widely received as a triumph of the demonstrations. However, it was noted in many quarters that similar announcements had been made in recent years to pacify the public without the unit actually being disbanded, and that the government had merely planned to reassign and review SARS officers to medical centres rather than disband the unit entirely. Protests have continued accordingly, and the Nigerian government has maintained a pattern of violent repression including the killing of demonstrators. There have been international demonstrations in solidarity with those happening in the country, and the movement has also grown increasingly critical of Muhammadu Buhari's government response to the protests.


title: End SARS

text: SARS officers have been alleged to profile young Nigerians, mostly males, based on fashion choices, tattoos and hairstyles. They were also known to mount illegal road blocks, conduct unwarranted checks and searches, arrest and detain without warrant or trial, rape women, and extort young male Nigerians for driving exotic vehicles and using laptops and iPhones. Nigerians have shared both stories and video evidence of how officers of SARS engaged in kidnapping, murder, theft, rape, torture, unlawful arrests, humiliation, unlawful detention, extrajudicial killings and extortion of Nigerian citizens. A large section of the victims of the abuses of SARS have been young male Nigerians.


title: End SARS

text: The Special Anti-Robbery Squad (SARS) was a branch of the Nigeria Police Force under the State Criminal Investigation and Intelligence Department (SCIID). It was founded in late 1992 as one of the 14 units in the Force Criminal Investigation and Intelligence Department, which was established to detain, investigate, and prosecute people involved in crimes like armed robbery, kidnapping, and other violent crimes. The squad was created as a masked police unit to perform undercover operations against violent crimes like armed robbery, car snatching, kidnapping, cattle rustling, and the bearing and use of illegal firearms.


title: End SARS

text: SARS had been accused of several human rights violations, illegal "stop and searches", illegal arrests and detentions, extrajudicial killings, sexual harassment of women and brutalising of young male Nigerians. The human rights abuses were documented in trending videos on social media.


title: End SARS

text: In 2017, Nigerian activists, youth and celebrities across the nation took to the streets in a peaceful protest to spread awareness of SARS brutality and extortions and to demand its disbanding. The protests also moved to social media using the hashtag #EndSARS.


title: End SARS

text: A 2016 report by Amnesty International, indicted SARS maintaining that the squad was responsible for human rights abuses, cruelty, degrading treatment of Nigerians in their custody, and other widespread torture. Some of the human rights abuses by SARS include the shooting of their detainees in the leg, mock executions and threats of execution, hanging and physical assault. A 2020 publication by the organisation documented 82 cases of abuses and extra judicial killings by SARS between January 2017 and May 2020.


title: End SARS

text: Amnesty International accused the SARS officials of regularly detaining young male Nigerians illegally and extorting money from their relatives. In 2018, Nigerian rapper Michael Ugochukwu Stephens professionally known Ruggedman joined the campaign to end police brutality by releasing a single titled, "Is Police Your Friend?" In 2017, a petition signed by 10,195 people was submitted to Nigeria's National Assembly calling for a total disbandment of SARS. A few Senators backed the call for total disbandment of the unit. Consideration was given to reforming the force, rather than full disbandment due to the number of cases falling.


title: End SARS

text: The campaigners moved from social media using the #EndSARS hashtag to an organized, peaceful protests in Abuja, Lagos, Ibadan, Osun, Benin, Ughelli, Warri, Ilorin, Ogbomosho, Owerri, Jos, Kaduna, Calabar and other Nigerian cities and states, threatening to continue if the government refused to disband the force.


title: End SARS

text: Not only were there campaigners in Nigeria utilising the hashtag and having protests but they were also done in London and some parts of America recognizing this situation as a global event.


title: End SARS

text: In response to the campaign, Nigeria Police Force Public Relations Officer Jimoh Moshood accused the campaigners of being "criminals". Despite this, Inspector General of Nigeria Police Force Ibrahim K. Idris ordered the reform and reorganisation of SARS.


title: End SARS

text: On Saturday 3 October 2020, a video showing a SARS police officer shooting a young Nigerian in front of Wetland Hotel, Ughelli, Delta State trended on the Internet. It was alleged that the police officers took away the young man's vehicle – a Lexus SUV. The trending video caused public outcry on social media, especially on Twitter, with the #ENDSARS hashtag trending.


title: End SARS

text: Just as the ENDSARS trend began on Twitter, on Monday 5 October 2020, another report surfaced of SARS officers killing a 20-year-old upcoming musician named Daniel Chibuike, popularly called Sleek in his neighbourhood. Sleek was said to be sitting in front of a hotel with a friend when the SARS officers approached them, prompting them to flee. According to an eyewitness, the SARS men pursued the pair, shouting "thief", before shooting Sleek as they ran through a supermarket. His friend was arrested.


title: End SARS

text: On Thursday 8 October 2020, nationwide protests on ENDSARS started after weeks of outrage and anger with videos and pictures showing police brutality, harassment and extortion in Nigeria. The protests were led predominantly by young Nigerians in different cities alongside many activists and celebrities. Nigeria Police Force disrupted the protests in some cities, throwing teargas, using water cannons and shooting at unarmed peaceful protesters as seen in Abuja and Osun. This led to the death of Jimoh Isiaq in Ogbomoso, Oyo State. By Wednesday, 14 October 2020, the End SARS protests were still on-going with young people in different parts of Nigeria intensifying their calls for reforms and accountability in police operations. On October 20 the Nigerian Army murdered protesters at the Lekki tollgate. The government and army deny these allegations till date.


title: End SARS

text: On Sunday, 11 October 2020, the protestors made a list of five demands to be met by the Federal Government of Nigeria. The demands which were signed by 'A Nigerian Youth' demanded for the immediate release of all arrested during the protests as well as justice and compensation for all who died through police brutality in Nigeria. They also demanded that an independent body be set up within 10 days to investigate and prosecute all reports of police misconduct. The protestors also asked for the psychological evaluation and retraining of SARS operatives before they are deployed to any other police unit. Lastly, they asked for adequate increase in the salaries for officers of the Nigerian police.


title: End SARS

text: In response to the public outcry on police brutality, the Inspector-General of the Nigeria Police banned the FSARS, Special Tactical Squad (STS), Intelligence Response Team (IRT), Anti-Cultism Squad and other tactical units from mounting of roadblocks, checkpoints, stop-and-search and other routine and patrols. Similar bans had been announced multiple times over the previous four years, causing citizens of Nigeria to question whether the bans would actually be upheld. There were further reports of SARS officers involved in killings across the country. As this was the fourth time that the Nigerian government had announced a similar ban on SARS activity, protesters insisted that the notorious police unit be entirely disbanded and wide-ranging reform of the force to follow.


title: End SARS

text: On 19 October 2020, President Muhammadu Buhari reacted to the continuation of the movement by warning young Nigerians of anarchists that were allegedly attempting to hijack the protests and stated that the federal government "would not tolerate anarchy in the country".


title: End SARS

text: On Tuesday, 20 October 2020, the Central Bank of Nigeria and its Governor, Godwin Emefiele obtained an exparte motion to freeze the accounts of notable participants in the End SARS protest. In an exclusive report by Peoples Gazette, court documents showed that the Central Bank of Nigeria failed to give any justification for the freezing order. Twenty protesters with banking with Access Bank plc, Fidelity Bank Nigeria, First Bank of Nigeria, Guaranty Trust Bank, United Bank for Africa and Zenith Bank had all accounts linked to them placed under "post no debit".


title: End SARS

text: Nigerian youths protested on EndSARS at the Lagos State Governor's House on Thursday 8 October and slept at the gate of the government house till Friday 9 October 2020 when the Deputy Governor addressed the protesters. Among the Lagos State EndSARS Protesters were celebrities Falz, Runtown, Don Jazzy, Olu Jacobs, Eedris Abdulkareem and a host of others including several comedians and other media personalities.


title: End SARS

text: On Friday, 9 October 2020, the Deputy Governor of Lagos State, Femi Hamzat addressed the protesters and acknowledged that police officers do not have the right to trample on the rights of law-abiding citizens based on their appearance or on items in their possession. He condemned police brutality and promised that the Lagos government will take action necessary to end it. The deputy governor also stated that four years previously, he had been harassed by SARS police who were not in uniform.


title: End SARS

text: The Lagos State House of Assembly held an emergency parliamentary sitting to deliberate the petition of the EndSARS protesters. The parliamentarians made a seven-point resolution, as follows: Nigeria's Senate and House of Assembly should probe FSARS, the Police Commissioner should protect protesters, molestation of youths should be stopped, institution of public inquiry on the extrajudicial killings by Senate President and the House of Representatives Speaker, proscription of SARS and its replacement by a new unit with a clear code of conduct, and sanction of illegalities.


title: End SARS

text: Nigerian youths protested on EndSARS, at the headquarters of Nigeria Police Force in Federal Capital Territory, Abuja and vow to camp at headquarters till Inspector-General of Police, Mohammed Adamu, addresses them.


title: End SARS

text: While the protest continued on Saturday 10 October 2020, the Nigerian police started dispersing the youths with tear gas and water. The co-convener of Bring Back Our Girls, Aisha Yesufu, Rinu Oduala, popularly called @SavvyRinu on Twitter, and other protesters were reportedly manhandled by the Nigerian police.


title: End SARS

text: The EndSARS protest in Ogbomosho, Oyo State turned violent as Nigerian police were alleged to have injured seven protesters and shot dead a young man known as Jimoh Isiaka during the protest, Traditional Rulers used the Nigerian Police to forcefully send back protesters. Jimoh Isiaka was taken to Bowen University Teaching Hospital for medical care and later died at the hospital. In response to the death of the protesters, the commissioner of police of Oyo State, Nwachukwu Enwonwu, denied the allegation that the police killed the protester. He said that the police used tear gas to prevent protesters from attacking and entering the police station. The governor of Oyo State, Seyi Makinde sent a condolence message on the demise of the protester and promised to investigate the incident.


title: End SARS

text: On Sunday, 11 October 2020, Nigeria's Inspector-General of Police, Mohammed Adamu announced the "dissolution" of SARS. Many Nigerians within the movement criticised the announcement, however, pointing out that similar promises had been made in earlier years and that the government's plan was to reassign SARS officers to other police departments rather than eliminate them from the force entirely. The protests continue despite the "dissolution" as many do not believe the pronouncement.


title: End SARS

text: David Adeleke, a popular musician known as Davido joined a group of #EndSARS protesters in Abuja to call for the end police brutality and the notorious police unit in the city. The police started dispersing the protesters with tear gas, live bullets and water cannons.


title: End SARS

text: On Monday, 12 October 2020, the Governor of Lagos State Babajide Sanwo-Olu and the Minister of Police Affairs, Maigari Dingyadi, urged protestors to believe that SARS has been disbanded. On Monday, 12 October 2020 the Rivers State Governor, Nyesom Wike announced that the End SARS protests are disallowed in Rivers State. He banned all forms of protests in Rivers State. On Monday, 12 October 2020, the Governor of Oyo State, Seyi Makinde barred Police from engaging with the protestors in order to avert further casualties from the pandemic.


title: End SARS

text: A bystander watching the protest was shot dead by members of the Nigeria Police Force in Surulere while leaving 4 injured and they also arrested and detained peaceful Protesters. The protests in Lagos at Lekki-Epe Expressway toll gate, Murtala Mohammed International airport toll gate, Alausa, Ikorodu Road and Yaba caused heavy traffic gridlock and crippled businesses as young people continued to demand #EndSARS #SARSMustEnd.


title: End SARS

text: Protests continued in Abuja as young people continued to march against police harassment, brutality and extortion. They blocked the Berger roundabout to draw attention to their demands. Earlier on in the day, the protestors had been challenged by Pro-SARS sympathizers who were marching in support of the Inspector General of Police Mohammed Adamu and the Nigerian President Muhammed Buhari under the aegis of Citizens Action for Good Governance.


title: End SARS

text: Protesters in Oyo State with placards calling for the disbandment of SARS, an end to police brutality extortion and extrajudicial killing demonstrated in front of University of Ibadan and Iwo Road in Ibadan. The protests locked down Iwo Road making vehicular movement to be at a standstill.


title: End SARS

text: On Tuesday, 13 October 2020, Ifeanyi Okowa the Governor of Delta State said that the #EndSARS protest is a result of failed leadership. The Governor also announced the constitution of a five-member Police Complaints Committee with two representatives from youth organisations. The Governor had earlier appealed to the police to desist from harassing the protesters as people were free to express grievances in a democratic dispensation. On Tuesday, 13 October 2020, the Public Relations Officer of the Nigerian Police Force, Frank Mba, announced the setting up of a Special Weapon and Tactics Team (SWAT) to replace SARS. The new outfit, which was expected to take off within the next 7 days, was to undergo psychological and medical evaluation to determine their fitness.


title: End SARS

text: The protest was taken to the National Assembly. Moving from Banex junction Abuja, protesters peacefully marched to the junction leading to the National Assembly around 2 p.m. where they were stopped by soldiers who violently resisted their movement and injured some protesters in the process. ARISE TV news crew who were recording the fracas at the entry of the National Assembly were attacked. Ferdinard Duruoha was one of the crew members who were assaulted while Francis Ogbonna a cameraman with the same news outfit was attacked the previous day while covering the announcement of dissolution of SARS by the Inspector General of Police.


title: End SARS

text: The Governor of Lagos State promised to set up a two hundred million naira (N200M) fund for residents of the State who have been victims of police brutality. He met with President Muhammadu Buhari to present the demands of the protesters in Lagos State. A video surfaced from this meeting showing the President chuckle as the Governor talked about his state's compensation fund for victims. The President's actions met a lot of negative criticisms from Nigerians.


title: End SARS

text: According to a press release signed by spokesman of the president, Femi Adesina the Nigerian Government had agreed to the five demands of the End SARS protestors. The agreement was reached at a meeting organised by the Office of the Inspector General of Police and National Human Rights Commission (NHRC) was attended by stakeholders which include officials of Ministry of Police Affairs and Police Service Commission, representatives of Civil Society organisations and activists from the entertainment industry and #EndSARS movement.


title: End SARS

text: The protests continued in Lagos. Young people carrying placards denouncing SARS and appealing for an end to police harassment, extortion and brutality blocked the Lagos-Ibadan expressway.


title: End SARS

text: On Wednesday, 14 October 2020, protesters in Lagos were attacked with cutlasses, sticks and charms. In Abuja, protesters were attacked by people with cutlasses and cudgels at Berger roundabout. Cars were destroyed and some of the protestors were injured.


title: End SARS

text: On Thursday, 15 October 2020, the prohibition of demonstrations in the Federal Capital Territory Security Committee was announced. The decision was taken at a meeting which held on Wednesday, 14 October 2020 and which was chaired by FCT Minister, Malam Muhammad Bello. The announcement recognised the rights of citizens to gather and demonstrate however, it went on to point out that the EndSARS protests were unruly, caused discomfort to people, violated COVID-19 protocols and should be discontinued in view of the fact that Government had met the demands of the protesters. Nigerians thought this absurd since there had been elections in Ondo and Edo along with massive rallies in preceding weeks. Buhari's daughter had also had her wedding ceremony. At the peak of the pandemic, Abba Kyari, late Chief of Staff to the President of Nigeria, was buried without adherence to COVID-19 guidelines.


title: End SARS

text: On Friday, 16 October 2020, the hacktivist group, Anonymous hacked the Twitter account of the National Broadcasting Commission and posted a message which stated ""We #Anonymous will continue supporting Nigerians"" in a support for the ongoing protests.


title: End SARS

text: Thousands of protesters gathered at the Admiralty Way Plaza toll gate, Lekki and at the Lagos State Government Secretariat, Alausa, Ikeja to hold a candlelight session for the various victims of SARS/police killings.


title: End SARS

text: A day after the FCTA banned protests across the Federal Capital Territory amidst fear of a second wave of the COVID-19 outbreak due to the protests, youths protesting against police brutality and abuses moved their protest from City gate to Airport road where they obstructed both incoming and outgoing commuters thereby causing a gridlock leaving thousands stranded.


title: End SARS

text: Following violent escalations which included attacks by agitators against both protesters and police, the governor of Lagos State, Babajide Sanwo-Olu, declared a state-wide 24-hour curfew effective 4:00 PM WAT on 20 October. During this time, images of some persons alleged to be working with the Lagos State Government and the Lekki Concession Company removing cameras (later confirmed by the Lagos State Government to be laser cameras and not CCTV cameras as earlier publicized on social media) at the toll gate circulated on and street lights at the toll gate vicinity were turned off. A few hours later, it was reported that armed men of the Nigerian Army arrived at the scene of the protest and opened fire on peaceful and unarmed protesters, thereby resulting in a disputed number of deaths. A clip of the shooting videoed by a brave Nigerian youth, DJ Switch, trended on the Internet showing how live round of bullets were being shot at innocent protesters who crouched on the ground, holding hands together and singing the Nigerian National Anthem. There were also reports that at least 50 other people were injured. However, the Lagos State government later reported that the shooting resulted in up to 25 injured, and only 2 dead. Despite the fact that the curfew was extended till 9:00 PM, soldiers of the Nigerian Army started shooting before 7:00 PM.


title: End SARS

text: In November 2020, the National Economic Council (NEC) announced that each state and the Federal Capital Territory (FCT), Abuja, should establish a judicial panel of inquiry to investigate cases of police brutality against protesters and compensate the victims as well as human rights violations. The Judicial Panel of Inquiry and Restitution for Victims of the Special Anti-Robbery Squad (SARS) released a report on November 15, 2021 sharing their findings.


title: End SARS

text: Following the killings on 20 October, video evidence showed that more shootings were still being carried out by the Nigerian Army and the Nigerian Police on the unarmed protesters. Some people also attacked and burnt buildings, vehicles, TV stations and raided the Oba of Lagos' palace. The governor of Lagos had said that there were no casualties from the incident of the previous day but later tweeted that there had been reports of one casualty which negated the report sent in by various Twitter and Instagram users who had live recordings of the killings. While the protesters gathered again at the Lekki toll gate where the shooting took place on Tuesday 20 October, they were forced out by police. While the protesters defied the curfew imposed by the Lagos state Governor, hoodlums burnt about 30 government buses at a bus station. Also burnt was Television Continental Station (TVC) linked to a former governor of the state, Bola Ahmed Tinubu, who is a national leader of the ruling All Progressives Congress (APC).


title: End SARS

text: About seven people were reportedly killed within 24 hours since soldiers opened fire at protesters in Lagos. Authorities did not deny carrying out a crackdown, but refused to claim the deaths as of 21 October 2020. Brutality by the police forces made the protesters more angry intensifying the scale of the protests.


title: End SARS

text: On Thursday, 22 October, it was reported that armed men began shooting at protesters in Oyigbo, Port Harcourt. The attackers allegedly broke into homes, killing people inside, and then torching down properties.


title: End SARS

text: After the Nigerian government announced that activities at the Lekki toll gate would restart, Nigerians not satisfied with the decision to restart activities at a symbolic site where reportedly unarmed citizens died during the End SARS protest called for a fresh protest to start at 7am on 13 February 2021. On 13 February 2021 security agencies were at the site, reportedly armed, and awaiting the protesters. It was reported that a Nigerian internet comedian named "Mr Macaroni" and others who came to observe the peaceful protest were arrested.