Misplaced Pages

#507492

64-495: The building is made with primarily ferrocemento and glass. Ferrocemento is a form of concrete construction made with thin cross-sections of concrete and metal wires (reinforcement) with re-usable forms, which Nervi pioneered in Italy and elsewhere. The Torino Esposizioni was converted into a temporary ice rink to host a number of ice hockey events at the 2006 Winter Olympics along with Palasport Olimpico . The temporary arena had

128-742: A boat with the system in 1848. Lambot exhibited the vessel at the Exposition Universelle in 1855 and his name for the material "ferciment" stuck. Lambot patented his boat in 1855 but the patent was granted in Belgium and only applied to that country. At the time of Monier's first patent, July 1867, he planned to use his material to create urns, planters, and cisterns. These implements were traditionally made from ceramics , but large-scale, kiln-fired projects were expensive and prone to failure. In 1875, Monier expanded his patents to include bridges and designed his first steel-and-concrete bridge. The outer layer

192-505: A few hundred ohms . The major advantage of these is that they can dissipate a lot of energy, and they self-reset; after the voltage across the device drops below the threshold, its resistance returns to being high. This makes them ideal for surge-protection applications; as there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in electrical substations , where they are employed to protect

256-514: A finer examination of the composition of ceramic artifacts and sherds to determine the source of the material and, through this, the possible manufacturing site. Key criteria are the composition of the clay and the temper used in the manufacture of the article under study: the temper is a material added to the clay during the initial production stage and is used to aid the subsequent drying process. Types of temper include shell pieces, granite fragments, and ground sherd pieces called ' grog '. Temper

320-422: A furnace, a pyroelectric crystal allowed to cool under no applied stress generally builds up a static charge of thousands of volts. Such materials are used in motion sensors , where the tiny rise in temperature from a warm body entering the room is enough to produce a measurable voltage in the crystal. In turn, pyroelectricity is seen most strongly in materials that also display the ferroelectric effect , in which

384-669: A glassy surface, making a vessel less pervious to water. Ceramic artifacts have an important role in archaeology for understanding the culture, technology, and behavior of peoples of the past. They are among the most common artifacts to be found at an archaeological site, generally in the form of small fragments of broken pottery called sherds . The processing of collected sherds can be consistent with two main types of analysis: technical and traditional. The traditional analysis involves sorting ceramic artifacts, sherds, and larger fragments into specific types based on style, composition, manufacturing, and morphology. By creating these typologies, it

448-492: A rotation process called "throwing"), slip casting , tape casting (used for making very thin ceramic capacitors), injection molding , dry pressing, and other variations. Many ceramics experts do not consider materials with an amorphous (noncrystalline) character (i.e., glass) to be ceramics, even though glassmaking involves several steps of the ceramic process and its mechanical properties are similar to those of ceramic materials. However, heat treatments can convert glass into

512-434: A semi-crystalline material known as glass-ceramic . Traditional ceramic raw materials include clay minerals such as kaolinite , whereas more recent materials include aluminium oxide, more commonly known as alumina . Modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide . Both are valued for their abrasion resistance and are therefore used in applications such as

576-423: A signal). The unit of time measured is the natural interval required for electricity to be converted into mechanical energy and back again. The piezoelectric effect is generally stronger in materials that also exhibit pyroelectricity , and all pyroelectric materials are also piezoelectric. These materials can be used to inter-convert between thermal, mechanical, or electrical energy; for instance, after synthesis in

640-418: A stable electric dipole can be oriented or reversed by applying an electrostatic field. Pyroelectricity is also a necessary consequence of ferroelectricity. This can be used to store information in ferroelectric capacitors , elements of ferroelectric RAM . The most common such materials are lead zirconate titanate and barium titanate . Aside from the uses mentioned above, their strong piezoelectric response

704-520: A very rich mix of sand and cement in a 3:1 ratio; when used for making boards, no gravel is used, so that the material is not concrete. Ferrocement is used to construct relatively thin, hard, strong surfaces and structures in many shapes such as hulls for boats, shell roofs, and water tanks. Ferrocement originated in the 1840s in France and the Netherlands and is the precursor to reinforced concrete . It has

SECTION 10

#1732845692508

768-419: A well built ferro concrete construction are the low weight, maintenance costs, and long lifetime in comparison with purely steel constructions. However, meticulous building precision is considered crucial, especially with respect to the cementitious composition and the way in which it is applied in and on the framework, and how or if the framework has been treated to resist corrosion. When a ferro concrete sheet

832-522: A wide range of other uses, including sculpture and prefabricated building components. The term "ferrocement" has been applied by extension to other composite materials , including some containing no cement and no ferrous material. The " Mulberry harbours " used in the D-Day landings were made of ferrocement, and their remains may still be seen at resorts like Arromanches . Cement and concrete are used interchangeably but there are technical distinctions and

896-556: Is a fluid mixture of Portland cement, sand, water and crushed stone aggregate which is poured into formwork (shuttering). Ferro-concrete is the original name of reinforced concrete (armored concrete) known at least since the 1890s and in 1903 it was well described in London's Society of Engineer's Journal but is now widely confused with ferrocement. The inventors of ferrocement are Frenchmen Joseph Monier who dubbed it "ciment armé" (armored cement) and Joseph-Louis Lambot who constructed

960-400: Is a system of construction using reinforced mortar or plaster (lime or cement , sand, and water) applied over an "armature" of metal mesh , woven, expanded metal, or metal-fibers, and closely spaced thin steel rods such as rebar . The metal commonly used is iron or some type of steel, and the mesh is made with wire with a diameter between 0.5 mm and 1 mm. The cement is typically

1024-444: Is applied to penetrate the mesh. During hardening, the assembly may be kept moist, to ensure that the concrete is able to set and harden slowly and to avoid developing cracks that can weaken the system. Steps should be taken to avoid trapped air in the internal structure during the wet stage of construction as this can also create cracks that will form as it dries. Trapped air will leave voids that allow water to collect and degrade (rust)

1088-467: Is employed. Ice templating allows the creation of macroscopic pores in a unidirectional arrangement. The applications of this oxide strengthening technique are important for solid oxide fuel cells and water filtration devices. To process a sample through ice templating, an aqueous colloidal suspension is prepared to contain the dissolved ceramic powder evenly dispersed throughout the colloid, for example Yttria-stabilized zirconia (YSZ). The solution

1152-468: Is exploited in the design of high-frequency loudspeakers , transducers for sonar , and actuators for atomic force and scanning tunneling microscopes . Temperature increases can cause grain boundaries to suddenly become insulating in some semiconducting ceramic materials, mostly mixtures of heavy metal titanates . The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through

1216-506: Is mechanically overloaded, it will tend to fold instead of break or crumble like stone or pottery. As a container, it may fail and leak but possibly hold together. Much depends on the techniques used in the construction. Using the example of the Mulberry Harbours, pre-fabricated units could be made for ports (such as Jamestown on St Helena) where conventional civil engineering is difficult. The disadvantage of ferro concrete construction

1280-480: Is not understood, but there are two major families of superconducting ceramics. Piezoelectricity , a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used to measure time in watches and other electronics. Such devices use both properties of piezoelectrics, using electricity to produce a mechanical motion (powering the device) and then using this mechanical motion to produce electricity (generating

1344-491: Is possible to distinguish between different cultural styles, the purpose of the ceramic, and the technological state of the people, among other conclusions. Besides, by looking at stylistic changes in ceramics over time, it is possible to separate (seriate) the ceramics into distinct diagnostic groups (assemblages). A comparison of ceramic artifacts with known dated assemblages allows for a chronological assignment of these pieces. The technical approach to ceramic analysis involves

SECTION 20

#1732845692508

1408-568: Is responsible for such diverse optical phenomena as night-vision and IR luminescence . Thus, there is an increasing need in the military sector for high-strength, robust materials which have the capability to transmit light ( electromagnetic waves ) in the visible (0.4 – 0.7 micrometers) and mid- infrared (1 – 5 micrometers) regions of the spectrum. These materials are needed for applications requiring transparent armor, including next-generation high-speed missiles and pods, as well as protection against improvised explosive devices (IED). In

1472-414: Is that they are stronger and more durable than some traditional building methods. Ferro concrete structures can be built quickly, which can have economic advantages. In India , ferro concrete is used often because the constructions made from it are more resistant to earthquakes . Earthquake resistance is dependent on good construction technique. In the 1970s, designers adapted their yacht designs to

1536-506: Is the labor-intensive nature of it, which makes it expensive for industrial application in the western world. In addition, threats to degradation (rust) of the steel components is a possibility if air voids are left in the original construction, due to too dry a mixture of the concrete being applied, or not forcing the air out of the structure while it is in its wet stage of construction, through vibration, pressurized spraying techniques, or other means. These air voids can turn to pools of water as

1600-425: Is then cooled from the bottom to the top on a platform that allows for unidirectional cooling. This forces ice crystals to grow in compliance with the unidirectional cooling, and these ice crystals force the dissolved YSZ particles to the solidification front of the solid-liquid interphase boundary, resulting in pure ice crystals lined up unidirectionally alongside concentrated pockets of colloidal particles. The sample

1664-472: Is then heated and at the same the pressure is reduced enough to force the ice crystals to sublime and the YSZ pockets begin to anneal together to form macroscopically aligned ceramic microstructures. The sample is then further sintered to complete the evaporation of the residual water and the final consolidation of the ceramic microstructure. During ice-templating, a few variables can be controlled to influence

1728-472: Is typically somewhere between the minimum wavelength of visible light and the resolution limit of the naked eye. The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks, structural defects, and hardness micro indentions. Most bulk mechanical, optical, thermal, electrical, and magnetic properties are significantly affected by the observed microstructure. The fabrication method and process conditions are generally indicated by

1792-399: Is usually identified by microscopic examination of the tempered material. Clay identification is determined by a process of refiring the ceramic and assigning a color to it using Munsell Soil Color notation. By estimating both the clay and temper compositions and locating a region where both are known to occur, an assignment of the material source can be made. Based on the source assignment of

1856-467: Is virtually lossless. Optical waveguides are used as components in Integrated optical circuits (e.g. light-emitting diodes , LEDs) or as the transmission medium in local and long haul optical communication systems. Also of value to the emerging materials scientist is the sensitivity of materials to radiation in the thermal infrared (IR) portion of the electromagnetic spectrum . This heat-seeking ability

1920-730: Is virtually unattainable. Ceramic A ceramic is any of the various hard, brittle , heat-resistant , and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay , at a high temperature. Common examples are earthenware , porcelain , and brick . The earliest ceramics made by humans were fired clay bricks used for building house walls and other structures. Other pottery objects such as pots, vessels, vases and figurines were made from clay , either by itself or mixed with other materials like silica , hardened by sintering in fire. Later, ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through

1984-886: The 1960s, scientists at General Electric (GE) discovered that under the right manufacturing conditions, some ceramics, especially aluminium oxide (alumina), could be made translucent . These translucent materials were transparent enough to be used for containing the electrical plasma generated in high- pressure sodium street lamps. During the past two decades, additional types of transparent ceramics have been developed for applications such as nose cones for heat-seeking missiles , windows for fighter aircraft , and scintillation counters for computed tomography scanners. Other ceramic materials, generally requiring greater purity in their make-up than those above, include forms of several chemical compounds, including: For convenience, ceramic products are usually divided into four main types; these are shown below with some examples: Frequently,

Torino Esposizioni - Misplaced Pages Continue

2048-526: The Hall-Petch equation, hardness , toughness , dielectric constant , and the optical properties exhibited by transparent materials . Ceramography is the art and science of preparation, examination, and evaluation of ceramic microstructures. Evaluation and characterization of ceramic microstructures are often implemented on similar spatial scales to that used commonly in the emerging field of nanotechnology: from nanometers to tens of micrometers (µm). This

2112-632: The Olympics were complete, the arena returned to hosting fairs and exhibitions. The building appears in a deleted scene from the 1969 film The Italian Job . A portion of the car chase was filmed as a dance between the Minis and police cars with a full orchestra playing " The Blue Danube " as accompaniment. The scene appears as an extra on home video releases. 45°02′55″N 7°40′56″E  /  45.04861°N 7.68222°E  / 45.04861; 7.68222 Ferrocement Ferrocement or ferro-cement

2176-494: The artifact, further investigations can be made into the site of manufacture. The physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition. Solid-state chemistry reveals the fundamental connection between microstructure and properties, such as localized density variations, grain size distribution, type of porosity, and second-phase content, which can all be correlated with ceramic properties such as mechanical strength σ by

2240-513: The brightness and contrast of a digital image. Guided lightwave transmission via frequency selective waveguides involves the emerging field of fiber optics and the ability of certain glassy compositions as a transmission medium for a range of frequencies simultaneously ( multi-mode optical fiber ) with little or no interference between competing wavelengths or frequencies. This resonant mode of energy and data transmission via electromagnetic (light) wave propagation , though low powered,

2304-497: The capacity of 4,320 people. The boards in the hockey rink are stiffer than in a permanent facility, while the glass has more give. The facility was converted into an ice rink by laying a sand base and refrigeration pipes into the base, and then freezing water ice atop the substrate. This is similar to the temporary outdoor rink the NHL used for its Heritage Classic game in Edmonton . After

2368-418: The ceramic family. Highly oriented crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with them tend to fall into one of two categories: either making the ceramic in the desired shape by reaction in situ or "forming" powders into the desired shape and then sintering to form a solid body. Ceramic forming techniques include shaping by hand (sometimes including

2432-471: The chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand very high temperatures, ranging from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F). The crystallinity of ceramic materials varies widely. Most often, fired ceramics are either vitrified or semi-vitrified, as is the case with earthenware, stoneware , and porcelain. Varying crystallinity and electron composition in

2496-534: The class of ceramic matrix composite materials, in which ceramic fibers are embedded and with specific coatings are forming fiber bridges across any crack. This mechanism substantially increases the fracture toughness of such ceramics. Ceramic disc brakes are an example of using a ceramic matrix composite material manufactured with a specific process. Scientists are working on developing ceramic materials that can withstand significant deformation without breaking. A first such material that can deform in room temperature

2560-416: The cured material absorbs moisture. If the voids occur where there is untreated steel, the steel will rust and expand, causing the system to fail. In modern practice, the advent of liquid acrylic additives and other advances to the grout mixture create slower moisture absorption over the older formulas, and also increase bonding strength to mitigate these failures. Restoration steps should include treatment to

2624-457: The electrical properties that show grain boundary effects. One of the most widely used of these is the varistor. These are devices that exhibit the property that resistance drops sharply at a certain threshold voltage . Once the voltage across the device reaches the threshold, there is a breakdown of the electrical structure in the vicinity of the grain boundaries, which results in its electrical resistance dropping from several megohms down to

Torino Esposizioni - Misplaced Pages Continue

2688-460: The group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, high moduli of elasticity , chemical resistance, and low ductility are the norm, with known exceptions to each of these rules ( piezoelectric ceramics , low glass transition temperature ceramics, superconductive ceramics ). Composites such as fiberglass and carbon fiber , while containing ceramic materials, are not considered to be part of

2752-582: The hardened product or to alter curing rates. These technologies, borrowed from the commercial tile installation trade, have greatly aided in the restoration of these structures. Chopped glass or poly fiber can be added to reduce crack development in the outer skin. (Chopped fiber could inhibit good penetration of the grout to steel mesh constructions. This should be taken into consideration and mitigated, or limited to use on outer subsequent layers. Chopped fibers may also alter or limit some wet sculpting techniques.) The economic advantage of ferro concrete structures

2816-632: The infrastructure from lightning strikes. They have rapid response, are low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application. Semiconducting ceramics are also employed as gas sensors . When various gases are passed over a polycrystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced. Under some conditions, such as extremely low temperatures, some ceramics exhibit high-temperature superconductivity (in superconductivity, "high temperature" means above 30 K). The reason for this

2880-468: The ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators (researched in ceramic engineering ). With such a large range of possible options for the composition/structure of a ceramic (nearly all of the elements, nearly all types of bonding, and all levels of crystallinity), the breadth of the subject is vast, and identifiable attributes ( hardness , toughness , electrical conductivity ) are difficult to specify for

2944-486: The material near its critical temperature, the dielectric effect remains exceptionally strong even at much higher temperatures. Titanates with critical temperatures far below room temperature have become synonymous with "ceramic" in the context of ceramic capacitors for just this reason. Optically transparent materials focus on the response of a material to incoming light waves of a range of wavelengths. Frequency selective optical filters can be utilized to alter or enhance

3008-445: The material until joule heating brings it to the transition temperature, at which point the circuit will be broken and current flow will cease. Such ceramics are used as self-controlled heating elements in, for example, the rear-window defrost circuits of automobiles. At the transition temperature, the material's dielectric response becomes theoretically infinite. While a lack of temperature control would rule out any practical use of

3072-461: The meaning of cement has changed since the mid-nineteenth century when ferrocement originated. Ferro- means iron although metal commonly used in ferro-cement is the iron alloy steel . Cement in the nineteenth century and earlier meant mortar or broken stone or tile mixed with lime and water to form a strong mortar. Today cement usually means Portland cement , Mortar is a paste of a binder (usually Portland cement), sand and water; and concrete

3136-410: The mechanical performance of materials and components. It applies the physics of stress and strain , in particular the theories of elasticity and plasticity , to the microscopic crystallographic defects found in real materials in order to predict the macroscopic mechanical failure of bodies. Fractography is widely used with fracture mechanics to understand the causes of failures and also verify

3200-412: The microstructure. The root cause of many ceramic failures is evident in the cleaved and polished microstructure. Physical properties which constitute the field of materials science and engineering include the following: Mechanical properties are important in structural and building materials as well as textile fabrics. In modern materials science , fracture mechanics is an important tool in improving

3264-718: The pore size and morphology of the microstructure. These important variables are the initial solids loading of the colloid, the cooling rate, the sintering temperature and duration, and the use of certain additives which can influence the microstructural morphology during the process. A good understanding of these parameters is essential to understanding the relationships between processing, microstructure, and mechanical properties of anisotropically porous materials. Some ceramics are semiconductors . Most of these are transition metal oxides that are II-VI semiconductors, such as zinc oxide . While there are prospects of mass-producing blue LEDs from zinc oxide, ceramicists are most interested in

SECTION 50

#1732845692508

3328-683: The root ceram- is the Mycenaean Greek ke-ra-me-we , workers of ceramic, written in Linear B syllabic script. The word ceramic can be used as an adjective to describe a material, product, or process, or it may be used as a noun, either singular or, more commonly, as the plural noun ceramics . Ceramic material is an inorganic, metallic oxide, nitride, or carbide material. Some elements, such as carbon or silicon , may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, and weak in shearing and tension. They withstand

3392-1041: The steel to arrest rust, using practices for treating old steel common in auto body repair. During the 1960s in Australia, New Zealand and the UK, home boatbuilders realised that, for a given budget, ferrocement enabled a much larger hull than otherwise possible. However, some builders failed to realise that the hull forms only a minor part of the overall cost because a larger boat would have very much higher fitting-out costs. Consequently, several homebuilt ferrocement boats became unfinished projects, or if finished, then badly executed, overweight, lumpy "horrors". Realising that their boats were not merely disappointing but also unsaleable, some builders insured their boats and fraudulently scuppered them for compensation. Insurance companies have long memories of such frauds, and today, even for well-built ferrocement boats, it has become difficult to get insurance coverage for third-party risks, while comprehensive cover

3456-410: The steel. Modern practice often includes spraying the mixture at pressure (a technique called shotcrete ) or some other method of driving out trapped air. Older structures that have failed offer clues to better practices. In addition to eliminating air where it contacts steel, modern concrete additives may include acrylic liquid " admixtures " to slow moisture absorption and increase shock resistance to

3520-812: The technique can be learned relatively quickly, allowing people to cut costs by supplying their own labor. In the 1930s through 1950s, it became popular in the United States as a construction and sculpting method for novelty architecture , examples of which are the Cabazon Dinosaurs and the works of Albert Vrana . The desired shape may be built from a multi-layered construction of mesh, supported by an armature, or grid, built with rebar and tied with wire. For optimum performance, steel should be rust-treated, ( galvanized ) or stainless steel . Over this finished framework, an appropriate mixture ( grout or mortar ) of Portland cement , sand and water and/or admixtures

3584-492: The then very popular backyard building scheme of building a boat using ferrocement. Its big attraction was that for minimum outlay and costs, a reasonable application of skill, an amateur could construct a smooth, strong and substantial yacht hull. A ferro-cement hull can prove to be of similar or lower weight than a fiber reinforced plastic (fiberglass), aluminium , or steel hull. There are basically three types of methods of ferrocement. They are following The advantages of

3648-453: The theoretical failure predictions with real-life failures. Ceramic materials are usually ionic or covalent bonded materials. A material held together by either type of bond will tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators , decreasing

3712-460: The toughness further, and reducing the tensile strength . These combine to give catastrophic failures , as opposed to the more ductile failure modes of metals. These materials do show plastic deformation . However, because of the rigid structure of crystalline material, there are very few available slip systems for dislocations to move, and so they deform very slowly. To overcome the brittle behavior, ceramic material development has introduced

3776-558: The use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates. Ceramics now include domestic, industrial, and building products, as well as a wide range of materials developed for use in advanced ceramic engineering, such as semiconductors . The word ceramic comes from the Ancient Greek word κεραμικός ( keramikós ), meaning "of or for pottery " (from κέραμος ( kéramos )  'potter's clay, tile, pottery'). The earliest known mention of

3840-446: The wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medical, electrical, electronics, and armor industries. Human beings appear to have been making their own ceramics for at least 26,000 years, subjecting clay and silica to intense heat to fuse and form ceramic materials. The earliest found so far were in southern central Europe and were sculpted figures, not dishes. The earliest known pottery

3904-425: Was found in 2024. If a ceramic is subjected to substantial mechanical loading, it can undergo a process called ice-templating , which allows some control of the microstructure of the ceramic product and therefore some control of the mechanical properties. Ceramic engineers use this technique to tune the mechanical properties to their desired application. Specifically, the strength is increased when this technique

SECTION 60

#1732845692508

3968-497: Was made by mixing animal products with clay and firing it at up to 800 °C (1,500 °F). While pottery fragments have been found up to 19,000 years old, it was not until about 10,000 years later that regular pottery became common. An early people that spread across much of Europe is named after its use of pottery: the Corded Ware culture . These early Indo-European peoples decorated their pottery by wrapping it with rope while it

4032-631: Was sculpted to mimic rustic logs and timbers, thereby also ushering faux bois (fake wood) concrete. In the first half of the twentieth century Italian Pier Luigi Nervi was noted for his use of ferro-cement, in Italian called ferro-cemento . Ferroconcrete has relatively good strength and resistance to impact. When used in house construction in developing countries, it can provide better resistance to fire, earthquake, and corrosion than traditional materials, such as wood, adobe and stone masonry. It has been popular in developed countries for yacht building because

4096-528: Was still wet. When the ceramics were fired, the rope burned off but left a decorative pattern of complex grooves on the surface. The invention of the wheel eventually led to the production of smoother, more even pottery using the wheel-forming (throwing) technique, like the pottery wheel . Early ceramics were porous, absorbing water easily. It became useful for more items with the discovery of glazing techniques, which involved coating pottery with silicon, bone ash, or other materials that could melt and reform into

#507492