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Sintering is a method for making objects from powder, by heating the material (below its melting point - solid state sintering) until its particles adhere to each other. A powder is a dry bulk Solid composed of a large number of very fine particles that may flow freely when shaken or tilted The melting point of a solid is the temperature range at which it changes state from solid to Liquid. Adhesion is the tendency of certain dissimilar molecules to cling together due to Attractive forces. Sintering is traditionally used for manufacturing ceramic objects, and has also found uses in such fields as powder metallurgy. The word ceramic is derived from the Greek word κεραμικός ( keramikos) Powder metallurgy is a forming and fabrication technique consisting of three major processing stages A special form of sintering still considered part of powder metallurgy, is liquid state sintering. Powder metallurgy is a forming and fabrication technique consisting of three major processing stages In liquid state sintering, at least one but not all elements are existing in a liquid state. Liquid state sintering is required for making cemented carbides or tungsten carbide. Tungsten carbide, WC, or tungsten semicarbide, W2C, is a chemical compound containing Tungsten and Carbon, similar

The word "sinter" comes from the Middle High German Sinter, a cognate of English "cinder". Middle High German (MHG German Mittelhochdeutsch) is the term used for the period in the history of the German language between 1050 and 1350 Cognates in Linguistics are words that have a common origin They may occur within a language such as shirt and skirt as two English words descended from A cinder is a pyroclastic material Cinders are extrusive Igneous rocks Cinders are similar to Pumice, which has so many cavities and is such low-density

Sintered bronze in particular is frequently used as a material for bearings, since its porosity allows lubricants to flow through it or remain captured within it. Bronze is any of a broad range of Copper alloys, usually with Tin as the main additive but sometimes with other elements such as Phosphorus A bearing is a device to permit constrained relative motion between two parts typically rotation or linear movement In the case of materials with high melting points such as Teflon and tungsten, sintering is used when there is no alternative manufacturing technique. Teflon is a Registered trademark and Brand name of the DuPont company for products made from three types of fluorine-containing polymers ( Fluoropolymers Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 In these cases very low porosity is desirable and can often be achieved.

Sintered bronze and stainless steel are used as filter materials in applications requiring high temperature resistance while retaining the ability to regenerate the filter element. For example, sintered stainless steel elements are used for filtering steam in food and pharmaceutical applications.

Static sintering is when a metal powder under certain external conditions may exhibit coalescence yet revert to its normal behavior when such conditions are absent. In most cases the density of a collection of grains increases as material flows into voids, causing a decrease in overall volume. Mass movements that occur during sintering consist of the reduction of total porosity by repacking, followed by material transport due to evaporation and condensation from diffusion. Evaporation is the process by which Molecules in a Liquid state (e Condensation is the change of the physical state of aggregation (or simply state of matter from gaseous phase into liquid phase Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement In the final stages, metal atoms move along crystal boundaries to the walls of internal pores, redistributing mass from the internal bulk of the object and smoothing pore walls. Surface tension is the driving force for this movement. For the work of fiction see Surface Tension (short story. Surface tension is a property of the surface of a Liquid that causes it to

Metallurgists can sinter most, if not all, metals. This applies especially to pure metals produced in vacuum which suffer no surface contamination. Many nonmetallic substances also sinter, such as glass, alumina, zirconia, silica, magnesia, lime, ice, beryllium oxide, ferric oxide, and various organic polymers. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many Zirconia redirects here For the Sailor Moon character see Dead Moon Circus. The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Periclase occurs naturally in contact Metamorphic rocks and is a major component of most basic Refractory bricks Lime is a general term for various naturally occurring Minerals and materials derived from them in which Carbonates Oxides and Hydroxides of Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia Beryllium oxide ( BeO) is a white crystalline oxide It is notable as it is an electrical insulator with a thermal conductivity higher than any other non-metal that actually Iron(III oxide —also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply Rust —is An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Sintering, with subsequent reworking, can produce a great range of material properties. Changes in density, alloying, or heat treatments can alter the physical characteristics of various products. An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has For instance, the tensile strength En of sintered iron powders remains insensitive to sintering time, alloying, or particle size in the original powder, but depends upon the density of the final product according to:

En/E = (D/d)3. Tensile strength \sigma_{UTS} or S_U is the Stress at which a material breaks or permanently deforms Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 4

where D is the density, E is Young's modulus and d is the maximum density of iron. In Solid mechanics, Young's modulus (E is a measure of the Stiffness of an isotropic elastic material

Particular advantages of this powder technology

Particular advantages of this powder technology include:

  1. the possibility of very high purity for the starting materials and their great uniformity
  2. preservation of purity due to the restricted nature of subsequent fabrication steps
  3. stabilization of the details of repetitive operations by control of grain size in the input stages
  4. absence of stringering of segregated particles and inclusions (as often occurs in melt processes)
  5. no requirement for deformation to produce directional elongation of grains

Many literary references exist on sintering dissimilar materials for solid/solid phase compounds or solid/melt mixtures in the processing stage. In Materials science, deformation is a change in the shape or size of an object due to an applied force. Any substance which melts may also become atomized using a variety of powder production techniques. When working with pure elements, one can recycle scrap remaining at the end of parts manufacturing through the powdering process for reuse.

Ceramic sintering

Sintering is part of the firing process used in the manufacture of pottery and other ceramic objects. Pottery is the Ceramic ware made by potters It also refers to a group of materials that includes Earthenware, Stoneware Some ceramic raw materials have a lower affinity for water and a lower plasticity index than clay, requiring organic additives in the stages before sintering. The Atterberg limits are a basic measure of the nature of a fine-grained Soil. Clay is a naturally occurring material composed primarily of fine-grained Minerals which show plasticity through a variable range of Water content, and The general procedure of creating ceramic objects via sintering of powders includes:

All the characteristic temperatures associated to phases transformation, glass transitions and melting points, occurring during a sinterisation cycle of a particular ceramics formulation (i. A deflocculant is an agent for thinning suspensions or slurries Spray drying is a commonly used method of drying a liquid feed through a hot gas Molding is the process of Manufacturing by shaping pliable raw material using a rigid frame or model called a pattern. e. tails and frits) can be easily obtained by observing the expansion-temperature curves during optical dilatometer thermal analysis. An optical dilatometer is a device for measuring changes in the dimensions of a specimen In fact, sinterisation is associated to a remarkable shrinkage of the material because glass phases flow, once their transition temperature is reached, and start consolidating the powdery structure and considerably reducing the porosity of the material.

There are two types of sintering: with pressure (also known as hot pressing), and without pressure. Pressureless sintering is possible with graded metal-ceramic composites, with a nanoparticle sintering aid and bulk molding technology. Pressureless sintering is the Sintering of a powder compact (sometimes at very high temperatures depending on the powder without applied pressure A variant used for 3D shapes is called hot isostatic pressing. Hot isostatic pressing (HIP is a Manufacturing process used to reduce the porosity of metals and influence the density of many ceramic materials

See also

References

External links

John Wiley & Sons Inc, also referred to as Wiley, is a global Publishing company that markets its products to professionals and consumers students and instructors

Dictionary

sintering

-verb

  1. Present participle of sinter.

-noun

  1. A process in which the particles of a powder are welded together by pressure and heating to a temperature below its melting point
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