The production takes place under vacuum or in an inert gaseous atmosphere. Request pdf thermal simulation of thermoelectric material by zonemelting technique the thermoelectric conversion efficiency of bite alloys is significantly affected by its microstructure. The float zone fz method is based on the zone melting principle and was invented by theuerer in 1962. Zone melting became widely known in 1952 as a result of the works of w. Bridgmann method the bridgmann technique is a method of growing single crystal ingots or boules. Czochralski or floating zone techniques that are usually applied for congruently melting compounds. The simplicity of this zone melting method contrasts to the. On the potential of zone melting for the growth of. Zone melting technique is that impurities tend to be concentrated in the melted portion of the sample.
A technology for the growth of functionally graded thermoelectric materials based on zone melting is described. Zone melting or zone refining or floating zone process or travelling melting zone is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along the crystal. The sample cylinder is placed in a furnace with a very narrow hot zone sometimes this is done using halogen lamps as heat sources. When ki 1, purification by zone melting becomes very difficult ideal zonemelting model mas of impurity added to melt zone mass of impurity removed from melt zone increase in mass of impurity in the melt zone mass balance on the impurity for a dz meltzone. Superconducting fese te single crystals grown by optical x. C and o were reduced to levels presented in the electronic grade silicon. This thermographic method is based on the measurement of the molten surface temperature via an infrared camera, as well as further data. Pdf zone melting is one of the most important techniques to produce electronic grade materials. As the zone travels, it redistributes impurities along the charge. Zone refining, as just described, is a batch technique, in that successive operations are. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed. Zone melting is a technique that was mainly applied for purifying congruently melting substances in a physical way. Pores with cylindrical shape, whose growth direction is parallel to the solidification direction, are observed in the rods. Us2897329a us685652a us68565257a us2897329a us 2897329 a us2897329 a us 2897329a us 685652 a us685652 a us 685652a us 68565257 a us68565257 a us 68565257a us 2897329 a us2897329 a us 2897329a authority us united states prior art keywords zone coil body molten induction prior art date 19570923 legal status the legal status is an assumption and is not a legal.
We have successfully removed arsenic from solid phosphorus by melting a narrow region and making the resulting liquid zone travel slowly through a relatively long ingot of phosphorus. When materials are purified by zone melting techniques the process is termed zone refining. Zonemelting chromatography involves placing a sample at some point in a solidified column of purified solvent and then distributing the sample through the solid solvent by repeated passes of the molten zone. In our experience, none of the entrainment methods is 100% reliable. It is fitting that the first book on zone melting should come from the author of the first paper on the subject. The dependence of the porosity and averaged pore diameter on the partial. Zone refining is a technique used to purify materials, mainly semiconductors by. Zone refining definition is a technique for the purification of a crystalline material and especially a metal in which a molten region travels through the material to be refined, picks up impurities at its advancing edge, and then allows the purified part to recrystallize at its opposite edge called also zone melting.
Impurity distribution produced by norrnal freezing and that produced by onepass zone melting are quite different. Expired lifetime application number inventor william g pfann current assignee the listed assignees. Fabrication of lotustype porous stainless steel by. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. Thin film growth through sputtering technique and its. He named the semi automatic process zone refining or zone. The partial zone melting technique seems to be one of the most appropriate methods for obtaining textured nbco samples 2. First results of functionally graded materials grown by this technique are shown. The liquid zones are formed by heating and by cooling the adjacent solids. The container is lowered slowly from the hot zone of the furnace in to the cold zone.
The dependence of the porosity and averaged pore diameter on the partial pressure of. Zone melting techniques basically enable one to manipulate distribution of soluble impurities or phases through a solid. Lotustype porous iron rods were fabricated by continuous zone melting technique under the pressure of 2. Iupac zone melting method of preconcentration z06750. Pdf purification is a primary application of zone melting, in which the. Purification of metallurgical silicon by horizontal zone melting. By using one of several zonemelting techniques known as.
The technique of containerless zone melting, also termed the floatingzone method, can be used advantageously if the liquid zone is short enough to be held by. This technique was named after its inventor bridgemann in 1925, stockbarger in1938. The limits of the technique and the influence of the material parameters are calculated from a simple material balance model. The pores with cylindrical shape, whose growth direction is parallel to the solidification direction, were. This technique is also used for the preparation of silicon for use in computer chips. Zone melting or zone refining or floating zone process is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along. The liquidsolid mushy zone is treated as a porous zone with porosity equal to the liquid fraction, and appropriate momentum sink. Introduction zone melting is a technique for purification by melt crystallization.
Zone refining is a technique used to purify materials, mainly semiconductors by melting a short region i. Melt growth 3 zonemelting traveling zone t gradient close to the growth interface pfann 1952, purification technique advantages control of impurities while growth reduce contamination of the melt by the crucible less heater power uniform doping obtained by zonerefining increase of grain size by zone refining. Zone melting dictionary definition zone melting defined. The partial zonemelting technique seems to be one of the most appropriate methods for obtaining textured nbco samples 2. Full text pdf 12562k abstracts references30 citedby1 lotustype porous stainless steel sus304l rods were fabricated by continuous zone melting technique under pressurised gases of hydrogen and inert gas such as argon or helium. So far, most work in the field of zone melting has been done on a small scale, use of heavier than 100pound ingots of certain metals notwithstanding. For ndbacuo system, zonemelting process takes place by movi ng a sample through a narrow hot zone with a thermal gradient. In zonemelting, a small molten zone or zones traverse a long charge of alloy or impure metal. The frequency of appearance of new papers has increased steadily. Zone melting article about zone melting by the free dictionary. Crystal growth is a challenging task and the technique followed for crystal growth depends upon the characteristics of the materials under investigation 36 43, such as its melting point, volatile nature, solubility in water or other organic solvents and so on. Heat balance equations take account of electron bombardment, heat capacity, radial conduction, axial conduction, and surface radiation. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind.
Zone melting is a group of similar methods of purifying crystals, in which a narrow region of a. The final distribution of the impurity depends on its distribution in the. Techniques for combining single crystal growth with zone melting are treated in some detail. In its common use for purification, the molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot.
Thermal simulation of thermoelectric material by zone. Nearly all industrially important metals, semiconductors, dielectrics, and inorganic and organic compounds more than 120 substancesmay undergo zone melting. However, there is no basic reason why tons rather than pounds cannot be treated. Oddly enough, onepass zone melting bottom is actually less effective as a re fining method than normal freezing top. A liquid zone is created by melting a small amount of material in relatively large or long solid charge or ingot. Continuous refiners have been designed and operated, and a suitable design theory exists 3. In general, the natural period of the subboundaries must be within about 50% of the. Zone melting is a method of separation by melting in which a molten zone traverses a long ingot of impure metal or chemical. Pdf investigation of influencing parameters on zone refining of. Ligasio4 by the cruciblefree floatingzone method with optical heating are considered. Zone melting, any of a group of techniques used to purify an element or a compound or control its composition by melting a short region i. Highlights mgsi 1,450 ppm of impurities was processed by 1 and 2 passes of zone melting at 1 and 10 mmmin.
In this technique, the melt interface is not tracked explicitly. The first paper on zone melting was published in july 1952. Zone refining technique purification of silicon youtube. Zone melting article about zone melting by the free. Insitu regrowth and purification by zone melting of. The ability to visually observe the locally heated melt, and ease of use and control of the image furnace make this method a promising and timeefficient way for. Solute transfer in zone refining of eutecticforming mixtures. Since then up to may 1956 some fifty or sixty papers devoted largely or entirely to some aspect of zone melting have appeared, while use of the method has been indicated briefly in many others. Purification of metallurgical silicon by horizontal zone. Traveling zone t gradient close to the growth interface pfann 1952, purification technique advantages control of impurities while growth reduce contamination of the melt by the crucible less heater power uniform doping obtained by zone refining increase of grain size by zone refining limitations contamination from crucible. Fabrication of porous highpurity iron with directional. For ndbacuo system, zone melting process takes place by movi ng a sample through a narrow hot zone with a thermal gradient. Thermal simulation of thermoelectric material by zonemelting.
Modeling solidi cation and melting modeling of continuous casting processes i. Pfann usa, who used it to produce germanium of high purity in a special container container zone melting. Introduction during the last decade the dc and rf sputteri ng techniques have been used extensively in their two configurations balanced and unbalanced magnetron. The use of high axial temperature gradients with intense stirring of the melt makes it possible to obtain crystals of satisfactory optical quality from stoichiometric melt, despite the incongruent character of the compound melting.
To perform container zone melting on a solid load placed in a container, a small melted region called a zone, which is shifted along the load, is created. Numerical and experimental investigation of arsenic removal process from phosphoric acid by vertical zone melting technique. Depending on the thermal characteristics, the following techniques are employed. Others, such as the valley entrainment technique shown in fig. Originally, a narrow heater generates a molten zone in the solid substance being in a horizontal boatlike crucible made of a material that must not pollute that substance. The traveling solvent floating zone tsfz technique among the traveling solvent techniques, the crucibleless technique of traveling solvent floating zone. If two of e elements, germanium and silicon, not been available in the desired in zone refining, which is probably the most important zone melting technique, a number of molten zones are passed through the charge in one direction. To the best of our knowledge, no other technique exists for growing a singlecrystal film from an amorphous or microcrystalline film on a substrate such as glass or ito.
It is fitting that the first book on zonemelting should come from the author of the first paper on the subject. We grabbed three howtos from the matrix team and they have six more you can check out. Zone refining definition of zone refining by merriamwebster. Electrical resistivity showed to be dependent on the b concentration, but not on the p or the total amount of impurities. Insitu regrowth and purification by zone melting of organic. Zm process reduced 98% of the total amount of impurities. Purification is a primary application of zone melting, in which the improvement of efficiency, production yield and minimum achievable impurity level are always the research focus due to the increasing demand for high purity metals. Purification of phosphorus by a zero pollution zone melting. The float zone fz method is based on the zonemelting principle and was invented by theuerer in 1962. Several workers have used this technique to study the molecular weight distribution of polystyrene. The solar grade silicon obtained from the union carbide process is then purified to 99. Purification of phosphorus by a zero pollution zone. Us3423189a us3423189da us3423189a us 3423189 a us3423189 a us 3423189a us 3423189d a us3423189d a us 3423189da us 3423189 a us3423189 a us 3423189a authority us united states prior art keywords tube zone charge melting void prior art date 196601 legal status the legal status is an assumption and is not a legal conclusion.
Sep 26, 2016 zone melting or zone refining or floating zone process is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along. Realization of the zone length measurement during zone refining. Heat balance equations take account of electron bombardment, heat capacity, radial. Zone melting definition of zone melting by the free dictionary. After going through this learning aid, learner will be able to interpret the concept of zone refining. Zone melting a crystallophysical method of refining materials that consists in the movement of a narrow fusion zone along a long solid rod made of the material that is being refined. An analog computer was used to simulate zone melting in smalldiameter tungsten rods of 0. Texture investigation of zonemelted nbco superconductor. Jun 29, 2017 the solar grade silicon obtained from the union carbide process is then purified to 99. Zone melting zone melting techniques of zone refining the liquid zones are formed by heating and by cooling the adjacent solids. Lotustype porous stainless steel sus304l rods were fabricated by the continuous zone melting technique under a pressurized mixed gas of hydrogen and inert gas such as argon or helium. A polycrystalline specimen is prepared, typically in the shape of a cylinder and placed into a crucible, with a seed crystal near the top of the crucible. Zone refining zone refining is a technique used to purify materials, mainly semiconductors by melting a short region i.
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