Zone Refining Pdf
Impurities are incorporated in the melting liquid and freezing solid. After going through this learning aid, learner will be able to Interpret the concept of Zone refining. Develop an understanding of zone refining with respect to the phase diagram.
And the coil is moved from one end to another. Finally, when the frame reaches the end, show using some appropriate tool the last yellow molten part is chopped off and the flame again goes back to the start on left most size. An electron beam or laser beams to heat the rod are also used.
The coil moves slowly down the tube, moving the molten zone to the end of the bar. Zone refining is a technique used to purify materials, mainly semiconductors by melting a short region i. The impurities concentrate in the melt, and are moved to one end of the ingot. Classify the kinds of materials or compounds that can be purified by the process of zone refining. The induction heating coil carrying a high frequency alternating current, melts a section of the metal bar in the tube.
Then a small amount of antimony is placed in the molten zone, which is passed through the pure germanium. Carbon dioxide-induced liberation of methane from laboratory-formed methane hydrates. Initially the whole rod is of same colour but as the burner moves along, the color of previous part should change, which looks more systematic or ordered. The rod is heated with the help of a heater coil which moves from one end to the other end melting the next zone and resolidifying the previous zone just passed.
Description of the action Show slide no. Induction heating is applicable to those substances that conduct electricity. Description of the action Show the next slide, i. Here, what we apply is the Lever Rule for the basic understanding of concept involved in Zone Refining. In solar cells float zone processing is particularly useful because the single crystal silicon grown has desirable properties.
Compute the percentage of solid and liquid phases for the given point B in the above phase diagram. Industrial processes Semiconductor growth Crystals Liquid-solid separation. As you can see, there is a cylindrical rod which contains element A with the impurity element B. From Wikipedia, the free encyclopedia. This process is based on a very important fact that the solid to crystallise first from the melt is purer in A or the element to be obtained than the liquid.
This when clicked should display the red color text, answers. The material to be purified by this process is taken in the form of long rod. Please make a photo similar to that in the final document. The bulk charge carrier lifetime in float-zone silicon is the highest among various manufacturing processes. Utilization of Wastewater Originated From Naturall.
Summary Zone refining is a technique used to purify materials, mainly semiconductors by melting a short region i. Now, when the last impure part is chopped off and the flame is once again ready to get started from left end, the vertical line from b to c and also downwards is drawn. There are many techniques involved in heating of the zone.
Hence every time we repeat the cycle, we get purer material or crystal and the ending impure part is chopped off. Description Audio of the narration action Show slide no. This is important in the manufacture of semiconductors, where two solutes of opposite conductivity type are used.
The coil or beam is slowly moved from one end to another end which continuously solidifies the. Also, dont show varied colors for different lines, this is just for explanation purpose, so chose any color other than black and use it for all the horizontal lines show. The principle is that the segregation coefficient k the ratio of an impurity in the solid phase to that in the liquid phase is usually less than one. This process is based on a very important fact that the solid to crystallize first from the melt is purer in A or the element to be obtained than the liquid.
This technique is also used for the preparation of silicon for use in computer chips. By melting a portion of such an ingot and slowly refreezing it, solutes in the molten region become distributed to form the desired n-p and p-n junctions.
In zone refining, solutes are segregated at one end of the ingot in order to purify the remainder, or to concentrate the impurities. Zone refining is based on the fact that the pure substance that has to be obtained from the impure sample has a melting point than the sample. The molten zone speed and width must be theoretically and practically considered depending upon the applications, the material chosen and the surrounding conditions. When high purity is required, such as in semiconductor industry, the impure end of the boule is cut off, autobiography of yogi pdf hindi and the refining is repeated.
The points should be shown one by one. Description of the action Audio narration Text to be displayed first show the picture and then Show the next slide, i. There is also a binary phase diagram shown below which runs parallel to the heating process and the graph proceeds accordingly as shown. 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.
This runs parallel to the flame in the upper rod. Application of Lever rule. The audio narration line marked in red color on previous slide should be so adjusted such that the process of chopping off and this line should coincide. The rod drawn is actually a cylindrical rod mostly of a metal and the yellow zone shown is heater coil.
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