Metallic glasses ppt
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Metallic glasses are metal alloys that are amorphous, meaning they lack long-range atomic order and have a glass-like structure. They can be produced through rapid cooling techniques that solidify the molten metal before crystallization occurs. Metallic glasses have strong, corrosion-resistant, and homogeneous properties due to their amorphous structure. They also exhibit a reversible glass-liquid transition when heated instead of melting. Potential applications of metallic glasses include use in transformer cores, sensors, surgical instruments, and electronic devices due to their electrical and magnetic properties.
Metallic glasses ppt
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- 3. Metallic glasses are the newly developed engineering materials. Metallic glasses share the properties of both metals and alloys. Most metals and alloys are crystaline,i.e., their atoms arranged in some regular pattern that extends over a long distance. In contrast,glass is an amorphous,brittle and transparent solid. Thus,metallic glasses are metal alloys that are amorphous.
- 4. The major advantages of such glasses are that they are generally homogeneous in composition,and offer strong and superior corrosion resistance. To have this perculiar property,metallic glasses are to be made by cooling a molten metal rapidly at a rate . Thus,the liquid reaching the glass transition temperature Tg solidifies as metallic glass.Again, upon heating, metallic glasses show a reversible glass-liquid transition at Tg. that is, they do not have a long range atomic order.
- 5. Various rapid cooling techniques such as spraying,spinning and laser deposition are used for the production of metallic glasses. The melt spinning process technique involved in the preparation of metallic glass is illustrated in figure. In this technique,there is a spinning disc made of copper. In order to prepare a metallic glass of a particular type, a suitable combination of metal- metal or metal-metalloid alloy in bits stoichiometric ratio is taken in a refractory tube having a fine nozzle at its bottom.The nozzle side of the tube is placed just over the spinning disc. PREPARATION
- 6. An induction heater attached to the refractory tube melts the alloy. This melt is kept above its melting point till it gets transformed into a homogeneous mixture. An inert gas such as helium is made to flow through the tube containing the homogeneous mixture. As a result the melt gets ejected through the nozzle. The ejected melt is cooled at a faster rate with the help of the spinnig cooled copper disc. The ejection rate can be increased by increasing the pressure of the inert gas. Thus,a glassy alloy ribbon satrts getting formed over the spinning disc. The thickness of the glassy ribbon may be varied by increasing or decreasing thr speed of the spinnig disc.
- 7. 1. The strength of metallic glasses is very high but they are lighter in weight. 2. They are ductile,malleable,brittle and opaque.The hardness is very high. 3. The toughness is very high,i.e.,the fracture resistant is very high. 4. They have high elasticity,i.e.,the yield strength is high. 5. They have high corrosion resistance. 6. They do not contain any crystalline defects like point defects,dislocation,stacking faults,etc. 7. They are soft magnetic materials.As a result,easy magnetisation and demagnetisation are possible. 8. They have high electrical resistivity which leads to a low eddy current loss. PROPERTIES OF METALLIC GLASSES:-
- 8. 1. Metallic glasses are used as transformer core material in high- power transformers.Usage of metallic glasses in transformers is found to improve the efficiency of power distribution in transformers.These transformers are used to convert high-voltage current into low-voltage current to be used for domestic appliances(120 V and 240V). 2. Because of their high electrical resistivity and nearly zero temperature coefficient of resistance,these materials are used in making cryothermometers,magnetoresistance sensors and computer memories. 3. As the magnetic properties of the metallic glasses are not affected by irradiation they are used in making containers for nuclear waste disposal. 4. These materials are used in the preparation of magnates for fusion reactors and magnets for levitated trains,etc. APPLICATONS:-
- 9. 1. Metallic glasses can also be used for making watch cases to replace Ni and other metals which can cause allergic reactions. 2. The excellent corrosion resistance property makes these materials ideal for cutting and in making surgical instruments. In addition,they can be used as a prosthetic material for implantation in the human body. 3. In future, the usage of metallic glasses in the electronic field can yield stronger,lighter and more easily moulded castings for personal electronic products. 4. Metallic glasses are used in tap reorders as heads,in the manufacture of sprongs and standard resistances.
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