Materials Used in Lamp Bulb
Various types of material are used to build a lamp. Insulating materials, conducting materials are the essential parts of a lamp set up. The details of those materials are given below.Glass
- As it is a transparent material, used as barrier. Light gets various colors depending on the color of the glass.
- It with stand the pressure of the gas inside the lamp.
- It is chemically no reactive and used to maintain the lamp as the thematic shield.
Soda Lime Silicate (Soda Glass)
- It has low melting point
- It is used in filament lamp.
- It is used with 67 % SiO2.
Lead Alkali Silicate
- It is used in the inner portion of the bulb glass.
- It has higher electrical resistivity.
- It used in higher wattage lamp, ex-cinema projector.
- It has higher temperature with stand capability.
- Thermal expansion co-efficient is very low.
Alumina silicate Glass
- It has lower thermal shock capability than borosilicate glass.
- It is used for low wattage lamp with most refractory convention.
- It is used in Tungsten halogen Lamp.
- It is transparent silica and pure silicon dioxide.
- It is having only ppm of other metals and OH- group ion.
Sodium Resistant Glass
- It is used for Na vapor lamp.
- Powerful reducing property of Na vapor produces rapid blackening. In normal glasses it happens. So small amount of silica or other readily reducing oxide is mixed with it.
- It has strain throughout life.
- The modern technology helped to develop to produces poly crystalline metal oxide bodies.
- Oxide made ceramics transparent or translucent.
- It includes alumina, magnesia; they are very rare earth oxides.
- It is pore free structure and permits the visible rays to transmit through it.
- In the high pressure lamp, they are being used because of transmitting light.
- In poly crystalline translucent lamp and poly crystalline alumina lamp ceramics are used.
- Ceramics are used as enclose material in high pressure Na and metal halide Lamp.
- Porcelain is used to make base or the end cap.
- It has good mechanical strength
- It possesses good thermal shock resistance and good electrical insulating property.
- It is having good resistance of attack of moisture.
- It is better than porcelain.
- It is made of talk, clay, small amount of alkali and alkaline earth oxide.
- Its ore is Scheelit (CaWO4), wolframaite (FeMn)WO4
- By chemical process tungsten is extracted and made it into the wire.
- Tungsten wire is wound on either on iron or molybdenum mandrel to make coil filament.
- Impurities (C, O, Fe, N) are strictly controlled to make this coil filament.
- By mixing AKS (Al, K and Si) extreme accuracy in coil geometry.
- Tungsten is mostly used in miniature lamp.
- This coil is coated with alkaline earth oxide.
- Its melting point is 2610oC.
- It is used to support the filament coil.
- Its coefficient f expansion matches some categories of glasses.
- It is used in glass metal shield in many cases.
- It is used in electroplating iron and steel.
- Small percentage of nickel with iron and steel increases the hardness and elasticity.
- Nickel steel combination has higher resistance against corrosion.
- It is used in lead in wire.
- In bi metallic strip of starter nickel is also used.
- This metal is non ferrous light weighted and non magnetic material.
- It is with high corrosion resistance.
- It has high ductility and malleability.
- It is easily available.
- Cheap in price,
- Aluminum cap is used in suspended lamps.
- It forms a small thick oxide layer.
- It does not corrode easily with normal weather.
- In many cases it is used to make good reflector.
- In a structural portion steel is used for fabrication of light equipment.
- Steel sheet has higher strength and lower cost.
- Hot rolled, cold rolled and porcelain enameling sheet are the types of steel.
- Hot rolled steel is used where smooth appearance is desired.
- Cold rolled is used in case of thinner portion with smooth surface appearance.
- Porcelain enameling has very less carbon content.
- It includes iron based alloys which contains sufficient chromium.
- It has higher resistance against corrosion.
- Its classification is based on presence of chromium from 12% to 30%.
- It is used in the luminaries, especially outdoor purpose where is a chance of presence of corrosive atmosphere.
- In conductor this metal is used extensively.
- In Bas bar, switch gear copper is also used.
- It ductile and malleable and strong material.
Non Ferrous Alloys
- Bronze (Cu + Sn), Brass (Cu + Zn) are non ferrous alloys.
- They are used in special luminaries.
- They have attractive color appearance.
- They are highly resistive against marine water.
- It is the alloy of Sn and Pb.
- It holds on to a surface.
- It is used at the end of the lamp cap for electrical connection.
- This material is used to absorb the gas as impurity produced inside the lamp during operation, as the produced gas lower the lamp performance.
- O2, CO2, CO etc are produced inside the shielded lamp bulb and they are known as getter.
- Getter material can be in the form of sheet or wire or surface deposit etc.
- Barium, tantalum, titanium, niobium, zirconium and some of their binary alloys are known as metallic getter.
- Red phosphor is known as non metallic getter material.