NCM Unit 6 Test

Hot dipping is a process of developing coating by

• Dipping the substrate into an aqueous electrolyte at room temperature

• Dipping the substrate in molten metal bath having low melting/fusion temperature

• Dipping the substrate in a solution which reacts with the substrate surface to form a compound

• Dipping the substrate in a aqueous electrolyte and passing electric current

Galvanizing is the term used to indicate:

• Zn coating

• Fe coating

• Al coating

• Sn coating

Aluminium is usually added while hot dip galvanizing of zinc for the following purpose:

• Al reduces the melting point of zinc bath

• Al suppresses the formation of Fe-Zn intermetallics

• Al increases the oxidation of Zn bath

• Al increases the strength of the coating

Thin film coating by physical vapor deposition (PVD) is amenable to:

• Only elemental metals

• Only pure metals or metallic alloys

• Only pure metals, alloys and intermetallic compounds

• Pure metals, alloys, semi-conductors, intermetallic + non-metallic compounds, composites

Identify the method from below which is not a typical PVD technique:

• Direct current (DC)

• Electro-plating

• Ion plating

• RF sputtering

PVD is most useful for:

• All the below

• Tribological application

• Aesthetic coating

• Semiconductor device fabrication

PVD is not effective to improve:

• Wear resistance

• Corrosion resistance

• Oxidation resistance

• Coefficient of friction

For PVD or sputtering, the substrate can be a:

• Conductor like metal

• Insulator like polymer

• Semi-conductor like silicon

• All of above

Ion plating, the process involves:

• Thermal evaporation followed by ionization within plasma and deposition as neutral atoms

• Sputtering followed ionization in plasma and deposition by implantation

• Sputtering followed by chemical reaction and deposition as neutral atoms

• Evaporation followed by acceleration and implantation as ions

Which is NOT true for CVD?

• Chemical reaction occurs at the substrate surface

• Multiple precursor in vapor state is needed

• Substrate or chamber is heated

• Target and deposit composition are the same