VERY SHORT ANSWER TYPE QUESTIONS
Q.1. Explain the term crystallography.
(PTU,Dec. 2015 )
Ans.Crystallography is that branch of science in which the internal structure of crystals, their properties, external or internal symmetries of crystals are studied. Thus, crystallography is the study of the crystal formation of solids including
1. X-ray determination of lattice structure,
2. Formation of crystal,
3. The shape and defects of crystals.
Q.2. Define alloy.
(PTU,May2015)
Ans A substance which is composed of two or more chemical elements such that metallic atoms predominate in composition and the metallic bond redominates is called an alloy. Thus, an alloy is a solid solution of metal elements (a single phase) or a mixture alloy of copper and zinc, where copper and zinc are its constituent elements of metallic phases (two or more solutions), eg brass is an alloy of copper and zinc ,where copper and zinc are it's constituent elements.
Q.3. What is polymorphism ?
(PTU,Dec, 2012, May 2014, 2017)
Ans. In polymorphism Poly' means 'many' and 'morphism' means 'forms Many of the metallic elements, non-metallic elements and compounds exists in more than one crystalline form (but one at a time) dependent upon temperature or external pressure or both. This phenomenon is called polymorphism.
Q.4. Sketch the close packed hexagonal crystal structure.
(PTU,Dec. 2016 May 2016)
Ans. Refer to Fig. 1.1.
Fig 1.1. HCP (Hexagonal Closed Pack) Structure
Q.5. Differentiate between recovery and recrystallization.
(PTU,May 2014, 2016)
Ans .The difference between recovery and recrystallization are as follows:
RECOVERY:
1. (a) Internal stress reduced,
(b) Mechanical pro rties and structural properties are hiv affected.
(c)During recovery electrical resistance decreases rapidly to rds the annealed value.
2. Recovery process occurs at low temperature
i.e., at 0.1 T
3.There is no change in grain size.
RECRYSTALLIZATION:
1.(a) Internal stresses are completely eliminated.
(b) Mechanical properties and structural properties are changed rapidly.
(c) There is further improvement in electrical conductivity and ductility.
2. It occurs at high temperature i.e. at 0.3 to 0.5 T.
3. Grain size increases slightly.
Grain size increases slightly.
Q.1. Explain the term crystallography.
(PTU,Dec. 2015 )
Ans.Crystallography is that branch of science in which the internal structure of crystals, their properties, external or internal symmetries of crystals are studied. Thus, crystallography is the study of the crystal formation of solids including
1. X-ray determination of lattice structure,
2. Formation of crystal,
3. The shape and defects of crystals.
Q.2. Define alloy.
(PTU,May2015)
Ans A substance which is composed of two or more chemical elements such that metallic atoms predominate in composition and the metallic bond redominates is called an alloy. Thus, an alloy is a solid solution of metal elements (a single phase) or a mixture alloy of copper and zinc, where copper and zinc are its constituent elements of metallic phases (two or more solutions), eg brass is an alloy of copper and zinc ,where copper and zinc are it's constituent elements.
Q.3. What is polymorphism ?
(PTU,Dec, 2012, May 2014, 2017)
Ans. In polymorphism Poly' means 'many' and 'morphism' means 'forms Many of the metallic elements, non-metallic elements and compounds exists in more than one crystalline form (but one at a time) dependent upon temperature or external pressure or both. This phenomenon is called polymorphism.
Q.4. Sketch the close packed hexagonal crystal structure.
(PTU,Dec. 2016 May 2016)
Ans. Refer to Fig. 1.1.
Fig 1.1. HCP (Hexagonal Closed Pack) Structure
Q.5. Differentiate between recovery and recrystallization.
(PTU,May 2014, 2016)
Ans .The difference between recovery and recrystallization are as follows:
RECOVERY:
1. (a) Internal stress reduced,
(b) Mechanical pro rties and structural properties are hiv affected.
(c)During recovery electrical resistance decreases rapidly to rds the annealed value.
2. Recovery process occurs at low temperature
i.e., at 0.1 T
3.There is no change in grain size.
RECRYSTALLIZATION:
1.(a) Internal stresses are completely eliminated.
(b) Mechanical properties and structural properties are changed rapidly.
(c) There is further improvement in electrical conductivity and ductility.
2. It occurs at high temperature i.e. at 0.3 to 0.5 T.
3. Grain size increases slightly.
Grain size increases slightly.
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