Unit 5 Material Science Important Question for New Materials in (AKTU)

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Important Questions For Material Science : 
*Unit-01     *Unit-02    
*Unit-03    *Unit-04 
*Unit-05    *Short-Q/Ans
*Question-Paper with solution 21-22 

Q1. What are ceramic materials? What are some common properties and applications of ceramic materials ?

Ans. A. Ceramics:

• 1. Ceramics are a mixture of metallic and nonmetallic elements with primarily ionic interatomic bonding.
• 2. These materials’ desirable qualities are often attained by a high temperature heat treatment technique known as firing.

B. Properties of Ceramics :

• 1. Ceramic materials are relatively stiff and strong as compared to the metals. 
• 2. Ceramic materials are very hard and brittle in nature.
• 3. These are highly susceptible to fracture due to presence of cracks and brittle nature.
• 4. Because they have poor electrical and thermal conductivity, they are good insulators and refractories.
• 5. Metals and plastics are less resistant to high temperatures and hostile conditions.
• 6. Ceramics also exhibit some magnetic behaviour.

C. Applications of Ceramics :

• 1. In firebricks and fireclay for lining of ovens and furnaces.
• 2. As artificial limbs, teeth etc. in biomedical/medical field.
• 3. In insulators (dielectrics) in electrical transmission and distribution.
• 4. In crockery in domestic uses, sanitary wares etc.
• 5. As ferrites in memory cores of computers.
• 6. As radiation shield for nuclear reactor.

Q2. What are different types of ceramics? Also write their properties.

Ans. Types of Ceramics with their Properties and Applications :

Q3. Classify composite material and explain them briefly.

Ans. A. Composite Materials :

• 1. Composite materials are multiphase materials that are created intentionally to have the properties of both materials utilised to construct a composite material.
• 2. Composites are a composition of a metal alloys, ceramics and polymers.

B. Classification of Composite Materials :

a. Particle Reinforced Composites :

• 1. Particle reinforcing is a means of strengthening the composite materials.
• 2. Particle reinforced composites gain stiffness while also increasing strength and toughness.
• 3. This type of composite is the most commonly utilised since it is widely available and inexpensive.
• 4. Particle reinforced composites are used in applications requiring high levels of wear resistance, such as road surfaces.
• 5. They are of two kinds :

i. Dispersion Strengthened Composites :

• 1. In dispersion strengthened composites, particles are comparatively smaller, and are of 0.01 – 0.1 μmin size.
• 2. Here the strengthening occurs at atomic/molecular level.
• 3. The strength of dispersion enhanced composites is maintained over long periods of time at high temperatures.
• 4. Example: Nickel alloy with addition of 3%, of ThO₂ (by volume), sintered aluminum powder etc.

ii. Large Particle Composites:

• 1. The dispersed phase in large particle composites is tougher and stiffer than the matrix.
• 2. Large particle composites are used with all three types of materials (metals, polymers and ceramics).
• 3. Example : Concrete, cements, tungsten .carbide etc.

b. Fibre Reinforced Composites :

• 1. A fibre reinforced composite (FRC) is a composite building material that consists of three components :
  • i. The fibres as the discontinuous or dispersed phase,
  • ii. The matrix as the continuous phase, and
  • iii. The fine interphase region also known as the interface.
• 2. FRC is created by cross-linking cellulosic fibre molecules with resins in a material matrix, resulting in a product with excellent structural qualities.
• 3.FRC can be recycled up to 20 times, which allows scrap FRC to be utilised indefinitely.
• 4. There are two types of fiber reinforced composites present:
  • i. Continuous or aligned fibre composites, and
  • ii. Discontinuous fibre composites.

c. Structural Composites :

• 1. Typically, a structural composite is made up of both homogeneous and composite components.
• 2. Its qualities are determined not only by the constituent material properties, but also by their geometrical design.
• 3. On the basis of their geometry it can be classified as :

i. Laminar Composites:

• 1. Layers of two-dimensional sheets or panels are layered and cemented together in laminar composites.
• 2.This shape causes a varied strength inside the composite. This strength varies from layer to layer.

ii. Sandwich Panels :

• 1. A sandwich panel is made up of two outer sheets that are separated by and adhered to a thicker core.
• 2. These are used to create weight beams with high stiffness and strength.
• 3. The outside sheets are often stiffer and stronger, whereas the core material is light in weight and has a low modulus of elasticity.

Q4. Discuss the applications, advantages and limitations of composites.

Ans. A. Applications :

• 1. Space vehicles and satellites,
• 2. Aircrafts,
• 3. Automobiles,
• 4. Pressure vessel and heat exchanger,
• 5. Building construction,
• 6. Machine components, and
• 7. Electronic components.

B. Advantages :

• 1. They have a unique combination of mechanical, chemical, structural, electrical, optical, and other desirable qualities.
• 2. They are lightweight materials with higher specific strength and modulus than traditional materials.
• 3. Composites can be moulded to any shape and dimension, and to any specification.
• 4. They have outstanding anti-chemical and anti-corrosion capabilities.
• 5. Composites are easier to make, repair, and fabricate than metals and RCC.
• 6. Assembling and disassembling of components is easy and quick.
• 7. Seepage and weathering problems are negligible.

C. Limitations :

• 1. They have flow flash and fire points.
• 2. They may develop undesired biological effects seen in polymers.
• 3.High temperature applications are not suitable for polymeric composites.
• 4. Cost of composites is still higher than many conventional materials.
• 5. The colours of composites often fade out after prolonged exposure to sunlight.

Q5. What are the open mold processes for production of FRPs (Fiber reinforced plastics) ? Explain each.

Ans. Open mold processes for production of FRPs are as follows :

a. Hand Lay-Up Process :

• 1. This is the most basic method of creating a fibre reinforced part. A gel coat is initially applied to the open mould in order to make a part utilising the hand lay-up method with fibreglass and polyester.
• 2. Fiber glass reinforcement is physically inserted in the mould, typically in the shape of a cloth or mat. The base resin, mixed with catalysts and accelerator, is then poured, brushed, or sprayed on.
• 3. Rollers or squeegees are used to fully moisten the reinforcement and remove entrapped air.

b. Spray-Up Process :

• 1. Spray-up production of fibre reinforced plastic shells is comparable to hand lay-up production and can be used to create boat hulls, tub shower sets, and other medium to large size designs.
• 2 . If fibreglass is utilised, continuous-strand roving is supplied through a chopper and spray gun combination that distributes chopped roving and catalysed resin into the mould at the same time.
• 3. Densifying the deposited laminate with a roller or squeegee removes air and ensures that the resin impregnates the reinforcing fibres. To get the appropriate thickness, many layers may be added.

c. Vacuum Bag Autoclave Process :

• 1. The vacuum bag moulding process is used to create high performance laminates, which are typically made from fibre reinforced epoxy systems.
• 2. This method’s composite materials are very significant for aircraft and aerospace applications.

d. Filament Winding Process :

• 1. The fibre reinforcement is fed through a resin bath and then wound on a suitable mandrel in this process.
• 2. When sufficient layers have been applied, the wound mandrel is cured either at ambient temperature or at an increased temperature in an oven. After that, the moulded item is removed from the mandrel.
• 3. This approach produces extraordinarily high tensile strengths in hollow cylinders due to the high degree of fibre orientation and fibre loading.
• 4. This method has applications in chemical and fuel storage tanks, pressure vessels, and rocket motor casings.

Q6. What are shape memory alloys? Give their advantages, disadvantages and applications.

Ans. A. Shape Memory Alloys :

• 1. A shape memory alloy is one that can be distorted when cold but returns to its original shape when heated.
• 2. Memory metal, memory alloy, smart metal, smart alloy, and muscle wire are some other names for it.
• 3. Shape memory alloy components can be lightweight, solid-state replacements to traditional actuators such as hydraulic, pneumatic, and motor-based systems. They are also useful for making hermetic couplings in metal tube.

B. Advantages of SMAs:

• 1. These have good elasticity.
• 2. Easy to fabricate.
• 3. These have good fatigue and wear resistance.
• 4. These are light weight materials.

C. Disadvantages of SMAs :

• 1. Lower maximum frequency compared to other micro actuator devices .
• 2. Initial cost is high.
• 3. Residual stresses developed in thin films .

D. Applications of SMAs :

• 1. Aircraft.
• 2. Robotics.
• 3. Orthopedic surgery.
• 4. Dentistry.

Material Science Important Links:

AKTU Important Links | Btech Syllabus

Important Links-Btech (AKTU) | Material Science Syllabus