Crystal Structures and Ratios Quiz

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Questions and Answers

What factor is NOT considered when selecting materials for a particular application?

Availability

Ease of manufacture

Environmental impact (correct)

Cost

Which property makes plastic a suitable choice for the outer casing of an electrical cable?

Magnetic properties

Malleability under heat

High thermal conductivity

Excellent electrical insulator (correct)

Why is brass used for the core of the electrical cable instead of silver?

Silver is too brittle for this application.

Brass has better tensile strength than silver.

Brass is lighter than silver.

Brass is more abundant and cheaper than silver. (correct)

Which of the following is NOT an engineering property of materials mentioned in the content?

Aesthetics Signup and view all the answers

Which characteristic of a material is especially crucial for electrical conductors?

Electrical conductivity Signup and view all the answers

What is one of the main benefits of studying metallurgy for material selection?

It provides a growing range of useful alloys. Signup and view all the answers

Which process allows materials to be easily shaped for various engineering uses?

Extrusion Signup and view all the answers

What is the main purpose of using alloys in engineering materials?

To enhance specific material characteristics Signup and view all the answers

What is the ideal c/a ratio for an HCP crystal structure?

1.633 Signup and view all the answers

Which metals have c/a ratios that are less than the ideal for HCP structure?

Magnesium and titanium Signup and view all the answers

What is the atomic packing factor (APF) for a Body Centered Cubic (BCC) structure?

0.68 Signup and view all the answers

How is the volume of a hexagonal close-packed (HCP) structure calculated?

By using the formula 3a²sin60 multiplied by c. Signup and view all the answers

What is the APF for the Face Centered Cubic (FCC) structure?

0.74 Signup and view all the answers

Which of the following describes metals with c/a ratios higher than ideality in the HCP structure?

They are elongated. Signup and view all the answers

What factor is necessary for calculating the hexagonal area needed for HCP?

Length of side a Signup and view all the answers

What is the relationship between the basal side a and height c in terms of the c/a ratio?

c = 1.633a Signup and view all the answers

What defines ferrous metals?

Metals containing a high proportion of iron Signup and view all the answers

Which application is primarily associated with ferrous metals?

Bridge building Signup and view all the answers

What is a characteristic of non-ferrous metals?

They lack mechanical strength when pure Signup and view all the answers

Which of the following materials is classified as a non-metallic material?

Glass Signup and view all the answers

What is the main use of rubber as mentioned?

Hydraulic and compressed air hoses Signup and view all the answers

Which application is preferred for ceramics?

High voltage insulators Signup and view all the answers

What process is used to create glass?

Melting and combining specific minerals Signup and view all the answers

What is a characteristic of composite materials like wood?

They are naturally occurring Signup and view all the answers

What is a composite material primarily characterized by?

The binding of two different phases. Signup and view all the answers

Which of the following is NOT a type of matrix used in composite materials?

Carbon fiber composite (CFCs) Signup and view all the answers

What unique properties do nano materials exhibit at the nanoscale?

Anomalous optical, magnetic, and electrical properties. Signup and view all the answers

Which statement best describes a unit cell in a crystal structure?

A repetitive block of atoms in a crystal lattice. Signup and view all the answers

What is the significance of the space lattice in solid materials?

It represents the arrangement of atoms and their interactions. Signup and view all the answers

In what application would composite materials primarily be utilized?

Aerospace and underwater technologies. Signup and view all the answers

What is the particle size of a nanometer in relation to a human hair?

Around 100,000 times smaller than a hair's diameter. Signup and view all the answers

Which of the following describes the primary function of diamonds in industrial applications?

Manufacturing cutting tools for high-speed operations. Signup and view all the answers

What is the coordination number of the Body Centered Cubic (BCC) crystal structure?

8 Signup and view all the answers

How many atoms are there in one unit cell of the Face Centered Cubic (FCC) crystal structure?

4 Signup and view all the answers

Which of the following elements has a BCC crystal structure?

Iron Signup and view all the answers

What is the atomic packing factor (APF) for the Hexagonal Close-Packed (HCP) structure?

0.74 Signup and view all the answers

In a Face Centered Cubic (FCC) crystal structure, how many nearest neighbors does each atom have?

12 Signup and view all the answers

What type of atom arrangement does the Hexagonal Close-Packed (HCP) structure utilize?

Atoms in a hexagonal prism Signup and view all the answers

Which of the following elements is typical of the FCC crystal structure?

Aluminum Signup and view all the answers

In terms of coordination number, how do HCP and FCC structures compare?

Both have a coordination number of 12 Signup and view all the answers

Study Notes

c/a Ratio in HCP Crystal Structure

The c/a ratio is the ratio of the height (c) of a hexagonal prism in an HCP crystal structure to its basal side (a).
The ideal c/a ratio for a tightly packed HCP structure is 1.633.
Cadmium and zinc have c/a ratios greater than the ideal ratio, indicating an elongated structure.
Magnesium, cobalt, zirconium, titanium, and beryllium have c/a ratios less than the ideal ratio, indicating a compressed structure.

Atomic Packing Factor (APF)

APF measures the proportion of space occupied by atoms in a crystal structure.
APF values are calculated using the volume of atoms and the volume of the unit cell.

BCC Crystal Structure

BCC structure has atoms at each corner of the cube and one atom at the center of the cube.
Coordination number is 8, meaning each atom is in contact with eight other atoms.
Examples of BCC metals include chromium, iron, and sodium.
Each unit cell contains two atoms.

FCC Crystal Structure

FCC structure has atoms at each corner of the cube and one atom at the center of each face.
Coordination number is 12.
Examples of FCC metals include aluminum and gold.
Each unit cell contains four atoms.

HCP Crystal Structure

HCP structure has atoms at each corner of a hexagonal prism, two atoms at top and bottom faces, and three atoms in between top and bottom face.
Similar to FCC, the HCP structure has an APF of 0.74, indicating tightly packed atoms.
Coordination number is 12.
Each unit cell contains six atoms.

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Description

Test your knowledge on various crystal structures, including HCP, BCC, and FCC. Explore important concepts such as c/a ratios and atomic packing factors. Understand the significance of these ratios in determining crystal properties and structures.