30 Questions
Which type of materials are specifically designed to withstand applied loads without failure?
Metals
Which of the following is NOT an example of an engineering material according to the text?
Gold
What property makes metals and alloys particularly useful for structural or load-bearing applications?
High ductility
Which category of materials has good electrical and thermal conductivity as mentioned in the text?
Metals
What characteristic of alloys allows them to provide improvements in specific properties?
Additions of metals or non-metals
Which of the following materials is particularly known for its shock resistance according to the text?
Cast Iron
Which type of bonding in engineered materials arises from the electrostatic attractive force between conduction electrons and positively charged metal ions?
Metallic bonds
In the context of composite materials, what property allows the production of hard, shock-resistant cutting tools?
Strength
What type of materials are used in components implanted into the human body for replacement of diseased or damaged parts?
Functional materials
Which industry heavily relies on composites like carbon fiber-reinforced polymers for their products?
Aerospace
What is the main purpose of using functional materials in engineering applications?
To provide specific desired functions
Which type of bond involves the sharing of free electrons among positively charged metal ions?
Metallic bond
Which type of polymers has molecular chains that are rigidly connected, resulting in brittleness?
Thermosetting polymers
What process is used to make thermoplastic polymers?
Molding their molten form
Which class of materials do silicon, germanium, and gallium arsenide belong to?
Semiconductors
What distinguishes composite materials from single materials?
Blending of properties
How are fiberglass composites made?
Dispersing glass fibers in a polymer matrix
What characterizes the electrical conductivity of semiconducting materials?
It is between that of ceramic insulators and metallic conductors
Why do ceramics need to be heated to very high temperatures before melting?
Due to their low thermal conductivity
What is the primary reason advanced ceramics are used in substrates for computer chips and wireless communications?
To house delicate electronic components in high-temperature environments
Which of the following best describes the property that makes ceramics both strong and hard, yet very brittle?
Lack of ductility
What type of ceramics are used to make traditional products such as bricks, tableware, and refractories?
Traditional ceramics
Why are some ceramics used as barrier coatings to protect metallic substrates in turbine engines?
To prevent corrosion and wear
Which property of ceramics has been enhanced by new processing techniques that allow them to be used in load-bearing applications?
Strength under compression
Which type of bond is responsible for holding oppositely charged ions together by a strong electrostatic attraction?
Ionic bond
What physical properties of metals are accounted for by metallic bonds?
Luster
Which type of bond involves the sharing of valence electrons among atoms?
Covalent bond
In which type of bonding are materials very strong and hard with high melting points?
Covalent bonding
Which bond exhibits the most reactivity in the correct medium due to charge separation?
Ionic bond
What physical property is NOT typically associated with materials bonded through covalent bonding?
High thermal conductivity
Study Notes
Classification of Engineering Materials
- Engineering materials are a group of materials used in the construction of man-made structures and components, with their main function being to withstand applied loads without failure.
- Examples of engineering materials include carbon steel, aluminum, cast iron, stainless steel, copper alloys, plastics, composites, and nickel alloys.
Metals and Alloys
- Metals and alloys include steels, aluminum, magnesium, zinc, cast iron, titanium, copper, and nickel.
- Alloys contain additions of one or more metals or non-metals and have good electrical and thermal conductivity, high strength, stiffness, ductility, and shock resistance.
- Alloys are particularly useful for structural or load-bearing applications, and provide improvement in a particular desirable property or permit better combinations of properties.
Ceramics
- Ceramics can be defined as inorganic crystalline materials, with beach sand and rocks being examples of natural ceramics.
- Advanced ceramics are made by refining naturally occurring ceramics and other special processes, and are used in substrates, sensors, actuators, capacitors, wireless communications, spark plugs, inductors, and electrical insulation.
- Ceramics are strong and hard but brittle, and have exceptional strength under compression.
Glass and Glass-Ceramics
- Glass is an amorphous material, often derived from a molten liquid.
Polymers
- Thermoplastic polymers have good ductility and formability, are made by shaping their molten form, and have long molecular chains that are not rigidly connected.
- Thermosetting polymers are stronger but more brittle due to tightly linked molecular chains, and are typically cast into molds.
Semiconductors
- Semiconductors have electrical conductivity between ceramic insulators and metallic conductors, and can be controlled to enable electronic devices such as transistors, diodes, etc.
Composite Materials
- Composite materials blend the properties of different materials, producing properties not found in any single material.
- Examples of composite materials include concrete, plywood, and fiberglass, which make use of glass fibers dispersed in a polymer matrix to produce lightweight, strong, ductile, and temperature-resistant materials.
Biomaterials
- Biomaterials are employed in components implanted into the human body to replace diseased or damaged parts, and are non-toxic and compatible with body tissue.
Atomic Bonding
- There are four important mechanisms by which atoms are bonded in engineered materials: metallic, covalent, ionic, and van der Waals bonds.
Metallic Bonding
- Metallic bonding arises from the electrostatic attractive force between conduction electrons and positively charged metal ions.
- Metallic bonding accounts for many physical properties of metals, such as strength, ductility, thermal and electrical resistivity and conductivity, opacity, and luster.
Covalent Bonding
- Covalent bonding forms strong and hard materials, such as diamond, silicon carbide, silicon nitride, and boron nitride, which have high melting points and are useful for high-temperature applications.
Ionic Bonding
- Ionic bonds are formed between a metal and a non-metal, holding oppositely charged ions together by a strong electrostatic attraction.
- Ionic bonds are the strongest of all bonds, have high melting and boiling points, and are strong conductors of electricity in their aqueous solutions or in their molten state.
Test your knowledge on the classification of engineering materials, including polymers and semiconductors. Learn about the characteristics of thermoplastic and thermosetting polymers, as well as the properties of semiconductors like silicon.
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