Republic of the Philippines
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CHAPTER 1 - NATURE OF MATERIALS
1.1 TYPES OF ENGINEERING MATERIALS
Engineering materials refers to the group of materials used in the construction of
manmade structures and components. The primary function of an engineering material is to
withstand applied loading without breaking and without exhibiting excessive deflection.
For example, the things we use every day, the cellular phones or the pen, are
manufactured through controlled processes. These gadgets make use of materials such as
copper, aluminium, tin, plastic, etc. in their fabrication. Civil construction works like bridges,
dams, houses, roads, and pavements are carried out with raw materials like stone, cement,
clay, paint, bar, steel, etc.
Everything we use in our everyday life can be tailored to use for specific cases. This
can be done efficiently if we know the properties of each material beforehand. Materials
have been extensively tested for their properties and classified into broad groups. From this
grouping, we can know the property of any group of material.
The major classifications of engineering materials include metals, ceramics,
polymers, and composites.
a.
METALS
Metals are materials that are mainly used in the field of engineering. Type of
chemical element characterized by its conductivity of heat and electricity, malleability,
ductility, and metallic luster.
Properties of Metals
1. Metals have high melting and boiling points, allowing them to remain solid in high
temperatures.
2. Metals are known for their ability to conduct electricity and heat due to free
electrons that move freely throughout the metal and carry electrical and thermal
current.
3. Metals are malleable and ductile, allowing them to be pounded, rolled into different
shapes, or drawn into wire without breaking.
4. Most metals have a shiny or metallic appearance known as luster, which reflects
light.
5. Metals are dense, solid materials that weigh more than nonmetals.
6. Most metals are naturally solid at room temperature, except for mercury, which is
liquid at room temperature.
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7. Metals can be mixed with other elements to form alloys, which are materials with
improved properties (such as increased strength or corrosion resistance).
8. Metals are prone to losing electrons and forming positive ions. This is because
the outermost electrons in a metal’s atoms are not strongly attracted to the positively
charged nucleus and can be easily removed.
Metals can be classified into two categories:
1. Ferrous Alloys
Ferrous alloys are used in the majority of metallic applications in different
engineering fields. These are metals in which iron is the prime constituent, they are
produced in larger quantities than any other metal type.
The presence of iron in this category of metals offers exceptional strength,
durability, and magnetic properties that can be used for a wide array of applications,
including construction, manufacturing, automotive, and infrastructure development
industries
Properties of Ferrous Metals:
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They are easily magnetized;
Capable of withstanding heavy loads and mechanical stresses;
Can endure harsh conditions and maintain their performances over time;
They also have high melting point; and
The abundance of iron in its composition makes it susceptible to corrosion.
Example of Ferrous Metals:
Ferrous metals include steel, cast iron, carbon steel, alloy steel, and wrought
iron as its example.
Engineering Application of Ferrous Metals:
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2.
Ferrous steel is produced as sheet for automobiles, appliances, and
containers
As plates for ships, boilers and bridges, as a structural member (such as Ibeams)
Bar products for leaf springs, gears ales, crankshaft and railroad rails
As music wire and as fasteners such as bolts, rivets and nuts
Ferrous materials comprise 70% to 80% by weight of virtually all structural
members and mechanical components.
Non-Ferrous Alloys
Nonferrous alloys belong to the category that doesn’t contain iron as their
primary element. Non-ferrous metals are renowned for their lightweight, excellent
thermal conductivity, corrosion resistance, and malleable properties, making them a
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perfect option for various applications where strength, durability, and resistance to
rust are paramount.
Properties of Non-Ferrous Metals:
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Non-ferrous metals have low density;
They are very ductile;
exhibit exceptional malleability; and
Non-Ferrous metals are not attracted to magnets.
Example of Non-Ferrous Metals:
Non-ferrous metals include aluminum, copper, lead, zinc, and tin as its
example.
Engineering Application of Non-Ferrous Aloys:
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Lead and its alloys are used in x-ray shields and storage batteries
Tin are used as coating for carbon steel cans that are used as food containers
Zinc alloys are used in padlocks, plumbing fixtures, automotive parts, and used
as coating for carbon steel to become galvanized steel
Chromium is used as coating for stainless steel
b. CERAMICS
Ceramics is a material that is neither metallic nor organic they are compounds
between the metallic and non-metallic elements chemically bound together. It may be
crystalline, glassy or both crystalline and glassy.
Ceramics are typically hard and chemically non-reactive and can be formed or
densified with heat. They are typically insulative to the passage of electricity and heat and
are more resistant to high temperature and harsh environment than polymers and metal.
We can divide this into three categories, Crystalline ceramics, Glasses, and Glassceramics.
1. Crystalline Ceramics
Most ceramics are crystalline. They tend to have high melting points and be
very hard and brittle. Their tensile strengths are limited by brittle fracture but their
compressive strengths are high. They retain high harnesses at elevated
temperatures.
Engineering Applications of Crystalline Ceramics:
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Typical application of ceramic crystalline are pottery, clay (such as brick, tile, and
sewer pipe);
They are also used in electronics industry;
They are also useful as refractories such as furnace innings;
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2.
Used as protective parts for power lines; and
Additionally development of ceramic engine for automobiles, and for ultra-hightemperature jet engines are also candidates for future application.
Glasses
Glasses are amorphous material, often, but not always, derived from a
molten liquid. The term “amorphous” refers to materials that do not have a regular,
periodic arrangement of atoms. They are categorized as noncrystalline ceramics,
because there is no regularity in the arrangement of its molecular constituents.
Glasses have lower strength but are flexible that’s why a wide range of
chemical and physical properties, such as mechanical, thermal, electrical, and in
particular optical properties make them the most useful class of material.
Engineering Application of Glasses:
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They can be used as chemical labware and cooking wares;
Used in construction and vehicle glazing;
They are also used as electronic components, and
Used as electrical insulators.
Glass-Ceramics
Glass-ceramics are the combination of crystalline ceramics and glass. They
are defined as composite materials constituted of crystals in a glassy matrix. This
combination between amorphous (glass) and crystalline states leads to a new type
of material having unique properties that can be adjusted.
Some glass-ceramics can be made optically transparent by keeping the size
of the crystals extremely small ( 6100 nm). Depending on the microstructure and the
chemical composition of glass-ceramics, their properties can be tuned to meet
demanding requirements.
In general, glass-ceramics exhibit almost zero thermal expansion and high
toughness. In addition, they are resistant to thermal shock and have a high impact
resistance.
Engineering Application of Glass-Ceramics:
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Household appliances uses glass-ceramics such as toaster and cooktops;
They are used as construction material;
Used in military (missiles) and optical applications;
Used as electronic components; and
It is also used in the medical field.
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c. POLYMERS
Polymers, or common synonym - Plastics, is a name derived from the deformability
associated with the fabrication of most polymeric products. The term polymer means “many
units,” and in this context, the term mer refers to a unit group of atoms of molecules that
defines a characteristic arrangement for a polymer.
They are produced using a process known as polymerization, where small
molecules consisting of one unit (known as monomers) or a few units (known as oligomers)
are chemically joined to create giant molecules.
Plastics are materials that are composed principally of naturally occurring and
modified or artificially made polymers often containing additives such as fibers, fillers,
pigments, and the like that further enhance their properties.
Application of Polymers:
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Available in wide variety of commercial forms such as fibers, thin films and sheets, and
foams;
They are used in clothing, toys, home appliances, structural and decorative items;
Used in coatings, paints, and adhesives;
They are also widely used in automobiles as tires, car bumpers, etc.;
They are used in constructions, window, flooring, rainwater, cladding, membranes,
pipes, glazing, seals, insulation, and signage
d. COMPOSITES
Composites are produced when two or more phases are used together to give a
combination of properties that cannot be attained otherwise. These materials involve some
combination of two or more components from the fundamental structural material types:
metals, ceramics, glasses, and polymers.
Composite materials may be selected to give unusual combinations of stiffness,
strength, weight, high-temperature performance, corrosion resistance, hardness, or
conductivity.
Composite materials have a wide range of example from construction use to
electronic uses which include mud bricks, wood, fiberglass, carbon fiber, reinforced
concrete, translucent concrete, and etc.
Engineering Application of Composite Material:
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Building, bridges, and structures;
Automobiles, aircrafts, and spacecrafts;
Wind turbine blades;
Household items, imitation granite, cultured marble sinks, and countertops; and
Electronic components.
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e. Advanced Materials
1. SEMICONDUCTOR MATERIALS
A semiconductor is a material that is between conductors and insulators in its
ability to conduct electrical current. An intrinsic semiconductor is one with
properties that are not controlled by impurities. An extrinsic semiconductor (n- or ptype) is preferred for devices since its properties are stable with temperature and can
be controlled using ion implantation or diffusion of impurities known as dopants.
These materials have an easily controlled electrical conductivity and, when
properly combined, can act as switches, amplifiers, or information storage devices.
They are the foundation of modern electronics, including radio, computers,
telephones, and many other devices. It is used for amplification of energy, switching,
energy conversion, sensors, and more.
Common products and components built with Semiconductor Materials:
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bipolar junction transistors
diodes
field-effect transistors
integrated circuits
Light-emitting diodes (LEDs)
metal-oxide semiconductor field-effect transistors (MOSFETs)
silicon-controlled rectifiers
2. BIOMATERIAL
Biomaterial are any matter, surface, or construct that interacts with biological
systems. They are employed in components implanted into the human body to
replace diseased or damaged body parts. These materials must not produce toxic
substances and must be compatible with body tissues (i.e., must not cause adverse
biological reactions).
All of the preceding materials—metals, ceramics, polymers, composites, and
semiconductors—may be used as biomaterials. They often are biodegradable, and
some are bio-absorbable, meaning they are eliminated gradually from the body after
fulfilling a function.
Biomaterial is mostly used in the medical field, it is used as medical implants
(heart valves, stents, and grafts, dental implants, and devices that stimulate nerve),
as a method to promote healing of human tissues (sutures, clips, and staples
used in wound closure), biosensor (blood glucose monitoring devices and brain
activity sensors), and drug-delivery systems (implantable chemotherapy wafers for
cancer patients).
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3. SMART MATERIALS
Smart (or intelligent) materials are a group of new and state-of-the-art
materials now being developed that will have a significant influence on many of our
technologies. The adjective smart implies that these materials are able to sense
changes in their environment and then respond to these changes in predetermined
manners—traits that are also found in living organisms.
Components of a smart material (or system) include some type of sensor
(that detects an input signal), and an actuator (that performs a responsive and
adaptive function). Actuators may be called upon to change shape, position, natural
frequency, or mechanical characteristics in response to changes in temperature,
electric fields, and/or magnetic fields.
Type of Smart Materials include, piezoelectric material, shape-memory
materials, halochromic material, chromoactive materials, magnetorheological
materials, and photoactive materials.
4.
NANOENGINEERED MATERIALS
Nanomaterials may be any one of the four basic types—metals, ceramics,
polymers, and composites. However, unlike these other materials, they are not
distinguished on the basis of their chemistry, but rather, size; the nano-prefix denotes
that the dimensions of these structural entities are on the order of a nanometer (10-9
m)—as a rule, less than 100 nanometers (equivalent to approximately 500 atom
diameters).
Uses of Nanoengineered Materials includes, food storage, food quality
control, food formulation and food packaging. They are also used in electronics,
electrical, biomedicine, and textile.
1.2 Engineering Materials Compositions
A.
Composition of Metals
The ferrous group of metals is composed mainly of iron. They may have small
amounts of other metals or other elements added such as carbon, manganese,
nickel, chromium, silicon, titanium, tungsten etc., to give the required properties.
Non-Ferrous are metals which do not contain any iron as a component.
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Alloy is a new metal which is formed by mixing two or more metals and
sometimes other elements together.
The most used metals are: Iron, Aluminum, Copper, Titanium, Zinc, Magnesium
etc.
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Iron is the basic component of steel. When carbon, a nonmetal, is added to
iron in amounts up to 2.1 %, the result is an alloy known as steel.
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In connection with the above mentioned steel is an alloy composed of iron
and other elements such as carbon, manganese, phosphorus, sulfur, nickel,
chromium, tungsten, niobium (columbium), titanium etc. Each element that is added
to the basic constituent of iron has some effect on the properties of the steel. The
alloying additions are responsible for many differences between the various types or
grades of steels.
Based on carbon content, the steels are divided into three main groups:
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Low carbon steels
Middle carbon steels
High carbon steels
The aluminium industry uses aluminium as cast and wrought aluminium alloys.
Regarding to the properties, titanium and titanium alloys can be divided into
three main groups:
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Corrosion resistant alloys
High strength alloys
High temperature alloys
The most widely used Copper and its alloys are in forms of brasses and bronzes.
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A Brass is defined as a copper-zinc alloy
A bronze is an alloy of copper and other metals
B. Composition of Ceramic
Ceramics are non-metallic, inorganic materials typically made by shaping and
then firing a mixture of minerals. The composition of ceramics can vary widely depending
on the specific type of ceramic being produced. However, there are some basic
components and elements commonly found in ceramic compositions.
Clay
Clay is a primary component in many ceramics. It is a natural material that is rich
in minerals such as kaolinite, illite, and montmorillonite. Clay provides plasticity to the
ceramic mix, allowing it to be easily shaped and molded. Different types of clay can be
used, including ball clay, kaolin, stoneware clay, and fireclay, each with its own unique
properties and applications.
Atomic and molecular nature of ceramic materials and their resulting
characteristics and performance in industrial applications. Industrial ceramics are
commonly understood to be all industrially used materials that are inorganic, nonmetallic
solids. Usually they are metal oxides (that is, compounds of metallic elements and
oxygen), but many ceramics (especially advanced ceramics) are compounds of metallic
elements and carbon, nitrogen, or sulfur. In atomic structure they are most often
crystalline, although they also may contain a combination of glassy and crystalline
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phases. These structures and chemical ingredients, though various, result in universally
recognized ceramic-like properties of enduring utility, including the following: mechanical
strength in spite of brittleness; chemical durability against the deteriorating effects of
oxygen, water, acids, bases, salts, and organic solvents; hardness, contributing to
resistance against wear; thermal and electrical conductivity considerably lower than that
of metals; and an ability to take a decorative finish.
C. Composition of Polymer
The composition of a polymer can vary widely depending on the specific type of
polymer and the monomers used in its production. However, the basic structure of a
polymer consists of repeating units of monomers. These monomers can be the same or
different, and the arrangement of monomers can greatly affect the properties of the
resulting polymer.
In addition to monomers, polymers may also contain various additives and
modifiers to enhance their properties. These can include plasticizers, stabilizers, fillers,
and colourants, among others. These additives can help improve the polymer's flexibility,
strength, stability, or appearance.
Polymers can be classified into different categories based on their composition
and properties. These include:
1. Thermoplastics: These polymers can be melted and reshaped multiple times without
undergoing significant chemical change. Examples include polyethylene,
polypropylene, and polystyrene.
2. Thermosetting polymers: These polymers undergo a chemical reaction during
moulding, which sets their shape permanently. They cannot be re-melted or
reprocessed once they are formed. Examples include epoxies, phenolics, and
polyurethanes.
3. Elastomers: These polymers have elastic properties and can return to their original
shape after being stretched. Examples include natural rubber and silicone rubber.
4. Fibres: These are polymers with a linear and highly oriented structure, which gives
them high tensile strength. Examples include nylon, polyester, and aramid fibers.
5. Biodegradable polymers: These polymers are designed to break down into natural
components when exposed to specific environmental conditions, helping to reduce
environmental impact.
6. Conducting polymers: These polymers have the ability to conduct electricity, making
them suitable for use in electronics and other high-tech applications.
D. Composition of Composite
The composite is a combination of two or more constituent materials with
significantly different physical or chemical properties, resulting in a final material with
characteristics that are different from those of its individual components. The
composition of a composite material is crucial in determining its properties, performance,
and applications.The composition of composites can be tailored to meet specific
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performance requirements for various applications. By selecting the appropriate
combination of matrix and reinforcement materials, along with controlling their
composition, manufacturers can engineer composites with desirable properties such as
high strength, stiffness, toughness, thermal stability, and corrosion resistance.
E. Composition of Semiconductors
The composition of semiconductors is vital to their functionality in electronic
devices and optoelectronic applications. Semiconductors are primarily composed of
particular elemental semiconductors and compound semiconductors, each with specific
atomic compositions that impart unique electrical and optical properties.
The composition of semiconductors is further tailored through doping, wherein
specific impurities are intentionally introduced to modulate the electrical conductivity and
electronic properties of the material. For example, adding elements like phosphorus,
arsenic, or antimony introduces extra electrons, resulting in n-type semiconductors, while
adding elements like boron, aluminium, or indium creates "holes" in the crystal lattice,
leading to p-type semiconductors.
Furthermore, the composition and structure of semiconductors are integral to the
fabrication of heterostructures and quantum structures, where layers of different
semiconductor materials are precisely engineered to create unique electronic, photonic,
and quantum computing devices. The controlled composition and arrangement of these
materials at the nanoscale enable the exploitation of quantum mechanical effects for
advanced functionality.
1.3 Chemical Bonding
The attraction between atoms, ions and molecules to form a chemical compound is
called chemical bond. A Chemical Bonding is a lasting attraction between atoms that
enables the formation of chemical compounds. The bond may result from the electrostatic
force of attraction between atoms with opposite charges or through the sharing of electrons.
Atoms that form bonds with other other atoms by sharing them or transferring them is
known as the Octet Rule.
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Atoms are stable when they have 8 valence electrons.
When the atoms have 8 electrons, it is called an octet.
Atoms must lose, gain or share electrons to attain the octet.
However, there are elements that have exceptions to this rule.;
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Hydrogen needs only one more to fill its valence shell.
Helium has a full valence shell - it is stable and does not bond with other atoms.
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Types of Chemical Bonding
Ionic Bonding
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When atoms gain or lose an electron, they become an ion.
This type of bonding occurs when one atom gives up one or more electrons to
another atom. This results in the formation of positive and negative ions, which are
held together by electrostatic forces. Ionic bonding typically occurs between metals
and non-metals.
Sodium chloride (NaCl) is the classic ionic material.
Covalent Bonding
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Atoms that share electrons form covalent bonds.
In covalent bonding, atoms share one or more pairs of electrons to achieve a more
stable electron configuration. This type of bonding occurs between non-metal atoms.
If the atoms have a covalent bond and are the same type of atom. They are diatomic
molecules. For example;
Two atoms that are covalently bonded will each contribute at least one electron to the
bond, and the shared electrons may be considered to belong to both atoms.
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Metallic Bonding
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Metallic bonding is the type of bonding found in metallic elements. This is the
electrostatic force of attraction between positively charged ions and delocalized outer
electrons.
Metallic bonding refers to the interaction between the delocalized electrons and the
metal nuclei.
Where the outer electrons are delocalized and free to move throughout the structure.
This leads to properties such as conductivity and malleability in metals.
Valence electrons are not bound to any particular atom in the solid and are more or
less free to drift throughout the entire metal. They may be thought of as belonging to
the metal as a whole, or forming a “sea of electrons” or an “electron cloud.”
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