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Materials science or materials engineering is an
interdisciplinary field involving the properties of matter and its applications
to various areas of
science and
engineering.This science investigates the relationship between the
structure of materials and their properties. It includes elements of
applied physics and
chemistry,
as well as
chemical,
mechanical,
civil and
electrical engineering. With significant media attention to
nanoscience and
nanotechnology in recent years, materials science has been propelled to the
forefront at many universities. It is also an important part of
forensic engineering and
forensic materials engineering, the study of failed products and components.
History
The material of choice of a given era is often its defining point; the
Stone Age,
Bronze Age,
and
Steel Age are examples of this. Materials science is one of the oldest forms
of engineering and applied science, deriving from the manufacture of
ceramics.
Modern materials science evolved directly from
metallurgy,
which itself evolved from mining. A major breakthrough in the understanding of
materials occurred in the late
19th
century, when
Willard Gibbs demonstrated that
thermodynamic properties relating to
atomic structure in various
phases are related to the physical properties of a material. Important
elements of modern materials science are a product of the
space race: the understanding and engineering of the metallic
alloys, and
silica and
carbon materials, used in the construction of space vehicles enabling the
exploration of space. Materials science has driven, and been driven by, the
development of revolutionary technologies such as
plastics,
semiconductors, and
biomaterials.
Before the 1960s (and in some cases decades after), many materials science
departments were named metallurgy departments, from a 19th and early 20th
century emphasis on metals. The field has since broadened to include every class
of materials, including: ceramics,
polymers, semiconductors, magnetic materials, medical implant materials and
biological materials.
Fundamentals of materials science
In materials science, rather than haphazardly looking for and discovering
materials and exploiting their properties, one instead aims to understand
materials fundamentally so that new materials with the desired properties can be
created.
The basis of all materials science involves relating the desired
properties and relative performance of a material in a certain application
to the structure of the atoms and phases in that material through
characterization. The major determinants of the structure of a material and thus
of its properties are its constituent chemical elements and the way in which it
has been processed into its final form. These, taken together and related
through the laws of
thermodynamics, govern a material�s
microstructure, and thus its properties.
An old adage in materials science says: "materials are like people; it is the
defects that make them interesting". The manufacture of a perfect
crystal of a
material is currently physically impossible. Instead materials scientists
manipulate the
defects in crystalline materials such as
precipitates, grain boundaries (Hall-Petch
relationship), interstitial atoms, vacancies or substitutional atoms, to
create materials with the desired properties.
Not all materials have a regular crystal structure.
Polymers display varying degrees of crystallinity, and many are completely
non-crystalline.
Glasses, some ceramics, and many natural materials are
amorphous, not possessing any long-range order in their atomic arrangements.
The study of polymers combines elements of chemical and statistical
thermodynamics to give thermodynamic, as well as mechanical, descriptions of
physical properties.
In addition to industrial interest, materials science has gradually developed
into a field which provides tests for condensed matter or solid state theories.
New physics emerge because of the diverse new material properties which need to
be explained.
Materials in industry
Radical materials advances can drive the creation of new products or even new
industries, but stable industries also employ materials scientists to make
incremental improvements and troubleshoot issues with currently used materials.
Industrial applications of materials science include materials design,
cost-benefit tradeoffs in industrial production of materials, processing
techniques (casting,
rolling,
welding,
ion implantation,
crystal growth,
thin-film deposition,
sintering,
glassblowing, etc.), and analytical techniques (characterization techniques
such as
electron microscopy,
x-ray diffraction,
calorimetry,
nuclear microscopy (HEFIB),
Rutherford backscattering,
neutron diffraction, etc.).
Besides material characterisation, the material scientist/engineer also deals
with the extraction of materials and their conversion into useful forms. Thus
ingot casting, foundry techniques, blast furnace extraction, and electrolytic
extraction are all part of the required knowledge of a metallurgist/engineer.
Often the presence, absence or variation of minute quantities of secondary
elements and compounds in a bulk material will have a great impact on the final
properties of the materials produced, for instance, steels are classified based
on 1/10th and 1/100 weight percentages of the carbon and other alloying elements
they contain. Thus, the extraction and purification techniques employed in the
extraction of iron in the blast furnace will have an impact of the quality of
steel that may be produced.
The overlap between physics and materials science has led to the offshoot
field of materials physics, which is concerned with the physical
properties of
materials. The approach is generally more macroscopic and applied than in
condensed matter physics. See
important publications in materials physics for more details on this field
of study.
The study of metal alloys is a significant part of materials science. Of all
the metallic alloys in use today, the alloys of iron (steel,
stainless steel,
cast iron,
tool steel,
alloy steels) make up the largest proportion both by quantity and commercial
value. Iron alloyed with various proportions of carbon gives low, mid and
high carbon steels. For the steels, the hardness and tensile strength of the
steel is directly related to the amount of carbon present, with increasing
carbon levels also leading to lower ductility and toughness. The addition of
silicon and graphitization will produce cast irons (although some cast irons are
made precisely with no graphitization). The addition of chromium, nickel and
molybdenum to carbon steels (more than 10%) gives us stainless steels.
Other significant metallic alloys are those of
aluminium,
titanium,
copper and
magnesium.
Copper alloys have been known for a long time (since the
Bronze Age),
while the alloys of the other three metals have been relatively recently
developed. Due to the chemical reactivity of these metals, the electrolytic
extraction processes required were only developed relatively recently. The
alloys of aluminium, titanium and magnesium are also known and valued for their
high strength-to-weight ratios and, in the case of magnesium, their ability to
provide electromagnetic shielding. These materials are ideal for situations
where high strength-to-weight ratios are more important than bulk cost, such as
in the aerospace industry and certain automotive engineering applications.
Other than metals, polymers and ceramics are also an important part of
materials science. Polymers are the raw materials (the resins) used to make what
we commonly call plastics. Plastics are really the final product, created after
one or more polymers or additives have been added to a resin during processing,
which is then shaped into a final form. Polymers which have been around, and
which are in current widespread use, include
polyethylene,
polypropylene,
PVC,
polystyrene,
nylons,
polyesters,
acrylics,
polyurethanes, and
polycarbonates. Plastics are generally classified as "commodity",
"specialty" and "engineering" plastics.
PVC (polyvinyl-chloride) is widely used, inexpensive, and annual production
quantities are large. It lends itself to an incredible array of applications,
from artificial leather to
electrical insulation and cabling,
packaging and
containers. Its fabrication and processing are simple and well-established.
The versatility of PVC is due to the wide range of
plasticisers and other additives that it accepts. The term "additives" in
polymer science refers to the chemicals and compounds added to the polymer base
to modify its material properties.
Polycarbonate would be normally considered an engineering plastic (other
examples include PEEK, ABS). Engineering plastics are valued for their superior
strengths and other special material properties. They are usually not used for
disposable applications, unlike commodity plastics.
Specialty plastics are materials with unique characteristics, such as
ultra-high strength, electrical conductivity, electro-fluorescence, high thermal
stability, etc.
It should be noted here that the dividing line between the various types of
plastics is not based on material but rather on their properties and
applications. For instance,
polyethylene (PE) is a cheap, low friction polymer commonly used to make
disposable shopping bags and trash bags, and is considered a commodity plastic,
whereas Medium-Density Polyethylene
MDPE is used for underground gas and water pipes, and another variety called
Ultra-high Molecular Weight Polyethylene
UHMWPE is an engineering plastic which is used extensively as the glide
rails for industrial equipment and the low-friction socket in implanted
hip joints.
Another application of material science in industry is the making of
composite materials. Composite materials are structured materials composed of
two or more macroscopic phases. An example would be steel-reinforced concrete;
another can be seen in the "plastic" casings of television sets, cell-phones and
so on. These plastic casings are usually a
composite material made up of a thermoplastic matrix such as
acrylonitrile-butadiene-styrene (ABS)
in which
calcium carbonate chalk,
talc,
glass fibres or
carbon fibres have been added for added strength, bulk, or electro-static
dispersion. These additions may be referred to as reinforcing fibres, or
dispersants, depending on their purpose.
Classes of materials (by bond types)
Materials science encompasses various classes of materials, each of which may
constitute a separate field. Materials are sometimes classified by the type of
bonding present between the atoms:
-
Ionic crystals
-
Covalent crystals
- Metals
-
Intermetallics
-
Semiconductors
- Polymers
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Composite materials
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Vitreous materials
Sub-fields of materials science
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Nanotechnology � rigorously, the study of materials where the effects of
quantum confinement, the
Gibbs-Thomson effect, or any other effect only present at the nanoscale
is the defining property of the material; but more commonly, it is the
creation and study of materials whose defining structural properties are
anywhere from less than a
nanometer to one hundred nanometers in scale, such as molecularly
engineered materials.
-
Microtechnology - study of materials and processes and their
interaction, allowing
microfabrication of structures of micrometric dimensions, such as
MicroElectroMechanical Systems (MEMS).
-
Crystallography � the study of how atoms in a solid fill space, the
defects associated with
crystal structures such as
grain boundaries and
dislocations, and the characterization of these structures and their
relation to physical properties.
-
Materials Characterization � such as diffraction with
x-rays,
electrons, or
neutrons, and various forms of
spectroscopy and
chemical analysis such as
Raman spectroscopy,
energy-dispersive spectroscopy (EDS),
chromatography,
thermal analysis,
electron microscope analysis, etc., in order to understand and define
the properties of materials. See also
List of surface analysis methods
-
Metallurgy � the study of metals and their alloys, including their
extraction,
microstructure and processing.
-
Biomaterials � materials that are derived from and/or used with
biological systems.
-
Electronic and
magnetic
materials � materials such as semiconductors used to create
integrated circuits,
storage media,
sensors, and other devices.
-
Tribology � the study of the wear of materials due to
friction
and other factors.
-
Surface science/Catalysis � interactions and structures between
solid-gas solid-liquid or solid-solid interfaces.
-
Ceramography � the study of the
microstructures of high-temperature materials and
refractories, including structural ceramics such as
RCC, polycrystalline
silicon carbide and
transformation toughened ceramics
Some practitioners often consider
rheology a
sub-field of materials science, because it can cover any material that flows.
However, modern rheology typically deals with non-Newtonian
fluid dynamics, so it is often considered a sub-field of
continuum mechanics. See also
granular material.
-
Glass Science � any non-crystalline material including inorganic
glasses, vitreous metals and non-oxide glasses.
-
Forensic engineering � the study of how products fail, and the vital
role of the materials of construction
-
Forensic materials engineering � the study of material failure, and the
light it sheds on how engineers specify materials in their product
Topics that form the basis of materials science
-
Thermodynamics,
statistical mechanics,
kinetics and
physical chemistry, for
phase stability, transformations (physical and chemical) and diagrams.
-
Crystallography and
chemical bonding, for understanding how atoms in a material are
arranged.
-
Mechanics, to understand the mechanical properties of materials and
their structural applications.
-
Solid-state physics and
quantum mechanics, for the understanding of the electronic, thermal,
magnetic, chemical, structural and optical properties of materials.
-
Diffraction and
wave mechanics, for the characterization of materials.
-
Chemistry and
polymer science, for the understanding of
plastics, colloids, ceramics, liquid crystals,
solid state chemistry, and polymers.
- Biology,
for the integration of materials into biological systems.
-
Continuum mechanics and
statistics, for the study of fluid flows and ensemble systems.
-
Mechanics of materials, for the study of the relation between the
mechanical behavior of materials and their microstructures.
Important Journals
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Chemistry of Materials
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Nature Materials
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Acta Materialia
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JOM
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Advanced Materials
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Computational materials science
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Advanced Functional Materials
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Journal of Materials Chemistry
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Journal of Materials Online - Open Access
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Metallurgical and Materials Transactions
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Journal of Materials Research
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Journal of Materials Science
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Federation of European Materials Science Societies Newsletter
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AMMTIAC eNews/Quarterly Advanced materials, manufacturing, and testing.
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