Solid is one of the four fundamental states of matter (the others
being liquid, gas, and plasma). In solids molecules are closely
packed. It is characterized by structural rigidity and resistance to
changes of shape or volume. Unlike a liquid, a solid object does not
flow to take on the shape of its container, nor does it expand to fill
the entire volume available to it like a gas does. The atoms in a
solid are tightly bound to each other, either in a regular geometric
lattice (crystalline solids, which include metals and ordinary ice) or
irregularly (an amorphous solid such as common window glass). Solids
cannot be compressed with little pressure whereas gases can be
compressed with little pressure because in gases molecules are loosely
The branch of physics that deals with solids is called solid-state
physics, and is the main branch of condensed matter physics (which
also includes liquids).
Materials science is primarily concerned with
the physical and chemical properties of solids. Solid-state chemistry
is especially concerned with the synthesis of novel materials, as well
as the science of identification and chemical composition.
1 Microscopic description
2 Classes of solids
2.5 Organic solids
2.6 Composite materials
3 Physical properties
5 External links
Model of closely packed atoms within a crystalline solid.
The atoms, molecules or ions which make up solids may be arranged in
an orderly repeating pattern, or irregularly. Materials whose
constituents are arranged in a regular pattern are known as crystals.
In some cases, the regular ordering can continue unbroken over a large
scale, for example diamonds, where each diamond is a single crystal.
Solid objects that are large enough to see and handle are rarely
composed of a single crystal, but instead are made of a large number
of single crystals, known as crystallites, whose size can vary from a
few nanometers to several meters. Such materials are called
polycrystalline. Almost all common metals, and many ceramics, are
Schematic representation of a random-network glassy form (left) and
ordered crystalline lattice (right) of identical chemical composition.
In other materials, there is no long-range order in the position of
the atoms. These solids are known as amorphous solids; examples
include polystyrene and glass.
Whether a solid is crystalline or amorphous depends on the material
involved, and the conditions in which it was formed. Solids which are
formed by slow cooling will tend to be crystalline, while solids which
are frozen rapidly are more likely to be amorphous. Likewise, the
specific crystal structure adopted by a crystalline solid depends on
the material involved and on how it was formed.
While many common objects, such as an ice cube or a coin, are
chemically identical throughout, many other common materials comprise
a number of different substances packed together. For example, a
typical rock is an aggregate of several different minerals and
mineraloids, with no specific chemical composition.
Wood is a natural
organic material consisting primarily of cellulose fibers embedded in
a matrix of organic lignin. In materials science, composites of more
than one constituent material can be designed to have desired
Classes of solids
Further information: Bonding in solids
The forces between the atoms in a solid can take a variety of forms.
For example, a crystal of sodium chloride (common salt) is made up of
ionic sodium and chlorine, which are held together by ionic bonds.
In diamond or silicon, the atoms share electrons and form covalent
bonds. In metals, electrons are shared in metallic bonding. Some
solids, particularly most organic compounds, are held together with
van der Waals forces resulting from the polarization of the electronic
charge cloud on each molecule. The dissimilarities between the types
of solid result from the differences between their bonding.
Main article: Metal
The pinnacle of New York's Chrysler Building, the world's tallest
steel-supported brick building, is clad with stainless steel.
Metals typically are strong, dense, and good conductors of both
electricity and heat. The bulk of the elements in the periodic
table, those to the left of a diagonal line drawn from boron to
polonium, are metals. Mixtures of two or more elements in which the
major component is a metal are known as alloys.
People have been using metals for a variety of purposes since
prehistoric times. The strength and reliability of metals has led to
their widespread use in construction of buildings and other
structures, as well as in most vehicles, many appliances and tools,
pipes, road signs and railroad tracks. Iron and aluminium are the two
most commonly used structural metals, and they are also the most
abundant metals in the Earth's crust. Iron is most commonly used in
the form of an alloy, steel, which contains up to 2.1% carbon, making
it much harder than pure iron.
Because metals are good conductors of electricity, they are valuable
in electrical appliances and for carrying an electric current over
long distances with little energy loss or dissipation. Thus,
electrical power grids rely on metal cables to distribute electricity.
Home electrical systems, for example, are wired with copper for its
good conducting properties and easy machinability. The high thermal
conductivity of most metals also makes them useful for stovetop
The study of metallic elements and their alloys makes up a significant
portion of the fields of solid-state chemistry, physics, materials
science and engineering.
Metallic solids are held together by a high density of shared,
delocalized electrons, known as "metallic bonding". In a metal, atoms
readily lose their outermost ("valence") electrons, forming positive
ions. The free electrons are spread over the entire solid, which is
held together firmly by electrostatic interactions between the ions
and the electron cloud. The large number of free electrons gives
metals their high values of electrical and thermal conductivity. The
free electrons also prevent transmission of visible light, making
metals opaque, shiny and lustrous.
More advanced models of metal properties consider the effect of the
positive ions cores on the delocalised electrons. As most metals have
crystalline structure, those ions are usually arranged into a periodic
lattice. Mathematically, the potential of the ion cores can be treated
by various models, the simplest being the nearly free electron model.
A collection of various minerals.
Main article: Minerals
Minerals are naturally occurring solids formed through various
geological processes under high pressures. To be classified as a
true mineral, a substance must have a crystal structure with uniform
physical properties throughout.
Minerals range in composition from
pure elements and simple salts to very complex silicates with
thousands of known forms. In contrast, a rock sample is a random
aggregate of minerals and/or mineraloids, and has no specific chemical
composition. The vast majority of the rocks of the Earth's crust
consist of quartz (crystalline SiO2), feldspar, mica, chlorite,
kaolin, calcite, epidote, olivine, augite, hornblende, magnetite,
hematite, limonite and a few other minerals. Some minerals, like
quartz, mica or feldspar are common, while others have been found in
only a few locations worldwide. The largest group of minerals by far
is the silicates (most rocks are ≥95% silicates), which are composed
largely of silicon and oxygen, with the addition of ions of aluminium,
magnesium, iron, calcium and other metals.
Si3N4 ceramic bearing parts
Ceramic solids are composed of inorganic compounds, usually oxides of
chemical elements. They are chemically inert, and often are capable
of withstanding chemical erosion that occurs in an acidic or caustic
environment. Ceramics generally can withstand high temperatures
ranging from 1000 to 1600 °C (1800 to 3000 °F). Exceptions
include non-oxide inorganic materials, such as nitrides, borides and
Traditional ceramic raw materials include clay minerals such as
kaolinite, more recent materials include aluminium oxide (alumina).
The modern ceramic materials, which are classified as advanced
ceramics, include silicon carbide and tungsten carbide. Both are
valued for their abrasion resistance, and hence find use in such
applications as the wear plates of crushing equipment in mining
Most ceramic materials, such as alumina and its compounds, are formed
from fine powders, yielding a fine grained polycrystalline
microstructure which is filled with light scattering centers
comparable to the wavelength of visible light. Thus, they are
generally opaque materials, as opposed to transparent materials.
Recent nanoscale (e.g. sol-gel) technology has, however, made possible
the production of polycrystalline transparent ceramics such as
transparent alumina and alumina compounds for such applications as
high-power lasers. Advanced ceramics are also used in the medicine,
electrical and electronics industries.
Ceramic engineering is the science and technology of creating
solid-state ceramic materials, parts and devices. This is done either
by the action of heat, or, at lower temperatures, using precipitation
reactions from chemical solutions. The term includes the purification
of raw materials, the study and production of the chemical compounds
concerned, their formation into components, and the study of their
structure, composition and properties.
Mechanically speaking, ceramic materials are brittle, hard, strong in
compression and weak in shearing and tension.
Brittle materials may
exhibit significant tensile strength by supporting a static load.
Toughness indicates how much energy a material can absorb before
mechanical failure, while fracture toughness (denoted KIc ) describes
the ability of a material with inherent microstructural flaws to
resist fracture via crack growth and propagation. If a material has a
large value of fracture toughness, the basic principles of fracture
mechanics suggest that it will most likely undergo ductile fracture.
Brittle fracture is very characteristic of most ceramic and
glass-ceramic materials which typically exhibit low (and inconsistent)
values of KIc.
For an example of applications of ceramics, the extreme hardness of
zirconia is utilized in the manufacture of knife blades, as well as
other industrial cutting tools. Ceramics such as alumina, boron
carbide and silicon carbide have been used in bulletproof vests to
repel large-caliber rifle fire.
Silicon nitride parts are used in
ceramic ball bearings, where their high hardness makes them wear
resistant. In general, ceramics are also chemically resistant and can
be used in wet environments where steel bearings would be susceptible
to oxidation (or rust).
As another example of ceramic applications, in the early 1980s, Toyota
researched production of an adiabatic ceramic engine with an operating
temperature of over 6000 °F (3300 °C).
Ceramic engines do
not require a cooling system and hence allow a major weight reduction
and therefore greater fuel efficiency. In a conventional metallic
engine, much of the energy released from the fuel must be dissipated
as waste heat in order to prevent a meltdown of the metallic parts.
Work is also being done in developing ceramic parts for gas turbine
engines. Turbine engines made with ceramics could operate more
efficiently, giving aircraft greater range and payload for a set
amount of fuel. However, such engines are not in production because
the manufacturing of ceramic parts in the sufficient precision and
durability is difficult and costly. Processing methods often result in
a wide distribution of microscopic flaws which frequently play a
detrimental role in the sintering process, resulting in the
proliferation of cracks, and ultimate mechanical failure.
Main article: Glass-ceramic
A high strength glass-ceramic cooktop with negligible thermal
Glass-ceramic materials share many properties with both
non-crystalline glasses and crystalline ceramics. They are formed as a
glass, and then partially crystallized by heat treatment, producing
both amorphous and crystalline phases so that crystalline grains are
embedded within a non-crystalline intergranular phase.
Glass-ceramics are used to make cookware (originally known by the
brand name CorningWare) and stovetops which have both high resistance
to thermal shock and extremely low permeability to liquids. The
negative coefficient of thermal expansion of the crystalline ceramic
phase can be balanced with the positive coefficient of the glassy
phase. At a certain point (~70% crystalline) the glass-ceramic has a
net coefficient of thermal expansion close to zero. This type of
glass-ceramic exhibits excellent mechanical properties and can sustain
repeated and quick temperature changes up to 1000 °C.
Glass ceramics may also occur naturally when lightning strikes the
crystalline (e.g. quartz) grains found in most beach sand. In this
case, the extreme and immediate heat of the lightning (~2500 °C)
creates hollow, branching rootlike structures called fulgurite via
Main article: Organic chemistry
The individual wood pulp fibers in this sample are around 10 µm in
Organic chemistry studies the structure, properties, composition,
reactions, and preparation by synthesis (or other means) of chemical
compounds of carbon and hydrogen, which may contain any number of
other elements such as nitrogen, oxygen and the halogens: fluorine,
chlorine, bromine and iodine. Some organic compounds may also contain
the elements phosphorus or sulfur. Examples of organic solids include
wood, paraffin wax, naphthalene and a wide variety of polymers and
Main article: Wood
Wood is a natural organic material consisting primarily of cellulose
fibers embedded in a matrix of lignin. Regarding mechanical
properties, the fibers are strong in tension, and the lignin matrix
resists compression. Thus wood has been an important construction
material since humans began building shelters and using boats.
be used for construction work is commonly known as lumber or timber.
In construction, wood is not only a structural material, but is also
used to form the mould for concrete.
Wood-based materials are also extensively used for packaging (e.g.
cardboard) and paper which are both created from the refined pulp. The
chemical pulping processes use a combination of high temperature and
alkaline (kraft) or acidic (sulfite) chemicals to break the chemical
bonds of the lignin before burning it out.
STM image of self-assembled supramolecular chains of the organic
semiconductor quinacridone on graphite.
Main article: Polymer
One important property of carbon in organic chemistry is that it can
form certain compounds, the individual molecules of which are capable
of attaching themselves to one another, thereby forming a chain or a
network. The process is called polymerization and the chains or
networks polymers, while the source compound is a monomer. Two main
groups of polymers exist: those artificially manufactured are referred
to as industrial polymers or synthetic polymers (plastics) and those
naturally occurring as biopolymers.
Monomers can have various chemical substituents, or functional groups,
which can affect the chemical properties of organic compounds, such as
solubility and chemical reactivity, as well as the physical
properties, such as hardness, density, mechanical or tensile strength,
abrasion resistance, heat resistance, transparency, color, etc.. In
proteins, these differences give the polymer the ability to adopt a
biologically active conformation in preference to others (see
Household items made of various kinds of plastic.
People have been using natural organic polymers for centuries in the
form of waxes and shellac which is classified as a thermoplastic
polymer. A plant polymer named cellulose provided the tensile strength
for natural fibers and ropes, and by the early 19th century natural
rubber was in widespread use. Polymers are the raw materials (the
resins) used to make what are commonly called plastics. Plastics are
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 carbon-based polyethylene,
polypropylene, polyvinyl chloride, polystyrene, nylons, polyesters,
acrylics, polyurethane, and polycarbonates, and silicon-based
silicones. Plastics are generally classified as "commodity",
"specialty" and "engineering" plastics.
Simulation of the outside of the
Space Shuttle as it heats up to over
1500 °C during re-entry
A cloth of woven carbon fiber filaments, a common element in composite
Main article: Composite material
Composite materials contain two or more macroscopic phases, one of
which is often ceramic. For example, a continuous matrix, and a
dispersed phase of ceramic particles or fibers.
Applications of composite materials range from structural elements
such as steel-reinforced concrete, to the thermally insulative tiles
which play a key and integral role in NASA's
Space Shuttle thermal
protection system which is used to protect the surface of the shuttle
from the heat of re-entry into the Earth's atmosphere. One example is
Carbon (RCC), the light gray material which
withstands reentry temperatures up to 1510 °C (2750 °F)
and protects the nose cap and leading edges of Space Shuttle's wings.
RCC is a laminated composite material made from graphite rayon cloth
and impregnated with a phenolic resin. After curing at high
temperature in an autoclave, the laminate is pyrolized to convert the
resin to carbon, impregnated with furfural alcohol in a vacuum
chamber, and cured/pyrolized to convert the furfural alcohol to
carbon. In order to provide oxidation resistance for reuse capability,
the outer layers of the RCC are converted to silicon carbide.
Domestic examples of composites can be seen in the "plastic" casings
of television sets, cell-phones and so on. These plastic casings are
usually a composite made up of a thermoplastic matrix such as
acrylonitrile butadiene styrene (ABS) in which calcium carbonate
chalk, talc, glass fibers or carbon fibers have been added for
strength, bulk, or electro-static dispersion. These additions may be
referred to as reinforcing fibers, or dispersants, depending on their
Thus, the matrix material surrounds and supports the reinforcement
materials by maintaining their relative positions. The reinforcements
impart their special mechanical and physical properties to enhance the
matrix properties. A synergism produces material properties
unavailable from the individual constituent materials, while the wide
variety of matrix and strengthening materials provides the designer
with the choice of an optimum combination.
Semiconductor chip on crystalline silicon substrate.
Main article: Semiconductors
Semiconductors are materials that have an electrical resistivity (and
conductivity) between that of metallic conductors and non-metallic
insulators. They can be found in the periodic table moving diagonally
downward right from boron. They separate the electrical conductors (or
metals, to the left) from the insulators (to the right).
Devices made from semiconductor materials are the foundation of modern
electronics, including radio, computers, telephones, etc.
Semiconductor devices include the transistor, solar cells, diodes and
integrated circuits. Solar photovoltaic panels are large semiconductor
devices that directly convert light into electrical energy.
In a metallic conductor, current is carried by the flow of electrons",
but in semiconductors, current can be carried either by electrons or
by the positively charged "holes" in the electronic band structure of
the material. Common semiconductor materials include silicon,
germanium and gallium arsenide.
Main article: Nanotechnology
Bulk silicon (left) and silicon nanopowder (right)
Many traditional solids exhibit different properties when they shrink
to nanometer sizes. For example, nanoparticles of usually yellow gold
and gray silicon are red in color; gold nanoparticles melt at much
lower temperatures (~300 °C for 2.5 nm size) than the gold
slabs (1064 °C); and metallic nanowires are much stronger
than the corresponding bulk metals. The high surface area of
nanoparticles makes them extremely attractive for certain applications
in the field of energy. For example, platinum metals may provide
improvements as automotive fuel catalysts, as well as proton exchange
membrane (PEM) fuel cells. Also, ceramic oxides (or cermets) of
lanthanum, cerium, manganese and nickel are now being developed as
solid oxide fuel cells (SOFC). Lithium, lithium–titanate and
tantalum nanoparticles are being applied in lithium ion batteries.
Silicon nanoparticles have been shown to dramatically expand the
storage capacity of lithium ion batteries during the
Silicon nanowires cycle without
significant degradation and present the potential for use in batteries
with greatly expanded storage times.
Silicon nanoparticles are also
being used in new forms of solar energy cells. Thin film deposition of
silicon quantum dots on the polycrystalline silicon substrate of a
photovoltaic (solar) cell increases voltage output as much as 60% by
fluorescing the incoming light prior to capture. Here again, surface
area of the nanoparticles (and thin films) plays a critical role in
maximizing the amount of absorbed radiation.
Main article: Biomaterials
Collagen fibers of woven bone
Many natural (or biological) materials are complex composites with
remarkable mechanical properties. These complex structures, which have
risen from hundreds of million years of evolution, are inspiring
materials scientists in the design of novel materials. Their defining
characteristics include structural hierarchy, multifunctionality and
self-healing capability. Self-organization is also a fundamental
feature of many biological materials and the manner by which the
structures are assembled from the molecular level up. Thus,
self-assembly is emerging as a new strategy in the chemical synthesis
of high performance biomaterials.
Physical properties of elements and compounds which provide conclusive
evidence of chemical composition include odor, color, volume, density
(mass per unit volume), melting point, boiling point, heat capacity,
physical form and shape at room temperature (solid, liquid or gas;
cubic, trigonal crystals, etc.), hardness, porosity, index of
refraction and many others. This section discusses some physical
properties of materials in the solid state.
Granite rock formation in the Chilean Patagonia. Like most inorganic
minerals formed by oxidation in the Earth's atmosphere, granite
consists primarily of crystalline silica SiO2 and alumina Al2O3.
The mechanical properties of materials describe characteristics such
as their strength and resistance to deformation. For example, steel
beams are used in construction because of their high strength, meaning
that they neither break nor bend significantly under the applied load.
Mechanical properties include elasticity and plasticity, tensile
strength, compressive strength, shear strength, fracture toughness,
ductility (low in brittle materials), and indentation hardness. Solid
mechanics is the study of the behavior of solid matter under external
actions such as external forces and temperature changes.
A solid does not exhibit macroscopic flow, as fluids do. Any degree of
departure from its original shape is called deformation. The
proportion of deformation to original size is called strain. If the
applied stress is sufficiently low, almost all solid materials behave
in such a way that the strain is directly proportional to the stress
(Hooke's law). The coefficient of the proportion is called the modulus
of elasticity or Young's modulus. This region of deformation is known
as the linearly elastic region. Three models can describe how a solid
responds to an applied stress:
Elasticity – When an applied stress is removed, the material returns
to its undeformed state.
Viscoelasticity – These are materials that behave elastically, but
also have damping. When the applied stress is removed, work has to be
done against the damping effects and is converted to heat within the
material. This results in a hysteresis loop in the stress–strain
curve. This implies that the mechanical response has a
Plasticity – Materials that behave elastically generally do so when
the applied stress is less than a yield value. When the stress is
greater than the yield stress, the material behaves plastically and
does not return to its previous state. That is, irreversible plastic
deformation (or viscous flow) occurs after yield which is permanent.
Many materials become weaker at high temperatures. Materials which
retain their strength at high temperatures, called refractory
materials, are useful for many purposes. For example, glass-ceramics
have become extremely useful for countertop cooking, as they exhibit
excellent mechanical properties and can sustain repeated and quick
temperature changes up to 1000 °C. In the aerospace industry,
high performance materials used in the design of aircraft and/or
spacecraft exteriors must have a high resistance to thermal shock.
Thus, synthetic fibers spun out of organic polymers and
polymer/ceramic/metal composite materials and fiber-reinforced
polymers are now being designed with this purpose in mind.
Normal modes of atomic vibration in a crystalline solid.
Because solids have thermal energy, their atoms vibrate about fixed
mean positions within the ordered (or disordered) lattice. The
spectrum of lattice vibrations in a crystalline or glassy network
provides the foundation for the kinetic theory of solids. This motion
occurs at the atomic level, and thus cannot be observed or detected
without highly specialized equipment, such as that used in
Thermal properties of solids include thermal conductivity, which is
the property of a material that indicates its ability to conduct heat.
Solids also have a specific heat capacity, which is the capacity of a
material to store energy in the form of heat (or thermal lattice
Video of superconducting levitation of YBCO
Electrical properties include conductivity, resistance, impedance and
capacitance. Electrical conductors such as metals and alloys are
contrasted with electrical insulators such as glasses and ceramics.
Semiconductors behave somewhere in between. Whereas conductivity in
metals is caused by electrons, both electrons and holes contribute to
current in semiconductors. Alternatively, ions support electric
current in ionic conductors.
Many materials also exhibit superconductivity at low temperatures;
they include metallic elements such as tin and aluminium, various
metallic alloys, some heavily doped semiconductors, and certain
ceramics. The electrical resistivity of most electrical (metallic)
conductors generally decreases gradually as the temperature is
lowered, but remains finite. In a superconductor however, the
resistance drops abruptly to zero when the material is cooled below
its critical temperature. An electric current flowing in a loop of
superconducting wire can persist indefinitely with no power source.
A dielectric, or electrical insulator, is a substance that is highly
resistant to the flow of electric current. A dielectric, such as
plastic, tends to concentrate an applied electric field within itself
which property is used in capacitors. A capacitor is an electrical
device that can store energy in the electric field between a pair of
closely spaced conductors (called 'plates'). When voltage is applied
to the capacitor, electric charges of equal magnitude, but opposite
polarity, build up on each plate. Capacitors are used in electrical
circuits as energy-storage devices, as well as in electronic filters
to differentiate between high-frequency and low-frequency signals.
Piezoelectricity is the ability of crystals to generate a voltage in
response to an applied mechanical stress. The piezoelectric effect is
reversible in that piezoelectric crystals, when subjected to an
externally applied voltage, can change shape by a small amount.
Polymer materials like rubber, wool, hair, wood fiber, and silk often
behave as electrets. For example, the polymer polyvinylidene fluoride
(PVDF) exhibits a piezoelectric response several times larger than the
traditional piezoelectric material quartz (crystalline SiO2). The
deformation (~0.1%) lends itself to useful technical applications such
as high-voltage sources, loudspeakers, lasers, as well as chemical,
biological, and acousto-optic sensors and/or transducers.
Materials can transmit (e.g. glass) or reflect (e.g. metals) visible
Many materials will transmit some wavelengths while blocking others.
For example, window glass is transparent to visible light, but much
less so to most of the frequencies of ultraviolet light that cause
sunburn. This property is used for frequency-selective optical
filters, which can alter the color of incident light.
For some purposes, both the optical and mechanical properties of a
material can be of interest. For example, the sensors on an infrared
homing ("heat-seeking") missile must be protected by a cover which is
transparent to infrared radiation. The current material of choice for
high-speed infrared-guided missile domes is single-crystal sapphire.
The optical transmission of sapphire does not actually extend to cover
the entire mid-infrared range (3–5 µm), but starts to drop off
at wavelengths greater than approximately 4.5 µm at room
temperature. While the strength of sapphire is better than that of
other available mid-range infrared dome materials at room temperature,
it weakens above 600 °C. A long-standing trade-off exists
between optical bandpass and mechanical durability; new materials such
as transparent ceramics or optical nanocomposites may provide improved
Guided lightwave transmission involves the field of fiber optics and
the ability of certain glasses to transmit, simultaneously and with
low loss of intensity, a range of frequencies (multi-mode optical
waveguides) with little interference between them. Optical waveguides
are used as components in integrated optical circuits or as the
transmission medium in optical communication systems.
Main article: Solar cell
A solar cell or photovoltaic cell is a device that converts light
energy into electrical energy. Fundamentally, the device needs to
fulfill only two functions: photo-generation of charge carriers
(electrons and holes) in a light-absorbing material, and separation of
the charge carriers to a conductive contact that will transmit the
electricity (simply put, carrying electrons off through a metal
contact into an external circuit). This conversion is called the
photoelectric effect, and the field of research related to solar cells
is known as photovoltaics.
Solar cells have many applications. They have long been used in
situations where electrical power from the grid is unavailable, such
as in remote area power systems, Earth-orbiting satellites and space
probes, handheld calculators, wrist watches, remote radiotelephones
and water pumping applications. More recently, they are starting to be
used in assemblies of solar modules (photovoltaic arrays) connected to
the electricity grid through an inverter, that is not to act as a sole
supply but as an additional electricity source.
All solar cells require a light absorbing material contained within
the cell structure to absorb photons and generate electrons via the
photovoltaic effect. The materials used in solar cells tend to have
the property of preferentially absorbing the wavelengths of solar
light that reach the earth surface. However, some solar cells are
optimized for light absorption beyond Earth's atmosphere as well.
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Wiki on equipment for handling and processing Bulk Solids
States of matter (list)
Gas / Vapor
Quantum spin liquid
Enthalpy of fusion
Enthalpy of sublimation
Enthalpy of vaporization
Latent internal energy
Equation of state
Macroscopic quantum phenomena
Order and disorder (physics)