Gallium Metal | In detail
Prepare to be amazed by gallium, the element that defies
expectations. Unlike its cold, rigid metal brethren, gallium melts in your
hand, transforming from a shiny ingot into a cool, liquid pool in your hand.
This playful metal boasts extraordinary properties, it wets glass like mercury,
shatters aluminum, and finds its way into cutting edge technologies like LED
lights and high-tech mirrors.
What is Gallium?
Gallium is a chemical element with the symbol Ga and atomic number 31. It belongs to the group 13 (group AIII) of the periodic table, which also includes aluminum, indium, and thallium.
Gallium is a soft, silvery metal
at standard temperature and pressure, and it has a melting point of
approximately 29.8 degrees Celsius, just above room temperature. It is notable
for its low melting point, which allows it to liquefy in one's hand. Gallium is
classified as a post-transition metal, and it exhibits both metallic and
non-metallic properties.
Note that:
- Gallium melts in your hand.
What is the source of Gallium?
Gallium does not occur as a free element in nature, but as Gallium (III) compounds. There are two main sources of gallium: primary sources, secondary sources.
1. Primary sources
Gallium is typically extracted as a byproduct during
the processing of aluminum ore (bauxite) and zinc ore (sphalerite).
When these ores are refined, gallium accumulates in the processing residues,
known as red mud for aluminum refining and flue dust for zinc
refining. These residues contain small concentrations of gallium, which can be
further processed to extract the metal.
2. Secondary sources
Recycling is also a significant source of gallium. As
gallium is used in various electronic and technological applications, such as
semiconductors and LEDs, end-of-life products containing gallium can be
recycled to recover the metal. This includes recycling processes for electronic
waste (e-waste) and industrial scrap.
Physical properties of Gallium
Gallium does not crystallize in any of the simple crystal structures. The stable phase under normal conditions is orthorhombic.
One of the most notable properties of gallium is its exceptionally low melting point of approximately 29.8 degrees Celsius (85.6 degrees Fahrenheit). This is just above room temperature, which allows gallium to melt in the palm of one's hand.
Gallium is relatively soft and can be easily cut with a knife. Its Mohs hardness is around 1.5 Young’s Modulus 9.8 GPa, making it softer than most other metals.
Gallium has a density of about 5.91 grams per cubic centimeter, making it denser than many common materials but still relatively light for a metal.
Gallium exhibits a high surface tension, which causes it to form spherical droplets when melted. This property is utilized in various applications, including its use in liquid metal cooling systems.
Gallium is a good conductor of electricity, like other metals. Its conductivity increases with decreasing temperature, making it useful in various electronic and semiconductor applications.
Under certain conditions, gallium can exhibit superconductivity, where it can conduct electricity without resistance. However, this typically requires extremely low temperatures.
Gallium exhibits moderate thermal conductivity, allowing it to efficiently transfer heat. This property is important in applications such as thermal management in electronics and in liquid metal cooling systems.
Under certain conditions, gallium can exhibit
superconductivity, where it can conduct electricity without resistance.
However, this typically requires extremely low temperatures.
Chemical properties of Gallium
Gallium is generally corrosion-resistant in most environments due to the protective oxide layer that forms on its surface. This makes it suitable for use in applications where resistance to corrosion is important.
Gallium reacts with water at or near room temperature to form gallium hydroxide (Ga (OH)3) and hydrogen gas. This reaction is not as vigorous as that of alkali metals but can still occur.
Gallium is soluble in many metals, including aluminum and other group 13 elements. This property is exploited in the production of alloys, where gallium can improve the mechanical and electrical properties of the resulting material.
Gallium and its compounds are generally considered
non-toxic to humans and animals, although ingestion of large amounts can cause
gastrointestinal irritation.
Gallium applications
Electronics:
Gallium is used in semiconductors, particularly in the
production of gallium arsenide (GaAs) chips, which are essential components in
high-frequency applications like mobile phones, microwave circuits, and
satellite communications.
LEDs (Light Emitting Diodes):
Gallium nitride (GaN) LEDs, which use gallium as a
key component, are employed in lighting applications due to their efficiency
and brightness.
Solar Panels:
Gallium is utilized in thin-film solar cells, offering a
lightweight and flexible alternative to traditional silicon-based solar panels.
Alloys:
Gallium is often alloyed with other metals to improve their
properties. For instance, gallium-aluminum alloys have low melting points and
are used in various applications like soldering and in some thermometers.
Note that:
- Gallium effortlessly forms alloys with other metals, simply by being placed on the metal.
- Gallium can be used to lower the melting point of other metals through alloying process.
- When gallium is alloyed with other metals, it disrupts the regular arrangement of atoms in the crystal lattice structure of the metal. This disruption weakens the metallic bonds, making it easier for the metal to undergo a phase transition from solid to liquid. The resulting alloy has a lower melting point than the original metal. So, you can cut any metal with your hand by adding gallium on it.
Thermometers:
Gallium-based thermometers, known as Galinstan
thermometers, are used in situations where mercury thermometers are not
suitable due to environmental or safety concerns.
Magnetostrictive Materials:
Gallium can be alloyed with other metals to create
magnetostrictive materials, which change shape in response to magnetic fields.
These materials find applications in sensors and actuators.
Gallium Alloys examples
1. Galinstan
Galinstan is primarily composed of three elements:
1. Gallium (Ga)
Gallium forms most of the alloy composition, typically
comprising around 68.5% by weight. Gallium is a soft, silvery metal with a low
melting point (29.76°C or 85.57°F), which gives Galinstan its liquid nature at
room temperature.
2. Indium (In)
Indium makes up approximately 21.5% of Galinstan. It
contributes to the alloy's low viscosity and ensures its stability
over a wide temperature range.
3. Tin (Sn)
Tin constitutes the remaining 10% of Galinstan. It helps to lower
the melting point of the alloy and improves its thermal conductivity.
- Galinstan Properties
Galinstan remains liquid at room temperature due to its low melting point, making it one of the few non-mercury liquid metals. This property enables its use in applications where traditional liquid metals like mercury are unsuitable.
Unlike mercury, which is highly toxic, Galinstan has low toxicity and is considered safer for handling, making it suitable for various consumer and industrial applications.
Galinstan exhibits excellent thermal conductivity, comparable to or even better than mercury. This property makes it useful in thermal management applications, such as liquid metal cooling systems for electronics.
Galinstan does not wet many common materials, including glass and ceramics, due to the formation of a thin oxide layer on its surface. This non-wettability property can be advantageous in specific applications.
Galinstan is also electrically conductive, allowing its use
in certain electronic applications where a conductive liquid is required.
- Galinstan Applications
Galinstan's unique combination of properties makes it
suitable for various applications, including
Thermometers and Barometers:
Galinstan can be used as a safer alternative to mercury in
thermometers and barometers due to its low toxicity and similar thermal
properties.
Cooling Systems:
Liquid metal cooling systems in electronics, such as
high-performance CPUs and LEDs, often employ Galinstan due to its high thermal
conductivity and low melting point.
Thermal Interface Materials:
Galinstan-based thermal interface materials are used to
improve heat transfer between electronic components and heat sinks.
Electrical Contacts:
Galinstan can be used in electrical contacts and switches
due to its electrical conductivity and liquid form.
Soft Robotics:
In soft robotics, Galinstan-filled flexible channels can
act as soft actuators or sensors due to the alloy's fluidic nature.
2. Gallium-Aluminum Alloys
1. Gallium
Typically ranges from around 0.5% to 5% by
weight, depending on the specific alloy and its intended use.
2. Aluminum
Forms most of the alloy composition, usually ranging from 95% to 99.5% by
weight.
- Gallium-Aluminum Alloys Properties
By adding gallium to aluminum, the melting point of the alloy can be significantly reduced compared to pure aluminum. This property is crucial for applications where low-temperature soldering is required to avoid damage to sensitive electronic components.
Gallium-aluminum alloys exhibit excellent wetting behavior, allowing them to form strong and reliable bonds with various substrate materials, including metals and ceramics. This property is essential for soldering applications, where proper wetting ensures effective adhesion and electrical conductivity.
Aluminum inherently possesses good corrosion resistance,
and the addition of gallium typically does not significantly alter this
property. Gallium-aluminum alloys can withstand exposure to moisture and
certain corrosive environments, making them suitable for use in aerospace and
other outdoor applications.
- Gallium-Aluminum Alloys Applications
Gallium-aluminum alloys find numerous applications in soldering, aerospace, thermal management.
One of the primary uses of gallium-aluminum alloys is in low-temperature soldering applications, particularly in electronics manufacturing. These alloys are used to create solder joints between electronic components and circuit boards without subjecting the components to excessive heat, thereby minimizing the risk of damage.
Aerospace:
Gallium-aluminum alloys are employed in certain aerospace
applications where lightweight materials with good mechanical properties and
corrosion resistance are required. They may be used in the construction of
structural components, fuel systems, and other aerospace assemblies.
In some cases, gallium-aluminum alloys are utilized in thermal management systems for electronic devices, where they can serve as low-temperature thermal interface materials or heat spreaders.
3. Gallium-Antimony (GaSb) Alloys
Common composition range for GaSb alloys is approximately 30% to 60% Ga by weight, and 40% to 70% Sb by weigh
- Gallium-Antimony (GaSb) Alloys Properties
GaSb is a semiconductor, meaning it has an electrical conductivity intermediate between that of conductors and insulators. This property allows for the control of electrical current flow and makes GaSb suitable for electronic devices.
GaSb has a relatively narrow bandgap, particularly compared to elemental semiconductors like silicon. This narrow bandgap makes GaSb well-suited for infrared (IR) applications, as it can absorb and emit IR radiation efficiently.
GaSb exhibits high electron mobility, which is a measure of how quickly electrons can move through the material when subjected to an electric field. High electron mobility is desirable for high-speed electronic devices, enabling rapid signal processing and data transmission.
Due to its narrow bandgap and high mobility, GaSb alloys are highly sensitive to infrared radiation. This sensitivity makes GaSb ideal for use in IR detectors, imaging systems, and optoelectronic devices.
GaSb alloys also possess promising thermoelectric
properties, allowing them to efficiently convert heat energy into electrical
energy and vice versa. This property is important for applications such as
energy harvesting and waste heat recovery.
- Gallium-Antimony (GaSb) Alloys Applications
Infrared Imaging:
GaSb-based photodetectors and focal plane arrays are used
in thermal imaging cameras, night vision devices, surveillance systems, and
other applications requiring IR sensing.
Optoelectronics:
GaSb alloys are used in the fabrication of IR light
sources, such as LEDs and laser diodes, as well as in optical sensors and
communication systems operating in the IR spectrum.
High-Speed Electronics:
GaSb-based transistors and other electronic devices are
employed in high-speed electronic circuits, radar systems, satellite
communication, and other applications requiring rapid signal processing.
Thermophotovoltaics:
GaSb alloys are investigated for use in thermophotovoltaic
systems, which convert thermal energy into electricity. This technology has
potential applications in power generation from waste heat sources and solar
energy conversion.
Scientific Research:
GaSb alloys are valuable for fundamental research in
semiconductor physics, materials science, and device engineering. They serve as
platforms for exploring novel electronic and optoelectronic phenomena and
developing advanced semiconductor technologies.
