Ceramics: Silicon oxynitride

Ceramics: Silicon oxynitride

While silicon oxynitride is technically defined as those ceramics with the general composition of SiOxNy (in the amorphous form, this means anything from SiO2 to Si3N4), the most well known form of this material has the chemical formula of Si2N2O. This is the only known intermediary crystalline phase, and can be found in small amounts in nature as the mineral sinoite, the crystal structure of which can be shown above. 

Most practical applications of this ceramic utilizes amorphous thin films of the material. The range of structures listed above allows for a range of properties that can be tuned based on the exact composition of the oxynitride in question (for example, SiO2 has a refractive index of 1.45, while Si3N4 has a refractive index of 2, which allows for a variety of waveguides to be constructed). 

The crystalline structure (Si2N2O), meanwhile, is known to be an excellent refractory material, with high chemical and oxidation resistance. Finally, these ceramics are occasionally doped with metal atoms, such as aluminum as a ceramic known as sialon, or lanthanides to produce phosphors. 

Sources/Further Reading: ( 1 ) ( 2 ) ( 3 – image 3 ) ( 4 ) ( 5 )

Image sources: ( 1 ) ( 2 )

Minerals: DickiteWith a composition of Al2Si2O…

Minerals: Dickite

With a composition of Al2Si2O5(OH)4, dickite is a sillicate mineral named after the Scottish metallurgical chemist Allan Brugh Dick, who first conducted experiments on the clay mineral (though he did not realize that the kaolin he was studying was actually more than one distinct mineral).

Dickite occurs with other clay minerals (and is often associated with quartz as well) in locations around the world and, as such, is hard to distinguish. X-ray diffraction is typically used to confirm the presence of dickite. It is a monoclinic crystal that is white in color (any other colors of dickite come from impurities). It has a Mohs hardness of between 1.5 and 2.

For more in depth information about dickite, check out what mindat.org, webmineral.com, handbookofmineralogy.org, and mineralatlas.eu have to say about it.

Sources/Further Reading: ( 1 – image 1 ) ( 2 ) ( 3 – image 3 ) ( 4 – image 4 )

Categories crystals, Materials Science, MaterialsPosts, Minerals, MyMSEPost, science, Uncategorized Tags

Polymers: PolysulfonesA category of polymers t…

Polymers: Polysulfones

A category of polymers technically defined as any polymer which contains a sulfonyl group, the term polysulfone is actually most often used in reference to 

polyarylethersulfones, in which the following structure is present: aryl-SO2-aryl. These polymers are thermoplastics, and known for their toughness and stability at high temperatures. 

Polysulfones are amorphous polymers typically prepared through condensation polymerizations and are rigid and high-strength. They stand up well in high-pressure environments and are often considered to be high-performance polymers. These polymers are often semi-transparent and resistant to creep and deformation at high temperatures under continuous loads. 

These polymers are fairly uncommon, due to the relatively high costs of production and the raw materials involved, and as such applications of polysulfones tend to be highly specialized. Because of their high service temperatures, they are sometimes used as flame retardants, or in medical applications requiring autoclave or steam sterilization. Another common application is in the form of membranes, with controllable poor sizes.

Sources/Further reading: ( 1 – image 1 ) ( 2 – image 2 ) ( 3 ) ( 4 )

Image 3.

Alloys: Hydronalium

Alloys: Hydronalium

Aluminum magnesium alloys are aluminum based alloys with anywhere from 0.5% to 13% magnesium. The addition of magnesium decreases the formability of the aluminum but allows for much better corrosion resistance. Hydronalium alloys are a subset family of these alloys that can have anywhere between 1% to 12% magnesium as well as small amounts of manganese (usually under 1%).

These alloys are most well known in Eastern Europe, having originated in Germany in the 1930s, and were widely used for shipbuilding in Poland. They are most well known for their resistance to seawater corrosion. Other applications include violin strings (in those variants ductile enough to be drawn into wire), luggage, and glasses frames (as shown above). Hydronalium alloys are also difficult to manufacture, specifically when it comes to casting, and as such are not relatively common.

Sources/Further Reading: ( 1 – image 4 ) ( 2 ) ( 3 )

Images sources: ( 1 ) ( 2 ) ( 3 )

Ferromagnetic Semiconductors Ferromagnetic se…

Ferromagnetic Semiconductors

Ferromagnetic semiconductors are materials that are capable of exhibiting both ferromagnetic and semiconducting behavior. Because of the contradictory crystal structure requirements for these two behaviors, the existence of these materials was not theorized until recently. It was not until the 1960s that the coexistence of semiconducting and magnetic properties was first observed in europium based chalcogenides and chromium based spinels. Unfortunately, both of these materials are natural ferromagnetic semiconductors with low Curie temperatures and poor reproducibility, making them poor candidates for any practical applications.

The main reason for interest in finding better ferromagnetic semiconductors lies in the fact that the spin of these materials can be used to manipulate the response of these materials to electrical and magnetic fields. Ferromagnetic semiconductors also exhibit magnetoresistance (the magnetic properties split the valence band into two bands, as shown above, which can be thought of as forming a parallel circuit) and magneto-optic effects (making the usage of ferromagnetic semiconductors in optical isolators and optical data storage devices feasible).

As a consequence of these properties ferromagnetic semiconductors have wide ranging applications, most notably in the field of spintronics. Many applications are still in the research and development phase but hold great promise. Prototype spin MOSFETs and bipolar transistors have already been developed, where the direction of spin affects the transistor characteristics (antiparallel spin yields high conductance whereas parallel spin yields low conductance). These materials can also be used to manufacture MRAM’s which are three times as dense as currently used RAMs, and have potential applications in quantum computing and neuromorphic computing.

The quest to obtain ferromagnetic semiconductors with Curie temperatures approaching room temperature has been extremely rewarding as the commercial viability of devices based on these materials is constantly increasing, but also because the search for such materials gives key insights into fundamental material behavior.

Sources/Further Reading: ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )

Image sources: ( 1 ) ( 2 ) ( 3 )

Written by: @deepesttheoristlady​; Edited by this blog. 

Suspension polymerization ( 2 ) is a form of r…

Suspension polymerization ( 2 ) is a form of radical polymerization in which the monomers are added to a solvent (often water) in which they are soluble, then reacted kinetically (i.e. mixed together to prompt a reaction). It is a widely used technique that is fairly easy to control, simply the various components of the reaction such as stirring speed or the volume fraction of the monomer present.

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Ceramics: Grade A lava

Ceramics: Grade A lava

A naturally occurring form of hydrous aluminum silicate, lava on its own is easily machinable. As such, when fired and processed as a ceramic (in the form of grade A lava), the resulting material is highly machinable. 

Grade A lava has good electrical and heat resistance, excellent resistance to thermal shock, and low thermal conductivity. Once fired in a kiln, lava also hardens significantly. Since lava is a natural material, however, the structure of the grains, color, and other natural properties are difficult to control and depend almost entirely on the raw material being mined. As such, the true processing conditions for creating grade A lava can vary. Generally, this material is not fired about 2000 F. 

Grade A lava is used in a variety of applications that tend to require materials that can withstand thermal cycling

Sources: ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )

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Interfacial polymerization ( 2 ) is a form of …

Interfacial polymerization ( 2 ) is a form of step-growth polymerization that creates thin film (or other nanostructured) polymers at the interfaces of two materials. These two materials are usually two immiscible liquids, with a different monomer in each liquid, reacting at the interface, but liquid-solid interactions as well as liquid-in-liquid emulsion reactions are also possible. 

Image sources: ( 1 ) ( 2 )

Precipitation polymerization ( 2 ) is a method…

Precipitation polymerization ( 2 ) is a method of polymerization in which a monomer and initiator are added to a solvent in which they are soluble in, but in which the resulting polymer is insoluble. As a result, particles of the polymer grow within the solution as the reaction proceeds, precipitating from the solvent.

Image sources: ( 1 ) ( 2 )

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