2D Materials: Dicalcium nitride

2D Materials: Dicalcium nitride

An electride material, dicalcium nitride (Ca2N) is a compound in which an electron functions as the anion. Because dicalcium nitride is a layered material, it can be considered to be a 2D electride with the formula [Ca2N]+e

This material has a hexagonal crystal structure and forms a shiny green plate like crystal in the bulk. As with graphene, mechanical exfoliation can be used to separate the layers. Similar materials, such as those with strontium in the place of calcium, have also been shown to exist. However, these such materials are still relatively unknown and used for almost exclusively for research (electrides themselves are considered to be a fairly recent discovery, first synthesized in the early 1980s). 

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

Glasses: Smart glass

Glasses: Smart glass

Smart materials are those materials specifically designed to have one or more properties that will change in a desired manner in response to an anticipated external stimuli. Smart glass, then, is any type of glass that fits this category, of which there are many.

Thermochromic glasses are glasses which change color (typically tint) in response to changes in heat. Often these glasses are responsive enough to change in direct response to sunlight, letting in more light (i.e. being more transparent) when the sun is not shining as brightly. This can help control the amount of light needed within a structure, as well as the energy consumption of heating or cooling, depending on the climate. Thermochromic windows are typically produced in layers, as shown in the upper left image above.

Electrochromic glasses, then, are glasses which change color (or tint) in response to the amount of voltage applied to the glass. These types of glasses (often used for windows) allow occupants to tint the glass at will, sometimes for the same reasons as mentioned above, but occasionally simply for comfort or privacy. Electrochromic glasses offer more control than thermochromic glasses, but it requires the ability to control the voltage as well. (The amount of electricity used, however, can be far less than the amount that could potentially be saved by allowing for natural lighting.)

Finally, photochromic glasses also have a similar effect, those these glasses react to the presence of light, not heat as with thermochromic glasses. Photochromic glasses are most popular in lenses.

Other types of smart glass include suspended particle and polymer dispersed liquid crystals. The latter is not actually a form of glass, but rather a layer between the glass. As with electrochromic glass, the application of voltage changes the tint, but PDLCs react much faster than electrochromic materials.

Technically speaking, it is often glazings added to glasses that help produce these effects, which is why windows of these types of glasses are constructed in layers. The movement of ions or electrons through the layers can often be the basis for the change in tint. As such, materials which claim to be ‘smart glass’ are typically combinations of glass and coatings, thin films, or other layers between the glass. There are, however, exceptions.

Sources/Further Reading: ( 1 – image 1 ) ( 2 – image 2 ) ( 3 – image 3 ) ( 4 – image 4 ) ( 5 – image 5 ) ( 6 ) ( 7 ) ( 8 ) ( 9 ) ( 10 )

Polymers: Polyacrylonitrile

Polymers:

Polyacrylonitrile

Most often used in copolymers, polyacrylonitrile (PAN) is a thermoplastic polymer that actually degrades before reaching its melting point. As such, it is typically only produced in the form of fibers. 

Homopolymers of this material have been used in applications such as hot gas filtration systems, awnings, and sails, however it is the applications of the various copolymers that are probably more recognizable to the typical consumer. Copolymers including PAN can be used as fibers in clothing and other textile applications. Some well known copolymers include Poly(styrene-co-acrylonitrile) (SAN) (a common replacement for polystyrene) and poly(acrylonitrile-co-butadiene-co–styrene) (ABS) (a strong, lightweight thermoplastic well known for its usage in LEGO blocks, as well as numerous other applications. 

Another application for PAN, however, is in the production of carbon fiber. It is estimated that around 90% of carbon fiber is produced using PAN as a precursor material. This is part of the reason for the high price of carbon fibers, given that PAN itself is not a cheap material (relatively speaking). 

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

Image 2.

Glasses: Low iron glass

Glasses: Low iron glass

Glass is known for its transparency, or its ability to allow the visible wavelengths of light to pass through it relatively unaltered. However, the primary constituents of silica-based glasses (the most well known type) usually have impurities that can be difficult to completely remove. Impure glass often has a greenish-tint to it, resulting from iron left behind. Low iron glass, therefore, is a form of ultrapure silica glass, in which the iron content has been carefully managed and reduced to allow for increased transparency (often by selecting raw materials that contain less iron). 

The difference in transmission can vary, and depends greatly on the thickness of the glass. Thinner sections of low iron glass usually have 2-3% greater transmission of light, but thicker glasses can have even higher percentages. (See chart in the upper right corner above.) There are no set compositions for most types of glass, but low iron glass most always has around 1/10 the amount of iron as other silica glass, or around 0.01% ferric oxide content.

Typical applications of this specialty glass include display, lighting, or architectural applications, as well as optical applications requiring clear visibility and solar panels. Several brand names for this material are UltraClear, Optiwhite, Starphire, Starlite, and Krystal Klear. Low iron glass can technically be used anywhere clear float glass is also used though, and can be processed in much the same ways as well, including lamination, toughening, and other treatments.

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

2D Materials: Germanene

2D Materials: Germanene

As with the other elements sharing the same group on the periodic table (carbon, silicon, tin, and even lead), germanium is capable of forming a two dimensional material on its own known as germanene. And, just as with the other 2D materials of the same group, germanene’s most intriguing applications to many researchers are those that take advantage of the material’s novel electronic properties. 

The synthesis of germanene was first reported in 2014, before tin and lead but after carbon and silicon. Unlike carbon, however, germanium does not have a layered structure that can be easily separated (relatively speaking) and, as such, germanene must be synthesized, often through molecular beam epitaxy – it cannot be exfoliated. Also, as shown in the upper left image above, germanene is not entirely flat due to the angle that forms between bonded germanium atoms. 

Germanene is still in the early stages of research, like many other 2D materials, and easier forms of synthesis, as well as a deeper understanding of its properties, need to be developed before any commercial applications can be considered. That being said, key areas of interest for germanene include high-performance field-effect transistors, and for the usage in studying Dirac fermions. It is important to note that germanene does not have a band gap, though the addition of hydrogen can create one.

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

Alloys: Spiegeleisen

Alloys: Spiegeleisen

A ferro manganese alloy, spiegelesien was considered to be a form of pig iron and thus used in steel making. Historically it was used as a way to add in manganese, an important component in steel, but as its composition typically only includes around 15% manganese it has since been replaced in modern processes by alloys and materials with higher manganese contents, often up to 80% manganese.

The term spiegelesien comes from the German spiegel and esien, meaning mirror (or specular) and iron, respectively, a comment on the reflective nature of this alloy’s appearance. 

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

Image 1.

Composites: Dental compomer

Composites: Dental compomer

Dental compomers are hybrid materials made from glass ionomer cement (a combination of silicate glass power and polyacrylic acid) and synthetic resins known as dental composites. (Their name also comes from a hybrid of these two materials: comp, from composite, and omer, from the glass ionomers.)

These composites are used solely in dentistry to create a material that balances the advantages and disadvantages of its two components. As seen in the image in the upper left above, compomers are stronger than glass ionomer cements, and are more capable of releasing fluoride than composite resins. The compositions can vary between brands, but generally speaking compomers are resin-based materials with glass filler particles, photoinitiators, and stabilizers. 

Used only in dentistry, compomers are good for restoring teeth in applications such as: “all types of cavities in deciduous teeth; cervical cavities (carious or non-carious) in adults; anterior proximal restorations in adults; small load-bearing restorations in adults”[Source 1].

Sources/Further Reading: ( 1 – images 1, 3, and 4 ) ( 2 ) ( 3 )

Image 2.

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.

Do NOT follow this link or you will be banned from the site!