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 )

International Year of the Periodic Table: Sili…

sci:

2019 has been
declared by UNESCO as the Year of the Periodic Table. To celebrate, we are
releasing a series of blogs about our favourite elements and their importance
to the chemical industry. Today’s blog focuses on silicon’s positive effects on
the body.

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A versatile player in human biology

Silicon was not originally regarded as an important element for human health, as it
was seen to have a larger presence in (other) animal and plant tissue. It was not until a 2002 ‘The American Journal of Clinical Nutrition’ paper that surmised that accumulating research found that silicon plays an important role in bone formation in
humans.  

Silicon was first known to ‘wash’ through biology with no toxological or
biological properties. However, in the 1970s, animal studies provided evidence
to suggest that silicon deficiency in diets produced defects in connective and
skeletal tissues. Ongoing research has added to these findings, demonstrating
the link between dietary silicon and bone health.

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Silicon plays an important role in protecting humans against
many diseases.  Silicon is an important trace mineral essential for strengthening joints.
Additionally, silicon is thought to help heal and repair fractures.

The most important source of exposure to silicon is your diet. According to two epidemiological studies (Int J Endocrinol. 2013: 316783 ;

J Nutr Health Aging. 2007 Mar-Apr; 11(2): 99–110) conducted, dietary silicon intake has been linked to higher bone mineral density.

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Silicon is needed to repair tissue, as it is important for
collagen synthesis – the most abundant protein in connective tissue in the body – which is needed for the strengthening of bones. 

However, silicon is very common in the body and therefore it is difficult to prove how essential it is to this process when symptoms of deficiency vary among patients. 

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There has also been a plausible link between Alzheimer’s disease
and human exposure to aluminium. Research has been underway to test whether
silicon-rich mineral waters can be used to reduce the body burden of aluminium
in individuals with Alzheimer’s disease. 

However, longer term study is needed
to prove the aluminium hypothesis of Alzheimer’s disease.

Tiffany Hionas is a Digital Media Intern at SCI. You can find more of her work here. 

Advanced NMR captures new details in nanopar…

Advanced NMR captures new details in nanoparticle structures

Advanced nuclear magnetic resonance (NMR) techniques at the U.S. Department of Energy’s Ames Laboratory have revealed surprising details about the structure of a key group of materials in nanotechology, mesoporous silica nanoparticles (MSNs), and the placement of their active chemical sites.

MSNs are honeycombed with tiny (about 2-15 nm wide) three-dimensionally ordered tunnels or pores, and serve as supports for organic functional groups tailored to a wide range of needs. With possible applications in catalysis, chemical separations, biosensing, and drug delivery, MSNs are the focus of intense scientific research.

“Since the development of MSNs, people have been trying to control the way they function,” said Takeshi Kobayashi, an NMR scientist with the Division of Chemical and Biological Sciences at Ames Laboratory. “Research has explored doing this through modifying particle size and shape, pore size, and by deploying various organic functional groups on their surfaces to accomplish the desired chemical tasks. However, understanding of the results of these synthetic efforts can be very challenging.”

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Researchers improve semiconductor laser on s…

Researchers improve semiconductor laser on silicon

Electrical engineering researchers have boosted the operating temperature of a promising new semiconductor laser on silicon substrate, moving it one step closer to possible commercial application.

The development of an “optically pumped” laser, made of germanium tin grown on silicon substrates, could lead to faster micro-processing speed of computer chips, sensors, cameras and other electronic devices—at much lower cost.

“In a relatively short time period—roughly two years—we’ve progressed from 110 Kelvin to a record temperature of 270K,” said Shui-Qing “Fisher” Yu, associate professor of electrical engineering. “We are now very close to room-temperature operation and moving quickly toward the application of a material that can significantly increase processing speed with much less power consumption.”

Yu leads a multi-institutional team of researchers on developing a laser injected with light, similar to an injection of electrical current. The improved laser covers a broader wavelength range, from 2 to 3 micrometers, and uses a lower lasing threshold, while capable of operating at 270 Kelvin, which is roughly 26 Farenheit.

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cenchempics: Water from thin air  Hundreds o…

cenchempics:

Water from thin air 

Hundreds of millions of people in the world lack access to safe water. Researchers like Rukmava Chatterjee, a PhD student in Sushant Anand’s lab at the Universitry of Illinois at Chicago, want to fix this problem by developing devices like this one, which can harvest water out of the air. This device consists of a cooled silicon surface impregnated with a wax layer that freezes a few degrees above 0 °C. When the surface comes in contact with humid air, the water in the air condenses and transfers heat to the wax layer. That small amount of heat melts the top of the wax layer, producing a hydrophobic liquid that lubricates the surface. The water droplets can then drip down the device and get collected.–

Manny Morone

Submitted by Rukmava Chatterjee

Chemistry in Pictures is accepting entries to its water-themed contest until July 3. Enter today!

Do science. Take pictures. Win money. Enter our photo contest here.

Related C&EN Content:

Can stripping the air of its moisture quench the world’s thirst?

Slippery microgrooves help harvest fog

Insects and plants inspire water harvesting surface.

Regular

Understanding the (ultra-small) structure of silicon nanocrystals

Chemists discover new information about structure of silicon nanocrystals

New research provides insight into the structure of silicon nanocrystals, a substance that promises to provide efficient lithium ion batteries that power your phone to medical imaging on the nanoscale.

The research was conducted by a team of University of Alberta chemists, lead by two PhD students in the Department of Chemistry, Alyx Thiessen and Michelle Ha.

“Silicon nanocrystals are important components for a lot of modern technology, including lithium ion batteries,” said, Thiessen, who is studying with Professor Jonathan Veinot. “The more we know about their structure, the more we’ll understand about how they work and how they can be used for various applications.”

In two recently published papers, the research team characterized the structure of silicon nanocrystals more quickly and accurately than ever before, using a cutting-edge technique known as dynamic nuclear polarization (DNP).

“Using the DNP technology, we were able to show that larger silicon nanocrystals have a layered structure that is disordered on the surface, with a crystalline core that is separated by a middle layer,” explained Ha, who is studying under the supervision of Assistant Professor Vladimir Michaelis. “This is the first time this has been documented in silicon nanocrystals.”

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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 )

Image source.

Less can be more: Semiconductor nanowires fo…

Less can be more: Semiconductor nanowires for flexible photovoltaics

Capturing and manipulating light at nanoscale is a key factor to build high efficiency solar cells. Researchers in the 3-D Photovoltaics group have recently presented a promising new design. Their simulations show that vertically stacked nanowires on top of ultrathin silicon films reduces the total amount of material needed by 90 percent while increasing the efficiency of the solar cell. These promising simulation results are an important step toward next-generation solar cells. The results have been published on May 23rd in Optics Express.

A strategy to reduce cost and rigidity of photovoltaics is to combine ultrathin silicon photovoltaic films with semiconductor nanowire solar cells. The mechanical flexibility and resilience of micrometer thin cells make them well suited to apply on curved surfaces.

The idea is to optically couple the two materials stacked on top of each other as a tandem cell: a gallium arsenide (GaAs) nanowire array on top of an ultrathin silicon (2um-thick) film. GaAs vertical nanowires are well-known semiconductor components in photovoltaic applications.

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Quantum world-first: Researchers reveal accu…

Quantum world-first: Researchers reveal accuracy of two-qubit calculations in silicon

For the first time ever, researchers have measured the fidelity – that is, the accuracy – of two-qubit logic operations in silicon, with highly promising results that will enable scaling up to a full-scale quantum processor.

The research, carried out by Professor Andrew Dzurak’s team in UNSW Engineering, was published today in the journal Nature.

The experiments were performed by Wister Huang, a final-year PhD student in Electrical Engineering, and Dr Henry Yang, a senior research fellow at UNSW.

“All quantum computations can be made up of one-qubit operations and two-qubit operations – they’re the central building blocks of quantum computing,” says Professor Dzurak.

“Once you’ve got those, you can perform any computation you want – but the accuracy of both operations needs to be very high.”

Read more.

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