A green method for producing crystalline supramolecular fibers promises to make polymer production more sustainable.
A polymer that catalyzes its own formation in an environmentally friendly solvent-free process has been developed by an all-RIKEN team of chemists. The discovery could lead to the development of inherently recyclable polymer materials that are made using a sustainable process.
Polymers are ubiquitous today, but they are detrimental to the environment through the accumulation of plastic waste and the unsustainable nature of conventional polymer manufacture. Polymers are generally made by linking together strings of building blocks, known as monomers, using covalent bonds. But these strong bonds make it difficult to take used, end-of-life plastic items and de-polymerize them to recover the monomers for reuse.
EPFL engineers have developed a low-temperature annealing method that maintains the structure of gold and silver when the two metals are combined in an alloy. Their discovery will prove useful in the manufacture of contact lenses, holographic optical elements and other optical components, since the new alloys reflect the full spectral range.
Gold, silver, copper and aluminum are widely used in the manufacture of optical components because of their reflective properties. Gold, for instance, reflects red light, while silver reflects blue light. These metals are also of interest to scientists, who study them at the nanoscale, since nanostructures have a completely different optical response than bulk materials. At this scale, light interacts differently than it would with the same metal in a larger quantity, such as in a gold bar. Engineers at the Nanophotonics and Metrology Laboratory (NAM), part of EPFL’s School of Engineering (STI), set themselves a challenge: to develop a material that reflects every color in the spectrum.
The direct band gap of AlN-based materials makes them suitable for fabricating DUV optoelectronic devices, which have a wide range of application prospects in the fields of curing, water and air disinfection, medicine and biochemistry. Therefore, achieving a high-quality epitaxy of AlN films is of particular importance to ensure the excellent performance of DUV photoelectric devices.
Currently, due to the lack of cost-effective homogenous substrates, the optimal choice to grow AlN films is usually to perform heteroepitaxial growth on sapphire. Unfortunately, the inherent mismatches between AlN and sapphire substrate inevitably introduce a variety of crystalline defects into the AlN epilayer. In particular, the large residual strain in the AlN film leads to the nonuniformity of the Al distribution in the upper AlGaN layer accompanied by wafer bending, which severely limits the device performance. Therefore, a feasible strategy is required to make a qualitative leap to realize high-quality growth of heteroepitaxial AlN films and to meet the application requirements of DUV optoelectronic devices.
Ammonia is commonly used in fertilizer because it has the highest nitrogen content of commercial fertilizers, making it essential for crop production. However, two carbon dioxide molecules are made for every molecule of ammonia produced, contributing to excess carbon dioxide in the atmosphere.
A team from the Artie McFerrin Department of Chemical Engineering at Texas A&M University consisting of Dr. Abdoulaye Djire, assistant professor, and graduate student Denis Johnson, has furthered a method to produce ammonia through electrochemical processes, helping to reduce carbon emissions. This research aims to replace the Haber-Bosch thermochemical process with an electrochemical process that is more sustainable and safer for the environment.
The researchers recently published their findings in Scientific Reports.
Since the early 1900s, the Haber-Bosch process has been used to produce ammonia. This process works by reacting atmospheric nitrogen with hydrogen gas. A downside of the Haber-Bosch process is that it requires high pressure and high temperature, leaving a large energy footprint. The method also requires hydrogen feedstock, which is derived from nonrenewable resources. It is not sustainable and has negative implications on the environment, expediting the need for new and environmentally friendly processes.
Researchers have developed a new fabrication process that allows infrared (IR) glass to be combined with another glass and formed into complex miniature shapes. The technique can be used to create complex infrared optics that could make IR imaging and sensing more broadly accessible.
“Glass that transmits IR wavelengths is essential for many applications, including spectroscopy techniques used to identify various materials and substances,” said research team leader Yves Bellouard from Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. “However, infrared glasses are difficult to manufacture, fragile and degrade easily in the presence of moisture.”
In the journal Optics Express, the researchers describe their new technique, which can be used to embed fragile IR glasses inside a durable silica matrix. The process can be used to create virtually any interconnected 3D shape with features measuring a micron or less. It works with a wide variety of glasses, offering a new way to fine-tune the properties of 3D optics with subtle combinations of glass.
In the year 1682 the Hafla hammer mill started to produce iron. It went on til 1924 when it ended. In 1934 the hammer was declared a national museum, and the old hammer smiths were there for one day working again.Since then it has been quiet,with the hammer smiths long gone. But the last few years enthusiasts have slowly restored the hammer, and today we were able to forge iron once again in the 333 year old smithy for the first time in a decade.
Domesticated chickens in the United States alone produce more than 2 billion pounds of feathers annually. Those feathers have long been considered a waste product, especially when contaminated with blood, feces or bacteria that can prove hazardous to the environment.
Nebraska’s Yiqi Yang is among a growing cadre of researchers looking to transform those feathers into fibers that find a place in natural fabrics. In that vein, Yang and his Husker colleagues are devising and testing methods to improve the properties of feather-derived fibers.
Those methods include cross-linking: chemically bonding long protein chains—including keratin, a water-resistant protein of feathers—to bolster the performance of the resulting fibers and fabrics. But that performance must still improve, and unwanted side effects of cross-linking be resolved, before feathers emerge as a greener alternative to petroleum-based materials—polyester, nylon—currently dominating the market.
The silicon-based tandem solar cell is regarded as the most promising strategy to break the theoretical efficiency limit of single-junction Si solar cells. With Si-based tandem solar cells as the bottom cells, the optimal bandgap of top cells is 1.7 eV, which enables high efficiency of ~45% for two-junction tandem solar cells. III-V semiconductors/Si and perovskites/Si tandem solar cells have achieved high efficiency levels of ~30%, proving their feasibility. However, the stability challenges of perovskite and the high-cost problem of III-V semiconductors largely limit their wide applications. Exploring new stable, low-cost, and bandgap 1.7 eV photovoltaic materials is of great significance in science and broad prospects in technology.
Cadmium selenide (CdSe), a binary II-VI semiconductor, enjoys great potential in the application of Si-based tandemsolar cells because of the suitable bandgap of ~1.7 eV, excellent optoelectronic properties, high stability, and low manufacturing cost. Nevertheless, the progress of CdSe thin-film solar cells remains as it was 30 years ago, and there are few systematic studies on CdSe thin-film solar cells in recent years.
Professor Tang Jiang and his team have proposed a method of rapid thermal evaporation (RTE) to obtain high-quality CdSe thin films and have designed CdSe thin-film solar cells. This study, entitled Rapid thermal evaporation for cadmium selenide thin-film solar cells, was published in Frontiers of Optoelectronics on Dec. 6, 2021.
Both hobbyists’ pottery and engineered high-performance ceramics are only useable after they are fired for hours at high temperatures, usually above 1000 °C. The sintering process that takes place causes the individual particles to “bake” together, making the material more compact and giving it the required properties, like mechanical strength.
In the journal Angewandte Chemie, American researchers have now demonstrated that sintering can also take place at significantly lower temperatures. This cold sintering process is based on the addition of small amounts of water to aid the key transport processes that densify the material.
“Since the stone age, ceramics have been fabricated by sintering at high temperatures,” reports Clive A. Randall from Pennsylvania State University (USA). “This includes the Venus of Doli Vestonice, one of the oldest ceramic objects.” The traditional firing process may now become unnecessary for many ceramic materials, because a broad spectrum of inorganic materials and composites can also be sintered between room temperature and 200 °C.
Heating iron can alter its structure and is one of the methods for making various types of steel with different properties. That process is similar to the formation of frost flowers: one iron crystal structure transforms into another at a nucleus point, and the process expands further from that point. This type of nucleation in materials has the largest impact on their final properties, but is still the least understood in the field of metallurgy. For example, we still know little about how and where exactly this nucleation starts. Researchers at TU Delft have now shed new light on this subject in their publication ‘Preferential Nucleation during Polymorphic Transformations’ in Scientific Reports(Nature) of Wednesday 3 August.
The researchers demonstrated this nucleation process live by heating an iron sample to 1,000 degrees in a specially produced furnace at the European Synchrotron Radiation Facility in Grenoble, and monitoring the transformation process using X-rays. In this way, they were able to identify the places and their properties that were the most likely starting points for the nucleation process of the transition from ferrite to austenite.
Carbon nanotubes that are prone to tangle like spaghetti can use a little special sauce to realize their full potential.
Rice University scientists have come up with just the sauce, an acid-based solvent that simplifies carbon nanotube processing in a way that’s easier to scale up for industrial applications.
The Rice lab of Matteo Pasquali reported in Science Advances on its discovery of a unique combination of acids that helps separate nanotubes in a solution and turn them into films, fibers or other materials with excellent electrical and mechanical properties.
The study co-led by graduate alumnus Robert Headrick and graduate student Steven Williams reports the solvent is compatible with conventional manufacturing processes. That should help it find a place in the production of advanced materials for many applications.
Fluorite is known for its beauty and color, but even so, it cannot be classified as a gemstone for it is to soft to be valued as such. Compared to other gems such as Amethyst, Ruby, or Emerald, which are around 7-10 on the mohs scale of hardness, Fluorite is only a 3.4 which knocks it off the official list. Even though it is not highly prized in the gem market it is prized by the chemical and industrial world. Fluorite also goes by Fluorspar which is used as a flux (coming from the Latin word for flow) in metallurgy because of its low melting point. It is often used to remove impurities like sulfur and phosphorus but also improve the fluidity of slag. In the United States it believed that anywhere between 20-60 pounds of fluorspar is used for every ton of metal, and it is often far above the metallurgic standards. In Chemistry it is used as a source of Fluorine(F), hydrofluoric acid(HF), and lastly the creation of metallurgical flux. Usually it has to be 97% CaF2 to be acid grade and the HF that comes from it is used in refrigeration and foam blowing agents, and many common fluorite chemical we all use.
The high clarity, pure, and translucent pieces of Fluorite are sometimes used as lenses for microscopes, telescopes, and cameras. The more colorful pieces, that often reach the richness of actual gems like Saphire, Topaz, or Ruby, are sometimes used for the bright and glossy look in ceramics and opalescent glass-making. For it to be actually useful in durable glazes and glass it should be 85%-96% actual CaF2.
Fluorite has one more notable intriguing feature. The stone is one of the few minerals in the world that is fluorescent, and the feature was actually named after this stone. This where the stone emits light because the electrons get excited by normal light and other levels of radiation and then later release the energy after. It absorbs X-rays and Ultraviolet or even just violet light and then releases it as a longer, lower energy wave length. It is a type of natural luminescence.
In work that could usher in more efficient, eco-friendly processes for the production of important metals like lithium, iron and cobalt, researchers from MIT and SLAC have mapped what is happening at the atomic level behind a particularly promising approach called metal electrolysis.
By creating maps for a wide range of metals, they not only determined which metals should be easiest to produce using this approach, but also identified fundamental barriers behind the efficient production of others. As a result, the researchers’ map could become an important design tool for optimizing the production of all these metals.
The work could also aid the development of metal-air batteries, cousins of the lithium-ion batteries used in today’s electric vehicles.
