The Periodic Table may not sound like a list of ingredients but, for a group of materials scientists, it’s the starting point for designing the perfect chemical make-up of tomorrow’s jet engines.
Inside a jet engine is one of the most extreme environments known to engineering.
In less than a second, a ton of air is sucked into the engine, squeezed to a fraction of its normal volume and then passed across hundreds of blades rotating at speeds of up to 10,000 rpm; reaching the combustor, the air is mixed with kerosene and ignited; the resulting gases are about a third as hot as the sun’s surface and hurtle at speeds of almost 1,500 km per hour towards a wall of turbines, where each blade generates power equivalent to the thrust of a Formula One racing car.
NASA research into flexible, high-temperature space materials may some day improve personal fire shelter systems and help wildland firefighters better survive dangerous wildfires. The CHIEFS team layers heat resistant materials together to try to design the most capable personal fire shelter…
Ordinary matter behaves very differently when subjected to extreme temperatures and pressures, such as that inside stellar and planetary cores. Conventional rules of condensed matter physics and plasma physics are not applicable in such scenarios. In particular, an extreme state known as “warm dense matter” (WDM) straddles the boundary of condensed matter physics and plasma physics.
One might think that such states can never be created in a terrestrial setting. But, in fact, short laser pulses that are only femtoseconds (10-15 s, or a quadrillionth of a second) long are intense enough to recreate such conditions in a laboratory. Conventional physical models that describe such states typically assume that electrons become excited by the laser pulse attain equilibrium within tens of femtoseconds while the ions remain “cold.” However, in doing so, the non-equilibrium dynamics of the electrons are completely disregarded.
Atomic-level flyovers show how impact sites of high-energy ions pin potentially disruptive vortices to keep high-current superconductivity flowing. High-energy gold ions impact the crystal surface from above at the sites indicated schematically by dashed circles. Measurement of the strength of…
Among the many discoveries on matter at high pressure that garnered him the Nobel Prize in 1946, scientist Percy Bridgman discovered five different crystalline forms of water ice, ushering in more than 100 years of research into how ice behaves under extreme conditions.
One of the most intriguing properties of water is that it may become superionic when heated to several thousand degrees at high pressure, similar to the conditions inside giant planets like Uranus and Neptune. This exotic state of water is characterized by liquid-like hydrogen ions moving within a solid lattice of oxygen.
Since this was first predicted in 1988, many research groups in the field have confirmed and refined numerical simulations, while others used static compression techniques to explore the phase diagram of water at high pressure. While indirect signatures were observed, no research group has been able to identify experimental evidence for superionic water ice – until now.
In a paper published today in Nature Physics, a research team from Lawrence Livermore National Laboratory (LLNL), the University of California, Berkeley and the University of Rochester provides experimental evidence for superionic conduction in water ice at planetary interior conditions, verifying the 30-year-old prediction.
The Olympic Charter declares that winter sports must be practiced on snow or ice. Both are frozen forms of water, which despite its ubiquity, is one of the strangest substances around. In addition to its tendency to expand as it freezes, ice is inherently slippery, and no one’s quite certain yet why.
Most people have heard the theory that ice skating is possible due to high pressure melting the ice beneath the narrow blade. But realistically, pressure melting should only work for ice down to about -3.5 degrees Celsius. By contrast, the ideal temperatures for figure skating and ice hockey are -5.5 and -9 degrees Celsius, respectively. Melting due to friction might account for slipperiness a few more degrees below freezing, but it doesn’t explain why ice can be slippery when you’re just standing on it.
When physicist Michael Faraday suggested in 1850 that ice has a thin liquid-like layer at its surface, many discounted the theory. But modern experimental techniques and computer simulations have shown that Faraday was right. Ice has a liquid-like layer some 1 to 100 nanometers thick at its surface, and this layer persists to temperatures below -30 degrees Celsius. The process is known as surface pre-melting and what causes it is an area of active research for physical chemists. Current theories include hydrogen bonding and even quantum mechanical effects. (Image credit: AP Photo/B. Armangue; research credit: R. Rosenberg;Y. Li and G. Somorjai;F. Paesani and G. Voth)
This opens FYFD’s two-week series on the physics and fluid dynamics of the Winter Olympics. Stay tuned! - Nicole
Thesecond law of thermodynamics implies that there is a directionality to the flow of energy - that it will always move from a point of higher potential to a point of lower potential - and that as energy flows through a process, it becomes harder for us to use it - i.e., it is more difficult to convert into work.
This is something we know on an intuitive level - we know devices that do work produce heat. A motor shaft spinning will heat the air around it. But we know this only goes one way - heating the air won’t make the shaft spin. The upshot is that it is very easy to convert work to heat. Converting heat to work is much harder. In fact, if we want to convert heat to work, we need a special class of device to do it. This is called a heat engine.
The particulars of individual heat engines can vary quite a bit, but they usually involve the manipulation of some sort of fluid (referred to as the working fluid) through a repeating cycle. That said, all heat engines operate in the same basic way on a fundamental level. They take in heat from a high temperature source and convert some of it to work. The rest they expel to a lower temperature sink.
A couple of things to note about this diagram and heat sinks in general:
1.The work out is a net term - that is, the heat engine requires some work input to operate. The net work out is the difference between the work put into the device and the work it produces.
2.The first law of thermodynamics tells us that energy is conserved throughout this process, meaning that the net work out and the waste heat out must sum to the heat in. Or, put another way, you can figure out the net work out by looking at the difference between the heat in and the heat out.
Tesla is at the forefront of industrial battery technology research.
Electric cars are accelerating commercially. General Motors has already sold 12,000 models of its Chevrolet Bolt and Daimler announced in September 2017 that it is to invest $1bn to produce electric cars in the US, with Investment bank ING, meanwhile, predicts that European cars will go fully electric by 2035.
‘Batteries are a global industry worth tens of billions of dollars, but over the next 10 to 20 years it will probably grow to many hundreds of billions per year,’ says Gregory Offer, battery researcher at Imperial College London. ‘There is an opportunity now to invest in an industry, so that when it grows exponentially you can capture value and create economic growth.’
The big opportunity for technology disruption lies in extending battery lifetime, says Offer, whose team at Imperial takes market-ready or prototype battery devices into their lab to model the physics and chemistry going on inside, and then figures out how to improve them.
Lithium batteries, the battery technology of choice, are built from layers, each connected to a current connector and theoretically generating equivalent power, which flows out through the terminals. However, improvements in design of packs can lead to better performance and slower degradation.
Lithium batteries need to be adapted for electric vehicle use.Image: Public Domain Pictures
For many electric vehicles, cooling plates are placed on each side of the battery cell, but the middle layers get hotter and fatigue faster. Offer’s group cooled the cell terminals instead, because they are connected to every layer. ‘You want the battery operating warmish, not too hot and not too cold,’ he says.
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.
Natural microstructures in transparent wood are key to lighting & insulation advantages
Engineers at the A. James Clark School of Engineering at the University of Maryland (UMD) demonstrate in a new study that windows made of transparent wood could provide more even and consistent natural lighting and better energy efficiency than glass.
In a paper just published in the peer-reviewed journal Advanced Energy Materials, the team, headed by Liangbing Hu of UMD’s Department of Materials Science and Engineering and the Energy Research Center lay out research showing that their transparent wood provides better thermal insulation and lets in nearly as much light as glass, while eliminating glare and providing uniform and consistent indoor lighting. The findings advance earlier published work on their development of transparent wood.
The transparent wood lets through just a little bit less light than glass, but a lot less heat, said Tian Li, the lead author of the new study. “It is very transparent, but still allows for a little bit of privacy because it is not completely see-through. We also learned that the channels in the wood transmit light with wavelengths around the range of the wavelengths of visible light, but that it blocks the wavelengths that carry mostly heat,” said Li.
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.
Elemental metals usually form simple, close-packed crystalline structures. Though lithium (Li) is considered a typical simple metal, its crystal structure at ambient pressure and low temperature remains unknown.
Lawrence Livermore National Laboratory (LLNL) researchers recently came up with a technique to obtain structural information for Li at conditions where traditional crystallographic methods are insufficient. Using this methodology, a decades-long puzzle finally may be solved.
Li is the lightest metal and least dense solid element at ambient conditions. Li and its compounds have several industrial applications, including heat-resistant glass and ceramics, lithium grease lubricants, flux additives for iron, steel and aluminum production, lithium batteries and lithium-ion batteries. These uses consume more than three quarters of lithium production.
“The superconductivity of alkali metals, and Li, is an issue that has been debated for many years,” said Stanimir Bonev, LLNL lead author of a paper appearing in a recent edition of Proceedings of the National Academy of Sciences. “Only recently superconductivity in Li at ambient pressure was observed. But to understand the superconducting properties, it is essential to know the crystal structure.”
Using the X-ray laser European XFEL, a research team has investigated how water heats up under extreme conditions. In the process, the scientists were able to observe water that remained liquid even at temperatures of more than 170 degrees Celsius. The investigation revealed an anomalous dynamic behavior of water under these conditions. The results of the study, which are published in the Proceedings of the National Academy of Sciences(PNAS), are of fundamental importance for the planning and analysis of investigations of sensitive samples using X-ray lasers.
European XFEL, an international research facility, which extends from the DESY site in Hamburg to the neighboring town of Schenefeld in Schleswig-Holstein, is home to the most powerful X-ray laser in the world. It can generate up to 27 000 intense X-ray flashes per second. For their experiments, the researchers used series of 120 flashes each. The individual flashes were less than a millionth of a second apart (exactly 0.886 microseconds). The scientists sent these pulse trains into a thin, water-filled quartz glass tube and observed the reaction of the water.
“We asked ourselves how long and how strongly water can be heated in the X-ray laser and whether it still behaves like water,” explains lead author Felix Lehmkühler from DESY. “For example, does it still function as a coolant at high temperatures?” A detailed understanding of superheated water is also essential for a large number of investigations on heat-sensitive samples, such as polymers or biological samples.
Image SL8285 - Man wearing sunglasses, thermogram. A thermogram shows the variation in temperature on the surface of an object, measured by the long-wave infrared radiation it emits. The temperature scale is color-coded and runs from purple (coldest), through blue, green, yellow and orange to red (warmest).
A temperature chart for my fellow Americans who can’t do the Celsius-Fahrenheit equation from memory and for people in the civilized countries who’re too busy making fun of Fahrenheit to do the conversions themselves.
After a few days of summery warm weather, cold is rearing its ugly head again in Finland :( In some areas the temperature dropped below freezing point last night, Naruska (a village in North-East Finland) being the coldest place with -1.7 °C. Brrrrr….
According to the statistics of the Finnish Meteorological Institutes, the beginning of this summer has been the coolest in half a century. It does feel so!
