In theory, water and electric current will cause electrolysis and produce oxygen and hydrogen as the water breaks apart. In practice, doing it well can be tricky. [Relic] shows an efficient way to produce an electrolysis cell using a few plastic peanut butter jars and some hardware.
The only tricky point is that you need hardware made of steel and not zinc or other materials. Well, that and the fact that the gasses you produce are relatively dangerous.
Diamonds are nearly perfect crystals, but not totally perfect. The defects in these crystals give the stones their characteristic colors. But one type of defect, the NV — nitrogen-vacancy — center, can hold a particular spin, and you can change that spin with the correct application of energy. [Asianometry] explains why this is important in the video below.
Interestingly, even at room temperature, an NV center stays stable for a long time. Even more importantly, you can measure the spin nondestructively by detecting light emissions from the center.
Entangled photons are an ideal choice for large-scale networks employing quantum encryption or similar, as photons can use fiber-optical cables to transmit them. One issue with using existing commercial fiber-optic lines for this purpose is that these have imperfections which can disrupt photon entanglement. This can be worked around by delaying one member of the pair slightly, but this makes using the pairs harder. Instead, a team at New York-based startup Qunnect used polarization entanglement to successfully transmit and maintain thousands of photons over the course of weeks through a section of existing commercial fiber, as detailed in the recently published paper by [Alexander N. Craddock] et al. in PRX Quantum (with accompanying press release).
The entangled photons were created via spontaneous four-wave mixing in a warm rubidium vapor. This creates a photon with a wavelength of 795 nm and one with 1324 nm. The latter of which is compatible with the fiber network and is thus transmitted over the 34 kilometers. To measure the shift in polarization of the transmitted photos, non-entangled photons with a known polarization were transmitted along with the entangled ones. This then allowed for polarization compensation for the entangled photos by measuring the shift on the single photons. Overall, the team reported an uptime of nearly 100% with about 20,000 entangled photons transmitted per second.
As a proof of concept it shows that existing fiber-optical lines could in the future conceivably be used for quantum computing and encryption without upgrades.
Sometimes a paper in a scientific journal pops up that makes you do a triple-take, case in point being a recent paper by [Aren Boyaci] and [Arindam Banerjee] in Physical Review E titled “Transition to plastic regime for Rayleigh-Taylor instability in soft solids”. The title doesn’t quite do their methodology justice — as the paper describes zipping a container filled with mayonnaise along a figure-eight track to look at the surface transitions. With the paper paywalled and no preprint available, we have to mostly rely the Lehigh University press releases pertaining to the original 2019 paper and this follow-up 2024 one.
Rayleigh-Taylor instability (RTI) is an instability of an interface between two fluids of different densities when the less dense fluid acts up on the more dense fluid. An example of this is water suspended above oil, as well as the expanding mushroom cloud during a explosion or eruption. It also plays a major role in plasma physics, especially as it pertains to nuclear fusion. In the case of inertial confinement fusion (ICF) the rapidly laser-heated pellet of deuterium-tritium fuel will expand, with the boundary interface with the expanding D-T fuel subject to RTI, negatively affecting the ignition efficiency and fusion rate. A simulation of this can be found in a January 2024 research paper by [Y. Y. Lei] et al.
As a fairly chaotic process, RTI is hard to simulate, making a physical model a more ideal research subject. Mayonnaise is definitely among the whackiest ideas here, with other researchers like [Samar Alqatari] et al. as published in Science Advances opting to use a Hele-Shaw cell with dyed glycerol-water mixtures for a less messy and mechanically convoluted experimental contraption.
What’s notable here is that the Lehigh University studies were funded by the Lawrence Livermore National Laboratory (LLNL), which explains the focus on ICF, as the National Ignition Facility (NIF) is based there.
This also makes the breathless hype about ‘mayo enabling fusion power’ somewhat silly, as ICF is even less likely to lead to net power production, far behind even Z-pinch fusion. That said, a better understanding of RTI is always welcome, even if one has to question the practical benefit of studying it in a container of mayonnaise.
A team at MIT led by [Professor Douglas Hart] has discovered a new, potentially revelatory method for the generation of hydrogen. Using seawater, pure aluminum, and components from coffee grounds, the team was able to generate hydrogen at a not insignificant rate, getting the vast majority of the theoretical yield of hydrogen from the seawater/aluminum mixture. Though the process does use indium and gallium, rare and expensive materials, the process is so far able to recover 90% of the indium-gallium used which can then be recycled into the next batch. Aluminum holds twice as much energy as diesel, and 40x that of Li-Ion batteries. So finding a way to harness that energy could have a huge impact on the amount of fossil fuels burned by humans!
Pure, unoxidized aluminum reacts directly with water to create hydrogen, as well as aluminum oxyhydroxide and aluminum hydroxide. However, any aluminum that has had contact with atmospheric air immediately gets a coating of hard, unreactive aluminum oxide, which does not react in the same way. Another issue is that seawater significantly slows the reaction with pure aluminum. The researchers found that the indium-gallium mix was able to not only allow the reaction to proceed by creating an interface for the water and pure aluminum to react but also coating the aluminum pellets to prevent further oxidization. This worked well, but the resulting reaction was very slow.
Apparently “on a lark” they added coffee grounds. Caffeine had already been known to act as a chelating agent for both aluminum and gallium, and the addition of coffee grounds increased the reaction rate by a huge margin, to the point where it matched the reaction rate of pure aluminum in deionized, pure water. Even with wildly varying concentrations of caffeine, the reaction rate stayed high, and the researchers wanted to find out specifically which part of the caffeine molecule was responsible. It turned out to be imidazole, which is a readily available organic compound. The issue was balancing the amount of caffeine or imidazole added versus the gallium-indium recovery rate — too much caffeine or imidazole would drastically reduce the recoverable amount of gallium-indium.
Continue reading “Hydrogen Generation With Seawater, Aluminum, And… Coffee?”
Researchers demonstrate sustainable 3D printing by using poly(N-isopropylacrylamide) solutions (PNIPAM), which speedily and reliably turn solid by undergoing a rapid phase change when in a salt solution.
This property has been used to 3D print objects by using a syringe tip as if it were a nozzle in a filament-based printer. As long as the liquid is being printed into contact with a salt solution, the result is a polymer that solidifies upon leaving the syringe.
What’s also interesting is that the process by which the PNIPAM-based solutions solidify is entirely reversible. Researchers demonstrate printing, breaking down, then re-printing, which is an awfully neat trick. Finally, by mixing different additives in with PNIPAM, one can obtain different properties in the final product. For example, researchers demonstrate making conductive prints by adding carbon nanotubes.
While we’ve seen the concept of printing with liquids by extruding them into a gel bath or similar approach, we haven’t seen a process that prides itself on being so reversible before. The research paper with all the details is available here, so check it out for all the details.
Initially only seeing brief popular use as the filament in incandescent lighting, carbon fibers (CF) experienced a resurgence during the 20th century as part of composite materials that are lighter and stronger than materials like steel and aluminium, for use in aircraft, boats and countless more applications. This rising popularity has also meant that the wider population is now exposed to fragments of CF, both from using CF-based products as well as from mechanically processing CF materials during (hobby) projects.
It is this popularity that has also led to the addition of short CF sections to FDM 3D printing filaments, where they improve the mechanical properties of the printed parts. However, during subsequent mechanical actions such as sanding, grinding, and cutting, CF dust is created and some fraction of these particles are small enough to be respirable. Of these, another fraction will bypass the respiratory system’s dust clearing mechanisms, to end up deep inside the lungs. This raises the question of whether CF fragments can be carcinogenic, much like the once very popular and very infamous example of asbestos mineral fibers.
Continue reading “On Carbon Fiber Types And Their Carcinogenic Risks”
