tungsten

17 Articles

Laser Etches Solar Absorbing Material

February 6, 2020 by 19 Comments

Having a laser cutter these days isn’t a big deal. But [Chunlei Guo], a professor at the University of Rochester, has a powerful femto-second pulse laser and used it to create what might be the perfect solar absorber. You can see a video about the work, below.

It stands to reason that white materials reflect most light and therefore absorb less energy than black materials — this is part of what makes a radiometer work. Tungsten, in particular, is a good metal for absorbing solar power, but this new laser treatment — which builds nanostructures on the surface of the metal — increases efficiency by 130% compared to untreated tungsten.

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A Beginner’s Guide To X-Ray Crystallography

January 21, 2020 by 6 Comments

In graduate school, I had a seminar course where one of the sections was about X-ray crystallography. I was excited, because being able to discern the three-dimensional structure of macromolecules just by shining X-rays on them seemed like magic to me. And thanks to a lackluster professor, after the section it remained just as much of a mystery.

If only I’d had [Steve Mould] as a teacher back then. His latest video does an outstanding job explaining X-ray crystallography by scaling up the problem considerably, using the longer wavelength of light and a macroscopic target. He begins with a review of diffraction patterns, those alternating light and dark bands of constructive and destructive interference that result when light shines on two closely spaced slits — the famous “Double-Slit Experiment” that showed light behaves both as a particle and as a wave and provided our first glimpse of quantum mechanics. [Steve] then doubled down on the double-slit, placing another pair of slits in the path of the first. This revealed a grid of spots rather than alternating bands, with the angle between axes dependent on the angle of the slit pairs to each other.

Photograph 51, an X-ray crystallogram of the B-form of DNA, by Gosling and Franklin, 1952. Source: Wikipedia

 

To complete the demonstration, [Steve] then used diffraction to image the helical tungsten filament of an incandescent light bulb. Shining a laser through the helix resulted in a pattern bearing a striking resemblance to what’s probably the most famous X-ray crystallogram ever: [Rosalind Franklin]’s portrait of DNA. It all makes perfect sense, and it’s easy to see how the process works when scaled down both in terms of the target size and the wavelength of light used to probe it.

Hats off to [Steve] for making something that’s ordinarily complex so easily understandable, and for filling in a long-standing gap in my knowledge.

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[Ben Krasnow] Builds A Mass Spectrometer

December 4, 2019 by 31 Comments

One of the features that made Scientific American magazine great was a column called “The Amateur Scientist.” Every month, readers were treated to experiments that could be done at home, or some scientific apparatus that could be built on the cheap. Luckily, [Ben Krasnow]’s fans remember the series and urged him to tackle a build from it: a DIY mass spectrometer. (Video, embedded below the break.)

[Ben] just released the video below showing early experiments with a copper tube contraption that was five months in the making; it turns out that analytical particle physics isn’t as easy as it sounds. The idea behind mas spectrometry is to ionize a sample, accelerate the ions as they pass through a magnetic field, and measure the deflection of the particles as a function of their mass-to-charge ratio. But as [Ben] discovered, the details of turning a simple principle into a working instrument are extremely non-trivial.

His rig uses filaments extracted from carefully crushed incandescent lamps to ionize samples of potassium iodide chloride; applied to the filament and dried, the salt solution is ionized when the filament is heated. The stream of ions is accelerated by a high-voltage field and streamed through a narrow slit formed by two razor blades. A detector sits orthogonal to the emitter across a powerful magnetic field, with a high-gain trans-impedance amplifier connected. With old analog meters and big variacs, the whole thing has a great mad scientist vibe to it that reminds us a bit of his one-component interferometer setup.

[Ben]’s data from the potassium sample agreed with expected results, and the instrument is almost sensitive enough to discern the difference between two different isotopes of potassium. He promises upgrades to the mass spec in the future, including perhaps laser ionization of the samples. We’re looking forward to that.

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Modified Tombstone Welder Contains A Host Of Hacks

September 12, 2019 by 30 Comments

State-of-the-art welding machines aren’t cheap, and for good reason: pushing around that much current in a controlled way and doing it over an entire workday takes some heavy-duty parts. There are bargains to be found, though, especially in the most basic of machines: AC stick welders. The familiar and aptly named “tombstone” welders can do the business, and they’re a great tool to learn how to lay a bead.

Tombstones are not without their drawbacks, though, and while others might buy a different welder when bumping up against those limits, [Greg Hildstrom] decided to hack his AC stick welder into an AC/DC welder with TIG. He details the panoply of mods he made to the welder, from a new 50 A cordset made from three extension cords where all three 12 gauge wires in each cord are connected together to make much larger effective conductors, to adding rectifiers and a choke made from the frame of a microwave oven transformer to produce DC output at the full 225 A rating. By the end of the project the tombstone was chock full of hacks, including a homemade foot pedal for voltage control, new industry-standard connectors for everything, and with the help of a vintage Lincoln “Hi-Freq” controller, support for TIG, or tungsten inert gas welding. His blog post shows some of the many test beads he’s put down with the machine, and the video playlist linked below shows highlights of the build.

This isn’t [Greg]’s first foray into the world of hot metal. A few years back we covered his electric arc furnace build, powered by another, more capable welder.

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X-Rays Are The Next Frontier In Space Communications

May 6, 2019 by 90 Comments

Hundreds of years from now, the story of humanity’s inevitable spread across the solar system will be a collection of engineering problems solved, some probably in heroic fashion. We’ve already tackled a lot of these problems in our first furtive steps into the wider galaxy. Our engineering solutions have taken humans to the Moon and back, but that’s as far as we’ve been able to send our fragile and precious selves.

While we figure out how to solve the problems keeping us trapped in the Earth-Moon system, we’ve sent fleets of robotic emissaries to do our exploration by proxy, to make the observations we need to frame the next set of engineering problems to be solved. But as we reach further out into the solar system and beyond, our exploration capabilities are increasingly suffering from communications bottlenecks that restrict how much data we can ship back to Earth.

We need to find a way to send vast amounts of data back as quickly as possible using as few resources as possible on both ends of the communications link. Doing so may mean turning away from traditional radio communications and going way, way up the dial and developing practical means for communicating with X-rays.

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Bask In The Warm Glow Of DIY Incandescent Bulbs

September 26, 2018 by 15 Comments

With most of the apparatus and instruments we now take for granted yet to be developed, the early pioneers of the Electric Age had to bring a lot to the lab besides electrical skills. Machining, chemistry, and metallurgy were all basic skills that the inventor either had to have or hire in. Most of these skills still have currency of course, but one that was once crucial – glassblowing – has sadly fallen into relative obscurity.

There are still practitioners of course, like [2SC1815] who is learning how to make homemade incandescent light bulbs. The Instructable is in both English and Japanese, and the process is explained in some detail. Basic supplies include soda-lime glass tubing and pre-coiled tungsten filaments. Support wires are made from Dumet, an alloy of iron, nickel, and cobalt with an oxidized copper cladding which forms a vacuum-tight seal with molten glass. The filament is crimped to the Dumet leads and pinched into a stem of glass tubing. A bulb is blown in another piece of tubing and the two are welded together, evacuated with a vacuum pump, and sealed. The bulbs are baked after sealing to drive off any remaining water vapor. The resulting bulbs have a cheery glow and a rustic look that we really like.

Of course, it’s not a huge leap from DIY light bulbs to making your own vacuum tubes. That’s how [Dalibor Farny] got started on his handmade Nixie business, after all.

Mechanisms: The Reed Switch

March 1, 2018 by 75 Comments

Just about everywhere you go, there’s a reed switch nearby that’s quietly going about its work. Reed switches are so ubiquitous that you’re probably never more than a few feet away from one at any given time, especially at home or in the car. You might have them on your doors and windows as part of a burglar alarm system. They keep your washing machine from running when the lid is open, and they put your laptop to sleep when you close the lid. They know if the car has enough brake fluid and whether or not your seat belt is fastened.

Reed switches are interesting devices with a ton of domestic and industrial applications. We call them switches, but they’re also sensors. In fact, they only do the work of a switch while they can sense a magnetic field. They are capable of switching AC or DC at low and high voltages, but they don’t need electricity to work. Since they’re sealed in glass, they are impervious to dirt, dust, corrosion, temperature swings, and explosive environments. They’re cheap, they’re durable, and in low-current applications they can last for about a billion actuations.

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