Metals Tech

A popular approach for the 3D printing of metals is to pass a laser spot over a layer of powder, which then melts and fuses together. The printer repeats that process for additional layers of powder to build up the desired part. The higher the density of laser power, the faster the printing process. The problem is that intense laser illumination can also introduce gas pockets into the material and degrade the mechanical properties. Just what constitutes too high a laser power density has been a matter of trial and error until now. By imaging with synchrotron x rays the formation of vapor pockets in irradiated metal, Anthony Rollett of Carnegie Mellon University, Tao Sun of Argonne National Laboratory, and their colleagues have found a simple rule to prevent laser-induced defects.

Using lasers to print 3D metal objects resembles laser welding, which operates in one of two modes depending on the power density of the laser. In conduction mode, shown in the left panel of the figure, a laser melts a shallow, hemispherical region of the metal. In keyhole mode (right panel), a laser with higher power density penetrates deeper and boils the material until a narrow vapor pocket is formed. The same modes occur in 3D printing when the laser melts the metal powder. To avoid the introduction of pores in the final product, manufacturers aim to remain in conduction mode. But in the absence of sophisticated imaging techniques, they won’t know which mode they are in until after the printing is done.

Using ultrahigh-speed synchrotron x-ray imaging, the researchers identified the dynamics of the transition from conduction to keyhole mode for both a stationary and a moving laser. For a stationary laser, all power densities above a threshold resulted in a keyhole mode with vapor holes of the same general shape. Sun and his colleagues also observed an intermediate power density regime (center panel) that was out of conduction mode and characterized by a fluctuating, conical vapor pocket. For a moving laser, the vapor depression’s shape varied substantially with the power and velocity of the laser. But the transition out of conduction mode was still straightforward: In power–velocity space, the transition is defined by a straight line, with higher power thresholds for faster laser velocities.

What was the biggest surprise? Nearly all the commonly used combinations of laser power and velocity are not in the conduction mode regime. Manufacturers had previously blamed the resulting defects and inhomogeneities on the type of metal powder or the laser power alone. The linear dependence introduced by Rollett and his colleagues offers a simple tool for manufacturers to reevaluate, improve, and potentially speed up their 3D printing.

Despite the South Korean government’s ambitious plans to create a hydrogen economy this year, oil refiners appear to be taking a passive stance, citing questions over profitability.

In January, the government announced its road map to boost the hydrogen economy, produce 6.2 million fuel cell vehicles by 2040 and eventually become the largest hydrogen car producer in the world.

The government said 50,000 tons of byproduct hydrogen are currently available to fuel 250,000 hydrogen cars. Byproduct hydrogen is made in the process of refining oil and making petrochemicals and steel.

In Korea, four major oil refining companies — S-Oil, GS Caltex, Hyundai Oilbank and SK Innovation — produce hydrogen byproducts through oil refining and petrochemical facilities in which they recently invested.

But some industry insiders say hydrogen byproducts from the oil refiners may not be enough to use for fueling hydrogen cars because the firms began to diversify their business into non-oil refining businesses, such as rechargeable batteries.

SK Innovation, which is the nation’s largest oil-refining firm and has recently expanded into petrochemicals, said, “Although we produce hydrogen byproducts, we have to reuse them for the chemical process, and it is significantly insufficient.”

The government said the estimate of 50,000 tons was made based on the past industry data but it can be changed based on demand and supply.

Kim Pyung-joong, an executive of the Korea Petrochemical Industry Association, said hydrogen byproducts could satisfy the government’s needs in the short term, but things may change in the future, as it is still “not generous” because byproducts are not something that can be produced arbitrarily.

Last week, Hyundai Motor announced it would invest 8 trillion won to build 500,000 hydrogen cars by 2030.

Another insider of an oil refining company, who asked for anonymity, said, “It seems the government began the move without fully having related infrastructure. Since the technology to produce hydrogen is in the early stages, the nation may have turn to imported fuel if it wants to push the drive.”

Charging stations are also another obstacle.

Despite the world’s first title, Korea is still behind in the distribution of fuel-cell cars due to the lack of infrastructure for producing, storing and charging fuel cells. As of October 2018, 5,715 cars were sold in the US, 3,359 cars were distributed in Japan, 926 cars in Europe and 794 cars in Korea.

There are currently only nine stations nationwide, with only two in Seoul, though the government aims to produce 4,000 hydrogen cars this year. This is compared to Japan, which is a rival in hydrogen. It has more than 100 charging stations.

Oil refining companies are hesitant to jump into the hydrogen station business due to uncertainties and high operating costs.

To create hydrogen-filling stations, there needs to be tanks to store hydrogen and reforming facilities to produce hydrogen and large sites. Running hydrogen tanks also generates high power costs.

“Because oil-refining companies do not produce hydrogen, they first have to find the hydrogen supplier and then they also need to find large site to have tanks in cities where this is hard to find. It is not easy to jump into the business because profit is not guaranteed,” said an oil-refining insider.

Shin Jae-haeng, chief operating officer of H2Korea, said, “Korea’s hydrogen technologies are concentrated on automobiles, and we lack technologies for production and storage hydrogen. It is necessary to have systematic research and development to build a hydrogen eco-system in the longer term.”

The debate about alternative fuels for cars risks coalescing into a them-and-us conversation depending on your thoughts about battery electric power. This is a pity as it’s causing many other alternative fuel options to be marginalised or forgotten about altogether by drivers.

However, while plug-in electric and hybrid cars take centre stage, for the time being, there’s also a great deal of research and development ongoing inside car companies with fuels such as hydrogen, bioethanol, LPG (liquified petroleum gas) and even steam.

Some of these other sources of propulsion for cars have been around a long time, but let’s not forget that electric cars were only beaten to mass market demand in the early 20th century because of cheap, widely available petrol and the greater range it offered.

Hydrogen fuel

Now, the internal combustion engine in its current form is facing an environmental and regulatory deadline, such as the UK’s stated intention to outlaw all new car sales of petrol- or diesel-only vehicles by 2040. This has focused attention on alternative fuels and, given concerns about electricity infrastructure being able to cope with an all-electric car park, means the time is ripe for a broader offer of fuels.

Hydrogen is the most commonly touted substitute for fossil fuels as it could be sold from filling stations in the same way petrol is. A big advantage for hydrogen is drivers don’t have to make any significant cultural shift in the way they run their car or fill it with fuel.

Environmentally, hydrogen has the huge appeal of producing nothing more toxic than clean water when used as a fuel. This is because the fuel cell it powers to make electricity combines the hydrogen with oxygen from the atmosphere, so it effectively works as an onboard generator to power the car rather than having to store electricity in large, heavy batteries and draw its energy from a plug-in source. This is what Hyundai is banking on with its Nexo and follows the Honda FCX Clarity and Toyota Mirai’s lead.

There are downsides to hydrogen as a fuel for vehicles. For starters, there is a very small network of filling stations, even in countries like Germany that have experimented and embraced it more than most. The cost of producing hydrogen in commercially sufficient quantities is expensive too unless sustainable, renewable and low-cost electricity is available for its manufacture. Lastly, the poor availability of this fuel means few car makers offer hydrogen-powered models and that makes those out there very expensive, so there’s a chicken-and-egg situation of who will invest first – the fuel provider or vehicle maker?

Autogas

This isn’t an issue with LPG, often called Autogas in continental Europe where it’s very popular. It’s been around a long time, has a proven record of cutting fuel bills as it’s much less heavily taxed than petrol or diesel, and most internal combustion engines can be converted to run on it. Along with compressed natural gas and propane that are very similar to LPG, it emits around 120 times less fine particulates than diesel, as well as producing less carbon dioxide.

Why, then, has LPG not gained more of a foothold? This is mainly due to LPG having a very ‘lean’ burn compared to petrol, so you have to combust more of it to get the same power. Most LPG-fuelled vehicles use it as an additional fuel alongside petrol, switching to LPG when the car is up to operating temperature. While fuel duty is low for LPG, it’s a worthwhile consideration as a fuel, though there are still tailpipe emissions with it.

Biodiesel

The same is true of biodiesel, which is made from crops such as rapeseed by the process of transesterification. It does require some energy to produce biodiesel, but the majority of carbon dioxide it emits when used in cars is offset by the plants grown to produce it. The bigger stumbling block is biodiesel costs more per litre to make than crude oil-derived diesel, which puts off many users.

Like biodiesel, alcohol-based fuels such as methanol, butanol and ethanol are made from sustainable crops. Unlike biodiesel, these fuels consume more greenhouse gasses as the crops grow than are emitted when the fuel is burnt in an engine. A lower energy density does mean you need to burn more alcohol to get the same given power as petrol. At present, only a handful of racing cars use pure alcohol for power, but it is available as E85, where 85% of the mix is ethanol.

Other fuels being worked on include nitrogen, water and solar, such as the One from Dutch firm Lightyear. It’s due on sale in 2020 with a claimed range of 500 miles and the company says it only needs to be charged from a socket once every few months.

Alongside the handful of hydrogen cars currently on sale like the Hyundai Nexo and Toyota Mirai, the Lightyear One is the only car looking for a different path to plug-in battery electric vehicles at present. What is certain, regardless of the fuel powering it, is the car will be with us for a very long time to come.

A (now) teenager from Memphis, Tennessee, might be the youngest person to have built a working fusion reactor. Jackson Oswalt reported the measurements of his experiment to the Open Source Fusor Research Consortium forum, where he got both the inspiration and suggestion for how to build such a device.

The term nuclear reactor might evoke images of radioactive material and a huge facility, but the one built by Oswalt is not like that. It is a fusion reactor, rather than a fission one that uses uranium to produce electricity. In the fusion reactor, hydrogen atoms are turned into a plasma and then pushed together until they become different atoms. In Oswalt’s case, he fused deuterium, a special type of hydrogen with a neutron and a proton in its nucleus.

“For those that haven’t seen my recent posts, it will come as a major surprise that I would even consider believing I had achieved fusion. However, over the past month, I have made an enormous amount of progress resulting from fixing major leaks in my system. I now have results that I believe to be worthy,” Oswalt wrote in a post on February 1, 2018.

The design and construction of this mini-reactor was not easy or cheap. It took Oswalt roughly a year and something between $8,000 and $10,000 to get it together and make it work. Oswalt stated that he achieved fusion on January 19, January 30, and January 31. The fusion of the deuterium atoms led to the release of neutrons – hallmarks that Oswalt and the Fusor verifiers are interested in spotting.

“You have to jump through the right hoops, and we have to believe you and see what you’ve done,” Richard Hull, a verifier with the research consortium and an administrator for its website, told Fox News. He regards Oswalt as the youngest in America and possibly the world to achieve such a feat. The previous record holder was Taylor Wilson, who achieved nuclear fusion in 2008 when he was 14.

Nuclear fusion is the physical process that powers every star in the Universe. It also holds the promise for clean, unlimited energy. As Oswalt demonstrated, we can make fusion happen, but what we are still struggling with is the ability to have sustained reactions that release more energy than we put in.

Filed Under: Energy Tech

MIT researchers have developed a novel cryptography circuit that can be used to protect low-power “internet of things” (IoT) devices in the coming age of quantum computing.

Quantum computers can in principle execute calculations that today are practically impossible for classical computers. Bringing quantum computers online and to market could one day enable advances in medical research, drug discovery, and other applications. But there’s a catch: If hackers also have access to quantum computers, they could potentially break through the powerful encryption schemes that currently protect data exchanged between devices.

Today’s most promising quantum-resistant encryption scheme is called “lattice-based cryptography,” which hides information in extremely complicated mathematical structures. To date, no known quantum algorithm can break through its defenses. But these schemes are way too computationally intense for IoT devices, which can only spare enough energy for simple data processing.

In a paper presented at the recent International Solid-State Circuits Conference, MIT researchers describe a novel circuit architecture and statistical optimization tricks that can be used to efficiently compute lattice-based cryptography. The 2-millimeter-squared chips the team developed are efficient enough for integration into any current IoT device.

The architecture is customizable to accommodate the multiple lattice-based schemes currently being studied in preparation for the day that quantum computers come online. “That might be a few decades from now, but figuring out if these techniques are really secure takes a long time,” says first author Utsav Banerjee, a graduate student in electrical engineering and computer science. “It may seem early, but earlier is always better.”

Moreover, the researchers say, the circuit is the first of its kind to meet standards for lattice-based cryptography set by the National Institute of Standards and Technology (NIST), an agency of the U.S. Department of Commerce that finds and writes regulations for today’s encryption schemes.

Joining Banerjee on the paper are Anantha Chandrakasan, dean of MIT’s School of Engineering and the Vannevar Bush Professor of Electrical Engineering and Computer Science, and Abhishek Pathak of the Indian Institute of Technology.

Efficient sampling

In the mid-1990s, MIT Professor Peter Shor developed a quantum algorithm that can essentially break through all modern cryptography schemes. Since then, NIST has been trying to find the most secure postquantum encryption schemes. This happens in phases; each phase winnows down a list of the most secure and practical schemes. Two weeks ago, the agency entered its second phase for postquantum cryptography, with lattice-based schemes making up half of its list.

In the new study, the researchers first implemented on commercial microprocessors several NIST lattice-based cryptography schemes from the agency’s first phase. This revealed two bottlenecks for efficiency and performance: generating random numbers and data storage.

Generating random numbers is the most important part of all cryptography schemes, because those numbers are used to generate secure encryption keys that can’t be predicted. That’s calculated through a two-part process called “sampling.”

Sampling first generates pseudorandom numbers from a known, finite set of values that have an equal probability of being selected. Then, a “postprocessing” step converts those pseudorandom numbers into a different probability distribution with a specified standard deviation — a limit for how much the values can vary from one another — that randomizes the numbers further. Basically, the random numbers must satisfy carefully chosen statistical parameters. This difficult mathematical problem consumes about 80 percent of all computation energy needed for lattice-based cryptography.

After analyzing all available methods for sampling, the researchers found that one method, called SHA-3, can generate many pseudorandom numbers two or three times more efficiently than all others. They tweaked SHA-3 to handle lattice-based cryptography sampling. On top of this, they applied some mathematical tricks to make pseudorandom sampling, and the postprocessing conversion to new distributions, faster and more efficient.

They run this technique using energy-efficient custom hardware that takes up only 9 percent of the surface area of their chip. In the end, this makes the process of sampling two orders of magnitude more efficient than traditional methods.

Splitting the data

On the hardware side, the researchers made innovations in data flow. Lattice-based cryptography processes data in vectors, which are tables of a few hundred or thousand numbers. Storing and moving those data requires physical memory components that take up around 80 percent of the hardware area of a circuit.

Traditionally, the data are stored on a single two-or four-port random access memory (RAM) device. Multiport devices enable the high data throughput required for encryption schemes, but they take up a lot of space.

For their circuit design, the researchers modified a technique called “number theoretic transform” (NTT), which functions similarly to the Fourier transform mathematical technique that decomposes a signal into the multiple frequencies that make it up. The modified NTT splits vector data and allocates portions across four single-port RAM devices. Each vector can still be accessed in its entirety for sampling as if it were stored on a single multiport device. The benefit is the four single-port REM devices occupy about a third less total area than one multiport device.

“We basically modified how the vector is physically mapped in the memory and modified the data flow, so this new mapping can be incorporated into the sampling process. Using these architecture tricks, we reduced the energy consumption and occupied area, while maintaining the desired throughput,” Banerjee says.

The circuit also incorporates a small instruction memory component that can be programmed with custom instructions to handle different sampling techniques — such as specific probability distributions and standard deviations — and different vector sizes and operations. This is especially helpful, as lattice-based cryptography schemes will most likely change slightly in the coming years and decades.

Adjustable parameters can also be used to optimize efficiency and security. The more complex the computation, the lower the efficiency, and vice versa. In their paper, the researchers detail how to navigate these tradeoffs with their adjustable parameters. Next, the researchers plan to tweak the chip to run all the lattice-based cryptography schemes listed in NIST’s second phase.

The work was supported by Texas Instruments and the TSMC University Shuttle Program.

McMaster researchers, working with partners at other universities, have created a motion-powered, fireproof sensor that can track the movements of firefighters, steelworkers, miners and others who work in high-risk environments where they cannot always be seen.

The low-cost sensor is about the size of a button-cell watch battery and can easily be incorporated into the sole of a boot or under the arm of a jacket—wherever motion creates a pattern of constant contact and release to generate the power the sensor needs to operate.

The sensor uses triboelectric, or friction-generated, charging, harvesting electricity from movement in much the same way that a person in socks picks up static electricity walking across a carpet.

The sensor can track the movement and location of a person in a burning building, a mineshaft or other hazardous environment, alerting someone outside if the movement ceases.

The key material in the sensor, a new carbon aerogel nanocomposite, is fireproof, and the device never needs charging from a power source.

“If somebody is unconscious and you are unable to find them, this could be very useful,” says Ravi Selvaganapathy, a professor of mechanical engineering who oversaw the project. “The nice thing is that because it is self-powered, you don’t have to do anything. It scavenges power from the environment.”

The research team—from McMaster, UCLA and University of Chemistry and Technology Prague—describes the new sensor in a paper published today in the journal Nano Energy.

The researchers explain that previously developed self-powered sensors have allowed similar tracking, but their materials break down at high temperatures, rendering them useless,

A self-powered sensor is necessary in extreme heat because most batteries also break down in high temperatures. The researchers have successfully tested the new technology at temperatures up to 300C—the temperature where most types of wood start to burn—without any loss of function.

“It’s exciting to develop something that could save someone’s life in the future,” said co-author Islam Hassan, a McMaster Ph.D. student in mechanical engineering. If firefighters use our technology and we can save someone’s life, that would be great.”

The researchers hope to work with a commercial partner to get the technology to market.