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Arc-Wind Tunnel to Test the Heat Resistance of Carbon Fiber Reinforced Ultra-High-Temperature Ceramic Matrix Composites

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As far as space shuttles and high-speed vehicles are concerned, wide usage has been done in carbon fiber-reinforced ultra-high-temperature ceramic (UHTC) matrix composites. But these composites experience an absence of oxidation resistance.

Researchers from the Tokyo University of Science evaluated the utility of C/UHTCMC at temperatures above 2000 degrees Celcius using arc-wind tunnel testing (pictured above). These results show degradation of the composite at high temperatures, which is an important result for the manufacture of advanced space shuttle orbiters.

In recent times, scientists from Japan tested the heat resistance of such composites at very high temperatures, thereby offering knowledge of the alterations required to avoid UHTC degradation. Their study findings could exhibit huge impacts on the manufacture of space shuttle orbiters.

Carbon fiber-reinforced carbon (C/C) is a composite material made of carbon fiber reinforced in a matrix of graphite or glassy carbon. It is ideally known as the best material utilized in hypersonic vehicles and space shuttle orbiters, which cruise at speeds surpassing Mach 5.

Since the 1970s, it has also been utilized in the brake system in Formula One racing cars. Although C/C exhibits outstanding mechanical properties at high temperatures and inert atmospheres, it lacks oxidation resistance in such conditions, thereby restricting its extensive use.

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Scientists have discovered that ultra-high-temperature ceramics (UHTCs), including transition metal carbides and diborides, display good oxidation resistance. In earlier studies, zirconium-titanium (Zr-Ti) alloy infiltration has displayed encouraging outcomes for enhancing the heat resistance of carbon fiber-reinforced UHTC matrix composites (C/UHTCMCs). But, their use at high temperatures (>2000 ℃) is yet to be identified.

Set against this backdrop, a research team from Japan has assessed the possible utility of Zr-Ti alloy-infiltrated C/UHTCMCs at temperatures above 2000 ℃.

Their study, headed by Junior Associate Professor Ryo Inoue from Tokyo University of Science (TUS), was reported in the Journal of Materials Science and made available online on October 27th, 2022.

The research team comprised Mr. Noriatsu Koide and Assistant Professor Yutaro Arai from TUS, Professor Makoto Hasegawa from Yokohama National University, and Dr. Toshiyuki Nishimura from the National Institute for Materials Science.

Speaking of the motive behind their study,

The research is an extension of the research and development of ceramics and ceramics-based composite materials. In recent years, we have received inquiries from several manufacturers of heavy industries regarding materials that can be used at temperatures above 2000 °C. We have also started to work with these manufacturers to develop new materials.

Ryo Inoue, Junior Associate Professor, Tokyo University of Science

The C/UHTCMC was manufactured utilizing melt infiltration, the most affordable method to fabricate such materials. To study the material’s applicability, three kinds of C/UHTCMCs were fabricated with three various alloy compositions.

The three alloy compositions utilized altered the atomic ratios of Zr: Ti. For the heat resistance to be characterized, the team utilized a technique known as arc-wind tunnel testing. This technique reveals the material to extremely high enthalpy airflow within a tunnel. This is similar to conditions that spacecraft tend to experience while re-entering the air.

The research group discovered that the amount of Zr present in the alloy exhibited a powerful effect on the degradation of the composite for all temperatures. This results from the thermodynamic choice for the oxidation of Zr-rich carbides than the Ti-rich carbides.

Furthermore, the Zr and Ti oxides developed on the composite surface avoided additional oxidation, and the oxide composition relied on the composition of the infiltrated alloys. Thermodynamic analysis disclosed that the oxides developed on the composite surface were composed of ZrO2, ZrTiO4, and TiO2 solid solutions.

At temperatures exceeding 2000 ℃, the samples’ thickness and weight are increased with the Zr content of the composites following the arc-wind tunnel tests. Also, the team noted that the melting point of the surface oxides went high as the Zr content increased.

For temperatures above 2600 ℃, the only oxides developed were liquid-phase, and it needs a thermodynamic design of the matrix composition to avoid the recession of UHTC composites.

We have successfully studied the degradation of C/UHTCMC at temperatures above 2000 ℃ using thermodynamic analysis. We have also shown that the matrix design needs modification to prevent the degradation of the composites. Our research has the potential to contribute to the realization of ultra-high-speed passenger aircraft, re-entry vehicle, and other hypersonic vehicles.

Ryo Inoue, Junior Associate Professor, Tokyo University of Science

Such outcomes could exhibit essential impacts on the production of high-speed vehicles and sophisticated space shuttle orbiters.

Journal Reference:

Koide, N., et al. (2022) Degradation of carbon fiber-reinforced ultra-high-temperature ceramic matrix composites at extremely high temperature using arc-wind tunnel tests. Journal of Materials Science. doi.org/10.1007/s10853-022-07861-x.

Source: https://www.tus.ac.jp/en/

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Q&A — Canadian astronaut Jeremy Hansen on all things space – CBC.ca

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Sunsets on the moon, the human spirit, and more 

If you could ask an astronaut any question about space, what would your question be?

Back in October 2023, kids had the opportunity to do just that during a screening of a documentary called Space Explorers: Moonrise on the ISS at Hot Docs in Toronto.

CBC Kids News contributor Ainara Alleyne sat down with Canadian astronaut Jeremy Hansen, who will be travelling to orbit the moon in September 2025.

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She asked some questions of her own and some from the audience.

So while we eagerly await for the first Canadian in history to orbit the moon, let’s find out what he has to say about space travel, human resilience and more. 

This interview has been edited for length and clarity. 

Q: What’s the most important quality in an astronaut? 

The most important thing is teamwork, by far. 

When we’re looking for astronauts, we go to great depths to look into the soul of the human and make sure this isn’t someone who just cares about themselves. Yes, they have all the skills we need and work hard, but they care about other people. 

The astronaut core spends about a day a month focusing just on improving on our abilities to take care of one another, communicate with one another and make sure that we’re going to be a high-performing team once we get to space.

Q: What training do astronauts do? 

Once you’re selected to be an astronaut, you go through two years of training to learn the basics.

We learn how to do spacewalks. We practise them in a space suit in a big pool in Houston (Texas) called the NASA Neutral Buoyancy Laboratory.

We learn, sort of like playing video games, how to control Canadarm2 on the ISS. 

Finally, we learn how to operate a spacecraft, how the space station works and we do a type of training where we go out and do a backpacking expedition just to practise our teamwork skills as a group.

NASA astronauts Sunita Williams and Josh Cassada are seen lowered into the water at NASA’s Neutral Buoyancy Laboratory (NBL) training facility in Houston, Texas, as part of their training in 2019. (Image credit: Mike Blake/Reuters)

Q: What is the coolest thing about space?

The thing I am most proud of with the space program is demonstrating to humanity that we can do amazing things when we work together. This is so important for our future on this planet. 

We’re now eclipsing eight billion people on this planet and the challenges we have ahead are significant. But space is showing us that if we really set big goals, we can do some crazy stuff as humans and we can solve these problems.

Hansen, left, and Jenni Gibbons, centre, take part in a demonstration of how astronauts will receive medical care during long-duration space missions and how that can be applied in remote regions here on Earth at the Canadian Space Agency in Longueuil, Quebec, on Feb. 5. (Image credit: Sidhartha Banerjee/The Canadian Press)

Q: What are you most excited about with the moon mission? 

I’m most excited about the view, by far. I’m going to see the Earth get small through the window, I’m going to see the moon get big through the window. At some point, I’m going to see an Earth rise from the other side of the moon, just like a sunrise, and that will be extraordinary.

Q: What do you think it will be like when you come back to Earth after the moon mission? 

Everyone is different. A lot of people feel nauseous. If you watch them walk around, they’re very deliberate because they don’t have their balance back yet and will always have somebody holding their arms. Their vestibular system, which helps them balance their body, has learned that there is no gravity for six months, and now it has to relearn gravity. It takes a while for your brain to remap that stuff.

Hansen, left, gives a high five to American astronaut Reid Wiseman while Victor Glover and Christina Hammock Koch applaud. They were celebrated on stage in April 2023 in Houston, Texas, as they were announced as the Artemis II crew during a NASA ceremony naming the four astronauts who will fly around the moon. (Image credit: Michael Wyke/The Associated Press)

Also, what doesn’t get used in orbit is all the little muscles that help you balance your body, and all of those have to be built back up.

Q: Do you feel that our generation can build a good future?

I do. I’ve seen some extraordinary things from humans. Your future is in your hands. Every human’s journey includes adversity. Each and every one of you will face challenge and failure, and it’s what you do with those challenges…. With a team, you can create a solution for every problem out there.

Have more questions? Want to tell us how we’re doing? Use the “send us feedback” link below. ⬇️⬇️⬇️
 

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Fluid in eye cells can 'boil' if you watch the eclipse without protection: expert – Delta Optimist

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Millions of people in parts of Eastern and Atlantic Canada will be able to see the rare solar eclipse happening on April 8. But they should only look up if they have proper eye protection, experts say. 

WHY IS WATCHING THE ECLIPSE MORE DANGEROUS THAN LOOKING AT THE SUN ON A NORMAL DAY?

When people look up at the sun normally, the intense brightness triggers pain that causes them to look away quickly before it can cause damage, said Dr. Philip Hooper, president of the Canadian Ophthalmological Society.

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But as the moon starts to block the sun in the period leading up to the total eclipse “there is significant light energy that’s coming from the sun, but we don’t appreciate pain. And so you can look at it long enough to do damage to the eye,” said Hooper, who is also an associate professor of ophthalmology at Western University in London, Ont. 

HOW DOES STARING AT THE SUN DAMAGE OUR EYES?

When you’re looking directly at the sun, intense visible light and infrared radiation are focused on the centre of the retina in the back of the eye. 

“It’s basically like taking a magnifying glass in the sun on a normal day and focusing that light on a piece of paper. It can get hot enough to burn the paper,” Hooper said. 

The sun has the same effect, because your eye concentrates that energy into a small area of the retina. 

“The temperature of the cells in that area can actually get high enough that the fluid in the cells actually boils and it damages the cells permanently,” he said. 

CAN I JUST PUT MY SUNGLASSES ON TO WATCH THE ECLIPSE?

No. Sunglasses do not provide protection, Hooper said. 

WHAT IF I STAY INSIDE AND WATCH THROUGH THE WINDOW?

Again, no. Windows offer no protection. 

IS IT SAFE TO WATCH THROUGH A PHONE CAMERA?

No.

“Eclipse or not, you shouldn’t look at the sun directly with the naked eye, or with a camera or telescope, without a (certified) solar filter. This can lead to irreversible eye damage,” says an eclipse safety video posted online by the Canadian Space Agency. 

Pointing your phone camera directly at the eclipse may also have other consequences. 

“Just remember that your camera on your phone has lenses just like eyeglasses do, and that light is coming in from the sun as soon as you open the shutter,” said Elaina Hyde, director of the Allan I. Carswell Observatory at York University in Toronto.

“At the very least you could expect to damage your camera. You won’t be able to see anything, again, because your phone is not able to handle that light.”

HOW DO I SAFELY WATCH THE ECLIPSE?

You’ll need special glasses with filters designed for eclipse watching, says the Canadian Space Agency website. 

Those glasses must have side protection so that light rays can’t enter, said Hooper. 

They must also have certified lenses, he said.

The certificationISO 12312-2 should be printed on the glasses, whichmeans the glasses meet international safety standards.  

While wearing the glasses, you should not be able to see anything unless you’re staring at the sun. 

“No matter how bright a light you are exposed to in your indoor environment, if you shone a very bright light through them, you’d see nothing. They’re totally black. That’s how dark they are,” Hooper said. 

The eclipse glasses should not be used if they are “scratched, punctured, torn, or otherwise damaged,” the American Astronomical Society says on its website, noting that people should inspect their glasses before using them. 

The society also says that children using the glasses during the eclipse must be supervised at all times. 

WHERE CAN I GET THE ISO 12312-2 CERTIFIED GLASSES?

Free eclipse-viewing glasses are available at many libraries, cities and school districts across Canada, according to the Royal Astronomical Society of Canada website.   

The American Astronomical Society has a list of companies and retailers in both Canada and the U.S. that sell certified solar eclipse glasses on its website.  

Some companies selling them in Quebec are listed on the Eclipse Quebec website. 

WHAT ABOUT WELDING GOGGLES?

Welding goggles come in a variety of shades, denoted by number, according to the Canadian Centre for Occupational Health and Safety website. 

The minimum darkness required to safely watch the eclipse is shade 13, said Hooper. 

“That’s much darker than the welding glasses or goggles that are typically used by welders. And they’re not widely available,” he said. 

IF I DON’T HAVE THE CERTIFIED GLASSES, IS THERE ANOTHER OPTION?

Another option for safe viewing is to make a projector so that you are never looking directly at the sun. It can be as basic as a piece of paper with a pinhole that projects the light from the sun onto the sidewalk, or a projector made out of a box. 

The Canadian Space Agency website has simple instructions on how to make a projector using an empty cardboard box, a sheet of white paper, aluminum foil, a pin, tape and scissors.  

For instructions, visit https://www.asc-csa.gc.ca/eng/youth-educators/activities/fun-experiments/eclipse-projector.asp 

-With files from Sonja Puzic

This report by The Canadian Press was first published March 29, 2024.

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.

Nicole Ireland, The Canadian Press

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The total solar eclipse in North America could shed light on a persistent puzzle about the sun – Phys.org

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The total solar eclipse in North America could shed light on a persistent puzzle about the sun

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The path of eclipse totality passes through Mexico, the US and Canada. Credit: NASA’s Scientific Visualization Studio

A total solar eclipse takes place on April 8 across North America. These events occur when the moon passes between the sun and Earth, completely blocking the sun’s face. This plunges observers into a darkness similar to dawn or dusk.

During the upcoming eclipse, the path of totality, where observers experience the darkest part of the moon’s shadow (the umbra), crosses Mexico, arcing north-east through Texas, the Midwest and briefly entering Canada before ending in Maine.

Total solar eclipses occur roughly every 18 months at some location on Earth. The last that crossed the US took place on August 21 2017.

An international team of scientists, led by Aberystwyth University, will be conducting experiments from near Dallas, at a location in the path of totality. The team consists of Ph.D. students and researchers from Aberystwyth University, Nasa Goddard Space Flight Center in Maryland, and Caltech (California Institute of Technology) in Pasadena.

There is valuable science to be done during eclipses that is comparable to or better than what we can achieve via space-based missions. Our experiments may also shed light on a longstanding puzzle about the outermost part of the sun’s atmosphere—its corona.

The sun’s intense light is blocked by the moon during a total solar eclipse. This means that we can observe the sun’s faint corona with incredible clarity, from distances very close to the sun, out to several solar radii. One radius is the distance equivalent to half the sun’s diameter, about 696,000km (432,000 miles).

Measuring the corona is extremely difficult without an eclipse. It requires a special telescope called a coronagraph that is designed to block out direct light from the sun. This allows fainter light from the corona to be resolved. The clarity of eclipse measurements surpasses even coronagraphs based in space.

We can also observe the corona on a relatively small budget, compared to, for example, spacecraft missions. A persistent puzzle about the corona is the observation that it is much hotter than the photosphere (the visible surface of the sun). As we move away from a hot object, the surrounding temperature should decrease, not increase. How the corona is heated to such high temperatures is one question we will investigate.

We have two main scientific instruments. The first of these is Cip (coronal imaging polarimeter). Cip is also the Welsh word for “glance,” or “quick look.” The instrument takes images of the sun’s corona with a polariser.

The light we want to measure from the corona is highly polarized, which means it is made up of waves that vibrate in a single geometric plane. A polarizer is a filter that lets light with a particular polarization pass through it, while blocking light with other polarizations.

The Cip images will allow us to measure fundamental properties of the corona, such as its density. It will also shed light on phenomena such as the solar wind. This is a stream of sub-atomic particles in the form of plasma—superheated matter—flowing continuously outward from the sun. Cip could help us identify sources in the sun’s atmosphere for certain solar wind streams.

Direct measurements of the magnetic field in the sun’s atmosphere are difficult. But the eclipse data should allow us to study its fine-scale structure and trace the field’s direction. We’ll be able to see how far magnetic structures called large “closed” magnetic loops extend from the sun. This in turn will give us information about large-scale magnetic conditions in the corona.

The second instrument is Chils (coronal high-resolution line spectrometer). It collects high-resolution spectra, where light is separated into its component colors. Here, we are looking for a particular spectral signature of iron emitted from the corona.

It comprises three , where light is emitted or absorbed in a narrow frequency range. These are each generated at a different range of temperatures (in the millions of degrees), so their relative brightness tells us about the coronal temperature in different regions.

Mapping the ‘s temperature informs advanced, computer-based models of its behavior. These models must include mechanisms for how the coronal plasma is heated to such high temperatures. Such mechanisms might include the conversion of magnetic waves to thermal plasma energy, for example. If we show that some regions are hotter than others, this can be replicated in models.

This year’s eclipse also occurs during a time of heightened solar activity, so we could observe a coronal mass ejection (CME). These are huge clouds of magnetized plasma that are ejected from the sun’s atmosphere into space. They can affect infrastructure near Earth, causing problems for vital satellites.

Many aspects of CMEs are poorly understood, including their early evolution near the sun. Spectral information on CMEs will allow us to gain information on their thermodynamics, and their velocity and expansion near the sun.

Our eclipse instruments have recently been proposed for a space mission called moon-enabled solar occultation mission (Mesom). The plan is to orbit the moon to gain more frequent and extended eclipse observations. It is being planned as a UK Space Agency mission involving several countries, but led by University College London, the University of Surrey and Aberystwyth University.

We will also have an advanced commercial 360-degree camera to collect video of the April 8 eclipse and the observing site. The video is valuable for public outreach events, where we highlight the work we do, and helps to generate public interest in our local star, the sun.

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The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.The Conversation

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The total solar eclipse in North America could shed light on a persistent puzzle about the sun (2024, March 28)
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