3D-printed ceramics – The Making of Making a Single Hypersonic Weapon


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Making a single hypersonic weapon or space launch vehicle is one thing. Mass producing them is quite another. The strong, heat-resistant ceramic components they require are extremely difficult to produce. Keith Button spoke to materials scientists who think they have the solution.

As aerospace engineers dream up new hypersonic weapons and space launch vehicles, they will need ceramic parts that can withstand temperatures as high as 2,700 degrees Celsius and drag forces of hundreds of kilograms that are encountered at speeds of Mach 5 and higher, such as on nose cones, wing leading edges and engine inlets.

The problem is: These ceramics are harder than titanium and brittle, making them tricky to work with.

Researchers at the U.S. Naval Research Laboratory are developing a method for making precise ceramic parts for hypersonic missiles and vehicles. These parts could be made by a 3D printer like this one. Credit: Cerambot

To make a ceramic part, a technician typically presses a soft clay-like material into a die to create an approximation of the desired shape, hardens it in a furnace and then grinds it down to the precise shape. This milling process can take months and result in chipped or cracked parts.

Materials engineers and chemists at the U.S. Naval Research Laboratory in Washington, D.C., are developing a 3D-printing method that could produce the precise ceramic part shape with no milling required. Components could be made by any aerospace manufacturer with a particular kind of off-the-shelf commercial 3D printer, a paste of metal and polymer devised by the NRL scientists, and a furnace to cure the parts.

EARLY RESEARCH

The idea of printing ceramic parts sprang from the NRL chemistry group’s development, starting about 12 years ago, of a polymer resin powder that it mixed with various metal powders to make refractory carbides, which are a type of extremely heat-resistant ceramic. The NRL researchers made pellets from the polymer resin mixed with metals like silicon, titanium or tungsten, and then smushed the pellets with a hydraulic press and die into simple shapes. When they heated these pressed shapes in a furnace filled with argon gas at 1,500 degrees Celsius — like firing a clay pot — the polymer resin charred into carbon and reacted with the metals to form a ceramic.

The researchers investigated the 3D-printing idea because they wanted to apply their polymer-metal ceramics chemistry to more complex shapes than the discs, spheres and cones that they were making, explains Boris Dyatkin, a materials research engineer at the NRL. With the die-press method, the size and shape of the ceramic part is dictated by the die, and some shapes aren’t possible with a die press. Also, “if you need to change the dimension of the part, or if you need to change a certain geometry aspect of it, it’s more tricky to do it quickly,” he says.

With 3D printing, “you’re basically getting more customization in terms of what kind of a ceramic you can make,’’ Dyatkin says.

Another commercial off-the-shelf 3D printer compatible with ceramics is made by 3D Potter. Credit: 3D Potter

PRINTER OPTIONS

When the NRL researchers began to work in earnest on the 3D-printing concept, in 2018, they first had to decide which type of 3D printing was best. They considered lots of printer options. One possibility was fused deposition modeling. A printer head mounted on a robotic arm deposits beads of molten polymer that harden, layer upon layer, to form the object. Another candidate was powder-bed 3D printing. A laser melts specks of powder as layers of the powder are added to a box-like bed, and these specks harden together to create a structure. The shape is revealed by removing the loose powder. Or, alternatively, a printer head injects binding material into the powder to create the structure.

The researchers settled on a 3D-printing method called robocasting. They based this decision on the advice of NanoArmor, a California research and development company that pays the NRL to make the ceramics and test them for the Missile Defense Agency’s hypersonic materials development program.

Normally, these robocasting printers make items ranging from pottery with intricate lattice structures to complex-shaped concrete panels for buildings. The printer’s robotic arm moves a printer head that extrudes beads of paste that harden as they dry.

These printers were attractive, because robocasting can print larger structures than other 3D-printing methods, and it’s cheap and simple. With virtually no training, “anybody could essentially print whatever they wanted to,” says Tristan Butler, a materials chemist at the NRL.

Robocasting also opens possibilities for creating new ceramic composites. Manufacturers could add ground-up carbon fibers, in powder form, to the paste to make a carbon-fiber composite ceramic, Dyatkin says. Or, under two concepts the researchers haven’t explored yet: 1. A printer could extrude paste onto woven carbon-fiber mesh. Or, 2. Without a printer, the mesh could be dipped into a less viscous version of the paste or the liquidy paste could be poured into a mold containing the mesh. With both concepts, the combined mesh and paste would be fired in a furnace to create the composite ceramic.

Researchers have 3D-printed hollow cylinders (shown) and tapered and conical discs several centimeters high as they refine their method. Credit: U.S. Naval Research Laboratory

Their big challenge was to make a paste that would be accepted by the printer and harden into parts that would be as dense as those they had made earlier. Generally, denser ceramics are stronger and more heat resistant.

They needed a binder to hold the mix together while dispersing the metal and resin molecules evenly throughout the paste.

The paste had to be liquid enough to flow through the printer head, but once extruded it couldn’t be too damp or too dry. “There’s kind of a delicate balance,” Butler says. “You don’t want it to dry too fast, because it will induce cracking. But you want it to dry quick enough that you can deposit multiple layers to build taller structures. It’s something you have to dial in.”

The key to achieving the right viscosity would be the choice of binder, which is a polymer and plasticizer that’s mixed in powdered form with the powdered resin and metal. Liquid is added to create the paste. Once a part is printed, it’s fired in a furnace to trigger the chemical reaction that turns the hardened paste into a ceramic, after burning off the binder.

The NRL researchers tried 10 to 15 binders common in 3D printing. Some were water-soluble and others alcohol-soluble. The scientists made pastes with each and created test discs. One of the water-soluble versions was chosen, because it proved best at creating a homogeneous mix of the right viscosity.

SpaceLiner is a hypersonic passenger craft concept created by the German Aerospace Center. In this illustration, the SpaceLiner orbiter separates from its reusable booster stage. Credit: German Aerospace Center

LOOKING AHEAD

At the moment, the shapes they’ve made by robocast printing are not as dense as those they’ve made with the die-pressed technique. The NRL researchers continue to search for the optimal heating rate for the furnace, meaning one that burns off the binder completely while fostering the resin and metal chemical bonds that must form to create a suitably dense ceramic. The researchers are also working toward printing objects — hollow cylinders and tapered and conical discs — that are taller and made from smaller beads of extruded paste, known as pixels in the industry. The smaller the pixels, the more precise and finely detailed the 3D-printed object can be. The NRL researchers are printing parts that are several centimeters tall made up of pixels that are just under a millimeter in diameter. They think eventually their printing method could produce parts as large as needed — building-size, in theory — of any shape. They haven’t set a pixel size target yet.

Another goal: Figuring out how to create 3D-printed ceramics that are as close as possible to the density of die-pressed ceramics. To test hardness, they employ a microindentation tester. A small sample of the ceramic is placed on the device’s platform, and a pin head measuring about 100 microns in diameter presses down on the surface to a preset pressure. The larger the microscopic indentation, the softer the material.

To assess how stable and strong the material will be when heated, they examine microscopic crystals in the ceramic with the help of an X-ray diffraction machine. A sample is placed on a pressure plate in the center of the machine; an X-ray tube shoots X-ray beams at the sample while a detector behind the sample rotates through a range of angles to pick up the reflected beams. The machine churns out graphs depicting the angles at which the X-rays are reflected by the crystals in the material and the intensity of the reflected X-rays. The various peaks in the graphs create signature patterns that software analyzes to identify the type and phase of metal or carbon crystals in the material, as well as size and volume of the crystals.

Another issue is that, so far, the 3D-printed ceramics have come out more porous than the pressed discs. In some cases, those microscopic gaps need to be filled to make the material denser and therefore stronger and more heat resistant. One option would be vapor infiltration. A gas in the furnace chemically reacts with the ceramic — either as it is forming or after it has formed — and fills in any pores. Another idea is to paint a solution on the 3D-printed object that would fill in the pores through a chemical reaction at lower temperatures, Butler says.

Even at this stage, the NRL researchers are thinking about how to make the process as easy as possible for aerospace manufacturers to adopt. The researchers sought advice from NanoArmor, whose executives have helped commercialize new materials and electronics technologies for several companies. Parts must be affordably mass produced, which means initial ingredients must be chosen with cost in mind. Efforts must be taken to eliminate any unnecessary steps. “We pushed down requirements about scaling up, about costs, about timing,” says Terrisa Duenas, NanoArmor chief executive. “A lot of times when you make a material, you don’t even think about how to scale it up. And it just seems like: ‘Well, we’ll multiply by three or 10 or whatever you need,’ but a lot of technologies don’t scale like that.”

Northwestern University scientists Successfully Combine a Nanomaterial effective at destroying Toxic Nerve Agents with Textile Fibers – Applications for Protective Suits and Masks


Abstract:

•Smart chemistry quickly makes toxic nerve gases nontoxic
•Material’s features bring it closer to practical use in the field 
•New approach is scalable and economical
•Seeks to replace current technology of activated carbon

This new composite material one day could be integrated into protective suits and face masks for use by people facing hazardous conditions, such as chemical warfare.

The material, a zirconium-based metal-organic framework (MOF), degrades in minutes some of the most toxic chemical agents known to mankind: VX and soman (GD), a more toxic relative of sarin.

“With the correct chemistry, we can render toxic gases nontoxic,” said Omar K. Farha, associate professor of chemistry in the Weinberg College of Arts and Sciences, who led the research. “The action takes place at the nanolevel.”

The authors write that their work represents, to the best of their knowledge, the first example of the use of MOF composites for the efficient catalytic hydrolysis of nerve agent simulants without using liquid water and toxic volatile bases — a major advantage.

The new composite material integrates MOFs and non-volatile polymeric bases onto textile fibers.

The researchers found the MOF-coated textiles efficiently detoxify nerve agents under battlefield-relevant conditions using the gaseous water in the air. They also found the material stands up over a long period of time to degrading conditions, such as sweat, atmospheric carbon dioxide and pollutants.

These features bring the promising material closer to practical use in the field.

“MOFs can capture, store and destroy a lot of the nasty material, making them very attractive for defense-related applications,” said Farha, a member of the International Institute for Nanotechnology. 

What Are MOF’s?

MOFs are well-ordered, lattice-like crystals. The nodes of the lattices are metals, and organic molecules connect the nodes. Within their very roomy pores, MOFs can effectively capture gases and vapors, such as nerve agents. 

It is these roomy pores that also can pull enough water from the humidity in the air to drive the chemical reaction in which water is used to break down the bonds of the nerve agent.

The approach developed at Northwestern seeks to replace the technology currently in use: activated carbon and metal-oxide blends, which are slower to react to nerve agents. Because the MOFs are built from simple components, the new approach is scalable and economical.

The research was supported by the Defense Threat Reduction Agency (grants HDTRA1-18-1-0003 and CB3934) and the National Science Foundation Graduate Research Fellowship (grant DGE-1842165). 

The title of the paper is “Integration of Metal–Organic Frameworks on Protective Layers for Destruction of Nerve Agents under Relevant Conditions.” The first authors are Zhijie Chen and Kaikai Ma, postdoctoral fellows in Farha’s research group.

Contacts:
Source contact: Omar Farha at o-farha@northwestern.edu

Copyright © Northwestern University

HDIAC SOAR Webinar: Uses of Nanotechnology on Surfaces for Military Applications: Video + Presentation


HDIAC Featured_Information_Resources

Homeland Defense & Security Information Analysis Center

 

Click on the Link below to see the Presentation and Notes:

Findings

• Overall
• Nanoceramics
• Metals/metal oxides: silver, copper, titanium dioxide, zinc oxide
• Carbon nanotubes
• Hard surfaces
• Advancements in nanoceramics
• Incorporating superhydrophobic characteristics into surfaces
themselves
• Soft surfaces
• Major advancements in antibacterial coatings
• Developments in smart textiles
• Incorporating nanomaterials into existing fibers/textiles
• Nondurable goods
• Anti-corrosive epoxy coatings with nanomaterials
• Biomedical applications

Homeland Defense & Security Information Analysis Center: PDF Presentation

The Aussie Company That’s Using Nanotechnology to Protect the US Military


south-africa-ii-nanotechnology-india-brazil_261.jpgAlexium [ASX:AJX] [OTCQX:AXXIY]  is a Perth-based chemical development company with offices in South Carolina.

This morning, they announced a deal that will see them supply US military forces with leading edge flame retardant fabrics.

Alexium has developed a chemical called Alexiflam™. It’s used as a fabric treatment, to make that fabric flame retardant. It’s marketed under different names, depending on which fabric it’s meant for. Ascalon™ is for nylon, Nycolon™ is for nylon-cotton blend fabrics, and Nuvalon™ is for poly-cotton blends. The exact way it works is a bit hush hush, for obvious reasons, including the fact that they supply the military. But if you have a look at their US patent application, the abstract says:

‘An enhanced protective cover includes a top and bottom textile layer and an air permeable, moisture-vapor-transmissive, expanded polytetrafluoroethylene membrane layer located between the two textile layersThe protective cover also includes a top layer coating or fibre treatment of a nano-ceramic material designed to increase the durability of the cover.

Alternatively, the upper layer of the protective cover may incorporate ceramic coated fibers or ceramic co-extruded fibers, or carbon nanotubes. The protective cover may also feature a fire resistant application. The top textile layer may also include a permanent, highly breathable and highly durable electro-static discharge feature added to the inside of the layer by laying down a carbon based printed pattern on the inside of the layer.’

They’ve also got an Australian patent, which was granted in 2012. This patent explains how the coating sticks to the fabric. It’s pretty dense reading, but you can check it out here.

So basically, they’ve got a very broad, very detailed patent application to cover fabric treatments which create multi-layered protection. The ‘durability’ thing is part of what the military is after. They don’t want anything that’s easily scratched, melted, or transferred onto other surfaces.

Alexium orders to ship Alexiflam™ to Greenwood Mills in huge quantities. Greenwood Mills is a 115-year old company that makes fabrics for the United States Military, amongst other things.

Alexium already has strong links with the US military. For example, in December last year, they announced that they’d got a contract to make a new and improved flame resistant uniform for the US Department of Defense (DoD). In 2013, tests at a DoD-sanctioned facility showed an Alexium product (‘Cleanshell’) effectively repels live chemical warfare agents like sarin gas and mustard gas. That same year, they won a contract to supply the US Marines to develop fire-retardant fabric treatments. Other contracts came before that. In fact, Alexium has a whole affiliate — Alexium Government Solutions — to deal with military contracts.

But this deal is especially important. The president of Alexium, Dirk Van Hyning, explained why. He said that ‘Whilst we have a strong and healthy business in the commercial sector, the sheer size of the Defense market and the fact that our chemistries clearly fit with the stringent performance requirements for military grade FR [flame retardant] fabrics, makes the Defense sector another strong market for Alexium both in the US and internationally. This new customer, with operations in the Defense sector, is a key part of that overall strategy.

Alexium CEO Nicholas Clark thinks it’ll also be good for their penetration into the commercial market. Greenwood Mills also makes things like denim for big American brands including Levi Strauss, Abercrombie & Fitch [NYSE:ANF], and Hollister.

So there you go — in a few years, you could be wearing military-grade super-jeans that can stand up to chemical warfare and make your bum look good.

Clark said that ‘This new customer shows not only the continuing growth in the range and size of our sales but also the increasing rate at which new orders are being received as the market in both the commercial and defense sectors become increasingly aware of the performance and cost benefits of our award winning environmentally friendly FR solutions.

@MIT Bacterial Cells produce Biofilms incorporating Nonliving Materials: Gold Nanoparticles and Quantum Dots


bacterial-cellCambridge, MA (Scicasts) – Inspired by natural materials such as bone — a matrix of minerals and other substances, including living cells — MIT engineers have coaxed bacterial cells to produce biofilms that can incorporate nonliving materials, such as gold nanoparticles and quantum dots.

These “living materials” combine the advantages of live cells, which respond to their environment, produce complex biological molecules, and span multiple length scales, with the benefits of nonliving materials, which add functions such as conducting electricity or emitting light.

bacterial-cell

An artist’s rendering of a bacterial cell engineered to produce amyloid nanofibers that incorporate particles such as quantum dots (red and green spheres) or gold nanoparticles. Image: Yan Liang

The new materials represent a simple demonstration of the power of this approach, which could one day be used to design more complex devices such as solar cells, self-healing materials, or diagnostic sensors, says Timothy Lu, an assistant professor of electrical engineering and biological engineering. Lu is the senior author of a paper describing the living functional materials in the March 23 issue of Nature Materials.

“Our idea is to put the living and the nonliving worlds together to make hybrid materials that have living cells in them and are functional,” Lu says. “It’s an interesting way of thinking about materials synthesis, which is very different from what people do now, which is usually a top-down approach.”

The paper’s lead author is Allen Chen, an MIT-Harvard MD-PhD student. Other authors are postdocs Zhengtao Deng, Amanda Billings, Urartu Seker, and Bijan Zakeri; recent MIT graduate Michelle Lu; and graduate student Robert Citorik.

Self-assembling materials

Lu and his colleagues chose to work with the bacterium E. coli because it naturally produces biofilms that contain so-called “curli fibres” — amyloid proteins that help E. coli attach to surfaces. Each curli fibre is made from a repeating chain of identical protein subunits called CsgA, which can be modified by adding protein fragments called peptides. These peptides can capture nonliving materials such as gold nanoparticles, incorporating them into the biofilms.

By programming cells to produce different types of curli fibres under certain conditions, the researchers were able to control the biofilms’ properties and create gold nanowires, conducting biofilms, and films studded with quantum dots, or tiny crystals that exhibit quantum mechanical properties. They also engineered the cells so they could communicate with each other and change the composition of the biofilm over time.

First, the MIT team disabled the bacterial cells’ natural ability to produce CsgA, then replaced it with an engineered genetic circuit that produces CsgA but only under certain conditions — specifically, when a molecule called AHL is present. This puts control of curli fiber production in the hands of the researchers, who can adjust the amount of AHL in the cells’ environment. When AHL is present, the cells secrete CsgA, which forms curli fibers that coalesce into a biofilm, coating the surface where the bacteria are growing.

The researchers then engineered E. coli cells to produce CsgA tagged with peptides composed of clusters of the amino acid histidine, but only when a molecule called aTc is present. The two types of engineered cells can be grown together in a colony, allowing researchers to control the material composition of the biofilm by varying the amounts of AHL and aTc in the environment. If both are present, the film will contain a mix of tagged and untagged fibres. If gold nanoparticles are added to the environment, the histidine tags will grab onto them, creating rows of gold nanowires, and a network that conducts electricity.

‘Cells that talk to each other’

The researchers also demonstrated that the cells can coordinate with each other to control the composition of the biofilm. They designed cells that produce untagged CsgA and also AHL, which then stimulates other cells to start producing histidine-tagged CsgA.

“It’s a really simple system but what happens over time is you get curli that’s increasingly labelled by gold particles. It shows that indeed you can make cells that talk to each other and they can change the composition of the material over time,” Lu says. “Ultimately, we hope to emulate how natural systems, like bone, form. No one tells bone what to do, but it generates a material in response to environmental signals.”

To add quantum dots to the curli fibres, the researchers engineered cells that produce curli fibers along with a different peptide tag, called SpyTag, which binds to quantum dots that are coated with SpyCatcher, a protein that is SpyTag’s partner. These cells can be grown along with the bacteria that produce histidine-tagged fibres, resulting in a material that contains both quantum dots and gold nanoparticles.

These hybrid materials could be worth exploring for use in energy applications such as batteries and solar cells, Lu says. The researchers are also interested in coating the biofilms with enzymes that catalyze the breakdown of cellulose, which could be useful for converting agricultural waste to biofuels. Other potential applications include diagnostic devices and scaffolds for tissue engineering.

“I think this is really fantastic work that represents a great integration of synthetic biology and materials engineering,” says Lingchong You, an associate professor of biomedical engineering at Duke University who was not part of the research team.

The research was funded by the Office of Naval Research, the Army Research Office, the National Science Foundation, the Hertz Foundation, the Department of Defense, the National Institutes of Health, and the Presidential Early Career Award for Scientists and Engineers.

The original article was written by Anne Trafton, MIT News Office.

Publication: Synthesis and patterning of tunable multiscale materials with engineered cells. Allen Y. Chen, Zhengtao Deng, Amanda N. Billings, Urartu O. S. Seker, Michelle Y. Lu, Robert J. Citorik, Bijan Zakeri, Timothy K. Lu. Nature Materials (March 23, 2014):http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat3912.html

 SOURCE
http://scicasts.com/material-science/2092-channels/bioengineering/tissue-engineering/7559-engineers-design-living-materials/

Laser Weapon System (LaWS) – “Star Wars Pas Deaux”


The Afloat Forward Staging Base (Interim) USS Ponce (ASB(I) 15) conducts an operational demonstration of the Office of Naval Research (ONR)-sponsored Laser Weapon System (LaWS) while deployed to the Arabian Gulf.

Register now for the February 4-5, 2015, Naval Future Force Science and Technology EXPO at the Walter E. Washington Convention Center in Washington, D.C. http://bit.ly/1pNqXqK

Micro-Rockets with ‘Water’ Fuel to Neutralize Chemical & Biological Warfare


1-rocket motor_news291014With fears growing over chemical and biological weapons falling into the wrong hands, scientists are developing microrockets to fight back against these dangerous agents, should the need arise. In the journal ACS Nano, they describe new spherical micromotors that rapidly neutralize chemical and biological agents and use water as fuel.

Joseph Wang and colleagues point out that titanium dioxide is one of the most promising materials available for degrading chemical and biological warfare agents. It doesn’t require harsh chemicals or result in toxic by-products.

1-rocket motor_news291014

Image: Spherical micromotors fueled by water can neutralize dangerous chemical and biological agents.
Credit: American Chemical Society

Current approaches using titanium dioxide, however, require that it be mixed in whatever solution that needs to be decontaminated. But there’s no way to actively mix titanium dioxide in waterways if chemical and biological agents are released into the environment. So scientists have been working on ways to propel titanium dioxide around to accelerate the decontamination process without the need for active stirring. But approaches so far have required fuel and other compounds that hinder neutralization. Wang’s team wanted to fix this problem.

To give titanium dioxide a source of thrust, the researchers coated it over a magnesium sphere core. When put in a watery environment, a single hole in the shell allows water to enter and react with the magnesium core. This produces hydrogen gas, which bubbles out and propels the titanium dioxide through the surrounding liquid. This enables it to more efficiently and rapidly contact and degrade harmful agents. When tested, the micromotors successfully neutralized nerve agents and anthrax-like bacteria in considerably less time compared to titanium dioxide microparticles that aren’t propelled.
Source: http://www.acs.org/…