Laser technique improves ultra-high temperature ceramic manufacturing for space and defense applications

Researchers have demonstrated a brand new approach that makes use of lasers to create ceramics that may face up to ultra-high temperatures, with purposes starting from nuclear energy applied sciences to spacecraft and jet exhaust methods.

The approach can be utilized to create ceramic coatings, tiles or advanced three-dimensional constructions, which permits for elevated versatility when engineering new gadgets and applied sciences.

The paper, “Synthesis of hafnium carbide (HfC) through one-step selective laser response pyrolysis from liquid polymer precursor,” is published within the Journal of the American Ceramic Society.

“Sintering is the method by which uncooked supplies—both powders or liquids—are transformed right into a ceramic materials,” says Cheryl Xu, co-corresponding writer of a paper on this analysis and a professor of mechanical and aerospace engineering at North Carolina State College.

“For this work, we targeted on an ultra-high temperature ceramic known as hafnium carbide (HfC). Historically, sintering HfC requires inserting the uncooked supplies in a furnace that may attain temperatures of at the very least 2,200 levels Celsius—a course of that’s time-consuming and energy-intensive.

“Our approach is quicker, simpler and requires much less power.”

The brand new approach works by making use of a 120-watt laser to the floor of a liquid polymer precursor in an inert atmosphere, resembling a vacuum chamber or a chamber full of argon. The laser sinters the liquid, turning it right into a stable ceramic. This can be utilized in two alternative ways.

First, the liquid precursor might be utilized as a coating to an underlying construction, resembling carbon composites utilized in hypersonic applied sciences like missiles and area exploration automobiles. The precursor might be utilized to the floor of the construction after which sintered with the laser.

“As a result of the sintering course of doesn’t require exposing your entire construction to the warmth of the furnace, the brand new approach holds promise for permitting us to use ultra-high-temperature ceramic coatings to supplies that could be broken by sintering in a furnace,” Xu says.

The second means that engineers could make use of the brand new sintering approach includes additive manufacturing, often known as 3D printing. Particularly, the laser sintering technique can be utilized along side a method that’s much like stereolithography.

On this approach, a laser is mounted on a desk that sits in a shower of the liquid precursor. To create a three-dimensional construction, researchers create a digital design of the construction after which “slice” that construction into layers. To start, the laser attracts the profile of the primary layer of the construction within the polymer, filling the profile in as if coloring in an image.

Because the laser “fills in” this space, thermal power converts the liquid polymer into ceramic. The desk then lowers just a little bit additional into the polymer tub, and a blade sweeps throughout the highest to even out the floor. The laser then sinters the second layer of the construction, and this course of repeats itself till you could have a completed product made from the sintered ceramic.

“It is truly a little bit of an oversimplification to say that the laser is just sintering the liquid precursor,” Xu says. “It’s extra correct to say that the laser first converts the liquid polymer right into a stable polymer after which converts the stable polymer right into a ceramic. Nonetheless, all of this occurs in a short time—it is primarily a one-step course of.”

In proof-of-concept testing, the researchers demonstrated that the laser sintering approach produced crystalline, phase-pure HfC from a liquid polymer precursor.

“That is the primary time we all know of the place somebody was in a position to create HfC of this high quality from a liquid polymer precursor,” Xu says. “And ultra-high temperature ceramics, because the identify suggests, are helpful for a variety of purposes the place applied sciences should face up to excessive temperatures, resembling nuclear power manufacturing.”

The researchers additionally demonstrated that laser sintering may very well be used to create high-quality HfC coatings of carbon-fiber bolstered carbon composites (C/C). Mainly, the ceramic coating bonded to the underlying construction and did not peel away.

“The HfC coatings on C/C substrates demonstrated sturdy adhesion, uniform protection, and potential to be used as thermal safety and an oxidation-resistant layer,” Xu says.

“That is notably helpful as a result of, along with hypersonic purposes, carbon/carbon constructions are utilized in rocket nozzles, brake disks and aerospace thermal safety methods resembling nostril cones and wing main edges.”

The brand new laser sintering approach can be considerably extra environment friendly than typical sintering in a number of methods.

“Our approach permits us to create ultra-high-temperature ceramic constructions and coatings in seconds or minutes, whereas typical methods take hours or days,” Xu says.

“And since laser sintering is quicker and extremely localized, it makes use of considerably much less power. What’s extra, our method produces the next yield. Particularly, laser sintering converts at the very least 50% of the precursor mass into ceramic. Typical approaches usually convert solely 20–40% of the precursor.

“Lastly, our approach is comparatively moveable,” Xu says. “Sure, it must be achieved in an inert atmosphere, however transporting a vacuum chamber and additive manufacturing gear is way simpler than transporting a strong, large-scale furnace.

“We’re enthusiastic about this advance in ceramics and are open to working with private and non-private companions to transition this expertise to be used in sensible purposes,” says Xu.