Feb/March_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | F E B R U A R Y / M A R C H 2 0 2 1 1 2 SURFACE ENGINEERING 3D PRINTING WITH COLD SPRAY A collaboration led by Cornell Uni- versity recently developed a 3D-printing technique that creates cellular metallic materials by using cold spray. According to the researchers, the materials have applications in thermal management, energy absorption, and biomedicine. The new method uses a nozzle of com- pressed gas to fire titanium alloy parti- cles at a substrate. During testing, the particles were between 45-106 microns in diameter and traveled at roughly 600 meters per second, faster than the speed of sound. Researchers used com- putational fluid dynamics to calibrate the alloy’s ideal speed. When launched at a slightly slower rate, the particles created a more porous structure, which is ideal for biomedical applications. Once the particles collided and bonded together, the researchers heat- ed the metal so the components would diffuse into each other and settle like a homo- geneous material. “We only focused on titanium alloys and biomedical applications, but the ap- plicability of this process could be beyond that,” they say. “Essentially, any metallic material that can endure plastic deforma- tion could benefit from this process. And it opens up a lot of opportunities for larger-scale industrial applications, like construction, trans- portation, and energy.” cornell.edu . NEW ATOMIC LAYER DEPOSITION METHOD Scientists at The University of Ala- bama in Huntsville (UAH) found a new way to deposit thin layers of atoms as a coating onto a substrate material at near room temperatures. Researchers applied ultrasonic atomization tech- nology to evaporate chemicals used in atomic layer deposition (ALD), a technique central to microelectronics manufacturing. Each ALD cycle deposits a layer a few atoms deep. The ALD process then repeats the deposition cycle hundreds or thousands of times. ALD processes typically rely onheatedgas-phasemole- cules that are evaporated from their sol- id or liquid form, like room humidifiers that use heat to vaporize water. Howev- er, in that particular ALD process, some chemical precursors are not stable and can decompose before reaching a suffi- cient vapor pressure for ALD. The UAH ultrasound invention makes it possible to use a wide range of reactive chemi- cals that are thermally unstable and not suitable for direct heating. “Ultrasonic atomization, as devel- oped by our research group, supplies low vapor pressure precursors because the evaporation of precursorswasmade through ultrasonic vibrating of the module,” explains associate professor Yu Lei. “Like the household humidi- fier, ultrasonic atomization generates a mist consisting of saturated vapor and micro-sized droplets. The droplets con- tinuously evaporate when the mist is delivered to the substrates by a carr- ier gas.” The new process uses a piezoelec- tric ultrasonic transducer placed in a liquid chemical precursor. Once started, the transducer begins to vibrate a few hundred thousand times per second and generates a mist of the chemical precursor. The small liquid droplets in the mist are quickly evaporated in the gas manifold under vacuum and mild heat treatment, leaving behind an even coat of the deposition material. “Using the room-temperature ultrasonic at- omization, new ALD processes could be developed using low volatility and unstable precursors,” says Lei. uah.edu . BRIEF ASB Industries, Barberton, Ohio, added a new thermal spray ABB robot manipulator to its equipment lineup. The new robot, with its small footprint, gives ASB the flexibility to use customized process fixtures that can adapt to its clients’ parts processing. The robot arm fits a variety of thermal spray guns. asbindustries.com. This image shows cells adhering to a titanium alloy created by cold-spray 3D printing, which demonstrates the material’s biocompatibility. Courtesy of Cornell University. Recent addition to ASB’s robot family.