July_August_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 | J U L Y / A U G U S T 2 0 1 9 7 MAKING MATERIALS WITH SOUND WAVES Predicted to be the defining ma- terial of the 21st century, metal-organ- ic frameworks (MOFs) are well suited for sensing and trapping substances at minute concentrations to purify water or air. They can also hold large amounts of energy for making better batteries and energy storage devices. Howev- er, the traditional process for creating MOFs is environmentally unsustainable. Researchers at RMIT University, Australia, demonstrated a new tech- nique that can produce a custom MOF in minutes by harnessing the power of high-frequency sound waves. MOFs are crystalline powders full of mole- cule-sized holes. During standard pro- duction, solvents and other contami- nants become trapped in the holes. To flush them out, a combination of vac- uum and high temperatures or harsh chemical solvents are often employed. With the new technique, research- ers use a microchip to produce high-fre- quency sound waves. By utilizing the waves to arrange and link the MOF com- ponents, researchers are able to create a highly ordered and porous network while simultaneously activating the MOF by pushing out solvents from the holes. OMG! OUTRAGEOUS MATERIALS GOODNESS The team says the new method produc- es MOFs with empty holes and a high surface area, eliminating the need for post-synthesis activation. So far, the ap- proach has been tested on copper and iron-base MOFs. The next step is to use other metals and scale up the process for mass production. www.rmit.edu.au. LARGE PARTS, LESS WASTE A novel additive manufacturing (AM) method developed by researchers at the DOE’s Oak Ridge National Labo- ratory (ORNL), Tenn., offers a promising alternative for achieving low cost, high quality production of large-scale met- al parts with less material waste than other methods. The team printed thin metal walls using a closed loop, feed- back controlled technique to provide uniform flat beads and layers at a cer- tain height. The system automatically regulates the printing process, creat- ing stable properties within the metal deposit and producing a high-quality build throughout the part. “We achieved a precise geometry for the components by using real-time feedback sensors to correct for abnor- malities,” says researcher Andrzej Nycz. “Because metal printed walls repre- sent the basic building blocks of parts manufactured with big area additive Conching is a long process of intense mixing, agitating, and aerating of liquid chocolate. ORNL researchers printed thin metal walls using large-scale metal AM. manufacturing, we expect the same stable properties to hold for parts print- ed with complex geometries.” ornl.gov. CONCHING SECRETS A team at the University of Edin- burgh, U.K., recently studied mixtures resembling liquid chocolate created by the process known as conching, devel- oped by Swiss confectioner Rudolf Lindt in 1879. The findings may enable pro- duction of confectionery with lower fat content and could help make chocolate manufacturing become more energy ef- ficient. The analysis suggests conching may alter the physical properties of the microscopic sugar crystals and other granular ingredients. The new research also reveals that conching, which involves mixing ingredients for several hours, produces smooth chocolate by breaking down lumps of ingredients into finer grains and reducing friction between parti- cles. Before the invention of conching, chocolate had a gritty texture. This is because the ingredients form rough, irregular clumps that do not flow smoothly when mixed with cocoa but- ter using other methods. The team’s insights could help improve processes used in other sectors that rely onmixing powders and liquids, such as ceramics manufacturing and cement production. www.ed.ac.uk . Acoustically built MOF and the microchip that makes high-frequency sound waves.