3D printing could change how we build parts for jet engines and power plants, but the process leaves microscopic holes that cause the materials to shatter.
Publishing in International Journal of Extreme Manufacturing , Prof. Fangyong Niu's team in Dalian University of Technology have fixed the problem by doing something unconventional: they added a microwave.
To build components that can survive extreme industrial heat, engineers rely on multiphase oxide ceramics, specifically mixtures of alumina, yttria-stabilized zirconia, and yttrium aluminum garnet. Conventional metals melt under these conditions, but shaping these heat-proof ceramics into complex parts is incredibly difficult and energy-intensive.
Laser 3D printing, which melts ceramic powder layer by layer, offers a flexible modern alternative. However, the laser acts like a surface blowtorch. The microscopic pool of melted rock heats and freezes so violently that gas bubbles get trapped inside as permanent voids. This rapid freezing also forces the material's internal crystals to grow in weak, predictable bands.
To eliminate these flaws, Prof. Niu's team built a hybrid machine. As the laser melts the ceramic, the entire printing zone is bathed in a 2.45 GHz microwave field. The results translate directly to massive improvements in structural stability.
The microwave field slashed the total amount of empty space inside the ceramic by 85.5%, bringing the porosity down to a near-zero 0.11%. The few remaining pores shrank by almost half, dropping to an average width of 38 micrometers. With fewer microscopic holes to act as starting points for cracks, the material can handle 22.2% more bending force before breaking, maxing out at 373.8 megapascals.
The secret lies in changing the physics of how the rock melts and cools. While a laser alone sears the surface, microwaves penetrate and heat the material volumetrically from the inside out. This deep internal heating keeps the tiny pool of liquid ceramic molten for 1.86 seconds, more than double the usual 0.85 seconds. That single extra second acts as a crucial mechanical escape window, allowing trapped gas bubbles to float up and exit before the material freezes.
The microwaves also attack the microscopic voids on a subatomic level. The energy accelerates free electrons inside the trapped gas, sparking an internal plasma that destroys the remaining bubbles through avalanche ionization.
At the same time, the zirconia phase within the ceramic acts like a microwave sponge, generating intense localized hot spots. These sudden temperature spikes force the growing crystals to jumble together in random directions instead of forming neat, easily breakable lines.
Currently, the team has only used this hybrid technique to print small test bars in a laboratory setting. But the fundamental physics prove that these critical structural flaws can be systematically erased. The researchers are now focused on scaling up this dual-energy strategy.
If successful, it could allow factories to reliably print massive, complex ceramic components capable of surviving the most extreme industrial environments on Earth.
International Journal of Extreme Manufacturing (IJEM, IF: 21.3 ) is dedicated to publishing the best advanced manufacturing research with extreme dimensions to address both the fundamental scientific challenges and significant engineering needs.
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International Journal of Extreme Manufacturing
In-situ microwave–laser hybrid additive manufacturing of nano Al2O3/YAG/ZrO2 ternary eutectic melt-growth ceramics: control of microstructural homogeneity and high densification
17-Feb-2026