A recent study published in Advanced Photonics Research examined how carbon black (CB) nanoparticles can improve the thermo-optical properties of polymer powders used in laser powder bed fusion of polymers (PBF-LB/P).
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Background
PBF-LB/P is a precision additive manufacturing method that uses focused laser beams to fuse polymer powders layer by layer. This approach allows for complex geometries and reduces material waste. As the field moves toward more energy-efficient production, near-infrared diode lasers are replacing traditional carbon dioxide (CO2) lasers. However, many polymers are transparent to near-infrared light, which limits laser absorption and reduces processing efficiency.
To overcome this, CB nanoparticles are added as radiation absorbers. Their high surface area and compatibility with polymers help improve energy absorption and processing performance. Despite these benefits, challenges such as particle agglomeration and changes to mechanical properties must be addressed. Properly managing the distribution and integration of CB nanoparticles is key to realizing their full potential in additive manufacturing.
Investigating Carbon Black Nanoparticles
The researchers studied how the amount, placement, and dispersion of CB nanoparticles affect the optical and thermal behavior of PA11 powders during PBF-LB/P. They used two approaches: surface-additivation (SA), where nanoparticles are applied to the outer surface of powder particles, and volume-additivation (VA), where nanoparticles are embedded throughout the material.
To analyze the powders, the team used several techniques:
- Differential scanning calorimetry (DSC) to examine thermal behavior.
- Scanning electron microscopy (SEM) for surface imaging.
- Laser diffraction to evaluate particle size distribution.
- Polarized light microscopy to study crystalline structures.
- A double integrating sphere setup with an 808 nm laser to measure effective attenuation coefficients, simulating real PBF-LB/P conditions.
Key Findings: Effects of Carbon Black on Powder Performance
The results showed clear differences between the two additivation methods. Surface-additivated powders exhibited stronger laser attenuation compared to volume-additivated ones.
At a low concentration of 0.005 vol% CB, SA powders increased the attenuation coefficient by approximately 2.8 times, while VA powders showed a 1.9-fold increase. This difference was attributed to the formation of a nanoparticle layer on the particle surfaces in SA samples, which created a more effective optical barrier.
In terms of particle size, SA preserved the original size range of PA11 powders. In contrast, VA caused noticeable reductions (up to 38 microns at higher CB concentrations) due to changes in crystallization during processing. Maintaining particle size between 45 and 90 microns is important for consistent performance in PBF-LB/P, so this change has practical implications.
The addition of CB also affected the crystallization behavior of the polymer. SA powders showed higher crystallinity and higher melting temperatures than unmodified PA11. The DSC analysis revealed an earlier onset of crystallization, which narrowed the processing window. This means laser and temperature settings must be more carefully controlled to prevent premature solidification.
Laser absorption measurements confirmed that pristine PA11 absorbs very little near-infrared light. However, CB-enhanced powders (especially those treated with surface-additivation) showed up to a 14-fold increase in effective laser absorption. These results highlight how important nanoparticle placement and dispersion are in controlling thermal and optical performance.
Potential Applications in Additive Manufacturing
This study has several takeaways for improving additive manufacturing. By adjusting how CB nanoparticles are added and distributed, manufacturers can improve the efficiency of laser processing and the quality of printed parts. Surface-additivation, in particular, provides strong improvements in laser absorption without significantly changing powder morphology.
The findings also support the development of polymer formulations that combine nano-additives with base materials to reduce energy use and material waste. These improvements could benefit industries where part performance and production efficiency are critical, such as aerospace, automotive, and healthcare.
While SA improves optical properties, VA may offer different benefits (such as thermal stability) but can also lead to challenges like reduced flowability and increased interparticle cohesion. Balancing these trade-offs will be important for tailoring powder performance to specific applications.
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Conclusion
The study demonstrated that carbon black nanoparticles can significantly improve the thermo-optical properties of PA11 powders used in PBF-LB/P. The position and dispersion of the nanoparticles play a key role in optimizing laser interaction, energy efficiency, and final part quality.
Future research should focus on refining nanoparticle integration methods, testing alternative additives, and evaluating the long-term performance of printed parts in real-world conditions. These efforts will help advance high-performance, sustainable materials tailored for additive manufacturing, supporting better process reliability and lower environmental impact.
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Journal Reference
Sommereyns, A., et al. (2025). Thermo-Optical Analysis of Surface- and Volume-Additivated Polymer Powders for Near-Infrared Laser Powder Bed Fusion. Advanced Photonics Research. DOI: 10.1002/adpr.202400207, https://advanced.onlinelibrary.wiley.com/doi/10.1002/adpr.202400207
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