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2,080 results on '"Boon, Nico"'

119. Preliminary insights into the coupling of qualitative and quantitative tests for self-healing of mortars

Author

Giordano, Franco Grosso, Madrid, Dulce Valdez, Boon, Nico, Cnudde, Veerle, and De Belie, Nele

Subjects
Mortar, Technology and Engineering, Self-healing, X-ray micro-CT, Durability
Abstract

Self-healing is a spontaneously occurring process during crack formation where CO2 and H2O are allowed in, leading to the formation of new carbonation and hydration products that can seal the crack. This well characterized phenomenon has proven useful as an effective method of extending the durability and service life of structures. Currently, multiple methods exist to assess the effectiveness of self-healing, yet coupled experiments that demonstrate quantitative and qualitative effects of the healing processes are scarce. In this work, a new technique is presented that couples water flow tests for recovery of durability, visual scans used to analyze surface healing and μCT for internal observation of crack morphology and dynamics. CEM II/A-LL 32.5R mortar was cast in cylinders of 45 mm diameter with a cast-in-hole and cracked at 7 days. Samples were placed in wet/dry cycles and water flow tests and superficial crack closure was assessed at 0 days, 28 days and 112 days after cracking. Finally, samples were scanned using μCT to demonstrate the potential of this novel protocol. The results highlight the importance of coupled tests to provide a more comprehensive evaluation of the healing process in mortars.

Published
2022
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128. The influence of H2 partial pressure on biogenic palladium nanoparticle production assessed by single‐cell ICP‐mass spectrometry.

Author

Law, Cindy Ka Y., Bolea‐Fernandez, Eduardo, Liu, Tong, Bonin, Luiza, Wallaert, Elien, Verbeken, Kim, De Gusseme, Bart, Vanhaecke, Frank, and Boon, Nico

Subjects
PARTIAL pressure, NANOPARTICLES, PALLADIUM, INDUCTIVELY coupled plasma mass spectrometry, NANOPARTICLE size, SPECTROMETRY
Abstract

The production of biogenic palladium nanoparticles (bio‐Pd NPs) is widely studied due to their high catalytic activity, which depends on the size of nanoparticles (NPs). Smaller NPs (here defined as <100 nm) are more efficient due to their higher surface/volume ratio. In this work, inductively coupled plasma‐mass spectrometry (ICP‐MS), flow cytometry (FCM) and transmission electron microscopy (TEM) were combined to obtain insight into the formation of these bio‐Pd NPs. The precipitation of bio‐Pd NPs was evaluated on a cell‐per‐cell basis using single‐cell ICP‐MS (SC‐ICP‐MS) combined with TEM images to assess how homogenously the particles were distributed over the cells. The results provided by SC‐ICP‐MS were consistent with those provided by "bulk" ICP‐MS analysis and FCM. It was observed that heterogeneity in the distribution of palladium over an entire cell population is strongly dependent on the Pd2+ concentration, biomass and partial H2 pressure. The latter three parameters affected the particle size, ranging from 15.6 to 560 nm, and exerted a significant impact on the production of the bio‐Pd NPs. The TEM combined with SC‐ICP‐MS revealed that the mass distribution for bacteria with high Pd content (144 fg Pd cell−1) indicated the presence of a large number of very small NPs (D50 = 15.6 nm). These results were obtained at high cell density (1 × 105 ± 3 × 104 cells μl−1) and H2 partial pressure (180 ml H2). In contrast, very large particles (D50 = 560 nm) were observed at low cell density (3 × 104 ± 10 × 102 cells μl−1) and H2 partial pressure (10–100 ml H2). The influence of the H2 partial pressure on the nanoparticle size and the possibility of size‐tuned nanoparticles are presented. [ABSTRACT FROM AUTHOR]

Published
2023
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