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On the self-damping nature of densification in photonic sintering of nanoparticles.

MacNeill W, Choi CH, Chang CH, Malhotra R - Sci Rep (2015)

Bottom Line: It is shown that smaller nanoparticles result in faster densification, with lower temperatures during sintering, as compared to larger nanoparticles.It is shown that photonic sintering is an inherently self-damping process, i.e., the progress of densification reduces the magnitude of subsequent photonic heating even before full density is reached.By accounting for this phenomenon, the developed coupled model better captures the experimentally observed sintering temperature and densification as compared to conventional photonic sintering models.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Oregon State University, Corvallis, Oregon, USA.

ABSTRACT
Sintering of nanoparticle inks over large area-substrates is a key enabler for scalable fabrication of patterned and continuous films, with multiple emerging applications. The high speed and ambient condition operation of photonic sintering has elicited significant interest for this purpose. In this work, we experimentally characterize the temperature evolution and densification in photonic sintering of silver nanoparticle inks, as a function of nanoparticle size. It is shown that smaller nanoparticles result in faster densification, with lower temperatures during sintering, as compared to larger nanoparticles. Further, high densification can be achieved even without nanoparticle melting. Electromagnetic Finite Element Analysis of photonic heating is coupled to an analytical sintering model, to examine the role of interparticle neck growth in photonic sintering. It is shown that photonic sintering is an inherently self-damping process, i.e., the progress of densification reduces the magnitude of subsequent photonic heating even before full density is reached. By accounting for this phenomenon, the developed coupled model better captures the experimentally observed sintering temperature and densification as compared to conventional photonic sintering models. Further, this model is used to uncover the reason behind the experimentally observed increase in densification with increasing weight ratio of smaller to larger nanoparticles.

No MeSH data available.


SEM images of sintered mixed 10 and 20 nm ink with weight ratio (a) 1:4 (b) 2:3 (c) 3:2 (d) 4:1; SEM images of sintered mixed 10 and 40 nm ink with weight ratio (e) 1:4 (f) 2:3 (g) 3:2 (h) 4:1; (i) cross sectional SEM image of sintered mixed 10 nm and 20 nm ink mixed in weight ratio 4:1.
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f3: SEM images of sintered mixed 10 and 20 nm ink with weight ratio (a) 1:4 (b) 2:3 (c) 3:2 (d) 4:1; SEM images of sintered mixed 10 and 40 nm ink with weight ratio (e) 1:4 (f) 2:3 (g) 3:2 (h) 4:1; (i) cross sectional SEM image of sintered mixed 10 nm and 20 nm ink mixed in weight ratio 4:1.

Mentions: Figure 2 shows SEM images of the unsintered and sintered nanoparticles, for the unmixed nanoparticle inks. Note that the 10 nm nanoparticles densify to a greater degree as compared to the larger nanoparticles. Larger scale SEM images of the sintered nanoparticles (in Supplementary Fig. S1 online) also reflect this phenomenon. Since the applied optical power and sintering time are the same for all the inks, it can be inferred that the 10 nm nanoparticles undergo faster densification than the larger nanoparticles. SEM images of the sintered nanoparticles for mixed 10 nm and 20 nm nanoparticles (Fig. 3) show that an increase in weight ratio of smaller to larger nanoparticles also results in faster densification. Larger scale SEM images are shown in Supplementary Figs S2 and S3 online. As the mixing ratio increases the morphology of the sintered material changes from one similar to that of the unmixed larger nanoparticle inks, to a morphology in which the larger nanoparticles are enclosed in a matrix of highly densified material. Figure 4 shows the evolution of the maximum temperature of the nanoparticles during photonic sintering. The peak temperature is higher for larger nanoparticles (Fig. 4a) and mixing nanoparticles of different sizes (Fig. 4b,c) reduces the temperature rise as compared to the unmixed larger nanoparticles of the corresponding size. Further, comparison of the experimentally measured temperatures to the melting point of Ag nanoparticles (Fig. 4d, after Alarifi et al.28) shows that nanoparticle melting does not occur during the photonic sintering experiments performed here. These observations raise the following questions.


On the self-damping nature of densification in photonic sintering of nanoparticles.

MacNeill W, Choi CH, Chang CH, Malhotra R - Sci Rep (2015)

SEM images of sintered mixed 10 and 20 nm ink with weight ratio (a) 1:4 (b) 2:3 (c) 3:2 (d) 4:1; SEM images of sintered mixed 10 and 40 nm ink with weight ratio (e) 1:4 (f) 2:3 (g) 3:2 (h) 4:1; (i) cross sectional SEM image of sintered mixed 10 nm and 20 nm ink mixed in weight ratio 4:1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595846&req=5

f3: SEM images of sintered mixed 10 and 20 nm ink with weight ratio (a) 1:4 (b) 2:3 (c) 3:2 (d) 4:1; SEM images of sintered mixed 10 and 40 nm ink with weight ratio (e) 1:4 (f) 2:3 (g) 3:2 (h) 4:1; (i) cross sectional SEM image of sintered mixed 10 nm and 20 nm ink mixed in weight ratio 4:1.
Mentions: Figure 2 shows SEM images of the unsintered and sintered nanoparticles, for the unmixed nanoparticle inks. Note that the 10 nm nanoparticles densify to a greater degree as compared to the larger nanoparticles. Larger scale SEM images of the sintered nanoparticles (in Supplementary Fig. S1 online) also reflect this phenomenon. Since the applied optical power and sintering time are the same for all the inks, it can be inferred that the 10 nm nanoparticles undergo faster densification than the larger nanoparticles. SEM images of the sintered nanoparticles for mixed 10 nm and 20 nm nanoparticles (Fig. 3) show that an increase in weight ratio of smaller to larger nanoparticles also results in faster densification. Larger scale SEM images are shown in Supplementary Figs S2 and S3 online. As the mixing ratio increases the morphology of the sintered material changes from one similar to that of the unmixed larger nanoparticle inks, to a morphology in which the larger nanoparticles are enclosed in a matrix of highly densified material. Figure 4 shows the evolution of the maximum temperature of the nanoparticles during photonic sintering. The peak temperature is higher for larger nanoparticles (Fig. 4a) and mixing nanoparticles of different sizes (Fig. 4b,c) reduces the temperature rise as compared to the unmixed larger nanoparticles of the corresponding size. Further, comparison of the experimentally measured temperatures to the melting point of Ag nanoparticles (Fig. 4d, after Alarifi et al.28) shows that nanoparticle melting does not occur during the photonic sintering experiments performed here. These observations raise the following questions.

Bottom Line: It is shown that smaller nanoparticles result in faster densification, with lower temperatures during sintering, as compared to larger nanoparticles.It is shown that photonic sintering is an inherently self-damping process, i.e., the progress of densification reduces the magnitude of subsequent photonic heating even before full density is reached.By accounting for this phenomenon, the developed coupled model better captures the experimentally observed sintering temperature and densification as compared to conventional photonic sintering models.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Oregon State University, Corvallis, Oregon, USA.

ABSTRACT
Sintering of nanoparticle inks over large area-substrates is a key enabler for scalable fabrication of patterned and continuous films, with multiple emerging applications. The high speed and ambient condition operation of photonic sintering has elicited significant interest for this purpose. In this work, we experimentally characterize the temperature evolution and densification in photonic sintering of silver nanoparticle inks, as a function of nanoparticle size. It is shown that smaller nanoparticles result in faster densification, with lower temperatures during sintering, as compared to larger nanoparticles. Further, high densification can be achieved even without nanoparticle melting. Electromagnetic Finite Element Analysis of photonic heating is coupled to an analytical sintering model, to examine the role of interparticle neck growth in photonic sintering. It is shown that photonic sintering is an inherently self-damping process, i.e., the progress of densification reduces the magnitude of subsequent photonic heating even before full density is reached. By accounting for this phenomenon, the developed coupled model better captures the experimentally observed sintering temperature and densification as compared to conventional photonic sintering models. Further, this model is used to uncover the reason behind the experimentally observed increase in densification with increasing weight ratio of smaller to larger nanoparticles.

No MeSH data available.