Bhagavathi Kandy Sharu, Simon George P, Cheng Wenlong, Zank Johann, Joshi Kapil, Gala Dharmesh, Bhattacharyya Arup R
IITB-Monash Research Academy, Powai, Mumbai 400076, India.
Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
ACS Omega. 2018 Oct 19;3(10):13584-13597. doi: 10.1021/acsomega.8b00579. eCollection 2018 Oct 31.
Multiwalled carbon nanotubes (MWCNTs) were incorporated into highly concentrated water-in-oil emulsions with the ultimate aim of achieving a uniform and effective dispersion of MWCNTs within the emulsion matrix. The emulsion was formulated in such a way, wherein the internal phase consists of higher than 90 wt %. By keeping the same aqueous-to-oil phase ratio, the amount of MWCNTs in the oil phase was systematically adjusted to investigate their effects on the microstructure development and rheological behavior of the emulsion. The addition of MWCNTs led to a reduced droplet size and also resulted in a narrower distribution of the droplet size. The rheological behavior of nanotube-incorporated emulsions was characterized with varying MWCNT concentrations and also as a function of the emulsification time. The rheological characteristics of the nanotube-incorporated emulsions were identical to those of the neat emulsion and were primarily governed by the variation in the droplet size and droplet-size distribution. However, the yield strain and cross-over strain were independent of the mean droplet size and polydispersity of the emulsion. Emulsions that have smaller droplets exhibited higher storage modulus ('), yield stress (τ), and apparent viscosity (η). For all refining times investigated, nanotube-incorporated emulsions have higher ', τ, and η values when compared to the neat emulsion, and these values further increased with the MWCNT concentration. This was primarily due to the decrease in the droplet size with MWCNT addition. Furthermore, our findings suggest that the incorporated MWCNTs did not induce any significant change in the rheological behavior of emulsions with identical droplet sizes, and it remained essentially unchanged with the concentration of MWCNTs. However, the nanotube-incorporated emulsions possessed solidlike behavior up to a higher applied stress when compared to a neat emulsion of identical droplet size.
将多壁碳纳米管（MWCNTs）掺入高浓度油包水乳液中，最终目的是使MWCNTs在乳液基质中实现均匀且有效的分散。乳液的配方设计使得内相含量高于90 wt%。在保持相同水油相比的情况下，系统地调整油相中MWCNTs的含量，以研究其对乳液微观结构发展和流变行为的影响。MWCNTs的加入导致液滴尺寸减小，并且液滴尺寸分布也变窄。对掺入纳米管的乳液的流变行为进行了表征，考察了不同MWCNT浓度以及乳化时间的影响。掺入纳米管的乳液的流变特性与纯乳液相同，主要由液滴尺寸和液滴尺寸分布的变化决定。然而，屈服应变和交叉应变与乳液的平均液滴尺寸和多分散性无关。具有较小液滴的乳液表现出更高的储能模量（'）、屈服应力（τ）和表观粘度（η）。在所研究的所有细化时间内，与纯乳液相比，掺入纳米管的乳液具有更高的'、τ和η值，并且这些值随着MWCNT浓度的增加而进一步增大。这主要是由于添加MWCNTs后液滴尺寸减小。此外，我们的研究结果表明，掺入的MWCNTs不会对具有相同液滴尺寸的乳液的流变行为产生任何显著变化，并且其流变行为基本上不会随MWCNTs浓度而改变。然而，与具有相同液滴尺寸的纯乳液相比，掺入纳米管的乳液在更高的外加应力下仍具有类似固体的行为。
