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Aspect Ratio Dependence of Isotropic-Nematic Phase Separation of Nanoplates in Gravity

Abhijeet Shinde
Abhijeet Shinde
, 
Xuezhen Wang
Xuezhen Wang
, 
Yi-Hsien Yu
Yi-Hsien Yu
 y 
Zhengdong Cheng
Zhengdong Cheng
   | 17 jul 2020
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Article Category: Research Article
Publicado en línea: 17 jul 2020
Páginas: 17 - 26
DOI: https://doi.org/10.2478/gsr-2016-0002
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© 2016 Abhijeet Shinde et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

A scanning electron microscope (SEM) image of the pristine ZrP disks.
A scanning electron microscope (SEM) image of the pristine ZrP disks.

Figure 2

Lateral size (diameter) distributions of nanoplates in group 1 to group 5 suspensions used in this study. The values were measured using Dynamic Light Scattering (DLS) and they were fit to the log-normal distribution function.
Lateral size (diameter) distributions of nanoplates in group 1 to group 5 suspensions used in this study. The values were measured using Dynamic Light Scattering (DLS) and they were fit to the log-normal distribution function.

Figure 3

Snapshots of a group 1 nanoplate suspension ( ξ=0.0059−0.0018+0.0049\xi = 0.0059_{- 0.0018}^{+ 0.0049} ) between crossed polarizers with a ZrP platelet volume fraction, ϕ = 1.75%, taken as a function of time. In the beginning, the suspension was in a metastable liquid state and then underwent the nucleation and growth of tactoids, followed by tactoid sedimentation, which was completed at time, t*, when a clear interface between isotropic and nematic phases had established.
Snapshots of a group 1 nanoplate suspension ( ξ=0.0059−0.0018+0.0049\xi = 0.0059_{- 0.0018}^{+ 0.0049} ) between crossed polarizers with a ZrP platelet volume fraction, ϕ = 1.75%, taken as a function of time. In the beginning, the suspension was in a metastable liquid state and then underwent the nucleation and growth of tactoids, followed by tactoid sedimentation, which was completed at time, t*, when a clear interface between isotropic and nematic phases had established.

Figure 4

(a) Transmittance profiles along vertical line in group 1 suspension with I/Io plotted at different times. Position of I-N interface is pointed with an arrow. The transmittance profile shows a sudden jump at 341 min, indicating the establishment of I-N interface. (b) Area under the transmittance curve in (a) for the region above the I-N interface was plotted as a function of time. Time t* corresponds to the point where area becomes zero.
(a) Transmittance profiles along vertical line in group 1 suspension with I/Io plotted at different times. Position of I-N interface is pointed with an arrow. The transmittance profile shows a sudden jump at 341 min, indicating the establishment of I-N interface. (b) Area under the transmittance curve in (a) for the region above the I-N interface was plotted as a function of time. Time t* corresponds to the point where area becomes zero.

Figure 5

Crossed polarizers images of group 1 nanoplate suspensions at various concentrations taken at (a) 1 h (b) 2 h (c) 5.5 h after homogenization. Left to right, ϕ = 0.0140, 0.0158, 0.0175, 0.0193, 0.0210, 0.0228, 0.0280, and 0.0350.
Crossed polarizers images of group 1 nanoplate suspensions at various concentrations taken at (a) 1 h (b) 2 h (c) 5.5 h after homogenization. Left to right, ϕ = 0.0140, 0.0158, 0.0175, 0.0193, 0.0210, 0.0228, 0.0280, and 0.0350.

Figure 6

Crossed polarizer images of aqueous suspensions of different aspect ratio and different concentrations of α-ZrP nanoplates. Left column shows textures of suspensions immediately after homogenization and the right column shows images when a clear interface between the Isotropic (I) and Nematic (N) phase was established. The ZrP nanoplate percentage by volume in each vial is labeled below. Group numbers of different samples are indicated on the left side at the beginning of each row.
Crossed polarizer images of aqueous suspensions of different aspect ratio and different concentrations of α-ZrP nanoplates. Left column shows textures of suspensions immediately after homogenization and the right column shows images when a clear interface between the Isotropic (I) and Nematic (N) phase was established. The ZrP nanoplate percentage by volume in each vial is labeled below. Group numbers of different samples are indicated on the left side at the beginning of each row.

Figure 7

Isotropic-nematic (I-N) phase separation time (t*, in hours) is plotted as a function of aspect ratio. The nematic fraction of the samples used to determine t* values was about 50%.
Isotropic-nematic (I-N) phase separation time (t*, in hours) is plotted as a function of aspect ratio. The nematic fraction of the samples used to determine t* values was about 50%.

Lateral diameters of nanoplates in five different types of suspensions used in this study.

GroupAverage Diameter (<d>) in nmStandard Deviation (σ) in nmPolydispersity (Δ = σ/<d>)Aspect Ratio (ξ = l/d)
145420846%0.0059−0.0018+0.00490.0059_{- 0.0018}^{+ 0.0049}
261613728%0.0045−0.0008+0.00120.0045_{- 0.0008}^{+ 0.0012}
393321228%0.0028−0.0005+0.00080.0028_{- 0.0005}^{+ 0.0008}
4110521625%0.0025−0.0004+0.00060.0025_{- 0.0004}^{+ 0.0006}
5135628826%0.0020−0.0003+0.00050.0020_{- 0.0003}^{+ 0.0005}
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