Impact of surfactant and clay platelets on electrokinetic potential and size distribution in carbon nanotubes aqueous suspensions

M. Manilo, K. Bohacs, N. Lebovka, S. Bárány

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7 Citations (Scopus)

Abstract

Stabilization of aqueous suspensions of carbon nanotubes (CNTs) is an acute task for a number of technological processes. The effects of cationic surfactant (cetyltrimethyl-ammonium bromide, CTAB) and clay platelets (Laponite RD® (Lap)) on the electrokinetic potential and aggregation stability/size distribution of CNTs have been studied. The studies were performed at constant pH (4.5 ± 0.1), and at different values of the added amount of the reagent, mass ratio between Lap/CNTs, aging time as well as duration of the suspension ultrasonic treatment. In a CTAB concentration interval of Cs = 3.64.10−5 − 1.82.10-2 wt.% a narrow monomodal size distribution was found. The median size of aggregates was 21–24 μm that is two times larger than the length of individual CNTs (5–10 μm). At higher CTAB concentrations (above critical micelle concentrations (CMC)), formation of aggregates with median size of 140–150 μm takes place, with preserving the monomodal size distribution. Aggregation of CNTs in this case probably occurs by deposition of individual CNT on the surface of primary aggregates. Addition of Lap platelets in the range from X = 0 to 0.4 (where X is the mass ratio of Lap/CNTs) causes a monotonic decrease of the ζ-potential of the CNTs from −40 mV to −30 mV with reaching its plateau value at X = 0.4–1.0. This evidences the high surface coverage of CNTs by Lap platelets at which the CNT + Lap complex acquires the ζ-potential value of Lap. In mixed CNT + Lap suspensions (X = 1.0), a bimodal particle size distribution was registered, with appearance of big aggregates (≈150–300 μm), both in dilute (Cs = 3.64.10−5 – 3.64.10-3 wt.%) and concentrated (Cs > Cs CMC) solutions. These big hybrid CNT + Lap aggregates were loose, rather unstable, and they could be easily destroyed by ultrasonic treatment.

Original languageEnglish
Pages (from-to)205-212
Number of pages8
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Volume544
DOIs
Publication statusPublished - May 5 2018

Fingerprint

Carbon Nanotubes
electrokinetics
Platelets
platelets
Surface-Active Agents
clays
Carbon nanotubes
Suspensions
Clay
Surface active agents
carbon nanotubes
surfactants
ammonium bromides
ultrasonic processing
Critical micelle concentration
mass ratios
clay
micelles
Agglomeration
Ultrasonics

Keywords

  • Carbon nanotubes
  • Cetyltrimethylammonium bromide
  • Electrokinetic potential
  • Laponite platelets
  • Size distribution

ASJC Scopus subject areas

  • Surfaces and Interfaces
  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

Cite this

@article{381e3e25c30847aea1fee99a0d416d22,
title = "Impact of surfactant and clay platelets on electrokinetic potential and size distribution in carbon nanotubes aqueous suspensions",
abstract = "Stabilization of aqueous suspensions of carbon nanotubes (CNTs) is an acute task for a number of technological processes. The effects of cationic surfactant (cetyltrimethyl-ammonium bromide, CTAB) and clay platelets (Laponite RD{\circledR} (Lap)) on the electrokinetic potential and aggregation stability/size distribution of CNTs have been studied. The studies were performed at constant pH (4.5 ± 0.1), and at different values of the added amount of the reagent, mass ratio between Lap/CNTs, aging time as well as duration of the suspension ultrasonic treatment. In a CTAB concentration interval of Cs = 3.64.10−5 − 1.82.10-2 wt.{\%} a narrow monomodal size distribution was found. The median size of aggregates was 21–24 μm that is two times larger than the length of individual CNTs (5–10 μm). At higher CTAB concentrations (above critical micelle concentrations (CMC)), formation of aggregates with median size of 140–150 μm takes place, with preserving the monomodal size distribution. Aggregation of CNTs in this case probably occurs by deposition of individual CNT on the surface of primary aggregates. Addition of Lap platelets in the range from X = 0 to 0.4 (where X is the mass ratio of Lap/CNTs) causes a monotonic decrease of the ζ-potential of the CNTs from −40 mV to −30 mV with reaching its plateau value at X = 0.4–1.0. This evidences the high surface coverage of CNTs by Lap platelets at which the CNT + Lap complex acquires the ζ-potential value of Lap. In mixed CNT + Lap suspensions (X = 1.0), a bimodal particle size distribution was registered, with appearance of big aggregates (≈150–300 μm), both in dilute (Cs = 3.64.10−5 – 3.64.10-3 wt.{\%}) and concentrated (Cs > Cs CMC) solutions. These big hybrid CNT + Lap aggregates were loose, rather unstable, and they could be easily destroyed by ultrasonic treatment.",
keywords = "Carbon nanotubes, Cetyltrimethylammonium bromide, Electrokinetic potential, Laponite platelets, Size distribution",
author = "M. Manilo and K. Bohacs and N. Lebovka and S. B{\'a}r{\'a}ny",
year = "2018",
month = "5",
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doi = "10.1016/j.colsurfa.2018.02.030",
language = "English",
volume = "544",
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TY - JOUR

T1 - Impact of surfactant and clay platelets on electrokinetic potential and size distribution in carbon nanotubes aqueous suspensions

AU - Manilo, M.

AU - Bohacs, K.

AU - Lebovka, N.

AU - Bárány, S.

PY - 2018/5/5

Y1 - 2018/5/5

N2 - Stabilization of aqueous suspensions of carbon nanotubes (CNTs) is an acute task for a number of technological processes. The effects of cationic surfactant (cetyltrimethyl-ammonium bromide, CTAB) and clay platelets (Laponite RD® (Lap)) on the electrokinetic potential and aggregation stability/size distribution of CNTs have been studied. The studies were performed at constant pH (4.5 ± 0.1), and at different values of the added amount of the reagent, mass ratio between Lap/CNTs, aging time as well as duration of the suspension ultrasonic treatment. In a CTAB concentration interval of Cs = 3.64.10−5 − 1.82.10-2 wt.% a narrow monomodal size distribution was found. The median size of aggregates was 21–24 μm that is two times larger than the length of individual CNTs (5–10 μm). At higher CTAB concentrations (above critical micelle concentrations (CMC)), formation of aggregates with median size of 140–150 μm takes place, with preserving the monomodal size distribution. Aggregation of CNTs in this case probably occurs by deposition of individual CNT on the surface of primary aggregates. Addition of Lap platelets in the range from X = 0 to 0.4 (where X is the mass ratio of Lap/CNTs) causes a monotonic decrease of the ζ-potential of the CNTs from −40 mV to −30 mV with reaching its plateau value at X = 0.4–1.0. This evidences the high surface coverage of CNTs by Lap platelets at which the CNT + Lap complex acquires the ζ-potential value of Lap. In mixed CNT + Lap suspensions (X = 1.0), a bimodal particle size distribution was registered, with appearance of big aggregates (≈150–300 μm), both in dilute (Cs = 3.64.10−5 – 3.64.10-3 wt.%) and concentrated (Cs > Cs CMC) solutions. These big hybrid CNT + Lap aggregates were loose, rather unstable, and they could be easily destroyed by ultrasonic treatment.

AB - Stabilization of aqueous suspensions of carbon nanotubes (CNTs) is an acute task for a number of technological processes. The effects of cationic surfactant (cetyltrimethyl-ammonium bromide, CTAB) and clay platelets (Laponite RD® (Lap)) on the electrokinetic potential and aggregation stability/size distribution of CNTs have been studied. The studies were performed at constant pH (4.5 ± 0.1), and at different values of the added amount of the reagent, mass ratio between Lap/CNTs, aging time as well as duration of the suspension ultrasonic treatment. In a CTAB concentration interval of Cs = 3.64.10−5 − 1.82.10-2 wt.% a narrow monomodal size distribution was found. The median size of aggregates was 21–24 μm that is two times larger than the length of individual CNTs (5–10 μm). At higher CTAB concentrations (above critical micelle concentrations (CMC)), formation of aggregates with median size of 140–150 μm takes place, with preserving the monomodal size distribution. Aggregation of CNTs in this case probably occurs by deposition of individual CNT on the surface of primary aggregates. Addition of Lap platelets in the range from X = 0 to 0.4 (where X is the mass ratio of Lap/CNTs) causes a monotonic decrease of the ζ-potential of the CNTs from −40 mV to −30 mV with reaching its plateau value at X = 0.4–1.0. This evidences the high surface coverage of CNTs by Lap platelets at which the CNT + Lap complex acquires the ζ-potential value of Lap. In mixed CNT + Lap suspensions (X = 1.0), a bimodal particle size distribution was registered, with appearance of big aggregates (≈150–300 μm), both in dilute (Cs = 3.64.10−5 – 3.64.10-3 wt.%) and concentrated (Cs > Cs CMC) solutions. These big hybrid CNT + Lap aggregates were loose, rather unstable, and they could be easily destroyed by ultrasonic treatment.

KW - Carbon nanotubes

KW - Cetyltrimethylammonium bromide

KW - Electrokinetic potential

KW - Laponite platelets

KW - Size distribution

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