Surfactant-Modified Silica Nanoparticles-Stabilized Magnetic Polydimethylsiloxane-in-Water Pickering Emulsions for Lubrication and Anticorrosion

Abstract

Traditional industrial lubricating emulsions usually contain a variety of constituents to fulfill their functional requirements in long-term stability, lubrication, and anticorrosion. The complexity of the constituents may produce difficulties for their preparation, storage, and recycling. To address this issue, here we design and prepare simple-component, switchable, and multifunctional Pickering emulsions using the green lubricating base oil polydimethylsiloxane, water, and silica nanoparticles m o d i fi e d w i t h a s e r i e s o f m a g n e t i c s u r f a c t a n t s (C n H 2n+1 N + (CH 3 ) 3 [XCl 3 Br] − , n = 12, 14, and 16, X = Ce, Fe, and Gd) as compositions. The Pickering emulsions are demonstrated to be highly stable, lubricative, and anticorrosive. Their magneto-responsiveness indicates a potential application as smart lubricants. Their reversible emulsification and demulsification, which allows an effective recycling and reuse of the composite nanoparticles, can be regulated by alternative centrifugation and homogenization or successive addition of the anionic surfactant sodium dodecyl sulfate and the magnetic cationic surfactants. Both their stability and lubricity can be optimized by using surfactant C 16 H 33 N + (CH 3 ) 3 [CeCl 3 Br] − (CTACe) as the surface coating for the silica particles. The deposition of CTACe-modified silica nanoparticles endows a metallic material with a high resistance to abrasion and corrosion. We envision that such emulsions, consisting of eco-friendly, biocompatible, and low-cost materials, could find extensive applications in sustainable chemistry and engineering.

A Microemulsion Superlubricant with Largely Switchable Friction

“…Magnetic cationic surfactants didodecyldimethylammonium tetrachlorocerate (DDACe), didodecyldimethylammonium tetrachloroferrate (DDAFe) and didodecyldimethylammonium tetrachlorogadolinate (DDAGd) were synthesized by mixing an equal molar amount of DDABr with CeCl3, FeCl3 and GdCl3, respectively, in methanol and stirring overnight at room temperature. 26,34 The solvents were then evaporated and the products were dried under reduced pressure at 80 ºC overnight, yielding white, orange and white solids for DDACe, DDAFe and DDAGd, respectively. Sample preparation.…”

“…It can be seen that the microemulsion exhibited unique absorption bands at around 900, 882, 722 and 397 eV in XPS Ce 3d, Fe 2p and N 1s spectra, corresponding to formation of CeO2 and ferric nitrides on a steel substrate. The results suggest that surfactant DDACe underwent tribochemical reactions to help effectively dissipate the mechanical energy generated during the frictional process, 34 thus contributing to achieving superlubrication. In addition, given that surfactants without [CeCl4]cannot result in ultralow friction under the same tribological conditions, hence, the exceptional lubrication should mainly stem from reactions of the Ce (III)-containing coordination anion, which led to formation of CeO2 products having been testified to possess excellent lubricity.…”

“…In addition, given that surfactants without [CeCl4]cannot result in ultralow friction under the same tribological conditions, hence, the exceptional lubrication should mainly stem from reactions of the Ce (III)-containing coordination anion, which led to formation of CeO2 products having been testified to possess excellent lubricity. [34][35][36] The absorption bands completely vanished at 50 ºC, indicating that the tribochemical reactions were suppressed, which consequently gave rise to a dramatically deteriorated lubrication of the DDACe/EG/n-hexane/water mixture.…”

Pluronic Induced Interparticle Attraction and Re-entrant Liquid–Liquid Phase Separation in Charged Silica Nanoparticle Suspensions

“…60 Such stabilization can be modulated by various electrolytes, ionic, nonionic, and zwitterionic surfactants, to bring about desired modification in the phase behavior of these silica suspensions. 56 In this paper, we show that introducing non-DLVO forces like steric and hydrophobic interaction in anionic Ludox TM-40 nanoparticle suspensions through physical adsorption of triblock copolymer EO 20 PO 70 EO 20 (Pluronic P123) micelles on the nanoparticle surfaces induces interparticle attraction and brings about liquid−liquid phase separation in the system. The observed phase separations are reversible in nature and are associated with a lower consolute temperature.…”

“…Among the nanoparticle systems that are explored for different applications, amorphous silica nanoparticles in normal and mesoporous forms remain one of the frontrunners due to their biocompatibility, low toxicity, ease of synthesis, and wide availability. − Various surface functionalized silica nanoparticulate systems are thus investigated and put into application in the fields of biomedical, food, and polymer processing, catalysis, Pickering emulsions, oil recovery, etc. ; and the numbers are increasing by the day. − In aqueous medium, these nanoparticles are electrostatically stabilized in alkaline pH as anionic entities with negative zeta potential through ionization of surface silanol groups .…”