Abrasion properties of self-suspended hairy titanium dioxide nanomaterials
Appl Nanosci
Abrasion properties of self-suspended hairy titanium dioxide nanomaterials
Jiao-xia Zhang 0 1
Si Liu 0 1
Chao Yan 0 1
Ya-ming Yu 0 1
Shi-yun Li 0 1
Xiao-jing Wang 0 1
Lei Wang 0 1
0 College of Materials Science and Engineering, Huaqiao University , 361021 Xiamen , China
1 School of Materials Science and Engineering, Jiangsu University of Science and Technology , Zhenjiang 212003 , China
Considering the excellent solubility of pyrrolidone ring organic compounds, the synthesized N(trimethoxysilyl) propyl-N-methyl-2-pyrrolidone chlorides was tethered onto titanium dioxide (TiO2) nanoparticles to improve dispersion of TiO2, and then polyethylene oxide (PEO) oligomer through ion exchange embraced the tethered TiO2 to obtain a novel self-suspended hairy TiO2 nanomaterials without any solvent. A variety of techniques were carried out to illustrate the structure and properties of the self-suspended hairy TiO2 nanomaterials. It was found that TiO2 nanoparticles embody monodispersity in the hybrid system though the ''false reunion'' phenomenon occurring due to nonpermanent weak physical cross-linking. Remarkably, self-suspended hairy TiO2 nanomaterials exhibit lower viscosity, facilitating maneuverable and outstanding antifriction and wear resistance properties, due to the synergistic lubricating effect between spontaneously forming lubricating film and nano-lubrication of TiO2 cores, overcoming the deficiency of both solid and liquid lubricants. This make them promising candidates for the micro-electromechanic/nano-electromechanic systems (MEMS/NEMS).
Friction and wear properties; Self-suspended hairy nanomaterials; TiO2 nanoparticles; Liquid-like behavior
Introduction
With the rapid development of nanotechnology, the
moving interface gap of micro-/nano-electromechanical
systems and magnetic recording system has been reduced to
nanometers for achieving more components on per unit,
faster response speed and better and more properties.
Therefore, nanotribology puts forward higher requirements
such as high thermal stability, excellent temperature
fluidity, low vapor pressure, good lubrication,
abrasion-resistance and self-repairing capacity
(Rojas et al. 2015; Ye
et al. 2001; Hussein et al. 2015; Tang et al. 2014)
. Solid
inorganic or liquid organic materials are the traditional
lubricants for controlling friction and wear, e.g., natural
and synthetic organics (animal fat, vegetable oil, refined
oil, silicone oil, esters, etc.), micro-/nanometal oxide
powder (MoS2, ZnO, etc.) and carbon materials. In general,
solid lubricants are usually added into the lube base oil to
reduce the interfacial friction and improve the load-bearing
capacity of the parts by their benign extreme pressure
grease, anti-oxide, anti-wear roles and so on. However,
solid lubricating additives cannot homogeneously disperse
well in the base oil, due to their easy agglomeration and
poor compatibility with the base oil. Compared with the
solid lubricants, liquid lubricants show different
advantages, such as long-term endurance, low mechanical noise,
promotion of thermal conductance and very low friction in
the elastohydrodynamic film regime
(Zheng et al. 2016)
.
Liquid lubricants can be directly used as lubricant without
the base oil, but their ability to bear the wear resistance
decreases due to the absence of solid nanoparticles
(Guo
et al. 2006)
.
Compared with traditional nanofluids, novel
self-suspended nanomaterials at room temperature through
covalent graft a soft organic corona onto the nanomaterials
surface have been proved to enhance the manipulation and
impart compatibility of nanoparticles
(Huang et al. 2016;
Li et al. 2015; Lei et al. 2008; Zheng et al. 2016; Warren
et al. 2006)
. Organic corona generally refers to a
surfaceactive agent, in which one end can tether nanoparticles and
the other can further bond with polymers. A series of
selfsuspended hairy nanomaterials based on various
nanoparticles such as TiO2, SiO2, graphene oxide and carbon
nanotubes have been fabricated using nanoparticles as
cores, surface functionalized with a charged corona, and
ionically tethered with oligomeric chains as a canopy to
balance the charge
(Zhang et al. 2009a, b, 2013; Yang et al.
2016c; Petit et al. 2013; Li et al. 2009, 2016a, b)
.
Selfsuspended hairy nanomaterials offer attractive possibilities
for particular applications, e.g., transportation,
microelectromechanical systems (MEMS), liquid electrolytes
and magnetic fluid. For the lubricating materials,
silicabased nanomaterials with liquid-like behavior used as
thickeners in traditional lubricating oils created lubricants
whose friction coefficients were lower than that of the base
oil, as demonstrated by Yang et al. (2016b) and
Kim and
Archer (2011)
. More importantly, wear resistance also was
reduced due to the localization of silica in the wear tracks
of the contact surface. The silica-based nanomaterial with
liquid-like
(Li et al. 2016a, b; Bai et al. 2016)
b (...truncated)