The unique structure
and physical properties of graphene and anatase
TiO2 make them suitable for use as additives for engine
lubricants. This study describes the use of dielectric barrier discharge
plasma-assisted ball milling to synthesize a multilayer graphene-reinforced
TiO2 composite nanolubricant additive (MGTC). A variety
of physical and chemical tests were performed to characterize the
resulting experimental materials, including X-ray diffraction (XRD),
Fourier transform infrared (FT-IR), Raman, X-ray photoelectron spectroscopy
(XPS), and scanning electron microscopy (SEM). Four-ball friction
and wear testing machines were used to study the tribological properties
and extreme pressure anti-wear properties of a base oil containing
0.1, 0.5, 1.0, and 1.5 wt % of the modified TiO2. Raman
spectroscopy, XPS, SEM, and energy-dispersive spectrometry (EDS) analyses
were used to examine and analyze the microstructure of the friction
pairs. As a result of the plasma-assisted ball milling process, expanded
graphite was successfully separated into multilayer graphene nanosheets,
and spherical TiO2 was successfully bonded to the nanosheets
of the multilayer graphene. The 1.0 wt % composite oil was found to
provide good friction reduction and wear resistance. It had a film
thickness of 27.5 nm, which was 167% thicker than base oil. Due to
its excellent dispersion stability, the MGTC nanocomposite exhibited
excellent lubrication performance, which was attributed to the formation
of carbon protective films, titanium dioxide deposition films, transfer
films, and the occurrence of nano ball effects on the surface of friction
pairs.
Poor lubrication performance of low-sulfur fuel leads to increased wear of diesel engine components. In order to improve the lubrication properties of low-sulfur fuel, we successfully prepared graphene lubricant additives by dielectric barrier discharge plasma-assisted ball milling. The tribological properties of graphene lubricant additives in two types of 0# diesel oils with different sulfur content were evaluated by high-frequency reciprocating rig (HFRR). The results indicated that the expanded graphite was exfoliated and refined into graphene sheets with nine layers by the synergistic effect of the heat explosive effect of the discharge plasma, the impact of mechanical milling function, and the cavitation effect of 0# diesel oil. The organic functional groups of 0# diesel oil were successfully grafted on the surface of graphene sheets. The addition of 0.03 wt % graphene resulted in 20% reduction in the friction coefficient (COF) and 28% reduction in wear scar diameter (WSD) compared to pure 0# diesel oil with a sulfur content of 310 mg/kg. The addition of 0.03 wt % graphene resulted in 24% reduction in the friction coefficient (COF) and 30% reduction in wear scar diameter (WSD) compared to pure 0# diesel oil with a sulfur content of 1.1 mg/kg. The formation of graphene tribofilm on rubbing surfaces improved the lubrication properties of low-sulfur fuel.
Phase change materials (PCMs) are widely used in new energy storage fields such as industrial waste heat recovery and solar heat recovery. However, the low thermal conductivity of PCMs causes the slow heat storage efficiency of PCMs, resulting in a large waste of waste heat. For the sake of increasing the heat storage rate of PCMs, a new type of pulsating heat pipe (PHP) phase change heat storage device is designed, which couples PHP with PCMs. For sake of further improve the heat storage efficiency of the novel device, a different filling working medium was used in the experiment. The results show that methanol is the best charging working fluid compared with water and ethanol, the corresponding heat storage time of methanol was reduced by 2500 seconds and 900 seconds, respectively. Therefore, methanol is the best charging medium, followed by water and ethanol.
K E Y W O R D Sfilling working medium, heat storage rate, pulsating heat pipe (PHP)
In order to study the effect of high hydrostatic pressure on the corrosion of low-alloy steels in deepsea environments. The electrochemical corrosion behavior of single-metal system and triple-metal coupled system of 907A steel, 921A steel and 1# steel under different hydrostatic pressures were studied by electrochemical, weight loss and morphology observation methods. The results show that the high hydrostatic pressure promotes the corrosion of low-alloy steel by changing the composition and morphology of corrosion products. In addition, there was also severe galvanic corrosion between the couples with a low potential difference (< 60 mV),907A steel was used as the anode of the three-metal coupled system, and 921A steel and 1# steel as the cathode. The galvanic coupling effect accelerates the pitting corrosion of 907A steel as an anode metal. When using multi-metal couplers with low potential differences, they should be protected by both coating protection and cathodic protection.
In this experimental investigation, a core–shell-structured
nano-lubricating additive was synthesized utilizing the dielectric
barrier discharge plasma (DBDP)-assisted ball grinding technique for
a duration of 5 h. The microstructural analysis of the nano-TiO2 powder was performed employing advanced methods such as X-ray
diffraction (XRD) and thermogravimetry–differential scanning
calorimetry (TG-DSC). The initial particle size of TiO2 was refined from 1 μm to a range of 150–200 nm, resulting
in a remarkable increase in lattice distortion rate by 88.2% and an
oil affinity enhancement of 200%. Through the introduction of CTAB’s
oil-compatible group onto the surface of nano-TiO2 particles,
a modified layer with a thickness of 21 nm possessing superior thermal
stability and an activation energy (E
a) of 600 kJ/mol was successfully produced. Molecular dynamics simulations
were conducted to elucidate the mechanism underlying the surface modification
of nano-TiO2 powder facilitated by DBDP-assisted ball grinding,
thereby revealing the pivotal role of electrostatic forces in the
organic modification of the TiO2 surface. It was found
that electrostatic forces dominantly govern the cetyl trimethyl ammonium
bromide (CTAB)–TiO2 composite interface model, contributing
to 70% of the total energy with a maximum energy proportion of −187.84
kcal/mol. To evaluate the lubrication performance of the composite
oil samples under boundary lubrication conditions, comprehensive assessments
were carried out using the four-ball method and reciprocating friction
experiments. The results demonstrated noteworthy enhancements in viscosity
index, dynamic viscosity, and oil film thickness within the composite
oil samples. Particularly, the composite oil containing 0.5 wt % TiO2@CTAB exhibited outstanding extreme pressure resistance, manifesting
a significant reduction of 41.7% in the average friction coefficient,
a considerable increase of 25.8% in wear spot diameter, and a substantial
elevation of 66.9% in maximum nonseizure load. Compared to the base
oil, the incorporation of 0.5 wt % TiO2@CTAB led to a notable
increment of 34.7% in oil film thickness, 6.7% in dynamic viscosity,
and 9% in viscosity index. In the tribological experiment simulating
marine diesel engines, the friction coefficient witnessed a remarkable
reduction by 65.8%, accompanied by a substantial decrease of 54.1%
in wear rate. This noteworthy improvement in boundary lubrication
conditions of the friction pair effectively mitigated friction and
wear. For comprehensive characterization of the wear marks, energy-dispersive
spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS) techniques
were employed to analyze the physical structure and chemical composition.
The implementation of TiO2@CTAB nano-lubricating additives
resulted in nanobearing and deposition effects, leading to a reduction
in contact area and surface roughness, thereby facilitating the restoration
of the friction pairs. These findings possess significant implications
for extending the service life of die...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.