Synergistic effects of hexagonal boron nitride nanoparticles and phosphonium ionic liquids as hybrid lubricant additives

Synergy between boron nitride or graphene nanoplatelets and tri(butyl)ethylphosphonium diethylphosphate ionic liquid as lubricant additives of triisotridecyltrimellitate oil

Dispersions based on hexagonal boron nitride, h-BN, nanoparticles, at 0.50, 0.75 and 1.0 wt.% mass concentrations, in an ester base oil composed mainly of trimethylolpropane trioleate, were investigated as potential nanolubricants. The stability of the dispersions was assessed to determine the reliability of the tribological, thermophysical and rheological measurements. Density and viscosity were measured from 278.15 to 373.15 K, while rheological behavior was analyzed at shear rates from 1 to 1000 s−1 at 283.15 K. Newtonian behavior was exhibited by all nanolubricants at the explored conditions, with the exception of the highest concentration at the lowest shear rates, where possible non-Newtonian behavior was observed. Tribological tests were performed under a normal load of 2.5 N. Wear was evaluated by means of a 3D profiler, scanning electron microscopy and confocal Raman microscopy. The best tribological performance was achieved by the 0.75 wt.% nanolubricant, with reductions of 25% in the friction coefficient, 9% in the scar width, 14% in the scar depth, and 22% of the transversal area, all with respect to the neat oil. It was observed that physical protective tribofilms are created between rubbing surfaces.

Tribological and Thermophysical Properties of Environmentally-Friendly Lubricants Based on Trimethylolpropane Trioleate with Hexagonal Boron Nitride Nanoparticles as an Additive

Additive manufacturing (AM) has recently become an increasingly popular form of production due to its advantages over traditional manufacturing methods, such as accessibility, the potential to produce parts with complex geometry, and reduced waste. For the widespread industry adoption of AM components, metal AM has the most potential. The most popular methods of metal AM are powder-based manufacturing techniques. Due to the layer-by-layer nature of AM, the mechanical and tribological properties of an additive manufactured part differs from those of traditionally manufactured components. For the technology to develop and grow further, the tribological properties of AM components must be fully explored and characterized. The choice of material, surface textures, and post-processing methods are shown to have significant impact on friction and wear. Therefore, this paper focuses on reviewing the existing literature with an emphasis on the development of advanced materials for AM applications as well as the optimization of the resulting surface quality via post-processing and presents areas of interest for further examination in this prospective technology.

https://www.mdpi.com/2504-4494/6/6/138/pdf?version=1668159997

Tribological Behavior of Additively Manufactured Metal Components

The widely use of metalworking fluids (MWFs) petroleum-based in the industry
have a negative impact to the environment and human. Thus, various initiatives have
been undertaken to develop bio-based MWFs especially from crude jatropha oil
(CJO). However, the main drawback of CJO is that it has low thermal-oxidative
stability. Therefore, the objective of this study is to develop a new formulation of
CJO-based MWFs. The newly developed modified jatropha oils (MJOs) were
formulated using transesterification process at various molar ratios of jatropha
methyl ester to trimethylolpropane (JME:TMP) denoted by MJO1 (3.1:1), MJO3
(3.3:1) and MJO5 (3.5:1). Later, the MJOs were blended with hexagonal boron
nitride (hBN) particles at various concentrations (0.05 to 0.5wt.%). MJOs with and
without hBN particles were analysed based on the physicochemical properties,
tribology behaviour test, orthogonal cutting and turning proses. From the results,
MJO5 showed an improvement at thermal (high viscosity index) and oxidative
stability (lubricant storage). MJO5c (MJO5+0.5wt.% of hBN particles) showed the
optimum physicochemical properties. In the contrary, MJO5a (MJO5+0.05wt.% of
hBN particles) exhibited excellent tribological behaviour as reduction of friction and
wear, with high tapping torque efficiency. In the orthogonal cutting process, MJO5a
recorded the lowest machining force and temperature, thus contributed to the
formation of thinner chips, small tool-chip contact length and reduction of the
specific energy. MJO5a produced an excellent result in the machinability test by
reducing the cutting force, cutting temperature and surface roughness stimulated
longer tool life and less tool wear. In conclusion, the MJO5a has a potential impact
on the lubricant market as a sustainable MWFs for the machining processes.

Performance evaluation of biodegradable metalworking fluids for machining process

Environmental issue have become very important year by year and several summit have been held on this subject globally.  As a result, research efforts have been focused on environmentally friendly materials, reducing energy usage and emissions. Hexagonal boron nitride (hBN) shows superior lubrication and has no sticking properties because of the structure of strong bonds between atoms in layers with the weak Van Der Walls bonds between layers. Also, hBN is an inorganic artificial material with high heat shock resistance, heat conduction, electrical insulation, chemical stability properties. These properties enable it to be used at various applications. In this study, friction and wear behaviors of products containing hBN were reviewed, in order to see effects on sustainable environment.

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Environmentally friendly material: Hexagonal boron nitride

Combining the geometrical freedom provided by laser powder bed fusion (L-PBF), a powder bed fusion additive manufacturing (AM) process, and tailoring the mechanical properties by the use of lattice structures, many applications benefit from lightweight lattice structures such as aerospace and biomedical. Many different aspects of the lattice structures produced by L-PBF have been addressed in the literature including weight reduction, energy damping, compression behavior, manufacturability, and surface characteristics. Although lattices are seen as a promising design tool, the influence of using lattices inside the part surface on the wear behavior of L-PBF specimens has not yet been addressed in the literature. In this study, the effect of different lattice structures varying in unit cell geometry and size, built along different directions on the wear behavior, is addressed using AISI 316L powder processed with L-PBF. Moreover, to understand the wear behavior in detail, microhardness and compression testing of the samples were accomplished. As a result, it is found that the microhardness measurements change by only 5% on different build directions, whereas the lattice type is a significant factor regarding the modulus of elasticity and absorbed energy per unit volume. Moreover, it is concluded that although the coefficient of friction has an average value of 0.7, it does not vary depending on the tested factors, whereas the specific wear rate is influenced by the build direction and part geometry. Thus, for applications where tribological properties are important, the effect of heat dissipation and cooling rate leading to microstructural changes needs to be considered when utilizing L-PBF.

Tribological and mechanical behavior of AISI 316L lattice-supported structures produced by laser powder bed fusion

Three‐dimensional (3D) modeling provides a suitable context for the improvement of students' higher order thinking skills as it involves challenging and complex learning tasks. For students to succeed in difficult learning tasks, it is necessary to determine the effects of the scaffolding type given to the students in the learning process. This study asserts that reflective and supportive scaffolding has a critical effect on the dependent variables. Reflective scaffolding enables students to explain their reflective processes and clarify their reflective behavior, using personal reflection as a learning tool. Supportive scaffolding provides a process to develop knowledge and guidance on what participants should consider. This study compares the effects of different scaffolding types (reflective or supportive), students' prior knowledge on students' use of metacognitive strategies, spatial ability self‐efficacy, and spatial anxiety in the 3D computer‐aided design course. A pretest and posttest 2 x 2 x 2 factorial quasi‐experimental model was used in the study. This study was carried out with 118 undergraduate mechanical engineering students. Analysis of covariance (ANCOVA) was used in the analysis of the data. The results showed that the supportive scaffolding group scored higher in the metacognitive strategies variable than the reflective scaffolding group. The supportive scaffolding group showed higher spatial ability than the reflective scaffolding group. This study provides engineering educators with an overview of the use of scaffolding types, their effects on the effectiveness of learning environments, and the design of these environments.

Comparing reflective and supportive scaffolding in 3D computer‐aided design course: Engineering students' metacognitive strategies, spatial ability self‐efficacy, and spatial anxiety

https://iopscience.iop.org/article/10.1149/2162-8777/ac2f1f/pdf

Gökçe Mehmet Ay

Papers

Environmentally friendly material: Hexagonal boron nitride

Tribological and mechanical behavior of AISI 316L lattice-supported structures produced by laser powder bed fusion

Comparing reflective and supportive scaffolding in 3D computer‐aided design course: Engineering students' metacognitive strategies, spatial ability self‐efficacy, and spatial anxiety

Optical and Nanomechanical Properties of C Coated BN Thin Film Deposited by Thermionic Vacuum Arc Technique