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Molybdenum disulfide (MoS2) is one of the most widely used solid lubricants applied in different ways on the surfaces under friction. In this work, AISI 316 austenitic stainless steel was coated with MoS2, using thermo-diffusion method at different temperatures and times. Coatings properties were investigated using SEM, EDX, XRD and FTIR, Hardness...
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Several studies have provided information on environmental nanoplastic particles/debris, but the in vitro cyto-genotoxicity is still insufficiently characterized. The aim of this study is to analyze the effects of polystyrene nanoparticles (PNPs) in the Hs27 cell line. The viability of Hs27 cells was determined following exposure at different time...
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... Hence, the lubrication is indispensable for their metal forming in practice. Manufacturing of eye-glass flames and medical parts disliked the contamination of lubricating oils; solid lubrication provides an only way to control the contact interface condition between the work and the dies [3,4]. After [5], the bulk ceramic dies suffered from severe adhesion of pure titanium plate to lower the limit of deep drawability. ...
Carbon supersaturation (CS) process was developed to prepare the CS-tool steel dies with massive carbon solute content toward the galling-free metal forming. The impinged carbon solutes diffused and agglomerated onto the hot spots at the die-work interface by stress gradient during the metal forming. This in situ formed free-carbon thin film worked as a tribofilm to reduce the friction and adhesive wear on the die-work interface. Titanium and titanium alloys were selected as a work material common to forging, near-net forming and fine blanking processes. The ball-on-disc method was employed to demonstrate the significant reduction of friction coefficient by CS-tool steels against the pure titanium ball. Upsetting process was used to describe the galling-free forging behavior even under the higher reduction of thickness than 50%. Pin-forming process was utilized to prove that taller pins than designed target were extruded and their height was preserved even with increasing the number of strokes. Fine blanking process was used to describe the integrity of CS-punch with higher grade of titanium gears. The in situ solid lubrication by formation of free-carbon tribofilm was discussed in each metal forming. In particular, the initial learning trial was proposed to shorten the incubation time for the free-carbon film coverage onto the hot spots.
The thermolytic growth of molybdenum disulfide thin films for solar cell applications is investigated. The thin films are spin‐coated and thermally annealed, and they show a sulfur‐deficient nanosheet structure with various spectral emissions. The intrinsic thin films are used to form heterostructures in silicon solar cells. Two types of Si solar cells are fabricated using a MoS 2 /p‐Si heterojunction structure and MoS 2 /SiO x /pn‐Si tunneling structure. The former heterojunction cell does not show photovoltaic cell character. However, the later oxide tunneling cell shows a short‐circuit current of 8.23 A, an open‐circuit voltage of 0.602 V, and a conversion efficiency of 14.6%. This indicates that the sulfur defect‐induced MoS 2 thin film shows an n‐type Ohmic character, but it might not form a stable interfacial charge depletion layer with p‐Si wafers in large‐scale cell fabrication.
High pressure die casting is an industrial metal casting process used to manufacture goods for use in many aspects of society. Within this manufacturing process, the tooling is subjected to chemical attack from molten aluminum while also being responsible for heat removal during solidification. The purpose of this study is to develop and test materials that allow the tools to better withstand the chemical attack, and to develop design rules to guide the use of additive manufacturing for improving the heat exchange function of by way of conformal cooling.
Within the material studies, a gooseneck with a niobium lining was developed to allow the successful implementation of hot chamber aluminum die casting. In addition, a manufacturing plan is described that will allow the niobium gooseneck design to be easily sourced by die casting companies. The material studies also included dunk testing of several coatings, including a plasma assisted chemical vapor deposition silicon doped diamond like carbon (PACVD Si-DLC). The Si-DLC coating performed the best in the dunk testing as compared to bare and nitrocarburized tool steel, and a number of other coating architectures.
Within the study of additively manufactured conformal cooling design, a finite difference model is developed that allows a simulated experiment that produced a number of useful equations that guide the design of die casting tooling. During the development of the models, it was discovered that little is known regarding the friction factors of additively manufactured steel pipes, so a factorial experiment was employed to empirically determine said friction factors. Charts allowing design engineers to quickly determine pressure drops and heat transfer coefficients of conformal cooling designs was produced as well.
A tool steel type SKD11 punch was plasma carburized at 673 K for 14.4 ks at 70 Pa to make carbon supersaturation. This carburized SKD11 punch was employed for upsetting the pure titanium wire with the diameter of 1.00 mm up to the reduction of thickness by 70% in a single shot. Its contact interface to titanium work was analyzed to describe the anti-galling behavior in this forging. Little trace of titanium proved that the galling process was suppressed by the in situ solid lubrication. The isolated free carbon agglomerates are wrought as a solid lubricant to sustain the galling-free forging process. This anti-galling upsetting reduced the residual strains in the forged wires. A long titanium wire with a length of 45 mm was incrementally upset to yield the titanium ribbon with a thickness of 0.3 mm, the width of 2.3 mm, and the length of 50 mm. The grain size of original pure titanium was much reduced to 2 μm on average. A micro-pillared microtexture was imprinted onto this forged titanium ribbon.
A bare AISI420J2 punch often suffers from severe adhesion of metallic titanium as well as titanium oxide debris particles in dry, cold forging of biomedical titanium alloys. This punch was plasma-carburized at 673 K for 14.4 ks to harden it up to 1200 HV on average and to achieve carbon supersaturation in the carburized layer. This plasma-carburized punch was employed in the cold, dry forging of a pure titanium wire into a flat plate while reducing the thickness by 70%. The contact interface width approached the forged workpiece width with increasing the reduction ratio. This smaller bulging deformation reveals that the workpiece is upset by homogeneous plastic flow with a lower friction coefficient. This low-friction and anti-galling forging process was sustained by an in situ solid lubrication mechanism. Unbound free carbon was isolated from the carbon-supersaturated AISI420J2 matrix and deposited as a thin tribofilm to protect the contact interface from mass transfer of metallic titanium.
We investigated the thermolytic deposition of MoS2 nanolayers for use in Si solar cells, a thin MoS2 nanolayer was grown on a crystalline Si substrate by the thermolysis method. The deposited MoS2 nanolayer and Si substrate were annealed and showed a transition from an amorphous to a crystalline phase as the annealing temperature increased. The MoS2 (002) crystalline peak at 14.04° appeared at an annealing temperature of 450ºC. The heterojunction interface of MoS2/np‐Si shows a mixed amorphous and crystalline phase. The Al/MoS2 has better Ohmic contact compared to Al/Si. The MoS2 nanolayer was introduced into the cell structure of a SiNx/a‐Si(n)/MoS2/np‐Si cell, the cell showed a photo‐conversion efficiency of 11.47%.
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The fabrication and application of a new type of cantilever for atomic force microscopes are presented. The beams of the cantilevers are made from a thin sheet of beryllium copper, featuring a bending stiffness in a wide range of 2-1900 N m⁻¹, onto which a ball is cemented, whose diameter can be in the range of 0.1-1 mm. The basic properties of the cantilevers (longitudinal and torsional rigidity, tip diameter and material) can be easily changed. The cost of fabricating the cantilevers is considerably lower compared to their commercial counterparts, whereas their quality is approximately the same. Using these cantilevers, it is possible to perform measurements of the tribological properties of material pairs such as steel-molybdenum disulfide (MoS2), steel-lead (Pb) and polymer-polymer. The larger radius of the cantilever tip also enables measurements of viscosity, and decreases the contact pressure, which is crucial in measurements of biological samples.
