scholarly journals Water-based lubrication of niobium nitride

Friction ◽  
2021 ◽  
Author(s):  
Kaifei Miao ◽  
Jia Wang ◽  
Qiang Zhao ◽  
Kaiwen Wang ◽  
Mao Wen ◽  
...  

AbstractWater-based lubrication has attracted wide attention as an oil-free lubrication method owing to its greener and cleaner lubrication means. However, due to operating in the water environment, most moving parts would inevitably suffer from abrasion, rusting, and aging problems. Developing a novel solid-water composite system with ultra-low friction and wear will open new possibilities for innovative lubrication material research and development. Here, we first revealed the water-based lubrication behavior of a high-hardness niobium nitride coating (NbN). In a three-phase contact environment (water, air, and NbN), oxidation and hydrolytic reactions of NbN result in the formation of “colloidal solutions”, containing Nb2O5 colloidal particles between the tribo-pairs. Utilizing the double electric layer repulsion and weak shear action of the “colloidal solution”, NbN achieves ultra-low friction and wear; the corresponding values are as low as 0.058 and 1.79 × 10−10 mm3·N−1·m−1, respectively. In addition, other VB transition metal nitrides (VB TMNs) exhibit the same low friction feature as NbN in the three-phase contact environment; the friction coefficients are even lower than those in an oil-based environment. The water-based lubrication of VB TMNs provides a new reliable scheme for optimizing solid-water composite lubrication systems without additives and is expected to be applied in environments with high humidity or insufficient water coverage.

Author(s):  
Johnathan S. Coursey ◽  
Jungho Kim

Surface wetting characteristics have been shown to affect the critical heat flux (CHF) observed during boiling. Surface oxidation is known to improve the ability of the fluid to wet the surface thus enhancing CHF. Nanofluids have also shown potential to enhance CHF, but the mechanisms are poorly understood. This study is targeted towards investigating whether or not nanofluids improve CHF by altering the surface energy. The surface energy of a heater was altered by oxidizing the surface to varying degrees or depositing metal onto the surface, and was characterized by measuring the advancing three-phase contact angle. Boiling curves were determined for water and ethanol based nanofluids with aluminum oxide nanoparticle concentrations from 0.001 g/l to 0.5 g/l as well as pure fluids on surfaces of varying surface energy. A 2.7 cm2 copper heater (polished or oxidized) was used for the water-based measurements. A 1.1 cm2 thick-film heater coated with glass and/or gold was used for the ethanol-based measurements. Boiling curves obtained using these fluid/surface combinations are discussed.


1999 ◽  
Vol 96 (9) ◽  
pp. 1335-1339 ◽  
Author(s):  
ALAN E. VAN GIESSEN, DIRK JAN BUKMAN, B.

2020 ◽  
Vol 55 (1) ◽  
pp. 32-37
Author(s):  
A. Yu. Vorob’ev ◽  
V. A. Nebol’sin ◽  
N. Swaikat ◽  
V. A. Yuriev

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Enno Wagner ◽  
Peter Stephan

In a special boiling cell, vapor bubbles are generated at single nucleation sites on top of a 20μm thick stainless steel heating foil. An infrared camera captures the rear side of the heating foil for analyzing the temperature distribution. The bubble shape is recorded through side windows with a high-speed camera. Global measurements were conducted, with the pure fluids FC-84 and FC-3284 and with its binary mixtures of 0.25, 0.5, and 0.75mole fraction. The heat transfer coefficient (HTC) in a binary mixture is less than the HTC in either of the single component fluid alone. Applying the correlation of Schlünder showed good agreement with the measurements (1982, “Über den Wärmeübergang bei der Blasenverdampfung von Gemischen,” Verfahrenstechnik, 16(9), pp. 692–698). Furthermore, local measurements were arranged with high lateral and temporal resolution for single bubble events. The wall heat flux was computed and analyzed, especially at the three-phase-contact line between liquid, vapor, and heated wall. The bubble volume and the vapor production rate were also investigated. For pure fluids, up to 50–60% of the latent heat flows through the three-phase-contact region. For mixtures, this ratio is clearly reduced and is about 35%.


2015 ◽  
Vol 143 ◽  
pp. 188-190 ◽  
Author(s):  
Yongfu Wang ◽  
Junmeng Guo ◽  
Jun Zhao ◽  
Delei Ding ◽  
Yongyong He ◽  
...  

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