Unknown

Dataset Information

0

Structured free-water clusters near lubricating surfaces are essential in water-based lubrication.


ABSTRACT: Water-based lubrication provides cheap and environmentally friendly lubrication and, although hydrophilic surfaces are preferred in water-based lubrication, often lubricating surfaces do not retain water molecules during shear. We show here that hydrophilic (42° water contact angle) quartz surfaces facilitate water-based lubrication to the same extent as more hydrophobic Si crystal surfaces (61°), while lubrication by hydrophilic Ge crystal surfaces (44°) is best. Thus surface hydrophilicity is not sufficient for water-based lubrication. Surface-thermodynamic analyses demonstrated that all surfaces, regardless of their water-based lubrication, were predominantly electron donating, implying water binding with their hydrogen groups. X-ray photoelectron spectroscopy showed that Ge crystal surfaces providing optimal lubrication consisted of a mixture of -O and =O functionalities, while Si crystal and quartz surfaces solely possessed -O functionalities. Comparison of infrared absorption bands of the crystals in water indicated fewer bound-water layers on hydrophilic Ge than on hydrophobic Si crystal surfaces, while absorption bands for free water on the Ge crystal surface indicated a much more pronounced presence of structured, free-water clusters near the Ge crystal than near Si crystal surfaces. Accordingly, we conclude that the presence of structured, free-water clusters is essential for water-based lubrication. The prevalence of structured water clusters can be regulated by adjusting the ratio between surface electron-donating and electron-accepting groups and between -O and =O functionalities.

SUBMITTER: Hou J 

PROVIDER: S-EPMC5095217 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

altmetric image

Publications

Structured free-water clusters near lubricating surfaces are essential in water-based lubrication.

Hou Jiapeng J   Veeregowda Deepak H DH   de Vries Joop J   Van der Mei Henny C HC   Busscher Henk J HJ  

Journal of the Royal Society, Interface 20161001 123


Water-based lubrication provides cheap and environmentally friendly lubrication and, although hydrophilic surfaces are preferred in water-based lubrication, often lubricating surfaces do not retain water molecules during shear. We show here that hydrophilic (42° water contact angle) quartz surfaces facilitate water-based lubrication to the same extent as more hydrophobic Si crystal surfaces (61°), while lubrication by hydrophilic Ge crystal surfaces (44°) is best. Thus surface hydrophilicity is  ...[more]

Similar Datasets

| S-EPMC4656248 | biostudies-literature
| S-EPMC6021025 | biostudies-literature
| S-EPMC7211481 | biostudies-literature
| S-EPMC5314357 | biostudies-literature
| S-EPMC5998041 | biostudies-literature
| S-EPMC1152688 | biostudies-other
| S-EPMC8395622 | biostudies-literature
| S-EPMC4306914 | biostudies-literature
| S-EPMC5857927 | biostudies-literature
| S-EPMC6002370 | biostudies-literature