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Lubricating Oils

[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]

Penn and ExxonMobil researchers uncover mechanisms behind performance of major antiwear additive in lubricants

March 13, 2015

One of the main modern antiwear lubricant additives is zinc dialkyldithiophosphate (ZDDP)—widely used in automotive lubricants—which forms crucial antiwear tribofilms at sliding interfaces. However, despite its importance in prolonging machinery life and reducing energy use, the mechanisms governing its tribofilm growth are not well-understood. This limits the development of replacements with better performance and catalytic converter compatibility.

Now, in a study published in the journal Science, researchers from the University of Pennsylvania and ExxonMobil, have uncovered the mechanisms governing the growth of ZDDP antiwear tribofilms at sliding interfaces. The study provides a way forward for scientifically testing new anti-wear additives. Being able to pinpoint the level of stress at which they begin to break down and form tribofilms allows researchers to compare various properties in a more rigorous fashion.

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Sub-micrometer carbon spheres as oil additives reduce engine friction up to 25%

March 06, 2015

Researchers at Purdue University have shown that adding ultra-smooth submicrometer carbon spheres to motor oil can reduce friction and wear typically seen in engines by up to 25%. The researchers also have shown how to potentially mass-produce the spheres, making them hundreds of times faster than previously possible using ultrasound to speed chemical reactions in manufacturing.

In a paper in the ACS journal Advanced Materials & Interfaces, they reported that the new lubricant composition—3% carbon spheres suspended in a reference SAE 5W30 engine oil—exhibited a substantial reduction in friction and wear (10 to 25%) compared to the neat oil, without change in the viscosity. Friction reduction was dependent on the sliding speed and applied load, and maximum reduction was achieved at the highest sliding speed in the boundary lubrication regime.

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Project developing electrically conductive lubricants to protect electric motors from discharges in the bearings

June 12, 2014

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The effect of insulating (upper right) and electrically conductive (lower right) lubricants. The insulating lubricant (yellow coating) can cause electrical discharges (red lightning bolts), which can damage the bearing’s raceways. If the lubricant is conductive (green coating), no electrical discharges occur. Source: Bosch. Click to enlarge.

A joint research project, funded by the German Federal Ministry for Education and Research, is investigating the development of ionic-fluid-enhanced electrically conductive lubricants to protect electric motors from the surface damage that can result from electrical discharges in the bearings (electrical discharge machining, or EDM). The initiative was launched to prepare for future vehicles which will require higher voltages than current models.

At present, 12 volts provide all conventional automotive electric systems—from lights and radios to air conditioners—with sufficient power. Within the next few years, the figure may rise to 48 volts to support a growing number of functions. The voltage levels of electric and hybrid vehicles are even higher: these vehicles can require as much as 400 volts. Higher voltage levels result in stronger alternating electric fields in alternators and electric motors, explained Dr. Gerd Dornhöfer, a Bosch scientist taking part in the “SchmiRmaL” project (Switchable intelligent tribological systems with minimal friction losses and maximum lifespan).

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DOE awards $17M to FY 2014 SBIR Phase II projects; includes Si/graphene anodes, motor windings, exhaust treatments

March 31, 2014

The US DOE recently awarded $17 million to 17 FY 2014 Small Business Innovation Research (SBIR) Phase II projects to further develop Phase I projects and to produce a prototype or equivalent within two years. The selected 17 awards represent the best of nearly 1,000 ideas submitted for the FY 2012/13 Broad Based Topic Solicitation, DOE said.

The selected projects include 6 vehicle-related technologies and 2 hydrogen and fuel cell technologies, as well as new hydropower, heat pump, solar and manufacturing technologies. Vehicle technologies span a range from new Si/graphene Li-ion anode materials and composites for motor windings to diesel aftertreatment and advanced lubricants. Selected vehicle and hydrogen technology projects are:

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Study finds lubricating oil the dominant source of primary organic aerosol from both diesel and gasoline vehicles

March 20, 2014

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Comparison plot showing mass fractions (Fm) of chemically characterized components of lubricating oils and POA. Credit: ACS, Worton et al. Click to enlarge.

Findings from a study by researchers at the University of California, Berkeley and Berkeley National Laboratory suggest that lubricating oil is the dominant source of primary organic aerosol (POA) from both gasoline- and diesel-powered vehicles. Unburned diesel fuel makes an additional smaller contribution, with an additional smaller contribution from unburned gasoline. A paper on the work is published in the ACS journal Environmental Science & Technology.

Motor vehicles are major sources of organic carbon emissions, with implications for human health and air quality, especially in urban areas. The emitted organic carbon is in the form of both primary particulate matter (PM) and gas phase organic compounds of a wide range of volatilities that can be oxidized in the atmosphere to form secondary organic aerosol (SOA). (Earlier post.) The majority of fine PM from vehicles is carbonaceous in the form of either black (BC) or organic carbon, the latter of which is directly emitted as primary organic aerosol (POA).

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