Inorganic nanolubricant additive

Dr. Neil Canter, Contributing Editor | TLT Tech Beat July 2010

New graphite technology improves lubricant performance and extends operating life.

KEY CONCEPTS
• A new inorganic nanolubricant additive derived from the combination of aluminum oxide, silicon oxide and plasma-treated graphite can improve lubricant performance.
• The inorganic nanolubricant additive functions as a self-regulating compound by forming a smooth submicron layer between rough metal surfaces that is continuously destroyed and rebuilt under boundary conditions.
• This additive can be added on top of any mineral oil-based lubricant and biolubricant. One case study shows significant lubricant and fuel consumption savings in a 15-month trial in the engine and gears of an ocean-going vessel.

The growing use of nanotechnology in lubricant applications is being driven because these small particles are able to move into small spaces in the interface between moving surfaces to provide benefits such as extreme pressure, friction reduction and decreased wear. A variety of interesting chemistries have been developed and commercialized for use in automotive and industrial lubricant applications.

In a previous article, inorganic boron-containing nanoparticles in an ester matrix have been found to exhibit lubricity, antiwear and extreme pressure properties (1). The boron component is based on potassium borate, which chelates to the metal to form a friction-reducing layer that also contributes extreme pressure characteristics.

A well-known solid lubricant that can be used in a neat form or in a dispersion is graphite. This material exhibits a low coefficient of friction and has very high thermal stability. It is used in applications ranging from metalworking forging compounds to mold-release agents.

A new technology has recently been developed that incorporates graphite with two other inorganic components to produce a mixture that can improve lubricant performance and extend operating life.

SELF-REGULATING
A new nanolubricant additive has been developed based on the combination of aluminum oxide, silicon oxide and plasma-treated graphite. This additive is known as NanoVit® Simon Goldsmith, business development manager for Efficiency Technologies Ltd., in Wolverton Mill, Milton Keynes, Buckinghamshire, U.K., says, “NanoVit is a collection of nanomaterials that form a self-regulating system under high temperature and pressure conditions. The aluminum component in this product meshes with metallic surfaces—the graphite is, of course, present to reduce friction and the silica component is present in a ball-shaped, ligand structure that traps lubricant oil molecules in this self-regulating system in order for them to be available continuously.”

The process for making the aluminum and silicon components is straightforward, according to Goldsmith. He adds, “The graphite is activated through an interesting aging process.”

The inorganic nanolubricant additive is an amorphous powder rather than crystalline to ensure that it does not adversely affect the metal surface. Goldsmith explains, “Crystalline materials are more likely to scratch the metal surface, leading to an increase in wear. Our product is amorphous and will protect rather than attack the metal surface.”

Upon introduction into a lubricant, the inorganic nanolubricant additive will form a layer that adheres to the metal surface, leading to a reduction in friction and wear as the temperature and pressure increase. A key aspect that explains how well this additive works is that it is a selfregulating compound.

Goldsmith says, “There are two aspects to the self-regulating ability of the inorganic nanolubricant additive. In an application such as a diesel engine, the additive forms a smooth submicron layer that flattens between the rough metal surfaces under high temperature and pressure conditions. As the surfaces interact with each other, the layer continuously is destroyed and rebuilt to maintain effectiveness.”

The particle size of the inorganic nanolubricant additive varies depending upon the conditions of the application. Goldsmith says, “The original particle size starts at 14 nanometers but can vary from 100 nanometers down to three nanometers. The size is directly related to the elastic effect of the interacting surfaces.”

Long-term wear protection is the key benefit of this additive. Goldsmith indicates that the performance is second to none. A secondary benefit is that the inorganic nanolubricant additive resurfaces a specific surface so that it can revert to how it should perform at an optimal level.”

One other benefit, as shown in Figure 3, is that the three components in the inorganic nanolubricant additive remove dirt that clings to the metal surface and detach it so that the dispersant package in the oil can remove it.


Figure 3. Besides reducing friction and wear, the inorganic nanolubricant additive moves dirt that can cling to the metal surface into the oil so that the dispersant package can remove it. (Courtesy of Efficiency Technologies Ltd.)

The inorganic nanolubricant additive can be added on top of any mineral oil-based lubricant and biolubricant. Goldmsmith says, “We also offer to blend our additive into a customer’s lubricant and can supply our additive in its solid powder form.”

The main applications for the inorganic nanolubricant additive are in motor oils and gear oils. Goldsmith indicates that the treat rate for the former is 20 milligrams per liter of lubricant and is 40 milligrams per liter of lubricant for the latter. Other applications include gas engines, generators and marine oils.” 

No matter the application, the inorganic nanolubricant additive dramatically improves the operating life of a lubricant. Goldsmith adds, “We have found that on average our product extends the operating life of a lubricant by five times.”

An extensive amount of testing has been done to demonstrate the efficacy of the inorganic nanolubricant additive. A notable study is the four-ball wear and extreme pressure work conducted at Lubeck University in Germany using DIN 51350.

In this study, the inorganic nanolubricant additive is used at a treat rate of one-thousandth of one percent to a 10W-40 diesel motor oil. As the load increased from 3,400 newtons to 12,000 newtons, the coefficient of friction dropped from 0.45 to 0.12. No welding was observed at 12,000 newtons, which is the maximum force that the machine can apply in this test.

The inorganic nanolubricant additive has been evaluated in a number of diesel engine oil applications. Of particular note is a study done to examine the impact the nanolubricant additive has in the main six-cylinder engine oil, gears and the auxiliary engines of an ocean-going vessel.

A substantial reduction in lubricant and fuel consumption was realized over a 15-month period. Goldsmith estimates that the savings are just under 300,000 Euros.

The only compatibility problem with this nanolubricant additive is water. Goldsmith says, “High water concentrations can destabilize our nanolubricant additive during the initial coat formation stage. Once it bonds, there is no further adverse effect, and, in fact, it acts as a protective coating as noted in the marine study.”

Further information can be found at www.nanovit.co.uk or by contacting Goldsmith at sgoldsmith@nanovit.co.uk. 

REFERENCE
1. Canter, N. (2009), “Boron Nanotechnology-Based Lubricant Additive,” TLT, 65 (8), pp. 12–13.

Neil Canter heads his own consulting company, Chemical Solutions, in Willow Grove, Pa. Ideas for Tech Beat items can be sent to him at neilcanter@comcast.net.