Papers by Keyword: Tribochemistry

Abstract: Waste cooking oils (WCOs) are widely considered in the scientific community as potential energy vector or source for bio-lubricants. This is because of the opportunity deriving from recycling and the difficulties in disposing of waste oils. Indeed, industrial plants for WCOs treatment include bio-refineries (bio-diesel, bio-lubricants, fine chemicals...) or simple recovery systems: the former ones assume triglycerides transformation into other compounds, according to the specific commercial destination; in the latter, triglycerides are preserved and the WCO is purified from by-products, formed during cooking process, in order to sell to the market. In an era scarred by CO₂ and petroleum dependency, biodegradable products, offer many advantages. In this scenario, nanostructured additives, which are pointed out as the step forward in lubricant technology, can exploit WCOs’ derivatives for compatibilization or as reactive components allowing improvements in nanolubricant fluids. This paper proposes a Cu nanoparticle-based additive, properly surface functionalized and prepared through a “wet chemistry” approach, to be involved in tribochemical reaction with epoxidized vegetable oil. The idea was to promote the formation of tribofilm under contact, exploiting energy generated during the movement.

Abstract: A type of new environmentally friendly lube additive---boron-nitrogen modified soybean oil was synthesized and characterized by infrared spectrum. Its effect on the friction and wear behavior of steel-steel and steel-aluminum alloy systems were investigated with a four-ball machine and an Optimol SRV friction and wear tester respectively. The morphographies of the worn surfaces were analyzed by means of scanning electron microscopy (SEM).The worn surfaces of the 2024Al alloy block were analyzed by means of X-ray photoelectron spectroscopy (XPS).The results show that the type of modified soybean oil as additives can obviously decrease the wear rate and friction coefficient of steel pair and steel-aluminum frictional pair. Its lubrication mechanism is inferred that a high strength adsorption film and/or tribochemistry reaction film on the worn surface of the Al alloy due the carrier effect of a long chain soybean oil, high reaction activities of nitrogen, electron-deficient of boron and their synergisms.

Abstract: A type of new environmentally friendly lube additive----boron-nitrogen containing modified soybean oil was synthesized and characterized by infrared spectrum. Its tribological properties in rapeseed oil were tested on the four balls tester. The morphographies and tribochemical species of the worn surfaces were analyzed by means of Scanning Electron Microscope (SEM) and X--ray Photoelectron Spectroscope (XPS). The results show that the type of modified soybean oil as additives can obviously increase the load-carrying capacity 、anti-wear and friction-reducing abilities of rapeseed oil. Its lubrication mechanism is inferred that a high strength adsorption film and/or tribochemistry reaction film on the worn surface of the Al alloy due the carrier effect of a long chain rapeseed oil, high reaction activities of nitrogen, electron-deficient of boron and their synergisms.

Abstract: The tribochemical effects of MoSi2 powder in the ball milling process have been studied by X-ray diffraction (XRD) and QM-4H milling machine. It has been found that the intensity of diffraction peak of MoSi2 powder is continuously decreased and the width increased with the increase of milling time. Specifically, the crystallite size decreased largely in the early stage of milling. Contrary to the above, the microstrain and the effective temperature factor increased considerably. After ninety hours of milling, the crystallite size had little changes. The relations among the tribochemical effect factors are as follows: the microstrain and the effective temperature factor increase with the decrease of the crystallite size. The microstrain increases with the increase of the effective temperature factor.

Abstract: Ceramics, especially nitrides, oxides and carbides, offer advantages over conventional tribological mating elements. Such solids usually are very stable chemically. However, under friction conditions they become quite reactive. It is even possible to say that the friction and wear behavior of ceramics might be more sensitive to the environment than friction and wear behavior of metals. Considering the present trend towards the incorporation of these ceramics in tribological applications, the importance of a more comprehensive understanding of the ceramic surface physics and chemistry cannot be overestimated. The primary aim of this paper is to present some physicochemical factors that may influence the wear process of ceramics and account for some specific tribological findings related to lubrication of these materials from the view-point of a better understanding of their tribochemistry. Model of ceramic reaction with water, implying the effect of triboelectron emission process, leads to the generation of acidic and basic active sites. The model is mostly focused on silicon nitride tribochemistry. It accounts well for the formation of specific silicon compounds from silicon nitride lubricated with water and alcohols. The model is based on the emission process of low-energy electrons during friction with generation of positively charged sites (Si+) and free radicals (N●). Interaction of the emitted low-energy electrons with water or alcohol molecules (HOH, ROH) produces negative HO‾ or RO‾ ions, respectively and hydrogen radicals (H●). The described model provides a better understanding of silicon nitride tribochemistry than previous ones. The same is due to other ceramics.