Some aspects of oil lubricant additivation with ZnO nanoparticles

This is a study on the tribological behaviour of ZnO nanoparticles as an additive in a polyalphaolefin (PAO6) and on the influence of dispersing agents (OL100 and OL300). Antiwear and extreme pressure tests were run on two four-ball machines. Firstly, it was demonstrated that OL300 has better dispersant properties than OL100, and also was found formation of aggregates for 1 and 1.5% of ZnO in PAO6 + 3% OL300 suspension. Ensuing SEM and EDS analysis of the worn surface highlighted a number of conclusions: OL100 and OL300 are potentially useful as wear reducer additives in PAO6, the non-coated ZnO nanoparticles had an abrasive behaviour, and ZnO nanoparticles do not act as anti-wear agent under certain conditions but in EP conditions they can decrease wear

Wear prevention characteristics of binary oil mixtures

This work presents the results of wear prevention tests carried out with mixtures of a polyalphaolefin (PAO 6) and two esters (TMP-05 and Sunflower oil, SO), on a four-ball machine tester. Results show that esters are excellent wear reducers when they are mixed with a low viscosity polyalphaolefin. The optimum ester percentages in PAO 6 were 5% and 15% for TMP-05 and SO, respectively. Better results than in pure PAO 6 occurred in all mixtures. The addition of esters (less than 15%) to PAO 6 hardly changed volume viscosity

Viscosity and tribology of copper oxide nanofluids

Nanofluids, a term proposed by Choi in 1995 [1], are composites consisting of solid nanoparticles with sizes varying generally from 1 to 100 nm dispersed in a liquid. Numerous nanoparticles used as oil additives have been investigated in recent years [2-7]. Results show that they deposit on the rubbing surface and improve the tribological properties of the base oil, displaying good friction and wear reduction characteristics even at concentrations below 2%wt. Although the viscosity of the nanofluids is a property of crucial importance for film forming, and hence friction and wear reduction, which are characteristic of lubricants, only Hwang et al. [8] have studied thermal characteristics, kinematic viscosity and tribological properties of nanofluids simultaneously. In this paper, we present measurements of dynamic viscosity of nanofluids formed by copper oxide nanoparticles dispersed in a polyalphaolefin, for temperatures and concentrations varying from 20 to 60ºC and 0.5 to 2% wt., respectively. Dependence of the nanofluid viscosity to the solid fraction and temperature was compared with existing models and its influence on lubrication was also analysed

Simulating the in situ condensation process of solar prominences

Prominences in the solar corona are a hundredfold cooler and denser than their surroundings, with a total mass of 1013 up to 1015 g. Here, we report on the first comprehensive simulations of three-dimensional, thermally and gravitationally stratified magnetic flux ropes where in situ condensation to a prominence occurs due to radiative losses. After a gradual thermodynamic adjustment, we witness a phase where runaway cooling occurs while counter-streaming shearing flows drain off mass along helical field lines. After this drainage, a prominence-like condensation resides in concave upward field regions, and this prominence retains its overall characteristics for more than two hours. While condensing, the prominence establishes a prominence-corona transition region where magnetic field-aligned thermal conduction is operative during the runaway cooling. The prominence structure represents a force-balanced state in a helical flux rope. The simulated condensation demonstrates a right-bearing barb, as a remnant of the drainage. Synthetic images at extreme ultraviolet wavelengths follow the onset of the condensation, and confirm the appearance of horns and a three-part structure for the stable prominence state, as often seen in erupting prominences. This naturally explains recent Solar Dynamics Observatory views with the Atmospheric Imaging Assembly on prominences in coronal cavities demonstrating horns.Publisher PDFPeer reviewe

Signatures of Coronal Heating Mechanisms

Alfven waves created by sub-photospheric motions or by magnetic reconnection in the low solar atmosphere seem good candidates for coronal heating. However, the corona is also likely to be heated more directly by magnetic reconnection, with dissipation taking place in current sheets. Distinguishing observationally between these two heating mechanisms is an extremely difficult task. We perform 1.5-dimensional MHD simulations of a coronal loop subject to each type of heating and derive observational quantities that may allow these to be differentiated.Comment: To appear in "Magnetic Coupling between the Interior and the Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200

Energy use and CO2 emissions of sweet potato production in Tarlac, Philippines

In this study, the energy use and carbon dioxide (CO2) emission of sweet potato production in Tarlac, Philippines were evaluated. Data were collected from 180 farmers using structured survey questionnaires and face to face interview. Accordingly, the total input and output energy of sweet potato production was 29326.78 and 53885.90 MJ ha-1, respectively. Chemical fertilizers and diesel fuel provided the biggest portion of the total energy consumption in sweet potato production. The energy use efficiency, specific energy and energy productivity was 1.84, 1.95 MJ kg-1 and 0.51 kg MJ-1. Indirect and non-renewable forms of energy dominated the share of the total input energy. The total GHG emission of sweet potato production was 1432.18 kg CO2eq ha-1 (0.095 kg CO2 kg-1). Non-renewable sources of energy such as diesel fuel and chemical fertilizers were the main contributors of GHGs emission at 53.35% and 43.36%, respectively. The use of renewable sources of input energy can lead to lesser GHG emission, more sustainable and environment-friendly agricultural production system for sweet potato. Energy management should be considered as vital strategy for resource conservation, climate protection and to promote sustainable agriculture for sweet potato production

Environmental performance of farmer-level corn production systems in the Philippines

Four corn production systems at farmer-level of operation were evaluated. Environmental performance such as energy use, energy efficiency, greenhouse gas emission (GHG) and carbon efficiency were determined. Data were collected from 60 corn producing farmers using survey questionnaires and face to face interview. The input energy to produce an output energy of 69,714.06 and 73,029.60 MJ/ha for sun drying and mechanical drying, respectively, were 22,346.27, 31, 469.75, 22, 399.05 and 31,522.53 MJ/ha for systems 1 (manual harvesting and sun drying), 2 (manual harvesting and mechanical drying), 3 (mechanical harvesting and sun drying) and 4 (mechanical harvesting and mechanical drying), respectively.  The highest energy input was observed for system 4 followed by system 2 because of the additional energy input of kerosene fuel during mechanical drying.  Non-renewable and indirect forms of energy had contributed most to the total input energy in all corn production systems.  In all systems evaluated, chemical fertilizer had the highest share in energy input followed by diesel fuel. Lower GHG emissions were measured for system 1 and 3 at 1276.5 and 1309.60 kg CO2eq per ha, respectively than system 2 and 4 at 2101.9 and 2135.0 kg CO2eq per ha due to additional non-renewable energy input like kerosene during mechanical drying.  A kilogram of dried corn grain emitted 0.27 to 28 kg CO2eq for system 1 and 3 and increased further to 0.42 to 0.43 kg CO2eq for systems 2 and 4.  The net carbon sequestered for systems 1, 2, 3 and 4 was 1785.98, 1662.36, 1776.94 and 1653.33 kg C/ha, respectively. The highest carbon efficiency ratio was observed for system 1 at 6.13 followed by system 3 at 5.98 due to non-utilization of fossil fuel during drying.  Generally, all corn production systems evaluated did not emit carbon beyond the carbon produced and sequestered in corn itself as indicated by their positive net carbon ratio

Corrosion activity and solubility in polar oils of three bis(trifluoromethylsulfonyl) imide/bis(trifluoromethylsulfonyl) amide ([NTF2]) anion-based ionic liquids.

The corrosion behaviour and solubility of three bis(trifluoromethylsulfonyl)amide1 ([NTf2]) anion-based ionic liquids: 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C12MIM][NTf2]), tributylmethylammonium bis(trifluoromethylsulfonyl)amide ([N4441][NTf2]), and methyltrioctylammonium bis(trifluoromethylsulfonyl)amide ([N1888][NTf2]), as a component in a mixture with different base oils were analysed. Six polar oils suitable for use in lubrication were utilized as base oil. Solubility tests were performed by using turbidimetry, and corrosion was checked at 4 v/v% by examining the roughness and chemical composition of the surface after 21 days. The results showed that long carbon chains in the cation improve the solubility greatly in diesters and slightly in polyolesters. Corrosion was not detected at this concentration

Wetting Properties of Seven Phosphonium Cation-Based Ionic Liquids

This paper studies the wetting properties of seven phosphonium cation-based ionic liquids: trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate [P66614][(iC8)2PO2], trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate [P66614][BEHP], trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide [P66614][NTf2], tributyltetradecylphosphonium dodecylbenzenesulfonate [P44414][DBS], tributylethylphosphonium diethylphosphate [P4442][DEP], trihexyltetradecylphosphonium dicyanamide [P66614][DCA], and trihexyltetradecylphosphonium chloride [P66614][Cl]. The surface tension was analyzed using the Gibbs free energy in a temperature range of 293-353 K, obtaining the expected linear decrease with temperature rise. The contact angle was measured on four different surfaces (AISI 52100 steel, CrN, TiN, and ZrN) and all liquids with high surface tensions interacting with hydrophobic systems displayed high contact angles as expected. The polarity fraction (PF) and the spreading parameter (SP) were estimated to complete and improve the wetting characterization of these ionic liquids, finding TiN-[P66614][BEHP] and TiN-[P66614][(iC8)2PO2] as the most favorable surface-ionic liquid combinations from a wetting point of view