摘要 :
In recent years, with the enhancement of environment awareness, there has been a progressive reduction in permitted phosphorus and sulfur levels in lubricants. Sulfur and phosphorus are the most important elements of antiwear addi...
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In recent years, with the enhancement of environment awareness, there has been a progressive reduction in permitted phosphorus and sulfur levels in lubricants. Sulfur and phosphorus are the most important elements of antiwear additives. Because of the reaction between additives, less mass of additives may have the same wear reducing properties when used together. However, there is uncertainty regarding the optimum amount and ratio of these additives. In this article, the influence of five kinds of antiwear additivessulfurized olefin cottonseed oil (T405), sulfurized isobutylene (SIB), tricresyl phosphate (TCP), molybdenum dialkyl dithiophosphates (MoDTC), zinc dialkyl dithiophosphate (ZDDP), and their combinationon lithium complex grease have been studied by single-factor and orthogonal experiments. The single-factor tests show that T405 and SIB work well under low temperature, whereas TCP and MoDTC work well under higher temperature; ZDDP are multifunctional additives. It was proved that base grease has better antiwear properties at 150 than at 75 degrees C. Additionally, sulfurized additives T405 and ZDDP and phosphate agent TCP could react better with lithium complex grease than the additives that have the same functional group. Furthermore, the results of orthogonal experiments show that the abrasion resistance of lithium complex grease is optimally best when T405, TCP, and ZDDP are blended with a ratio of 2:2:1. In addition, a synergistic effect between T405 and TCP is observed at ratios between 1:1 and 2:1. The morphology and element composition of the worn surfaces are examined by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). Based on the two kinds of technology, the friction and wear mechanism of additives also have been studied.
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The so-called biogenetic law of Haeckel, that the developing organism,in its growth from the egg to the adult stage, "recapitulates" the pasthistory of the race, was one of the most fascinating additions to thetheory of evolution ...
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The so-called biogenetic law of Haeckel, that the developing organism,in its growth from the egg to the adult stage, "recapitulates" the pasthistory of the race, was one of the most fascinating additions to thetheory of evolution which was made during the nineteenth century. Thepublication of the first edition of the Origin of Species took place in1859, and Haeckel's General Morphology, in which this law wasenunciated, appeared in 1866. The belief in the validity of this lawwas the stimulating impulse to zoological research for over forty years.The enthusiasm evoked by it, particularly in the younger men of thetime, can be understood when we reflect upon the clues actuallyavailable for following up the course of evolution.
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Extreme pressure (EP) lubricant additives form protective tribofilms at the site of contact using the heat and pressure of contact and relative motion. Common EP additives contain undesirable elements such as phosphorus and sulfur...
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Extreme pressure (EP) lubricant additives form protective tribofilms at the site of contact using the heat and pressure of contact and relative motion. Common EP additives contain undesirable elements such as phosphorus and sulfur. A novel EP lubricant additive, which contains no phosphorus and sulfur, is presented for generating lubricious carbon films. The additive consists of a surface-active molecule with a metastable cycloalkane ring, which dissociates readily during tribological contact to form lubricious carbon films. Friction and wear performance of PAO(4) with this additive under a range of loads and speeds were shown to be superior to that without the additive. Optical and scanning electron microscopy and Raman spectroscopy were used to analyze the tribofilms formed on post-test contact surfaces, providing direct evidence for the formation of carbon films. Quantitative kinetics for the carbon tribofilm formation was analyzed as a function of temperature and stress, from which the activation energy for carbon tribofilm formation was obtained.
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A combined structural/EPR/computational chemistry investigation is reported on the two paramagnetic hydrido-cluster salts [Rh6(PCy3)6H12][BArF 4] and [Rh6(PCy3)6H14][BArF 4], the latter being formed by reversible addition of H2 to...
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A combined structural/EPR/computational chemistry investigation is reported on the two paramagnetic hydrido-cluster salts [Rh6(PCy3)6H12][BArF 4] and [Rh6(PCy3)6H14][BArF 4], the latter being formed by reversible addition of H2 to the former, [BArF 4]- = [B{C6H3(CF3)2}4]-. The solid-state structure of [Rh6(PCy3)6H14][BArF 4] shows an expanded cluster core compared to previously reported [Rh6(PCy3)6H12][BArF 4] indicative of the addition of hydrogen to the cluster surface. This expansion correlates well with the calculated (PH3 replaces PCy3) structures. EPR measurements on [Rh6(PCy3)6H12][BArF 4] indicate two isomers at low temperature, which are tentatively assigned as diastereomers that result from locked phosphine rotation and bridging hydride/semi bridging hydride tautomerism. The EPR signal disappears above 60 K which is suggested to occur due to fast Raman-type relaxation—a phenomenon consistent with the calculated small SOMO/SOMO - 1 and SOMO/LUMO gaps. For [Rh6(PCy3)6H14][BArF 4] EPR measurements indicate two isomers, the proportion of which change with temperature and deuteration—one axial isomer and one rhombic isomer. DFT calculations on a number of plausible isomers give EPR parameters which fit the experimentally determined rhombic isomer to one in which there is an interstitial hydride in the cluster and thirteen hydride ligands on the surface, while the axial isomer has two dihydrogen-like ligands on the cluster surface. That these isomers lie close in energy comes from both the EPR measurements (as measured from equilibrium constants over a variable temperature range) and DFT calculations. Deuteration of the hydrides should favour the isomer with the lowest zero-point energy and this is the case, with the axial isomer (two D2 ligands on the surface) being favoured over the rhombic.
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ZnO nanorods arrays are respectively prepared under different vapor pressures with opening (OZN) or sealing (SZN) of the beaker. The results from time-resolved photoluminescence measurements indicate that sealing the beaker during...
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ZnO nanorods arrays are respectively prepared under different vapor pressures with opening (OZN) or sealing (SZN) of the beaker. The results from time-resolved photoluminescence measurements indicate that sealing the beaker during the growth process can effectively suppress the surface recombination of ZnO nanorods, and the suppression effect is even better than a 500 degrees C post-thermal treatment or OZN samples. The results from X-ray photoelectron spectroscopy measurements reveal that the main reason for this phenomenon is that the surfaces of the SZN samples are attached by groups related to NH3 instead of the main surface recombination centers such as OH and groups in the OZN samples. The ammonia surface treatment on both OZN and SZN samples further testifies that the absorption of the groups related to NH3 does not contribute to the surface recombination on the ZnO nanorods.
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A study of the antiwear characteristics of intentionally deteriorated zinc dialkyldithiophosphate (ZnDTP) was carried out. ZnDTPs were degraded to simulate used engine oil by reacting with cumenehydroperoxide (CHP), which models t...
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A study of the antiwear characteristics of intentionally deteriorated zinc dialkyldithiophosphate (ZnDTP) was carried out. ZnDTPs were degraded to simulate used engine oil by reacting with cumenehydroperoxide (CHP), which models the hydroperoxide present in combustion gas. Sample oils were analyzed by 31{sup left}P-NMR, showing that ZnDTP produces various kinds of phosphorus-containing oil-soluble compounds after reacting with CHP. It was found that the antiwear characteristic of ZnDTP deteriorated due to the degradation, and an acceleration of wear was observed in the highly degraded regions. The effect of the ashless dispersant on the antiwear characteristics of both the degraded and the nondegraded ZnDTP was studied. It was found that the dispersant reduced wear in the low-degradation region. The addition of the dispersant, however, had no effect on wear with further degradation, where the dispersant was almost entirely consumed in dispersing Zn-containing solids when the dispersant concentration was low. When the concentration was high, the dispersant showed wear reduction in the region of greater degradation. The antiwear action of the dispersant was discussed herein, based on its adsorption characteristics and micelle formation.
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Pyramiding (combining) of plant incorporated protectants (PIPs) with insecticidal activity in genetically engineered crops is a strategy used to improve efficacy as well as delay potential resistance for a specific group of target...
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Pyramiding (combining) of plant incorporated protectants (PIPs) with insecticidal activity in genetically engineered crops is a strategy used to improve efficacy as well as delay potential resistance for a specific group of targets. In some countries, a regulatory risk assessment is required for breeding "stacks" expressing multiple PIPs and these countries may require an assessment of potential interaction among the PIPs. This study evaluated whether combining soybean events MON 87551 and MON 87701 results in a toxicological interaction that effects a species that is controlled by each event. MON 87751 coexpresses the Cry1A.105 and Cry2Ab2 proteins and MON 87701 expresses the Cry1Ac protein. EC50 values for MON 87751 and MON 87701 were comparable in diet-incorporation bioassays using corn earworm (Lepidoptera: Noctuidae, Helicoverpa zea) and the observed combined activity of the stack was consistent with predictions of additivity (i.e., no interaction). Under the concentration and response addition models, predicted and observed median effect levels differed by <10%. These results demonstrate independent action at the median effect level between the insecticidal activity of MON 87751 and MON 87701. Taken together, no interaction between these PIPs and acceptable margins of safety for the individual proteins to nontarget organisms, it is appropriate to bridge back to the risk assessments for the individual products that demonstrated environmental safety of stack products containing both MON 87751 and MON 87701.
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Triphenyltin (TPT) often coexists with tributyltin (TBT) and Cu in coastal waters worldwide. The combined toxic effect of TPT and TBT has always been assumed to be additive without any scientific proof, and the combined effect of ...
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Triphenyltin (TPT) often coexists with tributyltin (TBT) and Cu in coastal waters worldwide. The combined toxic effect of TPT and TBT has always been assumed to be additive without any scientific proof, and the combined effect of Cu and TPT on marine organisms has not been vigorously studied. This study, therefore, investigated the acute toxicity of binary mixture of TPT/Cu and TPT/TBT to five selected marine species including Thalassiosira pseudonana, Skeletonema costatum, Tigriopus japonicus, Brachionus koreanus and Oryzias melastigrna. The interaction between TPT and TBT or Cu was modeled antagonistic based on concentration addition (CA) model, while it was synergistic according to response addition (RA) model. Both model well predicted the toxicity of binary mixtures to the five organisms. As for the environmental risk assessment, CA overestimated the toxicity in most cases and thus is a more conservative model than RA model for assessing the toxicity of these chemical mixtures. (C) 2017 Elsevier Ltd. All rights reserved.
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The novel efficient procedure has been developed for the conjugate addition of amines to electron deficient alkenes using the novel SO_3H functionalized ionic liquid as catalyst. The results showed that the novel catalyst owned hi...
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The novel efficient procedure has been developed for the conjugate addition of amines to electron deficient alkenes using the novel SO_3H functionalized ionic liquid as catalyst. The results showed that the novel catalyst owned high activities for the reactions with excellent yields within several minutes. Various amines and electron deficient alkenes were successfully transformed to the corresponding products in the catalytic system. Operational simplicity, without need of any solvent, low cost of the catalyst used, room temperature, high yields, reusability, excellent chemoselectivity and wide applicability are the key features of this methodology.
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