Dielectric submicroscopic phase characterisation of engine oil dispersed in jet fuel based on on‐line dielectric spectroscopy

The dielectric submicroscopic phase (DSP) characterisation of oxidised engine oils dispersed in 3# jet fuel has been analysed by on‐line dielectric spectroscopy (DES) in order to establish the correlation between engine oil oxidation degradation degrees and its DSP characteristics. Seven samples with different oxidation degradation degrees called oxidation‐series samples prepared by simulation oxidation have been analysed by Fourier transform infrared spectroscopy, and their insoluble content values according to GB/T8296 have been obtained. A series of dispersion systems composed of 0.3 ml oxidation‐series samples as the dispersed substances and 3 ml 3# jet fuel as the corresponding dispersion mediums have been designed and tested by on‐line DES during the dispersion processes, which resulted in seven series of dispersion‐series samples. Significant DES differences between the 3# jet fuel dispersion mediums and the dispersion systems have been obtained. During the dispersion process, the significant trends including dielectric enhancement stages and dielectric weakening stages have been observed according to both the raw on‐line DES spectra and DES distances, which resulted from the dielectric inhomogeneity and could be regarded as the main DSP characteristics of dispersion systems. The fact that the DSP characteristics were significantly different from the interfacial polarisation characteristics of heterogeneous systems has been verified by the on‐line DES Cole–Cole plots. It has also been proved that there the DSP characteristics of dispersion systems were consistent with their oxidation degradation degrees. And good regression performance can be obtained from both the on‐line DES distances on the basis of partial least squares and on‐line DES spectral data on the basis of multilinear‐partial least squares for insoluble contents and Fourier transform infrared spectroscopy oxidation peak areas. Copyright © 2017 John Wiley & Sons, Ltd.     

The effect of base oil oxidation on scuffing

In this work, the effect of base oil oxidation on scuffing was investigated. It was found that under mixed lubrication conditions there is a direct relationship between the level of base oil oxidation and the onset of scuffing, i.e., the greater the oxidation the lower the likelihood of scuffing. An oxidised base oil forms, among other products, carboxylic acids, which reduce scuffing failure in comparison with the parent oil. This was confirmed by the addition of a carboxylic acid directly to the base oil operating under the same mixed lubrication conditions. The removal of the carboxylic acids from the oxidised oil via column chromatography resulted in a scuffing failure performance equivalent to the parent oil. This revised version was published online in June 2006 with corrections to the Cover Date.     

Utilising Fenton reagent to simulate oxidation processes in turbine oil

To meet the demands of less‐sludge deposit and longer‐service life, turbine oils need to possess superior oxidation stability. Commercially available turbine oil nitrogen tetroxide (NTO) became green in an actual turbine, which was a risk of serious damage to turbine bearing and lubricating systems. By analysis of pH discoloration, infrared spectroscopy, it is found that the chromogenic materials in in‐service oil of NTO (UTO) were the oxidation products of diphenylamine antioxidant at low temperatures. Then, a method utilising Fenton reagent was developed to accelerate oxidation process for assessment of discoloration of turbine oil in service. By screening of experimental conditions, the colour and structure of chromogenic materials in accelerated oxidation products from NTO are the same as those of in‐service oil of NTO. Turbine oils in different formulation are oxidised by Fenton reagent in preceding condition. The colours of oxidation products are consistent with the results of ASTM D943 after 1000 h test. This study also provided a better understanding of the oxidation process affecting lubricants and the functional mode of the radical scavenger antioxidant. Copyright © 2013 John Wiley & Sons, Ltd.     

Low-cost potentiometric sensor based on a molecularly imprinted polymer for the rapid determination of matrine in herbal medicines

Abstract

A low-cost potentiometric sensor based on a molecularly imprinted polymer was developed for the determination of matrine in herbal medicine samples. The imprinted material was synthesized by the use of matrine as template, methacrylic acid (MAA) as the monomer, ethylene glycol dimethyl acrylate (EGDMA) as the cross linker, 2,2′-azo-bisisobutyronitrile (AIBN) as the initiator, and toluene and dodecanol as the porogenic agent. The electrode sensing membrane was fabricated by incorporating the ground imprinted particles into the polyvinyl chloride substrate that was subsequently incorporated into a laboratory constructed ion-selective electrode. The prepared imprinted sensor exhibited a rapid Nernst response across the concentration range from 1?×?10^?5 to 1?×?10^?1 M with a detection limit equal to 9.3?×?10^?6 M. The analytical capabilities support the direct determination of matrine in herbal medicine. The analytical results were verified by a standard ultraviolet absorption spectrophotometry protocol. The proposed sensor manifested a series of advantages, including high selectivity and sensitivity, enhanced stability and low cost, that provides a wide number of potential applications for herbal analysis.     

The influence of lubricating oil on deposits formation in a diesel engine under the operation condition of high power density

The requirements of higher power density and stricter regulations on emissions of internal combustion engines lead to lubricating oil's role shifting from simply lubricating to adapting higher power density and to achieving lower emissions. An important factor influencing an engine's power and emissions is the deposits in the engine. Lubricating oil is a chief contributor to deposits formation. The objective of this paper is to investigate the influence of lubricating oil on deposits formation when the engine is operated under high power density. Metal elements content in lubricating oil and changes to power and emissions were measured to verify deposits changes. Different power densities can be achieved by adjusting the fuel supply system in the engine. Three kinds of synthesised lubricating oils were used in the investigation. The temperature of the oil pan and cooling water was strictly controlled. The experimental results demonstrated well the influence of the quality of different kinds of oil on deposits formation. Copyright © 2013 John Wiley & Sons, Ltd.