The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform

Xiaobo Wang - One of the best experts on this subject based on the ideXlab platform.

Xinhu Wu - One of the best experts on this subject based on the ideXlab platform.

M Kasrai - One of the best experts on this subject based on the ideXlab platform.

  • a variable temperature mechanical analysis of zddp derived Antiwear films formed on 52100 steel
    Wear, 2007
    Co-Authors: Gavin Pereira, P R Norton, M Kasrai, Andreas Lachenwitzer, David Munozpaniagua, Weston T Capehart, Thomas A Perry, Yangtse Cheng
    Abstract:

    Abstract The nanomechanical properties of Antiwear films formed from zinc dialkyl-dithiophosphates (ZDDPs) on steel have been studied by nanoindentation techniques as a function of temperature. X-ray absorption P K- and L- near edge structure (XANES) spectroscopy has shown that films prepared from oils containing ZDDPs on 52100 steel (pin on flat coupons) consist primarily of medium chain polyphosphates with sulphur (S K-edge) predominantly present as sulphide. Using various scanning probe techniques, high-resolution topographic images and mechanical properties can be extracted at the same length scale. Using focused ion beam (FIB) milling we have compared real cross-sectional film thickness with a value estimated from the P K-edge XANES. We report the first measurements of the elastic modulus of the Antiwear films at elevated temperatures relevant to the automobile operating conditions (T ≤ 200 °C). The Antiwear films demonstrated a relatively constant indentation modulus over a wide range of temperatures consistent with their efficacy in reducing wear by preventing asperity contact.

  • nanometer scale chemomechanical characterization of Antiwear films
    Tribology Letters, 2004
    Co-Authors: Mark A Nicholls, P R Norton, G M Bancroft, M Kasrai, Than Do, B H Frazer, G De Stasio
    Abstract:

    We report the first nanometer scale chemical and mechanical (chemomechanical) characterization of selected features of a tribologically derived zinc dialkyl-dithiophosphate (ZDDP) Antiwear film. AFM permits identification of the features responsible for preventing wear. These features are identified by nearby microscale fiducial marks, and their mechanical properties are determined by imaging nanoindentation. The same features are then studied by X-ray photoelectron emission microscopy (X-PEEM), which provides both elemental and chemical information at ∼200 nm spatial resolution. The mechanical properties are then determined for the same features, which are formed of a polyphosphate glass. This information provides new insights into the mechanisms by which ZDDP Antiwears films are effective at inhibiting asperity contact between two metal surfaces

  • chemomechanical properties of Antiwear films using x ray absorption microscopy and nanoindentation techniques
    Tribology Letters, 2004
    Co-Authors: Mark A Nicholls, P R Norton, M Kasrai, B H Frazer, Michael G Bancroft, Gelsomina De Stasio, Lisa M Wiese
    Abstract:

    The first chemomechanical comparison between an Antiwear film formed from a solution containing zinc dialkyl-dithiophophates (ZDDPs) to a solution containing ZDDP plus a detergent (ZDDPdet) has been performed. X-ray absorption near-edge structure (XANES) analysis has shown a difference in the type of polyphosphate between each film. The ZDDPdet film has been found to contain short-chain polyphosphates throughout. X-ray photoelectron emission microscopy (X-PEEM) has provided detailed spatially resolved microchemistry of the films. The large pads in the ZDDP Antiwear film have long-chain polyphosphates at the surface and shorter-chain polyphosphates are found in the lower lying regions. The spatially resolved chemistry of the ZDDPdet film was found to be short-chain calcium phosphate throughout. Fiducial marks allowed for the re-location of the same areas with an imaging nanoindenter. This allowed the nanoscale mechanical properties, of selected Antiwear pads, to be measured on the same length scale. The indentation modulus of the ZDDP Antiwear pads were found to be heterogeneous, ~120 GPa at the center and ~90 GPa at the edges. The ZDDPdet Antiwear pads were found to be more uniform and have a similar indentation modulus of ~90 GPa. A theory explaining this measured difference, which is based on the probing depths of all techniques used, sheds new insight into the structure and mechanical response of ZDDP Antiwear films.

  • The use of X‐ray absorption spectroscopy for monitoring the thickness of Antiwear films from ZDDP
    Tribology Letters, 2000
    Co-Authors: M.l. Suominen Fuller, M Kasrai, L. Rodriguez Fernandez, G.r. Massoumi, W.n. Lennard, G M Bancroft
    Abstract:

    X‐ray absorption near edge structure (XANES) spectroscopy at the P K‐edge was used to monitor ZDDP Antiwear film thickness with rubbing time. Thermal immersion films of varying thickness were generated from the ZDDP and analysed using XANES spectroscopy and the particle induced X‐ray emission (PIXE) technique. P K‐edge XANES edge jumps and (1s → np) peak heights of the spectra were plotted against PIXE mass thickness values in order to establish calibration curves. Antiwear films were analysed using XANES spectroscopy, and average mass thicknesses were extrapolated from the calibration curves. A set of Antiwear films formed in the presence of ZDDP and then further rubbed in base oil (no ZDDP) showed no significant decrease in film thickness. A set of Antiwear films rubbed in the presence of ZDDP for various lengths of time showed an increase in film thickness, followed by thinning of the film. The decrease in film thickness is believed to be due to wear caused by the ZDDP solution decomposition products acting as an abrasive in the contact region.

  • the use of x ray absorption spectroscopy for monitoring the thickness of Antiwear films from zddp
    Tribology Letters, 2000
    Co-Authors: Suominen M Fuller, M Kasrai, G.r. Massoumi, W.n. Lennard, Rodriguez L Fernandez, G M Bancroft
    Abstract:

    X‐ray absorption near edge structure (XANES) spectroscopy at the P K‐edge was used to monitor ZDDP Antiwear film thickness with rubbing time. Thermal immersion films of varying thickness were generated from the ZDDP and analysed using XANES spectroscopy and the particle induced X‐ray emission (PIXE) technique. P K‐edge XANES edge jumps and (1s → np) peak heights of the spectra were plotted against PIXE mass thickness values in order to establish calibration curves. Antiwear films were analysed using XANES spectroscopy, and average mass thicknesses were extrapolated from the calibration curves. A set of Antiwear films formed in the presence of ZDDP and then further rubbed in base oil (no ZDDP) showed no significant decrease in film thickness. A set of Antiwear films rubbed in the presence of ZDDP for various lengths of time showed an increase in film thickness, followed by thinning of the film. The decrease in film thickness is believed to be due to wear caused by the ZDDP solution decomposition products acting as an abrasive in the contact region.

Yubao Li - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of tall oil fatty acid as Antiwear agent to improve the lubricity of ultra-low sulfur diesels
    Tribology International, 2017
    Co-Authors: Zhen Hu, Li Zhang, Yubao Li
    Abstract:

    The tall oil fatty acid (TOFA) used as Antiwear agent was applied respectively to the ultra-low sulfur non-additive diesel and ultra-low sulfur additive diesel. The effect of TOFA on the lubricity of the two kinds of ultra-low sulfur diesel was evaluated using the wear scar diameters (WSD) and coefficient of friction (COF). The results showed that the Antiwear agent could improve the lubricity of ultra-low sulfur non-additive 0# diesel effectively; both the WSD and COF were reduced significantly. When the content of TOFA Antiwear agent increased from 0 to 500 µg/g, the WSD of the non-additive 0# diesel decreased from initial 630 µm to 250 µm, reducing by 60.3%; the COF reduced by 95.7%, from initial 0.47 to 0.02. The wear scar on discs and the wear reflected by Fe element were reduced obviously. The TOFA Antiwear agent also showed a trend to reduce the metal content in the diesel friction solution, and there was no influence on other physical and chemical properties of the non-additive diesel. Similarly, the TOFA could also enhance the lubricity of commercial ultra-low sulfur additive 0# diesels. The polar organic substances of TOFA Antiwear agent have strong polarity, easy to adsorb on friction surface to form the lubricant protective film, to effectively reduce the friction and wear, thus improve the lubricity of the diesel.

K Fyfe - One of the best experts on this subject based on the ideXlab platform.

  • solution decomposition of zinc dialkyl dithiophosphate and its effect on Antiwear and thermal film formation studied by x ray absorption spectroscopy
    Tribology International, 1998
    Co-Authors: Marina Suominen L Fuller, M Kasrai, Michael G Bancroft, K Fyfe
    Abstract:

    A detailed study was undertaken to investigate the effect of ZDDP oil solution chemistry changes due to thermal decomposition, on Antiwear and thermal film chemistries, film thickness and wear. P and S K- and L-edge X-ray absorption near edge structure (XANES) spectroscopies were used to characterize film chemistry, and 31-P NMR spectroscopy was used to monitor the ZDDP oil solution chemistry. P L-edge XANES results of Antiwear films prepared from ZDDP oil solutions preheated at 150°C for various lengths of time, showed a decrease in polyphosphate chain length as ZDDP thermal solution decomposition progressed. Film thickness and wear increased with increasing ZDDP oil solution preheating time (decomposition). Antiwear films formed from ZDDP oil solutions preheated at a higher temperature (200°C) for 1 and 3 h, yielded thinner films and showed catastrophic wear. 31-P NMR spectra showed that no oil soluble P containing species were left in solution after heating at 200°C for 1 h and yet the 200°C, 6 h Antiwear film was found to be as thick as that generated from previously unheated solution. Wear was comparable to that obtained by using base oil alone. These films were found to be of short chain polyphosphate structure. ZDDP oil solution chemistry was also shown to have an effect on the chemistry of thermally generated films. Film chemistry changed with ZDDP oil solution heating time. A linkage isomer of ZDDP is proposed as an important precursor for film formation after analysis and comparison of an oil insoluble ZDDP decomposition product with the thermal and Antiwear film chemistries. As with the related Antiwear films, thermal film thickness was also shown to increase dramatically when ZDDP decomposition in solution increased. An overall mechanism for film formation, taking into account the ZDDP linkage isomer and the deposition of colloidal polyphosphate material, is proposed.

  • application of soft x ray absorption spectroscopy in chemical characterization of Antiwear films generated by zddp part i the effects of physical parameters
    Wear, 1997
    Co-Authors: M Kasrai, Michael G Bancroft, Marina Suominen L Fuller, K Fyfe
    Abstract:

    X-ray absorption near edge structure (XANES) spectroscopy has been used to study the chemical nature of the Antiwear films generated on steel surfaces using zinc dialkyldithiophosphates (ZDDPs). The spectra were recorded using total electron yield (TEY) and fluorescence yield (FY) to investigate the chemical nature of P, S, Ca, O and Fe on the surface and in the bulk, respectively. In the first part of this study, the effects of physical parameters on the composition and mechanism of Antiwear film formation is discussed. It has been found that lower concentration of ZDDP, higher temperature and higher load all increase the rate of ZDDP decomposition; and longer rubbing time, higher concentration of ZDDP, moderate temperature, higher load and smooth surfaces help to form long chain polyphosphates. The sulphur in the film in most of the cases is in the reduced form. The presence of sulphate in very short rubbing times or high temperatures has also been detected. When the spectra from the TEY mode and FY mode were compared, a layered structure was found in most of the films. In these films, there is a longer chain polyphosphate on the topmost surface and a shorter chain polyphosphate in the bulk. At short rubbing times and low temperature, unchanged ZDDP is also present in the film. Depth profiling using X-ray photoelectron spectroscopy showed that the Antiwear film formed in 30 min is thinner compared with a 12 hour film. Based on the above information, a new mechanism for Antiwear film formation is proposed.