scholarly journals On the mechanism of boundary lubrication. II. Wear prevention by addition agents

1940 ◽  
Vol 177 (968) ◽  
pp. 103-118 ◽  
Keyword(s):  
High Pressures ◽  
Preceding Paper ◽  
Accurate Method ◽  
Polar Compounds ◽  
Experimental Conditions ◽  
Group V ◽  
Highly Sensitive ◽  
Local Pressures ◽  
Steel Balls ◽  
Long Chain

If two metal surfaces slide over each other in the presence of a lubricant and under high load, high pressures and temperatures prevail a t those isolated spots which actually carry the load, leading to wear and possibly to breakdown. The action of wear preventing agents under these conditions has been studied in detail and it has been found that such agents are effective through their chemical polishing action, by which the load becomes distributed over a larger surface and local pressures and temperatures are decreased. Especially effective are compounds containing phosphorus or other elements of group V of the periodic system. These have been found to form a metal phosphide or homolog on the surface which is able to alloy with the metal surface, lowering its melting point markedly, and by this action aiding greatly in maintaining a polish. The wear experiments were carried out with a highly sensitive and accurate method which uses metal-plated steel balls as its sliding elements. Under the experimental conditions additions of 1.5% triphenyl phosphine or triphenyl arsine in white oil gave wear prevention factors of 7.2 and 12.2 respectively (relative to pure white oil). A further addition of 1% of a long chain polar compound is able to double the wear prevention factor obtained with the polishing agents and wear prevention factors as high as 17.6 have been observed. The specifically physical action of the long-chain polar compounds is discussed in the preceding paper.

scholarly journals On the mechanism of boundary lubrication. I. The action of long-chain polar compounds

1940 ◽  
Vol 177 (968) ◽  
pp. 90-102 ◽  
Keyword(s):  
Coefficient Of Friction ◽  
High Surface ◽  
Polar Compounds ◽  
Surface Orientation ◽  
Metallic Contact ◽  
Sliding Surfaces ◽  
The Coefficient Of Friction ◽  
Steel Balls ◽  
Sudden Decrease ◽  
Long Chain

The effect of long-chain polar compounds on the coefficient of kinetic friction under boundary conditions has been studied using the Boerlage four-ball friction apparatus in various modifications. With steel balls of the highest grade, coefficients of friction for a great number of lubricants were measured as a function of the relative velocity of the rubbing surfaces. The structure of thin films of these lubricants rubbed on polished mild steel surfaces was investigated by electron diffraction. It was found that lubricants showing little or no surface orientation had a constant coefficient of friction of about 0.1 over the available velocity range from 0 to 1 cm./sec. With oils which showed high surface orientation imparted by addition of long-chain polar compounds, a sudden decrease of the coefficient of the friction was observed at various velocities of the sliding surfaces, depending upon the com pound used. Investigation of a great number of compounds gave a direct correlation of this effect with molecular orientation: those compounds causing the effect to occur at the lowest velocities were found to be most highly oriented with their carbon chains most nearly perpendicular to the surface. Since such a change of the coefficient of friction can only be explained by the wedging of oil under the surface (oil drag), the effect was termed the ‘wedging effect’ leading to a type of lubrication which may be called ‘quasi-hydrodynamic’. By measuring the electrical resistance between the sliding surfaces it was found that the regions of sudden decrease of the coefficient of friction correspond to a change from metallic contact to extremely high resistance. The investigation shows that long-chain polar compounds act primarily by inducing the ‘wedging effect’ and not by giving a direct protection to the surface.

On the Negative Excess Isotherms for Methane Adsorption at High Pressure: Modeling and Experiment

SPE Journal ◽  
2019 ◽  
Vol 24 (06) ◽  
pp. 2504-2525 ◽  
Author(s):  
Jing Li ◽  
Keliu Wu ◽  
Zhangxin Chen ◽  
Kun Wang ◽  
Jia Luo ◽  
...  
Keyword(s):  
High Pressure ◽  
Mass Balance ◽  
High Pressures ◽  
Pore Wall ◽  
Void Volume ◽  
Excess Adsorption ◽  
Experimental Conditions ◽  
Accessible Volume ◽  
Adsorbed Phase

Summary An excess adsorption amount obtained in experiments is always determined by mass balance with a void volume measured by helium (He) –expansion tests. However, He, with a small kinetic diameter, can penetrate into narrow pores in porous media that are inaccessible to adsorbate gases [e.g., methane (CH4)]. Thus, the actual accessible volume for a specific adsorbate is always overestimated by an He–based void volume; such overestimation directly leads to errors in the determination of excess isotherms in the laboratory, such as “negative isotherms” for gas adsorption at high pressures, which further affects an accurate description of total gas in place (GIP) for shale–gas reservoirs. In this work, the mass balance for determining the adsorbed amount is rewritten, and two particular concepts, an “apparent excess adsorption” and an “actual excess adsorption,” are considered. Apparent adsorption is directly determined by an He–based volume, corresponding to the traditional treatment in experimental conditions, whereas actual adsorption is determined by an adsorbate–accessible volume, where pore–wall potential is always nonpositive (i.e., an attractive molecule/pore–wall interaction). Results show the following: The apparent excess isotherm determined by the He–based volume gradually becomes negative at high pressures, but the actual one determined by the adsorbate–accessible volume always remains positive.The negative adsorption phenomenon in the apparent excess isotherm is a result of the overestimation in the adsorbate–accessible volume, and a larger overestimation leads to an earlier appearance of this negative adsorption.The positive amount in the actual excess isotherm indicates that the adsorbed phase is always denser than the bulk gas because of the molecule/pore–wall attraction aiding the compression of the adsorbed molecules. Practically, an overestimation in pore volume (PV) is only 3.74% for our studied sample, but it leads to an underestimation reaching up to 22.1% in the actual excess amount at geologic conditions (i.e., approximately 47 MPa and approximately 384 K). Such an overestimation in PV also underestimates the proportions of the adsorbed–gas amount to the free–gas amount and to the total GIP. Therefore, our present work underlines the importance of a void volume in the determination of adsorption isotherms; moreover, we establish a path for a more–accurate evaluation of gas storage in geologic shale reservoirs with high pressure.

A rapid and accurate method for screening T-2 toxin in food and feed using competitive AlphaLISA

2021 ◽  
Vol 368 (6) ◽  
Author(s):  
Liwen Zhang ◽  
Qingyu Lv ◽  
Yuling Zheng ◽  
Xuan Chen ◽  
Decong Kong ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Accurate Method ◽  
Detection Methods ◽  
Cereal Crops ◽  
Detection Range ◽  
Highly Sensitive ◽  
Food And Feed ◽  
Good Repeatability ◽  
Feed Samples ◽  
Better Than

ABSTRACT T-2 is a common mycotoxin contaminating cereal crops. Chronic consumption of food contaminated with T-2 toxin can lead to death, so simple and accurate detection methods in food and feed are necessary. In this paper, we establish a highly sensitive and accurate method for detecting T-2 toxin using AlphaLISA. The system consists of acceptor beads labeled with T-2-bovine serum albumin (BSA), streptavidin-labeled donor beads and biotinylated T-2 antibodies. T-2 in the sample matrix competes with T-2-BSA for antibodies. Adding biotinylated antibodies to the test well followed by T-2 and T-2-BSA acceptor beads yielded a detection range of 0.03–500 ng/mL. The half-maximal inhibitory concentration was 2.28 ng/mL and the coefficient of variation was <10%. In addition, this method had no cross-reaction with other related mycotoxins. This optimized method for extracting T-2 from food and feed samples achieved a recovery rate of approximately 90% in T-2 concentrations as low as 1 ng/mL, better than the performance of a commercial ELISA kit. This competitive AlphaLISA method offers high sensitivity, good specificity, good repeatability and simple operation for detecting T-2 toxin in food and feed.

scholarly journals Near Infrared Absorption of Ethylene between 8200 cm-1 and 9500 cm-1 to High Pressures and Temperatures

1976 ◽  
Vol 31 (12) ◽  
pp. 1690-1695 ◽  
Author(s):  
F. W. Nees ◽  
M. Buback
Keyword(s):  
Infrared Absorption ◽  
High Frequency ◽  
Near Infrared ◽  
High Pressures ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Experimental Conditions ◽  
High Pressure High Temperature ◽  
Wide Range ◽  
Integrated Intensity

AbstractThe near infrared absorption of pure ethylene in the region of the second overtone of the C-H stretching fundamentals (8200 cm-1 to 9500 cm-1) was measured at supercritical temperatures (Tc = 9.5 °C) between 22 °C and 200 °C from 0.7 bar to 3000 bar. The density and temperature dependence of bandshape, maximum frequency and absorption intensity are reported and discussed. The bands observed within a wide range of experimental conditions are assigned to combination and overtone modes. The molar integrated intensity B̅λ determined between the wavelength of maximum absorption and the high frequency absorption boundary was observed to be independent of pressure and temperature. This enables spectroscopic concentration determinations on ethylene in high pressure - high temperature phase equilibria and reactions.

From the Mystery to the Understanding of the Self-Interstitials in Silicon

1980 ◽  
Vol 2 ◽  
Author(s):  
W. Frank ◽  
A. Seeger ◽  
U. Gösele
Keyword(s):  
High Temperature ◽  
The Self ◽  
Experimental Conditions ◽  
Group V ◽  
Group Iii ◽  
Enhanced Diffusion ◽  
Self Diffusion ◽  
Thermally Activated ◽  
Temperature Equilibrium ◽  
K Concentration

ABSTRACTOur present knowledge on self-interstitials in silicon and the rôle these defects play under widely different experimental conditions are surveyed. In particular, the following phenomena involving self-interstitials either in supersaturations or under high-temperature thermal-equilibrium conditions are considered: mobility-enhanced diffusion of self-interstitials below liquid-helium temperature, thermally activated diffusion of self-interstitials at inter-mediate temperatures (14O K to 600 K), concentration-enhanced diffusion of Group-III or Group-V elements in silicon at higher temperatures, and— as examples for high-temperature equilibrium phenomena — self-diffusion and diffusion of gold in silicon. This leads to the picture that the self-interstitials in silicon may occur in different electrical charge states and possess dumbbell configurations or are extended over several atomic volumes at intermediate or high temperatures, respectively.

scholarly journals Measurements of Photo-Induced Changes in Conjugated Polymers

1991 ◽  
Vol 228 ◽  
Author(s):  
Carleton H. Seager ◽  
Michael B. Sinclair ◽  
D. Mc Branch ◽  
A. J. Heeger ◽  
G. L. Baker
Keyword(s):  
Absorption Spectra ◽  
Light Transmission ◽  
Pump Light ◽  
General Shape ◽  
Experimental Conditions ◽  
Photothermal Deflection Spectroscopy ◽  
Highly Sensitive ◽  
Infra Red ◽  
Transmission Measurements ◽  
Induced Changes

ABSTRACTWe have used the highly sensitive technique of Photothermal Deflection Spectroscopy (PDS) to measure changes in the infra-red absorption spectra of MEHPPV, P3HT and Polydiacetylene-4BCMU induced by pumping these polymers with light above the π - π* transition energy. In contrast to previous chopped light transmission measurements of these effects, the PDS technique can directly measure the buildup or decay of the absorption coefficient, m, on the time scale of seconds to days. In the case of MEHPPV we observe that above-gap light causes the appearance of a broad infra-red peak in α, which continues to grow-in hours after the pump light is first applied. For this polymer the general shape of the absorption spectra in the unpumped state mimics the photo-induced changes, suggesting that remnant photo-induced states determine the maximum transparency observed under normal experimental conditions. For P3HT and to a lesser extent, MEHPPV, we also observe irreversible photo-induced absorption components which we tentatively identify with photo-induced oxidation of the polymer matrix.

Phase relationships in the Ti–Si–C system at high pressures

1992 ◽  
Vol 7 (6) ◽  
pp. 1473-1479 ◽  
Author(s):  
S. Sambasivan ◽  
W.T. Petuskey
Keyword(s):  
Silicon Carbide ◽  
Electron Probe ◽  
High Pressures ◽  
Kinetic Characteristics ◽  
Experimental Conditions ◽  
Backscattered Electron Imaging ◽  
Backscattered Electron ◽  
Electron Imaging ◽  
Clapeyron Slope ◽  
Phase Relationships

The compatibility of phases in the Ti–Si–C system was studied for pressures from 10 to 20 kbars (1 to 2 GPa) and temperatures from 1200 °C to 1500 °C via an interfacial reaction between titanium and silicon carbide. The interface was characterized by backscattered electron imaging and electron probe microanalysis. Ti3Si was stabilized at high pressures exhibiting an appreciable solubility for carbon (up to 9 at. %). At higher temperatures and lower pressures, it decomposed to Ti5Si3, Ti(Si, C), and TiCx according to the relation Ti3Si (Cz) = (0.70588)TiCx + (0.32437)Ti5Si3 + (0.67227)Ti (Si, C), where the mathematical coefficients were calculated using z = 0.4 and x = 0.5. No detectable quantities of carbon dissolved in Ti5Si3 under these conditions. A clapeyron slope of 0.08 (±0.01) kbar/K was measured for this reaction. The microstructure of the reaction zone and other general thermodynamic and kinetic characteristics are discussed for different experimental conditions.

Sign in / Sign up

Export Citation Format

Share Document