Alkyloxy‐s‐triazine derivatives with and without fluorine‐containing substituents as lubricants for steel–steel contact

Three alkyloxy‐s‐triazine derivatives were synthesized and their tribological properties as lubricants for steel–steel contact were evaluated using an Optimol SRV tester at 20°C and 100°C. Their thermal stabilities were also investigated by thermogravimetric analysis. The results show that the three alkyloxy‐s‐triazine lubricants have good thermal stability. Moreover, 2,4,6‐tris(1,1,5‐tri‐H‐octafluoropentyloxy)‐1,3,5‐s‐triazine (FPOT) possesses the best anti‐wear property and good load‐carrying capacity both at 20°C and 100°C. At 20°C the anti‐wear effectiveness of 2,4,6‐tris(n‐pentyloxy)‐1,3,5‐s‐triazine (POT) is the worst, while at 100°C that of the 1,1,5‐tri‐H‐octafluoropentyloxy and/or 1,1,7‐tri‐H‐dodecafluoroheptyloxy tri‐substituted s‐triazine mixture (FMOT) is the worst. In addition, the friction‐reducing properties of the two fluoroalkyloxy‐s‐triazines, FPOT and FMOT, are not as good as those of the non‐fluorine‐containing alkyloxy‐s‐triazine POT. Scanning electron spectroscopy with an energy dispersive analyzer of X‐ray and X‐ray photoelectron spectroscopy analyses of the worn surface indicate that during the rubbing process, tribochemical reactions occur between the lubricants and the metal surface to generate a complex boundary lubrication film comprised of FeF₂, Fe(OH)₂, organofluorine and organonitrogen compounds. Copyright © 2006 John Wiley & Sons, Ltd.     

Tribological study of novel S–N style 1,3,4-thiadiazole-2-thione derivatives in rapeseed oil

Two non-phosphorus and ashless 1,3,4-thiadiazole-2-thione derivatives, 5-dodecyldithio-3-phenly-1,3,4-thiadiazole-2-thione (DPTT) and 5-cetyldithio-3-phenyl-1,3,4-thiadiazole-2-thione (DHTT), were synthesized and their tribological behaviors as additives in rapeseed oil (RSO) were evaluated using a four-ball friction and wear tester. Their thermal stabilities and anticorrosive properties were investigated. The results indicate that the additives possess good thermal stabilities, corrosion inhibiting abilities and excellent load-carrying capacities. Moreover, they both have good anti-wear and friction-reducing property at relatively low concentration and under all test loads. The worn surfaces of the steel balls were observed using a scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It is supposed that the synthetic additives adsorb and react with the steel surfaces during the rubbing process and generate a surface protective film composed of sulfate, sulfide, iron oxide and organic nitrogen-containing compounds, which accounts for the better tribological behaviors of the base stock containing the synthetic additives as compared with the base stock alone.     

Vibrations of point-supported rectangular plates with variable thickness using a set of static tapered beam functions

This paper studies the free vibrations of point-supported rectangular plates with variable thickness using the Rayleigh–Ritz method. The domain of the plate is bounded by x=αa′, a′ (0α<1); y=βb′, b′ (0β<1) in the Cartesian coordinate system. The thickness of the plate varies continuously and is represented by a power function (x/a′)^s(y/b′)^t. Varieties of tapered rectangular plates can be described by giving s and t different values. A set of static tapered beam functions which are the solutions of a tapered beam (a unit width strip taken from the particular plate under consideration in one or the other direction parallel to its edges) under a Taylor series of static loads, are developed as the admissible functions for the vibration analysis of point-supported rectangular plates with variable thickness in one or two directions. The eigenfrequency equation is derived through the Rayleigh–Ritz approach, supplemented by the zero deflection conditions at the point-supports. A very simple program in common use has been compiled. The convergence study shows a small computational cost and the comparison with known solutions for point-supported rectangular plates with uniform thickness demonstrates the accuracy of the present method. Finally, some new numerical results are given, which may serve as the benchmarks for future research on the aforementioned problem.     

Tribological behavior of three novel triazine derivatives as additives in rapeseed oil

Three novel phosphorus-free triazine derivatives, referred to as ZOO, ZOS and ZDION, respectively, were synthesized. Their thermal stabilities and anticorrosive properties were investigated. Their tribological behaviors as additives in rapeseed oil were evaluated using four-ball friction and wear testers as well. The results suggest that all the synthesized compounds have good thermal stability, corrosion inhibiting ability and excellent tribological behavior. That is, ZOS has the best extreme pressure, antiwear and friction-reducing properties under a wide range of test conditions. And, ZOO generally possesses excellent load-carrying capacity and good antiwear and friction-reducing abilities. However, ZDION shows poor antiwear effectiveness in rapeseed oil, though it is capable of improving the load-carrying capacity and friction-reducing ability of the base stock under high concentration (>1.5 wt.%) and low load (<392 N). The worn surfaces of the steel balls were observed using a scanning electron microscope coupled with an energy dispersive spectrometer (SEM/EDS) and X-ray photoelectron spectroscope (XPS). It is supposed that the synthetic additives adsorb and react with the steel surfaces during the rubbing process and generate a surface protective film composed of sulfate, sulfide, iron oxide and N- and/or O-containing organic compounds, which accounts for the better tribological behaviors of the base stock containing the synthetic additives as compared with the base stock alone.     

Dependence of surface morphology on molecular structure and its influence on the properties of OLEDs

Most organic light-emitting diodes (OLEDs) have a multilayer structure composed of organic layers such as a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL) and an electron injection layer (EIL) sandwiched between two electrodes. The organic layers are thin solid films with a thickness from a few nano meters to a few tenths nano meter, respectively. Surface morphology of an organic thin solid film in OLEDs depends on the molecular structure of the organic material and has an affect on device performance. To analyze the effect of surface morphology of an organic thin solid film on fluorescence and electroluminescence (EL) properties, thin solid films of 4-(dicyanomethylene)-2-methyl-6-(julolidin-4-yl-vinyl)-4H-pyran (DCM2) and new red fluorophores, (2E,2′E)-3,3′-[4,4″-bis(dimethylamino)-1,1′:4′,1″-terphenyl-2′,5′-diyl]bis[2-(2-thienyl)acrylonitrile] (ABCV-Th) and (2Z,2′Z)-3,3′-[4,4″-bis(dimethylamino)-1,1′:4′,1″-terphenyl-2′,5′-diyl]bis(2-phenylacrylonitrile) (ABCV-P) were investigated by atomic force microscopy (AFM). The samples for EL and AFM measurement were fabricated by the high-vacuum thermal deposition (8×10⁻⁷ Torr) of organic materials onto the surface of indium tin oxide (ITO)-coated glass substrate, in which the layer structures of samples for AFM measurement and those for EL measurement were ITO/NPB (40 nm)/red emitters (80 nm) and ITO/NPB (40 nm)/red emitters (80 nm)/BCP (30 nm)/Liq (2 nm)/Al (100 nm), respectively. The analysis based on AFM measurements well supported that the photoluminescence properties and the device performance were very much dependent upon surface morphology of an organic thin layer.     

Study of the tribological behavior of S-(carboxylpropyl)-N-dialkyl dithiocarbamic acid as additives in water-based fluid

There has been a growing concern for the use of water-based fluids because of the worldwide interest in environmental issues. This has promoted the research and use of water-soluble additives as environmental friendly lubricants. A kind of potential water-soluble additive, S-(carboxylpropyl)-N-dialkyl dithiocarbamic acid was prepared in this work. The friction and wear behaviors of the synthesized compounds as an additive in water-based liquid were evaluated with a four-ball tester and a ring-on-block rig. The wear scar morphology of the ball and the chemical nature of the antiwear films generated on the steel counter face were investigated with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It was found that the synthesized additives had excellent antiwear, load-carrying and extreme pressure performance. The additive reacted with the counter-face metal and generated a surface protective film consisting of FeS, FeS₂, FeSO₄ and an absorbed compound containing N and acid.     

Plastic Scintillators Based on Polymethyl Methacrylate: <Emphasis Type="Italic">A Review</Emphasis>

The scintillation properties of plastic scintillators based on polymethyl methacrylate with various luminescent dyes are considered. It is shown that replacing the naphthalene conventionally used in these scintillators as a secondary solvent with octadeuteronaphthalene and 1,3-divinylbenzene will not alter either their scintillation efficiency and optical transparency, or their thermal, light, and radiation-damage stability; replacing it with 1,1,3-trimethyl-3-phenylindan, however, improves all these characteristics. It is demonstrated that n-terphenyl, 2,5-diphenyloxazole, 2-biphenyl-5-phenyl-1,3-oxazole, 2-biphenyl-(α-naphthyl)-1,3-oxazole, 2-phenyl-5-(4-biphenylyl)-1,3,4-oxadiazole, and 2-(4′-tret-butylphenyl)-5-(4″-biphenylyl)-1,3,4-oxadiazole can be used as luminescent activators, and n-bis-(o-methylstyryl)-benzene and 1,4-di-(5-phenyl-2-oxazolyl)-benzene are applicable as wavelength shifters.__________Translated from Pribory i Tekhnika Eksperimenta, No. 3, 2005, pp. 5–15.Original Russian Text Copyright © 2005 by Salimgareeva, Kolesov.     

Inverse approach for estimating rheological characteristics of adsorption layer in thin film EHL contacts

A modified Reynolds equation is derived for thin film elastohydrodynamic lubrication (TFEHL) by means of the viscous adsorption theory. This TFEHL theory can be used to explain the deviation between the measured film thickness and that predicted from the convenient elastohydrodynamic lubrication (EHL) theory under very thin film conditions. Results show that the thinner the film, the greater the ratio of the adsorption layer to the total film thickness becomes, and the greater the value of the pressure–viscosity index (z′). An inverse approach is proposed to estimate the pressure distribution based upon the film thickness measurement and to determine the pressure–viscosity index of oil film, and the thickness (δ) and the viscosity ratio (η^*) of the adsorption layer in TFEHL circular contacts. Based on TFEHL theory, the inverse approach can reduce z′ error, and provides a reasonably smooth curve of pressure profile by implementing the measurement error in the film thickness. This algorithm not only estimates the pressure, but also calibrates the film shape. Consequently, it predicts z′, η^*, and δ with very good accuracy. It can also be used to evaluate the lubrication performance from a film thickness map obtained from an optical EHL tester. Results show that the estimated value of z′ is in very good agreement with the experimental data.     

Sliding friction and wear performance of Ti6Al4V in the presence of surface-capped copper nanoclusters lubricant

The friction and wear properties of Ti₆Al₄V sliding against AISI52100 steel ball under different lubricative media of surface-capped copper nanoclusters lubricant—Cu nanoparticles capped with O,O′-di-n-octyldithiophosphate (Cu-DTP), rapeseed oil and rapeseed oil containing 1 wt% Cu-DTP was evaluated using an Optimol SRV oscillating friction and wear tester. The wear mechanism was examined using scanning electron microscopy (SEM) and X-ray photoelectron spectrosmeter (XPS). Results indicate that Cu-DTP can act as the best lubricant for Ti₆Al₄V as compared with rapeseed oil and rapeseed oil containing 1 wt% Cu-DTP. The applied load and sliding frequency obviously affected the friction and wear behavior of Ti₆Al₄V under Cu-DTP lubricating. The frictional experiment of the Ti₆Al₄V sliding against AISI52100 cannot continue under the lubricating condition of rapeseed oil or rapeseed oil containing 1 wt% Cu-DTP when the applied load are over 100 N. Surprisingly, the frictional experiment of Ti₆Al₄V sliding against AISI52100 steel can continue at the applied load of 450 N under Cu-DTP lubricating. The tribochemical reaction film containing S and P is responsible for the good wear resistance and friction reduction of Ti₆Al₄V under Cu-DTP at the low applied load. However, a conjunct effect of Cu nanoparticle deposited film and tribochemical reaction film containing S and P contributes to the good tribological properties of Ti₆Al₄V under Cu-DTP at the high-applied load.     

Effective viscosity of oils containing VI improver and its relation to wear

The effective viscosity of oils containing polymethacrylate and olefin copolymer additives has been determined using the electrical resistance technique in a rolling, four-ball machine. The effective viscosity is affected mainly by type, concentration and molecular weight of the polymer additive. The experimental results indicate that the thickening effect, following addition of a polymer, is decreased significantly in terms of film thickness, after frictional contact. The results of sliding wear tests correlate well with calculations of effective viscosity indicating that only the viscosity at high shear rates (> 10⁶s⁻¹) is responsible for the wear preventing property of these additives. No antiwear properties, in terms of boundary lubrication, are observed     

Oil-Soluble Fluorinated Compounds as Antiwear and Antifriction Additives

Many studies have been published on the use of solid fluorinated compounds as lubricants and lubricant additives, but much less has been done with oil-soluble fluorinated additives.

This paper describes a study of fluorinated telomers, especially fatty acids and their amine salts, for boundary lubrication (antiwear conditions). The antiwear effectiveness of these fluorinated compounds is compared with a commercial additive, zinc di-n-butyl dithiophosphate (ZDTP).

Modern analytical tools are used to study surface layers (XPS, automatic wetting balance), and wear particles (IR) to determine their antiwear mechanism. Special attention is given to fluorinated reaction film formation.     

Modeling of thermomechanical shear instability in machining

The modeling of thermomechanical shear instability in the machining of some difficult-to-machine materials leading to shear localization is presented. Shear instability was observed experimentally in high-speed machining (HSM) of some of the difficult-to-machine materials, such as hardened alloy steels (e.g. AISI 4340 steel), titanium alloys (e.g. Ti-6A1-4V), and nickel-base superalloys (e.g. Inconel 718) yielding cyclic chips. Based on an analysis of cyclic chip formation in machining, possible sources of heat (including preheating effects) contributing toward the temperature rise in the shear band are identified. They include the four primary heat sources, the four preheating effects of the primary heat sources, the image heat source due to the primary shear band heat source, and the preheating effect of this heat source. The temperature rise in the shear band due to each of the heat sources is calculated using Jaeger's classical model for stationary and moving heat sources. Based on this temperature, Recht's classical model of catastrophic shear instability in metals under dynamic plastic conditions developed in 1964 is extended by predicting analytically the conditions for the onset of shear localization. This is done by comparing the strength of material in the shear band, σ′ under the combined effects of thermal softening and strain hardening with that of the material in the vicinity of the shear band, σ where the material has undergone small strains (i.e. up to yield point) and at the temperature caused by the preheating heat sources. Thus, σ is nearly the original strength of the work material. If σ′ < σ, thermal softening predominates at the shear band and shear localization will be imminent. The cutting speed for the onset of shear localization can be predicted based on thermomechanical shear instability model presented here. High-speed machining results reported in the literature for an AISI 4340 steel agree reasonably well with the analytical values developed in this investigation.     

Tribological properties of phosphate esters as additives in rape seed oil

With the growing concern about environmental pollution, vegetable oils have begun to be applied as base oils for environmentally friendly lubricants. Additives containing phosphorus can be used for their excellent antiwear properties and low toxicity. In view of this, a study of a series of phosphate esters as additives in rape seed oil (RSO) was carried out using a four‐ball tester. The results indicate that phosphate esters possess very good load‐carrying capacity and good antiwear and friction‐reducing properties compared with RSO by itself. Surface analysis of the worn balls was carried out using X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The tribological mechanism of the additives is discussed on the basis of the experimental results.     

The tribological properties and action mechanism of Schiff base as a lubricating oil additive

In this paper, an organic compound containing a nitrogen element, Schiff base, is synthesised, and its tribological characteristics are evaluated by four-ball and Timken machines. Schiff base possesses friction-reducing and antiwear properties, especially under low load. Results from X-ray photoelectron spectroscopy (XPS) reveal that the binding energy of N_1s increases in the boundary film. Differential thermal analyses (DTA) indicate that Schiff base reacts with iron powder, forming complex compounds through hydroxy and azomethine. An action mechanism, with surface-complex compound films being formed on the surface, is proposed.     

Determining Generation–Recombination Characteristics of a Semiconductor–Dielectric Interface from the Current Kinetics of Surface Minority Carrier Generation

Conditions for the one-to-one characterization of the generation (G _s) and surface recombination (R _s) rates of minority charge carriers (MCCs) in a metal–oxide–semiconductor (MOS) structure (in the case of strong nonequilibrium depletion) by the MCC surface generation current (I(t)) flowing in an external circuit of this structure are revealed. These conditions are the following: (1) the generation current I is independent of the time t (until the structure enters an equilibrium state) and the voltage V _{g 0} corresponding to the initial nonequilibrium depletion and (2) the duration of current steps I(V _{g 0}) = const and, consequently, the equilibrium surface charge increase with increasing V _{g 0}. The observed kinetics of the MCC generation current for the MCCs induced in an n-Si MOS structure at 293 K experimentally confirms the realization of these conditions. The values of the generation and recombination rates G _s = 2.84 × 10¹⁰ cm^–2s^–1 and R _s = 6.82 cm s^–1 obtained from current levels I(V _{g 0}) = const are typical of high-quality Si MOS structure. Additionally measured capacitance–voltage characteristics were used to determine the interface state density at the Si/SiO₂ contact near the middle of the Si gap (N _ss(E) 6.4 × 10¹⁰ cm^–2eV^–1), which allowed the estimation of the effective capture cross section of these states _eff 1.4 × 10^–16 cm².     

A surface motor-driven planar motion stage integrated with an XYθZ surface encoder for precision positioning

This paper describes a surface motor-driven XY planar motion stage equipped with a newly developed XYθ_Z surface encoder for sub-micron positioning. The surface motor consists of four linear motors placed on the same surface, two pairs in the XY-axes. The magnetic array and the stator winding of the linear motor are mounted on the platen (the moving element) and the stage base, respectively. The platen can be moved in the X-direction by the X-linear motors, and in the Y-direction by the Y-linear motors. It can also be rotated about the Z-axis if the X- or Y-linear motors generate a moment about the Z-axis. The surface encoder consists of two two-dimensional angle sensors and an angle grid with two-dimensional sinusoidal waves on its surface. The angle grid is mounted on the platen of the stage which is levitated by air-bearings. The angle sensors and the air-bearing pads are fixed on the stage base so that the motion of the platen is not affected by the electronic cables and air hoses. The XY-positions and θ_Z rotation of the platen can be obtained from the angle sensor outputs with resolutions of approximately 20 nm and 0.2′′, respectively. The surface encoder is placed inside the stage so that the stage system is very compact in size. Experimental results indicate that precision positioning can be carried out independently in X, Y and θ_Z with resolutions of 200 nm and 1′′, respectively.     

Improvement in tribological performances of magnesium alloy using amide compounds as lubricating additives during sliding

The tribological characteristics of a magnesium alloy, AZ91D (die-casting), are investigated in a sliding lubricating system using various amide compounds as lubricating additives on a Timken type tester against a bearing steel (AISI52100) ring. Results indicate that a significant improvement in the tribological performance exists using the amide compounds as additives. The number of amido group (–CONH₂) in additive molecules and the molecular structure of amide compounds have significant effect on the tribological characteristics of magnesium alloy. Electromicroscopy reveals that the mild abrasive wear is a predominant wear mechanism of magnesium alloy using an amide additive while the dominated wear mechanism is a severe abrasive wear with severe material deformation using only base oil. Observation shows the formation of boundary film on the magnesium alloy. XPS analysis suggests the occurrence of tribo-chemical reactions between Mg and amide compounds with the formation of chemically stable compound (or complex) of magnesium and amide, as well as the formation of friction polymer.     

The Tribological Chemistry of Novel Triazine Derivatives as Additives in Synthetic Diester

Two novel triazine derivatives 2-tris(2-ethylhexyl)-3,3′,3″-(1,3,5-triazine-2,4,6-triyl)-tris(sulfanediyl)tripropanoate (TE TST) and 2-ethylhexyl-3-(4,6-dimercapto-1,3,5-triazin-2-ylthio) propanoate (EDTYP) were synthesized. Their tribological properties in synthetic diester were evaluated using a four-ball tribometer, and the thermal films and tribofilms were investigated using X-ray absorption near-edge structure (XANES) spectroscopy. The copper corrosion-inhibiting performance was explored as well. The additives can improve the extreme pressure performance of base stock. TETST displays good antiwear property and EDTYP possesses excellent friction-reducing ability. Surface analysis indicated that the thermal films are exclusively composed of FeSO₄, and the tribofilms are constituted by FeS, FeS₂, and FeSO₄. The mechanism obtained from the XANES analysis fit well with the results of tribological tests.     

Plate-like wear particle formation in a lubricated ball-on-plate friction pair

The mechanism of formation of plate-like wear particles in a ball-on-plate lubricated friction pair has been examined for wear constants of K < 10⁻¹⁰ (mm³ mm⁻¹ N⁻¹). The plate Vicker's hardness was 2.80–3.00 kN/mm², the sliding speed 1.74 m s⁻¹ and the load 50 N. The following mechanism is suggested: scratching of the surface and formation of ridges at the scratch border, lateral deformation of ridges and formation of thin sheets, and cracking and separation of plate-like particles from these sheets.     

Determination of the Minority Carrier Surface Thermogeneration Rate in Metal-Oxide-Semiconductor Structures

A metal-oxide-semiconductor (MOS) structure with the common field electrode insulated from the semiconductor by oxide layers h of different thicknesses allows the surface generation rate of minority charge carriers from current I(t) of nonequilibrium depletion state relaxation to be found. At the same time, it is possible in similar structures to observe the kinematics of electron-hole pair generation at the periphery of the field electrode (the edge generation effect). Measurements performed on an n-Si MOS structure with a stepwise change in oxide layer thickness (h ₁ = 100 Å and h ₂ = 3200 Å) allowed the generation rate at both the initial transient (t ∼ 10⁻⁵ s) stage of surface generation (4.34 × 10¹⁰ cm⁻² s⁻¹) and at the basic extremely slow stage (10.4 cm⁻² s⁻¹) to be reliably determined for the first time. The estimated peripheral generation rate of minority charge carriers (holes) was 7.8 × 10¹¹ cm⁻² s⁻¹.__________Translated from Pribory i Tekhnika Eksperimenta, No. 4, 2005, pp. 84–88.Original Russian Text Copyright © 2005 by Chucheva, Zhdan, Akhmedov, Kukharskaya.