Excellent melt lubrication of alkali metal polyphosphate glass for high temperature applications

A new class of high temperature lubricant of inorganic alkali metal polyphosphate was developed for hot metal forming, which involved a fundamental knowledge of melt lubrication. At elevated temperature a 55% reduction in friction and a 50% decrease in wear were achieved by the presence of the molten polyphosphate lubrication, as well as the excellent anti-oxidation capability at the rubbing steel/steel interface, which closely correlated with the tribo-induced hierarchical structure at the rubbing interface. This inorganic polyphosphate lubricant can be called a smart polymeric material, which will be an eco-friendly alternative for high temperature applications. This journal i

A FPC-ROOT Algorithm for 2D-DOA Estimation in Sparse Array

To improve the performance of two-dimensional direction-of-arrival (2D DOA) estimation in sparse array, this paper presents a Fixed Point Continuation Polynomial Roots (FPC-ROOT) algorithm. Firstly, a signal model for DOA estimation is established based on matrix completion and it can be proved that the proposed model meets Null Space Property (NSP). Secondly, left and right singular vectors of received signals matrix are achieved using the matrix completion algorithm. Finally, 2D DOA estimation can be acquired through solving the polynomial roots. The proposed algorithm can achieve high accuracy of 2D DOA estimation in sparse array, without solving autocorrelation matrix of received signals and scanning of two-dimensional spectral peak. Besides, it decreases the number of antennas and lowers computational complexity and meanwhile avoids the angle ambiguity problem. Computer simulations demonstrate that the proposed FPC-ROOT algorithm can obtain the 2D DOA estimation precisely in sparse array

Friction and anti-wear property of aqueous tri-block copolymer solutions in metal forming

Friction and anti-wear property of aqueous symmetrical tri-block normal PEOm-PPOn-PEOm and reverse PPOn-PEOm-PPOn copolymer solutions have been studied. The study focuses on the effect of the solution bulk temperatures and the copolymer block structures. It was found that the concentration and the length of the copolymer blocks affect the solution cloud points, friction and anti-wear property. When solution was supplied at bulk temperature above their cloud point, aqueous copolymer solutions were not able to develop effective adsorbed film resulting in high friction and severe wear. When the bulk temperatures were below the cloud point, the anti-wear property improved significantly and the dynamic friction is lower than that when the temperatures were above the cloud point. This demonstrates the importance of the supply temperature of this type of lubricant in metal forming. However by adding ethyl phosphate ester to the copolymer solutions further improved friction reducing property of the solutions was observed and the friction and anti-wear property of the lubricant become insensitive to bulk temperature. In the effort to understand the lubrication mechanism of the aqueous solutions, wear tracks were studied using scanning electron microscope (SEM) and atomic force microscope (AFM), and the surface wetting ability via contact angle measurements

Surface film adsorption and lubricity of soybean oil in-water emulsion and triblock copolymer aqueous solution: A comparative study

This paper investigates the surface film adsorption and lubricity of two different types of potential environmentally friendly cold metal forming lubricants: soybean vegetable oil in water VO/W emulsions and triblock copolymer aqueous solutions. The lubricants have different visual appearance, surface film adsorption characteristic, lubricity and surface cleaning behaviour. The effects of concentration, temperature and emulsification ultrasonic energy (for VO/W emulsion) are studied. The result shows that the soybean VO/W emulsions have stronger adsorption, superior lubricity and anti-wear property compared to the copolymer solutions. The effect of temperature is investigated at 30 °C and 65 °C which are below and above cloud point of the aqueous copolymer solutions. Both lubricants show improved friction and anti-wear property at 65 °C. However, tenacious residual film remained on the discs surface after surface cleaning indicates lower cleanability of the soybean VO/W emulsions compared to the copolymer solutions, postulating the need for extra post-processing cleaning operations after cold forming process with VO/W emulsion lubricant

Lubricant as a sticking-scale inhibitor on high temperature sliding contact

Sticking oxide scale is one of the most serious concerns on moving steel surfaces at elevated temperature. However, there has been limited research dedicated to overcoming this issue. In the present work, pin-on-disc testing was carried out to reveal the effects of lubrication on wear characteristics of High Speed Steel sliding against Stainless Steel 316 at 700 °C. Apart from improved friction behavior, the use of inorganic lubricant significantly inhibits material transfer onto the HSS surface which otherwise suffers growing adhered scale during dry sliding contact. In addition, it was found that prolonged exposure to lubrication induces phase transformation of the subsurface iron oxides. The Hematite-to-Magnetite conversion is believed to be a result of complex oxidation and tribological reactions. Multiple characterization techniques were used to thoroughly analyze the worn surfaces, the underlying oxide microstructure and the chemical nature of lubricated interface

Aminomethanesulfonic acid illuminates the boundary between full and partial agonists of the pentameric glycine receptor

To clarify the determinants of agonist efficacy in pentameric ligand-gated ion channels we examined a new compound, aminomethanesulfonic acid (AMS), a molecule intermediate in structure between glycine and taurine. Despite wide availability, to date there are no reports of AMS action on glycine receptors, perhaps because AMS is unstable at physiological pH. Here we show that at pH 5, AMS is an efficacious agonist, eliciting in zebrafish α1 glycine receptors a maximum single channel open probability of 0.85, much greater than that of β-alanine (0.54) or taurine (0.12), and second only to that of glycine itself (0.96). Thermodynamic cycle analysis of the efficacy of these closely related agonists shows supra-additive interaction between changes in the length of the agonist molecule and the size of the anionic moiety. Single particle cryo-EM structures of AMS-bound glycine receptors show that the AMS-bound agonist pocket is as compact as with glycine, and three-dimensional classification demonstrates that the channel populates the open and the desensitized states, like glycine, but not the closed intermediate state associated with the weaker partial agonists, β-alanine and taurine. Because AMS is on the cusp between full and partial agonists, it provides a new tool to help us understand agonist action in the pentameric superfamily of ligand-gated ion channels

Insights into the behavior of polyphosphate lubricant in hot rolling of mild steel

Hot rolling with a large reduction is usually performed to produce the fine-grained strips, which leads to a severe wear of work roll and affect substantially the strip quality. As a result, lubricants are usually introduced to reduce these problems, with inorganic polyphosphate glass polymer showing the most promising prospective. This study aims to provide a new insight into the lubrication film at roll/strip interface in hot rolling. A series of lubricated hot rolling tests were performed by a 40wt% sodium metaphosphate aqueous solution under 20-60% reduction, at 950-1150 °C and 0.5 m/s. Thermal behaviors of sodium polyphosphate and the rolled strip samples were analyzed by high temperature laser confocal microscope, Secondary Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX), Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM) etc. The results reveal that the lubrication film thickness at the roll/strip interface varied from 0.6 to 4.3 µm with the rolling load being reduced up to 6.1% and friction coefficient up to 16%. FIB and TEM analysis reveal that the polyphosphate film has an amorphous structure which was penetrated through by the oxide scale. It had been found that the polyphosphate lubrication performance was improved at a higher reduction and temperature, which contributes to the friction and oxidation-reduction