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The utilization of functional nano-additives provides us a novel research idea to deal with the in situ temperature sensing/monitoring of lubricating oil. In this work, monodispersed and luminescent calcium fluoride (CaF2) nanoparticles with surface modification were synthesized by a hydrothermal approach, which were employed as nano-additives for polyalphaolefin (PAO6) lubricating oil. Because of the surface modification of hydrophobic oleic acid molecule, the as-prepared CaF2 nanoparticles exhibited excellent oil solubility. The tribological results further suggested that after dispersing in PAO6 lubricating oil, the CaF2 nanoparticles could maintain its original friction and wear properties. In addition to the above basic characteristics for lubricating nano-additives, it was attractive to find that the as-synthesized CaF2 nanoparticles exhibited a doublet luminescence characteristic. The intensity ratio of the two emission peaks presented a nearly linear relationship to the surrounding temperature, which was also effective for CaF2 nanoparticles dispersed in PAO6 base oil. By comprehensive consideration of the oil dispersibility, tribological properties and temperature responsiveness, the as-synthesized CaF2 nanoparticles should be promising nano-additives for temperature monitoring of lubricating oil. [ABSTRACT FROM AUTHOR]

To develop new phosphor materials for optical temperature sensing application, a series of Yb3+-Tb3+ and Eu3+ doped Ca2Gd8(SiO4)6O2 (CGS) phosphors were designed by solid-state reaction method. Upon 980 nm excitation, the green emission of Tb3+ was observed in the CGS:0.8Yb3+, xTb3+ (0.08 ≤ x ≤ 1.2) phosphors, which could be mainly owing to the cooperative energy transfer from Yb3+ to Tb3+. The corresponding upconversion (UC) luminescence mechanism was studied by using the dependence of UC emission intensity on excitation powder. The temperature-dependence indicates that the ratio of the Tb3+ emission intensities of I5D4 and I5D3 changes with temperature, which shows a linear relationship. The high absolute sensitivity was achieved to be about 0.431 K−1. Upon 463 nm excitation, the Eu3+ 5D0,1-7FJ transitions were found in the Eu3+-activated CGS. The investigation on temperature-dependence reveals that with increasing temperature the intensities of 5D0-7FJ transitions decrease but those of 5D1-7FJ transitions increase gradually, owing to the thermally coupled 5D0 and 5D1 levels. The fluorescence lifetime based temperature sensing properties was studied in this sample. [ABSTRACT FROM AUTHOR]

A phosphate based composite ceramics system, (1 − x)SrZn(PO)- xTiO (0 ≤ x ≤ 0.5), was prepared by the solid-state reaction method, and the relations between the phase composition, crystal structure and microwave dielectric properties were investigated. The results show that only two phases of SrZn(PO) and TiO can be obtained in the whole range of x value, and high relative density can be archived for all compositions as suitable sintering temperatures were applied. In the variation process of phase composition ratio, lower increase of dielectric constant value (<14) and wide changing range of temperature coefficient of resonant frequency (from −76 to +110 ppm/°C) can be obtained synchronously. When the phase composition ratio x value are 0.5, composite ceramics above possesses microwave dielectric properties as ε = 12.011, Q × f = 24900 GHz and τ = +91 ppm/°C as the sintering temperature was 1000 °C. [ABSTRACT FROM AUTHOR]

The synthetic phenolic antioxidant tert-butyl hydroquinone (TBHQ) is frequently associated to adverse health effects. A polymerized film of crystal violet (CV) was prepared on the surface of a glass carbon electrode (GCE) by electropolymerization in alkaline solution, and then the modified electrode was successfully used to determine TBHQ. This electrode was characterized by scanning electron microscopy and electrochemical impedance spectra. The voltammetric behavior of TBHQ over an extended pH range using cyclic voltammetry at poly (crystal violet) modified glassy carbon electrode (PCV/GCE) was also studied. The resulting electrode exhibited excellent electrocatalytic activity towards the oxidation of TBHQ, and this was confirmed by the observed increased redox peak currents and shifted potentials. The electrochemical sensor can be applied to the quantification of TBHQ with a linear range covering 5 × 10-1 × 10 mol · L (with a correlation coefficient of 0.9969) and the limit detection was 3 × 10 mol · L(S/N = 3). The recovery was between 97.1 and 102 % in edible oil samples. The electrochemical sensor method was also compared with a HPLC method, which proves its capability in commercial market surveillance. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a half-cell reaction in water electrolysis for producing hydrogen gas. In industrial water electrolysis, the HER is often conducted in alkaline media to achieve higher stability of the electrode materials. However, the kinetics of the HER in alkaline medium is slow relative to that in acid because of the low concentration of protons in the former. Under the latter conditions, the entire HER process will require additional effort to obtain protons by water dissociation near or on the catalyst surface. Heterostructured catalysts, with fascinating synergistic effects derived from their heterogeneous interfaces, can provide multiple functional sites for the overall reaction process. At present, the activity of the most active known heterostructured catalysts surpasses (platinum-based heterostructures) or approaches (noble-metal-free heterostructures) that of the commercial Pt/C catalyst under alkaline conditions, demonstrating an infusive potential to break through the bottlenecks. This review summarizes the most representative and recent heterostructured HER catalysts for alkaline medium. The basics and principles of the HER under alkaline conditions are first introduced, followed by a discussion of the latest advances in heterostructured catalysts with/without noble-metal-based heterostructures. Special focus is placed on approaches for enhancing the reaction rate by accelerating the Volmer step. This review aims to provide an overview of the current developments in alkaline HER catalysts, as well as the design principles for the future development of heterostructured nano- or micro-sized electrocatalysts. [ABSTRACT FROM AUTHOR]