Optimal Design of Angular Displacement Sensor with Shared Magnetic Field Based on the Magnetic Equivalent Loop Method

Angular displacement sensor with shared magnetic field has strong environmental adaptability and high measurement accuracy. However, its 3-D structure is multi-pole double-layer structure, using time stepping finite element method (TSFEM) to optimize the structure is time-consuming and uneconomical. Therefore, a magnetic equivalent loop method (MELM) is proposed to simplify the optimal design of sensors. By reasonably setting the node position, the mechanical structure parameters, winding coefficients and input voltage of the sensor are integrated into a mathematical model to calculate of the induced voltage. The calculation results are compared with the simulation results, and a sensor prototype is made to test the optimized effect of the MELM

Positive Effect of Heat Treatment on Carbon-Supported CoS Nanocatalysts for Oxygen Reduction Reaction

It is of increasing interest and an important challenge to develop highly efficient less-expensive cathode catalysts for anion-exchange membrane fuel cells (AEMFCs). In this work, we have directly prepared a carbon-supported CoS nanocatalyst in a solvothermal route and investigated the effect of heat-treatment on electrocatalytic activity and long-term stability using rotating ring-disk electrode (RRDE). The results show that the heat-treatment below 400 °C under nitrogen atmosphere significantly enhanced the electrocatalytic performance of CoS catalyst as a function of annealed temperature in terms of the cathodic current density, the half-wave potential, the HO2− product and the number of electrons transferred. The CoS catalyst that annealed at 400 °C (CoS-400) has exhibited a promising performance with the half-wave potential of 0.71 V vs. RHE (the highest one for non-precious metal chalcogenides), the minimum HO2− product of 4.3% at 0.60 V vs. RHE and close to the 4-electron pathway during the oxygen reduction reaction in 0.1 M KOH. Also, the CoS-400 catalyst has comparable durability to the Pt/C catalyst

Co-intercalated layered double hydroxides as thermal and photo-oxidation stabilizers for polypropylene

An elegant and efficient approach consisting in the co-intercalation of stabilizing molecular anions is described here. The thermal stabilizer calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] (Irganox 1425, MP-Ca) and a photo-oxidation stabilizer (hindered amine light stabilizer, HALS) are co-intercalated into the interlayer regions of layered double hydroxides (LDH) in a one-step coprecipitation. These hybrid organic–inorganic materials are successively dispersed in polypropylene to form HnMn′-Ca2Al/PP composite films (with H = HALS and M = MP) through a solvent casting method. The corresponding crystalline structure, chemical composition, morphology as well as the resistance against thermal aging and photo-oxidation are carefully investigated by various techniques. The results show that the powdered HnMn′-Ca2Al-LDHs hybrid materials have a much higher thermal stability than MP-Ca and HALS before intercalation. In addition, the HnMn′-Ca2Al/PP composites exhibit a higher overall resistance against thermal degradation and photo-oxidation compared to LDHs intercalated with only HALS or MP. This underlines the benefit of the co-intercalation. The co-intercalated LDH materials pave a new way in designing and fabricating high-performance multifunctional additives for polymers

Low molecular weight hindered amine light stabilizers (HALS) intercalated MgAl-Layered double hydroxides: Preparation and anti-aging performance in polypropylene nanocomposites

International audienceA low molecular weight hindered amine light stabilizer (HALS), contains 2, 2, 6, 6-tetramethyl piperidine functional group has been successfully prepared and intercalated into the interlayer region of Mg-Al layered double hydroxides (LDH) via a co-precipitation method to produce HALS-LDH. Furthermore, a series of HALS-LDH/PP nanocomposites were fabricated by dispersing HALS-LDH in poly(propylene) (PP) in a solvent casting route. Through the accelerated aging test method, the morphological properties, the thermal-oxidative degradation and photo-oxidative degradation behavior of HALS-LDH/PP composites were carefully investigated. The results show that the thermal stability of HALS in HALS-LDH was improved compared to that of HALS free of LDH dispersed into PP, and there is no negative effect on the crystallization behavior of PP after the addition of HALS-LDH. Besides, the HALS-LDH significantly enhances synergistically the thermal- and photo-stability of PP compared when LDH platelets CO3-LDH or HALS are used separately. Under the experimental conditions, a mass loading of HALS-LDH optimized as 4 wt % in respect to PP was found to exhibit an excellent anti-aging performance for potential applications

Micrometer-sized dihydrogenphosphate-intercalated layered double hydroxides: synthesis, selective infrared absorption properties, and applications as agricultural films

International audienceHigh-performance heat-retention agents for multifunctional green agricultural films are today largely suitable to increase the production yield as well as to save energy. Here, an adapted ammonia releasing hydrothermal method was used to produce a series of micrometer-sized carbonate-layered double hydroxide (CO3-LDH) precursors of sizes ranging from 1.32 μm to 8.64 μm by simply adjusting the feeding Mg2+ concentration from 0.80 mol L−1 to 0.20 mol L−1. From these pristine LDH materials, μm-sized dihydrogenphosphate-intercalated LDHs (H2PO4-LDHs) were prepared by an anion-exchange method. The structure, the platelet size, and the associated selective IR absorption properties of the H2PO4-LDH and the derivative H2PO4-LDH/EVA composite as well as the related visible transmittance and the photostability of the H2PO4-LDH/EVA film were investigated. The results show that the selective IR absorption in the wavelength range of 7–14 μm enabling the heat retention of the H2PO4-LDHs and H2PO4-LDH/EVA composites depends on the corresponding number-averaged particle size of H2PO4-LDH in the range of 2.01 μm to 8.80 μm. Compared with EVA, the H2PO4-LDH/EVA composites demonstrate a significant improvement of selective IR absorption, while maintaining acceptable visible transmittance, and similar photostability. An optimized particle size of H2PO4-LDH of ca. 5.85 μm leads to 60% selective IR absorption and 64% selective IR absorption when dispersed in EVA, while the polymer free of filler exhibits less than 50% absorption in the 7–14 μm IR domain

Antioxidant intercalated Zn-containing layered double hydroxide: preparation, performance and migration properties.

International audienceA straightforward preparation of the antioxidant anion 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (DBHP), intercalated into layered double hydroxides (DBHP-LDH) via a co-precipitation method, and adjusting the (Mg, Zn, Al) metal ratio was reported. The influence of the Zn-containing LDH composition was studied by measuring the thermal stability and the DBHP anti-migration ability when dispersed into polypropylene (PP). The overall crystallinity of α-PP is found to remain similar with the dispersion of DBHP-LDH particles, but shaper diffraction peaks indicate the presence of larger crystallized domains, most probably arising from an anisotropic connection of smaller coherent PP domains with the help of PP chains diffusing inside the layered inorganic structure. The latter is acting as a coalescent agent yielding an intercalated PP nanocomposite structure with extended interfaces inducing a shift in the glass transition temperature to a higher temperature. The radical-scavenging activity of DBHP when interleaved between LDH layers is found to be conserved while an optimized cation composition for MgZnAl–DBHP is found for the thermo-oxidative stability in association with a lower DBHP migration among the PP nanocomposite series, making the resulting PP nanocomposite a highly promising candidate for possible applications

Layered double hydroxides as thermal stabilizers for Poly(vinyl chloride): A review

International audiencePoly(vinyl chloride) (PVC), an important thermoplastic polymer widely-used in various fields, requires the use of thermal stabilizers to enhance its thermal stability during polymer processing and practical applications because of the poor thermal stability. Layered double hydroxides (LDHs), two-dimensional anionic layered and versatile filler, are widely considered to be one kind of high-efficient and environment-friendly PVC thermal stabilizers. Interestingly, it is expected to gradually replace the traditional toxic thermal stabilizers such as lead salts. The recent development of LDH thermal stabilizers in PVC resins is here reviewed from four relevant aspects:the thermal stabilization mechanism provided by LDHs,-the chemical composition of metal layers and-of interlayer guests, and-the dispersion state of LDH in PVC composites. The review provides a current picture to help in the choice of manufacturing of high-performance LDH thermal stabilizers

Antioxidant intercalated hydrocalumite as multifunction nanofiller for Poly(propylene): Synthesis, thermal stability, light stability, and anti-migration property.

International audienceOne of the major issues for poly(propylene) PP concerns its protection towards oxidative phenomena resulting in polymer failure. Using known anti-oxidant (AO), Irganox 1425, an original approach is taking advantage of the counterion, cations Ca2+, in building hydrocalumite inorganic sheets, and concomitantly providing the AO anions to be immobilized within an inorganic host structure. Through the classical co-precipitation method, the hybrid assembly composed of AO molecules interleaved between hydrocalumite layered structure is successfully elaborated in one-step process free of contamination. Hydrocalumite (Ca2Al) belongs to the family of layered double hydroxides (LDH). The structure of the AO-LDH hybrid material is determined by means of XRD, FT-IR, while the radical-scavenging activity of AO-LDH is investigated using DPPH• (1,1-Diphenyl-2-picryl-hydrazyl) radical concentration variation. A series of AO-LDH/PP composites is then obtained by dispersing AO-LDH into PP at different loading ratios, and addressing the thermal stability, light stability and anti-migration of the resulting composites. The use of hydrocalumite vessel in confining AO molecules helps to increase the thermal stability and resistance against the photo oxidation while providing a barrier effect against organic species migration. An optimized of 4 wt% AO-LDH into PP results in the best radical-scavenging activity, 1 wt% is preferred to stabilize PP under light, the former formulation is the best compromise of all the series