A numerical study of accelerated moderate or intense low-oxygen dilution(MILD)combustion stability for methane in a lab-scale furnace by off-stoichiometric combustion technology

Moderate or intense lowoxygen dilution(MILD)combustion has become a promising lowNOX emission technology,while the delayed mixing of reactants and slower oxidation rate could potentially cause ignition instability in some scenarios.This paper proposes a new idea for enhancing the ignition stability for methane MILD combustion by combining with offstoichiometric combustion(OSC),and its performances have been numerically assessed through a comparison against the original MILD combustion burner.The results reveal although nonpremixed pattern has the lowest NO emission,it suffers from a larger liftoff distance,thus less ignition stability.Contrarily,both partiallypremixed and fully premixed patterns exhibit excellent ignition stability.Among the considered OSC conditions,the pattern of Inner ultrarich and Outer lean produces the lowest NO emission while maintains a high ignition stability.Furthermore,the enhancement of the combustion stability by implementing OSC to the original MILD combustion burner is shown by comparing the operational range of furnace wall temperature(Tf),CO and NO emissions,as well as the evolution of chemical flame.The comparison reveals that OSC can extend the lowest operational Tf from 900 K to 800 K.More importantly,OSC can significantly improve the ignition stability in the whole range of Tf as compared to the original MILD combustion burner.

Anomalous microstructure and magnetocaloric properties in off-stoichiometric La–Fe–Si and its hydride

In the present work we reported the phase formation, microstructure, magnetocaloric effect and hydrogenation behavior of La-rich La1.7Fe11.6Si1.4alloy. In this off-stoichiometric La（Fe,Si）13alloy, the Na Zn13-type La（Fe,Si）13matrix phase shows faceted grains, with the Cr5B3-type La5Si3 used as the secondary phase distributed intergranularly. Such a peculiar morphology quickly forms upon one day annealing. In La1.7Fe11.6Si1.4alloy, we have observed a significant field dependence of magnetostructural transition temperature（～ 6.3 K/T）, resulting in a large and table-like entropy change（△S～ 18 J/kg·K in 2 T） over a broad temperature range（～ 10 K）. Upon hydrogenation, the maximum value of △S keeps almost unchanged, while the Curie temperature increases up to 350 K. These results indicate that the investigated offstoichiometric La（Fe,Si）13alloy is a promising magnetic material for magnetic refrigerators.

Unlocking iron-based mixed-phosphate cathode for sodium-ion batteries through off-stoichiometry

The off-stoichiometric iron-based phosphate(Na_(3.12)Fe_(2.44)(P_(2)O_(7))_(2),denoted as Na3.12)as a low cost and high structure stability cathode material has been widely studied for sodium-ion batteries(SIBs).However,the lower theoretical specific capacity(117 mAh·g^(-1))has seriously limited its practical application.In this work,we incorporate varying proportion of sodium-iron phosphate(NaFePO_(4))into the Na3.12 to form a series of new high specific capacity mixed-phosphates Na_(3.12+x)Fe_(2.44+x)(P_(2)O_(7))_(2)(PO_(4))x cathode materials for SIBs.After optimizing the introduction amount of NaFePO_(4)into Na3.12,the practical reversible of Na_(3.12+x)Fe_(2.44+x)(P_(2)O_(7))_(2)(PO_(4))x increased from 92 to 125.2 mAh·g^(-1).The nano-size Na5.12Fe4.44(P2O7)2(PO4)2 cathode material shows a reversible specific capacity of 125.2 mAh·g^(-1)at 0.1 C in SIBs.Even at 60 C,it still exhibits a reversible specific capacity of 93.3 mAh·g^(-1)and keeps a capacity retention ratio of 87%after 3000 cycles at 20 C.Thereby,we present a novel approach to design a series of off-stoichiometric mixed-phosphates cathode materials for SIBs.

Surface-Engineered Li4Ti5O12 Nanostructures for High-Power Li-Ion Batteries

Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries.In this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio.A Li-deficient off-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate performances.However,after the solvothermal process,an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2.The Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates,respectively.Furthermore,the electrode exhibits an ultrahigh-charging-rate capability up to 1200C(60 mAh g−1;discharge limited to 100C).Unlike previously reported high-rate half cells,we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 cathode.The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity,respectively.Room-(25℃),low-(−10℃),and high-(55℃)temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.

Off-stoichiometry improves the photostructuring of thiol-enes through diffusion-induced monomer depletion

Thiol–enes are a group of alternating copolymers with highly ordered networks and are used in a wide range of applications.Here,“click”chemistry photostructuring in off-stoichiometric thiol–enes is shown to induce microscale polymeric compositional gradients due to species diffusion between non-illuminated and illuminated regions,creating two narrow zones with distinct compositions on either side of the photomask feature boundary:a densely cross-linked zone in the illuminated region and a zone with an unpolymerized highly off-stoichiometric monomer composition in the non-illuminated region.Using confocal Raman microscopy,it is here explained how species diffusion causes such intricate compositional gradients in the polymer and how offstoichiometry results in improved image transfer accuracy in thiol–ene photostructuring.Furthermore,increasing the functional group off-stoichiometry and decreasing the photomask feature size is shown to amplify the induced gradients,which potentially leads to a new methodology for microstructuring.