Tailoring the chemical heterogeneity of Mn-modified 0.75BiFeO3-0.25BaTiO3 ceramics for piezoelectric sensor applications

The Mn-modified 0.75BiFeO₃-0.25BaTiO₃ (75BFBTMn) piezoelectric ceramic possesses a high depolarization temperature of 500 °C and a large piezoelectric coefficient of 110 pC/N, showing the potential for high temperature piezoelectric sensors. However, 75BFBTMn ceramic usually suffers dielectric degradation and abrupt drop of piezoelectric coefficient in the range of 300 °C to 500 °C. Combined the high-energy synchrotron X-ray diffraction analysis with Backscatter-SEM results, it is demonstrated that the electrical thermal instability is owing to the existence of chemical inhomogeneity. The Air-annealing treatment is able to decrease the volume fraction of pseudo-cubic phase and the lattice distortion, removes the chemical inhomogeneity in the grain and free Bi₂O₃ at grain boundary, and then eliminates dielectric anomalies and piezoelectric degradation with temperature. These results indicate that air-annealing is a simple but effective method to eliminate the chemical inhomogeneity in 75BFBTMn ceramics, thereby improving the property thermal stability for high temperature piezoelectric sensor applications.     

Semiconductor Fe-doped SrTiO3-δ perovskite electrolyte for low-temperature solid oxide fuel cell (LT-SOFC) operating below 520 °C

High-temperature operation of solid oxide fuel cells causes several degradation and material issues. Lowering the operating temperature results in reduced fuel cell performance primarily due to the limited ionic conductivity of the electrolyte. Here we introduce the Fe-doped SrTiO_3-δ (SFT) pure perovskite material as an electrolyte, which shows good ionic conduction even at lower temperatures, but has low electronic conduction avoiding short-circuiting. Fuel cell fabricated using this electrolyte exhibits a maximum power density of 540 mW/cm² at 520 °C with Ni-NCAL electrodes. It was found that the Fe-doping into the SrTiO_3-δ facilitates the creation of oxygen vacancies enhancing ionic conductivity and transport of oxygen ions. Such high performance can be attributed to band-bending at the interface of electrolyte/electrode, which suppresses electron flow, but enhances ionic flow.     

Exploring the photocatalytic hydrogen production potential of titania doped with alumina derived from foil waste

The multifunctional potential of a catalyst previously synthesised for thermal processes is explored by investigating its activity for photocatalytic production of H₂ from glycerol, a by-product from the manufacture of bio-diesel. The studied catalyst contains TiO₂ doped with Al₂O₃ that was derived from aluminum foil waste. This catalyst showed higher photocatalytic activity than the analogous catalyst prepared with a commercial Al₂O₃. Pt and Pd act as electron traps while the Al₂O₃ demonstrated a promotional effect, partially through proton donation. Under optimum conditions, a steady-state of 4.2 mmol H₂ gTiO₂⁻¹ hr⁻¹ was produced, which is comparable to the 4.7 mmol H₂ gTiO₂⁻¹ hr⁻¹ obtained with Pt–TiO₂, which is a standard photocatalytic material. It should be noted that the reported Pt/Pd/TiO₂-ANFL catalyst has not yet been optimised and so this result is encouraging. It is hoped that these findings can inspire more sustainable and less expensive hydrogen production, including from biomass feedstocks such as glycerol.     

Analysis of nitrogen oxide emissions from modern vehicles using hydrogen or other natural and synthetic fuels in combustion chamber

The paper presents a calculated analysis of the equilibrium emission of nitrogen oxides on the exhaust of carburetor and diesel internal combustion engines. The temperature of fuel oxidation is assumed to be 1,400 °C while the pressure for carburetor and diesel engines is assumed to be 60 atm and 80 atm respectively. The studies have been carried out for natural and synthetic fuels such as hydrogen, ethanol, methanol, petroleum, diesel fuel and methane at the excess air coefficient corresponding to the fuel oxidation temperature of 1,400 °C. In the paper, the method for calculating the equilibrium composition based on the equilibrium constant and mass conservation equations has been applied. It is shown that with an increase in pressure from 1 atm to 60 atm for carburetor engines and up to 80 atm for diesel engines, the reaction of nitrogen dioxide formation may shift towards an increase in NO₂. The formation of NO may be not affected by the increase in pressure by virtue of the fact that the reaction proceeds without changes in the amount. It has been determined that NO is the major atmospheric pollutant. However, it would be advisable to use more extensively the fuels characterized by the lowest output of nitrogen dioxide (methane and methanol), since nitrogen dioxide (NO₂) related to the 2nd hazard class is appeared to be the most dangerous to humans. It has been revealed that the reduction in oxidation temperature using hydrogen as a fuel for electrochemical current generators may allow reducing nitrogen oxide emissions by more than an order of magnitude as compared to the best results for ICE.     

Catalytic gasification of food waste in supercritical water over La promoted Ni/Al2O3 catalysts for enhancing H2 production

Ni/Al₂O₃ catalyst is the one of promising catalysts for enhancing H₂ production from supercritical water gasification (SCWG) of biomass. However, due to carbon deposition, the deactivation of Ni/Al₂O₃ catalyst is still a serious issue. In this work, the effects of lanthanum (La) as promoter on the properties and catalytic performance of Ni/Al₂O₃ in SCWG of food waste were investigated. La promoted Ni/Al₂O₃ catalysts with different La loading content (3–15 wt%) were prepared via impregnation method. The catalysts were characterized using XRD, SEM, BET techniques. The SCWG experiments were carried out in a Hastelloy batch reactor in the operating temperature range of 420–480 °C, and evaluated based on H₂ production. The stability of the catalysts was assessed by the amount of carbon deposition on catalyst surface and their catalytic activity after reuse cycles. The results showed that 9 wt% La promoter is the optimal loading as Ni/9La–Al₂O₃ catalyst performed best performance with the highest H₂ yield of 8.03 mol/kg, and H₂ mole fraction of 42.46% at 480 °C. La promoted Ni/Al₂O₃ catalysts have better anti-carbon deposition properties than bare Ni/Al₂O₃ catalyst, resulting in better gasification efficiency after reuse cycles. Ni/9La–Al₂O₃ catalyst showed high catalytic activity in SCWG of food waste and had good stability as it was still active for enhancing H₂ production when used in SCWG for the third time, which indicated that La promoted Ni/Al₂O₃ catalysts are potential additive to improve the SCWG of food waste.     

Assessment of supercritical water gasification of food waste under the background of waste sorting: Influences of plastic waste contents

Waste sorting is being gradually implemented as a key measure for circular and sustainable development in China, food waste will be separately collected and separated from municipal solid waste (MSW), thus the plastic content in food waste also will be reduced. In this study, supercritical water gasification (SCWG) of food waste with different contents of plastic (0–3.5 wt%) was experimentally investigated to simulate the influence of waste sorting on the food waste treatment. The results showed that lower plastic content in food waste favored higher gas yield and gasification efficiencies. The highest H₂ yield and total gas yield were 3.11 mol/kg and 8.41 mol/kg in the plastic-free case, respectively. When the plastic content decreased from 3.5 wt% to 0 wt%, the cold gas efficiency (CGE), carbon conversion efficiency (CE) and hydrogen gasification efficiency (HE) increased by 125.97%, 173.48% and 94.09%, respectively. However, lower plastic content negatively affected the quality of produced syngas through decreasing H₂ mole fraction and LHV. The solid residues from SCWG of food waste with lower plastic content had higher ratio of fixed carbon to volatile matter (FC/VM). Based on the analysis of pyrolysis properties and combustion behavior, decreasing the plastic content in food waste helped to improve the thermal stability of solid residues. Moreover, lower plastic content resulted in a decrease of total organic carbon (TOC) concentration in liquid effluent, which is favorable for further treatment of liquid effluent.     

Dual application of Ti-catalyzed Li-RHC composite for H2 purification and CO methanation

2LiH + MgB₂ composite doped with TiO₂ (Li-RHC-Ti) is employed with a two-fold purpose: hydrogen purification under a H₂–CO (0.1 mol%) mixture and CO methanation. Upon dynamic cycling under CO–H₂ mixture, hydrogen release curves display a quite stable amount of pure hydrogen of about 10 wt%, short release times of around 60 min, and minor degradation. Gas analysis by Fourier transform infrared spectroscopy (FTIR) after a thermal dehydrogenation process of MgH₂ and LiBH₄ under CO evidence the conversion of CO to CH₄. Li-RHC-Ti dehydrogenated under CO shows the simultaneous formation of CH₄, CH₃OH, and B(CH₃)₃ in the gas phase. X-ray powder diffraction (XRPD) and FTIR characterizations of the solid phases of Li-RHC-Ti after both H₂–CO mixture and CO interactions demonstrate the formation of MgO, LiBO_2, and HCOO⁻ species. Li-RHC-Ti acts as a hydrogen source and promoter for the CO conversion. Reaction pathways are proposed based on experimental results and equilibrium composition calculations.     

Lactococcus lactis phages from the perspective of their diversity,thermal and biocidal resistance

Lactic acid bacteria (LAB), particularly Lactococcus lactis, are of great significance in dairy fermentations. Many LAB strains are susceptible to attack by phages that affect their technological, biochemical and physiological functions. Phages of L. lactis are a serious concern because of the economic importance of this bacterium in the dairy industry. Members of L. lactis phages belonging to the P335, 936 and c2 groups are more problematic for the dairy industry. Many phages of the 936 group are resistant to various thermal and biocidal treatments commonly used in the dairy industry. This article reviews the diversity of L. lactis bacteriophages of the P335, 936 and c2 groups and discusses their interaction with their bacterial hosts. In addition, this review provides an overview of the resistance of L. lactis phages to thermal treatments and chemical biocides, and highlights some novel strategies to destroy these phages.     

Experimental and numerical studies on corrosion failure of a three-limb pipe in natural gas field

A bursting incident occurred in a three-limb pipe, having 16Mn steel for the main pipe and 316L + L416 composite metal for the branch pipe, in a natural gas field. The failure analysis was performed by means of inspection, experiments and computational fluid dynamics (CFD) simulation. The CFD results indicated the radical change in the flow characteristics inside the three-limb pipe due to its upright structure and the formation of a low vortex in the downstream near the junction, which indicated the condensation of water vapor containing high salinity. The condensed brine saturated with CO₂ adhered to the inner wall surface of the main pipe. In such a corrosive medium, 16Mn steel acts as an anode and is preferentially corroded due to galvanic corrosion. In addition, the downstream area, covered by low vortex, exhibited high shear stress and droplet impingement stress, resulting in an increase in flow erosion. Thus, the failure of the three-limb pipe can be attributed to the synergistic effect of galvanic corrosion and flow erosion.     

Unique cyclic performance of post-treated carbide-derived carbon as an anode electrode

Carbide-derived carbon (CDC) is an attractive anode material for Li-ion battery applications because diverse pore textures and structures from amorphous to highly ordered graphite can be controlled by changing the synthesis conditions and precursor, respectively. To elucidate the unique cycling behavior of the post air-treated CDC anode, electrochemical performance was studied under variation of C-rates with structural changes before and after cycling. By tailoring the pore texture of CDCs as removal of amorphous phase by post air-activation, the anode electrode showed a high increase of capacity under prolonged cycling and under high C-rate conditions such as 0.3–1.0 C-rates. The discharge capacities of the treated CDC increased from 400 mAh g⁻¹ to 913 mAh g⁻¹ with increasing cycle number and were close to high initial irreversible value, 1250 mAh g⁻¹, at the 220th cycle under a 0.1C-rate condition, which are unique and unusual cyclic properties in carbon anode applications. Under high C-rate conditions, the discharge capacities started to increase from around 160 mAh g⁻¹ and values of 415 mAh g⁻¹, 372 mAh g⁻¹, and 336 mAh g⁻¹, were observed at 0.3, 0.5, and 1.0 C-rates, respectively, at 600 cycles, demonstrating stable capacity performance.