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In this study, ferrous composites (FexO4) were prepared by microreactor to activate peroxydisulfate (PDS) for the degradation of bisphenol A (BPA) with visible (Vis) light irradiation. X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) were used to characterize the morphology and crystal phase of FeXO4. Photoluminescence (PL) spectroscopy combined with amperometric tests were used to determine the role of PDS on the performance of photocatalytic reaction. The main reactive species and intermediates for BPA removal were determined by electron paramagnetic resonance (EPR) measurement and quenching experiments. The result indicated that singlet state oxygen (1O2) contributed more to the BPA degradation than that of other reactive radicals (·OH, SO4·− and ·O2−); these reactive radicals and 1O2 formed by the reaction between photo-generated electrons (e−) and holes (h+) of FexO4 and PDS. During this process, the consumption of e− and h+ also improved their separation efficiency and thus enhanced the degradation of BPA. In addition, the photocatalytic activity of FexO4 in Vis/FexO4/PDS system was 3.2-fold and 6.6-fold higher than that of single FexO4 and PDS under Vis light, respectively. The Fe2+/Fe3+ cycle could effectively drive the photocatalytic activation of PDS through indirect electron transfer and the formation of reactive radicals. This work illustrated that the degradation of BPA was rapidly in Vis/FexO4/PDS system mainly through 1O2, which further improve our understanding on the efficient removal of organic contaminants in the environment. [ABSTRACT FROM AUTHOR]

The micron-sized plate-like silver powders were prepared through wet-chemical reduction method using silver nitrate as the precursor, stearic acid as the dispersant, and ascorbic acid as the reducing agent. The effects of different types and the content of protective agents and the reaction solution adding methods on the shapes, particle size distribution, and other parameters of plate-like silver powders were investigated in the present work. When the sulfuric acid (2% of the mass of silver nitrate) is used as a protective agent, the plate-like silver powders with D50 = 6.52–11.48 μm were successfully prepared by adding the reducing solution into the silver nitrate solution dropwise. Moreover, the conductive silver paste made from as-prepared silver powders was screen printed on polyethylene terephthalate substrate to test the resistivity. Interestingly, the sintering time and temperature have significant effects on the resistivity, and the conductive paste exhibits a good conductivity of (2.19–2.27) × 10−6 Ω·m after sintering at 150 °C for 30 min. The results indicated that it is feasible to directly prepare plate-like silver powders by the wet-chemical reduction method, and the plate-like silver powders can be applied in the field of conductive silver paste. [ABSTRACT FROM AUTHOR]

Biodegradable potato starch-assisted nanoferrite and ferrite–semiconductor nanocomposites have been synthesized by the co-precipitation method for the degradation of MB dye under visible light irradiation. Ferrite and ferrite–semiconductor composites synthesized using biodegradable potato starch displayed remarkable dye degradation activity which can be further explored for photocatalysis application. XRD confirms the pure phases for Fe3O4 (FFO) and ZnO–Fe3O4 (ZFFO), but a secondary SITO phase for TiO2–Fe3O4 (TFFO) and microwave-annealed TiO2–Fe3O4 (TFFO-MWA) due to dynamics between Fe, Ti, and NaOH. FTIR and Raman spectra confirmed the characteristic peaks of the starch surfactant and ferrite and/or semiconducting phase. TEM micrographs demonstrated mixed morphology: spherical particles of size 5–10 nm and rod shape of size 14–67 nm in length and 4–21 nm in diameter. XPS showed different valence states along with satellite peaks besides confirming the elemental composition. BET studies showed type-IV isotherms with H3 adsorption hysteresis indicative of mesoporous structures with ZFFO having the highest surface area (85.9 m2 g−1), minimum pore size, and maximum pore volume, while TFFO-MWA having the lowest surface area (19.1 m2 g−1), maximum pore size, and minimum pore volume. The direct bandgap of FFO, ZFFO, TFFO, and TFFO-MWA samples is found to be 2.50, 2.47, 3.18, and 3.16 eV, respectively. The photocatalytic degradation of MB dye under visible light irradiation was achieved to be 93% in 285 min by FFO, 96% in 150 min by ZFFO, 99% in 180 min by TFFO, and 99% in 90 min by TFFO-MWA. The R2 values of adsorption kinetics studies validated that the kinetics can be best described by the first-order model for FFO, TFFO, TFFO-MWA, and second-order model for ZFFO considering the maximum R2 values being established. [ABSTRACT FROM AUTHOR]

Submicron zeolite has become the focus of research because of its high thermal stability, high catalytic activity, and uniform size. A rapid method for synthesizing submicron zeolite Y by using microwave heating is introduced in this work. The effect of directing agent, synthesis temperature, crystallization time, and alkali ratio on the synthesis of submicron zeolite Y is systematically investigated. XRD, SEM, and particle size investigations are carried out to characterize the obtained product. The experimental results show that adding directing agent, increasing the alkali ratio, increasing the temperature or prolonging the microwave radiation time are advantageous to the formation and growth of zeolite Y. However, the high alkali ratio leads to the dissolution of the generated crystal, while excessively increasing the temperature or crystallization time easily generates uneven-sized particles or causes crystal transformation. Submicron zeolite Y of particle size 0.5–0.8 μm accounting for 80% is synthesized at 110°C in just 2 h using alkali ratio of 3 under microwave heating. [ABSTRACT FROM AUTHOR]

This review highlights the synthesis, structure modification, morphology, and properties of nano manganese dioxide (MnO2). Though MnO2 has been widely employed for electrode materials due to its superior electrochemica1 performance, abundant storage, low cost, and environmental friendly nature, the usage in bioapplications and dye mineralisation studies have started since few decades only. Currently, nano MnO2 plays an important role in solar cell devices and gas sensing as it can be easily tunable into desired polymerphic structure and morphology. Herein, the use of nano MnO2 as advanced material in energy, gas sensing, biological application and wastewater remediation are described. Based on the recent research, the available preparation procedures, surface modification and applications of nanostructured MnO2 are systematically presented. Also, structure stabilization and performance improvement of nano MnO2 by doping or composite formation with metals, carbon materials, and conductive polymers are summerised. According to the latest research progress, new trends and strategies of nano MnO2 towards specific applications besides energy storage application are focused in this review, as well as a brief overview of the challenges and future perspectives of MnO2, synthetic methodologies, and their state-of-the-art applications in different fields are presented. [ABSTRACT FROM AUTHOR]

ZnO nanostructures have been synthesized by simple co-precipitation method in the presence or absence of surfactant (starch) and subsequent annealing at 500 and 800 °C for 5 h. The XRD results show ZnO and Zn5(OH)8Cl2·H2O phases in the absence, but only ZnO phase in the presence, of starch. The secondary phase diminishes upon annealing and only pure ZnO phase with improved crystallinity is realized at 800 °C. FTIR endorses different phases along with the starch surfactant by the representative modes. Diverse morphologies: hexagonal; tubular; spherical; and cluster morphologies are observed for different synthesis and annealing conditions. The direct band gap is found to be ~ 3.2 eV and experienced a red shift on annealing. The PL spectra consists of characteristic near band edge (NBE) emission in UV region and a broad emission in visible region corresponding to direct excitonic transitions and oxygen defect transitions, respectively. Samples having rod-like morphology as predominant exhibit strong UV and weak defect emissions, while those with spherical morphology as dominant display weak UV and broad defect emissions in PL. The quenching of NBE emission takes place on annealing, which is indicative of increase in non-radiative transitions or deformation of crystallinity or change in morphology. The PL emissions are strongly influenced by surfactant and annealing temperature. Such results offer new prospects for tuning and optimizing the properties of ZnO semiconductor for applications where the optical properties are decisive. [ABSTRACT FROM AUTHOR]

Dielectric properties are some of the main parameters of materials, determining their interaction with electromagnetic energy during microwave heating. The dielectric properties of spent automobile catalyst were measured by using the resonance cavity perturbation technique from room temperature to 800°C at 915 MHz and 2450 MHz. The effects of temperature and frequency on the dielectric constant, dielectric loss factor, loss tangent, and penetration depth were studied. The results indicate that spent automobile catalyst is weakly polar, making it difficult to transform electromagnetic energy into heat. The relaxation time and conductivity obtained by numerical calculations further explain from the microlevel that spent automobile catalyst cannot dissipate electromagnetic energy through dipole loss or conduction loss under microwave irradiation. This work describes an effective way to explore the dielectric heating mechanism and a basis for understanding the interactions between microwaves and spent automobile catalyst. [ABSTRACT FROM AUTHOR]

The effect of microwave roasting on aluminum extraction from mixtures of diasporic bauxite with sodium carbonate and calcium hydroxide has been studied. The phase constitution and leaching performance of the clinkers were studied under different roasting conditions. Dielectric and thermal investigations on raw slurry obtained from the mix revealed prominent microwave absorption characteristics. X-ray diffraction patterns established significant promotion of NaAlO2 phase. In the microwave field, the aluminum (Al)-bearing minerals, viz. AlOOH and Al2O3, reacted with Ca(OH)2 to form calcium aluminate and calcium aluminum silicate phases at rather low temperature in short time. Furthermore, increasing the temperature and time promoted the reactions of AlOOH and Al2O3 with Na2CO3 to form NaAlO2, resulting in high Al leaching rates. Remarkably, the Al extraction of the clinker microwave roasted at 800°C for 45 min was 82.24%, while the leaching rates of Na and Si were 90.2% and 8.4%, respectively. [ABSTRACT FROM AUTHOR]

In this paper, LaCaCoO-coated LiNiMnCoO is successfully prepared by the sol-gel method associated with microwave pyrolysis method. The structure and electrochemical properties of the LaCaCoO-coated LiNiCoMnO are investigated by using X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and charge/discharge tests. XRD analyses show that the LaCaCoO coating does not change the structure of LiNiCoMnO. The electrochemical performance studies demonstrate that 2 wt.% LaCaCoO-coated LiNiCoMnO powders exhibit the best electrochemical properties, with an initial discharge capacity of 156.9 mAh g and capacity retention of 98.9 % after 50 cycles when cycled at a current density of 0.2 C between 2.75 and 4.3 V. LaCaCoO coating can improve the rate performance because of the enhancement of the surface electronic/ionic transportation by the coating layer. EIS results suggest that the coating LaCaCoO plays an important role in suppressing the increase of cell impedance with cycling especially for the increase of charge-transfer resistance. [ABSTRACT FROM AUTHOR]

In this paper, ZrO-coated LiNiMnCoO is successfully prepared by the microwave pyrolysis method. The structure and electrochemical properties of the ZrO-coated LiNiCoMnO are investigated using x-ray diffraction, AC impedance, and charge/discharge tests, indicating that the lattice structure of LiNiCoMnO is unchanged after the coating but the cycling stability is improved. As the coating amount is 2 wt.%, initial capacity of the coated LiNiCoMnO decreases slightly. However, the cycling stability increases remarkably over the cut-off voltages of 2.75~4.3 V and the capacity retention reaches 93.1% after 50 cycles. Electrochemical impedance spectra results show that the increase of charge transfer resistance during cycling is suppressed significantly by coating with ZrO. [ABSTRACT FROM AUTHOR]