Joint unknown input observer for descriptor system based on interval observer.

In this paper, a novel joint unknown input observer (JUIO) is proposed for a class of descriptor systems. The unknown input (UI) to be estimated injects additively into both the state and output equations in a state space model. To the best of our knowledge, only a few contributions in existing work address this problem directly. To begin with, by introducing an auxiliary UI, the original system is transformed into a normal form in which the output is no longer affected by UI. In this way, the negative effect brought by the UI occurring in the output measurement is removed. An interval observer is developed to obtain upper and lower boundary estimates of the output of the reformulated system. After that, an algebraic relationship between the auxiliary UI and the states is established, and a UI reconstruction (UIR) method is developed. Based on the UIR, a JUIO comprising the UIR and a Luenberger-like state observer is developed to achieve asymptotic estimations of the UI and state simultaneously. Verifiable conditions for the existence of the proposed JUIO are given with respect to the original descriptor system. Finally, a simulation example is presented to verify the effectiveness of the proposed method.

Metal-organic frameworks (MOFs) for photoelectrocatalytic (PEC) reducing carbon dioxide (CO2) to hydrocarbon fuels.

MOF-based photoelectrocatalysis (PEC) using CO2 as an electron donor offers a green, clean, and extensible way to make hydrocarbon fuels under more tolerant conditions. Herein, basic principles of PEC reduction of CO2 and the preparation methods and characterization techniques of MOF-based materials are summarized. Furthermore, three applications of MOFs for improving the photoelectrocatalytic performance of CO2 reduction are described: (i) as photoelectrode alone; (ii) as a co-catalyst of semiconductor photoelectrode or as a substrate for loading dyes, quantum dots, and other co-catalysts; (iii) as one of the components of heterojunction structure. Challenges and future wave surrounding the development of robust PEC CO2 systems based on MOF materials are also discussed briefly.

Photo-thermal synergistic excitation: Feasible strategy to detect ethanol for wide bandgap ZIF-8 at low work temperature.

Zeolitic Imidazolate Framework-8 (ZIF-8) material was prepared by chemical precipitation method. The microstructure and physical properties of the as-prepared samples were characterized by XRD, BET, FESEM and UV spectrophotometer. The self-made four-channel measurement device was used to test the gas sensitivity of ZIF-8 material toward ethanol gas under photo-thermal synergistic excitation. The results showed that the sample was typical ZIF-8 (Eg = 4.96 eV) with a regular dodecahedron shape and the specific surface is up to 1793 m2/g. The as-prepared ZIF-8 has a gas response value of 55.04 to 100 ppm ethanol at 75°C and it shows good gas sensing selectivity and repeated stability. The excellent gas sensitivity can be attributed to the increase of free electron concentration in the ZIF-8 conduction band by photo-thermal synergistic excitation, and the large specific surface area of ZIF-8 material provides more active sites for gas-solid surface reaction. The reaction mechanism of ZIF-8 material under multi-field excitation was also discussed.

Research progress on photocatalytic reduction of CO2 based on ferroelectric materials.

Transforming CO2 into renewable fuels or valuable carbon compounds could be a practical means to tackle the issues of global warming and energy crisis. Photocatalytic CO2 reduction is more energy-efficient and environmentally friendly, and offers a broader range of potential applications than other CO2 conversion techniques. Ferroelectric materials, which belong to a class of materials with switchable polarization, are attractive candidates as catalysts due to their distinctive and substantial impact on surface physical and chemical characteristics. This review provides a concise overview of the fundamental principles underlying photocatalysis and the mechanism involved in CO2 reduction. Additionally, the composition and properties of ferroelectric materials are introduced. This review expands on the research progress in using ferroelectric materials for photocatalytic reduction of CO2 from three perspectives: directly as a catalyst, by modification, and construction of heterojunctions. Finally, the future potential of ferroelectric materials for photocatalytic CO2 reduction is presented. This review may be a valuable guide for creating reasonable and more effective photocatalysts based on ferroelectric materials.

Microwave Reactor with Combined Rigid and Flexible Stirring Paddles for Improving Fluid Heating Uniformity in Soft Manganese Ore Leaching Processes.

In order to overcome the apparent limitations of the inhomogeneous nature of large-scale microwave heating of fluids, a microwave reactor with a rigid-flexible combined stirring paddle is used to heat fluids, destabilizing the hot spots present in the microwave heating of fluids process. An integrated multiphysics field simulation model for calculating the microwave heating process with fluid was created for the purpose of clarifying the temperature field dispersion and fluid flow patterns in the reactor. By using the proposed model, the rigid-flexible combined stirring paddle is compared with the conventional single- and double-layer stirring paddle to highlight the benefits of the rigid-flexible combined stirring paddle in improving fluid heating uniformity. It was found experimentally that the leaching rate of soft manganese ore was increased by 7.08 and 5.22% compared to conventional single and double stirred paddles, respectively. In addition, the optimal stirrer parameters were investigated by the response surface method.

Synthesis of CuCo2S4@Expanded Graphite with crystal/amorphous heterointerface and defects for electromagnetic wave absorption.

The remarkable advantages of heterointerface and defect engineering and their unique electromagnetic characteristics inject infinite vitality into the design of advanced carbon-matrix electromagnetic wave absorbers. However, understanding the interface and dipole effects based on microscopic and macroscopic perspectives, rather than semi-empirical rules, can facilitate the design of heterointerfaces and defects to adjust the impedance matching and electromagnetic wave absorption of the material, which is currently lacking. Herein, CuCo2S4@Expanded Graphite heterostructure with multiple heterointerfaces and cation defects are reported, and the morphology, interfaces and defects of component are regulated by varying the concentration of metal ions. The results show that the 3D flower-honeycomb morphology, the crystal-crystal/amorphous heterointerfaces and the abundant cation defects can effectively adjust the conductive and polarization losses, achieve the impedance matching balance of carbon materials, and improve the absorption of electromagnetic wave. For the sample CEG-6, the effective absorption of Ku band with RLmin of -72.28 dB and effective absorption bandwidth of 4.14 GHz is realized at 1.4 mm, while the filler loading is only 7.0 wt. %. This article reports on the establishment of potential relationship between crystal-crystal/amorphous heterointerfaces, cation defects, and the impedance matching of carbon materials.

Enhanced Free-Radical Generation on MoS2 /Pt by Light and Water Vapor Co-Activation for Selective CO Detection with High Sensitivity.

Semiconductor-based gas sensors hold great promise for effective carbon monoxide (CO) detection. However, boosting sensor response and selectivity remains a key priority in moist conditions. In this study, a composite material, Pt quantum dots decorated MoS2 nanosheets (MoS2 /Pt), is developed as a highly sensitive material for CO detection when facilitated with visible light. The MoS2 /Pt sensor shows a significantly improved response (87.4%) with impressive response/recovery kinetics (20 s/17 s), long-term stability (60 days), and good selectivity to CO at high humidity (≈60%). It is confirmed both experimentally and theoretically that the MoS2 /Pt surface lowers the activation energy to convert CO to CO2 via the free radicals induced by the synergy of photochemical effects and water vapor. As a result, the MoS2 /Pt surface promotes both CO response and selectivity, providing fundamental clues to improve room-temperature semiconductor-based sensors for gas detection under extreme conditions.

Surface-Modified In2O3 for High-Throughput Screening of Volatile Gas Sensors in Diesel and Gasoline.

In this paper, with the help of the method of composite materials science, parallel synthesis and high-throughput screening were used to prepare gas sensors with different molar ratios of rare earths and precious metals modified In2O3, which could be used to monitor and warn the early leakage of gasoline and diesel. Through high-throughput screening, it is found that the effect of rare earth metal modification on gas sensitivity improvement is better than other metals, especially 0.5 mol% Gd modified In2O3 (Gd0.5In) gas sensor has a high response to 100 ppm gasoline (Ra/Rg = 6.1) and diesel (Ra/Rg = 5) volatiles at 250 °C. Compared with the existing literature, the sensor has low detection concentration and suitable stability. This is mainly due to the alteration of surface chemisorption oxygen caused by the catalysis and modification of rare earth itself.

Hydrothermal assisted synthesis of hierarchical SnO2 micro flowers with CdO nanoparticles based membrane for energy storage applications.

Hierarchical nanostructures with appropriate morphology and surface functionalities are highly desired to achieve an optimized electrochemical property for active electrode materials. This work renders the facile hydrothermal synthesis of CdO, SnO2, and CdO-SnO2 nanocomposite, and their capacitive performance was tested. The formation of the pure samples and their composite was committed by low-temperature Raman spectroscopy and x-ray diffraction studies which revealed the tetragonal and cubic structures of CdO and SnO2 powder samples with good crystallinity and purity. The morphological postmortem reveals the formation of nanoparticles morphology of CdO with a highly smooth surface appearance. Besides, the SnO2 illustrates the morphology of the micro flowers composed of ultrathin nanosheets. More specifically, the electrochemical properties indicate the pseudocapacitive charge storage mechanism based on cyclic voltammetry and chronopotentiometry analysis. The CdO-SnO2 composite electrode displayed a higher capacitance due to additional pores/space offered for active sites and continuously allowed electrolyte ions to interact with the inner/outer surface of the electrode. These exciting findings led us to design and fabricate battery hybrid supercapacitors (BHSC) from CdO-SnO2, and activated carbon (AC), referred to as CdO-SnO2//AC BHSC, attains a high power delivery (5717 W/kg), and a maximum energy density of 42 Wh/kg at low discharge rate. Noteworthy, a stable cycling performance was obtained with only 91.3% retention after 8000 cycling at a large discharge current of 10 A/g, denoting the magnificent durability of the active electrode material.

Improvements in Temperature Uniformity in Carbon Fiber Composites during Microwave-Curing Processes via a Recently Developed Microwave Equipped with a Three-Dimensional Motion System.

Curing processes for carbon-fiber-reinforced polymer composites via microwave heating are promising alternatives to conventional thermal curing because this technology results in nonhomogeneous temperature distributions, which hinder its further development in industries. This paper proposes a novel method for improving heating homogeneities by employing three-dimensional motion with respect to the prepreg laminate used in the microwave field by using a recently developed microwave system. The maximum temperature deviation on the surface of the laminate can be controlled within 8.7 °C during the entire curing process, and it produces an average heating rate of 1.42 °C/min. The FT-IR analyses indicate that microwave heating would slightly influence hydroxyl and methylene contents in the cured laminate. The DMA measurements demonstrate that the glass transition temperatures can be improved by applying proper microwave-curing processes. Optical microscopy and mechanical tests reveal that curing the prepreg laminate by using a multistep curing process that initially cures the laminate at the resin's lowest viscosity for 10 min followed by curing the laminate at a high temperature for a short period of time would be favorable for yielding a sample with low void contents and the desired mechanical properties. All these analyses are supposed to prove the feasibility of controlling the temperature difference during microwave-curing processes within a reasonable range and provide a cured laminate with improved properties compared with conventional thermally cured products.

In Situ Synthesis of Hierarchical Flower-like Sn/SnO2 Heterogeneous Structure for Ethanol GAS Detection.

In this study, morphogenetic-based Sn/SnO2 graded-structure composites were created by synthesizing two-dimensional SnO sheets using a hydrothermal technique, self-assembling into flower-like structures with an average petal width of roughly 3 um. The morphology and structure of the as-synthesized samples were characterized by utilizing SEM, XRD, XPS, etc. The gas-sensing characteristics of gas sensors based on the flower-like Sn/SnO2 were thoroughly researched. The sensor displayed exceptional selectivity, a rapid response time of 4 s, and an ultrahigh response at 250 °C (Ra/Rg = 17.46). The excellent and enhanced ethanol-gas-sensing properties were mainly owing to the three-dimensional structure and the rise in the Schottky barrier caused by the in situ production of tin particles.

Mechanism of microwave-assisted iron-based catalyst pyrolysis of discarded COVID-19 masks.

Inexpensive iron-based catalysts are the most promising catalysts for microwave pyrolysis of waste plastics, especially a large number of disposable medical masks (DMMs) with biological hazards produced by spread of COVID-19. However, most synthesized iron-based catalysts have very low microwave heating efficiency due to the enrichment state of iron. Here, we prepared FeAlOx catalysts using the microwave heating method and found that the microwave heating efficiency of amorphous iron and hematite is very low, indeed, these materials can hardly initiate pyrolysis at room temperature, which limits the application of iron-based catalysts in microwave pyrolysis. By contrast, a mixture of DMMs and low-valent iron oxides produced by hydrogen reduction at 500 °C can be heated by microwaves to temperatures above 900 °C under the same conditions. When the hydrogen reduction temperature was incerased to 800 °C, the content of metallic iron in the catalyst gradually increased from 0.34 to 21.43%, which enhanced the microwave response ability of the catalyst, and decreased the gas content in the pyrolysis product from 78.91 to 70.93 wt%; corresponding hydrogen yield also decreased from 29.03 to 25.02 mmolH2·g-1DMMs. Moreover, the morphology of the deposited solid carbon gradually changed from multi-walled CNTs to bamboo-like CNTs. This study clarifies the pyrolysis mechanism of microwave-assisted iron catalysts and lays a theoretical foundation for their application in microwave pyrolysis.

Microwave-enhanced reduction of manganese from a low-grade pyrolusite ore using pyrite: process optimization and kinetic studies.

The inefficient leaching of manganese is the main factor hindering the commercialization of the reduction process during manganese recovery using pyrite as the reducing agent. Hence, a new method for improving recovery efficiency and reducing the cost is required. This study uses microwave heating as a strengthening method to extract Mn2+ from pyrolusite and the leaching conditions are optimized. It was found that the extraction rate of Mn2+ could reach 95.07% under microwave heating through the conditions of H2SO4 is 1.2 mol/L, m(pyrolusite)/m(pyrite) equals to 10:2, leaching temperature is 90 ℃, and a liquid-solid (L/S) ratio of 10:1. The achieved extraction rate was higher than that of 75.08% under the conventional heating achieved at the same conditions. Besides, experimental studies have found that microwave heating can change the process and direction of chemical reactions, shorten the reaction time, and reduce sulfuric acid. Finally, the kinetic study indicates that the leaching process under microwave heating is controlled by surface chemical reactions. The equation of leaching kinetics is 1 - (1 - x)1/3 = 3425.32/r0·[H2SO4]1.316·[FeS2/MnO2]0.907·exp(- 45.03/(RT)·t. The activation energy is 45.03 kJ/mol. Meanwhile, through a scanning electron microscope and particle size analyzer, microwave heating has a significant influence on reducing the ore diameter and increasing the specific surface area of the sample. This study aims to provide an experimental trial case for studying the mechanism of microwave-enhanced leaching process during manganese recovery using pyrite as the reducing agent. The reported kinetics research may guide the development of the industrial application for Mn recovery.

Nanostructured nickel doped zinc oxide material suitable for magnetic, supercapacitor applications and theoretical investigation.

This Paper describes the synthesis of nickel doped ZnO is planned by chemical co-precipitation techniques. The prepared nanostructured nickel doped zinc oxide samples were analyzed by thermogravimetric differential thermal analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infra red (FTIR), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance (EPR), and cyclic voltametry (CV). Nanostructure nickel doped ZnO materials have developed as promising for the basis of its broad range of employing in diverse areas. The attractive properties of nickel doped ZnO materials are highly demanded in high-energy potential applications. The nickel doped zinc oxide materials are hexagonal wurtzite arrangement is confirmed by XRD. The morphological -features of FE-SEM show nickel doped zinc oxide NPs are the structure of spherical type with agglomeration. The calculated particle size 11 nm is confirmed by HR-TEM. EPR spectra of nickel doped zinc oxide nanoparticles are ferromagnetic nature. Further, CV studies of Ni doped ZnO materials of the specific capacitance value is 133 Fg-1 at the scan rate 10 mVs-1 it is suitable for super capacitor application. The quantum chemical calculations were done by using DFT techniques through B3LYP/LANL2DZ level of basis set.

Porous carbon materials derived from discarded COVID-19 masks via microwave solvothermal method for lithium­sulfur batteries.

With the spread of COVID-19, disposable medical masks (DMMs) have become a significant source of new hazardous solid waste. Their proper disposal is not only beneficial to the safety of biological systems but also useful to achieve considerable economic value. The first step of this study was to investigate the chemical composition of DMMs. It is primarily composed of polypropylene, polyethylene terephthalate and iron, with fibrous polypropylene accounting for approximately 80% of the total weight. Then, DMMs were sulfonated and oxidised by the microwave-driven concentrated sulfuric acid within 8 min based on the fact that the concentrated sulfuric acid exhibits a good microwave absorption capacity. The co-doping of sulfur and oxygen was achieved while improving the thermal stability of DMMs. Subsequently, the self-activation pyrolysis of sulfonated and oxidised DMMs (P-SO@DMMs) was further realized in low-flow-rate argon. The specific surface area of P-SO@DMMs increased from 2.0 to 830.9 m2·g-1. P-SO@DMMs sulfur cathodes have promising electrochemical properties because of their porous structures and the synergistic effect of sulfur and oxygen co-doping. The capacity of the samples irradiated by microwave for 10 min at 0.1, 0.2, 0.5, 1, 2 and 5 C were 1313.6, 1010.9, 816.5, 634.4, 513.4 and 453.1 mAh·g-1, respectively, and after returning to 0.2 C and continuing the cycle for 50 revolutions, maintained 50.5% of the initial capacity. After 400 cycles, its capacity is 38.1% of the initial capacity at 0.5 C. It is slightly higher than the electrochemical performance of the sample treated by microwave for 8 min and significantly higher than the sample treated by 6 min. This work converts structurally complex, biohazardous DMMs into porous carbon with high specific surface area by clean and efficient microwave solvothermal and self-activating pyrolysis, which facilitates the development of carbon based materials at low cost and large scale.

Multifunctional Benzo[4,5]thieno[3,2-b]benzofuran Derivative with High Mobility and Luminescent Properties.

Development of multifunctional materials and devices has garnered enormous attention in the field of organic optoelectronics; nevertheless, achieving high mobility together with strong luminescence in a single semiconductor remains a major bottleneck. Here, a new multifunctional semiconductor molecule, 2,7-diphenylbenzo[4,5]thieno[3,2-b]benzofuran (BTBF-DPh), that integrates high charge transporting [1]benzothieno[3,2-b][1]benzothiophene with a strongly emissive furan group, is synthesized and applied in three types of optoelectronic devices, including organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic phototransistors (OPTs). OLEDs based on BTBF-DPh as the emissive layer showed a blue emission with CIE coordinates of (0.151, 0.069) and a maximum current efficiency of 2.96 cd A-1 with an external quantum efficiency of 4.23%. Meanwhile, OFETs fabricated with BTBF-DPh thin film manifested a carrier mobility of 0.181 cm2 V-1 s-1, which is comparable to that of thiophene-based counterparts. Additionally, BTBF-DPh-based OPTs exhibited a maximum responsivity and detectivity of 2.07 × 103 A W-1 and of 5.6 × 1015 Jones, respectively. On the one hand, our rationally designed material, BTBF-DPh, has a dense and close-packed structure with an extended π-conjugation, facilitating charge transport through adjacent molecules. On the other hand, the weakened dipole-dipole interactions between BTBF-DPh molecules that resulted from the unambiguous J-aggregation and reduced spin-orbit coupling caused by replacing sulfur atom significantly suppress the exciton quenching, contributing to the improved photoluminescence performance. These results validate that our newly developed BTBF-DPh is a promising multifunctional organic semiconductor for optoelectronic devices.

Study on thermochemical characteristics properties and pyrolysis kinetics of the mixtures of waste corn stalk and pyrolusite.

As an alternative energy source for fossil energy, use of biomass pyrolysis to reduce pyrolusite is of great significance for energy conservation, emission reduction and environmental protection. Kinetics and thermodynamics of reducing pyrolusite using biomass pyrolysis was studied using thermogravimetric analysis analysis. Five non-isothermal methods, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Distributed Activation Energy Model, Starink and Friedman, were employed to calculate the pyrolysis kinetics and thermodynamic parameters. The results showed that pyrolusite reduction by biomass pyrolysis can be divided into four stages: drying stage (30-175 °C), rapid pyrolysis reduction stage (175-350 °C), slow pyrolysis reduction stage (350-680 °C) and char formation stage (680-900 °C). The apparent activation energy, reaction enthalpy, Gibbs free energy and entropy change of pyrolusite reduction by biomass pyrolysis was calculated ranges from 170 to 180 kJ/mol, 164 to 174 kJ/mol, 136.97 to 137.25 kJ/mol and 45.67 to 61.91 J/mol·K, respectively. This work provides theoretical basis and practical guidance for the reduction of pyrolusite by waste corn stalk.

Microwave Pyrolysis of Macadamia Shells for Efficiently Recycling Lithium from Spent Lithium-ion Batteries.

To reduce harm to the environment and human health and improve economic benefits, the large number of spent lithium-ion batteries that have been produced in recent years need to be reasonably recycled. The purpose of this article is to study a new method, microwave pyrolysis of the shells of macadamia nuts, for efficient recycling of lithium from spent lithium-ion batteries. XRD, SEM, and TGA analyses were used to observe the phase change during roasting. With the help of microwave heating and biomass pyrolysis, the decomposition temperature of Li(Ni1/3Co1/3Mn1/3)O2 was reduced to 300 °C. Carbonated water-soluble Li2CO3 was formed under the action of biochar. Accordingly, the effects of pyrolysis temperature (Pte), biomass dose (bio%), reduction roasting temperature (Rte) and reduction roasting time (Rti) on the leaching rate of lithium were studied, and the results indicated that 93.4% lithium could be leached under the following optimum conditions: bio% = 24, Pte = 500 °C, Rte = 750 °C, and Rti = 25 min. A lattice collapse model and coupling reaction theory explained the benefit of biomass pyrolysis on the decomposition of Li(Ni1/3Co1/3Mn1/3)O2. Finally, we designed a complete process for recycling the cathode powder of spent lithium-ion batteries. This study can guide industrial production to recover lithium-ion batteries in the future.

Microwave-absorbing properties of cathode material during reduction roasting for spent lithium-ion battery recycling.

As a hazardous material to the environment and human health, spent lithium-ion batteries need to be recycled in a reasonable way. To explore the effect of microwave heating on spent lithium-ion batteries (LIBs) recycling, the microwave-absorbing properties of a spent cathode powder (LiNixCoyMnzO2) were studied by measuring its dielectric properties from 25-900 °C at 2450 MHz under different conditions (temperature, carbon dose and apparent density). X-ray diffraction and thermogravimetric analysis (TGA) were used to study decomposition and reduction reactions in the heating process. The results indicated that the cathode material has good microwave-absorbing properties over the entire temperature range (25-900 °C), especially when mixed with carbon. As the reduction reactions proceed, the dielectric properties of the material increase rapidly from 600 °C, which means that microwave heating can promote a carbothermal reduction reaction. The effect of the carbon dose on the dielectric properties indicates that the carbothermal reduction reaction can fully occur when the carbon dose reaches 18%. Furthermore, the best microwave-absorbing performance can be achieved when the apparent density of the material is 1.41 g/cm3. These studies have established a basis for research towards the direct recovery of lithium from LIBs by microwave reduction roasting.

Microwave field: High temperature dielectric properties and heating characteristics of waste hydrodesulfurization catalysts.

The exploration of the dielectric properties of waste hydrodesulfurization catalysts has important guiding significance for the development of microwave heat treatment of waste hydrodesulfurization catalysts for the recovery of valuable metals. The resonant cavity perturbation technique was used to measure the dielectric properties of waste catalyst and the mixture of waste catalyst and Na2CO3 during roasting from room temperature to 700 °C at 2450 MHz. The heating properties of the waste catalyst and mixture of waste catalyst and Na2CO3 were determined in the microwave field. The results show that the waste catalyst and the mixture of waste catalyst and Na2CO3 exhibit strong microwave response capability, and the dielectric constant, dielectric loss factor, and dielectric loss tangent increase with increasing temperature; from 20 to 300 °C, the waste catalyst and the mixture of waste catalyst and Na2CO3 heated at a slower rate, while the material heated rapidly from 300 to 700 °C. In addition, the mechanism of microwave action has been proposed based on the study of dielectric properties and heating properties in the microwave field.