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A fundamental theory on pyrometallurgic direct smelting of waste printed circuit boards was investigated in this work. First, the effects of the Fe/SiO2 (mass ratio) and CaO/SiO2 (mass ratio) on the liquidus temperature and viscosity of slag were systematically analyzed at a PO2 value of 10–12 atm. Then, a verification experiment was carried out. Thermodynamic calculation results showed that the liquidus temperature of slag first decreased then increased as Fe/SiO2 and CaO/SiO2 were increased. At 1250°C, the viscosity of slag is lower than 0.5 Pa s in the Fe/SiO2 range of (0.8–1.2):1 and CaO/SiO2 range of (0.25–0.85):1. The verification experiment indicated that an alloy with high content copper can be obtained. Microanalysis of the alloy and slag demonstrated that the distinguishable crystal phase in the alloy mainly contained metallic copper, metallic iron, and a small amount of intermetallic compounds such as (Fe, Ni) and Ni3Sn2. The slag was mainly composed of fayalite (Fe2SiO4), calcium silicate (Ca2SiO4, CaSiO3), and gehlenite (Ca2Al2SiO7).

Low-cost catalysts with high activity are in immediate demand for energy storage and conversion devices. In this study, polyvinyl pyrrolidone was used as a complexing agent to synthesize La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) perovskite oxide. The obtained porous layered LSCF has a large specific surface area of 23.74 m2/g, four times higher than that prepared by the traditional sol-gel method (5.08 m2/g). The oxygen reduction reaction activity of the oxide in 0.1 mol/L KOH solution was studied using a rotating ring-disk electrode. In the tests, the initial potential of 0.88 V (vs. reversible hydrogen electrode) and the limiting diffusion current density of 5.02 mA/cm2 were obtained at 1600 r/min. Therefore, higher catalytic activity and stability were demonstrated, compared with the preparation of LSCF perovskite oxide by the traditional method.

A sulfuric acid system was used to recover Co from cobalt white alloy, and the leached cobalt was electrochemically dissolved.i This is a key step to separate the iron-silicon alloy phase from valuable metals when leaching cobalt white alloys with high silicon and iron contents. As an additive, sodium hypochlorite (NaClO) acts as an oxidant to break cobalt encapsulation and enhances leaching. It generates chloride ions, which further enhance Co leaching based on their corrosive ability. The results showed that the maximum leaching ratio of Co from the waste cobalt white alloy was 97.76%. Kinetic analysis showed that the apparent activation energy of Co leaching was 34.58 kJ/mol, and the surface chemical reaction was a controlling step for this process. The kinetic equation for the leaching of Co can be expressed as $$1 - \left( {1 - \alpha } \right)^{\frac{1}{3}} = 0.065t \times \left( {r_{0}^{ - 1} } \right) \times \left[ {{\text{H}}_{2} {\text{SO}}_{4} } \right]^{2.44} \times \exp \left( {\frac{ - 34580}{{8.314T}}} \right)$$ .

A large amount of acid-leaching residue is produced during the conventional Zn hydrometallurgy process, and this residue has a large concentration of a variety of valuable metals. The purpose of this study was to evaluate the ability of a procedure that entails the use of sulfation roasting, water leaching, and chlorination leaching (blowing oxygen technique) to recover Pb and Ag, followed by cooling crystallization and the replacement of Ag with lead sheet, to realize the full recovery of all valuable metals from zinc acid-leaching residue; consequently, good results were achieved. The best results were obtained under the following conditions: a sulfuric acid at 70% of the raw material quality, roasting temperature of 300 °C and roasting time of 2 h, followed by the process of leaching the roasted residue for 1 h by applying a water-to-solid ratio of 5:1 at room temperature. The recovery rates of Zn and Fe were 98.69% and 92.36%, respectively. The main parameters of the chlorine salt leaching system were as follows: Cl− concentration of 300 g/L, Fe3+ concentration of 25 g/L, acid concentration of 2 mol/L, liquid-to-solid ratio of 9 mL:1 g, temperature of 90 °C, and leaching time of 0.5 h; this leaching process was followed by filtration separation. These conditions resulted in high extents of leaching for Pb and Ag (i.e., 98.87% and 96.74%, respectively). Finally, the kinetics of the process of Ag leaching using Cl− ions in an oxygen-rich medium was investigated. It was found that the leaching process was controlled by the diffusion of the product layers, and the activation energy was 19.82 kJ/mol.

Direct carbon solid oxide fuel cells (DC-SOFCs) are promising for generating electricity cleanly and efficiently from solid carbon fuel. Biochar from Camellia oleifera shells is used in a tubular electrolyte-supported 2-cell DC-SOFC stack with a yttrium-stabilized zirconia (YSZ) electrolyte and silver–gadolinium-doped ceria (Ag-GDC) as symmetrical electrodes. The DC-SOFC exhibits comparable electrical performance to the same cell operated on hydrogen fuel and can cogenerate CO and electricity when fueled by biochar. The gas–electricity cogeneration performance of the DC-SOFC is tested under constant-current discharge in terms of electrical power output, CO output rate and purity, electrical conversion efficiency, and gas–electrical cogeneration conversion efficiency. The purity of the output CO can reach more than 80%. Considering the chemical energy of CO a part of the output power, the energy conversion efficiency of >70% is attained. Furthermore, the gas–electricity cogeneration performance is relatively stable before the biochar fuel is exhausted.

Rubidium in muscovite was selectively extracted using a chlorination roasting-water immersion method. The experimental results revealed that the chlorination effects of this metal were best when the roasting temperature was 800 °C. After 30 min of water immersion, the extraction rate of rubidium was the highest (96.71%), and XRD and SEM-EDS were used to analyze the migration transformation of elements and the phase changes that occurred during the chlorination roasting process. Finally, the non-isothermal kinetics of the muscovite chlorination roasting process was investigated via TG-DTA. The results revealed that the most probable mechanism for this process in non-isothermal conditions was the 3-D diffusion (Z-L-T) model with the integral form with g(a) = [(1-α)-1/3–1]2. The activation energy was determined to be 216.92 kJ·mol−1. Furthermore, the kinetic equation for fitting the results was formulated.

The development of low-cost, simple, and efficient methods to prepare high-performance anode materials is a huge challenge. In this work, Co3O4 with high crystallinity was prepared by a solution combustion method. When used as an anode electrode, it displayed excellent electrochemical performance. The reversible capacity remained at 1115.7 mAh g−1 after 100 cycles at 200 mA g−1. Moreover, the capacity retention rate reached 96.3% after 300 cycles at 1000 mA g−1. This excellent electrochemical performance can be attributed to the special macroporous structure of Co3O4, which can increase the contact area between the electrolyte and active material, improve the transport capacity of lithium ions, and effectively alleviate the volume change stress caused by charging and discharging. These results show that the solution combustion synthesis is simple and efficient, providing a low-cost production method for production of high-performance energy storage materials.

Synthetic rutile was prepared from titanium slag melt with low energy consumption and a small amount of additive (B2O3) in our previous work. The modification mechanism of titanium slag was not clear enough. The migration and enrichment behaviors of Ca and Mg elements during cooling and crystallization of boron-bearing titanium slag melt were characterized by XRF, FESEM, EMPA, and XPS. Results show that when additive (B2O3) is added, Ti elements are migrated and enriched in the area to generate rutile, while Ca, Mg, and B elements are migrated and enriched in another area to generate borate. With the additive (B2O3) amount increased, Ca and Mg element migration is complete and more thorough. Additive (B2O3) promotes rutile formation and inhibits the formation of anosovite during cooling and crystallization of titanium slag melt. With the additive (B2O3) amount increasing from 0% to 6%, the proportion of Ti3+ in the modified titanium slag reduces from 9.15% to 0%, and the proportion of Ti4+ increases from 90.85% to 100% under the same cooling and crystallization condition. The result will lay the foundation for the efficient preparation of synthetic rutile by adding B2O3 to the titanium slag melt.

This paper proposes an innovative carbothermal reduction roasting low-carbon redox refining process for recovering valuable metals, including copper, zinc, nickel, tin and lead, from electroplating sludge. First, the valuable metals are volatilized into the flue gas by carbothermal reduction roasting. At a reduction temperature of 1473 K, a carbon content of 20%, and a reaction time of 60 min, the ratio of Pb, Sn and Zn removal reached 90.77%, 95.14% and 99.92%, respectively. At an oxidation temperature of 1573 K, a SiO2 content of 6% and a reaction time of 180 min, a water-quenching slag suitable for building materials was obtained by low-carbon oxidation reduction refining. Finally, at a reduction temperature of 1473 K, 8% C addition, and a reaction time of 20 min, copper and nickel were enriched on an anode copper plate and the copper content reached more than 98%, meeting the requirements for copper electrolysis.

In this work, we demonstrate the morphology-controllable syntheses of CuS crystals by a facile hydrothermal/solvothermal method through merely changing the reaction solvents without employing any surfactants, templates or structure-directing agents. The dependence of electrochemical sensing properties for tartrazine (TT) and sunset yellow (SY) on the morphologies of CuS crystals (microspheres, hexagonal microsheets, sandwich-like plates, interlaced nanosheets and nanoflowers) was studied by voltammetric techniques. Among these CuS structures, the CuS nanoflowers constructed by textile-like nanosheets with a three-dimensional (3D) hierarchical porous structure hold the largest Brunauer–Emmett–Teller specific surface area (37.12 m2 g−1) and display the highest electrocatalytic activities to the TT and SY oxidations. Consequently, the CuS nanoflowers modified electrode exhibits outstanding electrochemical sensing performances, i.e. high sensitivities of 1.7331 and 0.2260 A M−1 for TT, and 0.4228 and 0.01564 A M−1 for SY, low detection limits of 0.012 μM for TT and 0.006 μM for SY, and satisfactory recoveries of 97.0–104.5% for TT and 99.0–105.0% for SY. Simultaneously, it also features excellent anti-interference, stability and reproducibility. The superior sensing performance of CuS nanoflowers may benefit from its unique 3D hierarchical porous architecture, which can facilitate the electrolyte infiltration and promote the active material utilization efficiency. Based on these findings, we can draw a reasonable conclusion that CuS with a flower-like structure is promising electrocatalysts for efficiently sensing TT and SY.

To find high-performance ternary borides as the hard phase of the cermets, first-principles calculation was applied to systematically investigate the structure, mechanical, electronic and thermal properties of 26 ternary borides MⅠxMⅡBx (x = 1 or 2). The phase stability and mechanical properties were evaluated by formation enthalpy and elastic constants. Debye temperatures were calculated to study the thermal conductivity, and the hardnesses of the candidates were predicted via the overlap populations calculation and hardness model. The results show that all the candidates possess thermodynamic and mechanical stability. Most of the MⅠxMⅡBx (x = 1 or 2) exhibit a better ductility than WC, except Ta2FeB2, Mo2MnB2, Nb2CrB2, Nb2FeB2 and Ti2ReB2. Moreover, sorted from high to low, Nb2CrB2, Mo2CoB2, W2MnB2, Mo2FeB2, Ti2ReB2, NbFeB, MoCoB, Mo2NiB2, Nb2FeB2, and Mo2NbB2 have a larger Debye temperature than WC. All the candidate ternary borides exhibit a lower hardness than WC, with the maximum hardness of 26.3 GPa for MoCoB. The analysis of electronic properties indicates that all the MⅠxMⅡBx (x = 1 or 2) exhibit metallic, ionic and covalent hybrid properties. The calculated results are expected to provide guideline for developing ternary boride-based cermets or coating materials that may replace WC-Co cermet.

The lack of homogeneous and matrix-matched scheelite reference materials makes it difficult for quantitative determination of rare earth element (REE) concentrations in scheelite via LA-ICP-MS. In this work, three REE-doped tungstate single crystals (i.e., Dy:NaGd(WO4)2, Yb:NaGd(WO4)2, and Nd:NaGd(WO4)2) were selected as calibration standards. REEs in these crystals were found to distribute homogeneously with desirable homogeneity (signal intensity RSD

The substantial antimicrobial efficacy of nanoparticles against phytopathogens has been extensively investigated for advanced agricultural applications. However, few reports have focused on soilborne pathogenic bacteria. The aim of this study was to obtain sustainably synthesized copper oxide nanoparticles (CuONPs) using papaya leaf extracts and investigate the bactericidal activity of these CuONPs against Ralstonia solanacearum, the cause of bacterial wilt, under laboratory and greenhouse conditions. The results showed that CuONPs possessed strong antibacterial activity and that all R. solanacearum were killed after exposure to 250 μg mL−1 CuONPs. CuONPs could interact with bacterial cells to prevent biofilm formation, reduce swarming motility and disturb ATP production. Ultrastructural observations by transmission electron microscopy (TEM) revealed that after interactions with CuONPs, bacterial cells suffered significantly from nanomechanical damage to the cytomembrane, accompanied by the absorption of multiple nanoparticles. In addition, molecular studies identified the downregulation mechanism of a series of genes involving pathogenesis and motility. The control efficiency of CuONPs in tobacco bacterial wilt disease management under greenhouse conditions was verified by root irrigation application, demonstrating that as-prepared CuONPs significantly reduced the disease occurrence and disease index. Our studies focused on developing biosynthesized nanoparticles as a biocompatible alternative for soilborne disease management.

Designing particles with a unique structure to accommodate volume variations on cycling is an effective strategy to improve the electrochemical performance of metal oxide anode materials for lithium-ion batteries (LIBs). Here, dandelion-like Co3O4 was prepared by a hydrothermal method following heat treatment. In a similar preparation method, by adding a structural modifier, i.e., sodium citrate, the dandelion-like Co3O4 could be transformed into multi-shelled hollow Co3O4 microspheres. These two different Co3O4 morphologies show different electrochemical behaviors as anode materials for LIBs. The multi-shelled hollow Co3O4 exhibited the better electrochemical performance. At a current density of 200 mA g−1, the reversible capacity after 200 cycles reached 1132 mAh g−1. Even at a very high current density, i.e., 1000 mA g−1, the reversible capacity was as high as 936 mAh g−1 after 300 cycles. Such an excellent electrochemical performance is mainly attributed to the multi-shelled hollow structure that can alleviate the volume variation during lithiation/delithiation; this further helps enhance the structural and cycling stability. It also proves that the electrochemical performance of the material can be enhanced by morphological modification.

To overcome the problem of arsenic separation and enrichment from an alkaline leaching solution in arsenic-containing dust, a CO32--type tri-n-octylmethyl-ammonium chloride (TOMAC) method for extracting thioarsenite is proposed in this paper. Considering an alkaline leaching solution as the research object, after vulcanization pretreatment, TOMAC transformation and organic phase saturated extraction capacity were measured, and the extraction mechanism was preliminarily studied. First, Cl−-type quaternary ammonium salt was effectively transformed to HCO3--type by treating organic phase with saturated NaHCO3five times. TOMAC was effectively transformed from HCO3- to CO32- type by alkaline washing with 1.0 mol/l NaOH solution; this washing was repeated thrice. Thereafter, the effects of organic phase composition, phase ratio, extraction time, and temperature on the extraction and separation of arsenic were investigated. The results show that under the conditions of 30% CO32--type TOMAC + 15% sec-octanol + 55% sulfonated kerosene, VO/VA = 1/1, and 5 min extraction at room temperature, the single-stage extraction rate of AsIII is 85.2%. The AsIII concentration in raffinate can be reduced to less than 1.33 × 10−3 mol/l by four-stage countercurrent extraction, and the extraction rate of AsIII can exceed 98.4%.

Rare earth element recovery in molten salt electrolysis is approximately between 91 and 93%, whereof 8% is lost in waste molten salt slag. Presently, minimal research has been conducted on the technology for recycling waste rare earth molten salt slag, which is either discarded as industrial garbage or mixed with waste slag into qualified molten salt. The development of a new approach toward the effective treatment of rare earth fluoride molten salt electrolytic slag, which can recycle the remaining rare earth and improve the utilization rate, is essential. Herein, weak magnetic iron separation, sulfuric acid leaching transformation, water leaching, hydrogen fluoride water absorption, and cycle precipitation of rare earth are used to recover rare earth from their fluoride molten salt electrolytic slag, wherein the thermodynamic and kinetic processes of sulfuric acid leaching transformation are emphatically studied. Thermodynamic results show that temperature has a great influence on sulfuric acid leaching. With rising temperature, the equilibrium constant of the reaction gradually increases, and the stable interval of NdF3 decreases, while that of Nd3+ increases, indicating that high temperature is conducive to the sulfuric acid leaching process, whereof the kinetic results reveal that the activation energy E of Nd transformation is 41.57 kJ/mol, which indicates that the sulfuric acid leaching process is controlled by interfacial chemical reaction. According to the Nd transformation rate equation in the sulfuric acid leaching process of rare earth fluoride molten salt electrolytic slag under different particle size conditions, it is determinable that with the decrease of particle size, the reaction rate increases accordingly, while strengthening the leaching kinetic process. According to the equation of Nd transformation rate in the sulfuric acid leaching process under different sulfuric acid concentration conditions, the reaction series of sulfuric acid concentration K = 6.4, which is greater than 1, indicating that increasing sulfuric acid concentration can change the kinetic-control region and strengthen the kinetic process.

In this work, Pd-decorated N-doped reduced graphene oxide (Pd/N-RGO) was successfully synthesized by a simple wet-chemical method without using any capping agent and stabilizer. The synthesized Pd/N-RGO composite has been carefully characterized by various techniques. The X-ray photoelectron spectra provide the evidence of successful incorporation of N into the N-RGO sheets, while the presence of Pd nanoparticles with the sizes of 5–20 nm on the N-RGO sheets was confirmed by the transmission electron microscopy. By integrating the advantages of the large surface area of N-RGO sheets and good electron transfer efficiency of Pd nanoparticles, the Pd/N-RGO-based sensor shows an improved electrocatalytic activity toward the estradiol oxidation. Therefore, the Pd/N-RGO composite can be used as an effective sensing platform for the non-enzymatic detection of estradiol. It also demonstrates that the fabricated sensor has two linear concentration ranges (0.1–2 and 2–400 μM) and a low detection limit (1.8 nM) for the estradiol detection. Finally, the resulting sensor was successfully used to detect estradiol in some real samples and the satisfactory recoveries of 96.0–103.9% were obtained. The prepared Pd/N-RGO composite with more distinct merits including simple manufacture, preferable reproducibility and long-term stability can be a promising candidate for the advanced electrode material in sensing applications.

A reaction-based near-infrared (NIR) fluorescent probe, (E)-4-(2-(4-(dicyanometh- ylene)-4H-chromen-2-yl)vinyl)phenyl picolinate (DCM-P), was designed and synthesized by employing the dicyanomethylene-4H-pyran chromophore as the fluorophore and the 2-picolinic ester group as the recognition unit. The proposed probe DCM-P showed significant NIR fluorescence “turn-on” response to Cu2+ with distinct colorimetric change from yellow to purple. The recognition mechanism of probe for Cu2+ was confirmed by fluorescence spectroscopy, 1H NMR spectra, HRMS spectrometry and TD-DFT calculations. The probe possesses the advantages of large Stokes shift (116 nm), applicability in physiological conditions, low detection limit (2.3 × 10−8 M), and high selectivity toward Cu2+ in presence of other metal ions. Encouraged by these desirable properties, the probe DCM-P was successfully used for quantitative determination of Cu2+ in real water samples and NIR fluorescence imaging of Cu2+ in living cells with satisfactory results.

This study investigated the effects of various types of paddles on the oxygen gas holdup in different regions at a temperature of 403 K, oxygen partial pressure of 0.6 MPa, and agitation rate of 500 r/min. The results illustrate that the application of a self-priming agitator can significantly promote a bubble holdup in a solution. Furthermore, experiments determining the effects of the agitation rate, temperature, and oxygen partial pressure on the gas holdup were carried out, where the gas holdup increased from 0.03% to 1.59% with an agitation rate of 200 to 700 r/min, from 0.83% to 1.06% with a temperature of 363 to 423 K, and from 0.50% to 1.27% with an oxygen pressure of 0.1 to 0.8 MPa. The kinetics of oxygen pressure acid leaching of marmatite using various types of paddles were also studied. The activation energies of Zn leaching when using various types of paddles were determined to be 53.23, 56.30, 59.76, and 67.58 kJ mol−1, which shows that the processes were controlled through the surface chemical reactions. Based on a comparison of the activation energies, the self-priming type agitator was shown to be optimal. Finally, a similar criteria relationship of a self-priming agitator was established using the principle of homogeneity and Buckingham's theorem. Comprehensively, an empirical equation of a gas holdup was deduced based on experimental data and a similarity theory, where the criterion equation was determined to bee = 7.20 × 10−10n2.63 T-1.52Pg0.45. It can be seen from the formula that the agitation rate has the greatest impact on the gas holdup during the pressure leaching process using a self-priming agitator.

Understanding the tail behavior of the probability distribution of structural strength is of paramount importance for reliability-based design of engineering structures. For brittle and quasibrittle structures, the tail distribution not only determines the design strength at a low failure probability, but also governs the functional form of the strength distribution of large-size structures. There exists clear evidence that the Weibull distribution is applicable to brittle structures. Based on the theory of extreme value statistics, the applicability of Weibull distribution suggests that the tail distribution must follow a power law. The justification of the power-law tail distribution was first proposed by Freudenthal based on an assumed type of flaw statistics and linear elastic fracture mechanics of non-interacting flaws. A series of recent studies suggested that the power-law tail can be explained by the transition rate theory governing the statistics of material failure at the nano-scale. In this study, we investigate the tail distribution by considering the randomness in both material strength and applied stress field. The present analysis adopts a nonlocal strength-based failure criterion, in which the spatial variability of the material strength is represented by an autocorrelated random field. The failure statistics of the structure is calculated as a first passage probability. We analyze this problem in 1D, 2D and 3D settings, and the results indicate that in all cases the tail distribution of the nominal structural strength follows a power law. It is shown that the power-law tail behavior of strength distribution stems from the tail distribution of material strength. The flaw statistics introduces additional randomness to the nominal structural strength, but does not dictate the power-law form of its tail distribution.

A nanohybrid composed of Ag@Cu2O heterogeneous nanocrystals supported on N-doped reduced graphene oxide (Ag@Cu2O/N-RGO) has been synthesized by a simple wet-chemical method. The resultant composite consists of N-RGO sheets fully and homogeneously coated with a dense layer of Ag@Cu2O nanocrystals. Both Ag and N-RGO are in direct contact with Cu2O, and Ag nanoparticles with sizes of 2–5 nm are mainly deposited on the surface of Cu2O cubes (edge length of 500 nm). The electrochemical studies reveal that the ternary Ag@Cu2O/N-RGO composite exhibit significantly enhanced electrocatalytic activity for H2O2 sensing compared with either the single component (N-RGO) or two component systems (Cu2O/N-RGO and Ag/N-RGO), which is mainly due to the synergetic catalysis of the ternary system. The nonenzymatic sensor based on Ag@Cu2O/N-RGO composite shows overwhelmingly superior comprehensive performance for the H2O2 detection over the documented Ag-based sensors. More specifically, it displays a rapid response (10 s) to H2O2 over a wide linear range of 54–700 nM with a high sensitivity of 1298.3 μA mM−1 cm−2 and a low detection limit of 10 nM. Moreover, the sensor also exhibits the preferable selectivity in the presence of biologically coactive compounds accompanied with long-term stability and good reproducibility.

In the present study, a fluorescent ion-imprinted sensor (FIIS) for rapid and convenient detection of Cu2+ ions was fabricated. A fluorescent polymerizable ligand, i.e., 4-(2-aminomethyl)pyridine-N-allylnaphthalimide, was designed and synthesized. The FIIS was prepared by surface functionalization of PVDF membrane with a thin layer of copper (II) ion-imprinted polymer using the synthesized ligand as the fluorescent functional monomer. The intensity of fluorescence emission of FIIS decreased linearly with the increase of copper (II) ions concentration in the range of 0–70.0 μM. The results of selectivity tests indicated that FIIS has high specific recognition ability for Cu2+ ions. The recoveries for the spiked samples were in the range of 96.4–104.4%, and the relative standard deviations (RSDs) were found to be 2.17–4.75%. The FIIS was successfully applied to the determination of copper (II) ions in real water samples. The Limits of detection (LODs) for Cu2+ ions in real water samples were in the range of 0.11–0.14 uM. The present study provided a feasible strategy for construction of fluorescent ion-imprinted sensor for convenient, sensitive and selective detection of metal ions.

In this work, the N doping together with Pd−Cu@Cu2O hybridization for graphene oxide was achieved by a combined process of hydrothermal treatment and chemical reduction, based on which a novel Pd−Cu@Cu2O cubes decorated N-doped reduced graphene oxide (Pd−Cu@Cu2O/N-RGO) hybrid was obtained. The synthesized Pd−Cu@Cu2O/N-RGO was detailedly characterized by various technologies. The results show that the low Pd loading Cu@Cu2O cubes with the sizes of 300–500 nm are well dispersed on N-RGO sheets, thereby avoiding the serious aggregation and maintaining a large electroactive surface area of the attained hybrid. Benefiting from the synergistic effect of the properties of Pd−Cu@Cu2O particles and N-RGO sheets, the Pd−Cu@Cu2O/N-RGO modified electrode exhibits remarkable electrocatalytic performance on the oxidation of tryptophan with the enhanced oxidation response and the lowered oxidation overpotential. Under the optimal conditions for the electrochemical detection of tryptophan, the constructed sensor displays a wide linear range (0.01–40.0 μM) and a low detection limit (1.9 nM), outperforming most of the reported hybrid-based sensors. The proposed sensor also features good selectivity, stability and reproducibility, which has been successfully applied for the detection of tryptophan in the urine and milk samples with satisfactory recoveries. All these results suggest that the Pd−Cu@Cu2O/N-RGO hybrid could be a promising and convenient material for the fabrication of high-performance electrochemical sensors.

In this study, surface morphology, inner structure and phase composition of anodic layers on Pb-Ag anode in fluoride/chloride-containing H 2 SO 4 solutions were investigated in the presence/absence of Mn 2 + . Additionally, corrosion morphology of metallic substrate and anodic potential variation of Pb-Ag anodes were studied as well. The influence of Mn 2 + on the anodic layer property and corrosion behavior of Pb-Ag anodes in fluoride/chloride-containing H 2 SO 4 solutions was then clarified. The results revealed that in the presence of Mn 2 + , anodic layer consisted of an external layer in MnO 2 /PbO 2 -PbSO 4 /MnO 2 structure and an inner layer adhering to the metallic substrate. Due to the coverage of an external layer, the corrosion of metallic substrate was relieved by the presence of Mn 2 + in fluoride/chloride-containing H 2 SO 4 solution. As was demonstrated, Mn 2 + decreased PbO 2 concentration in the inner layer, especially in fluoride-containing solution. In the presence of Mn 2 + , the anodic potential was higher than that in solutions without Mn 2 + due to larger thickness and resistance of anodic layer. In addition, the anodic potential was characterized by oscillation in Mn 2 + -containing solution, indicating low stability of anodic layer. Comparatively, the anodic layer formed in the presence of Mn 2 + and chloride ion was more stable than that in solutions containing Mn 2 + and fluoride ion.

Transition metal phosphide/carbon composites are promising electrocatalysts for oxygen reduction reaction (ORR). Herein, we propose a facile process to fabricate a bayberry-like N, P-enriched carbon nanospheres embedded with Fe2P nanocrystals (Fe2P/NPCs). Bayberry-like polyaniline nanospheres (PANI-NS) are firstly synthesized through microemulsion template method. Then, Fe is incorporated in PANI-NS during the hydrothermal treatment. Lastly FexP nanocrystals and N, P-enriched carbonaceous carriers are obtained by pyrolyzing the hydrothermal-treated PANI-NS. The resultant FexP/NPCs exhibit a uniform particle size (~250 nm), a large specific surface area (523 m2 g−1) and a homogeneous mesoporous structure (~3.46 nm). The phase structure of FexP depends on the Fe/P (molar ratio) during hydrothermal treatment. When Fe/P is around 0.2, a preferable Fe2P phase is obtained. The Fe2P/NPCs exhibit outstanding ORR electrocatalytic activity with a half-wave potential of 0.820 V (vs. RHE) and a diffusion-limited current density of 5.58 mA cm−2, comparable with commercial Pt/C. Moreover, Fe2P/NPCs possess a good duration stability and higher methanol tolerance than commercial Pt/C. When assembled in zinc-air batteries, Fe2P/NPCs contribute to an open circuit voltage of 1.449 V, a maximum power density of 128.38 mW cm−2, and a specific capacity of 691.0 mAh g−1, superior to the commercial Pt/C-based zinc-air battery.

Tailored designs/fabrications of hierarchical porous advanced electrode materials are of great importance for developing high-performance electrochemical sensors. Herein, we demonstrate a simple and low-cost in situ chemical approach for the facile synthesis of MnO 2 -embedded hierarchical porous carbon microspheres (MnO 2 /CM). By the characterizations of scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction and energy dispersive spectroscopy, we evidenced that the synthesized product were flower-like carbon microspheres (CM) assembled by the bent flakes with thickness of about several nanometers and MnO 2 nanorods were highly dispersed and successfully decorated on the CM layers, resulting in a rough surface and three-dimensional microstructure. The greatest benefit from the combined porous CM with MnO 2 nanorods is that the MnO 2 /CM modified electrode has the synergetic catalysis effect on the electro-oxidation of caffeic acid, leading to the remarkable increase in the electron transfer rate and significant decrease in the over-potential for the caffeic acid oxidation in contrast to the bare electrode and CM modified electrode. This implies that the prepared MnO 2 /CM can be employed as an enhanced electrocatalyst for the sensitive detection of caffeic acid. Under the optimum conditions, the anodic peak current of caffeic acid is linear with its concentration in the range of 0.01–15.00 μmol L −1 , and a detection limit of 2.7 nmol L −1 is achieved based on S/N = 3. The developed sensor shows good selectivity, sensitivity, reproducibility, and also excellent recovery in the detections of real samples, revealing the promising practicality of the sensor for the caffeic acid detection.

The authors report on a low temperature method for large-scale fabrication of cuprous oxide nanocubes deposited on nitrogen-doped reduced graphene oxide (Cu2O/N-RGO). The material was deposited in a glassy carbon electrode (GCE) where it is found to display enhanced electrocatalytic activity for oxidation of diethylstilbestrol (DES). The morphology and composition of Cu2O/N-RGO were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and energy-dispersive spectroscopy. The results demonstrate that the RGO is doped with 3.5% of nitrogen (atomic ratio), and that nanostructured Cu2O particles with controlled cubical morphology and an average size of about 450 nm have been homogeneously deposited on the surface of N-RGO sheets. The oxidation peak of DES was recorded at 0.315 V (vs. saturated calomel electrode) using differential pulse voltammetry. Under the optimal conditions, the modified GCE displays a linear response in the 0.3 to 150 μM DES concentration range, and the limit of detection is 10 nM. The method was applied to the determination of DES in spiked milk, meat and urine samples and gave excellent selectivity, stability and reproducibility.

In this work, a new type of fluorescent probe for detection of doxorubicin has been constructed by the combined use of fluorescence resonance energy transfer (FRET) technology and molecular imprinting technique (MIT). Using doxorubicin as the template, the molecularly imprinted polymer thin layer was fabricated on the surfaces of carbon dot (CD) modified silica by sol-gel polymerization. The excitation energy of the fluorescent donor (CDs) could be transferred to the fluorescent acceptor (doxorubicin). The FRET based fluorescent probe demonstrated high sensitivity and selectivity for doxorubicin. The detection limit was 13.8 nM. The fluorescent probe was successfully applied for detecting doxorubicin in doxorubicin-spiked plasmas with a recovery of 96.8–103.8%, a relative standard deviation (RSD) of 1.3–2.8%. The strategy for construction of FRET-based molecularly imprinted materials developed in this work is very promising for analytical applications.

Experiments have shown that the failure loads of Microelectromechanical Systems (MEMS) devices usually exhibit a considerable level of variability, which is believed to be caused by the random material strength and the geometry-induced random stress field. Understanding the strength statistics of MEMS devices is of paramount importance for the device design guarding against a tolerable failure risk. In this study, we develop a continuum-based probabilistic model for polycrystalline silicon (poly-Si) MEMS structures within the framework of first passage analysis. The failure of poly-Si MEMS structures is considered to be triggered by fracture initiation from the sidewalls governed by a nonlocal failure criterion. The model takes into account an autocorrelated random field of material tensile strength. The nonlocal random stress field is obtained by stochastic finite element simulations based on the information of the uncertainties of the sidewall geometry. The model is formulated within the contexts of both stationary and non-stationary stochastic processes for MEMS structures of various geometries and under different loading configurations. It is shown that the model agrees well with the experimentally measured strength distributions of uniaxial tensile poly-Si MEMS specimens of different gauge lengths. The model is further used to predict the strength distribution of poly-Si MEMS beams under three-point bending, and the result is compared with the Monte Carlo simulation. The present model predicts strong size effects on both the strength distribution and the mean structural strength. It is shown that the mean size effect curve consists of three power-law asymptotes in the small, intermediate, and large-size regimes. By matching these three asymptotes, an approximate size effect equation is proposed. The present model is shown to be a generalization of the classical weakest-link statistical model, and it provides a physical interpretation of the material length scale used in the weakest-link model.

Experimental data have made it abundantly clear that the strength of polycrystalline silicon (poly-Si) microelectromechanical systems (MEMS) structures exhibits significant variability, which arises from the random distribution of the size and shape of sidewall defects created by the manufacturing process. Test data also indicated that the strength statistics of MEMS structures depends strongly on the structure size. Understanding the size effect on the strength distribution is of paramount importance if experimental data obtained using specimens of one size are to be used with confidence to predict the strength statistics of MEMS devices of other sizes. In this paper, we present a renewal weakest-link statistical model for the failure strength of poly-Si MEMS structures. The model takes into account the detailed statistical information of randomly distributed sidewall defects, including their geometry and spacing, in addition to the local random material strength. The large-size asymptotic behavior of the model is derived based on the stability postulate. Through the comparison with the measured strength distributions of MEMS specimens of different sizes, we show that the model is capable of capturing the size dependence of strength distribution. Based on the properties of simulated random stress field and random number of sidewall defects, a simplified method is developed for efficient computation of strength distribution of MEMS structures.

The structural and transport properties of molten titanium slag have intuitive and important effects on the reaction efficiency of the smelting process, separation efficiency of slag and metal, and quality of titanium slag. Molecular dynamics simulations were carried out to characterize the structural and transport properties of titanium slag with various contents of alkaline earth oxide. The average CNTi-O (Coordination Number) increased from 5.99 to 6.04 while the average CNSi-O increased from 4.57 to 4.93 when the content of alkaline earth oxide increased from 3.5% to 31.5%. The Ti-O-Ti bond angle in the edge-sharing [TiO6] octahedron remained at 100.00°, while the Ti-O-Ti bond angle in the vertex-sharing [TiO6] octahedron increased from 125.25° to 127.04° with an increase in the content of alkaline earth oxide from 3.5% to 31.5%. A part of the Ti-O bond in the oxygen connection was replaced with the Mg-O bond as the content of alkaline earth oxide increased from 3.5% to 31.5%. The transformation in the oxygen connection reduced the structural strength of the system. The self-diffusion coefficients followed the order: Mg2+>Ca2+>Ti4+>O2−>Si4+. The viscosity of the system decreased from 0.098 Pa·s to 0.064 Pa·s as the content of alkaline earth oxide increased from 3.5% to 31.5%, which is in good accordance with the measured results. The results will contribute to predicting and controlling the transport properties of molten titanium slag and will lay the foundation for the efficient production of high-quality titanium slag.

Fine and uniform microstructures are essential for investment casting. In this study, water cooling-controlled solidification for aluminum alloy investment casting was investigated. Sound casting plates without shrinkage porosity were developed. Water cooling-controlled solidification was simulated with ProCAST by adding a user function. As an important parameter in determining mechanical properties, secondary dendrite arm spacing (SDAS) was simulated and measured under an optical microscope. Results show that SDAS significantly decreased during water cooling-controlled solidification casting. SDAS was less sensitive to wall thickness because of a high cooling rate. Fine fibrous eutectic silicon morphologies were obtained after modification. Sound cast with fine and uniform microstructures can be obtained with water cooling-controlled solidification casting.

Sinter-HIP combining vacuum and pressure in one-step sintering process has been applied to prepare ultrafine crystalline cemented carbide with a surface gradient layer enriched in binder. The effect of powder particle size on gradient formation and grain growth has been examined. The results show that the gradient layer thickness increases with decreasing WC and Ti(C,N) powder particle size. The number of abnormal WC grains increases with decreasing WC powder particle size. The formational mechanism of the gradient cemented carbide with ultrafine grains is discussed through analyzing the decomposability of nanoscale Ti(C,N), atomic diffusion and grain growth during one-step Sinter-HIP process.

Ultrafine crystalline functionally graded cemented carbides (FGCCs) with a surface zone enriched in binder phase were prepared by a one-step Sinter-HIP method. The influence of sintering pressure and cubic carbide composition on the formation of gradient layer was examined. The results show that the ultrafine FGCC with surface zone enriched in binder phase can be formed by the one-step Sinter-HIP method. The process of the gradient layer formation is accelerated under higher sintering pressure; the gradient layer thickness increases with the sintering pressure increasing. The gradient layer thickness is controlled by diffusion distance of cubic carbide formers, such as Ti, Ta and Nb. The addition of (Ta,Nb)C leads to decrease the thickness of gradient layer.

In this work, a simple, low-cost and eco-friendly strategy for fabricating the three-dimensional porous nitrogen-doped graphene (3D-N-GN) is demonstrated by combining the hydrothermal assembly and freeze-drying process without using any framework support. The desired features for 3D-N-GN, such as rich macroporosity, nitrogen-doping structure and high active surface area have been confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical techniques, respectively. In comparison with two-dimensional graphene (2D-GN) and nitrogen-doped graphene (2D-N-GN), 3D-N-GN makes a more negative shift in the oxidation peak potential of adenine together with a remarkable increase in the oxidation peak current, highlighting the importance of the nitrogen-doping and 3D construction of the graphene-based support for improving the electrocatalytic performance. It also indicates that 3D-N-GN can be used as an efficient electrocatalyst for adenine sensing. Furthermore, the sensing conditions are optimized and the resulting sensor displays excellent analytical performance in the detection of adenine at low concentrations ranging from 0.02 to 1.20 μM, with a detection limit of 8 nM. Finally, this proposed method not only exhibits preferable reproducibility, stability and adequate sensitivity, but also demonstrates good efficiency in the detection of adenine in biological fluids.

Fluorescent molecularly imprinted polymers (MIPs) have attracted increasing attentions in recent years due to their high selectivity and sensitivity for target molecules. In this study, two cholic acid imprinted fluorescent polymers, i.e., MIP1 and MIP2, were prepared using 4-dimethylamino-N-allylnaphthalimide (F1) and 4-piperazinyl-N-allylnaphthalimide (F2) as the fluorescent functional monomers, respectively. The fluorescence intensity of MIP1 decreased linearly with the increase of the template concentration in the range of 1.50-120.0 μM, while the fluorescence intensity of MIP2 increased linearly with the increase of the template concentration in the range of 0.40-110.0 μM. The detection limits of MIP1 and MIP2 for cholic acid were 0.42 and 0.083 μM, respectively. The mechanisms of the fluorescence responsive of the imprinted polymers were discussed. The results of fluorescence measurement and binding experiments demonstrated that both imprinted polymers have high recognition abilities and binding affinities for the template. The imprinted polymers have been successfully applied to the determination of cholic acid in human serums. The present study indicated that 1,8-naphthalimide can be used as a modular building block for design and construction of various fluorogenic molecularly imprinted materials for practical sensing and separation.

In this work, three kinds of bimetallic Prussian blue analogues (PBAs), i.e. KxNi [Fe(CN)6]·nH2O (NiFe-PBA), KxCo [Fe(CN)6]·nH2O (CoFe-PBA), and KxMn [Fe(CN)6]·nH2O (MnFe-PBA), were synthesized by a simple precipitation method under identical conditions. Their chemical compositions, structures, morphologies, valences of transition metals, and electrochemical sensing performances for 2-nitrophenol (2-NP) are examined in details. It is found that all the prepared PBAs hold face-centered-cubic structures with near perfect cube morphologies for NiFe-PBA and CoFe-PBA and truncated cube morphology for MnFe-PBA. For the electrochemical detection of 2-NP, a wide detection range of 1.0–700.0 μM was obtained at all PBAs modified electrodes together with the sensitivities of 443.3, 368.0, and 339.0 μA cm−2 mM−1 and detection limits of 0.28, 0.46, and 0.59 μM achieved at NiFe-PBA, CoFe-PBA, and MnFe-PBA modified electrodes, respectively. The superiority in electrochemical sensing performance of NiFe-PBA to CoFe-PBA and MnFe-PBA may stem from its higher conductivity, lager electroactive surface area, and better intrinsic catalytic property of the transition metal in its framework. Furthermore, the constructed NiFe-PBA-based sensor displays good repeatability, long-term stability, and high selectivity together with desirable recoveries (97.8–103.9%) for the assay of 2-NP in water samples. The present work is the first report on the PBAs-based electrochemical sensors for 2-NP detection, which may promise a future of PBAs or PBAs-based materials for sensing applications.

Molybdenum (Mo)-based transition metal oxides normally delivery superior energy density in lithium ion batteries through electrochemical conversion reactions. The main challenge for this kind of electrode material is to promote reversible transformation of Li2O and alleviate the volume expansion during lithiation/delithiation processes. Here, electrochemical reaction mechanism of CoMoO4 investigated by in-situ X-ray diffraction and ex-situ Transmission electron microscopy reveals the irreversible transformation from CoMoO4 to CoO and MoO3 in the first cycle. During subsequent charge/discharge process, high valence state cobalt ions originated from Co2+ provide additional capacity and promote the electrochemical reversible reaction between MoO3 and Li2O, thus facilitating the release of irreversible capacity. Benefited by the contributor of high valence state cobalt ion, when CoMoO4 was utilized as Li-storage anode, high reversible capacity (1585.5 mAh g−1 at 200 mA h−1 after 150 cycles) and excellent cyclic stability (~100% retention after 400 cycles at 1000 mA g−1) are delivered. Such an optimized anode material expands the potential to develop lithium-ion batteries with significantly higher energy density.

In this paper, the transverse tensile behavior and microscopic damage evolution of graphite fiber-reinforced aluminum composites were investigated by numerical and experimental methods. Micromechanical models based on realistic and assumptive fiber arrangements were established. In these models, the progressive damage procedure of the matrix alloy and the interface was incorporated. The validity of the models was assessed by comparing the predicted stress-strain curves with the experimental ones. The microscopic damage behavior of the matrix alloy and the interface was revealed and its contributions to macroscopic mechanical responses were analyzed in detail. The interaction of different damage mechanisms was further discussed on the basis of numerical and experimental results. The influences of interface, matrix alloy, and fiber volume fraction on damage evolution and mechanical behaviors were parametrically studied on the basis of the verified micromechanical model to provide insights into the damage mechanisms of the composites.

A novel treatment for removing As from a Cu electrolyte using titanium(IV) oxysulfate coprecipitation and carbothermal reduction is investigated. Experimental results show that under the conditions of an agitation speed of 200 r·min−1, a Ti:As molar ratio of 1.5, a processing time of 60 min at 80 °C, the results show that this As removal process can be conducted stably, the As precipitation efficiency is as high as 91.36%, and the concentration of As in the solution can be reduced to approximately 1.2 g·L−1. The regeneration of titanium(IV) oxysulfate is also investigated, and the NaOH leaching technique can be determined. Under the conditions of an agitation speed of 200 r·min−1, a Na:As molar ratio of 1.5, a liquid–solid ratio of 4/1 mL/g, an alkali-leaching time of 30 min at 25 °C, 98% of the As is leached from the precipitant. After the removal of As from the alkali solution via lime precipitation, a Ca-As residue is obtained. Subsequently, the carbothermal reduction of the Ca-As residue is investigated. Under the conditions of a C:As molar ratio of 1.75 and a recovery time of 60 min at 1000 °C, 99.98% of the As in the Ca-As residue is reduced.

Aiming at substantially improving the electrochemical sensing performance for guanine, we bring out a novel high-efficiency electrocatalyst composed of hierarchical sea urchin-like Prussian blue@palladium core–shell heterostructures supported on nitrogen-doped reduced graphene oxide (PB–U@Pd/N-RGO). The said PB-U@Pd/N-RGO was synthesized by a new and facile wet-chemistry method without using any surfactant and template. More impressively, we demonstrate a new strategy for morphology-controlled synthesis of Prussian blue via simply tuning the ratio of N,N′-dimethyl formamide and H2O in the mixed solvent. In-depth electrochemical characterizations demonstrate the superior electrocatalytic performance of PB-U@Pd/N-RGO toward the oxidation of guanine, which benefits from the synergistic effect of component materials and its unique core–shell heterostructure. Consequently, the constructed PB-U@Pd/N-RGO-based electrochemical sensor displays superb comprehensive performance for the guanine assay. To be specifical, the developed sensor exhibits wide detection range (0.01–85.0 μM), low detection limit (2.6 nM), good reproducibility, long-term stability, high sensitivity and selectivity together with acceptable recovery (97.0–104.0%) for the assay of guanine in biological samples. Such outstanding comprehensive performance is amongst the top of reports for the electrochemical sensing of guanine, promising practical applications in biosensing fields.

Anchored by the theory of extreme value statistics, Weibull distribution is the most widely used mathematical model for strength distribution of brittle structures. In a series of recent st...

In order to improve the diffusion kinetics of molecularly imprinted materials (MIMs), applying imprinting technology to mesoporous materials is a promising strategy. In the present study, an imprinting approach based on the combination of mesoporous silica materials and molecular imprinting technology is reported. Molecularly imprinted material (MIM) for 2,4-dichlorophenoxyacetic acid (2,4-D) was prepared by using 2,4-D as the template molecule, alkyne-modified β-cyclodextrin and propargyl amine as the combinatorial functional monomers and SBA-15 as the supporter. The functional monomers were anchored to the azide-modified SBA-15 by azide-alkyne Click reaction. The synthesized MIM was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), thermal gravimetric analysis (TGA), low-angle X-ray diffraction (XRD) and N2 adsorption-desorption analysis. The interactions between template and functional monomers were studied by proton NMR analysis and UV-vis experiments. The results of the equilibrium binding experiments and selective tests showed that the prepared MIM has binding affinity and specificity for a group of analytes which have similar size and shape to those of template. Binding kinetic experiments demonstrated that the present imprinting approach can effectively enhance the mass transfer rate. The solid phase extraction of 2,4-D using MIM as the adsorbent was investigated. The extraction conditions for the processes of loading, washing and eluting were optimized. The recoveries of the molecularly imprinted solid phase extraction (MISPE) column for 2,4-D were 76.3-88.9% with relative standard deviations (RSD) of 3.48-7.64%.

In this work, the metallic silver and non-metallic nitrogen co-doped reduced graphene oxide (Ag-N-RGO) was first synthesized by a simple and cost-effective strategy, and then a molecularly imprinted polymer (MIP) was formed in situ at the surface of the prepared composite via electropolymerization of o-phenylenediamine in the presence of salbutamol as the template molecule. The electrochemical characterizations demonstrate that the bifunctional graphene-based composite shows improved catalytic performance than that of pristine graphene doped with one-component or none. The MIP sensor based on Ag-N-RGO owns high porous surface structure, resulting in the increased current response and enhanced recognition capacity than that of non-imprinted sensor. The outstanding performance of the developed sensor derives from the combined advantages of Ag-N-RGO with effective catalytic property and MIP with excellent selectivity. Under the optimal conditions, the electrochemical response of the developed sensor is linearly proportional to the concentration of salbutamol in the range of 0.03-20.00µmolL-1 with a low detection limit of 7 nmol L-1. The designed sensor has exhibited the multiple advantages such as low cost, simple manufacture, convenient use, excellent selectivity and good reproducibility. Finally, the proposed method has been extended for the determinations of salbutamol in human urine and pork samples, and the satisfactory recoveries between 98.9-105.3% are achieved.