Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

Mixed phase sodium manganese oxide as cathode for enhanced aqueous zinc-ion storage

Aqueous zinc-ion batteries have been regarded as a promising alternative to large-scale energy storage, due to associated low-cost, improved safety and environmental friendliness. However, a high-performance cathode material for both rate capability and specific capacity is still a challenge. One kind of the more promising candidates are sodium manganese oxide(NMO) materials, although they suffer from individual issues and need to be further improved. Herein, we present a novel mixed phase NMO material composed of nearly equal amounts of Na(0.55)Mn2O4 and Na(0.7)MnO(2.05). The structured configuration with particle size of 200–500 nm is found to be beneficial towards improving the ion diffusion rate during the charge/discharge process. Compared with Na(0.7)MnO(2.05) and Na(0.55)Mn2O4, the mixed phase NMO demonstrates an enhanced rate capability and excellent long-term cycling stability with a capacity retention of 83% after 800 cycles. More importantly, the system also delivers an impressive energy density and power density, as 378 W·h·kg^-1 at 68.7 W·kg^-1, or 172 W·h·kg^-1 at 1705 W·kg^-1. The superior electrochemical performance is ascribed to the fast Zn^2+ diffusion rate because of a large ratio of capacitive contribution(63.9% at 0.9 m V·s^-1). Thus, the mixed phase route provides a novel strategy to enhance electrochemical performance, enabling mixed phase NMO as very promising material towards large-scale energy-storage applications.

Selective oxidation of biomass derived 5-hydroxymethylfurfural to 2,5-diformylfuran using sodium nitrite

A mild and simple process for the effective oxidation of 5-hydroxymethylfurfural（HMF） into 2,5-diformylfuran（DFF） has been developed using Na NO2 as the oxidant. Some important reaction parameters were investigated to optimize the oxidation of HMF into DFF. It was found that the reaction solvent was very crucial for this reaction. Trifluoroacetic acid was the best solvent for the oxidation of HMF into DFF by Na NO2.Under the optimal reaction condition, almost quantitative HMF conversion and high DFF yield of 90.4% were obtained after 1 h at room temperature.

Aldehyde-Sodium Alginate and Amino-Gelatin Preparation as Soft Tissue Adhesive

Sodium alginate and gelatin are both remarkable natural biomaterials; they all have been extensively applied in tissue engineering and other relative fields,due to their low price and good biocompatibility. In this paper,we oxidized sodium alginate with sodium periodate to convert 1,2-hydroxyl groups into aldehyde groups to get aldehyde-sodium alginate( A-SA). Gelatin was modified with ethylenediamine( ED) in the presence of water-soluble1-ethyl-3( 3-dimethylaminopropyl) carbodiimide( EDC) to introduce additional amino groups to get amino-gelatin. Upon mixing the A-SA and amino-gelatin aqueous solutions together,a gel rapidly formed based on the Schiff's base reaction between the aldehyde groups in A-SA and the amino groups in amino-gelatin.Fourier transform infrared spectroscopy( FTIR) analysis confirmed the characteristic peak of Schiff's base group in the hydrogel. The gelation time measure has confirmed the gelation time is dependent on the aldehyde group content in A-SA and amino group content in amino-gelatin. The fasted hydrogel formation takes place within 30 s. The entire test suggested that this gel could be a promising candidate as soft tissue adhesive.

Alkali and alkaline ions co-substitution of P2 sodium layered oxides for sodium ion batteries

Alkali and alkaline ion substitutions enhance the electrochemical properties of P2 sodium layered oxide,while the effect on electrochemical property enhancement of alkali and alkaline ions co-substitution is still unclear.In this work,the structural and electrochemical properties of the Li alkali and Mg alkaline ions co-substituted P2 layered oxide Na_(0.67)(Li_(0.5)Mg_(0.5))_(0.1)(Ni_(0.33)Mn_(0.67))_(0.9)O_(2)are investigated in detail.Compared to the pristine and single-ion substituted materials,the co-substituted material shows an enhanced cycling performance with a reversible ca-pacity of 127 mAh/g and a capacity retention of 75%over 100 cycles at 0.5C.Galvanostatic intermittent titration technique(GITT)and cyclic voltammetry(CV)results show that the Li and Mg synergistically improve the ion diffusion.Moreover,the structure stability is also improved by the Li and Mg co-substitution that is clarified by operando X-ray diffraction(XRD)measurements.These results explain the origin of the enhanced electrochemical properties of the Li/Mg co-substituted P2 layered oxides for sodium ion batteries.

Effect of SiO_2/Na_2O mole ratio on the properties of foam geopolymers fabricated from circulating fluidized bed fly ash

Geopolymers are three-dimensional aluminosilicates formed in a short time at low temperature by geopolymerization. In this pa-per, alkali-activated foam geopolymers were fabricated from circulating fluidized bed fly ash （CFA）, and the effect of SiO2/Na2O mole ratio （0.91-1.68） on their properties was studied. Geopolymerization products were characterized by mechanical testing, scanning electron mi-croscopy （SEM）, energy-dispersive X-ray spectroscopy （EDX）, and X-ray diffraction （XRD）. The results show that SiO2/Na2O mole ratio plays an important role in the mechanical and morphological characteristics of geopolymers. Foam samples prepared in 28 d with a SiO2/Na2O mole ratio of 1.42 exhibit the greatest compressive strength of 2.52 MPa. Morphological analysis reveals that these foam geo-polymers appear the relatively optimized pore structure and distribution, which are beneficial to the structure stability. Moreover, a combina-tion of the Si/Al atomic ratio ranging between 1.47 and 1.94 with the Na/Al atomic ratio of about 1 produces the samples with high strength.

Mineral transition and formation mechanism of calcium aluminate compounds in CaO-Al2O3-Na2O system during high-temperature sintering

The mineral transition and formation mechanism of calcium aluminate compounds in CaO-Al2O3-Na2O system during the hightemperature sintering process were systematically investigated using DSC-TG,XRD,SEM-EDS,FTIR,and Raman spectra,and the crystal structure of Na4Ca3(AlO2)10 was also simulated by Material Studio software.The results indicated that the minerals formed during the sintering process included Na4Ca3(AlO2)10,CaO·Al2O3,and 12 CaO·7 Al2O3,and the content of Na4Ca3(AlO2)10 could reach 92 wt%when sintered at 1200°C for 30 min.The main formation stage of Na4Ca3(AlO2)10 occurred at temperatures from 970 to 1100°C,and the content could reach82 wt%when the reaction temperature increased to 1100°C.The crystal system of Na4Ca3(AlO2)10 was tetragonal,and the cells preferred to grow along crystal planes(110)and(210).The formation of Na4Ca3(AlO2)10 was an exothermic reaction that followed a secondary reaction model,and its activation energy was 223.97 kJ/mol.

A method for recovery of iron,titanium,and vanadium from vanadium-bearing titanomagnetite

An innovative method for recovering valuable elements from vanadium-bearing titanomagnetite is proposed. This method involves two procedures： low-temperature roasting of vanadium-bearing titanomagnetite and water leaching of roasting slag. During the roasting process, the reduction of iron oxides to metallic iron, the sodium oxidation of vanadium oxides to water-soluble sodium vanadate, and the smelting separation of metallic iron and slag were accomplished simultaneously. Optimal roasting conditions for iron/slag separation were achieved with a mixture thickness of 42.5 mm, a roasting temperature of 1200°C, a residence time of 2 h, a molar ratio of C/O of 1.7, and a sodium carbonate addition of 70 wt%, as well as with the use of anthracite as a reductant. Under the optimal conditions, 93.67% iron from the raw ore was recovered in the form of iron nugget with 95.44% iron grade. After a water leaching process, 85.61% of the vanadium from the roasting slag was leached, confirming the sodium oxidation of most of the vanadium oxides to water-soluble sodium vanadate during the roasting process. The total recoveries of iron, vanadium, and titanium were 93.67%, 72.68%, and 99.72%, respectively.

A novel wet-spinning method of manufacturing continuous bio-inspired composites based on graphene oxide and sodium alginate

Nacre is a lightweight, strong, stiff, and tough material, which makes it a mimicking object for material design. Many attempts to mimic nacre by various methods resulted in the synthesis of artificial nacre with excellent properties. However, the fabrication procedure was very laborious and time-consuming due to the sequential steps, and only limited-sized materials could be obtained. Hence, a novel design enabling scalable production of high-performance artificial nacre with uniform layered structures is urgently needed. We developed a novel wet-spinning assembly technique to rapidly manufacture continuous nacre- mimic graphene oxide （GO, brick）-sodium alginate （SA, mortar） films and fibers with excellent mechanical properties. At high concentrations, the GO-SA mixtures spontaneously produced liquid crystals （LCs） due to the template effect of GO, and continuous, 6 m long nacre-like GO-SA films were wet-spun from the obtained GO-SA liquid crystalline （LC） dope with a speed of up to 1.5 m/min. The assembled macroscopic GO-SA composites inherited the alignment of the GO sheets from the LC phase, and their mechanical properties were investigated by a joint experimental-computational study. The tensile tests revealed that the maximum strength （0） and Young＇s modulus （E） of the obtained films reached 239.6 MPa and 22.4 GPa, while the maximum values of o and E for the fibers were 784.9 MPa and 58 GPa, respectively. The described wet-spinning assembly method is applicable for a large-scale and fast production of high-performance continuous artificial nacre.

A new approach for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid without using transition metal catalysts

The organic compound 2,5-furandicarboxylic acid（FDCA） has been identified by the US Department of Energy（DOE） as a valuable platform chemical for a wide range of industrial applications. Currently, the most popular route for FDCA synthesis is reported to be the oxidation of 5-hydroxymethylfurfural（HMF）by O_2 over the catalysis of noble metals（e.g., Au, Pt, Ru, and Pd）. However, the high costs of noble metal catalysts remain a major barrier for producing FDCA at an industrial scale. Herein, we report a transition metal-free synthesis strategy for the oxidation of HMF to FDCA under O_2 or ambient air. A simple but unprecedented process for the aerobic oxidation of HMF was carried out in organic solvents using only bases as the promoters. According to the high performance liquid chromatography（HPLC） analysis, excellent product yield（91%） was obtained in the presence of NaOH in dimethylformamide（DMF） at room temperature（25 ℃）. A plausible mechanism for the NaOH-promoted aerobic oxidation of HMF in DMF is also outlined in this paper. After the reaction, the sodium salt of FDCA particles were dispersed in the reaction mixture, making it possible for product separation and solvent reuse. The new HMF oxidation approach is expected to be a practical alternative to current ones, which depend on the use of noble metal catalysts.

Facile Synthesis of Layered Sodium Manganese Oxide for Application in Asymmetric Supercapacitor

Layered sodium manganese oxides(LSMOs),with two-dimensional channels for ion diffusion,have been regarded as the promising electrode materials in the application of asymmetric supercapacitors(ASCs).In this work,the layered Na0.5Mn2O4·1.5H2O was synthesized through a facile hydrothermal method by controlling the molar ratio of sodium and manganese.When the molar ratio of sodium to manganese is 3:1,Na0.5Mn2O4·1.5H2O has shown the best capacitance of 369 F/g with current density of 0.5 A/g,and maintained a capacitance of 265 F/g after 2000 cycles.The asymmetric supercapacitor consists of the sodium manages oxides as the positive electrode and active carbon(AC)as the negative electrode in 1 mol/L Na2SO4 solution.The voltage of the asymmetric supercapacitor has been expanded to 0~2 V with an energy density of 10.13 Wh/kg at a power density of 500 W/kg based on the total weight of both active electrode materials when the mass ratio of AC to Na0.5Mn2O4·1.5H2O was 3:1.

Synthesis and application of bilayer-surfactant-enveloped Fe_3O_4 nanoparticles: water-based bilayer-surfactant-enveloped ferrofluids

Superparamagnetic carbon-coated Fe3O4 nanoparticles with high magnetization（85 emu·g-（-1）） and high crystallinity were synthesized using polyethylene glycol-4000（PEG（4000）） as a carbon source.Fe3O4 water-based bilayer-surfactant-enveloped ferrofluids were subsequently prepared using sodium oleate and PEG（4000） as dispersants.Analyses using X-ray photoelectron spectroscopy,X-ray diffraction,and Fourier-transform infrared spectroscopy indicate that the Fe3O4 nanoparticles with a bilayer surfactant coating retain the inverse spinel-type structure and are successfully coated with sodium oleate and PEG（4000）.Transmission electron microscopy,vibrating sample magnetometry,and particle-size analysis results indicate that the coated Fe3O4 nanoparticles also retain the good saturation magnetization of Fe3O4（79.6 emu·g^-1） and that the particle size of the bilayer-surfactant-enveloped Fe3O4 nanoparticles is 42.97 nm,which is substantially smaller than that of the unmodified Fe3O4 nanoparticles（486.2 nm）.UV-vis and zeta-potential analyses reveal that the ferrofluids does not agglomerate for 120 h at a concentration of 4 g·L^-1,which indicates that the ferrofluids are highly stable.

The Releasing Effects of Captopril and Sodiun Nitroprusside on Endothelin-1 in Vascular Smooth Muscle Cell

Objective To investigate the influence of captoprial and SNP on the release of ET -1 in cultured VSMC of rats. Methods Measurement of endothelin - 1 levels by radioimmljnoassay in various concentrations of captopril and/or sodium nitroprusside in cultured vascular smooth muscle cell (VSMC) of rats. Results Both captopril and SNP could reduce the high ET - 1 levels of VSMC which were caused by Ang Ⅱ. There was a linear relationship between Ang Ⅱlevels and ET -1 production ( r = 0. 760, P <0. 001 ) . Conclusion Endothelin - 1 may accelerate the formation and development of atherosclerosis through inhibiting endogenous NO production by VSMC. ACEI or NO inhibition of ET -1 release could reduce atherosclerosis formation.

A soft tissue adhesive based on aldehyde-sodium alginate and amino-carboxymethyl chitosan preparation through the Schiff reaction

Sodium alginate and carboxymethyl chitosan have been extensively applied in tissue engineering and other relative fields due to their low price and excellent biocompatibility. In this paper, we oxidized sodium alginate with sodium periodate to convert 1,2-hydroxyl groups into aldehyde groups to get aldehyde-sodium alginate （A- SA）. Carboxymethyl chitosan was modified with ethylenediamine （ED） in the presence of water-soluble N-（3-Dimethylaminopropyl）-N＇-ethylcarbodiimide hydrochloride （EDC） to introduce additional amino groups to get amino-carboxymethyl chitosan （A-CS）. Upon mixing the A-SA and A-CS aqueous solutions together, a gel rapidly formed based on the Schiff＇s base reaction between aldehyde groups in A-SA and amino groups in A-CS. FTIR analysis confirmed the characteristic peak of Schiff＇s base group in the hydrogel. It was confirmed that the gelation time be dependent on the aldehyde group content in A-SA and amino group content in A-CS. The fasted hydrogel formation takes place within 10 min. The data of bonding strength and cytotoxicity measurement also showed that the hydrogel had good adhesion and biocompatibility. All these results support that this gel has the potential as soft tissue adhesive.

Mitochondrial dysfunction,oxidative stress and apoptotic induction in microglial BV-2 cells treated with sodium arsenate

The treatment of microglial BV-2 cells with sodium arsenate（As（V）：0.1-400 μmol/L — 48 hr）induces a dose-dependent response.The neurotoxic effects of high concentrations of As（V）（100,200 and 400 μmol/L） are characterized by increased levels of mitochondrial complexesⅠ,Ⅱ,and Ⅳ followed by increased superoxide anion generation.Moreover,As（V） triggers an apoptotic mode of cell death,demonstrated by an apoptotic SubG1 peak,associated with an alteration of plasma membrane integrity.There is also a decrease in transmembrane mitochondrial potential and mitochondrial adenosine triphosphate ATP.It is therefore tempting to speculate that As（V） triggers mitochondrial dysfunction,which may lead to defective oxidative phosphorylation subsequently causing mitochondrial oxidative damage,which in turn induces an apoptotic mode of cell death.

Electrochemical performance of NaCo_2O_4 as electrode for supercapacitors

Sub-micron-scaled sodium cobalt oxide （NaCo2O4） powders are prepared by a solid-state reaction method. Characterization using X-ray diffraction indicates that the synthesized NaCo2O4 has a hexagonal layered structure. The electrochemical performance of the NaCo2O4 electrodes is investigated using cyclic voltarnmetry and galvanostatic charge/discharge in NaOH solution. The results show that the specific capacitance of the NaCo2O4 electrode reaches 337 F/g over the potential range of 0.15-0.65 V at a mass normalized current of 50 mA/g. Moreover, NaCo2O4 exhibits very good stability and cycling performance as a supercapacitor material.

Supercritical water oxidation of polyvinyl alcohol and desizing wastewater: Influence of NaOH on the organic decomposition

Polyvinyl alcohol is a refractory compound widely used in industry. Here we report supercritical water oxidation of polyvinyl alcohol solution and desizing wastewater with and without sodium hydroxide addition. However, it is difficult to implement complete degradation of organics even though polyvinyl alcohol can readily crack under supercritical water treatment. Sodium hydroxide had a significant catalytic effect during the supercritical water oxidation of polyvinyl alcohol. It appears that the OH ion participated in the C-C bond cleavage of polyvinyl alcohol molecules, the CO2-capture reaction and the neutralization of intermediate organic acids, promoting the overall reactions moving in the forward direction. Acetaldehyde was a typical intermediate product during reaction. For supercritical water oxidation of desizing wastewater, a high destruction rate （98.25%） based on total organic carbon was achieved. In addition, cases where initial wastewater was alkaline were favorable for supercritical water oxidation treatment, but salt precipitation and blockage issues arising during the process need to be taken into account seriously.

A convenient catalytic oxidative 1,2-shift of arylalkenes for preparation of α-aryl ketones mediated by NaI

Using a catalytic amount of Nal and a stoichiometric oxidant Oxone-@,a convenient procedure has been developed for the catalytic oxidative 1,2-shift of arylalkenes in CH3CN/H2O at room temperature,which provides the corresponding α-aryl ketones in moderate to good yields.In this protocol,sodium iodide is first oxidized into hypoiodous acid,which reacts with arylalkene to afford iodohydrin.Then,the iodohydrin is transformed into the α-aryl ketone via an oxidative 1,2-shift rearrangement.