KMnO4 Solution Research Articles

Dual‐Role Surface Modification of Layered Oxide Cathodes for High‐Power Sodium‐Ion Batteries

AbstractP2‐type layered oxides have attracted extensive attentions due to their high reversible capacity and operating voltage when applied as cathode materials for sodium‐ion batteries (SIBs). However, the large ionic radius of Na+ and restricted 2D diffusion channels account for the inferior Na+ conductivity, limiting their practical application under large current densities. Herein, a facile dual‐role surface treatment on oxide precursors using KMnO4 solution is employed to generate K+ pillar and spinel‐like surface nanolayer in the layered oxide cathodes simultaneously. The substantial enhancement of Na kinetics is ascribed to the enlarged interlayer spacing in the lattice induced by K+ pillar and the formation of coherent spinel‐like surface structure derived from the decomposition of KMnO4, which satisfies the timely Na+ insertion/extraction and improves the rate performance. It is anticipated that this dual‐role strategy may provide a promising pathway for the development of the high‐power‐capability SIBs.

The Deposition Mechanism and Protective Properties of Manganese-Based Conversion Coatings on the Surface of AD31 Aluminum Alloy

The stage mechanism of manganese-containing conversion coatings (MCCs) formation on the surface of AD31 alloy (AA6063) in acidic (pH 3) KMnO4 solutions, as well as their structure, composition, and anticorrosion properties have been examined using scanning electron microscopy, energy dispersive X‑ray microanalysis, Raman spectroscopy, UV–Vis spectroscopy, electrochemical impedance spectroscopy, potentiodynamic polarization, and salt spray chamber tests. The conditions for obtaining MCCs have been optimized, and the feasibility of their use in multicomponent corrosion protection systems for the AD31 aluminum alloy has been shown.

In situ self-assembled biosupramolecular porphyrin nanofibers for enhancing photodynamic therapy in tumors.

Due to the complicated environment and high tissue hydraulic pressure in tumors that easily pumps the nanomedicines back to the systemic circulation, the concentration of released photosensitizers (PSs) retained in a tumor by a traditional nano-delivery system is very low, causing an unsatisfactory photodynamic therapy (PDT) effect. Therefore, we prepared a pH/H2O2-responsive nano-system (ZnP-OC-M) through modified porphyrin PS units with a long-unsaturated oleoyl chloride chain, and by the further introduction of hydrophilic hydroxyl groups and MnO2 through a cis-addition reaction between the unsaturated double bonds of oleoyl chloride and dilute KMnO4 solution. Making use of the sensitivity of MnO2 to the H2O2 in the acid environment of tumor cells, ZnP-OC-M selectively realized responsive disintegration and O2 generation. More importantly, the rich amphiphilic PS units were shedded simultaneously and spontaneously completed the self-assembly into nanofibers in situ by helical stacking, which displayed a 1.85-fold higher retention effect of PSs in vivo compared with free PS groups and showed a great tumor inhibition effect in enhancing PDT. This nanosystem effectively solves the problem of the low retention abilities leading to a poor PS concentration in a tumor, prolonging the treatment time window efficiently after only a single administration and achieving the purpose of PDT enhancement.

Template-assisted preparation of MnO2@MnO2 hollow nanospheres and their research of capacitance performance

MnO2@MnO2 hollow nanospheres were prepared by two-step SiO2 template method. Firstly, the core-shell structure SiO2@MnO2 (S@M) was prepared by hydrothermal treating SiO2 nanospheres in KMnO4 solution at 150 °C for 48 h. Then SiO2 was covered on the surface repeatedly of S@M to obtained SiO2@MnO2@SiO2 (S@M@S), and then SiO2@MnO2@SiO2@MnO2 (S@M@S@M) was formed after refluxing S@M@S in KMnO4 solution at 60 °C for 12 h. Finally, the SiO2 existed in both cores and the sandwich layers was etched along with immersing S@M@S@M in NaOH solution, and the MnO2@MnO2 hollow nanospheres were obtained. The electrochemical properties were measured by cyclic voltammetry (CV) and galvanic charge/discharge (GCD) using a three-electrode system in Na2SO4 electrolyte. The research results showed that the capacitance of MnO2@MnO2 with hollow structure of electrode materials was significantly increased compared with single-shelled MnO2, increasing from 210 F g−1 to 357 F g−1 at the scan rate of 5 mV s−1.

Mn3O4 nanocluster-graphene hybrid for energy storage and electrochemical sensing application

In this report, uniformly dispersed tri-manganese tetra-oxide (Mn3O4) nanoclusters on reduced graphene oxide (rGO) were synthesized and used as an electrode material for high-performance supercapacitor application. HRTEM images associated with SAED and EDS confirm the formation of Mn3O4 nanoclusters on rGO while FTIR shows clear evidence of Mn3O4 nanocluster deposition on rGO. The nanohybrid structure is unique showing uniformly distributed Mn3O4 nanoclusters of size from 2 to 20 nm with the majorities of the cluster sizes are in the range of ~ 5–11 nm. The nanoclusters exhibit trapped mesopores of size ~ 2 nm inside of the clusters surrounded with tiny Mn3O4 nanoparticles, which not only improves the surface properties but also enhances the electrochemical activities of rGO. We believe that the low-temperature, hydrothermal processing of KMnO4 solution leads to the development of such nanoclusters formed by limited growth of ultra-nanosized nucleates deposited on rGO surface under optimized time condition. The nanohybrid shows the highest capacitance value of 181 F/g at a current density of 0.3 A/g along with superior cyclic stability (with ~ 95% capacitance retention upon continuous 2000 cycle). The nanohybrid material was further utilized for electrochemical sensing of H2O2 where anodic current proportionally increases as a function of H2O2 concentrations. We believe that the nanohybrid material described here will have potential applications in the area of high-performance supercapacitor, catalysis, batteries, and non-enzymatic sensors.

NaCl‐Templated and Polyvinylpyrrolidone‐Assisted Fabrication of a MnO/C‐rGO Composite as a High‐Capacity Anode Material for Li‐Ion Batteries

A 3D hierarchically‐heterostructured manganese oxide/pyrolytic carbon and reduced graphene oxide composite material (MnO/PC‐rGO) is synthesized by the in situ redox reaction between a PC‐rGO carbon aerogel framework and KMnO4 solution, followed by heat treatment in an inert atmosphere. Herein, the 3D porous PC‐rGO carbon aerogel is prepared via crystal sodium chloride (NaCl)‐templated and polyvinylpyrrolidone (PVP)‐assisted freeze drying in the presence of graphene oxide (GO) and high‐temperature pyrolysis. As an anode material for lithium‐ion batteries, this composite exhibits a high charge capacity of ≈1030 mAh g−1 at 100 mA g−1 and 515 mAh g−1 at 2000 mA g−1. After cycling at 500 mA g−1 for 200 cycles, the capacity retention is ≈70%, demonstrating much superior lithium storage performance over the MnO/PC composite prepared under similar conditions. The superior electrochemical performance is ascribed to its good electrode kinetics behavior and the supernumerary capacity contribution of the PC‐rGO carbon framework due to the presence of rGO in the composite. As a synergic carbon support, the rGO can not only increase the specific capacity and rate capability but also improve the cyclability due to the enhanced electrical conductivity and the buffering effect of the flexible PC‐rGO against a large volume change during cycling.

Study on the surface ceramization of aluminum alloy

Aluminum alloy has been widely used as a metal material. However, it is usually vulnerable to corrosion, so the protection of aluminum alloy surface is particularly important. At present, the commonly used methods of surface protection of aluminium alloys are anodic oxidation, plasma micro-arc oxidation, chemical oxidation and so on. In this experiment, chemical protective coatings were prepared by chemical oxidation of Aluminium 1100 and 6063 treated with H2O2 or KMnO4 solution. The results showed that the oxidation capacity of H2O2 solution from 3% concentration to 15% concentration to Al1100 was successively enhanced. Moreover, the ceramic coating produced when the concentration of H2O2 is 12%-15% has a better effect, and the structures are cauliflower, concave and convex, and hydrophobic. It is expected that the surface has lotus leaf effect.

Tailoring the structure of supported δ-MnO2 nanosheets to raise pseudocapacitance by surface-modified carbon cloth

Coupling electrode composed of carbonaceous materials and metal oxides can effectively raise pseudocapacitance; however, due to the weak interaction between carbonaceous materials and metal oxides, structural control of the resultant coupling electrode remains a great challenge. Herein, surface-modified carbon cloth (SMCC), which is obtained by carbonizing the hydrothermal products of cetyltrimethylammonium bromide and glucose solution on carbon cloth (CC), is employed to regulate in-situ growth of δ-MnO2 in a KMnO4 and H2SO4 solution at hydrothermal condition. Structural characterizations indicate that surface modification renders SMCC to possess an oxygen-species-rich superhydrophilic surface, which in turn enables the supported δ-MnO2 to form the dense ultrathin nanosheets and abundant oxygen-vacancy (Vo) structure. Electrochemical tests demonstrate that the MnO2/SMCC can exhibit a specific capacitance of 508 F g−1 (792.5 C g−1) at 1 A g−1 under working potential range from −0.3 to 1.26 VAg/AgCl in three-electrode system, outperforming previously-reported δ-MnO2-based materials. Further, the detailed structural investigations identify that the oxygen species on SMCC dominate the generation of Vo in δ-MnO2 by reducing thickness and interface bonding, and the Vo in δ-MnO2 improves the pesudocapacitance by promoting the transition of Mn2+ to Mn4+.

Compositional, thermal and morphological characterization of recycled and modified elastomers for inclusion in commercial cement mixtures

Elastomers are natural or synthetic polymers used in the automotive, mining, mold, assembly and other industries, due to their mechanical resistance in a wide temperature range from 60 °C to 320 °C; however, the waste generated is not disposed of properly, especially in the manufacture of tires, which generates environmental problems like inadequate final disposal, generation of toxic gases and public health problems; Therefore, in order to recycle these wastes, the present investigation modified elastomers superficially in order to produce strong adhesion with inorganic compounds like cement, through oxidation and sulfonation processes. For this purpose, NaOH and KMnO4 solutions were prepared at a concentration of 5% and then impregnated in saturated NaHSO3 solution. Subsequently, the modified elastomer was morphologically characterized by scanning electron microscope, thermogravimetrically by differential scanning calorimeter; compositionally by infrared spectroscopy, Raman spectroscopy, X-ray fluorescence, energy dispersive X-ray analysis and hydrophobic tests using contact angle techniques, in order to establish morphological and chemical compatibility with inorganic compounds. Results evidenced inclusion of functional groups OH, C = O and SO3, the reduction of carbon present in weak bonds and the presence of inorganic components such as potassium, sodium, manganese and sulfur were evident. The scanning electron microscope shows an increase in the roughness and contact surface of the elastomer as a function of the inclusion of polar functional groups by surface chemical treatment. These characteristics are to generate greater inclusion and compatibility of elastomers of an organic nature in inorganic compounds like cement matrices.

Synthesis and Catalytic Activities of Manganese Oxides Prepared by Precipitation Method: Effects of Mixing Modes of Reactants and Calcination Process

The two phases of manganese oxides are prepared by two different mixing modes using the same precipitation method from the solutions of KMnO4 dan maltose, resulting in marked different phase structures and catalytic activities. The oxides synthesized by adding dropwise of the maltose solution into KMnO4 solution (method A) resulted in the formation of layer manganese oxide birnessite, which turns into tunnel structured manganese oxide cryptomelane following the calcination at 600°C for 4 hours. The simultaneous addition of KMnO4 solution and maltose solution (method B) also produced birnessite before calcination, but remain unchanged as birnessite phase after calcination with cryptomelane as minor product. The samples without calcination obtained from method A posseses higher surface area and poor crystallinity compared to that with calcination. The catalytic test using Fenton-like Reaction for methylene blue (MB) degradation indicated the tremendeous difference in their catalytic activities for both samples without and with calcination. The birnessite catalysts (without calcination) prepared using method A show the highest activity and are able to degrade 93% methylene blue within 10 minute, much higher than other samples.

Photolithographic Mask Fabrication Process Using Cr/Sapphire Carriers

Elaboration of the technology of novel photolithographic masks fabricated on sapphire substrates for UV and DUV application was described. The main technological steps of mask fabrication as Cr metallization deposition, selection of resist for lithography and Cr layer etching were developed and reported. The etching of Cr films was carried out through resist mask. Detailed study of Cr layer etching process was performed using different solutions such as KMnO4, HCl and ceric ammonium nitrate-based solutions to obtain good-quality structures with the smallest possible undercut of Cr layer and smooth edge. The mask fabrication process was validated by fabrication of test structures of microelectronic device using photolithography technique.

Plasma-induced redox reactions synthesis of nanosized α-, γ- and δ-MnO2 catalysts for dye degradation

Mesoporous α- and δ-MnO2 with specific surface areas of 98 and 186 m2/g, were obtained via plasmachemical-reduction of KMnO4 solutions induced by flashing them with a gliding arc plasma operated at respectively high and low voltages. Correspondingly, γ- and δ-MnO2 with 48 and 289 m2/g, were obtained via plasmachemical-oxidation of Mn(CH3COO)3 solutions. At lower humid airflow, the plasma also led during the reduction of KMnO4 to changes of structure and morphology, and to increased specific surface areas. These changes are hypothesized to be due to a variation of the amount of radicals generated by the plasma along its creation parameters. Performances of the prepared catalysts were evaluated in the oxidation of Tartrazin Yellow (TY) chosen as a model dye polluting wastewaters. TY bleaching was significantly different from one plasma-synthesized material to another. α-MnO2, being the best of the plasma synthesized material appears to be recyclable and resistant to dissolution. This contribution confirms the importance of mastering the structure and texture of MnO2 catalysts during their synthesis. Gliding arc plasma is revealed as an easy and efficient method to achieve so.

Production of a carrier-free standard 56Mn source for the NRC manganese salt bath

The National Research Council (NRC) of Canada's primary method for emission rate for radionuclide neutron sources utilizes a manganese salt bath which was last calibrated in the 1960s. At that time, an NRC RaBe neutron source was used to irradiate a solution of calcium permanganate to take advantage of the Szilard-Chalmers effect in producing the bulk 56Mn material for standardization and calibration of the bath. When attempting to repeat this exercise, a small amount (~100 kBq) was produced. This amount was sufficient for the standardization process but did not yield enough material to calibrate the bath to a sufficient level of precision.Improvements upon the previous separation scheme adopted at NRC for the separation of the 56Mn from the bulk irradiated material included the rinsing of the 56Mn dioxide precipitate using a mixture of sulfuric acid and hydrogen peroxide. While these improvements made in the separation chemistry improved the yield of 56Mn extraction from 60% to above 95% the maximum amount of activity was still quite low. Hence in March of 2018, the SLOWPOKE-2 Facility at the Royal Military College in Kingston, ON, was used to irradiate three vials of KMnO4 in solution. An estimated 2 GBq was produced and sent to NRC, from which the extraction procedure recovered essentially all of the available 56Mn.The 56Mn was standardized using the 4πβ−γ anti-coincidence counting system and confirmed using the CIEMAT/NIST primary method. The resulting bulk material was certified with an uncertainty of 0.8% (k = 2). Minor quantities of 65Zn, 69mZn and 42K were unexpectedly observed but were in minute quantities so as not to affect the results of the standardization or calibration. The standardized 56Mn artifact was used to calibrate the Secondary Standard Ionizing Radiation Chamber System (SSIRCS) for a more rapid deployment of the calibrant in the future.

Polyvinylidene fluoride membrane modified by tea polyphenol for dye removal

Polyvinylidene fluoride (PVDF) membranes were surface-modified via a simple coating method for improvement of the hydrophilicity performance. In this work, TP/PEI/PVDF modified membrane was successfully prepared by using tea polyphenol as a multifunctional coating. The physicochemical properties of membranes were characterized by Fourier transform infrared spectroscopy, X-ray energy-dispersive spectrometry, X-ray photoelectron spectroscopy scanning electron microscopy and atomic force microscopy. The water contact angle, pure water flux and methylene blue rejection ratio of membranes were investigated in detail. Compared with the pristine membrane, the water contact angle of the modified membrane decreased to 48.8°, and the rejection ratios were increased to 95.2% when the modified membrane was used to separate methylene blue. In addition, the modified membrane showed excellent antifouling performance in the experiment, and the flux recovery ratio still reached 84.6% after three fouling/washing cycles. In the oxidation experiment, the modified membranes were immersed in KMnO4 solution for 6 h, and the results show that the water contact angle, pure water flux and methylene blue rejection of the modified membranes only have changed slightly. Therefore, this study could have a great potential for widening the application of membranes in the treatment of dye wastewater containing oxidants.

Soil infiltration capacity of chemical oxidants used for risk reduction of soil contamination

Chemical oxidation has been applied to remove soil contaminants and thereby reduce human and ecological risks from contaminated sites. However, few studies have been conducted on the natural infiltration of oxidant solutions into unsaturated soil. Moreover, the infiltration capacity of oxidant solutions at various concentrations in unsaturated soil has not yet been studied. This study investigated the natural infiltration tendency of oxidant solutions like hydrogen peroxide (H2O2), potassium permanganate (KMnO4), and sodium persulfate (Na2S2O8), in sand and sandy loam. Cumulative infiltration was recorded from a soil column equipped with a Mariotte reservoir. The infiltration rate, sorptivity, and unsaturated hydraulic conductivity were obtained from the cumulative infiltration results. Na2S2O8 showed the highest infiltration rate in both sand and sandy loam, and the infiltration of Na2S2O8 increased as the concentration was increased from 0.05 to 1%. However, the infiltration of KMnO4 and H2O2 solutions was governed more by chemical reaction behavior than by liquid physical properties or soil hydraulic properties. The production of oxides and gas due to reaction induced clogging in flow paths, resulting in less infiltration. Infiltration of H2O2 at concentrations greater than 0.5% was not observed in sand or sandy loam due to gas formation and swelling.

Controllable synthesis of MnO2 with different structures for supercapacitor electrodes

In this paper, MnO2 with four different structures (nanosandwiches, microsticks, nanowires and microflowers) are synthesized through varying reaction conditions, including the concentration of KMnO4 solution and hydrothermal reaction temperature. Through comparing experimental data, it can be concluded that the microstructure of MnO2 plays a vital role in electrochemical performance. Among the four structures, the microflower has the largest specific surface area for more electroactive sites, and thus demonstrates an excellent charge storage performance of 185 F/g at a current density of 0.5 A/g and cycling stability with a capacitance retention rate of 85% and a coulombic efficiency of nearly 100% after 10,000 charge-discharge cycles.

Synthesis and characterization of graphene oxide nanosheets

Abstract Graphite is a 3-dimension carbon based material made up of millions of layers of graphene. By the oxidation of graphite using strong oxidizing agents, oxygenated functionalities are introduced in the graphite structure which not only expand the layer separation, but also make the material get dispersed in water. This property enables the graphite oxide to be exfoliated in water using sonication, ultimately producing single or few layer graphene known as graphene oxide (GO). This remains as a very important property when mixing the material with ceramic or polymer materials and trying to improve their electrical and mechanical properties. In this work, Graphene Oxide nanosheets was synthesized by modified hummer’s method. Materials such as graphite power, H2SO4 and KMnO4 solution was used as precursors. The solution formed by the precursors after desired experimental conditions was filtered and washed. Then the suspension was centrifuged and dried which resulted in Graphene Oxide nanosheets. The synthesized samples were characterized by XRD, Raman, FTIR and SEM analyses.

Effect of surface treatments and filler loading on the properties of hemp fiber/natural rubber composites

The aim of this present work was to study the effect of surface treatment methods, i.e., silane and permanganate on curing characteristics, dynamic mechanical, mechanical morphological and thermal properties of hemp fiber filled natural rubber composites. Hemp fiber surfaces were pretreated with an alkali solution and followed by a KMnO4 solution or (3-triethoxysilylpropyl) tetrasulfide (Si69). After that, the chemical, physical and morphological properties of untreated and treated hemp fiber samples were investigated by attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. It was found that the KMnO4 and silane (Si69) treatments affected the surface characteristics of hemp fibers. The curing characteristics of the rubber composites, i.e., scorch and curing times increased with increased fiber loading, except for 15 parts per hundred of rubber (phr) fiber level. The curing characteristics improved with the addition of KMnO4 or silane treated hemp fiber compared to unfilled natural rubber composites. At 5 phr fiber loading, it was found that silane treated hemp fiber filled natural rubber composite showed greater tensile strength and crosslink density in comparison with KMnO4 treated and untreated hemp fiber filled rubber composites. Good interface interaction between the silane treated hemp fiber and rubber matrix was observed in SEM images. Additionally, the thermal stability of rubber composites was unaltered with the incorporation of KMnO4 or silane treated hemp fibers.

Formation of ZnO films using the SILAR method

The thin ZnO films were deposited using the successive ionic layer adsorption and reaction (SILAR) method. The morphology, structure and composition of the thin ZnO films were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The optical properties of the thin ZnO layers, which were deposited onto glass substrates, were investigated using ultraviolet–visible spectrophotometry (UV/Vis). It was found that the optical properties of the ZnO films depend on the composition of anionic precursor solutions, which were used for deposition of the ZnO layers. Moreover, the highest band gap energy of 3.86 eV was obtained for the ZnO layer when the 0.026 mol l–1 Na2B4O7 + 0.002 mol l–1 KMnO4 solution was used as the anionic precursor solution for the deposition of ZnO layers.

Adsorption characteristics of volatile organic compounds onto lyocell-based activated carbon fibers

Fibrous adsorbents, such as activated carbon fibers (ACF) have acknowledged advantages of rapid adsorption rate and ease of modification compared with granular and powdered adsorbents. Based on the surface modification of lyocell-based ACF, we observed different surface characteristics of ACF samples with variation in the mixing ratio and impregnation time of H3PO4, NaCl, and KMnO4 solution. For an engineering application, we also explored the adsorption characteristics of thus-produced ACF samples onto volatile organic compounds (VOCs). Isothermal adsorption experiments were performed using toluene and benzene as adsorbates. Results indicate that both physical and chemical surface properties have an effect on the adsorption of volatile organic compounds (VOCs).