Mn Oxide Films Research Articles

Three Distinctive Steps for Heterogeneous Nucleation of Tunnel-Structured Mn Oxide on Quartz under Light Exposure.

Natural manganese (Mn) oxide coatings, resulting from the heterogeneous nucleation on foreign substances, have garnered interest based on their importance in the reaction with organic substances and in environmental systems. However, the heterogeneous nucleation of the natural Mn oxide coatings still remains elusive. Here, via fast photochemical oxidation of Mn2+(aq), we show that Mn(IV) oxide nuclei form and aggregate on quartz in three distinct successive stages: (i) a nanocrystalline film of unaligned grain forms, (ii) nanoislands develop on the film, and (iii) nanorods form on the nanoislands. Each stage has different crystalline structures and forms by aligned attachment of nanoscale precursors on the preceding surface. Crystal lattice analyses confirm the crystalline development, from the short-range order of the Mn oxide film to the long-range order of the nanorods. Also, the heterogeneous nucleation observed in this work produced groutellite-like tunnel structures of Mn oxide on quartz. This revealed pathway of the heterogeneous nucleation can offer a new perspective on the variety of poorly crystalline structures of natural Mn oxides found in the environment, which can affect elemental redox cycles, contaminant sequestration and removal, and soil carbon storage.

In-situ synthesis and performance evaluation of novel color coatings for galvanized steel

Traditional hot-dip galvanized coatings, typically single-silver in color, present increasing aesthetic challenges in diverse applications, while prevailing organic coating methods involve complex processes with high energy consumption and pollution emissions. In this study, a novel hot-dip process for in-situ synthesis of color coating on steel was proposed, capable of producing various uniform color coating. The microstructure of color coatings on steel was systematically examined, and an assessment of their corrosion and weather resistance was conducted. The results demonstrate the sequence of typical color variation is gold, purple, blue, cyan, red, green, and grey. By controlling the immersion temperature range, and regulating the final stable color of the oxide film. The coloration mechanism mainly is attributed to the light interference on the Mn oxide film. The cyan and brown coatings mainly consist of the dense rod-like ζ-FeZn13 phases which provide a structural foundation for corrosion resistance. Furthermore, the brown coating exhibited excellent weather resistance.

Vertically aligned MnO2 nanosheet electrode of controllable mass loading, counter to nanoparticulate carbon film electrode for use in supercapacitor

Abstract MnO2 electrode with nanosheet morphology, counter to carbon electrode in a supercapacitor shows promise for energy storage application. In this investigation, film electrodes of Mn-oxide and carbon with much higher and controllable mass loadings are grown by electrospray of respective precursors on Ni foam substrates. The electrospray deposition is conducted at room temperature to simplify the procedure. The evolution of nanosheet morphology of the Mn-oxide film due to electrochemical oxidation of Mn (II, III) to Mn (IV) valence state, implemented by multiple cyclic voltammetry (mCV) cycles on the calcined film is studied here. The CV and the charge-discharge curve show near-ideal behaviour with 0.5 M K2SO4 as electrolyte in asymmetric set-up, logging a capacitance of 115 F g−1 at 1 mA cm−2. The capacitance is retained to 93% of initial value after 5000 cycles at 20 mA cm−2. The specific energy and power are found to the levels of 62.3 Wh kg−1 and 5.2 kW kg−1 respectively, which appear promising in comparison to the values, reported in literature. The increase in calcination temperature from 350 °C to 500 °C resulted in interspersed agglomeration within nanosheet morphology after mCV cycles, and consequent loss of capacitance.

Preparation and Characterization of Transparent Conducting Mn and Ni-Doped Zinc Oxide Films Prepared by Successive Ionic Layer Adsorption and Reaction Method

This paper reported the preparation and characterization of transparent conducting oxide thin films. Undoped and doped ZnO thin films were prepared by SILAR method. The micro-structural and optical properties were investigated. X-ray diffraction patterns revealed that the prepared thin films are polycrystalline in nature and has a hexagonal structure. The micro-structural properties of prepared thin films were calculated and crystallite size tends to changes due to dopant. The texture coefficients have been evaluated and found to be greater than unity revealing high texturing of the film. Undoped and Mn-doped ZnO prefer the orientation of (002) but Ni-doped ZnO and Mn and Ni co-doped ZnO prefers (100) orientation. The transmittance spectra of pure and transition metal-doped films were plotted against UV-Vis-NIR region and found that the transmittance changes with dopant and nature of doping. The optical band gap values were found to be in the range of 3.00–3.39 eV. The optical constants such as extinction coefficient, refractive index, dielectric constant and optical conductivity were examined.

A 2-nm-Thick Mn Oxide on a Nitrogen-Stuffed Porous Carbon-Doped Organosilica as a Barrier of Cu Films

An ultrathin (e.g., ≤ 2 nm) barrier is needed for fabricating Cu interconnects associated with porous low-k (p-SiOCH) dielectrics with a high aspect ratio trenches/vias in the ultra large scale integrated circuits. To implement successfully the ultrathin Mn oxide barrier on the p-SiOCH dielectric for Cu interconnection, understanding is needed of how the Mn oxide is formed. This study investigated a 2-nm-thick Mn oxide film, deposited by sputtering with a biased-filter intermediating, as the barrier layer to prevent Cu from diffusion. Phase formation of the as-deposited Mn oxide was examined by X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy to confirm the formation of Mn2O3. The experimental results indicated that the formation of Mn2O3 barrier is highly effective in preventing the Cu film from diffusion and agglomeration. Thermal stability of the Cu film increased up to 550°C, 250°C greater than the p-SiOCH dielectric without the Mn2O3 film, when combining the nitrogen-stuffed treatment on the p-SiOCH dielectric and annealed the Mn2O3 before the Cu deposition. The structures of Mn2O3 barrier and p-SiOCH dielectric after nitrogen-stuffing treatments were analyzed to evaluate their applicability in Cu interconnects.

Effect of oxidation state of manganese in manganese oxide thin films on their capacitance performances

Mn oxides, which are relatively low cost with low toxicity and environmental friendly, are regarded as one of the most promising candidate materials for pseudo-capacitors. The oxidation state of Mn ion in the oxides (e.g.: +2, +3, +4, +6 and +7) is a very critical factor affecting the specific capacitance. Three Mn oxide films (crystalline Mn2O3, amorphous Mn2Ox, x ∼ 3.74 and crystalline Mn3O4) with different oxidation states of Mn were prepared using a pulsed laser deposition (PLD) method, which show different capacitance performances (crystalline Mn2O3 film > amorphous MnOx film > crystalline Mn3O4 film). X-ray absorption near edge structures (XANES) is applied to investigate the electronic structures of these films. Mn K-edge and L3,2-dege XANES results confirm that the bulk of the amorphous MnOx film is composed of MnO2 and Mn2O3 with Mn4+/Mn3+ ratio of about 3:1. Total electron yield (TEY) XANES at the Mn L3,2-edge which is surface-sensitive, suggests that the amorphous film also contains some Mn3O4 on the surface, which is proposed to be the reason why the amorphous MnOx film shows moderate pseudo-capacitance behavior in between the pure Mn2O3 and Mn3O4 films.

New insights into graphite paper as electrocatalytic substrate for oxygen evolution reaction

Designing highly efficient electrocatalysts for oxygen evolution reaction is important to meet the requirement of various renewable energy storage and conversion devices. Generally, the performance of OER catalysts can be significantly improved by synergistic action of the underlying conductive substrate. In this work, a commercial graphite paper was used as a facile substrate with catalytic activity. Graphite paper produced 10mAcm−2 at an overpotential of 447mV with a Tafel slope of 62mVdec−1. By depositing NiFe hydroxide or Mn oxide film onto the graphite paper, the electrode presented a superior activity for water oxidation, which was believed to be synergistically contributed by their available electrochemically active sites associated with the deposited film and the active substrate. High activities were also accompanied by remarkable durability at large current density levels. Our results illustrated a guideline to the design of inexpensive and highly active composite electrode for water oxidation.

Hierarchical Metal Oxide Topographies Replicated from Highly Textured Graphene Oxide by Intercalation Templating.

Confined assembly in the intersheet gallery spaces of two-dimensional (2D) materials is an emerging templating route for creation of ultrathin material architectures. Here, we demonstrate a general synthetic route for transcribing complex wrinkled and crumpled topographies in graphene oxide (GO) films into textured metal oxides. Intercalation of hydrated metal ions into textured GO multilayer films followed by dehydration, thermal decomposition, and air oxidation produces Zn, Al, Mn, and Cu oxide films with high-fidelity replication of the original GO textures, including "multi-generational", multiscale textures that have been recently achieved through extreme graphene compression. The textured metal oxides are shown to consist of nanosheet-like aggregates of interconnected particles, whose mobility, attachment, and sintering are guided by the 2D template. This intercalation templating approach has broad applicability for the creation of complex, textured films and provides a bridging technology that can transcribe the wide variety of textures already realized in graphene into insulating and semiconducting materials. These textured metal oxide films exhibit enhanced electrochemical and photocatalytic performance over planar films and show potential as high-activity electrodes for energy storage, catalysis, and biosensing.

Effect of Mn addition on corrosion properties of biodegradable Mg-4Zn-0.5Ca-xMn alloys

The corrosion properties of biodegradable Mg–4Zn–0.5Ca–xMn alloys (x = 0, 0.4, 0.8 wt%) in Hank's solution were investigated. According to the electrochemical measurements, the corrosion resistance of the alloys was effectively improved by Mn addition. In addition, the analysis of corroded surface with high resolution transmission electron microscopy (HR-TEM) and time of flight secondary ion mass spectrometry (ToF-SIMS) revealed that the depth of the corrosion product was decreased by Mn addition. It was observed that the microstructural changes had little effect on corrosion properties and Mn oxide film acts as a helpful barrier against chloride ions penetration.

Spin-Coated vs. Electrodeposited Mn Oxide Films as Water Oxidation Catalysts.

Manganese oxides (MnOx), being active, inexpensive and low-toxicity materials, are considered promising water oxidation catalysts (WOCs). This work reports the preparation and the physico-chemical and electrochemical characterization of spin-coated (SC) films of commercial Mn2O3, Mn3O4 and MnO2 powders. Spin coating consists of few preparation steps and employs green chemicals (i.e., ethanol, acetic acid, polyethylene oxide and water). To the best of our knowledge, this is the first time SC has been used for the preparation of stable powder-based WOCs electrodes. For comparison, MnOx films were also prepared by means of electrodeposition (ED) and tested under the same conditions, at neutral pH. Particular interest was given to α-Mn2O3-based films, since Mn (III) species play a crucial role in the electrocatalytic oxidation of water. To this end, MnO2-based SC and ED films were calcined at 500 °C, in order to obtain the desired α-Mn2O3 crystalline phase. Electrochemical impedance spectroscopy (EIS) measurements were performed to study both electrode charge transport properties and electrode–electrolyte charge transfer kinetics. Long-term stability tests and oxygen/hydrogen evolution measurements were also made on the highest-performing samples and their faradaic efficiencies were quantified, with results higher than 95% for the Mn2O3 SC film, finally showing that the SC technique proposed here is a simple and reliable method to study the electrocatalytic behavior of pre-synthesized WOCs powders.

Crystallographically-oriented Mn oxide nanorod/nanowire arrays electrodes

The fabrication of stainless steel electrode decorated with Mn oxide nanostructure arrays via a facile two-step solution-based method was present. Amorphous Mn oxide films were firstly electrodeposited, and then hydrothermally transformed into Mn oxide nanostructure with different crystal nature. A cation induced growth mechanism was proposed and the effect of stainless steel substrate was discussed. Supercapacitor electrodes based on the obtained nanostructured were thoroughly characterized. An increase in specific capacitance from 79Fg−1 to 301Fg−1 at 1Ag−1 after hydrothermal treatment was achieved, owing to the unique open-spaced array architecture and self-supported binder-free electrode. In addition, the Mn oxide electrode showed good structural activity in electrochemical degradation of MB solution. This preparation process offers a new way for the design and synthesis of self-supported metal hydroxide and oxide nanoarray electrode with the facile tuning method, which is promising for electrochemical energy storage, catalysis, and gas sensing applications.

Photoemission study of the identification of Mn silicate barrier formation on carbon containing low-κ dielectrics

In this study X-ray photoelectron spectroscopy (XPS) has been used to characterize manganese silicate Cu diffusion barrier layer formation on a range of ultralow-κ (ULK) carbon doped oxide (CDO) layers. Ultra-thin Si and Mn oxide films were deposited in order to provide accurate binding energy (BE) references for the Si 2p and O 1s core levels of the dielectric materials. The results indicate that there is a strong correlation between carbon content in the CDO films and the BE position of both the Si 2p and O 1s core level peaks. Furthermore, it has been shown that the full width half maximum (FWHM) of these peaks are significantly larger than those observed in SiO2 leading to complications in the analysis and identification of barrier layer formation on these low-κ substrates. In a separate experiment, the deposition and high temperature annealing of thin fully oxidized Mn layers (MnOy, where y⩾1) on these ULK CDO substrates suggests the formation of an interface layer consistent with MnSiO3 based on analysis of both the O 1s and Mn 2p core level spectra. It is also shown that the use of oxidized Mn films tend to minimize the formation of Mn carbide within the barrier layer region in agreement with previous studies on other CDO substrates.

Electrochemical Deposition of Manganese Oxides on Carbon Nanosheets

We report on electrodeposition of thin Mn-oxide films on Carbon Nanosheets (CNS) and explore the potential of this high-surface area Mn-oxide/nanocarbon for applications in fast charge/discharge thin-film lithium ion micro-batteries. We examined physical-chemical properties of Mn-oxide/CNS composite films electrodeposited on both flat substrates and high-aspect-ratio Si pillars coated with TiN and CNS. In addition to electrochemical methods, such as cyclic voltammetry (CV), Mn-oxide/CNS structures were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy (RS).

Manganese Oxide Anodized from Manganese Films Electrodeposited at Different Cathodic Currents and its Capacitive Performance

Nanostructured manganese oxide films were obtained by electro-oxidation of manganese films electrodeposited at two typical cathodic currents of 65 mA cm-2 (EDM-65 oxide) and 150 mA cm-2 (EDM-150 oxide) from sulfate solutions with additives. Obtained Mn oxide films were studied by scanning electron microscope, X-ray photoelectron spectroscopy, cyclic voltammetry and AC impedance. SEM study revealed that the Mn oxide films were mesoporous nanostructures on the EDM-150 oxide surface, while the EDM-65 oxide coating is homogeneous and compact. XPS results indicate that EDM-150 oxide had a higher content of anhydrous Mn oxide and structure water, which means that it had more anhydrous characteristics as compared to EDM-65 oxide. It was shown that porous nanostructured films showed good capacitive behavior for applications in electrochemical supercapacitors. The porous nanostructured films prepared at 150 mA cm-2 showed higher specific capacitance (SC) compared to the SC of the EDM-65 oxide films. The highest SC of 148 F g-1 in a voltage window of 0.8 V was obtained in 0.1 M Na2SO4 solutions at a scan rate of 25 mV s-1.

Electrochemical Deposition of Manganese Oxides on Carbon Nano-Sheets

We have electrodeposited Mn-oxide films on Carbon nano-sheets (CNS), thin (< 10 nm) vertical standing graphitic sheets, having in mind potential energy storage applications of this high-surface-area composite structure. We examined the deposition kinetics of Mn-oxides and physical-chemical properties of Mn-oxide/CNS composite films on substrates ranging from flat to high-aspect-ratio (HAR) Si pillars. We have also explored the possibility to integrate this process into production line typical for microelectronics industry.CNS was grown using RF-PECVD technique [1] onto both blanket 200 mm Si wafers coated with 70 nm thick PVD TiN, and wafer pieces with high-aspect-ratio Si pillars coated with 10 nm ALD TiN. CNS was grown on TiN from CH4/H2mixture [1] to a height of approximately 1 µm.Anodic electrodeposition of Mn-oxide, often also termed electrolytic manganese-dioxide (EMD), was performed on both blanket CNS/TiN/Si and patterned CNS/ALD TiN/Si samples using 0.3 M MnSO4·xH2O + 0.55 M H2SO4aqueous electrolyte. Plating experiments were performed using a three-electrode clip-on Teflon cell connected to a computer controlled Autolab potentiostat PGSTAT100 (Metrohm), with Ag/AgCl as a reference electrode (RE) and Pt mesh as a counter electrode (CE). Characterization of EMD/CNS films was performed using Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and X-ray photoelectron spectroscopy (XPS). Figure 1 shows SEM images of as-grown CNS (a) and EMD coverage as a function of deposition current (b and c). EMD is plated galvanostatically, and potential-time responses were analyzed to help optimize deposition parameters for desired film thickness and structural properties. The analysis was based on the theories of galvanostatic nucleation and growth [2], and proposed reaction mechanisms during galvanostatic deposition of EMD [3]. Further surface area enhancement was attempted through EMD/CNS deposition on HAR Si pillars coated with 10 nm ALD TiN. Figure 2 shows HAR ALD TiN/Si pillars before and after CNS and EMD deposition, respectively. CNS coating was applied to various ALD TiN/Si structures having different aspect ratios and spacing between pillars, and then followed by EMD deposition.A typical Raman spectrum of our EMD/CNS structure, shown in Figure 3, contained broad features in the range 450 to 730 cm-1 where characteristic EMD peaks are expected [4 and references therein], and showed characteristic CNS peaks in 1000 to 3500 cm-1range [5]. Thanks to its sensitivity to local structure/symmetry Raman spectroscopy proved to be a useful tool for characterization of disordered and defective EMD. We were able to detect EMD structural changes upon annealing at various temperatures and lithiation in anhydrous propylene carbonate solvent with 1 M LiClO4, and also monitor the effects of plating and post-plating processing on CNS.

Effects of manganese addition on microstructures and corrosion behavior of hot-dip zinc coatings of hot-rolled steels

In the present work, the Zn coatings of hot-rolled steel sheets with different Mn additions were prepared by hot dipping process. The effects of Mn addition on the microstructures and corrosion resistances of the hot-dip Zn coatings were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffractometry (XRD). The Mn distribution in δ-layer is lower than that of ζ-layer. Mn addition could promote the growth of δ-layer of the coating and inhibit the growth of the columnar ζ phase which morphology was changed to discontinuous phase. It is also found that the surface color of Zn–Mn coating varies with the dipping temperatures. Such phenomenon is supposed to be attributed to the optical interference effect of the Mn oxide film formed on the coating surface. For the corrosion behavior, the as-dipped and ζ layer-exposed Zn coatings were subjected to both Tafel polarization measurements and electrochemical impedance spectroscopy (EIS) tests in 3.5% NaCl solution. The results indicate that Mn addition enhances the corrosion resistance of the as-dipped coatings. The dense corrosion products formed on the top η layer of the Zn–Mn coatings after Tafel polarization corrosion are assumed to inhibit the further corrosion of the coating. However, minor effects of Mn addition to the anti-corrosion performance of ζ layer were noticed.

High supercapacitive performance of sol–gel ZnO-doped manganese oxide coatings

In the present study, ZnO-doped manganese (Mn) oxide coatings were prepared as a function of ZnO content (≤40at.%) by sol–gel process. After post heat treatment at 300°C, the influences of ZnO on the microstructural characteristics and pseudocapacitive performance of the Mn-oxide films were investigated. The structural analyses identified the sol–gel ZnO-doped Mn-oxide powder as a tetragonal Mn3O4 phase with a nanocrystalline structure. The formation of ZnxMn3−xO4 spinel occurred when ZnO content was ≥20at.%. The crystallite size of Mn-oxide powder increased when a small amount of ZnO was added, and then decreased when larger amounts were added. The cyclic voltammetry (CV) data showed that the specific capacitance (SC) of the Mn-oxide film in 1M Na2SO4 electrolyte can be increased from 236F/g to 301F/g at 25mV/s by doping with 10at.% ZnO. The formation of spinel tended to inhibit the SC value of the films. After activation of the Mn-oxide film, however, a relatively high cycling efficiency of >85% was obtained for all compositions after 1200 CV cycles.

Self-assembled manganese oxide structures through direct oxidation

The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures.

Surfactant-Induced Electrodeposition of Layered Manganese Oxide with Large Interlayer Space for Catalytic Oxidation of Phenol

Electrolysis of aqueous Mn2+ ions at an anodic potential of +1.0 V (vs Ag/AgCl) in the presence of cationic surfactants led to the formation of multilayered manganese oxides intercalated with the surfactant molecules. Their interlayer spacings are much larger than that (∼0.7 nm) of conventional birnessite; i.e., 3.1 nm with cetyltrimethyl ammonium (C16) and 2.4 nm with dodecyltrimethyl ammonium (C12). According to XPS analysis, the molar ratio of C16 to MnO2 was estimated to be 0.74, in which the C16 fraction of 0.42 is associated with Cl− anions and the other (0.32) interacts with negative charges on the Mn oxide layer. C16 surfactants accommodated between the Mn oxide layers were not ion-exchanged with Na+ ions in solution but extracted with ethanol. Anodic oxidation of the C16-intercalated Mn oxide (C16/MnO2) film took place in an aqueous Na2SO4 solution, accompanied with insertion of SO42- anions for charge compensation, and not deintercalation of the surfactants. As a result, the layered structure wi...

Doping of Cobalt into Multilayered Manganese Oxide for Improved Pseudocapacitive Properties

Anodic electrodeposition of layered manganese oxides has been carried out in a solution heated at various bath temperatures from 25 to . The crystallinity of the deposits increased with an increase in the bath temperature. Although ions were not involved in the deposition reaction at room temperature, at the elevated temperature the addition of gave rise to a catalytic current suggesting the formation of Co/Mn mixed oxide. No new X-ray diffraction peaks appeared with the insertion of ions in the structure, but their addition caused broadening of the peaks due to the Mn dioxide phase. This indicates that Co ions are not accommodated in the interlayer space but are well dispersed within the layers composed of edge-shared octahedra. The Co-doped Mn oxide film thus obtained exhibited much better pseudocapacitive performance than the undoped counterpart.