Metal Oxide Coatings Research Articles

Environmentally Benign Solution-Based Procedure for the Fabrication of Metal Oxide Coatings on Metallic Pigments.

Aluminum pigments were coated with Fe2O3 and CuO by solution‐based thermal decomposition of the urea nitrate compounds hexakisureairon(III)nitrate and tetrakisureacopper(II)nitrate. The deposition process was optimized to obtain homogeneously coated aluminum pigments. The growth of the surface coatings was controlled by investigation with scanning electron microscopy, energy dispersive X‐ray spectroscopy and static light scattering as well as infrared, X‐ray diffraction and thermogravimetric analysis. The iron precursor showed an incomplete decomposition in solution, incorporating traces of urea molecules inside the coatings while the copper precursor showed complete dissociation accompanied by in situ formation of amine complexes. The amount of organic residues resulting from ligand fragments in the final oxide coatings could be reduced to 22 % for the iron oxide and 12 % for the copper oxide by further temperature treatment in solution (259 °C). Colorimetric investigations of the obtained pigments revealed an excellent hiding power, outperforming the pigments used in current state‐of‐the‐art formulations.

Heterogeneous Metal Oxide Coatings with Magnetoactive Nickel, Cobalt, and Iron Phases Formed by the Method of Pulsed Microplasma Oxidation for Radiation Absorption in the Middle and Near-IR Regions

Heterogeneous coatings with high ability to absorb electromagnetic radiation in the middle (4000–400 cm–1) and near-IR regions (11000–2000 cm–1) are formed by the method of pulsed microplasma oxidation on aluminum and titanium alloys in inorganic electrolytes containing nickel, cobalt, and iron compounds. The electromagnetic radiation absorption is provided not only by the oxide coating itself, but also mainly by the heterogeneous metal particles of nickel, cobalt, and iron forming a dispersed metal phase and having magnetic properties that are incorporated into the coating pores by the method of microplasma oxidation under the action of a constant magnetic field. The influence of the electrolyte compositions and of the parameters of pulsed microplasma oxidation on the structure, composition, and radiation absorption properties of coatings is studied. It has been revealed that coatings formed in a phosphate-borate electrolyte with addition of nickel at a voltage of 300 V, a pulse duration of 100 μs, and a process duration of 5 min have the best absorption ability.

Nanoengineered Organic Electrodes for Highly Durable and Ultrafast Cycling of Organic Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have become increasingly important as next-generation energy storage systems for application in large-scale energy storage. It is very crucial to develop an eco-friendly and green SIB technique with superior performance for sustainable future use. Replacing the conventional inorganic electrode materials with green and safe organic electrodes will be a promising approach. However, the poor electrochemical kinetics, unstable electrode-electrolyte interface, high solubility of the electrodes in the electrolyte, and large amount of conductive carbon present great challenges for organic SIBs. In this study, the issues of organic electrodes are addressed through atomic-level manipulation of these organic molecules using a series of ultrathin (Å-level) metal oxide coatings (Al2 O3 , ZnO, and TiO2 ). Uniform and precise coatings on the perylene-3,4,9,10-tetracarboxylicacid dianhydride by gas-phase atomic layer deposition technique shows a stable interphase, enhanced electrochemical kinetics (71C, 10 A g-1 ), and excellent stability (89%-500 cycles) compared to conventional organic electrode (70%-200 cycles). Further studies reveal that the chemical stability of the metal oxide coating layer plays a critical role in influencing the redox behavior, and improving kinetics of organic electrodes. This study opens a new avenue for developing high-energy organic SIBs with performance equivalent to inorganic counterparts.

Electrochemical evaluation of IrO2–Ta2O5-MWCNT-coated anodes with different pretreatments of titanium substrate

Mixed metal oxide coatings of IrO2–Ta2O5 modified with multiwalled carbon nanotubes (MWCNTs) were applied on Ti anodes by thermal decomposition method. Effects of nanoporosities film formation and rough structures were examined on the electrocatalytic activity and stability of the anodes. In this respect, the electrochemical response of samples subjected to different pretreatments, including the formation of TiO2 nanotubes by anodizing and etching in 20% oxalic acid, was investigated by cyclic voltammetry, potentiodynamic polarization, galvanostatic, and impedance spectroscopy. IrO2–Ta2O5-MWCNT coating on the etched and anodized substrate formed a compact morphology with fewer cracks. Microstructural examination of coatings showed that the distribution of active IrO2 particles was changed by anodizing pretreatment. The charge transfer resistance of dimensionally stable electrode with anodizing surface preparation was approx. 32% lower than the etched sample due to the porous nature of the Ti/coating interface. The addition of MWCNT to IrO2–Ta2O5 coating on the etched Ti anode extended its service life by ~ 70%, while the formation of TiO2 nanotubes as the result of anodizing surface pretreatment reduced the electrode stability.

Double stabilization of silver molecular clusters in thin films

The evolution of spectral and luminescent properties of Ag-containing composite coatings prepared by liquid technique has been studied. Double stabilization allows forming thin oxide films containing luminescent small Agn (n < 5) molecular clusters using the liquid technique. These clusters are non-stable intermediate products during the formation of Ag nanoparticles from the ions and neutral atoms. It was found that small luminescent Agn molecular clusters (n < 5) formed in the solutions at the presence of polyvinylpyrrolidone (PVP) remain in PVP/metal nitrates composite coatings and in the calcined metal oxide coatings. Spatial separation of small Ag molecular clusters in the coatings by the oxide nanoparticles of ZnO and MgO prohibits silver clusters growth and non-luminescent silver nanoparticles formation and allows saving coatings’ luminescence properties during thermal treatment.

Surface modification techniques of titanium and titanium alloys for biomedical dental applications: A review

The materials used for biomedical applications include metal and their alloys, polymers, and ceramics. Of these, titanium (Ti) and titanium alloys are widely used as implant materials owing to its superior corrosion resistance and high mechanical strength. Although titanium has several advantages, being biologically inert, it cannot osseointegrate with the human cells. Thus, the surface of the titanium implant has a very important role, as it determines the rate of osseointegration and the success of the implant. The main objective of this review is to offer a thorough and detailed description of the most promising techniques used for the surface modification of titanium dental implants. A systematic classification of these methods is provided, followed by their advantages. Mechanical methods like acid etching and grit blasting, hydrogen peroxide treatment, acidic treatment, nitride coatings, hydroxyapatite coatings, metal oxide coatings and silver coatings have been analyzed and selected for this review. These methods have been experimentally proven to enhance the osseointegration rate, improving the biocompatibility and stability as well as the antibacterial properties of the implants. Thus, the surface modification of the titanium implant surface significantly improves the properties of the implant. However, further research is necessary to study the implant surface and the human cell interface in more detail and develop new surface modification techniques to manufacture implants with superior properties.

Role of Surface Acidity in the Surface Stabilization of the High-Voltage Cathode LiNi0.6Mn0.2Co0.2O2.

Metal oxide coatings have been reported to be an effective approach for stabilizing cathode interfaces, but the associated chemistry is unclear. In this work, thin films of TiO2, ZnO, and Cr2O3, which have different surface acidities/basicities, were used to modify the surface chemistry of LiNi0.6Mn0.2Co0.2O2 and study the acidity’s role in the cathode/electrolyte interphase composition and impedance under high-voltage cycling (4.5 V vs Li/Li+). Cathodes with more acidic surfaces provided higher initial specific capacity and capacity retention with cycling. More basic surfaces had higher initial impedance and greater impedance growth with cycling. These differences appeared to depend on the degree of LiPF6 salt decomposition at the interface, which was related to acidity, with more neutral surfaces having a LiF/LixPOyFz ratio close to unity, but basic surfaces had substantially more LiF. This chemistry was more significant than the cathode electrolyte interphase (CEI) thickness as the more acidic surfaces formed a thicker CEI than the basic surface, resulting in better capacity retention. These results suggest that the Brønsted acidity of cathodes directly influences electrolyte degradation, ion transport, and thus, cell lifetime.

Direct Electrochemical Deposition of Transparent Metal Oxide Thin Films from Polyoxometalates

Transition metal oxide coatings, owing to their unique combination of optoelectronic, electrochemical, and chemical properties, are at the forefront of functional thin films across diverse technolo...

Improving the Stability of Lithium Metal By Porous Metal Oxide Coating

Medium and large battery technology for energy storage devices or electric vehicles requires long life times and low cost as well as excellent safety. As a next generation high energy density type secondary battery, a lithium ion battery has been developed. However, when lithium metal cathodes is used, a redox reaction occurs at the interface between the electrode surface and the electrolyte, and lithium ions are eluted and lithium electrodeposits are concentrated. This phenomenon causes a problem that dendrite grows and causes an internal short circuit of the battery.In this study, metal oxide nanoparticles were coated to form a porous layer on the surface of lithium metal for suppressing dendrite growth and interfacial transport of lithium ions during charging/discharging. The porous metal oxide coated Li metal unit cell showed an improvement of life times with maintaining the initial potential difference during charging/discharging.

Continuous and Segmented Semiconducting Fiber‐like Nanostructures with Spatially Selective Functionalization by Living Crystallization‐Driven Self‐Assembly

AbstractFiber‐like π‐conjugated nanostructures are important components of flexible organic electronic and optoelectronic devices. To broaden the range of potential applications, one needs to control not only the length of these nanostructures, but the introduction of diverse functionality with spatially selective control. Here we report the synthesis of a crystalline‐coil block copolymer of oligo(p‐phenylenevinylene)‐b‐poly(2‐vinylpyridine) (OPV5‐b‐P2VP44), in which the basicity and coordinating/chelating ability of the P2VP segment provide a landscape for the incorporation of a variety of functional inorganic NPs. Through a self‐seeding strategy, we were able to prepare monodisperse fiber‐like micelles of OPV5‐b‐P2VP44 with lengths ranging from 50 to 800 nm. Significantly, the exposed two ends of OPV core of these fiber‐like micelles remained active toward further epitaxial deposition of OPV5‐b‐PNIPAM49 and OPV5‐b‐P2VP44 to generate uniform A‐B‐A and B‐A‐B‐A‐B segmented block comicelles with tunable lengths for each block. The P2VP domains in these (co‐)micelles can be selectively decorated with inorganic and polymeric nanoparticles as well as metal oxide coatings, to afford hybrid fiber‐like nanostructures. This work provides a versatile strategy toward the fabrication of narrow length dispersity continuous and segmented π‐conjugated OPV‐containing fiber‐like micelles with the capacity to be decorated in a spatially selective way with varying functionalities.

Continuous and Segmented Semiconducting Fiber-like Nanostructures with Spatially Selective Functionalization by Living Crystallization-Driven Self-Assembly.

Fiber-like π-conjugated nanostructures are important components of flexible organic electronic and optoelectronic devices. To broaden the range of potential applications, one needs to control not only the length of these nanostructures, but the introduction of diverse functionality with spatially selective control. Here we report the synthesis of a crystalline-coil block copolymer of oligo(p-phenylenevinylene)-b-poly(2-vinylpyridine) (OPV5 -b-P2VP44 ), in which the basicity and coordinating/chelating ability of the P2VP segment provide a landscape for the incorporation of a variety of functional inorganic NPs. Through a self-seeding strategy, we were able to prepare monodisperse fiber-like micelles of OPV5 -b-P2VP44 with lengths ranging from 50 to 800 nm. Significantly, the exposed two ends of OPV core of these fiber-like micelles remained active toward further epitaxial deposition of OPV5 -b-PNIPAM49 and OPV5 -b-P2VP44 to generate uniform A-B-A and B-A-B-A-B segmented block comicelles with tunable lengths for each block. The P2VP domains in these (co-)micelles can be selectively decorated with inorganic and polymeric nanoparticles as well as metal oxide coatings, to afford hybrid fiber-like nanostructures. This work provides a versatile strategy toward the fabrication of narrow length dispersity continuous and segmented π-conjugated OPV-containing fiber-like micelles with the capacity to be decorated in a spatially selective way with varying functionalities.

Fabrication and Study of a Composite Material Based on a Glass-Cloth with a Metal Oxide Coating

A multilayer material has been obtained on the basis of a prepreg modified by an aluminum layer, which is a precursor for fiberglass composite formation. An aluminum layer was preliminarily deposited on the prepreg by plasma spraying. Thereafter, a fiberglass composite with aluminum layers on the outer sides was formed using a modified prepreg and an oxide coating was fabricated on the aluminum surface by the method of plasma electrolytic oxidation. The proposed strategy can form the basis of a technology for the preparation of composites with an electrically conductive metal layer and increased fire resistance. The work presents data on the fabricated material’s structure and an evaluation of its fire resistance.

Study on the Influence of Multi-Layered Nano Metal Oxide Coating on Cutting Performance During Boring of Hardened Steel

Abstract Nowadays, the metal cutting industry is focussed on high production rate, better quality and good economic rate. In the boring process, the tool holder is subjected to excessive cutting force and surface roughness which affects the finished product. This can be avoided by using Multilayer Nano metal oxide coated tools which has a positive impact in improving cutting performance and coating was done in tool insert by dip, spin and spray technique for dry, semisolid and wet condition. In this paper, Aluminium oxide + zirconium oxide, titanium oxide + zirconium oxide and zirconium oxide were used as coating material. A 27 run cutting experiment was designed and cutting force and surface roughness was measured. Experimental results were optimized using Taguchi technique and from the results it was observed that two layered TiO2 +ZrO2 deposited in series provide a better cutting enactment against the Al2O3 +ZrO2 and ZrO2

Controlling wettability, wet strength, and fluid transport selectivity of nanopaper with atomic layer deposited (ALD) sub-nanometer metal oxide coatings.

Nanocellulosic films (nanopapers) are of interest for packaging, printing, chemical diagnostics, flexible electronics and separation membranes. These nanopaper products often require chemical modification to enhance functionality. Most chemical modification is achieved via wet chemistry methods that can be tedious and energy intensive due to post-processing drying. Here, we discuss the use of atomic layer deposition (ALD), a vapor phase modification technique, to quickly and simply make nanopaper hydrophobic and enhance its wet strength and durability. Specifically, we find that just “a few” ALD cycles (≤10) of either aluminum oxide or titanium oxide is sufficient to significantly increase the durability of cellulose nanofibril (CNF) paper in aqueous media, even under aggressive sonication conditions. Keeping the number of ALD cycles low makes the process more scalable for commodity manufacturing. We investigate whether this increase in wet strength is due to enhanced hydrophobic attractions or stronger hydrogen bonding between CNF fibers. The current evidence suggests that the latter mechanism is likely dominant, with ab initio calculations suggesting that newly created M–OH terminations on the cellulose nanofibrils increase hydrogen bond strength between fibers and impede CNF hydration and dispersion. ALD treated nanopapers are also found to preferentially transport hexane over water, suggesting their potential use in oil/water demulsification devices.

Controlled joule-heating of suspended glassy carbon wires for localized chemical vapor deposition

This paper demonstrates for the first time localized chemical vapor deposition of WO3-x on a suspended glassy carbon wire. A process based on the photopatterning of an SU-8 scaffold, the near-field electrospinning of an SU-8 fiber, and their pyrolysis yields a monolithic carbon structure featuring a glassy carbon wire of known diameter and length, suspended on a glassy carbon scaffold. The temperature required for the deposition of WO3-x is generated by passing current through the wire, which causes Joule heating. The deposition starts in the midpoint of the wire, and extends to its ends as the current is increased. The thickness and length of the coating are functions of the imposed current. The evolution of the coating can be monitored in real time by measuring the voltage vs current characteristic of the wire. We have deposited WO3-x coatings with thickness from 71 nm to 1.4 μm, in glassy carbon wires with diameters between 780 nm and 2.95 μm. The coatings are uniform and polycrystalline. The suspended glassy carbon wire is a generic platform for the deposition of many transition metal oxide (TMO) coatings, and opens the door to carbon-TMO structures for applications including catalysis and gas sensing.

Composite metal oxide coatings on chromium-nickel stainless steel produced by induction heat treatment

Metal oxide coatings were formed by induction heat treatment (IHT) on the surface of 12Cr18Ni10T stainless steel. The phase composition of these coatings comprised oxides of alloying elements, such as CrO2 (rutile-type phase), NiO, and slight amount of other oxides (Cr2O3, Fe2O3, Fe3O4). Nanosized morphology parameters were determined on the surface of steel samples with coatings subjected to low temperature IHT at T = 800–850 °C. The average size of nanograins was about 30–80 nm at an exposure within t = 30 s. The equivalent hardness value (Vickers scale, HV) of the near-surface layer was 445 ± 10 HV, which was slightly lower than the initial hardness value of untreated 12Cr18Ni10T steel. Hardness of the metal oxide coatings themselves H = 10.86 ± 4.47 GPa determined by the nanoindentation method was almost 4 times higher than the initial hardness of the steel surface. In vitro testing for biocompatibility of the metal oxide coatings confirmed that high morphological heterogeneity of the surface ensured excellent adhesion of cells.

Optimizing the TiO2 Content to Obtain the Highest Corrosion Resistance in Ir-Ru-Ta-Based Mixed Metal Oxide Coating in Oxygen Evolution Reaction Application

In this article, the role of TiO2 on deactivation and corrosion mechanism of a MMO coating was assessed in 1 M Na2SO4 solution. The Ti/40IrO2 + 30RuO2 + (30 − x)Ta2O5 + (x)TiO2 anodes were prepared by thermal decomposition method. Surface morphology and microstructure of the coatings were characterized by scanning electron microscopy, energy-dispersive spectroscopy and grazing incidence x-ray diffraction analysis. The electrochemical properties and corrosion behavior of these coatings were performed by accelerated lifetime test, investigation of active surface area (q*) and electrochemical impedance spectroscopy. The results showed that the uniform dissolution of the active surface layers was the main reason behind the anode deactivation. Furthermore, addition of titanium oxide up to 15% to the above-mentioned composition improved the performance of the anode and increased its working life up to 200 h.

Development of an Oxygen Sensitive Model Gel System to Detect Defects in Metal Oxide Coated Multilayer Polymeric Films

Metal oxide coated multilayered polymeric pouches provide a suitable alternative to foil-based packaging for shelf-stable products with extended shelf-life. The barrier performance of these films depends upon the integrity of the metal oxide coating which can develop defects as a result of thermal processing and improper handling. In this work, we developed a methodology to visually identify these defects using an oxygen-sensitive model gel system. Four pouches with different metal oxide coatings: MOA (Coated PET), MOB (SiOx -coated PET), MOC (Overlayer-AlOx -Organic-coated PET), MOD (Overlayer-SiOx -coated PET) were filled with water and retort-processed for 30 and 40 min at 121 °C. After processing, the pouches were cut open, dried and subsequently filled with a gel containing methylene blue that changes color in the presence of oxygen. The pouches were then stored at 23 and 40 °C for 180 and 90 days, respectively. Defects were identified by observing the localized color change from yellow to blue in the packaged gel. These observations were confirmed through measurement of oxygen and water vapor transmission rates, as well as SEM and CLSM analyses. The MOC pouches showed the least change in barrier properties after thermal processing. This was due to crosslinking in the organic coating and protection provided by the overlayer. The melting enthalpy of all films increased significantly (P < 0.05) after sterilization. This may increase the brittleness of the substrates after processing. Findings may be used to improve the barrier performance of metal oxide coated polymeric films intended for food packaging applications. PRACTICAL APPLICATION: In this study, we developed a methylene blue-based, oxygen-sensitive model gel system to identify defects in metal oxide coated polymeric structures induced by thermal processing and mechanical stresses. We also performed a comprehensive analysis of these defects through CLSM and SEM. The gel system and methodology developed may be useful in the design and development of high barrier metal oxide coated films.

Enhanced Catalyst Durability for Bio-Based Adipic Acid Production by Atomic Layer Deposition

Summary Atomic layer deposition (ALD) improves the durability of metal catalysts using nanoscale metal oxide coatings. However, targeted coating strategies and economic models are lacking for process-specific deactivation challenges that account for implications at scale. Herein, we apply Al2O3 ALD to Pd/TiO2 to increase durability during hydrogenation of muconic acid, a bio-based platform chemical, to adipic acid. Initial coating development and characterization are performed on the milligram scale using stop-flow ALD. Subsequently, ALD coating scale is increased by 3 orders of magnitude using fluidized bed ALD. Activity, leaching resistance, and thermal stability are evaluated at each synthesis scale. ALD-coated catalysts retain up to 2-fold greater muconic acid hydrogenation activity and undergo significantly less physical restructuring than uncoated Pd/TiO2 after high-temperature treatments, while reducing Pd leaching by over 4-fold. Techno-economic analysis for an adipic acid biorefinery supports increased ALD material costs through catalyst lifetime extension, underscoring the potential viability of this technology.

Comparison of chemical stability and corrosion resistance of group IV metal oxide films formed by thermal and plasma-enhanced atomic layer deposition

The wide applications of ultrathin group IV metal oxide films (TiO2, ZrO2 and HfO2) probably expose materials to potentially reactive etchants and solvents, appealing for extraordinary chemical stability and corrosion resistance property. In this paper, TiO2 ultrathin films were deposited on Si at 200 °C while ZrO2 and HfO2 were grown at 250 °C to fit their growth temperature window, by thermal atomic layer deposition (TALD) and plasma-enhanced ALD (PEALD). A variety of chemical liquid media including 1 mol/L H2SO4, 1 mol/L HCl, 1 mol/L KOH, 1 mol/L KCl, and 18 MΩ deionized water were used to test and compare chemical stability of all these as-deposited group IV metal oxides thin films, as well as post-annealed samples at various temperatures. Among these metal oxides, TALD/PEALD HfO2 ultrathin films exhibit the best chemical stability and anti-corrosion property without any change in thickness after long time immersion into acidic, alkaline and neutral solutions. As-deposited TALD ZrO2 ultrathin films have slow etch rate of 1.06 nm/day in 1 mol/L HCl, however other PEALD ZrO2 ultrathin films and annealed TALD ones show better anti-acid stability, indicating the role of introduction of plasma O2 in PEALD and post-thermal treatment. As-deposited TiO2 ultrathin films by TALD and PEALD are found to be etched slowly in acidic solutions, but the PEALD can decrease the etching rate of TiO2 by ~41%. After post-annealing, TiO2 ultrathin films have satisfactory corrosion resistance, which is ascribed to the crystallization transition from amorphous to anatase phase and the formation of 5% Si-doped TiO2 ultrathin layers on sample surfaces, i.e. Ti-silicate. ZrO2, and TiO2 ultrathin films show excellent corrosion endurance property in basic and neutral solutions. Simultaneously, 304 stainless steel coated with PEALD-HfO2 is found to have a lower corrosion rate than that with TALD-HfO2 by means of electrochemical measurement. The pre-treatment of plasma H2 to 304 stainless steel can effectively reduce interfacial impurities and porosity of overlayers with significantly enhanced corrosion endurance. Above all, the chemical stability and anti-corrosion properties of IV group metal oxide coatings can be improved by using PEALD technique, post-annealing process and plasma H2 pre-treatment to substrates.