Oxide Composites Research Articles

Temperature-dependent optical dispersion of composite cerium oxide and barium zirconate single layers and multi-layers

Temperature-dependent optical dispersion of composite cerium oxide and barium zirconate single layers and multi-layers

Bacterial cellulose-graphene oxide composite membranes with enhanced fouling resistance for bio-effluents management

Bacterial cellulose composites hold promise as renewable bioinspired materials for industrial and environmental applications. However, their use as free-standing water filtration membranes is hindered by low compressive strength, fouling, and poor contaminant selectivity. This study investigates the potential of bacterial cellulose-graphene oxide composites membranes for fouling resistance in pressure-driven filtration. Graphene oxide dispersed in poly(ethylene glycol) (PEG-400) is incorporated as a reinforcing filler into 3D network of bacterial cellulose using an in-situ synthesis method. The effect of graphene oxide on in situ fermentation yield and the formation of percolated-network in the composites shows that the optimal membrane properties are reached at a graphene oxide loading of 2 mg/mL. The two-dimensional graphene oxide nanosheets uniformly dispersed into the matrix of bacterial cellulose nanofibers via hydrogen-bonded interactions demonstrated nearly twofold higher water flux (380 L m−2 h−1) with a molecular weight cut-off ranging between 100–200 KDa and a sixfold increase in wet compression strength than pristine BC. When exposed to synthetic organic foulants and bacterial rich feed solutions, the composite membranes showed more than 95% flux recovery. Additionally, the membranes achieved over 95% rejection of synthetic natural organic matter and bacterial rich solutions, showcasing their enhanced fouling resistance and selectivity.

Cr2O3 Clusters on ZnO as Hydrogen Pools for Efficient Syngas‐To‐Light Olefins

AbstractInterfaces of mixed oxide are often considered the primary catalytic sites, yet the functionalities of the surrounding environments are less understood. Composite oxides, particularly ZnO‐Cr2O3, show high activity and selectivity for syngas conversion, with ZnO dissociating H2 to hydrides and Cr2O3 activating CO. However, hydrides on ZnO cannot remain stable at temperatures above room temperature. Focusing on the puzzlingly high performance despite ZnO's inability to stabilize active hydrides at reaction temperatures (300–400 °C), we clarified the roles of each phase using models of Cr2O3/ZnO and ZnO/Cr2O3. Cr2O3 clusters on ZnO effectively stabilize and store hydrides, significantly enhancing syngas conversion compared to individual oxides or ZnO/Cr2O3. An acetate/ketene pathway on Cr2O3/ZnO was identified, driven by the unique role of Cr2O3 clusters in regulating local hydride and CO coverages, unlike other routes observed on ZnO/Cr2O3. These insights advance the understanding of the active structures and functionalities of mixed oxides in catalysis.

Photodegradation stability of marine coatings derived from PVC binder loaded with composite metal oxides particles

Photodegradation stability of marine coatings derived from PVC binder loaded with composite metal oxides particles

Enhanced Mechanical Properties and Degradation Control of Poly(Lactic) Acid/Hydroxyapatite/Reduced Graphene Oxide Composites for Advanced Bone Tissue Engineering Application

This study explores the enhancement of poly(lactic acid) (PLA) matrix using calcium hydroxyapatite (cHAP) and reduced graphene oxide (rGO) for developing composite scaffolds aimed at bone regeneration applications. The PLA composites were fabricated through solvent evaporation and melt extrusion and characterized by various techniques, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and mechanical testing. The incorporation of cHAP and rGO significantly improved the thermal, mechanical, and morphological properties of the PLA matrix. Mechanical testing revealed that adding 10% cHAP and varying amounts of rGO (0.1%, 0.3%, 0.5%) enhanced tensile and compressive strengths, with the highest improvements observed at 0.5% rGO content. Thermal analysis showed increased thermal stability with higher degradation temperatures for the composites. Spectroscopic analyses confirmed the effective integration of cHAP and rGO into the PLA matrix with characteristic peaks of the fillers identified in the composite spectra. In vitro, degraded action tests in phosphate-buffered saline (PBS) at pH 7.4 over 12 months indicated that composites with higher rGO content exhibited lower mass loss and better mechanical stability. Furthermore, finite element analysis (FEA) simulations were performed to validate the experimental results, demonstrating a strong correlation between simulated and experimental compressive strengths. This novel approach demonstrates the potential of PLA/cHAP/rGO composites in creating effective and biocompatible scaffolds for tissue engineering, providing a comprehensive analysis of the synergistic effects of cHAP and rGO on the PLA matrix and offering a promising material for bone regeneration applications.

Graphene wrapped porous polyaniline/manganese oxide nanocomposites with enhanced structural stability and conductivity for high‐performance symmetric supercapacitor

AbstractManganese oxides have emerged as promising electrode materials for supercapacitors. Despite extensive efforts to improve their conductivity and structural stability through various manganese oxide/conductor nanocomposites, achieving efficient and reliable energy storage electrode materials has remained challenging. In this study, we propose a meticulous “dual enhancement” strategy, where three‐dimensional (3D) nanostructured polyaniline/manganese oxide composites (PM) are synthesized via an in situ method and further integrated with graphene wrapping to form polyaniline/manganese oxide/graphene nanocomposites (PMG). Electrochemical characterization reveals that PMG exhibits a remarkable specific capacitance of up to 403 F g−1 (at 1 A g−1), with a favorable capacitance retention of 80.2% after 5000 cycles, along with a wide potential window. This enhancement is attributed to the synergistic effects of polyaniline, which provides a supportive framework and electron transport pathways, and graphene, which offers external protection and enhances conductivity pathways. Assembled symmetrical supercapacitors demonstrate outstanding energy density (32.7–23.3 Wh kg−1) and power density (720–4500 W kg−1) at a high operating voltage of 1.8 V, surpassing the performance of many reported high‐performance supercapacitors. This study provides valuable insights for advancing manganese oxide electrode materials and is expected to catalyze their widespread adoption in energy storage applications.Highlights “Dual enhancement” is implemented by PANI supporting and rGO wrapping. The conductivity and structural stability of composite electrode is greatly enhanced. Improved capacitance (403 F g−1, 1 A g−1) and cycling stability (80.2%) is achieved. The symmetrical supercapacitor has high voltage and energy density (32.7 Wh kg−1).

Strong spherical V2O5/TiO2–SiO2 composites obtained by template combined with sol-gel method

This study is devoted to the preparation of strong spherical composites V2O5/TiO2–SiO2 by a combined template and sol-gel method. The composition, size and shape of the colloidal particles in butanol ash with tetrabutoxytitanium and tetraethoxysilane, as well as the physicochemical processes leading to the strengthening of the spherical agglomerates obtained using an anion exchanger with a gel structure, have been determined. Electrophoresis, small-angle X-ray scattering, and viscometry were used to demonstrate the presence in the sol of positively charged colloidal particles of lenticular and cylindrical shape, whose size, when the sol is stabilised, reaches 53 Å. The absorption of the sol by the anion exchanger in vanadium form is due to the equalisation of the osmotic pressure in the anion exchanger/sol system. Spherical composites with a diameter of 300 µm were obtained. It was shown by X-ray diffraction that the composites consist of V2O5 with an orthorhombic structure, TiO2 with an anatase structure, and amorphous silicon dioxide. The interaction at the interface between the phases of V2O5 with TiO2 and SiO2, which leads to the strengthening of the sphere of the V2O5/TiO2–SiO2 composite, has been demonstrated by IR and Raman spectroscopy. The results obtained can be used for the synthesis of MxOy/TiO2–SiO2 oxide composites with spherical agglomerates.

Relaxation dynamics and conductivity in poly(vinylidene fluoride)/graphene oxide composites

The αc relaxation, which originates from the crystalline phase of Poly(vinylidene fluoride), is studied in the composite system of Poly(vinylidene fluoride) and Graphene oxide. PVDF/GO composites were prepared using solvent casting. The crystalline phases in PVDF/GO composites were identified using XRD and quantified using FTIR. The thermal properties were analyzed using DSC, and the crystallization degrees were calculated. The electric modulus formalism is employed to understand the relaxation mechanism with temperature. AC conductivity studies reveal the activation energy for conduction in these composites.

Chemistry of Reduced Graphene Oxide: Implications for the Electrophysical Properties of Segregated Graphene-Polymer Composites.

Conductive polymer composites (CPCs) with nanocarbon fillers are at the high end of modern materials science, advancing current electronic applications. Herein, we establish the interplay between the chemistry and electrophysical properties of reduced graphene oxide (rGO), separately and as a filler for CPCs with the segregated structure conferred by the chemical composition of the initial graphene oxide (GO). A set of experimental methods, namely X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy, van der Paw and temperature-dependent sheet resistance measurements, along with dielectric spectroscopy, are employed to thoroughly examine the derived materials. The alterations in the composition of oxygen groups along with their beneficial effect on nitrogen doping upon GO reduction by hydrazine are tracked with the help of XPS. The slight defectiveness of the graphene network is found to boost the conductivity of the material due to facilitating the impact of the nitrogen lone-pair electrons in charge transport. In turn, a sharp drop in material conductivity is indicated upon further disruption of the π-conjugated network, predominantly governing the charge transport. Particularly, the transition from the Mott variable hopping transport mechanism to the Efros-Shklovsky one is signified. Finally, the impact of rGO chemistry and physics on the electrophysical properties of CPCs with the segregated structure is evaluated. Taken together, our results give a hint at how GO chemistry manifests the properties of rGO and the CPC derived from it, offering compelling opportunities for their practical applications.

Unraveling the Electrochemical Insights of Cobalt Oxide/Conducting Polymer Hybrid Materials for Supercapacitor, Battery, and Supercapattery Applications.

This review article focuses on the potential of cobalt oxide composites with conducting polymers, particularly polypyrrole (PPy) and polyaniline (PANI), as advanced electrode materials for supercapacitors, batteries, and supercapatteries. Cobalt oxide, known for its high theoretical capacitance, is limited by poor conductivity and structural degradation during cycling. However, the integration of PPy and PANI has been proven to enhance the electrochemical performance through improved conductivity, increased pseudocapacitive effects, and enhanced structural integrity. This synergistic combination facilitates efficient charge transport and ion diffusion, resulting in improved cycling stability and energy storage capacity. Despite significant progress in synthesis techniques and composite design, challenges such as maintaining structural stability during prolonged cycling and scalability for mass production remain. This review highlights the synthesis methods, latest advancements, and electrochemical performance in cobalt oxide/PPy and cobalt oxide/PANI composites, emphasizing their potential to contribute to the development of next-generation energy storage devices. Further exploration into their application, especially in battery systems, is necessary to fully harness their capabilities and meet the increasing demands of energy storage technologies.

The Degradation of Rhodamine B by an Electro-Fenton Reactor Constructed with Gas Diffusion Electrode and Heterogeneous CuFeO@C Particles

Compared with conventional Fenton processes, the electro-Fenton process consumes fewer chemicals and produces less sludge, as it can generate the required Fenton’s reagents in situ. In this work, an electro-Fenton reactor was constructed to treat synthetic rhodamine B (Rh B) wastewater, in which a gas diffusion electrode (GDE) was used as a cathode to produce H2O2, and heterogeneous CuFeO@C particles were used to generate Fe2+ in situ. The results indicated that the gas diffusion electrode made of elements N-S-B and r-graphene oxide (NSB-r-GO) composites produced more H2O2 than the one made from r-graphene oxide (r-GO), under the conditions of 0.1 mol ·L−1 Na2SO4 electrolyte, 10 mA·cm−2 current density, and 1.0 L·min−1 O2 flow rate, with the accumulated H2O2 production reaching 105.43 mg·L−1. Additionally, different iron morphologies, including octahedral Fe (II), octahedral Fe (III), and tetrahedral Fe (III), were found in the calcined CuFeO@C particles, approximately 1.0 mg·L−1 of iron ions dissolved in the electrolyte was detected, which worked simultaneously as conductive electrodes in a conceptual three-dimensional electrochemical reactor consisting of a gas diffusion electrode cathode, Ti/RuSn anode, and CuFeO@C particle electrodes. No external Fenton reagents were necessary.

Service life prediction model for biogenic acid corrosion: Advancement of life factor method for concrete sewer design

Current service life prediction models for concrete sewer design, including the widely used Life Factor Method (LFM), do not efficiently incorporate certain key corrosion contributing factors, such as material selection, concrete mix design, and sewer environment. This paper describes an advancement of the LFM model to cover these factors, broaden its usage, and improve concrete sewer design and applications. By integrating the first principles of the original LFM model, advanced knowledge from the literature, and results from field performance studies of various sewer concretes, a practical and relatively simple LFM model was advanced. With concrete mix design, oxide composition of all concrete ingredients, and sewer environmental and hydraulic conditions, the so-called ‘advanced LFM model’ could predict the corrosion rate of various concrete mixes. The model emphasised the influence of various modern binders, including calcium aluminate and calcium sulpho-aluminate cements, and various aggregate types including siliceous, calcareous, and alumina-based aggregates, when subjected to different sewer environments.

In-situ carbon integration on atomically dispersed platinum metal oxide nanocomposites for hydrogen evolution reaction

In this study, a novel in-situ carbon growth technique by a modified sol gel synthesis method is presented. The carbon support developed on a transition metal oxide composite transforms the electronic conductivity and is engineered for hydrogen evolution reaction by a dispersion of unit atomic concentration of platinum. Through two different synthesis techniques, platinum dispersion is implemented on the metal oxide-carbon system, one by direct sol-gel technique and another by chemical reduction technique, whereby a homogeneous dispersion of the noble metal on the composite is achieved. Carbon-based cerium oxide and titanium oxide composites are used as the base material, and one atomic percentage of platinum metal is ensured while synthesizing each of the carbon composites. The functionality of these catalysts towards hydrogen evolution reaction in a 0.5 M H2SO4 acidic media revealed the synthesis technique's uniqueness and the effect of metal support interaction that plays a vital role in the electrocatalytic activity. The intrinsic activity of the titania system, along with enhanced metal support interaction due to highly enriched platinum availability on the surface of the substrate, provides for strong electrochemical activity. The titanium oxide carbon composite with platinum dispersed by hydrazine reduction exhibited the finest activity with an overpotential of just 44 mV at j = 10 mA/cm2 and a tafel slope of 118 mV/dec. The gas chromatographic analysis on platinum supported titania catalyst showcased better performance by a margin of four times than the commercial three weight percentage platinum supported carbon.

Preparation of unique corn-stalk-like MnO₂/CoNi nanowires via in situ epitaxial attachment growth for monitoring environmental pollutant hydrazine

This paper presents the synthesis of a novel corn-stalk-like MnO₂/CoNi oxide composite using an in situ epitaxial attachment growth strategy, in which CoNi oxide nanosheets are anchored onto MnO₂ nanowires. The one-dimensional MnO₂ nanowires, with their large specific surface area, serve as a support to enhance the electronic conductivity of the CoNi oxides. Hexamethylenetetramine (HMTA) is employed as an alkaline linking agent, playing a key role in shaping the CoNi oxide nanosheets and ensuring their successful growth on the MnO₂ nanowires. The MnO₂/CoNi oxide composite-based electrochemical sensor exhibits excellent synergistic and interfacial effects, promoting electron transfer and charge migration. This composite material shows outstanding electrocatalytic performance for hydrazine detection, with a broad linear range (0.48−6106.58 μM), low detection limit (0.286 μM, S/N = 3), and high sensitivity (0.037 μA μM⁻1). Moreover, when tested for hydrazine detection in water samples, the sensor achieved a recovery rate of 95.7–105 %, highlighting its high sensitivity and rapid response in practical applications.

Influence of the oxidizing technique on the biocompatible and corrosion properties of Ti6Al4V in a physiological environment

This work aims to evaluate the corrosion and biocompatibility properties of oxide films generated on Ti6Al4V alloys using both traditional and novel methods. Oxide films were generated by anodization and plasma treatment to achieve a blue surface finish. The oxide films were then characterized and compared to a native film formed on the Ti6Al4V.Electrochemical tests, incorporating potentiodynamic tests and electrochemical impedance spectroscopy, were employed to define the electrochemical resistance of oxides in an environment simulating biological exposure. In vitro tests were conducted to study ion release and biocompatible properties over a 6-week period of exposure to a 0.9 wt% NaCl solution, at body temperature. Various spectroscopic techniques, including ToF-SIMS, XRD, and Raman analysis, were used to study the structure and chemistry of the oxide films. The sub-surface layer was analysed by microstructural investigation.The type of oxidation was found to have a key influence on the oxide composition, especially with respect to the depth distribution of the individual alloy elements through the oxide film. The oxidation process determines which of the alloying elements are released into the environment, as a result of the corrosion reactions.

Flower-like SnS2/rGO composites with efficient iodide-triiodide redox performance for counter electrodes in Pt-free dye-sensitized solar cells

The work function (WF) of the counter electrode (CE) predominantly determines the device performance of dye sensitized solar cells (DSSCs) as it controls the electron transfer rate for dye regeneration. Hence in this work, tin disulphide/reduced graphene oxide (SnS2/rGO) composites were synthesized with different wt.% of rGO (3, 5, 7, 10 %) and investigated their performance in DSSCs applications. At the outset, the formation of pristine SnS2 and SnS2/rGO composites were confirmed through X-ray diffraction and Raman spectral analysis. The morphological imaging revealed the micro flower-like structure of SnS2 with cross-sectional width of 5 ± 0.2 μm, and petal thickness ranges from 30.7 nm to 46.4 nm. The binding energy spectra confirms the 4+ oxidation state of Sn in both SnS2 and 7 wt% SnS2/rGO, suggesting that the rGO does not alter the chemical states of SnS2. Further, the peak-to-peak separation values obtained from Cylic-Voltammetry analysis were found to be 0.37 and 0.57 V for S7 and Pt CE respectively, indicating the rapid electrolyte reduction of 7 wt% SnS2/rGO. Finally, a photo conversion efficiency (PCE) of 7.3 % has been achieved with 7 wt% SnS2/rGO CE which is greater than that of the PCE with Pt CE (6.5 %) and also higher than that of pristine SnS2 with 4.7 %. The improved PCE is attributed to the reduced WF of the 7 wt% SnS2/rGO composite as measured from the Kelvin probe force microscopy analysis, enabling the rapid redox reaction towards triiodide reduction.

Easy fabrication of PVA-CaO-CuO composite films for efficient photocatalyst: Towards distinct luminescence property, morphology and thermal stability

PVA-CuO-CaO composites in the film form were synthesized by loading the different compositions of metal oxides (CuO and CaO) ranging from 5 to 25 wt% via solvent casting approach. The applications of the prepared composites as photocatalysts were assessed together with the findings of photoluminescence (PL) characteristics, optical clarity, morphological features, and thermal properties. Fourier-transformed infrared (FTIR), ultraviolet–visible (UV–vis), and photoluminescence (PL) spectra exposed the systematic and viableintegration of metal oxides (CuO-CaO) into the PVA matrix in PVA-CuO-CaO composites. The modifications of PL property of PVA-CuO-CaO composites were recognized rather than bare PVA. The prepared composite films exhibited excellent optical transparency irrespective of the addition of metal oxides. Both TGA and DSC data showed that the thermal properties of the composites could be significantly enhanced by incorporating CuO and CaO. DSC measurements demonstrated that the Tm of PVA-CuO-CaO composites is improved substantially (∼7 to 38 °C) than PVA. The distinct morphological structures of the obtained composites were identified with variations in CuO and CaO addition remaining diameter in the 30–200 nm range. The photocatalytic assessments revealed the better photocatalytic performance of PVA-CuO-CaO composites for removing methylene blue (MB) than bare PVA. By eliminating organic pollutants, the current study may provide a new perspective on the preparation of water-processable PVA-CuO-CaO photocatalysts for wastewater management.

Effects of Dynamic Surface Transformation on the Activity and Stability of Mixed Co‐Mn Cubic Spinel Oxides in the Oxygen Evolution Reaction in Alkaline Media

AbstractAn atomic‐scale understanding of how electrocatalyst surfaces reconstruct and transform during electrocatalytic reactions is essential for optimizing their activity and longevity. This is particularly important for the oxygen evolution reaction (OER), where dynamic and substantial structural and compositional changes occur during the reaction. Herein, a multimodal method is developed by combining X‐ray fine structure absorption and photoemission spectroscopy, transmission electron microscopy, and atom probe tomography with electrochemical measurements to interrogate the temporal evolution of oxidation states, atom coordination, structure, and composition on Co2MnO4 and CoMn2O4 cubic spinel nanoparticle surfaces upon OER cycling in alkaline media. Co2MnO4 is activated at the onset of OER due to the formation of ≈2 nm Co‐Mn oxyhydroxides with an optimal Co/Mn ratio of ≈3. As OER proceeds, Mn dissolution and redeposition occur for the CoMn oxyhydroxides, extending the OER stability of Co2MnO4. Such dynamic dissolution and redeposition are also observed for CoMn2O4, leading to the formation of less OER‐active Mn‐rich oxides on the nanoparticle surfaces. This study provides mechanistic insights into how dynamic surface reconstruction and transformation affect the activity and stability of mixed CoMn cubic spinels toward OER.

Geopolymers made using organic bases. Part III: Cast magnesium, yttrium, and zinc aluminosilicate and silicate ceramics

AbstractIt was shown in Part II of this series of articles that geopolymers synthesized with organic bases could be used as precursors to mullite and mullite + glass composites. A natural next step is to determine whether it is possible to synthesize materials outside the Al2O3·SiO2 and alkali oxide·Al2O3·SiO2 phase systems. Hence, the focus of this study was the use of geopolymer‐like processing to make preceramic bodies with magnesium, yttrium, and zinc aluminosilicate and silicate compositions. These preceramics were successfully fired into monolithic bodies of cordierite, mixed yttrium and aluminum silicates, yttrium disilicate, and willemite. The synthesis of these preceramics employed a guanidine silicate solution, a synthetic oxide powder, and in some cases metakaolin to reach the oxide composition of the ceramic. All solidified within 3 days at 20°C or 50°C, depending on the composition. For the first time, this study showed that Y2O3 and ZnO can react with silicate solutions to give some Y‐O‐Si and Zn‐O‐Si bonding analogous to Al‐O‐Si bonding in geopolymers. These results suggest that other silicate compositions may be possible, such as with the rare earth oxides, which might be valuable to process like a geopolymer rather than by traditional ceramic processing. However, the ceramics made here were generally porous due to the expansion of gases within the sample that were trapped by a viscous liquid phase during firing.

A Critical Review of the Synthesis and Applications of Spinel-Derived Catalysts to Bio-Oil Upgrading.

The transformation of renewable bio-oil into platform chemicals and bio-oil through catalytic processes embodies an efficient approach within the realm of advancing sustainable energy. Spinel-based catalysts have garnered significant attention owing to their ability to precisely tune metals within the framework, facilitating adjustments to structural, physical, and electronic properties, coupled with their remarkable thermal stability. This review aims to provide a comprehensive overview of recent advancements in spinel-based catalysts for upgrading bio-oil. Its objective is to shed light on their potential to address the limitations of conventional catalysts. Initially, a comprehensive analysis is conducted on different metal oxide composites in terms of their similarity and dissimilarity on properties. Subsequently, the synthesis methodologies are scrutinised and potential avenues for their modification are explored. Following this, an in-depth discussion ensues regarding the spinels ascatalysts or catalyst precursors for catalytic cracking, ketonisation, catalytic hydrodeoxygenation, steam and aqueous-phase reforming, andelectrocatalytic upgrading of bio-oil. Finally, the challenges and potential prospectsare addressed, with a specific focus on the machine learning - based approaches to optimise the structure and activity of spinel catalysts. This review aims to provide specific directions for further exploration and maximisation of the spinel catalysts in the bio-oil upgrading field.