Dioxide Composites Research Articles

Crystal structure dependent photocatalytic degradation of manganese and titanium oxides composites

Crystalline hexagonal disk-shaped anatase TiO2 within manganese oxide (Mn2O3) nanorods has been fabricated to form manganese oxide-titanium dioxide (MnT) composites following sonochemical approach. The unique morphology of the synthesized MnT provides higher surface area to enhance the adsorption efficiency and promotes electron–hole separation. This appears particularly promising for efficient photocatalysis. The photocatalytic decolorization efficiency (PD) of sonosynthesized MnT (S-MnT) was tested via decomposition of an organic pollutant, malachite green oxalate under ultraviolet irradiation and compared to that of sol–gel synthesized MnT (H-MnT). The profound impact of hydrogen peroxide (H2O2) addition on the photoactivity was tested. S-MnT with addition of sonicated H2O2 showed the best photoactivity (PD 99.61% in 50 min) in comparison to sol–gel synthesized H-MnT (PD 92.14% in 60 min). The mechanism of degradation was found to depend on the formation of superoxide radicals (O −·2 ), hydroxyl radicals (·OH) and the defect concentration. The role of ultrasound in the overall degradation process was also discussed. Photoluminescence studies demonstrate that Mn2+ ions are in an octahedral and tetrahedral coordination in both the composites which is favourable for light emission.

High energy and excellent stability asymmetric supercapacitor derived from sulphur-reduced graphene oxide/manganese dioxide composite and activated carbon from peanut shell

Nanorods/fibers, nanosheet and nano-flower like structure were effectively synthesized from sulphur-reduced graphene oxide (RGO-S) and sulphur-reduced graphene oxide/manganese dioxide (RGO-S/MnO2) composites for supercapacitor applications. Structural, chemical composition and morphological analysis reveal an effective synthesis of the RGO-S and RGO-S/MnO2 composite. Electrochemical measurements of the optimized mass loading of MnO2 on RGO-S in a three electrode configurations revealed a specific capacitance of 180.4 F g−1 compared to 75.2 F g−1 of the pristine sample at 1 A g−1 in 2.5 M KNO3 electrolyte. An assembled asymmetric device consists of optimized RGO-S/MnO2 as positive electrode and activated carbon from peanut shell (AC-PS) as a negative electrode delivered a high specific energy of 71.74 Wh kg−1 with its corresponding specific power of 850 W kg−1 at 1 A g−1. It was observed that even at high specific current of 5 A g−1 the device was able to maintain a specific energy of 55.30 Wh kg−1. An excellent stability with capacitance retention of 94.5% and columbic efficiency of 99.6% up to 10, 000 cycles was recorded for the device at 5 A g−1. The device demonstrated a very good stability after being subjected to a voltage holding of up to 90 h and an outstanding self-discharge of about 1.45 V was recorded within the first 10 h and 1.00 V after 72 h from its maximum potential of 1.7 V.

Design and Synthesis of a Biochar-Supported Nano Manganese Dioxide Composite for Antibiotics Removal From Aqueous Solution

Manganese dioxide nanoparticles were loaded onto biochar prepared from rice husk to obtain a biochar-supported manganese dioxide composite (BC/MnO2). The properties of this composite were studied through various advanced characterization techniques, combined with experiments on treating aqueous solutions of tetracycline hydrochloride (TC) and doxycycline (DC). The results showed that compared with the original biochar, MnO2 nanoparticles appeared on the surface of BC/MnO2, the carbon content decreased, and the oxygen content increased. Moreover, BC/MnO2 exhibited significantly larger total pore volume and specific surface area, and the pore structure of the biochar was improved. The effect of pH on the adsorption of TC and DC by BC/MnO2 was insignificant. With an increase in the adsorbent dose, the removal rates of TC and DC increased, and the removal ability of BC/MnO2 for TC was slightly higher than that for DC. The adsorption of TC and DC on the BC/MnO2 surface conformed to the Freundlich model. Compared with the pseudo-first-order kinetic model, the pseudo-second-order kinetic model (R2 = 0.999) better fitted the adsorption data, indicating that the adsorption process is controlled by chemical adsorption. In addition, the results of adsorption-desorption experiments indicated that BC/MnO2 have excellent regeneration ability. The experimental results of this study are significant for expanding the application of biochar composites in the treatment of aqueous solution containing antibiotics.

Formaldehyde Gas Sensor Based on Melamine Foam and Tin Dioxide Composites

Formaldehyde (HCHO) is a volatile organic compound (VOC). It can caused great harm to human and environment. Since the increasing concerns of this problem, to develop effective methods to detect this toxic and hazardous gas has become more and more important , which play an important role in personal safety and environment protection. In this study, melamine foam and tin oxide composites were prepared by in-situ growth and subsequent treatment by using a simple hydrothermal reaction. The morphology, structure and sensing properties of the composites were systematically studied. The results show that tin oxide nanoparticles can grow well on the melamine foam skeleton through a simple hydrothermal reaction and has a good stable morphology. It is found that the three-dimensional spherical/skeletal composite material has better gas sensitivity and selectivity to formaldehyde gas than the pristine tin dioxide under a suitable concentration. The response of the composite to 5 ppm formaldehyde gas can reach 30.0 at 120°C. The reactant of formaldehyde on the surface of the material was studied by in situ IR. At the same time, melamine foam has a certain flexibility, which will have a good development for flexible, miniaturized and wearable formaldehyde sensor. Keywords：melamine foam plastics；tin oxide；formaldehyde；gas sensor Figure 1

Removal of iodate from aqueous solution using diatomite/nano titanium dioxide composite as adsorbent

In this paper, diatomite/nano titanium dioxide composite (DNTD) was used as adsorbent to remove iodate from aqueous solution under different conditions. The maximum distribution coefficient could be up to 370 mL g−1 in acidic environment. The sorption speed is very fast and satisfies the pseudo-second-order equation. The sorption isotherm is well described by the Freundlich model. The sorption process is spontaneous and exothermic. Iodate was adsorbed by the silicon hydroxyl group of DNTD according to the characterization results. DNTD is a promising material for the treatment of iodine pollution in the environment. The diatomite/nano TiO2 composite has a complex pore structure. It adsorbs iodate quickly and efficiently. Iodate is adsorbed by the Si–OH group and reduced under the catalysis of nano TiO2. It has great potential in the treatment of iodine pollution.

Chemical sensing behaviour of PVA based composite

This study is conducted to enhance the sensitivity of polymer composite films in applications such as chemical sensing. For this purpose, polyvinyl alcohol (PVA) and zirconium dioxide (ZrO2) composites based gas sensors are fabricated via spin coating technique. The concentration of PVA and ZrO2 has been varied to investigate its effect on the properties of the films. The synthesized PVZr composites are characterized by XRD, FTIR and SEM. These characterization techniques are employed to study the structure and morphology of the deposited composite films. The 0.6 wt% PVA based gas sensors demonstrate increased sensitivity as compared to the others.

Experimental and theoretical studies of spherical β-cyclodextrin modified titanium dioxide composites for uranium removal

With the fast development of the nuclear industry, it is inevitable that a considerable amount of uranium (U) is discharged into the environment during mining, use, and disposal processes, which can result in serious radioactive contamination. In this study, the spherical β-cyclodextrin modified titanium dioxide (β-CD/TiO2) was prepared by a simple hydrothermal method for the capture of U(VI). The removal of U(VI) on β-CD/TiO2 was dependent on solution pH. The maximum adsorption capacity of β-CD/TiO2 at pH 5.0 reached 129.8 mg/g for U(VI). The thermodynamic study confirmed that the capture of U(VI) was a spontaneous process. According to the XPS analysis, the hydroxyl groups of β-CD/TiO2 were responsible for U(VI) removal, which was further demonstrated by DFT calculation at the molecular level. The findings presented in this study are important to the removal of radionuclides from wastewater.

Adsorptive removal of anionic dyes by graphene impregnated with MnO2 from aqueous solution

Graphene nanosheet-manganese dioxide (GN-MnO2) composite was synthesized by a microwave-assisted method. The physico-chemical properties of modified graphene (GN) were characterized by different techniques, such as scanning electron microscopes (SEM), Fourier-transform infrared spectrometers (FTIR), X-ray diffraction (XRD) and Raman spectroscopy. The effects of contact time, pH, concentration, temperature, and the dose of adsorbent on the adsorption attributes of Congo red (CR) and Acid green 25 (AG25) on GN-MnO2 composite was studied. The experimental facts of the isotherm were found to be more fitted with the Langmuir isotherm rather than the Freundlich one, while the pseudo-second-order kinetic model/curve was found to be fitted with experimental data, giving an indication that the experiment was controlled by chemical processes. The maximum adsorption capacities is derived from the Langmuir model equation at 303 K were 270.06 and 324.26 mg/g for CR and AG25, respectively. The thermodynamic study revealed that the adsorption of CR and AG25 dyes onto the GN-MnO2 was pretty much spontaneous in nature and showed that the GN-MnO2 was a decent adsorbent for the elimination of CR and AG25 ions in aqueous conditions. The column studies were conducted in varying flowrates (4−12 mL/min), and bed heights (0.5–1.5 cm), with a concentration of 100 mg/L, while at pH of 3 and 4 for CR and AG25, respectively. The adsorption capability increased with the increasing influent level and column depth while it was reduced by upturn in flow-rate. The results obtained were fitted well with the Bed Depth Service Time BDST and Thomas models.

Chitosan-TiO2: A Versatile Hybrid Composite.

In recent years, a strong interest has emerged in hybrid composites and their potential uses, especially in chitosan–titanium dioxide (CS–TiO2) composites, which have interesting technological properties and applications. This review describes the reported advantages and limitations of the functionalization of chitosan by adding TiO2 nanoparticles. Their effects on structural, textural, thermal, optical, mechanical, and vapor barrier properties and their biodegradability are also discussed. Evidence shows that the incorporation of TiO2 onto the CS matrix improves all the above properties in a dose-dependent manner. Nonetheless, the CS–TiO2 composite exhibits great potential applications including antimicrobial activity against bacteria and fungi; UV-barrier properties when it is used for packaging and textile purposes; environmental applications for removal of heavy metal ions and degradation of diverse water pollutants; biomedical applications as a wound-healing material, drug delivery system, or by the development of biosensors. Furthermore, no cytotoxic effects of CS–TiO2 have been reported on different cell lines, which supports their use for food and biomedical applications. Moreover, CS–TiO2 has also been used as an anti-corrosive material. However, the development of suitable protocols for CS–TiO2 composite preparation is mandatory for industrial-scale implementation.

Polyurethane-Based Composites: Effects of Antibacterial Fillers on the Physical-Mechanical Behavior of Thermoplastic Polyurethanes.

The challenge to manufacture medical devices with specific antibacterial functions, and the growing demand for systems able to limit bacterial resistance growth, necessitates the development of new technologies which can be easily produced at an industrial level. The object of this work was the study and the development of silver, titanium dioxide, and chitosan composites for the realization and/or implementation of biomedical devices. Thermoplastic elastomeric polyurethane was selected and used as matrix for the various antibacterial functions introduced during the processing phase (melt compounding). This strategy was employed to directly incorporate antimicrobial agents into the main constituent material of the devices themselves. With the exception of the composite filled with titanium dioxide, all of the other tested composites were shown to possess satisfactory mechanical properties. The best antibacterial effects were obtained with all the composites against Staphylococcus aureus: viability was efficiently inhibited by the prepared materials in four different bacterial culture concentrations.

The uptake of uranium and europium on the polyacrylamide/titanium dioxide composites

With the high-speed development of nuclear energy, radioactive contamination has attracted worldwide attention. In this study, the polyacrylamide/titanium dioxide composites (PAM/TiO2) were prepared for the simultaneous elimination of U(VI) and Eu(III). The results confirmed that the capture of radionuclides on PAM/TiO2 increased with the increase of temperature, suggesting an endothermic process. The maximum adsorption capacities of PAM/TiO2 were 146.5 mg/g for U(VI) and 38.8 mg/g for Eu(III), respectively. In the removal process, the adsorption of radionuclides only took place at the surface of PAM/TiO2 and did not destroy its phase structure. Especially, the existence of U(VI) could reduce the capture of Eu(III) on the composites and vice versa. According to the XPS analysis results, the main interaction mechanisms between the PAM/TiO2 composites and radionuclides were electrostatic attraction together with the amide groups. The findings presented herein can provide important information for the simultaneous elimination of radionuclides in environmental pollution control.

Preparation and Application of Manganese Dioxide/Graphene Composite in Lithium Sulfur Batteries

Graphene/manganese dioxide composites and grapheme /manganese dioxide/sulfur (G/MnO2/ S) composite cathode were prepared by hydrothermal method and by vapor permeation, respectively. Their structure, morphology and specific surface area were characterized by X-ray diffraction, electron microanalysis and nitrogen adsorption analysis. The composites show morphology of nanosheets, high specific surface area and even distribution of sulfur. The sulfur accounts for 75% in the G/ MnO2/S composite by thermogravimetric analysis. The electrochemical performance of G/S and G/ MnO2/S cathode were investigated. The G/ MnO2/ S composite cathodes show excellent rate performance and cycle stability. At a 0.2C current density, initial discharge specific capacity is 1 061 mA·h·g−1 and maintains 698 mA·h·g−1 after 100 cycles; At a 1C current density, maximum discharge capacity reaches 816 mA·h·g−1 and average capacity decreasing rate is only 0.073%/ cycle after running over 400 cycles. Electrochemical mechanism of the composites cathodes was analyzed. The sulfur adsorption of MnO2 inhibited the loss of active material sulfur, so, the electrochemical performance of the complex was improved.

Preparation of various manganese dioxide composites and their desulfurization performance

The performance of desulfurization materials plays a key role in desulfurization technology. In this study, different types of manganese dioxide (MnO2) composites were prepared to improve desulfurization performance. These composites were characterized intensively via SEM, XRD, XPS, and BET. Desulfurization performance was measured through thermogravimetry (TG), and the desulfurization mechanism of different types of MnO2 composite was investigated. Results showed that the desulfurization performances of MnO2 composites are determined by the combined effects of the materials’ pore structure, specific surface area, active components and Mn valence contents. The desulfurization performances of high specific surface area MnO2 and porous MnO2 were enhanced on account of their excellent physical structures. The desulfurization performance of alkali metal additive LiOH doped MnO2 improved through the addition of active components. The desulfurization performance of bimetallic oxide MnO2/CeO2 improved through the synergistic effect of bimetallic oxides. The desulfurization performance of carrier type MnO2/NaY improved through the dispersion of MnO2 particles. Among the composites obtained, porous MnO2 revealed the best desulfurization performance, this composite demonstrated an average SO2 capture rate of 0.283 gSO2/gmaterial·h within the first hour of reaction, and its SO2 capture capacity was 0.633 gSO2/gmaterial.

Synthesis of a hierarchical carbon fiber@cobalt ferrite@manganese dioxide composite and its application as a microwave absorber.

In this study, a novel hierarchical carbon fiber@cobalt ferrite@manganese dioxide (CF@CoFe2O4@MnO2) composite was facilely prepared via a sol–gel method and hydrothermal reaction. The morphology, structure, chemical and element composition, crystal form, elemental binding energy, magnetic behavior and microwave absorbing performance of the composite were carefully investigated. According to its hysteresis loops, the composite exhibits a typical soft magnetic behavior, with a Ms value of 30.2 emu g−1. Besides, the as-synthesized CF@CoFe2O4@MnO2 composite exhibits superior microwave absorption performance mainly due to reasonable electromagnetic matching, and its minimum reflection loss value can reach −34 dB with a sample thickness of just 1.5 mm. The composite can be regarded as an ideal microwave absorber.

Polyaniline-MnO2 composites prepared in-situ during oxidative polymerization of aniline for supercapacitor applications

Polyaniline-manganese dioxide (PAni-MnO2) composites of varying compositions were prepared by in situ chemical oxidative polymerization of aniline monomer in aqueous acidic medium in the presence of different amounts of MnO2 formed in situ by the reaction of MnSO4 with KMnO4. PAni was also synthesized from aniline in acidic solution using ammonium peroxydisulfate as an oxidant for use as a reference material. PAni and PAni-MnO2 composites were characterized by FT-IR spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). FT-IR spectra revealed the formation of PAni and PAni-MnO2 composites. SEM images showed different morphologies of PAni and PAni-MnO2 composites and spherical MnO2 particles were distributed in the PAni matrix. Modified graphite electrode was prepared with PAni and PAni-MnO2 composites using solvent casting technique. Supercapacitive performance of PAni and PAni-MnO2 composites in 0.5 M aqueous Na2SO4 electrolytic solution was investigated using cyclic voltammetric and chronopotentiometric techniques. The specific capacitance (Cs) of PAni-MnO2 composites as high as 242 F g−1 could be obtained which was stable up to 1000 cycles at a current density of 0.25 A g−1. Electrochemical capacitors were developed by fabricating graphite electrodes modified with PAni and PAni-MnO2 composite electrodes in the range of 0.0–0.8 V. The Cs of the materials was found to be 99 to 242 F g−1 at a current density of 0.10 A g−1 in the potential range of 0.0 to 0.8 V. These results indicate that PAni and PAni-MnO2 composites have potential for application in supercapacitors.

Fabrication and characterization of chitosan – hydroxyapatite – zirconium dioxide composites for biomedical applications

In this study, hydroxyapatite-chitosan-zirconium dioxide composites were fabricated with compression method. Composites (S1, S2, S3, S4, S5) were prepared by varying the composition of HA-CTS-ZrO2. Characterization of samples were done before and after immersion in Ringer’s solution with the help of XRD and SEM. The formation of apatite layer and porous structure on samples were observed which was further confirmed by using SEM analysis. The weight gain of the samples were measured at interval of 7, 14 and 21 days. The findings revealed that the sample S3 has better bioactivity and weight gain among the other samples.

Preparation of TiO2 supported on MDF biochar for simultaneous removal of methylene blue by adsorption and photocatalysis

AbstractBACKGROUNDThis article reports for the first time the preparation and characterization of biochar/titanium dioxide (TiO2) composites by pyrolysis from medium‐density fiberboard (MDF) biomass. Their adsorptive and photocatalytic activities were evaluated by removal of methylene blue (MB) dye from aqueous solutions with and without UV‐light irradiation.RESULTSCharacterization results suggested that the composite have different intrinsic characteristics in relation to the precursors. The biochar and TiO2 amounts of the composite significantly affected its performance. The MB removal efficiency with 1 g L−1 of the composite with 10% w/w TiO2 (B10T sample) was 2.3 and 2.2 times faster than that the B5T and B1T samples, respectively, and 1.5 times faster than TiO2 alone.CONCLUSIONThe loading of TiO2 significantly enhanced the adsorption performance of the composite and factors such as specific surface area, pore volume and pore size of the biochar synergistically promoted the photocatalytic activity of TiO2, coupled with a lower band gap for all composites produced. Both adsorption and photocatalytic efficiencies were confirmed to contribute to the degradation of the aqueous solution of MB by the hydroxyl radical (•OH) in lower molecular mass by‐products. The synthesized composite is a promising alternative sustainable material for removing chemical contaminants, since the biochar used as a support comes from the waste of the furniture industry. © 2019 Society of Chemical Industry

Investigation of mechanical properties of polymer composites used for orthopedic application

Abstract Poly Tetra Fluoro Ethylene and Titanium Dioxide composites were developed as alternative materials for orthopaedic applications. The amount of Titanium Dioxide (TiO2) incorporated into the Poly Tetra Fluoro Ethylene (PTFE) polymer matrix with the ranges of 5%, 10% and 15% of weight proportion and these materials were successfully fabricated by compression moulding. In this research work the density, compression strength, bending strength and hardness of composite materials have been determined. Above test results are compared with currently used orthopaedic implants and they are found satisfactory.

Photocatalytic Performance of SiO2/CNOs/TiO2 to Accelerate the Degradation of Rhodamine B under Visible Light.

A silicon dioxide/carbon nano onions/titanium dioxide (SiO2/CNOs/TiO2) composite was synthesized by a simple sol-gel method and characterized by the methods of X-ray diffraction (XRD), scanning electronic microscope (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR), thermogravimetric analysis (TG), differential scanning calorimeter (DSC) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). In this work, the photocatalytic activity of the SiO2/CNOs/TiO2 photocatalyst was assessed by testing the degradation rate of Rhodamine B (RhB) under visible light. The results indicated that the samples exhibited the best photocatalytic activity when the composite consisted of 3% CNOs and the optimum dosage of SiO2/CNOs/TiO2(3%) was 1.5 g/L as evidenced by the highest RhB degradation rate (96%). The SiO2/CNOs/TiO2 composite greatly improved the quantum efficiency of TiO2. This work provides a new option for the modification of subsequent nanocomposite oxide nanoparticles.

Spectral and thermal studies on polyaniline–titanium dioxide nanocomposites by inverted emulsion techniques

Inverted emulsion polymerization technique using benzoyl peroxide, as an initiator, was used to prepare conducting polyaniline (PANI)/nano titanium dioxide (TiO2) composites. Polyaniline ratio was varied between 10 and 90% based on the yield percentage. The prepared nanocomposites were analyzed further by Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and four probe conductivity. The FTIR spectrum of pure PANI and its composites with nano-TiO2 shows the vibrational bands due to benzenoid, quinoid ring stretching etc. Conductivity of pure polyaniline was observed to be 1.6 S cm−1 and upon the addition of nano-TiO2 the conductivity decreases. X-ray diffraction of PANI–nano TiO2 composites reveals that the crystalline nature of TiO2 is retained. TGA thermogram of nanocomposites monitored the thermal stability of pure PANI which improved by the addition of TiO2 in different ratios. SEM image reveal that nano-TiO2 particles are uniformly distributed in the PANI matrix.