Introduction Of Metal Oxides Research Articles

Vivid-Colored Electrorheological fluids with simultaneous enhancements in color clarity and Electro-Responsivity

HypothesisSurface modification of dielectric materials changes the dipole–dipole interactions under electric fields, thereby controlling the electrorheological (ER) response. The introduction of metal oxides onto mica templates and further coating of dyes is expected to simultaneously improve the color clarity and ER performance. ExperimentsDye-coated TiO2 platelets on mica are synthesized for high-performance colorful ER fluids. A sol–gel method is utilized to grow TiO2 on mica to prepare precursor light-colored mica/TiO2 materials, which are coated with appropriate dyes to enhance the vividness as determined by the Commission Internationale de clairage L*a*b* color system. The color expression and color clarity improvement are explained via the light interference effect and the presence of chromophores. FindingsThe uniform TiO2 layers can be obtained under low pH conditions with controlled nucleation kinetics. The addition of dyes to TiO2 increases the surface area and porosity of ER materials and introduces heteroatoms that act as positive factors. In practical ER applications, dye-coated TiO2-based ER fluids exhibit higher ER performances compared with the corresponding light-colored TiO2-based ER fluids. The vivid-colored ER fluids could provide an easy selection for a wide range of rheological systems requiring a specific magnitude of stress by confirming the color.

Freestanding TiO@heteroatom-doped hollow multi-channel carbon fibers for lithium-sulfur batteries

Lithium-sulfur batteries are a promising candidate for the future energy storage devices due to its ultra-high theoretical specific capacity. However, the sluggish redox reactions, large volume changes and “shuttle effect” of lithium-sulfur materials have limited its large scale applications. In this work, the hollow multi-channel structure of freestanding carbon fibers were prepared by coaxial electrospinning and following high temperature treatment, which can provide abundant void to relieve the volume expansion of sulfur cathodes during charge-discharge and facilitates the permeation of electrolyte. Then the titanium oxide was successfully incorporated into carbon fibers to enhance the adsorption capacity for soluble polysulfides (Li2Sn, 4 ≤n ≤ 8). Finally, the boron and phosphorus elements were doped into carbon fibers to improve the electronic conductivity of the cathodes. As result, the three-dimensional TiO@boron-doped hollow multi-channel carbon fibers/sulfur cathode with a sulfur loading of 2.26 mg cm−2 deliver a high specific capacity of 1070 mAh g−1 and good cycling performance with capacity decay rate of 0.096% per cycle over 300 cycles at 0.1 A g−1. The strategy of hollow multi-channel structure design, heteroatom-doping and introduction of metal oxides with polar surfaces will provide a new idea for high performance lithium-sulfur batteries.

Changes of cross-linked network and DC electrical properties of nanocomposite silicone rubber under thermal aging

Nano dielectrics have brought hope for solving the problem of cable insulation at high voltage levels. In this paper, nano Al2O3 and MgO are doped to silicone rubber and the nanocomposites are aged at 200 °C for 0-80 days. The electrical conductivity and DC breakdown characteristics of aged materials are investigated. The microscopic and elemental properties are also analysis. It is found that with the increase of thermal aging time, electrical conductivity of all sets decreases first and then increases, while the DC breakdown voltage experiences a process of first increasing and then decreasing. During the initial aging process, secondary vulcanization of silicone rubber occurs, however, the cross-linked network degrades with further aging, which could explain the changes in electrical properties. The introduction of metal oxides could react with exfoliated radicals to form s table compounds, thus, the performance of Al2O3 and MgO doped materials have better electrical properties under thermal aging.

Notes in accordions—organized MXene equipped with CeO2 for synergistically adsorbing and catalyzing polysulfides for high-performance lithium-sulfur batteries

Limited by the shuttle effect, the application of lithium-sulfur batteries is not impressive. As an organ layered two-dimensional (2D) material, MXene has a great electrical conductivity and high specific surface area. Meanwhile, the introduction of metal oxides can restrain the shuttle effect. Hence, this paper prepared CeO2/MXene as a cathode material of Li-S batteries. Ce and Ti can chemically adsorb S, and the interlayer structure of MXene can limit S while the interlayer space can alleviate volume expansion. The discharge capacity at 0.5 C is as high as 1051.1 mAh g−1, and 921.9 mAh g−1 after 200 cycles. The average coulombic efficiency is 97.75%. The organized MXene with CeO2 like notes in accordions are new efficient materials for lithium-sulfur batteries.

Composition and morphology effects on catalase mimetic activity of potential bioactive glasses

The catalase mimetic activity (CMA) of potential bioactive glasses based on Hench - 45S5 Bioglass® (46.1%SiO2-24.4%Na2O-26.9%CaO-2.6P2O5 mol%, called H), Kokubo bioactive glass (50%SiO2–25%Na2O–25%CaO mol%, called K) and mesoporous bioactive glass (80%SiO2–15%CaO–5%P2O5 mol%, called MBG) modified by the introduction of metal oxide (MO, M = Ti, V, Mn, Fe, Co, Cu, Zr and Ce) was tested in order to verify how their composition, morphology and synthesis procedure influence the ability to inhibit oxidative stress in terms of decomposition of hydrogen peroxide (H2O2), a common reactive oxygen species (ROS).The characterization was achieved on the glasses before and after the soaking in H2O2 in order to obtain information about the kinetic order, the rate and the type of mechanism related to the decomposition H2O2 process. In fact, the H2O2 decomposition can follow a radical mechanism (with the formation of OH radical) or a peroxide-complex mechanism. Tests in SBF solutions were performed in order to verify the bioactivity in term of hydroxyapatite (HA) formation.The introduction of metal oxide into the glass composition promotes the CMA and the better catalytic activities were gained for the Co-, Mn-, Cu-, Ce- and Fe-containing glasses. All these glasses follow a 1st order kinetics but only in the case of Ce-containing glasses (H_4.0Ce) we observe a peroxide-complex mechanism. The Ce-containing glasses preserve their catalytic activity also coated with alginate and the reduction of glass powder dimension enhances the rate of H2O2 decomposition. Mesoporous glasses with a high specific surface area show a higher H2O2 decomposition rate with respect to that of melt-quenched derived glasses. The introduction of Ce, Cu, V, Ti, Zr and Fe do not modify the bioactivity in terms of HA formation during SBF tests (respect to H bioactive glass) and the alginate coating delay the HA formation without inhibiting its formation. H_5.3Co and H_5.3Mn showed the best catalytic performance (highest k value) but they seem not bioactive until 28 days of SBF soaking.By the data analysis obtained in this manuscript, we can affirm that the Ce-containing glasses are the most promising potential bioactive glasses with antioxidant properties.

Development of Waste Red-Mud Nanoparticle Decorated Laser-Induced Graphene Flexible Sueprcapacitor

Environmental benign, inexpensive, flexible, smart energy storage micro-supercapacitors, with high energy and power densities and long-term cyclic stability are appealing for next generation energy storage devices. Conventionally, highly conducting carbon-based nanomaterials with high-surface areas are extensively used as supercapacitor electrode and the introduction of metal oxides (or conducting polymers) induces pseudocapacitance and can further enhances the specific capacitance and energy density. Red mud (RM), an aluminum industry waste by-product which is a rich source of hematite phase Fe2O3. RM is environmentally hazardous due to its alkalinity and is produced at an annual rate of ~ 110 million tonnes each year, much of which is not well utilized, and left to lie in large lakes; thus, methods of finding value-added applications for RM are well sought after. In this study, we used mechanical milling to produce uniform spherical RM nanoparticles and utilized these in a flexible micro-supercapacitor device. The as-synthesized nanoparticles were decorated over a laser induced porous 3D graphene (LIG) on a polyimide substrate. The composite electrode material was characterized using transmission electron microscopy (TEM), field effect scanning electron microscopy (FESEM), X-ray photo electron spectroscopy (XPS), Raman spectroscopy and cyclic voltammetry (CV). A solid-state ionic liquid based polymer gel electrolyte was produced using a mixture of ionic liquids {[EMI][TFSI] and [EMIM][BF4]} and a PVDF polymer. Inkjet printing technique was employed to produce the silver current collector and the as fabricated inter-digitated micro-supercapacitor device (Figure 1a) exhibited an areal capacitance of 203 mF cm-2 with a higher potential window of 2.7 V, high energy density of 0.018 mW h/cm2 at 0.66 mW/ cm2 power density. RM decoration increased the energy density of the device by 3.7 fold compared with pristine LIG device (Figure 1b). Rapid lateral ion flow in the planar architecture, presence of metal oxides (mostly hematite), higher electrochemically active surface area, better charge transfer kinetics were shown to yield improvements in the energy-density and the electrochemical performance of the device. An in-depth electrochemical study also revealed that the charge storage mechanism was governed by diffusion driven pseudocapacitance. The device exhibited good robustness and could resist bending and flexing and the prototype device exhibited to power a white-light LED (Figure 1c). Overall, this work demonstrates that RM may be used as a low-cost pseudocapacitive element in supercapacitor electrodes and aid in reducing the environmental impact of the aluminium production cycle by recycling this abundant waste product. Figure 1

Effect of additive on CuO-ZnO/SBA-15 catalytic performance of CO2 hydrogenation to methanol

AbstractThree kinds of porous catalysts CuO-ZnO/SBA-15 (CZ/SBA-15), CuO-ZnO-MnO2/SBA-15 (CZM/SBA-15) and CuO-ZnO-ZrO2/SBA-15 (CZZ/SBA-15) were synthesized by impregnation method with a siliceous framework mesoporous molecular sieve SBA-15. The performance of all catalysts for catalytic hydrogenation of CO2 to methanol was evaluated on a fixed bed reactor, combined with N2 adsorption-desorption (BET), X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), temperature programmed desorption (H2-TPD, CO2-TPD), N2O titration, X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) . The results show that the introduction of metal oxide in the catalyst changes the pore size and specific surface area of the SBA-15 molecular sieve support. The CuO-ZnO-MnO2/SBA-15 and CuO-ZnO-ZrO2/SBA-15 have high copper dispersion (DCu), large specific surface area (ACu), small surface CuO particle size, and easy to be reduced. Compared with the Mn-O cluster, the Zr-O cluster enhances the basic site and improves the methanol selectivity. In addition, CuO-ZnO-ZrO2/SBA-15 has the highest oxygen vacancy concentration and better catalytic activity among three catalysts. The methanol selectivity of CuO-ZnO-ZrO2/SBA-15 is 25.02%, which is 28% and 136.9% higher than those of CuO-ZnO/SBA-15 and CuO-ZnO-MnO2/SBA-15, respectively.

The construction of three-dimensionally ordered macroporous (Fe, Zn, Cu, Co)/LaMnO3 with controllable gelation rate and their catalytic combustion properties

The gelation rate of LaMnO3 colloid was successfully modulated by introducing trace of tartaric acid and nitric acid simultaneously to construct 3DOM LaMnO3. To enhance surface oxygen vacancies, Fe, Zn, Cu and Co metal oxides were introduced on the surface of 3DOM LaMnO3 to modulate their surface composition, respectively. The morphology, crystalline, composition and reducibility of the prepared catalysts were characterized by SEM, XRD, XPS and TPR, respectively. The results showed that the surface oxygen defects can be enhanced distinctly with the introduction of metal oxides. Among the four metal oxides modified LaMnO3, the Co/LaMnO3 sample exhibited highest oxygen defects content and lowest reduction temperature. The catalytic properties of the five samples follow as the order: LaMnO3 < Fe/LaMnO3 < Zn/LaMnO3 ≈ Cu/LaMnO3 < Co/LaMnO3, which is consisted with that of their surface oxygen vacancies content, indicating that oxygen vacancies content is a crucial factor on catalytic oxidation of ethyl acetate.

Improving the catalytic efficiency of carbon-based active sites by trace oxide promoters for highly productive olefin synthesis

The catalytic ODH activation energy on CNTs significantly decreased by the introduction of metal oxides. The propane turn-over efficiency of each original carbon-based active site consequently increased exponentially.

Hidrólise de celulose por catalisadores mesoestruturados NiO-MCM-41 e MoO3-MCM-41

This study was carried out to synthesize, characterize and evaluate the application of mesoestruturated catalysts MCM-41, 5%MoO3-MCM-41 and 5%NiO-MCM-41 in the hydrolysis of microcrystalline cellulose. XRD results indicate that the phase of mesoporous MCM-41 was obtained and that the introduction of metal oxides did not affect this mesoporous phase. About the heterogeneous hydrolysis reaction, it was observed that the increase in temperature results in a higher concentration of glucose and the catalyst 5%MoO3-MCM-41 provides the highest concentrations of glucose.

The Oxidation Activity and Acid-base Properties of V2O5-based Binary Catalysts

Abstract The oxidation of cis-2-butene, butadiene, and acetic acid was carried out by using a series of V2O5–XnOm (atomic ratio=9 : 1) catalysts with more than twenty metal oxides (XnOm). The results were compared with the dehydration activity for isopropyl alcohol (IPA), as a measure of acidity, and with the ratio, dehydrogenation activity for IPA/dehydration activity for IPA, used as a measure of the basicity of catalyst. The activity for the oxidation of butadiene and that for the isomerization of butene are correlated with the acidity, and the activity for the oxidation of acetic acid with the basicity of the catalyst. The selectivity to maleic anhydride from butene and butadiene is scarcely influenced by the introduction of metal oxides. Butene is mainly oxidized to acetic acid as a result of C–C fission. The selectivity to acetic acid is enhanced when the catalyst is highly acidic, decreasing with increase in basicity. It is concluded that the introduction of metal oxides into V2O5 modifies the acid-base properties of the catalyst, inducing a change in oxidation activity and selectivity.

Bonding Mechanisms in Glass to Metal Seals

The bonding mechanism of glass to metal seals was investigated on practical sealing materials. On three sorts of glasses (soda-lime glass, boro-silicate glass, and lead glass) to which various metal oxides were added, thermal expansion and contact angle against metals, as well as adherence strength, were measured.In soda-lime glass to iron metal seals, the introduction of iron oxide into the glass enhanced the corrosion of the metal surface, lowered the contact angle and strengthened the adherence. The change in the thermal expansion, slight as it was, suggested the loosening of network structure or the increase in “effective” chemical bonding. In these seals, physical or mechanical bonding, as well as chemical bonding, seemed to play an important role.In boro-silicate glass to iron-nickel-cobalt alloy seals, metal oxides introduced into the glass increased the thermal expansion considerably, lowered the contact angle and strengthened the adherence. As compared with the soda-lime glass to iron metal seals, mechanical bonding was rather weak, whereas chemical bonding became stronger. In practical sealing, bonding through oxide interlayer also seemed to participate in the glass to metal adherence.In glass to chromium seals, the introduction of metal oxides into the glass raised the contact angle, but had no effect on the adherent strength. Oxide interlayer formed by the reaction between molten glass and metal, seemed to play an important role.In glass to copper seals, adherence by chemical bonding seemed to be effective, but in practical sealing adherence through oxide interlayer seemed also important.