Effect Of Transition Metal Oxides Research Articles

The effect of transition metal oxides in the La/TiO2 structure for the photocatalytic degradation of malachite green under UV and visible light irradiation

Herein, La@MxOy/TiO2 (M = V, Cr, Mn and Fe) composite catalysts were prepared based on the sol–gel method as an effective adsorbent and photocatalyst for the degradation of malachite green from an aqueous solution under UV–Vis light. Under experimental conditions, a maximum adsorption capacity of 57.10% for the malachite green dye was achieved with La@Fe2O3/TiO2. Moreover, this composite showed 78.62% photodegradation efficiency for malachite green. A quadratic model constructed using the response surface method showed that the maximum efficiency of photodegradation of malachite green can be achieved at pH 11 and a process time of 35 min.

Catalytic effects of transition metal oxides on HTPB-based fuel polymer matrices

Low regression rate due to difficult pyrolysis is a major challenge in the practical application of terminated hydroxyl‑terminated polybutadiene (HTPB)-based fuels in hybrid rocket propulsion. Accelerating the decomposition of the polymer matrix is an effective method to improve the regression rate of HTPB fuels. To determine the difference in combustion performance between different transition metal oxides loaded HTPB-based fuels, nickel oxide (NiO), ferric oxide (Fe2O3), copper oxide (CuO) and manganese dioxide (MnO2) were introduced into the HTPB matrix at 5% mass fraction. The experimental results showed that the metal oxides could significantly catalyze the pyrolysis of HTPB-based fuels and enhance the fuel regression rate, and the catalytic effect was mainly concentrated in the middle and late stages of the thermal decomposition process of polybutadiene components. Among the four transition metal oxides, CuO and MnO2 showed better catalytic effects on the combustion performance of HTPB-based fuels in the high oxygen mass flux region, while NiO showed better catalytic effects in the low oxygen mass flux region. The present study compares the regression rate of fuel grains modified with different transition metal oxides, which provides a basis for the selection of future catalysts, verifies the catalytic effect of the transition metal oxides on the combustion of HTPB-based fuels and further analyzes the combustion reaction mechanism of the fuels.

Synthesis of CoMn‐LDH@MXene Hybrid Materials as Flame Retardant to Effectively Improve the Fire Safety of Thermoplastic Polyurethane

AbstractIn recent years, MXene 2D materials have shown good performance in enhancing the flame retardant properties of composite materials, but it is still tricky to improve the compatibility with the polymer matrix. This work explores a simple method for the synthesis of MXene based nanohybrids (CoMn‐LDH@MXene) by hydrothermal synthesis using MXene and layered double hydroxides (CoMn‐LDH) to construct a flame retardant system with excellent performance. The results show that the MXene nanosheets are less built up and more dispersed in the TPU collective due to the inclusion of LDH, giving the TPU composites excellent flame retardant and smoke suppressant properties. Compared to TPU without flame retardant, TPU composites with 2 wt% CoMn‐LDH@MXene reduced PHRR by 33.7 % and THR by 28.7 %. The TPU/2wt %CoMn‐LDH@MXene composites also showed better flame and smoke suppression performance, PSPR, TSP, PCO and PCO2 were reduced by 44.4 %, 22.7 %, 37.7 % and 27.2 % respectively, the production of Hydrocarbons and HCN were also reduced. Barrier effect of transition metal oxide catalysed carbon layer formation, combustion blocking effect of hybrid material nanosheets, cooling effect of water vapour from thermal decomposition of LDH and the gas phase dilution effect are the main reasons for the increased fire safety of TPU composites.

First-principles study of quantum capacitance of transition metal oxides and nitrogen functionalized graphene as electrode materials for supercapacitor

Graphene, with many advantages, is considered an active electrode material for the supercapacitors. However, its actual utilization performance is limited by its low specific capacitance caused by the poor quantum capacitance. In this article, we explored the effects of transition metal oxides (TMOs = MnO, FeO, CoO, NiO, CuO and ZnO) on the geometric structure, electronic properties, quantum capacitance (CQ) and surface storage charge (Q) of graphene-based materials using first-principles method. The findings of this article illustrate the TMOs could stably adsorb on the surface of graphene-based materials, making the systems exhibit metallic characteristic with conducive electron transfer. Around the Fermi level, introducing the electronic states of TMOs makes the modified graphene reveal a considerable CQ and Q in the negative applied voltages, especially the NiO-G system. Furthermore, the TMOs and nitrogen atoms co-modified graphene can further increase the quantum capacitance value, and the selection of electrode materials can be controlled by the N modification. The interesting results can provide a straightforward and effective strategy for designing the selection graphene-based material electrodes applied in high-energy supercapacitor.

Effect of transition metal oxide on microwave co-pyrolysis of sugarcane bagasse and Chlorella vulgaris for producing bio-oil

Bio-oil produced by biomass pyrolysis has been widely concerned because of its clean and sustainable advantages. In this work, the co-pyrolysis characteristics and product yield of sugarcane bagasse (BA) and Chlorella vulgaris (CV) under different CuO additions were studied using microwave oven. Then the components of bio-oil were identified by GC-MS. The results showed that co-pyrolysis optimized the pyrolysis characteristics and improved the yield and quality of bio-oil. B8C2 (BA/CV=8:2) group was the optimal mixing ratio with the maximum bio-oil yield and best pyrolysis characteristics. CuO promoted the bio-oil production of B8C2, and 50% CuO improved the pyrolysis characteristics most effectively. Besides, the co-pyrolysis of BA and CV played an obvious denitrification effect, promoted the formation of long-chain fatty acids, N-heterocycles, phenols and polycyclic aromatic hydrocarbons (PAHs), and increased the higher heating value (HHV) of bio-oil. CuO increased the contents of phenol and furans, and decreased acid value and sulfur content of bio-oil, thus making it more accessible for processing and utilisation at a later stage.

Thermal, chemical properties and structure evolution of medical neutral glasses modified by transition metal oxides

Against the endless new pandemics, market prospect of medical neutral glasses unprecedentedly enlarged. To obtain instructive guidance for optimizing neutral glass, the different effects of transition metal oxides (TiO2 and Fe2O3) on glasses properties and structure were studied in this work. Based on X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and performance analysis, Ti and Fe were certified as modifiers uniformly; but they showed selective influence on network structural units for the diverse adjustments on free oxygen and compensation cations: Fe2O3 is associated with arising of [BO4], and TiO2 promoted formation of [AlO4]. In general, TiO2 and Fe2O3 weakened thermal stability and partial chemical properties for altered network linkage and compactness, however, they enhanced water resistance due to a unique blocking function. With them co-doped, amber neutral glasses were acquired, which possessed the high thermal stability but lower chemical resistance. All glasses satisfy the related requirements for medical package application.

Effect of Transition-Metal Oxide M (M = Co, Fe, and Mn) Modification on the Performance and Structure of Porous CuZrCe Catalysts for Simultaneous Removal of NO and Toluene at Low–Medium Temperatures

Effect of Transition-Metal Oxide M (M = Co, Fe, and Mn) Modification on the Performance and Structure of Porous CuZrCe Catalysts for Simultaneous Removal of NO and Toluene at Low–Medium Temperatures

Chemical conversion based on the crystal facet effect of transition metal oxides and construction methods for sharp-faced nanocrystals.

In-depth research has found that the nanocrystal facet of transition metal oxides (TMOs) greatly affects their heterogeneous catalytic performance, as well as the property of photocatalysis, gas sensing, electrochemical reaction, etc. that are all involved in chemical conversion processes. Therefore, the facet-dependent properties of TMO nanocrystals have been fully and carefully studied by combining systematic experiments and theoretical calculations, and mechanisms of chemical reactions are accurately explained at the molecular level, which will be closer to the essence of reactions. Evidently, as an accurate investigation on crystal facets, well-defined TMO nanocrystals are the basis and premise for obtaining relevant credible results, and shape-controlled synthesis of TMO nanocrystals thereby has received great attention and development. The success in understanding of facet-dependent properties and shape-controlled synthesis of TMO nanocrystals is highly valuable for the control of reaction and the design of high-efficiency TMO nanocrystal catalysts as well as other functional materials in practical applications.

Effect of Transition Metal Oxide on Microwave Co-Pyrolysis of Sugarcane Bagasse and Chlorella Vulgaris to Produce Bio-Oil

Effect of Transition Metal Oxide on Microwave Co-Pyrolysis of Sugarcane Bagasse and Chlorella Vulgaris to Produce Bio-Oil

Enhanced aquathermolysis of extra-heavy oil by application of transition metal oxides submicro-particles in relation to steam injection processes

In order to investigate the catalytic effects of transition metal oxides submicro-particles on aquathermolysis of Liaohe extra-heavy crude oil, the catalysts NiO, α·Fe2O3 and Co3O4 are used and evaluated during the experiments. The optimum mass fraction of the catalyst and water was determined to be 5.0 wt% and 30 wt%, respectively. The optimum reaction time for aquathermolysis was 24 h, and the optimum reaction temperature was 240 °C. The analysis results showed the heavy oil was upgraded dramatically by addition of the catalysts based upon viscosity reduction, saturate/aromatics/resins/asphaltenes analyses, elemental analysis, Fourier transform infrared spectroscopy and gas chromatography. All results show the heavy oil is in situ updated dramatically by catalytic aquathermolysis under the optimum operating conditions. A five-lump model is proposed for estimating kinetic parameters of aquathermolysis and agrees well with the experimental data.

Evaporation behavior of SiO2 glass doped with various transition metal oxides

AbstractTo investigate the effect of transition metal oxides on the evaporation characteristic of SiO2 glass at 1700°C, nine transition metal oxides were added to SiO2 glass. The results show that V2O5, MoO3, and WO3 have little effect on the high‐temperature stability of SiO2 glass due to their evaporation at 1500‐1700°C. Besides, Nb2O5 and Ta2O5 reduce the evaporation of SiO2 by covering the surface of the sample. Moreover, by improving the content of cristobalite, the evaporation of the SiO2‐Cr2O3 sample decreases. Meanwhile, TiO2, ZrO2, and HfO2 are beneficial to decreasing the evaporation of SiO2 glass because Ti, Zr, and Hf diffuse into c‐SiO2. Meanwhile, the SiO2‐HfO2 sample possesses the least evaporation.

The Effects of Transition Metal Oxides (Me = Ti, Zr, Nb, and Ta) on the Mechanical Properties and Interfaces of B4C Ceramics Fabricated via Pressureless Sintering

There is little available research on how different transition metal oxides influence the behavior of B4C-based ceramics, especially for Ta2O5 and Nb2O5. B4C-MeB2 (Me = Ti, Zr, Nb, and Ta) multiphase ceramic samples were prepared via in situ pressureless sintering at 2250 °C, involving the mixing of B4C and MeOx powders, namely TiO2, ZrO2, Nb2O5, and Ta2O5. The phase constituents, microstructures, and mechanical properties of the samples were tested. The results indicated that different transition metal elements had different effects on the ceramic matrix, as verified through a comparative analysis. Additionally, the doped WC impurity during the ball milling process led to the production of (Me, W)B2 and W2B5, which brought about changes in morphology and performance. In this study, the Ta2O5-added sample exhibited the best performance, with elastic modulus, flexural strength, Vickers hardness, and fracture toughness values of 312.0 GPa, 16.3 GPa, 313.0 MPa, and 6.08 MPa·m1/2, respectively. The comprehensive mechanical properties were better than the reported values when the mass fraction of the second phase was around five percent.

Effects of transition metal oxides on pyrolysis properties of PVC

Polyvinyl chloride (PVC) produces a large amount of solid wastes because of its wide use. How to dispose quickly and harmlessly of the PVC solid wastes and turn into a resource is currently a major problem. In this paper, the experimental material was PVC. Thermogravimetric analyzer (TG) and pyrolysis-gas chromatography-mass spectrometer (Py-GC–MS) were used to study the pyrolysis characteristics of PVC with transition metal oxide. The effect of in-situ pyrolysis of PVC in N2 on transition metal oxides was studied in a SX3−4-10A muffle furnace. The composition of tars captured by the cold trap was analyzed by GC–MS. The residual carbon after pyrolysis was analyed by scanning electron microscope (SEM) and XRD. The results of PY-GC–MS and GC–MS showed that the two stages of PVC pyrolysis were advanced with the transition metal oxide.The decomposition peak temperature increased to make PVC pyrolysis more complete. The transition metal oxide reduced significantly the production of benzene, toluene, indene, naphthalene, anthracene and other compounds during the pyrolysis of PVC. The results of SEM and XRD showed that transition metal oxides absorbed HCl produced by pyrolysis and increased the amount of residual carbon in the system. These studies provided a theoretical basis for the pyrolysis rapidly of PVC.

Deoxygenation of triolein to green diesel in the H2-free condition: Effect of transition metal oxide supported on zeolite Y

H2-free deoxygenation is a very important process in producing high-quality biofuel without the use of H2 gas supply. Considering the costly price of the noble metals, transition metal (TM) based catalysts are more affordable, and the performance is comparable to the noble metal-based catalyst. In this study, TMO supported on zeolite Y catalysts (Ni-, Cu-, Co-, Zn- and Mn-Y) are prepared via wet-impregnation for deoxygenation of triolein, a model compound of non-edible oil under H2-free condition. The deoxygenation activity of TMO supported on zeolite Y is following the order of Ni-Y > Co-Y > Cu-Y > Mn-Y > Zn-Y. The nickel oxide supported on zeolite-Y (Ni-Y) shows the highest conversion up to 76.21 % with 84.28 % hydrocarbon selectivity after reacted at 380 °C for 2 h. Besides, the selectivity toward diesel range hydrocarbon is 92.61 %. The superior deoxygenation activity of Ni-Y can be related to synergistic effect between the reduced B/L and high hydrogenolysis ability of Ni that promote the decarboxylation reaction, suppress the cracking and polymerization of heavy hydrocarbon. Therefore, Ni-Y is a potential catalyst to obtain high quality green diesel from non-edible oil through catalytic deoxygenation without addition of external H2 source.

The influence of carbon-encapsulated transition metal oxide microparticles on reducing toxic gases release and smoke suppression of rigid polyurethane foam composites

The rapid development and massive consumption of rigid polyurethane foams (RPUF) has drawn attention to their fire safety related problems, such as the heat release and notable generation of smoke and toxic gases in fire. Three novel types of carbon-encapsulated transition metal oxide microparticles, Cu@C, Fe2O3@C and Cu2O@Fe2O3@C, were prepared via a simple hydrothermal method in this research. Potential smoke and toxicity suppression by the as-prepared carbon-encapsulated hybrids in flame-retardant RPUF composites with ammonium polyphosphate (APP) and dimethylmethylphosphonate (DMMP) were investigated. Compared with pure RPUFs, the peak heat release rate (pHRR) value of RPUF/A5-D5/5.0Fe2O3@C decreased by 40.5%, indicating the obvious improved flame retardancy. Besides, the related mechanisms of smoke suppression and toxic based on the catalytic effect of transition metal oxide was also proposed on the basis of experiment results.

The effect of transition metal oxides on the sintering and properties of ceramics in the ZrO2-Al2O3 system

The paper presents the results of the investigation of the transition metals oxides – cobalt and iron additives influence on the sintering and properties of the ceramic material based on ZrO2- Al2O3 system with 10 wt.% Al2O3. It is shown that the addition of the oxides resulted in the significant increase of the sintered ceramic materials ZrO2-10%Al2O3 strength and decrease of sintering temperature. The maximum bending strength was more than 800 MPa (sintered at 1450 °C) and porosity was less than 1%.

Effect of transition metal oxides on fabrication of in-situ synthesized Mg2B2O5 whisker porous ceramics

The porous ceramics with a skeleton structure of magnesium borate (Mg2B2O5) whiskers were in situ synthesized by firing a compact of high-energy ball milled mixtures containing the reactants of boric acid (H3BO3) and basic magnesium carbonate [(MgCO3)4 · Mg(OH)2 · 5H2O] (BMC), and the transition metal oxides (Fe2O3 and NiO) sintering aids. The effect of sintering aids on the phase transformation, morphology development of Mg2B2O5 whiskers and physical properties of porous ceramics were investigated. The results demonstrated that the addition of Fe2O3 inhibited the phase transition from monoclinic Mg2B2O5 to triclinic Mg2B2O5 and promoted the increase of average aspect ratio of whiskers, while introduction of NiO retarded whisker growth. An optimal synthesis temperature for well-developed porous structure of all samples is at 850 °C. Compared with samples sintered without and with sintering aid NiO, sample sintered with Fe2O3 has higher average aspect ratio of whisker and open porosity as well as compressive strength at the same temperature.

Temperature dependent current-voltage characteristics of Au/n-Si Schottky barrier diodes and the effect of transition metal oxides as an interface layer

Temperature dependent current–voltage (I‒V) characteristics of Au/n-type silicon (n-Si) Schottky barrier diodes have been investigated. Three transition metal oxides (TMO) are used as an interface layer between gold and silicon. The basic Schottky diode parameters such as ideality factor (n), barrier height (ϕb0) and series resistance (Rs) are calculated and successfully explained by the thermionic emission (TE) theory. It has been found that ideality factor decreased and barrier height increased with increased of temperature. The conventional Richardson plot of ln(I0/T2) vs. 1000/T is determined the activation energy (Ea) and Richardson constant (A*). Whereas value of ‘A*’ is much smaller than the known theoretical value of n-type Si. The temperature dependent I–V characteristics obtained the mean value of barrier height (ϕb0¯) and standard deviation (σs) from the linear plot of ϕap vs. 1000/T. From the modified Richardson plot of ln(I0/T2) ˗ (qσ)2/2(kT)2 vs. 1000/T gives Richardson constant and homogeneous barrier height of Schottky diodes. Main observation in this present work is the barrier height and ideality factor shows a considerable change but the series resistance value exhibits negligible change due to TMO as an interface layer.

Transition metal oxides in the electrocatalytic oxidation of methanol and ethanol on noble metal nanoparticles

In this contribution, we briefly describe the papers published over the past two years regarding the effects of transition metal oxides, utilized either as supports or as co-catalysts, on the electrochemical oxidation of methanol and ethanol on Pt and Pd nanoparticles. Oxides are inexpensive, easy to incorporate into catalysts and may also help to mitigate degradation. The difficulties of comparing results of different works that arise mainly from a wide diversity of experimental conditions, as well as some inconsistencies among reported data are discussed. Approaches that could lead to new understandings of the mechanisms of activity enhancement by oxides and the role of metal-support interactions are highlighted.

Preparation and Study of Bismuth Oxide Doped and co-Doped with Cobalt(III) and Holmium(III) via Sol-Gel Method

In this research work the solid-solutions of (Bi2O3)1-x (Co2O3)x, (x= 0.05, 0.1) (1), (Bi2O3)1-x (Ho2O3) x, (x= 0.025, 0.05) (2), and (Bi2O3)1-x-y (Co2O3)x (Ho2O3)y, (x=0.05) ; (y= 0.01, 0.02) (3) have been synthesized using sol-gel method. The effects of transition metal oxides doping on the crystallization and phase transition of the Bi2O3 were discussed by X-Ray Diffraction (XRD). The XRD pattern showed that 1 and 3, have Body Center Cubic (bcc) single phase; similar to γ- Bi2O3. While 2, has phase transition from bcc to tetragonal phase. The surface morphology of the samples was assessed by Scanning Electron Microscopy (SEM). Furthermore electrochemical properties of electrodes modifying by these new synthesized ceramics were studied by Cyclic Voltammetry (CV).