O2 Samples Research Articles

High-Performance Zr-Doped P3-Type Na0.67Ni0.33Mn0.67O2 Cathode for Na-Ion Battery Applications

Sodium-ion battery (SIB) technology started to bloom along with lithium-ion batteries (LIBs) as a supportive energy source to alleviate the cost of lithium sources for the development of energy storage devices and electric vehicles. Layered cathode materials are considered potential candidates to produce high-energy-density batteries. Among the layered cathode materials, P3-type cathodes are the least investigated in spite of their capacities, which are comparable to those of P2-type cathodes. P3-type cathodes show high polarization, leading to a poor cycle life, which impedes their extensive use in practical applications. In this work, we report on zirconium doping as an effective strategy to improve cycling stability and reduce voltage fading, another serious issue of layered cathode materials. It is found that an optimum composition of the P3-type cathode with Zr doping at the Mn site, leading to a composition of Na0.67Ni0.33Mn0.64Zr0.033O2, shows good electrochemical performance in terms of retention (89% after 100 cycles) when compared to Na0.67Ni0.33Mn0.60Zr0.067O2 (85% after 100 cycles) and an undoped sample (83% after 100 cycles). Also, remarkable performance is delivered by the Na0.67Ni0.33Mn0.64Zr0.033O2 sample, with a retention rate of 72% after 450 cycles. This result is also supported by an analysis of the amount of polarization for undoped and doped samples, which found that doping helps in improving the diffusion of ions, and the least polarization is obtained for the Na0.67Ni0.33Mn0.64Zr0.033O2 sample.

Dielectric and room temperature ferromagnetism in vacuum annealed Bi(Zn0.5Zr0.5)O3 modified PbTiO3 ceramics

Polycrystalline solid solutions of (1-x)PbTiO3-(x)Bi(Zn0.5Zr0.5)O3[x = 0.10, 0.20, 0.30] have been synthesized by using solid state reaction method and followed by air annealing (AA)/ vacuum annealing (VA). All the samples show single phase perovskite structure with tetragonal symmetry (P4mm). Structural parameters are calculated using the Rietveld refinement technique. With the help of Scanning Electron Microscope (SEM), the surface morphology of all the samples is recorded at room temperature. The influence of VA on dielectric parameters such as dielectric constant and tangent loss of the synthesized samples are studied and compared with that of AA samples. These results unfold superior dielectric properties of VA samples as compared to AA samples. Intriguingly, the VA samples exhibit exotic ferromagnetism in non-magnetic PbTiO3–Bi(Zn0.5Zr0.5)O3 samples, transforming these into room temperature magneto-electric multiferroics. Besides, both the ferroelectric and ferromagnetic order parameters were found to increase with the increase in Bi(Zn0.5Zr0.5)O3 doping in PbTiO3. The enhanced physical properties witnessed in VA PbTiO3–Bi(Zn0.5Zr0.5)O3 samples localized hopping of charge carriers confined to the grain.

Magneto-Optical Properties of Ni0.4Cu0.3Zn0.3Gd0.125Fe1.875O4 Nano Ferrite for Application of Soft Magnetic Material

Abstract: Ni0.4Cu0.3Zn0.3Gd0.125Fe1.875O4 spinel ferrite powder is successfully synthesized using sol-gel auto combustion technique. The structural, optical and magnetic properties investigated by using X-ray Diffractometer, FTIR Spectrometer, Scanning Electron Microscope and Vibrating Sample Magnetometer (VSM). XRD analysis confirmed that formation of Nano crystalline cubic spinel structure of the sample. The crystallite size of synthesized nanoparticles is about 29.45nm. The IR study support the confirmation spinel structure of Ni0.4Cu0.3Zn0.3Gd0.125Fe1.875O4 sample. Band gap energy Eg obtained using UV-Visible absorption data is about 2.4238 eV. The magnetic properties have been studied from VSM data shows that

Bipolar magnetic switching and large exchange-bias in Fe-substituted SmCrO3

Rare-earth orthochromite is an interesting system in the view of its complex magnetic ordering due to competing interaction between different magnetic ions. Here, Fe-substituted SmCrO3 samples were prepared by solid-state route to investigate their intriguing magnetic properties towards exploring its application potential. The magnetic studies revealed antiferromagnetic (AFM) ordering at Nèel temperature (T N) ∼ 181 K, magnetic compensation temperatures (T COMP) at ∼137 K and 50 K, and spin-reorientation temperature (T SR) at 64 K in SmCr0.8Fe0.2O3 sample. Additionally, the system exhibited negative magnetization under field-cooled conditions which allowed the field as well as temperature controllable magnetization switching behavior. Notably, the Fe-substituted SmCrO3 sample displayed a remarkable exchange bias (H EB) value of ∼1.39 T at 10 K due to the coexistence of ferromagnetic and AFM ordering at different cationic sites. The M–H loops recorded under positive and negative field-cooled conditions ruled out the minor-loop effect. Theoretical models applied on the training effect studies confirmed the observed exchange-bias effect.

BaSn0.96-XZr0.04MXO3 (M = Mn, Fe or Co, x = 0, 0.02) for spin-based devices: Ferromagnetic properties

In this study, Zr and/or Mn, Fe or Co ions were used to induce a robust room temperature ferromagnetic nature in perovskite BaSnO3 for high performance information applications. Dilute magnetic semiconductor compositions with formula of BaSn0.96-XZr0.04MXO3 (M = Mn, Fe, Co, x = 0, 0.02) have been synthesized at 1150 °C. For all compositions, mono-phase of cubic BaSnO3 structure with very small impurities of SnO2 were recorded based on X-ray diffraction analysis. The relation between ionic size of dopants and crystal dimension of BaSnO3 suggests the of Sn4+-site by Zr4+, Mn2+, Fe2+ or Co2+ ions. Extended absorption tails to visible light region were found for BaSn0.94Zr0.04Mn0.02O3 and BaSn0.94Zr0.04Co0.02O3 samples, owing to strong defect band transition absorption. Due to the addition of Zr and/or Mn, Fe or Co ions high refine of BaSnO3 morphology from inhomogeneous large grains to well distribute small one were seen. The XPS results of BaSn0.96Zr0.04O3 and BaSn0.94Zr0.04Co0.02O3 samples confirm that Ba, Sn, O and Zr are in the oxidation states of +II, +IV, −II and +IV/+III, respectively. Magnetically, incorporation of 4 wt% Zr4+ ions (empty 4d-orbital) induced a full-saturated spin ferromagnetic order with saturation magnetization of 1.16 emu/g, retentivity of 0.11 emu/g and coercivity of 147 Oe. Also, codoping by Zr/Co ions stimulates a full-saturated spin ferromagnetic order with saturation magnetization of 1.36 emu/g, retentivity of 0.17 emu/g and coercivity of 149 Oe. The empty 4d-Zr4+ ions have high ability in reversing the diamagnetic nature of BaSnO3 to ferromagnetic one through interaction with oxygen vacancies. The outer 4d-shell of Zr and 3d-orbital of Co with the oxygen vacancies induce the strong magnetic exchange interaction. Through looking into the previous studies on the magnetic properties of BaSnO3, the recorded saturation magnetization of 4 wt% Zr and 4 wt% Zr + 2 wt% Co ions are remarkable values.

Co-Doping of Al3+ and Ti4+ and Electrochemical Properties of LiNiO2 Cathode Materials for Lithium-Ion Batteries.

LiNiO2 cathode material for lithium-ion batteries has the advantages of high specific capacity, abundant resources, and low cost, but it suffers from difficulties in preparation, structural instability, and serious capacity decay. In this work, highly pure and layered structural LiNi0.95 Ala Ti0.05-a O2 (a=0, 0.025, 0.05) cathode materials were synthesized by a simply sol-gel method. The cation mixing of Ni2+ and Li+ , structural deterioration, irreversible conversion between H2 and H3 phases and unstable surface and CEI (Cathode-electrolyte interface) film can be effectively suppressed by co-doping with Al3+ and Ti4+ . A preferred LiNi0.95 Al0.025 Ti0.025 O2 sample provides a discharge specific capacity of 223 mAh g-1 at 0.1 C and 148.32 mAh g-1 at 5 C, a capacity retention of 72.7 % after 300 cycles at 1 C and a Li+ diffusion coefficient of about 2.0×10-9 cm2 s-1 .

Effect of Pr doping on structure and luminescence properties of ZrO2 nanoparticles

Pr3+ impurity transitions in monoclinic and cubic phases of ZrO2 have been investigated by photoluminescence and thermoluminescence (TL). Zr(1−x)Pr x O2 (0 ⩽ x ⩽ 0.015) samples were prepared by the combustion method. Rietveld refined x-ray diffraction results confirm that undoped ZrO2 has a monoclinic structure, whereas Pr doped ZrO2 samples are in mixed phase consisting of monoclinic and cubic structures. ZrO2 shows a broad defect-related emission peak centered at 500 nm under an excitation wavelength of 300 nm. A series of Pr3+-related emissions are observed at 512, 584, 612–640 nm due to 3P0 → 3H4, 3P1 + 1I6 → 3H5, 1D2 → 3H4 transitions and between 719 and 740 nm due to 1D2 → 3H5 transitions when excited with 454 nm. The PL decay lifetime of Zr0.996Pr0.004O2 is 1.55 μs for fixed λ ex = 300 nm and λ em = 612 nm. The TL glow curve of Zr0.99Pr0.01O2 shows a prominent peak at 695 K and secondary peaks at 508 K and 570 K, which are not observed in undoped ZrO2. The TL emission measured at 695 K confirms that Pr3+ replaces Zr4+ in cubic lattice sites of ZrO2. This work shows the relationship between the luminescence properties and different structures of ZrO2 and that supports the design of new materials for possible applications.

Fast polarization switching capability mediated by oxygen deficiency in Co-substituted SrFeO3-δ perovskites

In this study, a series of eco-friendly, oxygen-deficient SrFe1-xCoxO3-δ (x = 0.00, 0.33, 0.66, and 1.00) perovskite samples was prepared via a sol–gel-based auto-combustion route. Analysis of X-ray diffraction data confirmed the synthesis of the single-phase cubic perovskite structure for x = 0.00 to x = 0.66, whereas SrCoO3-δ had a single-phase tetragonal structure. The lattice constants decreased as the Co contents increased due to the smaller ionic radii of Co4+ ions. Field emission scanning electron microscopy images showed that the grain size decreased initially, but the size increased with the increase in Co substitution above x = 0.33. Ferroelectric behavior was analyzed under an electric field of 50 V/cm with a frequency of 50 Hz. The unsaturated polarization–electric field loops for SrFeO3-δ indicated relaxor-type ferroelectric behavior. The maximum polarization (Pmax) and remanent polarization (Pr) both decreased as the Co contents increased. The maximum recoverable energy density was recorded for SrFeO3-δ. However, the maximum energy storage efficiency of 66% was obtained for the SrFe0.67Co0.33O3 sample. These findings demonstrate that members of the SrFe1-xCoxO3-δ series, particularly with x = 0.33, could be potential candidates for use in energy and data storage devices, mainly due to the high value of Pmax − Pr, superior storage efficiency, and rapid polarization switching ability.

Multifunctional BaTi0.98M0.02O3 (M = V, Co, Mo) compositions: High dye-photodegradation and relative permittivity characteristics

In this study, the relative permittivity and photocatalytic properties of BaTi0.98M0.02O3 (M = V, Co, Mo) compositions have been investigated. Polycrystalline BaTiO3, BaTi0.98V0.02O3 BaTi0.98Co0.02O3 and BaTi0.98Mo0.02O3 powders were synthesized by solid state reaction method. The X-ray diffraction analysis of all samples confirmed the formation of tetragonal BaTiO3 phase without any impurities. The scanning electron microscope images showed the formation of irregular grains for BaTiO3 and BaTi0.98V0.02O3 samples while BaTi0.98Co0.02O3 and BaTi0.98Mo0.02O3 powders revealed spongy and uniform crystalline grains shapes, respectively. Remarkably, the incorporation of V, Co and Mo ions was reduced the UV band gap energy of BaTiO3 from 3.25 eV to 2.96, 2.98 and 2.92 eV, respectively. These results verify that V, Co and Mo doped BaTiO3 samples have the ability to absorb the visible light spectrum compared to pure one. The study of the dielectric properties showed that the BaTi0.98V0.02O3 and BaTi0.98Mo0.02O3 samples have a colossal relative permittivity of 14263 and 1658, respectively. Besides, BaTi0.98Mo0.02O3 as a photocatalyst exhibits superior photodegradation efficiencies of 90 and 100% towards 10 ppm Congo red solution under sunlight irradiation during 20 and 60 min, respectively. For 50 ppm CR, the photocatalytic activity of this catalyst was reached to 53% and 70% in 20 and 60 min, respectively. The highest performance of BaTi0.98Mo0.02O3 catalyst can be ascribed to high crystallinity, formation of oxygen vacancies, well charge separation and visible light absorption.

Role of polarization switching and domain patterns in the enhanced piezoelectric characteristics of a Pb-free ferroelectric system

The Pb-free piezoelectric BaTi1−x Sn x O3 system is a promising environmentally friendly ceramic due to its superior piezoresponse properties. The enhanced piezoresponse of this system has a strong correlation with its microscopic and macroscopic characteristics. In this work, the effects of structural and microstructural evolution on the piezoelectric properties of a BaTi0.97Sn0.03O3 (BST) compound are explored. Structural and piezoelectric analysis elucidates that the samples experiencing a field induced tetragonal to orthorhombic phase transformation exhibit better piezoresponse. In addition, the domain configurations have a strong correlation with the synthesis conditions, where the distribution of lamellar and/or stripe types of domain patterns show enhancement in comparison to those of labyrinth type with increase in sintering temperature. Rayleigh analysis confirms that the increase in the irreversible nature of non-180° domain walls can improve the d 33 values of the BST samples. Overall, the results illustrate that the stripe domain configurations and field induced polarization switching from tetragonal to orthorhombic phase favour superior piezoresponse in the samples.

Physical properties and photocatalytic activity of Cr doped TiO2 nanoparticles.

Nanocrystalline Ti1-x Crx O2 (0≤ x ≤0.20) samples are synthesized via acid-modified sol-gel process and characterized with various techniques, such as HRTEM, FESEM, Raman, XPS, DTA and VSM. The TEM image of TiO2 exhibits elongated nanoparticles with an average size of 10 nm. The HRTEM in combination with selected area electron diffraction (SAED) patterns reveals the interplanar spacing and polycrystalline nature of the samples, respectively. FESEM micrographs reveal non-uniform morphologies and less aggregation of the particles in the doped sample. Raman spectra ensure the phase purity of the samples and a blue shift on Cr doping. X-ray photoelectron spectra (XPS) predict the chemical state of the elements and oxygen vacancies in the prepared samples. The room temperature magnetic studies reveal a significant variation in the magnetic parameters on Cr doping in TiO2 . The differential thermal analysis (DTA) shows the structural phase transition at ∼630°C. The photocatalytic performance is studied for the degradation of methylene blue (MB) dye under visible-light irradiation. A higher photocatalytic efficiency is found for the 20% of Cr-doped TiO2 . These studies propose that the appropriate incorporation of Cr ions makes TiO2 very efficient for visible light-driven photocatalysts required for applications in wastewater treatment. In the present study, nanoparticles of TiO2 and Cr doped TiO2 by a cost-effective acid-modified sol-gel process. The effect of Cr doping on the microstructure, thermal, magnetic and photocatalytic properties of TiO2 were explored in detail. The transmission electron microscopy (TEM) images exhibit the presence of elongated nanoparticles with an average size of 10 nm. Field emission scanning electron microscopy (FESEM) was used to study the surface morphology of the synthesized materials, which revealed non-uniform morphologies and less aggregation of the particles in the Cr-doped sample. Energy dispersive x-ray spectroscopy (EDS) confirms the elemental compositions with the appropriate stoichiometry of the elements. Raman spectra ensure the phase purity of the materials and also a blue shift with the incorporation of Cr ions in TiO2 . X-ray photoelectron spectra (XPS) predict the chemical state of the elements and oxygen vacancies in the prepared samples. The magnetic nature of all the synthesized samples was examined through the vibrating sample magnetometer (VSM) and revealed weak ferromagnetic behavior of the samples. These results signify that the oxygen vacancies and defects play a crucial role in developing the ferromagnetic nature of oxide semiconductors. The differential thermal analysis (DTA) shows the structural phase transition at ∼630°C. The photocatalytic performance of the prepared samples was studied for the degradation of methylene blue (MB) dye under irradiation of visible light. A higher photocatalytic efficiency was found for the 20% of Cr-doped TiO2 . These studies propose that the appropriate incorporation of Cr ions makes TiO2 very efficient for visible light-driven photocatalysts required for applications in wastewater treatment. This article is protected by copyright. All rights reserved.

Amorphous/crystalline Cu1.5Mn1.5O4 with rich oxygen vacancies for efficiently photothermocatalytic mineralization of toluene

Searching a photothermal catalyst for significantly boosting photothermocatalytic mineralization of volatile organic compounds (VOCs) still remains a challenge. Herein, an amorphous/crystalline Cu1.5Mn1.5O4 catalyst with rich oxygen vacancies was firstly fabricated for photothermal mineralization of toluene. Compared to crystalline Cu1.5Mn1.5O4 samples, amorphous/crystalline Cu1.5Mn1.5O4 catalyst exhibited a more superior photothermal catalytic activity (92.3% toluene conversion and 82.9% CO2 yield) and stability. The collective experimental studies confirmed that oxygen vacancies could contribute to photothermal conversion capacity and low temperature reducibility of amorphous/crystalline Cu1.5Mn1.5O4, enhanced the activation of reactive oxygen species and the deep oxidation of toluene under full-spectrum light. In the meantime, visible light played an auxiliary role in toluene oxidation. Moreover, the possible photothermal reaction mechanism of toluene was investigated by in situ infrared spectroscopy technique. This study can provide new ideas for application of amorphous/crystalline bimetallic oxides in photothermal mineralization of VOCs.

Enhancement in the electromagnetic shielding properties of doped [formula omitted] magnetite nanoparticles [formula omitted

Fe3O4 nanoparticles (NPs) are one of the most investigated materials in the field of microwave absorbers. To further optimize the electromagnetic interference (EMI) shielding effectiveness, doped M0.01Fe2.99O4(M=Mn,Ni,Cu,Zn) NPs were synthesized through co-precipitation method. All samples were subjected to X-ray diffraction analysis to determine their crystal structure. Transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were performed to confirm the morphologies, distribution of elements, and valence of iron in the prepared nanoparticles, respectively. The dielectric and magnetic characteristics displayed a considerable improvement for the doped Fe3O4 samples, except Zn0.01Fe2.99O4 where the obtained values were found to be comparable to those of pure Fe3O4. These variations are described in terms of the homogeneously distributed microstructure, mixed spinel cationic distribution in the doped samples, and Fe2+/Fe3+ ratios at the octahedral interstitial sites. Moreover, the EMI shielding efficiency was measured in the X-band frequency range (8.2 – 12.4 GHz) using a wave guide approach. The total shielding effectiveness of Cu0.01Fe2.99O4 and Ni0.01Fe2.99O4 samples was found to be much higher than that of pure Fe3O4 with absorption being the dominant mechanism. This is most likely owing to their high dielectric permittivity, enhanced conductivity, and high magnetic permeability, which results in improved impedance matching and stronger microwave absorption. This suggests that these doped nanoparticles may be utilized as efficient electromagnetic absorbers.

Variation in the dielectric and magnetic characteristics of multiferroic LuFeO3 as a result of cobalt substitution at Fe sites

Due to its electrical, magnetic, and optical characteristics, LuFeO3 (LFO) has caught the scientific community's interest. In this study, the powders of LFO, LuFe0.95Co0.05O3, and LuFe0.90Co0.10O3 samples were prepared by using the well-known solid-state approach. The crystalline structure of the fabricated samples was examined by an X-ray diffractometer (XRD). It was found that the samples display secondary phases such as Lu2O3, Lutetium Tetraoxodiferrate, and Wüstite. It was shown by scanning electron microscope (SEM) that particle size decreases with Co doping. X-ray photoelectron spectroscopy (XPS) determined oxidation states for Fe and Co. It was presented that Fe has a mixture of 2 + and + 3 valance states in the LFO sample. Although LuFe0.95Co0.05O3 has only the 3 + state, LuFe0.90Co0.10O3 sample has coexisting metallic and 3 + states. The conductivity and dielectric constant of the undoped LFO sample were higher than those of Co doped LFO samples. A decrease in both the dielectric constant and conductivity was associated with a lack of Fe2+ ions and lattice distortions. Furthermore, it was argued that several conduction models must be developed to explain the conduction process in the analyzed samples. Magnetic experiments using a vibrating sample magnetometer (VSM) revealed that Co doping raises Mr values. We discuss that this increase in Mr values could be related to i) variations in the inclined angles of Fe3+ moments and ii) the growth of magnetocrystalline anisotropy's energy.

Development of <i>Moringa Oleifera</i> Gum Incorporated Juices and its Popularization

An experimental study was done in an attempt to utilize the benefits and uses of Moringa oleifera gum powder and to enhance the nutritive value of the products developed by incorporating it in orange (grape variety) and watermelon juices. The yield percentage of Moringa gum from the tree (once) was calculated. The gums were collected from the tree, processed and used for further purposes. The collected gum was determined for its physic-chemical properties. The watersoaked gum powder was incorporated in different ratios in standard orange and watermelon juice. The incorporated juices were analyzed for their improved nutrient content and sensory evaluation was done. The cost calculation for standard and incorporated juices was calculated. The developed products were popularized among young adult girl students through questionnaires and pamphlets. The nutritional importance of Moringa and Moringa gum was explained to the subjects. From the results, it was concluded that among the incorporated orange juice formulations O3 sample received the highest acceptability among the samples O, O1, O2 and O3 and in the incorporated watermelon juice formulations W2 variation received the highest overall acceptability among the samples. The nutrition quality of samples increased in the aspect of Crude fibre, Vitamin A, Iron, Calcium, Total antioxidants and Phytochemical-Flavonoids.

Computational Understandings of Cation Configuration-Dependent Redox Activity and Oxygen Dimerization in Lithium-Rich Manganese-Based Layered Cathodes

Lithium-rich manganese-based layered oxides have emerged as a fresh paradigm for developing advanced cathode materials with high energy density for next-generation lithium-ion batteries. Understanding lattice oxygen dimerization is quite essential for the optimal design of lithium-rich manganese-based cathode materials. Herein, based on density functional theory (DFT) calculations, a local Ni-honeycomb Li–Ni–Mn cation configuration for the Li1.22Ni0.22Mn0.56O2 cathode was carefully examined, which may coexist with the well-known local Li-honeycomb structure in experimentally synthesized Li1.2Ni0.2Mn0.6O2 samples. The local Li–Ni–Mn cation configurations have significant impacts on oxygen redox activity, transition metal atom migration, and oxygen dimerization in the charging process of LixNi0.22Mn0.56O2. It is found that there is no correlation between high lattice oxygen redox activity and easy oxygen dimerization, such as Li-honeycomb structures simultaneously exhibiting higher oxygen redox activities and higher activation energy barriers for prohibiting oxygen dimerization than Ni-honeycomb structures. The structural regulations of the local Li–Ni–Mn cation configuration by avoiding the local Ni-honeycomb structures to inhibit Mn migration and ease lattice oxygen dimerization and by making full use of the local Li-honeycomb structures would maximize performance of Li-rich Mn-based layered oxides. Such fresh insights provide us a fresh strategy to optimally design the local honeycomb structure for high-performance Li-rich Mn-based cathode materials.

Synthesis and characterization of highly conductive Ga/Y co-doped LLZO by facile combustion sol-gel method

In this study, garnet material with the composition of Li6.4Ga0.2La3Zr(2-x)YxO12(x = 0,0.1,0.3,0.5) were synthesized by combustion sol-gel method. Phase evolution were studied by X-ray diffraction analysis and Raman. The microstructure and ionic conductivity were investigated by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. Yttrium showed to be effective for promoting Densification while it did not affect the stability of cubic phase structure. However, high amounts of yttrium resulted in the formation of a secondary phase. Adding yttrium also caused microstructural grain growth. Maximum ionic conductivity (1.04 mS.cm−1 at 25 °C) was obtained in Li6.4Ga0.2La3Zr1.7Y0.3O12 sample with relative density of 96.6%. Compared to other reports with similar densities and ionic conductivities, lower sintering temperature and holding time were used in this work. This could be attributed to the effectivity of Ga/Y to promote sintering. Moreover, it may be originated from the good sinterability of combustion sol-gel synthesized powders. This synthesis method's reduced energy and time make it considerable for large-scale production.

Magnetically Separable Mixed-Phase α/γ-Fe2O3 Catalyst for Photo-Fenton-like Oxidation of Rhodamine B

Iron oxides are widely used as catalysts for photo-Fenton-like processes for dye oxidation. In this study, we report on the synthesis of an α/γ-Fe2O3 mixed-phase catalyst with magnetic properties for efficient separation. The catalyst was synthesized using glycine–nitrate precursors. The synthesized α/γ-Fe2O3 samples were characterized using scanning electron microscopy, X-ray diffraction spectroscopy (XRD), Raman shift spectroscopy, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM). The diffraction peaks were indexed with two phases, α-Fe2O3 as the main phase (79.6 wt.%) and γ-Fe2O3 as the secondary phase (20.4 wt.%), determined using the Rietveld refinement method. The presence of Fe2+ was attributed to oxygen vacancies. The mixed-phase α/γ-Fe2O3 catalyst exhibited remarkable photo-Fenton-like degradation performance for Rhodamine B (RhB) in neutral pH. The effects of operating parameters, including H2O2 concentration, catalyst concentration, and RhB concentration, on the degradation efficiency were investigated. The removal rates of color were 99.2% after 12 min at optimal conditions of photo-Fenton-like oxidation of RhB. The sample exhibited a high saturation magnetization of 28.6 emu/g. Additionally, the α/γ-Fe2O3 mixed-phase catalyst showed long-term stability during recycle experiments, with only a 5% decrease in activity.

DPF-produced TiN coatings on NiTi: biological and mechanical properties

One of the best ways to obtain TiN coatings is through the nitriding process by efficient methods such as dense plasma focus (DPF). The gas composition of the nitrogen environment is a crucial factor affecting the properties of the coating. In this study, three different atmospheres of 100%N2, 50%N2–50%O2, and 75%N2–25%Ar were used to investigate their impact on the mechanical and biological properties of TiN coatings on NiTi substrate. The operating condition that yielded the coating with the highest hardness, as well as the lowest contact angle and Ni ion release, was chosen as the optimum condition. According to the XRD results, TiN was recognized as the dominant phase which causes high hardness and prevents Ni ion release. Moreover, surface analyses determined that the sample coated in 50%N2 composition possessed higher hardness and as a result displayed better mechanical properties. Also, the improved microstructural properties lead to an enhanced coating/substrate adhesion strength. On the other hand, the reaction of TiO2 and TiN lead to the formation of TiN0.6O0.4 ternary compound and for this reason, the 50%N2–50%O2 sample exhibited better performance in preventing the release of the toxic nickel ion compared to the other samples. Finally, due to the presence of TiO2 and TiN0.6O0.4 in the sample surface treated at 50%N2–50%O2, better hydrophilicity was observed compared to other samples. Results confirm that the applied surface modification method is effective in increasing the mechanical and biological properties of the NiTi, where it may open numerous possibilities for efficient use in orthopedic applications.

A study on Sm2O3-doped Ba(Zr0.02Ti0.98)O3 ceramics for sensor applications

ABSTRACT Ba(Zr0.02Ti0.98)O3 (BZT) samples with various weight percentages of Sm2O3 (0.02–0.06) were synthesized and calcined at 1100°C for 4 h. Circular pellets were prepared using calcined powders and sintered at 1450°C for 2 h. The sintered and poled samples were used for the measurement of various electrical properties. Maximum piezoelectric charge constant (d 33) of 372 pC/N obtained for 0.02 wt.% Sm2O3-doped BZT. Dielectric constant (K = 15,855) at 100 Hz was found maximum for this composition at Curie temperature (T c) of 125°C. Scanning electron microscopy (SEM) study revealed a decrease in grain size with an increase in Sm2O3 content. Largely, a lower concentration of Sm2O3-doped BZT compositions with higher d 33 could be suitable for vibration sensor and accelerometer applications.