Increasing Calcination Temperature Research Articles

Effect of calcination temperatures on optical and magnetic properties of FeWO4 nanoparticles

Abstract Calcination temperature is a crucial parameter that can be easily controlled to induce a change in material properties. Herein, iron tungstate (FeWO4) was synthesized via a hydrothermal method using iron(II) sulfate heptahydrate and sodium tungstate dihydrate as precursors and calcined at the temperature between 300 oC and 700 oC. With increasing calcination temperature, the saturation magnetization of FeWO4 nanoparticles decreased from 6.6 emu/g for FeWO4 to 0.4 emu/g for FeWO4_700, whereas their band gaps increased from 1.95 eV for FeWO4 to 2.20 eV for FeWO4_700. More crystallinity and crystal defects, and morphological changes at higher calcination temperatures contributed to varying magneto-optical properties of FeWO4 nanoparticles.

Hydrophilic sol-gel TiO2 coating on procaine-loaded injector needle for painless clinical treatments

Titanium dioxide (TiO2) coatings are demanded in clinical applications due to their biocompatible, porosity, and semiconducting properties. Drug release studies take advantage of these unique aspects of TiO2 for painless injection for those who have to take medicine through the injection frequently. In this study, TiO2 was prepared via the sol-gel method with Titanium tetra isopropoxide (TTIP) precursor in alcohol solvent for pH 3, 4, and 5 values. The prepared solution was coated on stainless steel substrates and injectors via dip coating. Following these steps, samples were calcinated at various temperatures (100°C, 300°C, 500°C, 700°C). The structural, physical, and chemical composition, chemical bond, wettability, and drug-release properties of coated samples were researched. Contact angle values affirmed that high temperatures and ultraviolet (UV)-light irradiation made samples more hydrophilic (26°±5° at 700°C for pH 4). Procaine, a short-time period local anaesthetic, was chosen as a model drug. Increased calcination temperature and raised hydrophilicity led to improve the released drug amount. Drug release studies were carried out using Franz diffusion cells at 36.5°C. Samples at 500°C calcinated released the highest amount of drug (90%) for 45 sec injection time. This study shed light on how TiO2 coating can be successfully utilized for clinical applications in the future.

Structural and antibacterial properties of copper oxide nanoparticles: a study on the effect of calcination temperature

Nanoparticles of copper oxide were synthesized by the simple precipitation method. The influence of calcination temperature on the structural characteristics and antibacterial activity of the nanoparticles were evaluated. The nanoparticles were analyzed by Bruner-Emmett-Teller (BET) surface area and pore size analyzer, x-ray diffraction, transmission electron microscope and scanning electron microscope. The findings demonstrated the formation of copper oxide nanoparticles showing a monoclinic phase. Before calcination, the nanoparticles showed a high BET surface area with rod shape morphology and size range between 18–70 nm and after calcination, irregular spherical-like morphology with size range of 20–200 nm was observed. However, it was evident that the BET surface area decreased gradually with increasing calcination temperature, while the nanoparticle size increased forming an irregular spherical shape. Subsequently, the copper oxide nanoparticles demonstrated that they are highly effective for bacteria inactivation. The inactivation activity was found to be more effective with uncalcined nanoparticles than with calcined nanoparticles. This was due to the large nanoparticle sizes and the decrease in surface area obtained after calcination. Thus, it was noted that calcination of the as-prepared nanoparticles significantly affects the structural and antibacterial properties. Hence, for antibacterial application, calcination was not necessary as the nanoparticles showed excellent antibacterial results.

Effect of calcination temperature on structural, magnetic, and dielectric properties of Mg0.75Zn0.25Al0.2Fe1.8O4 ferrites

Based on the desire to improve material properties, the effects of temperature have begun to be investigated. It was found that for nano-sized powder materials, such as ferrites, the structural properties like crystal structure and grain size, as well as many magnetic and electrical properties depending on them, change with the calcination temperature. Considering these changes, the effect of calcination temperature on the structural, magnetic, and electrical properties of MZA ferrites (Mg0.75Zn0.25Al0.2Fe1.8O4) prepared by co-precipitation was investigated in this study. The produced MZA ferrites were calcined at three different temperatures (600, 700, and 800 °C). The X-ray diffraction results showed that the samples exhibited a cubic spinel structure. It was found that the crystal sizes (D_sch) calculated using the Debye-Scherrer equation increased with increasing calcination temperature (22.47, 33.53, and 42.53 nm). From the Williamson–Hall (W–H) plots, crystal sizes were calculated almost same as Debye–Scherrer crystal sizes. The nano-sized particles were examined by scanning electron microscope (SEM). Elemental analysis was performed using EDX. ν1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ u }_{1}$$\\end{document} and ν2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ u }_{2}$$\\end{document} absorption bands and O–H and C–H vibrations were detected in the FTIR spectra. Magnetic measurements were carried out at room temperature and in the range of ± 60 kOe under the applied field. Magnetic results are explained by superparamagnetism. Dielectric measurements were performed at room temperature and a frequency range of 20 Hz to 10 MHz. The dielectric properties can be explained by Maxwell–Wagner theory. Impedance spectroscopy study revealed that the relaxation mechanism is consistent with the Cole–Cole model. In AC conductivity studies at room temperature, it was found that the sample calcined at 600 °C would be suitable for energy storage devices.

Transforming seafood waste: Green mussel shell-derived hydroxyapatite as a catalyst for spirooxindole synthesis

Utilizing bioresources and renewable materials represents a sustainable approach in chemical reactions. This study aims to harness seafood waste from green mussel shells as a raw material to produce hydroxyapatite (HAp) and employ it as a heterogeneous catalyst for synthesizing spirooxindole compounds. The green mussel shells underwent varying temperature calcination to yield CaO, subsequently utilized in HAp synthesis. XRD analysis exhibited the characteristic peak pattern of HAp and revealed a reduction in crystal sizes with increased calcination temperatures for CaO formation. Additionally, FTIR analysis identified the constituent functional groups of HAp in the sample. SEM analysis revealed irregularly shaped HAp particles, with average sizes of 268.42 nm (HAp-800), 212.46 nm (HAp-900), and 184.6 nm (HAp-1000). Using HAp as a catalyst in synthesizing spirooxindole yielded a 64 % product yield and demonstrated reusability. Utilizing mussel shell-derived hydroxyapatite as a catalyst offers a cost-effective and environmentally friendly approach to achieving higher product yields.

Contribution of micropores in porous zirconia spheres to high optical transparency of dental resin composites.

Transparency to UV-Vis light and radiopacity of dental resin composites containing zirconia (ZrO2) fillers were investigated. The transparency of the resin composite containing porous ZrO2 spheres was much higher than that containing irregularly shaped ZrO2 particles. Calcination of the porous ZrO2 spheres at high temperatures led to dramatically reduced specific surface areas and pore volumes. The transparency of the resin composite containing the calcined porous ZrO2 spheres drastically decreased as the calcination temperature increased. Then, the enhanced UV-Vis transmittance of the resin composite containing porous ZrO2 spheres is attributed to the concentration and physical characteristics of the pores. The radiopacity of the resin composites containing porous ZrO2 spheres increased slightly with increasing calcination temperature. This study revealed that the internal structure of the ZrO2 fillers mainly influenced in the UV-Vis light transmittance of the resin composites.

Effect of calcination temperature on Co/sepiolite catalyst for hydrogen production by ethanol steam reforming: Co speciation from phyllosilicate to spinel

Hydrogen production via ethanol steam reforming (ESR) was conducted over amorphous sepiolite (SEP) supported Co based catalysts, deeming as a green and sustainable strategy for renewable energy. However, the subtle regulation to the ESR reactivity of Co/SEP catalysts still remains a challenge. Given the structure sensitive property of ESR, calcination temperature, as a vital regulation parameter, was used to control the key physicochemical properties of catalysts. By various characterization techniques, the results revealed that a calcination temperature mediated metal-support interaction was manifested in the form of Co speciation evolution. With increasing calcination temperature, the occurrence states of Co species change from Co oxides to Co-phyllosilicate then to Co-Al spinel. The ESR experiments indicated that Co/SEP-600 catalyst possessed a suboptimal activity via a dehydrogenation route and a 50 h stability due to a compromising among Co-phyllosilicate dominated MSI, texture, Co0 nanoparticle size and acid-base property. The further improvement of calcination temperature only brought about a poor stability of Co/SEP-700 with a phase transformation or a low activity of Co/SEP-800 with an irreducible Co-Al spinel. Hence, the interaction type of Co with SEP framework Si/Al atoms determined the ESR reactivity of the catalysts, which was modulated by the calcination temperature. Additionally, abundant graphitic coke deposition on the agglomerated Co0 grains was attributed the weak MSI, such as Co/SEP-400, while a slight coke deposition appeared at Co/SEP-800 with an irreducible Co-Al spinel phase.

Generation and role of novel catalytic sites for NH3-SCR in bio-derived Chlorella@Mn denitration catalyst driven by calcination temperature

More conventional low-temperature denitration catalysts are prepared chemically, and the active sites are mainly metal oxides. In this paper, the catalysts are prepared biologically, and novel denitration active sites of nonmetal-oxygen-metal are formed. The NOx conversion was first increased and then decreased with the increase of calcination temperature, and was below 20 % at 200 ℃ at a reaction temperature of 175 ℃, and was close to 100 % at calcination temperatures of 365 ℃ and 435 ℃, and was below 80 % at 600 ℃. Compared to the Chlorella@Mn catalyst prepared at 435 ℃, which possesses the highest specific surface area (104.7 m2/g), the Chlorella@Mn catalyst prepared at 365 ℃ possesses stronger NOx and NH3 adsorption performance, which is related to the presence of a large number of P-O-Mn and C-O-Mn bonds, the presence of P-O-Mn bond could enhance the electron transfer between P and Mn, C-O-Mn bond can enhance the redox performance. The calcination temperature between 365 ℃ and 435 ℃ is the equilibrium range for denitration performance. L-H and E-R reaction mechanisms presence on Chlorella@Mn catalysts at calcination temperatures from 305 ℃ to 600 ℃, the presence of P-O-Mn and C-O-Mn bonds can also promote the generation of active nitrate species. This study will provide some reference for research on the formation of novel denitration active sites using biological methods.

Effect of calcination temperature of titanium dioxide (TiO2) on adsorption performance of doxycycline hydrochloride

In this work, titanium dioxide (TiO2) was synthesized at different calcination temperatures by sol-gel method using butyl titanate as raw material. The effect of calcination temperature on the crystallinity and adsorption properties of TiO2 were investigated at 300 °C, 450 °C and 600 °C, respectively. The characteristics of TiO2 were analysed by X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption-desorption analyzer and zeta potential tester. The results showed that the crystal type, specific surface area and zeta potential of TiO2 nanoparticles changed with the increase of calcination temperature and the best performance of anatase crystals happened at the calcination temperature of 300 °C (TiO2@300) for doxycycline hydrochloride (DCH) adsorption. The equilibrium adsorption capacities of DCH was 28.97 mg/g with DCH removal rate of 86.92% at 0.03 g TiO2@300 addition in 100 ml 10 mg/L DCH solution. TiO2@300 could be a promising adsorbent.

Study of Effect of Calcinations Temperature on Structural and Magnetic Properties of MgMnO2-λ Nanocrystallines

The researchers are interested in studying nanoparticulates as a result of their specific Physical, Chemical and Biological traits. These nanoparticulates are additionally applicable to a wide array of industries, which includes solar cell coatings, transparent sunscreen, self-cleaning windows and scratch-resistant eyewear. Nanoparticulates have significant properties at nano scale because of high surface to volume ratio. The advanced properties of these nanoparticulates increase the interest of today’s researchers and scientist. The metal oxide nanoparticulates of MgO have enhanced properties in the field of industries, defense and medical world. Metal oxide nanoparticulates like MgO and MnO2 are currently the subject of substantial research because of their well-known antibacterial activity against several kinds of bacteria and their advanced uses in the field of storage for hydrogen gas. In the current work, pure MgO and Mn (10%) doped MgO nanoparticulates were prepared via a microwave irradiated chemical co precipitation process . The samples were further calcined at 200o , 400o , 600o and 800o Celsius for two hours constant heating. XRD, FTIR, FESEM, and VSM examinations have been conducted on the calcined materials. The XRD results revels that nanoparticulates were formed with FCC crystal structures and no phase transformation occurred with addition of Mn dopant concentration in MgO. However, the presence of Mn2+ ion in place of Mg2+ ion were recognized via broadening of peak resulted by micro strain lattice. The grain size of nanoparticulates were calculated by use of Debye Scherer estimation and crystalline size 29.47nm, 27.68nm, 36.80nm and 46.14 nm pattern shows that crystallite size increases with increase in calcinations temperature. The IR sharp peaks inspected at 409cm-1 (pure MgO/800OC), 395cm-1 (pure MgO/600oC), 402cm-1 (pure MgO/400oC) and 409cm-1 (pure MgO/200oC) respectively and for Mn doped MgO nanoparticulates sharp peaks inspected at 450 cm-1 (Mn10%/600OC),400cm1 (Mn20%/600oC) respectively and were attributed by O-Mn-O molecule vibration were confirmed the XRD analyses that is Mn2+ ion exist at Mg2+ lattice site. The electron microscopic image of sample shows that cauliflower leaf like structure was seen with size nanometer in scale. The VSM characteristic of sample concluded that saturation magnetization gradually decreases with increase of calcinations temperature and all substances were ferromagnetic in behavior. The materials have recommended property in applications as electromagnet formation.

Synthesis of Calcium Phosphate by Microwave Hydrothermal Method: Physicochemical and Morphological Characterization.

Bone loss in the alveolar ridge is a factor widely studied by dentists in implant surgeries, as it poses a major challenge for aesthetic and functional recovery in patients with large maxillary bone defects. Synthetic biomaterials function as grafts designed to replace and remodel bone tissue. Calcium phosphate is a biomaterial that has good properties such as biocompatibility and bioactivity, making it a reference in bone replacement treatments. A synthetic biomaterial such as calcium phosphate can be obtained by various synthesis techniques. The microwave hydrothermal method (HTMO) is a pathway that allows changes in synthesis parameters and significantly increases the transmission efficiency of materials such as synthetic calcium phosphate derivatives. The study proposes obtaining a biomaterial for bone grafting based on calcium phosphate by the microwave HTMO and evaluating its microstructural and physicochemical characteristics. The parameters tested in this process were temperature and reaction time. The calcium phosphate particulates were obtained by the microwave HTMO at temperatures of 110°C and 130°C for 60 min and calcined at 300°C, 500°C, and 700°C. Microstructural and physicochemical characterization analyses were carried out using scanning electron microscopy, Fourier transform infrared, and X-ray diffraction. The results obtained showed the presence of more than one calcium phosphate biological interest phase, as hydroxyapatite (HA), tricalcium phosphate (β-TCP), and octacalcium phosphate (OCP), highlighting with increasing calcination temperature, the β-TCP phase becomes evident. The proposed synthesis method was efficient in obtaining a biomaterial with suitable physical and chemical characteristics, with an association of crystalline phases of biological interest related to the increase in synthesis temperature and calcination temperature.

Aloe vera extract-assisted sol-gel synthesis of NiOx nanopyramids for supercapacitor application

Green synthesis of metal oxide nanoparticles is a cost-effective and sustainable approach that allows tailoring of the size and shape of the nanostructures for versatile applications. In this study, aloe vera extract-assisted sol-gel synthesis of nickel oxide nanoparticles (NiOx NPs) was explored for supercapacitor application. The NiOx NPs were synthesized at different aloe vera concentrations (2.5 and 5 wt%) and calcination temperatures (300, 400 and 500 °C). The phytochemical-assisted synthesis yielded NiOx nanopyramids with pores on their surface which widens as calcination temperature increases. As confirmed by XRD analysis, NiOx crystallite size also increased at higher calcination temperatures. Upon electrochemical characterization, NiOx-400B which was synthesized with 5 wt% aloe vera extract at 400 °C recorded the highest specific capacitance of 721 F g−1 at 1 A g-1 current density with the energy and power density of 10.38 Whkg−1 and 241.08 W kg-1 respectively. The charge storage mechanisms in the samples were gauged using Dunn's method which revealed that NiOx synthesized at higher calcination temperatures exhibited a greater contribution of the diffusion-controlled process. The optimized composition, NiOx-400B, also demonstrated excellent cycle stability by retaining up to 90.4 % of its original capacitance over 1500 cycles. This work is an attempt to investigate the viability of green synthesized nanoparticles in energy storage applications and the novel NiOx nanopyramid substantiates its prospect as a good electrode material for supercapacitors.

Probing the Structure Evolution of Na-Cu-Mn-O Based Layered Oxide Cathode Materials in Sodium Ion Batteries

Sodium-ion batteries (SIBs) are considered as potential energy storage devices for large-scale energy storage system and smart power grids applications because of the low cost and abundant distribution of sodium in the earth's crust and ocean [1]. The development of highly efficient cathode materials for superior sodium storage is crucial for the development of SIBs. Among all the cathode materials, sodium transition-metal layered oxides, especially P2 and O3-typed layered oxides are of more interest due to their high theoretical capacity and easy synthesis [2,3]. From a structural point of view, P2 phase has an open pathway from one prismatic site to adjacent sites for more facile Na ion diffusion than O3 homologue. Therefore, the P2 phase shows not only better kinetic properties but improved cyclic stability thanks to its high structural stability.However, the pristine Na2/3MnO2 in P2 phase usually suffer from poor reversibility and dramatic capacity and voltage decay upon cycling, which origins form below issues: 1) the Na+/vacancy order-disorder transition, 2) the phase transition at high charge voltages due to MnO6 layers gliding 3) the Jahn-Teller distortion derived from Mn4+/Mn3+ redox couple, 4) the migration and dissolution of transition metals.[4] Up to now, a variety of improvement methods (doping and coating) have been utilized to stimulate the application of P2-type Na2/3MnO2 material. In particular, copper, as a low cost and environmental friendliness element, has also been introduced to synthesize multiple layered transition metal materials, like Na0.68Cu0.34Mn0.66O2, Na0.68Cu0.34Mn0.50Ti0.16O2, Na2/3Mn0.72Cu0.22Mg0.06O2 and so on. Furthermore, various redox behavior and structural evolution have also been explored. However, the process of structural transition during calcinating at different temperatures have been ignored, which leads to the unexpected neglect of some unique features of metastable phases in sintering materials.In our current work, Na2/3Cu1/3Mn2/3O2 in various phases have been successfully synthesized by sol-gel method and subsequently calcinated at different temperatures. XRD results show that Na2/3Cu1/3Mn2/3O2 calcinated at 600 °C (NCMO-600) is the triclinic phase, with the increasing calcination temperatures, the Na2/3Cu1/3Mn2/3O2 subsequently transfers to the hexagonal phase at 800 °C (NCMO-800). Subsequent electrochemical measurements show that NCMO-800 exhibit the better cycle stability and almost no voltage decay in the long term cycling, while the NCMO-600 sample exhibited rapid voltage attenuation at about 30 cycles. Besides, in situ XRD patterns and XANES spectra for both cathodes indicate slight different structural transition and electronic structure changes during charge and discharge. In a word, the NCMO-600 material exhibit the larger electron transfer at low current densities while the NCMO-800 material show the better cycle stability and rate performance.

A Comparative Study on the Structural and Optical Properties of NiMoO4 Nanomaterials Synthesized by Hydrothermal and Solvothermal Route

AbstractIn the present work, a transition metal‐based ternary oxide of NiMoO4 nanomaterials is prepared by both hydrothermal and solvothermal methods with various synthesis conditions. Structural evolution as a function of increase in calcination temperature is also discussed. Scanning electron microscope (SEM) analysis presents the surface morphology of as‐prepared samples with an apparent change in the particle size under different synthesis conditions. Energy Dispersive X‐ray spectroscopy (EDAX) analysis confirms the chemical composition of the nanomaterials. Structural analysis by X‐Ray powder Diffraction (XRD) exhibits the formation of 𝛼 and β‐phase of NiMoO4 and further pure 𝛼‐phase is observed at calcination temperature of 650 °C. Fourier Transform Infrared spectroscopy (FTIR) indicates various functional groups present in NiMoO4 sample. UV–vis absorption spectra present a broad peak around 220–450 nm. A direct and indirect energy band gap of ≈2.2 and ≈1.9 eV, respectively is calculated for NiMoO4 nanomaterials synthesized at 180 and 220 °C for 24 h and calcinated at 650 °C. NiMoO4 nanomaterials and their composites find an application as electrode materials in supercapacitor.

Fabrication of iron doped titanium dioxide photocatalytic nanocomposite supported by water-quenched blast furnace slag and photocatalytic degradation of wastewater

Metallurgical solid waste blast furnace water quenched slag (WBFS) was employed as carrier materials to prepare Fe–TiO2/WBFS composite photocatalyst using a sol-gel method for improving both the photocatalytic activity and the high-value utilization of metallurgical solid waste. The Fe3+ doping technology was adopted to increase the utilization of solar energy. The influencing factors and photocatalytic activity were systematically evaluated by thermogravimetry/differential thermal analyser (TG-DSC), X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) method, scanning electron microscopy-energy spectrometer (SEM-EDS), X-ray photoelectric spectroscopy (XPS), UV–Vis absorption spectrum and photoluminescence spectra technology through the degradation rate of methylene blue (MB) solution. The results showed that the Fe3+ ions were successfully incorporated into the TiO2 lattice, which had no effect on the crystalline phase of TiO2 and expanded the spectral response range of TiO2 from the ultraviolet region to the visible light region. When the calcination temperature was at 450 °C and the number of Fe–TiO2 sol loading cycles was two times, the photocatalytic activity of Fe–TiO2/WBFS presented the strongest, and the degradation ratio of MB reach the maximum value of 98.9 %. A uniform and dense anatase TiO2 thin film was wrapped on the surface of WBFS. The photocatalytic activity first improved and then weakened with an increase of calcination temperature, Fe3+ doping amounts and the loading cycles of sol. The TiO2 film changed from thin to thick and uneven to uniform, until cracking and spalling phenomenon finally occurred with an increase of Fe–TiO2 sol loading cycle from 1 to 3 times. When the Fe–TiO2/WBFS was reused for four times, the degradation rate of MB could still show 67.4 %, being far higher than that of TiO2/WBFS of 25.4 %.

Phase variation of manganese oxide in the MnO@ZnO nanocomposite with calcination temperature and its effect on structural and biological activities

Having powerful antibacterial and antioxidant effects, zinc oxide and manganese oxide nanomaterials are of great interest. Here we have synthesized manganese oxide decorated zinc oxide (MZO) nanocomposites by co-precipitation method, calcined at different temperatures (300–750 °C) and studied various properties. Here the crystalline structure of the nanocomposite and phase change of the manganese oxide are observed with calcination temperature. The average crystalline size increases and the dislocation density and microstrain decrease with the increase in calcined temperature for the same structural features. The formation of composites was confirmed by XRD pattern and SEM images. EDAX spectra proved the high purity of the composites. Here, different biological properties change with the calcination temperature for different shapes, sizes and structures of the nanocomposite. Nanomaterial calcined at 750 °C provides the best anti-microbial activity against Escherichia coli, Salmonella typhimurium, Shigella flexneri (gram-negative), Bacillus subtilis and Bacillus megaterium (gram-positive) bacterial strain at 300 µg/mL concentration. The nanomaterial with calcination temperatures of 300 °C and 450 °C provided better antioxidant properties.

Effect of synthesis temperature on crystal structure, optical and magnetic properties of SmCuO3-δ ceramic phosphor

Effect of synthesis temperature on crystal structure, optical and magnetic properties of SmCuO3-δ ceramic phosphor is investigated in this work. The SmCuO3-δ ceramic has been synthesized using a sol-gel method. Rietveld analysis reveals that SmCuO3-δ ceramic crystallizes into coexisting tetragonal (I4/mmm) and monoclinic (C2/c) crystal structures. The phase fraction of the tetragonal and monoclinic phases strongly depends on the synthesis temperature. The crystallite size and particle size increase with increasing calcination temperature. The X-ray photoelectron spectroscopic spectra reveal the presence of (Cu2+, Cu3+) and (Sm2+, Sm3+) ions alongwith the oxygen vacancy centres in the phosphor. The SmCuO3-δ ceramic shows multiple magnetic phase transitions. The FTIR spectra show the presence of vibrational bands due to Cu-O and Sm-O groups. The optical band gap of the SmCuO3-δ phosphor decreases with an increase in calcination temperature and crystallite size. The photoluminescence excitation spectra show the peaks at 363, 402, 505 and 542 nm at the fixed emission wavelength of 609 nm, whereas the photoluminescence emission spectra contain peaks at 465, 515 and 609 nm at the fixed excitation wavelength of 402 nm. The photoluminescence emission intensity of the sample increases with the rising calcination temperature upto 900 °C and finally, it quenches at 1000 °C. Therefore, the SmCuO3-δ ceramic phosphor may be useful for solid state lighting, LEDs and magnetic devices.

Enhancement of microwave absorption properties of SrxFe12-yPr0.4o19-θ (x=0.6–1.3, y=0∼0.4) by tuning the calcination temperatures

SrxFe12-yPr0.4O19-θ (x = 0.6–1.3, y = 0∼0.4) powders have been synthesized by the sol-gel auto-combustion method. The effect of iron and strontium ion content and calcination temperatures on the structure, magnetic properties and microwave absorption properties has been studied. The X-ray diffraction patterns of samples confirm the formation of M-type strontium ferrite and indicate that the secondary phases change with the increase of calcination temperature and strontium content, thereby affecting the structure and properties of the material. XPS and Raman spectrum analysis shows that some praseodymium ions are in the Pr4+ oxidation state, leading to the existence of Fe2+ ions and oxygen defects (Od), which can certainly affect the magnetic and dielectric properties of the materials. The VSM results show that the saturation magnetization first increases and then decreases with the increase of strontium content at different calcination temperatures and Sr0·8Fe11.8Pr0.4O19-θ has obtained the maximum saturation magnetization of 81.20 emu/g and the coercivity of 4100 Oe. Increase in strontium content not only promotes the reaction, but also generates a second phase FePrzSr1-zO3-δ, increasing the dielectric and magnetic losses of the materials. The maximum reflection loss reaches −66.77 dB and the maximum effective absorption bandwidth is 4.76 GHz. Therefore, on the one hand, the valence state changes of some praseodymium ions result in the generation of Fe2+ ions and oxygen vacancies, thereby increasing dielectric and magnetic losses. On the other hand, the change of the second phases also affects the absorption performance of the material. ɑ-Fe2O3 is not conducive to improving magnetic and absorption properties, and PrFeO3 may improve magnetic properties. Perovskite type PrzSr1-zFeO3-δ has a large number of ion valence state changes inside, leading to increased dielectric and magnetic losses, which is beneficial for improving the absorption performance of the materials.

Design of active phase structure with high activity and stability in residue hydrotreating reactions

The catalyst with well-dispersed (Ni)MoS2 active phase characteristic of short slab length and low stacking numbers was designed by strengthening metal-support interaction (MSI) and metal dispersion, which displayed high activity and long-term stability in real-life residue hydrodesulfurization (HDS) reactions. Furthermore, the impacts of pseudo-boehmite and catalyst calcination temperature on surface properties were thoroughly investigated. Mo equilibrium adsorption method, Al27 NMR, XRD, Raman, UV–Vis DRS, and H2-TPR characterization showed that the hydroxyl groups concentration and tetrahedral cation vacancies increased upon reducing the pseudo-boehmite extrudates calcination temperature. Increasing calcination temperature of the catalysts further strengthened MSI, resulted in well-dispersed Mo species with enhanced MSI. Therefore, well-dispersed (Ni)MoS2 active phase was acquired on novel designed catalyst. XPS coupled with HRTEM indicated that the more potential active sites, less propensity for active phase evolution and gradual increase in sulfidation degree with processing time contributed to the high HDS performance of the designed active phase. This work can deepen our understanding toward evolution pattern of active phase during residue HDS catalysts, and give guidance for developing high performance catalyst by strengthening MSI and enhancing metal dispersion.

Impact of P3/P2 mixed phase on the structural and electrochemical performance of Na0.75Mn0.75Al0.25O2 cathode

The biphasic nature is known to enhance the structural stability and electrochemical properties of layered oxide cathodes. Herein, we have synthesised Na0.75Mn0.75Al0.25O2 (NMA) with different P2/P3 phase fractions, tuned by modifying the calcination temperature. Rietveld refinement of XRD data showed a continuous reduction in the P3 phase fraction with increased calcination temperature. NMA sample calcined at 650 °C (NMA-650) with ∼52 % P3 and 48 % P2 phases showed good rate performance and a high specific capacity of 150 mAh g−1 at 0.1 C with 80 % capacity retention after 200 cycles between 1.5 and 4.2 V. The enhanced electrochemical performance is attributed to the material's morphology and improved structural durability. Interestingly, operando Synchrotron XRD data of NMA-650 and NMA-750 (sample calcined at 750 °C) showed a continued existence of the P3 phase in both compounds during charging-discharging in the 1.5–4.2 V range. Further, the P3 unit cell showed only a 0.5 % increase in volume compared to 1.5 % in NMA-750 during cycling. The enhanced electrochemical properties of NMA-650 are attributed to the synergistic effect of P3/P2 phase coexistence in the material.