Increasing Calcination Temperature Research Articles

2,6-Diaminopyridine-Based Polyurea as an ORR Electrocatalyst of an Anion Exchange Membrane Fuel Cell

In order to yield more Co(II), 2,6-diaminopyridine (DAP) was polymerized with 4,4-methylene diphenyl diisocyanates (MDI) in the presence of Co(II) to obtain a Co-complexed polyurea (Co-PUr). The obtained Co-PUr was calcined to become Co, N-doped carbon (Co-N-C) as the cathode catalyst of an anion exchange membrane fuel cell (AEMFC). High-resolution transmission electron microscopy (HR-TEM) of Co-N-C indicated many Co-Nx (Co covalent bonding with several nitrogen) units in the Co-N-C matrix. X-ray diffraction patterns showed that carbon and cobalt crystallized in the Co-N-C catalysts. The Raman spectra showed that the carbon matrix of Co-N-C became ordered with increased calcination temperature. The surface area (dominated by micropores) of Co-N-Cs also increased with the calcination temperature. The non-precious Co-N-C demonstrated comparable electrochemical properties (oxygen reduction reaction: ORR) to commercial precious Pt/C, such as high on-set and half-wave voltages, high limited reduction current density, and lower Tafel slope. The number of electrons transferred in the cathode was close to four, indicating complete ORR. The max. power density (Pmax) of the single cell with the Co-N-C cathode catalyst demonstrated a high value of 227.7 mWcm-2.

Effect of the Calcination Temperature of LaNiO3 on the Structural Properties and Reaction Performance of Catalysts in the Steam Reforming of Methane

The steam reforming of methane (SRM) reaction is a significant process for efficient syngas generation and for promising distributed hydrogen production. In this work, a series of LaNiO3 oxides were prepared using the Pechini method, calcined from 600 °C to 900 °C and tested for the SRM reaction. Fresh, reduced, and used samples were characterized using STA-MS-FTIR, in situ and ex situ XRD, N2 physical adsorption, H2-TPR, TEM, TPO, and Raman. The results show that LaNiO3 begins to crystallize at about 550 °C, and the increase in calcination temperature results in the following differences in the properties of the LaNiO3 samples: larger LaNiO3 grains, smaller specific surface area, higher reduction temperature, smaller Ni0 grains reduced from the bulk phase, and stronger metal–support interaction. The maximum CH4 conversion could be achieved over LaNiO3 calcinated at 800 °C. In addition, the effect of steam-to-carbon ratio (S/C) on the performance of the SRM reaction was studied, and a S/C of 1.5 was found to be optimal for CH4 conversion. Too strong a metal–support interaction and too much unreacted steam causes a loss of catalytic activity. Finally, it was also proved using TPO and Raman that an increase in calcination temperature improves the carbon deposition resistance of the catalyst.

Influence of Rapid Heat Treatment on the Photocatalytic Activity and Stability of Strontium Titanates against a Broad Range of Pollutants

Strontium titanate (STO) photocatalysts were prepared via a slightly modified Pechini sol–gel method. A unique rapid calcination technique with a short exposure time was used to obtain crystalline products. The samples were characterized by X-ray diffractometry, scanning electron microscopy, diffuse reflectance spectroscopy, infrared spectroscopy, nitrogen adsorption–desorption measurements, and X-ray photoelectron spectroscopy. Their photocatalytic activity was evaluated by the photocatalytic oxidation of phenol, oxalic acid, and chlorophenol under UV light irradiation using commercial STO as a reference. These pollutants, together with glucose and propanol, were used to investigate the stability of the samples against various functional groups. All our samples exhibited higher photocatalytic activity than the commercial STO reference. With increasing calcination temperature, the crystallinity and primary crystallite sizes increased while the band gaps and specific surface areas decreased. The photocatalytic activity of the most efficient sample was explained by the presence of SrCO3 on its surface. The STO catalysts were highly stable as they largely retained their crystalline composition after exposure to chemicals with different functional groups. Finally, we compared the costs associated with the unique calcination technique with a more conventional one and found that our method is ~35% more cost-effective.

Effect of Calcination Temperature of SiO2/TiO2 Photocatalysts on UV-VIS and VIS Removal Efficiency of Color Contaminants

This paper presents the effect of fumed silica modification and calcination temperature on the physicochemical properties of photocatalysts and their activity under the UV-VIS and VIS light range. The materials were obtained by hydrolysis of titanium tetraisopropoxide (TTIP) combined with a calcination step. The obtained nanomaterials were characterized using analytical methods such as X-ray diffraction XRD, FT-IR/DRS infrared spectroscopy, UV-Vis/DRS spectroscopy and SEM scanning electron microscopy. BET specific surface area and zeta potential were also measured. It was observed that SiO2 modification inhibited the transformation phase of anatase to rutile and the increase in crystallite size during calcination. The calcination process contributed to a change in the surface character of photocatalysts under study from positively to negatively charged. The photocatalytic activity of samples was identified by determining the methylene blue decomposition under UV-VIS and VIS light. Experimental results showed that the addition of SiO2 and the calcination process increased the photoactivity. The obtained materials showed higher activity compared to the reference samples. It was found that the degree of dye removal increased along with increased calcination temperature. The highest activity was observed for photocatalyst SiO2(11.1%)/TiO2_600.

Research of characterization of zinc ferrite, titanium dioxide and their composites

In this paper, zinc calcines, sulfuric acid, ferric nitrate nine-hydrate, zinc nitrate hexahydrate, titanium oxide sulfate, sodium hydroxide and ammonia water were selected as raw materials, and the methods of sulfuric acid leaching and chemical coprecipitation were used to prepare purified zinc ferrite, synthetic zinc ferrite, synthetic titanium dioxide and its composite with purified zinc ferrite. And characterized by BET, UVVis and FTIR. The results showed that: SO42- existed in purified zinc ferrite. Purified zinc ferrite, synthetic zinc ferrite and purchased had different specific surface area, pore volume and average pore size. The specific surface area of synthetic zinc ferrite decreased with the increase of calcination temperature. The three kinds of zinc ferrite had good absorption of ultraviolet light and visible light. Purchased ferric acid had the strongest absorption of UV light and synthetic zinc ferrite had the strongest absorption of visible light, and purified zinc ferrite had the absorption of UV light and visible light between the two. The specific surface area of titanium dioxide prepared by chemical coprecipitation method was greatly affected by calcination temperature. With the increase of calcination temperature, the specific surface area decreased from 123.633 to 28.036m2·g-1, and the average pore diameter was less affected by calcination temperature. For the zinc ferrite/titanium dioxide composite prepared by chemical coprecipitation method, a certain amount of purified zinc ferrite was added to facilitate the absorption of visible light by titanium dioxide.

Effect of pH on the Synthesis of Silica Sol-Gel Tetraethylorthosilicate-Trimethylchlorosilan (TEOS-TMCS)

Sol-gel synthesis of silica employing the co-precursor trimethylchlorosilane (TMCS) and the precursor tetraethylorthosilicate (TEOS) was accomplished. The purpose of this investigation was to ascertain how pH affected the properties of synthetic silica. The synthesized hydrophobic silica was characterized using FTIR, TGA, and GSA to determine the effect of pH adjustment on the functional group characters, thermal properties, and pore morphology. The ratio between TEOS/TMCS was fixed at 75:25 and varied the pH (4, 6, 7, 8, and 10) and the calcination temperature (without calcination, 300℃ and 500℃). FTIR analysis showed that the number of C-H and Si-OH groups in the xerogel decreased with increasing calcination temperature. Xerogel formed at pH 6 provides the highest thermal stability among other pHs. The results from the BET analysis revealed that changes in pH directly affect the physical characteristics of the surface, making the resulting gel network less rigid and more susceptible to shrinkage of pore volume and diameter in the atmosphere. Meanwhile, in an alkaline medium, continuous condensation will occur so that the pore diameter and volume decrease. The high pore diameter and volume imply that pH 7 is ideal for preparing xerogels.

Nickel-iron catalyst for decomposition of methane to hydrogen and filamentous carbon: Effect of calcination and reaction temperatures

Nickel-ferrite Ni-Fe (molar ratio 1:2) were synthesised and calcined at different temperatures. The catalytic performances of Ni-Fe for methane decomposition and production of hydrogen and carbon nanostructures were evaluated at various calcination (350–800 °C) and reaction temperatures (700–800 °C). Fresh and spent catalysts were characterized using scanning electron microscopy (SEM), BET surface area, X-ray diffraction (XRD), TGA and Raman spectroscopy. XRD results revealed the formation of highly crystalline NiFe2O4 in calcined samples, while Ni-Fe alloys were observed in the spent catalysts. The NiFe2O4 catalyst has a mesoporous structure with monomodal pore distribution. The surface area decreased from 107.0 to 3.8 m2/g with increasing calcination temperature from 350 to 800 °C. Methane conversion, 48.50%, and hydrogen formation rate, 97.70 × 10-5 mol H2 g−1 min−1 was obtained at reaction temperature of 800 °C. The catalyst activity slightly improved by increasing calcination temperature. The SEM images of spent catalysts revealed the formation of some filamentous carbon over all spent catalysts except for that operated at reaction temperature of 700 °C. TGA studies revealed that the deposited carbon increased with increase in reaction and calcination temperatures and achieved 42.50 and 59.32 wt%, respectively. The graphitization and crystalline of the deposited carbon slightly decreases as calcination temperature increased.

One-Step Synthesis of Bunsenite Cadmium Oxide Nanoparticles

The present study proposes a simple synthesis technique for producing bunsenite cadmium oxide nanoparticles. A variety of techniques were used to determine the structure, morphology, elemental content, and optical properties of bunsenite cadmium oxide nanoparticles. The samples’ XRD spectra at 500 °C and above confirmed the presence of cubic bunsenite and cadmium oxide structures. The crystallite size was increased from 29 nm to 62 nm as the calcined temperature increased from 500 °C to 800 °C. The dispersion of the particles of bunsenite cadmium oxide improved with an increasing calcination temperature. An equivalent increasing trend was indicated by the mean grain size displayed via field emission scanning electron microscopy (FESEM) micrographs. Furthermore, the UV-Vis spectra showed that multiple energy band gaps attenuated as the calcination temperature increased. The mean particle size, as measured by transmission electron micrographs, appeared to increase in tandem with the calcination temperature. The obtained bunsenite and cadmium oxide nanoparticles have potential for employment in a wide range of semiconductor applications.

Magnesium Spinel Ferrites Development for FDM 3D-Printing Material for Microwave Absorption

The magnesium nanosized ferrite powder with formula MgFe2O4 was synthesized via a pyrochemical sol–gel glycine–nitrate method and annealed consistently at temperatures of up to 1300 °C. The MgFe2O4 ferrite samples’ microstructure was studied by SEM and XRD methods. According to the results of the studies, the increase in MgFe2O4 nanoparticles size from about 15 nm to micron-sized particles was observed when increasing annealing temperatures. The DC electrical conductivity of MgFe2O4 also clearly shows the change in conduction behavior of samples with increased calcination temperatures. The electromagnetic microwave properties of micron-sized particles of MgFe2O4 ferrite powder for a 1200 °C annealing temperature were studied for composites in paraffin matrix with produced magnetic filler mass concentration at 40% and 50%. The filament composites of polymer polylactic acid with MgFe2O4 ferrite powder samples were prepared by the FDM 3D-printing process and their microwave-absorbing properties were investigated. The application of developed PLA–MgFe2O4 ferrite filament for fabricating magnetic microwave-absorbing components also was demonstrated.

Evaluation of Structural and Functional Properties of La0.6Sr0.4MnO3 Perovskite Prepared by the Fast Solution Combustion Approach

A series of La0.6Sr0.4MnO3 (LSM) perovskite was made using the rapid solution combustion method, which was calcined by varying the temperatures. In order to determine how the calcination temperature affected the nanopowders produced and calcined at various temperatures, their microstructural, morphological, compositional, optical, and electrical properties were analyzed using corresponding characterization tools. The XRD results showed the coexistence of the rhombohedral polymorphs R-3c and Pm-3m for the perovskite phase under a calcination temperature of 1400 °C, which were eliminated with increased calcination temperature. The average grain size was found to increase with increasing calcination temperature. The EDS analysis showed better agreement of the stoichiometry with the theoretical composition. The apparent porosity decreased with increasing temperature due to the coalescence of sintering pores. The sample obtained after calcination at 1500 °C showed 10.3% porosity. The hardness also improved with increasing calcination temperature and reached a maximum value of 0.4 GPa, which matched the bulk density. A similar trend was observed in the resistivity studies as a function of temperature, and all the samples exhibited a low resistivity of ~1.4 Ω·cm in the temperature range of 500–600 °C. The optical characterization showed broad absorption at 560–660 nm and bandwidth values between 3.70 and 3.95 eV, according to the applied heat treatment.

Facile synthesis and characterisation of Mn0.5Zn0.5Fe2O4/Fe2O3 as a novel nanocomposite for studying analytical parameters affecting on photocatalytic degradation of basic fuchsin dye

ABSTRACT Restricted biodegradability, toxicity, and carcinogenicity of basic fuchsin dye are the principal reasons that motivate scientists to find methods to remove it. Photocatalytic degradation technology is simple, environmentally friendly, inexpensive, efficient, and does not yield secondary pollution. Most of the catalysts used to degrade basic fuchsin dye require expensive chemicals to prepare. Therefore, the novelty in our work comes from the utilisation of low-cost chemicals for the facile synthesis of Mn0.5Zn0.5Fe2O4/Fe2O3 nanocomposite using the pechini sol-gel method. The synthesised samples at 300, 600, and 900°C were encoded as F300, F600, and F900, respectively. The XRD confirmed that the average crystallite size of the F300, F600, and F900 samples is 95.08, 122.32, and 160.21 nm, respectively. Hence, as the calcination temperature increases, the crystallite size increases as a result of coagulation that occurs at higher temperatures. The FE-SEM images showed that the F300, F600, and F900 samples consist of spherical, (polyhedral and spherical), and (hexagonal and spherical) shapes with an average diameter of 258.64, 470.12, and 625.32 nm, respectively. This change in morphology at different temperatures is due to the discrepancy in the rate of liberation of organic matter at different temperatures. In the presence of hydrogen peroxide, 0.05 g of the Mn0.5Zn0.5Fe2O4/Fe2O3 nanocomposite degrade 100% of 25 mL of 25 mg/L of basic fuchsin dye at pH = 8 within 25 min. Consequently, the other side of the novelty of our work is the ability of the synthesised nanocomposite to effectively degrade a high concentration of the basic fuchsin dye in a short time.

Pengaruh Temperatur Kalsinasi Terhadap Gugus fungsi, Struktur mikro, Dan Kerapatan dislokasi Pada Material Katoda Baterai LiNiO2

Battery cathode material is one of the four determinants of energy storage capacity, which is used as a power source in electronic equipment. laptops, and electric vehicles. Synthesis of LiNiO2 battery cathode material by solid state method, and variations in calcination temperature from 700 oC, 775 oC, and 850 oC , as wll as a fixed time of 6 hours. The results of the analysis using the FTIR spectrum showed that the vibration mode correlated with the vibrations of the octahedral units of NiO6 and LiO6 in the wave number zone of 400 - 700 cm−1. Thus, the peak around 433 cm−1 is caused by the Li–O asymmetric strain vibration of LiO6 and the NiO6 bending vibration, namely [(Ni–O–Li)], occurring at 551-603 cm−1. The results of the observation of the microstructure with SEM showed the size of the micron with an uneven and homogeneous surface. The elemental compositions of Li and Ni metals were analyzed by EDXS showing that the metal content of Li and Ni decreased as the calcination temperature increased. The results of the crystal structure test using an X-ray diffractometer showed that with the increase in the calcination temperature, the average diameter of the crystallites decreased, but the average dislocation density increased and the mean micro-lattice strain also increased ( 0.4817% to 15.8079%) and in the Miller hkl index plane. (102), (104), (210), (108), and (113).

Synthesis and characterization of Yb3+ activated Lu2O3 nanoparticles doped optical fiber preform for high power laser application

Yb3+-activated Lu2O3 is known to exhibit excellent thermal conductance, which can be a potential candidate to develop high-power laser fiber. Here we report the synthesis of Yb3+-activated Lu2O3 nanoparticles following the homogeneous coprecipitation method along with their material and optical characterization. Five different samples were synthesized using different concentrations of Cetyl Trimethyl Ammonium Bromide (CTAB) as a cationic surfactant, Yb–Lu ratio in the presence/absence of aluminium (Al) as an additional dopant, followed by calcination at different temperatures. Differential thermal analysis (DTA) and thermogravimetry (TG) analysis were performed to optimize the thermal annealing condition while the X-ray diffraction (XRD) analysis shows the formation of a pure bixbyite structure with an average particle size of ∼ 15 nm at 800°C that reaches up to ∼ 120 nm with increasing calcination temperature to 1400°C. The field emission scanning electron microscope (FESEM) analysis shows nearly cubic morphology while high-resolution Transmission Electron Microscope (HRTEM) analysis confirms the crystalline nature and the average particle size corroborates with the XRD analysis result. The developed nanoparticle was found to exhibit characteristics of Yb-absorption and emission peaks showing no interference with Lu2O3. The emission intensity and fluorescence lifetime of the Yb3+-activated Lu2O3 nanoparticles were found to depend on the Yb concentration, average particle size, and presence of aluminium as a co-dopant. To evaluate the practical application of the developed nanoparticles, an optical preform is developed using synthesized nanoparticles as Yb-source through modified chemical vapor deposition (MCVD) coupled with solution doping (SD) technique and the initial performance of the preform is also reported.

A Two-Dimensional Guidance Strategy to Fabricate Perovskite Gadolinium Aluminate Ceramic Film

Gadolinium aluminate is an effective host for doping with various ions, and it can emit various colors. However, it is not easy to prepare transparent ceramics of gadolinium aluminate using traditional methods, although transparent ceramics are very suitable for solid lighting. In this work, a two-dimensional guidance strategy has been successfully carried out for perovskite-structured aluminate ceramic film. Through the two-dimensional interfacial reaction, GdAlO3:Eu3+ (GAP:Eu3+) transparent ceramic films were successfully fabricated using nanosheets exfoliated from layered gadolinium hydroxide, a rare earth source. The final films were tested by characterization techniques, including XRD, SEM, TEM, FT-IR, PLE/PL spectroscopy, temperature-dependent PL spectroscopy, and luminescence decay analysis. The perovskite film of transparent ceramics can be obtained by calcining LRH nanosheets on the substrate of amorphous alumina at 1550 °C in air with a reaction time of 2 h. During the interface reaction, temperature-dependent element diffusion takes the dominant role, and increased reactants take in the reaction with increasing calcination temperature. The grain for ceramic film is only 2–5 μm, which is much smaller than that for bulk ceramic. This is mainly due to the lower temperature and the interface diffusion. Ceramic film has a high transmittance larger than 90% at the visible range. Upon UV excitation at 254 nm, the film exhibits intense emission at the red wavelength range. The outcomes described in this work may have wide implications for transparent ceramics and layered rare-earth hydroxides.

Influence of charge compensation on the photoluminescence and temperature sensing of zinc titanate composites

Eu3+ activated zinc titanate red-emitting phosphors have been synthesized by a solid state reaction, and Li+ is added as the charge compensator to tune the optical performances of the phosphors. The structure of samples synthesized at different temperature reveals temperature dependence. The crystallization of particles is improved with increasing calcination temperature. The surface morphology and element distribution of the samples are observed by scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Various elements are evenly distributed in the matrix materials. The luminescence intensity of Eu3+ is effectively improved by co-doping Li+, and the luminescence intensity of the phosphor with Li+ content of 5 mol% and 7 mol% is twice than that of the phosphor without Li + when the annealing temperature is 600 °C. While the influence of Li + on the photoluminescence performance becomes weaker with the annealing temperature increasing. The highest relative sensitivity of 0.65%/K is obtained in the sample annealed at 1000 °C, which is not affected by the Li+ dopants.

Green Synthesis of NiO-SnO2 Nanocomposite and Effect of Calcination Temperature on Its Physicochemical Properties: Impact on the Photocatalytic Degradation of Methyl Orange

Background: Nickel stannate nanocomposites could be useful for removing organic and toxic water pollutants, such as methyl orange (MO). Aim: The synthesis of a nickel oxide-tin oxide nanocomposite (NiO-SnO2 NC) via a facile and economically viable approach using a leaf extract from Ficus elastica for the photocatalytic degradation of MO. Methods: The phase composition, crystallinity, and purity were examined by X-ray diffraction (XRD). The particles' morphology was studied using scanning electron microscopy (SEM). The elemental analysis and colored mapping were carried out via energy dispersive X-ray (EDX). The functional groups were identified by Fourier transform infrared spectroscopy (FTIR). UV-visible diffuse reflectance spectroscopy (UV-vis DRS) was used to study the optical properties such as the absorption edges and energy band gap, an important feature of semiconductors to determine photocatalytic applications. The photocatalytic activity of the NiO-SnO2 NC was evaluated by monitoring the degradation of MO in aqueous solution under irradiation with full light spectrum. The effects of calcination temperature, pH, initial MO concentration, and catalyst dose were all assessed to understand and optimize the physicochemical and photocatalytic properties of NiO-SnO2 NC. Results: NiO-SnO2 NC was successfully synthesized via a biological route using F. elastica leaf extract. XRD showed rhombohedral NiO and tetragonal SnO2 nanostructures and the amorphous nature of NiO-SnO2 NC. Its degree of crystallinity, crystallite size, and stability increased with increased calcination temperature. SEM depicted significant morphological changes with elevating calcination temperatures, which are attributed to the phase conversion from amorphous to crystalline. The elemental analysis and colored mapping show the formation of highly pure NiO-SnO2 NC. FTIR revealed a decrease in OH, and the ratio of oxygen vacancies at the surface of the NC can be explained by a loss of its hydrophilicity at increased temperatures. All the NC samples displayed significant absorption in the visible region, and a blue shift is seen and the energy band gap decreases when increasing the calcination temperatures due to the dehydration and formation of compacted large particles. NiO-SnO2 NC degrades MO, and the photocatalytic performance decreased with increasing calcination temperature due to an increase in the crystallite size of the NC. The optimal conditions for the efficient NC-mediated photocatalysis of MO are 100 °C, 20 mg catalyst, 50 ppm MO, and pH 6. Conclusions: The auspicious performance of the NiO-SnO2 NCs may open a new avenue for the development of semiconducting p-n heterojunction catalysts as promising structures for removing undesirable organic pollutants from the environment.

Influence of Calcination Temperatures on Gunningite-Based Gelatin Template and Its Application as Ibuprofen Adsorption

Gunningite has been successfully synthesized using the soft template method with the Pluronic F127-gelatin template. Gunningite was calcined at diverse temperatures of 500, 600, and 700 °C for 12 h and characterized by XRD, SEM, and FTIR. A UV-Vis Spectrophotometer measured the adsorption capacity of Gunningite against ibuprofen. The XRD results showed that the crystal sizes of Gunningite decreased from 35.41 to 28.31 nm with the increasing calcination temperature from 500 to 700 °C. Besides, the crystallinity degrees also increased from 49.94% to 56.13% as calcination temperature increased from 500 to 700 °C. The Gunningite formed aggregates in the form of tiny particles that merge and experience agglomeration. The FTIR spectra of the Gunningite samples demonstrated the functional groups –OH, Zn-OH, Zn-O-Zn, and gunningite vibrations. The maximum adsorption capacities of Gunningite to adsorb ibuprofen were 233.161 mg g−1 (500 °C), 219.543 mg g−1 (600 °C), and 227.033 mg g-1 (700 °C). The kinetic model of Gunningite on the ibuprofen adsorption followed the kinetic model of Ho and McKay.

A Novel Shift in the Absorbance Maxima of Methyl Orange with Calcination Temperature of Green Tin Dioxide Nanoparticle-Induced Photocatalytic Activity

Background: The photocatalytic degradation of toxic organic compounds has received great attention for the past several years. Dyes, such as methyl orange (MO), are one of the major pollutants which create environmental hazards in the hydrosphere, living organisms and human beings. During photocatalytic degradation, NPs are activated in the presence of UV–Vis radiation which in turn creates a redox environment in the system and behaves as a sensitizer for light-induced redox mechanisms. Tin oxide (SnO2) is one of the prominent, but less investigated, nanomaterials compared to titanium oxide (TiO2) and Zinc oxide (ZnO) nanoparticles (NPs). Methods: Herein, Buxus wallichiana (B. wallichiana) leaf extract was utilized as a reducing and capping agent for the biosynthesis of SnO2 NPs. The effects of the calcination temperature on their photocatalytic, structure and surface properties were then examined. The degree of crystallinity and the crystallite size were determined through X-ray diffraction (XRD) analysis. The pore size and surface area were calculated by Burnett–Emmitt–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods based on nitrogen desorption data. Morphological changes were assessed by scanning electron microscopy (SEM). The optical behavior was analyzed through UV–Vis diffuse reflectance spectroscopy (DRS) data and the band gap subsequently calculated. The photocatalytic efficiency of SnO2 NPs was evaluated by double beam UV–Vis spectrophotometry under the influence of initial MO concentration, catalyst dose and pH of MO solution. The surface functional moieties were identified using Fourier transform infrared (FTIR) spectroscopy. All the calcined SnO2 NPs were used as photocatalysts for the mineralization of MO in aqueous media. Results: The degree of crystallinity and the crystallite size increased with the calcination temperature. The transmittance edge obtained for all the calcined SnO2 NPs shows a maximum absorbance in the visible range (λ-max = 464 nm). Moving toward higher wavelengths, a sudden intense red shift (from 464 nm to 500 nm), attributed to the incorporation of a hydroxyl radical at the ortho-position in the benzene ring associated with the dimethylamine group of MO, was observed in the absorbance of the samples calcined up to 300 °C. The percentage degradation of MO was found to decrease with increasing calcination temperatures. The optimal photocatalytic activity toward MO (15 ppm) in a solution of pH = 6 was obtained with 15 mg SnO2 NPs calcined at 100 °C. Conclusions: UV–Vis absorption spectroscopy demonstrates that the absorption spectra of MO are strongly modified by the calcination temperature. This work opens new avenues for the use of SnO2 NPs as photocatalysts against the degradation of industrial effluents enriched with different dyes.

Formation of beryllium oxide nanofibers by polyvinyl alcohol/beryllium sulfate/polyethyleneimine composite precursors

Polyvinyl alcohol (PVA)/beryllium sulfate (BeSO4) precursor nanofibers are fabricated by electrospinning technique, mixing PVA aqueous solution with BeSO4 salt. The productivity is increased by adding polyethyleneimine (PEI) with PVA/BeSO4 spinning solution. The beryllium oxide (BeO) nanofibers are obtained by calcinating the PVA/BeSO4/PEI precursor nanofiber heated at 1000 °C or above. The crystallographic structure of BeO nanofibers is examined by X-ray diffraction. The thermal behaviors of the pure PVA nanofibers, BeSO4 salt, and PVA/BeSO4/PEI precursor nanofibers are studied by thermogravimetry analysis. The BeO nanofiber diameters are reduced with the increase in calcination temperatures. The specific surface area of the PVA/BeSO4/PEI precursor nanofibers is around 36.9 m2 g−1, and that of the BeO nanofibers calcined at 1200 °C is about 11.9 m2 g−1. The pore properties deteriorate due to sintering and blockage as the calcination temperature increases. This work introduces mesoporous BeO nanofibers for the very first time.

Analyzing the role of copper in the soot oxidation performance of BaMnO3-perovskite-based catalyst obtained by modified sol-gel synthesis

• Carbon black decreases the calcination temperature to obtain perovskite structure. • The distribution of copper depends on the calcination temperature. • The insertion of copper into the structure is promoted with calcination temperature. • BMC3-C600 shows the most stable performance during cyclic experiments. • The presence of copper on surface and of oxygen vacancies are promoted for BMC3-C600. A series of BaMn 0.7 Cu 0.3 O 3 solids were prepared by a modified sol-gel method in which carbon black (VULCAN XC-72R), and different calcination temperatures (BMC3-CX, where X indicates the calcination temperature) have been used. The fresh and used catalysts were characterized by ICP-OES, XRD, XPS, FESEM, TEM, O 2 -TPD and H 2 -TPR. The presence of a carbon black during sol-gel synthesis of BMC3 mixed oxide allows diminishing the calcination temperature needed to achieve the perovskite structure, but it hinders the formation of the BaMnO 3 polytype. The use of low calcination temperatures during synthesis reduces the sintering effects, and the mixed oxides present lower particle size, slightly higher BET surface areas and macropores with lower diameter than BMC3. The distribution of copper in BMC3-CX catalysts depends on the calcination temperature and copper insertion into the perovskite structure is promoted as the calcination temperature increases. All BMC3-CX catalysts are active for NO to NO 2 and NO x -assisted soot oxidation processes, but only BMC3-C600 and BMC3-C700 show higher catalytic activity than BMC3 reference catalyst. BMC3-C600 presents the best performance as it features a high amount of surface copper and oxygen vacancies that increase during reaction. The comparison between the performance of the two best catalysts of the BM-CX series (BM-C700) and the BMC3-CX series (BMC3-C600) suggests that the unique advantage of using copper in the modified sol-gel synthesis is an additional decrease of 100 °C in the calcination temperature used for the synthesis of the best catalyst, which is 700 °C for BM-CX and 600 °C for BMC3-CX.