Variation Of Calcination Temperature Research Articles

Multiferroic properties of Sr-doped BiFeO3 nanoparticles

The effects of ‘Sr-doping’ and ‘particle size’ on multiferroic properties of BiFeO3 nanoparticles were studied. Structural analysis revealed no influence on the rhombohedral structure of BiFeO3 with Sr-doping in the synthesized nanoparticles. The particle size of Sr-doped BiFeO3 nanoparticles was tailored by varying calcination temperature. The crystallite size got reduced with Sr-doping and also on decreasing the calcination temperature. Lattice strain was observed to enhance with reducing particle size of Sr-doped BiFeO3 nanoparticles. Magnetic measurements confirmed enhancement in magnetization via suppression of spin cycloidal structure with Sr-doping owing to creation of oxygen vacancies, enhanced lattice strain and reduction in particle size. Dielectric analysis revealed deterioration of dielectric constant of BiFeO3 with Sr-doping due to the formation of oxygen vacancies. Further, on reducing particle size of Sr-doped BiFeO3 nanoparticles, both saturation magnetization and dielectric constant values registered increase. Lowering of the magnetic phase transition temperature with particle size of Sr-doped BiFeO3 nanoparticles indicated weakening of magnetic exchange interactions.

Development of Sol Gel Derived Nanocrystalline TiO2 Thin Films via Indigenous Spin Coating Method

In this paper, indigenous spin coater apparatus was fabricated and characterized by depositing transparent semiconducting thin films of TiO2 on glass substrates for 90 s at 6000 rpm followed by calcination procedures. The influence of the calcination temperature (400–800 °C) on electrical, optical, structural and photocatalytic properties of nano-crystalline titanium dioxide (TiO2) thin film were studied by four point probes, absorbance spectrum, X-ray diffraction (XRD), and photocatalytic activity test respectively. It has been investigated that the effect of conductivity increase may be caused by the increase of temperature. The XRD results showed that TiO2 thin film calcined at 400 °C was anatase, and further transformed into the rutile phase at higher calcination temperature. The crystallite size of TiO2 thin films was increased with increasing calcination temperature. Experimental results depicts that structural and electrical properties of the films are highly dependent on the growth temperature. It was observed that with increasing growth temperature, the average visible transmittance of the deposited films is enhanced and the residual stress in the thin films is obviously relaxed. The optical band gap energy decreases with increasing calcination temperature upto certain limit. Photocatalytic activity of thin films, evaluated by disintegration of methyl blue, methyl orange and RhB, was increased with variation in calcination temperature for a particular range. At 700 °C, the TiO2 thin film showed the highest photocatalytic activity due to better crystallization of TiO2 in the composite thin film.

Sol–Gel Grown SnO2 Nanoparticles: Evaluation of Structure, Morphology, and Raman Spectra

Tin oxide (SnO2) nanoparticles (TONPs) were prepared using sol–gel method under different growth conditions. The influence of calcination temperature (450°C and 600°C) and molecular weight of polyethylene glycol (PEG 300 and PEG 4000) on the nanocrystallinity, surface morphology, and Raman spectra of as-prepared TONPs were evaluated. Variation of calcination temperature and dopant (sulfosuccinic acid, SA) was found to affect considerably the structure, surface morphology, and Raman activities of the TONPs. The size of TONPs estimated using Scherrer equation was discerned to be in the range of 15–32 nm. The observed intensity enhancement in the Raman vibrational modes at lower calcination temperature was attributed to the enlargement of TONPs size. The absorption of molecules at the TONPs surface led to a quenching in the A 2 g and Eu Raman peaks. Raman peaks centered around 673 cm−1, 799 cm−1, 640 cm−1 , and 432 cm−1 corresponding to A1g, B2g, A1g, and Eg modes, respectively have manifested highest peaks intensity. Furthermore, the enhancement of the Eg mode due to the addition of SA dopant was ascribed to the Jahn–Teller distortion mechanism.

Thermally assisted electro-active regions in SrMnO3 ceramics

Conditions were optimized to prepare SrMnO3 via sol-gel auto-combustion route, by varying calcination temperature from 600 to 1200 °C. Single phase synthesis was confirmed by X-ray diffraction in the sample calcined at 1000 °C for 4 h. Rietveld’s refinement was performed to obtain the detailed information regarding the structural parameters of the manganite sample. The effect of calcination temperature on dielectric, and impedance studies has been reported from a low (20 Hz) to a high frequency region (20 MHz) SrMnO3 ceramic samples. The dielectric response reveals electroactive regions in accordance with the Maxwell-Wagner model while the impedance analysis shows the dominant behaviour of microstructural grain boundaries. The resistive parameters were then optimized to calculate the grain/grain boundary capacitance. A possible combination of equivalent circuit is also fitted in order to determine the deviation from idealistic behaviour in impedance analysis. These circuits are also verified through frequency dependent conductivity response while the dependence of capacitance on temperature gives the information on the possible ferroelectric behaviour.

Synthesize and Analysis of Li1.33Mn1.67O4 as Adsorbent for Lithium Extraction of Lumpur Sidoarjo

Li1.33Mn1.67O4 (LMO) was successfully synthesized by solid state reaction method at temperature variation of 500, 600, and 700 °C. As-prepared samples are immersed in 1 lt 0.5M HCL for 24 hours to create vacant site for lithium ion. Lithium extraction process is employed by soaking the adsorbent LMO in 1 lt of Lumpur Sidoarjo for 24 hrs. SEM images of adsorbent with variation of calcination temperature show irregular shape with particles size in the range of 15-52 μm. The calcination temperature effects on the size of the grain and crystallinity of adsorbent. LMO 700 sample has the highest capacity of lithium adsorption with capacity of 29.8 mg/g. It is attributed to the high crystalline of LMO 700 sample compared with other samples.

Water effects on the acidic property of typical solid acid catalysts by 3,3-dimethylbut-1-ene isomerization and 2-propanol dehydration reactions

Two model reactions, namely the Brønsted-acidity-specific skeletal isomerization of 3,3-dimethylbut-1-ene for evaluating the Brønsted acidity and dehydration of 2-propanol for the overall acidity at the catalyst surface, were employed in this work to measure the effect of water on the surface acidic property of typical solid catalysts (HZSM-5, γ-Al2O3 and Nb2O5). For the isomerization reaction, water addition in the reaction feed produced little effect on the catalysis of HZSM-5 but significantly positive effect on the catalysis of Nb2O5; the typical Lewis acidic γ-Al2O3 showed no activity for this reaction in either the presence or absence of water. For the dehydration reaction, the effect of water was generally negative on the catalysis of every catalyst, demonstrating that water presence resulted in poisoning more or less of the Lewis acidity on the catalyst surface. Water poisoning of the Lewis acidity on Nb2O5 also resulted in generation of Brønsted acidity and the higher the H2O partial pressure (or H2O-to-substrate ratio) the higher the newly generated Brønsted acidity. However, generation of Brønsted acidity did not happen on γ-Al2O3 and HZSM-5, regardless of the H2O partial pressure. Three Nb2O5 samples with varying calcination temperature were involved, and their behavior clearly indicated that the water effects on Nb2O5 also depended sensitively on the sample calcination temperature. Moreover, water presence increased the activation energy and selectivity for di-isopropyl ether of the dehydration reaction over γ-Al2O3 and Nb2O5, and thus affected the acidity distribution at the catalyst surface during the reaction.

Zinc oxide nanoparticle energy band gap reduction triggers the oxidative stress resulting into autophagy-mediated apoptotic cell death

The physico-chemical properties of nanoparticle (NP), such as particle size, surface defects, crystallinity and accessible surface, affect NP photocatalytic activity that in turn defines the NP cytotoxic propensity. Since zinc oxide nanoparticle (ZnONP) energy band gap falls in a range of a semiconductor, the particle possesses photocatalytic activity. Hence, the study correlates energy band gap with cytotoxic propensity of ZnONP. To this end, ZnONPs with varying energy band gap are fabricated by varying calcination temperature. Cytotoxic propensity of the fabricated ZnONPs against HT1080 cell indicates that the particle with least energy band gap shows highest cytotoxicity. The data also indicate that the cytotoxicity is triggered primarily through reactive oxygen species (ROS)-mediated pathway. Additionally, the comet assay and γH2AX activity assay reveal that decreasing energy band gap of the particle increases DNA damaging propensity. Furthermore, cell cycle analysis indicates that the cell treatment with decreasing energy band gap ZnONP results in significant increase in cell population fraction in subG1 phase. Whereas, acridine orange binding assay and increased expression level of LC3II indicate that the cell tries to recover the stress by scavenging damaged cellular biomolecules and ROS using autophagosomes. Nevertheless, cell with the non-recoverable damages led into apoptotic cell death, as confirmed by Annexin V apoptosis assay, DNA fragmentation assay and 4,6-Diamidino-2-phenylindole dihydrochloride (DAPI) staining.

Utilization of Solid Acid SO42−/TiO2 as Catalyst to the Three‐Component Mannich Reaction at Ambient Temperature

The three‐component Mannich reaction of among dimethyl malonate, aromatic primary amine, and aromatic aldehyde was made successfully in the presence of solid acidic catalyst SO42−/TiO2, with excellent catalytic activity, as compared to SO42−/γ‐Al2O3 and SO42−/ZnO. To the best of our knowledge, SO42−/TiO2 prepared at varied calcination temperatures can perform different intensities of Lewis and Brønsted acidities. Because of this point, under the optimum conditions, the effect of SO42−/TiO2 (prepared at 200°C) was much more than that of SO42−/TiO2 (prepared at 300°C or 400°C) in the three‐component Mannich reaction. In observing ionization activation mode of the three‐component Mannich reaction, it disclosed that the plausible mechanism possibly undergoes formation of aldimines and transformation of aldimines into β‐amino esters by applying solid acidic catalyst SO42−/MxOy.

Promoting effects of thoria on the nickel-manganese mixed oxide catalysts for the aerobic oxidation of benzyl alcohol

Due to the recent advancement in the development of various characterization techniques, mixed metal oxide (MMO) based catalysts have gained tremendous attention in the field of catalysis. In this study, we demonstrated the synthesis of a series of novel MMO based catalysts by a facile co-precipitation method. The detailed structure and composition of thoria promoted NiMnO catalysts was investigated using various microscopic and spectroscopic techniques such as, SEM, EDAX, XRD, TGA, BET and TPR. In order to study the effect of the content of thorium oxide on the catalytic activity of the as-prepared material various samples were prepared by the addition of low quantities of thorium oxide with 1%, 3% and 5% on NiMnO. The catalytic performances of the as-prepared catalysts were evaluated towards the aerobic oxidation of benzyl alcohol using molecular oxygen as oxidant. Furthermore, in order to investigate the effect of the calcination temperatures on the catalytic activities of the as-prepared materials, the samples were calcined at three different temperatures at 300°C, 400°C and 500°C. The catalysts displayed significant enhancement in catalytic activity towards the catalytic conversion of benzyl alcohol (C6H5CH2OH) to benzaldehyde (C6H5CHO). Detailed kinetic studies of the reactions using gas chromatography have revealed that the variation of calcination temperature and the percentage of thoria had significant effect on the catalytic performances of the materials. Among all synthesized catalysts ThO2-(5%)-NiMnO catalyst calcined at 400°C exhibited the highest catalytic performance and stability for the selective oxidation of alcohols.

Synthesis and characterization of CdSe nanoparticles via thermal treatment technique

The synthesis of CdSe nanoparticles was undertaken via the thermal treatment method at varying calcination temperatures from 450 to 700°C in alternate oxygen and nitrogen environment. Selenium powder was dissolved in ethylenediamine at 200°C for 2h before mixing with the metal precursor, cadmium nitrate and the capping agent polyvinylpyrrolidone to materialize the CdSe nanoparticles upon calcination. A series of measurements were employed to analyze the structural, elemental and optical properties of the attained nanoparticles at room temperatures using FTIR, XRD, EDX, SEM and TEM spectroscopies. XRD patterns and FTIR spectra revealed of the fact that, prior to calcination, an amorphous phase of the unheated material has taken shape, which after calcination achieved the crystalline structure of CdSe nanoparticles. The CdSe nanoparticle samples confirmed to be pure cadmium and selenium through EDX and FTIR analyses. The TEM images showed that as the calcination temperature raised from 450 to 700°C the average particle size increased from 11 to 32nm and the optical band gap energy decreased from 2.36 to 1.80eV.

A Modified Thermal Treatment Method for the Up-Scalable Synthesis of Size-Controlled Nanocrystalline Titania

Considering the increasing demand for titania nanoparticles with controlled quality for various applications, the present work reports the up-scalable synthesis of size-controlled titanium dioxide nanocrystals with a simple and convenient thermal treatment route. Titanium dioxide nanocrystals with tetragonal structure were synthesized directly from an aqueous solution containing titanium (IV) isopropoxide as the main reactant, polyvinyl pyrrolidone (PVP) as the capping agent, and deionized water as a solvent. With the elimination of the drying process in a thermal treatment method, an attempt was made to decrease the synthesis time. The mixture directly underwent calcination to form titanium dioxide (TiO2) nanocrystalline powder, which was confirmed by FT-IR, energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analysis. The control over the size and optical properties of nanocrystals was achieved via variation in calcination temperatures. The obtained average sizes from XRD spectra and transmission electron microscopy (TEM) images showed exponential variation with increasing calcination temperature. The optical properties showed a decrease in the band gap energy with increasing calcination temperature due to the enlargement of the nanoparticle size. These results prove that direct calcination of reactant solution is a convenient thermal treatment route for the potential large-scale production of size-controlled Titania nanoparticles.

Novel Fe/MnK‐CNTs nanocomposites as catalysts for direct production of lower olefins from syngas

Novel Fe/MnK‐CNTs nanocomposites are developed as catalysts for direct production of lower olefins from syngas, delivering a high iron time yield of 337.2 μmolCO· ·s−1 with 51.3%C selectivity toward C2C4 olefins under the optimal reaction conditions (270°C, 2.0 MPa, 30,000 mL h−1 ). These catalysts are optimized by varying calcination temperature from 150 to 400°C. Multiple techniques including transmission electron microscopy, Elemental mapping, X‐ray diffraction, X‐ray photoelectron spectroscopy, H2‐temperature‐programmed reduction, and Raman were employed to reveal the relationship between the catalyst nature and unique catalytic behavior. In particular, the resultant catalyst from the calcination temperature of 220°C exhibits the highest selectivity of C2C4 olefins as well as good stability, which are enabled by the trade‐off among the effects of iron particle sizes, promoters, metal‐support interaction and support surface chemistry. Moreover, influences of reaction temperature, reaction pressure and space velocity are also investigated. © 2016 American Institute of Chemical Engineers AIChE J, 63: 154–161, 2017

Structural, magnetic and dielectric properties of pure and nickel-doped barium nanohexaferrites synthesized using chemical co-precipitation technique

AbstractNickel-doped barium nanohexaferrites with the chemical formula BaNixFe(12-x)O19 are prepared using the chemical co-precipitation technique. The calcination of the samples is done at 800°C for 4 h. In order to carry out the structural analysis that includes the crystallographic and the morphological investigations, X-ray diffraction and TEM are carried out to govern the phase, structure and the size of the crystal. By the use of Debye–Scherrer equation, the size of the crystallite is calculated to be in the range of 38–100 nm. TEM results reveal the magnetoplumbite structure of the hexaferrites. The M–H curve obtained using the Vibrating Sample Magnetometer computes the magnetic parameters like saturation magnetization, coercivity, remanence and verifies the behaviour of hexaferrites as hard magnetic materials. Further, the effect of variation in calcination temperature is also investigated on the values of magnetic parameters of hexaferrites. In order to carry out the investigations on the electri...

Synthesis of curcumin catalyzed by KF/Al2O3

Purpose The purpose of the study reported in this paper is to synthesis curcumin, which was reported to possess broad pharmacological effects and excellent dyeing properties, via Claisen-Schmidt condensation reaction catalysed by an efficient and green solid base catalyst, KF/Al2O3. Design/methodology/approach A series of catalysts with different KF loadings and varying calcination temperatures had been prepared, characterised by Brunauer–Emmett–Taller surface area, temperature-programmed desorption with CO2 using infrared spectroscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy, and tested in the Claisen–Schmidt condensation reaction. The effects of different reaction parameters such as temperature, the amount of catalyst, reactant ratio and time on the synthesis of curcumin were examined. The possibility of recycling the catalyst was also investigated in detail. Moreover, the reaction mechanism and the role of KF/Al2O3 in the synthetic process were discussed. Findings The study provides an efficient and green solid base catalyst, KF/Al2O3, and 64.3 per cent yield of curcumin was obtained under the optimum reaction conditions. Experimental results indicate that the third reused catalyst could retain part of the catalytic activity, and the regenerated one could be reused with reasonable catalytic activity. Besides, K3AlF6 was proposed as the active site of the catalyst for the reaction by the analysis of the characterization results of KF/Al2O3. Originality/value KF/Al2O3 was found to be an efficient catalyst for catalytic synthesis of curcumin and could be easily recycled several times. This information may be useful for further research and practical applications of curcumin.

Enhanced solar light photocatalytic properties of ZnO nanocrystals by Mg-doping via polyacrylamide polymer method

The photocatalytic performance of Mg-doped ZnO (MZO) nanoparticles, synthesized through the polyacrylamide polymer method, was investigated by the photodegradation of the methylene blue (MB) solution. The nanoparticles were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, and UV–vis absorption spectrum. The results demonstrate that the catalysts present different photodegradation performances with varying calcination temperatures of the as-synthesized Mg-doped ZnO precursor. It is found that the highest photodegradation of the MB solution was achieved by the catalyst with a 47nm particle size, which had the lowest oxygen vacancies. The influence of operational parameters of pH and initial dye concentration was evaluated. Catalyst activity remained at 95% of its initial value even after the photodegradation process was repeated for nine times. Moreover, three intermediate products, possessing the OH, O2− and h+ groups were detected in the photodegradation processes. Hence, we attribute the enhanced photocatalytic properties of the ZnO nanoparticles to the lower amount of oxygen vacancies, which are a consequence of Mg-doping preventing electron-hole recombination.

Fine Tuning of the Oxygen Evolution Reaction Activity and Stability of Hydrous Iridium Oxides By Thermal Treatment

In the future energy concept renewable wind and solar energy will play the dominating role. It is anticipated that due to the intermittent nature of power outcome from the renewable energy sources, there will be an energy surplus which can be efficiently stored. As an example hydrogen could be successfully produced by proton exchange membrane water electrolysis (PEM-WE). Alternatively carbon dioxide could be converted to a valuable product in an electrochemical reduction process. Up to now the oxygen evolution reaction (OER) will be the counter reaction for hydrogen evolution as well as CO2 reduction. Nowadays iridium is the main component of the anode catalyst in PEM-electrolysers since it shows the best performance in terms of activity and stability [1]. Due to the high price and scarcity of iridium, however, the goal for the near future is a better utilization and partial or complete replacement of this precious metal. Since no alternative with comparable performance is in the sight, current research efforts are directed towards increase in surface to mass ratio and specific activity of iridium catalysts. This can be achieved using nanoparticulated, highly porous materials [2]. Furthermore, introduction and leaching of a less noble metal [3] or tuning of the oxide structure, e.g. by varying calcination temperature should be considered [4, 5]. In this study a scanning flow cell (SFC) combined with an inductively coupled mass spectrometer (ICP-MS) is used to obtain synchronized time- and potential-resolved data on the OER-activity and dissolution of iridium electrodes [5, 6]. This should shed some light onto the stability of different kinds of iridium oxides used in literature by utilizing a model sputtered iridium film. The examined materials are iridium (hydrous)-oxides prepared electrochemically and treated thermally in the temperature range of 100 – 600 °C. X-ray photoelectron spectroscopy (XPS) is used to correlate the electrochemical behaviour with the surface composition. The obtained information on the electrocatalytic activity and stability together with data on the electrodes physicochemical properties and their temperature dependence are used in the discussion of OER mechanism on iridium oxide electrodes.

SINTESIS BARIUM M-HEXAFERRITTE (BaFe12-xNixO19) DOPING LOGAM NIKEL DENGAN METODE KOPRESIPITASI

Synthesis of Barium M-Hexaferrite (BaFe12-xNixO19) nickel metal doping have been done with co-precipitation method and its effect on temperature changes and substitution dopants. Basic materials used in the synthesis of BaCO3, FeCl3.6H2O, HCl, NH4OH and nickel metal. The process of synthesis of barium M-heksaferit conducted at the Faculty of Mathematics and Natural Sciences Analytical Laboratories Unram. This study used a variation of calcination temperature of 80, 400, 600 and 800°C for 4 hours with a variety of dopants 0; 0.4; 0.7 and 0.9. Synthesis results show that changes in the concentration of the dopant variables and calcination temperature indicate a tendency to change color to brown-black powder.Abstract: Barium Mhexaferrite, dopant, nickel, co-precipitation.

The Influence of Calcination Temperature on Quantitative Phase of Hematite from Iron Stone Tanah Laut

This research aims to form particles of hematite (α-Fe2O3) with a basis of mineral iron ore Fe3O4 from Tanah Laut. Magnetite Fe3O4 was synthesized using co-precipitation method. Further characterization using X-ray fluorescence (XRF) to obtain the percentage of the elements, obtained an iron content of 98.51%. Then characterized using thermo-gravimetric analysis and differential scanning calorimetry (TGA-DSC) to determine the calcination temperature, that at a temperature of 445 °C mass decreased by 0.369% due to increase in temperature. Further Characterization of X-ray diffraction (XRD) to determine the phases formed at the calcination temperature variation of 400 °C, 445 °C, 500 °C and 600 °C with a holding time of 5 hours to form a single phase α-Fe2O3 hematite. Testing with a particle size analyzer (PSA) to determine the particle size distribution, where test results indicate that the α-Fe2O3 phase of each having a particle size of 269.7 nm, 332.2 nm, 357.9 nm, 412.2 nm. The best quantity is shown at a temperature of 500 °C to form the hematite phase. This result is used as the calcination procedure to obtain a source of Fe ions in the manufacture of Lithium Ferro Phosphate.

Sol–gel synthesized BiFeO3 nanoparticles: Enhanced magnetoelelctric coupling with reduced particle size

The present study reports the effect of particle size on magnetic, electrical and magnetoelectric properties of BiFeO3 nanoparticles prepared by the sol–gel method. Structural analysis revealed rhombohedral phase of BiFeO3 nanoparticles. Varying calcination temperature successfully tailored their size in the range 27–153nm. The magnetic measurement confirmed enhanced ferromagnetism with reduced particle size, thereby revealing increase in suppression of spin spiral structure. Increasing density of uncompensated spins with reduced particle size enhances exchange bias. Electrical analyses-dielectric and ferroelectric-reveal decreasing losses with particle size, which results in enhanced dielectric constant and polarization values. Magnetic field dependent polarization substantiates the presence of magnetoelectric coupling. More the particle size reduction more the spin spiral suppression, and magnetic moments being oriented perpendicular to the ferroelectric axis [111], there results maximum polarization and subsequently, maximum magnetoelectric coupling.

The Effect of Calcination Temperature Variation on the Sensitivity of CO Gas Sensor from Zinc Oxide Material by Hydrothermal Process

Carbon monoxide (CO) is a poisonous gas and could be lethal towards human. A sensitive CO gas sensor isnecessary to prevent accidents caused by CO gas. ZnO is a semiconductor material having many applicationsincluding gas sensors. However ZnO is rarely reported to be used as CO gas sensor material. Therefore, in thisresearch, CO gas sensor has been prepared from ZnO material synthesized via hydrothermal process at 100°C for24 hours using ZnCl2 powder and NH4OH solution. The resulted ZnO gel was subsequently dried andspin-coated on a glass substrate. The ZnO-coated glasses were then calcined at various temperatures of 500°C,550°C, and 600°C for 30 minutes. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD),Brunauer-Emmet-Teller (BET) analysis were used to characterized the morphology, structure and active surfacearea of ZnO. The sensitivity of the ZnO material towards CO gas was measured using a potentiostat in achamber with operating temperatures 30°C, 50°C, and 100°C with each of gas concentration 10 ppm, 100 ppm,250 ppm, and 500 ppm. It was found that the sample calcined at 550oC showed the highest sensitivity towardsCO gas (0.82) due to the highest active surface area (47.2 m2g-1). It was also observed that the sensitivityincreased with the increasing of operating temperature and CO gas concentration.