Calcined Samples Research Articles

Application of microwave radiation for decrepitation of spodumene from the Kolmozerskoe deposit

The lithium-ion industry is experiencing a rapidly growing demand for compounds containing lithium. Spodumene is one of the primary industrial minerals used in the production of this metal. It exists in three polymorphic forms. In its natural state, it is known as α-spodumene, which possesses a high resistance to chemical attack due to its compact structure containing silicon and aluminum oxides. When subjected to microwave radiation, α-spodumene undergoes a transformation, first becoming the γ form and then transitioning to the β form. It is known that the β form can be chemically treated to extract lithium. In light of this, microwave exposure was applied to α-spodumene with the aim of decrepitation, followed by sulfuric acid decomposition of the mineral. The mineral was crushed into different sizes (1.0, 0.5, and 0.25 mm). Temperature changes, induced by both conventional and microwave heating, were analyzed. The heating process was continued for samples of various sizes until a temperature of 1200 °C was reached. Sulfation of calcined samples was carried out for 60 minutes at a temperature of 250 °C. After cooling to 22 °C, distilled water was added and mixed for 120 minutes in closed leaching vessels. To determine the recovery of valuable and associated components, leach cakes and the liquid phase were analyzed using inductively coupled plasma atomic emission spectrometry. Based on the analysis of experimental results, the feasibility of using microwave radiation for decrepitation of spodumene to extract lithium is confirmed. The influence of particle size on phase transformations and, consequently, the degree of lithium extraction from spodumene was investigated. It was found that the recovery of lithium during the microwave action and leaching process for particles smaller than 0.25 mm reached 96.82 %. Microwave heating resulted in lower recovery rates of “harmful” components, such as iron, sodium, and calcium, in the leaching process, leading to a higher purity of the resulting product.

Improving Cycling Electrochemical Performance of P2-Type Na2/3Mn2/3Ni1/3O2 by Controlling Its Crystallinity

1. IntroductionNa2/3Mn2/3Ni1/3O2 with P2-type structure is a positive electrode material for the sodium ion battery with relatively high reversible capacity of 170 mAh/g and average potential of 3.6 V (vs. Na/Na+). On the other hand, it is known that there is a problem in cycle stability due to the P2-O2 phase transition associated with Na insertion/removal and the structural change caused by O2 desorption at the high state of charge. In this study, we focus on the crystallinity of the layered structure to improve the electrochemical property of P2-type Na2/3(Mn2/3Ni1/3)O2 .The effect of crystallinity on the electrochemical property of the P2-Na2/3(Mn2/3Ni1/3)O2 was explored using the ball milling approach. 2. ExperimentsThe Na2/3(Mn2/3Ni1/3)O2 was prepared by mixing NaOH, Mn2O3, and Ni(OH)2 in a molar ratio of 2 : 2 : 1 and firing at 950°C for 3 h in air (sintered sample). The sintered sample was ball-milled with 4 mmφ ZrO2 balls in an 80 ml ZrO2 vial using a planetary ball mill (Fritsch, P-6) at 500 rpm for 2 h to obtain a sample with low crystallinity (milled sample). The resulting samples was mixed with Ketjen black and PTFE at a weight ratio of 84:8:8, and the sheet was pressed onto an Al mesh to form an electrode. The electrodes were dried under vacuum at 220 °C for 5 hours, and then half-cells were assembled using Na foil as the counter electrode and 1M NaPF6/EC-DEC as the electrolyte to evaluate electrode characteristics. The cell was galvanostatically charged and discharged using a BLS5500 (Keisokuki Center) with a current density of 10 mA g−1, in which the denominator represents the mass of the active material in the positive electrode. The crystal structure of the samples was evaluated using XRD (Rigaku UltimaIV, Cu K-α), XAS (BL14B2 at SPring-8, BL-11, Ritsumeikan SR center), X-ray total scattering measurement (SPring-8, BL22XU, 70 keV) and TEM. In addition, the electronic structure was investigated using the first-principles calculation program (VASP) based on density functional theory.3. Results and DiscussionFig. 1 shows XRD of Na2/3(Mn2/3Ni1/3)O2 after calcination and ball milling. The sintered sample showed a diffraction pattern attributed to the P2 structure, but the milled sample showed a broad profile and the detailed crystal structure could not be identified. However, a peak in the 002 plane around 2θ = 16° could be confirmed, and from the results of TEM observation and PDF analysis, it is considered that the milled sample also has a layered structure.Fig. 2 shows a comparison of charge-discharge profiles and cycle characteristics. In the charge-discharge profile of the sintered sample, potential flat areas due to Na ordering and P2-O2 phase transition can be observed, but that for the milled sample, these potential flat areas are not observed and the profile is on a slope, which indicates that the crystallinity degradation due to milling suppresses structural changes during the charge-discharge process. The initial charge-discharge capacities of the milled samples were 146 and 141 mAh/g, respectively, which were smaller than those of the calcined samples (175 and 146 mAh/g, respectively), indicating that the milling process did not significantly affect the Na insertion/desorption characteristics. Comparing the cycle characteristics shown in Fig. 2, the discharge capacity of the milled sample maintained more than 80% while the sintered sample deteriorated to the 37% of the initial capacity after 50 cycles, confirming that the milling treatment was effective in improving cycle characteristics.Detailed mechanism of the milling effect and redox process will be discussed in the presentation. Figure 1

Semiconducting and gas sensing performance of Magnetite nanoparticle systems of different morphologies

Magnetite nanoparticle systems with uniform morphological features were synthesized through co-precipitation and forced hydrolysis without using any surfactants or additives. The selected batches of the synthesized particle systems were calcined at 1200 °C for phase transformation. The as-synthesized and calcined samples were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectrometry (FTIR), and X-ray Diffraction (XRD). In addition, the as-prepared and commercial magnetite particles were then employed as gas sensors to detect ammonia. Furthermore, the semiconducting properties of the synthesized (magnetite-I magnetite-II & magnetite-III) and commercial magnetite-based sensors were studied in the temperature range from 30 °C to 270 °C which indicated the n-type semiconducting nature of the magnetite particles. While commercial magnetite did not show any response in the employed temperature range. Furthermore, the synthesized magnetite nanoparticle-based sensors showed good and highly reproducible performance toward 10 ppm ammonia with a gas response of 58.44%, 64.39%, and 59.02%, respectively. For instance, magnetite-II and III were more sensitive toward the detection of ammonia with quick response/recovery times of 2s/5.8s and 2.4s/6.2s than 40s/17s for magnetite-I-based sensors. In contrast, the commercial magnetite-based sensor showed a response of 13.59% and significantly longer response/recovery time at room temperature and did not respond to ammonia concentration even at high temperatures. It was attributed to the remarkable uniformity in morphology, porosity, and good crystallinity of the as-prepared nanoparticles compared to the commercial-based sensor. This study unfolds that morphological features of the gas sensor’s material could be the key factors for controlling their sensing properties.

Size dependent structural and magnetic properties of Co(1−x) Nix Cr2O4 nanoparticles (x = 0.15, 0.20)

This study examines the structural and magnetic characteristics of Co(1−x)NixCr2O4 (x = 0.15, 0.20) compounds synthesised using the co-precipitation technique and calcined at 500 °C and 900 °C respectively. X-ray diffraction studies reveal the structure of the synthesized samples is face-centered cubic with space group Fd-3m. The particle sizes and morphology were examined by using transmission electron microscopy, and the size ranges from 64 ± 10 nm to 105 ± 15 nm for the 900 °C and 7 ± 2 and 8 ± 2 nm for the 500 °C calcined samples. Field-cooling and zero-field-cooling magnetization measurement protocols were used to investigate the materials' magnetic characteristics. The Curie temperature (TC) decreases from 91 ± 0.5 K to 85 ± 0.3 K as the Ni concentration increases from x = 0.15–0.20. Additionally, an increase in the TC value is seen for both compositions when the particle size is decreased. Spiral ordering is observed at a transition temperature TS for the samples calcined at 900 °C, while no evidence for TS was seen for samples calcined at 500 °C. Magnetization measurements as a function of field, Mμ0H, at several constant temperatures, show that the coercivity reduces with an increase in temperature in all samples. The Co(1−x)NixCr2O4 (x = 0.15, 0.20) samples calcined at 900 °C exhibit superparamagnetic behaviour with a small ferrimagnetic hysteresis loop. Furthermore, this paper evaluates the contribution of ferrimagnetic, superparamagnetic, and paramagnetic phases to the total Mμ0H curve for Co(1−x)NixCr2O4 (x = 0.15, 0.20) calcined at 900 °C through simulation. In addition, a modified Langevin simulation, incorporating a particle size distribution term, is performed for the Co(1−x)NixCr2O4 (x = 0.15, 0.20) samples calcined at 500 °C. From the simulations, it is clear that all samples show evidence of significant superparamagnetic contributions to the total saturation magnetization because of the small particles present.

Hydrothermal extraction and physicochemical characterization of biogenic hydroxyapatite nanoparticles from buffalo waste bones for in vivo xenograft in experimental rats

Hydroxyapatite (HA) can be used in odontology and orthopedic grafts to restore damaged bone due to its stable chemical characteristics, composition, and crystal structural affinity for human bone. A three-step hydrothermal method was used for the extraction of biogenic calcined HA from the buffalo waste bones at 700 °C (HA-700) and 1000 °C (HA-1000). Extracts were analyzed by thermogravimetric analysis, differential scanning calorimetry, X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and in vivo examination of HA xenografts for femoral lesions in experimental rats. Crystallinity, purity, and morphology patterns showed that the HA main phase purity was 84.68% for HA-700 and 88.99% for HA-1000. Spherical HA nanoparticles were present for calcined HA-700 samples in the range 57–423 nm. Rats with critical bone lesions of 3 mm in diameter in the left femur treated with calcined HA-700 nanoparticles healed significantly (p < 0.001) faster than rats treated with HA-1000 or negative controls. These findings showed that spherical biogenic HA-700 NPs with a bud-like structure have the potential to stimulate both osteoconduction and bone remodeling, leading to greater bone formation potential in vivo. Thus, the calcined biogenic HA generated from buffalo waste bones may be a practical tool for biomedical applications.

Influence of heat treatment on the microstructure and surface groups of Stöber silica

Heat treatment is routinely utilized in preparing nanoporous materials (including Stöber silica), and can substantially affect their performance in diverse application fields. However, the effects of heat treatment at different temperatures on the structure and surface properties of Stöber silica have not been systematically investigated before. In this work, Stöber silica (washed with water or ethanol) was calcined at different temperatures (from 250 °C to 1000 °C), and the heat-treated samples were characterized through nitrogen adsorption at 77 K, scanning electron microscopy, simultaneous thermal analysis, elemental analysis, and Fourier-transform infrared spectroscopy. The results show that there is no significant difference in the morphology and particle size of the calcined samples. The internal micropores almost collapse after calcination at 500 °C, and the pores with a smaller diameter are the first to shrink during calcination. The variation in the number of the surface hydroxyl groups and ethoxyl groups with the calcination temperature is discussed in detail. The carbon content analysis and differential scanning calorimetry curves reveal that the surface ethoxyl groups (for the samples washed with ethanol) are completely removed after calcination at 500 °C. After calcination at temperatures above 800 °C, the hydroxyl groups almost completely condense into siloxanes. The specific surface area calculated according to the thermogravimetric mass loss and surface hydroxyl density is found to be significantly different from the measured Brunauer–Emmett–Teller specific surface area. Our results may offer practical guidance for the application of Stöber silica subjected to similar heat-treatment processes.

High temperature shock synthesis of superfine Ru nanoparticles anchored on TiO2 @nitrogen-doped carbon for pH-universal hydrogen evolution reaction

Due to energy crisis and environmental pollution, it is urgent to develop efficient and cheap catalysts for hydrogen production from water electrolysis. As a cheaper platinum group metal, Ru, a cheaper platinum group metal, is a highly competitive candidate to Pt because of the similar bond energy of M-H. Herein, TiO2 @nitrogen-doped carbon composite supported superfine Ru nanoparticles was synthesized by high temperature shock in a Joule furnace using Ti-MOF support (Ru/TiO2 @NC-J). In the extremely rapid process, MOF was quickly converted into highly conductive nitrogen-doped carbon with tiny TiO2 dispersed in it, and superfine Ru nanoparticles were generated simultaneously in less than 0.5 s. The obtained Ru/TiO2 @NC-J displays wonderful HER performance in the wide pH range. In 1.0 M KOH solution, the overpotential was as low as 11 mV at 10 mA cm−2 and a Tafel slope was 39.2 mV dec−1, which far exceeded the activity of Pt/C and conventional calcined samples as well as most of the recently reported catalysts. The as-developed electrocatalysts also showed excellent stability to accommodate large working current for long term test without obvious activity loss in universal pH range. Experimental investigations suggest that the strong metal-support interaction dominantly facilitate the activity of electrocatalytic hydrogen evolution reaction (HER), and stability of Ru/TiO2 @NC-J. This strategy provides a new and super-fast methodology to prepare low-budget and high-performance HER catalysts for practical applications.

The Role of Cerium Valence in the Conversion Temperature of H2Ti3O7 Nanoribbons to TiO2-B and Anatase Nanoribbons, and Further to Rutile.

CeO2-TiO2 is an important mixed oxide due to its catalytic properties, particularly in heterogeneous photocatalysis. This study presents a straightforward method to obtain 1D TiO2 nanostructures decorated with CeO2 nanoparticles at the surface. As the precursor, we used H2Ti3O7 nanoribbons prepared from sodium titanate nanoribbons by ion exchange. Two cerium sources with an oxidation state of +3 and +4 were used to obtain mixed oxides. HAADF-STEM mapping of the Ce4+-modified nanoribbons revealed a thin continuous layer at the surface of the H2Ti3O7 nanoribbons, while Ce3+ cerium ions intercalated partially between the titanate layers. The phase composition and morphology changes were monitored during calcination between 620 °C and 960 °C. Thermal treatment led to the formation of CeO2 nanoparticles on the surface of the TiO2 nanoribbons, whose size increased with the calcination temperature. The use of Ce4+ raised the temperature required for converting H2Ti3O7 to TiO2-B by approximately 200 °C, and the temperature for the formation of anatase. For the Ce3+ batch, the presence of cerium inhibited the conversion to rutile. Analysis of cerium oxidation states revealed the existence of both +4 and +3 in all calcined samples, regardless of the initial cerium oxidation state.

Synthesis and fabrication of HAp from fish scale waste to develop bone equivalent phantom

Radiotherapy is one of a method to treat cancer. Before irradiating a patient, we need to understand the dose deposition and interaction of radiation with body. We introduce a tissue equivalent material called phantom to study the interaction and dose deposition. This study mainly focuses to understand the interaction of radiation with the bones. Since there are many tissue equivalent phantoms available and are in use and there is no bone equivalent phantom, there is a need of phantom which should be bone equivalent. Thus our study focuses on fabrication of bone equivalent phantom that too made of fish shell waste, which make it easy to synthesis and makes it environment friendly. The fabrication and synthesis of Hap from fish scale waste by undergoing a series of processes to develop bone equivalent calcined and uncalcined samples were made. Before its been exposed using a Linear accelerator (Varian – Unique performance), the fabricated HAp samples undergone a CT test to verify the Hounsfield unit with the value that of bones in humans. After the confirmation of CT number of the fabricated samples and its exposure with the LINAC for different MUs (300 Mu/min and 500 MU/min), it's been read by a TLD reader and GM counter. Finally the readings from the TLD and GM counter of the exposed calcined and uncalcined samples were compared to understand the efficiency of both the samples.

Characterization and photocatalytic activity of ZnO nanoparticles by green synthesis method

In this work, zinc oxide nanoparticles have been synthesized by green synthesis technique using sodium hydroxide and zinc nitrate, with and without calcination. In this research, Myrtus communis extract was used along with three different alkaline molar ratios (0.5 M, 1 M, and 2 M) to successfully synthesize ZnO nanoparticles (NPs) from the same precursor. In the calcined samples, this process was carried out at 800 °C. X-ray diffraction, scanning electron microscopy, and diffuse reflectance spectra were used to explore the structural, morphological, and optical features of ZnO nanoparticles. The XRD peaks confirm the successfully synthesized hexagonal wurtzite zinc oxide and are in full conformity with the published data of the JCPDS: 36–145. With high absorption peaks at about 370 nm wavelength, UV-Vis spectroscopy further supported the ZnO NPs' strong optical properties. Morphology and topography were discovered by SEM analysis and displayed the evolution of ZnO nanowires around 10 µm length with calcination. No nanowire formation was observed in the uncalcined samples. The results demonstrated that the degradation efficiency of ZnO nanoparticles is dependent primarily on the UV exposure time and morpholgy. When ZnO with 1 M NaOH calcined at 800 °C is used, the maximum MB degradation of about 99% is achieved. Methyl blue photodegradation follows the first-order Langmuir–Hinshelwood kinetic model.

Novel physical sunscreen from one-dimensional TiO[formula omitted] nanowire: Synthesis, characterization and the effects of morphologies and particle size for use as a physical sunscreen

The performance of the one-dimensional (1D) morphology as an inorganic UV filter for sunscreens of titanium dioxide (TiO2) was evaluated in this research. The 1D TiO2 nanowires were prepared using solid TiO2 and 10 M NaOH as precursors via a modified hydrothermal method, followed by calcination at 400–900°C for 5 h. The influences of TiO2 loading, hydrothermal time and calcination temperature were studied on the morphologies of the as-prepared samples. The morphologies of the TiO2 nanowires were investigated using SEM and TEM techniques. The results found all the variables directly affected the particle size and shape of the TiO2 nanowires. The hydrothermal synthesis conditions using a TiO2 loading of 0.2 g at 220°C for 24 h (HTiO2) resulted in a particle size that was the longest and narrowest in length and diameter, respectively. The first product from the hydrothermal synthesis is H2Ti3O7, which can transform into TiO2(B) (TiO2@400), anatase (TiO2@700) and rutile (TiO2@900) by calcination at 400, 700 and 900 °C, respectively. The calcined samples were selected for a porcine skin penetration study. The 1D morphology particles were localized on the stratum corneum of the skin, while the comparison spherical particle penetrated the deeper layer. From the SPF test, the highest SPF is TiO2 anatase.

Investigation on structural, morphological and magnetic properties of Barium Cobaltite (BaCoO3) nanoparticle

Both the structural characteristics and the magnetic property of the polycrystalline BaCoO3(BCO) perovskite oxide have been thoroughly researched. The synthesis of polycrystalline BaCoO3 ceramics was accomplished using a solvothermal method. Through the use of thermogravimetric analysis, the thermal stability of BaCoO3 (TGA) was checked. In order to examine the crystal structures, microstructures, and surface chemical state properties of BCO ceramics, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) experiments were carried out. The XRD patterns indicate that the phases that were present in the calcined samples were hexagonal perovskite phases. The multilayer plated structure can be seen in SEM picturesand EDAX confirmed the elemental stoichiometry. Isothermal magnetization studies on the compound were carried out at room temperature (RT), and it was discovered that the complex possessed ferromagnetic properties. The deformed CoO6 that was found by Raman and XPS may be related to the oxygen defect known as perovskite. This faulty property suggests that BCO NPs have a ferromagnetic character.

The Multi-Analytical Characterization of Calcium Oxalate Phytolith Crystals from Grapevine after Treatment with Calcination

Calcium oxalate phytoliths are one of the most prominent types of Ca speciation in the plant kingdom, and they store extensive amounts of carbon in crystalline form. Ca phytoliths were investigated in the root, trunk, and bark of Vitis vinifera Chasselas from a vineyard in Alsace, France. A multi-analytical approach was used, which included SEM coupled with EDX spectroscopy, XRD, XRF, TGA, and 13C-NMR spectroscopy. These techniques revealed that phytoliths are composed of crystalline calcium oxalate monohydrate (whewellite). The whewellite crystals exhibited mostly equant or short-prismatic habits in all of the three studied grapevine parts, but bipyramidal crystals also occurred. Raphide crystals were only observed in the root, where they were abundant. Instead of using wet chemical procedures to extract the mineral components from the organic parts of the biomass, a thermal treatment via calcination was chosen. The suitable temperature of calcination was determined through TGA experiments. The calcination of the biomass samples at 250 °C enhanced the amounts of Ca phytoliths in the residual chars. The thermal treatment, however, affected the appearance of the Ca oxalate crystals by producing surfaces that displayed macroporosity and by creating fractures. For calcination at both 300 °C and 350 °C, Ca oxalate lost a molecule of carbon monoxide to form Ca carbonate, and the modifications of the original crystal surfaces were more pronounced than those observed after thermal treatment at 250 °C.

Investigation of specially designed bentonite samples as potential bricks with better radiation shielding properties

Bentonite clay, a naturally occurring very fine volcanic powder that lies mainly on the nano-scale, has been investigated during this study to assess the possibility of producing a brick with enhanced radiation shielding properties. Five samples were prepared based on natural bentonite and studied along with another three previously studied building bricks. Physical properties such as density and particle size distribution have been studied for bentonite clay before and after calcination and ball-milling. Radiation attenuation parameters, which assess shielding against both energetic photons and fast neutrons, were calculated theoretically employing specific friendly-user programs such as WinXCom, Auto-Zeff, NXCom, and MRCsC and other analytical calculations. Linear attenuation coefficients (μ) of bentonite samples were experimentally measured at 662 keV energy of Cs-137 and 1173 and 1332 keV energies of Co-60, gamma ray radioactive sources using NaI(Tl) inorganic scintillation detector. After that, a statistical comparison between theoretical and experimental (μ) values for all studied samples was conducted. It has been found that the density of the bentonite sample increases from 0.84 to 1.59 g/cm3 with calcination and pressing; moreover, ball-milled compressed calcined bentonite samples have shown promising γ-rays radiation shielding properties among the studied samples having (μ) values range between; 0.112–0.133 for Eγ equals 0.662 MeV, 0.090–0.110 for Eγ equals 1.173 MeV, and 0.087–0.105 for Eγ equals 1.332 MeV. Last but not least, an entire agreement between the theoretically obtained radiation attenuation parameters using the abovementioned tools and the experimentally measured ones is not a must, especially since other factors like average particle size and compression are not necessarily not considered upon using the tools above.

Effects of calcination on the dielectric properties and insulation resistance of Ba0.95Ca0.05TiO3 ceramics sintered in a reducing atmosphere

This study investigated the effects of calcination treatment on the densification, microstructure, and dielectric behavior of Ba0.95Ca0.05TiO3 (BCT) doped with acceptor and rare earth elements. The calcination process promoted sintering densification and enabled the densification of the green body at lower sintering temperatures. The electrical properties of the calcined samples showed higher dielectric constant, lower losses, and higher resistivity than the uncalcined samples. The increased conduction activation energies observed in the core and shell of the calcined BCT samples were attributed to the comparatively lower concentrations of Ti3+ and oxygen vacancy. The calcined BCT samples exhibited higher resistivity at room temperature and lower leakage currents at high temperatures, indicating superior reliability. This study demonstrates that the calcination of BCT can improve its dielectric properties and insulation resistance, leading to a higher dielectric constant, lower losses, and higher resistivity.

Preparation of Original and Calcined Layered Double Hydroxide as Low-Cost Adsorbents: The Role of the Trivalent Cation on Methylene Blue Adsorption.

Layered double hydroxides with the hydrotalcite-like structure, containing Mg2+, Al3+, and Fe3+ (with different Al/Fe ratios) in the layers, have been synthesized and fully characterized, as have the mixed oxides formed upon their calcination at 500 °C. Both series of solids (original and calcined ones) have been tested for methylene blue adsorption. In the case of the Fe-containing sample, oxidation of methylene blue takes place simultaneously with adsorption. For the calcined samples, their reconstruction to the hydrotalcite-like structure plays an important role in their adsorption ability.

Effect of Ammonia on the Synthesis of NMC541 Cathode Materials with the Sol-Gel Method

The research studied about the effect of ammonia on the synthesis of lithium-ion battery cathode materials LiNi0.5Mn0.4Co0.1O2 (NMC541) through a sol-gel method by modifying the mole ratio of ammonia to metal forming ratios (0.5; 1.0; 1.5; and 2.0). The precipitation formed at pH 11 and at temperature of 80oC. Characterization was carried out on samples resulting from pyrolysis (pyrolysis result), with calcination for once and twice at 850oC for 3 hours, X-ray diffraction pattern characterization, morphological characterization using scanning electron microscope (SEM), and conductivity characterization using an impedance capacitance conductance (LCR) meter. The result of the synthesis is in the form of spherical particles. The addition of ammonia affected the particle size distribution and stoichiometry of the metal forming NMC541, eventhough it was not significant. The ammonia to metal ratio of 1.5 (Sample N1.5-K) resulted in the distribution with the optimum particle homogeneity. The morphology of the pyrolysis and 3 hours-850oC calcined samples was dominated by spherical particles and agglomeration. Particle growth in the material is affected by heat treatment time. Samples with ammonia to metal ratio of 2.0 (N2.0-K) have the closest stoichiometry to NMC541. The total conductivity of the sample at a measurement frequency of 42Hz-1MHz is in the value range of 10-7–10-5 S.cm-1. The particle size is also affected by the calcination temperature. The effect of using ammonia in the synthesis process is not directly related to the electrical properties. However, it is related to the purity of NMC541. Samples of N1.5-K pyrolyzed result and samples of N1.0-K (3 hour 850 oC calcined) have optimum conductivity values. Agglomeration as a calcination effect lowers the conductivity value. The addition of 3 hours of calcination time does not significantly increase the conductivity value

Hydrogen production from sorption enhanced steam reforming of ethanol using bifunctional Ni and Ca-based catalysts doped with Mg and Al

This work evaluated the performance of nickel-based catalysts supported on CaO and CaO–MgO–Al2O3 in the sorption enhanced steam reforming of ethanol (SESRE) aiming the production of high purity H2. The catalysts were prepared by sol-gel method and characterized by different methods: Temperature programmed reduction (TPR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) with chemical element mapping, N2 physisorption and CO2 capture capacity determined by thermogravimetric analysis (TGA). XRD analysis showed that the predominant phases were CaO, MgO, CaCO3, Ca(OH)2 and NiO in the calcined samples and Ni0 in the reduced and passivated samples. TPR profiles indicated that all catalysts presented a high degree of reduction (Ni/CaMgAl-68 > Ni/CaMgAl-79 > Ni/Ca), although Ni/CaMgAl-X samples presented high reduction temperatures indicating the formation of NiAl2O4. The addition of MgO and Al2O3 to CaO was very beneficial since the deactivation coefficients, calculated by the TGA data modeling, decreased by a factor of 3.8 for Ni/CaMgAl-79 and by a factor of 4.3 for Ni/CaMgAl-68 when compared to the Ni/Ca catalyst. The catalytic tests in the SESRE showed that Ni/CaMgAl-79 catalyst had the best performance since it had the longest high purity hydrogen production time. In the pre-breakthrough period, the H2 mole fractions were close to 90% for all samples during all reaction cycles. After the reaction-regeneration cycles, the average crystallite size of CaO estimated by XRD increased around 38, 6 and 35% for Ni/Ca, Ni/CaMgAl-79 and Ni/CaMgAl-68, respectively. Thus, adding a dopant to the sorbent material proved to be an effective strategy to obtain a more stable catalyst capable to produce hydrogen of high purity.

Water treatment waste as supplementary cementitious material

The increase in demand for treated water causes the generation of waste from its process - Water Treatment Plant Sludge - WTS, to rise gradually. Alternatives are needed for the reuse of this waste in other chains, with Civil Construction being a segment that incorporates waste in techniques and products. This sludge is composed of soils that incorporate lime and aluminates in the phase of physical treatment of water. This work exposes the viability of using water treatment sludge with secondary cementitious potential, where sludge sample was calcined at 750 °C for three hours. Tests were produced comparing the finely ground calcined material with blast furnace slag. The results of X-ray diffractogram analysis showed that the material formed with calcination is metakaolinite. Thermogravimetric analyses indicated that the temperature plateau and the applied energy rate (calcination time) provided adequate dehydroxylation of the residue in the range of 507 °C to 580 °C. The effective pozzolanic was evaluated in the methods of Brazilian standards under the performance for compression with partial replacement of cement by 25%. The test results showed a high pozzolanic strength of WTS, close to the minimum standards required (90%) by the methods used, reaching 89% of the reference strength with the 100% calcined material sample and 92% and 96% obtained with WTS samples mixed with 32% and 50% of blast furnace slag, respectively. Demonstrating the technical feasibility of using the waste as a supplementary cementitious material in the incorporation of cement and in the production of mortars and concretes. The results obtained also expose that this waste can be used in low environmental impact concrete technology - LC3 for example, to be further studied in future research.

The Influence of Zn Doping on the Cation Distribution and Antibacterial Activity of CoFe2O4

Nanoparticles of formula Co1-xZnxFe2O4 (x = 0.0, 0.3, and 0.5) were prepared successfully using a citrate-auto-combustion method. This work studies the substitution effect of the Zn2+ ion on the physical, chemical, and structural properties of CoFe2O4. The structure of the prepared samples was determined via X-ray diffraction (XRD) and Fourier transformed infrared spectrometer (FTIR). X-ray diffraction of the investigated samples ensures that all the prepared samples crystallite into single structure. There is a variation of crystallite size with change in Zn concentration as it is observed that the crystallite size increased from 16.01 to 30.56 nm by increasing Zn concentration. The Fourier transform infrared spectra (FTIR) in range (390:4000) Cm−1 were used for studying the elastic properties of the prepared spinel ferrites. It is observed that, by increasing Zn concentration, all elastic moduli increased. The morphological and surface study of the calcined samples was investigated by scanning electron microscopy (SEM) and Gwyddion 2.45 software respectively. The roughness average (Ra) was 35.20 nm at x = 0 and increased to 46.6 nm at x = 0.5. At the room temperature, magnetic behavior of the all studied samples was studied. It is observed that the maximum saturation magnetization was 67.611emu/gm and it was related to Co0.7Zn0.3Fe2O4 while the highest value of exchange bias (HEB) was 2.15 Oe for Co0.5Zn0.5Fe2O4. The antibacterial activity of CoFe2O4, Co0.7Zn0.3Fe2O4, and Co0.5Zn0.5Fe2O4 was successfully tested against Escherichia coli and Staphylococcus aureus bacteria. The highest inhibition zone of Co1-xZnxFe2O4 values was 8 and 7.5 mm for E. coli and S. aureus, respectively, and these values were observed for x = 0.5. Generally, these results exhibit a high possible of ferrites for using in antibacterial applications.