Calcination Of Precursor Research Articles

Zinc titanates nanopowders: synthesis and characterization

Zinc titanates nanopowders viz.; Zn2TiO4, ZnTi3O8 and ZnTiO3 were synthesized through the thermal decomposition course of ZnC2O4.2H2O-TiO2 precursors mixture (1:1 mole ratio), prepared via a new co-precipitation method up to 900 °C. Thermogravimetric measurement (TG) was utilized to characterize the precursors mixture decomposition while x-ray diffraction (XRD), Fourier transform infra-red (FT-IR) were used to characterize the decomposition products as well as the phase transitions at different temperatures. XRD revealed the starting of titanates formation at 700 °C via detecting Zn2TiO4 along with ZnO and TiO2 (anatase) diffraction peaks. By increasing the calcination temperature to 800 °C, the ZnO content vanished with the appearing of Zn2Ti3O8 besides ZnTi2O4 and impurities of TiO2 (anatase). Finally at 900 °C, the Zn2Ti3O8 content was decomposed into ZnTiO3. Nitrogen adsorption-desorption isotherm of the calcined precursors mixture at 900 °C indicated low specific surface area of 7.1 m2 g−1 in accordance with the agglomeration nature estimated via transmission electron microscopy (TEM) study. The conductivity measurements showed semiconducting behavior of the prepared titanates with ferroelectric transition in the range 200 °C–308 °C. The obtained low dielectric value suggests the uses of present titanates as a co-fired ceramic or resonator ceramics.

Piezoelectric nanofoams with the interlaced ultrathin graphene confining Zn–N–C dipoles for efficient piezocatalytic H2 evolution under low-frequency vibration

Unique nanofoams consisting of interweaved ultrathin graphene confining Zn–N–C dipoles (ZnNG) are constructed via calcination of Zn-coordinated precursor. Due to the introduction of local polar Zn–N–C configurations, with hypersensitivity for mechanical stress, the piezoelectricity is created on the nonpiezoelectric graphene, and the hierarchical ZnNG exhibits obvious piezocatalytic activity of water splitting for H2 production even under mild agitation. The corresponding rate of H2 production is about 14.65 μmol g−1 h−1. It triggers a breakthrough in piezocatalytic H2 evolution under low-frequency vibration, and takes a significant step forward for piezocatalysis towards practical applications. Furthermore, the presented concept of confining atomic polar configuration for engineering piezoelectricity would open up new horizon for constructing new-type piezoelectrics based on both piezoelectric and nonpiezoelectric materials.

Plant polyphenol-involved coordination assembly-derived Mo3Co3C/Mo2C/Co@NC with phase regulation and interface engineering for efficient hydrogen evolution reaction electrocatalysis

Heterostructured Mo3Co3C/Mo2C/Co@NC catalysts were obtained by the calcination of tannic acid ligand-assembled precursors, enabling enhanced HER electrocatalysis through phase and interface regulation.

Sol-gel processing, spectral features and thermal stability of Li-stuffed Li6CaLa2Nb2O12:RE garnet phosphors (RE = Pr, Sm, Tb, Dy)

A series of garnet-type Li6CaLa2(1-x)Nb2O12:xRE phosphors (LCLN:xRE, RE = Pr, Sm, Tb and Dy) were prepared via sol-gel processing and subsequent calcination for the first time, with the course of phase evolution and the characteristics of the LCLN host and RE3+ luminescence being investigated in detail. It was found that ∼900–1000 °C is a suitable temperature for precursor calcination to produce the garnet phase and LCLN has a relatively low phonon energy (∼725 cm−1) and a relatively wide bandgap (∼4.53 eV) for luminescence. The LCLN:0.012Pr, LCLN:0.04Sm, LCLN:0.06 Tb and LCLN:0.06Dy typical phosphors were analyzed to have dominant excitation/emission bands at ∼278/489, 265/614, 268/549 and 264/581 nm, emission colors of white, orange, green and yellowish white, and fluorescence lifetimes of ∼0.43, 0.74, 0.90 and 0.44 ms, respectively. Temperature-dependent photoluminescence found that the four phosphors maintained ∼28, 37, 45 and 56% of their room-temperature intensities at 423 K, with activation energies for thermal quenching of ∼0.37, 0.29, 0.34 and 0.25 eV, respectively. The results demonstrated that the Li-stuffed LCLN garnet could be a suitable host for UV excitable multicolor phosphors.

Highly practical and reproducible BiVO4 thin film fabrication using automatic dip-coating machine towards for photoelectrocatalytic activities improvement

ABSTRACT This research developed a simple method for bismuth vanadate (BiVO4) thin film using an automatic dip-coating method. A precursor solution concentration, dipping speed, and calcination temperature were optimized to obtain the highest photoelectrocatalytic (PEC) BiVO4 electrode for water oxidation. The BiVO4 electrode was applied to organic dye degradation and studied the catalytic mechanism at the electrode surface. A calcination temperature of 450 °C was optimized for BiVO4 photoanode preparation for the highest PEC water oxidation and had good charge transfer process properties. The proposed automatic dip-coating method presents high efficiency for the large scale of BiVO4 electrode fabrication, and it was highly reproducible at a low relative standard deviation of less than 5%. The developed BiVO4 electrode can eliminate methyl red organic dyes by more than 70% within 1 hour. This research offers a new alternative approach for a simple, convenient, reproducible, and scaled-up method for semiconductor thin film fabrication.

Zeolite Imidazolate Frameworks-67 Precursor to Fabricate a Highly Active Cobalt-Embedded N-Doped Porous Graphitized Carbon Catalyst for the Thermal Decomposition of Ammonium Perchlorate.

The more apparent specific heat release at a lower high-temperature decomposition (HTD) temperature of ammonium perchlorate (AP) poses a challenge for the development of highly active catalysts. In this work, a well-designed cobalt-embedded N-doped porous graphitized carbon (Co@NC) catalyst is obtained by high-temperature calcination of a zeolite imidazolate frameworks-67 precursor, in which the cobalt catalytic active center realizes effective nanoscale dispersion; meanwhile, the cobalt and N-doped porous graphitized carbon can release considerable heat after oxidation, and the cobalt oxides have an excellent catalytic effect on reducing the HTD temperature of AP. The catalytic activity of Co@NC was tested by a differential thermal analytical method. The results indicated that the HTD peak of AP was significantly decreased by 100.5 °C, the apparent activation energy of the HTD reaction of AP was reduced by 82.0 kJ mol–1, and the heat release compared with pure AP increased 2.9 times. On teh basis of these findings, Co@NC is expected to be one of the best candidate materials for AP thermal decomposition.

Sintering temperature dependency on sodium‐ion conductivity for Na2Zn2TeO6 solid electrolyte

AbstractWe investigated the sintering temperature dependency on the properties of Na2Zn2TeO6 (NZTO) solid electrolyte synthesized via a conventional solid‐state reaction method. Sintering temperature of calcined NZTO powder, which was obtained by the calcination of precursor at 850℃, was changed in the range from 650 to 850℃. X‐ray diffraction analysis showed that P2‐type layered NZTO phase was formed in all sintered samples without forming any secondary phases. The relative densities of sintered NZTO samples were approximately 83%−85% for the samples sintered at 700℃ or higher. The all sintered samples showed sodium‐ion conductivity above 10−4 S cm−1 at room temperature and the highest conductivity of 4.0 × 10−4 S cm−1 in the sample sintered at 750℃. The sintering temperature to obtain the highest room temperature conductivity is 100℃ lower than that used in previous works. Such low sintering temperature compared to other Na‐based oxide solid electrolytes could be useful for co‐sintering with electrode active materials for fabrication of all‐solid‐state sodium‐ion battery.

Characterization and performance within the WGS reaction of Cu catalysts obtained from hydrotalcites

In large-scale industry, the WGS reaction is the most widely used method for the purification of hydrogen obtained from natural gas. This is a process that hinges on factors such as temperature, pressure, type of catalyst, etc. In this work, copper-based solids were obtained from hydrotalcites, which were characterized through various techniques and evaluated within the WGS reaction at different temperatures. Hydrotalcite-type precursors displayed thermal behaviors that depend on their composition, whereby higher temperatures become necessary for the collapse of the HTLc structure in the solids with higher zinc and aluminum content. The calcination of precursors led to the formation of CuO particles in all the materials, which were more resistant to the reduction processes as the aluminum content augmented. The catalysts were active in the reaction under study with C0.50Z0.25A0.25 being the most active material due to the higher content of metallic copper on the surface. The most effective material in terms of metallic copper content present on the surface was C0.33Z0.33A0.33, in which the occurrence of CuO was not evinced after its use, in addition to displaying the smallest particle size of Cu0 as well as, possibly, the existence of Cu–Zn interactions on the surface.

Ecofriendly K-decorated ZnO/Zn(Al,La)2O4 catalyst for hydrogen production – Effect of heterostructure on catalyst activity at steam‐lean process gas

The effect of ZnAlLa-LDHs calcinations temperature on physicochemical and catalytic properties of K-decorated Zn-Al-La mixed oxides for water-gas shift reaction was investigated. The fresh and spent catalysts were characterized using various methods including XRF, N2 adsorption, TG/DTG/MS, XRD, FT-IR, STEM-EDS and HRTEM. Catalysts activity tests were carried out in high-temperature water-gas shift (HT-WGS) reaction in kinetic regime within the temperature range of 330–400 °C and H2O/dry gas molar ratio in the range of 0.5–1. The relationship between the structural, surface morphology of catalysts and the activity in the HT-WGS reaction was studied. The presence of ZnO-Zn(AlLa)2O4 heterostructure decorated with potassium species enhances HT-WGS activity. Calcinations of ZnAlLa-LDH precursor at mild conditions creates a favorable morphology of the surface and results in relatively high activity similar to the standard HT-WGS catalyst (Fe-Cr-Cu). The highest activity in the HT-WGS reaction at lower steam/dry gas ratios was obtained for the ZnAlLa_600_K.

Green chemistry approach for the functionalization of reduced graphene and ZnO as efficient supercapacitor application

Graphene is an allotrope of carbon consisting of a single layer atoms in a two dimensional honeycomb lattice. It has excellent electrochemical stability and possible change in physical and chemical properties. Electrodes are the primary determinants of supercapacitor electrochemical efficiency, so designing and fabricating electrodes with acceptable structural and chemical properties is critical for developing high-performance energy storage devices. The force makes graphene easy to agglomerate the reduce of the specific surface area and ratio of capacity. In this study, the graphene oxide reduced by plant leaf and then ZnO/RGO composites were synthesized by hydrothermal preparation of precursors and then calcination of precursors into composites. The phase structure and micromorphology were characterized by XRD, SEM, Raman and FT-IR. It was found that ZnO nanoparticles were embedded in the graphene sheets and form a composite structure. The electrochemical properties of the material were tested. The results show that the incorporation of graphene and Zinc oxide acted as an electrode material. The results concluded that the ZnO/RGO composite has excellent cycle stability, after 2000 cycles the average specific capacitance retention remains 80%. This is benefit from the introduction of graphene sheets and ZnO uniformly load between the sheets of graphene. The nano structure of reduced graphene oxide provides a conductive nature and more active sites for electrochemical reaction. The results prove that the incorporation of graphene and Zinc oxide are effectively reversible nature and good electrode material.

Controllable Design and Preparation of Hollow Carbon-Based Nanotubes for Asymmetric Supercapacitors and Capacitive Deionization.

Carbon-based materials are important desirable materials in areas such as supercapacitors and capacitive deionization. However, traditional commercial materials are heterogeneous and prone to agglomeration in nanoscale and have structural limitation of electrochemical and desalination performance due to poor transport channels and low capacitance of prepared electrodes. Here, we introduce the facile strategy for controllable preparation of two types of hollow carbon-based nanotubes (HCTs) with amorphous mesoporous structures, which are synthesized by employing a MnO2 linear template method and calcination of polymer precursors. The porous N-doped HCT (NHCT) shows a specific capacitance of 412.6 F g-1 (1 A g-1), with 77.3% rate capability (20 A g-1). The fabricated asymmetric MnO2//NHCT supercapacitor displays the energy density of 55.8 Wh kg-1 at a power density of 803.9 W kg-1. Furthermore, two typical MnO2//HCT and MnO2//NHCT devices both show the selective desalination performance of sulfate, and the MnO2//NHCT device possesses a high deionization value of 11.37 mg g-1 (500 mg L-1 Na2SO4). These fabricated hollow carbon-based architectures with functional characteristics promise potential applications in energy and environmental related fields.

On the Effect of Flash Calcination Method on the Characteristics of Cobalt Catalysts for Ammonia Synthesis Process

AbstractThe influence of precursor calcination method on the properties of the cerium and barium promoted cobalt catalysts for ammonia synthesis was investigated. Three methods of cobalt‐cerium hydroxycarbonates mixture heat treatment were studied – flash, static and semi‐static calcination processes, differing in duration as well as heat and mass transfer conditions. Their effect on catalyst structural parameters, morphology, crystal structure and activity was determined. It was proven that compared to other heat treatment methods flash calcination of CoCe hydroxycarbonate precursor resulted with a catalyst of superior structural parameters and the highest activity in ammonia synthesis. However, the incomplete precursor transformation and insufficient active and promoter phases crystallization during this process were indicated. In order to improve surface activity and optimise properties of the catalyst it was stated that modification of flash calcination conditions is required.

Improved Electrochemical Performance of Li-Rich Layered Oxide Cathodes Enabled by a Two-Step Heat Treatment.

Lithium-rich layered oxide cathodes with high specific energy have become one of the most popular cathode materials for high-performance lithium-ion batteries. However, spinel phase formation due to the migration of transition metals and the release of lattice oxygen leads to the degradation of electrochemical performance. Here, we develop a synthesis approach for Li-rich layered oxide cathodes by a two-step heat-treatment process, which includes precursor calcination and pellet sintering. Compared with the sample prepared by the traditional one-step calcination, the oxide particles prepared by the two-step heat treatment show increased grain size from 217 to 425 nm. The Li-rich layered oxide cathodes with larger crystal grains indicate a mitigated formation of spinel phase and reduced voltage decay, which result in improved specific capacity, cycle stability, and rate capability. In addition, the thermal stability of the oxides is also improved. The improved electrochemical performance is because of the large single grains having a reduced contact area with a liquid electrolyte and the stable crystal lattice during cycling. Our strategy not only provides a simple and effective way to enhance the stability of the Li-rich layered oxide cathodes but also extends to the preparation of oxide powders with large grains.

Application of vanadyl hydrogen phosphate/KIT-6 composites as a catalyst for dehydration of sucrose

In this research work, the synthesis of well-ordered mesoporous structure KIT-6 silica-supported vanadyl hydrogen phosphate hemihydrate (VHP/KIT-6) catalysts possessing varying surface area was carried out, followed by being utilized in the dehydration of sucrose to 5-hydroxymethylfurfural (5-HMF) as a solid acid catalyst. The fabrication of two different VHP/KIT-6 catalysts was conducted using the impregnation approach through V2O5 reduction in alcoholic media. Then, the catalytic behavior presented by the prepared VHP/KIT-6 samples was compared with unsupported VHP and unsupported vanadyl pyrophosphate (VPP), which was prepared through the calcination of VHP precursor at 400 °C for 24 h. The prepared catalysts were characterized by different analyses, including ICP-OES, BET, XRD, NH3-TPD analysis, FT-IR spectroscopy, as well as SEM and TEM techniques. Furthermore, important parameters, including the catalyst type and weight, sucrose amount, time, temperature, and the type of solvent on sucrose dehydration, were also studied. It was observed that the highest catalytic activity in the dehydration reaction (5-HMF yield: 67%, sucrose conversion: > 94%) could be provided by the catalyst possessing the highest surface area. Moreover, the catalyst reusability was examined for consecutive four times, based on which no considerable change in the catalytic activity was observed.

Study on catalytic removal of toluene by metal oxides derived from hydrotalcite

Hydrotalcite (HT) precursor was synthesized by coprecipitation method, and the surface of HT precursor was modified. The mixed metal oxide (MO) catalyst was prepared by calcination of HT precursor, which was used to remove toluene from VOCs assisted by NTP technology. The catalytic performance of MO catalyst was investigated. The results show that the MO catalyst with good structure can be obtained after calcination of HT precursor before and after modification. The results of catalytic performance test showed that the initial concentration of toluene was 700 ppm, the gas flow rate was 600 mL/min, and the reaction time was 30 min, SIE of NTP was above 3.0 kJ/L, the toluene conversion rate reached above 90%. MO assisted NTP had better catalytic performance with lower energy consumption. The toluene treatment capacity per unit energy consumption increased from 15.3% to 20.6%, which had an increase of 34.6%.

Synthesis of Bi5O7I-MoO3 photocatalyst via simultaneous calcination of BiOI and MoS2 for visible light degradation of ibuprofen

In this study, a direct Z-scheme bismuth oxyiodide-molybdenum trioxide (Bi5O7I-MoO3) with uplifted visible light photocatalytic activity was fabricated for degradation of ibuprofen (IBU) via simultaneous calcination of BiOI and MoS2 precursors. The pristine and composite photocatalysts were characterized by various techniques prior to evaluation of the degradation activity. The XRD, FTIR, FESEM and TEM analysis confirmed that the Bi5O7I-MoO3 material with very close interface contact had been successfully fabricated in a composite. The UV–vis DRS results confirmed that the prepared photocatalysts is capable of absorbing visible light and that can improve the visible light photocatalytic performance. Under optimum conditions (catalyst dosage =20 mg and pH = 6.75), 15 mg L−1 of IBU was degraded with an efficiency of 89.2 % under visible light irradiation. The results displayed enhanced photocatalytic superiority towards IBU, which was attributed to the visible light harvesting properties and improved interfacial charge separation efficiency aided by the formed Z-scheme system, and increased life-time of charge carriers. According to the trapping experiments, O2−>OH > h+ played a crucial role in the degradation process in that given order. It was found that the Bi5O7I-MoO3 catalyst was stable with about 4.9 % lost in efficiency after 5 cycles of re-use. Furthermore, the effect of different environmental water parameters were tested in this study to mimic the real environmental water samples. The efficiencies obtained in these matrices were lower as anticipated. The total organic carbon obtained was 86.8 %. Thus, Bi5O7I-MoO3/visible light system shows great potential for applicability in treatment of wastewater contaminated by therapeutic compounds.

Electrochemical Performance of Vanadium Nitride/Carbon/N-Doped MWCNT As Anode Materials for Lithium-Ion Batteries

One of the interesting transition metal nitrides (TMNs) is the vanadium-based compounds that have been reported as a promising candidate as an anode material for lithium-ion batteries. The main issues of the vanadium nitride demonstrations are poor stability but good conductivity. In order to device the application of the vanadium-based electrode materials, a simple preparation method, and the enhancement of conductivity and increased cyclic stability are vital key factors. As a result, this work reports the simple method to prepare vanadium nitride dispersed on carbon matrix and enclosed over the N-doped multi-walled carbon nanotube (MWCNT) as an anode material for lithium-ion batteries. The electrode prepared via a simple synthesis method, cost-effective, and scalable. The conventional preparation method to syntheses TMNs is calcination of precursors in the presence of an ammonia gas atmosphere at high temperature. In the present work, the electrodes are obtained by heat-treating the mixture of ammonium metavanadate (NH4VO3), melamine, and N-doped multi-walled carbon nanotube inflow of nitrogen atmosphere. Galvanostatic discharging-charging (GDC) and Cyclic voltammetry (CV) of the assembled 2032-type stainless coin cells are carried out. The enhanced electrochemical performances can be ascribed to the synergistic effect from the hybrid compositions of vanadium nitrides/carbon and N-doped MWCNT. The detailed results on the above work will be discussed through the presentation and constructively that this work will provide an effective method to fabricate a good electrochemical performance of lithium-ion batteries with the simple anode material.

Model, Mixed and Non-mixed Oxide Catalysts for the Fischer–Trøpsch Reaction Derived from [M1M2(dba)2]: M1 = Co, Ni; M2 = Co, Ni and [M1M2(daaen)]: M1 = Cu; M2 = Co. Part 1: Supported on Non-porous Powder (Cab-O-Sil™)

Homo and hetero-dinuclear metal complexes were used as precursors to model, supported, mixed and non-mixed metal oxide catalysts. These metal complexes contained either Co(II) pairs, Ni(II) pairs, or the mixed pair: Co(II)–Ni(II) having the (dba) ligands. Another mixed pair, Cu(II)–Co(II) was prepared having the (daaen) ligand. Calcination and reduction of precursor supported on silica (Cab-O-Sil™) yielded catalysts that were active for the Fischer–Tropsch reaction. In a batch reactor, both Ni2(dba)2/SiO2 and NiCo(dba)2/SiO2 catalyst gave CH4 as the major product; whereas, the CuCo(daaen)/SiO2 catalyst produced carbon nanotubes as the major product. The Co2(dba)2/SiO2 catalyst was the most stable and active one towards the production of hydrocarbons in a batch reactor. Subsequent testing in a flow reactor revealed that the cobalt catalysts showed 99% CO conversion and 67% liquid hydrocarbon selectivity.

Oxidative Dehydrogenation of Propane over Ni–Al Mixed Oxides: Effect of the Preparation Methods on the Activity of Surface Ni(II) Species

4Ni–Al layered double hydroxide (LDH) precursors were prepared by the following three methods: constant pH coprecipitation, variable pH coprecipitation and urea hydrolysis. The 4Ni–Al mixed metal oxide (MMO) catalysts were obtained by the calcination of LDH precursors at 600 °C, and their catalytic performances in ODHP from 350 to 550 °C were tested. The 4Ni–Al MMO from the urea hydrolysis method showed a higher and more stable propylene selectivity of ca. 40% with propylene yield of ca.11% at 500 °C, and that from the constant pH coprecipitation method was followed, while oxidative cracking of propane occurred on the 4Ni–Al MMO from the variable pH coprecipitation method. It is considered to be closely related to the dispersion and stability of the surface Ni(II) species through comprehensive analysis of XRD, N2-adsorption-desorption, TEM, XPS, H2-TPR and In-situ electrical conductivity. The urea hydrolysis method with a low salt concentration, leading to an excellent stability of the surface Ni(II) species at high reaction temperature, should be selected to prepare Ni–Al MMO catalysts for ODHP instead of the traditional variable pH coprecipitation method with a high salt concentration.

CuO nanoparticles: preparation, characterization, optical properties, and antibacterial activities

Firstly, new copper precursor was prepared from the mixture of Cu(CH3COO)2∙H2O and salicylic acid (1:1 weight ratio) ground for 5 min, and secondly, copper oxide nanoparticles were prepared by calcination of copper precursor at 500 oC and 600 oC for 1.5 h. The products were characterized by Fourier Transform infrared (FT-IR), UV–Vis and photoluminescent (PL) spectroscopy, X-ray powder diffraction (XRD), and transmission electron microscopy (TEM). The FT-IR, UV–Vis, PL, and XRD analysis confirmed the formation of CuO nanoparticles of high purity with a monoclinic structure. TEM images showed that the nanoparticles in both samples had almost similar shape with high agglomeration. The optical band gap value was estimated to be 4.5 and 4.8 eV, respectively, for the as-prepared CuO at 500 and 600 oC, using Tauc’s plot. In addition, antibacterial activity against two gram-positive and two gram-negative stains were studied and the inhibition effect of the as-prepared CuO at 500 and 600 oC on gram-negative bacteria is higher than that on gram-positive bacteria