Influence Of Different Preparation Conditions Research Articles

Controllable preparation of Ag@Fe3O4 core-shell nanoparticles and evaporation characteristics of nanoparticles-modified carbon membranes

To improve the ability of the medium to capture solar energy, Ag@Fe3O4 core-shell nanoparticles (NPs) were prepared in this paper. The influences of different preparation conditions on the particle structure and photo-thermal properties were investigated, and the growth and spectral absorption properties of Ag@Fe3O4 NPs were analyzed. At the same time, nanoparticles-modified carbon membranes (NPCMs) were prepared by electrostatic adsorption method. The influences of radiation intensity and preparation concentration on photo-thermal properties were investigated, and the local evaporation mechanism of NPCMs was deeply explored. Experiments showed that changing the molar ratio of the precursor can effectively regulate the structure and optical properties of the NPs. The increase of the core radius of the NPs will increase the electric field strength (E) of the core surface and promote the absorption of light. Optimizing the temperature and heating time of the preparation process is very important for the successful realization of Fe3O4 coated Ag, while deepening the coupling between plasmons on the surface of adjacent NPs. Compared with the intensity of 5 sun, the evaporation efficiency at 2 sun is increased by 13.37%. The local evaporation effect caused by NPCMs makes the system still have good evaporation efficiency at low radiation intensity.

Preparation of Polystyrene/Polyacrylamide Core-Shell Microspheres via Microfluidizer-Assistant Emulsification Template Methods for Oil Recovery Enhancement

Polyacrylamide and its derivatives are commonly used functional polymers to enhance oil recovery in a water-flooding oilfield. By using its hydrophilic amide group to swell and gel in stratum water, it can plug the fractures and pore throats of underground. In order to improve the strength of polyacrylamide material, the polystyrene/polyacrylamide (PS/PAM) core-shell microspheres were successfully prepared by the microfluidizer-assistant emulsification template method. The influences of different preparation conditions, such as the different types and concentrations of surfactants, organic phase and oil/water ratios, on the morphology, diameter, and distribution of corresponding PS core have been systematically studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and laser light scattering analysis (LLS). Moreover, by the integration of porous meshes onto both inlet and outlet of the interaction chamber, the resultant polymer microspheres could be tuned larger due to the dual homogenization. Our procedure can provide a simple and general method to modulate the diameter of the polymer microspheres in the range of 30 nm to 3 μm with a narrow polydispersity index (PDI) of <0.2. The PS/PAM core-shell microspheres exhibited good water plugging performance.

Electromagnetic Properties and Microwave Absorption of Electrospun Fe2O3-Carbon Composite Nanofibers with Particle–Nanorod Structure

Multifunctional composite nanostructure prepared via electrospinning has attracted wide attention. In this study, Fe2O3-carbon composite nanofiber with particle–nanorod structure was successfully prepared via electrospinning and followed calcination. Then, the electromagnetic properties of this material have been fully characterized, and the influence of different preparation conditions on these properties has been studied. In addition, compared to pure [Formula: see text]-Fe2O3 nanoparticles and hollow Fe2O3 nanofibers, the composite nanofibers with a thickness of 2.64[Formula: see text]mm exhibited an additional absorption peak at a frequency of 13.92[Formula: see text]GHz and an enhancement in absorption at a frequency of 15.45[Formula: see text]GHz, which may be attributed to the increase in electrical loss introduced by amorphous carbon and the enhanced magnetic loss resulting from the multi-stage reflection introduced by the particle–nanorod structure. This study shows that the composite of Fe2O3 and carbon, and the introduction of the particle–nanorod structure can improve the microwave absorption efficiency of materials, and more nanocomposites can be designed like this to further improve their electromagnetic properties and absorption efficiency in the future.

Preparation and application of a novel biochar-supported red mud catalyst：Active sites and catalytic mechanism

A novel catalyst RM-BC(HP) was synthesized by hydrothermal treatment and pyrolysis (800 ℃) using red mud and coconut shells. Influence of different preparation conditions on catalyst performance was explored. SEM showed that RM-BC(HP) was porous and RM was successfully loaded on the outside surface and inside the pores of BC. XRD revealed that Fe2O3 in RM was reduced to Fe0 and Fe3O4 in the pyrolysis process, in which pyrolysis temperature and addition ratio of coconut shells were critical. TGA-MS, FT-IR and XPS were also applied to character the catalyst. 100% of AO7 was removed within 30 min with conditions of 2 mM PS, 50 mg/L AO7 and 0.5 g/L RM-BC(HP), and the Fe leaching was negligible. High removal rate was obtained in tap, river, and lake water. RM-BC(HP)/PS system also exhibited excellent degradation performance for other dyes (MB, MG and RhB) and antibiotics (TC, OTC and CTC). The mechanism studies demonstrated that PS was mainly activated by Fe0 and Fe2+ in RM-BC(HP) to produce different radicals, then 1O2 was generated by the reactions among these radicals to degrade AO7. Finally, nine intermediate products of AO7 were identified by FT-ICR-MS and a probable degradation pathway was proposed.

Highly mesoporous activated carbon synthesized by pyrolysis of waste polyester textiles and MgCl2: Physiochemical characteristics and pore-forming mechanism

Abstract Activation-pyrolysis of textile wastes was considered a sustainable technique to fabricate activated carbon. Highly mesoporous activated carbon was prepared from waste polyester textiles by employing MgCl2 as the activation and template agents. The influences of different preparation conditions on textual property and crystalline structure of carbon were identified by N2 adsorption-desorption isotherms and X-ray diffraction. The optimum pyrolysis temperature, time and mixing ratio for MgCl2/waste polyester textiles are 900 °C, 1.5 h and 5:5 with the carbon thus obtained manifested a surface area of 1307 m2/g, total pore volume of 3.56 cm3/g of which 98% is mesopore. The effect of MgCl2 on the full-cycle pyrolysis pathway of waste polyester textiles was systematically investigated by various characterization methods to explore the pore-forming mechanism of activated carbon. The results demonstrated that MgCl2 was capable of catalyzing the dehydrogenation, decarboxylic and cross-linking reaction of waste polyester textiles and inhibited the formation of tars during pyrolysis process, indicating that the addition of MgCl2 was conducive to the formation of carbonaceous materials and open pores. Meanwhile, acted as the template, MgO particles derived from the decomposition of MgCl2 could develop massive homogeneous mesopores in the carbon matrix.

Preparation of walnut shell-based activated carbon and its properties for simultaneous removal of H2S, COS and CS2 from yellow phosphorus tail gas at low temperature

Walnut shell-based activated carbon (WSBAC) was prepared used to simultaneously remove H2S, COS and CS2 from yellow phosphorus tail gas and closed carbide furnace tail gas. The influences of different preparation conditions (carbonization temperature, activating agent species, activating agent content, activation temperature) on the simultaneous removal efficiency of H2S, COS and CS2 were investigated. The results showed that the WSBAC carbonizated at 600 °C, then activated with 0.5 times KOH at 700 °C had the highest sulfur capacity (52.67 mgS/gWSBAC). The structure and surface properties of the catalysts were characterized by Brunauer–Emmett–Teller (BET) method, and the results showed that the high BET surface area (484.26 m2/g), high micropore volume (0.261 cm3/g) and more pore sizes of 0.3–1.8 nm were conducive to the simultaneous removal of H2S, COS and CS2. X-ray photoelectron spectroscopy results showed that the most of products on the exhausted WSBAC were S/SO4 2− species which accumulated on the WSBAC’s surface and had a negative effect on the adsorption activity.

Surface characterization studies of walnut-shell biochar catalysts for simultaneously removing of organic sulfur from yellow phosphorus tail gas

The influences of different preparation conditions for surface characteristics on removing organic sulfur were studied. From BET, XRD, FTIR, DRIFTS, TG/DTA, CO2-TPD results, it can be seen that these preparation conditions had great influences on the pore structure, specific surface area, crystal structure and surface functional groups. The micropore volume, amorphous structure and alkalinity site strength played major roles in desulfurization process. H2S was oxidized by oxygen containing functional groups, such as COO, CO. H2O molecule could be converted into some groups, such as CH and COH groups, and promoted the hydrolysis reaction. The strong alkalinity site was the key factor for chemical adsorption and hydrolysis. H2O molecule, CH, COH groups promoted the hydrolysis reaction and COO, CO groups promoted the oxidation of H2S on the surface of WSB. Meanwhile, the main desulfurization process over WSB after carbonization was adsorption and it changed to hydrolysis reaction after activation on the surface of WSB. Furthermore, the reaction mechanism was investigated by DRIFTS measurement according to the change of surface functional groups.

Structural and optical properties of CuMnCoOx spinel thin films prepared by a citric acid-based sol–gel dip coating route for solar absorber applications

CuMnCoOx thin films for solar thermal absorber applications were prepared by a citric acid-based sol–gel dip coating method. The citric acid (CA) and polyethylene glycol 200 (PEG 200) were selected as a complexing agent and an esterifying agent respectively. The influence of different preparation conditions, i.e. (Cu + Mn + Co)/CA molar ratios and PEG/CA molar ratios, on film structure and optical properties were studied. Texture properties (crystallinity, grain size, surface topography) were obtained by using X-ray diffraction, field emission scanning electron microscopy and atomic force microscopy. Adhesion strength and thermal stability of the films were also tested. Absorption study indicated that pure spinel phase with a particle size of ~18 nm was a decisive factor in improving the intrinsic solar-absorbing capacity. Meanwhile, the generation of the uneven pores (pore size ~300 nm) on the film surface further lengthened the absorb path in UV–Vis spectrum. The single films displaying the best reflectance spectra and the highest solar absorptance (α > 0.93) were deposited from solutions containing molar ratio (Cu + Mn + Co)/CA/PEG = 1, which were much higher than that reported in the literature (88 %). The study showed that the intrinsic absorbing ability of the transition-metal oxide absorbers could be expanded by using a citric acid-based sol–gel route.

Hydrothermal preparation and characterization of novel corncob-derived solid acid catalysts.

Novel corncob-derived solid acid catalysts were successfully synthesized for the first time by the hydrothermal method. The influences of different preparation conditions were investigated, and the structure-function relationships of the resulting catalysts were also discussed on the basis of the analysis of structure and composition. In comparison to conventional solid acid catalysts, the corncob-derived catalyst synthesized under optimized conditions exhibited higher catalytic activity in esterification reactions, yielding nearly 90% methyl oleate in only 2 h. The catalyst retained satisfactory catalytic activity for esterification, even after 8 reaction cycles. Solid-state magic angle spinning (MAS) (13)C nuclear magnetic resonance (NMR) investigations further indicated that the catalyst was composed of polycyclic aromatic carbon sheets bearing -SO3H, -COOH, and -OH groups in adequate amounts and with proper proportions, contributing to its excellent catalytic activity. This work provides a green method to synthesize solid acid catalysts from biomass wastes and may contribute to a holistic approach for biomass conversion.

Influences of Different Preparation Conditions on Catalytic Activity of Ag2O-Co3O4/γ-Al2O3for Hydrogenation of Coal Pyrolysis

A series of catalysts of Ag2O-Co3O4/γ-Al2O3was prepared by equivalent volume impregnation method. The effects of the metal loading, calcination time, and calcination temperatures of Ag and Co, respectively, on the catalytic activity were investigated. The optimum preparing condition of Ag2O-Co3O4/γ-Al2O3was decided, and then the influence of different preparation conditions on catalytic activity of Ag2O-Co3O4/γ-Al2O3was analyzed. The results showed the following: (1) at the same preparation condition, when silver loading was 8%, the Ag2O-Co3O4/γ-Al2O3showed higher catalyst activity, (2) the catalyst activity had obviously improved when the cobalt loading was 8%, while it was weaker at loadings 5% and 10%, (3) the catalyst activity was influenced by different calcination temperatures of silver, but the influences were not marked, (4) the catalyst activity can be influenced by calcination time of silver, (5) different calcination times of cobalt can also influence the catalyst activity of Ag2O-Co3O4/γ-Al2O3, and (6) the best preparation conditions of the Ag2O-Co3O4/γ-Al2O3were silver loading of 8%, calcination temperature of silver of 450°C, and calcinations time of silver of 4 h, while at the same time the cobalt loading was 8%, the calcination temperature of cobalt was 450°C, and calcination time of cobalt was 4 h.

Mechanical doping of ZnO powders

Massive Zn1−xFexO ternary oxides were prepared by mechanical milling from different starting materials as Fe2O3, α-Fe or FeO. The influence of different preparation conditions, such as initial concentrations, atmosphere and milling times on final products was investigated. The structure evolution and dopant incorporation in the wurtzite crystalline structure with milling time was analyzed by means of X-ray diffraction. The sample's magnetic character investigated by measurements in a Quantum Design MPMS-5S superconducting quantum interference device (SQUID) magnetometer consists of two superimposed signals, a ferromagnetic and a paramagnetic one.

PAC investigations on nanostructured materials

Because of its high local sensitivity the perturbed angular correlation spectroscopy (PAC) is well suited to study the local environment of radioactive probe atoms. In this way, the behaviour of probe atoms at interfaces, the influence of different preparation conditions on the formation of defect complexes, and the incorporation of impurity atoms is investigated whereby the probe atoms form either a constituent of the matrix or act as dopant atoms. First results of nanocrystalline WGa and CdS doped with the radioactive probe 111In are presented.

Vanadia-Titania Aerogels: I. Preparation, Morphological Properties, and Activity for the Selective Catalytic Reduction of NO by NH 3

Highly dispersed vanadia-titania aerogels with high surface area have been synthesized by a two-stage sol-gel process with ensuing high-temperature supercritical drying. A titania gel was prepared by the addition of an acidic hydrolysant to tetrabutoxy-titanium(IV) in methanolic solution. The vanadium alkoxide precursor was added after redispersing the titania gel. The influences of different preparation conditions on the morphological and chemical properties of the aerogels were studied. The aerogels were characterized by means of nitrogen physisorption, X-ray diffraction, transmission electron microscopy, and thermal analysis (thermogravity, differential thermal analysis) coupled with mass spectrometry. The meso- to macroporous vanadia-titania aerogels possess a BET surface area of 140 to 220 m 2 g −1 after calcination up to 673 K and contain well-developed anatase crystallites of ca. 10 nm mean size. Crystalline V 2O 5 was detected only for samples calcined at 723 K. Ah other aerogel catalysts, calcined at lower temperature, showed no indication for long-range ordered vanadia domains. Thermal analysis revealed that even calcination at 723 K was not sufficient for complete removal of organic residues, which were entrapped during supercritical drying. The catalytic properties of the aerogels were tested for the selective catalytic reduction of NO by NH 3. An increase in the vanadia loading from 5 to 30 wt% V 2O 5 resulted in a marked increase in overall as well as specific activity, whereas the apparent activation energy decreased from 66 to 55 kJ mol −1. An increase in the calcination temperature from 573 to 673 K led to a significant rise in the activity of the vanadia-titania aerogel catalyst. The aerogel with 30 wt% V 2O 5 showed a reaction rate referred to the vanadium content (turnover frequency) that is similar to that of multiply grafted well-dispersed vanadia/titania catalysts. Among all catalysts presented in this work, this aerogel exhibited the highest reaction rate per gram of catalyst.

Elastic Properties of Sputtered Thin Films: Influence of Different Preparation Conditions

ABSTRACTThis work presents the first results of a study aimed at better understanding the elastic behaviour of hard coatings produced by various techniques. This is important also in view of the need to be able to control the level of internal stresses, particularly in PVD coatings. It is well known that in extreme cases excessive internal stress can lead to complete film destruction. We devote this paper to reactively magnetron sputtered TiN, one of the most widely used compounds. Thin TiN films of different compositions were deposited on Si substrates and characterized by SEM, AES, XRD and Brillouin light scattering.

Interface analysis of the system Si/YBa2Cu3O7?x

The influence of different preparation conditions and substrate surface orientations on the superconducting properties of thin YBa2Cu3O7−x (YBCO) films on silicon was studied. Comparative electrical and surface spectroscopic measurements were performed. SAM and SIMS depth profile analysis show an enrichment of barium at the interface between the superconductor and silicon for samples with Tc<76 K. Comparison with XPS data obtained for thin silicon films on YBCO indicates the formation of barium and yttrium silicates at the interface under these conditions.

The morphological structure of polypropylene fibres

AbstractThe influence of different preparation conditions upon formation of the morphological structure of polypropylene fibres was studied by X‐ray method, scanning electron microscopy, and small‐angle light scattering technique. It was found that the formation process and the deformation of the morphologic structure in polypropylene fibres changed when using the traditional and the high velocity technologies, respectively.