Influence Of Preparation Conditions Research Articles

Controlled synthesis of porous FeCO3 microspheres and the conversion to α-Fe2O3 with unconventional morphology

Porous FeCO3 microspheres were synthesized via a facile surfactant- and template-free hydrothermal process. The diameters of FeCO3 microspheres are about 20±5μm. Each FeCO3 microsphere was self-assembled with a number of trilobed wheel-like subunits. The influence of preparation conditions, such as temperature, reaction time and content of urea on the phase composition and morphology were investigated. Based on time-dependent experiments, we proposed the possible formation mechanism for the self-assembled FeCO3 micro-spheres. After calcination at 650°C, α-Fe2O3 derived from FeCO3 retained the original size and morphology of FeCO3. The prepared α-Fe2O3 with the novel microstructure shows wide potential application as photocatalysts.

Influence of Preparation Conditions on the Structure of MCM-41 and Catalytic Performance of Ru/MCM-41 in Benzene Hydrogenation

The influence of the preparation conditions on the structures of mesoporous molecular sieve MCM-41 were studied. The prepared MCM-41 samples were characterised by nitrogen physical adsorption–desorption, powder X-ray diffraction, transmission electron microscopy, FT-IR spectroscopy, thermo gravimetric analysis, differential scanning calorimetry and water/benzene static adsorption technologies. Ru/MCM-41 catalysts were then prepared by double solvent impregnation method and tested for benzene hydrogenation to cyclohexene. The structure characteristics of MCM-41 have a great effect on cyclohexene selectivity in benzene hydrogenation process. Ruthenium supported on MCM-41 with moderate surface area, larger pore size and pore volume, better long-range-order of hexagonal mesoporous shows better catalytic performance for benzene hydrogenation to cyclohexene.

Influence of Preparation Conditions on Morphology of in-situ Synthesized Hollow Nickel-silica Spheres for Hydrolytic Dehydrogenation of Ammonia Borane

Influence of Preparation Conditions on Morphology of in-situ Synthesized Hollow Nickel-silica Spheres for Hydrolytic Dehydrogenation of Ammonia Borane

Esterification of levulinic acid with ethanol over sulfated mesoporous zirconosilicates: Influences of the preparation conditions on the structural properties and catalytic performances

Levulinic acid is considered one of the most important biomass-derived chemicals owing to its potential as a versatile building block to synthesize valuable fuels and chemicals. Levulinate esters, such as methyl levulinate and ethyl levulinate obtained via esterification of levulinic acid with alcohols, can in particular be used as fuel additives and plasticizers, and thus have a potential to replace a significant amount of petroleum-derived chemical feedstocks. In this article, sulfated zirconosilicates having P6mm hexagonal mesoporous structure were applied as solid acid catalysts to the esterification of levulinic acid with ethanol to produce ethyl levulinate, and the influences of preparation conditions on the structural properties and catalytic performances were investigated. A distinct correlation was observed between the catalytic activity and the density of acid sites, showing that dispersibility of the acid sites and the associated accessibility of the organic reactants play an important role in determining the overall activity. Among the catalysts tested, sulfated Zr–SBA-15 with optimum Zr content (Si/Zr ratio of 10.7) was found to be the best catalyst, the activity of which was far superior to that of conventional sulfated ZrO2. In addition, direct conversion of cellulosic sugars (glucose and fructose) into levulinate esters was also examined.

Influence of Preparation Conditions on the Dispersion Parameters of Sprayed In2S3films

In2S3 films were prepared by spray pyrolysis technique at various substrate temperatures (Tsub) and the spray solutions were mixtures of indium chloride (InCl3) and thiourea (SC(NH2)2). The films are preferentially oriented along the (220) plane and are of polycrystalline In2S3 with a cubic crystal structure. The refractive index dispersion curves of the films obey the single oscillator model and oscillator parameters changed with substrate temperature. The most significant result of the present study is to indicate that substrate temperature of the film can be used to modify the optical band gaps and optical constants of In2S3 films. The effect of Tsub on the optical dispersion of these films has been investigated.

Investigation into the occurrence forms of oxygen in hafnium nanopowders

The synthesis modes are studied with the purpose of developing hafnium powders with the lowest oxygen content. The results of investigations into the influence of preparation conditions on the occurrence forms of oxygen in hafnium nanopowders are considered. The studies were performed using the methods of analytical chemistry, X-ray diffractometry, and electron microscopy. The data of the phase and structural analyses, the results of microscopic investigations, the chemical analysis for oxygen, and the investigation of the samples for the presence of dissolved gases are presented.

Effect of preparation conditions on the hydrogen storage capacity of activated carbon adsorbents with super-high specific surface areas

A series of activated carbon adsorbents with super-high specific surface areas (SHAC) (SBET ≥ 2500 m2 g−1) was prepared and used to adsorb storage hydrogen. The results indicated that the structure of activated carbon adsorbents and hydrogen storage capacity are affected by preparation conditions. The influence of preparation conditions on hydrogen storage capacity can be attributed to changes in the structure of the prepared activated carbon adsorbents. The prepared adsorbents had high hydrogen storage capacity, reaching 5.65 wt % and 4.98 wt % when the adsorption temperatures were 0 °C and 25 °C, respectively, and the pressure was 9.0 MPa.

Performance Study and Structure Control of Carbon Aerogel

In this research the fabrication of carbon aerogel is reported. nanopore carbon aerogels were prepared via a sol-gel process with resorcinol and formaldehyde (RF) aerogels,which were cost-effectively manufacture form Rf wet gels by an ambient drying technique instead of conventional supercritical drying. The key of the work is to fabricate carbon aerogels with controllable nanopore structure, which means sharp pore size distribution and extremely high surface area.The influence of preparation condition of carbon aerogels was studied by scanning electron microscope and Micropore Physisorption Analyzer. The BET surface of the carbon aerogels are from 749m2/g to 1156m2/g .The size of the carbon nanoparticles are in the range of 20nm~40nm. The micro-pore volume and bore diameter can be controlled by gelation conditions such as RF mass fraction.

Influence of preparation conditions on 211 particle refinement in YBCO bulk superconductors with Ce addition

The influence of CeO2 and BaCeO3 addition and the influence of processing conditions on Y2BaCuO5 (Y211) particle size and particle distribution in melt-processed YBa2Cu3O7/Y2BaCuO5 (Y123/Y211) bulk superconductors with nominal composition Y1.5Ba2Cu3Ox was investigated. Ce dissolved in the peritectic melt can actively hinder the Y211 particle growth by the Ostwald ripening process at melting stage. At sintering of intensively milled samples, Y211 particles in the charge free of CeO2 are smaller than Y211 particles formed in the charge with CeO2 addition and this behaviour can be related to the melt formation around added CeO2. The Y211 particle refinement in the mildly milled samples with large Y123 particles in the pressed green bodies is caused by very dense Y211 skeleton resistant to melt formation at the sintering stage. This skeleton is a barrier for pollution of the sample from the substrate and from the seed. BaCeO3 added instead CeO2 causes significant Y211 particle refinement also in the samples with homogenously distributed Y211 particles.

Investigation of Cu- and Fe-Doped CsH3PMo11VO40 Heteropoly Compounds for the Selective Oxidation of Methacrolein to Methacrylic Acid

Selective oxidation of methacrolein to methacrylic acid was carried out over Cu- and Fe-doped acidic cesium salts of molybdovanadophosphoric acids. The influences of preparation conditions on the structure and catalytic properties of the catalysts were investigated. Results showed that the addition method of NH4+ in the precursors greatly affected the structure of the calcined catalysts. When MoO3, V2O5, and H3PO4 were used to prepare the parent heteropoly acid, which further reacted with the mixed metal nitrates to form the Keggin-type precursor, the addition of ammonia promoted the formation of single-phase cubic secondary structure of the precursor. After being calcined at 360 degrees C for 12 h, ammonium ions totally decomposed, and vanadium ions were partially expelled from the primary Keggin units. The catalytically less active MoO3 phase, observed in the sample calcined in air, did not exist in the sample calcined in N-2. When NH4VO3 was used to replace V2O5 and ammonia to prepare the precursor, the ammonium exhibited higher thermal stability, and the calcination atmosphere had almost no effect on the phase composition of the calcined catalysts. It is also found that Cu and Fe as counterions can improve the redox property and thereby enhance the performance of the catalyst.

Chitosan–gellan electrostatic complexes: Influence of preparation conditions and surfactant presence

Nanoparticles were obtained by electrostatic complexation between chitosan and gellan gum at different polysaccharide ratios. The effect of the chitosan:gellan ratio on the particle charge and particle size distribution was determined by dynamic light scattering measurements. The particle stability was studied during storage in an aqueous medium at 25°C for 100h. The effect of the preparation procedure (mixing steps) on the characteristics of the complexes was also determined. In addition, the influence of a nonionic surfactant (polysorbate-20) on the chitosan:gellan electrostatic complexes (PECs) was evaluated. The charge of the PECs depended on the polysaccharide ratio. During storage, structural reorganization of the complexes was observed. The mixture protocol was a determinant factor for PEC size. Multilayered particles formed by a 2-step mixing of polysaccharide solutions showed a considerable increase in size as compared to the complexes formed by a 1-step mixing. The PEC size, count rate and zeta potential were not affected by the presence of polysorbate-20.

The influence of preparation conditions and doping on the physicochemical and sensor properties of mesoporous tin oxide

Abstract The influence of conditions used for preparation of mesoporous materials and thin layers based on tin oxide on physicochemical and sensor properties of these materials were studied. Thermal stability, acidic, sorption and electric properties were studied. The advantage of thin (≈1 μm) thermostable nanocomposite layers with relatively high parameters of the porous structure ( V = 0.460 cm 3 /g, S ВЕТ = 440 m 2 /g) was shown. Obtained materials can be used for selective gas/vapor sensing.

Evaluation of the influence of preparation conditions on pharmacokinetics of bone-seeking radiopharmaceutical 188Re-labeled hydroxyethylidenediphosphonic acid monopotassium salt in rats

The in vivo biodistributions of the monopotassium salt of hydroxyethylidenediphosphonate labeled with 188Re (188Re-KHEDP) were studied in rats for drug batches prepared with and without Re carrier. Also, the pharmacokinetics of two batches of 188Re-KHEDP that were synthesized at different temperatures (20 and 100°C) were studied. The results showed that all 188Re-KHEDP preparations accumulated in bone. The excretory pathway of 188Re-KHEDP was through the kidneys. Only kidney and thyroid exhibited a relatively high drug uptake among the soft tissue organs. The results showed that carrier-added 188Re-KHEDP had better pharmacokinetic parameters than the carrier-free radiopharmaceutical as manifested by higher bone uptake and faster blood clearance. It was also found that the presence of Re carrier increased significantly the stability of 188Re-KHEDP. The skeleton-to-muscle ratio was 249.1 ± 42.1 for carrier-added 188Re-KHEDP and <21 for the carrier-free drug. The biodistributions of 188Re-KHEDP differed for drugs prepared at 20 and 100°C. The maximum skeleton-to-muscle and skeleton-to-blood ratios were 157.3 ± 24.4 and 21.4 ± 4.85 for 188Re-KHEDP prepared at 20°C and 467.2 ± 123.2 and 77.9 ± 11.9 for that prepared at 100°C. These results showed a statistically significant difference (p < 0.05) in favor of 188Re-KHEDP prepared at 100°C. The results indicated that all versions of 188Re-KHEDP had promising properties as potential therapeutic bone-metastasis agents. However, carrier-added 188Re-KHEDP and that prepared at 100°C exhibited better properties than the other types of the examined radiopharmaceutical.

Influence of Preparation Conditions on the Properties of Lithium Titanate Fabricated by a Solid-state Method

Lithium titanate (Li4Ti5O12) was prepared by a quasi solid-state method using water and ethanol as the solvents, in which Li2CO3 and TiO2 were used as the starting materials. In this work, the calcination temperature, molar ratio of Li to Ti, and sintering time were all well investigated. The obtained samples were thoroughly characterized by XRD and SEM, revealing that the above three factors not only affected the crystal structure, but also the morphologies of the resultant samples. Galvanostatic charge discharge curves were also employed to evaluate the electrochemical performance of the samples. The best electrochemical performance of the samples was observed when the molar ratio of Li to Ti, sintering temperature and time are 6:5, 850 oC and 12 hours, respectively. It was revealed that the smaller particle size and the higher crystallinity of the resultant samples were favorable to enhance the electrochemical performance.

Influence of preparation conditions on thermoelectric properties of Ba8Ga16Si30 clathrate by combining arc melting and spark plasma sintering methods

We have investigated the thermoelectric properties of clathrate samples with a nominal Ba8Ga16Si30 composition, prepared by combining arc melting and spark plasma sintering methods under different conditions. The carrier concentration of the samples greatly decreases from the order of 1021 cm−3 to 1020 cm−3 due to an increase in Ga content by changing the arc melting conditions. Consequently, the Seebeck coefficient increases and the thermal conductivity decreases while the electrical conductivity decreases. The effective mass, carrier mobility and lattice thermal conductivity are determined from an analysis using a single parabolic band model with alloy disorder and phonon scattering mechanisms. The thermoelectric figure of merit ZT significantly increases up to about 0.55 (900 K) for a carrier concentration of about 6×1020 cm−3 (RT). The simulation predicts that ZT can reach 0.8 (900 K) at the optimum carrier concentration (about 2×1020 cm−3) in the Ba8Ga16Si30 system.

Simultaneous Catalytic Hydrolysis of Carbonyl Sulfide and Carbon Disulfide over Modified Microwave Coal-Based Active Carbon Catalysts at Low Temperature

A series of microwave coal-based active carbon catalysts loaded by metal oxides were prepared by a sol–gel method and tested for the simultaneous catalytic hydrolysis of carbonyl sulfide (COS) and carbon disulfide (CS2) at relatively low temperatures of 50–70 °C. The influences of preparation conditions on catalytic activity were studied, which were the kinds and amount of additive, calcination temperatures, and types and content of alkali. The results show that catalysts with 5.0% Fe2O3 after calcining at 300 °C have superior activity for the simultaneous catalytic hydrolysis of COS and CS2. It also indicated that the catalytic hydrolysis activity increased with the basic intensity, following the order of KOH > K2CO3 > Na2CO3 > NaHCO3, and the optimum amount of KOH was 13%. The structure and surface properties were characterized by X-ray diffractometry (XRD), Brunauer-Emmett-Teller measurements (BET), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). The XRD and BET results revealed that the calcination temperature controlled the crystalline phase and generation of Fe2O3 and affected the properties of specific surface area and pore structure. The XPS results showed that most of COS and CS2 hydrolysis products were sulfate ion (SO42–) species, which accumulated on the active carbon’s surface and had a negative effect on the hydrolysis activity.

Influence of Preparation Conditions of the Solid Base Catalyst on the Performance of Synthesizing Polyglycerol

Different solid base catalysts used for the polymerization of glycerol were prepared by impregnation. Catalyst type and the preparation conditions were optimized on the base of polymerization degree. Results showed: the best catalyst was KF/Al2O3, and optimal condition for catalyst preparation was as follows: loading of 40% KF, calcinations temperature 600°C. The polymerization degree of 5.92 was obtained under the following reaction condition: the amount of catalyst 11.62,reaction temperature 250°C, reaction time 4 h.

Influence of preparation conditions on the catalytic activity of Fe-montmorillonites in phenol oxidation in aqueous solutions

The influence of preparation conditions on the catalytic activity of Fe-containing montmorillonites in phenol oxidation with hydrogen peroxide in aqueous solutions and on their resistance to washout of iron ions was examined.

Influence of preparation conditions on the performance of Ni-CaO-ZrO2 catalysts in the tri-reforming of methane

Ni-CaO-ZrO2 catalysts were prepared by co-precipitation under different conditions and used in the tri-reforming of methane; the influence of preparation conditions on methane conversion and catalytic stability was evaluated. The results indicated that the optimal parameters used to prepare Ni-CaO-ZrO2 catalysts include a calcination temperature of 973 K, a pH value of 10–12 for co-precipitation, and a reflux duration of 24 h. The catalyst prepared under the optimal conditions has a proper surface area and Ni–ZrO2 interaction; it exhibits promising catalytic activity and stability in methane tri-reforming and the methane conversion exceeds 70% under a temperature of 973 K and atmospheric pressure.

Influence of the preparation conditions on the properties of polymeric and hybrid cation exchange membranes

The present work deals with the influence of the membrane preparation conditions on the properties of polymeric and hybrid cation exchange membranes prepared by casting and solvent evaporation method. The polymer material used was the sulphonated derivative of an amorphous polyetheretherketone, known as PEEK-WC (sulphonated polymer is indicated as SPEEK-WC). Hybrid SPEEK-WC membrane containing inorganic proton conductors were also prepared at various loading (acid silicotungstate, ammonium and cesium silicotungstate).Different properties of the polymer electrolyte membranes (PEMs), like proton conductivity, ion exchange capacity, methanol permeability, water content and thermal stability, were examined as a function of solvent type, casting temperature and membrane post-treatment.The membrane cast using dimethyl sulphoxide (DMSO) as solvent, at higher temperature (45°C vs 30°C) and with acid post-treatments, resulted to be more conductive. It was found that polymer–solvent interactions play a determining role on the PEM microstructural organization and, as a consequence, on the proton transport pathway. The electrochemical properties of the PEMs are indeed closely related to their microstructure, especially the spatial distribution and nature of their ionic sites. The DMSO use as solvent increased also the thermal stability of the membranes (higher decomposition temperature of the sulphonic groups).