Influence Of Synthesis Procedure Research Articles

Influence of synthesis procedures on the preparation of strontium titanate nanoparticles and photocatalytic application for methylene blue degradation

SrTiO3 is a well-known photocatalyst with various applications, such as antibacterial agents, self-cleaning surfaces, and water and air conditioning. With the increased environmental pollution, SrTiO3 is one of the most studied perovskite photocatalysts, exhibiting pronounced photocatalytic activity for removing chemical pollutants and water splitting. In the present work, pure Strontium titanate (ST) nanoparticles were successfully prepared using high-energy ball milling and Pechini techniques and characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Fourier Transform Infrared spectroscopy (FTIR), scanning and transmission electron microscopy, respectively. Structural parameters were evaluated by Rietveld refinement analysis from XRD data, which confirmed the cubic system of SrTiO3 with Pm-3 m space group. Scanning electron microscope results showed that ST1 samples consisted of agglomerated and irregular-shaped structures between 20 and 40 nm, and in ST2, the particles were round-shaped and had an average size of 150 nm. The obtained nanoparticles were used for photocatalytic methylene blue (MB) degradation, and synthesis methods' influence on catalytic activity was investigated. The photocatalytic studies examining the decoloration of MB dye reveal the function of smaller particles in increasing the rate of reactions. The degradation rate constant of MB on the ST1 (Pechini-synthesized sample) and ST2 (high energy ball milled sample) is 0.0145 and 0.0112 min−1, respectively. The better photocatalytic activity of the ST1 demonstrated 93% degradation of dye under the solar light simulator. The photocatalytic reaction data provided well a first-order kinetic model.

Effect of Processing on Structure and Ionic Conductivity of Chlorine‐Rich Lithium Argyrodites

Lithium argyrodite solid electrolytes have attracted ever‐increasing attention for all‐solid‐state batteries due to their high ionic conductivity and low cost. However, the relation between structure and ionic transport for the halogen‐rich lithium argyrodites under different synthesis routes is still elusive. Herein, the influence of synthesis procedures, such as annealing conditions and balling milling, on the structure, ionic conductivity, and activation energy of the lithium argyrodite (e.g., Li5.5PS4.5Cl1.5, Li5.3PS4.3Cl1.7), is systematically investigated. Compared with high‐energy ball milling followed by annealing, using fast dry mixing followed by annealing can obtain comparable ionic conductivity of the chlorine‐rich lithium argyrodites. Single‐crystal LiNi0.83Co0.11Mn0.06O2‐based solid‐state battery with these electrolytes shows stable cycling performance, demonstrating that chlorine‐rich lithium argyrodite is a promising candidate for all‐solid‐state batteries.

The influence of synthesis conditions on the redox behaviour of LiFePO4 in aqueous solution

To contribute to the knowledge on the influence of synthesis procedure on the intercalation kinetics of lithium ions into phospho-olivines, LiFePO4/C composite samples (LFPC) were synthesized in two ways, the first one in a sol-gel procedure (SG), and the other in a solid-state reaction (SS). The X-ray diffractograms (XRD) of both samples overlapped with that of pure LiFePO4, taken from the crystallographic database. Scanning electron microscopy pictures indicated the high degree of interparticle sintering, which caused a considerable agglomerate growth. The results of potentiodynamic measurements in aqueous LiNO3 solution revealed that for SS sample, three times higher initial capacity from that of SG one, (amounting to 74 mAh g−1 at 5 mV s−1). However, capacity fade on rising scan rate is much more expressed for SS sample than for SG one. We suggest that a different degree of material utilization due to the incomplete coverage of olivine particles by carbon explains this difference. The technique of separation of diffusion and capacitance currents was applied in a kinetic analysis, but it was shown to be inappropriate. We suggest the inapplicability of classic CV theory to the intercalation system accompanied by phase transition. Instead, a model of ohmic resistance determination of process kinetics was considered. LFPC-SS sample delivers three times larger capacity in LiNO3, amounting to 74 mAh g−1 at 1 mV s−1.

Li-rich and Ni-rich transition metal oxides: Coating and core-shell structures

In this work, we consider influence of synthesis procedures, applying coatings, and formation of core-shell structures on the electrochemical performance of Ni-rich and Li-rich oxides. Li-rich Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials synthesized by different synthesis procedures exhibit different electrochemical behavior, especially those obtained by sol-gel combustion method. The TEM findings reveal the presence of monoclinic and trigonal phases in the Li-rich materials synthesized. TEM/ED/EDX microanalysis shows that the C2/m monoclinic phase appears to have a variable composition Li2[M]O3, where [M] = (Mn, Ni, Co). Whence, on the basis of monoclinic phase we can observe a restricted solid solution with 4 h-Wyckoff Mn-cation positions potentially being occupied by the mixture of three 3d-metal cations [M] = (Mn, Ni, Co). The cyclability of Li-rich oxides is improved by thin alumina films deposited by ALD directly on porous electrodes. The better capacity retention of modified electrodes is explained by suppressing reactions with electrolyte accompanied by growth of SEI film on cathode. The core-shell structures with Ni-rich core and gradient shell enriched with Mn were obtained by coprecipitation and applying the shell material onto LiNi0.8Co0.15Al0.05O2 as received. These structures show better cyclability and rate capability in the extended voltage range of 2.5–4.4 V than the core materials.

The Influence of Synthesis Procedure on Electrical and Mechanical Properties of Netlike Polyurethane/Carbon Nanotubes’ Composites

The Influence of Synthesis Procedure on Electrical and Mechanical Properties of Netlike Polyurethane/Carbon Nanotubes’ Composites

Influence of synthesis procedure on the morphology of bismuth oxide particles

A modified sol–gel procedure, based on the esterification reaction, was used to prepare the Bi 2O 3 precursor, which was then heated to 400 or 500 °C. β-Bi 2O 3 obtained at 400 °C showed well-shaped plate-like particles. The mixture β-Bi 2O 3/α-Bi 2O 3, obtained by prolonged heating at 400 °C, yielded pseudospherical particles having about 100 nm in size and much larger particles, as found by FE SEM. α-Bi 2O 3 obtained at 500 °C consisted of particles of varying shapes and sizes. Vitrification of α-Bi 2O 3 was also observed. XRD showed a small fraction of unidentified phase(s) in these samples. Different microstructures were obtained when the precipitation from aqueous Bi(NO 3) 3 solution with tetramethylammonium hydroxide at pH ∼ 14 was used. The precipitation at pH ∼ 3.5 yielded cloverleaf-like particles of good uniformity, which were assigned to BiOOH (isomorphous with (La 0.26Bi 0.24)Bi 0.5OOH. It was found that these particles were made up of much smaller primary BiOOH particles.

Influence of synthesis procedure on the YIG formation

The influence of synthesis procedure on the yttrium iron garnet (YIG; Y 3Fe 5O 12) formation has been investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Mössbauer and magnetization measurements. The samples were prepared by coprecipitation or ceramic processing using the starting molar ratio Y 2O 3/Fe 2O 3=3:5. The fractions of Y 2O 3, α-Fe 2O 3, YFeO 3 and YIG present in the samples depended on the method of materials processing and the calcination temperature. XRD of the thermally treated hydroxide coprecipitate at 1173 K showed the formation of YIG as a dominant phase, and YFeO 3 and Y 2O 3 as associated phases, whereas upon heating at 1473 K, YIG and a small amount of YFeO 3 were found. The samples produced by combining ball-milling of the starting powder and ceramic processing at 1573 K contained YIG and a smaller amount of YFeO 3, as found by XRD. It was shown that high-energy ball-milling with stainless steel can be substituted by milling with agate bowl and balls, thus decreasing the contamination of the oxide system due to wear. FT-IR and 57Fe Mössbauer spectroscopic measurements were in agreement with XRD; however, the smaller amount of YFeO 3 produced at 1573 K could not be detected with certainty by means of FT-IR and 57Fe Mössbauer spectroscopies. The magnetization values of end-products measured at 5 K were in agreement with their phase composition.

Influence of synthesis procedure on the formation and properties of zinc oxide

Formation and properties of zinc oxide were investigated in dependence on the synthesis procedure. Zinc oxide did not crystallize upon hydrothermal treatment of Zn(NO 3) 2 aqueous solutions containing urea, up to 160 °C. Hydrozincite was formed instead. Changes in the X-ray diffraction patterns and Fourier transform infrared (FT-IR) spectra were interpreted in terms of stacking disorder in hydrozincite crystals. Zinc oxide powder was obtained by thermal treatment in air of precipitated hydrozincite. The conditions for instantaneous synthesis of very fine zinc oxide particles were found. This procedure is based on addition of TMAH (tetramethylammonium hydroxide) solution to an ethanolic solution of zinc acetate dihydrate, up to pH∼14. On the other hand, addition of an equivalent volume of water to the ethanolic solution of zinc acetate dihydrate, prior to the addition of TMAH solution up to pH∼14, yielded ZnO flakes without any specific shape. All zinc oxide particles produced upon heating at 600 °C in air showed similar morphology and tendency to aggregation due to the sintering effect. The features of the FT-IR spectra of zinc oxide particles were related to their shapes.

Influence of synthesis procedure on the formation of RuO 2

The influence of synthesis procedure on the formation of RuO 2 was examined. The synthesis applied in the present work was based on the addition of strong organic alkali (tetramethylammonium hydroxide (TMAH)) into alcoholic or water solution of RuNO(NO 3) 3 and the precipitation of amorphous ruthenium hydrous oxide, which was further heated at high temperatures. The synthesis conditions for the preparation of nanocrystalline RuO 2, as a single phase, were found. XRD showed that amorphous ruthenium hydrous oxide, upon thermal treatment, easily transforms into RuO 2 and Ru. The molar fractions of these two phases depended on the heating temperature and atmosphere (air or argon). The samples were also characterized by laser Raman and Fourier-transform infrared (FT-IR) spectroscopies.