Influence Of Synthesis Conditions Research Articles

Pure TeO2 glass: Influence of synthesis conditions on linear and non-linear optical, magneto-optical and structural properties

The first systematic study of linear and non-linear optical, magneto-optical and structural properties of pure TeO2 glass is presented with regard to different synthesis and material processing conditions. Prepared glasses were synthesized by the intermittent quenching from 900 ∘C in platinum or alumina crucibles and characterized prior to and after optical polishing. The position of the long-wavelength/phonon absorption edge was investigated using various optical models and experimentally obtained data of refractive index and Verdet constants were used for the estimation of magneto-optical anomaly parameter. During synthesis in alumina crucible, up to about 11 wt.% of Al2O3 incorporates into the glass (verified by EDS/XRF and Raman/FTIR spectroscopy) partially transforming the original pure TeO2 glass backbone structure composed of [TeO4] trigonal bipyramids to [TeO3+1] and [TeO3] structural units with the expected integration of Al into Te − O − Al bridges. The presence of Al2O3 results in lowered density ρ (5.60 → 4.72 g cm−3), refractive index n1550 (2.086 → 1.927) and Verdet constant V632 (36.3 → 21.9 rad T−1 m−1) and in increased optical-band-gap energy Eg (3.69 → 3.72 eV) and Abbe number νD (19.9 → 26.9) compared to pure TeO2 glass prepared in platinum crucible. A dataset of the obtained complex optical parameters (refractive index and extinction coefficient) in the wide spectral range of 193 − 11000 nm is included in the supplementary part.

Absorption edge shift and broadening in nanostructured Al doped ZnO thin films

Samples of ZnO were prepared by sol-gel and deposited by dip-coating. The influence of synthesis conditions on the optical properties were studied in different sets of ZnO films, synthesized by alternately varying the following parameters: addition of additives to the precursor solution, Al doping percentage and number of layers. The optical properties of the obtained films were studied by transmittance, being typically >90 % at 600 nm. The absorption edge for undoped samples showed a structure due to exciton formation at room temperature. The bandgap energy Eg, was between (3.227 ± 0.010) eV and (3.275 ± 0.010) eV for undoped samples, increasing to (3352 ± 0.010) eV for Al doped ones (10 % Al/Zn in solution with additives). For intermediate 5 % doping the mean bandgap energy was (3.315 ± 0.015) eV. A similar value (3.320 eV ± 0.010) eV was obtained for 10 % Al/Zn when no additives were included. Doped samples showed a smoother absorption edge. This edge shape evolution was studied by Urbach band tail analysis. The Urbach band tail parameter EU increased with doping, varying from 30 meV to 90 meV and increasing as Eg increases. This correlation describes the influence of impurity states in the structure and optical properties of the material.

Synthesis of L-Lactide from Lactic Acid and Production of PLA Pellets: Full-Cycle Laboratory-Scale Technology.

Lactide is one of the most popular and promising monomers for the synthesis of biocompatible and biodegradable polylactide and its copolymers. The goal of this work was to carry out a full cycle of polylactide production from lactic acid. Process conditions and ratios of reagents were optimized, and the key properties of the synthesized polymers were investigated. The influence of synthesis conditions and the molecular weight of lactic acid oligomers on the yield of lactide was studied. Lactide polymerization was first carried out in a 500 mL flask and then scaled up and carried out in a 2000 mL laboratory reactor setup with a combined extruder. Initially, the lactic acid solution was concentrated to remove free water; then, the oligomerization and synthesis of lactide were carried out in one flask in the presence of various concentrations of tin octoate catalyst at temperatures from 150 to 210 °C. The yield of lactide was 67-69%. The resulting raw lactide was purified by recrystallization in solvents. The yield of lactide after recrystallization in butyl acetate (selected as the optimal solvent for laboratory purification) was 41.4%. Further, the polymerization of lactide was carried out in a reactor unit at a tin octoate catalyst concentration of 500 ppm. Conversion was 95%; Mw = 228 kDa; and PDI = 1.94. The resulting products were studied by differential scanning calorimetry, NMR spectroscopy and gel permeation chromatography. The resulting polylactide in the form of pellets was obtained using an extruder and a pelletizer.

Magnetic Chitosan Bionanocomposite Films as a Versatile Platform for Biomedical Hyperthermia.

Responsive magnetic nanomaterials offer significant advantages for innovative therapies, for instance, in cancer treatments that exploit on-demand delivery on alternating magnetic field (AMF) stimulus. In this work, biocompatible magnetic bionanocomposite films are fabricated from chitosan by film casting with incorporation of magnetite nanoparticles (MNPs) produced by facile one pot synthesis. The influence of synthesis conditions and MNP concentration on the films' heating efficiency and heat dissipation are evaluated through spatio-temporal mapping of the surface temperature changes by video-thermography. The cast films have a thickness below 100µm, and upon exposure to AMF (663kHz, 12.8 kA m-1), induce exceptionally strong heating, reaching a maximum temperature increase of 82 °C within 270 s irradiation. Further, it is demonstrated that the films can serve as substrates that supply heat for multiple hyperthermia scenarios, including: i) non-contact automated heating of cell culture medium, ii) heating of gelatine-based hydrogels of different shapes, and iii) killing of cancerous melanoma cells. The films are versatile components for non-contact stimulus with translational potential in multiple biomedical applications.

Sludge-derived biochar: A review on the influence of synthesis conditions on environmental risk reduction and removal mechanism of wastewater pollutants

Sludge-derived biochar: A review on the influence of synthesis conditions on environmental risk reduction and removal mechanism of wastewater pollutants

Effects of synthesis conditions on the crystal and local structures of high-entropy oxides Ln[formula omitted]O[formula omitted] (Ln = La-Yb, Y; M = Ti, Zr, Ce)

The synthesis and detailed study of six series of high-entropy complex oxides containing lanthanides (Ln) and transition metals with the general formula Ln2M2O7 (Ln = La-Yb, and Y; M = Ti, Zr, and Ce) with the number of different Ln cations not less than six in each case are reported. The influence of synthesis conditions (types of the Ln3+ and M4+ cations, calcination temperature) used in the synthesis via either coprecipitation or sol–gel method on the crystal and local structures of target materials is comprehensively surveyed. The studies were carried out using a combination of long- (s-XRD), medium- (Raman, FT-IR, SEM-EDS) and short-range (XAFS) sensitive techniques, as well as AES-ICP and STA. It was established that the ratio of the cation radii γ = r̄Ln3+/r̄M4+ is the main factor that determines the type of initially formed crystal structure. In the boundary region (γ∼ 1.42–1.47), the average radius of lanthanide cation (r̄Ln3+), along with the r̄Ln3+/r̄M4+ ratio, also plays a significant role in the type of the resulting crystal structure of the high-entropy lanthanide complex oxides. The presence of inhomogeneity in the distribution of elements in precursors significantly affects the phase composition of the resulting high-entropy oxides. An increase in the calcination temperature promotes not only the occurrence of subsequent phase transitions, but also an increase in the single-phase nature of the resulting high-entropy complex rare-earth oxides. At the same time, the cations included in the composition retain some independence, despite the fact that they occupy one crystallographic position in the resulting crystal structure.

Influence of Synthesis Conditions on the Crystal, Local Atomic, Electronic Structure, and Catalytic Properties of (Pr1−xYbx)2Zr2O7 (0 ≤ x ≤ 1) Powders

The influence of Yb3+ cations substitution for Pr3+ on the structure and catalytic activity of (Pr1−xYbx)2Zr2O7 powders synthesized via coprecipitation followed by calcination is studied using a combination of long- (s-XRD), medium- (Raman, FT-IR, and SEM-EDS) and short-range (XAFS) sensitive methods, as well as adsorption and catalytic techniques. It is established that chemical composition and calcination temperature are the two major factors that govern the phase composition, crystallographic, and local-structure parameters of these polycrystalline materials. The crystallographic and local-structure parameters of (Pr1−xYbx)2Zr2O7 samples prepared at 1400 °C/3 h demonstrate a tight correlation with their catalytic activity towards propane cracking. The progressive replacement of Pr3+ with Yb3+ cations gives rise to an increase in the catalytic activity. A mechanism of the catalytic cracking of propane is proposed, which considers the geometrical match between the metal–oxygen (Pr–O, Yb–O, and Zr–O) bond lengths within the active sites and the size of adsorbed propane molecule to be the decisive factor governing the reaction route.

Influence of Synthesis Conditions on the Performance of Palladium–Copper Ethanol-to-Butanol Conversion Catalysts

Influence of Synthesis Conditions on the Performance of Palladium–Copper Ethanol-to-Butanol Conversion Catalysts

Effects of Processing Conditions on the Properties of Monoammonium Phosphate Microcapsules with Melamine-Formaldehyde Resin Shell.

To develop monoammonium phosphate (MAP) as a novel acid source for durable intumescent fire retardants (IFR), MAP microcapsules (MCMAPs) containing MAP as the internal core and melamine-formaldehyde (MF) as the external shell were prepared by in situ polymerization in this study. The influences of synthesis conditions (including reaction temperature, polymerization time, and reaction pH value) on the properties of obtained MCMAPs (MAP content, yield, morphologies, and thermal properties) were then investigated systematically. The morphologies, chemical structures, and thermal properties were characterized by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetry analyzer (TGA). The results show that MAP was well encapsulated by MF resin. No microcapsules are obtained at <55 °C or with polymerization times <1 h. Optimal preparation conditions of reaction temperature, polymerization time, and reaction pH value are 75 °C, 3 h, and 5.5, respectively. Those results provide process reference and theoretical basis for preparing MCMAPs and could promote the application of MAP microcapsules in wood flame-retardant materials.

FORMATION OF CRYSTALLINE SiC IN NEAR-SURFACE SILICON LAYERS BY METHOD OF COORDINATED SUBSTITUTION OF ATOMS

In this work, monocrystalline films of silicon carbide were synthesized on the surface of a Si(100) silicon wafer using the method of coordinated substitution of atoms. The films were synthesized at temperatures of 1200 °C and 1300 °C for 20 minutes in a CO gas flow at a pressure of 0.8 Pa. The effect of 1200–1300 °C temperatures on the formation of single- and polycrystalline layers, as well as nanostructured SiC phases in the near-surface region of silicon by the method of atom substitution, is analyzed. The formation of a high-quality crystalline silicon carbide film and the influence of synthesis conditions on the total volume of SiC structural phases, microstructure and nanostructure of the surface are shown. It was found that an increase in temperature from 1200 °C to 1300 °C led to a more intensive formation of silicon carbide and an increase in the number of Si–C bonds by 1.9 times due to an increase in the thickness of the synthesized silicon carbide layer. There is an increase in the proportion of the crystalline phase due to a more intense transformation of the nuclei of nanocrystals into micro- and nanocrystals. Intense processes of penetration of carbon atoms deep into silicon at a temperature of 1300 °C with amorphization of its structure and the formation of Si-C, which can transform into crystalline phases at temperatures above 1300 °C, are assumed. The proportion of the SiC crystalline phase increases to 50.2% of the film volume due to the intensive transformation of nanocrystal nuclei into micro- and nanocrystals. It has been experimentally shown that the formation of various SiC structures on Si (100) occurs in full accordance with the main principles of the method of coordinated substitution of atoms.

Optimizing the synthesis of Ag/γ‐Al2O3 for selective reduction of NOx with C3H6: Experiments and modelling

AbstractAg/γ‐Al2O3 is an effective catalyst for the selective reduction of NOx (SCR) using propylene as a reducing agent. The catalyst performance is greatly influenced by the synthesis procedure. Various methods for synthesis of Ag/γ‐Al2O3 are analyzed, and their performance is examined via packed bed reactor experiments in this work. An optimal one‐pot synthesis method, single‐step sol–gel (SSG) synthesis, is explored systematically. The SSG‐synthesized catalyst shows better performance than those prepared via wet impregnation. The influence of synthesis conditions, specifically pH, on the textural and morphological properties of the SSG‐synthesized Ag/γ‐Al2O3, and therefore the activity for hydrocarbon‐based SCR in a packed‐bed reactor, are analyzed using experiments and simulations. The optimized catalyst demonstrates excellent performance (90% NOx conversion) for NOx reduction under nominal operating conditions with a wide activity temperature window (300–600°C). The catalyst shows good time‐on‐stream performance and is effective at higher inlet oxygen concentrations and space velocities. A global kinetic model, which uses synthesis‐pH‐dependent parameters, is proposed, and its ability to predict the activities of these catalysts is validated.

ДИЗАЙН НАНОЧАСТИЦ ОКСИДОВ ПЕРЕХОДНЫХ МЕТАЛЛОВ С КОНТРОЛИРУЕМОЙ РАЗМЕРНОСТЬЮ

The paper presents generalized experimental data on the influence of synthesis conditions on the structural features of MeO transition metal oxide nanoparticles in a polymer matrix synthesized by chemical condensation. The synthesis process includes the interaction of aqueous solutions of metal salts of varying concentrations with alkalis in the presence of an aqueous solution of the natural polysaccharide arabinogalactan. Controlled growth of oxide nanoparticles was achieved by encapsulation of emerging NPs in a polysaccharide matrix. The structural properties of the obtained samples were analyzed using X-ray diffraction, IR and UV spectroscopy, and TEM and SEM electron microscopy.

Broadband near-infrared luminescence properties of Sc2(MoO4)3:Cr3+ molybdates

The structural and spectroscopic properties of Sc2(MoO4)3 molybdate containing various concentrations of Cr3+ ions were investigated in a temperature range of 80–300 K. The samples were prepared using hydrothermal as well as solid-state reaction methods. The influence of synthesis conditions and the molybdenum source on the structural properties was studied by X-ray diffraction (XRD), IR (infrared), and Raman methods. The optical properties of Sc2(MoO4)3 samples doped with 0.1, 0.5, 1.0, and 2.0 % of Cr3+ ions were investigated. The broadband near-infrared (NIR) luminescence spectra generated from the 4T2 and 2E levels of Cr3+ ions may be attractive for NIR light-emitting diode (LED) applications. Emission decay profiles and the crystal field parameters of Cr3+ ions are discussed. In particular, the mechanism of photoluminescence generation and the thermal quenching path are described in detail.

Influence of synthesis conditions on the physicochemical and electrocatalytic properties of non-stoichiometric Ba2Sr2La2Ti4O12 perovskites

Present work studies the influence of the pretreatment milling media (deionized water (BLTOS-H) and isopropanol (BLTOS-i)) on the surface characteristics, structure, chemical composition and catalytic activity of non-stoichiometric Ba2Sr2La2Ti4O12 perovskites. The IR spectroscopy and XRD analyses shows a difference in the structure and phase composition of the two materials. X-ray photoelectron spectroscopy detects a Ba2+- and La3+-enriched and Sr2+-depleted surface. The BLTOS-i sample appears to exhibit higher specific surface area (SSA) and pore volume in comparison to BLTOS-H. The electrochemical tests showed that BLTOS-H sample have similar behavior to platinum at current densi-ties up to 10 mA cm-2, while BLTOS-i presented highest electrochemical performance among all tested samples over the entire current range.

Ga-Pt supported catalytically active liquid metal solutions (SCALMS) prepared by ultrasonication - influence of synthesis conditions on n-heptane dehydrogenation performance.

Supported catalytically active liquid metal solution (SCALMS) materials represent a recently developed class of heterogeneous catalysts, where the catalytic reaction takes place at the highly dynamic interface of supported liquid alloys. Ga nuggets were dispersed into nano-droplets in propan-2-ol using ultrasonication followed by the addition of Pt in a galvanic displacement reaction - either directly into the Ga/propan-2-ol dispersion (in situ) or consecutively onto the supported Ga droplets (ex situ). The in situ galvanic displacement reaction between Ga and Pt was studied in three different reaction media, namely propan-2-ol, water, and 20 vol% water containing propan-2-ol. TEM investigations reveal that the Ga-Pt reaction in propan-2-ol resulted in the formation of Pt aggregates on top of Ga nano-droplets. In the water/propan-2-ol mixture, the desired incorporation of Pt into the Ga matrix was achieved. The ex situ prepared Ga-Pt SCALMS were tested in n-heptane dehydrogenation. Ga-Pt SCALMS synthesized in pure alcoholic solution showed equal dehydrogenation and cracking activity. Ga-Pt SCALMS prepared in pure water, in contrast, showed mainly cracking activity due to oxidation of Ga droplets. The Ga-Pt SCALMS material prepared in water/propan-2-ol resulted in high activity, n-heptene selectivity of 63%, and only low cracking tendency. This can be attributed to the supported liquid Ga-Pt alloy where Pt atoms are present in the liquid Ga matrix at the highly dynamic catalytic interface.

Influence of Synthesis Conditions on the Structural, Optical, and Electrophysical Properties of TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O Nanocomposites

Nanocomposites based on anodic titanium oxide nanotubes with copper oxide nanoparticles were formed and their structural, optical, and electrophysical properties were studied. Defects in the structure of the samples were identified by electron paramagnetic resonance and it was shown that, as a result of copper oxide deposition, CuO nanoparticles were formed on the surface of nanotubes. It was found that the conductivity of the structure decreases by several orders of magnitude with an increase in the number of deposition cycles. It was shown that this effect could be associated with the formation of TiO2/CuO heterojunctions on the nanotube surface. It was shown for the first time that an increase in the content of copper oxide in TiO2/CuxO nanocomposites was accompanied by a decrease in conductivity and an increase in the number of defects. Keywords: titanium oxide, nanotubes, nanocomposites, copper oxide nanoparticles, defects, conductivity.

The influence of synthesis conditions, oligosaccharide additive and functional silane on the structure and composition of sol–gel silicas

The influence of synthesis conditions, oligosaccharide additive and functional silane on the structure and composition of sol–gel silicas

Green Synthesis of Nano-Zero Valence Iron with Green Tea and It's Implication in Lead Removal.

The nano-zero valence iron (nZVI) via green synthesis for heavy metal remediation has attracted many attentions due to its low-cost, environmental-safety, relative reproductivity, and high stability. However, influence of synthesis conditions on the physiochemical properties of nZVI via green tea extracts and the responding suspensibility, which is required for high reactivity, has not been fully elucidated. In this study, we investigated the zeta potentials, sedimentation and lead (Pb2+) removal capacity of various nZVIs synthesized using green tea extracts. The results showed that the tea extracts extracted at 80oC presented an excellent activity, which contributed to the outstanding suspensibility and reaction activity of nZVI synthesized in a volume ratio of 1:1 (tea extraction versus Fe2+ solution). Thus, the optimized nZVI was successfully prepared with a Pb2+ removal capacity (377.3mg/g), which was seven times stronger than 50.31mg/g of traditional chemical synthesized nZVI.

PHYSICO-CHEMICAL PROPERTIES OF MAGNETITES IN NANOCOMPOSITES ON THE TEXTILE BASES

The article is devoted to investigation of the physico-chemical properties of magnetites in nanocomposites on the textile bases. It studies of the structure and phase composition of nanocomposite materials on the polyamide and viscose textile bases. It is shown that magnetite particles synthesized in textile material with average sizes of 9.4 nm in viscose textile material and 9.7 nm in polyamide textile material. The influence of synthesis conditions on the size of magnetite nanocrystallites in textile material is established.

Influence of Synthesis Conditions on Physicochemical and Photocatalytic Properties of Ag Containing Nanomaterials

Silver (Ag) containing nanomaterials were successfully prepared by varying synthesis conditions to understand the influence of preparation conditions on the physicochemical and photocatalytic properties of these materials. Different analytical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Diffuse reflectance UV-vis spectra (DR UV-vis), X-ray photoelectron spectroscopy (XPS) measurements, and N2-physisorption were used to investigate the physicochemical properties of synthesized Ag containing nanomaterials. The samples (Ag-1 and Ag-2) prepared using AgNO3, NaHCO3, and polyvinylpyrrolidone (PVP) template exhibited pure Ag metal nanorods and nanoparticles; the morphology of Ag metal is influenced by the hydrothermal treatment. The Ag-3 sample prepared without PVP template and calcined at 250 °C showed the presence of a pure Ag2O phase. However, the same sample dried at 50 °C (Ag-4) showed the presence of a pure Ag2CO3 phase. Interestingly, subjecting the sample to hydrothermal treatment (Ag-5) has not resulted in any change in crystal structure, but particle size was increased. All the synthesized Ag containing nanomaterials were used as photocatalysts for p-nitrophenol (p-NP) degradation under visible light irradiation. The Ag-4 sample (pure Ag2CO3 with small crystallite size) exhibited high photocatalytic activity (86% efficiency at pH 10, p-NP concentration of 16 mg L−1, 120 min and catalyst mass of 100 mg) compared to the other synthesized Ag containing nanomaterials. The high photocatalytic activity of the Ag-4 sample is possibly due to the presence of a pure Ag2CO3 crystal structure with nanorod morphology with a low band gap energy of 1.96 eV and relative high surface area.