Initial Reactants Research Articles

Mixed-solvothermal synthesis and applications in sensing for Cu2+ and Fe3+ ions of flowerlike LaVO4:Eu3+ nanostructures

Rare-earth inorganic orthovanadates have been attracting considerable research interest because of their significant luminescent features. In this work, flowerlike LaVO4:Eu3+ nanostructures with strong photoluminescence were successfully synthesized via a solvothermal route at 160°C for 8h in the co-existences of Na2EDTA and CO(NH2)2, employing La(NO3)3 and NH4VO3 as the initial reactants, the water-glycol (water/EG) with the volume ratio of 1/2 as the solvent. XRD analysis showed that the final product belonged to tetragonal LaVO4 phase. It was found that Na2EDTA and CO(NH2)2 were indispensable in the formation of flowerlike LaVO4:Eu3+ nanostructures. The as-obtained flowerlike LaVO4:Eu3+ nanostructures exhibited strong emission peaks in the region of 500⿿700nm under the excitation of 335nm light. Interestingly, the abovementioned strong emission peaks could be quenched by Cu2+ or Fe3+ ions without the interference of other ions, indicating that the present product could be used as an optical sensor for the detection of the Cu2+ and Fe3+ ions in water systems.

Effect of Initial Reactants and Reaction Temperature on Molten Salt Synthesis of CuCo2O4 and Its Sustainable Energy Storage Properties

We have prepared CuCo2O4 using 0.5 M NaNO3 and 0.5 M LiNO3 molten salts at different temperatures (410 and 610 °C) in the air. This was later used as an anode material for LIBs. The morphology, structure, and electrochemical properties of the products were observed using various techniques such as scanning electron microscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller surface and density method, cyclic voltammetry, and galvanostatic cycling tests. The XRD patterns showed a minor CuO phase in addition to the major CuCo2O4 phase in most of the reactant and salt combination. CuCo2O4 prepared using copper sulfate and cobalt sulfate at 610 °C and copper sulfate and cobalt acetate at 410 °C showed the best performance with capacities of 848 mAh g–1 and 882 mAh g–1 and capacity retentions of 93% and 94%, respectively.

Synthesis, structure, and thermal stability of new scheelite-type Pb1−3x□xPr2x(MoO4)1−3x(WO4)3x ceramic materials

Monophasic polycrystalline samples of Pb1−3x□xPr2x(MoO4)1−3x(WO4)3x solid solution with limited homogeneity (0 < x ≤ 0.2222) and cationic vacancies (□) have been prepared by high-temperature annealing of PbMoO4/Pr2(WO4)3 mixtures composed of 40.00 mol% and less of praseodymium tungstate. Initial reactants and obtained ceramic materials were characterized by XRD, simultaneous DTA–TG, IR and UV–Vis–NIR techniques. The X-ray diffraction analysis showed that the monophasic samples crystallize in a tetragonal symmetry, with space group I4 1 /a (a scheelite-type structure), and PbMoO4 is a matrix of Pb1−3x□xPr2x(MoO4)1−3x(WO4)3x solid solution. Thermal stability of samples under study strongly depends on concentration of Pr3+ ions. The Pb0.9286□0.0238Pr0.0476(MoO4)0.9286(WO4)0.0714 solid solution (x = 0.0238) shows the highest melting point (1055 °C), and this value is slightly higher than the melting point of PbMoO4 (1040 °C). Lead molybdate and samples of Pb1−3x□xPr2x(MoO4)1−3x(WO4)3x solid solution are insulators having indirect band gap E g > 3 eV. The observed band gap of monophasic samples shows a nonlinear variation with a change of Pr3+ ions concentration in the scheelite framework.

Comparative study on the effects of nitrogen and carbon dioxide on methane/air flames

The measurement of flame temperature profile and flame computation were conducted to analyze the effects of carbon dioxide and nitrogen dilution on methane/air flames. Results indicated that carbon dioxide addition shows more significant effects on the thermal properties of flame, except for flame thickness. Flame kinetic analyses were implemented for the heat release of individual reaction. It is suggested that the heat release contribution of dominant reaction is primarily affected by flame stoichiometry, while the dilution shows weak effect. The concentrations of reactive species play important influences on the progress rate of reaction. The peak product of reactive species concentrations of the dominant reactions could be approximated by an exponent expression of the concentration of initial reactants and dilution rate, and a greater exponential index was obtained for the flames with carbon dioxide addition. The emission indices and combustion efficiency were evaluated to assess the profit in NO suppression and the loss in combustion deterioration. Results indicated that the profit-loss ratio is influenced by both flame equivalence ratio and the component of diluent gas. For rich methane/air flame, nitrogen dilution shows a greater value, while a larger benefit is obtained for stoichiometric flame diluted by carbon dioxide.

Синтез нового сложного бората KBaSm(BO3)2

A novel compound containing three cation alkali, alkali earth, rare earth orthoborate KBaSm(BO3)2 was synthesized by using two-step solid-state method. Results of powder X-ray diffraction analysis (XRD) and FTIR spectroscopy showed that this compound is isostructural with known compounds KBaY(BO3)2 [1] and KBaTbB2O6 [2] and refers to trigonal crystal system (RǮm space group with unit cell parameters of crystalline lattice а=5,4845(10) A, с=18,135(13), Z=3). KBaSm(BO3)2 was obtained at a temperature of 825°C from initial reactants: samarium (III) oxide, barium and potassium carbonates and boric acid. Among KBaSm(BO3)2 – KBaTb(BO3)2 – KBaY (BO3)2 observed a regular linear variation of unit cell parameters, as well as regular shift of the bands in the IR spectra, depending on the size of the rare earth cation.

Application of ultrasound to the synthesis of a new nanostructured Mn(II) supramolecular compound: A precursor for γ-Mn2O3 nanoparticles

A new nanostructured Mn(II) supramolecular compound [Mn(hpydcH2)2(H2O)4] (1) (hpydcH3=4-hydroxy-2,6-pyridinedicarboxylic acid) has been synthesized using a sonochemical process. The structure of compound 1 was determined by single crystal X-ray diffraction and it was revealed that each hpydcH2− anionic ligand has been coordinated to Mn(II) ion in a novel monodentate fashion leaving another functional carboxylic acid group intact. Compound 1 was also characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analysis. Thermal stability of compound 1 was studied by thermal gravimetric (TG) analysis and compared to that of its crystalline analogue. Subsequently, the role of concentration of the initial reactants on the size of nanostructures of compound 1, has been investigated. Compound 1 was proved to be a precursor for γ-Mn2O3 nanoparticles.

Experimental and Kinetic Study of Esterification of Acrylic Acid with Ethanol Using Homogeneous Catalyst

Abstract Esterification of acrylic acid with ethanol, catalyzed by sulfuric acid has been carried out in stirred batch reactor under atmospheric pressure. Different parameters such as effect of initial molar ratios of the reactants, effect of catalyst concentration, initial water and effect of temperature has been studied in the batch reactor. Different catalyst loading system (1–3 vol%), reaction temperatures (50–70 °C), initial reactants molar ratio (1:1–1:3) and water concentration in feed (0–20 vol%) was used in the reaction system. The temperature dependence is exponential and expressed by Arrhenius type of relationship. Kinetics parameters such as equilibrium constant, rate constants, activation energy and reaction enthalpy and entropy were estimated by experimental data. The rate equation has a remarkable fit to the data and was able to describe the behavior of the system at various reaction temperatures. Hydrochloric acid (HCl) and hydro iodic acid (HI) were also compared with sulphuric acid as catalyst for esterification of acrylic acid with ethanol. Sulphuric acid was found to be more efficient catalyst for esterification as it induces the maximum conversion of acrylic acid.

A global pathway selection algorithm for the reduction of detailed chemical kinetic mechanisms

A Global Pathway Selection (GPS) algorithm for the reduction of detailed kinetic mechanisms is proposed and validated. The approach consists of (1) the construction of element flux graphs for each considered element from the simulation data obtained using detailed chemical mechanisms, (2) the selection of important species that act as hubs that transfer significant element flux, and (3) the subsequent identification of the global pathway for each hub species by searching a certain number of shortest paths with the constructed element flux graphs from the initial reactants to the final products through the considered hub species. The skeletal mechanism is then obtained by removing the species and reactions that are not important to any identified global pathways. Validations are performed to generate skeletal mechanisms for the combustion of two fuels: n-dodecane, and the mixture of toluene, iso-octane, and n-heptane. For both cases, a series of mechanisms are generated using GPS, and the maximum error of ignition delays is similar or smaller comparing to the skeletal mechanisms generated using Path Flux Analysis method (Sun et al., 2010) with similar number of species. GPS is further compared with two methods using sensitivity analysis, which is usually effective but time consuming. By comparing simulation results of ignition delay, perfect stirred reactor (PSR) temperature, and laminar flame speed over a wide range of operating conditions, it is observed that a 35-species skeletal mechanism generated by GPS for n-dodecane shows similar overall accuracy compared with the 31-species skeletal mechanism obtained by Direct Relation Graph Aided Sensitivity Analysis (Vie et al., 2015). Further validation is conducted for the combustion of the mixture of toluene, n-heptane and iso-octane. A 276-species mechanism generated using DRG with error propagation followed by sensitivity analysis and reaction elimination (Niemeyer et al., 2014) shows larger errors for PSR temperature and ignition delay with fuel composition different from the raw database. However these errors can be reduced significantly if GPS-generated mechanism of similar size is tested.

DFT simulations and microkinetic modelling of 1-pentyne hydrogenation on Cu20 model catalysts

Adsorption and dissociation of H2 and hydrogenation of 1-pentyne on neutral and anionic Cu20 clusters have been investigated using the density functional theory and microkinetic modelling. Molecular adsorption of H2 is found to occur strictly at atop sites. The H2 dimer is activated upon adsorption, and the dissociation occurs with moderate energy barriers. The dissociated H atoms reside preferentially on 3-fold face and 2-fold edge sites. Based on these results, the reaction paths leading to the partial and total hydrogenation of 1-pentyne have been studied step-by-step. The results suggest that copper clusters can display selective activity on the hydrogenation of alkyne and alkene molecules. The hydrogenated products are more stable than the corresponding initial reactants following an energetic staircase with the number of added H atoms. Stable semi-hydrogenated intermediates are formed before the partial (1-pentene) and total (pentane) hydrogenation stages of 1-pentyne. The microkinetic model analysis shows that C5H10 is the dominant product. Increasing the reactants (C5H8/H2) ratio enhances the formation of products (C5H10 and C5H12).

Preparation of high-porosity TiOxCy powders from a single templating carbon source

TiOxCy powders with tunable composition and high specific surface areas have been synthesized by impregnation of porous carbon black with titanium isopropoxide and firing in argon at 1400°C. The compositional ratio of the individual ions can be controlled over a broad compositional range by tuning the stoichiometric ratio of the initial reactants. The resultant powders show no detectable oxide or carbonaceous impurity phases. The powders retain artefacts of the porosity of the templating carbon and yield specific surface areas as high as 108m2g−1, which makes them useful in catalytic/electrocatalytic applications.

New scheelite-type Cd1−3x⌷xGd2x(MoO4)1−3x(WO4)3x ceramics – their structure, thermal and magnetic properties

Polycrystalline samples of scheelite-type Cd1−3x⌷xGd2x(MoO4)1−3x(WO4)3x solid solution with limited homogeneity (0<x≤0.25) and cationic vacancies (denoted as ⌷) have successfully prepared by a high-temperature annealing of CdMoO4/Gd2(WO4)3 mixtures composed of 50.00mol% and less of gadolinium tungstate. Initial reactants and obtained ceramic materials were characterized by XRD, simultaneous DTA–TG, and SEM techniques. A phase diagram of the pseudobinary CdMoO4–Gd2(WO4)3 system was constructed. The eutectic point corresponds to 1404±5K and ~70.00mol% of gadolinium tungstate in an initial CdMoO4/Gd2(WO4)3 mixture. With decreasing of Gd3+ content in a CdMoO4 framework, the melting point of Cd1−3x⌷xGd2x(MoO4)1−3x(WO4)3x increases from 1406 (x=0.25) to 1419K (x=0.0833), and next decreases to 1408K (x=0). EPR method was used to identify paramagnetic Gd3+ centers in Cd1−3x⌷xGd2x(MoO4)1−3x(WO4)3x for different values of x parameter as well as to select biphasic samples containing both Cd0.25⌷0.25Gd0.50(MoO4)0.25(WO4)0.75 and Gd2(WO4)3.

Shape-controlled synthesis and performance comparison of Ni2P nanostructures

In this paper, a facile precursor phosphidation route was designed for morphology controlled synthesis of Ni2P nanostructures, employing NiCl2 and NaH2PO2 as the initial reactants in the presence of polyvinylpyrrolidone (PVP) and hexamethylenetetramine (HMT). Experiments showed that under the same hydrothermal conditions, NiHPO3·H2O nanorods and Ni nanospheres were separately obtained via only changing the original amount of HMT. The as-obtained NiHPO3·H2O nanorods and Ni nanospheres could be used as the precursors in low-temperature phosphidation reactions under a N2 atmosphere. Under the same phosphidation conditions, Ni2P nanorods and nanospheres were formed, respectively. The precursor and the final products were characterized by powder X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical performance and the catalytic properties of the Ni2P nanorods and nanospheres were investigated. It was found that the as-obtained Ni2P nanostructures displayed marked shape-dependent properties: the Ni2P nanorods presented better electrochemical performance, such as higher specific capacitance and more stable cycle features, and stronger catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in an excess NaBH4 solution than the Ni2P nanospheres.

Mechanism of zeolites crystal growth: new findings and open questions

This paper will review the crystal growth mechanism of zeolites and discuss some of the latest findings in this field. A great effort has been dedicated in recent years to improving the fundamental understanding of zeolite crystal growth during the synthesis process, with the overall aim of increasing control over the zeolite properties and structure. The latest studies on zeolite crystallization in colloidal (clear) suspensions, prepared by addition of organic and inorganic structural directing agents, in comparison to traditional gel synthesis and seed-approach will be discussed. Further understanding of the imperative dependence of zeolite crystallization kinetics' on the nature and mode of mixing of the initial reactants, leading to the formation of amorphous particles, intermediates, and final crystalline zeolites will be presented.

Regularities in the consumption of the initial reactants in various kinetic regimes

Using hydrogen oxidation as an example, it is demonstrated that, when gas ignition is prevented by means of inhibition, there is practically no consumption of the initial reactants because reaction chains do not form for lack of time and the rates of intermolecular reactions are insignificant. When the propagating flame and detonation wave are partially suppressed, the inhibitor is consumed only in chain termination reactions involving reactive intermediate species. Oxygen is additionally consumed in its reactions with products of incomplete inhibitor conversion.

Kinetic parameters of red pepper waste as biomass to solid biofuel

This work aimed to study the kinetic of thermal degradation of red pepper waste as solid biofuel to bioenergy production. The thermal degradation experiments were conducted at three heating rates, 5°C/min, 7.5°C/min and 10°C/min in a thermogravimetric analyzer and oxidative atmosphere. The kinetic analysis was carried out applying the isoconversional model of Ozawa–Flynn–Wall. The activation energy was considerate low and varied 29.49–147.25kJ/mol. The enthalpies revealed the energy difference between the reagent and the activated complex agreed with activation energies, the values of the pre-exponential factor indicated empirical first order reactions, Gibbs free energy varied from 71.77kJ/mol to 207.03kJ/mol and the changes of entropies had negative values, indicating that the degree of disorder of products formed through bond dissociations was lower than initial reactants. The calorific value was 19.5MJ/kg, considered a relevant result for bioenergy production.

Sonochemical synthesis of a new nano-sized cerium(III) supramolecular compound; Precursor for nanoceria

Using a sonochemical method, nanoparticles of a new Ce(III) supramolecular compound, (NAMH+)2[Ce4(pydc)6(pydcH)2(H2O)8]·8H2O (1), (H2pydc=2,6-pyridinedicarboxylic acid, NAM=nicotinamide), have been synthesized. Compound 1 was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analyses, and its structure was determined by X-ray crystallography. It has been revealed that its structure consists of tetra-nuclear building units that extend to a 3D supramolecular network via non-covalent interactions mainly hydrogen bonding. The thermal stability of complex 1 both for its crystals and nanostructures has been studied by the thermal gravimetric (TG) method and compared with each other. The role of ultrasound irradiation power and the concentration of initial reactants on the size and morphology of the nano-structured complex 1, has been investigated. Ceria nanoparticles were obtained upon the calcination of complex 1 at 800°C under atmospheric air. Furthermore, the fluorescent properties of complex 1 at room temperature were studied.

EFFECT OF CU-CO MIXED METAL OXIDES ON THE COMBUSTION OF PSAN-HTPB BASED SOLID PROPELLANTS

Composite propellants based on ammonium perchlorate (AP) as oxidizer are state-of-the-art. However, global environmental impact restricts AP-based propellants because of their high chlorine exhaust. Therefore, efforts are on to innovate propellants with clean exhaust. Ammonium nitrate (AN) has, thus, regained importance in the field of propellants and explosives, more specifically in insensitive formulations, because of its clean burning and low hazard. However, the stumbling block for the application of AN - as solid propellant oxidizer has been its dimensional instability caused by phase transformation which results in increase of volume and porosity of the propellant grain. This can be overcome by the use of phase stabilized ammonium nitrate (PSAN). In the present study AN phase stabilized by incorporating 10% KN to prepare composite solid propellant. Copper-Cobalt mixed metal oxides have been synthesized via citric acid complexing method. Three different catalysts were prepared with different Cu-Co molar ratios 1, 0.5 And 2 in the initial reactants. The synthesized catalysts were then added to the PSANHTPB(Phase Stabilized Ammonium Nitrate- Hydroxyl Terminated Poly-Butadiene) composite formulations. These propellant samples were subjected to burn rate measurement in a Crawford High Pressure Strand Burner and thermal degradation studies in Simultaneous Thermal Analyzer (STA). The thermal decomposition and burn rate of the propellant is observed maximum on the addition of Copper-Cobalt mixed metal oxide catalyst with molar ratio 2. A total of six propellant samples catalyzed and noncatalyzed and one preheated virgin sample were undertaken for the above analysis and results obtained are discussed. It has been observed that except the propellant sample with Cu-Co-III and virgin propellant where PSAN was prepared by solid mixing, other propellant samples were hard to burn.

Polyfunctional imidazoles: XI. Reaction of 1-aryl-4-chloro-5-(2-nitrovinyl)-1H-imidazoles with nonstabilized azomethine ylides. Synthesis of (1-aryl-4-chloro-1H-imidazol-5-yl)-substituted nitropyrrolidines and nitropyrrolizines

1-Aryl-4-chloro-5-(2-nitrovinyl)-1H-imidazoles reacted with azomethine ylide generated from sarcosine and formaldehyde to afford 1-aryl-4-chloro-5-(4-nitropyrrolidin-3-yl)-1H-imidazoles. The reaction of 1-aryl-4-chloro-5-(2-nitrovinyl)-1H-imidazoles with azomethine ylide generated from L-proline and isatin gave 2′-(1-aryl-4-chloro-1H-imidazol-5-yl)-1′-nitro-1′,2′,5′,6′,7′,7a′-octahydrospiro[indole-3,3′-pyrrolizin]-2(1H)-ones with high regioselectivity. The latter reaction was analyzed by calculating orbital coefficients and global and molecular reactivity indices of the dipole and dipolarophile, as well as the energies of the initial reactants, transition states, and products.

Properties of reactive Al:Ni compacts fabricated by radial forging of elemental and alloy powders

We explore rotary swaging of powders into solid compacts as an inexpensive means of producing reactive materials with refined microstructures and improved properties. Rotary swaging is a cold forging process that reduces the diameter of tubes, and in this study the tubes are packed with reactive combinations of elemental and alloy powders. The diameter reductions create a nearly fully dense compact from the powders and also reduce the average reactant spacing through plastic deformation. The extent of diameter reduction controls the microstructural refinement, observed through cross-sectional imaging. We correlate the observed changes in microstructure with reaction properties that are characterized using differential scanning calorimetry (DSC), hot-plate ignition studies, and velocity measurements. Exothermic peaks in DSC scans all shift to lower onset temperatures; hot plate ignition temperatures decrease; and reaction velocities rise as the degree of swaging is increased. We vary the shape of the initial reactants by substituting Ni flakes for Ni powders and find no improvement in microstructure or reaction properties, due to clumping of the Ni flakes during the initial compaction steps. We also vary chemistry by substituting Al-Mg alloy powders for Al powders and find that the alloy powders yield lower DSC exothermic peak temperatures, lower ignition temperatures, and higher reaction velocities compared to similar compacts with pure Al powders. This combination of results suggests that rotary swaging is an effective technique for producing reactive materials at low cost.

Biophysical characterization data on Aβ soluble oligomers produced through a method enabling prolonged oligomer stability and biological buffer conditions.

The data here consists of time-dependent experimental parameters from chemical and biophysical methods used to characterize Aβ monomeric reactants as well as soluble oligomer and amyloid fibril products from a slow (3–4 week) assembly reaction under biologically-relevant solvent conditions. The data of this reaction are both of a qualitative and quantitative nature, including gel images from chemical cross-linking and Western blots, fractional solubility, thioflavin T binding, size exclusion chromatograms, transmission electron microscopy images, circular dichroism spectra, and fluorescence resonance energy transfer efficiencies of donor–acceptor pair labels in the Aβ chain. This data enables future efforts to produce the initial monomer and eventual soluble oligomer and amyloid fibril states by providing reference benchmarks of these states pertaining to physical properties (solubility), ligand-binding (thioflavin T binding), mesoscopic structure (electron microscopy, size exclusion chromatography, cross-linking products, SDS and native gels) and molecular structure (circular dichroism, FRET donor-acceptor distance).Aβ1-40 soluble oligomers are produced that are suitable for biophysical studies requiring sufficient transient stability to exist in their “native” conformation in biological phosphate-saline buffers for extended periods of time. The production involves an initial preparation of highly monomeric Aβ in a phosphate saline buffer that transitions to fibrils and oligomers through time incubation alone, without added detergents or non-aqueous chemicals. This criteria ensures that the only difference between initial monomeric Aβ reactant and subsequent Aβ oligomer products is their degree of peptide assembly. A number of chemical and biophysical methods were used to characterize the monomeric reactants and soluble oligomer and amyloid fibril products, including chemical cross-linking, Western blots, fraction solubility, thioflvain T binding, size exclusion chromatography, transmission electron micrscopy, circular dichroism spectroscopy, and fluorescence resonance energy transfer.