Effects Of Reactant Concentration Research Articles

Synthesis of monodisperse spherical nano alumina by hydrothermal method and its mechanism study

Ultrafine alumina is widely used in advanced manufacturing industry, and its form, size and dispersion have important effects on its physicochemical properties and application characteristics. However, the superfine monodisperse spherical alumina is difficult to obtain in the actual synthesis process because the alumina precursor grain grows too fast and is easy to agglomerate. In this work, ammonium sulfate was added as the synthetic raw material to improve its dispersity. When the concentration reached 40% of the aluminum source concentration, the isometric alumina precursor with a particle size of about 35 nm was obtained under the condition of rapid cooling. The influence of ammonium sulfate on the chemical structure of the precursor was determined by Fourier Transform Infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of reactant concentration and reaction temperature on the morphology, particle size and dispersion of the precursor as well as its mechanism were discussed in detail, and the optimal synthesis method of the nano alumina precursor was obtained. Finally, two kinds of precursors were calcined at different temperatures to obtain the equiaxed γ-Al2O3 with a particle size of 20 nm and the monodisperse spherical α-Al2O3 with a particle size of 133 nm, respectively. In this study, nano alumina precursors were synthesized by a simple and reliable method, and monodisperse ultra-fine alumina with different particle size morphologies were obtained, which has great application prospects in precision polishing, special ceramic manufacturing and 3D printing.

Preparation and Degradation Performance Study of P(AM/GG/PEGDA) Nanocomposite Self-Degradation Gel Plugging Material.

Lost circulation is a world-class problem, and the contradiction between plugging and unplugging in reservoirs is a problem that needs to be solved urgently. The traditional LCM is not suitable for reservoirs and the complex subsequent operations. Currently, a self-degrading plugging material is proposed. In this paper, a new self-degradation plugging material, CKS-DPPG, was prepared by AM, GG, nano silica, and PEGDA. The effects of reactant concentration, pH, mineralization, etc., on the swelling and degradation performance of CKS-DPPG were investigated. The plugging capacity was tested by fracture plugging equipment, and the mechanism of self-degradation was revealed. The results show that the CKS-DPPG reached a 50% degradation rate in 54 h and complete degradation in 106 h at 80 °C and pH = 8. Low temperatures, high mineralization, and weak alkaline conditions prolong the complete degradation time of CKS-DPPG, which facilitates subsequent operations. The simulation of the 3 mm opening fracture plugging experiment showed that the pressure-bearing capacity reached 6.85 MPa and that a 0.16 MPa pressure difference could unplug after degradation. The ester bond of PEGDA is hydrolyzed under high-temperature conditions, and the spatial three-dimensional structure of CKS-DPPG becomes linear. The CKS-DPPG can effectively reduce subsequent unplugging operations and lower production costs.

Synthesis and electrocatalytic performance for hydrogen evolution reaction of ReSe2 nanosheets

Two-dimensional ReSe2 as catalyst for hydrogen evolution reaction (HER) has attracted attention due to its unique 1T′ structure and anisotropic physical properties in base planes. In this work, ReSe2 nanosheets were directly prepared on a carbon cloth (CC) substrate by hydrothermal synthesis technology. The reaction solution was prepared using ammonium perrhenium (NH4ReO4), sodium borohydride (NaBH4), selenium (Se) powder and deionized water. The effects of reactant concentrations and reaction time on the catalytic properties of the ReSe2 /CC for HER were researched. When the concentration of NH4ReO4, Se and NaBH4 is 0.05 M, 0.065 M and 0.200 M, ReSe2/CC shows the optimal HER catalytic properties with overpotential of 197 mV at current density of 10mAcm-2 , Tafel slope of 142 mVdec-1 and ECSA of 325cm2 . The formation mechanism and working mechanism in the HER process of ReSe2/CC are discussed.

Self-assembly assisted by microdroplet templates confinement for the preparation of ultramixed composite energetic particulates

Restricted by the macroscopic spatial scale conditions in traditional preparation methods, the improvement of delay precision of the delay composition gradually arrives at the bottleneck. Therefore, a microdroplet-confined coupling polymer self-assembly theory based on microfluidics was proposed to prepare ultramixed self-assembled composite energetic material particulates in order to make a breakthrough in its delay precision. Taking boron (B)/barium chromate (BaCrO4) delay composition as the research object, nano-BaCrO4 particles were prepared and microdroplet templates were generated by using the micromixing and microdispersing reaction systems respectively. With the excellent mixing efficiency of the micromixing reaction system, the effect of reactant concentration and temperature on crystal morphology and particle size of BaCrO4 was investigated, and the spectral response of BaCrO4 particles was analyzed on-line by using an on-line UV–vis spectrophotometer. The results indicated that the reactant concentration exerted a great influence on crystal morphology and particle size of BaCrO4, and the characteristic absorption peak of BaCrO4 was red-shifted regularly with the decrease of crystal thickness at low reactant concentration. Microdroplet templates for self-assembly of B/BaCrO4 nano-composite particles were generated by using a microdispersing reaction system, and the self-assembled B/BaCrO4 particulates were prepared. The particulates were characterized by thermal analysis and the delay precision was measured. The results exhibited that the composite energetic particulates with ultra-homogeneous mixing, excellent combustion performance and high delay precision were prepared. In summary, in this study, ultramixed self-assembled B/BaCrO4 particulates with high delay precision were prepared based on microfluidics, which can provide a novel technology and method for the preparation and mixing of other composites.

In-situ synthesis of KAUST-7 membranes from fluorinated molecular building block for H2/CO2 separation

A well-intergrown and defect-free tubular KAUST-7 membrane was fabricated via in-situ synthesis assisted by fluorinated molecular building block using green solvent of water on coarse asymmetric α-Al2O3 tubes. The strategy averted the serious corrosion of high-concentration hydrofluoric acid (HF) to α-Al2O3 supports due to the substitution of HF with the pre-synthesized NiNbOF5, overcoming the difficulty of serious corrosion to supports compared to traditional one-pot synthesis. The pH manipulation of synthesis solution is proved crucial to the fabrication of defect-free KAUST-7 membranes. In addition, effects of reactant concentration, crystallization temperature and reaction solvents on the morphology and separation performance of KAUST-7 membrane were investigated. The optimized KAUST-7 membrane M4 exhibited a H2 perm-selectivity of 17.7 over CO2 for H2/CO2 binary mixture with a H2 permeance of 2.2 × 10−7 mol m−2 s−1 Pa−1 at 25 °C and 1 bar, while the H2/CO2 separation factor just had a slight decrease when test temperature increased to 120 °C. The formation mechanism of KAUST-7 membranes via in-situ method in this work was investigated by exposing a bare α-Al2O3 tube into NiNbOF5 aqueous solution at the pH of 4.0 at 130 °C for 12 h. XPS and FT-IR observations revealed the formation of AlFxOy or AlFx species, which were deduced to be acted as linkers to connect with 2D Ni (II)-pyrazine layers, promoting the heterogeneous nucleation of KAUST-7 crystals on the surface of Al2O3 support.

Enzyme Induced Calcite Precipitation (EICP) for Engineering Application by Using Plant Based Biomaterials

This research investigated the effect of reactant concentrations, reaction medium, urease enzyme source, and calcium source on the precipitation rate of calcium carbonate (CaCO3). This project is aiming to develop a biochemical reaction by using Enzyme Induced Calcite Precipitation (EICP) technique. This new technique would help in replacing the traditional cementation for the dune sand stabilization and promise an environmentally friendly and sustainable approach in the field of construction materials. Jack beans and soybeans were employed as a substrate to catalyze the urea hydrolysis in the study. The sources of calcium used in the experiments were calcium chloride (CaCl2), eggshell and sesame. In addition, both seawater and distilled water were used as a reaction medium to distinguish the effect on calcium carbonate precipitation. The experiments showed that using sesame at a concentration of 4.5 g, 5 g of urea and 6 g of jack bean at 60 mL of distilled water, is the best reaction conditions to precipitate 100.288 g of calcium carbonate. Further, the results indicated that the calcium carbonate precipitation enhanced by using 5 g of urea, 5 g of CaCl2 and 5 g of soybean at 50 mL of seawater. The precipitation amount was 25.593 g. These results provide a useful way for the bio cementation by following the EICP technique to address the issues of environment friendly practice of ground improvement.

Experimental Investigation on Green Synthesis of FeNPs using <i>Azadirachta indica</i> Leaves

In nanotechnology, developing an environmentally friendly method for synthesizing iron nanoparticles (FeNPs) is an important aspect. According to recent studies, the use of secondary metabolites from plant leaf extract has recently emerged as a novel technology for synthesizing various nanoparticles. The leaf extract of Azadirachta indica was used to synthesize iron nanoparticles in this research. The effects of reactant concentrations, reaction temperature, and pH of the solution on the synthesis process of iron nanoparticles were studied. A UV-Visible Spectrophotometer that analyzed absorbance spectra was used to monitor the formation of iron nanoparticles in dispersion. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) characterized the morphology of iron nanoparticles, and results reveal the particles are spherical with an average size of 48 nm. The optimum conditions for synthesis are as follows: 15 % leaf extract, [FeCl3] = 1.0 mM, pH 6.0, and temperature 60 °C. The FTIR technique confirms that plant biomolecules induce the reduction of Fe3+ ions to FeNPs and act as a capping and stabilizing agent. Therefore, they have good stability for various applications.

Preparation of antimicrobial activated carbon fiber by loading with silver nanoparticles

Antibacterial activated carbon fiber (ACF) is required in water treatment because bacteria may accumulate and reproduce on the biocompatible ACF. In this paper, nano silver particles were loaded on ACF by vacuum impregnation and green reduction method, and the effects of reaction concentration, temperature and time were investigated, and the structure, antibacterial activities and adsorption performance of ACF were measured. The silver loaded ACF (prepared at 0.1 mmol/L of AgNO3, 50 °C for 1 h) shows high silver loading (0.13%), low Ag dissolution, excellent antibacterial activity, and wonderful adsorption capacity for phenol (290 mg/g, about 1.2 times that of pristine ACF), indicating great potential in water treatment applications. This work provides a green and economical method for the preparation of Ag@ACF.

Modeling a Biorefinery: Converting Pineapple Waste to Bioproducts and Biofuel

Many students may not be aware that renewable biological materials can be converted into multiple bioproducts and biofuels using a biorefinery process, a more sustainable alternative to conventional crude oil refineries. By using waste from pineapple, a plant material that most students are familiar with, a biorefinery can be modeled to demonstrate the benefits of a circular bioeconomy. Pineapple waste consists of the peel, core, and leaves that are often discarded after the fruit is processed for consumption. These “leftovers” or “residues” are rich sources of sugars and lignocellulosic biomass, which can be converted to value-added bioproducts and biofuel. In this article, the development and implementation of a high school laboratory activity that simulates a pineapple biorefinery is described. It was field tested with an Environmental Science class, in which students converted pineapple leaves into paper, and they fermented the sugars from the core and peel into bioethanol for fuel. Students investigated how different process variables influenced the tensile strength of their paper and the quantity of bioethanol produced. This lab introduces students to the potential of a circular bioeconomy and challenges them to integrate prior chemistry and biology knowledge to generate solutions to real-world sustainability problems. It can be used in chemistry classes to demonstrate stoichiometry, chemical reaction yield, chemical bonds, and the effect of reactant concentration on the rate of product formation.

Preparation and characterization of MnTiO3, FeTiO3, and CoTiO3 nanoparticles and investigation various applications: a review

The fabrication of nanoceramices and nanomaterials with desirable morphology, structure, and particle size is one of the most important fields in the nanoscience. In order to achieve this goal, the sol–gel method is one of the most applicable methods which allow us to attain desirable structures by changing some parameters. This review focuses on the synthesis of some MTiO3 (M = transition metals) by different routs owing to the technological importance of this group of materials. It also investigates different properties of such materials including photocatalytic, dielectric, optical and electrocatalytic behaviors. The conventional titanates of MnTiO3, FeTiO3, and CoTiO3 are introduced and furthermore, their syntheses have been clarified by proposing a related mechanism. The effects of reactants concentration, time and temperature reaction, surfactant, M2+ and Ti4+ sources, etc. on the particle size, morphology, and some properties of the obtained nanomaterials have been investigated. The size and morphology of the as-synthesized samples are studied by the X-ray diffraction, scanning electron microscopy and transmission electron microscopy images. The optical, magnetic, and photocatalytic properties of the MTiO3 are studied as well.

Size and shape tailored sol-gel synthesis and characterization of lanthanum phosphate (LaPO4) nanoparticles

Size and shape tailored stoichiometric lanthanum phosphate (LaPO4) nanoparticles were synthesized through an aqueous sol-gel technique. The effect of reactant concentration on the shape and size of nanoparticles was investigated. Shape evolution of nanoparticles was explained by the spherical diffusion growth mechanism. It was observed that by reducing the reactant concentration from high (100mol/m3) to very low (0.125mol/m3), the morphology of nanoparticles gradually changed from long nanorods to nanospheres. X-Ray diffraction (XRD) results indicate that hexagonal-to-monoclinic phase transformation initiated at lower temperatures in nanospheres compared to the nanorods. Nitrogen-adsorption measurements showed that although all samples are mesoporous, the nanorods synthesized at high concentrated solution had a markedly more specific surface area (e.g. at 100mol/m3 reactant concentration, surface area was 114m2/g). The dispersion stability of LaPO4 nanoparticles in aqueous solutions in a wide range of pH (1−12) was evaluated. Dynamic light scattering (DLS) analysis indicated that the sols with pH~2 and pH~10.3 with the corresponding zeta potentials of +40 and −32mv, provided the highest stability. Zeta-potential measurements of the suspensions revealed an isoelectric point (IEP) at pH~7.5.

Structure–property relationships of the thermal gelation of partially hydrolyzed polyacrylamide/polyethylenimine mixtures in a semidilute regime

In this work, the structure–property relationships of the thermal gelation of partially hydrolyzed polyacrylamide (PHPA) and polyethylenimine (PEI) mixtures were investigated under realistic conditions of temperature (80 °C) and salinity (total dissolved solids = 3.4 g/l) of the Algerian reservoir (Tin Fouye Tabankort) prior to a conformance control application. The reactants were characterized with regard to their hydrolysis degree or branching degree using 13C-nuclear magnetic resonance, and viscosity–average molecular weights ($$ \bar{M}_{\text{v}} $$) were estimated using the Mark–Houwink equation and intrinsic viscosities measurements. The polymers had molecular weights that varied from 5 to 10 × 106 g/mol for PHPAs with initial hydrolysis degrees between 6 and 20 mol%, while the molecular weights of the PEI were between 2 and 67 × 104 g/mol with a constant branching degree of 57–59. Consequently, the effect of steady shear on the gelation time was investigated followed by the effect of reactant concentrations, the polymer and cross-linker molecular weights, the polymer’s hydrolysis degree, the temperature and the initial pH. All experiments were conducted in a semidilute concentration regime while maintaining practical initial gelant viscosities. As a result, the gelation time was found to decrease with reactant concentrations, molecular weights and temperature (Ea = 62 kJ/mol) and to increase with hydrolysis degree.

Composite soft template-assisted construction of a flower-like β-Bi2O3/Bi2O2CO3 heterojunction photocatalyst for the enhanced simulated sunlight photocatalytic degradation of tetracycline

A three-dimensional (3D) flower-like β-Bi2O3/Bi2O2CO3 heterojunction photocatalyst was synthesized via decomposition of the precursor fabricated using a composite soft template, which was constructed from dl-aspartic acid and nonionic amphiphilic triblock copolymer (Pluronic F127). The morphology, phase structure, composition, effect of reactant concentration, and possible formation mechanism were systematically studied. The results showed that dl-aspartic acid was chosen as the coordination- and structure-directing agent, while F127 was used as the capping agent during preparation of the precursor. The as-prepared flower-like β-Bi2O3/Bi2O2CO3 heterojunction obtained after calcination of the self-sacrificing precursor at 290 °C showed excellent photocatalytic performance in the degradation of the refractory colorless antibiotic agent tetracycline (TC) under simulated sunlight irradiation, with 98.79% TC degradation being achieved within 60 min of irradiation. This excellent photocatalytic performance was attributed to the narrow band gap, heterojunction structure, and 3D hierarchical structure. The results further revealed that photogenerated holes (h+) and hydroxyl radicals (•OH) dominated the photocatalytic process. Furthermore, the β-Bi2O3/Bi2O2CO3 heterojunction catalyst was not photocorroded after six consecutive cycles, suggesting an excellent photostability.

Synthetic Method for Preparing High-Performance Europium-Doped Up-Conversion Ceramic Material Precursor

In this paper, a direct co-precipitation method was used to prepare antimony-doped calcium fluoride nanopowders (NPs). The effects of reaction concentration, reaction medium and lanthanum doping on the properties of calcium fluoride NPs were investigatedviaa control variable method and the best preparation conditions was identified. The structural analysis of the powder materials prepared in this work were carried out by XRD, SEM, ICP and other test methods. By analyzing the experimental data, we found that the best performance of Eu-doped CaF2NPs can be acquired under the reaction concentration of 1 mol/L in aqueous solution. In the same time, the NPs possess a high degree of dispersion with an average diameter of 22 nm, which is beneficial to the preparation of transparent Eu3+: CaF2ceramics with excellent up-conversion luminescence. The results show that the grain size, the crystallinity of the NPs and the amount of Eu infiltration have a decreasing tendency with the increasing reaction concentration, while the degree of agglomeration of the NPs can be enhanced by increasing the reaction concentration.

The Effects of Reactant Concentration and Air Flow Rate in the Consumption of Dissolved O₂ during the Photochemistry of Aqueous Pyruvic Acid.

The sunlight photochemistry of the organic chromophore pyruvic acid (PA) in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is highly sensitive to dissolved oxygen content, [O2(aq)], among other environmental conditions. Thus, herein we investigate the photolysis (λ ≥ 305 nm) of 10–200 mM PA at pH 1.0 in water covering the relevant range 0 ≤ [O2(aq)] ≤ 1.3 mM. The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is monitored in real time with a dissolved oxygen electrode. In addition, the rate of O2(aq) consumption is studied at air flow rates from 30.0 to 900.0 mL min−1. For the range of [PA]0 covered under air saturated conditions and 30 mL min−1 flow of air in this setup, the estimated half-lives of O2(aq) consumed by the photolytic radicals fall within the interval from 22 to 3 min. Therefore, the corresponding depths of penetration of O2(g) into water (x = 4.3 and 1.6 µm) are determined, suggesting that accumulation and small coarse mode aqueous particles should not be O2-depleted in the presence of sunlight photons impinging this kind of chromophore. These photochemical results are of major tropospheric relevance for understanding the formation and growth of secondary organic aerosol.

Efficient Inhibition of N2O during NO Absorption Process Using a CuO and (NH4)2SO3 Mixed Solution

The discovery of effective methods toward nitric oxide (NO) removal by solution is valuable for the cost-effective flue gas control. In this study, it is first reported that nitrous oxide (N2O) is obviously suppressed by using copper oxide (CuO) combined with (NH4)2SO3 (NS) solution. CuO has been characterized, and the effects of reactants concentration, additives, temperature, pH and powder size on NO absorption process have been evaluated. The selectivity of N2O can drop from 91.30% to 11.25% under the optimum experimental conditions. Furthermore, based on the method of single-factor analysis, the inhibition of N2O is identified as the coeffect of NS/CuO. In addition, the pathways of NO removal are divided into two parts—N2O formation and NO absorption—and its ratio is calculated in the range of 0.29–0.53. Because of the continuous supply of NS from ammonia desulfurization, this study opens the feasibility of simultaneous desulfurization and denitrification.

Solvothermal Synthesis and Magnetic Properties of Monodisperse Ni0.5Zn0.5Fe2O4Hollow Nanospheres

AbstractThe monodisperse Ni0.5Zn0.5Fe2O4nanospheres have been synthesized via a simple solvothermal method. The effects of reactant concentration on structural and magnetic properties have been studied. X-ray diffraction analysis results indicate that the lattice constant and crystallite size can be tuned by controlling reactant concentration. The nanosphere size monotonically decreases from 238 to 35 nm with increasing reactant concentration. The magnetic studies show that blocking temperature is enhanced, and these single-domain particles are superparamagnetism at room temperature. The hollow nanospheres exhibit a high saturation magnetization value of 52.6 emu/g. The nanospheres with various diameters exhibit different magnetic saturation values which may be caused by the domain structure, surface effects and the distribution of metal ions on A and B sites. These superparamagnetic Ni0.5Zn0.5Fe2O4nanospheres are expected to have potential application in biomedicine and magnetic fluid technology.

Synthesis and Characterisation of Bismuth Oxide Nanoparticles using Hydrothermal Method: The Effect of Reactant Concentrations and application in radiotherapy

High atomic number (Z) of bismuth oxide nanoparticles (Bi2O3 NPs) has more cell penetration and less adverse effects than conventional radiosensitisers. In this work, 60 nm and 90 nm of Bi2O3 NPs were successfully synthesised using the hydrothermal method by varying the bismuth nitrate, Bi(NO3)3 concentration. The properties of Bi2O3 NPs were characterised to determine the phase presence, crystallinity, morphology, elements presence and size of nanoparticles. The as-synthesised Bi2O3 NPs was in monoclinic Bi2O3 phase (ICDD 98-008-5622). As the Bi(NO3)3 concentration increased, the particle size of Bi2O3 NPs decreased due to less ions diffusion per nuclei. The morphology observation showed that Bi2O3 NPs were in rods form. The produced Bi2O3 NPs were subjected to cytotoxicity analysis and radiotherapy. Bi2O3 NPs did not induce cytotoxicity in breast cancer (mcf-7) cell lines at concentration from 0.05 µM. The radiotherapy performance of the as-prepared Bi2O3 NPs was obtained by calculating the sensitisation enhancement ratio (SER). The optimum result was found for 60 nm Bi2O3 NPs with SER of 3.45.

Microfluidic approach for in situ synthesis of nanoporous silver microstructures as on-chip SERS substrates

Nanoporous silver microstructures (np-AgMSs) were first in situ synthesized using a microfluidic system. Chloride induced precipitation with NH4OH was used to prepare AgCl as a sacrificial template. Exploiting the microfluidic platform, effects of reactant concentrations on the morphology of AgCl templates were studied by simply adjusting the input flow rates. The AgCl templates were subsequently reduced into Ag0 or np-AgMSs using chemical reduction. The synthesized np-AgMSs were tested as on-chip SERS substrates using p-aminothiophenol as an analyte. It was found that the np-AgMSs with multipod structures (tripod and tetrapod) provided the highest SERS signal compared to other structures. Finally, the multipod np-AgMSs were successfully used as on-chip SERS substrates for determination of thiocyanate in human saliva. Linearity of the proposed approach was found to be in the range of 1–20 μM with R2 = 0.9887. The LOD and LOQ were 0.1 and 1.5 μM, respectively. Accuracy of the system was investigated from % recovery of spiked thiocyanate standard solutions and found to be in the range of 90–110%. In addition, reproducible Raman signals of thiocyanate were achieved with relative standard deviations of less than 9% for both intraday and interday SERS measurements. These indicated high accuracy and precision of the whole system.

Synthesis of hollow Fe3O4 particles via one-step solvothermal approach for microwave absorption materials: effect of reactant concentration, reaction temperature and reaction time

Hollow Fe3O4 particles with variable crystal sizes were synthesized by one-step solvothermal method for lightweight and efficient microwave absorber applications. The reactant concentration, reaction temperature and reaction time are three key factors for morphology control of the products and can further influence the microwave absorption properties. The diameters of as-prepared hollow magnetite particles ranged from 200 to 1000 nm, while the shell thickness differed from 35 to 280 nm. It is found that the microwave absorption properties are improved along with the increasing of the hollow structure size which depend on the reaction conditions. The sample prepared at 200 °C for 36 h exhibited an optimal reflection loss of − 55.14 dB at 11.76 GHz with the thickness of 2.07 mm, while possessing the broadest effective bandwidth reaching 4.72 GHz (5.6–10.32 GHz) at 2.49 mm. The excellent microwave absorbing properties of such materials can be attributed to the high magnetic loss and favorable impedance matching property.