A robust combination of dysprosium vanadate/halloysite nanotubes: the electrochemical system for dimetridazole detection

Dimetridazole (DMD) is one of the significant antibiotic drugs of nitroimidazoles derivates that have attracted increasing attention in the medical field due to its pharmacological and toxicological activity. The development of high-performance sensors for continuous monitoring of DMD in food and environments is receiving increasing attention. Herein, an electrochemical platform was designed based on a dysprosium vanadate/halloysite nanotubes (DyV/HNTs) nanocomposite for the detection of DMD. The DyV/HNTs nanocomposite was examined by various spectroscopic and analytical techniques. The DyV/HNTs based electrochemical sensor reveals a distinctly higher electrocatalytic response to the reduction of DMD due to the good physiochemical properties compared to other electrodes. The DyV/HNTs based electrochemical sensor for DMD covered two linear ranges of 0.001–0.54 and 0.54–188 μM with a detection limit of 0.9 nm through the amperometric method, which is better than those previously reported. Furthermore, selectivity, stability, repeatability, and reproducibility studies were performed. Moreover, the fabricated DyV/HNTs sensor was successfully applied for the reliable discrimination of DMD in biological and water samples with satisfactory recovery values. The results indicated that this DyV/HNTs nanocomposite may be a promising electrochemical sensing platform for the determination of DMD.     

Fabrication of ball clay based low-cost ceramic membrane supports and their characterization for microfiltration application

In this study, the uniaxial pressing method was employed to fabricate low-cost ceramic membrane supports using inexpensive clays for microfiltration applications. The primary precursors used to make different membrane supports (S1–S3) were Ball clay and China clay. Thermogravimetric analysis (TGA), particle size distribution (PSD), contact angle measurements, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were performed in addition to water flux, porosity, water permeability, and average pore size measurements to characterize the membrane. SEM analysis revealed that the surface morphology of the membrane supports varies significantly depending on the raw material composition. The contact angle analysis of the supports revealed that they are hydrophilic, which is suitable for microfiltration applications. The water permeability, average pore size, and porosity of the membrane supports (S1–S3) were 4.31 × 10^?6 – 2.77 × 10^?6 m³/m²s kPa, 1.18–0.31 μm, 44–41%, respectively. Furthermore, the membranes' high pH and chlorine resistance show their suitability for use in harsh chemical cleaning. The production cost of membranes based on raw materials, pressing, and sintering was estimated to be Rs.1319/m² ($17.07), Rs. 978/m² ($12.66) and Rs. 924/m² ($11.96) for the supports S1, S2, and S3, respectively. Thus, membrane supports with low-cost clay materials are now suggested for microfiltration applications.     

An experimental investigation of the shear behaviour of polyethylenes with different structures

Rheological properties in shear flow are presented for four different polyethylene samples: a high density, a linear low density and two low density polyethylenes manufactured using different techniques. Tests have been performed with the aid of capillary types of instrument equipped with capillaries of various lengths at three different temperatures. End correction factors have been determined and true flow curves obtained. Swelling ratios for both unannealed and annealed samples have been determined as well as the shear rate and shear stress at which irregularities begin. In some cases generalized plots have been prepared and in all cases the rheological response is discussed in terms of molecular characteristics, in particular the average molecular weight, molecular weight distribution and degree of branching.     

Experiments on transport of hydrophobic particles and gas bubbles in porous media

Adhesion of hydrophobic colloids (clay minerals) on the surface of bubbles of air and the transport of the composite units formed by bubbles and mineral particles were observed in a glass micro model.When a clay mineral suspension flowed in a porous medium that contained bubbles of air trapped in small pores, particles accumulated preferentially on the upstream portion of the bubbles, and quasi-stable bubble-mineral particle units were formed. With an increase in the flow velocity, the particles moved along the interface between the bubble and the liquid and accumulated on the downstream portion of the bubbles. A large stress could mobilize the units which, occasionally, accumulated in larger voids.The mechanism suggested is adhesion of the particles on the surface of the bubble due to compression of their diffuse electrical double layer. The adsorbed particles can be moved by shear stresses which act in the region of water molecules between the well-organized layers of water on the surfaces of the bubble and the clay particles. A large enough shear stress causes the bubbles to become more streamlined, allowing them to move in the channel system. If in contact, the common lamina of the bubbles can withdraw and rupture.Bubbles transport from 20 to 50 times more particles than can be transported by average suspension.     

Bionanocomposites poly(ϵ-caprolactone)/organomodified Moroccan beidellite clay prepared by in situ ring opening polymerization: Characterizations and properties

In this study, a series of poly(?-caprolactone) (PCL)/clay bionanocomposites were prepared via in situ ring opening polymerization (ROP) of ?-caprolactone catalyzed by titanium butoxide. The natural Moroccan clay beidellite (BDT), used as nanocharge, was organomodified with cetyltrimethylammonium bromide, CTA, to obtain the organically modified 3CTA-BDT (3 = CTA/BDT equivalent feed ratio). Characteristics of the final nanocomposites are investigated by FTIR, SEC, XRD, SEM, TGA, DSC, optical tensiometry, thermal conductivity and water vapor sorption analysis. The intercalated/exfoliated morphologies, revealed by XRD and SEM analyses, confirm uniform dispersion of the nanoclay within the PCL matrix. Thermal stability of all the nanocomposites is improved by the addition of 3CTA-BDT clay compared to pure PCL polymer. The DSC data show that the addition of 3CTA-BDT particles promotes an increase in the disorder of the crystalline phase, which reduces the crystallinity degree. The hydrophobicity of Polymer/clay compatibility was analyzed by studying surface polarity degree of samples by contact angle measurements. Thermal conductivity and water vapor sorption was also discussed. The permeability (P), the sorption coefficient (S) and the diffusion coefficient (D), showed a significant decrease with increasing 3CTA-BDT loading.     

Hydrogels prepared from unsubstituted cellulose in NaOH/urea aqueous solution

Novel cellulose hydrogels were synthesized through a "one-step" method from cellulose, which was dissolved directly in NaOH/urea aqueous solution, by using epichlorohydrin as crosslinker. Structure and properties of the hydrogels were characterized by using SEM, NMR, and water absorption testing. The hydrogels are fully transparent and display macroporous inner structure. The equilibrium swelling ratios of the hydrogels in distilled water at 25 degrees C are in the range from 30 to 60 g H(2)O/g dry hydrogel. Moreover, the reswelling water uptake of the hydrogels could be achieved to more than 70% compared with their initial swelling states. This work provided a simple and fast method for preparing eco-friendly hydrogels from unsubstituted cellulose.     

Adaption of the Mechanism of Emulsion Polymerization to New Experimental Results

Summary: New experimental investigations of the 'classical' batch ab-initio emulsion polymerization of styrene reveal the important role of monomer droplets for the whole process. Monomer droplets with a size between a few and some hundreds of nanometers, which are formed by spontaneous emulsification as soon as styrene and water are brought into contact, have a strong influence on the particle nucleation, the particle morphology, and the swelling of the particles. Experimental results confirm that micelles of low molecular weight surfactants are not a major locus of particle nucleation. Brownian dynamics simulations show that the capture of matter by the particles (monomer or radicals) strongly depends on the polymer volume fraction and the size of the captured species (primary free radicals, oligomers, single monomer molecules, or clusters).     

Heavy ion induced damage in MgAl2O4, an inert matrix candidate for the transmutation of minor actinides

Magnesium aluminum spinel (MgAl₂O₄) is a material selected as a possible matrix for transmutation of minor actinides by neutron capture or fission in nuclear reactors. To study the radiation stability of this inert matrix, especially against fission product impact, irradiations with heavy energetic ions or clusters have been performed. The high electronic energy losses of the heavy ions in this material led to the formation of visible tracks as evidenced by transmission electron microscopy for 30 MeV C₆₀-Buckminster fullerenes and for ions of energy close to or higher than fission energy (²⁰⁹Bi with 120 MeV and 2.38 GeV energy). The irradiations at high energies showed a pronounced degradation of the spinel. Additionally, MgAl₂O₄ exhibited a large swelling for irradiation at high fluences with fission products of fission energy (here I-ions of 72 MeV) and at temperatures ≤ 500 °C. These observations are discussed from the technological point of view in the frame of using MgAl₂O₄ as an inert matrix for the transmutation of minor actinides.