Atomic-level understanding of interface interactions in a halloysite nanotubes–PLA nanocomposite

To understand the nature of the bonding mechanism between poly(lactic acid) (PLA) and halloysite nanotubes (HNT), a first-principles DFT study was performed on the adsorption behavior of the PLA monomer, lactic acid (LA), on the outer, inner, and edge surfaces of the HNT. The role of LA functional groups, and its orientation behavior in the formation of bonds with HNT are systematically studied. Analysis of the adsorption energy, total and partial electron density of states (DOS), electric charge transfer between LA atoms and HNT mineral surfaces shows that van der Waals attraction governs their interaction. The calculations of the most stable adsorption configurations of LA show that the predominant number of hydrogen bonds is determined by the activity of the carboxyl functional group of LA on the hydroxylated surfaces of HNT. The important role of the –OH surface groups in the mechanism of lactic acid binding has been established; their absence on the external siloxane surface significantly reduces the LA affinity for HNT. The binding energy of lactic acid on the hydroxylated internal and edge surfaces of the HNT is much higher (by about 275%) than on the external siloxane surface. Mulliken population analysis showed that the formation of a hydrogen bond with the LA atomic groups leads to a more significant redistribution of charge on the inner and edge surfaces of the HNT in comparison with its outer surface. Van der Waals attraction between the LA and HNTs, as well as hydrogen bonds, is responsible for the formation of the bonding mechanism in halloysite nanotubes-PLA nanocomposite. Our results are in accord with available literature.

The mechanism of bond formation between PLA and outer, inner and edge surfaces of HNT was established.     

Synthesis and study of C-substituted methylthio derivatives of cobalt bis(dicarbollide)

The C-methylthio derivatives of cobalt bis(dicarbollide) were synthesized by reaction of anhydrous CoCl₂ with nido-carborane [7-MeS-7,8-C₂B₉H₁₁]⁻ and isolated as a mixture of rac-[1,1′-(MeS)₂-3,3′-Co(1,2-C₂B₉H₁₀)₂]⁻ and meso-[1,2′-(MeS)₂-3,3′-Co(1,2-C₂B₉H₁₀)₂]⁻ isomers. The structures of both isomers were studied using DFT quantum chemical calculations. The most preferable geometry of rotamers and the stabilization energy of C-methylthio derivatives of cobalt bis(dicarbolide) were calculated. The (BEDT-TTF)[1,1′-(MeS)₂-3,3′-Co(1,2-C₂B₉H₁₀)₂] salt was prepared and its structure was determined by single crystal X-ray diffraction. The cisoid conformation of the rac-[1,1′-(MeS)₂-3,3′-Co(1,2-C₂B₉H₁₀)₂]⁻ anion is stabilized by short intramolecular CH⋯S hydrogen and BH⋯S chalcogen bonds between the dicarbollide ligands, that is in good agreement with the data of quantum chemical calculations.

The C-methylthio derivatives of cobalt bis(dicarbollide) rac-[1,1′-(MeS)₂-3,3′-Co(1,2-C₂B₉H₁₀)₂]⁻ and meso-[1,2′-(MeS)₂-3,3′-Co(1,2-C₂B₉H₁₀)₂]⁻ were synthesized and studied by DFT calculations and X-ray diffraction.     

One-step synthesis,characterization and properties of novel hybrid electromagnetic nanomaterials based on polydiphenylamine and Co–Fe particles in the absence and presence of single-walled carbon nanotubes

A one-step preparation method for hybrid electromagnetic nanomaterials based on polydiphenylamine (PDPA) and bimetallic Co–Fe particles in the absence and presence of single-walled carbon nanotubes (SWCNT) was proposed. During IR heating of PDPA in the presence of Co(ii) and Fe(iii) salts in an inert atmosphere at T = 450–600 °C, the polycondensation of diphenylamine (DPA) oligomers and dehydrogenation of phenyleneamine units of the polymer with the formation of C N bonds and reduction of metals by evolved hydrogen with the formation of bimetallic Co–Fe particles dispersed in a polymer matrix occur simultaneously. When carbon nanotubes are introduced into the reaction system, a nanocomposite material is formed, in which bimetallic Co–Fe particles immobilized on SWCNT are distributed in the matrix of the polymer. According to XRD data, reflection peaks of bimetallic Co–Fe particles at diffraction scattering angles 2θ = 69.04° and 106.5° correspond to a solid solution based on the fcc-Co crystal lattice. According to SEM and TEM data, a mixture of particles with sizes of 8–30 nm and 400–800 nm (Co–Fe/PDPA) and 23–50 nm and 400–1100 nm (Co–Fe/SWCNT/PDPA) is formed in the nanocomposites. The obtained multifunctional Co–Fe/PDPA and Co–Fe/SWCNT/PDPA nanomaterials demonstrate good thermal, electrical and magnetic properties. The saturation magnetization of the nanomaterials is M_S = 14.99–31.32 emu g⁻¹ (Co–Fe/PDPA) and M_S = 29.48–48.84 emu g⁻¹ (Co–Fe/SWCNT/PDPA). The electrical conductivity of the nanomaterials reaches 3.5 × 10⁻³ S cm⁻¹ (Co–Fe/PDPA) and 1.3 S cm⁻¹ (Co–Fe/SWCNT/PDPA). In an inert medium, at 1000 °C the residue is 71–77%.

In a self-organizing system within one stage under IR heating conditions, hybrid nanomaterials are formed with a structure that contains bimetallic Co–Fe particles, free or immobilized on the SWCNT surface, dispersed in the polymer PDPA matrix.     

Investigation of the Initial Corrosion Destruction of a Metal Matrix around Different Non-Metallic Inclusions on Surfaces of Pipeline Steels

Typical non-metallic inclusions in two industrial low-carbon steels for oil pipelines were investigated as three-dimensional objects on film filters after electrolytic extraction and filtration of metal samples. A method of soft chemical extraction using a 10%AA electrolyte was used to study the initial corrosion process in the steel matrix surrounding various non-metallic inclusions. To determine and compare “corrosive” inclusions and their influence on the initial stages of corrosion of the adjacent layer of the steel matrix, quantitative parameters (such as the diameter of the corrosion crater (D_cr) and pit (D_pit), and the relative dissolution coefficient of the metal matrix (KD) around various inclusions) were determined after chemical extraction. It was found that CaO-Al₂O₃-MgO oxides and TiN inclusions did not cause an initial corrosion of the steel matrix surrounding these inclusions. However, tensile stresses in the steel matrix occurred around CaS inclusions (or complex inclusions containing a CaS phase), which contributed to the initiation of corrosion around these inclusions.     

Taste differentiation in the context of suckling and independent, adultlike ingestive behavior

The present study compared intake of sweet (saccharin), bitter (quinine), and neutral (water) tastants available either in the context of suckling behavior through a surrogate nipple or independent adultlike feeding through an intraoral cheek cannula in 3-hr-old newborn rats lacking any suckling experience and 24-hr-old rats with regular experience with the dam's nipple. The new technique of online monitoring of fluid flow was applied for assessment of the temporal patterns of ingestion. Newborn and 1-day-old rats tested in the context of suckling behavior showed extremely low intake of quinine, moderate intake of water, and high intake of saccharin. In the same way, they demonstrated low intake of quinine and high intake of saccharin in the context of independent feeding, but intake of water was also high and comparable to that of saccharin. Suckling rats attained higher efficacy of fluid extraction from nipple than pups drinking from cannula. The differential responsiveness to quinine, saccharin, and water in suckling rats was also manifested through attachment behavior, with pups spending less time on the nipple providing quinine and more time on the nipple with saccharin than on the nipple providing water. These results suggest that neonates show taste differentiation as early as 3 hr after birth, and that this taste differentiation is more pronounced in the context of suckling behavior than in the context of adultlike, independent ingestion.     

Mutual Effect of Components of Protective Films Applied on Copper and Brass from Octadecylamine and 1,2,3-Benzotriazole Vapors

It has been shown by a set of corrosion, electrochemical and physical methods that a chamber corrosion inhibitor that consists of a mixture of octadecylamine (ODA) and benzotriazole (BTA) efficiently protects copper and brass from atmospheric corrosion and can be used for the temporary protection of metal items. The optimum temperatures of treatment with the ODA + BTA mixed inhibitor is 120 °C for brass and 100 °C for copper. One-hour treatment in ODA + BTA vapors at these temperatures results in the formation of nanosized adsorption films on the surface of these metals. These films stabilize the passive state and provide efficient temporary protection of metal items. The ODA + BTA inhibitor is superior to its components in terms of protective aftereffect. Our analysis of the mutual effect of BTA and ODA indicated that they show an antagonism of protective action on copper, but there is also a synergistic enhancement in the case of brass. Electrochemical impedance spectroscopy studies demonstrate that the inhibitors in question mainly act by using a blocking mechanism on copper and brass. Chamber treatment of the metals studied in vapors of the ODA + BTA mixture resulted in a noticeable hydrophobization of the copper surface and an insignificant effect on the brass surface. Chamber treatment of copper samples with artificially created polymodal roughness made it possible to obtain a superhydrophobic surface.     

Influence of Cryo-Processing and Post-SPD Annealing on Creep Behavior of CP Titanium

The commercial purity of VT1-0 titanium was processed by the rolling process and executed at elevated, room, and cryo-temperatures. These processings led to the formation of an ultrafine-grained microstructure, with the mean grain size at a nanometer level. Some of these materials were statically annealed at a temperature of 823 K for 1 h, which led to significant subgrains and grain coarsening. The constant load creep tests in tension were carried out in argon on all states of materials, at temperatures of 648–723 K and different ranges of applied stresses. From the value of the steady-state creep rate, the control creep mechanisms were determined. The microstructure analyses were carried out via SEM and TEM. It was found that titanium prepared at elevated and room temperatures have a higher creep strength than titanium prepared at cryo-temperatures. Furthermore, the post-SPD —annealing led to a significant decrease in the creep properties. The influence of the preparation temperature on the difference of the creep behavior were discussed and explained using the microstructure analyses of the tests’ samples.     

Nanocrystalline TiO2 doped by small amount of pre-synthesized colloidal CdS nanoparticles for photocatalytic degradation of 1,2,4-trichlorobenzene

The chemical stability and hydrophobic nature of chloroarenes make them a persistent environmental hazard. Modeling of 1,2,4-trichlorobenzene (1,2,4-TCB) degradation in alcohol-water solution under UV irradiation was carried out with the aim of probing how the 1,2,4-TCB might behave in the environment. The photocatalytic activity of both bare TiO₂ and TiO₂ doped by colloidal CdS nanoparticles synthesized by the sol-gel method has been investigated in the processes of 1,2,4-TCB photodegradation in the aqueous protic solvent. Non-sensitized TiO₂ cannot be regarded as catalyst for the 1,2,4-TCB photodecomposition. On the contrary, the CdS/TiO₂ composite accelerated the 1,2,4-TCB photodegradation process. The concentration of CdS/TiO₂ was shown to effect on the 1,2,4-TCB photolysis mechanisms, which resulted in the quantitative ratios of the 1,2,4-TCB photolysis products.