Novel Solid Silicon Oxycarbide Unmodified Carbon Nanotube Composite Coating: Structure, Topography and Mechanical Properties

A silicon oxycarbide-carbon nanotube coating on steel was synthesized using a novel approach utilizing unmodified carbon nanotubes (CNT), silane surfactant and large monomer-based silsesquioxane sol. This enabled the creation of very stable carbon nanotube dispersion, which in turn resulted in homogenous layers obtained in a simple dip-coating process. The samples were annealed in 800 °C in argon to obtain a uniform glassy silicon oxycarbide-based composite from a silsesquioxane precursor. The layers’ morphology and nanomechanical properties were investigated using a number of methods, including infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation, Accelerated Property Mapping (XPM) and Quantitative Nanomechanical Mapping—an Atomic Force Microscopy method (QNM-AFM)

Macromonomers as a Novel Way to Investigate and Tailor Silicon-Oxycarbide-Based Materials Obtained from Polymeric Preceramic Precursors

It has been shown that bifunctional monomers (D units), which are used to increase the carbon content in silicon oxycarbide precursors, can form volatile oligomers, thus affecting the amount of carbon available during the transition into the final material in the annealing process. Additionally, an uneven distribution of carbon-rich mers may lead to the formation of a free-carbon phase, instead of the incorporation of carbon atoms into the silicon matrix. In this study, a novel two-step approach was utilized. Firstly, a macromonomer containing a number of structural units with precise structure was synthesized, which was later polycondensed into a ceramic precursor. Chlorodimethylsilane modified 2,4,6,8-tetramethylcyclotetrasiloxane was used as a silicon oxycarbide precursor monomer containing both T and D structural units (i.e., silicon atoms bonded to three and two oxygen atoms, respectively), with well-defined interconnections between structural units. Such a macromonomer prevents the formation of small siloxane rings, and has a very limited number of possible combinations of structural units neighboring each silicon atom. This, after investigation using IR, XRD, TG and elemental analysis, gave insight into the effect of “anchoring” silicon atoms bonded to two methyl groups, as well as the impact of their distribution in comparison to the materials obtained using simple monomers containing a single silicon atom (structural unit)

Effect of Different Levels of Calcium and Addition of Magnesium in the Diet on Garden Snails’ (<i>Cornu aspersum</i>) Condition, Production, and Nutritional Parameters

Edible snails are an attractive protein source due to their high growth rate, cost-efficiency, and nutritional value. Calcium is crucial for snail growth, reproduction, and shell formation, while magnesium plays a role in enzyme function and muscle tone. This study aimed to optimise calcium and magnesium levels in Cornu aspersum diets to optimise the production and technological characteristics of the derived animal products. Snails were fed specific diets in controlled conditions with varying calcium and magnesium levels (44.3, 66.1, 88.7, 103.5 Ca g/kg feed and 3.3, 5.6, 7.2 Mg g/kg feed) for four months. Their growth, shell characteristics, and meat composition were evaluated. As calcium in the feed increased, carcass and shell weights were higher. Also, the crushing force of the shells was higher with increasing amount of calcium in the feed. In the group with 10.35% calcium and 0.72% magnesium, snail growth significantly slowed down after three months, with lower mortality. It is suggested that a shortened fattening cycle by 3–4 weeks compared to the magnesium-free diet is possible. However, based on meat, shell, mortality, and feed intake analysis, a 0.56% magnesium concentration in the feed seems to give better results, as magnesium content at 0.72% might be toxic to snails. Further investigation is to confirm the possibility of neutralising the negative effects of magnesium in the diet through increasing calcium and phosphorus intake

Photoinduced Energy and Electron Transfer in Micellar Multilayer Films

Micellar multilayer films were prepared from an amphiphilic comb-like polycation (“polysoap”) and the polyanion poly­(styrene sulfonate) (PSS) using alternate polyelectrolyte layer-by-layer (LbL) self-assembly. Linear growth of the film thickness was evidenced by UV–vis spectroscopy and spectroscopic ellipsometry. Imaging by atomic force microscopy (AFM) indicated that the micellar conformation adopted by the polycation in solutions was preserved in the films. Thus, hydrophobic photoactive molecules, which were solubilized by the hydrophobic nanodomains of the micellar polymer prior to deposition, could be transferred into the films. Photoinduced energy transfer was observed in the nanostructured multilayers between naphthalene (donor) and perylene (acceptor) molecules embedded inside the polymer micelles. The efficiency of the energy transfer process can be controlled to some extent by introducing spacer layers between the layers containing the donor or acceptor, revealing partial stratification of the micellar LbL films. Also, photoinduced electron transfer was evidenced between perylene (donor) and butyl viologen (acceptor) molecules embedded inside the multilayers by steady-state fluorescence spectroscopy. The obtained photoactive nanostructures are promising candidates for solar-to-chemical energy conversion systems

Carbon Nanofibers Coated with Silicon/Calcium-Based Compounds for Medical Application

The aim of this work was to develop a method for the manufacture of carbon nanofibers in the form of mats containing silicon and calcium compounds with potential biomedical application. Carbon nanofibers (ECNF) were prepared from the electrospun polyacrylonitrile (PAN) nanofibers. The electrospun polymer nanofibers were heat treated up to 1000°C to obtain carbon nanofibers. The surface of ECNF was covered with a silica-calcium sol (ECNF+Si/Ca) by dip-coating technique followed by the stabilization process. Both types of carbon nanofibers, i.e., the as-received and covered with the sol, were tested to confirm their osteoconductive properties. Biological tests were performed, including genotoxicity, cytotoxicity, and alkaline phosphatase (ALP) activity. Morphology of adhering cells to nanofiber surface was described. The nanofibers were subjected to a bioactivity test in contact with SBF artificial plasma. Biological tests have revealed that the nanofiber-modified ECNF+Si/Ca in contact with osteoblast cells were biocompatible, and the level of cytotoxicity was lower compared to the control. The ALP activity of the modified nanofibers was higher than nonmodified nanofibers and indicates potential applications of such carbon materials in the form of mats as a substrate for bone tissue regeneration