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The term 'wax bloom' is used to describe a thin whitish crystalline layer that develops on the surface of beeswax objects under specific conditions. This phenomenon is undesirable, especially in the cases of objects with aesthetic or informational value, such as wax sculptures or historical seals. A combination of solid-state NMR and FTIR measurements allowed to obtain fairly detailed insight into the problem and to suggest a probable mechanism of its development. Secondary crystallization of unsaturated hydrocarbons from beeswax was determined as a primary cause. After the macroscopic solidification of beeswax from the melt, these molecules remain for months in a highly mobile, liquid-like state. This facilitates their diffusion to the surface, where they eventually crystallize, forming the 'wax bloom' effect. Although these results are of particular interest with respect to the conservation of beeswax artifacts, they are relevant to this material in general and help with understanding its unique properties. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In recent years, there has been a growing interest in developing more reactive calcium silicate cements (CSCs) with superior bioactivity, self-setting properties and mechanical strength, allowing them to be used for various dental applications. In this study, we have produced a biphasic larnite/bredigite calcium magnesium silicate cement (CaMgSi) by the low-temperature sol-gel method and calcination of xerogels at 700 °C. The effect of boron (B) incorporation (0.25 and 0.5 mol) on the structural and physico-chemical properties of CaMgSi and boron-modified CaMgSi/0.25B and CaMgSi/0.5B cements was evaluated using various characterization techniques, such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM/TEM) and solid-state NMR spectroscopy (ssNMR). The results showed that with the increasing boron content, the cements hydration, self-setting and mechanical properties were improved. Hence, the final setting time of CaMgSi/0.5B cement decreased from 30 (undoped cement) to 19 min, while the compressive (CST) and diametral tensile strengths (DTS) increased almost twice to the highest values of 85 ± 9 MPa and 8.8 ± 1 MPa, respectively. The in-vitro bioactivity and degradation of cements were examined in simulated body fluid (SBF) solution during 8 weeks of soaking. Interestingly, the prevalence of calcite and aragonite crystals of various morphologies was observed on all cement surfaces, whereas a plate-like particles of precipitated calcium phosphate layer were found only in the boron-modified CaMgSi/0.25B and CaMgSi/0.5B cements. In addition, a very good antibacterial activity of the cement suspensions was revealed against all the tested bacteria, i.e. Staphylococcus aureus, Escherichia coli and Enterococcus faecalis, showing a promising result for potential use in dentistry. [ABSTRACT FROM AUTHOR]

A novel soft magnetic composite (SMC) based on spherical FeSi particles precisely covered by hybrid phenolic resin was designed. The hybrid resin including silica nano-rods chemically incorporated into the phenolic polymer matrix was prepared by the modified sol-gel method. A chemical bridge connecting silica nano-rods with the base polymeric net was verified by FTIR, 13C and 29Si NMR spectroscopy, whereas the shape and size of silica nano-rods were determined by TEM. It is shown that the modification of polymeric resin by silica nano-rods generally leads to the improved thermal and mechanical properties of the final samples. The hybrid resin serves as a perfect insulating coating deposited on FeSi particles and the core-shell particles can be further compacted by standard powder metallurgy methods in order to prepare final samples for mechanical, electric and magnetic testing. SEM images evidence negligible porosity, uniform distribution of the hybrid resin around FeSi particles, as well as, dimensional shape stability of the final samples after thermal treatment. The hardness, flexural strength and density of the final samples are comparable to the sintered SMCs, but they simultaneously exhibit much higher specific resistivity along with only slightly lower coercivity and permeability. [ABSTRACT FROM AUTHOR]

Abstract The detailed structural analysis of fibrous carbon electrode materials modified by Cu or Cu 3 P particles is designed for hydrogen evolution reaction (HER). Two different calcination temperatures and reduction atmospheres were used in order to uncover the most effective catalytic electrode material. The novel families of carbon fibrous electrode materials were prepared by low-cost and versatile needle-less electrospinning process. The chemical structure of prepared modified fibers was analyzed by XRD, 13C and 31P NMR spectroscopy. The morphology of the final samples and the location of Cu or Cu 3 P micro and nanoparticles were observed by SEM and TEM tomography. TEM XEDS mapping revealed the exact position of Cu, P, C and O elements within the matrix of fiber. The electrocatalytic activity for HER was evaluated by the linear sweep voltammetry, impedance spectroscopy and Tafel slopes analysis. The highest performance for HER was observed in the carbon fibers incorporating copper or copper phosphide nanoparticles thermally treated in argon atmosphere at 1000 °C and successively in hydrogen reduction atmosphere. Graphical abstract Unlabelled Image Highlights • Electrospinning was utilized for preparation of modified carbon fibers by Cu or Cu 3 P nanoparticles. • C/Cu/Cu 3 P fibers represent perspective electrocatalytic material for HER. • Effect of different carbonization atmospheres on the final morphology and HER activity was studied. • C/Cu/Cu 3 P fibers carbonized in Ar followed by H 2 atmosphere display best HER performance. [ABSTRACT FROM AUTHOR]

7Li–7Li correlation MAS NMR spectroscopy, interpreted using periodic DFT including molecular dynamics conformational sampling of Li+ sites, is employed to obtain the siting of Li+ at exchangeable positions of ferrierites and the local structure of these Li+ sites. The former is controlled by the Al siting in the zeolite framework. [ABSTRACT FROM AUTHOR]

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• Partially deacetylated chitin nanowhiskers (ChNWs) was extracted from shrimp wastes. • Deacetylation, dimensional, and stability of chitin whiskers were investigated. • Nanocomposite biofilms from hyaluronan and ChNWs were fabricated by casting method. • Physical, mechanical, and rheological properties of nanocomposite solutions were evaluated. • The antibacterial property and toxicity of the new films were measured and evaluated. Fabrication of nanocomposite biofilms with enhanced mechanical and antibacterial properties was successfully achieved from hyaluronan (HA) and partially deacetylated chitin nanowhiskers (ChNWs) by a casting-evaporation method. The hydrolysis process of chitin showed an important role in the dimensions, stability, and the crystallinity of extracted ChNWs in a time-dependent manner. The volume fraction of ChNWs nanofiller varying from (0.001 to 0.5) exhibited a great influence on the mechanical properties of the biofilms (young modulus, strength) was enhanced by the high load-bearing capacity of NWs compared with net HA film. The antibacterial activity of the nanocomposite biofilms exhibited significant bactericidal activity against different types of bacteria (−/+ gram). HA/ChNWs Nanocomposite biofilms did not show any toxicity against normal human dermal fibroblasts (NHDF) and human primary osteogenic sarcoma (Saos-2) cell lines. The new biofilms with unique properties like edibleness, environmental friendliness, high mechanical properties, antibacterial performance, and non-cytotoxicity that could be used in skin tissue regenerations, and drug delivery applications. [ABSTRACT FROM AUTHOR]