Effects of Metallic Impurities in Alkaline Electrolytes on Electro-Oxidation of Water and Alcohol Molecules

The presence of metallic impurities in the electrolyte greatly affects electrocatalytic performance. A systematic study on this topic can not only provide guidance for rigorous practices on electrochemical measurements, but also in-depth fundamental understanding on the mechanisms of the electrochemical reactions. Herein, nine types of metallic ions including Cu2+, Ni2+, Fe3+, Fe2+, Co2+, Mn2+, Zn2+, Ce3+ and Al3+ are intentionally introduced into the electrolytes with a controlled manner and their effects on electro-oxidation of water, 5-hydroxymethylfurfural (HMF) and glycerol are investigated in details. Among these metal ions, Co2+ has the most pronounced effects on H2O electro-oxidation while Cu2+ species displays superior activity toward HMF and glycerol electro-oxidation, but negligible effects on H2O electro-oxidation. Such a unique feature of Cu2+ can also be noted from electro-oxidation of other small molecules, such as ethylene glycol, ethanol and furfural. More importantly, the effects of metallic impurities are independent of the composition of the electrodes, only rely on the pH of the electrolytes. In-situ electrochemical Raman spectroscopy, control electrochemical experiments and X-ray photoelectron spectroscopy analyses reveal that the origin of impurity effects is attributed to the formation of hydroxides during the electrochemical measurements.

Influence of the complexing ability of b3+ cations in the composition of B2O3 flux on the characteristics of LiNbO3:b crystals

The Gibbs energy of the borates formation of trace amounts of metallic impurities (Al4B2O9, CaB2O4, CaB4O7, Ca2B2O5, Ca3B2O6, PbB2O4) in the lithium niobate charge is calculated. It is shown that the element boron, as an active complexing agent, in the composition of the B2O3 flux can prevent the transition of impurity metals, inevitably present in trace amounts in the charge of lithium niobate, into the structure of the lithium niobate crystal.

Metallurgical silicon refining using electron-beam plasma

The possibilities of plasma-chemical refining of metallurgical silicon have been demonstrated. It is shown that by electron-beam refining it is possible to reduce the concentration of phosphorus and boron, as well as the main metallic impurities by evaporation of both these impurities and their volatile compounds.

Electrolytic superconducting niobium coatings for a cryogyroscope rotor: creation and properties

Electrodeposition of niobium coatings on spherical substrates for a cryogyroscope rotor made of carbopyroceram was considered. A special design of the installation for obtaining coatings on spherical samples was created. The coatings were applied at a temperature of 750°C with the cathodic current density of 5·10−3 - 2–10−2 A·cm−2 and the electrolysis time of 8-12 h. It was found that the use of a cathodic current density of 2·10−2 A·cm−2 and higher is impractical, because there is a roughening of the coatings surface. The composition of electrolytic coatings was identified by XRD analysis. The macrostructure of niobium coatings was studied using electron microscopy. The concentration of metallic impurities in the niobium coatings was defined by spectral quantitative analysis. The content of gas impurities was determined by gas chromatography. The roughness, nonsphericity, and superconductive properties of niobium coatings were investigated.

Determination of Metallic Impurities by ICP-MS Technique in Eyeshadows Purchased in Poland. Part I

Eye shadows, which are products willingly and frequently used by women and even children, have been reported in literature to contain toxic metals. In this work, a total of 94 eye shadows samples available on the Polish market were collected. Eye shadow products have been selected in order to include several parameters important from the point of view of the typical consumer such as: product type (mat/pearl), consumer group (for adults and children), price range (very cheap, medium price, expensive and very expensive), color (twelve different colors were tested), manufacturer (eight brands were investigated) or country of production (four countries were included). The concentration of selected metals (Ag, Ba, Bi, Cd, Pb, Sr, Tl) was determined by ICP-MS technique after the sample extraction with a mixture of nitric acid and hydrogen peroxide in a microwave closed system. For Ag, Cd and Tl, some results were below the established limit of quantification for the employed technique. The presence of strontium, barium, lead and bismuth was confirmed in all studied samples. The obtained results for analyzed elements were, in general, quite comparable with the data reported by other authors. A small number of samples exceeding the permissible values (two samples were beyond the limit value for Cd of 0.5 mg/kg and one exceed the acceptable concentration for Pb of 10 mg/kg) also proves a relatively good condition of the Polish cosmetics market and suggests insubstantial risk for the potential consumers. The results gathered for some of the eye shadows intended for children turned out to be alarmingly high, in particular for elements such as Cd. The highest concentration of Cd reached almost 4 mg/kg, while of Pb amounted to 16 mg/kg. The presence of the statistically significant differences was confirmed for all included parameters with an exception of the color of the eye shadow. Considering the results acquired only for Cd and Pb with respect to the country of origin, the least contaminated cosmetics by metallic impurities seem to be the one produced in Canada, while the ones presenting the highest health risk among all studied eye shadows are make-up cosmetics originating from Poland and Italy. Multivariate analysis of a large data set using CA methods and PCA provided valuable information on dependencies between variables and objects.

Developments in Synthesis and Potential Electronic and Magnetic Applications of Pristine and Doped Graphynes

Doping and its consequences on the electronic features, optoelectronic features, and magnetism of graphynes (GYs) are reviewed in this work. First, synthetic strategies that consider numerous chemically and dimensionally different structures are discussed. Simultaneous or subsequent doping with heteroatoms, controlling dimensions, applying strain, and applying external electric fields can serve as effective ways to modulate the band structure of these new sp2/sp allotropes of carbon. The fundamental band gap is crucially dependent on morphology, with low dimensional GYs displaying a broader band gap than their bulk counterparts. Accurately chosen precursors and synthesis conditions ensure complete control of the morphological, electronic, and physicochemical properties of resulting GY sheets as well as the distribution of dopants deposited on GY surfaces. The uniform and quantitative inclusion of non-metallic (B, Cl, N, O, or P) and metallic (Fe, Co, or Ni) elements into graphyne derivatives were theoretically and experimentally studied, which improved their electronic and magnetic properties as row systems or in heterojunction. The effect of heteroatoms associated with metallic impurities on the magnetic properties of GYs was investigated. Finally, the flexibility of doped GYs’ electronic and magnetic features recommends them for new electronic and optoelectronic applications.