Effect of concentration of some nickel catalyst poisons in oils on the course of hydrogenation

Hydrogenation has been carried out in a“dead-end” type reactor with various types of nickel catalyst and with automatic recording of hydrogen absorption. Oils with varying concentrations of sulfur and phosporus compounds, fatty acids and their salts, as well as partly oxidized oil have been hydrogenated. The resulting kinetic curves are characteristic for each catalyst type and for each inhibitor. An increase in the poison concentration in the reaction system results in lengthening of the induction period apart from the decrease of catalyst activity.     

Development of tailored high-performance and durable electrocatalysts for advanced PEM fuel cells

A family of novel carbon materials with intermediate surface area and varying morphology and surface chemistry were used to prepare Pt/C catalysts by two different preparation procedures; a chemical impregnation method and a microwave-assisted polyol method. The catalysts were thoroughly characterized, and their electrochemical performance and stability were investigated with rotating disc electrode (RDE) cyclic voltammetric (CV) measurements. The intermediate-surface-area carbon supports gave catalysts with much greater support stability than a widely used standard catalyst. The novel catalysts had lower electrochemical surface area than the reference, but their specific electrocatalytic activity towards the oxygen-reduction reaction (ORR) was much higher, and some of them also featured higher mass-specific ORR activity than the reference. The series of catalysts prepared by the microwave-assisted polyol method featured smaller Pt nanoparticles and higher activities than those prepared by impregnation. On the other hand, the impregnated catalysts showed better durability of the Pt particles. The most promising catalysts were selected and elaborated in further optimized preparation procedures to obtain quantities sufficient for their use in proton-exchange membrane fuel cells (PEMFCs).     

Stable SiOC/Sn Nanocomposite Anodes for Lithium‐Ion Batteries with Outstanding Cycling Stability

Silicon oxycarbide/tin nanocomposites (SiOC/Sn) are prepared by chemical modification of polysilsesquioxane Wacker‐Belsil PMS MK (SiOC_MK) and polysiloxane Polyramic RD‐684a (SiOC_RD) with tin(II)acetate and subsequent pyrolysis at 1000 °C. The obtained samples consist of an amorphous SiOC matrix and in‐situ formed metallic Sn precipitates. Galvanostatic cycling of both composites demonstrate a first cycle reversible capacity of 566 mAhg^?1 for SiOC_MK/Sn and 651 mAhg^?1 for SiOC_RD/Sn. The superior cycling stability and rate capability of SiOC_RD/Sn as compared to SiOC_MK/Sn is attributed to the soft, carbon‐rich SiOC matrix derived from the RD‐684a polymer, which accommodates the Sn‐related volume changes during Li‐uptake and release. The poor cycling stability found for SiOC_MK/Sn relates to mechanical failure of the rather stiff and fragile, carbon‐poor matrix produced from PMS MK. Incremental capacity measurements outline different final Li–Sn alloy stages, depending on the matrix. For SiOC_RD/Sn, alloying up to Li₇Sn₂ is registered, whereas for SiOC_MK/Sn Li₂₂Sn₅ stoichiometry is reached. The suppression of Li₂₂Sn₅ phase in SiOC_RD/Sn is rationalized by an expansion restriction of the matrix and thus prevention of a higher Li content in the alloy. For SiOC_MK/Sn on the contrary, the matrix severely ruptures, providing an unlimited free volume for expansion and thus formation of Li₂₂Sn₅ phase.     

Iron-Sepiolite High-Performance Magnetorheological Polishing Fluid with Reduced Sedimentation

A sedimentation-stable magnetorheological (MR) polishing slurry on the basis of ferrofluid, iron particles, Al₂O_3, and clay nanofiller in the form of sepiolite intended for MR polishing has been designed, prepared, and its polishing efficiency verified. Added clay substantially improved sedimentation stability of the slurry, decreasing its sedimentation rate to a quarter of its original value (1.8 to 0.45 mg s⁻¹) while otherwise maintaining its good abrasive properties. The magnetisation curve measurement proved that designed slurry is soft magnetic material with no hysteresis, and its further suitability for MR polishing was confirmed by its magnetorheology namely in the quadratically increased yield stress due to the effect of applied magnetic field (0 to 600 kA m⁻¹). The efficiency of the MR polishing process was tested on the flat samples of injection-moulded polyamide and verified by surface roughness/3D texture measurement. The resulting new composition of the MR polishing slurry exhibits a long-term stable system with a wide application window in the MR polishing process.     

The characterization of carbonaceous species from CO hydrogenation on single crystal Ru(0001) and Ru(11¯20) catalysts with high-resolution electron energy-loss spectroscopy

The CO hydrogenation on single-crystal ruthenium catalysts has been studied utilizing an elevated-pressure micro-reactor and high resolution electron energy loss spectroscopy (HREELS). It is found that carbonaceous deposits identified following CO hydrogenation are essentially identical to those observed in the study of methane decomposition. Three distinct forms of carbonaceous intermediates are identified; these are methylidyne (CH), vinylidene (CCH₂), and graphitic carbonaceous species.     

Germline dinucleotide mutation in codon 883 of the RET proto-oncogene in multiple endocrine neoplasia type 2B without codon 918 mutation

The autosomal dominant multiple endocrine neoplasia type 2 syndromes (MEN 2) comprise three clinically distinct entities, MEN 2A, familial medullary thyroid carcinoma and MEN 2B, which share a common clinical feature: medullary thyroid carcinoma (MTC). MEN 2B is considered to have the most aggressive form of MTC. Therefore, early detection of MEN 2B in order to prevent potentially lethal MTC is important. More than 95% of all MEN 2B cases are caused by germline mutation at codon 918 (M918T) in exon 16 of the RET proto-oncogene. In this study, we demonstrate the presence of germline codon 883 mutation (A883F) in 2 of 3 unrelated MEN 2B cases without codon 918 mutation. Our data demonstrate a novel etiologic event which may have roles in predisposition to MEN 2B when present in the germline and in the pathogenesis of sporadic MTC when somatic.     

A study of the electronic structure and reactivity of V/TiO2(110) with metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS)

The interaction of vanadium with TiO₂(110) surface was studied with metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS) under ultrahigh vacuum (UHV) conditions. A strong interaction between vanadium and TiO₂ is observed with the addition of the first vanadium layer. Adsorption and reaction of ethanol to ethylene were investigated with MIES, UPS and temperature programmed desorption (TPD) and found to be sensitive to the surface electronic structure. In particular the temperature of ethylene evolution decreased by ~100 K with a change in the vanadium coverage from 0.5 to 5 ML.     

Determination of the grinding wheel profile and its setup for use in finishing cylindrical gears with an evolvent profile

The present work is a continuation of the first part of the article and is devoted to the geometric calculation of shape parameters of the working surfaces of disk-shaver teeth for use in finishing cylindrical gears with an evolvent profile. A method has been proposed for determining the shape of the working surfaces in disk-shaver teeth during the recessed shaving of cylindrical gears with technologically modified teeth. In this case, the machined gear tooth surfaces are discretely specified, and consequently familiar analytical methods of tool profiling are unacceptable.