Synthesis of Tribologically Favorable Coatings for Hot Extrusion Tools by Suspension Plasma Spraying

Up to now, no coating systems have been marketed in the field of direct hot extrusion, which provide both surface protection of the parts in contact with the billet (i.e., container and die) as well as a significant reduction of the frictional losses induced by the billet passing over the container walls. To dispense with the use of lubricants and to enhance the usable forming capacity and therefore the efficiency of the process, different oxide ceramics were prepared in one suspension and plasma sprayed to produce coatings. The aim was to reach a sufficient level of feedstock mixing to obtain deterministic solid solutions of the oxide phases in coatings resulting in a reduction of their coefficient of friction under dry sliding conditions. To achieve this objective, the high specific surface area of nanosized feedstock with primary particle sizes below 100?nm was used. By means of x-ray diffraction it could be proven, that the desired phases could be synthesized to varying ratios regarding the different coating systems considered here. Besides the experimental work, the fundamentals of the mixing process of different oxides are discussed with regard to the crystallographic aspects.     

Structural and optical properties of the Cu2ZnSnSe4 thin films grown by nano-ink coating and selenization

Quaternary semiconductor Cu₂ZnSnSe₄ (CZTSe) is a very promising alternative to semiconductors based on indium (In) and gallium (Ga) as solar absorber material due to its direct band gap, inherent high absorption coefficient (>10⁴ cm^?1) and abundance of cheap elements zinc (Zn) and tin (Sn). In this study, high quality CZTSe thin films were successfully synthesized by a green and low-cost solution based non-vacuum method, which involves spin coating non-toxic solvent-based CZTSe nano-inks onto Mo coated soda lime glass substrates followed by selenization with elemental Se vapor. The effect of selenization temperature on structural, morphological, compositional and optical properties of CZTSe films are investigated using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and photoluminescence spectroscopy. XRD and Raman analysis indicates that a tetragonal stannite-type structured CZTSe is formed. Depend on the selenization temperature, the dense and compact films with grain sizes from 200 nm (500 °C) up to about 1 μm (580 °C) are obtained. EDS measurement indicates that the composition ratios of the prepared CZTSe films are copper-poor and zinc-rich nature. The CZTSe films are p-type conductivity confirmed by a hot point probe method. Photoluminescence spectrum shows slightly asymmetric narrow bands with a maximum of intensity at 0.92 eV. The dependence of the photoluminescence on the excitation temperature reveals a decrease in the intensity of the photoluminescence bands. An absorption coefficient exceeding 10⁴ cm^?1 and the band gap energy about 0.87 eV of the studied films are determined by an absorption spectroscopy.     

Symmetrical craniofacial hypertrophy in patients with tertiary hyperparathyroidism and high‐dose cinacalcet exposure

We are reporting on a series of two patients with end‐stage renal disease on hemodialysis, presented for surgical parathyroidectomy secondary refractory hyperparathyroidism. Both patients had failed maximized medical managements, including higher‐than‐usual doses of the calcimimetic cinacalcet (270 and 180 mg/day, respectively). On physical exam, both patients had marked symmetrical craniofacial hypertrophy with coarse distortion of facial features, similar in appearance to past reports of Sagliker syndrome. On X‐ray and computed tomographic exam, they had peculiar areas of bone absorption on the skull, imitating the radiologic appearance of multiple myeloma. Bone biopsy of the maxilla, however, did not show the expected brown tumor, but rather described only fibrosis and reactive bone formations. This phenotype developed while being on cinacalcet, progressed despite escalation of therapy, and improved only after parathyroidectomy. Both patients developed massive “hungry bone syndrome” after parathyroidectomy necessitating prolonged IV calcium infusion. This pattern of severe facial distortion likely represented an adverse consequence of severe tertiary hyperparathyroidism, along with supraphysiologic dose of cinacalcet administration and 25‐hydroxy vitamin D deficiency in sensitive individuals. The genetic base of this observation remained unexplained.     

Biodegradation of phenol by Synechocystis sp. in media including triacontanol hormone

Phenol removal levels of Synechocystis sp. were investigated in BG11 media with 10 mg/L triacontanol (TRIA) and without it to test whether the hormone could increase the removal efficiency by increasing biomass. The assays were performed to determine the effect of light on degradation, in media with 119.0–492.8 mg/L phenol under light and dark conditions. At increasing phenol concentrations, the degradation ranged between 98.5 and 100% regardless of a dark or a light condition. Experiments were carried out under light to determine the optimum pH for effective degradation. Optimum pH was found to be 6.5 at 200 mg/L phenol with or without TRIA. Phenol degradation was investigated in the 120.2–826.9 mg/L range. Although 377.4 mg/L phenol was completely degraded in hormone controls within 120 h, degradation was increased by TRIA, and the process was completed in 96 h. These data suggest that Synechocystis sp. has potential for use in the treatment of wastewaters containing phenol.     

Tensile stress relaxation in unsaturated granular materials

The mechanics of granular media at low liquid saturation levels remain poorly understood. Macroscopic mechanical properties are affected by microscale forces and processes, such as capillary forces, inter-particle friction, liquid flows, and particle movements. An improved understanding of these microscale mechanisms is important for a range of industrial applications and natural phenomena (e.g. landslides). This study focuses on the transient evolution of the tensile stress of unsaturated granular media under extension. Experimental results suggest that the stress state of the material evolves even after cessation of sample extension. Moreover, we observe that the packing density strongly affects the efficiency of different processes that result in tensile stress relaxation. By comparing the observed relaxation time scales with published data, we conclude that tensile stress relaxation is governed by particle rearrangement and fluid redistribution. An increased packing density inhibits particle rearrangement and only leaves fluid redistribution as the major process that governs tensile stress relaxation.     

Synthesis of Quaternary,Long-Chain N-Alkyl Amides and Their Corrosion Inhibition in Acidic Media

New cationic surfactants were synthesized by the quaternization of a number of straight-chain amide derivatives with triethylamine or pyridine. The corrosion inhibition tests of the surface-active compounds were performed at room temperature for 24 h on carbon steel coupons in acidic media using the gravimetric method. The acidic media used were 1.5 M HCl and 1.5 M H₂SO₄. Almost all of the synthesized cationic surfactants showed efficient inhibition of corrosion in the test. To establish the inhibition efficiencies of the inhibitors, surface characterization studies (contact angle measurements, SEM analysis and optical profilometer images) of the metal coupons used were performed.