Diamond nucleation from the gas phase onto cold-worked Co-cemented tungsten carbide

Co-cemented tungsten carbide (WC–Co) substrates with fine (1 μm) and coarse (6 μm) grain size were sintered using 6 wt.% Co as a binder. The as-sintered samples were ground to the final geometry (10×10×3 mm3). After the grinding treatment, the full width at half maximum (FWHM) of the WC X-ray diffraction (XRD) peaks indicated a high level of strain in a few micrometers thick surface layer, according to the penetration depth of Cu Kα radiation. The as-ground substrates were submitted to a two-step etching procedure with Murakami's solution, to roughen the surface, and 10 s acid wash to etch surface cobalt out. The Murakami's etching time was varied between 1 and 20 min. Fine- and coarse-grained substrates submitted to different chemical etching times were characterized by scanning electron microscopy and XRD, and then submitted to short diamond nucleation runs in a Hot Filament Chemical Vapour Deposition reactor. Both FWHM of WC peaks and diamond nucleation density decreased by increasing the Murakami's etching duration, providing that the etched layer did not exceed 2 μm thickness. When a layer thicker than a couple of micrometers was removed by etching, diamond nucleation density was very low and no more dependent on etching time. This occurrence suggested that diamond nucleation density correlates well with the amount of residual strain at the substrate surface and can be tailored by a suitable control of strain-related defects produced by mechanical treatments

Dry turning of alumina/aluminum composites with CVD diamond coated Co-cemented tungsten carbide tools

Triangular (TPGN 160308) WC-6 wt.%Co inserts having different average grain sizes (1 and 3 µm) were submitted to surface roughening either by wet etching with Murakami's reagent or by a heat treatment in the hot filament chemical vapour deposition (HFCVD) reactor. The heat treatment was performed in a monohydrogen-rich atmosphere at substrate temperatures as high as 1000 degrees C. Scanning electron microscopy and energy-dispersive spectroscopy showed that this pre-treatment led to surface roughening of the as-ground inserts and to a lower surface Co concentration. Prior to deposition, all inserts were etched with an acid solution of hydrogen peroxide. Diamond coatings were deposited by HFCVD. The coated inserts were tested by dry machining of aluminum-matrix composite (Al-10%Al2O3) bars. Turning test results indicated that a proper combination of substrate pretreatment and microstructure can significantly improve tool life

Sol–gel synthesis, X-ray photoelectron spectroscopy and electrical conductivity of Co-doped (La, Sr)(Ga, Mg)O3−δ perovskites

La0.8Sr0.2Ga0.8Mg0.2−xCoxO3−δ (LSGMC) powders containing different amounts of Co (x = 0.05 and 0.085) were prepared by a citrate sol–gel method. The powders were used to prepare highly phase-pure LSGMC sintered pellets with controlled composition and fractional densities larger than 95%. For the first time, LSGMC materials were subjected to X-ray photoelectron spectroscopy (XPS) characterization. XPS data confirmed the presence of the dopants in the material and allowed to identify two different chemical states for Sr2+ and oxygen, both related to the oxygen-deficient perovskite structure of LSGMC. The conductivity of LSGMC sintered pellets containing different amounts of Co ions in the B sites of the perovskite lattice was assessed by electrochemical impedance spectroscopy (EIS) in the 250–750 °C temperature range. Conductivity values and apparent activation energies were in good agreement with previously published data referring to materials with same composition, but prepared by solid-state route. Therefore, the physicochemical and electrochemical characterization clearly demonstrated the ability of sol–gel methods to produce high-purity Co-doped LSGM perovskites, which represent promising solid electrolytes for intermediate-temperature SOFCs

Microstructural and morphological properties of homoepitaxial (001)ZnTe layers investigated by x-ray diffuse scattering

The microstructural and morphological properties of homoepitaxial (001)ZnTe layers are investigated by x-ray diffuse scattering. High resolution reciprocal space maps recorded close to the ZnTe (004) Bragg peak show different diffuse scattering features. One kind of cross-shaped diffuse scattering streaks along directions can be attributed to stacking faults within the epilayers. Another kind of cross-shaped streaks inclined at an angle of about 80deg with respect to the in-plane direction arises from the morphology of the epilayers. (abridged version

Y and Ni Co-doped BaZrO3 as a proton-conducting solid oxide fuel cell electrolyte exhibiting superior power performance

The fabrication of anode supported single cells based on BaZr0.8Y0.2O3-δ (BZY20) electrolyte is challenging due to its poor sinteractive nature. The acceleration of shrinkage behavior, improved sinterability and larger grain size were achieved by the partial substitution of Zr with Ni in the BZY perovskite. Phase pure Ni-doped BZY powders of nominal compositions BaZr0.8-xY0.2NixO3-δ were synthesized up to x = 0.04 using a wet chemical combustion synthesis route. BaZr0.76Y0.2Ni0.04O3-δ (BZYNi04) exhibited adequate total conductivity and the open circuit voltage (OCV) values measured on the BZYNi04 pellet suggested lack of significant electronic contribution. The improved sinterability of BZYNi04 assisted the ease in film fabrication and this coupled with the application of an anode functional layer and a suitable cathode, PrBaCo2O5+δ (PBCO), resulted in a superior fuel cell power performance. With humidified hydrogen and static air as the fuel and oxidant, respectively, a peak power density value of 428 and 240 mW cm-2 was obtained at 700 and 600°C, respectively

Los Centros Regionales, comparación y reflexiones sobre su contribución, un estudio de caso: la evaluación del Centro de Profesores del Norte

En el marco del Debate Educativo Nacional y de la intención manifiesta de alcanzar el grado universitario para la Formación Docente, es conveniente abrir el panorama incluyendo la posible inserción del Uruguay al contexto regional, evitándose de este modo el crónico e insistente análisis endógeno del problema educativo. Esta idea es congruente con lo emanado de las mesas de trabajo del Forum Mundial de Educación las cuales consideraron como fuera de contexto a nuestro modelo de Formación Docent

Constraints on the mantle sources of the Deccan traps from the petrology and geochemistry of the basalts of Gujarat state (Western India)

The late Cretaceous-early Tertiary flood basalts in the Gujarat area of the northwestern Deccan Traps (Kathiawar peninsula, Pavagadh hills and Rajpipla) exhibit a wide range of compositions, from picrite basalts to rhyolites; moreover, the basaltic rocks have clearly distinct TiO2 contents at any given degree of differentiation and strongly resemble the low-titanium and hightitanium basalts found in most of the Gondwana continental flood basalt (CFB) suites. Four magma groups are petrologically and geochemically distinguished: (1) A low-Ti group, characterized by rocks with varying SiO2 saturation, and with TiO2 <1.8 wt%, extremely low incompatible trace element abundances, low Zr/γ (av- 3.8), Ti/ V (av. 27), and a very slight large ion lithophile element (LJLE) enrichment over high field strength elements (HFSE). These rocks share some features with the Bushe Formation of the Western Ghats farther south, but have distinct geochemical characters, in particular the strong depletion in most incompatible trace elements. (2) A high-Ti group, characterized by a more K-rich character than the low-Ti rocks, and with a strong enrichment in incompatible elements, similar to average ocean island basalt (OIB), e.g. high TiO2 (>1.8 wt% in picrites), Nb (>19 p.p.m.) Zr/γ (av. 6.5) and Tt/V (av. 47). (3) An intermediate-Ti group, with TiO2 contents slightly lower than the high-Ti rocks at the same degree of evolution, and with correspondingly lower incompatible trace element contents and ratios, in particular K2O, Nb, Ba and Zr/Y (av. 5.2). (4) A potassium-rich group (KT), broadly similar in geochemical character to the high-Ti group but showing more extreme K, Rb and Ba enrichment (av. K20/Na20~l; Ba/Y~20). The most primitive low-Ti and high-Ti picrites, when corrected for low-pressure olivine fractionation, show distinct major (and trace) element geochemistry, in particular for CaO/AI2O3, CaO/TiO2 and Al2O3/TiO2, and moderate but significant variations in their SiO2 and Fe2Ost contents; these characteristics strongly suggest the involvement of different mantle sources, more depleted for the low-Ti picrites, and richer in cpxfor the high-Ti picrites, but with broadly the same pressures of equilibration (27-14 kbar). This, in turn, suggests a strong lateral heterogeneity in the Gujarat Trap mantle. Low-Ti picrites and related differentiates in Kathiawar are reported systematically for the first time here, and suggest the existence of HFSE-depleted mantle in the northwestern Deccan Traps, with extension at least to the Seychelles Islands and to the area of the Bushe Formation near Bombay in the pre-drift position, before the development of the Carlsberg Ridge. The absence of correlations between LILE/HFSE ratios and SiO2 argues against crustal contamination processes acting on the low-Ti picrites, possibly owing to their probably rapid uprise to the surface. Consequently, the mantle region of this rock group was probably re-enriched by small amounts of ULE-rich materials. The substantially higher, trace element enrichment of the least differentiated high-Ti picrites, relative to the basalts of the Ambe-noli and Mahableshwar Formations of the Western Ghats, testifies also to the presence of more incompatible element rich, OIB4ike mantle sources in northern and northwestern Gujarat. These sources were geochemicaily similar to the present-day Reunion mantle sources

Anthelmintics efficacy against intestinal strongyles in horses of Sardinia, Italy

Intestinal strongyles (IS) are the most important parasites of equids, due to their high prevalence worldwide, pathogenicity and the spread of drug-resistant populations. Despite the large number of horses bred in Sardinia Island, Italy, no data are available on the efficacy of anthelmintic compounds in the control of horse strongylosis. Therefore the aim of the present study was to evaluate the efficacy of five commercial anthelmintic formulations containing fenbendazole (FBZ), pyrantel (PYR), moxidectin (MOX) and two ivermectin formulations (IVM1 and IVM2) against IS in Sardinia by performing a fecal egg count reduction test (FECRT) and investigating the egg reappearance period (ERP) after treatment. In total, 74 horses from 7 farms were examined. Coprocultures performed for individual fecal samples collected at the day of the treatment revealed that cyathostomins were the predominant parasitic species (98.6%). The FECR for all horses belonging to the treatment groups after two weeks was ≥ 95% with a 95% C.I. > 90%. The expected ERP did not decrease in any of the treatment group as FECR values < 90% were found at D60 for FBZ, at D90 for PYR and IVM1, at D150 for IVM2. All horses treated with MOX showed FECRT > 90% for the entire duration of the trial until D150. The results of the present survey indicate that drug-resistant cyathostomin populations are not present in the examined horse population, contrariwise to what observed in other Italian and European regions. The reasons and implications of these results are discussed