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Aim: To compare the mechanical properties and metallurgic features of new and used Reciproc Blue and Reciproc instruments. Methodology: A total of 120 R25 Reciproc Blue and R25 Reciproc instruments were used. The morphological, chemical, mechanical, thermal and phase composition characteristics of new and ex vivo used files were investigated by scanning electron microscopy (FEG‐SEM) with energy dispersive X‐ray spectroscopy (EDS), focused ion beam analysis (FIB), micro‐Raman spectroscopy, FEG‐SEM metallography, X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and indentation tests. Usage‐induce degradation was evaluated. Ten new and ten used instruments per type were run until fracture occurred in a stainless steel artificial canal (60° angle of curvature, 4‐mm radius). Time to fracture and the length of the fractured fragment were recorded. Torque and angle of rotation at failure of ten new and ten used instruments for each type were measured according to ISO 3630‐1. The fracture surface of each fragment was examined. Two‐way analyses of variance was used to analyse the data statistically (α‐level 0.05). Results: SEM analysis revealed microcracks near the tip on both files after ex vivo usage tests. FIB imaging and micro‐Raman spectroscopy confirmed the presence of an oxide layer on the Reciproc Blue surface. There was no thinning of the coating after use. XRD revealed a reduction of martensite and R‐phase in Reciproc Blue after use. DSC analysis revealed different transformation temperatures for the instruments analysed. Reciproc Blue was significantly more flexible than Reciproc for both new and used samples (P < 0.05), and they were significantly more resistant to cyclic fatigue than Reciproc (P < 0.05). Ex vivo usage reduced the fatigue resistance of both files. Torsional resistance of Reciproc and Reciproc Blue was not reduced by simulated use (P > 0.05). Conclusions: The thermal treatment of Reciproc Blue was associated with a finer structure with smaller grains than Reciproc, which increased its fracture resistance and was also responsible for its reduced hardness and lower elastic modulus. Both files were safe during ex vivo usage in severely curved canals. [ABSTRACT FROM AUTHOR]

The research on high-velocity air-fuel (HVAF)-sprayed CrC-based materials has mostly focused on conventional CrC-25NiCr composition. In this paper, two alternative compositions (CrC-50NiCrMoNb and CrC-37WC-18NiCoCrFe) were sprayed with high-velocity oxy-fuel (HVOF) and HVAF spray processes to evaluate the material behavior during spraying and to provide characterization of the microstructures and mechanical properties of the coatings. For comparison, coatings from the CrC-25NiCr composition were sprayed with both processes. Spray diagnostics were carried out to obtain average particle velocity and temperature for each material and process combinations. The measured average in-flight particle data were 1800 °C and 700 m/s for HVOF process, and 1450 °C and 900 m/s for HVAF process. Characterization of the coating microstructures was carried out by scanning electron microscopy and X-ray diffraction. In addition, the carbon content of the feedstock powders and sprayed coatings was measured with carbon analyzer. The results show that carbide rebounding or selective deposition of particles with higher metal matrix content is the dominating reason for carbide loss during HVAF spraying, while carbide dissolution is an additional source for the HVOF spraying. Higher particle velocities and controlled temperature measured for the HVAF process produced dense coatings with improved toughness and more homogenous coating structure. [ABSTRACT FROM AUTHOR]

Aim To compare the phase transformation behaviour, the microstructure, the nano-hardness and the surface chemistry of electro-discharge machined HyFlex EDM instruments with conventionally manufactured HyFlex CM. Methodology New and laboratory used HyFlex EDM were examined by X-ray diffraction ( XRD) and differential scanning calorimetry ( DSC). Nano-hardness and modulus of elasticity were also investigated using a maximum load of 20 mN with a minimum of 40 significant indentations for each sample. Raman spectroscopy and field emission-scanning electron microscope ( FE- SEM) were used to assess the surface chemistry of HyFlex EDM. HyFlex CM were subjected to the same investigations and used as a comparison. Nano-indentation data were statistically analysed using the Student's t-test. Results XRD analysis on HyFlex EDM revealed the presence of martensite and rhombohedral R-phase, while a mixture of martensite and austenite structure was identified in HyFlex CM. DSC analysis also disclosed higher austenite finish (Af) temperatures for electro-discharge machining ( EDM) instruments. Significant differences in nano-hardness and modulus of elasticity were found between EDM and CM files ( P < 0.05). FE- SEM and EDS analyses confirmed that both new EDM and CM files were covered by an oxide layer. Micro-Raman spectroscopy assessed the presence of rutile-TiO2 . Conclusions HyFlex EDM revealed peculiar structural properties, such as increased phase transformation temperatures and hardness. Present results corroborated previous findings and shed light on the enhanced mechanical behaviour of these instruments. [ABSTRACT FROM AUTHOR]

The microstructure and micromechanical behavior of thermally sprayed Fe-based coatings manufactured with high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes were investigated. Fe-Cr-Ni-Si-B-C and Fe-Cr-Ni-Mo-Si-B-C powders were used as the feedstock materials. The coatings showed a highly dense microstructure with near-zero oxidation. The microstructure of the feedstock powders was better retained when sprayed with HVAF process. Differential scanning calorimetry revealed two small exothermic peaks at about 600 °C for the HVOF-sprayed coatings, without any increase in weight in thermogravimetric analysis. It suggested the re-precipitation of carbides that were dissolved during spraying due to the higher particle temperature reported by spray diagnostics system during the HVOF process (≈1800 °C) compared to the HVAF one (≈1400 °C). Micro- and nano-indentations helped to show the difference in inter-lamellar cohesive strength and, in turn, in the particle deposition mechanism. Coatings sprayed with Fe-Cr-Ni-Mo-Si-B-C composition possessed higher sliding wear resistance than that of Fe-Cr-Ni-Si-B-C due to higher nano-hardness. More specifically, HVOF-sprayed Fe-Cr-Ni-Mo-Si-B-C coating showed the largest intra-lamellar hardness, the largest elasticity, and high quality of particle interfaces which resulted in lower sliding wear rate. [ABSTRACT FROM AUTHOR]

Lowering the thermal energy and increasing the kinetic energy of hard metal particles sprayed by the newly developed HVAF systems can significantly reduce their decarburization, and increases the sliding wear and corrosion resistance of the resulting coatings, making the HVAF technique attractive, both economically and environmentally, over its HVOF predecessors. Two agglomerated and sintered feedstock powder chemistries, WC-Co (88/12) and WC-CoCr (86/10/4), respectively, with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Their dry sliding wear behaviors and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against AlO counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with the formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviors were evaluated via standard Neutral Salt Spray, Acetic Acid Salt Spray, accelerated corrosion test, and electrochemical polarization test at room temperature. The optimization of the tribological properties of the coatings is discussed, focusing on the suitable selection of primary carbide size for different working load applications. [ABSTRACT FROM AUTHOR]

This study examines the fundamental reactions that occur in-flight during the solution precursor plasma spraying (SPPS) of solutions containing Zr- and Y-based salts in water or ethanol solvent. The effect of plasma jet composition (pure Ar, Ar-H and Ar-He-H mixtures) on the mechanical break-up and thermal treatment of the solution, mechanically injected in the form of a liquid stream, was investigated. Observation of the size evolution of the solution droplets in the plasma flow by means of a laser shadowgraphy technique, showed that droplet break-up was more effective and solvent evaporation was faster when the ethanol-based solution was injected into binary or ternary plasma gas mixtures. In contrast with water-based solutions, residual liquid droplets were always detected at the substrate location. The morphology and structure of the material deposited onto stainless steel substrates during single-scan experiments were characterised by SEM, XRD and micro-Raman spectroscopy and were shown to be closely related to in-flight droplet behaviour. In-flight pyrolysis and melting of the precursor led to well-flattened splats, whereas residual liquid droplets at the substrate location turned into non pyrolysed inclusions. The latter, although subsequently pyrolysed by the plasma heat during the deposition of entire coatings, resulted in porous 'sponge-like' structures in the deposit. [ABSTRACT FROM AUTHOR]

In this study, hydroxyapatite (HAp) coatings were deposited on Ti plates by the high-velocity suspension flame spraying (HVSFS) technique. The process characteristic, the microstructure and phase composition of the coatings are significantly influenced by the solvent and by the design of the combustion chamber (CC) of the HVSFS torch. Water-based suspensions always lead to fairly low surface temperatures (≈350 °C), deposition efficiencies <40%, and produce coatings with low amount of crystalline HAp, which tend to dissolve very rapidly in simulated body fluid (SBF) solutions. DEG-based suspensions, when sprayed with properly-designed CCs, produce deposition efficiencies of 45-55% and high surface temperatures (550-600 °C). In these coatings, the degree of crystallinity increases from the bottom layer to the top layer, probably because the increasingly large surface temperature can eventually favour re-crystallisation of individual lamellae during cooling. These coatings are much more stable in SBF solutions. [ABSTRACT FROM AUTHOR]

The high-velocity suspension flame spraying technique (HVSFS) was employed in order to deposit 45S5 bioactive glass coatings onto titanium substrates, using a suspension of micron-sized glass powders dispersed in a water + isopropanol mixture as feedstock. By modifying the process parameters, five coatings with different thickness and porosity were obtained. The coatings were entirely glassy but exhibited a through-thickness microstructural gradient, as the deposition mechanisms of the glass droplets changed at every torch cycle because of the increase in the system temperature during spraying. After soaking in simulated body fluid, all of the coatings were soon covered by a layer of hydroxyapatite; furthermore, the coatings exhibited no cytotoxicity and human osteosarcoma cells could adhere and proliferate well onto their surfaces. HVSFS-deposited 45S5 bioglass coatings are therefore highly bioactive and have potentials as replacement of conventional hydroxyapatite in order to favour osseointegration of dental and prosthetic implants. [ABSTRACT FROM AUTHOR]

WC-CoCr coatings were HVOF-sprayed onto an AA6082T6 substrate. Thickness values between 50 and 150 μm were produced by stepwise increase of the number of torch scans. This increase made the coatings not only thicker but also denser. This was due both to peening effects and by modifications to the splat formation mechanism, investigated by focused ion beam technique. Thanks to such densification, the hardness, the wear and impact resistance, and the corrosion protectiveness of the layers increased with the number of torch scans. The largest improvement occurred from 2 to 3 torch scans. These coatings were also compared to anodized films: cermets had superior wear and impact resistance but offered less corrosion protection. [ABSTRACT FROM AUTHOR]

Thick thermal barrier coatings (TBCs), consisting of a CoNiCrAlY bond coat and yttria-partially stabilized zirconia top coat with different porosity values, were produced by air plasma spray (APS). The thermal fatigue resistance limit of the TBCs was tested by furnace cycling tests (FCT) according to the specifications of an original equipment manufacturer (OEM). The morphology, residual stresses, and micromechanical properties (microhardness, indentation fracture toughness) of the TBC systems before and after FCT were analyzed. The thermal fatigue resistance increases with the amount of porosity in the top coat. The compressive in-plane stresses increase in the TBC systems after thermal cycling; nevertheless the increasing rate has a trend contrary to the porosity level of top coat. The data suggest that the spallation happens at the TGO/top coat interface. The failure mechanism of thick TBCs was found to be similar to that of conventional thin TBC systems made by APS. [ABSTRACT FROM AUTHOR]

This article examines the usefulness of a thick thermally sprayed interlayer (plasma-sprayed Ni-50%Cr, plasma-sprayed Al2O3-13%TiO2, or high-velocity oxygen-fuel-sprayed WC-17%Co) for enhancing the wear resistance and the corrosion protectiveness of a diamond-like carbon (DLC)-based thin film deposited onto a carbon steel substrate. Scratch tests indicate that the Al2O3-13%TiO2 and WC-17%Co interlayers definitely increase the critical spallation load of the thin film, but the Al2O3-13%TiO2 interlayer itself undergoes brittle fracture under high-contact loads. Accordingly, during ball-on-disk tests at room temperature, no cracking and spallation occur in the DLC-based film deposited onto the WC-17%Co interlayer, whereas the one onto the Al2O3-13%TiO2 interlayer is rapidly removed because the interlayer itself is fractured. At 300 °C, by contrast, the DLC-based film on the Al2O3-13%TiO2 interlayer offers the best tribological performance, possibly thanks to the increased toughness of the ceramic interlayer at this temperature. Electrochemical polarization tests indicate that the thin film/WC-Co systems possess the lowest corrosion current density. [ABSTRACT FROM AUTHOR]

The microstructural, micromechanical (Vickers microindentation, scratch testing) and tribological (pin on disk tests against steel and alumina spherical pins) properties of three High velocity oxy–fuel (HVOF) sprayed Ni based alloy coatings, namely Diamalloy 4006 (Ni–20Cr–10W–9Mo–4Cu–1B–1C–1Fe), Tribaloy-700 (Ni–32Mo–16Cr–4Si–2Co) and Inconel-625 (Ni–22Cr–9Mo–4Nb), were characterised, both in the as sprayed condition and after thermal treatments at 600°C and 800°C. As deposited Tribaloy-700 possesses a low degree of crystallinity and lower hardness; crystalline intermetallics are formed after heat treatments, definitely improving mechanical strength and tribological resistance against 100Cr6 steel counterpart, but not against alumina counterpart. The Inconel-625 and Diamalloy 4006 as sprayed coatings consist of supersaturated crystalline solid solutions. The former is not much affected by heat treatments and has low hardness and poor tribological properties. The latter, instead, displays precipitation of secondary phases after heat treatment. Particularly, the 600°C treatment improves coating strength and wear resistance against steel, whereas the 800°C one is less effective, probably because it causes excessive crystal grain size increase. [ABSTRACT FROM AUTHOR]

The tribological behavior of high-velocity oxyfuel sprayed Co-28%Mo-17%Cr-3%Si coatings, both assprayed and after heat treatments at 200, 400, and 600 °C for 1 h, has been studied. The as-sprayed coating contains oxide stringers and is mostly amorphous. It has low hardness (∼6.7 GPa) and toughness and undergoes adhesive wear against 100Cr6 steel. The friction coefficient increases up to ∼0.9, so the flash temperature reaches a critical oxidation value; then, friction decreases and increases again. This phenomenon occurs periodically. Much adhesive wear occurs in the first stage. Abrasive wear prevails against alumina pin: the coating wear rate is lower because it possesses good plasticity. Thermal effects still occur. The 600 °C treatment causes formation of submicrometric crystals. Hardness increases (∼8.8 GPa), adhesive wear is prevented, the friction coefficient has no peaks. Against the alumina pin, wear rates remain similar to the as-sprayed case. Nevertheless, the friction coefficient has no peaks and its final value is lowered (from 0.84 to 0.75). [ABSTRACT FROM AUTHOR]

The effects of transportation and delay in processing of blood samples on the concentration of biomarkers are significant in epidemiological studies for which specimens are collected from participants at locations other than a designated center or laboratory. These sources of variability in measurement were studied by collecting two sets of blood samples from 51 men between 26 and 50 years of age. The first set was sent immediately to the laboratory for processing. The second set was transported by car for one hour and then returned to the laboratory for processing. Both sets were stored together at -80°C until the end of the study. Several blood constituents were evaluated. Vitamins, liver enzymes, and electrolytes showed no changes in concentration after transport by car for one hour. There were decreases in the concentrations of red and white blood cells, high-density-lipoprotein cholesterol, glucose, and creatinine after transportation. The transported total cholesterol, total testosterone, free testosterone, alkaline phosphatase, total bilirubin, and thiobarbituric acid-reactive substances increased in concentration. Although transportation and delay in processing of blood samples do not appear to greatly impact relative risk estimates, epidemiologists should be aware of these potential sources of variability in measurement and consider the consequences in their particular study. [ABSTRACT FROM AUTHOR]

The objective was to verify the hypothesis of a 'first uterine pass effect' or direct preferential vagina-to-uterus transport, suggested by the evidence of higher than expected uterine tissue concentrations after vaginal administration of progesterone; we used a human ex-vivo uterine perfusion model. A mixture of tritiated (3H) and unlabelled progesterone was applied to the cuff of vaginal tissue remaining attached to the cervix after hysterectomy. At the end of the perfusion period (up to 12 h), 3H and 14C radioactivity was measured in samples of uterine tissue. Tritiated water and [14C]dextran were tested to determine the extent of non-specific vagina-to-uterus transport (leaks). Finally, sections of uterine tissue exposed only to [3H]progesterone were prepared for autoradiography. By 4-5 h after application progesterone had diffused to the entire uterus and had reached a steady state; 4 h after application, progesterone concentrations reached 185 +/- 155 and 254 +/- 305 ng/100 mg of endometrial and myometrial tissue respectively. Endometrial extraction of progesterone was higher when the experiment was performed on uteri obtained during the luteal phase (280 +/- 156 ng/100 mg of endometrial tissue) than those removed during the proliferative phase of the menstrual cycle (74 +/- 28 ng/100 mg of endometrial tissue). These data demonstrate that a 'first uterine pass effect' occurs when drugs are delivered vaginally, thereby providing an explanation for the unexpectedly high uterine concentrations relative to the low serum concentration observed after vaginal administration. Hence, the vaginal route permits targeted drug delivery to the uterus, thereby maximizing the desired effects while minimizing the potential for adverse systemic effects. [ABSTRACT FROM PUBLISHER]