Immediate loading of dental implants is considered an excellent option to reestablish function and aesthetics in a short period of time, thereby reducing the psychological impact of edentulism. The ...aim of this study was to describe the incidence of complications in immediately loaded implant-supported single or partial maxillary provisional rehabilitations; to assess changes in patient quality of life (QoL); to evaluate patient overall satisfaction; and to determine whether the occurrence of complications affects these outcomes.
Patients requiring partial rehabilitation with implants in the maxilla were included in a prospective cohort study. In all cases, implant-based restoration with an immediate loading protocol was indicated. A provisional restoration was placed within 72 hours after implant placement. Patient QoL was measured at the first appointment and just before placing the final restoration, using two validated questionnaires. All mechanical and biological complications occurring up until placement of the final restoration were documented. A descriptive and bivariate analysis of the data was performed.
Thirty-five patients with 40 prostheses supported by 60 implants were analyzed. Three implant failures were observed, yielding a 95% survival rate. Five provisional prosthesis fractures and two prosthetic screw loosenings were recorded in four patients. A significant reduction in OHIP-14 score was observed. Likewise, significant differences were found in the results of the QoLFAST-10, with a mean difference in score of 7.3 between the initial and final evaluation.
Patients receiving immediately loaded implant-supported single or partial maxillary provisional rehabilitations seem to have a low risk of developing early mechanical (13.3%) or biological complications (5%). These patients appear to experience significant improvement in QoL and report excellent overall satisfaction with the treatment received - though the occurrence of complications seems to affect these outcomes.
A series of novel, active and easily synthesized nickel phosphide catalysts were prepared by means of temperature-programmed reduction (TPR) of Ni(HPO3H)2, and the role of the support on Ni2P ...formation and catalytic activity was studied. For this purpose four catalysts with a nickel loading of 10 wt % were synthesized by using two mesoporous supports, MCM-41 and zirconium doped MCM-41 (MCM-SiZr), as well as two commercial supports, SiO2 (Cab-osil) and γ-Al2O3. The dibenzothiophene (DBT) hydrodesulfurization (HDS) activity was measured for these Ni2P based catalysts, displaying good activity. All catalysts reached high DBT conversion values at high temperatures, with the DDS (direct desulfurization) route being favored, i.e. yielding mainly biphenyl (BP). Silica supported catalysts, Ni2P-10 (Si) and Ni2P-10 (Cab), proved highly stable with time on stream (48 h) with conversion values close to 100%. More acidic supports provided lower conversion values and underwent deactivation. Thus, Ni2P-10 (Zr) catalyst only presents a constant conversion of 80% after 48 h of reaction, but when the support is γ-Al2O3 deactivation occurs. Further, the analysis of the spent catalyst revealed the presence of sulfur on the surface, possibly forming a phosphosulfide phase. A poor result is obtained with Ni2P-10 (Al), which undergoes deactivation with time on stream. This is due to both a lower proportion of the Ni2P phase being present on the surface and the possible formation of NiS under the reaction conditions used.
Zeolites are well known crystalline aluminosilicates, which may be used in processes that take advantage of their molecular sieving effect, such as natural gas drying. They are often used in cyclic ...processes that swing pressure and/or temperature to perform adsorption and desorption steps. It is recognized that thermal stress may decrease process performance upon prolonged use. In this work, chabazite (CHA) zeolite with two different Si/Al ratios and compensating cations was investigated by thermally aging the samples using a laboratory-scale protocol. A Premature Aging Protocol – PAP was proposed that took into account the conditions which the adsorbent is exposed to in Temperature Swing Adsorption (TSA) process for natural gas drying. The sample was previously saturated with water and n-heptane vapors (as a reference hydrocarbon) followed by pressurization (30 bar) and heating (573 K) with a mixture of CO2 and CH4 (1:4, v/v). The Si/Al ratios of the CHA samples under study were 2 and 5 and the compensating cations were Na and K. Aged materials presented a lower CO2 and water vapor adsorption capacity with an increasing content of carbon in the bulk composition. The sample with higher Si/Al ratio (≈5) had a larger pore volume but adsorbed less water. Despite having the highest carbon content after aging and modest acidity, it was the most thermally stable sample, together with the sample containing potassium. Even with a lower Si/Al ratio (≈2), the presence of potassium provided the sample a protective effect against aging.
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•Thermal aging caused less severe degradation of the crystalline structure in samples with high Si/Al (5) and containing K.•All aged materials showed worsened textural characteristics, particularly for the Na sample with lower Si/Al (2).•Carbon builds up most in CHA with a high Si/Al (5) but does not significantly affect its water uptake.•CHA with Si/Al (5) has more Al than cations, which causes acid sites possibly responsible for carbon buildup upon aging.•The presence of potassium brings a sieving protective effect against coking and allows for robust water uptake.
Copper oxide supported on zinc oxide catalysts was tested for the photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes under UV irradiation at 25, 35 and 45 °C. These Cu/ZnO ...catalysts with variable copper loadings (2.5, 5 and 7.5 wt%) were prepared by impregnation and characterized by atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), N2 adsorption–desorption, transmission electron microscopy (TEM), diffuse reflectance UV–visible absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS). XRD and XPS data revealed that copper was in the form of copper oxide (CuO), and the crystal size was 240.8 and 49.3 nm for ZnO and CuO, respectively. Experiments showed that xCu/ZnO catalysts were highly active for MB and MO degradation compared with the zinc oxide supports due to the presence of copper oxide acting as an electron trap inhibiting electron-hole recombination. Furthermore, photodegradation activity was improved with increasing temperature. The 5Cu/ZnO catalyst exhibited greater degradation activity in both dyes, reaching 99% degradation at 45 °C after 15 and 75 min for MB and MO, respectively, due to its greater dispersion of CuO in ZnO and higher concentration of hydroxyl groups on the surface compared with other catalysts. Thermodynamic calculations indicated that the interaction of MB with the surface was stronger than that of MO and possibly related to the presence of hydroxyl groups on the surface, as indicated in the XPS results. The effects of different scavengers of the main species involved, such as hydroxyl radicals, superoxide radical anions and positive holes, were studied to propose photodegradation mechanisms of the dyes on these systems. The superoxide radical was the main reactive species during the photocatalytic degradation of MB and MO.
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•Pd-Nb catalysts were studied in the hydrodesoxygenation reaction of dibenzofuran at 275°C and 15bar of H2 of pressure.•Commercial fumed silica and zirconium phosphate heterostructure ...were used as supports.•Silica supported catalysts are much more active in HDO than those supported on porous phosphate heterostructure.•Bicyclohexane was the main product of the HDO reaction.
Bifunctional PdNb catalysts were studied in the hydrodesoxygenation (HDO) reaction of dibenzofuran (DBF) at 275°C and 15bar of H2 pressure. The influence of both the support employed (silica and zirconium phosphate heterostructure (PPH)) and the catalyst preparation procedure were evaluated in the catalytic response in the HDO reaction. The catalysts were prepared by incipient wetness impregnation by using two synthetic routes. The catalysts were characterized by means of X-ray diffraction (XRD), N2 adsorption-desorption, thermoprogrammed desorption of NH3 (TPD-NH3), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and elemental analysis. The results show that silica supported catalysts are much more active than those supported on PPH. While the characterization results point to a higher dispersion of the supported catalysts on PPH and better textural and acidic properties, the PdCl2 precursor salt remains on these catalysts even after calcination and catalytic tests, explaining the lower catalytic performance presented by these systems: fewer active centers and more residues of carbon. With respect to the preparation method, regardless the support employed, the catalysts synthesized by incorporating Pd after Nb incorporation and calcination, are more active, most probably due to a better phase dispersion and therefore to a higher amount of active centers.
The main features in cationic LTA zeolites that are likely to impact its potential hydrothermal stability are interconnected. The Al content and the compensating cation play an important role in the ...water adsorption but their influence on the zeolite performance in thermal cycles is yet to be understood. In this study, four LTA zeolite samples were synthetized with distinct Si/Al ratios in sodium and potassium forms. They underwent a Premature Aging Protocol (PAP) that took into account the operating conditions typically found in temperature swing adsorption processes. The Si/Al ratio per se did not impact in the crystallinity upon aging, but the presence of a high amount of potassium cations (Si/Al = 1) led to the amorphization of the zeolite structure. The results from XPS and NMR techniques indicate the Al migration from the outer surface to the inner cages occurs upon aging. Chemical analysis by XRF and ICP-OES associated with 27Al NMR analysis reveal that the presence of EFAl is particularly significant in the sample with the largest Si/Al ratio (5) and is correlated to a much larger C deposition upon aging. TG/DTG and TPD-NH3 experiments suggest that acid sites in the zeolite structures act as a double-edged sword, by enhancing water adsorption while also leading to carbon accumulation. CO2 isotherms at 0 ºC reveal the reduction of the microporosity after aging, whereas the Al content is proportional to the water adsorption uptake, particularly at low pressures (below 10 mbar). The material with an intermediate Si/Al ratio and in Na-form (LTAc-SiAl2-Na) combines excellent hydrothermal stability with a high-water affinity and uptake.
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•LTA zeolite with an intermediate _Si/Al_ ratio and in Na-form combines hydrophilicity and hydrothermal stability.•The presence of Extra-Framework Al is vehemently correlated to a much larger C deposition upon aging.•The Si/Al ratio per se did not impact the crystallinity upon aging.
This study aims to deepen the importance of the current collector used (GDL, Al foil or C-coated Al foil) when determining the performance of Li-S batteries.
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Lithium–sulfur batteries ...have been recognised as highly promising next-generation batteries, due to their low cost and high theoretical energy density. Despite numerous advances in this technology over the last decade, its commercialisation is still a challenge that has not yet been achieved. Many efforts have been made to improve the problems that these batteries present, mainly by investigating different cathode manufacturing strategies, testing novel Li anodes, new additives in the electrolytes, and modified separators or interlayers. However, the characteristics of the current collectors used in the preparation of the electrodes have been rarely addressed. Three commercial collectors are commonly used in basic research on Li–S batteries: Al foil, carbon coated Al foil (Al-C), and carbon paper (gas diffusion layer, GDL). In this work, a detailed study of the electrochemical response of these commercial collectors has been carried out. The tests were carried out on two S composites formed by carbons of a different natures, commercial carbon black and synthetic N-doped graphene. In addition, the S impregnation method was different, using either melt diffusion at 155 °C or ethylenediamine as S solvent, respectively. In both systems, the results were similar – the electrodes supported on GDL delivered higher specific capacities than those supported on Al and Al-C, with minimal differences between the two. Of the different collector properties examined to explain this behaviour, namely Al corrosion, electrical conductivities, surface-level composition, and surface texture, only the latter had a significant effect in the performance of GDL-based electrodes. SEM images revealed a rough and cracked surface formed by the agglomerated carbon particles that give rise to a complex pore system, predominantly consisting of macropores. All of these features are beneficial for a better anchoring of the active material on the collector surface, in addition to enhancing the wettability of the electrolyte and favouring reaction kinetics. In contrast, the Al-based collector possesses a very smooth and non-porous surface, detrimental to both the active material-substrate interface and the active material impregnation by the electrolyte.
Solid acid catalysts based on WO3–SiO2 and WO3–ZrO2–SiO2 were prepared by one-pot non-hydrolytic sol–gel method and tested in the gas phase glycerol dehydration to acrolein. Their structural and ...textural characteristics were determined by X-ray diffraction (XRD), N2 adsorption, X-ray energy dispersive spectroscopy (XEDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Their acid characteristics were studied by both temperature programmed desorption of ammonia (NH3-TPD) and FTIR of adsorbed pyridine. Under our operating conditions, all the catalysts were active and selective in the transformation of glycerol to acrolein, which was always the main reaction product. The high selectivity to acrolein is achieved on catalysts presenting a higher proportion of Brønsted acid sites. In addition, the role of oxygen in the feed on catalytic performance of these catalysts is also discussed.
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The BiFeO3 –NaNbO3 electroceramics, synthesized by the ceramic method, are studied aiming to obtain materials with a well-defined thermistor response coexisting with a relevant ...magnetic response. XRD data and Raman analysis reveal a structural transition as a function of composition. Compositional features explored from ICP, XPS and EDS measurements, suggest compositional heterogeneity leading to a cluster-type scenario implying NNO-rich and BFO-rich regions in the samples. Impedance spectroscopy data reveal the development of a PTCR thermistor response for x ≥ 0.5 near room temperature. The x = 0.9 ceramic shows resistivity changes of about six orders of magnitude in the first thermal cycle and maximum permittivity values of ∼ 105, much higher than those previously reported for BFO-doped ceramics. Magnetization data are interpreted in terms of the stabilization of superparamagnetic clusters. The response displayed by the x = 0.9 ceramic makes it a promising multifunctional material for device applications.
Wipe wastes have been used as a cellulosic source to synthesize biochars. Prior to the synthesis of the adsorbents by the pyrolysis of wipes wastes, this waste was treated to remove the pathogenic ...agents. Then, the wipe wastes were pyrolyzed between 500 and 900 °C to obtain biochars, whose microporosity increased proportionally to the pyrolysis temperature, achieving a maximum CO2-adsorption uptake of 2.53 mmol/g at a pressure of 760 mm of Hg and 25 °C for the biochar pyrolized at 900 °C. The synthesized biochars are also highly selective towards CO2-adsorption in CO2/N2 or CO2/H2 mixtures. Hence, these adsorbents have shown a great potential to be used in flue gas treatment and H2-purification processes. Biochar treatment with KOH further improves microporosity due to chemical activation although the addition of a large amount of KOH leads to excessive microporosity causing a collapse in the pore structure and decreasing CO2-adsorption capacity.
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