Display omitted
•The turnover rate for CO2 hydrogenation was independent of Ni particle size.•The selectivity for CH4 decreased in favor of CO on the smallest 1.3 nm Ni particles.•Supported Ni ...reduced to metal particles on ceria at lower temperature than on alumina.•The observed kinetics of methane formation on metallic Ni were unaffected by support.
Nickel nanoparticles were supported on CeO2 and evaluated in the hydrogenation of CO2 to CH4 at 538 K and 1 atm. Chemisorption of H2 was used to estimate the average Ni particle size, which ranged from 1.3 to 17 nm. The apparent activation energy for CH4 formation and turnover frequency for CO2 conversion was independent of Ni particle size. The smallest Ni particles (1.3 nm) were less selective to CH4. Comparisons to alumina-supported Ni reveal the same performance as Ni/CeO2 when normalized to active Ni atoms counted by H2 chemisorption. A beneficial effect of ceria relative to alumina is the enhanced reducibility of Ni as evaluated by H2 temperature-programmed reduction. The constancy of the turnover frequency on Ni particles suggests the acid-base and/or redox properties of the support do not play a significant role in the CO2 methanation reaction under the conditions of study, which contrasts many earlier works.
Total hip arthroplasty implant choice profoundly affects survivorship, complications, and failure modes. This study evaluates the long-term (average 18 year) outcomes of ceramic-on-ceramic hip ...arthroplasty using uncemented shells and stems. Despite an impressive 20-year cumulative percent revision of 5.9%, the hydroxyapatite proximally coated femoral components evaluated in this study have seen declining use since 2003.
A review of 349 consecutive total hip arthroplasties from 1999 to 2007 was matched to 272 cases with registry data. A survivorship analysis included 274 hips (Group A) after excluding patients lost to follow-up and navigated cases. Group B comprised 135 patients who had complete datasets spanning a minimum of 15 years.
Kaplan-Meier analysis identified a 95.6% survivorship plateau at 16 to 24 years, with no significant impact from age, sex, component size, or original pathology. In Group B, EuroQol-5 Dimensions-5 Levels (EQ5D5L) scores indicated favorable outcomes in mobility, self-care, activities, pain/discomfort, and anxiety/depression, with an EQ5D visual analog score mean of 79.24. Functional scores, including the Harris Hip Score, Oxford Hip Score, and Forgotten Joint Score, showed positive outcomes. Radiologic assessments revealed no osteolysis or loose components, with a mean Engh score of 21.69. Dorr classification identified bone quality variations. Better Engh scores corresponded to higher levels of patient satisfaction. Age at surgery was correlated with better functional scores, while sex influenced various outcomes.
This comprehensive study, spanning an average of 18.23 years, combined multiple patient-reported outcome measures with extensive clinical and radiologic follow-up. It reported a notably high survivorship rate for this implant combination but highlighted the declining use of the hydroxyapatite proximally coated femoral stem used in this study, potentially facing withdrawal risks in Australia.
Therapeutic Level IV.
•Influence of alumina content on fs-laser machining of zirconia-alumina composites was studied.•Significant influence of material composition on material removal behavior was demonstrated.•Single ...phase materials have larger laser ablation thresholds and smaller material removal rate than their composites.•A lower scan speed is preferred for single phase materials while a higher scan speed is beneficial for the composites.
Laser texturing of zirconia-alumina ceramics is a promising surface modification method for many applications, such as enhancing osseointegration of alumina toughened zirconia (ATZ) dental implants or improving friction behavior of zirconia toughened alumina (ZTA) hip replacement bearing components. The common problems in laser texturing of ATZ/ZTA ceramics are thermal cracking, low material removal rate (MRR), and laser-induced phase transformation (LIPT). Furthermore, the compositional variation of those ceramics will complicate these problems. In order to improve the manufacturing processability, ultrashort pulsed laser ablation behavior of ATZ/ZTA composites was investigated in this research. Single phase zirconia and alumina were found to have smaller MRRs than their composites, and this behavior was negatively correlated to the materials single-pulse laser ablation threshold. However, under multi-pulse laser irradiation, the ablation thresholds of all materials saturated to the same level, indicating that single phase materials were more sensitive to the incubation effect than their composites. This led to the MRRs of the single phase materials being reduced at larger scan speeds, while the MRRs of their composites remained independent of scan speed. It was also shown that single phase materials were less susceptible to thermal cracking than their composites under excessive heat accumulation. These results suggest that a lower scan speed is preferred for single phase materials in order to achieve a larger MRR, while a higher scan speed is beneficial for the composites for suppressing thermal cracking without compromising ablation efficiency. In addition, no LIPT was detected for zirconia dominated materials after laser ablation.
•Hydroxylated Al2O3 showed high activity for photodegradation of phenolic compounds.•α-Al2O3, boehmite and P-25 showed lower photocatalytic activity than Al2O3-400̊C.•Rietveld analysis indicates ...presence of hydroxyl groups in Al2O3annealed at 400̊C.•The generated hydroxyl groups are responsible for photocatalytic properties of Al2O.
Al2O3 was synthesized by the sol–gel method, dried at 100°C and annealed at 400, 500, 600 and 700°C, respectively. These materials were characterized and evaluated to be used as photocatalysts for the degradation of phenol in aqueous phase. Although Al2O3 is a well-known insulator, in the present study we show the feasibility of using Al2O3 synthesized by the sol–gel method as a catalyst for the photomineralization of hazardous organic molecules. The photocatalytic activity of these materials was higher than that of Degussa P-25 TiO2, and other commercial aluminas tested, particularly in the case of the sample of Al2O3 calcined at 400°C. The results of Nuclear Magnetic Resonance of solids (27AlMAS NMR) indicate that Al changes its coordination number during the calcination process. Rietveld refinement of the X-ray diffraction patterns denotes a notable hydroxylation in the Al2O3 structure, which was not removed by thermal treatments. Complementary spectroscopic studies (UV–Vis and FTIR) as well as the characterization of the textural properties are reported. It is proposed that UV irradiation of the hydroxylated Al2O3 induces an effective separation of the electron–hole pairs and hence, promotes the photodegradation of phenolic compounds.
In this study, microwave assisted ammonia decomposition reaction to produce high purity hydrogen over γ-Al2O3 supported molybdenum based catalysts were investigated and the effects of various ...promoters, rare-earth (lanthanum, cerium) and alkaline-earth (calcium and barium) elements on the catalytic activity were studied. Ammonia conversions of over 94 % were obtained over the unpromoted catalysts above 350 °C at a flow rate of 60 ml/min of pure ammonia. The overall hydrogen production rate per gram of catalyst was found to be 72.86 mmol/min.gcat with for 30 wt% Mo loaded unpromoted catalyst at 350 °C. The apparent activation energy (Ea) values for these catalysts were found to be around 85 kJ/mol. Among the promoters, Ba and Ce gave better performance below 350 °C than Ca and La and the optimum loading was found to be 4 wt% for them. Neither molybdenum nitride nor molybdenum carbide were detected in the spent form of the catalysts.
Display omitted
Hydrazine electro-oxidation (HzEO) and water oxidation reaction (WOR) offer high energy conversion efficiency and applicability in electrolysis cells and direct hydrazine fuel cells (DHFC). However, ...the unavailability of affordable and robust catalysts hinders the widespread commercialization of these devices. In this work, RuO2−CuO/Al2O3 ternary composites, synthesized by co-impregnation technique are presented as efficient novel electrocatalysts for HzEO and WOR. Average crystallite size of 59.2 nm, enlarged electrochemical surface area i.e., 0.87 cm2, nanosized pores and higher oxygen vacancies indicated a more facile and super-efficient catalysis phenomenon over ternary catalysts. Electrochemical analysis perceived via voltammetric cycling and impedance measurements complimented the structural modifications and produced an enhanced electrocatalytic output in alkaline environment. Higher diffusion coefficient (10.4 × 10 4 cm2 s−1), larger rate constant (6.3 × 10−7 cm s−1), reduced Rct (5.1 kΩ), and enhanced current density (9.3 mA cm−2) suggested a feasible and proficient catalysis mechanism over the 1.0% RuO2−CuO/Al2O3 electrode. Robust reactions occurred on the RuO2−CuO/Al2O3 catalysts paved a pathway towards their extensive electrochemical investigations for energy conversion processes.
RuO2–CuO/Al2O3 ternary metal oxide composite as bifunctional catalyst for HzEO and WOR displaying a low Rct and large oxidation current. Display omitted
•RuO2–CuO/Al2O3 metal oxide composites are synthesized by impregnation technique.•Mesoporous RuO2–CuO/Al2O3 nanomaterials are studied for electro-oxidation of water and N2H4.•The catalysts displayed bifunctionality being catalytically active in water oxidation and HzEO reactions.•Defects in electronic structure and enlarged oxygen deficiencies lead to promoted catalysis performance.
For the cost-effective fabrication of Na+-β/β"-alumina solid electrolyte, we developed a synthesizing-cum-sintering process as an alternative to the conventional solid-state reaction process. To ...improve mechanical and electric properties of Na+-β/β"-alumina, we added MnO2 and Ta2O5/YSZ (partially Y2O3-stabilized zirconia, 8.0 wt% fixed) as a dopant to the Na+-β/β"-alumina. For MnO2-doped specimens, the β"-alumina phase fraction, relative sintered density, and ionic conductivity increased when the MnO2 amount changed from 0.0 to 1.0 wt%. The maximum ionic conductivity, i.e., 1.0 × 10−1 S/cm at 350 °C, was achieved with the 1.0 wt% MnO2-doped Na+-β/β"-alumina sintered specimen. For Ta2O5-doped Na+-β/β"-alumina/YSZ composite sintered specimens, ionic conductivity increased when the Ta2O5 amount changed from 0.0 to 0.3 wt%. The 0.3 wt% added Ta2O5-doped Na+-β/β"-alumina/YSZ composite sintered specimen exhibited ionic conductivity as high as 1.1 × 10−1 S/cm at 350 °C.
For a full understanding of effects of nano-alumina on early-age hydration, hydration of a Portland cement blended with 5% of nano-alumina (γ-phase) was studied. Except for the well-known filler ...effect, a chemical effect of nano-alumina was identified in the study, which is related to its dissolving behavior in pore solution. The dissolution of nano-alumina leads to a high initial ettringite content even in the first 10 min, thus a higher initial heat release. The continuous dissolution of nano-alumina contributes to formation of additional ettringite, which consumes aqueous S species, promotes the depletion of gypsum, thus accelerating reaction of aluminate (C3A). The dissolution of nano-alumina may also be influenced by S species in pore solution during the induction period. Afterwards, the slow dissolution of nano-alumina only results in a slightly increased aqueous Al concentration for the further increase would be limited by Al-bearing hydrates such as ettringite and AFm phases.
•A cheap but effective photocatalyst was developed by Al powder and a sol–gel technique.•The developed mesoporous Ti-doped γAl2O3 xerogel showed exceptional catalytic potential.•Ti-γAl2O3 catalysed ...the formation of HO· when irradiated under ultraviolet A photons.•High degree of chemical and microbial water decontamination was attained.•Ti-γAl2O3 is a stable catalyst with relatively high reusability in the photocatalytic process.
In this work, a Ti-doped alumina (Ti-γAl2O3) xerogel (TAX) was synthesized from Al powder as a cost-effective precursor. Full physical, chemical, structural, and electrochemical characterization of the prepared materials were performed. It was shown that as-made Ti-γAl2O3 is a mesoporous nanomaterial with high specific surface area, uniform morphology, the existence of polyhedral coordinated Al3+ ions, many acidity active sites, high light absorption efficiency, and effective bandgap energy. These features made it an efficient photocatalyst for water photocatalytic treatment. In the photocatalytic process with the TAX as the catalyst irradiated by the ultraviolet A photons, around 97% of 10 mg/L Remdesivir (RDV) was degraded within 30 min (pH = 7, TAX = 100 mg/L), and elucidation of the degradation pathway was achieved; low adsorption and minimal O2·- contribution was found in the otherwise HO•-dominated photocatalytic process, as suggested by the scavenger tests. The Electron Paramagnetic Resonance spectroscopy validated the proposed species (but not 1O2), while the RDV degradation pathway towards mineralization was proposed by Liquid Chromatography–Mass Spectrometry analysis. Besides, concerning its applicability, the effect of operational parameters (pH, TAX, RDV, water matrix) was scrutinized and validated a notable performance over several consecutive reused cycles. Finally, almost 6.5 log E. coli inactivation was attained (in mild conditions), all indicating the high photocatalytic potential of this material.
PDF
