Oxygen transport in La0.5Sr0.5Fe1−yTiyO3− δ ( y =0.0, 0.2) membranes

The influence of partial substitution of Fe with Ti on the oxygen transport properties of La1−x Sr x FeO3 membranes was investigated in view of their application for oxygen separation. Samples of composition $$La_{{0.5}} Sr_{{0.5}} {\text{Fe}}_{{1 - y}} {\text{Ti}}_{y} {\text{O}}_{{3 - \delta }}$$ (y=0, 0.2) were prepared and their oxygen transport properties characterised by potential step relaxation and by oxygen permeation measurement in an air/argon gradient. With the first technique, chemical diffusion $${( {\widetilde{D}} )}$$ and surface exchange (k S) coefficients were obtained by fitting of the current relaxation data to a single expression valid over the complete time range. The Ti-substituted composition gave slightly larger values of $${\widetilde{D}}$$ and k S. The trend was opposite for the measured oxygen permeation flux. In the latter experience, ordering of oxygen vacancies was observed at lower temperature, reducing significantly the performance of the materia

Properties of B-site substituted La0.5Sr0.5FeO3−δ{\mathbf{La}}_{{0.5}} {\mathbf{Sr}}_{{0.5}} {\mathbf{FeO}}_{{3 - {\mathbf{\delta }}}} perovskites for application in oxygen separation membranes

Mixed ionic-electronic conducting $$La_{0.5} Sr_{0.5} Fe_{1 - x} B_x O_{3 - \delta }$$ (B: Al, Cr, Zr, Ga, Ti, Sn, Ta, V, Mg, and In with x = 0, 0.1, 0.2) perovskite materials were produced via solid-state synthesis. In order to study the effect of B-site substitution on the expansion behavior of these materials, their thermal expansion in air up to 900°C and isothermal expansion at the same temperature from air to Ar were measured by dilatometry. Ti and Ta were found to be the most effective substitutions in suppressing the isothermal expansion. The isothermal expansion at 900°C from air to Ar was reduced by 50% by substitution of 20% Ti or 10% Ta. Therefore, these compositions were further characterized by 4-probe total DC conductivity and permeation measurements under air/Ar gradient. The total conductivity of $$La_{0.5} Sr_{0.5} FeO_{3 - \delta }$$ was decreased by more than one order of magnitude at low temperatures and from 430S/cm, which is the maximum, to around 100S/cm at 500°C with the addition of Ti and Ta. The normalized oxygen permeation of LSF at 900°C decreased from 0.18 to 0.05μmol/cm2s and 0.07μmol/cm2s with the substitution of 20% Ti and 10% Ta, respectivel

Ethanol internal steam reforming in intermediate temperature solid oxide fuel cell

This study investigates the performance of a standard Ni-YSZ anode supported cell under ethanol steam reforming operating conditions. Therefore, the fuel cell was directly operated with a steam/ethanol mixture (3 to 1 molar). Other gas mixtures were also used for comparison to check the conversion of ethanol and of reformate gases (H2, CO) in the fuel cell. The electrochemical properties of the fuel cell fed with 4 different fuel compositions were characterized between 710 and 860°C by I-V and EIS measurements at OCV and under polarization. In order to elucidate the limiting processes, impedance spectra obtained with different gas compositions were compared using the derivative of the real part of the impedance with respect of the natural logarithm of the frequency. Results show that internal steam reforming of ethanol takes place significantly on Ni-YSZ anode only above 760°C. Comparisons of results obtained with reformate gas showed that the electrochemical cell performance is dominated by the conversion of hydrogen. The conversion of CO also occurs either directly or indirectly through the water-gas shift reaction but has a significant impact on the electrochemical performance only above 760°C

In-situ experimental benchmarking of solid oxide fuel cell metal interconnect solutions

The progress in the diffusion of solid oxide fuel cell (SOFC) as commercial devices is not paired by literature production. Articles describing the behaviour of SOFC stacks are rare because of confidentiality reasons for commercial suppliers while research centres prefer to focus on single components or low technology readiness level research. This article aim to fill this gap presenting the analysis of three short stacks run in operative conditions for 10 000 h each. The stacks are characterized through voltage vs time curves, electron microscopy, and electrochemical impedance spectroscopy. Focus is given on the interconnect; notably on the different types of coatings, varying for composition (MnCo2O4, MnCo1.8Fe0.2O4) and deposition technique (atmospheric plasma spray-APS, physical vapour deposition-PVD, wet powder spraying-WPS). Nitriding of the steel substrate as a solution to improve the chromium retention properties is tested as well

Oxygen transport and nonstoichiometry in SrFeO3-delta

Chemical diffusion (D) and surface exchange (k) coefficients for SrFeO3-delta were measured using an electrochemical cell combined with electrochemical impedance spectroscopy (EIS) and potential step technique (PS) in the temperature range of 850-915°C. A value of ~ 4x10-5 cm2/s and a k value of ~ 8x10-5 cm/s were obtained at 900°C. Slow scan (0.5-3 microV/s) cyclic voltametry (CV) was performed in the same temperature range, using the same electrochemical cell to obtain oxygen nonstoichiometry data. The oxygen nonstoichiometry (delta) at 900°C in air was determined as 0.4. A plateau corresponding to delta = 0.5 was observed below an oxygen partial pressure (pO2) of 10-6 atm. These results were shown to be consistent with the literature data. Nonstoichiometry data were further analysed using the existing defect models, and the limits of the independent point defect approximation and the necessity of considering interactions between point defects and clusters were established. Keywords: Strontium Ferrate/Ferrite; Oxygen transport; Oxygen nonstoichiometry

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_{3−<em>δ</em>} (BSCF) feedstock development and optimization for thermoplastic forming of thin planar and tubular oxygen separation membranes

This paper presents the processing steps for producing thin planar and tubular oxygen separation membranes by thermoplastic forming of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) with polystyrene (PS) and stearic acid (SA) as binder. The influence of powder content on the shape stability of thin membranes (tubular and planar structures) during the thermoplastic processing route was investigated. The effect of powder content on mixing torque and the rheological behavior were investigated. The effect of the powder content could be analytically described using the model proposed by Frankel and Acrivos. The deformation of free standing green bodies was investigated using disks. The result showed that increasing the powder content is remarkably effective to minimize the deformation of the membrane during the thermal debinding step. By using a high powder content (60 vol. %) and a multicomponent binder system composed of PS, SA and paraffin wax (PW), it was possible to achieve disks and thin wall tubular structures without deformation after sintering. Using capillary rheometer an unexpected decrease in the total extrusion pressure was measured for the feedstock containing PW. The change in apparent activation energy between 800–1000 °C was not related to the membrane properties

Clinical aspects of Mayer-Rokitansky-Kuester-Hauser syndrome: recommendations for clinical diagnosis and staging

BACKGROUND: The Mayer-Rokitansky-Kuester-Hauser (MRKH) syndrome is a malformation of the female genitals (occurring in one in 4000 female live births) as a result of interrupted embryonic development of the Müllerian (paramesonephric) ducts. This retrospective study examined the issue of associated malformations, subtyping, and the frequency distribution of subtypes in MRKH syndrome. METHODS: Fifty-three MRKH patients were investigated using a newly developed standardized questionnaire. Together with the results of clinical and diagnostic examinations, the patients were classified into the three recognized subtypes [typical, atypical and MURCS (Müllerian duct aplasia, renal aplasia, and cervicothoracic somite dysplasia)]. RESULTS: The typical form was diagnosed in 25 patients (47%), the atypical form in 11 patients (21%), and the most marked form—the MURCS type—in 17 patients (32%). Associated malformations were notably frequent among the patients. Malformations of the renal system were the most frequent type of accompanying malformation, with 23 different malformations in 19 patients, followed by 18 different skeletal changes in 15 patients. CONCLUSIONS: In accordance with the literature, this study shows that associated malformations are present in more than a third of cases. Therefore, new basic guidelines for standard diagnostic classification involving patients with suspected MRKH are presente

Noninferiority of cetuximab every-2-weeks versus standard once-weekly administration schedule for the first-line treatment of RAS wild-type metastatic colorectal cancer

Abstract Aim This study assessed whether cetuximab 500 mg/m2 administered every 2 weeks (Q2W), when combined with chemotherapy as a first-line (1L) treatment, was noninferior to the approved dose (400 mg/m2 followed by 250 mg/m2 once weekly [Q1W]) for overall survival (OS) in adults with RAS wild-type metastatic colorectal cancer (mCRC). Methods This pooled analysis included patients receiving 1L treatment with cetuximab Q1W or Q2W in combination with chemotherapy from post-authorisation studies with patient-level data available to the sponsor. Baseline characteristics were adjusted with a propensity score using inverse probability of treatment weighting (IPTW). Noninferiority in terms of OS was tested with a noninferiority margin for the hazard ratio (HR) of 1.25 using a Cox proportional hazards regression model. Secondary outcomes were progression-free survival (PFS), overall response rate (ORR) and rates of lung/liver metastases resection and serious adverse events. Results OS time was noninferior in the Q2W cohort (n = 554) compared to the Q1W cohort (n = 763), with a HR after IPTW (95% confidence interval) of 0.827 (0.715–0.956) and median OS times of 24.7 (Q1W) and 27.9 (Q2W) months. There were no major differences in PFS (HR: 0.915 [0.804–1.042]). The odds ratios (ORs) after IPTW for ORR (1.292 [1.031–1.617]) and the rates of lung/liver metastases resection (1.419 [1.043–1.932]) favoured the Q2W regimen. No differences were noted in the occurrence rate of any SAE between groups; the OR after IPTW was 1.089 (0.858–1.382). Conclusions The cetuximab Q2W regimen was noninferior to the Q1W regimen for OS in the 1L treatment of mCRC