Characterization of Chemical Densified Coating as Tritium Permeation Barrier

In a fusion blanket design, ceramic coating on structural materials has been considered to be used as a tritium permeation barrier. The Chemical Densified Coating (CDC) method has some advantage compared with another coating method. This method is capable to form densified coating on either the outer or the inner surface of a tube or a container. This process temperature is low (450°C). The fabrication technique of Cr₂O₃-SiO₂ coating had been developed using CDC method. However, Cr₂O₃-SiO₂ coating had open pores in the coating. For filling open pores, the densification treatment by CrPO₄ was examined. In this study, the verification of open pores, the thermal shock resistivity, the adhesion strength and the deuterium permeability were evaluated and compared with Cr₂O₃-SiO₂ (Type 1) coating and Cr₂O₃-SiO₂ including CrPO₄ (Type 2) coating. From these results, it was confirmed that Type 2 coating had a good adhesion property, and permeation reduction factor of SS316 with Cr₂O₃-SiO₂ including CrPO₄ coating reached about 1,000 at 600°C.     

Permeation of indomethacin from semisolid preparations through various semipermeable membranes

Objective: The aim of this study was to evaluate and compare the permeation of model drug indomethacin (IND) from various types of gels through several semipermeable membranes.

Methods: Permeation of IND from gels based on carbomer (CA), hydroxyethylcellulose (HEC), and polyacrylamid/laureth-7/isoparaffin was performed via diffusion cell method through membranes: shed snake skin, full thickness chicken skin, mucosa of pork small intestine, and cellophane.

Results: The least permeation of IND was observed in the case of shed snake skin and full thickness chicken skin. It did not exceed 5.4% of original amount in the preparation after 3?h of measurement regardless the type of gel. In the case of mucosa of pork small intestine and cellophane the permeated amount of IND ranged from 9.4 to 55.4% depending on the type of gelling agent used. There was also quite a significant influence of a gelling agent on the permeation of IND observed. The permeation of IND was highest from CA gel, where it ranged from 0.6 to 52.2% of original amount in the preparation depending on the type of membrane used. Gelling agent inhibiting the permeation the most was HEC, where the permeated amount of IND did not exceed 12.3% regardless the type of membrane used.

Conclusions: In general the permeated amount of IND through biological membranes containing stratum corneum represented just a small part of the amount in original preparation. Gelling agent has significant effect on the extent and rate of permeation.     

Oxygen Permeation and Stability of Ce0.8Gd0.2O2-δ-PrBaCo2-xFexO5＋δ Dual-phase Composite Membranes

Dual-phase membranes of 60 wt% Ce0.8Gd0.2O2-δ-40 wt% Pr Ba Co2exFexO3 d（0 x 2） were prepared by a combined citrate and ethylene diamine tetraacetic acid（EDTA） complexing method. X-ray diffraction（XRD）results revealed the good chemical compatibility between ion-conducting phase CGO and electron-conducting phases PBC2 xFxO after sintering in air. The Fe ionic dopant had a significant effect on the phase structure stability and oxygen permeability under CO2 atmosphere, which was confirmed by XRD, thermogravimetrye differential scanning calorimetry（TGeD SC）, scanning electron microscopy（SEM） and oxygen permeation experiments. CGOeP BC0.5F1.5O dual-phase membrane demonstrated a stable oxygen permeation flux of2.71x10-7mol cm 2s 1with 50 mol% He/CO2 as the sweep gas at 925 C, and this value was much higher than that of perovskite-type membranes. The rate-limiting step in the oxygen permeation process changed from the bulk diffusion to the surface oxygen exchange when the CGOeP BC0.5F1.5O membrane thickness decreased to 0.8 mm or less. Due to the high oxygen permeation fluxes and the excellent structural stability under CO2 atmosphere, the CGOeP BC0.5F1.5O membrane is a great potential candidate material for separating oxygen from air in the oxy-fuel combustion techniques.     

Gas transfer through wine closures: A critical review

BackgroundGas transfer, and especially oxygen, through wine closures has been studied since the 90's. It started with the problem of premature oxidation in wine. To that purpose, different techniques, issued from food packaging and wine analysis, have been developed to measure gas permeation through wine stoppers.Scope and approachThe objectives of this review is, first, to briefly remind the basic knowledge of gas transfer through materials and applied to wine stoppers. Then, after a short survey about the techniques of measurement, a compilation of all currently available permeation data has been done using the international system of units (when conversion was possible). This finally allowed to establish a critical appraisal between the different methods and closures.Key findings and conclusionsAlthough relying on different principles, with different accuracy (and respective pros and cons), all methods are well suited to investigate gas transfer through closures. The manometric method appears as the most versatile one, allowing to study all gases with various sample geometry. Whatever the method used, it appears that the technical stoppers are the lowest permeable ones to gas transfer, followed by screwcaps, natural corks and synthetic stoppers. Finally, it is worthy to note that the diffusion coefficient, as an intrinsic parameter, is the most relevant parameter to characterize the gas barrier properties of wine stoppers.     

Influence of the grain structure of yttria thin films on the hydrogen isotope permeation

Steel components are required in the infrastructure and the facilities of the hydrogen economy. The high hydrogen pressures in the hydrogen economy lead to embrittlement and surface corrosion of the steels. For the functionality of the facilities it is necessary to suppress the embrittlement and the surface corrosion of the steels by protective layers, e.g. ceramic thin films. With regard to fusion power plants ceramic thin films on the structural steel materials are also required. These thin films work as a tritium permeation barrier that is necessary to prevent the loss of the radioactive fuel inventory. Oxide thin films, e.g. Al₂O₃, Er₂O₃, and Y₂O₃, are promising candidates as tritium permeation barrier layers. In terms of the application in the first wall, this is especially true for yttrium due to its favorably short decay time after neutron activation compared to the other candidates. The Y₂O₃ layers with thicknesses of 0.5 μm–1 μm are deposited on both substrate sides by RF magnetron sputter deposition. Since the microstructure of the barrier layer plays an important role for the permeation reduction, layers with three different magnetron process modes and thus three different microstructures are prepared. After annealing the cubic crystal structure of all thin films is verified by X-ray diffraction and the different microstructures are investigated by scanning electron microscopy and transmission electron microscopy. The Y₂O₃ stoichiometry of all thin films and a chromium oxide material segregation at the interface are verified by analysis methods such as X-ray photoelectron spectroscopy. The permeation reduction factors of all thin films are determined in gas-driven deuterium permeation experiments. Corresponding to the three different microstructures, reduction factors of 25, 45, and 1100 are identified. Thus, the permeation reduction is strongly dependent on the Y₂O₃ microstructure. The measurement results suggest that a high density of grain boundaries leads to a high hydrogen permeation.     

Two-step sintering technique for enhancing mechanical and oxygen permeation properties of dual-phase oxygen transport membranes

The present work involved the application of a two-step sintering (TSS) technique for typical Ce_0.9Gd_0.1O_2?δ–La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ (GDC–LSCF) composites and its effect on the microstructure and resultantly mechanical and O₂-permeating properties. The samples obtained by conventional sintering (CS) performed at 1100, 1250, and 1400 °C for 3 h exhibited maximum flexural strength and hardness values of 142 MPa and 8.71 GPa, respectively. However, the application of a TSS procedure produced fine-grained microstructures with improved mechanical properties. In particular, with the use of a typical 1250/1200 TSS protocol, increases of approximately 31 % and 7% in the flexural strength and hardness values, respectively, were observed compared to those obtained using the CS method. Moreover, thick-film (～ 60 μm) GDC–LSCF membrane prepared by tape casting and the TSS technique showed remarkably 1.5–2 times higher oxygen permeation flux than membrane sintered by CS method. The results are discussed and explained in detail.     

Investigating the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life by in-situ hydrogen permeation

In this work, we investigate the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life of a high strength pipeline steel. Both fracture toughness test and fatigue life test are carried out under different hydrogen partial pressure. The experimental results show that with the increasing of hydrogen partial pressure, fracture toughness and fatigue life decrease and the decrease trends gradually flatten out. Hydrogen has a larger effect on fatigue life than fracture toughness. Only 3% hydrogen gas can cause a 67.7% decrease of fatigue life. The in-situ hydrogen permeation test is performed respectively in 2 MPa, 5 MPa and 8 MPa hydrogen partial pressure. With the increasing of hydrogen partial pressure, the increase trend of hydrogen permeation current gradually tends to be gentle, which indicates that the hydrogen atoms entering into the material gradually become saturated. This result can be used to clarify the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life.     

Synthesis at several length scales of zeolite A membranes using a continuous flow method

Zeolite A membranes were synthesized in the inner side of porous TiO₂ and α-Al₂O₃ tubular supports by a continuous method. The methodology was then used at several scales for preparing membranes on TiO₂ and α-Al₂O₃ supports with lengths of 6, 12 and 25 cm. Formation of an homogeneous zeolite film was confirmed by XRD and SEM in all supports. Single-gas permeation experiments (He, H₂, N₂ and n-C₃H₈) indicated that Knudsen diffusion was the predominant mechanism in both supports. All the synthesized membranes present high flux and moderate selectivity to water in water–ethanol mixtures.     

Hydrogen permeation in high strength steel under load in aqueous environment

Abstract

The hydrogen assisted cracking problem is one of the major causes of the failure occurring in the high strength steel structures used in various industries. In aqueous environment, hydrogen is generated by the hydrogen reduction reaction on the steel surface. With depletion of the high quality resources in oil and gas industry, the hydrogen assisted cracking problem becomes severe in sour environment, which contains high amount of H₂S. Understanding on the hydrogen permeation behaviour is crucial to deal properly with the hydrogen related problems since they are primarily determined by the hydrogen uptake and transport in the steel. The Devanathan–Stachurski method is widely used to evaluate electrochemically the hydrogen permeation behaviour. This method has been successfully used for the steel with no load. Under loading condition, this electrochemical test method has been modified to accommodate the externally applied load. However, the data require careful examination to validate the technical importance because of the stability and homogeneity of palladium layer coated on the steel surface under load. In this paper, the hydrogen permeation test method under loading condition will be reviewed for the high strength steels used in oil and gas industry. The factors affecting the hydrogen permeation in the high strength steel will be discussed in terms of the applied stress level and the sulphide film forming on the steel surface in sour environment.     

Hydrogen permeation across super‐thin membrane and the burning limitation in low‐temperature proton exchange membrane fuel cell

Hydrogen permeation across the membrane is unavoidable in proton exchange membrane fuel cells, especially for super‐thin membranes, which lowers the open‐circuit voltage and could even be a safety concern. In this paper, hydrogen permeation across two membranes (25‐um‐thick Nafion^® 211 and 18‐um‐thick reinforced composite membrane) are evaluated at various temperatures, relative humidity (RH), and gas pressure differences between the anode and cathode. The results indicate that the hydrogen permeation rate in both membranes increases almost exponentially with temperature and linearly with pressure differences. Compared with RH, the effects of temperature and pressure differences are more crucial to hydrogen permeability. However, the effect of RH on the hydrogen permeation is quite complicated. The permeability exhibits a minimum value at intermediate RH (approximately 40% RH) for both applied membranes. The permeability of Nafion^® 211 appears more sensitive to RH than that of reinforced composite membrane at elevated temperature. Copyright © 2013 John Wiley & Sons, Ltd.