Oxygen Permeation Rate Research Articles

Optimizing properties of nanoclay–nitrile rubber (NBR) composites using Face Centred Central Composite Design

The properties of acrylonitrile butadiene copolymer (NBR)–nanoclay composites were modelled using response surface methodology (RSM). A Face Centred Central Composite Design (FCCD) with four factors and three levels was used to obtain the relationship between nanocomposite properties and levels of ingredients. The factors considered in the design were silica content, nanoclay content, vulcanization system and dicumyl peroxide content. The nanocomposites were evaluated for tensile strength, modulus, elongation at break, oxygen permeation rate and effect of oil ageing on mechanical properties. Regression equations were generated to model the properties of interest and generate response surfaces and contour plots. The predicted properties of the nanocomposites were in good agreement with the experimental results. The contour plots were overlaid within the applied constraints to identify the combination of factor ranges that gives the optimal performance of the nanocomposites for application in control system bladders for launch vehicle applications.

Functional LSM–ScSZ/NiO–ScSZ dual-layer hollow fibres for partial oxidation of methane

In this study, a functional La 0.80Sr 0.20MnO 3−δ (LSM)–Scandia-Stabilized-Zirconia (ScSZ)/NiO–ScSZ dual-layer hollow fibre has been developed using a single-step co-extrusion and co-sintering process, and has been employed as a dual-layer hollow fibre membrane reactor for partial oxidation of methane. Oxygen permeation rate between 0.49 and 1.82 ml/min and methane conversion between 53.55% and 98.78% have been achieved when operating temperature is elevated from 920 to 1060 °C, together with a significant reduction in coke-deposition. Oxygen permeation through the outer LSM–ScSZ permeation layer (approximately 109.2 μm in thickness) is found to be the controlling step to methane conversion at the operating temperature below 990 °C, above which the excessive oxygen permeation results in formation of CO 2 and H 2O as by-products. The experimental results further suggest that the amount of NiO in the inner NiO–ScSZ layer should be optimised based on the factors such as catalytic activity/stability, porosity and mechanical strength in addition to the sintering behaviour which has to be matched to the outer LSM–ScSZ layer.

Thermodynamic evaluation of membrane based oxyfuel power plants with 700 ° C technology

Abstract Cryogenic air separation is the only available state-of-the-art technology for oxyfuel power plants and represents an important burden to the total plant efficiency. Nowadays, high temperature ceramic membranes, which are associated with significantly lower efficiency losses, are foreseen as the best candidate to challenge cryogenics for high tonnage oxygen production for this type of CCS power stations. In this study, two oxyfuel plant designs were developed, the first based on the state-of-the-art supercritical 600 °C hard coal plant Nordrhein-Westfalen and the second on the advanced ultra-supercritical 700 °C pulverized coal-fired power plant. The membrane-based air separation unit was modeled considering the three-end concept, where oxygen is transported across the membrane aided by a compressor at the feed side and by a vacuum pump at the permeate side. This paper analyzes the influence of both, the cryogenic and high temperature membrane air separation units on the net plant efficiency, considering the same boundary conditions and equivalent thermal integrations. Moreover, the oxygen permeation rate, heat recovery, and required membrane area are also evaluated at different membrane operating conditions.

10.2478/s11814-009-0263-y

Organic/inorganic hybrid coating materials were synthesized using acrylate end-capped polyester, 1,6-hexanediolacrylate, tetraethoxysilane (TEOS), and 3-trimethoxysilylpropylmethacrylate (TMSPM). The hybrid materials were cast onto a polycarbonate (PC) substrate and cured by UV irradiation to give a hybrid film with covalent linkage between the inorganic and the organic networks. The coating layer was characterized by FT-IR and 29Si-NMR, and pencil hardness and oxygen permeation rate of coated films were investigated. The pencil hardness of all samples examined in this study was higher than 1H, whereas that of uncoated PC substrate was 6B. The hardness enhancement after coating may due to incorporation of organic acrylate resin. The oxygen permeability coefficient of the film coated with hybrid material on 3-aminopropyltriethoxysilane (APTEOS) pretreated polycarbonate substrate was 1.67×10−3 GPU, the lowest value in this work, whereas that of uncoated PC substrate was 8.07×10−3 GPU. The lower oxygen permeation rates of these films are attributed to the good adhesion between organic/inorganic hybrid coating layer and PC substrate and a dense structure induced by an increase of network density.

Thermodynamic analysis of a hard coal oxyfuel power plant with high temperature three-end membrane for air separation

Cryogenic air separation is a mature state-of-the-art technology to produce the high tonnage of oxygen required for oxyfuel power plants. However, this technology represents an important burden to the net plant efficiency (losses between 8% and 12%-points). High temperature ceramic membranes, associated with significantly lower efficiency losses, are foreseen as the best candidate to challenge cryogenics for high tonnage oxygen production. Although this technology is still at an embryonic state of development, the three-end membrane operation mode offers important technical advantages over the four-end mode that can be a good technological option in the near future. This paper analyzes the influence of both, the cryogenic and three-end high temperature membrane air separation units on the net oxyfuel plant efficiency considering the same boundary conditions and different equivalent thermal integrations. Moreover, the oxygen permeation rate, heat recovery, and required membrane area are also evaluated at different membrane operating conditions. Using a state-of-the-art perovskite BSCF as membrane material, net plant efficiency losses up to 5.1%-points can be reached requiring around 400,000 m 2 of membrane area. Applying this membrane-based technology it is possible to improve the oxyfuel plant efficiency over 4%-points (compared with cryogenic technology); however, it is still necessary to develop new ceramic materials to reduce the amount of membrane area required.

Void volume variations in contact lens polymers

In this study, void size and free volume properties in different contact lens materials have been investigated in their hydrated state using positron annihilation lifetime spectroscopy (PALS). PALS is used to characterize the void size distributions inside the lens materials. Three different types of contact lenses were used (Balafilcon A, Hilafilcon B and Polymacon). Measurements on different contact lenses reveal significant differences between the materials, up to ∼ 100% difference in void volume was observed between Hilafilcon B and Balafilcon A, the latter having larger voids. As oxygen diffusion is strongly correlated with the void sizes, the results are in good agreement with the usage recommendations of the specific lens types (daily disposable lenses or 1 month continuous use lenses). The void sizes in monthly lenses (Balafilcon A) were found to decrease 25% under artificial aqueous tear (albumin-water solution) exposure in 4 weeks leading to a significant decrease in the oxygen permeation rate through the contact lens. Yet, the voids were still significantly larger than in disposable or semi-disposable lenses. We have showed that PALS is a viable method to probe the microstructure of biotechnologically relevant polymers and can be used to quantify the void properties in different types of contact lenses. Usage recommendations correlate well with measured void sizes and the median void size decreases during the incubation of albumin solution as a function of time. We anticipate the use of PALS for any polymer-based intracorneal/intraocular device in which diffusivity plays a crucial role.

ChemInform Abstract: Mixed Electronic-Oxide Ionic Conductivity and Oxygen Permeating Property in Ni Doped LaGaO3 Perovskite Oxide.

It was found that LaGaO3 perovskite oxide doped with Ni for Ga site exhibits a high mixed electronic-oxide ionic conduction. Oxygen permeation rate was increased with increasing Ni content and it attained to a maximum value of 2.15 cm3/min cm2 at 1273 K when 25 mol% Ni was doped.

High Oxygen Permeation Rate in La0.6Sr0.4Ti0.3Fe0.7O3 Thin Membrane on a Porous Support with Multichannel Structure for CH4 Partial Oxidation

A preparation of La0.6Sr0.4Ti0.3Fe0.7O3 (LSTF) perovskite oxide on a support with a unique multichannel structure achieved a high oxygen permeation rate. A LSTF thin membrane with 60 μm thickness was successfully prepared on the multichannel support with 30% porosity. The oxygen permeation rate was much improved by using the multichannel structured support, as the permeated oxygen was removed rapidly. On the other hand, partial oxidation of CH4 into CO and H2 is dominant on the LSTF membrane. The oxygen permeation rate increased as the thickness of the membrane and the porous support decreased, and a value of 13.3 cm3/(min cm2) was achieved at 1273 K under a CH4 partial oxidation condition.

Effect of Co doping on oxygen permeation in Sr 3Ti 2O 7 with Ruddlesden-Popper structure

Effects of transition metal dopant to Ti site in Sr 3Ti 2-xM xO 7 (M = Fe, Ga, Co) on the electrical conductivity and the oxygen permeation property were investigated. Among the examined dopants, it was found that doping Co is the most effective for improving the electrical conductivity and the oxygen permeation rate. With increasing Co amount, electrical conductivity and oxygen permeation rate monotonically increased and the highest oxygen permeation rate is achieved at Sr 3Ti 0.8Co 1.2O 7 among the Co doped sample. On this composition, the oxygen permeation rate from air to He is achieved a value of 2.02 cc/min.cm 2 at 1273 K.

Comparison of some coating techniques to fabricate barrier layers on packaging materials

Atomic layer deposition (ALD), electron beam evaporation, magnetron sputtering and a sol–gel method were used to deposit thin aluminum oxide coatings onto two different fiber-based packaging materials of commercial board grades coated with synthetic and biodegradable polymers. Significant decreases in both the water vapor and oxygen permeation rates were observed. With each technique the barrier performance was improved. However, among the techniques tested ALD was found to be most suitable. Our results moreover revealed that biodegradable polylactic acid-coated paperboard with a 25-nm thick layer of aluminum oxide grown by ALD on top of it showed promising barrier characteristics against water vapor and oxygen.

Perovskite membrane of La 1− xSr xTi 1− yFe yO 3− δ for partial oxidation of methane to syngas

The substitution of A-site alkali ions and B-site transition metal ions of the perovskite oxide oxygen-permeating membrane system of La 1− x Sr x Ti 1− y Fe y O 3− δ , (LSTF) has been studied for their application to the partial oxidation of methane to syngas. Both the substitution of Fe for Ti, and the substitution of Sr for La increased the p-type electronic and oxygen ionic conductivities to 155 and 0.47 S cm − 1 respectively. From 800 to 1000 °C, the temperature dependence of conductivity has been studied, and the thermal activation energy of the p-type electronic conductivity of La 0.6Sr 0.4Ti 0.1Fe 0.9O 3− δ was found to be 38 kJ/mol and those of the ionic conductivity of La 0.6Sr 0.4Ti 1− y Fe y O 3− δ ( y = 0.7 and 0.9) were 11 and 20 kJ/mol. The thermal expansion coefficients of LSTF were varied from 10.8 to 17.0 (× 10 − 6 /K − 1 ) by increasing the Fe substitution. La 0.6Sr 0.4Ti 0.3Fe 0.7O 3− δ was the optimized composition with a good trade-off of the high ion conductivity, 0.07 S cm − 1 , and good matching of the thermal expansion coefficient, 12.4 × 10 − 6 /K − 1 . It has been tested for the partial oxidation of methane to syngas and shows a high oxygen permeation rate of 13.8 cm 3/min/cm 2 at 1000 °C or 10.5 cm 3/min/cm 2 at 900 °C. In addition, High values of CH 4 conversion and CO selectivity were confirmed at 900 °C, 60.0% and 99.9% respectively.

Influence of sintering conditions on microstructure and oxygen permeation of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ (BSCF) oxygen transport membranes

Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ (BSCF) exhibits high oxygen permeability, which is why it is being discussed for gas separation (oxygen transport membrane, OTM) in zero-emission power plants using oxyfuel technology when the membrane is operated in a clean environment, i.e. no flue gas contact. We investigate the influence of membrane processing on microstructure and oxygen permeation. Pure-phase BSCF powder is synthesized using a modified Pechini method. For comparison, commercially available powder is also used, synthesized by a solid-state reaction. Disk-shaped membranes of various microstructures, i.e. closed porosities and grain sizes, are prepared by uniaxial pressing and sintering of the powders processed in different ways. The powders and membranes are characterized by methods including BET, SEM, XRD, and DSC. The microstructures obtained by different sintering conditions are investigated by SEM and TEM. Sintering at 1150 °C leads to incongruent melting of BSCF indicated by DSC. The liquid phase appears at three-phase boundaries grain–grain–air and consists of nearly pure cobalt oxide with small impurities of barium and strontium detected by TEM/EDX analysis. Oxygen permeation of the membranes is measured in an air/Ar gradient depending on temperature and membrane microstructure. The closed porosity of different processed membranes is varied between 2 and 15% with uniform grain sizes in the range of approx. 10 μm. The average grain size is increased from 10 to 45 μm by increasing the sintering temperature. Neither porosity nor the grain size significantly influences the oxygen permeation rate of 1-mm-thick disks in the investigated parameter range.

Crystal Structure, Diffusion Path, and Oxygen Permeability of a Pr2NiO4-Based Mixed Conductor (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+δ

We have investigated in situ the crystal structure, oxygen diffusion path, oxygen permeation rate, and electrical conductivity of a doped praseodymium nickel oxide, Pr(2)NiO(4)-based mixed conductor, (Pr(0.9)La(0.1))(2)(Ni(0.74)Cu(0.21)Ga(0.05))O(4+delta) (PLNCG) in air between 27 degrees C and 1015.6 degrees C. The PLNCG has a tetragonal I4/mmm K(2)NiF(4)-type structure which consists of a (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) perovskite unit and a (Pr(0.9)La(0.1))O rock salt unit in the whole temperature range. Both experimental and theoretical electron density maps indicated two-dimensional networks of (Ni(0.74)Cu(0.21)Ga(0.05))-O covalent bonds in PLNCG. Highest occupied molecular orbitals (HOMO) in PLNCG demonstrate that the electron-hole conduction occurs via Ni and Cu atoms in the (Ni(0.74)Cu(0.21)Ga(0.05))-O layer. The bulk oxygen permeation rate was high (137 mumol cm(-2) min(-1) at 1000 degrees C), and its activation energy was low (51 kJ mol(-1) at 950 degrees C). The Rietveld method, maximum-entropy method (MEM), and MEM-based pattern fitting analyses of neutron and synchrotron diffraction data indicate a large anisotropic thermal motion of the apical O2 oxygen at the 4e site (0, 0, z; z approximately 0.2) in the (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) perovskite unit. Neutron and synchrotron diffraction data and theoretical structural optimization show the interstitial oxygen (O3) atom at (x, 0, z) (x approximately 0.6 and z approximately 0.2). The nuclear density analysis indicates that the bulk oxide-ion diffusion, which is responsible for the high oxygen permeation rate, occurs through the interstitial O3 and anisotropic apical O2 sites. The nuclear density at the bottleneck on the oxygen diffusion path increases with temperature and with the oxygen permeation rate. The activation energy from the nuclear density at the bottleneck decreases with temperature, which is consistent with the decrease of the activation energy from oxygen permeation rate. The extremely low activation energy (12 kJ mol(-1) at 900 degrees C) from the nuclear density at the bottleneck indicates possible higher bulk oxygen permeation rates in quality single crystals and epitaxial thin films.

Effects of rock-salt layer on electronic and oxide ionic mixed conductivity in strontium titanate, SrO(SrTiO 3) n ( n = 1, 2, ∞)

Electronic conductivity and oxygen permeation properties of analogous compounds of SrO(SrTiO 3) n ( n = 1, 2) and SrTiO 3 were investigated. Electronic conductivity and oxide ion conductivity decrease with increasing n, and SrTiO 3 shows much higher conductivity. The effects of Co doping on oxide ion conductivity and electronic conductivity were also examined and it is observed that it is effective for increasing electrical conductivity and the oxygen permeation rate. Hall effect measurements suggests that the low electron-hole conductivity in Co-doped SrO(SrTiO 3) n ( n = 1, 2) can be assigned to a low mobility, which may result from the low electron and atomic density in the Sr–O rock-salt layer. Quantum mechanical calculations of the electron density also indicate low electron density in the rock-salt layer. This study reveals that the rock-salt layer consisting of Sr–O disturbs electron transfer in SrTiO X oxide and that the perovskite layer has much higher electronic and oxide ionic conductivity.

Oxygen Permeation Property in Nd Deficient Nd[sub 2]NiO[sub 4] Mixed Oxide Doped with Cu and Ga

Oxygen permeation property in Nd deficient Nd 2 NiO 4 was studied. The oxygen permeation rate increases with increasing Ga. Nd deficiency in Nd 2 NiO 4 is also useful for increasing the oxygen permeation rate. The improved oxygen permeation rate could be assigned to the increased amount of excess oxygen and stabilizing a tetragonal structure at a low temperature. The oxygen permeation rate of Nd 1.9 (Ni 0.75 Cu 0.25 ) 0.95 Ga 0.05 O 4 achieved a value of 3.6 cm 3 /min cm 2 from air to He at 1273 K with 0.5 mm thickness and this value belongs to the highest class in the reported oxygen permeation rate.

Measurement of Oxygen Permeability of Epoxy Polymers

This paper describes an experimental technique that refines and extends available methods to measure the oxygen permeability of polymers such as epoxies that cannot easily be prepared as thin films. A simple Fick’s law-based quasi-steady-state diffusion model was developed to extract the permeation coefficient from the experimental data. The validity of this technique was established by comparing results with published values. Tests were subsequently conducted to determine the oxygen permeation rates for five representative commercially available epoxy polymers. The results showed that the oxygen permeation rates for the different epoxies were comparable, making them all suitable for corrosion repair. This suggests that repair costs may be optimized by selecting the most cost-effective epoxy system. The applicability of the findings is discussed and an illustrative numerical example is presented.

LaSrAlFeO3-.DELTA. oxygen ion conducting membranes sintered under different atmosphere and HIP

La0.6Sr0.4AlxFe1−xO3−δ (LSAF) mixed ionic electronic conducting membranes have been sintered, and the substitution of Al for Fe reduced the density of the sintered body including large defect of pore channels. The sintering behavior of the La0.6Sr0.4Al0.1Fe0.9O3−δ samples have been studied under different oxygen partial pressure, PO_2, and a post process of hot isostatic pressing (HIP) has been carried out. The thermal expansion coefficients and the differential expansion ratios measured in air and under reducing atmosphere for these samples were 15.6 × 10−6/K−1 and 0.37%, respectively, and were not affected by the sintering process. The density of the sample sintered in air was 96.5% and the HIP increase the density of the sample up to 99.6%, eliminating the pores. The three point flexural strength of the HIP sample at 25 and 1000°C were 265 and 208 MPa, respectively, and the oxygen permeation rate of the HIP treated membranes with the thickness of 0.5 mm was 8 cc/min/cm2.

Interface-directed sol-gel: direct fabrication of the covalently attached ultraflat inorganic oxide pattern on functionalized plastics

For plastic electronics and optics, the fabrication of smooth, transparent and stable crack-free inorganic oxide films (and patterning) on flexible polymeric substrates with strong bonding strength and controllable thickness from nanometers to micrometers is a key but still remains a challenge. Among versatile inorganic oxides, silica oxide film as SiO x is especially important because this semiconductor material could provide crucial properties in devices or serve as a base layer for further multilayer construction. In this paper, we describe a new interface-directed sol-gel method to fabricate flexible high quality silicon oxide film onto commodity plastics. The resulting crack-free silica film has strong covalent bonding with polymer substrates, homogeneous morphology with ultralow roughness, highly optical transparency, tunable thickness from nm to μm, and easy patterning ability. Such fabrication strategy relies on a novel photocatalytic oxidation reaction by photosensitive ammonium persulfate (APS), which is able to fabricate highly reactive hydroxyl monolayer surface on inert polymeric substrates. This kind of hydroxylated surface could serve as nucleation and growth sites to initiate surface sol-gel process. As a result, well-defined SiO x film deposition (gelation) occurs, and patterned hydroxylation regions could be easily utilized to induce the formation of patterned oxide film arrays. Our strategy also excludes the requirements of clean room and vacuum devices so as to fulfill low-cost and fast fabrication demands. Two application examples from such high quality SiO x layer onto plastics are given but should not be limited within these. One is that oxygen permeation rate of SiO x deposited polymer film decreases 25 times than pristine polymer substrate, which is good for the potential packaging materials. The other one is that silanization monolayer, for example, 3-aminopropyltriethoxysilane (APTES), could be successfully constructed onto silica layer through classical silanization reaction, which is applicable for many potential purposes, for instance, proteins could be accordingly immobilized onto plastic support with effective signal-to-background ratio. Moreover, we further demonstrate that this interface-directed sol-gel strategy is a general method which could be successfully extended to other high quality oxide film fabrication, e.g., TiO2.

Mixed Oxide Ion and Hole Conductivity in Pr2 − αNi0.76 − xCu0.24GaxO4 + δ Membrane

The mixed conductivity and oxygen permeation properties of Pr-deficient were investigated. Among the dopants studied, the Ga-doped membrane was a superior mixed conductor, and it exhibited a high oxygen permeation rate compared with that of the other compositions. Examinations of membranes with different Ga concentrations revealed that the A-site cation-deficient composition, , had the highest permeability of (ca. ) from air to He at 1273 K in a 0.5 mm thick membrane. The oxygen permeation rate of decreased with thickness, indicating that the limiting factor is oxygen diffusivity in bulk. The Seebeck coefficient and oxygen permeation measurements suggest that the Ga dopant and Pr deficiency decreased the charge carrier density and improved the oxide ion conductivity. The estimated oxide ion conductivity in this material is a few times higher than that of the conventional mixed conductors such as Co-based perovskite.

Scratch resistance and oxygen barrier properties of acrylate-based hybrid coatings on polycarbonate substrate

Organic/inorganic hybrid coating materials were synthesized using acrylate end-capped polyester, 1,6-hexanediolacrylate, tetraethoxysilane (TEOS), and 3-trimethoxysilylpropylmethacrylate (TMSPM). The hybrid materials were cast onto a polycarbonate (PC) substrate and cured by UV irradiation to give a hybrid film with covalent linkage between the inorganic and the organic networks. The coating layer was characterized by FT-IR and 29Si-NMR, and pencil hardness and oxygen permeation rate of coated films were investigated. The pencil hardness of all samples examined in this study was higher than 1H, whereas that of uncoated PC substrate was 6B. The hardness enhancement after coating may due to incorporation of organic acrylate resin. The oxygen permeability coefficient of the film coated with hybrid material on 3-aminopropyltriethoxysilane (APTEOS) pretreated polycarbonate substrate was 1.67×10−3 GPU, the lowest value in this work, whereas that of uncoated PC substrate was 8.07×10−3 GPU. The lower oxygen permeation rates of these films are attributed to the good adhesion between organic/inorganic hybrid coating layer and PC substrate and a dense structure induced by an increase of network density.