Modelling Gas Transmission in Cylindrical Dynamic Accumulation Oxygen Transmission Rate Chambers to Explore Implications of Oxygen Sensor Location Relative to Samples

A model was developed to simulate oxygen accumulation in space and time within cylindrical dynamic accumulation chambers that are used to measure oxygen transmission rate (OTR) of materials. The model is based on Fick's law of diffusion and was validated against actual OTR measurements of polymer film samples. Measured OTR values and thicknesses were inputted into the model and oxygen concentrations outputted by the model. OTRs determined from the output of the model was in close agreement to within 0.3–3% of the measured OTR. Oxygen concentration versus time curves generated from model output oxygen concentrations and experimentally measured oxygen concentrations for three actual films were also in agreement. The model was then used to simulate results from three hypothetical test films at varying chamber lengths in order to evaluate effects of accumulation chamber dimensions relative to films on resulting OTR measurements. A typical design scenario was used, where the oxygen sensor is mounted on the chamber wall opposite the sample film. Results demonstrate that dynamic accumulation OTR instrument designers have considerable flexibility in choosing accumulation chamber dimensions because deviations in OTR are only expected to occur at impractically extreme chamber lengths (>10 m) for the entire envelope of OTRs expected for typical packaging films. Copyright © 2014 John Wiley & Sons, Ltd.     

Gasoline permeation resistance of the as‐blow‐molded and annealed polyethylene,polyethylene/polyamide,and polyethylene/modified polyamide bottles

An investigation of the gasoline permeation resistance of the as‐blow‐molded and annealed polyethylene, polyethylene (PE)/polyamide (PA), and polyethylene/modified polyamide (MPA) bottles is reported. The gasoline permeation resistance improves dramatically after blending PA and MPA barrier resins in PE matrices during blow‐molding, and the order of barrier improvement corresponds to the order of barrier improvement of the barrier resins added in PE. Somewhat unexpectedly, the gasoline permeation rates of the annealed PE and/or PE/PA bottles annealed at 90°C or higher temperatures increase significantly with the annealing temperature and time. On the contrary, the gasoline permeation resistance of the annealed PE/MPA bottles increase significantly as the annealing temperature and/or time increase. For instance, the gasoline permeation rate of the PE/MPA bottle annealed at 120°C for 32 h is about 190 times slower than that of the as‐blow‐molded PE bottle. Further investigations found that, after blending the MPA and PA barrier resins in PE matrices, the relatively nonpolar hydrocarbon components present in the gasoline fuels were significantly blocked, without permeation during the permeation tests, in which the as‐blow‐molded PE/MPA bottle inhibited the permeation of hydrocarbon components more successfully than did the as‐blow‐molded PE/PA bottle. In contrast, the amounts of polar components that permeated through the as‐blow‐molded PE/PA and PE/MPA bottles were very small and about the same as the amount that permeated through the as‐blow‐molded PE bottle. Possible mechanisms accounting for these interesting behaviors are proposed in this study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2827–2837, 2001     

氮-甲醇保护气氛对45CrNiMoVA高强钢氢致断裂的影响

采用化学成分分析、断口形貌分析、显微组织分析、力学性能测试等方法对断裂后的45CrNiMoVA钢制高强扭杆进行了分析,并开展了氮-甲醇保护气氛下零件表面氢含量的测定,探讨了氢致缺陷对高强钢零件扭转疲劳的影响机理,提出了防止渗氢的预防措施,并进行了试验验证。结果表明,在氮-甲醇保护气氛下进行高强钢加热可导致氢的侵入,产生氢脆现象,影响高强钢零件扭转疲劳寿命。将氮-甲醇可控气氛更改为氮气保护,配合花键部位人工涂刷防脱碳涂料可有效防止表面氧化脱碳。采用改进工艺,高强钢扭杆未发生断裂现象。     

Formulation,characterization and clinical evaluation of propranolol hydrochloride gel for transdermal treatment of superficial infantile hemangioma

The objective of the present study is to formulate and characterize propranolol hydrochloride (PPL?·?HCl) gel, and to evaluate the efficacy of this formulation in transdermal treatment for superficial infantile hemangioma (IH). The transdermal PPL?·?HCl gel was prepared by a direct swelling method, which chose hydroxypropyl methylcellulose (HPMC) as the matrix and used terpenes plus alcohols as permeation enhancer. Permeation studies of PPL?·?HCl were carried out with modified Franz diffusion cells through piglet skin. Our results pointed to that among all studied permeation enhancers, farnesol plus isopropanol was the most effective combination (Q_24, 6027.4?±?563.1?μg/cm², ER, 6.8), which was significantly higher than that of control gel (p?相似文献   

Novel cobalt-free tantalum-doped perovskite Ba Fe_(1-y)Ta_yO_(3-δ)with high oxygen permeation

Cobalt-free perovskite-type oxides Ba Fe_(1-y)Ta_yO_(3-δ)(0 ≤ y ≤ 0.2)were synthesized via a simple solid state reaction.The cubic perovskite structure can be obtained when y is over 0.1.Ba Fe_(0.9)Ta_(0.1)O_(3-δ)(BFT0.1)membrane shows the highest oxygen permeation flux,which can reach 1.6 ml·min~(-1)·cm~(-2)at 950 °C under the gradient of air/He.The O_2-TPD results reveal that Ba Fe_(0.9)Ta_(0.1)O_(3-δ)material shows an excellent reversibility and phase structure stability in air.The oxygen permeation flux is limited by the bulk diffusion when the membrane thickness is over 0.8 mm,and it is limited by both the bulk diffusion and the surface exchange when the membrane thickness is below 0.5 mm.Stable oxygen permeation fluxes are obtained during 180 h operation.     

Teflon AF2400/Ultem composite hollow fiber membranes for alcohol dehydration by high‐temperature vapor permeation

High‐temperature vapor permeation has a stringent requirement of membrane stability under harsh feed environments. This work reports the design of Teflon AF2400/Ultem composite hollow fiber (HF) membranes for alcohol dehydration via vapor permeation. Fabrication parameters such as Teflon concentration and coating time were systematically investigated. Interestingly, the fabricated composite HF membranes possess an unusual surface with honeycomb‐like microstructure patterns. Owing to the Teflon protective layer, the newly developed composite HF shows a promising and stable separation performance with a flux of 4265 gm^?2 h^?1 and a separation factor of 383 for 95% isopropanol dehydration at 125°C. The composite HF also performs well under extreme vapor feed compositions from 87 to 99 wt % isopropanol. In addition, it exhibits impressive separation performance for the dehydration of ethanol and n‐butanol. This work may provide useful insights of designing thermal‐stable and high‐performance composite polymeric membranes for vapor permeation. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1747–1757, 2016     

Oxygen transport kinetics of MIEC membranes coated with different catalysts

Oxygen permeation through mixed ionic‐electronic conducting membrane may be controlled by oxygen bulk diffusion and/or oxygen interfacial exchange kinetics. In this article, we chose BaCe_0.05Fe_0.95O_3‐δ (BCF) as a representative to study the oxygen transport resistances of the membrane coated with different porous catalysts, including BCF itself, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3‐δ (BSCF) and Sm_0.5Sr_0.5CoO_3‐δ (SSC). The oxygen transport resistances of bulk, gas‐solid interfaces of feed‐side and sweep‐side of the catalyst‐coated membranes can be separately obtained through a linear regression of experimental data according to an oxygen permeation model. The three resistances of the membrane coated with BCF catalyst are smaller than those of the membrane coated with BSCF and SSC catalysts, although BSCF catalyst itself has the fastest bulk diffusion and interfacial exchange kinetics. The catalytic activities of BSCF and SSC catalysts on BCF membranes are impacted by the transport kinetics of catalysts, microstructure of catalyst layers, and cationic inter‐diffusion between the membrane and catalysts. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2803–2812, 2016     

FeAl/Al_2O_3复合阻氚涂层制备技术的研究进展

FeAl/Al_2O_3复合膜层是聚变堆氚增殖包层及辅助涉氚系统结构材料首选的阻氚涂层。其制备过程通常需要铝化和氧化2个步骤,铝化是Al原子与基体Fe原子通过相互扩散在基体表面形成铁铝固溶体(Fe,Al)或Fe-Al金属间化合物过渡层;氧化是使铝化涂层表面选择性氧化形成Al_2O_3膜。该阻氚涂层的制备可采用物理气相沉积(PVD)、化学气相沉积(CVD)、热浸铝化(HDA)、包埋渗铝(PC)、等离子体喷涂(PS)和电化学沉积(ECD)等技术。相对而言,CVD、HDA和PC等3种技术有较好的应用前景,有望成为聚变堆中FeAl/Al_2O_3阻氚涂层工程化制备的候选技术而ECD技术因其制备过程容易控制、涂层性能稳定、可涂镀复杂结构件等特点在FeAl/Al_2O_3阻氚涂层制备方面颇具吸引力。     

火炸药多组分气体现场测量装置动态校准技术研究

利用自研的火炸药专用自动配气系统和实验室校准装置,通过混合气体校准以及"预估-校准-逼近"的方法,对火炸药气体现场测量装置进行了动态校准。结果表明,多组分气体动态校准技术实现了火炸药配方燃烧爆轰过程产生气体的准确测量。混合气体校准相对标准偏差RSD≤0.3%,保证了动态测量数值的有效统一和量值传递。