Enhancing the oxygen permeability of Ba0.5Sr0.5Co0.8Fe0.2O5 + δ membranes by coating RBaCo2O5 + δ(R= Pr, Nd, Sm, Gd) layers

The effects of a thin RBaCo₂O_5 + δ (R= Pr, Nd, Sm, Gd) layer coating on the oxygen permeation flux through Ba_0.5Sr_0.5Co_0.8Fe_0.2O_5 + δ(BSCF) membrane were investigated. Due to the high oxygen adsorption and desorption rate constants k_a and k_d of the RBaCo₂O_5 + δ (R112) materials and the porous structure of the coating layers, the oxygen permeation flux through the BSCF membranes can be enhanced remarkably. It was found that the reaction between Pr112 and BSCF also has significant influence on the oxygen permeation flux. The reaction between Pr112 and BSCF forms impurities which may block oxygen permeation flux. However, Nd112, Sm112, and Gd112 do not react seriously with BSCF, therefore, coating layers of these materials can significantly enhance the oxygen permeation flux of BSCF membranes.     

Hydrogen separation and stability study of ceramic membranes based on the system Nd5LnWO12

This contribution presents the preparation, permeation and stability study of mixed protonic-electronic conducting membranes based on the system Nd₅LnWO₁₂. The tungstates Ln₆WO₁₂ are proton conducting crystalline materials, which show sufficient protonic and electronic mixed conductivity and stability in moist CO₂ environments to consider them as potential candidates for the separation of hydrogen at high temperatures. Hydrogen separation properties of A-substoichiometric Nd₆WO₁₂ and Nd₅LaWO₁₂ were systematically analyzed, i.e. the influence of the H₂ concentration in feed stream, humidification degree and operating temperature on the hydrogen separation was studied. Finally, the stability of these materials at different temperatures and CO₂-rich and sulfur-containing environments was evaluated.     

Modern mass spectrometry for coatings

For the analysis of polymers soft ionization mass spectrometry, in which only molecular ions are observed, can provide the complete distribution of chains (length, composition, end-groups) in under ten minutes on microgram quantities of material. Moreover, molecular ion information of neat organic pigments or those present in crosslinked networks can also be furnished. No other analytical technique can supply these data in such a short time. The application of mass spectrometry to the characterization of materials used in today's high performance automotive coatings is presented. These include functional monomers, several acrylic copolymers, organic pigments and an epoxide prepolymer. While there are a variety of mass spectrometric techniques, in this paper we will highlight the techniques that we have found useful for the characterization of organic coating components. The selection of the mass spectrometric technique is dictated by the molecular weight of the material and to a lesser extent the chemical composition. We used potassium ionization of desorbed species (K⁺IDS) performed on a quadrupole mass spectrometer for materials under 1000 Daltons (Da). However, many of the ingredients used in current automotive finishes fall between 1000 and 10 000 Da. For these materials we used a Fourier transform mass spectrometer (FTMS) which is well suited for this mass range and boasts the highest resolution and mass accuracy available. Direct desorption/ionization using a carbon dioxide laser is our standard method of sample introduction. Recently, we coupled a gel permeation chromatograph to our FTMS using an electrospray ionization interface. This hyphenated technique offers one of the most powerful characterization methods for the coatings chemist.     

Temperature influence on transport parameters characteristic of Knudsen and Poiseuille flows

Single gas permeation experiments results using neon, argon, nitrogen and methane are reported. From gas permeation experiments the characteristic parameters of the Knudsen and Poiseuille transport mechanisms were determined by means of an equation derived from the “Dusty-Gas” model. The experiments were performed at different temperatures from 303.15 to 323.15 K, in order to study the temperature influence on those parameters. For PVDF and PCTE membranes the influence of the temperature on K_o and B_o parameters was not significant. Gas influence was also investigated for both types of membrane, a slight tendency of K_o to decrease with increase in molar mass and a very slight tendency of B_o to increase with increase in molar mass, although these trends were not fulfilled by neon gas.     

Characterization and In-vitro Permeation Study of Stearic Acid Nanoparticles containing Hinokitiol

Lipid nanoparticles containing hinokitiol (HKL) were prepared by a melt–emulsification method. Stearic acid was used as a lipid for the matrix material of the nanoparticles. According to results from transmission electron microscopy (TEM) and dynamic light scattering (DLS), most of the nanoparticles were less than 100 nm. When nanoparticles containing HKL were scanned on a differential scanning calorimeter, no endothermic peak of HKL was observed. This means that HKL in the lipid matrix of the nanoparticles is in a dissolved state. In an 18-h permeation study using hairless mouse skin mounted on a diffusion cell, the amount of HKL encapsulated in the nanoparticles transported to the receptor cell was five to ten times more than for HKL dissolved either ethanol or propylene glycol. Therefore, stearic acid nanoparticles strongly enhanced permeation of the skin by HKL.     

Hydrogen permeation in Fe-40 at.% Al alloy at different temperatures

The electrochemical permeation technique for studying transport and trapping of hydrogen in Fe-40 at.% Al alloy at temperatures of 5, 25, 45 and 65 °C was used in the paper. The influence of temperature on the effective hydrogen diffusion coefficient, hydrogen permeation rate and hydrogen solubility was determined. The activation energy of hydrogen diffusion in iron aluminide in the studied temperature range was also determined.     

Applications of sample preparation techniques in the analysis of pesticides and PCBs in food

Pesticides and polychlorinated biphenyls (PCBs) are found in various parts of the environment in quite small concentrations, but they accumulate and thus become a threat to human health and life. A review is focused on the application of some popular techniques for sample preparation in analysis of these compounds in food. Even with the emergence of advanced techniques of final analysis, complex matrices, such as food, require extensive sample extraction and purification. Traditional sample preparation techniques are time consuming and require large amount of solvents, which are expensive, generate considerable waste, contaminate the sample and can enrich it for analytes. There have been many sample preparation techniques proposed to meet the requirements connected with the multiplicity of food. Optimal sample preparation can reduce analysis time, sources of error, enhance sensitivity and enable unequivocal identification and quantification. Sample extraction and purification techniques are discussed and their most recent applications in food analysis are provided. This review pointed out that sample preparation is the critical step.     

多孔陶瓷膜毛细管冷凝分离传质模型

多孔陶瓷膜在毛细管冷凝传质机理的作用下能够有效地分离吸附性气体。而毛细管冷凝膜分离传质机理的研究还很不充分,目前,文献报道仅局限于纯组分气体的传质模型研究。本文以改性氧化铝膜对乙醇-水物系的蒸气渗透分离过程为研究对象,优选出了二元气体在毛细管冷凝膜分离过程中的组分渗透系数的计算模型;建立了多孔陶瓷膜的传质模型,对蒸气渗透分离过程的模拟证实了该模型的可靠性。     

高放废物地质处置库缓冲/回填材料的气体渗透问题研究进展

简要回顾和总结了国内外学者对处置库中的气体形成与渗透机制,注气试验装置与试验方法,以及气体渗透特性等方面的研究成果和最新进展。研究表明,深地质处置库运营过程中会由于金属无氧腐蚀等产生以氢气为主的多组分气体,气体在缓冲/回填材料中主要以对流–扩散渗流、黏性–毛细管两相流、局部膨胀通道渗流和沿宏观裂缝渗流等4种机制渗透。为此,各国学者先后研发了恒体积渗透装置、K0渗透装置、等向应力渗透装置和三轴渗透装置等注气试验装置,采用控制注气流量速率法或控制注气压力法开展了大量注气试验,发现缓冲/回填材料的气体渗透率和特征压力等渗透特性均与其物理性质和边界条件等诸多因素有关。考虑到处置库实际运营工况的复杂性,多场(热–水–化–力)多相(固–液–气)耦合条件下的缓冲/回填材料的气体渗透特性研究将是今后的一个重要工作方向。