Dry Gas Flow Research Articles

Bioactive dry extract production from Hymenaea courbaril L. bark via spouted bed drying

AbstractThe work aims to develop and optimize a powdered phytopharmaceutical product from the stem bark of Hymenaea courbaril L. (jatobá) by the spouted bed drying. The study commenced with the extraction of bioactive compounds present in the plant raw material by dynamic maceration using ethanol/water 70% (v/v) at a temperature of 50°C for 60 min, for the ratio stem bark: solvent mass of 1:10 (w/w). The extract quality was assessed by quantifying chemical markers via spectrophotometry (total polyphenols and tannins) and through antioxidant activity by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay. The extractive solution was concentrated, added with drying adjuvant, and submitted to spouted bed drying. Product quality was evaluated by moisture content (Xp), water activity (aW), powder diameter, total polyphenols, and tannins content (PT and TT), and antioxidant activity, expressed as the extract concentration needed to reduce 50% of the DDPH radical (IC50). Spouted bed drying performance was evaluated through the drying yield (REC), product accumulation (Ac), and thermal efficiency (η). The optimal processing conditions were: inlet gas temperature, Tgi: 150°C, the ratio of the mass feed flow rate of the concentrated extract to the evaporation capacity of the dryer, Ws/Wmax: 45%, and the drying gas flow rate relative to minimum spouting, Q/Qms: 1.85. Under these conditions, it is predicted to obtain a dried extract with Xp = 4.9% w/w, PT = 26.0% w/w, REC = 77.7% w/w, η = 44.3%, and Ac = 10% w/w, with adequate values of aW, TT, and high antioxidant activity.

Design modification and comparative analysis of glycol‐based natural gas dehydration plant

AbstractNatural gas production from reservoirs is often associated with water, which poses numerous challenges, such as methane hydrate formation, sludge, corrosion and flow assurance issues in gas processing plants and sales gas transmission pipelines. To effectively remove water from natural gas, there is a need to design, compare and modify dehydration plants. This study investigated the performance difference between a conventional triethylene glycol (TEG)‐based dehydration system with a cooler at the TEG inlet to the contactor, and a newly proposed TEG‐based dehydration system with a heat exchanger replacing the cooler at the TEG inlet with the contactor. The advanced process simulation software Aspen HYSYS was used to design and compare two dehydration system configurations. The modified design configuration exhibited better performance in terms of energy conservation and water‐removal capability. The material balance of molar flow, mass flow and volume flow of dry gas produced in the absorber/contactor column showed a higher volume of dry gas produced in the modified system configuration, indicating that it is a better design. The modified design configuration also produced dry gas within the recommended temperature range for underground storage and transmission. There was a significant difference in the percentage difference of 64% between the conventional and modified designs in terms of energy consumption, whereas the percentage differences of 0% and 0.6% showed nonsignificant and significant differences between the two plant design configurations. Both plant design configurations showed a significant reduction (from 0.005 to 0.0002 mol%) in the water composition of natural gas after the simulation.

Impact of Source Conditions on Collision Cross Section Determination by Trapped Ion Mobility Spectrometry.

Collision cross section (CCS) values determined in ion mobility-mass spectrometry (IM-MS) are increasingly employed as additional descriptors in metabolomics studies. CCS values must therefore be reproducible and the causes of deviations must be carefully known and controlled. Here, we analyzed lipid standards by trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) to evaluate the effects of solvent and flow rate in flow injection analysis (FIA), as well as electrospray source parameters including nebulizer gas pressure, drying gas flow rate, and temperature, on the ion mobility and CCS values. The stability of ion mobility experiments was studied over 10 h, which established the need for a delay-time of 20 min to stabilize source parameters (mostly pressure and temperature). Modifications of electrospray source parameters induced shifts of ion mobility peaks and even the occurrence of an additional peak in the ion mobility spectra. This behavior could be essentially explained by ion-solvent cluster formation. Changes in source parameters were also found to impact CCS value measurements, resulting in deviations up to 0.8%. However, internal calibration with the Tune Mix calibrant reduced the CCS deviations to 0.1%. Thus, optimization of source parameters is essential to achieve a good desolvation of lipid ions and avoid misinterpretation of peaks in ion mobility spectra due to solvent effects. This work highlights the importance of internal calibration to ensure interoperable CCS values, usable in metabolomics annotation.

Effect of Water Vapor on Hydrogen Isotopes Separation by Polymer Electrolyte Fuel Cell

IntroductionHydrogen isotopes are protium (H), deuterium (D) and tritium (T). D and T are important materials not only for fission and fusion reactors, but also for semiconductors since the strong hydrogen termination improves the durability. Various techniques for hydrogen isotope separation have been known for long time, but they have some drawbacks such as low separation efficiency and poor energy consumption. Therefore, new separation and purification methods are required.In polymer electrolyte fuel cell (PEFC), wettability is optimized well and small amount of Pt catalyst is used. The configuration is also key issue for the conventional method of water-hydrogen chemical exchange. Therefore, we investigated the effect of water in hydrogen isotope separation by PEFC [1].ExperimentalA mixture hydrogen gas of H2 and D2 was supplied to the PFEC. The separation factor for dry and wet gas flow was measured, respectively. Hydrogen gas and water vapor from PEFC were analyzed by quadrupole mass spectrometry (Q-mass) and Fourier infrared spectrometer (FTIR), respectively. The separation factor and mass balance were calculated.Results and discussionWhen no electricity was generated, FTIR results showed that D was enriched in water vapor. This is explained by a gas-phase chemical exchange reaction occurring on a platinum catalyst. When the PEFC was operated, the electrochemical reaction promoted the D separation. A large amount of D (about 45%) was transferred to water vapor during power generation. The separation factor was approximately 1.7, while it was approximately 1.3 for no generation. The present results suggested that gas-phase chemical exchange and the cell reaction had a synergistic effect on D separation.

Limits in reaching the anhydrous state of wood and cellulose

Water-sorption studies and certain organic chemistry reactions require water removal from cellulosic samples. This is hindered by the strong interaction of cellulosic materials with water, and it remains uncertain if a completely anhydrous state can be reached under common drying conditions. Here, different drying conditions were applied to wood and cellulose, and the residual moisture contents were quantified either gravimetrically or by coulometric Karl-Fischer titration. Vacuum-drying at 103 °C and ≤ 1 mbar for at least 360 min decreased the moisture content to ≤ 0.04%. However, in automated sorption balances, drying at atmospheric pressure under dry air or nitrogen flow left some samples with more than 1% moisture content. The residual moisture content obtained under dry gas flow was temperature dependent. Increasing the temperature up to 55 °C decreased the residual moisture content and cooling resulted in a moisture re-uptake, presumably due to small quantities of water vapor in the surrounding atmosphere. These effects must be considered in fundamental studies on water interactions of cellulosic materials.

Offline analysis of secondary formation markers in ambient organic aerosols by liquid chromatography coupled with time-of-flight mass spectrometry

The present study provides a comprehensive assessment of the quantitative analysis by high-performance liquid chromatography coupled with dual orthogonal electrospray ionization time-of-flight mass spectrometry (HPLC-ESI-TOF-MS) of pinene markers, biomass-burning related phenols, and other relevant carboxylic acids in atmospheric aerosol samples. Significant insights into the quantitative determination are offered on the basis of systematic experiments targeting the optimization of chromatographic separation, ionization source, and mass spectrometer performance. After testing three analytical columns, the best separation of the compounds of interest was achieved on a Poroshell 120 ECC18 column (4.6 × 50 mm, 2.7 µm) thermostated at 35 °C, operating in gradient elution mode with 0.1% acetic acid in water and acetonitrile at a 0.8 mL min−1 flow rate. Optimal operational conditions for the ESI-TOF-MS instrument were identified as a 350 °C drying gas temperature, 13 L min−1 drying gas flow rate, 60 psig nebulizer pressure, 3000 V for the ion transfer capillary, 60 V for the skimmer, and 150 V for the fragmentor. Additionally, the matrix effect on the ESI efficiency and the spike recovery factors of the compounds were tested. Method quantification limits can go as low as in the 0.88–48.0 μg L − 1 (3.67–200 pg m − 3, at 120 m3 of sampled air) range. The developed method was shown to be reliable for the quantification of the targeted compounds in real atmospheric aerosol samples. The accuracy in the molecular mass determination of less than 5 ppm and the acquisition in the full scan mode were shown to bring additional insights into the organic constituents in atmospheric aerosols.

Detecting Hexafluoroisopropanol Using Soft Chemical Ionization Mass Spectrometry and Analytical Applications to Exhaled Breath

Here we explore the potential use of proton transfer reaction/selective reagent ion-time-of-flight-mass spectrometry (PTR/SRI-ToF-MS) to monitor hexafluoroisopropanol (HFIP) in breath. Investigations of the reagent ions H3O+, NO+, and O2+• are reported using dry (relative humidity (rH) ≈ 0%) and humid (rH ≈ 100%)) nitrogen gas containing traces of HFIP, i.e., divorced from the complex chemical environment of exhaled breath. HFIP shows no observable reaction with H3O+ and NO+, but it does react efficiently with O2+• via dissociative charge transfer resulting in CHF2+, CF3+, C2HF2O+, and C2H2F3O+. A minor competing hydride abstraction channel results in C3HF6O+ + HO2• and, following an elimination of HF, C3F5O+. There are two issues associated with the use of the three dominant product ions of HFIP, CHF2+, CF3+, and C2H2F3O+, to monitor it in breath. One is that CHF2+ and CF3+ also result from the reaction of O2+• with the more abundant sevoflurane. The second is the facile reaction of these product ions with water, which reduces analytical sensitivity to detect HFIP in humid breath. To overcome the first issue, C2H2F3O+ is the ion marker for HFIP. The second issue is surmounted by using a Nafion tube to reduce the breath sample's humidity prior to its introduction into drift tube. The success of this approach is illustrated by comparing the product ion signals either in dry or humid nitrogen gas flows and with or without the use of the Nafion tube, and practically from the analysis of a postoperative exhaled breath sample from a patient volunteer.

Granulation of Silicon Nitride Powders by Spray Drying: A Review

Spray drying is a widely used method of converting liquid material (aqueous or organic solutions, emulsions and suspensions) into a dry powder. Good flowability, narrow size distribution, and controllable morphology are inherent in powders produced by spray drying. This review considers the granulation factors that influence the final properties of the silicon nitride dried powders. The first group includes the types of atomizers, manifolds, and drying chamber configurations. The process parameters fall into the second group and include the following: inlet temperature, atomizing air flow, feed flow rate, drying gas flow rate, outlet temperature, and drying time. Finally, the last group, feedstock parameters, includes many factors such as feed surface tension, feed viscosity, solvent type, solid particle concentration, and additives. Given the large number of factors affecting morphology, particle size and moisture, optimizing the spray drying process is usually achieved by the “trial and error” approach. Nevertheless, some factors such as the effect of a solvent, dispersant, binder, and sintering additives considered in the literature that affect the Si3N4 granulation process were reviewed in the work. By summarizing the data available on silicon nitride powder production, the authors attempt to tackle the problem of its emerging demand in science and industry.

Modeling the flow rate of dry part in the wet gas mixture using decision tree/kernel/non-parametric regression-based soft-computing techniques

Owing to its importance in extraction of natural gas from underground gas storage as well as its crucial role in determination of final gas mixture in the production facilities of gas/oil industry, the dry content of wet gas mixture needs to be calculated precisely. The present study explores the potential of different soft-computing techniques in estimation of the dry gas flow rate (kg/h) (output variable) of wet gas mixture based on two input variables of wet gas flow rate (kg/h) and absolute gas humidity (g/m3). Decision tree-based methods (M5P tree, random forest (RF), random tree (RT), and reduced error pruning tree (REPT) models), kernel function-based approaches (Gaussian process regression (GPR) and support vector machines (SVM)), and non-parametric regression-based technique (multivariate adaptive regression splines (MARS)) were implemented for the first time to estimate the dry gas flow rate, and their respective prediction performances were analyzed statistically. Coefficient of correlation (CC), Nash–Sutcliffe efficiency (NSE), root mean square error (RMSE), mean absolute error (MAE), Legates and McCabe's index (LMI), and Willmott's Index (WI) were used as the statistical indicators for validating the performance of each soft-computing model. While M5P model (MAE = 122.2382 kg/h, RMSE = 580.5626 kg/h, CC = 0.9875 for the testing data set) was better than other tree-based models (MAE = 363.2802–542.6119 kg/h, RMSE = 871.9363–1025.3444 kg/h, CC = 0.9587–0.9706 for the testing data set) and MARS model (MAE = 128.0083 kg/h, RMSE = 622.9515 kg/h, CC = 0.9852 for the testing data set), the statistical indicators approved the superiority of the radial basis kernel function-based GPR model (GPR-RBKF) model (MAE = 163.3266 kg/h, RMSE = 483.1359 kg/h, CC = 0.9915 for the testing data set) over other implemented models in predicting the dry gas flow rate. The findings highlighted the potential of soft-computing methodologies in precise estimation of dry gas flow rate in wet gas mixture, particularly, in situations where the measurement of such parameters with traditional deterministic models is practically not possible.

Optimization of a method to detect levothyroxine and related compounds in serum and urine by liquid chromatography coupled to triple quadrupole mass spectrometry

Thyroid hormones and their derivatives are structurally related to the non-essential amino acid tyrosine (4-hydroxyphenylalanine). However, there are physicochemical differences that make it difficult to apply an analytical method for their simultaneous detection. This work focused on the optimization of a method using liquid chromatography-electrospray ionization mass spectrometry to measure eight compounds related to levothyroxine (T4). In addition, the influence of the additives to the mobile phase, the solvents for liquid-liquid extraction and the influence of the hydrolysis of the conjugated analytes were studied.Optimization of MRM transitions and collision energy for analytes and capillary voltage, nebulizer gas pressure, nozzle voltage, sheath gas flow, sheath gas temperature, drying gas flow and drying gas temperature for ionization source was done. The recovery of analytes was studied using five solvents and six solvent systems to introduce them into the liquid-liquid extraction and matrix cleanup steps. Different additives to the mobile phase were evaluated as well as the effectiveness of enzymatic and chemical hydrolysis.The best MRM transitions and source parameters were settled in order to generate an optimized instrumental method. The addition of ammonium formate, ammonium fluoride, and acetic acid to the mobile phase showed no improvement in responses compared to classic 0.1% formic acid. The use of tert-butyl methyl ether: isopropanol (75: 25, V: V) showed a suitable recovery of analytes to perform a liquid-liquid extraction, and n-hexane might be an appropriate solvent if a cleanup step is needed. The stability of T3, T4 and thyronine, checked after the hydrolysis with extracts of E. coli and H. pomatia showed good results, contrary to chemical hydrolysis that showed a total degradation of T3 and T4.

Analyzing the combustion oscillation of a gas turbine for syngas based on the characteristic time-scale theory

When the ambient temperature is less than −10 °C in winter, the gas turbine for syngas in Huaneng Tianjin integrated gasification combined cycle (IGCC) power station has an evident combustion oscillation phenomenon, which seriously affects the production safety and efficiency. This study used the characteristic time-scale theory to guide the operation, thereby reducing the combustion oscillation of the gas turbine for syngas. The work progressed as follows. First, the boundaries of the combustion oscillation and maximum temperature safe limitations were defined based on the operational data from the extreme ambient temperature in summer and winter in the Huaneng Tianjin IGCC power station. Then, the mathematical model of combustion with critical parameters, such as ignition delay time, the adiabatic temperature of the flame, and flame speed, was constructed using the binary quadratic regression method under various combinations of dry syngas, natural gas, and steam flow rates. Finally, an operation scheme for reducing the combustion oscillation of the gas turbine for syngas in winter was designed, as well as the limitation boundary and computation model. This operation scheme can effectively reduce the combustion oscillation in winter; this was confirmed in actual operation. The results of this study should assist gas turbine designers in improving the safety, reliability, and stability of syngas turbines.

Analysis of flavonoids in citrus fruits by capillary zone electrophoresis coupled with quadrupole time-of-flight mass spectrometry using chemometrics

A rapid, efficient and simple method using capillary electrophoresis-electrospray ionization-quadrupole time-of-flight mass spectrometry (CE-ESI-Q-TOF-MS) was developed for the determination of the eight flavonoids (schaftoside, rutin, hesperidin, naringenin, naringin, violanthin, hesperitin and kaempferol) in 23 citrus samples. CE and ESI-Q-TOF conditions (e.g. nebulizer gas pressure, drying gas flow rate and temperature, sheath liquid composition, BGE composition and pH) were studied to obtain an optimal analytical identification and separation. The linear calibration was investigated ranged from 10 to 300 μg/mL for the six analytes, and had a good linearity with correlation coefficient of determination ranged from 0.9901 to 0.9995. The repeatability was tested by intra (n = 3) and the RSDs for migration time and peak area were within 0.43–2.30 % and 13.02–24.60 %, respectively. In addition, 23 investigated citrus samples were classified into 3 clusters according to different recognition program modes hierarchical cluster analysis and partial least squares discriminant analysis based on the peak areas of 8 target components.

Design of experiment-based LC-MS/MS method development for simultaneous estimation of nateglinide and metformin hydrochloride in rat plasma.

This research aims to develop and validate a bioanalytical method for simultaneous estimation of an antidiabetic combination using LC-MS/MS in rat plasma. Nateglinide and metformin hydrochloride are commonly used combination for clinical management of Type 2 diabetes. Hence, simultaneous determination in plasma is essential for the rapid analysis of samples from the pharmacokinetic studies. Statistical optimization was carried out for liquid chromatography (LC) parameters and mass spectroscopic (MS) parameters by design of experiment (DoE) (Design Expert Version 11, Stat Ease Inc., USA) approach. A 33 full factorial design was used for optimization of LC parameters; %methanol, %formic acid, and flow rate were selected as independent variables, whereas peak area and tailing factor were considered as dependent variables for both drugs. Box-Behnken design was used to optimize MS parameters including drying gas flow rate, nebulizing gas flow rate, DL temperature, heat block temperature, and positive voltage as independent factors, and responses selected were [M + H]+ intensity of nateglinide and metformin hydrochloride. The [M + H]+ intensity of the optimized method for nateglinide and metformin hydrochloride were 2,462,838 and 11,873,826, respectively. The model was found significant for optimizing LC and MS parameters with p < 0.05 for both nateglinide and metformin hydrochloride. The optimized method was validated as per the ICH-M10 guideline, which was accurate, precise, and selective. The method was cost-effective and capable of quantitating concentrations in picogram levels for nateglinide and metformin hydrochloride simultaneously.

Encapsulation of B. bassiana in Biopolymers: Improving Microbiology of Insect Pest Control.

The fungus Beauveria bassiana is widely used for pest control; however, biostability and dispersion for broth pulverization are limiting factors for its application in the field. In this context, formulation techniques such as microencapsulation are viable alternatives. The aim of this work is to optimize B. bassiana formulations by spray dryer and evaluate its stability and biological activity against Spodoptera cosmioides compared to ionic gelatinization formulations. The fungus was biocompatible with all evaluated biopolymers (lignin, cellulose, starch, humic substances, and alginate). The encapsulation by spray drying was optimized by factorial design in an inlet and outlet air temperature of 120°C and 68°C, respectively; aspirator rate of 35 m3·h−1, feed flow rate of 12 mL·min−1; and drying gas flow at 35 L·h−1. The ionic gelation capsules were obtained using a 0.5% quantity of conidia in a 1% sodium alginate solution dropped into a 0.5 mol·L−1 CaCl2 solution using a peristaltic pump. Spray drying provided smaller microcapsules than those by ionic gelation. Both techniques produced more stable conidia when exposed to temperature and UV-radiation than non-formulated B. bassiana. The formulations prepared by spray drying showed gains at aqueous dispersion. Biological assays against Spodoptera cosmioides showed a mortality rate of up to 90%. These results demonstrate the suitability of encapsulating B. bassiana conidia stably in aqueous dispersion without loss of viability and virulence.

Analysis of Flavonoids in Citrus Fruits by Capillary Zone Electrophoresis Coupled with Quadrupole Time-of-Flight Mass Spectrometry Using Chemometrics

A rapid, efficient and simple method using capillary electrophoresis-electrospray ionization-quadrupole time-of-flight mass spectrometry (CE-ESI-Q-TOF-MS) was developed for the determination of the eight flavonoids (schaftoside, rutin, hesperidin, naringenin, naringin, violanthin, hesperitin and kaempferol) in 23 citrus samples. CE and ESI-Q-TOF conditions (e.g. nebulizer gas pressure, drying gas flow rate and temperature, sheath liquid composition, BGE composition and pH) were studied to obtain an optimal analytical identification and separation. The linear calibration was investigated ranged from 10 to 300 μg/mL for the six analytes, and had a good linearity with correlation coefficient of determination ranged from 0.9901 to 0.9995. The repeatability was tested by intra (n = 3) and the RSDs for migration time and peak area were within 0.43–2.30% and 13.02–24.60%, respectively. In addition, 23 investigated citrus samples were classified into 3 clusters according to different recognition program modes hierarchical cluster analysis (HCA) and partial least squares discriminant analysis (PLS-DA) based on the peak areas of 8 target components.

Silencing corrugated pipes with liquid addition - Identification of the mechanisms behind whistling mitigation

Severe vibrations and sound production can occur in dry gas flow through corrugated pipes. The addition of very small amounts of liquid to the dry gas flow potentially mitigates these flow-induced vibrations (FIVs) and noise. The different mechanisms behind this whistling mitigation are studied in this work, where acoustic measurements are combined with flow visualization and droplet sizing. Different corrugation geometries are studied. It is shown that noise mitigation mainly occurs through a geometric alteration of the cavity mouth, resulting in a reduced acoustic source strength. Additional acoustic damping as a consequence of the presence of droplets has a very limited contribution to the mitigation of FIVs. A non-axisymmetric filling of the cavities of a corrugated pipe with liquid is more effective in reducing the acoustic output, compared to an axisymmetric filling. The liquid viscosity has a minor effect on the achieved noise mitigation. To predict the acoustic source strength for a particular cavity geometry a numerical method is developed, based on URANS simulations combined with Howe's energy corollary. An energy balance method is applied to obtain the acoustic source strength from experiments. The whistling frequencies are accurately predicted with the simulations, but the acoustic source strength is over-predicted by a factor 2. Trends in the source strength obtained from simulations, however, closely resemble the experimentally obtained results. The developed method provides an intuitive understanding of sound production by vortical flow structures and shows potential for the prediction of self-sustained oscillations in corrugated pipes.

The effect of ethanol evaporation on the properties of inkjet produced liposomes

BackgroundInkjet method has been used to produce nano-sized liposomes with a uniform size distribution. However, following the production of liposomes by inkjet method, the solvent residue in the product could have a significant effect on the properties of the final liposomes.ObjectiveThis research paper aimed to find a suitable method to remove ethanol content and to study its effect on the properties of the final liposomal suspension.MethodEgg phosphatidylcholine and lidocaine were dissolved in ethanol; and inkjet method at 80 kHz was applied to produce uniform droplets, which were deposited in an aqueous solution to form liposomes. Dry nitrogen gas flow, air-drying, and rotary evaporator were tested to remove the ethanol content. Liposome properties such as size, polydispersity index (PDI), and charge were screened before and after ethanol evaporation.ResultsOnly rotary evaporator (at constant speed and room temperature for 2 h) removed all of the ethanol content, with a final drug entrapment efficiency (EE) of 29.44 ± 6.77%. This was higher than a conventional method. Furthermore, removing ethanol led to liposome size reduction from approximately 200 nm to less than 100 nm in most samples. Additionally, this increased the liposomal net charge, which contributed to maintain the uniform and narrow size distribution of liposomes.ConclusionNano-sized liposomes were produced with a narrow PDI and higher EE compared to a conventional method by using an inkjet method. Moreover, rotary evaporator for 2 h reduced effectively the ethanol content, while maintaining the narrow size distribution.Graphical abstract

Effect of GDM Pairing on PEMFC Performance in Flow-Through and Dead-Ended Anode Mode.

Asymmetric gas diffusion media (GDM) pairing, which feature distinct GDM at the anode and cathode of the proton electrolyte membrane fuel cell (PEMFC), enhance water management compared to symmetric pairing of GDM (anode and cathode GDM are identical). An asymmetric pairing of Freudenberg GDM (H24C3 at anode and H23C2 at cathode) reduces ohmic resistances by up to 40% and oxygen transport resistances by 14% en route to 25% higher current density in dry gas flows. The asymmetric GDM pairing effectively hydrates the membrane electrode assembly (MEA) while minimizing liquid water saturation in the cathode compared to a commonly used symmetric GDM pairing of SGL 29BC at the anode and cathode. Superior water management observed with asymmetric GDM in flow-through mode is also realized in dead-ended anode (DEA) mode. Compared to the symmetric GDM pairing, the asymmetric GDM pairing with Freudenberg GDM increases cell voltage at all current densities, extends and stabilizes steady-state voltage behavior, slows voltage decay, and vastly reduces the frequency of anode purge events. These results support that the asymmetric Freudenberg GDM combination renders the PEMFC less prone to anode water saturation and performance loss from the anticipated increase in water back-diffusion during DEA mode operation.

Energy Level Alignment at Interfaces in Metal Halide Perovskite Solar Cells

Adv. Mater. Interfaces 2018, 5, 1800260 In the initially published version of this article, one word on the second page was wrong, the positions of the symbols “HOMO” and “LUMO” were misplaced in Figure 2 and the subparts in caption of figure 20 weren't identified correctly. Please find the correct sentence, Figure 2 and the caption of figure 20 below. The authors apologize for any inconvenience or misunderstanding this may have caused. The third sentence in paragraph 2 on page 2 is corrected as follows: When an organic layer contacts with metal, if vacuum level aligns, one can estimate the energy offsets at the organic/metal interface (e.g., the energy offset between the HOMO of spiro-OMeTAD and the Fermi level of Au) by simply comparing the ionization potential of bulk organic material and the work function (WF) of metal (as shown in the subpanel (i) of Figure 2b). Figure 20. UPS results of the as-prepared doped spiro-MeOTAD films and the films exposed to a) only H2O vapor (a relative humidity of 90%; which is generated by letting a stream of dry N2 gas flow through an H2O bubbler), b) only O2 (>99.5 of purity), and c) ambient air (a relative humidity of 50%) for 0, 3, 6, 18, and 39 h. The UPS spectra are shown in (i) and the corresponding energy level diagrams of them are shown in (ii), respectively. The substrate for UPS measurements is Si/Au. a,b) Reproduced with permission.[54] Copyright 2016, Wiley-VCH Verlag GmbH & Co. KGaA (c) Reproduced with permission.[88] Copyright 2015, Royal Society of Chemistry.

Dense Y-doped ion conducting perovskite films of BaZrO3, BaSnO3, and BaCeO3 for SOFC applications produced by powder aerosol deposition at room temperature

State-of-the-art solid oxide fuel cells (SOFC) are based on oxide ion conducting zirconia electrolytes, typically doped by yttria or scandia. Major drawback of these systems are their high operation temperatures of 800 °C and above. These are necessary for a sufficient ionic conductivity. Instead of oxide ions, also protonic charge carriers could be used in SOFC. The material classes of barium zirconates (BaZrO3), barium stannates (BaSnO3), and barium cerates (BaCeO3) are described as good proton conductors, especially when the B-site of the ABO3 perovskite structure is aliovalently doped by yttria. Their protonic conductivity values in the moderate temperature regime up to 600 °C are comparable to YSZ at 800 °C, making these compounds ideal candidates for a usage in future SOFC. Unfortunately, very high sintering temperatures up to 1800 °C are required to process dense and therefore gas-tight solid electrolyte membranes. However, a novel spray coating method called powder aerosol deposition (PAD, also known as AD) enables to form fully dense ceramic films directly at room temperature without any necessary sintering processes. Films are deposited from ceramic powders that are accelerated by a dry carrier gas flow under vacuum conditions.In this work, we investigated the film formation of three different barium based perovskite ceramics, namely yttria doped barium zirconate, barium stannate, and barium cerate by powder aerosol deposition. The optical and mechanical quality of films was evaluated using scanning electron microscopy and microhardness indentation and their crystallographic properties were characterized by X-ray diffraction. The electrical behavior was analyzed by electrochemical impedance spectroscopy and DC polarization methods up to temperatures of 1000 °C and 800 °C, respectively. Furthermore, a preliminary study about the film formation on porous electrodes was conducted.