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Nicergoline (NIC) is a semisynthetic ergot alkaloid derivative applied for treatment of dementia and other cerebrovascular disorders. The efficacy of sesame oil to slow and reverse the symptoms of neurodegenerative cognitive disorders has been proven. This work aimed to formulate and optimize sesame oil-based NIC-nanostructured lipid carriers (NIC–NLCs) for intranasal (IN) delivery with expected synergistic and augmented neuroprotective properties. The NIC–NLC were prepared using sesame oil as a liquid lipid. A three-level, three-factor Box–Behnken design was applied to statistically optimize the effect of sesame oil (%) of the total lipid, surfactant concentration, and sonication time on particle size, zeta potential, and entrapment efficacy as responses. Solid-state characterization, release profile, and ex vivo nasal permeation in comparison to NIC solution (NIC–SOL) was studied. In vivo bioavailability from optimized NIC–NLC and NIC–SOL following IN and IV administration was evaluated and compared. The optimized NIC–NLC formula showed an average particle size of 111.18 nm, zeta potential of −15.4 mV, 95.11% entrapment efficacy (%), and 4.6% loading capacity. The NIC–NLC formula showed a biphasic, extended-release profile (72% after 48 h). Permeation of the NIC–NLC formula showed a 2.3 enhancement ratio. Bioavailability studies showed a 1.67 and 4.57 fold increase in plasma and brain following IN administration. The results also indicated efficient direct nose-to-brain targeting properties with the brain-targeting efficiency (BTE%) and direct transport percentage (DTP%) of 187.3% and 56.6%, respectively, after IN administration. Thus, sesame oil-based NIC–NLC can be considered as a promising IN delivery system for direct and efficient brain targeting with improved bioavailability and expected augmented neuroprotective action for the treatment of dementia.

Ahmed Khames,1,2 Mohammad A Khaleel,3 Mohamed F El-Badawy,4,5 Ahmed OH El-Nezhawy6,7 1Department of Pharmaceutics and Industrial pharmacy, College of Pharmacy, Taif University, Taif 21974, Saudi Arabia; 2Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Beni-Suef University, Beni-Suef 62521, Egypt; 3Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden, Penang 11800, Malaysia; 4Department of Microbiology and Immunology, Faculty of Pharmacy, Misr University for Science and Technology, Cairo, Egypt; 5Department of Pharmaceutical Microbiology, College of Pharmacy, Taif University, Taif, Saudi Arabia; 6Department of Pharmaceutical Chemistry, College of Pharmacy, Taif University, Taif, Saudi Arabia; 7Department of Chemistry of Natural and Microbial Products, National Research Center, Dokki, Cairo, Egypt Background: Fungal keratitis (FK) is a serious pathogenic condition usually associated with significant ocular morbidity. Natamycin (NAT) is the first-line and only medication approved by the Food and Drug Administration for the treatment of FK. However, NAT suffers from poor corneal penetration, which limits its efficacy for treating deep keratitis. Purpose: The objective of this work was to prepare NAT solid lipid nanoparticles (NAT-SLNs) to achieve sustained drug release and increased corneal penetration. Methods: NAT-SLNs were prepared using the emulsification-ultrasonication technique. Box–Behnken experimental design was applied to optimize the effects of independent processing variables (lipid concentration [X1], surfactant concentration [X2], and sonication frequency [X3]) on particle size (R1), zeta potential (ZP; R2), and drug entrapment efficiency (EE%) (R3) as responses. Drug release profile, ex vivo corneal permeation, antifungal susceptibility, and cytotoxicity of the optimized formula were evaluated. Results: The optimized formula had a mean particle size of 42r.nm (radius in nanometers), ZP of 26mV, and EE% reached ~85%. NAT-SLNs showed an extended drug release profile of 10hours, with enhanced corneal permeation in which the apparent permeability coefficient (Papp) and steady-state flux (Jss) reached 11.59×10-2cmh-1 and 3.94molh-1, respectively, in comparison with 7.28×10-2cmh-1 and 2.48molh-1 for the unformulated drug, respectively. Antifungal activity was significantly improved, as indicated by increases in the inhibition zone of 8 and 6mm against Aspergillus fumigatus ATCC 1022 and a Candida albicans clinical isolate, respectively, and minimum inhibitory concentration values that were decreased 2.5-times against both of these pathogenic strains. NAT-SLNs were found to be non-irritating to corneal tissue. NAT-SLNs had a prolonged drug release rate, that improved corneal penetration, and increased antifungal activity without cytotoxic effects on corneal tissues. Conclusion: Thus, NAT-SLNs represent a promising ocular delivery system for treatment of deep corneal keratitis. Keywords: Natamycin, solid lipid nanoparticles, fungal keratitis, Box–Behnken design, ocular drug delivery, corneal permeation &nbsp

LiMn1.5Ni0.5O4 is one of the most promising cathode materials for use in either next generation lithium-ion batteries or all solid-state batteries. However, despite the significant Research and Development (R&D) carried out throughout the last two decades the material has not made serious inroads into market. One of the major reasons is the lack of consistency in the reported intrinsic properties and electrochemical performance owing to major controversies in synthesis, crystal structure and bulk and interfacial properties of LiMn1.5Ni0.5O4, notably in contact with electrolytes. This paper is a compelling review providing an assessment on the mainstream R&D dealing with the various crystal structures of LiMn1.5Ni0.5O4 and their evolutions observed during synthesis and cycling in correlation with their electrochemical performance. Influence of electrolytes and additives along with modifications through doping and surface treatments are interrelated, and the electronic and ionic transport properties of the ordered and disordered LiMn1.5Ni0.5O4 phases are discussed. Overall, this review provides a detailed assessment on LiMn1.5Ni0.5O4 and the underlying mechanisms governing its electrochemical performance broadly providing a focused framework for further advancement towards commercialization.

Background Limited drug penetration into solid tumors has been one of the potential causes of resistance to chemotherapy for the treatment of bladder cancer. The aim of the studies was to develop non-toxic nanoemulsion carriers of paclitaxel and to evaluate their ability to serve as a tool increasing and/or controlling the penetration of paclitaxel through the bladder tissue. Methods Various oil-in-water non-toxic self-nanoemulsifying formulations (SNEFs) were developed using Cremercoor MCT, Kollisolv MCT, Miglyol 812, 810, Capmul MCM, Imwitor 988, Imwitor 742 with TO106V, Tween 85, HCO30, Kolliphor EL and Cremophor RH40 at size ranges from approximately 19 to 110 nm that are capable of enhancing the solubility and stability of paclitaxel. Visual assessment was employed and droplet size measurement was taken into initial consideration for optimized SNEFs. Paclitaxel was added with the oil/surfactant mixture before dispersing the mixture in water to form SNEF. The penetration study of the optimal SNEFs formulation was compared with the raw paclitaxel dispersion using transwell apparatus. Results Initial characterisation and solubility studies showed that mixed glycerides of Kollisolv MCT/Imwitor 742 with water-soluble surfactant (high HLB) containing formulations generated highly efficient SNEFs as they are stable and produced lower nanodroplets with higher drug loading. The results have demonstrated that the SNEFs have good ability to retain its characteristics under conditions similar to that found in the urinary bladder up to 48 h. However, the results also showed that chemosensitivity of cancer cells exposed to paclitaxel was attenuated in the presence of SNEFs. Larger size SNEFs have shown to induce more inhibitory effects on paclitaxel activity. The reduction effects of SNEFs on doxorubicin (a relatively water-soluble drug) efficacy were almost absent, indication a poor loading of such compounds. Conclusion The reduction of the efficacy of SNEF loaded treatments does not give a strong indication of their ability to penetrate as examined their ability to penetrate through the cultivated multicell layers (MCL) of bladder cancer. However, these results may open the horizon to reflect the use of SNEFs in the introduction of intravenous paclitaxel because of its potential role in reducing the injection site toxicity.

LiNi0.5Mn1.5O4 is a promising high-voltage cathode for lithium-ion battery fast charging applications. Aware of its electrochemical stability issues, the material's surface is modified with small amounts of zirconia (ZrO2) ranging from 0.5 to 2 wt% using a scalable ball milling process. The advantage of the coating has been demonstrated in electrochemical measurements performed at room temperature and 55 ?C, and in cells discharged under high-rate conditions up to 80C. Of significance, the material coated with 1.0 wt% ZrO2 has been cycled at the 40C rate for over a thousand cycles and retains 86% of its initial capacity. The material with 2.0 wt% ZrO2 modification preserves 76% of its initial capacity when cycled at the 40C rate and 55 ?C. The coated materials have shown excellent cycling stability when subjected to 6C (10-min) fast charging and C/3 discharging for 300 cycles. Compared to the uncoated material, the interfacial resistance of the zirconia modified LiNi0.5Mn1.5O4 has been found to be much lower and does not significantly increase with increasing the coating amount. However, the electrochemical performances are still partly limited by both interfacial resistance at the beginning of charge and electrolyte diffusivity, particularly under higher rate cycling conditions. Overall, the strategy of ZrO2 surface modification applied to LiNi0.5Mn1.5O4 unveils the potential that the material could play in extreme fast charged electric vehicles. This research is sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory , managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy. Scopus

In this study, microstructure of a porosity-graded lanthanum strontium manganite (LSM) cathode of solid oxide fuel cells (SOFCs) has been characterized using focused ion beam (FIB) and scanning electron microscopy (SEM) combined with image processing. Two-point correlation functions of the two-dimensional (2D) images taken along the direction of porosity gradient are used to reconstruct a three-dimensional (3D) microstructure. The effective elastic modulus of the two-phase porosity-graded cathode is predicted using strong contrast (SC) and composite inclusion (CI) homogenization techniques. The effectiveness of the two methods in predicting the effective elastic properties of the porosity-graded LSM cathode is investigated in comparison with the results obtained from the finite element model (FEM).

In this paper, the fabrication and growth mechanism of net-shaped micropatterned self-organized thin-film TiO2 nanotube (TFTN) arrays on a silicon substrate are reported. Electrochemical anodization is used to grow the nanotubes from thin-film titanium sputtered on a silicon substrate with an average diameter of ~30 nm and a length of ~1.5 μm using aqueous and organic-based types of electrolytes. The fabrication and growth mechanism of TFTN arrays from micropatterned three-dimensional isolated islands of sputtered titanium on a silicon substrate is demonstrated for the first time using focused-ion-beam (FIB) technique. This work demonstrates the use of the FIB technique as a simple, high-resolution, and maskless method for high-aspect-ratio etching for the creation of isolated islands and shows great promise toward the use of the proposed approach for the development of metal oxide nanostructured devices and their integration with micro- and nanosystems within silicon-based integrated-circuit devices.

The use of self-healing glass as hermetic seals is a recent advancement in sealing technology development for the planar solid oxide fuel cells (SOFCs). Because of its capability to restore mechanical properties at elevated temperatures, the self-healing glass seal is expected to provide high reliability in maintaining the long-term structural integrity and functionality of SOFCs. To accommodate the design and evaluate the effectiveness of these engineered seals under various thermomechanical operating conditions, a computational modeling framework must be developed to accurately capture and predict the healing behavior of the glass material. In the present work, a mechanistic-based, two-stage model was developed to study the stress and temperature-dependent crack healing of the self-healing glass materials. The model initially was first calibrated by experimental measurements combined with kinetic Monte Carlo (kMC) simulation results and then implemented into finite element analysis (FEA). The effects of various factors, e.g., stress, temperature, and crack morphology, on the healing behavior of the glass were investigated and discussed.

Over their designed lifetime, high-temperature electrochemical devices, such as solid oxide fuel cells (SOFCs), can experience degradation in their electrochemical performance due to environmental conditions, operating conditions, contaminants, and other factors. Understanding the different degradation mechanisms in SOFCs and other electrochemical devices is essential to reducing performance degradation and increasing the lifetimes of these devices. In this paper, SOFC degradation mechanisms are evaluated, and a damage model is presented that describes performance degradation in SOFCs due to damage or degradation in the SOFC electrodes. A degradation classification scheme is presented, dividing the various SOFC electrode degradation mechanisms into categories based on their physical effects on the SOFC. The damage model and classification method are applied both to sulfur poisoning and antimony poisoning, which occur in the SOFC anode. For sulfur poisoning, the model can calculate degradation in SOFC performance based on the operating temperature of the fuel cell and the concentration of gaseous sulfur species in the anode. For antimony poisoning, the effects of nickel consumption from the anode matrix are investigated.

Ab initio methods based on density functional theory have been used to calculate the formation energies of intrinsic defects, including vacancies, interstitials, antisites and Frenkel pairs in YPO4 under the O-rich and Y2O3-rich, and the O-rich and Y-rich conditions. The larger size of the yttrium atom may give rise to higher formation energy of the phosphorus antisite defect. In general, the formation energies of anion interstitials are much smaller than those of cation interstitials for both conditions considered. It is of greatly interest to find that the relative stabilities among the same types of interstitials are independent of the reference states. The most stable configuration for oxygen interstitials is an O–O split interstitial near the Ta site, while the most stable configuration for cation interstitials is a tetrahedral interstitial near the Ta site. The cation split interstitials are unfavorable in YPO4, with much higher formation energies. Furthermore, the properties of Frenkel pairs are compared with those calculated using empirical potentials. The results reveal that both ab initio and empirical potential calculations show a similar trend in the formation energies of Frenkel pairs, but the formation energies obtained by empirical potentials are much larger than those calculated by ab initio method.

In this paper, the effect of the ferritic interconnect thickness on the delamination/spallation of the oxide scale was investigated experimentally and numerically. At the operating environment of solid oxide fuel cells (SOFCs), a combination of growth stress with thermal stresses may lead to scale delamination/buckling and eventual spallation during SOFC stack cooling, even leading to serious degradation of cell performance. The experimental and numerical results show that the interfacial shear stresses increase with the growth of the oxide scale and also with the thickness of the ferritic substrate, i.e., the thick ferritic substrate can easily lead to scale delamination and spallation.

A self-healing glass seal has the potential to restore its mechanical properties upon being reheated to the solid oxide fuel cell (SOFC) stack operating temperature. Such a self-healing feature is desirable for achieving high seal reliability during thermal cycling. Self-healing glass is also characterized by its low mechanical stiffness and high creep rate at SOFC operating temperatures. Therefore, the geometric stability and structural integrity of the glass seal system are critical to its successful application in SOFCs. This paper describes studies of the geometric stability and structural integrity of the self-healing glass seal system and the influence of various interfacial conditions during the operating and cooling-down processes using finite element analyses. For this purpose, the test cell used in the leakage tests for compliant glass seals, conducted at Pacific Northwest National Laboratory (PNNL), was taken as the initial modeling geometry. The effect of the ceramic stopper on the geometric stability of the self-healing glass sealants was studied first. Two interfacial conditions of the ceramic stopper and glass seals, i.e., bonded (strong) or unbonded (weak), were considered. Then the influences of interfacial strengths at various interfaces, i.e., stopper/glass, stopper/PEN, as well as stopper/IC plate, on the geometric stability and reliability of glass during the operating and cooling processes were examined.

We present a pore-scale model of a solid oxide fuel cell (SOFC) cathode. Volatile chromium species are known to migrate from the current collector of the SOFC into the cathode where over time they decrease the voltage output of the fuel cell. A pore-scale model is used to investigate the reactive transport of chromium species in the cathode and to study the driving forces of chromium poisoning. A multi-scale modeling approach is proposed which uses a cell level model of the cathode, air channel and current collector to determine the boundary conditions for a pore-scale model of a section of the cathode. The pore-scale model uses a discrete representation of the cathode to explicitly model the surface reactions of oxygen and chromium with the cathode material. The pore-scale model is used to study the reaction mechanisms of chromium by considering the effects of reaction rates, diffusion coefficients, chromium vaporization, and oxygen consumption on chromium's deposition in the cathode. The study shows that chromium poisoning is most significantly affected by the chromium reaction rates in the cathode and that the reaction rates are a function of the local current density in the cathode.

A phase-field model is developed to investigate the migration of vacancies, interstitials, and voids during irradiation in a thermal gradient. Void growth kinetics during irradiation are also modeled. The model accounts for the generation of defects including vacancies and interstitials associated with the radiation damage, recombination of vacancies and interstitials, defect diffusion, and defect sinks. The effect of void size, vacancy concentration, vacancy generation rate, recombination rate, and temperature gradient on a single void migration and growth is parametrically studied. The results demonstrate that a temperature gradient causes void migration and defect fluxes, i.e., the Soret effect, which affects void stability and growth kinetics. It is found that (1) void migration mobility is independent of void size, which is in agreement with the theoretical prediction under the assumption of bulk diffusion controlled migration; (2) void migration mobility strongly depends on the temperature gradient and (3) the effect of defect concentration, generation rate, and recombination rate on void migration mobility is minor although they strongly influence void growth kinetics.

Recent developments on decreasing the operating temperature for solid oxide fuel cells (SOFCs) have enabled the use of high-temperature ferritic alloys as interconnect materials. Oxide scale will inevitably grow on the ferritic interconnects in a high-temperature oxidation environment of SOFCs. The growth of the oxide scale induces growth stresses in the scale layer and on the scale/substrate interface. These growth stresses combined with the thermal stresses induced after stacking cooling by the thermal expansion coefficient mismatch between the oxide scale and the substrate may lead to scale delamination/buckling and eventual spallation, which may lead to serious cell performance degradation. Hence, the interfacial adhesion strength between the oxide scale and the substrate is crucial to the reliability and durability of the metallic interconnect in SOFC operating environments. In this article, we applied an integrated experimental/modeling methodology to quantify the interfacial adhesion strength between the oxide scale and the SS 441 metallic interconnect. The predicted interfacial strength is discussed in detail.

An integrated experimental/modeling approach was utilized to assess the structural integrity of Ni–yttria-stabilized zirconia (YSZ) porous anode supports during the solid oxide fuel cell (SOFC) operation on coal gas containing trace amounts of phosphorus impurities. Phosphorus was chosen as a typical impurity exhibiting strong interactions with the nickel followed by second phase formation. Tests were performed using Ni–YSZ anode-supported button cells exposed to 0.5–10 ppm of phosphine in synthetic coal gas at 700–800 °C. The extent of Ni–P interactions was determined by a post-test scanning electron microscopy (SEM) analysis. Severe damage to the anode support due to nickel phosphide phase formation and extensive crystal coalescence was revealed, resulting in electric percolation loss. The subsequent finite element stress analyses were conducted using the actual anode support microstructures to assist in degradation mechanism explanation. Volume expansion induced by the Ni phase alteration was found to produce high stress levels such that local failure of the Ni–YSZ anode became possible under the operating conditions.

This paper examines the electrochemical and direct internal steam–methane reforming performance of the solid oxide fuel cell when subjected to pressurization. Pressurized operation boosts the Nernst potential and decreases the activation polarization, both of which serve to increase cell voltage and power while lowering the heat load and operating temperature. A model considering the activation polarization in both the fuel and the air electrodes was adopted to address this effect on the electrochemical performance. The pressurized methane conversion kinetics and the increase in equilibrium methane concentration are considered in a new rate expression. The models were then applied in simulations to predict how the distributions of direct internal reforming rate, temperature, and current density are effected within stacks operating at elevated pressure. A generic 10 cm counter-flow stack model was created and used for the simulations of pressurized operation. The predictions showed improved thermal and electrical performance with increased operating pressure. The average and maximum cell temperatures decreased by 3% (20 °C) while the cell voltage increased by 9% as the operating pressure was increased from 1 to 10 atm.

This study utilizes nanoindentation to investigate and measure creep properties of a barium calcium alumino-silicate glass–ceramic used for solid oxide fuel cell seals (SOFCs). Samples of the glass–ceramic seal material were aged for 5, 50, and 100 h to obtain different degrees of crystallinity. Instrumented nanoindentation was performed on the samples with different aging times at different temperatures to investigate the strain rate sensitivity during inelastic deformation. The temperature dependent behavior is important since SOFCs operate at high temperatures (800–1000 °C). Results show that the samples with higher crystallinity were more resistant to creep, and the creep compliance tended to decrease with increasing temperature, especially with further aged samples.

High-temperature ferritic alloys are potential candidates as interconnect (IC) materials and spacers due to their low cost and coefficient of thermal expansion (CTE) compatibility with other components for most of the solid oxide fuel cells (SOFCs) . However, creep deformation becomes relevant for a material when the operating temperature exceeds or even is less than half of its melting temperature (in degrees of Kelvin). The operating temperatures for most of the SOFCs under development are around 1,073 K. With around 1,800 K of the melting temperature for most stainless steel, possible creep deformation of ferritic IC under the typical cell operating temperature should not be neglected. In this paper, the effects of IC creep behavior on stack geometry change and the stress redistribution of different cell components are predicted and summarized. The goal of the study is to investigate the performance of the fuel cell stack by obtaining the changes in fuel- and air-channel geometry due to creep of the ferritic stainless steel IC, therefore indicating possible changes in SOFC performance under long-term operations. The ferritic IC creep model was incorporated into software SOFC-MP and Mentat-FC, and finite element analyses were performed to quantify the deformed configuration of the SOFCmore » stack under the long-term steady-state operating temperature. It was found that the creep behavior of the ferritic stainless steel IC contributes to narrowing of both the fuel- and the air-flow channels. In addition, stress re-distribution of the cell components suggests the need for a compliant sealing material that also relaxes at operating temperature.« less

The creep behavior of glass or glass–ceramic sealant materials used in solid oxide fuel cells (SOFCs) becomes relevant under SOFC operating temperatures. In this paper, the creep of glass–ceramic sealants was experimentally examined, and a standard linear solid model was applied to capture the creep behavior of glass–ceramic sealant materials developed for planar SOFCs at high temperatures. The parameters of this model were determined based on the creep test results. Furthermore, the creep model was incorporated into finite-element software programs SOFC-MP and Mentat-FC developed at Pacific Northwest National Laboratory for multiphysics simulation of SOFCs. The effect of creep of glass–ceramic sealant materials on the long-term performance of SOFC stacks was investigated by studying the stability of the flow channels and the stress redistribution in the glass seal and on the various interfaces of the glass seal with other layers. Finite-element analyses were performed to quantify the stresses in various parts. The stresses in glass seals were released because of creep behavior during operations.

In this paper, we present an integrated experimental and modeling methodology in predicting the life of coated and uncoated metallic interconnect (IC) for solid oxide fuel cell (SOFC) applications. The ultimate goal is to provide cell designer and manufacture with a predictive methodology such that the life of the IC system can be managed and optimized through different coating thickness to meet the overall cell designed life. Crofer 22 APU is used as the example IC material system. The life of coated and uncoated Crofer 22 APU under isothermal cooling was predicted by comparing the predicted interfacial strength and the interfacial stresses induced by the cooling process from the operating temperature to room temperature, together with the measured oxide scale growth kinetics. It was found that the interfacial strength between the oxide scale and the Crofer 22 APU substrate decreases with the growth of the oxide scale, and that the interfacial strength for the oxide scale/spinel coating interface is much higher than that of the oxide scale/Crofer 22 APU substrate interface. As expected, the predicted life of the coated Crofer 22 APU is significantly longer than that of the uncoated Crofer 22 APU.

Multiple-step ultrasonic spray pyrolysis was developed to produce a gradient porous lanthanum strontium manganite (LSM) cathode on yttria-stabilized zirconia (YSZ) electrolyte for use in intermediate temperature solid oxide fuel cells (IT-SOFCs). The effect of solvent and precursor type on the morphology and compositional homogeneity of the LSM film was first identified. The LSM film prepared from organo-metallic precursor and organic solvent showed a homogeneous crack-free microstructure before and after heat treatment as opposed to aqueous solution. With respect to the effect of processing parameters, increasing the temperature and solution flow rate in the specific range of 520–580 °C leads to change the microstructure from a dense to a highly porous structure. Using a dilute organic solution a nanocrystalline thin layer was first deposited at 520 °C and solution flow rate of 0.73 ml/min on YSZ surface; then, three gradient porous layers were sprayed from concentrated solution at higher temperatures (540–580 °C) and solution flow rates (1.13–1.58 ml/min) to form a gradient porous LSM cathode film with ∼30 μm thickness. The microstructure, phase crystallinity and compositional homogeneity of the fabricated films were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive analysis of X-ray (EDX). Results showed that the spray pyrolized gradient film fabricated in the temperature range of 520–580 °C is composed of highly crystalline LSM phase which can remove the need for subsequent heat treatment.

The mechanical properties and response of two polypropylene (PP)-based composites have been determined for small strains and for a range of strain rates in the quasi-static domain. These two materials are talc-filled and unfilled high-impact PP. Uniaxial tensile tests were performed at different strain rates in order to characterize the mechanical response and the strain rate effect. The experimental results showed that both unfilled and talc-filled high-impact PP were sensitive to strain rate and exhibited nonlinear behavior even at relatively low strains. SEM analysis was conducted to obtain a better comprehension of deformation mechanisms involved during loading by observations of the microstructure evolution. For each of these two materials, two existing modeling approaches are proposed. The first one is a three-parameter nonlinear constitutive model based on the experimental results. The second is a micromechanically based approach for the elastic-viscoplastic behavior of the composite materials. The stress-strain curves predicted by these models are in fairly good agreement with our experimental results.

This paper describes the fabrication process for the thin cast-in-place laminate glazing systems to be used in cars of the future to achieve the weight reduction goals of FreedomCAR. The primary objective of the project is to reduce vehicle weight, improve fuel economy, and reduce vehicle emissions through the use of structurally reliable, high acoustic performance, and lightweight glazing systems with low manufacturing costs. Energy savings come from reducing weight by using thinner glazing: prior studies at Pacific Northwest National Laboratory (PNNL) have demonstrated a potential of 30% weight reductions compared with standard glazing system. Energy savings will also come from reducing interior heat loads; that, in turn, will reduce the demand for air conditioning. The evaluation of alternative glazing concepts seeks to improve acoustical performance such that reduced interior noise levels can be achieved while maintaining glazing at minimal thickness and weight levels. The most important factor in utilizing laminated glazing systems as vehicle side glass is its advantage in cost savings for material and manufacturing processes.

The interfacial adhesion strength between the oxide scale and the substrate is crucial to the reliability and durability of metallic interconnects in solid oxide fuel cell (SOFC) operating environments. It is necessary, therefore, to establish a methodology to quantify the interfacial adhesion strength between the oxide scale and the metallic interconnect substrate, and furthermore to design and optimize the interconnect material as well as the coating materials to meet the design life of an SOFC system. In this paper, we present an integrated experimental/analytical methodology for quantifying the interfacial adhesion strength between the oxide scale and a ferritic stainless steel interconnect. Stair-stepping indentation tests are used in conjunction with subsequent finite element analyses to predict the interfacial strength between the oxide scale and Crofer 22 APU substrate.

Interconnects in solid oxide fuel cells (SOFCs) provide the electrical connection between the individual cells, as well as separate the anode air from the cathode fuel for each cell. The recently developed anode-supported planar SOFCs design allows the cell working temperature to be 800oC and lower, which led to the proposed use of ferritic stainless steel as interconnects and current collectors in the SOFC systems. Many experimental studies have shown that metal based interconnects will go through surface oxidation under the typical operating temperature and environment of an SOFC system. Since the oxide scale is formed at the outer surface of interconnect, its microstructure (morphology, texture), properties (electrical, thermal and mechanical properties), and structural integrity/stability will have a significant impact on the performance of interconnect. In this paper, we study the oxide growth kinetics and stresses generated during scale growth the thermal cycling for Cr-Fe based alloy, e.g. Crofer 22 APU. The goal is to predict the interconnect life under typical operating conditions and thermal cycles. First, a mathematical model is developed based on the growth of scale and coupling relation between diffusion and stress field. The following phenomena are considered: 1) The predominant cationic diffusion and cation distribution withinmore » the oxide scale in transient state and steady state; 2) Chemical reaction within the scale as well as the growth kinetics of the oxide scale; 3) Stresses distribution during the oxidation, especially for mid- and long-term treatment; 4) Coupling relationship or interaction between oxidation induced stresses and mass diffusion within the scale. Next, thermal stresses generated due to temperature changes in thermal cycling are predicted using finite element analyses for different substrate and scale thickness. In general, very high compressive in-plane stresses are predicted for the oxide layer. Also, high shear stress is also predicted on the oxide/substrate interface. The predicted shear stress on the interface is used to compare with the experimentally determined bond strength to predict delamination. Finally, scale spallation and IC life prediction are predicted by comparing the compressive stress in the scale with the critical buckling load for the delaminated scale.« less

Numerical simulations were performed to determine the effect that varying the percent on-cell steam-methane reformation would have on the thermal, electrical, and mechanical performance of generic, planar solid oxide fuel cell stacks. The study was performed using three-dimensional model geometries for cross-, co-, and counter-flow configuration stacks of 10x10- and 20x20-cm cell sizes. The analysis predicted the stress and temperature difference would be minimized for the 10x10-cm counter- and cross-flow stacks when 40 to 50% of the reformation reaction occurred on the anode. Gross electrical power density was virtually unaffected by the reforming. The co-flow stack benefited most from the on-cell reforming and had the lowest anode stresses of the 20x20-cm stacks. The analyses also suggest that airflows associated with 15% air utilization may be required for cooling the larger (20x20-cm) stacks.

In this paper, we report predicted results for texture evolution in FCC metals under uniaxial compression test. These results are computed using a newly developed nonlinear rigid viscoplastic crystal plasticity model based on an intermediate interaction law. This interaction law is formulated by the minimization of a normalized error function which combines the local fields’ deviations, from the macroscopic ones, obtained by the classical upper bound (Taylor) and lower bound (Sachs) models. This interaction law leads to results lying between the upper and lower bound approaches by simply varying a scalar weight function ϕ (0 < ϕ < 1). A simple interaction law based on the linear mixture of the fields from the Taylor and Sachs models is also used. The results from these both the linear and nonlinear intermediate approaches are shown in terms of texture evolution under uniaxial compression. These results are discussed in comparison with the well known experimental textures in compressed FCC metals. Finally, we show that the linear intermediate approach yields fairly acceptable texture predictions under compression and that the fully non-linear approach predicts much better results. Nicht-lineare visko-plastische Modellierung der Texturveranderungen in Metallen mit kubischflachenzentriertem Kristallsystem : Druckversuch In diesem Artikel berichten wir uber Berechnungen der Veranderungen in der Textur von Metallen mit kubischflachenzentriertem Kristallsystem unter Druckspannung. Die Ergebnisse wurden mit einem neu-entwickelten nicht-linearen, starren visko-plastischen Modell berechnet, das auf einem mittleren Interaktionsgesetz beruht. Mit Hilfe eines optimierten Gewichtungsfaktors ϕ ergibt dieses Gesetz Werte, die sich zwischen denen der klassischen unteren (Sachs) und oberen (Taylor) Modelle befinden. Ein einfacheres Interaktionsgesetz, das auf der direkten Linearkombination der Ergebnisse der Modelle von Taylor und von Sachs beruht, wurde auch untersucht. Die Ergebnisse dieser beiden mittleren Modelle werden im Rahmen von einachsigen Druckspannungen prasentiert. Die berechneten Werte werden mit Messungen verglichen. Es wird gezeigt, dass das lineare Modell zu annehmbaren Voraussagen fuhrt, das nicht-lineare Modell jedoch wesentlich bessere Ergebnisse ergibt.

A simulation tool for modeling planar solid oxide fuel cells is demonstrated. The tool combines the versatility of a commercial computational fluid dynamics simulation code with a validated electrochemistry calculation method. Its function is to predict the flow and distribution of anode and cathode gases, temperature and current distributions, and fuel utilization. A three-dimensional model geometry, including internal manifolds, was created to simulate a generic, cross-flow stack design. Similar three-dimensional geometries were created for simulation of co-flow, and counterflow stack designs. Cyclic boundary conditions were imposed at the top and bottom of the model domains, while the lateral walls were assumed adiabatic. The three cases show that, for a given average cell temperature, similar fuel utilizations can result irrespective of the flow configuration. Temperature distributions however, which largely determine thermal stresses during operation, are dependent on the chosen design geometry/flow configuration. The co-flow case had the most uniform temperature distribution and the smallest thermal gradients, thus offers thermo-structural advantages over the other flow cases.

Interfacial analysis utilizing interfacial indentation methodology (where micro/nano indentation is performed at the oxide scale/substrate interface to create and propagate cracks at the interface) was completed for the 14,000 and 20,000 hours, 800oC surface modified specimens. The localized oxide thickness and crack lengths were measured after applying loads ranging from 0.2 to 1.8 N. Post-processing of the results to date indicate that the critical load for surface blasted (SB) surface modified specimens is greater than the equivalent surface grind (SG) surface modified specimens which is indicative of a ~ 25% increase in interfacial strength in the SB specimens in comparisons to the SG specimens. However, more data is needed to further quantify the interfacial strength and to reduce any uncertainty due to the approach applied.

Using density functional theory, a series of calculations of structural and electronic properties of hydrogen vacancies in a fully hydrogenated boron nitride (fH-BN) layer were conducted. By dehydrogenating the fH-BN structure, B-terminated vacancies can be created which induce complete spin polarization around the Fermi level, irrespective of the vacancy size. On the contrary, the fH-BN structure with N-terminated vacancies can be a small-gap semiconductor, a typical spin gapless semiconductor, or a metal depending on the vacancy size. Utilizing such vacancy-induced band gap and magnetism changes, possible applications in spintronics are proposed, and a special fH-BN based quantum dot device is designed. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Solid oxide fuel cells (SOFCs) are high temperature fuel cells, which are being developed for large scale and distributed power systems. SOFCs promise to provide cleaner, more efficient electricity than traditional fossil fuel burning power plants. Research over the last decade has improved the design and materials used in SOFCs to increase their performance and stability for long-term operation; however, there are still challenges for SOFC researchers to overcome before SOFCs can be considered competitive with traditional fossil fuel burning and renewable power systems. In particular degradation due to contaminants in the fuel and oxidant stream is a major challenge facing SOFCs. In this paper we discuss ongoing computational and experimental research into different degradation and design issues in SOFC electrodes. We focus on contaminants in gasified coal which cause electrochemical and structural degradation in the anode, and chromium poisoning which affects the electrochemistry of the cathode. Due to the complex microstructures and multi-physics of SOFCs, multi-scale computational modeling and experimental research is needed to understand the detailed physics behind different degradation mechanisms, the local conditions within the cell which facilitate degradation, and its effects on the overall SOFC performance. We will discuss computational modeling research of SOFCs at the macro-, meso- and nano-scales which is being used to investigate the performance and degradation of SOFCs. We will also discuss the need for a multi-scale modeling framework of SOFCs, and the application of computational and multi-scale modeling to several degradation issues in SOFCs.

Electricity production through the integration of coal gasification with solid oxide fuel cells (SOFCs) may potentially be an efficient technique for clean energy generation. However, multiple minor and trace components are naturally present in coals. These impurities in coal gas not only degrade the electrochemical performance of Ni-YSZ anode used in SOFCs, but also severely endanger the structural integrity of the Ni-YSZ anode. In this paper, effect of the trace impurity of the coal syngases on the mechanical degradation of Ni-YSZ anode was studied by using an integrated experimental/modeling approach. Phosphorus is taken as an example of impurity. Anode-support button cell was used to experimentally explore the migration of phosphorous impurity in the Ni-YSZ anode of SOFCs. X-ray mapping was used to show elemental distributions and new phase formation. The subsequent finite element stress analyses were conducted using the actual microstructure of the anode to illustrate the degradation mechanism. It was found that volume expansion induced by the Ni phase change produces high stress level such that local failure of the Ni-YSZ anode is possible under the operating conditions

Using density functional calculations, we investigate the geometries, electronic structures and magnetic properties of hexagonal BN sheets with 3d transition metal (TM) and nonmetal atoms embedded in three types of vacancies: V(B), V(N), and V(B+N). We show that some embedded configurations, except TM atoms in V(N) vacancy, are stable in BN sheets and yield interesting phenomena. For instance, the band gaps and magnetic moments of BN sheets can be tuned depending on the embedded dopant species and vacancy type. In particular, embedment such as Cr in V(B+N), Co in V(B), and Ni in V(B) leads to half-metallic BN sheets interesting for spin filter applications. From the investigation of Mn-chain (C(Mn)) embedments, a regular 1D structure can be formed in BN sheets as an electron waveguide, a metal nanometre wire with a single atom thickness.

A cell-level distributed electrochemistry (DEC) modeling tool has been developed to enable predicting trends in solid oxide fuel cell performance by considering the coupled and spatially varying multi-physics that occur within the tri-layer. The approach calculates the distributed electrochemistry within the electrodes, which includes the charge transfer and electric potential fields, ion transport throughout the tri-layer, and gas distributions within the composite and porous electrodes. The thickness of the electrochemically active regions within the electrodes is calculated along with the distributions of charge transfer. The DEC modeling tool can examine the overall SOFC performance based on electrode microstructural parameters, such as particle size, pore size, porosity, electrolyte- and electrode-phase volume fractions, and triple-phase-boundary length. Recent developments in electrode fabrication methods have lead to increased interest in using graded and nano-structured electrodes to improve the electrochemical performance of SOFCs. This paper demonstrates how the DEC modeling tool can be used to help design novel electrode microstructures by optimizing a graded anode for high electrochemical performance.

This report presents a hierarchical multiscale modeling scheme based on two-way information exchange. To account for all essential phenomena in waste forms over geological time scales, the models have to span length scales from nanometer to kilometer and time scales from picoseconds to millenia. A single model cannot cover this wide range and a multi-scale approach that integrates a number of different at-scale models is called for. The approach outlined here involves integration of quantum mechanical calculations, classical molecular dynamics simulations, kinetic Monte Carlo and phase field methods at the mesoscale, and continuum models. The ultimate aim is to provide science-based input in the form of constitutive equations to integrated codes. The atomistic component of this scheme is demonstrated in the promising waste form xenotime. Density functional theory calculations have yielded valuable information about defect formation energies. This data can be used to develop interatomic potentials for molecular dynamics simulations of radiation damage. Potentials developed in the present work show a good match for the equilibrium lattice constants, elastic constants and thermal expansion of xenotime. In novel waste forms, such as xenotime, a considerable amount of data needed to validate the models is not available. Integration of multiscale modeling withmore » experimental work is essential to generate missing data needed to validate the modeling scheme and the individual models. Density functional theory can also be used to fill knowledge gaps. Key challenges lie in the areas of uncertainty quantification, verification and validation, which must be performed at each level of the multiscale model and across scales. The approach used to exchange information between different levels must also be rigorously validated. The outlook for multiscale modeling of wasteforms is quite promising.« less

The migration mechanisms and the corresponding activation energies of Cr-vacancy (Cr-V) clusters and Cr interstitials in $\ensuremath{\alpha}\text{-Fe}$ have been investigated using the dimer and the nudged elastic-band methods. Dimer searches are employed to find the possible transition states of these defects and the lowest-energy paths are used to determine the energy barriers for migration. A substitutional Cr atom can migrate to a nearest-neighbor vacancy through an energy barrier of 0.56 eV but this simple mechanism alone is unlikely to lead to the long-distance migration of Cr unless there is a supersaturated concentration of vacancies in the system. The Cr-vacancy clusters can lead to long-distance migration of a Cr atom that is accomplished by Fe and Cr atoms successively jumping to nearest-neighbor vacancy positions, defined as a self-vacancy-assisted migration mechanism, with the migration energies ranging from 0.64 to 0.89 eV. In addition, a mixed Cr-Fe dumbbell interstitial can easily migrate through Fe lattices, with the migration energy barrier of 0.17, which is lower than that of the Fe-Fe interstitial. The on-site rotation of the Cr-Fe interstitial and Cr atom hopping from one site to another are believed to comprise the dominant migration mechanism. The calculated binding energies of Cr-V clusters are strongly dependent on the size of clusters and the concentration of Cr atoms in clusters.

High operating temperature of solid oxide fuel cells require that sealant must function at high temperature between 600o and 900oC and in the oxidizing and reducing environments of fuel and air. It should be noted that creep deformation becomes relevant for a material when the operating temperature is near or exceeds half of its melting temperature (in degrees of Kelvin). The operating temperatures for most of the solid oxide fuel cells (SOFC) under development in the SECA program are around 800oC, which exceeds the glass transition temperature Tg for most glass ceramic materials. The goal of the study is to develop a creep model to capture the creep behavior of glass ceramic materials at high temperature and to investigate the effect of creep of glass ceramic sealant materials on stresses in glass seal and on the various interfaces of glass seal with other layers. The self-consistent creep models were incorporated into SOFC-MP and Mentat FC, and finite element analyses were performed to quantify the stresses in various parts. The stress in glass seals were released due to its creep behavior during the operating environments.

A microstructure design framework for multiscale modeling of wear resistance in bioimplant materials is presented here. The increase in service lifetime of arthroplasty depends on whether we can predict wear resistance and microstructure evolution of a bioimplant material made from ultra high molecular weight polyethylene during processing. Experimental results show that the anisotropy introduced during deformation increases wear resistance in desired directions. After uniaxial compression, wear resistance along the direction, perpendicular to compression direction, increased 3.3 times. Micromechanical models are used to predict microstructure evolution and the improvement in wear resistance during processing. Predicted results agree well with the experimental data. These models may guide the materials designer to optimize processing to achieve better wear behavior along desired directions.

Summarizes work done to extend the electrochemical performance and methane reforming submodels to include the effects of pressurization and to demonstrate this new modeling capability by simulating large stacks operating on methane-rich fuel under pressurized and non-pressurized conditions. Pressurized operation boosts electrochemical performance, alters the kinetics of methane reforming, and effects the equilibrium composition of methane fuels. This work developed constitutive submodels that couple the electrochemistry, reforming, and pressurization to yield an increased capability of the modeling tool for prediction of SOFC stack performance.

Planar Solid Oxide Fuel Cells (SOFC) stacks are multi-material layered systems with different thermo-mechanical properties. Due to their severe thermal loading, these layers have to meet high demands to preserve their mechanical integrity without any cracks initiation and propagation. In this paper, cracks propagation in a typical unit cell of the stack which consists of positive electrode–electrolyte–negative electrode (PEN) is modeled. Based on the mechanical properties of each layer and their interfaces, an energy criterion as a function of crack length is used for the prediction of possible crack extensions in the PEN. An analysis of the competition between crack deflections in the interfaces and crack penetration in layers is presented.

Providing adequate and efficient cooling schemes for solid-oxide-fuel-cell (SOFC) stacks continues to be a challenge coincident with the development of larger, more powerful stacks. The endothermic steam-methane reformation reaction can provide cooling and improved system efficiency when performed directly on the electrochemically active anode. Rapid kinetics of the endothermic reaction typically causes a localized temperature depression on the anode near the fuel inlet. It is desirable to extend the endothermic effect over more of the cell area and mitigate the associated differences in temperature on the cell to alleviate subsequent thermal stresses. In this study, modeling tools validated for the prediction of fuel use, on-cell methane reforming, and the distribution of temperature within SOFC stacks, are employed to provide direction for modifying the catalytic activity of anode materials to control the methane conversion rate. Improvements in thermal management that can be achieved through on-cell reforming is predicted and discussed. Two operating scenarios are considered: one in which the methane fuel is fully pre-reformed, and another in which a substantial percentage of the methane is reformed on-cell. For the latter, a range of catalytic activity is considered and the predicted thermal effects on the cell are presented. Simulations of themore » cell electrochemical and thermal performance with and without on-cell reforming, including structural analyses, show a substantial decrease in thermal stresses for an on-cell reforming case with slowed methane conversion.« less

A novel nanocomposite cathode consisting of sulfur and hollow-mesoporous titania (HMT) embedded within carbon nanotubes (CNT), which is designated as S-HMT@CNT, has been obtained by encapsulating elemental sulfur into the pores of hollow-mesoporous, spherical TiO2 particles that are connected via CNT. A carbon-paper interlayer, referred to as dual functional porous carbon wall (DF-PCW), has been obtained by filling the voids in TiO2 spheres with carbon and then etching the TiO2 template with a chemical process. The DF-PCW interlayer provides a medium for scavenging the lithium polysulfides and suppressing them from diffusing to the anode side when it is inserted between the sulfur cathode and the separator. Lithium–sulfur cells fabricated with the thus prepared S-HMT@CNT cathode and the DF-PCW interlayer exhibit superior performance due to the containment of sulfur in TiO2 and improved lithium–ion and electron transports. The Li–S cells display high capacity with excellent capacity retention at rates as high as 1C, 2C, and 5C rates.

This report summarizes a parametric analysis performed to determine the effect of varying the percent on-cell reformation (OCR) of methane on the thermal and electrical performance for a generic, planar solid oxide fuel cell (SOFC) stack design. OCR of methane can be beneficial to an SOFC stack because the reaction (steam-methane reformation) is endothermic and can remove excess heat generated by the electrochemical reactions directly from the cell. The heat removed is proportional to the amount of methane reformed on the cell. Methane can be partially pre-reformed externally, then supplied to the stack, where rapid reaction kinetics on the anode ensures complete conversion. Thus, the thermal load varies with methane concentration entering the stack, as does the coupled scalar distributions, including the temperature and electrical current density. The endotherm due to the reformation reaction can cause a temperature depression on the anode near the fuel inlet, resulting in large thermal gradients. This effect depends on factors that include methane concentration, local temperature, and stack geometry.

This paper examines the effects of failure modes on the static strength and total energy absorption of aluminum spot-welded samples using experimental, statistical, and analytical approaches. The main failure modes for aluminum spot welds are nugget pullout and interfacial fracture. Two populations of aluminum spot welds were studied. Within each population, coupon configurations of lap shear, cross tension and coach peel were considered. Thirty replicate static strength tests were performed for each coupon configuration. The resulted peak load and energy absorption level associated with each failure mode was studied using statistical models. Next, an analytical model was developed to determine the failure mode of an aluminum resistance spot weld based on stress analysis. It is found that weld size, sheet thickness, and level of weld porosity and defects are the main factors determining the cross tension failure mode for an aluminum spot weld. The peak load and energy absorption levels for the cross tension and coach peel samples tested are found not to be very sensitive to the failure modes under static loading.