Interplay between Mechanical and Electrochemical Properties of Block Copolymer Electrolytes and its Effect on Stability against Lithium Metal Electrodes

We have studied the cycle life of two polyhedral oligomeric silsesquioxane-b-poly(ethylene oxide)-b-polyhedral oligomeric silsesquioxane (POSS-PEO-POSS) block copolymer electrolytes differing primarily in molecular weights and composition using lithium/polymer/lithium symmetric cells. The higher molecular weight electrolyte, labeled H, has a higher storage modulus, Gel. However, the volume fraction of the conducting phase in the low molecular weight electrolyte, labeled L, is higher and this leads to a four-fold increase in limiting current density, iL. Measurement of ionic conductivity provides insight into the reason for the observed differences in limiting current density. The average lifetime of symmetric cells with electrolyte L was slightly higher than that of cells with electrolyte H. The combined effect of mechanical and electrochemical properties of electrolytes on the stability of lithium electrodeposition was quantified by examining two dimensionless parameters, i/iL and Gel/GLi, introduced in the theory developed by Barai and Srinivasan [Phys. Chem. Chem. Phys., 19, 20493–20505 (2017)]. This theory predicts the regime of stable lithium electrodeposition as a function of these two parameters. Despite large differences in Gel and iL between the two electrolytes, we show that similar cell lifetimes are consistent with the theoretical predictions of unstable lithium electrodeposition without resorting to any adjustable parameters.

Polymer blends with ordered distribution of conductive filler

This review highlight approaches to the formation of an ordered distribution of conductive filler in polymer blends. This distribution leads to a significant decrease of the percolation threshold in the polymer mixture, i.e. to a decrease in the critical concentration of the filler, at which the transition of the system from a non-conductive to a conductive state occurs. This improves the mechanical properties of the composition and its processability. It is shown that the ordered structure of the filler is formed in the polymer blend upon mixing the components in the melt under the action of three factors - thermodynamic (the ratio between the values of the interfacial tension of the filler-polymer A and filler-polymer B, as well as between polymers A and B), kinetic (the ratio between viscosities of polymer components A and B) and technological (the intensity and temperature of processing, as well as the order of introduction of a filler into a heterogeneous polymer matrix, which can enhance or suppress the effect of thermodynamic or kinetic factors). On the example of the works performed by the author on mixtures of thermoplastics filled with electrically conductive carbon fillers such as carbon black and carbon nanotubes, as well as a metal filler - dispersed iron, with the involvement of literature data on filled polymer blends, the influence of each of the factors on the formation of an ordered structure of the conducting phase in polymer blends is shown.

Protonic Ceramic Fuel Cell with Bi-Layered Structure of BaZr0.1Ce0.7Y0.1Yb0.1O3–δ Functional Interlayer and BaZr0.8Yb0.2O3–δ Electrolyte

Widespread application of PCFCs will require higher performance even at lower temperatures (<600 °C). This paper reports development of a protonic ceramic fuel cell (PCFC) with a bi-layered proton-conducting phase structure consisting of a BaZr0.1Ce0.7Y0.1Yb0.1O3–δ (BZCYYb1711) functional interlayer and BaZr0.8Yb0.2O3–δ (BZYb20) electrolyte. In this PCFC, a zirconate-based oxide with high durability against CO2, BZYb20, is selected as the electrolyte material, and a BZCYYb1711 functional interlayer is applied between the dense BZYb20 electrolyte and a cathode to achieve higher power density and higher open-circuit voltage (OCV) of the PCFC. In cell fabrication via conventional wet process and co-sintering, although Ni diffusion occurs from NiO-BZYb20 anode into the approximately 8-µm-thick BZYb20 electrolyte, almost no Ni diffuses into the BZCYYb1711 functional interlayer. Compared to a PCFC without this functional interlayer, the proposed PCFC exhibits higher electrochemical performance. Results showed that the BZCYYb1711 functional interlayer reduces cathode polarization resistance and increase power density of the PCFC. Moreover, the OCV increases because the BZCYYb1711 functional interlayer suppresses the current leakage caused by hole conduction of the BZYb20 electrolyte. In conclusion, this bi-layered structure effectively improves both the power density and OCV of PCFCs.

Fabrication of YSZ-Carbon Felt Composite Materials by Spark Plasma Sintering Process

Dual-phase membrane composed of oxide ion conductor and electron conductor was fabricated for application to oxygen separation membranes. 8 mol% yttria-stabilized zirconia (8YSZ) and carbon felt were used for the oxide ion conducting phase and the electron conductiing phase, respectively. Carbon felt was impregnated with YSZ aqueous suspension (40 wt%), dried, then sintered by a spark plasma sintering (SPS) process under the applied pressure of 80 MPa at 1200, 1400 and 1600 ° C for 10 min. When sintered at 1600 ° C, the XRD pattern showed small peaks indicating the formation of the zirconium carbide phase, but the microstructure observed by SEM showed that the YSZ was well densified and tightly bonded with carbon felt. This method has been demonstrated to be an effective process for the fabrication of YSZ-Carbon composites with both phases percolation structure.

Pure oxygen separation from air using dual-phase SDC-SCFZ disc membrane: A modelling approach

Novel Ce0.8Sm0.2O1.9-SrCo0.4Fe0.55Zr0.05O3-δ (SDC-SCFZ) disc membranes consist of 25 wt.% SDC fluorite ionic conducting phase and 75 wt.% SCFZ perovskite mixed conducting phase, which is more promising than perovskite oxide SCFZ single-phase membrane in terms of the oxygen permeation flux. This work features a modelling approach to simulate the oxygen permeation fluxes of the SDC-SCFZ membrane. Simplified model equations from the Zhu model and Xu-Thomson model based on the limiting cases of surface exchange reactions and bulk diffusion are compared. The Zhu model is found to be more applicable for the membranes with overall good correlation and low sum of squared error. Furthermore, modelling studies revealed that the oxygen transport is limited by surface exchange reactions from 700 to 850 °C and a mixture of both limiting cases above 850 up to 950 °C. It is concluded that the membranes exhibit high oxygen permeation flux of up to 2×10−6 mol s−1 cm−2 at 950 °C with Pair of 5 atm and Po 2 of 0.005 atm. The optimum range of operating conditions of the membrane are found to be at 950 °C with minimum Pair of 1 atm and P11 2 lower than 0.025 atm.

A high-performance TE modulator/TM-pass polarizer using selective mode shaping in a VO2-based side-polished fiber

The reversible insulating-to-conducting phase transition (ICPT) of vanadium dioxide (VO2) makes it a versatile candidate for the implementation of integrated optical devices. In this paper, a bi-functional in-line optical device based on a four-layer stack of PMMA/graphene/VO2/graphene deposited on a side-polished fiber (SPF) is proposed. The structure can be employed as an ultra-compact TE modulator or a TM-pass polarizer, operating at 1.55 μm. We show that the ICPT characteristic can be used for polarization-selective mode shaping (PSMS) to manipulate orthogonal modes separately. On the one hand, as an optical modulator, the PSMS is used to modify mode profiles so that the TE mode attenuation is maximized in the off-state (and IL is minimized in the on-state), while the power carried by the TM mode remains unchanged. As a result, a TE modulator with an ultrahigh extinction ratio (ER) of about ER = 165 dB/mm and a very low insertion loss (IL) of IL = 2.3 dB/mm is achieved. On the other hand, the structure can act as a TM-pass polarizer featuring an extremely high polarization extinction ratio (PER) of about PER = 164 dB/mm and a low TM insertion of IL = 3.86 dB/mm. The three-dimensional heat transfer calculation for the ICPT process reveals that the response time of the modulator is in the order of few nanoseconds. Moreover, the required bias voltage of the proposed device is calculated to be as low as 1.1 V. The presented results are promising a key step towards the realization of an integrated high-performance in-line modulator/polarizer.

Are We Ready for Cell Therapy to Treat Stroke?

Clinical trials of cell therapies that target stroke started at the beginning of this century and they have experienced a significant boost in recent years as a result of promising data from basic research studies. The increase in the information available has paved the way to carry out more innovative and varied human studies. Efforts have focused on the search for a safe and effective treatment to stimulate neuro-regeneration in the brain and to reduce the sequelae of stroke in patients. Therefore, this review aims to evaluate the clinical trials using cell therapy to treat stroke published to date and assess their limitations. From 2000 to date, most of the published clinical trials have focused on phases I or II, and the vast majority of them demonstrate that stem cells are essentially safe to use when administered by different routes, with transient and mild adverse events that do not generally have severe consequences for health. In general, there is considerable variation in the trials in terms of statistical design, sample size, the cells used, the routes of administration, and the functional assessments (both at baseline and follow-up), making it difficult to compare the studies. From this general description, possibly the experimental protocol is the main element to improve in future studies. Establishing an adequate experimental and statistical design will be essential to obtain favorable and reliable results when conducting phase III clinical trials. Thus, it is necessary to standardize the criteria used in these clinical trials in order to aid comparison. Shortly, cell therapy will be a key approach in the treatment of stroke if adequate and comprehensive levels of recovery are to be achieved.

Methods for Using Ecological Momentary Assessment to Assess Weight-related Behaviors in the Home Environment of Children from Low-Income, Racially/Ethnically Diverse and Immigrant Households (Preprint)

BACKGROUND Ecological momentary assessment (EMA) is an innovative tool to capture in-the-moment health behaviors as people go about their regular lives. EMA is an ideal tool to measure weight-related behaviors, such as parent feeding practices, stress, and dietary intake, as these occur on a daily basis and vary across time and context. A recent systematic review recommended standardized reporting of EMA design for studies that address weight-related behaviors. OBJECTIVE This manuscript describes in detail the EMA design of the Family Matters study. METHODS Family Matters is an incremental, two-phased, mixed-methods study conducted with a racially/ethnically diverse and immigrant/refugee sample from largely low-income households designed to examine the risk and protective factors for childhood obesity in the home environment. The Family Matters study intentionally recruited White, Black, Hmong, Latino, Native American, and Somali parents with young children. Parents in Phase I of the study completed eight days of EMA on their smart phones, which included 1) signal-contingent surveys (e.g., asking about the parent’s stress at the time of the survey); 2) event-contingent surveys (e.g., descriptions of the meal the child ate); 3) end-of-day surveys (e.g., overall assessment of the child’s day).cribes in detail the EMA design of the Family Matters study. RESULTS A detailed description of EMA strategies, protocols, and methods used in Phase I of the Family Matters study is provided. Compliance with EMA surveys and participant time spent completing EMA surveys is presented, stratified by race/ethnicity. Additionally, lessons learned while conducting Phase I EMA are shared to document how EMA methods were improved and expanded upon for Phase II. CONCLUSIONS Results from this study provide an important next step in identifying best practices for EMA use in assessing weight-related behaviors in the home environment.

Analysis of La4Ni3O10±δ-BaCe0.9Y0.1O3-δ Composite Cathodes for Proton Ceramic Fuel Cells

Layered Ruddlesden-Popper (RP) lanthanide nickelates, Lnn+1NinO3n+1 (Ln = La, Pr, and Nd; n = 1, 2, and 3) have generated great interest as potential cathodes for proton conducting fuel cells (PCFCs). The high-order phase (n = 3) is especially intriguing, as it possesses the property of a high and metallic-type electronic conductivity that persists to low temperatures. To provide the additional requirement of high ionic conductivity, a composite electrode is here suggested, formed by a combination of La4Ni3O10±δ with the proton conducting phase BaCe0.9Y0.1O3-δ (40 vol%). Electrochemical impedance spectroscopy (EIS) is used to analyse this composite electrode in both wet (pH2O ~ 10−2 atm) and low humidity (pH2O ~ 10−5 atm) conditions in an O2 atmosphere (400–550 °C). An extended analysis that first tests the stability of the impedance data through Kramers-Kronig and Bayesian Hilbert transform relations is outlined, that is subsequently complemented with the distribution function of relaxation times (DFRTs) methodology. In a final step, correction of the impedance data against the short-circuiting contribution from the electrolyte substrate is also performed. This work offers a detailed assessment of the La4Ni3O10±δ-BaCe0.9Y0.1O3-δ composite cathode, while providing a robust analysis methodology for other researchers working on the development of electrodes for PCFCs.

Application of decomposition method for calculation of electrical conductivity of shungite based on the electron-microscopic cards of carbon distribution.

The outlook of using the shungite for covering large area which can protect something from electromagnetic radiation is described. As a main parameter which determines the efficiency of created screens is determined the specific electrical conductivity of shungite carbon. For the measuring of conductivity it is proposed to use the high-resolution raster electron microscopy which make be possible to obtain the card of carbon distribution in the scale of some nanometers. The method of binarization of this card is proposed. This binare card describes the spatial distribution of two phases – large-conducting and small-conducting. The large-conducting phase consist of graphene slides. The small-conducting phase consist of chaotic distributed atoms of carbon. On the basis of binare card it is constructed the flat-area block which is looked as net from square cells having two colours – black and white which correspond one by one to large and small-conducting phases. On the area of block it is selected tubes of current which consist of straight chains of black and white cells connected in succession. The whole resistance of block is determined by parallel connection of these tubes. It is proposed the procedure of constructing this symmetrical block along two coordinates. The scheme of this construction is proposed. The calculation of block resistivity along two coordinates is executed. On the basis of flat-area block it is constructed the space elementary block which has equal to each other resistance along three coordinates. For the determination of specific resistance of material as a whole it is carried out the procedure of decomposition which consist of presentation the unit volume of specimen as a set of elementary blocks. For the real specimens of shungite from two natural deposits it is made the calculation of specific resistance and specific conductivity of shungite carbon. It is established that the calculated data are coincide with data received by contact method in the accuracy of 30%. As a most advantage of proposed method it is established the possibility of conductivity measuring of carbon part of shungite in the scale of some units of nanometers.