Preparation and electrochemical characterization of gel polymer electrolyte based on electrospun polyacrylonitrile nonwoven membranes for lithium batteries

Electrospun membranes of polyacrylonitrile are prepared, and the electrospinning parameters are optimized to get fibrous membranes with uniform bead-free morphology. The polymer solution of 16 wt.% in N,N-dimethylformamide at an applied voltage of 20 kV results in the nanofibrous membrane with average fiber diameter of 350 nm and narrow fiber diameter distribution. Gel polymer electrolytes are prepared by activating the nonwoven membranes with different liquid electrolytes. The nanometer level fiber diameter and fully interconnected pore structure of the host polymer membranes facilitate easy penetration of the liquid electrolyte. The gel polymer electrolytes show high electrolyte uptake (>390%) and high ionic conductivity (>2 × 10⁻³ S cm⁻¹). The cell fabricated with the gel polymer electrolytes shows good interfacial stability and oxidation stability >4.7 V. Prototype coin cells with gel polymer electrolytes based on a membrane activated with 1 M LiPF₆ in ethylene carbonate/dimethyl carbonate or propylene carbonate are evaluated for discharge capacity and cycle property in Li/LiFePO₄ cells at room temperature. The cells show remarkably good cycle performance with high initial discharge properties and low capacity fade under continuous cycling.     

Nanoscale visualization of hot carrier generation and transfer at non-noble metal and oxide interface

The conversion efficiency of energy-harvesting devices can be increased by utilizing hot-carriers(HCs).However,due to ultrafast carrier-carrier scattering and t...     

Effects of trans-polyoctylene rubber (TOR) on the properties of NR/EPDM blends

trans-Polyoctylene rubber (TOR) was melt blended with an incompatible NR/EPDM (70/30) blend. Mixing torque and temperature were reduced as TOR was added to NR/EPDM blend. The curing characteristics of the blend were affected as TOR participated in vulcanization and became a part of network. A scanning electron micrograph demonstrated that addition of TOR improved the compatibility of the blend and thereby led to a finer phase morphology. The ozone resistance of the blends was determined in terms of a critical stress–strain parameter. The critical stored energy density for ozone cracking was significantly enhanced for the TOR containing rubber blend. It was believed that the improvement in ozone resistance arised from finely dispersed ozone-resistant EPDM particles in the blend. TOR caused an improvement in dynamic properties and an increase in tensile modulus, but a decrease in tensile stress and elongation at break of the rubber blend. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 749–756, 1999     

Global Hunger: A Challenge to Agricultural,Food, and Nutritional Sciences

Hunger has been a concern for generations and has continued to plague hundreds of millions of people around the world. Although many efforts have been devoted to reduce hunger, challenges such as growing competitions for natural resources, emerging climate changes and natural disasters, poverty, illiteracy, and diseases are posing threats to food security and intensifying the hunger crisis. Concerted efforts of scientists to improve agricultural and food productivity, technology, nutrition, and education are imperative to facilitate appropriate strategies for defeating hunger and malnutrition. This paper provides some aspects of world hunger issues and summarizes the efforts and measures aimed to alleviate food problems from the food and nutritional sciences perspectives. The prospects and constraints of some implemented strategies for alleviating hunger and achieving sustainable food security are also discussed. This comprehensive information source could provide insights into the development of a complementary framework for dealing with the global hunger issue.     

Factors Influencing the Adoption of Smart Wearable Devices

This article examined factors associated with the adoption of smart wearable devices. More specifically, this research explored the contributing and inhibiting factors that influence the adoption of wearable devices through in-depth interviews. The laddering approach was used in the interviews to identify not only the factors but also their relationships to underlying values. The wearable devices examined were a Smart Glass (Google Glass) and a Smart Watch (Sony Smart Watch 3). Two user groups, college students and working professionals, participated in the study. After the participants had the opportunity to try out each of the two devices, the factors that were most important in deciding whether to adopt or not to adopt the device were laddered. For the smart glasses, the most frequently mentioned factor was look-and-feel. For the smart watch, the availability of fitness apps was a key factor influencing adoption. In addition, factors which were linked to image, a personal value, were particularly important across both the student and working groups. This research provides support for the usefulness of the laddering approach to data collection and analysis, and provides some insight into key design criteria to better fit users’ needs and interests.     

Civic Technology and Community Building: Interaction Effects Between Integrated Connectedness to a Storytelling Network (ICSN) and Internet and Mobile Uses on Civic Participation

This study draws on communication infrastructure theory (CIT) to examine the extent to which expressive uses of Internet and mobile devices moderate the relationship between integrated connectedness to a storytelling network (ICSN) and offline and online civic participation. Data collected through a Web survey of a U.S. national online panel (N = 1201) reveal that the relationships of ICSN with offline and online civic participation are conditioned by locality‐oriented expressive uses of Internet and mobile media. With these findings, this study discusses theoretical insights, policy implications, and practical applications.     

Effects of contact surface area of chains on the mechanical properties of poly(methyl methacrylate-co-acrylate) ionomers

Summary The dynamic mechanical properties of a new ionomer system, poly(methyl methacrylate-co-sodium acrylate), were studied. In addition, to investigate the effect of the chemical structure of ionic group on the mechanical properties, the data obtained from the sodium acrylate ionomers were compared to those obtained from sodium methacrylate ionomers. The matrix and cluster T _gs for the methacrylates were found to be higher than those for the acrylates. It was argued that the difference in the T _gs might be explained with the concept of contact surface area of the chain. Received: 27 November 1998/Revised version: 6 January 1999/Accepted: 13 January 1999     

Fabrication and characterization of electrolyte membranes based on organoclay/tripropyleneglycol diacrylate/poly(vinylidene fluoride) electrospun nanofiber composites

Utilizing polymer electrospinning technology, novel electrolyte membranes based on poly(vinylidene fluoride) (PVDF)/organomodified clay (OC)/tripropyleneglycol diacrylate (TPGDA) composite nanofibers with a diameter of 100–400 nm were fabricated for application in lithium batteries. Ultraviolet photo‐polymerization of electrospun PVDF/OC/TPGDA nanofibers generated chemically crosslinked TPGDA‐grafted PVDF/OC nanofibers exhibiting robust mechanical and electrochemical properties. The prepared fibrous PVDF/OC/TPGDA electrolytes were characterized in terms of morphology, crystallinity, electrochemical stability, ionic conductivity and cell cycleability. Based on differential scanning calorimetry analysis, the crystallinity of PVDF decreased by ca 10% on employing the OC and TPGDA. Compared with pure PVDF film‐based electrolyte membranes, the TPGDA‐ and OC‐modified PVDF electrolyte membranes exhibited improved mechanical properties and various electrochemical properties. The OC‐ and TPGDA‐modified microporous membranes are promising candidates for overcoming the drawbacks of the lower mechanical stability of fibrous‐type electrolytes with further improvement of electrochemical performance. Copyright © 2009 Society of Chemical Industry     

Polymer nanocomposites reinforced with multi‐walled carbon nanotubes for semiconducting layers of high‐voltage power cables

Polymer nanocomposites reinforced with multi‐walled carbon nanotubes (MWCNTs) have been newly introduced for semiconducting layers of high‐voltage electrical power cables. Homogeneity of the MWCNT‐reinforced polymer nanocomposites was achieved by solution mixing, and their mechanical, thermal and electrical properties were investigated depending on the type of polymer. By changing the polymer matrix, the volume resistance of the MWCNT‐reinforced polymer nanocomposites could be varied by more than four orders of magnitude. Through systematic experiments and analysis, two possible factors affecting the volume resistance were found. One is the degree of crystallinity of the polymer used and the other is the change of MWCNT morphology under strain. By increasing the degree of crystallinity above a certain level, the volume resistance linearly increased. The MWCNTs embedded in the nanocomposites gradually protruded through the surface on stretching the sample and reversibly returned back to the original positions at a relatively small strain (below 20%). Based on the criteria of tensile properties and volume resistance, a poly[ethylene‐co‐(ethyl acrylate)]/MWCNT nanocomposite was selected as the best candidate for the semiconducting layers of high‐voltage electrical power cables. Copyright © 2009 Society of Chemical Industry