1,720,971 research outputs found
Gravure Printing for Lithium-Ion Batteries Manufacturing: A Review
Full text linkInterest in printed batteries is growing due to their applications in our daily lives, e.g., for portable and wearable electronics, biomedicals, and internet of things (IoT). The main advantages offered by printing technologies are flexibility, customizability, easy production, large area, and high scalability. Among the printing techniques, gravure is the most appealing for the industrial manufacture of functional layers thanks to its characteristics of high quality and high speed. To date, despite its advantages, such technology has been little investigated, especially in the field of energy since it is difficult to obtain functionality and adequate mass loading using diluted inks. In this review, the recent results for printed lithium-ion batteries are reported and discussed. A methodology for controlling the ink formulation and process based on the capillary number was proposed to obtain high printing quality and layer functionality. Specific concerns were found to play a fundamental role for each specific material and its performance when used as a film. Considering all such issues, gravure can provide high performance layers. A multilayer approach enables the desired layer mass loading to be achieved with advantages in terms of bulk homogeneity. Such results can boost the future industrial employment of gravure printing in the field of printed batteries
Solid-state pressureless sintering of silicon carbide below 2000ᄚC
No full textTo date, solid-state pressureless sintering of silicon carbide powder requires sintering aids and high sintering temperature (>2100. ᄚC) in order to achieve high sintered density (>95% T.D.). Two-step sintering (TSS) method can allow to set sintering temperature lower than that conventionally required. So, pressureless two-step sintering process was successfully applied for solid-state sintering (boron carbide and carbon as sintering additives) of commercial SiC powder at 1980. ᄚC. Microstructure and mechanical properties of TSS-SiC were evaluated and compared to those obtained with the conventional sintering (SSiC) process performed at 2130. ᄚC. TSS-SiC showed finer microstructure and higher flexural strength than SSiC with very similar density (98.4% T.D. for TSS-SiC and 98.6% T.D. for SSiC). ᄅ 2014 Elsevier Ltd
Evaluation of the stability of different encapsulated blue OLEDs
No full textOrganic light emitting diodes (OLEDs) are nowadays the most attractive technology for displays and lighting applications. However, their short lifetime remains the most important limit for their broad commercialization. In particular, blue OLEDs generally present the worst stability respect to the other colors. While the extrinsic degradation can be easily controlled by proper encapsulation, understanding the origins of the intrinsic degradation remains a challenge: up to now, the proposed mechanisms have not considered possible phenomena that can occur during OFF-time periods. In this study, intrinsic degradation phenomena have been studied through shelf life experiments performed at different storage conditions on two types of blue OLEDs. Experiments revealed that physical aging occurs for both types of devices, leading to irreversible time-dependent luminance loss
Gravure Printing for PVDF Thin-Film Pyroelectric Device Manufacture
No full textPyroelectric energy harvesting is one of the more recent and promising solid-state approaches for directly converting time-dependent temperature fluctuations into electric energy. Conventional printing technologies can offer many advantages for the production of pyroelectric thin-film-based devices, such as low cost, low temperature, the use of flexible substrates and shaping at the same time as deposition. Nevertheless, some issues related to low printed thickness and film-forming microstructure control need to be addressed. In this exploratory study, the possibility of exploiting the highly attractive gravure printing process for the potential industrial manufacture of flexible polyvinylidene fluoride (PVDF) thin-film pyroelectric devices was investigated. By the use of corona pre-treatment of the printing substrate and low-temperature polar solvent evaporation, multilayer gravure-printed PVDF pyroelectric devices were successfully manufactured for the first time, achieving a maximum generated current of 0.1 nA at 2.5 K/s from a device with an active area of 1 cm2. Considering the very low thermal inertia and performance scaling by the area expected for pyroelectric thin-film-based devices, combined with the upscaling potential of roll-to-roll gravure printing, our results provide new opportunities for on-demand, low-cost pyroelectric device manufacture and their integration in hybrid harvesters
Electron beam curing technology for very high-throughput manufacturing of flexible alternating current powder electroluminescent devices
No full textThick-film alternating current powder-based electroluminescent (ACPEL) succeeds on the market as mature technology for large-area light sources. An additional boost for its development may come from the radiation curing technology. Since it is totally compatible with high-speed roll-to-roll processing, radiation curing can offer multiple advantages to further lower costs and make easier the fabrication process of ACPEL devices. In this paper, the application of the electron beam (EB) curing technology to produce flexible ACPEL devices was explored for the first time. In particular, devices with emitting layer made by EB irradiation were successfully fabricated on poly(ethylene terephthalate) (PET) substrate. Device properties were evaluated and compared with those obtained using the conventional ultraviolet curing process. Smaller driving voltages and higher luminous output were observed for the EB treated samples as a consequence of a more cross-linked polymeric binder of the emitting layer generated. In addition, possible effects of EB overdose were also investigated; experiments revealed that excessively high doses can induce the degradation of both polymeric binder and emitting particles. Therefore, the feasibility of using the EB curing was proven to fabricate ACPEL devices, launching it as the next future technology for more sustainable, very fast, and one-step manufacturing of powder-based alternating current EL devices. © 2016 IEEE
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Studies on Morphological Evolution of Gravure-Printed ZnO Thin Films Induced by Low-Temperature Vapor Post-Treatment
Full text linkIn recent years, the morphology control of semiconductor nanomaterials has been attracting increasing attention toward maximizing their functional properties and reaching their end use in real-world devices. However, the development of easy and cost-effective methods for preparing large-scale patterned semiconductor structures on flexible temperature-sensitive substrates remains ever in demand. In this study, vapor post-treatment (VPT) is investigated as a potential, simple and low-cost post-preparative method to morphologically modify gravure-printed zinc oxide (ZnO) nanoparticulate thin films at low temperatures. Exposing nanoparticles (NPs) to acidic vapor solution, spontaneous restructuring pathways are observed as a consequence of NPs tending to reduce their high interfacial energy. Depending on the imposed environmental conditions during the treatment (e.g., temperature, vapor composition), various ZnO thin-film morphologies are produced, from dense to porous ones, as a result of the activation and interplay of different spontaneous interface elimination mechanisms, including dissolution–precipitation, grain boundary migration and grain rotation–coalescence. The influence of VPT on structural/optical properties has been examined via XRD, UV–visible and photoluminescence measurements. Controlling NP junctions and network nanoporosity, VPT appears as promising cost-effective, low-temperature and pressureless post-preparative platform for preparing supported ZnO NP-based films with improved connectivity and mechanical stability, favoring their practical use and integration in flexible devices
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Sintering and mechanical properties of β‐SiC powder obtained from waste tires
Full text linkPlasma synthesized SiC powder obtained from quartz and carbonaceous residue of waste tires was successfully sintered at 1925 °C by pressureless liquid-phase method using yttria and alumina as sintering aids (T-SiC). Comparison with sintered SiC obtained from commercial powder (C-SiC) put in evidence of similar sintered density (98%T.D.), but much finer microstructure of T-SiC than that of C-SiC. T-SiC also showed higher flexural strength than C-SiC both at room temperature (508 vs. 458 MPa) and at 1500 °C (280 vs. 171 MPa). Difference in liquid phase was responsible for the differences in hardness and fracture toughness. The high value of the Young’s modulus of T-SiC (427 MPa) confirmed the high degree of sinterability of this powder and that it can be a promising candidate for structural applications with high added value. © 2016, The Author(s)
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