1,720,970 research outputs found
잉크젯 프린트 헤드를 위한 새로운 금속 산화물 기반의 발열체 특성에 관한 연구
No full text학위논문(박사) - 한국과학기술원 : 신소재공학과, 2008.2, [ xiv, 189 p. ]The development of a page-wide array thermal inkjet printhead with the increased number of and array density of nozzles has recently been the focus of intensive efforts to raise printing speed and printing resolution for the application of TIJ printers. Since, however, a page-wide array thermal inkjet printhead consumes much more power to operate than conventional thermal inkjet printhead, the heat efficiency of thermal inkjet printhead should to be improved. In particular, a conventional SiN or SiC passivation layer of thermal inkjet printhead, which is used to protect underlying heating resistors, needs to be thinned or eliminated because these materials have a low thermal conductivity and act as an obstacle for heat transferring from heating resistor to ink.
Up to now, several materials have been considered in the printhead, such as polysilicon, , Ta-Al and TaN. In particular, TaN thin films (especially hexagonal ) have been known to have superior properties in fabricating accurate heater resistors for application inkjet printhead. Sputtered TaN thin films has a favorable properties such as a low TCR values, a sufficient resistivity, thermal stability, and high hardnesses. However, above mentioned heating resistor materials including cannot be used for this purpose because they are easily oxidized and corroded under the severe operation conditions such as high operation temperatures, chemical attacks by ink, and mechanical stresses arising from cavitation forces. Therefore, suitable heating resistor materials having strong antioxidation properties and anticorrosion properties, should be developed for a successful application. However, it is not easy because heating resistor materials should basically meet primary requirements such as a near zero temperature coefficient of resistance (TCR) for a stable ink ejection and a sufficient resistivity (>150 μΩ-cm) for making heating resistor of controllable thicknesses.
I...한국과학기술원 : 신소재공학과
Highly entangled hollow TiO2 nanoribbons templating diphenylalanine assembly
No full textWe introduce a biotemplating approach for creating highly entangled hollow TiO2 nanoribbons by combining peptide assembly with an atomic layer deposition process. An aromatic peptide of diphenylalanine was readily assembled into a hierarchical organogel consisting of highly entangled nanoribbons. Unlike ordinary biomaterials, the peptide nanoribbon framework exhibited a high level of thermal stability, such that it may undergo the further functionalization process of vacuum deposition without significant damage to its nanoscale structure. A nanoscale layer of anatase TiO2 was deposited on the nanoribbon framework by means of atomic layer deposition. After pyrolysis, a highly entangled nanotubular TiO2 framework was created successfully. The highly entangled TiO2 architecture exhibited UV-switchable wetting properties.This work was supported by the second stage of the Brain
Korea 21 Project, National Research Laboratory Program
(R0A-2008-000-20057-0), the KAIST EEWS Initiative (No.
EEWS0903, EEWS: Energy, Environment, Water, and
Sustainability), the Fundamental R&D Program for Core
Technology of Materials, and the National Core Research
Center Program (R15-2006-022-01001-0) funded by the Korean
government
Universal block copolymer lithography for metals, semiconductors, ceramics, and polymers
No full textA universal block copolymer lithography is developed for a broad spectrum of materials including metals, semiconductors, ceramics, and polymers by combining advanced film deposition techniques with block copolymer lithography. The figure presents a nanopatterned platinum film prepared by applying universal block copolymer lithography.We thank G. S. Kim and J.-H. Ahn for assistance with thin film
depositions, and S. S. Bae for assistance with SEM analysis. This
work was supported by the second stage of the Brain Korea 21
Project, the Korea Research Foundation (KRF-2005-003-D00085),
the Basic Research Program of the Korea Science & Engineering
Foundation (R01-2005- 000-10456-0), the Korean Ministry of
Science and Technology, and the Korean Ministry of Science and
Technology and Fundamental R&D Program for Core Technology of
Materials funded by the Korean Ministry of Commerce, Industry and
Energy. Also, this work was partially supported by grants-in-aid for
the National Core Research Center Program from MOST/KOSEF
(No. R15-2006-022-01001-0)
Improvement of the morphological stability by stacking RuO2 on ru thin films with atomic layer deposition
No full textStacked RuO2/Ru structures were produced by atomic layer deposition (ALD ) using an alternating supply of bis (ethylcyclopentadienyl) ruthenium [Ru(EtCp)(2)] and O-2 gas at a deposition temperature of 270 degrees C. The type of the deposited film, either Ru or RuO2, was controlled by the total pressure in the ALD system as well as the ratio of the adsorbed Ru ( EtCp )(2) to the partial pressure of O-2 in the following O-2 gas pulse. The resistivity of the deposited Ru and RuO2 thin films was about 15 and 70 mu Omega cm, respectively. The surface morphology of Ru films annealed in O-2 ambient was seriously degraded by surface oxidation. Moreover, RuO2 films were also agglomerated due to the residual stress releasing during the annealing process. However, a stacked RuO2/Ru structure produced using ALD maintained a smooth surface even at an annealing temperature of 800 degrees C in ambient O-2. Auger electron spectroscopy confirmed that the stacked RuO2/ Ru structure successfully blocked oxygen and silicon diffusion. Therefore, the stacked RuO2/ Ru structure produced by ALD is suitable for use as the bottom electrode material for high dielectric applications. (c) 2007 The Electrochemical Society.This work was supported by Korea Research Foundation Grant Funded by the Korean Government(MOEHRD)KRF-2005-005-J09702.
Korea Advanced Institute of Science and Technology assisted in meeting the publication costs of this article
Hierarchically layered nanocomposite electrodes formed by spray-injected MXene nanosheets for ultrahigh-performance flexible supercapacitors
No full textAlthough MXenes with outstanding electrical conductivity possess great potential as energy-storage materials for flexible supercapacitors (SCs), the electrochemical performance of the pure MXene-based SCs are often restricted by inherent limitations such as inferior energy densities and serious aggregation. Alternatively, it will be an effective strategy to develop rationally designed composite electrodes that can simultaneously provide both high electrical conductivity and large surface area via complementary functions of each constituent. Here, hierarchically layered MXene nanosheets on nickel cobalt sulfide/carbon cloth (Ti3C2Tx/NiCo2S4@CC, herein TNSC) was prepared through spray injection of MXene on nickel cobalt sulfide, which not only achieved an excellent specific capacitance at high current densities but also possess improved cycling stability. The optimized TNSC electrode shows maximum specific capacities of 2326F g(-1) at a current density of 1 A g(-1), and excellent cycling stability of 93.8% at 10 A g(-1). We show that these outstanding electrochemical performances can be achieved by a proper loading amount of surface-coated Ti3C2Tx, which can simultaneously enhance electrical conductivity and permeate ions to nickel cobalt sulfide. Furthermore, a quasi-solid-state flexible SC (QFSC) based on TNSC presents a high energy density of 57.5 W h kg(-1) at a power density of 800 W kg(-1) in a wide potential window of 1.6 V. Therefore, the excellent electrochemical performances of the TNSC electrode makes it as a prominent candidate for high-performance and flexible energy storage devices.
Synthesis of Bi2Te3 Single Crystals with Lateral Size up to Tens of Micrometers by Vapor Transport and Its Potential for Thermoelectric Applications
No full textBismuth telluride (Bi 2 Te 3 ) has recently attracted significant attention owing to its unique physical properties as a three-dimensional topological insulator and excellent properties as a thermoelectric material. Meanwhile, it is important to develop a synthesis process yielding high-quality single crystals over a large area to study the inherent physical properties and device applications of two-dimensional materials. However, the maturity of Bi 2 Te 3 vapor-phase synthesis is not good, compared to those of other semiconductor two-dimensional crystals. In this study, therefore, we report the synthesis of relatively large-area Bi 2 Te 3 crystals by vapor transport method, and we investigated the key process parameters for a synthesis of relatively thin and large-area Bi 2 Te 3 crystals. The most important factor determining the crystal synthesis was the temperature of the substrate. A Bi 2 Te 3 device exhibited a considerable photocurrent when the laser was irradiated inside the electrode area. This indicated that the photo-thermoelectric effect was the main mechanism of generation of photocurrent. The estimated Seebeck coefficient of the device was ∼196 μV/K, which is comparable to the previously reported high Seebeck coefficient of Bi 2 Te 3 . This synthesis method can guide the development and applications of various types of layered crystals with the space group of R3̄m. © Copyright 2019 American Chemical Society.1
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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