bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and magnetic properties on F-doped LiVO2 with two-dimensional triangular lattice
Authors: Li Yang , Li Xiaoxiang , Liu Lihua , Chen Ning , García Jose , Dávila Rafael , Faica Danny , Rivera Alfred , Rodríguez Pedro , Pérez Rubén , Cao Guohui 
Published: September 2011

ABSTRACTThe layered oxide LiVO2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO2 samples, and reported the F-doping effect on the structure and transition temperature Tt. The samples LiVO2-xFx (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature Tt increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO6 block in structure, which significantly influence the magnetic ordering transition temperature Tt.
Graphene Oxide as a Two-dimensional Surfactant
Authors: Koltonow Andrew R. , Kim Jaemyung , Cote Laura J. , Luo Jiayan , Huang Jiaxing 
Published: September 2011

AbstractGraphene oxide (GO) is a nonstoichiometric two-dimensional material obtained from the chemical oxidation and exfoliation of graphite, which has recently attracted intense research interest as a precursor for bulk production of graphene. GO has long been believed to be hydrophilic due to its dispersibility in water. Recent work in our group, however, has found that GO is actually a two-dimensional amphiphile; the edge of the sheet-like material is hydrophilic, while the basal plane of the material contains more hydrophobic graphitic nanodomains. To prove the concept, we demonstrate GO’s surface activity at an air-water interface, as well as its utility in dispersing insoluble aromatic materials such as toluene, graphite, and carbon nanotubes in water. As a colloidal surfactant which can be converted to a conducting material, GO presents unique possibilities for aqueous solution processing of organic electronic materials.
Patterning biopolymer surfaces by enzymatic soft lithography
Authors: Guyomard-Lack A. , Moreau C. , Delorme N. , Bardeau J.-F. , Cathala B. 
Published: September 2011

ABSTRACTA novel rapid and easy-to-use method for patterning surfaces on large scale is described. Micro-patterns were created by direct contact of trypsin-functionalized poly(dimethylsiloxane) (PDMS) stamps with poly-L-lysine (PLL) layer adsorbed on silicon surface. The catalytic process does not involve ink transfer and thus lateral diffusion is avoided. As a result duplication of the stamp pattern is highly enhanced comparatively to standard microcontact printing procedure where PLL is used as ink and transferred on silicon surface. Patterning was revealed by fluorescence microscopy and atomic force microscopy (AFM). Adsorption on the patterned surfaces of cellulose nanocrystals was investigated as an example of application.
Microwave Volumetric Probe Measurements of Field localization, Zero and Negative Index within Photonic Bandgap Metamaterial Structures
Authors: Kuster Eric , Moore Ricky L. , Blalock Stephen , Cieszynski Brian , Swarner John , Habib Matthew 
Published: September 2011

ABSTRACTElectromagnetic mode localization within photonic bandgap (PBG) crystals has been evidenced by external measurement of enhanced optical emission from quantum dots or photoemissive polymers that are placed within the structure. In this paper wavelength is decreased and photonic crystal dimensions increased to allow insertion of a loop probe in the PBG to directly measure volumetric electromagnetic fields; thereby producing a volume -frequency map of field amplitude and phase within the PBG. The unit cells of the PBG are formed from arrays of Alumina strips which are supported by surrounding acrylic supports. Electromagnetic fields of single, two and three layer PBGs are predicted and these compare well with measurement.Field localization within the PBG and transmission coefficients of the PBG, with and without electrical perturbations, are presented. Predictions assume layered unit cells formed from sections in which translational invariance along the Z-axis is assumed for zn-1 ≤ z ≤ zn for the nth section. Periodicity implies that field X dependence can be represented as a sum of Floquet modes and field solutions are found by mode matching techniques in combination with multimode cascade matrix formalism.Transmission coefficient is measured using a focused beam, network analyzer based system and volumetric fields within the PBG are measured using a loop probe antenna inserted between Alumina strips and moved to different positions. Measurements at 1600 frequencies over the 4-18 GHz band at each of 100 positions are made. PBG fields are calibrated to probe measurements at identical positions and frequencies but absent the PBG.Both electromagnetic model and measurement shows field localization and effective negative or zero indexes at multiple frequencies within the 4 to 18 GHz band. Volumetric field magnitudes increase by at least one order of magnitude and local field phase-frequency derivatives are negative or near zero near localization frequencies. Field localizations and transmission are sensitive to small perturbations of electrical properties or geometry. Wideband measurements of PBGs, perturbed by small cylindrical inserts placed at high field locations, allow precision measurements of an insert’s electromagnetic properties.
Data Mining-Aided Crystal Engineering for the Design of Transparent Conducting Oxides
Authors: Suh Changwon , Kim Kwiseon , Berry Joseph J. , Lee Jinsuk , Jones Wesley B. 
Published: September 2011

ABSTRACTThe purpose of this paper is to accelerate the pace of material discovery processes by systematically visualizing the huge search space that conventionally needs to be explored. To this end, we demonstrate not only the use of empirical- or crystal chemistry-based physical intuition for decision-making, but also to utilize knowledge-based data mining methodologies in the context of finding p-type delafossite transparent conducting oxides (TCOs). We report on examples using high-dimensional visualizations such as radial visualization combined with machine learning algorithms such as k-nearest neighbor algorithm (k-NN) to better define and visualize the search space (i.e. structure maps) of functional materials design. The vital role of search space generated from these approaches is discussed in the context of crystal chemistry of delafossite crystal structure.
A Structural and Electrochemical Study of Li2Ti6O13
Authors: Pérez-Flores J. C. , Kuhn A. , García-Alvarado F. 
Published: September 2011

ABSTRACTThe lithium titanate Li2Ti6O13 has been prepared from Na2Ti6O13 by Li ion exchange in molten LiNO3 at 325ºC. Chemical analysis and powder X-ray diffraction study of the reaction product, respectively, indicate that total Na/Li exchange takes place and the Ti-O framework of the Na2Ti6O13 parent structure is kept under those experimental conditions. The electrochemical characterization shows that Li2Ti6O13 is able to insert ca. 5 Li per formula unit under equilibrium conditions in the voltage range 1.5-1.0 V vs. Li+/Li. This corresponds to a specific discharge capacity of 250 mAh g-1. Lithium insertion occurs at an average equilibrium voltage of 1.5 V which is typical for oxides and titanates where Ti(IV)/Ti(III) is the active redox couple. After the first redox cycle a high reversible capacity is obtained (ca. 160 mAh g-1 at C/12, with a 70% capacity retention related to a phase transformation upon cycling). On the basis of these results, we are proposing Li2Ti6O13 as new lithium battery anode material to be further investigated.
ELABORATION AND CHARACTERIZATION OF La4Ni3O10 CATHODE MATERIAL (SOFC) BY SOL-GEL PROCESS
Authors: Cienfuegos Rene Fabian , Guerrero Leonardo Chávez , Carranza Sugeheidy , Jouanin Laurie , Marie Guillaume , Hinojosa Moisés 
Published: September 2011

ABSTRACTThe goal in this study was to synthesize a lanthanum - nickel phase (Ruddlesden-Popper phases) La4Ni3O10. This material was prepared using a polymeric route. An easy synthesis method is presented in order to obtain an economical cathode material, which can be used in Solid Oxide Fuel Cells (SOFC). The polymeric precursors were prepared following the Castillo method. The originality of this work was to optimize the ratio HMTA/ metallic salts from 1 to 6. The obtained powders were characterized by thermal analysis; Differential Scanning Calorimetry (DSC Q10 Instrument TA), Thermogravimetric Analysis (TGA - Q50 Instrument TA-) and X-ray diffractometer (Bruker, D8 Advance diffractometer), in order to determine the crystallized phase. Experiments 5 and 6 did not present coagulation but after few days, solution 5 was transformed into a gel. Gels 2 to 5 were heated in order to obtain a solid material. These powders are characterized by thermogravimetric and thermo-differential methods. The powders obtained at 800, 900 and 1000°C were analyzed by X-ray diffraction and it was found that the temperature to get to the La4Ni3O10 phase was 1000ºC.
Band Gap Opening of Graphene after UV/Ozone and Oxygen Plasma Treatments
Authors: Aria Adrianus I. , Gani Adi W. , Gharib Morteza 
Published: September 2011

ABSTRACTGraphene grown by Chemical Vapor Deposition (CVD) on nickel subsrate is oxidized by means of oxygen plasma and UV/Ozone treatments to introduce bandgap opening in graphene. The degree of band gap opening is proportional to the degree of oxidation on the graphene. This result is analyzed and confirmed by Scanning Tunnelling Microscopy/Spectroscopy and Raman spectroscopy measurements. Compared to conventional wet-oxidation methods, oxygen plasma and UV/Ozone treatments do not require harsh chemicals to perform, allow faster oxidation rates, and enable site-specific oxidation. These features make oxygen plasma and UV/Ozone treatments ideal candidates to be implemented in high-throughput fabrication of graphene-based microelectronics.
Nonlinear Mechanical Properties of Graphene Nanoribbons
Authors: Lu Qiang , Huang Rui 
Published: September 2011

ABSTRACTBased on atomistic simulations, the nonlinear elastic properties of monolayer graphene nanoribbons under quasistatic uniaxial tension are predicted, emphasizing the effect of edge structures (armchair and zigzag, without and with hydrogen passivation). The results of atomistic simulations are interpreted using a theoretical model of thermodynamics, which enables determination of the nonlinear functions for the strain-dependent edge energy and the hydrogen adsorption energy, for both zigzag and armchair edges. Due to the edge effects, the initial Young’s modulus of graphene nanoribbons under infinitesimal strain varies with the edge chirality and the ribbon width. Furthermore, it is found that the nominal strain to fracture is considerably lower for armchair graphene nanoribbons than for zigzag ribbons. Two distinct fracture mechanisms are identified, with homogeneous nucleation for zigzag ribbons and edge-controlled heterogeneous nucleation for armchair ribbons.
A Novel Method for Sorting Single Wall Carbon Nanotubes by Length
Authors: Ohmori Shigekazu , Saito Takeshi , Shukla Bikau , Yumura Motoo , Iijima Sumio 
Published: September 2011

ABSTRACTWe report a novel system for sorting single wall carbon nanotubes (SWCNTs) by length via cross-flow filtration with three membrane filters of different pore sizes, 1.0, 0.45, and 0.2 μm. SWCNTs dispersed in water with the help of polymer type detergents, such as sodium carboxymethylcellulose (CMC) and polyoxyethylene stearyl ether (Brij 700), were successfully fractionated into four samples, and the atomic force microscopy (AFM) observation of those samples confirmed that their length distribution peaks are within the expected ranges from pore sizes of used filters. However, the result of the similar filtration process using a non-polymer detergent, sodium dodecylbenzenesulfonate (SDBS), showed no pronounced correlation between the length distribution of SWCNTs and the pore size. The observed difference in the sorting phenomena caused by the detergent type suggests that the permeation property depends on the complex structure resulting from the dispersed SWCNTs and detergent molecules.
Ultrafast Switching Liquid Crystals for Electro-Optic Transmissive and Reflective Displays and Microscopic Lasers
Authors: Coles Harry J , Morris Stephen M , Castles Flynn , Hands Philip J W , Wilkinson Timothy D , Choi Su Soek 
Published: September 2011

ABSTRACTWe report on novel liquid crystals with extremely large flexoelectric coefficients in a range of ultra-fast photonic modes, namely 1) the uniform lying helix, that leads to in-plain switching, birefringence phase devices with 100 μs switching times at low fields, i.e.2-5 V/μm, and analogue or grey scale capability, 2) the uniform standing helix, using planar surface alignment and in-plane fields, with sub ms response times and optical contrasts in excess of 5000:1 with a perfect optically isotropic or black “off state”, 3) the wide temperature range blue phase that leads to field controlled reflective color, 4) chiral nematic optical reflectors electric field tunable over a wide wavelength range and 5) high slope efficiency, wide wavelength range tunable narrow linewidth microscopic liquid crystal lasers.
Rewritable Photopatterning of a Bisanthracene-Functionalized Mesogenic Compound by Photodimerization and Thermal Back-Reaction of the Anthracene Moiety
Authors: Kihara Hideyuki , Motohashi Masashi , Matsumua Kazunari , Yoshida Masaru 
Published: September 2011

ABSTRACTA new method for photopatterning of a bisanthracene-functionalized mesogenic compound 1 was developed. The monomer 1 had two anthracene moieties on each molecular end, and showed crystalline and liquid-crystalline phases at room temperature and at an elevated temperature, respectively. Upon UV irradiation of 1 in the molten state, intermolecular photodimerization of the anthracene moieties was induced, and consequently resulted in the formation of a linear polymer. In contrast to the monomer 1, the obtained polymer exhibited amorphous phase at room temperature. When 1 was irradiated with UV light through a photomask in the molten state, the irradiated areas changed to amorphous phase due to photopolymerization, whereas the non-irradiated areas remained the ordered phase. This phenomenon provided visual images with a clear contrast under polarized light. In addition, the images could be erased by heating the whole sample at a temperature above ca. 200 °C, because the amorphous phase changed to the ordered phase due to a reproduction of the monomer 1 from the polymer associated with thermal back-reaction of the anthracene photodimer. Photopatterning could be performed for the erased sample again and the process was found to be fairly reversible.
PZT Thick Films for 100 MHz Ultrasonic Transducers Fabricated Using Chemical Solution Deposition Process
Authors: Kochi Naoto , Iijima Takashi , Nakajima Takashi , Okamura Soichiro 
Published: September 2011

ABSTRACTTo achieve ultrasonic transducers operating above 100 MHz, square pillar shaped Pb1.1(Zr0.53Ti0.47)O3 thick film structures were fabricated using a chemical solution deposition (CSD) process. The fabricated sample showed well-saturated P-E hysteresis curve and butterfly-shaped longitudinal displacement curve. The fabricated samples generated more than 100 MHz ultrasonic waves with a pulser/receiver. Electrical impedance properties of the samples were measured with an impedance analyzer. A number of spurious resonant modes were observed in the frequency range from 40 to 300 MHz. The characteristics of the sample were investigated by finite element method (FEM). The FEM simulations were in good agreement with the experimental results. For free-standing (substrate free) 10-μm-thick PZT film models, the resonant frequency of the thickness vibration mode was estimated to be 160 MHz with the FEM simulations. These results indicate that the substrate affects the behavior of the spurious resonant modes. Therefore, a sample structure was designed using the FEM simulation. The FEM result suggests that the backside of the substrate should be removed to reduce the substrate effects. Consequently, the thickness vibration mode was observed clearly at 160 MHz. This structure is applicable to the micromachined ultrasonic transducers (MUT) operating in the thickness vibration mode above 100 MHz.
Reliability and stability of thin-film amorphous silicon MEMS on glass substrates
Authors: Sousa P. M. , Chu V. , Conde J. P. 
Published: September 2011

ABSTRACTIn this work, we present a reliability and stability study of doped hydrogenated amorphous silicon (n+-a-Si:H) thin-film silicon MEMS resonators. The n+-a-Si:H structural material was deposited using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) and processed using surface micromachining at a maximum deposition temperature of 110 ºC. n+-a-Si:H resonant bridges can withstand the industry standard of 1011 cycles at high load with no structural damage. Tests performed up to 3x1011 cycles showed a negligible level of degradation in Q during the entire cycling period which in addition shows the high stability of the resonator. In measurements both in vacuum and in air a resonance frequency shift which is proportional to the number of cycles is established. This shift is between 0.1 and 0.4%/1x1011 cycles depending on the applied VDC. When following the resonance frequency in vacuum during cyclic loading, desorption of air molecules from the resonator surface is responsible for an initial higher resonance frequency shift before the linear dependence is established.
Ultrafast Laser Alignment and Processing of Carbon Nanotube Films
Authors: Murphy Ryan D. , Abere Michael J. , Zhang Huanan , Sun Haiping , Torralva Ben , Mansfield John F. , Kotov Nick , Yalisove Steven M. 
Published: September 2011

ABSTRACTOrganized nanostructures are formed after irradiation of layers of randomly aligned single-wall carbon nanotube (SWNT)-polymer composites by a Ti:Sapphire 775 nm laser with a 150 fs pulse at fluences near 0.1 J/cm2. At varying peak fluences morphology is seen where the tubes are ejected from the substrate or formed into long, parallel structures of SWNT’s. These structures have been created on both glass substrates and carbon grids. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) investigation of the structures reveal that they are composed of bundled nanotubes typically 400 nm – 1 micron long. Large-area laser patterning of the film allows for structuring of the film without detrimental decreases in conductivity.
Large Thermoelectric Voltage in Point Contacts of Ni Ferromagnetic Metals
Authors: Kondo Kenji , Kaiju Hideo , Ishibashi Akira 
Published: September 2011

ABSTRACTRecently, we have proposed a spin quantum cross structure (SQCS) device toward the realization of novel spintronics devices. In this paper, we have investigated thermoelectric effects in point contacts (PCs) of Ni ferromagnetic metals using SQCS devices, theoretically and experimentally. The calculated results show that the thermoelectric voltage Vq changes from 0.48 mV to 2.12 mV with the temperature difference of PCs increasing from 10 K to 50 K. Also, the magnitude of the theoretical thermoelectric voltage agrees very well with that of the experimental result. PCs of SQCS devices with Ni electrodes can serve as spin dependent thermobatteries.
Dispersion of nanoparticles in media of biological interest
Authors: Carriere Marie , Casanova Axelle , Herlin Boime N. 
Published: September 2011

ABSTRACTNanoparticles (NP) are introduced in a growing number of commercial products, including food and beverage, daily use hygiene products such as toothpaste, or orally-administered drugs. To study the possible toxicity of these nanoparticles, a model system is the in vitro response of eukaryotic cells to the presence of NP. However, to understand the observed effects, it is clear that good physical and chemical characterization of NP, and in particular of their dispersion are needed. Indeed, the expected effects should be different if the study is dealing with agglomerates or isolated nanoparticles. For fundamental understanding, it appears important to work with nanoparticles as well dispersed as possible while being in relevant biological condition, i.e. cellular culture cell.In this context, we have studied the dispersion of a very common industrial titania NP (Degussa P25 produced in ton quantities). When dispersed in water, the suspensions of NP appear stable for weeks.. When transferred in the cell culture medium (DMEM) or if directly dispersed in DMEM, strong evolution of size is seen as well as sedimentation. To address this problem, we have compared different ways, coming from materials science, of dispersing NP in water with the idea to break in a preliminary step some of the necks between nanoparticles. The effect of dry ball milling, liquid ball milling, size of the balls and Ultrasonic dispersion will be compared. The best results were obtained from high power ultrasonic dispersion. To avoid direct aggregation, when going to DMEM, a “surfactant” relevant with biological studies (Foetal Bovine Serum (FBS)) was added in the suspension in order to coat the nanoparticles prior to transfer in DMEM (or other cell media). The result obtained with various surfactants and cell media will be presented. It must be noted that our best results were obtained in the FBS + DMEM medium.
Continuous Tunable Optical Detectors with a-Si:H Bias Sensitive Photodiodes
Authors: Merfort Christian , Seibel Konstantin , Bablich Andreas , Watty Krystian , Boehm Markus 
Published: September 2011

ABSTRACTToday’s image-based systems in civil security rely on sensors based either on CMOS or CCD technology, and they do not analyze color with sufficient equivalence to the human eye. The main reason for this is that the function of the fundamental color matching curves of the cones in the human eye can hardly be reproduced by technical systems [1]. Common color sensors are optimized for the three-area method in accordance with the standard DIN 5033-6. In civil security applications, for example, color sensors are used to identify the potential danger of whitish powder samples. Colorimetric classification based on the three-area method only provides suboptimal results [2], but not an unequivocal optical description. A series of tests performed at the IMT with more than 30 types of whitish powder samples were carried out with a spectrophotometer. These measurements showed that specimens with similar or different chemical compositions cannot be distinguished by the human eye, using the three-area method, exhibit characteristic differences in the CIE-L*a*b* measurement system under spectral method conditions. Until now, the realization of the spectral method on chip has been impossible with common color sensors. In this paper, we present a-Si:H-based bias-sensitive ni3p photodiodes, which have been fabricated successfully in a low temperature PECVD process. Present research focuses on the optimization of the continuous tunability of a-Si:H multispectral photodiodes, to increase the number of spectral stimulus specifications.