bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of 1D and 2D Theories of Thermoelastic Damping in Flexural Microresonators
Authors: Prabhakar Sairam , Vengallatore Srikar 
Published: April 2011

AbstractThermoelastic damping (TED) represents the lower limit of material damping in flexural mode micro- and nanoresonators. Current predictive models of TED calculate damping due to thermoelastic temperature gradients along the beam thickness only. In this work, we develop a two dimensional (2D) model by considering temperature gradients along the thickness and the length of the beam. The Green's function approach is shown to be a robust means of solving the coupled heat conduction equation in one and two dimensions. In the 1D model, curvature information is lost and, hence, the effects of structural boundary conditions and mode shapes on TED are not captured. In contrast, the 2D model retains curvature information in the expression for TED and can account for beam end conditions and higher order modes. The differences between the 1D and 2D models are systematically explored over a range of beam aspect ratios, frequencies, boundary conditions, and flexural mode shapes.
Bottom-up Fabrication of Individual SnO2 Nanowires-based Gas Sensors on Suspended Micromembranes
Authors: Romano-Rodriguez Albert , Hernandez-Ramirez Francisco , Prades Joan Daniel , Tarancon Albert , Casals Olga , Jimenez-Diaz Roman , Juli Miguel Angel , Morante Juan Ramon , Barth Sven , Mathur Sanjay , Helwig Andreas , Spannhake Jan , Mueller Gerhard 
Published: April 2011

AbstractBottom – up techniques were used to obtain gas sensors based on individual SnO2 nanowires placed over microhotplates with integrated heaters. These nanowires were electrically contacted to pre-patterned microelectrodes by means of Focused Ion Beam (FIB) nanofabrication methodologies. The performance of these sensors, which exhibit reproducible and stable responses, was evaluated as function of different gas atmospheres and dissipated power by the heater, demonstrating that this technological approach could be used to develop functional devices based on nanomaterials.
MEMS-Based MHz Silicon Ultrasonic Nozzles for Production of Monodisperse Drops
Authors: Song Y. L. , Cheng Chih H. , Wang Ning , Tsai Shirley C. , Chou Yuan F. , Lee Ching T. , Tsai Chen S. 
Published: April 2011

AbstractThis paper reports production of 4.5 μm-diameter monodisperse water drops using a micro electro-mechanical system (MEMS)-based 1 MHz 3-Fourier horn ultrasonic nozzle. The required electrical drive voltage for atomization was 6.5 V at 964±1 kHz that is in good agreements with the values obtained by impedance measurement and by the three-dimensional (3-D) simulation using a commercial finite element analysis program. Such small diameter drops with geometrical standard deviation (GSD) as small as 1.2 and 90% inhale-able fine particle fraction (<5.8 μm-diameter) were achieved in ultrasonic atomization for the first time. Therefore, the MEMS-based MHz ultrasonic nozzles should have potential application to targeted delivery of reproducible doses of medicine to the respiratory system.
Thermal Conductivity of Thermal Interface Materials
Authors: Fullem Travis Z. , Cotts Eric J. 
Published: April 2011

AbstractWhile detailed theories exist for thermal conduction due to electrons and phonons in crystalline solids, phonon scattering and transmission at solid/solid interfaces is not as well understood. Steady increases in the power density of microelectronic devices have resulted in an increasing need in the electronics industry for an understanding of thermal conduction in multilayered structures. The materials of interest in this study consist of a polymer matrix in which small (on the order of microns to tens of microns) highly conductive filler particles (such as Ag or alumina) are suspended. These materials are used to form a thermal interface material bondline (a fifty to several hundred micron bonding layer) between a power device and a heat spreader. Such a bondline contains many polymer/filler interfaces. Using a micro Fourier apparatus, the thermal conductivities of such thermal interface material (TIM) bondlines of various thicknesses, ranging from fifty microns to several hundred microns, have been measured. The microstructure of these bondlines has been investigated using optical microscopy and acoustic microscopy. Measured values of thermal conductivity are compared to values for bulk samples, and considered in terms of microstructural features such as filler particle depleted regions. The influence of polymer/filler particle interfaces in the TIM bondline on phonon transport through the bondline is also considered.
Enabling Technology Based on Leaky-Mode Resonance Effects in Periodic Films
Authors: Magnusson Robert , Shokooh-Saremi Mehrdad , Lee Kyu J. , Wawro Debra 
Published: April 2011

ABSTRACTThe physical properties of resonant leaky modes in periodically patterned layered materials are summarized. Representative examples of photonic device applications including filters, polarizers, wideband reflectors, tunable elements, and biosensors are discussed.
Characterization and In Vitro Bioactivity Study of Ternary Glass-ceramic Coatings
Authors: Chatzistavrou Xanthippi , Kontonasaki Eleana , Kantiranis Nikolaos , Papadopoulou Lamprini , Koidis Petros , Hatzikraniotis Evripides , Paraskevopoulos Konstantinos 
Published: April 2011

ABSTRACTThe aim of the present study was to test the in vitro bioactive behavior of two new ternary mixtures consisting of a glass-ceramic porcelain, a bioactive glass and alumina (PBA) as coatings on dental glass ceramic substrates. They consisted of bioactive glass- in the system SiO2-Na2O-CaO-P2O5−, powder from a leucite-fluorapatite glass ceramic and γ-Al2O3 in 50-42.5-7.5 wt % respectively, while coatings with the same two components in 50-50 wt % ratio, without Al2O3, served as control. The characterization of the coatings was performed by Scanning Microscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). The in vitro bioactivity was tested in Simulated Body Fluid (SBF) and the surfaces of reacted specimens were examined by SEM and FTIR. All coatings presented rough surface, while FTIR spectra revealed the characteristic peaks of the crystallized phases in the bioactive glass network and dental glass ceramic, i.e. Sodium Calcium Silicate (Na4Ca4Si6O18), Leucite (KAlSi2O6) and Fluorapatite (Ca5(PO4)3F), and furthermore the very limited participation of Al3+ in the bioactive glass network. In the coatings the main phases detected by XRD were, also, Na4Ca4Si6O18 and Leucite, dispersed in an amorphous glassy matrix. Furthermore, a transformation of γ-Al2O3 to δ-Al2O3 was observed and a new phase of Nepheline (Na7.15Al7.2Si8.8O32) was detected in traces. Apatite was developed sporadically on the surfaces of the PBA coatings after 30 days in SBF. These results demonstrate a slight retardation of bioactive response of the coatings of the ternary mixtures compared to dual ones consisting of dental glass ceramic and bioactive glass. The incorporation of Al2O3 can enhance the mechanical properties without a substantial degradation of bioactivity. This finding renders these coatings as promising composite materials for potential dental applications.
Fabrication and Characterization of Size- and Shape-Controlled C60 Nano/microcrystals by Solvent-Induced Reprecipitation Process (SIRP)
Authors: Masuhara Akito , Tan Zhenquan , Kasai Hitoshi , Nakanishi Hachiro , Oikawa Hidetoshi 
Published: April 2011

ABSTRACTWe have first developed useful Solvent-Induced Reprecipitation Process, and have first succeeded in fabricating C60 nano/microcrystals with various shape and size, using m-xylene and 2-propanol as good and poor solvents, respectively.It was found that the resulting C60 nano/microcrystals had a hexagonal crystal structure, and that were a kind of crystal solvates in which the molar ratio of C60 to m-xylene was 3:2. C60 nano/microcrystals could be said to be important nano components of integrated devices in electronics.
Multi-color Photoresponse Based on Interband and Intersubband Transitions in InAs and InGaAs Quantum Dot Photodetectors
Authors: Passmore Brandon Scott , Wu Jiang , Decuir Eric A. , Manasreh Omar , Lytvyn Peter M. , Kunets Vasyl P. , Salamo Greg J. 
Published: April 2011

ABSTRACTThe interband and intersubband transitions in self-assembled InAs and In0.3Ga0.7As quantum dots grown by molecular beam epitaxy have been investigated for their use in visible, near-, and mid-infrared detection applications. Devices based on InAs quantum dots embedded in an InxGa1−xAs (0 to 0.3) graded well and In0.3Ga0.7As quantum dots were fabricated in order to measure the temperature dependent (77 – 300 K) photoresponse. The dark current was measured in the temperature range of 77 to 300 K for the devices. Room temperature photoresponse ranging between 0.6 to 1.3 μm was observed for the InAs and In0.3Ga0.7As quantum dot photodetectors. Furthermore, a dual band photoresponse in the visible, near-, and mid-infrared spectral regions for both devices was observed at 77 K. Using a self-consistent solution of Schrödinger-Poisson equations, the peak position energies of the interband and intersubband transitions in the two multi-color quantum dot infrared photodetector structures was calculated.
Prediction of Energies of <100> Tilt Boundaries in Al-Pb Alloy
Authors: Purohit Y. , Irving D. L. , Scattergood R. O. , Brenner D. W. 
Published: April 2011

ABSTRACTEnergies for symmetric tilt grain boundaries in pure Al and in Al with substitutional Pb defects at coincident sites along the grain boundaries were calculated using a modified embedded atom method potential and density functional theory. The agreement between the analytic potential, the first principles calculations and experiment is reasonably good for the pure system. For the Al-Pb system both the analytic potential and first principles calculations predict that Pb segregation to the interface is energetically preferred compared to the dilute solution. The application of a disclination structural unit model to calculating grain boundary energies over the entire range of tilt angles is also explained.
High Yield Synthesis of single crystal FCC Silver Nanoparticles and their Size Control
Authors: Nakamura Hiroyuki , Shimizu Toshiyuki , Uehara Masato , Yamaguchi Yoshiko , Maeda Hideaki 
Published: April 2011

ABSTRACTFace centered cubic (FCC) single crystal silver nanoparticles(NPs) of nearly monodispersed particle size of 12nm were prepared by simple ripening multi-twined particles (MTP). The product yield was nearly 100% and growth mechanism was considered to be similar to Ostwald ripening but utilize chemical potential difference between MTP and FCC NPs. Controlling the ratio between defectless and defective particles before ripening by controlling kinetics of particle generation stage, it was possible to control the final defectless particle size from 7-18 nm maintaining almost 100% product yield.
Aluminum Nanoparticle Synthesis by Reduction of Halides with Na/K
Authors: Purdy Andrew P , Miller Joel B , Stroud Rhonda M , Pettigrew Katherine A 
Published: April 2011

ABSTRACTSolutions or mixtures of aluminum halides AlX3 (X = Cl, Br, I) or aluminum halide alkoxide (ROAlX2; R= i-Pr, X = Cl, Br) are prepared in toluene, or pentamethyldiethylenetriamine (PMDETA) and treated with a slight excess of 50:50 (wt.) sodium potassium alloy (Na/K). Upon agitation, the reaction takes place slowly. The reaction appears to be limited by the deposition of insoluble products on the surface of the Na/K since sonication in an ordinary ultrasonic cleaner is necessary to bring the reaction to completion in several hours. Aluminum nanoparticles (NPs) and Na and K halides are formed, and soluble Al compounds, are also formed in some cases. Lithium powder is used instead of Na/K to reduce Al(N(SiMe3)2)3 to Al NPs. In an effort to passivate the surface of the Al particles to oxidation or hydrolysis, various agents are added either during the reaction or afterward. The products are characterized by SEM, XRD, NMR, and TEM, and the stability to water and air is evaluated.
Doped Zirconia Luminescent Nanoparticles
Authors: Sample Jennifer , Zhang Dajie 
Published: April 2011

ABSTRACTNanoparticles that fluoresce or absorb light in the visible and near-IR wavelengths are desirable for a variety of applications including biological tagging for medical imaging purposes and for solar control glazing in the automobile industry. Semiconductor quantum dots are commercially available and dyed polymer nanoparticles as well as organic dye/silica core shell nanoparticles have also been demonstrated. We report the synthesis, characterization, and optical properties of another luminescent nanoparticle: doped zirconia. The zirconia nanoparticles reported in this study are doped with up to 10% of the lanthanide dopants Er, Gd, Nd and Eu. These materials emit in the visible and near-IR wavelengths depending on the dopant and are refractory, making them useful for high temperature applications. These cations were found to stabilize the cubic phase over the monoclinic phase of zirconia, at approximately 10% dopant, as characterized by X-ray diffraction. We report the luminescence spectra of these nanoparticles at various wavelengths which reveal emissions from the matrix as well as from the dopants.
Local Elastic Constants For Epoxy-Nanotube Composites From Molecular Dynamics Simulation
Authors: Frankland S. J. V. , Gates T. S. 
Published: April 2011

ABSTRACTA method from molecular dynamics simulation is developed for determining local elastic constants of an epoxy/nanotube composite. The local values of C11, C33, K12, and K13 elastic constants are calculated for an epoxy/nanotube composite as a function of radial distance from the nanotube. While the results possess a significant amount of statistical uncertainty resulting from both the numerical analysis and the molecular fluctuations during the simulation, the following observations can be made. If the size of the region around the nanotube is increased from shells of 1Å to 6Å in thickness, then the scatter in the data reduces enough to observe trends. All the elastic constants determined are at a minimum 20Å from the center of the nanotube. The C11, C33, and K12 follow similar trends as a function of radial distance from the nanotube. The K13 decreases greater distances from the nanotube and becomes negative which may be a symptom of the statistical averaging.
Effects of Relative Humidity and Nanoparticle Incorporation on Nanostructures of PS-b-PEO Diblock Copolymer
Authors: Wu Juntao , Zhao Minhua , Nguyen Tinh , Gu Xiaohong 
Published: April 2011

ABSTRACTThe morphological structures of polystyrene-block-poly(ethylene oxide), PS-b-PEO, have been investigated under humidity controlled environments during film formation. Well-defined cylindrical microdomains oriented normal to the surface were induced by the high humidity during spin coating. Effects of the relative humidity (RH) on such ordered structures have also been studied. The results show that, the orientation and the ordering of the copolymer structures are very sensitive to the humidity of the environment during the film formation. Such ordered structure is stable at a variety of the RHs, and the phase contrast between the cylindrical PEO domains and the PS matrix domains can be significantly enhanced by the elevated RH. After the incorporation of the nanoparticles, however, the morphological structures of the PS-b-PEO are modified.
Computer Simulation of Nanoparticle Aggregate Fracture
Authors: Hawa Takumi , Henz Brian , Zachariah Michael 
Published: April 2011

ABSTRACTNanoparticle aggregates have been found to possess unique mechanical properties. Aggregates of metal nanoparticles can be strained up to 100% before failure, and even typically brittle materials are observed to have a ductile failure mode. In this effort two materials; namely silver and silicon, were chosen to represent ductile and brittle materials, respectively. Aggregates with 2 to 6 particles were simulated using the molecular dynamics (MD) algorithm to determine the stress-strain behavior of the aggregate. Many interesting observations are made including the negligible affect of strain rate on ultimate tensile strength, and the direct relationship between Young's modulus and nanoparticle size.
Nanostructured indium tin oxide for application in optoelectronic devices
Authors: Fernando S. P. , Harris K. D. , Gerein N. J. , Brett M. J. 
Published: April 2011

ABSTRACTThe electrical resistivities of nanostructured films of indium tin oxide were measured. The films were prepared using glancing angle deposition, a physical vapour deposition technique. This technique was used to prepare nanostructured indium tin oxide thin films of various morphologies. Films consisting of vertical posts were electrically characterized using a probing station. Compared to a normally evaporated planar film, the nanostructured films were found to exhibit resistivities approximately two orders of magnitude greater. Development of the measurement technique is ongoing, and several ideas for improvement are described.
New Polypropylene-boron Oxide Composite with a High Tensile Strength: A Possible Method for the Conversion of Microcomposite to Nanocomposite
Authors: Chopra Shwetha , Ge Changfeng , Santhanam K S.V. 
Published: April 2011

ABSTRACTIndustrially viable blends having microstructures that can be converted into a nanostructured material by post chemical treatments, potentially should have a commercially viable solution to the development of nanostructured materials for practical applications. In this regard a polypropylene-boron oxide (PPBO) blend provides a model study here. In this paper we wish to report the synthesis of PPBO blends with different concentrations of boron oxide by melt grafting and through reactive extrusion. The tensile strengths of the ideal blend has been found to be 62% higher than polypropylene (PP). By chemically treating the blends for a period of 24 hours to 72 hours the tensile strength of the blends increased by 152%. The blends have been characterized by fourier transform infra red spectroscopy (FTIR) and scanning electron microscopy (SEM). An interesting characteristic of the PPBO blend has been the development of surface potential that changes upon visible light excitation. The increased tensile strength has been attributed to the conversion of micro structured blends to nanostructured blends. The improvement in thermal stability can be attributed to a good PP matrix-oxide interaction and also due to the thermal conductivity of the boron oxide. The good dispersion of the nanotubes in the polymer matrix allows the spreading of heat uniformly along the fiber.
Size Effects on the Plastic Deformation of Nanocomposites Prepared from SiCN and SiCNAlYO Nanopowders Synthesized by Laser Pyrolysis
Authors: Herlin-Boime Nathalie , Dez Romuald , Reynaud cecile , Besson Jean Louis , Vicens Jean 
Published: April 2011

ABSTRACTThe aim of this work was to synthesise nanopowders by laser pyrolysis in order to elaborate Si3N4-SiC nanocomposites exhibiting a high ductility at high temperature. The synthesis of SiCN and SiCNYAlO nanopowders with a good thermal stability has been developed from a liquid mixture based on hexamethyldisilazane with a gaseous precursor (silane, SiH4) and ammonia. Si3N4-SiC nanocomposites exhibiting almost theoretical density have been elaborated by hot pressing under 35 MPa at 1600°C either from SiCNYAlO nanopowders or from SiCN nanopowders mixed with commercial sintering aids nanopowders (6 wt% yttria and 3 wt% alumina) in ethanol and de-agglomerated by milling with Si3N4 balls. The densification behaviour is better for nanopowders containing in-situ additives. In addition, using prealloyed powders enables to simplify the elaboration process since the mixing step of the nanopowders is eliminated. The nanocomposites elaborated from the mixture (SiCN + commercial sintering aids) exhibit a different microstructure, depending on the drying process (under vacuum or in an oven) of the nanopowders after the mixing step: When drying was performed in a confined atmosphere, a noticeable amount of Si2N2O was detected in addition to β-Si3N4 and the average grain size was 60 nm, whereas the crystalline phases were α- and β-Si3N4, when the slurry was dried under vacuum and the average grain size was 200 nm. The creep behaviour of the two grades was assessed under compressive loading in air and the deformation appears strongly influenced by this change of the microstructure: A strong ductility was observed for the smallest grain size: a deformation as high as 45 % was measured under a compressive load of 180 MPa at 1350°C under air.
Characterization of Thermo-Electric Interface Material with Carbon Nanotubes
Authors: Thakre Piyush R , Bisrat Yordanos , Lagoudas Dimitris C 
Published: April 2011

ABSTRACTAn approach has been presented in the current work to fabricate and characterize nanocomposite systems for optimizing electrical and thermal properties without sacrificing mechanical properties. An epoxy matrix based nanocomposite system has been processed with different volume fractions of carbon nanotubes. The purpose was to tailor macroscale properties to meet competing performance requirements in microelectronics industy. The nanofiller consisted of comparatively low cost XD grade carbon nanotubes (XD-CNTs) that are optimized for electrical properties. This system was compared with another system consisting of single wall carbon nanotubes (SW-CNTs) as nano-reinforcements in epoxy matrix. The electrical percolation threshold (about seven orders of magnitude increase in electrical conductivity) measured by dielectric spectroscopy was found to be at lower loading weight fraction of SWCNTs (0.015 weight %) as compared to XD-CNTs (0.0225 weight %). However, the electrical conductivity after percolation was higher for XD-CNTs reinforced epoxy with respect to SW-CNTs filled nanocomposites. The governing mechanisms for this phenomenon were investigated using transmission optical microscope. The enhancement in thermal conductivity, measured using differential scanning calorimetry, was found to be moderate at lower weight loadings corresponding to electrical percolation. However, a 90% improvement in thermal conductivity was observed for 0.3 weight percent of XD-CNTs. Dynamic mechanical analysis was performed to measure the storage and loss modulus along with the glass transition temperature. No significant change in modulus values and glass transition temperature was measured for nanocomposites varied filler contents with respect to neat matrix.
Percolation of Diffusionally Evolved Two-Phase Systems
Authors: Brunini Victor Eric , Schuh Christopher A. , Carter W. Craig 
Published: April 2011

ABSTRACTAlthough the phase fractions in dual phase systems are often compared with the percolation threshold for a randomly-assembled composite, most two-phase systems are non-random by virtue of correlations introduced during processing or as a consequence of microstructural evolution. This study examines the two dimensional percolation threshold in systems with soft impingement, i.e., when the phase distribution is affected by diffusional interactions between growing second phase particles. Phase field modeling is used to simulate the nucleation and growth process, with many simulations conducted at various system sizes and equilibrium phase fractions to obtain percolation probabilities. The value of the percolation threshold in the thermodynamic limit is estimated based on the finite size scaling behavior of the system. The value of the critical exponent Î½ (the size scaling exponent) is also estimated.