bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication of MEMS Components Based on Ultrananocrystalline Diamond Thin Films and Characterization of Mechanical Properties
Authors: Sumant A. V. , Auciello O. , Krauss A. R. , Gruen D. M. , Ersoy D. , Tucek J. , Jayatissa A. , Stach E. , Moldovan N. , Mancini D. , Busmann H. G. , Meyer E. M. 
Published: April 2011

ABSTRACTThe mechanical, thermal, chemical, and tribological properties of diamond make it an ideal material for the fabrication of MEMS components. However, conventional CVD diamond deposition methods result in either a coarse-grained pure diamond structure that prevents high- resolution patterning, or in a fine-grained diamond film with a significant amount of intergranular non-diamond carbon. At Argonne National Laboratory, we are able to produce phase-pure ultrananocrystalline diamond (UNCD) films for the fabrication of MEMS components. UNCD is grown by microwave plasma CVD using C60-Ar or CH4-Ar plasmas, resulting in films that have 3-5 nm grain size, are 10-20 times smoother than conventionally grown diamond films, and can have mechanical properties similar to that of single crystal diamond. We used lithographic patterning, lift-off, and etching, in conjunction with the capability for growing UNCD on SiO2 to fabricate 2-D and 3-D UNCD-MEMS structures. We have performed initial characterization of mechanical properties by using nanoindentation and in-situ TEM indentor techniques. The values of Hardness (∼88 GPa) and Young's modulus (∼ 864 GPa) measured are very close to those of single crystal diamond (100 GPa and 1000 GPa respectively). The results show that UNCD is a promising material for future high performance MEMS devices.
Young's Modulus and Fracture Strength of Three Polysilicons
Authors: Sharpe W. N. , Jackson K. , Coles G. , LaVan D. A. 
Published: April 2011

ABSTRACTPolysilicon specimens from Cronos, Sandia, and Standard MEMS, Inc. were tested in tension. The specimens were nominally 6 or 20 μm wide and 250 or 1000 μm long. The Cronos and the Standard MEMS specimens had thicknesses of 1.5, 2.0, and 3.5 μm; whereas, the Sandia specimens were all 2.5 μm thick.There was no dramatic difference in Young's modulus for the three materials. A total of 117 tests were run, and the average modulus for all three materials was 157 ± 9 GPa. However, the strengths were quite different: 1.56 ± 0.25 GPa for the Cronos material, 2.85 ± 0.40 GPa for Sandia's, and 2.04 ± 0.30 GPa for the SMI polysilicon.
High-Cycle Fatigue of Polycrystalline Silicon Thin Films in Laboratory Air
Authors: Muhlstein C. L. , Brown S.B. , Ritchie R.O. 
Published: April 2011

ABSTRACTWhen subjected to alternating stresses, most materials degrade, e.g., suffer premature failure, due to a phenomenon known as fatigue. It is generally accepted that in brittle materials, such as ceramics, cyclic fatigue can only take place where there is some degree of toughening, implying that premature fatigue failure would not be expected in polycrystalline silicon where such toughening is absent. However, the fatigue failure of polysilicon is reported in the present work, based on tests on thirteen thin-film (2 μm thick) specimens cycled to failure in laboratory air (∼25°C, 30-50% relative humidity), where damage accumulation and failure of the notched cantilever beams were monitored electrically during the test. Specimen lives ranged from about 10 seconds to 34 days (5 × 105 to 1 × 1011 cycles) with the stress amplitude at failure being reduced to ∼50% of the low-cycle strength for lives in excess of 109 cycles.
Challenges in DMD™ Assembly and Test
Authors: Jacobs S. Joshua , Malone Joshua J. , Miller Seth A. , Gonzalez Armando , Robbins Roger , Lopes Vincent C. 
Published: April 2011

ABSTRACTThe Digital Micromirror Device™ (DMD™) developed at Texas Instruments is a spatial light modulator composed of 500,000 to 1.3 million movable micromachined aluminum mirrors. The DMD™ serves as the engine for the current generation of computer-driven slide and video projectors, and for next generation devices in digital television and movie projectors. The unique architecture and applications of the device present several packaging and test challenges. This paper provides a description of package humidity modeling and verification testing, as well as an overview of the automated optical testing and test equipment that have been developed to support manufacturing of the DMD™.
MEMS Materials and Fabrication Technology on Large Areas: The Example of an X-ray Imager
Authors: Daniel J.H. , Krusor B. , Lau R. , Lu J.P. , Wang Y. , Mulato M. , Apte R.B. , Street R.A. , Goredema A. , Boils-Boissier D.C. , Silver S.E. , Kazmaier P.M. 
Published: April 2011

ABSTRACTMicromachining has potential applications for large area image sensors and displays, but conventional MEMS technology, based on crystalline silicon wafers cannot be used. Instead, large area devices use deposited films on glass substrates. This presents many challenges for MEMS, both as regards materials for micro-machined structures and the integration with large area electronic devices. We are exploring the novel thick photoresist SU-8, as well as plating techniques for the fabrication of large area MEMS. As an example of its application, we have applied this MEMS technology to improve the performance of an amorphous silicon based image sensor array. SU-8 is explored as the structural material for the X-ray conversion screen and as a thick interlayer dielectric for the thin film readout electronics of the imager.
Formation of Biaxially Textured MgO Buffer Layers using Ion-Beam Assisted Pulsed Laser Deposition
Authors: Hühne Ruben , Beyer Christoph , Holzapfel Bernhard , Oertel Carl-Georg , Schultz Ludwig , Skrotzki Werner 
Published: April 2011

ABSTRACTMgO thin films were deposited on amorphous substrates using ion-beam assisted pulsed laser deposition. The texture formation was investigated in-situ with RHEED. The microstructure of the films was observed by AFM. Using an ion beam at an angle of 55° with respect to the substrate normal, strong nucleation textures develop. Above 250°C a cube texture is observed in films thinner than 10 nm. During further growth this nucleation texture changes in a way that the <200> direction becomes parallel to the ion beam. This change can be explained by the anisotropic sputter rate of MgO found in sputter experiments on single crystals. Moreover, MgO films were deposited homoepitaxially on MgO single crystals above 250°C with internal stresses dreasing with increasing deposition temperature. This result gives rise to hope that homoepitaxial growth of MgO on the nucleation layer without ion-beam assistance should be possible in future PLD-experiments keeping the desired cube texture in thicker films.
DTA/TGA Study of Eutectic Melting in the System BaF2-BaO-Y2O3-CuOx−H2O
Authors: Cook Lawrence P. , Wong-Ng Winnie , Suh Julia 
Published: April 2011

ABSTRACTDifferential thermal analysis and thermogravimetric analysis (DTA/TGA) experiments have been completed in the BaF2-BaO-Y2O3-CuOx-H2O system at various oxygen pressures to determine the effect of adding solid BaF2and gaseous H2O (at pH2O = 2.5 kPa) on the eutectic melting in the system BaO-Y2O3-CuOx. We have investigated the eutectic melting temperature over the range of pO2 = 20 Pa to pO2 = 0.1 MPa under the following conditions: 1) without BaF2 or H2O; 2) with H2O only; 3) with BaF2 only; 4) with both BaF2 and H2O. Results indicate that without BaF2 or H2O, eutectic melting is depressed from 917°C at pO2 = 0.1 MPa to 838°C at pO2 = 1 kPa. At oxygen pressures below 1 kPa, down to pO2 = 20 Pa, no further lowering of eutectic melting temperature was observed. The topologies of the temperature vs. log pO2 curves for various combinations of BaF2 and H2O were similar to that for the experiments without BaF2 or H2O, but all curves were shifted to lower temperatures. For the experiments with addition of BaF2 only, H2O only, and BaF2 with H2O, the eutectic melting temperatures as a function of pO2 were lowered by, respectively, 5°C - 15°C, 15°C - 25°C and 20°C - 30°C. Application of results to the “BaF2ex-situ” method of processing Ba2YCu3Ox coated conductors is discussed.
Superfluid Density in Ultrathin YBCO Films
Authors: Delimova Lyuba A. , Grekhov Igor V. , Liniichuk Ivan A. , Veselovsky Ivan A. , Traito Konstantin B. , Lahderanta Erkki 
Published: April 2011

ABSTRACTWe studied the transition of 8 nm-thick YBCO films deposited with and without YBaCuNbO buffer from the superconducting to resistive state due to the temperature or transport current increase. For both film types, the current –voltage characteristics and resistive transition followed the Kosterlitz-Thouless transition model. The superfluid densities were found from the Kosterlitz-Thouless transition temperature TKT to be about 3% and 1.3% of the total carrier density in YBCO with and without buffer, respectively. We believe that the low superfluid densities indicate the presence of weak links in the film.
Nanofiller Modification of Phase Stability in PS/PMMA Blends
Authors: Ji G. , Clement F. , Giannelis E.P. 
Published: April 2011

ABSTRACTThe effect of nanoparticles on the phase stability of an immiscible PS/PMMA blend was studied in thin film samples. Using AFM and selective dissolution we find that nanoparticles affect the domain evolution of the polymer blend. Annealing of the pure PS/PMMA blend at 190 °C leads to PS drops that protrude from the PMMA surface. Films containing the nanoparticles show similar surface features but these features become less regular and tend to get shallower and larger as the amount of nanoparticles increases. The characteristic length of the PS drops in the pure blend film is ∼ 7 microns and they cover 22 % of the surface. The corresponding numbers for the film containing 10% nanoparticles are 15 microns and 65%, respectively.
Investigation into the Thermal and Mechanical Behavior of PMMA/Alumina Nanocomposites
Authors: Ash Benjamin J. , Stone Jason , Rogers Diana F. , Schadler Linda S. , Siegel Richard W. , Benicewicz Brian C. , Apple Thomas 
Published: April 2011

ABSTRACTPolymethylmethacrylate (PMMA) nanocomposites were synthesized by free radical polymerization in the presence of various weight percentages of alumina (Al2O3) nanoparticles. The resulting nanocomposites show an average increase of 600% in strain-to-failure and the appearance of a well-defined yield point. Concurrently, the glass transition temperature (Tg) of the composites decreased 20°C, while the ultimate strength and the Young's modulus decreased by 20% and 15%, respectively.
Extracting Dispersion from Roughness
Authors: Tricot Claude 
Published: April 2011

ABSTRACTA mathematical analysis of surfaces may help to understand how the carbon black is dispersed into polymer. Rubber samples are broken out, and the rupture interface is scanned with a prolometer. The roughness is detected at the micron scale. Roughness functions are dened, measuring the average oscillations of the surface. The roughness behaviour is “fractal” for small scales until around 10 microns, then become linear. A roughness ratio is defined, depending both on the scale and on the mixing time. There is evidence to suggest that the roughness ratio does not depend on the polymer, but only on the dispersion of the filler. A dispersion factor is derived, and results are shown on three diserent compounds.
Nanofiller-Polymer Interactions At and Above the Glass Transition Temperature
Authors: Zhu Ai-jun , Sternstein Sanford S. 
Published: April 2011

ABSTRACTRheological data are reported for a series of fumed silica filled PVAc samples, using fillers of different specific surface areas and surface treatments. Data at the glass transition temperature and 45 C above Tg are presented. The addition of filler systematically increases Tg, and all samples obey time-temperature superposition. However, temperature normalized and frequency normalized plots of loss modulus indicate that there is no change in the dispersion of the glass transition, with the only exception being a surface modified with covalently bonded polymer chains. Thus, contrary to expectations, an increase in filler content or change in surface treatment has no effect on the relative shape of the relaxation time spectrum at the glass transition. At 45 C above Tg, different behavior is observed. The filler concentration has a major effect on the nonlinearity of dynamic moduli vs. strain amplitude, with higher filler content reducing the strain amplitude at which nonlinear behavior is observed. Specific filler surface treatments result in major changes in the shape of the loss factor versus strain amplitude relationship. These results suggest that interfacial interactions strongly modify the far-field polymer behavior with respect to chain entanglement slippage at large strains.
Restricted Dynamics in Polymer-Filler Systems
Authors: Arrighi V. , Gagliardi S. , Higgins Julia S. 
Published: April 2011

ABSTRACTComposites in which fibres or fillers are incorporated into a polymeric component exhibit improved mechanical strength compared to the polymer matrix. This reinforcement effect strongly depends on the properties of the interphase and the specific interactions between the polymer and the reinforcing additive.A wide range of experimental methods have been used to assess the effect of active fillers on the mobility of the polymer chains. The experimental results from NMR, dielectric spectroscopy and dynamical thermal analysis reveal that the mobility of chain units adjacent to the adsorbed surface differs considerably from the bulk.We have used quasielastic neutron scattering to investigate the dynamic properties of poly(dimethyl siloxane) (PDMS) filled with silica particles. This technique which probes the motion of the hydrogen atoms has been extensively used to study the local dynamics of polymeric materials. In this paper we show that QENS provides detailed information on the reduced mobility of chain segments in polymer-filler systems.QENS measurements were carried out on PDMS filled with hydrophilic Aerosil with different specific surface area (average diameter 7 and 20 nm). Detailed data analysis indicates that the QENS spectra of the polymer-filler composites can be described by the sum of two contributions: (a) a quasielastic component due to chains not affected by the presence of the fillers and (b) an elastic term from those chain segments strongly affected by the presence of fillers. The latter depends on the specific surface area of the particles and their weight fraction in the composite.
Polymer-Clay Nanocomposite Materials: Solution and Bulk Properties
Authors: Schmidt Gudrun , Nakatani Alan I. , Butler Paul D. , Ferreiro Vincent , -Karim Alamgir , Han Charles C. 
Published: April 2011

ABSTRACTThe influence of shear on viscoelastic polymer-clay solutions was investigated by means of small-angle neutron scattering (SANS) under shear. SANS measured the shearinduced orientation of polymer and platelets. With increasing shear rate an anisotropic scattering pattern developed. At higher shear rates, the scattering anisotropy increases due to the increased orientation of the clay platelets in the shear field. Cessation of shear leads to fast recovery demonstrating the system to be highly elastic. As a result of drying, these solutions produce translucent nanocomposite films with a microporous membrane character. Depending on the preparation and degree of polymer-clay film dispersion, it is possible to modify the morphology and elastic properties of nanocomposite materials. Atomic Force Microscopy (AFM) reveals the network character and the development of morphology as a function of polymer concentration. Preliminary SANS experiments on the films will be correlated to morphologies obtained from AFM.
A Preliminary Study on Rice Husk Filled Polypropylene Composite
Authors: Sun Luyi , -Xiao Min , Xiao Peng , Song Jianhua , Wang Weixing , Zhang Yafeng , Gong Kecheng 
Published: April 2011

ABSTRACTThe major inorganic component of the rice husk (RH) is silica (∼20%)[1]. In the past, the utilization of RH mainly concentrated on the ash of the rice husk, such as using rice husk ash (RHA) as filler in plastics, especially in polypropylene (PP). In this work, RH was directly used as filler in PP. Some treatments were applied to the RH. PP composites of different filler loadings were compounded using a laboratory size two-roll mixer at a temperature of 180° C for a period of 5 minutes. The tensile strength of the RH-PP composites increased steadily with increasing filler loading until about 20% loading. The impact strength of the composites decreased with the increasing filler loading. Torques and melt index (MI) of composites with various filler loadings were investigated. The MI of the composite decreased with the increasing filler loading. RH showed more potential than RHA as PP filler.
Figures of Merit for Electrically Conductive Polymer Composites
Authors: Grunlan Jaime C. , Gerberich William W. , Francis Lorraine F. 
Published: April 2011

ABSTRACTIn an effort to determine the optimal balance of electrical and mechanical performance for electrically conductive polymer composites, three figures of merit were evaluated. All three figures of merit displayed peaks and/or discontinuities at a particular filler loading. These loadings appear to correspond to the critical pigment volume concentration for a given system. Composite systems based upon latex as the matrix starting material showed peaks in the figures of merit at very low carbon black concentrations (10 vol%), while composites prepared with polymer solutions or melts had peaks above 20 vol% carbon black. These differences in behavior are attributed to differences in microstructural evolution that occur with filler loading.
Electrospinning of Polymeric Nanofibers: Analysis of Jet Formation
Authors: Senador Antonio E. , Shaw Montgomery T. , Mather Patrick T. 
Published: April 2011

ABSTRACTProducing nanofiber-diameter polymeric fibers presents an attractive and robust approach toward the processing of nanocomposites, with applications ranging from clear optical components to toughened structural materials. In this work, we are examining the electrospinning process for the production of nanometer-diameter polymer fibers, giving particular attention to the following key features: jet-initiation, fiber architecture, and fiber distribution. A wide range of polymer systems and polymer-solvent combinations were studied in order to broaden the applicability of our conclusions to other systems. Specifically, a dimensional analysis was applied to jet-formation data obtained by quantifying the conditions required for the expulsion of fibers from a charged capillary to a grounded collection plate. The relationships between various dimensionless groups were compared with the expressions for the critical voltage that have been proposed for electrospinning of polymer solutions.
The Influence of Block Copolymers on Silica-Filled Polyisoprene
Authors: Gurovich Daniel , Macosko Christopher W. , Tirrell Matthew 
Published: April 2011

ABSTRACTThe influence of PDMS-polyisoprene diblock copolymers on the dynamic rheological properties of silica-filled uncured polyisoprene was investigated. Unlike binary silica-polyisoprene systems, the ternary systems in our study showed a decrease in low-amplitude dynamic storage modulus (G') with room-temperature storage time. This aging behaviour is accompanied by an increase in the concentration PDMS segments at the filler-polymer interface, as measured by solid-state 1H NMR. The decrease in G' is thus attributed to a progressive disruption of a filler-filler network by selective block copolymer adsorption onto the filler surface.
Role of fractal features in the structure-property relationships of carbon black filled polymers
Authors: Ehrburger-Dolle Françoise , Hindermann-Bischoff Manuela , Geissler Erik , Rochas Cyrille , Bley Françoise , Livet Frédéric 
Published: April 2011

ABSTRACTCarbon black is widely used as a filler in order to modify the mechanical or the electrical properties of polymers. Such composites display significant non-linear effects. Moreover, examination of the large number of papers devoted to the physical properties of carbon black filled polymers indicates that each composite, even composites apparently consisting of similar matrixes and similar carbon blacks, may behave differently when prepared by different mixing methods. The present work aims to show that these particular behaviors can be related to the fact that carbon blacks used for composites are mass fractals of low dimensionality (Df ˂2) that are able to interpenetrate each other to an extent that depends on the filler-matrix surface interaction and on the volume fraction of filler.Small-angle X-ray scattering (SAXS) is a convenient method for studying disordered systems at length scales ranging between a few tenths and a few hundred nm. SAXS is therefore particularly advantageous for exploring the morphology of carbon black aggregates and their degree of interpenetration when dispersed in a matrix. Furthermore, the use of an area detector yields two-dimensional images and hence information about anisotropy of the arrangement of scatterers. It is shown that this arrangement profoundly influences the physical properties of the composites.Analysis of SAXS curves obtained for a rubber grade carbon black (N330) and for composites prepared by dispersing it into polyethylene or EPR will be presented. As an example, the temperature and frequency dependence of the electrical conductivity will be discussed and compared to theoretical models. Finally, the mutual consistency of the electrical and mechanical behavior, theoretical models and information deduced from the scattering curves will be shown.
Organoclay Nanoplatelets at the Air/water Interface
Authors: Shin Kwanwoo , Zhang Yimin , White Henry , Rafailovich Miriam H. , Sokolov Jonathan , Peiffer Dennis 
Published: April 2011

ABSTRACTWe have demonstrated that films of single clay platelets can be produced by the Langmuir technique where a solution of organoclay particles dissolved in xylene was spread at the air water interface. The total thickness of the layer was found to be 21 ± 3Å which is in good agreement with previous X-ray diffraction data. Scanning probe microscopy showed the individual platelets to be rectangular in shape with an aspect ratio in excess of 100 to 1 and of uniform organic surfactant coverage.
State of Dispersion of Reinforcing Silica in a Silicone Elastomer, as Investigated by Transmission Electron Microscopy
Authors: Field Rex J , Cambray Jeanne , Floess Joachim , Rouanet Stephane 
Published: April 2011

ABSTRACTCommercial silicone rubbers typically contain submicron particles dispersed within them, the particles being responsible for the mechanical properties required for commercial success. Fumed silica has long been used for the reinforcement of higher-perfomance silicone rubber compositions, but high-porosity aerogels can function as well. The object of the work here was to compare the state of dispersion of some high-porosity aerogels with that of a fumed silica.Model silicone HCR (“heat-cured rubber”) compositions were prepared, and their mechanical properties characterized. Thin sections of the rubbers were then examined by TEM.Much of the fumed silica had been dispersed to give sub-micron sized features, although a number of larger features were present. The hydrophobic aerogel, in contrast, had been dispersed to give even finer features in the rubber, with very few super-micron fragments. The state of dispersion of the hydrophilic aerogel was quite different, showing many poorly-broken down large fragments up to 5 µm or more in diameter. The visual appearance of the compound reflected this poorer state of dispersion.