bluuebunny/crossref_metadata_2025_split huggingface dataset:
Silica Fume, Bond Strength, and the Compressive Strength of Mortar
Authors: Darwin David , Zhenjia Shen , Harsh Shraddhakar 
Published: June 2019

ABSTRACTThe strength and strain-rate sensitivity of cement paste and mortar is studied as a function of water-cementitious material ratio (W/C) and silica fume content. W/C's of 0.30 and 0.35 are used for materials without silica fume, while W/C's ranging from 0.336 to 0.436 are used for material containing silica fume. The volume fractions of cement paste matrix and sand are held at 63 and 37 percent, respectively, for all mortars. Strain rates of 30, 3000, and 300,000 microstrain per second are used. The results indicate that materials with silica fume are less strain-rate sensitive of than materials without silica fume. The replacement of cement by silica fume appears to (1) reduce rather than increase the bond strength between cement paste and sand and (2) increase the compressive strength of mortar primarily by increasing the strength of the cement paste matrix.
Analysis of Synthetic Fiber Pull-Out from a Cement Matrix
Authors: Wang Youjiang , Li Victor C. , Backer Stanley 
Published: June 2019

ABSTRACTExperiments were conducted on specimens containing nylon or polypropylene monofilaments embedded in a precracked matrix. During pull-out tests, it was generally observed that the pulling force continued to increase after one or both sides of the filament had begun to slip out, even though one or both of the embedded filament lengths were decreasing. This indicated that the fiber/matrix shear stress increased with the fiber slippage distance. Examination of the extracted filaments under a scanning electron microscope (SEM) revealed the increased shear resistance to be the result of fiber surface abrasion. The severity of abrasion was observed to increase with the fiber slippage distance before complete pull-out. A theoretical model has been developed to predict the pull-out force versus displacement relationship based on given fiber/matrix shear strength as an increasing function of the slippage distance. The model gives good prediction in comparison with experimental results.
Study of Fiber Matrix Interfaces in Metakaoline-Opc Blended Cement GRC Composites
Authors: Ambroise J. , Dejean J. , Pera J. 
Published: June 2019

ABSTRACTDuctility is one of the main requirements of a reliable building material; the traditional LOP and MOR criteria do not reveal this quality. Other criteria based on deflection, energy or bond-slip relationships are presented. They are applied to four very different series of composites: very brittle, very ductile, and intermediate. The results point out that only the criteria based on the flexural test up to splitting, at a constant deflection rate, can reveal the higher ductility of the metakaoline-OPC blended matrix associated with AR glass. From this test, the bond-slip relationship can be determined. This leads to the definition of a comparative parameter which describes the mechanical interfacial compatibility of the matrix versus the fibers.
Bonding in Cementitious Composites: How Important is it?
Authors: Mindess Sidney 
Published: June 2019

ABSTRACTA number of different types of interfacial bonding occur in concrete, including:i) bonding between various phases (including anhydrous cement) in the hydrated cement paste (hcp) systemii) bonding between cement and aggregatesiii) bonding between cement or mortar and the fibres in fibre-reinforced concrete; andiv) bonding between concrete and steel reinforcing bars or prestressing cables.The importance of these types of bonds with respect to the mechanical behaviour of concrete is discussed. It is concluded that in some systems, the mechanical properties are governed primarily by the interfacial bond; in other systems, however, this bond has only a secondary effect.
The Effect of Bond Characteristics between Steel Slag Fine Aggregate and Cement Paste on Mechanical Properties of Concrete and Mortar
Authors: Yuji Wang 
Published: June 2019

ABSTRACTThe ordinary fine aggregate in concrete has been replaced by ground and sieved steel slag fine aggregate, treated and exposed to air for three months. Compared with concrete made from natural sand, properties such as compressive strength, flexural strength, elastic modulus, permeability and abrasion resistance are considerably improved. The improvement increases with a decrease in w/c ratio, an increase in curing time and an increase in the replacement weight of sand. These results are due to the fact that the steel slag contains some active minerals such as C3S, C2S, C4AF, etc., and shows favorable surface physical characteristics that improve the bond between steel slag particles and cement paste. The results of XRD, SEM and EPM microhardness showed that there are heavier concentration of ions, with finer crystals and a lower degree of CH orientation at the interfacial zone between steel slag particles and cement paste. The study also found small cementitious and fibrous C-S-H crystals growing from the fine aggregate, which are linked with hydrated products from cement paste making the bond and structural characteristic more favorable with cement. The steel slag fine aggregate is an active mineral similar to cement. The bond between the aggregate and cement paste is strengthened both physically and chemically.
Synthesis and Characterization of T12Ba2CaCu2O8 and T12Ba2Ca2Cu3O10
Authors: McMills Lauren E. H. , Li Shu , Zhang Zhen , Greenblatt Martha 
Published: June 2019

AbstractSingle-phase samples of T12Ba2CaCu2O8 and T12Ba2Ca2Cu3O10 have been prepared using a reliable and simple synthetic method. Samples were characterized by x-ray powder diffraction, magnetic susceptibility and four probe resistivity methods. The TcR=0 values for T12Ba2CaCu2O8 ranged from 100 to 105K, whereas those for T12Ba2Ca2Cu3O10 ranged from 96 to 107K. The relationship between the superconducting properties and the various preparation conditions are discussed.
Electron Cyclotron Resonance Hydrogenation of Poly-Si Thin Film Transistors on SiO2/Si Substrates
Authors: Liu Gand , Ditizio Robert A. , Fonash Stephen J. , Tran Nang 
Published: June 2019

ABSTRACTWe report the results of an ECR hydrogenation time-behavior study on polycrystalline silicon thin film transistors. The device characteristics, such as mobility, subthreshold slope, threshold voltage, off current and on/off current ratio, were measured as a function of the passivation time. It was found that there is an optimal passivation time for this particular TFT structure, and overexposure to ECR hydrogen plasma may cause the degradation of some device parameters.
Low Energy Ar Ion Bombardment of (001) Si: Defects and Surface Morphology
Authors: Murty M. V. R. , Atwater Harry A. , Watson Thomas J. 
Published: June 2019

ABSTRACTThe interaction of low energy Ar+ ions with several surface defect structures on (001) Si has been investigated using molecular dynamics simulation. The simulations suggest that ions with energy less than 20 eV selectively displace surface atoms without causing bulk damage, and that the displacement energies for different defect structures is different. The most important effect of ion bombardment on surface morphology is the increased formation rate of single adatoms, which may lead to smoother surfaces by enhanced coarsening at typical epitaxial temperatures. Simulations results also imply that the migration component of adatom diffusion is not significantly enhanced by ion bombardment at typical epitaxial temperatures (600 – 800 K).
The Role of Oxygen In the CF2Cl2 Reactive Ion Etching of Pecvd Films
Authors: Kuo Yue 
Published: June 2019

ABSTRACTAn extensive study on 02 effects on RIE of PECVD a-Si:H and SiNx has been carried out. Mixtures of CF2Cl2/HCI and CF2Cl2/CF3Cl were used as base gases. The addition of O2 into these gases changed the film etch rate and etch selectivity in different ways. Process results were interpreted by examining the plasma phase chemistry, the ion bombardment energy, and ESCA surface chemical states.
The Influence of HBr Discharge Ambience on Poly-Si/SiO2 Etching Selectivity
Authors: Ikawa E. , Tokashiki K. , Kikkawa T. , Teraoka Y. , Nishiyama I. 
Published: June 2019

ABSTRACTThe influence of HBr discharge ambience on SiO2 etching is investigated. A batch type parallel-plate reactive ion etching (RIE) dry etcher was used. The discharge ambience was changed by changing the numbers of poly-Si and SiO2 wafers in the same chamber. It is found that as the number of poly-Si wafers increased, the poly-Si etch rate slightly decreased due to a loading effect and SiO2 etching rate drastically increased. The selectivity of poly-Si / SiO2 decreased with increasing the ratio of the loaded poly-Si number in the same chamber. When A12O3 wafers instead of poly-Si wafers were loaded with SiO2 substrates, SiO2 etching rate enhancement did not occur. Therefore, increase of SiO2 etch rate could not be explained using a loading effect. From the results of mass analysis during etching in Si contained HBr plasma, etching products SiBrx (x=1,2,3) peaks were observed. Namely, when the Si etching products were supplied to SiO2 surface, SiO2 etch rate increased. In order to suppress the enhancement of SiO2 etch rate, the etch temperature must be reduced.
Ion Effects in Optical Films
Authors: Gibson U. J. 
Published: June 2019

ABSTRACTIon bombardment during growth of thin films has been shown to be a powerful technique for alteration of a wide variety of film properties from index of refraction and stoichiometry to density and abrasion resistance. A brief review of the deposition processes and ion effects of relevance to the production of optical films is presented. Application of the technique to some particular problems in films with both optical and protective roles, and the use of ion beams to alter the chemical composition and hence index of films will be discussed. Both homogeneous and spatially non-uniform coatings will be discussed, including generation of multilayer filters and gradient index structures in waveguiding films.
Modification Of Properties Of Ion-Beam-Sputtered Yttrium-Oxide Thin Films By Low-Energy Ion Bombardment
Authors: Klemm K. A. , Johnson L. F. , Moran M. B. 
Published: June 2019

ABSTRACTThe effect of low-energy ion bombardment on ion-beam-sputtered yttrium-oxide films was studied. Yttria films were subjected to argon ions accelerated by a potential of up to 500 V with current densities of up to 8 μA/cm2 and were deposited at differing substrate temperatures. Yttria films bombarded during deposition were found to be amorphous, and trends observed with increased ion energy include reduced amount of residual compressive stress, increased argon content, and decreased refractive index, depending on deposited energy and substrate temperature.
Dynamic Monte Carlo Simulation of Ion Beam and Plasma Techniques
Authors: Möller W. 
Published: June 2019

ABSTRACTA multiprojectile version of TRIDYN has been employed to simulate ion-induced effects which occur during ion-beam assisted deposition (IBAD) or plasma-assisted chemical vapour deposition (PECVD) of thin films.Simulations of the formation of boron nitride films deposited from evaporated boron and energetic nitrogen show an excellent agreement with experimental results for nitrogen concentrations below the stoichiometric limit. For high N/B flux ratios, non-collisional mechanisms (ion-induced outdiffusion, surface trapping of outdiffusing nitrogen) have been included in the simulations, again producing good agreement with the experimental results.Simulations of the PECVD of hydrocarbon films suffer from the poor knowledge of the neutral and ionic fluxes which contribute to the growth of the layers. Nevertheless, the composition of the films and its dependence on ion energy can be predicted with satisfactory agreement with experimental findings. A simple model of preferential displacement yields a reasonable average ratio of sp2and sp3coordinated carbon atoms. The energy dependence of the bond ratio is in contradiction to experimental observation.
Carbon Film Deposition On Silicon Using Low Energy Ion Beams
Authors: Fuguang Qin , Zhenyu Yao , Zhizhang Ren , Lee S.-T. , Bello I. , Feng X , Huang L. J. , Lau W. M. 
Published: June 2019

ABSTRACTDirect ion beam deposition of carbon films on silicon in the ion energy range of 15–500eV and temperature range of 25–800°C has been studied using mass selected C+ ions under ultrahigh vacuum. The films were characterized with X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy and diffraction analysis. Films deposited at room temperature consist mainly of amorphous carbon. Deposition at a higher temperature, or post-implantation annealing leads to formation of microcrystalline graphite. A deposition temperature above 800°C favors the formation of microcrystalline graphite with a preferred orientation in the (0001) direction. No evidence of diamond formation was observed in these films.
Optical Spectroscopic Profiling of Ion Beam Sputtering
Authors: Klein J. D. , Yen A. 
Published: June 2019

ABSTRACTThe optical emission spectra resulting from ion beam sputtering a BaTiO3 target were observed as a function of position. A collimated optical fiber bundle parallel to the plane of the sputter target was translated vertically and horizontally to spectroscopically profile the sputter process. The Ar contours provide an image of the incident beam and its distortion by the presence of the target. Comparison of the Ar and O contours indicate that the oxygen atmosphere in the vicinity of the target is determined by sputtering events as well as the incident beam. The shapes of the Ba and Ti contours are elliptical with some differences in intensity gradients. Comparison is made with species contours observed during rf sputtering of an Y-Ba-Cu-O target.
Ion/Neutral Beam Assisted Etching of Semiconductors: Chemical Modifications of the Adsorbed Phase
Authors: Tyrrell Glenn. C. , Marshall Duncan , Jackman Richard B. 
Published: June 2019

ABSTRACTThis paper addresses the fundamental aspects of etching semiconductors with inert gas beams in the presence of a suitable precursor gas. In particular, the changes that an energetic bombarding ion/neutral species cause to the surface and sub-surface region of a solid are considered, both in terms of the introduction of damage to the semiconductor and chemical processes that are provoked in the adsorbed states present. The implications for practical etching reactions are then discussed.
Stoichiometric Determination of Graphite Intercalation Compounds Using Rutherford Backscatiering Spectrometry
Authors: Salamanca-Riba L. , Elman B.S. , Dresselhaus M.S. , Venkatesan T. 
Published: June 2019

ABSTRACTRutherford backscattering spectrometry (RBS) is used to characterize the stoichiometry of graphite intercalation compounds (GIC). Specific application is made to several stages of different donor and acceptor compounds and to commensurate and incommensurate intercalants. A deviation from the theoretical stoichiometry is measured for most of the compounds using this non-destructive method. Within experimental error, the RBS results agree with those obtained from analysis of the (00ℓ) x-ray diffractograms and weight uptake measurements on the same samples.
Patterned Sol-Gel Structures by Micro Molding in Capillaries
Authors: Lochhead M. J. , Yager P. 
Published: June 2019

AbstractThe development of a variety of micro-optical chemical sensor and biosensor devices will rely on an ability to fabricate and effectively pattern physically and chemically sensitive materials. Toward this end, organically modified sol-gel materials are patterned onto a substrate using a benign technique called micro molding in capillaries (MIMIC). Closely spaced, organically modified silica ridges containing organic dyes are demonstrated. The mold consists of a micro channel-filled elastomeric master in contact with a glass substrate. Liquid sols fill the mold as a result of capillary action. A reservoir-channel system in the mold allows simultaneous casting of sols with different chemical compositions. After gelation, the elastomeric master is removed and sol-gel structures are left on the substrate. Cross-sectional dimensions of the ridges range from one to tens of micrometers, and can be centimeters in length. Because of the mild processing conditions, the method is especially attractive for solgel materials containing sensitive molecules such as indicator dyes and biomolecules. The technique holds promise for microfabricated sensor and integrated optics applications.
Optical Waveguiding (Pb, La)(Zr,Ti)O3 Thin Films Prepared by Pulsed Laser Deposition
Authors: Xiong S. B. , Liu Z. G. , Chen X. Y. , Guo X. L. , Yu T. , Zhu S. N. , Liu X. , Luo W. G. 
Published: June 2019

AbstractThe ferroelectric (Pb, La) (Zr,Ti)03 (PLZT(9.4/65/35)) optical waveguiding thin films have been prepared on SiO2 coated Si and on silica glass substrates by pulsed laser deposition. X-ray θ–2θ scans revealed that the films are single-phase pseudo-cubic perovskite. The surface chemical composition of the as grown films were determined by XPS. The ferroelectric properties of the films as grown on Pt/Ti coated silicon were demonstrated by using a modified Sawyer-Tower circuit, and the optical waveguiding properties of the films were characterized by using a rutile prism coupling method. The as grown films have an average transmittance of 80% in the wavelength range of 400˜2000nm and a refractive index of 2.2 at 632.8mn close to the bulk PLZT. The distinct m-lines of the guided TM and TE modes of the films as grown on SiO2 coated Si substrates have been observed.
A Low Temperature Direct Bonding Method Using an Electron-Beam Evaporated Silicon-Oxide Interlayer
Authors: Park H. W. , Ju B. K. , Lee Y. H. , Park J. H. , Lee N. Y. , Koh K. H. , Shin D. K. , Kang I. B. , Samaan N. , Haskard M. R. , Oh M. H. 
Published: June 2019

AbstractIn this work, we proposed a direct bonding method using interlayers for single crystalline silicon wafers and glass wafers. Various materials were used for interlayers of thermal oxide, sputtered nitride, electron-beam(E-beam) evaporated silicon oxide and molybdenum. After hydrophilization, samples were spin dried and mated together without external forces. Three types of solutions were used for hydrophilizing the samples. Changes of average surface roughness after hydrophilization of the single crystalline silicon wafer, thermal oxide and E-beam silicon-oxide were inspected using atomic force microscope(AFM). Bonding interfaces of the bonded pairs were observed by scanning electron microscope(SEM). Voids and non-contact areas of the bonding pairs were also inspected using infrared(IR) transmission microscope. Surface energy, tensile strength measurements and breaking tests were also done.
Micro-Raman Study of Stress Distribution and Thermal Relaxation of Oxidized Silicon Membranes
Authors: Malhaire C. , Guyot Y. , Berre M. Le , Champagnonn B. , Sibai A. , Barbier D. 
Published: June 2019

AbstractComposite SiO2/Si membranes are used in various type of sensors among them, resonant and pressure sensors. However due to a large thermal mismatch, residual induced stresses may affect the devices long term reliability especially for thin membranes (˜5 μm). In this study, we have characterized test structures consisting of SiO2/Si membranes with respective thickness ratio between 2 and 10. Micro-Raman Spectroscopy, well known to be an accurate, non destructive method to determine residual stresses in microelectronic devices, has shown to be a powerful testing technique to measure local stresses on micromachined structures such as membranes, with a high spatial (10 μm2 ) and stress resolution (8 MPa). At room temperature, Raman line (520 cm−1) shifts between 0.05 and 1 cm−1 are observed. Highest frequency shifts of 1cm−1 corresponds to a 230 MPa biaxial stress. Finite Element analysis (ANSYS) was used to model the thermal stress distribution over the micromachined bilayer membrane, yielding a satisfactorily agreement with the experimental results over a large membrane area. The Finite Element analysis was correlated with optical profilometer deflection measurements. Membrane deflections up to 48 μm (more than 10 times the membrane thickness) have been measured. Furthermore, Micro-Raman Spectroscopy results up to 300°C are shown and related to temperature dependent deflection measurements.
Mechanical Behavior of a Mems Acoustic Emission Sensor
Authors: Bahr D. F. , Wright J. S. , Francis L. F. , Moody N. R. , Gerberich W. W. 
Published: June 2019

AbstractThe elastic modulus and hardness of materials used in a MEMS acoustic emission sensor were determined using nanoindentation techniques. In addition to testing each individual material, the behavior of four candidate bottom electrode structures, two based on nitride layers and two based on oxide layers, have been evaluated. The multilayer nitride bottom electrode is relatively unaffected by a 950 °C annealing step; however, some evidence of second phase formation in the polycrystalline silicon layer has been observed. Increasing the thickness of the thermally grown silicon dioxide in the oxide based electrodes lowers the measured hardness of the top layer of platinum while increasing the measured modulus of the entire electrode at depths corresponding to the oxide film. Errors of up to 25% in the calculated area of indentation based on the indenter shape function occur for indentations which penetrate both the platinum and oxide films.
Development of a Micromirror Using Piezoelectric Excited and Actuated Structures
Authors: Maeda R. , Lee C. , Schroth A. 
Published: June 2019

AbstractThe design and fabrication process of a micro-mirror device is presented. The device is driven by sol-gel deposited PZT-layer actuators. The mirror is designed to be able to carry out scanning in two lateral directions, and additionally movement in vertical direction using a FEMsimulation tool. The established fabrication process is described.
Piezoelectric Force Sensing Pb(Zr,Ti)O3 Microcantilever Array for Multiprobe Scanning Force Microscopy
Authors: Itoh T. , Lee C. , Chu J. , Suga T. 
Published: June 2019

AbstractThis paper reports on a multiprobe scanning force microscope (SFM) utilizing an array of individually controlled piezoelectric Pb(Zr,Ti)O3 (PZT) microcantilevers. Each cantilever is unimorph beam including a sol-gel derived PZT thin film that has high piezoelectric constants in comparison with sputtered ZnO films. The cantilever is excited and actuated in z direction by applying ac and feedback dc voltages to the PZT layer. The variation of vibration amplitude is detected by measuring the change of current through the PZT layer. The 200-μm-long PZT microcantilever with the natural resonance frequency of 63.8 kHz has the high actuation sensitivity of 150 nmN and the maximum range of more than 1.5 μm. By actuating the self-excited cantilever to keep the current constant, we have succeeded in independent dynamic operation without z feedback actuation of the sample-side scanner. We have obtained independent parallel 2 × 1 images using two cantilevers of the array.