bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of Lime and Microstructural Development In Fly Ash-Portland Cement Systems
Authors: Larbi Joseph A. , Bijen Jan M. 
Published: March 2011

AbstractThe evolution and distribution of calcium hydroxide, CH, and the development of microstructure during the hydration of three low-calcium fly ash-Portland cement blends with water-solids ratio (w/s) of 0.40 have been investigated. During the first month of hydration, the CH content of the blends was found to be relatively higher than the plain mix, if a dilution effect due to replacement of cement by an inert material is taken into account. After 28 days of hydration the CH content in the blends began to decrease. SEM observations of specimens revealed the occurrence of large, well-crystallized CH plates in intimate contact with some of the fly ash particles at younger ages and even after six months of aging. The study also showed that the chemistry of the pore solution in contact with the hydrating cement system and the characteristics of the fly ashes, such as the glass content and the fineness of the ash particles seem to exert major influences on the rate of evolution of CH in the fly ash blends. Semi-quantitative X-ray diffraction analyses performed on specimens cast against polypropylene plastic plates used to “model coarse aggregates” showed reduction in the thickness of the interfacial zone for the fly ash-Portland cement pastes from about 60μm to less than 15μm within one month of hydration. In the case of the plain Portland cement paste no significant change was observed. The degree of orientation of CH crystals within the interfacial region also was significantly affected by the fly ashes, although by this age of hydration the CH data showed little or no evidence of pozzolanic reaction.
The Effect on Cement Mortar and Concrete by Admixture of Spray Drying Absorption Products
Authors: Jeppesen Kirsten G. 
Published: March 2011

AbstractSpray dried absorption products (SDA) having special characteristics are used as substitutes for cement in the preparation of mortars; the qualities of the resulting mixed mortars are described. Conditions are described for mortar mixes, data for which were presented at the MRS Fall Meeting 1987.The influence of the composition of the SDA on water requirement and setting time has been studied. A full scale project involving 3 precast, reinforced concrete front-elements containing 20 and 30 wt.% SDA is described. Strength development, mineralogical composition and corrosion were monitored for two years.A non-standard freeze-thaw experiment was performed which compares mortars containing SDA and fly ash (FA) and also shows the effect of superplasticizer.The possibility of improving the SDA by grinding has been tested and a limited improvement has been found. The strength of the mixed mortars seems slightly influenced by the grain size of SDAGypsum (CaSO4·2H2O), synthetic calcium-sulphite (CaSO3·½H2O) and 2 SDAs have been used as retarders for cement clinker. Mortar test prisms have been cast and comparative strengths after curing for 3 years are reported
Oxyanion Substituted Ettringites: Synthesis and Characterization; and their Potential Role In Immobilization of As, B, Cr, Se and V
Authors: Kumarathasan Premkumari , McCarthy Gregory J. , Hassett David J. , Pflughoeft-Hassett Debra F. 
Published: March 2011

AbstractLong-term batch leaching studies of composites of lignite combustion and gasification ashes with a calcium-based scrubber waste have shown the prominent formation of an ettringite structure phase, accompanied by reductions in solution concentrations of potentially hazardous elements such as boron and selenium. The possibility that oxyanions such as arsenate, borate, chromate, molybdate, selenate and vanadate might substitute for sulfate in the ettringite structure has been explored. There are literature reports of fully substituted borate, chromate and selenate [ettringites]*, and of two minerals with partial borate for sulfate substitution. X-ray diffraction phase pure products with chromate and selenate, substituted completely for the sulfate in ettringite, and with arsenate, borate and vanadate partially substituted for sulfate, have been synthesized at room temperature by mixing soluble Ca, Al and sulfate sources and maintaining a pH> 12 with NaOH additions. Attempts to substitute substantial amount of molybdate for sulfate were unsuccessful. The resulting phases were characterized chemically by ICAP spectrometry, ion chromatography and thermal analysis, and for phase purity and unit cell size by XRD. The speciation of the oxyanions in the substituted [ettringite] were confirmed by FTIR spectrometry. In solid solutions, the sulfate/oxyanion ratio was greater in the precipitated solid than in the synthesis solution. Chemical analyses of the [ettringites] did not give simple stoichiometries analogous to Ca6Al2(SO4)(OH)12 ·26H2O. Because nonstoichiometry can be attributed to numerous possibilities for charge balance and defects, structural formulae of the oxyanion substituted [ettringites] could not be established.
Indentation Fracture of Macro-Defect-Free (MDF) Cements
Authors: Chou Yeong-Shyung , Mecholsky J. J. , Silsbee M. R. , Roy D. M , Adair J. H. , Heiland P. 
Published: March 2011

AbstractThe fracture toughness of MDF (macro-defect-free) cement with different polymer contents has been investigated by the indentation-strength method and fracture surface analysis. It was found that the fracture toughness obtained by these two different techniques showed good agreement for the low (3 wt.%) polymer cement. The ultimate (apparent) toughnesses are 1.3 Mpam1/2 for low polymer content and 2.2 Mpam1/2 for high (8 wt.%) polymer content cement. Different microcracking and sponge-like microstructures have been observed and discussed.
A View Of Macro-Defect-Free (MDF) Pastes
Authors: Silsbee M. R. , Roy D. M. , Perez-Pena M. 
Published: March 2011

AbstractThe automated analysis of backscattered SEM images from polished surfaces of macro-defect-free cements based on ordinary portland cements is examined. A comparison of several techniques for the determination of pore size distributions in these materials is made.
Characterization and Cementitious Behavior of a Rhone-Poulenc Reactive Alumina
Authors: Agrawal Dinesh K. , Silsbee M. R. , Roy D. M. , Roy R. 
Published: March 2011

AbstractHighly reactive alumina (from Rhone-Poulenc), which is x-ray amorphous, offers a great potential as a new Al-source precursor for forming low-temperature chemically bonded ceramics. This alumina has been characterized for the first time. Its thermal behavior, structure, morphology, and hydration behavior have been determined using XRD, TGA, DTA, SEM, and TEM, and the data are compared with those of other conventional aluminas and precursors such as α-Al2O3, gibbsite, and boehmite.
The Hydration and Calcination Mechanism of Calcium Aluminate-Based Ultra-High Strength Cement with Calcium Sulphoaluminate Compound
Authors: Mino Iwao , Sakai Etsuo , Nishioka Asaaki , Daimon Masaki 
Published: March 2011

AbstractThe hardening shrinkage of calcium aluminate based ultra-high strength cement becomes nearly zero by using calcium sulphoaluminate compound, and very high bending strength can be obtained by calcinating at 300°-600°C. The starting materials are calcium aluminate, silica fume, calcium sulphoaluminate compound and superplasticizer, and the water-to-power ratio is 0.15–0.25. The main hydration products are C3AH6, AH3, C-S-H and ettringite, forming a densely packed structure, together with a large amount of unreacted cement particles. The hardening shrinkage is remarkably reduced, because of the ettringite formation in the early stage. The bending strength is about 55 MPa when calcined at 600°C. C12A7 is identified by XRD; needle-shaped skeletons of ettringite crystals are observed by SEM. It is suggested that chemically bonding substances are C12A7, amorphous A12O3, and C-S-H in calcined calcium aluminate based DSP with ettringite.
A Study of Low Porosity Polymerized β-C2S Paste
Authors: Ping Lu , Jing Zhao , Wei Shen 
Published: March 2011

AbstractIn this paper an active β-C2S was used to prepare compacted and polymerized pastes with low porosity. X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and tri-methy silanation-gel permeation chromatography (TMS-GPC) techniques were used to characterize the microstructure of the pastes both before and after additions of inorganic complexing ions, Fe2+and Ni2+, and organic silane VTES.The results indicate that both inorganic complexing ions and organic silane can play a role in the polymerization of the native silicate anions in the cement pastes. These materials lead to a distinct increase of pentamer, octamer, and polymer components in the pastes, resulting in a decrease in the average C/S ratio in the C-S-H phase. The samples obtained from this processing have very high mechanical strengths, up to a compressive strength of 316 MPa, and fracture surface energy of 43 J/m2.
Mechanical Properties of Silica Coatings
Authors: Cornett Kenneth D. , Fabes B. D. , Oliver W. C. 
Published: March 2011

ABSTRACTSilica coatings with as-deposited densities ranging from approximately 50-100% were deposited on sapphire substrates by electron beam evaporation and sol-gel techniques. The shrinkage, hardness, and etch rates of the coatings were measured after various heat treatments. Differences in shrinkage indicated that hardness was not controlled by bulk porosity alone. Most films exhibited a surface “crust” that was significantly harder, and etched more slowly than the interior of the sample. We propose that the differences in mechanical and chemical behavior are caused by Si-O network reorganization starting at the film/air interface.
Mechanical Properties of Thin Film Aluminum Fibers: Grain Size Effects
Authors: Steinwall James E. , Johnson H. H. 
Published: March 2011

ABSTRACTThin film aluminum fibers with grain sizes of 35 and 100 nm were pulled in a microtensile tester. The larger grains led to greater yield and tensile strengths but smaller strains to failure. Both samples had mechanical strengths 3–6 times greater than bulk aluminum. In addition, the small grained fibers had a strain rate sensitivity exponent of 0.26 suggesting diffusion controlled plastic deformation mechanisms.
Microscratci I Test on Carbon Films as Thin as 20 nm
Authors: Wu T. W. , shull A. L. , Lin J. 
Published: March 2011

ABSTRACTThe capabilities to monitor tangential force and acoustic emission have been added to the microscratch mode of the IBM microindenter. These two new monitoring devices combined with the existing normal loadcell enhance the ability of the microscratch test to measure mechanical properties of thin film materials. As a demonstration of the upgraded microindenter, scratch tests were performed on 11 0nm and 20nm thick carbon films deposited on Si <100> substrates. The scratch morphology was examined by scanning electron microscopy to correlate the mechanical data to corresponding failure mechanisms.In the case of the 110nm film, a brittle type fracture was taking place as the applied normal load exceeded a critical value. All three monitored outputs detected the first occurrence of the spallation ofthe film. In contrast to the thicker film, large scale spallation was not observed for thle 20nm film, and the acoustic emission detector did not show any significant output. An apparent friction coefficient(FR) is defined as the ratio ofthe tangential force to the normal load. FR is determined to be a useful parameter for monitoring the indenter's transition through the coating into the substrate, particularly in the case of small scale fracturing or simple ploughing through types of failure.
Ion Beam Annealing of Vapor-Deposited Carbon Film
Authors: Higuchi Kazuo , Noda Shoji , Iritani Sumiko , Ishiguro Tomoji , Kamigaito Osami 
Published: March 2011

ABSTRACTThe effects of ion implantation on microtexture of vapordeposited carbon film were studied by Raman, XRD, TEM and sheet resistivity measurements. Growth of graphitemicrocrystals in the film was found when the film was implanted at the temperature above about 500 K. while graphite-sheet in the as-deposited film was distorted when it was implanted at the temperature below 300 K. The critical temperature for the ion beam annealing was estimated to be about 350 K. Ion implantation also caused the increase of the adhesion strength of the carbon film to a substrate.
Mechanical Properties of Compositionally Modulated Au-Ni thin films using Indentation and Microbeam Deflection Techniques
Authors: Baker Shefford P. , Jankowski Alan F. , Hong Soonil , Nix William D. 
Published: March 2011

ABSTRACTThe “supermodulus effect” has been reported as an anomalous increase of as much as several hundred percent in the elastic moduli of compositionally-modulated thin metal films in a narrow range of modulation wavelength. The direct measurement of this effect has, however, been limited due to the very small dimensions of the test material. The mechanical properties of compositionally-modulated Au-Ni thin films (one of the first systems in which the supermodulus effect was reported) were studied on their substrates by indentation and microbeam-deflection techniques using a Nanoindenter. The films were fabricated by alternately sputtering Au and Ni onto [100] Si substrates for the indentation tests and onto prefabricated SiO2 cantilever beams with an initial Cr layer (for adhesion) for the beam deflection tests. All of the films have strong [111] textures and exhibit the structural characteristics of the films for which the modulus enhancement was reported. In particular, an increase in the average lattice parameter normal to the plane of the film over a narrow range of modulation wavelengths near 2 nm was noted. The modulation wavelengths range from 0.8 to 4.5 nm. The results from both indentation and microbeam deflection tests reveal no unusual plastic or elastic properties in these samples.
Measurement of Stresses in Thin Films Using Holographic Interferometry: Dependence on Atmospheric Conditions
Authors: Maden Michele A. , Tong Kun , Farris Richard J. 
Published: March 2011

ABSTRACTThe direct measurement of stresses in spin-coated thin films is crucial for understanding their end use capabilities. A new technique for measuring the residual biaxial curing stresses in spin coated polymer films has been developed. This technique uses holographic interferometry to observe the modes of vibration of a membrane under biaxial tension. The stress in the film can then be determined by application of the vibrating membrane equation. A great advantage of this technique is that the material constants of the film do not enter into the analysis. The only material parameter needed is the density. In thispaper, we will examine membranes of polyimide and biaxially stretched rubber and latex. It is possible, using this technique to resolve the principal stresses and directions in films with complicated stress states.
Stresses in Passivated Films
Authors: Flinn Paul A. 
Published: March 2011

ABSTRACTAlthough wafer curvature measurement provides a rapid and accurate determination of stress in a uniform thin film, the technique is not applicable to patterned films. To study the stress in metal lines, and the effect of passivation on that stress, it is necessary to use X-ray diffraction. To obtain the sensitivity and precision required, a generalized focusing diffractometer (GFD), that had been developed especially for work on thin films, was used in this study.The elastic strain tensors for aluminum and aluminum-silicon films and patterned lines were determined by X-ray diffraction. The corresponding stress tensors were calculated with the use of the known elastic constants of aluminum. The effect of various oxide and oxynitride passivations was investigated. Passivation over uniform metal films has very little effect, while passivation over patterned metal results in substantial triaxial tensile stress in the metal. Contrary to the conventional wisdom, high compressive stress in the passivation does not result in additional tensile stress in the metal. A possible explanation for the frequently observed deleterious effect (increased tendency for formation of cracks and voids) of highly compressive silicon nitride and silicon oxynitride passivations will be discussed.
Tribological and Mechanical Properties of Fe/Ti Multilayered films
Authors: Nastasi M. , Hirvonen J-P. , Jervis T. R. , Basu S. N. 
Published: March 2011

ABSTRACTA 900 Å as-deposited multilayered structure of alternating Fe and Ti on hardened tool steel has been examined for tribological and mechanical properties. The multilayer in contact with a 52100 steel ball counter surface possessed a 0.16 friction coefficient and showed good wear character after 1000 cycles in pin-on-disk experiments. Nanoindentation experiments show a 20 % increase in hardness for material in the wear track. Electron microscopy data suggests that the as-deposited bcc-Fe plus hcp-Ti multilayer composite transforms to a nanocrystalline alloy plus bcc-Fe by solid state reaction during pin-on-disk friction and wear test. The low friction observed in these surface films is attributed to the formation of a hard nanocrystalline alloy and improved interlayer and film/substrate adhesion which result during solid state reaction.
The Mechanical Properties of Cu/TiB2 Multilayer Structures
Authors: Hubbard Kevin M. , Basu S. N. , Hirvonen J-P. , Jervis T. R. , Nastasi M. 
Published: March 2011

ABSTRACTWe have investigated the hardness and tribological properties of Cu/TiB2 multilayer structures deposited on substrates of tempered martensitic steel. Films of Cu and TiB2 were also deposited as hardness standards. The wear properties of the films were found to be poor, because of lack of adhesion. However, the films do appear to have good fracture toughness. The hardness of the multilayer was 18% greater than that predicted by the law of mixtures applied to the reference standards and, when corrected for variations in substrate hardness, very nearly equal to that of the TiB2 film. Irradiation by 400 keY Ne-ions to doses of 1.0, 6.0, and 12×1015 ion/cm2 results in a slight hardening of the multilayer. The structure was found to have excellent stability against radiation damage.
Mechanical Properties of Nanocomposite Coatings Fabricated by Sputttering
Authors: Chow G. M. , Holtz R. L. , Wu C. Cm. , Edelstein A. S. , Schlesinger T. E. , Cammarata R. C. 
Published: March 2011

ABSTRACTA brief study of the microhardness of nanocomposite coatings fabricated by a new technique is reported. The new fabrication technique utilizes sputtering at high pressures in a thermal gradient to produce nanometer-size particles, which are then embedded in a matrix produced by conventional sputtering. The microstructures and microhardness of nanocomposite coatings of Al matrix reinforced by Mo particles (grain diameter ranging from 7 to 20 nm) are reported.
In Situ Study of Stresses Generated During the Formation of Cobalt Disilicide and the Effect of Post Silicide Processing
Authors: Sitaram A. R. , Kalb J. C. , Murarka S. P. 
Published: March 2011

ABSTRACTSelf aligned cobalt disilicide technology is emerging as an excellent choice for gate and interconnection and contact metallization in VLSI. The presence of an as deposited, intrinsic stress in the cobalt film and the generation of stresses during its subsequent reaction with the underlying silicon and during post silicide processing can affect the mechanical stability and the performance of the overall device structure. This study involved the in situ observation of the stresses generated in thin films of cobalt (or silicide formed on reaction) on silicon as they react during a continuously ramped and cooled temperature cycle. The results will be presented, and in the light of a well characterized reaction sequence, possible governing mechanisms will be presented and discussed.
Plasma Enhanced Chemical Vapor Deposition of Dielectric Films: Correlation of Stress to Film Structure and Plasma Characteristics
Authors: Srinivasan Radhika , Nguyen B. C. , Short A. P. 
Published: March 2011

ABSTRACTStress in dielectric films, including silicon dioxide, borosilicate glass, and silicon nitride, deposited using Plasma Enhanced Chemical Vapor Deposition have been studied. In each case the total stress was found to be strongly dependent on processing conditions. Deposition rates and film characteristics, such as refractive index, -OH content, (in the case of SiO2), total H content, Si-H and N-HI concentration (in the case of nitride), boron concentration (for BSG), have also been determined as fuctions of processing parameters. In addition, the emission spectra from the plasma itself has been studied. Correlations have been established whereever relevant.
Correlation between Processing, Composition, and Mechanical Properties of PECVD-SiN, Thin Films
Authors: Yu D. C. H. , Taylor J. A. 
Published: March 2011

ABSTRACTThe inter-relationship between plasma processing, composition, and mechanical properties of PECVD-SiNx, thin films was investigated. Results showed that by varying the gas feeding ratio of NH3/SiH4N2, one can obtain PECVD-SiNx, films of different composition and streu levels. For high stress films, the deposition rate is low, values of index of refraction and Si/N ratio are small. On the other hand, film density of such films is high; values of Young's modulus and N-H/Si-H relative bond density are large. A model which correlates film stress to that contributed by (1) lattice distortion induced by Si-H and NH bondings, (2) ion bombardment, (3) thermal mismatch between PECVD-SiNx films and silicon substrate, and (4) intrinsic stress introduced during the formation of covalent Si-N bonding is proposed and examined in this work.
Intrinsic Stress of Pecvd Silicon Oxynitride Films Deposited in a Hot-Wall Reactor
Authors: Aite K. , Koekoek R. 
Published: March 2011

ABSTRACTPlasma enhanced chemical vapor deposited ( PECVD ) silicon oxynitride films with refractive indices varying from 1.65 to 1.85 have been deposited in a hot-wall reactor using a SiH4/NH3/N2O gas mixture. A systematic investigation of the variation of the intrinsic stress of the deposited films with the parameters of deposition and the properties of the films, has been carried out. Our results show that silicon oxynitride films deposited in optimal conditions can support annealing temperatures of 900°C without cracking. The mechanical stresses in the films were determined by the Newton's fringes technique and a surface profiler. The film thickness was measured by ellipsometry at a wavelength of 632.8 nm. Fourier transform infrared spectroscopy ( FTIR ) was used to measure the hydrogen content of the films. The composition of the silicon oxynitride films was determined by Auger electron spectroscopy ( AES ) and Rutherford backscattering spectrometry ( RBS ).
Internal Stresses and Adhesion Properties of Film/Substrate Interfaces
Authors: Ignat M. , Chouaf A. , Normandon Ph. 
Published: March 2011

ABSTRACTThe evolution of internal stresses in Tungsten films deposited on Silicon substrates submitted to external stresses is discussed here. The stresses are estimated and measured by theoretical and experimental methods. The discussion of the internal stress evolution is shown to be dependent of the film/substrate interfaces, and of the loss of adhesion inducing stress relaxation.