bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contact Angle Measurement and Its Application To Sol-Gel
Processing
Authors: Stein D. J. , Maskara A. , Hæreid S. , Anderson J. , Smith D. M. 
Published: April 2011

ABSTRACTCapillary stresses during drying that result from the contact angle of a
liquid solvent to a gel, surface tension, and pore size have an immense
effect on the dried gel. The extent to which the gel shrinks is a balance
between the capillary stress and the solid matrix strength. The dynamic
contact angles and surface tensions of various solvents commonly employed in
sol-gel processing on silica gels of various surface chemistries have been
evaluated. A thin, dense coating of silica gel was formed by dip coating a
standard glass slide in an acid catalyzed silica sol and drying. Some of the
sample surfaces were organically modified. Dynamic contact angles were
determined using a modified Wilhelmy plate technique. Solvent surface
tensions were determined using the De Nouy ring technique. The bulk modulus
of wet gels were determined with a three point bend experiment. We have
found that contrary to previous investigators, who attributed different bulk
densities obtained after drying from various alcohols to contact angles
variations, gel shrinkage during drying is actually due to slightly
different surface tensions and degrees of depolymerization of the gel
network.
Grain Boundary Phase Analysis of Silicon Nitride by a Newly
Developed 300kv Field-Emission Electron Microscope
Authors: Bando Y. , Suematsu H. , Mitomo M. 
Published: April 2011

ABSTRACTThe grain boundary phase of silicon nitride containing additives
Y2O3 and Nd2O3 has been
studied by means of a newly developed 300kV field emission ATEM. The
composition of the two-grain boundary phase of about 1 nm thick is
successfully determined. It is then found that the compositions among the
grain boundaries are not the same and the additives of
Y2O3-Nd2O3 are poor in the
two-grain boundary, while they are rich in the triple points.
Liquid Crystal Templating Effects on Silica Gels Synthesized
using Quaternary Ammonium Surfactants
Authors: Dabadie T. , Ayral A. , Guizard C. , Cot L. , Robert J.C. , Poncelet O. 
Published: April 2011

ABSTRACTThe use of lyotropic liquid crystal phases is a promising tool in tailoring
the porous structure of inorganic gels. In this work, we examine the effect
of hexagonal liquid crystal phases produced with quaternary ammonium
surfactants on the textural ordering of silica gels.The sol-gel polymerization of the silicon alkoxide precursor
(tetramethoxysilane) is followed by 29Si NMR and rheological
measurements. The structural evolution of the material from the starting sol
to the thermally treated gel is studied using low angle X-ray diffraction.
The textural characteristics of the gels are correlated with the nature of
the surfactant molecules.
Stratification of Fullerenes
Authors: Levon K. , Weng D. , Mao J. , Lee H.K. 
Published: April 2011

ABSTRACTDodecylated C60 {(Do)nC60(H)n} and butylated C60 {(Bu)nC60(H)n} were synthesized. Spectroscopic and thermal methods, mass spectrometry, XPD, have been employed to characterize the products. X-ray Powder Diffraction (XPD) results reveal that the facecentered- cubic (fcc) structure of C60 expands to a primitive hexagonal structure upon butylation and to a layered structure upon dodecylation. Butylated C60 diffraction pattern has been indexed as a primitive hexagonal structure with ao = 11.5 angstroms and axial ratio = 1.169. The dodecylated C60 also shows sidechain melting behavior with a transition temperature of around 25°C. The paraffinic crystals are produced by the interdigitation of the sidechains. Butylated C60 does not show any sidechain melting.
Catalytic Growth of Carbon Nanofibers and Nanotubes
Authors: Terry R. , Baker K. , Rodriguez Nelly M. 
Published: April 2011

ABSTRACTCarbon nanofibers and nanotubes have been prepared from the decomposition of carbon containing gases with the aid of an iron catalyst particle. The physical characteristics as well as the degree of crystalline perfection of the structures were found to be dependent on the nature of the metal particle and the conditions at which the material was grown. Transmission electron microscopy revealed that nanofibers were obtained from large catalyst particles (>20 nm), whereas nanotubes were formed by the aid of smaller particles (<20 nm). The orientation of the graphitc platelets in the carbon nanofibers was dependent on the alignment of the planes at the rear faces of the iron particle that were responsible for the precipitation of carbon. Carbon nanofibers exhibited reactivity in carbon dioxide comparable to that of single crystal graphite under the same conditions.
Synthesis of Single Walled Buckytubes
Authors: Yadav Tapesh , Withers James C. , Seraphin Supapan , Wang Su , Zhou Dan 
Published: April 2011

ABSTRACTWe report here a study of alternative methods for producing single walled buckytubes. In this study, we prepared graphite electrodes packed with different metal or metal combinations. These electrodes were arced under similar conditions and the products so formed characterized with TEM. The results demonstrate that single walled tubes can be synthesized in many ways and at high yields. The results also suggest that the use of more than a single dopant may provide significant advantages in the commercial synthesis of buckytubes.
High Rate, High Quality, Diamond Synthesis by the Combustion Flame Process
Authors: Ravi K.V. , Olson D.S. , Koch C.A. 
Published: April 2011

ABSTRACTAmong the various low pressure techniques being developed for the synthesis of diamond films and bulk diamond slabs the combustion flame synthesis process has some distinct advantages. In this approach the combustion reaction between acetylene and oxygen is utilized to generate the requisite energy to activate excess acetylene in the gas mix leading to the deposition of diamond films on a temperature controlled substrate brought into contact with the flame. Other diamond synthesis approaches, such as microwave enhanced and the filament assisted chemical vapor deposition processes, and the various arc jet techniques utilize mixtures of hydrogen and methane as the process gases. Oxygen and oxidizing specie ( such as OH radicals) in the flame ambient may be much more effective than atomic hydrogen in promoting the growth of diamond over the growth of graphite and other non- diamond forms of carbon. In addition this technique enables the growth of diamond at high rates and is relatively easily scaled for large area synthesis. In this paper a discussion of this technique is presented drawing upon recent research by the authors as well as published work to present a general discussion of the issues involved in the development of this technique of low pressure diamond synthesis.
Pulsed-Laser Deposition and Characterization of Amorphous Diamondlike Carbon Films
Authors: Huai Y. , Broughton J. N. , Gat E. , Chaker M. , Borges C. F. M. , Beaudoin Y. , PÉpin H. , Moisan M. 
Published: April 2011

ABSTRACTUnhydrogenated amorphous carbon films were deposited by KrF pulsed laser ablation of graphite under a laser power density of 8×108 W/cm2. The films were characterized using x-ray reflectivity, optical transmittance, spectroscopic ellipsometry and Raman spectroscopy. The physical, optical and bonding properties of the films have been investigated in detail as functions of substrate temperatures Ts (22-300°C) and post-annealing temperatures. Films deposited at Ts, <200°C possessed diamond-like properties with mass densities p=2.8-3.1 g/cm3 and optical bandgaps Eg,=1.5-2.2 eV. Above Ts,=200°C, the films showed typical graphite characteristics. The diamond-like films annealed at temperatures up to 750°C show excellent thermal stability.
Evaluation of Graphitic Foams as Low Mass Structural Materials
Authors: Hall Richard B. , Hager Joseph W. 
Published: April 2011

ABSTRACTGraphitic foams offer exciting potential for mass savings in structures. A hypothetical family of graphitic foams having ligament mechanical properties identical to those of P120 graphite fiber is considered; the mechanical properties of the hypothetical foams are viewed as realistic upper bounds on the performance of this class of materials. Various commercially available materials are compared to the hypothetical foams for application to tension bars, beams in bending and buckling, and plates in bending and buckling.
DC-Magnetron Sputtered Silicon Carbide
Authors: Tenhover M. , Ruppel I. B. 
Published: April 2011

AbstractThe preparation and properties of relatively thick films of DC magnetron sputtered SiC films is described. The films were prepared using a new ceramic sputter target material. The new target material is called Hexoloy® SG–90. It is an electrically conductive, dense ceramic material which can be used as a sputter target to yield insulating amorphous SiC thin films on room temperature substrates.
Elastic Constant Effect on the Critical Thickness of an Epilayer
Authors: Zhang Tong-Yi 
Published: April 2011

AbstractThe effect of elastic constants on the critical thickness of an epilayer is investigated. The results indicate that the self energy of the dislocation is controlled by the soft phase between the epilayer and the substrate, while the interaction energy only depends on the elastic constants of the epilayer. It is easier for a dislocation to be formed if the substrate is softer than the epilayer, and consequently the critical thickness is smaller. On the other hand, a soft epilayer can have a large thickness without any mismatch dislocation.
Two Step Growth and Characterization of BaF2/Si(III) Heterostructures
Authors: Belenchuk A. , Fedorov A. , Lucash V. , Vasilyev A. , Zenchenco V. 
Published: April 2011

AbstractThe influence of growth conditions on structural perfections and epitaxial relation in BaF2 films on Si(111) are considered. It is shown that rotational-twin-free BaF2 films (A-type orientation) can be grown on Si(111) by two step growth method. It is also shown that a mixed (A+B)-type orientation, which usually observed in BaF2 films grown by conventional one step growth method, can be converted into A-type orientation by postgrowth annealing. The correlation between type of epitaxial orientation in BaF2 films and structures of interface is discussed.
Principal Residual Strains as A function of Depth for Sputter Deposited Mo Thin Films
Authors: Malhotra S. G. , Rek Z. U. , Parfitt L. J. , Yalisove S. M. , Bilello J. C. 
Published: April 2011

AbstractTraditionally, the magnitude of the stress in a thin film is obtained by measuring the curvature of the film-substrate couple; however, these techniques all measure the average stress throughout the film thickness. On a microscopic level, the details of the strain distribution as a function of depth through the thickness of the film can have important consequences in governing film quality and ultimate morphology. A new method for determining the magnitude of principal strains (strain eigenvalues) as a function of x-ray penetration depth using grazing incidence x-ray scattering for a polycrystalline thin film will be described. Results are reported for two Mo metallizations ˜ 500 Å and ˜1000 Å thick sputtered onto Si {100} substrates. The magnitude of the principal strains at several penetration depths was accomplished by an analysis of the diffraction peak shifts of at least six independent {hkl} scattering vectors from the Mo thin films. An out-of-plane strain gradient was identified in both Mo films and the strain eigenvalues were found to be anisotropic in nature. This new methodology should work with a variety of thin films and hence would provide quantitative insight into the evolution of thin film microstructure.
Yield Point Phenomena and Dislocation Velocities Underneath Indentations Into BCC Crystals
Authors: Gerberich W. W. , Venkataraman S. , Nelson J. , Huang H. , Lilleodden E. , Bonin W. 
Published: April 2011

AbstractIn a single material, hardnesses can range from 3σys up to the theoretical strength or approximately E/10 where σys and E are tensile yield strength and modulus. This variation results with decreasing depth of penetration. Such indentation size effects may be associated with surface contamination, passivation films and dislocation phenomena. Even where dislocation nucleation is relatively difficult as in GaAs, the hardness varies from about 1.5 to 15 GPa as the indentation depth decreased from about 100 nm to 10 nm. Similar size effects in BCC metals can give hardnesses which range from about 1 to 30 GPa as the indentations decrease from 1000 nm to 10 nm. Here, there are two types of “yield” phenomena which can be related to an organic contamination film and a dislocation pile-up induced oxide film fracture. As measured in single crystals of Fe, Mo, W, Ta and NiAl, this typically gives lower and upper “yield” points which range from 0.6 to 10 raN. When a dislocation pile-up breaks through the oxide film, velocities can be reasonably large due to the stress at the head of the pile-up. The average dislocation velocity of this avalanche is controlled, to first order, by the Peierls’ energy. A more exhaustive study of NiAl, with a B2/BCC type crystal structure shows that dislocation velocity can be related to the local pile-up stress and a Peierls’ barrier of about 2.2 eV.
An Explanation for the Shape of Nanoindentation Unloading Curves based on Finite Element Simulation
Authors: Bolshakov A. , Oliver W.C. , Pharr G.M. 
Published: April 2011

AbstractCurrent methods for measuring hardness and modulus from nanoindentation load-displacement data are based on Sneddon's equations for the indentation of an elastic half-space by an axially symmetric rigid punch. Recent experiments have shown that nanoindentation unloading data are distinctly curved in a manner which is not consistent with either the flat punch or the conical indenter geometries frequently used in modeling, but are more closely approximated by a parabola of revolution. Finite element simulations for conical indentation of an elastic-plastic material are presented which corroborate the experimental observations, and from which a simple explanation for the shape of the unloading curve is derived. The explanation is based on the concept of an effective indenter shape whose geometry is determined by the shape of the plastic hardness impression formed during indentation.
The Indentation Elastic Response - Indentation Shape and the Stress Distribution
Authors: Hendrix B. C. , Xu Ke-Wei , Liu Jun-Hai , He Jia-Wen 
Published: April 2011

AbstractThe unloading of an indentation provides information about the shape of the indentation and the elastic properties of the materials. The assumptions of axisymmetry and material isotropy are critically examined, and a model for transversely isotropic materials is compared to measurements on single crystals. The methods used to infer the area of the indentation from the unloading curve are examined. The area is a fundamental value for the determination of hardness, modulus, and other mechanical properties in the so-called nano-indentor and other continuously monitored indentor techniques. The models of elastic recovery which are currently used are found to lack the flexibility to model the parameters which determine indentation depth. If the current self-consistent model is extended to cover the important aspects of the unloading, the area of the indentation is still not determined uniquely. Guidelines for further development of a unique model are suggested.
Mechanical Properties and Wear Resistance of High Moment thin Film Head Materials
Authors: Deng H. , Inturi V. R. , Barnard J. A. 
Published: April 2011

AbstractMechanical and tribological properties of soft magnetic thin films with high permeability and low coercivity are very important for the application of these films in high-density recording heads. This paper reports our experimental observations on these important properties of FeTaN thin film head materials. Hardness(H) and Young’s modulus(E) for FeTaN sputtered films were determined by nanoindentation. Wear resistance of these films against commercial magnetic tapes was measured with a sphere-on-flat wear tester. The experimental results indicate that the FeTa films can be hardened when nitrogen is introduced. It was found in this study that the thermal stability of the mechanical properties such as hardness of thin films containing nitrogen is better than that of the film without nitrogen. However, our experiments also revealed that the wear resistance of FeTaN films decreases when the concentration of nitrogen increases and the hardness of the worn surface at a wear scar is lower than that of the unworn surface.
Measurement of Friction Coefficients Between Diamond-Like Carbon Coated VCR Head Drum And VCR Tapes
Authors: Lee Kwang-Ryeol , Eun Kwang Yong 
Published: April 2011

AbstractIn order to characterize friction and wear behavior between cylindrical specimens and flexible counterface materials such as magnetic tape, a tribometer is suggested. The tribometer is used to investigate the behavior between video cassette recorder (VCR) head drums and VCR tapes. Friction coefficients of uncoated and diamond-like carbon (DLC) film coated head drums of Al alloy are compared before and after a wear test. Before the wear test, an uncoated head drum shows friction coefficients ranging from 0.22 to 0.3 as the applied tension increases from 200 to 600 gf at the sliding speed of 0.16 m/s. The friction coefficients of DLC coated head drum are 14 to 30 % lower than those of uncoated head drums. At the sliding speed of 4.9 m/s, the friction coefficients of both uncoated and DLC coated drums are reduced to less than 0.1. After the wear test, however, the friction coefficients of uncoated head drums increase to the range from 0.3 and 0.47 depending on the applied tensions. Furthermore, the friction coefficients are not reduced even at the high sliding speed of 4.9 m/s. DLC coated head drums, on the other hand, exhibit similar friction coefficients to those before the wear test. Degradation of frictional property in the uncoated head drum is discussed in terms of the surface damages mainly due to magnetic metal oxide particles transferred from VCR tapes. This result shows that the DLC coating of VCR head drum can improve the friction and wear properties. It is also observed that the DLC coating can reduce the damage of VCR tapes.
Micro-Tribological Study of Cobalt Alloys with and Without a Carbon Coating
Authors: Wang Hsin-Fu , Nelson John C. , Gerberich William W. 
Published: April 2011

AbstractContinuous microscratch tests on an uncoated and a diamond-like carbon coated CoCrMo alloy were performed in air to evaluate the micro-friction and micro-tribology by utilizing a load and depth sensing instrument. By using a diamond-like carbon coating, the friction coefficient for a small applied load was found to decrease compared to the CoCrMo substrate. The hard diamond-like carbon coating prevents the local plastic yielding of the micro-contacts and the adhesion between the metal/metal surfaces during the microscratch tests. However, the effect of the diamond-like carbon coating on the friction was not seen when the applied load is high.
Modeling of Thermal Stresses in Composite Diamond Coatings and Mechanisms of Improvement of Adhesion
Authors: Fan W. D. , Jagannadham K. , Narayan J. 
Published: April 2011

AbstractThermal stress influences adhesion of many coatings applied on tool substrates. Management of thermal stresses is important for improvement of coatings and tool life. We have shown that stresses can be controlled by developing a composite layer of diamond with carbides and nitrides such as TiC or TiN. We have modeled the thermal stresses in these composite diamond coatings using finite element analysis. The composite diamond coatings consist of a discontinuous layer of diamond with an embedded layer of TiC or TiN, and a top layer of continuous diamond. For comparison, a single layer of diamond coating has also been used. The thermal stresses in these coatings on WC(Co) and Si3N4 tool substrates were calculated. Results show that the thermal stresses at the interface between the coatings and the substrate are relaxed after introducing the composite layers. This stress relaxation is responsible for the improvement of the adhesion of composite coatings.
Fracture behavior in Amorphous and Ceramic Coatings on Aluminum Alloy Substrate
Authors: Kameda J. , Ranjan R. 
Published: April 2011

AbstractFracture behavior in Ni-10 wt.%P amorphous (10 µm thick) and overlay Y2O3 stabilized ZrO2 (0-1.0 µm thick) ceramic coatings on Al alloy substrates has been investigated using small punch (SP) testing and acoustic emission (AE) techniques. SP tests showed that coating cracks extensively propagate along both the radial and tangential directions under the biaxial stress condition. The formation of cracks was more profoundly found in Ni-P amorphous coatings than in amorphous/ceramic coatings. The cumulative AE events were well correlated with the severity of coating cracking independent of the type of coatings. Ceramic coatings with a thickness of 0.25 and 1.0 µm led to a decrease in the fracture toughness by 15–20%, compared with a uncoated alloy. The coating effect on the fracture toughness is discussed in light of residual stresses induced during coating processing and the presence of coating cracks.
Evaluation of Diamond-Like Carbon as a Protective Coating for Holographic Filters
Authors: Yip Pearl W. , Dehmer Peter G. 
Published: April 2011

AbstractDiamond-like carbon (DLC), a hard, optically transparent, and chemically inert material, is becoming increasingly important for many applications. With the development of low-temperature deposition techniques, DLC can now be applied to many heat-sensitive polymers. This paper will discuss the application of a DLC coating as an abrasion and moisture barrier for three different laser-protective holographic filters. The objective of this investigation is to study the influence of the coating process on the holographic filters, and to determine the effectiveness of the DLC coating as the environmental seal for these filters. The DLC coated filters were characterized by UV/visible spectroscopy, scanning electron microscopy, before and after exposure in an environmental chamber set at 71°C, and 90% humidity. The structure and hardness of the DLC coating were evaluated respectively by Raman spectroscopy and nanoindentation method.
Measuring Methods for High–Power Characteristics of Piezoelectric Materials
Authors: Hirose Seiji , Takahashi Sadayuki , Uchino Kenji , Aoyagi Manabu , Tomikawa Yoshiro 
Published: April 2011

AbstractTwo kinds of measuring method of the high-power characteristics of piezoelectric transducers are described. One is the measurement method at the resonance frequency and another is the measurement method at the antiresonance frequency. The vibrational velocity dependences of the equivalent circuit constants and the temperature rise were measured by using each measurement method under the constant vibrational velocity control. These results are useful for designing the ultrasonic power devices such as the ultrasonic motor, and also useful for investigating the new advanced piezoelectric materials for high power use. Especially, by using the results obtained at the antiresonance frequency, a stable state driving method, named as antiresonance driving, with high-efficiency and low-temperature rise can be achieved.