bluuebunny/crossref_metadata_2025_split huggingface dataset:
Instability of Superplastic Aluminium Alloys
Authors: Iwasaki H. , Hayami S. , Higashi K. , Tanimura S. 
Published: March 2011

ABSTRACTThe influence of the strain hardening coefficient,γ,and the strain rate sensitivity exponent, m, on the onset and growth of necking has been pointed out in many models about plastic instability controlled by the mechanical properties of materials. In this paper, the instability parameter I (=(l-γ-m)/m) proposed by Hart is used to relate the values of m (=∂lnσ/∂lnέ) and γ (=∂σ/(σ·∂ε)) for some superplastic aluminium alloys. These values of m and γ were calculated from the load-elongation curve at various strain-rates in constant strain-rate tests with periodic m determinations by strain-rate departures of small magnitude. It will be shown that the strain hardening due to grain growth contributes to an increase in the stability of plastic deformation during superplastic flow. However the decrease of m due to dynamic grain growth with strain causes superplastic deformation to be unstable near the onset of fracture. The transition of I values from negative to positive coincides with a decrease in m value and flow stress.It is concluded that the development of necks can be characterized by an instability parameter I which include the effect of strain hardening caused by strain induced grain growth.
Effect of Hydrogen on the Superplastic Behavior of Ti-6Al-4V Alloy
Authors: Gong B. , Zeang C. B. , Lai Z. H. , Xu Z. S. 
Published: March 2011

ABSTRACTThe superplastic behaviour of Ti-6Al-4V alloy containing various amounts of hydrogen (0.07 ∼ 0.33wt%) has been investigated by tensile tests at temperatures of 800 ∼ 950°C. Results show that the solution of hydrogen in the alloy helps to reduce the flow stress with strain rate in the range of 1.67 ×10−4 ∼ 1.67×10−2 s−1 and makes the temperature of superplastlc deformation become Lower (810∼870°C). Nevertheless, it also causes a decrease of the strain rate sensitivity exponent and tensileelongation, However, by a suitable alloying with hydrogen (∼ 0.1wt%), the alloy can be made to undergo superplastlc deformation at a rather tow temperature (840°C) with an acceptable loss of superptastic ductility.
Fatigue Properties of SPF/DB Joints in 7475 Aluminum Alloy and Ti-6A1-4V Alloy
Authors: Mutoh Yoshiharu , Kobayashi Masaru , Tatemura Makoto , Yoshida Hideo 
Published: March 2011

ABSTRACTBonding strength and fatigue strength tests of SPF/DB joints in 7475 aluminum alloy and Ti-6Al-4V alloy were carried out. Their strengths of the joints using cryogenic rolled sheet were higher than those using conventional cold rolled sheet. Surface finish for removing oxide film was essential to obtain high-quality bond in aluminum alloy.
Superplastic Deformation Mechanisms in a Fine-Grained, Yttria-stabilized Tetragonal Zirconia Polycrystal (Y-TZP)
Authors: Nieh T. G. , Wadsworth J. 
Published: March 2011

ABSTRACTConcurrent grain growth, and in particular, dynamic grain growth, was observed to take place during superplastic deformation of Y-TZP. As a result of this concurrent grain growth, the measured strain rate sensitivity was found to be lower than that measured under constantstructure conditions. In the present paper, data obtained from the superplastic deformation of YTZP under constant-structure conditions are presented. It is demonstrated that the strain rate sensitivity values are generally higher than 0.5, when measured from the grain size-compensated data; this result suggests a grain boundary sliding mechanism. Microstructures from samples prior to and after superplastic deformation reveal grains which are essentially equiaxed; this observation is also consistent with a grain boundary sliding mechanism. Both high-resolution images of grain boundary triple points using transmission electron microscopy, and fracture surface studies using Auger electron spectroscopy and X-ray photoelectron spectroscopy indicate that there is no evidence for the presence of glassy phases at grain boundaries in Y-TZP.
Fractal Characterization of Cavity Shape Changes During Superplastic Deformation of High Strength Aluminium Alloy 7475
Authors: Xinggang Jiang , Jianzhong Cui , Longxiang Ma 
Published: March 2011

ABSTRACTThe fractal dimensions of cavities during superplastic deformation of high strength aluminium alloy 7475 were measured with different strain, temperature, strain rate, and grain size. The results show that the fractal dimension of cavities increases with the increase of strain. Deformation under lower temperature, higher strain rates, or for larger grain sizes corresponds to higher fractal dimensions of cavities. The higher the fractal dimension of cavities, the more complex the cavities' shapes and the more possible it is for the specimen to rupture.
Superplasticity in P/M Aluminium Alloys
Authors: Higashi K. , Tanimura S. , Ito T. 
Published: March 2011

ABSTRACTRecent advances in the technologies of powder metallurgy lead to the development of some superplastic aluminium alloys containing a deliberate addition of a large amount of Zr and /or Cr and Mn that exhibit the high strain rates superplasticity. For a few alloy systems, the large elongation more than 500% has been observed over the strain rates of 1×10−1s−1, which rates are two or three orders of magnitude faster than those at which superplasticity is found in conventional superplastic aluminium alloys produced by ingot metallurgy. The high strain-rates superplasticity obtained in both type of fully static recrystallized and dynamic recrystallized P/M aluminium alloys. The decreasing of initial size of grains and/or sub-grains leads to the increasing the strain-rates for superplastic flow in both types of alloys. The refinement of grains or sub-grains size is one of necessary and important to obtain the high strain-rates superplasticity.
An Experimental Study of Cavity Nucleation During Superplastic Deformation
Authors: Xinggang Jiang , Jianzhong Cui , Longxiang Ma 
Published: March 2011

ABSTRACTCavity nucleation during superplastic deformation of a high strength aluminium alloy has been studied using a high voltage electron microscope and an optical microscope. The results show that cavities nucleation is due only to superplastic deformation and not to pre-existing microvoids which may be introduced during thermomechanical processing. The main reason for cavity nucleation is the high stress concentration at discontinuties in the plane of the grain boundary due to grain boundary sliding.
Fibre Quality Factors in Papermaking — II The Importance of Fibre Coarseness
Authors: Seth R.S. 
Published: March 2011

ABSTRACTThe effects of fibre coarseness on the papermaking properties of softwood pulps have been demonstrated. While reducing fibre length or strength reduces mainly sheet strength, changes in fibre coarseness influence virtually all pulp properties — drainage, wet-web strength, and the structural, strength, and optical properties of the dry sheets. The effects are large, and are explained on the basis that coarser fibres have thicker walls, are fewer per unit pulp mass, and have smaller specific surface area. Implications for the quality of market chemical pulps are discussed.
Dependence of Fiber/Fiber Bonding on Some Papermaking Variables
Authors: Stratton Robert A. , Colson Norman L. 
Published: March 2011

ABSTRACTThe bond breaking load and bonded area of individual fiber/fiber bonds were measured using a new fiber load elongation recorder (FLER2) and Page's polarized light scattering technique, respectively. Lightly (570 mL CSF) and moderately (345 mL CSF) refined fibers with fines subsequently removed produced bonds of equal strength. Bonds between latewood fibers were substantially stronger than those between earlywood fibers. Polymeric strength aids interacting with the fibers by either covalent or ionic bonding increased the bond strength by a factor of two.
Model Study of Paper Elasticity and Drying Restraints
Authors: Niskanen Kaarlo J. 
Published: March 2011

ABSTRACTExperiments on laboratory paper sheets have indicated that under certain conditions the elastic modulus is inversely proportional to both the drying shrinkage and dimensional stability. Thus it appears that the elastic response of paper to mechanically and hygroscopically induced stresses is determined by the drying strain or shrinkage of the sheet. It is not clear, however, what effect the geometry of paper network and the properties of papermaking fibers have on the relationship between paper elasticity and drying restraints.We have developed a model for the study of the elastic properties of paper as a function of the drying shrinkage. The model is based on the assumption that there exists a unique relationship between the elastic properties and dried-in compression of fiber. As a consequence, the elastic properties of a fiber depend on its orientation relative to the principal axes of the paper sheet.The qualitative features obtained from the model calculations are consistent with experimental observations and independent of details of the elastic properties of fiber. It is clearly shown that no unique relationship exists between the drying strain and elastic modulus of the paper sheet. However, to a reasonable accuracy certain simple relatioships do exist that appear to be of general validity.
Paper Making Furnish as a Composite Blend. Some Wet End Interactions among Furnish Ingredients
Authors: Marton Joseph 
Published: March 2011

ABSTRACTC.A. Hogart defined paper as “a random bonded fibrous network carrying filler material“. A few thoughts related to this definition and pertaining to paper composites are presented.A typical papermaking furnish consists of a blend of cellulosic fibers and fines, inorganic fillers and additives. Composition varies according to end use requirements. The fiber network secures desired mechanical and strength properties, fillers contribute to esthetics and good optics. Filler retention is improved by using retention aids. Strength-loss due to filler, use is compensated for, by applying strength additives.Additives applied at the wet end interact with furnish components. The surface charge, accessible surface area and composition play a role in the interactions. Some typical interactions, involving cationic starch and polyacrylamide, are discussed.
A Mechanism for the Formation of Paper from a Heterogeneous Fiber-Water Mix
Authors: Gess J. M. 
Published: March 2011

ABSTRACTStudies are presented showing that formation of a sheet of paper from a heterogeneous mix of cellulose fibers and water at the forming section of a paper machine is a three-part process.The studies were carried out using the Weyerhaeuser-developed G/W Drainage/Retention System of following the forming portion of the papermaking process and is a summary of work carried out over a five-year period of time.
Polyaluminum Hydroxychloride Application in Neutral pH Rosin Sizing of Paper
Authors: Wortley Barbara H. , Steelhammer Joe C. 
Published: March 2011

ABSTRACTCommonly referred to as PAC, a series of polyhydroxide chlorides of aluminum with the general formula Aln(OH)mCl3n−m are being increasingly used as rosin size bonding agents, drainage aids and retention aids in papermaking.The manufacturing route chosen, the process kinetics and degree of neutralization affect the product produced and its reactions in the paper-making system. Production methods and procedures for quantifying the products produced are described.Dispersed rosin size and PAC can be applied to a papermaking system operating at pH 6 to 7.3.Sizing specifications are met and paper with non-slip characteristics, good machine glaze surface and printability is produced.
Fabrication of Composite Materials from Fibrous Precursors Using Paper Making Procedures
Authors: Zabasajja J. N. , Ahn Soonho , Wu Tony , Krishnagopalan A. , Tatarchuk B. J. 
Published: March 2011

ABSTRACTNovel composite materials have been fabricated from fibrous precursors using paper making procedures. Small metal fibers (2 μm in diameter) and carbon fiber bundles (20 μm in diameter) were combined with cellulose (as the binding agent) into an interwoven paper preform. The composite paper preform was then sintered at high temperatures in a controlled atmosphere, subsequently removing the cellulose and forming a sinter-bonded composite structure. The sinter bonding of the metal locked the metal fibers and provided high mechanical flexibility and structural integrity to the resulting composite structure. The composite structures were characterized using scanning electron microscopy, electrochemical and kinetic measurements. The optimization of these structures for high energy density applications was demonstrated through these measurements.
Novel Cationic Pigmentary Materials and their Use
Authors: Lauzon R.V. 
Published: March 2011

ABSTRACTPrevious work has shown that certain cationic solutes can adsorb “specifically” at the solid-solution interface [1,2]. To do this, a counterion must have a high enough “specific adsorption potential”. This is difficult to predict theoretically, and can best be studied is by electrokinetic titration.In this work, we have performed electrokinetic titrations of a diverse group of pigmentary materials such as clays, TiO2 and silicates. Using this information, we have cationized TiO2 and measured the effect on its retention in paper. A Dynamic Handsheet Mold was used for this work. Kaolin clay was also cationized and used to prepare cationic paper coatings.
Composite Systems of Lignocellulosics with Synthetic Polymers
Authors: Narayan Ramani , Neu Robert P. 
Published: March 2011

ABSTRACTIncompatible polymer blends are known to have inadequate mechanical properties due to poor adhesion and high interfacial tension between the phases. One such blend that displays this type of behavior is the cellulose acetate-polystyrene blend and is typical of lignocellulosic-synthetic polymer blend systems. Tailor-made cellulose acetate-polystyrene graft copolymers have been synthesized and used as compatibilizers (emulsifiers) to reduce the interfacial tension and improve interfacial mixing. Thermal analyses and morphological studies of the blends with and without the graft copolymer demonstrated that this was indeed the case.
Atomically Abrupt and Smooth Heterointerfaces: An Optical Investigation
Authors: Warwick Colin A. , Jan William Y. , Ourmazd Abbas , Harris Timothy D. , Christen JÜdrgen 
Published: March 2011

ABSTRACTLuminescence spectra from quantum wells are routinely interpreted in terms of atomically smooth and atomically abrupt interfaces. Here we show that this interpretation is inconsistent with photoluminescence, photoluminescence excitation, and quantitative microscopic (chemical lattice imaging) results. We argue that the discussion of interfacial roughness in terms of “an island size” is too naive. A full characterization of an interface requires the description of a “roughness spectrum”, specifying the amplitude of the interfacial corrugation vs corrugation wavelength over the relevant length scale.
Wedge Tem Characterization of Movpe GaInAs/InP Layers, Concentration Grading at Interfaces
Authors: Spycher R. , Stadelmann P.A. , Buffat P.A. 
Published: March 2011

ABSTRACTWedge Transmission Electron Microscopy has many advantages, one of which is the concentration determination in III-V semiconductors with a fairly good accuracy. This allows us to determine the concentration variation during the growth of GaInAs/InP multilayered structures and to deduce the concentration grading at the interface GaInAs/InP (As in InP) and the abruptness of the InP/GaInAs interface.
Atomic Layer Epitaxy
Authors: Usui Akira 
Published: March 2011

ABSTRACTAtomic layer epitaxy(ALE) of III-V compound semiconductors is reviewed. This technology has grown in recent years because of potential applications to nanometer-order structures as well as to monolayer/cycle growth with high-uniformity in growth thickness, and to excellent selective-area growth. Recent developments in chloride ALE of various compounds and heterostructures are described. Potentials of ALE for producing such fine structures are shown.
Interface Formation and the Heteroepitaxy of ZnSe on Si.
Authors: Bringans R. D. , Biegelsen D. K. , Ponce F. A. , Swartz L.-E. , Tramontana J. C. 
Published: March 2011

ABSTRACTZinc selenide films have been grown heteroepitaxially on Si(100) substrates by molecular beam epitaxy. The growth has been carried out for raised substrate temperatures and also at room temperature followed by solid-phase epitaxial (SPE) regrowth. The ZnSe films have been characterized by a number of surface-sensitive techniques and both the interface and the bulk material have been examined with high resolution transmission electron microscopy (HRTEM). We find that an interlayer, which is most likely SiSex, is present between the ZnSe film and the Si substrate for growths made at 300 °C and causes loss of epitaxy. In the case of room temperature deposition and SPE, it is absent, leading to good epitaxy. In the latter situation, the films are very uniform and there is a 4° rotation of the ZnSe crystal axes relative to those of the Si substrate.
Undoped GaAs with a Low Electron Concentration Grown on Si by Mocvd
Authors: Nozaki Shinji , Wu A. T. , Murray J. J. , George T. , Umeno M. 
Published: March 2011

ABSTRACTWe have successfully grown undoped GaAs of very high resistivity on Si by MOCVD. The back and side edges of the Si substrate were coated with a Si3N4/SiO2 stacked layer to suppress Si incorporation Into GaAs by the gas phase transport mechanism during MOCVD growth. A 3- μm-thick GaAs layer was grown on this Si substrate at 750 °C in an atmospheric MOCVD reactor using the two-step growth technique. The electron concentration measured by a Polaron C-V profiler is 3xl0l4 cm−3, as low as that of GaAs grown on GaAs substrate, up to the depth of 1.5 μm from the surface.
Selective Epitaxy of Compound Semiconductors in Movpe Growth: Growth, Modelling, and Applications
Authors: Kuech T.F. , Goorsky M. , Palevsky A. , Solomon P. , Tischler M.A. 
Published: March 2011

ABSTRACTSelective cpitaxial growth during metal-organic vapor phase epitaxy (MOVPE) can be accomplished over a wide range of growth conditions through the usC of alternative growth precursors. We have used chlorine-containing growth precursors, such as diethyl gallium chloride, (C2H5)2GaCl, to selectively grow GaAs and AlxGa1x As. The growth process has been thermodynamically modelled in order to estimate relative growth rates and alloy composition. This model indicates that near the growth front the growth process is chemically similar to the inorganic-based growth of compound semiconductors. This growth technique has been applied to the growth of extremely low resistance ohmic contact structures and quantum well structures.
Growth and Characterization of InP/GaAs on Soi by Mocvd
Authors: Karam N.H. , Haven V. , Vernon S.M. , Namavar F. , El-Masry N. , Haegel N. , Al-Jassim M.M. 
Published: March 2011

ABSTRACTEpitaxial InP films have been successfully deposited on GaAs coated silicon wafers with a buried oxide for the first time by MOCVD. The SOI wafers were prepared using the Separation by IMplantation of Oxygen (SIMOX) process. The quality of InP on SIMOX is comparable to the best of InP on Si deposited in the same reactor. Preliminary results on defect reduction techniques such as Thermal Cycle Growth (TCG) show an order of magnitude increase in the photoluminescence intensity and a factor of five reduction in the defect density. TCG has been found more effective than Thermal Cycle Annealing (TCA) in improving the crystalline perfection and optical properties of the deposited films.
Mbe Growth of High Quality (111)B GaAs, GaInAs, and AlInAs
Authors: Harshman P. , Malloy K.J. , Walker J. , Smith J.S. , Wang S. 
Published: March 2011

ABSTRACTGrowth of (111)B oriented GaAs, GaInAs, and AlInAs by MBE was investigated through a study of surface morphology, R.HEED patterns, and photoluminescence. Considering growth on both nominally oriented and 2 ° mis-oriented (111)B GaAs substrates, we have found that MBE growth in the (111)B direction proceeds quite differently than (100) growth. Except in the case of high substrate temperature growth on nominally oriented (111)B substrates, the growth of (111)B GaAs and GaInAs results in films which are characterized by macroscopically rough or faceted surfaces and by weak photoluminescence. We demonstrate that the surface morphology of these macroscopically rough films may be dramatically improved by growing with modulated Ga and In fluxes. Also, we find that AlAs and Al-containing alloys grow much more smoothly than GaAs on the (111)B surface. We report an AlAs/Al.5In.5As strained MQW structure which exhibits both good surface morphology and good photoluminescence spectra. Growth mechanisms which may explain the observed differences between (111)B and (100) MBE growth are proposed.
Heteroepitaxial Growth of ImP and GaInAs on GaAs Substrates Using Tertiarybutylarsine and Tertiarybutylphosphine
Authors: Chu Shirley S. , Chu T. L. , Yoo C. H. , Smith G. L. 
Published: March 2011

ABSTRACTThe heteroepitaxial growth of InP and GaInAs on GaAs substrates has been studied by using a new combination of source materials: ethyldimethylindium (EDMIn) and trimethylgallium (TMGa) or triethylgallium (TEGa) as group III sources, and tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBAs) as group V sources. The heteroepitaxial growth was carried out in a horizontal reactor in H2 under atmospheric pressure using a 2 kW quartz lamp as the substrate heater. Epitaxial InP layers of good surface morphology were obtained by using a two step process. The continuity and thickness of the buffer layer are important parameters. The InP layers deposited at 600°C are n-type, and the electron concentration decreases with decreasing TBP/EDMIn molar ratio. The 4.2 K photoluminescence of InP films is very similar to that of homoepitaxial InP films deposited at 600°C using trimethylindium (TMIn) and phosphine. Epitaxial GaxIn1–xAs layers with In composition varying from 3% to 53% have been deposltedi on GaAs substrates at 500° -550°C. A single growth step can be used for the deposition of GaxIn1–xAs with In composition of less than 20%. An InP buffer layer was used when the GaxIn1–xAS layer contains about 53% In. The composition of GaInAs was determined by optical absorption and photoluminescence techniques.
Heterostructure Nanoelectronics: A look into the Future
Authors: Barker John R. 
Published: March 2011

ABSTRACTThe combination of lateral patterning techniques with refined molecular beam epitaxy methods will give considerable opportunities for the fabrication and study of extended nanostructures in the coming decade. A first target will be the understanding and exploitation of a host of quantum transport phenomena discovered in the last few years. The prospect of practicable quantum devices and circuits which utilise the coherent wave properties of the electron remains problematic but a range of new devices which exploit the Coulomb blockade is under investigation. The latter hold promise for high temperature operation and strong immunity against quantum fluctuations. The next decade should see the first exploration of the granular electronic limit in which one carrier might be expected to represent one bit of information. The granular electronic regime will provide an important arena for the resolution of fundamental controversies in quantum mechanics.