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  • 1
    Electronic Resource
    Electronic Resource
    Transmission electron holography of silicon nanospheres with surface oxide layers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1296-1298 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Phase images of 20–30-nm-diam silicon spheres were collected by holographic methods in a field-emission transmission electron microscope. The spherical geometry enables the effect of specimen thickness on the electron-wave phase to be separated from the intrinsic Si electron-optical refractive effects allowing a determination of the mean inner potential Φ0. This work finds Φ0=11.9±0.9 V characterizing amorphous Si and 12.1±1.3 V characterizing crystalline Si. The phase images can resolve a 2-nm-thick native oxide layer and give Φ0 for SiO2=10.1±0.6 V. The phase data can quickly recognize a surface layer, and the effect of a surface layer on the determination of the bulk mean potential can be minimized. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118556
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  • 2
    Electronic Resource
    Electronic Resource
    Studies on damage removing efficiency of B11+ and BF+2 implanted Si0.84Ge0.16 epilayers by rapid thermal annealing (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 232-234 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality metastable pseudomorphic Si1−xGex epilayers were grown by ultrahigh vacuum chemical vapor deposition using Si2H6 and GeH4. These epilayers were implanted with 40 keV B11+ and 100 keV BF+2 ions at a dose of 1×1015 ions/cm2 and then annealed by rapid thermal annealing (RTA) processes at temperatures of 600, 650, 700, and 750 °C for 30 s duration. Double-crystal x-ray diffractometry was used to evaluate the level of the implant-induced damage and the damage removing efficiency of both ion implanted samples at different RTA conditions. The results show that the RTA process is more effective at removing damage from B11+ implanted samples than from those implanted with BF+2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116470
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  • 3
    Electronic Resource
    Electronic Resource
    Capillary wave scattering from a surfactant domain (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 1872-1885 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The study of capillary wave scattering by a circular region with different interfacial properties from the rest of an otherwise homogeneous interface is motivated by experiments on wave attenuation at a monolayer-covered air–water interface where domains of one surface phase are dispersed in a second surface phase. Here the scattering function is calculated for an incident wave of frequency ω (wavevector k0) scattering from an isolated circular domain of radius a with surface tension σ1 which is imbedded in an otherwise infinite interface of surface tension σ0. The underlying fluid is treated as irrotational and the three-dimensional flow problem coupling the heterogeneous surface to the underlying liquid is reduced to a set of dual integral equations, which are solved numerically. With this solution the scattering amplitudes and the total scattering cross sections are calculated as a function of the surface tension ratio σ0/σ1 and incident wavenumber k0a. The analogous problem of a discontinuous change in bending rigidity is also considered and the solution to the complete viscous problem is outlined in the Appendix. Experimental implications of these results are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868502
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  • 4
    Electronic Resource
    Electronic Resource
    Paired electrooxidation Part III: Production ofn-butyric acid fromn-butanol (1996)
    Springer
    Journal of applied electrochemistry 26 (1996), S. 543-545 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01021979
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of poly(N,N,N-trimethyl–N-2-methacryloxyethyl) ammonium chloride initiated by anodically generated Sn2+ cation (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 489-496 
    Details
    ISSN: 1572-8838
    Keywords: quaternary ammonium polymer ; sacrificial anode method ; Sn2+ cation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Cationic polymerization of N,N,N-trimethyl–N-2-methacryl oxyethyl ammonium chloride (DMAEM-MC) was studied using a new synthesis technique and new initiator system, Sn2+. The Sn2+ was produced by the electrolysis of a sacrificial anode. The polymer was prepared in a batch reactor using only Sn material as electrodes. Factors affecting the conversion and average molecular weight of the polymer by electrolysis were obtained. On the one hand, the results indicated that the agitation rate, initial pH, current density and assembly of electrodes significantly affected both conversion and polymer molecular weight. On the other hand, temperature and monomer concentration were minor factors in the electropolymerization, while these two factors were the major factors in conventional chemical methods. The optimal pHi and agitation rate were 5.50 and 0 rpm, respectively. The reaction rate increased with current density; however, the current efficiency decreased with increase in current density. The results also revealed that the optimum reaction temperature and monomer concentration were 25 ∘C and 0.73 m, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003442620442
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  • 6
    Electronic Resource
    Electronic Resource
    Graphic determination of kinetic parameters in temperature-programmed desorption of oxygen from alumeva-supported PdO (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 305-315 
    Details
    ISSN: 1572-8943
    Keywords: graphic method ; kinetic parameters ; PdO/Al2O3 ; TPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A graphic method is proposed to determine all of the kinetic parameters in Wigner-Polanyi equation of desorption. A desorption rate curve from a single temperature-programmed desorption experiment is required by this method to determine the order of reaction (n), the activation energy (E d) and the pre-exponential factor (v) of the equation. The proposed method has been applied to the oxygen desorption from PdO/Al2O3 samples prepared by impregnating γ-Al2O3 with H2PdCl4 solution used as examples. From the graphic method, the values ofn=2, andv=1.37±0.80×109 s−1 were successfully determined for the desorption. The value ofE d depended on the dispersion of palladium (D) on PdO/Al2O3 samples, and was expressed by the equation:E d=175+174D kJ·mol−1. This graphic method is a direct and time-saving technique, on comparing with other methods suggested in the literature, for analysis of data from temperature-programmed desorption of simple desorption processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979970
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  • 7
    Electronic Resource
    Electronic Resource
    Stress corrosion cracking of pyrotherm reformer tube for steam-reforming hydrogen production (1997)
    Springer
    Journal of materials science 32 (1997), S. 67-72 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A section of Pyrotherm G 25/35 Nb reformer tube was rupture-failed in a steam-reforming hydrogen plant and analysed to identify the causes of failure. Examination of the internal surface of the pipe indicated signs of heterogeneous corrosion attack in localized areas near to the primary crack site. Some of these areas were associated with fissures, although they did not penetrate through the pipe wall. Measurement of the pipe wall thickness revealed that fair amounts of the material had been consumed by corrosion. Cross-sectional examination of the dissected pipe in areas showing signs of corrosion attack and fissures revealed the presence of radial macrocracks, originating from the internal surface, and numerous microcracks in the pipe interior. Most microcracks were formed along the grain boundaries of the spin-cast microstructure. Further examination of the macrocracked surfaces revealed the presence of a granular microstructure, indicative of a brittle failure mode. Based on the characteristics exhibited by the macrocracking, the rupture failure of the reformer tube is attributed to stress corrosion cracking (SCC). The SCC is believed to be produced through synergistic reactions amongst sulfur-containing derivatives in the natural gas (feedstock), hydrogen and superheated steam in the processed gases under a mechanically-stressed environment. The presence of the mechanical stress is attributed to the bending of the pipe caused by improper suspension design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018562813044
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  • 8
    Electronic Resource
    Electronic Resource
    Damage characterization of two-dimensional woven and three-dimensional braided SiC-SiC composites (1996)
    Springer
    Journal of materials science 31 (1996), S. 232-241 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A comprehensive investigation of the room temperature behaviour of two-dimensional woven and three-dimensional braided SiC-SiC composites fabricated by the chemical vapour infiltration route has been conducted. A morphological study of the residual porosity in the composites revealed the existence of primarily two populations of pores: small intrayarn pores and larger interyarn pores. The sizes and the shapes of the two types of pores depended largely on the fibre architecture; the two step braided composite in which the majority of the fibre yarns were orientated along the axial direction exhibited the smallest pore size. The pore size and shapes in turn influenced the onset of damage in the composites under tensile loading. Damage was found to be initially matrix dominated, thus being essentially independent of the fibre architecture. At higher stress levels, however, fibre dominated damage prevailed. Unlike the tensile behaviour, where damage led to non-linearity in the stress-strain curve, the compressive behaviour of the composites was linear elastic almost up to failure. The off-axis tensile properties as well as compression after tension behaviour of the two-dimensional woven composites were also investigated. The information obtained from these tests provides the basis for the modelling of damage in these materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00355150
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  • 9
    Electronic Resource
    Electronic Resource
    Silicon carbide (NicalonTM) fibre-reinforced borosilicate glass composites: mechanical properties (1997)
    Springer
    Journal of materials science 32 (1997), S. 6459-6469 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The objective of this study was to assess the applicability of an extrinsic carbon coating to tailor the interface in a unidirectional NicalonTM–borosilicate glass composite for maximum strength. Three unidirectional NicalonTM fibre-reinforced borosilicate glass composites were fabricated with different interfaces by using (1) uncoated (2) 25 nm thick carbon-coated and (3) 140 nm thick carbon coated Nicalon fibres. The tensile behaviours of the three systems differed significantly. Damage developments during tensile loading were recorded by a replica technique. Fibre–matrix interfacial frictional stresses were measured. A shear lag model was used to quantitatively relate the interfacial properties, damage and elastic modulus. Tensile specimen design was varied to obtain desirable failure mode. Tensile strengths of NicalonTM fibres in all three types of composites were measured by the fracture mirror method. Weibull analysis of the fibre strength data was performed. Fibre strength data obtained from the fracture mirror method were compared with strength data obtained by single fibre tensile testing of as-received fibres and fibres extracted from the composites. The fibre strength data were used in various composite strength models to predict strengths. Nicalon–borosilicate glass composites with ultimate tensile strength values as high as 585 MPa were produced using extrinsic carbon coatings on the fibres. Fibre strength measurements indicated fibre strength degradation during processing. Fracture mirror analysis gave higher fibre strengths than extracted single fibre tensile testing for all three types of composites. The fibre bundle model gave reasonable composite ultimate tensile strength predictions using fracture mirror based fibre strength data. Characterization and analysis suggest that the full reinforcing potential of the fibres was not realized and the composite strength can be further increased by optimizing the fibre coating thickness and processing parameters. The use of microcrack density measurements, indentation–frictional stress measurements and shear lag modelling have been demonstrated for assessing whether the full reinforcing and toughening potential of the fibres has been realized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018642723310
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  • 10
    Electronic Resource
    Electronic Resource
    Stress corrosion cracking of leaded brass in a sulphuric acid environment (1998)
    Springer
    Journal of materials science 33 (1998), S. 3585-3590 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Free-cutting leaded brass is commonly used as sleeve fittings (also termed clamping ferrules) on polytetrafluoroethylene-lined flexible hoses for the filling and distribution of compressed gases, e.g., oxygen, nitrogen and carbon dioxide, for various industrial and medical applications. Some of the gas-filling and gas distribution facilities are located in the proximity of highly industrialized areas for the convenience of transportation, application and customer service. Therefore, the gas-filling and gas distribution gears are frequently exposed to the environment containing various chemical substances, which in the presence of ambient moisture and under the influence of mechanical and residual stresses in the material can effect an undesirable material degradation reaction. Stress corrosion cracking (SCC) has been identified to occur in C36000 Cu–Zn–Pb leaded brass ferrules under the synergistic reactions of a sulphuric acid production environment in a sustained tensile stress environment. The tensile stress was imparted to the material by the mechanical crimping process applied on the ferrules, and superimposed by cyclical high-pressure gas-cylinder-filling operations. The chemical species responsible for the SCC originated from the gaseous vapours and/or ionic derivatives of S-containing substances emitted from a neighbouring sulphuric acid production plant, which reacted with water and moisture condensates on the brass ferrule surfaces and effected the chemical corrosion reaction(s). SCC of the leaded brass ferrules gave rise to predominantly intergranular failures with fracture surfaces heavily decorated by corrosion products of various configurations. Most corrosion products were found to have embedded on the grain-boundary planes of the fracture surfaces, suggesting that grain-boundary short-circuit diffusion may have served as a viable mechanism for the SCC of C36000 leaded brass under the operating conditions of this case study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004699111365
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