| 1. |
- Engström, Anders, et al.
(författare)
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COMPUTER-SIMULATION OF DIFFUSION IN MULTIPHASE SYSTEMS
- 1994
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Ingår i: Metallurgical and Materials Transactions. A. - 1073-5623 .- 1543-1940. ; 25:6, s. 1127-1134
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Tidskriftsartikel (refereegranskat)abstract
- A general model to treat multicomponent diffusion in multiphase dispersions is presented. The model is based on multicomponent diffusion data and basic thermodynamic data and contains no adjustable parameters. No restriction is placed on the number of components or phases that take part in the calculations, as long as the necessary thermodynamic and kinetic data are available. The new model is implemented into the DICTRA software, which makes use of THERMO-CALC to handle the thermodynamics. The model is applied to carburization of Ni alloys and heat treatment of welded joints between dissimilar materials. In both cases, the diffusion is accompanied by carbide formation or dissolution. A good agreement between experiments and calculations is found, despite the fact that no adjustable parameters are needed.
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| 4. |
- Xiao, Zhaohua, 1962, et al.
(författare)
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Good selectivity between a NiCr mask and GaAs and AlGaAs by chemically assisted ion beam etching with Cl2 gas
- 1991
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Ingår i: Journal of the Electrochemical Society. - : Wiley. - 1945-7111 .- 0013-4651. ; 138, s. 3086-9
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Tidskriftsartikel (refereegranskat)abstract
- The authors report highly selective etching rates between a Ni-Cr mask and GaAs and AlGaAs layers as well as highly anisotropic profiles in these materials at a nanometer scale using the Ni-Cr mask and chemical assisted ion beam etching. The etching rates of Ni-Cr, GaAs, and AlGaAs depend on Cl2 gas flux. ion beam energy, and ion beam current density. Selectivities of the order of 40:1 and 8:1 between GaAs, respectively. Al0.29Ga0.71As and Ni0.7Cr0.3, were obtained at an ion beam energy of 500 eV, beam current density of 0.2 mA/cm2, and a Cl2 flow of 4.2 ml/min
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| 5. |
- Hammar, M., et al.
(författare)
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Investigation of chemically vapour deposited tungsten and tungsten silicide as contacts to n+ and p+ silicon areas
- 1990
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 185:1, s. 9-19
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten and WSi2 have been examined as contact barriers between aluminium and n+ - or p+ -Si. The specific contact resistivity and diode leakage current were evaluated after heat treatment at different temperatures. Rutherford backscattering spectrometry measurements, X-ray diffraction analysis, scanning electron microscopy and sheet resistance measurements were performed to study the thermal stabilities of the Al/W/Si and Al/WSi2/Si systems. The contact resistivities of chemically vapour deposited tungsten and WSi2 to n+ -Si with a surface concentration of 7.5 × 1019 cm-3 were 8 × 10-7 Ωcm2 and 9 × 10-7 Ωcm2 respectively. To p+ -Si with a surface concentration of 2.6 × 1019 cm-3, they were 5 × 10-6 and 1 × 10-6 Ωcm2. Diffusion of aluminium was revealed to occur above 475°C in the case of tungsten and at 475°C in the case of WSi2. The void formation in silicon substrates was observed after heat treatment at 500°C for the Al/WSi2/Si system. The increase in leakage current for the Al/W/Si and Al/WSi2/Si structures is related to the onset of Si-Al interpenetration. Alloy formation was observed at 500°C for tungsten contacts whereas W-Al or other alloys were not detected up to 600°C for the WSi2 contact.
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| 6. |
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| 7. |
- Gabriel, B. L., et al.
(författare)
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Site-specific adhesion of Staphylococcus epidermidis (RP12) in Ti-Al-V metal systems
- 1994
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 15:8, s. 628-634
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Tidskriftsartikel (refereegranskat)abstract
- Staphylococcus epidermidis (RP12) adhesion patterns were studied on the following titanium (Ti)-aluminium (Al)-vanadium (V) metal systems: (i) microfabricated samples consisting of Ti, Al and V islands deposited onto Ti or V substrata, (ii) pure Ti, Al and V metals, and (iii) medical grade Ti6Al4-V alloy. All of these surfaces were covered with their respective oxides formed upon exposure of the metals to air. Quantitative analysis of the number of cells bound per unit area indicates that S. epidermidis (RP12) exhibits greatest adhesion to pure V surfaces. When exposed to surfaces having controlled spatial variations in chemical composition on the 10 mu m scale (microfabricated samples), the bacteria preferentially populate V islands versus Ti or Al substrata. In the case of the biphasic Ti6Al4V alloy, the bacteria tend to adhere to V-rich, mixed phase regions and phase boundaries. These findings demonstrate that enhanced and preferential adhesion of S. epidermidis (RP12) occurs on V surfaces in TI-Al-V metal systems and suggest that bacterial interactions are influenced by surface oxide composition.
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| 8. |
- Jarfors, A., et al.
(författare)
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On the thermodynamics and kinetics of carbides in the aluminium-rich corner of the AlTiC phase diagram
- 1991
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Ingår i: Materials Science & Engineering. - 0921-5093 .- 1873-4936. ; 135:C, s. 119-123
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Tidskriftsartikel (refereegranskat)abstract
- Aluminium composites have a great potential because of their high strength-to-weight ratio. Carbides will in the future be powerful reinforcements. To be able to manufacture these it is of importance to know the thermodynamic properties and the kinetic limitations. The objective of this investigation is to study the equilibria between the carbides occurring in the AlTiC system as well as the initial precipitation and dissolution behaviour of these carbides. It can be shown that there is a change in stability between TiC and Al4C3, depending on both composition and temperature. To study the nucleation and precipitation behaviour of the carbides in liquid aluminium and aluminium alloys a set of alloys were melted and heated to an appropriate temperature in graphite crucibles. The effect of time and the effect of composition on the chemical reactions involving carbides have been investigated. A theoretical analysis of both the thermodynamics and kinetics was performed, giving a tentative explanation. © 1991.
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| 9. |
- Sundqvist, Bertil
(författare)
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High metallic resistivities and resistivity saturation : High-pressure and thermal expansion effects
- 1993
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Ingår i: Modern physics letters B. - 0217-9849. ; 7:8, s. 491-499
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- Some recent developments in the field of resistivity saturation in metallic materials are discussed, concentrating on effects of thermal expansion and high pressures. It is shown that thermal expansion effects can significantly modify the measured temperature dependence of the resistivity, and that high pressure studies are an important, but little used, source of information. Examples are shown for transition metals and alloys, high transition temperature superconductors, and graphite intercalation compounds.
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| 10. |
- Göthelid, M., et al.
(författare)
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Sn-induced surface reconstructions on the Ge(111) surface studied with scanning tunneling microscopy
- 1992
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Ingår i: Surface Science. - 0039-6028. ; 271:3, s. L357-L361
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Tidskriftsartikel (refereegranskat)abstract
- Scanning tunneling microscopy (STM) has been used to study different Sn induced reconstructions on the Ge(111) surface; namely the (7 × 7), (5 × 5) and ( 3 × 3) R30° structures. The first two have been confirmed to be of the dimer adatom stacking faults (DAS) type with adatoms mainly being Sn. The ( 3 × 3)R30° superstructure was found at different Sn depositions. At 0.4 monolayer (ML) Sn coverage a homogeneous Sn adatom layer is adsorbed on the(1 × 1) surface in threefold sites directly over second-layer atoms (T4), while at low coverage, 0.1 ML, the top layer is a mixture of Sn and Ge atoms. We also propose the chemical identities of the different atoms seen in the STM images as related to their apparent height. © 1992.
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