Surface segregation of Si on Fe single crystal surfaces and interaction with carbon

Rugy, H. De; Viefhaus, H.

doi:10.1016/0039-6028(86)90200-1

Cited by 80 publications

(14 citation statements)

References 42 publications

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“…It is known from LEED-experiments of binary Fe-X systems that Si and P are enriched within a c(2x2) structure at saturation level, which corresponds to a coverage of half a monolayer [4]. However, similar arguments do not hold for the (110) oriented surface.…”

Section: Resultsmentioning

confidence: 86%

“…The concentration of Si decreases even below the bulk concentration value. This arises from the well-known repulsive interaction between Si and C [4]. But silicon has a much higher bulk concentration than carbon and so carbon is repelled from the surface with increasing temperature.…”

Section: Methodsmentioning

confidence: 97%

“…First the formation of a c(2x2) structure on the (100) oriented surface can't be described by using the interaction coefficients D u [14] because this model is developed only considering nearest neighbour interactions. But a c(2x2) structure does not have nearest neighbour distances at all, as pointed out in [4]. So the calculations were performed using surface coverages | instead of mole fractions X which were used in the diagrams.…”

Section: Model Calculationsmentioning

confidence: 99%

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An experimental and theoretical study of surface segregation in a Fe-6at.%Si bicrystal

et al. 1997

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Abstract. The analysis of segregation phenomena in bicrystals is an important step for the understanding of combined effects of the elementary diffusion processes involved in the segregation in polycristalline SYstems. The segregation of Si and P in a Fe-6at.%Si bicrystal with a (100) and (110) surface has been investigated by means of AES (Auger electron spectroscopy). For these experiments the technique of a linearly increased temperature has been applied. Significant differences between the segregation kinetics at the two surfaces of the sample have been found on the one hand for the maximum coverage of P and on the other hand for the high temperature behaviour of Si. Additionally, model calculations based on the KTBIM (kinetic tight binding Ising model) have been performed to qualitatively describe the experimental results. It is shown, that the striking differences between the segregation behaviour at the two differently oriented surfaces can be explained by different segregation energies of P, whereas Si plays a minor role due to its relatively small segregation energy.Key words: Auger electron spectroscopy, iron, surface segregation, single crystal surfaces.as for surface segregation. Therefore, the knowledge of surface segregation is an important step to explain interface segregation phenomena. In this work the evolution of surface concentrations of Si, P, C, S, N and O on a Fe-6at.%Si bicrystal with a (100) and a (110) oriented surface have been measured by means of AES and SAM (scanning Auger microscopy) in order to gain data for a mathematical description of the surface segregation behaviour of Si and P and the interaction with grain boundary segregation. Measurements were performed by using the method of temperature programmed segregation [23.Additionally, the results are compared with a theoretical model for the segregation kinetics using the KTBIM under consideration of the surface structure which is formed by the segregands.Interface segregation of impurities such as Si and P can drastically change the material properties of iron and steel especially in connection with high temperatures and large temperature gradients during the production and use of the material. Segregation is determined by a complex combination of several diffusion mechanisms such as bulk diffusion, grain boundary diffusion and surface diffusion. To investigate the segregation phenomena a bicrystal is often used as a simple model system, which consists of two single crystals with a grain boundary between them perpendicular to the plain surface. As pointed out by [1] grain boundary segregation can be explained by using the same models * Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday ** To whom correspondence should be addressed ExperimentalThe measurements were performed using a Fe-6at.%Si bicrystal which contained a phosphorus concentration of about 70 ppm. The sample was metallographically polished before introducing it into a Perkin-Elmer 25-260 Auger spectrometer (beam energ...

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Section: Resultsmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 97%

Section: Model Calculationsmentioning

confidence: 99%

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An experimental and theoretical study of surface segregation in a Fe-6at.%Si bicrystal

et al. 1997

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“…Indeed, the segregation of C and Si, at low temperatures (300-600~ in a ternary Fe-Si-C system was found to be a consequence of simple site competition [21] and high repulsive interaction between the two elements [22]. This can explain the Si-O-C amorphous layer formation surrounding the catalyst ball.…”

Section: The Vls Catalystmentioning

confidence: 94%

High-resolution transmission electron microscopy on silicon carbide whiskers

et al. 1993

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SiC whiskers were grown from the reaction of silicon monoxide (SiO) with activated carbon containing iron impurities. Growth proceeds through a VLS growth mechanism with SiO and CO as reacting gases. HRTEM combined with EDS shows that the SiC whisker is topped by a Fe3Si catalyst droplet. The SiC whisker is found to be one-dimensionally disordered along the [111] growth direction of an fcc crystal structure. Although the catalyst droplet is usually larger than the top face of the whisker, we observed a number of situations where the diameter of the droplet was smaller. The study of the SiC-Fe3Si interface showed that the growth is nucleated from the edges.

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“…For surface segregation experiments in a vacuum system using AES, evaporation of the segregant may occur. Lea and Seah [37,40] evaluated the effect of surface evaporation concomitant with surface segregation with the following equation: (13) where E is the dimensionless parameter related to evaporation rate. The results show no divergence initially from the McLean result of equation (11).…”

Section: Theory Of Grain Boundary Segregationmentioning

confidence: 99%

Grain boundary segregation and intergranular fracture in Ferrite containing Mo, Si or Al

Heo

1996

Metals and Materials

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Roles of molybdenum, silicon or aluminum in ferritc on grain boundary segregation and hence on intergranular fracture have been investigated by using Auger electron spectroscopy (AES) and tensile test. Competitive segregation between sulfur and carbon or nitrogen, which caused the decrease below 7(10"C of sulfur content at the grain boundaries, was observed in the pure iron. The intergranular brittleness of the pure iron was caused by sulfur at the grain boundaries. When molybdenum was added to the pure iron, the sulfur contents at the grain boundaries were lowered in comparison to those in the pure iron. The molybdenum-bearing alloy showed higher fracture strength than that of the pure iron, and fractured mostly in the transgranular mode. This arises from the intrinsic effect of molybdenum on the grain boundaries as well as the decrease in sulfur content. In the 3.37 wt.%Si alloy, silicon and carbon or nitrogen competitively segregated to the grain boundaries, and such a compe:itive segregation was also observed between sulfur and carbon or nitrogen. The sulfur content at the grain boundaries decreased with increasing silicon content. The fracture modes in the 3.37-and 4.26 wt.%Si alloys were transgranular in the rolling direction, but were mostly intergranular in the transverse direction and in the as-rolled condition. The intergranular characteristic in the fracture behavior may be attributed to the detrimental effect of silicon as well as sulfur on the intergranular cohesion. Carbon and aluminum only were found at the grain boundaries of the aluminumbearing alloy. This suggests that aluminum is a strong repulser of sulfur or nitrogen at the grain boundaries. Additionally, it was found that aluminum has a detrimental effect on grain boundary strength of ferrite.

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Surface segregation of Si on Fe single crystal surfaces and interaction with carbon

Cited by 80 publications

References 42 publications

An experimental and theoretical study of surface segregation in a Fe-6at.%Si bicrystal

An experimental and theoretical study of surface segregation in a Fe-6at.%Si bicrystal

High-resolution transmission electron microscopy on silicon carbide whiskers

Grain boundary segregation and intergranular fracture in Ferrite containing Mo, Si or Al

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