This original work was awarder at 1999/2000 International Metallographic Contest Diploma.

Material: The silicate film (NaxSiyOz) on the surface of silicon. Magnification: x 1550 Explanation, technical and structural features:


Brief description of structure.

The structure of the silicate film on the surface of silicon.

The silicate film appears in atmosphere of gaseous natrium during the heating (1000°C) of silicon. The growth of crystals begins from the separate centers. The crystals grow as the spherulites. The crystals has a radial structure.


Preparation and photographing of the object.

The semi-conductor polycrystalline silicon was used. The surface was polished with HD diamond paste 0-1micron. They carried out a pickling of the solution in 20% HNO3 + 20%HF + 20%H2SO4+40%H2O during 1 minute after polishing. Silicon was maintained at the gas natrium atmosphere (1000°С) during 2 minutes. At this temperature the natrium evaporates and cooperates with silicon easily.

Monochrome photography has bad image. The colour photographic film, the «FUJIFILM» was used. The speed of a photographic film is 100. They carried out photographing at the illumination appropriating to a daylight spectrum. Therefore all colours are natural.


Technical and scientific importance of a problem.

1.This photo is the cogent argument of the film-mechanism of modifying (microalloying) of Al-Si alloys. The mechanism of modifying of structure is one of the most disputable questions in the physical metallurgy of Al-Si alloys. The famous investigator А. Bochvar, explains the effect of modifying by presence of films. (Film will be formed in Al-Si melt near growing silicon crystal. The form of growth and morphology of the crystals of silicon changes.). The А. Bochvar hypothesis is based on the analysis of properties Al-Si alloys. However nobody observed and investigated films earlier. Therefore А.Bochvar hypothesis is a debatable one. Similar films should be formed in Al-Si melt, which is modified by natrium.

2.The analysis of microstructure of the film shows that the crystals has a radial structure. The growth of crystals begins from the separate centers. The crystals grow as the spherulites. During the growth the crystal shapes become irregular. The crystals of polymers have similar radial structure and colouring. As a rule, the crystals of polymers have a spherical form and a radial structure and bright colouring. It allows to assume, that the film has a polymeric structure. The mechanism of growth and the structure of similar crystals were considered in the science of polymers. This photo considers the silicon and Al-Si melts structure from the positions of modern science of polymers. A new sight allows advance considerably at the understanding of processes in Al-Si alloys.

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All pictures and technical data used in this brochure are property of Haris Division. Unauthorized duplication is a violation of copyright law.

All pictures and technical data used in this brochure are property of Haris Division. Unauthorized duplication is a violation of copyright law.