Influence of phosphorus diffusion modes on the formation of defects in an oxide

Using optical microscopy, SEM, atomic force microscope and profilometer, the shape, size and impurity composition of local defects occurring in the silicon dioxide layer during phosphorus diffusion were determined. The reason for the formation of defects in the passivating oxide during phosphorus diffusion is the local melting of SiO2 in interaction with liquid drops of phosphoric-silicate glass. A decrease in the temperature of the phosphorus deposition process and the concentration of POCL3 in the gas stream leads to a decrease in the density of oxide defects.

Passivation-driven speciation, dealloying and purification

Kinetics of passivating oxide growth can drive nanoscale surface order/speciation. Combined with oxide growth and thermal expansion, trapped oxide crystals (‘ship-in-a-bottle’) or extrusion of metal fingerlings (‘spiky particles’) can be achieved.

Passivation on manganese monosilicide in sulfuric acid electrolytes

Several features of the electrode reactions that occur at the surface of transition metal silicide (high strength metal-silicon bond, the effect of chemical reactions and the formation of passivating oxide films) leading to high interest to intermetallic compounds. Anodic behavior of the MnSi electrode in solutions 0.5 M H2SO4 and 0.05 M H2SO4 + 0.45 M Na2SO4 was studied by polarization and impedance measurements. It was concluded that the surface of manganese silicide is coated with an oxide film similar in composition to SiO2. The thickness and resistivity of the oxide film were calculated depending on potential and concentration of sulfuric acid. Generalization and theoretical explanation of the research results may provide a basis for predicting corrosion resistance of metal-silicon alloys in a wide range of corrosive environments.

Chemically modifying the mechanical properties of core–shell liquid metal nanoparticles

Eutectic gallium–indium is a room temperature liquid metal that can be readily fabricated into nanoparticles. These particles form a thin, passivating oxide shell that can be chemically modified to change the mechanical properties of the particle.

Low-Temperature Carburization of AL-6XN Enabled by Provisional Passivation

Employing AISI-AL-6XN as example, we introduce a new method of surface activation for low-temperature carburization. This method consists of two steps: (i) removing the passivating surface oxide and a potentially existing severely plastically deformed surface layer (Beilby layer) by aqueous (liquid) hydrochloric acid, and (ii) immersion in ethanol and subsequent drying in nitrogen. Upon carburization with a gas mixture of acetylene, hydrogen, and nitrogen, this new method of surface activation enables the formation of a fully developed “case”, a uniform solid solution of interstitial carbon in austenite with carbon fractions up to 0.20 near the alloy surface. The underlying mechanism of surface activation is shown to involve the formation of a provisional passivating layer. It consists of chlorides or ethoxides that are insoluble in ethanol. It prevents the reformation of the regular Cr-rich passivating oxide layer and is readily removed upon heating and exposure to the carburizing gas. As the new activation method is quicker, more effective, and less destructive to furnace hardware than activation with hot gaseous hydrochloric acid that is currently applied in industrial manufacturing, it may have considerable technological impact.