Effect of Heat Treatment on the Composition of Surface Layers in Lithium Silicate Glass Exposed to Acid and Salt Solutions

The concentration distribution of lithium ions in the surface layers of the 27Li₂O–73SiO₂ (mol %) glass samples subjected and unsubjected to heat treatment under different conditions after exposure to 0.1 M HCl + y M LiCl (y = 0, 1.0, 5.0, and 10) solutions is studied by the HF-sectioning technique. It is found that the specific (molded) layer formed on the glass surface upon pouring of a glass melt into a cooled mold affects the leaching processes in both the initial and phase-separated glasses. In the absence of the molded layer, the leaching rate of the initial glass in the acid is lower than that of the phase-separated glass and higher than that of the crystallized glass. The leaching rate of the phase-separated and crystallized samples in the acid with an salt additive is higher than that of the initial salt. Chlorine ions in the acid solution bring about a weakening of the silicon–oxygen network. The profiles of the dissolution rate of glass in a 1% HF solution correlate with the concentration profiles of lithium.     

Deformation of lead blanks by direct impact in a gas-dynamic hammer system

A method is described for plotting dynamic diagrams of the deformation of lead blanks by direct impact in a gas-dynamic hammer system and diagrams plotted at speeds corresponding to hammer forging.     

The lining of the cars of short tunnel furnaces

A new design has been developed for the cars of PG-30 tunnel furnaces used to fire ceramic parts employed in the casting of aircraft engines. The refractory layer of the cars’ lining is made of several slabs that are joined to one another. The slabs are made of a specially developed mullite-corundum material with improved heat resistance. Use of the new cars has lengthened the time between routine repairs and reduced maintenance costs. The service life of the cars at temperatures up to 1600°C has been increased by a factor of 1.5.     

Hydroisomerization of n-dodecane on bifunctional catalysts containing mesoporous aluminosilicates

The hydroisomerization of n-dodecane on bifunctional catalysts with mesostructured aluminosilicates as an active component has been studied. Aluminosilicates with an Si/Al atomic ratio of 5 to 48 have been prepared using hexadecylamine as a template. Catalyst supports contained 35 wt % mesoporous material and 65 wt % ??-Al₂O₃. The platinum loading of the catalysts was 0.5% of the support mass. It has been found that the catalysts based on mesoporous aluminosilicates with an Si/Al ratio of 10 and 22 exhibit the highest selectivity. In their presence, the conversion reaches 43?C46 wt % with the selectivity for iso-C₁₂H₂₆ of more than 90%.