Vol 75, No 3-4 (2018)

Laser glass-welding technologies are reviewed. Welding technologies using continuous wave CO₂-laser radiation in the surface-heating regime and in a deep melting regime are presented. A technology of microwelding of glass by lasers with ultra-short pulses and high pulse repetition frequency is examined.

The phase composition, structure, elemental distribution, and hydrolytic stability of quench-hardened and tempered sodium-aluminum-phosphate (SAP) and sodium-aluminum(iron) phosphate (SAIP) glass materials containing 10 wt.% (above 100%) oxides of rare earth elements (REE) were studied. It is shown that all materials obtained by quench-hardening melts (except La-containing melts) were x-ray amorphous, while slowly cooled (tempered) melts partially or completely crystallized with different phases of orthophosphates being released. The rate of leaching of elements from tempered SAP glasses determined at 90°C is approximately one or two orders of magnitude higher than then for the quench-hardened glasses, and the leach rate of elements from quench-hardened SAIP glasses is lower than from quench-hardened SAP glasses.

A more accurate analytic method of determining the average hydraulic radius of a capillary on the basis of a three-dimensional model of the porous structure of materials that takes capillary geometry into account is proposed. The computational formula derived for the average radius is much more accurate than the generally used Kozeni relation. Good agreement with the experimental data is obtained. This model and a fundamentally new approach are used to develop a procedure and derive a computational expression for the average radius from data on the seepage of liquid into a porous material that is several-fold more accurate than existing ones. Computational results are presented.

The effect of introducing the superplasticizer Poliplast SP-3 into concrete mix, making it possible to regulate the constructional-engineering properties of the concrete, was studied. It was found that the mix with additive sets more quickly because of the peptizing action of the additive. It was also found that the strength and frost-resistance of the modified concrete were higher.

An integrated evaluation of the surface state of glazed porcelain by mechanical and optical means is made. It is shown that both methods can be used to determine the quality of a glazed surface, but they are more informative when used together. It is found that at the surface gloss is affected more by the width and not the depth of the asperities. In terms of the surface quality of feldspar glaze, samples made from hard porcelain are inferior to the sample made from bone china.

Water wetting films on a quartz surface were found to become unstable with increasing temperature. This is believed to be associated with the temperature dependence of the structure of the water in the layer at the wall. Aparameter characterizing the strength of the structural forces is calculated from measurements of the contact angle. The sign inversion of the parameter is associated with the forces of hydrophobic attraction predominating over the forces of hydrophilic repulsion in a definite temperature interval. The results of deferrization of glass quartz sands by flotation during thermal action on water wetting films are presented.

Heat-insulating materials based on sodium chloride modified liquid glass and salt wastes from the production of aluminum have been obtained without using conventional native materials. The presence of isometric and oval pores in the studied samples imparts mechanical strength to them. The x-ray phase composition revealed that the samples contain mullite and anorthite, which impart strength to heat-insulating materials. The formation of mullite is promoted by the high content of alkali and iron, which lower the crystallization temperature of mullite to 1100°C.

The properties of lightweight geopolymer materials (GM) based on refractory technogenic aluminosilicate wastes were studied. The effect of the ratio of the oxides SiO₂ and Al₂O₃ in the compositions of GM on the physical and mechanical properties of GM was investigated. It was found that SiO₂/Al2O₃ reduction in the GM composition results in higher density and strength and lower water absorption of the samples after a keeping period. After firing at temperatures 800 and 1000°C the strength of the samples becomes all the higher the lower the ratio SiO₂/Al₂O₃ in the composition. The heat resistance of the samples comprises four thermal cycles for high and more than seven cycles low ratio SiO₂/Al₂O₃.

X-ray amorphous powder was synthesized from a water solution of calcium acetate and a mixed-anionic \( \left({\mathrm{HPO}}_4^{2-}/{\mathrm{CO}}_3^{2-}\right) \) water solution, including ammonium hydrophosphate and ammonium carbonate, at room temperature without pH regulation. The powders synthesized from the mixed-anionic \( \left({\mathrm{HPO}}_4^{2-}/{\mathrm{CO}}_3^{2-}\right) \) solution can be recommended for fabricating composite materials with a polymer matrix or for obtaining ceramic containing tricalcium phosphate and calcite phases with firing temperature not exceeding 600°C.

Profiled leucosapphire, possessing a set of unique technical characteristics, is in the number of cases the only material that can be used as a base for new high-efficiency devices and setups operating under extreme conditions.