Formation Of Needle-shaped Crystals Research Articles

Effective Fine-Grained Concrete with High-Dispersed Additive Based on the Natural Mineral Wollastonite

Micro-fillers based on natural mineral wollastonite, modifying fine-grained concrete and improving its physical and mechanical characteristics, are developed and studied. The influence of the most common stabilizers on the aggregate stability of wollastonite-based microdispersed systems in the aquatic dispersion environment is considered. The optimal parameters, ensuring the production of micro-fillers in the form of stable suspensions, are developed. The application efficiency of the wollastonite-based filler due to its micro-reinforcing properties is revealed. These properties are specified by the formation of needle-shaped crystals by the ultrasonic dispersion in the aquatic environment, chemically related to cement-containing raw materials and contributing to the active selective adsorption of the binder hydration products. It has a significant influence on the rheological parameters of cement composites, on structure formation, as well as on their strength and deformation properties.

Effect of gauging solution densities on magnesia cement

A parametric study was conducted to investigate the effect of gauging solution density on the cementing properties of magnesia cement. It was found that setting time, compressive strength, moisture resisting efficiency, durability and bonding characteristics are improved by increasing the density of gauging solution up to 32°Be (Baumé scale). Scanning electron microscopy analysis of magnesia cement indicated the formation of needle-shaped crystals and a compact cement structure, confirming the experimental results.

Changes in the phase composition and structure of electrodeposited Sn–Co alloys in Sn–Co/Cu layer systems upon heating

Changes in the phase composition and structure of electrodeposited tin–cobalt (Sn–Co) alloy layers (5–10 μm) containing a limited quantity of Co (0.24, 2.4, 11.0, 17.0 or 26.5 wt.%) were studied using X-ray diffraction (XRD) and optical microscopy. The phase composition and coating structures of Sn–Co alloys in Sn–Co/Cu layers underwent considerable changes upon heating at 170 °C for 100–200 h and at 170 °C for 200 h followed by 205 °C for 20 h. The changes were dependent on the Co content in the alloy and the heating temperature. When examining the sample containing 11.0 wt.% cobalt, an unidentified phase containing a Sn–Co compound, CoSn 2 and CoSn 3 formed upon heating at 170 °C for 100, 140 and 200 h. The structure of the layer surface was composed of spherical crystallites. The formation of the unidentified phase possibly caused the formation of needle-shaped crystals in the structure consisting of spherical crystallites. When the Co content of the Sn–Co layer was increased to 17.0–26.5 wt.% and the sample was heated to 170 °C for 100–200 h, phases of CoSn, CoSn 2, Co 3Sn 2 and CoSn 3 were formed. The coating maintained its structure and was composed of spherical crystallites. In the Sn–Co/Cu system of layers containing 11.0, 17.0 or 26.5 wt.% Co, Sn–Cu intermetallic compounds (Cu 6Sn 5 and Cu 3Sn) did not form after heating at 170 °C for 200 h followed by 205 °C for 20 h.

Formation of an Addition Compound of Calcium Silicate and Sodium Fluoride

IN connexion with some experiments concerning the decomposition of calcium fluoride by fusing with silica and sodium carbonate, the formation of needle-shaped crystals was observed. The crystals were analysed, and it appeared that the formula of the compound must be Ca2SiO4NaF, as is seen from the following data: