Reproducibility of plastic measurements: The need to modify State Standard GOST 1186-87

A very important characteristic of coking coal is its clinkering ability, i.e., its ability to form a nonvolatile solid residue, consisting of disparate grains, on heating in specific conditions. The clinkering ability of the coal is determined by the properties of its plastic mass. Various methods may be used to evaluate the plastic-ductile properties of the coal. However, since the 1930s, the main method used to evaluate the clinkering properties of coal, within the nations of the former Soviet Union, has been the Sapozhnikov-Bazilevich plastometric method, because it provides more information than competing approaches. For the same reason, the thickness of the plastic layer, which is one of the parameters determined by this method, is used for coal classification in State Standard GOST 25543-88 (Lignite, Coal, and Anthracite: Genetic and TEchnological Classification) and its Ukrainian counterpart DSTU 3472-96 (Lignite, Coal, and Anthracite: Classification). This explains the strict requirements on the accuracy and reliability of the plastometric characteristics.     

Use of laser interferometers for measuring displacements of the surfaces of tested objects

A mathematical model and the results of the numerically simulated procedures of measuring displacements of tested objects’ surfaces with the use of laser interferometers are presented. Promising measurement techniques are substantiated, and recommendations for their use are given.     

Convergence and reproducibility in State Standard GOST 1186-87

Factors affecting plastometric measurements for coal are considered. The need to revise State Standard GOST 1186-87 is discussed.     

Effect of the conditions of sintering of sodium-reduced tantalum powders on their characteristics

The effect of the granulation and heat treatment of sodium-reduced tantalum powders with a specific surface area of 2.5–3.6 m²/g on the bulk density, the powder flow time, and the specific surface area of the powders and the specific capacitance of the anodes made of them is studied. It is shown that heat treatment of a granulated powder in vacuum at 1100°C or in a mixture with magnesium at 800°C makes it possible to achieve the required powder flow time.     

Determining deformation and strength of a filling mass during stoping by the inverse problem solving

The authors have developed a method for quantitative estimation of filling mass deformation and strength characteristics in the course of stoping at sheet ore deposits by the in situ measurements of relative displacements of points at the mined-out stope boundary. The article also analyzes the structure of objective functions of the formulated inverse coefficient problems for the elastic-plastic rock deformation model, and examines their solvability.     

Lignite oxidative desulphurization: notice 3—process technological aspects and application of products

International Journal of Coal Science & Technology - The study reviews the process of oxidative desulphurization of high-sulphur Ukrainian lignite, which was performed by coal treatment using...     

Effect of the oxygen content in a salt solution on the characteristics of sodium-reduced tantalum powders

The characteristics of the tantalum powders produced by sodium thermal reduction from salt melts based on K₂TaF₇ and NaCl with various amounts of added oxycompounds K₃TaOF₆ and K₂Ta₂O₃F₆ are studied. At a molar ratio of oxygen to tantalum of 1.25 in the initial melt, capacitor tantalum powders with a specific surface area more than 3 m²/g are produced. The specific capacitance of the anodes made from these powders reaches 58 mC/g.     

Sodium thermal reduction of tantalum powders from melts with tantalum pentaoxide additions

The effect of the oxygen concentration in a melt on the characteristics of sodium-reduced tantalum powders, which were produced from potassium heptafluotantalate-based melts with tantalum pentaoxide additions, is studied. An increase in the oxygen content in the initial melt from 0.35 to 2.0 wt % leads to an increase in the specific surface of the formed powder from 1.2 to 3.5 m²/g. The specific charge of anodes made from these powders is 37800–70700 CV/g.