The possibility of obtaining the vermiculite fire treatment at low temperature (burnt vermiculite) is considered in the article. The vermiculite structure features are investigated to reduce the subsequent burn temperature. By X-ray diffraction analysis it is established that the pre-treatment by a salt solution causes a change in the elementary cell of the vermiculite crystalline grid. It allows to receive the extended vermiculite under the lower burn temperature than in case of the ordinary non-treated vermiculite. To show the creation possibility of the building materials with burnt vermiculite the concrete unit weight and strength with gypsum and cement binder are studied. It is determined that the mentioned concrete strength is higher compared to concrete with ordinary vermiculite at the same density of these concretes. The thermal insulation properties are also significantly higher. The light concrete with vermiculite aggregate is used as the thermal-shield enclosing structures in building and structure constructions. The decrease of the vermiculite burn temperature will contribute to reducing the energy intensity of construction as a whole.
It has been noted that the information on magnetic properties of specific magnets available in the design and operation of magnetic separators/analyzers using magnetic fillers in the form of balls as the working body (polygradient type) is extremely limited, especially for magnets with varying sphericity coefficients (mutual ratios of characteristic sizes). Experiments using cylindrical samples (porous) as a ferromagnetic matrix rendered the induction data subsequently applied to establish the magnetic permeability, susceptibility, and magnetization values for the samples at various values of the length-todiameter ratio of φ = 1–16. The demagnetizing factor N was obtained and analyzed for the «short» samples (1 ≤ φ [φ]) in the range of magnetizing field strengths of 9–47 kA/m, taking into account the established transient value of φ = [φ] = 10–12 (when, at φ ≥ [φ], the magnetic properties of the sample correspond to the magnetic properties of its quasi-solid material). The analysis results for these data, required when assessing the actual magnetic properties of «short» working bodies, characteristic of polygradient magnetic separators/ analyzers, demonstrate the validity of the exponential dependence (decreasing with increasing) of their demagnetizing factor. The research was carried out with the financial support of the Ministry of Education and Science of the Russian Federation within the framework of the State Assignment in the field of science (project No. 0706-2020-0024) and of the Russian Foundation for Basic Research and the Royal Society of London under research project No. 20-52-10006.
When experimentally studying magnetic properties of the ferromagnetic materials, preferences are often given to a more convenient method involving the use of sufficiently long cylindrical samples with the L length and the D diameter placed in the solenoid field as an alternative to the method based on using classical samples of the toroidal shape (to exclude manifestations of the demagnetizing factor). Currently, required justification is practically missing for specific values of the relative L/D length, which would indicate such [L/D] values (for L/D ≥ [L/D]), at which magnetic properties of a sample (already long enough) correspond to magnetic properties of its material. While the existing recommendations such as [L/D] = 50 are postulated, let us note that relevant experimental studies of magnetic properties of the cylindrical samples with the L/D parameter targeted variation were not made. An attempt was made to fill this gap. For cylindrical steel samples with the different L/D values (from 1 to 50), families of the B magnetic induction and of the μ permeability field dependencies were obtained experimentally using the ballistic method. The sought [L/D] values were determined from the B and μ dependencies on the L/D by the junction abscissa of the ascending and self-similar branches. It was established that in the accepted field strength in the range of H = 0.94--54.2 kА/m magnetizing field, the [L/D] parameter is a variable substantially depending on H (and/or μ). It varies from [L/D] = 10--15 at H = 54.2 kA/m (μ = 30) to [L/D] = 50--60 at H = 4.7 kA/m (μ = 270). And at H < 4.7 kA/m, [L/D] > 50--60, i.e., more than is commonly believed. Thus, it was stated that the data on magnetic properties obtained when using even long samples (L/D = 50) and declared as data on the magnetic properties of the corresponding material, are only close to those with H < 4.7 kA/m. Phenomenological expressions were obtained for the [L/D] determination: exponential with the H argument and logarithmic with the μ argument
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