The MnO phase on the surface

The MnO2 phase on the surface of high-silica samples is characterized by a mesh structure consisting of nanorods about 10–20nm in diameter and 500–700nm in length, chemically cross-linked with the CL surface. The MnO2 phase in low-silica samples consists of oval-shaped particles of 50–100nm, scattered within the porous structure of the CL rock. The formation of the MnO2 phase in high-silica samples occurs in a fairly thin (12–50µm) layer with a high concentration (22.59–27.07%), while the layer in which the MnO2 phase forms in low-silica samples is 800–1100µm-thick, with a low concentration (2.64–3.58%). We have found that modification with MnO2 leads to increased mechanical and chemical strength of the resulting granular materials for all samples and virtually does not affect the volume of their sorption space. A MnO2 layer deposited on the surface of CL rock particles is easily permeable to small molecules (water, benzene), as well as to Mn2+ ions, but considerably hinders prostaglandin receptors by large molecules (methylene blue, sodium lauryl sulfate) into the internal pores of the particles. To summarize, the study we have carried out allowed to expand the notion of the structural and morphological properties of the MnO2 phase and the mechanism of its formation on the surface of clinoptilolite rocks obtained from different deposits.
Introduction The acoustoelastic pulse-echo method that has gained wide application in industry was first described by Benson and Raelson in their fundamental 1959 study [1]. The authors proposed a new method for measuring the stresses in an isotropic material. The phenomenon that the method is based on is in the difference of the velocities of transverse waves polarized parallel and perpendicular to the direction of stresses in the materials under load, i.e., the anisotropy of the stressed medium. This phenomenon has been termed the acoustoelastic effect and method for assessing the stress-strain state of structural elements is referred to as the acoustoelastic method.
Experimental procedure
Results and discussion Acoustic anisotropy was measured in the unstrained sample before the start of the tests; the measurements yielded values equal to 0.52% within the measurement error in all examined points. The longitudinal wave velocity in these points was 6.3610mm/µs. The test results are described below. Fig. 3 shows graphs for the distribution of acoustic anisotropy, obtained after 50,000 and 70,000 loading cycles with the magnitude of the external load reaching 108.6MPa, which corresponds to 1.44σ0.2 (the load curve preserved a weak hysteresis). It can be seen from the obtained curves that after 50,000 loading cycles, acoustic anisotropy no longer had a constant distribution in the material, and there were regions where the magnitude of acoustic anisotropy increased monotonically. After 70,000 cycles this trend was even more pronounced, while acoustic anisotropy was redistributed from the midpoints of the sample\'s working area, where it started to decrease, to the points located near the fillet transition where it kept increasing. Next, acoustic anisotropy and the velocities of longitudinal and transverse ultrasonic waves were measured in three stages after 80,000, 85,740 and 88,790 loading cycles with the external load corresponding to 118.1MPa (1.57σ0.2). The last measurement stage was carried out in 170 cycles, until the test sample fractured. Measurements of thickness and absolute elongation revealed that the sample acquired significant relative residual strain, amounting to 2.4%, 6.6% and 10.6%at the three respective stages. The highest residual plastic strain occurred in points of the working area closest to the fillet transitions. Fracture occurred after 88,960 loading cycles, with a neck forming near the fracture site around points 4–5. The acoustic anisotropy measurements at each of these stages are shown in Fig. 4.