Sorbents based on polyacrylonitrile fiber, containing ferrocyanides of transition metals and manganese oxides (CoMn-PAN and FeMn-PAN) or iron(III) hydroxide (CoFe-PAN) in their structure were obtained, as confirmed by the results of X-ray diffraction and energy-dispersive analyses. The selectivity of the obtained sorbents was investigated, along with their ability to sorb Cs, Ba (as an analog of Ra), P, and Be from various natural media, including river water and seawater with varying salinity of 18.2 and 33.8 ‰. The data show that the sorbents are universal for the recovery of artificial 137Cs and natural radionuclides from the natural environments, including complex salt composition (seawater). Researching the obtained sorbents during marine expeditions confirmed the efficiency of the obtained materials based on transition metal ferrocyanides and manganese oxides (CoMn-PAN and FeMn-PAN) for the sorption of 137Cs, 7Be, 210Pb, 210Po, 226Ra, 228Ra, and 234Th. Additionally, the sorbent based on transition metal ferrocyanides and iron(III) hydroxide (CoFe-PAN) was effective for the sorption of 137Cs, 7Be, 32P, 33P, 210Pb, 210Po, and 234Th. Based on the obtained results, methods for comprehensively determining artificial 137Cs and natural radionuclides using these sorbents were developed.

A mesoporous calcium silicate (CaSiO3) adsorbent was synthesized by alkaline hydrothermal conversion of boric acid production waste (borogypsum). The material demonstrated a high adsorption capacity for Co2+ ions. The capacity reached 220.8 mg/g. It was found that sorption proceeds predominantly via an ion exchange mechanism with the formation of a CaCoSi2O6 precursor. Dense (3.33 g/cm3) ceramic matrices with high compressive strength (481 MPa) and microhardness (~7.54 GPa) were obtained by spark plasma sintering (SPS) at 1 000 °C. The cobalt leaching rate from the matrices was 2.04×10–7 g/(cm2×day). This meets the requirements for solidified radioactive waste.

The paper presents the results of a study of synthetic wollastonite from boric acid production waste (borogypsum) on the physical, mechanical and tribological properties of polymer composite materials based on polytetrafluoroethylene. Wollastonite was synthesized from borogypsum by its hydrothermal treatment in alkaline medium and subsequent calcination of the obtained precipitate at 900-1000 degrees C for 1 h. The product with a specific surface area of 1.4 m(2)/g and a density of 3.06 g/cm(3) obtained under the above regimes is characterized by the presence of wollastonite of triclinic modification and the presence of CaSO4 anhydrite. The wollastonite particles are needle-shaped with a needle diameter of similar to 100 nm. Needle-shaped wollastonite particles are shown to be interconnected and form conglomerates and agglomerates ranging in size from 10 to 70 mu m. Particle agglomerates are characterized by a wide unimodal distribution of pores with a maximum of 3.78 nm with conical and slit-like shapes. It was found that the use of wollastonite results in increased wear resistance of polymer composites based on PTFE. Composites filled with 10 and 20 wt.% of wollastonite are characterized by a 700-fold decrease in the rate of mass wear relative to the initial polymer. Physical and mechanical studies of PCM show that the introduction of wollastonite increases compressive strength and modulus of elasticity. However, a decrease in strain-strength parameters was observed. Scanning electron microscopy shows the formation of secondary structures on friction surfaces, which plays a role in the adaptation of the composite to wear. The method of IR spectroscopy of friction surfaces registered the appearance of new peaks corresponding to hydroxyl, carbonyl and carboxyl compounds. This indicates a certain contribution of wollastonite particles to tribochemical processes.

This paper is devoted to the study of silicate coatings based on the CaSiO 3 –PbSiO 3 binary system showing promise as a material for spacecraft thermal control coatings. A comparative analysis of coatings produced using two different methods is performed: plasma spraying and gas dynamic cold spraying. Their structure and phase and elemental composition are examined.

We have studied general trends in the formation of nanostructured sodium aluminosilicates with a Si/Al ratio from 1 to 5 in a multicomponent aqueous system. Data are presented on the elemental composition, morphology, and thermal behavior of the synthesized compounds and their Cs + sorption performance under static conditions. The results demonstrate that the sorption capacity of the sodium aluminosilicates (89.3–328.2 mg/g) exceeds that of some reported sorbents, which opens up the possibility of employing such aluminosilicates for Cs + removal from aqueous solutions.

A mesoporous adsorbent based on calcium silicate CaSiO3 for the removal and immobilization of cobalt Co-60 radionuclides in durable ceramic CaCoSi2O6 matrices was synthesized by hydrothermal conversion of boric acid production waste. The obtained material had a high Co2+ ions adsorption capacity of 220.8 mg/g. Cobalt adsorption was carried out mainly by ion exchange, which led to the formation of CaCoSi2O6 precursor ceramic matrices. The use of spark plasma sintering (SPS) technology at an optimal temperature of 1000 degrees C allowed the safe immobilization of Co2+ ions in CaCoSi2O6 ceramic matrices characterized by density (3.33 g/cm(3)), compressive strength (481 MPa) and microhardness (similar to 9.81 GPa). Sintered CaCoSi2O6 ceramic samples were characterized by high hydrolytic stability (cobalt leaching rate R-Co similar to 10(-7) g/(cm(2) x day)) and complied with the requirements for cured highly active waste GOST R 50926 96/ANSI/ANS 16.1.

The paper studies the reflectivity and radiation resistance of calcium carbonate, which is often an accompanying component of wollastonite, a promising material as a pigment for spacecraft thermal control coatings. Synthetic calcium carbonate of the calcite modification was obtained in an aqueous medium, its phase composition, morphology and particle size were investigated. The study was carried out on a facility simulating outer space conditions, under irradiation of CaCO3 powders with accelerated electrons with an energy of 30 keV and a fluence of 110(16), 210(16) and 3 10(16) cm(-2). The spectra recording before and after the irradiation periods was conducted in vacuum in situ, which allows avoiding the interaction of irradiation-induced defects with atmospheric gases. A negligible optical degradation of calcite in the wavelength region of 250 and 600 nm is observed during irradiation, while the structure of CaCO3 does not undergo noticeable degradation according to IR spectroscopy.

In this work the method of obtaining composite ceramics based on perovskite and pyrochlore of compositions YxZrxSr1-3xTiO3 (x = 0.1, x = 0.2, x = 0.3) and Y2(ZrxTi)2O7 (x = 1) using the technology of reactive spark plasma sintering has been investigated. A comprehensive study of phase transformations, structure formation and physical and mechanical characteristics of ceramics depending on the ratio of Sr2+/Y3+/Zr4+ has been carried out by XRD, SEM, EDS and “diffraction movie” methods at the synchrotron radiation source. High hydrolytic stability of ceramics is proved and the mechanism of low leaching rate of Sr2+ < 10–7 g cm−2 day, Y3+ and Zr4+ < 10–5 g cm−2 day is described, which corresponds to GOST R 50926-96 and ANSI/ANS 16.1. The results of the work are promising for conditioning of radioactive waste and production of radioisotope products.

Using rice straw as a source of silicon, a new composite material containing wollastonite CaSiO3, silicon dioxide SiO2, and an organic component (cellulose and lignin) was obtained. It is shown that calcination up to 1200°C leads to crystallization of SiO2 in the form of quartz and cristobalite, while the bulk density increases from 2.48 to 3.01 g/cm3. Using IR spectroscopy, the features of crystallization processes during calcination were studied, as were the morphology of particles and the nature of their surface. It is shown that the reflection coefficient in the visible range and the whiteness for biogenic calcium silicate are higher than for wollastonite obtained from reagents and reaches 98.9

This paper considers the effect of wollastonite synthesized in the CaCl2-Na2SiO3-H2O model system at a temperature of 20 oC on the physical and mechanical properties and structure of ultrahigh molecular weight polyethylene. The possibility of optimizing the process of wollastonite synthesis is proposed, which consists in the interaction of the initial components in an aqueous solution at room temperature. The study of the synthesized powders revealed the formation of finely dispersed oval, porous particles. X-ray phase analysis of the synthesis product revealed the presence of an amorphous phase of wollastonite and calcite, which is consistent with its elemental composi-tion. It is shown that the introduction of wollastonite into the polymer matrix leads to a significant increase in the elastic modulus by 58% and compressive strength at a relative deformation of 25% by 27% compared to unfilled ultrahigh molecular weight polyethylene. It was shown that wollas-tonite structures of the polymer matrix, with the formation of spherulite formations smaller than those of the original polymer. IR spectroscopy revealed the presence of new peaks belonging to the ester group in composites containing wollastonite. The presence of a new oxygen-containing peak is due to the presence of adsorbed water and oxygen molecules in the pores of wollastonite, which leads to the activation of oxidative processes during the processing of composites. It is shown that the occurrence of oxidative processes and the evaporation of adsorbed water leads to weak interfa-cial interaction (weak adhesion) in the boundary region between the filler and the polymer matrix. However, the occurrence of oxidative processes within the amorphous phase causes an increase in the rigidity of the material. The method of differential scanning calorimetry established a decrease in the values of the enthalpy of melting and the degree of crystallinity with the introduction of wollastonite.

The development of drilling waste recycling technologies is a crucial task, primarily due to their negative impact on the environment, the increasing need for state control over compliance with environmental legislation by oil production companies, and the absence of universal technological solutions for their recycling and neutralization. This article provides a brief overview of various methods to recycle drilling waste for the production of different materials. Using drilling waste located in the Tyumen region as an example, the study demonstrates the potential of incorporating them as additives in fine-grained concrete.

This study investigates the impact of a binary filler on the physicomechanical and tribological properties, as well as structure, of polymeric composite materials based on ultra-high-molecular-weight polyethylene. The organic modifier—2-mercaptobenzothiazole and wollastonite particles synthesized from two different systems (modeled and derived from waste) were used as the binary filler. The synthesis of wollastonite was carried out in the complex model system (CaSO4·2H2O–SiO2·nH2O–KOH–H2O) and from technogenic waste (borogypsum). It was demonstrated that the introduction of the binary filler made it possible to obtain an optimal combination of mechanical and tribological properties. It was found that during the wear of polymeric composite materials loaded with organic fillers, the fillers migrate to the friction surface, providing a shield against abrasive wear of the steel counterface. Due to the modification of ultra-high-molecular-weight polyethylene by 2-mercaptobenzothiazole, the interdiffusion of polymeric matrix macromolecules and interphase coupling with wollastonite particles improve. The 2-mercaptobenzothiazole organic compound used as the filler facilitates the relaxation processes within the composite under external loads.

Abstract—The article presents data on the synthesis of nanostructured, X-ray amorphous lithium aluminosilicate, with a Si : Al ratio of 3 : 1. The composition, morphology, and thermal behavior were studied. The sorption isotherm of Cs+ ions was obtained under static conditions with a ratio of T : L = 1 : 400. The maximum sorption capacity, degree of extraction, and distribution coefficients of cesium were determined. Data on the sorption kinetics of Cs+ ions were obtained at temperatures 30 and 60°C, and the activation energy of the sorption process and diffusion coefficients were calculated.

The paper is focused on the study of the CaSiO3-PbSiO3 two-component system, which is promising for use as a basis for thermal control spacecraft coatings. The thermal behavior of silicate powders, their reflectivity, radiation resistance, as well as structural changes under electron irradiation with an energy of 30 keV, have been studied. When a mixture of α-CaSiO3-PbSiO3 powders is heated above the melting point of the binder component (800 °C), a phase transition of pseudo-wollastonite to β-CaSiO3 (wollastonite) is observed. The reflectivity of the powder mixture is lower than that of the original pure pigment of CaSiO3, which is explained by the presence of a silicate binder.

Calcium aluminosilicates synthesized by chemical modification of nanostructured synthetic Na zeolites were characterized. The sorption properties were studied for calcium aluminosilicates with SiO2 : Al2O3 ratios of 2 : 1, 4 : 1, 6 : 1, 8 : 1, and 10 : 1. The maximum capacity of these compounds to sorb Cs+ ions under static conditions from solutions without salt background was shown to reach 1.45 mmol/g (192.7 mg/g). The results of this work allow one to consider these compounds as promising materials for the sorption and immobilization of long-lived radionuclides.

An effective sorption material for the immobilization of cobalt radionuclides into highly safe and reliable solid-state matrices is proposed. The resulting silicate sorbent CaSiO3 had an amorphous mesoporous structure (ABET 53 m2/g) and a sorption capacity Co ions of 3.32 mmol/g. The physico-chemical characteristics of the CaCoSi2O6 sample obtained after Co2+ ions sorption were studied using XRD, N2 and Ar adsorption-desorption, SEM-EDX and TG/DTA methods. Solid-state silicate matrices characterized by high density values (2.86-3.16 g/cm3), compressive strength (150-637 MPa) and Vickers microhardness (1.80-5.25 GPa) were obtained by spark plasma sintering (SPS). The sample obtained at 1000 degrees C had the lowest values of Co2+ ions leaching (RCo ~10-7 g/(cm2xday)) and diffusion coefficient (De 1.73 x10-17 cm2/s) from silicate matrices. Thus, the obtained CaCoSi2O6 silicate matrices saturated with Co ions comply with the regulatory requirements of GOST R 50926-96 and ANSI/ANS 16.1 for 60Co immobilization. (c) 2022 Elsevier B.V. All rights reserved.

A new approach to the use of rice straw as a difficult-to-recycle agricultural waste was proposed. Potassium aluminosilicate was obtained by spark plasma sintering as an effective material for subsequent immobilization of 137Cs into a solid-state matrix. The sorption properties of potassium aluminosilicate to 137Cs from aqueous solutions were studied. The effect of the synthesis temperature on the phase composition, microstructure, and rate of cesium leaching from samples obtained at 800–1000 °C and a pressure of 25 MPa was investigated. It was shown that the positive dynamics of compaction was characteristic of glass ceramics throughout the sintering. Glass ceramics RS-(K,Cs)AlSi3O8 obtained by the SPS method at 1000 °C for 5 min was characterized by a high density of ∼2.62 g/cm3, Vickers hardness ∼ 2.1 GPa, compressive strength ∼231.3 MPa and the rate of cesium ions leaching of ∼1.37 × 10−7 g cm−2·day−1. The proposed approach makes it possible to safe dispose of rice straw and reduce emissions into the atmosphere of microdisperse amorphous silica, which is formed during its combustion and causes respiratory diseases, including cancer. In addition, the obtained is perspective to solve the problem of recycling long-lived 137Cs radionuclides formed during the operation of nuclear power plants into solid-state matrices.

To study the material based on the binary system Ti + Cu (50% atm), samples were produced from powders of commercially pure metals and additionally ground in a ball mill (final size about 12 µm) by spark plasma sintering. The following intermetallic phases were obtained in the materials: CuTi2, TiCu, and Ti3Cu4. The materials have a hardness of 363 and 385 HV (800 and 900 °C), a microhardness of 393 and 397 µHV, a density of 4.24 and 5.23 kg/m3, and resistance to corrosion in acids (weight gain + 0.002% after 24 h of testing according to ISO 16151 for a sample with 900 °C—the best result in comparison with steel 308, AA2024, CuA110Fe3Mn2). The hardness value varies due to the presence of pure metal agglomerates. The relationship between the temperature of spark plasma sintering and the characteristics of the material (material parameters improve with increasing temperature, segregation is reduced) is revealed.

The application of titanium and its alloys under friction conditions is severely restricted, owing to their poor wear resistance. The paper presents the results of studies of the composition, microstructure, and tribological properties of Ti-TiC-based composite coatings formed on titanium alloys by the electroarc treatment in an aqueous electrolyte using a graphite anode. It has been found that TiC grains have a different stoichiometry and do not contain oxygen. The grain size varies from hundreds of nanometers to tens of micrometers, and the micro-hardness of the treated surface reached the value of 29.5 GPa. The wear resistance of the treated surface increased approximately 40-fold, and the friction coefficient with steel decreased to 0.08–0.3 depending on the friction conditions. The formation of a composite material based on Ti-TiC will contribute to the effective protection of titanium alloys from frictional loads in engineering.