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A novel solid-phase synthetic approach was developed to produce a mineral-like composite ceramic based on strontium titanate (SrTiO3) and yttrium titanate (Y2Ti2O7) matrices for immobilizing radionuclides such as 90Sr and its daughter product 90Y, as well as lanthanides and actinides, via reactive spark plasma sintering technology (SPS-RS). Using XRD, SEM, and EDS analyses, the sintering kinetics of the initial mixed oxide reactants of composition YxSr1–1.5xTiO3 (x = 0.2, 0.4, 0.6 and 1) and structure-phase changes in the ceramics under SPS-RS conditions were investigated as a function of Y3+ content. In addition, a detailed study of phase transformation kinetics over time as a function of the heating temperature of the initial components (SrCO3, TiO2, and Y2O3) was conducted via in situ synchrotron XRD heating experiments. The composite ceramic achieved relatively high physicomechanical properties, including relative density between 4.92–4.64 g/cm3, Vickers microhardness of 500–800 HV, and compressive strength ranging from 95.5–272.4 MPa. An evaluation of hydrolytic stability and leaching rates of Sr2+ and Y3+ from the matrices was performed, demonstrating rates did not exceed 10−5–10−6 g·cm−2·day−1 in compliance with GOST R 50926-96 and ANSI/ANS 16.1 standards. The leaching mechanism of these components was studied, including the calculation of solution penetration depth in the ceramic bulk and ion diffusion coefficients in the solution. These findings show great promise for radioactive waste conditioning technologies and the manufacturing of radioisotope products. [ABSTRACT FROM AUTHOR]

The paper presents a reliable technology combining sol–gel synthesis and spark plasma sintering (SPS) to obtain SrTiO3 perovskite-type ceramics with excellent physicomechanical properties and hydrolytic stability for the long-term retention of radioactive strontium radionuclides. The Pechini sol–gel method was used to synthesize SrTiO3 powder from Sr(NO3)2 and TiCl3 (15%) precursors. Ceramic matrix samples were fabricated by SPS in the temperature range of 900–1200 °C. The perovskite structure of the synthesized initial SrTiO3 powder was confirmed by X-ray diffraction and thermal analysis results. Scanning electron microscopy revealed agglomeration of the nanoparticles and a pronounced tendency for densification in the sintered compact with increasing sintering temperature. Chemical homogeneity of ceramics was confirmed by energy dispersive X-ray analysis. Physicochemical characteristic studies included density measurement results (3.11–4.80 g·cm−3), dilatometric dependencies, Vickers microhardness (20–900 HV), and hydrolytic stability (10−6–10−7 g·cm−2·day−2), exceeding GOST R 50926-96 and ISO 6961:1982 requirements for solid-state matrices. Ceramic sintered at 1200 °C demonstrated the lowest strontium leaching rate of 10−7 g/cm2·day, optimal for radioactive waste (RAW) isolation. The proposed approach can be used to fabricate mineral-like forms suitable for RAW handling. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

This research introduces a method to enhance the biocompatibility of bioinert Al2O3-based ceramics by incorporating calcium phosphates (hydroxyapatite (HAp) and tricalcium phosphate (TCP)) into alumina via spark plasma sintering-reactive sintering (SPS-RS). TGA/DTG/DTA and XRD revealed phase formation of HAp and TCP and determined the main temperature points of solid-phase reactions occurring in situ during the sintering of the CaO-CaHPO4 mixture within the volume of Al2O3 under SPS-RS conditions in the range of 900–1200 °C. SEM, EDX, low temperature, and nitrogen physisorption were used to monitor changes in the morphology, structure, and elemental composition of bioceramics. Structural meso- and macroporosity, with a mean mesopore size of 10 nm, were revealed in the ceramic volume, while sintering temperature was shown to play a destructive role towards the porous inorganic framework. The physico-chemical characterization demonstrated increased relative density (up to 95.1%), compressive strength (640 MPa and above), and Vickers microhardness (up to 700 HV) depending on the HAp and TCP content and sintering temperature. Four bioceramic samples with different contents of HAP (20 and 50 wt.%) were bio-tested in in vivo models. The samples were implanted into the soft tissues under the superficial fascia of the thorax of a laboratory animal (a New Zealand White rabbit, female) in the area of the trapezius muscle and the broadest muscle of the back. Based on the results of the assessment of the surrounding tissue reaction, the absence of specific inflammation, necrosis, and tumor formation in the tissues during the implantation period of 90 days was proven. Microbial tests and dynamics of Pseudomonas aeruginosa bacterial film formation on bioceramic surfaces were studied with respect to HAp content (20 and 50 wt.%) and holding time (18, 24, and 48 h) in the feed medium. [ABSTRACT FROM AUTHOR]

This paper reports a method for the fabrication of mineral-like SrMoO4 ceramics with a powellite structure, which is promising for the immobilization of the high-energy 90Sr radioisotope. The reported method is based on the solid-phase "in situ" interaction between SrO and MoO3 oxides initiated under spark plasma sintering (SPS) conditions. Dilatometry, XRD, SEM, and EDX methods were used to investigate the consolidation dynamics, phase formation, and structural changes in the reactive powder blend and sintered ceramics. The temperature conditions for SrMoO4 formation under SPS were determined, yielding ceramics with a relative density of 84.0–96.3%, Vickers microhardness of 157–295 HV, and compressive strength of 54–331 MPa. Ceramic samples demonstrate a low Sr leaching rate of 10−6 g/cm2·day, indicating a rather high hydrolytic stability and meeting the requirements of GOST R 50926-96 imposed on solid radioactive wastes. The results presented here show a wide range of prospects for the application of ceramic matrixes with the mineral-like composition studied here to radioactive waste processing and radioisotope manufacturing. [ABSTRACT FROM AUTHOR]

The paper presents an original approach to the synthesis of polycalciumorganyl silsesquioxanes through the reaction of polyorganyl silsesquioxanes [RSiO1.5]n (where R is an ethyl and phenyl radical) with sea urchin skeleton under the conditions of mechanochemical activation. The novelty and practical significance of the present study lies in the use of an available natural raw source as a source of calcium ions to initiate the reaction of calcium silicate formation and create a matrix for the formation of a porous inorganic composite framework. The thermal stability of the introduced silicates, i.e., the ability to maintain a porous structure at high temperatures, is key to the production of an ordered porous material. The reaction scheme was proposed to be based on the interaction of calcium carbonate with the siloxane bond. FTIR, XRD, GPC, and TGA were used to study the composition and structure of the obtained materials. The cross-sectional area of the polymer chain and the volumes of the coherent scattering regions of the polymers obtained were calculated from the XRD data. To prepare the composites, the sea urchin skeleton was further modified with polycalciumorganyl silsesquioxanes in a toluene solution. To remove the sea urchin skeleton, the obtained biomimetic composites were treated with hydrochloric acid. The results of the morphological and surface composition studies are reported. The method proposed in the paper could be of fundamental importance for the possibility of obtaining structured porous composite materials for a wide range of practical applications, including for the purpose of creating a composite that may be a promising carrier for targeted delivery of chemotherapy agents. [ABSTRACT FROM AUTHOR]

This paper considers the results of an examination of painted pottery from prehistoric sites of the Prmor'ye region (Southern Russian Far East) in the northwestern part of the Sea of Japan basin. Red-painted and black-painted ceramic wares occur here only in the remains of the Yankovskaya archaeological culture dated to the 1st mil. BCE. Red painting appears as a colored surface coating, and black painting is represented by very simple drawn patterns. Until recently painting decorations have not been intentionally studied. The objects of our investigation are a small series of red-painted and black-painted ceramic fragments originated from archaeological sites. The methods of optical microscopy, SEM-EDS, and Raman spectroscopy were applied to the study of research materials. As a result, the data on characteristics of texture and composition of red and black paints were obtained. Both were determined to be pre-firing paints. Red paint is a clayish substance mixed with natural ochre pigment containing the hematite coloring agent. Black paint is carbon-based. Black carbon and burnt bone are recognized as colorants. The presented materials are new evidence of pottery paint technologies in prehistoric Eurasia. [ABSTRACT FROM AUTHOR]

Synthetic calcium silicates and phosphates are promising compounds for targeted drug delivery for the effective treatment of cancerous tumors, and for minimizing toxic effects on the patient's entire body. This work presents an original synthesis of a composite based on crystalline wollastonite CaSiO3 and combeite Na4Ca4(Si6O18), using a sea urchin Mesocentrotus nudus skeleton by microwave heating under hydrothermal conditions. The phase and elemental composition and structure of the obtained composite were studied by XRF, REM, BET, and EDS methods, depending on the microwave heating time of 30 or 60 min, respectively, and the influence of thermo-oxidative post-treatment of samples. The role of the sea urchin skeleton in the synthesis was shown. First, it provides a raw material base (source of Ca2+) for the formation of the calcium silicate composite. Second, it is a matrix for the formation of its porous inorganic framework. The sorption capacity of the composite, with respect to 5-fluorouracil, was estimated, the value of which was 12.3 mg/L. The resulting composite is a promising carrier for the targeted delivery of chemotherapeutic drugs. The mechanism of drug release from an inorganic natural matrix was also evaluated by fitting its release profile to various mathematical models. [ABSTRACT FROM AUTHOR]

Reconstructive and regenerative bone surgery is based on the use of high-tech biocompatible implants needed to restore the functions of the musculoskeletal system of patients. Ti6Al4V is one of the most widely used titanium alloys for a variety of applications where low density and excellent corrosion resistance are required, including biomechanical applications (implants and prostheses). Calcium silicate or wollastonite (CaSiO3) and calcium hydroxyapatite (HAp) is a bioceramic material used in biomedicine due to its bioactive properties, which can potentially be used for bone repair. In this regard, the research investigates the possibility of using spark plasma sintering technology to obtain new CaSiO3-HAp biocomposite ceramics reinforced with a Ti6Al4V titanium alloy matrix obtained by additive manufacturing. The phase and elemental compositions, structure, and morphology of the initial CaSiO3-HAp powder and its ceramic metal biocomposite were studied by X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller analysis methods. The spark plasma sintering technology was shown to be efficient for the consolidation of CaSiO3-HAp powder in volume with a Ti6Al4V reinforcing matrix to obtain a ceramic metal biocomposite of an integral form. Vickers microhardness values were determined for the alloy and bioceramics (~500 and 560 HV, respectively), as well as for their interface area (~640 HV). An assessment of the critical stress intensity factor KIc (crack resistance) was performed. The research result is new and represents a prospect for the creation of high-tech implant products for regenerative bone surgery. [ABSTRACT FROM AUTHOR]

The paper presents a method of obtaining functionally graded material (FGM) of heterogeneous (layered) type based on joined metals Cr-Ti-Fe-Co-Ni-Cu using spark plasma sintering (SPS) technology. The structure, elemental and phase composition of FGM obtained on the basis of joined metals with different values of the temperature coefficient of linear expansion (CTLE) were studied by SEM, EDS and XRD methods with regard to the phase states of the alloy system. Based on the Vickers microhardness data, the evaluation of the mechanical characteristics of FGM in the whole sample body and locally at the contact boundaries of the joined metals was carried out. The results of the study are new and represent a potential for FGM, as well as functionally graded coatings (FGC), which have special physical, chemical and mechanical properties and are highly demanded for the manufacture of structures and products for industrial applications. [ABSTRACT FROM AUTHOR]

The article considers the effect of a filler based on synthetic wollastonite (CaSiO3), which is introduced into a polymer matrix made of ultra-high molecular weight polyethylene, on the tribotechnical parameters of the produced polymer composite material. Behavioral features of composites after friction were investigated by infrared spectroscopy and scanning electron microscopy. It was found that the introduction of wollastonite into the polymer matrix contributed to a reduction in the friction coefficient by 23% and the wear rate by four times. In the micrographs of the friction surfaces of the obtained composite, the formation of new secondary structures oriented along the friction direction, different from the initial polymer matrix, was revealed. The presence of wear products (oxidized polymer groups) and CaSiO3 on the friction surfaces was recorded by infrared spectroscopy. It was established that the synthesized CaSiO3 particles were deformed under the action of shear forces and participated in tribochemical processes. [ABSTRACT FROM AUTHOR]

This paper considers the results of an examination of a polychrome glazed anthropomorphic ceramic figurine from the Prmor'ye region (southern Russian Far East) discovered at one of the Jin period (1115–1234 CE) archaeological sites. The study attests to the hypothesis about the attribution of this unique art object to the "red-and-green porcelain" produced in Northern China since the mid-Jin period. At present "the red-and-green porcelain" is the object of certain research interest as an important stage of Chinese ceramics history preceding the invention of famous porcelains with overglazed enamel decoration. The main technological features and material properties of the studied object were determined using analytical methods of optical and electron (SEM) microscopy with the use of X-ray elemental composition analysis (EDS, pXRF). The main result of the study presented in the paper includes evidence that the polychrome ceramic figurine found at the Anan'evka walled town in Primor'ey in the south of the Russian Far East belongs to the category of "red-and-green porcelain", or "red-green ware". As supposed, the figurine portrays Zen monk Budai—a person popular in Chinese arts and spiritual culture of the Song and Jin periods. Therefore, the polychrome ceramics figurine from the Primor'ye region may be considered today as the most northeastern case of "red-and-green porcelain" discovered in an archaeological context. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The investigation presented in this paper is a unique assemblage of ceramic casting molds discovered at one of the sites from the Bohai period (698–926) in the territory of the southern Russian Far East. The main research aim is to recognize probable traces of metal alloys cast in ceramic molds. Nondestructive pXRF and SEM-EDS methods were used as the research instruments for detecting the expected alloys' chemical components. As a result, the elements Pb, Sn, Cu, and As were indicated at the surfaces of the molds' cavities with evidence of carbonization caused by the casting process. Preliminarily, two groups of alloys were distinguished: lead-bearing alloys and lead-free alloys. Our new insights are in good accordance with the results of previous investigations on chemical compositions of bronzes from the Bohai period archaeological sites of the southern Russian Far East. In particular, data on the examination of ceramic molds confirm the conclusion that various kinds of copper alloys were known and used in the bronze casting craft of the Bohai period. [ABSTRACT FROM AUTHOR]

The paper presents an original method for the template synthesis of biomimetic porous composites using polyferrophenylsiloxane (PFPS) and the skeleton of the sea urchin Strongylocentrotus intermedius as a structuring template. The study aimed to form an organosilicon base of a composite with an inverted structure relative to the original structure of the sea urchin shell with a period of structure movement of about 20 µm and ceramic composites fabrication with the silicate base with an average pore size distribution of about 10 μm obtained by the reaction of PFPS with the inorganic base of the sea urchin test under conditions of calcination at 1000 °C followed by acid etching. The composition and morphology of the obtained composites were investigated by IR, XRD, XPS, EDX, and SEM techniques and by mercury porosimetry; the parameters of the porous structures depend on the selected methods of their synthesis. The proposed method is of fundamental importance for developing methods for the chemical synthesis of new biomimetics with a unique porosity architecture based on environmentally friendly natural raw materials for a vast practical application. [ABSTRACT FROM AUTHOR]

The paper describes the method for producing WC-10wt%Co hard alloy with 99.6% of the theoretical density and a Vickers hardness of ~1400 HV 0.5. Experimental data on densification dynamics, phase composition, morphology, mechanical properties, and grain size distribution of WC-10%wtCo using spark plasma sintering (SPS) within the range of 1000–1200 °C are presented. The high quality of the product is provided by the advanced method of high-speed powder mixture SPS-consolidation at achieving a high degree of densification with minimal calculated grain growth at 1200 °C. [ABSTRACT FROM AUTHOR]

This paper studied the effect of additives of 0.5–20 wt.% synthetic CaSiO3 wollastonite on the thermodynamic, mechanical, and tribological characteristics and structure of polymer composite materials (PCM) based on ultra-high-molecular weight polyethylene (UHMWPE). Using thermogravimetric analysis, X-ray fluorescence, scanning electron microscope, and laser light diffraction methods, it was shown that autoclave synthesis in the multicomponent system CaSO4·2H2O–SiO2·nH2O–KOH–H2O allows one to obtain neeindle-shaped nanosized CaSiO3 particles. It was shown that synthetic wollastonite is an effective filler of UHMWPE, which can significantly increase the deformation-strength and tribological characteristics of PCM. The active participation of wollastonite in tribochemical reactions occurring during friction of PCM by infrared spectroscopy was detected: new peaks related to oxygen-containing functional groups (hydroxyl and carbonyl) appeared. The developed UHMWPE/CaSiO3 materials have high wear resistance and can be used as triboengineering materials. [ABSTRACT FROM AUTHOR]

The article presents an original way of getting porous and mechanically strong CaSiO3-HAp ceramics, which is highly desirable for bone-ceramic implants in bone restoration surgery. The method combines wet and solid-phase approaches of inorganic synthesis: sol-gel (template) technology to produce the amorphous xonotlite (Ca6Si6O17·2OH) as the raw material, followed by its spark plasma sintering–reactive synthesis (SPS-RS) into ceramics. Formation of both crystalline wollastonite (CaSiO3) and hydroxyapatite (Ca10(PO4)6(OH)2) occurs "in situ" under SPS conditions, which is the main novelty of the method, due to combining the solid-phase transitions of the amorphous xonotlite with the chemical reaction within the powder mixture between CaO and CaHPO4. Formation of pristine HAp and its composite derivative with wollastonite was studied by means of TGA and XRD with the temperatures of the "in situ" interactions also determined. A facile route to tailor a macroporous structure is suggested, with polymer (siloxane-acrylate latex) and carbon (fibers and powder) fillers being used as the pore-forming templates. Microbial tests were carried out to reveal the morphological features of the bacterial film Pseudomonas aeruginosa that formed on the surface of the ceramics, depending on the content of HAp (0, 20, and 50 wt%). [ABSTRACT FROM AUTHOR]