A.s. Portnyagin

Institute of Chemistry Philippines · Far Eastern Branch of Russian Academy of Sciences

High phase and structural sensitivity of magnetic properties strongly impacts the fabrication quality of the permanent magnets, therefore revealing effects of synthesis conditions on physico-chemical characteristics of magnetic materials is of paramount importance for optimization of magnet production especially in case when non-conventional techni...

The paper presents an original method for open-type ionizing radiation source (IRS) fabrication by the means of spark plasma sintering-reactive sintering (SPS-RS) of SrTiO3 ceramics as an active zone component reinforced by the titanium alloy framework produced by additive technology. Rapid heating regimes of SPS-RS are described with the focus on...

The paper presents spark plasma sintering-reaction synthesis (SPS-RS) of SrTiO3-based mineral-like ceramics with a perovskite structure, which is promising for immobilization of Sr-90 radionuclides. Detailed time-resolved study of phase transformations taking place in the reactive mixture (SrCO3 and TiO2) within 20–1000 °C temperature range was con...

ZrO2-hydroxyapatite composite bioceramics is considered to be a promising material for bone defects recovery, at the same time there are virtually no “in vivo” biotests reported for this system combining modern imaging techniques, histological studies, and blood biochemical analysis. Here we have thoroughly researched biocompatibility of high quali...

An efficient method was presented to perform the hydrothermal synthesis of a nanocrystalline SrWO4 powder with the scheelite structure and the spark plasma sintering (SPS) of ceramics based on it. The composition, morphology, and structure of samples under various synthesis temperature conditions were studied by X-ray powder diffraction analysis, s...

The paper studies spark plasma sintering of UO2-based ceramics nuclear fuel obtained from a mixture of pristine urania with 2 and 8 wt.% of Y2O3 (integral fuel burnable absorber) produced by liquid-phase ultrasonic homogenizing. Densification dynamics of UO2-Y2O3 system is investigated for the first time in the temperature range up to 1250 °C under...

An original method for producing a ceramic material based on silicon carbide (SiC) and its composite with the addition of hafnium diboride (SiC–HfB2) from organic raw materials of natural origin is pre- sented. The originality of the method is in the use of the spark plasma sintering-reactive synthesis of a powdermixture based on the product of the...

The paper studies spark plasma sintering (SPS) of industrially used UO2-based fuel containing integral fuel burnable absorber (IFBA) of neutrons Gd2O3. Densification dynamics of pristine UO2 powder and the one added with 2 and 8 wt.% of Gd2O3 under ultrasonication in liquid has been studied under SPS conditions at 1050, 1250, and 1450 °C. Effect of...

We report high-pressure synchrotron X-ray powder diffraction data for the W-rich cubic ZrW 2-x Mo x O 8 (x=0.4) up to 10 GPa with open decompression. This study shows that cubic- ZrW 1.6 Mo 0.4 O 8 transforms to orthorhombic phase at the 5.04 GPa. Pressure-induced reversable amorphization of material was observed at 8.13 GPa. The obtained data sugg...

The paper studies an original way to obtain mineral-like ceramics matrices suitable for solid immobilization of a high-energy ⁹⁰Sr isotope, which are safe configurations of the active zones of ionizing irradiation sources. Spark plasma sintering-reactive synthesis (SPS-RS) has been implemented for the first time to fabricate SrWO4 ceramics via “in...

UO2-based nuclear fuel containing integral fuel burnable absorbers (IFBA) is an economically and technically efficient solution for optimization of nuclear power reactors operation. The paper studies a new way to obtain compound UO2-Eu2O3 pellet fuel using an unconventional spark plasma sintering technology (SPS). Earlier unknown data on densificat...

A hydrothermal synthesis of ZrW2-xMoxO8 (0≤x≤2) from the corresponding precursors is reported in this paper. High-temperature and high-pressure data are presented for the sample with x=1.6. An increase in temperature initiates the phase transition from tetragonal precursor to orthorhombic-ZrW2-xMoxO8 (x=1.6) with the subsequent formation of cubic a...

The paper studies synthetic osteoplastic powder biocomposite, which is bioactive and extremely relevant for bone defect recovery in dentistry and maxillo-facial surgery. Biocomposite fabrication strategy is based on an original sol-gel (template) synthesis of the porous wollastonite containing 30 wt.% of hydroxyapatite. The way to tailor porosity i...

In this paper we report high-pressure synchrotron x-ray powder diffraction data for the cubic ZrWMoO8. For the first time, extensive structural study of ZrWMoO8 solid solution as a function of pressure was performed. This study shows that disordered cubic-ZrWMoO8 (space group Pa3-) transforms to ordered cubic-ZrWMoO8 (space group P213) at low press...

The paper presents fabrication of WC-Ni-Fe hard metal alloy with the density up to 99.9% from theoretical, hardness ∼1303 HV, fracture toughness ∼12.4 MPa m0.5, compressive strength ∼1365 MPa and without open porosity. High quality of the materials is provided by the original synthesis route based on powder preparation and sintering. WC powder (par...

New prospective sources of valuable minerals, including substantial reserves of crystalline graphite, gold, platinum, rare earth elements, and diamondlike carbon, have been revealed by the authors in high-carbon rocks in the south of Russia’s Far East. A scheme has been developed for the hydrometallurgical recovery of strategic metals and extra-pur...

The work presents an original way to obtain porous and mechanically strong (to 560 MPa) ZrO 2 ceramics containing calcium phosphates, HAP (Ca 10 (PO 4 ) 6 (OH) 2 ) and TCP (Ca 3 (PO 4 ) 2 ), using SPS-RS technique. “In situ” formation of calcium phosphate phases (15 and 50 wt%) has been observed in the bulk of ZrO 2 arising from solid-phase interac...

High selectivity and ion-exchange character of birnessite-type sorbents make these materials promising for Sr-90 removal from radioactive wastes containing seawater. However, it is still debatable how their functional properties are related to the nature of active phases and structure and, therefore, routes to improve birnessite performance are vir...

The work presents a novel method for fabrication of the high-quality ionizing radiation source (IRS), which is promising to replace unsafe commercial products based on ¹³⁷ CsCl prohibited by IAEA. Spark plasma sintering (SPS) technique has been applied to produce dense ceramic and glass-ceramic matrixes from Cs-containing (˜13.5 wt.%) zeolite yield...

Direct sol-gel, novel template, and additional high-temperature reduction procedures for preparing iron oxides and their composites, showing promise for selective sorption of dissolved U(VI) from aqueous media of various acidities, are described. The sorption activity of the materials was studied, the kinetic curves of the sorption were obtained, a...

Spark plasma sintering (SPS) is a highly prospective technology providing rapid consolidation of nano-disperse compositions into structured ceramics with complex structural organization. Characterizing pore structure of such systems remains a challenge due to different types, size and shape of the pores as well as structural defects occurring in th...

The morphology, specific surface area, and sorption properties toward Sr-90 radionuclides in seawater of a sorption material based on manganese oxide have been investigated. The material was fabricated through interaction of KMnO4 and H2O2 with subsequent annealing at 500 °C. The sorbent is characterized with the mechanical strength sufficient for...

To date, kinetic computations have been carried out efficiently for a great variety of physico-chemical processes including crystallization, melting and solid–solid transitions. However, appropriate methods for the kinetic analysis of chemical reactions, especially multi-staged reactions, are currently lacking. Here we report on an alternative way...

Molybdenum compounds are industrially demanding as heterogeneous catalysts for oxidation of various organic substances. Highly porous structure of molybdenum-containing catalysts avoids surface's colmatation and prevents blocking catalytic sites that makes these materials play a key role in processes of hydrothermal oxidation of radionuclide organi...

Here we present a prospective method of sol-gel synthesis of highly porous wollastonite ceramic powders with controlled macroporous structure (mean pore size ~160 nm) and immobilized gold nanoparticles (particle size is less than 50 nm). The method's distinction is based on using the colloidal template (micelles of "core-shell" polymer latex) both...

The original way of synthesis of nanostructured iron oxides and based on them magnetic ceramics via sequential combination of sol-gel and SPS technologies has been suggested. High quality of nanostructured iron oxides is defined by porous structure (Sspec up to 47,3 м²/г) and by phase composition of mixed and individual crystal phases (γ-Fe2O3/Fe3O...

An original synthetic route to nanostructured iron oxides with porous structure and to their reduced derivatives, prospective for uranium (VI) uptake from water media, is presented. The uniqueness of method includes combination of sol-gel technology, which used for generating inorganic framework, and template synthesis for porous structure formatio...

The results of Spark Plasma Sintering (SPS) synthesis of different types of ceramic materials for various industrial applications are presented. A high quality of ceramics is achieved through the originality of the developed approach based on combining SPS technology with other methods of inorganic synthesis, for instance, with sol–gel technology....

High-temperature consolidation of nanostructured hematite (α-Fe2O3) powder has been performed using the method of spark plasma sintering (SPS). Magnetic ceramic materials based on individual (α-Fe2O3) and composite (α-Fe2O3-Fe3O4) formulations of high construction strength (Young modulus 249 MPa) have been fabricated. The peculiarities of changes i...

The sorption properties of materials based on iron oxides and their reduced forms with respect to uranium were studied. A description was made of a method for consolidation of porous iron oxides and its effect on such characteristics as porosity, magnetism, morphology, phase composition, and sorption properties. The mechanism of uranium sorption on...

In this work, we suggest a novel synthetic route combining sol–gel and SPS for the fabrication of porous ceramics based on wollastonite with bimodal pore size distributions (100–500 nm and 1–500 μm) and high mechanical strength (Young's modulus from 72.5 to 172 MPa). We studied peculiarities in the formation of the biporous silicate framework using...

In present work, new method of fabricating metal phosphates via interaction of metal oleates with tributylphosphate solution is presented. Developed method is the universal one for fabrication of nanosized powders and thinlayered coatings based on hydroxyapatite, which is doped with metal traces (Sr, Cu, Zn) and presenting essential basis of bone t...

The consolidation of highly porous nanostructured wollastonite powders was conducted via Spark Plasma Sintering (SPS) technique, and porous composite materials of high mechanical strength were obtained (Young׳s modulus over 60 MPa). Peculiarities of structural parameters variation of studied materials under SPS conditions within the temperature int...

Here we report on the method of synthesis in gel of a new heterocyclic aminopolymer-N-2-(4-pyridyl)ethylchitosan (4-PEC) via direct addition of 4-vinylpyridine to chitosan that yields a derivative with the substitution degree (DS) up to 0.8. The comparison of reactivity, thermal, spectroscopic, and sorption properties of a new derivative and its is...