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.
•Promising UO2-Y2O3 ceramic nuclear fuel pellets are fabricated via SPS technique.•Dynamics of UO2-Y2O3 SPS consolidation is comparatively analyzed with that of UO2-Gd2O3 and UO2-Eu2O3.•(U,Y)O2 solid ...solution formation by SPS is shown for the first time.•Stable pore formation is identified after addition 2 and 8 wt% of Y2O3.•The neutron absorption lab test is performed for SPS nuclear fuel samples with IFBAs.
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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 spark plasma sintering (SPS) conditions followed by a comparative analysis with UO2-Gd2O3 and UO2-Eu2O3 analogs. Earlier unknown data on formation of (U,Y)O2 solid solutions, isostructural to UO2, under SPS conditions is presented. Structural changes manifested in stable pore and defect occurrence within the ceramics bulk are shown to depend on Y2O3 amount proving the occurrence of the Kirkendall effect, which is commonly known phenomenon in the field of traditional methods of fuel manufacturing. Microhardness (HV), compressive strength (σcs) and density (ρ) are found to degrade in the presence of Y2O3, however their values remain within acceptable limits. For the first time, neutron-activation analysis is implemented as a laboratory means to assess neutron absorption efficiency of the SPS fuels containing various IFBA additives (Gd2O3, Eu2O3, Y2O3). These novel results contribute to the fundamental knowledge on the range of possible applications available owing to nonconventional SPS technology, thus extending the methods palette of fuel fabrication as well as providing new characterization approaches to probe important fuel properties for nuclear power engineering field.
An effective sorption material for the immobilization of cobalt radionuclides into highly safe and reliable solid-state matrices is proposed. The resulting silicate sorbent СaSiO3 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 СaCoSi2O6 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 °C had the lowest values of Co2+ ions leaching (RCo ~10−7 g/(cm2×day)) and diffusion coefficient (De 1.73 ×10−17 cm2/s) from silicate matrices. Thus, the obtained СaCoSi2O6 silicate matrices saturated with Co ions comply with the regulatory requirements of GOST R 50926–96 and ANSI/ANS 16.1 for 60Co immobilization.
•Amorphous CaSiO3 with 3.32 mmol/g Co ions sorption capacity was prepared.•SPS method allowed to obtain the CaCoSi2O6 matrices at 1000 °C for 2 min.•CaCoSi2O6 solid-state matrices exclude Co60 ions leaching and diffusion.•The characteristics of CaCoSi2O6 matrices exceeded the GOST and ANSI/ANS 16.1 requirements.
The possibilities of using chitosan and its composites with transition metal oxides for arsenic removal from solutions with low concentrations are discussed. Methods for the formation of composite ...sorbents based on chitosan and molybdenum in a composition with a carbon fiber providing improved physical and chemical properties with respect to the recovered component are considered. The sorption properties of the obtained materials under dynamic conditions for the purification of solutions from arsenic are compared. It is shown that the preliminary modification of the carbon fiber with chitosan by ionic gelation using sulfate ion and then by adsorption with molybdate ion leads to the production of an efficient sorption material that provides the purification of 1600 column volumes of an arsenic solution at an initial concentration of 105 μg L
–1
to a maximum permissible concentration of 50 μg L
–1
. The calculation methods show that the gel ability of sulfate and molybdate ions is approximately the same.
Orthoborates La
0.95 –
x
Eu
0.05
Tb
x
BO
3
, La
0.95
Eu
0.05
Bi
x
BO
3,
and La
0.95 –
x
Eu
0.05
Tb
0.02
Bi
y
BO
3
, as well as metaborates La
0.95 –
x
Eu
0.05
Tb
x
(BO
2
)
3
, La
0.95
Eu
0.05
Bi
x
...(BO
2
)
3
, and La
0.95 –
x
Eu
0.05
Tb
0.02
Bi
y
(BO
2
)
3
(
х =
0.005, 0.01, 0.02, 0.025, 0.05, 0.075;
у =
0.005, 0.01, 0.02, 0.025, 0.05, 0.075), have been synthesized by the extraction-pyrolytic method at lower temperatures and in shorter time as compared to the other known methods. The compounds have been studied by X-ray diffraction, IR and luminescence spectroscopy based on luminescence excitation and luminescence spectra. The unit cell parameters of ortho- and metaborates of various composition have been calculated. The structures of orthorhombic aragonite modification for orthoborates and monoclinic α-type modification for metaborates persist upon doping with Tb
3+
or Bi
3+
, as well as upon joint doping with Tb
3+
and Bi
3+
. At the same time, doping with the Eu
3+
ion-activator and sensitizer ions Tb
3+
or Bi
3+
leads to some changes in the unit cell parameters. The compounds show intense luminescence in the range 400–750 nm. The character of luminescence excitation spectra (λ
exc
= 615 nm) and Eu
3+
luminescence spectra (position of the
5
D
0
–
7
F
j
(
j
= 0, 1, 2, 3, 4) transition bands and relative intensities of the bands) remains unchanged with a change in the concentration of Tb
3+
or Bi
3+
dopant ions in the series of orthoborates or metaborates, which is evidence of the identical nearest environment of the Eu
3+
ion. The introduction of the Tb
3+
ion and a further increase in its concentration lead to a decrease in luminescence of all phosphors. The introduction of up to 5 mol % Bi
3+
into La
0.95 –
x
Eu
0.05
BO
3
and La
0.95 –
x
Eu
0.05
Tb
x
BO
3
orthoborates causes an increase in luminescence intensity, which can be associated with the possibility of energy transfer from Bi
3+
to Eu
3+
. The decrease in the integrated luminescence intensity in metaborates caused by doping with Tb
3+
and Bi
3+
ions can be explained by distinctive features of their crystal structure.
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.
The properties of zirconium ceramics can be improved by combination with calcium phosphate compounds, which impart bioactivity to the bioinert material. The effect of Ta
2
O
5
on some properties of ...ceramics was studied. Tantalum oxide doping increases the radiopacity of calcium phosphate zirconium ceramics, but deteriorates the mechanical and bioactive properties. This ceramics can be proposed as a material for replacing bone tissue defects. The material was shown to have sufficient strength, radiopacity, and developed microrelief and to contain a bioactive phase. The obtained materials meet conditions necessary for the replacement therapy. The method can be used to produce a material with specified characteristics for the manufacture of individual implants.
The photochemical behavior of β-diketonates of boron difluoride in poly(methyl methacrylate) was studied. Excimers of boron chelates are formed in the course of UV irradiation of polymer compositions ...accompanied by a bathochromic shift of the luminescence spectrum. The intensification (quenching) of luminescence of the polymer compositions during irradiation depends on the ratio of the quantum yields of the monomer and excimer luminescence of boron difluoride β-diketonates.
An efficient method was presented to perform the hydrothermal synthesis of a nanocrystalline SrWO
4
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, scanning electron microscopy, and energy-dispersive spectroscopy. The efficiency of the ultrafast (several minutes long) sintering of the nanocrystalline SrWO
4
powder was described by the dynamics of its consolidation as a function of the SPS time and temperature. The temperature of formation was determined for a single-phase SrWO
4
ceramic with a high relative density and a low strontium leaching rate of less than 10
–6
g/(cm
2
day), which is in demand as matrices for the reliable immobilization of the high-energy radionuclide strontium-90. For the first time, a method was implemented to produce a sample of a SrWO
4
ceramic–high-alloy steel coupled composite by SPS as a test article of an open ionizing radiation source. The method consists in the diffusion sintering of materials within a single step at 1000°C for 5 min with the mandatory use of a sintering additive in the form of a mixture of metals (70 wt % Ti + 30 wt % Ag). The results of this work showed the possibility of developing a high-tech solution for the production of high-performance radioisotope products by SPS.
Manganese oxides have been prepared on the surface of carbon fiber by simple methods: coprecipitation of manganese salts of different valence in the presence of fiber as a support or ...electrodeposition from Mn(II) salt solution on a carbon fiber cathode, in the presence of chitosan including, under oxidation with air oxygen conditions. The obtained samples have been characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Sorption properties of the composites toward As(V) have been studied. The relationships between sorption properties, structure, Mn valence, and manganese oxide surface morphology have been discussed.
