Materials

Research

13 pages, 5370 KiB

Open AccessArticle

An SPS-RS Technique for the Fabrication of SrMoO₄ Powellite Mineral-like Ceramics for ⁹⁰Sr Immobilization

by Anton A. Belov, Oleg O. Shichalin, Evgeniy K. Papynov, Igor Yu. Buravlev, Arseniy S. Portnyagin, Semen A. Azon, Alexander N. Fedorets, Anastasia A. Vornovskikh, Erhan S. Kolodeznikov, Ekaterina A. Gridasova, Anton Pogodaev, Nikolay B. Kondrikov, Yun Shi and Ivan G. Tananaev

Materials 2023, 16(17), 5838; https://doi.org/10.3390/ma16175838 - 25 Aug 2023

Cited by 2 | Viewed by 1157

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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15 pages, 2121 KiB

Open AccessArticle

Radionuclides’ Recovery from Seawater Using FIC and FIC A Sorbents

by Nikolay A. Bezhin, Vitaliy V. Milyutin, Natalia V. Kuzmenkova, Iuliia G. Shibetskaia, Ol’ga N. Kozlovskaia, Evgeniy V. Slizchenko, Victoria A. Razina and Ivan G. Tananaev

Materials 2023, 16(11), 4181; https://doi.org/10.3390/ma16114181 - 4 Jun 2023

Viewed by 1464

Abstract

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides’ activity in seawater and particulate matter. For the first time, the [...] Read more.

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides’ activity in seawater and particulate matter. For the first time, the radionuclides’ sorption from seawater was studied using sorbents based on activated carbon modified with iron(III) ferrocyanide (FIC) and based on activated carbon modified with iron(III) hydroxide (FIC A—activated FIC) obtained by FIC sorbent treatment with sodium hydroxide solution. The possibility of trace amounts of phosphorus, beryllium, and cesium recovery in laboratory conditions has been investigated. Distribution coefficients, dynamic, and total dynamic exchange capacities were determined. The physicochemical regularities (isotherm and kinetics) of sorption have been studied. The results obtained are characterized via Langmuir, Freindlich, and Dubinin–Radushkevich isotherm equations, as well as pseudo-first and pseudo-second-order kinetic models, intraparticle diffusion, and the Elovich model. Under expeditionary conditions, the sorption efficiency of ¹³⁷Cs using FIC sorbent, ⁷Be, ³²P, and ³³P—using FIC A sorbent with a single-column method by adding a stable tracer, as well as the sorption efficiency of radionuclides ²¹⁰Pb and ²³⁴Th with their natural content by FIC A sorbent in a two-column mode from large volumes of seawater was assessed. High values of efficiency of their recovery by the studied sorbents were achieved. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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13 pages, 1903 KiB

Open AccessArticle

⁷Be Recovery from Seawater by Sorbents of Various Types

by Nikolay A. Bezhin, Iuliia G. Shibetskaia, Ol’ga N. Kozlovskaia, Evgeniy V. Slizchenko and Ivan G. Tananaev

Materials 2023, 16(11), 4088; https://doi.org/10.3390/ma16114088 - 31 May 2023

Viewed by 1135

Abstract

For the first time, a comprehensive study of sorbents based on manganese dioxide was carried out for beryllium sorption from seawater in laboratory and expeditionary conditions. The possibility of using several commercially available sorbents based on manganese dioxide (Modix, MDM, DMM, PAN-MnO₂ [...] Read more.

For the first time, a comprehensive study of sorbents based on manganese dioxide was carried out for beryllium sorption from seawater in laboratory and expeditionary conditions. The possibility of using several commercially available sorbents based on manganese dioxide (Modix, MDM, DMM, PAN-MnO₂) and phosphorus(V) oxide (PD) for ⁷Be recovery from seawater for solving oceanological problems was evaluated. Beryllium sorption under static and dynamic conditions was studied. The distribution coefficients and dynamic and total dynamic exchange capacities were determined. Sorbents Modix (K_d = (2.2 ± 0.1) × 10³ mL/g) and MDM (K_d = (2.4 ± 0.2) × 10³ mL/g) showed high efficiency. The dependences of the degree of recovery on time (kinetics) and the capacity of the sorbent on the beryllium equilibrium concentration in solution (isotherm) were established. The data obtained were processed using kinetic models (intraparticle diffusion, pseudo-first and pseudo-second orders, Elovich model) and sorption isotherm equations (Langmuir, Freindlich, Dubinin–Radushkevich). The paper contains results of expeditionary studies to evaluate the sorption efficiency of ⁷Be from large volumes of the Black Sea water by various sorbents. We also compared the sorption efficiency of ⁷Be for the considered sorbents with aluminum oxide and previously obtained sorbents based on iron(III) hydroxide. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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16 pages, 4098 KiB

Open AccessArticle

Synthetic Calcium Silicate Biocomposite Based on Sea Urchin Skeleton for 5-Fluorouracil Cancer Delivery

by Evgeniy K. Papynov, Oleg O. Shichalin, Olesya V. Kapustina, Igor Yu. Buravlev, Vladimir I. Apanasevich, Vitaly Yu. Mayorov, Alexander N. Fedorets, Alexey O. Lembikov, Danila N. Gritsuk, Anna V. Ovodova, Sofia S. Gribanova, Zlata E. Kornakova and Nikolay P. Shapkin

Materials 2023, 16(9), 3495; https://doi.org/10.3390/ma16093495 - 1 May 2023

Cited by 5 | Viewed by 2471

Abstract

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 CaSiO [...] Read more.

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. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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19 pages, 6791 KiB

Open AccessArticle

Extractability of Rice Husk Waste Using Green Gamma Radiation for Dye Elimination in Laboratory-Scale Sorption System: Equilibrium Isotherm and Kinetic Analysis

by Zakia Alhashem, Ashraf H. Farha, Shehab A. Mansour and Maha A. Tony

Materials 2023, 16(9), 3328; https://doi.org/10.3390/ma16093328 - 24 Apr 2023

Viewed by 1703

Abstract

Nowadays, the use of natural materials and especially “waste” valorization has evolved and attracted the wide attention of scientists and academia. In this regard, the use of rice husk (RH) powder as a naturally abundant and cheap byproduct material is gaining superior attention. [...] Read more.

Nowadays, the use of natural materials and especially “waste” valorization has evolved and attracted the wide attention of scientists and academia. In this regard, the use of rice husk (RH) powder as a naturally abundant and cheap byproduct material is gaining superior attention. However, improving the physicochemical properties of such RH is still under research. In the current investigation, the modification of rice husk (RH) via γ-irradiation has shown to be a promising green tool to meet such a need. Clean, prepared, powdered RH samples were subjected to various γ-radiation doses, namely 5, 10, 15 and 25 kGy, and the corresponding samples were named as RH-0, RH-5, RH-10, RH-15, RH-15 and RH-25. Then, the samples were characterized via scanning electron microscopy (SEM). After irradiation, the samples showed an increase in their surface roughness upon increasing the γ-radiation up to 15 kGy. Furthermore, the sorption capacity of the irradiated RH samples was investigated for eliminating Urolene Blue (UB) dye as a model pharmaceutical effluent stream. The highest dye uptake was recorded as 14.7 mg/g, which corresponded to the RH-15. The adsorption operating parameters were also investigated for all of the studied systems and all adsorbents showed the same trend, of a superior adsorption capacity at pH 6.6 and high temperatures. Langmuir and Freundlich isotherm models were also applied for UB adsorption and an adequate fitted isotherm model was linked with Langmuir fitting. Moreover, the pseudo-second-order kinetic model provided the best fit for the adsorption data. Experimental assays confirmed that the UB dye could be successfully eradicated feasibly from the aqueous stream via a sustainable green methodology. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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11 pages, 3722 KiB

Open AccessArticle

First-Principles Study of Nitrogen Adsorption and Dissociation on ZrMnFe(110) Surface

by Qiaobin Yang, Fanhao Zeng, Meiyan Chen, Yu Dai, Yafang Gao, Rui Huang, Yi Gu and Jiangfeng Song

Materials 2023, 16(9), 3323; https://doi.org/10.3390/ma16093323 - 24 Apr 2023

Viewed by 1594

Abstract

The adsorption, dissociation and penetration processes of N₂ on the surface of ZrMnFe(110) were investigated using the first-principles calculation method in this paper. The results indicate that the vacancy Hollow 1 composed of 4Zr1Fe on the surface of ZrMnFe(110) is the best [...] Read more.

The adsorption, dissociation and penetration processes of N₂ on the surface of ZrMnFe(110) were investigated using the first-principles calculation method in this paper. The results indicate that the vacancy Hollow 1 composed of 4Zr1Fe on the surface of ZrMnFe(110) is the best adsorption site for the N₂ molecule and N atom, and the adsorption energies are 10.215 eV and 6.057 eV, respectively. Electron structure analysis indicates that the N₂ molecule and N atoms adsorbed mainly interact with Zr atoms on the surface. The transition state calculation shows that the maximum energy barriers to be overcome for the N₂ molecule and N atom on the ZrMnFe(110) surface were 1.129 eV and 0.766 eV, respectively. This study provides fundamental insight into the nitriding mechanism of nitrogen molecules in ZrMnFe. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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15 pages, 8779 KiB

Open AccessArticle

Estimation of ²²⁶Ra and ²²⁸Ra Content Using Various Types of Sorbents and Their Distribution in the Surface Layer of the Black Sea

by Ol’ga N. Kozlovskaia, Iuliia G. Shibetskaia, Nikolay A. Bezhin and Ivan G. Tananaev

Materials 2023, 16(5), 1935; https://doi.org/10.3390/ma16051935 - 26 Feb 2023

Cited by 3 | Viewed by 1516

Abstract

Radium isotopes have traditionally been used as tracers of surface and underground fresh waters in land–ocean interactions. The concentration of these isotopes is most effective on sorbents containing mixed oxides of manganese. During the 116 RV Professor Vodyanitsky cruise (22 April–17 May 2021), [...] Read more.

Radium isotopes have traditionally been used as tracers of surface and underground fresh waters in land–ocean interactions. The concentration of these isotopes is most effective on sorbents containing mixed oxides of manganese. During the 116 RV Professor Vodyanitsky cruise (22 April–17 May 2021), a study about the possibility and efficiency of ²²⁶Ra and ²²⁸Ra recovery from seawater using various types of sorbents was conducted. The influence of seawater flow rate on the sorption of ²²⁶Ra and ²²⁸Ra isotopes was estimated. It was indicated that the Modix, DMM, PAN-MnO₂, and CRM-Sr sorbents show the best sorption efficiency at a flow rate of 4–8 column volumes per minute. Additionally, the distribution of biogenic elements (dissolved inorganic phosphorus (DIP), silicic acid, and the sum of nitrates and nitrites), salinity, and ²²⁶Ra and ²²⁸Ra isotopes was studied in the surface layer of the Black Sea in April–May 2021. Correlation dependencies between the concentration of long-lived radium isotopes and salinity are defined for various areas of the Black Sea. Two processes control the dependence of radium isotope concentration on salinity: conservative mixing of riverine and marine end members and desorption of long-lived radium isotopes when river particulate matter meets saline seawater. Despite the high long-lived radium isotope concentration in freshwater in comparison with that in seawater, their content near the Caucasus shore is lower mainly because riverine waters meet with a great open seawater body with a low content of these radionuclides, and radium desorption processes take place in an offshore area. The ²²⁸Ra/²²⁶Ra ratio derived from our data displays freshwater inflow spreading over not only the coastal region, but also the deep-sea region. The lowered concentration of the main biogenic elements corresponds to high-temperature fields because of their intensive uptake by phytoplankton. Therefore, nutrients coupled with long-lived radium isotopes trace the hydrological and biogeochemical peculiarities of the studied region. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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15 pages, 4449 KiB

Open AccessArticle

Assessment of Seasonal Variability in Phosphorus Biodynamics by Cosmogenic Isotopes ³²P, ³³P around Balaklava Coast

by Mariya A. Frolova, Nikolay A. Bezhin, Evgeniy V. Slizchenko, Ol’ga N. Kozlovskaia and Ivan G. Tananaev

Materials 2023, 16(5), 1791; https://doi.org/10.3390/ma16051791 - 22 Feb 2023

Cited by 3 | Viewed by 1327

Abstract

The sorption efficiency of phosphorus from seawater by aluminum oxide and sorbents based on Fe(OH)₃ obtained by various methods (using prepared sodium ferrate or precipitation of Fe(OH)₃ with ammonia) was assessed. It was shown that phosphorus was recovered most efficiently at [...] Read more.

The sorption efficiency of phosphorus from seawater by aluminum oxide and sorbents based on Fe(OH)₃ obtained by various methods (using prepared sodium ferrate or precipitation of Fe(OH)₃ with ammonia) was assessed. It was shown that phosphorus was recovered most efficiently at a seawater flow rate of one-to-four column volumes per minute with a sorbent based on hydrolyzed polyacrylonitrile fiber with a precipitation of Fe(OH)₃ with ammonia. Based on the results obtained, a method for phosphorus isotopes recovery with this sorbent was suggested. Using this method, the seasonal variability of phosphorus biodynamics in the Balaklava coastal area was estimated. For this purpose, the short-lived isotopes of cosmogenic origin ³²P and ³³P were used. Volumetric activity profiles of ³²P and ³³P in particulate and dissolved forms were obtained. Based on ³²P and ³³P volumetric activity, indicators of phosphorus biodynamics were calculated: the time, rate, and degree of phosphorus circulation to inorganic and particulate organic forms. In spring and summer, elevated values of phosphorus biodynamic parameters were determined. This is explained by the peculiarity of the economic and resort activities of Balaklava, which negatively affect the state of the marine ecosystem. The results obtained can be used to assess the dynamics of changes in the content of forms of dissolved and suspended phosphorus, and the biodynamic parameters when performing a comprehensive environmental assessment of the state of coastal waters. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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13 pages, 39227 KiB

Open AccessArticle

Impacts of Temperature and Time on Direct Nitridation of Aluminium Powders for Preparation of AlN Reinforcement

by Samuel Rogers, Matthew Dargusch and Damon Kent

Materials 2023, 16(4), 1583; https://doi.org/10.3390/ma16041583 - 14 Feb 2023

Cited by 3 | Viewed by 2910

Abstract

Aluminium nitride (AlN) is an important technical ceramic with outstanding strength and thermal conductivity that has important applications for advanced heat sink materials and as a reinforcement for metal-based composites. In this study, we report a novel, straightforward and low-cost method to prepare [...] Read more.

Aluminium nitride (AlN) is an important technical ceramic with outstanding strength and thermal conductivity that has important applications for advanced heat sink materials and as a reinforcement for metal-based composites. In this study, we report a novel, straightforward and low-cost method to prepare AlN powder using a vacuum tube furnace for the direct nitridation of loose aluminium powder at low temperatures (down to 500

^{\circ}

C) under flowing high-purity nitrogen. Small amounts of magnesium powder (1 wt.%), combined with aluminium, promote nitridation. Here, we characterise the effects of time (up to 12 h) and temperature (490 to 560

^{\circ}

C) on nitridation with the aim to establish an effective regimen for the controlled synthesis of an aluminium nitride reinforcement powder for the production of metal matrix composites. The extent of nitridation and the morphology of the reaction products were assessed using scanning electron microscopy and X-ray diffraction analyses. AlN was detected for all nitriding temperatures ≥ 500

^{\circ}

C, with the highest yields of 80% to 85% obtained at 530

^{\circ}

C for times ≥ 1 h. At this temperature, nitridation proceeded rapidly, and there was extensive agglomeration of the reaction products making it difficult to reprocess into powder. At lower temperatures around 510

^{\circ}

C, a relatively high proportion of AlN was attained (>73% after 6 h) while retaining excellent friability so that it could be manually reprocessed to powder. The synthesised reinforcement consisted of micro- or nano-crystalline AlN comingled with metallic aluminium. The ratio of AlN and metallic aluminium can be readily controlled by varying the nitriding temperature. This provides a flexible and accessible method for the production of AlN-reinforcement powders suited to the production of metal matrix composites. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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10 pages, 12100 KiB

Open AccessArticle

Structure and Properties of Porous Ti₃AlC₂-Doped Al₂O₃ Composites Obtained by Slip Casting Method for Membrane Application

by Egor Kashkarov, Maksim Krinitcyn, Adilzhan Dyussambayev, Alexey Pirozhkov and Maksim Koptsev

Materials 2023, 16(4), 1537; https://doi.org/10.3390/ma16041537 - 12 Feb 2023

Cited by 1 | Viewed by 1503

Abstract

In the present work, porous composites were fabricated from pure Al₂O₃ and mixed Ti₃AlC₂/Al₂O₃ powder by slip casting and sintering. The effect of sintering temperature and different composition ratio on microstructure, phase composition, [...] Read more.

In the present work, porous composites were fabricated from pure Al₂O₃ and mixed Ti₃AlC₂/Al₂O₃ powder by slip casting and sintering. The effect of sintering temperature and different composition ratio on microstructure, phase composition, porosity and gas permeation flux of the fabricated materials was investigated. The microstructure and phase composition of the samples were analyzed by scanning electron microscopy and X-ray diffraction, respectively. The gas permeation experiments were performed using pure hydrogen at 0.1–0.9 MPa pressure. It is shown that a decrease in sintering temperature from 1500 to 1350 °C results in an increase in hydrogen permeation flux of the alumina from 5 to 25 mol/(m² × s), which is due to higher pore size and overall porosity of the samples. Sintering of Ti₃AlC₂/Al₂O₃ powder mixtures leads to the formation of Al₂O₃, Al₂TiO₅ and TiO₂ phases as a result of oxidation of the Ti₃AlC₂ phase, resulting in an increased pore size in the composites compared with pure alumina. The open porosity of composites increases from 3.4 to 40% with an increasing Ti₃AlC₂/Al₂O₃ ratio from 1/10 to 1/2, respectively. The composites with the highest porosity (40%) had a maximum permeation flux of 200 mol/(m² × s). The changes in the bending strength of the alumina and composite samples, depending on the microstructure and porosity, were also discussed. The investigated composites are considered promising materials for hydrogen separation membrane supports. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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24 pages, 14586 KiB

Open AccessArticle

(Na, Zr) and (Ca, Zr) Phosphate-Molybdates and Phosphate-Tungstates: I–Synthesis, Sintering and Characterization

by M. E. Karaeva, D. O. Savinykh, A. I. Orlova, S. A. Khainakov, A. V. Nokhrin, M. S. Boldin, S. Garcia-Granda, A. A. Murashov, V. N. Chuvil’deev, P. A. Yunin, A. A. Nazarov and N. Y. Tabachkova

Materials 2023, 16(3), 990; https://doi.org/10.3390/ma16030990 - 20 Jan 2023

Cited by 5 | Viewed by 1812

Abstract

Submicron-grade powders of Na_1-xZr₂(PO₄)_3-x(XO₄)_x compounds (hereafter referred to as NZP) and Ca_1-xZr₂(PO₄)_3-x(XO₄)_x compounds (hereafter, CZP), X = Mo, W (0 ≤ [...] Read more.

Submicron-grade powders of Na_1-xZr₂(PO₄)_3-x(XO₄)_x compounds (hereafter referred to as NZP) and Ca_1-xZr₂(PO₄)_3-x(XO₄)_x compounds (hereafter, CZP), X = Mo, W (0 ≤ x ≤ 0.5) were obtained by sol-gel synthesis. The compounds obtained were studied by X-ray diffraction phase analysis and electron microscopy. An increase in the W or Mo contents was shown to result in an increase in the unit cell volume of the NZP and CZP crystal lattices and in a decrease in the coherent scattering region sizes. Thermal expansion behavior at high temperatures of synthesized NZP and CZP compounds has been investigated. The dependencies of the parameters a and c on the heating temperature, as well as the temperature dependence of the crystal lattice unit cell volume V in the range from the room temperature up to 800 °C, were obtained. The dependencies of the average thermal expansion coefficient (α_av) and of the volume coefficient (β) on the W and Mo contents in the compositions of NZP and CZP compounds were studied. Ceramics Na_1-xZr₂(PO₄)_3-x(XO₄)_x with relatively high density (more than 97.5%) were produced by spark plasma sintering (SPS). The increase in the W or Mo contents in the ceramics leads to an increase in the relative density of NZP and to a decrease of the optimum sintering temperature. The mean grain size in the NZP ceramics decreases with increasing W or Mo contents. The study of strength characteristics has revealed that the hardness of the NZP ceramics is greater than 5 GPa, and that the minimum fracture toughness factor was 1 MPa·m^1/2. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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17 pages, 5470 KiB

Open AccessArticle

(Na, Zr) and (Ca, Zr) Phosphate-Molybdates and Phosphate-Tungstates: II–Radiation Test and Hydrolytic Stability

by M. E. Karaeva, D. O. Savinykh, A. I. Orlova, A. V. Nokhrin, M. S. Boldin, A. A. Murashov, V. N. Chuvil’deev, V. A. Skuratov, A. T. Issatov, P. A. Yunin, A. A. Nazarov, M. N. Drozdov, E. A. Potanina and N. Y. Tabachkova

Materials 2023, 16(3), 965; https://doi.org/10.3390/ma16030965 - 20 Jan 2023

Cited by 2 | Viewed by 2117

Abstract

This paper introduces the results of hydrolytic stability tests and radiation resistance tests of phosphate molybdates and phosphate tungstates Na_1−xZr₂(PO₄)_3−x(XO₄)_x, X = Mo, W (0 ≤ x ≤ 0.5). The ceramics [...] Read more.

This paper introduces the results of hydrolytic stability tests and radiation resistance tests of phosphate molybdates and phosphate tungstates Na_1−xZr₂(PO₄)_3−x(XO₄)_x, X = Mo, W (0 ≤ x ≤ 0.5). The ceramics characterized by relatively high density (more than 97.5%) were produced by spark plasma sintering (SPS) of submicron powders obtained by sol–gel synthesis. The study focused on hydrolytic resistance of the ceramics in static mode at room temperature. After 28 days of testing in distilled water, the normalized leaching rate was determined. It was found that the ceramics demonstrated high hydrolytic resistance in static mode: the normalized leaching rates for Mo- and W-containing ceramics were 31·10⁻⁶ and 3.36·10⁻⁶ g·cm⁻²·day⁻¹, respectively. The ceramics demonstrated high resistance to irradiation with 167 MeV Xe⁺²⁶ multiple-charged ions at fluences ranging from 1·10¹² to 6·10¹³ cm⁻². The Mo-containing Na_0.5Zr₂(PO₄)_2.5(XO₄)_0.5 ceramics were shown to have higher radiation resistance than phosphate tungstates. Radiation was shown to trigger an increase in leaching rates for W and Mo in the crystal structure of NZP ceramics. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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12 pages, 6737 KiB

Open AccessArticle

Tribological Properties of Ti-TiC Composite Coatings on Titanium Alloys

by Ivan G. Zhevtun, Pavel S. Gordienko, Dmitriy V. Mashtalyar, Yuriy N. Kulchin, Sofia B. Yarusova, Valeria A. Nepomnyushchaya, Zlata E. Kornakova, Sofia S. Gribanova, Danil V. Gritsuk and Alexander I. Nikitin

Materials 2022, 15(24), 8941; https://doi.org/10.3390/ma15248941 - 14 Dec 2022

Cited by 4 | Viewed by 1770

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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14 pages, 2424 KiB

Open AccessArticle

Excitonic Mechanisms of Stimulated Emission in Low-Threshold ZnO Microrod Lasers with Whispering Gallery Modes

by Andrey P. Tarasov, Arsen E. Muslimov and Vladimir M. Kanevsky

Materials 2022, 15(24), 8723; https://doi.org/10.3390/ma15248723 - 7 Dec 2022

Cited by 7 | Viewed by 1244

Abstract

Whispering gallery mode (WGM) ZnO microlasers gain attention due to their high Q-factors and ability to provide low-threshold near-UV lasing. However, a detailed understanding of the optical gain mechanisms in such structures has not yet been achieved. In this work, we study [...] Read more.

Whispering gallery mode (WGM) ZnO microlasers gain attention due to their high Q-factors and ability to provide low-threshold near-UV lasing. However, a detailed understanding of the optical gain mechanisms in such structures has not yet been achieved. In this work, we study the mechanisms of stimulated emission (SE) in hexagonal ZnO microrods, demonstrating high-performance WGM lasing with thresholds down to 10–20 kW/cm² and Q-factors up to ~3500. The observed SE with a maximum in the range of 3.11–3.17 eV at room temperature exhibits a characteristic redshift upon increasing photoexcitation intensity, which is often attributed to direct recombination in the inverted electron-hole plasma (EHP). We show that the main contribution to room-temperature SE in the microrods studied, at least for near-threshold excitation intensities, is made by inelastic exciton-electron scattering rather than EHP. The shape and perfection of crystals play an important role in the excitation of this emission. At lower temperatures, two competing gain mechanisms take place: exciton-electron scattering and two-phonon assisted exciton recombination. The latter forms emission with a maximum in the region near ~3.17 eV at room temperature without a significant spectral shift, which was observed only from weakly faceted ZnO microcrystals in this study. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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13 pages, 3930 KiB

Open AccessArticle

Morphology and Luminescence of Flexible Free-Standing ZnO/Zn Composite Films Grown by Vapor Transport Synthesis

by Ludmila A. Zadorozhnaya, Andrey P. Tarasov, Ivan S. Volchkov, Arsen E. Muslimov and Vladimir M. Kanevsky

Materials 2022, 15(22), 8165; https://doi.org/10.3390/ma15228165 - 17 Nov 2022

Cited by 3 | Viewed by 1326

Abstract

A method for fabricating flexible free-standing ZnO/Zn composite films from the vapor phase using a regular array of silicon microwhiskers as a substrate is presented. The structural and morphological peculiarities, as well as luminescent properties of the films, were studied. The films have [...] Read more.

A method for fabricating flexible free-standing ZnO/Zn composite films from the vapor phase using a regular array of silicon microwhiskers as a substrate is presented. The structural and morphological peculiarities, as well as luminescent properties of the films, were studied. The films have a hybrid structure consisting of two main microlayers. The first layer is formed directly on the tops of Si whiskers and has a thickness up to 10 µm. This layer features a polycrystalline structure and well-developed surface morphology. The second layer, which makes up the front side of the films, is up to 100 µm thick and consists of large microcrystals. The films show good bending strength—in particular, resistance to repeated bending and twisting—which is provided by a zinc metallic part constituting the flexible carrier of the films. ZnO photoluminescence was observed from both surfaces of the films but with conspicuous spectral differences. In particular, a significant weakening of ZnO green luminescence (more than 10 times) at an almost constant intensity of UV near-band edge emission was found for the polycrystalline side of the films as compared to the microcrystalline side. A high degree of homogeneity of the luminescent properties of the films over their area was demonstrated. The results obtained emphasize the relevance of further studies of such ZnO structures—in particular, for application in flexible devices, sensors, photocatalysis and light generation. Full article

(This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application)

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