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Akilbekov A, Kiryakov A, Baubekova G, Aralbayeva G, Dauletbekova A, Akylbekova A, Ospanova Z, Popov AI. Optical Characteristics of MgAl 2O 4 Single Crystals Irradiated by 220 MeV Xe Ions. MATERIALS (BASEL, SWITZERLAND) 2023; 16:6414. [PMID: 37834551 PMCID: PMC10573163 DOI: 10.3390/ma16196414] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 09/14/2023] [Accepted: 09/19/2023] [Indexed: 10/15/2023]
Abstract
In In this study, the optical properties of magnesium-aluminate spinel were examined after being irradiated with 220 MeV Xe ions. The research aimed to simulate the impact of nuclear fuel fission fragments on the material. The following measurements were taken during the experiments: transmission spectra in the IR region (190-7000) nm, optical absorption spectra in the range (1.2-6.5) eV, and Raman spectra were measured along the depth of ion penetration from the surface to 30 µm. A peak with a broad shape at approximately 5.3 eV can be observed in the optical absorption spectrum of irradiated spinel crystals. This band is linked to the electronic color centers of F+ and F. Meanwhile, the band with a maximum at ~(3-4) eV is attributed to hole color centers. Apart from the typical Raman modes of an unirradiated crystal, additional modes, A1g* (720 cm-1), and Eg* (385 cm-1), manifested mainly as an asymmetric shoulder of the main Eg mode, are also observed. In addition, the Raman spectroscopy method showed that the greatest disordering of crystallinity occurs in the near-surface layer up to 4 μm thick. At the same time, Raman scattering spectroscopy is sensitive to structural changes almost up to the simulated value of the modified layer, which is an excellent express method for certifying the structural properties of crystals modified by swift heavy ions.
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Affiliation(s)
- Abdirash Akilbekov
- L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan; (G.B.); (G.A.); (A.D.); (A.A.); (Z.O.)
| | - Arseny Kiryakov
- Ural Federal University, 21 Mira Str., 620002 Yekaterinburg, Russia;
| | - Guldar Baubekova
- L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan; (G.B.); (G.A.); (A.D.); (A.A.); (Z.O.)
| | - Gulnara Aralbayeva
- L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan; (G.B.); (G.A.); (A.D.); (A.A.); (Z.O.)
| | - Alma Dauletbekova
- L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan; (G.B.); (G.A.); (A.D.); (A.A.); (Z.O.)
| | - Aiman Akylbekova
- L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan; (G.B.); (G.A.); (A.D.); (A.A.); (Z.O.)
| | - Zhulduz Ospanova
- L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan; (G.B.); (G.A.); (A.D.); (A.A.); (Z.O.)
| | - Anatoli I. Popov
- Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., 1586 Riga, Latvia;
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Karipbayev ZT, Lisitsyn VM, Golkovski MG, Zhilgildinov ZS, Popov AI, Zhunusbekov AM, Polisadova E, Tulegenova A, Mussakhanov DA, Alpyssova G, Piskunov S. Electron Beam-Assisted Synthesis of YAG:Ce Ceramics. MATERIALS (BASEL, SWITZERLAND) 2023; 16:ma16114102. [PMID: 37297237 DOI: 10.3390/ma16114102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/26/2023] [Accepted: 05/26/2023] [Indexed: 06/12/2023]
Abstract
In this work, we present the results of the structure and luminescence properties of YAG:Ce (Y3Al5O12 doped with Ce3+ ions) ceramic samples. Their synthesis was carried out by sintering samples from the initial oxide powders under the powerful action of a high-energy electron beam with an energy of 1.4 MeV and a power density of 22-25 kW/cm2. The measured diffraction patterns of the synthesized ceramics are in good agreement with the standard for YAG. Luminescence characteristics at stationary/time-resolved regimes were studied. It is shown that under the influence of a high-power electron beam on a mixture of powders, it is possible to synthesize YAG:Ce luminescent ceramics with characteristics close to the well-known YAG:Ce phosphor ceramics obtained by traditional methods of solid-state synthesis. Thus, it has been demonstrated that the technology of radiation synthesis of luminescent ceramics is very promising.
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Affiliation(s)
- Zhakyp T Karipbayev
- Department of Technical Physics, L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan
| | - Victor M Lisitsyn
- Department of Materials Science, Engineering School, National Research Tomsk Polytechnic University, 30, Lenin Ave., Tomsk 634050, Russia
| | - Mikhail G Golkovski
- Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630000, Russia
| | - Zhassulan S Zhilgildinov
- Department of Technical Physics, L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan
| | - Anatoli I Popov
- Department of Technical Physics, L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan
- Institute of Solid State Physics, University of Latvia, LV-1063 Riga, Latvia
| | - Amangeldy M Zhunusbekov
- Department of Technical Physics, L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan
| | - Elena Polisadova
- Department of Materials Science, Engineering School, National Research Tomsk Polytechnic University, 30, Lenin Ave., Tomsk 634050, Russia
| | - Aida Tulegenova
- Department of Solid State and Nonlinear Physics, Al-Farabi Kazakh National University, 71, Al-Farabi Ave., Almaty 050040, Kazakhstan
| | - Dossymkhan A Mussakhanov
- Department of Technical Physics, L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan
| | - Gulnur Alpyssova
- Department of Radiophysics and Electronics, Karaganda Buketov University, Karaganda 100028, Kazakhstan
| | - Sergei Piskunov
- Department of Solid State and Nonlinear Physics, Al-Farabi Kazakh National University, 71, Al-Farabi Ave., Almaty 050040, Kazakhstan
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Experimental Study of Acid Etching and Conductivity of High-Temperature-Resistant Cross-Linked Acid. Processes (Basel) 2023. [DOI: 10.3390/pr11030722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023] Open
Abstract
Acid fracturing is one of the effective techniques for developing low-permeability carbonate reservoirs economically. With the increasing reservoir depth, the reservoir temperature and closure pressure increase, posing new challenges to the acid system. In this paper, a high-temperature-resistant cross-linked acid system is selected, which maintains a viscosity above 80 mPa·s in the temperature range of 120 °C to 140 °C and can effectively reduce acid leak-off. The acid system can not only open the reservoir and ensure the extension of the fracture, but also reduce the reaction rate between the acid and the reservoir and increase the etching distance. The rock slab acid etching and conductivity tests show that the optimum injection rate is 50 mL/min, the rock etching morphology is channel type, and the conductivity remains above 110 D·cm. However, as the acid concentration decreases, the rock slab conductivity decreases considerably, especially at 10% acid concentration, where the closure pressure rises to 15 MPa, and there is almost no conductivity. In particular, after the acid system is broken, the reacted acid can form a filter cake on the core surface, hindering further intrusion of the residue into the core and reducing reservoir damage. The study shows that high-temperature-resistant cross-linked acid systems can effectively improve the stimulation of deeply fractured carbonate reservoirs at high temperatures.
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Dong B, Yu C, Xing G, Di J, Ding J, Zhu Q, Zhu H, Deng C. Effect of In Situ Mg-Sialon on the Oxidation Behavior of Low-Carbon MgO-C Refractories. MATERIALS (BASEL, SWITZERLAND) 2023; 16:1892. [PMID: 36903008 PMCID: PMC10003835 DOI: 10.3390/ma16051892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 02/08/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
The in situ Mg-sialon in low-carbon MgO-C refractories was studied with respect to its oxidation behavior and mechanism at 1500 °C. The results indicated that the oxidation index and rate constant of low-carbon MgO-C refractories with Mg-sialon were 26.2% and 0.51 × 10-3 cm2/min at 1500 °C for 2 h, respectively. The formation of a dense MgO-Mg2SiO4-MgAl2O4 protective layer contributed to considerable oxidation resistance, and the generation of this thicker layer was due to the combined volume effect of Mg2SiO4 and MgAl2O4. The reduced porosity and more complex pore structure were also found in the refractories with Mg-sialon. Therefore, further oxidation was restricted as the oxygen diffusion path was effectively blocked. This work proves the potential application of Mg-sialon in improving the oxidation resistance of low-carbon MgO-C refractories.
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Affiliation(s)
| | - Chao Yu
- Correspondence: (C.Y.); (C.D.); Tel./Fax: +86-027-68862041 (C.D.)
| | | | | | | | | | | | - Chengji Deng
- Correspondence: (C.Y.); (C.D.); Tel./Fax: +86-027-68862041 (C.D.)
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Bie H, Chen H, Shan L, Tan CY, Al-Furjan MSH, Ramesh S, Gong Y, Liu YF, Zhou RG, Yang W, Wang H. 3D Printing and Performance Study of Porous Artificial Bone Based on HA-ZrO 2-PVA Composites. MATERIALS (BASEL, SWITZERLAND) 2023; 16:1107. [PMID: 36770115 PMCID: PMC9919799 DOI: 10.3390/ma16031107] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/25/2022] [Revised: 01/10/2023] [Accepted: 01/13/2023] [Indexed: 06/18/2023]
Abstract
An ideal artificial bone implant should have similar mechanical properties and biocompatibility to natural bone, as well as an internal structure that facilitates stomatal penetration. In this work, 3D printing was used to fabricate and investigate artificial bone composites based on HA-ZrO2-PVA. The composites were proportionally configured using zirconia (ZrO2), hydroxyapatite (HA) and polyvinyl alcohol (PVA), where the ZrO2 played a toughening role and PVA solution served as a binder. In order to obtain the optimal 3D printing process parameters for the composites, a theoretical model of the extrusion process of the composites was first established, followed by the optimization of various parameters including the spray head internal diameter, extrusion pressure, extrusion speed, and extrusion line width. The results showed that, at the optimum parameters of a spray head diameter of 0.2 mm, extrusion pressure values ranging from 1-3 bar, a line spacing of 0.8-1.5 mm, and a spray head displacement range of 8-10 mm/s, a better structure of biological bone scaffolds could be obtained. The mechanical tests performed on the scaffolds showed that the elastic modulus of the artificial bone scaffolds reached about 174 MPa, which fulfilled the biomechanical requirements of human bone. According to scanning electron microscope observation of the scaffold sample, the porosity of the scaffold sample was close to 65%, which can well promote the growth of chondrocytes and angiogenesis. In addition, c5.18 chondrocytes were used to verify the biocompatibility of the composite materials, and the cell proliferation was increased by 100% when compared with that of the control group. The results showed that the composite has good biocompatibility.
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Affiliation(s)
- Hongling Bie
- Artificial Intelligence Applications College, Shanghai Urban Construction Vocational College, Shanghai 201415, China
| | - Honghao Chen
- School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Lijun Shan
- Center of Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - C. Y. Tan
- Center of Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - M. S. H. Al-Furjan
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
- Collaborative Innovation Center of High-End Laser Manufacturing Equipment (National “2011 Plan”), Zhejiang University of Technology, Hangzhou 310023, China
| | - S. Ramesh
- Center of Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - Youping Gong
- School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Y. F. Liu
- Collaborative Innovation Center of High-End Laser Manufacturing Equipment (National “2011 Plan”), Zhejiang University of Technology, Hangzhou 310023, China
- Key Laboratory of E&M, Zhejiang University of Technology, Ministry of Education & Zhejiang Province, Hangzhou 310023, China
| | - R. G. Zhou
- School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou 310018, China
- Wenzhou Institute of Hangzhou Dianzi University, 3-4/F, Building B, Zhejiang Yungu, Nanyang Avenue, Yaoxi Street, Hangzhou 325038, China
| | - Weibo Yang
- Zhejiang Guanlin Machinery Limited Company, Huzhou 313300, China
| | - Honghua Wang
- Zhejiang Guanlin Machinery Limited Company, Huzhou 313300, China
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Opálek A, Švec P, Žemlička M, Štěpánek M, Štefánik P, Kúdela S, Beronská N, Iždinský K. Ni Porous Preforms Compacted with Al 2O 3 Particles and Al Binding Agent. MATERIALS (BASEL, SWITZERLAND) 2023; 16:988. [PMID: 36769993 PMCID: PMC9918079 DOI: 10.3390/ma16030988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 01/09/2023] [Accepted: 01/18/2023] [Indexed: 06/18/2023]
Abstract
This work presents an energy-efficient, cheap, and rapid production method of a metal-ceramic preform with open porosity suitable for liquid metal infiltration and filtration applications. It is based on cold isostatic pressing of a mixture of relatively hard Ni and Al2O3 powders with the addition of small amount of Al powders, acting as a binding agent. Open porosity is primarily controlled by Al2O3 particles partially separating Ni particles from mutual contacts. Cold isostatic pressed green compacts were subjected to thermal oxidation by heating in air to 600 °C, 700 °C, and 800 °C. The weight gain and open porosity of oxidized compacts were examined. The chemical composition and microstructure were analyzed by SEM-EDS and XRD techniques. The stability of preforms and the effect of thermal cycling on the open porosity were tested by thermal cycling in an inert Ar atmosphere in the temperature range up to 800 °C. It appeared that, in addition to NiO being an expected product of oxidation, Ni aluminides and spinel particles also played an important role in inter-particle bonding formation. Ni-NiO porous composites resist chemical corrosion and exhibit structural and chemical stability at higher temperatures and admixed Al2O3 particles do not deteriorate them. After subsequent infiltration with Al, it can offer a lower density than other materials, which could result in lower energy consumption, which is highly needed in industries such as the automotive industry.
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Affiliation(s)
- Andrej Opálek
- Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 13 Bratislava, Slovakia
| | - Peter Švec
- Institute of Physics, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 11 Bratislava, Slovakia
| | - Matúš Žemlička
- Institute of Construction and Architecture, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 03 Bratislava, Slovakia
| | - Matej Štěpánek
- Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 13 Bratislava, Slovakia
- Centre of Excellence for Advanced Materials Application, Slovak Academy of Sciences, Dúbravska Cesta 9, 845 11 Bratislava, Slovakia
| | - Pavol Štefánik
- Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 13 Bratislava, Slovakia
| | - Stanislav Kúdela
- Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 13 Bratislava, Slovakia
| | - Naďa Beronská
- Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 13 Bratislava, Slovakia
| | - Karol Iždinský
- Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 13 Bratislava, Slovakia
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Pang Y, Li D, Li X, Wang R, Ao X. Phase-Field Simulation of Temperature-Dependent Thermal Shock Fracture of Al 2O 3/ZrO 2 Multilayer Ceramics with Phase Transition Residual Stress. MATERIALS (BASEL, SWITZERLAND) 2023; 16:734. [PMID: 36676470 PMCID: PMC9862266 DOI: 10.3390/ma16020734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/04/2023] [Accepted: 01/09/2023] [Indexed: 06/17/2023]
Abstract
Compared with single-phase ceramics, the thermal shock crack propagation mechanism of multiphase layered ceramics is more complex. There is no experimental method and theoretical framework that can fully reveal the thermal shock damage mechanism of ceramic materials. Therefore, a multiphase phase-field fracture model including the temperature dependence of material for thermal shock-induced fracture of multilayer ceramics is established. In this study, the effects of residual stress on the crack propagation of ATZ (Al2O3-5%tZrO2)/AMZ (Al2O3-30%mZrO2) layered ceramics with different layer thickness ratios, layers, and initial temperatures under bending and thermal shock were investigated. Simulation results of the fracture phase field under four-point bending are in good agreement with the experimental results, and the crack propagation shows a step shape, which verifies the effectiveness of the proposed method. With constant thickness, high-strength compressive stress positively changes with the layer thickness ratio, which contributes to crack deflection. The cracks of the ceramic material under thermal shock have hierarchy and regularity. When the layer thickness ratio is constant, the compressive residual stress decreases with the increase in the layer number, and the degree of thermal shock crack deflection decreases.
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Affiliation(s)
- Yong Pang
- School of Civil Engineering and Architecture, Chongqing University of Science and Technology, Chongqing 401331, China
| | - Dingyu Li
- School of Civil Engineering and Architecture, Chongqing University of Science and Technology, Chongqing 401331, China
| | - Xin Li
- School of Civil Engineering and Architecture, Chongqing University of Science and Technology, Chongqing 401331, China
| | - Ruzhuan Wang
- Chongqing Key Laboratory of Nano-Micro Composite Materials and Devices, School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
| | - Xiang Ao
- College of Petroleum and Natural Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
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Chu C, Tang J, Zhao Z, Kong Y, Shen X. Fe Ions-Doped TiO 2 Aerogels as Catalysts of Oxygen Reduction Reactions in Alkaline Solutions. MATERIALS (BASEL, SWITZERLAND) 2022; 15:8380. [PMID: 36499876 PMCID: PMC9739684 DOI: 10.3390/ma15238380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/26/2022] [Accepted: 10/27/2022] [Indexed: 06/17/2023]
Abstract
Aerogels have interconnected networks and preeminent pore structures. When used as the catalysts for oxygen reduction reaction (ORR), they can facilitate the mass transfer and expose more active sites. Here, we synthesized the Fe-doped titanium oxide-based aerogels (TA/Fes) by the sol-gel method combined with thermal treatment. The specific surface areas of the TA/Fes ranged from 475 to 774 m2·g-1, and the pore volumes varied from 0.96 to 1.72 cm3·g-1. The doping effect of the Fe ions and the oxygen vacancies in anatase enhance the electrical conductivity, leading to the low Rct (313.3-828.2 Ω). All samples showed excellent stability (2.0-4.5 mV) and 4e- pathway. The limiting current density of TA/Fe3 reached 5.34 mA·cm-2, which was comparable to that of commercial Pt/C. The preparation method is inspiring and the as-prepared aerogel catalysts have potential in promoting the scale of fuel cells.
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Affiliation(s)
- Chen Chu
- College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China
- Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing 210009, China
| | - Jinqiong Tang
- College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China
- Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing 210009, China
| | - Zhiyang Zhao
- College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China
- Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing 210009, China
| | - Yong Kong
- College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China
- Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing 210009, China
| | - Xiaodong Shen
- College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China
- Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing 210009, China
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Postek E, Sadowski T. Dynamic Compression of a SiC Foam. MATERIALS (BASEL, SWITZERLAND) 2022; 15:8363. [PMID: 36499858 PMCID: PMC9736183 DOI: 10.3390/ma15238363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 11/19/2022] [Accepted: 11/21/2022] [Indexed: 06/17/2023]
Abstract
Silicon carbide foam is a material that can be used as reinforcement of interpenetrated composites. This paper presents an analysis of such a foam subjected to low and fast compression. The analysis is performed using the peridynamics (PD) method. This approach allows for an evaluation of failure modes and such effects of microcracks nucleation, their growth, and, finally, fragmentation. Furthermore, the material appears to behave qualitatively and quantitatively differently while subjected to low- and high-speed steel piston movement. Under slow compression case, damage appears in the entire specimen, but the shape of the structure is not changing significantly, whereas during the fast compression the sample is dynamically fragmented.
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Affiliation(s)
- Eligiusz Postek
- Institute of Fundamental Technological Research, Department of Information and Computational Science, Polish Academy of Sciences, Pawińskiego St. 5B, 02-106 Warsaw, Poland
| | - Tomasz Sadowski
- Faculty of Civil Engineering and Architecture, Department of Solid Mechanics, Lublin University of Technology, Nadbystrzycka St. 40, 20-618 Lublin, Poland
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Influence of multi-walled carbon nanotubes in polytetrafluoroethylene on the parameters of electronic structure and absorption of ultra-high-frequency radiation. APPLIED NANOSCIENCE 2022. [DOI: 10.1007/s13204-022-02659-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
AbstractUsing the methods of angular correlation of annihilation radiation (ACAR), attenuation of electromagnetic radiation in 1.5–2.2 GHz frequency range, and optical ellipsometry, it was shown that in composites of polytetrafluoroethylene (PTFE) + multi-walled carbon nanotubes (MWCNTs), a 2% decrease in the probability of annihilation of positrons in free volumes in PTFE leads to changes in other parameters of electronic structure of composites by 8–29%. Polytetrafluoroethylene is transparent to electromagnetic radiation, but after the addition of 10 wt.% or more of MWCNTs, the composites demonstrate 200–410-fold decrease in the electromagnetic radiation intensity when the radiation passes through a specimen with a thickness of ≈2 mm. It was found that the average radius of the free volumes and the probability of annihilation of positrons are determined by the defect and electronic structures of the polymer matrix only. The Fermi angle and the probability of positrons annihilation with free electrons are determined by the analogous structures of MWCNTs only. Since the electronic characteristics of the atoms and defects in the polymer matrix (at least outside the interphase) do not change, the changes in the other ACAR parameters are mainly due to changes in the imperfect MWCNTs’ atomic and electronic structures. The average radius of free volumes reaches its maximum value in the composite with 10 wt.% MWCNTs. It was found that in a specimen with 10 wt.% MWCNTs, the highest density of free electrons is observed due to charge transfer from free volumes to MWCNTs, and the highest electron density is observed on defects. A disorder of MWCNTs and their branched conductive network can form the ‘tails’ of electronic density of states in a band gap. Thus, composite with 10 wt.% MWCNTs has the highest absorption coefficient for electromagnetic radiation.
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Structural and Luminescent Peculiarities of Spark Plasma Sintered Transparent MgAl2O4 Spinel Ceramics Doped with Cerium Ions. INORGANICS 2022. [DOI: 10.3390/inorganics10100153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
In the present study, the concentration series of MgAl2O4:Ce3+ ceramics have been fabricated by the Spark Plasma Sintering (SPS) method. Cerium-doping concentration was varied within a range of 0.1–5 wt.%. The prepared ceramics have been tested using the various experimental techniques: X-ray diffraction (XRD), scanning electron microscopy, as well as optical and cathodoluminescence spectroscopy. According to XRD, all synthesized samples are biphasic with structural impurities. The cerium ion concentration effect on the cathodoluminescent characteristics of MgAl2O4:Ce3+ ceramics has been studied in terms of emission intensity and decay time. Before annealing the concentration, quenching is observed. The optimal doping Ce3+ concentration was determined to be 5 wt.% after temperature annealing at 1300 °C. The successfully prepared spinel ceramics could be potentially applying for high-energy electrons detection.
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Study of Structural, Strength, and Thermophysical Properties of Li2+4xZr4−xO3 Ceramics. TECHNOLOGIES 2022. [DOI: 10.3390/technologies10030058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The work is devoted to the study of technology that can be used to obtain lithium-containing ceramics of the Li2+4xZr4−xO3 type using the method of solid-phase synthesis combined with thermal annealing at a temperature of 1500 °C. A distinctive feature of this work is the preparation of pure Li2ZrO3 ceramics with a high structural ordering degree (more than 88%) and density (95–97% of the theoretical density). During the study, it was found that a change in the content of initial components for synthesis does not lead to the formation of new phase inclusions; however, an increase in the LiClO4·3H2O and ZrO2 components leads to changes in the size of crystallites and dislocation density, which lead to the strengthening of ceramics to external mechanical influences. The results of the measurements of thermophysical characteristics made it possible to establish that the compaction of ceramics and a decrease in porosity lead to an increase in the thermal conductivity coefficient of 3–7%.
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