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1.
《Ceramics International》2022,48(16):22943-22952
In this study, we fabricated and characterized six new nanopowders representing variations of La2O3–Fe2O3–Bi2O3, i.e., 100Bi2O3, 30Fe2O3–70Bi2O3, 3La2O3–27Fe2O3–70Bi2O3, 7La2O3–23Fe2O3–70Bi2O3, 10La2O3–20Fe2O3–70Bi2O3, and 20La2O3–10Fe2O3–70Bi2O3 (represented by 100B, 30F70B, 3L27F70B, 10L20F70B, and 20L10F70B, respectively). These nanopowders were prepared by the microwave-assisted hydrothermal synthesis method. Saponin extract from soapnuts was used as the nanoparticle capping agent. The structural, optical, and gamma radiation characteristics were measured, calculated, and analysed, respectively. The chemical structures of the nanocomposites influenced their optical and radiation shielding characteristics. The optical bandgaps of the 100B, 30F70B, 3L27F70B, 7L23F70B, 10L20F70B, and 20L10F70B nanopowders were 3.16, 3.13, 3.43, 3.45, 3.46, and 3.58 eV, respectively. The ranges of the mass attenuation coefficients of the nanopowders were computed, using XCOM, to be 0.0412–5.1624, 0.0401–4.5406, 0.0401–4.5285, 0.0401–4.5129, 0.0401–0.5015, and 0.0400–4.4156 cm2/g, respectively, and the ranges of mass energy absorption coefficients were found to be 0.0232–1.7525, 0.0228–1.5484, 0.0228–1.5598, 0.0288–1.5746, 0.0228–1.5853, and 0.0227–1.6192 cm2/g, respectively, for photon energies in the range of 0.1–10 MeV. The order of the dose rate trend was as follows: 30F70B < L27F70B < 7L23F70B < 10L20F70B < 20L10F70B. Analysis of the photon interaction parameters showed that the synthesized nanopowders could function well as fillers in radiation-shielding matrices. 相似文献
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Phase composition, microstructure and electrical conductivity of glass ceramics in the VO2–V2O5–P2O5–SnO2 and VO2–V2O5–P2O5–Cu2O–SnO2 systems have been studied. Only crystalline phases VO2, SnO2 and vanadium phosphate glass of the V2O5–P2O5 system have been found in glass ceramic compositions in the VO2–V2O5–P2O5–SnO2 system. Besides the above-mentioned phases, probably the X-ray lines of V3O5, V4O7, V5O9, V6O11, V7O13, V4O9, V6O13, V2O5, SnO2, SnO, Sn2O3, Sn3O4 and CuO phases are observed in the X-ray spectra of glass ceramics in the VO2–V2O5–P2O5–Cu2O–SnO2 system. According to SEM/EDS data, these phases were observed as submicrometer fine-crystalline inclusions in glass on the surface of VO2 crystallites and between them. The formation of these phases was caused by the redox processes in the liquid phase during glass ceramics synthesis. The important role of tin oxides possessing high electrical conductivity and vanadium oxides exhibiting a low temperature of metal–semiconductor phase transition in the stabilization of glass ceramics electrical properties related to the phase transition in VO2 has been established. 相似文献
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《Journal of the European Ceramic Society》2022,42(13):5820-5830
Cerium oxide doped with oxides of rare earth elements is a multifunctional material, a wide range of uses which is associated with its unique physicochemical properties. Phase diagrams of multicomponent systems are the physicochemical basis for the creation of new materials with improved characteristics.In this work, phase equilibria in ternary CeO2–La2O3–Dy2O3 and binary La2O3–Dy2O3 systems in the whole concentration range were studied. No new phases have been identified in these systems. An isothermal section of the phase diagram of the CeO2–La2O3–Dy2O3 system at a temperature of 1500 °С is constructed. No new phases have been detected in the system. It was found that in the studied ternary system solid solutions are formed on the basis of (F) modification of CeO2 with structure of fluorite type, monoclinic (B), cubic (C) and hexagonal (A) modifications of Ln2O3.In the La2O3–Dy2O3 binary system (1500–1100 °С) three types of solid solutions are formed: based on hexagonal modification A-La2O3, monoclinic modification B-Dy2O3 and cubic modification C-Dy2O3 separated by two-phase fields (A+B) and (B+C), respectively. The boundaries of the regions of homogeneity of solid solutions based on A-La2O3 are determined by compositions containing 35–40, 20–25, 15–20 mol% Dy2O3 at 1500, 1250, 1100 °C, respectively. From the obtained data it follows that the solubility of Dy2O3 in the hexagonal modification of lanthanum oxide is 39 mol% at 1500 °C, 23 mol. % at 1250 °C and 16 mol% at 1100 °C. The limits of existence of solid solutions based on monoclinic B-modification are determined by compositions containing 30–35, 65–60 (1250 °С), 35–40, 55–60 (1100 °С) 40–45, 70–75 (1500 °C) mol% Dy2O3.In the studied system, with a decrease in temperature from 1500° to 1100°C, there is a decrease in the solubility of La2O3 in the crystal lattice of cubic solid solutions of C-type from 16 to 10 mol%. 相似文献
6.
《应用陶瓷进展》2013,112(5):235-237
AbstractThe influence of Cr2O3, TiO2 and ZrO2 on the sintering, crystallisation and machinability of SiO2–Al2O3–MgO–K2O–B2O3–F glasses was investigated. Optimum fluoromica glass ceramic compositions with desirable sintering behaviour and machinability were obtained by addition of titanium and chromium oxides to the base glass. Texture and relative intensity of mica phase Imica/ISi were determined by XRD analysis and the particle size distribution of chips was studied by drilling. Microhardness and bending strength were also investigated. The relative intensity of mica phase and microhardness were found to be compatible with the experimental results. 相似文献
7.
Effect of Alumina Reactivity on the Densification and Properties of Al2O3–Cr2O3 Refractories
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Mithun Nath Vakiti Pradeep Reddy Somnath Sinhamahapatra Kausik Dana Arup Ghosh Himansu Sekhar Tripathi 《International Journal of Applied Ceramic Technology》2015,12(3):608-613
Alumina‐chrome (Al2O3–Cr2O3) refractories with Al2O3:Cr2O3 molar ratio 1:1 were synthesized in the temperature range of 1400–1700°C by conventional solid–oxide reaction route. The effect of different aluminas (viz., hydrated and calcined) on the densification, microstructure, and properties of Al2O3–Cr2O3 refractories was investigated without changing the Cr2O3 source. The starting materials were analyzed to determine the chemical composition, mineralogy, density, surface area, and particle size. Sintered materials were characterized in terms of densification, phase assemblage, and mechanical strength at room temperature and at higher temperatures. Microstructural evolution at different sintering temperature was correlated with sintering characteristics. It can be concluded that the Al2O3–Cr2O3 refractories prepared with hydrated alumina as Al2O3 source show better densification and hot mechanical strength than corresponding calcined variety. 相似文献
8.
《Journal of the European Ceramic Society》2006,26(10-11):2129-2133
We studied the low temperature sintering and the reaction in BaO–Sm2O3–4TiO2 ceramics with boron-based additives for the application to microwave dielectric devices. The amount of the boride glasses of B2O3 and BaB2O4 was varied from 1 to 10 wt.% and the green compacts were sintered in the temperature range of 900–1200 °C for 2 h. When B2O3 was added, second phases of Sm2Ti2O7, BaTi(BO3)2, Ba2Ti9O20, and TiO2 were formed, while BaB2O4 addition resulted in the formation of BaSm2Ti4O12 single phase without second phases. On the basis of these results, it is regarded that the B2O3 is a reactive glass and the BaB2O4 is a non-reactive glass. The second-phase development, sintering behavior and microwave dielectric characteristics of BaO–Sm2O3–4TiO2 ceramics were examined. 相似文献
9.
Kohei Yoshimoto Atsunobu Masuno Motoi Ueda Hiroyuki Inoue Hiroshi Yamamoto Tatsunori Kawashima 《Journal of the American Ceramic Society》2018,101(8):3328-3336
La2O3–Ga2O3–M2O5 (M = Nb or Ta) ternary glasses were fabricated using an aerodynamic levitation technique, and their glass‐forming regions and thermal and optical properties were investigated. Incorporation of adequate amounts of Nb2O5 and Ta2O5 drastically improved the thermal stabilities of the glasses against crystallization. Optical transmittance measurements revealed that all the glasses were transparent over a wide wavelength range from the ultraviolet to the mid‐infrared. The refractive indices of the glasses increased and the Abbe number decreased upon substituting Ga2O3 with Nb2O5, and the decrease in the Abbe number was significantly suppressed when Ta2O5 was incorporated into the glass. As a result, excellent compatibility between high refractive index and lower wavelength dispersion was realized in La2O3–Ga2O3–Ta2O5 glasses. Analysis based on the single‐oscillator Drude–Voigt model provided more systematical information and revealed that this compatibility was due to an increase in the electron density of the glass. 相似文献
10.
《Ceramics International》2020,46(1):186-195
The Al2O3/SiO2–B2O3–Al2O3–Na2O glass/Al2O3 joints reinforced cooperatively by glass matrix and in-situ Al4B2O9 whiskers were obtained via a low-melting borosilicate glass braze. The composition of glass seam transformed from SiO2–B2O3–Na2O to SiO2–B2O3–Al2O3–Na2O due to continuous diffusion and dissolution of Al2O3. An appropriate amount of [AlO4] units introduced into the glass braze played a vital role in strengthening the glass network structure resulting to considerably improved mechanical strength of the glass seam. Meanwhile, plenty of in-situ Al4B2O9 whiskers growing from the Al2O3/glass braze interface to the center of glass seam in various directions generated. Three-dimensional crisscross structures were fabricated at the Al2O3/glass braze interface domains, where were enhanced by crack-bridging and pull-out effect of the whiskers. Generally, ascribed to the cooperative reinforcement of the glass matrix in the seam and in-situ Al4B2O9 whiskers at Al2O3/glass braze interface domains through reactions of Al2O3 and borosilicate glass braze, strength of the as-brazed joints was promoted prominently. The shear strength of the joints reached a maximum of 61 MPa brazed at 1050 °C for 60 min. 相似文献
11.
《Ceramics International》2022,48(21):31636-31651
The lack of thermodynamic data such as the phase diagram of CaO–SiO2–Nb2O5–Fe2O3–TiO2 system has seriously hampered the comprehensive utilization of niobium, titanium and other resources in the Bayan Obo tailing. In this study, phase equilibria of the CaO–SiO2–Nb2O5–Fe2O3–TiO2 system at 1200 °C were investigated using high temperature equilibrium experiment for the first time, and the CaTiO3–Ca10Nb2Si6O27–Ca2SiO4–Ca2Nb2O7 solid phase coexistence region was determined. Afterwards, based on the high temperature equilibrium experiments, the liquidus surfaces of the liquid + CaTiO3 and liquid + SiO2 equilibrium coexistence regions in CaO–SiO2–Nb2O5-5wt% Fe2O3–TiO2 system at 1200 °C were calculated using mathematical methods of interpolation and fitting. Finally, the 1200 °C isothermal phase diagrams of CaO–SiO2–Nb2O5-5wt%Fe2O3–TiO2 system were plotted. The results of the study can provide theoretical guidance for the enrichment and extraction processes of niobium and titanium resources in the Bayan Obo tailing. 相似文献
12.
Thermal Stability,Optical Transmittance,and Refractive Index Dispersion of La2O3–Nb2O5–Al2O3 Glasses
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Kohei Yoshimoto Atsunobu Masuno Hiroyuki Inoue Yasuhiro Watanabe 《Journal of the American Ceramic Society》2015,98(2):402-407
La2O3–Nb2O5–Al2O3 high‐refractive‐index glasses were fabricated by containerless processing, and the glass‐forming region was determined. The thermal stability, density, optical transmittance, and the refractive index dispersion of these glasses were investigated. All the glasses were colorless and transparent in the visible to near infrared (NIR) region and had high refractive index with low wavelength dispersion. Some of these glasses were found to have significantly high glass‐forming ability. These results indicate that the ternary glasses are suitable for optical applications in the visible to NIR region. The effects of the substitution of Al2O3 for Nb2O5 on optical properties were discussed on the basis of the Drude–Voigt equation. It was suggested that the substitution of Al2O3 for Nb2O5 increased the molecular density and suppressed a decrease in the refractive index, even when both the average oscillator strength and inherent absorption wavelength decreased in La2O3–Nb2O5–Al2O3 glasses. These results are helpful for designing new optical glasses controlled to have a higher refractive index and lower wavelength dispersion. 相似文献
13.
《Journal of the European Ceramic Society》2005,25(6):899-902
Sintering, crystallization and machinability behavior of the SiO2–Al2O3–MgO–K2O–B2O3–F glasses were investigated. The optimum fluormica glass–ceramics with desirable sintering behavior and machinability were obtained by addition of PbO and P2O5 glass formers. Various parameters, e.g. the morphology of the mica crystal, relative intensity of the mica phase, the particle size distribution of chips obtained by drilling, microhardness, and the strength differences of glass–ceramics before and after drilling (Δσ) were investigated and compared with naked eye experiments. 相似文献
14.
Phase equilibria of the ZnO–SiO2, Al2O3–SiO2 and ZnO–Al2O3–SiO2 systems at liquidus were characterized at 1340–1740 °C in air. The ZnO–Al2O3 subsolidus phase equilibria were derived from the experiments with the SiO2- and CaO + SiO2-containing slags. High-temperature equilibration on silica or platinum substrates, followed by quenching and direct measurement of Zn, Al, Si and Ca concentrations in the phases with the electron probe X-ray microanalysis (EPMA) was used to accurately characterize the system. Special attention was given to zincite phase that was shown to consist of two separate ranges of compositions: round-shaped low-Al zincite (<2 mol.% AlO1.5) and platy high-Al zincite (4–11 mol.% AlO1.5). A technique was developed for more accurate measurement of the ZnO solubility in the low-ZnO phases (corundum, mullite, tridymite and cristobalite) surrounded by the ZnO-containing slag, using l-line for Zn instead of K-line, avoiding the interference of secondary X-ray fluorescence. Solubility of ZnO was found to be below 0.03 mol.% in corundum and cristobalite, and below 0.3 mol.% in mullite. Present experimental data were used to obtain a self-consistent set of parameters of the thermodynamic models for all phases in this system using FactSage computer package. The modified quasichemical model with two sublattices (Zn2+, Al3+, Si4+) (O2?) was used for the liquid slag phase; the compound energy formalism was used for the spinel (Zn2+,Al3+)[Zn2+,Al3+,Va]2O2-4 and mullite Al3+2(Al3+,Si4+) (O2?,Va)5 phases; the Bragg-Williams formalism was used for the zincite (ZnO, Al2O3); other solid phases (tridymite and cristobalite SiO2, corundum Al2O3, and willemite Zn2SiO4) were described as stoichiometric. Present study is a part of the research program on the characterization of the multicomponent Pb–Zn–Cu–Fe–Ca–Si–O–S–Al–Mg–Cr–As–Sn–Sb–Bi–Ag–Au–Ni system. 相似文献
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The effect of Gd2O3-doping on the crystal structure, surface morphology and chemical composition of the Gd2O3–HfO2 system is reported. Gd2O3–HfO2 ceramics with variable composition were prepared by varying the Gd2O3 composition in the range of 0–38 mol% balanced HfO2. X-ray diffraction (XRD) analysis indicates that the Gd2O3 concentration influences the crystal structure of the Gd2O3–HfO2 ceramics. Pure HfO2 and Gd2O3 crystallize in monoclinic and body centered cubic structure, respectively. The Gd2O3–HfO2 ceramics exhibit mixed monoclinic and fluorite structure when the Gd2O3 concentration is varied from 4 to 12 mol%. At 20 mol% of Gd2O3, existence of only the fluorite phase was found. Increasing the Gd2O3 concentration to 38 mol% results in the formation of single-phase pyrochlore Gd2Hf2O7 (a = 5.258 Å). 相似文献
16.
Muddiyada Vishnu Muthamma Shivappa Gudennavar Bubbly Shivappa Bharamappa Gudennavar 《应用聚合物科学杂志》2020,137(44):49366
Epoxy resin filled with suitable high Z elements can be a potential shield for X-rays and γ-rays. In this work, we present the γ-ray attenuation properties of epoxy composites filled with (0–30 wt%) Tantalum pentoxide (Ta2O5) and Ta2O5-Bi2O3, which were prepared by open mold cast technique. X-ray diffraction patterns showed crystalline peaks of Ta2O5 and bismuth oxide (Bi2O3) in the prepared epoxy-Ta2O5 and epoxy-Ta2O5-Bi2O3 composites. Homogeneity of the samples at higher filler wt% was revealed by SEM images. Mechanical characterization showed the enhanced mechanical strength of epoxy-Ta2O5-Bi2O3 composites compared to epoxy-Ta2O5. Higher storage modulus and glass transition temperature of the epoxy-Ta2O5-Bi2O3 composites showed enhanced stiffness and thermal stability when compared to neat and epoxy-Ta2O5. Decrease in the value of tan(δ) at higher content of filler loadings indicated the good adhesion between filler and matrix. Mass attenuation coefficients of epoxy-Ta2O5 (30 wt%) composites at γ-ray energies 59.54 and 662 keV were found to be 0.876 cm2 g–1 and 0.084 cm2 g–1, while that of epoxy-Ta2O5-Bi2O3 (30 wt% Bi2O3) composite were 1.271 cm2 g–1 and 0.088 cm2 g–1, respectively. The epoxy-5% Ta2O5-30% Bi2O3 composites with higher μ/ρ value and tensile strength may be a potential γ-ray shield in various radiation environments. 相似文献
17.
Baofu Qiu Xiaoming Duan Zhuo Zhang Delong Cai Ning Liao Peigang He Dechang Jia Yu Zhou 《Ceramics International》2021,47(1):73-79
The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock. 相似文献
18.
《Journal of the European Ceramic Society》2020,40(12):4184-4190
Materials based on CeO2–La2O3–Er2O3 system are promising candidates for a wide of applications, but the phase relationship has not been studied systematically previously. To address this challenge, the isothermal section of the phase diagram for 1500 °C was investigated. The phase relations in the CeO2–La2O3–Er2O3 ternary system at 1500 °C were studied by X-ray diffraction and scanning electron microscopy in the overall concentration range. To study phase relationships at 1500 °C the as-repared samples were thermally treated in two stages: at 1100 °C (for 300 in air) and then at 1500 °C (for 70 h in air) in the furnaces with heating elements based on Fecral (H23U5T) and Superkanthal (MoSi2), respectively. The solid solutions based on various polymorphous forms of constituent phases and with perovskite-type structure of LaErO3 (R) with orthorhombic distortions were revealed in the system. No new phases were found. The isothermal section of the phase diagram for the CeO2–La2O3–Er2O3 system has been constructed. It was established that in the ternary CeO2–La2O3–Er2O3 system there exist fields of solid solutions based on hexagonal (A) modification of La2O3, cubic modification of CeO2 with fluorite-type structure (F), cubic modification Er2O3 and with perovskite-type structure of LaErO3 (R) with orthorhombic distortions. The maximal solubility of ceria in LaErO3 was found to be around ∼ 2 mol% CeO2 along the section CeO2–(50 mol % La2O3 –50 mol% Er2O3). 相似文献
19.
《Catalysis communications》2010,11(15):2018-2022
Commercial Cu–ZnO–Al2O3 catalysts are used widely for steam reforming of methanol. However, the reforming reactions should be modified to avoid fuel cell catalyst poisoning originated from carbon monoxide. The modification was implemented by mixing the Cu–ZnO–Al2O3 catalyst with Pt–Al2O3 catalyst. The Pt–Al2O3 and Cu–ZnO–Al2O3 catalyst mixture created a synergetic effect because the methanol decomposition and the water–gas shift reactions occurred simultaneously over nearby Pt–Al2O3 and Cu–ZnO–Al2O3 catalysts in the mixture. A methanol conversion of 96.4% was obtained and carbon monoxide was not detected from the reforming reaction when the Pt–Al2O3 and Cu–ZnO–Al2O3 catalyst mixture was used. 相似文献
20.
Nader Rahemi Mohammad Haghighi Ali Akbar Babaluo Mahdi Fallah Jafari Pooya Estifaee 《Journal of Industrial and Engineering Chemistry》2013,19(5):1566-1576
Ni/Al2O3 and Ni/Al2O3–ZrO2 nanocatalysts synthesized via impregnation and treated with non-thermal plasma were investigated in dry reforming of methane. The results showed that plasma treatment produces highly dispersed nanoparticles with a high surface area. Strong interaction between active phase and support particles in plasma-treated catalysts can be concluded based on XRD and XPS results. Smaller Ni particles with narrow particle size distribution were observed in plasma-treated Ni/Al2O3–ZrO2 nanocatalyst. The catalytic activity of plasma-treated Ni/Al2O3–ZrO2 was higher than that of conventional catalyst, resulting in operating conditions with considerably lower temperatures. Long reaction times confirmed the stability of the plasma-treated Ni/Al2O3–ZrO2 nanocatalyst. 相似文献