共查询到20条相似文献,搜索用时 15 毫秒
1.
A novel approach for the preparation of blue-color giving zirconia nanopowders by doping of 3?mol% Y2O3 through simple one-step hydrothermal process is proposed. A blue-color giving yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) powders were prepared by urea-based solution, zirconium acetate, CoCl2·6H2O and AlCl3 precursors in hydrothermal vessel at 24?h, 150?°C and 20 bars. Based on the results, the synthesized blue-color giving Y-TZP nanopowders have entirely tetragonal structure as mono phase with 3.8?±?0.2?nm average grain size and (Y, Co, Al)xZrO2; x?≤?0.03?at. with chemical composition. Thermal treatment was also applied to synthesized Y-TZP powders at 1200?°C and 1450?°C to observe the color evolution. Only sharp blue was obtained in Y-TZP powders resulting the development of zirconia-cobalt aluminate spinel (ZrO2-CoAl2O4) composite ceramic structure for both temperatures after heat-treatment. Herein, not only formation of CoAl2O4 but also incorporation of cobalt (Co) and aluminum (Al) into the Y-TZP grains plays a critical role on evolving of blue color. This synthesized Y-TZP nanopowders can be a good candidate for one-step production of blue-color sintered ZrO2-CoAl2O4 spinel composite ceramics in numerous ceramic applications due to their superior structural and functional properties. 相似文献
2.
S. Ghosh K.S. PalN. Dandapat A.K. MukhopadhyayS. Datta D. Basu 《Ceramics International》2011,37(3):1115-1119
Commercial Al powder was exposed to microwave radiation for 45 min. The as received and microwave heated Al powders were characterized by X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM). XRD of the microwave treated Al powder confirmed the formation of Al-Al2O3 composite. FTIR studies and EDX analysis indicated the transformation of Al powder into Al-Al2O3 core-shell composite powder after microwave processing. SEM showed that the morphology of the microwave processed Al powder was quite different from that of the as-received Al powder. TEM image of the microwave treated Al powder supported the FTIR and EDX data. 相似文献
3.
ZnO nanostructures were grown by microwave assisted wet-chemical growth, at different microwave powers and for different growth durations. The grown nanostructures were analysed for their morphological, structural, compositional and optical characteristics. The total microwave power per growth run (product of microwave power and growth duration, with units in watt-min), has a linear relationship with most of the characteristics of the grown ZnO nanostructures. It is shown that by altering the microwave power per growth run, the morphology of the individual ZnO nanostructure can be changed from cones with hexagonal cross section, to faceted hexagonal nanorods, to hollow hexagonal nanorods. It is observed that, while the fast growth rate along the high energy polar faces (0001) and (000ī) of ZnO is the reason behind the formation of one dimensional ZnO structures (cones and rods), the process of formation of hallow ZnO rods is due to further etching/material-removal from the tip of the rods, at high microwave power conditions at long growth durations. 相似文献
4.
Enrico Kleebusch Christian Patzig Thomas Höche Christian Rüssel 《Ceramics International》2018,44(16):19818-19824
Glass-ceramics based on lithium-alumo-silicate glasses are commercially important for a wide range of applications, due to their special properties, like a vanishing thermal expansion. In order to tailor these properties, the composition of the glass and the temperature/time schedule are crucial factors. For the industrial production of most lithium-alumo-silicate glasses, high melting temperatures are required due to the high viscosities of the respective melt compositions. In this study, a simplified lithium-alumo-silicate glass composition with ZrO2 as nucleating agent, on the basis of the commercially available Robax® composition, is studied. Adding boron oxide leads to lower viscosities of the glass melt and notably lower melting temperatures may be supplied. The resulting glass is investigated using X-ray diffraction and transmission electron microscopy. During the crystallization process, phases such as ZrO2 and β-quartz types are formed. The microstructure of the glass ceramics is notably coarser than that of glass-ceramics which are obtained from lithium-alumo-silicate glasses of standard compositions. EDX-analyses indicate a considerable enrichment of chemical elements in comparatively small areas of the microstructure. Especially boron oxide is found to be enriched in the residual glass of the investigated glass-ceramics. 相似文献
5.
Mohammad Reza Tohidifar 《Ceramics International》2018,44(4):3699-3706
The present research systematically investigated the novel low-temperature fabrication of a multi-walled carbon nanotube (MWCNT)/barium titanate nanocomposite using a two-step mixing technique. The synthesis was conducted using different amounts of MWCNT (0.25%, 0.5%, 1%, 2%, 4%, and 8% wt) with different compositions of (Bi2O3 + B2O3) as a sintering aid. Scanning and transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, three-point bending strength, Vickers hardness indentation and Archimedean technique were used to characterize the as-synthesized specimens. It was found that the appropriate content of sintering aid (Bi2O3+B2O3) strongly decreased the sintering temperature from 1200 °C to 950 °C. The results also revealed that any sintering aid with the optimum composition that included 30% (mol) Bi2O3 was optimal for a sintering aid content of 6% (wt). Consequently, the highest values of the flexural strength and fracture toughness were achieved by applying the optimal amounts of MWCNT (1% wt) and sintering aid (6% wt). 相似文献
6.
《Ceramics International》2019,45(12):15143-15155
Designing biocompatible superparamagnetic mesoporous nanoparticles for advanced healthcare applications has received much attention. In this research, we have synthesized intrinsic mesoporous superparamagnetic hydroxyapatite (HAp) nanoparticles using bio-waste of black Chlamys varia seashell as a calcium source by sodium dodecyl sulfate (SDS)–enabled microwave-assisted synthesis approach. The synthesized Fe-doped HAp nanoparticles were characterized using various characterization techniques to know the phase purity and morphological features. The incorporation of Fe greatly affected the morphology of HAp nanoparticles without affecting their crystalline phase. Superparamagnetic behavior was observed with the incorporation of Fe in the HAp nanoparticles. Further, saturation magnetization was enhanced with higher incorporation of Fe ions. The cytotoxicity studies of the synthesized pure and Fe-doped HAp samples conducted using a human osteoblasts cell line (MG63), which indicated that Fe-doped HAp nanoparticles are biocompatible. Further, antibacterial activity analysis also confirmed their excellent antibacterial performance against different pathogens. Hence, SDS-enabled microwave-assisted synthesis approach using seashell as a calcium source would be a better approach for the production of intrinsic mesoporous superparamagnetic HAp nanoparticles for various biomedical applications, such as drug targeting, hyperthermia cancer therapy, and magnetic resonance imaging. 相似文献
7.
Houssem Sellemi Sandrine Coste Amor Ben Ali Richard Retoux Leila Samia Smiri Philippe Lacorre 《Ceramics International》2013,39(8):8853-8859
Powders of oxide-ion conductor La2Mo2O9 presenting nanodomains were synthesized by using polyol processes. The influence of different process parameters on the structure and particles morphology was determined. By the classical polyol process, whatever the polyol solvent used (ethylene glycol, diethylene glycol, 1,2-propanediol and tetraethylene glycol) platelet particles with dimensions of few hundred nanometers long and around twenty nanometers thick were observed, as agglomerates of small sub-particles. Only with diethylene glycol, pure La2Mo2O9 was obtained, whereas with microwave assistance, ethylene glycol also leads to pure product. For both ethylene and diethylene glycol solvent, the microwave assisted process resulted in either agglomerates or desert roses conglomerates after heat treatments at 500 °C for 5 min or 2 h. Specific surface areas, ranging between 23 and 36 m2 g?1, have been measured for pure La2Mo2O9 powders. 相似文献
8.
Tao Han Ruiying Luo Guangyuan Cui Lianyi Wang 《Journal of the European Ceramic Society》2019,39(5):1743-1756
SiC-nanowire-reinforced SiCf/SiC composites were successfully fabricated through an in situ growth of SiC nanowires on SiC fibres via chemical vapour infiltration. The dielectric and microwave absorption properties of the composites were investigated within the frequency range of 8.2–12.4 GHz at 25–600 °C. The electric conductivity and complex permittivity of the composites displayed evident temperature-dependent behaviour and were enhanced with increasing temperature. The composites exhibited superior microwave absorption abilities with a minimum reflection loss value of ?47.5 dB at 11.4 GHz and an effective bandwidth of 2.8 GHz at 600 °C. Apart from the contribution of the interconnected SiC nanowire network and multiple reflections, the excellent microwave absorption performance was attributed to dielectric loss that originated from SiC nanowires with abundant stacking faults and heterostructure interfaces. Results suggested that the composites are promising candidates for high-temperature microwave absorbing materials. 相似文献
9.
Jesús Prado-GonjalRainer Schmidt David ÁvilaUlises Amador Emilio Morán 《Journal of the European Ceramic Society》2012,32(3):611-618
Rare-earth chromite ErCrO3 powder was synthesized from metal nitrate precursors using microwave synthesis. (Micro-) structural characterizations were performed using X-ray diffraction, Rietveld refinement, High Resolution Transmission Electron Microscopy and Electron Micro-Diffraction. Magnetization vs. temperature measurements revealed anti-ferromagnetism with TNeel ≈ 135 K. An anti-ferrimagnetic moment of ≈0.4 μB was determined from magnetization vs. applied field measurements. Temperature dependent impedance spectroscopy (IS) indicated 3 dielectric relaxation processes: electrode interface, grain boundary and bulk. The intrinsic bulk activation energy was found to be 0.27 eV and the dielectric permittivity ?r was ≈23 in excellent agreement with Clausius-Mossotti predictions and showed no perceptible temperature dependence. This and the low ?r value suggested that ErCrO3 is a dielectric rather than ferroelectric compound. IS measurements with applied dc bias revealed the signs of an unconventional type of Schottky barrier at the metallic Au electrode/ceramic ErCrO3 interface. 相似文献
10.
《Ceramics International》2017,43(16):13264-13275
The focus of the study was on providing insights into interconnections between sintering and development of the crystalline microstructure, and consequently variations in dielectric behavior of four steatites fabricated from a low-cost raw material, i.e. talc. The changes, induced by the alternations of the binders (bentonite, kaolin clay) and fluxing agents (BaCO3, feldspar), were monitored in the temperature range 1000° to 1250 °C in which complete densification and re-crystallization of the investigated structures were accomplished. The critical points in the synthesis of steatite materials were assessed by instrumental analyses. Crystallinity changes and mineral phase transition during sintering were monitored by X-ray diffraction technique. Microstructural visualization of the samples and the spatial arrangements of individual chemical elements were achieved via scanning electron microscopy accompanied with EDS mapping. The thermal stability was observed on the green mixtures using differential thermal and thermo gravimetric analyses. Electrical measurements recorded variations of the dielectric constant (εr) and loss tangent (tan δ) as a function of the sintering temperature. The investigation highlighted critical design points, as well as the optimal combinations of the raw materials for production of the steatite ceramics for advanced electrical engineering applications. 相似文献
11.
Ce2(WO4)3 ceramics have been synthesized by the conventional solid-state ceramic route. Ce2(WO4)3 ceramics sintered at 1000 °C exhibited ?r = 12.4, Qxf = 10,500 GHz (at 4.8 GHz) and τf = −39 ppm/°C. The effects of B2O3, ZnO–B2O3, BaO–B2O3–SiO2, ZnO–B2O3–SiO2 and PbO–B2O3–SiO2 glasses on the sintering temperature and microwave dielectric properties of Ce2(WO4)3 were investigated. The Ce2(WO4)3 + 0.2 wt% ZBS sintered at 900 °C/4 h has ?r = 13.7, Qxf = 20,200 GHz and τf = −25 ppm/°C. 相似文献
12.
Silvia Bierlich Timmy Reimann Frauke Gellersen Arne F. Jacob Jörg Töpfer 《Journal of the European Ceramic Society》2019,39(10):3077-3081
Sc3+ substituted M-type ferrites are effective microwave magnetic materials with a ferromagnetic resonance frequency in the range of 20 GHz–50 GHz. We report on the fabrication of oriented ferrite thick films as microwave components for application in the Ka-band at 30 GHz. Films of BaFe11.5.Sc0.5O19 were prepared by screen-printing on alumina substrates, drying in an external magnetic field, and sintering at 900 °C. Low-temperature sintering is achieved through use of a mixed BBSZ/CuO sintering aid. A strong anisotropy of the sintered ferrite films is revealed by XRD analysis. Microwave properties of the films were determined in a coplanar waveguide setup. The ferromagnetic resonance frequency of the films is at 30 GHz and the textured films possess good nonreciprocal properties which scale with film thickness. The films were tested in a Y-junction circulator, and represent promising materials for self-biased microwave components fabricated in thick film technology. 相似文献
13.
Xiaofeng Yuan Xian Xue Fei Jin Hong Wang 《Journal of the European Ceramic Society》2019,39(14):4156-4159
The solid solution (Na1-xAgx)2WO4 (x = 0.1, 0.2) ceramics with ultra-low sintering temperatures were prepared by a modified solid-state reaction method. Through introducing Ag+ substitution at the Na+-site, the sintering temperature of the (Na1-xAgx)2WO4 ceramics have been lowered from 565℃ to 510–520℃, while their dielectric lose is still keeping low. The (Na0.9Ag0.1)2WO4 ceramic can be sintered well at 520℃ with a permittivity of 5.8, a Q × f value of 97 600 GHz and a temperature coefficient of ?70 ppm/℃ at 12.6 GHz. After being sintered at 510℃, the (Na0.8Ag0.2)2WO4 ceramic possesses the best properties with a permittivity of 6.1, a Q × f value of 70 600 GHz and a temperature coefficient of ?72 ppm/℃ at a frequency of 12.5 GHz. Due to the excellent dielectric properties, the (Na1-xAgx)2WO4 (x = 0.1, 0.2) ceramics are potential candidate for Low-Temperature Co-fired Ceramics (LTCC) applications. 相似文献
14.
Xian Xue Xiaofeng Yuan Rong Ma Qibin Yuan Hong Wang 《Journal of the European Ceramic Society》2019,39(13):3744-3748
In this study, the novel temperature-stable (1-x)Ag2MoO4-xAg0.5Bi0.5MoO4 microwave dielectric ceramics were prepared by a modified solid-state reaction method. The phase composition, microstructures and microwave dielectric properties of the (1-x)Ag2MoO4-xAg0.5Bi0.5MoO4 ceramics were investigated. All the compounds can be sintered well at ultra-low temperatures (<540 °C). The XRD and SEM analysis indicate that the Ag2MoO4 and the Ag0.5Bi0.5MoO4 can coexist with each other. When x = 0.65, the ceramics exhibit the best microwave dielectric properties with a relative permittivity of 23.9, a Q × f value of 16,200 GHz (at 7.3 GHz) and a near-zero TCF value of -2.4 ppm/°C at 520 °C. The results indicate that temperature-stable (1-x)Ag2MoO4-xAg0.5Bi0.5MoO4 ceramics are promising candidates for low temperature co-fired ceramics (LTCC) applications. 相似文献
15.
Jaime Jiménez-Becerril Irma García-SosaIgnacio A. Rivero 《Ceramics International》2011,37(8):3627-3630
The synthesis of basic aluminum sulfate (BAS) was promoted by the microwave heating of a mixture of aluminum sulfate, aluminum nitrate, and sodium hydroxide. The heating process was facilitated by microwaves set at different temperatures and reaction time durations. The obtained products were characterized by X-ray diffraction and scanning electronic microscopy. Crystallographic and morphological analysis revealed BAS, boehmite, or a mixture of both products, depending on the reaction conditions. 相似文献
16.
Uroš Prah Tadej Rojac Magdalena Wencka Mirela Dragomir Andraž Bradeško Andreja Benčan Rachel Sherbondy Geoff Brennecka Zdravko Kutnjak Barbara Malič Hana Uršič 《Journal of the European Ceramic Society》2019,39(14):4122-4130
Designing multicaloric single-phase materials with combined electro- and magnetocaloric effects is still at its initial stage and presents a number of challenges. One of the main challenges encountered so far is to reduce the excessive electrical conductivity, which leads to the appearance of Joule heating that might completely degrade the electrocaloric response. In this work, multicaloric Pb(Fe0.5Nb0.5)O3 material was successfully prepared exhibiting pronounced electrocaloric effect above room temperature and maximum magnetocaloric effect at cryogenic temperature. The conductivity was suppressed by controlling the sintering temperature. The ceramic sintered at 1000 °C exhibits maximum electrocaloric effective cooling of 0.88 °C at 28 °C and maximum magnetocaloric effect of 0.14 °C at ?271 °C. The caloric properties can be further improved by doping Pb(Fe0.5Nb0.5)O3 with manganese. In comparison to the undoped sample, Pb(Fe0.5Nb0.5)O3 doped with 0.5 mol% of manganese exhibits three times higher maxima of electrocaloric effective cooling (2.47 °C at 80 °C) and magnetocaloric temperature change (0.44 °C at ?271 °C). 相似文献
17.
(Ba1?xRx)(Ti1?xHox)O3 (R = La, Pr, Nd, Sm; x ≥ 0.04) (BRTH) ceramics were prepared using a mixed oxides method. The solubility limits in BRTH with R = La, Pr, Nd, Sm were determined by XRD to be x = 0.11, 0.12, 0.06, and 0.14, respectively. The ionic radius of R at Ti-site plays a decisive role in the solubility limit in BRTH. Only BRTH with R = La satisfied Vegard's law. The multiplicity of photoluminescence (PL) signals of Nd3+/Ho3+ and Sm3+/Ho3+ in Raman scattering under 532-nm excitation laser and the high-permittivity abnormality for the denser BRTH with R = Sm and at x = 0.07 were reported. The PL provided the evidence of a small number of Ho3+ at Ba-site in BRTH and it was determined that the number of Ba-site Ho3+ ions increased from 0.05 at% at R = La to 0.19 at% at R = Sm with increasing atomic number of light rare earth. BRTH exhibited a much broadened dielectric-temperature characteristics, marked by ×5 T, ×6 T, ×7 T, and ×8 S dielectric specifications for BRTH with R = La, Pr, Nd, Sm and at x = 0.06, respectively, and they exhibited lower dielectric loss (tan δ < 0.015) at room temperature. The dielectric-peak temperature (Tm) of BRTH decreased linearly at a rate of less than ?21 °C/%(R/Ho). The defect chemistry, solubility limit, lower dielectric loss, and dielectric abnormality are discussed. 相似文献
18.
Tatevik Minasyan Marina Aghayan Le Liu Sofiya Aydinyan Lauri Kollo Irina Hussainova Miguel A. Rodríguez 《Journal of the European Ceramic Society》2018,38(11):3814-3821
Additive manufacturing is gaining increasing attention as it provides cost-effective and waste-less production of materials with multi-axis geometries. Selective laser sintering of ceramics is very challenging in terms of poor sinterability caused by low thermal shock resistance and insufficient electron conductivity blocking absorption of laser beam energy.Here, we present a novel strategy for manufacturing dense, hierarchically structured ceramics, particularly, MoSi2-based composites by selective laser sintering. MoSi2-Si composite powders were prepared by combustion synthesis technique, where the ceramic grains were covered with different amount of Si. MoSi2-Si powder was consolidated by selective laser sintering reaching 92% of density. The hardness of the manufactured samples varied with the amount of Si and applied laser current from 7.7–11.4?GPa. The maximum value of the compressive strength was determined to be 636?MPa. The manufactured MoSi2-Si was subjected to nitridation, which resulted in the growth of Si3N4 fibres on the surface and pores of the samples. 相似文献
19.
A new approach in the synthesis of amorphous SiBCN has been suggested using high-energy shaker ball mill. Hexagonal boron nitride (h-BN), graphite (C) and amorphous silicon (Si) were blended according to the mole ratio of 1:1:1, and then ball milled by different ball-to-powder mass ratio, diameter of ball and milling time. The structural evolution at different stages of milling has been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution electron microscopy (HREM) and electron energy-loss spectroscopy (EELS). The results showed that the SiBCN powders were mainly amorphous with some nanocrystlline phases. The thermal stability of SiBCN powders has been analyzed by thermogravimetry in argon. Mass loss occurred at high temperature, especially above 1000 °C. 相似文献
20.
Junfeng Xiang Lijing Xie Feinong Gao Jie Yi Siqin Pang Xibin Wang 《Ceramics International》2018,44(10):11765-11777
In industrial forming and machining process, the large plastic deformation of material takes place in wide loading ranges of strain-rate and forming temperature. A satisfactory modelling of quasi-static and dynamic material behaviors is of great importance for understanding physical process and processes optimization. A dependence-based integrated methodology, together with an improved weighted multi-objective parameter identification strategy is presented for the development of phenomenological constitutive model and the parameter identification using experimental data from quasi-static and dynamic tests with instantaneous strain rate variations and plastic strain-related temperature changes. The improved multi-objective parameter identification model is reformulated by introducing three weighting factors for valuing different measure errors and fit standard errors in individual objective function corresponding to each test, considering the sampling point number and active material parameter number under different loading conditions, and balancing optimization opportunity of quasi-static and dynamic sub-objective functions. The methodology is verified for feasibility through illustrative constitutive identification for SiCp/Al composites. This may provide a methodology of constitutive modelling for predicting material behaviors in quasi-static and dynamic modes equally well. 相似文献