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排序方式: 共有9673条查询结果,搜索用时 15 毫秒
21.
《Ceramics International》2022,48(8):10885-10894
Lead-free bismuth sodium titanate-strontium titanate (NBT-ST) dielectric ceramic materials have been extensively investigated energy storage materials because of their relaxor characteristics. In this study, four different lanthanide elements were introduced into the ferroelectric NBT-ST ceramic to improve their relaxor properties. The introduction of the lanthanide resulted in an increase in disorder at location A within the perovskite lattice and improved relaxor characteristics, leading to a stored energy density of more than 3.5 J/cm3. In particular, an ultrahigh recoverable stored energy density of 4.94 J/cm3 and efficiency of 88.45% were achieved at 440 kV/cm when the NBT-ST ceramic was modified with neodymium. The modified ceramic also exhibited good thermal stability in the range of 30–120 °C, as well as a fast discharge time of ~153 ns, indicating that Nd-incorporated NBT-ST is a promising candidate for electrical energy storage ceramic. 相似文献
22.
Qiang Liu Xinyu Mao Xiaoying Li Penghui Chen Xin Liu Ziyu Liu Danyang Zhu Haohong Chen Tengfei Xie Jiang Li 《Journal of the American Ceramic Society》2021,104(10):4927-4931
0.5 at.% Cr:ZnGa2O4 precursor was synthesized by the co-precipitation method with nitrates as raw materials, using ammonium carbonate as the precipitant. Low-agglomerated Cr:ZnGa2O4 powders with an average particle size of 43 nm were obtained by calcining the precursor at 900℃ for 4 h. Using the powders as starting materials, 0.5 at.% Cr:ZnGa2O4 ceramics with an average grain size of about 515 nm were prepared by presintering at 1150℃ for 5 h in air and HIP post-treatment at 1100℃ for 3 h under 200 MPa Ar. The in-line transmittance of 0.5 at.% Cr:ZnGa2O4 ceramics with a thickness of 1.3 mm reaches 59.5% at the wavelength of 700 nm. The Cr:ZnGa2O4 ceramics can be effectively excited by visible light and produce persistent luminescence at 700 nm. For Cr:ZnGa2O4 transparent ceramics, the brightness of afterglow was larger than 0.32 mcd/m2 after 30 min, which is far superior to that of Cr:ZnGa2O4 persistent luminescence powders. 相似文献
23.
《Journal of the European Ceramic Society》2022,42(5):2523-2534
TiO2 is an ideal substitute to ZrSiO4 ceramic opacifier, yet it is limited to application because of the undesirable yellowing resulting from rutile formation. Herein, the SiO2-CaCO3-TiO2 composite opacifier (Si-Ca-Ti) was constructed. The glaze used Si-Ca-Ti presents a superior opacification performance than ZrSiO4 opacified glaze without causing yellowing, showing L*, a*, b* values of 94.81, -0.67 and 3.23. By comparison, the glaze using SiO2, CaCO3, and TiO2 mixture shows lower opacification and yellowish surface with L* and b* values of 92.99 and 5.36. It is revealed that there is a close interface bonding among SiO2, CaCO3 and TiO2 in Si-Ca-Ti, which promotes their combination reaction to generate opacification phase titanite and inhibit rutile formation when sintering, resulting in the white surface and opacification improvement of the glaze. This study proposes a green and efficient strategy to achieve white and highly opacified glaze for sanitary ceramics, exhibiting good application prospect. 相似文献
24.
《Ceramics International》2022,48(11):15364-15370
This study reports on the preparation and mechanical properties of a novel SiCnf/SiC composite. The single crystal SiC nanofiber(SiCnf) reinforced SiC ceramic matrix composites (CMC) were successfully fabricated by hot pressing the mixture of β-SiC powders, SiCnf and Al–B–C powder. The effects of SiCnf mass fraction as well as the hot-pressing temperature on the microstructure and mechanical properties of SiCnf/SiC CMC were systematically investigated. The results demonstrated that the 15 wt% SiCnf/SiC CMC obtained by hot pressing (HP) at 1850 °C with 30 MPa for 60 min possessed the maximum flexural strength and fracture toughness of 678.2 MPa and 8.33 MPa m1/2, respectively. The nanofibers pull out, nanofibers bridging and cracks deflection were found by scanning electron microscopy, which are believed can strengthen and toughen the SiCnf/SiC CMC via consuming plenty of the fracture energy. Besides, although the relative density of the prepared SiCnf/SiC CMC further increased with the sintering temperature rose to 1900 °C, the further coarsend composites grains results in the deterioration of the mechanical properties for the obtained composites compared to 1850 °C. 相似文献
25.
Iryna Smokovych Manja Krüger Michael Scheffler 《Journal of the European Ceramic Society》2019,39(13):3634-3642
Silica-based coating systems were developed using polymer derived ceramics (PDCs) technology. Ceramic composites on the base of a SiO2 and SiNO matrix and homogeneously distributed Mo5SiB2, SiB6, Si and B fillers were manufactured. The coating systems have low porosity and provide a high oxidation resistance up to 100 h at 800 °C and 1100 °C in air. The influence of temperature and atmosphere of pyrolysis on the polymer precursor, the volume fraction of filler materials on the chemical composition of compacts as well as their high-temperature oxidation protection was investigated. 相似文献
26.
Hao Li Pengcheng Zhang Shengquan Yu Hongyu Yang Bin Tang Fuhai Li Shuren Zhang 《Ceramics International》2019,45(9):11639-11647
Mg2(Ti1-xSnx)O4 (x?=?0–1) ceramics were prepared through conventional solid-state method. This paper focused on the dependence of microwave dielectric properties on crystal structural characteristics via crystal structure refinement, Raman spectra study and complex chemical bond theory. XRD spectrums delineated the phase information of a spinel structure, and structural characteristic of these compositions were achieved with the help of Rietveld refinements. Raman spectrums were used to depict the correlations between vibrational phonon modes and dielectric properties. The variation of permittivity is ascribed to the Mg2(Ti1-xSnx)O4 average bond covalency. The relationship among the B-site octahedral bond energy, tetrahedral bond energy and temperature coefficient are discussed by defining on the change rate of bond energy and the contribution rate of octahedral bond energy. The quality factor is affected by systematic total lattice energy, and the research of XPS patterns illustrated that oxygen vacancies can be effectively restrained in rich oxygen sintering process. Obviously, the microwave dielectric properties of Mg2(Ti1-xSnx)O4 compounds were obtained (= 12.18, ?=?170,130?GHz, ?=??53.1?ppm/°C, x?=?0.2). 相似文献
27.
《Journal of the European Ceramic Society》2020,40(12):3824-3828
Reactive hot pressing was utilized to synthesize and densify four ZrB2 ceramics with impurity contents low enough to avoid obscuring the effects of dopants on thermal properties. Nominally pure ZrB2 had a thermal conductivity of 141 ± 3 W/m K at 25 °C. Additions of 3 at% of Ti, Y, or Hf decreased the thermal conductivity by 20 %, 30 %, and 40 %, respectively. The thermal conductivity of (Zr,Hf)B2 was similar to ZrB2 synthesized from commercial powders containing the natural abundance of Hf as an impurity. This is the first study to demonstrate that Ti and Y additions decrease the thermal conductivity of ZrB2 ceramics and report intrinsic values for thermal conductivity and electrical resistivity of ZrB2 containing transition metal additions. Previous studies were unable to detect these effects because the natural abundance of Hf present masked the effects of these additions. 相似文献
28.
Daylon Black Ryan Harper Patrick Ward Jacob Davlin Omar Bentancourt Donald Plumlee Jim Browning 《International Journal of Applied Ceramic Technology》2020,17(5):2393-2406
A low temperature co-fired ceramic (LTCC) material system has been used to develop a protype field emission cathode structure for use in an experimental magnetron oscillator. The structure is designed for used with 30 gated field emission array (GFEA) die electrically connected through silver metal traces and electrical vias. To approximate a cylinder, the cathode structure (48 mm long and 13.7 mm in diameter) is comprised of 10 faceted plates which cover the GFEA dies. Slits in the facet plates allow electron injection. The GFEA die (3 mm × 8 mm) are placed in axial columns of 3 and spaced azimuthally around a cylindrical support structure in a staggered configuration resulting in 10 azimuthal locations. LTCC manufacturing techniques were developed in order to fabricate the newly designed cathode with seven layers wrapped to form the cylinder with electrical traces and vias. Two different cathode wrapping techniques and two different via filling techniques were studied and compared. Two different facet plate manufacturing techniques were studied. Finally, four different support stand configurations for firing the cylindrical structure were also compared with a square post stand having the best circularity and linearity measurements of the fired structure. 相似文献
29.
Manal Benyoussef Moneim Zannen Jamal Belhadi Bouchaib Manoun Jean-Luc Dellis Mimoun El Marssi Abdelilah Lahmar 《Ceramics International》2018,44(16):19451-19460
In this work, Na0.5(Bi1-xDyx)0.5TiO3 (0?≤?x?≤?15%) ceramics were prepared via solid state reaction method and were characterized. A stable and pure perovskite phase was revealed by X-ray diffraction analysis for all compositions and a symmetry change from rhombohedral to orthorhombic phase was detected beyond 10% of Dy substitution. The incorporation of Dy3+ into Sodium Bismuth Titanate (Na0.5Bi0.5TiO3) matrix allows a substantial decrease of the coercive field, an increase in the resistivity, and leads to a high stability of the dielectric permittivity (??/?(150?°C) ≤?±?15%) over a wide temperature range. Furthermore, this system was found to exhibit improved energy storage properties at high temperatures with a maximum energy density of 1.2?J/cm3 obtained for 2%Dy composition at 200?°C. The obtained results are very promising for energy storage capacitors operating at high temperatures. 相似文献
30.
《Ceramics International》2018,44(18):22473-22480
The compact green bodies, prepared via a novel solid-liquid mixing method of precursors, were successfully pyrolyzed to obtain the dense bulk SiAlCN ceramics at 1000 °C. It can be seen from their SEM that they have uniform and dense microstructure, indicating that this method can be used to prepare bulk ceramics. In order to verify that they can be used as sensor heads, their temperature-resistance characteristics and repeatability were tested. The results show that the conductive mechanism belongs to Arrhenius's Tailed-State and Extended-State in the temperature range of 500–650 °C and 650–930 °C, respectively. And it shows that SiAlCN ceramics can be used as the sensor heads for high-temperature sensors. 相似文献