共查询到20条相似文献,搜索用时 11 毫秒
1.
Because of outstanding performances of the SiC fiber-reinforced ceramic matrix composites in aircraft/aerospace systems, two silicon carbide fiber-reinforced oxide matrices (SiCf/oxides) composites have been prepared by a precursor infiltration and sintering method. Results indicate that the flexural strength of the SiCf/Al2O3–SiO2 composite reaches 159 MPa, whereas that of the SiCf/Al2O3 composite is only 50 MPa. The high-temperature microwave absorption properties of the composite are significantly enhanced due to choosing Al2O3 and SiO2 as the hybrid matrices. Particularly, the minimum reflection loss (RL) value of the SiCf/Al2O3–SiO2 composite reaches −37 dB in the temperature of 200 °C at 8.6 GHz, and the effective absorption bandwidth (RL ≤ −5 dB) is 4.2 GHz (8.2–12.4 GHz) below 400 °C. The superior microwave absorption properties at high temperatures indicate that the SiCf/Al2O3–SiO2 composite has promising applications in civil and military areas. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47097. 相似文献
2.
Ngo Tran Ruey-Bin Yang Woo Hyun Jeong Do Hung Manh The-Long Phan Bo Wha Lee 《Journal of the American Ceramic Society》2022,105(6):4122-4134
Controlling material structure and its electromagnetic properties, including complex permittivity and permeability, could enhance the microwave absorption performance of the material in terms of reflection loss and effective absorption bandwidth. In this study, La-substituted barium hexaferrite, Ba3−xLaxCo2Fe24O41 (x = 0, 0.1, 0.3, and 0.5) compounds were successfully prepared using the solid-state reaction method, and their corresponding microstructures, static magnetic properties, and electromagnetic features in 2–18 GHz were investigated. The doping of La content increased saturation magnetization, coercivity, and remnant magnetization. The Ba2.7La0.3Co2Fe24O41 epoxied sample with 3.5 mm thickness possessed an excellent microwave absorption of −47.3 dB at 3.52 GHz, and its corresponding effective absorption bandwidths were 3.75 GHz (2.25–6 GHz) and 0.57 GHz (17.43–18 GHz). It is shown that doping with various La concentrations on Ba3Co2Fe24O41 can be used as an effective technique to tune the performance of microwave absorbers based on barium hexaferrite. 相似文献
3.
Yichen Wang Peng Xiao Wei Zhou Heng Luo Zhuan Li Wenbo Chen Yang Li 《Ceramics International》2018,44(4):3606-3613
Carbon-rich SiC powders with high dielectric loss were prepared via pyrolysis of polycarbosilane (PCS). The effects of pyrolysis temperature on microstructures, dielectric response and microwave absorption properties in X-band (8.2–12.4 GHz) of PCS-derived SiC powders were investigated. The PCS-derived SiC powders are mainly composed of SiC nanocrystal, turbostratic carbon and amorphous phase (SiC and/or C). The size of SiC nanocrystals and the graphitization degree of carbon both increase with the elevation of pyrolysis temperature. Furthermore, the residual carbon is transformed from amorphous into turbostratic structure with a phenomenon of regional enrichment. Moreover, the relative complex permittivity increases notably with the higher pyrolysis temperature. Meanwhile, the dielectric loss tangent increases from 0.19 to 0.57, while the microwave impedance decreases from 73.20 to 53.58. The optimal reflection loss of ?35 dB for PCS-derived SiC powders is obtained when the pyrolysis temperature is 1500 °C, which exhibits a great application prospect in microwave absorbing materials. 相似文献
4.
《Journal of the European Ceramic Society》2020,40(3):728-734
Antioxidant materials with high permittivity are highly desirable for thin, microwave-absorbing materials at high temperature (MAMHT) due to their great impedance matching. In this work, composite ceramics composed of BaTiO3 and MgAl2O4 (BTMAS) synthesized by a traditional solid-state sintering method have been studied for their high temperature microwave dielectric properties. When the temperature rose between 473 K–573 K, the real part of permittivity (ε’) of BTMAS increased significantly relative to room temperature. As the temperature increased further to 873 K, ε’ gradually fell. Based on the collection of permittivities obtained by the inverse resolution of specific reflectivity, BT36 (36 mol % BaTiO3) was suitable for 1.1 mm thick microwave-absorbing materials from 300 K – 873 K. The envisaged material had an absorption bandwidth of 2 GHz (RL<-5 dB) which could move between microwave X-band as the temperature changed. Therefore, there is great potential for BTMAS in reducing the thickness of MAMHT. 相似文献
5.
《Ceramics International》2023,49(6):9191-9202
Recently, the public does not avoid the use of RF/microwave communication and non-communication devices, which means they will be constantly exposed to radiation from those devices, which will worsen their health in the long term, as well as there will be interference and coupling effects between devices. In this paper, a novel and high-performance absorber material is created and analyzed. The microscopic and macroscopic properties of Gadolinium Manganite (GdMnO3), Molybdenum Diselenide (MoSe2), and three mixtures of GdMnO3-MoSe2 (GdMo) with 20, 30, and 40% filler loading were investigated. The procedure for producing the five materials was explained and described in detail. The mixture of GdMo with 20, 30, and 40 wt% filler loading has the features of GdMnO3 and MoSe2. For macroscopic analysis, the measured relative complex permittivity and permeability of the five synthesized materials are modeled using the Lorentz dispersion model. Among the five study materials, GdMo with 40 wt% filler loading shows the highest electric and magnetic losses with loss tangent, tan δe ≈ 0.228 and tan δm ≈ 0.38 where the absorption performance is better compared to its pristine components, namely GdMnO3 and MoSe2. Based on the transmission theory of metal plate backing materials, the GdMo with 40 wt% filler loading and thicknesses ranging from 0.0014 m to 0.0021 m, which is terminated by a metal plate on the back side, exhibited the optimum microwave absorption performance with a minimum reflection loss value better than ?20 dB at X-band operating frequency. Without a metal backing, a 0.008 m thickness of GdMo with 40 wt% can achieve reflection loss, RL of ?10 dB from 9.2 GHz to 12.4 GHz, and RL of ?20 dB from 11.1 GHz to 12.4 GHz. 相似文献
6.
Yujie Ma Fan Yang Sijie Kou Fang Ye Jimei Xue Xiaomeng Fan Shangwu Fan Laifei Cheng 《Ceramics International》2021,47(17):24393-24402
The combination of multiple loss characteristics is an effective approach to achieve broadband microwave wave absorption performance. The Fe-doped SiOC ceramics were synthesized by polymer derived ceramics (PDCs) method at 1500 °C, and their dielectric and magnetic properties were investigated at 2–18 GHz. The results showed that adding Fe content effectively controlled the composition and content of multiphase products (such as Fe3Si, SiC, SiO2 and turbostratic carbon). Meanwhile, the Fe promoted the change of the grain size. The Fe3Si enhanced the magnetic loss, and the SiC and turbostratic carbon generated by PDCs process significantly increased the polarization and conductance loss. Besides, the magnetic particles Fe3Si and dielectric particles SiO2 improved the impedance matching, which was beneficial to EM wave absorption properties. Impressively, the Fe-doped SiOC ceramics (with Fe addition of 3 wt %) presented the minimum reflection coefficient (RCmin) of ?20.5 dB at 10.8 GHz with 2.8 mm. The effective absorption bandwidth (EAB, RC < ?10 dB) covered a wide frequency range from 5 GHz to 18 GHz (covered the C, X and Ku-band) when the absorbent thickness increased from 2 mm to 5 mm. Therefore, this research opens up another strategy for exploring novel SiOC ceramics to design the good EM wave-absorbing materials with broad absorption bandwidth and thin thickness. 相似文献
7.
Xue Guo Yurun Feng Xiao Lin Yu Liu Hongyu Gong Yujun Zhang 《Journal of the European Ceramic Society》2018,38(4):1327-1333
The polymer-derived SiCN ceramics were synthesized at different annealing temperature (900 ~ 1400 °C). The XRD, SEM, FT-IR, Raman and XPS were used to analyze the phase composition and microstructure. The result indicated that the crystallization degree and content of free carbon gradually improved with the increase of annealing temperature. The resistivity, dielectric and microwave absorption properties of the samples were studied at 2 ~ 18 GHz. The resistivity decreased gradually as the annealing temperature rose. The dielectric constant of sample decreased with the increase of frequency in 1 ~ 5 MHz. The existence of free carbon could improve the dielectric properties of polymer-derived SiCN ceramics at high frequency. The reflectance of the sample synthesized at 1100 °C was below ?10 dB (> 90% absorption) in a wide frequency range of 6 ~ 16 GHz and the maximum value of dielectric loss angle tangent was about 0.6 at 16 GHz. 相似文献
8.
Enhanced dielectric and microwave absorption properties of Cr/Al2O3 coatings deposited by low‐power plasma spraying
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Liang Zhou Meng Chen Yanli Dong Zhanwei Yuan 《Journal of the American Ceramic Society》2017,100(2):620-626
Low‐power plasma‐sprayed Cr/Al2O3 coatings have been developed for their potential application as broad bandwidth, thin thickness, lightweight, and strong microwave‐absorbing materials. The dielectric and microwave absorption properties of the as‐sprayed coatings were studied in the X‐band (from 8.2 to 12.4 GHz). High complex permittivity of the coatings was obtained because of a large number of internal boundaries and the conductive networks. Meanwhile, a significant enhancement of microwave absorption properties of the coating was achieved due to the enhanced interfacial polarization and conductance loss. The reflection loss (RL) <?10 dB of the Al2O3–15Cr coating was obtained from 9.8 to 11.4 GHz by choosing an appropriate coating thickness, and an optimal minimum reflection loss (RLmin) of ?45.35 dB was achieved at 10.3 GHz with a thin thickness of 1.32 mm. 相似文献
9.
Ngo Tran Min Young Lee Hong Hanh Nguyen Woo Hyun Jeong Ngoc Toan Dang Le Anh Thi The-Long Phan Bo Wha Lee 《Journal of the American Ceramic Society》2021,104(7):3376-3386
We prepared Ba3−xYxCo2Fe24O41 (Y-Co2Z, x = 0, 0.2, and 0.4) by the solid-state reaction method. Y-Co2Z and polyaniline (PANI) composites (named as Y-P0, Y-P2, and Y-P4) were prepared by using the in-situ polymerization method. The Y-doping played an important role in the variation of lattice parameters, a and c. The combination of Y-doping and PANI modified the magnetic properties of the composites, which could be observed by the changing of the saturation magnetization and coercivity. This combination had also affected the electromagnetic properties of composites through the measurements of complex permittivity and permeability. Using the transmission line theory, we calculated refection loss (RL) of composites with the variation thickness of 1.00–2.50 mm. Our composites tuned the minimum RL from the X band (RL = −29.6 dB at 11.4 GHz for Y-P2) to Ku band (RL = −16.3 dB at 15.7 GHz for Y-P4 and RL = −26.4 dB at 16.6 GHz for Y-P4). For maximum effective bandwidth, our composites covered a huge range from the S and C bands (Y-P0 with 3.9 GHz in the range of 3.4–7.3 GHz) through the X band (Y-P2 with 3.9 GHz in the range of 9.0–12.9 GHz) to the Ku band (Y-P4 with 4.0 GHz in the range of 13.8–17.8 GHz). Those properties proved that the composites could act as promising absorbers in the S, C, X, and Ku bands. 相似文献
10.
Sungjoon Choi Jae-Hyoung You Chris Yeajoon Bon Seung-young Park Sang-Im Yoo 《Ceramics International》2021,47(6):7571-7581
Enhanced microwave absorption properties were successfully achievable from SrFe2-xZnxFe16O27 (SrFe2-xZnxW; x = 0.0, 0.5, 1.0, and 2.0) hexaferrite filler-epoxy resin matrix composites. The composite samples were fabricated with the filler volume fractions (Vf) of 30, 50, 70, and 90%. Compared with fully Zn-substituted SrZn2W composite (x = 2.0), unsubstituted and partially Zn-substituted SrFe2-xZnxW (x = 0.0, 0.5, and 1.0) composites exhibited much higher real and imaginary parts of complex permittivity (εr), which is attributable to higher electron hopping between Fe2+ and Fe3+ ions, and also slightly higher real and imaginary parts of complex permeability (μr) due to higher saturation magnetization (Ms). Among all samples, a 2.8 mm-thick SrFe1·5Zn0·5W (x = 0.5) composite with the Vf of 90% exhibited the most appropriate for application in the region of 3.4–3.8 GHz, having the minimum reflection loss (RLmin) of ?46 dB at 3.6 GHz with the bandwidth of 0.43 GHz (3.38–3.81 GHz) below ?10 dB, while a 2.15 mm-thick SrFeZnW (x = 1.0) composite with the Vf of 70% showed the most appropriate for application in the region of 5.9–7.1 GHz, possessing the RLmin value of ?23.7 dB at 6.6 GHz with the bandwidth of 1.38 GHz (5.85–7.23 GHz) below ?10 dB. Consequently, partially Zn-substituted SrW-type hexaferrites are very promising microwave absorbers for 5G mobile communications in the Ku band (0.5–18 GHz). 相似文献
11.
Wen Bin Hong Lei Li Han Yan Xiang Ming Chen 《Journal of the American Ceramic Society》2019,102(10):5934-5940
HBO2-II ceramics were prepared by cold sintering with 10wt% dehydrated ethanol as the transient liquid phase. When the processing temperature is 30°C, the relative density of the mechanically robust HBO2-II ceramics increases from 77.5% to 84.5% with increasing the uniaxial pressure from 200 to 500 MPa. It changes less than 0.2% for higher pressure up to 700 MPa. Under a constant uniaxial pressure of 500 MPa, the relative density further increases to 94.7% for the processing temperature of 120°C. HBO2-I is observed as the secondary phase when the processing temperature is 150°C. In comparison, the compacts prepared in the absence of ethanol are fragile, and the relative densities are 78.5%-84.5% for the processing temperatures of 30-120°C and uniaxial pressure of 500 MPa. It is indicated that ethanol promotes the densification significantly through the dissolution-precipitation mechanism. The permittivity increases with increasing the processing temperature, while the Qf value decreases. The optimal properties with the relative density of 94.7%, εr = 4.21, Qf = 47 500 GHz, and τf = −70.0 ppm/°C were obtained in the single-phase HBO2-II ceramics cold sintered at 120°C under 500 MPa for 10 minutes. The relative density and Qf value are significantly higher than those of the HBO2-II ceramic prepared by sintering the H3BO3 compact at 180°C for 2 hours (70.3% and 32 700 GHz, respectively). The results indicate that the nonaqueous solvent can also be used as the transient liquid phase for cold sintering, so that more materials that are unstable or insoluble in water can be densified by this method. 相似文献
12.
《Ceramics International》2022,48(13):18567-18578
In this study, SiC interphase was prepared via a precursor infiltration-pyrolysis process, and effects of dipping concentrations on the mechanical, high-temperature dielectric and microwave absorption properties of the SiCf/SiC/Mu composites had been investigated. Results indicated that different dipping concentrations influenced ultimate interfacial morphology. The SiC interphase prepared with 5 wt% PCS/xylene solution was smooth and homogeneous, and no bridging between the fiber monofilament could be observed. At the same time, SiC interphase prepared with 5 wt% PCS/xylene solution had significantly improved mechanical properties of the composite. In particular, the flexural strength of the composite prepared with 5 wt% PCS/xylene solution reached 281 MPa. Both ε′ and ε′′ of the SiCf/SiC/Mu composites were enhanced after preparing SiC interphase at room temperature. The SiCf/SiC/Mu composite prepared with 5 wt% PCS/xylene solution showed the maximum dielectric loss value of 0.38 at 10 GHz. Under the dual action of polarization mechanism and conductance loss, both ε′ and ε′′ of the SiCf/SiC/Mu composites enhanced as the temperature increased. At 700 °C, the corresponding bandwidth (RL ≤ ?5 dB) of SiCf/SiC/Mu composites prepared with 5 wt% PCS/xylene solution can reach 3.3 GHz at 2.6 mm. The SiCf/SiC/Mu composite with SiC interphase prepared with 5 wt% PCS/xylene solution is expected to be an excellent structural-functional material. 相似文献
13.
LiCoO2的制备及电化学性能研究 总被引:7,自引:1,他引:7
采用高温固相反应法在工业级别的设备上制备了一系列LiCoO2样品。运用SEM和XRD分析技术研究了样品微观形貌和晶相结构。将LiCoO2样品制成工作电极,组装了试验电池进行充放电循环测试。结果表明,不同原料来源对LiCoO2结构与电化学性能有一定的影响。烧结温度对LiCoO2晶相结构、晶化程度、结构致密性及稳定性有显著影响。在800℃和900℃条件下合成的LiCoO2都具有电化学活性,首次充电容量均大于130mA.h.g^-1。 相似文献
14.
Binbin Li Bangxiao Mao Haiquan Huang Xingbang Wang Tao He 《International Journal of Applied Ceramic Technology》2020,17(4):1869-1881
Lightweight and strong microwave adsorption property have become the foremost crucial factors in the practical application of modern microwave absorbers. This study mainly dealt with synthesize of bamboo-like β-SiC nanowires with high-performance microwave absorption property via a polymer pyrolysis CVD (PPCVD) approach. The PPCVD process was conducted by cleverly placing the polymer powders into two temperature zones to produce reactant gases with alternating concentrations. The morphological study revealed that the nodes exhibited abundant stacking faults as compared to the stem segments, which was beneficial for the microwave losses. The optimal reflection loss value of −35.47 dB was gained at 18 GHz corresponding to 2.0-mm absorber thickness, and the corresponding −10 dB bandwidth (>90% absorption) was 3.22 GHz. It has turned out that the as-prepared nanowires could be applied at different frequencies by adjusting the thickness. Especially, it exhibits a good prospect in the fields of ultrathin absorbers. Furthermore, the microwave absorption mechanisms of the nanowires were explored. This present investigation has opened a high-efficient facile approach to develop ultrathin, lightweight, and high-performance microwave absorbers. 相似文献
15.
16.
《Ceramics International》2020,46(17):27352-27361
Lightweight, broadband microwave absorbing materials, with strong absorption capacities, are an urgent demand for practical applications. The microstructural and microwave absorption properties of LaFeO3 samples prepared by a sol-gel method using different amounts of Sr are investigated systematically. X-ray diffraction and Rietveld refinement studies showed that Sr2+ doping can distort the crystal structure of LaFeO3, leading to lattice expansion and spin tilt of the Fe-O-Fe bond angle. The improvement of magnetic properties mainly originates from the synergistic effect of the bond angle spin tilt and crystal structure defects. Oxygen vacancies will be generated due to the fluctuations in the valence state of Fe3+ resulting from the substitution of La3+ by Sr2+ as deduced from the X-ray photoelectron spectroscopy analysis. The generation of oxygen vacancies, electronic hopping and polarization loss may be one of the main reasons for changes in the electromagnetic parameters. The minimum reflection loss (RL) of La1–xSrxFeO3 nanoparticles with the Sr doping of 0.2 can reach approximately -39.3 dB at 10 GHz for the thickness of 2.2 mm, and the effective absorption bandwidth (RL ≤ -10 dB) can reach approximately 2.56 GHz. In addition, the La1–xSrxFeO3 nanoparticles also can obtain better microwave absorbing performance in the C-band (4–8 GHz) with the minimum RL of -36.8 dB for the matching thickness of 3.0 mm and Sr content of 0.3. Consequently, La1–xSrxFeO3 nanoparticles are promising materials for use in a high-performance and adjustable electromagnetic wave absorber, particularly in C-band and X-band. 相似文献
17.
18.
Lei Li Wen Bin Hong Xiao Jian Yan Xiang Ming Chen 《International Journal of Applied Ceramic Technology》2019,16(5):2047-2052
The transparent B2O3 bulks were prepared by quenching B2O3 melt or cooling it down to room temperature with the rate of 0.1-1°C/min. The quenched sample exhibited the dense microstructure, while the pores were observed for low cooling rates, and this is consistent with the slight decrease in density and permittivity (εr) with decreasing the cooling rate. Both the amorphous and cubic phases of B2O3 were indicated by XRD, and the content of the cubic phase increased with the decrease in cooling rate, which was responsible for the decreasing Qf value with the lower cooling rate. The temperature coefficient of resonant frequency (τf) was insensitive to the cooling rate, and the microwave dielectric properties with εr = 3.86-3.97, Qf = 3,200-5,300 GHz and τf = −48.9 to −42.8 ppm/°C were obtained in the B2O3 bulks. The reported microwave dielectric properties of B2O3 bulk are helpful to estimate the effects of the residual B2O3 on the properties of the microwave dielectric ceramics with B2O3 and H3BO3 as the sintering aid. 相似文献
19.