共查询到20条相似文献,搜索用时 93 毫秒
1.
Composites consisting of strontium stabilized bismuth oxide (Bi1.14Sr0.43O2.14 SSB) and silver were investigated as cathodes for intermediate-temperature solid oxide fuel cells with doped ceria electrolyte. There were no chemical reactions between the two components. The microstructure of the interfaces between composite cathodes and Ce0.8Sm0.2O1.9 (SDC) electrolytes was examined by scanning electron microscopy (SEM). Impedance spectroscopy measurements show that the performance of cathode fired at 700℃ is the best. When the content of Ag2O is 70wt%, polarization resistance values for the SSB-Ag cathodes are as low as 0.2Ωcm2 at 700℃ and 0.29Ωcm2 at 650℃. These results are much smaller than some of other reported composite cathodes on doped ceria electrolyte and indicate that SSB-Ag composite is a potential cathode material for intermediate temperature SOFCs. 相似文献
2.
徐庆 《武汉理工大学学报(材料科学英文版)》2008,23(3):386-390
Ln0.6Sr0.4Co0.2Fe0.2O3 (Ln=La, Pr, Nd, Sm) perovskite-type complex oxides were synthesized using a glycine-nitrate process, and the structure, electrical conducting and thermal expansion properties of the resulting ceramics were examined with regard to the nature of the lanthanide cations. The results indicated that the La, Pr and Nd specimens had a rhombohedral symmetry, while an orthorhombic structure was determined for the Sm specimen. The pseudo-cubic lattice constant decreased with smaller lanthanide cations. It was found that the electrical conducting properties declined with decreasing lanthanide cation size. Fortunately, all the compositions remained rather high electrical conductivities exceeding 650 Ω ^-1m·cm^-1 in the intermediate temperature range (600-800 ℃). An appreciable thermal expansion increase at high temperatures was detected for all the compositions. Decreasing the size of the lanthanide cations resulted in an increase of thermal expansion. With respect to the high electrical conductivities, the Ln0.6Sr0.4Co0.8Fe0.2O3 oxides are considered to be acceptable as mixed conducting component in composite cathode designs together with doped ceria electrolytes. 相似文献
3.
Two types of secondary emitter materials, the rare earth oxides (RE2O3) doped Mo cermet cathodes and the Y2O3-W matrix pressed cathode, are introduced in this paper. According to the calculation results, Y2O3 exhibits the best secondary emission property among Y2O3, La2O3, CeO2 and Lu2O3. The rare earth oxides co-doped Mo cathodes in which Y2O3 is the main active substance exhibit better secondary emission property than single RE2O3 doped Mo cathode. The results obtained by the Monte-Carlo calculation method show that the secondary electron emission property is strongly related to the grain size of the cathode. The decreasing of the grain size reduces the positive charge effect of the rare earth oxide due to the electrons supplement from the metal to the rare earth oxide, whereby the secondary electrons are easier to escape into the vacuum. Y2O3 is introduced into Ba-W cathode to fabricate a pressed Y2O3-W matrix dispenser cathode. The result indicates that the secondary emission yield of the Ba-W cathode increases from 2.13 to 3.51 by adding Y2O3, and the thermionic emission current density (J 0) could reach 4.18 A/cm2 at 1050 °Cb. 相似文献
4.
Al2 O3/Al composite was fabricated by the reaction between SiO2 and molten aluminum. The microstructures of the composite obtained under different reaction conditions were analyzed. The
formation mechanism of the composite microstructure was discussed. Results show that the reaction kinetics is influenced remarkably
by the reaction temperature, reaction time and the quantity of SiO2. The morphologies of Al2O3 have different features, depending on the reaction temperature. The composite has equaxed Al2O3 grains when materials reacted below 1200°C, and the composite is composed of a large number of fine Al2O3 grains and aluninum. The composite has a frame-shaped Al2O3 microstructure at the reaction temperature of above 1250°C.
CHENG Xiao-min: Born in 1964
Funded by the National Natural Science Foundation of China (No. 91522) 相似文献
5.
徐莉 《武汉理工大学学报(材料科学英文版)》2009,24(3):354-358
Nanocomposites MgFe2O4/SiO2 were successfully synthesized by the sol-gel method in the presence of N, N-dimethylformamide (DMF). The formation of pure MgFe2O4 was confirmed by powder X-ray diffraction (XRD) and electron diffraction. The structural evolution of MgFe2O4 nanocrystals was followed by powder X-ray diffraction and IR absorption spectroscopy. The formation of spinel structure of
MgFe2O4 started at 800 °C, and completed at 900 °C. The transmission electron microscopy (TEM) measurements suggest that the particle
sizes increase with the increasing annealing temperature, and the mean particle sizes of the spherical samples annealed at
800 °C, 900 °C and 1 050 °C are ca. 3 nm, 8 nm and 11 nm, respectively. Magnetization measurements at room temperature and 78 K indicate superparamagnetic nature
of these MgFe2O4 nanocrystals.
Funded by the National Natural Science Foundation of China(No. 30771676), the Natural Science Foundation of Jiangsu Province
(No. BK20081842), and the Foundation of Nanjing Bureau of Personal for the Returned Overseas Chinese Excellent Scholars 相似文献
6.
KoKai Tseng YaChu Yang ChienChang Juan TsungShune Chin CheWei Tsai JienWei Yeh 《中国科学:技术科学(英文版)》2018,61(2):184-188
A light-weight high-entropy alloy (LWHEA) Al20Be20Fe10Si15Ti35 has been developed to have unique mechanical properties and oxidation resistance. One major and two minor phases are observed in the as-cast microstructure. The density of the alloy is 3.91 g cm?3, and its hardness is HV 911, which is higher than quartz. The hardness and hardness to density ratio are the highest of all light-weight alloys reported before. In addition, it has excellent oxidation resistance at 700°C and 900°C, which far exceeds that of Ti-6Al-4V. Thus, the combination of properties is promising for high-temperature applications, which require light weight, wear-resistant and oxidation-resistant components. 相似文献
7.
吴顺华 《武汉理工大学学报(材料科学英文版)》2010,25(5):730-733
The effect of ZnO-B2O3(ZB) glass addition on the sintering behavior, microstructures and microwave dielectric properties of BaO-Nd2O3-TiO2-Bi2O3 (BNTB) system was investigated with the aid of X-ray diffraction, scanning electron microscopy and capacitance meter. It
is found that the ZB glass addition, acting as a sintering aid, can effectively lower the sintering temperature of BNTB system
to 850 °C. The dielectric constant of BNTB-ZB ceramics increases with the increase of soaking time and the value of dielectric
loss decreased with increasing soak time. The optical dielectric properties at 1 GHz of ɛ=74, tan δ=4×10−4, and TCC=25 ppm/°c were obtained for the BNTB system doped with 25 wt% ZB glass sintered at 850 °C for 2 h, representing
that the BNTB-ZB ceramics could be promising for multilayer low temperature co-fired ceramics applications. 相似文献
8.
王启岁 《武汉理工大学学报(材料科学英文版)》2018,33(1):97-101
To improve the cyclic stability at high temperature and thermal stability, the spherical Al2O3-modified Li(Ni0.5Co0.2Mn0.3)O2 was synthesized by a modified co-precipitation method, and the physical and electrochemical properties were studied. The TEM images showed that Li(Ni0.5Co0.2Mn0.3)O2 was modified successfully with nano-Al2O3. The discharge capacity retention of Al2O3-modified Li(Ni0.5Co0.2Mn0.3)O2 maintained about 99% after 200 cycles at high temperature (55 °C), while that of the bare one was only 86%. Also, unlike bare Li(Ni0.5Co0.2Mn0.3)O2, the Al2O3-modified material cathode exhibited good thermal stability. 相似文献
9.
Na2O-Al2O3-SiO2 glass-ceramics doped with Er3+ ions were synthesized by the conventional melt quenching technique at a low melting temperature. The samples were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis-NIR scanning spectrophotometry, and fluorescence spectrometry. The results show that the main crystalline phase of glass-ceramics is nepheline.The best heat-treatment process is at 520 °C for 2 h. Because the up-conversion luminescence and near infrared luminescence properties of glass doped with Eu3+ are studied in detail. 相似文献
10.
何峰 《武汉理工大学学报(材料科学英文版)》2016,31(6):1267-1271
Influence of aluminum addition on the structures and properties of SiO2-B2O3-Al2O3-CaO vitrified bond at low sintering temperature and high strength was discussed. FTIR and XRD analyses were used to characterize the structures of the basic vitrified bond with different contents of aluminum. The bending strength and the thermal expansion coefficients were also tested. Meanwhile, the microstructures of composite specimens at sintering temperature of 660 °C were observed by scanning electron microscope (SEM). The experimental results showed that the properties of vitrified bond with 1wt% aluminum were improved significantly, where the bending strength, Rockwell hardness, and thermal expansion coefficient of the vitrified bond reached 132 MPa, 63 HRB, and 6.73×10-6 °C-1, respectively. 相似文献
11.
YuanChao Du XiaoPeng Huang KeYu Zhang Feng Liang QiuXia Li YaoChun Yao YongNian Dai 《中国科学:技术科学(英文版)》2017,60(1):58-64
Safety is important to lithium ion battery materials. The thermal stability of LiFePO4/C-LiMn2O4 blended cathode materials is characterized by using TG, XRD, and SEM etc. The results show that LiFePO4/C-LiMn2O4 possesses a worse thermal stability than pure spinel LiMn2O4 and pure olivine LiFePO4/C. When LiFePO4/C-LiMn2O4 blended cathode materials are sintered at 500°C under Ar atmosphere, the sintered cathode materials emit O2, and appear impurity phases (Li3PO4, Fe2O3, Mn3O4). It is deduced that some chemical reactions take place between different materials, which leads to a worse discharge specific capacity. LiFePO4/C-LiMn2O4 blended cathode materials, therefore, need to be managed and controlled strictly for the sake of thermal stability and safety. 相似文献
12.
陈力颖 《武汉理工大学学报(材料科学英文版)》2008,23(5):647-651
The microwave dielectric properties and microstructure of BaTi4.3ZnyO9.6+y +0.02 mol% SnO2+0.01 mol% MnCO3+x mol% Nb2O5(x=0-0.05, y=0-0.08) system ceramics were studied as a function of the amount of ZnO and Nb2O5 doped. Addition of (y=0-0.05) ZnO and (x=0-0.025) Nb2O5 enhanced the reactivity and decreased the sintering temperature effectively. It also increased the dielectric constant ε r and quality factor Q(=1/tan 8) of the system due to the substitution of Ti^4+ ions with incorporating Zn^2+and Nb^5+ ions, which was analyzed by the reaction ZnO+Nb2O5+ 3 TiTxTi →ZnTi+ 2NbTi+3TiO2. When the system doped with (y=0.05) ZnO and (x=0.025) Nb205 were sintered at 1 160 ℃ for 6 h, the εr. Qf0 value and rfwere 36.5, 42 000 GHz, and+1.8 ppm/℃, respectively, at 5 GHz. 相似文献
13.
余军 《武汉理工大学学报(材料科学英文版)》2007,22(3):478-481
Nafion/Silicon oxide composite membranes were produced via in situ sol-gel reaction of tetraethylorthosilicate (TEOS) in Nafion membranes. The physicochemical properties of the membranes were studied by FT-IR,TG-DSC and tensile strength. The results show that the silicon oxide is compatible with the Nation membrane and the thermo stability of Nation/Silicon oxide composite membrane is higher than that of Nation membrane. Furthermore, the tensile strength of Nation/Silicon oxide composite membrane is similar to that of the Nation membrane. The proton conductivity of Nation/Silicon oxide composite membrane is higher than that of Nation membrane. When the Nation/Silicon oxide composite membrane was employed as an electrolyte in H2/O2 PEMFC, a higher current density value (1 000 mA/cm^2 at 0.38 V) than that of the Nafion1135 membrane (100 mA/cm^2 at 0.04 V) was obtained at 110 ℃. 相似文献
14.
王觅堂 《武汉理工大学学报(材料科学英文版)》2016,31(4):830-834
ZnO-B2O3-SiO2-Al2O3-Na2O glass doped with nucleating agent TiO2 was prepared with melting-quenching method and the effect of nucleating agent on the crystallization behavior and phase evolution of this glass was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The experimental results show that the glass transition temperature and the first crystallization temperature decrease from 630 °C and 765 °C to 595 °C and 740 °C, respectively, with introduction of TiO2 into glass. There is no diffraction peaks in the XRD pattern but it is no longer transparent for the base glass without nucleating agent after heat treatment, which suggests the serious phase separation occurred, and the observation by SEM indicates that the phase separation is developed by nucleation and growth mechanism. However, there are two different crystals ZnAl2O4 and NaAlSiO4 present in the glass containing TiO2 after heat treating at 575 °C for 2 h and 740 °C for 6 h, respectively. What is interesting is that NaAlSiO4 disappears as the crystallization time at 740 °C increases from 6 h to 12 h, and more ZnAl2O4 crystal is formed, namely, the further formation of ZnAl2O4 is at cost of NaAlSiO4 with increasing crystallization time. And observation of the morphology of glass ceramics shows great difference with increasing crystallization time. Moreover, the ability of ZnO-B2O3-SiO2-Al2O3-Na2O glass ceramics against attacking of 1M HCl solution is increased by the crystals precipitated in heat treatment process. 相似文献
15.
Ferroelectric Ba0.7Sr0.3TiO3(BST) and partially Pb^2+ substituted for Ba^2+ ceramics (Ba0.7-xPbx)Sr0.3TiO3 (x=0.1-0.4, BPST) were prepared by using conventional solid-reaction method. XRD analysis shows that the samples microstructure changes from cubic phase to tetragonal one with the Pb^2+ content increasing. ESEM analysis shows that the Pb^2+ substituted samples have a denser and more uniform surface morphology than that of pure BST. Measured electrical properties suggest that the Pb^2+ substitution for Ba^2+ in the BST system enhances the ferroelectric performance obviously when x=0.2. In addition, the substitution increases the samples Curie temperature (To) r (Ba0.5Pb0.2)Sr0.3TiO3 ceramic has good ferroelectric properties measured at a maximal electric field of 30 kV/cm under the condition of room temperature. The corresponding saturated polarization (Ps), remnant polarization (Pr) and coercive field (Ec) is respectively 15.687 μC/cm^2, 8.100 μ C/cm^2 and 6.611 kV/cm. The measured Tc of (Ba0.5Pb0.2)Sr0.3TiO3 is 117 ℃. 相似文献
16.
FAN Jinpeng ZHAO Daqing XU Zening & WU Minsheng . Department of Mechanical Engineering Tsinghua University Beijing China . Key Laboratory for Advanced Manufacturing by Materials Processing Technology Tsinghua University Beijing China 《中国科学E辑(英文版)》2005,48(6):622-631
Since their discovery by Iijima[1], carbon nanotubes (CNTs) have been the focus in novel materials research. Theoretical and experimental studies show[2-9] that CNTs have extraordinary mechanical and electrical properties. Krishnan et al.[2] have reported that the mean value of Young’s modulus of single-wall nanotubes (SWNTs) is 1.25 TPa. Yu et al.[3] measured Yang’s modulus of multi-wall nanotubes (MWNTs) between 270 and 950 GPa and breaking strength between 11 and 63 GPa. The ele… 相似文献
17.
Carbon was coated on the surface of Li2MnSiO4 to improve the electrochemical performance as cathode materials, which were synthesized by the solution method followed by heat treatment at 700 °C and the solid-state method followed by heat treatment at 950 °C. It is shown that the cycling performance is greatly enhanced by carbon coating, compared with the pristine Li2MnSiO4 cathode obtained by the solution method. The initial discharge capacity of Li2MnSiO4/C nanocomposite is 280.9 mAh/g at 0.05 C with the carbon content of 33.3 wt%. The reasons for the improved electrochemical performance are smaller grain size and higher electronic conductivity due to the carbon coating. The Li2MnSiO4/C cathode material obtained by the solid-state method exhibits poor cycling performance, the initial discharge capacity is less than 25 mAh/g. 相似文献
18.
Zhaofeng Li 《武汉理工大学学报(材料科学英文版)》2008,23(6):859-862
The phase structure and electrical properties of pure and La2O3-doped Bi-InO3-PbTiO3 (BI-PT) ceramics were studied respectively. In (1 -x)BI-xPT (x=0.72-0.80) ceramics, the stability of tetragonal phase increased with increasing x, and pure perovskite structure was obtained for x=-0.80 ceramics. The phase transition temperature range was between 575 ℃ and 600 ℃ for x=0.72-0.80 ceramics, higher than that of PT (-490 ℃). The c/a ratio almost linearly decreased with increasing La2O3 content in x-0.80 ceramics. It is believed that Pb^2+ vacancies were formed by La^3+ substituting Pb^2+ in La2O3-doped BI-PT ceramics. Tc shifted to lower temperature by 30 ℃/mol% La2O3. The maximum dielectric constant 8557 around 559 ℃ was exhibited in 0.5mol%-doped BI-0.80PT ceramics. La2O3-doped ceramics could be poled resulting from decreasing of c/a ratio and improving of dielectric loss and resistivity. The maximum piezoelectric coefficient d33 was 12 pC/N for 2mol%-doped BI-0.80PT ceramics. 相似文献
19.
Synthesis and Dielectric Properties of Ba3NaBiNb10O30 Ceramics 总被引:1,自引:0,他引:1
FANGLiang ZHANGHui HONGXue-kun LIUHan-xing 《武汉理工大学学报(材料科学英文版)》2003,18(1):22-24
A new niobate Ba3 NaBiNb10O30 was synthesized by the solid state reaction. The reaction mixture was characterized by thermogravimetric and differential thermal analysis ( TG-DTA ), X-ray diffraction and dielectric constant measurements. The results show that Ba3NaBiNb10O30 has an orthorhombic tungsten bronze structure with space group Cmm2 and the unit cell parameters are a = 1. 7660( 1 ) mm, a = 1. 7626( 1 ) mm, c = 0.78621(6) mm, Z = 4. Ba3 NaBiNb10O30 undergoes two phase transitions at 200℃ and 400℃, respeaively. 相似文献
20.
贺海燕 《武汉理工大学学报(材料科学英文版)》2009,24(3):359-362
Fatigue-free Bi3.2La0.8Ti3O12 ferroelectric thin films were successfully prepared on p-Si (100) substrates using metalorganic solution deposition process. The orientation and formation of 5-layers thin films
were studied under different processing conditions using XRD. Experimental results indicate that increase in annealing time
at 700 °C after preannealing for 10 min at 400 °C can remarkably increase (200)-orientation of the films derived from the
precursor solutions with two contents of citric acid. Meanwhile, high content of citric acid increases the film thickness
and is conducive to the a-orientation of the films with the preannealing, and low concentration of the solution is conducive to the c-orientation of
the films without the preannealing. 相似文献