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1.
CeO2在氧化催化反应中的作用 总被引:13,自引:3,他引:13
从CeO2 所属的萤石型氧化物结构特点出发 ,对CeO2 内部的电子缺陷、氧离子及其空穴等在催化氧化中的作用进行分析 ,指出CeO2 在氧化催化剂中所起的修饰作用与它的价态变化———Ce4 /Ce3 间的转换 ,以及CeO2 与Cu等过渡金属之间的相互作用密切相关。更重要的是 ,此类催化体系 (如Cu CeO2 )是具有较高的电子 离子混合导电能力的混合型导体 ,且CeO2 易于存储、传输氧 ,可以协助O2 -从电解质向阳极传递 ,将阳极氧化反应面扩大至TPB面以外 ,减小界面阻力 ,加快氧化反应速率。此特性使其在以甲烷为燃料的固体电解质燃料电池阳极开发领域成为一种值得关注的备选材料。 相似文献
2.
贾树山 《国外电子测量技术》2011,30(10):28-30
烧结烟气脱硫控制系统,属于钢铁行业烧结机脱硫技术领域,所述的控制系统适用于湿法烧结烟气脱硫系统.烧结烟气脱硫控制系统即通过传感器把烟气的现场数据在有效时间内传递到控制柜的中央处理单元,并加以分析,进而有效控制脱硫装置的运行参数.使引风机、氧化压缩机、石灰乳泵、浆液循环泵、烟气热交换器等的工作状况与烟气工况相匹配.该技术... 相似文献
3.
Abstract The synthesis and characterization of lead cation-incorporated strontium bismuth tantalate ferroelectrics were investigated. Monophasic layered perovskites were successfully prepared, and the formation of solid solutions of lead-doped SrBi2Ta2O9 was corroborated. The value of lattice parameter c monotonicly increased with an increase in the lead content. The sinterability of the formed powder was poor; however, adding excess bismuth oxide markedly facilitated the sintering process. After sintering, the specimens exhibited strong preferred c-axis orientation. The degree of c-axis orientation significantly varied with the sintering temperature and the doping amount of lead species. SEM analysis indicated that the variation in the morphology of the grains was related to the degree of c-axis preferred orientation. The lead-doped specimens exhibited ferroelectric properties with well saturated P-E loops. Both the remanent polarization and the coercive field increased with the doping amount of lead cations. 相似文献
4.
A systematic investigation of cerium and stannum doped 0.94(Bi0.5Na0.5)TiO3−0.06BaTiO3 (Sn&Ce-BNT6BT) based lead-free piezoelectric ceramics is undertaken to understand the influence of sintering temperature
on electrical properties. The X-ray diffraction patterns showed that all of the Sn&Ce-BNT6BT ceramics exhibited a single perovskite
structure with the co-existence of the rhombohedral and tetragonal phase. The smaller grain size of Sn&Ce-BNT6BT ceramics
was obtained at lower sintering temperature, and more cubical grains of Sn&Ce-BNT6BT ceramics were obtained at higher sintering
temperature. The temperature dependence of dielectric permittivity of the compositions exhibited strong dispersion with the
increasing temperature, and the dielectric loss tangent increased dramatically while the temperature over 225∘C. The depolarization temperature T
d
of Sn&Ce-BNT6BT ceramics sintered at 1160∘C was 92.6∘C. The remnant polarizations P
r
for Sn&Ce-BNT6BT ceramics sintered at 1120 and 1200∘C were found to be 28.8 and 33.4 μC/cm2 at room temperature, respectively. 相似文献
5.
Barium Strontium Titanate (BST) solid solution is a strong candidate material for application in tunable ferroelectric devices.
In this research, we have synthesized and characterized nanocrystalline BST (Ba0.7Sr0.3TiO3) powder with average particle-diameter of 15 nm through a simple sol-gel process, using barium acetate, strontium acetate
and titanium isopropoxide as the precursors. In this process, stoichiometric proportions of barium acetate and strontium acetate
were dissolved in acetic acid followed by refluxing, and addition of titanium (IV) isopropoxide to form BST gel. The gel was
analyzed using Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA). The as-formed gel was dried
at 200 °C and then calcined in the temperature range of 400 to 800 °C for crystallization. Phase evolution during calcination
was studied using X-ray diffraction (XRD) technique. Particle size, morphology and the lattice fringes of the calcined powder
were characterized by high-resolution transmission electron microscopy (HR-TEM). To study the effects of sintering on BST
nanopowder, green ceramic specimens were prepared by uniaxial compaction and then sintered at 950–1,100 °C under atmospheric
conditions. Sintered specimens were analyzed for phase composition, grain size and geometric bulk density. 相似文献
6.
Acceptor doped-ceria is a possible electrolyte material for the IT-SOFC (intermediate temperature solid oxide fuel cell) due
to its high oxygen-ion conductivity. However, its use has been limited by its mechanical weakness and the appearance of electronic
conductivity in reducing condition. In this study, alumina was selected as an additive in the doped-ceria to see if it increases
the oxygen-ion conductivity and mechanical strength. Effects of alumina addition in doped ceria were studied as a function
of alumina content and acceptor (Gd) content.
The electrical conductivity of (Ce1−x
Gd
x
O2−δ)1−y
+ (Al2O3)
y
(x = 0–0.35, y = 0–0.10) was measured by using impedance spectroscopy. The grain conductivity of Ce0.8Gd0.2O2-δ (GDC20) with 5 mol% alumina increased ∼3 times from that of GDC20 at 300∘C. The grain conductivity was even ∼2 times higher than that of Ce0.9Gd0.1O2−δ (GDC10) at 300∘C. The electrical conductivity of GDC20 without alumina addition, measured at 500∘C in air, rapidly decreased after exposure to reducing condition (Po2∼10−22 atm) at 800∘C. However, the decrease was much slower in GDC20 with alumina addition, indicating the improved mechanical strength.
Among the examined compositions, (Ce0.75Gd0.25 O2-δ)0.95 + (Al2O3)0.05 (GDC25A5) showed the highest conductivity at most temperatures. 相似文献
7.
Takeo Hyodo Anja Bieberle-Hütter Joshua L. Hertz Harry L. Tuller 《Journal of Electroceramics》2006,17(2-4):695-699
Preparation of macroporous gadolinia-doped ceria (CGO) films was attempted by r.f. magnetron sputtering. A polymethylmethacrylate
(PMMA) microsphere film was fabricated as a template on a Pt-coated silicon substrate by dripping a PMMA microsphere aqueous
dispersion onto the substrate. CGO was deposited onto the PMMA microspheres by sputtering; the PMMA microspheres were found
to shrink during the sputtering, and thus the CGO also coated the surface of PMMA microspheres beneath the top layer of the
film. Films (ca. 1.5 μm thick) consisting of three dimensional arrays of hollow CGO microspheres (ca. 700 nm in diameter)
with large porosity were obtained after annealing the CGO/PMMA microsphere composite film. 相似文献
8.
采用传统氧化物陶瓷工艺制备低饱和磁化强度(4πMs)钇铁石榴石铁氧体,研究不同烧结温度时Al3+取代对材料气孔率(P)和收缩率(η)等烧结性能的影响。根据不同烧结温度样品收缩率的拟合直线计算Al3+取代样品的烧结活化能,并结合热重-差热(TG-DSC)联合分析研究Al^3+取代量对活化能的影响机制。结果表明,Y3Al5O12铁氧体的成相温度高于Y3Fe5O12铁氧体的成相温度;1420℃烧结时,随着Al3+取代量x由0.6增大至1.4,烧结活化能从191 kJ/mol增大到257 kJ/mol,烧结更加困难,烧结样品的P从1.63%增大到3.60%,η从16.62%减小到14.38%。 相似文献
9.
10.
采用固相反应法制备Ba2Co0.2Zn0.9Cu0.9Fe12O22(Co2Y)铁氧体粉末,通过添加不同量的Bi2O3-H3BO3-SiO2-ZnO(BBSZ)玻璃在不同温度下进行烧结,研究掺杂BBSZ玻璃对Co2Y六角铁氧体材料的烧结行为、显微结构和电磁性能的影响。结果表明,适量的BBSZ玻璃掺杂能得到晶粒均匀、结构致密的Co2Y铁氧体材料,起到良好的低温助烧作用。BBSZ玻璃掺杂为0.8wt%的Co2Y型铁氧体在900℃获得较好的电磁性能及致密性:ρ=5.33g/cm3,μi=9.19,ε=18.13,tanδμ(200MHz)=0.0235,tanδε(200MHz)=0.0018。 相似文献
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12.
13.
Low temperature sintering and microwave dielectric properties of Ba3Ti5Nb6O28 with B2O3 and CuO additions 总被引:1,自引:0,他引:1
Jeong-Ryeol Kim Dong-Wan Kim Sung Hun Yoon Kug Sun Hong 《Journal of Electroceramics》2006,17(2-4):439-443
The low sintering temperature and the good dielectric properties such as high dielectric constant (ε
r
), high quality factor (Q × f), and small temperature coefficient of resonant frequency (TCF) are required for the application of chip passive components
in wireless communication low temperature co-fired ceramics (LTCC). In the present study, the sintering behaviors and dielectric
properties of Ba3Ti5Nb6O28 ceramics were investigated as a function of B2O3-CuO content. The pure Ba3Ti5Nb6O28 system showed a high sintering temperature (1250∘C) and had the good microwave dielectric properties: Q × f of 10,600 GHz, ε
r
of 37, TCF of −12 ppm/∘C. The addition of B2O3-CuO was revealed to lower the sintering temperature of Ba3Ti5Nb6O28, 900∘C and to enhance the microwave dielectric properties: Q × f of 32,500 GHz, ε
r
of 40, TCF of 9 ppm/∘C. From the X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) studies, these phenomena were explained
in terms of the reduction of oxygen vacancies and the formation of secondary phases having the good microwave dielectric properties. 相似文献
14.
为了提高铝的耐蚀性以及活化性能,用电化学方法研究了在4 mol/L KOH溶液中,环保型添加剂乌洛托品[六次甲基四胺(CH2)6N4]、吐温-80和明胶对铝阳极(99.999%)电化学性能的影响,结果表明,添加0.5%乌洛托品,不仅使铝的析氢腐蚀速度降低(缓蚀率70%),又能最大程度保持铝阳极的活性(与铝在4 mol/L KOH水溶液中的情况非常接近),开路电位Eocp由-1.765 V负移到-1.865 V.当分别添加0.5%吐温-80和1%明胶时,则铝的缓蚀率达80.54%和74.46%,且Eocp负移出现最大值(-1.950 V和-1.960 V),但铝的极化稍微有所增加. 相似文献
15.
Abstract Effect of post-sintering treatment on PTCR behavior of (Sr0.2Ba0.8)TiO3 materials prepared by microwave-sintering (ms) process was compared to that prepared by rapid thermal sintering (RTS) process. The microwave-sintering process needed only 1130°C-40 min to effectively densify (Sr0.2Ba0.8)TiO3 materials. The grain size was around 6 μm and PTCR characteristics was around ρmax/ρmin≈ 101.75, with Tc = 50°C. Lowering the cooling rate after sintering substantially increases the resistivity jump (ρmax/ρmin) from 102 to 103.4, without altering the microstructure. The annealing at 1250°C for 2 h markedly increased the resistivity jump to (ρmax/ρmin)≈106. On the other hand, the rapid thermal sintering (RTS) process required 1320°C-30 min to fully develop the good microstructure (~15 μm) and PTCR property (ρmax/ρmin ~ 103.0). Post-sintering process, including cooling rate control and annealing, did not improve the electrical properties of these samples, that is ascribed to the slow-cooling rate characteristics of RTS-process for a temperature lower than 800°C. 相似文献
16.
17.
采用球形Ni0.5Co0.2Mn0.3(OH)2前驱体与Li2CO3混合,通过高温烧结合成层状Li Ni0.5Co0.2Mn0.3O2正极材料,研究了合成时间对材料结构及电化学性能的影响。扫描电子显微镜法(SEM)表明Li Ni0.5Co0.2Mn0.3O2正极材料与前驱体形貌均为理想的球形。X射线衍射光谱法(XRD)分析表明,在不同合成时间下合成的样品均为具有层状结构的纯相物质。电化学性能测试表明,900℃12 h合成的样品具有最优的电化学性能,在2.7~4.4 V电压区间,0.1 C、1 C、5 C的首次放电比容量分别达到195.2、158.4和114.9 m Ah/g,1 C循环10次容量保持率为98.9%。 相似文献
18.
Satyanarayan Patel K. S. Srikanth Arif Ali Baig Moghal Niyaz Ahamad Madhar 《Integrated ferroelectrics》2016,176(1):95-108
This article presents the effect of processing parameters on the ferroelectric hysteresis behavior of Ba0.85Sr0.15Zr0.1Ti0.9O3 (BSZT) ceramics. The ferroelectric hysteresis scaling relations for coercive field (Ec) and remnant polarization (Pr) as a function of temperature have been proposed. The power law temperature exponents based on scaling were systematically established for all the hysteresis parameters. The temperature dependent scaling of Ec and Pr at sintering temperature of 1400, 1425, 1450 and 1475°C yields EcαT0.43, EcαT0.84, EcαT0.50, EcαT0.37 and PrαT?1.73, PrαT?1.55, PrαT?1.73, PrαT?1.69 respectively. Additionally, the scaling relations for the samples sintered at 1450°C at different time intervals of 3, 4, 5 and 6 hrs were also established. Finally, to understand the domain dynamics, back switching polarization (Pbc) as a function of temperature (T) was also estimated by Arrhenius law and the average activation energy was evaluated. 相似文献
19.
20.
锡含量对铅锡合金析氧行为的影响 总被引:1,自引:0,他引:1
采用气体收集、线性电位扫描和交流阻抗等方法,研究了不同锡含量的铅锡合金电极在H4SO4中的析氧行为.随着锡含量的增加,氧气析出的体积逐渐减少,析氧电流逐渐减小,铅锡舍金电极上的析氧电化学电阻增大,电容减小.掺锡抑制了氧气的析出. 相似文献