共查询到20条相似文献,搜索用时 31 毫秒
1.
HUA WANG LI LIU JI-WEN XU CHANG-LAI YUAN LING YANG 《Bulletin of Materials Science》2013,36(3):389-393
[Pb 0·95(La1???y Bi y ) 0·05][Zr0·53Ti0·47]O3 (PLBZT) ferroelectric thin films have been synthesized on indium tin oxide (ITO)-coated glass by sol–gel processing. PLBZT thin films were annealed at a relatively low temperature of 550 °C in oxygen ambient. Effects of Bi doping on structure, dielectric and ferroelectric properties of PLBZT were investigated. Bi doping is useful in crystallization of PLBZT films and promoting grain growth. When the Bi-doping content ${\mathit{y}}$ is not more than 0·4, an obvious improvement in dielectric properties and leakage current of PLBZT was confirmed. However, when the Bi-doping content is more than 0·6, the pyrochlore phase appears and the remnant polarization P r of PLBZT thin films is smaller than that of $\left({Pb}_{{1-x}} {\bf La}_{x}\right)\!\!\left({Zr}_{{1-y}} {Ti}_{y}\right){O}_{3}$ (PLZT) thin films without Bi doping. PLBZT thin films with excessive Bi-doping content are easier to fatigue than PLZT thin films. 相似文献
2.
Wenbin Yang Litong Zhang Laifei Cheng Yongsheng Liu Laifei Cheng Weihua Zhang 《Applied Composite Materials》2009,16(2):83-92
A two-layered self healing coating with a B4C internal layer and a SiC external layer is prepared on C/SiC composite by chemical vapor deposition (CVD). Microstructure
and component of the coating was analyzed by SEM, EDS, and XRD. Oxidation behavior of SiC-B4C coated C/SiC composite was compared with SiC-SiC coated C/SiC in an environment of at 700°C, 1,000°C and 1,200°C for 100 h, respectively. It is demonstrated that the SiC-B4C coating is more efficient to protect the composite from oxidation than SiC-SiC coating below 1,000°C due to the self healing
behavior. After oxidized at 700°C for 100 h, the residual flexural strength of SiC-B4C coated C/SiC is about 86%, and that of SiC-SiC coated is about 64%. While after oxidized at 1,200°C, the former is about
86% and the later is about 89%. This is due to the enhanced evaporation of B2O3 at higher temperature. 相似文献
3.
Won-Seung Cho Kyeongsoon Park 《Journal of Materials Science: Materials in Electronics》2000,11(4):319-324
The effects of bulk porosity on the thermoelectric properties of porous n-type ${\text{Fe}}_{{\text{0}}{\text{.94}}} {\text{Co}}_{{\text{0}}{\text{.06}}} {\text{Si}}_{\text{2}} $ compounds prepared by pressureless sintering were examined. A small amount of metallic phase ?-FeSi remained after annealing at 800 °C for 100 h. As the sintering temperature increased from 1150 to 1175 °C, the phase transition to β-FeSi2 during annealing occurred more rapidly. The porous specimen, sintered at 1150 °C for 2 h with coarse powders (<45 μm) and then annealed at 800 °C for 100 h, showed the highest Seebeck coefficient of $ - 363_{\mu } {VK}^{ - {1}} $ at 400 °C and the highest power factor of ${\text{1}}{\text{.57}} \times 10^{ - 3} {\text{Wm}}^{ - 1} {\text{K}}^{ - 2} $ at 400 °C. 相似文献
4.
JuanJuan Xing Masaki Takeguchi Miyoko Tanaka Yoshiko Nakayama 《Journal of Materials Science》2012,47(13):5254-5262
The NiO/YSZ interface prepared by depositing NiO on a single crystal YSZ (111) substrate has been investigated by transmission
electron microscopy. As deposited, a very thin nickel layer ascribing to the nonstoichiometry at the very beginning growth
of NiO and an amorphous silica phase resulting from silicon segregation were present at the interface. The orientational relationship
of NiO (1[`1] 1) (1\overline{1} 1) //Ni (1[`1] 1) (1\overline{1} 1) //YSZ (1[`1] 1) (1\overline{1} 1) with NiO [110]//Ni [110]//YSZ [110] was observed. The microstructural and chemical changes at the NiO/YSZ interface after
being heated in vacuum and hydrogen indicated different reduction mechanisms. In vacuum, the reaction
\textNiO ? \textNi + 1/ 2 \text O 2 ( \textg ) {\text{NiO}} \to {\text{Ni}} + 1/ 2 {\text{ O}}_{ 2} \left( {\text{g}} \right) was prevailing at the interface between NiO and pre-existing Ni, which led to the thickening of nickel layer. In hydrogen, the reduction initiated on the NiO surface was dominant,
following the chemical equation H2 + OO (NiO) → H2O (g) + VO
.. (NiO) + 2e (Ni). 相似文献
5.
The interface structure of an Al2O3/Nb/Al2O3 sandwich produced by solid-state diffusion bonding was investigated in detail by various transmission electron microscopy (TEM) methods. The joint possessed at one interface a
,
, and on the other interface a
and
orientation relationship. At both interfaces, misfit dislocations formed to compensate the lattice mismatch as found by high-resolution transmission electron microscopy (HRTEM). Electron energy-loss near edge structure (ELNES) studies revealed that the interface is terminating with an Al layer resulting in Al–Nb bonds. Identical sandwiches were investigated on the meso- and macroscopic scale by performing compression tests and simultaneously monitoring the strain development at (001)Nb and crystal faces. The full-field optical strain measurements (FFOM) revealed that the strain is localized at the interfaces when observed at the (001)Nb face while it is along the maximum shear directions of 36–54° inclined to the interface when observed at the face. The strain localization along a specific maximum shear direction results in the cleavage of Al2O3, always initiating from the interface possessing the
and
orientation relationship. 相似文献
6.
This paper concerns the studies of temperature and frequency behavior of the complex impedance, electric modulus, and electric conductivity due to an ionic current in liquid γ-butyrolactone (GBL) and γ-valerolactone (GVL). The frequency of the applied electric stimulus (500?Hz to 5?MHz) corresponds to the static dielectric regime of the lactones. The studies were performed in the temperature range of 263 K to 313 K. It was shown that in the static dielectric case, the dc ionic conductivity (σ DC) and the static dielectric permittivity ${(\varepsilon_{\rm s})}$ determine the relaxational behavior of the impedance (Z*) and the electric modulus (M*) of the molecular liquids and both spectra are of the Debye-type characterized by the same conductivity relaxation time (τ σ ). Both σ DC and τ σ of GBL and GVL fairly well fulfill an Arrhenius temperature dependence with very similar values of the thermal activation energy ${{\rm E}_{\sigma_{\rm DC}} \approx {\rm E}_{\tau_\sigma} \approx 25 \,{\rm kJ} \, . \, {\rm mol}^{-1}}$ . The temperature dependence of the static dielectric permittivity and its temperature derivative is analyzed and interpreted in terms of the dipolar aggregation in the studied lactones. 相似文献
7.
F. Stemme M. Bruns H. Geßwein M. Schroeder M. Sazegar M. D. Drahus R.-A. Eichel F. Paul C. Azucena J. R. Binder 《Journal of Materials Science》2013,48(9):3586-3596
The effects of fluorine co-doping by means of a post-thermal annealing process of iron-doped BST thin films in a fluorine-containing atmosphere have been investigated. XPS and ToF-SIMS sputter depth profiling verified a homogeneous fluorine distribution in the thin films. By employing EPR, it was shown that singly charged ( $ {\text{Fe}}_{\text{Ti}}^{\prime } $ – $ {\text{V}}_{\text{O}}^{ \cdot \cdot } $ )· defect complexes, as well as ‘isolated’ $ {\text{Fe}}_{\text{Ti}}^{\prime } $ centres with a distribution of $ {\text{F}}_{\text{O}}^{ \cdot } $ sites in remote coordination spheres exist in the fluorinated films. Tunability enhancement due to fluorine co-doping as well as a Q-factor enhancement due to iron doping is demonstrated. 相似文献
8.
Satyendra V. Vikram D. M. Phase Vishal S. Chandel 《Journal of Materials Science: Materials in Electronics》2010,21(9):902-905
Solid-state reaction synthesised K2Ti6O13 lead-free ceramic was characterized using XRD, SEM, and X-band EPR, at room temperature. EPR-spectra showed the presence
of
( \textFe\textTi¢ - V\textO ·· ) \left( {{\text{Fe}}_{\text{Ti}}^{\prime } - V_{\text{O}}^{ \bullet \bullet } } \right) defect associate dipoles, in orthorhombic phase, responsible for the broadening of the dielectric anomaly identified in the
ε
r (T) plots at T
C
~ 300 °C. This anomaly resembled a ferroelectric–paraelectric type phase transition following Curie–Weiss type trend. Besides,
dielectric loss mechanism jointly represented electrical conduction, dipole orientation, and space charge polarization. 相似文献
9.
H. Oyanagi N. L. Saini A. Tsukada M. Naito 《Journal of Superconductivity and Novel Magnetism》2005,18(5-6):731-735
Local lattice anomalies in optimally doped T-(La,Sr)2CuO4 single crystal like thin films (T c?=?43.4 K) grown by molecular-beam epitaxy have been studied by the in-plane polarized Cu K-edge extended X-ray absorption fine structure (EXAFS). The results indicate temperature-dependent local atomic displacements which are anomalous at the T c and below a higher temperature T s as demonstrated by a change in the mean square relative displacement of the Cu–O bond $\sigma _{{\rm Cu}-{\rm O}}^2$ , i.e., a sharp drop at the T c and a gradual deviation from a noncorrelated Debye-like behavior below T s where the spatial inhomogeneity appears. We find that the magnitude of the Cu–O displacement changes at the T c, $\Delta \sigma _{{\rm Cu}-{\rm O}}^2$ is enhanced by compressive strain while the tendency of charge segregation is suppressed. The results suggest that the uniaxial pressure effects stabilize the system by decreasing the onset temperature and magnitude of spatial heterogeneity. 相似文献
10.
Light-weight, cellular β-SiAlON/SiC ceramics were produced via dip-coating of an Al/Si-powder containing preceramic polymer
slurry into corrugated cardboard. The coated cardboard preforms were pyrolyzed in Ar-atmosphere at 1200°C, where the cellulose
fibres decomposed into carbon. Simultaneously the Al/Si melt infiltrated into the porous carbon and formed β-SiC. Subsequent
nitridation at temperatures between 1200–1530°C resulted in the formation of a β-SiC-containing
composite. Different pre-oxidation treatment resulted in a variation of the oxygen content in the solid solution phase (z = 0.6–1.2). 相似文献
11.
S. R. Nalage M. A. Chougule Shashvati Sen V. B. Patil 《Journal of Materials Science: Materials in Electronics》2013,24(1):368-375
Nickel oxide (NiO) sensor films were prepared on glass substrate by a sol–gel spin coating technique. These films were characterized for their structural and morphological properties by means of X-ray diffraction, field emission scanning microscopy and atomic force microscopy. The NiO films are oriented along (200) plane with the cubic crystal structure. These films were utilized in nitrogen dioxide gas (NO2) sensor. The dependence of the NO2 response on operating temperature, NO2 concentration was investigated. The NiO film showed selectivity for NO2 over Cl2 compared to H2S $ \left( {{\text{S}}_{{{\text{NO}}_{ 2} }} /{\text{S}}_{{{\text{Cl}}_{ 2} }} = 3 7. 5,{\text{ S}}_{{{\text{NO}}_{ 2} }} /{\text{S}}_{{{\text{H}}_{ 2} {\text{S}}}} = 3. 4} \right) $ . The maximum NO2 response of 23.3 % with 85 % stability at gas concentration of 200 ppm at 200 °C was achieved. The response time of 20 s and recovery time of 498 s was also recorded with same operating parameters. 相似文献
12.
Susumu Ikeno Kenji Matsuda Toshimasa Matsuki Toshiaki Suzuki Noriaki Endo Tokimasa Kawabata Yasuhiro Uetani 《Journal of Materials Science》2007,42(14):5680-5685
The formation mechanism of spinels on Al2O3 particles in the Al2O3/Al–1.0 mass% Mg2Si alloy composite material has been investigated by transmission electron microscopy (TEM) in order to determine the crystallographic
orientation relationship. A thin sample of the Al2O3/Al–Mg–Si alloy composite material was obtained by the FIB method, and the orientation relationship between Al2O3 and MgAl2O4, which was formed on the surface of Al2O3 particles, was discovered by the TEM technique as follows:
At the interface between the Al2O3 and the matrix the MgAl2O4 (spinel) crystals had facets of {111} planes. Spinels were not grown as thin films, but as particles consisting of {111}
planes. They grow towards both the matrix and the Al2O3 particles. 相似文献
13.
A polymer composite of Ag-metal reinforced polyvinyl alcohol (PVA) is synthesized in shape of thin laminates of 200–300 μm
thickness. The process involves a chemical Ag+ dispersion in PVA and in-situ
reduction-reaction with active PVA molecules under hot conditions (with stirring) in water at 60–70°C temperature. The product
results in a metal Ag-polymer complex dispersed in the solution. After evaporating part of water, a derived viscous solution
is casted (in hot conditions) in shape of a thin laminate in a glass mould. In addition to chemical reducer, active OH-groups
(free from H-bonding) in PVA molecules of refreshed surfaces act as head groups to adsorb Ag+ and drive a directional
growth. Short fibrils of Ag-metal thus occur in reaction over the PVA molecules. Casting thin laminates from a liquid sample
Ag-PVA allows the fibrils (also the polymer molecules) to align along the surface. Selected Ag-contents up to 5.0 wt.% in
Ag-PVA laminates are studied in terms of scanning electron micrograph, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction.
Average size, morphology and aspect ratio (ϕ) vary in Ag-metal depending on the Ag-content. As long Ag-metal fibrils as 2–5 μm,
ϕ=35, occur in a sample of 2.0 wt.% Ag. The Ag-metal reflects in two characteristic 3d5/2 and 3d/3/2 XPS bands of 368.3 and 374.1 eV respectively. 相似文献
14.
A low-viscosity 60 SnO–40 P2O5 (mol%) glass was reheated at 280 °C (about 45 °C above the glass-transition temperature) for 20 min in various atmospheres
(Ar, air, and O2), then the structure- and surface-related properties were examined. It was found that increase in
\textP\textO 2 {\text{P}}_{{{\text{O}}_{ 2} }} increases surface hardness, reduces optical transmittance, and improves chemical durability. The above phenomena are explained
in terms of the increased oxidation tendency of Sn2+ to Sn4+ on the glass surface during reheating in increased
\textP\textO 2 {\text{P}}_{{{\text{O}}_{ 2} }} . 相似文献
15.
The presence of hydrogen dissolved within iron-magnesium oxides and silicates results in an increase in the rate of Fe–Mg
interdiffusion. Experimental data and point defect models suggest that the increased interdiffusivity is due to an increase
in the total metal-vacancy concentration through stabilization of proton-vacancy defect associates in a hydrous environment.
In the case of (Mg1–x
Fe
x
)O, interdiffusion experiments under hydrothermal conditions at a fluid pressure of ∼0.3 GPa yield similar dependencies of
interdiffusivity on Fe-content, oxygen fugacity, and temperature as under dry conditions, but interdiffusion coefficients
are a factor of ∼3 larger. These data suggest that the increased interdiffusivities in (Mg1–x
Fe
x
)O result from incorporation of defect associates formed between a metal vacancy and a single proton, For (Mg1–x
Fe
x
)2SiO4, interdiffusion under hydrothermal conditions over a range of fluid pressures reveals a significant difference in the dependence
of interdiffusivity on Fe content than obtained under dry conditions, combined with a strong dependence on water fugacity.
These data indicate that the increased diffusivities in (Mg1–x
Fe
x
)2SiO4 result from incorporation of defect associates involving a metal vacancy and 2 protons, It is anticipated that, at higher water fugacities, Fe–Mg interdiffusion in both materials will become dominated by these
latter defects and that the interdiffusivity will increase linearly with water fugacity but will be independent of oxygen
fugacity and iron concentration.
相似文献
David L. KohlstedtEmail: |
16.
Boris Nijikovsky Jacob J. Richardson Magnus Garbrecht Steven P. DenBaars Wayne D. Kaplan 《Journal of Materials Science》2013,48(4):1614-1622
The microstructure of ZnO films synthesized from low-temperature (90 °C) aqueous solution on (111) MgAl2O4 single crystal substrates was characterized by X-ray diffraction, high-resolution scanning electron microscopy, conventional and high-resolution transmission electron microscopy. To examine the thermally activated microstructural evolution of the ZnO, both as-deposited and annealed films were characterized. The ZnO films were confirmed to have a ZnO $ [10\bar{1}0](0001)\left\| {{\text{MgAl}}_{ 2} {\text{O}}_{4} [011](1\bar{1}1)} \right. $ orientation relationship, with Zn polarity normal to the surface. Despite their highly oriented nature, the ZnO films have a columnar grain structure with low-angle (<2.5°) grain boundaries. In addition to lattice dislocations forming low-angle grain boundaries, threading dislocations were observed, emanating from the interface with the substrate. In annealed films, thermally generated voids were observed and appeared to preferentially form at grain boundaries and dislocations. Based on these characterization results, mechanisms are proposed for film growth and microstructural evolution. Finally, the diffusion coefficient of vacancies via dislocations at grain boundaries in the produced ZnO films was estimated. 相似文献
17.
Peng Zhu Linfei Liu Shengping Zhu Guina Xiao Ying Wang Da Xu Yijie Li 《Journal of Superconductivity and Novel Magnetism》2012,25(6):1641-1645
$\mathrm{GaBa}_{2}\mathrm{Cu}_{3}\mathrm{O}_{7\mbox{-}\delta}$ thin films have been grown on CeO2 cap layer by RF magnetic sputtering with different oxygen/argon partial pressure ratio from 2:1 to 1:5. The CeO2 cap layers were fabricated by pulse laser deposition (PLD) on YSZ/CeO2/Ni-5%W alloy substrate and had good properties in structure and surface morphology. We study the relationship between oxygen/argon ratio and the performance of the $\mathrm{GaBa}_{2}\mathrm{Cu}_{3}\mathrm{O}_{7\mbox{-}\delta}$ film in order to find out the optimized deposition condition. The structure and surface morphology of the $\mathrm{GaBa}_{2}\mathrm{Cu}_{3}\mathrm{O}_{7\mbox{-}\delta}$ thin films were measured by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Atomic force microscopy (AFM). It was found that the texture and surface performance of $\mathrm{GaBa}_{2}\mathrm{Cu}_{3}\mathrm{O}_{7\mbox{-}\delta}$ film, such as growth orientation, grain roughness, grain size and surface morphology, are deeply affected by the oxygen/argon ratio. And the film??s performance was the best when the oxygen/argon partial pressure ratio is 1:1. 相似文献
18.
Synthesis and optical transmission of MgB2 thin films on optically transparent glass are reported. In the 400–1000 nm regime as deposited films show high metallic reflectivity
and very little transmission. After deposition, the films were annealed ex situ and rendered superconducting with T
c of 38 K, approaching that of the bulk material. The reaction conditions where quite soft ∼10 min at 550°C. The optical absorption
coefficient, α and photon energy, E followed a Tauc-type behavior,
= _T (E - E_g )(\alpha E)^{1/2} = \beta _T (E - E_{\rm g} ). The band gap (E
g) was observed to peak at 2.5 eV; but, the slope parameter β
T
behaved monotonically with reaction temperature. Our results indicate that an intermediate semiconducting phase is produced
before the formation of the superconducting phase; also optical measurements provide valuable information in monitoring the
synthesis of MgB2 from its metallic constituents. In addition these films have interesting optical properties that may be integrated into optoelectronics. 相似文献
19.
C. Lecoutre Y. Garrabos E. Georgin F. Palencia D. Beysens 《International Journal of Thermophysics》2009,30(3):810-832
Light transmission measurements performed in SF6 close to its liquid–gas critical point are used to obtain turbidity data in the reduced temperature range (T is temperature, T
c is the critical temperature). Automatic experiments (ALICE 2 facility) were made at a near critical density, i.e., , in the one-phase homogeneous region, under the microgravity environment of the Mir Space Station ( is the average density, ρ
c is the critical density). The turbidity data analysis verifies the theoretical crossover formulations for the isothermal
compressibility and the correlation length ξ. These latter formulations are also used to analyze very near T
c thermal diffusivity data obtained under microgravity conditions by Wilkinson et al. (Phys. Rev. E 57 436, 1998). 相似文献
20.
Velocity Distribution of Vibration-driven Granular Gas in Knudsen Regime in Microgravity 总被引:1,自引:0,他引:1
M. Hou R. Liu G. Zhai Z. Sun K. Lu Y. Garrabos P. Evesque 《Microgravity science and technology》2008,20(2):73-80
Dynamics of quasi-2D dissipative granular gas is studied in micro-gravity condition (of the order of 10 − 4 g) in the limit of Knudsen regime. The gas, made of 4 spheres, is confined in a square cell enforced to follow linear sinusoidal
vibration in ten different vibration modes. The trajectory of one of the particles is followed for 2 hours, and is reconstructed
from video data by particle tracking. From statistical analysis, we find that (i) loss due to wall friction is small, (ii)
trajectory looks ergodic in space, and (iii) distribution ρ(ν) of speed follows an exponential distribution, i.e., , with being a characteristic velocity along a direction parallel (y) or perpendicular (x) to vibration direction. This law deviates
strongly from the Boltzmann distribution of speed in molecular gas. Comparisons of this result with previous measurements
in earth environment, and what was found in 3D cell (Falcon et al., Europhys Lett 74:830, 2006) performed in environment of about ±5 ×10 − 2 g are given. 相似文献