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1.
Qiang Li 《中国科学E辑(英文版)》2009,52(7):1919-1922
Nanostructured Fe40Ni40P14B6 alloy ingots of 3–5 mm in diameter could be synthesized by a metastable liquid state spinodal decomposition method. For undercooling
ΔT > 260 K, the microstructure of the undercooled specimen had exhibited liquid state spinodal decomposition in the undercooled
liquid state. The microstructure could be described as two intertwining networks with small grains dispersed in them. For
undercooling ΔT > 290 K, the overall microstructure of the specimen changed into a granular morphology. The average grain sizes of the small
and large grains are ≅ 30 nm and ≅ 80 nm, respectively. These prepared samples are soft magnets with saturation magnetization
B
s
≅ 0.744 T.
Supported by the Hong Kong Research Grants Council the National Natural Science Foundation of China (Grant No. 50861007) and
Xinjiang University Doctoral Research Start-up Grant (Grant No. BS050102) 相似文献
2.
SUHao WUShun-hua YANHai-yang 《武汉理工大学学报(材料科学英文版)》2004,19(4):62-64
The dielectric ceramics with a main crystal phase of MGTiO3 and additional crystal phase of CaTiO3 were prepared by the conventional electronic ceramics technology .the strucures of MgTiO3 are ilmenitetype,and belong to hexagonal syngony.the ratio of MgTiO3 to Ca TiO3 doping on the dielectric properties of MGTiO3-CaTiO3(MCT)ceranics were inrestigated.the addition of B2O3 decreases the sintering temperatnre and results in rapid desification without obrious negative effect on the Q values of the system(Q=1/tan ).B2O3 exists as liquid phase in the sintering process,promoting the reactions as a singering agent. 相似文献
3.
《中国科学E辑(英文版)》2009,(6)
The high-dense nanocrystalline BaTiO3(BT)ceramics with grain size smaller than 100nm have been successfully prepared by the two step sintering and the spark plasma sintering(SPS)process.The successive transitions in nanograin BT ceramics from rhombohedral to orthorhombic,tetragonal and cubic transitions,similar to those in coarse BT ceramics,were revealed by in-situ temperature dependent Raman spectrum.The multiphase coexistence and the diffused phase transition character were demonstrated in the 8nm nanocr... 相似文献
4.
The environmental problem caused by refrigerant has become the focus all over the world. As the most typical natural refrigerant,
CO2, of course, becomes the research focus. This paper introduces the development and application status of CO2 refrigeration and heat pump technology. The researches on CO2 refrigeration and heat pump, carried out by Thermal Energy Research Institute, Tianjin University, also are presented in
this paper.
Supported by the National Natural Science Foundation of China (Grant Nos. 50676064, 50506019) and the National Hi-Tech Research
and Development Program of China (“863” Project) (Grant No. 2007AA05Z262) 相似文献
5.
Cu2ZnSnS4 (CZTS) thin films were successfully fabricated on glass substrates by sulfurizing Cu-Sn-Zn multilayer precursors, which were
deposited by ion beam sputtering and RF magnetron sputtering, respectively. The structural, electrical and optical properties
of the prepared films under various processing conditions were investigated in detail. Results showed that the as-deposited
CZTS thin films with the precursors by both ion beam sputtering and RF magnetron sputtering have a composition near stoichiometric.
The crystallization of the samples, however, has a strong dependence on the atomic percent of constituents of the prepared
CZTS films. A single phase stannite-type structure CZTS with a large absorption coefficient of 104/cm in the visible range could be obtained after sulfurization at 520°C for 2 h. The samples relative to the RF magnetron
sputtering showed a low resistivity of 0.073 Ωcm and band gap energy of about 1.53 eV. The samples relative to the ion beam
sputtering exhibited a resistivity of 0.36 Ωcm and the band gap energy is about 1.51 eV.
Supported by the National Natural Science Foundation of China (Grant No. 10574106), the Planned Science and Technology Project
of Guangdong Province (Grant No.2003C05005) and the Natural Science Fund of Zhanjiang Normal University (Grant No.200801) 相似文献
6.
Poly ethylene oxide (PEO)x−V2O5−V2O5−MoO3 (x=0, 0.5, 1) films were prepared by the sol-gel method. The synthesis and structure of the films were investigated by XRD,
TG-DTA, FTIR, etc. The results show that V2O5−MoO3 xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1. 7898 nm at x=1 after the nanocomposite
films were dried, and PEO in the interlayer changes the interface structure by forming hydrogen bonds with V=0 bands. CV measurement
indicates that the intercalation of PEO improves insertion/extration properties of Li+ ions in the interlayer.
ZHENG Jin-xia: Born in 1976
Funded by the National Natural Science Foundation of China (No. 50172036) and Natural Science Foundation of Hubei Province(No.
2001ABB083) 相似文献
7.
BaTi4O9-doped Ba0.6Sr0.4TiO3 (BST) composite ceramics were prepared by the conventional solid-state reaction and their structure, dielectric nonlinear
characteristics and microwave dielectric properties were investigated. The secondary phase of the orthorhombic structure Ba4Ti13O30 is formed among BST composite ceramics with the increase of BaTi4O9. At the same time, a duplex or bimodal grains size distribution shows fine grains in a coarse grain matrix. The degree of
frequency dispersion of dielectric permittivity below T
m is increased initially and then decreased with respect to BaTi4O9. As the BaTi4O9 content increases, the tunability of composite ceramics decreases, while the Q value increases. Interestingly, 70 wt% BaTi4O9-doped BST has a tunability ∼4.0% (under 30 kV/cm biasing) versus a permittivity ∼68 and quality factor ∼134.1 (at ∼3.2 GHz).
Supported by the Ministry of Science and Technology of China through 973-project (Grant No. 2009CB623302), the Cultivation
Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China (Grant No.707024), Shanghai Committee
of Science and Technology (Grant No. 07DZ22302), and Shanghai Foundation Project under 06JC14070 相似文献
8.
HANMin-fang LIBo-tao PENGSu-ping 《武汉理工大学学报(材料科学英文版)》2004,19(3):10-13
The manufacture process of 8 mol% Y2O3 stabilized ZrO2 ( YSZ ) from nano powders, including the forming and sintering stages, was studied. During the forming process of YSZ powders, the relative density of YSZ increases lineally with the forming press, and the sintering linear shrinkage of YSZ to the forming press compiles to the parabola trend. When the forming press exceeding 500MPa, the samples with lower shrinkage and high density were obtained. The sintering temperature of YSZ decreases greatly because of the small size and high active surface of YSZ powders. As a result, the beginning sintering temperature of YSZ made in the experiment is as low as 825℃, and the end sintering temperature is 1300-1350℃ . The relative density of YSZ ceramic by solid sintering at 1300-1350℃ is more than 97% , with little and small pores in the uniform microstructure. 相似文献
9.
Magnetite Fe3O4 walnut spherical particles and octahedral microcrystals were successfully synthesized from K4 [Fe (CN)6], K3 [Fe (CN)6] and NaOH reagents via a simple hydrothermal process. And the uniform morphology of octahedral microcrystals was obtained
in the presence of ethylene glycol. The morphology and structure of products were characterized by powder X-ray diffraction,
scanning electron microscopy and transmission electron microscopy. The results showed that the Fe3O4 walnut spherical particles and octahedral microcrystals were single crystals with the face-center cubic structure and with
size distributions from 2.2 to 8.6 μm and 1.6 to 12.5 μm, respectively. Their magnetic properties were detected by a vibrating
sample magnetometer at room temperature. The walnut spherical particles exhibited a ferromagnetic behavior with the coercive
force (Hc), saturation magnetization (Ms) and remanent magnetization (Mr) being 150.57 Oe, 97.634 and 12.05 emu/g, respectively.
For the octahedral microcrystals they were 75.28 Oe, 101.90 and 6.69 emu/g, respectively. Different sizes of walnut spherical
particles were controlled synthesized through adjusting the NaOH concentration. It was found that ethylene glycol molecules
have a significant effect on the formation of Fe3O4 octahedra. A possible mechanism was also proposed to account for the growth of these Fe3O4 products.
Supported by Fund of weinan Teachers University (Grant No. 08YKZ008), the National Natural Science Foundation of China (Grant
No. 20573072) and Doctoral Fund of Ministry of Education of China (Grant No. 20060718010) 相似文献
10.
Sm3(Fe,Ti)29Nx/α-Fe dual-phase nanometer magnetic material was fabricated through rapid solidification, crystallization and nitridation of Sm-Fe (Ti) alloy. The effect of combination of rapid solidification and Ti alloy addition on the phase formation and microstructure of the Sm-Fe alloy is investigated in this paper. The microstructure of amorphous phase and dual-phase nano-grain crystals before and after crystallization annealing were observed using a high-resolution transmission electron microscope (HREM). The dual-phase nano-grains after annealing were compacted together with a clear interface with the direct exchange-coupling mechanism. Different annealing processes were used to examine the melt-spun alloy. Comparison of the images of SEM showed that annealing at 750℃ for 10 min was most suitable to get homogeneous and nano-grains. No obvious kink was detected in the second quadrant of the hysteresis loop like a single hard magnet, and strong exchange coupling was found between hard magnets and soft magnets. 相似文献
11.
HaiLing Zhu JunYing Zhang TianMin Wang LiuGang Wang Xiang Lan BaiBiao Huang 《中国科学E辑(英文版)》2009,52(8):2175-2179
Aiming at reducing the recombination of photo-induced carriers in semiconductor photocatalytic process, we prepared TiO2 thin film with its surface modified by a connected Cu micro-grid via a microsphere lithography strategy, which showed higher
photocatalytic activity than the pure TiO2 film. The improvement of photocatalytic activity of Cu micro-grid to the TiO2 film is due to the charge carrier separation and electron transfer by the conducting metal grid. The photocatalytic activity
was improved as metal loading increased, which obtained the best performance at a certain loading amount, and then decreased
at higher loading amount. This phenomenon was attributed to the metal’s bulk effect which could be explained by the relationship
between the energetic positions and the metal cluster size.
Supported by the National Natural Science Foundation of China (Grant Nos. 50672003, 50872005) and the National Basic Research
Program of China (“973” Project) (Grant No. 2007CB613302) and the Fok Ying Tong Education Foundation (Grant No. 111050) 相似文献
12.
The phonon spectrum of ordered zincblende Si50Ge50 alloy is calculated by ab initio method. The energy band structure at zero pressure and the pressure dependence of phonon dispersion curves are shown up to
20 GPa. The calculation finds a pressure-induced softening of the transverse acoustic phonon mode and the mode frequency reaching
zero at about 14 GPa, which indicate breaking of the symmetry and formation of a new phase under high pressure.
Supported by the National Natural Science Foundation of China (Grant No. 50771090), the State Key Program for Basic Research
of China (Grant No. 2005CB724404) and the Program for Changjiang Scholars and Innovative Team (Grant No. IRT0650) 相似文献
13.
YuanZheng Yue Yue Hao Qian Feng JinCheng Zhang XiaoHua Ma JinYu Ni 《中国科学E辑(英文版)》2009,52(9):2762-2766
We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic-layer deposited (ALD)
Al2O3 as the gate dielectric. Through further decreasing the thickness of the gate oxide to 3.5 nm and optimizing the device fabrication
process, a device with maximum transconductance of 150 mS/mm was produced. The drain current of this 0.8 μm gate-length MOS-HEMT
could reach 800 mA/mm at +3.0 V gate bias. Compared to a conventional AlGaN/GaN HEMT of similar design, better interface property,
lower leakage current, and smaller capacitance-voltage (C-V) hysteresis were obtained, and the superiority of this MOS-HEMT
device structure with ALD Al2O3 gate dielectric was exhibited.
Supported by the National Natural Science Foundation of China (Grant No. 60736033) and the National Basic Research Program
of China (“973“) (Grant No. 51327020301) 相似文献
14.
Dynamic extending nonlinear H∞ control and its application to hydraulic turbine governor 总被引:1,自引:0,他引:1
There exists a large class of nonlinear systems with uncertainties, such as hydraulic turbine governors, whose robust control problem is hard to solve by means of the existing robust control approaches. For this class of systems, this work presents a dynamic extending H∞ controller via both differential geometry and H∞ theory. Furthermore, based on differential game theory, it has been verified that the proposed control strategy has robustness in the sense that the disturbance can be attenuated effectively because the L2-gain from the disturbance input to the regulation output signal could be reduced to any given level. Thirdly, a robust control strategy for hydraulic turbine governor is designed according to the proposed extending H∞ control method, and has been developed into a real control equipment. Finally the field experiments are carried out which show clearly that the developed control equipment can enhance transient stability of power systems more effectively than the conventional controller. 相似文献
15.
MeiYa Li Ling Pei Jun Liu BenFang Yu DongYun Guo XiaoHua Sun XingZhong Zhao 《中国科学E辑(英文版)》2008,51(11):1843-1849
Ferroelectric Bi3.25La0.75Ti3O12 (BLT) and Bi3.15Nd0.85Ti3O12 (BNT) thin films were fabricated on Pt/TiO2/SiO2/Si (100) substrates by a modified sol-gel technique. X-ray diffraction indicated that these films were of single phase with
random polycrystalline orientations. The surface morphologies of the films were observed by scanning electron microscope,
showing uniform, dense films with grain size of 50–100 nm. Well-saturated hysteresis loops of the films were obtained in metal-ferroelectric-metal
type capacitors with Cu top electrodes at an applied voltage of 400 kV/cm, giving the remanent polarization (2P
r) and coercive field (2E
c) values of the films of 25.1 μC/cm2 and 203 kV/cm for BLT, and 44.2 μC/cm2 and 296 kV/cm for BNT, respectively. Moreover, these capacitors did not show fatigue behaviors after up to 1.75×1010 switching cycles at the test frequency of 1 MHz, suggesting a fatigue-free character. The influences of the La3+ and Nd3+ doping on the properties of the films were comparatively discussed.
Supported by the National Key Basic Research and Development Program of China (Grant No. 2006CB932305) and the Natural Science
Foundation of Hubei Province, China (Grant No. 2004ABA082) 相似文献
16.
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
17.
The homogeneous glass sample for the ( 1 - x ) As2S3-xCdBr2, where x=0. 015,0. 035,0.05, was prepared by the conventional melt-quenched method. Amorphoas ( 1 - x ) As2S3-xCdBr2 alloys were determined by X-ray diffraction, thermal compreheasive analysis and Raman scattering. The glass transittion temperature (TR) deereases a bit with the addition of CdBr2 . Based on the experimental data, the microstrtucture is considered to be the discrete molecule species of AsBr3 and Cd - S atomic bonds or clusters are honigeneously dispersed in a disordered polymer network formed by AsS3 pyramids interlinked by sulfur bridges. 相似文献
18.
Experiments of simultaneous removal of SO2 and NO from simulated flue gas, using NaClO2 solution as the absorbent, were carried out in a self-designed bubble reactor, and high simultaneous removal efficiencies
of SO2 and NO were obtained under the optimal experimental conditions. The mechanism of simultaneous removal based on NaClO2 acid solutions was proposed by analyzing the removal products. Possibility and limitation of the desulfurization and denitrification
using NaClO2 acid solutions were calculated by thermodynamic methods. Experimental results of reaction kinetics for simultaneous desulfurization
and denitrification indicated that the oxidation-absorption processes of SO2 and NO were divided into two zones, namely the fast and slow reaction zones. In the slow reaction zones both were zero order
reactions, and in the fast reaction zones, the reaction order, rate constant and activation energy of SO2 reaction with absorbent were 1.4, 1.22 (mol·L−1)−0.4·s−1 and 66.25 kJ·mol−1, respectively, and 2, 3.15×103 (mol·L−1) −1·s−1, and 42.50 kJ·mol−1 for NO reaction, respectively.
Supported by the National High-Tech Research and Development Program of China (“863” Project) (Grant No. 2007AA061803) 相似文献
19.
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
20.
Based on the traditional sintering model incorporating the characteristic of microwave sintering, the ionic conductance diffusion
mechanism in microwave sintering was studied. A flat-ball model was presented to describe the kinetics process in microwave
sintering, and was applied to the sintering process of TZP and ZrO2-Al2O3 ceramics. The results indicate that the shrinkage rate of materials in microwave sintering is proportional to t
2/3 and r
−4/3, respectively, where t is the sintering time and r is the particle radius. Whereas, the shrinkage rate of materials in conventional sintering is proportional to sintering time
t
2/5. Our model suggests that microwave sintering is faster than conventional sintering, which shows a good agreement with the
experimental observation in sintering process of TZP and ZrO2-Al2O3.
Supported by the State Key Program of National Natural Science of China (Grant No. 50332010) and the National Key Technology
Research and Development Program for Resource and Environment of China (Grant Nos. 2006BAB12B03, 2006BAB12B05) 相似文献